共查询到20条相似文献，搜索用时 15 毫秒
1.
In this paper, an algorithm to design a shortest-time route for a ship to avoid a tropical cyclone (TC) is proposed. The proposed algorithm takes into account the influence of the changing winds and sea waves on ship’s speed and the corresponding risk using the forecasts from a numerical weather prediction model. Experimental results show that the new algorithm is able to save more time comparing with the traditional sector diagram typhoon avoidance method. In the application of the new algorithm to the navigation practice, the distance between adjacent alternative waypoints should be adjusted to meet the navigational needs, and the route should be updated simultaneously with TC forecasts from a numerical weather prediction model. 相似文献
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Xiaoling Wang Wenlong Chen Zhengyin Zhou Yushan Zhu Cheng Wang Zhen Liu 《Natural Hazards》2017,86(3):1147-1174
Dense buildings are the major factor affecting urban flood routing. Currently, the study of urban dam-break flood routing primarily focuses on a simplified terrain model and 2D shallow water equations, which ignore the effects of dense urban buildings. Furthermore, the complex interactions between the dam-break wave and the wall surfaces of buildings are not reflected in the results. To tackle these problems, three-dimensional flood routing with a high-precision digital model of an urban area is studied in this paper. Firstly, the vector data of various land types is extracted from a remote sensing image, and the NURBS algorithm based on the TIN algorithm is introduced to construct a three-dimensional terrain model. Coupled with the vector data and the terrain model, a three-dimensional digital model of the urban area is established. Next, a three-dimensional \(k{-}\varepsilon\) turbulence model is proposed for the flood routing simulation. A polyhedral grid with a second-order accuracy and a discrete format is used to divide the digital model of the urban area, and the governing equations are solved using the PISO algorithm. Finally, the superiority of the 3D mathematical model and the computational efficiency of the polyhedral mesh model are validated according to the urban flood routing experiments of Testa and Soares-Frazão. An urban reservoir, located in SZ City, China, is modelled to show that a dam-break flood in an urban area exhibits significant three-dimensional characteristics. Moreover, due to the surrounding buildings, the flood exhibits complex three-dimensional turbulence phenomena, including collision, reflection and vortices. 相似文献
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A route alignment planning has various stages. At different stages, multi-criteria decision analysis (MCDA) is required. This paper integrates geographical information system (GIS) and MCDA for designing the optimum route alignment. A GIS-based model using the multi-criteria decision analysis for finding the optimum route alignment to design major road from a source to a destination within two locations is proposed. Three different levels of analysis were performed in this study such as criteria map analysis, surface cost analysis, and least-cost path analysis. The optimum route has the least cost and satisfies other environmental, technical, social, and economic criteria. The proposed model is implemented to design optimum route alignment between two locations in the outer area of Allahabad City, India. Four route alignments are created, and one of the best routes is chosen. 相似文献
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基于GIS的区域交通通达性模型的研究与开发 总被引：1，自引：0，他引：1
SONG Qin-chang LIU Wan-song REN You-gui QIAO Jin-hai XIAO Yang XU Jun-qiang College of GeoExploration Science Technology Jilin University Changchun China 《吉林大学学报(地球科学版)》2006,(Z2)
介绍了基于栅格数据的区域通达性模型的设计和实现思路,提出了以GIS为基础平台,以地图为载体,整合各种资源,建立区域通达度模型的方法,讨论了基于栅格数据的最佳路径分析方法,综合考虑各种影响因素,通过计算最小累加费用值确定最佳路径。 相似文献
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扩散波的时空反演与洪水实时预报技术 总被引：2，自引：1，他引：1
以扩散波方程描述天然河道中的洪水波运动规律。将数学物理反问题理论和离散反演算法与河道流量演算相结合提出了扩散波实时预报的方法。该法的特点是在求解流量场Ｑ（ｘ,ｔ）的同时反演计算扩散波波速Ｃ（ｘ,ｔ）和扩散系数Ｄ（ｘ,ｔ）,根据不断监测的新信息系列,直接利用原偏微分方程进行参数的实时校正和预报过程实时修正。 相似文献
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马斯京根法参数的一种数学估计方法 总被引：10，自引：3，他引：7
应用最小二乘原理进行了马斯京根法参数的最优估计。这种数学估计方法避免了常用的度错法的盲目性和不确定性,并具有确定模型参数快速、最优和唯一性等特点。在实际河道洪水演算中取得了较好的应用效果。 相似文献
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Xiu Zongxiang Xu Qiang Shan Zhigang Sun Yongfu Xie QiuHong Song Yupeng 《Natural Hazards》2021,108(2):2225-2248
Submarine landslides are a great hazard to offshore pipelines. The comparison and optimisation of pipeline routing schemes to reduce the potential submarine landslide risk is a key issue in offshore oil and gas development engineering. This paper presents an improved group decision-making evaluation method for offshore pipeline routing optimisation in areas prone to submarine landslides. An information integrity variable is proposed to adjust the relative weight of each factor considering the incompleteness of the engineering geological survey information and data. The credibility level of each expert involved in the evaluation, which is calculated based on the similarity and difference of the experts’ judgment matrices, is introduced to correct the information integrity variable, relative weights, and memberships. The group decision-making for offshore pipeline routing selection is then obtained based on the principle of the majority rule. Finally, a case of pipeline routing optimisation in the submarine canyon area of the Baiyun depression, northern South China Sea, is assessed by using the proposed method. The result shows that the proposed group decision-making method can enhance the objectivity of the assessment for the offshore pipeline routing optimisation under a subjective environment.
