scholarly journals Measurements of dust deposition velocity in a wind-tunnel experiment

2014 ◽  
Vol 14 (17) ◽  
pp. 8869-8882 ◽  
Author(s):  
J. Zhang ◽  
Y. Shao ◽  
N. Huang
Keyword(s):  
Wind Tunnel ◽  
Deposition Velocity ◽  
Wind Tunnel Experiment ◽  
Dust Particles ◽  
Dust Deposition ◽  
Data Set ◽  
Wind Speeds ◽  
Deposition Velocities ◽  
Development And Validation ◽  
Single Instrument

Abstract. In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from PDA (particle dynamics analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and thus the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure dust deposition velocities for different particle sizes, wind speeds and surface conditions. For sticky-smooth wood and water surfaces, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire data set is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable data set of dust deposition velocities is obtained, which is valuable for the development and validation of dust deposition schemes.

scholarly journals Measurements of dust deposition velocity in a wind-tunnel experiment

2014 ◽  
Vol 14 (7) ◽  
pp. 9439-9474 ◽  
Author(s):  
J. Zhang ◽  
Y. Shao ◽  
N. Huang
Keyword(s):  
Wind Tunnel ◽  
Deposition Velocity ◽  
Wind Tunnel Experiment ◽  
Dust Particles ◽  
Dust Deposition ◽  
Wind Speeds ◽  
Deposition Velocities ◽  
Development And Validation ◽  
Single Instrument ◽  
Entire Dataset

Abstract. In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from the PDA (Particle Dynamics Analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and therefore the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure the dust deposition velocities for different particle sizes, wind speeds and surface conditions. For a sticky-smooth wood surface and a water surface, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire dataset is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable dataset of dust deposition velocity is obtained, which is of considerable value for the development and validation of dust deposition schemes.

Wind Tunnel Studyon Vortex-Induced Vibration Characteristics of Long-Span Suspension Bridges with Single Cable Plane

2014 ◽  
Vol 633-634 ◽  
pp. 1263-1266
Author(s):  
Huang Yu
Keyword(s):  
Wind Tunnel ◽  
Suspension Bridge ◽  
Wind Tunnel Experiment ◽  
Vibration Characteristics ◽  
Torsional Stiffness ◽  
Suspension Bridges ◽  
Vortex Induced Vibration ◽  
Long Span Bridges ◽  
Wind Speeds ◽  
Long Span

For modern long-span bridges, both the optimization of aerodynamic shape and the increase of torsional stiffness according to the result of the wind tunnel experiment could avoid the flutter instability.Vortex-inducedvibration with relatively large amplitude happens easily at low wind speeds. In this paper, based on wind tunnel experiment, by studying on the vortex-induced vibration characteristics of a long-span suspension bridge with single cable plane, aerodynamic measures for easing the vortex-induced vibration are given.

scholarly journals Field comparison of dry deposition samplers for collection of atmospheric mineral dust: results from single-particle characterization

2019 ◽  
Vol 12 (12) ◽  
pp. 6647-6665 ◽  
Author(s):  
Andebo Waza ◽  
Kilian Schneiders ◽  
Jan May ◽  
Sergio Rodríguez ◽  
Bernd Epple ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fluid Dynamics ◽  
Scanning Electron Microscopy ◽  
Deposition Rate ◽  
Dry Deposition ◽  
Deposition Velocity ◽  
Passive Samplers ◽  
Dust Deposition ◽  
Deposition Velocities ◽  
Scanning Electron

Abstract. Frequently, passive dry deposition collectors are used to sample atmospheric dust deposition. However, there exists a multitude of different instruments with different, usually not well-characterized sampling efficiencies. As a result, the acquired data might be considerably biased with respect to their size representativity and, as a consequence, also composition. In this study, individual particle analysis by automated scanning electron microscopy coupled with energy-dispersive X-ray analysis was used to characterize different, commonly used passive samplers with respect to their size-resolved deposition rate and concentration. This study focuses on the microphysical properties, i.e., the aerosol concentration and deposition rates as well as the particle size distributions. In addition, computational fluid dynamics modeling was used in parallel to achieve deposition velocities from a theoretical point of view. Scanning electron microscopy (SEM)-calculated deposition rate measurements made using different passive samplers show a disagreement among the samplers. Modified Wilson and Cooke (MWAC) and Big Spring Number Eight (BSNE) – both horizontal flux samplers – collect considerably more material than the flat plate and Sigma-2 samplers, which are vertical flux samplers. The collection efficiency of MWAC increases for large particles in comparison to Sigma-2 with increasing wind speed, while such an increase is less observed in the case of BSNE. A positive correlation is found between deposition rate and PM10 concentration measurements by an optical particle spectrometer. The results indicate that a BSNE and Sigma-2 can be good options for PM10 measurement, whereas MWAC and flat-plate samplers are not a suitable choice. A negative correlation was observed in between dust deposition rate and wind speed. Deposition velocities calculated from different classical deposition models do not agree with deposition velocities estimated using computational fluid dynamics (CFD) simulations. The deposition velocity estimated from CFD was often higher than the values derived from classical deposition velocity models. Moreover, the modeled deposition velocity ratios between different samplers do not agree with the observations.

