金属材料摩擦挤压合金化研究

本文以LF6铝合金作为基材，Ni粉作为合金化添加粉末，试验用摩擦挤压的方法进行金属材料的合金化。利用X射线衍射仪及Topas（2）X射线分析软件进行物相分析。并测试了合金化区域的显微硬度。结果表明：摩擦挤压区域有Al3Ni以及AlNi3化合物生成，并且发现生成的金属间化合物Al3Ni含量高于AlNi3化合物含量；生成的Al3Ni和AlNi3的晶格常数增大，晶粒尺寸细小，几乎达到亚微米级；生成Ak3Ni的显微硬度达到520HV。研究结果表明：用摩擦挤压的方法能够实现金属材料的合金化。     

正等测椭圆的简捷画法

在研究传统菱形法绘制正等测椭圆的基础上，运用逻辑分析和几何分析的方法，提出了一种六点共圆、三线共点的椭圆简捷画法，作图简便、快捷，效率高。     

Model-based orientation-independent 3-D machine vision techniques

Orientation-dependent techniques for the identification of a three-dimensional (3-D) object by a machine vision system are represented in parts. In the first part, the data consist of intensity images of polyhedral objects obtained by a single camera, while in the second part, the data consist of range images of curved objects obtained by a laser scanner. In both cases, the attributed graph representation of the 3-D object surface is used to drive the respective algorithm. In this representation, a graph node represents a surface path and a link, the adjacency between two patches. The attributes assigned to nodes are moment invariants of the corresponding face for polyhedral objects. For range images, the Gaussian curvature is used as a segmentation criterion for providing symbolic shape attributes. Identification is achieved by an efficient graph-matching algorithm used to match the graph obtained from the data to a subgraph of one of the model graphs stored in the computer memory     

弹用涡喷发动机润滑油系统动密封结构研究

论述了某弹用涡喷发动机动密封结构工作原理及泄漏失效形式，对润滑系统的动密封结构进行了密封元件的研制，配合零件间隙的设计和台架模拟的试验研究，掌握了该发动机动密封的磨损机理，台架试验结果证明了其动密封结构设计的合理性。     

Analysis of some modified ordered statistic CFAR: OSGO and OSSOCFAR

It is necessary for automatic detection radars to be adaptive to variations in background clutter in order to maintain a constant false alarm rate (CFAR). A CFAR based on an ordered statistic technique (OS CFAR) has some advantages over the cell-averaging technique (CA CFAR), especially in clutter edges or multiple target environments; unfortunately the large processing time required by this technique limits its use. The authors present two new OS CFARs that require only ahlf the processing time. One is an ordered statistic greatest of CFAR (OSGO), while the other is an ordered statistic smallest of CFAR (OSSO). The OSGO CFAR has the advantages of the OS CFAR with only a negligible increment to the CFAR loss     

XMM-Newton observations of low luminosity Be/X-ray candidates

A small number of early Be stars exhibit X-ray luminosities intermediate between those typical of early type stars and those radiated by Be/X-ray binaries in the quiescent state. We report on XMM-Newton observations of two such Be stars, HD 161103 and SAO 49725 which were originally discovered in a systematic cross-correlation between the ROSAT all-sky survey and SIMBAD. The new observations confirm the X-ray luminosity detected by ROSAT (L_X  10³² erg s⁻¹) and the hardness of their X-ray spectra (thin thermal with kT  8–10 keV or power law with photon index of 1.7) which are both unusual for normal early type stars. We discuss the possible origin of this excess X-ray emission in the light of the models proposed for γ-Cas, magnetic disc-star interaction or accretion onto a compact companion object, neutron star or white dwarf, and compare the properties of these two sources with those of the new massive systems discovered in the XMM- Newton/SSC survey of the Galactic plane.     

Structural development of the X-ray limb flare of 30 April 1980

We describe the development of the limb flare of 30 April 1980, 20:20 UT, as observed by the Hard X-ray Imaging Spectrometer (HXIS) aboard the Solar Maximum Mission (SMM). It consisted of a short-lived bright nucleus (FWHM < 10,000 km), just inside the Sun's limb; a longer lasting tongue, extending to a height of 30,000 km, and a more complicated feature, approximately situated at the Sun's limb. The tongue was a pre-existing magnetic structure that started emitting X-rays only a few seconds after the bright nucleus, and which had a slightly higher temperature than the nucleus; its X-ray emission may be caused by electrons escaped from the nucleus.     

Contributions from nearby pulsars to the local cosmic ray electron spectrum

PSR J0437-4715 is one of the closest millisecond pulsars (MSPs) to Earth, lying at a distance of ∼140 pc. This pulsar has a characteristic age of 4.9 Gyr and a relatively low spindown power of ∼10³⁴ ergs/s. During its rather long lifetime, a large fraction of the energy output has been in the form of multi-TeV electrons. In this paper, we investigate the possible contribution of this nearby MSP to the local interstellar electron spectrum (LIS). The old age of the system justifies a steady-state evaluation of the contribution from this pulsar to the LIS. We calculate the electron spectrum at the light cylinder in the framework of a General Relativistic polar cap (PC) model, and use this as an injection spectrum in a diffusion model. The younger Geminga pulsar is also very close to Earth and warrants investigation. A steady-state approach is however no longer justified, so we use an impulsive injection model. We will present results of a study of the contribution from these pulsars to the cosmic ray (CR) LIS. Our calculations show that pulsars like Geminga can make a non-negligible contribution to the LIS.     

Teaching astronomy for pre-service elementary teachers: A comparison of methods

This study investigates the effect of text structure and “hands-on” methods in the acquisition of the concepts of moon phases and seasons for pre-service elementary teachers. The goal is to evaluate the most appropriate method for facilitating conceptual change. The presentation of two main misconceptions associated with each concept (moon phases and seasons) is tested. Sixty pre-service elementary teachers are divided into three same size experimental groups after a pre-test on their knowledge about astronomy: one group read a simple expository text that presents factual information about seasons and moon phases, another group read a refutation text that moreover presents explicitly two main and usual misconceptions about each concept and arguments to refute them; the last group participates to a refutation modelling activity by testing, for each concept, three hypothesis: the scientific explanation and the two common misconceptions. The hands-on method is used as a way to refute the pre-conceptions thanks to a collaborative activity in small groups.