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351.
Y. Kim S. Choi J. Lee W. Yoo J. Sohn 《International Journal of Automotive Technology》2011,12(4):521-527
In this study, a large bus is tested to measure its dynamic response by the single-lane change test and the rapid stop test.
A full car model is established by ADAMS/Car for computer simulation. For multibody modeling of a large bus, user-defined
templates are used in the simulation. Simulation results of the single-lane change test and the rapid braking test are compared
to the results of the physical experiments, in which several sensors are installed to measure the vehicle’s responses. The
results obtained from the simulation show good agreement with the tests’ results. A dynamic model for the MR(magnetic-rheological)
damper is also developed by employing the Magic Formula model, which is widely used in the nonlinear modeling of a tire. Bump
simulation of a full car with the MR damper is carried out to verify the performance of the MR damper. The comparison of the
simulation results obtained with the MR damper model to the results obtained with the traditional passive damper model showed
improved response of the vehicle with the MR damper. 相似文献
352.
This paper discusses the final investigation into the effect of fuel stratification on flame propagation. In previous works,
the characteristics under the no port-generated swirl condition and the low-swirl condition were considered. For this purpose,
the initial flame development and propagation were visualized under different axially stratified states in a modified optical
single-cylinder SI engine. The images were captured by an intensified CCD camera through the quartz window mounted in the
piston. Stratification was controlled by the combination of the port swirl ratio and injection timing. These were averaged
and processed to characterize the flame propagation. The flame stability was estimated by the weighted average of flame area
and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance and
through the mean absolute deviation of the propagation direction. The results show that the LML is expanded remarkably under
the high-swirl cases up to the highest relative AFRs of 1.71 and 1.75 between 140 and 160CA. In addition, similar to the low-swirl
condition, the flame-flow interaction determines the direction of flame propagation, and the governing roles of the two factors
vary according to the swirl level; the flow is more important at the higher swirl conditions, and the flame is more important
at the lower swirl condition. Finally, fast and stable flame propagation can be achieved under the preferably stratified condition,
which is induced by the suitable combination of the high swirl and injection timing. 相似文献
353.
354.
Runyu Wang 《WMU Journal of Maritime Affairs》2011,10(2):143-165
Since the 1980s, the precautionary principle has been drawing more and more international attention. This became particularly
clear during the series of Conferences on the Protection of the North Sea, which addressed marine environmental protection,
and initiated the application of the principle into maritime affairs. Although a unified concept of the precautionary principle
is lacking, some typical formulations have been concluded in regional treaties and international documents, and components
of the principle can be summarised (Part I and Part II). The precautionary principle has been adopted by international documents
involving different fields of law of the sea, and been addressed by international courts and tribunals (Part III). While the
precautionary principle is still not part of customary international law (Part IV), its increasing level of worldwide acceptance
suggests that it will become a customary international law in the future. 相似文献
355.
Terry L. Friesz Taeil Kim Changhyun Kwon Matthew A. Rigdon 《Transportation Research Part B: Methodological》2011,45(1):176-207
In this paper we present a dual-time-scale formulation of dynamic user equilibrium (DUE) with demand evolution. Our formulation belongs to the problem class that Pang and Stewart (2008) refer to as differential variational inequalities. It combines the within-day time scale for which route and departure time choices fluctuate in continuous time with the day-to-day time scale for which demand evolves in discrete time steps. Our formulation is consistent with the often told story that drivers adjust their travel demands at the end of every day based on their congestion experience during one or more previous days. We show that analysis of the within-day assignment model is tremendously simplified by expressing dynamic user equilibrium as a differential variational inequality. We also show there is a class of day-to-day demand growth models that allow the dual-time-scale formulation to be decomposed by time-stepping to yield a sequence of continuous time, single-day, dynamic user equilibrium problems. To solve the single-day DUE problems arising during time-stepping, it is necessary to repeatedly solve a dynamic network loading problem. We observe that the network loading phase of DUE computation generally constitutes a differential algebraic equation (DAE) system, and we show that the DAE system for network loading based on the link delay model (LDM) of Friesz et al. (1993) may be approximated by a system of ordinary differential equations (ODEs). That system of ODEs, as we demonstrate, may be efficiently solved using traditional numerical methods for such problems. To compute an actual dynamic user equilibrium, we introduce a continuous time fixed-point algorithm and prove its convergence for effective path delay operators that allow a limited type of nonmonotone path delay. We show that our DUE algorithm is compatible with network loading based on the LDM and the cell transmission model (CTM) due to Daganzo (1995). We provide a numerical example based on the much studied Sioux Falls network. 相似文献
356.
