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Dataset for the Southampton doctoral thesis: Computational Modelling of Particle Tribocharging in Small, High-Speed Cyclones
No full textDataset supports the thesis: Computational Modelling of Particle Tribocharging in Small, High-Speed Cyclones.
DESCRIPTION OF THE DATA
Various python scripts and a C source file for Lagrangian particle tracking and the Eulerian particle model.
Python code written in Python 3 and uses standard modules from an Anaconda package installation.
This dataset contains:
2dtg_particles.py - A python script for Lagrangian particle tracking in a 2d Taylor-Green flow field.
brownian_motion.py - A python script validating a Brownian motion particle model against an analytical solution.
cash_rk45.py - A python script containing an embedded Runga-Kutta 4/5 scheme.
cunningham_slip.py - A python script which computes the Cunningham Slip Correction Factor for a spherical particle.
fvm_2d.py - A python script containing a 2D finite-volume method solver for the Eulerian particle model in a 2D Talor-Green flow field.
hertzian.c - A C file which calculates the trajectories of 2 particles colliding assuming a Hertzian collision.
hertzian_integral.py - A python script which numerically evaluates the Hertzian integral.
rankine_vortex.py - A python script which computes and plots an ideal Rankine vortex.
source_sympy.py - A python script which uses symbolic algebra to check the source term maths is correct.
test_fvm_2d.py - A python script containing unit tests for fvm_2d.py.
test_hertzian.py - A python script containing tests for hertzian.c.
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Computational modelling of particle tribocharging in small, high-speed cyclones
No full textSmall, high-speed cyclones are used in domestic vacuum cleaners to separate sub-micron sized particulates from an air stream using no moving parts. The complex fluid flow within the cyclone is turbulent and highly-swirling, with small sub-micron particles encountering and responding to fluid structures of a wide spatial and temporal range. The process of particle separation in these cyclonic devices is not well-known and accurate numerical prediction of separation efficiency remains a computationally expensive task. In addition to this, particles are known to exchange charge through collisions, in a process known as tribocharging, which can cause smaller particles to agglomerate into larger structures. This thesis aims to develop a computationally inexpensive particle model able to predict the transport of particle charge which is valid in this highly-swirling flow for small particles. Models of particle tribocharging in the literature have only been validated for particles many orders of magnitude larger than those of interest here. Novel experiments were performed where sub-micron particles were aerodynamically focused to impact a metal plate using an aerosol beam. The results validated the physics of charge transfer at these small scales, with an equilibrium level for the voltage on the plate reached which charged analogous to a capacitor charging circuit. These measurements provided estimates of tune-able constants for a simple capacitor-like tribocharging model from the literature. Capturing collisions between particles in a Lagrangian reference frame is prohibitively expensive computationally, therefore an Eulerian particle model was chosen which can deal with collisions efficiently. The Equilibrium Eulerian method for computing the Eulerian particle velocity field for low Stokes number particles was validated in an analytical Taylor-Green flow. This flow field features fluid gradients and strong streamline curvature, with the length and velocity scales matched with the smallest turbulent scales in a representative cyclone. Strengths and weaknesses of the model were assessed in this challenging flow field, with an Eulerian sub-model for the transport of particle charge implemented. A large eddy simulation of a small, high-speed cyclone was performed with high wall resolution. Flow rates and pressure drop were matched to experimental evidence and partially resolved turbulent structures were observed along the cyclone walls. Lagrangian particle tracking provided a separation efficiency which matched experiment except for the smallest 0.1µm particles. Particles were observed travelling in distinct streaky bands by the walls which matched video evidence obtained experimentally. The Eulerian particle model provided an excellent match to the Lagrangian particle result for separation efficiency, with banding of large 1µm particles by the walls able to be captured, matching both the Lagrangian particles and experiment. The transport of charge and resulting electric field in the cyclone showed significant tribocharging occurring at the cone tip of the cyclone and by the walls which is novel. This work is expected to inform future cyclone design to improve the separation efficiency of small particles
Online Learning in Northeastern Pennsylvania K-12 Public Schools: Status and Administrative Perceptions
