导弹迎击时飞机的最佳逃逸策略研究

研究了飞机在被导弹迎面攻击时的最佳逃逸策略。首先建立了弹-机追逃对抗飞行数学模型,提出了几种突防方案,即机动变轨技术、抛射诱饵以及综合这两种突防方案,通过大量飞行数值仿真直观地比较了各种突防策略,得出了飞机躲避导弹袭击的最佳策略——作非常规机动并且同时发射诱饵弹。     

低温退火温度对Laves相Cr2Nb固相热反应合成的影响

研究了退火时间为3h时，退火温度对Cr-Nb机械合金化（MA）粉的Laves相Cr2Nb固相热反应合成的影响规律，获得了30hMA粉在退火时间为3h时能使Laves相Cr2Nb固相热反应合成充分进行的最低退火温度。优化出的cr2Nb固相热反应合成低温退火温度，可为通过MA＋热压（或烧结）工艺路线制备具有微／纳米晶结构的高强高韧Cr2Nb合金或Cr2Nb基复合材料提供理论指导。     

Zr和脉冲磁场对Mg-Y-Zn-Ca合金组织及压缩性能的影响

对比研究了未处理、Zr处理、脉冲磁场处理及脉冲磁场-Zr复合处理对长周期结构增强Mg-5Y-2.5Zn-1.2Ca合金凝固组织及压缩性能的影响,同时考察了复合处理条件下脉冲电压和频率对合金的影响。结果表明,Zr处理、脉冲磁场处理、复合处理后,合金的凝固组织和压缩性能均有所改善,其中复合处理的效果最好;与未处理合金相比,复合处理后合金的抗压强度和压缩率分别提高43.9%和15.4%。在0~300V内,随着脉冲电压增大,合金的平均晶粒尺寸逐渐减小;在1~10Hz内,随着脉冲频率增大,合金的平均晶粒尺寸先减小后增大,转折点为5Hz。晶粒尺寸越小,合金的第二相分布越均匀。合金的压缩性能与其晶粒尺寸基本对应。     

摩擦焊焊接块体非晶体合金Zr65Cu12．5Al7．5Ni15

采用传统摩擦焊焊接方法连接具有良好非晶形成能力的Zr65Cu12．5Al7．5Ni15（at％）块体非晶合金。微区X射线衍射结果显示，整个焊接接头保持了非晶特性，无晶化反应发生。对摩擦焊焊接方法成功连接块体非晶合金Zr65Cu12．5Al7．5Ni15的原因进行了分析。     

基于"工程制图"云教材的云班课建设与应用

随着信息技术与教育教学的深度融合,集在线教学与实体课堂教学为一体的混合 式教学模式越来越被广大教师所接受。为此,介绍了面向认知规律和自主学习的“工程制图”云 教材在内容和表现形式上的创新之处及在此基础上进行的云班课线上资源建设,并利用云平台 开展了课前知识传递、课内精讲重、难点和知识的实际运用、课后知识拓展等丰富的教学活动。 通过对学生学习轨迹的全程记录和跟踪,为过程性多元化评价提供了数据,有效促进了学生自 主学习,使教与学的互动性更强,取得了较好的效果,为普通高校开展“以学生为中心”的教学 提供了借鉴和参考。     

Ultrasonic vibration assisted grinding of hard and brittle linear micro-structured surfaces

