A multi-scale computational strategy for structured thin sheets

Engineering trends show an increasing use of multi-layered and structured thin sheets in innovative applications where the layer thickness approaches the microstructural scale. This paper presents a strategy to homogenize the actual three-dimensional heterogeneous sheet towards a shell continuum. Consistent scale transition relations are derived, providing the ability to solve the (generalized) stress-strain fields on both the microstructural and the engineering scale are obtained in a direct and coupled manner.     

Experimental and Theoretical Study on High Strength Steel Extended Endplate Connections After Fire

In order to reveal more information and better understanding on the behavior and failure mechanisms of high strength steel (HSS) extended endplate connections at ambient temperature and after fire, an experimental and theoretical study has been conducted and presented in this paper. The provisions of Eurocode 3 are verified with the test results. Because strength of bolts decreases more rapidly than that of structural steels, failure modes of endplate connections may change after fire. Hence, a series of equations are proposed to predict failure modes of endplate connections after fire. Furthermore, FE simulations which can predicate the performance of HSS extended endplate connections with reasonable accuracy are adopted to study the behaviors of the connections after cooling down from various fire temperatures and to validate the accuracy of the proposed equations. Moreover, a parametric study is carried out to explore an optimization design method. It is found that the current provisions of EC3 can justifiably predict failure modes and plastic flexural resistances of HSS extended endplate connections both at ambient temperature and cooling down from 550 °C, but it is not the case for their initial rotational stiffness and rotation capacity. In order to avoid brittle failure mode of endplate connections after fire, appropriately increasing the diameter or grade of bolts in the design is suggested. What is more, the match of steel grade and thickness of column flange and endplate as well as beam should be considered in the optimization design of beam-column endplate connections.     

Channelled optical fibre photoreactor for improved air quality control

An optical fibre reactor with 30 hexagonal-shaped channels distributed within the optical fibre structure was investigated as a gas-phase photocatalytic reactor. TiO₂ photocatalyst, with SiO₂ sol acting as a binder, was coated on the channel walls at a thickness of 1.5 μm. Effective light propagation lengths of 3.4 and 4.9 cm were observed for incidental angles of 81.5° and 87.1°, respectively. The TiO₂-coated channelled optical fibre reactor (COFR) was assessed for the photocatalytic degradation of gas-phase ethylene. The photocatalytic reaction rate of ethylene degradation was linear with respect to the incident photons. The reaction rate order for the incident photons was determined to be 0.93. Despite a longer effective light propagation length for an incidental angle of 87.1°, the quantum yield was independent of the incidental angle. The independence of the quantum yield on the incident photons and the angle of light incidence was attributed to the COFR design, where the propagating light was wholly confined within the reactor and, in turn, more effectively utilised by the TiO₂.     

正交异性钢桥面板改造的组合粘结系统

<正>交异性钢桥面板改造的问题在于既有钢板与第二个钢板的粘结,以降低应力和增加正交异性钢板的使用寿命。通过试验和分析,对梁的弯曲性能进行参数研究。试验考虑不同厚度、温度和跨度的影响。从试验结果可见,应力降低与温度无关。最小化第二块钢板的厚度及最大化粘结层厚度,可降低重量,增加组合结构的刚度,这是最有效的解决方法。组合梁的弹性性能和屈服荷载取决于钢板的性能,温度的影响不显著。然而,粘结层的受剪最终导致梁的破坏,而粘结层的性能受温度的影响较大。     

Detection of Legionella spp. and some of their amoeba hosts in floating biofilms from anthropogenic and natural aquatic environments

Floating biofilms develop at the water-air interface and harbor numerous microorganisms, some of which are human pathogens like Legionella pneumophila. The presence of Legionella spp. and especially L. pneumophila in such biofilms was investigated. In parallel, the occurrence of Naegleria spp., Acanthamoeba spp., Willaertia spp., Vahlkampfia spp. and Hartmanella spp. was determined and it was examined whether Acanthamoeba spp. isolates were naturally infected with L. pneumophila bacteria. Eight anthropogenic and 37 natural aquatic environments were sampled between June and August 2005. Both Legionella spp. and L. pneumophila were present in 100% of the floating biofilms of the anthropogenic aquatic systems. Eighty-one percent of all natural floating biofilm samples were positive for Legionella spp. and 70% of these samples were positive for L. pneumophila. Legionella concentrations were in the range of 10(1)-10(2)cells/cm(2). Naegleria spp. and Acanthamoeba spp., two well-known L. pneumophila amoeba hosts, were present in 50-92% and 67-72% of floating biofilm samples, respectively. Acanthamoeba spp. isolates appeared to be naturally infected with L. pneumophila bacteria as proved by fluorescent in situ hybridization.     

