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Baoqing Deng, Qiong Ding, Daqiang Ge
The Eulerian-Eulerian approach is used to simulate the two phase flow of air and water in a dissolved air flotation (DAF) tank. Unsteady simulation is adopted to obtain the quasi-steady result. The two dimensional model cannot capture the three dimensional feature of flow pattern in the tank. The three dimensional model reproduces the stratification structure observed in the experiment and obtains the satisfactory volume fraction of air bubbles in the separation zone. To account for the turbulence effect, four two-equation turbulence models are evaluated...
July 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Mei Bai, Jianlei Sun, Owen T Denmead, Deli Chen
Accurate measurement of ammonia (NH3) emissions from livestock pens is challenging. Two micrometeorological techniques, the integrated horizontal flux (IHF) and the backward Lagrangian stochastic (bLS) dispersion techniques were used to measure NH3 emissions from an isolated cattle pen (20 × 20 m) in Victoria, Australia. The bLS technique is simple and insensitive to the presence of animals, but typically gives discontinuous measurements due to the need for target wind directions and wind conditions above accepted thresholds...
July 12, 2017: Environmental Pollution
Christian Vergara, Davide Le Van, Maurizio Quadrio, Luca Formaggia, Maurizio Domanin
We study the effects of transition to turbulence in abdominal aortic aneurysms (AAA). The presence of transitional effects in such districts is related to the heart pulsatility and the sudden change of diameter of the vessels, and has been recorded by means of clinical measures as well as of computational studies. Here we propose, for the first time, the use of a large eddy simulation (LES) model to accurately describe transition to turbulence in realistic scenarios of AAA obtained from radiological images...
July 12, 2017: Medical Engineering & Physics
Ö D Gürcan
A discretization of the wave-number space is proposed, using nested polyhedra, in the form of alternating dodecahedra and icosahedra that are self-similarly scaled. This particular choice allows the possibility of forming triangles using only discretized wave vectors when the scaling between two consecutive dodecahedra is equal to the golden ratio and the icosahedron between the two dodecahedra is the dual of the inner dodecahedron. Alternatively, the same discretization can be described as a logarithmically spaced (with a scaling equal to the golden ratio), nested dodecahedron-icosahedron compounds...
June 2017: Physical Review. E
B Dorschner, S S Chikatamarla, I V Karlin
Entropic lattice Boltzmann methods have been developed to alleviate intrinsic stability issues of lattice Boltzmann models for under-resolved simulations. Its reliability in combination with moving objects was established for various laminar benchmark flows in two dimensions in our previous work [B. Dorschner, S. Chikatamarla, F. Bösch, and I. Karlin, J. Comput. Phys. 295, 340 (2015)JCTPAH0021-999110.1016/] as well as for three-dimensional one-way coupled simulations of engine-type geometries in B...
June 2017: Physical Review. E
Rixin Yu, Andrei N Lipatnikov
A three-dimensional (3D) direct numerical simulation (DNS) study of the propagation of a reaction wave in forced, constant-density, statistically stationary, homogeneous, isotropic turbulence is performed by solving Navier-Stokes and reaction-diffusion equations at various (from 0.5 to 10) ratios of the rms turbulent velocity U^{'} to the laminar wave speed, various (from 2.1 to 12.5) ratios of an integral length scale of the turbulence to the laminar wave thickness, and two Zeldovich numbers Ze=6.0 and 17...
June 2017: Physical Review. E
Amdad Chowdury, Wieslaw Krolikowski
We study the exact first-order soliton and breather solutions of the integrable nonlinear Schrödinger equations hierarchy up to fifth order. We reveal the underlying physical mechanism which transforms a breather into a soliton. Furthermore, we show how the dynamics of the Akhmediev breathers which exist on a constant background as a result of modulation instability, is connected with solitons on a zero background. We also demonstrate that, while a first-order rogue wave can be directly transformed into a soliton, higher-order rogue wave solutions become rational two-soliton solutions with complex collisional structure on a background...
