A new approach for the estimation of the axial velocity using ultrasound

The most used estimation method for calculating the blood velocity in commercial scanners is the autocorrelation approach. The calculation of the mean velocity used in this method depends on the center frequency of the interacting ultrasound pulse which downshifts as a function of depth, introducing a bias. A new velocity estimator for the mean axial velocity is presented. The estimation principle is based on the 2D Fourier transform and the Radon transform. The input data are a sequence of RF data forming a 2D data input, one column for each pulse emission. A 2D segment is selected for a specific depth. This data segment is first transformed by a 2D Fourier transform, and the result is then transformed by a Radon transform. The center of gravity for the angles of the lines intersecting the origin of the R-theta coordinate system in the Radon domain gives the mean axial velocity for the data segment. The benefit of this method is an estimate of the mean axial velocity which is independent of the center frequency of the propagating ultrasound pulse. The estimate will only depend on f(s) and f(pr f). Results of the estimation method is presented based on both simple generated RF harmonic data for different signal/noise ratios and simulated acoustic RF responses from a 3D measurement situation with an array transducer and a tube with plug flow. The new method shows improvement with a factor of 1.5-4 on the standard deviation on the estimated mean velocity for the simulated case.     

高效率获得阵列信号光源的新途径

根据图像反差倒转的概念,提出了一种高效率产生多光束照明信号的新方法.这种技术可望应用于研制阵列处理器或光计算机所需的阵列信号光源.本文给出了产生阵列信号光源的实验结果,并进行了讨论.     

一种根据布朗运动测量玻尔兹曼常量的新方法

利用显微镜和CCD图像采集工具对聚丙烯小球的布朗运动进行了研究,通过拍摄粒子运动图像并利用MATLAB程序进行图片处理,读取每一时刻布朗粒子的坐标.基于对大量数据的统计分析,计算出了玻尔兹曼常量,与理论值的相对误差约为4%.同时,验证了布朗运动位移服从正态分布以及粒子位移均方值与时间成正比的关系.     

A new method for spectral decomposition using a bilinear Bayesian approach

A frequent problem in analysis is the need to find two matrices, closely related to the underlying measurement process, which when multiplied together reproduce the matrix of data points. Such problems arise throughout science, for example, in imaging where both the calibration of the sensor and the true scene may be unknown and in localized spectroscopy where multiple components may be present in varying amounts in any spectrum. Since both matrices are unknown, such a decomposition is a bilinear problem. We report here a solution to this problem for the case in which the decomposition results in matrices with elements drawn from positive additive distributions. We demonstrate the power of the methodology on chemical shift images (CSI). The new method, Bayesian spectral decomposition (BSD), reduces the CSI data to a small number of basis spectra together with their localized amplitudes. We apply this new algorithm to a 19F nonlocalized study of the catabolism of 5-fluorouracil in human liver, 31P CSI studies of a human head and calf muscle, and simulations which show its strengths and limitations. In all cases, the dataset, viewed as a matrix with rows containing the individual NMR spectra, results from the multiplication of a matrix of generally nonorthogonal basis spectra (the spectral matrix) by a matrix of the amplitudes of each basis spectrum in the the individual voxels (the amplitude matrix). The results show that BSD can simultaneously determine both the basis spectra and their distribution. In principle, BSD should solve this bilinear problem for any dataset which results from multiplication of matrices representing positive additive distributions if the data overdetermine the solutions.     

A new concept of white light generation using a nano-waveguide for the solar radiation collection use

We propose a novel system of a nano-waveguide that can be used to generate the continuous optical spectrum, i.e. white light. A system consists of two micro-ring resonators and a nano-ring resonator that can be integrated into a single system. The large bandwidth signal is generated using a soliton pulse propagating within a Kerr-type nonlinear medium, whereas the continuous bandwidth or wavelength of light signal can be performed. Results obtained have shown the potential of using such a system for white light source generation and amplification, which is discussed. The amplified pulse can be stored within a nano-waveguide, which is allowed to form the continuous spectrum after amplification. Alternatively, the low-level solar radiation can be amplified, and the bandwidth signals can also be enlarged.     

A new approach to measure the ocean temperature using Brillouin lidar

An approach of lidar measurements of ocean temperature through measuring the spectral linewidth of the backscattered Brillouin lines is presented. An empirical equation for the temperature as a function of Brillouin linewidth and salinity is derived. Theoretical results are in good agreement with the experimental data. The equation also reveals the dependence of the temperature on the salinity and Brillouin linewidth.It is shown that the uncertainty of the salinity has very little impact on the temperature measurement.The uncertainty of this temperature measurement methodology is approximately 0.02 ℃.     

