Simulation and experiment of starting transient flow field of the hydrostatic bearing based on dynamic mesh method

A new method is developed to assess and analyze the dynamic performance of hydrostatic bear-ing oil film by using an amulets-layer dynamic mesh technique.It is implemented using C Language to compile the UDF program of a single oil film of the hydrostatic bearing.The effects of key lubrica-tion parameters of the hydrostatic bearing are evaluated and analyzed under various working condi-tions, i.e.under no-load, a load of 40t, a full load of 160t, and the rotation speed of 1r/min, 2r/min, 4r/min, 8r/min, 16r/min, 32r/min.The transient data of oil film bearing capacity under different load and rotation speed are acquired for a total of 18 working conditions during the oil film thickness changing.It allows the effective prediction of dynamic performance of large size hydrostatic bearing.Experiments on hydrostatic bearing oil film have been performed and the results were used to define the boundary conditions for the numerical simulations and validate the developed numerical model.The results showed that the oil film thickness became thinner with the increase of the operat-ing time of the hydrostatic bearing, both the oil film rigidity and the oil cavity pressure increased sig-nificantly, and the increase of the bearing capacity was inversely proportional to the cube of the change of the film thickness.Meanwhile, the effect of the load condition on carrying capacity of large size static bearing was more important than the speed condition.The error between the simula-tion value and the experimental value was 4 .25%.     

Multiple feature fusion in convolutional neural networks for action recognition

Action recognition is important for understanding the human behaviors in the video, and the video representation is the basis for action recognition. This paper provides a new video representation based on convolution neural networks (CNN). For capturing human motion information in one CNN, we take both the optical flow maps and gray images as input, and combine multiple convolutional features by max pooling across frames. In another CNN, we input single color frame to capture context information. Finally, we take the top full connected layer vectors as video representation and train the classifiers by linear support vector machine. The experimental results show that the representation which integrates the optical flow maps and gray images obtains more discriminative properties than those which depend on only one element. On the most challenging data sets HMDB51 and UCF101, this video representation obtains competitive performance.     

BotGuard: Lightweight real-time botnet detection in software defined networks

The distributed detection of botnets may induce heavy computation and communication costs to network devices. Each device in related scheme only has a regional view of Internet, so it is hard to detect botnet comprehensively. In this paper, we propose a lightweight real-time botnet detection framework called Bot-Guard, which uses the global landscape and flexible configurability of software defined network (SDN) to identify botnets promptly. SDN, as a new network framework, can make centralized control in botnet detection, but there are still some challenges in such detections. We give a convex lens imaging graph (CLI-graph) to depict the topology characteristics of botnet, which allows SDN controller to locate attacks separately and mitigate the burden of network devices. The theoretical and experimental results prove that our scheme is capable of timely botnet detecting in SDNs with the accuracy higher than 90% and the delay less than 56 ms.     

An efficient certificateless aggregate signature scheme

Aggregate signature can aggregate n signatures on n messages from n signers into a single signature that convinces any verifier that n signers sign the n messages, respectively. In this paper, by combining certificateless public key cryptography and aggregate signatures, we propose an efficient certificateless aggregate signature scheme and prove its security. The new scheme is proved secure against the two representative types adversaries in certificateless aggregate signature under the assumption that computational Diffie-Hellman problem is hard. Furthermore, from the comparison of the computation cost of the new scheme with some existing certificateless aggregate signature schemes in group sum computation, scalar multiplication computation, Hash computation and abilinear pairings computation, it concludes that the new scheme reduces the computation cost in scalar multiplication computation in half and maintains the same in the other computation costs.     

Deterioration Process of the Hybrid Films during Wear Test——Polyacrylate Emulsion Modified by Silica Particles

The hybrid materials are widely used in various fields for excellent performance. However, there are few researches studying their failure process. In order to prepare the hybrid materials with better performance, the failure process needs to be well studied. Two kinds of silica/polyacrylate films are successfully prepared to study the effect of organic-inorganic interaction on performance. The average diameter of silica particles is measured to be around 342 nm by scanning electron microscope (SEM). Wear test demonstrates the hybrid film, which is obtained by grafting polyacrylate onto silica particles, possesses more excellent properties than the one filled directly with silica particles. The stronger interaction between organic and inorganic components leads to a better distribution of inorganic particles within the polymer matrix. In this work, a model is presented to illustrate the deterioration process of the hybrid films, which allows us to further understand the hybrid materials.     

Effect of konjac glucomannan on sodium alginate membrane

This paper introduces a blended membrane which is prepared by coagulation of sodium alginate and konjac glucomannan(KGM) in an aqueous solution, and studies the effect of different concentrations of KGM on sodium alginate films. The structural characterization of prepared blend film was implemented by scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FT-IR), and the optimum ratio was determined by comparing fracture elongation, moisture absorption and moisture retention. The results indicate that the two polysaccharide molecules, sodium alginate and KGM, in the blend membrane have a good compatibility. The surface of blend film is smooth and uniform. The addition of KGM can significantly improve the moisture absorption and moisture retention performance of sodium alginate film, and its mechanical performance is also improved to some extent. The ratio of sodium alginate and KGM is 3.2∶1.5.     

广义单调性与广义凸性

在广义单调性方面做进一步的推广,并建立函数的广义凸性与其梯度向量的广义单调性之间的等价关系.首先,建立F单调映射、F伪单调映射和F拟单调映射概念.其次,利用可微F凸(伪凸、拟凸)函数的梯度等价刻画,结合广义单调映射概念以及微分性质,研究广义凸性与广义单调性的内在联系:在一定条件下,f是K上的F凸函数,当且仅当?f是K上...     

新形势下美国对华科技竞争战略的特点、走向与应对 ——基于美国重点智库报告的分析

随着中美科技竞争日益加剧,美国对华科技竞争战略的特点和走向备受关注.首先,结合拜登及核心对华团队的政策主张,总结出其科技竞争战略具有"追求美国领先、重返多边体系、注重意识形态和聚焦有限目标"四大基本特点.其次,结合美国相关重点智库研究报告,研判美国对华科技竞争战略走向具体呈现3个方面,即以"小院高墙"为原则的技术保护、...