Modeling and analysis of passive worm propagation in the P2P file-sharing network

A number of worms, named P2P (peer-to-peer) passive worms, have recently surfaced, which propagate in P2P file-sharing networks and have posed heavy threats to these networks. In contrast to the majority of Internet worms, it is by exploiting users’ legitimate activities instead of vulnerabilities of networks in which P2P passive worms propagate. This feature evidently slows down their propagation, which results in them not attracting an adequate amount of attention in literature. Meanwhile, this feature visibly increases the difficulty of detecting them, which makes it very possible for them to become epidemic. In this paper, we propose an analytical model for P2P passive worm propagation by adopting epidemiological approaches so as to identify their behaviors and predict the tendency of their propagation accurately. Compared with a few existing models, dynamic characteristics of P2P networks are taken into account. Based on this proposed model, the sufficient condition for the global stability of the worm free equilibrium is derived by applying epidemiological theories. Large scale simulation experiments have validated both the proposed model and the condition.     

蜗轮蜗杆副在机动、手动进给传动机构中的应用

一种新型机动、手动进给传动机构,在传动链起始端都用蜗轮蜗杆副,利用蜗轮蜗杆副反向传动自锁的特点,达到机动进给时自锁手动进给,而手动进给时又自锁机动进给的结果。     

一种新型双基座滑板装置

开发研制了一种新型双基座滑板装置。该装置采用双基座滑板移动、双静压蜗杆、蜗母条同步驱动结构;具有承受载荷大,动、静刚度高,精度高,同步性和精度保持性好的特点。     

蜗杆传动机构加速与制动时的转矩

蜗杆传动机构作为一种结构紧凑的减速机构在大速比场合应用广泛.但一般计算转矩时通常只考虑蜗轮蜗杆匀速传动的场合,而不适用于加速与制动时的情形.特别是在以惯性载荷为主的伺服系统中,其加、减速时的转矩不同于常规稳态转矩.文中首次采用由理论转矩计算出的实际转矩可以精确地控制系统,尤其是在蜗杆传动机构用于伺服系统加、减速时,性能...     

A method for predicting hobbing tool wear based on CNC real-time monitoring data and deep learning

Intelligent monitoring and diagnosis of tool status are of great significance for improving the manufacturing efficiency and accuracy of the workpiece. It is difficult to quickly and accurately predict the wear state of worm gear hob under different working conditions. This paper proposes a novel approach to predict hob wear status based on CNC real-time monitoring data. Based on the open platform communication unified architecture (OPC UA) technology and orthogonal test, the machine data of motor power, current, etc. related to tool wear are collected online in the worm gear machining process. And then, an improved deep belief network (DBN) is used to generate a tool wear model by training data. A growing DBN with transfer learning is introduced to automatically decide its best model structure, which can accelerate its learning process, improve training efficiency and model performance. The experiment results show that the proposed method can effectively predict hob wear status under multi-cutting conditions. To show the advantages of the proposed approach, the performance of the DBN is compared with the traditional back propagation neural network (BP) method in terms of the mean-squared error (MSE). The compared results show that this tool wear prediction method has better prediction accuracy than the traditional BP method during worm gear hobbing.     

NUM1060HG数控系统在蜗杆砂轮磨齿机上的应用

蜗杆砂轮磨齿机YK7236用于成批生产中磨削直齿和螺旋齿、圆柱轮，也可以磨削鼓形齿和锥齿等齿向修形齿轮。本机床工作原理和滚齿机相似，即用蜗杆砂轮与齿轮(工件)连续展成啮合原理来磨削。机床可采用位移磨削方法和普通磨削方法以适应高效磨削和精密磨削。该机床充分利用了NUM1060HG数控系统)开放的环境，使用MMI工具开发软件，制作了适合于蜗杆砂轮磨齿机磨削工艺的友好的人机对话界面，使得机床用户更加容易操作。     

计算机病毒入侵的途径与防治研究

计算机病毒往往会利用计算机操作系统的弱点进行传播,提高系统的安全性是防病毒的一个重要方面。但完美的系统是不存在的,过于强调提高系统的安全性将使系统多数时间用于病毒检查,系统失去了可用性、实用性和易用性。另一方面,信息保密的要求让人们在泄密和抓住病毒之间无法选择。     

蜗轮蜗杆副的空间操作器应用研究

随着机器人技术在空间领域的发展,需要有一种结构紧凑、简单可靠的机械机构用于机器人末端操作器的传动。蜗轮蜗杆副具有传动简便等优点,特别适于作为对夹式操作器的传动机构。针对蜗轮蜗杆副空间环境适应性研究尚不充分的问题,采用分析和试验相结合的方法对蜗轮蜗杆在机器人操作器中的安装实现、润滑、振动、高低温及寿命进行了研究。利用热真空罐、振动台等测试手段模拟空间环境对研制的蜗轮蜗杆副进行了空间环境适应性测试。研究结果表明通过合理的设计,蜗轮蜗杆副可以具备空间应用的能力,能够满足空间环境要求。     

浅释蜗轮蜗杆传动中齿形的影响与改善

指出在蜗轮蜗杆减速装置中,齿形是否准确,是影响蜗轮蜗杆传动质量的主要原因之一。文章先对蜗杆的齿形进行了分析,又指出如何提高蜗轮蜗杆齿形的准确性问题,其他是有效提高蜗轮蜗杆的传动效率、降低传动噪声和温升的重要手段。并针对ZA型蜗轮蜗杆齿形的加工工艺及齿形的成形加以分析和探讨,总结出了ZA型蜗轮蜗杆齿形传动中的问题,提出了改善的方案,即在ZA型蜗轮蜗杆传动中,采用磨削蜗杆的齿形,克服由于齿形不准所造成的不良影响,来改善传动质量,提高产品品质。     

滚齿机静压工作台设计

开发研制了数控高精度双蜗杆蜗轮消隙静压工作台,该工作台具有高效、高精度、高刚度的特点.