scholarly journals The Variation of Riverbed Material due to Tropical Storms in Shi-Wen River, Taiwan

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
Chin-Ping Lin ◽  
Yu-Min Wang ◽  
Samkele S. Tfwala ◽  
Ching-Nuo Chen
Keyword(s):  
Grain Size ◽  
Geometric Mean ◽  
Size Variation ◽  
Annual Rainfall ◽  
Geometric Standard Deviation ◽  
Roughness Coefficient ◽  
Bed Form ◽  
Subsurface Material ◽  
Typhoon Season ◽  
Bed Material

Taiwan, because of its location, is a flood prone region and is characterised by typhoons which brings about two-thirds to three quarters of the annual rainfall amount. Consequently, enormous flows result in rivers and entrain some fractions of the grains that constitute the riverbed. Hence, the purpose of the study is to quantify the impacts of these enormous flows on the distribution of grain size in riverbeds. The characteristics of riverbed material prior to and after the typhoon season are compared in Shi-Wen River located at southern Taiwan. These include grain size variation, bimodality, and roughness coefficient. A decrease (65%) and increase (50%) in geometric mean size of grains were observed for subsurface and surface bed material, respectively. Geometric standard deviation decreased in all sites after typhoon. Subsurface material was bimodal prior to typhoons and polymodal after. For surface material, modal class is in the gravel class, while after typhoons it shifts towards cobble class. The reduction in geometric mean resulted to a decrease in roughness coefficient by up to 30%. Finally, the relationship of Shields and Froude numbers are studied and a change in the bed form to antidunes and transition form is observed, respectively.

scholarly journals Finite element modelling of microstructural changes during equal channel angular drawing of pure aluminium

2021 ◽  
Author(s):  
Serafino Caruso ◽  
Stano Imbrogno
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Finite Element ◽  
Size Variation ◽  
Fe Model ◽  
Pure Aluminium ◽  
Continuous Dynamic Recrystallization ◽  
Research Activities ◽  
Hardness Change ◽  
Continuous Dynamic

AbstractGrain refinement by severe plastic deformation (SPD) techniques, as a mechanism to control microstructure (recrystallization, grain size changes,…) and mechanical properties (yield strength, ultimate tensile strength, strain, hardness variation…) of pure aluminium conductor wires, is a topic of great interest for both academic and industrial research activities. This paper presents an innovative finite element (FE) model able to describe the microstructural evolution and the continuous dynamic recrystallization (CDRX) that occur during equal channel angular drawing (ECAD) of commercial 1370 pure aluminium (99.7% Al). A user subroutine has been developed based on the continuum mechanical model and the Hall-Petch (H-P) equations to predict grain size variation and hardness change. The model is validated by comparison with the experimental results and a predictive analysis is conducted varying the channel die angles. The study provides an accurate prediction of both the thermo-mechanical and the microstructural phenomena that occur during the process characterized by large plastic deformation.

scholarly journals Key factors affecting single scattering albedo calculation: Implications for aerosol climate forcing

2017 ◽  
Author(s):  
Duseong S. Jo ◽  
Rokjin J. Park ◽  
Jaein I. Jeong ◽  
Gabriele Curci ◽  
Hyung-Min Lee ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Radiative Forcing ◽  
Transport Model ◽  
Geometric Mean ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Geometric Standard Deviation ◽  
Physical Parameters ◽  
Chemical Transport Model ◽  
Aerosol Mass

Abstract. Single Scattering Albedo (SSA), the ratio of scattering efficiency to total extinction efficiency, is an essential parameter used to estimate the Direct Radiative Forcing (DRF) of aerosols. However, SSA is one of the large contributors to the uncertainty of DRF estimations. In this study, we examined the sensitivity of SSA calculations to the physical properties of absorbing aerosols, in particular, Black Carbon (BC), Brown Carbon (BrC), and dust. We used GEOS-Chem 3-D global chemical transport model (CTM) simulations and a post-processing tool for the aerosol optical properties (FlexAOD). The model and input parameters were evaluated by comparison against the observed aerosol mass concentrations and the Aerosol Optical Depth (AOD) values obtained from global surface observation networks such as the global Aerosol Mass Spectrometer (AMS) dataset, the Surface Particulate Matter Network (SPARTAN), and the Aerosol Robotic Network (AERONET). The model was generally successful in reproducing the observed variability of both the Particulate Matter 2.5 μm (PM2.5) and AOD (R ~ 0.76) values, although it underestimated the magnitudes by approximately 20 %. Our sensitivity tests of the SSA calculation revealed that the aerosol physical parameters, which have generally received less attention than the aerosol mass loadings, can cause large uncertainties in the resulting DRF estimation. For example, large variations in the calculated BC absorption may result from slight changes of the geometric mean radius, geometric standard deviation, real and imaginary refractive indices, and density. The inclusion of BrC and observationally-constrained dust size distributions also significantly affected the SSA, and resulted in a remarkable improvement for the simulated SSA at 440 nm (bias was reduced by 44–49 %) compared with the AERONET observations. Based on the simulations performed during this study, we found that the global aerosol direct radiative effect was increased by 10 % after the SSA bias was reduced.

