摘要 :
With the rapid growth of air transportation, airport gates have become scarce and expensive resources. When aircraft parking demand exceeds gate capacity, there will be more ungated flights to which additional delays would be adde...
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With the rapid growth of air transportation, airport gates have become scarce and expensive resources. When aircraft parking demand exceeds gate capacity, there will be more ungated flights to which additional delays would be added. So it is important to estimate actual or delay-related airport gate capacity so as to make wise decision in flights scheduling or airport planning. This paper proposes a method to estimate delay-related airport gate capacity by establishing a metric for gate service level, referred to as “aftereffect delay”. With the analysis of the propagation and possible dissipation process of the aftereffect delay time, this paper develops formulae to quantify aftereffect delay. These formulae are used to develop a capacity assessment model to maximize the number of aircraft that can use a gate, given a limit on aftereffect delay. Moreover a case study developed from data from Beijing International Airport is given. The result is both theoretical and practical valuable.
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摘要 :
With the rapid growth of air transportation, airport gates have become scarce and
expensive resources. When aircraft parking demand exceeds gate capacity, there will be more
ungated flights to which additional delays would be ad...
展开
With the rapid growth of air transportation, airport gates have become scarce and
expensive resources. When aircraft parking demand exceeds gate capacity, there will be more
ungated flights to which additional delays would be added. So it is important to estimate
actual or delay-related airport gate capacity so as to make wise decision in flights scheduling
or airport planning. This paper proposes a method to estimate delay-related airport gate
capacity by establishing a metric for gate service level, referred to as “aftereffect delay”. With
the analysis of the propagation and possible dissipation process of the aftereffect delay time,
this paper develops formulae to quantify aftereffect delay. These formulae are used to develop
a capacity assessment model to maximize the number of aircraft that can use a gate, given a
limit on aftereffect delay. Moreover a case study developed from data from Beijing
International Airport is given. The result is both theoretical and practical valuable.
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摘要 :
In this paper, a helical gear pair is taken as the research object. Considering the backlash and considering the tooth meshing error caused by gear manufacturing, installation and wear, the distributed meshing nonlinear dynamics m...
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In this paper, a helical gear pair is taken as the research object. Considering the backlash and considering the tooth meshing error caused by gear manufacturing, installation and wear, the distributed meshing nonlinear dynamics model of the helical gear pair is established. The dynamic model includes the lateral vibration DOFs, torsion DOFs and rolling DOFs of the gear pair. Based on the helical gear dynamics model, in order to make the tooth surface load distribution uniform, the drum shape modification method of helical gear pair is proposed. Through the research of dynamic drum shape modification, the optimal modification parameters are obtained, so that the tooth surface dynamic load distribution is uniform, and the tooth surface load distribution center of gravity is close to the tooth surface center position, which alleviates the rollover phenomenon.
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Surface characteristics of asphalt pavement have significant impacts on road noise. However, the quantitative relationship between them is not completely clarified. The objective of this paper is to quantify the effect of asphalt ...
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Surface characteristics of asphalt pavement have significant impacts on road noise. However, the quantitative relationship between them is not completely clarified. The objective of this paper is to quantify the effect of asphalt pavement surface characteristics on road noise. Firstly, based on acoustics theory, we determined the pavement roughness (IRI) and texture depth (TD) as the factors affecting road noise. Secondly, we conducted a series of field tests, collecting the road noise inside and outside the automobile and measuring the IRI and TD. Finally, we statistically obtained the relationships among interior vehicle noise and exterior vehicle noise, the IRI and ID of the pavement. The result shows that road noise, neither inside nor outside the vehicle, is significant to the TD. Interior vehicle noise is linearly related to the IRI, which rises with the increase of IRI. In addition, exterior vehicle noise can be considered to have a quadric relationship with (I)n(IRI · TD).
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摘要 :
Surface characteristics of asphalt pavement have significant impacts on road noise. However, the quantitative relationship between them is not completely clarified. The objective of this paper is to quantify the effect of asphalt ...
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Surface characteristics of asphalt pavement have significant impacts on road noise. However, the quantitative relationship between them is not completely clarified. The objective of this paper is to quantify the effect of asphalt pavement surface characteristics on road noise. Firstly, based on acoustics theory, we determined the pavement roughness (IRI) and texture depth (TD) as the factors affecting road noise. Secondly, we conducted a series of field tests, collecting the road noise inside and outside the automobile and measuring the IRI and TD. Finally, we statistically obtained the relationships among interior vehicle noise and exterior vehicle noise, the IRI and ID of the pavement. The result shows that road noise, neither inside nor outside the vehicle, is significant to the TD. Interior vehicle noise is linearly related to the IRI, which rises with the increase of IRI. In addition, exterior vehicle noise can be considered to have a quadric relationship with (I)n(IRI · TD).
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摘要 :
With shrinking pavement maintenance budgets and increasing maintenance needs,
highway agencies are moving toward pavement preventive maintenance (PPM). However,
due to the lack of analytical systems and sufficient data, many decis...
