Study of an eletrostatically actuated torsional micromirror with compliant planar springs

This paper presents modelling, fabrication and testing of a torsional micromirror suspended by two compliant ortho-planar springs attached at the sides. The proposed cantilevered serpentine spring is a single-chain frame, composed of nine beam segments to form a serpentine together with an initial segment and a final segment. Castigliano theory is used to formulate the spring constants under certain loads. Two equivalent spring constants for the micromirror are obtained according to structure analysis. The 2-DOF model for torsion and bending of the micromirror is presented. Finite element analysis (FEA) of the coupled domain of the structure is performed to verify the analytical results. Further validation of the prediction is carried out through static testing of a fabricated micromirror using a PSD (position sensing detector) sensor based experimental set-up. Due to relative compliancy of the dominant torsion mode, the fabricated micromirror is actuated to some angle at a lower voltage. The comparison between FEA and analytical results shows good agreement, demonstrating the accuracy prediction by the derived model. Small deviation from experiments is expected due to the nonlinear nature of electrostatic field.     

A simple mass-action model for the eukaryotic heat shock response and its mathematical validation

The heat shock response is a primordial defense mechanism against cell stress and protein misfolding. It proceeds with the minimum number of mechanisms that any regulatory network must include, a stress-induced activation and a feedback regulation, and can thus be regarded as the archetype for a cellular regulatory process. We propose here a simple mechanistic model for the eukaryotic heat shock response, including its mathematical validation. Based on numerical predictions of the model and on its sensitivity analysis, we minimize the model by identifying the reactions with marginal contribution to the heat shock response. As the heat shock response is a very basic and conserved regulatory network, our analysis of the network provides a useful foundation for modeling strategies of more complex cellular processes.     

RANGE PARAMETERS IN METALS AND ALLOYS

The formulae for calculating the electronic stopping power.for heavy ion implanting into metalare derived by using Wigner-Sietz radius r_s,equivalent charge,Fermi velocity and Ziegler'svalues of hydrogen electronic stopping power.Meanwhile the.formulae of electronic stoppingpower S_e(E)for alloys with boride or CsCl structure are also proposed.The calculated resultsare found as follows:these formulae are suitable only for mono-or bi-borides,but not forborides with more complex structure such as Cr_5B_3 or W_2B_5;the coefficient γ,of S_e(E)for al-loys with CsCI structure deviating from Bragg's S_e(E)is directly proportional to charge trans-fer in alloy.This means the larger the charge transfer is,the more stronger the metallic bondis.Hence the S_e(E)created by metallic bond in alloys will increase; there is a tendency for it toincrease with increasing separation of two components in alloy on either side of Cr group atsame periods,when the two components are in different periods,the tendency is more larger.     

氮气辅助氙离子束增强沉积TiN薄膜及其机械性能

本文提出一个合成TiN硬质薄膜的新方法,在氮气氛中,电子束蒸发沉积Ti的同时,用40keV的氙离子束对其进行轰击而合成TiN薄膜,该方法优于PVD和CVD之处在于合成温度低,薄膜与基体结合力强,其临界载荷达4.2kg,Knoop硬度达2200kg/mm~2,具有良好的耐磨损性能,报道了所合成的TiN薄膜在工业上应用的一些结果。     

强流脉冲离子束辐照W6Mo5Cr4V2高速钢表面改性研究

利用强流脉冲离子束(HIPIB)技术对W6Mo5Cr4V2高速钢进行表面辐照处理，HIPIB主要由C^n (70％)和H^ (30％)组成，束流密度为160A／cm^2，加速电压为250kV，脉冲宽度为80—100ns，能流密度为3—4J／cm^2，脉冲次数分别为1，3和5次,利用XRD，SEM和EPMA研究了HIPIB辐照处理前后该高速钢表面层结构和成分的变化，结果表明，HIPIB辐照处理使该高速钢表面层发生由马氏体α′-Fe向奥氏体γ-Fe转变，其表面产生许多火山口状熔坑，熔坑中心处富含离子束元素成分，熔坑的形成可以用“雨滴”模型进行解释,由于HIPIB辐照压缩波的影响，处理后在深度达200μm左右的范围内该高速钢的显微硬度提高，表面层耐磨性能提高近2倍，而且耐腐蚀性能也有所提高。     

