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791.
Coastal lands provide popular outdoor recreation opportunities including beach recreation, fishing, boating, and wildlife viewing. Published studies measuring the demand for access to coastal lands generally have focused on the recreational value of intensively used beaches, which comprise only a portion of the New England coastline. This article examines the recreational demand for coastal access to a local, free‐access site in southern New England. The study uses data obtained from on‐site interviews conducted during the summer of 1995 at Gooseberry Island, Massachusetts. The estimated average value of a visitor‐day during the summer season is $3.06 for weekdays and $4.18 for weekends and holidays. While these values are at the low end of the range of values published in existing literature addressing beach recreation, the aggregate value of recreation benefits derived from public access to undeveloped coastal areas likely are significant. 相似文献
792.
Optimal ship tracking on a navigation route between two ports: a hydrodynamics approach 总被引:1,自引:0,他引:1
J. K. Panigrahi C. P. Padhy D. Sen J. Swain O. Larsen 《Journal of Marine Science and Technology》2012,17(1):59-67
The optimal trajectory from Calcutta port to Mumbai port is charted for a tanker transshipping from the East coast to the
West coast of India during rough weather. Rough weather is simulated over Indian seas using the state-of-the-art WAM numerical
wave model (WAMDI Group in J Phys Oceanogr 18:1775–1810, 1988), assimilating satellite (IRS-P4) wind fields. These simulated wave fields and two-dimensional (2D) directional wave spectrum
are an absolute representation of the irregular seaway. Hence, the same for the monsoon month of August 2000 formed the input
basis for this study. Loss of ship speed due to the wave field (i.e., nonlinear motion of the tanker in waves) and associated
sea-keeping characteristics in the seaway are estimated (Bhattacharya in Dynamics of marine vehicles, Wiley, New York, 1978). The approach adopted in this paper is unique in that it takes into account both voluntary and involuntary speed reductions
of the ship. It helps in ship tracking by the optimum route using inverse velocity as the weight function for the path in
an efficient way. Dijkstra’s algorithm [Numer Math 1(3):269–271, 1959] is applied in an iterative manner for determining the optimum track. The optimum track information has broad scope for use
in modern shipping industry for obtaining safe and least-time routing by avoiding schedule delays with economic fuel consumption. 相似文献
793.
Kenneth F.D. Hughey Geoffrey N. Kerr Ross Cullen 《Transportation Research Part D: Transport and Environment》2011,16(8):575-578
Based on a public survey of registered voters, we explore four options for internalising the social and environmental costs of road transport. The options were presented together with generalised factual information about their benefits and costs. Respondents are highly supportive of fuel use efficiency standards and exhaust gas quality standards, with lesser support for proposed initiatives of road user charges and speed reduction. Demographic analysis of responses enables identification of those who might favour or oppose particular options. In this case women are identified as being strongly supportive of the speed reduction option. 相似文献
794.
795.
J. Hwang D. Lee K. Huh H. Na H. Kang 《International Journal of Automotive Technology》2011,12(1):119-124
The longitudinal and lateral vehicle control techniques have been widely used in several active driver assistance systems.
The adaptive cruise control, lane keeping assistant control, vehicle platooning and stop-and-go control are typical examples
of the most important applications. In this study, a novel path planning method is proposed considering the driving environment
such as road shape, ego vehicle and surrounding vehicles’ movement. The relative distance and velocity between the ego vehicle
and surrounding vehicles are identified with respect to the predicted lane shape in front of the ego vehicle. Based on the
identified information, the road shape and surrounding vehicles are mapped into the intensity image and the desired vector
for the ego vehicle’s movement is determined by the maximum intensity density tracing method. The desired vehicle path is
followed by the acceleration/deceleration control and the steering assist control, respectively. In order to evaluate the
performance of the proposed system, simulations are conducted and compared with ACC systems. 相似文献
796.
J. Xu Y. B. Li X. Chen D. Y. Ge B. H. Liu M. Y. Zhu T. H. Park 《International Journal of Automotive Technology》2011,12(5):687-695
During accident, the interlayer of windshield plays an important role in the crash safety of automotive and protection of
pedestrian or passenger. The understanding of its energy absorption capability is of fundamental importance. Conventional
interlayer material of automotive windshield is made by Polyvinyl butyral (PVB). Recently, a new candidate of high-performance
nanoporous energy absorption system (NEAS) has been suggested as a candidate for crashworthiness. For the model problem of
pedestrian head impact with windshield, we compare the energy absorption capabilities of PVB and NEAS interlayers, in terms
of the contact force, acceleration, velocity, head injury criteria, and energy absorption ratio, among which results obtained
from PVB interlayers are validated by literature references. The impact speed is obtained from virtual test field in PC-CRASH,
and the impact simulations are carried out using explicit finite element simulations. Both the accident speed and interlayer
thickness are varied to explore their effects. The explicit relationships established among the energy absorption capabilities,
impact speed, and interlayer material/thickness, are useful for safety evaluation as well as automotive design. It is shown
that the NEAS interlayer may absorb more energy than PVB interlayer and it may be a competitive candidate for windshield interlayer. 相似文献
797.
W. K. Park S. D. Mun H. K. Lee G. E. Yang 《International Journal of Automotive Technology》2011,12(5):705-712
Compressed air can be used as an energy source for brake systems in medium-heavy and heavy-duty commercial vehicles. The moisture
in compressed air, which is due to high temperature and humidity, can be eliminated by using an air dryer. In this paper,
drying performance data for a cartridge were obtained and used to develop a drying performance program, to predict the moisture
and relative humidity in the air tanks of vehicles. The on-load time, off-load time, air flow, duty cycle, humidity and dew
point temperature were calculated according to air consumption. The validity of the program was verified, and it was shown
to be able to predict humidity changes in the air tank. The air tank capacity was increased from 100 to 130 to reduce the
duty cycle. Therefore, the regeneration rate decreased from 18% to 15%, but the dew point depression temperature (ΔT) remained
above 30°C. The duty cycle decreased from 50% to 43%, and the total operation time and power consumption of the air compressor
were reduced. In conclusion, fuel savings were obtained by changing the parameters to optimize the system. 相似文献
798.
799.
There have now been over three decades of experience with rate-making freedom for all modes of intercity freight transport in the United States. Most evidence suggests that regulatory change has been beneficial for the rail industry and its users. Despite evidence of positive impacts of regulatory reform of U.S. freight transport, there is limited evidence related to long-term pricing trends by commodity in the deregulated era. Moreover, U.S. shipper groups have called for increased regulation of U.S. railroads, citing increased rates and profits, and monopoly pricing to “captive shippers.” This study estimates U.S. railroad revenue-marginal cost ratios for seven different commodities between 1986 and 2008. Interestingly, we find no significant increase in revenue-cost margins for commodities thought to be “most captive” (coal and chemicals), while finding large increases for some commodities thought to be “non-captive.” These results may provide insight into the impacts of regulatory reform in other countries, where there are similar concerns of equitable pricing and financial viability. They suggest that a move toward a more market-based pricing system can enhance railroad viability without harming those with fewer transport options. 相似文献
800.
J. H. Jeong D. W. Jung O. T. Lim Y. D. Pyo Y. J. Lee 《International Journal of Automotive Technology》2014,15(6):861-869
This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (?4°CA aTDC, ?2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (?4°CA aTDC, ?2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy. 相似文献