1,722,189 research outputs found
Remarks on Yu Miao and Shoufang Xu's paper "almost sure convergence of weighted sums"
Full text linkThis work was partially supported by the Fundacao para a Ciencia e a Tecnologia (Portuguese Foundation for Science and Technology) through the project PEst-OE/MAT/UI0297/2014 (Centro de Matematica e Aplicacoes).It is pointed out that a general theorem presented in Yu Miao and Shoufang Xu's paper has a serious gap. In this small note, a counterexample for this theorem is provided exhibiting a triangular array of real numbers and a sequence of independent identically distributed random variables for which its conclusion fails. An reformulation of Yu Miao and Shoufang Xu's general theorem is performed making this statement true.publishersversionpublishe
Using hardware performance counters for detecting control hijacking attacks
No full textControl Hijacking Attack (CHA) is one of the significant ways to exploit the buffer related vulnerability. New code reuse techniques used for the control hijacking attack can circumvent existing security measures. For example, the latest attacks such as Return Oriented Programming use fragments of the existing code base to create an attack. Since this code is already existing code in the system, the Data Execution Prevention methods cannot prevent the execution of this reorganised code. Existing software-based Control Flow Integrity can prevent this attack, but the algorithm and overhead are enormous. Hardware Performance Counters provide support for hardware level detection methods for against control hijacking attack. We proposed a detection method based on the supervision of Hardware Performance Counters (HPCs), and which is a lightweight detection for CHA to solve the monitoring restrictions of other software and hardware security measures, which has a small running overhead. This detection method supports faster information collection, shorter response times, and lower system consumption compared to software level detection. Simulation tests on Gem5 prove that this detection method can be used to detect CHA
A distributed randomized method for the identification of switched ARX systems
No full textThe identification of switched systems amounts to a mixed integer nonlinear optimization problem, where the continuous variables are associated to the model parameterizations of the different modes, and the discrete ones are related to the switching signal (each data sample is assigned to a mode, and switching occurs when the mode assignment changes over time). In the batch form of the identification problem, the combinatorial complexity increases exponentially with the size of the training set, which makes the precise identification of the switching signal the most challenging task in the identification problem. To tackle this complexity we propose a distributed optimization approach, based on the solution of multiple instances of a much simpler problem, where switching can occur only at specific time instants (different for each subproblem), and an information sharing mechanism that preserves likely switching times to improve the local solutions. We employ an adapted version of a previously developed randomized algorithm to solve the individual subproblems. Another important feature of the proposed method is an a posteriori heuristic correction method, that is applied to further refine the switching locations based on the estimated local models before the information sharing phase. The performance of the proposed algorithm is analyzed and compared with other methods on synthetic datasets
Identification of switched nonlinear ARX systems using a randomized algorithm
No full textThe identification of switched nonlinear systems is a mixed discrete and continuous optimization problem that involves complex combinatorial problems, such as the selection of the local model structures and the estimation of the switching signal. In particular, switchings can occur at any time, which makes the combinatorial complexity of the latter task increase exponentially with the number of data. In this work, we employ a randomized scheme to estimate the switching locations: a probability distribution is used to represent the locations of a finite number of switchings and a sample-andevaluate strategy is employed to tune it. This strategy smoothly integrates with a previously developed randomized method devoted to the identification of the nonlinear local models and the mode switching sequence to produce a full switched system identification method. The proposed solution has been tested on a benchmark example to verify its effectiveness and efficiency compared to existing works
FIGURE 2. A in Rohdea grandiflora (Asparagaceae), a new species from southern Gansu, China
No full textFIGURE 2. A. Inflorescence of Rohdea grandiflora. B. Inflorescence of R. pachynema (some perianth lobes removed). C & D. Flower of R. pachynemaPublished as part of Feng, Hui Zhe, Yu, Miao, Fang, Hong Lin & Han, Qing Xiang, 2022, Rohdea grandiflora (Asparagaceae), a new species from southern Gansu, China, pp. 208-212 in Phytotaxa 552 (3) on page 210, DOI: 10.11646/phytotaxa.552.3.5, http://zenodo.org/record/677700
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Sea Ice Semantic Segmentation with Sentinel-2 Data Based on Adaptive Sample Training on U-Net Network
No full textThe rapid melting of Arctic sea ice presents significant opportunities and challenges for humanity. The formation of numerous channels between the ice offers potential for Arctic navigation. The identification and semantic segmentation of sea ice is a crucial task in sea ice monitoring. To reduce the influence of complex climatic conditions in the Arctic region on the robustness of the sea ice segmentation model, this paper proposes a sea ice semantic segmentation model based on adaptive training sample selection on U-Net for Sentinel-2 data. The method adaptively selects training samples through unsupervised iterative clustering and inputs them into U-Net network for image segmentation. In addition, the iterative efficiency of clustering is improved by building subspaces. The experimental results on Sentinel-2 data show that the proposed method can effectively achieve sea ice segmentation with a high positive detection rate and low false alarm rate
A switched nonlinear system identification method with switching location refinement
Full text linkThe identification of switched nonlinear systems involves solving a combinatorial problem that simultaneously addresses sample-mode assignment and nonlinear model structure selection. The complexity of this problem is often prohibitive, since mode switchings can take place at arbitrary times. To reduce it to an affordable level, one can constrain the mode switchings to occur only at few specific instants. This approach is effective if combined with a refinement strategy, that corrects the number and locations of the switchings. In this paper, one such strategy is discussed, which employs a local optimization process to correct the position of switchings, and is also capable of detecting redundant modes. An iterative method, applying an identification step and a refinement step at all iterations, is tested on a numerical example to illustrate the effectiveness of the refinement strategy. The method does not require prior assumptions on the number of modes
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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