In this paper, a novel ultrasonic vibration assisted grinding (UVAG) technique was presented for machining hard and brittle linear micro-structured surfaces. The kinematics of the UVAG for micro-structures was first analyzed by considering both the vibration trace and the topological features on the machined surface. Then, the influences of the ultrasonic vibration parameters and the tilt angle on the ground quality of micro-structured surfaces were investigated. The experimental results indicate that the introduction of ultrasonic vibration is able to improve the surface quality (The roughness SR_a was reduced to 78 nm from 136 nm), especially in guaranteeing the edge sharpness of micro-structures. By increasing the tilt angle, the surface roughness can be further reduced to 56 nm for a 59% improvement in total. By using the preferred UVAG parameters realized by orthogonal experiments, a micro cylinder array with surface roughness of less than 50 nm and edge radius of less than 1 μm was fabricated. The primary and secondary sequence of the grinding parameters obtained by the orthogonal experiments are as follows: feed rate, tilt angle of workpiece, depth of grinding, vibration frequency and amplitude. The spindle speed in the range of 1000 rpm–3000 rpm does not significantly affect the machined micro-structured surface roughness. Finally, more micro-structures including a micro V-groove array and a micro pyramid array were machined on binderless WC as well as SiC ceramic by means of the UVAG technique. The edge radius on the V-grooves and pyramids are both less than 1 μm, indicating the feasibility of UVAG in machining hard and brittle micro-structured surfaces for an improved surface quality.     

Synthesis and complex permeability of Co/SiO2 nanocomposites

In this paper, a simple sol–gel combined hydrogen reduction synthesis of Co/SiO₂ nanocomposites was reported. The specific magnetization of the sample can be as high as 146.34 emu/g even including silica, which is a non-magnetic material. The real part μ′ of the permeability for Co/SiO₂ nanocomposites is almost independent of frequency up to at least 10 MHz, at the same time, the loss of μ″ is very small. Our method provides a promising route to achieve soft magnetic material with good magnetic properties, especially in the high-frequency range.     

Vibration-assisted dry polishing of fused silica using a fixed-abrasive polisher

Glass is a ubiquitous but essential material in everyday life and industry. The most common method for polishing glass involves the use of free abrasives. However, this method is basically non-deterministic and lacks efficiency. Therefore, vibration has been employed to aid fixed-abrasive polishing in our research. It is found that the vibration can increase the material removal rate while maintain surface quality in fixed abrasive polishing. Normalized Preston coefficients that are the index of the polishing capability of a certain polishing process considerably increase in vibration-assisted polishing process. A mathematic model is set up to interpret the increase in material removal rate for vibration process. The modeled results show that the vibration can improve material removal by increasing vibration amplitude in vertical direction while the horizontal vibration contributes little to increasing material removal rate, which agrees well with experimental results. Aside from material removal, surface morphology of polished glass was also modeled for both vibration and conventional processes. Both experimented and simulated morphology evidence that the vibration some periodic structure on polished surface. The possible mechanism in dry fixed abrasive polishing was also chemically analyzed and a probable mechanism is put forward to clarify the material removal in dry fixed abrasive polishing.     

Measurement of phase equilibria in Zr-Ni-Sc ternary system

Phase relations in Zr-Ni-Sc ternary system were investigated experimentally through alloy sampling approach. Isothermal sections at 973, 1173, and 1273 K were constructed from the results of electron probe microanalysis (EPMA) and X-ray diffraction (XRD). No ternary phase has been detected in all these sections. Combining experiment and reasonable speculation, 12, 15 and 13 three-phase zones were obtained at 973, 1173 and 1273 K, respectively. Liquid region with a large composition range at 1273 K was found although its real boundary was estimated. The intermetallic compounds, Ni₂Sc, NiSc and NiSc₂, exhibit remarkable ternary solubility of Zr along the isoconcentration of Ni.     

Investigation of two-phase Mg-Gd-Ni alloys with highly stable long period stacking ordered phases

The effects of the Ni addition on the microstructures of Mg-2Gd-xNi (at.%, x = 0, 0.25, 0.5 and 1) alloys were systematically investigated. A series of two-phase Mg-Gd-Ni alloys consisting of long period stacking ordered (LPSO) phase and α-Mg were obtained. The LPSO phase presented block-like shape and was distributed between α-Mg dendrite arms. Its volume fraction was found to be proportional to the Ni content, ranging from 0 to ∼40% with the Ni content increasing from 0 to 1 at.%. After a heat treatment at 500 °C for 100 h, the LPSO phase experienced a structure transformation from 18R to 14H but was hardly dissolved into the α-Mg matrix, which evidenced a high thermal stability. The mechanism for the effects of the Ni addition on the formation of the LPSO phase was discussed.