Molecular dynamics study on nanotube-resonators with mass migration applicable to both frequency-tuner and data-storage-media

We investigated the cantilevered carbon-nanotube-resonator including electromigratively movable nanoparticle via classical molecular dynamics simulations and continuum model. The change of the effective mass value, which was closely correlated with the position change of the encapsulated nanoparticle, could be regressed by a power function, the resonance frequency of the carbon-nanotube-resonator could be tuned by controlling the nanoparticle’s position, and the possible frequency-shift-ranges then reached 18–85%. The suggested device could be served as a data-storage-media for electromechanical nonvolatile-memory as well as a frequency-tuner.     

Codes based on BCK-algebras

The notion of a BCK-valued function on a set is introduced, and related properties are investigated. Codes generated by BCK-valued functions are established.     

The Navier–Stokes-αβ equations as a platform for a spectral multigrid method to solve the Navier–Stokes equations

This paper describes a spectral multigrid method for spatially periodic homogeneous and isotropic turbulent flows. The method uses the Navier–Stokes-αβ equations to accelerate convergence toward solutions of the Navier–Stokes equations. The Navier–Stokes-αβ equations are solved on coarse grids at various levels and the Navier–Stokes equations are solved on the “nest grid”. The method uses Crank–Nicolson time-stepping for the viscous terms, explicit time-stepping for the remaining terms, and Richardson iteration to solve linear systems encountered at each time step and on each grid level. To explore the computational efficiency of the method, comparisons are made with results obtained from an analogous spectral multigrid method for the Navier–Stokes equations. These comparisons are based on computing work units and residuals for multigrid cycles. Most importantly, we examine how choosing different values of the length scales α and β entering the Navier–Stokes-αβ equations influence the efficiency and accuracy of these multigrid schemes.     

Optimisation of location and dimension of SMC precharge in compression moulding process

The main goal of the present study is to optimise the precharge conditions such as the precharge location and dimensions that give significant effects on the mechanical performance of composite structures manufactured by the compression moulding process. As preliminary step of optimisation, we developed a manufacturing simulation program to predict the fibre volume fraction and fibre orientation. And coupled with this simulation program and a structural analysis program, a genetic algorithm (GA) is implemented to optimise the precharge conditions. The penalty function method and the repair algorithm are modified for handling constraints. The repair algorithm is applied to a symmetric structure and an arbitrary shape structure to find optimal precharge conditions.     

无线传感器网络中d-Hop 2-连通容错支配集的分布式构造算法

无线传感器网络随节点移动组成自我维持的自组织系统,采用连通支配集的虚拟骨干技术可使平面网络系统层次化而简化节点路由、管理和维护。但大规模无线传感器网络的连通支配集节点数目依然庞大,d-hop连通支配集可以大大减小支配集节点数目。另外,由于存在节点失效、链路断裂等无线特性,虚拟骨干网需要具备一定的容错性。在单位圆盘图网络模型中为构建精简且具有容错能力的虚拟骨干网,提出d-hop 2-连通支配集的分布式构造算法,先构造d-hop独立支配集后再连通形成d-hop 2-连通支配集。并从理论和仿真上对算法的复杂度、近似比和算法性能作了进一步探讨和验证。     

无线传感器网络中2-连通k-支配的容错连通支配集构造

无线传感器网络可采用连通支配集的虚拟骨干技术使平面网络层次化,但传感器节点的失效和链路的断裂会导致网络失败,虚拟骨干网最好具有容错性好、可靠性高的特性.对此,提出具有容错性的2-连通 -支配集的构造算法,以节点自身和邻域信息分布式地构造 -支配节点,利用最小生成树和块-割点图将 -支配节点2-连通.理论分析和实验仿真表明此算法具有较好的算法性能比,在中等规模网络中会产生更少的具有容错性的 -支配节点,可节省传感器节点的能量消耗和网络的通信开销.     

A theoretical and experimental investigation of the tool-tip vibration and its influence upon surface generation in single-point diamond turning

This paper presents a theoretical and experimental investigation of the influence of tool-tip vibration on surface generation in single point diamond turning (SPDT). Although it is well known that the relative vibration between the tool and the workpiece plays an important role in the surface generation in single-point diamond turning, most of the prior work has been focused on studying the relative tool-work vibration in the infeed (thrust force) direction while the significant contribution of the effect of the tool-tip vibration in the cutting force direction has been overlooked. In the present study, two characteristic peaks (twin peaks) are identified and found to be corresponding to the tool-tip vibrations by power spectrum density (PSD) analyses. The vibrations possess the features of small amplitude but high frequency. A physical model is proposed to capture the dominant factor based on the characteristic and it reveals that the twin peaks are attributed by the impact between the tool tip and workpiece and the process damping effect. Hence, a geometric model of surface roughness is proposed to take account of tool-tip vibration and it is verified through a series of experiments. The simulation results have been found to agree well with the experimental results.     

Dieless drawing steel wires using a dielectric heating method and modeling the process dynamics

Modern industries require the production of multi-functional, inorganic, micron-sized metal wires. This study suggests a novel method that could potentially offer a highly efficient dieless drawing technology for manufacturing thin stainless steel fibers. The method is based on a hot-working principle, using microwaves as the heat source and SiC as the susceptor. Experimental trials with a laboratory rig showed that the new system worked effectively for drawing the stainless steel wires and should be able to realize the diameter attenuation with a diameter reduction of up to 21%. The theoretical model describing the deformation behavior of the stainless steel wires in the working zone along with the constitutive equation of Bingham model modified with a power law and Zener–Hollomon parameter turned out to match very good with the actual results of the experiment. The coefficient of variation of the drawn wire diameter increased, as the draw ratio increased, which could be attributed to the occurrence of the narrow necking zone.     

Optimization of Co-content in C14 Laves phase multi-component alloys for NiMH battery application

The structural, electrochemical, and gas phase hydrogen storage properties of predominantly C14 crystalline phase alloys with partial replacement by Co (up to 2.5 at%) are reported. Minor phases, including C15 and cubic TiNi, were found by X-ray diffraction and contributed to the improved hydrogen diffusion through the alloy. The optimal Co-content of between 1.0 and 1.5 at% provides easy activation, high gas phase capacity, and a high discharge capacity. An optimized alloy formula also provided the smallest metallic nickel cluster size embedded in the surface oxide and the largest number of nickel clusters. In sealed cell studies, a Co-content of 1.5% gives the best performance in formation, cycle life, and charge retention, but has worse specific power and low temperature performance than some other compositions. The high-rate dischargeabilities at lower rates were found to be limited by surface reactions, not bulk diffusion.     

Synthesis,characterization and application of biopolymer-ionic liquid composite membranes

Biopolymer composite membranes based on chitosan doped with an ionic liquid (IL) 1-ethyl 3-methylimidazolium thiocyanate (EMImSCN) have been developed and characterized. The doped ionic liquid films show remarkable enhancement in ionic conductivity (σ). The Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and X-ray diffraction studies (XRD) affirmed the composite nature, good incorporation of ionic liquid and reduction in crystallinity of films, respectively. The interaction between ionic liquid, chitosan and iodide polymer electrolyte matrix was evaluated by cyclic voltammetry. The fabricated dye sensitized solar cell (DSSC) using this new biopolymer electrolyte membranes shows promising performance.