毫米波测云雷达的特点及其研究现状与展望

云在大气的能量分配、辐射传输,尤其是水循环系统中有不可忽视的作用。云探测对云物理、人工影响天气、气候变化和航空航天等领域有重要意义,是大气科学研究的热点之一。尽管目前已经发展了很多种遥感设备对云进行观测(如激光雷达、卫星、云幂仪等),但这些设备无法得到高时空分辨率的云水平和垂直结构,而毫米波雷达是云三维精细结构探测的重要工具。由于毫米波雷达具有更接近小粒子尺度的短波长,因此更适合用来探测弱云,同时毫米波雷达也存在衰减严重的缺点。介绍了毫米波雷达的特点以及其探测小粒子的优势;对比分析了其与新一代多普勒天气雷达、晴空风廓线雷达的差异,得出：毫米波雷达具有高时空分辨率,能够更精确地反映云的垂直和水平结构,比普通天气雷达更适合监测云的变化。概括了国内外毫米波测云雷达的发展现状以及在云物理研究方面的情况,并展望了国内毫米波雷达未来研究的方向。     

Structure of CB 26 protoplanetary disk derived from millimeter dust continuum maps

Observations of the circumstellar disk in the Bok globule CB 26 at 110, 230, and 270 GHz are presented together with the results of the simulations and estimates of the disk parameters. These observations were obtained using the SMA, IRAM Plateau de Bure, and OVRO interferometers. The maps have relatively high angular resolutions (0.4??-1??), making it possible to study the spatial structure of the gas-dust disk. The disk parameters are reconstructed via a quantitative comparison of observational and theoretical intensity maps. The disk model used to construct the theoretical maps is based on the assumption of hydrostatic and radiative equilibrium in the vertical direction, while the radial surface-density profile is described phenomenologically. The system of equations for the transfer of the infrared and ultraviolet radiation is solved in the vertical direction, in order to compute the thermal structure of the disk. The disk best-fit parameters are derived for the each map and all the maps simultaneously, using a conjugate gradient method. The degrees of degeneracy of the parameters describing the thermal structure and density distribution of the disk are analyzed in detail. All three maps indicate the presence of an inner dust-free region with a diameter of approximately 35 AU, in agreement with the conclusions of other studies. The inclination of the disk is 78°, which is smaller than the value adopted in our earlier study of rotating molecular outflows from CB 26. The model does not provide any evidence for the growth of dust particles above a _max ?? 0.02 cm.     

Modeling of protostellar clouds and their observational properties

A physical model and two-dimensional numerical method for computing the evolution and spectra of protostellar clouds are described. The physical model is based on a system of magneto-gas-dynamical equations, including ohmic and ambipolar diffusion, and a scheme for calculating the thermal and ionization structure of a cloud. The dust and gas temperatures are determined when calculating the thermal structure of the cloud. The results of computing the dynamical and thermal structure of the cloud are used to model the transfer of continuum and molecular-line radiation in the cloud. Results are presented for clouds in hydrostatic and thermal equilibrium. The evolution of a rotating magnetic protostellar cloud that is compressed starting from a quasi-static equilibrium state is also considered. Spectral maps for optically thick lines of linear molecules are analyzed. The influence of the magnetic field and rotation can lead to a redistribution of angular momentum in the cloud and the formation of a characteristic rotational-velocity structure. As a result, the distribution of the velocity centroid of the molecular lines can acquire an hourglass shape. It is planned in future to use the developed program package and a model for the chemical evolution of clouds to interpret and model in detail observed starless and protostellar cores.     

The dynamics of correlations in open-star cluster models

Two-time and two-point (two-particle) correlations are calculated for several parameters of the stellar motions, the densities, and the phase densities of model open clusters, in the vicinities of the cluster stars. The correlation times and correlation radii are determined in spaces of the parameters considered. The distributions of the two-point correlations for the distances between stars in the coordinate and velocity spaces of the stars are calculated. The local maxima of these distributions are used to determine the parameters of density waves, the potential, and the phase density in the model clusters. Analysis of the fine structure of regions of concentration in the two-point correlations in space of mutual distances between stars suggests the formation of polarization clouds near a number of such distances between stars. The distributions of the phase-density correlations are calculated, and the dynamics of these distributions analyzed. The dispersions of these distributions depend strongly on the presence of broad ??wings?? in the distributions (i.e., of strong correlations in the system). These dispersions are considered as a measure of the degree of correlation of phase-density fluctuations in model clusters. A growth in the correlations with time is observed for 50% of the cluster models considered. Flows of the phase-density correlations are investigated. A dominant correlation flow from the region of strong to the region of weak correlations is identified, leading to a flow of kinetic energy toward the cluster center. The rate at which this flow heats the model cluster core is estimated. Signs of weak turbulence are detected in the stellar motions in the model cluster cores with the highest degree of non-stationary in the regular field.     

Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10

Archival infrared Spitzer Space Telescope observations are used to study the dust component of the ISM in the irregular galaxy IC 10. The dust distribution in the galaxy is compared to the distributions of the Hα and [S II] emission, neutral gas and CO clouds, and ionizing radiation sources. The distribution of polycyclic aromatic hydrocarbons (PAHs) in the galaxy is shown to be highly non-uniform, with the fraction of these particles in total dust mass reaching 4%. On the whole, PAHs avoid bright H II regions and correlate with the atomic and molecular gas. This pattern suggests that they form in the dense interstellar gas. It is suggested that the observed metallicity dependence of the PAH abundance shows up not only globally (at the level of the entire galaxy), but also locally (at least, at the level of individual H II regions). No conclusive evidence for shock destruction of PAHs in the IC 10 galaxy has been found.     

Infrared emission and the destruction of dust in HII regions

The generation of infrared (IR) radiation and the observed IR-intensity distribution at wavelengths of 8, 24, and 100 µm in the ionized hydrogen region around a young, massive star is investigated. The evolution of the HII region is treated using a self-consistent chemical-dynamical model in which three dust populations are included—large silicate grains, small graphite grains, and polycyclic, aromatic hydrocarbons (PAHs). A radiative transfer model taking into account stochastic heating of small grains and macromolecules is used to model the IR spectral energy distribution. The computational results are compared with Spitzer and Herschel observations of the RCW 120 nebula. The contributions of collisions with gas particles and the radiation field of the star to stochastic heating of small grains are investigated. It is shown that a model with a homogeneous PAH content cannot reproduce the ring-like IR-intensity distribution at 8 µm. A model in which PAHs are destroyed by ultraviolet radiation of the star, generating region HII, provides a means to explain this intensity distribution. This model is in agreement with observations for realistic characteristic destruction times for the PAHs.     

Physical conditions in photodissociation regions from observations of carbon radio recombination lines and IR fine-structure lines of CII and OI

Observations of the C56α line—the first carbon radio recombination line in the millimeter waveband—in the directions of the Orion Bar, NGC 2024, and W3 are reported. The results are analyzed together with data for the IR fine-structure lines of CII and OI, enabling unambiguous determination of the temperature and density in the photodissociation regions separating the HII regions and parent molecular clouds.     

二氧化碳注入下岩层变形和流体运移分析:(Ⅱ)实例分析

第I部分[1]提出了一个两相流-岩层流固耦合模型,为了应用该模型对超临界二氧化碳注入过程中岩层力学响应和流体运移进行评估,采用Comsol商业程序,提出了相应的数值分析方法。给出了模型参数的确定方法,并采用室内试验数据对模型进行了验证;通过现场的温度和压力条件以及岩层的Van Genuchten参数,确定了二氧化碳的密度和黏度。基于三轴压缩试验、有效应力系数试验和渗透性试验,对力学模型及耦合关系中的参数进行了验证。最后给出一个应用实例,该岩层位于地下680⁷00 m深度,宽度为100 m,分析了不同二氧化碳注入速率下注入压力的演化规律,得到了岩层中孔隙压力、竖向应变和损伤变量的分布,并对二氧化碳的运移规律也进行了分析。研究结果为超临界二氧化碳注入过程中岩层力学响应和流体运移的评估提供了理论基础。     

Rainfall intensity characteristics at coastal and high altitude stations in Kerala

Rainfall intensities measured at a few stations in Kerala during 2001–2005 using a disdrometer were found to be in reasonable agreement with the total rainfall measured using a manual rain gauge. The temporal distributions of rainfall intensity at different places and during different months show that rainfall is of low intensity (< 10 mm/hr), 65% to 90% of the time. This could be an indication of the relative prevalence of stratiform and cumuliform clouds. Rainfall was of intensity < 5 mm/hr for more than 95% of the time in Kochi in July 2002, which was a month seriously deficient in rainfall, indicating that the deficiency was probably due to the relative absence of cumuliform clouds. Cumulative distribution graphs are also plotted and fitted with the Weibull distribution. The fit parameters do not appear to have any consistent pattern. The higher intensities also contributed significantly to total rainfall most of the time, except in Munnar (a hill station). In this analysis also, the rainfall in Kochi in July 2002 was found to have less presence of high intensities. This supports the hypothesis that the rainfall deficiency was probably caused by the absence of conditions that favoured the formation of cumuliform clouds.     

