河北省粮食生产发展趋势及其地区差异

河北省2002年粮食作物播种面积为6484.4千hm2,其中小麦占37.8%,玉米39.7%;粮食、棉花、油料的种植比例为15.9:1.0:1.6。北部四地市粮食播面占全省的23.3%,南部七地市76.7%。2002年粮食总产2435.8万t,为1949年的5.2倍;粮食单产3756kg/hm2,为1949年的5.8倍;人均粮食362kg,为1949年的2.4倍。北部地区粮食总产占全省的17.2%,南部地区82.8%。据回归分析与双向差分建模分析,2010年粮食总产可达3087.5万t,粮食单产4478kg/hm2,人均粮食460kg。据灰关联分析,影响粮食总产的主要因子有:粮食单产、农副产品收购价格总指数(1978年=100)、农业机械总动力、农村用电量、农田化肥施用量与有效灌溉面积等。根据笔者预测,若2010年农业机械总动力达8989万kw,农村用电量240.8亿kwh,农田化肥施用量356.1万t,有效灌面4549.2千hm2,则其粮食单产可达4664kg/hm2;若2010年仍保持2000年小麦播面所占比例(0.387),玉米播面所占比例达0.439,则其单产可达4387kg/hm2。     

Burial and exhumation of the Hoh Xil Basin,northern Tibetan Plateau: Constraints from detrital (U-Th)/He ages

The uplift and associated exhumation of the Tibetan Plateau has been widely considered a key control of Cenozoic global cooling. The south-central parts of this plateau experienced rapid exhumation during the Cretaceous–Palaeocene periods. When and how the northern part was exhumed, however, remains controversial. The Hoh Xil Basin (HXB) is the largest late Cretaceous–Cenozoic sedimentary basin in the northern part, and it preserves the archives of the exhumation history. We present detrital apatite and zircon (U-Th)/He data from late Cretaceous–Cenozoic sedimentary rocks of the western and eastern HXB. These data, combined with regional geological constraints and interpreted with inverse and forward model of sediment deposition and burial reheating, suggest that the occurrence of ca. 4–2.7 km and ca. 4–2.3 km of vertical exhumation initiated at ca. 30–25 Ma and 40–35 Ma in the eastern and western HXB respectively. The initial differential exhumation of the eastern HXB and the western HXB might be controlled by the oblique subduction of the Qaidam block beneath the HXB. The initial exhumation timing in the northern Tibetan Plateau is younger than that in the south-central parts. This reveals an episodic exhumation of the Tibetan Plateau compared to models of synchronous Miocene exhumation of the entire plateau and the early Eocene exhumation of the northern Tibetan Plateau shortly after the India–Asia collision. One possible mechanism to account for outward growth is crustal shortening. A simple model of uplift and exhumation would predict a maximum of 0.8 km of surface uplift after upper crustal shortening during 30–27 Ma, which is insufficient to explain the high elevations currently observed. One way to increase elevation without changing exhumation rates and to decouple uplift from upper crustal shortening is through the combined effects of continental subduction, mantle lithosphere removal and magmatic inflation.     

Modelling the advance–retreat cycle of a tidewater glacier with simple sediment dynamics

We present a simple coupled glacier-sediment model to simulate the evolution of a tidewater glacier. The model is based on a consideration of the total mass budget of a glacier, whereas ice mechanics are fully parameterized. The calving rate at the glacier terminus is assumed to be proportional to the water depth. We show that the formation of a morainic shoal has a profound influence on the response of a tidewater glacier to climatic forcing. For a slow periodic forcing of the equilibrium-line altitude, the model glacier advances steadily into the estuary, builds up a submarine terminal moraine, and then retreats rapidly when a critical point is hit. For a slowly increasing equilibrium-line altitude, at a rate as low as 1 m per 5 years, we find terminus retreat rates of up to 10 km in 50 years. Our model suggests that, although the response of tidewater glaciers to external forcing is strongly nonlinear, the onset of retreat is controlled by climate change.     

散乱数据插值的HASM方法

本文运用高精度曲面建模(HASM)方法,研究了空间散乱数据插值算法,并以陕西咸阳彬县大佛寺煤矿区的实测数据为案例,使用交叉统计检验方法比较分析HASM方法与地理信息系统(GIS)领域中常用传统插值方法的空间插值结果。结果表明,HASM方法具有较高的精度。本文还分析了传统常用插值方法的一些统计结果,得出一些结论,这些结论对于使用常用传统GIS空间插值方法的研究者有很好的参考作用。     

The value of a physically based model versus an empirical approach in the prediction of ephemeral gully erosion for loess-derived soils

A data set on soil losses and controlling factors for 58 ephemeral gullies has been collected in the Belgian loess belt from March 1997 to March 1999. Of the observed ephemeral gullies, 32 developed at the end of winter or in early spring (winter gullies) and 26 ephemeral gullies developed during summer (summer gullies). The assessed data have been used to test the physically based Ephemeral Gully Erosion Model (EGEM) and to compare its performance with the value of simple topographical and morphological indices in the prediction of ephemeral gully erosion.Analysis shows that EGEM is not capable of predicting ephemeral gully cross-sections well. Although conditions for input parameter assessment were ideal, some parameters such as channel erodibility, critical flow shear stress and local rainfall depth showed great uncertainty. Rather than revealing EGEM's inability of predicting ephemeral gully erosion, this analysis stresses the problematic nature of physically based models, since they often require input parameters that are not available or can hardly be obtained.With respect to the value of simple topographical and morphological indices in predicting ephemeral gully erosion, this study shows that for winter gullies and summer gullies, respectively, over 80% and about 75% of the variation in ephemeral gully volume can be explained when ephemeral gully length is known. Moreover, when previously collected data for ephemeral gullies in two Mediterranean study areas and the data for summer gullies formed in the Belgian loess belt are pooled, it appears that one single length (L)–volume (V) relation exists (V=0.048 L^1.29; R²=0.91). These findings imply that predicting ephemeral gully length is a valuable alternative for the prediction of ephemeral gully volume. A simple procedure to predict ephemeral gully length based on topographical thresholds is presented here. Secondly, the empirical length–volume relation can also be used to convert ephemeral gully length data extracted from aerial photos into ephemeral gully volumes.     

