Articles de revues : « Finite coherence length »

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Shinohara, Yuya, et Yoshiyuki Amemiya. « Effect of finite spatial coherence length on small-angle scattering ». Journal of Applied Crystallography 48, n^o 6 (13 octobre 2015) : 1660–64. http://dx.doi.org/10.1107/s160057671501715x.

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This study shows that forward scattering at the origin of reciprocal space contributes to the scattering intensity profiles of ultra-small-angle scattering. The forward scattering corresponds to a Fourier transform of the X-ray coherent volume on a sample. This contribution is usually ignored in the study of small-angle scattering, while it is fully considered in the fields of X-ray imaging, such as coherent X-ray diffraction imaging and X-ray ptychography. This effect is explicitly illustrated in the context of small-angle scattering, and the effect of a finite spatial coherence length on small-angle scattering is discussed.

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Jacoboni, Carlo, et Paolo Bordone. « Wigner transport equation with finite coherence length ». Journal of Computational Electronics 13, n^o 1 (2 octobre 2013) : 257–63. http://dx.doi.org/10.1007/s10825-013-0510-7.

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Baesens, C., et R. S. MacKay. « Finite coherence length for equilibrium states of generalized adiabatic Holstein models ». Journal of Mathematical Physics 38, n^o 4 (avril 1997) : 2104–14. http://dx.doi.org/10.1063/1.532197.

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Tomita, Makoto, et Hiroshi Ikari. « Influence of finite coherence length of incoming light on enhanced backscattering ». Physical Review B 43, n^o 4 (1 février 1991) : 3716–19. http://dx.doi.org/10.1103/physrevb.43.3716.

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Hayashi, Masahito, Kun Fang et Kun Wang. « Finite Block Length Analysis on Quantum Coherence Distillation and Incoherent Randomness Extraction ». IEEE Transactions on Information Theory 67, n^o 6 (juin 2021) : 3926–44. http://dx.doi.org/10.1109/tit.2021.3064009.

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Gong, Zhiben, Yingjian Wang et Yi Wu. « Finite temporal measurements of the statistical characteristics of the atmospheric coherence length ». Applied Optics 37, n^o 21 (20 juillet 1998) : 4541. http://dx.doi.org/10.1364/ao.37.004541.

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CRISAN, M., et I. GROSU. « BOSE–EINSTEIN QUASICONDENSATION IN 2D SYSTEMS ». Modern Physics Letters B 19, n^o 17 (30 juillet 2005) : 821–27. http://dx.doi.org/10.1142/s0217984905008852.

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We calculate the finite temperature correlation function, the coherence length and the critical temperature for a two-dimensional (2D) bosonic system, which presents the quasicondensation (a finite number of occupied states with p0≠0 momentum) effect at very low temperatures. This state, discovered experimentally, appear below a critical temperature for a finite number of particles.

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Rajput, B. S., et Sandeep Kumar. « Superconductivity due to Condensation of Monopoles around RCD Strings in SU(2) Gauge Theory ». Advances in High Energy Physics 2010 (2010) : 1–22. http://dx.doi.org/10.1155/2010/768054.

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The study of the condensation of monopoles and the resulting chromomagnetic superconductivity have been undertaken in restricted chromodynamics of SU(2) gauge theory. Constructing the RCD Lagrangian and the partition function for monopoles in terms of string action and the action of the current around the strings, the monopole current in RCD chromo magnetic superconductor has been derived and it has shown that in London' limit the penetration length governs the monopole density around RCD string in chromo magnetic superconductors while with finite (nonzero) coherence length the leading behavior of the monopole density at large distances from the string is controlled by the coherence length and not by the penetration length.

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BEATO, V., et H. ENGEL. « COHERENCE RESONANCE PHENOMENA IN AN EXCITABLE SYSTEM DRIVEN BY COLORED NOISE ». Fluctuation and Noise Letters 06, n^o 01 (mars 2006) : L85—L94. http://dx.doi.org/10.1142/s0219477506003173.

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We study the coherence of noise-induced excitations in a modified stochastic Oregonator model for the light-sensitive Belousov-Zhabotinsky (BZ) reaction assuming that the intensity of the applied illumination is a spatio-temporal stochastic field with finite correlation time and correlation length. For a single excitable element, we find coherence resonance (CR) with respect to the correlation time. In the spatially extended medium of diffusively coupled excitable elements, we observe CR for suitable combinations of the correlation time and length of the noise.

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Westfahl, Harry, Sérgio A. Lordano Luiz, Bernd C. Meyer et Florian Meneau. « The coherent radiation fraction of low-emittance synchrotrons ». Journal of Synchrotron Radiation 24, n^o 3 (24 mars 2017) : 566–75. http://dx.doi.org/10.1107/s1600577517003058.

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In this work the coherence properties of the synchrotron radiation beam from an X-ray undulator in a fourth-generation storage ring are analyzed. A slightly focused X-ray beam is simulated using a wavefront propagation through a non-redundant array of slits and the mutual coherence function is directly obtained and compared with the Gaussian–Schell approximation. The numerical wave propagation and the approximate analytical approaches are shown to agree qualitatively, and it is also shown that, when the coherent fraction is selected by a finite aperture before the focusing element, even achromatic focusing systems like total reflection mirrors become slightly chromatic. This effect is also well accounted for in the Gaussian–Schell model. The wavefront propagation simulation through the non-redundant array was repeated with an imperfect mirror demonstrating that, although the wavefront is distorted, its coherent length is practically unchanged.

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CRISAN, M., I. TIFREA, D. BODEA et I. GROSU. « CRITICAL BEHAVIOR OF A TWO-DIMENSIONAL DILUTE BOSE GAS ». Modern Physics Letters B 15, n^o 20 (30 août 2001) : 837–46. http://dx.doi.org/10.1142/s0217984901002634.

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We applied the Renormalization Group method at finite temperature to reconsider the two-dimensional dilute Bose gas. The general flow equations are obtained for the case of arbitrary dimensions, and by considering the two-dimensional limit, we estimate the value of the critical temperature, coherence length and specific heat. The value of the critical temperature is in agreement with previous calculations performed using the t-matrix method. The coherence length and the specific heat present a non-universal behavior, a logarithmic temperature dependence in the critical region being identified.

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Mattiucci, Nadia, Giuseppe D'Aguanno, Michael Scalora et Mark J. Bloemer. « Coherence length for second-harmonic generation in nonlinear, one-dimensional, finite, multilayered structures ». Journal of the Optical Society of America B 24, n^o 4 (15 mars 2007) : 877. http://dx.doi.org/10.1364/josab.24.000877.

