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In satellite remote sensing, the hyperspectral sensor acquires high-spectral-resolution and low-spatial-resolution hyperspectral images (HSIs). Conversely, the multispectral sensor acquires low-spectral-resolution and high-spatial-resolution multispectral images (MSIs). Thus, HSI and MSI fusion is required to promote both spatial and spectral resolutions. Currently, most algorithms are based on the assumption that the HSI and MSI are perfectly aligned. However, this is hardly achievable in real scenarios when the two sensors acquire images from different viewpoints. In this article, we propose a fusion algorithm that consists of two stages, i.e., image registration and image fusion. For image registration, we introduce the normalized edge difference (NED) for image similarity measure considering the different resolutions of the original images. For image fusion, we incorporate the interpolation process in the spatial degradation model to compensate for the interpolation error. Experimental results show that our algorithm performs better than the state of the arts for unaligned image fusion. [ABSTRACT FROM AUTHOR]

Hashing-based approximate nearest neighbors search has attracted broad research interest, due to its low computational cost and fast retrieval speed. The hashing technique maps the data points into binary codes and, meanwhile, preserves the similarity in the original space. Generally, we need to solve a discrete optimization problem to learn the binary codes and hash functions, which is NP-hard. In the literature, most hashing methods choose to solve a relaxed problem by discarding the discrete constraints. However, such a relaxation scheme will cause large quantization error, which makes the learned binary codes less effective. In this paper, we present an equivalent continuous formulation of the discrete hashing problem. Specifically, we show that the discrete hashing problem can be transformed into a continuous optimization problem without any relaxations, while the transformed continuous optimization problem has the same optimal solutions and the same optimal value as the original discrete hashing problem. After transformation, the continuous optimization methods can be applied. We devise the algorithms based on the idea of DC (difference of convex functions) programming to solve this problem. The proposed continuous hashing scheme can be easily applied to the existing hashing models, including both supervised and unsupervised hashing. We evaluate the proposed method on several benchmarks and the results show the superiority of the proposed method compared with the state-of-the-art hashing methods. [ABSTRACT FROM AUTHOR]

Out-of-focus blur is a common image degradation phenomenon that occurs in case of lens defocusing. The out-of-focus blur kernel is usually modeled as a Gaussian function or a uniform disk in previous work. In this paper, we propose that it can be more accurately depicted using the generalized Gaussian (GG) function. This is motivated by the theoretical analysis of the out-of-focus blur and the practical observation of real blur kernels. We show that as the out-of-focus blur kernels are of specific shapes, the GG function can be further simplified to a single-parameter model. We estimate the parameter of the GG blur kernel from image patches containing step edges, and obtain the clear image by non-blind image deblurring. Experimental results validate that the proposed GG blur kernel estimation algorithm outperforms the state-of-the-art ones deploying either parametric (disk and Gaussian) or nonparametric kernels, and consequently benefits the image deblurring process. [ABSTRACT FROM AUTHOR]

In this brief, we analyze the damage caused by malware-induced cyber attacks in Cyber-Physical Power Systems (CPPSs). Incubation period and detection probability of the malware are considered in our analytical framework. From attacker’s perspective, the trade-off between attack effectiveness and detection risk is studied to help choose the best attack timing and obtain the maximum payoff. Moreover, we conduct case studies in CPPSs formed by coupling IEEE 118-Bus System with scale-free communication networks. Simulation results reveal that the maximum expected payoff for the attacker is affected by the coupling pattern and the structure of communication network in CPPSs. [ABSTRACT FROM AUTHOR]

Multispectral imaging plays a vital role in the area of computer vision and computational photography. As spectral band images can be misaligned due to imaging device movement or alternation, image registration is necessary to avoid spectral information distortion. The current registration measures specialized for multispectral data are typically robust yet complex, requiring excessive computation. The common measures such as sum of squared differences (SSD) and sum of absolute differences (SAD) are computationally efficient whereas they perform poorly on multispectral data. To cope with this challenge, we propose a structure consistency boosting (SCB) transform that aims at boosting the structural similarity of multispectral images. With SCB, the common measures can be employed for multispectral image registration. The SCB transform exploits the fact that inherent edge structures maintain relative saliency locally despite the nonlinear variation between band images. A statistical prior of the natural image, which is based on the gradient-intensity correlation, is explored to build a parametric form of SCB. Experimental results validate that the SCB transform outperforms current similarity enhancement algorithms, and performs better than the state-of-the-art multispectral registration measures. Thanks to the generality of the statistical prior, the SCB transform is also applicable to various multimodal data such as flash/no-flash images and medical images. [ABSTRACT FROM AUTHOR]