scholarly journals Composition and mixing state of atmospheric aerosols determined by electron microscopy: method development and application to aged Saharan dust deposition in the Caribbean boundary layer

2018 ◽  
Author(s):  
Konrad Kandler ◽  
Kilian Schneiders ◽  
Martin Ebert ◽  
Markus Hartmann ◽  
Stephan Weinbruch ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Boundary Layer ◽  
South America ◽  
Deposition Velocity ◽  
Sea Salt ◽  
Dust Particles ◽  
Geometric Standard Deviation ◽  
Dust Deposition ◽  
Mixing State ◽  
The Caribbean

Abstract. The microphysical properties, composition and mixing state of mineral dust, sea-salt and secondary compounds were measured by active and passive aerosol sampling followed by electron microscopy and X-ray fluorescence in the Caribbean marine boundary layer. Measurements were carried out at Ragged Point, Barbados during June/July 2013 and August 2016. Techniques were developed to conclude from collected aerosol on atmospheric concentrations and aerosol mixing-state, and different models were compared. It became obvious that in the diameter range with the highest dust deposition the models disagree by more than two orders of magnitude. Aerosol at Ragged Point was dominated by dust, sea-salt and soluble sulfates in varying proportions. Contribution of sea-salt was dependent on local wind speed. Sulfate concentrations were linked to long-range transport from Africa/Europe and South America/Southern Atlantic Ocean. Dust sources were in Western Africa. The total dust deposition observed was 10 mg m−2 d−1 (range 0.5–47 mg m−2 d−1), of which 0.67 mg m−2 d−1 was iron and 0.001 mg m−2 d−1 phosphorus. Iron deposition had two sources, mainly silicate particles from Africa, and particularly in 2016 a lower contribution of small iron-rich particles from South America or Barbados of probably anthropogenic origin. Dust particles were mixed internally to a minor fraction (10 %), mostly with sea-salt and less frequently with sulfate. It was estimated that average dust deposition velocity under ambient conditions is increased by the internal mixture by 30–140 % for particles between 1 and 10 µm dust aerodynamic diameter, with approximately 35 % at the mass median diameter of deposition (7.0 µm). For this size, an effective deposition velocity of 6.4 mm/s (geometric standard deviation of 3.1 over all individual particles) was observed.

scholarly journals Composition and mixing state of atmospheric aerosols determined by electron microscopy: method development and application to aged Saharan dust deposition in the Caribbean boundary layer

2018 ◽  
Vol 18 (18) ◽  
pp. 13429-13455 ◽  
Author(s):  
Konrad Kandler ◽  
Kilian Schneiders ◽  
Martin Ebert ◽  
Markus Hartmann ◽  
Stephan Weinbruch ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Boundary Layer ◽  
Deposition Velocity ◽  
Sea Salt ◽  
Dust Particles ◽  
Geometric Standard Deviation ◽  
Dust Deposition ◽  
Mixing State ◽  
Velocity Models ◽  
The Caribbean

Abstract. The microphysical properties, composition and mixing state of mineral dust, sea salt and secondary compounds were measured by active and passive aerosol sampling, followed by electron microscopy and X-ray fluorescence in the Caribbean marine boundary layer. Measurements were carried out at Ragged Point, Barbados during June–July 2013 and August 2016. Techniques are presented and evaluated, which allow for statements on atmospheric aerosol concentrations and aerosol mixing state based on collected samples. It became obvious that in the diameter range with the highest dust deposition the deposition velocity models disagree by more than 2 orders of magnitude. Aerosol at Ragged Point was dominated by dust, sea salt and soluble sulfates in varying proportions. The contribution of sea salt was dependent on local wind speed. Sulfate concentrations were linked to long-range transport from Africa and Europe, and South America and the southern Atlantic Ocean. Dust sources were located in western Africa. The dust silicate composition was not significantly varied. Pure feldspar grains were 3 % of the silicate particles, of which about a third were K-feldspar. The average dust deposition observed was 10 mg m−2 d−1 (range of 0.5–47 mg m−2 d−1), of which 0.67 mg m−2 d−1 was iron and 0.001 mg m−2 d−1 phosphorus. Iron deposition was mainly driven by silicate particles from Africa. Dust particles were mixed internally to a minor fraction (10 %), mostly with sea salt and less frequently with sulfate. It was estimated that the average dust deposition velocity under ambient conditions is increased by the internal mixture by 30 %–140 % for particles between 1 and 10 µm dust aerodynamic diameter, with approximately 35 % at the mass median diameter of deposition (7.0 µm). For this size, an effective deposition velocity of 6.4 mm s−1 (geometric standard deviation of 3.1 over all individual particles) was observed.