scholarly journals Measurements in a highly polluted Asian mega city: observations of aerosol number size distribution, modal parameters and nucleation events

2005 ◽  
Vol 5 (1) ◽  
pp. 57-66 ◽  
Author(s):  
P. Mönkkönen ◽  
I. K. Koponen ◽  
K. E. J. Lehtinen ◽  
K. Hämeri ◽  
R. Uma ◽  
...  
Keyword(s):  
Size Distribution ◽  
Urban Areas ◽  
Geometric Mean ◽  
Formation Rate ◽  
Geometric Standard Deviation ◽  
Modal Parameters ◽  
Number Size Distribution ◽  
High Concentrations ◽  
Rural Sites ◽  
Aitken Mode

Abstract. Diurnal variation of number size distribution (particle size 3-800nm) and modal parameters (geometric standard deviation, geometric mean diameter and modal aerosol particle concentration) in a highly polluted urban environment was investigated during October and November 2002 in New Delhi, India. Continuous monitoring for more than two weeks with the time resolution of 10min was conducted using a Differential Mobility Particle Sizer (twin DMPS). The results indicated clear increase in Aitken mode (25-100nm) particles during traffic peak hours, but towards the evenings there were more Aitken mode particles compared to the mornings. Also high concentrations of accumulation mode particles (>100nm) were detected in the evenings only. In the evenings, biomass/refuse burning and cooking are possible sources beside the traffic. We have also shown that nucleation events are possible in this kind of atmosphere even though as clear nucleation events as observed in rural sites could not be detected. The formation rate of 3nm particles (J3) of the observed events varied from 3.3 to 13.9cm-3s-1 and the growth rate varied from 11.6 to 18.1nmh-1 showing rapid growth and high formation rate, which seems to be typical in urban areas.

scholarly journals Facies Evaluation and Depositional Environments of Carbonates of the Bagh Group, Dhar District, Madhya Pradesh, India

2021 ◽  
Vol 38 (1) ◽  
pp. 33-40
Author(s):  
Sreejita Chatterjee ◽  
Dhiren Kumar Ruidas
Keyword(s):  
Grain Size ◽  
Large Scale ◽  
Energy Condition ◽  
Size Variation ◽  
High Energy ◽  
Depositional Environments ◽  
Small Scale ◽  
Peninsular India ◽  
Sedimentary Structures ◽  
Nodular Limestone

A significant event of marine transgression took place in Central India during Late Turonian-Coniacian. Fossiliferous marine succession of Bagh Group is one of the few carbonate successions exposed in peninsular India which was in focus of the current study for understanding this event. The signatures of this event were identified in the carbonate succession. The carbonates of Bagh Group are composed of two formations: the lower part is represented by Nodular limestone Formation which is overlain by Bryozoan limestone Formation at the top. On the basis of grain size variation and sedimentary structures, the Nodular limestone is divisible into three facies: facies ‘A’, facies ‘B’ and facies ‘C’. A hardground exists between facies B and facies C. Lack of sedimentary structures and high mud content indicates low energy depositional setting for the Nodular limestone Formation. Similarly, Bryozoan limestone Formation is divisible into five facies: facies ‘D’, facies ‘E’, facies ‘F’, facies ‘G’ and facies ‘H’ based on grain size variation and sedimentary structures. All of these five facies are fossiliferous. Glauconites are present within facies ‘G’ and have two modes of occurrence - as infilling within Bryozoan limestone and as altered feldspar. Presence of both small- and large-scale cross-stratification in Bryozoan limestone with lesser mud content are indicative of high energy shallow marine conditions. Large-scale cross-stratifications are possibly representing tidal bars while the small scale cross stratifications are formed in inter bar setting. Presence of reactivation surfaces within facies ‘E’ also supports their tidal origin. Increase in depositional energy condition is also evident from dominated by packstone facies.

scholarly journals Assessment of thoron contribution to indoor radon exposure in Canada

2022 ◽  
Author(s):  
Jing Chen
Keyword(s):  
Detection Limit ◽  
Indoor Environment ◽  
Metropolitan Areas ◽  
Indoor Radon ◽  
Geometric Mean ◽  
Pooled Analysis ◽  
Geometric Standard Deviation ◽  
Radon Exposure ◽  
Canadian Population ◽  
Almost All

AbstractFrom 2007 to 2013, simultaneous radon (222Rn) and thoron (220Rn) measurements were conducted in a total of 3534 residential homes in 34 metropolitan areas covering 71% of the Canadian population. While radon levels were above the detector’s detection limit in almost all homes, thoron concentrations were measurable in only 1738 homes. When analysis was limited to homes where thoron concentrations exceeded the detection limit, a pooled analysis confirmed that thoron is log-normally distributed in the indoor environment, and the distribution was characterized by a population-weighted geometric mean of 13 Bq/m3 and a geometric standard deviation of 1.89. Thoron contribution to indoor radon dose varied widely, ranging from 1.3 to 32% geographically. This study indicated that on average, thoron contributes 4% of the radiation dose due to total indoor radon exposure (222Rn and 220Rn) in Canada.

