A method for optimizing the cosine response of solar UV diffusers
Pulli, Tomi; Kärhä, Petri; Ikonen, Erkki
2013-07-01
Instruments measuring global solar ultraviolet (UV) irradiance at the surface of the Earth need to collect radiation from the entire hemisphere. Entrance optics with angular response as close as possible to the ideal cosine response are necessary to perform these measurements accurately. Typically, the cosine response is obtained using a transmitting diffuser. We have developed an efficient method based on a Monte Carlo algorithm to simulate radiation transport in the solar UV diffuser assembly. The algorithm takes into account propagation, absorption, and scattering of the radiation inside the diffuser material. The effects of the inner sidewalls of the diffuser housing, the shadow ring, and the protective weather dome are also accounted for. The software implementation of the algorithm is highly optimized: a simulation of 109 photons takes approximately 10 to 15 min to complete on a typical high-end PC. The results of the simulations agree well with the measured angular responses, indicating that the algorithm can be used to guide the diffuser design process. Cost savings can be obtained when simulations are carried out before diffuser fabrication as compared to a purely trial-and-error-based diffuser optimization. The algorithm was used to optimize two types of detectors, one with a planar diffuser and the other with a spherically shaped diffuser. The integrated cosine errors—which indicate the relative measurement error caused by the nonideal angular response under isotropic sky radiance—of these two detectors were calculated to be f2=1.4% and 0.66%, respectively.
Anomalous diffusion and dielectric relaxation in an N-fold cosine potential.
Coffey, W T; Kalmykov, Yu P; Titov, S V
2003-06-01
The fractional Klein-Kramers (Fokker-Planck) equation describing the fractal time dynamics of an assembly of fixed axis dipoles rotating in an N-fold cosine potential representing the internal field due to neighboring molecules is solved using matrix continued fractions. The result can be considered as a generalization of the solution for the normal Brownian motion in a cosine periodic potential to fractional dynamics (giving rise to anomalous diffusion) and also represents a generalization of Fröhlich's model of relaxation over a potential barrier. The solution includes both inertial and strong internal field effects, which in combination produce a strong resonance peak (Poley absorption) at high frequencies due to librations of the dipoles in the potential, an anomalous relaxation band at low frequencies mainly arising from overbarrier relaxation, and a weaker relaxation band at midfrequencies due to the fast intrawell modes. The high-frequency behavior is controlled by the inertia of the dipole, so that the Gordon sum rule for dipolar absorption is satisfied, ensuring a return to optical transparency at very high frequencies. Application of the model to the broadband (0-THz) dielectric loss spectrum of a dilute solution of the probe dipolar molecule CH2Cl2 in glassy decalin is demonstrated.
Research of Diffusion of Cu in CoN and CoSiN Thin Films%Cu 在 CoN 和 CoSiN 薄膜中的扩散研究
Institute of Scientific and Technical Information of China (English)
张在玉; 陈秀华
2013-01-01
The thin films of Cu/CoN/Si and Cu/CoSiN/Si were prepared on n - type silicon substrate by magnetron sputtering and annealed at different temperature .Their surface morphology were tested by atomic force microscopy (AFM) .Cu content with diffusion distance changes under different temperature were obtained by scanning electron microscopy (SEM) analysis methods . Then calculation and analysis were done on the diffusion of Cu in Cu/CoN/Si and Cu/CoSiN/Si systems via the Second Law of Fick . It can be obtained that the diffusion coefficient expression of Cu in CoN and CoSiN film are 8.98 × 10 - 11 exp ( - 0.45 eV/kT) cm2/s and 5.39 × 10 - 11 exp ( - 0.49 eV/kT) cm2/s during medium temperature (300 ℃ ~ 700 ℃ ) , respectively .% 利用磁控溅射的方法在 n 型硅基底制备了 Cu/CoN/Si （100）和 Cu/CoSiN/Si （100）薄膜，并对它们进行了不同温度的退火.用原子力显微镜观察了它们的表面形貌.用扫描透射电镜能谱分析法得到了在不同退火温度下铜在上面两种薄膜中浓度与表面距离的分布，然后利用菲克第二定律对 Cu/CoN/Si 和 Cu/CoSiN/Si 体系中 Cu 的扩散进行了计算和分析，得出中温条件（300℃～700℃）下 Cu 在 CoN 和 CoSiN 两种薄膜中的扩散系数表达式分别为8.98×10－11 exp （－0.45 eV/kT） cm 2/s 和5.39×10－11 exp （－0.49 eV/kT） cm 2/s.
Zhou, Jianqin
2011-01-01
The discrete cosine transform (DCT), introduced by Ahmed, Natarajan and Rao, has been used in many applications of digital signal processing, data compression and information hiding. There are four types of the discrete cosine transform. In simulating the discrete cosine transform, we propose a generalized discrete cosine transform with three parameters, and prove its orthogonality for some new cases. A new type of discrete cosine transform is proposed and its orthogonality is proved. Finally, we propose a generalized discrete W transform with three parameters, and prove its orthogonality for some new cases.
Radon diffusion coefficients in soils of varying moisture content
Papachristodoulou, C.; Ioannides, K.; Pavlides, S.
2009-04-01
Radon is a naturally occurring radioactive gas that is generated in the Earth's crust and is free to migrate through soil and be released to the atmosphere. Due to its unique properties, soil gas radon has been established as a powerful tracer used for a variety of purposes, such as exploring uranium ores, locating geothermal resources and hydrocarbon deposits, mapping geological faults, predicting seismic activity or volcanic eruptions and testing atmospheric transport models. Much attention has also been given to the radiological health hazard posed by increased radon concentrations in the living and working environment. In order to exploit radon profiles for geophysical purposes and also to predict its entry indoors, it is necessary to study its transport through soils. Among other factors, the importance of soil moisture in such studies has been largely highlighted and it is widely accepted that any measurement of radon transport parameters should be accompanied by a measurement of the soil moisture content. In principle, validation of transport models in the field is encountered by a large number of uncontrollable and varying parameters; laboratory methods are therefore preferred, allowing for experiments to be conducted under well-specified and uniform conditions. In this work, a laboratory technique has been applied for studying the effect of soil moisture content on radon diffusion. A vertical diffusion chamber was employed, in which radon was produced from a 226Ra source, was allowed to diffuse through a soil column and was finally monitored using a silicon surface barrier detector. By solving the steady-state radon diffusion equation, diffusion coefficients (D) were determined for soil samples of varying moisture content (m), from null (m=0) to saturation (m=1). For dry soil, a D value of 4.1×10-7 m2s-1 was determined, which increased moderately by a factor of ~3 for soil with low moisture content, i.e. up to m ~0.2. At higher water fractions, a decrease
Innovation diffusion on time-varying activity driven networks
Rizzo, Alessandro; Porfiri, Maurizio
2016-01-01
Since its introduction in the 1960s, the theory of innovation diffusion has contributed to the advancement of several research fields, such as marketing management and consumer behavior. The 1969 seminal paper by Bass [F.M. Bass, Manag. Sci. 15, 215 (1969)] introduced a model of product growth for consumer durables, which has been extensively used to predict innovation diffusion across a range of applications. Here, we propose a novel approach to study innovation diffusion, where interactions among individuals are mediated by the dynamics of a time-varying network. Our approach is based on the Bass' model, and overcomes key limitations of previous studies, which assumed timescale separation between the individual dynamics and the evolution of the connectivity patterns. Thus, we do not hypothesize homogeneous mixing among individuals or the existence of a fixed interaction network. We formulate our approach in the framework of activity driven networks to enable the analysis of the concurrent evolution of the interaction and individual dynamics. Numerical simulations offer a systematic analysis of the model behavior and highlight the role of individual activity on market penetration when targeted advertisement campaigns are designed, or a competition between two different products takes place.
Steerable Discrete Cosine Transform
Fracastoro, Giulia; Fosson, Sophie; Magli, Enrico
2017-01-01
In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely, a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, an...
Steerable Discrete Cosine Transform
Fracastoro, Giulia; Fosson, Sophie M.; Magli, Enrico
2017-01-01
In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, and enables precise matching of directionality in each image block, achieving improved coding efficiency. The optimal rotation angles for SDCT can be represented as solution of a suitable rate-distortion (RD) problem. We propose iterative methods to search such solution, and we develop a fully fledged image encoder to practically compare our techniques with other competing transforms. Analytical and numerical results prove that SDCT outperforms both DCT and state-of-the-art directional transforms.
Diffusive boundary layers over varying topography
Dell, R. W.
2015-03-25
Diffusive bottom boundary layers can produce upslope flows in a stratified fluid. Accumulating observations suggest that these boundary layers may drive upwelling and mixing in mid-ocean ridge flank canyons. However, most studies of diffusive bottom boundary layers to date have concentrated on constant bottom slopes. We present a study of how diffusive boundary layers interact with various idealized topography, such as changes in bottom slope, slopes with corrugations and isolated sills. We use linear theory and numerical simulations in the regional ocean modeling system (ROMS) model to show changes in bottom slope can cause convergences and divergences within the boundary layer, in turn causing fluid exchanges that reach far into the overlying fluid and alter stratification far from the bottom. We also identify several different regimes of boundary-layer behaviour for topography with oceanographically relevant size and shape, including reversing flows and overflows, and we develop a simple theory that predicts the regime boundaries, including what topographies will generate overflows. As observations also suggest there may be overflows in deep canyons where the flow passes over isolated bumps and sills, this parameter range may be particularly significant for understanding the role of boundary layers in the deep ocean.
On Local Integrated Cosine Functions
Institute of Scientific and Technical Information of China (English)
SHI Jin-e; ZHENG Wei-xing
2001-01-01
Suppose X is a Banach space, and A is a closed operator. We give some equivalent conditions between A generating a local integrated cosine functions and the existence of solutions of abstract Cauchy problems.
Sines and Cosines. Part 1 of 3
Apostol, Tom M. (Editor)
1992-01-01
Applying the concept of similarities, the mathematical principles of circular motion and sine and cosine waves are presented utilizing both film footage and computer animation in this 'Project Mathematics' series video. Concepts presented include: the symmetry of sine waves; the cosine (complementary sine) and cosine waves; the use of sines and cosines on coordinate systems; the relationship they have to each other; the definitions and uses of periodic waves, square waves, sawtooth waves; the Gibbs phenomena; the use of sines and cosines as ratios; and the terminology related to sines and cosines (frequency, overtone, octave, intensity, and amplitude).
Cosine tuning minimizes motor errors.
Todorov, Emanuel
2002-06-01
Cosine tuning is ubiquitous in the motor system, yet a satisfying explanation of its origin is lacking. Here we argue that cosine tuning minimizes expected errors in force production, which makes it a natural choice for activating muscles and neurons in the final stages of motor processing. Our results are based on the empirically observed scaling of neuromotor noise, whose standard deviation is a linear function of the mean. Such scaling predicts a reduction of net force errors when redundant actuators pull in the same direction. We confirm this prediction by comparing forces produced with one versus two hands and generalize it across directions. Under the resulting neuromotor noise model, we prove that the optimal activation profile is a (possibly truncated) cosine--for arbitrary dimensionality of the workspace, distribution of force directions, correlated or uncorrelated noise, with or without a separate cocontraction command. The model predicts a negative force bias, truncated cosine tuning at low muscle cocontraction levels, and misalignment of preferred directions and lines of action for nonuniform muscle distributions. All predictions are supported by experimental data.
Li, Huicong; Peng, Rui; Wang, Feng-Bin
2017-01-01
This paper performs qualitative analysis on an SIS epidemic reaction-diffusion system with a linear source in spatially heterogeneous environment. The main feature of our model lies in that its total population number varies, compared to its counterpart proposed by Allen et al. [2]. The uniform bounds of solutions are derived, based on which, the threshold dynamics in terms of the basic reproduction number is established and the global stability of the unique endemic equilibrium is discussed when spatial environment is homogeneous. In particular, the asymptotic profile of endemic equilibria is determined if the diffusion rate of the susceptible or infected population is small or large. The theoretical results show that a varying total population can enhance persistence of infectious disease, and therefore the disease becomes more threatening and harder to control.
A Diffusive System Driven by a Battery or by a Smoothly Varying Field
Bodineau, T.; Derrida, B.; Lebowitz, J. L.
2010-08-01
We consider the steady state of a one dimensional diffusive system, such as the symmetric simple exclusion process (SSEP) on a ring, driven by a battery at the origin or by a smoothly varying field along the ring. The battery appears as the limiting case of a smoothly varying field, when the field becomes a delta function at the origin. We find that in the scaling limit the long range pair correlation functions of the system driven by a battery are very different from the ones known in the steady state of the SSEP maintained out of equilibrium by contact with two reservoirs, even when the steady state density profiles are identical in both models.
Consensus analysis of networks with time-varying topology and event-triggered diffusions.
Han, Yujuan; Lu, Wenlian; Chen, Tianping
2015-11-01
This paper studies the consensus problem of networks with time-varying topology. Event-triggered rules are employed in diffusion coupling terms to reduce the updating load of the coupled system. Two strategies are considered: event-triggered strategy, that each node observes the state information in an instantaneous way, to determine the next triggering event time, and self-triggered strategy, that each node only needs to observe the state information at the event time to predict the next triggering event time. In each strategy, two kinds of algorithms are considered: the pull-based algorithm, that the diffusion coupling term of every node is updated at the latest observations of the neighborhood at its triggered time, and push-based algorithm, the diffusion coupling term of every node uses the state information of its neighborhood at their latest triggered time. It is proved that if the coupling matrix across time intervals with length less than some given constant has spanning trees, then the proposed algorithms can realize consensus. Examples with numerical simulation are provided to show the effectiveness of the theoretical results.
Energy Technology Data Exchange (ETDEWEB)
McConathy, R.K.
1983-03-01
The study describes the gradients of stomatal size and density in the crown of a mature forest-grown tulip-poplar (Liriodendron tulipifera L.) in eastern Tennessee. These data are used to predict leaf resistance to vapor diffusion in relation to stomatal width and boundary layer resistance. Stomatal density on individual leaves did not vary, but density increased with increasing crown height. Stomatal size decreased with increasing height of leaves within the crown. Stomatal size and density variations interacted to result in a constant number of stomata per leaf at all crown heights. Stomatal diffusive resistance values calculated from stomatal measurements and varying environmental parameters indicated that stomatal resistance controlled transpiration water losses only at small apertures (<0.6 ..mu..m). Boundary layer resistance was controlling at large stomatal apertures (>0.6 ..mu..m) and at low wind speeds (approx.100 cm/s). Under normal forest conditions tulip-poplar stomatal resistance exercised more control over transpiration than did boundary layer resistance.
Cosine-Based Clustering Algorithm Approach
Directory of Open Access Journals (Sweden)
Mohammed A. H. Lubbad
2012-02-01
Full Text Available Due to many applications need the management of spatial data; clustering large spatial databases is an important problem which tries to find the densely populated regions in the feature space to be used in data mining, knowledge discovery, or efficient information retrieval. A good clustering approach should be efficient and detect clusters of arbitrary shapes. It must be insensitive to the outliers (noise and the order of input data. In this paper Cosine Cluster is proposed based on cosine transformation, which satisfies all the above requirements. Using multi-resolution property of cosine transforms, arbitrary shape clusters can be effectively identified at different degrees of accuracy. Cosine Cluster is also approved to be highly efficient in terms of time complexity. Experimental results on very large data sets are presented, which show the efficiency and effectiveness of the proposed approach compared to other recent clustering methods.
Spatially varying regularization based on retrieved support in diffuse optical tomography
Sabir, Sohail; Cho, Sanghoon; Cho, Seunryong
2017-03-01
Diffuse optical tomography (DOT) is a promising noninvasive imaging modality capable of providing the functional characteristics (oxygen saturation and hemodynamic states) of thick biological tissue by quantifying the optical parameters. The parameter recovery problem in DOT is a nonlinear, ill-posed and ill conditioned inverse problem. The non-linear iterative methods are usually employed for image reconstruction in DOT by utilizing Tikhonov based regularization approach. These methods employ l2-norm based regularization where the constant regularization parameter is determined either empirically or generalized cross validation methods or L curve method. The reconstructed images look smoother or noisy depending on the chosen value of the regularization constant. Moreover the edges information of the inclusions appeared to be blurred in such constant regularization methods. In this study we proposed a method to retrieve and utilized a non-zero support (possible tumor location) to generate a spatially varying regularization map. The inclusions locations were determined by considering the imaging problem as a multiple measurements vector (MMV) problem. Based on the recovered inclusion positions spatially regularization map was generated to be used in non-linear image reconstruction framework. The results retrieved with such spatially varying priors shows slightly improved image reconstruction in terms of better contrast recovery, reduction in background noise and preservation of edge information of inclusions compared with the constant regularization approach.
Directory of Open Access Journals (Sweden)
Chuangxia Huang
2009-01-01
Full Text Available This paper is concerned with pth moment exponential stability of stochastic reaction-diffusion Cohen-Grossberg neural networks with time-varying delays. With the help of Lyapunov method, stochastic analysis, and inequality techniques, a set of new suffcient conditions on pth moment exponential stability for the considered system is presented. The proposed results generalized and improved some earlier publications.
Berezhkovskii, A. M.; Pustovoit, M. A.; Bezrukov, S. M.
2007-04-01
Brownian dynamics simulations of the particle diffusing in a long conical tube (the length of the tube is much greater than its smallest radius) are used to study reduction of the three-dimensional diffusion in tubes of varying cross section to an effective one-dimensional description. The authors find that the one-dimensional description in the form of the Fick-Jacobs equation with a position-dependent diffusion coefficient, D(x ), suggested by Zwanzig [J. Phys. Chem. 96, 3926 (1992)], with D(x ) given by the Reguera-Rubí formula [Phys. Rev. E 64, 061106 (2001)], D(x )=D/√1+R'(x)2, where D is the particle diffusion coefficient in the absence of constraints, and R(x ) is the tube radius at x, is valid when ∣R'(x)∣⩽1. When ∣R'(x)∣>1, higher spatial derivatives of the one-dimensional concentration in the effective diffusion equation cannot be neglected anymore as was indicated by Kalinay and Percus [J. Chem. Phys. 122, 204701 (2005)]. Thus the reduction to the effective one-dimensional description is a useful tool only when ∣R'(x)∣⩽1 since in this case one can apply the powerful standard methods to analyze the resulting diffusion equation.
On distributional assumptions and whitened cosine similarities
DEFF Research Database (Denmark)
Loog, Marco
2008-01-01
Recently, an interpretation of the whitened cosine similarity measure as a Bayes decision rule was proposed (C. Liu, "The Bayes Decision Rule Induced Similarity Measures,'' IEEE Trans. Pattern Analysis and Machine Intelligence, vol. 29, no. 6, pp. 1086-1090, June 2007. This communication makes th...... the observation that some of the distributional assumptions made to derive this measure are very restrictive and, considered simultaneously, even inconsistent....
Directory of Open Access Journals (Sweden)
Vladimir V. Lyubimov
2007-01-01
Full Text Available The possibility of improving the spatial resolution of diffuse optical tomograms reconstructed by the photon average trajectories (PAT method is substantiated. The PAT method recently presented by us is based on a concept of an average statistical trajectory for transfer of light energy, the photon average trajectory (PAT. The inverse problem of diffuse optical tomography is reduced to a solution of an integral equation with integration along a conditional PAT. As a result, the conventional algorithms of projection computed tomography can be used for fast reconstruction of diffuse optical images. The shortcoming of the PAT method is that it reconstructs the images blurred due to averaging over spatial distributions of photons which form the signal measured by the receiver. To improve the resolution, we apply a spatially variant blur model based on an interpolation of the spatially invariant point spread functions simulated for the different small subregions of the image domain. Two iterative algorithms for solving a system of linear algebraic equations, the conjugate gradient algorithm for least squares problem and the modified residual norm steepest descent algorithm, are used for deblurring. It is shown that a 27% gain in spatial resolution can be obtained.
An observer for an occluded reaction-diffusion system with spatially varying parameters
Kramer, Sean; Bollt, Erik M.
2017-03-01
Spatially dependent parameters of a two-component chaotic reaction-diffusion partial differential equation (PDE) model describing ocean ecology are observed by sampling a single species. We estimate the model parameters and the other species in the system by autosynchronization, where quantities of interest are evolved according to misfit between model and observations, to only partially observed data. Our motivating example comes from oceanic ecology as viewed by remote sensing data, but where noisy occluded data are realized in the form of cloud cover. We demonstrate a method to learn a large-scale coupled synchronizing system that represents the spatio-temporal dynamics and apply a network approach to analyze manifold stability.
Sines and Cosines. Part 3 of 3
Apostol, Tom M. (Editor)
1994-01-01
In this 'Project Mathematics' series video, the addition formulas of sines and cosines are explained and their real life applications are demonstrated. Both film footage and computer animation is used. Several mathematical concepts are discussed and include: Ptolemy's theorem concerned with quadrilaterals; the difference between a central angle and an inscribed angle; sines and chord lengths; special angles; subtraction formulas; and a application to simple harmonic motion. A brief history of the city Alexandria, its mathematicians, and their contribution to the field of mathematics is shown.
Sines and Cosines. Part 2 of 3
Apostol, Tom M. (Editor)
1993-01-01
The Law of Sines and the Law of Cosines are introduced and demonstrated in this 'Project Mathematics' series video using both film footage and computer animation. This video deals primarily with the mathematical field of Trigonometry and explains how these laws were developed and their applications. One significant use is geographical and geological surveying. This includes both the triangulation method and the spirit leveling method. With these methods, it is shown how the height of the tallest mountain in the world, Mt. Everest, was determined.
Cosine-Gaussian Schell-model sources.
Mei, Zhangrong; Korotkova, Olga
2013-07-15
We introduce a new class of partially coherent sources of Schell type with cosine-Gaussian spectral degree of coherence and confirm that such sources are physically genuine. Further, we derive the expression for the cross-spectral density function of a beam generated by the novel source propagating in free space and analyze the evolution of the spectral density and the spectral degree of coherence. It is shown that at sufficiently large distances from the source the degree of coherence of the propagating beam assumes Gaussian shape while the spectral density takes on the dark-hollow profile.
Quantum Discrete Cosine Transform for Image Compression
Pang, C Y; Guo, G C; Pang, Chao Yang; Zhou, Zheng Wei; Guo, Guang Can
2006-01-01
Discrete Cosine Transform (DCT) is very important in image compression. Classical 1-D DCT and 2-D DCT has time complexity O(NlogN) and O(N²logN) respectively. This paper presents a quantum DCT iteration, and constructs a quantum 1-D and 2-D DCT algorithm for image compression by using the iteration. The presented 1-D and 2-D DCT has time complexity O(sqrt(N)) and O(N) respectively. In addition, the method presented in this paper generalizes the famous Grover's algorithm to solve complex unstructured search problem.
Discrete cosine transform algorithms, advantages, applications
Rao, K R
1990-01-01
This is the first comprehensive treatment of the theoretical aspects of the discrete cosine transform (DCT), which is being recommended by various standards organizations, such as the CCITT, ISO etc., as the primary compression tool in digital image coding. The main purpose of the book is to provide a complete source for the user of this signal processing tool, where both the basics and the applications are detailed. An extensive bibliography covers both the theory and applications of the DCT. The novice will find the book useful in its self-contained treatment of the theory of the DCT, the de
Directory of Open Access Journals (Sweden)
Qiankun Song
2007-06-01
Full Text Available Impulsive bidirectional associative memory neural network model with time-varying delays and reaction-diffusion terms is considered. Several sufficient conditions ensuring the existence, uniqueness, and global exponential stability of equilibrium point for the addressed neural network are derived by M-matrix theory, analytic methods, and inequality techniques. Moreover, the exponential convergence rate index is estimated, which depends on the system parameters. The obtained results in this paper are less restrictive than previously known criteria. Two examples are given to show the effectiveness of the obtained results.
Directory of Open Access Journals (Sweden)
Cao Jinde
2007-01-01
Full Text Available Impulsive bidirectional associative memory neural network model with time-varying delays and reaction-diffusion terms is considered. Several sufficient conditions ensuring the existence, uniqueness, and global exponential stability of equilibrium point for the addressed neural network are derived by M-matrix theory, analytic methods, and inequality techniques. Moreover, the exponential convergence rate index is estimated, which depends on the system parameters. The obtained results in this paper are less restrictive than previously known criteria. Two examples are given to show the effectiveness of the obtained results.
Lee, Chu-Yu; Bennett, Kevin M; Debbins, Josef P
2013-05-01
The aim of this study was to investigate the microstructural sensitivity of the statistical distribution and diffusion kurtosis (DKI) models of non-monoexponential signal attenuation in the brain using diffusion-weighted MRI (DWI). We first developed a simulation of 2-D water diffusion inside simulated tissue consisting of semi-permeable cells and a variable cell size. We simulated a DWI acquisition of the signal in a volume using a pulsed gradient spin echo (PGSE) pulse sequence, and fitted the models to the simulated DWI signals using b-values up to 2500 s/mm(2). For comparison, we calculated the apparent diffusion coefficient (ADC) of the monoexponential model (b-value=1000 s/mm(2)). In separate experiments, we varied the cell size (5-10-15 μm), cell volume fraction (0.50-0.65-0.80), and membrane permeability (0.001-0.01-0.1mm/s) to study how the fitted parameters tracked simulated microstructural changes. The ADC was sensitive to all the simulated microstructural changes except the decrease in membrane permeability. The ADC increased with larger cell size, smaller cell volume fraction, and larger membrane permeability. The σstat of the statistical distribution model increased exclusively with a decrease in cell volume fraction. The Kapp of the DKI model was exclusively increased with decreased cell size and decreased with increasing membrane permeability. These results suggest that the non-monoexponential models of water diffusion have different, specific microstructural sensitivity, and a combination of the models may give insights into the microstructural underpinning of tissue pathology.
Borland, C D; Cox, Y
1991-12-01
1. To examine the effect of varying oxygen partial pressure (PAO2) on nitric oxide (DLNO) and carbon monoxide (DLCO) diffusing capacity (transfer factor), 10 subjects performed combined DLCO/DLNO measurements with the inspired mixture made up with three different oxygen concentrations (25%, 18% and 15%) to give PAO2 values of 12-20 kPa. 2. A novel method is described for calculating membrane diffusing capacity (DM) and pulmonary capillary volume (Qc) from DLNO and DLCO. 3. The mean DMCO was 52.89 mmol min-1 kPa-1 and Qc was 0.056 litre. Reducing PAO2 from 20 to 12 kPa resulted in an increase in DLCO = -0.124 (O2%) + 11.67 (P less than 0.001) and a fall in DLNO = 0.538 (O2%) + 32.01 (P less than 0.001) and a fall in DLNO/DLCO = 0.107 (O2%) + 2.52 (P less than 0.001). DM (P = 0.59) and Qc (P = 0.64) also tended to fall with falling PAO2. 4. It appears more likely that the minor reduction in DLNO that we have observed with falling PAO2 is due to diffusion rather than reaction limitation.
Perceptual image coding with discrete cosine transform
Tan, Ee-Leng
2015-01-01
This book first introduces classic as well as recent computational models for just-noticeable-difference (JND) applications. Since the discrete cosine transform (DCT) is applied in many image and video standards (JPEG, MPEG-1/2/4, H.261/3), the book also includes a comprehensive survey of computational models for JND that are based on DCT. The visual factors used in these computational models are reviewed in detail. Further, an extensive comparative analysis of these models using quantitative and qualitative performance criteria is presented, which compares the noise shaping performance of these models with subjective evaluation and the accuracy between the estimated JND thresholds and subjective evaluation. There are many surveys available on computational models for JND; however, these surveys seldom compare the performance of computational models that are based on DCT. The authors’ survey of the computational models and their in-depth review of the visual factors used in them will help readers understand...
A Matrix Hyperbolic Cosine Algorithm and Applications
Zouzias, Anastasios
2011-01-01
Wigderson and Xiao presented an efficient derandomization of the matrix Chernoff bound using the method of pessimistic estimators. Based on their construction, we present a derandomization of the matrix Bernstein inequality which can be viewed as generalization of Spencer's hyperbolic cosine algorithm. We apply our construction to several problems by analyzing its computational efficiency under two special cases of matrix samples; one in which the samples have a group structure and the other in which they have rank-one outer-product structure. As a consequence of the former case, we present a deterministic algorithm that, given the multiplication table of a finite group of size n, constructs an Alon-Roichman expanding Cayley graph of logarithmic degree in O(n^2 log^3 n) time. For the latter case, we present a fast deterministic algorithm for spectral sparsification of positive semi-definite matrices (as defined in [Sri10]) which implies directly an improved deterministic algorithm for spectral graph sparsific...
Discrete cosine transform using modified DPCM
Pogribny, Wlodzimierz; Drechny, Marcin
2004-07-01
Differential modulations such as Delta Modulation (DM) are used for representing digital signals in small word length codes. They allow high fast acting and simplicity of specialized processors. The use of DM for the economical representation and efficient processing of the signals needs the development of the existing methods and the working out of simple and fast processing methods in real time. Therefore Discrete Cosine Transform (DCT) methods were proposed in mixed formats which have the advantages both DCT with PCM and DCT with DM. In this work there have been studied the ways of choosing DM parameters in order to use them in these methods. On the basis of the worked out computer simulation program, the accuracy of DCT with DM algorithms has been examined by means of processing signals like noise and voice. The use of DCT algorithms in DM formats is expedient to realization of neural systems.
Application of Cosine Zone Plates to Image Encryption
Institute of Scientific and Technical Information of China (English)
GE Fan; CHEN Lin-Fei; ZHAO Dao-Mu
2008-01-01
@@ We analyse the diffraction result of optical field after Cosine zone plate, and theoretically deduce its transform matrix. Under some conditions, its diffraction distribution is a mixture of fractional Fourier spectra. Then we use Cosine zone plate and its diffraction result to image encryption. Possible optical image encryption and decryption implementations are proposed, and some numerical simulation results are also provided.
Narea, J. Freddy; Muñoz, Aarón A.; Castro, Jorge; Muñoz, Rafael A.; Villalba, Caroleny E.; Martinez, María. F.; Bravo, Kelly D.
2013-11-01
Human skin has been studied in numerous investigations, given the interest in knowing information about physiology, morphology and chemical composition. These parameters can be determined using non invasively optical techniques in vivo, such as the diffuse reflectance spectroscopy. The human skin color is determined by many factors, but primarily by the amount and distribution of the pigment melanin. The melanin is produced by the melanocytes in the basal layer of the epidermis. This research characterize the spectral response of the human skin using the coefficients of Fourier series expansion. Simulating the radiative transfer equation for the Monte Carlo method to vary the concentration of the melanocytes (fme) in a simplified model of human skin. It fits relating the Fourier series coefficient a0 with fme. Therefore it is possible to recover the skin biophysical parameter.
ANALYSIS OF TRANSMISSION CHARACTERISTICS OF COSINE GEAR DRIVE
Institute of Scientific and Technical Information of China (English)
WANG Jian; LUO Shanming; CHEN Lifeng; CHEN Lei; HU Huarong
2008-01-01
Based on the mathematical model of a novel cosine gear drive, a few characteristics, such as the contact ratio, the sliding coefficient, and the contact and bending stresses, of this drive are analyzed. A comparison study of these characteristics with the involute gear drive is also carried out. The influences of design parameters including the number of teeth and the pressure angle on the contact and bending stresses are studied. The following conclusions are achieved: the contact ratio of the cosine gear drive is about 1.2 to 1.3, which is reduced by about 20% in comparison with that of the involute gear drive. The sliding coefficient of the cosine gear drive is smaller than that of the involute gear drive. The contact and bending stresses of the cosine gear drive are lower than those of the involute gear drive. The contact and bending stresses decrease with the growth of the number of teeth and the pressure angle.
Institute of Scientific and Technical Information of China (English)
LIU Yong; TANG Guang-yu; TANG Rong-biao; PENG Yi-feng; LI Wei
2010-01-01
Background Recent studies suggest that bone marrow adipose tissue might play a role in the pathogenesis of osteoporosis. There are inconsistent findings on the relationship among marrow fat content, bone mineral density and apparent diffusion coefficient (ADC). This study aimed to prospectively explore the efficacy of MR spectroscopy (MRS)and diffusion-weighted MR imaging (DWI) in detecting vertebral marrow changes in postmenopausal women with varying bone densities.Methods Both MRS and DWI of the lumber spine were performed in 102 postmenopausal women (mean age,(67.3±6.5) years; range, 55-83 years), who underwent dual X-ray absorptiometry. Marrow fat content and ADC were compared and correlated among three groups: 24 with normal bone density, 31 with osteopenia and 47 with osteoporosis.Results Vertebral marrow fat content was significantly increased in the osteoporotic group ((65.60±7.68)%, P <0.001)and the osteopenic group ((57.68±6.45)%, P <0.001), when compared with the normal bone density group ((51.67±3.27)%). ADC values were significantly decreased in the osteoporotic group ((0.39±0.03)×10-3mm2/s, P <0.001)and in the osteopenic group ((0.42±0.02)×10-3mm2/s, P <0.001), when compared with the normal bone density group ((0.47±0.03)×10-3 mm2/s). The marrow fat content negatively correlated with both bone density (r=-0.731, P <0.001)and marrow ADC (r=-0.572, P <0.001). The bone density positively correlated with the ADC values (r=0.802, P<0.001).Conclusions Postmenopausal women experience a corresponding increase in vertebral marrow fat content as the bone density decreases. Marrow fat content and ADC correlate to the bone density. MRS and DWI may indirectly assess the early bone marrow changes in postmenopausal women.
Gan, Qintao
2017-01-01
In this paper, the exponential synchronization problem of generalized reaction-diffusion neural networks with mixed time-varying delays is investigated concerning Dirichlet boundary conditions in terms of p-norm. Under the framework of the Lyapunov stability method, stochastic theory, and mathematical analysis, some novel synchronization criteria are derived, and an aperiodically intermittent control strategy is proposed simultaneously. Moreover, the effects of diffusion coefficients, diffusion space, and stochastic perturbations on the synchronization process are explicitly expressed under the obtained conditions. Finally, some numerical simulations are performed to illustrate the feasibility of the proposed control strategy and show different synchronization dynamics under a periodically/aperiodically intermittent control.
Yadav, Vivek Kumar; Chandra, Amalendu
2013-06-14
A first principles study of the dynamics of supercritical methanol is carried out by means of ab initio molecular dynamics simulations. In particular, the fluctuation dynamics of hydroxyl stretch frequencies, hydrogen bonds, dangling hydroxyl groups, and orientation of methanol molecules are investigated for three different densities at 523 K. Apart from the dynamical properties, various equilibrium properties of supercritical methanol such as the local density distributions and structural correlations, hydrogen bonding aspects, frequency-structure correlations, and dipole distributions of methanol molecules are also investigated. In addition to the density dependence of various equilibrium and dynamical properties, their dependencies on dispersion interactions are also studied by carrying out additional simulations using a dispersion corrected density functional for all the systems. It is found that the hydrogen bonding between methanol molecules decreases significantly as we move to the supercritical state from the ambient one. The inclusion of dispersion interactions is found to increase the number of hydrogen bonds to some extent. Calculations of the frequency-structure correlation coefficient reveal that a statistical correlation between the hydroxyl stretch frequency and the nearest hydrogen-oxygen distance continues to exist even at supercritical states of methanol, although it is weakened with increase of temperature and decrease of density. In the supercritical state, the frequency time correlation function is found to decay with two time scales: One around or less than 100 fs and the other in the region of 250-700 fs. It is found that, for supercritical methanol, the times scales of vibrational spectral diffusion are determined by an interplay between the dynamics of hydrogen bonds, dangling OD groups, and inertial rotation of methanol molecules and the roles of these various components are found to vary with density of the supercritical solvent. Effects
Propagation Dynamics of Nonspreading Cosine-Gauss Water-Wave Pulses.
Fu, Shenhe; Tsur, Yuval; Zhou, Jianying; Shemer, Lev; Arie, Ady
2015-12-18
Linear gravity water waves are highly dispersive; therefore, the spreading of initially short wave trains characterizes water surface waves, and is a universal property of a dispersive medium. Only if there is sufficient nonlinearity does this envelope admit solitary solutions which do not spread and remain in fixed forms. Here, in contrast to the nonlinear localized wave packets, we present both theoretically and experimentally a new type of linearly nondispersive water wave, having a cosine-Gauss envelope, as well as its higher-order Hermite cosine-Gauss variations. We show that these waves preserve their width despite the inherent dispersion while propagating in an 18-m wave tank, accompanied by a slowly varying carrier-envelope phase. These wave packets exhibit self-healing; i.e., they are restored after bypassing an obstacle. We further demonstrate that these nondispersive waves are robust to weakly nonlinear perturbations. In the strong nonlinear regime, symmetry breaking of these waves is observed, but their cosine-Gauss shapes are still approximately preserved during propagation.
Improved cosine similarity measures of simplified neutrosophic sets for medical diagnoses.
Ye, Jun
2015-03-01
In pattern recognition and medical diagnosis, similarity measure is an important mathematical tool. To overcome some disadvantages of existing cosine similarity measures of simplified neutrosophic sets (SNSs) in vector space, this paper proposed improved cosine similarity measures of SNSs based on cosine function, including single valued neutrosophic cosine similarity measures and interval neutrosophic cosine similarity measures. Then, weighted cosine similarity measures of SNSs were introduced by taking into account the importance of each element. Further, a medical diagnosis method using the improved cosine similarity measures was proposed to solve medical diagnosis problems with simplified neutrosophic information. The improved cosine similarity measures between SNSs were introduced based on cosine function. Then, we compared the improved cosine similarity measures of SNSs with existing cosine similarity measures of SNSs by numerical examples to demonstrate their effectiveness and rationality for overcoming some shortcomings of existing cosine similarity measures of SNSs in some cases. In the medical diagnosis method, we can find a proper diagnosis by the cosine similarity measures between the symptoms and considered diseases which are represented by SNSs. Then, the medical diagnosis method based on the improved cosine similarity measures was applied to two medical diagnosis problems to show the applications and effectiveness of the proposed method. Two numerical examples all demonstrated that the improved cosine similarity measures of SNSs based on the cosine function can overcome the shortcomings of the existing cosine similarity measures between two vectors in some cases. By two medical diagnoses problems, the medical diagnoses using various similarity measures of SNSs indicated the identical diagnosis results and demonstrated the effectiveness and rationality of the diagnosis method proposed in this paper. The improved cosine measures of SNSs based on cosine
Minimum Phase Property of Chebyshev-Sharpened Cosine Filters
Directory of Open Access Journals (Sweden)
Miriam Guadalupe Cruz Jiménez
2015-01-01
Full Text Available We prove that the Chebyshev sharpening technique, recently introduced in literature, provides filters with a Minimum Phase (MP characteristic when it is applied to cosine filters. Additionally, we demonstrate that cascaded expanded Chebyshev-Sharpened Cosine Filters (CSCFs are also MP filters, and we show that they achieve a lower group delay for similar magnitude characteristics in comparison with traditional cascaded expanded cosine filters. The importance of the characteristics of cascaded expanded CSCFs is also elaborated. The developed examples show improvements in the group delay ranged from 23% to 47% at the cost of a slight increase of usage of hardware resources. For an application of a low-delay decimation filter, the proposed scheme exhibits a 24% lower group delay, with 35% less computational complexity (estimated in Additions per Output Sample and slightly less usage of hardware elements.
Directory of Open Access Journals (Sweden)
Jagdish PRAKASH
2014-01-01
Full Text Available This paper studies flow, heat, and mass transfer characteristics of unsteady mixed convective magnetohydrodynamic (MHD flow of a heat absorbing fluid in an accelerated vertical wavy plate, subject to varying temperature and mass diffusion, with the influence of buoyancy, thermal radiation and Dufour effect. The momentum, energy and mass diffusion equations are coupled non-linear partial differential equations, which are solved by perturbation technique. The features of the fluid flow, heat and mass transfer characteristics are analyzed by plotting graphs, and the physical aspects are discussed in detail to interpret the effects of significant parameters of the problem.doi:10.14456/WJST.2014.69
Fan, Xiaofei; Zhang, Xian; Wu, Ligang; Shi, Michael
2017-01-01
This paper is concerned with the finite-time stability problem of the delayed genetic regulatory networks (GRNs) with reaction-diffusion terms under Dirichlet boundary conditions. By constructing a Lyapunov-Krasovskii functional including quad-slope integrations, we establish delay-dependent finite-time stability criteria by employing the Wirtinger-type integral inequality, Gronwall inequality, convex technique, and reciprocally convex technique. In addition, the obtained criteria are also reaction-diffusion-dependent. Finally, a numerical example is provided to illustrate the effectiveness of the theoretical results.
STRONGLY CONTINUOUS INTEGRATED COSINE OPERATOR FUNCTIONS WITH GROWTH ω
Institute of Scientific and Technical Information of China (English)
Meiying Wang; Guoxiang Chen
2007-01-01
For a continuous increasing function ω: [0, ∞) → (0, ∞) of finite exponetial type, we establish a Hille-Yosida type theorem for strongly continuous integrated cosine operator functions with O(ω). It includes the well-known polynomially bounded and exponentially bounded cases.
A Classroom Note on Generating Examples for the Laws of Sines and Cosines from Pythagorean Triangles
Sher, Lawrence; Sher, David
2007-01-01
By selecting certain special triangles, students can learn about the laws of sines and cosines without wrestling with long decimal representations or irrational numbers. Since the law of cosines requires only one of the three angles of a triangle, there are many examples of triangles with integral sides and a cosine that can be represented exactly…
Institute of Scientific and Technical Information of China (English)
Hua-zhong Tang; Gerald Warnecke
2006-01-01
This paper presents a class of high resolution local time step schemes for nonlinear hyperbolic conservation laws and the closely related convection-diffusion equations, by projecting the solution increments of the underlying partial differential equations (PDE)at each local time step. The main advantages are that they are of good consistency, and it is convenient to implement them. The schemes are L∞ stable, satisfy a cell entropy inequality, and may be extended to the initial boundary value problem of general unsteady PDEs with higher-order spatial derivatives. The high resolution schemes are given by combining the reconstruction technique with a second order TVD Runge-Kutta scheme or a Lax-Wendroff type method, respectively.The schemes are used to solve a linear convection-diffusion equation, the nonlinear inviscid Burgers' equation, the one- and two-dimensional compressible Euler equations, and the two-dimensional incompressible Navier-Stokes equations. The numerical results show that the schemes are of higher-order accuracy, and efficient in saving computational cost,especially, for the case of combining the present schemes with the adaptive mesh method [15]. The correct locations of the slow moving or stronger discontinuities are also obtained,although the schemes are slightly nonconservative.
Kim, Yikeun; Kim, Sehun; Kim, Sungwon; Lee, Haeyoung; Oak, Chulho; Ahn, Yeh-Chan
2017-02-01
This experiment was conducted by using the diffuse optical spectroscopy based on near-infrared light. The near-infrared light in the water window was used to see the change of molecular concentration in the living tissue. The experiment subject was New Zealand rabbits weighing 3 +/- 0.3 kg. VX2 tumor cells were injected into the inside of the chest wall of rabbits. The concentration of indocyanine green (ICG) has been observed once every three days, after the size of the pleural tumor grew up over 1cm. We used five different wavelengths (732, 758, 805, 840, and 880 nm) with known ICG spectrum. The distance between light source and detector probes was fixed by 1 cm. The probes were placed on the skin right above the tumor with an aid of laparoscope. ICG was injected into rabbits via ear vein. The diffused light was measured through the tumor with time course using a spectrometer. These measured data enabled us to observe the change of ICG concentration in real time with respect to the baseline without ICG. ICG was present longer in tumor compared to normal tissue. This phenomenon is thought to be due to the excessive angiogenesis in the tumor tissue. Since this method can be applied to other cases easily, it is thought that there is a possibility of cancer screening with less cost and simple equipment.
Stamova, Ivanka; Stamov, Gani
2017-09-08
In this paper, we propose a fractional-order neural network system with time-varying delays and reaction-diffusion terms. We first develop a new Mittag-Leffler synchronization strategy for the controlled nodes via impulsive controllers. Using the fractional Lyapunov method sufficient conditions are given. We also study the global Mittag-Leffler synchronization of two identical fractional impulsive reaction-diffusion neural networks using linear controllers, which was an open problem even for integer-order models. Since the Mittag-Leffler stability notion is a generalization of the exponential stability concept for fractional-order systems, our results extend and improve the exponential impulsive control theory of neural network system with time-varying delays and reaction-diffusion terms to the fractional-order case. The fractional-order derivatives allow us to model the long-term memory in the neural networks, and thus the present research provides with a conceptually straightforward mathematical representation of rather complex processes. Illustrative examples are presented to show the validity of the obtained results. We show that by means of appropriate impulsive controllers we can realize the stability goal and to control the qualitative behavior of the states. An image encryption scheme is extended using fractional derivatives. Copyright © 2017 Elsevier Ltd. All rights reserved.
A Parallel Approach to Cosine Calculation Using OpenCL
Directory of Open Access Journals (Sweden)
Faris Cakaric
2015-03-01
Full Text Available Fast calculation of high-precision cosine function becomes increasingly important in many areas of computer science. This paper proposes an algorithm for high-performance calculation of cosine function using Maclaurin series and by exploiting benefits of parallelisation. It presents several parallel implementations of this algorithm in OpenCL framework, improving them from naïve to the optimised implementation. The paper shows comparison of time of execution when the algorithm is executed sequentially on CPU and in parallel on GPU, confirming enormous decrease in time of execution when algorithm executes in parallel. Finally, the paper draws conclusions about the scalability of algorithm and percentage of total time of execution wasted on communication overheads.
Du, Shan; Shehata, Mohamed; Badawy, Wael; Rahman, Choudhury A.
2013-03-01
In this paper, we proposed a discrete cosine transform (DCT)-based attnuation and accentuation method to remove lighting effects on face images for faciliating face recognition task under varying lighting conditions. In the proposed method, logorithm transform is first used to convert a face image into logarithm domain. Then discrete cosine transform is applied to obtain DCT coefficients. The low-frequency DCT coefficients are attenuated since illumination variations mainly concentrate on the low-frequency band. The high-frequency coefficients are accentuated since when under poor illuminations, the high-frequency features become more important in recognition. The reconstructed log image by inverse DCT of the modified coefficients is used for the final recognition. Experiments are conducted on the Yale B database, the combination of Yale B and Extended Yale B databases and the CMU-PIE database. The proposed method does not require modeling and model fitting steps. It can be directly applied to single face image, without any prior information of 3D shape or light sources.
Compressed wideband spectrum sensing based on discrete cosine transform.
Wang, Yulin; Zhang, Gengxin
2014-01-01
Discrete cosine transform (DCT) is a special type of transform which is widely used for compression of speech and image. However, its use for spectrum sensing has not yet received widespread attention. This paper aims to alleviate the sampling requirements of wideband spectrum sensing by utilizing the compressive sampling (CS) principle and exploiting the unique sparsity structure in the DCT domain. Compared with discrete Fourier transform (DFT), wideband communication signal has much sparser representation and easier implementation in DCT domain. Simulation result shows that the proposed DCT-CSS scheme outperforms the conventional DFT-CSS scheme in terms of MSE of reconstruction signal, detection probability, and computational complexity.
Compressed Wideband Spectrum Sensing Based on Discrete Cosine Transform
Directory of Open Access Journals (Sweden)
Yulin Wang
2014-01-01
Full Text Available Discrete cosine transform (DCT is a special type of transform which is widely used for compression of speech and image. However, its use for spectrum sensing has not yet received widespread attention. This paper aims to alleviate the sampling requirements of wideband spectrum sensing by utilizing the compressive sampling (CS principle and exploiting the unique sparsity structure in the DCT domain. Compared with discrete Fourier transform (DFT, wideband communication signal has much sparser representation and easier implementation in DCT domain. Simulation result shows that the proposed DCT-CSS scheme outperforms the conventional DFT-CSS scheme in terms of MSE of reconstruction signal, detection probability, and computational complexity.
Cosine problem in EPRL/FK spinfoam model
Vojinovic, Marko
2014-01-01
We calculate the classical limit effective action of the EPRL/FK spinfoam model of quantum gravity coupled to matter fields. By employing the standard QFT background field method adapted to the spinfoam setting, we find that the model has many different classical effective actions. Most notably, these include the ordinary Einstein-Hilbert action coupled to matter, but also an action which describes antigravity. All those multiple classical limits appear as a consequence of of the fact that the EPRL/FK vertex amplitude has cosine-like large spin asymptotics. We discuss some possible ways to eliminate the unwanted classical limits.
Cosine problem in EPRL/FK spinfoam model
Vojinović, Marko
2014-01-01
We calculate the classical limit effective action of the EPRL/FK spinfoam model of quantum gravity coupled to matter fields. By employing the standard QFT background field method adapted to the spinfoam setting, we find that the model has many different classical effective actions. Most notably, these include the ordinary Einstein-Hilbert action coupled to matter, but also an action which describes antigravity. All those multiple classical limits appear as a consequence of the fact that the EPRL/FK vertex amplitude has cosine-like large spin asymptotics. We discuss some possible ways to eliminate the unwanted classical limits.
Cosine Similarity Measure of Interval Valued Neutrosophic Sets
Directory of Open Access Journals (Sweden)
Said Broumi
2014-09-01
Full Text Available In this paper, we define a new cosine similarity between two interval valued neutrosophic sets based on Bhattacharya’s distance [19]. The notions of interval valued neutrosophic sets (IVNS, for short will be used as vector representations in 3D-vector space. Based on the comparative analysis of the existing similarity measures for IVNS, we find that our proposed similarity measure is better and more robust. An illustrative example of the pattern recognition shows that the proposed method is simple and effective.
Adaptive cosine transform image coding with variable block size and constant block distortion
Daut, David G.; Wu, Jia-Chyi
1996-02-01
An adaptive discrete cosine transform (DCT) image coding system is implemented with the same average distortion designated for each variable size image block. The variable block size segmentation is performed using a quadtree data structure by dividing the perceptually more important regions of an image into smaller size blocks compared to the size of blocks containing lesser amounts of spatial activity. Due to the nonstationarity of real-world images, each image block is described by a space-varying nonstationary Gauss-Markov random field. The space-varying autoregressive parameters are estimated using an on-line modified least- squares estimator. For each assumed space-varying nonstationary image block, a constant average distortion is assigned and the code rate for each image block is allowed to vary in order to meet the fixed distortion criterion. Simulation results show that reconstructed images coded at low average distortion, based on an assumed space-varying nonstationary image model, using variable size blocks and with variable bit rate per block possess high-quality subjective (visual) and objective (measured) quality at low average bit rates. Performance gains are achieved due to the distortion being distributed more uniformly among the blocks as compared with fixed-rate, stationary image transform coding schemes.
