1米太阳望远镜光谱仪像旋转及消旋控制     

柳光乾  付玉  程向明 《天文研究与技术》2012,(1):86-92

光谱仪是1 m太阳望远镜的主要终端设备之一,该望远镜采用地平式的机架结构和修正的格里高利光学系统。在望远镜跟踪太阳时,由于地平式望远镜的自身运动特点和光学系统中平面反射镜的存在,其光谱仪狭缝所在平面上的太阳像随时间绕主光轴旋转,因此光谱仪必须进行消旋才能正常工作。首先深入研究了光谱仪狭缝平面上像的旋转变化,分析其旋转范围、速度和加速度随时角变化的特性,然后根据光谱仪消旋精度并结合像的旋转特性提出伺服系统位置检测和驱动电机的主要性能指标,最后给出光谱仪消旋伺服控制方案。  相似文献   

Microbial influence on erosion,grain transport and bedform genesis in sandy substrates under unidirectional flow     

JAMES W. HAGADORN  CONOR MCDOWELL 《Sedimentology》2012,59(3):795-808

Interpreting the physical dynamics of ancient environments requires an understanding of how current‐generated sedimentary structures, such as ripples and dunes, are created. Traditional interpretations of these structures are based on experimental flume studies of unconsolidated quartz sand, in which stepwise increases in flow velocity yield a suite of sedimentary structures analogous to those found in the rock record. Yet cyanobacteria, which were excluded from these studies, are pervasive in wet sandy environments and secrete sufficient extracellular polysaccharides to inhibit grain movement and markedly change the conditions under which sedimentary structures form. Here, the results of flume experiments using cyanobacteria‐inoculated quartz sand are reported which demonstrate that microbes strongly influence the behaviour of unconsolidated sand. In medium sand, thin (ca 0·1 to 0·5 mm thick) microbial communities growing at the sediment–water interface can nearly double the flow velocity required to produce the traditional sequence of ripple→dune→plane‐bed lamination bedforms. In some cases, these thin film‐like microbial communities can inhibit the growth of ripples or dunes entirely, and instead bed shear stresses result in flip‐over and rip‐up structures. Thicker (ca≥1 mm thick) microbial mats mediate terracing of erosional edges; they also, foster transport of multi‐grain aggregates and yield a bedform progression consisting of flip‐overs→roll‐ups→rip‐ups of bound sand.  相似文献   

新疆西准噶尔巴尔鲁克蛇绿混杂岩带发现蓝闪片岩   总被引：3，自引：0，他引：3  

赵文平  贾振奎  温志刚  李育敬 《西北地质》2012,(2):136-138

通过1∶25万区调修测工作,确认了巴尔鲁克蛇绿构造混杂岩(带)的存在.在野外调查与研究工作中,发现该蛇绿岩(带)组分较为齐全,在其中还发现了蓝闪片岩,这对研究巴尔鲁克蛇绿构造混杂岩(带)及本地区的地质构造演化具有重要意义.  相似文献   

白云鄂博矿区北部韧性剪切带特征及其构造意义   总被引：1，自引：0，他引：1  

王俊  吕洪波  章雨旭  柳建勇  李旭平  黄敏  孟庆伟 《地质学报》2012,86(5):785-792

在白云鄂博主矿北西约6.5km处的查干楚鲁一带,有一条近东西向延伸的断层带,前人在该带中部识别出了蛇绿岩混杂堆积。本文作者在蛇绿岩东部的大理岩质糜棱岩中发现鞘褶皱、拉伸线理及旋转碎斑系等变形构造,在大理岩周围发现石英岩型宏观压力影构造,在变质石英砂岩中识别出褶劈理以及方解石脉等相关构造,在这条东西向断裂带北边发现典型的黄铁矿型压力影。根据上述特征判断,查干楚鲁一带为一条近东西向延伸的韧性剪切带,同时具有NEE—SWW向逆左旋走滑的特征。该带揭示出蒙古洋板块与华北板块在晚古生代汇聚拼合的基本格局。  相似文献   

世界海拔8000m以上雪山研究     

米德生 《冰川冻土》2012,34(2):382-391

实地科考,广博查询,长期探索,坚韧追求,人类首次、全面解开世界海拔8 000m以上雪山之迷:海拔8 000m级雪山地有17处(其中3处山地为新发现),面积共11.95414km2,海拔8 000m以上独立山峰39座.世界海拔8 000m级山地和山峰地貌形态、相互关系,己在即将出版的"世界八千米雪山地图集"中得到表示.该图集比例尺1∶100000,等高距40m,幅面550mm×790mm.该图集由序言、7幅地图和后记组成,是世界第一部关于海拔8 000m级雪山地图集.  相似文献   

