基于发光二极管探测器的太阳光度计的研究

介绍了一种采用商用发光二极管作为探测器的新型太阳光度计。阐述了系统的结构以及该仪器在监测气溶胶光学厚度领域的应用,并与传统的太阳光度计进行了对比试验。试验表明,两种仪器具有很好的一致性。     

Optoelectronic system of the aerosol photometer in the detector of molecular condensation nuclei

We study the light scattering by aerosol particles and air in the photometer of the molecular condensation nuclei, as well as the sensitivity of the photodector of the photometer. The interference nature of light scattering by aerosol particles is established and is found to be comparable (in order of magnitude) with the scattering of light by air in the photometer. The sensitivity of the photometer can be increased by more than an order of magnitude due to optimization of the optoelectronic part of the photometer. The detection threshold for the target component of the gas analyzer is attained at the spontaneous ionization background level and not at the limiting sensitivity level of the photodetector.     

Soliton-Like Bi-plasma Polaron

In the framework of phonon-plasmon cooperative effect mechanism, the differential equation for the wavefunction of the travelling soliton-like bi-plasma polaron (BPP) is derived. Then it is proven that the solution can be simply one-dimensional form. Meanwhile, the velocity range of the travelling soliton-like BPP is studied, thereby, we found that the quantity η=ε_∞/ε₀ of the materials, where the travelling soliton-like BPP can exist, should be very small, i.e. η→0. This result is consistent with the recently reported ones. Finally, an analytic approximation solution is given.     

Influence of the spectral power distribution of a LED on the illuminance responsivity of a photometer

The measurement accuracy in the photometric quantities measured through photometer head is determined by the value of the spectral mismatch correction factor (c(S_t,S_s)), which is defined as a function of spectral power distribution of light sources, besides illuminance responsivity of the photometer head used. This factor is more important when photometric quantities of the light-emitting diode (LED) style optical sources, which radiate within relatively narrow spectral bands as compared with that of other optical sources, are being measured. Variations of the illuminance responsivities of various V(λ)-adopted photometer heads are discussed. High-power-colored LEDs, manufactured by Lumileds Lighting Co., were used as light sources and their relative spectral power distributions (RSPDs) were measured using a spectrometer-based optical setup. Dependences of the c(S_t,S_s) factors of three types of photometer heads (f₁′=1.4%, f₁′=0.8% and f₁′=0.5%) with wavelength and influences of the factors on the illuminance responsivities of photometer heads are presented.     

差分吸收光谱技术监测气溶胶光学厚度及大气能见度的研究

介绍了一种基于闪烁氙灯光源、利用差分光谱吸收(DOAS)技术监测大气气溶胶的新方法。提出用大气能见度确定系统校正参量的可行做法,解决了差分光谱吸收探测气溶胶领域原始光强难以测量的难题。并对350~650 nm范围内的气溶胶光学厚度进行反演,通过与多道太阳光度计的对比证实方法的可行性,实验中发现气溶胶光学厚度与悬浮颗粒物(SPM)浓度具有很好的相关性。同时,利用气溶胶550 nm处的消光系数确定大气能见度。     

Optimization of the piezoelectric transducer response by means of electrical correcting circuits

A method of shortening the transient response of a piezoelectric transducer is described. It can be applied to thickness mode piezoelectric transducers of arbitrary electromechanical coupling. The system incorporates electrical correcting circuits and can produce a transient response with a duration much shorter than the transit time of an ultrasonic wave travelling through the piezoelectric plate.     

