Dynamic investigation on composite flexible multi-body system considering thermal effect

The dynamic performance of composite flexible multi-body system under the simultaneous action of thermal fields and driving constraint is analyzed. Based on strain-displacement relation of the Mindlin plate theory which includes transverse shear deformation, and considering thermal effect, variation equations of laminated plate are derived by the principle of virtual work. The finite element method is used for discretization. According to kinematics constraint relation, dynamic equations for spatial slider-crank system are established. Simulation results show that spatial deformation (torsion deformation) appears in the multi-layered composite slider-crank mechanism which is simulated with planar motions. Furthermore, the influence of coupling between thermal expansion and flexible deformations of non-symmetrical composite plates on the large overall motion under the uniform temperature field is investigated. Finally, significant change in constraint force due to the spatial deformation is shown.     

Novel mesh technique and its application in the wind field simulation for flexible spatial structure

In this paper, novel mesh techniques are proposed for wind field simulation of flexible spatial structure. For mesh generation, an interpolation strategy is presented to obtain a mesh system with variable density. Two spatial structure examples are used to examine the efficiency and applicability of this technique. Then based on the structured mesh system generated by the technique, the mesh nodal coordinates are updated to adapt the moving boundary conditions by means of the mapping interpolation functions and some examples are given to verify the effectiveness. Furthermore, the constrained counterforce distribution technique and projection interpolation strategy are developed to implement the data exchange on the interaction surface of wind and structure. Finally, the computational accuracy is numerically validated.     

Numerical analysis and experimental study of the effect of workpiece thickness on flow field in laser cutting

Based on Navier-Stokes equation and renormalization group (RNG) onflow model, the 3D symmetrical impinging jet model of laser cutting is established by adopting a taper nozzle and a convergence nozzle. Numerical simulation of gas flow in laser cutting is used to investigate the effect of workpiece thickness on flow field of assist gas in cutting slot. The isolines of static pressure as well as the distributions of static pressure and velocity are analyzed in details with different workpiece thickness, and the trend of dynamics characteristics of gas jet is shown in the study. For taper nozzles and convergence nozzles, the dynamic structure of assist gas being close to the lower surface of workpiece is exacerbated while the cutting quality and cutting efficiency become worse with the increasing of workpiece thickness. The parallel degree between assist gas and the axis of convergence nozzle is better than that of taper nozzle after the gas goes out of the nozzles. Two typical subsonic nozzles are designed for the cutting experiment at the end of the paper.     

Mechanical behaviors of the foot after individual releases of plantar fascia and ligaments during the balanced standing

To quantify mechanical effects of plantar fascia and ligaments on the arch structure, a 3D finite element model of the foot was created to simulate the balanced standing posture. Four cases after individual releases of plantar fascia, spring ligament, long and short plantar ligaments were simulated respectively to compare their consequences to the predictions of the intact structure. It was founded that the foot arch didn’t collapse obviously after any individual release of these structures. As plantar fascia was released, tensions of plantar ligaments were largely increased. Long and short plantar ligaments performed mutual compensation functions.     

Mesh motion approach based on spring analogy method for unstructured meshes

Mesh motion strategy is one of the key points in many fluid-structure interaction problems. One popular technique used to solve this problem is known as the spring analogy method. In this paper a new mesh update approach based on the spring analogy method is presented for the effective treatment of mesh moving boundary problems. The proposed mesh update technique is developed to avoid the generation of squashed invalid elements and maintain mesh quality by considering each element shape and grid scale to th...     

H_∞ Autopilot Design for Autonomous Underwater Vehicles

The design approach of H∞ autopilot for autonomous underwater vehicles (AUVs) is proposed. Comprised by the three sub-controllers,i.e. speed,heading and depth controllers,the designed autopilot has advantage over existing H∞ control of AUVs. The overshoot in speed,heading and depth control systems under step commands is restricted by refining the weighting function for robust stability. The dynamic performance of heading and depth control systems is improved by feeding back yaw rate and pitch angle,respecti...     

Fully secure revocable attribute-based encryption

Distributed information systems require complex access control which depends upon attributes of protected data and access policies. Traditionally, to enforce the access control, a file server is used to store all data and act as a reference to check the user. Apparently, the drawback of this system is that the security is based on the file server and the data are stored in plaintext. Attribute-based encryption (ABE) is introduced first by Sahai and Waters and can enable an access control mechanism over encrypted data by specifying the users’ attributes. According to this mechanism, even though the file server is compromised, we can still keep the security of the data. Besides the access control, user may be deprived of the ability in some situation, for example paying TV. More previous ABE constructions are proven secure in the selective model of security that attacker must announce the target he intends to attack before seeing the public parameters. And few of previous ABE constructions realize revocation of the users’ key. This paper presents an ABE scheme that supports revocation and has full security in adaptive model. We adapt the dual system encryption technique recently introduced by Waters to ABE to realize full security.     

论蓬莱出土的高丽古船在韩国船舶史上的意义

1984年和2005年在山东省蓬莱市所发掘的4艘古船中,根据船体舷板的连接方式判断,第3号船和第4号船公认为是高丽船.由于蓬莱第4号船的船体的残存量很少,因此无法推断其原来的结构特点,但被称之为高丽船的第3号船,因其比较完整地保存了船底板、舷板以及其他相关部件,可供我们推断其结构特点.第3号船的舷板是采用传统韩船的制造方式进行连接,在船体内部并没有设置加龙木而是采用设置隔舱板的方法提高船体的横向强度.韩国船舶史界普遍认为传统的韩船是通过设置加龙木来提高船体的横向强度,因此蓬莱出土的高丽古船,在韩国的学术界乃至在中国的学术界都引起了相当大的争论.在这篇论文中,准备初步探讨拥有隔舱板的韩国古船--蓬莱3号船,在韩国船舶史研究方面带来的意义;同时回顾-下所谓"在韩船中没有隔舱板"观点的形成过程,以及在考察蓬莱高丽古船的发掘概况和结构特征的基础上,重新整理其他学者对蓬莱3号船的有关观点.     

Research on Spatially Adaptive High-Order Total Variation Model for Weak Fluorescence Image Restoration

Photoacoustic imaging acquires the absorption contrast of biological tissue with ultrasound resolution. It has been broadly investigated in biomedicine for animal and clinical studies. Recently, a micro-electro-mechanical system (MEMS) scanner has been utilized in photoacoustic imaging systems to enhance their performance and extend the realm of applications. The review provides a recap of recent developments in photoacoustic imaging using MEMS scanner, from instrumentation to applications. The topics include the design of MEMS scanner, its use in photoacoustic microscopy, miniature imaging probes, development of dual-modality systems, as well as cutting-edge bio-imaging studies.     

Full Duplex Communications for Next Generation Cellular Networks: The Capacity Gain

Full duplex communication highly improves spectrum efficiency of a wireless communication link. However, when it is applied to a cellular network, the capacity gain from this technology remains unknown. The reason is that full duplex communication changes the aggregate interference experienced by each communication link in cellular networks. In this paper, the capacity gain from full duplex communication is studied for cellular networks of 4G and beyond, where the same frequency channel is adopted in each cell. A two-layer Poisson point process (PPP) is adopted to model the network topology, and stochastic geometry is employed to derive the coverage probability and the average capacity of typical link in a cellular network. On the basis of these derived parameters, the capacity gain from full duplex communication is determined. Numerical results reveal that without mutual interference cancellation (MIC), the capacity gain is small under various power levels; with perfect MIC at base stations, the capacity gain can exceed 60%; with imperfect MIC at base stations, the capacity gain decreases quickly even with a slight drop of MIC performance.