Development and Validation of a Cognitive Reserve Index in HIV

2021 ◽  
pp. 1-9
Author(s):  
Navaldeep Kaur ◽  
Lesley K. Fellows ◽  
Marie-Josée Brouillette ◽  
Nancy Mayo
Keyword(s):  
Cognitive Reserve ◽  
Study Entry ◽  
Video Gaming ◽  
Everyday Functioning ◽  
Data Set ◽  
Multiple Indicators ◽  
And Performance ◽  
Competitive Games ◽  
Development And Validation

Abstract Objectives: In the neuroHIV literature, cognitive reserve has most often been operationalized using education, occupation, and IQ. The effects of other cognitively stimulating activities that might be more amenable to interventions have been little studied. The purpose of this study was to develop an index of cognitive reserve in people with HIV, combining multiple indicators of cognitively stimulating lifetime experiences into a single value. Methods: The data set was obtained from a Canadian longitudinal study (N = 856). Potential indicators of cognitive reserve captured at the study entry included education, occupation, engagement in six cognitively stimulating activities, number of languages spoken, and social resources. Cognitive performance was measured using a computerized test battery. A cognitive reserve index was formulated using logistic regression weights. For the evidence on concurrent and predictive validity of the index, the measures of cognition and self-reported everyday functioning were each regressed on the index scores at study entry and at the last follow-up [mean duration: 25.9 months (SD 7.2)], respectively. Corresponding regression coefficients and 95% confidence intervals (CIs) were computed. Results: Professional sports [odds ratio (OR): 2.9; 95% CI 0.59–14.7], visual and performance arts (any level of engagement), professional/amateur music, complex video gaming and competitive games, and travel outside North America were associated with higher cognitive functioning. The effects of cognitive reserve on the outcomes at the last follow-up visit were closely similar to those at study entry. Conclusion: This work contributes evidence toward the relative benefit of engaging in specific cognitively stimulating life experiences in HIV.

scholarly journals Dust Deposition on the Gulf of California Caused by Santa Ana Winds

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 275 ◽  
Author(s):  
Christian A. Álvarez ◽  
José N. Carbajal ◽  
Luis F. Pineda-Martínez ◽  
José Tuxpan ◽  
David E. Flores
Keyword(s):  
Gulf Of California ◽  
Dust Emission ◽  
Positive Influence ◽  
Dust Particles ◽  
Weather Research And Forecasting ◽  
Western Coast ◽  
Emission Rates ◽  
Dust Deposition ◽  
Santa Ana ◽  
Santa Ana Winds

Numerical simulations revealed a profound interaction between the severe dust storm of 2007 caused by Santa Ana winds and the Gulf of California. The weather research and forecasting model coupled with a chemistry module (WRF-CHEM) and the hybrid single-particle Lagrangian integrated trajectory model (HYSPLIT) allowed for the estimation of the meteorological and dynamic aspects of the event and the dust deposition on the surface waters of the Gulf of California caused by the erosion and entrainment of dust particles from the surrounding desert regions. The dust emission rates from three chosen areas (Altar desert, Sonora coast, and a region between these two zones) and their contribution to dust deposition over the Gulf of California were analyzed. The Altar Desert had the highest dust emission rates and the highest contribution to dust deposition over the Gulf of California, i.e., it has the most critical influence with 96,879 tons of emission and 43,539 tons of dust deposition in the gulf. An increase of chlorophyll-a concentrations is observed coinciding with areas of high dust deposition in the northern and western coast of the gulf. This kind of event could have a significant positive influence over the mineralization and productivity processes in the Gulf of California, despite the soil loss in the eroded regions.

Sign in / Sign up

Export Citation Format

Share Document