Why ‘the uplift of the Tibetan Plateau’ is a myth

The often-used phrase ‘the uplift of the Tibetan Plateau’ implies a flat-surfaced Tibet rose as a coherent entity, and that uplift was driven entirely by the collision and northward movement of India. Here, we argue that these are misconceptions derived in large part from simplistic geodynamic and climate modeling, as well as proxy misinterpretation. The growth of Tibet was a complex process involving mostly Mesozoic collisions of several Gondwanan terranes with Asia, thickening the crust and generating complex relief before the arrival of India. In this review, Earth system modeling, paleoaltimetry proxies and fossil finds contribute to a new synthetic view of the topographic evolution of Tibet. A notable feature overlooked in previous models of plateau formation was the persistence through much of the Cenozoic of a wide east–west orientated deep central valley, and the formation of a plateau occurred only in the late Neogene through compression and internal sedimentation.     

Uplift,climate and biotic changes at the Eocene–Oligocene transition in south-eastern Tibet

The uplift history of south-eastern Tibet is crucial to understanding processes driving the tectonic evolution of the Tibetan Plateau and surrounding areas. Underpinning existing palaeoaltimetric studies has been regional mapping based in large part on biostratigraphy that assumes a Neogene modernization of the highly diverse, but threatened, Asian biota. Here, with new radiometric dating and newly collected plant-fossil archives, we quantify the surface height of part of the south-eastern margin of Tibet in the latest Eocene (∼34 Ma) to be ∼3 km and rising, possibly attaining its present elevation (3.9 km) in the early Oligocene. We also find that the Eocene–Oligocene transition in south-eastern Tibet witnessed leaf-size diminution and a floral composition change from sub-tropical/warm temperate to cool temperate, likely reflective of both uplift and secular climate change, and that, by the latest Eocene, floral modernization on Tibet had already taken place, implying modernization was deeply rooted in the Palaeogene.     

Herpetological phylogeographic analyses support a Miocene focal point of Himalayan uplift and biological diversification

The Himalaya are among the youngest and highest mountains in the world, but the exact timing of their uplift and origins of their biodiversity are still in debate. The Himalayan region is a relatively small area but with exceptional diversity and endemism. One common hypothesis to explain the rich montane diversity is uplift-driven diversification—that orogeny creates conditions favoring rapid in situ speciation of resident lineages. We test this hypothesis in the Himalayan region using amphibians and reptiles, two environmentally sensitive vertebrate groups. In addition, analysis of diversification of the herpetofauna provides an independent source of information to test competing geological hypotheses of Himalayan orogenesis. We conclude that the origins of the Himalayan herpetofauna date to the early Paleocene, but that diversification of most groups was concentrated in the Miocene. There was an increase in both rates and modes of diversification during the early to middle Miocene, together with regional interchange (dispersal) between the Himalaya and adjacent regions. Our analyses support a recently proposed stepwise geological model of Himalayan uplift beginning in the Paleocene, with a subsequent rapid increase of uplifting during the Miocene, finally giving rise to the intensification of the modern South Asian Monsoon.     

大学生科技创新能力培养模式的思考

科技创新能力是个人在某一科学技术领域具备发明创新综合实力的体现,已成为当代大学生培养的一项重要内容,反映了自我提升和社会发展进步的实际需要。本文从教材建设、课堂教学和实验室建设三个方面对高校如何提高大学生科技创新能力进行了探析,并提出了几点建议。     

江西省萍乡市源泣隐伏煤田区地质特征及找矿方向浅析

源澈地区所见的老地层不是“古隆起”,而是由多个滑覆体依次堆叠的滑覆构造形成的外来岩系,这些外来岩系之下,隐伏着大片的安源煤系。同时,源澎地区的主要含煤地层为上三叠纪安源群紫家冲组（T3a）,属萍乡市开采的主要煤层。因此,源溢地区是一个理想的寻找隐伏煤田的地区。     

CAS Biologists in Shanghai Step up Cooperation with Their West European Peers

~~projects by Chinese and Ger-man biologists. Based on thesuccess of the guest lab, a pro-gram to set up research groupsof junior scientists was initi-ated in 1994 and to date fourhigh-ranking young scholarshave joined the Shanghaiinstitutes. After obtaining theirPh. D degrees in the US, PeiGang and Hu Gengxi were in-vited to serve as heads of twogroups, in 1994 and 1996respectively. With the jointsupport from the Chinese andGerman sides, the junior sci-tical platform for cDNA array, the…     

