共查询到20条相似文献,搜索用时 843 毫秒
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K. Henschel B. Hellwig F. Amtage J. Vesper M. Jachan C. H. Lücking J. Timmer B. Schelter 《The European physical journal. Special topics》2008,165(1):25-34
The analysis of multi-dimensional biomedical systems requires analysis techniques, which are able to deal with multivariate
data consisting of both time series as well as point processes. Univariate and bivariate analysis techniques in the frequency
domain for time series and point processes are established and investigated, although the number of investigations is strongly
biased towards time series. Actual multivariate techniques for time series or hybrids of time series and point processes are
scarcely addressed. Here, we present spectral analysis techniques which are able to analyse point processes as well as time
series. Thereby, univariate, bivariate as well as multivariate techniques are discussed. Applications to simulated as well
as real-world data reveal the abilities of the proposed techniques. 相似文献
3.
G. -Q. Hai N. Studart G. E. Marques F. M. Peeters P. M. Koenraad 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
The multisubband electron transport properties are studied for doped single quantum well and gated double asymmetric quantum well structures. The effects due to intersubband interaction and screening of the ionized impurity scattering are also investigated. We show that intersubband coupling plays an essential role in describing the screening properties as well as the effect of ionized impurity scattering on the mobility in a doped single quantum well. For coupled double quantum well structures, negative transconductance is found theoretically which is due to resonant tunneling between the two quantum wells. 相似文献
4.
《Waves in Random and Complex Media》2013,23(4):543-553
This paper obtains the solitary wave as well as the shock wave solutions of the Degasperis–Procesi equation. Both regular nonlinearity as well as power law nonlinearity are considered. The constraint relations are identified in the process of obtaining the nonlinear wave solutions. 相似文献
5.
C. H. Ma D. P. Hutchinson K. L. Vander Sluis D. K. Mansfield H. Park L. C. Johnson 《International Journal of Infrared and Millimeter Waves》1986,7(3):421-426
The results of the first Faraday rotation measurement on the TFTR tokamak are presented. Data are reported on ohmic-as well as neutral-beam-heated plasmas including solid pellet injections. The procedure and the results of the calibration, are described. The effects of various errors in the measurements as well as the problem of cross coupling laser beams are studied. 相似文献
6.
G K Khandpur 《Pramana》1978,10(3):257-266
Interaction of electromagnetic waves penetrating into anisotropic semi-infinite collisional plasma embedded in a uniform external
magnetic field is studied using half range Fourier transforms. General field equations are developed for fractionally accommodating
boundary and a particular case of specular reflection is discussed both for right handed as well as left handed circularly
polarized modes. Anisotropy effects are found to be more prominent in the continuum mode of field component. Anisotropy as
well as collisions make the field to attain a constant value at a shorter distance. Left handed polarized modes are found
to be more penetrating than right handed modes. Surface impedance is calculated and effects of collisions as well as anisotropy
are discussed. 相似文献
7.
Quantum well devices feature heterostructures of very thin epitaxial layers of group III-V and II-VI semiconductor materials.
Quantum well devices are integrated monolithically with various optoelectronics devices to provide photonic integrated circuits.
The representative structure could be realized with GaAs wells with GaAlAs barriers for wavelengths around 0.9 μm and InGaAsP
are used for longer wavelengths. Together with quantum well, superlattice structure is another popular design for InGaAs Avalanche
Photo Diode (APD). Quantum well structures find their applications in improved lasers, superlattice for photodiodes, modulators
and switches. Consequences of quantum well theory are available today in terms of quantum wires and quantum dots. Upon the
application of the normal electric field to quantum well structures, exciton pairs becomes more and more confined and the
sharp exciton absorption peaks are observed. The effect is termed as “Quantum Confined Stark Effect”. The electro-absorption effect is approximately 50 times larger in multiple quantum well structures than it is in bulk semiconductors.
Another electro-absorption effect known as “Franz Keldysh Effect” has been employed in monolithic waveguide detector. These effects lead to electro-absorption lasers (EAL) as well as electro-absorption
laser modulators (EML). 相似文献
8.
We report the observation of very well resolved polygonal domain (not island) trough networks in thin glass films. The linear troughs are observed by electron microscopy to be as narrow as 30 A and the hexagonal domain diameters are as large as 1000 (± 100) A. The composition dependence of the average diameters of the polygonal structures correlates well with the glass-forming tendency and agrees very well with the predictions of a recent topological model. 相似文献
9.
In this work, the linear and nonlinear optical properties are studied theoretically in asymmetric (CdS/ZnSe/BeTe)/(ZnSe/BeTe) quantum wells. The electronic states are calculated using the envelope wave function approximation and the intersubband transition energies are studied as a function of CdS and ZnSe well thicknesses as well as doping concentration. The optimum parameters carrying out the transition energy 0.8 eV (1.55 μm wavelength) are given. Results are presented for the linear, the third order nonlinear optical absorption and the refractive index changes in the studied heterostructure. Results show that the changes in the linear and the third order nonlinear optical absorption as well as refractive index change are as important as the temperature is high, the nonlinear terms must be taken into consideration especially near the resonance. 相似文献
10.
N. Van den Bergh 《Letters in Mathematical Physics》1986,11(2):141-146
A proof is given that shearfree perfect fluids, the metric of which is conformally related to a vacuum solution, are either of Petrov type D, as well as locally rotationally symmetric, or are conformally flat. In both cases the general solutions are well known. 相似文献
11.
