Chaff cloud jamming suppression based on wavelet transform

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.     

The enforcement of shipping standards under UNCLOS

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.     

Color image segmentation by edge linking and region grouping

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.     

Efficient democratic group signatures with threshold traceability

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.     

填料性能对预应力锚拉式桩板墙影响的数值分析

预应力锚拉式桩板墙是一种得到广泛应用的新型支挡结构,本文通过建立耦合分析数值模型对桩板墙的受力特征进行了有限元分析。通过分析了解填料的力学参数(变形模量、摩擦角、粘聚力)对桩板墙位移、弯矩、土压力以及锚固端接触应力和自由段轴力的变化。揭示填料力学性能对预应力锚拉式桩板墙的影响,为类似工程的设计提供参考。     

An analysis of the determinants of children’s weekend physical activity participation

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.     

Seabed scene simulation and its realization in extending Vega

Realistic simulation of underwater scene is always difficult because of the special and complex vision effects in underwater space. Seabed is an important part of underwater environment. This paper describes the methods for seabed scene simulation based on OpenGL. It includes construction of fluetuant terrain based on the random sinusoidal algorithm, simulation of seabed flicker effect by means of circular texture mapping and generation of turbidity effect by using fog techniques. For the application based on the leading high level 3D development environment-Vega, underwater scene simulation is still a difficulty since there is no module for it. Based on the analysis of Vega software and the research on seabed scene simulation methods, a Vega extending module named “Underwater Space” was created through developing module class and extending lynx interface. The module class was designed through developing DLL written in C . The Lynx was extended through developing keyword configure file, GUI configure file and lynx plug-in DLL. The problem that Vega can‘t simulate underwater space, is elementarily resolved. The results show that this module is efficient, easy using, and the seabed scene images am vivid.     

Identity-based threshold decryption on access structure

For the applied limitation of the existing threshold decryption schemes based on the (t, n) structure, an identity-based threshold decryption scheme which can be applied on the access structure is proposed through designing a special distribution algorithm of the private key shares. The generation and distribution of private key shares, the encryption, the decryption and the combination are introduced in detail. The validity and security of the scheme are proved and analyzed. Comparisons with the existing schemes show that the proposed scheme is more flexible.