A digital signature with message recovery is a signature that the message itself (or partial of the message) is not required
to be transmitted together with the signature. It has the advantage of small data size of communication comparing with the
traditional digital signatures. In this paper, combining both advantages of the message recovery signatures and the certificateless
cryptography, we propose the first certificatelss signature scheme with message recovery. The remarkable feature of our scheme
is that it can achieve Girault’s Level-3 security while the conventional certificateless signature scheme only achieves Level-2
security. The security of the scheme is rigorously proved in the random oracle model based on the hardness of the k bilinear Diffie-Hellman inverse (k-BDHI) problem. 相似文献
User selection is necessary for multiuser multiple-input multiple-output (MIMO) downlink systems with block diagonalization
(BD) due to the limited free spatial transmit dimensions. The pure user selection algorithms can be improved by performing
receive antenna selection (RAS) to increase sum rate. In this paper, a joint user and antenna selection algorithm, which performs
user selection for sum rate maximization in the first stage and then performs antenna selection in the second stage, is proposed.
The antenna selection process alternately drops one antenna with the poorest channel quality based on maximum determinant
ranking (MDR) from the users selected during the first stage and activates one antenna with the maximum norm of projected
channel from the remaining users. Simulation results show that the proposed algorithm significantly outperforms the algorithm
only performing user selection as well as the algorithm combining user selection with MDR receive antenna selection in terms
of sum rate. 相似文献
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
The aim of this study was to assess proof of concept and usability of a maritime service website prototype in a full-mission ship bridge simulator through Swedish mariners’ experiences and perceptions. This test was part of the European Commission’s EfficienSea2 project for e-navigation. The prototype was intended as an aid to existing standard systems and methodologies for planning, executing and monitoring voyages. The study began with 5 days of simulator trials focused on today’s standard practices. This served as a baseline to compare to subsequent 4 days of simulator trials testing the prototype. For data collection, observations, video footage, interviews, and eye tracking were used. Data analysis included breaking apart the qualitative data to capture the perceptions of the participants, and a preliminary analysis of eye-tracking data as a complement. The results suggested that the prototype could be more suitable for a route planning stage, that the participants were familiar with similar existing solutions from other manufacturers, and that the contents of the tool would be most beneficial if integrated within the Electronic Chart Display and Information Systems (ECDIS). There is a pressing need for the novel solutions to be user needs-driven, integrated with the existing technologies, and standardized across the domain, and these processes must go hand-in-hand with accounting for all involved stakeholders, procedures, regulations, and training, as this will alter the course of shipping. 相似文献
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
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
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
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 Zq, except the PVSS output. 相似文献
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
The fatigue behaviour of longitudinal stiffeners of oil tankers and container ships, subjected to dynamic loads, is analysed. The following dynamic load components are considered: hull girder vertical wave bending moment, alone and combined with the horizontal wave bending moment, hydrodynamic pressure and inertial forces caused by cargo acceleration.
The spectral method was selected to calculate the fatigue damage, based on S—N curves and Miner's rule. Following this approach, the fatigue damage may be calculated as a function of a stress parameter Ωp, which represents the cumulative effect of wave induced loads in the unit of time and incorporates the combined effects of stress level and its occurring frequency.
Simple formulas for Ωp of oil tankers and container ships are given, obtained from the results of hydrodynamic analyses performed on several ships, in different wave environments.
Several examples show the applicability of the methods to real ship structures. The method, however, still needs to be calibrated because of the simplifying hypotheses introduced in the loading conditions. 相似文献