Binding energies of a charged exciton as a function of well width of a GaAs/GaAlAs corrugated quantum well are investigated. The calculations have been performed by the variational method based on a two parametric trial wave function within a single band effective mass approximation. We have also included the effect of nonparabolicity of the conduction band of GaAs. We study the spectral dependence of the charged exciton in a GaAs/GaAlAs corrugated quantum well as a function of well width. The photoionization cross section for the charged exciton placed at the center of the quantum well is computed as a function of normalized photon energy. The cross-section behavior as a function of incident energy is entirely different in the two cases of radiation being x-direction (along the growth direction) or z-direction. The interband emission energy as a function of well width is calculated and the dependence of the photoionization cross section on photon energy is carried out for the charged excitons. The resulting spectra are brought out for light polarized along and perpendicular to the growth direction. The results show that the charged exciton binding energy, interband emission energy and the photoionization cross section depend strongly on the well width. Our results are compared with the other existing literature available. 相似文献
12.
科里奥利力在流量测量中的应用 总被引:3,自引:0,他引:3
本文阐述了如何利用科里奥利力精确测量管道中介质的质量流量的原理和方法,并描述了利用科里奥利力的质量流量计的类型和典型结构及其发展情况. 相似文献
13.
L.A. Crum 《Ultrasonics》1984,22(5):215-223
A general review is given of the mechanism of rectified diffusion. The equations that describe the threshold acoustic pressure amplitude as well as the growth rate are presented. Simplified versions of the complicated threshold equation are also obtained for two regions that are of particular interest. Graphical representations of the equations for a variety of physical parameters are given as well as a comparison between the available measurements and the theoretical predictions. Finally, some suggested areas of future research in this area are presented. 相似文献
14.
It is well known that attractive condensates do not posses a stable ground state in three dimensions. The widely used Gross-Pitaevskii theory predicts the existence of metastable states up to some critical number N(cr)(GP) of atoms. It is demonstrated here that fragmented metastable states exist for atom numbers well above N(cr)(GP). The fragments are strongly overlapping in space. The results are obtained and analyzed analytically as well as numerically. The implications are discussed. 相似文献
15.
《Superlattices and Microstructures》1994,15(2):221
The themal population in photocarrier systems coupled by hole mixing tunneling is studied by an analysis of the high energy tails in cw photoluminescence spectra of asymmetric coupled double wells. Photocarriers in wide well are heated due to hole transfer from the narrow well through resonant tunneling as well as by photon heating. The influences of the excitation intensity and lattice temperature on the tunneling transfer and thermal population are discussed. 相似文献
16.
T. Butz 《Hyperfine Interactions》1989,52(3):189-228
Analytic expressions are presented for powder and single crystal perturbation functions in ®–®-angular correlations for static interactions. Magnetic dipole interactions for arbitrary spin as well as non-axially symmetric electric quadrupole interactions up to spin 5/2 are treated. Symmetry properties of all matrices involved are discussed, as well as their consequences for the perturbation functions. A new complementarity rule for powder perturbation functions is presented. 相似文献
17.
Huynh Vinh Phuc Nguyen Thi Thu Thao Le Dinh Tran Cong Phong 《Journal of Physics and Chemistry of Solids》2014
Phonon-assisted cyclotron resonance (PACR) in GaAs quantum well (QW) structure is investigated via multi-photon absorption process when electrons interact with the confined acoustic phonon through deformation potential. The additional peaks in the absorption spectrum due to transitions between Landau levels accompanied with the emission and absorption of phonons are indicated. The dependence of absorption power on the temperature, magnetic field and well width is presented. Using profile method, we obtain PACR-linewidth as profiles of the curves. The temperature, magnetic field and well width dependences of the PACR-linewidth are investigated. The results are compared with those in the case of mono-photon absorption process, as well as in the electron-bulk acoustic phonon interaction. The results show that the multi-photon absorption process is strong enough to be detected in PACR. 相似文献
18.
A. Szczurek T. Pietrycki A. Rybarska G. Ślipek 《The European physical journal. Special topics》2008,155(1):191-200
We discuss correlations in azimuthal angle as well as
correlations in two-dimensional space of transverse momenta of two jets
as well as photon and jet.
Some kt-factorization subprocesses are included for the first
time in the literature.
Different unintegrated gluon/parton distributions are used in
the kt-factorization approach. The results depend on UGDF/UPDF used.
The collinear NLO 2 ↦3 contributions dominate over
kt-factorization cross section at small relative azimuthal
angles as well as for asymmetric transverse momentum configurations. 相似文献
19.
A. A. Goncharov P. I. Ignatenko V. V. Petukhov V. A. Konovalov G. K. Volkova V. A. Stupak V. A. Glazunova 《Technical Physics》2006,51(10):1340-1343
The structure, as well as the phase and elemental compositions, of tantalum diboride-based nanostructured films deposited by rf magnetron sputtering under various conditions are studied by X-ray diffraction, electron microscopy, and secondary ion mass spectrometry. The physicomechanical properties of the films (hardness, as well as elastic and plastic properties) are determined. The maximum hardness and elastic modulus of the synthesized films are 42 are 240 GPa, respectively. The grain size is found to influence the physicomechanical and electrical properties of the films. 相似文献
20.
In the present work, we consider both localized (e.g. peakon and breather) and extended waveforms (peakon-lattice and breather-lattice, as well as some periodic ones) that arise in the context of the short-pulse equation, as emanating from their sine-Gordon equation analogs. Through direct numerical simulations, we find that the most robust solution is the breather, although some of the single-hump variants of the periodic solutions may be preserved upon the time dynamics as well. Multi-peakon, as well as multi-breather and multi-hump profiles more generally are found to be subject to symmetry-breaking instabilities and are, thus, less robust. 相似文献