Effect of Curing Temperature on the Morphology and Hydration of Mg O Expansive Material in Paste

The morphologies and hydration properties of Mg O expansive material at different curing temperatures were investigated. When the curing temperature varies from 25 ℃ to 50 ℃,the conductivity of Mg O rises from 40 to80 μs/cm,the hydration product of Mg O expansive material curing in water for 28 days is from 1.5—2 mm to 2—2.5 μm in length through SEM observation,and the expansion of pastes with 5% of the magnesium oxide is from0.36% up to 1.01%,it is increased by 2.78 times. When the content of cement paste increases to 95% and cured in water for 90 days,the brucite forms as hexaflaggy-shaped crystal,which is less than 0.1 μm and tends to aggregates.The effect of curing temperature on the hydration of Mg O expansive material is obvious.     

Water Loss from Young Planets

Good progress has been made in the past few years to better understand the XUV evolution trend of Sun-like stars, the capture and dissipation of hydrogen dominant envelopes of planetary embryos and protoplanets, and water loss from young planets around M dwarfs. This chapter reviews these recent developments. Observations of exoplanets and theoretical works in the near future will significantly advance our understanding of one of the fundamental physical processes shaping the evolution of solar system terrestrial planets.     

推力作用下变质量柔性自旋飞行器稳定性分析

针对变质量柔性自旋飞行器推力作用下稳定性问题，以Timoshenko梁为模型，考虑陀螺效应和剪切效应，基于有限元法建立系统振动方程，分析质量变化、推力作用和自旋转速对系统振动的影响，采用自适应Newmark法求解系统的振动响应。结果表明：质量和推力能够改变固有频率、进动频率和临界转速；受质量变化影响，自旋转速与临界转速相等时，飞行器发生短暂共振，共振响应峰值最大时刻与此重合时刻相比稍有延迟。     

Advances in Researches on the Middle and Upper Atmosphere in 2008-2010

This paper summarizes the results of the researches on the middle and upper atmosphere obtained by Chinese scientists in 2008-2010. The focuses are specifically placed on the researches being associated with ground-based observation capability development, dynamical processes, the property of atmospheric circulation and the chemistry-climate coupling of the middle atmospheric layers.     

MPI和Pthread混合编程在NCS算法中的设计和实现

根据星载合成孔径雷达（Synthetic Aperture Radar,SAR）实时和准实时成像的需求,论文设计和实现了一种混合编程模式的非线性CS（Nonlinear Chirp Scaling, NCS）成像算法。此方法基于SMP（Symmetric Multiprocessing）集群系统,利用MPI（Message Passing Interface）和Pthread混合编程,实现了多进程和多线程的两级流水线并行成像处理。通过在HP刀片系统上的实验验证和结果分析,这种混合编程的流水线NCS并行成像算法既能较好适应前端系统传输一景原始回波数据时间不小于8s的情况,又能较好适应大规模原始回波数据堆积并且等待处理的情况。     

考虑土渐近状态特性的应力应变关系

在经典弹塑性理论框架下,根据SMP(Spatially Mobilized Plane)破坏准则并结合变换应力方法,通过引入准弹性体积模量的概念,建立了用增量法表示的考虑土渐近状态特性的三维应力应变关系式.针对三轴压缩应力条件,给出了相应的简化应力应变增量矩阵,以三轴压缩试验中的常规三轴压缩、不排水剪切和控制应变增量比的3种应力路径为例,推导出了便于应用的应力应变增量关系式.最后,利用文中的公式进行了预测分析和试验对比,结果表明:新推导的公式能方便地预测考虑渐近状态特性下土的应力应变关系,并能合理描述试验结果.     

基于图像骨架和贪婪算法的无人机航路规划

针对无人机在执行低空突防任务时最大生存概率以及自身飞行约束的要求,对传统的人工势场法进行改进,提出基于图像骨架和贪婪算法的航路规划方法.对可飞区域提取图像骨架生成赋权图,采用Dijkstra方法搜索最小代价路径实现航路初规划;提出了曲率可控的贪婪算法对初规划结果进行优化,使最终的路径同时满足最小转弯半径和最短航程的要求.仿真结果表明该方法是一种有效的航路规划方法.     

鸭翼/边条对融合体型机身大攻角气动特性影响

通过对融合体型机身进行表面测压和PIV(Particle Image Velocimetry)流动显示实验,研究了大攻角下鸭翼/边条对机身气动特性的影响规律.结果表明:加装鸭翼后攻角小于50°时机头区流动变化不大,超过50°攻角后,机头区法向力显著下降,并且随着攻角增加受影响区域向头部方向扩大;加装鸭翼致使鸭翼区截面法向力大幅增加.加装边条改善了边条区流动,边条涡对机头涡产生有利诱导,增大了边条区法向力.加装边条/鸭翼时,对机头区及鸭翼区流场的影响由鸭翼起主控作用,对边条区流场的影响由边条起主控作用.     

航空零件数控加工的特点

随着近年来国内各类军民机的研制,国内主要航空企业在航空数控加工技术方面积累了大量的技术经验,解决了一系列关键技术难题,初步形成了以飞机大型复杂结构件制造为代表的关键技术优势。但是,随着我国大飞机项目的启动,航空零件数控加工技术将面临更大的挑战。     

科氏质量流量计全数字闭环系统的设计与实现

科氏质量流量计(CMF,Coriolis Mass Flowmeter)全数字闭环系统,采用现场可编程门阵列(FPGA,Field Programmable Gate Array)和现代数字信号处理方法对CMF传感器进行稳定精确的闭环控制,实时性和精度较高.以高速并行器件FPGA为运算和控制核心,在相位控制中引入FIFO(First In First Out)组件,通过控制FIFO的读、写请求信号来改变时间差,实现对拾振和激励信号的相位差准确、稳定的控制;采用不连续和连续幅值控制相结合的非线性幅值控制方法,快速、准确地设定幅值,适应性强,实现对拾振信号幅值的良好控制,并控制拾振信号以稳定的幅值输出,提高CMF的测量精度和稳定性.实流标定对比实验结果表明:CMF数字闭环在零点稳定性、动态响应特性和重复性方面都优于模拟闭环,并在一定程度上提高了CMF的测量精度.