1,771 research outputs found
Design of Video Retrieval System Using MPEG-7 Descriptors
AbstractThe paper proposes a content-based video retrieval system designed using MPEG-7 (multimedia content description interface), which provides a standard description for a video. The system consists of three parts: shot boundary detection, feature extraction and similarity measurement. In shot boundary detection, cut and dissolve can be detected using the histogram difference and skipping image difference, respectively. In feature extraction part, two MPEG-7 visual descriptors, Color Structure Descriptor (CSD) and Edge Histogram Descriptor (EHD), are used to represent the color feature and edge feature of the key frames. Lastly, the similarity between key frames is calculated using dynamic-weighted feature similarity calculation. The proposed system is tested on three kinds of videos. Promising results are obtained in terms of both effectiveness and efficiency
AdvDiff: Generating Unrestricted Adversarial Examples using Diffusion Models
Unrestricted adversarial attacks present a serious threat to deep learning
models and adversarial defense techniques. They pose severe security problems
for deep learning applications because they can effectively bypass defense
mechanisms. However, previous attack methods often utilize Generative
Adversarial Networks (GANs), which are not theoretically provable and thus
generate unrealistic examples by incorporating adversarial objectives,
especially for large-scale datasets like ImageNet. In this paper, we propose a
new method, called AdvDiff, to generate unrestricted adversarial examples with
diffusion models. We design two novel adversarial guidance techniques to
conduct adversarial sampling in the reverse generation process of diffusion
models. These two techniques are effective and stable to generate high-quality,
realistic adversarial examples by integrating gradients of the target
classifier interpretably. Experimental results on MNIST and ImageNet datasets
demonstrate that AdvDiff is effective to generate unrestricted adversarial
examples, which outperforms GAN-based methods in terms of attack performance
and generation quality
Model Aerodynamic Tests with a Wire-driven Parallel Suspension System in Low-speed Wind Tunnel
AbstractOwing to the advantages of wire-driven parallel manipulator, a new wire-driven parallel suspension system for airplane model in low-speed wind tunnel is constructed, and the methods to measure and calculate the aerodynamic parameters of the airplane model are studied. In detail, a static model of the wire-driven parallel suspension is analyzed, a mathematical model for describing the aerodynamic loads exerted on the scale model is constructed and a calculation method for obtaining the aerodynamic parameters of the model by measuring the tension of wires is presented. Moreover, the measurement system for wire tension and its corresponding data acquisition system are designed and built. Thereafter, the wire-driven parallel suspension system is placed in an open return circuit low-speed wind tunnel for wind tunnel tests to acquire data of each wire tension when the airplane model is at different attitudes and different wind speeds. A group of curves about the parameters for aerodynamic load exerted on the airplane model are obtained at different wind speeds after the acquired data are analyzed. The research results validate the feasibility of using a wire-driven parallel manipulator as the suspension system for low-speed wind tunnel tests
Comment on "Optimal convex approximations of quantum states"
In a recent paper, M. F. Sacchi [Phys. Rev. A 96, 042325 (2017)] addressed
the general problem of approximating an unavailable quantum state by the convex
mixing of different available states. For the case of qubit mixed states, we
show that the analytical solutions in some cases are invalid. In this Comment,
we present complete analytical solutions for the optimal convex approximation.
Our solutions can be viewed as correcting and supplementing the results in the
aforementioned paper.Comment: 4 pages, 2 figure
Complete characterization of qubit masking
We study the problem of information masking through nonzero linear operators
that distribute information encoded in single qubits to the correlations
between two qubits. It is shown that a nonzero linear operator cannot mask any
nonzero measure set of qubit states. We prove that the maximal maskable set of
states on the Bloch sphere with respect to any masker is the ones on a
spherical circle. Any states on a spherical circle on the Bloch sphere are
maskable, which also proves the conjecture on maskable qubit states given by
Modi et al. [Phys. Rev. Lett. 120, 230501 (2018)]. we provide explicitly
operational unitary maskers for all maskable sets. As applications, different
protocols for secret sharing are introduced.Comment: 6 pages, 3 figure
Deterministic versus probabilistic quantum information masking
We investigate quantum information masking for arbitrary dimensional quantum
states. We show that mutually orthogonal quantum states can always be served
for deterministic masking of quantum information. We further construct a
probabilistic masking machine for linearly independent states. It is shown that
a set of d dimensional states, , , can be probabilistically masked by a general
unitary-reduction operation if they are linearly independent. The maximal
successful probability of probabilistic masking is analyzed and derived for the
case of two initial states.Comment: 5 pages, 1 figure
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