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991.
In this paper,we calculate the branching ratios and the direct CP-violating asymmetries for decays B0 →a00(980)π0,a0+(980)π-,a0-(980)π+ and B- →a00(980)π-,a0-(980)π0 by employing the perturbative QCD(pQCD) factorization approach at the leading order.We found that(a) the pQCD predictions for the branching ratios are around(0.4-2.8)×10-6,consistent with currently available experimental upper limits;(b) the CP asymmetries of B0 →a00(980)π0 and B- →a0-(980)π0 decays can be large,about(70-80)% for α=100-. 相似文献
992.
J.-Ph. Jay F. Le Berre S.P. Pogossian M.V. Indenbom 《Journal of magnetism and magnetic materials》2010,322(15):2203-2214
Two techniques of measurements of thin film magnetostriction are compared: direct, when changes of the substrate curvature caused by the film magnetization are controlled, and inverse (“indirect”), when the modification of the magnetic anisotropy induced by the substrate deformation (usually bending) is measured. We demonstrate how both the elastic strength of the substrate and the effective magneto-mechanical coupling between the substrate deformation and magnetic anisotropy of the film depend on different conditions of bending. Equations to be used for magnetostriction value determination in typical cases are given and critical parameters for the corresponding approximations are identified. 相似文献
993.
The band artifact in steady-state free precession can be reduced by synthesizing the multiple images obtained through different phase increments of successive radiofrequency pulses. Even though the complex summation method was reported to be effective in reducing the band artifact, it has the pitfalls of intensity abnormality and sensitivity to the phase abnormality. Two new methods have been developed for more reliable reduction of the band artifact than the complex summation method. One method is to sum the complex images partially and to take the maximum intensity of the partially summed images. The other method is to sum the free induction decay (FID) and primary echo components of the Fourier series that are obtained through Fourier analysis of the complex base images. Both proposed methods were compared with other magnitude (maximum intensity projection, spectrally decomposed synthesis, sum-of-squares, nonlinear averaging) and complex-based (complex summation, magnitude-weighted complex summation) methods experimentally at 3 T for the phantom and volunteer's head imaging. Both proposed methods were confirmed to maintain the advantage of the complex summation in reducing both the dark and bright band artifacts while reducing the intensity abnormality and sensitivity to the phase abnormality from that of the complex summation method over a wide range of flip angles and relaxation times. 相似文献
994.
Sodium borate and fluoroborate glasses doped with trivalent samarium (Sm3+) were prepared and their detailed spectroscopic analysis was carried out. The FTIR spectra reveal that, the glasses contain BO3, BO4, non-bridging oxygen and strong OH− bonds. From the optical absorption spectra, Judd-Ofelt intensity parameters (Ωλ, λ=2, 4 and 6) have been evaluated and are in turn used to predict radiative properties such as radiative transition probability (A), stimulated emission cross section () and branching ratios (βR) for the excited levels of Sm3+ ions in sodium borate and sodium fluoroborate glasses. The dependence of the spectral characteristics of Sm3+ ions due to compositional changes have been examined and reported. The value is found to decrease with the decrease in the sodium content in the glass. The decay from the 4G5/2 level is found to be non-exponential indicating a cross-relaxation among the Sm3+ ions. 相似文献
995.
A.S. Bennal N.M. Badiger 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(10):1363-1371
The K-L total vacancy transfer probabilities (ηKL) of selected elements in the atomic range 42≤Z≤82 have been determined using a weak gamma source. The targets are excited by 123.6 keV gamma photons from a weak 57Co source and K X-ray photons are measured by an ORTEC type GMX-10P HPGe detector coupled to 8 K multichannel analyzer. By measuring the K X-ray intensity ratio and K shell fluorescence yield, the K to L total vacancy transfer probabilities have been determined. Measured values have been compared with theoretical and other experimental values. 相似文献
996.
Narendra Singh 《Optik》2010,121(15):1427-1437
We propose a new method for digital image watermarking using gyrator transform and chaotic maps. Four chaotic maps have been used in the proposed technique. The four chaotic maps that have been used are the logistic map, the tent map, the Kaplan-Yorke map and the Ikeda map. These chaotic maps are used to generate the random phase masks and these random phase masks are known as chaotic random phase masks. A new technique has been proposed to generate the single chaotic random phase mask by using two chaotic maps together with different seed values. The watermark encoding method in the proposed technique is based on the double random phase encoding method. The gyrator transform and two chaotic random phase masks are used to encode the input image. The mean square error, the peak signal-to-noise ratio and the bit error rate have been calculated. Robustness of the proposed technique has been evaluated in terms of the chaotic maps, the number of the chaotic maps used to generate the CRPM, the rotation angle of the gyrator transform and the seed values of the chaotic random phase masks. Optical implementation of the technique has been proposed. The computer simulations are presented to verify the validity of the proposed technique. 相似文献
997.
On the basis of the electromagnetic field mode matching theory, the coupling efficiency ratio from spatial light to Bragg fiber is analyzed, which shows that the coupling efficiency ratio is related to the radius of focused facular, the core radius of Bragg fiber and wave number of the core. By optimizing the value of such parameters appropriately, the Bragg fiber coupling efficiency ratio can be improved. It is also important for the analysis of the coupling efficiency of Bragg fiber, which can be applied to the free optical communication system and laser radar system. 相似文献
998.
This paper discloses results of measuring the effective radiating area (AER) and the beam non-uniformity ratio (RBN) for US transducers at 5.0 MHz. Measurements were carried out at Laboratory of Ultrasound of the Brazilian National Institute of Metrology, Standardization, and Industrial Quality. As reliability proof of system’s adequacy, uncertainties were assessed. The calculation protocol was developed based on standard IEC 61689:2007. Type A uncertainty was estimated after four repetitions of the full procedure for the determination of AER and RBN, and Type B uncertainty was estimated from the mathematical model for both calculations, obtained from IEC 61689:2007 and the guide to the expression of uncertainty in measurement. The procedure presented herein represents the state of the art regarding metrology for testing therapeutic ultrasound devices, and its application results in fundamental aspects to support their evaluation regarding quality assurance, for instance, for a certification process due safety and performance. 相似文献
999.
有源相控阵雷达系统技术参数测试 总被引:1,自引:1,他引:0
有源相控阵雷达采用分布式的发射机和接收机,雷达发射系统的辐射功率和接收系统的灵敏度等指标无法直接测量.通过测量有源相控阵雷达中雷达辐射功率与发射天线增益积和接收天线增益与系统噪声温度比来反映雷达系统指标是合理的,并给出了相应的测量方法. 相似文献
1000.