粤北常绿阔叶林乔木优势种群结构与格局动态

在粤北车八岭自然保护区内选择具有代表性的常绿阔叶林群落设置2 hm~2的固定样地,应用相邻格子法进行每木调查,分析乔木层优势种群结构、分布格局及生态位特征,探讨群落结构和动态及其内在联系.结果表明:(1)该群落主要优势种为米锥Castanopsis carlesii,乔木层优势树种径级结构为"L"型,群落处于相对稳定的增长阶段;(2)结合垂直分布型结构与生态位宽度分析,可知群落中米锥、荷木Schima superba等占据资源位较多,个体数量及幼苗储备丰富,对资源的竞争力最大;鸭公青Neolitsea chuii及栓叶安息香Styrax suberifolia等次之,尾尖叶柃Eurya acuminata对资源的利用和竞争力最差;(3)应用方差均值比、Lloyd平均拥挤度和聚块指数以及负二项分布指数对优势种群进行格局分析,各种群整体格局均为集群分布,但是在不同的发育阶段,随着径阶增加,种群格局逐渐由集群分布过渡到随机分布.这既与物种本身的生态和生物学特性有关,也与外界环境有密切关系.     

基于天宫二号数据的西南石漠化地区植被分类

为更好地对西南石漠化地区植被进行动态监测,将天宫二号可见光近红外数据作为一种新的数据源应用于该区域的植被分类。基于单一时相多数据源的天宫二号可见光近红外数据和Landsat8全色波段数据,采用面向对象的决策树分类法,将实验区一分为非植被、耕地、草地、灌木和乔木;基于多时相单一数据源的天宫二号可见光近红外数据,采用基于像元的决策树分类法,将实验区二分为非植被、耕地、草地、常绿灌木林、落叶灌木林、常绿阔叶林和落叶阔叶林。实验设计的3个关键点为:确定准确合理的植被分类体系、选择适宜的辅助信息改善分类效果、结合影像特征确定分类方法。结果表明,2组实验分类总体精度不低于0.70,kappa系数不低于0.61。     

广东南澳岛中华楠群落结构及种间相关性分析

基于广东南澳岛中华楠Machilus chinensis群落调查,分析了群落的结构特征、物种多样性和种间相关性.结果表明,1 400 m2的样地中,共有维管束植物45种,隶属29科39属.群落的主要优势树种为中华楠、台湾相思Acacia confusa、鸭脚木Schefflera octophylla,整个群落的Shannon-Wiener多样性指数、Margalef丰富度指数及Pielou均匀度指数均表现为灌木层＞乔木层＞草本层.16个乔木层优势树种的Pearson相关系数检验中有9个种对存在显著相关.     

C/C复合材料的压缩强度分布与可靠性评估

针对碳/碳（C/C）复合材料力学性能离散的特点，开展穿刺C/C复合材料压缩强度分布与可靠性评估研究。首先通过残差分析确定用于强度分布分析的样本数量，然后通过线性回归分析获得两参数Weibull分布、正态分布及对数正态分布模型的参数，进而探究穿刺C/C复合材料的压缩强度分布规律，最后通过Kolmogorov-Smirnov检验、Anderson-Darling检验和极大似然方法对3种强度分布模型进行拟合优度检验。结果表明：用于获得穿刺C/C复合材料压缩强度分布的最少样本数量应不少于30；Weibull分布、正态分布和对数正态分布模型均可表征穿刺C/C复合材料的压缩强度分布，其中Weibull分布的拟合优度最高；基于强度分布模型可得到不同可靠度所对应的穿刺C/C复合材料的设计强度参考值。     

冰灾对车八岭山地常绿阔叶林区系和群落的影响

研究了2008年年初南方冰雪冻雨灾害对车八岭常绿阔叶林不同区系的冠层植被所造成的影响.结果显示,研究样地内温带分布的乔木受损比例高于热带分布的乔木受损比例.X~2检验说明不同区系间的冠层乔木个体受损比例差异显著(P<0.01);东亚分布及其变型受损个体比例最小,热带亚洲至热带非洲分布及变型、东亚和北美间断分布及其变型、热带亚洲分布及其变型受损个体比例较大.冠层乔木都以重度受损为主,中度受损和轻度受损个体数都远小于前者.CCA多元分析显示,株数密度、平均胸高断面积、坡度、海拔各自对不同物种的受损乔木的分布有显著影响(Monte Carlo test,P=0.010 0).优势种米槠Castanopsis carlesii受损植株的分布与群落的平均胸高断面积显著正相关;亚优势种栲Castanopsis fargesii、鸭公青Neolitsea chuii、尾尖叶柃Eurya acuminata受损植株的分布与坡度显著负相关;亚优势种荷木Schima superb与海拔显著正相关.总之,在相同的生境中能够占据林冠优势层的区系类型往往受灾更严重.     

