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111.
Of different model-based methods in vision based human tracking, many state of the art works focus on the stochastic optimization
method to search in a very high dimensional space and try to find the optimal solution according to a proper likelihood function.
Seldom works perform a framework of interactive multiple models (IMM) to track a human for challenging problems, such as uncertainty
of motion styles, imprecise detection of feature points and ambiguity of joint location. This paper presents a two-layer filter
framework based on IMM to track human motion. First, a method of model based points location is proposed to detect key feature
points automatically and the filter in the first layer is performed to estimate the undetected points. Second, multiple models
of motion are learned by the prior motion data with ridge regression and the IMM algorithm is used to estimate the quaternion
vectors of joints rotation. Finally, experiments using real images sequences, simulation videos and 3D voxel data demonstrate
that this human tracking framework is efficient. 相似文献
112.
Radar target signals and chaff cloud jamming signals have different characters by the wavelet transform. The wavelet coefficients
of radar target signals are highly correlated with its near-and-near-scale wavelet coefficients, however the correlativity
between the wavelet coefficients of chaff cloud jamming signals and its near-and-near scale wavelet coefficients is less significant.
Based on the binary-base discrete wavelet transform and the correlation algorithm, the method of target entropy to estimate
standard variance of the jamming signals and each scale is proposed to ensure reasonable threshold, to suppress chaff cloud
signals and finally to reconstruct mixed signals by the improved spatially selective noise filtration (ISSNF) method. The
extensive simulation results show that the proposed method can availably suppress chaff cloud jamming and decontaminate target
echo. 相似文献
113.
Bevan Marten 《WMU Journal of Maritime Affairs》2011,10(1):45-61
This article discusses the enforcement of shipping standards, with a particular focus on Part XII of UNCLOS. Section 6 of
Part XII contains the only comprehensive set of vessel-related enforcement provisions in the Convention, but the Part’s scope
is limited to “the preservation and protection of the marine environment.” Therefore, not all shipping standards fall clearly
within Part XII’s ambit, including those centered on safety, security, and crewing considerations. The enforcement provisions
of Section 6 are favorable to flag states and their vessels, and Section 7 contains a number of safeguards for their benefit,
so it is in the interests of these parties to have coastal state enforcement governed by Part XII. However, the ability of
coastal states to establish and enforce shipping standards that apply within the territorial sea extends to more than just
environmental matters. The result is that different standards give rise to different enforcement powers, depending on the
maritime zone in which a vessel is located, even if those standards arise from the same international agreement. It is suggested
that to remedy these problems, UNCLOS would need to be amended in order to provide a comprehensive enforcement regime for
the enforcement of shipping standards. 相似文献
114.
A novel method toward color image segmentation is proposed based on edge linking and region grouping. Firstly, the edges extracted
by the Canny detector are linked to form regions. Each of the end points of edges is connected by a direct line to the nearest
pixel on another edge segment within a sub-window. A new distance is defined based on the feature that the edge tends to preserve
its original direction. By sampling the lines to the image, the image is over-segmented to labeled regions. Secondly, the
labeled regions are grouped both locally and globally. A decision tree is constructed to decide the importance of properties
that affect the merging procedure. Finally, the result is refined by user’s selection of regions that compose the desired
object. Experiments show that the method can effectively segment the object and is much faster than the state-of-the-art color
image segmentation methods. 相似文献
115.
Democratic group signature (DGS) is a group-oriented primitive with great flexibilities, i.e., no group manager, anonymity,
and traceability. In a DGS scheme with (t, n)-threshold traceability, any subset of not less than t members can jointly reveal the identity of the signer while preserving security even in the presence of an active adversary
can corrupt up to t − 1 group members. This paper proposes an efficient DGS scheme. We use publicly verifiable secret sharing (PVSS) to distribute
the trapdoor via which the real signer is revealed. The computation cost and communication overhead of our DGS signatures
are greatly reduced, compared with the existing work. For example, the size of the resulting signature contains only 2n + 1 elements of Z
q
, except the PVSS output. 相似文献
116.
An analysis of the determinants of children’s weekend physical activity participation 总被引:1,自引:0,他引:1
This paper examines the out-of-home, weekend, time-use patterns of children aged 5–17 years, with a specific emphasis on their
physical activity participation. The impact of several types of factors, including individual and household demographics,
neighborhood demographics, built environment characteristics, and activity day variables, on physical activity participation
is analyzed using a joint nested multiple discrete–continuous extreme value-binary choice model. The sample for analysis is
drawn from the 2000 San Francisco Bay Area Travel Survey. The model developed in the paper can be used to assess the impacts
of changing demographics and built environment characteristics on children’s physical activity levels. 相似文献
117.
The value of form factor k at different drafts is important in predicting full-scale total resistance and speed for different types of ships. In the ITTC community, most organizations predict form factor k using a low-speed model test. However, this method is problematic for ships with bulbous bows and transom. In this article, a Computational Fluid Dynamics (CFD)-based method is introduced to obtain k for different type of ships at different drafts, and a comparison is made between the CFD method and the model test. The results show that the CFD method produces reasonable k values. A grid generating method and turbulence model are briefly discussed in the context of obtaining a consistent k using CFD. 相似文献
118.
It has been a focus of debate for a large time on construction methods for large-span loess tunnel. Reasonable construction
method has much effect on stability of tunnel and construction schedule. Deformation and failure of surrounding rock are quite
complex. Associating with the large-span loess tunnel of Zhengzhou—Xi’an high-speed passenger rail line in China, large scale
model test with geometric proportion 1:20 is applied to study on dynamic mechanical behavior of various construction methods.
They include full-face excavation with support and no support, and benching method with support. It is found that pre-deformation
and stress accumulation take place ahead of working face. The effects of three construction methods are further studied, particularly
in terms of tunnel displacement and stress changes. It is revealed that benching method transfers load to an unexcavated area,
limits horizontal deformation, reduces stress concentration effectively, lengthens the distance between location of peak for
stress concentration and working face, and consequently increases stability. The model test results not only supply theoretical
foundation for determination of reasonable construction method, but also can act as reference for similar tunnel and underground
engineering construction. 相似文献
119.
In this paper, a new algorithm which integrates the powerful firefly algorithm(FA) and the ant colony optimization(ACO) has been used in tracking control of ship steering for optimization of fractional-order proportional-integral-derivative(FOPID) controller gains. Particle swarm optimization(PSO) algorithm is also used to optimize FOPID controllers, and their performances are compared. It is found that FA optimized FOPID controller gives better performance than others. Sensitivity analysis has been carried out to see the robustness of optimum FOPID gains obtained at nominal conditions to wide changes in system parameters, and the optimum FOPID gains need not be reset for wide changes in system parameters. 相似文献
120.
山地城市如重庆,具有纵坡大、降雨多的特点,其全透水沥青路面结构型式与平原地区有所不同。为研究荷载作用下山地城市全透水沥青路面结构力学响应情况,借助有限元方法建立全透水沥青路面结构的三维模型,通过改变基层+蓄水层组合厚度、蓄水层模量及土基模量3个因素,分析弯沉、蓄水层层底拉应力和土基顶面压应变的响应情况。结果表明土基模量对弯沉有显著影响,基层+蓄水层组合厚度对蓄水层层底拉应力和土基顶面压应变有显著影响,因此,可通过增加基层+蓄水层组合厚度和增大土基模量的方式来提高全透水沥青路面的强度。 相似文献