Mean flow, turbulent structures, and SPOD analysis of thermal mixing in a T-junction with variation of the inlet flow profile

This paper investigates the effects of different inlet flow profiles on thermal mixing within a T-junction using CFD simulations with the IDDES-SST turbulence model. The different combinations of inlet flow profiles are related to different stage in the flow entry region. The effects of the inlet flow profile on the mean and transient flow behaviour are assessed, while a spectral proper orthogonal decomposition and power spectral density analysis are performed to assess the underlying flow structures and the predominant frequency modes. It is found that the vortical structures associated with the horseshoe and hovering vortex systems consist of a single roll-up vortex for cases with uniformly distributed boundary conditions (BCs) at the branch inlet whereas a double roll-up vortex is observed for the other cases. The double roll-up vortex enhances the mixing locally due to the entrainment of fluid from the branch pipe in these vortical structures, which then results in a lower mean temperature distribution. The appearance of the secondary vortex pair and the nested vortices is delayed for cases with uniformly distributed BCs at the branch inlet, which again results in lower thermal mixing and consequently higher values of mean temperature when compared with the other cases. It is also found that the vorticity related to the counter-rotating vortex pair as well as to the second pair of vortices rotating in the opposite direction is higher for cases with uniformly distributed BCs at the branch inlet. Lastly, the combinations of inlet flow profiles lead to different coherent structures, and the dominant frequencies are of a Strouhal number of around 0.7 for uniformly distributed profiles at the branch inlet and in the range 0.4–0.5 for the other cases

Improvements in prevalence trend fitting and incidence estimation in EPP 2013

OBJECTIVE: Describe modifications to the latest version of the Joint United Nations Programme on AIDS (UNAIDS) Estimation and Projection Package component of Spectrum (EPP 2013) to improve prevalence fitting and incidence trend estimation in national epidemics and global estimates of HIV burden. METHODS: Key changes made under the guidance of the UNAIDS Reference Group on Estimates, Modelling and Projections include: availability of a range of incidence calculation models and guidance for selecting a model; a shift to reporting the Bayesian median instead of the maximum likelihood estimate; procedures for comparison and validation against reported HIV and AIDS data; incorporation of national surveys as an integral part of the fitting and calibration procedure, allowing survey trends to inform the fit; improved antenatal clinic calibration procedures in countries without surveys; adjustment of national antiretroviral therapy reports used in the fitting to include only those aged 15–49 years; better estimates of mortality among people who inject drugs; and enhancements to speed fitting. RESULTS: The revised models in EPP 2013 allow closer fits to observed prevalence trend data and reflect improving understanding of HIV epidemics and associated data. CONCLUSION: Spectrum and EPP continue to adapt to make better use of the existing data sources, incorporate new sources of information in their fitting and validation procedures, and correct for quantifiable biases in inputs as they are identified and understood. These adaptations provide countries with better calibrated estimates of incidence and prevalence, which increase epidemic understanding and provide a solid base for program and policy planning

Medical Student Perceptions of Feedback and Feedback Behaviors Within the Context of the “Educational Alliance”

Purpose: Using the "educational alliance" as a conceptual framework, the authors explored medical students' beliefs about feedback and how their feedback behaviors reflect their perceptions. Method: Five focus groups (four to six medical students each) at one UK medical school in 2015 were used to capture and elucidate learners' feedback perceptions and behaviors within the context of the learner-educator relationship. A map of key feedback opportunities across the program was used as a tool for exploring student engagement with the feedback process. Qualitative data were analyzed using an approach based on grounded theory principles. Results: Three learner feedback behaviors emerged: recognizing, using, and seeking feedback. Five core themes influencing these behaviors were generated: learner beliefs, attitudes, and perceptions; relationships; teacher attributes; mode of feedback; and learning culture. Conceptual models illustrating the relationships between the themes and each behavior were developed. Learning culture influenced all three behaviors with a wide context of influences. Conclusions: Ensuring that feedback leads to improved performance requires more than training educators in best practices. The conceptual models support the educational alliance framework and illustrate the context and complexity of learning culture surrounding the educational relationship, learner, and feedback exchange. The educational alliance approach is underpinned by a mutual understanding of purpose and responsibility. Enhancing learners' feedback literacy skills seems to be the key aspect of the educational alliance in need of attention. Empowering learners to recognize, seek, and use feedback received within diverse learning cultures is essential

Seasonality in the Surface Energy Balance of Tundra in the Lower Mackenzie River Basin

