TP-650颗粒增强钛基复合材料的性能与组织特征

研究了TP-650颗粒增强钛基复合材料的性能与组织.结果表明复合材料的室温静拉伸强度随热处理温度的升高而增加.经炉冷处理TP-650棒材的室温拉伸强度比油冷或空冷处理的要高.TP-650的使用温度比传统高温钛合金IM1834,Ti-1100要高50℃～100℃.500℃以上,复合材料表现出良好的高温稳定性能.显微组织显示了TiC颗粒弥散分布,复合材料组织均匀,TiC和基体冶金结合,界面较小.

SiC长纤维增强钛合金基复合材料的界面研究

研究了SiC/TC4和SiC/Ti40复合材料在不同热处理态下的界面行为。结果表明,SiC/Ti40复合材料相邻两纤维间存在TiC析出物,在1 000℃处理后,TiC析出物消失;2种复合材料界面反应厚度随处理温度升高和时间延长而增大;SCS-6 SiC/TC4和SiC/Ti40复合材料界面产物均为Ti5Si3。

一种快速分层递阶DSmT近似推理融合方法(B)

针对Dezert-Smarandache Theory(DSmT),随着鉴别框架中焦元数目的增多,其组合推理运算成指数增长,已成为制约该理论广泛应用与发展的瓶颈问题.为了解决这个难题,本文在进一步深入研究仅单子焦元赋值几个关键问题的基础上,主要针对超幂集空间中部分单子和冲突焦元具有信度赋值的情况,通过比例分配原则,把冲突焦元的信度赋值分配到相应的单子焦元上,然后根据仅单子焦元情形下的近似推理方法进行处理,即利用二叉树分组技术对单子焦元进行刚性分组,实现细粒度超幂集空间向粗粒度超幂集空间映射.最后通过从计算效率、信息损失和相似度的角度分别比较新、老方法,比较结果充分地验证了新方法的优越性.

一种快速分层递阶DSmT近似推理融合方法(A)

本文提出了一种分层递阶的DSmT快速近似推理融合方法,该方法针对超幂集空间中仅单子焦元具有信度赋值的情况,利用二叉树或三叉树分组技术对其刚性分组,与此同时,对每个信息源对应的各个分组焦元进行信度赋值求和,以便实现细粒度超幂集空间向粗粒度超幂集空间映射.然后运用DSmT组合规则和比例冲突分配规则对粗化超幂集空间的两个信息源进行融合,保存该融合结果作为父子之间节点连接权值,然后对每个分组焦元信度赋值归一化处理,通过设定树的深度,来确定分层递阶的次数.最后通过从多个角度比较新、老方法,从而充分地验证了新方法的优越性.

钛基复合材料的高周疲劳性能研究

研究了TiC粒子增强的钛基复合材料的室温轴向高周疲劳性能。测试Kt=1的试样时采用的试验频率为76Hz,R=0.06和R=-1时,复合材料的室温疲劳强度分别为594MPa和494MPa。试验结果表明TiC粒子增强的钛基复合材料的室温高周疲劳性能与细晶组织的Ti-6Al-4V和IMI834的相当。复合材料内含有较细小的薄片状组织,这种组织为α+β相互相交错构成,这种细小的α+β相间的层状组织对于阻止疲劳裂纹的扩展和提高疲劳裂纹的扩展寿命有重要作用。退火后的复合材料疲劳裂纹扩展区规则且较宽广,从而也使复合材料具有较高的疲劳强度,疲劳裂纹扩展寿命延长。

基于ESMS过滤器的信息融合理论研究及SLAM应用

本文解决了多源信息融合时信息源选择的难题,提出了一种广义的证据支持贴近度过滤器来选择最一致的证据源,并耦合基于DSmT和PCR5的融合机,应用于PioneerII移动机器人的SLAM;通过对运行在虚拟环境中的一个虚拟机器人(自身携带16个Sonar传感器),感知周围环境信息,对有或没有ESMS过滤器两种情况下的环境地图重构效果进行比较,充分验证了ESMS过滤器作为信息融合源选择先决条件的优点。

