Sums of two-dimensional spectral triples
DEFF Research Database (Denmark)
Christensen, Erik; Ivan, Cristina
2007-01-01
We study countable sums of two dimensional modules for the continuous complex functions on a compact metric space and show that it is possible to construct a spectral triple which gives the original metric back. This spectral triple will be finitely summable for any positive parameter. We also co...
Two dimensional nonlinear spectral estimation techniques for breast cancer localization
International Nuclear Information System (INIS)
Stathaki, P.T.; Constantinides, A.G.
1994-01-01
In this paper the problem of image texture analysis in the presence of noise is examined from a higher-order statistical perspective. The approach taken involves the use of two dimensional second order Volterra filters where the filter weights are derived from third order cumulants of the two dimensional signal. The specific application contained in this contribution is in mammography, an area in which it is difficult to discern the appropriate features. The paper describes the fundamental issues of the various components of the approach. The results of the entire texture modelling, classification and segmentation scheme contained in this paper are very encouraging
Vortex merging and spectral cascade in two-dimensional flows
DEFF Research Database (Denmark)
Nielsen, A.H.; He, X.; Juul Rasmussen, J.
1996-01-01
The merging of two identical vortices is studied numerically using a spectral code. It is noted that the enstrophy cascade is most active on the distorted vortex boundaries, with a Kolmogorov-like spectrum E(k) approximate to k(-alpha), alpha less than or equal to 4, developed at high wave numbers....... The inverse energy cascade is completed when the vortices merge into one of larger size. (C) 1996 American Institute of Physics....
Two dimensional spectral camera development for cartilage monitoring
Kuehn, A.; Graf, A.; Wenzel, U.; Princz, S.; Miller, R.; Mantz, H.; Hessling, M.
2015-07-01
In the joint project "BioopTiss" between the Ulm University Medical Center and Ulm University of Applied Sciences, a bioreactor is under development to grow facial cartilage by the methods of tissue engineering. In order to ensure a sufficient quality of the cartilage for implantation, the cartilage growth must be monitored continuously. Current monitoring methods destroy the cultured cartilage so that it is no longer suitable for implantation. Alternatively, it is possible to analyze the cartilage using fluorescence spectroscopy with UV light excitation. This allows a non-invasive assessment of cartilage in terms of composition and quality. The cultured cartilage tissue can reach a size of several square centimeters. For recording fluorescence spectra of every point of the cartilage sample, a highly sensitive spectral camera has been developed which allows distinguishing collagen I from collagen II non-invasively by their fluorescence. This spectral camera operates according to the computed tomography imaging spectrometry (CTIS) principle, which allows obtaining many spectra of a small area with only one snapshot.
Stopping power of two-dimensional spin quantum electron gases
Zhang, Ya; Jiang, Wei; Yi, Lin
2015-04-01
Quantum effects can contribute significantly to the electronic stopping powers in the interactions between the fast moving beams and the degenerate electron gases. From the Pauli equation, the spin quantum hydrodynamic (SQHD) model is derived and used to calculate the stopping power and the induced electron density for protons moving above a two-dimensional (2D) electron gas with considering spin effect under an external in-plane magnetic field. In our calculation, the stopping power is not only modulated by the spin direction, but also varied with the strength of the spin effect. It is demonstrated that the spin effect can obviously enhance or reduce the stopping power of a 2D electron gas within a laboratory magnetic field condition (several tens of Tesla), thus a negative stopping power appears at some specific proton velocity, which implies the protons drain energy from the Pauli gas, showing another significant example of the low-dimensional physics.
Two dimensional radiated power diagnostics on Alcator C-Moda)
Reinke, M. L.; Hutchinson, I. H.
2008-10-01
The radiated power diagnostics for the Alcator C-Mod tokamak have been upgraded to measure two dimensional structure of the photon emissivity profile in order to investigate poloidal asymmetries in the core radiation. Commonly utilized unbiased absolute extreme ultraviolet (AXUV) diode arrays view the plasma along five different horizontal planes. The layout of the diagnostic set is shown and the results from calibrations and recent experiments are discussed. Data showing a significant, 30%-40%, inboard/outboard emissivity asymmetry during ELM-free H-mode are presented. The ability to use AXUV diode arrays to measure absolute radiated power is explored by comparing diode and resistive bolometer-based emissivity profiles for highly radiative L-mode plasmas seeded with argon. Emissivity profiles match in the core but disagree radially outward resulting in an underprediction of Prad of nearly 50% by the diodes compared to Prad determined using resistive bolometers.
Nikkhoo, M.; Goli, M.; Najafi Alamdari, M.; Naeimi, M.
2008-05-01
Two-dimensional spectral analysis of spatial data is known as a handy tool for illustrating such data in frequency domain in all earth science disciplines. Conventional methods of spectral analysis (i.e. Fourier method) need an equally spaced data set which is, however, rarely possible in reality. In this paper we developed the least-squares spectral analysis in two dimensions. The method was originally proposed by Vanicek 1969 to be applied to one- dimensional irregularly sampled data. Applying this method to two-dimensional irregularly sampled data also results in an undistorted power spectrum, since during the computation of which, no interpolation process is encountered. As a case study two-dimensional spectrum of GPS leveling data over North America were computed as well as spectrum of Geoid undulations derived from EIGEN-GL04C model. Due to the derived spectra of two data sets, a very good fitness of two is shown in long and medium wavelengths. We also computed the power spectrum of gravity anomalies over North America and compared it with the other ones derived from interpolated data (by different methods). Spectral behavior of these methods is discussed as well.
Jellali, Nabiha; Najjar, Monia; Ferchichi, Moez; Rezig, Houria
2017-07-01
In this paper, a new two-dimensional spectral/spatial codes family, named two dimensional dynamic cyclic shift codes (2D-DCS) is introduced. The 2D-DCS codes are derived from the dynamic cyclic shift code for the spectral and spatial coding. The proposed system can fully eliminate the multiple access interference (MAI) by using the MAI cancellation property. The effect of shot noise, phase-induced intensity noise and thermal noise are used to analyze the code performance. In comparison with existing two dimensional (2D) codes, such as 2D perfect difference (2D-PD), 2D Extended Enhanced Double Weight (2D-Extended-EDW) and 2D hybrid (2D-FCC/MDW) codes, the numerical results show that our proposed codes have the best performance. By keeping the same code length and increasing the spatial code, the performance of our 2D-DCS system is enhanced: it provides higher data rates while using lower transmitted power and a smaller spectral width.
Investigation of a two-dimensional spectral element method for Helmholtz's equation
International Nuclear Information System (INIS)
Mehdizadeh, Omid Z.; Paraschivoiu, Marius
2003-01-01
A spectral element method is developed for solving the two-dimensional Helmholtz's equation, which is the equation governing time-harmonic acoustic waves. Computational cost for solving Helmholtz's equation with the Galerkin finite element method increases as the wave number increases, due to the pollution effect. Therefore a more efficient numerical method is sought. The comparison between a spectral element method and a second-order finite element method shows that the spectral element method leads to fewer grid points per wavelength and less computational cost, for the same accuracy. It also offers the same advantage as the finite element method to address complex geometry and general material property. Some simple examples are addressed and compared with the exact solutions to confirm the accuracy of the method. For unbounded problems, the symmetric perfectly matched layer (PML) method is applied to treat the non-reflecting boundary conditions. In the PML method, a fictitious absorbing layer is introduced outside the truncated boundary
Suppressing sampling noise in linear and two-dimensional spectral simulations
Kruiger, Johannes F.; van der Vegte, Cornelis P.; Jansen, Thomas L. C.
2015-02-01
We examine the problem of sampling noise encountered in time-domain simulations of linear and two-dimensional spectroscopies. A new adaptive apodization scheme based on physical arguments is devised for suppressing the noise in order to allow reducing the number of used disorder realisations, but introducing only a minimum of spectral aberrations and thus allowing a potential speed-up of these types of simulations. First, the method is demonstrated on an artificial dimer system, where the effect on slope analysis, typically used to study spectral dynamics, is analysed. It is, furthermore, tested on the simulated two-dimensional infrared spectra in the amide I region of the protein lysozyme. The cross polarisation component is investigated, particularly sensitive to sampling noise, because it relies on cancelling of the dominant diagonal spectral contributions. In all these cases, the adaptive apodization scheme is found to give more accurate results than the commonly used lifetime apodization scheme and in most cases better than the gaussian apodization scheme.
DEFF Research Database (Denmark)
Yura, Harold; Hanson, Steen Grüner
2012-01-01
Methods for simulation of two-dimensional signals with arbitrary power spectral densities and signal amplitude probability density functions are disclosed. The method relies on initially transforming a white noise sample set of random Gaussian distributed numbers into a corresponding set with the......Methods for simulation of two-dimensional signals with arbitrary power spectral densities and signal amplitude probability density functions are disclosed. The method relies on initially transforming a white noise sample set of random Gaussian distributed numbers into a corresponding set...... with the desired spectral distribution, after which this colored Gaussian probability distribution is transformed via an inverse transform into the desired probability distribution. In most cases the method provides satisfactory results and can thus be considered an engineering approach. Several illustrative...
Two dimensional simulation of high power laser-surface interaction
International Nuclear Information System (INIS)
Goldman, S.R.; Wilke, M.D.; Green, R.E.L.; Johnson, R.P.; Busch, G.E.
1998-01-01
For laser intensities in the range of 10 8 --10 9 W/cm 2 , and pulse lengths of order 10 microsec or longer, the authors have modified the inertial confinement fusion code Lasnex to simulate gaseous and some dense material aspects of the laser-matter interaction. The unique aspect of their treatment consists of an ablation model which defines a dense material-vapor interface and then calculates the mass flow across this interface. The model treats the dense material as a rigid two-dimensional mass and heat reservoir suppressing all hydrodynamic motion in the dense material. The computer simulations and additional post-processors provide predictions for measurements including impulse given to the target, pressures at the target interface, electron temperatures and densities in the vapor-plasma plume region, and emission of radiation from the target. The authors will present an analysis of some relatively well diagnosed experiments which have been useful in developing their modeling. The simulations match experimentally obtained target impulses, pressures at the target surface inside the laser spot, and radiation emission from the target to within about 20%. Hence their simulational technique appears to form a useful basis for further investigation of laser-surface interaction in this intensity, pulse-width range. This work is useful in many technical areas such as materials processing
Retrieval of spectral and dynamic properties from two-dimensional infrared pump-probe experiments.
Chelli, Riccardo; Volkov, Victor V; Righini, Roberto
2008-07-15
We have developed a fitting algorithm able to extract spectral and dynamic properties of a three level oscillator from a two-dimensional infrared spectrum (2D-IR) detected in time resolved nonlinear experiments. Such properties go from the frequencies of the ground-to-first and first-to-second vibrational transitions (and hence anharmonicity) to the frequency-fluctuation correlation function. This last is represented through a general expression that allows one to approach the various strategies of modeling proposed in the literature. The model is based on the Kubo picture of stochastic fluctuations of the transition frequency as a result of perturbations by a fluctuating surrounding. To account for the line-shape broadening due to pump pulse spectral width in double-resonance measurements, we supply the fitting algorithm with the option to perform the convolution of the spectral signal with a Lorentzian function in the pump-frequency dimension. The algorithm is tested here on 2D-IR pump-probe spectra of a Gly-Ala dipeptide recorded at various pump-probe delay times. Speedup benchmarks have been performed on a small Beowulf cluster. The program is written in FORTRAN language for both serial and parallel architectures and is available free of charge to the interested reader. (c) 2008 Wiley Periodicals, Inc.
Moghaderi, Hamid; Dehghan, Mehdi; Donatelli, Marco; Mazza, Mariarosa
2017-12-01
Fractional diffusion equations (FDEs) are a mathematical tool used for describing some special diffusion phenomena arising in many different applications like porous media and computational finance. In this paper, we focus on a two-dimensional space-FDE problem discretized by means of a second order finite difference scheme obtained as combination of the Crank-Nicolson scheme and the so-called weighted and shifted Grünwald formula. By fully exploiting the Toeplitz-like structure of the resulting linear system, we provide a detailed spectral analysis of the coefficient matrix at each time step, both in the case of constant and variable diffusion coefficients. Such a spectral analysis has a very crucial role, since it can be used for designing fast and robust iterative solvers. In particular, we employ the obtained spectral information to define a Galerkin multigrid method based on the classical linear interpolation as grid transfer operator and damped-Jacobi as smoother, and to prove the linear convergence rate of the corresponding two-grid method. The theoretical analysis suggests that the proposed grid transfer operator is strong enough for working also with the V-cycle method and the geometric multigrid. On this basis, we introduce two computationally favourable variants of the proposed multigrid method and we use them as preconditioners for Krylov methods. Several numerical results confirm that the resulting preconditioning strategies still keep a linear convergence rate.
On the detection of corrosion pit interactions using two-dimensional spectral analysis
International Nuclear Information System (INIS)
Jarrah, Adil; Nianga, Jean-Marie; Iost, Alain; Guillemot, Gildas; Najjar, Denis
2010-01-01
A statistical methodology for detecting pits interactions based on a two-dimensional spectral analysis is presented. This method can be used as a tool for the exploratory analysis of spatial point patterns and can be advanced as an alternative of classical methods based on distance. One of the major advantages of the spectral analysis approach over the use of classical methods is its ability to reveal more details about the spatial structure like the scale for which pits corrosion can be considered as independent. Furthermore, directional components of pattern can be investigated. The method is validated in a first time using numerical simulations on random, regular and aggregated structures. The density of pits, used in the numerical simulations, corresponds to that assessed from a corroded aluminium sheet. In a second time, this method is applied to verify the independence of the corrosion pits observed on the aforementioned aluminium sheet before applying the Gumbel theory to determine the maximum pit depth. Indeed, the property of independence is a prerequisite of the Gumbel theory which is one of the most frequently used in the field of safety and reliability.
Analytic structure and power series expansion of the Jost function for the two-dimensional problem
International Nuclear Information System (INIS)
Rakityansky, S A; Elander, N
2012-01-01
For a two-dimensional quantum-mechanical problem, we obtain a generalized power series expansion of the S-matrix that can be done near an arbitrary point on the Riemann surface of the energy, similar to the standard effective-range expansion. In order to do this, we consider the Jost function and analytically factorize its momentum dependence that causes the Jost function to be a multi-valued function. The remaining single-valued function of the energy is then expanded in the power series near an arbitrary point in the complex energy plane. A systematic and accurate procedure has been developed for calculating the expansion coefficients. This makes it possible to obtain a semi-analytic expression for the Jost function (and therefore for the S-matrix) near an arbitrary point on the Riemann surface and use it, for example, to locate the spectral points (bound and resonant states) as the S-matrix poles. The method is applied to a model similar to those used in the theory of quantum dots. (paper)
Farag, Marwa H.; Hoenders, Bernhard J.; Knoester, Jasper; Jansen, Thomas L. C.
2017-01-01
The effect of Gaussian dynamics on the line shapes in linear absorption and two-dimensional correlation spectroscopy is well understood as the second-order cumulant expansion provides exact spectra. Gaussian solvent dynamics can be well analyzed using slope line analysis of two-dimensional
Design of two-dimensional coils for wireless power transmission to in vivo robotic capsule.
Lee, Seon-Woo; Kim, Jong-Dae; Son, Ju-Hyun; Ryu, Mun-Ho; Kim, Jongwon
2005-01-01
This paper presents a design of two dimensional receiving coils to provide hundreds of milli-watt power via inductive link to in vivo robotic capsules, whose orientation are practically undetermined. The wireless power transmission system consists of a transmitter powered by class E power amplifier, and receiver with 2-dimensional antenna, rectifier, and voltage regulator. Two types of 2-dimensional antennas are designed and evaluated by theoretic and experimental analysis. Experimental results show that the proposed 2-D receiving antenna could deliver the power homogeneously against its orientation, with less than 20% of variation of the possible maximum power.
Polarizational stopping power of heavy-ion diclusters in two-dimensional electron liquids
International Nuclear Information System (INIS)
Ballester, D.; Fuentes, A. M.; Tkachenko, I. M.
2007-01-01
The in-plane polarizational stopping power of heavy-ion diclusters in a two-dimensional strongly coupled electron liquid is studied. Analytical expressions for the stopping power of both fast and slow projectiles are derived. To go beyond the random-phase approximation we make use of the inverse dielectric function obtained by means of the method of moments and some recent analytical expressions for the static local-field correction factor
Crustal geomagnetic field - Two-dimensional intermediate-wavelength spatial power spectra
Mcleod, M. G.
1983-01-01
Two-dimensional Fourier spatial power spectra of equivalent magnetization values are presented for a region that includes a large portion of the western United States. The magnetization values were determined by inversion of POGO satellite data, assuming a magnetic crust 40 km thick, and were located on an 11 x 10 array with 300 km grid spacing. The spectra appear to be in good agreement with values of the crustal geomagnetic field spatial power spectra given by McLeod and Coleman (1980) and with the crustal field model given by Serson and Hannaford (1957). The spectra show evidence of noise at low frequencies in the direction along the satellite orbital track (N-S). indicating that for this particular data set additional filtering would probably be desirable. These findings illustrate the value of two-dimensional spatial power spectra both for describing the geomagnetic field statistically and as a guide for diagnosing possible noise sources.
Kadhim, Rasim Azeez; Fadhil, Hilal Adnan; Aljunid, S. A.; Razalli, Mohamad Shahrazel
2014-10-01
A new two dimensional codes family, namely two dimensional multi-diagonal (2D-MD) codes, is proposed for spectral/spatial non-coherent OCDMA systems based on the one dimensional MD code. Since the MD code has the property of zero cross correlation, the proposed 2D-MD code also has this property. So that, the multi-access interference (MAI) is fully eliminated and the phase induced intensity noise (PIIN) is suppressed with the proposed code. Code performance is analyzed in terms of bit error rate (BER) while considering the effect of shot noise, PIIN, and thermal noise. The performance of the proposed code is compared with the related MD, modified quadratic congruence (MQC), two dimensional perfect difference (2D-PD) and two dimensional diluted perfect difference (2D-DPD) codes. The analytical and the simulation results reveal that the proposed 2D-MD code outperforms the other codes. Moreover, a large number of simultaneous users can be accommodated at low BER and high data rate.
Kim, Kwon-Ho; Kumar, Brijesh; Lee, Keun Young; Park, Hyun-Kyu; Lee, Ju-Hyuck; Lee, Hyun Hwi; Jun, Hoin; Lee, Dongyun; Kim, Sang-Woo
2013-01-01
Direct current (DC) piezoelectric power generator is promising for the miniaturization of a power package and self-powering of nanorobots and body-implanted devices. Hence, we report the first use of two-dimensional (2D) zinc oxide (ZnO) nanostructure and an anionic nanoclay layer to generate piezoelectric DC output power. The device, made from 2D nanosheets and an anionic nanoclay layer heterojunction, has potential to be the smallest size power package, and could be used to charge wireless nano/micro scale systems without the use of rectifier circuits to convert alternating current into DC to store the generated power. The combined effect of buckling behaviour of the ZnO nanosheets, a self-formed anionic nanoclay layer, and coupled semiconducting and piezoelectric properties of ZnO nanosheets contributes to efficient DC power generation. The networked ZnO nanosheets proved to be structurally stable under huge external mechanical loads.
Enhanced thermoelectric power in two-dimensional transition metal dichalcogenide monolayers
Pu, Jiang
2016-07-27
The carrier-density-dependent conductance and thermoelectric properties of large-area MoS2 and WSe2 monolayers are simultaneously investigated using the electrolyte gating method. The sign of the thermoelectric power changes across the transistor off-state in the ambipolar WSe2 transistor as the majority carrier density switches from electron to hole. The thermopower and thermoelectric power factor of monolayer samples are one order of magnitude larger than that of bulk materials, and their carrier-density dependences exhibit a quantitative agreement with the semiclassical Mott relation based on the two-dimensional energy band structure, concluding the thermoelectric properties are enhanced by the low-dimensional effect.
Spectral editing through laser-flash excitation in two-dimensional photo-CIDNP MAS NMR experiments
Sai Sankar Gupta, Karthick Babu; Daviso, Eugenio; Jeschke, Gunnar; Alia, A.; Ernst, Matthias; Matysik, Jörg
2014-09-01
In solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR experiments, strong signal enhancement is observed from molecules forming a spin-correlated radical pair in a rigid matrix. Two-dimensional 13C-13C dipolar-assisted rotational resonance (DARR) photo-CIDNP MAS NMR experiments have been applied to obtain exact chemical shift assignments from those cofactors. Under continuous illumination, the signals are enhanced via three-spin mixing (TSM) and differential decay (DD) and their intensity corresponds to the electron spin density in pz orbitals. In multiple-13C labelled samples, spin diffusion leads to propagation of signal enhancement to all 13C spins. Under steady-state conditions, direct signal assignment is possible due to the uniform signal intensity. The original intensities, however, are inaccessible and the information of the local electron spin density is lost. Upon laser-flash illumination, the signal is enhanced via the classical radical pair mechanism (RPM). The obtained intensities are related to isotropic hyperfine interactions aiso and both enhanced absorptive and emissive lines can be observed due to differences in the sign of the local isotropic hyperfine interaction. Exploiting the mechanism of the polarization, selectivity can be increased by the novel time-resolved two-dimensional dipolar-assisted rotational resonance (DARR) MAS NMR experiment which simplifies the signal assignment compared to complex spectra of the same RCs obtained by continuous illumination. Here we present two-dimensional time-resolved photo-CIDNP MAS NMR experiments providing both directly: signal assignment and spectral editing by sign and strength of aiso. Hence, this experiment provides a direct key to the electronic structure of the correlated radical pair.
Khodel, V A
2001-01-01
Spectral functions of strongly correlated two-dimensional electron systems in solids are studied on the assumption that these systems undergo as phase transition, called fermion condensation, whose characteristic feature is flattening of the electron spectrum epsilon (p). Unlike the previous models in the present study, the decay of single-particle states is properly taken into account. Results of calculations are shown to be in qualitative agreement with ARPES data. The universal behavior of the ration Im EPSILON(p, epsilon, T)/T as a function of x = epsilon/T are found to be reproduced reasonably well. However, in the present model this behavior is destroyed in vicinities of the van Hove points where the fermion condensate resides
Nori, F.; Merlin, R.; Haas, S.; Sandvick, A.; Dagotto, E.
1996-03-01
We calculate(F. Nori, R.Merlin, S. Haas, A.W. Sandvik, and E. Dagotto, Physical Review Letters) 75, 553 (1995). the Raman spectrum of the two-dimensional (2D) spin-1/2 Heisenberg antiferromagnet by exact diagonalization and quantum Monte Carlo techniques on clusters of up to 144 sites. On a 16-site cluster, we consider the phonon-magnon interaction which leads to random fluctuations of the exchange integral. Results are in good agreement with experiments on various high-Tc precursors, such as La_2CuO4 and YBa_2Cu_3O_6.2. In particular, our calculations reproduce the broad lineshape of the two-magnon peak, the asymmetry about its maximum, the existence of spectral weight at high energies, and the observation of nominally forbidden A_1g scattering.
Foster, Samuel; Thesberg, Mischa; Neophytou, Neophytos
2017-11-01
Nanocomposites are promising candidates for the next generation of thermoelectric materials since they exhibit extremely low thermal conductivities as a result of phonon scattering on the boundaries of the various material phases. The nanoinclusions, however, should not degrade the thermoelectric power factor, and ideally should increase it, so that benefits to the ZT figure of merit can be achieved. In this work we employ the nonequilibrium Green's function quantum transport method to calculate the electronic and thermoelectric coefficients of materials embedded with nanoinclusions. For computational effectiveness we consider two-dimensional nanoribbon geometries, however, the method includes the details of geometry, electron-phonon interactions, quantization, tunneling, and the ballistic to diffusive nature of transport, all combined in a unified approach. This makes it a convenient and accurate way to understand electronic and thermoelectric transport in nanomaterials, beyond semiclassical approximations, and beyond approximations that deal with the complexities of the geometry. We show that the presence of nanoinclusions within a matrix material offers opportunities for only weak energy filtering, significantly lower in comparison to superlattices, and thus only moderate power factor improvements. However, we describe how such nanocomposites can be optimized to limit degradation in the thermoelectric power factor and elaborate on the conditions that achieve the aforementioned mild improvements. Importantly, we show that under certain conditions, the power factor is independent of the density of nanoinclusions, meaning that materials with large nanoinclusion densities which provide very low thermal conductivities can also retain large power factors and result in large ZT figures of merit.
First operation of a powerful FEL with two-dimensional distributed feedback
Agarin, N V; Bobylev, V B; Ginzburg, N S; Ivanenko, V G; Kalinin, P V; Kuznetsov, S A; Peskov, N Yu; Sergeev, A S; Sinitsky, S L; Stepanov, V D
2000-01-01
A W-band (75 GHz) FEL of planar geometry driven by a sheet electron beam was realised using the pulse accelerator ELMI (0.8 MeV/3 kA/5 mu s). To provide the spatial coherence of radiation from different parts of the electron beam with a cross-section of 0.4x12 cm two-dimensional distributed feedback systems have been employed using a 2-D Bragg resonator of planar geometry. The resonator consisted of two 2-D Bragg reflectors separated by a regular waveguide section. The total energy in the microwave pulse of microsecond duration was 100 J corresponding to a power of approx 100 MW. The main component of the FEL radiation spectrum was at 75 GHz that corresponded to the zone of effective Bragg reflection found from 'cold' microwave testing of the resonator. The experimental data compared well with the results of theoretical analysis.
International Nuclear Information System (INIS)
Vaeth, W.
1979-04-01
The correlation of signal components at different frequencies like higher harmonics cannot be detected by a normal power spectral density measurement, since this technique correlates only components at the same frequency. This paper describes a special method for measuring the correlation of two signal components at different frequencies: the CRISS power spectral density. From this new function in frequency analysis, the correlation of two components can be determined quantitatively either they stem from one signal or from two diverse signals. The principle of the method, suitable for the higher harmonics of a signal as well as for any other frequency combinations is shown for the digital frequency analysis technique. Two examples of CRISS power spectral densities demonstrates the operation of the new method. (orig.) [de
Wang, Z. J.; Liu, Yen; Kwak, Dochan (Technical Monitor)
2002-01-01
The framework for constructing a high-order, conservative Spectral (Finite) Volume (SV) method is presented for two-dimensional scalar hyperbolic conservation laws on unstructured triangular grids. Each triangular grid cell forms a spectral volume (SV), and the SV is further subdivided into polygonal control volumes (CVs) to supported high-order data reconstructions. Cell-averaged solutions from these CVs are used to reconstruct a high order polynomial approximation in the SV. Each CV is then updated independently with a Godunov-type finite volume method and a high-order Runge-Kutta time integration scheme. A universal reconstruction is obtained by partitioning all SVs in a geometrically similar manner. The convergence of the SV method is shown to depend on how a SV is partitioned. A criterion based on the Lebesgue constant has been developed and used successfully to determine the quality of various partitions. Symmetric, stable, and convergent linear, quadratic, and cubic SVs have been obtained, and many different types of partitions have been evaluated. The SV method is tested for both linear and non-linear model problems with and without discontinuities.
Yu, Ge; Yang, Ren-jie; Lü, Ai-jun; Tan, En-zhong
2015-08-01
New approach for discriminant analysis of adulterated milk is proposed based on combining hetero-spectral two-dimensional (2D) near-infrared (NIR) and mid-infrared (IR) correlation spectroscopy along with multi-way partial least squares discriminant analysis (NPLS-DA). Firstly, 36 pure milk samples were collected and 36 adulterated milk with starch samples (0.01 to 1 g · L(-1)) were prepared by adding appropriate mass of starch into pure milk. Then, one-dimensional NIR transmittance spectra and IR attenuated total reflection spectra of pure milk and adulterated milk with starch were measured at room temperature. And the synchronous 2D NIR-IR (4200~4800 vs. 900~1700 cm(-1)) correlation spectra of all samples were calculated. Due to the trace of adulterants, the synchronous 2D IR-NIR correlation spectral differences between adulterated milk with starch and pure milk are very subtle. Consequently, it was impossible to directly distinguish whether the sample was pure milk or adulterated milk. Finally, 2D IR-NIR correlation spectra were to build a discriminant model to classify adulterated milk and pure milk. The classification accuracy rates of samples in calibration set and in prediction set were 95.8% and 100% respectively. Also, the NPLS-DA models were built based on 2D NIR and 2D IR correlation spectra, respectively. The classification accuracy rates of samples in prediction set were 95.8%. Comparison results showed that the NPLS-DA model could provide better results using 2D NIR-IR correlation spectra than using 2D NIR, and 2D IR correlation spectra. The proposed method can not only effectively extract the feature information of adulterants in milk, but also explores a new perspective method for detection of adulterated food.
The static and dynamic screening of power loss of a two-dimensional electron gas
Bennett, C.; Balkan, N.; Tanatar, B.; Celik, H.; Cankurtaran, M.
1998-07-01
Experimental results concerning the well-width dependence of the acoustic-phonon-assisted energy relaxation of a two-dimensional electron gas in GaAs/Ga1 - xAlxAs quantum-well structures are compared with theoretical models that involve piezoelectric and deformation-potential scattering and the effects of static and dynamic screening of the electron-acoustic phonon interaction. It is shown that screening only slightly modifies the predictions of the approximate calculations.
Integrable two dimensional supersystems
International Nuclear Information System (INIS)
Tripathy, K.C.; Tripathy, L.K.
1988-08-01
The integrability of two dimensional time-dependent classical systems is examined in N=2 superspace using Dirac's second class constraints. The invariants involving quadratic powers in velocities for super harmonic oscillator and super Kepler potentials have been derived. (author). 5 refs
A two-dimensional simulator of the neutronic behaviour of low power fast reactors
International Nuclear Information System (INIS)
Penha, M.A.V.R. da.
1984-01-01
A model to simulate the temporal neutronic behaviour of fast breeder reactors was developed. The effective cross-sections are corrected, whenever the reactor state change; by using linear correlations and interpolation schemes with data contained in a library previously compiled. This methodology was coupled with a simplified spatial neutronic calculation to investigate the temporal behaviour of neutronic parameters such as breeding gain, flux and power. (Author) [pt
All-optical cryptography of M-QAM formats by using two-dimensional spectrally sliced keys.
Abbade, Marcelo L F; Cvijetic, Milorad; Messani, Carlos A; Alves, Cleiton J; Tenenbaum, Stefan
2015-05-10
There has been an increased interest in enhancing the security of optical communications systems and networks. All-optical cryptography methods have been considered as an alternative to electronic data encryption. In this paper we propose and verify the use of a novel all-optical scheme based on cryptographic keys applied on the spectral signal for encryption of the M-QAM modulated data with bit rates of up to 200 gigabits per second.
Two-Dimensional Neutronic and Fuel Cycle Analysis of the Transatomic Power Molten Salt Reactor
Energy Technology Data Exchange (ETDEWEB)
Betzler, Benjamin R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division; Powers, Jeffrey J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division; Worrall, Andrew [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division; Robertson, Sean [Transatomic Power Corporation, Cambridge, MA (United States); Dewan, Leslie [Transatomic Power Corporation, Cambridge, MA (United States); Massie, Mark [Transatomic Power Corporation, Cambridge, MA (United States)
2017-01-15
This status report presents the results from the first phase of the collaboration between Transatomic Power Corporation (TAP) and Oak Ridge National Laboratory (ORNL) to provide neutronic and fuel cycle analysis of the TAP core design through the Department of Energy Gateway for Accelerated Innovation in Nuclear, Nuclear Energy Voucher program. The TAP design is a molten salt reactor using movable moderator rods to shift the neutron spectrum in the core from mostly epithermal at beginning of life to thermal at end of life. Additional developments in the ChemTriton modeling and simulation tool provide the critical moderator-to-fuel ratio searches and time-dependent parameters necessary to simulate the continuously changing physics in this complex system. Results from simulations with these tools show agreement with TAP-calculated performance metrics for core lifetime, discharge burnup, and salt volume fraction, verifying the viability of reducing actinide waste production with this design. Additional analyses of time step sizes, mass feed rates and enrichments, and isotopic removals provide additional information to make informed design decisions. This work further demonstrates capabilities of ORNL modeling and simulation tools for analysis of molten salt reactor designs and strongly positions this effort for the upcoming three-dimensional core analysis.
Two-Dimensional Correlation Analysis of pH-induced Raman Spectral Changes of α-Lactalbumin
Energy Technology Data Exchange (ETDEWEB)
Park, Yeonju; Kim, Yeseul; Vikram, Kunwar; Jung, Young Mee [Kangwon National University, Chuncheon (Korea, Republic of); Czarnik-Matusewicz, Boguslawa [University of Wrocław, Wrocław (Poland)
2016-05-15
In this study, spectral changes in aromatic amino acid residues, such as tyrosine (Tyr) and tryptophan (Trp), in bovine holo-ALA were investigated at varying pH values by Raman spectroscopy. PCA and 2D correlation spectroscopy were applied to the pH-induced Raman spectra of bovine holo-ALA to obtain a deeper understanding of the conformational changes in the polypeptide backbone. We can confirm that the Tyr residues are buried inside the protein as the pH decreases. The secondary structure change primarily occurred in the N-state (pH 7-4), and the Tyr residues changed during the A-state (pH 3-1). We are currently investigating the overall correlation between the side chain and peptide backbone in the transition of ALA from the N-state to the A-states during pH variations; the results of these analyses will be reported elsewhere.
Diniz, M. R.; Riffel, R. A.; Riffel, R.; Crenshaw, D. M.; Storchi-Bergmann, T.; Fischer, T. C.; Schmitt, H. R.; Kraemer, S. B.
2017-08-01
We present a near-infrared (near-IR) study of the spectral components of the continuum in the inner 500 × 500 pc2 of the nearby Seyfert galaxy Mrk 573 using adaptive optics near-IR integral field spectroscopy with the instrument near-infrared integral field spectrograph of the Gemini North Telescope at a spatial resolution of ˜50 pc. We performed spectral synthesis using the starlight code and constructed maps for the contributions of different age components of the stellar population: young (age ≤100 Myr), young-intermediate (100 age ≤ 700 Myr), intermediate-old (700 Myr age ≤ 2 Gyr) and old (age > 2 Gyr) to the near-IR K-band continuum, as well as their contribution to the total stellar mass. We found that the old stellar population is dominant within the inner 250 pc, while the intermediate-age components dominate the continuum at larger distances. A young stellar component contributes up to ˜20 per cent within the inner ˜70 pc, while hot dust emission and featureless continuum components are also necessary to fit the nuclear spectrum, contributing up to 20 per cent of the K-band flux there. The radial distribution of the different age components in the inner kiloparsec of Mrk 573 is similar to those obtained by our group for the Seyfert galaxies Mrk 1066, Mrk 1157 and NGC 1068 in previous works using a similar methodology. Young stellar populations (≤100 Myr) are seen in the inner 200-300 pc for all galaxies contributing with ≥20 per cent of the K-band flux, while the near-IR continuum is dominated by the contribution of intermediate-age stars (t = 100 Myr-2 Gyr) at larger distances. Older stellar populations dominate in the inner 250 pc.
International Nuclear Information System (INIS)
Moraes, Manoel; Diaz, Marcos
2009-01-01
The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in Hα, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman and O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 x 10 -4 M sun is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.
Kawarada, Hiroshi; Yamada, Tetsuya; Xu, Dechen; Tsuboi, Hidetoshi; Kitabayashi, Yuya; Matsumura, Daisuke; Shibata, Masanobu; Kudo, Takuya; Inaba, Masafumi; Hiraiwa, Atsushi
2017-02-20
Complementary power field effect transistors (FETs) based on wide bandgap materials not only provide high-voltage switching capability with the reduction of on-resistance and switching losses, but also enable a smart inverter system by the dramatic simplification of external circuits. However, p-channel power FETs with equivalent performance to those of n-channel FETs are not obtained in any wide bandgap material other than diamond. Here we show that a breakdown voltage of more than 1600 V has been obtained in a diamond metal-oxide-semiconductor (MOS) FET with a p-channel based on a two-dimensional hole gas (2DHG). Atomic layer deposited (ALD) Al 2 O 3 induces the 2DHG ubiquitously on a hydrogen-terminated (C-H) diamond surface and also acts as both gate insulator and passivation layer. The high voltage performance is equivalent to that of state-of-the-art SiC planar n-channel FETs and AlGaN/GaN FETs. The drain current density in the on-state is also comparable to that of these two FETs with similar device size and V B .
Zumbühl, Stefan; Scherrer, Nadim C; Eggenberger, Urs
2014-01-01
The interpretation of standard Fourier transform infrared spectra (FT-IR) on oil-based paint samples often suffers from interfering bands of the different compounds, namely, binder, oxidative aging products, carboxylates formed during aging, and several pigments and fillers. The distinction of the aging products such as ketone and carboxylic acid functional groups pose the next problem, as these interfere with the triglyceride esters of the oil. A sample preparation and derivatization technique using gaseous sulfur tetrafluoride (SF4), was thus developed with the aim to discriminate overlapping signals and achieve a signal enhancement on superposed compounds. Of particular interest in this context is the signal elimination of the broad carboxylate bands of the typical reaction products developing during the aging processes in oil-based paints, as well as signal interference originating from several typical pigments in this spectral range. Furthermore, it is possible to distinguish the different carbonyl-containing functional groups upon selective alteration. The derivatization treatment can be applied to both microsamples and polished cross sections. It increases the selectivity of the infrared spectroscopy technique in a fundamental manner and permits the identification and two-dimensional (2D) localization of binder components in aged paint samples at the micrometer scale. The combination of SF4 derivatization with high-resolution 2D FT-IR focal plane array (FPA) imaging delivers considerable advances to the study of micro-morphological processes involving organic compounds.
Torrungrueng, D; Johnson, J T
2001-10-01
The forward-backward method with a novel spectral acceleration algorithm (FB/NSA) has been shown to be a highly efficient O(Ntot) iterative method of moments, where Ntot is the total number of unknowns to be solved, for the computation of electromagnetic (EM) wave scattering from both one-dimensional and two-dimensional (2-D) rough surfaces. The efficiency of the method makes studies of backscattering enhancement from moderately rough impedance surfaces at large incident angles tractable. Variations in the characteristics of backscattering enhancement with incident angle, surface impedance, polarization, and surface statistics are investigated by use of the 2-D FB/NSA method combined with parallel computing techniques. The surfaces considered are Gaussian random processes with an isotropic Gaussian spectrum and root-mean-square surface heights and slopes ranging from 0.5 lambda to lambda and from 0.5 to 1.0, respectively, where lambda is the EM wavelength in free space. Incident angles ranging from normal incidence up to 70 degrees are considered in this study. It is found that backscattering enhancement depends strongly on all parameters of interest. America
Sun, Fusheng; Li, Yaqing; Wang, Xiang; Chi, Zhilai; Yu, Guanghui
2017-04-01
Understanding the binding characteristics of copper (Cu) to different functional groups in soil dissolved organic matter (DOM) is important to explore Cu toxicity, bioavailability and ultimate fate in the environment. However, the methods used to explore such binding characteristics are still limited. Here, two-dimensional correlation spectroscopy (2DCOS) integrated with Fourier transform infrared (FTIR), 29 Si nuclear magnetic resonance (NMR), 27 Al NMR, and synchrotron-radiation-based FTIR spectromicroscopy were used to explore the binding characteristics of Cu to soil DOM as part of a long-term (23 years) fertilization experiment. Compared with no fertilization and inorganic fertilization (NPK), long-term pig manure fertilization (M) treatment significantly increased the concentration of total and bioavailable Cu in soils. Furthermore, hetero-spectral 2DCOS analyses demonstrated that the binding characteristics of Cu onto functional groups in soil DOM were modified by fertilization regimes. In the NPK treatment, Cu was bound to aliphatic C, whereas in the manure treatment SiO groups had higher affinity toward Cu than aliphatic C. Also, the sequence of binding of functional groups to Cu was modified by the fertilization treatments. Moreover, synchrotron-radiation-based FTIR spectromicroscopy showed that Cu, clay minerals and sesquioxides, and C functional groups were heterogeneously distributed at the micro-scale. Specifically, clay-OH as well as mineral elements had a distribution pattern similar to Cu, but certain (but not all) C forms showed a distribution pattern inconsistent with that of Cu. The combination of synchrotron radiation spectromicroscopy and 2DCOS is a useful tool in exploring the interactions among heavy metals, minerals and organic components in soils. Copyright © 2017 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Anon.
1991-01-01
This chapter addresses the extension of previous work in one-dimensional (linear) error theory to two-dimensional error analysis. The topics of the chapter include the definition of two-dimensional error, the probability ellipse, the probability circle, elliptical (circular) error evaluation, the application to position accuracy, and the use of control systems (points) in measurements
Huth, Tobias; Schroeder, Indra; Hansen, Ulf-Peter
2006-01-01
Two-dimensional (2D) dwell-time analysis of time series of single-channel patch-clamp current was improved by employing a Hinkley detector for jump detection, introducing a genetic fit algorithm, replacing maximum likelihood by a least square criterion, averaging over a field of 9 or 25 bins in the 2D plane and normalizing per measuring time, not per events. Using simulated time series for the generation of the "theoretical" 2D histograms from assumed Markov models enabled the incorporation of the measured filter response and noise. The effects of these improvements were tested with respect to the temporal resolution, accuracy of the determination of the rate constants of the Markov model, sensitivity to noise and requirement of open time and length of the time series. The 2D fit was better than the classical hidden Markov model (HMM) fit in all tested fields. The temporal resolution of the two most efficient algorithms, the 2D fit and the subsequent HMM/beta fit, enabled the determination of rate constants 10 times faster than the corner frequency of the low-pass filter. The 2D fit was much less sensitive to noise. The requirement of computing time is a problem of the 2D fit (100 times that of the HMM fit) but can now be handled by personal computers. The studies revealed a fringe benefit of 2D analysis: it can reveal the "true" single-channel current when the filter has reduced the apparent current level by averaging over undetected fast gating.
Directory of Open Access Journals (Sweden)
Royo Pedro
2009-01-01
Full Text Available Abstract Introduction An imaging diagnosis after an iterative cesarean delivery is reviewed demonstrating a fine ultrasound-pathologic correlation. Case presentation A 33-year-old woman (G3, P3 presented referring intense dysmenorrhea and intermenstrual spotting since her third cesarean delivery, 1 year before. A cesarean section dehiscence with utero-peritoneal fistula was diagnosed by transvaginal ultrasound. Conclusion We can conclude that transvaginal two-dimensional power Doppler and three-dimensional ultrasound are highly accurate in detecting cesarean section dehiscence and uterine fistula.
El-Amin, Mohamed
2010-11-27
A boundary layer analysis was presented to study the non-Darcy-free convection of a power-law fluid over a non-isothermal two-dimensional body embedded in a porous medium. The Ostwald-de Waele power-law model was used to characterize the non-Newtonian fluid behavior. Similarity solutions were obtained with variations in surface temperature or surface heat flux. In view of the fact that most of the non-Newtonian fluids have large Prandtl numbers, this study was directed toward such fluids. The effects of the porous medium parameters, k1 and k2, body shape parameter, m, and surface thermal variations parameter, p, as well as the power-law index, n, were examined. © 2010 Springer Science+Business Media B.V.
International Nuclear Information System (INIS)
Truong, Nguyen-Vu; Wang, Liuping; Wong, Peter K.C.
2008-01-01
Power demand forecasting is of vital importance to the management and planning of power system operations which include generation, transmission, distribution, as well as system's security analysis and economic pricing processes. This paper concerns the modeling and short-term forecast of daily peak power demand in the state of Victoria, Australia. In this study, a two-dimensional wavelet based state dependent parameter (SDP) modelling approach is used to produce a compact mathematical model for this complex nonlinear dynamic system. In this approach, a nonlinear system is expressed by a set of linear regressive input and output terms (state variables) multiplied by the respective state dependent parameters that carry the nonlinearities in the form of 2-D wavelet series expansions. This model is identified based on historical data, descriptively representing the relationship and interaction between various components which affect the peak power demand of a certain day. The identified model has been used to forecast daily peak power demand in the state of Victoria, Australia in the time period from the 9th of August 2007 to the 24th of August 2007. With a MAPE (mean absolute prediction error) of 1.9%, it has clearly implied the effectiveness of the identified model. (author)
Osserman, Robert
2011-01-01
The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o
Two-dimensional ferroelectrics
Energy Technology Data Exchange (ETDEWEB)
Blinov, L M; Fridkin, Vladimir M; Palto, Sergei P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation); Bune, A V; Dowben, P A; Ducharme, Stephen [Department of Physics and Astronomy, Behlen Laboratory of Physics, Center for Materials Research and Analysis, University of Nebraska-Linkoln, Linkoln, NE (United States)
2000-03-31
The investigation of the finite-size effect in ferroelectric crystals and films has been limited by the experimental conditions. The smallest demonstrated ferroelectric crystals had a diameter of {approx}200 A and the thinnest ferroelectric films were {approx}200 A thick, macroscopic sizes on an atomic scale. Langmuir-Blodgett deposition of films one monolayer at a time has produced high quality ferroelectric films as thin as 10 A, made from polyvinylidene fluoride and its copolymers. These ultrathin films permitted the ultimate investigation of finite-size effects on the atomic thickness scale. Langmuir-Blodgett films also revealed the fundamental two-dimensional character of ferroelectricity in these materials by demonstrating that there is no so-called critical thickness; films as thin as two monolayers (1 nm) are ferroelectric, with a transition temperature near that of the bulk material. The films exhibit all the main properties of ferroelectricity with a first-order ferroelectric-paraelectric phase transition: polarization hysteresis (switching); the jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; the increase in the transition temperature with applied field; double hysteresis above the phase transition temperature; and the existence of the ferroelectric critical point. The films also exhibit a new phase transition associated with the two-dimensional layers. (reviews of topical problems)
Parchevsky, V. M.; Guryanova, V. V.
2017-01-01
A computational and experimental procedure for construction of the two-dimensional separation curve (TDSC) for a horizontal steam generator (SG) at a nuclear power station (NPS) with VVER-reactors. In contrast to the conventional one-dimensional curve describing the wetness of saturated steam generated in SG as a function of the boiler water level at one, usually rated, load, TDSC is a function of two variables, which are the level and the load of SGB that enables TDSC to be used for wetness control in a wide load range. The procedure is based on two types of experimental data obtained during rated load operation: the nonuniformity factor of the steam load at the outlet from the submerged perforated sheet (SPS) and the dependence of the mass water level in the vicinity of the "hot" header on the water level the "cold" end of SG. The TDSC prediction procedure is presented in the form of an algorithm using SG characteristics, such as steam load and water level as the input and giving the calculated steam wetness at the output. The zoneby-zone calculation method is used. The result is presented in an analytical form (as an empirical correlation) suitable for uploading into controllers or other controls. The predicted TDSC can be used during real-time operation for implementation of different wetness control scenarios (for example, if the effectiveness is a priority, then the minimum water level, minimum wetness, and maximum turbine efficiency should be maintained; if safety is a priority, then the maximum level at the allowable wetness and the maximum water inventory should be kept), for operation of NPS in controlling the frequency and power in a power system, at the design phase (as a part of the simulation complex for verification of design solutions), during construction and erection (in developing software for personnel training simulators), during commissioning tests (to reduce the duration and labor-intensity of experimental activities), and for training.
Power Spectral Density Conversions and Nonlinear Dynamics
Directory of Open Access Journals (Sweden)
Mostafa Rassaian
1994-01-01
Full Text Available To predict the vibration environment of a payload carried by a ground or air transporter, mathematical models are required from which a transfer function to a prescribed input can be calculated. For sensitive payloads these models typically include linear shock isolation system stiffness and damping elements relying on the assumption that the isolation system has a predetermined characteristic frequency and damping ratio independent of excitation magnitude. In order to achieve a practical spectral analysis method, the nonlinear system has to be linearized when the input transportation and handling vibration environment is in the form of an acceleration power spectral density. Test data from commercial isolators show that when nonlinear stiffness and damping effects exist the level of vibration input causes a variation in isolator resonant frequency. This phenomenon, described by the stationary response of the Duffing oscillator to narrow-band Gaussian random excitation, requires an alternative approach for calculation of power spectral density acceleration response at a shock isolated payload under random vibration. This article details the development of a plausible alternative approach for analyzing the spectral response of a nonlinear system subject to random Gaussian excitations.
Power Spectral Density and Hilbert Transform
2016-12-01
2002. Pierce J. An introduction to information theory : symbols, signals , and noise. New York (NY): Dover Publications; 1980. Soumekh M. Fourier array...NOTES 14. ABSTRACT This technical report focuses on the Hilbert transform and some of its applications for digital signal processing. Herein we...review power spectral density and complex exponentials, and illustrate how the Hilbert transform converts a real signal (real in the sense of a real time
Analysis techniques for two-dimensional infrared data
Winter, E. M.; Smith, M. C.
