Generalization and propagation of spiraling Bessel beams with a helical axicon

A generalized type of spiral Bessel beam has been demonstrated by using a spatially displaced helical axicon （HA）. The topological charge of the spiraling Bessel beams is determined by the order of the input Laguerre Gaussian （LG） beam and the topological charge of the HA. The obtained spiraling Bessel beams have an LG type of modulation along their propagation direction and exhibit annihilation-reconstruction properties. Theoretical analysis is presented, including that of the stability, propagation distance, topological charge, and spiraling dynamic characteristics. The mathematical and numerical results show that the propagation distance and helical revolution of the spiraling Bessel beams can be controlled through choosing appropriate radius of the HA.

Phase properties of odd and even circular states

Phase properties of the even and odd circular states are studied within the Hermitian phase formalism of Pegg and Barnett. Exact analytical formulas for the distribution function and the variance of the phase operator are obtained and used to examine whether or not the even and odd circular states exhibit photon-number squeezing and phase squeezing.

An uplink power control algorithm using traditional iterative model for cognitive radio networks

Based on the analysis of the feature of cognitive radio networks,a relevant interference model was built.Cognitive users should consider especially the problem of interference with licensed users and satisfy the signal-to-interference noise ratio(SINR) requirement at the same time.According to different power thresholds,an approach was given to solve the problem of coexistence between licensed user and cognitive user in cognitive system.Then,an uplink distributed power control algorithm based on traditional iterative model was proposed.Convergence analysis of the algorithm in case of feasible systems was provided.Simulations show that this method can provide substantial power savings as compared with the power balancing algorithm while reducing the achieved SINR only slightly,since 6% SINR loss can bring 23% power gain.Through further simulations,it can be concluded that the proposed solution has better effect as the noise power or system load increases.

Measurement of thermal expansion coefficient of nonuniform temperature specimen

A new technique is developed to measure the longitudinal thermal expansion coefficient of C/C composite material at high temperature. The measuring principle and components of the apparatus are described in detail. The calculation method is derived from the temperature dependence of the thermal expansion coefficient. The apparatus mainly consists of a high temperature environmental chamber, a power circuit of heating, two high-speed pyrometers, and a laser scanning system. A long solid specimen is resistively heated to a steady high-temperature state by a steady electrical current. The temperature profile of the specimen surface is not uniform because of the thermal conduction and radiation. The temperature profile and the total expansion are measured with a high-speed scanning pyrometer and a laser slit scanning measuring system, respectively. The thermal expansion coefficient in a wide temperature range （1000 - 3800 K） of the specimen can therefore be obtained. The perfect consistency between the present and previous results justifies the validity of this technique.

Development of infrared spectral radiation measurement system of a non-luminous flame

The spectral radiation characteristic of a non-luminous flame is analyzed. The apparatus and the calibration procedure based on infrared emission spectrometry for measurements of the flame are introduced. The influence of background radiation and stray light on the measurement results could be reduced and suppressed by the design of thermolator and digital lock-in technique. A blackbody cavity was used as reference emission source to calibrate the system that completed absolute measurement. The spectral mea- surement range is 1-20μm. The least measuring distance and the lowest power detected at the entrance pupil are 550 mm and 10^-9 W/cm^2, respectively. The experimental results show that the measure error is less than 10%.

Measurement of thermophysical properties by a pulse-heating technique

A technique is described for the dynamic measurement of selected thermophysical properties of electrically conducting solids in the temperature range from 1100 K to the melting point. Based on rapid resistive self-heating of the specimen from room temperature to any desired high temperature in several seconds by the passage of an electical current pulse through it, this technique measures the pertinent quantities such as current, voltage, randiance temperature, with sub-millisecond time resolution. The pulse-heating technique is applied to strip specimens. The radiance temperature is measured by high-speed pyrometry, normal spectral emissivity of the strips is measured by integrating sphere reflectometry. The normal spectral emissivity results are used to compute the true temperature of the specimens. The heat capacity, electrical resistivity, total hemispherical emissivity are evaluated in the temperature range from 1100 K to the melting point.

Image Restoration Phase-Filtering Lateral Superresolution Confocal Microscopy

Image restoration phase-filtering lateral superresolution confocal microscopy, a new approach, is proposed to achieve lateral superresolution using a confoeal microscope. This approach uses a lateral superresolution pupil filter to preliminarily improve its lateral resolution and uses a siagle-image superresolution restoration technique based on a maximum likelihood estimate to further improve its lateral resolution. The new approach has the advantages of a low cost and the remarkable superresolution effect without excessive system complexity. Experiments indicate that the proposed approach can improve the lateral resolution of a confocal microscope from 0.3μm to less than 0.1 μm when λ = 632.8 nm and NA=0.85.