SiC长纤维增强阻燃钛合金基复合材料的界面行为

研究了SiC Ti40复合材料在不同热处理态下的界面行为。结果表明 ,SiC Ti40复合材料相邻两纤维间存在TiC析出物 ,在 1 0 0 0℃处理时 ,TiC析出物消失 ;SiC Ti40复合材料界面反应厚度与处理时间的平方根呈线性关系 ,温度超过 80 0℃ ,界面厚度明显增加 ;SCS 6SiC Ti40复合材料界面产物为Ti5Si3 。

Study on SCS-6/Ti-6A1-4V Composite

Fiber reinforced titanium matrix composite is considered as a superior material for advanced lightweight aerospace application. Fiber/matrix interfacial reaction has a significant effect on the mechanical properties of the composites. The SCS-6 SiC fiber reinforced Ti-6Al-4V matrix composite was prepared by foil-fiber-foil (FFF) method at ONERA, France. Stripe samples were cut from the as-consolidated composites and sealed in silicon carbide tube. One group of the samples were annealed for 58h at 550°C, 700°C, 850°C and 1000°C, the other group were annealed at 1000°C for 43h, 58h, 80h, lOOh, respectively. The interface investigation indicated that the connection between SiC fiber and the matrix is favorite in the composite. And the interface width for as-consolidated composite is only about 0.8um. The interface width increase with the prolong of annealing time and the increase of annealing temperature. But the increment for the latter is not as high as the former one, which means the annealing time may be the prior factor to influence the interface reaction. The interface width for the composite annealed at 1000°C for lOOh is about 20um. Interface composition of the composite detected by EDX is as follows: Ti 87.58 wt %, V 4.91 wt %, Al 4.06wt%, Si 3.45 wt %.

空时自适应处理导论：雷达环境与支柱(英文)

主要是为了说明机载雷达环境下,空时自适应处理(STAP)对于不同任务(或雷达功能)的作用与影响,包括用于地面动目标探测的空对地任务或用于探测空中目标空对空任务。特别关注的是距离多普勒域内的杂波定位,它将为STAP需求提供基准,且也用于解释特定应用间的关键差别。由真实信号获取的典型结果用于说明预期优势。

稀薄流中的光学诊断法(英文)

综述了ONERA(法国宇航院)在高超声速流中采用激光或电子束等光学技术实现非接触式精确测量上已取得的进展。点、视线和成像测量均属可能。点的测量采用X射线辐射和相干反 -Stokes Raman散射(CARS)探测的电子束荧光(EBF)实现。不要求空间分辨率时,二极管激光吸收分光术给出沿一条线集成的结果。采用高能脉冲电子枪的EBF成像术也很有成效。在多种高超声速高焓设备中,旋转和振动的氮和氧化氮总量以及在激波和边界层中分辨旋转态的速度也都已做了测量。

气液两相流下离心泵性能分析的数据处理方法

This paper presents what should be best practice data reduction procedures for pump performance analysis with emphasis on two-phase inlet flow conditions.This becomes a mandatory step especially when pumps performances are degraded in case of liquid gas mixture at inlet section.Most of following recommendations are based on existing rules that must be recalled for researchers and end users performing centrifugal pump tests and more specifically when comparing the results between each other or/and withCFDapproaches.

Detecting exoplanets with FAST?

We briefly review the various proposed scenarios that may lead to nonthermal radio emissions from exoplanetary systems(planetary magnetospheres, magnetosphere-ionosphere and magnetospheresatellite coupling, and star-planet interactions), and the physical information that can be drawn from their detection. The latter scenario is especially favorable to the production of radio emission above 70 MHz. We summarize the results of past and recent radio searches, and then discuss FAST characteristics and observation strategy, including synergies. We emphasize the importance of polarization measurements and a high duty-cycle for the very weak targets that radio-exoplanets prove to be.

Characterization of the stability and dynamics of a laser-produced plasma expanding across a strong magnetic field

Magnetized laser-produced plasmas are central to many studies in laboratory astrophysics,in inertial confinement fusion,and in industrial applications.Here,we present the results of large-scale three-dimensional magnetohydrodynamic simulations of the dynamics of a laser-produced plasma expanding into a transverse magnetic field with a strength of tens of teslas.The simulations show the plasma being confined by the strong magnetic field into a slender slab structured by the magnetized Rayleigh–Taylor instability that develops at the plasma–vacuum interface.We find that when the initial velocity of the plume is perturbed,the slab can develop kink-like motions that disrupt its propagation.