Cosine edge modes in a periodically driven quantum system
Satija, Indubala I.; Zhao, Erhai
2016-12-01
Time-periodic (Floquet) topological phases of matter exhibit bulk-edge relationships that are more complex than static topological insulators and superconductors. Finding the edge modes unique to driven systems usually requires numerics. Here we present a minimal two-band model of Floquet topological insulators and semimetals in two dimensions where all the bulk and edge properties can be obtained analytically. It is based on the extended Harper model of quantum Hall effect at flux one-half. We show that periodical driving gives rise to a series of phases characterized by a pair of integers. The model has a most striking feature: the spectrum of the edge modes is always given by a single cosine function, ω (ky) ∝cosky where ky is the wave number along the edge, as if it is freely dispersing and completely decoupled from the bulk. The cosine mode is robust against the change in driving parameters. It also persists in the semimetallic phases with Dirac points.
Daneyko, Anton; Hlushkou, Dzmitry; Baranau, Vasili; Khirevich, Siarhei; Seidel-Morgenstern, Andreas; Tallarek, Ulrich
2015-08-14
In recent years, chromatographic columns packed with core-shell particles have been widely used for efficient and fast separations at comparatively low operating pressure. However, the influence of the porous shell properties on the mass transfer kinetics in core-shell packings is still not fully understood. We report on results obtained with a modeling approach to simulate three-dimensional advective-diffusive transport in bulk random packings of monosized core-shell particles, covering a range of reduced mobile phase flow velocities from 0.5 up to 1000. The impact of the effective diffusivity of analyte molecules in the porous shell and the shell thickness on the resulting plate height was investigated. An extension of Giddings' theory of coupled eddy dispersion to account for retention of analyte molecules due to stagnant regions in porous shells with zero mobile phase flow velocity is presented. The plate height equation involving a modified eddy dispersion term excellently describes simulated data obtained for particle-packings with varied shell thickness and shell diffusion coefficient. It is confirmed that the model of trans-particle mass transfer resistance of core-shell particles by Kaczmarski and Guiochon [42] is applicable up to a constant factor. We analyze individual contributions to the plate height from different mass transfer mechanisms in dependence of the shell parameters. The simulations demonstrate that a reduction of plate height in packings of core-shell relative to fully porous particles arises mainly due to reduced trans-particle mass transfer resistance and transchannel eddy dispersion. Copyright © 2015 Elsevier B.V. All rights reserved.
Analytic discrete cosine harmonic wavelet transform based OFDM system
Indian Academy of Sciences (India)
M N Suma; S V Narasimhan; B Kanmani
2015-02-01
An OFDM based on Analytic Discrete Cosine HarmonicWavelet Transform (ADCHWT_OFDM) has been proposed in this paper. Analytic DCHWT has been realized by applying DCHWT to the original signal and to its Hilbert transform. ADCHWT has been found to be computationally efficient and very effective in improving Bit Error Rate (BER) and Peak to Average Power Ratio (PAPR) performance. Improvement compared to that of Haar-WT OFDM and DFT OFDM is achieved without employing Cyclic Prefix BER is 0.002 for ADCHWT OFDM compared to Haar WT, DFT OFDM which have BER of 0.06 and 0.4, respectively, at 15 dB SNR. PAPR is also reduced by 3 dB compared to DFT OFDM and 0.3 dB reduction compared to Haar WT OFDM.
Performance Evaluation of Image Fusion Based on Discrete Cosine Transform
Directory of Open Access Journals (Sweden)
Ramkrishna Patil
2013-05-01
Full Text Available Discrete cosine transform (DCT is used for fusion of two different images and for image compression. Image fusion deals with creating an image by combining portions from other images to obtain an image in which all of the objects are in focus. Two multi focus images are used for image fusion. Different fusion algorithms are used and their performance is evaluated using evaluation metrics such as PSNR, SSIM, Spatial Frequency, Quality Index, Structural Content, Mean Absolute Error. Fusion performance is not good while using the algorithms with block size less than 64x64 and also the block size of 512x512. Contrast, amplitude and energy based image fusion algorithms performed well. The fused images are comparable with the reference image. Only the image size is considered but blurring percentage is not considered. These algorithms are very simple and might be suitable for real time applications
Query By Image Content using Discrete Cosine Transform
Directory of Open Access Journals (Sweden)
P.A.Hemalatha
2013-04-01
Full Text Available The need for Query By Image Content (QBIC peaked up due to the increase in the size of image database. The proposed method chooses appropriate feature extraction methods to extract the features, shape and color to enhance the retrieval efficiency and accuracy. It employs SRM (Statistical Region Merging algorithm for segmentation and uses DCT (Discrete Cosine Transform on the segmented image to obtain the shape feature vector. Color feature is obtained by considering the RGB components in the image. The processed feature vectors are collected in the feature database which is then compared with the query image’s feature vector. When the difference matches a specific threshold, the most similar images are retrieved automatically.
Cosine Based Latent Factor Model for Precision Oriented Recommendation
Directory of Open Access Journals (Sweden)
Bipul Kumar
2016-01-01
Full Text Available Recommender systems suggest a list of interesting items to users based on their prior purchase or browsing behaviour on e-commerce platforms. The continuing research in recommender systems have primarily focused on developing algorithms for rating prediction task. However, most e-commerce platforms provide ‘top-k’ list of interesting items for every user. In line with this idea, the paper proposes a novel machine learning algorithm to predict a list of ‘top-k’ items by optimizing the latent factors of users and items with the mapped scores from ratings. The basic idea is to learn latent factors based on the cosine similarity between the users and items latent features which is then used to predict the scores for unseen items for every user. Comprehensive empirical evaluations on publicly available benchmark datasets reveal that the proposed model outperforms the state-of-the-art algorithms in recommending good items to a user.
Full-frame compression of discrete wavelet and cosine transforms
Lo, Shih-Chung B.; Li, Huai; Krasner, Brian; Freedman, Matthew T.; Mun, Seong K.
1995-04-01
At the foreground of computerized radiology and the filmless hospital are the possibilities for easy image retrieval, efficient storage, and rapid image communication. This paper represents the authors' continuous efforts in compression research on full-frame discrete wavelet (FFDWT) and full-frame discrete cosine transforms (FFDCT) for medical image compression. Prior to the coding, it is important to evaluate the global entropy in the decomposed space. It is because of the minimum entropy, that a maximum compression efficiency can be achieved. In this study, each image was split into the top three most significant bit (MSB) and the remaining remapped least significant bit (RLSB) images. The 3MSB image was compressed by an error-free contour coding and received an average of 0.1 bit/pixel. The RLSB image was either transformed to a multi-channel wavelet or the cosine transform domain for entropy evaluation. Ten x-ray chest radiographs and ten mammograms were randomly selected from our clinical database and were used for the study. Our results indicated that the coding scheme in the FFDCT domain performed better than in FFDWT domain for high-resolution digital chest radiographs and mammograms. From this study, we found that decomposition efficiency in the DCT domain for relatively smooth images is higher than that in the DWT. However, both schemes worked just as well for low resolution digital images. We also found that the image characteristics of the `Lena' image commonly used in the compression literature are very different from those of radiological images. The compression outcome of the radiological images can not be extrapolated from the compression result based on the `Lena.'
Multifocus watermarking approach based on discrete cosine transform.
Waheed, Safa Riyadh; Alkawaz, Mohammed Hazim; Rehman, Amjad; Almazyad, Abdulaziz S; Saba, Tanzila
2016-05-01
Image fusion process consolidates data and information from various images of same sight into a solitary image. Each of the source images might speak to a fractional perspective of the scene, and contains both "pertinent" and "immaterial" information. In this study, a new image fusion method is proposed utilizing the Discrete Cosine Transform (DCT) to join the source image into a solitary minimized image containing more exact depiction of the sight than any of the individual source images. In addition, the fused image comes out with most ideal quality image without bending appearance or loss of data. DCT algorithm is considered efficient in image fusion. The proposed scheme is performed in five steps: (1) RGB colour image (input image) is split into three channels R, G, and B for source images. (2) DCT algorithm is applied to each channel (R, G, and B). (3) The variance values are computed for the corresponding 8 × 8 blocks of each channel. (4) Each block of R of source images is compared with each other based on the variance value and then the block with maximum variance value is selected to be the block in the new image. This process is repeated for all channels of source images. (5) Inverse discrete cosine transform is applied on each fused channel to convert coefficient values to pixel values, and then combined all the channels to generate the fused image. The proposed technique can potentially solve the problem of unwanted side effects such as blurring or blocking artifacts by reducing the quality of the subsequent image in image fusion process. The proposed approach is evaluated using three measurement units: the average of Q(abf), standard deviation, and peak Signal Noise Rate. The experimental results of this proposed technique have shown good results as compared with older techniques.
Simple and fast cosine approximation method for computer-generated hologram calculation.
Nishitsuji, Takashi; Shimobaba, Tomoyoshi; Kakue, Takashi; Arai, Daisuke; Ito, Tomoyoshi
2015-12-14
The cosine function is a heavy computational operation in computer-generated hologram (CGH) calculation; therefore, it is implemented by substitution methods such as a look-up table. However, the computational load and required memory space of such methods are still large. In this study, we propose a simple and fast cosine function approximation method for CGH calculation. As a result, we succeeded in creating CGH with sufficient quality and made the calculation time 1.6 times as fast at maximum compared to using the look-up table of the cosine function on CPU implementation.
Multi-View Distributed Video Coding Based on Discrete Cosine
Directory of Open Access Journals (Sweden)
Guanqun Liu
2014-07-01
Full Text Available To investigate the allocation scheme of the multi-view distributed video coding (DVC, the corresponding improvements are proposed correspondingly for traditional multi-view DVC. Traditional multi-view DVC (Wyner-Ziv DVC encodes for all areas of Wyner-Ziv frame indiscriminately based on Turbo or LDPC. In this kind of encoding process, with regard to violent motor area, decoder can’t decode violent motor area accurately and also send more solicited message to feedback channel, which lowers the code efficiency and decodes inaccurately for violent motor area, it causes a part of area distortion in the image. In this paper, a distributed video encryption algorithm is proposed which based on discrete cosine transform (DCT. The algorithm combines decision criteria of ROI to get violent motor area and non-violent motor area. For violent motor area, to extract low frequency coefficient of DCT as DCT-R algorithm to assist decoder end to decode, decoder utilizes low frequency coefficient of DCT which has already been decoded to carry on bi-directional movement evaluation. Simulation experiment tests and verifies the improved algorithm effectiveness of proposed multi-view DVC in this paper
Discrete-cosine-transform-based image compression applied to dermatology
Cookson, John P.; Sneiderman, Charles; Rivera, Christopher
1991-05-01
The research reported in this paper concerns an evaluation of the impact of compression on the quality of digitized color dermatologic images. 35 mm slides of four morphologic types of skin lesions were captured at 1000 pixels per inch (ppi) in 24 bit RGB color, to give an approximate 1K X 1K image. The discrete cosine transform (DCT) algorithm, was applied to the resulting image files to achieve compression ratios of about 7:1, 28:1, and 70:1. The original scans and the decompressed files were written to a 35 mm film recorder. Together with the original photo slides, the slides resulting from digital images were evaluated in a study of morphology recognition and image quality assessment. A panel of dermatologists was asked to identify the morphology depicted and to rate the image quality of each slide. The images were shown in a progression from highest level of compression to original photo slides. We conclude that the use of DCT file compression yields acceptable performance for skin lesion images since differences in morphology recognition performance do not correlate significantly with the use of original photos versus compressed versions. Additionally, image quality evaluation does not correlate significantly with level of compression.
Traveling Wave Solutions of ZK-BBM Equation Sine-Cosine Method
Directory of Open Access Journals (Sweden)
Sadaf Bibi
2014-03-01
Full Text Available Travelling wave solutions are obtained by using a relatively new technique which is called sine-cosine method for ZK-BBM equations. Solution procedure and obtained results re-confirm the efficiency of the proposed scheme.
Complex source point theory of paraxial and nonparaxial cosine-Gauss and Bessel-Gauss beams.
Sheppard, Colin J R
2013-02-15
It shown how cosine-Gauss and Bessel-Gauss beams can be generated using the complex source point theory. Paraxial beams are treated first. An analytic expression is derived for the nonparaxial cosine-Gaussian beam, based on the complex source point approach, and numerical results are presented to illustrate its behavior. A way to generate nonparaxial Bessel-Gauss beams is also indicated.
L'Introduction et la diffusion de la variété d'igname C18 en région ...
African Journals Online (AJOL)
SARAH
: C18, IBS, ... d'une variété donnée à être utilisée dès la récolte ... été ainsi des variétés comme Florido, Brazo. Fuerte et ... problèmes résolus. Elimination des ..... d'apprentissage des techniques culturales liées à l'adoption ...
Regular Discrete Cosine Transform and its Application to Digital Images Representation
Directory of Open Access Journals (Sweden)
Yuri A. Gadzhiev
2011-06-01
Full Text Available Discrete cosine transform DCT-I, unlike DCT-II, does not concentrate the energy of a transformed vector sufficiently well, so it is not used practically for the purposes of digital image compression. By performing regular normalization of the basic cosine transform matrix, we obtain a discrete cosine transform which has the same cosine basis as DCT-I, coincides as DCT-I with its own inverse transform, but unlike DCT-I, it does not reduce the proper ability of cosine transform to the energy concentration. In this paper we consider briefly the properties of this transform, its possible integer implementation for the case of 8x8-matrix, its applications to the image itself and to the preliminary rgb colour space transformations, furthermore we investigate some models of quantization, perform an experiment for the estimation of the level of digital images compression and the quality achieved by use of this transform. This experiment shows that the transform can be sufficiently effective for practical use, but the question of its comparative effectiveness with respect to DCT-II remains open.
Phase retrieval based on cosine grating modulation and transport of intensity equation
Chen, Ya-ping; Zhang, Quan-bing; Cheng, Hong; Qian, Yi; Lv, Qian-qian
2016-10-01
In order to calculate the lost phase from the intensity information effectively, a new method of phase retrieval which based on cosine grating modulation and transport of intensity equation is proposed. Firstly, the cosine grating is loaded on the spatial light modulator in the horizontal and vertical direction respectively, and the corresponding amplitude of the light field is modulated. Then the phase is calculated by its gradient which is extracted from different direction modulation light illumination. The capability of phase recovery of the proposed method in the presence of noise is tested by simulation experiments. And the results show that the proposed algorithm has a better resilience than the traditional Fourier transform algorithm at low frequency noise. Furthermore, the phase object of different scales can be retrieved using the proposed algorithm effectively by changing the frequency of cosine grating, which can control the imaging motion expediently.
Directory of Open Access Journals (Sweden)
Jinyu Lu
2014-01-01
Full Text Available A novel iris biometric watermarking scheme is proposed focusing on iris recognition instead of the traditional watermark for increasing the security of the digital products. The preprocess of iris image is to be done firstly, which generates the iris biometric template from person's eye images. And then the templates are to be on discrete cosine transform; the value of the discrete cosine is encoded to BCH error control coding. The host image is divided into four areas equally correspondingly. The BCH codes are embedded in the singular values of each host image's coefficients which are obtained through discrete cosine transform (DCT. Numerical results reveal that proposed method can extract the watermark effectively and illustrate its security and robustness.
α-times Integrated Regularized Cosine Functions and Second Order Abstract Cauchy Problens
Institute of Scientific and Technical Information of China (English)
张寄洲; 陶有山
2001-01-01
In this paper, α -times integrated C-regularized cosine functions and mild α-times integrated C-existence families of second order are introduced. Equivalences are proved among α -times integrated C-regularized cosine function for a linear operator A, C-wellposed of (α + 1)-times abstract Cauchy problem and mild α -times integrated C-existence family of second order for A when the commutable condition is satisfied. In addition, if A = C-1AC, they are also equivalent to A generating the α -times integrated C-regularized cosine finction.The characterization of an exponentially botnded mild α -times integrated C-existence family of second order is given out in terms of a Laplace transform.
Cross-correlation function based multipath mitigation technique for cosine-BOC signals
Institute of Scientific and Technical Information of China (English)
Huihua Chen; Weimin Jia; Minli Yao
2013-01-01
We propose a new multipath mitigation technique based on cross-correlation function for the new cosine phased binary off-set carrier (cosine-BOC) modulated signals, which wil most likely be employed in both European Galileo system and Chinese Com-pass system. This technique is implemented to create an optimum cross-correlation function via designing the modulated symbols of the local signal. And the structure of the code tracking loop for cosine-BOC signals is quite simple including only two real correla-tors. Results demonstrate that the technique efficiently eliminates the ranging errors in the medium and long multipath regions with respect to the conventional receiver correlation techniques.
BRAIN TUMOR CLASSIFICATION BASED ON CLUSTERED DISCRETE COSINE TRANSFORM IN COMPRESSED DOMAIN
Directory of Open Access Journals (Sweden)
V. Anitha
2014-01-01
Full Text Available This study presents a novel method to classify the brain tumors by means of efficient and integrated methods so as to increase the classification accuracy. In conventional systems, the problem being the same to extract the feature sets from the database and classify tumors based on the features sets. The main idea in plethora of earlier researches related to any classification method is to increase the classification accuracy.The actual need is to achieve a better accuracy in classification, by extracting more relevant feature sets after dimensionality reduction. There exists a trade-off between accuracy and the number of feature sets. Hence the focus in this study is to implement Discrete Cosine Transform (DCT on the brain tumor images for various classes. Using DCT, by itself, it offers a fair dimension reduction in feature sets.Later on, sequentially K-means algorithm is applied on DCT coefficients to cluster the feature sets. These cluster information are considered as refined feature sets and classified using Support Vector Machine (SVM is proposed in this study. This method of using DCT helps to adjust and vary the performance of classification based on the count of the DCT coefficients taken into account. There exists a good demand for an automatic classification of brain tumors which grealtly helps in the process of diagnosis. In this novel work, an average of 97% and a maximum of 100% classification accuracy has been achieved. This research is basically aiming and opening a new way of classification under compressed domain. Hence this study may be highly suitable for diagnosing under mobile computing and internet based medical diagnosis.
Chattopadhyay, Sudipta
2009-01-01
Quadrature Phase Shift Keying (QPSK) and Offset Quadrature Phase Shift Keying (OQPSK) are two well accepted modulation techniques used in Code Division Multiple Access (CDMA) system. The Pulse Shaping Filters play an important role in digital transmission. The type of Pulse Shaping Filter used, and its behavior would influence the performance of the communication system. This in turn, would have an effect on the performance of the Mobile Communication system, in which the digital communication technique has been employed. In this paper we have presented comparative study of some performance parameters or performance metrics of a digital communication system like, Error Vector Magnitude (EVM), Magnitude Error, Phase Error and Bandwidth Efficiency for a QPSK transmission system. Root Raised Cosine (RRC) and Raised Cosine (RC) Pulse shaping filters have been used for comparison. The measurement results serve as a guideline to the system designer to select the proper pulse shaping filter with the appropriate valu...
Flow past superhydrophobic surfaces with cosine variation in local slip length
Asmolov, Evgeny S; Harting, Jens; Vinogradova, Olga I
2012-01-01
Anisotropic super-hydrophobic surfaces have the potential to greatly reduce drag and enhance mixing phenomena in microfluidic devices. Recent work has focused mostly on cases of super-hydrophobic stripes. Here, we analyze a relevant situation of cosine variation of the local slip length. We derive approximate formulae for maximal (longitudinal) and minimal (transverse) directional effective slip lengths that are in good agreement with the exact numerical solution and lattice-Bolzmann simulations for any surface slip fraction. The cosine texture can provide a very large effective (forward) slip, but it was found to be less efficient in generating a transverse flow as compared to super-hydrophobic stripes.
Discovering Trigonometric Relationships Implied by the Law of Sines and the Law of Cosines
Skurnick, Ronald; Javadi, Mohammad
2006-01-01
The Law of Sines and The Law of Cosines are of paramount importance in the field of trigonometry because these two theorems establish relationships satisfied by the three sides and the three angles of any triangle. In this article, the authors use these two laws to discover a host of other trigonometric relationships that exist within any…
The relation between Pearson’s correlation coefficient r and Salton’s cosine measure
Egghe, L.; Leydesdorff, L.
2009-01-01
The relation between Pearson's correlation coefficient and Salton's cosine measure is revealed based on the different possible values of the division of the L1-norm and the L2-norm of a vector. These different values yield a sheaf of increasingly straight lines which together form a cloud of points,
The relation between Pearson’s correlation coefficient r and Salton’s cosine measure
Egghe, L.; Leydesdorff, L.
2009-01-01
The relation between Pearson's correlation coefficient and Salton's cosine measure is revealed based on the different possible values of the division of the L1-norm and the L2-norm of a vector. These different values yield a sheaf of increasingly straight lines which together form a cloud of points,
Local discrete cosine transformation domain Volterra prediction of chaotic time series
Institute of Scientific and Technical Information of China (English)
张家树; 李恒超; 肖先赐
2005-01-01
In this paper a local discrete cosine transformation (DCT) domain Volterra prediction method is proposed to predict chaotic time series, where the DCT is used to lessen the complexity of solving the coefficient matrix. Numerical simulation results show that the proposed prediction method can effectively predict chaotic time series and improve the prediction accuracy compared with the traditional local linear prediction methods.
Improved SNR of MST RADAR Signals by Cosine Hyperbolic Window over Kaiser Window
Directory of Open Access Journals (Sweden)
Prof. B. Ramesh Reddy Dr. A. Subbarami Reddy Dr. P. Chandrashekar Reddy
2012-02-01
Full Text Available In this paper, the effect of window shape parameter “” in Cosine Hyperbolic Window Function on the SNR values of MST RADAR returns has been investigated. Six sets of multibeam observations of the lower atmosphere made by the Indian Mesosphere-Stratosphere-Troposphere (MST RADAR are used for the result analysis. Prior to the Fourier Transformation, the in-phase and quadrature components of the RADAR echo samples are weighted with the recently proposed new class of adjustable window based on the Cosine Hyperbolic Window Function. The effects of data weighting with the variation of the window shape parameter “” of the Cosine Hyperbolic Window Function is presented. It is observed that the increase of “” increases the SNR values and a good improvement is reported. Optimum value of the shape parameter “” for the Cosine Hyperbolic Window Function is suggested to analyze the MST RADAR signals. The results also shows that, the improvement of SNR of noisy data due to the effect of side lobe reduction and demands for the design of optimal windows.
Institute of Scientific and Technical Information of China (English)
Chujun Zheng; Peng Han; Hongsen Chang
2006-01-01
@@ A new one-step four-quadrant spatial phase-shifting Fourier transform digital holography is presented for recording of cosine transform coefficients, because cosine transform is a real-even symmetric Fourier transform. This approach implements four quadrant spatial phase shifting at a time using a special phase mask, which is located in the reference arm, and the phase distributions of its four-quadrants are 0, π/2, π,and 3π/2 respectively. The theoretical analysis and computer simulation results show that cosine transform coefficients of real-valued image can be calculated by capturing single four-quadrant spatial phase-shifting Fourier transform digital hologram.
Medical Image Watermarking in Sub-block Three-dimensional Discrete Cosine Transform Domain
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Baoru Han
2016-03-01
Full Text Available Digital watermarking can be applied to protection of medical images privacy, hiding of patient's diagnosis information and so on. In order to improve the ability of resisting geometric attacks, a new watermarking algorithm for medical volume data in sub-block three-dimensional discrete cosine transform domain is presented. The original watermarking image is scrambled by a Chebyshev chaotic neural network so as to improve watermarking security. Sub-block three-dimensional discrete cosine transform and perceptual hashing are used to construct zero-watermarking. In this way it does not produce medical image distortion and gives the algorithm the ability to resist geometric attacks. Experimental results show that the algorithm has good security, and it has good robustness to various geometric attacks.
Directory of Open Access Journals (Sweden)
Viholainen Ari
2006-01-01
Full Text Available The recently introduced exponentially modulated filter bank (EMFB is a -channel uniform, orthogonal, critically sampled, and frequency-selective complex modulated filter bank that satisfies the perfect reconstruction (PR property if the prototype filter of an -channel PR cosine modulated filter bank (CMFB is used. The purpose of this paper is to present various implementation structures for the EMFBs in a unified framework. The key idea is to use cosine and sine modulated filter banks as building blocks and, therefore, polyphase, lattice, and extended lapped transform (ELT type of implementation solutions are studied. The ELT-based EMFBs are observed to be very competitive with the existing modified discrete Fourier transform filter banks (MDFT-FBs when comparing the number of multiplications/additions and the structural simplicity. In addition, EMFB provides an alternative channel stacking arrangement that could be more natural in certain subband processing applications and data transmission systems.
Petrache, Horia I
2011-01-01
In classical physics, the familiar sine and cosine functions appear in two forms: (1) geometrical, in the treatment of vectors such as forces and velocities, and (2) differential, as solutions of oscillation and wave equations. These two forms correspond to two different definitions of trigonometric functions, one geometrical using right triangles and unit circles, and the other employing differential equations. Although the two definitions must be equivalent, this equivalence is not demonstrated in textbooks. In this manuscript, the equivalence between the geometrical and the differential definition is presented assuming no a priori knowledge of the properties of sine and cosine functions. We start with the usual length projections on the unit circle and use elementary geometry and elementary calculus to arrive to harmonic differential equations. This more general and abstract treatment not only reveals the equivalence of the two definitions but also provides an instructive perspective on circular and harmon...
Directory of Open Access Journals (Sweden)
R. P. Meenaakshi Sundari
2014-01-01
Full Text Available In this study by using the modified Wallace tree multiplier, an error compensated adder tree is constructed in order to round off truncation errors and to obtain high through put discrete cosine transform design. Peak Signal to Noise Ratio (PSNR is met efficiently since modified Wallace Tree method is an efficient, hardware implementable digital circuit that multiplies two integers resulting an output with reduced delays and errors. Nearly 6% of delays and around 1% of gate counts are reduced. The number of look up tables consumed is 2% lesser than that of the previous multipliers. Thus an area efficient discrete cosine transform is built to achieve high throughput with minimum gate counts and delays for the required Peak Signal to Noise Ratio when compared to the existing DCT’s.
Institute of Scientific and Technical Information of China (English)
李建平; 唐远炎; 严中洪; 张万萍
2001-01-01
Based on sine and cosine functions, the compactly supported orthogonal wavelet filter coefficients with arbitrary length are constructed for the first time. When/N = 2k- 1 and N = 2k , the unified analytic constructions of orthogonal wavelet filters are put forward,respectively. The famous Daubechies filter and some other well-known wavelet filters are tested by the proposed novel method which is very useful for wavelet theory research and many application areas such as pattern recognition.
Application of DFT Filter Banks and Cosine Modulated Filter Banks in Filtering
Lin, Yuan-Pei; Vaidyanathan, P. P.
1994-01-01
None given. This is a proposal for a paper to be presented at APCCAS '94 in Taipei, Taiwan. (From outline): This work is organized as follows: Sec. II is devoted to the construction of the new 2m channel under-decimated DFT filter bank. Implementation and complexity of this DFT filter bank are discussed therein. IN a similar manner, the new 2m channel cosine modulated filter bank is discussed in Sec. III. Design examples are given in Sec. IV.
Application of DFT Filter Banks and Cosine Modulated Filter Banks in Filtering
Lin, Yuan-Pei; Vaidyanathan, P. P.
1994-01-01
None given. This is a proposal for a paper to be presented at APCCAS '94 in Taipei, Taiwan. (From outline): This work is organized as follows: Sec. II is devoted to the construction of the new 2m channel under-decimated DFT filter bank. Implementation and complexity of this DFT filter bank are discussed therein. IN a similar manner, the new 2m channel cosine modulated filter bank is discussed in Sec. III. Design examples are given in Sec. IV.
Dynamical manipulation of Cosine-Gauss beams in a graphene plasmonic waveguide.
He, Xueqing; Ning, Tigang; Li, Rujiang; Pei, Li; Zheng, Jingjing; Li, Jing
2017-06-12
In this paper, we theoretically propose for the first time that graphene monolayer can be used to manipulate the Cosine-Gauss beams (CGBs). We show that both the transverse oscillation period and propagation length of a CGB can be dynamically manipulated by utilizing the tunability of the graphene's chemical potential. The graphene-based planar plasmonic waveguide provides a good platform to investigate the propagation properties of CGBs, which is potentially compatible to the microelectronic technology.
Recursive Architecture for the Forward and Inverse Modified Discrete Cosine Transfer
Institute of Scientific and Technical Information of China (English)
LUJunming; JIANGGuoxiong; LINZhenghui
2003-01-01
Recursive algorithms have been found very effective for realization using software and very large scale integrated circuit (VLSI) techniques. In this paper, an efficient recursive algorithm for the forward and inverse modified discrete cosine transfer (IMDCT) with arbitrary length is presented. This new recursive structure for the transform kernels of the MDCT and IMDCT can reduce the computational complexity. The proposed regular ar-chitecture is particularly suitable for parallel VLSI realiza-tion.
A Ramp Cosine Cepstrum Model for the Parameter Estimation of Autoregressive Systems at Low SNR
Directory of Open Access Journals (Sweden)
Zhu Wei-Ping
2010-01-01
Full Text Available A new cosine cepstrum model-based scheme is presented for the parameter estimation of a minimum-phase autoregressive (AR system under low levels of signal-to-noise ratio (SNR. A ramp cosine cepstrum (RCC model for the one-sided autocorrelation function (OSACF of an AR signal is first proposed by considering both white noise and periodic impulse-train excitations. Using the RCC model, a residue-based least-squares optimization technique that guarantees the stability of the system is then presented in order to estimate the AR parameters from noisy output observations. For the purpose of implementation, the discrete cosine transform, which can efficiently handle the phase unwrapping problem and offer computational advantages as compared to the discrete Fourier transform, is employed. From extensive experimentations on AR systems of different orders, it is shown that the proposed method is capable of estimating parameters accurately and consistently in comparison to some of the existing methods for the SNR levels as low as −5 dB. As a practical application of the proposed technique, simulation results are also provided for the identification of a human vocal tract system using noise-corrupted natural speech signals demonstrating a superior estimation performance in terms of the power spectral density of the synthesized speech signals.
Damour, Thibault Marie Alban Guillaume
2003-01-01
We review some string-inspired theoretical models which incorporate a correlated spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring unnatural fine-tunings of parameters, a variation of the fine-structure constant as large as that recently ``observed'' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universality of free fall, such as MICROSCOPE and STEP. Recent claims by Bekenstein that fine-structure-constant variability does not imply detectable violations of the equivalence principle are shown to be untenable.
Modeling contact angle hysteresis of a liquid droplet sitting on a cosine wave-like pattern surface.
Promraksa, Arwut; Chen, Li-Jen
2012-10-15
A liquid droplet sitting on a hydrophobic surface with a cosine wave-like square-array pattern in the Wenzel state is simulated by using the Surface Evolver to determine the contact angle. For a fixed drop volume, multiple metastable states are obtained at two different surface roughnesses. Unusual and non-circular shape of the three-phase contact line of a liquid droplet sitting on the model surface is observed due to corrugation and distortion of the contact line by structure of the roughness. The contact angle varies along the contact line for each metastable state. The maximum and minimum contact angles among the multiple metastable states at a fixed viewing angle correspond to the advancing and the receding contact angles, respectively. It is interesting to observe that the advancing/receding contact angles (and contact angle hysteresis) are a function of viewing angle. In addition, the receding (or advancing) contact angles at different viewing angles are determined at different metastable states. The contact angle of minimum energy among the multiple metastable states is defined as the most stable (equilibrium) contact angle. The Wenzel model is not able to describe the contact angle along the three-phase contact line. The contact angle hysteresis at different drop volumes is determined. The number of the metastable states increases with increasing drop volume. Drop volume effect on the contact angles is also discussed.
Directory of Open Access Journals (Sweden)
Zulfan
2016-07-01
Full Text Available This article discusses a new method for the detection of forgery images generated by copy-move technique. Copy-move technique is one of image forgery techniques which taking a particular object from its original image and add it on that image for the purpose of increasing the number of or changing the same object in the original image. This study aims to detect the forged image generated by the copy-move techniques and copy-move forged image that has been modified by the rotation operation and histogram equalization. Detection feature used is Ordinal Measure of Discrete Cosine Transform coefficient (OM-DCT. Detection starts with division of the image into a block size of BXB (B = 16x16, 32x32 and 64x64 and two-dimensional DCT was performed to each of blocks. The feature distance from the original to the fake image, was calculated by the Euclidian distance and each feature has a distance of less than or equal to the threshold value (T according to the observations will be marked as a forged part. The results show that there are blocks detected on the copy-move image, whether on the unmodified copy-move forge image or those which modified by the rotation operation and histogram equalization. The number of blocks that are found in the copy-move object varies according to the size of the detection block used.
Institute of Scientific and Technical Information of China (English)
Liu Weidong; Zhu Hua; Zhou Shengqiang; Bai Yalei; Wang Yuan; Zhao Chunsheng
2013-01-01
A novel 0-Poisson's ratio cosine honeycomb support structure of flexible skin is proposed.Mechanical model of the structure is analyzed with the energy method,finite element method (FEM) and experiments have been performed to validate the theoretical model.The in-plane characteristics of the cosine honeycomb are compared with accordion honeycomb through analytical models and experiments.Finally,the application of the cosine honeycomb on a variable camber wing is studied.Studies show that mechanical model agrees well with results of FEM and experiments.The transverse non-dimensional elastic modulus of the cosine honeycomb increases (decreases) when the wavelength or the wall width increases (decreases),or when the amplitude decreases (increases).Compared with accordion honeycomb,the transverse non-dimensional elastic modulus of the cosine honeycomb is smaller,which means the driving force is smaller and the power consumption is less during deformation.In addition,the cosine honeycomb can satisfy the deforming requirements of the variable camber wing.
FROM BOUNDED FAMILIES OF LOCALIZED COSINES TO BI-ORTHOGONAL RIESZ BASES VIA SHIFT-INVARIANCE
Institute of Scientific and Technical Information of China (English)
Charles K. Chui; Shi Xianliang
2001-01-01
The notion of bi-inner product functionals P(f ,g) ＝ ∑ ＜ f ,f. ＞＜ g ,g. ＞ generated by two Bessel seqnsences {fn} and {gn} of functions from L2 was introduced in our earlier work[5] as a vehicle to identify dual frames and bi-orthogonal Riesz bases of L2. The objective was to find conditions under which P is a constant multiple of the inner product ＜f ,g ＞ of L2. A necessary and sufficient condition derived in [5]is that P is both spatial shift-invariant and phase shift-invariant. Although these two shift-invariance proper ties are, in general, unrelated, it could happen that one is a consequence of the other for certain clases of Bessel sequences {fn} and {gn}. In this paper, we show that, indeed, for localized cosines with two-over lapping windows (i. e. , only adjacent window functions are allowed to overlap ) , spatial shift-inrvariance of P is already sufficient to guarantee that P is a constant multiple of the inner product, while phase shift-in variance is not. Hence, phase shift-invariance of P for two-overlapping localized cosine Bessel sequences is a consequence of spatial shift-invariance, but the eonverse is not valid. As an application, we also show thattwo families of localized cosines with uniformly bounded and two-overlapping windows are bi-orthogonal Riesz bases of L2, if and only if Pis spatial shi ft-invariant. In addition, we apply this result to generalize a result on characterization of dual localized codne bases in our earlier work in [3] to the multivariate set- ting. A method for computing the dual windows is also given in this paper.
Cosine directions using Rao-Blackwell Theorem and Hausdorff metric in Quasars
Bell, Byron E
2015-01-01
This analysis will determine the equations of the cosine directions for all flux of the optical spectrum in quasars. Studies on Hausdorff metric will greatly enhance our understanding of quasars distances. This study will complete steps in the classification of quasars by finding the minimum variance of flux by using the RaoBlackwell Theorem. The papers of C. R. Rao and D. Blackwell will be examined to clarify more of the above theorem. Keywords: Theory of Flux, SDSS, Quasars, Redshift (z), Population Perimeters, Regression Analysis
Shinbori, Eiji; Takagi, Mikio
1992-11-01
A new image magnification method, called 'IM-GPDCT' (image magnification applying the Gerchberg-Papoulis (GP) iterative algorithm with discrete cosine transform (DCT)), is described and its performance evaluated. This method markedly improves image quality of a magnified image using a concept which restores the spatial high frequencies which are conventionally lost due to use of a low pass filter. These frequencies are restored using two known constraints applied during iterative DCT: (1) correct information in a passband is known and (2) the spatial extent of an image is finite. Simulation results show that the IM- GPDCT outperforms three conventional interpolation methods from both a restoration error and image quality standpoint.
Rapid Prototyping of Field Programmable Gate Array-Based Discrete Cosine Transform Approximations
Directory of Open Access Journals (Sweden)
Trevor W. Fox
2003-05-01
Full Text Available A method for the rapid design of field programmable gate array (FPGA-based discrete cosine transform (DCT approximations is presented that can be used to control the coding gain, mean square error (MSE, quantization noise, hardware cost, and power consumption by optimizing the coefficient values and datapath wordlengths. Previous DCT design methods can only control the quality of the DCT approximation and estimates of the hardware cost by optimizing the coefficient values. It is shown that it is possible to rapidly prototype FPGA-based DCT approximations with near optimal coding gains that satisfy the MSE, hardware cost, quantization noise, and power consumption specifications.
Discrete cosine and sine transforms general properties, fast algorithms and integer approximations
Britanak, Vladimir; Rao, K R; Rao, K R
2006-01-01
The Discrete Cosine Transform (DCT) is used in many applications by the scientific, engineering and research communities and in data compression in particular. Fast algorithms and applications of the DCT Type II (DCT-II) have become the heart of many established international image/video coding standards. Since then other forms of the DCT and Discrete Sine Transform (DST) have been investigated in detail. This new edition presents the complete set of DCT and DST discrete trigonometric transforms, including their definitions, general mathematical properties, and relations to the optimal Karhune
A new Watermarking System based on Discrete Cosine Transform (DCT) in color biometric images.
Dogan, Sengul; Tuncer, Turker; Avci, Engin; Gulten, Arif
2012-08-01
This paper recommend a biometric color images hiding approach An Watermarking System based on Discrete Cosine Transform (DCT), which is used to protect the security and integrity of transmitted biometric color images. Watermarking is a very important hiding information (audio, video, color image, gray image) technique. It is commonly used on digital objects together with the developing technology in the last few years. One of the common methods used for hiding information on image files is DCT method which used in the frequency domain. In this study, DCT methods in order to embed watermark data into face images, without corrupting their features.
Fast 2-D 8×8 discrete cosine transform algorithm for image coding
Institute of Scientific and Technical Information of China (English)
JI XiuHua; ZHANG CaiMing; WANG JiaYe; BOEY S. H.
2009-01-01
A new fast two-dimension 8×8 discrete cosine transform (2D 8×8 DCT) algorithm based on the charac-teristics of the basic images of 2D DCT is presented. The new algorithm computes each DCT coefficient in turn more independently. Hence, the new algorithm is suitable for 2D DCT pruning algorithm of prun-ing away any number of high-frequency components of 2D DCT. The proposed pruning algorithm ls more efficient than the existing pruning 2D DCT algorithms in terms of the number of arithmetic opera-tions, especially the number of multiplications required in the computation.
Soliton solution for nonlinear partial differential equations by cosine-function method
Energy Technology Data Exchange (ETDEWEB)
Ali, A.H.A. [Mathematics Department, Faculty of Science, Menoufia University, Shebein El-Koom (Egypt); Soliman, A.A. [Department of Mathematics, Faculty of Education (AL-Arish), Suez Canal University, AL-Arish 45111 (Egypt)], E-mail: asoliman_99@yahoo.com; Raslan, K.R. [Mathematics Department, Faculty of Science, Al-Azhar University, Nasr-City, Cairo (Egypt)
2007-08-20
In this Letter, we established a traveling wave solution by using Cosine-function algorithm for nonlinear partial differential equations. The method is used to obtain the exact solutions for five different types of nonlinear partial differential equations such as, general equal width wave equation (GEWE), general regularized long wave equation (GRLW), general Korteweg-de Vries equation (GKdV), general improved Korteweg-de Vries equation (GIKdV), and Coupled equal width wave equations (CEWE), which are the important soliton equations.
Rapid Prototyping of Field Programmable Gate Array-Based Discrete Cosine Transform Approximations
Fox, Trevor W.; Turner, Laurence E.
2003-12-01
A method for the rapid design of field programmable gate array (FPGA)-based discrete cosine transform (DCT) approximations is presented that can be used to control the coding gain, mean square error (MSE), quantization noise, hardware cost, and power consumption by optimizing the coefficient values and datapath wordlengths. Previous DCT design methods can only control the quality of the DCT approximation and estimates of the hardware cost by optimizing the coefficient values. It is shown that it is possible to rapidly prototype FPGA-based DCT approximations with near optimal coding gains that satisfy the MSE, hardware cost, quantization noise, and power consumption specifications.
Institute of Scientific and Technical Information of China (English)
KANG Xiao-Ping; L(U) Bai-Da
2006-01-01
@@ The analytical expression characterizing the propagation of nonparaxial truncated cosine-Gaussian (CoG) beams in free space is derived, and some special cases are discussed. The extended power in the bucket (PIB) is proposed to characterize the beam quality of nonparaxial truncated beams in the far field. It is shown that the extended PIB is applicable to nonparaxial truncated beams, and the PIB of nonparaxial truncated CoG beams depends on the decentred parameter, waist-width-to-wavelength ratio, truncation parameter, and bucket size chosen.
Transfer Scheme Evaluation Model for a Transportation Hub based on Vectorial Angle Cosine
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Li-Ya Yao
2014-07-01
Full Text Available As the most important node in public transport network, efficiency of a transport hub determines the entire efficiency of the whole transport network. In order to put forward effective transfer schemes, a comprehensive evaluation index system of urban transport hubs’ transfer efficiency was built, evaluation indexes were quantified, and an evaluation model of a multi-objective decision hub transfer scheme was established based on vectorial angle cosine. Qualitative and quantitative analysis on factors affecting transfer efficiency is conducted, which discusses the passenger satisfaction, transfer coordination, transfer efficiency, smoothness, economy, etc. Thus, a new solution to transfer scheme utilization was proposed.
Wang, Zhong-peng; Chen, Shou-fa; Zhou, Yang; Chen, Ming; Tang, Jin; Chen, Lin
2014-09-01
In this paper, the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal is reduced by combining the discrete cosine transform (DCT) with clipping in optical intensity-modulated direct-detection (IM/DD) OFDM systems. First, the data are transformed into new modified data by DCT. Second, the proposed scheme utilizes the clipping technique to further reduce the PAPR of OFDM signal. We experimentally demonstrate that the optical OFDM transmission system with this proposed scheme can achieve significant performance improvement in terms of PAPR and bit error rate (BER) compared with the original optical OFDM systems.
Efficient image coding method based on adaptive Gabor discrete cosine transforms
Wang, Hang; Yan, Hong
1993-01-01
The Gabor transform is very useful for image compression, but its implementation is very complicated and time consuming because the Gabor elementary functions are not mutually orthogonal. An efficient algorithm that combines the successive overrelaxation iteration and the look-up table techniques can be used to carry out the Gabor transform. The performance of the Gabor transform can be improved by using a modified transform, a Gabor discrete cosine transform (DCT). We present an adaptive Gabor DCT image coding algorithm. Experimental results show that a better performance can be achieved with the adaptive Gabor DCT than with the Gabor DCT.
Concatenated wavelet/modified Hadamard-structured discrete cosine transform (MHDCT) coding of images
Barazande-Pour, Majid; Mark, Jon W.
1995-04-01
Wavelet transform (WT) is concatenated with the modified Hadamard-structured discrete cosine transform (MHDCT) to encode image signals. As the outer code, the WT decomposes the image signals into uncorrelated low resolution and detailed signal components. As inner codes, the MHDCT adaptively encodes the low resolution signal, while the detailed signals are encoded using pulse code modulation (PCM). The concatenated coding approach offers the possibility of regulated coding for progressive transmission of the image signals over communication networks. Results of image coding using the concatenated WT/MHDCT coder are presented.
Rigid Body Attitude Control Based on a Manifold Representation of Direction Cosine Matrices
Nakath, David; Clemens, Joachim; Rachuy, Carsten
2017-01-01
Autonomous systems typically actively observe certain aspects of their surroundings, which makes them dependent on a suitable controller. However, building an attitude controller for three degrees of freedom is a challenging task, mainly due to singularities in the different parametrizations of the three dimensional rotation group SO(3). Thus, we propose an attitude controller based on a manifold representation of direction cosine matrices: In state space, the attitude is globally and uniquely represented as a direction cosine matrix R ∈ SO(3). However, differences in the state space, i.e., the attitude errors, are exposed to the controller in the vector space ℝ3. This is achieved by an operator, which integrates the matrix logarithm mapping from SO(3) to so(3) and the map from so(3) to ℝ3. Based on this representation, we derive a proportional and derivative feedback controller, whose output has an upper bound to prevent actuator saturation. Additionally, the feedback is preprocessed by a particle filter to account for measurement and state transition noise. We evaluate our approach in a simulator in three different spacecraft maneuver scenarios: (i) stabilizing, (ii) rest-to-rest, and (iii) nadir-pointing. The controller exhibits stable behavior from initial attitudes near and far from the setpoint. Furthermore, it is able to stabilize a spacecraft and can be used for nadir-pointing maneuvers.
STUDY ON RECTANGULAR WAVEGUIDE GRATING SLOW-WAVE STRUCTURE WITH COSINE-SHAPED GROOVES
Institute of Scientific and Technical Information of China (English)
Lu Zhigang; Wei Yanyu; Gong Yubin; Wu Zhoumiao; Wang Wenxiang
2007-01-01
This paper focuses on a new rectangular waveguide grating Slow-Wave Structure(SWS)with cosine-shaped grooves and studies the propagation characteristics of the wave in the SWS.By using the approximate field-matching conditions,the dispersion equation and the coupling impedance of this circuit are obtained.The dispersion curves and coupling impedances of the fundamental wave are calculated and the influences of the various geometrical dimensions are discussed.The results show that the bandwidth of the cosine-shaped groove SWS is much wider than that of rectangular-shaped groove one.And reducing the groove width can broaden the frequency-band and decrease the phase-velocity,while increment of the groove-depth can also decrease phase-velocity.For above cases,the coupling impedance is more than 16Ω.The present analysis will be helpful on further study and design of the RF systems used in millimeter wave Traveling Wave Tube(TWT).
Cosine-Modulated Multitone for Very-High-Speed Digital Subscriber Lines
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Lin Lekun
2006-01-01
Full Text Available In this paper, the use of cosine-modulated filter banks (CMFBs for multicarrier modulation in the application of very-high-speed digital subscriber lines (VDSLs is studied. We refer to this modulation technique as cosine-modulated multitone (CMT. CMT has the same transmitter structure as discrete wavelet multitone (DWMT. However, the receiver structure in CMT is different from its DWMT counterpart. DWMT uses linear combiner equalizers, which typically have more than 20 taps per subcarrier. CMT, on the other hand, adopts a receiver structure that uses only two taps per subcarrier for equalization. This paper has the following contributions. (i A modification that reduces the computational complexity of the receiver structure of CMT is proposed. (ii Although traditionally CMFBs are designed to satisfy perfect-reconstruction (PR property, in transmultiplexing applications, the presence of channel destroys the PR property of the filter bank, and thus other criteria of filter design should be adopted. We propose one such method. (iii Through extensive computer simulations, we compare CMT with zipper discrete multitone (z-DMT and filtered multitone (FMT, the two modulation techniques that have been included in the VDSL draft standard. Comparisons are made in terms of computational complexity, transmission latency, achievable bit rate, and resistance to radio ingress noise.
Directory of Open Access Journals (Sweden)
GENO PETER .P
2010-09-01
Full Text Available The single phase fully controlled converter is used to convert single phase A.C supply to D.C supply. Such converter finds application in dc motor loads for motoring and electrical braking of the motor. There are two types of control schemes to control the firing of thyristors, they are Cosine wave crossing control and Ramp comparator control. In this paper, cosine wave crossing control is used for the control circuit. The advantage of this scheme is that the output voltage is proportional to the control voltage ie., the output voltage is independent of the variation of input voltage. The various protections such as over current, short circuit, under voltage protections etc are included. The main objective of this project is to design an efficient, simple, robust and economical control circuit thereby making the fully controlled converter. The fully controlled converter uses four thyristors . It is a two quadrant converter was voltage polarity can reverse, but current direction cannot reverse because of unidirectional nature of thyristors. In this paper, I have presented the control circuit for the thyristors along with the protection circuits to control Dc Motors of rating 220V,5.8 A and 1500rpm .
Viholainen, Ari; Alhava, Juuso; Renfors, Markku
2006-12-01
The recently introduced exponentially modulated filter bank (EMFB) is a[InlineEquation not available: see fulltext.]-channel uniform, orthogonal, critically sampled, and frequency-selective complex modulated filter bank that satisfies the perfect reconstruction (PR) property if the prototype filter of an[InlineEquation not available: see fulltext.]-channel PR cosine modulated filter bank (CMFB) is used. The purpose of this paper is to present various implementation structures for the EMFBs in a unified framework. The key idea is to use cosine and sine modulated filter banks as building blocks and, therefore, polyphase, lattice, and extended lapped transform (ELT) type of implementation solutions are studied. The ELT-based EMFBs are observed to be very competitive with the existing modified discrete Fourier transform filter banks (MDFT-FBs) when comparing the number of multiplications/additions and the structural simplicity. In addition, EMFB provides an alternative channel stacking arrangement that could be more natural in certain subband processing applications and data transmission systems.
The tanh and sine-cosine methods for higher order equations of Korteweg-de Vries type
Energy Technology Data Exchange (ETDEWEB)
Alquran, Marwan; Al-Khaled, Kamel, E-mail: marwan04@just.edu.jo, E-mail: kamel@just.edu.jo [Department of Mathematics and Statistics, Jordan University of Science and Technology, Irbid 22110 (Jordan)
2011-08-01
The aim of this paper is twofold. Firstly, the tanh method with the aid of Mathematica is used to obtain exact soliton solutions for a new fifth-order nonlinear integrable evolution equation. Secondly, the sine-cosine and the rational sine-cosine methods are proposed for constructing more general exact solutions of the soliton type for two nonlinear evolution equations arising in nonlinear science and theoretical physics, namely the symmetric regularized long wave equation and a new model of the Korteweg-de Vries type, which gives a more realistic version of shallow water waves.
Full-Color Computational Imaging with Single-Pixel Detectors Based on a 2D Discrete Cosine Transform
Liu, Bao-Lei; Wu, Ling-An
2016-01-01
We propose and demonstrate a computational imaging technique that uses structured illumination based on a two-dimensional discrete cosine transform to perform imaging with a single-pixel detector. A scene is illuminated by a projector with two sets of orthogonal patterns, then by applying an inverse cosine transform to the spectra obtained from the single-pixel detector a full-color image is retrieved. This technique can retrieve an image from sub-Nyquist measurements, and the background noise is easily canceled to give excellent image quality. Moreover, the experimental setup is very simple.