水利水电工程岩基抗剪强度参数二维分布模型构造的Copula方法

基于国内103个水利水电工程1 174组岩基抗剪强度试验数据,采用Copula函数研究岩基抗剪强度参数联合分布模型,探讨水利水电工程中岩基抗剪强度参数联合分布模型构建方法。利用最小二乘法求出岩基抗剪强度参数试验数据的相关统计参数,基于AIC准则识别出岩基抗剪强度参数边缘分布。选择4种Copula函数构造岩基抗剪强度参数二维分布模型,探讨了基于Copula函数的岩基抗剪强度参数二维分布模型的优越性。结果表明：水利水电工程岩基抗剪强度参数存在明显的统计负相关性。Copula方法能够构造具有任意边缘分布和任意相关结构的岩基抗剪强度参数联合分布模型,它为构造抗剪强度参数联合分布模型提供了一种简便的工具。已知岩基抗剪强度参数的边缘分布函数和相关系数不能唯一确定岩基抗剪强度参数的联合概率分布模型,在抗剪强度参数边缘分布函数和相关系数完全相同的前提下,不同Copula函数建立的抗剪强度参数联合概率分布模型差异显著。与常用的抗剪强度参数二维正态分布模型相比,基于Copula函数的抗剪强度参数二维分布模型具有较强的灵活性,它能更好地拟合原始观测数据。水利水电工程中惯用小值平均法确定标准值,当摩擦系数取较小值时,不同Copula函数构造的黏聚力的条件累积分布函数差异显著,这将对抗剪强度参数标准值的选取以及相应的设计方案具有明显的影响。     

The structure of the radio galaxy 3C388 at decameter wavelengths

Observations of the structure of the radio galaxy 3C338 at decameter wavelengths obtained using the URAN-1 and URAN-2 radio interferometers are presented. The structure of this object at these wavelengths differs appreciably from images obtained at higher frequencies. The most probable simple models for the radio brightness distributions at 25 and 20 MHz are determined: two extended components with sizes from 40″ to 50″ whose centers are separated by 90″–100″ in position angle about 100°, and a single compact component 9″×4″ in size, whose flux density does not exceed 10% of the total flux density of the radio galaxy.     

Application of infrared thermography for temperature distributions in fluid-saturated porous media

Infrared thermography has increasingly gained importance because of environmental and technological advancements of this method and is applied in a variety of disciplines related to non-isothermal flow. However, it has not been used so far for quantitative thermal analysis in saturated porous media. This article suggests infrared thermographic approach to obtain the entire surface temperature distribution(s) in water-saturated porous media. For this purpose, infrared thermal analysis is applied with in situ calibration for a better understanding of the heat transfer processes in porous media. Calibration is achieved with a combination of invasive sensors which are inserted into the medium and non-invasive thermal sensors in which sensors are not inserted to measure temperatures but it works through the detection of infrared radiation emitted from the surface. Thermocouples of relatively thin diameter are used to minimize the disturbance for flow. Thermocouples give the temperature values at specified positions inside the porous medium, and these values are compared with the values suggested by the infrared thermographic device at the same positions, in the calibration exercise. The calibration process was repeated for different temperatures and flow rates to get the temperature distributions of the whole material inside the system. This technique enables us to measure accurate two-dimensional temperature distributions, which is not possible by using thermocouples only. Continuous point heat sources at different flow rates and temperatures are studied experimentally. Additionally, it offers numerical simulations of the experiments utilizing a finite element-based model. A two-dimensional density and viscosity-dependent flow and transport model accounting for thermal dispersion is utilized to simulate the experimental results. Possible small heat losses from the surface are incorporated in the model according to the properties and thickness of the Plexiglass material used for the construction of the experiment tank. The numerical results agree well with the experimental observations.     

