渭北人工防雹的研究与思考

分析了渭北优势果业区的地理、气象条件,通过渭北苹果优生区与世界苹果生长最适区气象条件的比较,渭北苹果生长的7项指标均符合世界苹果生长最适区的条件,是苹果产业发展的最优地区之一。但发源于白于山、子午岭、六盘山、黄龙山等地的冰雹,对渭北苹果产量和品质造成一定的影响。为了减少冰雹灾害的损失,在渭北人工防雹基地工程建设的同时,加强人工防雹科学研究的内容,从冰雹云预报预警、三维冰雹云模式、雷达探测、决策指挥、空域申请、作业实施、效果评估等方面分别提出了研究和建设内容。     

渤海海域莱州湾凹陷油气超晚期成藏与油气运移滞后效应

油气运移滞后效应是指油气从烃源岩中生成并排出的时间早,而聚集成藏的时间晚,油气经历了长时间长距离运移,已聚集成藏的油气相态与成熟度低于现今烃源岩成熟演化的现象.这种油气运移滞后效应在东部新生代陆相断陷盆地中普遍存在,在斜坡带表现最为明显.通过利用地球化学分析,平衡剖面技术、盆地模拟、包裹体分析等手段,对渤海海域莱州湾凹...     

济南市一次持续大雾过程分析

利用常规气象观测资料对2007年12月20-23日济南市一次持续大雾天气过程的大尺度天气背景、地面气压场、温度对数压力图以及单站气象要素进行了分析,结果表明:雾是在稳定的大气层结下出现的天气现象,根据大气稳定层结的状况及变化,可以判断大雾天气的有无及生消时间;近地面逆温和低空逆温同时存在,表明大气层结非常稳定,近地面逆温有利于近地面层水汽积累,低空逆温使近地面层水汽不易扩散而聚集,有利于近地面层维持潮湿,持续几天出现大雾;连续几天大气层结都处于稳定状态,地面风力很小,这些都限制了近地面层的水汽向外耗散,底层相对湿度较大,为大雾的形成提供了充沛的水汽条件.     

南京冬季城、郊下垫面能量平衡特征分析

本文利用2006年2月17日-3月2日在南京市区和郊区测得的辐射、湍流通量和脉动风速资料,定量分析了城、郊不同下垫面辐射收支、热量平衡特征及各分量的变化,结果表明:(1)不同天气条件下辐射平衡特征城、郊有一定差异,在晴天时差异最大,在下雪天时差异最小,但多云时更接近各辐射分量城、郊差异的平均特征;(2)城、郊下垫面感热和潜热分布不均,尤其是潜热城、郊对比有较大差异;(3)观测期间平均波文比(Qh/Qe)市区为7.8,与荒漠干旱地区接近,郊区为1.8.     

The STAGES view of red spirals and dusty red galaxies: mass-dependent quenching of star formation in cluster infall

We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ∼0.17 using rest-frame near-ultraviolet–optical spectral energy distributions, 24-μm infrared data and Hubble Space Telescope morphologies from the STAGES data set. The cluster sample is based on COMBO-17 redshifts with an rms precision of  σ _cz ≈ 2000 km s⁻¹  . We find that 'dusty red galaxies' and 'optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only four times lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of  log  M _*/M_⊙=[10, 11]  where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific star formation rate (SFR) of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At  log  M _*/M_⊙ < 10  , such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note that edge-on spirals play a minor role; despite being dust reddened they form only a small fraction of spirals independent of environment.     

The Origin of the Element Eu in Extremely Metal-poor Halo Stars

The fast neutron capture process (the r-process) occurs in the neutron-rich circumstance. However its concrete physical environment is not very clear. With recent progress in observations, many extremely metal-poor halo stars have been discovered. They have two characteristics: one is the overabundance of fast neutron elements with the relative abundance consistent with that of the sun; the other is that fast neutron element contents in stars at the same metal abundance have a very large dispersion. This provides a particular way to study the origin of the r-process. Simulation was used to study the galaxy's evolution process and the resulting dispersion of fast neutron nuclide contents in stars. The model of galaxy evolution obtained in this way not only contains spontaneous star formation in the gas region, but also includes the star formation excited by the supernova explosion. It is shown from our results that the supernovae at the low mass end should be the place producing the fast neutron nuclides. In addition, it is also shown that the non-uniformity of the galaxy evolution caused by the supernova explosion is not enough to explain the observed dispersion of fast neutron element contents in halo stars. This problem should be further studied.     

