The use of operational modal analysis and mode tracking for insight into polar vessel operations

Accurate dynamic models of flexible ship structures are required to predict structural vibration caused by environmental loads. Knowledge of dynamic or modal properties are important, for example, to study fatigue damage. In this paper, operational modal analysis (OMA) is used to identify the vibration characteristics of a polar vessel from full-scale acceleration measurements. Five modes are tracked over a range of different operating and environmental conditions, including calm, open water, two ice cases and an open water storm. Compared to the calm, open water conditions, vertical bending modes were generally affected the most by the operating environment, with natural frequency and damping increasing up to 3.7 and 349 %, respectively, in ice. Severity of two-node and three-node vertical bending responses, quantified using a root-mean-square value, were found to be especially large during the open water storm case. Temporal behaviour of two-node and three-node vertical bending due to wave-slamming further contained multiple whipping responses, pointing towards possible cumulative damage over a large number of stress cycles occurring at the midship. Higher damping in ice resulted in responses with lower magnitudes and shorter durations.     

逆向物流管理理论与应用

该文通过实施体验和行业特点重新解读了逆向物流的定义和特点,分析了开展的必要性和当前的主要制约因素,指出开展过程中遇到的主要问题,进行总结和思考,结合自身开展业务取得的经验成果,提出了解决逆向物流运行发展中的存在问题的方法。     

基于内部控制和IT建设双重视角的操作风险控制研究

操作风险是国有商业银行所面临的一项重要风险,而信息化环境下的内部控制是操作风险控制的重要措施。经验性的解析揭示了信息化建设与内部控制对操作风险控制的微观传导机制,从而为国有商业银行实施有效的风险控制提供了现实性的理论借鉴。     

质量管理体系在测井企业中的有效运行探析

本文阐述了测井企业运行质量管理体系的必要性,介绍ISO9000质量管理体系在测井企业中的实现与控制,分析总结质量管理体系在实际应用中的方法。     

Real time prediction of operational safety limits for dynamic positioning of an FPSO in a Deepwater Artificial Seabed system

Aiming to overcome the limitations of conventional offshore field development concepts (dry tree or subsea tree) for petroleum production in ultra-deep water, a new alternative offshore field development solution, termed as Deepwater Artificial Seabed (DAS) system, is proposed. The DAS system works in concert with dynamic positioning (DP) floaters, such as dynamically positioned Floating Production, Storage and Offloading (FPSO) vessels. Rather than relying on the passive mooring system, the DP maintains the reliable position of the FPSO with steering and propulsion units. Nonetheless, critical DP failures, which has potential to cause the drift-off scenario for the FPSO, poses a serious threat to the structural safety of the DAS system. Therefore, it is crucial to establish operational limits for the DP FPSO to prevent such accidents. In this study, a 3-phase probabilistic modelling methodology is proposed to predict safety limits for the operation of the DP FPSO. A surrogate model is established by the Support Vector Machine (SVM) algorithm so as to decrease the computational cost due to the generation of large statistical samples. The statistical distribution of the operational safety limits of FPSO is simulated by the successive approximations through the fully-coupled drift-off analysis. The accuracy of the proposed methodology is verified by a series of mathematical tests. In order to validate the effectiveness of the methodology, the safety limit prediction of the FPSO for the DAS system is taken as a case study. The critical positions of the FPSO are predicted in real time and provides ample time and information for operators’ decision-making by the visualization of the safe moving range of the FPSO. The study contributes to the safety control of DP operations on floating production units in an efficient manner.     

Predicting the operational acceptance of airborne flight reroute requests using data mining

For tools that generate more efficient flight routes or reroute advisories, it is important to ensure compatibility of automation and autonomy decisions with human objectives so as to ensure acceptability by the human operators. In this paper, the authors developed a proof of concept predictor of operational acceptability for route changes during a flight. Such a capability could have applications in automation tools that identify more efficient routes around airspace impacted by weather or congestion and that better meet airline preferences. The predictor is based on applying data mining techniques, including logistic regression, a decision tree, a support vector machine, a random forest and Adaptive Boost, to historical flight plan amendment data reported during operations and field experiments. Cross validation was used for model development, while nested cross validation was used to validate the models. The model found to have the best performance in predicting air traffic controller acceptance or rejection of a route change, using the available data from Fort Worth Air Traffic Control Center and its adjacent Centers, was the random forest, with an F-score of 0.77. This result indicates that the operational acceptance of reroute requests does indeed have some level of predictability, and that, with suitable data, models can be trained to predict the operational acceptability of reroute requests. Such models may ultimately be used to inform route selection by decision support tools, contributing to the development of increasingly autonomous systems that are capable of routing aircraft with less human input than is currently the case.     

列车交会压力波与运行速度的关系

随着列车速度的提高,列车交会时产生的瞬态压力冲击对行车安全、旅客舒适性均产生严重影响。根据多次实车试验结果和理论分析,将列车交会分为列车静止交会、等速交会和不等速交会3种工况,研究了3种工况的列车交会压力波与运行速度之间的关系,得到一系列回归关系式。研究结果表明:静止列车上的压力波与交会列车运行速度的平方成正比;两列车等速交会时,列车上的压力波幅值与两交会列车的运行速度和相对速度的平方成正比;两列车不等速交会时,高速列车承受的压力波幅值小于与之交会的低速列车所承受的压力波幅值;两列车等速交会时的压力波大于一方列车静止时交会的压力波。     

浅谈水泥混凝土路面修复设计

水泥混凝土路面的修复整治已经成为广大市政建设工作者关注和研究的—个重要课题。在水泥混凝土路面上做沥青加铺层,具有“刚柔相济”的特点,路基强度高,稳定性好,路面平整、无接缝,行车舒适,能够大大改善旧路面的使用性能。     

Meta-frontier function approach to operational efficiency for shipping companies

ABSTRACT

This study uses a meta-frontier function approach to estimate operational efficiency and technology gaps for shipping companies. Researchers have evaluated the relative efficiency of shipping firms with the assumption that shipping firms operate under one frontier technology. However, the assumption of one frontier technology is being argued by efficiency literature. Therefore, this study estimates relative efficiency of shipping firms in different market segments (dry bulk, liquid bulk, and containerized cargo), possibly operating with different technologies and, hence, under different frontiers. This study uses a meta-frontier function approach that allows us to distinguish separate frontiers for different groups and decompose efficiency scores relative to the meta-frontier. Data used in this study is collected from Thomson One Banker from 2001-2013 in the form of unbalanced panel data. Empirical results suggest that dry bulk firms’ production technology is more advanced than others and the production frontier is the closest to that of the meta-frontier. In addition, efficiency scores are all low, but containerized cargo firms achieve higher technological efficiency than the other two groups. It is also suggested that containerized cargo and liquid bulk firms should prioritize improvements in their production technology and dry bulk firms should prioritize improving group efficiency.     

论郑和航海精神与我国和谐海洋观

长期以来我国对具有中国特色的新海洋观理论的探讨研究,几近空白。郑和下西洋六百多年,留下了历史的追思与遗憾,文章论述了郑和航海精神与历史遗产;认为今天的很多经济社会问题是郑和那个时代所没有的。提出了具有我国特色的和谐海洋观观点。指出经略海洋把全球资源配置与经济目的紧密联系起来;谋划海洋获取优质能源等资源,走可持续的和谐发展道路;促进国际和平,走交流合作之路;应是今天中国和谐海洋观的三个重要组成部分。