肇东和亳县陨石中的黑包体及其成因意义

肇东、毫县陨石中的黑包体在总体成分、形状、大小上与陨石球粒相似,但两者的内部结构以及矿物组合不同。黑包体中矿物呈密堆状,主要由细粒橄榄石以及其它硅酸盐微晶组成,不含火成玻璃等特点表明黑包体未经历过熔融,它们可能是形成球粒的毛坯。因此认为球粒的形成有三个阶段:星云凝聚形成尘粒—尘粒吸积形成黑包体—黑包体熔融形成球粒。     

Impact of land use covers upon karst processes in a typical Fengcong depression system of Nongla, Guangxi, China

The direction and intensity of karst processes can be deeply affected by soil physical and chemical variations which were resulted from land use. Taking Nongla Fengcong depression area, Mashan County, Guangxi as an example, authors discussed the impact of land use on karst processes based on the data of field limestone tablet. The results showed that the corrosional rates at varied soil depth are quite different. Corrosional rate in woodland and orchard is mostly bigger than 20 mg/a, which is much higher than that in tilled land and shrub. Generally, corrosional rate decreased from orchard, woodland, tilled land, fallow land and shrub successively, in which soil organic matter (OM) and soil pH are two major controlling factors: corrosion process is controlled remarkably by soil OM in woodland and orchard. The higher the organic matter content is and the less the pH value is, the higher the corrosional rate is. Owing to lower organic matter content, the corrosional rate is mainly affected by soil CO₂ in tilled land and shrub.     

Depositional processes on oceanic island shelves – Evidence from storm‐generated Neogene deposits from the mid‐North Atlantic

Oceanic islands – such as the Azores in the mid‐North Atlantic – are periodically exposed to large storms that often remobilize and transport marine sediments along coastlines, and into deeper environments. Such disruptive events create deposits – denominated tempestites – whose characteristics reflect the highly dynamic environment in which they were formed. Tempestites from oceanic islands, however, are seldom described in the literature and little is known about storm‐related sediment dynamics affecting oceanic island shelves. Therefore, the geological record of tempestite deposits at oceanic islands can provide invaluable information on the processes of sediment remobilization, transport and deposition taking place on insular shelves during and after major storms. In Santa Maria Island (Azores), a sequence of Neogene tempestite deposits was incorporated in the island edifice by the ongoing volcanic activity (thus preserved) and later exposed through uplift and erosion. Because it was overlain by a contemporary coastal lava delta, the water depth at the time of deposition could be inferred, constituting an excellent case‐study to gain insight on the still enigmatic processes of insular shelf deposition. Sedimentological, palaeontological, petrographic and palaeo‐water depth information allowed the reconstruction of the depositional environment of these sediments. The sequence typifies the characteristics of a tempestite (or successive tempestites) formed at ca 50 m depth, in a steep, energetic open insular shelf, and with evidence for massive sediment remobilization from the nearshore to the middle or outer shelf. The authors claim that cross‐shelf transport induced by storm events is the main process of sediment deposition acting on steep and narrow shelves subjected to high‐energetic environments, such as the insular shelves of open‐sea volcanic islands.     

Zircon age and Nd–Hf isotopic composition of the Yunnan Tethyan belt,southwestern China

The Baoshan block of the Tethyan Yunnan, southwestern China, is considered as northern part of the Sibumasu microcontinent. Basement of this block that comprises presumably greenschist-facies Neoproterozoic metamorphic rocks is covered by Paleozoic to Mesozoic low-grade metamorphic sedimentary rocks. This study presents zircon ages and Nd–Hf isotopic composition of granites generated from crustal reworking to reveal geochemical feature of the underlying basement. Dating results obtained using the single zircon U–Pb isotopic dilution method show that granites exposed in the study area formed in early Paleozoic (about 470 Ma; Pingdajie granite) and in late Yanshanian (about 78–61 Ma, Late Cretaceous to Early Tertiary; Huataolin granite). The early Paleozoic granite contains Archean to Mesoproterozoic inherited zircons and the late Yanshanian granite contains late Proterozoic to early Paleozoic zircon cores. Both granites have similar geochemical and Nd–Hf isotopic charateristics, indicating similar magma sources. They have whole-rock T _DM(Nd) values of around 2,000 Ma and zircon T _DM(Hf) values clustering around 1,900–1,800 and 1,600–1,400 Ma. The Nd–Hf isotopic data imply Paleoproterozoic to Mesoproterozoic crustal material as the major components of the underlying basement, being consistent with a derivation from Archean and Paleoproterozoic terrains of India or NW Australia. Both granites formed in two different tectonic events similarly originated from intra-crustal reworking. Temporally, the late Yanshanian magmatism is probably related to the closure of the Neotethys ocean. The early Paleozoic magmatism traced in the Baoshan block indicates a comparable history of the basements during early Paleozoic between the SE Asia and the western Tethyan belt, such as the basement outcrops in the Alpine belt and probably in the European Variscides that are considered as continental blocks drifting from Gondwana prior to or simultaneously with those of the SE Asia.     

