Total Lagrangian particle method for the large-deformation analyses of solids and curved shells

A high-accuracy smoothed-particle hydrodynamics (SPH) method for a large-deformation solid is developed from two aspects: improving the completeness of the approximation function and deducing the governing equation in the undeformed configuration. On the basis of Combescure’s researches and our previous studies, the SPH shell theory based on the Mindlin–Ressiner plate is detailed, which has overcome the unbridgeable drawbacks of solid modeling of thin structures and pushed forward the engineering applications of solving large-deformation and other nonlinear issues. Afterward, several treatments of SPH solid and shell are carried out, including the hourglass mode, boundary conditions and irregular structures; moreover, the corresponding validations are also conducted to reveal the feasibility and effectiveness of the proposed treatments. Finally, the accuracy of the present SPH program is verified further through two benchmarks of a curved shell.     

Contact properties determination of macroscopic fine disperse glass particles via compression tests in normal direction

The paper describes the deformation behavior of spherical, dry and non-porous particles during a single particle compression test in normal direction. Therefore a compression tester was built. Industrial used soda lime glass particles with two macroscopic fine disperse sizes (d_1,50,3 = 284.30 μm and d_2,50,3 = 513.20 μm) were applied as model material to investigate the micromechanical contact behavior. In order to influence the elastic-plastic contact properties of particles, the surfaces were altered with chemical modification by means of silanization.The determination of various micromechanical contact properties (e.g. adhesion force, modulus of elasticity and contact stiffness) was carried out model-based with the contact model ‘stiff particles with soft contacts’ by means of a back-calculation.It could be shown that the model-based determination of material properties was a good alternative compared to the comprehensive tensile tests and pull-off force measurements.In addition to the gained normal force-displacement data in normal direction, the friction limits for tangential loading and rolling with the load-dependent adhesion force were model-based determined.     

Low temperature synthesis of ultrafine non vermicular α-alumina from aerosol decomposition of aluminum nitrates salts

In this paper, spherical, smooth and unagglomerated ultrafine amorphous powder particles were prepared by ultrasonic spray pyrolysis (USP) of easy-handling aqueous aluminum nitrate salts increasing the precursor solute concentration to 0.5 mol L^?1 and reducing the pyrolysis temperature to 700 °C. The transformation of the USP alumina powders into α-Al₂O₃ was studied using combination of X-ray diffraction, electron microscopy, infrared spectroscopy, BET surface area, thermogravimetry and differential thermal analysis. A downward shift of the onset temperature of α-phase transformation to 900 °C has been detected using a larger precursor solution concentration and performing a milling before calcination due to an increase in the surface density of defects, in surface area and in anisotropic particle shape. Additional post-milling of the low calcined powders allowed the preparation of agglomerate-free pure ultrafine α-Al₂O₃ powder particles (～100 nm, 28 m² g^?1), free of vermicular microstructures.     

Tonometer prism sterilisation: a local and UK national survey.

PURPOSE: First to audit local adherence to a protocol of use of an alcohol wipe for each tonometry, and secondly to assess current practice nationally in the UK. METHOD: The audit was carried out at two units: The West Kent Eye Centre at the Princess Royal University Hospital (Orpington, UK) and Queen Mary's Hospital (Sidcup, UK). The standard set for this audit was 100% sterilisation. During a 1-week period in November 2005, the number of alcohol wipes was counted in each consultation room after outpatient clinics, with the doctors being assessed blind to the survey. The number of Goldman applanation tonometry intra-ocular pressures recorded by each clinician was counted by inspection of the medical records of patients seen. Secondly, departments listed in the UK Directory of Training Posts were contacted by telephone and the senior nurse was interviewed. They were asked directly about their department's tonometer prism sterilisation and management. RESULTS: The local audit showed only 54% of tonometry measurements were associated with sterilisation using an alcohol-impregnated wipe. The national survey included 140 of the 152 UK training departments. Thirty-three (23.6%) departments used disposable tonometer prisms routinely. The remaining 107 (76.4%) used non-disposable prisms. Eighty-five (60.7%) departments provided sodium hypochlorite for prism sterilisation, with 69 (81.2%) of these departments providing more than one prism/clinician to allow full exposure to the disinfectant. Twenty-two (15.7%) departments used alcohol wipes. Only 8 (7.5%) of the 107 departments using non-disposable prisms tracked these prisms, despite Royal College of Ophthalmologists guidelines that they should be. These same 8 (7.5%) departments replaced the non-disposable prisms as per manufacturer guidelines. 19.3% of charge nurses were aware of a policy for tonometry in patients with, or at risk of, prion disease. CONCLUSIONS: This study highlights that sterilisation of tonometer prisms was inconsistent in a local audit. Nationally, practices were varied. The majority of ophthalmology departments continued to use non-disposable tonometer prisms, but few seemed aware of the Royal College of Ophthalmologists' recommendation that disposable prisms are used in patients at risk of prion disease, and few track tonometer heads or replace them according to manufacturers guidelines. Use of disposable tonometer prisms would seem to reduce concerns about sterilisation, as well as prevent spread of common pathogens.     

