An Estimate of Microwave low-Brightness-Temperature Regions' Heights Obtained Measuring Their Rotation Velocity     

Brajša  R.  Ruždjak  V.  Vršnak  B.  Wöhl  H.  Pohjolainen  S.  Urpo  S. 《Solar physics》1999,184(2):281-296

Daily full-disk solar maps obtained at 37 GHz in the years 1979, 1980, 1981, 1982, 1987, 1988, 1989, 1990, and 1991 are analysed and compared with full-disk solar maps in H. A search for a difference in the measured angular rotation velocity for two classes of microwave low-brightness-temperature regions (LTRs), associated and not associated with H filaments, is performed. Procedures with and without statistical weights, assigned to angular rotation velocities according to the tracing time, are applied and the statistical significance of the results is discussed. A higher angular rotation velocity is measured for LTRs associated with H filaments than for the not-associated ones. This angular velocity difference is interpreted as a consequence of a height difference between these two types of LTR tracers. Changes of the solar differential rotation velocity during the activity cycle measured using LTRs as tracers are explained by the measured cycle-dependence of the association rate between LTRs and H filaments. Similarly, the north–south asymmetry in the solar rotation velocity measured tracing LTRs is explained by the measured north–south asymmetry in the association rate between LTRs and H filaments. The rotation velocity of LTRs and H filaments is on the average more rigid in comparison with sunspots.  相似文献   

The system of the Milky Way, LMC and SMC     

Adam Ružčka 《Astrophysics and Space Science》2003,284(2):519-522

A simple sticky-particle numerical model has been developed in order to check whether extended structures of gas created due to the dynamical evolution of the Galaxy and the Magellanic Clouds system can be explained as remnants of a tidal interaction. Influence of dissipative nature of gaseous medium has been taken into account. The most remarkable features are: the Magellanic Stream, the common HI envelope surrounding both the LMC and SMC and the bridge extended between the Clouds. In contrast to previous works of Murai and Fujimoto (1980), Gardiner et al. (1994) and H and Rohlfs (1994) no presumptions were done on the actual galactocentric velocities of the Magellanic Clouds. The mean values of the LMC and SMC velocity vectors obtained from the Hipparcos proper motion measurements (Kroupa and Bastian, 1997) were used in order to verify whether they allow to reproduce the observed HI distribution. Numerical simulations showed that tidal forces are really significant for the evolution of extended structures such as the Magellanic Stream but this approach becomes unsufficient for the internal regions of galaxies where self-gravity and dissipative properties of the gas cannot be neglected. More precise proper motion measurements are urgently needed. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

地图印前计算机辅助设计软件系统研究与实践   总被引：1，自引：0，他引：1  

安如  潘涛  王慧麟  赵萍 《测绘工程》2002,11(4):29-32

介绍地图印前系统在我国产业部门应用概况及计算机图形辅助设计软件用于地图印前系统的三个共性问题。以计算机图形辅助设计软件MicroStation95为例,详细探讨该软件用于地图印前制作所涉及的技术要点。并以《南京市教育地图》为例,对用该软件进行彩色地图编制与出版的优点与局限性进行了探讨。  相似文献   

A Method to Determine the Solar Synodic Rotation Rate and the Height of Tracers     

Roša  D.  Vršnak  B.  Božić  H.  Brajša  R.  Ruždjak  V.  Schroll  A.  Wöhl  H. 《Solar physics》1998,179(2):237-252

The dependence of the measured apparent synodic solar rotation rate on the height of the chosen tracer is studied. A significant error occurs if the rotation rate is determined by tracing the apparent position of an object above the photospheric level projected on the solar disc. The centre-to-limb variation of this error can be used to determine simultaneously the height of the object and the true synodic rotation rate. The apparent (projected) heliographic coordinates are presented as a function of the height of the traced object and the coordinates of its footpoint. The relations obtained provide an explicit expression for the apparent rotation rate as a function of the observed heliographic coordinates of the tracer, enabling an analytic least-squares fit expression to determine simultaneously the real synodic rotation rate and the height of the tracer.  相似文献   

东海区鲳鱼资源利用现状分析     

柳卫海  詹秉义 《广东海洋大学学报》1999,(1)

通过对东海区鲳鱼近年群体组成变化及银鲳生物学特性变化来分析目前鲳鱼资源利用状况,结果表明：一方面,虽然近年鲳鱼产量大幅增加,但其平均体重、优势叉长组成及年龄组成均出现明显下降,资源状况日益恶化；另一方面,1龄鱼已占渔获的93．68％,目前捕捞现行点开捕年龄tc=1和捕捞死亡系数F＝2．51,单位补充量繁殖力相对百分比P＜1．9％,单位补充量渔获量(Yw／R)为70g／尾,均显示已处于严重的生物学型捕捞过度．建议渔业管理部门大力削减作业渔船约50％,严格控制捕捞强度,逐步推迟开捕年龄至3龄以上,使鲳鱼资源真正能够永续利用。  相似文献   

Innovation-based urbanization: Evidence from 270 cities at the prefecture level or above in China     

Lyu  Lachang  Sun  Feixiang  Huang  Ru 《地理学报(英文版)》2019,29(8):1283-1299

Journal of Geographical Sciences - With the rapid development of knowledge economy, a number of important shifts are emerging in urbanization pattern across the world. Traditional urbanization...  相似文献   

