液压传感间接测量水位计的研制及其应用

压力式水位计在水文自动测报系统中很难推广的主要原因是泥沙对传感器的影响,泥沙不但会使传感器测量精度达不到测验要求,而且由于泥沙淤积还会给水位计的日常维护带来很大不便。目前进口传感器测量精度高、稳定性能好,但仍避免不了泥沙的影响。针对这一问题,提出了一种新型压力式水位计———液压传感间接测量水位计,该水位计解决了泥沙对压力式水位计的影响,是一种具有很大发展前景的水位测量仪器。     

"渗流-管流耦合模型"的物理模拟及其数值模拟

井孔 -含水系统问题是当今水文地质学最重要的研究课题之一。长期以来 ,水文地质模型中对井孔的刻画基本上都是引用“热传导”中的“线汇”理论 ,需要人工预先给定线汇 线源的流量或水头的分配 ,其正确性或适用性至今没有得到理论证明。陈崇希 (1993 )提出的“渗流 -管流耦合模型”和“等效渗透系数”在理论上已解决多个水文地质问题 ,也用于几个实例 ,本文再用物理模拟检验其可靠性。论文针对具有典型意义的河床下水平井或傍河垂直井地下水流问题做了砂槽物理模拟 ,并用基于“渗流 -管流耦合模型”和“等效渗透系数”的数值方法仿真模拟了此条件下地下水流的规律。成果表明 ,数值模拟观测孔水头动态相当好地再现了物理模拟结果。论文指出了“渗流 -管流耦合模型”和“等效渗透系数”在井孔 -含水系统问题上的广泛应用前景。     

Differential spaces of critical geography

This intervention address some of the social and epistemological mechanisms that construct an `international' writing space imbued with an Anglo-American hegemony. This is done by way of three examples, each making it possible to infer one of the general mechanisms at work. Taking off from the, comment, by the way of examples from Denmark, tries to illustrate how a truthful acknowledgement of the contextuality of geographical knowledges can multiply the spaces of critical geography--in the end enriching Anglo-American and non-Anglo-American debates alike.     

地球重力场、重力、重力梯度在三维直角坐标系中的表达式

现代卫星重力测量主要利用星载GPS接收机、加速度计、星载测距仪等来确定重力卫星的轨道 ,削弱非保守力的干扰 ,由此根据卫星的位置、速度及其变率来确定地球重力场。而上述GPS等星载仪器所提供的数据 ,包括卫星轨道坐标及其速率、扰动加速度、星间距离及其变率 ,都是以三维直角坐标 (x ,y ,z)的形式表示的 ,因此 ,地球重力场、重力和重力梯度在三维直角坐标系中的表达式在卫星重力解算中具有实际意义     

Splash-saltation trajectories of soil particles under wind-driven rain

It is usually recognized that relatively large amounts of soil particles cannot be transported by raindrop splashes under windless rain. However, the splash-saltation process can cause net transportation in the prevailing wind direction since variations in splash-saltation trajectory due to the wind are expected in wind-driven rain. Therefore, determining the combined effect of rain and wind on the process should enable improvement of the estimation of erosion for any given prediction technique. This paper presents experimental data on the effects of slope aspect, slope gradient, and horizontal wind velocity on the splash-saltation trajectories of soil particles under wind-driven rain. In a wind tunnel facility equipped with a rainfall simulator, the rains driven by horizontal wind velocities of 6, 10, and 14 m s⁻¹ were allowed to impact three agricultural soils packed into 20×55 cm soil pans placed at both windward and leeward slopes of 7%, 15%, and 20%. Splash-saltation trajectories were measured by trapping the splashed particles at distances downwind on a 7-m uniform slope segment in the upslope and downslope directions, respectively, for windward and leeward slopes. Exponential decay curves were fitted for the mass distribution of splash-saltation sediment as a function of travel distance, and the average splash-saltation trajectory was derived from the average value of the fitted functions. The results demonstrated that the average trajectory of a raindrop-induced and wind-driven soil particle was substantially affected by the wind shear velocity, and it had the greatest correlation (r=0.96 for all data) with the shear velocity; however, neither slope aspect nor slope gradient significantly predicted the splash-saltation trajectory. More significantly, a statistical analysis conducted with nonlinear regression model of C₁(u_*²/g) showed that average trajectory of splash saltation was approximately three times greater than that of typical saltating sand grain.     

