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1.
Emilio Ferrari Riccardo Manzini Arrigo Pareschi Alessandro Persona Alberto Regattieri 《先进运输杂志》2003,37(3):243-272
The present research deals with car pooling as a means of making better use of existing infrastructure and as a means of reducing traffic congestion with all its associated induced effects. Car pooling schemes involve several drivers getting together to share a private vehicle simultaneously, in order to reach their destinations points according to a semi‐common route rather than each driver using their own vehicle. The Car Pooling Problem belongs to the non‐polynomial computational complexity family of operations problems. In the current literature there are only a few studies on this optimization problem: the research group has designed several different new automatic and heuristic data processing routines to support efficient matching in car pool schemes. These are based on savings functions and belong to two distinct macro classes of algorithms to give two different modelings of this problem. They offer average savings of more than 50% in traveled distances demonstrating the effectiveness of a trivial matching scheme for real applications. 相似文献
2.
Yusuke Tahara Daniele Peri Emilio Fortunato Campana Frederick Stern 《Journal of Marine Science and Technology》2008,13(2):95-116
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. 相似文献
3.
A cooperative waiting strategy based on elliptical areas for the Dynamic Pickup and Delivery Problem with Time Windows 下载免费PDF全文
The purpose of this paper to present a cooperative scheduling algorithm for solving the Dynamic Pickup and Delivery Problem with Time Windows (DPDPTW). The idea behind cooperative waiting strategies is to calculate simultaneously the waiting times for all nodes in the solution. Classical non‐cooperative scheduling algorithms perform the scheduling for each route independently of the scheduling of the other routes. We present the Cooperative Scheduling Problem (CSP) based on the elliptical areas generated by vehicles waiting at their nodes. The CSP is solved by means of a genetic algorithm and is evaluated by using a set of benchmarks based on real‐life data found in the literature. Initially, two waiting strategies are presented: Wait‐Early‐Time scheduling and Balanced‐Departure scheduling. Extensive empirical simulations have been carried out by analyzing the degree of dynamism and the average waiting time, a new concept defined to take into account the gap between the time windows of pickup and delivery nodes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
4.
Manivannan Kandasamy Daniele Peri Seng Keat Ooi Pablo Carrica Frederick Stern Emilio F. Campana Philip Osborne Jessica Cote Neil Macdonald Nic de Waal 《Journal of Marine Science and Technology》2011,16(2):143-156
The wakes of high-speed passenger-only ferries that operated through Rich Passage, on the Seattle-Bremerton ferry route, caused
beach erosion and damage to habitat. A task was initiated to design a low-wake high-speed vessel using multi-fidelity CFD
based design optimization by using low-fidelity potential flow solvers for initial global design optimization and by using
URANS solvers for high-fidelity tuning of the optimized design. This simulation based design process involved a close collaboration
between ship designers, and hydrodynamics and CFD specialists, whose collective expertise guided the evolution of the design
based on both hydrodynamic and structural aspects. The initial hull shape optimization using potential flow code was carried
out by blending three different initial concepts provided by the designers. Subsequently, URANS was used to evaluate the potential
flow optimized hull and to further optimize the hull configuration parameters, namely, the centre-of-gravity, demihull spacing,
foil location, foil angle and slenderness ratio at different displacement conditions. The URANS based configuration optimization
also took into account the far field wakes’ energy spectrum with an objective of reducing the energetic, low frequency far
field wakes which are associated with beach flattening on the mixed sand and gravel beaches. Calculation of the far field
wake using URANS would require an unfeasibly large domain size; therefore, a Havelock code with a source distribution matching
the URANS calculated near field wave elevation was used to propagate the wakes into the far field. The end result of the optimization
was a design with significantly reduced far field wake, which is currently being built for experimental testing. 相似文献
5.