1978-01-01
In order to evaluate infrared detection and remote sensing systems, it is necessary to know the characteristics of the observational environment. For both scanning and staring sensors, the spatial characteristics of the background may be more of a limitation to the performance of a remote sensor than system noise. This limitation is the so-called spatial clutter limit and may be important for systems design of many earth application and surveillance sensors. The data used in this study is two dimensional radiometric data obtained as part of the continuing NASA remote sensing programs. Typical data sources are the Landsat multi-spectral scanner (1.1 micrometers), the airborne heat capacity mapping radiometer (10.5 - 12.5 micrometers) and various infrared data sets acquired by low altitude aircraft. Techniques used for the statistical analysis of one dimensional infrared data, such as power spectral density (PSD), exceedance statistics, etc. are investigated for two dimensional applicability. Also treated are two dimensional extensions of these techniques (2D PSD, etc.), and special techniques developed for the analysis of 2D data.
Piezoelectricity in Two-Dimensional Materials
Wu, Tao
2015-02-25
Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.
Development of Jet Noise Power Spectral Laws
Khavaran, Abbas; Bridges, James
2011-01-01
High-quality jet noise spectral data measured at the Aero-Acoustic Propulsion Laboratory (AAPL) at NASA Glenn is used to develop jet noise scaling laws. A FORTRAN algorithm was written that provides detailed spectral prediction of component jet noise at user-specified conditions. The model generates quick estimates of the jet mixing noise and the broadband shock-associated noise (BBSN) in single-stream, axis-symmetric jets within a wide range of nozzle operating conditions. Shock noise is emitted when supersonic jets exit a nozzle at imperfectly expanded conditions. A successful scaling of the BBSN allows for this noise component to be predicted in both convergent and convergent-divergent nozzles. Configurations considered in this study consisted of convergent and convergent- divergent nozzles. Velocity exponents for the jet mixing noise were evaluated as a function of observer angle and jet temperature. Similar intensity laws were developed for the broadband shock-associated noise in supersonic jets. A computer program called sJet was developed that provides a quick estimate of component noise in single-stream jets at a wide range of operating conditions. A number of features have been incorporated into the data bank and subsequent scaling in order to improve jet noise predictions. Measurements have been converted to a lossless format. Set points have been carefully selected to minimize the instability-related noise at small aft angles. Regression parameters have been scrutinized for error bounds at each angle. Screech-related amplification noise has been kept to a minimum to ensure that the velocity exponents for the jet mixing noise remain free of amplifications. A shock-noise-intensity scaling has been developed independent of the nozzle design point. The computer program provides detailed narrow-band spectral predictions for component noise (mixing noise and shock associated noise), as well as the total noise. Although the methodology is confined to single
Quasi-two-dimensional holography
International Nuclear Information System (INIS)
Kutzner, J.; Erhard, A.; Wuestenberg, H.; Zimpfer, J.
1980-01-01
The acoustical holography with numerical reconstruction by area scanning is memory- and time-intensive. With the experiences by the linear holography we tried to derive a scanning for the evaluating of the two-dimensional flaw-sizes. In most practical cases it is sufficient to determine the exact depth extension of a flaw, whereas the accuracy of the length extension is less critical. For this reason the applicability of the so-called quasi-two-dimensional holography is appropriate. The used sound field given by special probes is divergent in the inclined plane and light focussed in the perpendicular plane using cylindrical lenses. (orig.) [de
Two dimensional plasma simulation code
International Nuclear Information System (INIS)
Hazak, G.; Boneh, Y.; Goshen, Sh.; Oreg, J.
1977-03-01
An electrostatic two-dimensional particle code for plasma simulation is described. Boundary conditions which take into account the finiteness of the system are presented. An analytic solution for the case of crossed fields plasma acceleration is derived. This solution serves as a check on a computer test run
Lee, W P Cathie; Wong, Fhu-Hin; Attenborough, Nicole K; Kong, Xin Ying; Tan, Lling-Lling; Sumathi, S; Chai, Siang-Piao
2017-07-15
In the present work, two-dimensional bismuth oxybromide (BiOBr) was synthesized and coupled with co-catalyst molybdenum disulphide (MoS 2 ) via a simple hydrothermal process. The photoactivity of the resulting hybrid photocatalyst (MoS 2 /BiOBr) was evaluated under the irradiation of 15 W energy-saving light bulb at ambient condition using Reactive Black 5 (RB5) as model dye solution. The photo-degradation of RB5 by BiOBr loaded with 0.2 wt% MoS 2 (MoBi-2) exhibited more than 1.4 and 5.0 folds of enhancement over pristine BiOBr and titanium dioxide (Degussa, P25), respectively. The increased photocatalytic performance was a result of an efficient migration of excited electrons from BiOBr to MoS 2 , prolonging the electron-hole pairs recombination rate. A possible charge transfer diagram of this hybrid composite photocatalyst, and the reaction mechanism for the photodegradation of RB5 were proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.
Stability analysis of two-dimensional digital recursive filters
Alexander, W. E.; Pruess, S. A.
1980-01-01
A new approach to the stability problem for the two-dimensional digital recursive filter is presented. The bivariate difference equation representation of the two-dimensional recursive digital filter is converted to a multiinput-multioutput (MIMO) system similar to the state-space representation of the one-dimensional digital recursive filter. In this paper, a pseudo-state representation is used and three coefficient matrices are obtained. A general theorem for stability of two-dimensional digital recursive filters is derived and a very useful theorem is presented which expresses sufficient requirements for instability in terms of the spectral radii of these matrices.
Advancements of two dimensional correlation spectroscopy in protein researches.
Tao, Yanchun; Wu, Yuqing; Zhang, Liping
2018-05-15
The developments of two-dimensional correlation spectroscopy (2DCOS) applications in protein studies are discussed, especially for the past two decades. The powerful utilities of 2DCOS combined with various analytical techniques in protein studies are summarized. The emphasis is on the vibration spectroscopic techniques including IR, NIR, Raman and optical activity (ROA), as well as vibration circular dichroism (VCD) and fluorescence spectroscopy. In addition, some new developments, such as hetero-spectral 2DCOS, moving-window correlation, and model based correlation, are also reviewed for their utility in the investigation of the secondary structure, denaturation, folding and unfolding changes of protein. Finally, the new possibility and challenges of 2DCOS in protein research are highlighted as well. Copyright © 2018 Elsevier B.V. All rights reserved.
Two dimensional image correlation processor
Yao, Shi-Kai
1992-06-01
Two dimensional images are converted into a very long 1-dimensional data stream by means of raster scan. It is shown that the 1-dimensional correlation function of such long data streams is equivalent to the raster scan converted data of 2-dimensional correlation function of images. Real time correlation of high resolution two-dimensional images has been demonstrated using commercially available components. The advantages of this approach includes programmable electronics reference images, easy interface to objects of interest using conventional image collection optics, real time operation with high resolution images using off-the shelf components, and usefulness in the form of either black and white or full colored images. Such system would be versatile enough for robotics vision, optical inspection, and other pattern recognition and identification applications.
Two-dimensional topological photonics
Khanikaev, Alexander B.; Shvets, Gennady
2017-12-01
Originating from the studies of two-dimensional condensed-matter states, the concept of topological order has recently been expanded to other fields of physics and engineering, particularly optics and photonics. Topological photonic structures have already overturned some of the traditional views on wave propagation and manipulation. The application of topological concepts to guided wave propagation has enabled novel photonic devices, such as reflection-free sharply bent waveguides, robust delay lines, spin-polarized switches and non-reciprocal devices. Discrete degrees of freedom, widely used in condensed-matter physics, such as spin and valley, are now entering the realm of photonics. In this Review, we summarize the latest advances in this highly dynamic field, with special emphasis on the experimental work on two-dimensional photonic topological structures.
Two-dimensional critical phenomena
International Nuclear Information System (INIS)
Saleur, H.
1987-09-01
Two dimensional critical systems are studied using transformation to free fields and conformal invariance methods. The relations between the two approaches are also studied. The analytical results obtained generally depend on universality hypotheses or on renormalization group trajectories which are not established rigorously, so numerical verifications, mainly using the transfer matrix approach, are presented. The exact determination of critical exponents; the partition functions of critical models on toruses; and results as the critical point is approached are discussed [fr
Gyroscope with two-dimensional optomechanical mirror
Davuluri, Sankar; Li, Kai; Li, Yong
2017-11-01
We propose an application of two-dimensional optomechanical oscillator as a gyroscope by detecting the Coriolis force which is modulated at the natural frequency of the optomechanical oscillator. Dependence of gyroscope's sensitivity on shot noise, back-action noise, thermal noise, and input laser power is studied. At optimal input laser power, the gyroscope's sensitivity can be improved by increasing the mass or by decreasing the temperature and decay rate of the mechanical oscillator. When the mechanical oscillator's thermal occupation number, n th, is zero, sensitivity improves with decrease in frequency of the mechanical oscillator. For {n}{{th}}\\gg 1, the sensitivity is independent of the mechanical oscillator's frequency.
Energy Spectra of Vortex Distributions in Two-Dimensional Quantum Turbulence
Directory of Open Access Journals (Sweden)
Ashton S. Bradley
2012-10-01
Full Text Available We theoretically explore key concepts of two-dimensional turbulence in a homogeneous compressible superfluid described by a dissipative two-dimensional Gross-Pitaeveskii equation. Such a fluid supports quantized vortices that have a size characterized by the healing length ξ. We show that, for the divergence-free portion of the superfluid velocity field, the kinetic-energy spectrum over wave number k may be decomposed into an ultraviolet regime (k≫ξ^{-1} having a universal k^{-3} scaling arising from the vortex core structure, and an infrared regime (k≪ξ^{-1} with a spectrum that arises purely from the configuration of the vortices. The Novikov power-law distribution of intervortex distances with exponent -1/3 for vortices of the same sign of circulation leads to an infrared kinetic-energy spectrum with a Kolmogorov k^{-5/3} power law, which is consistent with the existence of an inertial range. The presence of these k^{-3} and k^{-5/3} power laws, together with the constraint of continuity at the smallest configurational scale k≈ξ^{-1}, allows us to derive a new analytical expression for the Kolmogorov constant that we test against a numerical simulation of a forced homogeneous, compressible, two-dimensional superfluid. The numerical simulation corroborates our analysis of the spectral features of the kinetic-energy distribution, once we introduce the concept of a clustered fraction consisting of the fraction of vortices that have the same sign of circulation as their nearest neighboring vortices. Our analysis presents a new approach to understanding two-dimensional quantum turbulence and interpreting similarities and differences with classical two-dimensional turbulence, and suggests new methods to characterize vortex turbulence in two-dimensional quantum fluids via vortex position and circulation measurements.
1/f noise in two-dimensional fluids
International Nuclear Information System (INIS)
Cable, S.B.; Tajima, T.
1994-10-01
We derive an exact result on the velocity fluctuation power spectrum of an incompressible two-dimensional fluid. Employing the fluctuation-dissipation relationship and the enstrophy conversation, we obtain the frequency spectrum of a 1/f form
Two-dimensional capillary origami
International Nuclear Information System (INIS)
Brubaker, N.D.; Lega, J.
2016-01-01
We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.
Two-dimensional capillary origami
Energy Technology Data Exchange (ETDEWEB)
Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu
2016-01-08
We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.
Two-dimensional fourier transform spectrometer
DeFlores, Lauren; Tokmakoff, Andrei
2013-09-03
The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.
Han, Jin-Woo; Rim, Taiuk; Baek, Chang-Ki; Meyyappan, M
2015-09-30
Gas sensors based on metal-oxide-semiconductor transistor with the polysilicon gate replaced by a gas sensitive thin film have been around for over 50 years. These are not suitable for the emerging mobile and wearable sensor platforms due to operating voltages and powers far exceeding the supply capability of batteries. Here we present a novel approach to decouple the chemically sensitive region from the conducting channel for reducing the drive voltage and increasing reliability. This chemically gated field effect transistor uses silicon nanowire for the current conduction channel with a tin oxide film on top of the nanowire serving as the gas sensitive medium. The potential change induced by the molecular adsorption and desorption allows the electrically floating tin oxide film to gate the silicon channel. As the device is designed to be normally off, the power is consumed only during the gas sensing event. This feature is attractive for the battery operated sensor and wearable electronics. In addition, the decoupling of the chemical reaction and the current conduction regions allows the gas sensitive material to be free from electrical stress, thus increasing reliability. The device shows excellent gas sensitivity to the tested analytes relative to conventional metal oxide transistors and resistive sensors.
Ardila-Rey, Jorge Alfredo; Rojas-Moreno, Mónica Victoria; Martínez-Tarifa, Juan Manuel; Robles, Guillermo
2014-02-19
Partial discharge (PD) detection is a standardized technique to qualify electrical insulation in machines and power cables. Several techniques that analyze the waveform of the pulses have been proposed to discriminate noise from PD activity. Among them, spectral power ratio representation shows great flexibility in the separation of the sources of PD. Mapping spectral power ratios in two-dimensional plots leads to clusters of points which group pulses with similar characteristics. The position in the map depends on the nature of the partial discharge, the setup and the frequency response of the sensors. If these clusters are clearly separated, the subsequent task of identifying the source of the discharge is straightforward so the distance between clusters can be a figure of merit to suggest the best option for PD recognition. In this paper, two inductive sensors with different frequency responses to pulsed signals, a high frequency current transformer and an inductive loop sensor, are analyzed to test their performance in detecting and separating the sources of partial discharges.
Directory of Open Access Journals (Sweden)
Jorge Alfredo Ardila-Rey
2014-02-01
Full Text Available Partial discharge (PD detection is a standardized technique to qualify electrical insulation in machines and power cables. Several techniques that analyze the waveform of the pulses have been proposed to discriminate noise from PD activity. Among them, spectral power ratio representation shows great flexibility in the separation of the sources of PD. Mapping spectral power ratios in two-dimensional plots leads to clusters of points which group pulses with similar characteristics. The position in the map depends on the nature of the partial discharge, the setup and the frequency response of the sensors. If these clusters are clearly separated, the subsequent task of identifying the source of the discharge is straightforward so the distance between clusters can be a figure of merit to suggest the best option for PD recognition. In this paper, two inductive sensors with different frequency responses to pulsed signals, a high frequency current transformer and an inductive loop sensor, are analyzed to test their performance in detecting and separating the sources of partial discharges.
Pseudospectral reduction of incompressible two-dimensional turbulence
Bowman, John C.; Roberts, Malcolm
2012-05-01
Spectral reduction was originally formulated entirely in the wavenumber domain as a coarse-grained wavenumber convolution in which bins of modes interact with enhanced coupling coefficients. A Liouville theorem leads to inviscid equipartition solutions when each bin contains the same number of modes. A pseudospectral implementation of spectral reduction which enjoys the efficiency of the fast Fourier transform is described. The model compares well with full pseudospectral simulations of the two-dimensional forced-dissipative energy and enstrophy cascades.
SHJAR Jet Noise Data and Power Spectral Laws
Khavaran, Abbas; Bridges, James
2009-01-01
High quality jet noise spectral data measured at the Aeroacoustic Propulsion Laboratory at the NASA Glenn Research Center is used to examine a number of jet noise scaling laws. Configurations considered in the present study consist of convergent and convergent-divergent axisymmetric nozzles. The measured spectral data are shown in narrow band and cover 8193 equally spaced points in a typical Strouhal number range of 0.0 to 10.0. The measured data are reported as lossless (i.e., atmospheric attenuation is added to measurements), and at 24 equally spaced angles (50deg to 165deg) on a 100-diameter (200-in.) arc. Following the work of Viswanathan, velocity power factors are evaluated using a least squares fit on spectral power density as a function of jet temperature and observer angle. The goodness of the fit and the confidence margins for the two regression parameters are studied at each angle, and alternative relationships are proposed to improve the spectral collapse when certain conditions are met. As an immediate application of the velocity power laws, spectral density in shockcontaining jets are decomposed into components attributed to jet mixing noise and shock noise. From this analysis, jet noise prediction tools can be developed with different spectral components derived from different physics.
Two-dimensional Quantum Gravity
Rolf, Juri
1998-10-01
This Ph.D. thesis pursues two goals: The study of the geometrical structure of two-dimensional quantum gravity and in particular its fractal nature. To address these questions we review the continuum formalism of quantum gravity with special focus on the scaling properties of the theory. We discuss several concepts of fractal dimensions which characterize the extrinsic and intrinsic geometry of quantum gravity. This work is partly based on work done in collaboration with Jan Ambjørn, Dimitrij Boulatov, Jakob L. Nielsen and Yoshiyuki Watabiki (1997). The other goal is the discussion of the discretization of quantum gravity and to address the so called quantum failure of Regge calculus. We review dynamical triangulations and show that it agrees with the continuum theory in two dimensions. Then we discuss Regge calculus and prove that a continuum limit cannot be taken in a sensible way and that it does not reproduce continuum results. This work is partly based on work done in collaboration with Jan Ambjørn, Jakob L. Nielsen and George Savvidy (1997).
Optimizing separations in online comprehensive two-dimensional liquid chromatography.
Pirok, Bob W J; Gargano, Andrea F G; Schoenmakers, Peter J
2018-01-01
Online comprehensive two-dimensional liquid chromatography has become an attractive option for the analysis of complex nonvolatile samples found in various fields (e.g. environmental studies, food, life, and polymer sciences). Two-dimensional liquid chromatography complements the highly popular hyphenated systems that combine liquid chromatography with mass spectrometry. Two-dimensional liquid chromatography is also applied to the analysis of samples that are not compatible with mass spectrometry (e.g. high-molecular-weight polymers), providing important information on the distribution of the sample components along chemical dimensions (molecular weight, charge, lipophilicity, stereochemistry, etc.). Also, in comparison with conventional one-dimensional liquid chromatography, two-dimensional liquid chromatography provides a greater separation power (peak capacity). Because of the additional selectivity and higher peak capacity, the combination of two-dimensional liquid chromatography with mass spectrometry allows for simpler mixtures of compounds to be introduced in the ion source at any given time, improving quantitative analysis by reducing matrix effects. In this review, we summarize the rationale and principles of two-dimensional liquid chromatography experiments, describe advantages and disadvantages of combining different selectivities and discuss strategies to improve the quality of two-dimensional liquid chromatography separations. © 2017 The Authors. Journal of Separation Science published by WILEY-VCH Verlag GmbH & Co. KGaA.
Flow transitions in two-dimensional foams.
Gilbreth, Christopher; Sullivan, Scott; Dennin, Michael
2006-11-01
For sufficiently slow rates of strain, flowing foam can exhibit inhomogeneous flows. The nature of these flows is an area of active study in both two-dimensional model foams and three dimensional foam. Recent work in three-dimensional foam has identified three distinct regimes of flow [S. Rodts, J. C. Baudez, and P. Coussot, Europhys. Lett. 69, 636 (2005)]. Two of these regimes are identified with continuum behavior (full flow and shear banding), and the third regime is identified as a discrete regime exhibiting extreme localization. In this paper, the discrete regime is studied in more detail using a model two-dimensional foam: a bubble raft. We characterize the behavior of the bubble raft subjected to a constant rate of strain as a function of time, system size, and applied rate of strain. We observe localized flow that is consistent with the coexistence of a power-law fluid with rigid-body rotation. As a function of applied rate of strain, there is a transition from a continuum description of the flow to discrete flow when the thickness of the flow region is approximately ten bubbles. This occurs at an applied rotation rate of approximately 0.07 s-1.
Two-dimensional signal analysis
Garello, René
2010-01-01
This title sets out to show that 2-D signal analysis has its own role to play alongside signal processing and image processing.Concentrating its coverage on those 2-D signals coming from physical sensors (such as radars and sonars), the discussion explores a 2-D spectral approach but develops the modeling of 2-D signals and proposes several data-oriented analysis techniques for dealing with them. Coverage is also given to potential future developments in this area.
Two-dimensional heterostructures for energy storage
Energy Technology Data Exchange (ETDEWEB)
Gogotsi, Yury G. [Drexel Univ., Philadelphia, PA (United States); Pomerantseva, Ekaterina [Drexel Univ., Philadelphia, PA (United States)
2017-06-12
Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. As a result, we also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.
Development of Jet Noise Power Spectral Laws Using SHJAR Data
Khavaran, Abbas; Bridges, James
2009-01-01
High quality jet noise spectral data measured at the Aeroacoustic Propulsion Laboratory at the NASA Glenn Research Center is used to examine a number of jet noise scaling laws. Configurations considered in the present study consist of convergent and convergent-divergent axisymmetric nozzles. Following the work of Viswanathan, velocity power factors are estimated using a least squares fit on spectral power density as a function of jet temperature and observer angle. The regression parameters are scrutinized for their uncertainty within the desired confidence margins. As an immediate application of the velocity power laws, spectral density in supersonic jets are decomposed into their respective components attributed to the jet mixing noise and broadband shock associated noise. Subsequent application of the least squares method on the shock power intensity shows that the latter also scales with some power of the shock parameter. A modified shock parameter is defined in order to reduce the dependency of the regression factors on the nozzle design point within the uncertainty margins of the least squares method.
EMG spectral indices and muscle power fatigue during dynamic contractions.
González-Izal, M; Malanda, A; Navarro-Amézqueta, I; Gorostiaga, E M; Mallor, F; Ibañez, J; Izquierdo, M
2010-04-01
The purpose of this study was to examine acute exercise-induced changes on muscle power output and surface electromyography (sEMG) parameters (amplitude and spectral indices of muscle fatigue) during a dynamic fatiguing protocol. Fifteen trained subjects performed five sets consisting of 10 leg presses (10RM), with 2min rest between sets. Surface electromyography was recorded from vastus medialis (VM) and lateralis (VL) and biceps femoris (BF) muscles. A number of EMG-based parameters were compared for estimation accuracy and sensitivity to detect peripheral muscle fatigue. These were: Mean Average Voltage, median spectral frequency, Dimitrov spectral index of muscle fatigue (FI(nsm5)), as well as other parameters obtained from a time-frequency analysis (Choi-Williams distributions) such as mean and variance of the instantaneous frequency and frequency variance. The log FI(nsm5) as a single parameter predictor accounted for 37% of the performance variance of changes in muscle power and the log FI(nsm5) and MFM as a two factor combination predictor accounted for 44%. Peripheral impairments assessed by sEMG spectral index FI(nsm5) may be a relevant factor involved in the loss of power output after dynamic high-loading fatiguing task. 2009 Elsevier Ltd. All rights reserved.
Two-dimensional multifractal cross-correlation analysis
International Nuclear Information System (INIS)
Xi, Caiping; Zhang, Shuning; Xiong, Gang; Zhao, Huichang; Yang, Yonghong
2017-01-01
Highlights: • We study the mathematical models of 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Present the definition of the two-dimensional N 2 -partitioned multiplicative cascading process. • Do the comparative analysis of 2D-MC by 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Provide a reference on the choice and parameter settings of these methods in practice. - Abstract: There are a number of situations in which several signals are simultaneously recorded in complex systems, which exhibit long-term power-law cross-correlations. This paper presents two-dimensional multifractal cross-correlation analysis based on the partition function (2D-MFXPF), two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) and two-dimensional multifractal cross-correlation analysis based on the detrended moving average analysis (2D-MFXDMA). We apply these methods to pairs of two-dimensional multiplicative cascades (2D-MC) to do a comparative study. Then, we apply the two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) to real images and unveil intriguing multifractality in the cross correlations of the material structures. At last, we give the main conclusions and provide a valuable reference on how to choose the multifractal algorithms in the potential applications in the field of SAR image classification and detection.
Topology optimization of two-dimensional waveguides
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard; Sigmund, Ole
2003-01-01
In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....
Atmospheric turbulence profiling with unknown power spectral density
Helin, Tapio; Kindermann, Stefan; Lehtonen, Jonatan; Ramlau, Ronny
2018-04-01
Adaptive optics (AO) is a technology in modern ground-based optical telescopes to compensate for the wavefront distortions caused by atmospheric turbulence. One method that allows to retrieve information about the atmosphere from telescope data is so-called SLODAR, where the atmospheric turbulence profile is estimated based on correlation data of Shack–Hartmann wavefront measurements. This approach relies on a layered Kolmogorov turbulence model. In this article, we propose a novel extension of the SLODAR concept by including a general non-Kolmogorov turbulence layer close to the ground with an unknown power spectral density. We prove that the joint estimation problem of the turbulence profile above ground simultaneously with the unknown power spectral density at the ground is ill-posed and propose three numerical reconstruction methods. We demonstrate by numerical simulations that our methods lead to substantial improvements in the turbulence profile reconstruction compared to the standard SLODAR-type approach. Also, our methods can accurately locate local perturbations in non-Kolmogorov power spectral densities.
Discussion of the specific method of power spectral density
Ren Huan; Jiang Xiao Dong; Peng Jing; Ye Lin; Huang Zu Xin; Tang Can
2002-01-01
The wavefront power spectral density (PSD) can give the spatial frequency distribution of wavefront aberration, limit the waviness and the roughness, and specify the large components employed in high power density solid-state laser for inertial confinement fusion (ICF). The definition and the calculation of the PSD are given. In experiment, a large phase shifting Fizeau interferometer was used to test the transmissive wavefront of a Nd glass, creating the one dimension wavefront PSD. Same time, relationship between the PSD and the RMS is shown
Two-Dimensional Fourier Transform Analysis of Helicopter Flyover Noise
SantaMaria, Odilyn L.; Farassat, F.; Morris, Philip J.
1999-01-01
A method to separate main rotor and tail rotor noise from a helicopter in flight is explored. Being the sum of two periodic signals of disproportionate, or incommensurate frequencies, helicopter noise is neither periodic nor stationary. The single Fourier transform divides signal energy into frequency bins of equal size. Incommensurate frequencies are therefore not adequately represented by any one chosen data block size. A two-dimensional Fourier analysis method is used to separate main rotor and tail rotor noise. The two-dimensional spectral analysis method is first applied to simulated signals. This initial analysis gives an idea of the characteristics of the two-dimensional autocorrelations and spectra. Data from a helicopter flight test is analyzed in two dimensions. The test aircraft are a Boeing MD902 Explorer (no tail rotor) and a Sikorsky S-76 (4-bladed tail rotor). The results show that the main rotor and tail rotor signals can indeed be separated in the two-dimensional Fourier transform spectrum. The separation occurs along the diagonals associated with the frequencies of interest. These diagonals are individual spectra containing only information related to one particular frequency.
Two-dimensional bipolar junction transistors
Gharekhanlou, Behnaz; Khorasani, Sina; Sarvari, Reza
2014-03-01
Recent development in fabrication technology of planar two-dimensional (2D) materials has introduced the possibility of numerous novel applications. Our recent analysis has revealed that by definition of p-n junctions through appropriate patterned doping of 2D semiconductors, ideal exponential I-V characteristics may be expected. However, the theory of 2D junctions turns out to be very different to that of standard bulk junctions. Based on this theory of 2D diodes, we construct for the first time a model to describe 2D bipolar junction transistors (2D-BJTs). We derive the small-signal equivalent model, and estimate the performance of a 2D-BJT device based on graphone as the example material. A current gain of about 138 and maximum threshold frequency of 77 GHz, together with a power-delay product of only 4 fJ per 1 μm lateral width is expected at an operating voltage of 5 V. In addition, we derive the necessary formulae and a new approximate solution for the continuity equation in the 2D configuration, which have been verified against numerical solutions.
Development of Two-Dimensional NMR
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 11. Development of Two-Dimensional NMR: Strucure Determination of Biomolecules in Solution. Anil Kumar. General Article Volume 20 Issue 11 November 2015 pp 995-1002 ...
Conoscopic holography: two-dimensional numerical reconstructions.
Mugnier, L M; Sirat, G Y; Charlot, D
1993-01-01
Conoscopic holography is an incoherent light holographic technique based on the properties of crystal optics. We present experimental results of the numerical reconstruction of a two-dimensional object from its conoscopic hologram.
Directory of Open Access Journals (Sweden)
Jorge Alfredo Ardila-Rey
2015-10-01
Full Text Available Both in industrial as in controlled environments, such as high-voltage laboratories, pulses from multiple sources, including partial discharges (PD and electrical noise can be superimposed. These circumstances can modify and alter the results of PD measurements and, what is more, they can lead to misinterpretation. The spectral power clustering technique (SPCT allows separating PD sources and electrical noise through the two-dimensional representation (power ratio map or PR map of the relative spectral power in two intervals, high and low frequency, calculated for each pulse captured with broadband sensors. This method allows to clearly distinguishing each of the effects of noise and PD, making it easy discrimination of all sources. In this paper, the separation ability of the SPCT clustering technique when using a Rogowski coil for PD measurements is evaluated. Different parameters were studied in order to establish which of them could help for improving the manual selection of the separation intervals, thus enabling a better separation of clusters. The signal processing can be performed during the measurements or in a further analysis.
TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION
International Nuclear Information System (INIS)
Wang, Yougang; Xu, Yidong; Chen, Xuelei; Park, Changbom; Kim, Juhan
2015-01-01
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array
Dirac cones in two-dimensional borane
Martinez-Canales, Miguel; Galeev, Timur R.; Boldyrev, Alexander I.; Pickard, Chris J.
2017-11-01
We introduce two-dimensional borane, a single-layered material of BH stoichiometry, with promising electronic properties. We show that, according to density functional theory calculations, two-dimensional borane is semimetallic, with two symmetry-related Dirac cones meeting right at the Fermi energy Ef. The curvature of the cones is lower than in graphene, thus closer to the ideal linear dispersion. Its structure, formed by a puckered trigonal boron network with hydrogen atoms connected to each boron atom, can be understood as distorted, hydrogenated borophene [Mannix et al., Science 350, 1513 (2015), 10.1126/science.aad1080]. Chemical bonding analysis reveals the boron layer in the network being bound by delocalized four-center two-electron σ bonds. Finally, we suggest high pressure could be a feasible route to synthesize two-dimensional borane.
Two-dimensional x-ray diffraction
He, Bob B
2009-01-01
Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea
Time-variant power spectral analysis of heart-rate time series by ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
HRTS) signal is a popular method for evaluating the cardiovascular con- trol system. The spectral parameters, viz. percentage power in low frequency band. (%PLF), percentage power in high frequency band (%PHF), power ratio of low.
Power Spectral Density Evaluation of Laser Milled Surfaces
Directory of Open Access Journals (Sweden)
Raoul-Amadeus Lorbeer
2017-12-01
Full Text Available Ablating surfaces with a pulsed laser system in milling processes often leads to surface changes depending on the milling depth. Especially if a constant surface roughness and evenness is essential to the process, structural degradation may advance until the process fails. The process investigated is the generation of precise thrust by laser ablation. Here, it is essential to predict or rather control the evolution of the surfaces roughness. Laser ablative milling with a short pulse laser system in vacuum (≈1 Pa were performed over depths of several 10 µm documenting the evolution of surface roughness and unevenness with a white light interference microscope. Power spectral density analysis of the generated surface data reveals a strong influence of the crystalline structure of the solid. Furthermore, it was possible to demonstrate that this effect could be suppressed for gold.
Dipolar vortices in two-dimensional flows
DEFF Research Database (Denmark)
Juul Rasmussen, J.; Hesthaven, J.S.; Lynov, Jens-Peter
1996-01-01
The dynamics of dipolar vortex solutions to the two-dimensional Euler equations is studied. A new type of nonlinear dipole is found and its dynamics in a slightly viscous system is compared with the dynamics of the Lamb dipole. The evolution of dipolar structures from an initial turbulent patch...
Analytical simulation of two dimensional advection dispersion ...
African Journals Online (AJOL)
The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would migrate ...
Analytical Simulation of Two Dimensional Advection Dispersion ...
African Journals Online (AJOL)
ADOWIE PERE
ABSTRACT: The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would ...
Two-dimensional position sensitive neutron detector
Indian Academy of Sciences (India)
A two-dimensional position sensitive neutron detector has been developed. The detector is a 3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Å neutrons.
Stability of two-dimensional vorticity filaments
International Nuclear Information System (INIS)
Elhmaidi, D.; Provenzale, A.; Lili, T.; Babiano, A.
2004-01-01
We discuss the results of a numerical study on the stability of two-dimensional vorticity filaments around a circular vortex. We illustrate how the stability of the filaments depends on the balance between the strain associated with the far field of the vortex and the local vorticity of the filament, and we discuss an empirical criterion for filament stability
Two-dimensional membranes in motion
Davidovikj, D.
2018-01-01
This thesis revolves around nanomechanical membranes made of suspended two - dimensional materials. Chapters 1-3 give an introduction to the field of 2D-based nanomechanical devices together with an overview of the underlying physics and the measurementtools used in subsequent chapters. The research
A novel two dimensional particle velocity sensor
Pjetri, O.; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.
2013-01-01
In this paper we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0x2.5x0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to
Two-dimensional microstrip detector for neutrons
Energy Technology Data Exchange (ETDEWEB)
Oed, A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)
1997-04-01
Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.
Spatial and Spectral Brightness Enhancement of High Power Semiconductor Lasers
Leidner, Jordan Palmer
The performance of high-power broad-area diode lasers is inhibited by beam filamentation induced by free-carrier-based self-focusing. The resulting beam degradation limits their usage in high-brightness, high-power applications such as pumping fiber lasers, and laser cutting, welding, or marking. Finite-difference propagation method simulations via RSoft's BeamPROP commercial simulation suite and a custom-built MATLAB code were used for the study and design of laser cavities that suppress or avoid filamentation. BeamPROP was used to design a tapered, passive, multi-mode interference cavity for the creation of a self-phase-locking laser array, which is comprised of many single-mode gain elements coupled to a wide output coupler to avoid damage from local high optical intensities. MATLAB simulations were used to study the effects of longitudinal and lateral cavity confinement on lateral beam quality in conventional broad-area lasers. This simulation was expanded to design a laser with lateral gain and index prescription that is predicted to operate at or above state-of-the-art powers while being efficiently coupled to conventional telecom single-mode optical fibers. Experimentally, a commercial broad-area laser was coupled in the far-field to a single-mode fiber Bragg grating to provide grating-stabilized single-mode laser feedback resulting in measured spectral narrowing for efficient pump absorption. Additionally a 19 GHz-span, spatially resolved, self-heterodyne measurement was made of a broad-area laser to study the evolution/devolution of the mode content of the emitted laser beam with increasing power levels.
Epileptic seizure prediction based on a bivariate spectral power methodology.
Bandarabadi, Mojtaba; Teixeira, Cesar A; Direito, Bruno; Dourado, Antonio
2012-01-01
The spectral power of 5 frequently considered frequency bands (Alpha, Beta, Gamma, Theta and Delta) for 6 EEG channels is computed and then all the possible pairwise combinations among the 30 features set, are used to create a 435 dimensional feature space. Two new feature selection methods are introduced to choose the best candidate features among those and to reduce the dimensionality of this feature space. The selected features are then fed to Support Vector Machines (SVMs) that classify the cerebral state in preictal and non-preictal classes. The outputs of the SVM are regularized using a method that accounts for the classification dynamics of the preictal class, also known as "Firing Power" method. The results obtained using our feature selection approaches are compared with the ones obtained using minimum Redundancy Maximum Relevance (mRMR) feature selection method. The results in a group of 12 patients of the EPILEPSIAE database, containing 46 seizures and 787 hours multichannel recording for out-of-sample data, indicate the efficiency of the bivariate approach as well as the two new feature selection methods. The best results presented sensitivity of 76.09% (35 of 46 seizures predicted) and a false prediction rate of 0.15(-1).
Entanglement Entropy in Two-Dimensional String Theory.
Hartnoll, Sean A; Mazenc, Edward A
2015-09-18
To understand an emergent spacetime is to understand the emergence of locality. Entanglement entropy is a powerful diagnostic of locality, because locality leads to a large amount of short distance entanglement. Two-dimensional string theory is among the very simplest instances of an emergent spatial dimension. We compute the entanglement entropy in the large-N matrix quantum mechanics dual to two-dimensional string theory in the semiclassical limit of weak string coupling. We isolate a logarithmically large, but finite, contribution that corresponds to the short distance entanglement of the tachyon field in the emergent spacetime. From the spacetime point of view, the entanglement is regulated by a nonperturbative "graininess" of space.
Two-dimensional sensitivity calculation code: SENSETWO
International Nuclear Information System (INIS)
Yamauchi, Michinori; Nakayama, Mitsuo; Minami, Kazuyoshi; Seki, Yasushi; Iida, Hiromasa.
1979-05-01
A SENSETWO code for the calculation of cross section sensitivities with a two-dimensional model has been developed, on the basis of first order perturbation theory. It uses forward neutron and/or gamma-ray fluxes and adjoint fluxes obtained by two-dimensional discrete ordinates code TWOTRAN-II. The data and informations of cross sections, geometry, nuclide density, response functions, etc. are transmitted to SENSETWO by the dump magnetic tape made in TWOTRAN calculations. The required input for SENSETWO calculations is thus very simple. The SENSETWO yields as printed output the cross section sensitivities for each coarse mesh zone and for each energy group, as well as the plotted output of sensitivity profiles specified by the input. A special feature of the code is that it also calculates the reaction rate with the response function used as the adjoint source in TWOTRAN adjoint calculation and the calculated forward flux from the TWOTRAN forward calculation. (author)
Two-dimensional ranking of Wikipedia articles
Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.
2010-10-01
The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.
Two-dimensional confinement of heavy fermions
International Nuclear Information System (INIS)
Shishido, Hiroaki; Shibauchi, Takasada; Matsuda, Yuji; Terashima, Takahito
2010-01-01
Metallic systems with the strongest electron correlations are realized in certain rare-earth and actinide compounds whose physics are dominated by f-electrons. These materials are known as heavy fermions, so called because the effective mass of the conduction electrons is enhanced via correlation effects up to as much as several hundreds times the free electron mass. To date the electronic structure of all heavy-fermion compounds is essentially three-dimensional. Here we report on the first realization of a two-dimensional heavy-fermion system, where the dimensionality is adjusted in a controllable fashion by fabricating heterostructures using molecular beam epitaxy. The two-dimensional heavy fermion system displays striking deviations from the standard Fermi liquid low-temperature electronic properties. (author)
Toward two-dimensional search engines
International Nuclear Information System (INIS)
Ermann, L; Shepelyansky, D L; Chepelianskii, A D
2012-01-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank–CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed. (paper)
Plasmonics with two-dimensional conductors
Yoon, Hosang; Yeung, Kitty Y. M.; Kim, Philip; Ham, Donhee
2014-01-01
A wealth of effort in photonics has been dedicated to the study and engineering of surface plasmonic waves in the skin of three-dimensional bulk metals, owing largely to their trait of subwavelength confinement. Plasmonic waves in two-dimensional conductors, such as semiconductor heterojunction and graphene, contrast the surface plasmonic waves on bulk metals, as the former emerge at gigahertz to terahertz and infrared frequencies well below the photonics regime and can exhibit far stronger subwavelength confinement. This review elucidates the machinery behind the unique behaviours of the two-dimensional plasmonic waves and discusses how they can be engineered to create ultra-subwavelength plasmonic circuits and metamaterials for infrared and gigahertz to terahertz integrated electronics. PMID:24567472
Two-dimensional Kagome photonic bandgap waveguide
DEFF Research Database (Denmark)
Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou
2000-01-01
The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....
Superintegrability on the two dimensional hyperboloid
International Nuclear Information System (INIS)
Akopyan, E.; Pogosyan, G.S.; Kalnins, E.G.; Miller, W. Jr
1998-01-01
This work is devoted to the investigation of the quantum mechanical systems on the two dimensional hyperboloid which admit separation of variables in at least two coordinate systems. Here we consider two potentials introduced in a paper of C.P.Boyer, E.G.Kalnins and P.Winternitz, which haven't been studied yet. An example of an interbasis expansion is given and the structure of the quadratic algebra generated by the integrals of motion is carried out
Moderator feedback effects in two-dimensional nodal methods for pressurized water reactor analysis
International Nuclear Information System (INIS)
Downar, T.J.
1987-01-01
A method was developed for incorporating moderator feedback effects in two-dimensional nodal codes used for pressurized water reactor (PWR) neutronic analysis. Equations for the assembly average quality and density are developed in terms of the assembly power calculated in two dimensions. The method is validated with a Westinghouse PWR using the Electric Power Research Institute code SIMULATE-E. Results show a several percent improvement is achieved in the two-dimensional power distribution prediction compared to methods without moderator feedback
Power Spectral Density Specification and Analysis of Large Optical Surfaces
Sidick, Erkin
2009-01-01
The 2-dimensional Power Spectral Density (PSD) can be used to characterize the mid- and the high-spatial frequency components of the surface height errors of an optical surface. We found it necessary to have a complete, easy-to-use approach for specifying and evaluating the PSD characteristics of large optical surfaces, an approach that allows one to specify the surface quality of a large optical surface based on simulated results using a PSD function and to evaluate the measured surface profile data of the same optic in comparison with those predicted by the simulations during the specification-derivation process. This paper provides a complete mathematical description of PSD error, and proposes a new approach in which a 2-dimentional (2D) PSD is converted into a 1-dimentional (1D) one by azimuthally averaging the 2D-PSD. The 1D-PSD calculated this way has the same unit and the same profile as the original PSD function, thus allows one to compare the two with each other directly.
A smile insensitive method for spectral linewidth narrowing on high power laser diode arrays
Yang, Zining; Wang, Hongyan; Li, Yuandong; Lu, Qisheng; Hua, Weihong; Xu, Xiaojun; Chen, Jinbao
2011-10-01
To eliminate the smile effect in spectral linewidth narrowing on high power laser diode arrays, we have introduced a plane reflective mirror into a common Littrow configuration external cavity to enhance the correlation among emitters. By this way, we obtained uniform spectral distribution among emitters of a 64-elements laser diode array with 35 GHz linewidth and 41 W output laser power.
Electromagnetically induced two-dimensional grating assisted by incoherent pump
Energy Technology Data Exchange (ETDEWEB)
Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang, E-mail: wrg@snnu.edu.cn
2017-04-25
We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication. - Highlights: • Two-dimensional grating is coherently induced in four-level atoms. • Phase and gain-phase gratings are obtained assisted by incoherent pump. • The diffraction power is improved due to the enhanced refraction modulation. • The gratings can be utilized as multi-channel all-optical splitter and router.
Fundamental interactions of vortical structures with boundary layers in two-dimensional flows
DEFF Research Database (Denmark)
Coutsias, E.A.; Lynov, Jens-Peter
1991-01-01
The effect of no-slip walls on the evolution of coherent, vortical structures in two-dimensional flows is studied by numerical calculations. The calculations are based on an accurate and efficient spectral scheme which has been developed for the solution of the 2D Navier-Stokes equations in the v......The effect of no-slip walls on the evolution of coherent, vortical structures in two-dimensional flows is studied by numerical calculations. The calculations are based on an accurate and efficient spectral scheme which has been developed for the solution of the 2D Navier-Stokes equations...... down of vortex dipoles by "vortex shielding"....
Versatile two-dimensional transition metal dichalcogenides
DEFF Research Database (Denmark)
Canulescu, Stela; Affannoukoué, Kévin; Döbeli, Max
Two-dimensional transition metal dichalcogenides (2D-TMDCs), such as MoS2, have emerged as a new class of semiconducting materials with distinct optical and electrical properties. The availability of 2D-TMDCs with distinct band gaps allows for unlimited combinations of TMDC monolayers (MLs...... vacancies. We have found that the absorption spectra of the MoS2 films exhibit distinct excitonic peaks at ~1.8 and ~2 eV when grown in the presence of a sulfur evaporation beam as compared to those deposited in vacuum. The structure of the PLD-grown MoS2 films will be further discussed based Raman...
Binding energy of two-dimensional biexcitons
DEFF Research Database (Denmark)
Singh, Jai; Birkedal, Dan; Vadim, Lyssenko
1996-01-01
Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....
Parallel comprehensive two-dimensional gas chromatography.
Yan, DanDan; Tedone, Laura; Koutoulis, Anthony; Whittock, Simon P; Shellie, Robert A
2017-11-17
We introduce an information rich analytical approach called parallel comprehensive two-dimensional gas chromatography (2GC×2GC). This parallel chromatography approach splits injected samples into two independent two-dimensional column ensembles and provides two GC×GC separations by using contra-directional thermal modulation. The first-dimension ( 1 D) and second-dimension ( 2 D) columns are connected using planar three-port microchannel devices, which are supplied with supplementary flow via two pressure controller modules. Precise carrier gas flow control at the junction of the 1 D and 2 D columns permits independent control of flow conditions in each separation column. The 2GC×2GC approach provides two entirely independent GC×GC separations for each injection. Analysis of hop (Humulus lupulus L.) essential oils is used to demonstrate the capability of the approach. The analytical performance of each GC×GC separation in the 2GC×2GC experiment is comparable to individual GC×GC separation with matching column configurations. The peak capacity of 2GC×2GC is about 2 times than that of single GC×GC system. The dual 2D chromatograms produced by this single detector system provide complementary separations and additional identification information by harnessing different selectivity provided by the four separation columns. Copyright © 2017 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Andrieux, Chantal
1976-03-01
The neutronic evolution of the reacteur Sena during the first and second cycles is presented. The experimental power distributions, obtained from the in-core instrumentation evaluation code CIRCE are compared with the theoretical powers calculated with the two-dimensional diffusion-evolution code EVOE. The CIRCE code allows: the study of the evolution of the principal parameters of the core, the comparison of the results of measured and theoretical estimates. Therefore this study has a great interest for the knowledge of the neutronic evolution of the core, as well as the validation of the refinement of theoretical estimation methods. The core calculation methods and requisite data for the evaluation of the measurements are presented after a brief description of the SENA core and its inner instrumentation. The principle of the in-core instrumentation evaluation code CIRCE, and calculation of the experimental power distributions and nuclear core parameters are then exposed. The results of the evaluation are discussed, with a comparison of the theoretical and experimental results. Taking account of the approximations used, these results, as far as the first and second cycles at SENA are concerned, are satisfactory, the deviations between theoretical and experimental power distributions being lower than 3% at the middle of the reactor and 9% at the periphery [fr
Perestrelo, Rosa; Petronilho, Sílvia; Câmara, José S; Rocha, Sílvia M
2010-05-14
An analytical methodology based on headspace solid phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-ToFMS) was developed for the identification and quantification of the toxic contaminant ethyl carbamate (EC) directly in fortified wines. The method performance was assessed for dry/medium dry and sweet/medium sweet model wines, and for quantification purposes, calibration plots were performed for both matrices using the ion extraction chromatography (IEC) mode (m/z 62). Good linearity was obtained with a regression coefficient (r(2)) higher than 0.981. A good precision was attained (R.S.D. wines. The quantification limits (LOQ) and recovery for dry wines were 14.38 microg/L and 88.6%, whereas for sweet wines were 9.16 microg/L and 99.4%, respectively. The higher performance was attained with sweet model wine, as increasing of glucose content improves the volatile compound in headspace, and a better linearity, recovery and precision were achieved. The analytical methodology was applied to analyse 20 fortified Madeira wines including different types of wine (dry, medium dry, sweet, and medium sweet) obtained from several harvests in Madeira Island (Portugal). The EC levels ranged from 54.1 microg/L (medium dry) to 162.5 microg/L (medium sweet). 2010 Elsevier B.V. All rights reserved.
Two-dimensional electronic spectroscopy with birefringent wedges
Energy Technology Data Exchange (ETDEWEB)
Réhault, Julien; Maiuri, Margherita; Oriana, Aurelio; Cerullo, Giulio [IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)
2014-12-15
We present a simple experimental setup for performing two-dimensional (2D) electronic spectroscopy in the partially collinear pump-probe geometry. The setup uses a sequence of birefringent wedges to create and delay a pair of phase-locked, collinear pump pulses, with extremely high phase stability and reproducibility. Continuous delay scanning is possible without any active stabilization or position tracking, and allows to record rapidly and easily 2D spectra. The setup works over a broad spectral range from the ultraviolet to the near-IR, it is compatible with few-optical-cycle pulses and can be easily reconfigured to two-colour operation. A simple method for scattering suppression is also introduced. As a proof of principle, we present degenerate and two-color 2D spectra of the light-harvesting complex 1 of purple bacteria.
Two-dimensional spectrophotometry of planetary nebulae by CCD imaging
International Nuclear Information System (INIS)
Jacoby, G.H.; Africano, J.L.; Quigley, R.J.; Western Washington Univ., Bellingham, WA)
1987-01-01
The spatial distribution of the electron temperature and density and the ionic abundances of O(+), O(2+), N(+), and S(+) have been derived from CCD images of the planetary nebulae NGC 40 and NGC 6826 taken in the important emission lines of forbidden O II, forbidden O III, H-beta, forbidden N II, and forbidden S II. The steps required in the derivation of the absolute fluxes, line, ratios, and ionic abundances are outlined and then discussed in greater detail. The results show that the CCD imaging technique for two-dimensional spectrophotometry can effectively compete with classical spectrophotometry, providing the added benefits of complete spatial coverage at seeing-disk spatial resolution. The multiplexing in the spatial dimension, however, results in a loss of spectral information, since only one emission line is observed at any one time. 37 references
Two-dimensional electronic spectroscopy with birefringent wedges
Réhault, Julien; Maiuri, Margherita; Oriana, Aurelio; Cerullo, Giulio
2014-12-01
We present a simple experimental setup for performing two-dimensional (2D) electronic spectroscopy in the partially collinear pump-probe geometry. The setup uses a sequence of birefringent wedges to create and delay a pair of phase-locked, collinear pump pulses, with extremely high phase stability and reproducibility. Continuous delay scanning is possible without any active stabilization or position tracking, and allows to record rapidly and easily 2D spectra. The setup works over a broad spectral range from the ultraviolet to the near-IR, it is compatible with few-optical-cycle pulses and can be easily reconfigured to two-colour operation. A simple method for scattering suppression is also introduced. As a proof of principle, we present degenerate and two-color 2D spectra of the light-harvesting complex 1 of purple bacteria.
