提高GPS高程拟合模型精度的有效方法

在调兵山地区,选择76大地高和正常高都已知的点作为原始数据,采用多项式拟合加权平均法建立该地区大地水准面,包括泰勒二次多项式加权平均法和双二次多项式加权平均法。通过实例发现,泰勒二多项式曲面加权平均法和双二次多项式加权平均法对高程异常的短波项有很好的改进效果,拟合残差值比较大的点采用泰勒二次多项式曲面加权平均法和双二次多项式加权平均法残差值变小,大大提高了拟合模型的精度,改善了拟合模型。     

Morphological changes on meander point bars associated with flow structure at different discharges

This study investigates the impact of flow structure of different discharges on meander point bar morphology. We carried out mobile and terrestrial laser scanning campaigns before and after a flood on two sandy‐bed point bars. Between the scans, the flow structure was examined using an Acoustic Doppler Current Profiler at three flow stages. The results indicated that a meander point bar both affects and in turn, is itself modified by the flow at different discharges. The lower flow stages also have a significant effect on point bar morphology, especially on deposition over the bar head. Secondary circulation is responsible for scroll bar formation on the point bar margin beyond the apex. Flow separation at the inner bank, by contrast, does not require secondary circulation, but is dependent on flow depth over the point bar. A sudden increase in depth beyond the point bar top causes decreased stream power over the bar tail. The flow separation and decreased stream power cause a slow flow zone and net deposition over point bar tail. The backwater effect, if evident, may strengthen the process. Thus, filling over the bar tail seems generic for point bars and independent on secondary flow. Chutes and chute bars, scroll bars, bar head filling and bar platform filling, by contrast, require special fluvio‐morphological circumstances discussed in this paper. Whilst this paper confirms that the three‐dimensional flow structure has a major effect on point bar morphology, the flow structure seems to depend on how the point bar affects the flow trajectory which, in turn, depends upon the flow stage. Finally, the shape of the bend and the grain size distribution control the impacts of the flow structure, leading to divergent morphologies of point bars with certain generic features. Copyright © 2012 John Wiley & Sons, Ltd.     

Modulation of the flow structure by progressive bedforms in the Kinoshita meandering channel

An in‐house fully three‐dimensional general‐purpose finite element model is applied to solve the hydrodynamic structure in a periodic Kinoshita‐generated meandering channel. The numerical model solves the incompressible Reynolds‐averaged Navier–Stokes equations for mass and momentum, while solving the k ? ε equations for turbulence. The free surface is described by the rigid‐lid approximation (using measured water surface data) for flat (smooth‐bed) and self‐formed (rough‐bed) conditions. The model results are compared against experimental measurements in the ‘Kinoshita channel’, where three‐dimensional flow velocities and turbulence parameters were measured. This validation was carried out for the upstream‐valley meander bend orientation under smooth (flat bed) conditions. After validation, several simulations were carried out to predict the hydrodynamics in conditions where either it was not possible to perform measurements (e.g. applicability of the laboratory acoustic instruments) and to extrapolate the model to other planform configurations. For the flat smooth‐bed case, a symmetric (no skewness) planform configuration was modeled and compared to the upstream‐skewed case. For the self‐formed rough‐bed case, prediction of the hydrodynamics during the progression of bedforms was performed. It appears that the presence of bedforms on a bend has the following effects: (i) the natural secondary flow of the bend is disrupted by the presence of the bedforms, thus depending on the location of the dune, secondary flows might differ completely from the traditional orientation; (ii) an increment on both the bed and bank shear stresses is induced, having as much as 50% more fluvial erosion, and thus a potential increment on the migration rate of the bend. Implications on sediment transport and bend morphodynamics are also discussed in the paper. Copyright © 2013 John Wiley & Sons, Ltd.     

应用精细油藏描述技术实现S3区可持续发展

对S3区开展的精细油藏描述,发现由于储层胶结性差、埋深浅、笼统注采以及防砂措施不配套等因素影响,整个区块出现储量动用不均衡,原开发方式已经不适应油藏的开发形式的需要。在油藏开发调整中,进行平面开发区域的合理划分与重组。针对不同区域储层特征、沉积特点、水驱开发特征、现有井网完整程度和剩余油分布状况,对不同区域采用适合的开发方式,实现在同一区块采用多元的开发方式进行整体二次开发,使该区块生产能力得到改善。     

Diagenesis of organic matter in a 400 m organic rich sediment core from offshore Namibia using solid state 13C NMR and FTIR