利用载荷减少引起的湖底变形探讨西藏古大湖演变史

西藏可能曾存在一个面积达15万平方公里的“古大湖”，当古大湖的湖水流失时，地壳会因为载荷减少而产生形变，造成岩石层的回弹和倾斜，考察因此而产生的湖相沉积物间不整合角能为古大湖的研究提供新的佐证。本文通过简化的力学模型计算证明，湖水减少引起的湖底倾斜量微不足道、难以观测，总的变形量也不大，仅数十米，但这种抬升速率可能极其迅速，其环境、气候、地貌等方面的效应值得进一步研究。     

青藏高原隆升与新特提斯海退却对亚洲中纬度阶段性气候干旱的影响

亚洲内陆是北半球最大、最广阔的中纬度干旱区,且不同于世界上分布于副热带高压控制下的干旱区。现今的亚洲中纬度干旱区深居内陆,远离各大洋的水汽来源。亚洲中纬度干旱区究竟如何形成?历经了怎样的干旱化过程?其形成演化的动力机制是什么?这些一直是悬而未决的问题。事实上,亚洲中纬度干旱区发展成今天所见的干旱荒漠,并不是短时间内实现的,而是经历了漫长的阶段性演化进程,是在新生代以来印度、阿拉伯、非洲板块与欧亚大陆的碰撞,青藏高原的隆升,新特提斯海的退却以及新生代全球气候变冷与海平面下降等区域和全球要素共同作用下,从半湿润—半干旱—干旱—极端干旱渐进演化而来。历经了始新世的半湿润气候,渐新世的半湿润-半干旱气候和中新世末期以来的干旱-极端干旱气候。     

中国汽车产业技术创新政策效果分析

汽车产业是我国社会经济发展的支柱产业,政府出台多项政策支持产业技术创新。文章以技术创新政策作为研究对象,在国内外学者的研究基础上,运用因子分析、熵权法和灰色综合评价法,从整体效果、经济效益、技术投入、技术产出方面对中国汽车产业技术创新政策效果进行实证研究。通过研究发现,国家政策基本上支持了汽车产业创新发展,总体取得良好效果,经济效益具有跌宕起伏状态,技术投入呈波浪状上升态势,技术产出持续增长。但是,在某些年份政策效果并不理想,产业发展依赖财政资金,必须及时调整支持政策,建立适合新时期发展的产业技术创新体系。     

武汉城市圈经济-资源-环境系统发展的时空特征

运用SPSS13.0数理统计软件,建立都市圈经济-资源-环境系统(ERE)评价指标体系,引入层次分析法,构建ERE系统发展函数,以武汉城市圈为例,系统揭示武汉城市圈ERE系统各子系统发展的时空规律:(1)时间演化上,经济子系统保持指数增长速度,整个圈域经济处于高速运行中;资源子系统波动变化明显,整体上呈先上升、再下降、后上升的倒S型曲线,表现为缓慢上升、快速下降、迅速抬升三个阶段特征;环境子系统整体上呈指数律快速发展,除了在1999年出现一定程度下滑外,整个环境系统呈良性发展态;(2)空间分异上,经济子系统城际差异明显,形成以武汉为核心的三等级圈层结构,资源环境子系统整体受经济发展方式影响显著,呈现三集团发展态势。由于经济发展、资源环境条件、历史基础、政策机制等差异,武汉城市圈城际资源环境系统整体发展空间不对应,形成四大类型:资源环境好—经济发展型、资源环境好—经济滞后型、资源环境差—经济发展型、资源环境差—经济滞后型。     