疲劳寿命分散系数的确定与应用研究

疲劳寿命分散系数是评估飞机结构疲劳寿命与航空发动机轮盘寿命试验的重要技术参数之一。阐述了国内外疲劳寿命分散系数研究的成果,针对工程中实际寿命分布问题中最常见的对数正态分布和威布尔分布的形式,给出了基于试验样本最差、中值、最好及第k试验寿命的分散系数表达式;重点分析总结对数正态分布标准差和威布尔分布中形状参数的选取,同应力多危险部位分散系数研究及其随应力的变化规律;通过2个例子分析了疲劳分散系数在轮盘低循环疲劳寿命工程计算中的应用,认为疲劳寿命分散系数应在不同温度和应变比,对数正态分布标准差,同应力多危险部位,3参数的威布尔分布,工程化应用等方面开展进一步研究。     

疲劳寿命分布模型及其拟合优度检验

从细观损伤力学的角度出发,建立了几种常用寿命分布所对应的物理模型,给出了相应分布中参数矢量的似然估计表达式,并采用先进拟合优度检验方法对母体分布进行了假设检验。在假定母体服从正态分布、对数正态分布或Ｗｅｉｂｕｌ分布的条件下,计算了相应疲劳寿命的Ｂ基值。     

等离子喷涂Cr_3C_2-NiCr涂层的气孔率统计分析

研究了等离子喷涂Cr3C2 NiCr涂层的气孔率服从正态分布、对数正态分布和韦伯分布的拟合优度。在统计分析的基础上 ,考察了喷枪移动速率和涂层厚度对涂层气孔率的影响。结果表明 ,在不同喷枪移动速率下喷涂不同厚度涂层 ,其气孔率均同时显著地服从正态分布、对数正态分布和韦伯分布 ,它们的变异系数在 0 .17～ 0 . 4 8,韦伯模数在 2 .0～ 6 . 2 ;根据不同分布估计出的平均值的置信区间基本相同。在相同的喷涂工艺参数条件下 ,厚度小于10 0 μm的涂层的气孔率较高 ;当涂层的厚度较厚时 ,涂层的气孔率为一常数。在 50 ,75和10 0m/min三种喷枪移动速率中 ,以 75m/min喷枪移动速率喷涂涂层的气孔率最低。     

同条件多组定数截尾试验整体数据融合方法

针对正态分布、对数正态分布、极值分布和Weibull分布等位置一尺度分布,提出一种同条件多组定数截尾试验的整体数据融合方法,能够对相同试验条件下的多组定数截尾试验数据进行综合分析,给出位置参数和尺度参数的整体融合估计,并在此基础上建立百分佗值的点估计和区间估计.与传统方法相比,该方法具有信息量大、精度高的特点,能够进行...     

疲劳损伤阀值研究

 提出了一种新的疲劳损伤阀值,它是一个随机变量。疲劳寿命在一定显著水平下服从对数正态分布,由此可以证明疲劳损伤阀值服从正态分布。另外,通过统计检验,验证线性累积损伤也服从正态分布。因此,新定义的疲劳损伤阀值与线性累积损伤之间在分布形态上是一致的。还给出了带有可靠度和置信度的疲劳损伤阀值。     

ICP-AES法测定纯铜中的Bi,Sb,As,Fe,Ni,Pb,Sn,Zn,Ag的方法

研究了ICP-AES法测定纯铜中的Bi,Sb,As,Fe,Ni,Pb,Sn,Zn和Ag等9个元素的分析方法.进行了基体元素铜对9个分析元素的光谱干扰研究,选择了合适的分析谱线,同时测定了分析方法的检出限.     

Abundances,Ionization States,Temperatures, and FIP in Solar Energetic Particles

The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding the physical processes that control populations of energetic particles. The early surprise in solar energetic particles (SEPs) was 1000-fold enhancements in \({}^{3}\mbox{He}/{}^{4}\mbox{He}\) from resonant wave-particle interactions in the small “impulsive” SEP events that emit electron beams that produce type III radio bursts. Further studies found enhancements in Fe/O, then extreme enhancements in element abundances that increase with mass-to-charge ratio \(A/Q\), rising by a factor of 1000 from He to Au or Pb arising in magnetic reconnection regions on open field lines in solar jets. In contrast, in the largest SEP events, the “gradual” events, acceleration occurs at shock waves driven out from the Sun by fast, wide coronal mass ejections (CMEs). Averaging many events provides a measure of solar coronal abundances, but \(A/Q\)-dependent scattering during transport causes variations with time; thus if Fe scatters less than O, Fe/O is enhanced early and depleted later. To complicate matters, shock waves often reaccelerate impulsive suprathermal ions left over or trapped above active regions that have spawned many impulsive events. Direct measurements of ionization states \(Q\) show coronal temperatures of 1–2 MK for most gradual events, but impulsive events often show stripping by matter traversal after acceleration. Direct measurements of \(Q\) are difficult and often unavailable. Since both impulsive and gradual SEP events have abundance enhancements that vary as powers of \(A/Q\), we can use abundances to deduce the probable \(Q\)-values and the source plasma temperatures during acceleration, ≈3 MK for impulsive SEPs. This new technique also allows multiple spacecraft to measure temperature variations across the face of a shock wave, measurements otherwise unavailable and provides a new understanding of abundance variations in the element He. Comparing coronal abundances from SEPs and from the slow solar wind as a function of the first ionization potential (FIP) of the elements, remaining differences are for the elements C, P, and S. The theory of the fractionation of ions by Alfvén waves shows that C, P, and S are suppressed because of wave resonances during chromospheric transport on closed magnetic loops but not on open magnetic fields that supply the solar wind. Shock waves can accelerate ions from closed coronal loops that easily escape as SEPs, while the solar wind must emerge on open fields.     

