城市扩张的空间模式研究——以杭州市为例

以杭州市中心城区的多时相TM/ETM+遥感影像为数据源,采用建设用地扩张强度、空间自相关方法等,分析了杭州市1991~2010年间城市扩张的时空特征,并探讨其扩张的空间模式及其演化.结果表明：（1）杭州市城区快速扩展,各街道 乡镇扩张程度存在明显差异;（2）杭州城市扩张的“热点”方位变化大致为：城北-城西-多方位-城东,其变迁规律与杭州城市扩张模式的总体变化规律一致;（3）杭州市城市扩张的空间模式主要有边缘式、填充式、自发式和线性轴状,且随城市演化过程总体遵循以下轨迹：首先,主城表现为边缘式为主、填充式为辅的扩张;其次,外围自发式的扩张形成了副城;接下来主副城都表现为从填充为主、边缘为辅的扩张转变为边缘为主、填充为辅的扩张;而线性轴状扩张是沿交通线发展并贯穿整个城市空间的演化过程.     

带有两个重夸克的重子谱计算中几个困难问题的研究

由两个重夸克和一个轻夸克组成的重子可以看作是一个两体系统.它的两个重夸克组成一个玻色型的双夸克团.利用B–S方程导出了它的轻夸克和重的双夸克之间的等效相互作用势.在利用这种势计算重子质量的过程中,发现有几个困难问题需要深入探讨.它们是:(1)算符排序,(2)由非相对论展开带来的误差,(3)自旋–自旋耦合,(4)在标量双夸克组成的重子态和矢量双夸克组成的重子态之间的混合.本文详细地讨论并适当地处理了这些问题.     

Theoretical Calculations of Thermal Shifts of Ground-StateZero-Field-Splitting for Ruby

By taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d³ electronic configuration, the thermal shifts (TS) of the ground-state zero-field-splitting (GSZFS) due to EPI for ruby have microscopic-theoretically been calculated; the contribution to TS of GSZFS from thermal expansion has also been calculated. The results are in very good agreement with experiments. It is found that the contributions from the first-order perturbation of the second-order term in EPI Hamiltonian are dominant in the Raman term and optical-branch term for TS of GSZFS; the different between the TS due to EPI of t₂^{3 4}A₂±(1/2) e₂ (G₂) level and the TS due to EPI of t₂^{3 4}A₂±(3/2) e₂ (G₁) level gives rise to the TS due to EPI of GSZFS, which is very small in comparison with the TS due to EPI of G₂ or G₁ level. Among various terms in TS of GSZFS, Raman term is the largest one and the signs of the Raman term and optical-branch term are opposite to the sign of the thermal-expansion term; the optical-branch term plays an important role in TS of GSZFS and increases rapidly with temperature; all various contributions to TS of GSZFS have to be taken into account, since the subtle balance among them determines the total result. The comparison between the features of TS of GSZFS and those of TS of R₁ and R₂ lines has been made. For TS of GSZFS, the contribution from thermal expansion is especially important; the neighbor-level term is insignificant.     

On the analyticity of the pressure in the hierarchical dipole gas

The convergence of the Mayer expansion is proved by estimating directly the convergence radius.     

Defect of the five-thirds law using the Wiener-Hermite expansion

Application of the refined Wiener-Hermite expansion with moderate to high Reynolds numbers Re to homogeneous, isotropic turbulence is presented. The results show a defect to Kolmogorov's five-thirds law, increase in the absolute value of the exponent comparable with many theoretical predictions. Midrange spectra up to fluctuation Reynolds numbers of 10⁸ show little, if any, dependence of the defect on Re, as long as the initial spectra do not deviate too far from their equilibrium states. The renormalization scheme has also been proven to have no effect on the final shape of the spectrum.     

Intelligent reversible watermarking technique in medical images using GA and PSO

The advances in recording, editing, and broadcasting multimedia contents in digital form motivate to protect these digital contents from illegal use, such as duplication, manipulation, and redistribution. However, watermarking algorithms are designed to satisfy requirements of applications, as different applications have different concerns. We intend to design a watermarking algorithm for applications which require high embedding capacity and imperceptibility, to maintain the integrity of the host signal as well as embedded information. Reversible watermarking is a promising technique which satisfies our requirements. In this paper, we concentrate on improving the watermark capacity and reducing the perceptual degradation of an image. We investigated the Luo's [1] additive interpolation-error expansion algorithm and enhanced it by incorporating with two intelligent techniques: genetic algorithm (GA), and particle swarm optimization (PSO). Genetic algorithm is applied to exploit the correlation of image pixel values to obtain better estimation of neighboring pixel values, which results in optimal balance between information storage capacity and imperceptibility. Particle swarm optimization (intelligent technique) is also applied for the same purpose. Experimental results show that PSO and GA nearly give the same results, but GA outperforms the PSO. Experimental results also reveal that the proposed strategy outperforms the state of art works in terms of perceptual quality and watermarking payload.     

Two-pion interferometry for a partially coherent evolution source

We give the formulas of two-pion Hanbury-Brown-Twiss (HBT) correlation function for a partially coherent evolution pion-emitting source, using quantum probability amplitudes in a path-integral formalism. The multiple scattering of the particles in the source is taken into consideration based on Glauber scattering theory. Two-pion interferometry with effects of the multiple scattering and source collective expansion is examined for a partially coherent source of hadronic gas with a finite baryon density and evolving hydrodynamically. We do not find observable effect of either the multiple scattering or the source collective expansion on HBT chaotic parameter.     

Limit theorems in financial market models

Invariance principle states that a scaled simple random walk converges to the standard Brownian motion.In this article, we present a discrete time stochastic process, which reflects a microstructure of market dynamics, and prove a convergence to a scaling limit process with a drift term and a jump term. These terms are derived from a macroscopic condition on volumes traded in some time intervals. The mathematical tools for obtaining our results are Dobrushin-Hryniv theory and the method of cluster expansion developed in mathematical studies of statistical mechanics.     

为2007年亚奥赛物理实验命题的体会

笔者被聘为2007年亚奥赛物理实验命题,经过半年多的努力终于将科研成果——激光测温合理地转换为一个奥赛实验试题——干涉法测量玻璃热膨胀系数和折射率温度系数,本文主要介绍了命题过程及体会.     

Expansion,injection and micro-explosion phenomena during the full combustion cycle of mixed fuel droplets of ethyl alcohol and biodiesel

In this study, mixed fuel droplets of ethyl alcohol and biodiesel with different volumes or ratios were prepared and the related expansion, injection and micro-explosion phenomena were investigated. During the tests, a mixed-fuel droplet was hung on a high-temperature-resistant Cr-Ni wire, which was transported to the preheating piston for heating and then was ignited automatically. Micro-needles and an infusion set also were employed to prepare mixed droplets with identical ratios but different volumes. Using a single-lens-reflex (SLR) camera, colour videos that captured the combustion process of the mixed droplets were taken and were processed into colour images using Adobe Premiere Pro CC. The colour image series were analysed to determine the ignition delay time, the burnout time and the flame characteristics during combustion of mixed droplets with different ratios. Instantaneous grey images were obtained by means of high-speed photography during combustion of the mixed droplets with different volumes and different ratios, and of droplets of E40 (in which the volume ratio of ethyl alcohol was 40%). Using Image pro plus and Origin software, the variation of normalised mean droplet diameter with time over the whole combustion cycle was calculated and the underlying reasons for various combustion phenomena were analysed.