Local and landscape effects on spatial patterns of mangrove forest during wetter and drier periods: Moreton Bay,Southeast Queensland,Australia

Land use/cover and mangrove spatial changes were assessed for ten sites and their sub-catchments in Southeast Queensland, Australia. Two time periods were involved: 1972–1990, a period of relatively high rainfall, and 1990–2004, which was significantly drier. Aerial photographs and Landsat satellite imagery were used to map the inter-tidal wetlands and classify the land use/cover in the sub-catchments. A Maximum Likelihood Classification was used to map three types of land cover: agriculture, built-up and plantation forest. Mangroves (mainly Avicennia marina) were the focus as they have been recorded over recent decades encroaching into salt marsh. The Mangrove-Salt marsh Interface (MSI) Index was developed to quantify the relative opportunity for mangroves to expand into salt marshes, based on the shared boundary between them. The index showed a consistent relationship with mangrove expansion and change. To address problems of high dimensionality and multi-collinearity of predictor variables, a Partial Least Squares Regression (PLSR) model was used. A key finding of this research was that the contribution of environmental variables to spatial changes in the mangroves was altered following a reduction in rainfall. For example, agriculture had more influence on mangrove expansion and change during the wet period than during the dry period.     

宽基线立体影像Harris-Laplace特征的最小二乘匹配算法

针对宽基线立体影像匹配的困难,本文提出一种基于Harris-Laplace的最小二乘匹配算法.算法基于Harris-Laplace特征检测器获得精度较高的初始特征点,对初始特征点进行NCC匹配,并应用基本矩阵F与单应矩阵H估计剔除误匹配点对,采用距离加权最小二乘匹配算法进行扩展匹配并同时保留定位精度较高的原始Harri...     

模拟退火算法在控制网平差中的应用

线性最小二乘估计在对非线性函数进行线性近似的过程中会产生模型误差,而一些非线性参数估计方法可能因为函数复杂而难以求导,法方程系数矩阵秩亏或呈病态矩阵时难以求解,非线性迭代解法有时对初始值的选择存在依赖性,不恰当的初始值会导致迭代无法收敛。针对这些问题,引入了模拟退火算法,介绍了该算法的基本原理、计算步骤和收敛性,并以3个控制网平差应用为例,说明该算法具有无需求导求逆,简洁实用,易于编程等优势,并能实现全局优化,获得高精度的平差结果。     

Life‐cycle cost assessment of RC and ECC frames using structural optimization

In this study life‐cycle cost (LCC) assessment of structural frames is performed. Two different materials, reinforced concrete (RC) and reinforced engineered cementitious composites (ECC), with different response characteristics are used to model the frames. ECC is characterized by high tensile ductility and energy absorption and reduced crack widths when compared to conventional concrete. However, the material is more expensive than conventional concrete; therefore, in order to quantify the potential benefits that could be obtained by replacing concrete with ECC, the life‐cycle performance is evaluated in an optimization framework. Three different structural frames are considered: an RC only frame, an ECC only frame and a multi‐material (MX) frame in which ECC is selectively applied at the potential plastic hinge locations while the remainder of the frame is made of RC. The structural capacity and earthquake demand are evaluated using rigorous analysis methods to capitalize on different characteristics of concrete and ECC, and both aleatory and epistemic uncertainties are incorporated into the LCC formulation. It is found that both the initial and LCC of frames that use ECC are lower due to savings in material and labor cost of transverse reinforcement for the former and due to increased capacity and reduced demand for the latter. Copyright © 2012 John Wiley & Sons, Ltd.     