A new soliton communication band for optical networking redundancy using a Gaussian soliton generation

We present a novel communication band of the tunable multi-Gaussian soliton system, whereas the large bandwidth signals of the spatial soliton pulses can be generated after propagating within the nonlinear ring resonator system. A Gaussian pulse input with 20 ns pulse width, 2 W peak power, the center wavelength at 1300 nm is propagated into the nonlinear ring resonator system. Using the appropriate parameters relating to the practical device such as micro-ring radii, coupling coefficients, linear and nonlinear refractive index, we found that the multi-soliton pulse obtained have shown the potential of application for a new dense wavelength division multiplexing (DWDM) band. The soliton pulse width and free spectrum range of 400 and 7 fm are obtained, respectively, which can be used to increase the channel capacity in soliton communication. Furthermore, the soliton power obtained is available for system and link redundancy, where the output soliton power of 12 W is achieved.     

A simplified approach for the generation of projection data for cone beam geometry

To test a developed reconstruction algorithm for cone beam geometry, whether it is transmission or emission tomography, one needs projection data. Generally, mathematical phantoms are generated in three dimensions and the projection for all rotation angles is calculated. For non-symmetric objects, the process is cumbersome and computation intensive. This paper describes a simple methodology for the generation of projection data for cone beam geometry for both transmission and emission tomographies by knowing the object’s attenuation and/or source spatial distribution details as input. The object details such as internal geometrical distribution are nowhere involved in the projection data calculation. This simple approach uses the pixilated object matrix values in terms of the matrix indices and spatial geometrical coordinates. The projection data of some typical phantoms (generated using this approach) are reconstructed using standard FDK algorithm and Novikov’s inversion formula. Correlation between the original and reconstructed images has been calculated to compare the image quality.     

A new perturbative approach for the anharmonic oscillator

A new perturbative approach is presented and applied to the anharmonic oscillator. Estimating the large-order behaviour by means of the Lipatov method, the new perturbation expansion turns out to be convergent for the partition function at non-zero temperature. Although the new perturbation expansion is not convergent for the ground-state energy, it nevertheless provides accurate approximations, even in situations which cannot be treated by standard perturbation techniques, like the strong coupling regime.     

A new approach for diagnostics of dense magnetoactive plasmas using the effect of parametrically induced transparency

We study theoretically the effect of parametrically induced transparency. The main idea of this effect is transport of the upper-hybrid radiation of overdense toroidal plasmas in vacuum through the opaque region by parametric shift of the radiation frequency. We propose that the microwave radiation employed for electron-cyclotron heating at the second cyclotron harmonic in tokamaks is used as the drive wave. Calculations performed for the TEXTOR tokamak demonstrate that this effect is promising for diagnostics of dense plasmas in toroidal devices if a gyrotron with an ouput power of several hundred kilowatts is used. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 6, pp. 508–521, June 2007.     

从Pleiades剖析新一代高性能小卫星技术发展

综述了著名的新一代极限性能高分辨小卫星Pleiades,说明了该卫星的技术特点,同时给出了其关键技术指标,并且有针对性地剖析了Pleiades在多星组网轨道设计、一体化超分辨焦平面设计、一体化综合电子学设计及敏捷姿态控制系统设计等方面所采用的先进技术和设计理念。在此基础上,提出了适应我国国情的小卫星新技术发展方向,包括CMOS TDI模式成像技术、高动态范围视频成像技术、基于可重构模块的柔性化集成技术、基于软件总线的星载软件设计技术以及星载一体化设计技术等,为今后我国研发具有更高的地面分辨率、在轨成像效率和成像质量的新一代高性能小卫星提供了新的思路。     

A new approach to produce spread-out Bragg peak using the MINUIT fit

A new approach to obtain a spread-out Bragg peak (SOBP) using the MINUIT fit is presented. The SOBP has been adopted in proton therapy in order to irradiate a proton beam equally over the tumor along the beam direction. In principle, an SOBP can be easily obtained by using several Bragg peaks from different beam energies, since the position of the peak varies with the energy. However, this is not practical in real medical situations, because the beam energy is fixed by the accelerator. Thus, a modulation method has been employed to obtain an SOBP, where the position of Bragg peak is controlled by a modulator with varying thickness. In this study, we use the GEANT4 package to simulate a generic proton therapy apparatus. A modulator with thickness control is assumed in the proton therapy setup and a set of Bragg peaks is obtained from the GEANT4 simulation. Assuming that the position and the size of the tumor are known, we first determine which Bragg peaks should be used in the fit. Then a MINUIT fit is applied to calculate the weights of each Bragg peak in order to maximize the flatness of the SOBP while minimizing the dose in the normal tissue area, thus maximizing the dose in the tumor. The fit has turned out to be very robust and converges quickly. Since the MINUIT is a small size library and the proposed SOBP fit shows stable behavior, this method can be readily applied to the real therapy.     