Analytic expressions for the black-sky and white-sky albedos of the cosine lobe model.
Goodin, Christopher
2013-05-01
The cosine lobe model is a bidirectional reflectance distribution function (BRDF) that is commonly used in computer graphics to model specular reflections. The model is both simple and physically plausible, but physical quantities such as albedo have not been related to the parameterization of the model. In this paper, analytic expressions for calculating the black-sky and white-sky albedos from the cosine lobe BRDF model with integer exponents will be derived, to the author's knowledge for the first time. These expressions for albedo can be used to place constraints on physics-based simulations of radiative transfer such as high-fidelity ray-tracing simulations.
Directory of Open Access Journals (Sweden)
Chin-Chen Chang
2009-03-01
Full Text Available In this paper, a new oblivious fragile watermarking using discrete cosine transform is proposed. It is inspired by Wong's public key watermarking scheme proposed in 1998 and aims to improve its vulnerability towards possible attacks indicated by Barreto and Holliman. Instead of making use of contextual information and making it an inter-block dependent scheme, as suggested by Barreto, we adopt another approach to retain its blockwise independent property. Our scheme can avoid the conditions necessary for such attacks to befeasible. Furthermore, our scheme extracts the inherent image features and embeds them into this image as the watermark. This relieves users from having to maintain a database of watermarks from various sources. Experimental results show that the watermark insertion procedure has little effect on the visual quality of the watermarked image. They also show our scheme can locate the modifications made to the watermarked image, including imagescaling, cropping, geometric distortion, pixel value changes, etc.
Lightweight Floating-Point Arithmetic: Case Study of Inverse Discrete Cosine Transform
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Fang Fang
2002-09-01
Full Text Available To enable floating-point (FP signal processing applications in low-power mobile devices, we propose lightweight floating-point arithmetic. It offers a wider range of precision/power/speed/area trade-offs, but is wrapped in forms that hide the complexity of the underlying implementations from both multimedia software designers and hardware designers. Libraries implemented in C++ and Verilog provide flexible and robust floating-point units with variable bit-width formats, multiple rounding modes and other features. This solution bridges the design gap between software and hardware, and accelerates the design cycle from algorithm to chip by avoiding the translation to fixed-point arithmetic. We demonstrate the effectiveness of the proposed scheme using the inverse discrete cosine transform (IDCT, in the context of video coding, as an example. Further, we implement lightweight floating-point IDCT into hardware and demonstrate the power and area reduction.
Face Recognition Using Discrete Cosine Transform for Global and Local Features
Chadha, Aman R; Roja, M Mani
2011-01-01
Face Recognition using Discrete Cosine Transform (DCT) for Local and Global Features involves recognizing the corresponding face image from the database. The face image obtained from the user is cropped such that only the frontal face image is extracted, eliminating the background. The image is restricted to a size of 128 x 128 pixels. All images in the database are gray level images. DCT is applied to the entire image. This gives DCT coefficients, which are global features. Local features such as eyes, nose and mouth are also extracted and DCT is applied to these features. Depending upon the recognition rate obtained for each feature, they are given weightage and then combined. Both local and global features are used for comparison. By comparing the ranks for global and local features, the false acceptance rate for DCT can be minimized.
An adaptive 3-D discrete cosine transform coder for medical image compression.
Tai, S C; Wu, Y G; Lin, C W
2000-09-01
In this communication, a new three-dimensional (3-D) discrete cosine transform (DCT) coder for medical images is presented. In the proposed method, a segmentation technique based on the local energy magnitude is used to segment subblocks of the image into different energy levels. Then, those subblocks with the same energy level are gathered to form a 3-D cuboid. Finally, 3-D DCT is employed to compress the 3-D cuboid individually. Simulation results show that the reconstructed images achieve a bit rate lower than 0.25 bit per pixel even when the compression ratios are higher than 35. As compared with the results by JPEG and other strategies, it is found that the proposed method achieves better qualities of decoded images than by JPEG and the other strategies.
Warped Discrete Cosine Transform-Based Low Bit-Rate Block Coding Using Image Downsampling
Directory of Open Access Journals (Sweden)
Ertürk Sarp
2007-01-01
Full Text Available This paper presents warped discrete cosine transform (WDCT-based low bit-rate block coding using image downsampling. While WDCT aims to improve the performance of conventional DCT by frequency warping, the WDCT has only been applicable to high bit-rate coding applications because of the overhead required to define the parameters of the warping filter. Recently, low bit-rate block coding based on image downsampling prior to block coding followed by upsampling after the decoding process is proposed to improve the compression performance for low bit-rate block coders. This paper demonstrates that a superior performance can be achieved if WDCT is used in conjunction with image downsampling-based block coding for low bit-rate applications.
Off-axial elliptical cosine-Gaussian beams and their propagation properties
Institute of Scientific and Technical Information of China (English)
Lu Zhang-De
2007-01-01
In this paper, a new kind of light beam called off-axial elliptical cosine-Gaussian beam (ECosGBs) is denned by using the tensor method. An analytical propagation expression for the ECosGBs passing through axially nonsymmetrical optical systems is derived by using vector integration. The intensity distributions of ECosGBs on the input plane, on the output plane with the equivalent Presnel number being equal to 0.1 and on the focal plane are respectively illustrated for the propagation properties. The results indicate that an ECosGB is eventually transformed into an elliptical cosh-Gaussian beam. In other words, ECosGBs and cosh-Gaussian beams act in a reciprocal manner after propagation.
Inner-product of strain rate vector through direction cosine in coordinates for disk forging
Institute of Scientific and Technical Information of China (English)
ZHAO De-wen; JIN Wen-zhong; WANG Lei; LIU Xiang-hua
2006-01-01
A new linear integration for plastic power was proposed. The effective strain rate for disk forging with bulge was expressed in terms of two-dimensional strain rate vector, and then its direction cosines were determined by the ratio of coordinate increments. Furthermore, inner-product of the vector for plastic power was term integrated by term and summed. Thereafter, through a formula for determination of bulge an analytical solution of stress effective factor was obtained. Finally, through compression tests, the calculated results of above formula were compared with those of Avitzur's approximate solution and total indicator readings of the testing machine. It is indicated that the calculated compression forces are basically in agreement with the measured ones if the pass reduction is less than 13.35%.However, when the reduction gets up to 25.34% and 33.12%, the corresponding errors between the calculated and measured results also get up to 6% and 13.5%, respectively.
Effect of oceanic turbulence on the propagation of cosine-Gaussian-correlated Schell-model beams
Ding, Chaoliang; Liao, Lamei; Wang, Haixia; Zhang, Yongtao; Pan, Liuzhan
2015-03-01
On the basis of the extended Huygens-Fresnel principle, the analytic expression for the cross-spectral density function of the cosine-Gaussian-correlated Schell-model (CGSM) beams propagating in oceanic turbulence is derived and used to investigate the spectral density and spectral degree of coherence of CGSM beams. The dependence of the spectral density and spectral degree of coherence of CGSM beams on the oceanic turbulence parameters including temperature-salinity balance parameter ω, mean square temperature dissipation rate χT and energy dissipation rate per unit mass ɛ is stressed and illustrated numerically. It is shown that oceanic turbulence plays an important role in the evolution of spectral density and spectral degree of coherence of CGSM beams upon propagation.
Ground target detection based on discrete cosine transform and Rényi entropy for imaging ladar
Xu, Yuannan; Chen, Weili; Li, Junwei; Dong, Yanbing
2016-01-01
The discrete cosine transform (DCT) due to its excellent properties that the images can be represented in spatial/spatial-frequency domains, has been applied in sequence data analysis and image fusion. For intensity and range images of ladar, through the DCT using one dimension window, the statistical property of Rényi entropy for images is studied. We also analyzed the change of Rényi entropy's statistical property in the ladar intensity and range images when the man-made objects appear. From this foundation, a novel method for generating saliency map based on DCT and Rényi entropy is proposed. After that, ground target detection is completed when the saliency map is segmented using a simple and convenient threshold method. For the ladar intensity and range images, experimental results show the proposed method can effectively detect the military vehicles from complex earth background with low false alarm.
A Class of Multi-Channel Cosine Modulated IIR Filter Banks
Vanka, Sundaram; Prabhu, K M M; Aravind, R
2007-01-01
This paper presents a class of multi-channel cosine-modulated filter banks satisfying the perfect reconstruction (PR) property using an IIR prototype filter. By imposing a suitable structure on the polyphase filter coefficients, we show that it is possible to greatly simplify the PR condition, while preserving the causality and stability of the system. We derive closed-form expressions for the synthesis filters and also study the numerical stability of the filter bank using frame theoretic bounds. Further, we show that it is possible to implement this filter bank with much lower number of arithmetic operations when compared to FIR filter banks with comparable performance. The filter bank's modular structure also lends itself to efficient VLSI implementation.
Butler, Samuel D; Nauyoks, Stephen E; Marciniak, Michael A
2015-06-01
Of the many classes of bidirectional reflectance distribution function (BRDF) models, two popular classes of models are the microfacet model and the linear systems diffraction model. The microfacet model has the benefit of speed and simplicity, as it uses geometric optics approximations, while linear systems theory uses a diffraction approach to compute the BRDF, at the expense of greater computational complexity. In this Letter, nongrazing BRDF measurements of rough and polished surface-reflecting materials at multiple incident angles are scaled by the microfacet cross section conversion term, but in the linear systems direction cosine space, resulting in great alignment of BRDF data at various incident angles in this space. This results in a predictive BRDF model for surface-reflecting materials at nongrazing angles, while avoiding some of the computational complexities in the linear systems diffraction model.
High Performance Discrete Cosine Transform Operator Using Multimedia Oriented Subword Parallelism
Directory of Open Access Journals (Sweden)
Shafqat Khan
2015-01-01
Full Text Available In this paper an efficient two-dimensional discrete cosine transform (DCT operator is proposed for multimedia applications. It is based on the DCT operator proposed in Kovac and Ranganathan, 1995. Speed-up is obtained by using multimedia oriented subword parallelism (SWP. Rather than operating on a single pixel, the SWP-based DCT operator performs parallel computations on multiple pixels packed in word size input registers so that the performance of the operator is increased. Special emphasis is made to increase the coordination between pixel sizes and subword sizes to maximize resource utilization rate. Rather than using classical subword sizes (8, 16, and 32 bits, multimedia oriented subword sizes (8, 10, 12, and 16 bits are used in the proposed DCT operator. The proposed SWP DCT operator unit can be used as a coprocessor for multimedia applications.
A Complete Video Coding Chain Based on Multi-Dimensional Discrete Cosine Transform
Directory of Open Access Journals (Sweden)
T. Fryza
2010-09-01
Full Text Available The paper deals with a video compression method based on the multi-dimensional discrete cosine transform. In the text, the encoder and decoder architectures including the deﬁnitions of all mathematical operations like the forward and inverse 3-D DCT, quantization and thresholding are presented. According to the particular number of currently processed pictures, the new quantization tables and entropy code dictionaries are proposed in the paper. The practical properties of the 3-D DCT coding chain compared with the modern video compression methods (such as H.264 and WebM and the computing complexity are presented as well. It will be proved the best compress properties could be achieved by complex H.264 codec. On the other hand the computing complexity - especially on the encoding side - is lower for the 3-D DCT method.
The monthly-averaged and yearly-averaged cosine effect factor of a heliostat field
Energy Technology Data Exchange (ETDEWEB)
Al-Rabghi, O.M.; Elsayed, M.M. (King Abdulaziz Univ., Jeddah (Saudi Arabia). Dept. of Thermal Engineering)
1992-01-01
Calculations are carried out to determine the dependence of the monthly-averaged and the yearly-averaged daily cosine effect factor on the pertinent parameters. The results are plotted on charts for each month and for the full year. These results cover latitude angles between 0 and 45[sup o]N, for fields with radii up to 50 tower height. In addition, the results are expressed in mathematical correlations to facilitate using them in computer applications. A procedure is outlined to use the present results to preliminary layout the heliostat field, and to predict the rated MW[sub th] reflected by the heliostat field during a period of a month, several months, or a year. (author)
A Digital Image Watermarking Method in the Discrete Cosine Transformation Domain
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Mohammad Reza Khammar
2012-01-01
Full Text Available In this paper, a watermarking method has been proposed based on Discrete Cosine Transform(DCT which can be used in order to protect copyrighting and to provide right of image ownership. In this method, the original image transferred to DCT domain after dividing into non-overlapped blocks 8×8 and to the same method, watermark image which can be whether a firm mark or any desired image from owner of the art work, after dividing into non-overlapped blocks 4×4, transferred to DCT domain. Watermark image coefficients after one step coding composed with low frequency coefficients of original image and create the final watermark image. On the other hand, the process of reforming watermarked image and extracting the original watermark on the secondary side is extractable by using original image and with reverse mechanism. Experiments show that this method in encountering with a number of routine attacks has a good resistance.
Lightweight Floating-Point Arithmetic: Case Study of Inverse Discrete Cosine Transform
Fang, Fang; Chen, Tsuhan; Rutenbar, Rob A.
2002-12-01
To enable floating-point (FP) signal processing applications in low-power mobile devices, we propose lightweight floating-point arithmetic. It offers a wider range of precision/power/speed/area trade-offs, but is wrapped in forms that hide the complexity of the underlying implementations from both multimedia software designers and hardware designers. Libraries implemented in C++ and Verilog provide flexible and robust floating-point units with variable bit-width formats, multiple rounding modes and other features. This solution bridges the design gap between software and hardware, and accelerates the design cycle from algorithm to chip by avoiding the translation to fixed-point arithmetic. We demonstrate the effectiveness of the proposed scheme using the inverse discrete cosine transform (IDCT), in the context of video coding, as an example. Further, we implement lightweight floating-point IDCT into hardware and demonstrate the power and area reduction.
Image Content Based Retrieval System using Cosine Similarity for Skin Disease Images
Directory of Open Access Journals (Sweden)
Sukhdeep Kaur
2013-09-01
Full Text Available A content based image retrieval system (CBIR is proposed to assist the dermatologist for diagnosis of skin diseases. First, after collecting the various skin disease images and their text information (disease name, symptoms and cure etc, a test database (for query image and a train database of 460 images approximately (for image matching are prepared. Second, features are extracted by calculating the descriptive statistics. Third, similarity matching using cosine similarity and Euclidian distance based on the extracted features is discussed. Fourth, for better results first four images are selected during indexing and their related text information is shown in the text file. Last, the results shown are compared according to doctor’s description and according to image content in terms of precision and recall and also in terms of a self developed scoring system.
Performance of quadrature overlapped raised-cosine modulation over nonlinear satellite channels
Divsalar, D.; Simon, M. K.
1981-01-01
This paper considers the performance evaluation of Staggered Quadrature Overlapped Raised Cosine (SQORC) signal transmission through wideband nonlinear satellite channels in the presence of uplink and downlink additive Gaussian noise. Expressions for the bit error rate are derived for a general transponder model with AM-AM and AM-PM conversion. It is shown that the bit error rate of SQORC is one-half of the sum of the bit error rate of MSK at 2/3 of the uplink signal-to-noise ratio and the bit error rate of Quadriphase Phase-Shift Keying QPSK at 4/3 of the uplink signal-to-noise ratio, whereas the spectrum of SQROC is the product of MSK and QPSK spectra. Numerical results are presented for a transponder which is modelled as a hard limiter.
Hybrid discrete cosine transform-discrete wavelet transform for progressive image compression
Boukaache, Abdennour; Doghmane, Noureddine
2012-01-01
In this paper, we propose an image compression algorithm that uses a hybrid transform and an improved modified set partitioning in hierarchical trees (SPIHT) coding algorithm. The proposed transform uses the subband discrete cosine transform to decompose the image into multiresolution subbands where the discrete wavelet transform is then used to code the low frequencies. Then, we use the SPIHT coding method to code the transformed coefficients. For the SPIHT algorithm, we have proposed a method to reduce the distortion introduced by the SPIHT technique between the original and reconstructed images. The obtained results show the efficiency of the proposed hybrid method in terms of peak signal-to-noise ratio and visual quality.
α-times Integrated Cosine Operator Functions with Growth ω%具ω增长阶的α次积分余弦算子函数
Institute of Scientific and Technical Information of China (English)
王梅英; 许飞
2011-01-01
For a continuous, increasing function ω: [0, ∞) - C of finite exponential type,we establish a Hille-Yosida type theorem for strongly continuous α-times(α ＞ 0) integrated cosine operator functions with O(ω). It includes the corresponding results for n-times integrated cosine operator functions that are polynomially bounded and exponentially bounded.
Institute of Scientific and Technical Information of China (English)
胡啸宇; 王苏; 闫宇航; 黄凯; 刘占权; 陈义学
2013-01-01
Microscopic depletion correction is one of the commonly used techniques that could improve the historical effect and attain higher precision of diffusion calculation and alleviate the inaccuracy caused by historical effect .Core simulator of COSINE project (core and system integrated engine for design and analysis ) has developed a hybrid macroscopic-microscopic depletion model to track important isotopes during each depletion history and correct the macro cross sections .The basic theory was discussed in this paper . The effect and results of microscopic depletion correction were also analyzed .T he preliminary test results demonstrate that the microscopic depletion model is effective and practicable for improving the precision of core calculation .%微观燃耗是一种改善历史效应的常用技术之一，有利于提高全堆扩散计算精度，改善由于历史效应所造成的堆芯相关参数计算值与测量值的误差。堆芯物理热工与系统安全分析一体化软件包（COSINE软件包）堆芯分析程序引入微观燃耗计算模块，建立宏观-微观燃耗混合模型，实时跟踪每个燃料组件在运行历史中重要核素的核子密度，并实时修正宏观截面。本文介绍COSINE软件包堆芯分析程序为实现微观燃耗修正所采用的基本理论，分析核素跟踪和微观燃耗修正对全堆扩散计算精度的影响，同时给出引入微观燃耗修正前后的初步计算结果。初步的计算结果表明，微观燃耗修正模型对于提高计算精度是有效可行的。
Brouwer, Lucas Nathan
Advances in superconducting magnet technology have historically enabled the construction of new, higher energy hadron colliders. Looking forward to the needs of a potential future collider, a significant increase in magnet field and performance is required. Such a task requires an open mind to the investigation of new design concepts for high field magnets. Part I of this thesis will present an investigation of the Canted-Cosine-Theta (CCT) design for high field Nb3Sn magnets. New analytic and finite element methods for analysis of CCT magnets will be given, along with a discussion on optimization of the design for high field. The design, fabrication, and successful test of the 2.5 T NbTi dipole CCT1 will be presented as a proof-of-principle step towards a high field Nb3Sn magnet. Finally, the design and initial steps in the fabrication of the 16 T Nb3Sn dipole CCT2 will be described. Part II of this thesis will investigate the CCT concept extended to a curved magnet for use in an ion beam therapy gantry. The introduction of superconducting technology in this field shows promise to reduce the weight and cost of gantries, as well as open the door to new beam optics solutions with high energy acceptance. An analytic approach developed for modeling curved CCT magnets will be presented, followed by a design study of a superconducting magnet for a proton therapy gantry. Finally, a new magnet concept called the "Alternating Gradient CCT" (AG-CCT) will be introduced. This concept will be shown to be a practical magnet solution for achieving the alternating quadrupole fields desired for an achromatic gantry, allowing for the consideration of treatment with minimal field changes in the superconducting magnets. The primary motivation of this thesis is to share new developments for Canted-Cosine-Theta superconducting magnets, with the hope this design will improve technology for high energy physics and ion beam cancer therapy.
Directory of Open Access Journals (Sweden)
Robert M. Yamaleev
2013-01-01
Full Text Available The hyperbolic cosines and sines theorems for the curvilinear triangle bounded by circular arcs of three intersecting circles are formulated and proved by using the general complex calculus. The method is based on a key formula establishing a relationship between exponential function and the cross-ratio. The proofs are carried out on Euclidean plane.
DCT-Based Characterization of Milk Products Using Diffuse Reflectance Images
DEFF Research Database (Denmark)
Sharifzadeh, Sara; Skytte, Jacob Lercke; Clemmensen, Line Katrine Harder;
2013-01-01
We propose to use the two-dimensional Discrete Cosine Transform (DCT) for decomposition of diffuse reflectance images of laser illumination on milk products in different wavelengths. Based on the prior knowledge about the characteristics of the images, the initial feature vectors are formed at ea...
Pal, Arup Kumar
2017-01-01
Digital image watermarking has emerged as a promising solution for copyright protection. In this paper, a discrete cosine transform (DCT) and singular value decomposition (SVD) based hybrid robust image watermarking method using Arnold scrambling is proposed and simulated to protect the copyright of natural images. In this proposed scheme, before embedding, watermark is scrambled with Arnold scrambling. Then, the greyscale cover image and encrypted watermark logo are decomposed into non-overlapping blocks and subsequently some selected image blocks are transformed into the DCT domain for inserting the watermark blocks permanently. For better imperceptibility and effectiveness, in this proposed algorithm, watermark image blocks are embedded into singular values of selected blocks by multiplying with a feasible scaling factor. Simulation result demonstrates that robustness is achieved by recovering satisfactory watermark data from the reconstructed cover image after applying common geometric transformation attacks (such as rotation, flip operation, cropping, scaling, shearing and deletion of lines or columns operation), common enhancement technique attacks (such as low-pass filtering, histogram equalization, sharpening, gamma correction, noise addition) and jpeg compression attacks. PMID:28680684
Human motion tracking using mean shift clustering and discrete cosine transform
Islam, M. M.; Alam, M. S.
2007-04-01
Human motion tracking is an active area of research in computer vision and machine intelligence. It has many applications in video surveillance and human-computer interface. Most of the existing algorithms track multiple humans in a given image. This paper proposes a detection approach which can track a specific person from a crowded environment. Mean shift clustering algorithm is employed in the difference image to get the candidate cluster which is found to converge within few iterations. The number of clusters and the cluster centers are automatically derived by mode seeking with the mean shift procedure. Discrete cosine transform is applied to each cluster and to the known target to extract features of the clusters and the target. To get the target cluster from a given image, Mahalanobis distance is measured between each transformed candidate cluster and the target. The cluster with the minimum distance is taken as the desired target. Tracking is carried out by updating the cluster parameters over time using the mean shift procedure.
Spread spectrum image data hiding in the encrypted discrete cosine transform coefficients
Zhang, Xiaoqiang; Wang, Z. Jane
2013-10-01
Digital watermarking and data hiding are important tools for digital rights protection of media data. Spread spectrum (SS)-based watermarking and data-hiding approaches are popular due to their outstanding robustness, but their security might not be sufficient. To improve the security of SS, a SS-based image data-hiding approach is proposed by encrypting the discrete cosine transform coefficients of the host image with the piecewise linear chaotic map, before the operation of watermark embedding. To evaluate the performance of the proposed approach, simulations and analyses of its robustness and security are carried out. The average bit-error-rate values on 100 real images from the Berkeley segmentation dataset under the JPEG compression, additive Gaussian noise, salt and pepper noise, and cropping attacks are reported. Experimental results show that the proposed approach can maintain the high robustness of traditional SS schemes and, meanwhile, also improve the security. The proposed approach can extend the key space of traditional SS schemes from 10 to 10 and thus can resist brute-force attack and unauthorized detection watermark attack.
A New Audio Watermarking Method Based on Discrete Cosine Transform with a Gray Image
Directory of Open Access Journals (Sweden)
Mohammad Ibrahim Khan
2012-09-01
Full Text Available Many effective watermarking algorithms have been proposed and implemented for digital images anddigital video. However, a few algorithms have been proposed for audio watermarking. This is due to thefact that, human auditory system (HAS is far more complex and sensitive than human visual system (HVS.In this research work, a new method of embedding image data into the audio signal and additive audiowatermarking algorithm based on Discrete Cosine Transformation (DCT domain is proposed. First, theoriginal audio is transformed into DCT domain. The DCT coefficients are divided into a fixed number ofsubsections and the energy of each subsection is calculated. Next, watermark is generated from image byimage processing algorithm. Watermarks are then embedded into selected peaks of highest energysubsection. Experimental results demonstrate that the watermark is inaudible and this algorithm is robustto common operations of digital audio signal processing, such as noise addition, re-sampling, requantization and so on. To evaluate the performance of the proposed audio watermarking method,subjective and objective quality tests including Bit Error Rate (BER and Signal to Noise ratio (SNR areconducted.
Al-Mansoori, Saeed; Kunhu, Alavi
2013-10-01
This paper proposes a blind multi-watermarking scheme based on designing two back-to-back encoders. The first encoder is implemented to embed a robust watermark into remote sensing imagery by applying a Discrete Cosine Transform (DCT) approach. Such watermark is used in many applications to protect the copyright of the image. However, the second encoder embeds a fragile watermark using `SHA-1' hash function. The purpose behind embedding a fragile watermark is to prove the authenticity of the image (i.e. tamper-proof). Thus, the proposed technique was developed as a result of new challenges with piracy of remote sensing imagery ownership. This led researchers to look for different means to secure the ownership of satellite imagery and prevent the illegal use of these resources. Therefore, Emirates Institution for Advanced Science and Technology (EIAST) proposed utilizing existing data security concept by embedding a digital signature, "watermark", into DubaiSat-1 satellite imagery. In this study, DubaiSat-1 images with 2.5 meter resolution are used as a cover and a colored EIAST logo is used as a watermark. In order to evaluate the robustness of the proposed technique, a couple of attacks are applied such as JPEG compression, rotation and synchronization attacks. Furthermore, tampering attacks are applied to prove image authenticity.
Hermite-cosine-Gaussian laser beam and its propagation characteristics in turbulent atmosphere.
Eyyuboğlu, Halil Tanyer
2005-08-01
Hermite-cosine-Gaussian (HcosG) laser beams are studied. The source plane intensity of the HcosG beam is introduced and its dependence on the source parameters is examined. By application of the Fresnel diffraction integral, the average receiver intensity of HcosG beam is formulated for the case of propagation in turbulent atmosphere. The average receiver intensity is seen to reduce appropriately to various special cases. When traveling in turbulence, the HcosG beam initially experiences the merging of neighboring beam lobes, and then a TEM-type cosh-Gaussian beam is formed, temporarily leading to a plain cosh-Gaussian beam. Eventually a pure Gaussian beam results. The numerical evaluation of the normalized beam size along the propagation axis at selected mode indices indicates that relative spreading of higher-order HcosG beam modes is less than that of the lower-order counterparts. Consequently, it is possible at some propagation distances to capture more power by using higher-mode-indexed HcosG beams.
The Cosine Error: A Bayesian Procedure for Treating a Non-repetitive Systematic Effect
Directory of Open Access Journals (Sweden)
Lira Ignacio
2016-08-01
Full Text Available An inconsistency with respect to variable transformations in our previous treatment of the cosine error example with repositioning (Metrologia, vol. 47, pp. R1–R14 is pointed out. The problem refers to the measurement of the vertical height of a column of liquid in a manometer. A systematic effect arises because of the possible deviation of the measurement axis from the vertical, which may be different each time the measurement is taken. A revised procedure for treating this problem is proposed; it consists in straightforward application of Bayesian statistics using a conditional reference prior with partial information. In most practical applications, the numerical differences between the two procedures will be negligible, so the interest of the revised one is mainly of conceptual nature. Nevertheless, similar measurement models may appear in other contexts, for example, in intercomparisons, so the present investigation may serve as a warning to analysts against applying the same methodology we used in our original approach to the present problem.
ECG signal compression using combined modified discrete cosine and discrete wavelet transforms.
Ahmed, S M; Al-Ajlouni, A F; Abo-Zahhad, M; Harb, B
2009-01-01
A new hybrid two-stage electrocardiogram (ECG) signal compression method based on the modified discrete cosine transform (MDCT) and discrete wavelet transform (DWT) is proposed. The ECG signal is partitioned into blocks and the MDCT is applied to each block to decorrelate the spectral information. Then, the DWT is applied to the resulting MDCT coefficients. Removing spectral redundancy is achieved by compressing the subordinate components more than the dominant components. The resulting wavelet coefficients are then thresholded and compressed using energy packing and binary-significant map coding technique for storage space saving. Experiments on ECG records from the MIT-BIH database are performed with various combinations of MDCT and wavelet filters at different transformation levels, and quantization intervals. The decompressed signals are evaluated using percentage rms error (PRD) and zero-mean rms error (PRD(1)) measures. The results showed that the proposed method provides low bit-rate and high quality of the reconstructed signal. It offers average compression ratio (CR) of 21.5 and PRD of 5.89%, which would be suitable for most monitoring and diagnoses applications. Simulation results show that the proposed method compares favourably with various state-of-the-art ECG compressors.
Sanchetta, Alexandre Cruz; Leite, Emilson Pereira; Honório, Bruno César Zanardo
2013-08-01
We propose a preprocessing methodology for well-log geophysical data based on Fast Independent Component Analysis (FastICA) and Discrete Cosine Transform (DCT), in order to improve the success rate of the K-NN automatic classifier. The K-NN have been commonly applied to facies recognition in well-log geophysical data for hydrocarbon reservoir modeling and characterization. The preprocess was made in two different levels. In the first level, a FastICA based dimenstion reduction was applied, maintaining much of the information, and its results were classified; In second level, FastICA and DCT were applied in smoothing level, where the data points are modified, so individual points have their distance reduced, keeping just the primordial information. The results were compared to identify the best classification cases. We have applied the proposed methodology to well-log data from a petroleum field of Campos Basin, Brazil. Sonic, gamma-ray, density, neutron porosity and deep induction logs were preprocessed with FastICA and DCT, and the product was classified with K-NN. The success rates in recognition were calculated by appling the method to log intervals where core data were available. The results were compared to those of automatic recognition of the original well-log data set with and without the removal of high frequency noise. We conclude that the application of the proposed methodology significantly improves the success rate of facies recognition by K-NN.
AUTO-DARBOUX TRANSFORMATION AND EXACT SOLUTIONS OF THE BRUSSELATOR REACTION DIFFUSION MODEL
Institute of Scientific and Technical Information of China (English)
闫振亚; 张鸿庆
2001-01-01
Firstly, using the improved homogeneous balance method, an auto-Darboux transformation (ADT) for the Brusselator reaction diffusion model is found. Based on the ADT, several exact solutions are obtained which contain some authors' results known.Secondly, by using a series of transformations, the model is reduced into a nonlinear reaction diffusion equation and then through using sine- cosine method, more exact solutions are found which contain soliton solutions.
Kochiya, Yuko; Hirabayashi, Akari; Ichimaru, Yuhei
2017-09-16
To evaluate the dynamic nature of nocturnal heart rate variability, RR intervals recorded with a wearable heart rate sensor were analyzed using the Least Square Cosine Spectrum Method. Six 1-year-old infants participated in the study. A wearable heart rate sensor was placed on their chest to measure RR intervals and 3-axis acceleration. Heartbeat time series were analyzed for every 30 s using the Least Square Cosine Spectrum Method, and an original parameter to quantify the regularity of respiratory-related heart rate rhythm was extracted and referred to as "RA (RA-COSPEC: Respiratory Area obtained by COSPEC)." The RA value is higher when a cosine curve is fitted to the original data series. The time sequential changes of RA showed cyclic changes with significant rhythm during the night. The mean cycle length of RA was 70 ± 15 min, which is shorter than young adult's cycle in our previous study. At the threshold level of RA greater than 3, the HR was significantly decreased compared with the RA value less than 3. The regularity of heart rate rhythm showed dynamic changes during the night in 1-year-old infants. Significant decrease of HR at the time of higher RA suggests the increase of parasympathetic activity. We suspect that the higher RA reflects the regular respiratory pattern during the night. This analysis system may be useful for quantitative assessment of regularity and dynamic changes of nocturnal heart rate variability in infants.
Indian Academy of Sciences (India)
S C PRASANNA; S P JOY VASANTHA RANI
2016-10-01
This brief presents an efficient binary common subexpression elimination (BCSE)-based approach for designing reconfigurable interpolation root-raised cosine (RRC) finite-impulse-response (FIR) filter, whose coefficients change during runtime for multistandard wireless communication system called software-defined radio (SDR). Reconfiguration can be done conveniently by storing the coded coefficients in the lookup tables (LUTs), and loading the required coefficient set over the interpolation filter. In the proposed method based on 4-bit BCSE algorithm, first the number of binary common subexpressions (BCSs) formed in the coefficients is reduced. Hence, multiplexers, shifters, and adders in the multiplier structure are reduced, which results in theimprovement of operating frequency. The number of addition operations is further reduced using programmable adders and an efficient polyphase interpolation structure is implemented to reduce the hardware cost. The proposed design has 49.5% less area-delay product and 28.6% improved frequency of operation when comparedto a 2-bit BCSE-based technique reported earlier when implemented on Xilinx field-programmable gate array (FPGA) device XC2VP4FF672-6. Similarly, the proposed design supports 93.14 MHz operating frequency, which is 59.2% and 74.2% greater when compared to 2-bit BCSE- and 3-bit BCSE-based approach when implemented on XC2V3000FF1152-4. The proposed structure also shows improved performance in terms of speed and area when compared to distributed arithmetic (DA)-based and multiply-accumulate (MAC)-based approaches.
Directory of Open Access Journals (Sweden)
Ndour, A.
2017-01-01
Full Text Available Climate change and cotton production in Senegal: alternate dissemination strategies of varieties. Description of the subject. Climate change challenges the strategy of varietal diffusion, employed by the Senegalese cotton company (SODEFITEX, based on the distinction of two cultivars: one adapted to humid conditions and the other to drought. Based on data collected in an experimental station and farmer plots from 2004 to 2011, the study provides an assessment of that strategy. Objectives. The aim of the study was to evaluate both the methodology used for varietal selection and the performance of released and candidate cultivars, under contrasted water environments due to variability in rainfall (spatial and temporal and crop management. Method. The methodology used allowed the identification of the occurrence of severe water stress during the critical cotton development phases (flowering and boll development and its effect on seed cotton yield and fiber quality. The resulting indicator of plant water status was then inserted into our statistical analysis as an environmental covariate. Results. The resulting indicator allowed the discrimination of seed cotton yield in the experimental station as well as in on-farm experiments. Despite an effect of cultivar on ginning outturn and fiber quality, all cultivars showed similar resilience to water status. Conclusions. Despite a lack of cultivar adaptation to water stress, results support the adoption of a single cultivar in the whole production basin. However, the diffusion strategy would benefit from a better consideration of farmer cropping conditions, which would thus allow for the evaluation of cultivars by the producers.
Comparative analysis of isotropic diffusion weighted imaging sequences
Vellmer, Sebastian; Stirnberg, Rüdiger; Edelhoff, Daniel; Suter, Dieter; Stöcker, Tony; Maximov, Ivan I.
2017-02-01
Visualisation of living tissue structure and function is a challenging problem of modern imaging techniques. Diffusion MRI allows one to probe in vivo structures on a micrometer scale. However, conventional diffusion measurements are time-consuming procedures, because they require several measurements with different gradient directions. Considerable time savings are therefore possible by measurement schemes that generate an isotropic diffusion weighting in a single shot. Multiple approaches for generating isotropic diffusion weighting are known and have become very popular as useful tools in clinical research. Thus, there is a strong need for a comprehensive comparison of different isotropic weighting approaches. In the present work we introduce two new sequences based on simple (co)sine modulations and compare their performance to established q-space magic-angle spinning sequences and conventional DTI, using a diffusion phantom assembled from microcapillaries and in vivo experiments at 7 T. The advantages and disadvantages of all compared schemes are demonstrated and discussed.
Neuhaus-Steinmetz, Ulrich; Balzer, Ivonne; Hardeland, Rüdiger
1990-03-01
Although the geophysical periodicity of the earth's rotation corresponds to a biological cyclicity of ca. 24 h, cellular temporal organization comprises a multifrequency time structure, in which ultradian rhythms may be regarded as subelements of the circadian oscillator. In Euglena gracilis kept under conditons in which various cellular functions oscillate with a circadian period, tyrosine aminotransferase activity exhibited predominantly an ultradian cycle, whereas its circadian frequency was only weakly expressed. Ultradian period lengths were in the range of 4 5 h, as demonstrated by least squares fitting of cosines and of a non-sinusoidal regression function.
Digital Repository Service at National Institute of Oceanography (India)
Talaulika, M.; Suresh, T.; Desa, E.S.; Inamdar, A.
stream_size 42805 stream_content_type text/plain stream_name Limnol_Oceanogr-Meth_12_74a.pdf.txt stream_source_info Limnol_Oceanogr-Meth_12_74a.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 1... that influences the underwater average cosine includes sea surface conditions, the incident illumination at the sea surface, phase function of scattering (McCormick 1995), scattering (Berwald et al. 1995). Stramska et al. (2000) modeled μ (λ) in terms of Ed...
Someswara Rao, Chinta; Viswanadha Raju, S
2016-03-01
In this paper, we consider correlation coefficient, rank correlation coefficient and cosine similarity measures for evaluating similarity between Homo sapiens and monkeys. We used DNA chromosomes of genome wide genes to determine the correlation between the chromosomal content and evolutionary relationship. The similarity among the H. sapiens and monkeys is measured for a total of 210 chromosomes related to 10 species. The similarity measures of these different species show the relationship between the H. sapiens and monkey. This similarity will be helpful at theft identification, maternity identification, disease identification, etc.
Abousleman, Glen P.; Marcellin, Michael W.; Hunt, Bobby R.
1994-07-01
A system is presented for compression of hyperspectral imagery which utilizes trellis coded quantization (TCQ). Specifically, TCQ is used to encode transform coefficients resulting from the application of an 8X8X8 discrete cosine transform. Side information and rate allocation strategies are discussed. Entropy-constrained codebooks are designed using a modified version of the generalized Lloyd algorithm. This entropy constrained system achieves a compression ratio of greater than 70:1 with an average PSNR of the coded hyperspectral sequence exceeding 40.5 dB.
Directory of Open Access Journals (Sweden)
Rohit Jain, Rajshree Taparia
2012-12-01
Full Text Available This research paper deals with the implementation of face recognition system using neural network Importance of face recognition system has speed up in the last few decades. A face recognition system is one of the biometric information processing. The developed algorithm for the face recognition system formulates an image-based approach, which uses the Two-Dimensional Discrete Cosine Transform (2D-DCT for image compression and the Self- Organizing Map (SOM Neural Network for recognition purpose, simulated in MATLAB. By using 2D-DCT we extract image vectors and these vectors becomes the input to neural network classifier, which uses self-organizing map, algorithm to recognize familiar faces (trained and faces with variations in expressions, illumination changes, tilt of 5 to 10 degrees. Again face Recognition system is developed with principal component analysis (PCA instead of Two Dimensional Discrete Cosine Transform (2D-DCT and self-Organizing Map (SOM Neural Network for recognition purpose. The crux of proposed algorithm is its beauty to use unsupervised single neural network as classifier.
Hu, Xiaohong; Liu, Yuanshan; Xu, Xin; Feng, Ye; Zhang, Wenfu; Wang, Weiqiang; Song, Jiazheng; Wang, Yishan; Zhao, Wei
2015-10-10
Based on the normalized spatiotemporal Lugiato-Lefever equation, the evolutions of cosine-modulated stationary fields relating to the generation of single-free spectral range (FSR) or multi-FSR Kerr frequency combs in a microresonator with anomalous dispersion are studied numerically. The research results show that a single-FSR comb arises when a dissipative soliton pulse or multiple nonequidistant soliton pulses form in the cavity. Compared with the smooth and regular spectral structure of a single soliton pulse, the comb corresponding to the uneven distribution of multiple soliton pulses exhibits a complex and irregular profile. When the stable intracavity field consists of a "roll" Turing pattern or N(N>1) evenly distributed soliton pulses separated by 2π/N, multi-FSR combs can be generated. In the case of the "roll" Turing pattern solution, it is found that third-order dispersion could modify the comb mode spacing and decrease the intensity of high-order comb modes. For the situation of multiple soliton pulse generation, the simulation results indicate that both the number and locations of the soliton pulses can be actively controlled through the careful selection of modulation frequency. In addition, for the selected cosine-modulated initial field profile, only those modes with the mode numbers being equal to an integer multiple of N can be greatly amplified by the parametric gain during propagation in the microresonator. This process eventually leads to the formation of a N-FSR frequency comb.
Near-wall diffusion tensor of an axisymmetric colloidal particle
Lisicki, Maciej; Wajnryb, Eligiusz
2016-01-01
Hydrodynamic interactions with confining boundaries often lead to drastic changes in the diffusive behaviour of microparticles in suspensions. For axially symmetric particles, earlier numerical studies have suggested a simple form of the near-wall diffusion matrix which depends on the distance and orientation of the particle with respect to the wall, which is usually calculated numerically. In this work, we derive explicit analytical formulae for the dominant correction to the bulk diffusion tensor of an axially symmetric colloidal particle due to the presence of a nearby no-slip wall. The relative correction scales as powers of inverse wall-particle distance and its angular structure is represented by simple polynomials in sines and cosines of the particle's inclination angle to the wall. We analyse the correction for translational and rotational motion, as well as the translation-rotation coupling. Our findings provide a simple approximation to the anisotropic diffusion tensor near a wall, which completes a...
Amemiya, Naoyuki; Miyahara, Hidetoshi; Ogitsu, Toru; Kurusu, Tsutomu
By using differential geometry, we modeled the three-dimensional shapes of the coil ends of cosine-theta magnets while considering local edge-wise bend, local flat-wise bend, and torsion of coated conductors. We focus on the feasibility of winding coil ends against the stress caused by bending. We discussed the feasibility of winding based on two assumptions to form coil ends: all turns of coated conductors are free from edge-wise bend; faces of all turns of coated conductors are completely parallel. Using the first assumption, we designed a cosine-theta dipole magnet wound with coated conductors.
Directory of Open Access Journals (Sweden)
Bieda Robert
2016-06-01
Full Text Available This paper describes a method which determines the parameters of an object orientation in 3D space. The rotation angles calculation bases on the signals fusion obtained from the inertial measurement unit (IMU. The IMU measuring system provides information from a linear acceleration sensors (accelerometers, the Earth’s magnetic field sensors (magnetometers and the angular velocity sensors (gyroscopes. Information about the object orientation is presented in the form of direction cosine matrix whose elements are observed in the state vector of the non-stationary Kalman filter. The vector components allow to determine the rotation angles (roll, pitch and yaw associated with the object. The resulting waveforms, for different rotation angles, have no negative attributes associated with the construction and operation of the IMU measuring system. The described solution enables simple, fast and effective implementation of the proposed method in the IMU measuring systems.
Pan, Sung B.; Park, Rae-Hong
1997-12-01
A two-dimensional (2-D) very large scale integration (VLSI) architecture using a unified systolic array for fast computation of the discrete cosine transform (DCT), the discrete sine transform (DST), and the discrete Hartley transform (DHT) is proposed. The N-point discrete transform is decomposed into even- and odd-numbered frequency samples and they are computed independently at the same time. The proposed unified systolic array architecture can compute the DCT, the DST, and the DHT by defining different coefficient values specific for each transform. We also present another architecture for computation of the DHT, a modified version of the unified systolic array structure, which is faster than the unified architecture by a factor of 2. In addition, the proposed unified architecture can be employed for computation of the inverse DCT (IDCT), the inverse DST (IDST), and the inverse DHT (IDHT) with some modifications.
Diffuse sound field: challenges and misconceptions
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2016-01-01
incident intensity distribution (directional diffusion or isotropy). In practice, reverberation chambers are assumed to be acoustically diffuse, and important acoustic quantities measured in there, i.e., sound absorption, scattering, transmission, and power, etc. However, the measured quantities vary...
Zhang, B.; Van der Weide, J.A.M.; Oosterlee, C.W.
2012-01-01
In this article, we propose an efficient pricing method for Asian options with early–exercise features. It is based on a two–dimensional integration and a backward recursion of the Fourier coefficients, in which several numerical techniques, like Fourier cosine expansions, Clenshaw–Curtis quadrature
Zhang, B.; Van der Weide, J.A.M.; Oosterlee, C.W.
2012-01-01
In this article, we propose an efficient pricing method for Asian options with early–exercise features. It is based on a two–dimensional integration and a backward recursion of the Fourier coefficients, in which several numerical techniques, like Fourier cosine expansions, Clenshaw–Curtis quadrature
Fukuyama, Hidenao
Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.
Fluorosis varied treatment options
Sherwood I
2010-01-01
Fluorosis has been reported way back in 1901. The treatment options for fluorosis are varied depending upon individual cases. This article comes from Madurai in India where its surrounding towns are fluorosis-prone zones. The purpose of this article is to report various treatment options available for dental fluorosis; this is the first time that complete full mouth rehabilitation for dental fluorosis is being reported. This article also dwells on the need for the dentists to be aware of thei...
On the Symmetry of Molecular Flows Through the Pipe of an Arbitrary Shape (I) Diffusive Reflection
Kusumoto, Yoshiro
Molecular gas flows through the pipe of an arbitrary shape is mathematically considered based on a diffusive reflection model. To avoid a perpetual motion, the magnitude of the molecular flow rate must remain invariant under the exchange of inlet and outlet pressures. For this flow symmetry, the cosine law reflection at the pipe wall was found to be sufficient and necessary, on the assumption that the molecular flux is conserved in a collision with the wall. It was also shown that a spontaneous flow occurs in a hemispherical apparatus, if the reflection obeys the n-th power of cosine law with n other than unity. This apparatus could work as a molecular pump with no moving parts.
Alqudami, Nasser; Kim, Shin-Dug
2014-11-01
Discrete cosine transform (DCT) is one of the major operations in image compression standards and it requires intensive and complex computations. Recent computer systems and handheld devices are equipped with high computing capability devices such as a general-purpose graphics processing unit (GPGPU) in addition to the traditional multicores CPU. We develop an optimized parallel implementation of the forward DCT algorithm for the JPEG image compression using the recently proposed Open Computing Language (OpenCL). This OpenCL parallel implementation combines a multicore CPU and a GPGPU in a single solution to perform DCT computations in an efficient manner by applying certain optimization techniques to enhance the kernel execution time and data movements. A separate optimal OpenCL kernel code was developed (CPU-based and GPU-based kernels) based on certain appropriate device-based optimization factors, such as thread-mapping, thread granularity, vector-based memory access, and the given workload. The performance of DCT is evaluated on a heterogeneous environment and our OpenCL parallel implementation results in speeding up the execution of the DCT by the factors of 3.68 and 5.58 for different image sizes and formats in terms of workload allocations and data transfer mechanisms. The obtained speedup indicates the scalability of the DCT performance.
Energy Technology Data Exchange (ETDEWEB)
Modesto-Costa, Lucas; Canuto, Sylvio [Instituto de Física, Universidade de São Paulo, CP 66318, 05314-970 São Paulo (Brazil); Mukherjee, Prasanta K., E-mail: profpkmukherjee@gmail.com [Department of Physics, Ramakrishna Mission Vivekananda University, P.O. Belur Math, Howrah, West Bengal 711202 (India)
2015-03-15
A detailed investigation of the magnetic dipolar and quadrupolar excitation energies and transition probabilities of helium isoelectronic He, Be{sup 2+}, C{sup 4+}, and O{sup 6+} have been performed under exponential cosine screened Coulomb potential generated in a plasma environment. The low-lying excited states 1s{sup 2}:{sup 1}S{sup e} → 1sns:{sup 3}S{sup e}{sub 0}, and 1snp:{sup 3}P{sup o}{sub 2} (n = 2, 3, 4, and 5) are considered. The variational time-dependent coupled Hartree-Fock scheme has been used. The effect of the confinement produced by the potential on the structural properties is investigated for increasing coupling strength of the plasma. It is noted that there is a gradual destabilization of the energy of the system with the reduction of the ionization potential and the number of excited states. The effect of the screening enhancement on the excitation energies and transition probabilities has also been investigated and the results compared with those available for the free systems and under the simple screened Coulomb potential.
Shih, Cheng-Ting; Wu, Jay; Lin, Hsin-Hon; Chang, Shu-Jun; Chuang, Keh-Shih
2014-08-01
Several positron emission tomography (PET) scanners with special detector block arrangements have been developed in recent years to improve the resolution of PET images. However, the discontinuous detector blocks cause gaps in the sinogram. This study proposes an adaptive discrete cosine transform-based (aDCT) filter for gap-inpainting. The gap-corrupted sinogram was morphologically closed and subsequently converted to the DCT domain. A certain number of the largest coefficients in the DCT spectrum were identified to determine the low-frequency preservation region. The weighting factors for the remaining coefficients were determined by an exponential weighting function. The aDCT filter was constructed and applied to two digital phantoms and a simulated phantom introduced with various levels of noise. For the Shepp-Logan head phantom, the aDCT filter filled the gaps effectively. For the Jaszczak phantom, no secondary artifacts were induced after aDCT filtering. The percent mean square error and mean structure similarity of the aDCT filter were superior to those of the DCT2 filter at all noise levels. For the simulated striatal dopamine innervation study, the aDCT filter recovered the shape of the striatum and restored the striatum to reference activity ratios to the ideal value. The proposed aDCT filter can recover the missing gap data in the sinogram and improve the image quality and quantitative accuracy of PET images.
Wang, Lu; Xu, Lisheng; Zhao, Dazhe; Yao, Yang; Song, Dan
2015-04-01
Because arterial pulse waves contain vital information related to the condition of the cardiovascular system, considerable attention has been devoted to the study of pulse waves in recent years. Accurate acquisition is essential to investigate arterial pulse waves. However, at the stage of developing equipment for acquiring and analyzing arterial pulse waves, specific pulse signals may be unavailable for debugging and evaluating the system under development. To produce test signals that reflect specific physiological conditions, in this paper, an arterial pulse wave generator has been designed and implemented using a field programmable gate array (FPGA), which can produce the desired pulse waves according to the feature points set by users. To reconstruct a periodic pulse wave from the given feature points, a method known as piecewise Gaussian-cosine fitting is also proposed in this paper. Using a test database that contains four types of typical pulse waves with each type containing 25 pulse wave signals, the maximum residual error of each sampling point of the fitted pulse wave in comparison with the real pulse wave is within 8%. In addition, the function for adding baseline drift and three types of noises is integrated into the developed system because the baseline occasionally wanders, and noise needs to be added for testing the performance of the designed circuits and the analysis algorithms. The proposed arterial pulse wave generator can be considered as a special signal generator with a simple structure, low cost and compact size, which can also provide flexible solutions for many other related research purposes.
Jenkins, Steven T.; Hilkert, J. M.