“亚洲水塔”变化的灾害效应与减灾对策

青藏高原及周边地区被誉为"亚洲水塔",其自然环境复杂,气候差异显著,地貌类型多样,冰川发育,地壳隆升和河流下切作用强烈,导致滑坡、泥石流、洪水、冰崩雪崩、冰湖溃决等山地灾害发育。灾害呈现出突发性强、危害范围广、破坏严重、链式效应明显等特点,且沿构造断裂带、高山深切峡谷集中分布,受水平和垂直地带性气候条件和局地水热条件控制,不同海拔区的灾害类型、诱发因素和对气候变化的响应有所差异。气候变暖导致的温度升高和降雨增多对灾害发生的水源、物源、能量和条件组合都有所影响,导致灾害的孕灾环境变得易于成灾。未来全球气候变暖将加剧灾害的危险性,而灾害风险也会随着人口和经济体量的增加而升高。目前,还缺乏系统的基础数据和对"亚洲水塔"变化下灾害发生机制的深入认识,从而难以准确预测未来气候变化下的灾害风险,提出有针对性的风险防控对策。为了有效应对气候变化导致的灾害风险,应针对性地进行综合灾害考察,利用高新技术系统获取第一手灾害数据,建立灾害数据库,深化对孕灾环境、形成机理和灾变机制的认识,研究灾害对气候变化的响应规律,预测气候变化条件下灾害的发展趋势,研发针对特大灾害的监测和防控技术,建立多国协调的灾害防控信息共享和减灾协同机制,提高应对灾害风险的能力。     

淫羊藿属(小檗科)花瓣的演化和地理分布格局的研究

淫羊藿属的种数与60年前大不相同，现在已知约有50种。该属种类间断地分布于日本至北非 的阿尔及利亚之间的广大地区，这一分布格局表明了该属的古老性质。它们在欧亚大陆的分布极不均 匀，约有80％的种类产于中国中部至东南部，而且根据花瓣的演化分析结果表明，只有中国的淫羊藿属 植物具有连续不断的演化过程。由此可见，中国中部至东南部成为北半球淫羊藿属植物的汇集中心是 有充分根据的。淫羊藿属种类基本上是林地草本植物，常生于水青冈林下，为林下草本层的优势种，而 且该属的分布格局与第三纪植物属——水青冈属在欧亚大陆的分布格局极为相似，说明淫羊藿属植物 在早第三纪时期已广泛分布于北半球。中新世时期由于中亚地区气候变干，加之印度板块向欧亚大陆 俯冲并引起喜马拉雅山脉隆起，致使中亚地区进一步干旱，水青冈属和淫羊霍属植物随之消失，进而导致其东亚—地中海、西亚间断分布格局的形成。     

青藏古植被的演变与青藏高原的隆起

 西藏北部，在早石炭世晚期位于欧亚古陆的南缘，其植物群与当时印度次大     陆的不同。在晚二叠世，藏北属华夏植物区(即大羽羊齿植物区)；印度河-雅鲁     藏布江大断裂带以南的地区出现舌羊齿植物群，  因而属冈瓦纳古陆的一部分。     到晚三叠世藏北植物群的面貌与我国西南同时代的植物群相似，与印度的则迥     然不同，显示藏北晚三叠世的植物群与南半球植物群也没有直接联系。  柴达木     侏罗纪植物群和拉萨附近早白垩世植物群与北半球的植物群有密切的关系。日     喀则晚白垩世植物群和阿里早始新世植物群也是如此。他们与印度德干玄武岩     夹层中出现的古新世植物群和印度北部始新世植物群也没有联系。  当时，西藏     的北部和南部属于两个不同的古陆，欧亚古陆和冈瓦纳古陆。  两者之间应有一     个很宽阔的特提斯海。因而，青藏的植物化石强有力地支持了大陆漂移的观点，     印度地块在晚侏罗世—白垩纪时是由非洲东南隅分离向北漂移，到始新世才与     亚洲连接，成为现在的南亚次大陆。  欧亚大陆与印度地块的接合线或许就是印     度河－雅鲁藏布江大断裂带。     　　从晚石炭世到早始新世的植物群的性质上看，藏北地势多半低洼。     中新世时，西藏中部和北部的植被是以落叶阔叶林为主，虽然某些地区有一     些常绿树存在，反映在中新世以前西藏中部和北部的地面已经上升到一定的程     度。在上新世时，藏北的常绿阔叶林逐渐减缩。柴达木盆地的植被转变成落叶     阔叶林－针叶林，以后转变成草原和半荒漠或荒漠，显示西藏和青海的地面进一     步抬升。     　　到晚上新世，藏北和青海的植被再行演变。然而，喜马拉雅地区的植被仍然     具有常绿栎林和雪松林。可能那时喜马拉雅山不像现在那么高。印度洋的季风     可以吹过喜马拉雅山，没有高山的阻碍。     　　第四纪是青藏山系和青藏地面上升最剧烈的时期。此时藏北已无常绿阔叶     树的存在。  到第四纪后期西藏大部分地区的植被逐渐演变为高寒荒漠。  最后，    青藏高原变成现在的情况。     

