地形在高大金字塔沙山形成发育过程中的作用——以敦煌鸣沙山-月牙泉地区为例

地形在金字塔沙山形成发育过程中起着重要的作用。金字塔沙山通常形成于山前地带,应属于地形屏障影响下形成的一种沙丘类型。首先,上升气流的发育是山前风阻区气流的主要特征,地形屏障是上升气流发生发展的主要原因。沙山的坡脚、坡中及坡顶分别是上升气流的启动区、发育区及衰退区。上升气流是沙山增高增大发育的主要机制。其次,金字塔沙山多发育于局地环流发育较强的地带,局地环流与区域风况配置是形成复杂沙丘类型的重要因素。本区局地环流偏南风不仅持续时间长,且受到鸣沙山微地形的影响,下坡气流较强。实地观测结果破解了常规气候台观测数据难以揭示上升气流及局地环流对金字塔沙丘形成发育的影响。第三,下附地形在沙山形成发育过程中决定着沙丘发育的“临界尺度”,即丘体达到“临界尺度”的时候,坡面上升气流及风速放大作用逐渐显现,促使丘体增高增大发育,随着沙丘形态与上升气流的互馈作用进一步增强,金字塔沙丘逐渐形成演化为高大沙山。实地观测进一步证实了金字塔沙山是纵向（横向）沙丘形变的一种形式。并提出了金字塔沙山在地形条件下形成演化的一种新模式。     

新疆阿拉套山花岗岩类的岩石化学

新疆阿拉套山南坡东西向展布的花岗岩石的岩石化学研究表明，本区同时存在Ｉ型和Ｓ型两种类型的花岗岩，其分布受构造环境控制，靠近古板块缝合线为Ｉ型花岗岩分布区、远离古板块缝合线为Ｓ型花岗岩分布区。源岩性质和作用强弱等因素可能是造成岩石化学成分差异的原因。     

荒漠生态系统C、N、P生态化学计量研究进展

生态化学计量学是通过研究生物有机体主要元素含量及其比值的变化关系,揭示生态系统各组分间元素循环规律的一门学科,生态化学计量也是荒漠生态系统研究的重要内容。因此,综合掌握水分和养分限制环境下C、N、P生态化学计量的关系对揭示荒漠生态系统植物的限制性元素、土壤营养的供给能力、养分的有效性等都具有重要的意义。基于此,回顾和分析了国内外荒漠生态系统C、N、P生态化学计量最新研究和动态,分别从植物、凋落物、土壤、土壤微生物、土壤酶进行较为系统的评述,讨论了植物-土壤-微生物-酶四者的关系,提出了荒漠生态系统C、N、P生态化学计量的未来研究方向,期望为全面理解固沙植被的演变过程、稳定性维持机制及其科学管理提供理论指导。     

BORDER PORT MANZHOULh URBAN FUNCTION AND SPACE DEVELOPMENT

Manzhouli is the largest land port city on the Sino-Russia border, transit cargo through the land port amount-ed to 5.95 million tons, transit tourists were 304 500 in 2000. It stands at the joint place of China, Mongolia and Russi-a, faces to Siberia area of Russia, receives direct support from the Northeast China and Bohai Sea Rim Area, and possess-es priorities in geographical location, land port infrastructure, water resources, coal resources, tourist resources andgreat potentiality in economic cooperation with Russia. The future urban function is a key port on the First Eurasia Continen-tal Bridge. Manzhouli Port will keep its first place between China and Russia land transport, and it is forecasted that thetransit amount through Manzhouli Port will go up to 10 million tons in 2005 and 20 million tons in 2010. It will be construct-ed to be a trade center of the peripheral area extending to Russia and Mongolia, a key export-oriented processing industri-al zone supported by industries such as export processing industries, export agriculture, trade services, technology trad-ing and the other service industries. It keeps being a well-known touring city for trade, shopping, sightseeing, vocation,local food, recreation and cultural events. To build Manzhouli Export Processing Industry Zone will improve city econom-ic structure, and the main sectors are organic food processing, livestock products processing, garment and furniture indus-try. Moreover, Manzhouli Export Processing Industry Zone will eventually be upgraded to be a border free trade zone.The city functional transition will inevitably affect urban spatial restructure and its expansion. The city space transforma-tion will develop as such: one development axis of No. 301 highway paralleling with Bin - Zhou(Harbin - Manzhouli) rail-way which cuts through central part of Manzhouli City, and links Zhalainuocr District with central city; three urban unitsincluding central city, Zhalainuocr District and Manzhouli Interchange Trade Zone; cohesion with Aoerjin and Cuogangpastures; regional dual-nuclei structure of Hailaer City and Manhzouli City; and the Manzhouli-Zabaykalsk Free TradeZone.     