LENUS (Irish Health Repository)
Mahon, P
2012-02-03
BACKGROUND: In this study we analyse the behaviour, potential clinical application and optimal cortical sampling location of the spectral parameters: (i) relative alpha and beta power; (ii) spectral edge frequency 90%; and (iii) spectral entropy as monitors of moderate propofol-induced sedation. METHODS: Multi-channel EEG recorded from 12 ASA 1 (American Society of Anesthesiologists physical status 1) patients during low-dose, target effect-site controlled propofol infusion was used for this analysis. The initial target effect-site concentration was 0.5 microg ml(-1) and increased at 4 min intervals in increments of 0.5 to 2 microg ml(-1). EEG parameters were calculated for 2 s epochs in the frequency ranges 0.5-32 and 0.5-47 Hz. All parameters were calculated in the channels: P4-O2, P3-O1, F4-C4, F3-C3, F3-F4, and Fp1-Fp2. Sedation was assessed clinically using the OAA\\/S (observer\\'s assessment of alertness\\/sedation) scale. RESULTS: Relative beta power and spectral entropy increased with increasing propofol effect-site concentration in both the 0.5-47 Hz [F(18, 90) = 3.455, P<0.05 and F(18, 90) = 3.33, P<0.05, respectively] and 0.5-32 Hz frequency range. This effect was significant in each individual channel (P<0.05). No effect was seen of increasing effect-site concentration on relative power in the alpha band. Averaged across all channels, spectral entropy did not outperform relative beta power in either the 0.5-32 Hz [Pk=0.79 vs 0.814 (P>0.05)] or 0.5-47 Hz range [Pk=0.81 vs 0.82 (P>0.05)]. The best performing indicator in any single channel was spectral entropy in the frequency range 0.5-47 Hz in the frontal channel F3-F4 (Pk=0.85). CONCLUSIONS: Relative beta power and spectral entropy when considered over the propofol effect-site range studied here increase in value, and correlate well with clinical assessment of sedation.
Two dimensional NMR studies of polysaccharides
International Nuclear Information System (INIS)
Byrd, R.A.; Egan, W.; Summers, M.F.
1987-01-01
Polysaccharides are very important components in the immune response system. Capsular polysaccharides and lipopolysaccharides occupy cell surface sites of bacteria, play key roles in recognition and some have been used to develop vaccines. Consequently, the ability to determine chemical structures of these systems is vital to an understanding of their immunogenic action. The authors have been utilizing recently developed two-dimensional homonuclear and heteronuclear correlation spectroscopy for unambiguous assignment and structure determination of a number of polysaccharides. In particular, the 1 H-detected heteronuclear correlation experiments are essential to the rapid and sensitive determination of these structures. Linkage sites are determined by independent polarization transfer experiments and multiple quantum correlation experiments. These methods permit the complete structure determination on very small amounts of the polysaccharides. They present the results of a number of structural determinations and discuss the limits of these experiments in terms of their applications to polysaccharides
Two-dimensional materials for ultrafast lasers
International Nuclear Information System (INIS)
Wang Fengqiu
2017-01-01
As the fundamental optical properties and novel photophysics of graphene and related two-dimensional (2D) crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches (or saturable absorbers) for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out. (paper)
Two dimensional generalizations of the Newcomb equation
International Nuclear Information System (INIS)
Dewar, R.L.; Pletzer, A.
1989-11-01
The Bineau reduction to scalar form of the equation governing ideal, zero frequency linearized displacements from a hydromagnetic equilibrium possessing a continuous symmetry is performed in 'universal coordinates', applicable to both the toroidal and helical cases. The resulting generalized Newcomb equation (GNE) has in general a more complicated form than the corresponding one dimensional equation obtained by Newcomb in the case of circular cylindrical symmetry, but in this cylindrical case , the equation can be transformed to that of Newcomb. In the two dimensional case there is a transformation which leaves the form of the GNE invariant and simplifies the Frobenius expansion about a rational surface, especially in the limit of zero pressure gradient. The Frobenius expansions about a mode rational surface is developed and the connection with Hamiltonian transformation theory is shown. 17 refs
Ward identities in two-dimensional gravity
International Nuclear Information System (INIS)
Polchinski, J.
1991-01-01
We study the decoupling of null states in two-dimensional gravity, using methods of critical string theory. We identify a family of null states which fail to decouple due to curvature and boundary terms. This gives relations involving amplitudes at different genus. At genus zero, these determine certain operator product coefficients. At genus one, they determine the partition function. At higher genus, we obtain a relation similar in form to the Painleve equation, but due to an incomplete understanding of a certain ghost/curvature term we do not have a closed relation for the partition function. Our results appear to correspond to the L 0 and L 1 equations in the topological and matrix model approaches. (orig.)
Two dimensional compass model with Heisenberg interactions
Pires, A. S. T.
2018-04-01
We consider a two dimensional compass model with a next and a next near Heisenberg term. The interactions are of two types: frustrated near neighbor compass interactions of amplitudes Jx and Jy, and next and next near neighbor Heisenberg interactions with exchanges J1 and J2 respectively. The Heisenberg interactions are isotropic in spin space, but the compass interactions depend on the bond direction. The ground state of the pure compass model is degenerated with a complex phase diagram. This degeneracy is removed by the Heisenberg terms leading to the arising of a magnetically ordered phase with a preferred direction. We calculate the phase diagrams at zero temperature for the case where, for J2 = 0, we have an antiferromagnetic ground state. We show that varying the value of J2, a magnetically disordered phase can be reached for small values of the compass interactions. We also calculate the critical temperature for a specified value of parameters.
Strategies for Interpreting Two Dimensional Microwave Spectra
Martin-Drumel, Marie-Aline; Crabtree, Kyle N.; Buchanan, Zachary
2017-06-01
Microwave spectroscopy can uniquely identify molecules because their rotational energy levels are sensitive to the three principal moments of inertia. However, a priori predictions of a molecule's structure have traditionally been required to enable efficient assignment of the rotational spectrum. Recently, automated microwave double resonance spectroscopy (AMDOR) has been employed to rapidly generate two dimensional spectra based on transitions that share a common rotational level, which may enable automated extraction of rotational constants without any prior estimates of molecular structure. Algorithms used to date for AMDOR have relied on making several initial assumptions about the nature of a subset of the linked transitions, followed by testing possible assignments by "brute force." In this talk, we will discuss new strategies for interpreting AMDOR spectra, using eugenol as a test case, as well as prospects for library-free, automated identification of the molecules in a volatile mixture.
Modified black holes in two dimensional gravity
International Nuclear Information System (INIS)
Mohammedi, N.
1991-11-01
The SL(2,R)/U(1) gauged WZWN model is modified by a topological term and the accompanying change in the geometry of the two dimensional target space is determined. The possibility of this additional term arises from a symmetry in the general formalism of gauging an isometry subgroup of a non-linear sigma model with an antisymmetric tensor. It is shown, in particular, that the space-time exhibits some general singularities for which the recently found black hole is just a special case. From a conformal field theory point of view and for special values of the unitary representation of SL(2,R), this topological term can be interpreted as a small perturbation by a (1,1) conformal operator of the gauged WZWN action. (author). 26 refs
Thermal properties of two-dimensional materials
International Nuclear Information System (INIS)
Zhang Gang; Zhang Yong-Wei
2017-01-01
Two-dimensional (2D) materials, such as graphene, phosphorene, and transition metal dichalcogenides (e.g., MoS 2 and WS 2 ), have attracted a great deal of attention recently due to their extraordinary structural, mechanical, and physical properties. In particular, 2D materials have shown great potential for thermal management and thermoelectric energy generation. In this article, we review the recent advances in the study of thermal properties of 2D materials. We first review some important aspects in thermal conductivity of graphene and discuss the possibility to enhance the ultra-high thermal conductivity of graphene. Next, we discuss thermal conductivity of MoS 2 and the new strategy for thermal management of MoS 2 device. Subsequently, we discuss the anisotropic thermal properties of phosphorene. Finally, we review the application of 2D materials in thermal devices, including thermal rectifier and thermal modulator. (topical reviews)
Two-dimensional electroacoustic waves in silicene
Zhukov, Alexander V.; Bouffanais, Roland; Konobeeva, Natalia N.; Belonenko, Mikhail B.
2018-01-01
In this letter, we investigate the propagation of two-dimensional electromagnetic waves in a piezoelectric medium built upon silicene. Ultrashort optical pulses of Gaussian form are considered to probe this medium. On the basis of Maxwell's equations supplemented with the wave equation for the medium's displacement vector, we obtain the effective governing equation for the vector potential associated with the electromagnetic field, as well as the component of the displacement vector. The dependence of the pulse shape on the bandgap in silicene and the piezoelectric coefficient of the medium was analyzed, thereby revealing a nontrivial triadic interplay between the characteristics of the pulse dynamics, the electronic properties of silicene, and the electrically induced mechanical vibrations of the medium. In particular, we uncovered the possibility for an amplification of the pulse amplitude through the tuning of the piezoelectric coefficient. This property could potentially offer promising prospects for the development of amplification devices for the optoelectronics industry.
Equivalency of two-dimensional algebras
International Nuclear Information System (INIS)
Santos, Gildemar Carneiro dos; Pomponet Filho, Balbino Jose S.
2011-01-01
Full text: Let us consider a vector z = xi + yj over the field of real numbers, whose basis (i,j) satisfy a given algebra. Any property of this algebra will be reflected in any function of z, so we can state that the knowledge of the properties of an algebra leads to more general conclusions than the knowledge of the properties of a function. However structural properties of an algebra do not change when this algebra suffers a linear transformation, though the structural constants defining this algebra do change. We say that two algebras are equivalent to each other whenever they are related by a linear transformation. In this case, we have found that some relations between the structural constants are sufficient to recognize whether or not an algebra is equivalent to another. In spite that the basis transform linearly, the structural constants change like a third order tensor, but some combinations of these tensors result in a linear transformation, allowing to write the entries of the transformation matrix as function of the structural constants. Eventually, a systematic way to find the transformation matrix between these equivalent algebras is obtained. In this sense, we have performed the thorough classification of associative commutative two-dimensional algebras, and find that even non-division algebra may be helpful in solving non-linear dynamic systems. The Mandelbrot set was used to have a pictorial view of each algebra, since equivalent algebras result in the same pattern. Presently we have succeeded in classifying some non-associative two-dimensional algebras, a task more difficult than for associative one. (author)
Two-dimensional linear discriminant analysis for classification of three-way chemical data.
Silva, Adenilton C da; Soares, Sófacles F C; Insausti, Matías; Galvão, Roberto K H; Band, Beatriz S F; Araújo, Mário César U de
2016-09-28
The two-dimensional linear discriminant analysis (2D-LDA) algorithm was originally proposed in the context of face image processing for the extraction of features with maximal discriminant power. However, despite its promising performance in image processing tasks, the 2D-LDA algorithm has not yet been used in applications involving chemical data. The present paper bridges this gap by investigating the use of 2D-LDA in classification problems involving three-way spectral data. The investigation was concerned with simulated data, as well as real-life data sets involving the classification of dry-cured Parma ham according to ageing by surface autofluorescence spectrometry and the classification of edible vegetable oils according to feedstock using total synchronous fluorescence spectrometry. The results were compared with those obtained by using the spectral data with no feature extraction, U-PLS-DA (Partial Least Squares Discriminant Analysis applied to the unfolded data), and LDA employing TUCKER-3 or PARAFAC scores. In the simulated data set, all methods yielded a correct classification rate of 100%. However, in the Parma ham and vegetable oil data sets, better classification rates were obtained by using 2D-LDA (86% and 100%), compared with no feature extraction (76% and 77%), U-PLS-DA (81% and 92%), PARAFAC-LDA (76% and 86%) and TUCKER3-LDA (86% and 93%). Published by Elsevier B.V.
Time-variant power spectral analysis of heart-rate time series by ...
Indian Academy of Sciences (India)
Frequency domain representation of a short-term heart-rate time series (HRTS) signal is a popular method for evaluating the cardiovascular control system. The spectral parameters, viz. percentage power in low frequency band (%PLF), percentage power in high frequency band (%PHF), power ratio of low frequency to high ...
Optimal Padding for the Two-Dimensional Fast Fourier Transform
Dean, Bruce H.; Aronstein, David L.; Smith, Jeffrey S.
2011-01-01
One-dimensional Fast Fourier Transform (FFT) operations work fastest on grids whose size is divisible by a power of two. Because of this, padding grids (that are not already sized to a power of two) so that their size is the next highest power of two can speed up operations. While this works well for one-dimensional grids, it does not work well for two-dimensional grids. For a two-dimensional grid, there are certain pad sizes that work better than others. Therefore, the need exists to generalize a strategy for determining optimal pad sizes. There are three steps in the FFT algorithm. The first is to perform a one-dimensional transform on each row in the grid. The second step is to transpose the resulting matrix. The third step is to perform a one-dimensional transform on each row in the resulting grid. Steps one and three both benefit from padding the row to the next highest power of two, but the second step needs a novel approach. An algorithm was developed that struck a balance between optimizing the grid pad size with prime factors that are small (which are optimal for one-dimensional operations), and with prime factors that are large (which are optimal for two-dimensional operations). This algorithm optimizes based on average run times, and is not fine-tuned for any specific application. It increases the amount of times that processor-requested data is found in the set-associative processor cache. Cache retrievals are 4-10 times faster than conventional memory retrievals. The tested implementation of the algorithm resulted in faster execution times on all platforms tested, but with varying sized grids. This is because various computer architectures process commands differently. The test grid was 512 512. Using a 540 540 grid on a Pentium V processor, the code ran 30 percent faster. On a PowerPC, a 256x256 grid worked best. A Core2Duo computer preferred either a 1040x1040 (15 percent faster) or a 1008x1008 (30 percent faster) grid. There are many industries that
Radiation effects on two-dimensional materials
Energy Technology Data Exchange (ETDEWEB)
Walker, R.C. II; Robinson, J.A. [Department of Materials Science, Penn State, University Park, PA (United States); Center for Two-Dimensional Layered Materials, Penn State, University Park, PA (United States); Shi, T. [Department of Mechanical and Nuclear Engineering, Penn State, University Park, PA (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States); Silva, E.C. [GlobalFoundries, Malta, NY (United States); Jovanovic, I. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States)
2016-12-15
The effects of electromagnetic and particle irradiation on two-dimensional materials (2DMs) are discussed in this review. Radiation creates defects that impact the structure and electronic performance of materials. Determining the impact of these defects is important for developing 2DM-based devices for use in high-radiation environments, such as space or nuclear reactors. As such, most experimental studies have been focused on determining total ionizing dose damage to 2DMs and devices. Total dose experiments using X-rays, gamma rays, electrons, protons, and heavy ions are summarized in this review. We briefly discuss the possibility of investigating single event effects in 2DMs based on initial ion beam irradiation experiments and the development of 2DM-based integrated circuits. Additionally, beneficial uses of irradiation such as ion implantation to dope materials or electron-beam and helium-beam etching to shape materials have begun to be used on 2DMs and are reviewed as well. For non-ionizing radiation, such as low-energy photons, we review the literature on 2DM-based photo-detection from terahertz to UV. The majority of photo-detecting devices operate in the visible and UV range, and for this reason they are the focus of this review. However, we review the progress in developing 2DMs for detecting infrared and terahertz radiation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Photodetectors based on two dimensional materials
Zheng, Lou; Zhongzhu, Liang; Guozhen, Shen
2016-09-01
Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on. Project supported by the National Natural Science Foundation of China (Nos. 61377033, 61574132, 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.
Two-dimensional topological photonic systems
Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng
2017-09-01
The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.
Two-dimensional atomic crystals beyond graphene
Kaul, Anupama B.
2014-06-01
Carbon-based nanostructures have been the center of intense research and development for more than two decades now. Of these materials, graphene, a two-dimensional (2D) layered material system, has had a significant impact on science and technology over the past decade after monolayers of this material were experimentally isolated in 2004. The recent emergence of other classes of 2D graphene-like layered materials has added yet more exciting dimensions for research in exploring the diverse properties and applications arising from these 2D material systems. For example, hexagonal-BN, a layered material closest in structure to graphene, is an insulator, while NbSe2, a transition metal di-chalcogenide, is metallic and monolayers of other transition metal di-chalcogenides such as MoS2 are direct band-gap semiconductors. The rich spectrum of properties that 2D layered material systems offer can potentially be engineered ondemand, and creates exciting prospects for using such materials in applications ranging from electronics, sensing, photonics, energy harvesting and flexible electronics over the coming years.
Seismic isolation of two dimensional periodic foundations
Energy Technology Data Exchange (ETDEWEB)
Yan, Y.; Mo, Y. L., E-mail: yilungmo@central.uh.edu [University of Houston, Houston, Texas 77004 (United States); Laskar, A. [Indian Institute of Technology Bombay, Powai, Mumbai (India); Cheng, Z.; Shi, Z. [Beijing Jiaotong University, Beijing (China); Menq, F. [University of Texas, Austin, Texas 78712 (United States); Tang, Y. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2014-07-28
Phononic crystal is now used to control acoustic waves. When the crystal goes to a larger scale, it is called periodic structure. The band gaps of the periodic structure can be reduced to range from 0.5 Hz to 50 Hz. Therefore, the periodic structure has potential applications in seismic wave reflection. In civil engineering, the periodic structure can be served as the foundation of upper structure. This type of foundation consisting of periodic structure is called periodic foundation. When the frequency of seismic waves falls into the band gaps of the periodic foundation, the seismic wave can be blocked. Field experiments of a scaled two dimensional (2D) periodic foundation with an upper structure were conducted to verify the band gap effects. Test results showed the 2D periodic foundation can effectively reduce the response of the upper structure for excitations with frequencies within the frequency band gaps. When the experimental and the finite element analysis results are compared, they agree well with each other, indicating that 2D periodic foundation is a feasible way of reducing seismic vibrations.
Comparative Two-Dimensional Fluorescence Gel Electrophoresis.
Ackermann, Doreen; König, Simone
2018-01-01
Two-dimensional comparative fluorescence gel electrophoresis (CoFGE) uses an internal standard to increase the reproducibility of coordinate assignment for protein spots visualized on 2D polyacrylamide gels. This is particularly important for samples, which need to be compared without the availability of replicates and thus cannot be studied using differential gel electrophoresis (DIGE). CoFGE corrects for gel-to-gel variability by co-running with the sample proteome a standardized marker grid of 80-100 nodes, which is formed by a set of purified proteins. Differentiation of reference and analyte is possible by the use of two fluorescent dyes. Variations in the y-dimension (molecular weight) are corrected by the marker grid. For the optional control of the x-dimension (pI), azo dyes can be used. Experiments are possible in both vertical and horizontal (h) electrophoresis devices, but hCoFGE is much easier to perform. For data analysis, commercial software capable of warping can be adapted.
Stress distribution in two-dimensional silos
Blanco-Rodríguez, Rodolfo; Pérez-Ángel, Gabriel
2018-01-01
Simulations of a polydispersed two-dimensional silo were performed using molecular dynamics, with different numbers of grains reaching up to 64 000, verifying numerically the model derived by Janssen and also the main assumption that the walls carry part of the weight due to the static friction between grains with themselves and those with the silo's walls. We vary the friction coefficient, the radii dispersity, the silo width, and the size of grains. We find that the Janssen's model becomes less relevant as the the silo width increases since the behavior of the stresses becomes more hydrostatic. Likewise, we get the normal and tangential stress distribution on the walls evidencing the existence of points of maximum stress. We also obtained the stress matrix with which we observe zones of concentration of load, located always at a height around two thirds of the granular columns. Finally, we observe that the size of the grains affects the distribution of stresses, increasing the weight on the bottom and reducing the normal stress on the walls, as the grains are made smaller (for the same total mass of the granulate), giving again a more hydrostatic and therefore less Janssen-type behavior for the weight of the column.
Asymptotics for Two-dimensional Atoms
DEFF Research Database (Denmark)
Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip
2012-01-01
We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....
Spectral Analysis of Polynomial Nonlinearity with Applications to RF Power Amplifiers
Directory of Open Access Journals (Sweden)
G. Tong Zhou
2004-09-01
Full Text Available The majority of the nonlinearity in a communication system is attributed to the power amplifier (PA present at the final stage of the transmitter chain. In this paper, we consider Gaussian distributed input signals (such as OFDM, and PAs that can be modeled by memoryless or memory polynomials. We derive closed-form expressions of the PA output power spectral density, for an arbitrary nonlinear order, based on the so-called Leonov-Shiryaev formula. We then apply these results to answer practical questions such as the contribution of AM/PM conversion to spectral regrowth and the relationship between memory effects and spectral asymmetry.
A microprocessor based on a two-dimensional semiconductor
Wachter, Stefan; Polyushkin, Dmitry K.; Bethge, Ole; Mueller, Thomas
2017-04-01
The advent of microcomputers in the 1970s has dramatically changed our society. Since then, microprocessors have been made almost exclusively from silicon, but the ever-increasing demand for higher integration density and speed, lower power consumption and better integrability with everyday goods has prompted the search for alternatives. Germanium and III-V compound semiconductors are being considered promising candidates for future high-performance processor generations and chips based on thin-film plastic technology or carbon nanotubes could allow for embedding electronic intelligence into arbitrary objects for the Internet-of-Things. Here, we present a 1-bit implementation of a microprocessor using a two-dimensional semiconductor--molybdenum disulfide. The device can execute user-defined programs stored in an external memory, perform logical operations and communicate with its periphery. Our 1-bit design is readily scalable to multi-bit data. The device consists of 115 transistors and constitutes the most complex circuitry so far made from a two-dimensional material.
Theory and application of the RAZOR two-dimensional continuous energy lattice physics code
International Nuclear Information System (INIS)
Zerkle, M.L.; Abu-Shumays, I.K.; Ott, M.W.; Winwood, J.P.
1997-01-01
The theory and application of the RAZOR two-dimensional, continuous energy lattice physics code are discussed. RAZOR solves the continuous energy neutron transport equation in one- and two-dimensional geometries, and calculates equivalent few-group diffusion theory constants that rigorously account for spatial and spectral self-shielding effects. A dual energy resolution slowing down algorithm is used to reduce computer memory and disk storage requirements for the slowing down calculation. Results are presented for a 2D BWR pin cell depletion benchmark problem
Interaction of two-dimensional magnetoexcitons
Dumanov, E. V.; Podlesny, I. V.; Moskalenko, S. A.; Liberman, M. A.
2017-04-01
We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector k→∥ = 0 , taking into account the influence of the excited Landau levels (ELLs) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field. It is shown that the account of the ELLs gives rise to the repulsion between the spinless magnetoexcitons with k→∥ = 0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g (0) ∼ 1 / B) . In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 2D magnetoexcitons with k→∥ = 0 . The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g (0) 1 /√{ B} .
Dynamics of two-dimensional bubbles
Piedra, Saúl; Ramos, Eduardo; Herrera, J. Ramón
2015-06-01
The dynamics of two-dimensional bubbles ascending under the influence of buoyant forces is numerically studied with a one-fluid model coupled with the front-tracking technique. The bubble dynamics are described by recording the position, shape, and orientation of the bubbles as functions of time. The qualitative properties of the bubbles and their terminal velocities are described in terms of the Eötvos (ratio of buoyancy to surface tension) and Archimedes numbers (ratio of buoyancy to viscous forces). The terminal Reynolds number result from the balance of buoyancy and drag forces and, consequently, is not an externally fixed parameter. In the cases that yield small Reynolds numbers, the bubbles follow straight paths and the wake is steady. A more interesting behavior is found at high Reynolds numbers where the bubbles follow an approximately periodic zigzag trajectory and an unstable wake with properties similar to the Von Karman vortex street is formed. The dynamical features of the motion of single bubbles are compared to experimental observations of air bubbles ascending in a water-filled Hele-Shaw cell. Although the comparison is not strictly valid in the sense that the effect of the lateral walls is not incorporated in the model, most of the dynamical properties observed are in good qualitative agreement with the numerical calculations. Hele-Shaw cells with different gaps have been used to determine the degree of approximation of the numerical calculation. It is found that for the relation between the terminal Reynolds number and the Archimedes number, the numerical calculations are closer to the observations of bubble dynamics in Hele-Shaw cells of larger gaps.
Two-dimensional silica opens new perspectives
Büchner, Christin; Heyde, Markus
2017-12-01
In recent years, silica films have emerged as a novel class of two-dimensional (2D) materials. Several groups succeeded in epitaxial growth of ultrathin SiO2 layers using different growth methods and various substrates. The structures consist of tetrahedral [SiO4] building blocks in two mirror symmetrical planes, connected via oxygen bridges. This arrangement is called a silica bilayer as it is the thinnest 2D arrangement with the stoichiometry SiO2 known today. With all bonds saturated within the nano-sheet, the interaction with the substrate is based on van der Waals forces. Complex ring networks are observed, including hexagonal honeycomb lattices, point defects and domain boundaries, as well as amorphous domains. The network structures are highly tuneable through variation of the substrate, deposition parameters, cooling procedure, introducing dopants or intercalating small species. The amorphous networks and structural defects were resolved with atomic resolution microscopy and modeled with density functional theory and molecular dynamics. Such data contribute to our understanding of the formation and characteristic motifs of glassy systems. Growth studies and doping with other chemical elements reveal ways to tune ring sizes and defects as well as chemical reactivities. The pristine films have been utilized as molecular sieves and for confining molecules in nanocatalysis. Post growth hydroxylation can be used to tweak the reactivity as well. The electronic properties of silica bilayers are favourable for using silica as insulators in 2D material stacks. Due to the fully saturated atomic structure, the bilayer interacts weakly with the substrate and can be described as quasi-freestanding. Recently, a mm-scale film transfer under structure retention has been demonstrated. The chemical and mechanical stability of silica bilayers is very promising for technological applications in 2D heterostacks. Due to the impact of this bilayer system for glass science
Two-dimensional vibrational-electronic spectroscopy
Courtney, Trevor L.; Fox, Zachary W.; Slenkamp, Karla M.; Khalil, Munira
2015-10-01
Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE) to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (νCN) and either a ligand-to-metal charge transfer transition ([FeIII(CN)6]3- dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN)5FeIICNRuIII(NH3)5]- dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific νCN modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a wide range of complex molecular, material, and biological systems.
Drifting plasmons in open two-dimensional channels: modal analysis
International Nuclear Information System (INIS)
Sydoruk, O
2013-01-01
Understanding the properties of plasmons in two-dimensional channels is important for developing methods of terahertz generation. This paper presents a modal analysis of plasmonic reflection in open channels supporting dc currents. As it shows, the plasmons can be amplified upon reflection if a dc current flows away from a conducting boundary; de-amplification occurs for the opposite current direction. The problem is solved analytically, based on a perturbation calculation, and numerically, and agreement between the methods is demonstrated. The power radiated by a channel is found to be negligible, and plasmon reflection in open channels is shown to be similar to that in closed channels. Based on this similarity, the oscillator designs developed earlier for closed channels could be applicable also for open ones. The results develop the modal-decomposition technique further as an instrument for the design of terahertz plasmonic sources. (paper)
Two-Dimensional Organic-Inorganic Hybrid Perovskite Photonic Films.
Meng, Ke; Gao, Shanshan; Wu, Longlong; Wang, Geng; Liu, Xin; Chen, Gang; Liu, Zhou; Chen, Gang
2016-07-13
Organic-inorganic hybrid perovskites have created enormous expectations for low-cost and high-performance optoelectronic devices. In prospect, future advancements may derive from reaping novel electrical and optical properties beyond pristine perovskites through microscopic structure design and engineering. Herein, we report the successful preparation of two-dimensional inverse-opal perovskite (IOP) photonic films, featuring unique nanostructures and vivid colors. Further compositional and structural managements promise optical property and energy level tunability of the IOP films. They are further functionalized in solar cells, resulting in colorful devices with respectable power conversion efficiency. Such concept has not been previously applied for perovskite-based solar cells, which could open a route for more versatile optoelectronic devices.
Two dimensional analysis of a high temperature gaseous radiation receiver
Mcfall, K. A.; Mattick, A. T.
1992-01-01
The characteristics of the Flowing Gas Radiation Receiver (FGRR), a device that absorbs solar radiation volumetrically in a gas to produce high temperatures for space propulsion and power applications, are analyzed using a two-dimensional axisymmetric numerical model of the flow and radiation fields within a diffusely reflecting channel. The results show that an FGRR system is capable of generating temperatures in excess of 3000 K with collection efficiencies of approximately 75 percent for a channel with a reflectivity of 0.9. For a collinear radiation source, outflow temperatures of 3193 and 3092 K were achieved for axial and radial flow inputs, respectively, with receiver efficiencies of 0.82 and 0.76.
Electrical and optoelectronic properties of two-dimensional materials
Wang, Qiaoming
Electrical and optoelectronic properties of bulk semiconductor materials have been extensively explored in last century. However, when reduced to one-dimensional and two-dimensional, many semiconductors start to show unique electrical and optoelectronic behaviors. In this dissertation, electrical and optoelectronic properties of one-dimensional (nanowires) and two-dimensional semiconductor materials are investigated by various techniques, including scanning photocurrent microscopy, scanning Kelvin probe microscopy, Raman spectroscopy, photoluminescence, and finite-element simulations. In our work, gate-tunable photocurrent in ZnO nanowires has been observed under optical excitation in the visible regime, which originates from the nanowire/substrate interface states. This gate tunability in the visible regime can be used to enhance the photon absorption efficiency, and suppress the undesirable visible-light photodetection in ZnO-based solar cells. The power conversion efficiency of CuInSe2/CdS core-shell nanowire solar cells has been investigated. The highest power conversion efficiency per unit area/volume is achieved with core diameter of 50 nm and the thinnest shell thickness. The existence of the optimal geometrical parameters is due to a combined effect of optical resonances and carrier transport/dynamics. Significant current crowding in two-dimensional black phosphorus field-effect transistors has been found, which has been significantly underestimated by the commonly used transmission-line model. This current crowding can lead to Joule heating close to the contacts. New van der Waals metal-semiconductor junctions have been mechanically constructed and systematically studied. The photocurrent on junction area has been demonstrated to originate from the photothermal effect rather than the photovoltaic effect. Our findings suggest that a reasonable control of interface/surface state properties can enable new and beneficial functionalities in nanostructures. We
Spectral, spatial and temporal control of high-power diode lasers through nonlinear optical feedback
van Voorst, P.D.
2008-01-01
A high-power diode laser offers multi-Watt output power from a small and efficient device, which makes them an interesting source for numerous applications. The spatial and spectral output however, are of reduced quality which limits the applicability. This limited quality is connected to the design
Effect of a pulsed power supply on the spectral and electrical characteristics of HID lamps
International Nuclear Information System (INIS)
Chammam, Abdeljelil; Elloumi, Hatem; Mrabet, Brahim; Charrada, Kamel; Stambouli, Mongi; Damelincourt, Jean Jacques
2005-01-01
Results of spectral and photometric measurements are presented for pulsed power operated high intensity discharges (HIDs). This investigation is related to the application of a pulsed power supply for pile driving of HID lamps. Specifically, we are interested in controlling the spectral response radiation of visible and ultraviolet (UV) lines for tertiary treatment of water using UV radiation. Simulations based on a physical model of the lamps were conducted. These results relate to the radial temperature, line intensity and electrical properties (voltage, power and conductivity). Good agreement has been found between the results of the simulations and the experimental findings
Power spectral density analysis of optical substrates for gravitational-wave interferometry.
Walsh, C J; Leistner, A J; Oreb, B F
1999-08-01
The power spectral density of surface-relief variations on polished optical surfaces across microscopic through to macroscopic spatial scales is calculated from measurements on substrates that are being produced for the Laser Interferometer Gravitational-Wave Observatory (LIGO). These spectra give a guide to the scattering properties of the surface, which in turn critically influence the performance of LIGO. Measurements obtained by use of a full-aperture interferometer and an interference microscope with two different objectives are combined to produce one-dimensional power spectral density representations of the surfaces across spatial frequencies ranging from 0.1 to 8000 cm(-1). These measurements from different instruments are in good agreement with an analytic power spectrum that varies as nu(-1.5), where nu is the spatial frequency. Some anomalies in the power spectral density spectra can be related to aspects of the polishing process.
Spontaneous baroreflex by sequence and power spectral methods in humans.
Hughson, R L; Quintin, L; Annat, G; Yamamoto, Y; Gharib, C
1993-11-01
Beat-by-beat variations in blood pressure and RR-interval are interrelated by the actions of baroreflex and non-baroreflex responses. This study had two purposes: (1) to examine the spontaneous relationships between RR-interval and systolic blood pressure to determine the relative occurrence of baroreflex and non-baroreflex responses in humans, and (2) to compare the beat-sequence method with a cross spectral estimate of the baroreflex response slope. Eight healthy men were studied during 10 h of quiet, seated rest, and six men and three women were studied during rest, rest plus fixed pace breathing, and a cold pressor test. RR-interval and continuous, non-invasive arterial blood pressure were measured with a computerized system. A baroreflex sequence was defined by a series of at least three consecutive heart beats in which systolic pressure and the following RR-interval either both increased or both decreased. A non-baroreflex relationship was defined by sequences of at least three beats by opposite directional changes of RR-interval and systolic pressure of that beat. The results showed that there were approximately 30% as many non-baroreflex compared to baroreflex slopes. Individual subject mean baroreflex and non-baroreflex slopes were highly correlated (r = 0.72, P < 0.001). Absolute slope values were not different, and they were unaffected by time, fixed pace breathing, or cold pressor test. The data showed the relatively simple beat-by-beat sequence method to yield spontaneous baroreflex response slopes that were quantitatively similar to, and highly correlated with (r = 0.85-0.94), baroreflex response slopes calculated by spectral analysis methods.
Spectral coherence model for power fluctuations in a wind farm
DEFF Research Database (Denmark)
Vigueras-Rodriguez, A.; Sørensen, Poul Ejnar; Viedma, A.
2012-01-01
This paper provides a model for the coherence between wind speeds located in a horizontal plane corresponding to hub height of wind turbines in a large wind farm. The model has been developed using wind speed and power measurements from the 72 Wind Turbines and two of the meteorological masts from...
Spectral Properties of Homogeneous and Nonhomogeneous Radar Images
DEFF Research Database (Denmark)
Madsen, Søren Nørvang
1987-01-01
On the basis of a two-dimensional, nonstationary white noisemodel for the complex radar backscatter, the spectral properties ofa one-look synthetic-aperture radar (SAR) system is derived. It isshown that the power spectrum of the complex SAR image is sceneindependent. It is also shown that the sp...
Directory of Open Access Journals (Sweden)
Jun Takeda
2010-04-01
Full Text Available In this review, we demonstrate a real-time time-frequency two-dimensional (2D pump-probe imaging spectroscopy implemented on a single shot basis applicable to excited-state dynamics in solid-state organic and biological materials. Using this technique, we could successfully map ultrafast time-frequency 2D transient absorption signals of β-carotene in solid films with wide temporal and spectral ranges having very short accumulation time of 20 ms per unit frame. The results obtained indicate the high potential of this technique as a powerful and unique spectroscopic tool to observe ultrafast excited-state dynamics of organic and biological materials in solid-state, which undergo rapid photodegradation.
Simulations of two-dimensional electronic correlation spectra
International Nuclear Information System (INIS)
Kim, Hack Jin; Jeon, Seung Joon
2001-01-01
Two-dimensional (2D) correlation method, which generates the synchronous and the asynchronous 2D spectrum by complex cross correlation of the Fourier transformed spectra, is an analysis method for the changes of the sample spectrum induced by various perturbations. In the present work, the 2D electronic correlation spectra have been simulated for the cases where the sample spectrum composed of two gaussian bands changes linearly. When only the band amplitudes of the sample spectrum change, the synchronous spectrum shows strong peaks at the band centers of the sample spectrum, but the asynchronous spectrum does not make peaks. When the sample spectrum shifts without changing intensity and width, the synchronous spectrum shows peaks around the initial and final positions of the band maximum and the asynchronous spectrum shows long peaks spanning the shifting range. The band width change produces the complex 2D correlation spectra. When the sample spectrum shifts with band broadening, the width change by 50 % of full width at half maximum (FWHM) does not give so large an effect on the correlation spectrum as the spectral shift by one half of FWHM of the sample spectrum
Almost two-dimensional treatment of drift wave turbulence
International Nuclear Information System (INIS)
Albert, J.M.; Similon, P.L.; Sudan, R.N.
1990-01-01
The approximation of two-dimensionality is studied and extended for electrostatic drift wave turbulence in a three-dimensional, magnetized plasma. It is argued on the basis of the direct interaction approximation that in the absence of parallel viscosity, purely 2-D solutions exist for which only modes with k parallel =0 are excited, but that the 2-D spectrum is unstable to perturbations at nonzero k parallel . A 1-D equation for the parallel profile g k perpendicular (k parallel ) of the saturated spectrum at steady state is derived and solved, allowing for parallel viscosity; the spectrum has finite width in k parallel , and hence finite parallel correlation length, as a result of nonlinear coupling. The enhanced energy dissipation rate, a 3-D effect, may be incorporated in the 2-D approximation by a suitable renormalization of the linear dissipation term. An algorithm is presented that reduces the 3-D problem to coupled 1- and 2-D problems. Numerical results from a 2-D spectral direct simulation, thus modified, are compared with the results from the corresponding 3-D (unmodified) simulation for a specific model of drift wave excitation. Damping at high k parallel is included. It is verified that the 1-D solution for g k perpendicular (k parallel ) accurately describes the shape and width of the 3-D spectrum, and that the modified 2-D simulation gives a good estimate of the 3-D energy saturation level and distribution E(k perpendicular )
Application of CRAFT in two-dimensional NMR data processing.
Krishnamurthy, Krish; Sefler, Andrea M; Russell, David J
2017-03-01
Two-dimensional (2D) data are typically truncated in both dimensions, but invariably and severely so in the indirect dimension. These truncated FIDs and/or interferograms are extensively zero filled, and Fourier transformation of such zero-filled data is always preceded by a rapidly decaying apodization function. Hence, the frequency line width in the spectrum (at least parallel to the evolution dimension) is almost always dominated by the apodization function. Such apodization-driven line broadening in the indirect (t 1 ) dimension leads to the lack of clear resolution of cross peaks in the 2D spectrum. Time-domain analysis (i.e. extraction of frequency, amplitudes, line width, and phase parameters directly from the FID, in this case via Bayesian modeling into a tabular format) of NMR data is another approach for spectral resonance characterization and quantification. The recently published complete reduction to amplitude frequency table (CRAFT) technique converts the raw FID data (i.e. time-domain data) into a table of frequencies, amplitudes, decay rate constants, and phases. CRAFT analyses of time-domain data require minimal or no apodization prior to extraction of the four parameters. We used the CRAFT processing approach for the decimation of the interferograms and compared the results from a variety of 2D spectra against conventional processing with and without linear prediction. The results show that use of the CRAFT technique to decimate the t 1 interferograms yields much narrower spectral line width of the resonances, circumventing the loss of resolution due to apodization. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Lie algebra contractions on two-dimensional hyperboloid
International Nuclear Information System (INIS)
Pogosyan, G. S.; Yakhno, A.
2010-01-01
The Inoenue-Wigner contraction from the SO(2, 1) group to the Euclidean E(2) and E(1, 1) group is used to relate the separation of variables in Laplace-Beltrami (Helmholtz) equations for the four corresponding two-dimensional homogeneous spaces: two-dimensional hyperboloids and two-dimensional Euclidean and pseudo-Euclidean spaces. We show how the nine systems of coordinates on the two-dimensional hyperboloids contracted to the four systems of coordinates on E 2 and eight on E 1,1 . The text was submitted by the authors in English.
Splitting rules for the electronic spectra of two-dimensional SML quasilattices
Chen, Fuming; Yang, Xiangbo; Xing, Da; Li, Feng
2004-12-01
In the framework of single-electronic tight-binding nearest-interaction transfer model, after establishing the method of constructing a class of two-dimensional SML quasilattices, we have studied the spectral properties of two-dimensional SML quasilattices by means of a decomposition-decimation method based the renormalization-group technique. It is found that the spectra have a variety of multifurcating structures, the total spectra are symmetrical, and every spectral line splits into odd sub-bands in the higher hierarchy. The analytic results show that under the first approximation, there exist only six kinds of clusters and the bare energy splits into thirteen subbands, and under the second approximation, several kinds of new spitting manners occur, e.g., 1:33, 1:19. The analytical results are confirmed by numerical simulations.
EEG spectral power in phasic and tonic REM sleep: different patterns in young adults and children.
Simor, Péter; Gombos, Ferenc; Szakadát, Sára; Sándor, Piroska; Bódizs, Róbert
2016-06-01
Rapid eye movement sleep is composed of phasic and tonic periods, two distinguishable microstates in terms of arousal thresholds and sensory processing. Background electroencephalogram oscillations are also different between periods with (phasic state) and periods without (tonic state) eye movements. In Study 1, previous findings analysing electroencephalogram spectral power in phasic and tonic rapid eye movement sleep were replicated, and analyses extended to the high gamma range (52-90 Hz). In Study 2, phasic and tonic spectral power differences within a group of 4-8-year-old children were examined. Based on the polysomnographic data of 20 young adults, the phasic state yielded increased delta and theta power in anterior sites, as well as generally decreased high alpha and beta power in comparison to the tonic state. Moreover, phasic periods exhibited greater spectral power in the lower and the higher gamma band. Interestingly, children (n = 18) exhibited a different pattern, showing increased activity in the low alpha range during phasic periods. Moreover, during phasic in contrast to tonic rapid eye movement sleep, increased low and high gamma and enhanced low gamma band power emerged in anterior and posterior regions, respectively. The current findings show that spectral activity within the high gamma range substantially contributes to the differences between phasic and tonic rapid eye movement sleep, especially in adults. Moreover, the current data underscore the heterogeneity of rapid eye movement sleep, and point to marked differences between young adults and children regarding phasic/tonic electroencephalogram spectral power. These results suggest that the differentiation between phasic and tonic rapid eye movement periods undergoes maturation. © 2016 European Sleep Research Society.
Explorative data analysis of two-dimensional electrophoresis gels
DEFF Research Database (Denmark)
Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine
2004-01-01
Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...
Optimizing separations in online comprehensive two-dimensional liquid chromatography
Pirok, Bob W.J.; Gargano, Andrea F.G.; Schoenmakers, Peter J.
2018-01-01
Online comprehensive two-dimensional liquid chromatography has become an attractive option for the analysis of complex nonvolatile samples found in various fields (e.g. environmental studies, food, life, and polymer sciences). Two-dimensional liquid chromatography complements the highly popular
Beginning Introductory Physics with Two-Dimensional Motion
Huggins, Elisha
2009-01-01
During the session on "Introductory College Physics Textbooks" at the 2007 Summer Meeting of the AAPT, there was a brief discussion about whether introductory physics should begin with one-dimensional motion or two-dimensional motion. Here we present the case that by starting with two-dimensional motion, we are able to introduce a considerable…
Two-dimensional black holes and non-commutative spaces
International Nuclear Information System (INIS)
Sadeghi, J.
2008-01-01
We study the effects of non-commutative spaces on two-dimensional black hole. The event horizon of two-dimensional black hole is obtained in non-commutative space up to second order of perturbative calculations. A lower limit for the non-commutativity parameter is also obtained. The observer in that limit in contrast to commutative case see two horizon
RF power amplifier techniques for spectral efficiency and software-defined radio
Shrestha, R.
2010-01-01
Modern wireless standards use spectrally efficient complex modulation schemes and multiple carriers. The modulated RF signal in such systems has a variable envelope with high peak to average power ratio (PAPR) thus requiring linear amplification in the transmitter path. However, linear amplifiers
RF Power Amplifier Techniques for Spectral Efficiency and Software-Defined Radio
Shrestha, R.
2010-01-01
Modern wireless standards use spectrally efficient complex modulation schemes and multiple carriers. The modulated RF signal in such systems has a variable envelope with high peak to average power ratio (PAPR) thus requiring linear amplification in the transmitter path. However, linear amplifiers
Detection of the power lines in UAV remote sensed images using spectral-spatial methods.
Bhola, Rishav; Krishna, Nandigam Hari; Ramesh, K N; Senthilnath, J; Anand, Gautham
2018-01-15
In this paper, detection of the power lines on images acquired by Unmanned Aerial Vehicle (UAV) based remote sensing is carried out using spectral-spatial methods. Spectral clustering was performed using Kmeans and Expectation Maximization (EM) algorithm to classify the pixels into the power lines and non-power lines. The spectral clustering methods used in this study are parametric in nature, to automate the number of clusters Davies-Bouldin index (DBI) is used. The UAV remote sensed image is clustered into the number of clusters determined by DBI. The k clustered image is merged into 2 clusters (power lines and non-power lines). Further, spatial segmentation was performed using morphological and geometric operations, to eliminate the non-power line regions. In this study, UAV images acquired at different altitudes and angles were analyzed to validate the robustness of the proposed method. It was observed that the EM with spatial segmentation (EM-Seg) performed better than the Kmeans with spatial segmentation (Kmeans-Seg) on most of the UAV images. Copyright © 2017 Elsevier Ltd. All rights reserved.
Finite element simulation of a two-dimensional standing wave thermoacoustic engine
de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries
2013-01-01
Thermoacoustic engines use heat to produce acoustic power. The subject of this manuscript is modeling of thermoacoustic engines. A finite element simulation has been performed on a theoretical example of a two-dimensional standing wave thermoacoustic engine. The simulation solves the linearized
Calculation of the electrical of induction heating coils in two dimensional axissymmetric geometry
Energy Technology Data Exchange (ETDEWEB)
Nerg, J.; Partanen, J. [Lappeenranta University of Technology (Finland). Department of Energy Technology, Laboratory of Electrical Engineering
1997-12-31
The effect of the workpiece temperature on the electrical parameters of a plane, spiral inductor is discussed. The effect of workpiece temperature on the electrical efficiency, power transfer to the workpiece and electromagnetic distortion are also presented. Calculation is performed in two dimensional axissymmetric geometry using a FEM program. (orig.) 5 refs.
Two dimensional NMR of liquids and oriented molecules
Energy Technology Data Exchange (ETDEWEB)
Gochin, M.
1987-02-01
Chapter 1 discusses the quantum mechanical formalism used for describing the interaction between magnetic dipoles that dictates the appearance of a spectrum. The NMR characteristics of liquids and liquid crystals are stressed. Chapter 2 reviews the theory of multiple quantum and two dimensional NMR. Properties of typical spectra and phase cycling procedures are discussed. Chapter 3 describes a specific application of heteronuclear double quantum coherence to the removal of inhomogeneous broadening in liquids. Pulse sequences have been devised which cancel out any contribution from this inhomogeneity to the final spectrum. An interpretation of various pulse sequences for the case of /sup 13/C and /sup 1/H is given, together with methods of spectral editing by removal or retention of the homo- or heteronuclear J coupling. The technique is applied to a demonstration of high resolution in both frequency and spatial dimensions with a surface coil. In Chapter 4, multiple quantum filtered 2-D spectroscopy is demonstrated as an effective means of studying randomly deuterated molecules dissolved in a nematic liquid crystal. Magnitudes of dipole coupling constants have been determined for benzene and hexane, and their signs and assignments found from high order multiple quantum spectra. For the first time, a realistic impression of the conformation of hexane can be estimated from these results. Chapter 5 is a technical description of the MDB DCHIB-DR11W parallel interface which has been set up to transfer data between the Data General Nova 820 minicomputer, interfaced to the 360 MHz spectrometer, and the Vax 11/730. It covers operation of the boards, physical specifications and installation, and programs for testing and running the interface.
Two dimensional NMR of liquids and oriented molecules
International Nuclear Information System (INIS)
Gochin, M.