Effects of strong ground motion on the susceptibility of gully type debris flows

Typhoon Herb in 1996 caused widespread debris flows in central Taiwan. The 7.3 Chi-Chi earthquake on September 21, 1999, which also took place in central Taiwan, induced many landslides in the region. These landslides turned into debris flows when Typhoon Toraji struck Taiwan in 2001. This research selects three regions which suffered a ground motion class of 5, 6, and 7 on the Richter scale during the Chi-Chi earthquake as study areas. Air photos from 1997 and 2001 of these regions are used to map the gully-type debris flows that took place after Typhoons Herb and Toraji, respectively. The gullies adjacent to the debris flow, but without a trace of debris flows, are also mapped as the non-debris flow data. The topography, hydrogeology, and rainfall factors – where debris flow occurred and in which there was no occurrence of debris flows in these gullies were retrieved from DTM, geological maps, and iso-countour maps, and of rainfall through GIS processing. These characteristic are introduced into a probabilistic neural network to build a predicting model for the probability of the occurrence of debris flows. Three series of cross analyses are conducted to compare the probability of the occurrence of debris flows of the same dataset predicted by different prediction models. The results reveal that the susceptibility of debris flows was elevated after the Chi-Chi earthquake struck. The upsurge of susceptibility was more obvious for the regions that received a higher class of ground motion.     

内蒙古苏莫查干敖包萤石矿区流纹岩锆石SHRIMP定年及地质意义

内蒙古苏查（苏莫查干敖包）萤石矿区晚古生代火山沉积岩分布广泛,主要岩石类型有碳泥质板岩、结晶灰岩、凝灰岩、千枚岩、英安岩和流纹岩,其中碳泥质板岩和流纹岩为苏查特大型萤石矿床的顶和底板围岩。采用锆石SHRIMP UPb铅法分别对底板围岩中蚀变流纹岩和顶板围岩中未蚀变流纹岩样品进行了同位素年代测定,所获数据分别为276±10 Ma和271±8 Ma。蚀变和未蚀变流纹岩的形成时间均为海西晚期（早二叠世）。苏查萤石矿区早二叠世流纹岩是华北陆台与西伯利亚板块从碰撞挤压到松弛张裂转折期,酸性岩浆喷发活动的产物,其成岩物质来自壳、幔混合源。早二叠世流纹岩的出现不仅标志着苏查到西里庙地区海西期构造岩浆活动的终结,同时也为苏查特大型萤石矿床的成矿作用提供了动力、热力和物质来源。早二叠世流纹岩成岩时代的厘定不仅为阐明华北陆台北缘西段构造演化历史提供了科学依据,而且对于查明流纹岩的原岩性质和圈定新的萤石矿床找矿靶区也具有重要意义。     

四川犍为晚侏罗世一新的肉食龙类

记述了四川盆地西南部晚侏罗世上沙溪庙组顶部的中国盗龙型肉食龙类化石材料,并依此建立一新属新种——犍为乐山龙 (Leshansaurus qianweiensis gen. et sp. nov.)。它以上枕骨中嵴呈尖峰状,额骨最大长度与最大宽度之比约2.86,基蝶骨之基翼骨突细长,环椎间椎体马蹄形,背椎横突相当细长,背椎和荐椎神经棘非常薄,荐椎椎体具有明显的腹嵴,肠骨内侧髋臼缘存在一明显的嵴等特征区别于其他肉食龙类。犍为乐山龙是目前所知四川盆地产出层位最高的肉食龙材料,它的发现扩大了肉食龙类的时代分布和地理分布,对探讨肉食龙的演化具有比较重要的意义。     

Distribution and significance of novel low molecular weight sterenes in an immature evaporitic sediment from the Jinxian Sag,North China

An unusual series of C₂₂–C₂₇ monounsaturated sterenes and C₂₄–C₃₀ tetracyclic terpanes (17,21-secohopanes) were detected in relatively high concentrations in an immature evaporitic marl sediment of the Jinxian Sag, Bohai Bay Basin, North China. The site of unsaturation in these novel sterenes is assigned tentatively to the D ring on the basis of mass spectral interpretation, which also distinguishes them from reported unsaturated sterenes. Other hydrocarbon biomarker or stable isotope characteristics are indicative of microbial (e.g. methyl hopanes), phytoplankton or higher plant (depleted δ¹³C values of isoprenoids and hopanes) inputs and an anoxic carbonate depositional environment (hexacyclic hopanes; tetracyclic terpanes). The hydrocarbon composition showed no obvious biodegradation and the relatively high concentration of unsaturated terpenoids (e.g. gammacerene) and low values of other established maturity parameters (T_s/T_m = 0.23; R_o = 0.44%; T_max = 417 °C), are consistent with sediments of low maturity. The novel, low molecular weight sterenes and the tetracyclic terpanes may be early diagenetic products of microbial sources in a carbonate environment.