Improvement of the Viscous Penalty Method for Particle-Resolved Simulations

A numerical study of the parameters controlling the viscous penalty method is investigated to better set up Particle-Resolved Direct Numerical Simulations (PR-DNS) of particulate flows. Based on this analysis, improvements of the methods are proposed in order to reach an almost second order convergence in space. The viscous penalty method is validated in Stokes regime by simulating a uniform flow past a fixed isolated cylinder. Moreover, it is also utilized in moderate Reynolds number regime for a uniform flow past a square configuration of cylinder and compared in terms of friction factor to the well-known Ergun correlation.

Numerical study of convective heat transfer in static arrangements of particles with arbitrary shapes:A monolithic hybrid lattice Boltzmann-finite difference-phase field solver

A compressible lattice Boltzmann-finite difference method is extended by the phase-field approach into a monolithic scheme to study fluid flow and heat transfer through regular arrangements of solid bodies of circular,elliptical and irregular shapes.The advantage of using the phase-field method is demon-strated both in its simplicity of accounting for flow and thermal boundary conditions at solid surfaces with irregular shapes and in the capability of generating such complex-shaped objects.For an array of discs,numerical results for the overall solid-to-gas heat transfer rate are validated via experiments on flow through arrays of hot cylinders.The thus validated compressible LB-FD-PF hybrid scheme is used to study the dependence of heat transfer on flow and thermal boundary conditions(Reynolds number,temperature difference between the hot solid bodies and the inlet gas),porosity as well as on the shape of solid objects.Results are rationalized in terms of the residence time of the gas close to the solid body and downstream variations of gas velocity and temperature.Perspective for further applications of the proposed methodology are also discussed.

Spatially resolved investigation of flame particle interaction in a two dimensional model packed bed

This study investigates the interaction between a premixed methane-air flame and particles inside a model packed bed.The opacity of the spherical packed beds to visible light poses a major barrier to the implementation of highly resolved optical diagnostics,so that no detailed experimental data were so far available for the validation of numerical simulation.Here,a two-dimensional cylindrical packed bed design is set up,which enables direct line-of-sight optical measurements without loss of spatial reso-lution over the fluid region between the particles.In this study,the case of cold metallic cylindrical particles(T=377 K)relevant to start-up of a reactor is investigated using internal particle cooling,which also allows cylinder specific heat transfer rate measurements by differential temperature measurements on the coolant streams.The two dimensional assumption is first verified by measuring the inflow ve-locity and cylinder temperature profile along the cylinders.Chemiluminescence imaging is then per-formed using a telecentric lens to observe the position and geometry of the two-dimensional flame front with respect to the surrounding cylinders without loss of resolution.Simultaneously,the cylinder-specific flame to cylinder heat transfer rates and cylinder surface temperature are measured.As the flame is closely surrounded by the three cooled cylinders,intense heat transfer is observed in this region corresponding to 25±2.5%of the flame thermal power.Flames were stabilised at different positions depending on inflow velocity and equivalence ratio,and a direct correlation between flame to cylinder stand-off distance and the heat transfer rate normalised to the flame thermal power was found for both top and side cylinders.Also,sidewall quenching distances to the curved cylinder surfaces were evaluated,and seem to be influenced by the presence of a warm recirculation zone behind the cylinders.This investigation provides fully resolved flame front position and heat transfer rates for a known geometry and cylinder thermal boundary conditions,and provides validation data for numerical simulations of this high flame particle coupling case.

Multi-point temperature measurements in packed beds using phosphor thermometry and ray tracing simulations

Packed bed reactors are commonly found in the process industry,for example in flame-assisted calci-nation for cement production.Understanding the heat transfer inside the bed is essential for process control,product quality and energy efficiency.Here we propose a technique to determine the internal temperature distribution of packed beds based on a combination of lifetime-based phosphor ther-mometry,ray tracing simulations,and assimilation of temperature data using finite element heat transfer simulations.To establish and validate the technique,we considered a reproducible regular packing of 6 mm diameter aluminum spheres,with one of the spheres in the top layer being electrically heated.If a sphere inside the packing is coated with thermographic phosphors and excitation light is directed to-wards the packing,luminescence from the coated sphere exits the packed bed after multiple reflection and the sphere's temperature can be determined.Isothermal measurements showed that the temper-ature obtained by phosphor thermometry is independent of the luminescent sphere location.When imaging the luminescence on a camera,the luminescence distribution in recorded image depended,however,on the position of the sphere.Therefore,in setups with multiple phosphor-coated spheres,their signals can be separated using a least squares fit.We demonstrate the approach using a setup with three luminescent spheres and validated the temperature readings against thermocouple measurements.To obtain the spatial signatures for individual sphere positions required for the least squares fit,ray tracing simulations were used.These provide an efficient alternative to single sphere measurements that are only practical for regular spherical packed beds.Multi-point measurements were used as input to a finite element heat transfer simulations to determine parameters such as particle-to-particle air gap distance.With these,the full temperature distribution inside the bed could be assimilated from the measured values.

