A peridynamic Reissner-Mindlin shell theory

In this work, we have developed a state-based peridynamics theory for nonlinear Reissener-Mindlin shells to model and predict large deformation of shell structures with thick wall. The nonlocal peridynamic theory of solids offers an integral formulation that is an alternative to traditional local continuum mechanics models based on partial differential equations. This formulation is applicable for solving the material failure problems involved in discontinuous displacement fields. The governing equations of the state-based peridynamic shell theory are derived based on the nonlocal balance laws by adopting the kinematic assumption of the Reissner and Mindlin plate and shell theories. In the numerical calculations, the stress points are employed to ensure the numerical stability. Several numerical examples are conducted to validate the nonlocal structure mechanics model and to verify the accuracy as well as the convergence of the proposed shell theory.     

改性壳聚糖基抗菌食品包装材料的研究进展

壳聚糖作为绿色天然的可降解材料,是塑料较为理想的替代品,也是食品包装行业的优选功能性材料。为体现壳聚糖的抗菌性在食品包装行业的应用价值,对壳聚糖的抗菌机理及抗菌性的影响因素进行梳理与分析。研究发现,壳聚糖的抗菌性不仅与其分子结构有关,还与其相对分子质量、脱乙酰化程度以及外界环境等有关;通过总结改善壳聚糖抗菌性的方法以及壳聚糖基包装材料在果蔬、肉制品等食品中的应用,发现改性后的壳聚糖在抗菌性增强的同时,阻隔性、机械性等也有一定的改善,并且该包装材料在果蔬、肉制品的食品包装中具有抗菌保鲜性。综述改性壳聚糖基抗菌食品包装材料的研究进展,以期为制备绿色抗菌性食品包装材料提供理论基础及研究思路,推动功能性食品包装材料的开发与应用。     

图像分类模型的对抗样本攻防研究综述

深度学习模型在图像分类领域的能力已经超越了人类,但不幸的是,研究发现深度学习模型在对抗样本面前非常脆弱,这给它在安全敏感的系统中的应用带来了巨大挑战。图像分类领域对抗样本的研究工作被梳理和总结,以期为进一步地研究该领域建立基本的知识体系,介绍了对抗样本的形式化定义和相关术语,介绍了对抗样本的攻击和防御方法,特别是新兴的可验证鲁棒性的防御,并且讨论了对抗样本存在可能的原因。为了强调在现实世界中对抗攻击的可能性,回顾了相关的工作。在梳理和总结文献的基础上,分析了对抗样本的总体发展趋势和存在的挑战以及未来的研究展望。     

The Research on 220GHz Multicarrier High-Speed Communication System

This paper presents our investigation into a 220 GHz multicarrier highspeed communication system based on solid state transceivers.The proposed system has eased the demand of high sampling rate analog-to-digital converter(ADC)by providing several signal carriers in microwave band and converting them to 220 GHz channel.The system consists of a set of 220 GHz solid-state transceiver with 2 signal carriers,two basebands for 4 GSPS ADCs.It has achieved 12.8 Gbps rate real-time signal transmission using 16QAM modulation over a distance of 20 m without any other auxiliary equipment or test instruments.The baseband algorithm overcomes the problem of frequency difference generates by non-coherent structure,which guarantees the feasibility of long-distance transmission application.Most importantly,the proposed system has already carried out multi-channel 8K video parallel transmission through switch equipment,which shows the multicarrier high-speed communication system in submillimeter wave has great application prospects.To the best of the authors’knowledge,this is the first all-solid-state electronics multicarrier communication system in submillimeter and terahertz band.     

Classification-Based Fraud Detection for Payment Marketing and Promotion

Nowadays, many payment service providers use the discounts and other marketing strategies to promote their products. This also raises the issue of people who deliberately take advantage of such promotions to reap financial benefits. These people are known as ‘scalper parties’ or ‘econnoisseurs’ which can constitute an underground industry. In this paper, we show how to use machine learning to assist in identifying abnormal scalper transactions. Moreover, we introduce the basic methods of Decision Tree and Boosting Tree, and show how these classification methods can be applied in the detection of abnormal transactions. In addition, we introduce a graph computing method, which implicitly describes the characteristics of people and merchants through node correlation, in order to mine deep features. Because of the volume of large data, we carried out reasonable block calculation, and succeeded in reducing a large amount of data to a series of segments, thereby decreasing the computational resources and memory requirements. Compared with other work on abnormal transaction detection, we pay more attention to creating and using the portraits of merchants or individuals to assist in decision-making. After data analysis and model building, we find that focusing on only one transaction or one day does not yield a comprehensive number of characteristics, and many characteristics can be obtained by examining the transactions of a person or a merchant over a period of time. Furthermore, a large number of characteristics can be obtained from transactions in a period of time. After GBDT (Gradient Boosting Decision Tree) based classification prediction and analysis, we can conclude that there is a clear distinction between abnormal trading shops and conventional shops, facilitating the clustering of abnormal merchants. By filtering transaction data from multiple dimensions, multiple sub-graphs can be obtained. After hierarchical clustering, the abnormal trading group is mined and classified according to its features. Finally, we build a scoring model and apply it to the big data platform of one of China’s largest payment service providers to help enterprises identify abnormal trading groups and specific marketing strategies.     