倾向性评分匹配法评估手术联合术中放疗在肝癌治疗中的安全性及有效性

目的 倾向性评分匹配法（Propensity Score Matching,PSM）评估手术联合术中放疗治疗原发性肝癌的安全性及疗效。方法 收集2009~2012年于笔者医院肝胆外科行手术联合术中放疗（intraoperative electron radiotherapy,IOERT）的18例原发性肝癌（primary liver cancer,PLC）患者的临床资料,其中16例经术后病理证实为肝细胞癌（hepatocellular carcinoma,HCC）,2例为肝内胆管细胞癌（intrahepatic cholangiocarcinomas,ICC）;采用倾向性评分匹配方法,按照1∶2比例从同期行单纯手术的原发性肝癌患者中筛选出36例做为对照组（32例HCC,4例ICC）,比较两组患者术中及术后并发症发生情况及HCC患者术后早期（2年内）复发率。结果 所有患者均获随访,随访率100%。两组患者术中出血量、术后3个月内肝功能、凝血功能、血常规及术后住院天数的比较,差异均无统计学意义（P>0.05）,仅在手术时长方面,联合IOERT组长于单纯手术组（P=0.000）。此外,联合IOERT组术后出现1例急性肾功能衰竭和1例胸腔积液,单纯手术组术后出现1例肝创面出血。在疗效方面,以两组48例HCC患者为研究对象,联合IOERT组的HCC患者为16例,其中6例在2年内复发,早期复发率为37.5%;单纯手术组的HCC患者为32例,20例在2年内复发,早期复发率为62.5%,两组早期复发率的比较,差异无统计学意义（P=0.101）。结论 手术联合术中放疗治疗原发性肝癌安全可行,尽管联合放疗组早期复发率低于单纯手术组,但差异并无统计学意义。     

VLL方法在自动获取建筑物高程中的应用

铅垂线轨迹法(VLL,Vertical Line Locus)是一种直接解求高程的方法,将该方法加以改进,并将其应用在建筑物高程信息的获取中,实现了自动批量获取建筑物高程信息的目的,并具有一定的精度。实验表明,该方法效率较高,可靠性较好。     

土壤铅含量高光谱遥感反演中波段选择方法研究

利用高光谱遥感数据进行了南京郊外土壤重金属元素铅的含量反演,由于高光谱数据波段众多,波段选择或变换至关重要。比较了基于次贪婪的前向选择模型的最小角度拟合和基于遗传算法进行波段选择的最小二乘和偏最小二乘拟合,结果发现基于遗传算法的偏最小二乘反演结果优于全波段的偏最小二乘,表明波段选择在高光谱反演重金属中是有益的。尽管采取了波段选择后的各方法在反演时均能达到70%以上的训练精度,但因遗传算法搜索的解空间范围更宽广,使得基于遗传算法的偏最小二乘优于前向选择模型的最小角度拟合。最后还比较了基于遗传算法的普通最小二乘和偏最小二乘拟合,结果表明偏最小二乘更优,因此在高光谱反演重金属含量当中,偏最小二乘精度较高,而在波段选择方法中,遗传算法更优。     

岩土压力传感器匹配误差的特性

在介绍了岩土压力传感器匹配误差概念的基础上,论述了匹配误差的稳定性、等效性、真实性和实用性以及各特性之间的相关性。通过研究得出：匹配误差特性的核心是稳定性;传感器刚性饼状设计是保证稳定性的必要条件;等效匹配误差不一定是真实的,但即使是不真实,也不影响实用性。     

二次曲面与最小二乘配置的组合模型在GPS高程异常拟合中的应用

在工程实践应用中,为了有效利用GPS高程数据,减少对传统水准测量的依赖,提高GPS高程异常的拟合精度便显得十分重要。为此,本文在介绍二次曲面拟合和最小二乘配置拟合基本原理分析、算法过程推导的基础上,提出了一种新的高程异常拟合方法。首先在二次曲面拟合的基础上,计算得到原始观测数据与拟合数据之间的残差序列,然后采用最小二乘配置模型对包括二次曲面拟合模型误差的综合误差进行优化减弱,最后得到新的高程异常。通过实例,将二次曲面拟合法,最小二乘配置法与文中提出的新方法进行比较分析。结果表明：新的组合方法的拟合预测精度要明显优于最小二乘配置及二次曲面拟合。     

脐带缆在潜器下放过程中的运动建模与仿真

潜器在下放布置过程中需要考虑变长度的脐带缆对其运动的影响,在考虑流的情况下,对脐带缆的有限差分模型进行了改进,并采用最小二乘方法求解由时间和空间上的中心差分格式离散后的非线性方程组。为了验证模型改进的有效性,将潜器在均匀定常流中水平匀速直航时的数值解与该特殊情况下的解析解进行比较,两组解的吻合不仅证实了模型改进的有效性,而且表明上述数值计算方法是可靠且有效的。在潜器下放布置运动给定的情况下,脐带缆的运动仿真结果表明,潜器姿态角的调整会对拖曳点处的缆绳张力大小和变化趋势产生显著的影响,流在改变缆绳空间形状的同时引起了缆绳对潜器作用力和力矩的非线性和时变性,脐带缆总是阻止潜器自身动力对运动速度和姿态角的改变,且对纵荡运动的影响最大。