基于WOA-BP算法的海底管道腐蚀速率预测

管道腐蚀速率的影响因素众多且各因素协同作用,构成异常复杂的腐蚀体系,很难对其进行准确预测。针对单一BP模型由于初始权值和阈值的选取不当容易陷入局部最优等问题,引入WOA算法优化BP神经网络对海底管道腐蚀速率进行预测,并与GA和PSO算法优化BP预测模型进行对比,验证WOA-BP模型的预测效果和可行性。结果表明：WOA-BP模型的平均绝对百分误差和均方根误差分别为3.689%和0.1537,远低于单一BP、PSO-BP、GA-BP模型,具有较高的预测精度和稳定性,可以为海底管道内腐蚀防护和油气管道流动保障提供决策支持。     

Book Review

In this paper, we examine the applicability of spatial optimization as a generative modelling technique for sustainable land‐use allocation. Specifically, we test whether spatial optimization can be used to generate a number of compromise spatial alternatives that are both feasible and different from each other. We present a new spatial multiobjective optimization model, which encourages efficient utilization of urban space through infill development, compatibility of adjacent land uses, and defensible redevelopment. The model uses a density‐based design constraint developed by the authors. The constraint imposes a predefined level of consistent neighbourhood development to promote contiguity and compactness of urban areas. First, the model is tested on a hypothetical example. Further, we demonstrate a real‐world application of the model to land‐use planning in Chelan, a small environmental amenity town in the north‐central region of the State of Washington, USA. The results indicate that spatial optimization is a promising method for generating land‐use alternatives for further consideration in spatial decision‐making.     

Ecologically based landscape pattern optimization in northwest of Beijing

Supported by the technologies of remote sensing (RS) and geographical information system (GIS), we chose northwest of Beijing as a study area and gave priority to understanding of the spatial-temporal characteristics of landscape pattern change through visually interpreted Landsat TM images of 1989, 1996 and 2005. It is believed that there were a series of landscape ecological problems caused by city expansion: landscape ecological connectivity was low; landscape structure was simplified; the fragmentation of green land patch was more obvious on the plain areas, moreover, spatial distribution of green land was unbalanced. For this reason, this study adopted accumulative cost distance model, combined with ecosystem services and spatial interactions of landscape types, analyzed the spatial difference of the ecological function and the compactness of landscape structure in the study area, and further discussed the landscape pattern optimization proposal. We find that it is essential to protect and establish ecological sources, to establish urban ecological corridors, and to establish ecological nodes at the landscape ecological strategic positions so as to intensify spatial relationships among landscape elements and maintain continuity of landscape ecological process and pattern in the course of city expansion. The methods and final results from this study are expected to be useful for landscape ecological planning in Beijing region.     

确定连续系统参数的时域方法

提出一种确定连续系统参数的时域方法。该方法利用方波输入和系统稳定性，离析出输出采样信号与结构参数的内在联系，推导出确定连续系统结构参数的算法．指出该算法与辨识方法相结合，可实现对含随机干扰的连续系统结构参数的估计．     

几种梯度场计算的数值算法及其地学应用

梯度作为标量场在空间上最重要的微观变化特征,能较好地反映其在空间上的变化趋势。本文介绍了中心差分算子、相邻梯度因子和Sobel梯度算子三种梯度数值算法。以点电荷在三维空间中产生的电势场构造了一标量场,通过理论公式求解了其梯度值,并将理论梯度值与三种数值算法的结果进行了对比与统计分析,验证了三种梯度数值算法的有效性和适用性。结果表明,排除场源的影响后,Sobel梯度算子相较其它两种数值算法更逼近于理论梯度值。最后,利用Sobel梯度算子求取了某铜矿区可控源音频大地电磁法(CSAMT)三维视电阻率场的梯度场,用梯度场刻画了视电阻率在空间上的变化趋势,提高了对三维地下空间的电性分布规律和地质情况的认识。     