1987-02-01
Chapter 1 discusses the quantum mechanical formalism used for describing the interaction between magnetic dipoles that dictates the appearance of a spectrum. The NMR characteristics of liquids and liquid crystals are stressed. Chapter 2 reviews the theory of multiple quantum and two dimensional NMR. Properties of typical spectra and phase cycling procedures are discussed. Chapter 3 describes a specific application of heteronuclear double quantum coherence to the removal of inhomogeneous broadening in liquids. Pulse sequences have been devised which cancel out any contribution from this inhomogeneity to the final spectrum. An interpretation of various pulse sequences for the case of 13 C and 1 H is given, together with methods of spectral editing by removal or retention of the homo- or heteronuclear J coupling. The technique is applied to a demonstration of high resolution in both frequency and spatial dimensions with a surface coil. In Chapter 4, multiple quantum filtered 2-D spectroscopy is demonstrated as an effective means of studying randomly deuterated molecules dissolved in a nematic liquid crystal. Magnitudes of dipole coupling constants have been determined for benzene and hexane, and their signs and assignments found from high order multiple quantum spectra. For the first time, a realistic impression of the conformation of hexane can be estimated from these results. Chapter 5 is a technical description of the MDB DCHIB-DR11W parallel interface which has been set up to transfer data between the Data General Nova 820 minicomputer, interfaced to the 360 MHz spectrometer, and the Vax 11/730. It covers operation of the boards, physical specifications and installation, and programs for testing and running the interface
Third sound in one and two dimensional modulated structures
International Nuclear Information System (INIS)
Komuro, T.; Kawashima, H., Shirahama, K.; Kono, K.
1996-01-01
An experimental technique is developed to study acoustic transmission in one and two dimensional modulated structures by employing third sound of a superfluid helium film. In particular, the Penrose lattice, which is a two dimensional quasiperiodic structure, is studied. In two dimensions, the scattering of third sound is weaker than in one dimension. Nevertheless, the authors find that the transmission spectrum in the Penrose lattice, which is a two dimensional prototype of the quasicrystal, is observable if the helium film thickness is chosen around 5 atomic layers. The transmission spectra in the Penrose lattice are explained in terms of dynamical theory of diffraction
ONE-DIMENSIONAL AND TWO-DIMENSIONAL LEADERSHIP STYLES
Directory of Open Access Journals (Sweden)
Nikola Stefanović
2007-06-01
Full Text Available In order to motivate their group members to perform certain tasks, leaders use different leadership styles. These styles are based on leaders' backgrounds, knowledge, values, experiences, and expectations. The one-dimensional styles, used by many world leaders, are autocratic and democratic styles. These styles lie on the two opposite sides of the leadership spectrum. In order to precisely define the leadership styles on the spectrum between the autocratic leadership style and the democratic leadership style, leadership theory researchers use two dimensional matrices. The two-dimensional matrices define leadership styles on the basis of different parameters. By using these parameters, one can identify two-dimensional styles.
Numerical evaluation of two-dimensional harmonic polylogarithms
Gehrmann, T
2002-01-01
The two-dimensional harmonic polylogarithms $\\G(\\vec{a}(z);y)$, a generalization of the harmonic polylogarithms, themselves a generalization of Nielsen's polylogarithms, appear in analytic calculations of multi-loop radiative corrections in quantum field theory. We present an algorithm for the numerical evaluation of two-dimensional harmonic polylogarithms, with the two arguments $y,z$ varying in the triangle $0\\le y \\le 1$, $ 0\\le z \\le 1$, $\\ 0\\le (y+z) \\le 1$. This algorithm is implemented into a {\\tt FORTRAN} subroutine {\\tt tdhpl} to compute two-dimensional harmonic polylogarithms up to weight 4.
Two-dimensional materials based transparent flexible electronics
Yu, Lili; Ha, Sungjae; El-Damak, Dina; McVay, Elaine; Ling, Xi; Chandrakasan, Anantha; Kong, Jing; Palacios, Tomas
2015-03-01
Two-dimensional (2D) materials have generated great interest recently as a set of tools for electronics, as these materials can push electronics beyond traditional boundaries. These materials and their heterostructures offer excellent mechanical flexibility, optical transparency, and favorable transport properties for realizing electronic, sensing, and optical systems on arbitrary surfaces. These thin, lightweight, bendable, highly rugged and low-power devices may bring dramatic changes in information processing, communications and human-electronic interaction. In this report, for the first time, we demonstrate two complex transparent flexible systems based on molybdenum disulfide (MoS2) grown by chemical vapor method: a transparent active-matrix organic light-emitting diode (AMOLED) display and a MoS2 wireless link for sensor nodes. The 1/2 x 1/2 square inch, 4 x 5 pixels AMOLED structures are built on transparent substrates, containing MoS2 back plane circuit and OLEDs integrated on top of it. The back plane circuit turns on and off the individual pixel with two MoS2 transistors and a capacitor. The device is designed and fabricated based on SPICE simulation to achieve desired DC and transient performance. We have also demonstrated a MoS2 wireless self-powered sensor node. The system consists of as energy harvester, rectifier, sensor node and logic units. AC signals from the environment, such as near-field wireless power transfer, piezoelectric film and RF signal, are harvested, then rectified into DC signal by a MoS2 diode. CIQM, CICS, SRC.
Directory of Open Access Journals (Sweden)
José Roberto Cárdenas
2017-05-01
Full Text Available The theoretical limit given by the Shannon Capacity equation has been the origin of communications systems based on the interchange between bandwidth and power. This article explores the interchange between the power spectral density and the reflections that can be generated in a communications channel, with the ultimate aim of being able to decrease the power spectral density for the same capacity. The reflections can be expressed as a number of controlled reflections or by a reflection coefficient. The channels studied show that this exchange is possible. A new model based on feedback circuits was found to represent a transmission line, which was useful to study the MISO channel formed by several transmission lines of different length. A geometric elliptic dispersion model to represent a SISO channel was studied too.
Electronic properties of two-dimensional MoS2 and its nanoribbons: a theoretical study
Hsu, Cheng-Hsiang; Soleimanikahnoj, Sina; Karimi, Farhad; Knezevic, Irena
Recent advances in producing monolayer and bilayer molybdenum disulfide (MoS2) have generated considerable interest in its fundamental properties. Two-dimensional MoS2 has a variety of intriguing but unexplored electronic and optical properties that are dependent on the number of layers in the material. Here, we present calculations of the electronic properties of two-dimensional MoS2 and its nanoribbons based on a semi-empirical tight-binding model and ballistic quantum transport theory. Utilizing simulation results, we discuss the potential of two-dimensional MoS2 and its nanostructures for low-power electronic applications. UW-Madison Hilldale Undergraduate Research Fellowship.
Effective viscosity of two-dimensional suspensions: Confinement effects
Doyeux, Vincent; Priem, Stephane; Jibuti, Levan; Farutin, Alexander; Ismail, Mourad; Peyla, Philippe
2016-08-01
We study the rheology of a sheared two-dimensional (2D) suspension of non-Brownian disks in the presence of walls. Although it is of course possible today with modern computers and powerful algorithms to perform direct numerical simulations that fully account for multiparticle 3D interactions in the presence of walls, the analysis of the simple case of a 2D suspension provides valuable insights and helps in the understanding of 3D results. Due to the direct visualization of the whole 2D flow (the shear plane), we are able to give a clear interpretation of the full hydrodynamics of semidilute confined suspensions. For instance, we examine the role of disk-wall and disk-disk interactions to determine the dissipation of confined sheared suspensions whose effective viscosity depends on the area fraction ϕ of the disks as ηeff=η0[1 +[η ] ϕ +β ϕ2+O (ϕ3) ] . We provide numerical estimates of [η ] and β for a wide range of confinements. As a benchmark for our simulations, we compare the numerical results obtained for [η ] and β for very weak confinements with analytical values [η] ∞ and β∞ obtained for an infinite fluid. If the value [η] ∞=2 is well known in the literature, much less is published on the value of β . Here we analytically calculate with very high precision β∞=3.6 . We also reexamine the 3D case in the light of our 2D results.
Critical behavior of a two-dimensional complex fluid: Macroscopic and mesoscopic views
Choudhuri, Madhumita; Datta, Alokmay
2016-04-01
Liquid disordered (Ld) to liquid ordered (Lo) phase transition in myristic acid [MyA, CH3(CH2) 12COOH ] Langmuir monolayers was studied macroscopically as well as mesoscopically to locate the critical point. Macroscopically, isotherms of the monolayer were obtained across the 20 ∘C-38 ∘Ctemperature (T ) range and the critical point was estimated, primarily from the vanishing of the order parameter, at ≈38 ∘C. Mesoscopically, domain morphology in the Ld-Lo coexistence regime was imaged using the technique of Brewster angle microscopy (BAM) as a function of T and the corresponding power spectral density function (PSDF) obtained. Monolayer morphology passed from stable circular domains and a sharp peak in PSDF to stable dendritic domains and a divergence of the correlation length as the critical point was approached from below. The critical point was found to be consistent at ≈38 ∘Cfrom both isotherm and BAM results. In the critical regime the scaling behavior of the transition followed the two-dimensional Ising model. Additionally, we obtained a precritical regime, over a temperature range of ≈8 ∘C below Tc, characterized by fluctuations in the order parameter at the macroscopic scale and at the mesoscopic scale characterized by unstable domains of fingering or dendritic morphology as well as proliferation of a large number of small sized domains, multiple peaks in the power spectra, and a corresponding fluctuation in the peak q values with T . Further, while comparing temperature studies on an ensemble of MyA monolayers with those on a single monolayer, the system was found to be not strictly ergodic in that the ensemble development did not strictly match with the time development in the system. In particular, the critical temperature was found to be lowered in the latter. These results clearly show that the critical behavior in fatty acid monolayer phase transitions have features of both complex and nonequilibrium systems.
Phenomenology of two-dimensional stably stratified turbulence under large-scale forcing
Kumar, Abhishek
2017-01-11
In this paper, we characterise the scaling of energy spectra, and the interscale transfer of energy and enstrophy, for strongly, moderately and weakly stably stratified two-dimensional (2D) turbulence, restricted in a vertical plane, under large-scale random forcing. In the strongly stratified case, a large-scale vertically sheared horizontal flow (VSHF) coexists with small scale turbulence. The VSHF consists of internal gravity waves and the turbulent flow has a kinetic energy (KE) spectrum that follows an approximate k−3 scaling with zero KE flux and a robust positive enstrophy flux. The spectrum of the turbulent potential energy (PE) also approximately follows a k−3 power-law and its flux is directed to small scales. For moderate stratification, there is no VSHF and the KE of the turbulent flow exhibits Bolgiano–Obukhov scaling that transitions from a shallow k−11/5 form at large scales, to a steeper approximate k−3 scaling at small scales. The entire range of scales shows a strong forward enstrophy flux, and interestingly, large (small) scales show an inverse (forward) KE flux. The PE flux in this regime is directed to small scales, and the PE spectrum is characterised by an approximate k−1.64 scaling. Finally, for weak stratification, KE is transferred upscale and its spectrum closely follows a k−2.5 scaling, while PE exhibits a forward transfer and its spectrum shows an approximate k−1.6 power-law. For all stratification strengths, the total energy always flows from large to small scales and almost all the spectral indicies are well explained by accounting for the scale-dependent nature of the corresponding flux.
Adenosine deaminase polymorphism affects sleep EEG spectral power in a large epidemiological sample.
Directory of Open Access Journals (Sweden)
Diego Robles Mazzotti
Full Text Available Slow wave oscillations in the electroencephalogram (EEG during sleep may reflect both sleep need and intensity, which are implied in homeostatic regulation. Adenosine is strongly implicated in sleep homeostasis, and a single nucleotide polymorphism in the adenosine deaminase gene (ADA G22A has been associated with deeper and more efficient sleep. The present study verified the association between the ADA G22A polymorphism and changes in sleep EEG spectral power (from C3-A2, C4-A1, O1-A2, and O2-A1 derivations in the Epidemiologic Sleep Study (EPISONO sample from São Paulo, Brazil. Eight-hundred individuals were subjected to full-night polysomnography and ADA G22A genotyping. Spectral analysis of the EEG was carried out in all individuals using fast Fourier transformation of the signals from each EEG electrode. The genotype groups were compared in the whole sample and in a subsample of 120 individuals matched according to ADA genotype for age, gender, body mass index, caffeine intake status, presence of sleep disturbance, and sleep-disturbing medication. When compared with homozygous GG genotype carriers, A allele carriers showed higher delta spectral power in Stage 1 and Stages 3+4 of sleep, and increased theta spectral power in Stages 1, 2 and REM sleep. These changes were seen both in the whole sample and in the matched subset. The higher EEG spectral power indicates that the sleep of individuals carrying the A allele may be more intense. Therefore, this polymorphism may be an important source of variation in sleep homeostasis in humans, through modulation of specific components of the sleep EEG.
Micromachined two dimensional resistor arrays for determination of gas parameters
van Baar, J.J.J.; Verwey, Willem B.; Dijkstra, Mindert; Dijkstra, Marcel; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.; Elwenspoek, Michael Curt
A resistive sensor array is presented for two dimensional temperature distribution measurements in a micromachined flow channel. This allows simultaneous measurement of flow velocity and fluid parameters, like thermal conductivity, diffusion coefficient and viscosity. More general advantages of
Proteome research : two-dimensional gel electrophoresis and identification methods
National Research Council Canada - National Science Library
Rabilloud, Thierry, 1961
2000-01-01
"Two-dimensional electrophoresis is the central methodology in proteome research, and the state of the art is described in detail in this text, together with extensive coverage of the detection methods available...
Partition function of the two-dimensional nearest neighbour Ising ...
Indian Academy of Sciences (India)
Abstract. The partition function for two-dimensional nearest neighbour Ising model in a non-zero magnetic field have been derived for a finite square lattice of 16, 25, 36 and 64 sites with the help of ...
Multisoliton formula for completely integrable two-dimensional systems
International Nuclear Information System (INIS)
Chudnovsky, D.V.; Chudnovsky, G.V.
1979-01-01
For general two-dimensional completely integrable systems, the exact formulae for multisoliton type solutions are given. The formulae are obtained algebrically from solutions of two linear partial differential equations
Paul, Jagannath
Advent of ultrashort lasers made it possible to probe various scattering phenomena in materials that occur in a time scale on the order of few femtoseconds to several tens of picoseconds. Nonlinear optical spectroscopy techniques, such as pump-probe, transient four wave mixing (TFWM), etc., are very common to study the carrier dynamics in various material systems. In time domain, the transient FWM uses several ultrashort pulses separated by time delays to obtain the information of dephasing and population relaxation times, which are very important parameters that govern the carrier dynamics of materials. A recently developed multidimensional nonlinear optical spectroscopy is an enhanced version of TFWM which keeps track of two time delays simultaneously and correlate them in the frequency domain with the aid of Fourier transform in a two dimensional map. Using this technique, the nonlinear complex signal field is characterized both in amplitude and phase. Furthermore, this technique allows us to identify the coupling between resonances which are rather difficult to interpret from time domain measurements. This work focuses on the study of the coherent response of a two dimensional electron gas formed in a modulation doped GaAs/AlGaAs quantum well both at zero and at high magnetic fields. In modulation doped quantum wells, the excitons are formed as a result of the inter- actions of the charged holes with the electrons at the Fermi edge in the conduction band, leading to the formation of Mahan excitons, which is also referred to as Fermi edge singularity (FES). Polarization and temperature dependent rephasing 2DFT spectra in combination with TI-FWM measurements, provides insight into the dephasing mechanism of the heavy hole (HH) Mahan exciton. In addition to that strong quantum coherence between the HH and LH Mahan excitons is observed, which is rather surprising at this high doping concentration. The binding energy of Mahan excitons is expected to be greatly
Structures of two-dimensional three-body systems
International Nuclear Information System (INIS)
Ruan, W.Y.; Liu, Y.Y.; Bao, C.G.
1996-01-01
Features of the structure of L = 0 states of a two-dimensional three-body model system have been investigated. Three types of permutation symmetry of the spatial part, namely symmetric, antisymmetric, and mixed, have been considered. A comparison has been made between the two-dimensional system and the corresponding three-dimensional one. The effect of symmetry on microscopic structures is emphasized. (author)
The Two-Dimensional Analogue of General Relativity
Lemos, José P. S.; Sá, Paulo M.
1993-01-01
General Relativity in three or more dimensions can be obtained by taking the limit $\\omega\\rightarrow\\infty$ in the Brans-Dicke theory. In two dimensions General Relativity is an unacceptable theory. We show that the two-dimensional closest analogue of General Relativity is a theory that also arises in the limit $\\omega\\rightarrow\\infty$ of the two-dimensional Brans-Dicke theory.
Two-Dimensionally-Modulated, Magnetic Structure of Neodymium Metal
DEFF Research Database (Denmark)
Lebech, Bente; Bak, P.
1979-01-01
The incipient magnetic order of dhcp Nd is described by a two-dimensional, incommensurably modulated structure ("triple-q" structure). The ordering is accompanied by a lattice distortion that forms a similar pattern.......The incipient magnetic order of dhcp Nd is described by a two-dimensional, incommensurably modulated structure ("triple-q" structure). The ordering is accompanied by a lattice distortion that forms a similar pattern....
Study on the correlations between color rendering indices and the spectral power distribution.
Lin, Yue; Deng, Zhonghua; Guo, Ziquan; Liu, Zhuguang; Lan, Hai; Lu, Yijun; Cao, Yongge
2014-06-30
The intrinsic spectrally resolved sensitivity (ISRS) of color rendering indices (CRIs) is investigated by using spectral loss simulations. It is demonstrated that R(a) exhibits large sensitivities around 444, 480, 564, and 622 nm, while for R(9) the sensitivity peaks are around 461, 581 and 630 nm, which all shift slightly with the correlated color temperature. If considering the ISRS as a bridge between the spectral power distribution of LED and its CRI, one could obtain a high CRI by minimizing the deviation between the shapes of the illuminant spectrum and the reference spectrum, both after modulations by the ISRS as a weighting function. This approach, recommended as a guideline for the spectra design aiming at a high CRI, is described and justified in depth via a mathematical model. This method is spectra-oriented and could largely facilitate the spectra design.
The theory of critical phenomena in two-dimensional systems
International Nuclear Information System (INIS)
Olvera de la C, M.
1981-01-01
An exposition of the theory of critical phenomena in two-dimensional physical systems is presented. The first six chapters deal with the mean field theory of critical phenomena, scale invariance of the thermodynamic functions, Kadanoff's spin block construction, Wilson's renormalization group treatment of critical phenomena in configuration space, and the two-dimensional Ising model on a triangular lattice. The second part of this work is made of four chapters devoted to the application of the ideas expounded in the first part to the discussion of critical phenomena in superfluid films, two-dimensional crystals and the two-dimensional XY model of magnetic systems. Chapters seven to ten are devoted to the following subjects: analysis of long range order in one, two, and three-dimensional physical systems. Topological defects in the XY model, in superfluid films and in two-dimensional crystals. The Thouless-Kosterlitz iterated mean field theory of the dipole gas. The renormalization group treatment of the XY model, superfluid films and two-dimensional crystal. (author)
Two-Dimensional Materials for Sensing: Graphene and Beyond
Directory of Open Access Journals (Sweden)
Seba Sara Varghese
2015-09-01
Full Text Available Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, have shown great promise for gas sensing applications due to their high surface-to-volume ratio, low noise and sensitivity of electronic properties to the changes in the surroundings. Two-dimensional nanostructured semiconducting metal oxide based gas sensors have also been recognized as successful gas detection devices. This review aims to provide the latest advancements in the field of gas sensors based on various two-dimensional materials with the main focus on sensor performance metrics such as sensitivity, specificity, detection limit, response time, and reversibility. Both experimental and theoretical studies on the gas sensing properties of graphene and other two-dimensional materials beyond graphene are also discussed. The article concludes with the current challenges and future prospects for two-dimensional materials in gas sensor applications.
Moisture estimation in power transformer oil using acoustic signals and spectral kurtosis
International Nuclear Information System (INIS)
Leite, Valéria C M N; Veloso, Giscard F C; Borges da Silva, Luiz Eduardo; Lambert-Torres, Germano; Borges da Silva, Jonas G; Pinto, João Onofre Pereira
2016-01-01
The aim of this paper is to present a new technique for estimating the contamination by moisture in power transformer insulating oil based on the spectral kurtosis analysis of the acoustic signals of partial discharges (PDs). Basically, in this approach, the spectral kurtosis of the PD acoustic signal is calculated and the correlation between its maximum value and the moisture percentage is explored to find a function that calculates the moisture percentage. The function can be easily implemented in DSP, FPGA, or any other type of embedded system for online moisture monitoring. To evaluate the proposed approach, an experiment is assembled with a piezoelectric sensor attached to a tank, which is filled with insulating oil samples contaminated by different levels of moisture. A device generating electrical discharges is submerged into the oil to simulate the occurrence of PDs. Detected acoustic signals are processed using fast kurtogram algorithm to extract spectral kurtosis values. The obtained data are used to find the fitting function that relates the water contamination to the maximum value of the spectral kurtosis. Experimental results show that the proposed method is suitable for online monitoring system of power transformers. (paper)
Component Cell-Based Restriction of Spectral Conditions and the Impact on CPV Module Power Rating
Energy Technology Data Exchange (ETDEWEB)
Muller, Matthew T [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Steiner, Marc [Fraunhofer Institute for Solar Energy Systems ISE; Siefer, Gerald [Fraunhofer Institute for Solar Energy Systems ISE; Bett, Andreas W. [Fraunhofer Institute for Solar Energy Systems ISE
2018-01-26
One approach to consider the prevailing spectral conditions when performing CPV module power ratings according to the standard IEC 62670-3 is based on spectral matching ratios (SMRs) determined by the means of component cell sensors. In this work, an uncertainty analysis of the SMR approach is performed based on a dataset of spectral irradiances created with SMARTS2. Using these illumination spectra, the respective efficiencies of multijunction solar cells with different cell architectures are calculated. These efficiencies were used to analyze the influence of different component cell sensors and SMR filtering methods. The 3 main findings of this work are as follows. First, component cells based on the lattice-matched triple-junction (LM3J) cell are suitable for restricting spectral conditions and are qualified for the standardized power rating of CPV modules - even if the CPV module is using multijunction cells other than LM3J. Second, a filtering of all 3 SMRs with +/-3.0% of unity results in the worst case scenario in an underestimation of -1.7% and overestimation of +2.4% compared to AM1.5d efficiency. Third, there is no benefit in matching the component cells to the module cell in respect to the measurement uncertainty.
Ashkinazi, M L
2010-01-01
Spectral power of theta and alpha EEG-bands at different stages of visual set was studied in 5-7-year-old children. Children with a plastic set had greater alpha-band spectral power values than children with a rigid set. At set formation stage children with a rigid set displayed an increase of theta-band EEG-power, which is a manifestation of "immature" arousal reaction. Children with a plastic set displayed at set formation stage an increase of alpha-band spectral power in bilateral occipital brain areas. Dynamics of EEG spectral power differed in children before and after 6 years of age. At set formation stage 5-6-year-olds displayed an above-mentioned "immature" arousal reaction, and 6-7-year-olds--an increase of alpha-band spectral power in occipital brain areas. At set actualization stage 6-7-year-olds displayed an increase of alpha-band spectral power in right posterior brain areas. At set extinction in this group a bilateral decrease of alpha-band spectral power in mid-frontal areas was observed. An importance for a quick set-shifting of certain brain areas' involvement in the process of visual perception is discussed.
Power spectral density measurements with 252Cf for a light water moderated research reactor
International Nuclear Information System (INIS)
King, W.T.; Mihalczo, J.T.
1979-01-01
A method of determining the reactivity of far subcritical systems from neutron noise power spectral density measurements with 252 Cf has previously been tested in fast reactor critical assemblies: a mockup of the Fast Flux Test Facility reactor and a uranium metal sphere. Calculations indicated that this measurement was feasible for a pressurized water reactor (PWR). In order to evaluate the ability to perform these measurements with moderated reactors which have long prompt neutron lifetimes, measurements were performed with a small plate-type research reactor whose neutron lifetime (57 microseconds) was about a factor of three longer than that of a PWR and approx. 50% longer than that of a boiling water reactor. The results of the first measurements of power spectral densities with 252 Cf for a water moderated reactor are presented
The power spectral density of digital modulations transmitted over nonlinear channels
Divsalar, D.; Simon, M. K.
1982-01-01
This paper examines by analytical methods the power spectral densities of digital modulations (in particular, staggered and unstaggered quadrature modulations) passed through band-limited nonlinear channels. Previously observed (by computer simulation or hardware measurement) behavior of such spectra with regard to the suppression or restoration of its sidelobes after passing through the nonlinearity is verified analytically. Several examples corresponding to specific quadrature modulations and filter-nonlinearity combinations are presented as illustrations of the general results.
Statistical algorithm for automated signature analysis of power spectral density data
International Nuclear Information System (INIS)
Piety, K.R.
1977-01-01
A statistical algorithm has been developed and implemented on a minicomputer system for on-line, surveillance applications. Power spectral density (PSD) measurements on process signals are the performance signatures that characterize the ''health'' of the monitored equipment. Statistical methods provide a quantitative basis for automating the detection of anomalous conditions. The surveillance algorithm has been tested on signals from neutron sensors, proximeter probes, and accelerometers to determine its potential for monitoring nuclear reactors and rotating machinery
High-Resolution Two-Dimensional Optical Spectroscopy of Electron Spins
Directory of Open Access Journals (Sweden)
M. Salewski
2017-08-01
Full Text Available Multidimensional coherent optical spectroscopy is one of the most powerful tools for investigating complex quantum mechanical systems. While it was conceived decades ago in magnetic resonance spectroscopy using microwaves and radio waves, it has recently been extended into the visible and UV spectral range. However, resolving MHz energy splittings with ultrashort laser pulses still remains a challenge. Here, we analyze two-dimensional Fourier spectra for resonant optical excitation of resident electrons to localized trions or donor-bound excitons in semiconductor nanostructures subject to a transverse magnetic field. Particular attention is devoted to Raman coherence spectra, which allow one to accurately evaluate tiny splittings of the electron ground state and to determine the relaxation times in the electron spin ensemble. A stimulated steplike Raman process induced by a sequence of two laser pulses creates a coherent superposition of the ground-state doublet which can be retrieved only optically because of selective excitation of the same subensemble with a third pulse. This provides the unique opportunity to distinguish between different complexes that are closely spaced in energy in an ensemble. The related experimental demonstration is based on photon-echo measurements in an n-type CdTe/(Cd,MgTe quantum-well structure detected by a heterodyne technique. The difference in the sub-μeV range between the Zeeman splittings of donor-bound electrons and electrons localized at potential fluctuations can be resolved even though the homogeneous linewidth of the optical transitions is larger by 2 orders of magnitude.
Traditional Semiconductors in the Two-Dimensional Limit
Lucking, Michael C.; Xie, Weiyu; Choe, Duk-Hyun; West, Damien; Lu, Toh-Ming; Zhang, S. B.
2018-02-01
Interest in two-dimensional materials has exploded in recent years. Not only are they studied due to their novel electronic properties, such as the emergent Dirac fermion in graphene, but also as a new paradigm in which stacking layers of distinct two-dimensional materials may enable different functionality or devices. Here, through first-principles theory, we reveal a large new class of two-dimensional materials which are derived from traditional III-V, II-VI, and I-VII semiconductors. It is found that in the ultrathin limit the great majority of traditional binary semiconductors studied (a series of 28 semiconductors) are not only kinetically stable in a two-dimensional double layer honeycomb structure, but more energetically stable than the truncated wurtzite or zinc-blende structures associated with three dimensional bulk. These findings both greatly increase the landscape of two-dimensional materials and also demonstrate that in the double layer honeycomb form, even ordinary semiconductors, such as GaAs, can exhibit exotic topological properties.
International Nuclear Information System (INIS)
Wang Haitao; He Shuyan; Zhang Zhengming; Yu Suyuan
2009-01-01
Artificial time histories are key data inputs for the calculation of floor spectra of the containment building in nuclear power plants. The application of the single-ground-motion analysis method shall meet the requirements of envelop of the power spectral density as well as fitting of the target response spectrum. This paper presents a generation algorithm of artificial time histories in order to meet the needs of both fitting of the target response spectrum and envelop of the power spectral density. The Fourier amplitude spectrum is modified within the effective frequency bandwidths defined for the target response spectrum and power spectral density respectively in this algorithm, and iterations are used in order to meet the corresponding requirements. The numerical examples demonstrate that the artificial time history generated by this algorithm reaches high fitting precision to the target response spectrum and meets the need of envelop of the power spectral density. (authors)
Two dimensional convolute integers for machine vision and image recognition
Edwards, Thomas R.
1988-01-01
Machine vision and image recognition require sophisticated image processing prior to the application of Artificial Intelligence. Two Dimensional Convolute Integer Technology is an innovative mathematical approach for addressing machine vision and image recognition. This new technology generates a family of digital operators for addressing optical images and related two dimensional data sets. The operators are regression generated, integer valued, zero phase shifting, convoluting, frequency sensitive, two dimensional low pass, high pass and band pass filters that are mathematically equivalent to surface fitted partial derivatives. These operators are applied non-recursively either as classical convolutions (replacement point values), interstitial point generators (bandwidth broadening or resolution enhancement), or as missing value calculators (compensation for dead array element values). These operators show frequency sensitive feature selection scale invariant properties. Such tasks as boundary/edge enhancement and noise or small size pixel disturbance removal can readily be accomplished. For feature selection tight band pass operators are essential. Results from test cases are given.
Two-Dimensional Superfluidity of Exciton Polaritons Requires Strong Anisotropy
Directory of Open Access Journals (Sweden)
Ehud Altman
2015-02-01
Full Text Available Fluids of exciton polaritons, excitations of two-dimensional quantum wells in optical cavities, show collective phenomena akin to Bose condensation. However, a fundamental difference from standard condensates stems from the finite lifetime of these excitations, which necessitates continuous driving to maintain a steady state. A basic question is whether a two-dimensional condensate with long-range algebraic correlations can exist under these nonequilibrium conditions. Here, we show that such driven two-dimensional Bose systems cannot exhibit algebraic superfluid order except in low-symmetry, strongly anisotropic systems. Our result implies, in particular, that recent apparent evidence for Bose condensation of exciton polaritons must be an intermediate-scale crossover phenomenon, while the true long-distance correlations fall off exponentially. We obtain these results through a mapping of the long-wavelength condensate dynamics onto the anisotropic Kardar-Parisi-Zhang equation.
Hamiltonian formalism of two-dimensional Vlasov kinetic equation.
Pavlov, Maxim V
2014-12-08
In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented.
A nonperturbative treatment of two-dimensional quantum gravity
International Nuclear Information System (INIS)
Gross, D.J.; Migdal, A.A.
1990-01-01
We propose a nonperturbative definition of two-dimensional quantum gravity, based on a double scaling limit of the random matrix model. We develop an operator formalism for utilizing the method of orthogonal polynomials that allows us to solve the matrix models to all orders in the genus expansion. Using this formalism we derive an exact differential equation for the partition function of two-dimensional gravity as a function of the string coupling constant that governs the genus expansion of two-dimensional surfaces, and discuss its properties and consequences. We construct and discuss the correlation functions of an infinite set of pointlike and loop operators to all orders in the genus expansion. (orig.)
Control Operator for the Two-Dimensional Energized Wave Equation
Directory of Open Access Journals (Sweden)
Sunday Augustus REJU
2006-07-01
Full Text Available This paper studies the analytical model for the construction of the two-dimensional Energized wave equation. The control operator is given in term of space and time t independent variables. The integral quadratic objective cost functional is subject to the constraint of two-dimensional Energized diffusion, Heat and a source. The operator that shall be obtained extends the Conjugate Gradient method (ECGM as developed by Hestenes et al (1952, [1]. The new operator enables the computation of the penalty cost, optimal controls and state trajectories of the two-dimensional energized wave equation when apply to the Conjugate Gradient methods in (Waziri & Reju, LEJPT & LJS, Issues 9, 2006, [2-4] to appear in this series.
High-power direct diode laser output by spectral beam combining
Tan, Hao; Meng, Huicheng; Ruan, Xu; Du, Weichuan; Wang, Zhao
2018-03-01
We demonstrate a spectral beam combining scheme based on multiple mini-bar stacks, which have more diode laser combining elements, to increase the combined diode laser power and realize equal beam quality in both the fast and slow axes. A spectral beam combining diode laser output of 1130 W is achieved with an operating current of 75 A. When a 9.6 X de-magnifying telescope is introduced between the output mirror and the diffraction grating, to restrain cross-talk among diode laser emitters, a 710 W spectral beam combining diode laser output is achieved at the operating current of 70 A, and the beam quality on the fast and slow axes of the combined beam is about 7.5 mm mrad and 7.3 mm mrad respectively. The power reduction is caused by the existence of a couple resonator between the rear facet of the diode laser and the fast axis collimation lens, and it should be eliminated by using diode laser chips with higher front facet transmission efficiency and a fast axis collimation lens with lower residual reflectivity.
Critical Behaviour of a Two-Dimensional Random Antiferromagnet
DEFF Research Database (Denmark)
Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.
1976-01-01
A neutron scattering study of the order parameter, correlation length and staggered susceptibility of the two-dimensional random antiferromagnet Rb2Mn0.5Ni0.5F4 is reported. The system is found to exhibit a well-defined phase transition with critical exponents identical to those of the isomorphous...... pure materials K2NiF4 and K2MnF4. Thus, in these systems, which have the asymptotic critical behaviour of the two-dimensional Ising model, randomness has no measurable effect on the phase-transition behaviour....
Nonlinear excitations in two-dimensional molecular structures with impurities
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Rasmussen, Kim; Christiansen, Peter Leth
1995-01-01
We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence of the imp......We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence...... excitations. Analytical results are in good agreement with numerical simulations of the nonlinear Schrodinger equation....
Two-dimensional nonlinear equations of supersymmetric gauge theories
International Nuclear Information System (INIS)
Savel'ev, M.V.
1985-01-01
Supersymmetric generalization of two-dimensional nonlinear dynamical equations of gauge theories is presented. The nontrivial dynamics of a physical system in the supersymmetry and supergravity theories for (2+2)-dimensions is described by the integrable embeddings of Vsub(2/2) superspace into the flat enveloping superspace Rsub(N/M), supplied with the structure of a Lie superalgebra. An equation is derived which describes a supersymmetric generalization of the two-dimensional Toda lattice. It contains both super-Liouville and Sinh-Gordon equations
Two-dimensional SCFTs from D3-branes
Energy Technology Data Exchange (ETDEWEB)
Benini, Francesco [Blackett Laboratory, Imperial College London,South Kensington Campus, London SW7 2AZ (United Kingdom); International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste (Italy); Bobev, Nikolay [Instituut voor Theoretische Fysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Crichigno, P. Marcos [Institute for Theoretical Physics and Spinoza Institute, Utrecht University,Leuvenlaan 4, 3854 CE Utrecht (Netherlands)
2016-07-05
We find a large class of two-dimensional N=(0,2) SCFTs obtained by compactifying four-dimensional N=1 quiver gauge theories on a Riemann surface. We study these theories using anomalies and c-extremization. The gravitational duals to these fixed points are new AdS{sub 3} solutions of IIB supergravity which we exhibit explicitly. Along the way we uncover a universal relation between the conformal anomaly coefficients of four-dimensional and two-dimensional SCFTs connected by an RG flow across dimensions. We also observe an interesting novel phenomenon in which the superconformal R-symmetry mixes with baryonic symmetries along the RG flow.
Densis. Densimetric representation of two-dimensional matrices
International Nuclear Information System (INIS)
Los Arcos Merino, J.M.
1978-01-01
Densis is a Fortran V program which allows off-line control of a Calcomp digital plotter, to represent a two-dimensional matrix of numerical elements in the form of a variable shading intensity map in two colours. Each matrix element is associated to a square of a grid which is traced over by lines whose number is a function of the element value according to a selected scale. Program features, subroutine structure and running instructions, are described. Some typical results, for gamma-gamma coincidence experimental data and a sampled two-dimensional function, are indicated. (author)
Quantum melting of a two-dimensional Wigner crystal
Dolgopolov, V. T.
2017-10-01
The paper reviews theoretical predictions about the behavior of two-dimensional low-density electron systems at nearly absolute zero temperatures, including the formation of an electron (Wigner) crystal, crystal melting at a critical electron density, and transitions between crystal modifications in more complex (for example, two-layer) systems. The paper presents experimental results obtained from real two-dimensional systems in which the nonconducting (solid) state of the electronic system with indications of collective localization is actually realized. Experimental methods for detecting a quantum liquid–solid phase interface are discussed.
Spin dynamics in a two-dimensional quantum gas
DEFF Research Database (Denmark)
Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank
2014-01-01
We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimp......We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...... with nonlocal Einstein-Podolsky-Rosen entanglement....
Chiral anomaly, fermionic determinant and two dimensional models
International Nuclear Information System (INIS)
Rego Monteiro, M.A. do.
1985-01-01
The chiral anomaly in random pair dimension is analysed. This anomaly is perturbatively calculated by dimensional regularization method. A new method for non-perturbative Jacobian calculation of a general chiral transformation, 1.e., finite and non-Abelian, is developed. This method is used for non-perturbative chiral anomaly calculation, as an alternative to bosonization of two-dimensional theories for massless fermions and to study the phenomenum of fermion number fractionalization. The fermionic determinant from two-dimensional quantum chromodynamics is also studied, and calculated, exactly, as in decoupling gauge as with out reference to a particular gauge. (M.C.K.) [pt
Two-dimensional spin diffusion in multiterminal lateral spin valves
Saha, D.; Basu, D.; Holub, M.; Bhattacharya, P.
2008-01-01
The effects of two-dimensional spin diffusion on spin extraction in lateral semiconductor spin valves have been investigated experimentally and theoretically. A ferromagnetic collector terminal of variable size is placed between the ferromagnetic electron spin injector and detector of a conventional lateral spin valve for spin extraction. It is observed that transverse spin diffusion beneath the collector terminal plays an important role along with the conventional longitudinal spin diffusion in describing the overall transport of spin carriers. Two-dimensional spin diffusion reduces the perturbation of the channel electrochemical potentials and improves spin extraction.
Impact of comprehensive two-dimensional gas chromatography with mass spectrometry on food analysis.
Tranchida, Peter Q; Purcaro, Giorgia; Maimone, Mariarosa; Mondello, Luigi
2016-01-01
Comprehensive two-dimensional gas chromatography with mass spectrometry has been on the separation-science scene for about 15 years. This three-dimensional method has made a great positive impact on various fields of research, and among these that related to food analysis is certainly at the forefront. The present critical review is based on the use of comprehensive two-dimensional gas chromatography with mass spectrometry in the untargeted (general qualitative profiling and fingerprinting) and targeted analysis of food volatiles; attention is focused not only on its potential in such applications, but also on how recent advances in comprehensive two-dimensional gas chromatography with mass spectrometry will potentially be important for food analysis. Additionally, emphasis is devoted to the many instances in which straightforward gas chromatography with mass spectrometry is a sufficiently-powerful analytical tool. Finally, possible future scenarios in the comprehensive two-dimensional gas chromatography with mass spectrometry food analysis field are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Separation of complex fringe patterns using two-dimensional continuous wavelet transform.
Pokorski, Krzysztof; Patorski, Krzysztof
2012-12-10
A method for processing fringe patterns containing additively superimposed multiple fringe sets is presented. It enables to analyze different fringe families present in a single image separately. The proposed method is based on a two-dimensional continuous wavelet transform. A robust ridge extraction algorithm for a single fringe set extraction is presented. The method is fully automatic and requires no user interference. Spectral separation of fringe families is not required. Simulations are presented to verify performance and advantage of the proposed method over the Fourier transform based technique. Method validity has been confirmed using experimental images.
Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes
Energy Technology Data Exchange (ETDEWEB)
Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole L.; Harilal, Sivanandan S.; Hartig, Kyle C.; Jovanovic, Igor
2017-06-19
We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security applications.
Analysis of spectral power distributions for multichannel platforms in a patient room application
Kim, James J.; Esposito, Tony; Maniccia, Dorene; Rizzo, Patricia
2017-09-01
We have developed an innovative lighting system prototype for a patient room application that integrates a multi-channel luminaire platform into indoor general area luminaires. This system is energy efficient, spectrally tunable, and supports the visual and nonvisual needs of occupants. We evaluated the performance of two separate multichannel platforms in different luminaire types, using a unique color-processing algorithm. The LED modeling and simulations enabled optimization of spectral power distributions, color, light output, and efficacy. This paper discusses the complicated results of SPDs developed for the patient room application, especially how they are effective for positively supporting the human visual and non-visual (circadian) systems. Additionally, application measurements demonstrate the large impact of the application space on the resulting SPD of a luminaire, calling into question the feasibility of using traditional field measurements to validate luminaire performance.
Two-dimensional gel electrophoresis: glass tube-based IEF followed by SDS-PAGE.
Matsumoto, Hiroyuki; Haniu, Hisao; Kurien, Biji T; Komori, Naoka
2012-01-01
The genome information combined with data derived from modern mass spectrometry enables us to determine the identity of a protein once it is isolated from a complex mixture. Two-dimensional gel electrophoresis established more than three decades ago serves as a powerful protocol to isolate many proteins at once for such protein analysis. In the first two decades, the original procedure to use a glass tube-based isoelectric focusing (IEF) had been commonly used. Since an IEF in glass tubes is rather difficult to maneuver, a new method to use an IEF on a thin agarose slab backed by a plastic film (IPG Dry Strip) has been invented and is now widely used. In this chapter, we describe the original protocol that uses a glass tube-based IEF because, the capacity of protein loading and resolving power of this type of classic two-dimensional gel is still indispensible.
Phase Coexistence in Two-Dimensional Passive and Active Dumbbell Systems
Cugliandolo, Leticia F.; Digregorio, Pasquale; Gonnella, Giuseppe; Suma, Antonio
2017-12-01
We demonstrate that there is a macroscopic coexistence between regions with hexatic order and regions in the liquid or gas phase over a finite interval of packing fractions in active dumbbell systems with repulsive power-law interactions in two dimensions. In the passive limit, this interval remains finite, similar to what has been found in two-dimensional systems of hard and soft disks. We did not find discontinuous behavior upon increasing activity from the passive limit.
Longitudinal and transverse modes dispersion in two-dimensional ...
African Journals Online (AJOL)
The dynamical properties of two-dimensional Yukawa fluids in the domain of weak and intermediate coupling parameters were analyzed through molecular dynamics (MD) simulation. The dispersion relation for both the longitudinal and transverse modes were obtained and compared with random phase approximation ...
Two-dimensional static deformation of an anisotropic medium
Indian Academy of Sciences (India)
The problem of two-dimensional static deformation of a monoclinic elastic medium has been studied using the eigenvalue method, following a Fourier transform. We have obtained expressions for displacements and stresses for the medium in the transformed domain. As an application of the above theory, the particular ...
Types of two-dimensional N = 4 superconformal field theories
Indian Academy of Sciences (India)
Superconformal field theory; free field realization; string theory; AdS-CFT correspon- dence. PACS Nos 11.25.Hf; 11.25.-w; 11.30.Ly; 11.30.Pb. Conformal symmetries in two space-time dimensions have been very extensively studied owing to their applications both in string theory and two-dimensional statistical systems.
Conformal QED in two-dimensional topological insulators
Menezes Silva Da Costa, Natália; Palumbo, Giandomenico; de Morais Smith, Cristiane
2017-01-01
It has been shown recently that local four-fermion interactions on the edges of two-dimensional time-reversal-invariant topological insulators give rise to a new non-Fermi-liquid phase, called helical Luttinger liquid (HLL). In this work, we provide a first-principle derivation of this
Stress and mixed boundary conditions for two-dimensional ...
Indian Academy of Sciences (India)
For plate bending and stretching problems in two-dimensional (2D) dodecagonal quasi-crystal (QC) media, the reciprocal theorem and the general solution for QCs are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all order. The method developed by Gregory and Wan is ...
Two-dimensional profiling of Xanthomonas campestris pv. viticola ...
African Journals Online (AJOL)
However, the analysis of the 2D-PAGE gel images revealed a larger number of spots in the lysis method when compared to the others. Taking ... Keywords: Bacterial canker, Vitis vinifera, proteomics, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional gel electrophoresis (2D-PAGE).
Vortex scaling ranges in two-dimensional turbulence
Burgess, B. H.; Dritschel, D. G.; Scott, R. K.
2017-11-01
We survey the role of coherent vortices in two-dimensional turbulence, including formation mechanisms, implications for classical similarity and inertial range theories, and characteristics of the vortex populations. We review early work on the spatial and temporal scaling properties of vortices in freely evolving turbulence and more recent developments, including a spatiotemporal scaling theory for vortices in the forced inverse energy cascade. We emphasize that Kraichnan-Batchelor similarity theories and vortex scaling theories are best viewed as complementary and together provide a more complete description of two-dimensional turbulence. In particular, similarity theory has a continued role in describing the weak filamentary sea between the vortices. Moreover, we locate both classical inertial and vortex scaling ranges within the broader framework of scaling in far-from-equilibrium systems, which generically exhibit multiple fixed point solutions with distinct scaling behaviour. We describe how stationary transport in a range of scales comoving with the dilatation of flow features, as measured by the growth in vortex area, constrains the vortex number density in both freely evolving and forced two-dimensional turbulence. The new theories for coherent vortices reveal previously hidden nontrivial scaling, point to new dynamical understanding, and provide a novel exciting window into two-dimensional turbulence.
Two-dimensional effects in nonlinear Kronig-Penney models
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Christiansen, Peter Leth; Rasmussen, Kim
1997-01-01
An analysis of two-dimensional (2D) effects in the nonlinear Kronig-Penney model is presented. We establish an effective one-dimensional description of the 2D effects, resulting in a set of pseudodifferential equations. The stationary states of the 2D system and their stability is studied...
Two-dimensional hazard estimation for longevity analysis
DEFF Research Database (Denmark)
Fledelius, Peter; Guillen, M.; Nielsen, J.P.
2004-01-01
We investigate developments in Danish mortality based on data from 1974-1998 working in a two-dimensional model with chronological time and age as the two dimensions. The analyses are done with non-parametric kernel hazard estimation techniques. The only assumption is that the mortality surface i...... for analysis of economic implications arising from mortality changes....
Solitary wave solutions of two-dimensional nonlinear Kadomtsev ...
Indian Academy of Sciences (India)
2017-09-13
Sep 13, 2017 ... Home; Journals; Pramana – Journal of Physics; Volume 89; Issue 3. Solitary wave solutions of ... Nonlinear two-dimensional Kadomtsev–Petviashvili (KP) equation governs the behaviour of nonlinear waves in dusty plasmas with variable dust charge and two temperature ions. By using the reductive ...
Image Making in Two Dimensional Art; Experiences with Straw and ...
African Journals Online (AJOL)
Image making in art is professionally referred to as bust in Sculpture andPortraiture in Painting. ... havebeen used to achieve these forms of art; like clay cement, marble, stone,different metals and, fibre glass in the three dimensional form; We also have Pencil, Charcoal Pastel and, Acrylic oil-paint in two dimensional form.
Seismically constrained two-dimensional crustal thermal structure of ...
Indian Academy of Sciences (India)
The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to ...
(Bombyx mori L.) using two-dimensional polyacrylami
Indian Academy of Sciences (India)
Unknown
Fountoulakis M, Schuller E, Hardmeier R, Berndt P and Lubec. G 1999 Rat brain proteins: Two-dimensional protein data- base and variation in the expression level; Electrophoresis 20. 3527–3579. Hiroshi Fujii, Junji Tochinara, Yutaka Kawaguchi and Sakagu- chi B 1988 Existence of carotenoids binding protein in larval.
Solitary wave solutions of two-dimensional nonlinear Kadomtsev ...
Indian Academy of Sciences (India)
Aly R Seadawy
2017-09-13
Sep 13, 2017 ... We considered the two-dimensional DASWs in colli- sionless, unmagnetized cold plasma consisting of dust fluid, ions and electrons. The dynamics of DASWs is governed by the normalized fluid equations of nonlin- ear continuity (1), nonlinear motion of system (2) and. (3) and linear Poisson equation (4) as.
Polaron dynamics in a two-dimensional anharmonic Holstein model
DEFF Research Database (Denmark)
Zolotaryuk, Yaroslav; Christiansen, Peter Leth; Juul Rasmussen, Jens
1998-01-01
A generalized two-dimensional semiclassical :Holstein model with a realistic on-site potential that contains anharmonicity is studied. More precisely, the lattice subsystem of anharmonic on-site oscillators is supposed to have a restricting core. The core plays the role of an effective saturation...
Sound waves in two-dimensional ducts with sinusoidal walls
Nayfeh, A. H.
1974-01-01
The method of multiple scales is used to analyze the wave propagation in two-dimensional hard-walled ducts with sinusoidal walls. For traveling waves, resonance occurs whenever the wall wavenumber is equal to the difference of the wavenumbers of any two duct acoustic modes. The results show that neither of these resonating modes could occur without strongly generating the other.
Two-dimensional NMR studies of allyl palladium complexes of ...
Indian Academy of Sciences (India)
Administrator
h3-Allyl complexes are intermediates in organic synthetic reactions such as allylic alkylation and amination. There is growing interest in understanding the structures of chiral h3-allyl intermediates as this would help to unravel the mechanism of enantioselective C–C bond forming reactions. Two-dimensional NMR study is a.
Vibrations of thin piezoelectric shallow shells: Two-dimensional ...
