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931.
The characteristics of auto-ignition and micro-explosion behaviors of one-dimensional arrays of fuel droplets suspended in
a chamber with high surrounding temperature were investigated experimentally with various droplet spacings, numbers of droplet
and surrounding temperatures. The fuels used were pure n-decane and emulsified n-decane with varied water contents ranging
from 10 to 30%. All experiments were performed under atmospheric conditions with high surrounding temperatures. An imaging
technique using a high-speed camera was adopted to measure ignition delay, flame lifetime, and flame spread speed. The camera
was also used to observe micro-explosion behaviors. As the droplet array spacing increased, the ignition delay also increased,
regardless of water content. However, the lifetime of the droplet array decreased as the droplet spacing increased. The micro-explosion
starting time remained unchanged regardless of the number of the droplets or the droplet spacing; however, it tended to be
delayed slightly as the water percentage and droplet spacing increased. 相似文献
932.
This work presents an experiment on the relationships between subjective and objective evaluations of vehicle handling. Ten
cars were examined objectively in several open-loop driving dynamics manoeuvres and subjectively by test persons in typical
traffic situations. Results are extracted from a stationary test (the Slowly Increasing Steer Test), and a dynamical test
(the Frequency Response Test). The subjective measurements are obtained from drivers on a rural road course via a questionnaire,
which was developed to separately investigate the quantity level perception, the so-called “Niveau”, and the more qualitative
“Liking”. These subjective “measurements” are embedded into a two-channel definition of “Steering Comfort” as a genus for
“Steering Discomfort” and “Character”. The article concentrates on developing a statistical method for the consideration of
correlations amongst the subjective/objective data. In doing so, the variance in example subjective Niveau ratings can be
significantly explained by several objective quantities. Indicators for co-domains of validated discomfort characteristics
and hints for endeavouring character Liking ranges are detected. 相似文献
933.
This paper establishes the simulation model of a city bus on the basis of the EQ6110 bus prototype and its experimental data.
According to the actual urban driving cycle, the fuel economy and the traction performance of the EQ6110 city bus have been
simulated, and factors such as the driving cycle, the loss of power to engine accessories, the gear-shifting strategy, the
fuel shut-off strategy of the engine, etc., which influence on the bus’s fuel economy, are also quantitatively analyzed. Some
conclusions are drawn as follows: (1) driving cycles have a great influence on the fuel economy of a city bus; (2) under the
typical urban driving cycle of the public bus in China, the engine fuel shut-off strategy can save about 1 to 1.5 percent
of the fuel consumption; and (3) the optimized gear-shifting rules can save 6.7 percent of the fuel consumption. Experimental
results verify that the fuel economy for the EQ6110 public bus is improved by 7.2 pecent over the actual Wuhan urban driving
cycle of the current public bus in China. 相似文献
934.
Low viscosity engine oil can improve a vehicle’s fuel economy by decreasing the friction between the engine components. Frictional
torque varies with the velocity change due to different viscosity characteristics of SAE grade 5W-20, 5W-30 and 5W-40 engine
oils. The viscosity for each of these grades was measured to outline the effect low viscosity engine oils have on engine friction,
which may lead to improved fuel economy. Engine oil seal frictional torque increases with the shaft rotational speed for all
three engine oil grades. A decrease in engine oil seal frictional torque was confirmed when low viscosity engine oil was used.
Also, the leak-free performance of the engine oil with the seal satisfied the life limit durability test criteria. Thus, low
viscosity engine oil may be used to improve fuel economy by decreasing the frictional loss of the engine oil seal while having
no negative impact on performance due to leak-free functioning. 相似文献
935.
This paper presents a steering control method for lane-following in a vehicle using an image sensor. With each image frame
acquired from the sensor, the steering control method determines target position and direction, and constructs a travel path
from the current position to the target position either as an Arc-path or S-path. The steering angle is calculated from the
travel path thus generated, and the vehicle follows the travel path via motor-control. The method was tested using a vehicle
dubbed as KAV (Korea Autonomous Vehicle) along an expressway (Seoul Inner Beltway) trajectory with a variety of radii (50
m ∼ 300 m) while traveling at a speed of 60 km/h to 80 km/h. Compared with an experienced human driver, the method showed
little much difference in performance in terms of lane-center deviation. The proposed method is currently employed for high
speed autonomous driving as well as for stop and go traffic. 相似文献
936.
