频域正则求逆小波域维纳滤波图像复原

采用频域正则化求逆和小波域维纳滤波去噪的方法对已知线性降晰模型的含噪图像进行图像复原。实验结果表明,本文算法的复原效果明显优于频域维纳滤波复原和小波域正则反卷积复原。     

生物组织成像中用反相位脉冲技术提高二次谐波信噪比的研究

本文基于有限振幅声波在介质中的非线性传播理论,分析了反相位脉冲技术对生物组织中二次谐波增强的原理.实验中利用反相位脉冲激发超声换能器,对生物组织中传播的非线性信号相加分析.结果表明反相位脉冲技术可有效抑制基波及奇次谐波信号,而可增强偶次谐波信号6dB.与滤波器滤波法相比,反相位脉冲技术在抑制基波信号的同时,可有效地提高二次谐波的信噪比,因而在生物组织的二次谐波成像中具有广阔的应用前景.     

Estimation of surface snow properties using combined millimeter-wave backscatter and near-infrared reflectance measurements

Knowledge of surficial snow properties such as grain size, surface roughness, and free-water content provides clues to the metamorphic state of snow on the ground, which in turn yields information on weathering processes and climatic activity. Remote sensing techniques using combined concurrent measurements of near-infrared passive reflectance and millimeter-wave radar backscatter show promise in estimating the above snow parameters. Near-infrared reflectance is strongly dependent on snow grain size and free-water content, while millimeter-wave backscatter is primarily dependent on free-water content and, to some extent, on the surface roughness. A neural-network based inversion algorithm has been developed that optimally combines near-infrared and millimeter-wave measurements for accurate estimation of the relevant snow properties. The algorithm uses reflectances at wavelengths of 1160 nm, 1260 nm and 1360 nm, as well as co-polarized and cross-polarized backscatter at a frequency of 95 GHz. The inversion algorithm has been tested using simulated data, and is seen to perform well under noise-free conditions. Under noise-added conditions, a signal-to-noise ratio of 32 dB or greater ensures acceptable errors in snow parameter estimation.     

Preparation and performance of polysulfone-sulfonated poly(ether ether ketone) blend ultrafiltration membranes. Part I

Ultrafiltration membranes were prepared from blends with polysulfone (PSf) and sulfonated poly(ether ether ketone) (SPEEK) by phase inversion technique. The blend membranes were prepared with polymer composition from 0 to15 wt%. Sulfonated poly(ether ether ketone) was used to improve the performance and permeability of blended membranes. The effects of polymer composition on compaction, pure water flux, water content, and membrane hydraulic resistance were studied. The membranes were also subjected to the determination of pore statistics and molecular weight cut-off (MWCO) determination studies by using different molecular weight of proteins. The porosity, pore size of the membranes increased with increasing concentrations of SPEEK in the casting solution. Similarly, the MWCOs of the blend membranes ranged from 20 to 45 kDa, depending on the various polymer blend compositions. The pure water flux of the PSf/SPEEK blend membranes increases from 16.7 to 61.5 l m⁻² h, when the concentration of SPEEK increased from 0 to 15 wt%. Scanning electron microscope (SEM) results qualitative evidence for the trends observed for the pore statistics and MWCO studies.     

调谐耦合场作用下的无反转光放大

 讨论了调谐耦合场作用下的Λ型三能级系统中的无反转光放大（AWI）现象,调谐耦合场同时激励两个基态精细结构能级与激发态能级之间的跃迁,使系统同时呈现电磁诱导透明（EIT）和自发诱导相干凹陷两种特性,而且当调节这个耦合场的频率失谐量在某一特定范围时,系统会在EIT信号上叠加出现AWI现象。研究结果表明：该系统中EIT和自发诱导相干凹陷之间存在能量转移现象,当EIT上出现AWI现象时,虽然激发态能级与基态能级之间没有出现粒子数反转,但是两个基态精细结构能级之间出现了粒子数反转。     

A new way to evaluate the Probability and Fresnel integrals

In this article, we show how Laplace Transform may be used to evaluate variety of nontrivial improper integrals, including Probability and Fresnel integrals. The algorithm we have developed here to evaluate Probability, Fresnel and other similar integrals seems to be new. This method transforms the evaluation of certain improper integrals into evaluation of improper integrals of the corresponding Laplace transform, which in many cases are much easier.     

Thermodynamic Differentiation of the Two Sides of Azabuckybowl through Complexation with Square Planar Platinum(II)

The precise control of the two faces, concave/convex faces, is an attractive challenge to realizing novel dynamic molecular systems. Herein, we report the synthesis, X-ray crystal structure, and bowl-to-bowl inversion behavior of a platinum complex with azabuckybowl as a monodentate ligand. X-ray crystallography revealed that the azabuckybowl is orthogonally coordinated to the plane containing the Pt center and other ligands. One and two-dimensional NMR studies have also confirmed that this complex was observed as mixtures of two isomers, although the isomeric ratio was highly biased. Theoretical calculations indicate that the difference in thermodynamic stability of these isomers is due to the direction of the concave/convex face of an azabuckybowl ligand.     

利用时域波形快速反演海底单参数的方法

海底单参数反演由于反演维数少, 较之多维反演具有实施简单快捷的优点. 首先定义小掠射角下反射损失随掠射角变化率F_dB为单个参数描述海底性质, 构建单参数反演模型; 其次, 从简正波与射线理论出发, 对时域脉冲波形与海底反射性质之间的关系进行了推导, 并讨论衰减机制; 最后, 基于该关系设计出利用最小二乘法对时域波形进行反演的方法. 对北黄海实验数据进行了实际反演, 通过海底采样验证反演结果对海底性质估计的正确性, 同时基于反演结果的传播损失预报值与实测值符合良好. 该方法实施仅需要单个水听器, 待测物理量少, 所获结果较为可靠, 且能满足大多数应用的需要. 关键词： 单参数 地声反演 浅海 海底反射损失     

$(f,g)$-反演的一些应用

我们给出了马欣荣的关于$(f, g)$-反演的三种应用. 在$(f, g)$-演中通过取具体的函数和序列, 我们推出了一些关于超几何级数与调和数的恒等式. 然后我们给出了一些关于$q$-超几何项的反演关系. 最后, 我们将$(f, g)$-反演和$q$-微分算子结合, 得到了一些$q$-级数恒等式.     

Ramanujan's Master Theorem for Hermitian Symmetric Spaces

In this paper we generalize Ramanujan's Master Theorem to the context of a Siegel domain of Type II, which is the Hermitian symmetric space of a real non-compact semisimple Lie group of finite center. That is, the spherical transform of a spherical series can be expressed in terms of the coefficients of this series.