Flows of cohesive granular media Mandal, Sandip; Gans, Adrien; Nicolas, Maxime ...
EPJ Web of Conferences,
01/2021, Letnik:
249
Journal Article, Conference Proceeding
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Cohesive granular media have broad applications in industries. However, our understanding of their flow behavior is still limited compared to dry granular media, although rich knowledge about their ...static and plastic properties has been gained. In this paper, we provide some insights into the flow behavior of cohesive granular media from our recent numerical studies using an inclined plane and a plane shear cell. We evidence that the cohesive nature of flows is significantly affected by material properties of the particles like stiffness and inelasticity in addition to the inter-particle adhesion and introduce the concept of “effective” adhesion, which incorporates the effects of these three variables. We propose constitutive relations involving dimensionless inertial number and “effective” cohesion number, based on the “effective” adhesion to describe the rheology. We also show that increasing adhesion increases the hysteresis in granular media, evidencing the existence of a prominent shear weakening branch in the friction coefficient
versus
inertial number rheological curve. Moreover, we reveal that this increasing hysteresis gives rise to the increasing occurrence of shear banding instability, pointing to the increasing possibility of jamming in cohesive granular media. Finally, we present a promising experimental approach to investigate the flow behavior of cohesive granular materials, based on a simple method of preparing a long time stable medium with a controlled adhesion between particles.
In the present work, the adsorption of carcinogenic pentavalent arsenic (As(V)) from an aqueous solution was studied using mesoporous cerium oxide (MCO). The MCO was synthesized in the precipitation ...process and confirmed by FT-IR, SEM-EDX, XRD, and BET instrumental techniques. Batch adsorption showed that 95% of As(V) was removed in the optimum conditions of 0.60 g/L adsorbent dose, 10 mg/L initial concentration, time 30 min, and pH 3. Pseudo-second-order kinetics and the Langmuir isotherm model were fitted to the experimental data. The MCO had a high surface area of 191.97 m.sup.2/g and a maximum adsorption capacity of 58.25 mg/g at pH 3. MCO could be able to remove 88% and 82% in the first and second cycles after being desorbed with 0.1 M NaOH solution. The Zeta potential and FTIR studies suggested that electrostatic attraction and ligand exchange mechanisms were responsible for As(V) adsorption. Keywords: mesoporous cerium oxide, As(V), adsorption, desorption and removal.
The fluoride ion removal from aqueous solution using synthesized Mg-Cr-Cl layered double hydroxide has been reported.Mg-Cr-Cl was characterized by X-ray powder diffraction,Fourier-transform ...infrared,thermo-gravimetric analysis,differential thermal analysis,and scanning electron microscope.Adsorption experiments were carried out in batch mode as a function of adsorption dosages,contact time,pH,and initial fluoride concentration to get optimum adsorption capacity.The adsorption kinetic study showed that the adsorption process followed first order kinetics.The fluoride removal was 88.5% and 77.4% at pH 7 with an adsorbent dose of 0.6 g/100 mL solution and initial fluoride concentration of 10 mg/L and 100 mg/L,respectively.The equilibrium was established at 40 min.Adsorption experiment data were fitted well with Langmuir isotherm with R 2 = 0.9924.Thermodynamic constants were also measured and concluded that the adsorption process was spontaneous and endothermic in nature.The removal percentage decreased slowly with increasing pH.This process is suitable for industrial effluents.The regeneration of the material is not possible.
The Coronavirus disease 2019 (COVID-19) pandemic poses a serious public health concern worldwide. Certain regions of the globe were severely affected in terms of prevalence and mortality than other. ...Although the cause for this pattern is not clearly understood, lessons learned from previous epidemics and emerging evidences suggest the major role of ecological factors like ambient air pollutants (AAP) and meteorological parameters in increased COVID-19 incidence. The present study aimed to understand the impact of these factors on SARS-CoV-2 transmission and their associated mortality in major cities of India.
This study used secondary AAP, meteorological and COVID-19 data from official websites for the period January-November 2020, which were divided into Pre-lockdown (January-March 2020), Phase I (April to June 2020) and Phase II (July to November 2020) in India. After comprehensive screening, five major cities that includes 48 CPCB monitoring stations collecting daily data of ambient temperature, particulate matter PM
and
were analysed. Spearman and Kendall's rank correlation test was performed to understand the association between SARS-CoV-2 transmission and AAP and, meteorological variables. Similarly, case fatality rate (CFR) was determined to compute the correlation between AAP and COVID-19 related morality.
The level of air pollutants in major cities were significantly reduced during Phase I compared to Pre-lock down and increased upon Phase II in all the cities. During the Phase II in Delhi, the strong significant positive correlation was observed between the AAP and SARS-CoV-2 transmission. However, in Bengaluru, Hyderabad, Kolkata and Mumbai AAP levels were moderate and no correlation was noticed. The relation between AT and SARS-CoV-2 transmission was inconclusive as both positive and negative correlation observed. In addition, Delhi and Kolkata showed a positive association between long-term exposure to the AAP and COVID-19 CFR.
