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911.
J. Kim 《International Journal of Automotive Technology》2010,11(3):331-337
A methodology is presented for estimating vehicle handling dynamics, which are important to control system design and safety
measures. The methodology, which is based on an extended Kalman filter (EKF), makes it possible to estimate lateral vehicle
states and tire forces on the basis of the results obtained from sinusoidal steering stroke tests that are widely used in
the evaluation of vehicle and tire handling performances. This paper investigates the effect of vehicle-road system models
on the estimation of lateral vehicle dynamics in the EKF. Various vehicle-road system models are considered in this study:
vehicle models (2-DOF, 3-DOF, 4-DOF), tire models (linear, non-linear) and relaxation lengths. Handling tests are performed
with a vehicle equipped with sensors that are widely used by vehicle and tire manufacturers for handling maneuvers. The test
data are then used in the estimation of the EKF and identification of lateral tire model coefficients. The accuracy of the
identified values is validated by comparing the RMS error between experimentally measured states and regenerated states simulated
using the identified coefficients. The results show that the relaxation length of the tire model has a notable impact on the
estimation of lateral vehicle dynamics. 相似文献
912.
The marine shipping industry faces challenges to reduce engine exhaust emissions and greenhouse gases (GHGs) from ships, and in particular, carbon dioxide. International regulatory bodies such as the International Maritime Organization and National Environmental Agencies of many countries have issued rules and regulations to drastically reduce GHG and emissions emanating from marine sources. This study investigates the possibility of using natural gas and hydrogen as alternative fuels to diesel oil for marine gas turbines and uses a mathematical model to assess the effect of these alternative fuels on gas turbine thermodynamic performance. Results show that since natural gas is categorized as a hydrocarbon fuel, the thermodynamic performance of the gas turbine cycle using natural gas was close to that of the diesel case. However, the gas turbine thermal efficiency was found to be slightly lower for natural gas and hydrogen fuels compared to diesel fuel. 相似文献
913.
Supply chain finance (SCF) is concerned because of its service efficiency for the real economy. Beside the bank, some enterprises have provided the SCF service. E-commerce platform firms develop small and micro loan system in China. A given small enterprise can apply for a loan through its platform. Based on the latest SCF developments and the relevant literature, this study focuses on the coordination mechanism of SCF. We construct a game theory model including supplier, retailer and financial service provider to analyze the decision making of them. We find the optimal solution to the supplier, retailer and financial service provider. 相似文献
914.
Kwang Hyo Jung Kyung Chun Kim Sang Youl Yoon Seong Hun Kwon Ho Hwan Chun Moon Chan Kim 《Journal of Marine Science and Technology》2006,11(4):270-278
Stereoscopic particle image velocimetry measurements were made in a wind tunnel using a prototype waterjet model. The main
wind tunnel provided the vehicle velocity and a secondary wind tunnel was set up as the waterjet propulsion model. Pressure
distributions along the ramp and lip sides inside the duct were measured for three jet velocity to vehicle velocity ratios.
Three-dimensional velocity fields were obtained at the intake entrance and the nozzle exit of the waterjet system. The flow
into the duct was faster in the lip region than on the ramp side. Because of the variation in intake geometry from a rectangular
to a circular section and because of the sudden curvature change on the lip side, a pair of counter-rotating vortices was
observed in the mean velocity field at the nozzle exit. In addition, the turbulent kinetic energy correlated with the vortex
pair was stronger on the lip side than in other areas. Dominant large-scale structures were extracted by using a snapshot
proper orthogonal decomposition analysis. It was found that most of the turbulent kinetic energy was attributed to at least
three vortices near the nozzle exit. This detailed three-dimensional velocity field will be useful for the verification of
CFD simulations applied to the waterjet system. 相似文献
915.
Christian Bueger 《WMU Journal of Maritime Affairs》2012,11(1):15-31
That piracy needs to be addressed onshore is a widely shared assumption. While the majority of counter-piracy measures focus
on the sea, a number of onshore counter-piracy initiatives have been launched. We can observe the seeds of an alternative
land-based policy approach. One set of land-based programs aims at strengthening the legal and security state apparatus to
better deter and punish pirates. The other set of programs aims at addressing local populations on regional, clan or village
levels. Such projects aim at increasing surveillance, sensitizing populations for the consequences of piracy, and providing
rehabilitation or alternative livelihood opportunities. In this article, I review the latter type of projects and discuss
the promises and difficulties of addressing piracy by such measures. I discuss five major problems: knowledge problems, implementation
problems, counterintuitive consequences, tensions towards other parts of counter-piracy strategy, and the securitization of
aid. 相似文献
916.