Abstract Traditional transport infrastructure assessment methodologies rarely include the full range of strategic benefits for the transportation system. One of these benefits is the contribution to cross‐border integration, critical for the European integration process. However, this is a key issue in strategic planning and decision‐making processes, as its inclusion may increase the probability of large‐scale transport infrastructure projects being funded. This paper presents a methodology for the measurement of the contribution of transport infrastructure plans to European integration. The methodology is based on the measurement of the improvement in network efficiency in cross‐border regions of neighbouring countries, via accessibility calculations in a Geographical Information System support. The methodology was tested by applying it to the ambitious road and rail network extensions included in the Spanish Strategic Transport and Infrastructure Plan (PEIT) 2005–2020. The results show significant and important network efficiency improvements of the PEIT outside the Spanish border. For the road mode, while the Spanish average accessibility improvement accounts for 2.6%, average improvements in cross‐border regions of France and Portugal are of 1.8%. And for the rail mode, the corresponding Spanish value is 34.5%, whereas in neighbouring regions it accounts for 20.2%. These results stress the significant importance of this strategic benefit and the consequent need for its inclusion in strategic planning processes. Finally, the paper identifies the potential of the methodology when applied at different administrative levels, such as the local or state levels. 相似文献
6.
Yusuke Tahara Daniele Peri Emilio Fortunato Campana Frederick Stern 《Journal of Marine Science and Technology》2011,16(4):412-433
Numerical optimization of the initial design of a fast catamaran (high-speed sealift research model B, HSSL-B) has been carried
out through a simulation-based design (SBD) framework, based on an advanced free-surface unsteady Reynolds-averaged Navier–Stokes
(URANS) solver and a potential flow solver, and global optimization (GO) algorithms. The potential flow computational fluid
dynamics (CFD) SBD was used to guide the more expensive URANS CFD SBD. The fluid-dynamic analysis of the flow past the catamaran
proved that the use of the URANS solver was fundamental in dealing with the multihull interference problem. In the case investigated,
the separation distance was small and the viscous flow quite distorted by the proximity of the hulls, so that only viscous
solvers could correctly capture the flow details. Sinkage and trim effects, due to the high speed range and again to the small
separation distance investigated, are also relevant. The initial HSSL-B geometry and three optimization problems, including
single- and multiobjective optimization problems, proposed by designers from Bath Iron Works, were successfully optimized/solved,
and finally an experimental campaign was carried out to validate the optimal design. A new verification and validation methodology
for assessing uncertainties and errors in simulation-based optimization was used based on the trends, i.e., the differences
between the numerically predicted improvement of the objective function and the actual improvement measured in a dedicated
experimental campaign, including consideration of numerical and experimental uncertainties. Finally, the success of the optimization
processes was confirmed by the experimental measurements, and trends for total resistance, sinkage, and trim between the original
and optimal designs were numerically and experimentally verified and validated. 相似文献
7.
Manivannan Kandasamy Seng Keat Ooi Pablo Carrica Frederick Stern Emilio F. Campana Daniele Peri Philip Osborne Jessica Cote Neil Macdonald Nic de Waal 《Journal of Marine Science and Technology》2011,16(2):157-167
This paper details the CFD validation studies carried out as a prerequisite for multi-fidelity CFD-based design optimization
of high-speed passenger-only ferries aimed at reducing far-field wake energy that causes beach erosion. A potential flow program
(WARP) and a URANS program (CFDSHIP) were validated using full-scale measurements of resistance, sinkage, trim, and far-field
wake train obtained over a wide range of speeds for two high-speed semi-planing foil-assisted catamarans: Spirit (LOA-22 m)
and 1060 (LOA-17 m). This study posed a unique combination of challenges for CFD modeling: the foil appended geometry required
complicated surface overset grids, the effect of the waterjet and wind resistance had to be modeled, and a method had to be
devised to extrapolate the calculated near-field elevation to get the far-field wake train using Havelock sources. A more
concentrated effort was applied to the URANS verification and validation which forms the focus of this paper. The results
show that URANS is able to accurately predict the resistance and motions for both vessels when coupled with models that account
for the propulsors and air resistance. The overall accuracy of URANS for the performance analysis of the foil-assisted, semi-planing
catamarans was adequate to warrant its use as a tool for subsequent design and optimization of a new vessel with significantly
reduced wakes. 相似文献
8.
