异常气温作用于水稻一维能量模型的数值分析

应用动力学方程建立四川内江市水稻的生长模型,通过FORCAL和MATLAB对方程参数拟合,并进行数值分析和定性分析,为水稻产量预报和气温对水稻生物量的影响评估提供科学依据。在传统的一维能量模型基础上,将水稻对外界能量的摄取能力与水稻生长季中的气温变化规律联系起来,得到水稻的生长曲线x（t）,并通过相平面轨迹得到x—T曲线,定性分析水稻的临界气温和最快生长率出现时间。通过低温对水稻分蘖期和高温对生殖生长期影响的比较,得出如下结论：水稻后期受高温影响比前期受低温影响严重。     

开放式空间基础信息平台的发展特征与技术内涵

基于测绘和地理信息产业发展背景,针对日益增长的数据融合、实时共享、深度处理和个性化的需求,对数字城市中测绘服务特征进行分析,重点介绍符合云计算模型的开放式计算环境、多路径数据更新、多源数据一体化集成、全尺度城市编码、自适应空间数据处理和动态在线制图等理论、方法与关键技术。在此基础上,研制开发了开放式空间基础信息平台,并成功应用于数字深圳的建设中。     

侧视雷达影像距离-共面模型严密定位

本文对现有侧视雷达遥感影像的几何构像模型在摄影测量应用中的不足进行了理论分析,以外方位元素作为定向参数,依次建立了像点坐标显函数形式的距离-共面(R-Cp)方程、地心直角坐标系中星载侧视雷达影像的距离-共面方程、以及星载侧视雷达遥感影像的严密定位模型,并进行了稀少控制点条件的星载TerraSAR-X影像定位试验。理论和试验表明,本文所建立的R-Cp严密定位模型,使得雷达影像像点量测坐标作为摄影测量观测值的属性得到体现,容易吸收和利用光学遥感影像基于共线方程模型发展起来的成熟的数字摄影测量数据处理方法,有利于提高雷达遥感影像摄影测量数据处理的严密性、稳定性、可靠性及数据处理效率。     

地面降水诊断方程对降水过程的定量诊断

降水, 尤其是强降水 (暴雨), 对国家经济发展、 社会建设以及人民生活影响巨大, 然而由于同降水相关的物理过程非常复杂, 因此, 对降水的研究与预测十分困难。过去有关降水的研究大多关注水汽及水汽辐合 (输送) 的影响, 对与降水有关的水汽收支研究较多。Gao et al.(2005a) 率先将大气中水汽和云中水凝物 (云水、 雨水、 云冰、 雪及霰等) 的变化方程结合起来, 得到一个地面降水诊断方程, 从而可以将与降水有关的大气中水汽和云的演变过程在同一框架下定量地分析研究。本文利用一套21天长度的热带云分辨尺度模拟资料, 通过计算地面降水诊断方程中的局地水汽变化、 水汽辐合辐散率、 地面蒸发率以及云的变化率等各项, 分析了这些物理过程对降水的贡献, 指出局地水汽和云的变化率、 水汽辐合率, 地面蒸发率等均对地面降水有重要贡献。区域平均资料分析表明, 若水汽辐合与局地大气变干共存, 则产生强降水; 若存在水汽辐合但局地大气增湿或者存在水汽辐散但局地大气变干, 则引起中等强度降水; 若水汽辐散与局地大气增湿共存, 则造成弱降水。将降水划分成对流和层状降水进行分析发现, 对流降水率一般大于层状降水率, 水汽辐合是对流降水最主要的水汽源, 而局地大气变干则是层状降水最主要的水汽源。区域平均局地大气变干主要发生在降水性层状云区, 而最强的局地大气增湿则发生在对流云区和晴空区; 最强的局地云的消散发生在层状云区, 而最强的局地云的发展发生在对流云区。     

mKdV Equation for Solitary Rossby Waves with Linear Topography Effect in Barotropic Fluids

The modify Korteweg-de Vries (mKdV) equations, governing the evolution of the amplitude of solitary Rossby waves, are derived from quasi-geostrophic vorticity equation by using the perturbation method. The result manifests that the linear topography effect with the change of latitude can induce solitary Rossby wave.     

Joint PDF Modelling of Turbulent Flow and Dispersion in an Urban Street Canyon

The joint probability density function (PDF) of turbulent velocity and concentration of a passive scalar in an urban street canyon is computed using a newly developed particle-in-cell Monte Carlo method. Compared to moment closures, the PDF methodology provides the full one-point one-time PDF of the underlying fields containing all higher moments and correlations. The small-scale mixing of the scalar released from a concentrated source at the street level is modelled by the interaction by exchange with the conditional mean (IECM) model, with a micro-mixing time scale designed for geometrically complex settings. The boundary layer along no-slip walls (building sides and tops) is fully resolved using an elliptic relaxation technique, which captures the high anisotropy and inhomogeneity of the Reynolds stress tensor in these regions. A less computationally intensive technique based on wall functions to represent the boundary layers and its effect on the solution are also explored. The calculated statistics are compared to experimental data and large-eddy simulation. The present work can be considered as the first example of computation of the full joint PDF of velocity and a transported passive scalar in an urban setting. The methodology proves successful in providing high level statistical information on the turbulence and pollutant concentration fields in complex urban scenarios.     

A new mixing equation for bed material composition in bed form dominant conditions

Vertical mixing beneath the bed surface and its effect on sediment composition has long been underestimated. This paper proposes a mixing equation to illustrate the temporal and spatial variations of bed material composition for bed form dominant rivers. A continuous mass conservation equation for elevation-specific nonuniform bed material composition is initially presented. A vertical mixing equation is finally derived as a diffusion-type partial differential equation with a source term charact...     

Chromothermal oscillations and collapse of strange stars to black holes: astrophysical implications

We study the effects of temperature on strange stars. It is found that the maximum mass of the star decreases with the increase of temperature, as at high temperatures the equations of state become softer. Moreover, if the temperature of a strange star increases, keeping its baryon number fixed, its gravitational mass increases and its radius decreases. This leads to a limiting temperature, where it turns into a black hole. These features are the result of a combined effect of the change of gluon mass and the quark distribution with temperature. We report on a new type of radial oscillation of strange stars, driven by what we call 'chromothermal' instability. We also discuss the relevance of our findings in the astrophysics of core collapse supernovae and gamma-ray bursts.     

准饱和多孔介质中圈闭气体对渗透系数的影响

含圈闭气体的地下水流称为准饱和流,准饱和流中的圈闭气体对含水层渗透系数有重大影响。通过柱试验开展了粉砂、细砂、中砂和粗砂4种介质圈闭气体饱和度与准饱和渗透系数关系的研究。结果表明:圈闭气体饱和度明显受介质的粒径影响,在细粒介质中圈闭气体饱和度明显较大;4种介质圈闭气体饱和度在0~15%范围内,准饱和渗透系数与完全饱和相比减少了32.82%~56.38%,且准饱和渗透系数与圈闭气体饱和度之间可表达为一个负线性相关的经验公式;该公式与Faybishenko公式等效,但形式简单,参数较少,使用方便;准饱和渗透系数的变化规律可概化为圈闭气体占据了原有的有效孔隙,造成原有效孔隙度减少,从而使渗透系数减小。利用该理论,Kozeny-Carman方程能较准确地描述准饱和渗透系数的变化规律,而基于哈根-泊肃叶方程的渗透系数公式则存在较大误差,不适用于描述准饱和渗透系数;试验结果证明了室内测定饱和渗透系数时排除圈闭气体的必要性。