Sedimentological and Geochemical Charectesization of Manaveli and Cuddalore Formations, Puducherry Basin, India

2020 ◽  
Vol 37 (2) ◽  
pp. 115-130
Author(s):  
Shyam Narayan Mude ◽  
Shyam Yawale ◽  
Vishal Choudhari
Keyword(s):  
Grain Size ◽  
Discriminant Function ◽  
Function Analysis ◽  
Size Variation ◽  
Source Area ◽  
Climatic Conditions ◽  
Sieve Analysis ◽  
Element Geochemistry ◽  
Statistical Parameters ◽  
Chemical Index

Sedimentological and Geochemical Charectesization  of Manaveli and Cuddalore Formations, Puducherry Basin, India   Shyam N. Mude, Shyam Yawale and Vishal Choudhari   Department of Geology, Fergusson College (Autonomous), Pune- 411004, India Email: [email protected]; [email protected]   Abstract: The lithostratigraphically rocks of Puducherry basin (Sub-basin of Cauvery Basin) have been classified as Valudavur, Mettuveli, Karasur, Manaveli, Cuddalore formations in ascending order of deposition. The sedimentological and geochemical studies of sediments from Manavali (Paleocene) and Cuddalore (Mio-Pliocene) formations were carried out to understand grain size variation and distribution of major oxides and trace elements.  The sieve analysis was used to study grain size variation and on the basis of grain sizes various geo-statistical parameters were calculated to understand depositional environment. The discriminant function analysis of the sediments from the Cuddalore Formation infers that mostly the sedimentation was occurred in fluvio-deltaic environment with incursions of shallow marine environment whereas bivariate plots suggests that the deposition was occurred in riverine to deltaic environment. The major element geochemistry of the Manaveli and Cuddalore formations have been carried out to understand the provenance, paleoclimate and source area weathering conditions. The values of CIA (Chemical Index of Alteration), CIW (Chemical Index of Weathering), ICV (Index of Compositional Variability) and PIA (Plagioclase Index of Alteration) of the sediments infer high weathering was occurred in source area of sediments for Manaveli and Cuddalore formations.  The ratio (Al2O3+K2O+Na2O)/SiO2 indicate semi-humid climatic conditions during deposition of Cuddalore Formation whereas Manaveli Formation was deposited in semi-arid climatic conditions. The discriminant function diagram (A-CN-K Plot), suggest Quartzose sedimentary provenance for Cuddalore and Mafic igneous provenance for Manaveli Formation.     Keywords:  Grain Size, Geochemistry, Manaveli, Cuddalore, Puducherry Basin

Feasibility study: Proposed alternative to N95 respirator during the personal protective equipment shortage from COVID-19 pandemic

2021 ◽  
Vol 19 (7) ◽  
pp. 192-202
Author(s):  
Ahel El Haj Chehade, MD ◽  
Jesintha Stephenson, MD ◽  
Evan Floyd, PhD ◽  
Jean Keddissi, MD, FCCP ◽  
Tony Abdo, MD ◽  
...  
Keyword(s):  
Pulse Oximetry ◽  
Feasibility Study ◽  
Personal Protective Equipment ◽  
Geometric Mean ◽  
Face Mask ◽  
The United States ◽  
Geometric Standard Deviation ◽  
Protective Equipment ◽  
Health Administration ◽  
Fit Testing

Introduction: Having an adequate supply of personal protective equipment during the COVID-19 pandemic has been a constant challenge for hospitals across the United States. In the event of shortages, our assembled mask might offer noninferior protection compared to an N95 respirator. Objective: To study the ability of an assembled mask to pass a quantitative fit testing.Methods: We conducted a feasibility study at the Oklahoma City Veteran Affairs Health Care System. Volunteers were fitted with an assembled mask made of either a Hans Rudolph half-face mask or a Respironics Performax full-face mask, attached to an Iso-Gard HEPA light Filter 28022 through a Performax SE elbow hinge. Quantitative fit testing was conducted using the Occupation Safety and Health Administration fit testing protocol. The primary outcome was the percentage of participants who pass the quantitative fit test. Secondary outcomes included the overall fit factor (FF), average FF for different exercises, changes in pulse oximetry and endtidal CO2 at 0 and 15 minutes, willingness to use the mask, and visibility assessment.Results: Twenty participants completed the study, and all (100 percent) passed the quantitative fit testing. The overall FF had a geometric mean of 2,317 (range: 208-16,613) and a geometric standard deviation of 3.8. The lowest FF was recorded while the subjects were talking. Between time 0 and 15 minutes, there was no clinically significant change in pulse oximetry and end-tidal CO2 levels. Most participants reported “very good” visibility and were “highly likely” to use the Hans Rudolph half-face mask in the case of shortage.Conclusion: Our assembled respirator offers noninferior protection to N95 respirators in the setting of hypothetical protective equipment shortage.

Sign in / Sign up

Export Citation Format

Share Document