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Dan Mei, Meng Wen, Yuzheng Zhu, Xuemei Xu, Futang Xing
In atmospheric environment, the layout difference of urban buildings has a powerful influence on accelerating or inhibiting the dispersion of particle matters (PM). In industrial cities, buildings of variable heights can obstruct the diffusion of PM from industrial stacks. In this study, PM dispersed within building groups was simulated by Reynolds-averaged Navier-Stokes equations coupled Lagrangian approach. Four typical street building arrangements were used: (a) a low-rise building block with Height/base H/b = 1 (b = 20 m); (b) step-up building layout (H/b = 1, 2, 3, 4); (c) step-down building layout (H/b = 4, 3, 2, 1); (d) high-rise building block (H/b = 5)...
April 20, 2018: Journal of the Air & Waste Management Association
Longqian Xu, Xiaojun Xu, Guangzhu Cao, Shuli Liu, Zhengyang Duan, Shumin Song, Mingyao Song, Mengjiao Zhang
This study evaluates the performance of a continuous electrocoagulation system (batch recirculation mode) on the simultaneous removal of Zn2+ , Cd2+ , and Mn2+ from real smelting wastewater by using Fe-Fe electrodes. Several parameters are evaluated to determine the optimal operating conditions. These conditions include the type of power supply (p), current density (j), aeration intensity (v), flow rate (u), and anions (SO4 2- and SO3 2- ). At current density = 10-20 mA/cm2 , the DC power supply performs better than the APC power supply in treating wastewater...
April 16, 2018: Journal of Environmental Management
Pierre Ronco
Gabriel Richet, one of the fathers of the French and international Nephrology, was a man remarkable for his courage, vision and empathy. He was proud and brave, and he presented himself proud of being brave. He opens his interview speaking about his youth, when he was injured, and went back to the fight. He cites the number of stitches he received, but doesn't cite being decorated with the Légion d'Honneur, one of the highest honours of the French Republic. This anecdote perfectly illustrates his elegance and detachment from awards and self-satisfaction...
April 19, 2018: BMC Nephrology
Peter R Schreiner
"… The value and meaning of scientific truth has not been overcome by postmodernism or post-factual tendencies. Just because politics is mostly a representation of opinions, this does not imply that truth has become irrelevant. Quite the opposite, the value of truth is growing in turbulent times and for scientists it constitutes the currency of credibility and accountability …" Read more in the Guest Editorial by Peter R. Schreiner.
April 19, 2018: Angewandte Chemie
Isabel A Houghton, Jeffrey R Koseff, Stephen G Monismith, John O Dabiri
Biologically generated turbulence has been proposed as an important contributor to nutrient transport and ocean mixing1-3 . However, to produce non-negligible transport and mixing, such turbulence must produce eddies at scales comparable to the length scales of stratification in the ocean. It has previously been argued that biologically generated turbulence is limited to the scale of the individual animals involved 4 , which would make turbulence created by highly abundant centimetre-scale zooplankton such as krill irrelevant to ocean mixing...
April 18, 2018: Nature
Vijay Govindarajan, John Mousel, H S Udaykumar, Sarah C Vigmostad, David D McPherson, Hyunggun Kim, Krishnan B Chandran
Highly resolved three-dimensional (3D) fluid structure interaction (FSI) simulation using patient-specific echocardiographic data can be a powerful tool for accurately and thoroughly elucidating the biomechanics of mitral valve (MV) function and left ventricular (LV) fluid dynamics. We developed and validated a strongly coupled FSI algorithm to fully characterize the LV flow field during diastolic MV opening under physiologic conditions. Our model revealed that distinct MV deformation and LV flow patterns developed during different diastolic stages...
April 18, 2018: Scientific Reports
Kathleen A Schiro, Fiaz Ahmed, Scott E Giangrande, J David Neelin
A substantial fraction of precipitation is associated with mesoscale convective systems (MCSs), which are currently poorly represented in climate models. Convective parameterizations are highly sensitive to the assumptions of an entraining plume model, in which high equivalent potential temperature air from the boundary layer is modified via turbulent entrainment. Here we show, using multiinstrument evidence from the Green Ocean Amazon field campaign (2014-2015; GoAmazon2014/5), that an empirically constrained weighting for inflow of environmental air based on radar wind profiler estimates of vertical velocity and mass flux yields a strong relationship between resulting buoyancy measures and precipitation statistics...