2008-04-01
Pointing and tracking applications usually require relative gimbal angles to be measured for reporting and controlling the line-of-sight angular position. Depending on the application, angular resolution and/or accuracy might jointly or independently determine the angle transducer requirements. In the past decade, encoders have been increasingly taking the place of inductive devices where the measurement of angles over a wide range is required. This is primarily due to the fact that encoders are now achieving very high resolution in smaller sizes than was previously possible. These advances in resolution are primarily due to improved encoder disk and detector technology along with developments in interpolation techniques. Measurement accuracy, on the other hand, is primarily determined by mounting and bearing eccentricity as it is with all angular measurement devices. For very demanding accuracy requirements, some type of calibration of the assembled system may be the only solution, in which case transducer repeatability is paramount. This paper describes a unique encoder-to-digital tracking converter concept for improving interpolation of optical encoders. The new method relies on Fraunhofer diffraction models to correct the non-ideal sin/cos outputs of the encoder detectors. Diffraction model concepts are used in the interpolation filters to predict the phase of non-ideal sin and cosine encoder outputs. The new method also minimizes many of the open loop pre-processing requirements and assumptions that limit interpolation accuracy and rate loop noise performance in ratiometric tracking converter designs.
Schullcke, Benjamin; Gong, Bo; Krueger-Ziolek, Sabine; Soleimani, Manuchehr; Mueller-Lisse, Ullrich; Moeller, Knut
2016-05-01
Lung EIT is a functional imaging method that utilizes electrical currents to reconstruct images of conductivity changes inside the thorax. This technique is radiation free and applicable at the bedside, but lacks of spatial resolution compared to morphological imaging methods such as X-ray computed tomography (CT). In this article we describe an approach for EIT image reconstruction using morphologic information obtained from other structural imaging modalities. This leads to recon- structed images of lung ventilation that can easily be superimposed with structural CT or MRI images, which facilitates image interpretation. The approach is based on a Discrete Cosine Transformation (DCT) of an image of the considered transversal thorax slice. The use of DCT enables reduction of the dimensionality of the reconstruction and ensures that only conductivity changes of the lungs are reconstructed and displayed. The DCT based approach is well suited to fuse morphological image information with functional lung imaging at low computational costs. Results on simulated data indicate that this approach preserves the morphological structures of the lungs and avoids blurring of the solution. Images from patient measurements reveal the capabilities of the method and demonstrate benefits in possible applications.
Directory of Open Access Journals (Sweden)
Lei Lei
2016-01-01
Full Text Available An important application of speaker recognition is forensics. However, the accuracy of speaker recognition in forensic cases often drops off rapidly because of the ill effect of ambient noise, variable channel, different duration of speech data, and so on. Therefore, finding a robust speaker recognition model is very important for forensics. This paper builds a new speaker recognition model based on wavelet cepstral coefficient (WCC, i-vector, and cosine distance scoring (CDS. This model firstly uses the WCC to transform the speech into spectral feature vecors and then uses those spectral feature vectors to train the i-vectors that represent the speeches having different durations. CDS is used to compare the i-vectors to give out the evidence. Moreover, linear discriminant analysis (LDA and the within-class covariance normalization (WCNN are added to the CDS algorithm to deal with the channel variability problem. Finally, the likelihood ratio estimates the strength of the evidence. We use the TIMIT database to evaluate the performance of the proposed model. The experimental results show that the proposed model can effectively solve the troubles of forensic scenario, but the time cost of the method is high.
Energy Technology Data Exchange (ETDEWEB)
Shih, Cheng-Ting; Lin, Hsin-Hon; Chuang, Keh-Shih [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Wu, Jay, E-mail: jwu@mail.cmu.edu.tw [Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung 40402, Taiwan (China); Chang, Shu-Jun [Health Physics Division, Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan 32546, Taiwan (China)
2014-08-15
Purpose: Several positron emission tomography (PET) scanners with special detector block arrangements have been developed in recent years to improve the resolution of PET images. However, the discontinuous detector blocks cause gaps in the sinogram. This study proposes an adaptive discrete cosine transform-based (aDCT) filter for gap-inpainting. Methods: The gap-corrupted sinogram was morphologically closed and subsequently converted to the DCT domain. A certain number of the largest coefficients in the DCT spectrum were identified to determine the low-frequency preservation region. The weighting factors for the remaining coefficients were determined by an exponential weighting function. The aDCT filter was constructed and applied to two digital phantoms and a simulated phantom introduced with various levels of noise. Results: For the Shepp-Logan head phantom, the aDCT filter filled the gaps effectively. For the Jaszczak phantom, no secondary artifacts were induced after aDCT filtering. The percent mean square error and mean structure similarity of the aDCT filter were superior to those of the DCT2 filter at all noise levels. For the simulated striatal dopamine innervation study, the aDCT filter recovered the shape of the striatum and restored the striatum to reference activity ratios to the ideal value. Conclusions: The proposed aDCT filter can recover the missing gap data in the sinogram and improve the image quality and quantitative accuracy of PET images.
Fluorosis varied treatment options
Directory of Open Access Journals (Sweden)
Sherwood I
2010-01-01
Full Text Available Fluorosis has been reported way back in 1901. The treatment options for fluorosis are varied depending upon individual cases. This article comes from Madurai in India where its surrounding towns are fluorosis-prone zones. The purpose of this article is to report various treatment options available for dental fluorosis; this is the first time that complete full mouth rehabilitation for dental fluorosis is being reported. This article also dwells on the need for the dentists to be aware of their local indigenous pathologies to treat it in a better manner.
Advanced manufacturing: Technology diffusion
Energy Technology Data Exchange (ETDEWEB)
Tesar, A.
1995-12-01
In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.
Helium diffusion in carbonates
Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.
2013-12-01
The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion
The Closed Form on a Kind of Log-cosine and Log-sine Integral%一类log-cosine和log-sine积分的闭形式
Institute of Scientific and Technical Information of China (English)
商妮娜; 秦惠增
2012-01-01
We consider some recursion formulas for the partial derivative of Beta function. Using these recursion formulas, we give the closed form of the log-cosine and log-sine integral.%考虑了Beta函数偏导数的递推公式的表示问题.利用Beta函数偏导数的递推公式,给出一类log-cosine和log-sine积分的闭形式.
Yin, SS; Chan, SC; Tsui, KM; Xie, XM
2008-01-01
This paper studies the theory and design of a class of perfect reconstruction (PR) uniform causal-stable infinite-impulse response (IIR) cosine modulated filter banks (CMFBs). The design approach is also applicable to the design of PR recombination nonuniform (RN) IIR CMFBs. The polyphase components of the prototype filters of these IIR CMFBs are assumed to have the same denominator so as to simplify the PR condition. In designing the proposed IIR CMFB, a PR FIR CMFB with similar specificatio...
级联COSINE滤波器在抽取滤波中的研究%Research on cascaded COSINE filter in decimation filter
Institute of Scientific and Technical Information of China (English)
刘俊
2011-01-01
In order to solve the problem that side lobe suppression of traditional Cascaded Integrator Comb (CIC) filter is not enough in high-speed decimation filter system ,this paper compares cascade COSINE decimation filter and principle derivation of conventional CIC decimation filter,and analyses that cascade COSINE filter has great similarities with CIC filter on the frequency characteristics,along with a good low-pass characteristics and the implementation of hardware,meeting the case of high-speed decimation filter. According to the simulation by MATLAB,it can obtain that during taken the 32-fold integer,the first side lobe attenuation of cascade COSINE filter is about 2 times that of traditional CIC filter. That means,cascade COSINE filter has better side lobe suppression than that of conventional CIC filter.%为了解决高速抽取滤波器系统中传统CIC滤波器旁瓣抑制不够的问题,通过对级联COSINE抽取滤波器和传统CIC抽取滤波器的原理推导进行对比,分析出级联COSINE滤波器在幅频特性上同CIC滤波器具有很大相似之处,且在满足高速抽取滤波器的情况下,同时具备很好的低通特性和硬件实现性.通过MATLAB仿真实验得到,级联COSINE滤波器在进行32倍整数抽取时,第一旁瓣衰减约是传统CIC滤波器的2倍,进而说明相对于传统CIC滤波器,级联COSINE滤波器具有更好的旁瓣抑制性能.
Chadha, Aman; Bhatia, M G
2011-01-01
This paper describes the design and simulation of an 8-bit dedicated processor for calculating the Sine and Cosine of an Angle using CORDIC Algorithm (COordinate Rotation DIgital Computer), a simple and efficient algorithm to calculate hyperbolic and trigonometric functions. We have proposed a dedicated processor system, modeled by writing appropriate programs in VHDL, for calculating the Sine and Cosine of an angle. System simulation was carried out using ModelSim 6.3f and Xilinx ISE Design Suite 12.3. A maximum frequency of 81.353 MHz was reached with a minimum period of 12.292 ns. 126 (3%) slices were used. This paper attempts to survey the existing CORDIC algorithm with an eye towards implementation in Field Programmable Gate Arrays (FPGAs). A brief description of the theory behind the algorithm and the derivation of the Sine and Cosine of an angle using the CORDIC algorithm has been presented. The system can be implemented using Spartan3 XC3S400 with Xilinx ISE 12.3 and VHDL.
Echterhoff, J.; Simonis, I.; Atkinson, R.
2012-04-01
The infrastructure to gather, store and access information about our environment is improving and growing rapidly. The increasing amount of information allows us to get a better understanding of the current state of our environment, historical processes and to simulate and predict the future state of the environment. Finer grained spatial and temporal data and more reliable communications make it easier to model dynamic states and ephemeral features. The exchange of information within and across geospatial domains is facilitated through the use of harmonized information models. The Observations & Measurements (O&M) developed through OGC and standardised by ISO is an example of such a cross-domain information model. It is used in many domains, including meteorology, hydrology as well as the emergency management. O&M enables harmonized representation of common metadata that belong to the act of determining the state of a feature property, whether by sensors, simulations or humans. In addition to the resulting feature property value, information such as the result quality but especially the time that the result applies to the feature property can be represented. Temporal metadata is critical to modelling past and future states of a feature. The features, and the semantics of each property, are defined in domain specific Application Schema using the General Feature Model (GFM) from ISO 19109 and usually encoded following ISO 19136. However, at the moment these standards provide only limited support for the representation and handling of time varying feature data. Features like rivers, wildfires or gas plumes have a defined state - for example geographic extent - at any given point in time. To keep track of changes, a more complex model for example using time-series coverages is required. Furthermore, the representation and management of feature property value changes via the service interfaces defined by OGC and ISO - namely: WFS and WCS - would be rather complex
Senoo, Y.
The influence of vaneless diffusers on flow in centrifugal compressors, particularly on surge, is discussed. A vaneless diffuser can demonstrate stable operation in a wide flow range only if it is installed with a backward leaning blade impeller. The circumferential distortion of flow in the impeller disappears quickly in the vaneless diffuser. The axial distortion of flow at the diffuser inlet does not decay easily. In large specific speed compressors, flow out of the impeller is distorted axially. Pressure recovery of diffusers at distorted inlet flow is considerably improved by half guide vanes. The best height of the vanes is a little 1/2 diffuser width. In small specific speed compressors, flow out of the impeller is not much distorted and pressure recovery can be predicted with one-dimensional flow analysis. Wall friction loss is significant in narrow diffusers. The large pressure drop at a small flow rate can cause the positive gradient of the pressure-flow rate characteristic curve, which may cause surging.
varying elastic parameters distributions
Moussawi, Ali
2014-12-01
The experimental identication of mechanical properties is crucial in mechanics for understanding material behavior and for the development of numerical models. Classical identi cation procedures employ standard shaped specimens, assume that the mechanical elds in the object are homogeneous, and recover global properties. Thus, multiple tests are required for full characterization of a heterogeneous object, leading to a time consuming and costly process. The development of non-contact, full- eld measurement techniques from which complex kinematic elds can be recorded has opened the door to a new way of thinking. From the identi cation point of view, suitable methods can be used to process these complex kinematic elds in order to recover multiple spatially varying parameters through one test or a few tests. The requirement is the development of identi cation techniques that can process these complex experimental data. This thesis introduces a novel identi cation technique called the constitutive compatibility method. The key idea is to de ne stresses as compatible with the observed kinematic eld through the chosen class of constitutive equation, making possible the uncoupling of the identi cation of stress from the identi cation of the material parameters. This uncoupling leads to parametrized solutions in cases where 5 the solution is non-unique (due to unknown traction boundary conditions) as demonstrated on 2D numerical examples. First the theory is outlined and the method is demonstrated in 2D applications. Second, the method is implemented within a domain decomposition framework in order to reduce the cost for processing very large problems. Finally, it is extended to 3D numerical examples. Promising results are shown for 2D and 3D problems.
Steerable Discrete Cosine Transform
Magli, Enrico; Fracastoro, Giulia
2015-01-01
Block-based separable transforms tend to be inefficient when blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, designing a new transform that can be steered in any chosen direction and that is defined in a rigorous mathematical way. This new steerable DCT allows to rotate in a flexible way pairs of basis vectors, enabling precise matching o...
Sodium diffusion in boroaluminosilicate glasses
DEFF Research Database (Denmark)
Smedskjaer, Morten M.; Zheng, Qiuju; Mauro, John C.
2011-01-01
of isothermal sodium diffusion in BAS glasses by ion exchange, inward diffusion, and tracer diffusion experiments. By varying the [SiO2]/[Al2O3] ratio of the glasses, different structural regimes of sodium behavior are accessed. We show that the mobility of the sodium ions decreases with increasing [SiO2]/[Al2O......3] ratio, revealing that sodium is more mobile when it acts as a charge compensator to stabilize network formers than when it acts as a creator of non-bridging oxygens on tetrahedrally-coordinated silicon and trigonal boron. The impacts of both the addition of iron and its redox state on the sodium...... be attributed to the fact that for sodium inward diffusion, the charge compensation for electron holes is a rather slow process that limits the rate of diffusion. (C) 2011 Elsevier B.V. All rights reserved....
Energy Technology Data Exchange (ETDEWEB)
Kostorz, G. [Eidgenoessische Technische Hochschule, Angewandte Physik, Zurich (Switzerland)
1996-12-31
While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs.
Lee, Sungman; Kim, Jongyul; Moon, Myung Kook; Lee, Kye Hong; Lee, Seung Wook; Ino, Takashi; Skoy, Vadim R.; Lee, Manwoo; Kim, Guinyun
2013-02-01
For use as a neutron spin polarizer or analyzer in the neutron beam lines of the HANARO (High-flux Advanced Neutron Application ReactOr) nuclear research reactor, a 3He polarizer was designed based on both a compact solenoid coil and a VBG (volume Bragg grating) diode laser with a narrow spectral linewidth of 25 GHz. The nuclear magnetic resonance (NMR) signal was measured and analyzed using both a built-in cosine radio-frequency (RF) coil and a pick-up coil. Using a neutron transmission measurement, we estimated the polarization ratio of the 3He cell as 18% for an optical pumping time of 8 hours.
Haba, Z
2009-02-01
We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.
A sensor node lossless compression algorithm for non-slowly varying data based on DMD transform
Ren, Xuejun; Liu, Jianping
2013-03-01
Efficient utilization of energy is a core area of research in wireless sensor networks. Data compression methods to reduce the number of bits to be transmitted by the communication module will significantly reduce the energy requirement and increase the lifetime of the sensor node. Based on the lifting scheme 2-point discrete cosine transform (DCT), this paper proposed a new reversible recursive algorithm named Difference-Median-Difference (DMD) transform for lossless data compression in sensor node. The DMD transform can significantly reduce the spatio-temporal correlations among sensor data and can smoothly run in resource limited sensor nodes. Through an entropy encoder, the results of DMD transform can be compressed more compactly based on their statistical characteristics to achieve compression. Compared with the typical lossless algorithms, the proposed algorithm indicated better compression ratios than others for non-slowly-varying data, despite a less computational effort.
Zhang, Yushu; Xiao, Di; Wen, Wenying; Tian, Yuan
2013-12-01
In some special multimedia applications, only the regions with semantic information should be provided better protection whereas the other smooth regions can be free of encryption. However, most of the existing multimedia security schemes only consider bits and pixels rather than semantic information during their encryption. Motivated by this, we propose an edge-based lightweight image encryption scheme using chaos-based reversible hidden transform and multiple-order discrete fractional cosine transform. An image is first carried out by the edge detection based on advanced CNN structure with adaptive thresholds to assess data significance in the image. The detection output is a binary image, in which a “1” reflects the detected pixel whereas a “0” is opposite. Both the detected image and the original image are divided into non-overlapping pixel blocks in the same way, respectively. Whether each block is encrypted or not depends on the significance judged by the corresponding detected block. The significant block is performed by reversible hidden transform followed by multiple-order discrete fractional cosine transform parameters and orders of these two transforms are determined by a two dimensional cross chaotic map. Experiment results show the significant contour features of an image that have been largely hidden only by encrypting about half pixels in the average sense. The keys are extremely sensitive and the proposed scheme can resist noise attack to some extent.
余弦齿轮的加工方法及其仿真研究%Research on Generation and Process Simulation of Cosine Gear
Institute of Scientific and Technical Information of China (English)
徐攀; 罗善明; 王建; 赵红斌
2011-01-01
A new method of two step machining method for the cosine gear is introducted paper, and the mathematical model of two - step machining method is established.First, the tool path of two - step machining method is verified by using Matlab, and the coordinates of tooth profile curve are collected via tool enveloping method, and then solid model of arbitrary tool profile is created with Pro/E.last, the simulation of NC milling on 3 - axis NC milling machine is carried out.By manufacturing a cosine gear, correctness of the simulation results (obtained by the software Matlab and Pro/E) and feasibility of the machining process are proved.%介绍了一种余弦齿轮滚铣两步加工新方法,建立了余弦齿轮滚铣两步加工的数学模型.在此基础上,利用Matlab验证了滚铣两步加工刀具轨迹,并通过采集刀具包络生成的齿廓曲线坐标,创建了余弦齿轮的实体模型,最后进行了三轴数控铣削仿真,并成功加工了余弦齿轮,验证了模型的正确性和加工方法的可行性.
Liang, Lili; Liu, Han
2013-12-01
Dual-tree transforms have recently received much attention for the properties of shift-invariance and directional-selectivity. However, their designs generally encounter fractional-delay constraints, and become more complicated for providing linear-phase (LP) individual filters and flexible directional-selectivity, two important properties in image processing. In this paper, we propose an alternative shift-invariant and directional-selective transform-the dual-tree cosine-modulated filter bank (DTCMFB). In the proposed DTCMFB, its primal and dual filter banks are derived by cosine-modulating one LP prototype filter, and thus its design involves no fractional-delay constraints. Meanwhile, the derived modulation technique guarantees each individual filter to be LP and the LP condition is satisfied without any constraint on the prototype filter. By separable operations, the DTCMFB is extended to two-dimensions. The resulting 2D DTCMFB can provide much more flexible directional-selectivity. Finally, several simulations are given to verify the proposed DTCMFB, and the experiments on nonlinear approximation and image denoising are presented to demonstrate its potential in image processing.
Bouncing universes with varying constants
Energy Technology Data Exchange (ETDEWEB)
Barrow, John D [DAMTP, Centre for Mathematical Sciences, Cambridge University, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Kimberly, Dagny [Theoretical Physics, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2BZ (United Kingdom); Magueijo, Joao [Theoretical Physics, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2BZ (United Kingdom)
2004-09-21
We investigate the behaviour of exact closed bouncing Friedmann universes in theories with varying constants. We show that the simplest BSBM varying alpha theory leads to a bouncing universe. The value of alpha increases monotonically, remaining approximately constant during most of each cycle, but increasing significantly around each bounce. When dissipation is introduced we show that in each new cycle the universe expands for longer and to a larger size. We find a similar effect for closed bouncing universes in Brans-Dicke theory, where G also varies monotonically in time from cycle to cycle. Similar behaviour occurs also in varying speed of light theories.
Bouncing Universes with Varying Constants
Barrow, J D; Magueijo, J; Barrow, John D.; Kimberly, Dagny; Magueijo, Joao
2004-01-01
We investigate the behaviour of exact closed bouncing Friedmann universes in theories with varying constants. We show that the simplest BSBM varying-alpha theory leads to a bouncing universe. The value of alpha increases monotonically, remaining approximately constant during most of each cycle, but increasing significantly around each bounce. When dissipation is introduced we show that in each new cycle the universe expands for longer and to a larger size. We find a similar effect for closed bouncing universes in Brans-Dicke theory, where $G$ also varies monotonically in time from cycle to cycle. Similar behaviour occurs also in varying speed of light theories.
Near-wall diffusion tensor of an axisymmetric colloidal particle
Lisicki, Maciej; Cichocki, Bogdan; Wajnryb, Eligiusz
2016-07-01
Hydrodynamic interactions with confining boundaries often lead to drastic changes in the diffusive behaviour of microparticles in suspensions. For axially symmetric particles, earlier numerical studies have suggested a simple form of the near-wall diffusion matrix which depends on the distance and orientation of the particle with respect to the wall, which is usually calculated numerically. In this work, we derive explicit analytical formulae for the dominant correction to the bulk diffusion tensor of an axially symmetric colloidal particle due to the presence of a nearby no-slip wall. The relative correction scales as powers of inverse wall-particle distance and its angular structure is represented by simple functions in sines and cosines of the particle's inclination angle to the wall. We analyse the correction for translational and rotational motion, as well as the translation-rotation coupling. Our findings provide a simple approximation to the anisotropic diffusion tensor near a wall, which completes and corrects relations known from earlier numerical and theoretical findings.
Hereditary Diffuse Gastric Cancer
... Hereditary Diffuse Gastric Cancer Request Permissions Hereditary Diffuse Gastric Cancer Approved by the Cancer.Net Editorial Board , 11/2015 What is hereditary diffuse gastric cancer? Hereditary diffuse gastric cancer (HDGC) is an inherited ...
Diffusion coefficient in photon diffusion theory
Graaff, R; Ten Bosch, JJ
2000-01-01
The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to
Diffusion coefficient in photon diffusion theory
Graaff, R; Ten Bosch, JJ
2000-01-01
The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to
Effect of diffuser width on rotating stall in centrifugal blower with vaneless diffuser
Energy Technology Data Exchange (ETDEWEB)
Kim, J.H. [Small and Medium Industry Promotion Corporation (Korea); Cho, K.R. [Yonsei University, Seoul (Korea)
2001-10-01
It is generally known that radial vane blowers with vaneless diffuser may generate mostly only a rotating stall but backward curved vane blowers may do both an impeller and a diffuser rotating stalls. In this study, it was found from the numerical and experimental results that the diffuser rotating stall does not appear in a radial vane because of the suppression for the diffuser stall appearance by occuring of impeller rotating stall in a large flow rate coefficient. The diffuser rotating stalls occurring when the width of diffuser is broaden for a backward curved vane blower are classified definitely by the diffuser flow rate coefficient defined by adopting the varying diffuser width. (author). 12 refs., 9 figs.
Csébfalvi, Balázs
2013-09-01
In this paper, Cosine-Weighted B-spline (CWB) filters are proposed for interpolation on the optimal Body-Centered Cubic (BCC) lattice. We demonstrate that our CWB filters can well exploit the fast trilinear texture-fetching capability of modern GPUs, and outperform the state-of-the-art box-spline filters not just in terms of efficiency, but in terms of visual quality and numerical accuracy as well. Furthermore, we rigorously show that the CWB filters are better tailored to the BCC lattice than the previously proposed quasi-interpolating BCC B-spline filters, because they form a Riesz basis; exactly reproduce the original signal at the lattice points; but still provide the same approximation order.
Directory of Open Access Journals (Sweden)
Szu-Wei Lee
2014-03-01
Full Text Available Knowledge of the discrete cosine transform coefficient distribution (DCT-DIST is important for the encoder design. For example, rate control relies on this knowledge to estimate a possible bit rate and then decide proper coding parameters before the actual encoding task is performed. Therefore the rate control performance is fairly dependent on how accurately the DCT-DIST is modelled. The spatial enhancement layer (SL DCT-DIST for H.264 scalable video coding (SVC is studied in this Letter. SL DCT-DIST knowledge is furthermore used to derive a novel rate model. Our results can help design a proper rate control module for the H.264/SVC encoder.
Directory of Open Access Journals (Sweden)
Navneet Kaur
2013-05-01
Full Text Available Orthogonalfrequency Division multiplexing (OFDM is the most familiar word intelecommunicationand wireless communication systems as it provides enhanced spectral efficiency than Frequency divisionmultiplexing (FDM.Although itissustaininganorthogonal relationbetweencarriers but highpeak toaverage power ratio (PAPRis oneof the main disadvantages of OFDMsystem.Various PAPR reductiontechniques have beenused,including techniques based oncompanding. Incompanding,-Lawcompandinghas potential toreducethePAPRof OFDMsignals.-Law Compandingtechniquepreserves thedynamic range of samples at low amplitudes.Anew methodnamed as precoding which ishaving less complexity compared to the other power reductiontechniquesis proposed to reduce PAPR.This paper put forward combinationof two existing techniques namely-LawCompanding Transformand Discrete Cosine Transform-IIprecoding technique.The simulationresults show that, the proposedcombinedscheme givesbetter result for PAPR Reductionand resultsin no distortion
Varying c and Particle Horizons
Chimento, L P; Pavón, D; Chimento, Luis P; Jakubi, Alejandro S; Pavon, Diego
2001-01-01
We explore what restrictions may impose the second law of thermodynamics on varying speed of light theories. We find that the attractor scenario solving the flatness problem is consistent with the generalized second law at late time.
Diffusing diffusivity: a new derivation and comparison with simulations
Indian Academy of Sciences (India)
ROHIT JAIN; K L SEBASTIAN
2017-07-01
Many experiments are now available where it has been shown that the probability distribution function (pdf) for the position of a Brownian particle diffusing in a heterogeneous medium is not Gaussian. However, in spite of this non-Gaussianity, the mean square displacement (MSD) still remains Fickian, i.e., ⟨x²⟩ ∝ T . One possible explanation of this non-Gaussian yet Brownian behavior is that the diffusivity of the particle itself is “diffusing”. Chubynsky and Slater (Phys. Rev. Lett. 113 098302 2014) proposed a model of “diffusing diffusivity” which they were able to solve analytically at small time scales, but simulations were performed for intermediate to large time scales.We present here a class of diffusing diffusivity models and show that the problem of calculating pdf for the position of diffusing particle is equivalent to calculating the survival probability of a particle undergoing Brownian motion in the presence of a sink.We give exact analytical results for all time scales and show that the pdf is non-Gaussian at short times which crosses over to a Gaussian at longtimes. The MSD is also shown to vary linearly with time at all times. We find that our results reproduce the numerical results of Chubynsky and Slater quite well.
Institute of Scientific and Technical Information of China (English)
潘磊; 李丽娟; 丁婷婷
2013-01-01
First, referring to the rectangular heliostat field of the eSolar tower power plant, an arrangement of dense axial symmetry staggered distribution through parameters design was gotten. Then, a mathematical model of cosine efficiency was established, and the variation tendency of solar incidence angle at different time in the daytime was simulated, the result of cosine efficiency in the area of north and south field was obtained. Finally, the cosine efficiency distribution of rectangular heliostat field has been used to research further. Simulation results validate the trend of solar incidence angle, and the influence of tower's height on cosine efficiency.%参考eSolar塔式发电站中的矩形定日镜场,通过参数设计得到密集的轴对称交错排列布置方案；建立了余弦效率的数学模型,对一天中不同时刻的太阳入射角变化趋势进行了仿真,得出位于接收塔南北区域余弦效率状况；对矩形定日镜场的余弦效率分布做了进一步研究.仿真结果验证了太阳入射角的变化趋势,并得出塔的高度对余弦效率的影响.
Institute of Scientific and Technical Information of China (English)
全国萍; 刘占权; 王苏; 王常辉; 胡啸宇; 许花; 陈义学
2013-01-01
The core code of COSINE package uses NEM to solve diffusion equation and NEM is based on the node homogenization theory .In the AP1000 core design process , there are some reasons w hich cause material heterogeneity in the axial direction ,such as the fuel assembly dividing into several areas with different enrichments , the arrangement of spacer grid and the insertion of control rod , and it is needed to be rehomogenization .The re-homogenization can bring error into NEM calculation result because of some hypothesis . The directive phenomenon of the error is control rod cusping effect .Sub-node technology was proposed to solve the material heterogeneity in the axial direction problem in this paper ,and the differential worth of control rod was calculated .The results show that the control rod cusping effect greatly reduces because of the sub-node technology .%COSINE软件包堆芯物理分析程序采用节块展开法（NEM ）进行中子扩散方程的求解，NEM 以节块均匀化理论为基础。在A P1000堆芯核设计过程中，由于燃料组件的多种轴向材料分区方式、定位格架分布及控制棒插入均会引起节块轴向材料不均匀，需进行再均匀化处理。由于再均匀化过程基于一些假设，给NEM计算带来了一定误差。这种误差最为直接的表现形式为控制棒的尖端效应。本文采用了子网格技术来处理轴向材料不均匀性的问题，并给出了初步验证结果，计算了控制棒的微分价值曲线。计算结果表明，子网格的应用有效地缓解了控制棒尖端效应的影响。
MULTIVARIATE VARYING COEFFICIENT MODEL FOR FUNCTIONAL RESPONSES.
Zhu, Hongtu; Li, Runze; Kong, Linglong
2012-10-01
Motivated by recent work studying massive imaging data in the neuroimaging literature, we propose multivariate varying coefficient models (MVCM) for modeling the relation between multiple functional responses and a set of covariates. We develop several statistical inference procedures for MVCM and systematically study their theoretical properties. We first establish the weak convergence of the local linear estimate of coefficient functions, as well as its asymptotic bias and variance, and then we derive asymptotic bias and mean integrated squared error of smoothed individual functions and their uniform convergence rate. We establish the uniform convergence rate of the estimated covariance function of the individual functions and its associated eigenvalue and eigenfunctions. We propose a global test for linear hypotheses of varying coefficient functions, and derive its asymptotic distribution under the null hypothesis. We also propose a simultaneous confidence band for each individual effect curve. We conduct Monte Carlo simulation to examine the finite-sample performance of the proposed procedures. We apply MVCM to investigate the development of white matter diffusivities along the genu tract of the corpus callosum in a clinical study of neurodevelopment.
1/f noise: diffusive systems and music
Energy Technology Data Exchange (ETDEWEB)
Voss, R.F.
1975-11-01
Measurements of the 1/f voltage noise in continuous metal films are reported. At room temperature, samples of pure metals and bismuth (with a carrier density smaller by 10/sup 5/) of similar volume had comparable noise. The results suggest that the noise arises from equilibrium temperature fluctuations modulating the resistance. Spatial correlation of the noise implied that the fluctuations obey a diffusion equation. The empirical inclusion of an explicit 1/f region and appropriate normalization lead to excellent agreement with the measured noise. If the fluctuations are assumed to be spatially correlated, the diffusion equation can yield an extended 1/f region in the power spectrum. The temperature response of a sample to delta and step function power inputs is shown to have the same shape as the autocorrelation function for uncorrelated and correlated temperature fluctuations, respectively. The spectrum obtained from the cosine transform of the measured step function response is in excellent agreement with the measured 1/f voltage noise spectrum. Spatially correlated equilibrium temperature fluctuations are not the dominant source of 1/f noise in semiconductors and metal films. However, the agreement between the low-frequency spectrum of fluctuations in the mean-square Johnson noise voltage and the resistance fluctuation spectrum measured in the presence of a current demonstrates that in these systems the 1/f noise is also due to equilibrium resistance fluctuations. Loudness fluctuations in music and speech and pitch fluctuations in music also show the 1/f behavior. 1/f noise sources, consequently, are demonstrated to be the natural choice for stochastic composition. 26 figures, 1 table. (auth)
Diffusion archeology for diffusion progression history reconstruction.
Sefer, Emre; Kingsford, Carl
2016-11-01
Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.
2015 MICCAI Workshop on Computational Diffusion MRI
Ghosh, Aurobrata; Kaden, Enrico; Rathi, Yogesh; Reisert, Marco
2016-01-01
These Proceedings of the 2015 MICCAI Workshop “Computational Diffusion MRI” offer a snapshot of the current state of the art on a broad range of topics within the highly active and growing field of diffusion MRI. The topics vary from fundamental theoretical work on mathematical modeling, to the development and evaluation of robust algorithms, new computational methods applied to diffusion magnetic resonance imaging data, and applications in neuroscientific studies and clinical practice. Over the last decade interest in diffusion MRI has exploded. The technique provides unique insights into the microstructure of living tissue and enables in-vivo connectivity mapping of the brain. Computational techniques are key to the continued success and development of diffusion MRI and to its widespread transfer into clinical practice. New processing methods are essential for addressing issues at each stage of the diffusion MRI pipeline: acquisition, reconstruction, modeling and model fitting, image processing, fiber t...
Metal diffusion in smoothed particle hydrodynamics simulations of dwarf galaxies
Williamson, David John; Kawata, Daisuke
2016-01-01
We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows, and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths, by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]-[Fe/H] distribution in the gas, and cuts off the gas metallicity distribution function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between "metal mass-loading" (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even...
DEFF Research Database (Denmark)
Christoffersen, Peter; Feunoua, Bruno; Jeon, Yoontae
We estimate a continuous-time model with stochastic volatility and dynamic crash probability for the S&P 500 index and find that market illiquidity dominates other factors in explaining the stock market crash risk. While the crash probability is time-varying, its dynamic depends only weakly on re...
Mass Varying Neutrinos in Supernovae
Rossi-Torres, F; de Holanda, P C; Peres, O L G
2010-01-01
We study limits for the mass varying neutrino model, using constrains from supernova neutrinos placed by the r-process condition, $Y_e<0.5$. Also, we use this model in a supernova environment to study the regions of survival probability in the oscillation space parameter ($\\tan^2\\theta$ and $\\Delta m^2_0$), considering the channel $\
DEFF Research Database (Denmark)
Christoffersen, Peter; Feunoua, Bruno; Jeon, Yoontae
We estimate a continuous-time model with stochastic volatility and dynamic crash probability for the S&P 500 index and find that market illiquidity dominates other factors in explaining the stock market crash risk. While the crash probability is time-varying, its dynamic depends only weakly...... on return variance once we include market illiquidity as an economic variable in the model....
Esmaklassiline Karlovy Vary / Jaanus Noormets
Noormets, Jaanus
2007-01-01
Ilmar Raagi mängufilm "Klass" võitis 42. Karlovy Vary rahvusvahelise filmifestivalil kaks auhinda - ametliku kõrvalvõistlusprogrammi "East of the West" eripreemia "Special mention" ja Euroopa väärtfilmikinode keti Europa Cinemas preemia. Ka Asko Kase lühifilmi "Zen läbi prügi linastumisest ning teistest auhinnasaajatest ning osalejatest
Optimistlik Karlovy Vary / Jaan Ruus
Ruus, Jaan, 1938-2017
2007-01-01
42. Karlovy Vary rahvusvahelise filmifestivali auhinnatud filmidest (žürii esimees Peter Bart). Kristallgloobuse sai Islandi-Saksamaa "Katseklaasilinn" (režii Baltasar Kormakur), parimaks režissööriks tunnistati norralane Bard Breien ("Negatiivse mõtlemise kunst"). Austraallase Michael James Rowlandi "Hea õnne teekond" sai žürii eripreemia
Eestlased Karlovy Varys / J. R.
J. R.
2007-01-01
Ilmar Raagi mängufilm "Klass" osaleb 42. Karlovy Vary rahvusvahelise filmifestivali võistlusprogrammis "East of the West" ja Asko Kase lühimängufilm "Zen läbi prügi" on valitud festivali kõrvalprogrammi "Forum of Independents"
Esmaklassiline Karlovy Vary / Jaanus Noormets
Noormets, Jaanus
2007-01-01
Ilmar Raagi mängufilm "Klass" võitis 42. Karlovy Vary rahvusvahelise filmifestivalil kaks auhinda - ametliku kõrvalvõistlusprogrammi "East of the West" eripreemia "Special mention" ja Euroopa väärtfilmikinode keti Europa Cinemas preemia. Ka Asko Kase lühifilmi "Zen läbi prügi linastumisest ning teistest auhinnasaajatest ning osalejatest
Liang, Yaru; Liu, Guoping; Zhou, Nanrun; Wu, Jianhua
2015-02-01
Based on the fractional discrete cosine transform with multiple generating sequences (MGSFrDCT) and the dependent scrambling and diffusion (DSD), an image encryption algorithm is proposed, in which the multiple-generating sequences greatly enlarge the key space of the encryption system. The real-valued output of MGSFrDCT is beneficial to storage, display and transmission of the cipher-text. During the stage of confusion and diffusion, the locations and values of all MGSFrDCT transformed coefficients change due to DSD, and the initial values and fractional orders of encryption system depend not only on the cipher keys but also on the plain-image due to introduction of a disturbance factor, which allows the encryption system to resist the known-plaintext and chosen-plaintext attacks. Experimental results demonstrate that the proposed encryption algorithm is feasible, effective and secure and able to resist common classical attacks.
Convection-driven spherical shell dynamos at varying Prandtl numbers
Käpylä, P J; Olspert, N; Warnecke, J; Brandenburg, A
2016-01-01
(abidged) Context: Stellar convection zones are characterized by vigorous high-Reynolds number turbulence at low Prandtl numbers. Aims: We study the dynamo and differential rotation regimes at varying levels of viscous, thermal, and magnetic diffusion. Methods: We perform three-dimensional simulations of stratified fully compressible magnetohydrodynamic convection in rotating spherical wedges at various thermal and magnetic Prandtl numbers. Results: We find that the rotation profiles for high thermal diffusivity show a monotonically increasing angular velocity from the bottom of the convection zone to the top and from the poles toward the equator. For sufficiently rapid rotation, a region of negative radial shear develops at mid-latitudes as the thermal diffusivity is decreased. This coincides with a change in the dynamo mode from poleward propagating activity belts to equatorward propagating ones. Furthermore, the cyclic solutions disappear at the highest magnetic Reynolds numbers. The total magnetic energy ...
Energy Technology Data Exchange (ETDEWEB)
Sidabras, Jason W.; Anderson, James R.; Mainali, Laxman; Hyde, James S. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States); Strangeway, Robert A. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States); Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201 (United States); Mett, Richard R. [Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States); Department of Chemistry and Physics, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201 (United States)
2016-03-15
Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE{sub 10} mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in
Evidence Combination Method Based on Included Angle Cosine%基于夹角余弦的证据组合方法
Institute of Scientific and Technical Information of China (English)
胡嘉骥; 李新德; 王丰羽
2015-01-01
Dempster-Shafer theory of evidence combination is widely used in the field of information fusion. However, it has a counter intuitive problem in highly conflictive evidence combination. Aiming at this problem, the source of evidence is analyzed, and then an evidence combination method based on cosine is proposed. Firstly, Pignistic probability is utilized to analyze the evidence source. Next, conflictive evidence is identified by comparing the included angle cosine with the threshold. Conflictive evidence is revised according to the variable correction factor generated from the relationship among evidences and the probability assignment of non-conflictive evidences. Finally, Dempster-Shafer rule is utilized to combine evidences. Experimental results show that the proposed method is effective in handing highly conflictive evidences and the combination result obtained in the case of multi-conflictive evidences is good. The proposed method can be widely used in the field of multi-source information fusion, pattern recognition and uncertain information decision-making.%Dempster-Shafer证据合成理论广泛应用于信息融合领域，但在证据高度冲突时存在反直观问题。针对此问题，文中从证据源展开分析，提出基于夹角余弦的冲突证据合成方法。该方法首先利用Pignistic概率分析证据源，然后通过夹角余弦与阈值比较识别冲突证据，并利用证据间关系生成可变修正因子和非冲突证据的概率分配，对冲突证据进行修正。最后利用Dempster-Shafer规则完成证据合成。实验表明，该方法可有效处理高冲突证据，尤其在多个冲突证据时也能获得较好的合成效果，可应用于多源信息融合、模式识别、不确定信息决策等领域。
Sidabras, Jason W; Strangeway, Robert A; Mett, Richard R; Anderson, James R; Mainali, Laxman; Hyde, James S
2016-03-01
Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE10 mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in
Holographic flow visualization of time-varying shock waves
Decker, A. J.
1981-01-01
Rapid-double-exposure, diffuse-illumination holography is evaluated analytically and experimentally as a flow visualization method for time-varying shock waves. Conditions are determined that minimize the distance (localization error) between the surface or curve of interference-fringe localization and the shock surface. Treated specifically are the cases of shock waves in a transonic compressor rotor for which there is laser anemometer data for comparison and shock waves in a flutter cascade.
Institute of Scientific and Technical Information of China (English)
包建勤; 张廷蓉; 霍雅洁
2013-01-01
Under paraxial approximation,using generalized Huygens-Fresnel diffraction integral,the propagation expressions of cosine-Gaussian beam through the left-handed material slab are got,and the influence of propagation properties of cosine-Gaussian beam due to the negative refractive index of left-handed material slab and the modulation parameter of cosine-Gaussian beam is studied.The results of the study show that:whether in the left-handed materials slab or image space,the location of the axial maximum light intensity is the position where cosine-Gaussian beam is focused,and the negative refractive index of the left-handed material slab will change the position of the cosine-Gaussian beam focusing.The negative refractive index will change the shape of the axial light intensity distribution in the internal of the lefthanded material slab,but it won't change the shape of the axial light intensity distribution in image space.Whether in the internal of slab or image space,the modulation parameters of cosine-Gaussian beam can influence the axial and transverse light intensities.%在傍轴近似下,利用广义惠更斯-菲涅尔衍射积分公式得到了余弦高斯光束通过左手平板材料的传输公式,研究了左手平板材料的负折射率与余弦高斯光束的调制参数对光束传输特性的影响.结果表明:余弦高斯光束无论在左手平板材料内部传输还是在像空间传输,轴上的最大光强位置是光束聚焦的位置,左手平板材料的负折射率会改变光束聚焦的位置；在介质内部,平板材料的负折射率会改变轴上光强分布的形状,但不会改变像空间轴上的光强分布形状；无论是在平板材料内部还是像空间,余弦高斯光束的调制参数对轴上与横向光强都会产生影响.
Harmonic functions with varying coefficients
Directory of Open Access Journals (Sweden)
Jacek Dziok
2016-05-01
Full Text Available Abstract Complex-valued harmonic functions that are univalent and sense preserving in the open unit disk can be written in the form f = h + g ‾ $f=h+\\overline{g}$ , where h and g are analytic. In this paper we investigate some classes of univalent harmonic functions with varying coefficients related to Janowski functions. By using the extreme points theory we obtain necessary and sufficient convolution conditions, coefficients estimates, distortion theorems, and integral mean inequalities for these classes of functions. The radii of starlikeness and convexity for these classes are also determined.
Linearized Bekenstein Varying Alpha Models
Pina-Avelino, P; Oliveira, J C
2004-01-01
We study the simplest class of Bekenstein-type, varying $\\alpha$ models, in which the two available free functions (potential and gauge kinetic function) are Taylor-expanded up to linear order. Any realistic model of this type reduces to a model in this class for a certain time interval around the present day. Nevertheless, we show that no such model is consistent with all existing observational results. We discuss possible implications of these findings, and in particular clarify the ambiguous statement (often found in the literature) that ``the Webb results are inconsistent with Oklo''.
Linearized Bekenstein varying α models
Avelino, P. P.; Martins, C. J.; Oliveira, J. C.
2004-10-01
We study the simplest class of Bekenstein-type, varying α models, in which the two available free functions (potential and gauge kinetic function) are Taylor-expanded up to linear order. Any realistic model of this type reduces to a model in this class for a certain time interval around the present day. Nevertheless, we show that no such model is consistent with all existing observational results. We discuss possible implications of these findings, and, in particular, clarify the ambiguous statement (often found in the literature) that “the Webb results are inconsistent with Oklo.”
Time-varying cosmological term
Socorro, J.; D'oleire, M.; Pimentel, Luis O.
2015-11-01
We present the case of time-varying cosmological term using the Lagrangian formalism characterized by a scalar field ϕ with standard kinetic energy and arbitrary potential V(ϕ). This model is applied to Friedmann-Robertson-Walker (FRW)cosmology. Exact solutions of the field equations are obtained by a special ansats to solve the Einstein-Klein-Gordon equation and a particular potential for the scalar field and barotropic perfect fluid. We present the evolution on this cosmological term with different scenarios.
Diffusion coefficients in viscous sodium alginate solutions
Aoki, K.; Wang, B; Chen, J.; Nishiumi, T.
2012-01-01
Sodium alginate solution, being viscous hydrocolloid, was examined voltammetricallyin the context of viscous effects by use of a ferrocenyl compound as a redox probe.Voltammograms were almost independent of concentrations of sodium alginate even ina solid-like state. Diffusion coefficients of the ferrocenyl compound did not vary withviscosity evaluated by a viscometer. Ionic conductivity of sodium alginate was alsoindependent of the viscosity. In contrast, diffusion coefficients of the latex ...
Varying Constants, Gravitation and Cosmology
Directory of Open Access Journals (Sweden)
Jean-Philippe Uzan
2011-03-01
Full Text Available Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Varying Constants, Gravitation and Cosmology.
Uzan, Jean-Philippe
2011-01-01
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Varying Constants, Gravitation and Cosmology
Uzan, Jean-Philippe
2011-12-01
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
Directory of Open Access Journals (Sweden)
Jian Sun
2016-07-01
Full Text Available Hydraulic pump degradation feature extraction is a key step of condition-based maintenance. In this article, a novel method based on high-frequency harmonic local characteristic-scale decomposition sub-signal separation and discrete cosine transform high-order singular entropy is proposed. In order to reduce noises and other disturbances, the vibration signal is processed by the local characteristic-scale decomposition modified by the high-frequency harmonic. Sub-signal with sensitive information is obtained by blind source separation of the selected intrinsic scale components. Furthermore, the discrete cosine transform high-order spectral analysis algorithm is proposed to extract singular entropies of Shannon and Tsallis to be the degradation features of the hydraulic pump. Analysis of the hydraulic pump experiment demonstrates that the proposed method is feasible and effective in indicating the performance degradation of the hydraulic pump.
Knudsen gas in a finite random tube: transport diffusion and first passage properties
Comets, Francis; Schütz, Gunter M; Vachkovskaia, Marina
2010-01-01
We consider transport diffusion in a stochastic billiard in a random tube which is elongated in the direction of the first coordinate (the tube axis). Inside the random tube, which is stationary and ergodic, non-interacting particles move straight with constant speed. Upon hitting the tube walls, they are reflected randomly, according to the cosine law: the density of the outgoing direction is proportional to the cosine of the angle between this direction and the normal vector. Steady state transport is studied by introducing an open tube segment as follows: We cut out a large finite segment of the tube with segment boundaries perpendicular to the tube axis. Particles which leave this piece through the segment boundaries disappear from the system. Through stationary injection of particles at one boundary of the segment a steady state with non-vanishing stationary particle current is maintained. We prove (i) that in the thermodynamic limit of an infinite open piece the coarse-grained density profile inside the...
Diffusion tensor imaging with multiple diffusion-weighted gradient directions
Institute of Scientific and Technical Information of China (English)
Shan Jiang; Meixia Liu; Tong Han; Weihua Liu
2011-01-01
Diffusion tensor MRI (DT-MRI or DTI) is emerging as an important non-invasive technology for elucidating internal brain structures.It has recently been utilized to diagnose a series of diseases that affect the integrity of neural systems to provide a basis for neuroregenerative studies.Results from the present study suggested that neural tissue is reconstructed with multiple diffusion-weighted gradient directions DTI,which varies from traditional imaging methods that utilize 6 gradient directions.Simultaneously,the diffusion tensor matrix is obtained by multiple linear regressions from an equation of echo signal intensity.The condition number value and standard deviation of fractional anisotropy for each scheme can be used to evaluate image quality.Results demonstrated that increasing gradient direction to some extent resulted in improved effects.Therefore,the traditional 6 and 15 directions should not be considered optimal scan protocols for clinical DTI application.In a scheme with 20 directions,the condition number and standard deviation of fractional anisotropy of the encoding gradients matrix were significantly reduced,and resulted in more clearly and accurately displayed neural tissue.Results demonstrated that the scheme with 20diffusion gradient directions provided better accuracy of structural renderings and could be an optimal scan protocol for clinical DTI application.
Barrow, John D
2014-01-01
In a recent paper we demonstrated how the simplest model for varying alpha may be interpreted as the effect of a dielectric material, generalized to be consistent with Lorentz invariance. Unlike normal dielectrics, such a medium cannot change the speed of light, and its dynamics obey a Klein-Gordon equation. This work immediately suggests an extension of the standard theory, even if we require compliance with Lorentz invariance. Instead of a wave equation, the dynamics may satisfy a local algebraic relation involving the permittivity and the properties of the electromagnetic field, in analogy with more conventional dielectric (but still preserving Lorentz invariance). We develop the formalism for such theories and investigate some phenomenological implications. The problem of the divergence of the classical self-energy can be solved, or at least softened, in this framework. Some interesting new cosmological solutions for the very early universe are found, including the possibility of a bounce, inflation and e...
Varying constants, Gravitation and Cosmology
Uzan, Jean-Philippe
2010-01-01
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. It is thus of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We thus detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describ...
Exploration of Periodically Varying Graphs
Flocchini, Paola; Santoro, Nicola
2009-01-01
We study the computability and complexity of the exploration problem in a class of highly dynamic graphs: periodically varying (PV) graphs, where the edges exist only at some (unknown) times defined by the periodic movements of carriers. These graphs naturally model highly dynamic infrastructure-less networks such as public transports with fixed timetables, low earth orbiting (LEO) satellite systems, security guards' tours, etc. We establish necessary conditions for the problem to be solved. We also derive lower bounds on the amount of time required in general, as well as for the PV graphs defined by restricted classes of carriers movements: simple routes, and circular routes. We then prove that the limitations on computability and complexity we have established are indeed tight. In fact we prove that all necessary conditions are also sufficient and all lower bounds on costs are tight. We do so constructively presenting two worst case optimal solution algorithms, one for anonymous systems, and one for those w...
Time-Varying Fundamental Constants
Olive, Keith
2003-04-01
Recent data from quasar absorption systems can be interpreted as arising from a time variation in the fine-structure constant. However, there are numerous cosmological, astro-physical, and terrestrial bounds on any such variation. These includes bounds from Big Bang Nucleosynthesis (from the ^4He abundance), the Oklo reactor (from the resonant neutron capture cross-section of Sm), and from meteoretic lifetimes of heavy radioactive isotopes. The bounds on the variation of the fine-structure constant are significantly strengthened in models where all gauge and Yukawa couplings vary in a dependent manner, as would be expected in unified theories. Models which are consistent with all data are severly challenged when Equivalence Principle constraints are imposed.
Weighted approximation with varying weight
Totik, Vilmos
1994-01-01
A new construction is given for approximating a logarithmic potential by a discrete one. This yields a new approach to approximation with weighted polynomials of the form w"n"(" "= uppercase)P"n"(" "= uppercase). The new technique settles several open problems, and it leads to a simple proof for the strong asymptotics on some L p(uppercase) extremal problems on the real line with exponential weights, which, for the case p=2, are equivalent to power- type asymptotics for the leading coefficients of the corresponding orthogonal polynomials. The method is also modified toyield (in a sense) uniformly good approximation on the whole support. This allows one to deduce strong asymptotics in some L p(uppercase) extremal problems with varying weights. Applications are given, relating to fast decreasing polynomials, asymptotic behavior of orthogonal polynomials and multipoint Pade approximation. The approach is potential-theoretic, but the text is self-contained.
