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881.
The rapid and continuing changes in travel and mobility needs in India over the last decade necessitates the development and
use of dynamic models for travel demand forecasting rather than cross-sectional models. In this context, this paper investigates
mode choice dynamics among workers in Chennai city, India over a period of five years (1999–2004). Dynamics in mode choice
is captured at four levels: exogenous variable change, state-dependence, changes in users’ sensitivity to attributes, and
unobserved error terms. The results show that the dynamic models provide a substantial improvement (of over 500 log-likelihood
points and ρ2 increases from 44% to 68%) over the cross-sectional model. The performance was compared using two illustrative policy scenarios
with important methodological and practical implications. The results indicate that cross-sectional models tend to provide
inflated estimates of potential improvement measures. Improving the Level of Service (LOS) alone will not produce the anticipated
benefits to transit agencies, as it fails to overcome the persistent inertia captured in the state-dependence factors. The
results and models have important applications in the context of growing motorization and congestion management in developing
countries.
相似文献
P. BhargaviEmail: |
882.
Stated choice experiments have proven to be a powerful tool in eliciting preferences across a broad range of choice settings.
This paper outlines the elements of a group-based experiment designed for interdependent urban freight stakeholders, along
with the procedure to administer the questionnaire sequentially. The focus is on the design of a computer-assisted personal
survey instrument and the value in disseminating the details of a new approach to design and collect stated choice data for
interacting agents. The paper also discusses how to specify a reference alternative, and then how to recruit appropriate real-market
or representative decision-making group members to participate in a subsequent phase of the survey, which incorporates the
reference alternative and contextual information from an initial phase. The empirical strategy, set out in some detail, provides
a new framework within which to understand more fully the role that specific attributes, such as variable user charges, influencing
freight distribution chains might play, and who in the supply chain is affected by specific attributes in terms of willingness
to pay for the gains in distribution efficiency.
相似文献
Andrew CollinsEmail: |
883.
884.
Proshanto K. Mukherjee 《WMU Journal of Maritime Affairs》2007,6(1):21-36
This article provides a synoptic overview of the concept of general average which is one of the saving acts in maritime law.
Its principles were entrenched in the Roman law which acknowledged its origins being rooted in the Sea Law of Rhodes. Its
evolution as customary law through the medieval maritime codes of the Mediterranean region is also traced in the article.
The reader is then brought into the modern era of the international regime of general average through the advent of the York-Antwerp
Rules. The basic principles of general average loss, including expenditures and sacrifices, and general average contributions
are introduced through references to a number of leading cases. The current status of this ancient law and practice and debates
over its future are briefly addressed in conclusion. 相似文献
885.
K. Kim J. Kim K. S. Huh K. Yi D. Cho 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2006,44(5):369-386
This paper presents a new multi-vehicle simulator for platoon simulation. The main new feature of the developed simulator is a network structure for the real-time simulation of multiple vehicles, each with a detailed powertrain and engine model. It has a small initial delay, which is determined by the number of connected PCs, but the actual simulation is performed and displayed in real-time after this initial and one-time delay. Several longitudinal controllers, including a PID controller with gain scheduling, an adaptive controller, and a fuzzy controller, are also implemented in the simulator. Various system parameters can be modified interactively in the simulator screen, which is very useful for simulating a platoon of heterogeneous vehicles, in which vehicles with different dynamics and different longitudinal controllers may be involved. The simulator provides an excellent tool to develop vehicle longitudinal controllers and to study platoon behaviors. The developed simulator is also effective in testing the effects of nonlinearities neglected in the controller design phase, such as actuator delays and gear shifting schedule. 相似文献
886.
Using MATLAB/Simulink, we constructed a comprehensive simulation model for the fuel cell hybrid vehicle (FCHV) power train
in parallel with a power control strategy that uses a logic threshold approach implemented with a hybrid control unit (HCU).
The simulation implements power flow and power distribution under different vehicle operating modes using the accelerator
and decelerator pedal positions deduced from the driving schedule as primary inputs. The HCU control strategy also incorporates
regenerative braking and recharging for recovery of battery capacity. Using the D-optimality method for selection of the optimal
experiment values, three control threshold variables for the HCU are selected to maximize the hydrogen fuel economy under
certain driving cycles. The proposed method provides the optimal configuration of the FCHV model, which has the capability
of achieving the requested drive power while also meeting the vehicle driving schedule and recovery needs of the state of
charge (SOC) battery, with lower fuel consumption levels. 相似文献
887.