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GEORGELIN, Y., M. KNECHT, Y. LEBLANC et J. C. WALLET. « FINITE TEMPERATURE LINEAR RESPONSE THEORY OF ANYONIC SUPERCONDUCTIVITY ». Modern Physics Letters B 05, n^o 03 (10 février 1991) : 211–25. http://dx.doi.org/10.1142/s0217984991000265.

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We extend a zero temperature non-relativistic anyonic superconductivity model to the finite temperature case. Making use of the finite temperature linear response theory, we calculate temperature corrections to various parameters of zero temperature superconductivity such as the London penetration depth, the acoustic phonon velocity and the coherence length. These results are qualitatively compared to known experimental results. Our results are expected to be valid in the low temperature regime.

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Kim, Seong-Hu, et Yong-Hwa Park. « Interaural Coherence Estimation for Speech Processing in Reverberant Environment ». Applied Sciences 10, n^o 3 (22 janvier 2020) : 769. http://dx.doi.org/10.3390/app10030769.

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Interaural coherence is used to quantify the effects of reverberation on speech, and previous studies applied the conventional method using all previous time data in the form of an infinite impulse response filter to estimate interaural coherence. To consider a characteristic of speech that continuously changes over time, this paper proposes a new method of estimating interaural coherence using time data within a finite length of speech, which is called the quasi-steady interval. The length of the quasi-steady interval is determined with various frequency bands, reverberation times, and short-time Fourier transform (STFT) variables through numerical experiment, and it decreased as reverberation time decreased and the frequency increased. In this interval, a diffuse speech, which is an infinite sum of reflected speeches of different propagating paths, is uncorrelated between two microphones apart from each other; thus, the coherence is close to zero. However, a direct speech measured at the two microphones has steady amplitude and phase difference in this internal; thus, the coherence is close to one. Moreover, the new method is the form of a finite impulse response filter that has a linear phase delay or zero phase delay with respect to speech to frequency; thus, the same or zero time delay for each frequency is applied to the power spectral density. Therefore, the coherence estimation of the new method is closer to the ideal value than the conventional one, and the coherence is accurately estimated at the time–frequency bins of direct speech, which is time-varying according to speech variation.

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LEBLANC, Y., et J. C. WALLET. « MORE ON FINITE TEMPERATURE ANYON SUPERCONDUCTIVITY ». Modern Physics Letters B 06, n^o 26 (10 novembre 1992) : 1623–37. http://dx.doi.org/10.1142/s0217984992001332.

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In the framework of finite temperature linear response theory, we analyze to a greater extent the nature of anyonic superconductivity. Using identities among Laguerre polynomials and Bessel functions, we provide simple and useful expressions for the response function in the form of high temperature expansions. The physical penetration depth as well as the Landau-Ginzburg coherence length are calculated for all temperatures. We find that for statistics restricted by n≪450, anyon superconductors are type II local (London) superconductors at low temperature and type I non-local (Pippard) superconductors at high temperature. The threshold temperature is also obtained.

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Jin, Long, Zirui Zhang, Nuo Wang, Zixin Liu, Yuwei Deng et Yanhua Fu. « Intensity Distribution of Partially Coherent Array Finite Airy Beams Propagating in Atmospheric Turbulence ». International Journal of Optics 2021 (5 février 2021) : 1–11. http://dx.doi.org/10.1155/2021/6649144.

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Based on the extended Huygens–Fresnel integral and the Rytov phase structure function, the closed-form expression of a partially coherent array finite Airy beams (PCAFABs) cutting through the Kolmogorov atmospheric turbulence is derived in the space domain under the paraxial approximation. The characteristics of the PCAFABs evoluting in the atmospheric environment are investigated in detail on the basis of the derived wave propagation formulae. We mainly illustrate the intensity profile of this beam changed with the truncation parameter, coherence length, and turbulence factor at several cross sections of the atmospheric space by means of numerical figures. It is convinced that the present concept and derived conclusions will provide useful exploration for learning the optical properties of the PCAFABs transmitting in the atmospheric turbulence, especially for free-space optical communication area.

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Suzaki, Yoshifumi, Hiromu Iwata, Keisuke Nakayama, Yasuo Mizutami, Makoto Yamauchi, Eiji Izumikawa, Takashi Yokouchi et Seiki Ejima. « Apodization Method Owing to the Finite Length of UV Laser Coherence in Fabricating Fiber Bragg Gratings ». Japanese Journal of Applied Physics 45, n^o 12 (7 décembre 2006) : 9100–9102. http://dx.doi.org/10.1143/jjap.45.9100.

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Rypina, Irina I., Timothy Getscher, Lawrence J. Pratt et Tamay Ozgokmen. « Applying dynamical systems techniques to real ocean drifters ». Nonlinear Processes in Geophysics 29, n^o 4 (7 octobre 2022) : 345–61. http://dx.doi.org/10.5194/npg-29-345-2022.

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Abstract. This paper presents the first comprehensive comparison of several different dynamical-systems-based measures of stirring and Lagrangian coherence, computed from real ocean drifters. Seven commonly used methods (finite-time Lyapunov exponent (FTLE), trajectory path length, trajectory correlation dimension, trajectory encounter volume, Lagrangian-averaged vorticity deviation, dilation, and spectral clustering) were applied to 144 surface drifters in the Gulf of Mexico in order to map out the dominant Lagrangian coherent structures. Among the detected structures were regions of hyperbolic nature resembling stable manifolds from classical examples, divergent and convergent zones, and groups of drifters that moved more coherently and stayed closer together than the rest of the drifters. Many methods highlighted the same structures, but there were differences too. Overall, five out of seven methods provided useful information about the geometry of transport within the domain spanned by the drifters, whereas the path length and correlation dimension methods were less useful than others.

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Lee, K. L., et F. L. Yang. « Asymptotic analysis for the propagation and arresting process of a finite dry granular mass down a rough incline ». Journal of Fluid Mechanics 806 (30 septembre 2016) : 234–53. http://dx.doi.org/10.1017/jfm.2016.590.

