中国西部沙漠化与沙尘风暴问题探讨

我国西部地表植被向恶性循环方向发展 ,土地沙漠化面积迅速增长 ,沙尘风暴日趋频繁。分析中国西部沙漠化和沙尘风暴存在的主要问题 ,进一步探讨沙漠化和沙尘风暴形成的原因和对国民经济发展所造成的危害 ,因地制宜提出了相应的治理对策

从沙尘暴看黄土的沉积及黄土高原的形成

以近年来我国西北地区多发的沙尘暴现象为缘起 ,对沙尘暴的特征、发生机制等进行了讨论 ;论述了沙尘暴引起的降尘与黄土的堆积和沉积的过程 ;黄土堆积沉积的年龄、颗粒成分等 ;以及沙尘暴与黄土高原的形成之间的关系 ,同时论述了黄土高原的环境变迁 .认为高空均质粉尘的降落是不均匀的 ;高空降尘是突发的 ,而风及流水对堆积粉尘的改造是长期和连续的

黄土高原降雨空间分布的不均匀性研究

根据黄土高原13条流域的降雨资料，分三种雨型即局地强对流条件引起的小范围、短历时、高强度的局地性暴雨（A型暴雨），峰面型降雨夹有局地雷暴性质的较大范围、中历时、中强度暴雨（B型暴雨），峰面型降雨引起的大面积、长历时、低强度暴雨（C型暴雨）；选用流域面雨量离差系数Cv、流域降雨不均匀系数η和流域最大点与最小点降雨量比值系数α三种指标，分析了次降雨空间分布的不均匀性。

CLIGEN降水要素在黄土塬区的适应性评估

CLIGEN是目前较全面产生降水要素(降水量、历时、达到最大降水强度的时间与降水总历时的比率、最大降水强度与平均降水强度的比率)的天气发生器,其生成降水要素的质量直接影响水文和农业响应模型的输出结果。利用黄土高原长武1957—2001年的日气象观测数据、王东沟流域1988—2001年的降水要素数据和CLIGEN生成的100年日气象数据,对CLIGEN模型产生日、月、年降水量的均值和方差、概率分布、降水极端值和降水历时、强度进行评估。结果表明:CLIGEN对日、月和年降水量均值的模拟效果较好,相对误差都不大于1.0%;对标准差的模拟结果偏低,相对误差的绝对值小于6.6%;没有模拟出日降水量的概率分布,但是较好地模拟出了月和年降水量的概率分布;对日、月和年最大降水量的模拟误差较大,表明CLIGEN对极值的模拟精度有待提高。CLIGEN很好地模拟出连续降水的频率,但是连续干旱天数在20 d以内的累积频率的平均相对误差为8.9%;CLIGEN产生的最大降水强度与平均降水强度的比率高于实测数据;相对于实测数据,CLIGEN模拟的降水历时和降水量具有相同的趋势,对小降水量或短历时的模拟结果偏高,对大降水量或长历时的模拟结...

Folate-Conjugated Micelles and Their Folate-Receptor-Mediated Endocytosis

A folate-conjugated copolymer PEG-PLA-PLL/folate was synthesized and mixed with pure PEG-PLA-PLL and a fluorescent model drug mFITC to prepare folate-conjugated micelles. The distribution of micelles was studied on cancer-cell-bearing mice via frozen slicing. The results show that mFITC is successfully encapsulated into folate(+) and folate(-)micelles; PEG-PLA-PLL micelles the latter can be internalized by both HeLa and CHO cells without selectivity due to their cationic surface charges, while folate(+)micelles exhibit more preferential endocytosis by HeLa cells than by CHO cells. The folate(-)micelles showed retention in both organs and tumors. The folate(+)micelles are a promising active targeting drug delivery system for FR over-expressing cells and they accumulate in tumor beds.

Size and time of day affect the response of postlarvae and early juvenile grooved tiger prawns Penaeus semisulcatus De Haan (Decapoda:Penaeidae) to natural and artificial seagrass in the laboratory

Juvenile tiger prawns (Penaeus semisulcatus De Haan and P. esculentus Haswell) show a strong association with vegetated habitats and are rarely caught on non-vegetated areas. This pattern of distribution may be caused by postlarvae selecting vegetation when they settle, or to differences in post-settlement mortality in different habitats. In this study, we examined whether the postlarvae and early juvenile stages of P. semisulcatus would distinguish between seagrass (Zostera capricorni Aschers) without epiphytes, artificial seagrass and bare substratum in the laboratory. The responses of prawns reared from the egg to different stages of postlarval and juvenile development were tested to determine whether, and when, each size class showed a response to a particular habitat. Five size classes of postlarvae (average carapace lengths [CL] of 1.2, 1.4, 1.6, 1.7 and 2.0 mm) were offered a choice between Z. capricorni and bare sand. Small size classes of postlarvae either did not respond to Z. capricorni (1.2 and 1.6 mm CL), or were more abundant on bare substratum than Z. capricorni. In contrast, the largest size classes of postlarvae (1.7 and 2.0 mm CL) were more abundant on Z. capricorni during the day but not at night. The behaviour of postlarvae changed markedly at a size of 1.7 mm CL (22 days from the first nauplius): smaller postlarvae frequently swam in the water column; 1.7 and 2.0 mm CL postlarvae spent much more. time resting on the substrate and perched on seagrass leaves. This size at which postlarvae first respond to seagrass during the day, and show mainly benthic behaviour, is similar to the size at which they are found on shallow seagrass beds in northern Australia. Large postlarvae (2.7 mm CL) and juveniles (4.1 mm CL) both were more abundant on artificial seagrass than bare sand during the day but not at night, indicating that they respond to structured habitats. When large postlarvae (2.4 mm CL) and juveniles (3.5 mm CL) were offered a choice between Z. capricorni without epiphytes and artificial seagrass, they were more abundant on the Z. capricorni, which suggests that chemical cues from seagrass may explain some of the responses of P. semisulcatus to seagrass. (C) 1997 Elsevier Science B.V.