Indian Academy of Sciences (India)
In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two-dimensional eigenvalue problem.
Magnetoelectronic transport of the two-dimensional electron gas in ...
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 72; Issue 2 ... CdSe quantum wells; 2D electron gas; magneto-electronic transport. Abstract. Hall mobility and magnetoresistance coefficient for the two-dimensional (2D) electron transport parallel to the heterojunction interfaces in a single quantum well of CdSe are ...
g Algebra and two-dimensional quasiexactly solvable Hamiltonian ...
Indian Academy of Sciences (India)
g2 algebra via one special representation in the x–y two-dimensional space. Then, by choosing an appropriate set of ..... Gen. 40, 212 (2005). [3] S Grigorian and S T Yau, Commun. Math. Phys. 287, 459 (2009). [4] L Fernandez-Jambrina and L M Gonzalez-Romero, Class. Quant. Grav. 16, 953 (1999). [5] A Belhaj, J. Phys.
Two-Dimensional Light Diffraction from an EPROM Chip
Ekkens, Tom
2018-01-01
In introductory physics classes, a laser pointer and a compact disc are all the items required to illustrate diffraction of light in a single dimension. If a two-dimensional diffraction pattern is desired, double axis diffraction grating material is available or a CCD sensor can be extracted from an unused electronics device. This article presents…
Avoiding acidic region streaking in two-dimensional gel ...
Indian Academy of Sciences (India)
2014-07-21
Jul 21, 2014 ... used, as an alternative for costly 2DE-quantification kits. Our designed protocols are ..... 7 IPG 17 cm strips: (i) made by OP then DNase/RNase treated and (ii) made by OP with optimized IEF. (D) 2DE image of (i) E. coli ..... Proteomic analysis of human saliva from lung cancer patients using two-dimensional ...
Solar Internal Rotation and Dynamo Waves: A Two Dimensional ...
Indian Academy of Sciences (India)
tribpo
Solar Internal Rotation and Dynamo Waves: A Two Dimensional. Asymptotic Solution in the Convection Zone ... We calculate here a spatial 2 D structure of the mean magnetic field, adopting real profiles of the solar internal ... of the asymptotic solution in low (middle) and high (right panel) latitudes. field is shifted towards the ...
Two-dimensional models in statistical mechanics and field theory
International Nuclear Information System (INIS)
Koberle, R.
1980-01-01
Several features of two-dimensional models in statistical mechanics and Field theory, such as, lattice quantum chromodynamics, Z(N), Gross-Neveu and CP N-1 are discussed. The problems of confinement and dynamical mass generation are also analyzed. (L.C.) [pt
Two-Dimensional Mesoscale-Ordered Conducting Polymers
Liu, Shaohua; Zhang, Jian; Dong, Renhao; Gordiichuk, Pavlo; Zhang, Tao; Zhuang, Xiaodong; Mai, Yiyong; Liu, Feng; Herrmann, Andreas; Feng, Xinliang
2016-01-01
Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of
Two-dimensional generalized harmonic oscillators and their Darboux partners
International Nuclear Information System (INIS)
Schulze-Halberg, Axel
2011-01-01
We construct two-dimensional Darboux partners of the shifted harmonic oscillator potential and of an isotonic oscillator potential belonging to the Smorodinsky–Winternitz class of superintegrable systems. The transformed solutions, their potentials and the corresponding discrete energy spectra are computed in explicit form. (paper)
Two-dimensional weak pseudomanifolds on eight vertices
Indian Academy of Sciences (India)
We explicitly determine all the two-dimensional weak pseudomanifolds on 8 vertices. We prove that there are (up to isomorphism) exactly 95 such weak pseudomanifolds, 44 of which are combinatorial 2-manifolds. These 95 weak pseudomanifolds triangulate 16 topological spaces. As a consequence, we prove that there ...
Inter-layer Cooper pairing of two-dimensional electrons
International Nuclear Information System (INIS)
Inoue, Masahiro; Takemori, Tadashi; Yoshizaki, Ryozo; Sakudo, Tunetaro; Ohtaka, Kazuo
1987-01-01
The authors point out the possibility that the high transition temperatures of the recently discovered oxide superconductors are dominantly caused by the inter-layer Cooper pairing of two-dimensional electrons that are coupled through the exchange of three-dimensional phonons. (author)
Symmetry Reductions of Two-Dimensional Variable Coefficient Burgers Equation
Zhang, Xiao-Ling; Li, Biao
2005-05-01
By use of a direct method, we discuss symmetries and reductions of the two-dimensional Burgers equation with variable coefficient (VCBurgers). Five types of symmetry-reducing VCBurgers to (1+1)-dimensional partial differential equation and three types of symmetry reducing VCBurgers to ordinary differential equation are obtained.
Interior design of a two-dimensional semiclassical black hole
International Nuclear Information System (INIS)
Levanony, Dana; Ori, Amos
2009-01-01
We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the black hole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.
Interior design of a two-dimensional semiclassical black hole
Levanony, Dana; Ori, Amos
2009-10-01
We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the black hole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.
Vibrations of thin piezoelectric shallow shells: Two-dimensional ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two- dimensional eigenvalue problem. Keywords. Vibrations; piezoelectricity ...
Two-dimensional microwave band-gap structures of different ...
Indian Academy of Sciences (India)
Abstract. We report the use of low dielectric constant materials to form two- dimensional microwave band-gap structures for achieving high gap-to-midgap ratio. The variable parameters chosen are the lattice spacing and the geometric structure. The se- lected geometries are square and triangular and the materials chosen ...
Nonlinear dynamic characterization of two-dimensional materials
Davidovikj, D.; Alijani, F.; Cartamil Bueno, S.J.; van der Zant, H.S.J.; Amabili, M.; Steeneken, P.G.
2017-01-01
Owing to their atomic-scale thickness, the resonances of two-dimensional (2D) material membranes show signatures of nonlinearities at forces of only a few picoNewtons. Although the linear dynamics of membranes is well understood, the exact relation between the nonlinear response and the resonator's
Level crossings in complex two-dimensional potentials
Indian Academy of Sciences (India)
Two-dimensional P T -symmetric quantum-mechanical systems with the complex cubic potential 12 = 2 + 2 + 2 and the complex Hénon–Heiles potential HH = 2 + 2 + (2 − 3/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both ...
Image Making in Two Dimensional Art; Experiences with Straw and ...
African Journals Online (AJOL)
Image making in art is professionally referred to as bust in Sculpture andPortraiture in Painting. It is an art form executed in three dimensional (3D)and two dimensional (2D) formats respectively. Uncountable materials havebeen used to achieve these forms of art; like clay cement, marble, stone,different metals and, fibre ...
Optical properties of two-dimensional magnetoelectric point scattering lattices
DEFF Research Database (Denmark)
Hansen, Per Lunnemann; Sersic, Ivana; Koenderink, A. Femius
2013-01-01
We explore the electrodynamic coupling between a plane wave and an infinite two-dimensional periodic lattice of magnetoelectric point scatterers, deriving a semianalytical theory with consistent treatment of radiation damping, retardation, and energy conservation. We apply the theory to arrays...
Magnetoelectronic transport of the two-dimensional electron gas in ...
Indian Academy of Sciences (India)
Abstract. Hall mobility and magnetoresistance coefficient for the two-dimensional (2D) electron transport parallel to the heterojunction interfaces in a single quantum well of. CdSe are calculated with a numerical iterative technique in the framework of Fermi–Dirac statistics. Lattice scatterings due to polar-mode longitudinal ...
Divorticity and dihelicity in two-dimensional hydrodynamics
DEFF Research Database (Denmark)
Shivamoggi, B.K.; van Heijst, G.J.F.; Juul Rasmussen, Jens
2010-01-01
A framework is developed based on the concepts of divorticity B (≡×ω, ω being the vorticity) and dihelicity g (≡vB) for discussing the theoretical structure underlying two-dimensional (2D) hydrodynamics. This formulation leads to the global and Lagrange invariants that could impose significant...... constraints on the evolution of divorticity lines in 2D hydrodynamics....
Supersymmetric quantum mechanics for two-dimensional disk
Indian Academy of Sciences (India)
Supersymmetric quantum mechanics for two-dimensional disk. AKIRA SUZUKI1, RANABIR DUTT2 and RAJAT K BHADURI1,3. 1Department of Physics, Tokyo University of Science, Tokyo 162-8601, Japan. 2Department of Physics, Visva Bharati University, Santiniketan 731 235, India. 3Department of Physics and ...
Phase conjugated Andreev backscattering in two-dimensional ballistic cavities
Morpurgo, A.F.; Holl, S.; Wees, B.J.van; Klapwijk, T.M; Borghs, G.
1997-01-01
We have experimentally investigated transport in two-dimensional ballistic cavities connected to a point contact and to two superconducting electrodes with a tunable macroscopic phase difference. The point contact resistance oscillates as a function of the phase difference in a way which reflects
Noninteracting beams of ballistic two-dimensional electrons
International Nuclear Information System (INIS)
Spector, J.; Stormer, H.L.; Baldwin, K.W.; Pfeiffer, L.N.; West, K.W.
1991-01-01
We demonstrate that two beams of two-dimensional ballistic electrons in a GaAs-AlGaAs heterostructure can penetrate each other with negligible mutual interaction analogous to the penetration of two optical beams. This allows electrical signal channels to intersect in the same plane with negligible crosstalk between the channels
Two-dimensional optimization of free-electron-laser designs
Prosnitz, D.; Haas, R.A.
1982-05-04
Off-axis, two-dimensional designs for free electron lasers are described that maintain correspondence of a light beam with a synchronous electron at an optimal transverse radius r > 0 to achieve increased beam trapping efficiency and enhanced laser beam wavefront control so as to decrease optical beam diffraction and other deleterious effects.
Protein mapping by two-dimensional high performance liquid chromatography
Wagner, K.; Racaityte, K.; Unger, K.K.; Miliotis, T.; Edholm, L.E.; Bischoff, Rainer; Marko-Varga, G
2000-01-01
Current developments in drug discovery in the pharmaceutical industry require highly efficient analytical systems for protein mapping providing high resolution, robustness, sensitivity, reproducibility and a high throughput of samples. The potential of two-dimensional (2D) HPLC as a complementary
Colloidal interactions in two-dimensional nematic emulsions
Indian Academy of Sciences (India)
These were reported to lead to a variety of novel self-organized colloidal structures, such as linear chains [5,6], periodic lattices [7], anisotropic clusters [3], and cellular structures [8] that are stabilized, in general, by topological defects. More recently, two-dimensional (2D) inverted nematic emulsions were also stud- ied and ...
Tagging multiphoton ionization events by two-dimensional photoelectron spectroscopy
de Groot, Mattijs; Broos, Jaap; Buma, Wybren Jan
2007-01-01
Two-dimensional photoelectron spectroscopy has been used to supply process-specific labels to multiphoton ionization events. Employing these tags, the authors can construct excitation and photoelectron spectra along predefined excitation routes in the neutral manifold and ionization routes to the
A very useful experiment of two dimensional po- tential mapping ...
Indian Academy of Sciences (India)
A very useful experiment of two dimensional po- tential mapping, namely electrolytic tank model, for graduate and post graduate level physics stu- dents is given here. Laplace's equation is solved for the above and the results are compared with the experiment. The agreement· is so good that this is extended to complex ...
Bounds on the capacity of constrained two-dimensional codes
DEFF Research Database (Denmark)
Forchhammer, Søren; Justesen, Jørn
2000-01-01
Bounds on the capacity of constrained two-dimensional (2-D) codes are presented. The bounds of Calkin and Wilf apply to first-order symmetric constraints. The bounds are generalized in a weaker form to higher order and nonsymmetric constraints. Results are given for constraints specified by run...
Complex dynamical invariants for two-dimensional complex potentials
Indian Academy of Sciences (India)
Abstract. Complex dynamical invariants are searched out for two-dimensional complex poten- tials using rationalization method within the framework of an extended complex phase space characterized by x = x1 + ip3, y = x2 + ip4, px = p1 + ix3, py = p2 + ix4. It is found that the cubic oscillator and shifted harmonic oscillator ...
Level crossings in complex two-dimensional potentials
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 73; Issue 2. Level crossings in complex two-dimensional potentials. Qing-Hai Wang. Volume 73 Issue 2 August 2009 pp ... Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both potentials respect the P T symmetry, the ...
Weakly nonlinear analysis of two dimensional sheared granular flow
Saitoh, K.; Hayakawa, Hisao
2011-01-01
Weakly nonlinear analysis of a two dimensional sheared granular flow is carried out under the Lees-Edwards boundary condition. We derive the time dependent Ginzburg–Landau equation of a disturbance amplitude starting from a set of granular hydrodynamic equations and discuss the bifurcation of the
Fermi liquid of two-dimensional polar molecules
Lu, Z.K; Shlyapnikov, G.V.
2012-01-01
We study Fermi-liquid properties of a weakly interacting two-dimensional gas of single-component fermionic polar molecules with dipole moments d oriented perpendicularly to the plane of their translational motion. This geometry allows the minimization of inelastic losses due to chemical reactions
Zero sound in a two-dimensional dipolar Fermi gas
Lu, Z.K.; Matveenko, S.I.; Shlyapnikov, G.V.
2013-01-01
We study zero sound in a weakly interacting two-dimensional (2D) gas of single-component fermionic dipoles (polar molecules or atoms with a large magnetic moment) tilted with respect to the plane of their translational motion. It is shown that the propagation of zero sound is provided by both
Two-dimensional gel electrophoresis analysis of different parts of ...
African Journals Online (AJOL)
Two-dimensional gel electrophoresis analysis of different parts of Panax quinquefolius L. root. ... From these results it was concluded that proteomic analysis method was an effective way to identify the different parts of quinquefolius L. root. These findings may contribute to further understanding of the physiological ...
TreePM Method for Two-Dimensional Cosmological Simulations ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
paper. The 2d TreePM code is an accurate and efficient technique to carry out large two-dimensional N-body simulations in cosmology. This hybrid code combines the 2d Barnes and Hut Tree method and the 2d Particle– ..... ment, we need less than 75 MB of RAM for a simulation with 10242 particles on a. 10242 grid.
Spectral and Power-Efficiency Trade-off in Fixed-Grid Optical Networks
Directory of Open Access Journals (Sweden)
Sridhar Iyer
2017-09-01
Full Text Available The improvement of spectral efficiency in the MLR networks can be obtained by the reduction of sub-band spacing, or by minimizing the spacing of the sub-bands that operate at varied data rates. However, due to the presence of physical layer impairments, minimization in sub-band spacing leads to adverse effects on the channel(s transmission reach. As a result there occurs an increase in the consumed power due to the requirement of increase in regeneration of the signal. In the current work we propose an improved DWDM grating in view of obtaining higher spectral efficiency. For a system, with and without Forward Error Correction capabilities (i for various SLR solutions, we find and compare power consumption values of the components with respect to the total traffic, and (ii for different MLR and SLR solutions, for a fixed QoT, we evaluate the minimum values of the sub-band and the channel spacing, and also evaluate and compare the power-efficiency with the distance of transmission.
ENERGY-DEPENDENT POWER SPECTRAL STATES AND ORIGIN OF APERIODIC VARIABILITY IN BLACK HOLE BINARIES
International Nuclear Information System (INIS)
Yu Wenfei; Zhang Wenda
2013-01-01
We found that the black hole candidate MAXI J1659–152 showed distinct power spectra, i.e., power-law noise (PLN) versus band-limited noise (BLN) plus quasi-periodic oscillations (QPOs) below and above about 2 keV, respectively, in observations with Swift and the Rossi X-ray Timing Explorer during the 2010 outburst, indicating a high energy cutoff of the PLN and a low energy cutoff of the BLN and QPOs around 2 keV. The emergence of the PLN and the fading of the BLN and QPOs initially took place below 2 keV when the source entered the hard intermediate state and settled in the soft state three weeks later. The evolution was accompanied by the emergence of the disk spectral component and decreases in the amplitudes of variability in the soft and hard X-ray bands. Our results indicate that the PLN is associated with an optically thick disk in both hard and intermediate states, and the power spectral state is independent of the X-ray energy spectral state in a broadband view. We suggest that in the hard or intermediate state, the BLN and QPOs emerge from the innermost hot flow subjected to Comptonization, while the PLN originates from the optically thick disk farther out. The energy cutoffs of the PLN and the BLN or QPOs then follow the temperature of the seed photons from the inner edge of the optically thick disk, while the high frequency cutoff of the PLN follows the orbital frequency of the inner edge of the optically thick disk as well.
Directory of Open Access Journals (Sweden)
J E Lugo
Full Text Available The relationship between muscle anatomy and physiology and its corresponding electromyography activity (EMGA is complex and not well understood. EMGA models may be broadly divided in stochastic and motor-unit-based models. For example, these models have successfully described many muscle physiological variables such as the value of the muscle fiber velocity and the linear relationship between median frequency and muscle fiber velocity. However they cannot explain the behavior of many of these variables with changes in intramuscular temperature, or muscle PH acidity, for instance. Here, we propose that the motor unit action potential can be treated as an electromagnetic resonant mode confined at thermal equilibrium inside the muscle. The motor units comprising the muscle form a system of standing waves or modes, where the energy of each mode is proportional to its frequency. Therefore, the power spectral density of the EMGA is well described and fit by Planck's law and from its distribution we developed theoretical relationships that explain the behavior of known physiological variables with changes in intramuscular temperature or muscle PH acidity, for instance.EMGA of the calf muscle was recorded during posture maintenance in seven participants and during controlled isometric contractions in two participants. The power spectral density of the EMGA was then fit with the Planckian distribution. Then, we inferred nine theoretical relationships from the distribution and compared the theoretically derived values with experimentally obtained values.The power spectral density of EMGA was fit by Planckian distributions and all the theoretical relationships were validated by experimental results.Only by considering the motor unit action potentials as electromagnetic resonant modes confined at thermal equilibrium inside the muscle suffices to predict known or new theoretical relationships for muscle physiological variables that other models have failed
Directory of Open Access Journals (Sweden)
Sang-Kyun Kim
2016-07-01
Full Text Available In this paper, we propose a robust voice activity detection (VAD algorithm to effectively distinguish speech from non-speech in various noisy environments. The proposed VAD utilizes power spectral deviation (PSD, using Teager energy (TE to provide a better representation of the PSD, resulting in improved decision performance for speech segments. In addition, the TE-based likelihood ratio and speech absence probability are derived in each frame to modify the PSD for further VAD. We evaluate the performance of the proposed VAD algorithm by objective testing in various environments and obtain better results that those attained by of the conventional methods.
Energy Technology Data Exchange (ETDEWEB)
Minaki, S.; Ishihara, Y.; Todaka, T.; Harada, K. [Doshisha University, Kyoto (Japan); Oshiro, T.; Nakamura, H. [Japan quality Assurance Organization, Tokyo (Japan)
1997-11-25
As to the influence of spectral solar radiation to generating power of solar cells, a study was conducted from the aspects of season, time zone, intensity of solar radiation, etc. In the study, spectral responsive variation correction coefficients were introduced as evaluation values expressing the influence of spectral solar radiation. For the spectral distribution, an all sky spectral pyranometer by wavelength was used, and data were used which were obtained in the measurement in experimental facilities of the solar techno center. Concerning solar cell relative spectral sensitivity values, used were relative spectral sensitivity values of monocrystal and amorphous standard solar cells to the short-circuit current. Spectral response variation correction coefficients are coefficients correcting variations in conversion efficiency of solar cells due to changes in the spectral distribution. The changes of spectral responsive variation correction coefficients were studied using data obtained during April 1994 and March 1996. As a result, it was found that the coefficients showed large changes in summer and small ones in winter and that amorphous solar cells indicate this trend conspicuously. 3 refs., 6 figs., 3 tabs.
Directory of Open Access Journals (Sweden)
Huiguo Chen
2017-01-01
Full Text Available Based on the Kanai-Tajimi power spectrum filtering method proposed by Du Xiuli et al., a genetic algorithm and a quadratic optimization identification technique are employed to improve the bimodal time-varying modified Kanai-Tajimi power spectral model and the parameter identification method proposed by Vlachos et al. Additionally, a method for modeling time-varying power spectrum parameters for ground motion is proposed. The 8244 Orion and Chi-Chi earthquake accelerograms are selected as examples for time-varying power spectral model parameter identification and ground motion simulations to verify the feasibility and effectiveness of the improved bimodal time-varying modified Kanai-Tajimi power spectral model. The results of this study provide important references for designing ground motion inputs for seismic analyses of major engineering structures.
Chua, Victor; Vissers, Michael; Law, Stephanie A.; Vishveshwara, Smitha; Eckstein, James N.
2015-03-01
We simulate the consequences of the superconducting proximity effect on the DC current response of a semiconductor-superconductor proximity device within the quasiclassical formalism in the diffusively disordered limit. The device is modeled on in-situ fabricated NS junctions of superconducting Nb films on metallic doped InAs films, with electrical terminals placed in an N-S-N T-junction configuration. Due to the non-collinear configuration of this three terminal device, a theoretical model based on coupled two dimensional spectral and distributional Usadel equations was constructed and numerically solved using Finite-Elements methods. In the regime of high junction conductance, our numerical results demonstrate strong temperature and spatial dependencies of the proximity induced modifications to spectral and transport properties. Such characteristics deviate strongly from usual tunnel junction behavior and aspects of this have been observed in prior experiments[arXiv:1402.6055].
Vibrational two-dimensional correlation spectroscopy (2DCOS) study of proteins
Noda, Isao
2017-12-01
A tutorial is provided for the generalized two-dimensional correlation spectroscopy (2DCOS), which is applicable to the vibrational spectroscopic study of proteins and related systems. In 2DCOS, similarity or dissimilarity among variations of spectroscopic intensities, which are induced by applying an external perturbation to the sample, is examined by constructing correlation spectra defined by two independent spectral variable axes. By spreading congested or overlapped peaks along the second dimension, apparent spectral resolution is enhanced and interpretation of complex spectra becomes simplified. A set of simple rules for the intensities and signs of correlation peaks is used to extract insightful information. Simulated IR spectra for a model protein are used to demonstrate the specific utility of 2DCOS. Additional tools useful in the 2DCOS analysis of proteins, such as data segmentation assisted with moving-window analysis, 2D codistribution analysis, Pareto scaling, and null-space projection are also discussed.
Two-dimensional correlation analysis of spectra collected without knowing sampling order
Noda, Isao
2018-03-01
Two-dimensional correlation spectroscopy (2DCOS) without a priori knowledge of meaningful spectral sampling order is considered. Construction of synchronous 2D correlation spectrum does not require the knowledge of sampling order, and disrelation spectrum derived from synchronous spectrum possesses useful features similar to those of asynchronous spectrum. Disrelation analysis may provide enhanced spectral resolution and distinction of bands arising from different sources but not the sequential order of intensity variations. Dataset sampled in an arbitrary or scrambled order may be reassembled into a more structured form by rank ordering the spectra with the intensity of a select band. If there is no meaningful data structure, asynchronous 2D correlation should not be attempted, although synchronous and disrelation spectra may still be useful. The intrinsic ambiguity in the direction of sampling order may sometimes be resolved using additional physical information known about the sample system.
Fourier analysis of cell-wise Block-Jacobi splitting in two-dimensional geometry
International Nuclear Information System (INIS)
Rosa, M.; Warsa, J. S.; Kelley, T. M.
2009-01-01
A Fourier analysis is conducted in two-dimensional (2D) geometry for the discrete ordinates (S N ) approximation of the neutron transport problem solved with Richardson iteration (Source Iteration) using the cell-wise Block-Jacobi (BJ) algorithm. The results of the Fourier analysis show that convergence of cell-wise BJ can degrade, leading to a spectral radius equal to 1, in problems containing optically thin cells. For problems containing cells that are optically thick, instead, the spectral radius tends to 0. Hence, in the optically thick-cell regime, cell-wise BJ is rapidly convergent even for problems that are scattering dominated, with a scattering ratio c close to 1. (authors)
16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers
DEFF Research Database (Denmark)
Müller, André; Vijayakumar, Deepak; Jensen, Ole Bjarlin
2011-01-01
Up to 16 W output power has been obtained using spectral beam combining of two 1063 nm DBR-tapered diode lasers. Using a reflecting volume Bragg grating, a combining efficiency as high as 93.7% is achieved, resulting in a single beam with high spatial coherence. The result represents the highest...... output power achieved by spectral beam combining of two single element tapered diode lasers. Since spectral beam combining does not affect beam propagation parameters, M2-values of 1.8 (fast axis) and 3.3 (slow axis) match the M2- values of the laser with lowest spatial coherence. The principle...... of spectral beam combining used in our experiments can be expanded to combine more than two tapered diode lasers and hence it is expected that the output power may be increased even further in the future....
16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers.
Müller, André; Vijayakumar, Deepak; Jensen, Ole Bjarlin; Hasler, Karl-Heinz; Sumpf, Bernd; Erbert, Götz; Andersen, Peter E; Petersen, Paul Michael
2011-01-17
Up to 16 W output power has been obtained using spectral beam combining of two 1063 nm DBR-tapered diode lasers. Using a reflecting volume Bragg grating, a combining efficiency as high as 93.7% is achieved, resulting in a single beam with high spatial coherence. The result represents the highest output power achieved by spectral beam combining of two single element tapered diode lasers. Since spectral beam combining does not affect beam propagation parameters, M2-values of 1.8 (fast axis) and 3.3 (slow axis) match the M2-values of the laser with lowest spatial coherence. The principle of spectral beam combining used in our experiments can be expanded to combine more than two tapered diode lasers and hence it is expected that the output power may be increased even further in the future.
Piazza, C; Cantiani, C; Tacchino, G; Molteni, M; Reni, G; Bianchi, A M
2014-01-01
The ability to process rapidly-occurring auditory stimuli plays an important role in the mechanisms of language acquisition. For this reason, the research community has begun to investigate infant auditory processing, particularly using the Event Related Potentials (ERP) technique. In this paper we approach this issue by means of time domain and time-frequency domain analysis. For the latter, we propose the use of Adaptive Autoregressive (AAR) identification with spectral power decomposition. Results show EEG delta-theta oscillation enhancement related to the processing of acoustic frequency and duration changes, suggesting that, as expected, power modulation encodes rapid auditory processing (RAP) in infants and that the time-frequency analysis method proposed is able to identify this modulation.
Correlations of Power-law Spectral and QPO Features In Black Hole Candidate Sources
Fiorito, Ralph; Titarchuk, Lev
2004-01-01
Recent studies have shown that strong correlations are observed between low frequency QPO s and the spectral power law index for a number of black hole candidate sources (BHCs), when these sources exhibit quasi-steady hard x-ray emission states. The dominant long standing interpretation of QPO's is that they are produced in and are the signature of the thermal accretion disk. Paradoxically, strong QPO's are present even in the cases where the thermal component is negligible. We present a model which identifies the origin of the QPO's and relates them directly to the properties of a compact coronal region which is bounded by the adjustment from Kepleriaa to sub-Kelperian inflow into the BH, and is primarily responsible for the observed power law spectrum. The model also predicts the relationship between high and low frequency QPO's and shows how BH's can be unique identified from observations of the soft states of NS's and BHC's.
A recommended procedure for estimating the cosmic-ray spectral parameter of a simple power law
Howell, L W
2002-01-01
A simple power law model with single spectral index alpha sub 1 is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10 sup 1 sup 3 eV. Two procedures for estimating alpha sub 1 --the method of moments and maximum likelihood (ML)--are developed and their statistical performance are compared. The ML procedure is shown to be the superior approach and is then generalized for application to real cosmic-ray data sets. Several other important results, such as the relationship between collecting power and detector energy resolution and inclusion of a non-Gaussian detector response function, are presented. These results have many practical benefits in the design phase of a cosmic-ray detector as they permit instrument developers to make important trade studies in design parameters as a function of one of the science objectives.
International Nuclear Information System (INIS)
Howell, L.W.
2002-01-01
The method of Maximum Likelihood (ML) is used to estimate the spectral parameters of an assumed broken power law energy spectrum from simulated detector responses. This methodology, which requires the complete specificity of all cosmic-ray detector design parameters, is shown to provide approximately unbiased, minimum variance, and normally distributed spectra information for events detected by an instrument having a wide range of commonly used detector response functions. The ML procedure, coupled with the simulated performance of a proposed space-based detector and its planned life cycle, has proved to be of significant value in the design phase of a new science instrument. The procedure helped make important trade studies in design parameters as a function of the science objectives, which is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose rigorous practical limits to the design envelope. This ML methodology is then generalized to estimate broken power law spectral parameters from real cosmic-ray data sets
Howell, Leonard W.
2002-01-01
The method of Maximum Likelihood (ML) is used to estimate the spectral parameters of an assumed broken power law energy spectrum from simulated detector responses. This methodology, which requires the complete specificity of all cosmic-ray detector design parameters, is shown to provide approximately unbiased, minimum variance, and normally distributed spectra information for events detected by an instrument having a wide range of commonly used detector response functions. The ML procedure, coupled with the simulated performance of a proposed space-based detector and its planned life cycle, has proved to be of significant value in the design phase of a new science instrument. The procedure helped make important trade studies in design parameters as a function of the science objectives, which is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose rigorous practical limits to the design envelope. This ML methodology is then generalized to estimate broken power law spectral parameters from real cosmic-ray data sets.
X-ray Spectral Measurements of the JMAR High-Power Laser-plasma Source
Whitlock, Robert R.; Dozier, Charles M.; Newman, Daniel A.; Turcu, I. C. Edmond; Gaeta, Celestino J.; Cassidy, Kelly L.; Powers, Michael F.; Kleindolph, Thomas; Morris, James H.; Forber, Richard A.
2002-10-01
X-ray spectra of Cu plasmas at the focus of a four-beam, solid-state diode-pumped laser have been recorded. This laser-plasma X-ray source is being developed for JMAR's lithography systems aimed at high- performance semiconductor integrated circuits. The unique simultaneous overlay of the four sub-nanosecond laser beams at 300 Hertz produces a bright, point-plasma X-ray source. PIN diode measurements of the X-ray output indicate that the conversion efficiency (ratio of X-ray emission energy into 2π steradians to incident laser energy) was approximately 9 percent with average X-ray power yields of greater than 10 Watts. Spectra were recorded on calibrated Kodak DEF film in a curved-crystal spectrograph. A KAP crystal (2d = 26.6 Angstroms) was used to disperse the 900 eV to 3000 eV spectral energies onto the film. Preliminary examination of the films indicated the existence of Cu and Cu XX ionization states. Additional spectra as a function of laser input power were also recorded to investigate potential changes in X-ray yields. These films are currently being analyzed. The analysis of the spectra provide absolute line and continuum intensities, and total X-ray output in the measured spectral range.
Nucleation of two-dimensional islands on Si (111) during high-temperature epitaxial growth
Energy Technology Data Exchange (ETDEWEB)
Sitnikov, S. V., E-mail: sitnikov@isp.nsc.ru; Kosolobov, S. S.; Latyshev, A. V. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)
2017-02-15
The process of two-dimensional island nucleation at the surface of ultra large Si (111) during hightemperature epitaxial growth is studied by in situ ultrahigh-vacuum reflection electron microscopy. The critical terrace size D{sub crit}, at which a two-dimensional island is nucleated in the center, is measured in the temperature range 900–1180°C at different silicon fluxes onto the surface. It is found that the parameter D{sub crit}{sup 2} is a power function of the frequency of island nucleation, with the exponent χ = 0.9 ± 0.05 in the entire temperature range under study. It is established that the kinetics of nucleus formation is defined by the diffusion of adsorbed silicon atoms at temperatures of up to 1180°C and the minimum critical nucleus size corresponds to 12 silicon atoms.
Rheological properties of the soft-disk model of two-dimensional foams
DEFF Research Database (Denmark)
Langlois, Vincent; Hutzler, Stefan; Weaire, Denis
2008-01-01
The soft-disk model previously developed and applied by Durian [D. J. Durian, Phys. Rev. Lett. 75, 4780 (1995)] is brought to bear on problems of foam rheology of longstanding and current interest, using two-dimensional systems. The questions at issue include the origin of the Herschel-Bulkley re......The soft-disk model previously developed and applied by Durian [D. J. Durian, Phys. Rev. Lett. 75, 4780 (1995)] is brought to bear on problems of foam rheology of longstanding and current interest, using two-dimensional systems. The questions at issue include the origin of the Herschel......-Bulkley relation, normal stress effects (dilatancy), and localization in the presence of wall drag. We show that even a model that incorporates only linear viscous effects at the local level gives rise to nonlinear (power-law) dependence of the limit stress on strain rate. With wall drag, shear localization...
Tuning spin transport across two-dimensional organometallic junctions
Liu, Shuanglong; Wang, Yun-Peng; Li, Xiangguo; Fry, James N.; Cheng, Hai-Ping
2018-01-01
We study via first-principles modeling and simulation two-dimensional spintronic junctions made of metal-organic frameworks consisting of two Mn-phthalocyanine ferromagnetic metal leads and semiconducting Ni-phthalocyanine channels of various lengths. These systems exhibit a large tunneling magnetoresistance ratio; the transmission functions of such junctions can be tuned using gate voltage by three orders of magnitude. We find that the origin of this drastic change lies in the orbital alignment and hybridization between the leads and the center electronic states. With physical insight into the observed on-off phenomenon, we predict a gate-controlled spin current switch based on two-dimensional crystallines and offer general guidelines for designing spin junctions using 2D materials.
Duality-invariant class of two-dimensional field theories
Sfetsos, K
1999-01-01
We construct a new class of two-dimensional field theories with target spaces that are finite multiparameter deformations of the usual coset G/H-spaces. They arise naturally, when certain models, related by Poisson-Lie T-duality, develop a local gauge invariance at specific points of their classical moduli space. We show that canonical equivalences in this context can be formulated in loop space in terms of parafermionic-type algebras with a central extension. We find that the corresponding generating functionals are non-polynomial in the derivatives of the fields with respect to the space-like variable. After constructing models with three- and two-dimensional targets, we study renormalization group flows in this context. In the ultraviolet, in some cases, the target space of the theory reduces to a coset space or there is a fixed point where the theory becomes free.
Transient two-dimensional fuel-concentration measurement technique
Konishi, Tadashi; Naka, Syuji; Ito, Akihiko; Saito, Kozo
1997-11-01
We propose a nonintrusive experimental technique, the transient fuel-concentration measurement technique (TFMT), that is capable of being used to measure two-dimensional profiles of transient fuel concentrations over an open liquid fuel surface. The TFMT is based on single-wavelength holographic interferometry; its response time is less than 1 s and spatial resolution is 0.1 mol. % /0.1 mm. It was applied to measure both methanol vapor and n-propanol vapor concentrations. To assess the accuracy of the technique, our results were compared with steady-state methanol and n-propanol fuel-vapor concentrations measured by other researchers with a microsampling technique combined with gas chromatography. We found the TFMT to be accurate for on-line monitoring of two-dimensional profiles of fuel-vapor concentrations.
Quasi-two-dimensional thermoelectricity in SnSe
Tayari, V.; Senkovskiy, B. V.; Rybkovskiy, D.; Ehlen, N.; Fedorov, A.; Chen, C.-Y.; Avila, J.; Asensio, M.; Perucchi, A.; di Pietro, P.; Yashina, L.; Fakih, I.; Hemsworth, N.; Petrescu, M.; Gervais, G.; Grüneis, A.; Szkopek, T.
2018-01-01
Stannous selenide is a layered semiconductor that is a polar analog of black phosphorus and of great interest as a thermoelectric material. Unusually, hole doped SnSe supports a large Seebeck coefficient at high conductivity, which has not been explained to date. Angle-resolved photoemission spectroscopy, optical reflection spectroscopy, and magnetotransport measurements reveal a multiple-valley valence-band structure and a quasi-two-dimensional dispersion, realizing a Hicks-Dresselhaus thermoelectric contributing to the high Seebeck coefficient at high carrier density. We further demonstrate that the hole accumulation layer in exfoliated SnSe transistors exhibits a field effect mobility of up to 250 cm2/V s at T =1.3 K . SnSe is thus found to be a high-quality quasi-two-dimensional semiconductor ideal for thermoelectric applications.
Two dimensional analytical model for a reconfigurable field effect transistor
Ranjith, R.; Jayachandran, Remya; Suja, K. J.; Komaragiri, Rama S.
2018-02-01
This paper presents two-dimensional potential and current models for a reconfigurable field effect transistor (RFET). Two potential models which describe subthreshold and above-threshold channel potentials are developed by solving two-dimensional (2D) Poisson's equation. In the first potential model, 2D Poisson's equation is solved by considering constant/zero charge density in the channel region of the device to get the subthreshold potential characteristics. In the second model, accumulation charge density is considered to get above-threshold potential characteristics of the device. The proposed models are applicable for the device having lightly doped or intrinsic channel. While obtaining the mathematical model, whole body area is divided into two regions: gated region and un-gated region. The analytical models are compared with technology computer-aided design (TCAD) simulation results and are in complete agreement for different lengths of the gated regions as well as at various supply voltage levels.
Recombination in one- and two-dimensional fitness landscapes.
Avetisyan, Zh; Saakian, David B
2010-05-01
We consider many-site mutation-recombination models of molecular evolution, where fitness is a function of a Hamming distance from one (one-dimensional case) or two (two-dimensional case) sequences. For the one-dimensional case, we calculate the population distribution dynamics for a model with zero fitness and an arbitrary symmetric initial distribution and find an error threshold transition point in the single-peak fitness model for a given initial symmetric distribution. We calculate the recombination period in the case of a single-peak fitness function, when the original population is located at one sequence, at some Hamming distance from the peak configuration. Steady-state fitness is calculated with finite genome length corrections. We derive analytical equations for the two-dimensional mutation-recombination model.
Two-dimensional time dependent Riemann solvers for neutron transport
International Nuclear Information System (INIS)
Brunner, Thomas A.; Holloway, James Paul
2005-01-01
A two-dimensional Riemann solver is developed for the spherical harmonics approximation to the time dependent neutron transport equation. The eigenstructure of the resulting equations is explored, giving insight into both the spherical harmonics approximation and the Riemann solver. The classic Roe-type Riemann solver used here was developed for one-dimensional problems, but can be used in multidimensional problems by treating each face of a two-dimensional computation cell in a locally one-dimensional way. Several test problems are used to explore the capabilities of both the Riemann solver and the spherical harmonics approximation. The numerical solution for a simple line source problem is compared to the analytic solution to both the P 1 equation and the full transport solution. A lattice problem is used to test the method on a more challenging problem
Dynamics of vortex interactions in two-dimensional flows
DEFF Research Database (Denmark)
Juul Rasmussen, J.; Nielsen, A.H.; Naulin, V.
2002-01-01
The dynamics and interaction of like-signed vortex structures in two dimensional flows are investigated by means of direct numerical solutions of the two-dimensional Navier-Stokes equations. Two vortices with distributed vorticity merge when their distance relative to their radius, d/R-0l. is below...... a critical value, a(c). Using the Weiss-field, a(c) is estimated for vortex patches. Introducing an effective radius for vortices with distributed vorticity, we find that 3.3 ... is effectively producing small scale structures and the relation to the enstrophy "cascade" in developed 2D turbulence is discussed. The influence of finite viscosity on the merging is also investigated. Additionally, we examine vortex interactions on a finite domain, and discuss the results in connection...
Two-dimensional Simulations of Correlation Reflectometry in Fusion Plasmas
International Nuclear Information System (INIS)
Valeo, E.J.; Kramer, G.J.; Nazikian, R.
2001-01-01
A two-dimensional wave propagation code, developed specifically to simulate correlation reflectometry in large-scale fusion plasmas is described. The code makes use of separate computational methods in the vacuum, underdense and reflection regions of the plasma in order to obtain the high computational efficiency necessary for correlation analysis. Simulations of Tokamak Fusion Test Reactor (TFTR) plasma with internal transport barriers are presented and compared with one-dimensional full-wave simulations. It is shown that the two-dimensional simulations are remarkably similar to the results of the one-dimensional full-wave analysis for a wide range of turbulent correlation lengths. Implications for the interpretation of correlation reflectometer measurements in fusion plasma are discussed
Vortex annihilation and inverse cascades in two dimensional superfluid turbulence
Lucas, Andrew; Chesler, Paul M.
2015-03-01
The dynamics of a dilute mixture of vortices and antivortices in a turbulent two-dimensional superfluid at finite temperature is well described by first order Hall-Vinen-Iordanskii equations, or dissipative point vortex dynamics. These equations are governed by a single dimensionless parameter: the ratio of the strength of drag forces to Magnus forces on vortices. When this parameter is small, we demonstrate using numerical simulations that the resulting superfluid enjoys an inverse energy cascade where small scale stirring leads to large scale vortex clustering. We argue analytically and numerically that the vortex annihilation rate in a laminar flow may be parametrically smaller than the rate in a turbulent flow with an inverse cascade. This suggests a new way to detect inverse cascades in experiments on two-dimensional superfluid turbulence using cold atomic gases, where traditional probes of turbulence such as the energy spectrum are not currently accessible.
Two-dimensional turbulence in three-dimensional flows
Xia, H.; Francois, N.
2017-11-01
This paper presents a review of experiments performed in three-dimensional flows that show behaviour associated with two-dimensional turbulence. Experiments reveal the presence of the inverse energy cascade in two different systems, namely, flows in thick fluid layers driven electromagnetically and the Faraday wave driven flows. In thick fluid layers, large-scale coherent structures can shear off the vertical eddies and reinforce the planarity of the flow. Such structures are either self-generated or externally imposed. In the Faraday wave driven flows, a seemingly three-dimensional flow is shown to be actually two-dimensional when it is averaged over several Faraday wave periods. In this system, a coupling between the wave motion and 2D hydrodynamic turbulence is uncovered.
CORPORATE VALUATION USING TWO-DIMENSIONAL MONTE CARLO SIMULATION
Directory of Open Access Journals (Sweden)
Toth Reka
2010-12-01
Full Text Available In this paper, we have presented a corporate valuation model. The model combine several valuation methods in order to get more accurate results. To determine the corporate asset value we have used the Gordon-like two-stage asset valuation model based on the calculation of the free cash flow to the firm. We have used the free cash flow to the firm to determine the corporate market value, which was calculated with use of the Black-Scholes option pricing model in frame of the two-dimensional Monte Carlo simulation method. The combined model and the use of the two-dimensional simulation model provides a better opportunity for the corporate value estimation.
Explorative data analysis of two-dimensional electrophoresis gels
DEFF Research Database (Denmark)
Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine
2004-01-01
Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...... of gels is presented. First, an approach is demonstrated in which no prior knowledge of the separated proteins is used. Alignment of the gels followed by a simple transformation of data makes it possible to analyze the gels in an automated explorative manner by principal component analysis, to determine...... if the gels should be further analyzed. A more detailed approach is done by analyzing spot volume lists by principal components analysis and partial least square regression. The use of spot volume data offers a mean to investigate the spot pattern and link the classified protein patterns to distinct spots...
Two-dimensional cephalometry and computerized orthognathic surgical treatment planning.
Kusnoto, Budi
2007-07-01
Cephalometric radiographs provide for standardized skull/facial views that allow for comparison over time to assess growth in an individual, and to compare that individual against standardized population norms. Cephalometric analysis and surgical prediction are done by robust cephalometric imaging software that can rapidly analyze the radiograph, and retrace and recalculate the analysis for a variety of possible surgical outcomes; however, the validity of the prediction depends on the accuracy of the records, the algorithm specific to the software, and the specifics of the patient population. Three-dimensional digital imaging to replace conventional two-dimensional photographic images and CT scans, with corresponding cephalometric analysis to replace two-dimensional cephalometric films, is already on the horizon.
Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown
Energy Technology Data Exchange (ETDEWEB)
Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)
2016-01-04
Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.
The stability of a two-dimensional rising bubble
International Nuclear Information System (INIS)
Nie, Q.; Tanveer, S.
1995-01-01
The stability of an inviscid two-dimensional bubble subject to two-dimensional disturbances is considered and the bubbles are found to be linearly stable for all Weber numbers, for which a steady solution is known. Certain aspects of the nonlinear initial value problem are also studied. An initial condition that consists of a superposition of a suitable symmetric eigenmode (of the linear stability operator) on a steady state is found to result in pinching of the bubble neck as it tends to oscillate about the steady state. An estimate of the threshold amplitude of such a disturbance needed to cause breakup of a large aspect ratio bubble is obtained. The presence of gravity appears to inhibit this pinching process
Linear negative magnetoresistance in two-dimensional Lorentz gases
Schluck, J.; Hund, M.; Heckenthaler, T.; Heinzel, T.; Siboni, N. H.; Horbach, J.; Pierz, K.; Schumacher, H. W.; Kazazis, D.; Gennser, U.; Mailly, D.
2018-03-01
Two-dimensional Lorentz gases formed by obstacles in the shape of circles, squares, and retroreflectors are reported to show a pronounced linear negative magnetoresistance at small magnetic fields. For circular obstacles at low number densities, our results agree with the predictions of a model based on classical retroreflection. In extension to the existing theoretical models, we find that the normalized magnetoresistance slope depends on the obstacle shape and increases as the number density of the obstacles is increased. The peaks are furthermore suppressed by in-plane magnetic fields as well as by elevated temperatures. These results suggest that classical retroreflection can form a significant contribution to the magnetoresistivity of two-dimensional Lorentz gases, while contributions from weak localization cannot be excluded, in particular for large obstacle densities.
Directional detection of dark matter with two-dimensional targets
Directory of Open Access Journals (Sweden)
Yonit Hochberg
2017-09-01
Full Text Available We propose two-dimensional materials as targets for direct detection of dark matter. Using graphene as an example, we focus on the case where dark matter scattering deposits sufficient energy on a valence-band electron to eject it from the target. We show that the sensitivity of graphene to dark matter of MeV to GeV mass can be comparable, for similar exposure and background levels, to that of semiconductor targets such as silicon and germanium. Moreover, a two-dimensional target is an excellent directional detector, as the ejected electron retains information about the angular dependence of the incident dark matter particle. This proposal can be implemented by the PTOLEMY experiment, presenting for the first time an opportunity for directional detection of sub-GeV dark matter.
Directional detection of dark matter with two-dimensional targets
Hochberg, Yonit; Kahn, Yonatan; Lisanti, Mariangela; Tully, Christopher G.; Zurek, Kathryn M.
2017-09-01
We propose two-dimensional materials as targets for direct detection of dark matter. Using graphene as an example, we focus on the case where dark matter scattering deposits sufficient energy on a valence-band electron to eject it from the target. We show that the sensitivity of graphene to dark matter of MeV to GeV mass can be comparable, for similar exposure and background levels, to that of semiconductor targets such as silicon and germanium. Moreover, a two-dimensional target is an excellent directional detector, as the ejected electron retains information about the angular dependence of the incident dark matter particle. This proposal can be implemented by the PTOLEMY experiment, presenting for the first time an opportunity for directional detection of sub-GeV dark matter.
Robust L1-norm two-dimensional linear discriminant analysis.
Li, Chun-Na; Shao, Yuan-Hai; Deng, Nai-Yang
2015-05-01
In this paper, we propose an L1-norm two-dimensional linear discriminant analysis (L1-2DLDA) with robust performance. Different from the conventional two-dimensional linear discriminant analysis with L2-norm (L2-2DLDA), where the optimization problem is transferred to a generalized eigenvalue problem, the optimization problem in our L1-2DLDA is solved by a simple justifiable iterative technique, and its convergence is guaranteed. Compared with L2-2DLDA, our L1-2DLDA is more robust to outliers and noises since the L1-norm is used. This is supported by our preliminary experiments on toy example and face datasets, which show the improvement of our L1-2DLDA over L2-2DLDA. Copyright © 2015 Elsevier Ltd. All rights reserved.
Folding two dimensional crystals by swift heavy ion irradiation
International Nuclear Information System (INIS)
Ochedowski, Oliver; Bukowska, Hanna; Freire Soler, Victor M.; Brökers, Lara; Ban-d'Etat, Brigitte; Lebius, Henning; Schleberger, Marika
2014-01-01
Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS 2 and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS 2 does not
Folding two dimensional crystals by swift heavy ion irradiation
Energy Technology Data Exchange (ETDEWEB)
Ochedowski, Oliver; Bukowska, Hanna [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Freire Soler, Victor M. [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Departament de Fisica Aplicada i Optica, Universitat de Barcelona, E08028 Barcelona (Spain); Brökers, Lara [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Ban-d' Etat, Brigitte; Lebius, Henning [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France); Schleberger, Marika, E-mail: marika.schleberger@uni-due.de [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany)
2014-12-01
Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS{sub 2} and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS{sub 2} does not.
Logarithmic Superdiffusion in Two Dimensional Driven Lattice Gases
Krug, J.; Neiss, R. A.; Schadschneider, A.; Schmidt, J.
