Improvement of compression performance of fiber reinforced polymer（繊維強化複合材料の圧縮特性の向上）

信州大学(Shinshu university)博士（工学）ThesisRUAN FANGTAO. Improvement of compression performance of fiber reinforced polymer（繊維強化複合材料の圧縮特性の向上）. 信州大学, 2015, 博士論文. 博士（工学）, 甲第646号, 平成28年03月20日授与.doctoral thesi

Mechanical Enhancement of UHMWPE Fibers by Coating with Carbon Nanoparticles

Fiber-reinforced plastic (FRP) is composed of reinforced fibers and matrix resin, and has high specific strength and low-density materials. Because of the orientation of the fibers within them, FRPs are prone to buckling damage when under compression along the axial direction of the fiber, especially flexible organic ones. The compressive performance of FRP is largely dependent on fiber properties. the buckling load of FRP will increase with the increasing of fiber's. In this study, we developed a way to improve the compressive and bending strength of ultra-high molecular weight polyethylene (UHMWPE) fibers. Carbon nanotubes (CNTs) and vapor-grown carbon fibers (VGCFs) were coated on the surface of UHMWPE fibers by pyrrole vapor deposition. The transverse compressive strength and bending strength of single UHMWPE fibers were determined by microcompression and single fiber bending measurements, respectively. The experiment result showed that coating UHMWPE fibers with CNTs and VGCFs increased both their transverse compressive strength and bending strength. It is excepted that the improved fiber would applied in FRP for better compressive performance.ArticleFIBERS AND POLYMERS. 15(4):723-728 (2014)journal articl

Doubly-Irregular Repeat-Accumulate Codes over Integer Rings for Multi-user Communications

Structured codes based on lattices were shown to provide enlarged capacity for multi-user communication networks. In this paper, we study capacity-approaching irregular repeat accumulate (IRA) codes over integer rings $\mathbb{Z}_{2^{m}}$ for $2^m$-PAM signaling, $m=1,2,\cdots$. Such codes feature the property that the integer sum of $K$ codewords belongs to the extended codebook (or lattice) w.r.t. the base code. With it, \emph{% structured binning} can be utilized and the gains promised in lattice based network information theory can be materialized in practice. In designing IRA ring codes, we first analyze the effect of zero-divisors of integer ring on the iterative belief-propagation (BP) decoding, and show the invalidity of symmetric Gaussian approximation. Then we propose a doubly IRA (D-IRA) ring code structure, consisting of \emph{irregular multiplier distribution} and \emph{irregular node-degree distribution}, that can restore the symmetry and optimize the BP decoding threshold. For point-to-point AWGN channel with $$-PAM inputs, D-IRA ring codes perform as low as 0.29 dB to the capacity limits, outperforming existing bit-interleaved coded-modulation (BICM) and IRA modulation codes over GF($2^m$). We then proceed to design D-IRA ring codes for two important multi-user communication setups, namely compute-forward (CF) and dirty paper coding (DPC), with $2^m$-PAM signaling. With it, a physical-layer network coding scheme yields a gap to the CF limit by 0.24 dB, and a simple linear DPC scheme exhibits a gap to the capacity by 0.91 dB.Comment: 30 pages, 13 figures, submitted to IEEE Trans. Signal Processin

ハイパフォーマンスコンピューティングを用いたRCトンネル接合部材の数値シミュレーション

学位の種別:課程博士University of Tokyo(東京大学

Towards Robust Video Instance Segmentation with Temporal-Aware Transformer

Most existing transformer based video instance segmentation methods extract per frame features independently, hence it is challenging to solve the appearance deformation problem. In this paper, we observe the temporal information is important as well and we propose TAFormer to aggregate spatio-temporal features both in transformer encoder and decoder. Specifically, in transformer encoder, we propose a novel spatio-temporal joint multi-scale deformable attention module which dynamically integrates the spatial and temporal information to obtain enriched spatio-temporal features. In transformer decoder, we introduce a temporal self-attention module to enhance the frame level box queries with the temporal relation. Moreover, TAFormer adopts an instance level contrastive loss to increase the discriminability of instance query embeddings. Therefore the tracking error caused by visually similar instances can be decreased. Experimental results show that TAFormer effectively leverages the spatial and temporal information to obtain context-aware feature representation and outperforms state-of-the-art methods