A. Momenimovahed J. S. Olfert M. D. Checkel S. Pathak V. Sood L. Robindro S. K. Singal A. K. Jain M. O. Garg 《International Journal of Automotive Technology》2013,14(1):1-11
Nanoparticle and gas-phase emission factors are presented for a liquefied petroleum gas (LPG) passenger vehicle and are compared to gasoline operation. A bi-fuel LPG-gasoline vehicle certified for use on either fuel was used as the test vehicle so that a direct comparison of the emissions could be made based on fuel choice. These values were considered along with previous studies to determine the relative change in particulate emissions due to fuel choice over a wide range of vehicles and operating conditions. The vehicle examined in this study was tested on a chassis dynamometer for both steadystate and transient conditions. Transient test cycles included the US FTP72 driving cycle, Japanese driving cycle and modified Indian driving cycle while steady-state tests were done at vehicle speeds ranging from 10–90 km/hr in various transmission gears. Exhaust particle size distributions were measured in real-time using a differential mobility spectrometer (DMS50), and particle number and particle mass emission factors were calculated. For both fuels, the majority of the particles ranged from 5 to 160 nm in terms of particle diameter, with typically more than 85% of the particles in the nucleation mode (between 5–50 nm). In most cases, the vehicle produced a greater fraction of larger (accumulation mode) particles when fuelled on LPG. Using the data in the literature as well as the data in the current study, gasoline fuel produces 4.6 times more particles in terms of number and 2.1 times more particles in terms of mass. 相似文献
888.
A first order mass balance of six different trace metals (Mn, Fe, Pb, Zn, Cu, Ni) was presented for a 1-year period for the different compartments of the Adriatic Sea: compartment 1 (northern Adriatic Sea), compartment 2 (central Adriatic Sea and surface layer of the southern Adriatic Sea) and compartment 3 (deep water of the southern Adriatic Sea). The Adriatic Sea appeared to be a source of dissolved Cu, Mn and Fe for the Mediterranean Sea through the Strait of Otranto whereas for dissolved Zn and Pb the Adriatic Sea appeared to be a net sink. For dissolved Ni, inputs and outputs through the Strait of Otranto balanced each other. The residence times of all metals in compartment 1 were significantly shorter than that of water indicating significant removal. In compartments 2 and 3, residence times of Mn and Fe were relatively short suggesting removal from the water column whereas for the other metals their residence times were similar to that of water. Calculations of turnover times of metals with respect to different processes showed that in compartments 1 and 2, sedimentation was the main process that affected the content of the reservoirs whereas in compartment 3, the water flux exchanges played an important role for Zn, Cu and Ni.Most of the metals clearly undergo a very dynamic cycle of sedimentation/remobilization particularly in the Northern Adriatic Sea. In the northern Adriatic Sea, most of the Mn and Fe in deposited sediment were remobilized. This was related to diagenetic processes involving the utilisation and solubilisation of Mn and Fe oxides, which occur in the surface of the sediment in the northern Adriatic Sea. In the central Adriatic Sea, remobilization of Mn and Fe was less than in the northern Adriatic Sea, suggesting that diagenesis processes appear deeper in the sediment. Advective transport of sediment was a major source of metals for the deep basin. As much as 80% of the sediments in the South Adriatic Pit might be advected from the shelf. Remobilization fluxes in the South Adriatic Pit were significantly less than in the Northern and Central Adriatic Sea reflecting hemi-pelagic sediments. 相似文献
889.
Options-Based Multi-Objective Evaluation of Product Platforms 总被引:1,自引:0,他引:1
JAVIER P. GONZALEZ-ZUGASTI KEVIN N. OTTO CLIFFORD A. WHITCOMB 《Naval Engineers Journal》2007,119(3):89-106
A platform is the set of elements and interfaces that are common to a family of products. Design teams must choose among feasible platform concepts upon which a product family could be based, often involving new technologies. Multiple performance objectives need to be considered. A standard approach is to convert the performance outcomes into financial figures, which can then be weighed against the required investments. However, it is not always possible to transform performance outcomes (benefits) into monetary terms, such as in defense or highly technical projects. A multi-objective form of real-options-based platform selection is developed. Systems are compared based on multiple technical and economic goals, incorporating uncertainty by representing the unknown factors during the subsequent development process with probability distributions. The range of uncertain outcomes is integrated into single expected measures of effectiveness, which can then be applied to select the most appropriate platform and set of support product variants. An application to the design of platform-based families of naval high-speed ships is shown. 相似文献
890.
Akhil K. Vaish Shijie Chen Neeraja S. Sathe Ralph E. Folsom Promod Chandhok Kuo Guo 《Transportation》2010,37(6):825-848
The National Household Transportation Survey (NHTS) was designed at the national level, and for most states it does not have
a large enough sample to produce reliable estimates, especially for subdomains (e.g., age groups) within a state. Using the
2001 NHTS, we produced small area estimates (SAEs) of the percentage of persons among four age groups (17 or younger, 18–39,
40–54, and 55 or older) having high daily person-miles of travel (more than 87.5 miles a day, which is the 90th percentile for daily person-miles traveled) and associated prediction intervals
for all 50 states and the District of Columbia. The survey weighted hierarchical Bayes (Folsom et al., Proc of the Sect on
Surv Res Methods of the Am Stat Assoc 371–375, 1999) small area estimation (SAE) methodology was used to produce state-level SAEs. This paper describes the methodology and shows
that SAE can be an effective technique for producing reliable state-level estimates from large, national surveys like the
NHTS. In particular, the prediction interval relative widths for SAEs were, on average, 31–48% narrower than the corresponding
design-based confidence interval widths, whereas for small states the reduction was around 47–63%. 相似文献