Experimental study of hydrogen-rich/oxygen-rich gas-gas injectors

Five types of coaxial injectors were investigated experimentally using hot hydrogen-rich gas and oxygen-rich gas, which were respectively provided by a GH2/GO2 hydrogen-rich perburner and a GH2/GO2 oxygen-rich preburner. The injectors were the shear coaxial injector, the oxidizer post expansion coaxial injector, the fuel impinging coaxial injector, the central body coaxial injector, and the shear tri-coaxial injector. The characteristic velocity efficiency and the combustor＇s wall temperatures were obtained for different design parameters through the experiments. It can be con- cluded that angles of the oxidizer post expansion and the fuel impinging have little influence on the combustion performance and the wall temperatures. The contact area between fuel and oxidizer and the mass flow rate have significant impacts on the combustion performance. The shear tri-coaxial injector has the best combustion performance but also the highest wall temperatures among the five types of injectors.     

基于变速积分的高速电机磁悬浮控制系统设计

针对磁悬浮高速电机的磁轴承-转子系统,设计了基于MCU+FPGA的数字控制系统。为实现转子系统的高转速下稳定控制,在建立了磁轴承-转子闭环控制系统模型的基础上,针对常规PID控制系统的超调振荡问题和PD控制系统的转子位移静差问题,利用变速积分的思想设计了改进的PID控制器。实验表明,在消除了系统静差的同时明显减小了系统的超调量和调节时间,说明设计的控制系统具有很好的动态特性和稳态精度。     

喷射成形过程雾化熔滴质量流率空间分布的研究

喷射成形是材料领域新出现的高新科学技术。本文研究了喷射成形雾化熔滴射流质量流率和沉积速率的分布规律，建立了它的空间分布函数。结果表明随着雾化压力的增加和沉积距离减小，雾化喷射流变得更集中。     

Provocative radio transients and base rate bias: A Bayesian argument for conservatism

Most searches for alien radio transmissions have focused on finding omni-directional or purposefully earth-directed beams of enduring duration. However, most of the interesting signals so far detected have been transient and non-repeatable in nature. These signals could very well be the first data points in an ever-growing data base of such signals used to construct a probabilistic argument for the existence of extraterrestrial intelligence. This paper looks at the effect base rate bias could have on deciding which signals to include in such an archive based upon the likely assumption that our ability to discern natural from artificial signals will be less than perfect.     

浅论无人机机载卫通天线尺寸与数字信号传输带宽关系

卫星通信是无人机中继通信的重要手段。本文对无人机卫星通信链路中飞机总体设计关注的机载卫通天线尺寸选择问题进行了较详细的计算、探讨。     

Quantum dosimetry and online visualization of X-ray and charged particle radiation in commercial aircraft at operational flight altitudes with the pixel detector Timepix

We investigate the application of the hybrid semiconductor pixel detector Timepix for precise characterization, quantum sensitivity dosimetry and visualization of the charged particle radiation and X-ray field inside commercial aircraft at operational flight altitudes. The quantum counting capability and granularity of Timepix provides the composition and spectral-characteristics of the X-ray and charged-particle field with high sensitivity, wide dynamic range, high spatial resolution and particle type resolving power. For energetic charged particles the direction of trajectory and linear energy transfer can be measured. The detector is operated by the integrated readout interface FITPix for power, control and data acquisition together with the software package Pixelman for online visualization and real-time data processing. The compact and portable radiation camera can be deployed remotely being controlled simply by a laptop computer. The device performs continuous monitoring and accurate time-dependent measurements in wide dynamic range of particle fluxes, deposited energy, absorbed dose and equivalent dose rates. Results are presented for in-flight measurements at altitudes up to 12 km in various flights selected in the period 2006–2013.     

