Calibration of ultrahigh vacuum gauge from 10 Pa to 10 Pa by the two-stage flow-dividing system

A new two-stage flow-dividing system has been developed for the calibration of ultrahigh vacuum gauges from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂. This system is designed based on the techniques for our previously developed calibration system in the range from 10⁻⁷ Pa to 10⁻² Pa. Three modifications were performed to extend the calibration pressure to a lower range. The relative standard uncertainty of the generated pressure (k = 1) is in the range from 2.3% to 2.6%, from 10⁻⁹ Pa to 10⁻⁵ Pa. The characteristics of ultrahigh vacuum gauges were also examined by using this system. The stabilities of the pressure reading, the linearity, the temperature dependence, and the long-term stability were examined. These results show that the calibration of ultrahigh vacuum gauges is possible in the range from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂ with the uncertainty of about 6.0% (k = 2) by this new system.     

INRIM continuous expansion system as high vacuum primary standard for gas pressure measurements below 9 × 10 Pa

The continuous expansion system can be considered the state of the art for pressure measurement in the ultra high vacuum range. In the last years, at INRIM, a new continuous expansion system was designed, assembled and characterized. The system is the high vacuum primary standard in the pressure range from 1 × 10⁻⁶ Pa to 9 × 10⁻² Pa with relative standard uncertainty ranging from 2.1% at 1 × 10⁻⁶ Pa down to 0.4% at 9 × 10⁻² Pa. The system is based on the passing of a measured gas flow through a fixed and known conductance. The gas flow is generated and measured by a primary gas flowmeter based on the constant-pressure-variable-volume method.In the first part of the paper both a correction for the effect of transitional flow through the orifice and a new analytical evaluation of orifice conductance are presented. In the second part the accuracy of the system and the pressure uncertainty evaluation are described.     

The new method of traceability of a force-balanced piston gauge used as primary vacuum standard

The force-balanced piston gauge is a primary vacuum standard developed in the 1990s. The general principle of the instrument was first presented in Ooiwa A (Metrologia 30 (1994) 607). Non-rotating piston is connected to an electronic dynamometer and centered by means of transient gas flow in a double tapered gap between piston and cylinder. More details about it can be found in Delajoud, Girard(NCSL International Workshop and Symposium 2002; Vakuum Forschung Praxis 15 (2003) 24) and Tesar, Prazak(Vacuum 67 (2002) 307).Czech Metrology Institute developed its own method of the primary traceability of this instrument through the determination of its effective area. In this paper, there will be described experimental setup of this comparison as well as the experimental results from the traceability calibrations of the effective area in gauge and absolute mode using experimental method of hydrostatic comparison with the classical rotating piston balances and a digital non-rotating piston balance. It will, of course, include the uncertainty budget of this way of traceability and the final uncertainty of the pressure generation of the instrument.     

The new state special primary standard for the unit of electrical potential (the volt) in the frequency range 10–3·10<Superscript>7</Superscript> Hz

The structure and principal metrological characteristics are considered for the new State special primary standard for the volt.     

LixCoO2 (0<x<-1): A new cathode material for batteries of high energy density

A new system Li_xCoO₂ (0<x〈-1) has been prepared by electrochemical extraction of lithium from the parent LiCoO₂ ordered rock-salt structure. Measured open-circuit voltages with respect to lithium metal are approximately twice those of Li_xTiS₂ (0〈-x〈-1), and a theoretical energy density of 1.11 kWh kg^?1 is calculated for $\text{Li}{}_{\mathrm{x}}\text{CoO}{}_2\text{Li}$. Preliminary voltage-composition curves show low overvoltages and good reversibility for current densities up to 4 mA cm^?2 over a large range of x.     

A new proposal for assessment of the fatigue strength of steel butt‐welded joints improved by peening (HFMI) under constant amplitude tensile loading

Experimental fatigue data for butt‐welded joints in as‐welded condition and under constant amplitude tensile loading were analysed using the effective notch stress system and a new master curve analysis that takes the local stress ratio, R_local, into account. The local stresses needed for computation of R_local are calculated with the notch strain approach in conjunction with the reference radius concept. The main focus was to predict with the derived master curve the fatigue strength of peened butt‐welded joints. The lowest surface residual stresses after peening were first estimated based on reported measurements and an analytical lower bound result. The predictions showed quite similar strength dependences and FAT values as reported for high‐frequency mechanical impact treated welds for applied stress ratio R = 0.1. The benefits of peening reduce faster for higher strength steels when R increases. When R = 0.5, the FATs are practically the same for all steel grades.     