Generation of waves in an elastic plate by a torsional moment and a horizontal force

An approximate solution is determined for the motion of an infinite elastic plate, excited by a torsional moment (with the axis of the moment normal to the plate) and by a horizontal force (parallel to the plate). The driving moment and force are sinusoidal in time and applied to a small rigid indenter with a circular base, fixed to the plate. The solution is obtained from a three-dimensional approach but is evaluated only for low frequencies, where the wavelengths of the quasi-longitudinal, tranverse and bending waves are much larger than the thickness of the plate. For the case of excitation with a torsional moment, the solution contains two parts, one describing a travelling transverse wave and the other a local reaction. The local reaction is built up of two infinite sums of Love waves with imaginary wave numbers. The driving-point admittance due to the local reaction is larger than the admittance due to the tranverse wave when the diameter of the indenter is smaller than about twice the thickness of the plate. For the case of excitation with a horizontal force, the solution contains three parts that describe travelling waves (quasi-longitudinal, transverse and bending) and two parts that describe the local reaction (infinite sums of Lamb and Love waves). The admittances due to the three types of travelling waves are all of the same order of magnitude. The admittance due to the local reaction is of importance when the frequency is relatively high and the diameter of the identer much smaller than the thickness of the plate. For both cases of excitation, the admittance due to the local reaction increases with increasing thickness of the plate and tends to the value found for a semi-infinite medium.     

Spectral and emission characteristics of LED and its application to LED-based sun-photometry

In recent years, light-emitting diodes (LEDs) have found applications in fields like space science instrumentation in addition to its use in illumination. Sun photometry is one of the techniques for measuring aerosol optical depth. Photometers generally consisting of an interference filter and a photo-detector, measures the intensity of radiation in the wavelength band of the interference filter. LED alone replaces both the interference filter and the detector and works as a spectrally selective photo-detector. The spectral response (extinction spectra) of LED is required to calculate the aerosol optical depth. In general, it is assumed that the emission spectra and spectral response should be same. It has been found experimentally that the emission spectra and spectral response are different. The peak wavelength at which the maximum emission occurs is found to be higher than the peak of the spectral response curve. The FWHM of both are also found to be different. A typical example of Langley plot obtained from the LED-based Sun photometer is shown and optical depth obtained with this is compared with the conventional Sun photometer.     

Multiple-stage liquid crystal tuned filter

A voltage controlled multiple-stage tunable filter with broad continuous tuning range was studied in theory and experiment. Four liquid crystal retarders, two quartz plates with certain integral ratio phase retardations and five polarization films were assembled into a traditional Lyot filter. The tunable function was achieved by using the electro-birefringence effect of liquid crystal. The result of numerical simulation showed that the spectral resolution was ∼10 nm around bands of 500-700 nm; side forms rejection ratio and FWHM changed in contrast to considering and not considering the birefringence dispersion effect of liquid crystal and quartz; the shape of filtered light displayed by spectral photometer would be affected by spectrum bands of light source in spectral photometer. A four-stage tunable filter was made and tested, experiment results agreed with the numerical simulation results very well, the research results could be applied as reference for the study of broad spectrum tunable filters.     

Nonlinear waves in the nonequilibrium systems of the oscillatory type. Part II

The paper is the continuation of the preceding one (Part I). In the part II we consider the inhomogeneous quasistationary wave patterns which result from collisions of the travelling waves with close wave-vectors, and which may be regarded as narrow stationary spectral packages consisting of the quasimonochromatic travelling waves. Then we consider the long-wave oscillatory system. It is well known that in the absence of dispersion this system possesses the potential which makes it possible to compare the absolute stability of different quasistationary states. We make an attempt to construct an analogous quantity for the dispersive system. We argue that this quantity should be of the type of the potential production (an analogue of the entropy production in the nonequilibrium thermodynamics) rather than a generalization of the potential itself. Though we have no rigorous proof that our quantity indeed determines the absolute stability, we demonstrate that this hypothesis is verisimilar.     

用干涉方法测量薄膜应力

基于基片弯曲法和牛顿环的基本原理,使用He-Ne激光器、扩束镜、凸透镜和带分光镜的移测显微镜,搭建了薄膜应力测量装置.采用直流溅射法制备了厚度为30~144 nm的银薄膜,衬底采用厚度为0.15 mm、直径为18 mm的圆形玻璃片.实验发现,薄膜厚度对银薄膜的内应力有显著的影响,在薄膜厚度很小时,随着薄膜厚度的增加,应力迅速增大,达到最大值后,随着厚度的继续增加,薄膜应力下降较快并趋于稳定值.     