碳酸盐岩碳同位素地层学研究中数据的有效性   总被引：3，自引：0，他引：3  

樊茹  邓胜徽  张学磊 《地层学杂志》2010,34(4)

碳酸盐岩碳稳定同位素组成数据能否有效地反应原始大洋的同位素组成是稳定同位素地层学研究成败的关键,因此,如何准确地判断碳同位素比值的有效性成为该稳定同位素地层学研究中的焦点问题之一。碳同位素值有效性受成岩作用、地层缺失、样品处理过程等多方面因素影响,但成岩作用是诸多因素中最普遍、最主要的,因而正确判别碳同位素值可靠性通常也就是对样品及其同位素组成经受成岩改造程度的评定。确保碳同位素测试结果可靠应主要把握前期严格选样和后期数据分析两个重要环节。前期选样包括野外和室内两步,是在宏观尺度上对数据可靠性的把握;后期数据分析则主要是在严格选样的基础上,利用碳(及附带的氧)同位素自身数据特征以及借助Mn、Fe、Sr等微量元素特征从元素级别的微观角度对同位素值有效性做出进一步判别。  相似文献   

Eutrophication,health risk assessment and spatial analysis of water quality in Gucheng Lake,China   总被引：1，自引：1，他引：0  

Feng Cun Yu  Guo Hua Fang  Xiang Wen Ru 《Environmental Earth Sciences》2010,59(8):1741-1748

The water characteristics of the Gucheng Lake, such as eutrophication, health and spatial distribution, were investigated. On the basis of the trophic state index (TSI) and entropy weight, a synthesized trophic state index (STSI) model was established to assess lake eutrophication condition through calculating STSI, choosing TP, TN, COD, BOD and NH₃-N as trophic variables. The STSI ranged from 50.58 to 62.44, which showed that the water has been between eutrophic and supereutrophic. A histogram was applied to health risk assessment which was analyzed from carcinogenic substances (Cr⁺⁶, As and Cd) and non-carcinogenic substances (hydroxybenzene, Pb, Hg, CN⁻ and NH₃), and the results showed that the former was much greater than the latter for effect. The total risk for each resident caused by all pollutants ranged from 5.18E-05 to 8.34E-05, which is far higher than the standard, recommended by Sweden Bureau of Environment Protection and Holland Ministry of Building and Environment Protection (1.0E-05). Cluster analysis was used to detect similarities and dissimilarities among the seven sampling sites and explain the observed clustering in terms of affected conditions. Twenty-one variables were used to divide seven sampling sites into three groups, namely, north lake, south lake and lake center.  相似文献   

南沙群岛南科1井白云岩发育特征及铁白云石成因机制的初步研究*     

韩雪  徐维海  罗云  黎刚  刘建国  朱小畏  程俊  苗莉  向荣  颜文 《热带海洋学报》2022,41(5):74-88

南海自新生代以来发育了大量的碳酸盐岩台地和生物礁, 并普遍发生白云岩化作用, 具有广阔的油气勘探前景。文章通过开展岩相学观察、矿物学分析、常微量元素和碳氧同位素分析, 同时结合Fe组分及Fe同位素地球化学分析, 对南沙群岛南科1井白云岩的发育特征和成岩环境进行了系统研究。结果表明: 南科1井上中新统—下更新统白云岩主要形成于近地表环境中, 溶蚀孔隙发育, 残余结构明显。白云岩层中发育有多个与暴露成因有关的界面, 未发现石膏层的存在。同时, 白云岩普遍具有低Fe、Mn和Sr的特征以及与现代海水相似的REE分布模式, δ¹³C和δ¹⁸O多为正值, 但不存在相关性。整体来看, 白云岩可能形成于轻微蒸发海水的渗透回流作用, 还受到了与古气候变冷有关的海平面下降的控制。此外, 南科1井岩芯中多个层位发育铁白云石, 并且集中分布在暴露面附近。Fe组分和Fe同位素组成结果显示, 白云岩中Fe主要来源于海水中碳酸盐的沉淀, 成岩过程中基本不存在额外的陆源或热液来源的Fe混入。铁白云石主要形成于低温和浅埋藏环境中, 大气淡水对生物骨架、生物碎屑以及自生碳酸盐矿物的淋滤-溶解作用为其提供了重要的物质来源。作为生物礁体暴露地表期间的产物, 铁白云石的发育层位可能指示着低海平面时期。  相似文献   

近55年广西融水县降水气候特征分析     

谭敏玲  何如  罗红磊 《气象研究与应用》2014,35(3):27-30

利用融水县气象站1959-2013年的降水资料,采用数理统计和线性倾向估计分析方法,分析了融水县降水分布特征及其变化规律。结果表明：融水县降水分配不均,主要集中在4-8月,6月最多,5月次之;年暴雨日数6.9d,暴雨持续时间多为1d,最长4d;近55年来融水县年降水量和汛期（4-9月）降水量均呈减少趋势,每10年分别减少16mm和6mm,而主汛期（5-8月）的降水量却呈增多趋势,每10年增加13mm,这预示着融水县未来降水可能更趋于集中在主汛期（5-8月）,发生洪涝灾害的几率可能增多。此外,一日最大降水量呈增多趋势,预示未来降雨强度可能增大;春、秋季的降水量呈减少趋势,提示未来发生春旱、秋旱的几率可能增多。  相似文献