Institute of Scientific and Technical Information of China (English)
赵雁
2012-01-01
Since Cohen-Crossberg neural network was first proposed by M. Cohen and S. Grossberg(IEEE Trans Syst Man Cybernet, 1983 ,SMC-13 -.815-826.), many researchers have done extensive studies on this subject due to their extensive applications in many fields such as associative memory, signal and image processing and combinatorial optimization. Because of the random perturbation and reaction-diffusion, the equilibrium point of stochastic reacnon-diflusion Cohen-Grossberg neural networks with delays sometimes does not exist. So,we should study the existence of attracting set and invariant set of it. In this paper, we establish a method to study the existence of attracting set and invariant set of stochastic reaction-diffusion Cohen-Grossberg neural networks with delays. By using Ito formula, the properties of M-cone and inequality technique, we obtain some sufficient conditions ensuring the existence of attracting set and invariant set of stochastic reaction-diffusion Cohen-Grossberg neural networks with delays. The sufficient conditions are easily checked in practice by simple algebra methods and have a wider adaptive range. Examples are also given to illustrate the efficiency of the obtained results.%从M.Cohen和S.Grossberg(IEEE Trans Sys Man Cyber,1983,13:815 -826.)提出Cohen - Grossberg神经网络以来,由于它在信号和图像处理、联想记忆、组合优化等中的广泛应用,因此受到了广泛的关注和研究.由于随机干扰和反应扩散,时滞Cohen - Grossberg随机反应扩散神经网络的平衡点往往不存在,这时,往往研究其吸引集和不变集的存在性.建立了一种研究时滞Cohen - Grossberg随机反应扩散神经网络的吸引集与不变集的方法.通过应用Ito公式、时滞微分不等式技巧和M-矩阵性质,获得了判定变时滞Cohen - Grossberg随机反应扩散神经网络存在吸引集和不变集的充分条件.所获得的充分条件在实践当中可以用简单的代数方法验证,因此有
Time varying networks and the weakness of strong ties
Karsai, Márton; Perra, Nicola; Vespignani, Alessandro
2014-02-01
In most social and information systems the activity of agents generates rapidly evolving time-varying networks. The temporal variation in networks' connectivity patterns and the ongoing dynamic processes are usually coupled in ways that still challenge our mathematical or computational modelling. Here we analyse a mobile call dataset and find a simple statistical law that characterize the temporal evolution of users' egocentric networks. We encode this observation in a reinforcement process defining a time-varying network model that exhibits the emergence of strong and weak ties. We study the effect of time-varying and heterogeneous interactions on the classic rumour spreading model in both synthetic, and real-world networks. We observe that strong ties severely inhibit information diffusion by confining the spreading process among agents with recurrent communication patterns. This provides the counterintuitive evidence that strong ties may have a negative role in the spreading of information across networks.
Metal Diffusion in Smoothed Particle Hydrodynamics Simulations of Dwarf Galaxies
Williamson, David; Martel, Hugo; Kawata, Daisuke
2016-05-01
We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]-[Fe/H] distribution in the gas and cuts off the gas metallicity distribution function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between “metal mass-loading” (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even when the diffusion coefficient is calculated in different ways. The effectiveness of outflows at removing metals from dwarf galaxies and the metal distribution of the gas is thus dependent on the strength of diffusion. By contrast, we show that the metallicities of stars are not strongly dependent on the strength of diffusion, provided that some diffusion is present.
Hui, Zi; Tang, Xiaoyue; Li, Wei; Greneche, Jean-Marc; Wang, Qiuping A.
2015-04-01
In this work, we study the problem of diffusing a product (idea, opinion, disease etc.) among agents on spatial network. The network is constructed by random addition of nodes on the planar. The probability for a previous node to be connected to the new one is inversely proportional to their spatial distance to the power of α. The diffusion rate between two connected nodes is inversely proportional to their spatial distance to the power of β as well. Inspired from the Fick's first law, we introduce the diffusion coefficient to measure the diffusion ability of the spatial network. Using both theoretical analysis and Monte Carlo simulation, we get the fact that the diffusion coefficient always decreases with the increasing of parameter α and β, and the diffusion sub-coefficient follows the power-law of the spatial distance with exponent equals to -α-β+2. Since both short-range diffusion and long-range diffusion exist, we use anomalous diffusion method in diffusion process. We get the fact that the slope index δ in anomalous diffusion is always smaller that 1. The diffusion process in our model is sub-diffusion.
Pandey, Anukul; Singh, Butta; Saini, Barjinder Singh; Sood, Neetu
2016-12-01
In this paper, a joint use of the discrete cosine transform (DCT), and differential pulse code modulation (DPCM) based quantization is presented for predefined quality controlled electrocardiogram (ECG) data compression. The formulated approach exploits the energy compaction property in transformed domain. The DPCM quantization has been applied to zero-sequence grouped DCT coefficients that were optimally thresholded via Regula-Falsi method. The generated sequence is encoded using Huffman coding. This encoded series is further converted to a valid ASCII code using the standard codebook for transmission purpose. Such a coded series possesses inherent encryption capability. The proposed technique is validated on all 48 records of standard MIT-BIH database using different measures for compression and encryption. The acquisition time has been taken in accordance to that existed in literature for the fair comparison with contemporary state-of-art approaches. The chosen measures are (1) compression ratio (CR), (2) percent root mean square difference (PRD), (3) percent root mean square difference without base (PRD1), (4) percent root mean square difference normalized (PRDN), (5) root mean square (RMS) error, (6) signal to noise ratio (SNR), (7) quality score (QS), (8) entropy, (9) Entropy score (ES) and (10) correlation coefficient (r x,y ). Prominently the average values of CR, PRD and QS were equal to 18.03, 1.06, and 17.57 respectively. Similarly, the mean encryption metrics i.e. entropy, ES and r x,y were 7.9692, 0.9962 and 0.0113 respectively. The novelty in combining the approaches is well justified by the values of these metrics that are significantly higher than the comparison counterparts.
Amemiya, Naoyuki; Sogabe, Yusuke; Sakashita, Masaki; Iwata, Yoshiyuki; Noda, Koji; Ogitsu, Toru; Ishii, Yusuke; Kurusu, Tsutomu
2016-02-01
Electromagnetic field analyses were carried out to study the influence of coated-conductor magnetisation, i.e. the screening (shielding) current, on the field quality of a dipole magnet in a rotating gantry for hadron cancer therapy. The analyses were made on the cross section of a cosine-theta dipole magnet in a rotating gantry for carbon ions, which generated 2.90 T of magnetic field. The temporal profile (temporal variation) of the magnet current was determined based on the actual excitation schemes of the magnets in the rotating gantry. The experimentally determined superconducting property of a coated conductor was considered, and we calculated the temporal evolutions of the current-density distributions in all the turns of coated conductors in the magnet. From the obtained current-density distributions, we calculated the multipole components of the magnetic field and evaluated the field quality of the magnet. The deviation in the dipole component from its designed value was up to approximately 25 mT, which was approximately 1% of the designed maximum dipole component. Its variation between repeated excitations was approximately 0.03%, and it drifted approximately 0.06% in 10 s. Some compensation schemes might be required to counteract such influence of magnetisation on the dipole component. Meanwhile, the higher multipole components were small, stable, and sufficiently reproducible for a magnet in rotating gantries, i.e. |b 3| ˜ 1.1 × 10-3 and |Δb 3| ˜ 0.2 × 10-3 in 10 s.
频闪光源和交变光源对蝗虫趋光响应的试验%Experiment of locust phototactic response to flash and cosine alternating light
Institute of Scientific and Technical Information of China (English)
刘启航; 周强
2011-01-01
To provide theoretical reference and technical parameters for designing locusts' LED trapping light, optimization of flash light's frequency and cosine alternating light's shining cycle parameter for locusts' phototactic behavior were conducted by LED light source and phototaxis behavior trial equipment with comparison method. The efficiency difference of flash light, cosine alternating and constant light was studied,and the efficiency principle of flash light and cosine alternating light on locusts' phototaxis behavior was also discussed. The results show that locusts' phototactic response can be affected by spectrum,shining frequency and cycle, and violet flash light with shining interval of 30 ms has the best efficiency to locusts' phototactic response. Cosine alternating violet light with shining cycle of 640 ms is superior to flash light and other cosine alternating light for locusts' phototactic response. The phototactic response of flash violet light with shining interval of 30 ms is inferior to that of cosine alternating volet blue and green flash light with shining cycle of 640 ms. According to the illumination threshold of locusts' sensitve spectrum,the efficiency range of locusts' phototactic response can be extended by reasonable combination of cosine alternating light and flash light.%为给光场耦合调控性蝗虫诱导LED光源的研制提供技术支持,利用LED光源和行为试验装置采用对比试验法,进行了蝗虫趋光响应频闪光频率和交变光周期的优选以及蝗虫对频闪光、余弦交变光相对恒定光的增效差异,探讨了频闪光和余弦交变光对蝗虫趋光增效的机理.结果显示:光谱色光照、发光频率及发光周期范围影响蝗虫的趋光响应,其中发光间隔为30 ms的频闪紫光对蝗虫的趋光增效优于其他频闪光,蝗虫对发光周期为640 ms的余弦交变紫光的趋光响应相对于频闪光、周期交变光、恒定光最优,且蝗虫对周期为640 ms的余
Gait phase varies over velocities.
Liu, Yancheng; Lu, Kun; Yan, Songhua; Sun, Ming; Lester, D Kevin; Zhang, Kuan
2014-02-01
We sought to characterize the percent (PT) of the phases of a gait cycle (GC) as velocity changes to establish norms for pathological gait characteristics with higher resolution technology. Ninety five healthy subjects (49 males and 46 females with age 34.9 ± 11.8 yrs, body weight 64.0 ± 11.7 kg and BMI 23.5 ± 3.6) were enrolled and walked comfortably on a 10-m walkway at self-selected slower, normal, and faster velocities. Walking was recorded with a high speed camera (250 frames per second) and the eight phases of a GC were determined by examination of individual frames for each subject. The correlation coefficients between the mean PT of the phases of the three velocities gaits and PT defined by previous publications were all greater than 0.99. The correlation coefficient between velocity and PT of gait phases is -0.83 for loading response (LR), -0.75 for mid stance (MSt), and -0.84 for pre-swing (PSw). While the PT of the phases of three velocities from this study are highly correlated with PT described by Dr. Jacquenlin Perry decades ago, actual PT of each phase varied amongst these individuals with the largest coefficient variation of 24.31% for IC with slower velocity. From slower to faster walk, the mean PT of MSt diminished from 35.30% to 25.33%. High resolution recording revealed ambiguity of some gait phase definitions, and these data may benefit GC characterization of normal and pathological gait in clinical practice. The study results indicate that one should consider individual variations and walking velocity when evaluating gaits of subjects using standard gait phase classification.
Directory of Open Access Journals (Sweden)
R. H. Oliveira
2004-06-01
Full Text Available A deficiência tardia de potássio na cultura do algodoeiro tem ocorrido com freqüência nas regiões do cerrado brasileiro. Um dos motivos poderia ser atribuído à baixa disponibilidade de água nessa época. Assim, procurou-se quantificar a contribuição da difusão e do fluxo de massa no suprimento de K às raízes do algodoeiro de acordo com a disponibilidade do nutriente e de água. Para tanto, realizou-se um experimento em vasos em casa de vegetação, utilizando amostras da camada arável (0-20 cm de um Latossolo Vermelho típico, com 330 mg kg-1 de argila. O experimento constou de duas doses de potássio (15 e 121 mg dm-3 , na forma de KCl, e quatro conteúdos de água (-0,03; -0,1; -0,5 e -1,0 MPa. As plantas foram colhidas aos 53 dias da emergência. A difusão foi o principal mecanismo de transporte de K no solo, variando de 72 a 96 % do total absorvido pelo algodoeiro. A influência do conteúdo de água do solo sobre os mecanismos de transporte de K foi maior em solos com maior concentração deste nutriente, razão por que o fluxo de massa cresce em importância em solos mais secos.Late season potassium (K deficiency has been observed quite frequently for cotton crops in the Brazilian cerrado region. One possible reason for such a problem could be the low water availability at this period of the season. Thus, an experiment was conducted in order to quantify the relative contribution of mass flow and diffusion in supplying K to cotton roots, as affected by soil water and K availability. The arable layer of a typic Red Latosol (Haplortox, with 630 mg kg-1 sand, 40 mg kg-1 silt, and 330 mg kg-1 clay was sampled and filled into 5 L pots. The treatments were two K rates (15 and 121 mg dm-3, applied as potassium chloride, and four levels of soil water (-0.03, -0.1, -0.5, and -1.0 MPa. Two cotton plants were grown in each pot and harvested 53 days after plant emergence. Diffusion was the main transport mechanism of K to cotton roots
Ojambati, Oluwafemi S; Vellekoop, Ivo M; Lagendijk, Ad; Vos, Willem L
2016-01-01
We show that the spatial distribution of the energy density of optimally shaped waves inside a scattering medium can be described by considering only a few of the lowest eigenfunctions of the diffusion equation. Taking into account only the fundamental eigenfunction, the total internal energy inside the sample is underestimated by only 2%. The spatial distribution of the shaped energy density is very similar to the fundamental eigenfunction, up to a cosine distance of about 0.01. We obtained the energy density inside a quasi-1D disordered waveguide by numerical calculation of the joined scattering matrix. Computing the transmission-averaged energy density over all transmission channels yields the ensemble averaged energy density of shaped waves. From the averaged energy density obtained, we reconstruct its spatial distribution using the eigenfunctions of the diffusion equation. The results from our study have exciting applications in controlled biomedical imaging, efficient light harvesting in solar cells, en...
Kutzner, Mickey; Pearson, Bryan
2017-01-01
Diffusion is a truly interdisciplinary topic bridging all areas of STEM education. When biomolecules are not being moved through the body by fluid flow through the circulatory system or by molecular motors, diffusion is the primary mode of transport over short distances. The direction of the diffusive flow of particles is from high concentration…
Bidondo, Alejandro
2002-11-01
This acoustic diffusion research presents a pragmatic view, based more on effects than causes and 15 very useful in the project advance control process, where the sound field's diffusion coefficient, sound field diffusivity (SFD), for its evaluation. Further research suggestions are presented to obtain an octave frequency resolution of the SFD for precise design or acoustical corrections.
Kutzner, Mickey; Pearson, Bryan
2017-02-01
Diffusion is a truly interdisciplinary topic bridging all areas of STEM education. When biomolecules are not being moved through the body by fluid flow through the circulatory system or by molecular motors, diffusion is the primary mode of transport over short distances. The direction of the diffusive flow of particles is from high concentration toward low concentration.
Reduced dielectric response in spatially varying electric fields
DEFF Research Database (Denmark)
Hansen, Jesper Schmidt
2015-01-01
In this paper, the dynamical equation for polarization is derived. From this the dielectric response to a spatially varying electric field is analyzed showing a reduced response due to flux of polarization in the material. This flux is modeled as a diffusive process through linear constitutive...... relations between the flux and the gradient of the polarization. Comparison between the theory and molecular dynamics simulations confirms this effect. The effect is significant for small length scale electric field variations and the inclusion of the flux is thus important in nanoscale modeling...
Diffusion Weighted and Trace Images
Directory of Open Access Journals (Sweden)
Helen Nayeri
2009-01-01
completely restricted. For example, myelin fiber and neurofibril orientation in white matter possesses a preferred direction for water proton movement. The rate of water diffusion varies with direction due to biological constrains. This feature causes protons to diffuse faster along the path of least resistance, causing the ADC to be anisotropic, or directionally dependent. The orientation of the anisotropy is correlated to the direction of the tract of myelinated axons. In the cerebral cortex, there are three whit matter tracts; 1. Association; 2. Projection; and 3.commissural, that are oriented in different directions. In order to have an isotropic or trace image, DWIs are sensitized in the X-Y-and Z directions. The signal intensity in each voxel is the average of the other three images, thereby minimizing anisotropic nature of the biological medium and delineating the affected area. While it is of interest to minimize diffusion anisotropy in stroke imaging, the ability to detect anisotropic differences is useful for the study of normal anatomy and white matter pathology. "nDWI has become a standard part of the diagnostic work-up of intracranial pathology. "nDue to increased sensitivity of DWI for detecting ischemic changes in the hyperacute time period (restricted diffusion because of cytotoxic edema; it has emerged as the gold standard for acute ischemic stroke diagnosis. The particular advantage of this technique is the delineation of potential tissue at risk; the aim for most therapeutic efforts. In addition to providing information about lesion location, volume, and vascular distribution, DWI allows characterization of lesion evolution using the change in the ADC. Using only conventional imaging and clinical symptoms the distinction of an abscess from a cystic or necrotic tumor is difficult. It has been shown that such distinction would be more reliably made using DWI and ADC values. Due to highly viscous combination of inflammatory cell, debris, and bacteria in a
Nonlinear scale space with spatially varying stopping time.
Gilboa, Guy
2008-12-01
A general scale space algorithm is presented for denoising signals and images with spatially varying dominant scales. The process is formulated as a partial differential equation with spatially varying time. The proposed adaptivity is semi-local and is in conjunction with the classical gradient-based diffusion coefficient, designed to preserve edges. The new algorithm aims at maximizing a local SNR measure of the denoised image. It is based on a generalization of a global stopping time criterion presented recently by the author and colleagues. Most notably, the method works well also for partially textured images and outperforms any selection of a global stopping time. Given an estimate of the noise variance, the procedure is automatic and can be applied well to most natural images.
Institute of Scientific and Technical Information of China (English)
雷国梁; 岳田
2014-01-01
利用经典的Feller-Trotter型算子在Cω空间中局部小o饱和定理，建立了Banach空间X上C余弦算子函数概率表示的局部小o饱和定理。%The authors used local“o”saturation theorem in Cωspace for classical Feller-Trotter operators to set up the local saturation theorem for probabilistic representations of exponentially bounded C-cosine functions in Banach space X.
Institute of Scientific and Technical Information of China (English)
丁婷婷; 祝雪妹
2012-01-01
定日镜在接受和反射太阳辐射能至吸热器的过程中,存在着诸多损失.不正当的聚光镜场布置方案将引起过量的损失,其余弦损失所占的比例最大.因而有必要对定日镜处于不同坐标位置的余弦效率进行研究.首先建立了塔式太阳能热发电中余弦效率的数学模型.其次通过对阴影和阻挡损失——聚光场密度的折衷考虑,选择规则且灵活的放射状交错排列方式,得到圆形聚光镜场.最后在圆形镜场中对夏至日不同时间的余弦效率进行仿真,并从仿真结果中得到一些结论.基于这些结论,可重新定义定日镜的布置方案和检修策略,以便于获得更多的太阳辐射能,降低其成本.%Heliostats have some losses in the process of receiving and reflecting solar radiation. Improper helio-stat layout results in excessive losses, among these losses, cosine efficiency accounted for the largest proportion. So, it is necessary to study on the cosine efficiency of the heliostats at different coordinates. In this paper, mathematical model of cosine efficiency in solar power tower plant was established. Then, there are trade-offs among shadowing, blocking losses and heliostats field density, and the regular and flexible radical staggered configuration was chosen as an optimal field layout, which generate of densest circular heliostat fields. Furthermore, summer solstice is used to simulate at different solar time, while the distribution of cosine efficiency was analyzed. From simulated graphics show that some useful results. Based on this principle, placement and maintenance strategy of heliostats should be made so as to collect more solar energy and reduce cost.
Metric diffusion along foliations
Walczak, Szymon M
2017-01-01
Up-to-date research in metric diffusion along compact foliations is presented in this book. Beginning with fundamentals from the optimal transportation theory and the theory of foliations; this book moves on to cover Wasserstein distance, Kantorovich Duality Theorem, and the metrization of the weak topology by the Wasserstein distance. Metric diffusion is defined, the topology of the metric space is studied and the limits of diffused metrics along compact foliations are discussed. Essentials on foliations, holonomy, heat diffusion, and compact foliations are detailed and vital technical lemmas are proved to aide understanding. Graduate students and researchers in geometry, topology and dynamics of foliations and laminations will find this supplement useful as it presents facts about the metric diffusion along non-compact foliation and provides a full description of the limit for metrics diffused along foliation with at least one compact leaf on the two dimensions.
Tracer diffusivity and effective temperature in bacterial suspensions
Patteson, Alison E; Purohit, Prashant K; Arratia, Paulo E
2015-01-01
The dynamics of tracer particles in \\textit{E. coli} suspensions are experimentally investigated as a function of particle size and bacteria concentration. We find that tracer diffusivity is enhanced due to particle-bacteria interactions and varies non-monotonically with particle size, exhibiting a peak at sizes comparable to the bacterial length. The time scale characterizing the transition from ballistic to diffusive regime increases monotonically with \\textit{E. coli} concentration and particle size. Diffusivity measurements are then used to estimate suspension effective temperature, which varies nonlinearly with tracer size, suggesting that measures of activity are probe size dependent.
Diffusion formalism and applications
Dattagupta, Sushanta
2013-01-01
Within a unifying framework, Diffusion: Formalism and Applications covers both classical and quantum domains, along with numerous applications. The author explores the more than two centuries-old history of diffusion, expertly weaving together a variety of topics from physics, mathematics, chemistry, and biology. The book examines the two distinct paradigms of diffusion-physical and stochastic-introduced by Fourier and Laplace and later unified by Einstein in his groundbreaking work on Brownian motion. The author describes the role of diffusion in probability theory and stochastic calculus and
Inpainting using airy diffusion
Lorduy Hernandez, Sara
2015-09-01
One inpainting procedure based on Airy diffusion is proposed, implemented via Maple and applied to some digital images. Airy diffusion is a partial differential equation with spatial derivatives of third order in contrast with the usual diffusion with spatial derivatives of second order. Airy diffusion generates the Airy semigroup in terms of the Airy functions which can be rewritten in terms of Bessel functions. The Airy diffusion can be used to smooth an image with the corresponding noise elimination via convolution. Also the Airy diffusion can be used to erase objects from an image. We build an algorithm using the Maple package ImageTools and such algorithm is tested using some images. Our results using Airy diffusion are compared with the similar results using standard diffusion. We observe that Airy diffusion generates powerful filters for image processing which could be incorporated in the usual packages for image processing such as ImageJ and Photoshop. Also is interesting to consider the possibility to incorporate the Airy filters as applications for smartphones and smart-glasses.
From Sturm-Liouville problems to fractional and anomalous diffusions
D'Ovidio, Mirko
2010-01-01
Some fractional and anomalous diffusions are driven by equations involving fractional derivatives in both time and space. Such diffusions are processes with randomly varying times. In representing the solutions to those diffusions, the explicit laws of certain stable processes turn out to be fundamental. This paper directs one's efforts towards the explicit representation of solutions to fractional and anomalous diffusions related to Sturm-Liouville problems of fractional order associated to fractional power function spaces. Furthermore, we study a new version of the Bochner's subordination rule and we establish some connections between subordination and space-fractional operator
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Natural gas diffusion through the cap rock is mainly by means ofdissolving in water, so its concentration can be replaced by solubility, which varies with temperature, pressure and salinity in strata. Under certain geological conditions the maximal solubility is definite, so the diffusion com-putation can be handled approximately by stable state equation. Furthermore, on the basis of the restoration of the paleo-buried history, the diffusion is calculated with the dynamic method, and the result is very close to the real diffusion value in the geological history.
Pinheiro, J.P.; Domingos, R.F.
2005-01-01
The impact of the spherical diffusion contribution in labile trace metal speciation by stripping techniques was studied. It was shown that the relative error in the calculation of the stability constants caused by assuming linear diffusion varies with the efficiency of stirring, the diffusion coeffi
An Examination of the Acceptance, Adoption, and Diffusion of Smartphone Devices with Senior Citizens
Reneau, James M.
2013-01-01
This research looked at the process of the diffusion of an innovation in the context of smartphones with American senior citizens. The subject of diffusion, or spread of a technology, is a rich and varied topic with more than 60 years of research. Much of this diffusion research does not go beyond the study of the original acceptance of a new…
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Olsen, Ole Fogh; Sporring, Jon
2006-01-01
. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Fogh Olsen, Ole; Sporring, Jon
2007-01-01
. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....
Bronnen van diffuse bodembelasting
Lijzen JPA; Ekelenkamp A; LBG; DGM/BO
1995-01-01
Ten behoeve van het preventieve bodembeleid was onvoldoende duidelijk welke bijdrage diverse bronnen leveren aan diffuse bodembelasting. Doel van deze inventarisatie was beschikbare kennis over diffuse bodembelasting te bundelen en kennis-lacunes aan te geven. Nevendoel is het beschrijven van de
DEFF Research Database (Denmark)
Schultz, Ulrik Pagh
2007-01-01
, self-reconfigurable robots, we present the concept of distributed control diffusion: distributed queries are used to identify modules that play a specific role in the robot, and behaviors that implement specific control strategies are diffused throughout the robot based on these role assignments...... perform simple obstacle avoidance in a wide range of different car-like robots constructed using ATRON modules...
离散余弦小波包变换及语音信号压缩感知%Discrete cosine wavelet packet transform and compressed sensing for speech signal
Institute of Scientific and Technical Information of China (English)
张长青; 陈砚圃
2014-01-01
针对语音信号压缩感知问题,在研究语音离散余弦变换(Discrete Cosine Transform,DCT)系数和小波包变换(Wavelet Packet Transform,WPT)特性的基础上构造了离散余弦小波包变换(Discrete Cosine Wavelet Packet Transform,DCWPT).DCWPT首先获取语音信号的DCT域系数,结合语音频谱特性选取部分DCT系数进行WPT变换,从而得到比DCT系数更加稀疏的DCWPT系数.为将此变换直接用于压缩感知,构造了DCWPT的正交稀疏分解矩阵并分析了其稀疏表示性能.结合稀疏表示基优化了正交匹配追踪重构算法,提出了基于DCWPT的语音信号压缩感知框架.通过压缩重构对照实验,采用主客观评价指标,得出该方法优于传统基于DCT的语音压缩感知方法的结论.
Michaud, Georges; Richer, Jacques
2015-01-01
This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling. In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...
Time-varying interaction leads to amplitude death in coupled nonlinear oscillators
Indian Academy of Sciences (India)
Awadhesh Prasad
2013-09-01
A new form of time-varying interaction in coupled oscillators is introduced. In this interaction, each individual oscillator has always time-independent self-feedback while its interaction with other oscillators are modulated with time-varying function. This interaction gives rise to a phenomenon called amplitude death even in diffusively coupled identical oscillators. The nonlinear variation of the locus of bifurcation point is shown. Results are illustrated with Landau–Stuart (LS) and Rössler oscillators.
Computational simulations of vorticity enhanced diffusion
Vold, Erik L.
1999-11-01
Computer simulations are used to investigate a phenomenon of vorticity enhanced diffusion (VED), a net transport and mixing of a passive scalar across a prescribed vortex flow field driven by a background gradient in the scalar quantity. The central issue under study here is the increase in scalar flux down the gradient and across the vortex field. The numerical scheme uses cylindrical coordinates centered with the vortex flow which allows an exact advective solution and 1D or 2D diffusion using simple numerical methods. In the results, the ratio of transport across a localized vortex region in the presence of the vortex flow over that expected for diffusion alone is evaluated as a measure of VED. This ratio is seen to increase dramatically while the absolute flux across the vortex decreases slowly as the diffusion coefficient is decreased. Similar results are found and compared for varying diffusion coefficient, D, or vortex rotation time, τv, for a constant background gradient in the transported scalar vs an interface in the transported quantity, and for vortex flow fields constant in time vs flow which evolves in time from an initial state and with a Schmidt number of order unity. A simple analysis shows that for a small diffusion coefficient, the flux ratio measure of VED scales as the vortex radius over the thickness for mass diffusion in a viscous shear layer within the vortex characterized by (Dτv)1/2. The phenomenon is linear as investigated here and suggests that a significant enhancement of mixing in fluids may be a relatively simple linear process. Discussion touches on how this vorticity enhanced diffusion may be related to mixing in nonlinear turbulent flows.
GPU Generation of Large Varied Animated Crowds
Isaac Rudomin; Benjamín Hernández; Oriam de Gyves; Leonel Toledo; Ivan Rivalcoba; Sergio Ruiz
2013-01-01
..We discuss several steps in the process of simulating and visualizing large and varied crowds in real time for consumer-level computers and graphic cards (GPUs). Animating varied crowds using a diversity of models and animations (assets) is complex and costly. One has to use models that are expensive if bought, take a long time to model, and consume too much memory and computing resources. We discuss methods for simulating, generating, animating and rendering crowds of varied aspect and a d...
A new varied-time photonic crystals
Wu, Xiang-Yao; Ma, Ji; Liu, Xiao-Jing; Liang, Yu; Li, Hong; Chen, Wan-Jin; Yuan, Hong-chun; Li, Heng-Mei
2015-01-01
In this paper, we have firstly proposed a new one-dimensional varied-time photonic crystals, i.e., the refractive indices of media $A$ and $B$ are the time functions. We consider the varied-time photonic crystals of refractive indices period variation and calculate the transmissivity and electronic field distribution with and without defect layer, which are different from the conventional photonic crystals, which transmissivity and electronic field distribution are static, but the varied-time...
Inflationary Phase with Time Varying Fundamental Constants
Berman, M S; Berman, Marcelo S.; Trevisan, Luis A.
2002-01-01
Following Barrow, and Barrow and collaborators, we find a cosmological JBD model, with varying speed of light and varying fine structure constant, where the deceleration parameter is -1,causing acceleration of the Universe.Indeed, we have an exponential inflationary phase. Plancks time, energy, length,etc.,might have had different numerical values in the past, than those available in the litterature, due to the varying values for speed of light, and gravitational constant.
A new varied-time photonic crystals
2015-01-01
In this paper, we have firstly proposed a new one-dimensional varied-time photonic crystals, i.e., the refractive indices of media $A$ and $B$ are the time functions. We consider the varied-time photonic crystals of refractive indices period variation and calculate the transmissivity and electronic field distribution with and without defect layer, which are different from the conventional photonic crystals, which transmissivity and electronic field distribution are static, but the varied-time...
Effective diffusivity of passive scalars in rotating flow
Imazio, P Rodriguez
2012-01-01
We use direct numerical simulations to compute turbulent transport coefficients for passive scalars in turbulent rotating flows. Effective diffusion coefficients in the directions parallel and perpendicular to the rotations axis are obtained by studying the diffusion of an imposed initial profile for the passive scalar, and calculated by measuring the scalar average concentration and average spatial flux as a function of time. The Rossby and Schmidt numbers are varied to quantify their effect on the effective diffusion. It is find that rotation reduces scalar diffusivity in the perpendicular direction. The perpendicular diffusion can be estimated from mixing length arguments using the characteristic velocities and lengths perpendicular to the rotation axis. Deviations are observed for small Schmidt numbers, for which turbulent transport decreases and molecular diffusion becomes more significant.
Diffusion and sorption of organic micropollutants in biofilms with varying thicknesses
DEFF Research Database (Denmark)
Torresi, Elena; Polesel, Fabio; Bester, Kai
2017-01-01
, propranolol, citalopram, venlafaxine, erythromycin, clarithromycin and roxithromycin), revealing the importance of electrostatic interactions with solids. Sorption equilibria were likely not reached within the duration of batch experiments (4 h), particularly for the thickest biofilm, requiring...... and the sorption of 23 micropollutants were investigated in novel moving bed biofilm reactor (MBBR) carriers with controlled biofilm thickness (50, 200 and 500 μm) using targeted batch experiments (initial concentration = 1 μg L−1, for X-ray contrast media 15 μg L−1) and mathematical modelling. We assessed...
Diffusion variétale du palmier à huile (Elaeis guineensis Jacq.
Directory of Open Access Journals (Sweden)
Durand-Gasselin Tristan
2000-03-01
Full Text Available La productivité du palmier à huile au cours du siècle passé a connu une croissance importante où l’amélioration génétique a pris une large part. Elle a connu un rythme de croissance assez comparable à celui obtenu pour des plantes annuelles de pays tempérés (blé, maïs, tournesol, etc.. Il est possible de dégager les étapes importantes qui ont marqué l’histoire de l’amélioration. Après une assez longue période de sélection massale, l’exploitation du gène « shell », dont l’hérédité a été découverte par Beirnaert en 1939, a apporté une amélioration de 30% [1]. Vers 1960, l’exploitation de l’hétérosis des croisements inter-origines apporte une nouvelle amélioration de 10% environ [2]. Enfin, deux cycles de sélection récurrente ont été achevés par différentes équipes et chacun a apporté 12 à 18% d’amélioration de la productivité. En 1991, la valeur moyenne des semences commerciales, plantées dans de bonnes conditions, était proche de 6,7 tonnes d’huile par hectare et par an [3]. Aujourd’hui, elle est de l’ordre de 7,2 t/ha/an [4]. Ces gains quantitatifs ont été accompagnés de progrès qualitatifs importants comme la diminution de la vitesse de croissance, l’augmentation du pourcentage d’huile dans les régimes ou l’acquisition d’une forte résistance à la fusariose en Afrique de l’Ouest [5]. La qualité du futur matériel végétal devrait être sensiblement améliorée par l’utilisation d’une base génétique élargie dans les programmes d’amélioration [6]. En effet, les stations de recherche disposent d’une bonne diversité génétique rassemblée lors de nombreuses prospections réalisées en Afrique (pour E. guineensis et sur une espèce apparentée en Amérique latine (pour E. oleifera. Ces collections apportent de nouveaux caractères de qualité de l’huile, de résistance à la fusariose, qui sévit en Afrique, ou à la pourriture du cœur en Amérique latine. Le progrès génétique disponible en expérimentation doit être intégré dans les semences vulgarisées au plus vite et en quantité suffisante. Cependant, pour la reproduction du meilleur matériel, il existe des contraintes liées à la biologie des semences qui compliquent et ralentissent cette vulgarisation. En raison d’une dormance difficile à lever, les semences de palmier à huile sont distribuées sous forme de graines germées et leur distribution demande une organisation particulière.
Amplitude equations for isothermal double diffusive convection
Energy Technology Data Exchange (ETDEWEB)
Becerril, R.; Swift, J.B. [Center for Nonlinear Dynamics and Department of Physics, University of Texas, Austin, Texas 78712 (United States)
1997-05-01
Amplitude equations are derived for isothermal double diffusive convection near threshold for both the stationary and oscillatory instabilities as well as in the vicinity of the codimension-2 point. The convecting fluid is contained in a thin Hele-Shaw cell that renders the system two dimensional, and convection is sustained by vertical concentration gradients of two species with different diffusion rates. The locations of the tricritical point for the stationary instability and the codimension-2 point are found. It is shown that these points can be made well separated (in the Rayleigh number R{sub s} of the slow diffusing species) as the Lewis number varies. Hence the behavior near these points should be experimentally accessible. {copyright} {ital 1997} {ital The American Physical Society}
Cherniak, D. J.; Van Orman, J. A.
2014-03-01
Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.
Cosmology with matter diffusion
Calogero, Simone
2013-01-01
We construct a viable cosmological model based on velocity diffusion of matter particles. In order to ensure the conservation of the total energy-momentum tensor in the presence of diffusion, we include a cosmological scalar field $\\phi$ which we identify with the dark energy component of the Universe. The model is characterized by only one new degree of freedom, the diffusion parameter $\\sigma$. The standard $\\Lambda$CDM model can be recovered by setting $\\sigma=0$. If diffusion takes place ($\\sigma >0$) the dynamics of the matter and of the dark energy fields are coupled. We argue that the existence of a diffusion mechanism in the Universe can serve as a theoretical motivation for interacting models. We constrain the background dynamics of the diffusion model with Supernovae, H(z) and BAO data. We also perform a perturbative analysis of this model in order to understand structure formation in the Universe. We calculate the impact of diffusion both on the CMB spectrum, with particular attention to the integr...
Contagion dynamics in time-varying metapopulation networks
Perra, Nicola; Liu, Suyu; Baronchelli, Andrea
2014-03-01
The metapopulation framework is adopted in a wide array of disciplines to describe systems of well separated yet connected subpopulations. The subgroups/patches are often represented as nodes in a network whose links represent the migration routes among them. The connections has been so far mostly considered as static, but in general evolve in time. Here we address this case by investigating simple contagion processes on time-varying metapopulation networks. We focus on the SIR process, and determine analytically the mobility threshold for the onset of an epidemic spreading in the framework of activity-driven network models. We find profound differences from the case of static networks. The threshold is entirely described by the dynamical parameters defining the average number of instantaneously migrating individuals, and does not depend on the properties of the static network representation. Remarkably, the diffusion and contagion processes are slower in time-varying graphs than in their aggregated static counterparts, the mobility threshold been even two orders of magnitude larger in the first case. The presented results confirm the importance of considering the time-varying nature of complex networks.
Time varying effects in survival analysis
DEFF Research Database (Denmark)
Scheike, Thomas H.
2002-01-01
additive risk model; counting process; proportional hazards model; semi-parametric models; survival data; time-varying effects; nonparametric testing......additive risk model; counting process; proportional hazards model; semi-parametric models; survival data; time-varying effects; nonparametric testing...
Fractal analysis of time varying data
Vo-Dinh, Tuan; Sadana, Ajit
2002-01-01
Characteristics of time varying data, such as an electrical signal, are analyzed by converting the data from a temporal domain into a spatial domain pattern. Fractal analysis is performed on the spatial domain pattern, thereby producing a fractal dimension D.sub.F. The fractal dimension indicates the regularity of the time varying data.
Diffusion of limonene in polyethylene.
Limm, W; Begley, T H; Lickly, T; Hentges, S G
2006-07-01
Diffusion coefficients of limonene in various linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) resins have been determined from sorption data using a thermogravimetric methodology. From these data, one can determine whether polymer synthesis parameters such as the choice of catalytic process or co-monomer result in substantial differences in how much food packaging additives might migrate to food. For example, LLDPE is currently manufactured using either one of two distinct catalytic processes: Ziegler-Natta (ZN) and metallocene, a single-site catalyst. ZN catalysis is a heterogeneous process that has dominated polyolefin synthesis over the last half-century. It involves a transition metal compound containing a metal-carbon bond that can handle repeated insertion of olefin units. In contrast, metallocene catalysis has fewer than 20 years of history, but has generated much interest due to its ability to produce highly stereospecific polymers at a very high yield. In addition to high stereospecificity, metallocene-catalysed polymers are significantly lower in polydispersity than traditional ZN counterparts. Absorption and desorption testing of heat-pressed films made from LLDPE and LDPE resins of varying processing parameters indicates that diffusion coefficients of limonene in these resins do not change substantially.
Theories on diffusion of technology
DEFF Research Database (Denmark)
Munch, Birgitte
Tracing the body of the diffusion proces by analysing the diffusion process from historical, sociological, economic and technical approaches. Discussing central characteristics of the proces of diffusion og CAD/CAM in Denmark.......Tracing the body of the diffusion proces by analysing the diffusion process from historical, sociological, economic and technical approaches. Discussing central characteristics of the proces of diffusion og CAD/CAM in Denmark....
Various diffusion magnetic resonance imaging techniques for pancreatic cancer
Institute of Scientific and Technical Information of China (English)
Meng-Yue Tang; Xiao-Ming Zhang; Tian-Wu Chen; Xiao-Hua Huang
2015-01-01
Pancreatic cancer is one of the most common malignanttumors and remains a treatment-refractory cancer with a poor prognosis. Currently, the diagnosis of pancreatic neoplasm depends mainly on imaging and which methods are conducive to detecting small lesions. Compared to the other techniques, magnetic resonance imaging(MRI) has irreplaceable advantages and can provide valuable information unattainable with other noninvasive or minimally invasive imaging techniques. Advances in MR hardware and pulse sequence design have particularly improved the quality and robustness of MRI of the pancreas. Diffusion MR imaging serves as one of the common functional MRI techniques and is the only technique that can be used to reflect the diffusion movement of water molecules in vivo. It is generally known that diffusion properties depend on the characterization of intrinsic features of tissue microdynamics and microstructure. With the improvement of the diffusion models, diffusion MR imaging techniques are increasingly varied, from the simplest and most commonly used technique to the more complex. In this review, the various diffusion MRI techniques for pancreatic cancer are discussed, including conventional diffusion weighted imaging(DWI), multi-b DWI based on intra-voxel incoherent motion theory, diffusion tensor imaging and diffusion kurtosis imaging. The principles, main parameters, advantages and limitations of these techniques, as well as future directions for pancreatic diffusion imaging are also discussed.
DEFF Research Database (Denmark)
Zhang, Chen; Yu, Tao; Heiselberg, Per Kvols
-cooling period and night cooling potential. The investment cost of this ventilation system is about 5-10% lower than the conventional ones, because the acoustic ceiling could be directly applied as air diffuser and the use of plenum to distribute air reduces the cost of ductwork. There is a growing interest...... is not well structured with this system. These become the motivations in developing the design guide. This design guide aims to establish a systematic understanding of diffuse ceiling ventilation and provide assistance in designing of such a system. The guide is targeted at design engineers, architects...... and manufacturers and the users of diffuse ceiling technology. The design guide introduces the principle and key characteristics of room air distribution with diffuse ceiling ventilation. It provides an overview of potential benefit and limitations of this technology. The benefits include high thermal comfort, high...
DEFF Research Database (Denmark)
Zhang, Chen; Yu, Tao; Heiselberg, Per Kvols
with conventional ventilation systems (mixing or displacement ventilation), diffuse ceiling ventilation can significantly reduce or even eliminate draught risk in the occupied zone. Moreover, this ventilation system presents a promising opportunity for energy saving, because of the low pressure loss, extended free......Diffuse ceiling ventilation is an innovative ventilation concept where the suspended ceiling serves as an air diffuser to supply fresh air into the room. Due to the large opening area, air is delivered to the room with very low velocity and no fixed direction, therefore the name ‘diffuse’. Compared......-cooling period and night cooling potential. The investment cost of this ventilation system is about 5-10% lower than the conventional ones, because the acoustic ceiling could be directly applied as air diffuser and the use of plenum to distribute air reduces the cost of ductwork. There is a growing interest...
Seismic Fault Preserving Diffusion
Lavialle, Olivier; Germain, Christian; Donias, Marc; Guillon, Sebastien; Keskes, Naamen; Berthoumieu, Yannick
2007-01-01
This paper focuses on the denoising and enhancing of 3-D reflection seismic data. We propose a pre-processing step based on a non linear diffusion filtering leading to a better detection of seismic faults. The non linear diffusion approaches are based on the definition of a partial differential equation that allows us to simplify the images without blurring relevant details or discontinuities. Computing the structure tensor which provides information on the local orientation of the geological layers, we propose to drive the diffusion along these layers using a new approach called SFPD (Seismic Fault Preserving Diffusion). In SFPD, the eigenvalues of the tensor are fixed according to a confidence measure that takes into account the regularity of the local seismic structure. Results on both synthesized and real 3-D blocks show the efficiency of the proposed approach.
Seismic fault preserving diffusion
Lavialle, Olivier; Pop, Sorin; Germain, Christian; Donias, Marc; Guillon, Sebastien; Keskes, Naamen; Berthoumieu, Yannick
2007-02-01
This paper focuses on the denoising and enhancing of 3-D reflection seismic data. We propose a pre-processing step based on a non-linear diffusion filtering leading to a better detection of seismic faults. The non-linear diffusion approaches are based on the definition of a partial differential equation that allows us to simplify the images without blurring relevant details or discontinuities. Computing the structure tensor which provides information on the local orientation of the geological layers, we propose to drive the diffusion along these layers using a new approach called SFPD (Seismic Fault Preserving Diffusion). In SFPD, the eigenvalues of the tensor are fixed according to a confidence measure that takes into account the regularity of the local seismic structure. Results on both synthesized and real 3-D blocks show the efficiency of the proposed approach.
Isomorphism, Diffusion and Decoupling
DEFF Research Database (Denmark)
Boxenbaum, Eva; Jonsson, Stefan
2017-01-01
This chapter traces the evolution of the core theoretical constructs of isomorphism, decoupling and diffusion in organizational institutionalism. We first review the original theoretical formulations of these constructs and then examine their evolution in empirical research conducted over the past...
DEFF Research Database (Denmark)
Pries-Heje, Jan; Baskerville, Richard
2014-01-01
approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...... resulting from the design were two-day training workshops conceptually anchored to TBP. The design theory was evaluated through execution of eight diffusion workshops involving three different groups in the same company. The findings indicate that the match between the practice and the context materialized...... that the behavior will be effective). These two factors were especially critical if the source context of the best practice is qualitatively different from the target context into which the organization is seeking to diffuse the best practice....
Peppin, Stephen S. L.
2009-01-01
Diffusion and permeation are discussed within the context of irreversible thermodynamics. A new expression for the generalized Stokes-Einstein equation is obtained which links the permeability to the diffusivity of a two-component solution and contains the poroelastic Biot-Willis coefficient. The theory is illustrated by predicting the concentration and pressure profiles during the filtration of a protein solution. At low concentrations the proteins diffuse independently while at higher concentrations they form a nearly rigid porous glass through which the fluid permeates. The theoretically determined pressure drop is nonlinear in the diffusion regime and linear in the permeation regime, in quantitative agreement with experimental measurements. © 2009 Walter de Gruyter, Berlin, New York.
Brzoska, A M; Negele, J W; Thies, M
2004-01-01
A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops is formulated as a symmetry property related to the center symmetry of the underlying gauge theory. The results are expressed in terms of an effective Wilson loop action and compared with various limits of SU(2) Yang-Mills theory.
Directory of Open Access Journals (Sweden)
K. Banoo
1998-01-01
equation in the discrete momentum space. This is shown to be similar to the conventional drift-diffusion equation except that it is a more rigorous solution to the Boltzmann equation because the current and carrier densities are resolved into M×1 vectors, where M is the number of modes in the discrete momentum space. The mobility and diffusion coefficient become M×M matrices which connect the M momentum space modes. This approach is demonstrated by simulating electron transport in bulk silicon.
Energy Technology Data Exchange (ETDEWEB)
Mielke, U.
1979-01-01
We measured in 287 persons the pulmonary CO diffusion capacity with the steady-state and the single breath methods, applying apnoeic periods of 4 and 10 seconds duration. The aspects methodical significance, polyclinical applicability and pathognostic relevance with respect to other approved pulmonary functional tests are discussed. Differing pulmonary diffusion capacity values found in normal persons or in patients suffering from silicosis, pulmonary fibrosis, Boeck's disease or rheumatoid arthritis, were investigated and critically evaluated.
Diffusion in nanocrystalline solids
Chadwick, Alan V.
2016-01-01
Enhanced atomic migration was an early observation from experimental studies into nanocrystalline solids. This contribution presents an overview of the available diffusion data for simple metals and ionic materials in nanocrystalline form. It will be shown that enhanced diffusion can be interpreted in terms of atomic transport along the interfaces, which are comparable to grain boundaries in coarse-grained analogues. However, the method of sample preparation is seen to play a major role in...
Institute of Scientific and Technical Information of China (English)
罗善明; 吴晓铃; 徐攀; 王建
2011-01-01
基于齿轮啮合原理和数控加工理论,提出一种余弦齿廓滚铣两步加工新方法,即首先利用标准渐开线滚刀滚切出渐开线变位齿轮作为粗加工,并使其加工余量最小;再在此基础上利用立式三轴数控铣床进行铣削成形精加工.建立余弦齿廓滚切加工最小变位系数的数学模型,推导出余弦齿廓铣齿运动的空间转换矩阵,得到三轴数控铣齿成形的通用运动控制模型,分别确定滚齿和铣削的加工刀具选择方法,避免加工过程中出现"过切"及"欠切"现象.最后通过具体实例进行Matlab和Pro/E加工仿真,验证理论模型的正确性和加工方法的可行性.%A two-step method to manufacture a cosine tooth profile is presented based on the gear meshing principle and computer numerical control (CNC) machining theory. The first step as a rough machining is to generate a modlfied-tooth gear by using a standard involute hobbing cutter in order to obtain a minimal machining allowance. Secondly, a spherical milling cutter is used to generate the cosine tooth profile on a three-axis CNC milling machine. The mathematical model of the minimum modification coefficient used in the first step is established. The space transformation matrix of milling the cosine gear profile is derived, and the kinematic control model of generation of three-aixs CNC milling machine is obtained. Selection methods of cutters for hobbing and milling are determined respectively in order to avoid the overcut and undercut phenomena. The simulation results of the machining process of a specific example obtained by the software Matlab and Pro/E demonstrates the kinematic control model is correct and the machining method is feasible.
Institute of Scientific and Technical Information of China (English)
郭玲; 李劲松
2012-01-01
基于矢量衍射理论,研究了连续型相位光瞳滤波器对径向偏振光束在焦点区域成像效果的影响.设计了一种余弦函数形式的连续相位型光瞳滤波器,实现了缩小径向偏振光束的横向焦斑.利用Matlab优化工具箱,以超分辨性能参数G为优化目标,以斯特雷尔比S为约束条件,对余弦函数形式的连续相位型光瞳滤波器进行优化并给出了几组优化结果.优化结果表明所设计的余弦函数形式的连续相位型光瞳滤波器在数值孔径为0.8时对于缩小径向偏振光横向焦斑有明显的效果.关于此种连续相位光瞳滤波器的计算结果,对实际中制作相位光瞳滤波器有一定参考价值.%Based on vectorial diffraction theory, optical imaging system with continuous phase optical pupil filter for radially polarized beam is investigated. A continuous phase filter with cosine function is proposed and a sharper focus of radially polarized beam is obtained. This kind of filter is optimized with Matlab optimization toolbox and the aim of optimization is to reduce the superresolution parameter G with the Strehl ratio S as a constraint. Some examples of optimization are given. The optimization results show that there is a significant improvement on sharper focus by using this continuous phase filter with cosine function when the numerical aperture is 0.8. The numerical results about the continuous phase filter with cosine function will also help the manufacturing of actual devices.
An inverse approach to determining spatially varying arterial compliance using ultrasound imaging
Mcgarry, Matthew; Li, Ronny; Apostolakis, Iason; Nauleau, Pierre; Konofagou, Elisa E.
