Analysis and Improvement of a Threshold Signature Scheme Based on the General Access Structure

AbstractHua-wang Qin et al. proposed a novel threshold signature scheme based on the general access structure in order to break the applied limitation of the conventional threshold signature schemes. The security of the scheme was analyzed in this paper, and it is pointed out that the scheme is insecure because it cannot withstand conspiracy attacks and what's more, the identity of signer cannot be investigated. To overcome these security vulnerabilities, this paper proposed an improved threshold signature scheme, and the security analysis results show that the improved scheme can not only resist the conspiracy attack, but also have the properties of anonymity and traceability simultaneously

Interaction between Schwann Cells and Osteoblasts In Vitro

Aim Given the well-known properties of Schwann cells in promoting nerve regeneration, transplanting Schwann cells into implant sockets might be an effective method to promote sensory responses of osseointegrated implants. The aim of this study was to evaluate the interaction between Schwann cells and osteoblasts. Methodology Schwann cells derived from the sciatic nerves of neonatal rat were co-culured with osteoblasts using Transwell inserts. The proliferation of Schwann cells in the co-culture system was evaluated using methylthiazol tetrazolium (MTT) colorimetric method. Moreover, the secretions and mRNA levels of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time PCR, respectively. In order to test the effect of Schwann cells on osteoblasts, alkaline phosphatase (ALP) staining and Alizerin red staining were performed as well. Results: Schwann cells, which were co-cultured with the osteoblasts, showed an intact proliferation during the observation period. Moreover, the gene expression and synthesis of BDNF and NGF were not impaired by the osteoblasts. Meanwhile, co-cultured osteoblasts exhibited a significant increase in the proliferation on day 3 and 6 (P< 0.05). Co-culture of these two types of cells also led to a more intense staining of ALP and an elevated number of calcified nodules. Conclusion: These findings demonstrate that, in the in vitro indirect co-culture environment, Schwann cells can maintain their normal ability to synthesize neurotrophins, which then enhance the proliferation and differentiation of osteoblasts

Growth of uniform cobalt nano magnetic dots on titanum dioxide surface

This research investigated the growth of cobalt magnetic nanodots on the rutile TiO2 (110) surface. Well ordered TiO2 (110) surface was prepared in the Ultra High Vacuum (UHV) via Ar+ sputtering and annealing. Co was deposited in-situ by Molecular Beam Epitaxy (MBE). Characterization of the growth was performed in-situ by a Variable Temperature Scanning Tunneling Microscope (VT-STM). The TiO2 (110) surface was proven to promote the Volmer-Weber growth of Co nanodots. The cobalt atoms formed small clusters at the stage of initial growth. As the coverage increased, the size and density of clusters increased. It was discovered that there existed a stable dot size, especially after a delicate post-annealing. Statistical analysis showed the stable size of nanodots was 4.0 ± 0.5 nm. The existence of the stable dot size was supported theoretically based on jellium model. An optimal set of fabrication parameters was established for the uniform magnetic nanodot growth

Cloze Test Helps: Effective Video Anomaly Detection via Learning to Complete Video Events

As a vital topic in media content interpretation, video anomaly detection (VAD) has made fruitful progress via deep neural network (DNN). However, existing methods usually follow a reconstruction or frame prediction routine. They suffer from two gaps: (1) They cannot localize video activities in a both precise and comprehensive manner. (2) They lack sufficient abilities to utilize high-level semantics and temporal context information. Inspired by frequently-used cloze test in language study, we propose a brand-new VAD solution named Video Event Completion (VEC) to bridge gaps above: First, we propose a novel pipeline to achieve both precise and comprehensive enclosure of video activities. Appearance and motion are exploited as mutually complimentary cues to localize regions of interest (RoIs). A normalized spatio-temporal cube (STC) is built from each RoI as a video event, which lays the foundation of VEC and serves as a basic processing unit. Second, we encourage DNN to capture high-level semantics by solving a visual cloze test. To build such a visual cloze test, a certain patch of STC is erased to yield an incomplete event (IE). The DNN learns to restore the original video event from the IE by inferring the missing patch. Third, to incorporate richer motion dynamics, another DNN is trained to infer erased patches' optical flow. Finally, two ensemble strategies using different types of IE and modalities are proposed to boost VAD performance, so as to fully exploit the temporal context and modality information for VAD. VEC can consistently outperform state-of-the-art methods by a notable margin (typically 1.5%-5% AUROC) on commonly-used VAD benchmarks. Our codes and results can be verified at github.com/yuguangnudt/VEC_VAD.Comment: To be published as an oral paper in Proceedings of the 28th ACM International Conference on Multimedia (ACM MM '20). 9 pages, 7 figure

