Supervised SAR Image MPM Segmentation Based on Region-Based Hierarchical Model

This letter presents a novel method of supervised multiresolution segmentation for synthetic aperture radar images. The method uses a region-based half-tree hierarchical Markov random field model for multiresolution segmentation. To form the region-based multilayer model, the watershed algorithm is employed at each resolution level independently. The nodes of a quadtree in the proposed model are defined as regions instead of pixels. The relationship over scale is studied, and the region-based upward and downward maximization of posterior marginal estimations are deduced. The experimental results for the segmentation of homogeneous areas prove the region-based model much better in terms of robustness to speckle and preservation of edges compared to the pixel-based hierarchical model and the Gibbs sampler with the single-resolution model     

改进粒子滤波器的室内地磁匹配精度研究

针对粒子滤波算法在室内地磁分布的连续性变化中会发生滤波发散,加之算法中重采样步骤使该现象恶化,直接导致室内定位过程中目标丢失的问题。该文受Hausdorff距离度量法中点集匹配思想的启发,提出了一种利用初定位误差作为最大粒子匹配距离的约束思想,通过缩小匹配空间的区域范围的方法来解决传统算法的发散问题。最后实验表明,此方法解决了粒子滤波器在地磁匹配中出现的滤波发散现象,同时使得定位结果更加快速收敛。     

大地测量学实践教学改革的探索

大地测量学是测绘工程专业的一门理论性和实践性很强的重要专业基础课。从强化课堂基础实验、重视课程设计、建立生产实习考核体系等3个方面提出了实践教学改革措施,在帮助学生巩固加深理论知识,提高学生运用知识分析解决问题的能力和实践创新能力等方面具有重要的意义。     

考虑土-结构相互作用的振动台实时子结构试验仿真分析

本文基于状态空间方程进行了实时子结构试验的初步探索,提出了一种新的实时子结构试验方法。通过simulink仿真发现,这种方法能很好地再现整体分析的结构反应。最后,对考虑土-结构相互作用的振动台实时子结构试验进行了仿真分析。     

Possible Sources of Forecast Errors Generated by the Global/Regional Assimilation and Prediction System for Landfalling Tropical Cyclones. Part Ⅱ: Model Uncertainty

This paper investigates the possible sources of errors associated with tropical cyclone (TC) tracks forecasted using the Global/Regional Assimilation and Prediction System (GRAPES). In Part I, it is shown that the model error of GRAPES may be the main cause of poor forecasts of landfalling TCs. Thus, a further examination of the model error is the focus of Part II. Considering model error as a type of forcing, the model error can be represented by the combination of good forecasts and bad forecasts. Results show that there are systematic model errors. The model error of the geopotential height component has periodic features, with a period of 24 h and a global pattern of wavenumber 2 from west to east located between 60°S and 60°N. This periodic model error presents similar features as the atmospheric semidiurnal tide, which reflect signals from tropical diabatic heating, indicating that the parameter errors related to the tropical diabatic heating may be the source of the periodic model error. The above model errors are subtracted from the forecast equation and a series of new forecasts are made. The average forecasting capability using the rectified model is improved compared to simply improving the initial conditions of the original GRAPES model. This confirms the strong impact of the periodic model error on landfalling TC track forecasts. Besides, if the model error used to rectify the model is obtained from an examination of additional TCs, the forecasting capabilities of the corresponding rectified model will be improved.     

Controlling factors of the δ 11B-pH proxy and its research direction

Significant boron isotope fractionation occurs in nature (?70 ‰ to +75 ‰) due to the high geochemical reactivity of boron and the large relative mass difference between ¹⁰B and ¹¹B. Since the 1990s, reconstruction of ancient seawater pH using the isotopic composition of boron in bio-carbonates (δ ¹¹B_carb), and then calculation of the past pCO₂ have become important issues for the international isotope geochemistry community, and are called the δ ¹¹B-pH proxy. Although many achievements have been made by this proxy, various aspects of boron systematics require rigorous evaluation. Based on the previous researches, mechanism of boron isotope fractionation, variation of boron isotope (δ ¹¹B) in nature (especially in bio-carbonates) and controlling factors of the δ ¹¹B-pH proxy, such as the dissociation constant of B(OH)₃ in seawater (pK_a), the δ ¹¹B of seawater (δ ¹¹B_SW), the boron isotopic fractionation factor between B(OH) ₄ ^? and B(OH)₃ (α _4–3), and the incorporated species of boron into bio-carbonates, are reviewed in detail and the research directions of this proxy are proposed. Generally, the controversy about pK_a, δ ¹¹B_sw, and α _4–3 is relatively less, but whether boron incorporated into bio-carbonates only in the form of B(OH) ₄ ^? remains doubtful. In the future, it is required that the physicochemical processes that control boron incorporation into carbonates be rigorously characterized and that the related chemical and isotopic fractionation be quantified. It is also necessary and important to establish a “best-fit empirically equation” between δ ¹¹B_carb and pH of seawater based on the precipitation experiments of inorganic or culture experiments of corals or foraminifera. In addition, extended application of the δ ¹¹B-pH proxy to the earlier part of the Phanerozoic relying on the Brachiopods is worthy of studying. Like other geochemical indicators, there are limiting factors of δ ¹¹B; however, it remains a very powerful tool in the reconstruction of past seawater pH at present.     

南海夏季风爆发日期和强度的短期气候预测方法研究

利用合成及相关统计方法，研究冬季南海季风指数与850hPa风场、500hPa高度、海表温度、OLR等环境场的相互关系及其影响南海夏季风活动的可能机制。指出冬季南海季风指数及环境场的异常特征可以作为预测南海夏季风活动的前兆信号。在此基础上建立了预测南海夏季风爆发日期和强度的概念模型，1998－2001年的预测试验取得了较好成绩。     

上高县紫皮大蒜种植气候适宜性区划

基于紫皮大蒜生长周期和当地农业气象条件,得到上高县紫皮大蒜气候适宜性指标：10—11月的最低气温、10月至次年4月的平均气温和平均降水量以及2—4月的累计日照时数。利用1970—2020年宜春市和新余市辖区内共12个地面观测站的气象资料,采用GIS建立上高县紫皮大蒜种植区划因子地理空间分析模型。依据分区等级指标,将上高县划分为最适宜、一般适宜和不适宜3个紫皮大蒜气候种植区。     

从工程实践浅析基桩高应变法检测承载力误差问题

高应变法检测是基桩检测技术的一种重要手段,但是该方法检测承载力存在误差,因此受到许多争议。本文以广东惠州地区两项工程的检测实践为例,分别采用前后两组不同拟合参数,对检测数据进行了承载力拟合计算,分别得出了前后两种不同的计算结果。并通过动、静两种方法的对比检测,分析了高应变法检测承载力误差产生的主要原因,粗略探讨了对高应变法检测的一些认识。     

一种可能的短期前震

分析大地震前小地震时、空分布发现,1973年2月6日炉霍7.9级地震1974年4月22日溧阳5.5级地震及1976年5月29日龙陵7.3级地震前约3个月内,2级以上小地震有沿一定方向(顺时或逆时)逐个发生,从而形成环的现象。溧阳和龙陵地震发生在环内一侧或其附近,而炉霍大地震则离环较远,但处于同一构造带。根据蠕变曲线有非线性增加段及其时间特征,它可定为短期前震,並且可能表现了震前固体潮触发蠕滑的过程。