This study details seasonal characteristics in the annual surface energy balance of upland and lowland tundra during the 1998–99 water year (Y2). It contrasts the results with the 1997–98 water year (Y1) and relates the findings to the climatic normals for the lower Mackenzie River basin region. Both years were much warmer than the long-term average, with Y1 being both warmer and wetter than Y2. Six seasons are defined as early winter, midwinter, late winter, spring, summer, and fall. The most rapid changes in the surface energy balance occur in spring, fall, and late winter. Of these, spring is the most dynamic, and there is distinct asymmetry between rates of change in spring and those in fall. Rates of change of potential insolation (extraterrestrial solar radiation) in late winter, spring, and fall are within 10% of one another, being highest in late winter and smallest in spring. Rates of change in air temperature and ground temperature are twice as large in spring as in fall and late winter, when they are about the same. Rates of change in components of the energy balance in spring are twice and 4 times as large as in fall and late winter, respectively. The timing of snowpack ripening and snowmelt is the major agent determining the magnitude of asymmetry between fall and spring. This timing is a result of interaction between the solar cycle, air temperature, and snowpack longevity. Based on evidence from this study, potential surface responses to a 18C increase in air temperature are small to moderate in most seasons, but are large in spring when increases range from 7% to 10% of average surface energy fluxes

The 1979 Southeastern Virginia Urban Plume Study (SEV-UPS): Surface and airborne studies

The operation of two surface monitoring stations (one in downtown Norfolk, Virginia, one south of the city near the Great Dismal Swamp) and the collection of 40 hours of airborne measurements is described. Surface site measurements of ozone, oxides of nitrogen, sulfur dioxide, temperature, dew point, b sub seat, and condensation nuclei were made. Instrument calibrations, quality assurance audits, and preliminary data analysis in support of the Urban Plume Study were also made. The air pollution problems that were addressed are discussed. Data handling procedures followed for the surface stations are presented. The operation of the aircraft sampling platform is described. Aircraft sampling procedures are discussed. A preliminary descriptive analysis of the aircraft data is given along with data or plots for surface sites, airborne studies, hydrocarbon species, and instrument performance audits. Several of the aircraft flights clearly show the presence of an urban ozone plume downwind of Norfolk in the direction of the mean wind flow

In situ sensors for measurements in the global trosposphere

Current techniques available for the in situ measurement of ambient trace gas species, particulate composition, and particulate size distribution are reviewed. The operational specifications of the various techniques are described. Most of the techniques described are those that have been used in airborne applications or show promise of being adaptable to airborne applications. Some of the instruments described are specialty items that are not commercially-available. In situ measurement techniques for several meteorological parameters important in the study of the distribution and transport of ambient air pollutants are discussed. Some remote measurement techniques for meteorological parameters are also discussed. State-of-the-art measurement capabilities are compared with a list of capabilities and specifications desired by NASA for ambient measurements in the global troposphere

21st century reform efforts in undergraduate quantitative biology education: Conversations, initiatives, and curriculum change in the United States of America

In the United States, there are multiple reports from both mathematics and biology communities that address the quantitative preparation of undergraduate life science students. Many of these reports make broad recommendations for the revision of life science curriculum to incorporate more quantitative techniques. Here, we review initiatives and progress in the United States on the state of quantitative biology education in the context of the mathematics education, biology research frontiers, and the funding system and other sources of support for systemic change to meet new demands

Boundary spanning in the context of stakeholder engagement in collaborative water management

Boundary spanners are individuals able to reach across organizational borders to build relationships and interconnections to help better manage complex problems. What is not clear, however, are the skills that allow boundary spanners to cross diverse scales, sectors, and organizations. To address this gap, we use a qualitative case study approach to examine evidence for how boundary spanning skills are implemented in the context of stakeholder engagement for addressing water challenges in agricultural settings. We employ a hybrid deductive-inductive thematic analysis approach to examine interview data collected with 25 stakeholder participants as well as direct observation of engagement behavior. Interview instruments were designed to elicit responses related to six deductively derived skills of boundary spanning: relationship builder, authentic leadership, trustworthiness, autonomy, perspective-taking, and effective science communication. Our inductive analysis identified evidence for three additional boundary spanning skills. Our study finds that some boundary spanning skills were exhibited more than others, and their frequency of use varied throughout the engagement process, and certain skills were used interchangeably. This research provides guidance on what boundary spanning looks like in action, and thus provides guidance on identifying and enhancing these skills in stakeholder engagement for water resource management

A review of residual stress analysis using thermoelastic techniques

Thermoelastic Stress Analysis (TSA) is a full-field technique for experimental stress analysis that is based on infra-red thermography. The technique has proved to be extremely effective for studying elastic stress fields and is now well established. It is based on the measurement of the temperature change that occurs as a result of a stress change. As residual stress is essentially a mean stress it is accepted that the linear form of the TSA relationship cannot be used to evaluate residual stresses. However, there are situations where this linear relationship is not valid or departures in material properties due to manufacturing procedures have enabled evaluations of residual stresses. The purpose of this paper is to review the current status of using a TSA based approach for the evaluation of residual stresses and to provide some examples of where promising results have been obtained