基于MODIS数据定量判识沙尘暴方法的对比研究

利用MODIS数据,结合具体实例,对比研究当前几种利用光谱特征定量判识沙尘暴的方法。从理论上剖析各方法的原理,分析其优劣,并提出一套新的算法的组合方式。研究结果表明,新的组合算法有不小的改进：①大大降低了单一算法在不同时间或地区图像中阈值取值不稳定的影响,减少了图像噪声造成的误判,增强了其通用性和稳定性;②明显减弱了太...     

工程开挖活动诱发堆积层滑坡变形机理及加固效果分析

位于川西高原雅砻江两河口水电站库区的杜米村移民安置点由于切坡建房,诱发后山斜坡强烈变形,威胁移民安置点和S220省道安全。首先,基于现场调查、测绘、钻探、槽探等勘查手段,查明了滑坡发育的工程地质条件和变形特征;通过对滑体和滑带土开展室内直剪、反复剪试验,以及对滑床基岩进行抗压强度试验,结合反分析,合理确定了滑坡稳定性计算参数。然后,采用有限元程序Phase2建立滑坡数值计算模型,模拟再现了滑坡在开挖前、开挖后、降雨后的应力、变形特征和稳定性变化过程,在此基础上分析了滑坡的变形机理。研究认为：不良的地形地貌、地质结构和地下水是滑坡发生的内在因素,坡脚开挖是滑坡变形启动的诱发因素,后期持续降雨入渗是滑坡变形加剧直至失稳破坏的直接因素;开挖导致滑体前缘抗滑力降低、滑带和开挖边坡坡脚产生剪应力集中是滑坡变形启动的力学机制,而饱水和持续剪切变形导致滑带土强度不断衰减接近饱和残余状态是滑坡变形加剧的本质原因;滑坡的变形破坏模式为牵引式蠕滑-拉裂。最后,采用有限元强度折减法对加固治理后的滑坡稳定性进行了计算分析。结果表明：天然条件下滑坡变形主要出现在桩后填土,降雨条件下变形范围扩大至强变形区,地震条件下变形范围进一步扩大至整个滑坡范围;三种工况下滑坡的稳定系数均能达到设计要求,表明加固设计方案和工程结构参数是合理的。研究成果可为类似滑坡工程案例的机理研究及防治提供参考。     

Reconstruction of the layer anisotropic elastic parameters and high-resolution fracture characterization from P-wave data: a case study using seismic inversion and Bayesian rock physics parameter estimation

Wide-azimuth seismic data can be used to derive anisotropic parameters on the subsurface by observing variation in subsurface seismic response along different azimuths. Layer-based high-resolution estimates of components of the subsurface anisotropic elastic tensor can be reconstructed by using wide-azimuth P-wave data by combining the kinematic information derived from anisotropic velocity analysis with dynamic information obtained from amplitude versus angle and azimuth analysis of wide-azimuth seismic data. Interval P-impedance, S-impedance and anisotropic parameters associated with anisotropic fracture media are being reconstructed using linearized analysis assuming horizontal transverse anisotropy symmetry. In this paper it is shown how additional assumptions, such as the rock model, can be used to reduce the degrees of freedom in the estimation problem and recover all five anisotropic parameters. Because the use of a rock model is needed, the derived elastic parameters are consistent with the rock model and are used to infer fractured rock properties using stochastic rock physics inversion. The inversion is based on stochastic rock physics modelling and maximum a posteriori estimate of both porosity and crack density parameters associated with the observed elastic parameters derived from both velocity and amplitude versus angle and azimuth analysis. While the focus of this study is on the use of P-wave reflection data, we also show how additional information such as shear wave splitting and/or anisotropic well log data can reduce the assumptions needed to derive elastic parameter and rock properties.     