Sensitivity of soil parameters in unsaturated zone modelling and the relation between effective,laboratory and in situ estimates

Simulation of soil moisture content requires effective soil hydraulic parameters that are valid at the modelling scale. This study investigates how these parameters can be estimated by inverse modelling using soil moisture measurements at 25 locations at three different depths (at the surface, at 30 and 60 cm depth) on an 80 by 20 m hillslope. The study presents two global sensitivity analyses to investigate the sensitivity in simulated soil moisture content of the different hydraulic parameters used in a one‐dimensional unsaturated zone model based on Richards' equation. For estimation of the effective parameters the shuffled complex evolution algorithm is applied. These estimated parameters are compared to their measured laboratory and in situ equivalents. Soil hydraulic functions were estimated in the laboratory on 100 cm³ undisturbed soil cores collected at 115 locations situated in two horizons in three profile pits along the hillslope. Furthermore, in situ field saturated hydraulic conductivity was estimated at 120 locations using single‐ring pressure infiltrometer measurements. The sensitivity analysis of 13 soil physical parameters (saturated hydraulic conductivity (K_s), saturated moisture content (θ_s), residual moisture content (θ_r), inverse of the air‐entry value (α), van Genuchten shape parameter (n), Averjanov shape parameter (N) for both horizons, and depth (d) from surface to B horizon) in a two‐layer single column model showed that the parameter N is the least sensitive parameter. K_s of both horizons, θ_s of the A horizon and d were found to be the most sensitive parameters. Distributions over all locations of the effective parameters and the distributions of the estimated soil physical parameters from the undisturbed soil samples and the single‐ring pressure infiltrometer estimates were found significantly different at a 5% level for all parameters except for α of the A horizon and K_s and θ_s of the B horizon. Different reasons are discussed to explain these large differences. Copyright © 2004 John Wiley & Sons, Ltd.     

ESTIMATING RATES OF DENUDATION USING COSMOGENIC ISOTOPE ABUNDANCES IN SEDIMENT

We propose, as a testable hypothesis, a basin-scale approach for interpreting the abundance of in situ produced cosmogenic isotopes, an approach which considers explicitly both the isotope and sediment flux through a drainage basin. Unlike most existing models, which are appropriate for evaluating in situproduced cosmogenic isotope abundance at discrete points on Earth's surface, our model is designed for interpreting isotope abundance in sediment. Because sediment is a mixture of materials, in favourable cases derived from throughout a drainage basin, we suggest that measured isotope abundances may reflect spatially averaged rates of erosion. We investigate the assumptions and behaviour of our model and conclude that it could provide geomorphologists with a relatively simple means by which to constrain the rate of landscape evolution if a basin is in isotopic steady state and if sampled sediments are well mixed.     

准噶尔盆地中部永进地区走滑断裂发育特征及成因物理模拟

永进地区位于准噶尔盆地中部,最近发现了多个与走滑断层相关的含油气构造,但关于走滑断层的发育特征及成因机制研究程度不够深入。本文通过三维地震资料精细解释,在研究区三叠系—侏罗系内识别出近东西向、北西西向以及北东东向的三组走滑断裂体系,平面上呈“网格状”展布,剖面上具有不同深度几何学形态差异展布特征。在此基础上基于相似性原理设计四组砂箱模拟对比实验,重现研究区构造演化过程。模拟结果表明,这类走滑断裂的形成与基底先存断层的发育位置有关,是受先存构造和地层属性双重控制的广布式走滑断裂系统,从而建立了研究区的断裂系统成因模式。研究成果对具有相似地质背景地区的走滑断裂成因解释具有借鉴意义。     

Numerical modelling of deep sea air-lift

Deep sea air-lifting of solid particles from depth of 1600 m is simulated with a mathematical model of the three-phase flow in an upward pipe. The computations are carried out for an axisymmetric domain in a transient way. Phase distributions, pressure and velocity profiles together with flow rates for all phases are presented and analysed. The influence of the pipe diameter on the air-lift efficiency was studied for air-lift pipes of different lengths and found to be significant. The lifting efficiency increases with the increase of the pipe diameter due to the reduction of the wall friction influence on the flow. In addition, the efficiency also increases with the increase of the solid particles volume fraction at the inlet. The presented numerical model can be utilized during various stages of the design of the air-lift pumps to help answer fundamental questions on the process, and during their operation to select optimal process parameters and to address possible problems.     

Numerical simulation research on multi-electrodes resistivity imaging survey array

Multi-electrodes Resistivity Imaging Survey （MRIS） is an array method of electrical survey. In practice how to choose a reasonable array is the key to get reliable survey results. Based on four methods of MRIS such as Wenner, Schlumberger, Pole-pole and Dipole-dipole the authors established the model, by studying the result of the forward numerical simulation modeling and inverse modeling, and analyzed the differences among the different forms of detection devices.