2016-08-01
The mechanical properties of arteries are implicated in a wide variety of cardiovascular diseases, many of which are expected to involve a strong spatial variation in properties that can be depicted by diagnostic imaging. A pulse wave inverse problem (PWIP) is presented, which can produce spatially resolved estimates of vessel compliance from ultrasound measurements of the vessel wall displacements. The 1D equations governing pulse wave propagation in a flexible tube are parameterized by the spatially varying properties, discrete cosine transform components of the inlet pressure boundary conditions, viscous loss constant and a resistance outlet boundary condition. Gradient descent optimization is used to fit displacements from the model to the measured data by updating the model parameters. Inversion of simulated data showed that the PWIP can accurately recover the correct compliance distribution and inlet pressure under realistic conditions, even under high simulated measurement noise conditions. Silicone phantoms with known compliance contrast were imaged with a clinical ultrasound system. The PWIP produced spatially and quantitatively accurate maps of the phantom compliance compared to independent static property estimates, and the known locations of stiff inclusions (which were as small as 7 mm). The PWIP is necessary for these phantom experiments as the spatiotemporal resolution, measurement noise and compliance contrast does not allow accurate tracking of the pulse wave velocity using traditional approaches (e.g. 50% upstroke markers). Results from simulations indicate reflections generated from material interfaces may negatively affect wave velocity estimates, whereas these reflections are accounted for in the PWIP and do not cause problems.
Stenhouse, Iona; O'Neill, Hugh; Lister, Gordon
2010-05-01
Diffusion rates in natural ilmenite of composition Fe0.842+ Fe0.163+Mn0.07Mg0.01Ti 0.92O3 from the Vishnevye Mountains (Urals, Russia) have been measured at 1000° C. Experiments were carried out in a one atmosphere furnace with oxygen fugacity controlled by flow of a CO-CO2 gas mixture, over a period of four hours. The diffusant source was a synthetic ilmenite (FeTiO3) powder doped with trace amounts of Mg, Co, Ni, Zr, Hf, V, Nb, Ta, Al, Cr, Ga and Y. Since, the natural ilmenite crystal contained Mn it was also possible to study diffusion of Mn from the ilmenite crystal. The experiments were analysed using the electron microprobe and scanning laser ablation ICP-MS. Diffusion profiles were measured for Al, Mg, Mn, Co, Ni, Ga, and Y. Diffusion of Cr, Hf, Zr, V, Nb and Ta was too slow to allow diffusion profiles to be accurately measured for the times and temperatures studied so far. The preliminary results show that diffusion in ilmenite is fast, with the diffusivity determined in this study on the order of 10-13 to 10-16 m2s-1. For comparison, Chakraborty (1997) found interdiffusion of Fe and Mg in olivine at 1000° C on the order of 10-17 to 10-18m2s-1 and Dieckmann (1998) found diffusivity of Fe, Mg, Co in magnetite at 1200° C to be on the order of 10-13 to 10-14 m2s-1. The order in which the diffusivity of the elements decreases is Mn > Co > Mg ≥ Ni > Al ≥ Y ≥ Ga, that is to say that Mn diffuses the fastest and Ga the slowest. Overall, this study intends to determine diffusion parameters such as frequency factor, activation energy and activation volume as a function of temperature and oxygen fugacity. This research is taking place in the context of a larger study focusing on the use of the garnet-ilmenite system as a geospeedometer. Examination of the consequences of simultaneous diffusion of multiple elements is a necessity if we are to develop an understanding of the crystal-chemical controls on diffusion (cf Spandler & O'Neill, in press). Chakraborty
Varying Alpha and the Electroweak Model
Kimberly, D; Kimberly, Dagny; Magueijo, Joao
2003-01-01
Inspired by recent claims for a varying fine structure constant, alpha, we investigate the effect of ``promoting coupling constants to variables'' upon various parameters of the standard model. We first consider a toy model: Proca's theory of the massive photon. We then explore the electroweak theory with one and two dilaton fields. We find that a varying alpha unavoidably implies varying W and Z masses. This follows from gauge invariance, and is to be contrasted with Proca' theory. For the two dilaton theory the Weinberg angle is also variable, but Fermi's constant and the tree level fermion masses remain constant unless the Higgs' potential becomes dynamical. We outline some cosmological implications.
Diffusion-driven multiscale analysis on manifolds and graphs: top-down and bottom-up constructions
Szlam, Arthur D.; Maggioni, Mauro; Coifman, Ronald R.; Bremer, James C., Jr.
2005-08-01
Classically, analysis on manifolds and graphs has been based on the study of the eigenfunctions of the Laplacian and its generalizations. These objects from differential geometry and analysis on manifolds have proven useful in applications to partial differential equations, and their discrete counterparts have been applied to optimization problems, learning, clustering, routing and many other algorithms.1-7 The eigenfunctions of the Laplacian are in general global: their support often coincides with the whole manifold, and they are affected by global properties of the manifold (for example certain global topological invariants). Recently a framework for building natural multiresolution structures on manifolds and graphs was introduced, that greatly generalizes, among other things, the construction of wavelets and wavelet packets in Euclidean spaces.8,9 This allows the study of the manifold and of functions on it at different scales, which are naturally induced by the geometry of the manifold. This construction proceeds bottom-up, from the finest scale to the coarsest scale, using powers of a diffusion operator as dilations and a numerical rank constraint to critically sample the multiresolution subspaces. In this paper we introduce a novel multiscale construction, based on a top-down recursive partitioning induced by the eigenfunctions of the Laplacian. This yields associated local cosine packets on manifolds, generalizing local cosines in Euclidean spaces.10 We discuss some of the connections with the construction of diffusion wavelets. These constructions have direct applications to the approximation, denoising, compression and learning of functions on a manifold and are promising in view of applications to problems in manifold approximation, learning, dimensionality reduction.
Tavatult jahe Karlovy Vary / Jaanus Noormets
Noormets, Jaanus
2011-01-01
1.-10. juulini toimunud Karlovy Vary 46. filmifestivalist (muusikafilmide alajaotuses näidati Marianne Kõrveri dokumentaalfilmi "Erkki-Sven Tüür: 7 etüüdi piltides" (2010) programmis "A Musical Odyssey")
Inhomogeneous Universe Models with Varying Cosmological Term
Chimento, L P; Chimento, Luis P.; Pavon, Diego
1998-01-01
The evolution of a class of inhomogeneous spherically symmetric universe models possessing a varying cosmological term and a material fluid, with an adiabatic index either constant or not, is studied.
Institute of Scientific and Technical Information of China (English)
I. I. Guseinov
2012-01-01
Simpler formulas are derived for one-range addition theorems for the integer and noninteger n generalized exponential type orbitals,momentum space orbitals,and hyperspherical harmonics with hyperbolic cosine (GETO HC,GMSO HC,and GHSH HC) in position,momentum and four-dimensional spaces,respectively.The final results are expressed in terms of one-range addition theorems of complete orthonormal sets of ψα-exponential type orbitals,(φ)α-momentum space orbitals and zα-hyperspherical harmonics.We notice that the one-range addition theorems for integer and noninteger n-Slater type orbitals and Gaussian type orbitals in position,momentum and four dimensional spaces are special cases of GETO HC,GMSO HC,and GHSH HC.The theorems presented can be useful in the accurate study of the electronic structure of atomic and molecular systems.
衍射增强成像中余弦曲线拟合方法的噪声分析%Noise analysis of cosine fitting radiography for diffraction enhanced imaging
Institute of Scientific and Technical Information of China (English)
鲍园; 王研; 朱佩平; 吴自玉
2015-01-01
衍射增强成像是一种功能强大的相位衬度成像技术，其信息分离研究一直都是研究热点。提出了一种简便的信息分离方法——余弦曲线拟合法(Cosine Fitting Radiography, CFR)，该方法具有简便、样品所受辐射剂量低等优点。利用同步辐射实验和蒙特卡罗仿真方法，从角度信号成像模型出发解释了此方法，同时从噪声传递角度分析了该方法的性能和给出定量的评价指标，建立了衍射增强成像和光栅微分干涉成像之间更直观的联系。对理解衍射增强成像系统的噪声行为和提高信噪比具有一定的参考意义。%Background: Diffraction enhanced imaging (DEI) is a powerful phase contrast imaging technique. Purpose: This study aims to investigate the noise properties of a new simple cosine fitting radiography for DEI based on the angular signal response imaging prototype. Methods: The rocking curve can be treated as a angular signal response and a simple multi-information retrieval algorithm based on the cosine function fitting. A comprehensive analysis of noise properties in DEI, based on a noise model including the fluctuation of the photon source, and a bias of the analyzer crystal are also given. The validations have been performed with Monte Carlo simulations based on the Geant4 toolkit combined with the refractive process of X-ray and synchrotron radiation experimental data. Results: The cosine fitting radiography (CFR) has been verified by Monte Carlo simulations and experimental data which are in good agreement with each other. The noise penalty is drastically reduced with high photon flux, high visibility and high angular precision. Conclusions: Based on the angular signal response function prototype, we analyze and calculate the noise properties of DEI. In addition, the analytical method can build a strong connection between DEI and grating-based phase contrast imaging (GDPCI) and widely suitable for all kinds of
Matrix-dependent multigrid-homogenization for diffusion problems
Energy Technology Data Exchange (ETDEWEB)
Knapek, S. [Institut fuer Informatik tu Muenchen (Germany)
1996-12-31
We present a method to approximately determine the effective diffusion coefficient on the coarse scale level of problems with strongly varying or discontinuous diffusion coefficients. It is based on techniques used also in multigrid, like Dendy`s matrix-dependent prolongations and the construction of coarse grid operators by means of the Galerkin approximation. In numerical experiments, we compare our multigrid-homogenization method with homogenization, renormalization and averaging approaches.
Institute of Scientific and Technical Information of China (English)
王海燕; 邓洪高; 刘庆华
2012-01-01
For wide band active noise control (ANC) system, as a result of the non-ideal characteristic and downsam-pling of the analysis filter banks, the aliasing problem between subband signals in the subband adaptive filter structure is introduced. An interpolated finite impulse response filter (IFIR) is employed to indirectly design the cosine-modulated filter banks prototype filter with high-stopband attenuation to achieve stopband energy minimization, in order to directly eliminate the aliasing problem between subband signals. It has low computational complexity. And compensation the error path delay avoids the delay of cosine-modulated filter banks. Simulation results show that this algorithm has good performance in the broadband gauss white noise and broadband color signal, especially for broadband color signal.%针对宽带有源噪声控制(ANC)系统,在采用子带自适应滤波结构时,由分析滤波器组的非理想特性及下采样原因引起的子带信号混叠问题,采用内插脉冲响应技术问接设计了一种高阻带衰减的低通原型滤波器,使得阻带能量最小化来直接消除子带信号间的混叠问题,具有较低的计算复杂度.同时,通过采用补偿误差通道延迟的方法来消除由分析滤波器组产生的延迟.仿真实验结果表明,该算法在宽带高斯白噪声和宽带有色信号下都具有较好的收敛性能,尤其对宽带有色信号.
Multidimensional diffusion MRI
Topgaard, Daniel
2017-02-01
Principles from multidimensional NMR spectroscopy, and in particular solid-state NMR, have recently been transferred to the field of diffusion MRI, offering non-invasive characterization of heterogeneous anisotropic materials, such as the human brain, at an unprecedented level of detail. Here we revisit the basic physics of solid-state NMR and diffusion MRI to pinpoint the origin of the somewhat unexpected analogy between the two fields, and provide an overview of current diffusion MRI acquisition protocols and data analysis methods to quantify the composition of heterogeneous materials in terms of diffusion tensor distributions with size, shape, and orientation dimensions. While the most advanced methods allow estimation of the complete multidimensional distributions, simpler methods focus on various projections onto lower-dimensional spaces as well as determination of means and variances rather than actual distributions. Even the less advanced methods provide simple and intuitive scalar parameters that are directly related to microstructural features that can be observed in optical microscopy images, e.g. average cell eccentricity, variance of cell density, and orientational order - properties that are inextricably entangled in conventional diffusion MRI. Key to disentangling all these microstructural features is MRI signal acquisition combining isotropic and directional dimensions, just as in the field of multidimensional solid-state NMR from which most of the ideas for the new methods are derived.
Allshouse, Michael; Barad, Mike; Peacock, Thomas
2009-11-01
When a density-stratified fluid encounters a sloping boundary, diffusion alters the fluid density adjacent to the boundary, producing spontaneous along-slope flow. Since stratified fluids are ubiquitous in nature, this phenomenon plays a vital role in environmental transport processes, including salt transport in rock fissures and ocean-boundary mixing. Here we show that diffusion-driven flow can be harnessed as a remarkable means of propulsion, acting as a diffusion-engine that extracts energy from microscale diffusive processes to propel macroscale objects. Like a sailboat tacking into the wind, forward motion results from fluid flow around an object, creating a region of low pressure at the front relative to the rear. In this case, however, the flow is driven by molecular diffusion and the pressure variations arise due to the resulting small changes in the fluid density. This mechanism has implications for a number of important systems, including environmental and biological transport processes at locations of strong stratification, such as pycnoclines in oceans and lakes. There is also a strong connection with other prevalent buoyancy-driven flows, such as valley and glacier winds, significantly broadening the scope of these results and opening up a new avenue for propulsion research.
Primary diffuse leptomeningeal gliosarcomatosis.
Moon, Ju Hyung; Kim, Se Hoon; Kim, Eui Hyun; Kang, Seok-Gu; Chang, Jong Hee
2015-04-01
Primary diffuse leptomeningeal gliomatosis (PDLG) is a rare condition with a fatal outcome, characterized by diffuse infiltration of the leptomeninges by neoplastic glial cells without evidence of primary tumor in the brain or spinal cord parenchyma. In particular, PDLG histologically diagnosed as gliosarcoma is extremely rare, with only 2 cases reported to date. We report a case of primary diffuse leptomeningeal gliosarcomatosis. A 68-year-old man presented with fever, chilling, headache, and a brief episode of mental deterioration. Initial T1-weighted post-contrast brain magnetic resonance imaging (MRI) showed diffuse leptomeningeal enhancement without a definite intraparenchymal lesion. Based on clinical and imaging findings, antiviral treatment was initiated. Despite the treatment, the patient's neurologic symptoms and mental status progressively deteriorated and follow-up MRI showed rapid progression of the disease. A meningeal biopsy revealed gliosarcoma and was conclusive for the diagnosis of primary diffuse leptomeningeal gliosarcomatosis. We suggest the inclusion of PDLG in the potential differential diagnosis of patients who present with nonspecific neurologic symptoms in the presence of leptomeningeal involvement on MRI.
Establishing the diffuse correlation spectroscopy signal relationship with blood flow.
Boas, David A; Sakadžić, Sava; Selb, Juliette; Farzam, Parisa; Franceschini, Maria Angela; Carp, Stefan A
2016-07-01
Diffuse correlation spectroscopy (DCS) measurements of blood flow rely on the sensitivity of the temporal autocorrelation function of diffusively scattered light to red blood cell (RBC) mean square displacement (MSD). For RBCs flowing with convective velocity [Formula: see text], the autocorrelation is expected to decay exponentially with [Formula: see text], where [Formula: see text] is the delay time. RBCs also experience shear-induced diffusion with a diffusion coefficient [Formula: see text] and an MSD of [Formula: see text]. Surprisingly, experimental data primarily reflect diffusive behavior. To provide quantitative estimates of the relative contributions of convective and diffusive movements, we performed Monte Carlo simulations of light scattering through tissue of varying vessel densities. We assumed laminar vessel flow profiles and accounted for shear-induced diffusion effects. In agreement with experimental data, we found that diffusive motion dominates the correlation decay for typical DCS measurement parameters. Furthermore, our model offers a quantitative relationship between the RBC diffusion coefficient and absolute tissue blood flow. We thus offer, for the first time, theoretical support for the empirically accepted ability of the DCS blood flow index ([Formula: see text]) to quantify tissue perfusion. We find [Formula: see text] to be linearly proportional to blood flow, but with a proportionality modulated by the hemoglobin concentration and the average blood vessel diameter.
Directory of Open Access Journals (Sweden)
Ahti Jaatinen-Värri
2014-01-01
Full Text Available The effect of the width of the vaneless diffuser on the stage performance and flow fields of a centrifugal compressor is studied numerically and experimentally. The diffuser width is varied by reducing the diffuser flow area from the shroud side (i.e., pinching the diffuser. Seven different diffuser widths are studied with numerical simulation. In the modeling, the diffuser width b/b2 is varied within the range 1.00 to 0.50. The numerical results are compared with results obtained in previous studies. In addition, two of the diffusers are further investigated with experimental measurement. The main finding of the work is that the pinch reduces losses in the impeller associated with the tip-clearance flow. Furthermore, it is shown that a too large width reduction causes the flow to accelerate excessively, resulting in a highly nonuniform flow field and flow separation near the shroud.
Energy Technology Data Exchange (ETDEWEB)
Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.
1980-05-01
Experiments on diffusion of /sup 137/Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of /sup 137/Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000/sup 0/C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ..delta..E of the equation D/epsilon = (D/epsilon)/sub 0/ exp (-..delta..E/RT) are about 4 x 10/sup -2/ cm/sup 2//s and 30 kcal/mole, respectively.
Vrentas, James S
2013-01-01
The book first covers the five elements necessary to formulate and solve mass transfer problems, that is, conservation laws and field equations, boundary conditions, constitutive equations, parameters in constitutive equations, and mathematical methods that can be used to solve the partial differential equations commonly encountered in mass transfer problems. Jump balances, Green’s function solution methods, and the free-volume theory for the prediction of self-diffusion coefficients for polymer–solvent systems are among the topics covered. The authors then use those elements to analyze a wide variety of mass transfer problems, including bubble dissolution, polymer sorption and desorption, dispersion, impurity migration in plastic containers, and utilization of polymers in drug delivery. The text offers detailed solutions, along with some theoretical aspects, for numerous processes including viscoelastic diffusion, moving boundary problems, diffusion and reaction, membrane transport, wave behavior, sedime...
Convection-driven spherical shell dynamos at varying Prandtl numbers
Käpylä, P. J.; Käpylä, M. J.; Olspert, N.; Warnecke, J.; Brandenburg, A.
2017-02-01
Context. Stellar convection zones are characterized by vigorous high-Reynolds number turbulence at low Prandtl numbers. Aims: We study the dynamo and differential rotation regimes at varying levels of viscous, thermal, and magnetic diffusion. Methods: We perform three-dimensional simulations of stratified fully compressible magnetohydrodynamic convection in rotating spherical wedges at various thermal and magnetic Prandtl numbers (from 0.25 to 2 and from 0.25 to 5, respectively). Differential rotation and large-scale magnetic fields are produced self-consistently. Results: We find that for high thermal diffusivity, the rotation profiles show a monotonically increasing angular velocity from the bottom of the convection zone to the top and from the poles toward the equator. For sufficiently rapid rotation, a region of negative radial shear develops at mid-latitudes as the thermal diffusivity is decreased, corresponding to an increase of the Prandtl number. This coincides with and results in a change of the dynamo mode from poleward propagating activity belts to equatorward propagating ones. Furthermore, the clearly cyclic solutions disappear at the highest magnetic Reynolds numbers and give way to irregular sign changes or quasi-stationary states. The total (mean and fluctuating) magnetic energy increases as a function of the magnetic Reynolds number in the range studied here (5-151), but the energies of the mean magnetic fields level off at high magnetic Reynolds numbers. The differential rotation is strongly affected by the magnetic fields and almost vanishes at the highest magnetic Reynolds numbers. In some of our most turbulent cases, however, we find that two regimes are possible, where either differential rotation is strong and mean magnetic fields are relatively weak, or vice versa. Conclusions: Our simulations indicate a strong nonlinear feedback of magnetic fields on differential rotation, leading to qualitative changes in the behaviors of large
Position-dependent diffusion of light in disordered waveguides
Yamilov, Alexey G; Redding, Brandon; Payne, Ben; Noh, Heeso; Cao, Hui
2014-01-01
Diffusion has been widely used to describe a random walk of particles or waves, and it requires only one parameter -- the diffusion constant. For waves, however, diffusion is an approximation that disregards the possibility of interference. Anderson localization, which manifests itself through a vanishing diffusion coefficient in an infinite system, originates from constructive interference of waves traveling in loop trajectories -- pairs of time-reversed paths returning to the same point. In an open system of finite size, the return probability through such paths is reduced, particularly near the boundary where waves may escape. Based on this argument, the self-consistent theory of localization and the supersymmetric field theory predict that the diffusion coefficient varies spatially inside the system. A direct experimental observation of this effect is a challenge because it requires monitoring wave transport inside the system. Here, we fabricate two-dimensional photonic random media and probe position-dep...
Size dependence of tracer diffusion in a laponite colloidal gel.
Petit, Laure; Barentin, Catherine; Colombani, Jean; Ybert, Christophe; Bocquet, Lydéric
2009-10-20
Using a fluorescence recovery after photobleaching (FRAP) technique, we present measurements of probe diffusion in a colloidal glass-a Laponite suspension. By varying the probe size over 2 orders of magnitude, as well as the concentration of the colloidal glass, we evidence and quantify the deviations of the probe diffusivity from the bulk Stokes-Einstein expectations. These experiments suggest that the probe diffusion in the dynamically arrested Laponite structure is mainly controlled by the ratio between the probe size and the typical clay platelets interdistance. Comparing with a simple hindered diffusion mechanism, the reduction of tracer diffusion is discussed in terms of the hydrodynamic interaction of the probe with the Laponite structure. Finally, these results can be interpreted in terms of a scale dependent viscosity of the colloidal glass.
Self-diffusion of wet particles in rotating drums
Liu, P. Y.; Yang, R. Y.; Yu, A. B.
2013-06-01
Axial mixing of wet particles in rotating drums was investigated by the discrete element method with the capillary force explicitly considered. Different flow regimes were observed by varying the surface tension of liquid and keeping other conditions unchanged. The analysis of the concentration and mean square displacement of particles indicated that the axial motion of wet particles was a diffusive process characterised by Fick's law. Particle diffusivity decreased with increasing inter-particle cohesion and drum filling level but increased with increasing drum rotation speed. Two competing mechanisms were proposed to explain these effects. A theoretical model based on the relation between local diffusivity and shear rate was developed to predict particle diffusivity as a function of drum operation conditions. It was also observed that despite the high inhomogeneity of particle flow in rotating drums, the mean diffusivity of flow exhibited a strong correlation with granular temperature, defined as the mean square fluctuating velocity of particles.
How heterogeneous timing of participation across people improves diffusion
Akbarpour, Mohammad
2016-01-01
Recent studies have shown that non-Poisson ("bursty") behaviors in human interactions can impede the diffusion of information or infectious diseases in social networks. Those studies generally consider models in which nodes are independently active according to the same random timing process, and vary that timing. In reality, people differ widely in the patterns of their active periods of interaction. In this paper, we develop a simple model of diffusion on networks in which agents can differ in the autocorrelation of their activity patterns. We show that bursty behavior does not always hurt the diffusion, and depending on the features of the environment, having some (but not all) of the population being bursty significantly helps diffusion. Moreover, we prove that in a variety of settings maximizing diffusion requires heterogeneous activity patterns across agents and does not involve any Poisson behavior.
Peterson, N.
1982-01-01
The more useful experimental techniques for determining grain-boundary diffusion are briefly described followed by a presentation of results that shed light on the models and mechanisms of grain-boundary and dislocation diffusion. Studies of the following grain-boundary diffusion phenomena will be considered ; anisotropy in grain-boundary diffusion, effect of orientation relationship on grain-boundary diffusion, effect of boundary type and dislocation dissociation, lattice structure, correlat...
Variational denoising of partly textured images by spatially varying constraints.
Gilboa, Guy; Sochen, Nir; Zeevi, Yehoshua Y
2006-08-01
Denoising algorithms based on gradient dependent regularizers, such as nonlinear diffusion processes and total variation denoising, modify images towards piecewise constant functions. Although edge sharpness and location is well preserved, important information, encoded in image features like textures or certain details, is often compromised in the process of denoising. We propose a mechanism that better preserves fine scale features in such denoising processes. A basic pyramidal structure-texture decomposition of images is presented and analyzed. A first level of this pyramid is used to isolate the noise and the relevant texture components in order to compute spatially varying constraints based on local variance measures. A variational formulation with a spatially varying fidelity term controls the extent of denoising over image regions. Our results show visual improvement as well as an increase in the signal-to-noise ratio over scalar fidelity term processes. This type of processing can be used for a variety of tasks in partial differential equation-based image processing and computer vision, and is stable and meaningful from a mathematical viewpoint.
A novel method to evaluate spin diffusion length of Pt
Energy Technology Data Exchange (ETDEWEB)
Zhang, Yan-qing; Sun, Niu-yi; Che, Wen-ru [Shanghai Key Laboratory of Special Artificial Microstructure and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Shan, Rong, E-mail: shan.rong@hotmail.com [Shanghai Key Laboratory of Special Artificial Microstructure and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Zhu, Zhen-gang, E-mail: zgzhu@ucas.ac.cn [School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049 (China)
2016-05-01
Spin diffusion length of Pt is evaluated via proximity effect of spin orbit coupling (SOC) and anomalous Hall effect (AHE) in Pt/Co{sub 2}FeAl bilayers. By varying the thicknesses of Pt and Co{sub 2}FeAl layer, the thickness dependences of AHE parameters can be obtained, which are theoretically predicted to be proportional to the square of the SOC strength. According to the physical image of the SOC proximity effect, the spin diffusion length of Pt can easily be identified from these thickness dependences. This work provides a novel method to evaluate spin diffusion length in a material with a small value.
Nonlocal electrical diffusion equation
Gómez-Aguilar, J. F.; Escobar-Jiménez, R. F.; Olivares-Peregrino, V. H.; Benavides-Cruz, M.; Calderón-Ramón, C.
2016-07-01
In this paper, we present an analysis and modeling of the electrical diffusion equation using the fractional calculus approach. This alternative representation for the current density is expressed in terms of the Caputo derivatives, the order for the space domain is 0numerical methods based on Fourier variable separation. The case with spatial fractional derivatives leads to Levy flight type phenomena, while the time fractional equation is related to sub- or super diffusion. We show that the mathematical concept of fractional derivatives can be useful to understand the behavior of semiconductors, the design of solar panels, electrochemical phenomena and the description of anomalous complex processes.
Phase transformation and diffusion
Kale, G B; Dey, G K
2008-01-01
Given that the basic purpose of all research in materials science and technology is to tailor the properties of materials to suit specific applications, phase transformations are the natural key to the fine-tuning of the structural, mechanical and corrosion properties. A basic understanding of the kinetics and mechanisms of phase transformation is therefore of vital importance. Apart from a few cases involving crystallographic martensitic transformations, all phase transformations are mediated by diffusion. Thus, proper control and understanding of the process of diffusion during nucleation, g
Ingrin, Jannick; Zhang, Peipei
2016-04-01
Hydrogen mobility in gem quality zircon single crystals from Madagascar was investigated through H-D exchange experiments. Thin slices were annealed in a horizontal furnace flushed with a gas mixture of Ar/D2(10%) under ambient pressure between 900 ° C to 1150 ° C. FTIR analyses were performed on oriented slices before and after each annealing run. H diffusion along [100] and [010] follow the same diffusion law D = D0exp[-E /RT], with log D0 = 2.24 ± 1.57 (in m2/s) and E = 374 ± 39 kJ/mol. H diffusion along [001] follows a slightly more rapid diffusion law, with log D0 = 1.11 ± 0.22 (in m2/s) and E = 334 ± 49 kJ/mol. H diffusion in zircon has much higher activation energy and slower diffusivity than other NAMs below 1150 ° C even iron-poor garnets which are known to be among the slowest (Blanchard and Ingrin, 2004; Kurka et al. 2005). During H-D exchange zircon incorporates also deuterium. This hydration reaction involves uranium reduction as it is shown from the exchange of U5+ and U4+ characteristic bands in the near infrared region during annealing. It is the first time that a hydration reaction U5+ + OH- = U4+ + O2- + 1/2H2, is experimentally reported. The kinetics of deuterium incorporation is slightly slower than hydrogen diffusion, suggesting that the reaction is limited by hydrogen mobility. Hydrogen isotopic memory of zircon is higher than other NAMs. Zircons will be moderately retentive of H signatures at mid-crustal metamorphic temperatures. At 500 ° C, a zircon with a radius of 300 μm would retain its H isotopic signature over more than a million years. However, a zircon is unable to retain this information for geologically significant times under high-grade metamorphism unless the grain size is large enough. Refrences Blanchard, M. and Ingrin, J. (2004) Hydrogen diffusion in Dora Maira pyrope. Physics and Chemistry of Minerals, 31, 593-605. Kurka, A., Blanchard, M. and Ingrin, J. (2005) Kinetics of hydrogen extraction and deuteration in
Wu Zhuo Qun; Li Hui Lai; Zhao Jun Ning
2001-01-01
Nonlinear diffusion equations, an important class of parabolic equations, come from a variety of diffusion phenomena which appear widely in nature. They are suggested as mathematical models of physical problems in many fields, such as filtration, phase transition, biochemistry and dynamics of biological groups. In many cases, the equations possess degeneracy or singularity. The appearance of degeneracy or singularity makes the study more involved and challenging. Many new ideas and methods have been developed to overcome the special difficulties caused by the degeneracy and singularity, which
Directory of Open Access Journals (Sweden)
R.T. DeHoff
2002-09-01
Full Text Available The phenomenological formalism, which yields Fick's Laws for diffusion in single phase multicomponent systems, is widely accepted as the basis for the mathematical description of diffusion. This paper focuses on problems associated with this formalism. This mode of description of the process is cumbersome, defining as it does matrices of interdiffusion coefficients (the central material properties that require a large experimental investment for their evaluation in three component systems, and, indeed cannot be evaluated for systems with more than three components. It is also argued that the physical meaning of the numerical values of these properties with respect to the atom motions in the system remains unknown. The attempt to understand the physical content of the diffusion coefficients in the phenomenological formalism has been the central fundamental problem in the theory of diffusion in crystalline alloys. The observation by Kirkendall that the crystal lattice moves during diffusion led Darken to develop the concept of intrinsic diffusion, i.e., atom motion relative to the crystal lattice. Darken and his successors sought to relate the diffusion coefficients computed for intrinsic fluxes to those obtained from the motion of radioactive tracers in chemically homogeneous samples which directly report the jump frequencies of the atoms as a function of composition and temperature. This theoretical connection between tracer, intrinsic and interdiffusion behavior would provide the basis for understanding the physical content of interdiffusion coefficients. Definitive tests of the resulting theoretical connection have been carried out for a number of binary systems for which all three kinds of observations are available. In a number of systems predictions of intrinsic coefficients from tracer data do not agree with measured values although predictions of interdiffusion coefficients appear to give reasonable agreement. Thus, the complete
Diffusion in advanced materials
Murch, Graeme; Belova, Irina
2014-01-01
In the first chapter Prof. Kozubski and colleagues present atomisticsimulations of superstructure transformations of intermetallic nanolayers.In Chapter 2, Prof. Danielewski and colleagues discuss a formalism for themorphology of the diffusion zone in ternary alloys. In Chapter 3, ProfessorsSprengel and Koiwa discuss the classical contributions of Boltzmann andMatano for the analysis of concentration-dependent diffusion. This isfollowed by Chapter 4 by Professor Cserháti and colleagues on the use of Kirkendall porosity for fabricating hollow hemispheres. In Chapter 5,Professor Morton-Blake rep
Directory of Open Access Journals (Sweden)
Fabio Marchesoni
2013-08-01
Full Text Available The longstanding problem of Brownian transport in a heterogeneous quasi one-dimensional medium with space-dependent self-diffusion coefficient is addressed in the overdamped (zero mass limit. A satisfactory mesoscopic description is obtained in the Langevin equation formalism by introducing an appropriate drift term, which depends on the system macroscopic observables, namely the diffuser concentration and current. The drift term is related to the microscopic properties of the medium. The paradoxical existence of a finite drift at zero current suggests the possibility of designing a Maxwell demon operating between two equilibrium reservoirs at the same temperature.
Digital repetitive control under varying frequency conditions
Ramos, Germán A; Olm, Josep M
2013-01-01
The tracking/rejection of periodic signals constitutes a wide field of research in the control theory and applications area. Repetitive Control has proven to be an efficient way to face this topic. However, in some applications the frequency of the reference/disturbance signal is time-varying or uncertain. This causes an important performance degradation in the standard Repetitive Control scheme. This book presents some solutions to apply Repetitive Control in varying frequency conditions without loosing steady-state performance. It also includes a complete theoretical development and experimental results in two representative systems. The presented solutions are organized in two complementary branches: varying sampling period Repetitive Control and High Order Repetitive Control. The first approach allows dealing with large range frequency variations while the second allows dealing with small range frequency variations. The book also presents applications of the described techniques to a Roto-magnet plant and...
Varying alpha and the electroweak model
Energy Technology Data Exchange (ETDEWEB)
Kimberly, Dagny; Magueijo, Joao
2004-03-25
Inspired by recent claims for a varying fine structure constant, alpha, we investigate the effect of 'promoting coupling constants to variables' upon various parameters of the standard model. We first consider a toy model: Proca theory of the massive photon. We then explore the electroweak theory with one and two dilaton fields. We find that a varying alpha unavoidably implies varying W and Z masses. This follows from gauge invariance, and is to be contrasted with Proca theory. For the two dilaton theory the Weinberg angle is also variable, but Fermi's constant and the tree level fermion masses remain constant unless the Higgs potential becomes dynamical. We outline some cosmological implications.
Chechkin, A V; Metzler, R; Sokolov, I M
2016-01-01
A growing number of biological, soft, and active matter systems are observed to exhibit normal diffusive dynamics with a linear growth of the mean squared displacement, yet with a non-Gaussian distribution of increments. Based on the Chubinsky-Slater idea of a diffusing diffusivity we here establish and analyse a complete minimal model framework of diffusion processes with fluctuating diffusivity. In particular, we demonstrate the equivalence of the diffusing diffusivity process in the short time limit with a superstatistical approach based on a distribution of diffusivities. Moreover, we establish a subordination picture of Brownian but non-Gaussian diffusion processes, that can be used for a wide class of diffusivity fluctuation statistics. Our results are shown to be in excellent agreement with simulations and numerical evaluations.
Solar mass-varying neutrino oscillations.
Barger, V; Huber, Patrick; Marfatia, Danny
2005-11-18
We propose that the solar neutrino deficit may be due to oscillations of mass-varying neutrinos (MaVaNs). This scenario elucidates solar neutrino data beautifully while remaining comfortably compatible with atmospheric neutrino and K2K data and with reactor antineutrino data at short and long baselines (from CHOOZ and KamLAND). We find that the survival probability of solar MaVaNs is independent of how the suppression of neutrino mass caused by the acceleron-matter couplings varies with density. Measurements of MeV and lower energy solar neutrinos will provide a rigorous test of the idea.
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Sporring, Jon; Fogh Olsen, Ole
2008-01-01
. To address this problem, we introduce a photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way, we preserve important illumination features, while...
DEFF Research Database (Denmark)
Pries-Heje, Jan; Baskerville, Richard
2014-01-01
Both the practice and the research literature on information systems attach great value to the identification and dissemination of information on “best practices”. In the philosophy of science, this type of knowledge is regarded as technological knowledge because it becomes manifest in the succes......Both the practice and the research literature on information systems attach great value to the identification and dissemination of information on “best practices”. In the philosophy of science, this type of knowledge is regarded as technological knowledge because it becomes manifest...... in the successful techniques in one context. While the value for other contexts is unproven, knowledge of best practices circulates under an assumption that the practices will usefully self-diffuse through innovation and adoption in other contexts. We study diffusion of best practices using a design science...... approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...
Model of information diffusion
Lande, D V
2008-01-01
The system of cellular automata, which expresses the process of dissemination and publication of the news among separate information resources, has been described. A bell-shaped dependence of news diffusion on internet-sources (web-sites) coheres well with a real behavior of thematic data flows, and at local time spans - with noted models, e.g., exponential and logistic ones.
DEVELOPMENT, DIFFUSION, AND EVALUATION.
GUBA, EGON G.
THE KNOWLEDGE GAP BETWEEN INITIAL RESEARCH AND FINAL USE IS DISCUSSED IN TERMS OF THE FOUR STATES OF THE THEORY-PRACTICE CONTINUUM (RESEARCH, DEVELOPMENT, DIFFUSION, AND ADOPTION). THE TWO MIDDLE STAGES ARE EMPHASIZED. RESEARCH AND DEVELOPMENT CENTERS, REGIONAL EDUCATIONAL LABORATORIES, AND TITLE III PROJECTS ARE SUGGESTED AS AGENCIES RESPONSIBLE…
Sack, Jeff
2005-01-01
OsmoBeaker is a CD-ROM designed to enhance the learning of diffusion and osmosis by presenting interactive experimentation to the student. The software provides several computer simulations that take the student through different scenarios with cells, having different concentrations of solutes in them.
Pelleg, Joshua
2016-01-01
This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. Solutions of Fick’s second law for constant D, diffusion in grain boundaries and dislocations are presented along with a look at the atomistic approach for the random motion of atoms. In the second part, the author discusses diffusion in several technologically important ceramics. The ceramics selected are monolithic single phase ones, including: A12O3, SiC, MgO, ZrO2 and Si3N4. Of these, three refer to oxide ceramics (alumina, magnesia and zirconia). Carbide based ceramics are represented by the technologically very important Si-ca...
Vlaskin, Vladimir A; Barrows, Charles J; Erickson, Christian S; Gamelin, Daniel R
2013-09-25
A diffusion-based synthesis of doped colloidal semiconductor nanocrystals is demonstrated. This approach involves thermodynamically controlled addition of both impurity cations and host anions to preformed seed nanocrystals under equilibrium conditions, rather than kinetically controlled doping during growth. This chemistry allows thermodynamic crystal compositions to be prepared without sacrificing other kinetically trapped properties such as shape, size, or crystallographic phase. This doping chemistry thus shares some similarities with cation-exchange reactions, but proceeds without the loss of host cations and excels at the introduction of relatively unreactive impurity ions that have not been previously accessible using cation exchange. Specifically, we demonstrate the preparation of Cd(1-x)Mn(x)Se (0 ≤ x ≤ ∼0.2) nanocrystals with narrow size distribution, unprecedentedly high Mn(2+) content, and very large magneto-optical effects by diffusion of Mn(2+) into seed CdSe nanocrystals grown by hot injection. Controlling the solution and lattice chemical potentials of Cd(2+) and Mn(2+) allows Mn(2+) diffusion into the internal volumes of the CdSe nanocrystals with negligible Ostwald ripening, while retaining the crystallographic phase (wurtzite or zinc blende), shape anisotropy, and ensemble size uniformity of the seed nanocrystals. Experimental results for diffusion doping of other nanocrystals with other cations are also presented that indicate this method may be generalized, providing access to a variety of new doped semiconductor nanostructures not previously attainable by kinetic routes or cation exchange.
DEFF Research Database (Denmark)
Zhang, Chen
both thermal comfort and energy efficient aspects. The present study aims to characterize the air distribution and thermal comfort in the rooms with diffuse ceiling ventilation. Both the stand-alone ventilation system and its integration with a radiant ceiling system are investigated. This study also...
Rappoldt, C.
1992-01-01
The structure of an aggregated soil is characterized by the distribution of the distance from an arbitrary point in the soil to the nearest macropore or crack. From this distribution an equivalent model system is derived to which a diffusion model can be more easily applied. The model system consist
Nonmonotonic diffusion in crowded environments
Putzel, Gregory Garbès; Tagliazucchi, Mario; Szleifer, Igal
2015-01-01
We study the diffusive motion of particles among fixed spherical crowders. The diffusers interact with the crowders through a combination of a hard-core repulsion and a short-range attraction. The long-time effective diffusion coefficient of the diffusers is found to depend non-monotonically on the strength of their attraction to the crowders. That is, for a given concentration of crowders, a weak attraction to the crowders enhances diffusion. We show that this counterintuitive fact can be understood in terms of the mesoscopic excess chemical potential landscape experienced by the diffuser. The roughness of this excess chemical potential landscape quantitatively captures the nonmonotonic dependence of the diffusion rate on the strength of crowder-diffuser attraction; thus it is a purely static predictor of dynamic behavior. The mesoscopic view given here provides a unified explanation for enhanced diffusion effects that have been found in various systems of technological and biological interest. PMID:25302920
Filmihullu eluvesi voolab Karlovy Varys / Margit Tõnson
Tõnson, Margit, 1978-
2010-01-01
Karlovy Vary rahvusvahelisest filmifestivalist. Filmidest "Mr. Nobody" (rež. Jaco Van Dormaeli), "Kasside ema Teresa" (rež. Pawel Sala) ja "The Arbor" (rež. Clio Barnardi). Nimekiri võitnud töödest ja viimastel aastatel festivalil näidatud Eesti mängufilmidest
Efficient Estimation in Heteroscedastic Varying Coefficient Models
Directory of Open Access Journals (Sweden)
Chuanhua Wei
2015-07-01
Full Text Available This paper considers statistical inference for the heteroscedastic varying coefficient model. We propose an efficient estimator for coefficient functions that is more efficient than the conventional local-linear estimator. We establish asymptotic normality for the proposed estimator and conduct some simulation to illustrate the performance of the proposed method.
Cosmo MSW effect for mass varying neutrinos
Hung, P Q; Hung, Pham Quang; P\\"as, Heinrich
2003-01-01
We consider neutrinos with varying masses which arise in scenarios relating neutrino masses to the dark energy density in the universe. We point out that the neutrino mass variation can lead to level crossing and thus a cosmo MSW effect, having dramatic consequences for the flavor ratio of astrophysical neutrinos and the composition of the relic neutrino background.
2010-01-01
45. Karlovy Vary filmifestivali võistlusprogrammis "East of the West" märgiti ära Veiko Õunpuu film "Püha Tõnu kiusamine". Peaauhind läks rumeenlase Cristi Puiu filmile "Aurora". Grand prix´sai Augustĺ Vila film "La mosquitera". Teisi preemiasaajaid
Filmihullu eluvesi voolab Karlovy Varys / Margit Tõnson
Tõnson, Margit, 1978-
2010-01-01
Karlovy Vary rahvusvahelisest filmifestivalist. Filmidest "Mr. Nobody" (rež. Jaco Van Dormaeli), "Kasside ema Teresa" (rež. Pawel Sala) ja "The Arbor" (rež. Clio Barnardi). Nimekiri võitnud töödest ja viimastel aastatel festivalil näidatud Eesti mängufilmidest
Ellipsometry with randomly varying polarization states
Liu, F.; Lee, C. J.; Chen, J. Q.; E. Louis,; van der Slot, P. J. M.; Boller, K. J.; F. Bijkerk,
2012-01-01
We show that, under the right conditions, one can make highly accurate polarization-based measurements without knowing the absolute polarization state of the probing light field. It is shown that light, passed through a randomly varying birefringent material has a well-defined orbit on the Poincar s
[Diffusion-weighted MRI of the prostate].
Mueller-Lisse, U G; Mueller-Lisse, U L; Zamecnik, P; Schlemmer, H-P W; Scherr, M K
2011-03-01
Diffusion-weighted magnetic resonance imaging (DWI) can complement MRI of the prostate in the detection and localization of prostate cancer, particularly after previous negative biopsy. A total of 13 original reports and 2 reviews published in 2010 demonstrate that prostate cancer can be detected by DWI due to its increased cell density and decreased diffusiveness, either qualitatively in DWI images or quantitatively by means of the apparent diffusion coefficient (ADC). In the prostate, the ADC is influenced by the strength of diffusion weighting, localization (peripheral or transitional zone), presence of prostatitis or hemorrhage and density and differentiation of prostate cancer cells. Mean differences between healthy tissue of the peripheral zone and prostate cancer appear to be smaller for ADC than for the (choline + creatine)/citrate ratio in MR spectroscopy. Test quality parameters vary greatly between different studies but appear to be slightly better for combined MRI and DWI than for MRI of the prostate alone. Clinical validation of DWI of the prostate requires both increased technical conformity and increased numbers of patients in clinical studies.
Factors Affecting Diffusion of Ions in Soils
Institute of Scientific and Technical Information of China (English)
LICHENG－BAO; YANGDING－QING
1993-01-01
In this work the diffusion coefficients of Na+,K+,Ca2+,NO3- and Cl- ions were estimated in terms of measuring apparent direct current (DC) conductivities of latosol,red soil and yellow-brown earth containing,respectively,NaNO3,NCl,and CaCl2 of different concentrations (0.005,0.05,0.10,and 0.15 mol/L) in the case of moisture contents ranging from wet to water saturation.The results showed that when bulk density,moisture content,and electrolyte concentration were constant,the diffusion coefficients of cations were in the order Na+>K+>Ca2+ except for Na+ and K+ in latosol,while the order for anions was NO3->Cl-.The diffusion coefficients (Di) of cations and anions were linearly proportional to volumetric moisture content (θ） as electrolyte concentration and bulk density were unchanged.When moisture content and bulk density were constant,the diffusion coefficients of cations decreased,to varying extents,with the increase of electrolyte concentration,and the decrement in different soils followed the order yellow-brown earth> red soil> latosol,but the decrement order of different cations was Na+>K+>Ca2+.
Magnetic orientation of nontronite clay in aqueous dispersions and its effect on water diffusion.
Abrahamsson, Christoffer; Nordstierna, Lars; Nordin, Matias; Dvinskikh, Sergey V; Nydén, Magnus
2015-01-01
The diffusion rate of water in dilute clay dispersions depends on particle concentration, size, shape, aggregation and water-particle interactions. As nontronite clay particles magnetically align parallel to the magnetic field, directional self-diffusion anisotropy can be created within such dispersion. Here we study water diffusion in exfoliated nontronite clay dispersions by diffusion NMR and time-dependant 1H-NMR-imaging profiles. The dispersion clay concentration was varied between 0.3 and 0.7 vol%. After magnetic alignment of the clay particles in these dispersions a maximum difference of 20% was measured between the parallel and perpendicular self-diffusion coefficients in the dispersion with 0.7 vol% clay. A method was developed to measure water diffusion within the dispersion in the absence of a magnetic field (random clay orientation) as this is not possible with standard diffusion NMR. However, no significant difference in self-diffusion coefficient between random and aligned dispersions could be observed.
NMR relaxation and water self-diffusion studies in whey protein solutions and gels.
Colsenet, Roxane; Mariette, François; Cambert, Mireille
2005-08-24
The changes in water proton transverse relaxation behavior induced by aggregation of whey proteins are explained in terms of the simple molecular processes of diffusion and chemical exchange. The water self-diffusion coefficient was measured in whey protein solutions and gels by the pulsed field gradient NMR method. As expected, water self-diffusion was reduced with increased protein concentrations. Whatever the concentration, the water molecules were free to diffuse over distances varying from 15 to 47 mum. Water diffusion was constant over these distances, demonstrating that no restrictions were found to explain the water hindrance. The modification in protein structure by gelation induced a decrease in water diffusion. The effects of protein concentration on water diffusion are discussed and modeled. Two approaches were compared, the obstruction effect induced by a spherical particle and the cell model, which considered two water compartments with specific self-diffusion coefficients.
Oscillatory variation of anomalous diffusion in pendulum systems
Indian Academy of Sciences (India)
G Sakthivel; S Rajasekar
2011-03-01
Numerical studies of anomalous diffusion in undamped but periodically-driven and parametrically-driven pendulum systems are presented. When the frequency of the periodic driving force is varied, the exponent , which is the rate of divergence of the mean square displacement with time, is found to vary in an oscillatory manner. We show the presence of such a variation in other statistical measures such as variance of position, kurtosis, and exponents in the power-exponential law of probability distribution of position.
Varying-coefficient functional linear regression
Wu, Yichao; Müller, Hans-Georg; 10.3150/09-BEJ231
2011-01-01
Functional linear regression analysis aims to model regression relations which include a functional predictor. The analog of the regression parameter vector or matrix in conventional multivariate or multiple-response linear regression models is a regression parameter function in one or two arguments. If, in addition, one has scalar predictors, as is often the case in applications to longitudinal studies, the question arises how to incorporate these into a functional regression model. We study a varying-coefficient approach where the scalar covariates are modeled as additional arguments of the regression parameter function. This extension of the functional linear regression model is analogous to the extension of conventional linear regression models to varying-coefficient models and shares its advantages, such as increased flexibility; however, the details of this extension are more challenging in the functional case. Our methodology combines smoothing methods with regularization by truncation at a finite numb...
Varying flexibilities in systems of organised decentralisation
DEFF Research Database (Denmark)
Ilsøe, Anna; Andersen, Søren Kaj
information, collective agreements and interviews with representatives from tradeunions and employers' associations in Germany and Denmark. Based on our preliminary findings three explanatory theses for further research are developed in the article: 1) The level of specification, i.e. the level where...... response to this pressure from the company level can be described as a form of organised decentralisation in both countries, the response within the Danish collective bargaining system can be characterised as a proactive organised decentralisation while the response of the German system should rather...... be while the response of the German system should rather be interpreted as a reactive organised decentralisation. 3) The varying regulation of working time flexibility in Germany and Denmark implies varying risks in the regulation. In Germany lacking competencies in small or medium-sized companies lead...
Varying flexibilities in systems of organised decentralisation
DEFF Research Database (Denmark)
Ilsøe, Anna; Andersen, Søren Kaj
information, collective agreements and interviews with representatives from tradeunions and employers' associations in Germany and Denmark. Based on our preliminary findings three explanatory theses for further research are developed in the article: 1) The level of specification, i.e. the level where...... response to this pressure from the company level can be described as a form of organised decentralisation in both countries, the response within the Danish collective bargaining system can be characterised as a proactive organised decentralisation while the response of the German system should rather...... be while the response of the German system should rather be interpreted as a reactive organised decentralisation. 3) The varying regulation of working time flexibility in Germany and Denmark implies varying risks in the regulation. In Germany lacking competencies in small or medium-sized companies lead...
Fractal model of anomalous diffusion.
Gmachowski, Lech
2015-12-01
An equation of motion is derived from fractal analysis of the Brownian particle trajectory in which the asymptotic fractal dimension of the trajectory has a required value. The formula makes it possible to calculate the time dependence of the mean square displacement for both short and long periods when the molecule diffuses anomalously. The anomalous diffusion which occurs after long periods is characterized by two variables, the transport coefficient and the anomalous diffusion exponent. An explicit formula is derived for the transport coefficient, which is related to the diffusion constant, as dependent on the Brownian step time, and the anomalous diffusion exponent. The model makes it possible to deduce anomalous diffusion properties from experimental data obtained even for short time periods and to estimate the transport coefficient in systems for which the diffusion behavior has been investigated. The results were confirmed for both sub and super-diffusion.
Diffusion in porous crystalline materials
Krishna, R.
2012-01-01
The design and development of many separation and catalytic process technologies require a proper quantitative description of diffusion of mixtures of guest molecules within porous crystalline materials. This tutorial review presents a unified, phenomenological description of diffusion inside meso-
On a time varying fine structure constant
Berman, M S; Berman, Marcelo S.; Trevisan, Luis A.
2001-01-01
By employing Dirac LNH, and a further generalization by Berman (GLNH), we estimate how should vary the total number of nucleons, the energy density, Newton Gravitational constant, the cosmological constant, the magnetic permeability and electric permitivity, of the Universe,in order to account for the experimentally observed time variation of the fine structure constant. As a bonus,we find an acceptable value for the deceleration parameter of the present Universe, compatible with the Supernovae observations.