The microwave radiation of the corona above a large single sunspot in right- and left-circular polarization

Results of a study of the corona above a large sunspot in the active region NOAA 10105 with a penumbra size of ～70″ observed in September 2002 are reported. Maps of the active region and emission spectra were constructed using observational data from the NoRH, SSRT, and RATAN-600 telescopes. The sizes and brightness temperatures of the microwave emission above the sunspot are determined. SOHO/MDI and Kitt Peak magnetograms, as well as CaII K line images obtained at the Meudon Observatory, are compared. The derived characteristics are interpreted as cyclotron emission of thermal plasma, assuming a dipole structure for themagnetic field. A stable darkening at the sunspot center observed at short wavelengths and only in the ordinary emission mode was detected. A jump-like change was observed in the structure of the sunspot source in the ordinary emission mode, due to an increase in the size and spectral flux density. These results demand a fundamental correction of model concepts about cyclotron emission sources above sunspots, since they are at variance with the initial assumptions. It is suggested that, at the top of the transition region, the cyclotron emission source may be represented only by the third gyrolevel, but is observed in the extraordinary and ordinary emission modes (in contrast to the generally accepted model, which has a combination of the second and third gyrolevels). Taking into account the new observational data may allow us to refine model distributions of the main parameters of the coronal plasma above sunspots (the electron temperature and density) and information about the character of the magnetic field.     

Experimental and theoretical bond critical point properties for model electron density distributions for earth materials

Generalized X-ray scattering factor model experimental electron density distributions and bond critical point, bcp, properties generated in recent studies for the earth materials stishovite, forsterite, fayalite and cuprite with high energy single crystal synchrotron X-ray diffraction data and those generated with high resolution diffraction data for coesite and senarmonite were found to be adequate and in relatively good agreement, ~5% on average, with those calculated with quantum chemical methods with relatively robust basis sets. High resolution low energy single crystal diffraction data, recorded for the molecular sieve AlPO₄-15, were also found to yield model electron density distribution values at the bcp points for the AlO and PO bonded interactions that are in relatively good to moderately good agreement with the theoretical values, but the Laplacian values of the distribution at the points for the two bonded interactions were found to be in relatively poor agreement. In several cases, experimental bcp properties, generated with conventional low energy X-ray diffraction data for several rock forming minerals, were found overall to be in poorer agreement with the theoretical properties. The overall agreement between theoretical bcp properties generated with computational quantum methods and experimental properties generated with synchrotron high energy radiation not only provides a basis for using computational strategies for studying and modeling structures and their electron density distributions, but it also provides a basis for improving our understanding of the crystal chemistry and bonded interactions for earth materials. Theoretical bond critical point properties generated with computational quantum methods are believed to rival the accuracy of those determined experimentally. As such the calculations provide a powerful and efficient method for evaluating electron density distributions and the bonded interactions for a wide range of earth materials.Dedicated to Professor Robert F. Stewart of Carnegie Mellon University on his retirement for his brilliant and original work modeling electron density distributions.     

塔里木盆地柯坪隆起典型沉积岩类的热红外光谱特征研究

塔里木盆地西北缘柯坪隆起一些典型碎屑岩、碳酸盐岩及蒸发岩的热红外发射光谱曲线的分析表明:利用残余辐射谱带（又叫低发射率带）的中心波长位置可以确定沉积岩中的主要矿物成份，并可利用残余辐射谱带的强度判断矿物成份含量的多少。这对于利用热红外多光谱遥感技术直接找矿具有重要意义。     

岩石抗剪强度参数的理论概率分布形态研究

岩石抗剪强度参数的概率分布形态是岩石工程可靠度分析和设计的基础。在考虑完整岩石压缩强度为服从正态分布随机变量的条件下,针对Mohr-Coulomb和Drucker-Prager屈服准则的线性系数形式,基于随机变量函数分布理论推导出岩石抗剪强度参数内摩擦角 和黏聚力 的概率密度函数。 和 概率密度函数显示：不仅岩石压缩强度和抗剪强度参数概率分布具有非一致性,而且根据不同屈服准则计算得出的岩石抗剪强度参数概率分布也具有非一致性。在进一步分析屈服准则系数具有不同变异系数和相关系数时的抗剪强度参数概率密度函数特征的基础上,提出根据概率分布的偏度和峰度确定一般情况下抗剪强度参数概率分布形态的方法,从理论上解决岩石压缩强度与抗剪强度参数分布的协调性问题。最后,对大理岩常规三轴压缩试验得出的抗剪强度参数进行大样本统计分析,验证了其概率密度函数理论推导的正确性以及概率分布形态确定方法的合理性。该研究为实际岩石强度概率分析时选择抗剪强度参数合理概率分布形式提供了理论指导。     

Estimation of dust fallout rates in the northern Arabian Gulf

The penetration of dust clouds over a sea surface is modelled as a sediment transport-diffusion problem. The model is used to determine the steady state concentration field of two-dimensional dust clouds during offishore dust storms. The rates of dust deposition into the sea can then be calculated from the obtained concentration fields. The model was applied to offshore dust storms blowing over the Arabian Gulf, yielding estimated dust sedimentation rates of 0–8 mm yr^?1. This is substantially higher, by several orders of magnitude, than dust fallout estimates in most seas of the world. The calculated fallout rates are in line with the results of existing field measurements.     