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This work presents an asymptotic analysis for the propagation and arresting process of a two-dimensional finite granular mass down a rough incline in a shallow configuration. Bulk shear stress and arresting mechanism are formulated according to the coherence length model that considers momentum transport at a length scale over which grains are spatially correlated. A Bagnold-like streamwise velocity and a non-zero transverse velocity are solved and integrated into a surface kinematic condition to give an advection–diffusion equation for the bulk surface profile, $h(x,t)$, that is solved using the matched asymptotic method. These flow solutions are further employed to determine composite solutions for a flow-front trajectory and a local coherence length, $l(x,t)$, which reveals smooth growth of $h(x,t)$ and $l(x,t)$ from zero at the propagating front with $l(x,t)\ll h(x,t)$. At the rear, $h(x,t)$ vanishes but $l(x,t)$ asymptotes to a constant that depends on inclination angle. According to the arresting mechanism, the location where $l(x,t)\sim h(x,t)$ is solved to the leading order to locate the deposition front so that its propagation dynamics can be derived. A finite flow arrest time, $T_{d}$, and the corresponding finite run-out distance, $L_{d}$, are evaluated when all the flowing mass has passed the deposition front and are employed to construct a modified front trajectory with the deposition effect. The predicted run-out distance and front trajectory profile compare reasonably well with experimental data in the literature on inclinations at angles higher than the material repose angle.

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Islam, Saiful, Johan Stiens, Gert Poesen, Irina Jaeger et Roger Vounckx. « Passive Frequency Selective Surface Array as a Diffuser for Destroying Millimeter Wave Coherence ». Active and Passive Electronic Components 2008 (2008) : 1–6. http://dx.doi.org/10.1155/2008/391745.

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This paper presents the design, construction, and testing of grounded frequency selective surface (FSS) array as a diffuser for destroying millimeter wave coherence which is used to eliminate speckle in active millimeter wave imaging. To create stochastically independent illumination patterns, we proposed a diffuser based on random-phase distributions obtained by changing the incident frequency. The random-phase diffuser was obtained by mixing up the phase relations between the cells of a deterministic function (e.g., beam splitter). The slot length of FSS is the main design parameter used to optimize the phase shifting properties of the array. The critical parameters of the diffuser array design, such as phase relation with slot lengths, losses, and bandwidth, are discussed. We designed the FSS arrays with finite integral technique (FIT), fabricated by etching technique, and characterized theS-parameters with a free-space MVNA, and measured the radiation patterns with a BWO in motorized setup.

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Yun, Chol-Song, Chol-Jin Kang, Chang-Il Kim et Song-Chan Li. « Magnetic field dependence of partially-separated Andreev bound states in semiconductor-superconductor nanowires with finite coherence length ». Physica B : Condensed Matter 612 (juillet 2021) : 412887. http://dx.doi.org/10.1016/j.physb.2021.412887.

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Baraff, G. A. « Model for the effect of finite phase-coherence length on resonant transmission and capture by quantum wells ». Physical Review B 58, n^o 20 (15 novembre 1998) : 13799–810. http://dx.doi.org/10.1103/physrevb.58.13799.

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Kim, Su-Chan, et Hyun M. Jang. « Pb()O3-type Perovskites : Part II. Short-range Order Parameter as a Criterion of the Distinction Between Relaxor and Normal Ferroelectrics ». Journal of Materials Research 12, n^o 8 (août 1997) : 2127–33. http://dx.doi.org/10.1557/jmr.1997.0285.

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A classification scheme of Pb()O3-type perovskites with respect to the B-site order parameters was proposed based on the theoretical calculation of the short-range order parameter (σ) using the pair-correlation model. The calculated order parameters predict that a Pb()O3-type perovskite without any charge difference between B′ and B″ cations [e.g., Pb(Zr1/2Ti1/2)O3 (PZT)] is represented by a completely disordered state with the absence of a finite coherence length. On the other hand, a Pb()O3-type perovskite system having different ionic charges is characterized either by the short-range ordering with a nanoscale coherence length or by the macroscopic long-range ordering, depending on the magnitude of ionic charge difference between B′ and B″ ions. The normal ferroelectricity in Pb()O3-type complex perovskites was then correlated either with a completely disordered state (σ = 0) or with a perfectly ordered state (σ = 0), whereas the relaxor behavior was attributed to the nanoscale short-range ordering (0 < σ < 1) in the configuration of the B-site cations.

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Chabchoub, Amin, Kento Mozumi, Norbert Hoffmann, Alexander V. Babanin, Alessandro Toffoli, James N. Steer, Ton S. van den Bremer, Nail Akhmediev, Miguel Onorato et Takuji Waseda. « Directional soliton and breather beams ». Proceedings of the National Academy of Sciences 116, n^o 20 (26 avril 2019) : 9759–63. http://dx.doi.org/10.1073/pnas.1821970116.

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Solitons and breathers are nonlinear modes that exist in a wide range of physical systems. They are fundamental solutions of a number of nonlinear wave evolution equations, including the unidirectional nonlinear Schrödinger equation (NLSE). We report the observation of slanted solitons and breathers propagating at an angle with respect to the direction of propagation of the wave field. As the coherence is diagonal, the scale in the crest direction becomes finite; consequently, beam dynamics form. Spatiotemporal measurements of the water surface elevation are obtained by stereo-reconstructing the positions of the floating markers placed on a regular lattice and recorded with two synchronized high-speed cameras. Experimental results, based on the predictions obtained from the (2D + 1) hyperbolic NLSE equation, are in excellent agreement with the theory. Our study proves the existence of such unique and coherent wave packets and has serious implications for practical applications in optical sciences and physical oceanography. Moreover, unstable wave fields in this geometry may explain the formation of directional large-amplitude rogue waves with a finite crest length within a wide range of nonlinear dispersive media, such as Bose–Einstein condensates, solids, plasma, hydrodynamics, and optics.

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Lubatsch, Andreas, et Regine Frank. « A Self-Consistent Quantum Field Theory for Random Lasing ». Applied Sciences 9, n^o 12 (18 juin 2019) : 2477. http://dx.doi.org/10.3390/app9122477.

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The spatial formation of coherent random laser modes in strongly scattering disordered random media is a central feature in the understanding of the physics of random lasers. We derive a quantum field theoretical method for random lasing in disordered samples of complex amplifying Mie resonators which is able to provide self-consistently and free of any fit parameter the full set of transport characteristics at and above the laser phase transition. The coherence length and the correlation volume respectively is derived as an experimentally measurable scale of the phase transition at the laser threshold. We find that the process of stimulated emission in extended disordered arrangements of active Mie resonators is ultimately connected to time-reversal symmetric multiple scattering in the sense of photonic transport while the diffusion coefficient is finite. A power law is found for the random laser mode diameters in stationary state with increasing pump intensity.

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DI CASTRO, DANIELE, MARCELLO COLAPIETRO et GINESTRA BIANCONI. « METALLIC STRIPES IN OXYGEN DOPED La2CuO4 ». International Journal of Modern Physics B 14, n^o 29n31 (20 décembre 2000) : 3438–43. http://dx.doi.org/10.1142/s0217979200003927.