2018-03-01
The spreading of density fluctuations in two-dimensional driven diffusive systems is marginally anomalous. Mode coupling theory predicts that the diffusivity in the direction of the drive diverges with time as (ln t)^{2/3} with a prefactor depending on the macroscopic current-density relation and the diffusion tensor of the fluctuating hydrodynamic field equation. Here we present the first numerical verification of this behavior for a particular version of the two-dimensional asymmetric exclusion process. Particles jump strictly asymmetrically along one of the lattice directions and symmetrically along the other, and an anisotropy parameter p governs the ratio between the two rates. Using a novel massively parallel coupling algorithm that strongly reduces the fluctuations in the numerical estimate of the two-point correlation function, we are able to accurately determine the exponent of the logarithmic correction. In addition, the variation of the prefactor with p provides a stringent test of mode coupling theory.
Constraints and hidden symmetry in two-dimensional gravity
Energy Technology Data Exchange (ETDEWEB)
Barcelos-Neto, J. (Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21945-970 (Brazil))
1994-01-15
We study the hidden symmetry of Polyakov two-dimensional gravity by means of first-class constraints. These are obtained from the combination of Fourier mode expansions of the usual (second-class) constraints of the theory. We show that, more than the usual SL(2,[ital R]), there is a hidden Virasoro symmetry in the theory. The results of the above analysis are also confirmed from the point of view of a geometrical symplectic treatment.
Two-dimensional simulation of the MHD stability, (1)
International Nuclear Information System (INIS)
Kurita, Gen-ichi; Amano, Tsuneo.
1976-03-01
The two-dimensional computer code has been prepared to study MHD stability of an axisymmetric toroidal plasma with and without the surrounding vacuum region. It also includes the effect of magnetic surfaces with non-circular cross sections. The linearized equations of motion are solved as an initial value problem. The results by computer simulation are compared with those by the theory for the cylindrical plasma; they are in good agreement. (auth.)
Decaying Two-Dimensional Turbulence in a Circular Container
Schneider, Kai; Farge, Marie
2005-01-01
We present direct numerical simulations of two-dimensional decaying turbulence at initial Reynolds number 5×104 in a circular container with no-slip boundary conditions. Starting with random initial conditions the flow rapidly exhibits self-organization into coherent vortices. We study their formation and the role of the viscous boundary layer on the production and decay of integral quantities. The no-slip wall produces vortices which are injected into the bulk flow and tend to compensate the...
Stochastic and collisional diffusion in two-dimensional periodic flows
International Nuclear Information System (INIS)
Doxas, I.; Horton, W.; Berk, H.L.
1990-05-01
The global effective diffusion coefficient D* for a two-dimensional system of convective rolls with a time dependent perturbation added, is calculated. The perturbation produces a background diffusion coefficient D, which is calculated analytically using the Menlikov-Arnold integral. This intrinsic diffusion coefficient is then enhanced by the unperturbed flow, to produce the global effective diffusion coefficient D*, which we can calculate theoretically for a certain range of parameters. The theoretical value agrees well with numerical simulations. 23 refs., 4 figs
An energy principle for two-dimensional collisionless relativistic plasmas
International Nuclear Information System (INIS)
Otto, A.; Schindler, K.
1984-01-01
Using relativistic Vlasov theory an energy principle for two-dimensional plasmas is derived, which provides a sufficient and necessary criterion for the stability of relativistic plasma equilibria. This energy principle includes charge separating effects since the exact Poisson equation was taken into consideration. Applying the variational principle to the case of the relativistic plane plasma sheet, the same marginal wave length is found as in the non-relativistic case. (author)
New Two-Dimensional Polynomial Failure Criteria for Composite Materials
Zhao, Shi Yang; Xue, Pu
2014-01-01
The in-plane damage behavior and material properties of the composite material are very complex. At present, a large number of two-dimensional failure criteria, such as Chang-Chang criteria, have been proposed to predict the damage process of composite structures under loading. However, there is still no good criterion to realize it with both enough accuracy and computational performance. All these criteria cannot be adjusted by experimental data. Therefore, any special properties of composit...
Two-dimensional heat conducting simulation of plasma armatures
International Nuclear Information System (INIS)
Huerta, M.A.; Boynton, G.
1991-01-01
This paper reports on our development of a two-dimensional MHD code to simulate internal motions in a railgun plasma armature. The authors use the equations of resistive MHD, with Ohmic heating, and radiation heat transport. The authors use a Flux Corrected Transport code to advance all quantities in time. Our runs show the development of complex flows, subsequent shedding of secondary arcs, and a drop in the acceleration of the armature
Topological field theories and two-dimensional instantons
International Nuclear Information System (INIS)
Schaposnik, F.A.
1990-01-01
In this paper, the author discusses some topics related to the recently developed Topological Field Theories (TFTs). The first part is devoted to a discussion on how a TFT can be quantized using techniques which are well-known from the study of gauge theories. Then the author describes the results that we have obtained in collaboration with George Thompson in the study of a two-dimensional TFT related to the Abelian Higgs model
Warranty menu design for a two-dimensional warranty
International Nuclear Information System (INIS)
Ye, Zhi-Sheng; Murthy, D.N. Pra
2016-01-01
Fierce competitions in the commercial product market have forced manufacturers to provide customer-friendly warranties with a view to achieving higher customer satisfaction and increasing the market share. This study proposes a strategy that offers customers a two-dimensional warranty menu with a number of warranty choices, called a flexible warranty policy. We investigate the design of a flexible two-dimensional warranty policy that contains a number of rectangular regions. This warranty policy is obtained by dividing customers into several groups according to their use rates and providing each group a germane warranty region. Consumers choose a favorable one from the menu according to their usage behaviors. Evidently, this flexible warranty policy is attractive to users of different usage behaviors, and thus, it gives the manufacturer a good position in advertising the product. When consumers are unaware about their use rates upon purchase, we consider a fixed two-dimensional warranty policy with a stair-case warranty region and show that it is equivalent to the flexible policy. Such an equivalence reveals the inherent relationship between the rectangular warranty policy, the L-shape warranty policy, the step-stair warranty policy and the iso-probability of failure warranty policy that were extensively discussed in the literature. - Highlights: • We design a two-dimensional warranty menu with a number of warranty choices. • Consumers can choose a favorable one from the menu as per their usage behavior. • We further consider a fixed 2D warranty policy with a stair-case warranty region. • We show the equivalence of the two warranty policies.
Stability theory for a two-dimensional channel
Troshkin, O. V.
2017-08-01
A scheme for deriving conditions for the nonlinear stability of an ideal or viscous incompressible steady flow in a two-dimensional channel that is periodic in one direction is described. A lower bound for the main factor ensuring the stability of the Reynolds-Kolmogorov sinusoidal flow with no-slip conditions (short wavelength stability) is improved. A condition for the stability of a vortex strip modeling Richtmyer-Meshkov fluid vortices (long wavelength stability) is presented.
Effective mass of two-dimensional He3
International Nuclear Information System (INIS)
Boronat, J.; Casulleras, J.; Grau, V.; Krotscheck, E.; Springer, J.
2003-01-01
We use structural information from diffusion Monte Carlo calculations for two-dimensional He 3 to calculate the effective mass. Static effective interactions are constructed from the density and spin-structure functions using sum rules. We find that both spin and density fluctuations contribute about equally to the effective mass. Our results show, in agreement with recent experiments, a flattening of the single-particle self-energy with increasing density, which eventually leads to a divergent effective mass
SU(1,2) invariance in two-dimensional oscillator
Energy Technology Data Exchange (ETDEWEB)
Krivonos, Sergey [Bogoliubov Laboratory of Theoretical Physics,Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Nersessian, Armen [Yerevan State University,1 Alex Manoogian St., Yerevan, 0025 (Armenia); Tomsk Polytechnic University,Lenin Ave. 30, 634050 Tomsk (Russian Federation)
2017-02-01
Performing the Hamiltonian analysis we explicitly established the canonical equivalence of the deformed oscillator, constructed in arXiv:1607.03756, with the ordinary one. As an immediate consequence, we proved that the SU(1,2) symmetry is the dynamical symmetry of the ordinary two-dimensional oscillator. The characteristic feature of this SU(1,2) symmetry is a non-polynomial structure of its generators written in terms of the oscillator variables.
Two-dimensional gel electrophoretic method for mapping DNA replicons.
Nawotka, K A; Huberman, J A
1988-01-01
We describe in detail a method which allows determination of the directions of replication fork movement through segments of DNA for which cloned probes are available. The method uses two-dimensional neutral-alkaline agarose gel electrophoresis followed by hybridization with short probe sequences. The nascent strands of replicating molecules form an arc separated from parental and nonreplicating strands. The closer a probe is to its replication origin or to the origin-proximal end of its rest...
On Two-Dimensional Quaternion Wigner-Ville Distribution
Directory of Open Access Journals (Sweden)
Mawardi Bahri
2014-01-01
Full Text Available We present the two-dimensional quaternion Wigner-Ville distribution (QWVD. The transform is constructed by substituting the Fourier transform kernel with the quaternion Fourier transform (QFT kernel in the classical Wigner-Ville distribution definition. Based on the properties of quaternions and the QFT kernel we obtain three types of the QWVD. We discuss some useful properties of various definitions for the QWVD, which are extensions of the classical Wigner-Ville distribution properties.
Acoustic transparency in two-dimensional sonic crystals
Energy Technology Data Exchange (ETDEWEB)
Sanchez-Dehesa, Jose; Torrent, Daniel [Wave Phenomena Group, Department of Electronic Engineering, Polytechnic University of Valencia, C/ Camino de Vera s/n, E-46022 Valencia (Spain); Cai Liangwu [Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)], E-mail: jsdehesa@upvnet.upv.es
2009-01-15
Acoustic transparency is studied in two-dimensional sonic crystals consisting of hexagonal distributions of cylinders with continuously varying properties. The transparency condition is achieved by selectively closing the acoustic bandgaps, which are governed by the structure factor of the cylindrical scatterers. It is shown here that cylindrical scatterers with the proposed continuously varying properties are physically realizable by using metafluids based on sonic crystals. The feasibility of this proposal is analyzed by a numerical experiment based on multiple scattering theory.
Analysis of two dimensional signals via curvelet transform
Lech, W.; Wójcik, W.; Kotyra, A.; Popiel, P.; Duk, M.
2007-04-01
This paper describes an application of curvelet transform analysis problem of interferometric images. Comparing to two-dimensional wavelet transform, curvelet transform has higher time-frequency resolution. This article includes numerical experiments, which were executed on random interferometric image. In the result of nonlinear approximations, curvelet transform obtains matrix with smaller number of coefficients than is guaranteed by wavelet transform. Additionally, denoising simulations show that curvelet could be a very good tool to remove noise from images.
On the Initial Singularity Problem in Two Dimensional Quantum Cosmology
Gamboa, J.
1995-01-01
The problem of how to put interactions in two-dimensional quantum gravity in the strong coupling regime is studied. It shows that the most general interaction consistent with this symmetry is a Liouville term that contain two parameters $(\\alpha, \\beta)$ satisfying the algebraic relation $2\\beta - \\alpha =2$ in order to assure the closure of the diffeomorphism algebra. The model is classically soluble and it contains as general solution the temporal singularity. The theory is quantized and we...
Negative differential Rashba effect in two-dimensional hole systems
Habib, B.; Tutuc, E.; Melinte, S.; Shayegan, M.; Wasserman, D.; Lyon, S. A.; Winkler, R.
2004-01-01
We demonstrate experimentally and theoretically that two-dimensional (2D) heavy hole systems in single heterostructures exhibit a \\emph{decrease} in spin-orbit interaction-induced spin splitting with an increase in perpendicular electric field. Using front and back gates, we measure the spin splitting as a function of applied electric field while keeping the density constant. Our results are in contrast to the more familiar case of 2D electrons where spin splitting increases with electric field.
Spontaneous spiral formation in two-dimensional oscillatory media
Kettunen, Petteri; Amemiya, Takashi; Ohmori, Takao; Yamaguchi, Tomohiko
1999-08-01
Computational studies of pattern formation in a modified Oregonator model of the Belousov-Zhabotinsky reaction is described. Initially inactive two-dimensional reaction media with an immobilized catalyst is connected to a reservoir of fresh reactants through a set of discrete points distributed randomly over the interphase surface. It is shown that the diffusion of reactants combined with oscillatory reaction kinetics can give rise to spontaneous spiral formation and phase waves.
Canard solutions of two-dimensional singularly perturbed systems
Energy Technology Data Exchange (ETDEWEB)
Chen Xianfeng [Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200240 (China)]. E-mail: chenxf@sjtu.edu.cn; Yu Pei [Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200240 (China); Department of Applied Mathematics, University of Western Ontario London, Ont., N6A 5B7 (Canada); Han Maoan [Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang Weijiang [Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200240 (China)
2005-02-01
In this paper, some new lemmas on asymptotic analysis are established. We apply an asymptotic method to study generalized two-dimensional singularly perturbed systems with one parameter, whose critical manifold has an m-22 th-order degenerate extreme point. Certain sufficient conditions are obtained for the existence of canard solutions, which are the extension and correction of some existing results. Finally, one numerical example is given.
Bayer, Andreas; Unger, Andreas; Köhler, Bernd; Küster, Matthias; Dürsch, Sascha; Kissel, Heiko; Irwin, David A.; Bodem, Christian; Plappert, Nora; Kersten, Maik; Biesenbach, Jens
2016-03-01
The demand for high brightness fiber coupled diode laser devices in the multi kW power region is mainly driven by industrial applications for materials processing, like brazing, cladding and metal welding, which require a beam quality better than 30 mm x mrad and power levels above 3kW. Reliability, modularity, and cost effectiveness are key factors for success in the market. We have developed a scalable and modular diode laser architecture that fulfills these requirements through use of a simple beam shaping concept based on two dimensional stacking of tailored diode bars mounted on specially designed, tap water cooled heat sinks. The base element of the concept is a tailored diode laser bar with an epitaxial and lateral structure designed such that the desired beam quality in slow-axis direction can be realized without using sophisticated beam shaping optics. The optical design concept is based on fast-axis collimator (FAC) and slow-axis collimator (SAC) lenses followed by only one additional focusing optic for efficient coupling into a 400 μm fiber with a numerical aperture (NA) of 0.12. To fulfill the requirements of scalability and modularity, four tailored bars are populated on a reduced size, tap water cooled heat sink. The diodes on these building blocks are collimated simply via FAC and SAC. The building blocks can be stacked vertically resulting in a two-dimensional diode stack, which enables a compact design of the laser source with minimum beam path length. For a single wavelength, up to eight of these building blocks, implying a total of 32 tailored bars, can be stacked into a submodule, polarization multiplexed, and coupled into a 400 μm, 0.12NA fiber. Scalability into the multi kW region is realized by wavelength combining of replaceable submodules in the spectral range from 900 - 1100 nm. We present results of a laser source based on this architecture with an output power of more than 4 kW and a beam quality of 25 mm x mrad.
Quantum oscillations in quasi-two-dimensional conductors
Galbova, O
2002-01-01
The electronic absorption of sound waves in quasi-two-dimensional conductors in strong magnetic fields, is investigated theoretically. A longitudinal acoustic wave, propagating along the normal n-> to the layer of quasi-two-dimensional conductor (k-> = left brace 0,0,k right brace; u-> = left brace 0,0,u right brace) in magnetic field (B-> = left brace 0, 0, B right brace), is considered. The quasiclassical approach for this geometry is of no interest, due to the absence of interaction between electromagnetic and acoustic waves. The problem is of interest in strong magnetic field when quantization of the charge carriers energy levels takes place. The quantum oscillations in the sound absorption coefficient, as a function of the magnetic field, are theoretically observed. The experimental study of the quantum oscillations in quasi-two-dimensional conductors makes it possible to solve the inverse problem of determining from experimental data the extrema closed sections of the Fermi surface by a plane p sub z = ...
Observations of two-dimensional monolayer zinc oxide
Energy Technology Data Exchange (ETDEWEB)
Sahoo, Trilochan, E-mail: trilochansahoo@gmail.com [Department of Physics and Nanotechnology, SRM University, Kattankulathur, 603203 Tamilnadu (India); Nayak, Sanjeev K. [Institute of Physics, Martin Luther University Halle-Wittenberg, Von Seckendorff Platz 1, 06120 Halle (Germany); Chelliah, Pandian [Department of Physics and Nanotechnology, SRM University, Kattankulathur, 603203 Tamilnadu (India); Rath, Manasa K.; Parida, Bhaskar [Division of Advanced Materials Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of)
2016-03-15
Highlights: • Synthesis of planer ZnO nanostructure. • Observation of multilayered and monolayer ZnO. • DFT calculation of (10-10), (11-20) and (0 0 0 1) planes of ZnO. • Stability of non-polar (10-10) and (11-20) planes of ZnO. - Abstract: This letter reports the observations of planar two-dimensional ZnO synthesized using the hydrothermal growth technique. High-resolution transmission electron microscopy revealed the formation of a two-dimensional honeycomb lattice and aggregated structures of layered ZnO. The nonpolar (10-10) and (11-20) planes were present in the X-ray diffraction patterns, but the characteristic (0 0 0 1) peak of bulk ZnO was absent. The study found that nonpolar freestanding ZnO structures composed of a single or few layers may be more stable and may have a higher probability of formation than their polar counterparts. The stability of the nonpolar two-dimensional hexagonal ZnO slabs is supported by density functional theory studies.
Two-Dimensional Identification of Fetal Tooth Germs.
Seabra, Mariana; Vaz, Paula; Valente, Francisco; Braga, Ana; Felino, António
2017-03-01
To demonstrate the efficiency and applicability of two-dimensional ultrasonography in the identification of tooth germs and in the assessment of potential pathology. Observational, descriptive, cross-sectional study. Prenatal Diagnosis Unit of Centro Hospitalar de Vila Nova de Gaia / Espinho-Empresa Pública in Portugal. A total of 157 white pregnant women (median age, 32 years; range, 14 to 47 years) undergoing routine ultrasound exams. Description of the fetal tooth germs, as visualized by two-dimensional ultrasonography, including results from prior fetal biometry and detailed screening for malformations. In the first trimester group, ultrasonography identified 10 tooth germs in the maxilla and 10 tooth germs in the mandible in all fetuses except for one who presented eight maxillary tooth germs. This case was associated with a chromosomal abnormality (trisomy 13) with a bilateral cleft palate. In the second and third trimesters group, ultrasonography identified a larger range of tooth germs: 81.2% of fetuses showed 10 tooth germs in the maxilla and 85.0% of fetuses had 10 tooth germs in the mandible. Hypodontia was more prevalent in the maxilla than in the mandible, which led us to use qualitative two-dimensional ultrasonography to analyze the possible association between hypodontia and other variables such as fetal pathology, markers, head, nuchal, face, and spine. We recommend using this method as the first exam to evaluate fetal morphology and also to help establish accurate diagnosis of abnormalities in pregnancy.
H₂ sensing properties of two-dimensional zinc oxide nanostructures.
Tonezzer, Matteo; Iannotta, Salvatore
2014-05-01
In this work we have grown particular zinc oxide two-dimensional nanostructures which are essentially a series of hexagonal very thin sheets. The hexagonal wurtzite crystal structure gives them their peculiar shape, whose dimensions are few microns wide, with a thickness in the order of 25 nm. Such kind of nanostructure, grown by thermal oxidation of evaporated metallic zinc on a silica substrate, has been used to fabricate conductometric gas sensors, investigated then for hydrogen gas detection. The "depletion layer sensing mechanism" is clarified, explaining how the geometrical factors of one- and two-dimensional nanostructures affect their sensing parameters. The comparison with one-dimensional ZnO nanowires based structures shows that two-dimensional nanostructures are ideal for gas sensing, due to their tiny thickness, which is comparable to the depletion-layer thickness, and their large cross-section, which increases the base current, thus lowering the limit of detection. The response to H₂ has been found good even to sub-ppm concentrations, with response and recovery times shorter than 18s in the whole range of H₂ concentrations investigated (500 ppb-10 ppm). The limit of detection has been found around 200 ppb for H₂ gas even at relatively low working temperature (175 °C). Copyright © 2014 Elsevier B.V. All rights reserved.
Procedures for two-dimensional electrophoresis of proteins
Energy Technology Data Exchange (ETDEWEB)
Tollaksen, S.L.; Giometti, C.S.
1996-10-01
High-resolution two-dimensional gel electrophoresis (2DE) of proteins, using isoelectric focusing in the first dimension and sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) in the second, was first described in 1975. In the 20 years since those publications, numerous modifications of the original method have evolved. The ISO-DALT system of 2DE is a high-throughput approach that has stood the test of time. The problem of casting many isoelectric focusing gels and SDS-PAGE slab gels (up to 20) in a reproducible manner has been solved by the use of the techniques and equipment described in this manual. The ISO-DALT system of two-dimensional gel electrophoresis originated in the late 1970s and has been modified many times to improve its high-resolution, high-throughput capabilities. This report provides the detailed procedures used with the current ISO-DALT system to prepare, run, stain, and photograph two-dimensional gels for protein analysis.
Directory of Open Access Journals (Sweden)
D. A. Fetisov
2015-01-01
Full Text Available The controllability conditions are well known if we speak about linear stationary systems: a linear stationary system is controllable if and only if the dimension of the state vector is equal to the rank of the controllability matrix. The concept of the controllability matrix is extended to affine systems, but relations between affine systems controllability and properties of this matrix are more complicated. Various controllability conditions are set for affine systems, but they deal as usual either with systems of some special form or with controllability in some small neighborhood of the concerned point. An affine system is known to be controllable if the system is equivalent to a system of a canonical form, which is defined and regular in the whole space of states. In this case, the system is said to be feedback linearizable in the space of states. However there are examples, which illustrate that a system can be controllable even if it is not feedback linearizable in any open subset in the space of states. In this article we deal with such systems.Affine systems with two-dimensional control are considered. The system in question is assumed to be equivalent to a system of a quasicanonical form with two-dimensional zero dynamics which is defined and regular in the whole space of states. Therefore the controllability of the original system is equivalent to the controllability of the received system of a quasicanonical form. In this article the sufficient condition for an available solution of the terminal problem is proven for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. The condition is valid in the case of an arbitrary time interval and arbitrary initial and finite states of the system. Therefore the controllability condition is set for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. An example is given which illustrates how the proved
You, Youbo; Bai, Lijun; Dai, Ruwei; Xue, Ting; Zhong, Chongguang; Liu, Zhenyu; Wang, Hu; Feng, Yuanyuan; Wei, Wenjuan; Tian, Jie
2012-03-01
As an ancient therapeutic technique in Traditional Chinese Medicine, acupuncture has been used increasingly in modern society to treat a range of clinical conditions as an alternative and complementary therapy. However, acupoint specificity, lying at the core of acupuncture, still faces many controversies. Considering previous neuroimaging studies on acupuncture have mainly employed functional magnetic resonance imaging, which only measures the secondary effect of neural activity on cerebral metabolism and hemodynamics, in the current study, we adopted an electrophysiological measurement technique named magnetoencephalography (MEG) to measure the direct neural activity. 28 healthy college students were recruited in this study. We filtered MEG data into 5 consecutive frequency bands (delta, theta, alpha, beta and gamma band) and grouped 140 sensors into 10 main brain regions (left/right frontal, central, temporal, parietal and occipital regions). Fast Fourier Transformation (FFT) based spectral analysis approach was further performed to explore the differential band-limited power change patterns of acupuncture at Stomach Meridian 36 (ST36) using a nearby nonacupoint (NAP) as control condition. Significantly increased delta power and decreased alpha as well as beta power in bilateral frontal ROIs were observed following stimulation at ST36. Compared with ST36, decreased alpha power in left and right central, right parietal as well as right temporal ROIs were detected in NAP group. Our research results may provide additional evidence for acupoint specificity.
An Application of Spectral Kurtosis to Separate Hybrid Power Quality Events
Directory of Open Access Journals (Sweden)
Juan José González de la Rosa
2015-09-01
Full Text Available For the development of the future smart grid, the detection of power quality events is a key issue for the power system monitoring. Voltage sags, swells, harmonics (variations and interruptions, which produce large losses for commercial and industrial consumers, are the main events to be considered due to the sensitivity of equipment to these electrical anomalies. The steady-state events are even more frequently accompanied by transients, the discrimination and localization being far more exigent and requiring advanced signal separating tools to be incorporated in the measurement equipment. This paper shows the event detection performance of the spectral kurtosis as a signal separating tool in the frequency domain. The disturbances under test are hybrid signals resulting from the coupling between amplitude defects and non-desired higher frequencies. Being a fourth-order spectrum, the kurtosis is confirmed as a noise-resistant tool that enhances impulsiveness, therefore characterizing the electrical anomalies. In the beginning of the analysis, the voltage sag is established as a reference; then, the disturbances (oscillatory transients and harmonics are coupled at the starting and ending instants of the sag, resulting in complex hybrid events. The results show that the spectral kurtosis enhances the detection Energies 2015, 8 9778 of both types of events (steady state and transients, which are outlined in a bump shape in the fourth-order frequency pattern and centered in the main carrier frequency. Indeed, while the oscillatory transients are associated with softer and lower-amplitude peaks, the harmonics correspond to crisper and higher ones. As these mixed electrical faults are very common in the actual power grid, the article postulates the higher-order spectra to be implemented in prospective online measurement instruments.
Foist, Rod B; Schulze, H Georg; Ivanov, Andre; Turner, Robin F B
2011-05-01
Two-dimensional correlation spectroscopy (2D-COS) is a powerful spectral analysis technique widely used in many fields of spectroscopy because it can reveal spectral information in complex systems that is not readily evident in the original spectral data alone. However, noise may severely distort the information and thus limit the technique's usefulness. Consequently, noise reduction is often performed before implementing 2D-COS. In general, this is implemented using one-dimensional (1D) methods applied to the individual input spectra, but, because 2D-COS is based on sets of successive spectra and produces 2D outputs, there is also scope for the utilization of 2D noise-reduction methods. Furthermore, 2D noise reduction can be applied either to the original set of spectra before performing 2D-COS ("pretreatment") or on the 2D-COS output ("post-treatment"). Very little work has been done on post-treatment; hence, the relative advantages of these two approaches are unclear. In this work we compare the noise-reduction performance on 2D-COS of pretreatment and post-treatment using 1D (wavelets) and 2D algorithms (wavelets, matrix maximum entropy). The 2D methods generally outperformed the 1D method in pretreatment noise reduction. 2D post-treatment in some cases was superior to pretreatment and, unexpectedly, also provided correlation coefficient maps that were similar to 2D correlation spectroscopy maps but with apparent better contrast.
Arbogast, Luke W; Delaglio, Frank; Schiel, John E; Marino, John P
2017-11-07
Two-dimensional (2D) 1 H- 13 C methyl NMR provides a powerful tool to probe the higher order structure (HOS) of monoclonal antibodies (mAbs), since spectra can readily be acquired on intact mAbs at natural isotopic abundance, and small changes in chemical environment and structure give rise to observable changes in corresponding spectra, which can be interpreted at atomic resolution. This makes it possible to apply 2D NMR spectral fingerprinting approaches directly to drug products in order to systematically characterize structure and excipient effects. Systematic collections of NMR spectra are often analyzed in terms of the changes in specifically identified peak positions, as well as changes in peak height and line widths. A complementary approach is to apply principal component analysis (PCA) directly to the matrix of spectral data, correlating spectra according to similarities and differences in their overall shapes, rather than according to parameters of individually identified peaks. This is particularly well-suited for spectra of mAbs, where some of the individual peaks might not be well resolved. Here we demonstrate the performance of the PCA method for discriminating structural variation among systematic sets of 2D NMR fingerprint spectra using the NISTmAb and illustrate how spectral variability identified by PCA may be correlated to structure.
Comprehensive two-dimensional liquid chromatography for polyphenol analysis in foodstuffs.
Cacciola, Francesco; Farnetti, Sara; Dugo, Paola; Marriott, Philip John; Mondello, Luigi
2017-01-01
Polyphenols are a class of plant secondary metabolites that are recently drawing a special interest because of their broad spectrum of pharmacological effects. As they are characterized by an enormous structural variability, the identification of these molecules in food samples is a difficult task, and sometimes having only a limited number of commercially available reference materials is not of great help. One-dimensional liquid chromatography is the most widely applied analytical approach for their analysis. In particular, the hyphenation of liquid chromatography to mass spectrometry has come to play an influential role by allowing relatively fast tentative identification and accurate quantification of polyphenolic compounds at trace levels in vegetable media. However, when dealing with very complex real-world food samples, a single separation system often does not provide sufficient resolving power for attaining rewarding results. Comprehensive two-dimensional liquid chromatography is a technique of great analytical impact, since it offers much higher peak capacities than separations in a single dimension. In the present review, we describe applications in the field of comprehensive two-dimensional liquid chromatography for polyphenol analysis in real-world food samples. Comprehensive two-dimensional liquid chromatography applications to nonfood matrices fall outside the scope of the current report and will not be discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
2D Spatial Frequency Considerations in Comparing 1D Power Spectral Density Measurements
International Nuclear Information System (INIS)
Takacs, P.Z.; Barber, S.; Church, E.L.; Kaznatcheev, K.; McKinney, W.R.; Yashchuk, V.Y.
2010-01-01
The frequency footprint of ID and 2D profiling instruments needs to be carefully considered in comparing ID surface roughness spectrum measurements made by different instruments. Contributions from orthogonal direction frequency components can not be neglected. The use of optical profiling instruments is ubiquitous in the measurement of the roughness of optical surfaces. Their ease-of-use and non-contact measurement method found widespread use in the optics industry for measuring the quality of delicate optical surfaces. Computerized digital data acquisition with these instruments allowed for quick and easy calculation of surface roughness statistics, such as root-mean-square (RMS) roughness. The computing power of the desktop computer allowed for the rapid conversion of spatial domain data into the frequency domain, enabling the application of sophisticated signal processing techniques to be applied to the analysis of surface roughness, the most powerful of which is the power spectral density (PSP) function. Application of the PSD function to surface statistics introduced the concept of 'bandwidth-limited' roughness, where the value of the RMS roughness depends critically upon the spatial frequency response of the instrument. Different instruments with different spatial frequency response characteristics give different answers when measuring the same surface.
On the causes of spectral enhancements in solar wind power spectra
Unti, T.; Russell, C. T.
1976-01-01
Enhancements in power spectra of the solar-wind ion flux in the frequency neighborhood of 0.5 Hz had been noted by Unti et al. (1973). It was speculated that these were due to convected small-scale density irregularities. In this paper, 54 flux spectra calculated from OGO 5 data are examined. It is seen that the few prominent spectral peaks which occur were not generated by density irregularities, but were due to several different causes, including convected discontinuities and propagating transverse waves. A superposition of many spectra, however, reveals a moderate enhancement at a frequency corresponding to convected features with a correlation length of a proton gyroradius, consistent with the results of Neugebauer (1975).
A Hard X-Ray Power-Law Spectral Cutoff in Centaurus X-4
DEFF Research Database (Denmark)
Chakrabarty, Deepto; Tomsick, John A.; Grefenstette, Brian W.
2015-01-01
The low-mass X-ray binary Cen X-4 is the brightest and closest (hard power-law tail of unknown...... origin. We report here on a simultaneous observation of Cen X-4 with NuSTAR (3-79 keV) and XMM-Newton (0.3-10 keV) in 2013 January, providing the first sensitive hard X-ray spectrum of a quiescent neutron star transient. The 0.3-79 keV luminosity was 1.1 x 10^(33) erg/s (for D=1kpc), with around 60...... percent in the thermal component. We clearly detect a cutoff of the hard spectral tail above 10 keV, the first time such a feature has been detected in this source class. Comptonization and synchrotron shock origins for the hard X-ray emission are ruled out on physical grounds. However, the hard X...
Lee, Jinyong; Lee, Hyun Sook; Kim, Sunghyun; Hwang, Do Guwn
2012-05-01
We have compared the aging index of the second derivatives of photoplethysmography (PPG) with the power spectral density (PSD) from PPG signals to investigate the effect of a strong pulsed electromagnetic field (PEMF) on the improvement of vascularization in the capillary vessels of the finger. The PEMF stimulator was composed of an elliptical coil of 10 turns and 12 cm × 5 cm, and its maximum field and transition time were 0.48 T and 0.102 ms, respectively. It is not easy to analyze the stimulus effect of blood vessel from raw signals of PPG, and aging index of vascularization from the second derivatives of PPG. A PSD analysis in the frequency domain was introduced to reduce artifacts due to change in the posture of the subjects, the environment, acoustic noise, etc. For ages in the 50s, the PSD analysis before and after PEMF stimulus was rather more reliable than the second derivatives of the PPG.
PSD computations using Welch's method. [Power Spectral Density (PSD)
Energy Technology Data Exchange (ETDEWEB)
Solomon, Jr, O M
1991-12-01
This report describes Welch's method for computing Power Spectral Densities (PSDs). We first describe the bandpass filter method which uses filtering, squaring, and averaging operations to estimate a PSD. Second, we delineate the relationship of Welch's method to the bandpass filter method. Third, the frequency domain signal-to-noise ratio for a sine wave in white noise is derived. This derivation includes the computation of the noise floor due to quantization noise. The signal-to-noise ratio and noise flood depend on the FFT length and window. Fourth, the variance the Welch's PSD is discussed via chi-square random variables and degrees of freedom. This report contains many examples, figures and tables to illustrate the concepts. 26 refs.
Enders, Philip; Adler, Werner; Kiessling, David; Weber, Vincent; Schaub, Friederike; Hermann, Manuel M; Dietlein, Thomas; Cursiefen, Claus; Heindl, Ludwig M
2018-03-24
To characterize the two-dimensional parameter Bruch's membrane opening minimum rim area (BMO-MRA) in spectral domain optical coherence tomography (SD-OCT) of the optic nerve head (ONH) compared to minimum rim width (BMO-MRW) and retinal nerve fibre layer (RNFL) thickness in a large patient cohort. Case-control, cross-sectional study of 705 eyes of 445 participants. A total of 449 eyes with glaucoma, 67 eyes with ocular hypertension and 189 healthy controls, underwent SD-OCT and confocal laser scanning tomography (CSLT), visual field testing and clinical examination. Morphometric ONH parameters, visual field function and diagnostic power were compared. Main outcome measures were SD-OCT-derived BMO-MRA, BMO-MRW, RNFL thickness and CSLT-derived rim area (DM-RA). Mean ONH area was 2.11 ± 0.57 mm 2 ; mean BMO area was 1.89 ± 0.45 mm 2 . Correlation of mean deviation in visual field to morphometric parameters was ρ = 0.70, (p 0.05), while DM-RA correlated significantly worse (ρ = 0.55; p receiver operating characteristics, the calculated area under the curve (AUC) and sensitivity at 90% specificity to differentiate glaucoma were 0.87% and 70.1% for BMO-MRA, 0.86% and 68.1% for RNFL thickness, 0.84% and 66.0% for BMO-MRW, 0.82% and 51.3% for DM-RA. In a heterogenous clinical cohort of glaucoma patients, all analysed SD-OCT parameters excel DM-RA of CSLT. The two-dimensional parameter BMO-MRA shows comparable levels of diagnostic power to detect glaucoma compared to established parameters BMO-MRW and RNFL thickness. Given higher comparability between ONH sizes, BMO-MRA might become an additional standard tool in SD-OCT imaging for glaucoma. © 2018 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.
A HARD X-RAY POWER-LAW SPECTRAL CUTOFF IN CENTAURUS X-4
Energy Technology Data Exchange (ETDEWEB)
Chakrabarty, Deepto; Nowak, Michael A. [MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Tomsick, John A.; Boggs, Steven E.; Craig, William W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Grefenstette, Brian W.; Fürst, Felix; Harrison, Fiona A.; Rana, Vikram [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Psaltis, Dimitrios [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Bachetti, Matteo; Barret, Didier [Observatoire Midi-Pyrénées, Université de Toulouse III - Paul Sabatier, F-31400 Toulouse (France); Christensen, Finn E. [Division of Astrophysics, National Space Institute, Technical University of Denmark, DK-2800 Lyngby (Denmark); Hailey, Charles J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Kaspi, Victoria M. [Department of Physics, McGill University, Montreal, PQ H3A 2T8 (Canada); Miller, Jon M. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Wik, Daniel R.; Zhang, William W. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wilms, Jörn, E-mail: deepto@mit.edu [Dr. Karl-Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Universität Erlangen-Nürnberg, D-96049 Bamberg (Germany)
2014-12-20
The low-mass X-ray binary (LMXB) Cen X-4 is the brightest and closest (<1.2 kpc) quiescent neutron star transient. Previous 0.5-10 keV X-ray observations of Cen X-4 in quiescence identified two spectral components: soft thermal emission from the neutron star atmosphere and a hard power-law tail of unknown origin. We report here on a simultaneous observation of Cen X-4 with NuSTAR (3-79 keV) and XMM-Newton (0.3-10 keV) in 2013 January, providing the first sensitive hard X-ray spectrum of a quiescent neutron star transient. The 0.3-79 keV luminosity was 1.1×10{sup 33} D{sub kpc}{sup 2} erg s{sup –1}, with ≅60% in the thermal component. We clearly detect a cutoff of the hard spectral tail above 10 keV, the first time such a feature has been detected in this source class. We show that thermal Comptonization and synchrotron shock origins for the hard X-ray emission are ruled out on physical grounds. However, the hard X-ray spectrum is well fit by a thermal bremsstrahlung model with kT{sub e} = 18 keV, which can be understood as arising either in a hot layer above the neutron star atmosphere or in a radiatively inefficient accretion flow. The power-law cutoff energy may be set by the degree of Compton cooling of the bremsstrahlung electrons by thermal seed photons from the neutron star surface. Lower thermal luminosities should lead to higher (possibly undetectable) cutoff energies. We compare Cen X-4's behavior with PSR J1023+0038, IGR J18245–2452, and XSS J12270–4859, which have shown transitions between LMXB and radio pulsar modes at a similar X-ray luminosity.
Statistical mechanics of two-dimensional and geophysical flows
International Nuclear Information System (INIS)
Bouchet, Freddy; Venaille, Antoine
2012-01-01
The theoretical study of the self-organization of two-dimensional and geophysical turbulent flows is addressed based on statistical mechanics methods. This review is a self-contained presentation of classical and recent works on this subject; from the statistical mechanics basis of the theory up to applications to Jupiter’s troposphere and ocean vortices and jets. Emphasize has been placed on examples with available analytical treatment in order to favor better understanding of the physics and dynamics. After a brief presentation of the 2D Euler and quasi-geostrophic equations, the specificity of two-dimensional and geophysical turbulence is emphasized. The equilibrium microcanonical measure is built from the Liouville theorem. Important statistical mechanics concepts (large deviations and mean field approach) and thermodynamic concepts (ensemble inequivalence and negative heat capacity) are briefly explained and described. On this theoretical basis, we predict the output of the long time evolution of complex turbulent flows as statistical equilibria. This is applied to make quantitative models of two-dimensional turbulence, the Great Red Spot and other Jovian vortices, ocean jets like the Gulf-Stream, and ocean vortices. A detailed comparison between these statistical equilibria and real flow observations is provided. We also present recent results for non-equilibrium situations, for the studies of either the relaxation towards equilibrium or non-equilibrium steady states. In this last case, forces and dissipation are in a statistical balance; fluxes of conserved quantity characterize the system and microcanonical or other equilibrium measures no longer describe the system.
Two-dimensional polyacrylamide gel electrophoresis of intracellular proteins
International Nuclear Information System (INIS)
Ojima, N.; Sakamoto, T.; Yamashita, M.
1996-01-01
Since two-dimensional electrophoresis was established by O'Farrell for analysis of intracellular proteins of Escherichia coli, it has been applied to separation of proteins of animal cells and tissues, and especially to identification of stress proteins. Using this technique, proteins are separated by isoelectric focusing containing 8 m urea in the first dimension and by SDS-PAGE in the second dimension. The gels are stained with Coomassie Blue R-250 dye, followed by silver staining. In the case of radio-labeled proteins, the gels are dried and then autoradiographed. In order to identify a specific protein separated by two-dimensional electrophoresis, a technique determining the N-terminal amino acid sequence of the protein has been developed recently. After the proteins in the gel were electrotransferred to a polyvinylidene difluoride membrane, the membrane was stained for protein with Commassie Blue and a stained membrane fragment was applied to a protein sequencer. Our recent studies demonstrated that fish cells newly synthesized various proteins in response to heat shock, cold nd osmotic stresses. For example, when cellular proteins extracted from cold-treated rainbow trout cells were subjected to two-dimensional gel electrophoresis, the 70 kDa protein was found to be synthesized during the cold-treatment. N-Terminal sequence analysis showed that the cold-inducible protein was a homolog of mammalian valosin-containing protein and yeast cell division cycle gene product CDC48p. Furthermore, the sequence data were useful for preparing PCR primers and a rabbit antibody against a synthetic peptide to analyze a role for the protein in the function of trout cells and mechanisms for regulation
Shchesnovich, Valery S; Desyatnikov, Anton S; Kivshar, Yuri S
2008-09-01
We study, analytically and numerically, the dynamics of interband transitions in two-dimensional hexagonal periodic photonic lattices. We develop an analytical approach employing the Bragg resonances of different types and derive the effective multi-level models of the Landau-Zener-Majorana type. For two-dimensional periodic potentials without a tilt, we demonstrate the possibility of the Rabi oscillations between the resonant Fourier amplitudes. In a biased lattice, i.e., for a two-dimensional periodic potential with an additional linear tilt, we identify three basic types of the interband transitions or Zener tunnelling. First, this is a quasi-one-dimensional tunnelling that involves only two Bloch bands and occurs when the Bloch index crosses the Bragg planes away from one of the high-symmetry points. In contrast, at the high-symmetry points (i.e., at the M and Gamma points), the Zener tunnelling is essentially two-dimensional, and it involves either three or six Bloch bands being described by the corresponding multi-level Landau-Zener-Majorana systems. We verify our analytical results by numerical simulations and observe an excellent agreement. Finally, we show that phase dislocations, or optical vortices, can tunnel between the spectral bands preserving their topological charge. Our theory describes the propagation of light beams in fabricated or optically-induced two-dimensional photonic lattices, but it can also be applied to the physics of cold atoms and Bose-Einstein condensates tunnelling in tilted two-dimensional optical potentials and other types of resonant wave propagation in periodic media.
Graphene and Two-Dimensional Materials for Optoelectronic Applications
Directory of Open Access Journals (Sweden)
Andreas Bablich
2016-03-01
Full Text Available This article reviews optoelectronic devices based on graphene and related two-dimensional (2D materials. The review includes basic considerations of process technology, including demonstrations of 2D heterostructure growth, and comments on the scalability and manufacturability of the growth methods. We then assess the potential of graphene-based transparent conducting electrodes. A major part of the review describes photodetectors based on lateral graphene p-n junctions and Schottky diodes. Finally, the progress in vertical devices made from 2D/3D heterojunctions, as well as all-2D heterostructures is discussed.
Network patterns in exponentially growing two-dimensional biofilms
Zachreson, Cameron; Yap, Xinhui; Gloag, Erin S.; Shimoni, Raz; Whitchurch, Cynthia B.; Toth, Milos
2017-10-01
Anisotropic collective patterns occur frequently in the morphogenesis of two-dimensional biofilms. These patterns are often attributed to growth regulation mechanisms and differentiation based on gradients of diffusing nutrients and signaling molecules. Here, we employ a model of bacterial growth dynamics to show that even in the absence of growth regulation or differentiation, confinement by an enclosing medium such as agar can itself lead to stable pattern formation over time scales that are employed in experiments. The underlying mechanism relies on path formation through physical deformation of the enclosing environment.
Two-dimensional carbon fundamental properties, synthesis, characterization, and applications
Yihong, Wu; Ting, Yu
2013-01-01
After a brief introduction to the fundamental properties of graphene, this book focuses on synthesis, characterization and application of various types of two-dimensional (2D) nanocarbons ranging from single/few layer graphene to carbon nanowalls and graphene oxides. Three major synthesis techniques are covered: epitaxial growth of graphene on SiC, chemical synthesis of graphene on metal, and chemical vapor deposition of vertically aligned carbon nanosheets or nanowalls. One chapter is dedicated to characterization of 2D nanocarbon using Raman spectroscopy. It provides extensive coverage for a
Two-dimensional Lagrangian simulation of suspended sediment
Schoellhamer, David H.
1988-01-01
A two-dimensional laterally averaged model for suspended sediment transport in steady gradually varied flow that is based on the Lagrangian reference frame is presented. The layered Lagrangian transport model (LLTM) for suspended sediment performs laterally averaged concentration. The elevations of nearly horizontal streamlines and the simulation time step are selected to optimize model stability and efficiency. The computational elements are parcels of water that are moved along the streamlines in the Lagrangian sense and are mixed with neighboring parcels. Three applications show that the LLTM can accurately simulate theoretical and empirical nonequilibrium suspended sediment distributions and slug injections of suspended sediment in a laboratory flume.
Blind deconvolution of two-dimensional complex data
Energy Technology Data Exchange (ETDEWEB)
Ghiglia, D.C.; Romero, L.A.
1994-01-01
Inspired by the work of Lane and Bates on automatic multidimensional deconvolution, the authors have developed a systematic approach and an operational code for performing the deconvolution of multiply-convolved two-dimensional complex data sets in the absence of noise. They explain, in some detail, the major algorithmic steps, where noise or numerical errors can cause problems, their approach in dealing with numerical rounding errors, and where special noise-mitigating techniques can be used toward making blind deconvolution practical. Several examples of deconvolved imagery are presented, and future research directions are noted.
Two-dimensional collapse calculations of cylindrical clouds
International Nuclear Information System (INIS)
Bastien, P.; Mitalas, R.
1979-01-01
A two-dimensional hydrodynamic computer code has been extensively modified and expanded to study the collapse of non-rotating interstellar clouds. The physics and the numerical methods involved are discussed. The results are presented and discussed in terms of the Jeans number. The critical Jeans number for collapse of non-rotating cylindrical clouds whose length is the same as their diameter is 1.00. No evidence for fragmentation has been found for these clouds, but fragmentation seems quite likely for more elongated cylindrical clouds. (author)
Focused two-dimensional antiscatter grid for mammography
International Nuclear Information System (INIS)
Makarova, O.V.; Moldovan, N.; Tang, C.-M.; Mancini, D.C.; Divan, R.; Zyryanov, V.N.; Ryding, D.C.; Yaeger, J.; Liu, C.
2002-01-01
We are developing freestanding high-aspect-ratio, focused, two-dimensional antiscatter grids for mammography using deep x-ray lithography and copper electroforming. The exposure is performed using x-rays from bending magnet beamline 2-BM at the Advanced Photon Source (APS) of Argonne National Laboratory. A 2.8-mm-thick prototype freestanding copper antiscatter grid with 25 (micro)m-wide parallel cell walls and 550 (micro)m periodicity has been fabricated. The progress in developing a dynamic double-exposure technique to create the grid with the cell walls aligned to a point x-ray source of the mammography system is discussed
Optical Two Dimensional Fourier Transform Spectroscopy of Layered Metal Dichalcogenides
Dey, P.; Paul, J.; Stevens, C. E.; Kovalyuk, Z. D.; Kudrynskyi, Z. R.; Romero, A. H.; Cantarero, A.; Hilton, D. J.; Shan, J.; Karaiskaj, D.; Z. D. Kovalyuk; Z. R. Kudrynskyi Collaboration; A. H. Romero Collaboration; A. Cantarero Collaboration; D. J. Hilton Collaboration; J. Shan Collaboration
2015-03-01
Nonlinear two-dimensional Fourier transform (2DFT) measurements were used to study the mechanism of excitonic dephasing and probe the electronic structure of the excitonic ground state in layered metal dichalcogenides. Temperature-dependent 2DFT measurements were performed to probe exciton-phonon interactions. Excitation density dependent 2DFT measurements reveal exciton-exciton and exciton-carrier scattering, and the lower limit for the homogeneous linewidth of excitons on positively and negatively doped samples. U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0012635.
Quantum computation with two-dimensional graphene quantum dots
International Nuclear Information System (INIS)
Li Jie-Sen; Li Zhi-Bing; Yao Dao-Xin
2012-01-01
We study an array of graphene nano sheets that form a two-dimensional S = 1/2 Kagome spin lattice used for quantum computation. The edge states of the graphene nano sheets are used to form quantum dots to confine electrons and perform the computation. We propose two schemes of bang-bang control to combat decoherence and realize gate operations on this array of quantum dots. It is shown that both schemes contain a great amount of information for quantum computation. The corresponding gate operations are also proposed. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Quantum algebras for two-dimensional Cayley-Klein Geometries
International Nuclear Information System (INIS)
Herranz, F.J.; Ballesteros, A.; Olmo, M.A. del; Santander, M.