A new synthetic detection technique for trackside acoustic identification of railroad roller bearing defects

The detection of railroad roller bearing defects is of great importance for railway traffic. The acoustic defective bearing detector (ADBD) via a trackside acoustic detection system (TADS) is a popular and reliable tool for trackside identification of railroad bearing incipient defects. However, the defective trackside acoustic signal of bearing is confronted with three challenges: demodulation of acoustic signal, removal of Doppler effect and enhancement of defect frequency. This paper proposes a synthetic detection technique to overcome these difficulties successively. In the technique, the signal envelope is first extracted by a new variable-resolution ridge demodulation (VRRD) method. Then the Doppler effect is removed in the envelope via a dynamic signal resampling method. Finally, the rectified defect frequency is enhanced through the means of logarithmic transformation and piecewise linear detrending. The VRRD technique extracts the envelope from the signal time–frequency distribution (TFD) along the Doppler shift curve of resonance frequency traced by an improved ridge extraction algorithm. The resampling method is carried out on the envelope according to the Doppler shift curve of defect frequency obtained by the same ridge extraction algorithm. The sidebands around defect frequency can be suppressed by the logarithmic transformation and the low-frequency non-linear trend can be removed by the detrending method. The signal amplitude is unified at the same time. Two practical bearing signals with inner-race and outer-race defects separately verify the effectiveness of proposed technique.     

A new approach for colored watermarking image into gray scale image using wavelet fusion

With the quick growth of technologies and great spread of the Internet, many challenges face data hiding. Nevertheless, significant data may be protected by burring it in an image as a watermark. This paper shows an efficient data hiding watermarking approach for color image by using singular value decomposition (SVD), multi-level discrete wavelet transform (DWT) and wavelet fusion. The main idea in this work is to separate the color image into its basic components (three channels); red, green, and blue. Then, fuse every channel with an image which is gray scale and integrate the three fused images into one gray scale fused image. Finally, the fused image is burred into a cover gray scale image to produce the watermarked image by using DWT and SVD. The proposed approach evaluation is done by using several images and different hacking on the transmitted image. The experimental results show that the marked images which are generated by the proposed approach are tolerant to versatile attacks such as Gaussian, blur, wrap, and cropping. Above all, the extracted watermark images are recognized even when the watermarked images suffered from attacks.     

A new approach to the retrieval of surface properties from earthshine measurements

Instruments such as the MODIS and MISR radiometers on EOS AM-1, and POLDER on ADEOS have been deployed for the remote sensing retrieval of surface properties. Typically, retrieval algorithms use linear combinations of semi-empirical bidirectional reflectance distribution function (BRDF) kernels to model surface reflectance. The retrieval proceeds in two steps; first, an atmospheric correction relates surface BRDF to top-of-atmosphere (TOA) reflectances, then regression is used to establish the linear coefficients used in the kernel combination. BRDF kernels may also depend on a number of physical or empirical non-linear parameters (e.g. ocean wind speed for a specular BRDF); such parameters are usually assumed known. A major source of error in this retrieval comes from lack of knowledge of planetary boundary layer (PBL) aerosol properties.In this paper, we present a different approach to surface property retrieval. For the radiative transfer simulations, we use the discrete ordinate LIDORT model, which has the capability to generate simultaneous fields of radiances and weighting functions in a multiply scattering multi-layer atmosphere. Surface-atmosphere coupling due to multiple scattering and reflection effects is treated in full; the use of an atmospheric correction is not required. Further, it is shown that sensitivities of TOA reflectances to both linear and non-linear surface BRDF parameters may be established directly by explicit analytic differentiation of the discrete ordinate radiative transfer equations. Surface properties may thus be retrieved directly and conveniently from satellite measurements using standard non-linear fitting methods. In the fitting for BRDF parameters, lower-boundary aerosol properties can either be retrieved as auxiliary parameters, or they can be regarded as forward model parameter errors. We present examples of simulated radiances and surface/aerosol weighting functions for combinations of multi-angle measurements at several different wavelengths, and we perform some examples of self-consistent non-linear fitting to demonstrate feasibility for this kind of surface property retrieval.     

A new formulation for the bethe approach to lattice statistics

An improved mathematical treatment is given for the approximate statistics of the Ising problem based on configurations of local Bethe clusters. The essential step in the development is to write the configuration probability for the Bethe cluster in terms of the probabilities for subclusters. Exact statistical mechanical results are used to interrelate the probabilities. The technique is illustrated first for a simple ferromagnetic lattice and then applied to the order-disorder problems of binary and ternary alloys on the face centered cubic lattice. In each ease the final equations which need solution are derived by strictly algebraic means. The improvement in mathematical treatment is such that these equations are identical with high order approximations of the very different cluster variation method.     

A new set of basis functions for the discrete geometric approach

By exploiting the geometric structure behind Maxwell’s equations, the so called discrete geometric approach allows to translate the physical laws of electromagnetism into discrete relations, involving circulations and fluxes associated with the geometric elements of a pair of interlocked grids: the primal grid and the dual grid.     

A new approach for the determination of the C ls binding energy

The binding energy of the C 1s-level of clean pyrolytic graphite and amorphous carbon has been measured by means of the excitation-curve technique. Values ofE _{C 1s} ^B =284.31±0.2 eV for graphite and amorphous carbon have been found.