In vivo evaluation of a new composite mesh (10% polypropylene/90% poly-<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) for hernia repair

The increasing use of mesh insertion for groin hernia repair is dashed by a worrying prevalence of chronic pain frequently related as a reaction to the biomaterial implantation. Thus, new biocompatible prosthesis, designed as a composite material associating polypropylene (PP) and long-term absorbable material, are now under development. In the present study, the typical commercially available Prolene mesh has been compared to two new meshes designed with 3-fold less PP, either alone (light PP) or associated with poly-L-lactic acid (PP-PLA) accounting for 90% of the mesh weight. These PP-mesh variants were implanted in an extraperitoneal position within the abdominal wall of 90 rats. Mesh adhesion and size were determined at autopsy 2, 4 and 8 weeks after implantation (10 animals per group) and morphometric parameters of the host tissues by light microscopy. Prolene and light PP-meshes presented intra-corporeal shrinkage and tissue adhesion, both more pronounced with light-PP, whilst PP-PLA meshes were not affected in spite of a strongest fibrosis. In contrast to Prolene and even more with light PP meshes, inflammation and cell-mediated immune responses were reduced without occurrence of angiogenesis or oedema. All these findings advocate together for a better tolerance of this new composite biomaterial, more likely due to a low macrophage response that appeared statistically correlated to the absence of mesh shrinkage and to a decreased adhesion to the tissue. On the basis of these experimental observations, it could be expected that the better tolerance of this composite biomaterial may avoid both long-term pain and recurrence when used as plug in groin hernia repair.     

Synthesis and characterization of LiCo0.3−xGaxNi0.7O2 (x = 0, 0.05) as a cathode material for lithium ion battery

The single phase of LiCo_0.3−xGa_xNi_0.7O₂ (x = 0, 0.05) was synthesized by a sol–gel method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance. The powders are homogeneous and have a good-layered structure. The synthesized LiCo_0.25Ga_0.05Ni_0.7O₂ exhibits better electrochemical performance with an initial discharge capacity of 180.0 mAh g⁻¹ and a capacity retention of 95.2% after 50 cycles between 2.8 and 4.4 V at 0.2C rate. The study on the structural evolution of the material during the cycling shows that Ga-doping improves the structure stability of LiCo_0.3Ni_0.7O₂ at ambient temperature and 55 °C. Meanwhile, Ga-doping not only suppresses the alternating current (AC) impedance of LiCo_0.3Ni_0.7O₂ but also promotes the Li⁺ diffusion in LiCo_0.3Ni_0.7O₂. Furthermore, thermal stability of the charged LiCo_0.25Ga_0.05Ni_0.7O₂ is improved, which may be attributed to the retard of O₂ evolution in LiCo_0.3Ni_0.7O₂ and the suppression of electrolyte oxidation during cycling by Ga-doping_.     

A cell‐based smoothed discrete shear gap method (CS‐FEM‐DSG3) based on the C0‐type higher‐order shear deformation theory for dynamic responses of Mindlin plates on viscoelastic foundations subjected to a moving sprung vehicle

A cell‐based smoothed discrete shear gap method (CS‐FEM‐DSG3) based on the first‐order shear deformation theory (FSDT) was recently proposed for static and dynamic analyses of Mindlin plates. In this paper, the CS‐FEM‐DSG3 is extended to the C⁰‐type higher‐order shear deformation plate theory (C⁰‐HSDT) and is incorporated with damping–spring systems for dynamic responses of Mindlin plates on viscoelastic foundations subjected to a moving sprung vehicle. At each time step of dynamic analysis, one four‐step procedure is performed including the following: (1) transformation of the weight of a four‐wheel vehicle into the sprung masses at wheels; (2) dynamic analysis of the sprung mass of wheels to determine the contact forces; (3) transformation of the contact forces into loads at nodes of plate elements; and (4) dynamic analysis of the plate elements on viscoelastic foundations. The accuracy and reliability of the proposed method are verified by comparing its numerical solutions with those of other available numerical results. Copyright © 2014 John Wiley & Sons, Ltd.