共查询到20条相似文献,搜索用时 109 毫秒
1.
C. J. Cellarius L. A. Dicks R. Turner 《Zeitschrift für Physik A Hadrons and Nuclei》1970,231(2):119-127
A new method of Langmuir probe analysis for non-Maxwellian plasmas is proposed. The method consists of computer fitting a mathematical function to the normal probe voltage-current characteristic, assuming two groups of electrons, each with a Maxwellian distribution. The advantages of the method are that both the temperatures and the densities of the two groups may be determined and that the electron energy distribution function is a tractable mathematical function. The two groups are proven to be very nearly Maxwellian in the pressure range of 1.8 to 3.8 torr helium and the results are in excellent qualitative agreement with results obtained spectroscopically by other authors. 相似文献
2.
We propose a novel approach to estimate the phase distribution in the presence of nonlinear response of the PZT. The proposed method is an outcome of two different concepts based on the discrete chirp Fourier transform (DCFT) and the maximum-likelihood estimator for the estimation of nonlinear phase step. The robustness of the proposed method is tested for various magnitudes of nonlinearity and harmonics. Comparison of our proposed method with the bench marking algorithm by Hibino et al.'s six and nine sample algorithm in the presence of noise shows that our method is highly efficient. 相似文献
3.
发光二极管路灯光强空间分布的非线性优化设计 总被引:1,自引:0,他引:1
道路照明的首要目的是满足使用者的视觉需求,在此前提下还应尽可能降低能耗实现节能环保,这两点均与道路灯具的光强空间分布密切相关。而很难用一种通用的光强分布适用不同的道路和灯具安装条件。针对主干路、次干路、支路3种典型道路类型,提出了根据具体道路、安装条件以及驾驶员视觉光环境需求逆向设计灯具最节能光强空间分布的思路,并建立了以驾驶员视觉光环境需求为约束、以灯具总光通量最小为目标的非线性优化模型,将路面照度分布表述为余弦多项式并利用分级优化方法进行了求解。得到了3种典型道路条件下发光二极管(LED)路灯的最佳光强空间分布,相比现基于照度均匀分布设计的LED路灯光强分布,驾驶员视觉光环境质量显著改善,且灯具节能30%左右。 相似文献
4.
L. Mashev 《Applied Physics A: Materials Science & Processing》1978,17(2):189-192
A method to compute the propagating modes of graded index waveguides with an arbitrary refractive index distribution is proposed,
based on the variational method applied to the integral wave equation. The method is applied to two refractive index distributions:
a Gaussian index distribution and a complementary error-function index distribution. The results are compared with the predictions
of perturbation analysis and are experimentally verified by measuring the mode spectrum of a Ti-diffused LiNbO3 waveguide. 相似文献
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The application of a maximum entropy method (MEM) for analysis of time-resolved fluorescence data is discussed. A developed
version of MEM has been tested using simulated kinetic data. Based on computed results, practical criteria have been established
to determine whether the lifetime distribution of emitting centers is described by a discrete spectrum (a set of two or three
exponentials) or by a continuous one (mono- or bimodal distribution of exponentials). The proposed method has been used to
analyze the fluorescence decay kinetics of thioflavin T (ThT) intercalated into amyloid fibrils. The presence of two peaks
in the lifetime distribution of emitting centers has been explained by the existence in fibrils of two types of binding centers
substantially differing in microenvironment rigidity. This suggestion is supported by the results of fluorescence quenching
of intercalated ThT with the quencher KI. 相似文献
9.
A. A. Bobrov E. S. Glushkov A. A. Zimin A. V. Kapitonova G. V. Kompaniets V. I. Nosov R. P. Petrushenko O. N. Smirnov 《Physics of Atomic Nuclei》2012,75(13):1586-1595
A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors. 相似文献
10.
D. A. Denisov 《Acoustical Physics》2007,53(5):589-593
A method of calculating the deviations of the speed of sound in a mixed solution containing two types of cations and two types of anions from the speed of sound in pure water by using the known ion concentrations in the solution and the concentration dependences of the speed of sound in binary solutions of the salts entering the mixed solution is proposed. The method is based on the ionic strength rule and the equiprobable ion distribution hypothesis. The calculated values of the deviations of the speed of sound in a mixed solution from the speed of sound in pure water (for solution temperatures of 15 and 25°C) are in fairly good agreement with experimental data. The proposed method is applied for calculating the speed of sound in seawater. 相似文献
11.
制作铊玻璃自聚焦透镜的两步离子交换工艺分析 总被引:3,自引:1,他引:2
本文分析了用一次离子交换工艺制备的自聚焦透镜的径向折射率分布规律,讨论了所能获得的最佳分布工艺条件。在此基础上提出了两步离子交换的新方法。计算表明用两步离子交换工艺制备的自聚焦透镜的折射率分布可以更接近理想分布. 相似文献
12.
Ayman Alzaatreh Mohammad Aljarrah Ayanna Almagambetova Nazgul Zakiyeva 《Entropy (Basel, Switzerland)》2021,23(2)
The traditional linear regression model that assumes normal residuals is applied extensively in engineering and science. However, the normality assumption of the model residuals is often ineffective. This drawback can be overcome by using a generalized normal regression model that assumes a non-normal response. In this paper, we propose regression models based on generalizations of the normal distribution. The proposed regression models can be used effectively in modeling data with a highly skewed response. Furthermore, we study in some details the structural properties of the proposed generalizations of the normal distribution. The maximum likelihood method is used for estimating the parameters of the proposed method. The performance of the maximum likelihood estimators in estimating the distributional parameters is assessed through a small simulation study. Applications to two real datasets are given to illustrate the flexibility and the usefulness of the proposed distributions and their regression models. 相似文献
13.