Stabilization of Slowly Varying Switched Linear Systems
Institute of Scientific and Technical Information of China (English)
ZHANG Bing; LIANG Tong
2012-01-01
The stabilization problem of systems that switch among a finite set of slowly varying linear systems with arbitrary switching frequency is discussed.It is shown that if the entries of the pointwise stabilizing feedback gain matrix are continuously differentiable functions of the entries of the system coefficient matrices,then the closed-loop system is uniformly asymptotically stable if the rate of time variation of the system coefficient matrices is sufficiently small.
APPLICATION OF TIME-VARYING VISCOUS GROUT IN GRAVEL- FOUNDATION ANTI-SEEPAGE TREATMENT*
Institute of Scientific and Technical Information of China (English)
CHENG Peng-da; LI Lu; TANG Ju; WANG Dao-zeng
2011-01-01
The time-varying viscosity of common grout and the controllable grout are measured with a rotation viscometer in experiments. The time-varying viscosity of grout is analyzed according to the characteristics in the process of anti-seepage treatment for gravel foundation. The principle of effective stress for porous medium is applied to analyzes the fluid-structure coupling in grouting. In the consideration of coupling physical variables, dynamic models of porosity, permeability and viscosity are constructed.The difiusion radius can thus be defined by the foundational porosity. The distribution of holes in field experiments is designed according to the diffusion radius of grout. Then, the permeability test is designed to verify the grout effect. The calculated diffusion radius coincides with experimental results, and the permeability meets the requirements of the project, which is valuable for the anti-seepage treatment in gravel foundation.
Directory of Open Access Journals (Sweden)
Kenneth Burgi
2016-11-01
Full Text Available Phase front modulation was previously used to refocus light after transmission through scattering media. This process has been adapted here to work in reflection. A liquid crystal spatial light modulator is used to conjugate the phase scattering properties of diffuse reflectors to produce a converging phase front just after reflection. The resultant focused spot had intensity enhancement values between 13 and 122 depending on the type of reflector. The intensity enhancement of more specular materials was greater in the specular region, while diffuse reflector materials achieved a greater enhancement in non-specular regions, facilitating non-mechanical steering of the focused spot. Scalar wave optics modeling corroborates the experimental results.
Directory of Open Access Journals (Sweden)
Roberto Cipriani
2011-06-01
Full Text Available It is quite likely that the origins of prayer are to be found in ancient mourning and bereavement rites. Primeval ritual prayer was codified and handed down socially to become a deep-rooted feature of people’s cultural behavior, so much so, that it may surface again several years later, in the face of death, danger, need, even in the case of relapse from faith and religious practice. Modes of prayer depend on religious experience, on relations between personal prayer and political action, between prayer and forgiveness, and between prayer and approaches to religions. Various forms of prayer exist, from the covert-hidden to the overt-manifest kind. How can they be investigated? How can one, for instance, explore mental prayer? These issues regard the canon of diffused religion and, therefore, of diffused prayer.
Galactic Diffuse Polarized Emission
Indian Academy of Sciences (India)
Ettore Carretti
2011-12-01
Diffuse polarized emission by synchrotron is a key tool to investigate magnetic fields in the Milky Way, particularly the ordered component of the large scale structure. Key observables are the synchrotron emission itself and the RM is by Faraday rotation. In this paper the main properties of the radio polarized diffuse emission and its use to investigate magnetic fields will be reviewed along with our current understanding of the galactic magnetic field and the data sets available. We will then focus on the future perspective discussing RM-synthesis – the new powerful instrument devised to unlock the information encoded in such an emission – and the surveys currently in progress like S-PASS and GMIMS.
New varying speed of light theories
Magueijo, J
2003-01-01
We review recent work on the possibility of a varying speed of light (VSL). We start by discussing the physical meaning of a varying $c$, dispelling the myth that the constancy of $c$ is a matter of logical consistency. We then summarize the main VSL mechanisms proposed so far: hard breaking of Lorentz invariance; bimetric theories (where the speeds of gravity and light are not the same); locally Lorentz invariant VSL theories; theories exhibiting a color dependent speed of light; varying $c$ induced by extra dimensions (e.g. in the brane-world scenario); and field theories where VSL results from vacuum polarization or CPT violation. We show how VSL scenarios may solve the cosmological problems usually tackled by inflation, and also how they may produce a scale-invariant spectrum of Gaussian fluctuations, capable of explaining the WMAP data. We then review the connection between VSL and theories of quantum gravity, showing how ``doubly special'' relativity has emerged as a VSL effective model of quantum space...
Anomalous diffusion of epicentres
Sotolongo-Costa, Oscar; Posadas, A; Luzon, F
2007-01-01
The classification of earthquakes in main shocks and aftershocks by a method recently proposed by M. Baiesi and M. Paczuski allows to the generation of a complex network composed of clusters that group the most correlated events. The spatial distribution of epicentres inside these structures corresponding to the catalogue of earthquakes in the eastern region of Cuba shows anomalous anti-diffusive behaviour evidencing the attractive nature of the main shock and the possible description in terms of fractional kinetics.
Ramiro-H, Manuel; Cruz-A, Enrique
2016-01-01
Between August 19 and 21, the Feria del Libro de las Ciencias de la Salud (Healthcare Book Fair) took place in the Palacio de Medicina in Mexico City. Archives of Medical Research, Revista Médica del IMSS, and Saber IMSS, three of the main instruments of knowledge diffusion of the Instituto Mexicano del Seguro Social, assisted to this book fair, which was organized by the Facultad de Medicina of UNAM.
DEFF Research Database (Denmark)
Pries-Heje, Jan; Baskerville, Richard
2014-01-01
Both the practice and the research literature on information systems attach great value to the identification and dissemination of information on “best practices”. In the philosophy of science, this type of knowledge is regarded as technological knowledge because it becomes manifest in the succes...... that the behavior will be effective). These two factors were especially critical if the source context of the best practice is qualitatively different from the target context into which the organization is seeking to diffuse the best practice.......Both the practice and the research literature on information systems attach great value to the identification and dissemination of information on “best practices”. In the philosophy of science, this type of knowledge is regarded as technological knowledge because it becomes manifest...... approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...
Visualization of molecular excitons diffusion
Salamatova, Evgeniia; Kozlov, Oleg V.; Luponosov, Yuriy N.; Solodukhin, Alexander N.; Toropynina, Viktoria Y.; Ponomarenko, Sergei A.; Pshenichnikov, Maxim S.
2016-09-01
Small organic molecules of the push-pull architecture are rapidly gaining their status in the organic electronics applications. In densely packed molecular films, both intra- and intermolecular interactions play an essential role for the device performance. Here we study two different molecules, a highly symmetric star-shaped one and its newly synthesized single arm analogue, for their photophysical properties. Both chromophores were dissolved in a solid matrix at different concentrations to vary their separation and therefore intermolecular coupling. We show that in both molecules the population relaxation accelerates by more than a factor of 10 at shorter intermolecular distances due to self-quenching thereby reducing the exciton survival time. The transient anisotropy dynamics are also quite similar, with their substantial acceleration at shorter interchromophore distances due to exciton diffusion caused by the Förster-like resonance energy transfer. However, the anisotropy values are noticeably lower for the star-shaped molecule because of intramolecular mixing of different polarization states. Finally, a model is presented that accounts for the observed results.
Sodium diffusion in boroaluminosilicate glasses
DEFF Research Database (Denmark)
Smedskjaer, Morten M.; Zheng, Qiuju; Mauro, John C.
2011-01-01
diffusivity are explored in terms of the structural role of ferric and ferrous ions. By comparing the results obtained by the three approaches, we observe that both the tracer Na diffusion and the Na-K interdiffusion are significantly faster than the Na inward diffusion. The origin of this discrepancy could...
Snow isotope diffusion rates measured in a laboratory experiment
Van der Wel, L. G.; Gkinis, V.; Pohjola, V. A.; Meijer, H. A. J.
2011-01-01
The diffusion of stable water isotopes in snow was measured in two controlled laboratory experiments. Two batches of snow of different isotopic composition were stacked alternately with varying layer thicknesses. The stack was stored in a freezer room at constant temperature for several months, and
Diffusion Characteristics of Toluene into Natural Rubber/Linear Low Density Polyethylene Blends
Obasi, Henry C.; Okoro Ogbobe; Isaac O. Igwe
2009-01-01
The sorption and diffusion of toluene through blends of natural rubber (NR) and linear low density polyethylene (LLDPE) of varying compositions were studied at 35, 55, and 65°C by conventional weight-gain experiments. The effects of blend ratio on the diffusion, sorption, and permeation coefficients were determined. The sorption data were used to estimate the activation energies of diffusion and permeation, parameters which were found to show a decrease when the amount of NR or LLDPE was incr...
New varying speed of light theories
Energy Technology Data Exchange (ETDEWEB)
Magueijo, Joao [Blackett Laboratory, Imperial College of Science, Technology and Medicine, South Kensington, London SW7 2BZ (United Kingdom)
2003-11-01
We review recent work on the possibility of a varying speed of light (VSL). We start by discussing the physical meaning of a varying-c, dispelling the myth that the constancy of c is a matter of logical consistency. We then summarize the main VSL mechanisms proposed so far: hard breaking of Lorentz invariance; bimetric theories (where the speeds of gravity and light are not the same); locally Lorentz invariant VSL theories; theories exhibiting a colour-dependent speed of light; varying-c induced by extra dimensions (e.g. in the brane-world scenario); and field theories where VSL results from vacuum polarization or CPT violation. We show how VSL scenarios may solve the cosmological problems usually tackled by inflation, and also how they may produce a scale-invariant spectrum of Gaussian fluctuations, capable of explaining the WMAP data. We then review the connection between VSL and theories of quantum gravity, showing how 'doubly special' relativity has emerged as a VSL effective model of quantum space-time, with observational implications for ultra-high energy cosmic rays (UHECRs) and gamma ray bursts. Some recent work on the physics of 'black' holes and other compact objects in VSL theories is also described, highlighting phenomena associated with spatial (as opposed to temporal) variations in c. Finally, we describe the observational status of the theory. The evidence is currently slim-redshift dependence in the atomic fine structure, anomalies with UHECRs, and (to a much lesser extent) the acceleration of the universe and the WMAP data. The constraints (e.g. those arising from nucleosynthesis or geological bounds) are tight but not insurmountable. We conclude with the observational predictions of the theory and the prospects for its refutation or vindication.
New varying speed of light theories
Magueijo, João
2003-11-01
We review recent work on the possibility of a varying speed of light (VSL). We start by discussing the physical meaning of a varying-c, dispelling the myth that the constancy of c is a matter of logical consistency. We then summarize the main VSL mechanisms proposed so far: hard breaking of Lorentz invariance; bimetric theories (where the speeds of gravity and light are not the same); locally Lorentz invariant VSL theories; theories exhibiting a colour-dependent speed of light; varying-c induced by extra dimensions (e.g. in the brane-world scenario); and field theories where VSL results from vacuum polarization or CPT violation. We show how VSL scenarios may solve the cosmological problems usually tackled by inflation, and also how they may produce a scale-invariant spectrum of Gaussian fluctuations, capable of explaining the WMAP data. We then review the connection between VSL and theories of quantum gravity, showing how 'doubly special' relativity has emerged as a VSL effective model of quantum space-time, with observational implications for ultra-high energy cosmic rays (UHECRs) and gamma ray bursts. Some recent work on the physics of 'black' holes and other compact objects in VSL theories is also described, highlighting phenomena associated with spatial (as opposed to temporal) variations in c. Finally, we describe the observational status of the theory. The evidence is currently slim—redshift dependence in the atomic fine structure, anomalies with UHECRs, and (to a much lesser extent) the acceleration of the universe and the WMAP data. The constraints (e.g. those arising from nucleosynthesis or geological bounds) are tight but not insurmountable. We conclude with the observational predictions of the theory and the prospects for its refutation or vindication.
Epidemic Diffusion on Complex Networks
Institute of Scientific and Technical Information of China (English)
WU Xiao-Yan; LIU Zong-Hua
2007-01-01
Boyh diffusion and epidemic are well studied in the stochastic systems and complex networks,respetively.Here we combine these two fields and study epidemic diffusion in complex networks.Instead of studying the threshold of infection,which was focused on in previous works,we focus on the diffusion.behaviour.We find that the epidemic diffusion in a complex network is an anomalous superdiffusion with varyingg diffusion exponext γand that γ is influenced seriously by the network structure,such as the clustering coefficient and the degree distribution.Numerical simulations have confirmed the theoretical predictions.
Advanced diffusion processes and phenomena
Öchsner, Andreas; Belova, Irina
2014-01-01
This topical volume on Advanced Diffusion Processes and Phenomena addresses diffusion in a wider sense of not only mass diffusion but also heat diffusion in fluids and solids. Both diffusion phenomena play an important role in the characterization of engineering materials and corresponding structures. Understanding these different transport phenomena at many levels, from atomistic to macro, has therefore long attracted the attention of many researchers in materials science and engineering and related disciplines. The present topical volume captures a representative cross-section of some of the
Tracking time-varying coefficient-functions
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg; Nielsen, Torben Skov; Joensen, Alfred K.;
2000-01-01
is a combination of recursive least squares with exponential forgetting and local polynomial regression. It is argued, that it is appropriate to let the forgetting factor vary with the value of the external signal which is the argument of the coefficient functions. Some of the key properties of the modified method......, but otherwise unknown, functions of a low-dimensional input process. These coefficient functions are estimated adaptively and recursively without specifying a global parametric, form, i.e. the method allows for online tracking of the coefficient functions. Essentially, in its most simple form, the method...
Tracking Time-Varying Coefficient-Functions
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg; Nielsen, Torben Skov; Joensen, Alfred K.;
1999-01-01
of recursive least squares with exponential forgetting and local polynomial regression. However, it is argued, that it is appropriate to let the forgetting factor vary with the value of the external signal shich is argument of the coeffieient-functions.The properties of the modified method are sutdied......A conditional parametric ARX-model is an ARX-model in which the parameters re replaced by smooth functions of an, possibly multivariate, externalinput signal. These functions are called coefficient functions is suggested. Essentially, in its most simple form, this method is a combination...
A time-varying magnetic flux concentrator
Kibret, B.; Premaratne, M.; Lewis, P. M.; Thomson, R.; Fitzgerald, P. B.
2016-08-01
It is known that diverse technological applications require the use of focused magnetic fields. This has driven the quest for controlling the magnetic field. Recently, the principles in transformation optics and metamaterials have allowed the realization of practical static magnetic flux concentrators. Extending such progress, here, we propose a time-varying magnetic flux concentrator cylindrical shell that uses electric conductors and ferromagnetic materials to guide magnetic flux to its center. Its performance is discussed based on finite-element simulation results. Our proposed design has potential applications in magnetic sensors, medical devices, wireless power transfer, and near-field wireless communications.
Image Based Rendering under Varying Illumination
Institute of Scientific and Technical Information of China (English)
Wang Chengfeng (王城峰); Hu Zhanyi
2003-01-01
A new approach for photorealistic rendering of a class of objects at arbitrary illumination is presented. The approach of the authors relies entirely on image based rendering techniques. A scheme is utilized for re-illumination of objects based on linear combination of low dimensional image representations. The minimum rendering condition of technique of the authors is three sample images under varying illumination of a reference object and a single input image of an interested object. Important properties of this approach are its simplicity, robustness and speediness. Experimental results validate the proposed rendering approach.
Diffusion in intermetallic compounds studied using short-lived radioisotopes
Diffusion – the long range movement of atoms – plays an important role in materials processing and in determining suitable applications for materials. Conventional radiotracer methods for measuring diffusion can determine readily how distributions of radioactive probe atoms in samples evolve under varying experimental conditions. It is possible to obtain limited information about atomic jump rates and pathways from these measurements; however, it is desirable to make more direct observations of the atomic jumps by using experimental methods that are sensitive to atomic scale processes. One such method is time-differential perturbed $\\gamma$–$\\gamma$-angular correlation spectroscopy (PAC). Two series of PAC experiments using $^{111m}$Cd are proposed to contribute to fundamental understanding of diffusion in intermetallic compounds. The goal of the first is to determine the dominant vacancy species in several Li$_{2}$-structured compounds and see if the previously observed change in diffusion mechanism th...
Simple deterministic dynamical systems with fractal diffusion coefficients
Klages, R
1999-01-01
We analyze a simple model of deterministic diffusion. The model consists of a one-dimensional periodic array of scatterers in which point particles move from cell to cell as defined by a piecewise linear map. The microscopic chaotic scattering process of the map can be changed by a control parameter. This induces a parameter dependence for the macroscopic diffusion coefficient. We calculate the diffusion coefficent and the largest eigenmodes of the system by using Markov partitions and by solving the eigenvalue problems of respective topological transition matrices. For different boundary conditions we find that the largest eigenmodes of the map match to the ones of the simple phenomenological diffusion equation. Our main result is that the difffusion coefficient exhibits a fractal structure by varying the system parameter. To understand the origin of this fractal structure, we give qualitative and quantitative arguments. These arguments relate the sequence of oscillations in the strength of the parameter-dep...
Vessel enhancing diffusion: a scale space representation of vessel structures.
Manniesing, Rashindra; Viergever, Max A; Niessen, Wiro J
2006-12-01
A method is proposed to enhance vascular structures within the framework of scale space theory. We combine a smooth vessel filter which is based on a geometrical analysis of the Hessian's eigensystem, with a non-linear anisotropic diffusion scheme. The amount and orientation of diffusion depend on the local vessel likeliness. Vessel enhancing diffusion (VED) is applied to patient and phantom data and compared to linear, regularized Perona-Malik, edge and coherence enhancing diffusion. The method performs better than most of the existing techniques in visualizing vessels with varying radii and in enhancing vessel appearance. A diameter study on phantom data shows that VED least affects the accuracy of diameter measurements. It is shown that using VED as a preprocessing step improves level set based segmentation of the cerebral vasculature, in particular segmentation of the smaller vessels of the vasculature.
Asymptotic Properties of Solutions of Parabolic Equations Arising from Transient Diffusions
Institute of Scientific and Technical Information of China (English)
A.M. Il'in; R.Z. Khasminskii; G. Yin
2002-01-01
This work is concerned with asymptotic properties of a class of parabolic systems arising from singularly perturbed diffusions. The underlying system has a fast varying component and a slowly changing component. One of the distinct features is that the fast varying diffusion is transient. Under such a setup, this paper presents an asymptotic analysis of the solutions of such parabolic equations. Asymptotic expansions of functional satisfying the parabolic system are obtained. Error bounds are derived.
Local Rank Inference for Varying Coefficient Models.
Wang, Lan; Kai, Bo; Li, Runze
2009-12-01
By allowing the regression coefficients to change with certain covariates, the class of varying coefficient models offers a flexible approach to modeling nonlinearity and interactions between covariates. This paper proposes a novel estimation procedure for the varying coefficient models based on local ranks. The new procedure provides a highly efficient and robust alternative to the local linear least squares method, and can be conveniently implemented using existing R software package. Theoretical analysis and numerical simulations both reveal that the gain of the local rank estimator over the local linear least squares estimator, measured by the asymptotic mean squared error or the asymptotic mean integrated squared error, can be substantial. In the normal error case, the asymptotic relative efficiency for estimating both the coefficient functions and the derivative of the coefficient functions is above 96%; even in the worst case scenarios, the asymptotic relative efficiency has a lower bound 88.96% for estimating the coefficient functions, and a lower bound 89.91% for estimating their derivatives. The new estimator may achieve the nonparametric convergence rate even when the local linear least squares method fails due to infinite random error variance. We establish the large sample theory of the proposed procedure by utilizing results from generalized U-statistics, whose kernel function may depend on the sample size. We also extend a resampling approach, which perturbs the objective function repeatedly, to the generalized U-statistics setting; and demonstrate that it can accurately estimate the asymptotic covariance matrix.
Seasonally Varying Reference Atmospheres for East Asia
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Vertical profiles of seasonally varying pressure, temperature, water vapor, and trace gases (O3, N2O, CO,CH4), representing atmospheric conditions up to a height of 100 km over the East Asia region (30°-50°N,110°-150°E) were constructed by using various observation data, model outputs of atmospheric thermodynamic parameters, and gaseous concentrations. Optical characteristics of the obtained East Asia reference atmospheres were compared with those from typical midlatitude summer and winter atmospheres. It was noted that, in the water vapor field, there are major differences between the two model atmospheres during the summer. The resultant impact during the summer of water vapor difference on incoming solar fluxes at the surface and emitted terrestrial fluxes at the top of the atmosphere are 14.3 W m-2 and 6.5 W m-2,respectively. On the other hand, the winter difference between East Asian and midlatitude atmospheres appears to be insignificant. Reference atmospheres for the spring and fall are also available. Utilizing the constructed atmospheric profiles as inputs to the radiative transfer model, it is expected that the constructed seasonally varying reference atmospheres can facilitate better descriptions of optical properties in East Asia.
Varying prior information in Bayesian inversion
Walker, Matthew; Curtis, Andrew
2014-06-01
Bayes' rule is used to combine likelihood and prior probability distributions. The former represents knowledge derived from new data, the latter represents pre-existing knowledge; the Bayesian combination is the so-called posterior distribution, representing the resultant new state of knowledge. While varying the likelihood due to differing data observations is common, there are also situations where the prior distribution must be changed or replaced repeatedly. For example, in mixture density neural network (MDN) inversion, using current methods the neural network employed for inversion needs to be retrained every time prior information changes. We develop a method of prior replacement to vary the prior without re-training the network. Thus the efficiency of MDN inversions can be increased, typically by orders of magnitude when applied to geophysical problems. We demonstrate this for the inversion of seismic attributes in a synthetic subsurface geological reservoir model. We also present results which suggest that prior replacement can be used to control the statistical properties (such as variance) of the final estimate of the posterior in more general (e.g., Monte Carlo based) inverse problem solutions.
Institute of Scientific and Technical Information of China (English)
2015-01-01
Sampling is the bridge between analog source signal and digital signal. Based on image signal in the fractional Fourier domain(FRFT), fractional cosine domain(FRCT) with sparse features, this article makes a preliminary comparison of the performance of gray image compression perception in the above two kinds of transform domain. This article uses the method of orthogonal matching pursuit (OMP) to reconstruct the original signal, uses local hada code matrix as measurement matrix, and uses the peak signal-to-noise ratio (PSNR) and mean square error (MSE) as the objective evaluation standard.%模拟信号的数字采样是模拟通向数字信息世界的纽带。本文基于图像信号在分数阶Fourier域(FRFT)、分数阶余弦域(FRCT)域具有稀疏性的特性，对灰度图像压缩感知在以上两种变换域的性能做了初步比较。本文采用正交匹配追踪法(OMP)重构原信号，采用局部哈达码矩阵作为测量矩阵，采用峰值信噪比(PSNR)和均方误差(MSE)作为客观评价标准。
Institute of Scientific and Technical Information of China (English)
曾鸣; 王慧敏; 张东纯; 苏宝库
2001-01-01
It is the key factor of guaranteeing the performance index of the excitation power supply system that has been designed for the sine and cosine precision reference of high precision excitation power supply with closed loop control. The paper adopts reliable frequency division technique and programmable logic device technique, insures the stability and reliability of designed circuits. The long period usage indicates the validity of the design method and satisfies the requirements of the system precision index.%因为设计高精度的闭环激磁电源正、余弦精密基准是保证闭环激磁电源性能指标的关键，所以采用可靠的分频技术和可编程逻辑芯片技术，以确保设计电路的稳定性和可靠性.运行实践证明：该设计方法能满足系统精度指标的要求.
Institute of Scientific and Technical Information of China (English)
陈继宇; 张涛锋; 孙建安; 石玉仁; 马明义
2011-01-01
采用余弦微分求积法(CDQM)对(1+1)维非线性KdV-Burgers方程进行了数值求解.结果表明,所得数值解与方程的精确解相比具有明显的高精度且稳定性高,相对于其他常用方法,且公式简单,使用方便;计算量小,时间复杂性好.%The cosine expansion based differential quadrature method(CDQM) has been used to obtain numerical solutions to the (1+1)-dimensional nonlinear KdV-Burgers equation. The numerical solutions are compared with the exact solutions, The results show that the numerical solutions are in good agreement with the exact solutions. Compared with some regulate methods, the computation efforts are relatively smaller and the time of computation is shorter, it is also seen that the formulas of the method are very simple and easy to use.
Institute of Scientific and Technical Information of China (English)
章复熹
2004-01-01
@@ Coupled diffusion processes (or CDP for short) model the systems of molecular motors,which attract much interest from physicists and biologists in recent years[1,2,9,14,4,7,21]. The protein moves along a filament called the track, and it is crucial that there are several inner states of the protein and the underlying chemical reaction causes transitions among different inner states,while chemical energy can be converted to mechanical energy by rachet effects[5,3,2,14,12].
Phosphorus out-diffusion in laser molten silicon
Energy Technology Data Exchange (ETDEWEB)
Köhler, J. R.; Eisele, S. J. [Institut für Photovoltaik (ipv), Universität Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart (Germany)
2015-04-14
Laser doping via liquid phase diffusion enables the formation of defect free pn junctions and a tailoring of diffusion profiles by varying the laser pulse energy density and the overlap of laser pulses. We irradiate phosphorus diffused 100 oriented p-type float zone silicon wafers with a 5 μm wide line focused 6.5 ns pulsed frequency doubled Nd:YVO{sub 4} laser beam, using a pulse to pulse overlap of 40%. By varying the number of laser scans N{sub s} = 1, 2, 5, 10, 20, 40 at constant pulse energy density H = 1.3 J/cm{sup 2} and H = 0.79 J/cm{sup 2} we examine the out-diffusion of phosphorus atoms performing secondary ion mass spectroscopy concentration measurements. Phosphorus doping profiles are calculated by using a numerical simulation tool. The tool models laser induced melting and re-solidification of silicon as well as the out-diffusion of phosphorus atoms in liquid silicon during laser irradiation. We investigate the observed out-diffusion process by comparing simulations with experimental concentration measurements. The result is a pulse energy density independent phosphorus out-diffusion velocity v{sub out} = 9 ± 1 cm/s in liquid silicon, a partition coefficient of phosphorus 1 < k{sub p} < 1.1 and a diffusion coefficient D = 1.4(±0.2)cm{sup 2}/s × 10{sup −3 }× exp[−183 meV/(k{sub B}T)].
Simulations of (an)isotropic diffusion on curved biological surfaces.
Sbalzarini, Ivo F; Hayer, Arnold; Helenius, Ari; Koumoutsakos, Petros
2006-02-01
We present a computational particle method for the simulation of isotropic and anisotropic diffusion on curved biological surfaces that have been reconstructed from image data. The method is capable of handling surfaces of high curvature and complex shape, which are often encountered in biology. The method is validated on simple benchmark problems and is shown to be second-order accurate in space and time and of high parallel efficiency. It is applied to simulations of diffusion on the membrane of endoplasmic reticula (ER) in live cells. Diffusion simulations are conducted on geometries reconstructed from real ER samples and are compared to fluorescence recovery after photobleaching experiments in the same ER samples using the transmembrane protein tsO45-VSV-G, C-terminally tagged with green fluorescent protein. Such comparisons allow derivation of geometry-corrected molecular diffusion constants for membrane components from fluorescence recovery after photobleaching data. The results of the simulations indicate that the diffusion behavior of molecules in the ER membrane differs significantly from the volumetric diffusion of soluble molecules in the lumen of the same ER. The apparent speed of recovery differs by a factor of approximately 4, even when the molecular diffusion constants of the two molecules are identical. In addition, the specific shape of the membrane affects the recovery half-time, which is found to vary by a factor of approximately 2 in different ER samples.
Varying seizure semiology according to age.
Nordli, Douglas R
2013-01-01
The clinical manifestations of seizures change in a predictable fashion with advancing age. For focal seizures these changes can be summarized into domains similar to those used in developmental models. These include fine motor, communication, and gross motor manifestations. Instead of socialization the fourth domain for seizure semiology concerns synchronization. Focal seizures in the very young tend to be simpler with fewer fine motor manifestations. Auras are uncommon, even in young children with some linguistic skill and it is often difficult to discern alteration of consciousness. Infantile focal seizures can present with spasms or even diffuse tonic seizures. In terms of synchronization, orderly secondary generalization is rarely seen so that primary generalized clonic seizures are rarely recorded in infants. Amongst so-called "generalized" seizures spasms are most often seen in the first year of life. Absence seizures, myoclonic-astatic and generalized tonic-clonic seizures are all usually not seen until after age 2 years. A full description of the clinical details of seizures is probably the most important part of the epilepsy history. A detailed knowledge of seizure semiology can make the history more effective and also in the identification of the correct seizure classification. Copyright © 2013 Elsevier B.V. All rights reserved.
Inventory Replenishment Policy with Time-Varying Demand and Shortages Considering Time-Varying Costs
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
In this paper, a generalized EOQ model is developed with time-varying demand and shortages considering time-varying costs. The solution procedure is shown for determining the op timal replenishment policy over a finite time horizon during which the replenishment periods are assumed to be constant. The existence and uniqueness of the optimal replenishment policy are pre sented. The procedure is illustrated with two special cases of linear and non-linear demands and costs. Two numerical examples are also given.
Institute of Scientific and Technical Information of China (English)
Xin-yu Lai; Nan-rong Zhao
2013-01-01
Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts.A generalized Langevin equation is adopted to describe the diffusion dynamics.Mode-coupling theory is employed to calculate the memory kernel of friction.For simplicity,only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism.The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site model with Percus-Yevick closure.The effect of nanoparticle size and that of the polymer size are clarified explicitly.The structural functions,the friction kernel,as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length.We find that for small nanoparticles or short chain polymers,the characteristic short time non-Markov diffusion dynamics becomes more prominent,and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant.This constant due to the microscopic contributions will decrease with the increase of nanoparticle size,while increase with polymer size.Furthermore,our result of diffusion constant from modecoupling theory is compared with the value predicted from the Stokes-Einstein relation.It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers.Inversely,when nanonparticle is big,or polymer chain is short,the hydrodynamic contribution might play a significant role.
Diffusion in Solids Fundamentals, Methods, Materials, Diffusion-Controlled Processes
Mehrer, Helmut
2007-01-01
Diffusion is a vital topic in solid-state physics and chemistry, physical metallurgy and materials science. Diffusion processes are ubiquitous in solids at elevated temperatures. A thorough understanding of diffusion in materials is crucial for materials development and engineering. This book first gives an account of the central aspects of diffusion in solids, for which the necessary background is a course in solid state physics. It then provides easy access to important information about diffuson in metals, alloys, semiconductors, ion-conducting materials, glasses and nanomaterials. Several diffusion-controlled phenomena, including ionic conduction, grain-boundary and dislocation pipe diffusion, are considered as well. Graduate students in solid-state physics, physical metallurgy, materials science, physical and inorganic chemistry or geophysics will benefit from this book as will physicists, chemists, metallurgists, materials engineers in academic and industrial research laboratories.
Gan, Qintao; Lv, Tianshi; Fu, Zhenhua
2016-04-01
In this paper, the synchronization problem for a class of generalized neural networks with time-varying delays and reaction-diffusion terms is investigated concerning Neumann boundary conditions in terms of p-norm. The proposed generalized neural networks model includes reaction-diffusion local field neural networks and reaction-diffusion static neural networks as its special cases. By establishing a new inequality, some simple and useful conditions are obtained analytically to guarantee the global exponential synchronization of the addressed neural networks under the periodically intermittent control. According to the theoretical results, the influences of diffusion coefficients, diffusion space, and control rate on synchronization are analyzed. Finally, the feasibility and effectiveness of the proposed methods are shown by simulation examples, and by choosing different diffusion coefficients, diffusion spaces, and control rates, different controlled synchronization states can be obtained.
Tsekov, R
2015-01-01
Diffusion of normal alkanes in one-dimensional zeolites is theoretically studied on the basis of the stochastic equation formalism. The calculated diffusion coefficient accounts for the vibrations of the diffusing molecule and zeolite framework, molecule-zeolite interaction, and specific structure of the zeolite. It is shown that when the interaction potential is predominantly determined by the zeolite pore structure, the diffusion coefficient varies periodically with the number of carbon atoms of the alkane molecule, a phenomenon called resonant diffusion. A criterion for observable resonance is obtained from the balance between the interaction potentials of the molecule due to the atomic and pore structures of the zeolite. It shows that the diffusion is not resonant in zeolites without pore structure, such as ZSM-12. Moreover, even in zeolites with developed pore structure no resonant dependence of the diffusion constant can be detected if the pore structure energy barriers are not at least three times high...
Cerebral perfusion changes in traumatic diffuse brain injury. IMP SPECT studies
Energy Technology Data Exchange (ETDEWEB)
Ito, Hiroshi; Kawashima, Ryuta; Fukuda, Hiroshi [Tohoku Univ., Sendai (Japan). Inst. of Development, Aging and Cancer; Ishii, Kiyoshi; Onuma, Takehide
1997-05-01
Diffuse brain injury (DBI) is characterized by axonal degeneration and neuronal damage which cause diffuse brain atrophy. We have investigated the time course of abnormalities in cerebral perfusion distribution in cases of DBI by using Iodine-123-IMP SPECT, and the relationship to the appearance of diffuse brain atrophy. SPECT scans were performed on eight patients with diffuse brain injury due to closed cranial trauma in acute and chronic stages. All patients showed abnormalities in cerebral perfusion with decreases in perfusion, even in non-depicted regions on MRI, and the affected areas varied throughout the period of observation. Diffuse brain atrophy appeared in all patients. In some patients, diffuse brain atrophy was observed at or just after the time when the maximum number of lesions on SPECT were seen. The abnormalities in cerebral perfusion in cases of DBI might therefore be related to axonal degeneration and neuronal damage which causes diffuse brain atrophy. (author)
The diffusion of microfinance.
Banerjee, Abhijit; Chandrasekhar, Arun G; Duflo, Esther; Jackson, Matthew O
2013-07-26
To study the impact of the choice of injection points in the diffusion of a new product in a society, we developed a model of word-of-mouth diffusion and then applied it to data on social networks and participation in a newly available microfinance loan program in 43 Indian villages. Our model allows us to distinguish information passing among neighbors from direct influence of neighbors' participation decisions, as well as information passing by participants versus nonparticipants. The model estimates suggest that participants are seven times as likely to pass information compared to informed nonparticipants, but information passed by nonparticipants still accounts for roughly one-third of eventual participation. An informed household is not more likely to participate if its informed friends participate. We then propose two new measures of how effective a given household would be as an injection point. We show that the centrality of the injection points according to these measures constitutes a strong and significant predictor of eventual village-level participation.
Gardiner, Thomas
2013-10-01
Anisotropic thermal diffusion in magnetized plasmas is an important physical phenomena for a diverse set of physical conditions ranging from astrophysical plasmas to MFE and ICF. Yet numerically simulating this phenomenon accurately poses significant challenges when the computational mesh is misaligned with respect to the magnetic field. Particularly when the temperature gradients are unresolved, one frequently finds entropy violating solutions with heat flowing from cold to hot zones for χ∥ /χ⊥ >=102 which is substantially smaller than the range of interest which can reach 1010 or higher. In this talk we present a new implicit algorithm for solving the anisotropic thermal diffusion equations and demonstrate its characteristics on what has become a fairly standard set of test problems in the literature. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-5687A.
An ETAS model with varying productivity rates
Harte, D. S.
2014-07-01
We present an epidemic type aftershock sequenc (ETAS) model where the offspring rates vary both spatially and temporally. This is achieved by distinguishing between those space-time volumes where the interpoint space and time distances are small, and those where they are considerably larger. We also question the nature of the background component in the ETAS model. Is it simply a temporal boundary correction (t = 0) or does it represent an additional tectonic process not described by the aftershock component? The form of these stochastic models should not be considered to be fixed. As we accumulate larger and better earthquake catalogues, GPS data, strain rates, etc., we have the ability to ask more complex questions about the nature of the process. By fitting modified models consistent with such questions, we should gain a better insight into the earthquake process. Hence, we consider a sequence of incrementally modified ETAS type models rather than `the' ETAS model.
Photon Propagation in Slowly Varying Electromagnetic Fields
Karbstein, F.
2017-03-01
Effective theory of soft photons in slowly varying electromagnetic background fields is studied at one-loop order in QED. This is of relevance for the study of all-optical signatures of quantum vacuum nonlinearity in realistic electromagnetic background fields as provided by high-intensity lasers. The central result derived in this article is a new analytical expression for the photon polarization tensor in two linearly polarized counterpropagating pulsed Gaussian laser beams. Treating the peak field strengths of both laser beams as free parameters, this field configuration can be considered as interpolating between the limiting cases of a purely right- or left-moving laser beam (if one of the peak field strengths is set equal to zero) and the standing-wave type scenario with two counter-propagating beams of equal strength.
Optical vortex array in spatially varying lattice
Kapoor, Amit; Senthilkumaran, P; Joseph, Joby
2015-01-01
We present an experimental method based on a modified multiple beam interference approach to generate an optical vortex array arranged in a spatially varying lattice. This method involves two steps which are: numerical synthesis of a consistent phase mask by using two-dimensional integrated phase gradient calculations and experimental implementation of produced phase mask by utilizing a phase only spatial light modulator in an optical 4f Fourier filtering setup. This method enables an independent variation of the orientation and period of the vortex lattice. As working examples, we provide the experimental demonstration of various spatially variant optical vortex lattices. We further confirm the existence of optical vortices by formation of fork fringes. Such lattices may find applications in size dependent trapping, sorting, manipulation and photonic crystals.
Time varying arctic climate change amplification
Energy Technology Data Exchange (ETDEWEB)
Chylek, Petr [Los Alamos National Laboratory; Dubey, Manvendra K [Los Alamos National Laboratory; Lesins, Glen [DALLHOUSIE U; Wang, Muyin [NOAA/JISAO
2009-01-01
During the past 130 years the global mean surface air temperature has risen by about 0.75 K. Due to feedbacks -- including the snow/ice albedo feedback -- the warming in the Arctic is expected to proceed at a faster rate than the global average. Climate model simulations suggest that this Arctic amplification produces warming that is two to three times larger than the global mean. Understanding the Arctic amplification is essential for projections of future Arctic climate including sea ice extent and melting of the Greenland ice sheet. We use the temperature records from the Arctic stations to show that (a) the Arctic amplification is larger at latitudes above 700 N compared to those within 64-70oN belt, and that, surprisingly; (b) the ratio of the Arctic to global rate of temperature change is not constant but varies on the decadal timescale. This time dependence will affect future projections of climate changes in the Arctic.
Varied Clinical Manifestations of Amebic Colitis.
Cooper, Chad J; Fleming, Rhonda; Boman, Darius A; Zuckerman, Marc J
2015-11-01
Invasive amebiasis is common worldwide, but infrequently observed in the United States. It is associated with considerable morbidity in patients residing in or traveling to endemic areas. We review the clinical and endoscopic manifestations of amebic colitis to alert physicians to the varied clinical manifestations of this potentially life-threatening disease. Copyright ©Most patients present with watery or bloody diarrhea. Less common presentations of amebic colitis include abdominal pain, overt gastrointestinal bleeding, exacerbation of inflammatory bowel disease, or the incidental association with colon cancer. Amebic liver abscesses are the most frequent complication. Rectosigmoid involvement may be found on colonoscopy; however, most case series have reported that the cecum is the most commonly involved site, followed by the ascending colon. Endoscopic evaluation should be used to assist in the diagnosis, with attention to the observation of colonic inflammation, ulceration, and amebic trophozoites on histopathological examination.
Photon propagation in slowly varying electromagnetic fields
Karbstein, Felix
2016-01-01
We study the effective theory of soft photons in slowly varying electromagnetic background fields at one-loop order in QED. This is of relevance for the study of all-optical signatures of quantum vacuum nonlinearity in realistic electromagnetic background fields as provided by high-intensity lasers. The central result derived in this article is a new analytical expression for the photon polarization tensor in two linearly polarized counter-propagating pulsed Gaussian laser beams. As we treat the peak field strengths of both laser beams as free parameters this field configuration can be considered as interpolating between the limiting cases of a purely right- or left-moving laser beam (if one of the peak field strengths is set to zero) and the standing-wave type scenario with two counter-propagating beams of equal strength.
String theory, cosmology and varying constants
Damour, Thibault
In string theory the coupling `constants' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation values of some (a priori) massless scalar fields (dilaton, moduli). This naturally leads one to expect a correlated variation of all the coupling constants, and an associated violation of the equivalence principle. We review some string-inspired theoretical models which incorporate such a spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring a very unnatural fine-tuning of parameters, a variation of the fine-structure constant as large as that recently `observed' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universality of free fall, such as MICROSCOPE and STEP.
String theory, cosmology and varying constants
Damour, Thibault Marie Alban Guillaume
2002-01-01
In string theory the coupling ``constants'' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation values of some (a priori) massless scalar fields (dilaton, moduli). This naturally leads one to expect a correlated variation of all the coupling constants, and an associated violation of the equivalence principle. We review some string-inspired theoretical models which incorporate such a spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring a very unnatural fine-tuning of parameters, a variation of the fine-structure constant as large as that recently ``observed'' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universa...
Decaying Lambda cosmology, varying G and holography
Carneiro, S
2004-01-01
We discuss a class of uniform and isotropic, spatially flat, decaying Lambda cosmologies, in the realm of a model where the gravitation constant G is a function of the cosmological time. Besides the usual de Sitter solution, the models at late times are characterized by a constant ratio between the matter and total energy densities. One of them presents a coasting expansion where the matter density parameter is equal to 1/3, and the age of the universe satisfies Ht = 1. From considerations in line with the holographic conjecture, it is argued that, among the non-decelerating solutions, the coasting expansion is the only acceptable from a thermodynamic viewpoint, and that the time varying cosmological term must be proportional to the square of the Hubble parameter, a result earlier obtained using different arguments.
Time-Varying Graphs and Dynamic Networks
Casteigts, Arnaud; Quattrociocchi, Walter; Santoro, Nicola
2010-01-01
The past few years have seen intensive research efforts carried out in some apparently unrelated areas of dynamic systems -- delay-tolerant networks, opportunistic-mobility networks, social networks -- obtaining closely related insights. Indeed, the concepts discovered in these investigations can be viewed as parts of the same conceptual universe; and the formal models proposed so far to express some specific concepts can be viewed as fragments of a larger formal description of this universe. The main contribution of this paper is to integrate the existing partial models proposed in the literature into a unified framework, which we call TVG (for time-varying graphs). Using this framework, it is possible to express directly in the same formalism not only the concepts common to all those different areas, but also those specific to each. As part of the framework definition, we identify a hierarchy of classes of TVGs, defined with respects to basic properties to which correspond necessary conditions and impossibi...
Cross-diffusion effects in isothermal double diffusive
Energy Technology Data Exchange (ETDEWEB)
Becerril, R. [Michoacan Univ. Michoacana de San Nicolas de Hidalgo, Michoacan (Mexico). Inst. de Fisica y Mathematicas
2000-11-01
The nonlinear coefficients of the amplitude equations for the stationary, oscillatory and codimension-2 point bifurcations are calculated for isothermal double diffusive convection with cross-diffusion. The locations of the tricritical point for the stationary instability and the codimension-2 point are also found. Thereby the separation between these points in parameter space can be calculated as a function of rescaled cross-diffusion constants.
The Pearson diffusions: A class of statistically tractable diffusion processes
DEFF Research Database (Denmark)
Forman, Julie Lyng; Sørensen, Michael
The Pearson diffusions is a flexible class of diffusions defined by having linear drift and quadratic squared diffusion coefficient. It is demonstrated that for this class explicit statistical inference is feasible. Explicit optimal martingale estimating func- tions are found, and the corresponding...... volatility models with Pearson volatility process. For the non-Markov models explicit optimal prediction based estimating functions are found and shown to yield consistent and asymptotically normal estimators...
Detecting causality in policy diffusion processes
Grabow, Carsten; Macinko, James; Silver, Diana; Porfiri, Maurizio
2016-08-01
A universal question in network science entails learning about the topology of interaction from collective dynamics. Here, we address this question by examining diffusion of laws across US states. We propose two complementary techniques to unravel determinants of this diffusion process: information-theoretic union transfer entropy and event synchronization. In order to systematically investigate their performance on law activity data, we establish a new stochastic model to generate synthetic law activity data based on plausible networks of interactions. Through extensive parametric studies, we demonstrate the ability of these methods to reconstruct networks, varying in size, link density, and degree heterogeneity. Our results suggest that union transfer entropy should be preferred for slowly varying processes, which may be associated with policies attending to specific local problems that occur only rarely or with policies facing high levels of opposition. In contrast, event synchronization is effective for faster enactment rates, which may be related to policies involving Federal mandates or incentives. This study puts forward a data-driven toolbox to explain the determinants of legal activity applicable to political science, across dynamical systems, information theory, and complex networks.
The Pearson diffusions: A class of statistically tractable diffusion processes
DEFF Research Database (Denmark)
Forman, Julie Lyng; Sørensen, Michael
estimators are shown to be consistent and asymptotically normal. The discussion covers GMM, quasi-likelihood, and non- linear weighted least squares estimation too, and it is discussed how explicit likeli- hood or approximate likelihood inference is possible for the Pearson diffusions. A complete model....... Special attention is given to a skew t-type distribution. Explicit formulae for the conditional moments and the polynomial eigenfunctions are derived. The analyti- cal tractability is inherited by transformed Pearson diffusions, integrated Pearson diffusions, sums of Pearson diffusions, and stochastic...
On the scaling limits of Galton Watson processes in varying environment
Bansaye, Vincent
2011-01-01
Renormalized sequences of Galton Watson processes converge to Continuous State Branching Processes (CSBP), characterized by a L\\'evy triplet of two numbers and a measure. This paper investigates the case of Galton Watson processes in varying environment and provides an explicit sufficient condition for finite-dimensional convergence in terms of convergence of a characteristic triplet of measures. We recover then classical results on the convergence of Galton Watson processes and we can add exceptional environments provoking positive or negative jumps at fixed times. We also apply this result to derive new results on the Feller diffusion in varying environment and branching processes in random environment. Our approach relies on the backward differential equation satisfied by the Laplace exponent and provides results about explosion, absorption and extinction. Thus, this paper exhibits a general class of CSBP in varying environment which is characterized by a triplet of measures. This provides a first step tow...
Simulation of gas diffusion through inhomogeneous layered snow and firn
Whelsky, A. N.; Albert, M. R.
2014-12-01
Diffusion of gases through snow and firn is important for air-snow transfer in temperate regions and decoding ice core climate records from the polar regions. The diffusion process depends on a number of factors, including temperature and chemical concentration gradients, layering and pore structure of the snow and firn, and fractionation of gases. Assessing the potential impact of layering on of gases through the firn column over time is crucial for understanding the natural archive of past atmospheric composition. Existing 1-D firn air models include gravitational settling and thermal diffusion in order to explain seasonal anomalies found in firn-air measurements but have not considered the possibility of inhomogeneous firn structure and layering effects in time-varying simulations. This work presents development, testing, and use of a multidimensional numerical diffusion model for investigating impacts of spatial heterogeneity of firn layering over time, in addition to thermal and gravitational effects on gas diffusion in firn. The model is verified using existing data. Results of numerical experiments are presented that show impacts of varying the spatial structure of firn on the magnitude of the impact on gas profiles in firn. Comparison of numerical results with published firn air field studies will be discussed.
Osmosis and Diffusion Conceptual Assessment
Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts
2011-01-01
Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified from the previously published Diffusion and Osmosis Diagnostic Test (DODT) and some newly developed items. The ODCA, a validated instrument containing ...
Variable helium diffusion characteristics in fluorite
Wolff, R.; Dunkl, I.; Kempe, U.; Stockli, D.; Wiedenbeck, M.; von Eynatten, H.
2016-09-01
Precise analysis of the diffusion characteristics of helium in fluorite is crucial for establishing the new fluorite (U-Th-Sm)/He thermochronometer (FHe), which potentially provides a powerful tool for dating ore deposits unsuitable for the application of conventional geochronometers. Incremental helium outgassing experiments performed on fluorites derived from a spectrum of geological environments suggest a thermally activated volume diffusion mechanism. The diffusion behaviour is highly variable and the parameters range between log D0/a2 = 0.30 ± 0.27-7.27 ± 0.46 s-1 and Ea = 96 ± 3.5-182 ± 3.8 kJ/mol. Despite the fact that the CaF2 content of natural fluorites in most cases exceeds 99 weight percent, the closure temperature (Tc) of the fluorite (U-Th-Sm)/He thermochronometer as calculated from these diffusion parameters varies between 46 ± 14 °C and 169 ± 9 °C, considering a 125 μm fragment size. Here we establish that minor substitutions of calcium by rare earth elements and yttrium (REE + Y) and related charge compensation by sodium, fluorine, oxygen and/or vacancies in the fluorite crystal lattice have a significant impact on the diffusivity of helium in the mineral. With increasing REE + Y concentrations F vacancies are reduced and key diffusion pathways are narrowed. Consequently, a higher closure temperature is to be expected. An empirical case study confirms this variability: two fluorite samples from the same deposit (Horni Krupka, Czech Republic) with ca. 170 °C and ca. 43 °C Tc yield highly different (U-Th-Sm)/He ages of 290 ± 10 Ma and 79 ± 10 Ma, respectively. Accordingly, the fluorite sample with the high Tc could have quantitatively retained helium since the formation of the fluorite-bearing ores in the Permian, despite subsequent Mesozoic burial and associated regional hydrothermal heating. In contrast, the fluorite with the low Tc yields a Late Cretaceous age close to the apatite fission track (AFT) and apatite (U-Th)/He ages (AHe
Liu, Xunliang; Peng, Fangyuan; Lou, Guofeng; Wen, Zhi
2015-12-01
Fundamental understanding of liquid water transport in gas diffusion media (GDM) is important to improve the material and structure design of polymer electrolyte membrane (PEM) fuel cells. Continuum methods of two-phase flow modeling facilitate to give more details of relevant information. The proper empirical correlations of liquid water transport properties, such as capillary characteristics, water relative permeability and effective contact angle, are crucial to two phase flow modeling and cell performance prediction. In this work, researches on these properties in the last decade are reviewed. Various efforts have been devoted to determine the water transport properties for GDMs. However, most of the experimental studies are ex-situ measurements. In-situ measurements for GDMs and extending techniques available to study the catalyst layer and the microporous layer will be further challenges. Using the Leverett-Udell correlation is not recommended for quantitative modeling. The reliable Leverett-type correlation for GDMs, with the inclusion of the cosine of effective contact angle, is desirable but hard to be established for modeling two-phase flow in GDMs. A comprehensive data set of liquid water transport properties is needed for various GDM materials under different PEM fuel cell operating conditions.
