Study of temperature and precipitation change in upstream mountain area of the Hexi inland river basin since 1960s

All rivers in the Hexi inland region of Gansu Province, China, originate from the northern slope of the Qilian Mountains. They are located in the southern portion of the region and respectively belong to the three large river systems from east to west, the Shiyang, Heihe and Shule river basins. These rivers are supplied by precipitation, snowmelt and ice-melt runoff from the Qilian Mountain area. Therefore, changes of precipitation and temperature in the upstream watersheds of these rivers have an important effect on changes of mountainous runoff and reasonable utilization of water resources in this region. For this reason, the Qilian Mountain area, upstream watersheds and runoff forming areas of these rivers are chosen as the study area. The change characteristics and variation trend of temperature and precipitation in this area under the backdrop of global warming are analyzed based on observational data of relational weather and hydrologic stations in the area. Results show that temperatures in the upriver mountain areas of these three large river basins have been increasing, although the increasing degree is differentially affected by global warming. The rising extent of annual and seasonal temperatures in the upstream mountain area of the Shule river basin located in the western Qilian Mountains, were all largest over the past 50 years. Precipitation in the upstream mountain areas of Hexi region’ three river basins located respectively in the western, middle and eastern Qilian Mountains have been presenting an increasing trend to varying degrees as a whole for more than 50 years. This means that climate in the upstream mountain areas of Hexi region’ three river basins are becoming increasingly warmer and moister over the past 50 years, which will be very good for the ecological environment and agricultural production in the region.     

四川省酉阳土家族苗族自治县经济综合开发的新设想

地处武陵山区的酉阳土家族苗族自治县,是国家重点扶贫县之一。要在“八五”期间稳定群众温饱、迅速脱贫致富,必须坚持山区经济的综合开发,即系列开发抓支柱、科学开发抓普及,规模开发抓集约、立体开发抓庭院。     

长江岸线的空间功能、开发问题及管理对策

基于长江岸线空间功能的理念,从历史演变的角度梳理了长江岸线开发功能分异的过程,总结了岸线开发功能定位的科学依据,并剖析了长江岸线开发的区域功能。归纳了长江岸线开发条件评估的技术体系,并综合分析了长江干流（宜宾以下）岸线的开发条件状况及利用现状,提出了长江岸线资源利用中存在的缺少科学的开发时序安排、资源潜力没有得到充分发挥、功能布局不合理、不当开发易造成生态破坏、缺少有效的管理机制等问题。最后,从推进法制建设,破除行政壁垒,建立有偿使用机制,促进功能协调等方面提出加强岸线资源管理的对策,以期为长江岸线科学有效管理与保护提供借鉴。     

三维空间中沙粒旋转对其跃移轨迹的影响

风沙流中沙粒旋转通常具有明显的三维旋转特性。本文通过数值建模考察了三维空间中不同沙粒旋转状态所产生的Magnus力对其跃移运动轨迹特征的影响。在三维坐标系中,X、Y、Z轴分别表示水平、垂直和横向方向,气流沿X方向流动,沙粒起跳时位于XY平面内。结果表明,跃移沙粒仅绕Z轴旋转起跳时,初始起跳角速度的增大会导致在XY平面内的跃移高度和跃移距离减小而降落角增大,但Z方向没有运动发生。跃移沙粒仅绕X轴或Y轴旋转起跳时,绕X轴或Y轴的初始起跳角速度的变化对在XY平面内的跃移轨迹特征量没有显著影响,但沙粒偏离XY平面的偏离距离和偏离角的绝对值随起跳角速度绝对值的增加而增大。因此,沙粒起跳旋转状态对其跃移轨迹有重要的影响。     

中国地震台网与美国地震台网测定震级的对比(Ⅱ) #8209;面波震级

采用正交回归方法， 利用中国地震局地球物理研究所（IGCEA）和美国地质调查局国家地震信息中心（USGS/NEIC）1983——2004年的观测资料，对这两个机构测定的面波震级进行了系统的比较，得到了中国地震台网与美国地震台网面波震级之间的关系式. 结果表明，由于使用的震级计算公式和观测仪器不同，IGCEA测定的面波震级总体上要比NEIC测定的结果偏高0.2级；对于3.5~4.5级的地震，IGCEA测定的震级比NEIC测定的震级偏高0.3级；对于5.0~6.5级的地震，IGCEA偏高0.2级；对于7.0级以上的地震，IGCEA偏高小于0.1级.      

团簇同位素的基本原理与地质应用*

团簇同位素指的是含有2个及2个以上的重同位素结合在一起形成的同位素体。团簇同位素的数值定义为同位素体的相对丰度偏离随机分布状态的程度。测量该相对丰度较低的同位素体需要高精度的质谱仪,难点在于利用同位素组成已知的参考气体和不同同位素组成的加热气体,以获得绝对参考体系下的数值。团簇同位素体的相对丰度非常低,但是具有非常独特的物理和化学性质。比如碳酸盐矿物中¹³C¹⁸O¹⁶O的丰度对温度具有敏感性,而与矿物的全岩同位素以及矿物形成时期的流体性质无关,因此可以利用测量的碳酸盐团簇同位素来获得矿物的生长温度,再利用矿物的氧同位素(δ¹⁸O),根据传统的氧同位素温度计原理,可以进一步获得矿物的生长流体(水)的氧同位素。目前,团簇同位素温度计已经在古气候(温度)重建、古高度恢复、碳酸盐岩的成岩作用以及甲烷的成因分析等方面得到了广泛应用。评估深埋高温过程引起的C-O化学键重置对碳酸盐团簇同位素的影响、测试仪器产生对团簇同位素的非线性误差校正、以及其他丰度更低的团簇同位素体或大分子的团簇同位素的测量,是下一步的研究方向。     

