异质性“通道”与跨国公司地方化结网——以苏州工业园为例

在经济全球化时代,跨国公司是开发区形成、发展和演进的关键驱动力量。在多种异质性行为主体交互作用所形成的＂学习场＂中,跨国公司要实现其全球化和本土化战略,就必须与开发区政府和本土企业之间建立有效的地方化结网＂通道＂。其中,＂政策通道＂首先为其提供了最基本的＂通道＂保障,成为跨国公司进驻开发区的初始动因。通过技术、市场等各...     

长航道乘潮水位计算新方法研究及应用

随着航道建设规模和航道里程增加,长航道乘潮水位的计算成为航道设计遇到的新技术难题之一。针对多潮位站控制长航道乘潮水位计算问题,提出了乘潮水位计算的多站联合典型潮曲线法。通过构建典型潮曲线,使乘潮累积频率、乘潮历时、潮波传播延时和潮波变形等关键要素同时呈现。基于构建的典型潮曲线,进一步探讨了长航道全程同一乘潮水位、分段变乘潮水位,以及进港、出港等不同情况下乘潮水位的设计取值方法,并以珠江崖门航道为例进行了实例分析,进一步说明了本方法的实用可行。     

长江中游曲流河段河道的近代演化过程研究

曲流河是冲积平原河流中的重要河型之一,曲流河的河道演变对冲积平原的建设与演化起着非常重要的作用。地处江汉平原的长江中游藕池口至城陵矶段河道是最典型的曲流河段,其曲流河道的几何形态和变化过程较为复杂,对该段河道演化过程的研究在河流的开发利用及水利工程建设中具有很好的理论指导意义。本研究通过对历史资料和多期卫星遥感影像的解译与分析,表明长江中游藕池口至城陵矶河段的曲流河道演化在受自然和人类活动双重影响的情况下,该河段河道的演化仍然维持曲流河特征。受大洪水的切滩作用及松滋口、太平口和藕池口3个分流口对洞庭湖的分水分沙的影响,该段河道的演化过程较为复杂。自然裁弯取直和人工裁弯取直在一定程度上改变着河道演化的进程,但由裁弯取直及上游水利工程引起的纵坡降增加产生的冲淤变化将会维持河道的稳定,同时在该河段实施的护岸工程也会抑制河流的横向侵蚀,曲流河段河道演化进入自调整和自组织过程。     

一种微结构颗粒体分布特征的分析方法

在扫描电镜法（SEM）图像二值化基础上,建立了以颗粒体面积为变量的面积累计曲线表示方法,进而建立了该曲线的曲率系数和颗粒体面积分布特点的不均匀系数。基于瓜州砂质粉土和天津黏土的SEM图像,分析了不同面积比对应的颗粒体特征。研究表明,砂质粉土和黏土的颗粒体面积累计曲线、曲率系数和不均匀系数具有明显的差异性。砂质粉土的颗粒体面积累计曲线是一条平滑的曲线,表现为不良级配土的粒径分布特点;而黏土的颗粒体面积累计曲线具有明显的台阶,表现为某粒组缺失的粒径分布特点。另外,砂质粉土的颗粒体面积累计曲线曲率系数和不均匀系数均明显大于黏土的对应系数。该分析方法可以用来量化不同土的SEM照片之间的差异,从而为岩土微结构的定量化研究提供了一条新的思路。     

Precoding Based Channel Prediction for Underwater Acoustic OFDM

The life duration of underwater cooperative network has been the hot topic in recent years. And the problem of node energy consuming is the key technology to maintain the energy balance among all nodes. To ensure energy efficiency of some special nodes and obtain a longer lifetime of the underwater cooperative network, this paper focuses on adopting precoding strategy to preprocess the signal at the transmitter and simplify the receiver structure. Meanwhile, it takes into account the presence of Doppler shifts and long feedback transmission delay in an underwater acoustic communication system. Precoding technique is applied based on channel prediction to realize energy saving and improve system performance. Different precoding methods are compared. Simulated results and experimental results show that the proposed scheme has a better performance, and it can provide a simple receiver and realize energy saving for some special nodes in a cooperative communication.     

Late quaternary sediment sources, storage and transfers within mountain basins using clast lithological analysis: Pineta Basin, central Pyrenees, Spain

Understanding basin-wide sediment dynamics, both spatially and temporally, is an important antecedent to eventual quantitative interpretation of sediment transfer within mountain fluvial systems. This paper describes an attempt to trace sediment transfer modes and pathways using clast lithological analysis in a small mountain basin strongly influenced by glaciation: the Pineta Basin in the central Pyrenees of Spain. The paper interprets slope–channel interaction by encompassing the whole basin, enabling staged sedimentary pathways to be revealed. Additionally, bed-material textures of the modern rivers and youngest La Sarra Terrace were investigated to provide further information on the geomorphic coupling of the system. Relatively few studies have taken this approach. Glacial and later, fluvial systems transferred the sediments creating laterally extensive, polylithological sediment stores. Local depositional systems overprint this inherited signature. To what extent depends on the size and energy of the local system. Significant impacts are made by conduits, such as large-scale fluvially dominated fans and waterfalls, which deliver local lithologies to the main river. Conduits may be part of the main river system or part of the tributary system. Conduits are the most important elements when considering provenance studies and theoretical modelling.     

