室内构造变形物理场观测系统的设计与实施

建立一个完整配套的室内地震预报实验场观测系统是深入进行地震预报理论研究，提高物理预报准确率，检验各种预报方法的重要手段。为此，设计试制了一套多通道、高分辨率、宽动态、宽频带的数字化实验观测系统。该系统可以联接多种传感器，用于多参数物理场的同步动态观测     

硫化氢形成与C2+气态烷烃形成的同步性研究几个模拟实验的启示

硫酸盐热还原（TSR）是高含硫天然气形成的主要原因,但是参与TSR反应的主要烃类组分仍存在争议。在对比分析湿气—硫酸镁反应体系、甲烷—硫酸钙反应体系以及重烃—硫酸镁反应体系模拟实验的基础上,通过对TSR化学反应表达式的分析以及化学动力学、热力学等理论的探讨,结合实际地质资料,认为甲烷是C₂₊烃类参与TSR反应的产物,TSR的发生与C₂₊气态烷烃的产生具有同步性,TSR的反应速率随着C₂₊气态烷烃的增加而加快,当湿气裂解为干气后,硫化氢含量几乎不再增加,从而形成干气伴生硫化氢。根据油气生成演化阶段分析,认为TSR主要发生在热裂解生凝析气阶段,原油裂解为硫化氢伴生天然气后,压力系统发生改变,天然气重新聚集成藏,如果构造环境发生改变就会进一步调整成藏。因此,天然气中硫化氢含量不仅受生成条件控制,还受运移通道、保存条件等因素控制。     

Groundwater availability in the shallow aquifers of the southern voltaian system: a simulation and chemical analysis

A steady state groundwater flow simulation model was developed using available well data and general hydrogeological and geological information, for the Afram Plains area, Ghana. The hydrochemistry of groundwater from wells in the area was then evaluated to determine its suitability for irrigation and domestic uses. The assessment of the irrigation quality of groundwater from this area was based on salinity (EC) and sodium adsorption ratios (SAR), residual sodium carbonate (RSC), and permeability indices (PI). The simulation model reveals that groundwater in the Afram Plains area generally flows from the midsections in the neighborhood of Tease and surrounding areas, where significant recharge takes place, to the outer regions and discharges into the Volta Lake in the southern and eastern sections of the area. Flow magnitude and piezometric maps suggest that there is probably of less potential for groundwater extraction for sustainable irrigation in the central regions of the area, when compared to the other discharge areas. This study reveals that more than 70% of the samples analyzed fall within the C2–S1 category, referring to the medium level salinity and low sodium. Medium salinity waters may be used for irrigation on coarse textured soils with good permeability. About 15% of the data fall within the C3–S2 category, referring to water of high salinity and medium sodicity. High salinity, medium sodicity irrigation water cannot be used on fine-grained soils where drainage is restricted. This is because restricted flow is likely to result in the accumulation of salts in the root zones of crops, leading to salinity and soil clogging crisis. About 3% falls within the C3–S3 (high salinity, high sodicity) category. This category requires special soil management including improved drainage, heavy leaching and the use of chemical amendments on the water. Only one point plots within the extreme salinity–sodicity range. Concentrations of fluoride, arsenic and other natural elements in the area generally fall well within the world health standards for domestic water.     

Simulation of axis-symmetric seismic waves in fluid-filled boreholes in the presence of a drill string

A numerical algorithm for simulation of 2-D (axis-symmetric) wave propagation using a multidomain approach is proposed. The method uses a cylindrical coordinate system, Chebyshev and Fourier differential operators to calculate the spatial derivatives along the radial and vertical direction, respectively, and a Runge–Kutta time-integration scheme. The numerical technique is based on the solution of the equations of momentum conservation combined with the stress–strain relations of the fluid (drilling mud) and isotropic elastic media (drill string and formation). Wave modes and radiated waves are simulated in the borehole-formation system. The algorithm satisfies the reciprocity condition and the results agree with an analytical solution and low-frequency simulation of wave-propagation modes reported in the literature. Examples illustrating the propagation of waves are presented for hard and soft formations. Moreover, the presence of casing, cement, and formation heterogeneity have been considered. Since the algorithm is based on a direct (grid) method, the geometry and the properties defining the media at each grid point, can be general, i.e., there are no limitations such as planar interfaces or uniform (homogeneous) properties for each medium.      

Improving the capability of an integrated CA-Markov model to simulate spatio-temporal urban growth trends using an Analytical Hierarchy Process and Frequency Ratio

The creation of an accurate simulation of future urban growth is considered one of the most important challenges in urban studies that involve spatial modeling. The purpose of this study is to improve the simulation capability of an integrated CA-Markov Chain (CA-MC) model using CA-MC based on the Analytical Hierarchy Process (AHP) and CA-MC based on Frequency Ratio (FR), both applied in Seremban, Malaysia, as well as to compare the performance and accuracy between the traditional and hybrid models. Various physical, socio-economic, utilities, and environmental criteria were used as predictors, including elevation, slope, soil texture, population density, distance to commercial area, distance to educational area, distance to residential area, distance to industrial area, distance to roads, distance to highway, distance to railway, distance to power line, distance to stream, and land cover. For calibration, three models were applied to simulate urban growth trends in 2010; the actual data of 2010 were used for model validation utilizing the Relative Operating Characteristic (ROC) and Kappa coefficient methods Consequently, future urban growth maps of 2020 and 2030 were created. The validation findings confirm that the integration of the CA-MC model with the FR model and employing the significant driving force of urban growth in the simulation process have resulted in the improved simulation capability of the CA-MC model. This study has provided a novel approach for improving the CA-MC model based on FR, which will provide powerful support to planners and decision-makers in the development of future sustainable urban planning.     