Energy Technology Data Exchange (ETDEWEB)
Schrof, Julian, E-mail: julian.schrof@ise.fraunhofer.de; Müller, Ralph; Benick, Jan; Hermle, Martin [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstrasse 2, D-79110 Freiburg (Germany); Reedy, Robert C. [National Renewable Energy Laboratory (NREL), 15013 Denver West Parkway, Golden, Colorado 80401 (United States)
2015-07-28
Boron diffusivity reduction in extrinsically doped silicon was investigated in the context of a process combination consisting of BBr{sub 3} furnace diffusion and preceding Phosphorus ion implantation. The implantation of Phosphorus leads to a substantial blocking of Boron during the subsequent Boron diffusion. First, the influences of ion implantation induced point defects as well as the initial P doping on B diffusivity were studied independently. Here, it was found that not the defects created during ion implantation but the P doping itself results in the observed B diffusion retardation. The influence of the initial P concentration was investigated in more detail by varying the P implantation dose. A secondary ion mass spectrometry (SIMS) analysis of the BSG layer after the B diffusion revealed that the B diffusion retardation is not due to potential P content in the BSG layer but rather caused by the n-type doping of the crystalline silicon itself. Based on the observations the B diffusion retardation was classified into three groups: (i) no reduction of B diffusivity, (ii) reduced B diffusivity, and (iii) blocking of the B diffusion. The retardation of B diffusion can well be explained by the phosphorus doping level resulting in a Fermi level shift and pairing of B and P ions, both reducing the B diffusivity. Besides these main influences, there are probably additional transient phenomena responsible for the blocking of boron. Those might be an interstitial transport mechanism caused by P diffusion that reduces interstitial concentration at the surface or the silicon/BSG interface shift due to oxidation during the BBr{sub 3} diffusion process. Lifetime measurements revealed that the residual (non-blocked) B leads to an increased dark saturation current density in the P doped region. Nevertheless, electrical quality is on a high level and was further increased by reducing the B dose as well as by removing the first few nanometers of the silicon surface after
Schrof, Julian; Müller, Ralph; Reedy, Robert C.; Benick, Jan; Hermle, Martin
2015-07-01
Boron diffusivity reduction in extrinsically doped silicon was investigated in the context of a process combination consisting of BBr3 furnace diffusion and preceding Phosphorus ion implantation. The implantation of Phosphorus leads to a substantial blocking of Boron during the subsequent Boron diffusion. First, the influences of ion implantation induced point defects as well as the initial P doping on B diffusivity were studied independently. Here, it was found that not the defects created during ion implantation but the P doping itself results in the observed B diffusion retardation. The influence of the initial P concentration was investigated in more detail by varying the P implantation dose. A secondary ion mass spectrometry (SIMS) analysis of the BSG layer after the B diffusion revealed that the B diffusion retardation is not due to potential P content in the BSG layer but rather caused by the n-type doping of the crystalline silicon itself. Based on the observations the B diffusion retardation was classified into three groups: (i) no reduction of B diffusivity, (ii) reduced B diffusivity, and (iii) blocking of the B diffusion. The retardation of B diffusion can well be explained by the phosphorus doping level resulting in a Fermi level shift and pairing of B and P ions, both reducing the B diffusivity. Besides these main influences, there are probably additional transient phenomena responsible for the blocking of boron. Those might be an interstitial transport mechanism caused by P diffusion that reduces interstitial concentration at the surface or the silicon/BSG interface shift due to oxidation during the BBr3 diffusion process. Lifetime measurements revealed that the residual (non-blocked) B leads to an increased dark saturation current density in the P doped region. Nevertheless, electrical quality is on a high level and was further increased by reducing the B dose as well as by removing the first few nanometers of the silicon surface after the BBr3
Diffuse parenchymal lung disease
Directory of Open Access Journals (Sweden)
Sara Tomassetti
2017-04-01
Full Text Available Between September 2015 and August 2016 there were >1500 publications in the field of diffuse parenchymal lung diseases (DPLDs. For the Clinical Year in Review session at the European Respiratory Society Congress that was held in London, UK, in September 2016, we selected only five articles. This selection, made from the enormous number of published papers, does not include all the relevant studies that will significantly impact our knowledge in the field of DPLDs in the near future. This review article provides our personal view on the following topics: early diagnosis of idiopathic pulmonary fibrosis, current knowledge on the multidisciplinary team diagnosis of DPLDs and the diagnostic role of transbronchial cryobiopsy in this diagnostic setting, insights on the new entity of interstitial pneumonia with autoimmune features, and new therapeutic approaches for scleroderma-related interstitial lung disease.
Hereditary diffuse gastric cancer
DEFF Research Database (Denmark)
van der Post, Rachel S; Vogelaar, Ingrid P; Carneiro, Fátima
2015-01-01
Germline CDH1 mutations confer a high lifetime risk of developing diffuse gastric (DGC) and lobular breast cancer (LBC). A multidisciplinary workshop was organised to discuss genetic testing, surgery, surveillance strategies, pathology reporting and the patient's perspective on multiple aspects......, including diet post gastrectomy. The updated guidelines include revised CDH1 testing criteria (taking into account first-degree and second-degree relatives): (1) families with two or more patients with gastric cancer at any age, one confirmed DGC; (2) individuals with DGC before the age of 40 and (3...... the high mortality associated with invasive disease, prophylactic total gastrectomy at a centre of expertise is advised for individuals with pathogenic CDH1 mutations. Breast cancer surveillance with annual breast MRI starting at age 30 for women with a CDH1 mutation is recommended. Standardised endoscopic...
Diffuse interstellar absorption bands
Institute of Scientific and Technical Information of China (English)
XIANG FuYuan; LIANG ShunLin; LI AiGen
2009-01-01
The diffuse interstellar bands (DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s, the exact nature of DIBs still remains unclear. This article reviews the history of the detec-tions of DIBs in the Milky Way and external galaxies, the major observational characteristics of DIBs, the correlations or anti-correlations among DIBs or between DIBs and other interstellar features (e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise), and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.
Diffuse interstellar absorption bands
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The diffuse interstellar bands(DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s,the exact nature of DIBs still remains unclear. This article reviews the history of the detections of DIBs in the Milky Way and external galaxies,the major observational characteristics of DIBs,the correlations or anti-correlations among DIBs or between DIBs and other interstellar features(e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise),and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.
Nonlocal diffusion and applications
Bucur, Claudia
2016-01-01
Working in the fractional Laplace framework, this book provides models and theorems related to nonlocal diffusion phenomena. In addition to a simple probabilistic interpretation, some applications to water waves, crystal dislocations, nonlocal phase transitions, nonlocal minimal surfaces and Schrödinger equations are given. Furthermore, an example of an s-harmonic function, its harmonic extension and some insight into a fractional version of a classical conjecture due to De Giorgi are presented. Although the aim is primarily to gather some introductory material concerning applications of the fractional Laplacian, some of the proofs and results are new. The work is entirely self-contained, and readers who wish to pursue related subjects of interest are invited to consult the rich bibliography for guidance.
Fractional Chemotaxis Diffusion Equations
Langlands, T A M
2010-01-01
We introduce mesoscopic and macroscopic model equations of chemotaxis with anomalous subdiffusion for modelling chemically directed transport of biological organisms in changing chemical environments with diffusion hindered by traps or macro-molecular crowding. The mesoscopic models are formulated using Continuous Time Random Walk master equations and the macroscopic models are formulated with fractional order differential equations. Different models are proposed depending on the timing of the chemotactic forcing. Generalizations of the models to include linear reaction dynamics are also derived. Finally a Monte Carlo method for simulating anomalous subdiffusion with chemotaxis is introduced and simulation results are compared with numerical solutions of the model equations. The model equations developed here could be used to replace Keller-Segel type equations in biological systems with transport hindered by traps, macro-molecular crowding or other obstacles.
Reversible Diffusion by Thermal Fluctuations
Donev, Aleksandar; Fai, Thomas G.; vanden-Eijnden, Eric
A model for diffusion in liquids that couples the dynamics of tracer particles to a fluctuating Stokes equation for the fluid is investigated in the limit of large Schmidt number. In this limit, the concentration of tracers is shown to satisfy a closed-form stochastic advection-diffusion equation that is used to investigate the collective diffusion of hydrodynamically-correlated tracers through a combination of Eulerian and Lagrangian numerical methods. This analysis indicates that transport in liquids is quite distinct from the traditional Fickian picture of diffusion. While the ensemble-averaged concentration follows Fick's law with a diffusion coefficient that obeys the Stokes-Einstein relation, each instance of the diffusive mixing process exhibits long-ranged giant fluctuations around its average behavior. We construct a class of mesoscopic models for diffusion in liquids at different observation scales in which the renormalized diffusion coefficient depends on this scale. This indicates that the Fickian diffusion coefficient in liquids is not a material constant, but rather, changes with the scale at which experimental measurements are performed.
Diffusion in Jammed Particle Packs.
Bolintineanu, Dan S; Grest, Gary S; Lechman, Jeremy B; Silbert, Leonardo E
2015-08-21
Using random walk simulations we explore diffusive transport through monodisperse sphere packings over a range of packing fractions ϕ in the vicinity of the jamming transition at ϕ(c). Various diffusion properties are computed over several orders of magnitude in both time and packing pressure. Two well-separated regimes of normal "Fickian" diffusion, where the mean squared displacement is linear in time, are observed. The first corresponds to diffusion inside individual spheres, while the latter is the long-time bulk diffusion. The intermediate anomalous diffusion regime and the long-time value of the diffusion coefficient are both shown to be controlled by particle contacts, which in turn depend on proximity to ϕ(c). The time required to recover normal diffusion t* scales as (ϕ-ϕ(c))(-0.5) and the long-time diffusivity D(∞)∼(ϕ-ϕ(c))0.5, or D(∞)∼1/t*. It is shown that the distribution of mean first passage times associated with the escape of random walkers between neighboring particles controls both t* and D(∞) in the limit ϕ→ϕ(c).
Diffusion effects in undulator radiation
Directory of Open Access Journals (Sweden)
Ilya Agapov
2014-11-01
Full Text Available Quantum diffusion effects in undulator radiation in semiclassical approximation are considered. Short-term effects on the electron beam motion are discussed and it is shown that approaches based on diffusion approximation with drift-diffusion coefficients derived from undulator or bending magnet radiation spectrum, and on Poisson statistics with radiation spectrum defined by the local beding field, all lead to similar results in terms of electron energy spread for cases of practical interest. An analytical estimate of the influence of quantum diffusion on the undulator radiation spectrum is derived.
Time-varying modeling of cerebral hemodynamics.
Marmarelis, Vasilis Z; Shin, Dae C; Orme, Melissa; Rong Zhang
2014-03-01
The scientific and clinical importance of cerebral hemodynamics has generated considerable interest in their quantitative understanding via computational modeling. In particular, two aspects of cerebral hemodynamics, cerebral flow autoregulation (CFA) and CO2 vasomotor reactivity (CVR), have attracted much attention because they are implicated in many important clinical conditions and pathologies (orthostatic intolerance, syncope, hypertension, stroke, vascular dementia, mild cognitive impairment, Alzheimer's disease, and other neurodegenerative diseases with cerebrovascular components). Both CFA and CVR are dynamic physiological processes by which cerebral blood flow is regulated in response to fluctuations in cerebral perfusion pressure and blood CO2 tension. Several modeling studies to date have analyzed beat-to-beat hemodynamic data in order to advance our quantitative understanding of CFA-CVR dynamics. A confounding factor in these studies is the fact that the dynamics of the CFA-CVR processes appear to vary with time (i.e., changes in cerebrovascular characteristics) due to neural, endocrine, and metabolic effects. This paper seeks to address this issue by tracking the changes in linear time-invariant models obtained from short successive segments of data from ten healthy human subjects. The results suggest that systemic variations exist but have stationary statistics and, therefore, the use of time-invariant modeling yields "time-averaged models" of physiological and clinical utility.
Microsatellites in varied arenas of research
Directory of Open Access Journals (Sweden)
K S Remya
2010-01-01
Full Text Available Microsatellites known as simple-sequence repeats (SSRs or short-tandem repeats (STRs, represent specific sequences of DNA consisting of tandemly repeated units of one to six nucleotides. The repetitive nature of microsatellites makes them particularly prone to grow or shrink in length and these changes can have both good and bad consequences for the organisms that possess them. They are responsible for various neurological diseases and hence the same cause is now utilized for the early detection of various diseases, such as, Schizophrenia and Bipolar Disorder, Congenital generalized Hypertrichosis, Asthma, and Bronchial Hyperresponsiveness. These agents are widely used for forensic identification and relatedness testing, and are predominant genetic markers in this area of application. The application of microsatellites is an extending web and covers the varied scenarios of science, such as, conservation biology, plant genetics, and population studies. At present, researches are progressing round the globe to extend the use of these genetic repeaters to unmask the hidden genetic secrets behind the creation of the world.
Comparative Analysis of Frames with Varying Inertia
Directory of Open Access Journals (Sweden)
Prerana Nampalli
2015-01-01
Full Text Available This paper presents an elastic seismic response of reinforced concrete frames with 3 variations of heights, i.e. (G+2, (G+4, (G+6 storey models are compared for bare frame and frame with brick infill structures which have been analyzed for gravity as well as seismic forces and their response is studied as the geometric parameters varying from view point of predicting behavior of similar structures subjected to similar loads or load combinations. In this study, two different cases are selected i.e. frames with prismatic members and frames with non-prismatic members. The structural response of various members when geometry changes physically, as in case of linear and parabolic haunches provided beyond the face of columns at beam column joints or step variations as in case of stepped haunches was also studied. Frames have been analyzed statically as well as dynamically using ETABS-9.7.4 software referring IS: 456-2000, IS: 1893 (Part-12002 and the results so obtained are grouped into various categories
The Strength of Varying Tie Strength
Bruggeman, Jeroen
2012-01-01
"The Strength of Weak Ties" argument (Granovetter 1973) says that the most valuable information is best collected through bridging ties with other social circles than one's own, and that those ties tend to be weak. Aral and Van Alstyne (2011) added that to access complex information, actors need strong ties ("high bandwidth") instead. These insights I generalize by pointing at actors' interest to avoid spending large resources on low value information. Weak ties are well-suited for relatively simple information at low transmission and tie maintenance costs, whereas for complex information, the best outcomes are expected for those actors who vary their bandwidths along with the value of information accessed. To support my claim I use all patents in the USA (two million) over the period 1975-1999. I also show that in rationalized fields, such as technology, bandwidth correlates highly with the value of information, which provides support for using this proxy if value can't be measured directly. Finally, I show ...
Modelling tourists arrival using time varying parameter
Suciptawati, P.; Sukarsa, K. G.; Kencana, Eka N.
2017-06-01
The importance of tourism and its related sectors to support economic development and poverty reduction in many countries increase researchers’ attentions to study and model tourists’ arrival. This work is aimed to demonstrate time varying parameter (TVP) technique to model the arrival of Korean’s tourists to Bali. The number of Korean tourists whom visiting Bali for period January 2010 to December 2015 were used to model the number of Korean’s tourists to Bali (KOR) as dependent variable. The predictors are the exchange rate of Won to IDR (WON), the inflation rate in Korea (INFKR), and the inflation rate in Indonesia (INFID). Observing tourists visit to Bali tend to fluctuate by their nationality, then the model was built by applying TVP and its parameters were approximated using Kalman Filter algorithm. The results showed all of predictor variables (WON, INFKR, INFID) significantly affect KOR. For in-sample and out-of-sample forecast with ARIMA’s forecasted values for the predictors, TVP model gave mean absolute percentage error (MAPE) as much as 11.24 percent and 12.86 percent, respectively.
Dermatophyte susceptibility varies towards antimicrobial textiles.
Hammer, Timo R; Mucha, Helmut; Hoefer, Dirk
2012-07-01
Dermatophytoses are a widespread problem worldwide. Textiles in contact with infected skin can serve as a carrier for fungus propagation. Hitherto, it is unknown, whether antifungal textiles could contribute in controlling dermatophytes e.g. by disrupting the chain of infection. Testing of antimicrobial fabrics for their antifungal activities therefore is a fundamental prerequisite to assess the putative clinical relevance of textiles for dermatophyte prevention. Fabrics finished with either didecyldimethylammonium chloride (DDAC), poly-hexamethylenbiguanide, copper and two silver chloride concentrations were tested for their antifungal activity against Trichophyton rubrum, Trichophyton mentagrophytes and Candida albicans. To prove dermatophyte susceptibility towards the textiles, swatches were subjected to DIN EN 14199 (Trichophyton sp.) or DIN EN ISO 20743 (C. albicans) respectively. In addition, samples were embedded, and semi-thin sections were analysed microscopically. While all samples showed a clear inhibition of C. albicans, activity against Trichophyton sp. varied significantly: For example, DDAC completely inhibited T. rubrum growth, whereas T. mentagrophytes growth remained unaffected even in direct contact to the fibres. The results favour to add T. mentagrophytes as a test organism in textile dermatophyte efficacy tests. Microscopic analysis of swatches allowed detailed evaluation of additional parameters like mycelium thickness, density and hyphae penetration depth into the fabric.
Varied acceptance of clinical trial results.
Klimt, C R
1989-12-01
The subject of varied acceptance of clinical trial results is discussed in the context of review of trials with which I have been involved and my subjective evaluation of their impact on the practice of clinical medicine. My experience goes back to 1949 and a World Health Organization trial of hyperimmune gamma globulin against rabies. This was followed by a large trial of secondary prevention of poliomyelitis. I participated in the planning and initiation of the first chronic disease trial, the University Group Diabetes Program (UGDP). The latter lasted for 15 years and its ramifications continue to this day. My next trial was the Coronary Drug Project (CDP), a complex trial with more than 8,000 patients. The trials of aspirin and aspirin combined with persantine (the CDPA, AMIS, PARIS I, and PARIS II) followed. My last three trials were a trial of photocoagulation in diabetic retinopathy (DRS), a six-country trial of the antiarrhythmic drug mexiletine (IMPACT), and a study involving two diagnostic procedures for pulmonary embolism (PIOPED). When one considers, in retrospect, the plethora of trials one is struck by the uniform absence of a priori considerations of the impact on medical practice, or likely lack thereof, of possible outcomes.
A Generalized Theory of Varying Alpha
Barrow, John D
2011-01-01
In this paper, we formulate a generalization of the simple Bekenstein-Sandvik-Barrow-Magueijo (BSBM) theory of varying alpha by allowing the coupling constant, \\omega, for the corresponding scalar field \\psi\\ to depend on \\psi. We focus on the situation where \\omega\\ is exponential in \\psi\\ and find the late-time behaviours that occur in matter-dominated and dark-energy dominated cosmologies. We also consider the situation when the background expansion scale factor of the universe evolves in proportion to an arbitrary power of the cosmic time. We find the conditions under which the fine structure `constant' increases with time, as in the BSBM theory, and establish a cosmic no-hair behaviour for accelerating universes. We also find the conditions under which the fine structure `constant' can decrease with time and compare the whole family of models with astronomical data from quasar absorption spectra. Finally, we show that spatial variations on sub-horizon scales can dominate over the cosmological time evolut...
Haldar, Justin P; Leahy, Richard M
2013-05-01
This paper presents a novel family of linear transforms that can be applied to data collected from the surface of a 2-sphere in three-dimensional Fourier space. This family of transforms generalizes the previously-proposed Funk-Radon Transform (FRT), which was originally developed for estimating the orientations of white matter fibers in the central nervous system from diffusion magnetic resonance imaging data. The new family of transforms is characterized theoretically, and efficient numerical implementations of the transforms are presented for the case when the measured data is represented in a basis of spherical harmonics. After these general discussions, attention is focused on a particular new transform from this family that we name the Funk-Radon and Cosine Transform (FRACT). Based on theoretical arguments, it is expected that FRACT-based analysis should yield significantly better orientation information (e.g., improved accuracy and higher angular resolution) than FRT-based analysis, while maintaining the strong characterizability and computational efficiency of the FRT. Simulations are used to confirm these theoretical characteristics, and the practical significance of the proposed approach is illustrated with real diffusion weighted MRI brain data. These experiments demonstrate that, in addition to having strong theoretical characteristics, the proposed approach can outperform existing state-of-the-art orientation estimation methods with respect to measures such as angular resolution and robustness to noise and modeling errors. Copyright © 2013 Elsevier Inc. All rights reserved.
Experiment of gas diffusion and its diffusion mechanism in coal
Institute of Scientific and Technical Information of China (English)
Li Xiangchun; Nie Baisheng; Zhang Ruming; Chi Leilei
2012-01-01
In coal,the gas mainly exists in a free or an adsorption state.When the coal containing gas is damaged,gas desorption and diffusion will occur which can result in gas disaster.This research on gas desorption and diffusion provides a theoretical basis for gas disaster mechanism and prevention.The influence of pressure and temperature on gas diffusion is studied by the experiment.And the mechanism of pressure and temperature on gas diffusion is also analysed.The research results indicate that gas diffusion capacity increases with increasing temperature under the same pressure for the same coal sample.This is mainly because the temperature increases,gas molecular hot motion is severer,kinetic energy of gas molecular increases,and gas desorption quickens,therefore gas diffusion capacity changes stronger.Under other unchanged conditions,the greater gas adsorption balance pressure,the more gas adsorption content,and the higher the initial gas concentration.When gas diffusion begins,the greater the gas concentration gradient,the faster the gas diffusion speeds.
Turing instability in reaction-diffusion systems with nonlinear diffusion
Energy Technology Data Exchange (ETDEWEB)
Zemskov, E. P., E-mail: zemskov@ccas.ru [Russian Academy of Sciences, Dorodnicyn Computing Center (Russian Federation)
2013-10-15
The Turing instability is studied in two-component reaction-diffusion systems with nonlinear diffusion terms, and the regions in parametric space where Turing patterns can form are determined. The boundaries between super- and subcritical bifurcations are found. Calculations are performed for one-dimensional brusselator and oregonator models.
An explicit high order method for fractional advection diffusion equations
Sousa, Ercília
2014-12-01
We propose a high order explicit finite difference method for fractional advection diffusion equations. These equations can be obtained from the standard advection diffusion equations by replacing the second order spatial derivative by a fractional operator of order α with 1convergence of the numerical method through consistency and stability. The order of convergence varies between two and three and for advection dominated flows is close to three. Although the method is conditionally stable, the restrictions allow wide stability regions. The analysis is confirmed by numerical examples.
Liquid Film Diffusion on Reaction Rate in Submerged Biofilters
DEFF Research Database (Denmark)
Christiansen, Pia; Hollesen, Line; Harremoës, Poul
1995-01-01
Experiments were carried out in order to investigate the influence of liquid film diffusion on reaction rate in a submerged biofilter with denitrification and in order to compare with a theoretical study of the mass transfer coefficient. The experiments were carried out with varied flow, identified...... by the empty bed velocity of inflow and recirculation, respectively 1.3, 2.8, 5.6 and 10.9 m/h. The filter material consisted of 3 mm biostyren spheres. The results indicate that the influence of liquid film diffusion on reaction rate can be ignored....
A Fractional Fokker-Planck Model for Anomalous Diffusion
anderson, Johan; Moradi, Sara
2014-01-01
In this paper we present a study of anomalous diffusion using a Fokker-Planck description with fractional velocity derivatives. The distribution functions are found using numerical means for varying degree of fractionality observing the transition from a Gaussian distribution to a L\\'evy distribution. The statistical properties of the distribution functions are assessed by a generalized expectation measure and entropy in terms of Tsallis statistical mechanics. We find that the ratio of the generalized entropy and expectation is increasing with decreasing fractionality towards the well known so-called sub-diffusive domain, indicating a self-organising behavior.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xiaodong, E-mail: xzhang39@utk.edu [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D. [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Hayward, Jason P. [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Oak Ridge National Lab, Oak Ridge, TN 37831 (United States)
2016-07-01
Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick’s second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.
Zhang, Xiaodong; Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D.; Hayward, Jason P.
2016-07-01
Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick's second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.
Hierarchical set of models to estimate soil thermal diffusivity
Arkhangelskaya, Tatiana; Lukyashchenko, Ksenia
2016-04-01
Soil thermal properties significantly affect the land-atmosphere heat exchange rates. Intra-soil heat fluxes depend both on temperature gradients and soil thermal conductivity. Soil temperature changes due to energy fluxes are determined by soil specific heat. Thermal diffusivity is equal to thermal conductivity divided by volumetric specific heat and reflects both the soil ability to transfer heat and its ability to change temperature when heat is supplied or withdrawn. The higher soil thermal diffusivity is, the thicker is the soil/ground layer in which diurnal and seasonal temperature fluctuations are registered and the smaller are the temperature fluctuations at the soil surface. Thermal diffusivity vs. moisture dependencies for loams, sands and clays of the East European Plain were obtained using the unsteady-state method. Thermal diffusivity of different soils differed greatly, and for a given soil it could vary by 2, 3 or even 5 times depending on soil moisture. The shapes of thermal diffusivity vs. moisture dependencies were different: peak curves were typical for sandy soils and sigmoid curves were typical for loamy and especially for compacted soils. The lowest thermal diffusivities and the smallest range of their variability with soil moisture were obtained for clays with high humus content. Hierarchical set of models will be presented, allowing an estimate of soil thermal diffusivity from available data on soil texture, moisture, bulk density and organic carbon. When developing these models the first step was to parameterize the experimental thermal diffusivity vs. moisture dependencies with a 4-parameter function; the next step was to obtain regression formulas to estimate the function parameters from available data on basic soil properties; the last step was to evaluate the accuracy of suggested models using independent data on soil thermal diffusivity. The simplest models were based on soil bulk density and organic carbon data and provided different
Institute of Scientific and Technical Information of China (English)
卫俊霞; 相里斌; 高晓惠; 段晓峰
2011-01-01
The classification and de-aliasing methods with respect to multi-spectra and hyper-spectra have been widely studied in recent years. And both K-mean clustering algorithm and spectral similarity algorithm are familiar classification methods. The present paper improved the K-mean clustering algorithm by using spectral similarity match algorithm to perform a new spectral classification algorithm. Two spectra with the farthest distance first were chosen as reference spectra. The Euclidean distance method or spectral angle cosine method then were used to classify data cube on the basis of the two reference spectra, and delete the spectra which belongs to the two reference spectra. The rest data cube was used to perform new classification according to a third spectrum, which is the farthest distance or the biggest angle one corresponding to the two reference spectra. Multi-spectral data cube was applied in the experimental test. The results of K-mean clustering classification by ENVI, compared with simulation results of the improved K-mean algorithm and the spectral angle cosine method, demonstrated that the latter two classify two air bubbles explicitly and effectively, and the improved K-mean algorithm classifies backgrounds better, especially the Euclidean distance method can classify the backgrounds integrally.%近年来对高光谱与多光谱进行分类去混的研究方法很多,K-均值聚类算法与光谱相似度计算算法都属于成熟的分类算法.作者在对其研究基础上,将K-均值算法进行改进,并融入光谱相似度匹配算法,形成一种新的光谱分类算法,找出两条距离最远的光谱作为参考光谱,用欧氏距离法或夹角余弦法对数据立方体进行分类,并且从数据立方体中删除属于这两条谱线的其余谱线,同时找出与两条参考光谱距离最远或者夹角最大者作为第三条参考光谱,对剩余数据立方体进行新的分类,并在此算法上用多光谱数据立方体进行
Functional Piezocrystal Characterisation under Varying Conditions
Directory of Open Access Journals (Sweden)
Xiaochun Liao
2015-12-01
Full Text Available Piezocrystals, especially the relaxor-based ferroelectric crystals, have been subject to intense investigation and development within the past three decades, motivated by the performance advantages offered by their ultrahigh piezoelectric coefficients and higher electromechanical coupling coefficients than piezoceramics. Structural anisotropy of piezocrystals also provides opportunities for devices to operate in novel vibration modes, such as the d36 face shear mode, with domain engineering and special crystal cuts. These piezocrystal characteristics contribute to their potential usage in a wide range of low- and high-power ultrasound applications. In such applications, conventional piezoelectric materials are presently subject to varying mechanical stress/pressure, temperature and electric field conditions. However, as observed previously, piezocrystal properties are significantly affected by a single such condition or a combination of conditions. Laboratory characterisation of the piezocrystal properties under these conditions is therefore essential to fully understand these materials and to allow electroacoustic transducer design in realistic scenarios. This will help to establish the extent to which these high performance piezocrystals can replace conventional piezoceramics in demanding applications. However, such characterisation requires specific experimental arrangements, examples of which are reported here, along with relevant results. The measurements include high frequency-resolution impedance spectroscopy with the piezocrystal material under mechanical stress 0–60 MPa, temperature 20–200 °C, high electric AC drive and DC bias. A laser Doppler vibrometer and infrared thermal camera are also integrated into the measurement system for vibration mode shape scanning and thermal conditioning with high AC drive. Three generations of piezocrystal have been tested: (I binary, PMN-PT; (II ternary, PIN-PMN-PT; and (III doped ternary, Mn
How specific halide adsorption varies hydrophobic interactions.
Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus
2016-03-11
Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.
Loop delay compensation for baseband predistorter based on raised cosine filter%基于升余弦滤波的基带预失真环路延迟补偿
Institute of Scientific and Technical Information of China (English)
娄景艺; 高俊; 屈晓旭
2011-01-01
There are deficiencies in traditional loop delay (LD) estimation and compensation methods such as the complex LD estimation process, the slow convergence speed, and influence of the aliasing distortion of compensating operation on the performance of the predistorter. Therefore, a novel LD estimation and compensation method for baseband predistorter was proposed, namely the golden section method for the LD research and the raised cosine filter for LD compensation. This method has such advantages as fast convergence speed, high convergence precision and less aliasing distortion. As for the NMSE of the predistorter, this method can optimize 17 dB better than the other traditional methods.%传统的基带预失真环路延迟估计和补偿方法估计过程复杂,收敛速度慢,补偿信号存在混迭失真,影响预失真系统的性能.为此,提出了一种新的基带预失真器环路延迟估计和补偿方法,该方法采用黄金分割法完成环路延迟搜索,用升余弦滤波器完成环路延迟补偿.其环路延迟估计搜索速度快,准确度高,环路延迟补偿后信号失真小,应用该方法的基带预失真系统NMSE指标较传统方法优化17 dB.
Institute of Scientific and Technical Information of China (English)
张永宏; 曹健; 王丽华
2012-01-01
人脸特征提取是人脸识别中重要的一个环节.提出了一种新的方法,利用DCT对人脸图像压缩降维,然后对DCT系数用20组Gabor小波滤波,滤波后的结果采用选择性分块统计方法提取特征向量.最后把特征向量用改进型感知器算法进行分类.以VC ++6.0为开发平台在Yale人脸库和ORL人脸库上对该方法进行了测试.实验表明,该方法与常用的PCA、LDA等特征提取方法相比可以有效降低运算时间,并提高识别率.%Face feature extraction is an important part of face recognition. A new method is presented which u-ses discrete cosine transform( DCT) for face images compression and dimension reduction, then the DCT coefficients is filtered by using 20 groups of Gabor wavelet, the selective block statistics method is used to extract eigenvectors from the result of filtering. Finally, the eigenvectors with modified perception algorithm are classified. It is tested on the Yale face database and ORL face database with VC + + 6. 0. Experiment shows that compared with the commonly used feature extraction methods such as PCA and LDA, the new method can reduce the calculation and increase the identification effectively.
Climate and hillslope degradation vary in concert; 85 ka to present, eastern Sierra Nevada, CA, USA
Madoff, Risa D.; Putkonen, Jaakko
2016-08-01
Degradation in the landscape results when the interactions of climate, substrate, and biota dislodge and transport sediment that is mantling landforms. Rates of degradation through time control landform stability and resiliency. Therefore, records of past degradation rates can be used to inform us on how a given landscape responded to significant changes in past climates. For example, climate has varied at many temporal scales, and some of the largest recent shifts enabled the glacial advances and retreats in time scales of 20-100 ka. Therefore, it is reasonable to expect that the rate of landscape degradation has also varied at similar time scales. However, the general hillslope diffusion equation that is commonly used to model cross-profiles of hillslopes on time scales of thousands to tens of thousands of years typically relies on a constant and optimized rate parameter to generate a model cross-profile approximating the current observed landform cross-profile. Using a time-varying diffusivity parameter, we generated three separate degradation scenarios for the Mono Basin moraine in the eastern Sierra Nevada, CA, USA, in order to assess the potential impact of varying past climates on sediment transport. We used published paleoclimate records in the study area and modern rates of surface degradation from climates that correspond broadly to those paleoclimates. The results indicate that, in this case, the climate driven and, therefore, time-dependent degradation model produces a good fit between the modeled and observed landform profiles. Results showed that, when the surface elevations of the reference case (constant optimized diffusivity) were compared through time to the surface elevations of the time-dependent model, the differences were relatively small. The largest deviation was found to occur during the Last Glacial Maximum (LGM). We found that for investigations into the geological effects of climate change in glacial and polar regions, the use of time-varying
Finite element form of FDV for widely varying flowfields
Richardson, G. A.; Cassibry, J. T.; Chung, T. J.; Wu, S. T.
2010-01-01
We present the Flowfield Dependent Variation (FDV) method for physical applications that have widely varying spatial and temporal scales. Our motivation is to develop a versatile numerical method that is accurate and stable in simulations with complex geometries and with wide variations in space and time scales. The use of a finite element formulation adds capabilities such as flexible grid geometries and exact enforcement of Neumann boundary conditions. While finite element schemes are used extensively by researchers solving computational fluid dynamics in many engineering fields, their use in space physics, astrophysical fluids and laboratory magnetohydrodynamic simulations with shocks has been predominantly overlooked. The FDV method is unique in that numerical diffusion is derived from physical parameters rather than traditional artificial viscosity methods. Numerical instabilities account for most of the difficulties when capturing shocks in these regimes. The first part of this paper concentrates on the presentation of our numerical method formulation for Newtonian and relativistic hydrodynamics. In the second part we present several standard simulation examples that test the method's limitations and verify the FDV method. We show that our finite element formulation is stable and accurate for a range of both Mach numbers and Lorentz factors in one-dimensional test problems. We also present the converging/diverging nozzle which contains both incompressible and compressible flow in the flowfield over a range of subsonic and supersonic regions. We demonstrate the stability of our method and the accuracy by comparison with the results of other methods including the finite difference Total Variation Diminishing method. We explore the use of FDV for both non-relativistic and relativistic fluids (hydrodynamics) with strong shocks in order to establish the effectiveness in future applications of this method in astrophysical and laboratory plasma environments.
Diffusion of gases in metal containing carbon aerogels
Energy Technology Data Exchange (ETDEWEB)
Marques, L.M.; Conceicao, F.L.; Carrott, M.M.L. Ribeiro; Carrott, P.J.M. [Evora Univ. (Portugal). Centro de Quimica de Evora
2011-02-15
Carbon aerogels containing Fe, Ni, Cu or no metal were prepared by carbonisation of polymer aerogels synthesised from 2,4-dihydroxybenzoic acid and formaldehyde and modified by CVD of benzene. Uptakes and diffusion coefficients of CO{sub 2}, CH{sub 4}, N{sub 2} and O{sub 2} were measured and the results compared with those obtained using a commercial carbon molecular sieve. The results indicated that the diffusion of light gas molecules in carbon aerogels cannot be interpreted solely on the basis of micropore diffusion, but that the very high mesopore volumes of the aerogel monoliths exert a strong influence on the kinetics of diffusion in these materials. The mesoporosity is decreased when the % solids used during synthesis of the polymer precursor increases and this resulted in kinetic behaviour which was more similar to that predicted by Fickian or LDF models. Increasing % solids was also accompanied by generally slower diffusion rates and generally lower uptakes. The single gas uptakes and diffusion coefficients could be altered by varying the % solids used during synthesis of the polymer precursor, by introducing different metals into the polymer hydrogel by ion exchange, or by CVD of benzene on the carbon aerogel. (author)
Zador, Zsolt; Magzoub, Mazin; Jin, Songwan; Manley, Geoffrey T; Papadopoulos, Marios C; Verkman, A S
2008-03-01
Diffusion in brain extracellular space (ECS) is important for nonsynaptic intercellular communication, extracellular ionic buffering, and delivery of drugs and metabolites. We measured macromolecular diffusion in normally light-inaccessible regions of mouse brain by microfiberoptic epifluorescence photobleaching, in which a fiberoptic with a micron-size tip is introduced deep in brain tissue. In brain cortex, the diffusion of a noninteracting molecule [fluorescein isothiocyanate (FITC)-dextran, 70 kDa] was slowed 4.5 +/- 0.5-fold compared with its diffusion in water (D(o)/D), and was depth-independent down to 800 microm from the brain surface. Diffusion was significantly accelerated (D(o)/D of 2.9+/-0.3) in mice lacking the glial water channel aquaporin-4. FITC-dextran diffusion varied greatly in different regions of brain, with D(o)/D of 3.5 +/- 0.3 in hippocampus and 7.4 +/- 0.3 in thalamus. Remarkably, D(o)/D in deep brain was strongly dependent on solute size, whereas diffusion in cortex changed little with solute size. Mathematical modeling of ECS diffusion required nonuniform ECS dimensions in deep brain, which we call "heterometricity," to account for the size-dependent diffusion. Our results provide the first data on molecular diffusion in ECS deep in brain in vivo and demonstrate previously unrecognized hindrance and heterometricity for diffusion of large macromolecules in deep brain.
Diffusion measurements by Raman spectroscopy
DEFF Research Database (Denmark)
Hansen, Susanne Brunsgaard; Shapiro, Alexander; Berg, Rolf W.;
Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt......Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt...
Selected Dissemination/Diffusion Strategies.
Schmitt, Marshall L.
This analysis of selected diffusion and dissemination methods used by developer-demonstrator projects in the National Diffusion Network discusses strategies under the following headings: managing the project, developing materials, disseminating information, conducting awareness sessions, training personnel, using certified trainers, providing…
Osmosis and Diffusion Conceptual Assessment
Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts
2011-01-01
Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified…
Preliminary Investigation of Supersonic Diffusers
1945-05-01
No. L5D20 This pressure was measured with a large mercury manometer . The total ’head after diffusion can be assumed equal to the static pressure at...of the entering kinetic energy. A mercury manometer was used to measure the difference between the total heads before and after diffusion. ‘J!hesetwo
Molecular dynamics simulation of diffusivity
Institute of Scientific and Technical Information of China (English)
Juanfang LIU; Danling ZENG; Qin LI; Hong GAO
2008-01-01
Equilibrium molecular dynamics simulation was performed on water to calculate its diffusivity by adopting different potential models. The results show that the potential models have great influence on the simulated results. In addition, the diffusivities obtained by the SPCE model conform well to the experimental values.
The diffusion of constitutional rights
Goderis, B.V.G.; Versteeg, M.
2014-01-01
Constitutions are commonly regarded as uniquely national products, shaped by domestic ideals and politics. This paper develops and empirically investigates a novel hypothesis, which is that constitutions are also shaped by transnational influence, or “diffusion.” Constitutional rights can diffuse th
Diffusion measurements by Raman spectroscopy
DEFF Research Database (Denmark)
Hansen, Susanne Brunsgaard; Shapiro, Alexander; Berg, Rolf W.
Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt......Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt...
Diffusion of childbearing within cohabitation.
Vitali, Agnese; Aassve, Arnstein; Lappegård, Trude
2015-04-01
The article analyzes the diffusion of childbearing within cohabitation in Norway, using municipality data over a 24-year period (1988-2011). Research has found substantial spatial heterogeneity in this phenomenon but also substantial spatial correlation, and the prevalence of childbearing within cohabitation has increased significantly over time. We consider several theoretical perspectives and implement a spatial panel model that allows accounting for autocorrelation not only on the dependent variable but also on key explanatory variables, and hence identifies the key determinants of diffusion of childbearing within cohabitation across space and over time. We find only partial support for the second demographic transition as a theory able to explain the diffusion of childbearing within cohabitation. Our results show that at least in the first phase of the diffusion (1988-1997), economic difficulties as measured by increased unemployment among men contributed to the diffusion of childbearing within cohabitation. However, the most important driver for childbearing within cohabitation is expansion in education for women.
Heat transfer, diffusion, and evaporation
Nusselt, Wilhelm
1954-01-01
Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.
Experimental Investigation of Radio-Turbulence Induced Diffusion -- Final Report
Energy Technology Data Exchange (ETDEWEB)
Spitz, H. B.; Usman, S.
2005-07-07
The outcome of this research project suggests that the transport of radon in water is significantly greater than that predicted solely by molecular diffusion. The original study was related to the long term storage of {sup 226}Ra-bearing sand at the DOE Fernald site and determining whether a barrier of water covering the sand would be effective in reducing the emanation of {sup 222}Rn from the sand. Initial observations before this study found the transport of radon in water to be greater than that predicted solely by molecular diffusion. Fick's law on diffusion was used to model the transport of radon in water including the impact associated with radioactive decay. Initial measurements suggested that the deposition of energy in water associated with the radioactive decay process influences diffusion and enhances transport of radon. A multi-region, one-dimensional, steady-state transport model was used to analyze the movement of radon through a sequential column of air, water and air. An effective diffusion coefficient was determined by varying the thickness of the water column and measuring the time for transport of {sup 222}Rn through of the water barrier. A one-region, one-dimensional transient diffusion equation was developed to investigate the build up of radon at the end of the water column to the time when a steady-state, equilibrium condition was achieved. This build up with time is characteristic of the transport rate of radon in water and established the basis for estimating the effective diffusion coefficient for {sup 222}Rn in water. Several experiments were conducted using different types and physical arrangements of water barriers to examine how radon transport is influenced by the water barrier. Results of our measurements confirm our theoretical analyses which suggest that convective forces other than pure molecular diffusion impact the transport of {sup 222}Rn through the water barrier. An effective diffusion coefficient is defined that
Diffusion in membranes: Toward a two-dimensional diffusion map
Directory of Open Access Journals (Sweden)
Toppozini Laura
2015-01-01
Full Text Available For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.
Naik, Nikhil; Barsi, Christopher; Velten, Andreas; Raskar, Ramesh
2014-05-01
Imaging through complex media is a well-known challenge, as scattering distorts a signal and invalidates imaging equations. For coherent imaging, the input field can be reconstructed using phase conjugation or knowledge of the complex transmission matrix. However, for incoherent light, wave interference methods are limited to small viewing angles. On the other hand, time-resolved methods do not rely on signal or object phase correlations, making them suitable for reconstructing wide-angle, larger-scale objects. Previously, a time-resolved technique was demonstrated for uniformly reflecting objects. Here, we generalize the technique to reconstruct the spatially varying reflectance of shapes hidden by angle-dependent diffuse layers. The technique is a noninvasive method of imaging three-dimensional objects without relying on coherence. For a given diffuser, ultrafast measurements are used in a convex optimization program to reconstruct a wide-angle, three-dimensional reflectance function. The method has potential use for biological imaging and material characterization.
Takamizawa, Hisashi; Shimizu, Yasuo; Inoue, Koji; Nozawa, Yasuko; Toyama, Takeshi; Yano, Fumiko; Inoue, Masao; Nishida, Akio; Nagai, Yasuyoshi
2016-10-01
The effect of P or B predoping on As diffusion in polycrystalline Si was investigated by atom probe tomography. In all samples, a high concentration of As was found at grain boundaries, indicating that such boundaries are the main diffusion path. However, As grain-boundary diffusion was suppressed in the B-doped sample and enhanced in the P-doped sample. In a sample codoped with both P and B, As diffusion was somewhat enhanced, indicating competition between the effects of the two dopants. The results suggest that As grain-boundary diffusion can be controlled by varying the local concentration of P or B.
Multidimensional diffusion processes
Stroock, Daniel W
1997-01-01
From the reviews: "… Both the Markov-process approach and the Itô approach … have been immensely successful in diffusion theory. The Stroock-Varadhan book, developed from the historic 1969 papers by its authors, presents the martingale-problem approach as a more powerful - and, in certain regards, more intrinsic-means of studying the foundations of the subject. […] … the authors make the uncompromising decision not "to proselytise by intimidating the reader with myriad examples demonstrating the full scope of the techniques", but rather to persuade the reader "with a careful treatment of just one problem to which they apply". […] Most of the main tools of stochastic-processes theory are used, ..but it is the formidable combination of probability theory with analysis … which is the core of the work. […] I have emphasized the great importance of the Stroock-Varadhan book. It contains a lot more than I have indicated; in particular, its many exercises conain much interesting material. For immediat...
Transdermal diffusion of xenon in vitro using diffusion cells
Verkhovsky, A.; Petrov, E.
2015-11-01
The aim of this research was to study the diffusion rate of xenon through guinea pig skin and how viscosity of cosmetic component capryl/capric triglyceride (CCT) facilitates to deliver xenon to surface of skin patches. They were placed in Franz cell for 24 hours and diffusion rate and permeability of xenon were calculated. Thus diffusion rate was 0.031 mg/hour*cm2 and permeability was 0.003 cm/hour. Using Brookfield viscometer it was shown that viscosity of CCT decreased upon increasing xenon concentration. Obtained results can be utilized in developing of new xenon containing drugs for topical administration.
Diffusion weighted imaging in the liver
Kele, Petra G.; van der Jagt, Eric J.
2010-01-01
Diffusion weighted magnetic resonance imaging (DWI) is an imaging technique which provides tissue contrast by the measurement of diffusion properties of water molecules within tissues. Diffusion is expressed in an apparent diffusion coefficient (ADC), which reflects the diffusion properties unique t
Diffusion of aroma compounds in stirred yogurts with different complex viscosities.
Déléris, Isabelle; Lauverjat, Clémentine; Tréléa, Ioan Cristian; Souchon, Isabelle
2007-10-17
To better understand aroma release in relation to yogurt structure and perception, the apparent diffusivity of aroma compounds within complex dairy gels was determined using an experimental diffusion cell. Apparent diffusion coefficients of four aroma compounds (diacetyl, ethyl acetate, ethyl hexanoate, and linalool) at 7 degrees C in yogurts (varying in composition and structure) ranged from 0.07 x 10 (-10) to 8.91 x 10 (-10) m (2) s (-1), depending on aroma compounds and on product structure. The strong effect of yogurt fat content on the apparent diffusivity of hydrophobic compounds was revealed (15-fold and 50-fold decreases in the apparent diffusion coefficient of linalool and ethyl hexanoate, respectively). Protein composition seemed to have a greater effect than that of mechanical treatment. However, variations in the apparent diffusion coefficient for the considered products remained limited and cannot completely explain differences in flavor release and in perception that were previously observed.
Pawar, Nisha; Donth, Claudia; Weiss, Matthias
2014-08-18
Character and rapidity of protein diffusion in intracellular fluids are key determinants of the dynamics and steady state of a plethora of biochemical reactions. So far, an anomalous diffusion in cytoplasmic fluids with viscoelastic and even glassy characteristics has been reported in a variety of organisms on several length scales and timescales. Here, we show that the contiguous fluid of former cytoplasm and nucleoplasm features an anisotropically varying diffusion of macromolecules during eukaryotic cell division. In metaphase, diffusion in the contiguous nucleocytoplasmic fluid appears less anomalous along the spindle axis as compared to perpendicular directions. As a consequence, the long-time diffusion of macromolecules preferentially points along the spindle axis, leading to prolonged residence of macromolecules in the spindle region. Based on our experimental data, we suggest that anisotropic diffusion facilitates the encounter and interaction of spindle-associated proteins, e.g., during the formation of a dynamic spindle matrix. Copyright © 2014 Elsevier Ltd. All rights reserved.
Diffuse Scattering from Relaxor PMN-xPT
Krogstad, Matthew; Rosenkranz, Stephan; Osborn, Raymond; Wozniak, Justin; Ye, Feng; Ruff, Jacob; Gehring, Peter; Ye, Zuo-Guang; Phelan, Daniel
Relaxor ferroelectrics possess intriguing electromechanical and dielectric properties, the microscopic physics of which is widely regarded to be related to local, correlated atomic displacements from long-range symmetry. However, despite numerous studies over the last few decades, the details of how short range correlations and disorder drive the relaxor behavior remain unresolved. Single crystal diffuse scattering provides a powerful probe of such deviations from an average structure correlated over varying length scales, and over the last few years, techniques and instruments for measuring diffuse scattering with both x-rays and neutrons have seen a dramatic improvement, allowing for large volumes of reciprocal space to be measured in little time. We present our recent complementary neutron and x-ray measurements on solid solutions of PMN-xPT which revealed new structure to the diffuse scattering of relaxors close to the morphotropic phase boundary.
Systematic Optimization of Boron Diffusion for Solar Cell Emitters
Ebrahimi, P.; Kolahdouz, M.; Iraj, M.; Ganjian, M.; Aghababa, H.; Asl-Soleimani, E.; Radamson, Henry H.
2017-02-01
To achieve p-n junctions for n-type solar cells, we have studied BBr3 diffusion in an open tube furnace, varying parameters of the BBr3 diffusion process such as temperature, gas flows, and duration of individual process steps, i.e., predeposition and drive-in. Then, output parameters such as carrier lifetime, sheet resistance, and diffusion profile were measured and statistically analyzed to optimize the emitter characteristics. Statistical analysis (factorial design) was finally employed to systematically explore the effects of the set of input variables on the outputs. The effect of the interactions between inputs was also evaluated for each output, quantified using a two-level factorial method. Temperature and BBr3 flow were found to have the most significant effect on different outputs such as carrier lifetime, junction depth, sheet resistance, and final surface concentration.
Reliability theory for diffusion processes on interconnected networks
Khorramzadeh, Yasamin; Youssef, Mina; Eubank, Stephen
2014-03-01
We present the concept of network reliability as a framework to study diffusion dynamics in interdependent networks. We illustrate how different outcomes of diffusion processes, such as cascading failure, can be studied by estimating the reliability polynomial under different reliability rules. As an example, we investigate the effect of structural properties on diffusion dynamics for a few different topologies of two coupled networks. We evaluate the effect of varying the probability of failure propagating along the edges, both within a single network as well as between the networks. We exhibit the sensitivity of interdependent network reliability and connectivity to edge failures in each topology. Network Dynamics and Simulation Science Laboratory, Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061, USA.
Self diffusion and wetting transition of fluids in carbon nanotubes
Sahu, Pooja; Ali, Sk. M.; Shenoy, K. T.
2016-05-01
Carbon Nanotubes (CNTs) have been shown to be promising for use in fluid filtration and purification processes, as an alternative to commonly practiced polymer based membranes. Recently, it has been shown from the Molecular Dynamics (MD) simulations that the CNTs can be used as a viable alternative of polymer based membranes due to its feasibility to transport the very high flux compared to polymer based membranes. Now, the question naturally arises, what is the reason for fast fluid transport through the nanopores of CNTs of specific diameter. Diffusion of fluids can be used as a signature of transport through nanochannels and MD simulations can be effectively used to calculate the diffusion of fluids. Hence, the present study is aimed at performing the MD simulations to investigate the wetting transition and the diffusivity of polar and non-polar fluids in nanochannels of varied diameters of CNTs.