Automated Crowdturfing Attacks and Defenses in Online Review Systems

Malicious crowdsourcing forums are gaining traction as sources of spreading misinformation online, but are limited by the costs of hiring and managing human workers. In this paper, we identify a new class of attacks that leverage deep learning language models (Recurrent Neural Networks or RNNs) to automate the generation of fake online reviews for products and services. Not only are these attacks cheap and therefore more scalable, but they can control rate of content output to eliminate the signature burstiness that makes crowdsourced campaigns easy to detect. Using Yelp reviews as an example platform, we show how a two phased review generation and customization attack can produce reviews that are indistinguishable by state-of-the-art statistical detectors. We conduct a survey-based user study to show these reviews not only evade human detection, but also score high on "usefulness" metrics by users. Finally, we develop novel automated defenses against these attacks, by leveraging the lossy transformation introduced by the RNN training and generation cycle. We consider countermeasures against our mechanisms, show that they produce unattractive cost-benefit tradeoffs for attackers, and that they can be further curtailed by simple constraints imposed by online service providers

JNK pathway promotes hepatocyte apoptosis by inhibiting Bcl-2 and upregulating expressions of Bim, caspase-3 and caspase-9 after cardiopulmonary bypass

Purpose: To study the effect of Jun N-terminal kinase (JNK) signaling pathway on hepatocyte apoptosis in vivo and in vitro, and to elucidate the mechanism of action. Methods: TdT-mediated dUTP Nick-End Labeling (TUNEL) method was used to determine apoptosis in control and cardiopulmonary bypass (CPB) groups at 0, 3 and 6 hours after rat surgery. The expressions of JNK and p-c-Jun in liver tissues at 0, 3 and 6 h after surgery, and the levels of p-c-Jun, Bcl-2 and Bim following overexpression of JNK, were determined using Western blot assay. Human liver cell line HL-7702 was cultured and transfected with over-expressed JNK plasmid and empty plasmid. Proliferation of HL-7702 cells after JNK over-expression was assessed by Cell Counting Kit-8 (CCK-8), while quantitative real-time polymerase chain reaction (RT-qPCR) was employed to evaluate mRNA expression levels of caspase-3 and caspase-9 mRNA after JNK over-expression. Apoptosis of the cells was determined by flow cytometry (FC) after JNK over-expression. Results: FC results showed that the number of apoptotic hepatocytes increased after JNK overexpression in hepatocytes while TUNEL assay results demonstrated that hepatocyte apoptosis increased in CPB group, when compared to control group; furthermore, the number of apoptotic cells gradually increased within 6 h after surgery. The expressions of JNK and p-c-Jun were higher in CPB group than in control group, and increased gradually in both groups within 6 h after surgery. Overexpression of JNK decreased the proliferation of hepatocytes, and also lowered protein expression levels of p-c-Jun and Bim; on the other hand, the protein expression levels of Bcl-2 fell, while mRNA expression levels of caspase-3 and caspase-9 mRNA increased. Conclusion: JNK pathway promotes hepatocyte apoptosis after cardiopulmonary bypass by inhibiting Bcl-2 pathway and promoting the expressions of Bim caspase-3 and caspase-9. Keywords: Cardiopulmonary bypass, Apoptosis, JNK pathway, Bim, caspase-3 and caspase-

A New Viscoelastic Mechanics Model for the Creep Behaviour of Fibre Reinforced Asphalt Concrete

Based on the Burgers model, by adding a damper unit, this paper proposes a new viscoelastic model with five units and eight parameters to characterize the viscoelastic deformation of fibre reinforced asphalt concrete (FRAC). According to the creep tests of FRAC beams, this paper studies both the parameters in the model and the viscoelastic behaviour of FRAC with different fibre volume fraction and aspect ratio. In this model, this paper establishes the viscoelastic constitutive equation of asphalt concrete, which takes into account the impacts of fibre content characteristic parameter. Both the experimental study and theoretical analysis show that the new model has a high correlation with the results of creep experiment and plays a key role in describing the whole creep process of FRAC. The fibre content characteristic parameter can comprehensively reflect the effects of the fibre volume fraction and aspect ratio on the viscoelastic behaviour of FRAC. Within the range of this test, the optimum fibre volume fraction, fibre aspect ratio and fibre content characteristic parameter are 0.35%, 324 and 1.13