A Time‐Simultaneous Prediction Box for a Multivariate Time Series

A sample‐based method in Kolsrud (Journal of Forecasting 2007; 26 (3): 171–188) for the construction of a time‐simultaneous prediction band for a univariate time series is extended to produce a variable‐ and time‐simultaneous prediction box for a multivariate time series. A measure of distance based on the L_∞ ‐norm is applied to a learning sample of multivariate time trajectories, which can be mean‐ and/or variance‐nonstationary. Based on the ranking of distances to the centre of the sample, a subsample of the most central multivariate trajectories is selected. A prediction box is constructed by circumscribing the subsample with a hyperrectangle. The fraction of central trajectories selected into the subsample can be calibrated by bootstrap such that the expected coverage of the box equals a prescribed nominal level. The method is related to the concept of data depth, and thence modified to increase coverage. Applications to simulated and empirical data illustrate the method, which is also compared to several other methods in the literature adapted to the multivariate setting. Copyright © 2015 John Wiley & Sons, Ltd.     

Use of space by the marsupials Gracilinanus microtarsus (Gardner and Creighton, 1989) and Marmosops incanus (Lund, 1840) in an Atlantic Forest of southeastern Brazil

The use of space by animals is determined by environmental conditions, biological and ecological adaptations and interactions and mostly by resource availability. We sampled two species of Neotropical mammals to investigate their use of different strata in Atlantic Forest habitat in Brazil, as well as the home range sizes and movements of both sexes of each species. We found no difference in home ranges and movements between the sexes and species, but we found differences in the use of strata, with Gracilinanus microtarsus mostly using the canopy and Marmosops incanus using the ground. Gracilinanus microtarsus males mostly use the understorey in the wet season and the canopy in the dry season. We believe that these patterns of strata use reflect intrinsic characteristics of the species; and the shifts in resources and interspecific competition, which are lower in the dry season, seem to be responsible for the shifts in space use observed for G. microtarsus males. We recommend studies with spool-and-line techniques or radio tracking to further test refined hypotheses regarding the use of space, including the role of territoriality in females.     

乌苏里江水深遥感反演

文中在分析卫星遥感测深机理的基础上,利用SVCHR-1024高光谱成像仪确定了可见光反演水深的最佳波段,通过对HJ星CCD数据各波段反射率、波段比值组合对水体、水深的敏感性分析,建立了适合于乌苏里江的单波段对数水深反演模型,从而快速获取乌苏里江河道地形信息,并探测了河道深泓线,整体精度达到80%以上.遥感反演水深可快速探测河道深泓线的方法,为乌苏里江河势演变研究提供了新的思路.     

时变流动性深度模型

使用超高频数据,并利用流动性深度指标,研究流动性的动态特征、影响因素以及检验市场微观结构理论.结果支持基于信息不对称下的市场微观结构理论.研究还表明耐心交易可以降低交易成本.     

“网约车新政”政策议程设置的多源流分析

《网络预约出租汽车经营服务管理暂行办法》确立了网约车在中国的合法地位。本文使用多源流理论分析该《暂行办法》是如何进入决策者视野、走上政策议程的。网约车监管与治理问题的构建(问题源流)、各方观点及政策主张(政策源流)、政府机构与其他利益代表方的立场(政治源流),这3个源流在政策窗口打开时交汇,由交通运输部将网约车新政提上政策议程。     

