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801.
The effects of a moving gate on dam break flow experiments are numerically considered in this paper. The dam break flow process is modelled by a sudden gate release. A Constrained Interpolation Profile (CIP)-based model is employed to solve the Navier-Stokes equations with the free surface boundary condition to deal with the water-air-gate interactions. In addition, the VOF-type THINC/SW method is used to capture the free surface. The movable gate is simulated by an immersed boundary, and a gate motion formula is proposed from existing experimental data and applied in the dam break flow computations. The difference between the water profile and pressure domain with/without gate motion is examined. The dam breaks with different gate motions are discussed as well. The numerical results show that the proposed gate motion formula correlates well with the numerical modelling, and the gate motion has a significant influence in the water collapse process and cannot be neglected in the study of dam break. 相似文献
802.
G. C. Pereira M. M. F. Oliveira L. P. Andrade R. P Espíndola K. G. van Hecke N. F. F. Ebecken 《Journal of Marine Science and Technology》2016,21(4):651-662
Coastal zones are among the most productive areas in the world, offering a wide variety of valuable habitats and ecosystems services. Despite the low population density in the Brazilian coastal zone, their distribution is quite concentrated near some coastal cities and state capitals. This concentration places enormous pressure on coastal resources. Therefore, the main objective of this paper is to present an overview on the current status of SiMoCo (Sistema de Monitoramento Costeiro, or Coastal Monitoring System in English) project as a possible early warning system that can be integrated to the Brazilian Coastal Management Information System. This prototype platform provides a real-time access to the composition, organization and simulation of planktonic communities. First, our results demonstrate such a system detecting a target dinoflagellate; second, we apply structural and functional indexes to compare and characterize the ecological networks from two different coastal areas. Conclusions are made about SiMoCo’s feasibility and its possible contribution to the decision-making process within integrated coastal zone management (ICZM) strategies. 相似文献
803.
Anil Kumar Dash Praveen Perumpulissery Chandran Mohammed Kareem Khan Vishwanath Nagarajan Om Prakash Sha 《Journal of Marine Science and Technology》2016,21(4):689-708
In this paper, a mathematical model is developed for the maneuvering motion of a naval ship and bifurcations of its equilibrium are identified in roll-coupled motion. The subject ship is a high-speed surface combatant with twin-propeller twin-rudder system. Captive model tests are conducted for the ship using planar motion mechanism. Maneuvering coefficients are calculated by polynomial curve fitting of the test data. Uncertainty distribution in the coefficients is assumed same as that of the curve fitting errors. Uncertainty in the model coefficients is propagated to full-scale simulation results by the stochastic response surface method (SRSM). This method is computationally efficient as compared to standard Monte Carlo simulation technique. The SRSM uses polynomial chaos expansion of orthogonal to fit any probability distribution. Bifurcation analysis of the mathematical model is performed by varying the vertical center of gravity as the bifurcation parameter. Hopf bifurcation is identified. It is found that the bifurcations occur due to the coupling of roll motion with sway, yaw motion and rudder angle. In the presence of wind, roll angle response in bifurcation diagram is discussed. 相似文献
804.
In this paper, shock sterilization using the motions of microbubbles induced by underwater shock waves is verified experimentally. A bio-experiment is carried out using marine Vibrio sp.. Underwater shock waves are produced by electric discharge in a semi-ellipsoidal discharge reflector. The shock waves are focused to increase the pressure that the generated microbubbles are exposed to. The microbubbles are generated independently. The microbubble generator can produce microbubbles of around 50 μm diameter by means of Kelvin–Helmholz instability and Venturi effect. Propagation behavior of shock waves and generation process of microbubbles are captured by high-speed camera. The experimental results show that the supply of microbubbles increases the potential of shock sterilization. In addition, it is found that shock waves without microbubbles also have the capacity of sterilization, and this means that cavitation bubbles generated behind converging shock waves contribute to inactivating marine bacteria. 相似文献
805.