1993-01-01
Simultaneous quantization of the quasi-simple groups of motions of the nine two-dimensional Cayley-Klein geometries is obtained by defining a deformed Hopf structure on their enveloping algebras. The spaces of points and lines of the classical CK geometries are homogeneous spaces of their motion groups. Both the well known classical non-euclidean geometries and the (1+1) kinematical geometries are included within this scheme. Their corresponding quantum algebras preserve a scheme of contractions, symmetries and dualities based on the classical one. (Author)
Graphene surface plasmon bandgap based on two dimensional Si gratings
Directory of Open Access Journals (Sweden)
Yueke Wang
2017-11-01
Full Text Available A graphene/Si system, which is composed of a two-dimensional subwavelength silicon gratings and a graphene sheet, is designed to realize the complete band gap in infrared region for graphene surface plasmons (GSPs theoretically. The complete band gap originates from the strong scatterings, which is caused by the periodical distribution of effective refractive index. The band structure has been calculated using the plane wave expansion method, and full wave numerical simulations are conducted by finite element method. Thanks to the tunable permittivity of graphene, the band structure can be easily tuned, which provides a way to manipulate in-plane GSPs’ propagation.
Two-Dimensional Electron System in Electromagnetic Radiation Field
Lungu, Radu Paul; Manolescu, Andrei
We consider a two-dimensional electron gas in the presence of a monochromatic linear polarized electromagnetic field, within the Floquet formalism. The Floquet states have a simple relation with the energy eigenstates in the absence of the field. Therefore the single-particle and the two-particle Green functions of the many-body system with Coulomb interactions, in the radiation field, can be formally calculated by the standard diagrammatic techniques, as for the conservative system. We derive the elementary excitations of quasi-particle type, the plasma dispersion relation, and the ground state quasi-energy, and we relate them to the corresponding results for the conservative system.
Saddle-points of a two dimensional random lattice theory
International Nuclear Information System (INIS)
Pertermann, D.
1985-07-01
A two dimensional random lattice theory with a free massless scalar field is considered. We analyse the field theoretic generating functional for any given choice of positions of the lattice sites. Asking for saddle-points of this generating functional with respect to the positions we find the hexagonal lattice and a triangulated version of the hypercubic lattice as candidates. The investigation of the neighbourhood of a single lattice site yields triangulated rectangles and regular polygons extremizing the above generating functional on the local level. (author)
Two-dimensional N = 2 Super-Yang-Mills Theory
Directory of Open Access Journals (Sweden)
August Daniel
2018-01-01
Full Text Available Supersymmetry is one of the possible scenarios for physics beyond the standard model. The building blocks of this scenario are supersymmetric gauge theories. In our work we study the N = 1 Super-Yang-Mills (SYM theory with gauge group SU(2 dimensionally reduced to two-dimensional N = 2 SYM theory. In our lattice formulation we break supersymmetry and chiral symmetry explicitly while preserving R symmetry. By fine tuning the bar-mass of the fermions in the Lagrangian we construct a supersymmetric continuum theory. To this aim we carefully investigate mass spectra and Ward identities, which both show a clear signal of supersymmetry restoration in the continuum limit.
Two-dimensional Kaehler Einstein spaces and gravitational instantons
International Nuclear Information System (INIS)
Tseytlin, A.A.
1980-01-01
A new class of solutions of the euclidean Einstein equations with Λ-term ( A-class ) is found by solving the complex two-dimensional Kaehler Einstein equations with the following realization of complex metrics. The A-Class includes two gravitational instantons already known: the CP 2 and the Eguchi-Hanson metric, and allows a U(1)-generalized spin structure. It is shown that all Einstein euclidean two-axial Bianchi type IX metrics are exhausted by the Taub-NUT-de Sitter family and the A-class. (orig.)
Quantum skyrmions in two-dimensional chiral magnets
Takashima, Rina; Ishizuka, Hiroaki; Balents, Leon
2016-10-01
We study the quantum mechanics of magnetic skyrmions in the vicinity of the skyrmion-crystal to ferromagnet phase boundary in two-dimensional magnets. We show that the skyrmion excitation has an energy dispersion that splits into multiple bands due to the combination of magnus force and the underlying lattice. Condensation of the skyrmions can give rise to an intermediate phase between the skyrmion crystal and ferromagnet: a quantum liquid, in which skyrmions are not spatially localized. We show that the critical behavior depends on the spin size S and the topological number of the skyrmion. Experimental signatures of quantum skyrmions in inelastic neutron-scattering measurements are also discussed.
Thermal neutron diffraction on two-dimensional lattices
International Nuclear Information System (INIS)
Stern, T.
1974-06-01
This thesis deals with the problem of neutron diffraction from a two-dimensional lattice. The neutron spin is not taken into account. Firstly the scalar wave field is treated by means of differential equations (Helmholtz) and secondly by the equivalent integral equation formulation (Kirchoff-Weber). Finally, using the methods of the Green function, the reflected and transmitted wave fields are represented as integral transformations of a certain source function. In respect to the calculation of the amplitudes of the diffraction waves the third method seems to be the best one for the purpose of the physical interpretation and the applicability of numerical methods. (C.R.)
Stable corrugated state of the two-dimensional electron gas
International Nuclear Information System (INIS)
Mendez-Moreno, R.M.; Moreno, M.; Ortiz, M.A.
1991-01-01
A corrugated and stable ground state is found for the two-dimensional electron gas in both the normal paramagnetic and the fully polarized phases. The self-consistent Hartree-Fock method is used with a modulated set of trial wave functions within the deformable jellium model. The results for high metallic densities reproduce the usual noncorrugated ferromagnetic electron-gas behavior. A transition to a paramagnetic corrugated state for values of r s ∼6.5 is predicted. At lower densities r s ∼30, a second transition to a corrugated ferromagnetic phase is suggested
Quantum wells physics and electronics of two-dimensional systems
Shik, A
1998-01-01
This invaluable book is devoted to the physics, technology and device applications of semiconductor structures with ultrathin layers where the electronic properties are governed by the quantum-mechanical laws. Such structures called quantum wells or structures with the two-dimensional electron gas, have become one of the most actively investigated objects in modern solid state physics. Electronic properties of quantum wells differ dramatically from those of bulk semiconductors, which allows one to observe new types of physical phenomena, such as the quantum Hall effect and many other so-far-un
Pattern formation in two-dimensional square-shoulder systems
International Nuclear Information System (INIS)
Fornleitner, Julia; Kahl, Gerhard
2010-01-01
Using a highly efficient and reliable optimization tool that is based on ideas of genetic algorithms, we have systematically studied the pattern formation of the two-dimensional square-shoulder system. An overwhelming wealth of complex ordered equilibrium structures emerge from this investigation as we vary the shoulder width. With increasing pressure three structural archetypes could be identified: cluster lattices, where clusters of particles occupy the sites of distorted hexagonal lattices, lane formation, and compact particle arrangements with high coordination numbers. The internal complexity of these structures increases with increasing shoulder width.
Field analysis of two-dimensional focusing grating
Borsboom, P.P.; Frankena, H.J.
1995-01-01
The method that we have developed [P-P. Borsboom, Ph.D. dissertation (Delft University of Technology, Delft, The Netherlands); P-P. Borsboom and H. J. Frankena, J. Opt. Soc. Am. A 12, 1134–1141 (1995)] is successfully applied to a two-dimensional focusing grating coupler. The field in the focal region has been determined for symmetrical chirped gratings consisting of as many as 124 corrugations. The intensity distribution in the focal region agrees well with the approximate predictions of geo...
The Penalty Cost Functional for the Two-Dimensional
Directory of Open Access Journals (Sweden)
Victor Onomza WAZIRI
2006-07-01
Full Text Available This paper constructs the penalty cost functional for optimizing the two-dimensional control operator of the energized wave equation. In some multiplier methods such as the Lagrange multipliers and Pontrygean maximum principle, the cost of merging the constraint equation to the integral quadratic objective functional to obtain an unconstraint equation is normally guessed or obtained from the first partial derivatives of the unconstrained equation. The Extended Conjugate Gradient Method (ECGM necessitates that the penalty cost be sequentially obtained algebraically. The ECGM problem contains a functional which is completely given in terms of state and time spatial dependent variables.
Quasi-integrability and two-dimensional QCD
International Nuclear Information System (INIS)
Abdalla, E.; Mohayaee, R.
1996-10-01
The notion of integrability in two-dimensional QCD is discussed. We show that in spite of an infinite number of conserved charges, particle production is not entirely suppressed. This phenomenon, which we call quasi-integrability, is explained in terms of quantum corrections to the combined algebra of higher-conserved and spectrum-generating currents. We predict the qualitative form of particle production probabilities and verify that they are in agreement with numerical data. We also discuss four-dimensional self-dual Yang-Mills theory in the light of our results. (author). 25 refs, 4 figs, 1 tab
Two-dimensional fermionic correlations in topologically nontrivial backgrounds
Energy Technology Data Exchange (ETDEWEB)
Manias, M.V.; Naon, C.M.; Trobo, M.L. (Departamento de Fisica, Universidad Nacional de La Plata, Casilla de Correo No. 67, 1900 La Plata, Buenos Aires (Argentina))
1993-04-15
By using a path-integral approach to the study of two-dimensional massless fermionic models in nontrivial sectors, we compute certain special correlation functions which are nonvanishing only when nontrivial topology is taken into account. In particular, we derive the first explicit expression for the so-called nonminimal Green's function. We introduce one specific topological charge distribution for which this correlation function takes a simple form. We also comment on the application of our results to the analysis of massive fermions in topological backgrounds.
On bosonization ambiguities of two dimensional quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Dias, S.A.; Silva Neto, M.B.
1996-02-01
We study bosonization ambiguities in two dimensional quantum electrodynamics in the presence and in the absence of topologically charged gauge fields. The computation of fermionic correlation functions gives us a mechanism to fix the ambiguities in nontrivial topologies, provided that we do not allow changes of sector as we evaluate functional integrals. This removes an infinite arbitrariness from the theory. In the case of trivial topologies, we find upper and lower bounds for the Jackiw-Rajaraman parameter, corresponding to the limiting cases of regularizations which preserve gauge or chiral symmetry. (author). 19 refs.
Ultrafast Charge Transfer Visualized by Two-Dimensional Electronic Spectroscopy
Directory of Open Access Journals (Sweden)
Mančal T.
2013-03-01
Full Text Available Two-dimensional electronic spectroscopy (2D-ES is used to investigate ultrafast excited-state dynamics in a lutetium bisphthalocyanine dimer. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra. The combination of density matrix propagation and quantum chemical calculations results in a molecular view of the charge transfer dynamics and highlights the role of the counter-ion in providing an energetic perturbation which promotes charge transfer across the complex.
Two-dimensional Bose and Fermi gases beyond weak coupling
França, Guilherme; LeClair, André; Squires, Joshua
2017-07-01
Using a formalism based on the two-body S-matrix we study two-dimensional Bose and Fermi gases with both attractive and repulsive interactions. Approximate analytic expressions, valid at weak coupling and beyond, are developed and applied to the Berezinskii-Kosterlitz-Thouless (BKT) transition. We successfully recover the correct logarithmic functional form of the critical chemical potential and density for the Bose gas. For fermions, the BKT critical temperature is calculated in BCS and BEC regimes through consideration of Tan’s contact.
Mass/Count Variation: A Mereological, Two-Dimensional Semantics
Directory of Open Access Journals (Sweden)
Peter R Sutton
2016-12-01
Full Text Available We argue that two types of context are central to grounding the semantics for the mass/count distinction. We combine and develop the accounts of Rothstein (2010 and Landman (2011, which emphasize (non-overlap at a context. We also adopt some parts of Chierchia’s (2010 account which uses precisifying contexts. We unite these strands in a two-dimensional semantics that covers a wide range of the puzzling variation data in mass/count lexicalization. Most importantly, it predicts where we should expect to find such variation for some classes of nouns but not for others, and also explains why.
Anisotropic mass density by two-dimensional acoustic metamaterials
Energy Technology Data Exchange (ETDEWEB)
Torrent, Daniel; Sanchez-Dehesa, Jose [Wave Phenomena Group, Department of Electronic Engineering, Polytechnic University of Valencia, C/Camino de Vera s/n, E-46022 Valencia (Spain)], E-mail: jsdehesa@upvnet.upv.es
2008-02-15
We show that specially designed two-dimensional arrangements of full elastic cylinders embedded in a nonviscous fluid or gas define (in the homogenization limit) a new class of acoustic metamaterials characterized by a dynamical effective mass density that is anisotropic. Here, analytic expressions for the dynamical mass density and the effective sound velocity tensors are derived in the long wavelength limit. Both show an explicit dependence on the lattice filling fraction, the elastic properties of cylinders relative to the background, their positions in the unit cell, and their multiple scattering interactions. Several examples of these metamaterials are reported and discussed.
Minimal quantization of two-dimensional models with chiral anomalies
International Nuclear Information System (INIS)
Ilieva, N.
1987-01-01
Two-dimensional gauge models with chiral anomalies - ''left-handed'' QED and the chiral Schwinger model, are quantized consistently in the frames of the minimal quantization method. The choice of the cone time as a physical time for system of quantization is motivated. The well-known mass spectrum is found but with a fixed value of the regularization parameter a=2. Such a unique solution is obtained due to the strong requirement of consistency of the minimal quantization that reflects in the physically motivated choice of the time axis
Magnetism and pairing of two-dimensional trapped fermions.
Chiesa, Simone; Varney, Christopher N; Rigol, Marcos; Scalettar, Richard T
2011-01-21
The emergence of local phases in a trapped two-component Fermi gas in an optical lattice is studied using quantum Monte Carlo simulations. We treat temperatures that are comparable to or lower than those presently achievable in experiments and large enough systems that both magnetic and paired phases can be detected by inspection of the behavior of suitable short-range correlations. We use the latter to suggest the interaction strength and temperature range at which experimental observation of incipient magnetism and d-wave pairing are more likely and evaluate the relation between entropy and temperature in two-dimensional confined fermionic systems.
Confinement and dynamical regulation in two-dimensional convective turbulence
DEFF Research Database (Denmark)
Bian, N.H.; Garcia, O.E.
2003-01-01
In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low......-frequency bursting in the fluctuation level and the convective heat flux integral, both resulting in a state of large-scale intermittency. The first one involves the control of convective transport by sheared mean flows. This regulation relies on the conservative transfer of kinetic energy from tilted fluctuations...
Cavalier perspective plots of two-dimensional matrices. Program Stereo
International Nuclear Information System (INIS)
Los Arcos Merino, J.M.
1978-01-01
The program Stereo allows representation of a two-dimensional matrix containing numerical data, in the form of a cavalier perspective, isometric or not, with an angle variable between 0 deg and 180 deg. The representation is in histogram form for each matrix row and those curves which fall behind higher curves and therefore would not be seen are suppressed. It has been written in Fortran V for a Calcomp-936 digital plotter operating off-line with a Univac 1106 computer. Drawing method, subroutine structure and running instructions are described in this paper. (author)
A Chain-Detection Algorithm for Two-Dimensional Grids
Bonham, Paul; Iqbal, Azlan
2016-01-01
We describe a general method of detecting valid chains or links of pieces on a two-dimensional grid. Specifically, using the example of the chess variant known as Switch-Side Chain-Chess (SSCC). Presently, no foolproof method of detecting such chains in any given chess position is known and existing graph theory, to our knowledge, is unable to fully address this problem either. We therefore propose a solution implemented and tested using the C++ programming language. We have been unable to fi...
Inverse radiative transfer problems in two-dimensional heterogeneous media
International Nuclear Information System (INIS)
Tito, Mariella Janette Berrocal
2001-01-01
The analysis of inverse problems in participating media where emission, absorption and scattering take place has several relevant applications in engineering and medicine. Some of the techniques developed for the solution of inverse problems have as a first step the solution of the direct problem. In this work the discrete ordinates method has been used for the solution of the linearized Boltzmann equation in two dimensional cartesian geometry. The Levenberg - Marquardt method has been used for the solution of the inverse problem of internal source and absorption and scattering coefficient estimation. (author)
Stable two-dimensional dispersion-managed soliton
International Nuclear Information System (INIS)
Abdullaev, Fatkhulla Kh.; Baizakov, Bakhtiyor B.; Salerno, Mario
2003-01-01
The existence of a dispersion-managed soliton in two-dimensional nonlinear Schroedinger equation with periodically varying dispersion has been explored. The averaged equations for the soliton width and chirp are obtained which successfully describe the long time evolution of the soliton. The slow dynamics of the soliton around the fixed points for the width and chirp are investigated and the corresponding frequencies are calculated. Analytical predictions are confirmed by direct partial differential equation (PDE) and ordinary differential equation (ODE) simulations. Application to a Bose-Einstein condensate in optical lattice is discussed. The existence of a dispersion-managed matter-wave soliton in such system is shown
Directory of Open Access Journals (Sweden)
Haiwen Li
2018-01-01
Full Text Available The estimation speed of positioning parameters determines the effectiveness of the positioning system. The time of arrival (TOA and direction of arrival (DOA parameters can be estimated by the space-time two-dimensional multiple signal classification (2D-MUSIC algorithm for array antenna. However, this algorithm needs much time to complete the two-dimensional pseudo spectral peak search, which makes it difficult to apply in practice. Aiming at solving this problem, a fast estimation method of space-time two-dimensional positioning parameters based on Hadamard product is proposed in orthogonal frequency division multiplexing (OFDM system, and the Cramer-Rao bound (CRB is also presented. Firstly, according to the channel frequency domain response vector of each array, the channel frequency domain estimation vector is constructed using the Hadamard product form containing location information. Then, the autocorrelation matrix of the channel response vector for the extended array element in frequency domain and the noise subspace are calculated successively. Finally, by combining the closed-form solution and parameter pairing, the fast joint estimation for time delay and arrival direction is accomplished. The theoretical analysis and simulation results show that the proposed algorithm can significantly reduce the computational complexity and guarantee that the estimation accuracy is not only better than estimating signal parameters via rotational invariance techniques (ESPRIT algorithm and 2D matrix pencil (MP algorithm but also close to 2D-MUSIC algorithm. Moreover, the proposed algorithm also has certain adaptability to multipath environment and effectively improves the ability of fast acquisition of location parameters.
Two-dimensional magnetohydrodynamic equilibria with flow and studies of equilibria fluctuations
International Nuclear Information System (INIS)
Agim, Y.Z.
1989-08-01
A set of reduced ideal MHD equations is derived to investigate equilibria of plasmas with mass flow in general two-dimensional geometry. These equations provide a means of investigating the effects of flow on self-consistent equilibria in a number of new two-dimensional configurations such as helically symmetric configurations with helical axis, which are relevant to stellarators, as well as axisymmetric configurations. It is found that as in the axisymmetric case, general two-dimensional flow equilibria are governed by a second-order quasi-linear partial differential equation for a magnetic flux function, which is coupled to a Bernoulli-type equation for the density. The equation for the magnetic flux function becomes hyperbolic at certain critical flow speeds which follow from its characteristic equation. When the equation is hyperbolic, shock phenomena may exist. As a particular example, unidirectional flow along the lines of symmetry is considered. In this case, the equation mentioned above is always elliptic. An exact solution for the case of helically symmetric unidirectional flow is found and studied to determine flow effects on the magnetic topology. In second part of this thesis, magnetic fluctuations due to the thermally excited MHD waves are investigated using fluid and kinetic models to describe stable, uniform, compressible plasma in the range above the drift wave frequency and below the ion cyclotron frequency. It is shown that the fluid model with resistivity yields spectral densities which are roughly Lorentzian, exhibit equipartition with no apparent cutoff in wavenumber space and a Bohm-type diffusion coefficient. Under certain conditions, the ensuing transport may be comparable to classical values. For a phenomenological cutoff imposed on the spectrum, the typical fluctuating-to-equilibrium magnetic field ratio is found to be of the order of 10 -10
International Nuclear Information System (INIS)
Ehrhardt, J.
1979-01-01
Theoretical and experimental investigations on detection systems for small narrow-band components in noise signals were conducted. These detectionn systems are based on the continuous surveillance of the power spectral density for characteristic peaks. Detection sensitivity for auto- and cross-correlation measurements was computed for signals with normally distributed amplitudes in dependence of signal coherence. The derived detection criteria allowed the comparison of auto- and cross-power spectral density surveillance. Theoretical results were confirmed in a number of experimental parameter studies. Special theoretical investigations were done for the optimal detection of local sodium boiling in liquid-metal fast breeder reactors
The emergence of geometry: a two-dimensional toy model
Alfaro, Jorge; Puigdomenech, Daniel
2010-01-01
We review the similarities between the effective chiral lagrangrian, relevant for low-energy strong interactions, and the Einstein-Hilbert action. We use these analogies to suggest a specific mechanism whereby gravitons would emerge as Goldstone bosons of a global SO(D) X GL(D) symmetry broken down to SO(D) by fermion condensation. We propose a two-dimensional toy model where a dynamical zwei-bein is generated from a topological theory without any pre-existing metric structure, the space being endowed only with an affine connection. A metric appears only after the symmetry breaking; thus the notion of distance is an induced effective one. In spite of several non-standard features this simple toy model appears to be renormalizable and at long distances is described by an effective lagrangian that corresponds to that of two-dimensional gravity (Liouville theory). The induced cosmological constant is related to the dynamical mass M acquired by the fermion fields in the breaking, which also acts as an infrared re...
Two-dimensional theory and simulation of free electron lasers
International Nuclear Information System (INIS)
Kwan, T.J.T.; Cary, J.R.
1981-01-01
Two-dimensional homogeneous theory of free-electron lasers with a wiggler magnetic field of constant wavelength is formulated. It has been found from the theory that waves propagating obliquely with respect to the electron beam are always unstable with appreciable growth rates; therefore, mode competition among the on-axis and off-axis modes is an important consideration in the design of the free-electron laser. Furthermore, electromagnetic waves with group velocities opposite to the direction of electron beam propagation are absolutely unstable if k/sub o/v/sub o/ > ω/sub pe/(1/γ/sup 3/2/ + 1/γ/sup 1/2/). Due to strong nonlinear saturation levels of the low-frequency absolute instability, the dynamics of the electron beam and the generation of the high-frequency electromagnetic radiation can be severely affected. Two-dimensional particle simulations show that the efficiency of generation of the on-axis high-frequency electromagnetic wave decreases significantly due to instability of the off-axis modes. In addition, complete disruption of the electron beam and laser oscillation due to the onset of the absolute instability have been observed in simulations
Growth and characterization of two-dimensional nanostructures
International Nuclear Information System (INIS)
Herrera Sancho, Oscar Andrey
2008-01-01
Two dimensional nanostructures of palladium, nickel, silver and gadolinium were grown by means of physical evaporation in atmospheres of high vacuum and ultra high vacuum. The qualitative characterization, in situ, of the nanostructures was carried out with techniques of surface analysis: Auger electron spectroscopy and X-ray photoelectron spectroscopy (XPS). The model for the quantification of contaminants in the nanostructures, was proposed by Seah and Shirley, and was made using the spectra XPS measured in situ in the atmospheres of vacuum. For the two-dimensional nanostructures of gadolinium of thicknesses 8 Å, 16 Å, 24 Å, 32 Å, 36 Å, 44 Å, 50 Å, 61 Å, 77 Å, 81 Å, 92 Å and 101 Å, were obtained optical spectra of transmission measured in situ. An band of absorption centered at approximately 2,40 eV is obtained by an increase in the dynamic conductivity from the optical constants, i.e. refractive index and extinction coefficient, of the nanostructure of gadolinium. In addition, the optical constants for the gadolinium nanostructures have presented a maximum of 80 Å of thickness and then it was continued a decreasing tendency toward the values that were reported in the literature for bulk of gadolinium. (author) [es
Two-dimensional photonic crystal polarizer modulated by silicon resin
Tan, Chunhua; Huang, Xuguang
2007-11-01
Photonic crystals(PCs)have many potential applications because of their ability to control light-wave propagation. In this paper, we theoretically investigate the tunability of light propagation in photonic crystal waveguides in two-dimensional photonic crystals with square lattices composed of heat-resistant silicon resin. Waveguides can be obtained by the infiltration of silicon resin into air regions in two-dimensional photonic crystals composed of air holes with square lattices of dielectric cylinders. The refractive index of silicon resin can be changed by manipulating the temperature of the sample. Numerical simulation by solving Maxwell's equations using the plane wave expansion(PWE) method shows that the band gaps can be continuously tuned by silicon resin, accordingly the light propagation in photonic crystal waveguides can be controlled. The band gap is analyzed in the temperature range of 20°C-120°C. In our work, the gap map for a square lattice of dielectric cylinders is also simulated. The method can separate TM- and TE-polarized modes in the waveguide. Such a mechanism of band gap adjustment should open up a new application for designing field-sensitive polarizer in photonic integrated circuits.
Two-dimensional nuclear magnetic resonance of quadrupolar systems
Energy Technology Data Exchange (ETDEWEB)
Wang, Shuanhu [Univ. of California, Berkeley, CA (United States)
1997-09-01
This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to a series of aluminum containing materials is then presented. The superior resolution enhancement through MQMAS is exploited to detect the five- and six-coordinated aluminum in many aluminosilicate glasses. Combining the MQMAS method with other experiments, such as HETCOR, greatly expands the possibility of the use of MQMAS to study a large range of problems and is demonstrated in Chapter 5. Finally, the technique switching-angle spinning (SAS) is applied to quadrupolar nuclei to fully characterize a quadrupolar spin system in which all of the 8 NMR parameters are accurately determined. This dissertation is meant to demonstrate that with the combination of two-dimensional NMR concepts and new advanced spinning technologies, a series of multiple-dimensional NMR techniques can be designed to allow a detailed study of quadrupolar nuclei in the solid state.
Comparative Skeletal Muscle Proteomics Using Two-Dimensional Gel Electrophoresis
Murphy, Sandra; Dowling, Paul; Ohlendieck, Kay
2016-01-01
The pioneering work by Patrick H. O’Farrell established two-dimensional gel electrophoresis as one of the most important high-resolution protein separation techniques of modern biochemistry (Journal of Biological Chemistry 1975, 250, 4007–4021). The application of two-dimensional gel electrophoresis has played a key role in the systematic identification and detailed characterization of the protein constituents of skeletal muscles. Protein changes during myogenesis, muscle maturation, fibre type specification, physiological muscle adaptations and natural muscle aging were studied in depth by the original O’Farrell method or slightly modified gel electrophoretic techniques. Over the last 40 years, the combined usage of isoelectric focusing in the first dimension and sodium dodecyl sulfate polyacrylamide slab gel electrophoresis in the second dimension has been successfully employed in several hundred published studies on gel-based skeletal muscle biochemistry. This review focuses on normal and physiologically challenged skeletal muscle tissues and outlines key findings from mass spectrometry-based muscle proteomics, which was instrumental in the identification of several thousand individual protein isoforms following gel electrophoretic separation. These muscle-associated protein species belong to the diverse group of regulatory and contractile proteins of the acto-myosin apparatus that forms the sarcomere, cytoskeletal proteins, metabolic enzymes and transporters, signaling proteins, ion-handling proteins, molecular chaperones and extracellular matrix proteins. PMID:28248237
Human lymphocyte polymorphisms detected by quantitative two-dimensional electrophoresis
International Nuclear Information System (INIS)
Goldman, D.; Merril, C.R.
1983-01-01
A survey of 186 soluble lymphocyte proteins for genetic polymorphism was carried out utilizing two-dimensional electrophoresis of 14 C-labeled phytohemagglutinin (PHA)-stimulated human lymphocyte proteins. Nineteen of these proteins exhibited positional variation consistent with independent genetic polymorphism in a primary sample of 28 individuals. Each of these polymorphisms was characterized by quantitative gene-dosage dependence insofar as the heterozygous phenotype expressed approximately 50% of each allelic gene product as was seen in homozygotes. Patterns observed were also identical in monozygotic twins, replicate samples, and replicate gels. The three expected phenotypes (two homozygotes and a heterozygote) were observed in each of 10 of these polymorphisms while the remaining nine had one of the homozygous classes absent. The presence of the three phenotypes, the demonstration of gene-dosage dependence, and our own and previous pedigree analysis of certain of these polymorphisms supports the genetic basis of these variants. Based on this data, the frequency of polymorphic loci for man is: P . 19/186 . .102, and the average heterozygosity is .024. This estimate is approximately 1/3 to 1/2 the rate of polymorphism previously estimated for man in other studies using one-dimensional electrophoresis of isozyme loci. The newly described polymorphisms and others which should be detectable in larger protein surveys with two-dimensional electrophoresis hold promise as genetic markers of the human genome for use in gene mapping and pedigree analyses
Numerical method for two-dimensional unsteady reacting flows
International Nuclear Information System (INIS)
Butler, T.D.; O'Rourke, P.J.
1976-01-01
A method that numerically solves the full two-dimensional, time-dependent Navier-Stokes equations with species transport, mixing, and chemical reaction between species is presented. The generality of the formulation permits the solution of flows in which deflagrations, detonations, or transitions from deflagration to detonation are found. The solution procedure is embodied in the RICE computer program. RICE is an Eulerian finite difference computer code that uses the Implicit Continuous-fluid Eulerian (ICE) technique to solve the governing equations. One first presents the differential equations of motion and the solution procedure of the Rice program. Next, a method is described for artificially thickening the combustion zone to dimensions resolvable by the computational mesh. This is done in such a way that the physical flame speed and jump conditions across the flame front are preserved. Finally, the results of two example calculations are presented. In the first, the artificial thickening technique is used to solve a one-dimensional laminar flame problem. In the second, the results of a full two-dimensional calculation of unsteady combustion in two connected chambers are detailed
Strain-engineered growth of two-dimensional materials.
Ahn, Geun Ho; Amani, Matin; Rasool, Haider; Lien, Der-Hsien; Mastandrea, James P; Ager Iii, Joel W; Dubey, Madan; Chrzan, Daryl C; Minor, Andrew M; Javey, Ali
2017-09-20
The application of strain to semiconductors allows for controlled modification of their band structure. This principle is employed for the manufacturing of devices ranging from high-performance transistors to solid-state lasers. Traditionally, strain is typically achieved via growth on lattice-mismatched substrates. For two-dimensional (2D) semiconductors, this is not feasible as they typically do not interact epitaxially with the substrate. Here, we demonstrate controlled strain engineering of 2D semiconductors during synthesis by utilizing the thermal coefficient of expansion mismatch between the substrate and semiconductor. Using WSe 2 as a model system, we demonstrate stable built-in strains ranging from 1% tensile to 0.2% compressive on substrates with different thermal coefficient of expansion. Consequently, we observe a dramatic modulation of the band structure, manifested by a strain-driven indirect-to-direct bandgap transition and brightening of the dark exciton in bilayer and monolayer WSe 2 , respectively. The growth method developed here should enable flexibility in design of more sophisticated devices based on 2D materials.Strain engineering is an essential tool for modifying local electronic properties in silicon-based electronics. Here, Ahn et al. demonstrate control of biaxial strain in two-dimensional materials based on the growth substrate, enabling more complex low-dimensional electronics.
Thermal expansion of two-dimensional itinerant nearly ferromagnetic metal
International Nuclear Information System (INIS)
Konno, R; Hatayama, N; Takahashi, Y; Nakano, H
2009-01-01
Thermal expansion of two-dimensional itinerant nearly ferromagnetic metal is investigated according to the recent theoretical development of magneto-volume effect for the three-dimensional weak ferromagnets. We particularly focus on the T 2 -linear thermal expansion of magnetic origin at low temperatures, so far disregarded by conventional theories. As the effect of thermal spin fluctuations we have found that the T-linear thermal expansion coefficient shows strong enhancement by assuming the double Lorentzian form of the non-interacting dynamical susceptibility justified in the small wave-number and low frequency region. It grows faster in proportional to y -1/2 as we approach the magnetic instability point than two-dimensional nearly antiferromagnetic metals with ln(1/y s ) dependence, where y and y s are the inverses of the reduced uniform and staggered magnetic susceptibilities, respectively. Our result is consistent with the Grueneisen's relation between the thermal expansion coefficient and the specific heat at low temperatures. In 2-dimensional electron gas we find that the thermal expansion coefficient is divergent with a finite y when the higher order term of non-interacting dynamical susceptibility is taken into account.
Flexoelectricity in two-dimensional crystalline and biological membranes
Ahmadpoor, Fatemeh; Sharma, Pradeep
2015-10-01
The ability of a material to convert electrical stimuli into mechanical deformation, i.e. piezoelectricity, is a remarkable property of a rather small subset of insulating materials. The phenomenon of flexoelectricity, on the other hand, is universal. All dielectrics exhibit the flexoelectric effect whereby non-uniform strain (or strain gradients) can polarize the material and conversely non-uniform electric fields may cause mechanical deformation. The flexoelectric effect is strongly enhanced at the nanoscale and accordingly, all two-dimensional membranes of atomistic scale thickness exhibit a strong two-way coupling between the curvature and electric field. In this review, we highlight the recent advances made in our understanding of flexoelectricity in two-dimensional (2D) membranes--whether the crystalline ones such as dielectric graphene nanoribbons or the soft lipid bilayer membranes that are ubiquitous in biology. Aside from the fundamental mechanisms, phenomenology, and recent findings, we focus on rapidly emerging directions in this field and discuss applications such as energy harvesting, understanding of the mammalian hearing mechanism and ion transport among others.
Two-Dimensional Gel Electrophoresis and 2D-DIGE.
Meleady, Paula
2018-01-01
Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) continues to be one of the most versatile and widely used techniques to study the proteome of a biological system. In particular, a modified version of 2D-PAGE, two-dimensional difference gel electrophoresis (2D-DIGE), which uses differential labeling of protein samples with up to three fluorescent tags, offers greater sensitivity and reproducibility over conventional 2D-PAGE gels for differential quantitative analysis of protein expression between experimental groups. Both these methods have distinct advantages in the separation and identification of thousands of individual proteins species including protein isoforms and post-translational modifications. This review will discuss the principles of 2D-PAGE and 2D-DIGE including limitations to the methods. 2D-PAGE and 2D-DIGE continue to be popular methods in bioprocessing-related research (particularly on recombinant Chinese hamster ovary cells), which will also be discussed in the review chapter.
On Space Efficient Two Dimensional Range Minimum Data Structures
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Davoodi, Pooya; Rao, S. Srinivasa
2012-01-01
of the problem, the lower bound is tight up to a constant factor. In two dimensions, we complement the lower bound with an indexing data structure of size O(N/c) bits which can be preprocessed in O(N) time to support O(clog 2 c) query time. For c=O(1), this is the first O(1) query time algorithm using a data......The two dimensional range minimum query problem is to preprocess a static m by n matrix (two dimensional array) A of size N=m⋅n, such that subsequent queries, asking for the position of the minimum element in a rectangular range within A, can be answered efficiently. We study the trade-off between...... the space and query time of the problem. We show that every algorithm enabled to access A during the query and using a data structure of size O(N/c) bits requires Ω(c) query time, for any c where 1≤c≤N. This lower bound holds for arrays of any dimension. In particular, for the one dimensional version...
On Space Efficient Two Dimensional Range Minimum Data Structures
DEFF Research Database (Denmark)
Davoodi, Pooya; Brodal, Gerth Stølting; Rao, S. Srinivasa
2010-01-01
, the lower bound is tight up to a constant factor. In two dimensions, we complement the lower bound with an indexing data structure of size O(N/c) bits additional space which can be preprocessed in O(N) time and achieves O(clog2 c) query time. For c = O(1), this is the first O(1) query time algorithm using......The two dimensional range minimum query problem is to preprocess a static two dimensional m by n array A of size N = m · n, such that subsequent queries, asking for the position of the minimum element in a rectangular range within A, can be answered efficiently. We study the trade-off between...... optimal O(N) bits additional space. For the case where queries can not probe A, we give a data structure of size O(N· min {m,logn}) bits with O(1) query time, assuming m ≤ n. This leaves a gap to the lower bound of Ω(Nlogm) bits for this version of the problem....
Development of two dimensional electrophoresis method using single chain DNA
International Nuclear Information System (INIS)
Ikeda, Junichi; Hidaka, So
1998-01-01
By combining a separation method due to molecular weight and a method to distinguish difference of mono-bases, it was aimed to develop a two dimensional single chain DNA labeled with Radioisotope (RI). From electrophoretic pattern difference of parent and variant strands, it was investigated to isolate the root module implantation control gene. At first, a Single Strand Conformation Polymorphism (SSCP) method using concentration gradient gel was investigated. As a result, it was formed that intervals between double chain and single chain DNAs expanded, but intervals of both single chain DNAs did not expand. On next, combination of non-modified acrylic amide electrophoresis method and Denaturing Gradient-Gel Electrophoresis (DGGE) method was examined. As a result, hybrid DNA developed by two dimensional electrophoresis arranged on two lines. But, among them a band of DNA modified by high concentration of urea could not be found. Therefore, in this fiscal year's experiments, no preferable result could be obtained. By the used method, it was thought to be impossible to detect the differences. (G.K.)
Detector-Response Correction of Two-Dimensional γ-Ray Spectra from Neutron Capture
Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.
2015-05-01
The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.
Detector-Response Correction of Two-Dimensional γ-Ray Spectra from Neutron Capture
Directory of Open Access Journals (Sweden)
Rusev G.
2015-01-01
Full Text Available The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ and 113Cd(n, γ reactions.
Xiao, Qian; Gu, Xiaohong; Tan, Suo
2014-12-01
Drying process of aqueous sodium alginate solutions at 50°C was investigated by ATR-FTIR spectroscopy and two-dimensional correlation infrared spectroscopy. Two-dimensional asynchronous spectrum at 1,800-1,350 cm(-1) wavenumber could be resolved into five separate bands, which were assigned to O-H bending vibrations in water (around 1,645 cm(-1)), antisymmetric and symmetric stretching vibrations of free and hydrogen-bonded COO(-) groups of alginate (around 1,595, 1,412, 1,572 and 1,390 cm(-1), respectively). As the drying process progressed, absorbance bands at around 1,127 and 1,035 cm(-1) significantly shifted to lower wavenumbers (1120 and 1027cm(-1), respectively). Suggesting that oxygen atoms at the 2th and 3th position in the pyranose ring might have hydrogen bonded with water or alginate chains. Further analysis using 2D asynchronous correlation spectroscopy between 1800-1500 and 1200-960 cm(-1) wavenumber regions revealed the sequence of spectral changes during the drying process. Copyright © 2014 Elsevier Ltd. All rights reserved.
Modeling of the financial market using the two-dimensional anisotropic Ising model
Lima, L. S.
2017-09-01
We have used the two-dimensional classical anisotropic Ising model in an external field and with an ion single anisotropy term as a mathematical model for the price dynamics of the financial market. The model presented allows us to test within the same framework the comparative explanatory power of rational agents versus irrational agents with respect to the facts of financial markets. We have obtained the mean price in terms of the strong of the site anisotropy term Δ which reinforces the sensitivity of the agent's sentiment to external news.
Energy Technology Data Exchange (ETDEWEB)
Rucker, S.P.
1991-07-01
Magnetic couplings between protons, such as through-space dipole couplings, and scalar J-couplings depend sensitively on the structure of the molecule. Two dimensional nuclear magnetic resonance experiments provide a powerful tool for measuring these couplings, correlating them to specific pairs of protons within the molecule, and calculating the structure. This work discusses the development of NMR methods for examining two such classes of problems -- determination of the secondary structure of flexible molecules in anisotropic solutions, and primary structure of large biomolecules in aqueous solutions. 201 refs., 84 figs., 19 tabs.
Numerical model for two-dimensional hydrodynamics and energy transport. [VECTRA code
Energy Technology Data Exchange (ETDEWEB)
Trent, D.S.
1973-06-01
The theoretical basis and computational procedure of the VECTRA computer program are presented. VECTRA (Vorticity-Energy Code for TRansport Analysis) is designed for applying numerical simulation to a broad range of intake/discharge flows in conjunction with power plant hydrological evaluation. The code computational procedure is based on finite-difference approximation of the vorticity-stream function partial differential equations which govern steady flow momentum transport of two-dimensional, incompressible, viscous fluids in conjunction with the transport of heat and other constituents.
Evaluation of localized muscle fatigue using power spectral density analysis of the electromyogram
Lafevers, E. V.
1974-01-01
Surface electromyograms (EMGs) taken from three upper torso muscles during a push-pull task were analyzed by a power spectral density technique to determine the operational feasibility of the technique for identifying changes in the EMGs resulting from muscular fatigue. The EMGs were taken from four subjects under two conditions (1) in shirtsleeves and (2) in a pressurized space suit. This study confirmed that frequency analysis of dynamic muscle activity is capable of providing reliable data for many industrial applications where fatigue may be of practical interest. The results showed significant effects of the pressurized space suit on the pattern of shirtsleeve fatigue responses of the muscles. The data also revealed (1) reliable differences between muscles in fatigue-induced responses to various locations in the reach envelope at which the subjects were required to perform the push-pull exercise and (2) the differential sensitivity of muscles to the various reach positions in terms of fatigue-related shifts in EMG power.
The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum
Galvin, T. J.; Seymour, N.; Marvil, J.; Filipović, M. D.; Tothill, N. F. H.; McDermid, R. M.; Hurley-Walker, N.; Hancock, P. J.; Callingham, J. R.; Cook, R. H.; Norris, R. P.; Bell, M. E.; Dwarakanath, K. S.; For, B.; Gaensler, B. M.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Lenc, E.; McKinley, B.; Morgan, J.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.
2018-02-01
We have acquired radio-continuum data between 70 MHz and 48 GHz for a sample of 19 southern starburst galaxies at moderate redshifts (0.067 < z < 0.227) with the aim of separating synchrotron and free-free emission components. Using a Bayesian framework, we find the radio continuum is rarely characterized well by a single power law, instead often exhibiting low-frequency turnovers below 500 MHz, steepening at mid to high frequencies, and a flattening at high frequencies where free-free emission begins to dominate over the synchrotron emission. These higher order curvature components may be attributed to free-free absorption across multiple regions of star formation with varying optical depths. The decomposed synchrotron and free-free emission components in our sample of galaxies form strong correlations with the total-infrared bolometric luminosities. Finally, we find that without accounting for free-free absorption with turnovers between 90 and 500 MHz the radio continuum at low frequency (ν < 200 MHz) could be overestimated by upwards of a factor of 12 if a simple power-law extrapolation is used from higher frequencies. The mean synchrotron spectral index of our sample is constrained to be α = -1.06, which is steeper than the canonical value of -0.8 for normal galaxies. We suggest this may be caused by an intrinsically steeper cosmic ray distribution.
A Recommended Procedure for Estimating the Cosmic Ray Spectral Parameter of a Simple Power Law
Howell, Leonard W.; Rose, M. Franklin (Technical Monitor)
2000-01-01
A simple power law model consisting of a single spectral index a(f(sub i)) is believed to be an adequate description of the galactic cosmic ray (GQ proton flux at energies below 1013 eV. Two procedures for estimating a(f(sub i)), referred as (1) the method of moments, and (2) maximum likelihood, are developed and their statistical performance compared. I concluded that the maximum likelihood procedure attains the most desirable statistical properties and is hence the recommended statistic estimation procedure for estimating a1. The maximum likelihood procedure is then generalized for application to a set of real cosmic ray data and thereby makes this approach applicable to existing cosmic ray data sets. Several other important results, such as the relationship between collecting power and detector energy resolution, as well as inclusion of a non-Gaussian detector response function, are presented. These results have many practical benefits in the design phase of a cosmic ray detector because they permit instrument developers to make important trade studies in design parameters as a function of one of the science objectives, which is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose practical limits to the design envelope.
COBRA/TRAC analysis of two-dimensional thermal-hydraulic behavior in SCTF reflood tests
International Nuclear Information System (INIS)
Iwamura, Takamichi; Ohnuki, Akira; Sobajima, Makoto; Adachi, Hiromichi
1987-01-01
The effects of radial power distribution and non-uniform upper plenum water accumulation on thermal-hydraulic behavior in the core were observed in the reflood tests with Slab Core Test Facility (SCTF). In order to examine the predictability of these two effects by a multi-dimensional analysis code, the COBRA/TRAC calculations were made. The calculated results indicated that the heat transfer enhancement in high power bundles above quench front was caused by high vapor flow rate in those bundles due to the radial power distribution. On the other hand, the heat transfer degradation in the peripheral bundles under the condition of non-uniform upper plenum water accumulation was caused by the lower flow rates of vapor and entrained liquid above the quench front in those bundles by the reason that vapor concentrated in the center bundles due to the cross flow induced by the horizontal pressure gradient in the core. The above-mentioned two-dimensional heat transfer behaviors calculated with the COBRA/TRAC code is similar to those observed in SCTF tests and therefore those calculations are useful to investigate the mechanism of the two-dimensional effects in SCTF reflood tests. (author)
CT calibration for two-dimensional scaling of proton pencil beams
International Nuclear Information System (INIS)
Szymanowski, Hanitra; Oelfke, Uwe
2003-01-01
For proton dose calculations in heterogeneous media, it was shown in a previous work that the conventional pencil beam approach based on pathlength scaling does not properly account for scattering effects in nonwater media (Szymanowski and Oelfke 2002 Phys. Med. Biol. 47 3313-30). A two-dimensional scaling method was therefore introduced, which is able to predict with high accuracy the propagation of proton pencil beams both along the depth and the lateral directions in inhomogeneous media. In order to integrate this improved pencil beam algorithm in a CT based treatment planning system, two CT calibration curves are needed. The first one relates the Hounsfield numbers to the relative stopping powers, as for the conventional pencil beam approach. The second curve is to relate the Hounsfield numbers to the material-specific lateral scaling factors. The purpose of this work is to provide the CT calibration curves needed for the integration of the pencil beam algorithm featuring the two-dimensional scaling method. Similarly to as suggested by Schneider et al (1996 Phys. Med. Biol. 41 111-24) for the calibration curve in terms of stopping powers, we follow a stoichiometric procedure to get the calibration curve in terms of material-specific lateral scaling factors. The calibration curves for a CT scanner of the type Siemens Somatom Plus 4 are obtained from the analytical calculation of the CT Hounsfield numbers, relative stopping powers and material-specific lateral scaling factors for human biological tissues
The art of Spectral Management; Downstream power back-off for VDSL2 - Whitepaper DSL04
Brink, R.F.M. van den
2009-01-01
Spectral Management (SpM) involves managing an access network such that different systems can co-exist with each other. In relation to DSL systems, spectral management ensures that they can co-exist within the same cable. The use of spectral signal limits (specified via mandatory access rules) is
The art of Spectral Management ; Upstream power back-off for VDSL2 - Whitepaper DSL05
Brink, R.F.M. van den
2009-01-01
Spectral Management (SpM) involves managing an access network such that different systems can co-exist with each other. In relation to DSL systems, spectral management ensures that they can co-exist within the same cable. The use of spectral signal limits (specified via mandatory access rules) is
Two dimensional recursive digital filters for near real time image processing
Olson, D.; Sherrod, E.
1980-01-01
A program was designed toward the demonstration of the feasibility of using two dimensional recursive digital filters for subjective image processing applications that require rapid turn around. The concept of the use of a dedicated minicomputer for the processor for this application was demonstrated. The minicomputer used was the HP1000 series E with a RTE 2 disc operating system and 32K words of memory. A Grinnel 256 x 512 x 8 bit display system was used to display the images. Sample images were provided by NASA Goddard on a 800 BPI, 9 track tape. Four 512 x 512 images representing 4 spectral regions of the same scene were provided. These images were filtered with enhancement filters developed during this effort.
Thermal transport in a two-dimensional Z2 spin liquid
Metavitsiadis, Alexandros; Pidatella, Angelo; Brenig, Wolfram
2017-11-01
We study the dynamical thermal conductivity of the two-dimensional Kitaev spin model on the honeycomb lattice. We find a strongly temperature dependent low-frequency spectral intensity as a direct consequence of fractionalization of spins into mobile Majorana matter and a static Z2 gauge field. The latter acts as an emergent thermally activated disorder, leading to the appearance of a pseudogap which closes in the thermodynamic limit, indicating a dissipative heat conductor. Our analysis is based on complementary calculations of the current correlation function, comprising exact diagonalization by means of a complete summation over all gauge sectors, as well as a phenomenological mean-field treatment of thermal gauge fluctuations, valid at intermediate and high temperatures. The results will also be contrasted against the conductivity discarding gauge fluctuations.
Coherent Two-Dimensional Terahertz Magnetic Resonance Spectroscopy of Collective Spin Waves.
Lu, Jian; Li, Xian; Hwang, Harold Y; Ofori-Okai, Benjamin K; Kurihara, Takayuki; Suemoto, Tohru; Nelson, Keith A
2017-05-19
We report a demonstration of two-dimensional (2D) terahertz (THz) magnetic resonance spectroscopy using the magnetic fields of two time-delayed THz pulses. We apply the methodology to directly reveal the nonlinear responses of collective spin waves (magnons) in a canted antiferromagnetic crystal. The 2D THz spectra show all of the third-order nonlinear magnon signals including magnon spin echoes, and 2-quantum signals that reveal pairwise correlations between magnons at the Brillouin zone center. We also observe second-order nonlinear magnon signals showing resonance-enhanced second-harmonic and difference-frequency generation. Numerical simulations of the spin dynamics reproduce all of the spectral features in excellent agreement with the experimental 2D THz spectra.
Cassandre : a two-dimensional multigroup diffusion code for reactor transient analysis
International Nuclear Information System (INIS)
Arien, B.; Daniels, J.