针对大视差图像拼接的显性子平面配准

目的 针对图像拼接中大视差图像难以配准的问题,提出一种显性子平面自动配准算法。方法 假设大视差图像包含多个显性子平面且每个平面内所含特征点密集分布。对该假设进行了验证性实验。所提算法以特征点分布为依据,通过聚类算法实现子平面分割,进而对子平面进行局部配准。首先,使用层次聚类算法对已匹配的特征点聚类,通过一种本文设计的拼接误差确定分组数目,并以各组特征点的聚类中心为新的聚类中心对重叠区域再聚类,分割出目标图像的显性子平面。然后,求解每个显性子平面的投影参数,并采用就近原则分配非重叠区域的单应性矩阵。结果 采用公共数据集对本文算法进行测试,并与Auto-Stitching、微软Image Composite Editor两种软件及全局投影拼接方法（Baseline）、尽可能投影算法（APAP）进行对比,采用均方根误差作为配准精度的客观评判标准。实验结果表明,该算法在拼接大视差图像时,能有效地配准局部区域,解决软件和传统方法由误配准引起的鬼影、错位等问题。其均方根误差比Baseline方法平均减小55%左右。与APAP算法相比,均方根误差平均相差10%左右,但可视化配准效果相同且无需调节复杂参数,可实现自动配准。结论 提出的显性子平面自动配准算法,通过分割图像所含子平面进而实现局部配准。该方法具有较高的配准精度,在大视差图像配准方面,优于部分软件及算法,可应用于图像拼接中大视差图像的自动配准。     

Euryhaline Hydrogel with Constant Swelling and Salinity-Enhanced Mechanical Strength in a Wide Salinity Range

In nature, many biological organisms possess a unique osmoregulation feature that enables them to survive in environments of different salinity, which is called euryhaline characteristics (e.g., salmon that can survive in freshwater and seawater). Drawing inspiration from these salinity-tolerant organisms, here a strategy that integrates two polymer chain segments with different salinity tolerances is reported to produce a euryhaline hydrogel with stable water retention, constant swelling properties, superoleophobicity, and low-adhesion to oil in aqueous environments over a wide range of salinity. The formation of internal dynamic complementary crosslinks is a key structural factor of the euryhaline attributes. The euryhaline hydrogel-coated meshes can be successfully utilized in various oil/aqueous phase separation in a wide range of salinity. Furthermore, by creating a double network with dynamic bonds, superior euryhaline hydrogel with unique salinity-enhanced mechanical strength can be obtained. It is anticipated that the euryhaline hydrogel will have broad application prospects in complex and variable ionic environments.     

Bioinspired Tumor Calcification Enables Early Detection and Elimination of Lung Cancer

Precise diagnosis of cancer in an early stage and treatments with a reliable response, high selectivity, and negligible side effects is urgently needed. However, current cancer management involves low-resolution metrics and delayed visual confirmation of tumor foci in imaging findings, and the toxicity of chemo- and radiotherapy unavoidably damages normal tissue and disrupts the immune balance of cancer patients. Here, a polypeptide is synthesized that preferentially targets lung cancer cells rather than normal lung epithelial cells and induces calcium precipitation specifically on the plasma membrane of lung cancer cells without additional supplementary calcium. Polypeptide-induced cellular calcification can ideally facilitate medical imaging for identifying early-stage lung cancer and distinguish cancer from benign nodules. Physiological and spontaneous calcification of tumors is induced by polypeptides and sharply prolongs the survival of tumor-bearing mice without evidence of systemic side effects. This tumor cell-selective calcification process provides an attractive, safe, and unprecedented approach for accurately visualizing and treating cancer in patients with early-stage disease in the clinic. It has broad implications in developing simple physiological reactions for diagnosing and treating cancer and provides a new horizon for drug discovery.     

基于水足迹的黄河流域生态补偿标准研究

流域生态补偿机制的建立为黄河流域生态保护与高质量发展提供了重要保障。基于水足迹视角,探讨了黄河流域九省(区)2011—2020年水资源利用情况,确定了生态补偿的主、客体及生态补偿标准。结果表明：黄河流域水足迹整体呈现增长态势,构成比例从大到小依次为农业、工业、生活、出口虚拟水、进口虚拟水足迹和生态水足迹;黄河流域生态补偿标准存在波动变化且为补偿主体,2015年补偿标准最高,为3 415.42×10⁸元,2020年最低,为12.75×10⁸元,补偿金额年均值为1 772.51×10⁸元。宁夏回族自治区、山西省、河南省和山东省为生态补偿的主体呈上升趋势,补偿金额年均值排名为河南省＞山东省＞山西省＞宁夏回族自治区。四川省是处于较快上升趋势的生态补偿客体,受补偿金额年均值为3 060.09×10⁸元;青海省为较慢上升趋势的生态补偿客体,补偿金额年均值为1 340.14×10⁸元。甘肃省是由生态补偿主体逐渐转变为客体;内蒙古自治区仅在2013年为生态补偿客体,其他年份则为补偿主体;陕西省生态补偿的主、客体身份不断发生变化。黄河流域应发挥区域优势推动农业高质量发展,建立完善的生态补偿机制,通过创新节水技术和提高用水效率等方式缓解水资源需求压力。