A computationally-efficient, semi-implicit, iterative method for the time-integration of reacting flows with stiff chemistry

A semi-implicit preconditioned iterative method is proposed for the time-integration of the stiff chemistry in simulations of unsteady reacting flows, such as turbulent flames, using detailed chemical kinetic mechanisms. Emphasis is placed on the simultaneous treatment of convection, diffusion, and chemistry, without using operator splitting techniques. The preconditioner corresponds to an approximation of the diagonal of the chemical Jacobian. Upon convergence of the sub-iterations, the fully-implicit, second-order time-accurate, Crank–Nicolson formulation is recovered. Performance of the proposed method is tested theoretically and numerically on one-dimensional laminar and three-dimensional high Karlovitz turbulent premixed n-heptane/air flames. The species lifetimes contained in the diagonal preconditioner are found to capture all critical small chemical timescales, such that the largest stable time step size for the simulation of the turbulent flame with the proposed method is limited by the convective CFL, rather than chemistry. The theoretical and numerical stability limits are in good agreement and are independent of the number of sub-iterations. The results indicate that the overall procedure is second-order accurate in time, free of lagging errors, and the cost per iteration is similar to that of an explicit time integration. The theoretical analysis is extended to a wide range of flames (premixed and non-premixed), unburnt conditions, fuels, and chemical mechanisms. In all cases, the proposed method is found (theoretically) to be stable and to provide good convergence rate for the sub-iterations up to a time step size larger than 1 μs. This makes the proposed method ideal for the simulation of turbulent flames

Number of Siblings and Friendship Nominations Among Adolescents

Abstract Considerable social science research questions the benefit of siblings. The most prominent example is the consistent negative association between sibship size and educational outcomes. But more recent work among kindergartners uncovered a potentially positive outcome-greater social skills-at least for those who have at least one sibling. We extend this line of inquiry to adolescence to see if there are long-term negative consequences of growing up without any siblings. Analyzing 13,466 youths from the National Longitudinal Study of Adolescent Health, we find no evidence that only children receive fewer peer nominations of friendship than youths with one (or more than one) sibling(s). Our results suggest that the previously observed social skills deficit among only children in kindergarten appears to be overcome by adolescence

Design and Demonstration of a New Small-Scale Jet Noise Experiment

A facility capable of acoustic and velocity field measurements of high-speed jets has recently been built and tested. The anechoic chamber that houses the jet has a 2.1 m × 2.3 m × 2.5 m wedge tip to wedge tip working volume. We aim to demonstrate that useful experiments can be performed in such a relatively small facility for a substantially lower cost than in larger facility. Rapid prototyping allows for quick manufacturing of both simple and complex geometry nozzles. Sideline and 30° downstream acoustic measurements between 400 Hz and 100 kHz agree well with accepted results. Likewise, nozzle exit-plane data obtained using particle image velocimetry are in good agreement with other studies

Leadership, the logic of sufficiency and the sustainability of education

The notion of sufficiency has not yet entered mainstream educational thinking, and it still has to make its mark upon educational leadership. However, a number of related concepts – particularly those of sustainability and complexity theory – are beginning to be noticed. This article examines these two concepts and uses them to critique the quasi-economic notion of efficiency, before arguing that the concept of sufficiency arises naturally from this discussion. This concept, originally derived from environmental thinking, has both metaphorical and practical impact for educational organizations and their leadership. An examination of three possible meanings suggests that while an embrace of an imperative concept of sufficiency seems increasingly necessary, its adoption would probably lead to a number of other problems, as it challenges some fundamental societal values and assumptions. Nevertheless, the article argues that these need to be addressed for the sake of both sustainable leadership and a sustainable planet

Development and implementation of “handshake rounds”: An antibiotic stewardship intervention for hospitalized adult patients with hematologic malignancies

Abstract Objective: To design and implement “handshake rounds” as an antibiotic stewardship intervention to reduce inpatient intravenous (IV) antibiotic use in patients with hematologic malignancies. Design: Quasi-experimental analysis of antibiotic use (AU) and secondary outcomes before and and after handshake rounds were implemented. Setting: Quaternary-care, academic medical center. Patients: Hospitalized adults with hematologic malignancies receiving IV antibiotics. Methods: We performed a retrospective review of a preintervention cohort prior to the intervention. A multidisciplinary team developed criteria for de-escalation of antibiotics, logistics of handshake rounds, and outcome metrics. Eligible patients were discussed during scheduled handshake rounds between a hematology–oncology pharmacist and transplant–infectious diseases (TID) physician. Prospective data were collected over 30 days in the postintervention cohort. Due to small sample size, 2:1 matching was used to compare pre- to and postintervention AU. Total AU in days of therapy per 1,000 patient days (DOT/1,000 PD) was reported. Mean AU per patient was analyzed using Wilcoxon rank-sum test. A descriptive analysis of secondary outcomes of pre- and postintervention cohorts was performed. Results: Total AU was substantially lower after the intervention, with 517 DOT/1,000 PD compared to 865 DOT/1,000 PD before the intervention. There was no statistically significant difference in the mean AU per patient between the 2 cohorts. There was a lower rate of 30-day mortality in the postintervention cohort and rates of ICU admissions were similar. Conclusions: Conducting handshake rounds is a safe and effective way to implement an antibiotic stewardship intervention among high-risk patient population such as those with hematologic malignancies

Climate change curricula for adult audiences in agriculture and forestry: A review

Agricultural and forestry advisers and other technical service providers play an important role in supporting farmers and foresters to adapt to climate change. However, not all agricultural and forestry advisers are comfortable talking about climate change with land managers. While there is a demonstrated interest related to climate related professional development, few examples of curricula developed with the express purpose of serving this audience and a systematic review of these curricula has not been conducted. To address this gap, we reviewed 12 curricula which were developed and implemented between 2001 and 2017. The goal of this review is to apply the lessons learned from a range of climate change-focused curricula to new, regionally or sector-specific educational programs targeting both agricultural advisers and innovative farmers. Our findings suggest that developers of future educational programs consider the following: (a) the specific needs of their audience, including topical interests and learning needs; (b) the use of interdisciplinary teams for curricula development; (c) trade-offs associated with inclusivity and depth of course content; and (d) the advantages of project-based education approaches suited for adult learning audiences. By applying these concepts to future curricula, these curricula are likely to have the greatest level of impact

Re-examining the Unified Theory of Acceptance and Use of Technology (UTAUT): Towards a Revised Theoretical Model

YesBased on a critical review of the Unified Theory of Acceptance and Use of Technology (UTAUT), this study first formalized an alternative theoretical model for explaining the acceptance and use of information system (IS) and information technology (IT) innovations. The revised theoretical model was then empirically examined using a combination of meta-analysis and structural equation modelling (MASEM) techniques. The meta-analysis was based on 1600 observations on 21 relationships coded from 162 prior studies on IS/IT acceptance and use. The SEM analysis showed that attitude: was central to behavioural intentions and usage behaviours, partially mediated the effects of exogenous constructs on behavioural intentions, and had a direct influence on usage behaviours. A number of implications for theory and practice are derived based on the findings