分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-04-06
摘要: Cylindrical Nd-Fe-B magnets with different height reductions were prepared by hot deformation method. The inhomogeneity of the magnetic performance along the radial direction was revealed with a closed circuit B-H apparatus while that along the axial dire
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-03-30
摘要: In order to improve the coercivity of hot-pressed magnets with hydrogenation disproportionation desorption recombination (HDDR) powders being the precursor, diffusion processing of an NdCu eutectic alloy is employed for grain boundary modification, result
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-03-30
摘要: In order to improve the coercivity of hot-pressed magnets with hydrogenation disproportionation desorption recombination (HDDR) powders being the precursor, diffusion processing of an NdCu eutectic alloy is employed for grain boundary modification, result
提交时间: 2017-05-02
摘要: Nd24Fe65.5-xRMxB0.97Tb7.0Dy1.1Co1.0Al0.2Cu0.23 [RM=Nb, Zr, Ti; x=0.2, 0.4, 0.6] magnets with high property were prepared by powder metallurgy process. The measurements of high temperature magnetic properties indicate that the value of alpha [temperature c
提交时间: 2017-05-02
摘要: The chemical bath deposition [CBD] and the grain boundary diffusion method were combined to diffuse the heavy rare earth for obtain the thick magnets with high coercivity and low heavy rare earth. The jet mill powders were soaked into the alcohol solution
提交时间: 2017-05-02
摘要: The electroplating pretreatment of NdFeB magnets was simulated in this study, and the effect of the pickling process on element, matrix morphology and texture was discussed. The results showed that in the ordinary circumstance the acid solution concentrat
提交时间: 2017-05-02
摘要: The 2:17 type Sm-Co sintered magnets were made with strips and ingots, separately. The phase structure and microstructure of the cast alloys and their effects on magnetic properties of the magnets have been comparatively studied. X-ray diffraction analysi
提交时间: 2017-05-02
摘要: The influence of the RE-rich phase distribution in the precursor alloys on the anisotropy of the hydrogenation disproportionation desorption recombination [HDDR] processed powders is investigated. The homogenized ingot alloy and the as-cast strip casting
提交时间: 2017-05-02
摘要: We report an approach to improve the electric resistivity of Nd-Fe-B die-upset magnets without sacrificing their magnetic properties very much. NdF3 fine powders were segmentally added in the die filling with MQU-F powders and then were die-upset for magn
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the Universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5-layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wavefront sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.