Costas Lambrou 《WMU Journal of Maritime Affairs》2012,11(1):129-141
A prominent feature of modern day piracy is the ransom that is demanded for the safe release of the ship, cargo and crew.
The recent upsurge of this type of piracy, in areas of the world that are of strategic importance to the shipping industry,
has created many challenges for shipowners, underwriters and the law relating to marine insurance. The aim of this paper is
to examine how the marine insurance market is being affected by the threat of modern day piracy, and seeks to identify the
options that are available for the recovery of a ransom payment by the shipowner. Moreover, this study aims to identify the
legal issues that might prevent a shipowner from recovering a ransom payment under an insurance policy or from the other interests
in a common adventure. The study establishes that a reasonably made ransom payment by the shipowner will amount to an extraordinary
expense that is taken to minimise or avert a loss. Such an act can generally be recovered under the insurance policy as a
sue and labour expense or from other interests in the common adventure as a general average expense. However, illegality,
unseaworthiness and exemption clauses in a marine policy are identified as being legal issues that may prevent a shipowner
from recovering the ransom payment. Some of these problems may be overcome if clauses are carefully drafted to specifically
cater for modern day piracy in a marine insurance policy. Several inconsistencies may also be resolved by transferring the
piracy peril to war risks cover. The shipowner’s duty is to respond to the changing circumstances, by ensuring that his vessel
is sufficiently equipped and the crew is properly trained to resist a hijacking. 相似文献
917.
918.
The collapse of the ventilated cavitation occurring on a cylindrical vehicle during the water-exit is numerically researched. The numerical model employs the finite volume method to solve the multiphase Reynoldsaveraged Navier-Stokes (RNNS) equations and uses the volume of fluid (VOF) method to capture the free surface. A practical water wave environment that the vehicle usually encounters is reproduced in a numerical wave flume, so that the water wave’s effect on the cavity collapse flow regime is investigated. The main feature of the waterexit collapse of a ventilated cavity is studied under the wave-free condition. The result indicates that a collapsing ventilated cavity experiences two stages, in which the pattern of cavity evolution is different. In the early stage, the cavity undergoes a rapid shrinkage as a closed body. In the late stage, the cavity releases gas from the front due to the increase of the cavity pressure. The water wave effect is investigated at three typical wave phases: the wave crest, the wave trough and the wave node. Results show that when the vehicle is launched under the wave node, the cavity collapse regime remains fairly axisymmetric and is similar to the wave-free case. However, when the vehicle is launched under the wave crest and trough, the cavity evolution presents highly three-dimensional (3D) features. The results of predicted cavity size, pressure distributions and hydrodynamic forces at different wave phases show that the wave effect is relatively weak at the wave node but becomes apparent at the wave crest and trough. 相似文献
919.
This paper presents theoretical analysis of unconventional forging process of hollowed shaft from Ti-6Al-4V alloy in a three-slide
forging press. This method in comparison with other metal forming methods allows for obtaining of hollowed products. The designed
process is verified theoretically by means of numerical simulations based on finite element method with assumption of 3D state
of strain. The following factors are considered in the analysis: material flow kinematics, strain distribution, temperature
distribution and force of process. On the basis of results, it is stated that the application of designed technology allows
for obtaining of a product of assumed quality. A comparison is made between material consumption in analyzed process and material
consumption in typical metal forming methods, also in used at present technology of shaft manufacturing by machining only.
It is stated that the application of forging in the three-slide forging press allows for a considerable decrease of manufacturing
costs due to material savings and decrease of labor consumption of operations at finishing. 相似文献
920.
In this paper, a 3D time domain technique is adopted to calculate the coupled hydrodynamic interaction between two bodies without flare in waves. For verifying the code, two same cylinders are selected to calculate coupled hydrodynamic effects by comparison with the results obtained by 3D frequency method which has been proved to be efficient for solving such problems. In order to improve efficiency of calculation, the effect of history time has been discussed, and an improved method is presented. Moreover, the effect of lateral separation distance is also discussed in detail. The technique developed here may serve as a more rigorous tool to analyze the related transient problems of two ships doing underway replenishment in waves. 相似文献