April 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
J Squire, E Quataert, M W Kunz
In collisionless and weakly collisional plasmas, such as hot accretion flows onto compact objects, the magnetorotational instability (MRI) can differ significantly from the standard (collisional) MRI. In particular, pressure anisotropy with respect to the local magnetic-field direction can both change the linear MRI dispersion relation and cause nonlinear modifications to the mode structure and growth rate, even when the field and flow perturbations are very small. This work studies these pressure-anisotropy-induced nonlinearities in the weakly nonlinear, high-ion-beta regime, before the MRI saturates into strong turbulence...
December 2017: Journal of Plasma Physics
David S Trossman, Brian K Arbic, David N Straub, James G Richman, Eric P Chassignet, Alan J Wallcraft, Xiaobiao Xu
Motivated by the substantial sensitivity of eddies in two-layer quasi-geostrophic (QG) turbulence models to the strength of bottom drag, this study explores the sensitivity of eddies in more realistic ocean general circulation model (OGCM) simulations to bottom drag strength. The OGCM results are interpreted using previous results from horizontally homogeneous, two-layer, flat-bottom, f-plane, doubly periodic QG turbulence simulations and new results from two-layer β -plane QG turbulence simulations run in a basin geometry with both flat and rough bottoms...
August 2017: Journal of Physical Oceanography
Jeffrey Andrew Tuhtan, Juan Francisco Fuentes-Perez, Gert Toming, Matthias Schneider, Richard Schwarzenberger, Martin Schletterer, Maarja Kruusmaa
The lateral line system provides fish with advanced mechanoreception over a wide range of flow conditions. Inspired by the abilities of their biological counterparts, artificial lateral lines have been developed and tested exclusively under laboratory settings. Motivated by the lack of flow measurements taken in the field which consider fluid-body interactions, we built a fish-shaped lateral line probe. The device is outfitted with 11 high-speed (2.5 kHz) time-synchronized pressure transducers, and designed to capture and classify flows in fish passage structures...
April 9, 2018: Bioinspiration & Biomimetics
Vytautas Ostasevicius, Yahor Tretsyakou-Savich, Mantas Venslauskas, Agne Bertasiene, Vladimir Minchenya, Pavel Chernoglaz
Time-consuming design and manufacturing processes are a serious disadvantage when adapting human cardiovascular implants as they cause unacceptable delays after the decision to intervene surgically has been made. An ideal cardiovascular implant should have a broad range of characteristics such as strength, viscoelasticity and blood compatibility. The present research proposes the sequence of the geometrical adaptation procedures and presents their results. The adaptation starts from the identification of a person's current health status while performing abdominal aortic aneurysm (AAA) imaging, which is a point of departure for the mathematical model of a cardiovascular implant...
April 6, 2018: Biomedizinische Technik. Biomedical Engineering
Anna V Romanova, Kirill V Horoshenkov, Anton Krynkin
The pattern of the free surface of the turbulent flow in a partially filled circular pipe contains information on the underlying hydraulic processes. However, the roughness of the free surface of flow and its temporal variation in a pipe is a dynamic and non-stationary process that is difficult to measure directly. This work examines a new acoustic method that is used to study the characteristics of the free surface roughness under controlled laboratory conditions. The acoustic method makes use of a continuous sine wave that is transmitted through the air above the turbulent flow of water over a section of the pipe instrumented with an array of wave probes and microphones...
April 5, 2018: Sensors
Massimo De Pietro, Luca Biferale, Guido Boffetta, Massimo Cencini
Turbulent flows governed by the Navier-Stokes equations (NSE) generate an out-of-equilibrium time irreversible energy cascade from large to small scales. In the NSE, the energy transfer is due to the nonlinear terms that are formally symmetric under time reversal. As for the dissipative term: first, it explicitly breaks time reversibility; second, it produces a small-scale sink for the energy transfer that remains effective even in the limit of vanishing viscosity. As a result, it is not clear how to disentangle the time irreversibility originating from the non-equilibrium energy cascade from the explicit time-reversal symmetry breaking due to the viscous term...
