Identification of potential sites for deep-ocean waste isolation with a geographic site-selection model

Identification of optimal sites for the isolation of waste on the abyssal seafloor was performed with two approaches: by the traditional method of map overlays of relevant attributes, and by a specially developed, automated Site-Selection Model (SSM). Five initial, Surrogate Sites, identified with the map-overlay approach, were then compared with the more rigorously produced scores from the SSM. The SSM, a process for optimization of site locations, accepts subjective, expert-based judgments and transforms them into a quantitative, reproducible, and documented product. The SSM is adaptable to any siting scenario. Forty-one factors relevant to the isolation scenario, including 21 weightable factors having a total of 123 scorable categories, have been entered into the SSM. Factors are grouped under project definition, unique environments, anthropogenic, geologic, biologic, weather, oceanographic and distance criteria. The factor scores are linked to a georeferenced database array of all factors, corresponding to 1°×1° latitude–longitude squares. The SSM includes a total of 2241 one-degree squares within 1000 n.m. of the U.S. coasts, including the western North Atlantic, the Gulf of Mexico, and the eastern North Pacific. Under a carefully weighted and scored scenario of isolation, the most favorable sites identified with the SSM are on the Hatteras and Nares Abyssal Plains in the Atlantic. High-scoring sites are also located in the Pacific abyssal hills province between the Murray and Molokai Fracture Zones. Acceptable 1° squares in the Gulf of Mexico are few and of lower quality, with the optimum location on the northern Sigsbee Abyssal Plain. Two of the five Surrogate Site locations, on the Hatteras and Sigsbee Abyssal Plains, correspond to the best SSM sites in each ocean area. Two Pacific and a second Atlantic Surrogate Site are located in low-scoring regions or excluded by the SSM. Site-selection results from the SSM, although robust, are an initial attempt to quantify the site-selection process. The SSM database exposes a significant lack of high-quality information for many areally mappable attributes on the abyssal seafloor, particularly bottom-current speed and measures of biologic productivity and flux. Terminologies and classifications of some measures, such as sediment types, suffer from parochialism and vary by ocean. Considerable research is needed even for a broad understanding of the environmental measures required to make sound societal decisions about use of the abyssal seafloor for disposal or other purposes.     

Public transport provision in sparsely populated arid areas

Arid areas are characterized by dispersed patterns of population and economic activities in a hot and dry environment. Although basic human needs are identical everywhere, patterns of travel behaviour in arid lands are different from the patterns in more humid areas. The different behavioural patterns imply somewhat different demand patterns for transport services in general and transit services in particular. Good access to the scattered small communities and more so to the remote urban centres is of prime concern in the sparsely populated arid areas. And the demand patterns themselves raise the need to develop unusual types of service based on local conditions. This article presents the effects of the arid spatial and climatic conditions on transit demand and supply. After examining the service standards required in the sparselands and using the Israeli Negev region as an example, guidelines for developing regional transit systems in these arid areas are put forward.     

URANS simulations of static and dynamic maneuvering for surface combatant: part 2. Analysis and validation for local flow characteristics

Part 2 of this two-part paper presents the analysis and validation results of local flow characteristics for a surface combatant Model 5415 bare hull under static and dynamic planar motion mechanism simulations. Unsteady Reynolds averaged Navier–Stokes (URANS) computations are carried out by a general-purpose URANS/detached eddy simulation research code CFDShip-Iowa Ver. 4. The objective of this research is to investigate the capability of the code in relation to the computational fluid dynamics-based maneuvering prediction method. In the current study, the ship is subjected to static drift, steady turn, pure sway and pure yaw motions at Froude number 0.28. The free surface, three dimensional vortical structure and, the validation of two dimensional local flow quantities together with the available experimental data are of the interest in the current study. Part 1 provides the verification and validation results of forces and moment coefficients, hydrodynamic derivatives, and reconstructions of forces and moment coefficients from resultant hydrodynamic derivatives.     

EFD and CFD for KCS heaving and pitching in regular head waves

The KCS container ship was investigated in calm water and regular head seas by means of EFD and CFD. The experimental study was conducted in FORCE Technology’s towing tank in Denmark, and the CFD study was conducted using the URANS codes CFDSHIP-IOWA and Star-CCM+ plus the potential theory code AEGIR. Three speeds were covered and the wave conditions were chosen in order to study the ship’s response in waves under resonance and maximum exciting conditions. In the experiment, the heave and pitch motions and the resistance were measured together with wave elevation of the incoming wave. The model test was designed and conducted in order to enable UA assessment of the measured data. The results show that the ship responds strongly when the resonance and maximum exciting conditions are met. With respect to experimental uncertainty, the level for calm water is comparable to PMM uncertainties for maneuvering testing while the level is higher in waves. Concerning the CFD results, the computation shows a very complex and time-varying flow pattern. For the integral quantities, a comparison between EFD and CFD shows that the computed motions and resistance in calm water is in fair agreement with the measurement. In waves, the motions are still in fair agreement with measured data, but larger differences are observed for the resistance. The mean resistance is reasonable, but the first order amplitude of the resistance time history is underpredicted by CFD. Finally, it seems that the URANS codes are in closer agreement with the measurements compared to the potential theory.     