中国第三纪植被和植物区系历史及分区

被子植物的发展(或称辐射)是与古气候、古地理环境密切相关的，诸因素的变化相互影响及制 约，形成植物发展的阶段性。这种阶段变革及划分与传统的地质时代划分——断带，不尽一致，因而讨论 植物地理分区问题应以发展的不同阶段为基础，致使分区更为合理。     在晚白垩纪中晚期，被子植物已成为植物区系中的优势成分，从它出现以来的发展演化大致可划分 为四个阶段：(1)初始期  被子植物初次出现，具有叶形小、叶边全缘、叶脉缺乏规律性、脉级分化程度低 等原始性特点，同时在区系中的种数及个体数量均为极少数，此时大约在早白垩纪的中晚期；(2)极盛时 期被子植物发展具有一定规模至占绝对优势，此时叶形增大，叶脉有了规律性，脉级分化逐渐完善，在 植物区系中所占比例达40％一60％，以致占绝对优势，主要科属出现了，时间在晚白垩至老第三纪；(3) 草本植物繁盛阶段  由于在新第三纪时气候逐渐转凉，早期的一些木本植物消灭了，以草本植物渐增多 至大量扩散为特点，时间约在中新世至上新世；(4)第四纪阶段  此时我国由于山岳冰川随全球性气候 冷暖变化而进退，影响植物的分布及发展，植物区系的总面貌与现代接近或略有差别。   本文亦重点讨论了植物发展的第二、第三阶段的植物地理分区。     

西藏蔷薇科植物的区系特点和地理分布

The Rosaceae is one of the five largest families of Xizang flora,  consisting of 30 genera with 242 species,  the total number of species is slightly less than those of Compositae,  Graminae,  Leguminosae and Ericaceae in Xizang,  amounting to 62.5% of the total number of genera and 28% of the total number of species of the rosaceous flora in China.       The four subfamilies of Rosaceae including primitive,  intermediate and advanced groups have been found in Xizang.  These groups consist of 11 types of floristic ele- ments,  i.e. 4 genera belong to cosmopolitan,  9 genera belong to North Temperate,  3,  E. Asian-N.  American,  3 Sino-Himalayan,  3 Sino-Japanesa,  2 Old World Temperate,  1 Temperate Asian,  2 Mediterranean-W. and O. Asian,  1 C. Asian,  I Tropical Asian and 1 endemic to China. It is obvious that Rosaceae in Xizang comprises holarctic,  Ancient Me- diterranean and paleotropical elements,  among which the temperate components are the most dominant.  The characteristics of the floristic composition of Rosaceae in Xizang may be summarized as follows:       (1) Xizang abounds in both genera and species of the family which are diverse in forms,  including the primitive,  intermediate and advanced groups, (2) The geographi- cal elements are rather complex,  mostly belonging to the temperate,  among which the Sino- Himalayan components and the elements endemic to China are dominant, (3) The proportion of plants endemic to China and distributed in Xizang is much higher than those endemic to Xizang itself,  but there exist newly arisen species and infraspecific forms or varieties which show that the speciation is apparently still active in Xizang. The rosaceous flora of Xizang is a combination of old and new floristic elements,  based on the old floristic components,  affected by the upheaval of the Himalayas,  the differen- tiation and speciation have been taking place in the long history.       The geographical distribution of Rosaceae in Xizang may be divided into 5 regions, i.e. the northeastern,  southeastern,  southern,  northwestern and northern.  The rosaceous plants are most abundant in the southeastern area,  next in southern area,  fewer in the northeastern and very rare in the northwestern and northern regions.  The general ten- dency of the distribution of Rosaceae in Xizang is that the number of species gradually decreases from the southeast to the northwest and the habit gradually changes from trees,  shrubs and herbaceous plants in the southeast to cushion-like scrubs and dwarf perennial herbs in the northwest.  These facts clearly show that the uplift of the Hi- malayas has deeply affected the phytogeographical distribution of Xizang Rosaceae.       The rosaceous flora of Xizang has close relationships with those of the adjoring regions,  i.e. Yunnan and Sichuan.  Besides,  it is connected with floras of Nepal,  Sikkim, Bhutan nothern Buram and nothern India,  but silghtly influenced by the Ancient Medi- terranean flora.     

