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921.
Giorgio Contento Guido Lupieri Marco Venturi Tiziana Ciuffardi 《Journal of Marine Science and Technology》2011,16(2):181-201
The present study is aimed at determining the confidence limits of design wave parameters derived from numerical modeling—for
both extremes and operational conditions—over the Central and Western Mediterranean Sea. The paper presents the methodology
and results of an extensive validation activity conducted on a chain of medium-resolution third-generation wave models used
for hindcast purposes. The stringent requirements of state-of-the-art coastal and offshore engineering applications over this
area make the adoption of medium- or high-resolution hindcast wave and wind models almost mandatory because of the complex
coastal geometry, bathymetry, and orography that in turn lead to large variations of the design wave parameters even within
small regions. The chains of nested meteorological and wave models used in this hindcast study belong to the ETA and WaveWatch III
families, respectively. In this study the wind and wave numerical models have been run over the past 20 years, with increasing
resolutions of the wave models from 0.2° up to 0.04°. The results presented herein have 0.1° resolution for both wind and
wave models. The wave data obtained are compared with available measurements from 14 wave buoys in coastal zones in the Central
and Western Mediterranean Sea. 相似文献
922.
Levent Kirkayak Vinicius Aguiar de Souza Katsuyuki Suzuki Hideyuki Ando Hidetoshi Sueoka 《Journal of Marine Science and Technology》2011,16(3):354-365
It is estimated that around 10,000 containers are lost during maritime transportation every year, representing an economic
loss to the liner industry. Regulations and norms used to calculate values to secure them to the ship’s deck account for static
loads only, neglecting more realistic conditions. This paper describes an approach to simulate a two-tier scaled model of
a 20-ft ISO freight container and its linking connectors, denominated twist locks, subject to a dynamical load induced by
its base. To analyze this problem two methods were employed: a shaking table test and finite-element analysis. Results of
this study indicate that the numerical model built to simulate two-tier container stack dynamics is a promising tool for further
studies. Moreover, the model is able to predict conditions close to real situations faced by container stacks while stored
on deck. 相似文献
923.
Jinggao Li I. Kim S. Lee S. Han C. Lee S. Cheon W. Lee K. An G. Cho J. Hwang D. Mun 《Journal of Marine Science and Technology》2011,16(1):76-83
In the shipbuilding industry, different computer-aided design (CAD) systems are used for different design domains, structure, and outfitting. We need to exchange data among different CAD systems such as Tribon, AutoCAD, Intergraph or PDMS to complete the whole design and production process. There are two approaches to data exchange. One is direct translation; the other is indirect translation, which is based on a neutral format. If we use a neutral format, the data specification is open to the public and the design model can be used by other CAD systems, including next-generation CAD systems. In this paper, we propose an indirect method that uses ISO 10303 (STandard for the Exchange of Product model data) AP227 and ISO 15926 to define neutral formats. A separate ShapeDB is constructed to manage the geometry information, referenced to the catalogue data defined by ISO 15926. An experimental implementation for data exchange between Tribon and PDMS is described. 相似文献
924.
The experimental procedure to predict the full-scale performance of the CRP-POD propulsion system is studied. In the CRP-POD
system, the RPM ratio of the two propellers is not mechanically fixed, in contrast with conventional CRP systems. Therefore
the existing procedure for conventional CRP systems is not appropriate for evaluating the performance of each propeller. In
this paper, the characteristics of the CRP-POD system, designed for a 9,600 TEU class container carrier, are studied experimentally.
Based on this study, a procedure for propulsive performance prediction for CRP-POD propulsion ships is suggested. 相似文献
925.
Tomohiro Takai Manivannan Kandasamy Frederick Stern 《Journal of Marine Science and Technology》2011,16(4):434-447
The accurate prediction of waterjet propulsion using computational fluid dynamics (CFD) is of interest for performance analyses
of existing waterjet designs as well as for improvement and design optimization of new waterjet propulsion systems for high-speed
marine vehicles. The present work is performed for three main purposes: (1) to investigate the capability of a URANS flow
solver, CFDSHIP-IOWA, for the accurate simulation of waterjet propelled ships, including waterjet–hull interactions; (2) to
carry out detailed verification and validation (V&V) analysis; and (3) to identify optimization opportunities for intake duct
shape design. A concentrated effort is applied to V&V work and performance analysis of waterjet propelled simulations which
form the focus of this paper. The joint high speed sealift design (JHSS), which is a design concept for very large high-speed
ships operating at transit speeds of at least 36 knots using four axial flow waterjets, is selected as the initial geometry
for the current work and subsequent optimization study. For self-propelled simulations, the ship accelerates until the resistance
equals the prescribed thrust and added tow force, and converges to the self propulsion point (SPP). Quantitative V&V studies
are performed on both barehull and waterjet appended designs, with corresponding experimental fluid dynamics (EFD) data from
1/34 scale model testing. Uncertainty assessments are performed on iterative convergence and grid size. As a result, the total
resistance coefficient for the barehull case and SPP for the waterjet propelled case are validated at the average uncertainty
intervals of 7.0 and 1.1%D, respectively. Predictions of CFD computations capture the general trend of resistance over the speed range of 18–42 knots,
and show reasonable agreement with EFD with average errors of 1.8 and 8.0%D for the barehull and waterjet cases, respectively. Furthermore, results show that URANS is able to accurately predict the
major propulsion related features such as volume flow rate, inlet wake fraction, and net jet thrust with an accuracy of ~9%D. The flow feature details inside the duct and interference of the exit jets are qualitatively well-predicted as well. It
is found that there are significant losses in inlet efficiency over the speed range; hence, one objective for subsequent optimization
studies could be maximizing the inlet efficiency. Overall, the V&V work indicates that the present approach is an efficient
tool for predicting the performance of waterjet propelled JHSS ships and paves the way for future optimization work. The main
objective of the optimization will be reduction of powering requirements by increasing the inlet efficiency through modification
of intake duct shape. 相似文献
926.
