Have tropical marine protected areas worked? An initial analysis of their success

A multinomial choice framework was used to analyze data from hypothetical storm forecast scenarios administered via mail survey to a random sample of U.S. Gulf Coast residents. Results indicate that the issuance of a mandatory evacuation notice and the presence of higher wind speeds had the largest influence on increasing the likelihood of evacuation. Age, race, disability, distance, and education were significant in explaining one's decision to wait relative to choosing to evacuate. Blacks and disabled individuals were strictly less likely to wait and more likely to make an immediate evacuation decision. Hurricane Katrina evacuees and those with an evacuation destination identified were also more likely to decide to evacuate, but were also more likely to wait before deciding. Results indicate that residents of mobile homes were more likely to either evacuate or wait before making a decision, but strictly less likely not to evacuate. Respondents very confident in being rescued were strictly more likely not to evacuate. Results indicate that not having an evacuation destination identified was the most influential factor regarding the likelihood of not knowing what choice to make.     

Prediction of the interaction between a simple moving vehicle and an infinite periodically supported rail – Green's functions approach

This paper herein describes the interaction between a simple moving vehicle and an infinite periodically supported rail, in order to signalise the basic features of the vehicle/track vibration behaviour in general, and wheel/rail vibration, in particular. The rail is modelled as an infinite Timoshenko beam resting on semi-sleepers via three-directional rail pads and ballast. The time-domain analysis was performed applying Green's matrix of the track method. This method allows taking into account the nonlinearities of the wheel/rail contact and the Doppler effect. The numerical analysis is dedicated to the wheel/rail response due to two types of excitation: the steady-state interaction and rail irregularities. The study points out to certain aspects regarding the parametric resonance, the amplitude-modulated vibration due to corrugation and the Doppler effect.     

Origin软件在隧道监控量测数据处理中的应用

介绍Origin软件的基本功能及其应用。利用Origin软件实现了对量测数据的绘图、非线性拟合等处理,获得可靠的参数及直观的图形。以石龙山隧道施工监控中量测数据处理的实例,并据此指导了隧道的开挖作业和支护结构的设计与施工。     

桥梁超重荷载与限载标准的确定

为了分析公路运营中超重荷载对桥梁的影响，以陕西省府谷-店塔公路上运煤超载车辆为调查对象，根据车辆装载特点和轴型分布特征，将超载车辆分为9种类型，分析了9种车型的超载、超限情况；利用线性回归，得出超载与超限的函数关系。利用等代荷载方法，与公路-Ⅰ级荷载相比较，确定出9种车型的限载系数和限载标准，评价了限载后车辆荷载特性，认为车辆限载后宜使用多轮、多轴运营车型。     

Theoretical analysis of natural frequency of externally prestressed concrete beam based on rigidity correction

A dynamic test on externally prestressed simply supported concrete beams separately with three typical types of tendon distributions was conducted. The results show that the natural frequencies of the beams increase with the increase in the prestressing force at,the tensioning stage, and the natural frequencies decrease after the cracks occur in the beams. Following the calculation formula of natural frequency of externally prestressed beam, which was reported in a literature, the natural frequencies of the experimental beams are calculated, and big errors are found between the test results and the calculated ones of natural frequency values. As a result, this paper has tried to adopt two methods to correct the rigidity parameter of the concrete beam in the formula for natural frequency calculation, and to use the corrected formula to calculate the frequencies of the experimental beams. The calculation results indicate a good consistency with the experimental ones, which verifies the feasibility of the corrected formula.     

钡星重元素丰度的参数化研究

提出了一种计算钡星重元素丰度的参数化方法,利用此方法对7颗钡星进行了参数化研究,计算出这些星的最佳拟合参数及其重元素丰度.对核合成参数进行了讨论,将重元素丰度的计算结果与观测值进行了比较,结果符合较好,证明了文中提出的模型的有效性.     

A polynomial chaos approach to the analysis of vehicle dynamics under uncertainty

The ability of ground vehicles to quickly and accurately analyse their dynamic response to a given input is critical to their safety and efficient autonomous operation. In field conditions, significant uncertainty is associated with terrain and/or vehicle parameter estimates, and this uncertainty must be considered in the analysis of vehicle motion dynamics. Here, polynomial chaos approaches that explicitly consider parametric uncertainty during modelling of vehicle dynamics are presented. They are shown to be computationally more efficient than the standard Monte Carlo scheme, and experimental results compared with the simulation results performed on ANVEL (a vehicle simulator) indicate that the method can be utilised for efficient and accurate prediction of vehicle motion in realistic scenarios.     

散货船运输市场周期性分析与预测

国际散货船航运市场在国际航运市场中占有举足轻重的地位,其走势具有周期性,可以预测船舶航运市场的整体趋势,进一步对全球经济形势分析预测。通过对克拉克森报告进行分析和调研,根据调研结果并结合新冠疫情影响确定了散货船航运市场的主要影响因素,采用相关股票指数和数据对各影响因素量化,对历史数据建立时滞模型并进行多元回归分析,进而建立时滞回归模型,构造了代价函数并采用梯度下降法建立多变量线性回归模型,得出表征散货船市场情况的波罗的海指数(BDI)与影响其走势的几种主要因素之间的代数关系,从而用近几年各影响因素的值来预测未来几个月内波罗的海指数的发展趋势,为船市的进一步布局规划提供参考。     

浅谈水闸工程中的消能防冲计算

消能防冲计算是水闸工程设计中的重要环节,消力池、海漫段、防冲槽等消能防冲设施的结构尺寸都需要通过计算确定.水闸设计规范给出了相应的消能防冲计算公式.结合工程实例,从计算水位组合的选取、河道不冲流速及允许流量的计算、闸门开度及过闸流量的确定、消能防冲计算过程、消能防冲设施布置等几个方面对水闸工程中的消能防冲计算及消能防冲设施设计进行了简要介绍.     

有限水深中破损船舶的运动与波浪载荷研究

由于有限水深中船舶搁浅和触礁等严重破损事故频发,为了减少事故的发生,对有限水深中船舶破损后的运动及波浪载荷的研究显得十分必要。文章基于三维势流理论,引入有限水深自由面Green函数,在频域内使用奇点分布法对一艘首部破损进水的散货船在有限水深中的运动与波浪载荷展开了计算,并根据劳氏船级社规范做了短期预报。短期预报结果表明,该散货船破损进水后,船体所受垂向和水平波浪弯矩均比破损前有明显增加,且在较浅水深中变化更为显著。