纤维增强钛基复合材料横向拉伸性能数值模拟

为研究SiC/Ti-6AL-4V纤维增强钛基复合材料在横向拉伸载荷下的力学特性,建立了三维细观有限元模型;利用ANSYS软件接触单元和内聚力材料模型,对其制备残余热应力及横向拉伸载荷下的界面脱粘、基体失效进行了数值模拟。结果表明:考虑界面材料属性的细观力学有限元单胞模型,可较好地模拟纤维增强钛基复合材料在横向拉伸载荷下的界面脱粘、基体失效;横向拉伸载荷下,复合材料基体细观结构内部应力分布不均导致基体材料利用率下降,是造成复合材料横向强度低于基体材料强度的主要原因。     

中纬电离层暴负相开始时间与磁暴主相开始时间的对应关系

本文假设在磁暴主相期间,由于极光椭圆带处的空气被加热上升,从而使高纬高空出现富含分子的气体。这些气体由于扩散及与中性风的相互作用会向中低纬移动,其所到之处电子消失系数增加,从而导致负相电离层暴的发生。计算给出了全球中纬电离层暴负相的开始时间与磁暴主相开始时间之间的关系,并讨论了负相电离层暴发生的"时间禁区"问题。结果与有关统计结果符合得很好。      

双级径向旋流器对燃烧性能的影响

为保证航空发动机燃烧室具有良好的气动雾化性能并实现稳定、高效地燃烧,设计6种带有旋向相反的双级径向旋流器方案的单头部燃烧室,通过双级径向旋流器设计参数对燃烧性能影响的数值计算,得到不同主、副旋流器旋流数对燃烧室性能的影响规律,并进行试验验证。结果表明:数值计算与试验结果基本吻合。双级径向旋流燃烧室的燃烧效率超过99.9%,双级径向旋流器存在最佳的匹配方案,该方案使得燃烧室形成合适的回流区,并得到均匀的出口温度场。     

Design and analysis of a hypersonic inlet with an integrated bump/forebody

Numerical simulations and experiments showed that bump inlet had a remarkable effect on boundary layer diversion of supersonic flow.However, the design and analysis of bump in hypersonic flow was still few.In this paper, the mechanism of a supersonic bump inlet is introduced to the design of hypersonic forebody.A hypersonic inlet with an integrated bump/forebody is obtained by the Method Of Characteristics(MOC) based on a chin inlet.Numerical simulations show that the modified inlet achieves diversion of low-speed flow.Besides, the integrated bump/-forebody is also beneficial to inlet start.During the starting process, the shape of the separation zone is rebuilt by the modified forebody surface which makes spillage much easier.This new design leads to a reduction of the self-start Mach number by 0.95.     

Comparative study of the influence of natural convection on directional solidification of Al–3.5 wt% Ni and Al–7 wt% Si alloys

We present numerical simulations of thermosolutal convection for directional solidification of Al–3.5 wt% Ni and Al–7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al–7 wt% Si, but not in Al–3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant.     

Novel method for reconstruction of hyperspectral resolution images from multispectral data for complex coastal and inland waters

Hyperspectral resolution image products of a synthetic sensor featuring the high spatial resolution of the space-borne sensor can offer cost-effective means for enhancing our current capabilities in terms of providing an array of images in lieu of designing an expensive system for image acquisition, which can serve the expanding needs of the scientific and user communities for various critical water color applications. Despite several studies on enhancing the capability of land remote sensing sensors, full spectrum reconstruction of water color images with varying spectral bands is hampered by the lack of methods and accurate atmospheric correction procedures. In the present work, a novel method is developed for reconstruction of hyperspectral resolution images from high spatial-resolution Sentinel 2 Multispectral Instrument (MSI) data representative of many complex waters in coastal and inland zones. This method uses a deep neural network (DNN) with multiple blocks of deconvolution and dense layers. The spectral reconstruction of hyperspectral resolution images from multispectral data was based on rigorous training data from the atmospherically-corrected and validated HICO normalized water-leaving radiance products (with spectral resolution 438-868 nm sampled at 5.7 nm) of diverse water types. The generalizability and versatility of the DNN method was tested and evaluated systematically by means of various qualitative and quantitative analyses using concurrent space-borne (MSI and HICO) and in-situ measurements from different regional waters. Reconstructed hyperspectral resolution radiances obtained from the MSI images closely matched with independent HICO and MSI measurements within the desired accuracy. Successful reconstruction and validation of the hyperspectral radiances indicate that the proposed state-of-the-art method provides possible future directions for enhancing our current capabilities of space-borne sensors for various research purposes and societal applications at local, regional and global scales.     