Diffraction of electrons on the travelling electromagnetic wave

The quantum effect of diffraction scattering of the electron on the travelling electromagnetic wave in the presence of the third body has been found. As the third body, the refracting medium, the division bounds of different mediums or any inhomogenity of it, the atomic nucleus, screens, openings (giving diffraction emission) etc. may appear. The cause of this effect is physically connected with the real absorption and emission of non-vacuum quanta, the concrete mechanism of which is conditioned by the direct and inverse induced Cherenkov, transitional, bremsstrahlung, diffraction effects respectively. Owing to the real absorption-emission the scattering is inelastic, so the diffraction on the travelling wave is accompanied by the acceleration of electrons (one half decelerates).     

量子点场效应单光子探测器二维电子气载流子浓度研究

设计了一种基于场效应晶体管的量子点场效应单光子探测器(quantum dot field effect transistor,QDFET),建立了二维电子气(two-dimensional electron gas,2DEG)的薛定谔方程和泊松方程,通过对薛定谔方程和泊松方程的自洽求解,对2DEG的载流子浓度进行了模拟。模拟结果显示,AlGaAs的Al组分、δ掺杂层的掺杂浓度以及隔离层的厚度对于2DEG的载流子浓度均有影响。为了使2DEG具有较高的载流子浓度,AlGaAs的Al组分应为0.2~0.4,δ掺杂浓度应为6~8×10~(13)/cm~2,隔离层厚度应在50nm以下。通过对2DEG的载流子浓度进行研究,可以掌握2DEG载流子浓度的影响因素,从而通过优化QDFET结构,可提高2DEG的载流子浓度。这对于高灵敏度QDFET的制备具有重要的意义和应用价值。     

Diffraction of love waves by two staggered perfectly weak half-planes

Summary Love wave travelling in a layer of uniform thickness overlying a half-space is assumed to be incident on two parallel but staggered perfectly weak half-planes lying in the upper layer. The diffracted field is calculated using the modified Wiener-Hopf technique and contour integration method. The diffracted waves satisfy the dispersion relations appropriate to different regions formed by the perfectly weak half-planes. To the memory of M. H. Kazi     

Revisiting the moving force problem

The problem of the vibration of a beam subject to a travelling force is considered. The purpose of the study is to develop simple tools for finding the maximum deflection of a beam for any given velocity of the travelling force. It is shown that, for given boundary conditions, there exists a unique response-velocity dependence function. A technique to determine this function is suggested, which is based on the assumption that the maximum beam response can be adequately approximated by means of the first beam mode. To illustrate this, the maximum response function is calculated analytically for a simply supported (SS) beam and constructed numerically for a clamped-clamped beam. The effect of the higher modes on the maximum response is investigated, and the relative error of the one-mode approximation for a SS beam is constructed. The estimates obtained substantiate the assumption about adequacy of the one-mode approximation in a wide range of velocities; in particular, the relative error in the neighborhood of the velocity that results in the largest response is less than one percent.     

Investigation of the Mueller Matrix elements of the liquid crystal cell illuminated with a broad band light source

The Mueller Matrix (MM) elements of the planar liquid crystal cell which is illuminated with a broad band light source was investigated and six MM elements were experimentally measured as functions of wavelength in the range of 500–800 nm at different cell alignment angles. Analysis of the MM curves were used to explain how the state of the linearly polarized light changes at the output of the LC cell. The trends of the MM curves were found to be in agreement with the recent studies on Mueller Stokes characterization of the LC based electro-optical devices. The values at different wavelengths correspond to different phase retardation values, hence it is parallel to changing the cell thickness. It is also found that the state of the polarization ellipse of the travelling light is an important factor that affects the amount of light depolarization.     