Electric field measurements in the solar wind,bow shock,magnetosheath, magnetopause,and magnetosphere

Electric field measurements are reported at 11 magnetopause crossings that occurred during a single in-bound ISEE-1 satellite pass near a local time of 1030. In combination with magnetic field data, these measurements show the existence of electric field components tangential to the actual magnetopause in the frame of rest of the magnetopause on every crossing of the current carrying layers associated with the 11 magnetopause traversals. These tangential electric field components were oriented with respect to the magnetopause sheet currents such that there was an electrical power dissipation of between 30 and 110 W km^-2 on 10 of the 11 crossings. These results are in agreement with requirements of reconnection theories. Histograms of the normal electric field components and of the orientation, velocity, and thickness of the current carrying layer are presented. Suggestions of the existence of a parallel electric field in the magnetosheath near the magnetopause and of propagation of large amplitude waves along the magnetopause are also made.     

ICP-OES法测定钛合金中稀土元素Y,La,Pr,Sm,Ce,Gd和Nd

进行了用电感耦合等离子体发射光谱法(ICP-OES)法测定钛合金中稀土元素Y,La,Pr,Sm,Ce,Gd和Nd的研究.研究样品的溶解,待测稀土元素分析谱线的选择,钛合金基体及共存元素对稀土元素测量的影响等,确定了待测稀土元素的分析线,校准曲线采用基体匹配消除基体效应的影响,对仪器测量条件进行优化.进行了加入回收实验.精密度和准确度结果表明:本方法快速、准确,可以满足钛合金中的稀土元素的测定要求,RSD<4%,回收率98%～105%.     

Coronal activity in F-, G-, and K-type stars

Summary Soft X-ray (0.3–3.5 keV) observations with the Imaging Proportional Counter (IPC) onboard Einstein Observatory are presented for a sample of some 20 cool stars of luminosity classes III–V. The results are compared with the Ca II H and K emission, which had served as a selection criterion.The specific X-ray flux F_X is an increasing function of the specific Ca II H and K line-core flux F_H+K. This correlation can be considerably improved by replacing F_H+K by the excess flux (F_H+K) above a certain lower limit which varies with B-V. This relation holds with little scatter over the two decades in F_X in our sample. The F_X-F_H+K relation shows no significant dependence on spectral type or luminosity class, it suits close binaries as well as single stars. However, the coronal X-ray temperature T_c strongly depends on the luminosity class: T_c 3 10⁶ K for dwarfs and 10⁷ K for giants.The results are interpreted in the framework of magnetic activity. The X-ray emission and the excess Ca II H and K flux are attributed to magnetic structure in the corona and chromosphere, the magnetic features emerging from the stellar convective envelope, where they are generated by dynamo action.     

ICP-AES法测定钛基复合材料中的Sn, Zr, Nb, Ta, Nd和Fe的研究

采用ICP-AES法对钛基复合材料中的合金元素Sn,Zr,Nb,Ta,Nd,Fe的测定进行了研究,着重进行了基体元素及待测元素Sn,Zr,Nb,Ta,Nd,Fe之间干扰试验及各元素在测定浓度范围内的线性相关性试验,进行了酸度试验及Ta,Nb,Zr的酸不溶试验,测定了钛基复合材料中上述六元素的含量,得到了较好的精密度和准确度.方法简便可靠,可获得满意的分析结果.     

在意大利米兰巡逻

<正>撒一鸣,上海机场分局浦东候机楼派出所的一名内保民警,今年5月2日至13日,他有幸被公安部选派参加了为期二周的中意首次联合警务巡逻活动,这是中国警方首次与外国警方开展合作,意义非凡。层层选拔此次远赴意大利巡逻对我来说可谓故地重游。我出生于1982年,父母曾长期在意大利工作生活,自己在意大利摩纳德完成了初中学业。此后,几经权衡,父母决定回上海发展,我也放弃了永久居留权,后报考公安专科学校成为了一名人民警     

Shared knowledge in computational fluid dynamics,electromagnetics, and magneto-aerodynamics

The rich heritage of computational fluid dynamics (CFD) has provided an in-depth knowledge for computational electromagnetics, computational magneto-aerodynamics, and multidisciplinary technology development in aerospace science. Current progress in these developing disciplines and their roots in CFD are detailed. Highlights of the frontier expanding potential for CFD by combining aerodynamics, electromagnetics, and chemical kinetics for aerospace science are also presented.