This paper presents a novel optimization-based approach for dynamic positioning (DP) of a fully actuated underwater vehicle equipped with an onboard ultrashort baseline transceiver to provide relative position information of two earth-fixed transponders near the vehicle. The DP system error is defined by the transponders’ positions compared to the desired values, which occur at the vehicle’s target pose (position and orientation). The proposed DP strategy is composed of two loops in a hierarchical structure. In the kinematic loop, the nonlinear model predictive control is used to generate the desired velocity by optimizing a cost function of the predictive trajectories under the constraints of velocity and transponder bearings over a limited time horizon. In the dynamic loop, the neural network model reference adaptive control with pseudo control hedging is utilized to ensure the asymptotical convergence of velocity tracking errors in the presence of uncertainties associated with unknown model parameters, currents and thruster dynamics. The effectiveness of the proposed control scheme is illustrated by comprehensive simulations. 相似文献
806.
Antti Talvitie 《Transportation》2008,35(3):375-393
The paper unpacks the planning process into its component parts: model, process, technique, and goals—the “good thing”. The
paper advances the concept that planning, policy-making, and organizational restructuring can be analyzed under the same framework.
Each of the four components is described and reductionist examples are presented to clarify the intention and to illustrate
the technique that the transport analyst teams employ in their work. The examples cover both successes and failures. They
point toward the enormous scientific task ahead for planning to become meaningful and relevant to the problems of today. Finally,
in the frame of the willingness to pay, the paper puts forward a case for an institutional framework for a financially autonomous road administration. Similarly
organized, administered, and managed entities are relevant also for other transport modes.
Antti Talvitie is a Professor (part time) at the Helsinki University of Technology. He has private practice as consultant and as psychoanalyst in the Washington DC area. Previously, Mr. Talvitie worked in the World Bank; was GM of Viatek Consulting Engineers in Espoo Finland; served as Director of Highway Construction and Maintenance in the Finnish Road Administration; and was Professor in the US, including Chairmanship of the Department Civil Engineering at the University of Buffalo. Mr. Talvitie holds Ph.D. in Civil Engineering from Northwestern University, Evanston, IL, and Certificate in Psychoanalysis from the Boston Graduate School of Psychoanalysis. 相似文献
Antti TalvitieEmail: |
Antti Talvitie is a Professor (part time) at the Helsinki University of Technology. He has private practice as consultant and as psychoanalyst in the Washington DC area. Previously, Mr. Talvitie worked in the World Bank; was GM of Viatek Consulting Engineers in Espoo Finland; served as Director of Highway Construction and Maintenance in the Finnish Road Administration; and was Professor in the US, including Chairmanship of the Department Civil Engineering at the University of Buffalo. Mr. Talvitie holds Ph.D. in Civil Engineering from Northwestern University, Evanston, IL, and Certificate in Psychoanalysis from the Boston Graduate School of Psychoanalysis. 相似文献
807.
This study explores the relationships between adoption and consideration of three travel-related strategy bundles (travel
maintaining/increasing, travel reducing, and major location/lifestyle change), linking them to a variety of explanatory variables.
The data for this study are the responses to a fourteen-page survey returned by nearly 1,300 commuting workers living in three
distinct San Francisco Bay area neighborhoods in May 1998. We first identified patterns of adoption and consideration among
the bundles, using pairwise correlation tests. The test results indicate that those who have adopted coping strategies continue
to seek for improvements across the spectrum of generalized cost, but perhaps most often repeating the consideration of a
previously-adopted bundle. Furthermore, we developed a multivariate probit model for individuals’ simultaneous consideration
of the three bundles. It is found that in addition to the previous adoption of the bundles, qualitative and quantitative Mobility-related
variables, Travel Attitudes, Personality, Lifestyle, Travel Liking, and Sociodemographics significantly affect individual
consideration of the strategy bundles. Overall, the results of this study give policy makers and planners insight into understanding
the dynamic nature of individuals’ responses to travel-related strategies, as well as differences between the responses to
congestion that are assumed by policy makers and those that are actually adopted by individuals.