June 2017: Physical Review. E
Yan Yang, W H Matthaeus, T N Parashar, P Wu, M Wan, Y Shi, S Chen, V Roytershteyn, W Daughton
Analysis of the Vlasov-Maxwell equations from the perspective of turbulence cascade clarifies the role of electromagnetic work, and reveals the importance of the pressure-strain relation in generating internal energy. Particle-in-cell simulation demonstrates the relative importance of the several energy exchange terms, indicating that the traceless pressure-strain interaction "Pi-D" is of particular importance for both electrons and protons. The Pi-D interaction and the second tensor invariants of the strain are highly localized in similar spatial regions, indicating that energy transfer occurs preferentially in coherent structures...
June 2017: Physical Review. E
Thomas Y Sheffield, Benno Rumpf
We investigate statistical properties of wave turbulence by monitoring the dynamics of ensembles of trajectories. The system under investigation is a simplified model for surface gravity waves in one and two dimensions with a square-root dispersion and a four-wave interaction term. The simulations of decaying turbulence confirm the Kolmogorov-Zakharov spectral power distribution of wave turbulence theory. Fourth-order correlations are computed numerically as ensemble averages of trajectories. The shape, scaling, and time evolution of the correlations agree with the predictions of wave turbulence theory...
June 2017: Physical Review. E
Giacomo Bonciolini, Edouard Boujo, Nicolas Noiray
The problem of output-only parameter identification for nonlinear oscillators forced by colored noise is considered. In this context, it is often assumed that the forcing noise is white, since its actual spectral content is unknown. The impact of this white-noise forcing assumption upon parameter identification is quantitatively analyzed. First, a Van-der-Pol oscillator forced by an Ornstein-Uhlenbeck process is considered. Second, the practical case of thermoacoustic limit cycles in combustion chambers with turbulence-induced forcing is investigated...
June 2017: Physical Review. E
Alexander Vladimirovich Frolov, Tatjana Gennadjevna Vaikhanskaya, Olga Petrovna Melnikova, Anatoly Pavlovich Vorobiev, Ludmila Michajlovna Guel
BACKGROUND: The development of prognostic factors of life-threatening ventricular tachyarrhythmias (VTA) and sudden cardiac death (SCD) continues to maintain its priority and relevance in cardiology. The development of a method of personalised prognosis based on multifactorial analysis of the risk factors associated with life-threatening heart rhythm disturbances is considered a key research and clinical task. AIM: To design a prognostic and mathematical model to define personalised risk for life-threatening VTA in patients with chronic heart failure (CHF)...
2017: Kardiologia Polska
Benjamin R Halls, Naibo Jiang, Terrence R Meyer, Sukesh Roy, Mikhail N Slipchenko, James R Gord
High-speed (20 kHz rate), volumetric laser-induced-fluorescence imaging of combustion intermediates such as a formaldehyde (CH<sub>2</sub>O) and polycyclic aromatic hydrocarbon (PAH) species is demonstrated for tracking the four-dimensional (4D) evolution of turbulent flames. The third-harmonic, 355 nm output of a burst-mode Nd:YAG laser with a 130 mJ/pulse is expanded to 30 mm diameter for volume illumination of the base region of a methane-hydrogen jet diffusion flame. Eight simultaneous images from different viewing angles are used to collect the resulting fluorescence signal for reconstruction of 200 time-sequential three-dimensional volumes over 10 ms duration...
July 15, 2017: Optics Letters
Aoife Brady, René Berlich, Nina Leonhard, Teresa Kopf, Paul Böttner, Ramona Eberhardt, Claudia Reinlein
It is anticipated that ground-to-geostationary orbit (GEO) laser communication will benefit from pre-compensation of atmospheric turbulence for laser beam propagation through the atmosphere. Theoretical simulations and laboratory experiments have determined its feasibility; extensive free-space experimental validation has, however, yet to be fulfilled. Therefore, we designed and implemented an adaptive optical (AO)-box which pre-compensates an outgoing laser beam (uplink) using the measurements of an incoming beam (downlink)...