1986-12-01
CASSANDRE is a two-dimensional (x-y or r-z) finite element neutronics code with thermohydraulics feedback for reactor dynamics prior to the disassembly phase. It uses the multigroup neutron diffusion theory. Its main characteristics are the use of a generalized quasistatic model, the use of a flexible multigroup point-kinetics algorithm allowing for spectral matching and the use of a finite element description. The code was conceived in order to be coupled with any thermohydraulics module, although thermohydraulics feedback is only considered in r-z geometry. In steady state criticality search is possible either by control rod insertion or by homogeneous poisoning of the coolant. This report describes the main characterstics of the code structure and provides all the information needed to use the code. (Author)
Superintegrability in two-dimensional Euclidean space and associated polynomial solutions
International Nuclear Information System (INIS)
Kalnins, E.G.; Miller, W. Jr; Pogosyan, G.S.
1996-01-01
In this work we examine the basis functions for those classical and quantum mechanical systems in two dimensions which admit separation of variables in at least two coordinate systems. We do this for the corresponding systems defined in Euclidean space and on the two dimensional sphere. We present all of these cases from a unified point of view. In particular, all of the spectral functions that arise via variable separation have their essential features expressed in terms of their zeros. The principal new results are the details of the polynomial base for each of the nonsubgroup base, not just the subgroup cartesian and polar coordinate case, and the details of the structure of the quadratic algebras. We also study the polynomial eigenfunctions in elliptic coordinates of the N-dimensional isotropic quantum oscillator. 28 refs., 1 tab
Passive tracer in a flow corresponding to two-dimensional stochastic Navier–Stokes equations
International Nuclear Information System (INIS)
Komorowski, Tomasz; Peszat, Szymon; Szarek, Tomasz
2013-01-01
In this paper we prove the law of large numbers and central limit theorem for trajectories of a particle carried by a two-dimensional Eulerian velocity field. The field is given by a solution of a stochastic Navier–Stokes system with non-degenerate noise. The spectral gap property, with respect to the Wasserstein metric, for such a system was shown in Hairer and Mattingly (2008 Ann. Probab. 36 2050–91). In this paper we show that a similar property holds for the environment process corresponding to the Lagrangian observations of the velocity. Consequently we conclude the law of large numbers and the central limit theorem for the tracer. The proof of the central limit theorem relies on the martingale approximation of the trajectory process. (paper)
Energy Technology Data Exchange (ETDEWEB)
Bizimana, Laurie A.; Brazard, Johanna; Carbery, William P.; Gellen, Tobias; Turner, Daniel B., E-mail: dturner@nyu.edu [Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003 (United States)
2015-10-28
Coherent multidimensional optical spectroscopy is an emerging technique for resolving structure and ultrafast dynamics of molecules, proteins, semiconductors, and other materials. A current challenge is the quality of kinetics that are examined as a function of waiting time. Inspired by noise-suppression methods of transient absorption, here we incorporate shot-by-shot acquisitions and balanced detection into coherent multidimensional optical spectroscopy. We demonstrate that implementing noise-suppression methods in two-dimensional electronic spectroscopy not only improves the quality of features in individual spectra but also increases the sensitivity to ultrafast time-dependent changes in the spectral features. Measurements on cresyl violet perchlorate are consistent with the vibronic pattern predicted by theoretical models of a highly displaced harmonic oscillator. The noise-suppression methods should benefit research into coherent electronic dynamics, and they can be adapted to multidimensional spectroscopies across the infrared and ultraviolet frequency ranges.
Bizimana, Laurie A; Brazard, Johanna; Carbery, William P; Gellen, Tobias; Turner, Daniel B
2015-10-28
Coherent multidimensional optical spectroscopy is an emerging technique for resolving structure and ultrafast dynamics of molecules, proteins, semiconductors, and other materials. A current challenge is the quality of kinetics that are examined as a function of waiting time. Inspired by noise-suppression methods of transient absorption, here we incorporate shot-by-shot acquisitions and balanced detection into coherent multidimensional optical spectroscopy. We demonstrate that implementing noise-suppression methods in two-dimensional electronic spectroscopy not only improves the quality of features in individual spectra but also increases the sensitivity to ultrafast time-dependent changes in the spectral features. Measurements on cresyl violet perchlorate are consistent with the vibronic pattern predicted by theoretical models of a highly displaced harmonic oscillator. The noise-suppression methods should benefit research into coherent electronic dynamics, and they can be adapted to multidimensional spectroscopies across the infrared and ultraviolet frequency ranges.
Takeuchi, K; Yamamoto, N
2011-06-20
A cathodoluminescence technique using a 200-keV transmission electron microscope revealed the dispersion patterns of surface plasmon polaritons (SPPs) in a two-dimensional plasmonic crystal with cylindrical hole arrays. The dispersion curves of the SPP modes involving the Γ point were derived from the angle-resolved spectrum patterns. The contrast along the dispersion curves changed with the polarization direction of the emitted light due to the property of the SPP modes. The SPP modes at the Γ point were identified from the photon maps, which mimicked standing SPP waves in a real space. The beam-scan spectral images across the plasmonic crystal edge clearly demonstrated the dependence of the SPP to light conversion efficiency on the emission angle and polarization of light.
Power spectral density of a single Brownian trajectory: what one can and cannot learn from it
Krapf, Diego; Marinari, Enzo; Metzler, Ralf; Oshanin, Gleb; Xu, Xinran; Squarcini, Alessio
2018-02-01
The power spectral density (PSD) of any time-dependent stochastic process X t is a meaningful feature of its spectral content. In its text-book definition, the PSD is the Fourier transform of the covariance function of X t over an infinitely large observation time T, that is, it is defined as an ensemble-averaged property taken in the limit T\\to ∞ . A legitimate question is what information on the PSD can be reliably obtained from single-trajectory experiments, if one goes beyond the standard definition and analyzes the PSD of a single trajectory recorded for a finite observation time T. In quest for this answer, for a d-dimensional Brownian motion (BM) we calculate the probability density function of a single-trajectory PSD for arbitrary frequency f, finite observation time T and arbitrary number k of projections of the trajectory on different axes. We show analytically that the scaling exponent for the frequency-dependence of the PSD specific to an ensemble of BM trajectories can be already obtained from a single trajectory, while the numerical amplitude in the relation between the ensemble-averaged and single-trajectory PSDs is a fluctuating property which varies from realization to realization. The distribution of this amplitude is calculated exactly and is discussed in detail. Our results are confirmed by numerical simulations and single-particle tracking experiments, with remarkably good agreement. In addition we consider a truncated Wiener representation of BM, and the case of a discrete-time lattice random walk. We highlight some differences in the behavior of a single-trajectory PSD for BM and for the two latter situations. The framework developed herein will allow for meaningful physical analysis of experimental stochastic trajectories.
Energy Technology Data Exchange (ETDEWEB)
Butkus, Vytautas; Gelzinis, Andrius; Valkunas, Leonas [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania); Center for Physical Sciences and Technology, Savanoriu Ave. 231, 02300 Vilnius (Lithuania); Augulis, Ramūnas [Center for Physical Sciences and Technology, Savanoriu Ave. 231, 02300 Vilnius (Lithuania); Gall, Andrew; Robert, Bruno [Institut de Biologie et Technologies de Saclay, Bât 532, Commissariat à l’Energie Atomique Saclay, 91191 Gif sur Yvette (France); Büchel, Claudia [Institut für Molekulare Biowissenschaften, Universität Frankfurt, Max-von-Laue-Straße 9, Frankfurt (Germany); Zigmantas, Donatas [Department of Chemical Physics, Lund University, P.O. Box 124, 22100 Lund (Sweden); Abramavicius, Darius, E-mail: darius.abramavicius@ff.vu.lt [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania)
2015-06-07
Energy transfer processes and coherent phenomena in the fucoxanthin–chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of Q{sub y} transitions of chlorophylls a and c. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) a and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the Q{sub y} transition of Chl c revealed previously not identified, mutually non-interacting chlorophyll c states participating in femtosecond or picosecond energy transfer to the Chl a molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the vibrations-assisted coherent energy transfer between Chl c and Chl a and the overall spatial arrangement of chlorophyll molecules.
Hurst, Miranda N.; Delong, Robert K.
2016-09-01
Two dimensional fluorescence difference spectroscopy (2D FDS) detects nanoparticle interactions following surface functionalization and biomolecule loading by generating a spectral signature of the fluorescent intensity per excitation and emission wavelengths. Comparing metal oxide nanoparticles revealed a unique spectral signature per material composition. 2D FDS showed to be sensitive to changes in surface properties between ZnO NPs synthesized by different methods. ZnO NP loaded with glycol chitosan, polyacrylic acid (PAA), or methoxy polyethylene glycol (mPEG) exhibited a distinct spectral signature shift. ZnO NP loaded with Torula Yeast RNA (TYRNA)(640 nm), polyinosinic: polycytidylic acid (pIC)(680 nm), or splice switching oligonucleotide (SSO)(650 nm) each revealed a shift in emission. Ras-Binding domain (RBD) at three concentrations (25, 37.5, 50 μg/mL) showed that fluorescent intensity was inversely related to the concentration of protein loaded. These data support 2D FDS as a novel technique in identifying nanoparticles and their surface interactions as a quality assurance tool.
Berezinskii–Kosterlitz–Thouless transition and two-dimensional melting
Ryzhov, V. N.; Tareyeva, E. E.; Fomin, Yu D.; Tsiok, E. N.
2017-12-01
The main aspects of the theory of phase transitions in two-dimensional degenerate systems (Berezinskii–Kosterlitz–Thouless, or BKT, transitions) are reviewed in detail, including the transition mechanism, the renormalization group as a tool for describing the transition, and how the transition scenario can possibly depend on the core energy of topological defects (in particular, in thin superconducting films). Various melting scenarios in two-dimensional systems are analyzed, and the current status of actual experiments and computer simulations in the field is examined. Whereas in three dimensions melting always occurs as a single first-order transition, in two dimensions, as shown by Halperin, Nelson, and Young, melting via two continuous BKT transitions with an intermediate hexatic phase characterized by quasi-long-range orientational order is possible. But there is also a possibility for a first-order phase transition to occur. Recently, one further melting scenario, different from that occurring in the Berezinskii–Kosterlitz–Thouless–Halperin–Nelson–Young theory, has been proposed, according to which a solid can melt in two stages: a continuous BKT-type solid–hexatic transition and then a first-order hexatic-phase–isotropic-liquid phase transition. Particular attention is given to the melting scenario as a function of the potential shape and to the random pinning effect on two-dimensional melting. In particular, it is shown that random pinning can alter the melting scenario fundamentally in the case of a first-order transition. Also considered is the melting of systems with potentials having a negative curvature in the repulsion region–potentials that are successfully used in describing the anomalous properties of water in two dimensions. This review is an extended version of the report “Old and new in the physics of phase transitions” presented at the scientific session of the Physical Sciences Division of the Russian Academy of
Bao, Ya-Nan; Zeng, Yi-Wei; Guo, Ran; Ablikim, Mesude; Shi, Hai-Fang; Yang, Li-Min; Yang, Zhan-Lan; Xu, Yi-Zhuang; Noda, Isao; Wu, Jin-Guang
2017-12-07
3 A 2g → 3 T 1g (P) transition band of Ni 2+ is used to probe the coordination of Ni 2+ . Two-dimensional asynchronous spectra (2DCOS) are generated using the Double Asynchronous Orthogonal Sample Design (DAOSD), Asynchronous Spectrum with Auxiliary Peaks (ASAP) and Two-Trace Two-Dimensional (2T2D) approaches. Cross peaks relevant to the 3 A 2g → 3 T 1g (P) transition band of Ni 2+ are utilized to probe coordination between Ni 2+ and various ligands. We studied the spectral behavior of the 3 A 2g → 3 T 1g (P) transition band when Ni 2+ is coordinated with ethylenediaminetetraacetic acid disodium salt (EDTA). The pattern of cross peaks in 2D asynchronous spectrum demonstrates that coordination brings about significant blue shift of the band. In addition, the absorptivity of the band increases remarkably. The interaction between Ni 2+ and galactitol is also investigated. Although no clearly observable change is found on the 3 A 2g → 3 T 1g (P) transition band when galactitol is introduced, the appearance of cross peak in 2D asynchronous spectrum demonstrates that coordination indeed occurs between Ni 2+ and galactitol. Furthermore, the pattern of cross peak indicates that peak position, bandwidth and absorptivity of the 3 A 2g → 3 T 1g (P) transition band of Ni(galactitol) x 2+ is considerably different from those of Ni(H 2 O) 6 2+ . Thus, 2DCOS is helpful to reveal subtle spectral variation, which might be helpful in shedding light on the physical-chemical nature of coordination. Copyright © 2017. Published by Elsevier B.V.
International Nuclear Information System (INIS)
Schaffer, J.P.; Shaughnessy, E.J.; Jones, P.L.
1984-01-01
A deconvolution procedure which corrects Doppler-broadened positron annihilation spectra for instrument resolution is described. The method employs fast Fourier transforms, is model independent, and does not require iteration. The mathematical difficulties associated with the incorrectly posed first order Fredholm integral equation are overcome by using power spectral analysis to select a limited number of low frequency Fourier coefficients. The FFT/power spectrum method is then demonstrated for an irradiated high purity single crystal sapphire sample. (orig.)
Intruder Motion in Two-Dimensional Shaken Granular Beds
International Nuclear Information System (INIS)
Ma Huan-Ping; Lv Yong-Jun; Zheng Ning; Shi Qing-Fan; Li Liang-Sheng
2014-01-01
The dynamical behavior of an intruder immersed in a two-dimensional shaken granular bed is experimentally investigated. With two types of background particles, f−Γ phase diagrams depicting the intruder's motion are measured and compared. It is found that even with the same size and density ratio of the intruder to the background particles, the intruder exhibits a distinct behavior at given vibrational conditions: rising behavior in one granular bed; sinking behavior in another granular bed. We slightly tune the size and density ratio to confirm the reliability of the experimental results. In addition, we examine the influences of interstitial air, convection and the initial position on the intruder's motion, speculating that the opposite motion could be traced to the material properties of the background particles
Two-dimensional neutron scintillation detector with optimal gamma discrimination
International Nuclear Information System (INIS)
Kanyo, M.; Reinartz, R.; Schelten, J.; Mueller, K.D.
1993-01-01
The gamma sensitivity of a two-dimensional scintillation neutron detector based on position sensitive photomultipliers (Hamamatsu R2387 PM) has been minimized by a digital differential discrimination unit. Since the photomultiplier gain is position-dependent by ±25% a discrimination unit was developed where digital upper and lower discrimination levels are set due to the position-dependent photomultiplier gain obtained from calibration measurements. By this method narrow discriminator windows can be used to reduce the gamma background drastically without effecting the neutron sensitivity of the detector. The new discrimination method and its performance tested by neutron measurements will be described. Experimental results concerning spatial resolution and γ-sensitivity are presented
Analysis of Two-Dimensional Electrophoresis Gel Images
DEFF Research Database (Denmark)
Pedersen, Lars
2002-01-01
This thesis describes and proposes solutions to some of the currently most important problems in pattern recognition and image analysis of two-dimensional gel electrophoresis (2DGE) images. 2DGE is the leading technique to separate individual proteins in biological samples with many biological...... and pharmaceutical applications, e.g., drug development. The technique results in an image, where the proteins appear as dark spots on a bright background. However, the analysis of these images is very time consuming and requires a large amount of manual work so there is a great need for fast, objective, and robust...... methods based on image analysis techniques in order to significantly accelerate this key technology. The methods described and developed fall into three categories: image segmentation, point pattern matching, and a unified approach simultaneously segmentation the image and matching the spots. The main...
On wakefields with two-dimensional planar geometry
International Nuclear Information System (INIS)
Chao, A.W.; Bane, K.L.F.
1996-10-01
In order to reach higher acceleration gradients in linear accelerators, it is advantageous to use a higher accelerating RF frequency, which in turn requires smaller accelerating structures. As the structure size becomes smaller, rectangular structures become increasingly interesting because they are easier to construct than cylindrically symmetric ones. One drawback of small structures, however, is that the wakefields generated by the beam in such structures tend to be strong. Recently, it has been suggested that one way of ameliorating this problem is to use rectangular structures that are very flat and to use flat beams. In the limiting case of a very flat planar geometry, the problem resembles a purely two-dimensional (2-D) problem, the wakefields of which have been studied
Three-dimensional versus two-dimensional vision in laparoscopy
DEFF Research Database (Denmark)
Sørensen, Stine D; Savran, Mona Meral; Konge, Lars
2016-01-01
were cohort size and characteristics, skill trained or operation performed, instrument used, outcome measures, and conclusions. Two independent authors performed the search and data extraction. RESULTS: Three hundred and forty articles were screened for eligibility, and 31 RCTs were included...... through a two-dimensional (2D) projection on a monitor, which results in loss of depth perception. To counter this problem, 3D imaging for laparoscopy was developed. A systematic review of the literature was performed to assess the effect of 3D laparoscopy. METHODS: A systematic search of the literature...... in the review. Three trials were carried out in a clinical setting, and 28 trials used a simulated setting. Time was used as an outcome measure in all of the trials, and number of errors was used in 19 out of 31 trials. Twenty-two out of 31 trials (71 %) showed a reduction in performance time, and 12 out of 19...
Two-dimensional echocardiographic features of right ventricular infarction
International Nuclear Information System (INIS)
D'Arcy, B.; Nanda, N.C.
1982-01-01
Real-time, two-dimensional echocardiographic studies were performed in 10 patients with acute myocardial infarction who had clinical features suggestive of right ventricular involvement. All patients showed right ventricular wall motion abnormalities. In the four-chamber view, seven patients showed akinesis of the entire right ventricular diaphragmatic wall and three showed akinesis of segments of the diaphragmatic wall. Segmental dyskinetic areas involving the right ventricular free wall were identified in four patients. One patient showed a large right ventricular apical aneurysm. Other echocardiographic features included enlargement of the right ventricle in eight cases, paradoxical ventricular septal motion in seven cases, tricuspid incompetence in eight cases, dilation of the stomach in four cases and localized pericardial effusion in two cases. Right ventricular infarction was confirmed by radionuclide methods in seven patients, at surgery in one patient and at autopsy in two patients
Discrete formulation for two-dimensional multigroup neutron diffusion equations
International Nuclear Information System (INIS)
Vosoughi, Naser; Salehi, Ali A.; Shahriari, Majid
2003-01-01
The objective of this paper is to introduce a new numerical method for neutronic calculation in a reactor core. This method can produce the final finite form of the neutron diffusion equation by classifying the neutronic variables and using two kinds of cell complexes without starting from the conventional differential form of the neutron diffusion equation. The method with linear interpolation produces the same convergence as the linear continuous finite element method. The quadratic interpolation is proven; the convergence order depends on the shape of the dual cell. The maximum convergence order is achieved by choosing the dual cell based on two Gauss' points. The accuracy of the method was examined with a well-known IAEA two-dimensional benchmark problem. The numerical results demonstrate the effectiveness of the new method
Suspension and simple optical characterization of two-dimensional membranes
Northeast, David B.; Knobel, Robert G.
2018-03-01
We report on a method for suspending two-dimensional crystal materials in an electronic circuit using an only photoresists and solvents. Graphene and NbSe2 are suspended tens of nanometers above metal electrodes with clamping diameters of several microns. The optical cavity formed from the membrane/air/metal structures enables a quick method to measure the number of layers and the gap separation using comparisons between the expected colour and optical microscope images. This characterization technique can be used with just an illuminated microscope with a digital camera which makes it adaptable to environments where other means of characterization are not possible, such as inside nitrogen glove boxes used in handling oxygen-sensitive materials.
Two-dimensional void reconstruction by neutron transmission
International Nuclear Information System (INIS)
Zakaib, G.D.; Harms, A.A.; Vlachopoulos, J.
1978-01-01
Contemporary algebraic reconstruction methods are utilized in investigating the two-dimensional void distribution in a water analog from neutron transmission measurements. It is sought to ultimately apply these techniques to the determination of time-averaged void distribution in two-phase flow systems as well as for potential usage in neutron radiography. Initially, projection data were obtained from a digitized model of a hypothetical two-phase representation and later from neutron beam traverses across a voided methacrylate plastic model. From 10 to 15 views were incorporated, and decoupling of overlapped measurements was utilized to afford greater resolution. In general, the additive Algebraic Reconstruction Technique yielded the best reconstructions, with others showing promise for noisy data. Results indicate the need for some further development of the method in interpreting real data
Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs.
Mannix, Andrew J; Zhou, Xiang-Feng; Kiraly, Brian; Wood, Joshua D; Alducin, Diego; Myers, Benjamin D; Liu, Xiaolong; Fisher, Brandon L; Santiago, Ulises; Guest, Jeffrey R; Yacaman, Miguel Jose; Ponce, Arturo; Oganov, Artem R; Hersam, Mark C; Guisinger, Nathan P
2015-12-18
At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes. Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal. Copyright © 2015, American Association for the Advancement of Science.
Selective growth of two-dimensional phosphorene on catalyst surface.
Qiu, L; Dong, J C; Ding, F
2018-02-01
Although the study of black phosphorene (BP) and its isomers has attracted enormous attention, the method of synthesizing high-quality samples in a large area is still pending. Here we explore the potential of using the chemical vapor deposition method to synthesize large-area two-dimensional (2D) phosphorene films on metal surfaces. Our ab initio calculations show that BP can be synthesized by using tin (Sn) as a catalyst, while one of its isomers, blue phosphorene (BLP), is very possible to be synthesized by using most other metals, such as Ag and Au. Besides, our study also suggests that the large binding energy between the 2D phosphorene and the active metal substrate may prohibit the exfoliation of the 2D phosphorene for real applications and, therefore, tin, silver and gold are predicted to be the most suitable catalysts for the synthesis of BP and BLP.
Cooperation in two-dimensional mixed-games
International Nuclear Information System (INIS)
Amaral, Marco A; Silva, Jafferson K L da; Wardil, Lucas
2015-01-01
Evolutionary game theory is a common framework to study the evolution of cooperation, where it is usually assumed that the same game is played in all interactions. Here, we investigate a model where the game that is played by two individuals is uniformly drawn from a sample of two different games. Using the master equation approach we show that the random mixture of two games is equivalent to play the average game when (i) the strategies are statistically independent of the game distribution and (ii) the transition rates are linear functions of the payoffs. We also use Monte-Carlo simulations in a two-dimensional lattice and mean-field techniques to investigate the scenario when the two above conditions do not hold. We find that even outside of such conditions, several quantities characterizing the mixed-games are still the same as the ones obtained in the average game when the two games are not very different. (paper)
Charge ordering in two-dimensional ionic liquids
Perera, Aurélien; Urbic, Tomaz
2018-04-01
The structural properties of model two-dimensional (2D) ionic liquids are examined, with a particular focus on the charge ordering process, with the use of computer simulation and integral equation theories. The influence of the logarithmic form of the Coulomb interaction, versus that of a 3D screened interaction form, is analysed. Charge order is found to hold and to be analogous for both interaction models, despite their very different form. The influence of charge ordering in the low density regime is discussed in relation to well known properties of 2D Coulomb fluids, such as the Kosterlitz-Thouless transition and criticality. The present study suggests the existence of a stable thermodynamic labile cluster phase, implying the existence of a liquid-liquid "transition" above the liquid-gas binodal. The liquid-gas and Kosterlitz-Thouless transitions would then take place inside the predicted cluster phase.
Spin precession in inversion-asymmetric two-dimensional systems
International Nuclear Information System (INIS)
Liu, M.-H.; Chang, C.-R.
2006-01-01
We present a theoretical method to calculate the expectation value of spin in an inversion-asymmetric two-dimensional (2D) system with respect to an arbitrarily spin-polarized electron state, injected via an ideal point contact. The 2D system is confined in a [0 0 1]-grown quantum well, where both the Rashba and the Dresselhaus spin-orbit couplings are taken into account. The obtained analytical results allow more concrete description of the spatial behaviors of the spin precession caused individually by the Rashba and the Dresselhaus terms. Applying the calculation on the Datta-Das spin-FET, whose original design considers only the Rashba effect inside the channel, we investigate the possible influence due to the Dresselhaus spin-orbit coupling. Concluded solution is the choice of ±[1±10], in particular [1 1 0], as the channel direction
Entropic Barriers for Two-Dimensional Quantum Memories
Brown, Benjamin J.; Al-Shimary, Abbas; Pachos, Jiannis K.
2014-03-01
Comprehensive no-go theorems show that information encoded over local two-dimensional topologically ordered systems cannot support macroscopic energy barriers, and hence will not maintain stable quantum information at finite temperatures for macroscopic time scales. However, it is still well motivated to study low-dimensional quantum memories due to their experimental amenability. Here we introduce a grid of defect lines to Kitaev's quantum double model where different anyonic excitations carry different masses. This setting produces a complex energy landscape which entropically suppresses the diffusion of excitations that cause logical errors. We show numerically that entropically suppressed errors give rise to superexponential inverse temperature scaling and polynomial system size scaling for small system sizes over a low-temperature regime. Curiously, these entropic effects are not present below a certain low temperature. We show that we can vary the system to modify this bound and potentially extend the described effects to zero temperature.
Thermoelectric transport in two-dimensional giant Rashba systems
Xiao, Cong; Li, Dingping; Ma, Zhongshui; Niu, Qian
Thermoelectric transport in strongly spin-orbit coupled two-dimensional Rashba systems is studied using the analytical solution of the linearized Boltzmann equation. To highlight the effects of inter-band scattering, we assume point-like potential impurities, and obtain the band-and energy-dependent transport relaxation times. Unconventional transport behaviors arise when the Fermi level lies near or below the band crossing point (BCP), such as the non-Drude electrical conducivity below the BCP, the failure of the standard Mott relation linking the Peltier coefficient to the electrical conductivity near the BCP, the enhancement of diffusion thermopower and figure of merit below the BCP, the zero-field Hall coefficient which is not inversely proportional to and not a monotonic function of the carrier density, the enhanced Nernst coefficient below the BCP, and the enhanced current-induced spin-polarization efficiency.
Sample preparation guidelines for two-dimensional electrophoresis.
Posch, Anton
2014-12-01
Sample preparation is one of the key technologies for successful two-dimensional electrophoresis (2DE). Due to the great diversity of protein sample types and sources, no single sample preparation method works with all proteins; for any sample the optimum procedure must be determined empirically. This review is meant to provide a broad overview of the most important principles in sample preparation in order to avoid a multitude of possible pitfalls. Sample preparation protocols from the expert in the field were screened and evaluated. On the basis of these protocols and my own comprehensive practical experience important guidelines are given in this review. The presented guidelines will facilitate straightforward protocol development for researchers new to gel-based proteomics. In addition the available choices are rationalized in order to successfully prepare a protein sample for 2DE separations. The strategies described here are not limited to 2DE and can also be applied to other protein separation techniques.
Thermal conductivity of disordered two-dimensional binary alloys.
Zhou, Yang; Guo, Zhi-Xin; Cao, Hai-Yuan; Chen, Shi-You; Xiang, Hong-Jun; Gong, Xin-Gao
2016-10-20
Using non-equilibrium molecular dynamics simulations, we have studied the effect of disorder on the thermal conductivity of two-dimensional (2D) C 1-x N x alloys. We find that the thermal conductivity not only depends on the substitution concentration of nitrogen, but also strongly depends on the disorder distribution. A general linear relationship is revealed between the thermal conductivity and the participation ratio of phonons in 2D alloys. Localization mode analysis further indicates that the thermal conductivity variation in the ordered alloys can be attributed to the number of inequivalent atoms. As for the disordered alloys, we find that the thermal conductivity variation can be described by a simple linear formula with the disorder degree and the substitution concentration. The present study suggests some general guidance for phonon manipulation and thermal engineering in low dimensional alloys.
Topological Valley Transport in Two-dimensional Honeycomb Photonic Crystals.
Yang, Yuting; Jiang, Hua; Hang, Zhi Hong
2018-01-25
Two-dimensional photonic crystals, in analogy to AB/BA stacking bilayer graphene in electronic system, are studied. Inequivalent valleys in the momentum space for photons can be manipulated by simply engineering diameters of cylinders in a honeycomb lattice. The inequivalent valleys in photonic crystal are selectively excited by a designed optical chiral source and bulk valley polarizations are visualized. Unidirectional valley interface states are proved to exist on a domain wall connecting two photonic crystals with different valley Chern numbers. With the similar optical vortex index, interface states can couple with bulk valley polarizations and thus valley filter and valley coupler can be designed. Our simple dielectric PC scheme can help to exploit the valley degree of freedom for future optical devices.
Two-dimensional plasma photonic crystals in dielectric barrier discharge
International Nuclear Information System (INIS)
Fan Weili; Dong Lifang; Zhang Xinchun
2010-01-01
A series of two-dimensional plasma photonic crystals have been obtained by filaments' self-organization in atmospheric dielectric barrier discharge with two water electrodes, which undergo the transition from square to square superlattice and finally to the hexagon. The spatio-temporal behaviors of the plasma photonic crystals in nanosecond scale have been studied by optical method, which show that the plasma photonic crystal is actually an integration of different transient sublattices. The photonic band diagrams of the transverse electric (TE) mode and transverse magnetic mode for each sublattice of these plasma photonic crystals have been investigated theoretically. A wide complete band gap is formed in the hexagonal plasma photonic crystal with the TE mode. The changes of the band edge frequencies and the band gap widths in the evolvement of different structures are studied. A kind of tunable plasma photonic crystal which can be controlled both in space and time is suggested.
Electromagnetic two-dimensional analysis of trapped-ion eigenmodes
Energy Technology Data Exchange (ETDEWEB)
Kim, D.; Rewoldt, G.
1984-11-01
A two-dimensional electromagnetic analysis of the trapped-ion instability for the tokamak case with ..beta.. not equal to 0 has been made, based on previous work in the electrostatic limit. The quasineutrality condition and the component of Ampere's law along the equilibrium magnetic field are solved for the perturbed electrostatic potential and the component of the perturbed vector potential along the equilibrium magnetic field. The general integro-differential equations are converted into a matrix eigenvalue-eigenfunction problem by expanding in cubic B-spline finite elements in the minor radius and in Fourier harmonics in the poloidal angle. A model MHD equilibrium with circular, concentric magnetic surfaces and large aspect ratio is used which is consistent with our assemption that B << 1. The effect on the trapped-ion mode of including these electromagnetic extensions to the calculation is considered, and the temperature (and ..beta..) scaling of the mode frequency is shown and discussed.
Nematic Equilibria on a Two-Dimensional Annulus
Lewis, A. H.
2017-01-16
We study planar nematic equilibria on a two-dimensional annulus with strong and weak tangent anchoring, in the Oseen–Frank theoretical framework. We analyze a radially invariant defect-free state and compute analytic stability criteria for this state in terms of the elastic anisotropy, annular aspect ratio, and anchoring strength. In the strong anchoring case, we define and characterize a new spiral-like equilibrium which emerges as the defect-free state loses stability. In the weak anchoring case, we compute stability diagrams that quantify the response of the defect-free state to radial and azimuthal perturbations. We study sector equilibria on sectors of an annulus, including the effects of weak anchoring and elastic anisotropy, giving novel insights into the correlation between preferred numbers of boundary defects and the geometry. We numerically demonstrate that these sector configurations can approximate experimentally observed equilibria with boundary defects.
Self-organized defect strings in two-dimensional crystals.
Lechner, Wolfgang; Polster, David; Maret, Georg; Keim, Peter; Dellago, Christoph
2013-12-01
Using experiments with single-particle resolution and computer simulations we study the collective behavior of multiple vacancies injected into two-dimensional crystals. We find that the defects assemble into linear strings, terminated by dislocations with antiparallel Burgers vectors. We show that these defect strings propagate through the crystal in a succession of rapid one-dimensional gliding and rare rotations. While the rotation rate decreases exponentially with the number of defects in the string, the diffusion constant is constant for large strings. By monitoring the separation of the dislocations at the end points, we measure their effective interactions with high precision beyond their spontaneous formation and annihilation, and we explain the double-well form of the dislocation interaction in terms of continuum elasticity theory.
Photostrictive Two-Dimensional Materials in the Monochalcogenide Family
Haleoot, Raad; Paillard, Charles; Kaloni, Thaneshwor P.; Mehboudi, Mehrshad; Xu, Bin; Bellaiche, L.; Barraza-Lopez, Salvador
2017-06-01
Photostriction is predicted for group-IV monochalcogenide monolayers, two-dimensional ferroelectrics with rectangular unit cells (the lattice vector a1 is larger than a2) and an intrinsic dipole moment parallel to a1. Photostriction is found to be related to the structural change induced by a screened electric polarization (i.e., a converse piezoelectric effect) in photoexcited electronic states with either px or py (in-plane) orbital symmetry that leads to a compression of a1 and a comparatively smaller increase of a2 for a reduced unit cell area. The structural change documented here is 10 times larger than that observed in BiFeO3 , making monochalcogenide monolayers an ultimate platform for this effect. This structural modification should be observable under experimentally feasible densities of photexcited carriers on samples that have been grown already, having a potential usefulness for light-induced, remote mechano-optoelectronic applications.
Surface Ship Shock Modeling and Simulation: Two-Dimensional Analysis
Directory of Open Access Journals (Sweden)
Young S. Shin
1998-01-01
Full Text Available The modeling and simulation of the response of a surface ship system to underwater explosion requires an understanding of many different subject areas. These include the process of underwater explosion events, shock wave propagation, explosion gas bubble behavior and bubble-pulse loading, bulk and local cavitation, free surface effect, fluid-structure interaction, and structural dynamics. This paper investigates the effects of fluid-structure interaction and cavitation on the response of a surface ship using USA-NASTRAN-CFA code. First, the one-dimensional Bleich-Sandler model is used to validate the approach, and second, the underwater shock response of a two-dimensional mid-section model of a surface ship is predicted with a surrounding fluid model using a constitutive equation of a bilinear fluid which does not allow transmission of negative pressures.
Rigorous results in space-periodic two-dimensional turbulence
Kuksin, Sergei; Shirikyan, Armen
2017-12-01
We survey the recent advance in the rigorous qualitative theory of the 2d stochastic Navier-Stokes system that is relevant to the description of turbulence in two-dimensional fluids. After discussing briefly the initial-boundary value problem and the associated Markov process, we formulate results on the existence, uniqueness, and mixing of a stationary measure. We next turn to various consequences of these properties: strong law of large numbers, central limit theorem, and random attractors related to a unique stationary measure. We also discuss the Donsker-Varadhan and Freidlin-Wentzell type large deviations, the inviscid limit, and asymptotic results in 3d thin domains. We conclude with some open problems.
Superconductivity in engineered two-dimensional electron gases
Chubukov, Andrey V.; Kivelson, Steven A.
2017-11-01
We consider Kohn-Luttinger mechanism for superconductivity in a two-dimensional electron gas confined to a narrow well between two grounded metallic planes with two occupied subbands with Fermi momenta kF L>kF S . On the basis of a perturbative analysis, we conclude that non-s -wave superconductivity emerges even when the bands are parabolic. We analyze the conditions that maximize Tc as a function of the distance to the metallic planes, the ratio kF L/kF S , and rs, which measures the strength of Coulomb correlations. The largest attraction is in p -wave and d -wave channels, of which p wave is typically the strongest. For rs=O (1 ) we estimate that the dimensionless coupling λ ≈10-1 , but it likely continues increasing for larger rs (where we lose theoretical control).
Effective-range dependence of two-dimensional Fermi gases
Schonenberg, L. M.; Verpoort, P. C.; Conduit, G. J.
2017-08-01
The Feshbach resonance provides precise control over the scattering length and effective range of interactions between ultracold atoms. We propose the ultratransferable pseudopotential to model effective interaction ranges -1.5 ≤kF2Reff2≤0 , where Reff is the effective range and kF is the Fermi wave vector, describing narrow to broad Feshbach resonances. We develop a mean-field treatment and exploit the pseudopotential to perform a variational and diffusion Monte Carlo study of the ground state of the two-dimensional Fermi gas, reporting on the ground-state energy, contact, condensate fraction, momentum distribution, and pair-correlation functions as a function of the effective interaction range across the BEC-BCS crossover. The limit kF2Reff2→-∞ is a gas of bosons with zero binding energy, whereas ln(kFa )→-∞ corresponds to noninteracting bosons with infinite binding energy.
Fluid dynamics of two-dimensional pollination in Ruppia maritima
Musunuri, Naga; Bunker, Daniel; Pell, Susan; Pell, Fischer; Singh, Pushpendra
2016-11-01
The aim of this work is to understand the physics underlying the mechanisms of two-dimensional aquatic pollen dispersal, known as hydrophily. We observed two mechanisms by which the pollen released from male inflorescences of Ruppia maritima is adsorbed on a water surface: (i) inflorescences rise above the surface and after they mature their pollen mass falls onto the surface as clumps and disperses on the surface; (ii) inflorescences remain below the surface and produce air bubbles which carry their pollen mass to the surface where it disperses. In both cases dispersed pollen masses combined under the action of capillary forces to form pollen rafts. This increases the probability of pollination since the capillary force on a pollen raft towards a stigma is much larger than on a single pollen grain. The presence of a trace amount of surfactant can disrupt the pollination process so that the pollen is not transported or captured on the water surface. National Science Foundation.
Two-dimensional assemblies from crystallizable homopolymers with charged termini
He, Xiaoming; Hsiao, Ming-Siao; Boott, Charlotte E.; Harniman, Robert L.; Nazemi, Ali; Li, Xiaoyu; Winnik, Mitchell A.; Manners, Ian
2017-04-01
The creation of shaped, uniform and colloidally stable two-dimensional (2D) assemblies by bottom-up methods represents a challenge of widespread current interest for a variety of applications. Herein, we describe the utilization of surface charge to stabilize self-assembled planar structures that are formed from crystallizable polymer precursors by a seeded growth approach. Addition of crystallizable homopolymers with charged end-groups to seeds generated by the sonication of block copolymer micelles with crystalline cores yields uniform platelet micelles with controlled dimensions. Significantly, the seeded growth approach is characterized by a morphological memory effect whereby the origin of the seed, which can involve a quasi-hexagonal or rectangular 2D platelet precursor, dictates the observed 2D platelet shape. This new strategy is illustrated using two different polymer systems, and opens the door to the construction of 2D hierarchical structures with broad utility.
Splitting rules for spectra of two-dimensional Fibonacci quasilattices
Yang, Xiangbo; Liu, Youyan
1997-10-01
In the framework of the single-electron tight-binding on-site model, after establishing the method of constructing a class of two-dimensional Fibonacci quasilattices, we have studied the rules of energy spectra splitting for these quasilattices by means of a decomposition-decimation method based on the renormalization-group technique. Under the first approximation, the analytic results show that there exist only six kinds of clusters and the electronic energy bands split as type Y and consist of nine subbands. Instead of the on-site model, the transfer model should be used for the higher hierarchy of the spectra, the electronic energy spectra split as type F. The analytic results are confirmed by numerical simulations.
Soliton nanoantennas in two-dimensional arrays of quantum dots
Gligorić, G.; Maluckov, A.; Hadžievski, Lj; Slepyan, G. Ya; Malomed, B. A.
2015-06-01
We consider two-dimensional (2D) arrays of self-organized semiconductor quantum dots (QDs) strongly interacting with electromagnetic field in the regime of Rabi oscillations. The QD array built of two-level states is modelled by two coupled systems of discrete nonlinear Schrödinger equations. Localized modes in the form of single-peaked fundamental and vortical stationary Rabi solitons and self-trapped breathers have been found. The results for the stability, mobility and radiative properties of the Rabi modes suggest a concept of a self-assembled 2D soliton-based nano-antenna, which is stable against imperfections In particular, we discuss the implementation of such a nano-antenna in the form of surface plasmon solitons in graphene, and illustrate possibilities to control their operation by means of optical tools.
Oscillation of Two-Dimensional Neutral Delay Dynamic Systems
Directory of Open Access Journals (Sweden)
Xinli Zhang
2013-01-01
Full Text Available We consider a class of nonlinear two-dimensional dynamic systems of the neutral type (x(t-a(tx(τ1(tΔ=p(tf1(y(t, yΔ(t=-q(tf2(x(τ2(t. We obtain sufficient conditions for all solutions of the system to be oscillatory. Our oscillation results when a(t=0 improve the oscillation results for dynamic systems on time scales that have been established by Fu and Lin (2010, since our results do not restrict to the case where f(u=u. Also, as a special case when =ℝ, our results do not require an to be a positive real sequence. Some examples are given to illustrate the main results.
The first principle calculation of two-dimensional Dirac materials
Lu, Jin
2017-12-01
As the size of integrated device becoming increasingly small, from the last century, semiconductor industry is facing the enormous challenge to break the Moore’s law. The development of calculation, communication and automatic control have emergent expectation of new materials at the aspect of semiconductor industrial technology and science. In spite of silicon device, searching the alternative material with outstanding electronic properties has always been a research point. As the discovery of graphene, the research of two-dimensional Dirac material starts to express new vitality. This essay studied the development calculation of 2D material’s mobility and introduce some detailed information of some approximation method of the first principle calculation.
Persistence of Precursor Waves in Two-dimensional Relativistic Shocks
Energy Technology Data Exchange (ETDEWEB)
Iwamoto, Masanori; Amano, Takanobu; Hoshino, Masahiro [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Matsumoto, Yosuke, E-mail: iwamoto@eps.s.u-tokyo.ac.jp [Department of Physics, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522 (Japan)
2017-05-01
We investigated the efficiency of coherent upstream large-amplitude electromagnetic wave emission via synchrotron maser instability in relativistic magnetized shocks using two-dimensional particle-in-cell simulations. We considered a purely perpendicular shock in an electron–positron plasma. The coherent wave emission efficiency was measured as a function of the magnetization parameter σ , which is defined as the ratio of the Poynting flux to the kinetic energy flux. The wave amplitude was systematically smaller than that observed in one-dimensional simulations. However, it continued to persist, even at a considerably low magnetization rate, where the Weibel instability dominated the shock transition. The emitted electromagnetic waves were sufficiently strong to disturb the upstream medium, and transverse filamentary density structures of substantial amplitude were produced. Based on this result, we discuss the possibility of the wakefield acceleration model to produce nonthermal electrons in a relativistic magnetized ion–electron shock.
Flat Chern Band in a Two-Dimensional Organometallic Framework
Liu, Zheng; Wang, Zheng-Fei; Mei, Jia-Wei; Wu, Yong-Shi; Liu, Feng
2013-03-01
By combining exotic band dispersion with nontrivial band topology, an interesting type of band structure, namely, the flat Chern band, has recently been proposed to spawn high-temperature fractional quantum Hall states. Despite the proposal of several theoretical lattice models, however, it remains doubtful whether such a “romance of flatland” could exist in a real material. Here, we present a first-principles design of a two-dimensional indium-phenylene organometallic framework that realizes a nearly flat Chern band right around the Fermi level by combining lattice geometry, spin-orbit coupling, and ferromagnetism. An effective four-band model is constructed to reproduce the first-principles results. Our design, in addition, provides a general strategy to synthesize topologically nontrivial materials by virtue of organic chemistry and nanotechnology.
Two-dimensional analysis of motion artifacts, including flow effects
International Nuclear Information System (INIS)
Litt, A.M.; Brody, A.S.; Spangler, R.A.; Scott, P.D.
1990-01-01
The effects of motion on magnetic resonance images have been theoretically analyzed for the case of a point-like object in simple harmonic motion and for other one-dimensional trajectories. The authors of this paper extend this analysis to a generalized two-dimensional magnetization with an arbitrary motion trajectory. The authors provide specific solutions for the clinically relevant cases of the cross-sections of cylindrical objects in the body, such as the aorta, which has a roughly one-dimensional, simple harmonic motion during respiration. By extending the solution to include inhomogeneous magnetizations, the authors present a model which allows the effects of motion artifacts and flow artifacts to be analyzed simultaneously
Custom acetabular component design with interactive two-dimensional CT
International Nuclear Information System (INIS)
Magid, D.; Millet, C.; Brooker, A.F. Jr.; Fishman, E.K.
1990-01-01
This paper reports on a revision of failed acetabular components that must accommodate existing segmental and cavitary bone defects and global loss of bone stock. Two-dimensional CT can be used to determine which patients may benefit from a custom acetabulum and to design such a prosthesis. Ninety-one sequential failed hip arthroplasties were reviewed to find 12 potential custom cup candidates, of whom seven underwent CT assessment and subsequent cup design and placement. Coronal and sagittal CT was used to review existing bone stock and bone defects, to measure and map the contour of the defect into which the new cup must fit and to determine the precise placement, angulation, and depth of screw holes to provide purchase for the new cup. A template was produced for approval, followed by cup manufacture and placement
Statistical thermodynamics of a two-dimensional relativistic gas.
Montakhab, Afshin; Ghodrat, Malihe; Barati, Mahmood
2009-03-01
In this paper we study a fully relativistic model of a two-dimensional hard-disk gas. This model avoids the general problems associated with relativistic particle collisions and is therefore an ideal system to study relativistic effects in statistical thermodynamics. We study this model using molecular-dynamics simulation, concentrating on the velocity distribution functions. We obtain results for x and y components of velocity in the rest frame (Gamma) as well as the moving frame (Gamma;{'}) . Our results confirm that Jüttner distribution is the correct generalization of Maxwell-Boltzmann distribution. We obtain the same "temperature" parameter beta for both frames consistent with a recent study of a limited one-dimensional model. We also address the controversial topic of temperature transformation. We show that while local thermal equilibrium holds in the moving frame, relying on statistical methods such as distribution functions or equipartition theorem are ultimately inconclusive in deciding on a correct temperature transformation law (if any).
Two-dimensional atom localization induced by a squeezed vacuum
Wang, Fei; Xu, Jun
2016-10-01
A scheme of two-dimensional (2D) atom localization induced by a squeezed vacuum is proposed, in which the three-level V-type atoms interact with two classical standing-wave fields. It is found that when the environment is changed from an ordinary vacuum to a squeezed vacuum, the 2D atom localization is realized by detecting the position-dependent resonance fluorescence spectrum. For comparison, we demonstrate that the atom localization originating from the quantum interference effect is distinct from that induced by a squeezed vacuum. Furthermore, the combined effects of the squeezed vacuum and quantum interference are also discussed under appropriate conditions. The internal physical mechanism is analyzed in terms of dressed-state representation. Project supported by the National Natural Science Foundation of China (Grant Nos. 11574179 and 11204099) and the Natural Science Foundation of Hubei Province, China (Grant No. 2014CFC1148).
Efficient two-dimensional compressive sensing in MIMO radar
Shahbazi, Nafiseh; Abbasfar, Aliazam; Jabbarian-Jahromi, Mohammad
2017-12-01
Compressive sensing (CS) has been a way to lower sampling rate leading to data reduction for processing in multiple-input multiple-output (MIMO) radar systems. In this paper, we further reduce the computational complexity of a pulse-Doppler collocated MIMO radar by introducing a two-dimensional (2D) compressive sensing. To do so, we first introduce a new 2D formulation for the compressed received signals and then we propose a new measurement matrix design for our 2D compressive sensing model that is based on minimizing the coherence of sensing matrix using gradient descent algorithm. The simulation results show that our proposed 2D measurement matrix design using gradient decent algorithm (2D-MMDGD) has much lower computational complexity compared to one-dimensional (1D) methods while having better performance in comparison with conventional methods such as Gaussian random measurement matrix.
Two-dimensional fruit ripeness estimation using thermal imaging
Sumriddetchkajorn, Sarun; Intaravanne, Yuttana
2013-06-01
Some green fruits do not change their color from green to yellow when being ripe. As a result, ripeness estimation via color and fluorescent analytical approaches cannot be applied. In this article, we propose and show for the first time how a thermal imaging camera can be used to two-dimensionally classify fruits into different ripeness levels. Our key idea relies on the fact that the mature fruits have higher heat capacity than the immature ones and therefore the change in surface temperature overtime is slower. Our experimental proof of concept using a thermal imaging camera shows a promising result in non-destructively identifying three different ripeness levels of mangoes Mangifera indica L.
Sieving hydrogen isotopes through two-dimensional crystals.
Lozada-Hidalgo, M; Hu, S; Marshall, O; Mishchenko, A; Grigorenko, A N; Dryfe, R A W; Radha, B; Grigorieva, I V; Geim, A K
2016-01-01
One-atom-thick crystals are impermeable to atoms and molecules, but hydrogen ions (thermal protons) penetrate through them. We show that monolayers of graphene and boron nitride can be used to separate hydrogen ion isotopes. Using electrical measurements and mass spectrometry, we found that deuterons permeate through these crystals much slower than protons, resulting in a separation factor of ≈10 at room temperature. The isotope effect is attributed to a difference of ≈60 milli-electron volts between zero-point energies of incident protons and deuterons, which translates into the equivalent difference in the activation barriers posed by two-dimensional crystals. In addition to providing insight into the proton transport mechanism, the demonstrated approach offers a competitive and scalable way for hydrogen isotope enrichment. Copyright © 2016, American Association for the Advancement of Science.