Chris M.J. Tampère Ruben CorthoutDirk Cattrysse Lambertus H. Immers 《Transportation Research Part B: Methodological》2011,45(1):289-309
Node models for macroscopic simulation have attracted relatively little attention in the literature. Nevertheless, in dynamic network loading (DNL) models for congested road networks, node models are as important as the extensively studied link models. This paper provides an overview of macroscopic node models found in the literature, explaining both their contributions and shortcomings. A formulation defining a generic class of first order macroscopic node models is presented, satisfying a list of requirements necessary to produce node models with realistic, consistent results. Defining a specific node model instance of this class requires the specification of a supply constraint interaction rule and (optionally) node supply constraints. Following this theoretical discussion, specific macroscopic node model instances for unsignalized and signalized intersections are proposed. These models apply an oriented capacity proportional distribution of the available supply over the incoming links of a node. A computationally efficient algorithm to solve the node models exactly is included. 相似文献
357.
This paper documents the efforts to operationalize the conceptual framework of MIcrosimulation Learning-based Approach to
TRansit Assignment (MILATRAS) and its component models of departure time and path choices. It presents a large-scale real-world
application, namely the multi-modal transit network of Toronto which is operated by the Toronto Transit Commission (TTC).
This large-scale network is represented by over 500 branches with more than 10,000 stops. About 332,000 passenger-agents are
modelled to represent the demand for the TTC in the AM peak period. A learning-based departure time and path choice model
was adopted using the concept of mental models for the modelling of the transit assignment problem. The choice model parameters
were calibrated such that the entropy of the simulated route loads was optimized with reference to the observed route loads,
and validated with individual choices. A Parallel Genetic Algorithm engine was used for the parameter calibration process.
The modelled route loads, based on the calibrated parameters, greatly approximate the distribution underlying the observed
loads. 75% of the exact sequence of transfer point choices were correctly predicted by the off-stop/on-stop choice mechanism.
The model predictability of the exact sequence of route transfers was about 60%. In this application, transit passengers were
assumed to plan their transit trip based on their experience with the transportation network; with no prior (or perfect) knowledge
of service performance. 相似文献
358.
This paper establishes a link between an activity-based model for the Greater Toronto Area (GTA), dynamic traffic assignment,
emission modelling, and air quality simulation. This provides agent-based output that allows vehicle emissions to be tracked
back to individuals and households who are producing them. In addition, roadway emissions are dispersed and the resulting
ambient air concentrations are linked with individual time-activity patterns in order to assess population exposure to air
pollution. This framework is applied to evaluate the effects of a range of policy interventions and 2031 scenarios on the
generation of vehicle emissions and greenhouse gases in the GTA. Results show that the predicted increase of approximately
2.6 million people and 1.3 million jobs in the region by 2031 compared to 2001 levels poses a major challenge in achieving
meaningful reductions in GHGs and air pollution. 相似文献
359.
In an attempt to reduce CO2 emissions from motorized transport, the Taiwanese government introduced an idling stop policy for vehicles in early 2007.
This paper seeks to quantify the environmental benefits of the policy based on a stated preference analysis. Motorcyclists
were surveyed at urban intersections in Taiwan, to identify the amount of time they would be willing to turn off their engines
while waiting at traffic lights (the WTO). A contingent valuation framework based on stated preference questions was designed
to determine the WTO. Results obtained from the Spike model showed that the average motorcyclist’s WTO is 82 s. In another
analysis, in which other variables were taken into consideration, such as the possibility that the policy will be enacted
as legislation, the expected WTO increased to 101 s. In both cases, an idling stop policy would have positive environmental
effects, reducing gasoline usage by 1021 L per hour and reducing CO2 emissions by 0.56 metric tons per hour at the intersection studied during peak periods. 相似文献
360.
Yiguang XuanCarlos F. Daganzo Michael J. Cassidy 《Transportation Research Part B: Methodological》2011,45(5):769-781
A separate turn phase is often used on the approach leg to an intersections with heavy left turns. This wastes capacity on the approach because some of its lanes cannot discharge during its green phases. The paper shows that the problem can be eliminated by reorganizing traffic on all the lanes upstream of an intersection using a mid-block pre-signal. If drivers behave deterministically, the capacity that can be achieved is the same as if there were no left turns. However, if the reorganization is too drastic, it may be counterintuitive to drivers. This can be remedied by reorganizing traffic on just some of the available lanes. It is shown that such partial reorganization still increases capacity significantly, even if drivers behave randomly and only one lane is reorganized. The paper shows how to optimize the design of a pre-signal system for a generic intersection. It also identifies both, the potential benefits of the proposed system for a broad class of intersections, and the domain of application where the benefits are most significant. 相似文献