新疆萨尔托海石英菱镁岩中发育的韧性剪切带及其对金矿的控制   总被引：3，自引：2，他引：1  

邱添  朱永峰 《岩石学报》2012,28(7):2250-2256

萨尔托海金矿产在达拉布特蛇绿混杂岩带中。本文首次在该金矿区厘定出韧性剪切带,糜棱岩或者糜棱岩化石英菱镁岩中构成糜棱面理的矿物(铬云母、石英)形成于韧性剪切变形过程中,而切割糜棱面理的方解石-石英-黄铜矿-白云母脉代表脆性变形阶段的流体活动。根据矿物组合相互切割关系,识别出三期构造变形:早期NE向韧性变形(形成铬云母-石英组合)之后,发生了应力方向显著不同的破裂,形成NNW向分布的方解石-石英-黄铜矿-白云母脉;再晚期,应力方向又恢复到NE向,发育了浅层次的脆性构造破坏,形成了白云母-石英细脉。韧性剪切变形向脆性变形转换期间形成了石英-碳酸盐脉,其中往往含硫化物和自然金,此阶段是萨尔托海金矿的主要成矿时期。韧性剪切带控制着萨尔托海地区的金矿分布,成矿作用主要受沿剪切带迁移流体的控制,穿切糜棱面理的方解石-石英-黄铜矿-白云母脉是主要的找矿标志。韧性剪切带对金矿的显著控制表明,韧脆性转换期间形成的含硫化物石英碳酸盐脉以及相伴生的热液蚀变使金富集成矿,矿体一般赋存在断裂构造复杂的膨胀部位。萨尔托海金矿的成因与蛇绿岩的形成和演化没有关系。对韧性剪切带的系统研究是在该地区取得找矿勘探突破的关键。  相似文献   

T213L31全球中期数值天气预报系统2m温度预报误差源分析   总被引：9，自引：0，他引：9  

佟华  姚明明  王雨  陈起英  管成功 《气象》2006,32(2):52-57

T213L31全球中期数值天气预报系统的2m温度预报存在系统性偏低的问题，对业务预报影响很大，针对这一问题就产生原因对模式系统进行分析定位。经过一系列分析，通过对模式地形高度与观测站地形高度的比较，以及通过采用欧洲中心与国家气象中心的陆面过程初值得到的2m温度的比较，认为2m温度的误差是由于模式地形高度与实际地形高度存在较大差异以及2m温度预报对陆面过程所需的初值如土壤湿度等的敏感而实际采用特定值代替初始场的不科学性造成的。  相似文献   

Gaseous and Particulate Oxidation Products Analysis of a Mixture of α-pinene + β-pinene/O3/Air in the Absence of Light and α-pinene + β-pinene/NOx/Air in the Presence of Natural Sunlight     

M. Jaoui  R. M. Kamens 《Journal of Atmospheric Chemistry》2003,44(3):259-297

The gas and particle phase reaction products of a mixture of the atmospherically important terpenes -pinene and -pinene with the atmospheric oxidants O₃ and OH/NO_x were investigated using both gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) for identification and quantification of reaction products. The nighttime oxidation of a mixture of -pinene and -pinene in the presence of O₃/air, and the daytime oxidation of a mixture of -pinene + -pinene with NO_x air in the presence of natural sunlight were carried out in the University of North Carolina's large outdoor smog chamber (190 m³) located in Chatham County, North Carolina. Mass balances for gaseous and aerosol reaction products are reported over the course of the reaction. More than twenty-nine products were identified and/or quantified in this study. On average, measured gas and particle phase products accounted for 74 to 80% of the reacted -pinen/-pinene mixture carbon. Measurements show that a number of reaction products were found in both O₃ and NO_x system [pinonaldehyde, pinic acid, pinonic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, 4-oxonopinone, 1-hydroxy-nopinone, 3-hydroxy-nopinone, and nopinone]. Pinonic acid, pinic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, and 10-hydroxypinonic acid were observed in the early stage in the aerosol phase and may play an important role in the early formation of secondary aerosols.  相似文献   

Short Time Lyapunov Indicators in the Restricted Three-Body Problem     

Zsolt Sàndor  Róbert Balla  Ferenc Téger  Bálint Érdi 《Celestial Mechanics and Dynamical Astronomy》2001,79(1):29-40

We applied the method of the short time Lyapunov indicators to the planar circular and to the planar elliptic restricted three-body problem in order to study the structure of the phase space in some selected regions. In the circular case we computed the short-time averages of the stretching numbers to distinguish between regular and chaotic domains of the phase space. The results obtained in this way are in good agreement with the corresponding Poincaré's surface of sections. Using the short time Lyapunov indicators we determined the detailed structure of the phase space in the semi-major axis-eccentricity plane of the test particle both in the circular and in the elliptic restricted problem (in the latter case for some values of the eccentricities of the primaries) and we studied the main features of the phase space.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

GPS-Based On-Board Orbit Determination of a Satellite Using Extended H ∞ Filtering Algorithms     

Jinlu Kuang  Soonhie Tan  Youfa Wang 《Celestial Mechanics and Dynamical Astronomy》2004,88(2):103-122

In this paper the extended H filtering algorithms for the design of the GPS-based on-board autonomous navigation system for a low earth orbit (LEO) satellite are introduced. The dynamic process models for the estimation of position, velocity and acceleration from the GPS measurements are established. The nominal orbit of the small LEO satellite is determined by using the 7th–8th order Runge—Kutta algorithms. Three filtering approaches are applied to smooth the orbit solutions, respectively, based upon the simulated GPS pseudo range observables using the Satellite Navigation Tool Box. The simulation shows that the observed orbit errors obtained by using the extended H filtering algorithms can be reduced to a lower level than the observed orbit errors in the sense of RMS within 12 h of tracking time by using the H filtering algorithms and the extended Kalman filtering algorithms under the appropriately designed parameters. Based upon the position errors predicted by the three filtering algorithms after the last observation, we find that the extended H filtering algorithm provides the least position errors of the user satellite.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献