Constraining the Mass Distribution of Cluster Galaxies by Weak Lensing

Analysing the weak lensing distortions of the images of faint background galaxies provides a means to constrain the average mass distribution of cluster galaxies and potentially to test the extent of their dark matter haloes as a function of the density of their environment. The observable image distortions are a consequence of the interplay between the effects of a global cluster mass distribution and the perturbations resulting from individual cluster galaxies. Starting from a reconstruction of the cluster mass distribution with conventional techniques, we apply a maximum likelihood method to infer the average properties of an ensemble of cluster galaxies. From simulations this approach is found to be reliable as long as the galaxies including their dark matter haloes only contribute a small fraction to the total mass of the system. If their haloes are extended, the galaxies contain a substantial mass fraction. In this case our method is still applicable in the outer regions of clusters, where the surface mass density is low, but yields biased estimates of the parameters describing the mass profiles of the cluster galaxies in the central part of the cluster. In that case it will be necessary to resort to more sophisticated strategies by modelling cluster galaxies and an underlying global mass distribution simultaneously. We conclude that galaxy–galaxy lensing in clusters provides a unique means to probe the presence and extent of dark haloes of cluster galaxies.     

雷州话与普通话声母声调对比研究

雷州话声母系统与普通话声母系统相比较,双唇音、舌尖中音、舌根音基本相同;雷州话多了一个双唇音,一个喉头音;普通话多了一个唇齿音;普通话有舌尖前音、舌尖后音、舌面音三组声母,而雷州话只有一组类似普通话舌尖前音的声母(有专家认为是舌叶音),这是雷州话声母系统和普通话声母系统的差异,也是雷州人学习普通话的障碍。雷州话声调系统与普通话声调系统相比较,在调类及调值上相差极大。但重要的还是雷州话有入声,普通话则没有。通过比较研究雷州话与普通话声母声调方面的异同,发现雷州人学习普通话的难点,从而对症下药,发挥正迁移、克服负迁移,纠正“雷式普通话”这样的语音异化现象。     

区域重力场相对基准的建立

针对地震系统各区域重力网的现状,提出了一种在没有绝对重力测量资料的情况下,利用网区多年积累的观测资料,建立区域重力场相对基准的方法。实验证明,采用该方法建立的区域重力场相对基准,精度优于５０ｎｍ·ｓ－２,不仅有利于地震重力前兆信息的提取,而且能优化和评定区域重力网的质量,标定和检测重力仪参数及其变化。     

Repacking practice for G-3 engineering driller power unit with drive shaft of dual channel reverse circulation

In order to satisfy operating requirements for constant core drilling technology in reverse circulation with hollow-through DTH,the power unit of G-3 engineering driller was ameliorated. The new one with dual channel drive shaft, achieved the perfect assemble with transmission structure of the original power unit. It could interconvert according to need by using two sets of drive shafts with direct and reverse circulation. The repacked G-3 engineering driller carried on experiment in the field test in Luanchuan molybdenum mine of Henan, whose effect was very good.     

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Scalar field haloes as gravitational lenses

A non-topological soliton model with a repulsive scalar self-interaction of the Emden type provides a constant-density core, similarly as the empirical Burkert profile of dark matter (DM) haloes. As a further test, we derive the gravitational lens properties of our model, in particular, the demarcation curves between 'weak' and 'strong' lensing. Accordingly, strong lensing with typically three images is almost three times more probable for our solitonic model than for the Burkert fit. Moreover, some prospective consequences of a possible flattening of DM haloes are indicated.