Acrylic blends based on polyaniline. Factorial design

Processable conducting materials for large-scale utilization were prepared by mechanical mixing of polyaniline (PANI) paste and commercially acrylic resin. Doped PANI with organic phosphorus acid was synthesized. These blends can be used for the production of semiconductive paints with good corrosion resistance. By mixing doped PANI with commercially acrylic acid (SMP 63 AZUR SA) hard semiconducting and low elastic films are obtain. The effect of four variables was simultaneously studied: PANI (concentration), stirring speed (ST), mixing time (MT), dispersing agent (DA). Due to the number of variables, a factorial-design was chosen in order to reduce the number of experiments required in order to obtain coatings with high hardness and elasticity and semiconductive behavior. The results indicated that the influences of control factors decrease in order: PANI (concentration), mixing time (MT), dispersing agent (DA) and stirring speed (ST). From the studied variables, the resistance is significantly influenced by the two control factors PANI and MT.     

Generation-IV nuclear power: A review of the state of the science

The Generation-IV consortium seeks to develop a new generation of nuclear energy systems for commercial deployment by 2020–2030. These systems include both the reactors and their fuel-cycle facilities. The aim is to provide significant improvements in economics, safety, sustainability, and proliferation resistance. The systems selected for development are the very high-temperature gas-cooled reactor (VHTR), the sodium-cooled fast reactor (SFR), the gas-cooled fast reactor (GFR), the lead-cooled fast reactor (LFR), the molten salt reactor (MSR) and the super-critical water-cooled reactor (SCWR). UK organisations plan to contribute to the first three of these systems because of its existing capabilities and experience with gas-cooled systems, graphite cores, and SFRs. The science base for the VHTR and SFR systems is reasonably established, although there are gaps. For the VHTR, these include the performance of graphite at high neutron doses, and the performance of the fuel. For the SFR, the behaviour of fuels containing minor actinides, and processes for their recycling and refabrication into new fuel, must be established. The GFR presents many technical challenges, because it would need fuel and structural materials capable of withstanding extremes of fast neutron flux and high temperatures. Adequate heat removal from the core under fault conditions is likely to determine its feasibility.     

Frequency tuning AFM optical levers using a slot

Presented here is a theoretical analysis and experimental validation for the passive frequency tuning of atomic force microscope (AFM) optical levers. The natural frequencies of the optical lever are a function of material, geometry, and elastic properties of the microstructure. In this regard, the geometry of the structure can be altered in post-fabrication using such methods as laser drilling or focused ion beam machining. Several slot sizes are investigated and the eigenvalues obtained are mapped as a function of the slot length and width. In this regard, the elastic property of the optical lever can be tuned through material removal in either a mass or stiffness reduction arrangement in which a particular slot size and configuration is machined into the optical lever structure. In this work a slot cut into the optical lever using focused ion beam machining is used to passively tune the natural frequencies and mode shapes of suspended microcantilever structures used for optical lever scanning such as in AFM probes. This analysis will contribute to the performance optimization of AFM probes and microresonators. The Rayleigh–Ritz energy method is used for the theoretical analysis and a non-contact optical test method is used to obtain the natural frequency of several slotted AFM optical levers.     

Comparison of hydrodynamic parameters for countercurrent and cocurrent flow through packed beds

Hydrodynamic parameters have been determined in common equipment, i.e., same column and liquid and gas distributors, for cocurrent and countercurrent two-phase flow through fixed beds. The piston/dispersion exchange model (PDE) with usual Danckwerts' boundary conditions (closed/closed system) has been used to describe the liquid flow. A new imperfect pulse method has been used to estimate the PDE model parameters directly from the experimentally nonideal input and output response. The transition between trickle flow and pulse flow, for two-phase downflow, and the occurrence of flooding, for countercurrent flow, has been investigated using a macroscopic model for the two-phase flow.