An information hiding method based on the optical interference principle is proposed. In this method, a secret image can be obtained by two light beams' interference. One of the beams is modulated by our assigned host image; and the other is modulated by a noise-like complex distribution, which is regard as the encrypted image. The transmission of the encrypted image can be implemented by hiding it in the host image to prevent the communication from being perceived by unauthorized person. In addition, this method can also realize simultaneous encryption and hiding for two images. A series of numerical simulation results are presented to verify the feasibility of our proposed method. 相似文献
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Nobuo Sugimoto 《Optical Review》1999,6(6):539-544
A new lidar method for measuring water cloud particle size is proposed, and the feasibility of the measurement is discussed. The method utilizes the phenomenon known as the glory which is observed in open air. The proposed lidar consists of a multicolor laser transmitter and two receiver systems looking at the scattering from the target cloud with different scattering angles. Results of the theoretical study show that a system with five laser wavelengths (355, 532, 750, 1064 and 1500 nm) and two receivers located at scattering angles of 180 and 177.5–179 deg is useful for measuring particle size (mode radius of the size distribution) in a range of 4 to 12μm. 相似文献
16.
S. Nikolov 《Solid State Communications》1983,48(9):761-763
A mathematical method for decomposition of symmetrical Mössbauer spectra of amorphous magnetic materials is proposed. The method consists of two procedures: positioning and synthesis by convolution followed by substration of 2,3,4,5-lines beginning from the outside 1,6-lines. The resultant spectrum containing only the 1,6-components makes it easy to find the hyperfine magnetic field distribution in the sample. 相似文献
17.
S. W. Lovesey 《Journal of statistical physics》1978,19(4):367-390
The renormalization group method proposed by 't Hooft is developed for the study of scaling properties of some models of nonequilibrium phenomena. For one of two models studied in detail, the Langevin equation for the random variables contains a bilinear streaming velocity and the stationary probability distribution is Gaussian. The time-dependent Ginzburg-Landau model is chosen as a second example because it illustrates the advantage of the 't Hooft method of not having to specify a particular renormalization point. The scaling exponents for a model of the liquid-gas phase transition are calculated in lowest order to illustrate application of the method to a multifield system. 相似文献
18.
PurposeThe aim of this study was to propose a channel combination method for |B1+| mapping methods using phase difference to reconstruct |B1+| map.Theory and methodsPhase-based |B1+| mapping methods commonly consider the phase difference of two scans to measure |B1+|. Multiple receiver coils acquire a number of images and the phase difference at each channel is theoretically the same in the absence of noise. Affected by noise, phase difference is approximately governed by Gaussian distribution. Considering data from all channels as samples, estimation can be achieved by maximum likelihood method. With this method, all phase differences at each channel are combined into one. In this study, the proposed method is applied with Bloch-Siegert shift |B1+| mapping method. Simulations are performed to illustrate the phase difference distribution and demonstrate the feasibility and facility of the proposed method. Phantom and vivo experiments are carried out at 1.5 T scanner equipped with 8-channel receiver coil. In all experiments, the proposed method is compared with weighted averaging (WA) method.ResultsSimulations revealed appropriateness of approximating the distribution of phase difference to Gaussian distribution. Compared with WA method, the proposed method reduces errors of |B1+| calculation. Phantom and vivo experiments provide further validation.ConclusionConsidering phase noise distribution, the proposed method achieves channel combination by finding the estimation from data acquired by multiple receivers coil. The proposed method reduces |B1+| reconstruction errors caused by noise. 相似文献
19.
Under the frame work of Mie theory, a method has been developed to calculate the absorbance spectra of nanoparticles suspension containing a size distribution. The silver nanoparticles of two different sizes were first synthesized using a chemical reduction method and characterized by UV-Visible spectroscopy, dynamic light scattering, and transmission electron microscopy techniques. A model size-distribution were proposed and fitted to the experimental absorbance spectra using the described method. Better semiqualitative fitting to the experimental spectra were obtained by our proposed model in comparison to those obtained by single particle model. 相似文献
20.
In this study, a non-staggered grid SIMPLER pressure solution algorithm, which is able to produce correct pressure distribution directly if correct velocities are given, is proposed to solve the pressure distribution for PIV experiments. The cell face pseudo velocity required in the pressure equation is approximated by a simple linear average of the adjacent nodal pseudo velocities so that the velocity and pressure are collocated without causing the checkerboard pressure distribution problem. In addition, the proposed pressure solution algorithm has the features that upwind effects of the convective terms are considered, boundary conditions are not required, and the pressure distribution obtained can be used to correct the velocity field so that the continuity equation is satisfied. These features make the present algorithm a superior method to calculate the pressure distribution for PIV experiments. The pressure field solved is realistic and accurate. The proposed pressure equation solver is first calibrated with a two-dimensional cavity flow. It is found that the results are almost identical to the exact solution of the test flow. The algorithm is then applied to analyze a uniform flow past two side-by-side circular cylinders in a soap film channel. With the velocity and pressure distributions successfully measured, the structures of the complex shedding flow patterns are clearly manifested. 相似文献