A review of methods for determining structural fire severity—Part II: Analysis and review

There is a risk of a building suffering unsustainable structural damage in the event of a large fire. Therefore, it is necessary to design buildings to withstand expected fires. A widely used simplified calculation method is the so-called “time-equivalence” method. There are significant concerns about the suitability of this method. This paper is part II of a twofold study examining the state of the art of time-equivalence methods. The purpose of this paper is to identify methods and/or analysis concepts which show the potential for use in modern design. A SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis is used for this purpose. However, as there is a large number of time-equivalence methods to assess, a numerical case study is first undertaken to identify methods which have sufficient accuracy to warrant further study. These analyses found that, while none of the time-equivalence methods studied have sufficient accuracy for use in their present form, the methods derived using the equal energy concept provide a good basis to model the effects of fire on a structure. This study recommends that a new time-equivalence method be developed using the equal energy approach.     

Fermi level pinning in Co-doped BaTiO3: Part II. Defect chemistry models

A first-principles informed grand canonical defect chemistry model capable of accounting for non-stoichiometry and partial equilibration of different sub-lattices is developed and used to study Mg and Mn doped, and (Mg+Y) and (Mn+Y) co-doped BaTiO₃ to elucidate the role of Mn and Y in improving the resistivity and resistance degradation of BaTiO₃ as observed by Ryu et al. in Part I of this series of papers. The model qualitatively captures the behavior of the samples in all conditions, reproducing the observed carrier plateau and increased resistivity of (Mn+Y) co-doped BaTiO₃, and expected trends in the concentrations of free oxygen vacancies with doping. These trends reflect the observed differences in degradation characteristics, and help explain the substantially improved degradation resistance of the (Mn+Y) co-doped samples. Our model adds to the mechanism proposed by Yeoh et al. that the Fermi level is pinned by the multivalent character of Mn_Ti in (Mn+Y) co-doped BaTiO₃ by giving insight into the role of barium vacancies, the site preferences of the dopants, and defect complexes in this mechanism. These insights provide a set of criteria in the search for sets of co-dopants with similar behaviors.     

Which visual measures affect change in driving difficulty after first eye cataract surgery?

Objective

To investigate self-reported driving difficulty before and after first eye cataract surgery and determine which visual measures are associated with changes in self-reported driving difficulty after surgery.

Methods

A cohort of 99 older drivers with bilateral cataract were assessed the week before and 12 weeks after first eye cataract surgery. Visual measures including visual acuity, contrast sensitivity, stereopsis and useful field of view were assessed. Self-reported driving difficulty was measured via the Driving Habits Questionnaire. Cognitive status was assessed using the Mini Mental State Examination. Regression analysis was undertaken to determine the association between changes in visual measures and self-reported driving difficulty after first eye cataract surgery.

Results

Overall, self-reported driving difficulty improved after first eye cataract surgery. However, 16% of participants did not improve and driving difficulty worsened in 11% following surgery. Improvement in driving difficulty score after first eye cataract surgery was associated with improved contrast sensitivity in the operated eye (p < 0.001), new glasses after surgery (p < 0.001), and fewer chronic health conditions (p = 0.016).

Conclusion

Contrast sensitivity rather than visual acuity was a significant factor affecting change in self-reported driving difficulty after first eye cataract surgery for bilateral patients. This has implications for driver licensing authorities worldwide that rely heavily on visual acuity as a measure of visual fitness to drive.     

Robust reduction of graphene fluoride using an electrostatically biased scanning probe

We report a novel and easily accessible method to chemically reduce graphene fluoride （GF） sheets with nanoscopic precision using high electrostatic fields generated between an atomic force microscope （AFM） tip and the GF substrate. Reduction of fluorine by the electric field produces graphene nanoribbons （GNR） with a width of 105-1,800 nm with sheet resistivity drastically decreased from 〉1 TΩ.sq.^-1 （GF） down to 46 kΩ.sq.^-1 （GNR）. Fluorine reduction also changes the topography, friction, and work function of the GF. Kelvin probe force microscopy measurements indicate that the work function of GF is 180-280 meV greater than that of graphene. The reduction process was optimized by varying the AFM probe velocity between 1.2 μm.s^-1 and 12 μm.s^-1 and the bias voltage applied to the sample between -8 and -12 V. The electrostatic field required to remove fluorine from carbon is -1.6 V.nm-1. Reduction of the fluorine may be due to the softening of the C-F bond in this intense field or to the accumulation and hydrolysis of adventitious water into a meniscus.     