Modeling of single- and multimode photonic-crystal planar waveguides with the plane-wave admittance method

One-foil targets emit most transition radiation (TR) power in storage ring synchrotrons. Such one-foil TR emitting targets (OFTRTs) are optimized, with respect to the foil material and the foil thickness, for use as X-ray lithography (XRL) sources. The best possible elemental material and the foil thickness of OFTRTs for XRL are determined for our storage ring synchrotrons MIRROIRCLE-20SX and MIRRORCLE-6X, which operate with electrons accelerated to 20 MeV and 6 MeV, respectively. It is shown that the XRL efficiency of a OFTRT, with an optimum thickness, increases when the elemental foil material has a lower atomic number Z. The best elemental OFTRT, for performing XRL by MIRRORCLE-20SX, should contain one Be foil with a thickness of d≅240 nm, while the second best OFTRT should be made of one C foil with d≅220 nm. The best elemental OFTRT, for performing XRL by MIRRORCLE-6X, should contain one C foil with d≅35 nm, while the second best OFTRT should be made of one Be foil with d≅100 nm, because there are no thinner Be foils. The XRL efficiency of a C-foil OFTRT increases when a higher-density foil is used. A OFTRT containing one foil of a given material with optimum thickness, in MIRRORCLE-20SX, has approximately 100 times larger XRL efficiency in comparison with such a target in MIRRORCLE-6X. PACS 41.50.+h; 29.25.-t; 81.16.Nd; 41.60.Ap; 29.20.Dh     

Theoretical model and quantification of reflectance photometer

The surface morphology of lateral flow （LF） strip is examined by scanning electron microscope （SEM） and the diffuse reflection of porous strip with or without nanogold particles is investigated. Based on the scattering and absorption of nanogold particles, a reflectance photometer is developed for quantification of LF strip with nanogold particles as reporter. The integration of reflection optical density is to indicate the signals of test line and control line. As an example, serial dilutions of microalbunminuria （MAU） solution are used to calibrate the performance of the reflectance photometer. The dose response curve is fitted with a four-parameter logistic mathematical model for the determination of an unknown MAU concentration. The response curve spans a dynamic range of 5 to 200 μg/ml. The developed reflectance photometer can realize simple and quantitative detection of analyte on nanogold-labeled LF strip.     

Application of the (G^{\prime}/G)-expansion method for the Burgers, Burgers–Huxley and modified Burgers–KdV equations

In this work, we present travelling wave solutions for the Burgers, Burgers–Huxley and modified Burgers–KdV equations. The (G′/G)-expansion method is used to determine travelling wave solutions of these sets of equations. The travelling wave solutions are expressed by the hyperbolic functions, the trigonometric functions and the rational functions. It is shown that the proposed method is direct, effective and can be used for many other nonlinear evolution equations in mathematical physics.     

The existence and stability of travelling waves with transition layers for some singular cross-diffusion systems

This paper is concerned with the existence and the stability of travelling waves for a class of quasilinear cross-diffusion systems describing two competing or predator-prey species. Firstly, by geometric singular perturbation method, the existence of travelling waves with transition layers is proved, which extends the results of Hosono and Mimura [Y. Hosono, M. Mimura, Singular perturbation approach to travelling waves in competing and diffusion species models, J. Math. Kyoto Univ. 22 (1982) 435–461] and Gardner [R.A. Gardner, Topological Methods Arising in the Study of Travelling Waves, Reaction–Diffusion Equations, Clarendon Press, Oxford, 1990, pp. 173–198] for non-cross-diffusion systems and Wu [Y. Wu, The existence of travelling waves for a cross-diffusion system with small parameter, Beijing Math. 3 (1997) 74–85] to more general cross-diffusion systems. Applying the stability index method introduced in Alexsander et al. [J. Alexsander, R.A. Gardner, C.K.R.T. Jones, A topological invariant arising in the stability analysis of travelling waves, J. Die Reine Angewandte Math. 410 (1990) 167–212] and Gardner and Jones [R.A. Gardner, C.R.K.T. Jones, Stability of travelling wave solutions of diffusive predator–prey systems, Trans. Am. Soc. 327 (1991) 465–524] to the more general eigenvalue problem induced by the quasilinear cross-diffusion systems, by detailed spectral and topological analysis, the travelling waves with transition layers for the cross-diffusion systems are proved to be stable, which also extends the results of Gardner and Jones [R.A. Gardner, C.R.K.T. Jones, Stability of travelling wave solutions of diffusive predator–prey systems, Trans. Am. Soc. 327 (1991) 465–524] to the more general systems.