要素集聚对高技术产业创新能力发展的影响研究

基于1996年至2016年的我国省际面板数据,本文聚焦产业要素集聚视角研究高技术产业创新能力的来源,利用莫兰指数(Moran′s I)进行空间相关检验,通过LM等系列检验确定本研究采用空间杜宾模型。结论指出：（1）总体来看我国高技术产业创新能力具有显著的空间集聚特点,创新能力存在区域间的空间正相关;（2）劳动、技术、人才、规模等要素集聚及税收优惠政策都对地区内高技术产业各阶段创新能力发展具有积极作用,资本集聚对产业创新转化存在逆向作用;（3）FDI和政策支持都对我国高技术产业总体创新能力存在约束,原因是FDI与政府资金目的导向差异性所致。     

工程共同体中的“岗位”和“岗位人”——工程共同体研究之五

在以企业为主要表现形式的工程活动共同体中,作为其成员的个体各自占据一定的岗位而发挥其作用,每个个体都是＂本位人＂和＂岗位人＂的统一。文章着重分析了作为＂个体＂的个人和作为＂集体＂的工程共同体的动态关系。个体通过招聘过程而在工程共同体中＂出场＂,然后是在工作岗位起作用的＂在场＂和离开工程共同体的＂退场＂。文章最后部分运用中国哲学的阴阳理论对人性问题和本位人和岗位人的相互关系进行了简要分析。     

根平方平均的最优凸组合不等式

本文得到最大值α和最小值β,使得对所有的a,b>0,a≠b双向不等式αC(a,b)+(1-α)A(a,b)相似文献   

Robust self-triggered MPC with fast convergence for constrained linear systems

In this paper, a robust self-triggered model predictive control (MPC) scheme is proposed for linear discrete-time systems subject to additive disturbances, state and control constraints. To reduce the amount of computation on controller sides, MPC optimization problems are only solved at certain sampling instants which are determined by a novel self-triggering mechanism. The main idea of the self-triggering mechanism is to choose inter-sampling times by guaranteeing a fast decrease in optimal costs. It implies a fast convergence of system states to a compact set where it is ultimately bounded and a reduction of computation times to stabilize the system. Once the state enters a terminal region, the system can be stabilized to a robust invariant set by a state feedback controller. Robust constraint satisfaction is ensured by utilizing the worst-case set-valued predictions of future states in such a way that recursive feasibility is guaranteed for all possible realisations of disturbances. In the case where a priority is given to reducing communication costs rather than improvement in control performance in a neighborhood of the origin, a feedback control law based on nominal state predictions is designed in the terminal region to avoid frequent feedback. Performances of the closed-loop system are demonstrated by a simulation example.     

Website usage metrics: A re-assessment of session data

Metrics derived from user visits or sessions provide a means of evaluating Websites and an important insight into online information seeking behaviour, the most important of them being the duration of sessions and the number of pages viewed in a session, a possible busyness indicator. However, the identification of session (termed often ‘sessionization’) is fraught with difficulty in that there is no way of determining from a transactional log file that a user has ended their session. No one logs out. Instead a session delimiter has to be applied and this is typically done on the basis of a standard period of inactivity. To date researchers have discussed the issue of a time out delimiter in terms of a single value and if a page view time exceeds the cut-off value the session is deemed to have ended. This approach assumes that page view time is a single distribution and that the cut-off value is one point on that distribution. The authors however argue that page time distribution is composed of a number of quite separate view time distributions because of the marked differences in view times between pages (abstract, contents page, full text). This implies that a number of timeout delimiters should be applied. Employing data from a study of the OhioLINK digital journal library, the authors demonstrate how the setting of a time out delimiter impacts on the estimate of page view time and the number of estimated session. Furthermore, they also show how a number of timeout delimiters might apply and they argue that this gives a better and more robust estimate of the number of sessions, session time and page view time compared to an application of a single timeout delimiter.