The recursive component mode synthesis method (RCMS) has been implemented for the finite element analysis model of an automobile
structure as an efficient free vibration analysis tool. The RCMS method is intended to obtain a better performance relative
to the block Lanczos method, which is a traditional method in the industry of obtaining eigenvalues, while obtaining the acceptable
accuracy. A numerical example of the automobile finite element model demonstrates the outstanding performance of RCMS compared
to the block Lanczos method. 相似文献
937.
Intelligent transportation systems have been promoted as a means to improve both the efficiency and safety of the road network. The effectiveness of advanced technologies in improving road safety has been an area of research which has thus far yielded mixed results. In order to ensure that advanced technologies deliver on their intended outcomes, more research has to be devoted to understanding road users' perceptions and reactions to these systems. This study examines drivers' perceptions of the use of dynamic message signs and their self‐reported reactions to the messages displayed. In general, drivers support the use of highway electronic boards for traffic incident reports and weather information which have an impact on traffic delays and level of service. They also think that it is a good idea to display road safety messages and to remind drivers to drive safely and be courteous on the roads. Moreover, most drivers reported that they do read and think about the messages displayed and react positively to some of the road safety messages. 相似文献
938.
Deconstructing development density: Quality, quantity and price effects on household non-work travel
Smart growth and transit-oriented development proponents advocate increasing the density of new land development and infill redevelopment. This is partly in order to reduce auto use, by reducing distances between trip origins and destinations, creating a more enjoyable walking environment, slowing down road travel, and increasing the market for transit. But research investigating how development density influences household travel has typically been inadequate to account for this complex set of hypotheses: it has used theoretically unjustified measures, has not accounted for spatial scale very well, and has not investigated potentially important combinations of measures. Using data from a survey of metropolitan households in California, measures of development density corresponding to the main hypotheses about how density affects travel—activity density affecting distance traveled, network load density affecting the speed of auto travel, and built form density affecting the quality of walking—are tested as independent variables in models of auto trip speed and individual non-work travel. Residential network load density is highly negatively correlated with the speed of driving, and is also highly correlated with non-work travel, both singly and in combination with other measures. Activity density and built form density are not as significantly related, on their own. These results suggest that denser development will not influence travel very much unless road level-of-service standards and parking requirements are reduced or eliminated. 相似文献
939.
Dimitrios A. Tsamboulas Anastasios Nikoleris 《Transportation Research Part A: Policy and Practice》2008,42(10):1274-1282
There are cases when passengers are willing to pay a premium to reduce the travel time, in particular when the trip has to be made. This paper aims to provide insight into factors that determine passengers’ willingness to pay to reduce travel time for their ground access to an airport. A methodology is developed that comprises two steps: the identification of the passengers with zero willingness to pay and from the rest the estimation of the additional price they are willing to pay to reduce their travel time. For the first step a Probit model was formulated and for the second a linear regression model. To this purpose, data has been collected employing stated preference from passengers at the Athens International Airport. It has been found that a high percentage of passengers have zero willingness to pay, and of the remaining ones those using public transport have a significant willingness to pay to reduce access travel time. The methodology and the models are structured in such a way that their transferability to any airport environment is possible, thus providing a useful tool for decisions relating to airport ground access measures. 相似文献
940.
A link-node complementarity model and solution algorithm for dynamic user equilibria with exact flow propagations 总被引:2,自引:0,他引:2
Xuegang Ban Henry X. Liu Michael C. Ferris Bin Ran 《Transportation Research Part B: Methodological》2008,42(9):823-842
In this paper, we propose a link-node complementarity model for the basic deterministic dynamic user equilibrium (DUE) problem with single-user-class and fixed demands. The model complements link-path formulations that have been widely studied for dynamic user equilibria. Under various dynamic network constraints, especially the exact flow propagation constraints, we show that the continuous-time dynamic user equilibrium problem can be formulated as an infinite dimensional mixed complementarity model. The continuous-time model can be further discretized as a finite dimensional non-linear complementarity problem (NCP). The proposed discrete-time model captures the exact flow propagation constraints that were usually approximated in previous studies. By associating link inflow at the beginning of a time interval to travel times at the end of the interval, the resulting discrete-time model is predictive rather than reactive. The solution existence and compactness condition for the proposed model is established under mild assumptions. The model is solved by an iterative algorithm with a relaxed NCP solved at each iteration. Numerical examples are provided to illustrate the proposed model and solution approach. We particularly show why predictive DUE is preferable to reactive DUE from an algorithmic perspective. 相似文献