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With shrinking pavement maintenance budgets and increasing maintenance needs,
highway agencies are moving toward pavement preventive maintenance (PPM). However,
due to the lack of analytical systems and sufficient data, many decisions made by
highway agencies today often lean heavily on judgments and/or empirical experiences.
This paper presents a study of scheduling preventive maintenance (PM) on the project
level for different pavement families based on conditions in Beijing, China. An
optimization method is proposed to find the best PM strategy based on life-cycle cost
benefit analysis. Pavement condition prediction models and treatment effectiveness
models are developed and calibrated based on data collected from field investigations and
a pavement management system (PMS) of historical database in Beijing. Based on a
recent case study, it is found that micro-surfacing and a 2.5 cm HMA overlay are the two
most frequently employed PM treatments and that they are mainly applied when
pavements are still in good condition. Maintenance cycles are mostly in the range of 3 to
5 years. A sensitivity analysis indicates that whether user cost is considered has a
significant impact on the optimal PM strategy. However, the optimal strategy is not
sensitive to variations in maintenance and user costs. The method developed in this paper
can be applied to schedule PM in pavement management practices, and can also guide
future research.
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摘要 :
With shrinking pavement maintenance budgets and increasing maintenance needs,
highway agencies are moving toward pavement preventive maintenance (PPM). However,
due to the lack of analytical systems and sufficient data, many dec...
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With shrinking pavement maintenance budgets and increasing maintenance needs,
highway agencies are moving toward pavement preventive maintenance (PPM). However,
due to the lack of analytical systems and sufficient data, many decisions made by
highway agencies today often lean heavily on judgments and/or empirical experiences.
This paper presents a study of scheduling preventive maintenance (PM) on the project
level for different pavement families based on conditions in Beijing, China. An
optimization method is proposed to find the best PM strategy based on life-cycle cost
benefit analysis. Pavement condition prediction models and treatment effectiveness
models are developed and calibrated based on data collected from field investigations and
a pavement management system (PMS) of historical database in Beijing. Based on a
recent case study, it is found that micro-surfacing and a 2.5 cm HMA overlay are the two
most frequently employed PM treatments and that they are mainly applied when
pavements are still in good condition. Maintenance cycles are mostly in the range of 3 to
5 years. A sensitivity analysis indicates that whether user cost is considered has a
significant impact on the optimal PM strategy. However, the optimal strategy is not
sensitive to variations in maintenance and user costs. The method developed in this paper
can be applied to schedule PM in pavement management practices, and can also guide
future research.
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摘要 :
This paper presents an equilibrium-compensation-based sliding mode control scheme for achieving accurate steering angle tracking in a single-track two-wheeled robot subject to mismatched disturbances. To mitigate the impact of the...
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This paper presents an equilibrium-compensation-based sliding mode control scheme for achieving accurate steering angle tracking in a single-track two-wheeled robot subject to mismatched disturbances. To mitigate the impact of these disturbances, we propose a novel module called the equilibrium compensator. Additionally, to deal with the non-minimum phase characteristic of the system, the output redefinition method is employed to transform the system into a minimum phase system. A nominal sliding mode controller is then designed for the external subsystem, and an extended state observer is utilized to estimate the system state and disturbance. Altogether, accurate steering tracking is achieved by applying the nominal sliding mode controller to the compensated state. The effectiveness of the proposed control scheme is validated through experiments conducted on a robot prototype.
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The extraction of affine invariant features plays an important role in many computer vision tasks. Region-based methods can achieve high accuracy with expensive computation. Whereas, contour-based techniques need less computation ...
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The extraction of affine invariant features plays an important role in many computer vision tasks. Region-based methods can achieve high accuracy with expensive computation. Whereas, contour-based techniques need less computation but their performance is strongly dependant on the boundary extraction. To combine region-based and contour-based methods together for data reduction, central radial transform (CRT) is proposed in this paper. Any object is converted into a closed curve. Then, Fourier descriptor is conducted on the obtained closed curve. The derived features are invariant to affine transform, and are called quasi Fourier descriptors (QFDs). In compare with some related methods, CRT has eliminated shearing in affine transform. Consequently, parameterization and extra transforms have been avoided. Experimental results show affine invariance of the proposed QFD. In comparison with some region-based methods, the proposed QFD is more robust to additive noise.
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Human visual system relies on both binocular stereo cues and monocular focusness cues to gain effective 3D perception. In computer vision, the two problems are traditionally solved in separate tracks. In this paper, we present a u...
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Human visual system relies on both binocular stereo cues and monocular focusness cues to gain effective 3D perception. In computer vision, the two problems are traditionally solved in separate tracks. In this paper, we present a unified learning-based technique that simultaneously uses both types of cues for depth inference. Specifically, we use a pair of focal stacks as input to emulate human perception. We first construct a comprehensive focal stack training dataset synthesized by depth-guided light field rendering. We then construct three individual networks: a Focus-Net to extract depth from a single focal stack, a EDoF-Net to obtain the extended depth of field (EDoF) image from the focal stack, and a Stereo-Net to conduct stereo matching. We show how to integrate them into a unified BDfF-Net to obtain high-quality depth maps. Comprehensive experiments show that our approach outperforms the state-of-the-art in both accuracy and speed and effectively emulates human vision systems.
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