Sangho Choo is a Research Associate at The Korea Transport Institute. His research interests include travel demand modeling, travel survey methods with GPS, and travel behavior modeling. Patricia L. Mokhtarian is a professor of Civil and Environmental Engineering, chair of the interdisciplinary Transportation Technology and Policy MS/PhD program, and Associate Director for Education of the Institute of Transportation Studies at the University of California, Davis. She has been modeling travel behavior and attitudes for more than 30 years. 相似文献
Patricia L. Mokhtarian (Corresponding author)Email: |
Sangho Choo is a Research Associate at The Korea Transport Institute. His research interests include travel demand modeling, travel survey methods with GPS, and travel behavior modeling. Patricia L. Mokhtarian is a professor of Civil and Environmental Engineering, chair of the interdisciplinary Transportation Technology and Policy MS/PhD program, and Associate Director for Education of the Institute of Transportation Studies at the University of California, Davis. She has been modeling travel behavior and attitudes for more than 30 years. 相似文献
808.
This paper presents a comprehensive econometric modelling framework for daily activity program generation. It is for day-specific
activity program generations of a week-long time span. Activity types considered are 15 generic categories of non-skeletal
and flexible activities. Under the daily time budget and non-negativity of participation rate constraints, the models predict
optimal sets of frequencies of the activities under consideration (given the average duration of each activity type). The
daily time budget considers at-home basic needs and night sleep activities together as a composite activity. The concept of
composite activity ensures the dynamics and continuity of time allocation and activity/travel behaviour by encapsulating altogether
the activity types that are not of our direct interest in travel demand modelling. Workers’ total working hours (skeletal
activity and not a part of the non-skeletal activity time budget) are considered as a variable in the models to accommodate
the scheduling effects inside the generation model of non-skeletal activities. Incorporation of previous day’s total executed
activities as variables introduces day-to-day dynamics into the activity program generation models. The possibility of zero
frequency of any specific activity under consideration is ensured by the Kuhn-Tucker optimality conditions used for formulating
the model structure. Models use the concept of random utility maximization approach to derive activity program set. Estimations
of the empirical models are done using the 2002–2003 CHASE survey data set collected in Toronto.
相似文献
Eric J. MillerEmail: |
809.
The majority of comparisons between state transportation systems do not control for characteristics that may vary greatly
between states (e.g., vehicle miles traveled). A shortcoming of such analyses is that a state’s individual characteristics
can be highly influential in determining how transportation policy is set and funds are spent. The purpose of this paper is
to extend previous efforts to create groups of similar peer states by developing a new methodological framework that incorporates
demographic, temporal, and locational variability into the peer group delineations. We collected historical data for 42 variables
on transportation infrastructure, population, economy, growth, topography and weather. To examine trends before and after
the passage of ISTEA we gathered data over two time periods: 1985 through 1990 and 1995 through 2000. Using principal components
analysis (PCA) we reduced variables into seven components, and then statistically clustered states into peer groups for each
time period based on the components and the remaining variables. We identified a range of cluster solutions and demonstrate
how cluster statistics help to describe the contextual basis behind the peer grouping. The results of this study are to provide
government agencies, researchers and the public with a systematic methodological framework for identifying peer states that
reflect similar attributes contributing to the development and maintenance of state transportation systems.
相似文献
Debbie A. Niemeier (Corresponding author)Email: |
810.
This paper analyzes transportation mode choice for short home-based trips using a 1999 activity survey from the Puget Sound
region of Washington State, U.S.A. Short trips are defined as those within the 95th percentile walking distance in the data,
here 1.40 miles (2.25 km). The mean walking distance was 0.4 miles (0.6 km). The mode distribution was automobile (75%), walk
(23%), bicycle (1%), and bus (1%). Walk and bicycle are found less likely as the individual’s age increases. People are more
likely to drive if they can or are accustomed to. People in multi-person families are less likely to walk or use bus, especially
families with children. An environment that attracts people’s interest and provides activity opportunities encourages people
to walk on short trips. Influencing people’s choice of transport mode on short trips should be an important part of efforts
encouraging the use of non-automobile alternatives.
相似文献
Gudmundur F. UlfarssonEmail: |