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We have investigated the charge ordering in an oxygen doped La 2 CuO 4 crystal by diffuse high-resolution x-ray diffraction using synchrotron radiation. The micro-strain ε in the CuO 2 plane is close to the micro-strain ε0 for the formation of static charge ordered phases. The crystal shows the co-existence of a first phase with an insulating crystal of charge strings and a second superconducting phase of "supestripes". The first insulating phase is due to charges at the critical doping 1/8 self trapped into a crystal of ordered strings of finite length (~60 Å) and a commensurate period of 4 lattice units. The superconducting phase shows diffuse diffraction peaks with short coherence length due to fluctuations of stripes with an incommensurate period of about 4.8 unit cells and length longer than 500 Å.

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Parra, Carolina, Francis C. Niestemski, Alex W. Contryman, Paula Giraldo-Gallo, Theodore H. Geballe, Ian R. Fisher et Hari C. Manoharan. « Signatures of two-dimensional superconductivity emerging within a three-dimensional host superconductor ». Proceedings of the National Academy of Sciences 118, n^o 16 (12 avril 2021) : e2017810118. http://dx.doi.org/10.1073/pnas.2017810118.

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Spatial disorder has been shown to drive two-dimensional (2D) superconductors to an insulating phase through a superconductor–insulator transition (SIT). Numerical calculations predict that with increasing disorder, emergent electronic granularity is expected in these materials—a phenomenon where superconducting (SC) domains on the scale of the material’s coherence length are embedded in an insulating matrix and coherently coupled by Josephson tunneling. Here, we present spatially resolved scanning tunneling spectroscopy (STS) measurements of the three-dimensional (3D) superconductor BaPb1−xBixO3 (BPBO), which surprisingly demonstrate three key signatures of emergent electronic granularity, having only been previously conjectured and observed in 2D thin-film systems. These signatures include the observation of emergent SC domains on the scale of the coherence length, finite energy gap over all space, and strong enhancement of spatial anticorrelation between pairing amplitude and gap magnitude as the SIT is approached. These observations are suggestive of 2D SC behavior embedded within a conventional 3D s-wave host, an intriguing but still unexplained interdimensional phenomenon, which has been hinted at by previous experiments in which critical scaling exponents in the vicinity of a putative 3D quantum phase transition are consistent only with dimensionality d = 2.

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Abiuso, Paolo, Harry J. D. Miller, Martí Perarnau-Llobet et Matteo Scandi. « Geometric Optimisation of Quantum Thermodynamic Processes ». Entropy 22, n^o 10 (24 septembre 2020) : 1076. http://dx.doi.org/10.3390/e22101076.

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Differential geometry offers a powerful framework for optimising and characterising finite-time thermodynamic processes, both classical and quantum. Here, we start by a pedagogical introduction to the notion of thermodynamic length. We review and connect different frameworks where it emerges in the quantum regime: adiabatically driven closed systems, time-dependent Lindblad master equations, and discrete processes. A geometric lower bound on entropy production in finite-time is then presented, which represents a quantum generalisation of the original classical bound. Following this, we review and develop some general principles for the optimisation of thermodynamic processes in the linear-response regime. These include constant speed of control variation according to the thermodynamic metric, absence of quantum coherence, and optimality of small cycles around the point of maximal ratio between heat capacity and relaxation time for Carnot engines.

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CAMPI, G., D. DI CASTRO, C. DELL'OMO, S. AGRESTINI, N. L. SAINI, A. BIANCONI, G. BIANCONI, L. BARBA et M. COLAPIETRO. « TEMPERATURE AND X-RAY ILLUMINATION EFFECTS IN OXYGEN DOPED La2CuO4 ». International Journal of Modern Physics B 17, n^o 04n06 (10 mars 2003) : 836–41. http://dx.doi.org/10.1142/s0217979203016698.

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We have investigated charge ordering in an oxygen doped La 2 CuO 4.1 crystal by high resolution x-ray diffraction using synchrotron radiation. Thanks to the high brilliance synchrotron radiation it has been possible to record a large number of weak superstructure spots due to charge ordering around the main peaks of the average structure. A study of the charge modulations with stage 3.5, and their behaviour as a function of the temperature and the intensity of the x-ray incident flux is reported. We are able to distinguish a microscopic decomposition in; 1) a stable domain, due to charges self trapped into a crystal of static ordered strings of finite length (~ 145 Å) and; 2) bubbles of 'superstripes' showing, as a function of photon dose, a decreasing coherence length at T = 220 K.

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TRIVEDI, NANDINI, YEN LEE LOH, KARIM BOUADIM et MOHIT RANDERIA. « ASPECTS OF LOCALIZATION ACROSS THE 2D SUPERCONDUCTOR-INSULATOR TRANSITION ». International Journal of Modern Physics : Conference Series 11 (janvier 2012) : 22–37. http://dx.doi.org/10.1142/s2010194512006137.

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It is well known that the metal-insulator transition in two dimensions for non-interacting fermions takes place at infinitesimal disorder. In contrast, the superconductor-to-insulator transition takes place at a finite critical disorder (on the order of Vc ~ 2t), where V is the typical width of the distribution of random site energies and t is the hopping scale. In this article we compare the localization/delocalization properties of one and two particles. Whereas the metal-insulator transition is a consequence of single-particle Anderson localization, the superconductor-insulator transition (SIT) is due to pair localization – or, alternatively, fluctuations of the phase conjugate to pair density. The central question we address is how superconductivity emerges from localized single-particle states. We address this question using inhomogeneous mean field theory and quantum Monte Carlo techniques and make several testable predictions for local spectroscopic probes across the SIT. We show that with increasing disorder, the system forms superconducting blobs on the scale of the coherence length embedded in an insulating matrix. In the superconducting state, the phases on the different blobs are coherent across the system whereas in the insulator long-range phase coherence is disrupted by quantum fluctuations. As a consequence of this emergent granularity, we show that the single-particle energy gap in the density of states survives across the transition, but coherence peaks exist only in the superconductor. A characteristic pseudogap persists above the critical disorder and critical temperature, in contrast to conventional theories. Surprisingly, the insulator has a two-particle gap scale that vanishes at the SIT despite a robust single-particle gap.

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Chaudhari, Mayank K., Bipin K. Singh et Praveen C. Pandey. « Enhanced light trapping in dye-sensitized solar cell by coupling to 1D photonic crystal and accounting for finite coherence length ». Journal of Modern Optics 64, n^o 21 (18 août 2017) : 2385–93. http://dx.doi.org/10.1080/09500340.2017.1363918.