Our findings support the hypothesis that the particulate matter upon exceeding the satisfactory level serves as an important cofactor in increasing the risk of SARS-CoV-2 transmission and related mortality. These findings would help public health experts to understand the SARS-CoV-2 transmission against ecological variables in India and provides supporting evidence to healthcare policymakers and government agencies for formulating strategies to combat the COVID-19.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Pine needles are the waste of pine forest and produced in a substantial amount every year during the fall. If not extracted from forest bed, they cause a widespread forest fire. In this study, pine ...needles were converted to char at different temperatures using a screw type pyrolyzer with an aim to find out the effect of thermal stress on the properties of chars and their intended end uses. The chars were evaluated for intrinsic physico-chemical transformations in comparison with the raw pine needles. Differences between chars produced in three temperatures and the raw biomass were studied by thermogravimetric analysis. It was found that the char produced at higher temperature showed a superior profile of apparent activation energy as compared with the char from low temperature. Coats–Redfern kinetics was used to compare the activation energies of chars and raw biomass, which showed that the char obtained from higher temperature had better thermal stability. From this study it can be concluded that chars produced at low temperatures in the screw reactor are useful as source of fuel, whereas the char of higher temperature is suitable for soil application and preparation of activated char.
Background and objective Anemia, particularly iron deficiency anemia (IDA), presents a significant global health challenge, particularly among children under the age of five years in developing ...nations. Concurrently, febrile convulsions (FC) affect up to 5% of neurologically healthy children aged 6-60 months, causing considerable distress among parents. There is a suggested correlation between fever and iron deficiency, which may exacerbate neurological risks, potentially lowering seizure thresholds and increasing the risk of FC. However, studies investigating the relationship between IDA and FC have shown conflicting results. In light of this, this study aimed to explore this relationship among children aged 6-60 months in Eastern India, an area where this association has yet to be thoroughly investigated. Materials and methods The case-control study included children aged 6-60 months. The cases consisted of children presenting with FC, while controls comprised children in the same age group presenting with febrile illness but without seizures. Informed consent was obtained, a detailed history was taken, and clinical examinations were conducted for both groups. Blood investigations were performed to diagnose IDA according to WHO criteria: hemoglobin <11 gm/dl with the classical triad of low mean corpuscular volume (MCV), low mean corpuscular hemoglobin (MCH), and low mean corpuscular hemoglobin concentration (MCHC) for age. Data analysis was performed using the R-based software Jamovi 2.4.8. with appropriate statistical tests. Results We included 81 cases and 80 controls. The study found a statistically significant association between IDA and FC with an odds ratio (OR) of 2.25 95% confidence interval (CI): 1.03-4.91; p=0.039. Additionally, the study revealed that hemoglobin levels, MCH, MCV, and MCHC were lower among cases compared to controls, while the red cell distribution width (RDW) was higher. Both these findings regarding RBC indices were statistically significant (p<0.05). Conclusions Our findings indicate a statistically significant association between IDA and FC among children under five years of age. Implementing measures to prevent IDA and strengthening existing strategies may help alleviate the burden of FC in this vulnerable population.
Thiophene appended rhodaminehydrazone derivative, RDHDTCA allows selective colorimetric and fluorescence recognition of Cu(2+) as low as 2.4 × 10(-8) M. RDHDTCA is capable to detect intracellular ...Cu(2+) in human breast cancer cells, MCF7 under fluorescence microscope.
AbstractGlobal warming causes glacial mass loss, leading to the growth of high-mountain glacial lakes. The presence of glacial lakes poses a significant threat to downstream communities, as they can ...produce destructive Glacial Lake Outburst Floods (GLOFs). Timely basin-scale inventory and GLOF susceptibility assessments are crucial, considering past GLOF events in the Himalayan region. Here, an updated inventory of glacial lakes in the Chenab basin, Western Himalayas was generated based on Sentinel-2 datasets for 2022. We assessed temporal changes and GLOF susceptibility for glacial lakes (>0.05 km2) through a multi-criteria based Analytical Hierarchical Process, classifying them into low, medium, high, and very high susceptibility classes. The results reveal 419 lakes (>0.001 km2; 9.97 ± 0.67 km2) in the basin in 2022. Glacial lakes (>0.05 km2) area increased by ∼75%, from 3.92 ± 0.58 to 6.86 ± 0.25 km2 during 1990–2022. Of the 42 lakes (>0.05 km2) evaluated, four showed very high GLOF susceptibility. The study emphasizes the impact of local geomorphology and glacier-lake interaction under warming climate, likely to increase the GLOF susceptibility in the region. Regular monitoring and detailed fieldwork for these susceptible lakes are crucial for early warning and disaster risk reduction for downstream communities.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
30.
Insights into the rheology of cohesive granular media Mandal, Sandip; Nicolas, Maxime; Pouliquen, Olivier
Proceedings of the National Academy of Sciences - PNAS,
04/2020, Letnik:
117, Številka:
15
Journal Article
Recenzirano
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Characterization and prediction of the “flowability” of powders are of paramount importance in many industries. However, our understanding of the flow of powders like cement or flour is sparse ...compared to the flow of coarse, granular media like sand. The main difficulty arises because of the presence of adhesive forces between the grains, preventing smooth and continuous flows. Several tests are used in industrial contexts to probe and quantify the “flowability” of powders. However, they remain empirical and would benefit from a detailed study of the physics controlling flow dynamics. Here, we attempt to fill the gap by performing intensive discrete numerical simulations of cohesive grains flowing down an inclined plane. We show that, contrary to what is commonly perceived, the cohesive nature of the flow is not entirely controlled by the interparticle adhesion, but that stiffness and inelasticity of the grains also play a significant role. For the same adhesion, stiffer and less dissipative grains yield a less cohesive flow. This observation is rationalized by introducing the concept of a dynamic, “effective” adhesive force, a single parameter, which combines the effects of adhesion, elasticity, and dissipation. Based on this concept, a rheological description of the flow is proposed for the cohesive grains. Our results elucidate the physics controlling the flow of cohesive granular materials, which may help in designing new approaches to characterize the “flowability” of powders.
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