Geophysical signatures associated with fluid flow and gas hydrate occurrence in a tectonically quiescent sequence, Qiongdongnan Basin, South China Sea

Interpretation of high-resolution two-dimensional (2D) and three-dimensional (3D) seismic data collected in the Qiongdongnan Basin, South China Sea reveals the presence of polygonal faults, pockmarks, gas chimneys and slope failure in strata of Pliocene and younger age. The gas chimneys are characterized by low-amplitude reflections, acoustic turbidity and low P-wave velocity indicating fluid expulsion pathways. Coherence time slices show that the polygonal faults are restricted to sediments with moderate-amplitude, continuous reflections. Gas hydrates are identified in seismic data by the presence of bottom simulating reflectors (BSRs), which have high amplitude, reverse polarity and are subparallel to seafloor. Mud diapirism and mounded structures have variable geometry and a great diversity regarding the origin of the fluid and the parent beds. The gas chimneys, mud diapirism, polygonal faults and a seismic facies-change facilitate the upward migration of thermogenic fluids from underlying sediments. Fluids can be temporarily trapped below the gas hydrate stability zone, but fluid advection may cause gas hydrate dissociation and affect the thickness of gas hydrate zone. The fluid accumulation leads to the generation of excess pore fluids that release along faults, forming pockmarks and mud volcanoes on the seafloor. These features are indicators of fluid flow in a tectonically-quiescent sequence, Qiongdongnan Basin. Geofluids (2010) 10, 351-368.

Application of forecasting structural cracks technique of 3D move in Chengdao buried hill

3DMove software, based on the three-dimension structural model of geologic interpretation, can forecast reservoir cracks from the point of view of formation of the structural geology, and analyze the characteristics of the cracks. 3DMove software dominates in forecasting cracks. We forecast the developments and directions of the cracks in Chengbei buried hill with the application of forecasting technique in 3DMove software, and obtain the chart about strain distributing on top in buried hill and the chart about relative density and orientation and the chart about the analysis of crack unsealing. In Chengbei 30 buried hill zone, north-west and north-east and approximately east-west cracks in Cenozoic are very rich and the main directions in every fault block are different. Forecasting results that are also verified by those of drilling approximately accord with the data from well logging, the case of which shows that the technique has the better ability in forecasting cracks, and takes more effects on exploration and exploitation of crack reservoir beds in ancient buried hill reservoirs.

Geomorphic and hydrodynamic responses in salt marsh-tidal creek systems, Jiangsu, China

Salt marsh-tidal creek systems as a coastal geomorphological unit represent an important natural resource. The present study on Jiangsu salt marshes, eastern China, shows that variations in tidal current velocities in salt marsh creeks are controlled by the local tidal wave characteristics and the bed slope and elevation of the salt marshes and creeks. Likewise, the tidal currents modify the geomorphology of the salt marsh-tidal creek systems by transporting sediments and causing erosion/deposition. Storm events, which appear to have cyclical changes in their intensity relating to sunspot activities, can affect the geomorphic evolution of such systems. Further, in response to accelerated sea-level rise, accretional rates on salt marshes may increase. The tidal creeks have the function of transporting water and sediment onto the salt marsh surface; further, the energy of tidal currents and waves are dissipated within the salt marsh-tidal creek system. Hence, this coastal system has a potential value for coastal protection.

Source of a floating dust episode over the Qingdao region and dust throughput to the ocean

A floating dust weather happened on March 11-12, 1995 over the Qingdao region. Its sources and throughput to the ocean were studied. The result indicated that the floating dust was caused by the dust storm that starred in northwestern China and developed in northern China. 21 x 10(6)t fine soil particles were carried to the ocean during the episode.

Numerical calculation of the response of the south China sea to typhoon imbudo

The response of the South China Sea (SCS) to Typhoon Imbudo was examined using POM model. The results indicated that SST decreased by 2-6 degrees C with a rightward-biased response as Typhoon Imbudo passed across the SCS. Due to a strong mixing process, the mixed layer (ML) depth deepened as much as 10-60 m and ML heat budget lost 824.78 W/m(2), which was OF dominated by the vertical mixing. By the response of upper ML heat transport, the temperature below the ML increased and oscillated near the inertial period. Furthermore, strong inertial currents were generated by the storm with the max currents up to 1.4 m/s in the upper ML.