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Eichmann, B., et M. Kachelrieß. « Impact of the finite life-time of UHECR sources ». Journal of Cosmology and Astroparticle Physics 2023, n^o 02 (1 février 2023) : 053. http://dx.doi.org/10.1088/1475-7516/2023/02/053.

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Abstract The observational data on ultrahigh energy cosmic rays (UHECR), in particular their mass composition, show strong indications for extremely hard spectra of individual mass groups of CR nuclei at Earth. In this work, we show that such hard spectra can be the result of the finite life-time of UHECR sources, if a few individual sources dominate the UHECR flux at the highest energies. In this case, time delays induced by deflections in the turbulent extragalactic magnetic field as well as from the diffusive or advective escape from the source environment can suppress low-energy CRs, leading to a steepening of the observed spectrum. Considering radio galaxies as the main source of UHECRs, we discuss the necessary conditions that few individual sources dominate over the total contribution from the bulk of sources that have been active in the past. We provide two proof-of-principle scenarios showing that for a turbulent extragalactic magnetic field with a strength B and a coherence length l coh, the life-time of a source at a distance d src should satisfy t act ∼ (B/1 nG)2 (d src/10 Mpc)2 (l coh/1 Mpc) Myr to obtain the necessary hardening of the CR spectrum at Earth.

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Crist, Buckley, et Paul R. Howard. « Lineshape Analysis of X-ray Diffraction Profiles : Polyethylene and Model Copolymers ». Advances in X-ray Analysis 34 (1990) : 519–29. http://dx.doi.org/10.1154/s0376030800014841.

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Studies of the shapes of X-ray diffraction peaks from synthetic polymers are still rather uncommon. One probable cause of this situation is the small peak-to-background ratio in most polymer diffraction experiments; it is difficult to achieve precise line profiles for quantitative analysis. Increased utilization of automated data collection/analysis systems and more intense X-ray sources should alleviate this restriction. We suspect, furthermore, that confusion about nomenclature has impeded the acceptance of lineshape analysis for polymers. The peak broadening mechanisms which are generally considered are finite coherence length or crystal size, lattice parameter fluctuation, and displacement disorder of the second kind. Both latter mechanisms have, unfortunately, been referred to as “strains” or “microstrains”. Metallurgists have traditionally expressed displacement disorder as a (length dependent) “microstrain”, and this convention has been adopted in some studies of polymer diffraction. Other work on polymers, however, has termed lattice parameter fluctuation as “microstrain“. The inconsistent use of this term can imply a nonexistent relation between two distinct phenomena.

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BRANDOW, B. H. « VALENCE-FLUCTUATION MECHANISM FOR CUPRATE SUPERCONDUCTIVITY ». International Journal of Modern Physics B 08, n^o 19 (30 août 1994) : 2667–719. http://dx.doi.org/10.1142/s021797929400107x.

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We explore the concept that the above-T c state is a normal Fermi liquid with strong correlations of the type found in valence-fluctuation and heavy-fermion materials. Experimental evidence and theoretical arguments for this phase are presented. Using an Anderson lattice model Hamiltonian, and a variational many-body formalism, the finite-U mechanism for s-like (full point-group symmetry) pairing is examined in detail. At the mean field or (1/N)0 level of approximation, the pairing tendency is strongly opposed by a magnetic tendency arising from a Gutzwiller version of hybridization renormalization. Pairing does not seem possible for realistic Hamiltonian parameters. This finite-U treatment has, however, now been extended to the (1/N)1 level of approximation. The lattice aspect is found to play a major and unexpected role here, leading to strong suppression of the magnetic tendency. This refined treatment is now found to provide adequate pairing attraction, for reasonable Hamiltonian parameters. Superconductivity is found only when the charge transfer energy Δ CT is quite large, Δ CT ≳ U, but there is evidence that Δ CT is indeed of this magnitude in the cuprate materials. Adequate band narrowing (mass enhancement or heaviness) and a very short coherence length are also obtained, in reasonable agreement with experiment. The quasiparticle interaction at the Fermi surface is strongly repulsive. This provides a reasonable source for the large and linear resistivity, as well as for other aspects of marginal-Fermi-liquid phenomenology. Evidence is found for a strong reduction of T c due to pair-breaking by the quasiparticle scattering. The main (fully self-consistent) calculations assume in-plane isotropy. However, a simplified calculation with a more realistic (anisotropic) band structure for the CuO 2 plane is found to provide a highly anisotropic gap, which may or may not have nodes. There is considerable evidence for such types of gap structure. Because a connection is found here between anomalously short coherence length and anomalously high resistivity, we suggest that this mechanism is also operating within other families of "exotic" superconductors.

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Ruzanski, Evan, John C. Hubbert et V. Chandrasekar. « Evaluation of the Simultaneous Multiple Pulse Repetition Frequency Algorithm for Weather Radar ». Journal of Atmospheric and Oceanic Technology 25, n^o 7 (1 juillet 2008) : 1166–81. http://dx.doi.org/10.1175/2007jtecha1042.1.

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Abstract Performance of the simultaneous multiple pulse repetition frequency algorithm (SMPRF) for recovery of mean power and mean Doppler velocity is investigated using simulated weather radar data. Operation and functionality of the algorithm is described; methods to estimate mean power values using statistical inversion and to estimate mean velocity from unevenly spaced autocorrelation function samples are presented and analyzed. A simulation technique for constructing multiple pulse repetition interval data is described and the algorithm performance results are presented for an example SMPRF code using three weather profiles. This leads to the development of an error structure related to factors influencing moment recovery, including finite-length time series effects, the effects of overlaid echoes that create an effective signal-to-noise ratio that limits moment recovery performance, and the effects of spectrum width and radar frequency related to coherence time.

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Alok Dua, Mathias Clobes et Thomas Höbbel. « Dynamic Analysis of Overhead Transmission Line under Turbulent Wind Loading ». Electronic Journal of Structural Engineering 15 (1 juin 2015) : 46–54. http://dx.doi.org/10.56748/ejse.15201.

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This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode. Finite element design software SAP2000 was used to model towers and power-lines. Nonlinear dynamic analysis including the large displacement effects was carried out. Macroscopic aspects of wind coherence along element length and integration time step were investigated. An approach is presented to compare the probabilistic dynamic response due to 7 different stochastically simulated wind fields with the response according to EN-50341. The developed model is used to study the response recorded on a test line due to the actual wind speed time history recorded. It was found that static load as calculated from EN-50341 underestimates the response of conductor cables. The response of coupled system considering towers and cables was found to be different from response of only cables with fixed supports.