短期集合降水概率预报试验

以MM5模式作为试验模式, 通过选取不同的物理过程参数化方案产生8个集合成员, 分别用平均法、相关法和Rank法对2001年11月至2002年5月期间的22个降水个例进行短期集合降水概率预报试验。试验结果显示对小雨—大暴雨6类降水的概率预报, Rank法的综合预报效果明显好于相关法和平均法, 相关法的综合预报效果与平均法基本相同; 无论从均方误差角度还是从命中率和假警报率的相对大小角度, 对小雨、中雨、大雨和暴雨各量级以上降水的概率预报, Rank法的平均预报效果是三种方法中最好的, 相关法的平均预报效果与平均法相同; Rank法好于平均法的平均幅度从均方误差角度较大, 从命中率和假警报率的相对大小角度则较小。平均而言, 三种方法对各量级以上降水的概率预报都是有技巧预报, 对量级小的降水的概率预报技巧高于对量级大的降水的概率预报技巧。     

Subarea characteristics of the long-range correlations and the index χ for daily temperature records over China

Daily temperature records including daily minimum, maximum, and average temperature from 190 meteorological stations over China during 1951–2000 are analyzed from two perspectives: (a) long-term persistence in direction of time varies, and (b) standard deviation in direction of amplitude varies. By employing the detrended fluctuation analysis (DFA), we find all the temperature records are long-term correlated, while the exponent α obtained from DFA varies from different districts of China due to different climate conditions, such as the southwest monsoon, subtropical high, northeast cold vortex, and the Tibetan plateau, etc. After we take the standard deviation into account, a new index χ?=?α?×?σ, which has been proposed recently, can be obtained. By further rescaling it as $ \chi = \overline \chi - {{1} \left/ {5} \right.} \times {\sigma_{{\overline \chi }}} $ , we find an obvious change of χ for these three kinds of time series, from which the whole China can be divided into two groups, which are comparatively consistent with dry/wet distributions in the south–north areas over China.     

山西国际旅游市场营销目标选择研究

在梳理旅游市场营销目标选择方法的基础上,对原有竞争态模型进行扩展,分析山西省主体客源国的亲景度和市场发展指数,并基于两个指数的组合,建立旅游市场相对竞争态模型,将山西的主体客源国市场分为兴旺型、崛起型、成熟型和停滞型,并结合旅游市场绝对竞争格局,依据各类型市场的特征,确定山西省国际旅游市场的营销目标。     

城镇化与旅游发展背景下的乡村文化研究：学术争鸣与研究方向

快速城镇化和旅游发展背景下的乡村文化衰落现象,已经成为制约国家新型城镇化战略和乡村旅游发展的重大紧迫问题。以乡村文化保护为主线,通过综述乡村文化的研究进展,围绕城镇化和旅游发展对乡村文化是“繁荣”还是“衰落”、是“原真”保护还是“创新”利用、是景观“美化”还是文化“重构”等学术争论的焦点问题,提出了乡村文化保护利用和恢复重构的研究思路、研究方向及主要科学问题。强调应运用区域性、综合性的地理思维和人地关系的视角,综合集成多学科理论和多种研究方法与现代技术,聚焦引领性科学问题,关注城镇化对乡村文化胁迫效应测度及其影响过程与机制分析,重视乡村文化的科学保护、旅游活化利用、旅游村镇化与村镇旅游化、特色田园乡村建设和乡村多元价值提升,运用社区恢复力理论构建乡村文化恢复模型,依据文化基因、乡愁记忆等理论和建构主义方法确定乡村文化重构内涵,构建符合中国乡村特点的文化重构模式,从而为乡村振兴、乡村文化保护和乡村旅游持续发展提供理论支撑和实践依据,为国内学者进行乡村文化和乡村旅游研究提供借鉴和启示。     

基坑开挖与支护FLAC数值模拟计算及分析

介绍了FLAC-2D,根据基坑工程具体实例,采用FLAC-2D对基坑开挖及其支护结构状态进行计算和分析;并模拟了在未进行支护条件下的基坑开挖,得出了基坑土体在支护和未支护条件下,土体的应力状态、位移等值线图、位移矢量图、最终沉降量和结构受力.计算结果也证明了支护结构设计的合理性,对工程设计及施工分别起到了验证和预测的作用.     

潍坊涌泉庄膨润土、沸石岩、珍珠岩矿床矿层结构及其成因

本文阐述了涌泉庄火山－沉积型膨润土、沸石岩、珍珠岩三位一体矿床的矿层内部结构，将划分为Ａ，Ｂ，Ｃ，Ｄ，Ｅ五种类型。提出了矿床的形成是成矿原岩在外界条件作用下连续去硅的过程，对三矿的共生在成因方面得到了一致的解释。