Integrating aeromagnetic data and Landsat-8 imagery for detection of post-accretionary shear zones controlling hydrothermal alterations: The Allaqi-Heiani Suture zone,South Eastern Desert,Egypt

The Arabian-Nubian Shield (ANS) underwent a regional carbonation event with CO₂ fluxes derived from the mantle and circulated along post-accretionary shear zones, thus affecting the redistribution of gold mineralization. Formerly, the analyses of remotely-sensed data have suggested regions of gold mineralization linked to the post-accretionary structured framework, but the results were insufficient for detailed prospecting in the ANS. In this research, aeromagnetic data and Landsat-8 imagery were integrated for delineating new high potential zones of gold mineralization in the Allaqi-Heiani Suture (AHS) zone, the ANS, South Eastern Desert (SED) of Egypt. Aeromagnetic data were enhanced using the Center for exploration targeting (CET) grid enhancement technique to detect the main structures that control hydrothermal alterations in the study area. Principal Component Analysis (PCA) technique and ratios of spectral bands were applied to Landsat-8 data for mapping zones of hydrothermal alteration associated with gold mineralization. The traced structural elements from RTP, CET and Landsat-8 maps were statistically plotted and interpreted using rose diagrams. These diagrams indicated that the NW and NE trends are the most dominant in the RTP map and that the intersection zones obtained from the CET analysis are aligned along the NW-oriented trend. While the NNW, WNW and NE trends were the most dominant ones in Landsat maps. The integration of the results indicates several new high potential zones of gold and Cu/Ni mineralization types, which are mostly concentrated at the western part of the AHS zone. The hydrothermal alteration zones and associated gold mineralization are strongly linked to NW, NE, E-W and WNW trending lineaments. The approach used in this study can be applied to other parts of the ANS and other regions with similar geological conditions around the world.     

中热值合成气扩散燃烧速度特性的实验研究

针对CH4和中热值合成气的旋流燃烧室进行了PIV测量,获得了不同燃料燃烧对火焰流场变化的影响。实验结果表明：在相同入口条件下,合成气燃烧时的火焰张角略大,回流区宽度和回流强度均高于CH4火焰,燃气流量较低时,合成气火焰的湍流强度更大,燃气流量增大后,CH4的燃烧脉动速度逐渐增大并超过合成气。     

扁平型外转子混合磁悬浮飞轮动力学分析

针对扁平型外转子磁悬浮飞轮,考虑轴向被动悬浮刚度影响,采用理论模型与数值模拟相结合的方法,对系统静态悬浮和稳定旋转两种工况下的动力学特性进行了研究.结果表明,静态悬浮时,轴向刚度的变化对径向摆动固有频率影响明显,径向刚度的变化主要影响系统径向刚体平动固有频率,振型交换区内系统振型为转子刚体平动与摆动的叠加;稳定旋转时,轴向刚度的变化主要影响低速圆锥涡动频率,径向刚度的变化主要影响圆柱涡动频率.     

论邓小平经济理论与现代区域经济理论的竞合

我国社会主义建设的总设计师邓小平同志虽然不是区域经济学家,但是他的许多经济思想具有相当的超前性,在很多方面与现代区域经济学理论出现竞合。我国各个区域都应该深入领会邓小平经济理论并以其为指导加快发展。