CORNet: An OBS metro ring network with QoS support and fairness control

The rapid evolution of networks has been driven by new advances in enabling technologies and the explosive growth of Internet traffic. Optical Burst Switching (OBS) is not only cost-effective, but also provides high throughput, high bandwidth utilization, and low transmission latency. These benefits make OBS a viable solution for next-generation Metro Area Networks (MANs) in which the traffic models will be changed more dramatically than in today’s networks. This paper employs Wavelength Division Multiplexing (WDM) technology to construct a loss-free OBS metro ring architecture designated as the Collision-free Optic-burst Ring Network (CORNet). The proposed architecture ensures a collision-free transmission of data bursts, while retaining the advantage of the statistical multiplexing provided by conventional OBS networks. A novel distributed Medium Access Control (MAC) protocol to integrate the support of differentiated service and fairness access in CORNet is presented. The proposed Quality of Service (QoS) provisioning mechanism adopts a bandwidth-reservation approach which combines real-time transmission establishment and termination routines. Furthermore, a credit-based fairness control scheme is designed to guarantee the transmission fairness of best-effort traffic. Simulation results are presented to demonstrate that the proposed CORNet system provides good performance for real-time traffic while simultaneously providing significant performance improvements for best-effort traffic.     

重力应激下心血管循环系统建模仿真研究进展

重力应激通过改变血液流体静压对人体心血管循环系统产生不利影响。了解心血管循环系统在不同重力应激下的工作机制,有利于建立合理有效的防护措施。总结了人体心血管循环系统的建模方法,回顾了适用于重力应激下的心血管循环系统模型的发展进程,阐述了重力变化对心血管循环系统影响的研究及应用现状,介绍了作者的研究成果,并指明了未来的研究发展方向。     

寒地建筑外界面形态研究

建筑外界面的形态是建筑的第一印象和构成建筑整体形象的关键之处.本文旨在探讨寒冷地区建筑设计中外界面形态的问题,从视觉因素入手,阐明建筑的结构、材料等方面对它的影响和表达,探索寒地建筑外界面形态的特殊性,进而寻求适应寒地气候条件及环境的建筑外界面设计方法.     

模糊评价法表征复合材料层合板低能量冲击行为

通过模糊综合评判的方式,建立复合材料低能量冲击表面损伤与其失效的数学判据。复合材料受到冲击后的表面损伤是冲击程度最直观的表现,因此,对复合材料冲击行为的分析,应基于其表面损伤来进行。本研究选择的观测工具为超景深显微镜,观测、探究了复合材料试样受到冲击后的表面损伤情况,建立损伤程度与材料冲击门槛值之间的数值关系。经实验验证,该数值关系可以精确判断材料是否失效。同时也验证了不同厚度的复合材料,其失效时的表面损伤有某些共同特性,本文给出的判据可以在树脂基复合材料中通用。     

Performance of fiber reinforced asphalt concrete under environmental temperature and water effects

This paper studies the reinforcing effects and mechanisms of fibers for asphalt concrete (AC) mixtures under the environment temperature and water effects. Four typical fiber types – polyester, polyacrylonitrile, lignin and asbestos – are studied. Laboratory tests were conduct on the fiber reinforced AC (FRAC) to measure its strength, strain and fatigue behavior. Results show that fibers have significantly improved AC’s rutting resistance, fatigue life, and toughness. The flexural strength and ultimate flexural strain, and the split indirect tensile strength (SITS) at low temperature have also improved. The polymer fibers (polyester and polyacrylonitrile) have improved rutting resistance, fatigue life, and SITS more significantly than lignin and asbestos fibers, which may be primarily due to their greater networking function; while lignin and asbestos fibers result in greater flexural strength and ultimate flexural strain, which may be primarily due to their greater asphalt stabilization effect. However, fiber’s effect under the water freezing–thaw effect does not seem promising, and the SITS of FRAC with lignin and asbestos fibers even reduces to some extent under this effect. It is also found that a fiber content of 0.35% by mass of mixture achieves the optimum performance outputs of rutting resistance and SITS for polyester fiber.     

Multicriteria optimization of cold-formed thin-walled beams with generalized open shape under different loads

The paper presents an analysis of the optimal design of cold-formed beams with generalized open shapes under pure bending, uniformly distributed loads, concentrated loads and axial loads with constant bending moment. The optimization problem includes the cross section area as the first objective function and the deflection of a beam as the second one. The geometric parameters of cross sections are selected as design variables. The set of constraints includes global stability condition, selected forms of local stability conditions, strength condition and technological and constructional requirements in a form of geometric relations. The strength and stability conditions are formulated and analytically solved using mathematical equations. The optimization problem is formulated and solved with help of the Pareto concept of optimality. The numerical procedure, based on the Messac normalized constraint method, include discrete, continuous and discrete-continuous sets of design variables. Results of the numerical analysis for different loads of beams with monosymmetrical cross section shapes are presented in tables.     

渡槽伸缩缝嵌缝硅橡胶密封材料的制备性能及应用研究

该文介绍了硅橡胶制备方法,分析了其组成结构与性能之间的关系,并将其用于渡槽伸缩缝嵌缝密封止水,提出施工工艺和质量控制措施.     

Structural health monitoring of bonded composite repairs – A critical comparison between ultrasonic Lamb wave approach and surface mounted crack sensor approach

The effectiveness of the Lamb waves Acoustic-Ultrasound Structural Health Monitoring (SHM) technique for the determination of the adhesive joint failure was evaluated and compared to that of another SHM technique: Surface Mountable Crack Sensor (SMCS). A commercially available Acoustic-Ultrasound system was used. The SMCS consists of a “hot spot” monitoring system based on a three-layer electrically insulating and conductive paint. An electrical signal is used as a boolean operator for the characterization of the passage of damage through the sensor and the underlying material. The coupons consisted of carbon fiber substrates with boron patches bonded to them. The advantages and disadvantages of both techniques are discussed. It has been demonstrated that the Lamb waves Acoustic-Ultrasound technique possesses the capability to identify and quantify damage in a bonded repair. The SMCS proved to be a successful SHM technique for the monitoring of the formation of a disbond at the edges of the patch. All results were validated using the C-Scan ultrasound method.