July 15, 2017: Optics Letters
A Strugarek, P Beaudoin, P Charbonneau, A S Brun, J-D do Nascimento
The magnetic fields of solar-type stars are observed to cycle over decadal periods-11 years in the case of the Sun. The fields originate in the turbulent convective layers of stars and have a complex dependency upon stellar rotation rate. We have performed a set of turbulent global simulations that exhibit magnetic cycles varying systematically with stellar rotation and luminosity. We find that the magnetic cycle period is inversely proportional to the Rossby number, which quantifies the influence of rotation on turbulent convection...
July 14, 2017: Science
Bhupesh Kumar, Alok Kumar, Ganesh Kumar, Harkant Singh
Congenital coronary artery fistula is an uncommon anomaly. Transcatheter coil embolization or Amplatzer vascular plug device closure of fistula is often done in symptomatic patients with safe accessibility to the feeding coronary artery. Embolization of Amplatzer vascular plug device is rare. We report an 11-year-old male child who presented to us with increasing shortness of breath for 7 years. He had a history of Amplatzer vascular plug device closure of right coronary-cameral fistula 8 years back. Echocardiography demonstrated a dilated aneurysmal right coronary artery with turbulent jet entering into the right ventricle (RV) and device embolized into the left pulmonary artery (LPA)...
July 2017: Annals of Cardiac Anaesthesia
Bjarte Hannisdal, Kristian Agasøster Haaga, Trond Reitan, David Diego, Lee Hsiang Liow
Common species shape the world around us, and changes in their commonness signify large-scale shifts in ecosystem structure and function. However, our understanding of long-term ecosystem response to environmental forcing in the deep past is centred on species richness, neglecting the disproportional impact of common species. Here, we use common and widespread species of planktonic foraminifera in deep-sea sediments to track changes in observed global occupancy (proportion of sampled sites at which a species is present and observed) through the turbulent climatic history of the last 65 Myr...
July 12, 2017: Proceedings. Biological Sciences
Peter A Jaques, Lee Portnoff
The risk of workers' exposure to aerosolized particles has increased with the upsurge in the production of engineered nanomaterials. Currently, a whole-body standard test method for measuring particle penetration through protective clothing ensembles is not available. Those available for respirators neglect the most common challenges to ensembles, because they use active vacuum-based filtration, designed to simulate breathing, rather than the positive forces of wind experienced by workers. Thus, a passive method that measures wind-driven particle penetration through ensemble fabric has been developed and evaluated...
July 12, 2017: Journal of Occupational and Environmental Hygiene
Neil Andersson
In conventional randomised controlled trials (RCTs), researchers design the interventions. In the Camino Verde trial, each intervention community designed its own programmes to prevent dengue. Instead of fixed actions or menus of activities to choose from, the trial randomised clusters to a participatory research protocol that began with sharing and discussing evidence from a local survey, going on to local authorship of the action plan for vector control.Adding equitable stakeholder engagement to RCT infrastructure anchors the research culturally, making it more meaningful to stakeholders...
May 30, 2017: BMC Public Health
Philippa Martyr
OBJECTIVE: To provide a brief biography of Western Australian colonial lunacy superintendent Dr Henry Calvert Barnett. METHOD: A range of primary sources were consulted. RESULTS: Barnett was a complex man: a caring and forward-thinking practitioner who had a colourful and turbulent private life. CONCLUSIONS: Barnett's contribution to mental health service development in Western Australia was genuine and worthwhile, and should be recognised...
July 1, 2017: Australasian Psychiatry: Bulletin of Royal Australian and New Zealand College of Psychiatrists
Caoimhe McKerr, Nic Coetzee, Obaghe Edeghere, Shakeel Suleman, Neville Q Verlander, Krishna Banavathi
BACKGROUND: In 2011, 15 deep-seated Propionibacterium acnes infections were identified in patients following craniotomies in a hospital in the UK. AIM: To describe the outbreak and report findings from the investigation undertaken in order to identify the source & risk factors and inform control measures. METHODS: Data were obtained from hospital clinical records and included patient and surgical variables. Cases were defined as patients with microbiologically confirmed deep or organ space surgical site infection (SSI) caused by P...
July 7, 2017: Journal of Hospital Infection
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