1PN近似下脉冲星导航的观测方程及精度分析

完整推导1PN度规形式下脉冲到达时间方程与脉冲星导航的观测方程。分析导航观测中的相对论影响;给出观测方程的级数展开形式,在此基础上分析脉冲星历表参数对观测时间的影响;讨论行星星历误差对观测时间的影响;推导星体扁率引起的测量时延表达式,分析不同星体扁率引起的时延量级。     

临近空间伪卫星区域独立组网布局研究

当前临近空间技术是人们研究的热点,在临近空间建立伪卫星区域独立组网系统可以满足地面导航定位的需求。本文分析了卫星精度因子的计算方法,提出基于经验的伪卫星区域优化布局搜索算法,找到一种最优的临近空间伪卫星区域独立组网布局,利用MATLAB进行仿真。与其他几种相同高度的伪卫星布局做仿真比较,结果显示,本文提出的伪卫星布局的DOP值较小,并给出了一些重要的结论。     

基于SCS和USLE的程海总磷总氮参照状态推断

将流域入湖的氮磷负荷分为点源和非点源两部分,基于SCS模型和USLE模型,分别计算流域入湖的溶解态和颗粒态非点源负荷,根据工业、城镇生活及规模养殖废水排放,计算了流域入湖的点源负荷。通过计算的入湖负荷和现有的湖泊氮磷浓度数据,建立了湖泊氮磷质量守恒模型。根据计算的逐年入湖氮磷负荷和建立的湖泊氮磷质量守恒模型,逆推逐年的湖泊氮磷浓度,确定湖泊氮磷参照状态。应用建立的模型推断程海的TP、TN参照状态分别为0.014 mg/L和0.247 mg/L。构建的湖泊氮磷参照状态推断模型,所需资料少,概念清晰,在资料缺乏的其他湖泊流域具有推广应用价值。     

A Roche model for uniformly rotating rings

A Roche model for describing uniformly rotating rings is presented, and the results are compared with the numerical solutions to the full problem for polytropic rings. In the thin ring limit, the surfaces of constant pressure including the surface of the ring itself are given in analytical terms, even in the mass-shedding case.     

Relativistic mean-field theory equation of state of neutron star matter and a Maxwellian phase transition to strange quark matter

The equation of state of neutron star matter is examined in terms of the relativistic mean-field theory, including a scalar-isovector δ-meson effective field. The constants of the theory are determined numerically so that the empirically known characteristics of symmetric nuclear matter are reproduced at the saturation density. The thermodynamic characteristics of both asymmetric nucleonic matter and β-equilibrium hadron-electron npe-plasmas are studied. Assuming that the transition to strange quark matter is an ordinary first-order phase transition described by Maxwell's rule, a detailed study is made of the variations in the parameters of the phase transition owing to the presence of a δ-meson field. The quark phase is described using an improved version of the bag model, in which interactions between quarks are accounted for in a one-gluon exchange approximation. The characteristics of the phase transition are determined for various values of the bag parameter within the range B ∈ [60,120]MeV/fm³ and it is shown that including a δ-meson field leads to a reduction in the phase transition pressure P ₀ and in the concentrations n _N and n _Q at the phase transition point. Translated from Astrofizika, Vol. 52, No. 1, pp. 147–164 (February 2009).     

Reconstruction of Mediterranean sea level fields for the period 1945–2000

The distribution of sea level in the Mediterranean Sea is recovered for the period 1945–2000 by using a reduced space optimal interpolation analysis. The method involves estimating empirical orthogonal functions from satellite altimeter data spanning the period 1993–2005 that are then combined with tide gauge data to recover sea level fields over the period 1945–2000. The reconstruction technique is discussed and its robustness is checked through different tests. For the altimetric period (1993–2000) the prediction skill is quantified over the whole domain by comparing the reconstructed fields with satellite altimeter observations. For past times the skill can only be tested locally, by validating the reconstruction against independent tide gauge records. The reconstructed distribution of sea level trends for the period 1945–2000 shows a positive peak in the Ionian Sea (up to 1.5 mm yr^− 1) and a negative peak of − 0.5 mm yr^− 1 in a small area to the south-east of Crete. Positive trends are found nearly everywhere, being larger in the western Mediterranean (between 0.5 and 1 mm yr^− 1) than in the eastern Mediterranean (between 0 and 0.5 mm yr^− 1). The estimated rate of mean sea level rise for the period 1945–2000 is 0.7 ± 0.2 mm yr^− 1, i.e. about a half of the rate estimated for global mean sea level. These overall results do not appear to be very sensitive to the distribution of tide gauges. The poorest results are obtained in open-sea regions with intense mesoscale variability not correlated with any tide gauge station, such as the Algerian Basin.     

A semi-analytical solution for the three-dimensional advection–diffusion equation considering non-local turbulence closure

Atmospheric air pollution turbulent fluxes can be assumed to be proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection–diffusion equation. Moreover, large eddies are able to mix scalar quantities in a manner that is counter to the local gradient. In this work we present a semi-analytical solution for the three-dimensional steady-state advection–diffusion equation, considering non-local turbulence closure using the Generalized Integral Advection Diffusion Multilayer Technique (GIADMT). We report some examples of applications of the new solution for two different datasets and for a water tank experiment.     

SM植物胶冲洗液的流变性分析与探讨

文章介绍了冲洗液的几种常见流变模式,并对这几种流变模式的流变曲线及其特点作了简单分析总结。通过多次室内试验测得SM植物胶冲洗液的各项流变参数,并根据这些参数作出它的流变曲线,通过与传统流变曲线作对比总结出SM植物胶冲洗液的流变方程表达模式为幂律模式;结合实践中常见的一些现象并通过两组不同的特征试验证明SM植物胶冲洗液为粘弹性流体而非传统观念上的假塑性流体;与传统泥浆对比试验证明SM植物胶冲洗液的流变性能优越;文章结尾对SM植物胶冲洗液的流变参数作了简单的分析讨论。     

评估集合卡曼滤波反演土壤湿度廓线的性能

集合卡曼滤波由于易于使用而被广泛地应用到陆面数据同化研究中,它是建立在模型为线性、误差为正态分布的假设上,而实际土壤湿度方程是高度非线性的,并且当土壤过干或过湿时会发生样本偏斜.为了全面评估它在同化表层土壤湿度观测来反演土壤湿度廓线的性能,特引入不需要上述假设的采样重要性重采样粒子滤波,比较非线性和偏斜性对同化算法的影响.结果显示:不管是小样本还是大样本,集合卡曼滤波都能快速、准确地逼近样本均值,而粒子滤波只有在大样本时才能缓慢地趋近;此外,集合卡曼滤波的粒子边缘概率密度及其偏度和峰度与粒子滤波完全不同,前者粒子虽不完全满足正态分布,但始终为单峰状态,而后者粒子随同化推进经历了单峰到双峰再到单峰的变化.