相似文献10.
近些年来,深度学习网络的兴起极大地推动了人工智能技术在地震数据处理、反演以及解译等领域的应用.地震波阻抗反演是石油地震勘探领域的一项关键技术,其反演精度在圈定油气储层构造中起到非常重要的作用.提出了一种基于数据驱动时间卷积网络（temporal convolution network,TCN）模型的地震波阻抗反演方法,旨在无需建立初始反演模型,直接利用工区的少量测井标签数据,以地震振幅数据为输入,将波阻抗反演转化为时间序列建模任务,最终输出地下模型的阻抗信息.采用Marmousi2数据集对基于TCN的波阻抗反演模型进行训练、验证和测试,结果显示,在测试集上该模型预测结果的皮尔逊系数和决定系数分别达到97.92%和95.95%,并对远离训练区域的波阻抗信息预测有着良好的泛化性,且在预测时间和预测精度等方面都要明显优于前人的相关研究工作.上述结果表明,TCN时间序列深度学习模型在复杂地层波阻抗反演中具有一定优越性和应用前景,为地震波阻抗反演提供了新思路. 相似文献
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对于沉船打捞作业,穿千斤工序是关乎其成败的重要一步,但目前我国的沉船打捞穿千斤作业主要采用潜水员水下手持攻泥器攻打大直径千斤洞作业,劳动强度大,效率低,至今已有10多名潜水员因穿千斤作业伤亡。在对比“攻泥机器人”和已应用的HDD技术穿千斤作业的优缺点后．论文提出了HDD技术穿千斤作业的新工艺,以高效服务于沉船打捞穿千斤作业。 相似文献
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全波形反演是一种全新的地震成像方法,主要利用全波形信息反演地下介质参数,通过非线性优化波场理论值和观测值的残差实现波形反演。基于时间域声波方程,建立了时间域波场残差目标函数,以分层模型为例,分别从波场精度、目标函数收敛性和运行时间3个方面,比较了共轭梯度（Conjugate Gradient,CG）算法和拟牛顿算法（Broyden-Fletcher-Goldfarb-Shanno,BFGS）反演的效果。同时,应用共轭梯度法对正、逆断层模型和Marmousi模型进行了速度结构反演。反演结果表明:共轭梯度法计算效率较高,反演得到的速度模型精度更高,反演效果较好,是一种有效的波形反演方法。 相似文献
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H Kruhl 《Geoforum》1973,4(2):19-38
After giving a brief historical review on the discovery of ocean wind systems, the kinds and benefits of marine weather forecasts, storm warning services, and storm flood services are explained. The activities and effects of ship-borne weather services are described. A major use of meteorological material is made in navigation, and optimum ship routing methods are generally descussed. Ice accretion may cause severe danger to ships and is a main navigational hazard. Cold ocean currents, upwelling areas, and zones of rapid changes of air temperature are fields of danger for cargo in ships. Techniques for avoiding such risks are discussed. Finally, observations at sea, the basis of all marine meteorological work, are discussed. 相似文献
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建立了适用于栅格单元系统的基于运动波理论的降尺度新安江模型(KWXAJ)。在栅格单元中采用新安江模型计算产流,运动波模型进行坡面汇流演算。模型中,为考虑上游坡地单元入流的径流入渗(run-on)效应,在进行坡地产流计算时,降雨及上游坡面流及壤中出流被同时作为来水输入新安江模型。在运动波模型中,糙率系数依据土地利用方式及洪水量级确定。选取淮河史灌河流域黄泥庄以上集水区域,作为研究区域。用流域历史上的13次洪水过程来率定和验证此模型。研究表明,run-on机制对流域产汇流预测有重要影响,其显著影响流域内土壤蓄水量时空分布,进而改变产汇流机制。数据分析还显示,不考虑run-on机制将导致模拟洪峰滞后。 相似文献
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Displacement back analysis is a common method to identify mechanical geo‐material parameters using the monitored displacement. How to obtain a global optimum solution in large space search of highly non‐linear multimodal is a key point of optimum back analysis. The paper presents a new back analysis that is an integration of evolutionary support vector machines (SVMs), numerical analysis and genetic algorithm. The non‐linear relationship between the mechanical geo‐material parameters to be identified and the corresponding displacement values of key points is learned and represented by evolutionary SVMs in global optimum. Numerical analysis is used to create training and testing samples for recognition of SVMs. Then, performing a global optimum search on the obtained SVMs using genetic algorithm can identify the mechanical geo‐material parameters. The proposed algorithm is tested by back analysis of an elastic plate and an elastic–plastic plate and used to recognize mechanical parameters of subclay, strongly weathered tuff and weakly weathered tuff of Bachimen slope, Funing expressway, Fujian, China. The results indicate that applicability of the proposed algorithm with enough accuracy. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Optimum reaction time, performance and exhaust emissions of biodiesel produced by microwave irradiation 总被引：3，自引：3，他引：0
A. A. Refaat S. T. El Sheltawy K. U. Sadek 《International Journal of Environmental Science and Technology》2008,5(3):315-322