Tbit/s line-rate satellite feeder links enabled by coherent modulation and full-adaptive optics

Free-space optical(FSO)communication technologies constitute a solution to cope with the bandwidth demand of future satellite-ground networks.They may overcome the RF bottleneck and attain data rates in the order of Tbit/s with only a handful of ground stations.Here,we demonstrate single-carrier Tbit/s line-rate transmission over a free-space channel of 53.42 km between the Jungfraujoch mountain top(3700 m)in the Swiss Alps and the Zimmerwald Observatory(895 m)near the city of Bern,achieving net-rates of up to 0.94 Tbit/s.With this scenario a satellite-ground feeder link is mimicked under turbulent conditions.Despite adverse conditions high throughput was achieved by employing a full adaptive optics system to correct the distorted wavefront of the channel and by using polarization-multiplexed high-order complex modulation formats.It was found that adaptive optics does not distort the reception of coherent modulation formats.Also,we introduce constellation modulation–a new four-dimensional BPSK(4D-BPSK)modulation format as a technique to transmit high data rates under lowest SNR.This way we show 53 km FSO transmission of 13.3 Gbit/s and 210 Gbit/s with as little as 4.3 and 7.8 photons per bit,respectively,at a bit-error ratio of 1∙10−3.The experiments show that advanced coherent modulation coding in combination with full adaptive optical filtering are proper means to make next-generation Tbit/s satellite communications practical.

Optimization of a hydrogen-based hybrid propulsion system under aircraft performance constraints

This paper addresses the topic of the conceptual design of a regional aircraft with hybrid electric propulsion based on hydrogen fuel cells.It aims at providing an optimization-based method to design a hybrid propulsive system comprising two power sources(jet fuel and hydrogen)for the generation of the required propulsive power and at studying the impact of fuel cell technologies on the aircraft performances.Indeed,by performing optimizations for two hybrid propulsive systems using either low temperature or high temperature proton-exchange membrane fuel cells,this study provides a preliminary assessment of the impact of the fuel cell operating temperature on the system design and the overall aircraft performance.First,this paper gives a description of the baseline turboprop regional aircraft with a focus on its high speed and low speed flight performances which will serve as requirements for the design of the hybrid aircraft.Then,the hybrid electric architecture and the sizing models of the propulsion system are presented.Finally,optimizations are performed to design two parallel hybrid propulsive systems based on different fuel cells technologies and aimed at minimizing the block fuel per passenger over a mission of 200 n mile.Results show how the proposed methodology and models lead to design two propulsive systems capable of reducing the fuel consumption per passenger by more than 30%compared to the baseline aircraft.The study also shows that the choice of fuel cell operating temperature has a first-order impact on the total mass.

Novel moderate transformation of fuzzy membership function into basic belief assignment

In information fusion,the uncertain information from different sources might be modeled with different theoretical frameworks.When one needs to fuse the uncertain information represented by different uncertainty theories,constructing the transformation between different frameworks is crucial.Various transformations of a Fuzzy Membership Function(FMF)into a Basic Belief Assignment(BBA)have been proposed,where the transformations based on uncertainty maximization and minimization can determine the BBA without preselecting the focal elements.However,these two transformations that based on uncertainty optimization emphasize the extreme cases of uncertainty.To avoid extreme attitudinal bias,a trade-off or moderate BBA with the uncertainty degree between the minimal and maximal ones is more preferred.In this paper,two moderate transformations of an FMF into a trade-off BBA are proposed.One is the weighted average based transformation and the other is the optimization-based transformation with weighting mechanism,where the weighting factor can be user-specified or determined with some prior information.The rationality and effectiveness of our transformations are verified through numerical examples and classification examples.