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511.
512.
A combination of published and new radiometric dates on uplifted Holocene fossil beaches from northeastern Sicily and southern Calabria (southern Italy) is compared with the altitude of the inner margin of the Last Interglacial (LIg) (Late Pleistocene, 124 ka) and older marine terraces in order to gain a regional-scale outline of uplift rates and their temporal changes in a region which is one of the fastest uplifting sectors of the Central Mediterranean Sea. Late Holocene radiocarbon dates from Ioppolo (southern Calabria) and Ganzirri (northeast Sicily), two newly discovered sites are here presented for the first time. The Holocene uplift rates are highest at St. Alessio and Taormina in eastern Sicily (2.4 mm/y) and at Scilla in southwestern Calabria (2.1 mm/y), two sites located across the Messina Straits and which separate the island of Sicily from mainland Italy. Uplift rates decrease towards the south and north from this centre of uplift. Late Holocene uplift rates show an apparent increase of between 64 and 124% when compared with the longer-term uplift rates calculated from the LIg highstand terraces. Furthermore, we discovered that the locations of fastest Late Pleistocene and Late Holocene uplift rates spatially coincide. To what extent the Holocene increase in uplift rates results from incomplete elastic strain release along the major extensional faults which frame the seismotectonic of the area, or indicate a true change in regional tectonic processes, is not resolved. Nonetheless, the heterogeneity of uplift, with a well-defined centre that crosses the Messina Straits, and its persistence at different time-scales indicates a tight connection between wider regional processes and fault-related displacement in controlling crustal instability in this area.  相似文献   
513.
以济南市为样本,基于该市改革开放后历年的统计数据,采用国际上常用的IU、NU标准值法判断其城镇化与工业化的关系并进行分析.研究发现,济南市城镇化的发展由过去的严重滞后于工业化逐步趋向于与工业化发展相协调的状态;不同城市的自然环境和区位条件有差别,城镇化和工业化的发展又具有一定的地域性和时序性.因此,以城市为对象,探讨其城镇化与工业化的关系,既能丰富这一领域的理论研究,又能为城市的城镇化和工业化进程提供实践参考.  相似文献   
514.
山体效应及其对林线分布的影响(英文)   总被引:7,自引:2,他引:5  
The concept of mass elevation effect(massenerhebungseffect,MEE) was intro-duced by A.de Quervain about 100 years ago to account for the observed tendency for temperature-related parameters such as tree line and snowline to occur at higher elevations in the central Alps than on their outer margins.It also has been widely observed in other ar-eas of the world,but there have not been significant,let alone quantitative,researches on this phenomenon.Especially,it has been usually completely neglected in developing fitting mod-els of timberline elevation,with only longitude or latitude considered as impacting factors.This paper tries to quantify the contribution of MEE to timberline elevation.Considering that the more extensive the land mass and especially the higher the mountain base in the interior of land mass,the greater the mass elevation effect,this paper takes mountain base elevation(MBE) as the magnitude of MEE.We collect 157 data points of timberline elevation,and use their latitude,longitude and MBE as independent variables to build a multiple linear regres-sion equation for timberline elevation in the southeastern Eurasian continent.The results turn out that the contribution of latitude,longitude and MBE to timberline altitude reach 25.11%,29.43%,and 45.46%,respectively.North of northern latitude 32°,the three factors’ contribu-tion amount to 48.50%,24.04%,and 27.46%,respectively;to the south,their contribution is 13.01%,48.33%,and 38.66%,respectively.This means that MBE,serving as a proxy indi-cator of MEE,is a significant factor determining the elevation of alpine timberline.Compared with other factors,it is more stable and independent in affecting timberline elevation.Of course,the magnitude of the actual MEE is certainly determined by other factors,including mountain area and height,the distance to the edge of a land mass,the structures of the mountains nearby.These factors need to be included in the study of MEE quantification in the future.This paper could help build up a high-accuracy and multi-scale elevation model for alpine timberline and even other altitudinal belts.  相似文献   
515.