No full textNortheastern Pennsylvania administrators have limited availability of data related to online and blended learning. Through the use of an electronic survey, incorporating closed- and open-ended questions, the study examined the status of fully online and blended learning in K-12 public schools in Northeastern Pennsylvania and analyzed administrators’ perceived importance of and barriers to fully online and blended learning. Results of the study revealed perceptions related to the importance of meeting the needs of specific students and desire to expand programs, as well as barriers related to potential growth. Recommendations include revisions to and creation of online and blended learning policy, establishing district wide teams engaged in the planning and implementation of online and blended programs, and additional study to address the limited data on stakeholder perceptions.ProQuest Traditional Publishing Optio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Fatigue and salivary cortisol in relapsing-remitting multiple sclerosis: an investigation in everyday life
No full textMultiple sclerosis (MS) is a chronic autoimmune disease characterised by inflammatory attacks on the central nervous system. Fatigue is a common symptom in MS, yet its aetiology, exacerbating factors, and manifestation in everyday life are unclear. Given its role in regulating inflammation, energy metabolism and stress responses, cortisol is a relevant psychobiological target for MS fatigue research. The primary aims of this thesis were to examine diurnal fatigue patterns and contextual effects of daily stressors and mood in people with relapsing-remitting MS (RRMS); explore cortisol secretory activity in RRMS in everyday life; and investigate associations of cortisol with fatigue at baseline and change in fatigue 6 months later. Data were collected in an ecological momentary assessment study incorporating repeated real-time selfreports and salivary cortisol assessments over 4 consecutive weekdays in an RRMS group (n = 38) and healthy control group (n = 38), matched for age and sex.Statistical analysis was predominantly by multilevel modelling. The analysis presented in the first empirical chapter (Chapter 3) demonstrated that RRMS fatigue typically follows an increasing (but decelerating) within-day fatigue trajectory, distinct from linear trajectories in controls. Fatigue was sensitive to stressor and mood fluctuations within-subjects in both groups. The analysis presented in the second empirical chapter (Chapter 4) described larger cortisol awakening responses in RRMS compared to controls, but similar diurnal cortisol slopes. Cortisol reactivity to daily life stressors was apparent in both groups, mediated by self-reported distress. A systematic review was conducted (presented in Chapter 5) showing attenuated diurnal cortisol variability is most-frequently associated with fatigue across clinical populations; cortisol output appeared less relevant. However, the analysis presented in the final empirical chapter (Chapter 6) showed greater cortisol variability in the morning (larger cortisol responses to awakening) was associated with RRMS fatigue. Flatter diurnal cortisol slopes were associated with fatigue in controls. Chronic stress and depressive symptoms did not moderate associations, and there was no relationship between cortisol and change in fatigue 6 months later in either group. The original research presented confirms MS fatigue is not a stable symptom experience in everyday life, is sensitive to psychosocial contextual factors, and is associated with cortisol, potentially via pro-inflammatory immune mediators
Daily life stress and the cortisol awakening response: testing the anticipation hypothesis
Full text linkThe cortisol awakening response (CAR) is a distinct facet of the circadian cortisol rhythm associated with various health conditions and risk factors. It has repeatedly been suggested that the CAR could be a result of the anticipated demands of the upcoming day (stress anticipation) and could support coping with daily life stress. In a sample of 23 healthy participants CARs were assessed on two consecutive days by measures of salivary cortisol upon awakening (S1) and 30 and 45 minutes later, which were aggregated to the area under the curve increase (AUCI). Stress anticipation was assessed immediately after awakening. On the same days, daily life stress and distress were assessed six times per day based on a quasi-randomized design using handheld computers. Associations were tested by day using regression analysis and standard multilevel/mixed effects models for longitudinal data. The CAR AUCI moderated the effect of daily life stress on distress; higher CAR increases were associated with attenuated distress responses to daily life stress on both days (day 1: p?=?.039; day 2: p?=?.004) adjusted for age, gender, sleep quality, time of awakening and oral contraceptive use. Lagged-effects and redundancy models showed that this effect was not due to prior-day CAR increases but specific for same day CARs. On day 2, associations between daily life stress and distress were stronger when individuals showed a higher S1 cortisol level, but this effect was similar for S1 on day 1, and the day 2 effect of S1 became non-significant when S1 on day 1 was controlled. No associations were found between stress anticipation and CARs. Findings indicate that the CAR increase is associated with successful coping with same-day daily life stress
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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