当前经济增长的周期性、阶段性特征及政策思路

根据经济周期谷底的特性以及中美两国经济紧密关联和经济周期越来越契合的规律,可以印证2009年就是新一轮经济周期的谷底,由此可以断定当前处于复苏阶段.然而近三年来我国经济增速持续下滑至谷底以下,这一反常现象是由于经济短周期冲高回落与经济增长阶段转换相互叠加造成的.河南省与全国经济周期高度一致,时滞半年左右.在高速经济增长阶段河南省潜在经济增长率比全国高出2个百分点,中高速阶段高出1.5个百分点.河南省近几年经济增速深度下滑,其关键原因是投资增速下滑,其根本原因是结构升级缓慢.未来河南经济要摆脱持续下行趋势,保持经济中高速增长,应坚持调结构、扩投资、促改革的政策思路,“调结构”是根本,“扩投资”是基础,“促改革”是保障.     

An aggregate flow based scheduler in multi-task cooperated UAVs network

Unmanned Aerial Vehicles (UAVs) cooperative multi-task system has become the research focus in recent years. However, the existing network frameworks of UAVs are not flexible and efficient enough to deal with the complex multi-task scheduling, because they are not able to perceive the different features. In this paper, a novel cooperated UAVs network framework for multi-task scheduling is proposed. It is a three-layer network including a core layer, an aggregation layer and an execution layer, which enhances the efficiency of multi-task distribution, aggregation and transmission. Furthermore, an AggreGate Flow (AGFlow) based scheduler is dedicatedly designed to maximize the task completion rate, whose key point is to aggregate flows belonging to one task during the multi-task transmission of UAVs network and to allocate priority by calculating the urgency-level of each AGFlow. Simulation results demonstrate that, compared with that of state-of-the-art scheduler, the average task completion rate of AGFlow based scheduler is raised by 0.278.     

Variations of geomagnetic cutoff rigidity in the southern hemisphere close to 70°W (South-Atlantic Anomaly and Antarctic zones) in the period 1975–2010

We report the existence of rapid variations in (effective) geomagnetic cutoff rigidity (Rc) between the equatorial and Antarctic zones adjacent to the Andes Mountains, revealed by the variation rate of geomagnetic cutoff rigidity (VRc) in the period 1975–2010. Our analysis is based on empirical records and theoretical models of the variations in cosmic rays and on the structure of geomagnetic fields. These have given us a different view of variations in Rc in time and space along the 70°W meridian, where secular variations in the geomagnetic field are strongly influenced by the proximity of the South Atlantic Magnetic Anomaly (SAMA), one of the most important characteristics of the terrestrial magnetic field that affects our planet, close from the equator to the 50°S parallel and from South America to South Africa. The VRc presents rapid changes in mid-latitudes where SAMA exerts its influence despite the existence of smooth changes in the geomagnetic field. This shows that these changes occur mainly in the spatial configuration, rather than in the temporal evolution of Rc. The analysis was performed using measurements from the Chilean Network of Cosmic Rays and Geomagnetism Observatories, equipped with BF-3 and latest generation He-3 neutron monitors, Fluxgate magnetometers, geomagnetic reference field (IGRF) and Tsyganenko 2001 model (just for completeness).     

针栓式喷注单元雾化角模型分析

为了实现不同径向孔形的针栓式喷注器雾化角的准确预测，从动量守恒方程出发建立了液膜撞击液膜和液膜撞击液束的雾化角理论修正模型。对于液膜撞击液膜的喷注单元，模型中通过理论推导引入了2个变形因子，将撞击的几何变形效应与雾化角关联；对于液膜撞击液束，通过引入阻塞率定义有效撞击动量比，同时将液束入口孔形的影响隐含考虑在变形因子中，最后根据高速摄影试验结果和数值仿真结果获得了对应的变形因子组合系数，使得新的雾化角模型适应性更广、准确性更高。结果表明：引入变形因子和阻塞率的理论模型预测值与试验及数值仿真结果吻合很好；对于液膜撞击液膜，变形因子基本维持在0.9~1.1，根据试验结果及仿真结果，变形因子推荐值为C₁=0.99和C₂=1.06；对于液膜撞击液束，变形因子推荐值为C₁=0.75和C₂=1.25。该模型根据实际出口的轴向动量和合成总动量计算雾化角，隐含考虑了撞击作用造成的影响，较根据撞击前入口的轴向动量和合成总动量计算雾化角的常用模型预测值准确度显著提高，为针栓式喷注器的理论研究和工程设计提供了重要参考。