Near-Space Wide-Swath Radar Imaging With Multiaperture Antenna

Near-space, defined as the altitude region between 20 and 100 km, offers many capabilities that are not accessible for low Earth-orbit (LEO) satellites or airplanes because it is above storm and not constrained by orbital mechanics and high fuel consumption. Hence, a high flying speed can be obtained for the maneuvering vehicles operating in near-space. This offers a promising solution to simultaneous high-resolution and wide-swath synthetic aperture radar (SAR) imaging. As such, one near-space wide-swath SAR imaging technique is presented in this letter. The system configuration, signal model, and imaging scheme are described. An example near-space SAR system is designed, and its imaging performance is analyzed. Simulation results show that near-space maneuvering vehicle SAR indeed seems to be a promising solution to wide-swath SAR imaging.

海浪、天文潮与风暴潮耦合数值模拟研究

本文研究了国际上刚刚兴起的海浪，天文潮及风暴潮耦合数值模式，考虑了天文潮与风暴潮的相互作用对海浪的影响（简称TSW）。研究表明，TSW的影响依不同的时间、地点和风力强弱而不同，在某些时刻和地点，TSW对波高的影响超过1M，对波向的影响达30#deg#。WTS的影响对天文潮与风暴潮耦合水位起调制作用，在风暴发生初期大一些，后期小一些。

污水生化处理过程仿真及在A~2/O工艺改进中的应用

基于国际水协会IWA发布的国际评价基准Benchmark,建立了与污水处理厂实际特性相近的标准仿真平台。对污水处理传统A2/O工艺做了合理改进,在不影响出水水质的情况下,取消内回流。应用该平台分别对晴天、雨天与暴雨三种天气的工艺过程模拟,验证了工艺改进的合理性。仿真结果表明,与传统A2/O工艺相比,出水指标差别不大,但污泥泵能耗降低约50%。

元谋盆地河湖相沉积记录的上新世印度季风转型事件

The Indian monsoon, an integral part of the global climate system, has been extensively investigated during the past decades. Most of the proxy records are derived from marine sediments and focused on time periods of the late Miocene and Pleistocene. The Pliocene represents a period when Earth’s boundary conditions underwent dramatic changes. However, variations of the Indian monsoon during the Pliocene and its forcing mechanisms have remained unclear. The Yuanmou Basin, located in the region of the Indian monsoon, provides an ideal target for understanding the Pliocene history of Indian monsoon variations. Detailed investigations on the lithostratigraphy, magnetostratigraphy and limnology of a 650-m-thick fluvio-lacustrine sedimentary sequence from the basin are carried out in the present study. The clay and clay-plus-fine-silt fractions of the sediments are referred to the midlake-facies components, and changes in the percentages of both fractions generally reflect changes in the water level of the lakes developed in the basin closely related to variations in the intensity of the Indian monsoon. Whereas the greenish-gray lacustrine mud beds represent the environment of deep-water lakes, and the frequency of individual lacustrine mud beds is considered to indicate the frequency of the deep-water lakes developed in the basin associated with the variability of the Indian monsoon. The proxy data suggest that the Indian monsoon experienced abrupt shifts at 3.53, 3.14, 2.78 and 2.42 Ma, respectivey. 1) Since 3.53 Ma, the midlake-facies components displayed a general trend of increase in the concentrations, accompanied by an increase in the sedimentation rate from an average ~10 to 25 cm ka–1. The data suggest that high stands of the lakes in the basin rose progressively, implying a gradual intensification of the Indian monsoon since that time. This shift occurred coeval with the accelerated uplift of the northern Tibetan Plateau, denoting a close link between the Indian monsoon strengthening and the Tibetan Plateau uplifting. 2) 2.78 Ma ago, the concentrations of the midlake-facies components decreased abruptly and the dominant fraction of the sediments turned to fluvial sands. The data indicate that lakes in the basin disappeared, reflecting a dramatic decline in the intensity of the Indian monsoon at that time. This shift coincided with the formation of extensive Northern Hemisphere ice sheets, implying a quick response of the low-latitude monsoon regime to the high-latitude glaciation. 3) At 3.14 Ma, the initial appearance of blackish-grey mud beds with long durations and occasional occurrences of lacustrine mud beds indicate that the basin was overall dominated by shallow lakes, implying a shift to decreased variability of the Indian monsoon at that time. At 2.42 Ma, an increase in the frequency and a decrease in the duration of the lacustrine mud beds suggest that deep-water lakes were frequently developed in the basin, denoting a shift to increased variability of the Indian monsoon at that time. The former shift coincides with the onset of large-scale glaciation in the circum Atlantic region and the latter corresponds to the inception of predominance of the 41 ka periodicity in Northern Hemisphere ice-sheet cover fluctuations, presumably suggesting a physical link between the Indian monsoon system and the high-latitude ice sheets in the Northern Hemisphere.