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Ashoka, A., Bhagyashree K. S. et S. V. Bhat. « Magnetic Field Induced Berezinskii-Kosterlitz-Thouless Correlations in 3-Dimensional Manganites ». MRS Advances 5, n^o 44 (2020) : 2251–60. http://dx.doi.org/10.1557/adv.2020.320.

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AbstractIdeal two-dimensional (2D) Heisenberg magnets lack long range magnetic order. However, the XY model with spins confined to a plane shows a topological phase transition at a finite temperature corresponding to binding and unbinding of vortices. Experimental evidence for such Berezinskii-Kosterlitz-Thouless (BKT) transitions has been difficult to obtain in condensed matter systems, where, even a weak interlayer coupling that is invariably present leads to long-range order, pre-empting the BKT transition. The BKT signatures are still discernible above the long-range ordering temperature, however, in the characteristic exponential temperature dependence of the coherence length of the fluctuations. In this work we report that an applied magnetic field can induce such BKT correlations not only in quasi 2-dimensional systems but also in nominally 3-dimensional manganites undergoing antiferromagnetic transitions. We arrive at this unexpected conclusion based on our studies of temperature dependence of electron paramagnetic resonance (EPR) linewidth ΔH(T) of Cr3+ doped bismuth strontium manganite Bi0.5Sr0.5Mn1-xCrxO3 (x= 0.04, 0.1) (BSMCO04 and BSMCO10).

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Kesharpu, Kaushal K., Vladislav D. Kochev et Pavel D. Grigoriev. « Evolution of Shape and Volume Fraction of Superconducting Domains with Temperature and Anion Disorder in (TMTSF)2ClO4 ». Crystals 11, n^o 1 (17 janvier 2021) : 72. http://dx.doi.org/10.3390/cryst11010072.

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In highly anisotropic organic superconductor (TMTSF)2ClO4, superconducting (SC) phase coexists with metallic and spin-density wave phases in the form of domains. Using the Maxwell-Garnett approximation (MGA), we calculate the volume ratio and estimate the shape of these embedded SC domains from resistivity data at various temperature and anion disorder, controlled by the cooling rate or annealing time of (TMTSF)2ClO4 samples. We found that the variation of cooling rate and of annealing time affect differently the shape of SC domains. In all cases the SC domains have oblate shape, being the shortest along the interlayer z-axis. This contradicts the widely assumed filamentary superconductivity along the z-axis, used to explain the anisotropic superconductivity onset. We show that anisotropic resistivity drop at the SC onset can be described by the analytical MGA theory with anisotropic background resistance, while the anisotropic Tc can be explained by considering a finite size and flat shape of the samples. Due to a flat/needle sample shape, the probability of percolation via SC domains is the highest along the shortest sample dimension (z-axis), and the lowest along the sample length (x-axis). Our theory can be applied to other heterogeneous superconductors, where the size d of SC domains is much larger than the SC coherence length ξ, e.g., cuprates, iron-based or organic superconductors. It is also applicable when the spin/charge-density wave domains are embedded inside a metallic background, or vice versa.

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Zhang, Xiaolei, Yanzhong Ju et Fuwang Wang. « Statistical Analysis of Wind-Induced Dynamic Response of Power Towers and Four-Circuit Transmission Tower-Line System ». Shock and Vibration 2018 (2018) : 1–18. http://dx.doi.org/10.1155/2018/5064930.

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Only one wind field model loading the transmission tower or the tower-line system was investigated in the previous studies, while the influence of two different wind field models was not considered. In addition, only one sample of the wind speed random process was used in the past numerical simulations, and the multiple dynamic response statistical analysis should be carried out. In this paper, statistical analysis of the wind-induced dynamic response of single towers and the transmission tower-line system is performed with the improved accuracy. A finite element model of the transmission tower-line system (the tower consisted of both steel tubes and angel steels) is established by ANSYS software. The analysis was performed by three statistical methods. The effects of the length of the time history and of the number of samples were investigated. The frequency histograms of samples follow the Gaussian distribution. The characteristic statistical parameters of samples were random. The displacements and the axial forces of the low tower are larger than those of the high tower. Two wind field models were applied to simulate the wind speed time history. In field 1 model, Davenport wind speed spectrum and Shiotani coherence function were applied, while in field 2 model Kaimal wind speed spectrum and Davenport coherence function were used. The results indicate that wind field 1 is calmer than wind field 2. The displacements and the axial forces of the tower-line system are less than those of single towers, which indicate damping of wind-induced vibrations by the transmission line. An extended dynamic response statistical analysis should be carried out for the transmission tower-line system.

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Beniamini, Paz, Pawan Kumar et Ramesh Narayan. « Faraday depolarization and induced circular polarization by multipath propagation with application to FRBs ». Monthly Notices of the Royal Astronomical Society 510, n^o 3 (28 décembre 2021) : 4654–68. http://dx.doi.org/10.1093/mnras/stab3730.

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ABSTRACT We describe how the observed polarization properties of an astronomical object are related to its intrinsic polarization properties and the finite temporal and spectral resolutions of the observing device. Moreover, we discuss the effect that a scattering screen, with non-zero magnetic field, between the source and observer has on the observed polarization properties. We show that the polarization properties are determined by the ratio of observing bandwidth and coherence bandwidth of the scattering screen and the ratio of temporal resolution of the instrument and the variability time of screen, as long as the length over which the Faraday rotation induced by the screen changes by ∼π is smaller than the size of the screen visible to the observer. We describe the conditions under which a source that is 100 per cent linearly polarized intrinsically might be observed as partially depolarized, and how the source’s temporal variability can be distinguished from the temporal variability induced by the scattering screen. In general, linearly polarized waves passing through a magnetized scattering screen can develop a significant circular polarization. We apply the work to the observed polarization properties of a few fast radio bursts (FRBs), and outline potential applications to pulsars.

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Zeng, Fuqiang, Wenzheng Yue et Chao Li. « Dispersion analysis of borehole sonic measurements by Hilbert transform and band-pass filters ». GEOPHYSICS 83, n^o 4 (1 juillet 2018) : D127—D150. http://dx.doi.org/10.1190/geo2017-0580.1.