An optimum step-size assignment for incremental LMS adaptive networks based on average convergence rate constraint

This paper presents an optimum step-size assignment for incremental least-mean square adaptive networks in order to improve its robustness against the spatial variation of observation noise statistics over the network. We show that when the quality of measurement information (in terms of observation noise variances) is available, we can exploit it to adjust the step-size parameter in an adaptive network to obtain better performance. We formulate the optimum step-size assignment as a constrained optimization problem and then solve it via the Lagrange multipliers approach. The derived optimum step-size for each node requires information from other nodes, thus with some justifiable assumptions, near-optimum solutions are derived that depend only on local information. We show that the incremental LMS adaptive network with near-optimal step sizes has improved robustness and steady-state performance. Simulation results are also presented to support the theoretical results.     

A novel integration of a green power-to-ammonia to power system: Reversible solid oxide fuel cell for hydrogen and power production coupled with an ammonia synthesis unit

Renewable energy is a key solution in maintaining global warming below 2 °C. However, its intermittency necessitates the need for energy conversion technologies to meet demand when there are insufficient renewable energy resources. This study aims to tackle these challenges by thermo-electrochemical modelling and simulation of a reversible solid oxide fuel cell (RSOFC) and integration with the Haber Bosch process. The novelty of the proposed system is usage of nitrogen-rich fuel electrode exhaust gas for ammonia synthesis during fuel cell mode, which is usually combusted to prevent release of highly flammable hydrogen into the environment. RSOFC round-trip efficiencies of 41–53% have been attained when producing excess ammonia (144 kg NH₃/hr) for the market and in-house consumption respectively. The designed system has the lowest reported ammonia electricity consumption of 6.4–8.21 kWh/kg NH₃, power-to-hydrogen, power-to-ammonia, and power-generation efficiencies of 80%, 55–71% and, 64–66%.     

Temporal search as a function of the variability of interfood intervals.

We attempted to determine whether timing theories developed primarily to explain performance in fixed-interval reinforcement schedules are also applicable to variable intervals. Groups of rats were trained in lever boxes on peak procedures with a 30-, 45-, or 6O-s interval, or a 30- to 6O-s uniform distribution (Experiment 1); a 60-s fixed and 1- to 121-s uniform distribution between and within animals (Experiment 2); and a procedure in which the interval between food and next available food gradually changed from a fixed 60 s to a uniform distribution between 0 and 120 s (Experiment 3). In uniform interval schedules rats made lever responses at particular times since food, as measured by the distribution of food-food intervals, the distribution of postreinforcement pauses, and the mean response rate as a function of time since food. Qualitative features of this performance are described by a multiple-oscillator connectionist theory of timing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do people with low self-esteem really want to feel better? Self-esteem differences in motivation to repair negative moods.

This research examined the hypothesis that people with low self-esteem (LSE) are less motivated than people with high self-esteem (HSE) to repair their negative moods. In Study 1, participants completed diaries in response to either a success or a failure in their everyday lives. Participants described what they intended to do next and the reasons behind those plans. After failure, fewer LSE than HSE participants expressed a goal to improve their mood. A follow-up investigation (Study 2) suggested that this difference was not due to a self-esteem difference in knowledge of mood repair strategies. In Study 3, after undergoing a negative mood induction, fewer LSE than HSE participants chose to watch a comedy video, even though both groups believed the comedy video would make them happy. Studies 4 and 5 explored possible reasons why LSE people are less motivated than HSE people to repair their negative moods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the nucleus raphe obscurus in the inhibition of rostral ventrolateral medullary neurones induced by stimulation in the ventrolateral periaqueductal grey matter of the rabbit

The uptake, partitioning, and release of ingredients such as water, oil, surfactant, and ions are important factors to understand and control in the design and manufacture of detergent and personal products. Although conventional pulse NMR (PNMR) spectroscopy continues to be used to analyse bulk molecular mobility and phase composition, more recently MR imaging techniques have created unique opportunities for gaining spatial information about these processes in ways that are noninvasive and potentially quantitative. This paper describes the evaluation of MRI and associated PNMR techniques to study transport in three relevant cases: ion diffusion (e.g., fluoride) in concentrated dispersions, oil transport through powders, and water ingress into porous powders (zeolite). Results are presented to illustrate the potential of multiple pulse and gradient echo MRI methods for dealing with the short T2 scenarios that represent a common problem in quantitative imaging of water in solid-containing composites involving, for instance, zeolite, or silica. Pore-size characterisation results are also presented.