上海黏性土剪切带形成的数值模拟分析

各种工程事故表明：现有的土力学计算模型均未考虑应变局部化问题,故不能解释这些工程事故的发生,因此应变局部化和剪切带形成的研究成为国际土力学界研究热点之一。数值模拟是研究剪切带形成的一个重要内容。在数值模拟中首先进行剪切带形成条件的研究,接着考虑土质不均匀性的影响,引入弱单元和强单元,进行弱单元与强单元影响力的研究。     

Profiles of blue and infrared diffuse interstellar bands

The paper presents a survey of profiles of reasonably strong diffuse interstellar bands (DIBs) based on the extensive set of high-resolution spectra acquired with the aid of echelle spectrographs installed at the 2-m Terskol, 2-m Pic du Midi and 1-m SAO telescopes. The surveyed diffuse interstellar bands cover the spectral ranges of blue and near-infrared, i.e the DIBs not surveyed by Krełowski & Schmidt . The possible modifications caused by stellar and telluric lines are discussed. The very broad features such as 4430 are not discussed because the shapes of their profiles, extracted from echelle spectra, are very uncertain. The signal-to-noise (S/N) ratios of the spectra are not high enough to enable discussion of the profiles of numerous weak interstellar features discovered recently.     

ANALYSIS OF THE CHARACTERISTICS OF SUSTAINED TORRENTIAL RAINS IN JUNES DURING 1958-2000

Day-to-day precipitation data of Junes during the 43 years of 1958-2000 from stations to the south of Yangtze River are used to divide regions and run statistical analysis of sustained torrential rainfall processes. A preliminary analysis is then made based on it and the results show that June is the month in which torrential rains in the southern half of China take place frequently and sustained torrential rains occur at the same time in South China and the area to the south of Yangtze River. In addition, the analysis gives the basic features of sustained torrential rains of June in China and their interannual variability patterns, with the suggestion that the amount of these events increases significantly after the 1990s. Lastly, the sustained torrential rains occurring in Junes of 1994, 1998 and 2005 in the southern half of China are taken as examples in the research on the basic patterns and formation mechanisms of the evolution of double rain-bands during the rain season in South China and the area to the south of Yangtze River. The analysis shows that the large scale environment field in which sustained torrential rains occur is related to the stable sustaining of the South Asia High and upper level jet streams.     

The excitation and kinematical properties of H2 and [Fe ii] in the HH 46/47 bipolar outflow

Long-slit spectra of the molecular outflow Herbig–Haro (HH) 46/47 have been taken in the J and K near-infrared bands. The observed H₂ line emission confirms the existence of a bright and extended redshifted counter-jet outflow south-west of HH 46. In contrast with the optical appearance of this object, we show that this outflow seems to be composed of two different emission regions characterized by distinct heliocentric velocities. This implies an acceleration of the counter-jet.
The observed [Fe  ii ] emission suggests an average extinction of 7–9 visual magnitudes for the region associated with the counter-jet.
Through position–velocity diagrams, we show the existence of different morphologies for the H₂ and [Fe  ii ] emission regions in the northern part of the HH 46/47 outflow. We have detected for the first time high-velocity (−250 km s⁻¹) [Fe  ii ] emission in the region bridging HH 46 to HH 47A. The two strong peaks detected can be identified with the optical positions B8 and HH 47B.
The H₂ excitation diagrams for the counter-jet shock suggest an excitation temperature for the gas of T _ex≈2600 K . The lack of emission from the higher energy H₂ lines, such as the 4–3 S(3) transition, suggests a thermal excitation scenario for the origin of the observed emission. Comparison of the H₂ line ratios with various shock models yielded useful constraints about the geometry and type of these shocks. Planar shocks can be ruled out whereas curved or bow shocks (both J- and C-type) can be parametrized to fit our data.     

IRAS 20231+3440区外流激发源的性质研究

给出红外点源IRAS 20231 3440附近恒星形成区近红外．JHK’和H2成像观测结果，以及与该IRAS点源成协的近红外点源IRS1的K波段分光观测结果．．JHK’观测显示该区域存在嵌埋的年轻星天体，H2窄波段观测揭示了若干个氢分子发射结点，其中有几个结点排列成线形，暗示分子氢喷流的存在．喷流的北部与已知观测的分子外流成协，表明二者之间存在联系．喷流的走向提示IRS1可能是其激发源，对IRS1的K波段分光观测给出了进一步的证据．从近红外、MSX及IRAS资料估计出IRS1的能谱分布，表明它是一个处于ClassI状态的中等质量的年轻星天体．     

Diffuse interstellar bands in low E (B – V) objects

We analyse spectra of slightly reddened, early-type stars in which the major diffuse interstellar bands at 5870 and 5797 Å are either strong or weak in relation to E(B – V) . It is demonstrated that among the low E(B – V) objects one can find stars obscured by 'sigma' as well as 'zeta' type clouds. The profiles of the diffuse bands seem not to be dependent on the total opacities of the interstellar clouds. We also discuss the physical conditions leading to the formation of the diffuse band carriers in low-opacity interstellar clouds; the carriers are apparently formed in media in which one can observe complex velocity fields.     