Studies on induction hardening of powder-metallurgy-processed Fe-Cr/Mo alloys

Induction hardening of dense Fe-Cr/Mo alloys processed via the powder-metallurgy route was studied. The Fe-3Cr-0.5Mo, Fe-1.5Cr-0.2Mo, and Fe-0.85Mo pre-alloyed powders were mixed with 0.4wt%, 0.6wt%, and 0.8wt% C and compacted at 500, 600, and 700 MPa, respectively. The compacts were sintered at 1473 K for 1 h and then cooled at 6 K/min. Ferrite with pearlite was mostly observed in the sintered alloys with 0.4wt% C, whereas a carbide network was also present in the alloys with 0.8wt% C. Graphite at prior particle boundaries led to deterioration of the mechanical properties of alloys with 0.8wt% C, whereas no significant induction hardening was achieved in alloys with 0.4wt% C. Among the investigated samples, alloys with 0.6wt% C exhibited the highest strength and ductility and were found to be suitable for induction hardening. The hardening was carried out at a frequency of 2.0 kHz for 2-3 s. A case depth of 2.5 mm was achieved while maintaining the bulk (interior) hardness of approximately HV 230. A martensitic structure was observed on the outer periphery of the samples. The hardness varied from HV 600 to HV 375 from the sample surface to the interior of the case hardened region. The best combination of properties and hardening depth was achieved in case of the Fe-1.5Cr-0.2Mo alloy with 0.6wt% C.     

南京长江第四大桥钢箱梁铺装层温度影响系数分析

为了减少现有的钢桥面铺装层车辙深度预估的误差,提出基于长期实测数据的钢桥面铺装车辙评估模型的温度影响系数计算公式。首先对南京长江第四大桥的实测温度概率统计后采用双高斯函数表征其分布;在此基础上修正了现有车辙评估模型中的温度影响系数公式,并利用车辙实测数据对车辙评估模型计算值进行验证。研究结果表明:钢箱梁复合浇筑式铺装层温度可通过双高斯分布描述其概率分布;计入温度影响系数的车辙深度与实际车辙值之间误差较小,相对误差为15.2%。     

基于积分分离式PID控制的耕深调节系统研究

耕作过程中保持耕深稳定是提高耕作质量的重要措施之一.以小型耕耘机的后悬挂旋耕部件为研究对象,提出了一种基于积分分离式PID控制的耕深自动测量和调节的系统,采用双倾角传感器检测耕深,消除了田块自身与绝对水平面倾角的误差影响,通过在误差信号的处理中使用积分分离式PID控制算法,利用Simulink中的SimHydraulic模块对耕深控制系统进行动态仿真研究,与未加入PID控制算法时的仿真结果进行比较,发现几乎消除了系统的耕深超调现象.同时,将响应时间由4.0s左右缩短到1.4s左右,使耕深控制系统的动态响应达到较好的效果.田间试验结果表明,当耕深设定为10cm和16cm时,实测耕深稳定性变异系数分别为6.05%和3.54%,均低于10%,达到了农业机械作业标准所规定的旋耕作业农艺要求.     

大尺寸工程模型试验中的相似材料配比试验研究

大型物理模型试验是研究复杂工程问题的重要方法,如何快速、准确地确定相似材料配比是试验中至关重要的一环.为降低试验成本、简化试验步骤、充分调用原料性能,采用河砂、水泥和石膏这三种最普通的原料,以骨胶比(河砂与水泥石膏的质量比)和水膏比(水泥与石膏的质量比)为变量,进行了45组对比试验,对相似材料的物理及动、静力学参数进行了研究.获得了以河砂、水泥和石膏为原料配制的相似材料各物理量的变化区间;探讨了骨胶比和水膏比对相似材料各物理量的控制作用,并对比了其敏感性;基于多元线性回归分析建立了各因素与物理量间的定量关系,得到的拟合公式能较好地描述相似材料的性质.     

考虑强度参数时间和深度效应边坡稳定性分析

针对风化软岩及残积土边坡抗剪强度参数值通常具有深度和时间上的变异性的特点,提出了考虑抗剪强度参数深度和时间效应的风化软岩及风化残积土边坡稳定性分析极限平衡条分法;基于蒙特卡罗抽样思想,提出了一种能同时搜索边坡最危险圆弧滑面及相应最小安全系数的随机搜索算法.最后通过算例对比分析了考虑力学强度参数深度和时间效应前后的边坡临界滑面位置及最小安全系数的变化,分析结果表明:力学强度参数的深度和时间效应对边坡稳定性的影响不容忽视.