东南极拉斯曼丘陵石榴斜长角闪岩中角闪石的~(40)Ar-~(39)Ar年龄及其地质意义

本文对东南极拉斯曼丘陵出露的石榴斜长角闪岩中的角闪石进行了４０Ａｒ－３９Ａｒ年龄测定,分别得到角闪石视年龄１５８６Ｍａ、１０１１～１０８０Ｍａ、７６１Ｍａ和５２９～５８２Ｍａ,角闪石坪年龄１０３６Ｍａ和５５４Ｍａ,角闪石Ａｒ－Ａｒ等时线年龄１０１０Ｍａ,这些同位素年龄证据,首次完整地记录了该区所经历的几乎所有构造变质热事件,为近几年国内外地质学家关于该区构造变质热事件争论的焦点问题,即晚元古代的１０００Ｍａ格林维尔事件（Ｇｒｅｎｖｉｌｉａｎ）与早古生代的５００Ｍａ泛非事件（Ｐａｎ－Ａｆｒｉｃａｎ）孰轻孰重以及前者是否存在,提供了答案。角闪石的４０Ａｒ－３９Ａｒ年龄测定结果表明,拉斯曼丘陵地区经历了复杂的多期变质演化历史,其原岩可能形成于早－中元古代,占主导地位的应该是晚元古代的１０００Ｍａ格林维尔事件,而５００Ｍａ泛非事件则是晚期较强烈的变质热事件。     

Is the jet of AO 0235+164 rotating?

We present the VLBI map of a superluminal radio source AO 0235+164 at 5 GHz. This shows that the object's radio structure is dominated by a strong, nearly unresolved core with two extended asymmetric weak jet components. Based on the variation of its flux density with time at 5 GHz, we suggest that the flux density of AO 0235+164 exhibits two periodic variations: a shorter-period variation of 1.81±0.06 yr and a longer-period one of 3.64±0.08 yr. These two periodic variations could be the result of the joint action of jet outbursts and jet rotation.     

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射电天文台址电子设备电磁辐射评估

射电望远镜具有极高的系统灵敏度,且系统内、系统间及台址内电子设备众多,电磁环境复杂,科学合理地评估台址内电子设备辐射发射对射电天文观测的影响,对系统电磁兼容性设计、无线电管理、屏蔽改造等有重要的指导意义。浅析了射电望远镜系统灵敏度及射电天文领域仪器设备辐射发射相关评估标准;基于射电望远镜系统灵敏度及观测需求,计算了南山25 m射电望远镜馈源口面干扰电平限值,并给出了天线旁瓣增益的计算方法;提出一种基于干扰电平限值、旁瓣增益、干扰测量、路径衰减的电子设备电磁辐射评估方法,并针对南山25 m射电望远镜天线驱动电磁辐射进行了评估,给出了屏蔽需求。     

常量元素氧化物含量及其比值揭示的中晚全新世以来玛曲高原的环境演变

对玛曲高原具有代表性的黄土-古土壤-风成砂剖面(OL剖面)常量元素氧化物含量及其比值的地球化学特征分析表明:(1)常量元素氧化物总含量为91.93%且SiO₂(67.93%) >Al₂O₃(11.2%) >Fe₂O₃(3.97%) >CaO(3.76%)>K₂O(2.16%) >Na₂O(1.81%) >MgO(1.1%);(2)玛曲高原处于较弱的脱Ca、Na初级风化阶段,并伴有碳酸盐的淋失;(3)玛曲高原的气候经历了冷干-凉润-温湿-凉干的冷暖旋回。依据常量元素氧化物含量及其比值揭示的环境特征并结合¹⁴C测年将玛曲高原中晚全新世以来的环境演变划分为4.6 ka BP以前的风沙活动强烈期、4.6～4.3 ka BP的风沙活动较弱期、4.3～0.3 ka BP的固结成壤期和0.3 ka BP至今的风沙活动增强期4个阶段。