Atmospheric Ion-induced Aerosol Nucleation

Ion-induced nucleation has been suggested to be a potentially important mechanism for atmospheric aerosol formation. Ions are formed in the background atmosphere by galactic cosmic rays. A possible connection between galactic cosmic rays and cloudiness has been However, the predictions of current atmospheric nucleation models are highly uncertain because the models are usually based on the liquid drop model that estimates cluster thermodynamics based on bulk properties (e.g., liquid drop density and surface tension). Sulfuric acid (H₂SO₄) and water are assumed to be the most important nucleating agents in the free troposphere. Measurements of the molecular thermodynamics for the growth and evaporation of cluster ions containing H₂SO₄ and H₂O were performed using a temperature-controlled laminar flow reactor coupled to a linear quadrupole mass spectrometer as well as a temperature-controlled ion trap mass spectrometer. The measurements were complemented by quantum chemical calculations of the cluster ion structures. The analysis yielded a complete set of H₂SO₄ and H₂O binding thermodynamics extending from molecular cluster ions to the bulk, based on experimental thermodynamics for the small clusters. The data were incorporated into a kinetic aerosol model to yield quantitative predictions of the rate of ion-induced nucleation for atmospheric conditions. The model predicts that the negative ion-H₂SO₄-H₂O nucleation mechanism is an efficient source of new particles in the middle and upper troposphere.     

磁层氧离子向磁鞘泄漏的机制和效应

１９９７年 １月 １０日磁暴期间， Ｇｅｏｔａｉｌ卫星在向阳侧的磁鞘中观测到了磁层氧离子突增事件．这些氧离子的出现和磁鞘中存在很强的南向行星际磁场有关．事件期间向阳面发生了准静态的磁重联，氧离子流存在由北向南的速度分量．通量突增过程具有逆向和正向能量色散现象，磁层内部只有氧离子有可能被梯度漂移输送到重联区，所以只有氧离子在磁鞘中持续地被观测到．估计氧离子的逃逸速率为 ０．６１× １０２３／ｓ，大约为环电流氧离子输入率的 ３３％．大量的环电流氧离子由磁层跑到了磁鞘，导致环电流指数 ＡＳＹ－Ｈ呈现明显的非对称性．     

重金属胁迫对紫花苜蓿种子萌发的影响

本文利用发芽试验，依据土壤环境质量标准设置单一重金属铜、锌、镉胁迫浓度，研究其对紫花苜蓿种子萌发的影响；并在此基础上研究三种重金属复合污染对紫花苜蓿的胁迫作用。结果表明，在单一重金属胁迫条件下，当溶液中铜和锌的浓度分别达到20mg／L和80mg／L时，紫花苜蓿根芽长受到明显的抑制，与对照相比，差异极显著。在重金属铜、锌、镉复合污染条件下，铜、锌之间存在明显的交互作用，镉的存在会加剧铜、锌对紫花苜蓿的胁迫作用。     

航空重油发动机燃油供给系统动力学模型分析

针对航空重油发动机燃油供给系统,建立了包括一维管路流动模型、液力模型、机械模型以及电磁模型在内的完整系统数学模型.该系统模型仿真了在系统机械部件高速运动作用下,燃油供给系统内以波的扰动形式传播的非定常流动,计算得到了系统内的压力波动特性,并最终预测了系统喷油规律.经试验验证,仿真结果与试验数据吻合,该模型具有较好的准确性和较好的应用前景.      