Post license advanced driver training programs in the US and early programs in Europe have often failed to accomplish their stated objectives because, it is suspected, that drivers gain self perceived driving skills that exceed their true skills—leading to increased post training crashes. The consensus from the evaluation of countless advanced driver training programs is that these programs are a detriment to safety, especially for novice, young, male drivers.Some European countries including Sweden, Finland, Austria, Luxembourg, and Norway, have continued to refine these programs, with an entirely new training philosophy emerging around 1990. These ‘post-renewal’ programs have shown considerable promise, despite various data quality and availability concerns. These programs share in common a focus on teaching drivers about self assessment and anticipation of risk, as opposed to teaching drivers how to master driving at the limits of tire adhesion. The programs focus on factors such as self actualization and driving discipline, rather than low level mastery of skills. Drivers are meant to depart these renewed programs with a more realistic assessment of their driving abilities. These renewed programs require considerable specialized and costly infrastructure including dedicated driver training facilities with driving modules engineered specifically for advanced driver training and highly structured curriculums. They are conspicuously missing from both the US road safety toolbox and academic literature. Given the considerable road safety concerns associated with US novice male drivers in particular, these programs warrant further attention.This paper reviews the predominant features and empirical evidence surrounding post licensing advanced driver training programs focused on novice drivers. A clear articulation of differences between the renewed and current US advanced driver training programs is provided. While the individual quantitative evaluations range from marginally to significantly effective in reducing novice driver crash risk, they have been criticized for evaluation deficiencies ranging from small sample sizes to confounding variables to lack of exposure metrics. Collectively, however, the programs sited in the paper suggest at least a marginally positive effect that needs to be validated with further studies. If additional well controlled studies can validate these programs, a pilot program in the US should be considered. 相似文献
927.
928.
Standard economic policy evaluation allows the realization of projects if the aggregated economic benefit outweighs their
costs. The use of one single aggregated welfare measure for evaluating and ranking projects has often been criticized for
many reasons. A major issue is that differentiated effects on individuals or subgroups of the population are not taken into
consideration. This leads to the need for transport planning tools that provide additional information for politicians and
decision makers. The microscopic multi-agent simulation approach presented in this paper is capable of helping to design better
solutions in such situations. In particular, it is shown that the inclusion of individual income in utility calculations allows
a better understanding of problems linked to public acceptance. First, individual income-contingent utility functions are
estimated based on survey data in order to describe human mobility behavior. Subsequently, using the MATSim framework, the
implementation is tested in a test scenario. Furthermore, and going beyond Franklin (2006), it is shown that the approach works in a large-scale real world example. Based on a hypothetical speed increase of public
transit, effects on the welfare distribution of the population are discussed. It is shown that the identification of winners
and losers seems to be quite robust. However, results indicate that a conversion or aggregation of individual utility changes
for welfare analysis is highly dependent on the functional form of the utility functions as well as on the choice of the aggregation
procedure. 相似文献
929.
930.
Estimating a model of dynamic activity generation based on one-day observations: Method and results 总被引:1,自引:0,他引:1
Theo A. Arentze Dick Ettema Harry J.P. Timmermans 《Transportation Research Part B: Methodological》2011,45(2):447-460
In this paper we develop and explore an approach to estimate dynamic models of activity generation on one-day travel-diary data. Dynamic models predict multi-day activity patterns of individuals taking into account dynamic needs as well as day-varying preferences and time-budgets. We formulate an ordered-logit model of dynamic activity-agenda-formation decisions and show how one-day observation probabilities can be derived from the model as a function of the model’s parameters and, with that, how parameters can be estimated using standard loglikelihood estimation. A scale parameter cannot be identified because information on within-person variability is lacking in one-day data. An application of the method to data from a national travel survey illustrates the method. A test on simulated data indicates that, given a pre-set scale, the parameters can be identified and that estimates are robust for a source of heterogeneity not captured in the model. This result indicates that dynamic activity-based models of the kind considered here can be estimated from data that are less costly to collect and that support the large sample sizes typically required for travel-demand modeling. We conclude therefore that the proposed approach opens up a way to develop large-scale dynamic activity-based models of travel demand. 相似文献