Although rates and mechanisms of early diagenesis have been well studied, the effects of microbial metabolism on the molecular composition of the sedimentary organic matter (SOM) over long periods of time need more investigation. In this study, we characterize the early diagenesis of marine SOM from organic rich sediments of the Ocean Drilling Program site 1082 located off Namibia, in the vicinity of the Benguela coastal upwelling system. We used both Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (¹³C NMR) to assess the quantitative partitioning of the organic carbon into major compound classes (aliphatic, aromatic, ester, carboxylic, amide and carbons from carbohydrates). Then, we calculate the SOM composition in the main biomolecules (proteins, carbohydrates, lipids and lignin) on the basis of previous ¹³C NMR based estimates of the molecular composition of the organic mixtures. Results show that the SOM is still labile at 7 m below the seafloor (mbsf) and composed of about 25% proteins and 15% carbohydrates. With increasing depth, the protein content exponentially decreases to 13% at 367 mbsf, whereas the carbohydrate content decreases linearly to 11%. The lignin and lipid content consistently represent around 10% and 40% of the SOM, respectively, and show an increase with depth, due mostly to selective enrichment as the more labile components are lost by degradation. Thus, these components of the SOM are considered refractory at the depth scale considered. The calculated remineralization rates are extremely slow ranging from 5.6 mol C m⁻³ ky⁻¹ at the top of the core to 0.2 mol C m⁻³ ky⁻¹ according to the organic carbon flux to the seafloor. Knowing the labile carbon losses, we propose a method to calculate the initial TOC before the diagenesis took place.     

细长输流管内外流耦合振动特性研究

管内流动会影响输流管的振动响应,目前关于输流弹性管涡激振动方面的研究较少。基于计算流体力学(CFD)方法,开展内外流对细长输流弹性管振动特性影响的研究。首先在不考虑内流的情况下将弹性管涡激振动数值预报结果与模型试验数据进行对比,验证了数值方法的可靠性。再者考虑内外流耦合作用情况下,对不同内流流速下细长输流弹性管振动位移时—空分布、顺流向最大平均偏移、振动轨迹、内部横向涡的形成与分布等进行了对比分析。结果发现,与外流流速相比,内流流速的增加虽然难以改变弹性管的主振模态,但对沿管体的振动强度影响显著。顺流向最大偏移处管体运动轨迹发生明显的变形和跳跃。在剪切外流和均匀内流对弹性管的联合作用下,沿管跨方向模态间能量转换频繁,伴随着间歇性出现或消失的沿弹性管传播的行波组分,这主要归因于复杂的双重流固耦合系统(外流—管体,内流—管体)。在内流以附加质量力、离心力和科氏力形式的激励下,弹性管内二次流现象明显。在振动过程中,内部横向涡沿管壁生成、脱落并逐渐散布于整个横截面。     

Multi-scale variability of water discharge and sediment load into the Bohai Sea from 1950 to 2011

This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales: 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.     

Wait公式与Millington经验公式预测地波时延的比较

为了了解用于预测沿光滑分段均匀混合路径传播的地波时延的Millington经验公式的实用性,对Millington经验公式和用于预测沿光滑分段均匀混合路径传播的地波时延的严格的Wait公式进行了比较。在Wait积分法用计算机软件实现的基础上,用上述2种方法分别计算多条实际路径的地波二次相位因子,并对计算结果进行了比较。比较结果表明,在实际工程应用中用Millington经验公式进行地波时延预测符合应用要求。     

Achieving the Impossible: The 1∶500 000 ‘Irrigation Map’ of South Africa, 1935–1937

Abstract

Since 1906, South Africa boasted an excellent geodetic framework, and in 1920 an official Trigonometrical Survey Office (TSO) was established. In spite of these achievements, the country, by the 1930s, still lacked reliable topographical maps. One reason for this was that the secondary and tertiary triangulations of the country were still incomplete; another was that the decision-making process as regards surveys and mapping rested with a variety of statutory bodies instead of just one. In 1934, A. D. Lewis, Director of the Department of Irrigation, committed his department to execute a general topographical survey of the country and produce a topographical map on a scale of 1∶500?000. Lewis’ decision met with much resistance from within the country and abroad, but the project was completed in a record period of 4 years. Published just before the Second World War, the map was of inestimable value to the South African Defense Force. It not only became the standard topographical map of large parts of South Africa for many years, but its contents also figured in the first map series of the TSO.     

Pupils' knowledge and awareness of geography when starting upper secondary school in Norway

The author, an upper secondary teacher in geography, has conducted various surveys and questionnaires among pupils every year, for 30 years. The article examines his pupils' knowledge of geography when they start upper secondary school. During their first lesson in geography they are presented with a questionnaire designed to test their knowledge of concepts, places, and causal relationships. In addition, they are asked about their perceptions of geography and expectations when they start to study a new subject. The author finds it valuable and important as a teacher to know what his pupils have learned during their lower secondary education because such information could be used to adapt upper secondary education in geography to the pupils' abilities. Further, it is important to motivate, create expectations, and develop awareness of geography. In addition to discussing pupils' knowledge of geography, the article shows briefly how school curricula and geography teaching have changed in Norwegian lower secondary schools since the early 1970s.