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Dispersion analysis of waves can reveal important mechanical properties of the formation around the borehole. The traditional dispersion analysis methods are affected by wave modes and aliasing. A new method is developed to perform dispersion analysis of borehole array acoustic logging, which combines the semblance of time-slowness coherence based on differential phase (STC-DP) processing and band-pass filters. Unlike the classic STC method, STC-DP is not sensitive to the window length. Two kinds of band-pass filters, the multiple filter technique and the finite-impulse response filter, are used. The band-pass filters can decompose the waveform signal into a series of waveforms in the frequency-time domain. In contrast to traditional dispersion analysis methods, there is no knowledge of wave modes. The new method can extract multimode dispersion curves, especially for the weak wave mode. For most dispersion analysis methods, the aliasing will appear in the high-frequency band when the scanning range of slowness is large enough. The aliased modes might interfere with other true modes, but the aliased modes are quite different from other true modes in the time-slowness grid. Therefore, aliased modes can be removed in the time-slowness grid based on the modal dispersion curves. Synthetic and field examples are used to verify the advantages of the proposed method over traditional dispersion analysis methods.

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BUSH, JOHN W. M., et ANDREW W. WOODS. « Vortex generation by line plumes in a rotating stratified fluid ». Journal of Fluid Mechanics 388 (10 juin 1999) : 289–313. http://dx.doi.org/10.1017/s0022112099004759.

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We present the results of an experimental investigation of the generation of coherent vortical structures by buoyant line plumes in rotating fluids. Both uniform and stratified ambients are considered. By combining the scalings describing turbulent plumes and geostrophically balanced vortices, we develop a simple model which predicts the scale of the coherent vortical structures in excellent accord with laboratory experiments.We examine the motion induced by a constant buoyancy flux per unit length B, released for a finite time ts, from a source of length L into a fluid rotating with angular speed Ω = f/2. When the plume discharges into a uniformly stratified environment characterized by a constant Brunt–Väisälä frequency, N>f, the fluid rises to its level of neutral buoyancy unaffected by the system rotation before intruding as a gravity current. Rotation has a strong impact on the subsequent dynamics: shear develops across the spreading neutral cloud which eventually goes unstable, breaking into a chain of anticyclonic lenticular vortices. The number of vortices n emerging from the instability of the neutral cloud, n = (0.65±0.1)Lf1/2/ (t1/2sB1/3), is independent of the ambient stratification, which serves only to prescribe the intrusion height and aspect ratio of the resulting vortex structures. The experiments indicate that the Prandtl ratio characterizing the geostrophic vortices is given by P = Nh/(fR) = 0.47±0.12; where h and R are, respectively, the half-height and radius of the vortices. The lenticular vortices may merge soon after formation, but are generally stable and persist until they are spun-down by viscous effects.When the fluid is homogeneous, the plume fluid rises until it impinges on a free surface. The nature of the flow depends critically on the relative magnitudes of the layer depth H and the rotational lengthscale Lf = B1/3/f. For H>10Lf, the ascent phase of the plume is influenced by the system rotation and the line plume breaks into a series of unstable anticylonic columns of characteristic radius (5.3±1.0)B1/3/f which typically interact and lose their coherence before surfacing. When H<10Lf, the system rotation does not influence the plume ascent, but does control the spreading of the gravity current at the free surface. In a manner analogous to that observed in the stratified ambient, shear develops across the surface current, which eventually becomes unstable and generates a series of anticyclonic surface eddies with characteristic radius (1.6±0.2)B1/3t1/3s /f2/3. These surface eddies are significantly more stable than their columnar counterparts, but less so than the lenticular eddies arising in the uniformly stratified ambient.The relevance of the study to the formation of coherent vortical structures by leads in the polar ocean and hydrothermal venting is discussed.

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Hattendorff, Johannes, Stefan Seidlmayer, Hubert A. Gasteiger et Ralph Gilles. « Li-ion half-cells studied operando during cycling by small-angle neutron scattering ». Journal of Applied Crystallography 53, n^o 1 (1 février 2020) : 210–21. http://dx.doi.org/10.1107/s160057671901714x.

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Small-angle neutron scattering (SANS) was recently applied to the in situ and operando study of the charge/discharge process in Li-ion battery full-cells based on a pouch cell design. Here, this work is continued in a half-cell with a graphite electrode cycled versus a metallic lithium counter electrode, in a study conducted on the SANS-1 instrument of the neutron source FRM II at the Heinz Maier-Leibnitz Zentrum in Garching, Germany. It is confirmed that the SANS integrated intensity signal varies as a function of graphite lithiation, and this variation can be explained by changes in the squared difference in scattering length density between graphite and the electrolyte. The scattering contrast change upon graphite lithiation/delithiation calculated from a multi-phase neutron scattering model is in good agreement with the experimentally measured values. Due to the finite coherence length, the observed SANS contrast, which mostly stems from scattering between the (lithiated) graphite and the electrolyte phase, contains local information on the mesoscopic scale, which allows the development of lithiated phases in the graphite to be followed. The shape of the SANS signal curve can be explained by a core–shell model with step-wise (de)lithiation from the surface. Here, for the first time, X-ray diffraction, SANS and theory are combined to give a full picture of graphite lithiation in a half-cell. The goal of this contribution is to confirm the correlation between the integrated SANS data obtained during operando measurements of an Li-ion half-cell and the electrochemical processes of lithiation/delithiation in micro-scaled graphite particles. For a deeper understanding of this correlation, modelling and experimental data for SANS and results from X-ray diffraction were taken into account.

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Zimnyakov, Dmitry, Elena Isaeva, Anna Isaeva et Sergey Volchkov. « Band-Limited Reference-Free Speckle Spectroscopy : Probing the Fluorescent Media in the Vicinity of the Noise-Defined Threshold ». Applied Sciences 10, n^o 5 (29 février 2020) : 1629. http://dx.doi.org/10.3390/app10051629.

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A method of reference-free speckle spectroscopy based on the statistical analysis of intensity spatial fluctuations of the spectrally-selected multiple-scattered fluorescence radiation is examined in the case of the finite-band spectral selection of fluorescence light emitted by the laser-pumped random medium, and detection conditions far from the ideal case. Intensity fluctuations are recorded during point-to-point scanning of the surface of a random multiple-scattering medium, which is characterized by the dependences of the second- and third-order statistical moments of intensity on the wavelength of detected spectrally selected light. In turn, the statistical moments of intensity fluctuations are determined by the average propagation path of fluorescent radiation in the medium. This makes it possible to analyze the features of the light-medium interactions at a scale of the order of the transport mean free path of radiation propagation in the medium. Depending on the spectral selection conditions, the method is applicable for characterizing micro- or nano-structured fluorescent layers with thicknesses from tens of micrometers to several millimeters. In the examined case, the finite-band spectral selection results in the values of coherence length of the detected fluorescence radiation compared with the ensemble-averaged absolute value of the path-length difference between the stochastically interfering and spectrally selected partial contributions to the fluorescence field. In addition, non-ideal detection conditions (usage of a multimode optical fiber in the light-collecting unit) cause additional strong damping of the detected speckle intensity fluctuations. These factors lead to a remarkable suppression of spatial fluctuations of the fluorescence intensity in the course of spatially- and spectrally-resolved surface scanning of the laser-pumped probed random medium. Nevertheless, with appropriate procedures of the intrinsic noise reduction and data correction, the obtained spectral dependencies of the normalized third-order statistical moment of the band-limited fluorescence intensity clearly indicate the fluorescence propagation features in the probed multiple-scattering random media (such as a strong influence of the scattering strength and multiple self-absorption–re-emission events on the average propagation path of light in the medium).The possibilities of noise reduction and data correction in the case of applying the band-limited reference-free spectroscopic instrumentation with low spectral and spatial resolution are illustrated by the experimental results obtained using the Rhodamine-6G-doped and continuous wave (CW)-laser-pumped layers of the densely packed titania and silica particles.

