Aspect angle for interstellar magnetic field in SN 1006

A number of important processes taking place around strong shocks in supernova remnants (SNRs) depend on the shock obliquity. The measured synchrotron flux is a function of the aspect angle between interstellar magnetic field (ISMF) and the line of sight. Thus, a model of non-thermal emission from SNRs should account for the orientation of the ambient magnetic field. We develop a new method for the estimation of the aspect angle, based on the comparison between observed and synthesized radio maps of SNRs, making different assumptions about the dependence of electron injection efficiency on the shock obliquity. The method uses the azimuthal profile of radio surface brightness as a probe for orientation of ambient magnetic field because it is almost insensitive to the downstream distribution of magnetic field and emitting electrons. We apply our method to a new radio image of SN 1006 produced on the basis of archival Very Large Array and Parkes data. The image recovers emission from all spatial structures with angular scales from a few arcsec to 15 arcmin. We explore different models of injection efficiency and find the following best-fitting values for the aspect angle of SN 1006:  φ_o= 70^o± 4.2^o  if the injection is isotropic,  φ_o= 64^o± 2.8^o  for quasi-perpendicular injection (SNR has an equatorial belt in both cases) and  φ_o= 11^o± 0.8^o  for quasi-parallel injection (polar-cap model of SNR). In the last case, SN 1006 is expected to have a centrally peaked morphology contrary to what is observed. Therefore, our analysis provides some indication against the quasi-parallel injection model.     

Where are Swiftγ-ray bursts beyond the 'synchrotron deathline'?

We study time-resolved spectra of the prompt emission of Swift γ-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low-energy photon indices harder than 2/3 are consistent with Swift data. We perform a systematic search of the episodes of the spectral hardening down to the photon indices  ≤2/3  in the prompt emission spectra of Swift GRBs. We show that the data of the Burst Alert Telescope (BAT) instrument on board of Swift are consistent with BATSE data, if one takes into account differences between the two instruments. Much lower statistics of the very hard spectra in Swift GRBs are explained by the smaller field of view and narrower energy band of the BAT telescope.     

Interpretation and implications of the non-detection of GeV spectrum excess by the Fermi Gamma-ray Space Telescope in most gamma-ray bursts

Since the launch of the Fermi Gamma-ray Space Telescope on 2008 June 11, significant detections of high-energy emission have been reported only in six gamma-ray bursts (GRBs) until now. In this work we show that the lack of detection of a GeV spectrum excess in almost all GRBs, though somewhat surprising, can be well understood within the standard internal shock model and several alternatives like the photosphere internal shock (gradual magnetic dissipation) model and the magnetized internal shock model. The delay of the arrival of the >100 MeV photons from some Fermi bursts can be interpreted too. We then show that with the polarimetry of prompt emission these models may be distinguishable. In the magnetized internal shock model, a high linear polarization level should be typical. In the standard internal shock model, a high linear polarization level is still possible but much less frequent. In the photosphere internal shock model, the linear polarization degree is expected to be roughly anticorrelated with the weight of the photosphere/thermal component, which may be a unique signature of this kind of model. We also briefly discuss the implications of the current Fermi GRB data on the detection prospects of the prompt PeV neutrinos. The influences of the intrinsic proton spectrum and the enhancement of the neutrino number at some specific energies, due to the cooling of pions (muons), are outlined.     

岩体动态应力在地震机理中的作用研究

根据冲击动力学理论,采用三维动态有限元方法,模拟研究了地壳中的冲击波对地震触发的影响,自然界中随机载荷产生的冲击波导致了库仑应力的减小,引发块体间（或块体内）的错动,因而在地震的触发中,动态应力起很大的作用。     

断层垂向封油气性综合定量评价方法探讨及应用

在断层垂向上封油气机理及影响因素分析的基础上,通过物理模拟建立了原油通过断裂带运移速度与断层填充物粒度、倾角和泥质含量之间的函数关系。根据断裂带粒度、泥质含量和倾角,基于求取油气通过断裂带运移速度的大小,建立了利用油气通过断裂带运移速度研究断层垂向封油气性的综合定量评价方法。将该方法分别应用于库车坳陷克拉2气田和车古20潜山主要断层垂向封气和油性评价中,评价结果与实际地质条件吻合较好,表明该方法用于评价断层对油气的垂向封闭性均是可行的,是一种综合定量的评价方法。     

2009年南京冬季一次平流雾成因分析

利用常规气象观测资料和NCEP 1°×1°的再分析资料,对2009年12月1—2日南京地区一次浓雾天气过程产生的大尺度天气背景、气象要素及各种物理量进行分析,结果表明:高空弱脊和地面弱高压的控制有效抑制对流的发展,为这次浓雾的形成提供有利的环流形势;地面弱冷空气的影响,低层弱的辐合上升及中高层下沉增温作用,促使多层逆温存在,为雾的形成提供有利的层结条件;前期降水条件、近地层偏东风场及暖干盖作用为雾的形成提供了丰富的水汽条件;另外污染物集聚,也为雾的形成提供了丰富的凝结核。     

化学改性土的工程分类研究

在已有研究成果和课题组工作的基础上,确立了化学改性土的分类原则,并将其分为5类:即无机类改性土、有机类改性土、无机有机复合类改性土、化学物理类改性土和污染土;给出了各类土的定义,并对它们的成因、工程性质、机理、用途以及优缺点进行了比较详细的分析.研究表明:5类化学改性土具有各自的工程性质特点和形成机理,并适用于不同的工程用途;其改性效果取决于改性材料的性质、被改性土的性质以及改性工艺等,其中化学-物理类改性土的工程性质最具有优势,而污染土一般不能满足工程的环境和强度要求,需要采取一定的措施后,才能作为工程材料使用.化学改性土在环境岩土工程领域中具有广阔的应用前景.     

基于Oracle的国土资源基础数据组织方法

Oracle数据库管理系统已成为我国国家级和省级国土资源基础数据库建设的主流技术平台。该文就国家级和省级数据库的建设,提出了在Oracle数据库技术环境下,如何在物理上合理组织和布局各种类型的数据,如何设置和管理各衍生数据,如何实施数据完整性要求,其目的是实现国土资源基础数据的高效管理和可持续更新支持,更好地满足国土资源基础数据库之上各业务应用系统运转的要求。