April 6, 2018: European Physical Journal. E, Soft Matter
J M van der Hoop, M L Byron, K Ozolina, D L Miller, J L Johansen, P Domenici, J F Steffensen
Fish swimming energetics are often measured in laboratory environments which attempt to minimize turbulence, though turbulent flows are common in the natural environment. To test whether the swimming energetics and kinematics of shiner perch Cymatogaster aggregata (a labriform swimmer) were affected by turbulence, two flow conditions were constructed in a swim-tunnel respirometer. A low-turbulence flow was created using a common swim-tunnel respirometry setup with a flow straightener and fine-mesh grid to minimize velocity fluctuations...
April 3, 2018: Journal of Experimental Biology
Yong Han, Peng Gao, Jiaolong Huang, Tongxiao Zhang, Jianjun Zhuang, Maohai Hu, Yonghua Wu
Atmospheric visibility and turbulence are important meteorological factors in light propagation and optical communication, air quality prediction, and climate environment model. They are often measured separately by the conventional instruments, but the interaction between aerosol (closely relate to visibility) and turbulence may potentially influence their measurement accuracy. In this paper, a novel instrument, the atmospheric visibility and turbulence optical meter (AVTOM), is developed to synchronously measure atmospheric visibility and turbulence intensity through a transmission method...
March 19, 2018: Optics Express
Darek J Bogucki, Julian A Domaradzki, Paul von Allmen
Lidar is one of few remote sensing methods available to researchers to sense below the oceanic air-surface. We present polarimetric lidar measurements of turbulence in a laboratory generated turbulent flow. We found that the nearforward light depolarization characterized by the depolarization rate γ(z), varies with the turbulent flow parameter: χ(z)∊(z)1/4 , where χ(z) and ∊(z) are the respective depth dependent, temperature variance, and turbulent kinetic energy dissipation rates. The presence of particles in the flow modifies the values of γ in such a way that the ratio γ(z)/α(z) becomes independent of the particle concentration and depends only on χ(z)∊(z)1/4 ...
March 19, 2018: Optics Express
Matthew Hopgood, Gavin Reynolds, Richard Barker
We use computational fluid dynamics to compare the shear rate and turbulence in an advanced in vitro gastric model (TIMagc) during its simulation of fasted state Migrating Motor Complex phases I and II, with the United States Pharmacopeia Paddle Dissolution Apparatus II (USPII). A specific focus is placed on how shear rate in these apparatus effects erosion-based solid oral dosage forms. The study finds that tablet surface shear rates in TIMagc are strongly time-dependant and fluctuate between 0.001 and 360 s-1 ...
March 30, 2018: Journal of Pharmaceutical Sciences
Eric Sirois, Wenbin Mao, Kewei Li, Joseph Calderan, Wei Sun
Clinical use of transcatheter aortic valves (TAVs) has been associated with abnormal deployment, including oval deployment and under-expansion when placed into calcified aortic annuli. In this study, we performed an integrated computational and experimental investigation to quantify the impact of abnormal deployment at the aortic annulus on TAV hemodynamics. A size 23 mm generic TAV computational model, developed and published previously, was subjected to elliptical deployment at the annulus with eccentricity levels up to 0...
April 2, 2018: Artificial Organs
Chensheng Wu, Jonathan Ko, John R Rzasa, Daniel A Paulson, Christopher C Davis
We find that ideas in optical image encryption can be very useful for adaptive optics in achieving simultaneous phase and amplitude shaping of a laser beam. An adaptive optics system with simultaneous phase and amplitude shaping ability is very desirable for atmospheric turbulence compensation. Atmospheric turbulence-induced beam distortions can jeopardize the effectiveness of optical power delivery for directed-energy systems and optical information delivery for free-space optical communication systems. In this paper, a prototype adaptive optics system is proposed based on a famous image encryption structure...
March 20, 2018: Applied Optics
Yalçın Ata, Yahya Baykal
Effect of anisotropy on the average bit error rate (BER) is investigated when an asymmetrical Gaussian beam is propagated in an anisotropic turbulent ocean. BER is found to decrease in response to an increase in anisotropy levels in the x and y directions. Higher average signal-to-noise ratio, wavelength, and microscale length yield smaller BER values. BER starts to rise with an increase in the asymmetrical beam source size in the x and y directions, source size ratio in the x and y directions, salinity and temperature contribution factor, the dissipation of the mean squared temperature, and the propagation distance...
March 20, 2018: Applied Optics
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