Matteo Diez Wei He Emilio F. Campana Frederick Stern 《Journal of Marine Science and Technology》2014,19(2):143-169
A framework for assessing convergence and validation of non-intrusive uncertainty quantification (UQ) methods is studied and applied to a complex industrial problem in ship design, namely the high-speed Delft Catamaran advancing in calm water, with variable Froude number and geometry. Relationship between UQ studies and deterministic verification and validation is discussed. Computations are performed using high- (URANS) and low- (potential flow) fidelity simulations. Froude number has expected value and standard deviation equal to 0.5 and 0.05, respectively, on a truncated normal distribution. Geometric uncertainty is related to the research space of a simulation-based design optimization, and assessed through the Karhunen–Loève expansion (KLE). Monte Carlo method with Latin hypercube sampling (MC-LHS) is used to compute expected value, standard deviation, distribution and uncertainty intervals for resistance, sinkage and trim. MC-LHS with CFD is used as a benchmark for validating less costly UQ methods, including MC-LHS with metamodels and standard quadrature formulas. Gaussian quadrature is found the most efficient method; however, MC-LHS with metamodels is preferred since provides with confidence intervals and distributions in a straightforward way and at reasonably small computational cost. UQ results are compared to earlier deterministic single- and multi-objective optimization; reduced-dimensional KLE studies for geometric variability indicate that stochastic optimization would not be of great benefit for the present problem. 相似文献
9.
During the February 1981 cruise FIBEX MD-25 between 30–50°E and 61–64°S, hydrography showed the presence of two gyres, confirmed by the geostrophic circulation relative to 1000 m from Levitus climatology, at the borders of these gyres concentrations of highly morphologically differentiated krill were found. Gaussian component analysis of krill samples, pooled by sectors, showed three cohorts of Euphausia superba in the western sector and one in the eastern sector. Across the sampling area, Thysanoessa macrura and E. superba occurred at separate stations. Analysis of cohorts in T. macrura separated two size groups in both the western and the eastern sectors. The use of a Differentiation Index (D.I.) [Färber-Lorda, J., 1990. Somatic length relationships and ontogenetic morphometric differentiation of Euphausia superba and Thysanoessa macrura of the southwest Indian Ocean during summer (February 1981). Deep-Sea Res. 37, 1135–1143.], based on somatic lengths, allows studying certain morphological differences within the populations sampled. Morphologically different and bigger males II (D.I. from 2.8 to 3.5) were present only in the southern transect while smaller males I (D.I. from 3.5 to 5.0) were present over the entire area. Biochemical composition of both species showed significant differences among stations for protein, lipids, and carbohydrates. A significant difference in lipid content was found between males I, and males II. For T. macrura, percentage of lipid content in mature animals was much higher than that in E. superba. The D.I. size distribution showed that when populations of E. superba were highly differentiated (corresponding to mature animals) in morphology, lipid content was high, and they were located near a gyre. Differences in morphometry can influence distribution of the species, because different developing stages have different swimming capacities. It is shown that, together with hydrography and trophic conditions, lipid content and morphometry of krill populations, are different but complementary aspects that help to understand krill ecology and distribution. 相似文献
10.
中庭式地铁车站因用大量横梁取代楼板来形成中庭大开口(顶层和中层楼板的开口率均超过50%),且站厅层无柱,站台层采用宽高比达7.5的薄壁柱,车站结构抵抗横向变形比如地震作用的能力,成为值得担忧的一个问题.为此,针对埋置于人工模型土中的中庭式地铁车站模型,进行了一系列1g振动台试验,探究中庭式地铁车站结构的地震响应特征,以... 相似文献