一次触发闪电金属汽化通道的亮度与电流特征

2022年夏季在广州从化人工引雷试验场的一次触发闪电过程中, 获取了近距离的高分辨率图像、通道底部电流波形和高速摄像数据。此次触发闪电的高分辨率图像清晰展现了多回击过程金属汽化通道段的空间位移, 汽化通道在连续电流过程中呈现类似火焰的发光特征。结合高速摄像与通道底部电流数据, 研究回击与连续电流过程中金属汽化通道段亮度与电流强度的相关性, 结果表明:相比于回击峰值电流, 其平方与回击峰值亮度的相关性更强, 相关系数分别为0.940和0.955(均达到0.001显著性水平)。对于伴随长连续电流的回击过程, 回击下降部分与之后连续电流过程光电线性相关性拟合的斜率有明显差异。叠加在长连续电流过程上的多个M分量脉冲亮度峰值相对于电流峰值时间滞后, 较小的脉冲峰值电流对应较大的亮度峰值滞后时间。     

The impact of single natural vegetation elements on flow characteristics

In this experimental study, measurements were conducted to explore the impacts of different forms of individual natural vegetative elements within the flow domain on velocity and turbulence characteristics. All the experiments were performed in a flume measuring 26 m in length, 0·98 m in width and 0·85 m in depth, and real tree saplings were utilized to represent the vegetation element. In order to analyse this commonly observed nature phenomenon in floodplains, trees with wide trunks were classified into three groups on the basis of their volume versus height relation. Throughout the velocity measurements three acoustic Doppler velocimeters were employed. Time‐averaged velocity, streamwise and vertical turbulence intensities and turbulent kinetic energy parameters were examined. Additionally, a formulation that gives the velocity profile at a certain distance downstream of vegetation was introduced and the validity of the proposed formulation was checked with experimental data. It is seen that despite their porous structures, the presence of vegetation considerably disturbs the flow field and dissipates a remarkable amount of energy by turbulence. Copyright © 2008 John Wiley & Sons, Ltd.     

Hydrologic procedures of storm event watershed models: a comprehensive review and comparison

Currently, many watershed models are available that have various complexities, strengths, and weaknesses. The basic mathematical foundations of these mathematical models are often overlooked due to high demands on convenient applications with graphical user interfaces. Although this and other factors are important while selecting a model, the mathematical foundation should also be taken into account, as performance or efficiency and accuracy of a model depend on its simplicity or complexity. A comprehensive review of 14 storm event watershed models was conducted. Hydrologic procedures (rainfall excess, flow routing, and subsurface flow) of the models are presented and compiled. Among the procedures, flow routing has the most influence on model performances (speed and accuracy). Overland and channel flow routing procedures using different flow‐governing equations, having various approximations and solved by different methods, are compared based on their relative levels of physical bases, complexities, and expected accuracies in simulating the dynamics of water flow. Models using more mathematical terms in the flow‐governing equations are more physically based and expected to be more accurate than models using approximations, however, are more complex due to more intensive but approximate numerical schemes (inefficient). Models using approximate equations with analytical solutions may provide a balance between complexity and accuracy. The review and comparisons are useful to modellers, water resources managers, and researchers in understanding the basic foundations of the models and making informed selections for practical applications or further developments. Other factors such as data intensiveness, user friendliness, and resource requirements are also important considerations. Copyright © 2011 John Wiley & Sons, Ltd.     

Boninitic and tholeiitic basaltic lavas and dikes from dispersed Jurassic East Othris ophiolitic units,Greece: petrogenesis and geodynamic implications

ABSTRACT

Pillow lavas, massive lava flows, and sub-volcanic dikes of tholeiitic basaltic composition are found to be members of the Vrinena, Aerino, Eretria, and Velestino dispersed Middle–Upper Jurassic ophiolitic units in East Othris. The Vrinena and Eretria ophiolitic units appear to have been emplaced onto the Pelagonian continental margin during the Upper Jurassic–Lower Cretaceous, whereas the Aerino and Velestino units seem to have been finally emplaced during post-Palaeocene times. Geochemically these are divided into two groups: Group I includes subduction-related boninites and low-Ti basalts from the Vrinena and Aerino units, and Group II high-Ti basalts show spreading-type characteristics occurring in the Eretria and Velestino units. Primary magma of the Group I volcanics appears to have been formed after high partial melting degrees (~18%) of a highly depleted harzburgitic mantle source, under relatively high temperatures (mantle potential temperature ~1372°C). Petrogenetic modelling also suggests that the primary magma of the Group II volcanics were formed after lower partial melting degrees (~7%) of a moderately depleted mantle source. The petrological and geochemical data from the East Othris dispersed and diversely emplaced ophiolitic units provide evidence of a common intra-oceanic supra-subduction zone (SSZ) origin within the Pindos oceanic strand of the Western Tethys. Specifically, Group I lavas and dikes from Vrinena seem to represent the extrusive part of an almost complete fore- to island-arc ophiolitic sequence. Dikes of Aerino most likely correspond to fore-arc magmatic material that intruded within exhumed serpentinized ultramafic rocks through a subduction channel that developed close to the slab and towards the fore-arc and the accretionary prism. The Group II volcanics either corresponded to a fore-arc magmatic expression, which extruded earlier than Group I volcanics and prior to the establishment of a mature subduction zone, or represent back-arc to island-arc magmatism that was contemporaneous to the fore-arc magmatic activity during rollback subduction.