一种电离层活跃期的三频TECR周跳处理算法

针对电离层活跃期现有三频周跳处理方法难以正确探测与修复周跳和阈值设定不合理的问题,借鉴双频TECR算法,提出一种能够削弱电离层延迟影响的三频TECR算法。三频TECR组合与三频码相无几何无电离层组合均能有效削弱电离层延迟对周跳探测的影响,并能自适应地确定合理阈值。利用三频实测数据对算法进行验证的结果表明,该方法能够有效消除电离层延迟影响,实现电离层活跃期周跳的动态探测与修复。     

基于雷达资料的定量降水预报外推算法试验

摘要：目前贵州在短时临近降水预报客观算法方面研究匮乏,而短时强降水常常给贵州造成严重的洪涝灾害和地质灾害。将短时临近降水预报应用于气象防灾减灾、电网输电线路安全预警、水利防洪自动化方面是未来重要的研究应用方向。本文基于灾害天气短时临近系统（Severe Weather Automatic Nowcast System,SWAN）的定量降水预报(QPF)产品进行0～2小时QPF外推试验研究。利用贵州省地面自动站数据、SWAN 输出的1h-QPF产品、SWAN 1h定量降水估测(QPE)产品。选取2018年3次典型暴雨个例进行试验,采用融合订正技术,利用相似离度算法对降水强度位相进行调整、Weibull分布算法对降水极值分布进行订正、改进后的交叉相关法(Improved Cross-correlation Extrapolation Method,COTREC)进行降水外推预报。通过主客观检验对比,初步说明基于Weibull分布算法的降水极值订正对降水极值分布有很好的模拟效果。融合订正外推的贵州省短时临近定量降水预报产品（Nowcasting precipitation forecast of GuiZhou,下文简写为GZ_NPF）在大于5mm以上量级降水的TS检验中评分更高。GZ_NPF的空报率明显降低,但空报率降低的代价是漏报率相对提高。GZ_NPF总的相对误差减小,格点总降水量与实况总降水量更为接近。试验说明新的融合订正外推算法提高了0～2h短时临近降水的预报能力。     

基于电子地图和Dijkstra算法路径规划的实现

随着城市化水平的提高,人们在道路选择问题上可能需要考虑的并非仅仅是"空间距离"的最短,还有"时间最短",本文应用Dijkstra算法解决城市中出行交通道路选择的问题,对距离最短和时间最短路径分别进行讨论,用VB语言实现算法,并且在电子地图上绘制出所求出的路径,以便人们更直接地观看到结果,基本上解决了道路选择问题。     

基坑土钉支护设计的简单算法研究

土钉支护技术在深基坑开挖和支护中已得到了广泛的应用,但对其工作机制和计算方法的研究尚不完善。目前数值模拟算法较多,但其本构模型准确地选择及相关参数的确定需要进行大量的三轴试验或真三轴试验。基于此,提出3个假设,建立简单的计算模型,并对土钉的工作机制深入研究,得到土钉拉力的“二半支抛物线”分布规律,推导出土钉支护设计的解析算法相关公式。以徐州彭城地下广场深基坑土钉支护工程为例,进行土钉拉力现场测试,对基坑水平位移、沉降进行观测,所测数据验证了文中公式的可靠性,为类似基坑工程的设计和施工提供参考。     

海底声学底质分类的ELM-AdaBoost方法

基于自适应增强算法（AdaBoost）结合极限学习机（ELM）,通过迭代、调整、优化ELM分类器之间的权值,从而构建了具有强鲁棒性、高精度的ELM-AdaBoost强分类器,增强了现有的ELM分类器的稳定性。以珠江口海区侧扫声呐图像为实验数据,对礁石、砂、泥3类典型底质进行分类识别,该方法的平均分类精度超过90%,优于单一ELM分类器的平均分类精度85.95%,也优于LVQ、BP等传统分类器,且在分类所耗时间上也远少于传统分类器。实验结果表明,本文构建的ELM-AdaBoost方法可有效应用于海底声学底质分类,可满足实时底质分类的需求。