The non-linear redshift-space power spectrum of galaxies

We study the power spectrum of galaxies in redshift space, with third-order perturbation theory to include corrections that are absent in linear theory. We assume a local bias for the galaxies: i.e., the galaxy density is sampled from some local function of the underlying mass distribution. We find that the effect of the non-linear bias in real space is to introduce two new features: first, there is a contribution to the power which is constant with wavenumber, whose nature we reveal as essentially a shot-noise term. In principle this contribution can mask the primordial power spectrum, and could limit the accuracy with which the latter might be measured on very large scales. Secondly, the effect of second- and third-order bias is to modify the effective bias (defined as the square root of the ratio of galaxy power spectrum to matter power spectrum). The effective bias is almost scale-independent over a wide range of scales. These general conclusions also hold in redshift space. In addition, we have investigated the distortion of the power spectrum by peculiar velocities, which may be used to constrain the density of the Universe. We look at the quadrupole-to-monopole ratio, and find that higher order terms can mimic linear theory bias, but the bias implied is neither the linear bias, nor the effective bias referred to above. We test the theory with biased N -body simulations, and find excellent agreement in both real and redshift space, providing the local biasing is applied on a scale whose fractional rms density fluctuations are < 0.5.     

An excursion set model for the distribution of dark matter and dark matter haloes

A model of the gravitationally evolved dark matter distribution, in the Eulerian space, is developed. It is a simple extension of the excursion set model that is commonly used to estimate the mass function of collapsed dark matter haloes. In addition to describing the evolution of the Eulerian space distribution of the haloes, the model allows one to describe the evolution of the dark matter itself. It can also be used to describe density profiles, on scales larger than the virial radius of these haloes, and to quantify the way in which matter flows in and out of Eulerian cells. When the initial Lagrangian space distribution is white noise Gaussian, the model suggests that the Inverse Gaussian distribution should provide a reasonably good approximation to the evolved Eulerian density field, in agreement with numerical simulations. Application of this model to clustering from more general Gaussian initial conditions is discussed at the end.     

Testing the nonsysmmetric gravitational theory with rotation curves of galaxies

We use the rotation curves of 13 galaxies to test the nonsymmetric gravitaional theory (NGT). If we follow Moffat's assumption of a constant mass-to-light for all galaxies then we shall find that the two supposedly universal constants r₀, L₀ to show a large scatter. By regarding the mass-to-light ratio as a free parameter for each galaxy, and adjusting the values of r₀, L₀, we find that NGT can well account for the observed rotation curves. Further, the mass-to-light ratios so found show the well-known trend along the Hubble morphological sequence.     

Study on the fractal character of magnetic anomaly fields and the delineation of tectonic elements in the South China Sea

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用等效球Mie理论计算冰云光学特性的一种新方法

对由六角形冰晶粒子组成的冰云的１４种冰晶尺度分布,分别用等效球Ｍｉｅ理论和射线光学理论计算了它们在从可见光到近红外谱区的１７个波长上的散射特性参量。并利用由等效球Ｍｉｅ理论获得的散射参数及冰晶尺度分布特征参量ｒｅ（有效半径）建立了冰云光学特性的参数化公式。这些参数化公式的最大相对误差小于５％。     

“THE END OF MODERN HISTORY”?*

ABSTRACT. The first half of the twentieth century marked both an end to confidence in human control of the earth and a prelude to the contemporary era of intense environmental concern after 1950. This conspectus of the environmental history/historical geography of the transitional years between 1900 and 1950 focuses on rising concerns over resource supplies and exploitation, particularly land settlement, timber supplies, soil erosion, and river-basin control. Conservation and the pervasiveness of ecological thinking and analogy form a strong underlying theme.     

河南省黄河中游水土流失区林业重点治理工程可行性研究

从项目建设的必要性和紧迫性、建设内容、效益分析等方面论证了项目的可行性。项目规划营造林３８．９万ｈｍ２,总投资１２．７７亿元。经测算,项目实施后,生态、社会、经济效益分别为４４．１７,１８．９５,１０３．７５亿元,综合效益达１６６．８７亿元,而且使项目区的水土流失基本得到控制,生态环境得到根本改善,抗御自然灾害的能力提高     

山区资源开发的互补转换理论

通过从结构与功能上对山区资源进行重新分类及相对优劣势分析,提出了合理开发山区资源的“山区资源开发互补转换理论”.     

阿尔卑斯山区的危险区区划

通过介绍荒溪治理林业工程体系的基本原理,论述了阿尔卑斯山区危险区区划的重要性、产生背景、现状、原理和方法,并对其区划存在的问题和局限性进行了系统分析,以期为我国开展山地自然灾害防治工作提供借鉴资料．