Holiday Destination Choice Behavior Analysis Based on AFC Data of Urban Rail Transit

For urban rail transit, the spatial distribution of passenger flow in holiday usually differs from weekdays. Holiday destination choice behavior analysis is the key to analyze passengers’ destination choice preference and then obtain the OD (origin-destination) distribution of passenger flow. This paper aims to propose a holiday destination choice model based on AFC (automatic fare collection) data of urban rail transit system, which is highly expected to provide theoretic support to holiday travel demand analysis for urban rail transit. First, based on Guangzhou Metro AFC data collected on New Year’s day, the characteristics of holiday destination choice behavior for urban rail transit passengers is analyzed. Second, holiday destination choice models based on MNL (Multinomial Logit) structure are established for each New Year’s days respectively, which takes into account some novel explanatory variables (such as attractiveness of destination). Then, the proposed models are calibrated with AFC data from Guangzhou Metro using WESML (weighted exogenous sample maximum likelihood) estimation and compared with the base models in which attractiveness of destination is not considered. The results show that the ρ2 values are improved by 0.060, 0.045, and 0.040 for January 1, January 2, and January 3, respectively, with the consideration of destination attractiveness

Quantum state tomography via non-convex Riemannian gradient descent

The recovery of an unknown density matrix of large size requires huge computational resources. The recent Factored Gradient Descent (FGD) algorithm and its variants achieved state-of-the-art performance since they could mitigate the dimensionality barrier by utilizing some of the underlying structures of the density matrix. Despite their theoretical guarantee of a linear convergence rate, the convergence in practical scenarios is still slow because the contracting factor of the FGD algorithms depends on the condition number $\kappa$ of the ground truth state. Consequently, the total number of iterations can be as large as $O(\sqrt{\kappa}\ln(\frac{1}{\varepsilon}))$ to achieve the estimation error $\varepsilon$. In this work, we derive a quantum state tomography scheme that improves the dependence on $\kappa$ to the logarithmic scale; namely, our algorithm could achieve the approximation error $\varepsilon$ in $O(\ln(\frac{1}{\kappa\varepsilon}))$ steps. The improvement comes from the application of the non-convex Riemannian gradient descent (RGD). The contracting factor in our approach is thus a universal constant that is independent of the given state. Our theoretical results of extremely fast convergence and nearly optimal error bounds are corroborated by numerical results.Comment: Comments are welcome

Newly discovered Upper Paleolithic sites from the Tsagaan Turuut river valley, Mongolia

In this article, we report artefacts found at the valley of Tsagaan Turuut River in the Khangai Mountain ranges in Central Mongolia. The artefacts were identified based upon core morphology, tool types and retouch. Regarding the core reduction techniques, single striking platform and single reduction platform cores are dominant. Although the tools on flake blanks predominant, tools such as points and knives with massive blades also occur. Side scraper, point, borer, combination tool, and borers are types that are less represented within the collection. This tool collection is highly similar to several IUP and EUP sites (Chikhen-2; Tolbor-4, 15 and 16) in Mongolia in terms of its reduction techniques and tool morphology. On a larger scale, it is similar to those of Early Upper Paleolithic sites in Trans-Baikal and Altai Mountains in Russia and North China