URANS and DES analysis for a Wigley hull at extreme drift angles

Vortical structures and associated instabilities for flows around the Wigley hull for a wide range of drift angles (10° ≤ α ≤ 60°) with free surface are identified and analyzed. Quantitative verification and validation are conducted on three systematically refined grids with comparison to the experimental data for α = 10°. Analysis of the flow pattern shows a strong correlation between the vortical structures and free-surface wave elevation. For α = 10° and 30°, the flows remain steady and vortices are generated at the keel and fore and aft perpendiculars of the hull. The strength and complexity of these vortices increase with increasing α. At α = 45°, flow becomes unsteady without any significant change in the main flow pattern. At α = 60°, a complex and unsteady flow field on the leeward side of the hull is formed with a large recirculation region from the aft to the fore end, which prevents the flow coming from below the keel from moving up and generating the keel vortices observed at lower drift angles. Karman-like and helical instabilities are analyzed. The effect of Froude number is more apparent for large than for small drift angles.     

轨道交通的产学研新模式——麻省理工学院/波多黎各地铁项目简介

波多黎各于20世纪90年代初才开始发展城市轨道交通,但因为善于利用后发优势,通过产学研的结合,充分考虑了地铁工程的多学科特性,走出一条有波多黎各特色的道路,成为美国和国际公共交通领域技术交流的典范.主要介绍了其产学研的项目,它由负责地铁项目的政府主管部门、波多黎各大学和美国麻省理工学院共同组织实施,历经地铁前期规划、修建、调试、运营和政策分析等全部过程,共13年的时间.这种方式提高了工程的质量和施工效率,推动当地轨道交通辅助产业的发展,加快了新技术的应用及研究,培养了一大批轨道交通的规划运营人才,为拉丁美洲城市轨道交通建设提供了一个新模式.波多黎各的经验对于我国当前的城市轨道交通建设同样具有借鉴意义.     

Computational fluid dynamics-based multiobjective optimization of a surface combatant using a global optimization method

The main objective of this article is to describe the development of two advanced multiobjective optimization methods based on derivative-free techniques and complex computational fluid dynamics (CFD) analysis. Alternatives for the geometry and mesh manipulation techniques are also described. Emphasis is on advanced strategies for the use of computer resource-intensive CFD solvers in the optimization process: indeed, two up-to-date free surface-fitting Reynolds-averaged Navier-Stokes equation solvers are used as analysis tools for the evaluation of the objective function and functional constraints. The two optimization methods are realized and demonstrated on a real design problem: the optimization of the entire hull form of a surface combatant, the David Taylor Model Basin—Model 5415. Realistic functional and geometrical constraints for preventing unfeasible results and to get a final meaningful design are enforced and discussed. Finally, a recently proposed verification and validation methodology is applied to assess uncertainties and errors in simulation-based optimization, based on the differences between the numerically predicted improvement of the objective function and the actual improvement measured in a dedicated experimental campaign. The optimized model demonstrates improved characteristics beyond the numerical and experimental uncertainty, confirming the validity of the simulation-based design frameworks.     

Future electricity demand from battery‐powered vehicles

An important decision faced by airline schedulers is how to adapt the flight schedule and aircraft assignment to unforeseen perturbations in an established schedule. In the face of unforeseen aircraft delays, schedulers have to decide which flights to delay, and when delays become excessive, which to cancel. Current scheduling models deal with simple decision problems of delay or cancellation, but not with both simultaneously. But in practice the optimal decision may involve results from the integration of both flight cancellations and delays. In Part I of this paper, a quadratic programming model for the integration decision problem is given. The model can formulate the integration of flight cancellations and delays as well as some special cases, such as the ferrying of surplus aircraft and the possibility of swapping different types of aircraft. In this paper, based on the special structure of the model, an effective algorithm is presented, sufficient computational experiments are conducted and some results are reported. These show that we can expect to obtain a sufficiently good solution in terms of reasonable CPU time.