Statistical modeling of reliability in logic devices

Due to continuous technology scaling VLSI circuits feature an increasing susceptibility to transient faults. While complete elimination of errors cannot be guaranteed, current mitigation techniques based on circuit improvement or architectural measures cause a large overhead in terms of area and energy consumption. A more efficient possibility to cope with transient faults can be to tolerate hardware errors at low physical levels and handle them at higher system levels. This can be achieved by reusing error handling capabilities – such as channel decoders – or introducing specialized error correction blocks that take advantage of the system characteristics by concentrating the effort on the components and bits most crucial for system operation. To enable this approach the influence of hardware errors on system performance needs to be evaluated, requiring spatial and temporal models of error propagation in the system. Since Monte Carlo simulation of complex systems is not feasible, a statistical modeling technique of logic gates and circuits is introduced. This approach allows modeling of noise and variability influences on logic gates as well as correlation due to reconvergent fan-out with an error of 5% compared to Monte Carlo simulation but with considerably less runtime.     

Whole-body kinetics and dosimetry of L-3--123I-iodo-alpha-methyltyrosine

BACKGROUND: Desflurane anesthesia can produce cerebral metabolic depression and increase cerebral blood flow. We evaluated the effect of desflurane on brain tissue oxygen pressure (PO2), carbon dioxide pressure (PCO2) and pH during neurosurgery. METHODS: Following a craniotomy, the dura was opened and a Paratrend 7 sensor, which measures PO2, PCO2, pH and temperature, was inserted into brain tissue. In 6 control patients in group 1, anesthesia was maintained constant with 3% end-tidal desflurane over 60 min, including a 30-min stabilization period. In group 2, 9 patients were ventilated with 3% desflurane under baseline conditions. After a 30-min stabilization period, baseline tissue gases and pH were measured and end-tidal desflurane was increased to 6% and then 9% for 15-min intervals. Mean arterial pressure (MAP) was maintained with intravenous phenylephrine. RESULTS: Under baseline conditions, cardiovascular and brain tissue measures were similar between the 2 groups. Increasing end-tidal desflurane from 3% to 9% produced burst-suppression EEG in all patients and significantly increased tissue PO2 and pH and decreased PCO2. No parameters changed significantly in the control group during steady-state anesthesia. CONCLUSION: These results show that 9% desflurane can improve brain tissue metabolic status before temporary brain artery occlusion if cerebral perfusion pressure is maintained. This may be particularly important in patients with symptoms of ischemia before surgery.     

Effect of additives on the melt rheology and thermal degradation of poly[(R)‐3‐hydroxybutyric acid]

Thermal degradation of poly[(R)−3‐hydroxybutyric acid] (PHB) during melt mixing results in random chain scission that produces shorter polymer chains containing crotonic and carboxyl end groups. One way of preventing this serious reduction of molar mass is to add agents that react with at least two of the newly generated end groups. Different types of commercially available additives known to react with carboxyl group, namely bis(3,4‐epoxycyclohexylmethyl) adipate (BECMA), 2,2'‐bis(2‐oxazoline) (BOX), trimethylolpropane tris(2‐methyl‐1‐aziridinepropionate) (PETAP), triphenyl phosphate (TPP), tris(nonylphenyl) phosphate (TNPP), polycarbodiimide (PCDI), and poly(methyl metharylate‐co‐glycidyl methacrylate) (GMA.MMA) were mixed with PHB by cocasting from solution in chloroform. Dynamic rheology as well as measurements of molar masses before and after dynamic analysis was used to evaluate the effect of the additives on the melt stability of PHB. Measurements of the dynamic shear modulus and the molar mass of molten PHB with the additives PCDI and GMA.MMA showed a minor improvement on the thermal stability. Furthermore, TPP and TNPP did not affect the thermal stability of PHB, whereas the presence of BECMA, BOX, and PETAP gave a strong decrease of the dynamic modulus compared with neat PHB. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41836.     

Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): A pilot study.

Heart rate telemetry was explored as a means to access animal emotion during social interactions under naturalistic conditions. Heart rates of 2 middle-ranking adult females living in a large group of rhesus macaques (Macaca mulatta) were recorded along with their behavior. Heart rate changes during 2 types of interactions were investigated, while controlling for the effects of posture and activity. The risk of aggression associated with the approach of a dominant individual was expected to provoke anxiety in the approachee. This prediction was supported by the heart rate increase after such an approach. No increase was found when the approacher was a kin or a subordinate individual. The tension-reduction function of allogrooming was also supported. Heart rate decelerated faster during the receipt of grooming than in matched control periods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)