基于时空车流灰度的城市交通热点分析

随着城市规模的扩张和汽车数量的增加,拥堵和雾霾等受交通影响的现象变得越来越严重,城市交通热点发现与分析是改善交通状况的关键技术之一。根据城市中典型浮动车(出租车)的时空轨迹数据,基于图像分析理论,提出城市交通热点的空间分布分析方法。首先,根据浮动车数据,形成车流轨迹的时空分布灰度图。其次,通过将浮动车的轨迹数据映射到高精度城市交通网格上,探索了轨迹数据和城市热点区域之间的关联关系。进一步地依据车流轨迹的时空分布,发现车流密度的极值。最后,结合影响区域的参数利用高斯曲面拟合对时空灰度图像进行了热点区域分析,获得城市交通热点的空间分布。将分析结果在地图上标定,准确地反映了城市交通热点区域的详细位置及空间分布,从而给出了一种有效、直观的城市交通热点分析方法。研究结果对于城市交通规划和交通实时信息发布具有实用价值。     

Model test and simulation of a ship with wavefoils

The paper describes model tests of a tanker with two fixed bow-mounted foils (wavefoils), for resistance and motion reduction in waves. Measured ship resistance, wavefoil thrust and ship motions were compared with time-domain simulations. The wavefoil forces were calculated using a slightly modified Leishman–Beddoes dynamic stall model, with a two-way coupling to the ship motions. In typical sea states in head seas, employing the wavefoils reduced ship resistance by 9–17%, according to scaled model test resistance. Heave and pitch were reduced by −11% to 32% and 11% to 25%, respectively. The foils affect the flow around the hull. This should be considered when selecting the wavefoil location in the design process.     

Methods and approaches to modelling the Anthropocene

The ‘Anthropocene’ concept provides a conceptual framework that encapsulates the current global situation in which society has an ever-greater dominating influence on Earth System functioning. Simulation models used to understand earth system dynamics provide early warning, scenario analysis and evaluation of environmental management and policies. This paper aims to assess the extent to which current models represent the Anthropocene and suggest ways forward. Current models do not fully reflect the typical characteristics of the Anthropocene, such as societal influences and interactions with natural processes, feedbacks and system dynamics, tele-connections, tipping points, thresholds and regime shifts. Based on an analysis of current model representations of Anthropocene dynamics, we identify ways to enhance the role of modeling tools to better help us understand Anthropocene dynamics and address sustainability issues arising from them. To explore sustainable futures (‘safe and operating spaces’), social processes and anthropogenic drivers of biophysical processes must be incorporated, to allow for a spectrum of potential impacts and responses at different societal levels. In this context, model development can play a major role in reconciling the different epistemologies of the disciplines that need to collaborate to capture changes in the functioning of socio-ecological systems. Feedbacks between system functioning and underlying endogenous drivers should be represented, rather than assuming the drivers to be exogenous to the modelled system or stationary in time and space. While global scale assessments are important, the global scale dynamics need to be connected to local realities and vice versa. The diversity of stakeholders and potential questions requires a diversification of models, avoiding the convergence towards single models that are able to answer a wide range of questions, but without sufficient specificity. The novel concept of the Anthropocene can help to develop innovative model representations and model architectures that are better suited to assist in designing sustainable solutions targeted at the users of the models and model results.     

行星际中间激波的演化

本文采用特征线方法和激波装配法,对磁流体中间激波在行星际空间的演化过程进行数值模拟。主要结论如下:（1） 2→4型中间激波通过向下游发出后向慢压缩波使下游态磁场减幅,通过向上游发出前向快压缩波使上游态磁场增幅,以致2→4型中间激波迅速经导灭激波向慢激波转化;所发出的前向快压缩波经非线性变陡形成快激波。（2）1→3型中间激波首先通过向下游发出前向慢稀疏波而很快变成1→3=4型临界中间激波,并瞬间转变为由前向快激波和前向2→4型中间激波构成的激波系统。其中,2→4型中间激波可在其前导快激波的下游传播较远的距离,有可能为 IAU 附近的飞船观测到,但最终导灭激波转变为慢激波。     

Kriging and Semivariogram Deconvolution in the Presence of Irregular Geographical Units

This paper presents a methodology to conduct geostatistical variography and interpolation on areal data measured over geographical units (or blocks) with different sizes and shapes, while accounting for heterogeneous weight or kernel functions within those units. The deconvolution method is iterative and seeks the point-support model that minimizes the difference between the theoretically regularized semivariogram model and the model fitted to areal data. This model is then used in area-to-point (ATP) kriging to map the spatial distribution of the attribute of interest within each geographical unit. The coherence constraint ensures that the weighted average of kriged estimates equals the areal datum.This approach is illustrated using health data (cancer rates aggregated at the county level) and population density surface as a kernel function. Simulations are conducted over two regions with contrasting county geographies: the state of Indiana and four states in the Western United States. In both regions, the deconvolution approach yields a point support semivariogram model that is reasonably close to the semivariogram of simulated point values. The use of this model in ATP kriging yields a more accurate prediction than a naïve point kriging of areal data that simply collapses each county into its geographic centroid. ATP kriging reduces the smoothing effect and is robust with respect to small differences in the point support semivariogram model. Important features of the point-support semivariogram, such as the nugget effect, can never be fully validated from areal data. The user may want to narrow down the set of solutions based on his knowledge of the phenomenon (e.g., set the nugget effect to zero). The approach presented avoids the visual bias associated with the interpretation of choropleth maps and should facilitate the analysis of relationships between variables measured over different spatial supports.