潜在震源区震级上限不确定性研究

潜在震源区的震级上限（Mu）是指在该潜在震源区内可能发生的最大地震的震级．预期未来发生超过该震级地震的概率趋于0．本文运用误差分析及逻辑树等方法,并结合发震模型的数值模拟得到的大震合成目录等结果,系统分析并最终得到了不同途径给出的不同类型潜在震源区震级上限的不确定性．该结果可直接应用于包括地震区划在内的工程地震以及活动断裂危险性评价等工作中．      

The generation and its sealing condition of natural gas in the Tadong area

Focusing on the two natural gas exploration geological problems with abundant source of oil cracking gas in the late stage and the sealing condition of the oil cracking gas reservoir, the kinetics of oil cracking gas and the evaluation parameters of gas cap rock are adopted to the study on the natural gas accumulation conditions in the Tadong area. Both the study on the kinetics of oil cracking gas and the statistical results of reservoir bitumen reveal that the geological formation of oil cracking gas in the Tadong area is located in the top of Cambrian. Two kinds of oil cracking gas geological models at least, namely well Mandong-1’s early rapid generation model (Middle Ordovician-end Silurian) and peak cracking model (with the natural gas conversion rate >90%), namely well Yingnan-2’s two-stage generation model of oil cracking gas, have been set up. The oil cracking gas of Yingnan-2 in the late stage is very significant in the evaluation of natural gas exploration in the Tadong area. The evaluation results of the cap rock show that the microscopic parameters of cap rock from the lower assemblage of Cambrian-Ordovician are better than those from the upper assemblage. The former has strong capillary sealing ability and higher cap rock breakthrough pressure than the upper assemblage, with strong sealing ability, so that natural gas dissipates mainly by diffusion. According to the above investigations, the lower assemblage Cambrian-Ordovician natural gas of Kongquehe slope, Tadong low uplift and Yingjisu depression in the Tadong area prospects well.     

基于农户行为的耕地质量评价指标体系 构建的理论与方法

从农户土地利用目标变化相关理论出发, 依据在不同经济发展阶段下, 农户土地利用目 标的产量最大化、产量与利润最优化和利润最大化三个阶段的变化特征, 创建了基于农户土地利 用目标变化的“压力- 状态- 效应- 响应”逻辑框架模型; 并据不同经济发展阶段下的“压力- 状态- 效应- 响应”的变化特征, 构建了基于农户土地利用目标变化的耕地质量评价指标体系。这一评价 指标体系的建立为我国在不同经济发展阶段下, 从农户尺度上进行耕地质量保护提供政策依据。     

混凝土芯水泥土搅拌桩的有限元研究

混凝土芯水泥土搅拌桩是适用于软土地基处理的一种新型复合桩 , 具有施工方便 、造价低廉 、单桩承载力高等优点 。 在静试验的基础上, 采用弹塑性有限元方法研究了该桩在竖向荷载下的力学性状 ,包括桩土和桩内外芯应力比 , 荷载的传递, 桩侧塑性区分布以及沉降特性等 。     

粉喷桩在汕头商住楼工程中的试验与应用

通过对汕霜大型建筑采用粉喷桩处理地基的工程试验研究,论证了在巨厚层软土地区采用长短桩间排布设方式是解决下卧层强度问题的有效途径之怀,为深欠土地区的地基处理及基础选型提供了宝贵的实践经验。     

观测天体光谱的纤维光学方法及2.16m望远镜实用系统

本文描述了近年来广泛发展起来的天体物理实测技术中的一项重要进展——纤维光学分光技术方法在天体光谱观测中的应用及2.16m望远镜实用系统的特点和初步应用结果     

Characterization and Application of S-Band Polarimetric Radar and X-Band Phased Array Radar for a Tornadic Storm Event on June 16,2022

The X-band phased array radar offers faster scanning speed and higher spatial resolution compared to the S-band radar, making it capable of enhancing tornado monitoring and early warning capabilities. This study analyzed the char- acteristics and nowcasting signals of a tornado case that occurred on June 16, 2022 in the Guangzhou region. Our findings indicate that the violent contraction of rotation radius and the dramatic increase in rotation speed were important signal characteristics associated with tornado formation. The X-band phased array radar, with its high temporal and spatial resolution, provided an opportunity to capture early warning signals from polarimetric characteristics. The X-band phased array radar demonstrated noteworthy ability to identify apparent tornado vortex signature (TVS) features in a 10-minute lead time, surpassing the capabilities of the CINRAD/SA radar. Additionally, due to its higher scanning frequency, the X- band phased-array radar was capable of consistently identifying TVS with shorter intervals, enabling a more precise tracking of the tornado’s path. The application of professional radars, in this case, provides valuable insights for the monitoring of evolutions of severe local storms and even tornadoes and the issuance of early warning signals.