Properties of enhanced mobile membranes via coloured Petri nets

Enhanced mobile membranes represent a rule-based formalism involving parallelism and mobility dependent on available resources. A translation of this formalism into coloured Petri nets is provided in order to analyse some important properties (reachability, boundedness, liveness, fairness) in enhanced mobile membranes.     

Dielectric,ferroelectric and field-induced strain behavior of K0.5Na0.5NbO3-modified Bi0.5(Na0.78K0.22)0.5TiO3 lead-free ceramics

Lead-free piezoelectric (1 ? x)Bi_0.5(Na_0.78K_0.22)_0.5TiO₃–xK_0.5Na_0.5NbO₃ (BNKT–xKNN, x = 0–0.10) ceramics were synthesized using a conventional, solid-state reaction method. The effect of KNN addition on BNKT ceramics was investigated through X-ray diffraction (XRD), dielectric, ferroelectric and electric field-induced strain characterizations. XRD revealed a pure perovskite phase with tetragonal symmetry in the studied composition range. As the KNN content increased, the depolarization temperature (T_d) as well as maximum dielectric constant (?_m) decreased. The addition of KNN destabilized the ferroelectric order of BNKT ceramics exhibiting a pinched-type hysteresis loop with low remnant polarization (11 μC/cm²) and small piezoelectric constant (27 pC/N) at 3 mol% KNN. As a result, at x = 0.03 a significant enhancement of 0.22% was observed in the electric field-induced strain, which corresponds to a normalized strain (S_max/E_max) of ～434 pm/V. This enhancement is attributed to the coexistence of ferroelectric and non-polar phases at room temperature.     

Analytically derived fragility relationships for the modern high‐rise buildings in the UAE

Investigating and planning for the expected damage that may hit the earthquake‐prone areas in the UAE should be undertaken in order to predict and mitigate earthquake losses. This paper discusses a framework for developing an essential driving engine in loss estimation systems, namely fragility relationships. Six reference structures, varying in height from 10 to 60 storeys, are selected due to the concentrated economic and human assets in this class of buildings. The reference structures are designed according to the building codes and construction practice adopted in this region. Inelastic fibre‐based simulation models are developed for the buildings using a verified analysis platform, which enables monitoring the spread of yielding and cracking during the multi‐step cyclic analysis. The ground motion uncertainty is accounted for using 20 input ground motions conforming to the latest understanding of the seismo‐tectonic characteristics of the UAE. A large number of inelastic pushover and incremental dynamic collapse analyses are deployed for the reference structures to derive the fragility relationships. The study illustrates the significance of assessing the vulnerability of a population of high‐rise buildings under the effect of various seismic scenarios and the need for expanding this study to cover other classes of structures in this region. Copyright © 2010 John Wiley & Sons, Ltd.     

溶胶-凝胶法制备KH-570改性纳米二氧化钛及其表征

以钛酸丁酯(TBOT)为前驱物,盐酸为催化剂,γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH-570)为改性剂,采用溶胶-凝胶法原位制备了KH-570改性的纳米二氧化钛,研究了KH-570用量对纳米二氧化钛表面改性效果的影响,并采用红外光谱(FT-IR)、X射线衍射(XRD)、粒径分析等手段对纳米二氧化钛进行了表征。结果表明:KH-570接枝到纳米二氧化钛表面,纳米二氧化钛为锐钛矿型;随着KH-570用量的增大,接枝率先上升然后稍有下降,当KH-570用量为TBOT质量的14.57%时,接枝率达到25.6%;与未加KH-570制备的二氧化钛相比,KH-570改性纳米TiO2的平均粒径减小且分布变窄,亲油性得到明显提高。