Mid-infrared imaging of WL 16: the spatial distribution of the hydrocarbon emission features

We present arcsec-resolution images at 8.2, 10.0 and 11.3 μm of the unusual young object WL 16 in Ophiuchus, which has an extended envelope of fluorescing hydrocarbon molecules. To the limit of achieved sensitivity, the faint 10.0-μm continuum has a surface-brightness distribution that is not distinguishable from those at 8.2 and 11.3 μm, where the luminosity is known to be dominated by the polycyclic aromatic hydrocarbon (PAH) emission features. We conclude that the 10-μm continuum either arises from non-equilibrium heating of small dust grains that are well mixed with the hydrocarbons or is quasi-continuous emission from the PAH particles themselves, rather than thermal equilibrium emission from macroscopic dust grains, and that there is no significant silicate absorption variation across the source. The extended hydrocarbon emission may trace a flattened, equatorial distribution of circumstellar material or arise in bipolar lobes. The former case is slightly favoured, based on currently available data, and would imply that WL 16 is a relatively evolved Herbig Ae star, the equatorial plane of which has been almost cleared of normal dust, leaving only fluorescing hydrocarbons and larger coagulated particles as a possibly transient fossil of the original circumstellar disc.     

ETM+全色波段及其多光谱波段图像的融合应用

Landsat-7ETM+的全色波段与多光谱波段有相同的太阳高度角和其他环境条件,影像获取时间一致,两种不同分辨率的数据可以不经配准而实现高精度融合。目前常用的图像融合方法很多,究竟哪种方法更适合于ETM+图像,本次试验采用HIS变换、Brovey变换、SFIM变换、加权融合4种方法,分别实现ETM+Pan与ETM+的多光谱波段的融合,并从空间纹理信息、光谱真实性2个方面进行定量和定性地评价。研究表明,从综合角度出发,基于SFIM变换的融合方法产生的光谱扭曲和失真较小,同时很大程度地保持了高分辨率的全色波段的空间纹理细节信息,是一种适合于ETM+图像融合的较佳方法。     

不同植被红边指数在城市草地健康判别中的对比研究

遥感红边指数与表征绿色植物生长状况的重要生化参数有密切的关系,是植被长势监测的重要因子。为寻找出最适用于城市草地生长状况监测的红边指数,本文基于Sentinel-2A数据,对比分析了不同红边指数在城市草地健康状况估算方面的差异。本文以福州市和厦门市的城市草地为例,在全面分析各种健康水平草地光谱响应特征差异的基础上,选取了6种与草地生化参数相关的红边指数,即红边位置REP、地面叶绿素指数MTCI、归一化差值红边指数NDRE1、新型倒红边叶绿素指数IRECI、红边叶绿素指数CI_red-edge以及叶绿素吸收指数MCARI2,然后采用独立样本T检验及欧式距离对这6种红边指数在草地健康判别中的优劣进行了定量对比。结果表明：IRECI指数对草地健康状况最为敏感,该指数在不同健康等级草地的值域区间和均值都存在显著性差异,其判别总精度均大于85%;NDRE1和MCARI2指数次之,其他3个指数则难以判别草地的健康状况。因此,在基于Sentinel-2A影像的城市草地健康遥感判别中,推荐使用IRECI指数。     

A search for the 53-MHz OH line near G48.4−1.4 using the National MST Radar Facility

We present the results of a search for the ground-state hyperfine transition of the OH radical near 53 MHz using the National Mesosphere–Stratosphere–Troposphere (MST) Radar Facility at Gadanki, India. The observed position was G48.4−1.4 near the Galactic plane. The OH line is not detected. We place a 3σ upper limit for the line flux density at 39 Jy from our observations. We also did not detect recombination lines (RLs) of carbon, which were within the frequency range of our observations. The 3σ upper limit of 20 Jy obtained for the flux density of carbon RLs, along with observations at 34.5 and 327 MHz, are used to constrain the physical properties of the line-forming region. Our upper limit is consistent with the line emission expected from a partially ionized region with electron temperature, density and path lengths in the range 20–300 K, 0.03–0.3 cm⁻³ and 0.1–170 pc, respectively.