Experimental study on electrical resistivity measurement of a specimen at high temperature

A new technique is developed to measure the electrical resistivity of conductor with a nonuniform tem- perature profile. The calculation method is derived from the temperature dependence of the electrical resistivity. The apparatus consists mainly of a high temperature environmental chamber, a power circuit of heating, a twenty-wavelength pyrometer, and a scanning pyrometer. After getting the resistance from the voltage drop of the specimen, the electrical resistivity in a wide temperature range of the specimen can be obtained by our calculation model. Preliminary results of the electrical resistivity of SRM 8424 over a wide temperature range （1000-3000 K） are presented. The perfect consistency between the measurement results and the nominal values justifies the validity of this technique.

Calculation method for particle mean diameter and particle size distribution function under dependent model algorithm

In total light scattering particle sizing technique, the relationship among Sauter mean diameter D32, mean extinction efficiency Q, and particle size distribution function is studied in order to inverse the mean diameter and particle size distribution simply. We propose a method which utilizes the mean extinction efficiency ratio at only two selected wavelengths to solve D32 and then to inverse the particle size distribution associated with Q and D32. Numerical simulation results show that the particle size distribution is inversed accurately with this method, and the number of wavelengths used is reduced to the greatest extent in the measurement range. The calculation method has the advantages of simplicity and rapidness.

New enhancement of infrared image based on human visual system

Infrared images are firstly analyzed using the multifractal theory so that the singularity of each pixel can be extracted from the images. The multifractal spectrum is then estimated, which can reflect overall characteristic of an infrared image. Thus the edge and texture of an infrared image can be accurately extracted based on the singularity of each pixel and the multifractal spectrum. Finally the edge pixels are classified and enhanced in accordance with the sensitivity of human visual system to the edge profile of an infrared image. The experimental results obtained by this approach are compared with those obtained by other methods. It is found that the proposed approach can be used to highlight the edge area of an infrared image to make an infrared image more suitable for observation by human eyes.

Measuring normal spectral emissivities of niobium by a pulse-heating technique:1000K to the melting point

The normal spectral emissivity of niobium strip specimen is measured using a new pulse-heating reflectometric technique. The hemispherical spectral reflectivity of the surface of a strip tangent to an integrating sphere is determined by a high-speed lock-in technique. At the same time, the radiance tem- perature of the strip is measured by the multi-wavelength high-speed pyrometer from approximately 1000 K to the melting point. Details of the measurement method and of the related calibration techniques are reported. Results of the normal spectral emissivity of niobium at 633, 753, 827, and 905 nm from room temperature to its melting point are presented. The accuracy of spectral emissivities is estimated better than 5%.

Double-image sharing encryption based on associated fractional Fourier transform and gyrator transform

We present a novel method for realizing double-image encryption algorithm by combining the images in different transform domains. Two original images are encrypted into two interim images by fractional Fourier transform and gyrator transform, respectively. The two encrypted images can be obtained by means of the addition and subtraction of the two interim images. This is defined as a double-image sharing scheme, in which the original images are encrypted into two parts. The original images cannot be recovered only with any one of the two interim images. Numerical simulation experiments demonstrate the validity of the algorithm.

Method for changing brightness temperature into true temperature based on twice recognition method

The channel output of a multi-wavelength pyrometer is the brightness temperature rather than the true temperature. Twice recognition method is put forward to change the brightness temperatures of a multiwavelength pyrometer into the true temperatures of targets. Using the data offered by Dr. F. Righini, the experimental results show that the difference between the calculated true temperature based on twice recognition method and the real true temperature is within ±20 K. The method presented in this paper is feasible and effective for the true temperature measurement of targets.

Virtual source for rotational symmetric Lorentz-Gaussian beam

The virtual source for generation of rotational symmetric Lorentz-Gaussian （RLG） wave whose propagating dynamics present the rotational symmetry is identified. Closed-form expressions, including integral and differential representations, are derived for this kind of Lorentz-Gaussian （LG） wave, thereby yielding paraxial approximation of the RLG beam in the appropriate regime. From the spectral representation of this wave, the first three order corrections of nonparaxial approximations are determined for a corresponding paraxial RLG beam. Moreover, the relationship between the RLG beam and the Hermite-Gaussian beam is revealed.