热障涂层在线/离线磷光温度测量技术研究进展

精确测量涡轮叶片表面热障涂层温度对航空发动机和地面燃气轮机设计和研制具有极其重要的意义。近年来,基于热像磷光材料磷光特性的热障传感涂层在线测温技术与热历史磷光涂层离线测温技术得到了迅猛发展。前者通过在线测量高温下磷光信号来获取实时温度信息,后者通过离线测量经高温服役后的磷光材料不可逆磷光信号变化来获取服役温度信息。这两项技术都适用于高温、高腐蚀环境下热障涂层非干涉、非接触式和高精度温度测量,具有广阔的应用前景。从热障涂层在线/离线测温原理与方法、磷光材料与制备及应用3个方面详细介绍了热障涂层在线/离线测温技术的研究现状与技术特点,并对这两种技术的发展进行了展望。     

高能激光光束质量的测量

高能激光广泛应用于科研、工业和军事等领域,其光束质量的精确计量对激光器性能的评价及化学和固体激光武器系统的作战效能的评估至关重要。提出一种高能强激光光束质量测量装置,能实时观察光束强度分布变化,通过数据处理系统可获得光束直径、束散角、光束指向稳定性及M2因子等光束质量参数,最后分析和讨论了各测量参数的测量不确定度。     

Investigation of the Influence of Magnetic Anomalies on Ion Distributions at Mars

Using data from the Mars Express Ion Mass Analyzer (IMA) we investigate the distribution of ion beams of planetary origin and search for an influence from Mars crustal magnetic anomalies. We have concentrated on ion beams observed inside the induced magnetosphere boundary (magnetic pile-up boundary). Some north-south asymmetry is seen in the data, but no longitudinal structure resembling that of the crustal anomalies. Comparing the occurrence rate of ion beams with magnetic field strength at 400 km altitude below the spacecraft (using statistical Mars Global Surveyor results) shows a decrease of the occurrence rate for modest (< 40 nT) magnetic fields. Higher magnetic field regions (above 40 nT at 400 km) are sampled so seldom that the statistics are poor but the data is consistent with some ion outflow events being closely associated with the stronger anomalies. This ion flow does not significantly affect the overall distribution of ion beams around Mars.     

重载航空负载模拟器非线性最优前馈补偿控制

重载航空负载模拟器是用来模拟"C919"、"运-20"等重载飞机舵面工作载荷的地面仿真平台。设计了一种重载航空负载模拟器,采用非对称缸作为执行机构以在小体积下完成大载荷加载。为了消除多余力对重载航空负载模拟器加载精度的影响,分析了非对称缸正反向运动和大载荷变化下伺服阀流量增益的非线性变化对前馈补偿函数的影响,并设计了非线性参数估计控制器。同时分析了加速度等动态参数变化和静态参数的误差对多余力消除的影响,设计了参数最优控制器。仿真和试验结果均表明,相比于传统前馈补偿控制器,所设计的非线性最优前馈补偿控制器下的加载精度和多余力抑制能力提高了50%以上。     

角接触球轴承在高速大载荷工况下滑油中断耐受能力分析

通过研究角接触球轴承断油故障的故障复现现象,发现断油耐受能力不足的初期故障模式为滚动体与内圈之间发生三点接触。使用三点接触分析法对轴承断油耐受能力进行计算,结合相似轴承的计算分析,结果表明:垫片角越大,轴承抗断油能力越差,垫片角为25°的情况下轴承抗断油能力较差。通过断油后轴承的瞬态温度场分析,结合三点接触分析法,确定原设计状态的轴承断油耐受时间为25 s,不具备耐受断油30 s的能力。根据分析的结论,将该轴承的垫片角减小到19°,落实改进措施后的轴承通过了试验器验证和发动机试车验证。      

RPC-ICA: The Ion Composition Analyzer of the Rosetta Plasma Consortium

The Ion Composition Analyzer (ICA) is part of the Rosetta Plasma Consortium (RPC). ICA is designed to measure the three-dimensional distribution function of positive ions in order to study the interaction between the solar wind and cometary particles. The instrument has a mass resolution high enough to resolve the major species such as protons, helium, oxygen, molecular ions, and heavy ions characteristic of dusty plasma regions. ICA consists of an electrostatic acceptance angle filter, an electrostatic energy filter, and a magnetic momentum filter. Particles are detected using large diameter (100 mm) microchannel plates and a two-dimensional anode system. ICA has its own processor for data reduction/compression and formatting. The energy range of the instrument is from 25 eV to 40 keV and an angular field-of-view of 360° × 90° is achieved through electrostatic deflection of incoming particles.