Recently, hashing-based approximate nearest neighbors search has attracted considerable attention, especially in big data applications, due to its low computation cost and fast retrieval speed. In the literature, most of the existing hashing algorithms are centralized. However, in many large-scale applications, the data are often stored or collected in a distributed manner. In this situation, the centralized hashing methods are not suitable for learning hash functions. In this paper, we consider the distributed learning to hash problem. We propose a novel distributed graph hashing model for learning efficient hash functions based on the data distributed across multiple agents over network. The graph hashing model involves a graph matrix, which contains the similarity information in the original space. We show that the graph matrix in the proposed distributed hashing model can be decomposed into multiple local graph matrices, and each local graph matrix can be constructed by a specific agent independently, with moderate communication and computation cost. Then, the whole objective function of the distributed hashing model can be represented by the sum of local objective functions of multiple agents, and the hashing problem can be formulated as a nonconvex constrained distributed optimization problem. For tractability, we transform the nonconvex constrained distributed optimization problem into an equivalent bi-convex distributed optimization problem. Then we propose two algorithms based on the idea of alternating direction method of multipliers to solve this problem in a distributed manner. We show that the proposed two algorithms have moderate communication and computational complexities, and both of them are scalable. Experiments on benchmark datasets are given to demonstrate the effectiveness of the proposed methods [ABSTRACT FROM AUTHOR]

Multispectral imaging is of wide application for its capability in acquiring the spectral information of scenes. Due to hardware limitation, multispectral imaging device usually cannot achieve high-spatial resolution. To address the issue, this paper proposes a multispectral image super-resolution algorithm, referred as SRIF, by fusing the low-resolution multispectral image and the high-resolution (HR) RGB image. It deals with the general circumstance that image intensity is linear to scene radiance for multispectral imaging devices while is nonlinear and unknown for most RGB cameras. The SRIF algorithm first solves the inverse camera response function and a spectral sensitivity function of RGB camera, and establishes the linear relationship between multispectral and RGB images. Then the unknown HR multispectral image is efficiently reconstructed according to the linear image degradation models. Meanwhile, the edge structure of the reconstructed HR multispectral image is kept in accordance with that of the RGB image using a weighted total variation regularizer. The effectiveness of the SRIF algorithm is evaluated on both public datasets and our image set. Experimental results validate that the SRIF algorithm outperforms the state-of-the-arts in terms of both reconstruction accuracy and computational efficiency. [ABSTRACT FROM AUTHOR]

This paper is concerned with the problem of distributed multitask learning over networks, which aims to simultaneously infer multiple node-specific parameter vectors in a collaborative manner. Most of the existing works on the distributed multitask problem modeled the task relatedness by assuming some similarities of parameter vectors in an explicit way. In this paper, we implicitly model the similarity of parameter vectors by assuming that the parameter vectors share a common low-dimensional predictive structure on hypothesis spaces, which is learned using the available data in networks. A distributed structure learning algorithm for the in-network cooperative estimation problem is then derived based on the block coordinate descent method integrated with the inexact alternating direction method of multipliers technique. Simulations on both synthetic and real-world datasets are given to verify the effectiveness of the proposed algorithm. In the case that each node shares a common predictive subspace, it is demonstrated that the proposed multitask algorithm outperforms the noncooperative learning algorithm. Moreover, the use of the inexact approach can significantly reduce the communication bandwidth and still provide the same optimal solution as the corresponding centralized approach. [ABSTRACT FROM AUTHOR]

Multispectral imaging system is of wide application in relevant fields for its capability in acquiring spectral information of scenes. Its limitation is that, due to the large number of spectral channels, the imaging process can be quite time-consuming when capturing high-resolution (HR) multispectral images. To resolve this limitation, this paper proposes a fast multispectral imaging framework based on the image sensor pixel-binning and spectral unmixing techniques. The framework comprises a fast imaging stage and a computational reconstruction stage. In the imaging stage, only a few spectral images are acquired in HR, while most spectral images are acquired in low resolution (LR). The LR images are captured by applying pixel binning on the image sensor, such that the exposure time can be greatly reduced. In the reconstruction stage, an optimal number of basis spectra are computed and the signal-dependent noise statistics are estimated. Then the unknown HR images are efficiently reconstructed by solving a closed-form cost function that models the spatial and spectral degradations. The effectiveness of the proposed framework is evaluated using real-scene multispectral images. Experimental results validate that, in general, the method outperforms the state of the arts in terms of reconstruction accuracy, with additional $20\times $ or more improvement in computational efficiency. [ABSTRACT FROM PUBLISHER]