Seasonal variation of the total electron content, maximum electron density and equivalent slab thickness at a South-American station

Total electron content (TEC) and foF2 ionosonde data obtained at Tucumán (26.9°S; 65.4°W) from April 1982 to March 1983 (high solar activity period) are analyzed to show the seasonal variation of TEC, NmF2 (proportional to square of foF2) and the equivalent slab thickness EST. Bimonthly averages of the monthly median for January–February, April–May, July–August and October–November have been considered to represent summer, autumn, winter and spring seasons, respectively. The results show that the higher values of TEC and maximum electron density of F2-layer NmF2 are observed during the equinoxes (semiannual anomaly). During daytime, both in TEC and in NmF2 the seasonal or winter anomaly can be seen. At nighttime, this effect is not observed. Also, the observed NmF2 values are used to check the validity of International Reference Ionosphere (IRI) to predict the seasonal variability of this parameter. In general, it is found that averaged monthly medians (obtained with the IRI model) overestimate averaged monthly median data for some hours of the day and underestimate for the other hours.     

Channel adjustments of the lower Trinity River,Texas, downstream of Livingston Dam

Channel cross‐sectional changes since construction of Livingston Dam and Lake Livingston in 1968 were studied in the lower Trinity River, Texas, to test theoretical models of channel adjustment, and to determine controls on the spatial extent of channel response. High and average flows were not significantly modified by the dam, but sediment transport is greatly reduced. The study is treated as an opportunistic experiment to examine the effects of a reduction in sediment supply when discharge regime is unchanged. Channel scour is evident for about 60 km downstream, and the general phenomena of incision, widening, coarsening of channel sediment and a decrease in channel slope are successfully predicted, in a qualitative sense, by standard models of channel response. However, there is no consistent channel response within this reach, as various qualitatively different combinations of increases, decreases or no change in width, depth, slope and roughness occur. These multiple modes of adjustment are predicted by the unstable hydraulic geometry model. Between about 60 km and the Trinity delta 175 km downstream of the dam, no morphological response to the dam is observed. Rather than a diminution of the dam's effects on fluvial processes, this is due to a fundamental change in controls of the fluvial system. The downstream end of the scour zone corresponds to the upstream extent of channel response to Holocene sea level rise. Beyond 60 km downstream, the Trinity River is characterized by extensive sediment storage and reduced conveyance capacity, so that even after dam construction sediment supply still exceeds transport capacity. The channel bed of much of this reach is near or below sea level, so that sea level rise and backwater effects from the estuary are more important controls on the fluvial system than upstream inputs. Copyright © 2005 John Wiley & Sons, Ltd.     

Channel geometry of mountain streams in New Zealand

A dataset of 21 study reaches in the Porter and Kowai rivers (eastern side of the South Island), and 13 study reaches in Camp Creek and adjacent catchments (western side of the South Island) was used to examine downstream hydraulic geometry of mountain streams in New Zealand. Streams in the eastern and western regions both exhibit well-developed downstream hydraulic geometry, as indicated by strong correlations between channel top width, bankfull depth, mean velocity, and bankfull discharge. Exponents for the hydraulic geometry relations are similar to average values for rivers worldwide. Factors such as colluvial sediment input to the channels, colluvial processes along the channels, tectonic uplift, and discontinuous bedrock exposure along the channels might be expected to complicate adjustment of channel geometry to downstream increases in discharge. The presence of well-developed downstream hydraulic geometry relations despite these complicating factors is interpreted to indicate that the ratio of hydraulic driving forces to substrate resisting forces is sufficiently large to permit channel adjustment to relatively frequent discharges.     

Discussion on Characteristics of Crustal Deformation along the Zhangjiakou-Bohai Sea Seismotectonic Zone

INTRODUCTIONThe Zhangjiakou-Penglai fault zone has drawnextensive attentionfromseismologists and geologistssince it was determinedinthe1980’s(Zheng Binghua,et al.,1981).Ma Xingyuan,et al.(1989)consideredit asthe north boundaryof North China sub-block.Int…     

PRESSURE GRADIENT FROM THE CONTRIBUTION OF BOTH GEOTHERMAL AND GRAVITY IN THE LITHOSPHERE

1 Introduction The pressure, a scalar quantity, is defined as P = F/S (F is force, S is the area for F) which can be widely used for both solid and fluid. The formula P = g ρh (g-gravitation acceleration,ρ-density, h-depth) is only used for even density static solid and fluid. The delivery of pressure in the fluid follows the law of Pascal, and the average pressure of uneven density fluid can be calculated with the formula of P = g ρh. The temperature influence on pressure is notHU Ba…