黄土粉尘搬运过程的动力学物理模型

通过对黄土粉尘重力沉降过程的动力学分析,给出了黄土粉尘粒度分布的数学表达,讨论了粉尘沉积通量随搬运距离、粒径变化的物理过程,首次确定了估算粉尘搬运距离和风力强度的计算方法,为区分粉尘搬运距离和风力强度对粒度的影响及其它们在冰期间冰期中的差异提供了物理学的判别依据。分析结果表明： 1)在重力沉降作用下,粉尘沉降通量随搬运距离的变化服从几何分布,具有沉降通量随搬运距离的增加迅速减小,越粗的粉尘颗粒其沉降通量初值越大,同时下降速度也越迅速的特点; 2)如果用携粉尘气流的水平通量作代表风力强度,则粉尘搬运距离与粒度分布曲线上重力沉降部分最高点的粉尘沉降通量成反比,风力强度与该点对应粒径的平方和粉尘搬运距离成正比。因此,根据该点的粉尘沉降通量和对应粒径,可以估算粉尘的搬运距离和风力强度。根据上述理论对渭南阳郭中学S0～L1黄土－古土壤剖面进行了粉尘搬运距离和风力强度的估算： 首先,从粒度分布中提取出3个对数正态分布的独立组份; 然后利用粗粒组份的参数计算粉尘搬运距离和风力强度。分析结果表明粉尘搬运距离具有冰期近、间冰期远的特点,风力强度的变化则具有冰期弱、间冰期强的特点,LGM时段的风力强度比MIS 3阶段大,但小于全新世适宜期,而LGM时期粉尘搬运距离并未明显减小,因此,可能黄土粒度的变化并非反映了冬季风的变化,而是反映了夏季风的变化,夏季风是通过影响粉尘源区来影响粉尘粒度的变化。     

Parameters for the dust envelope of the protoplanetary nebula IRAS 18062+2410

We have calculated a model for the dust envelope of the protoplanetary nebula IRAS 18062+2410 using observations from the ultraviolet to the far infrared. We assume that the envelope is spherically symmetrical and consists of identical silicate grains with a radius of 0.10 micron, and with the number density of the grains inversely proportional to the square of the distance. The optical depth of the envelope, whose inner boundary is 1.40×10^?3 pc from the center of the star, is 0.050 at 10 microns. At the inner envelope boundary, the temperature of the dust grains is 410 K and their density is 2.7×10^?7 cm^?3. Using calculations of stellar evolution at the stage following the exit from the asymptotic giant branch, we estimate the dust envelope’s expansion velocity to be 12 km/s. The mass-loss rate of the star preceding the ejection of the envelope was about 4.5×10^?6 M _⊙/yr. The observed excess of far-IR flux is not associated with the continuum radiation of the nebula, and may provide evidence for the presence of dust ejected by the star in earlier stages of its evolution.     

A model for the spectrum of Sakurai's object (V4334 Sgr)

Theoretical spectral energy distributions for Sakurai's object at 300–1000 nm are derived. A model-atmosphere grid with T _eff=5000–6250 K and logg=0.0–1.0 is computed for the chemical composition of Sakurai's object using opacity sampling including molecular and atomic absorption. Opacity due to absorption in 20 band systems of diatomic molecules is computed using the JOLA technique. The theoretical fluxes are compared with the observed energy distribution in a spectrum of Sakurai's object taken in April 1997. It is shown that (a) the theoretical energy distributions agree well qualitatively with the observed spectrum and depend strongly on the effective temperature; (b) C₂ and CN molecular bands are dominant in the visible and near-infrared spectrum, while atomic absorption is important at UV and blue wavelengths; and (c) comparison of the observed and computed spectra yields an effective temperature for Sakurai's object in April 1997 T _eff≈5250–5500 K. The dependence of the computed spectra at 300–1000 nm on the input parameters and adopted approximations is also discussed.