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MA, Y. L., et X. X. DAI. « PHENOMENOLOGICAL IMPLICATIONS OF HIGH-Tc SUPERCONDUCTIVITY ». International Journal of Modern Physics B 06, n^o 14 (20 juillet 1992) : 2499–519. http://dx.doi.org/10.1142/s0217979292001250.

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We develop a phenomenological model for high-T c superconductors. Some main features are emerging in copper oxides: characteristic quasi two-dimensional Cu-O planes, strong correlation of antiferromagnetism, existence of a vortex lattice structure, and observation of a small coherence length and a large penetration depth. These features indicate that the superconductive pair is reasonably constrained to a small volume in real space and may be conceived of as a string-carrying vortex, and therefore can be well simulated by the dual phenomenological local boson fields [Formula: see text] and Φ. The various mean-field ground states of the system are discussed. The field equations of motion are originally solved to get approximate analytical soliton solutions. The effective Hamiltonian is formulated by a variational method for finite temperatures. The model parameter behaviour described by the relationship of the variational parameters is investigated. We discuss the critical temperature T c , the specific heat cV and its jump Δc at T c , and the critical magnetic fields H c1 and H c2 . These results are in agreement with experimental observations, especially the critical behaviours and the zero temperature values. The model also allows interpretation of the variation of T c with oxygen vacancy x and that with doping fraction δ in Cu-O planes, as well as the dependence of γ (defined as the specific heat coefficient of the T-linear term) on δ.

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Wu, Jian, Bing-Lin Gu, Jing-Zhi Yu et Yoshiyuki Kawazoe. « Coherent Transport through Carbon Nanotubes with Finite Length ». Materials Transactions, JIM 41, n^o 5 (2000) : 571–73. http://dx.doi.org/10.2320/matertrans1989.41.571.

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Shragge, Jeffrey, Jihyun Yang, Nader Issa, Michael Roelens, Michael Dentith et Sascha Schediwy. « Low-frequency ambient distributed acoustic sensing (DAS) : case study from Perth, Australia ». Geophysical Journal International 226, n^o 1 (26 mars 2021) : 564–81. http://dx.doi.org/10.1093/gji/ggab111.

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SUMMARY Ambient wavefield data acquired on existing (so-called ‘dark fibre’) optical fibre networks using distributed acoustic sensing (DAS) interrogators allow users to conduct a wide range of subsurface imaging and inversion experiments. In particular, recorded low-frequency (<2 Hz) surface-wave information holds the promise of providing constraints on the shear-wave velocity (VS) to depths exceeding 0.5 km. However, surface-wave analysis can be made challenging by a number of acquisition factors that affect the amplitudes of measured DAS waveforms. To illustrate these sensitivity challenges, we present a low-frequency ambient wavefield investigation using a DAS data set acquired on a crooked-line optical fibre array deployed in suburban Perth, Western Australia. We record storm-induced microseism energy generated at the nearby Indian Ocean shelf break and/or coastline in a low-frequency band (0.04−1.80 Hz) and generate high-quality virtual shot gathers (VSGs) through cross-correlation and cross-coherence interferometric analyses. The resulting VSG volumes clearly exhibit surface wave energy, though with significant along-line amplitude variations that are due to the combined effects of ambient source directivity, crooked-line acquisition geometry and the applied gauge length, fibre coupling, among other factors. We transform the observed VSGs into dispersion images using two different methods: phase shift and high-resolution linear Radon transform. These dispersion images are then used to estimate 1-D near-surface VS models using multichannel analysis of surface waves (MASW), which involves picking and inverting the estimated Rayleigh-wave dispersion curves using the particle-swarm optimization global optimization algorithm. The MASW inversion results, combined with nearby deep borehole information and 2-D elastic finite-difference modeling, show that low-frequency ambient DAS data constrain the VS model, including a low-velocity channel, to at least 0.5 km depth. Thus, this case study illustrates the potential of using DAS technology as a tool for undertaking large-scale surface wave analysis in urban geophysical and geotechnical investigations to depths exceeding 0.5 km.

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Okamoto, Taka-aki, et Iehisa Nezu. « Spatial evolution of coherent motions in finite-length vegetation patch flow ». Environmental Fluid Mechanics 13, n^o 5 (3 mars 2013) : 417–34. http://dx.doi.org/10.1007/s10652-013-9275-6.

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Kumbhakar, Dharmadas. « Nonlinear Coherent Directional Coupler : Coupled Mode Theory and BPM Simulation ». International Journal of Optics 2012 (2012) : 1–8. http://dx.doi.org/10.1155/2012/173250.

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Finite difference beam propagation method is an accurate numerical procedure, used here to explore the switching dynamics of a nonlinear coherent directional coupler. The coupling lengths derived from this simulation are compared with coupled mode theories. BPM results for the critical power follow the trend of the coupled mode theories, but it lies in between two coupled mode theories. Coupled mode theory is sensitive to numerical approximations whereas BPM results practically do not depend on grid size and longitudinal step size. Effect of coupling-region-width and core-width variations on critical power and coupling length is studied using BPM to look at the aspects of optical power-switch design.

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JANA, DEBNARAYAN. « UNIVERSAL DIAMAGNETISM : EXACT RESULTS AND APPLICATIONS ». International Journal of Modern Physics B 15, n^o 19n20 (10 août 2001) : 2811–20. http://dx.doi.org/10.1142/s0217979201006379.

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Diamagnetism is a universal pheneomenon of spinless boson system at any finite temperature regardless of their interactions. We present here the exact, non-perturbative results of universal diamagnetism of charged scalar fields at any finite temperature. As an application, we study the effect of anisotropy of two coherence lengths on diamagnetic susceptibility of Cooper pairs in an arbitrary d-dimensions above the transition temperature.

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