Origin of Taiwan Canyon and its effects on deepwater sediment

The continental slope of the Taiwan Shoal, which has cultivated numerous submarine canyons, is located in a passive continental margin environment. However, the trend of the Taiwan Canyon, with its 45° intersection angle, is obviously different from that of the erosion valley downward along the continental slope. A distinct break is present in the lower segment of the Taiwan Canyon, which then extends from west to east parallel to the continental slope until finally joining the Manila Trench. By utilizing multiple-beam water depth data, high-resolution seismic data, and sediment cores, this study describes the topographic characteristics of the Taiwan Canyon and provides a preliminary discussion on the origin of the Taiwan Canyon and its effect on deepwater sediment. The terrain, landform, and sediment of the Taiwan Canyon exhibit segmentation characteristics. The upper segment is characterized primarily by erosion, downward cutting with a V shape, and wide development of sliding, slumping, and other gravity flow types. The middle segment is characterized mostly by U-shaped erosion-sedimentation transition and development of an inner levee. The lower segment is characterized primarily by sedimentation and development of a sediment wave. The bottom current has a significant reworking effect on the interior sediments of the canyon and forms reworked sands. The formation and evolution of the Taiwan Canyon is closely related to sediment supply, gravity sliding(slumping), faulting activities, and submarine impaling. Given the sufficient terrigenous clastic supply, the sediments along the continental shelf edge continuously proceed seaward; gliding and slumping in the front edge provide driving forces for the formation of the canyon. Faulting activities result in stratum crushing, and the gravity flow takes priority in eroding the relatively fragile stratum. Thus, the direction of the extension of the canyon crosses the surrounding erosion valley obliquely. Seamounts are formed through submarine impaling. Owing to seamount blocking, the lower segment of the canyon is turned toward the east–west direction. Large amounts of sediments overflow at the turning, forming sediment waves.     

Localisation and phase transition of acoustic waves in a soft medium containing air bubbles

We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are particularly investigated in various cases for distinguishing efficiently the acoustic localisation from the effects of acoustic absorption caused by the viscosity of medium. The numerical results reveal the phenomenon of `phase transition' characterized by an unusual collective oscillation of bubbles, which is an effective criterion to unambiguously identify the acoustic localisation in the presence of viscosity. Within the localisation region, the phenomenon of phase transition persists, and a remarkable decrease in the fluctuation of the oscillation phases of bubbles is observed. The localisation phenomenon will be impaired by the enhancement of the viscosity factors, and the extent to which the acoustic wave is localised may be determined by appropriately analyzing the values of the oscillation phases or the amount of reduction of the phase fluctuation. The results are particularly significant for the practical experiments in an attempt to observe the acoustic localisation in such a medium, which is in general subjected to the interference of the great ambiguity resulting from the effect of acoustic absorption.     

Wind tunnel investigation of horizontal and vertical sand fluxes of ascending and descending sand particles in aeolian sand transport

The horizontal and vertical sand mass fluxes in aeolian sand transport are investigated in a wind tunnel by PTV (particle tracking velocimetry). According to the particle velocity and volume fraction of each individual particle from PTV images, the total horizontal sand mass flux, the horizontal mass fluxes of ascending and descending sand particles, and upward and downward vertical sand fluxes are analyzed. The results show that the horizontal mass fluxes of ascending and descending sand particles generally decrease with the increase of height and can be described by an exponential function above about 0.03 m height. At the same friction velocity, the decay heights of the total horizontal sand mass flux and the horizontal mass fluxes of ascending and descending sand particles are very similar. The proportion of horizontal mass flux of ascending sand particles is generally about 0.3–0.42, this means the horizontal mass flux of descending sand particles makes an important contribution to the total horizontal sand mass flux. Both the upward and downward vertical sand mass fluxes generally decrease with height and they are approximately equal at the same height and friction velocity. The relation between upward (or downward) vertical sand mass flux and horizontal sand mass flux can be described by a power function. The present study is used to help understand the transport of ascending and descending sand particles. Copyright © 2016 John Wiley & Sons, Ltd.     

嫦娥二号探测器在轨运行视景仿真系统的研究与实现

针对嫦娥二号探测器在轨运行阶段的仿真需求,充分发挥视景仿真的优势,利用嫦娥一号探测器获得的地形和影像数据、日地月嫦娥二号探测器星历数据,基于OSG(OpenScene Graph)设计了针对嫦娥二号任务的在轨运行视景仿真系统。论述了该系统的开发平台,系统总体框架,并对系统的实现进行了详细描述。论述了月球模型数据构建,嫦娥二号探测器构建,星历数据库构建与访问,仿真实体空间位置的实时更新,CCD立体相机探测过程的仿真,视点的控制等实现方法。仿真结果表明系统完全能满足嫦娥二号任务在轨运行仿真的要求,并已应用于嫦娥二号任务执行过程中。