While transesterification is well established, there remain considerable inefficiencies in existing transesterification processes. In this study an alternative energy stimulant, “microwave irradiation” was used for the production of the alternative energy source, biodiesel. The optimum parametric conditions obtained from the conventional technique were applied using microwave irradiation in order to compare both systems. The results showed that application of radio frequency microwave energy offers a fast, easy route to this valuable biofuel with advantages of enhancing the reaction rate and improving the separation process. The methodology allows for the use of high free fatty acid content feedstock, including used cooking oil; hence it helps to reduce the cost of production which constitutes a major hurdle towards widespread commercialization of biodiesel. The study also showed that the optimum reaction time for microwave-enhanced biodiesel production should be highly respected. Exceeding the optimum reaction time will lead to deterioration of both biodiesel yield and purity. This paper also reported the performance and exhaust emissions from a diesel engine when fuelled with a petroleum diesel fuel and two different biodiesel fuels; one obtained by the conventional technique and the other by microwave irradiation. It was concluded that microwave-enhanced biodiesel is not, at least, inferior to that produced by the conventional technique. 相似文献
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A real-time operation optimization model for flood management in river-reservoir systems 总被引：1，自引：1，他引：0
In this paper, a new methodology has been developed for real-time flood management in river-reservoir systems. This methodology
is based upon combining a Genetic Algorithm (GA) reservoir operation optimization model for a cascade of two reservoirs, a
hydraulic-based flood routing simulation model in downstream river system, a Geographical Information System (GIS) based database,
and application of K-Nearest Neighbor (K-NN) algorithm for development of optimal operating rules. The GA optimization model
estimates the optimal hourly reservoirs’ releases to minimize the flood damages in the downstream river. GIS tools have also
been used for specifying different land-uses and damage functions in the downstream floodplain and it has been linked to the
unsteady module of HEC-RAS flood routing model using Hec-GeoRAS module. An innovative approach has also been developed using
K-NN algorithm to formulate the optimal operating rules for a system of two cascade reservoirs based on optimal releases obtained
from the optimization model. During a flood event, the K-NN algorithm searches through the historical flood hydrographs and
optimal reservoir storages determined by the optimization model to find similar situations. The similarity between the hydrographs
is quantified based on the slopes of rising and falling limbs of inflow hydrographs and reservoir storages at the beginning
of each hourly time step during the flood events for two cascade reservoirs. The developed methodology have been applied to
the Bakhtiari and Dez River-Reservoir systems in southwest of Iran. The results show that the proposed models can be effectively
used for flood management and real-time operation of cascade river-reservoir systems. 相似文献
20.
The case of a freak wave collision with the ship in the Agulhas current is described. The explanation of the appearance of the freak wave as a result of wind-wave transformation in the Agulhas current is given. Swell is captured and intensified by the counter-current and is located in the neighbourhood of the maximum value of the current velocity, as a result of which there is a great concentration of wave-energy density. The superposition of wind and sea with swell transformed by the current promotes the formation of the freak waves. Using a simple mathematical analysis, an optimal ship track is proposed which could reduce the risk of collision with a freak wave. 相似文献