Employing DEA model and Malmquist productivity index, this paper probes into the urban efficiencies of 24 typical resources-based cities in China and their changes from 2000 to 2008. The research finds that the overall efficiencies of the resources-based cities are just at a general level, and only a few of them reach the optimal level. The scale efficiency is the major determining factor of the achievement of overall efficiency, the effect of which, never-theless, is reducing. From the perspective of classification characteristics, the re-sources-based cities in northeastern region have been in the front rank in terms of overall efficiency, pure technical efficiency and scale efficiency. There is a certain positive correlation between urban population scale and urban efficiency. The analysis of urban efficiency changes shows that the changes in overall efficiency of resources-based cities from 2000 to 2008 had a weak improving tendency. Both the technical change index and productivity change index decreased, indicating that the urban efficiency did not improve during this pe-riod, and the tendency of technical recession and productivity decline was obvious. In terms of the classification of urban efficiency changes, the urban overall efficiency improved in each of the four regions from 2000 to 2008, among which western region witnessed the greatest increase. Cities with different resource types have improved their urban overall efficiencies except steel-based cities. The urban overall efficiency increased in resources-based cities of different scales, with greater improvement in small and medium-sized cities than in big cities.  相似文献   
516.
The long baseline simultaneous multiband ( BVRI ) observations of blazar 3C 273 are presented. We have made 758 optical multiband observations with the Yunnan Astronomical Observatory (YAO) 103 cm and Shanghai Astronomical Observatory (SHAO) 156 cm from 2003 January to 2005 April. In our observational campaign, the average colour indices are   B − V = 0.21, V − R = 0.26  and   R − I = 0.31  . The mean magnitudes in B, V, R and I are 12.895, 12.698, 12.441 and 12.139, respectively. The source is in a steady state over observational campaign. The correlations between colour index and brightness are discussed. We find that the correlations of   B − V   versus B ,   V − R   versus V and   R − I   versus R have significant negative correlation, while   B − V   versus V ,   V − R   versus R and   R − I   versus I have positive correlation. These strong correlations imply that the spectrum becomes bluer (flatter) when the source becomes brighter, and redden (softer) when the source fades both in intraday and long-term variability. The spectral evolution trends of 3C 273 are consistent with those of BL Lac objects.  相似文献   
517.
KÖhler方程是云物理学中的一个基础公式,是云滴形成理论的重要组成部分。我们在研究中对KÖhler公式推导和假设提出了一些疑问,如未考虑液滴生长过程中浓度、范德霍夫系数等变化对方程所产生的影响,并给出了解决方式,同时利用另一种推导方式讨论KÖhler公式的应用,加强了KÖhler方程与实际云滴核化过程的结合。  相似文献   
518.
519.
The multiband nonthermal emissions in radio,X-ray,and very high-energy (VHE)γ-ray bands from two distant blazars,H 2356-309 and 1ES 1218+304,have been detected,and,especially from recent observations with the Suzaku,MAGIC and VERITAS telescopes,clearly reveal nonthermal power-law spectra. We study the broadband nonthermal spectra of the two sources by using a combination of a onezone homogeneous synchrotron self-Compton (SSC) model and an inhomogeneous conical jet model,where the new external background light (EBL) model is taken into account. The results show that (1) the nonthermal emissions of the two blazars,ranging from X-rays to VHE γ-rays,are from the homogeneous zone whereas the emissions in the radio bands can be explained as the radiation from the inhomogeneous conical jet; (2) a strict lower-limit EBL model can be used to explain their observed spectra well.  相似文献   
520.
文章根据国际通用数据库中关于社会经济指标和温室气体排放等方面权威数据,同时分析世界各主要经济集团、国家和地区的经济发展和温室气体排放水平和过程.采用近40年来各国家和地区的人均国内生产总值(GDP)和人均温室气体排放两个指标,将世界主要国家和地区划分成6种不同的国家型: 低人均碳排放贫困国家(ⅠA)、低人均碳排放相对富裕国家(ⅡA)、低人均碳排放富裕国家(ⅢA)、高人均碳排放相对富裕国家(ⅡB)、高人均碳排放富裕国家(ⅢB)和高人均碳排放贫困国家(ⅠB).研究时段上,ⅠB类国家极少出现,前5类分别对应于世界最贫困地区、主要发展中国家、经济发展较快的经济转型国家、富裕岛屿地区以及北美和欧洲富裕国家.数据分析表明,各国与地区的经济发展与温室气体排放之间有密切联系,各国家型的经济发展和温室气体排放的组合关系长期比较稳定.1970~2005年间,大多数国家和地区经济发展水平有明显提高,而人均温室气体排放变化不太明显,即人均温室气体排放较高国家,排放水平长期居高不下,人均低排放国家温室气体排放增加不明显; 国家型的主要变化过程是ⅠA转向ⅡA和ⅡB转向ⅢB,分别发生在20世纪70年代和20世纪70年代末到80年代.了解这一变化过程,对认识各国经济发展与温室气体排放的关系及其历史过程,对理解各方的减排目标和策略,对我国在以后气候外交谈判的立场选择等方面都具有重要的启发作用.  相似文献   
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