N-Sulfonylation of amines, imides, amides and anilides using p-TsCl in presence of atomized sodium in EtOH-THF under sonic condition

A simple, facile and an efficient procedure for the N-sulfonylation of amines, imides, amides and anilides using p-TsCl in the presence of atomized sodium in a mixture of EtOH-THF under sonic condition is developed. The method is rapid, mild and inexpensive; yields are high and the reactions go to completion within 2-8 min. © 2015 Elsevier B.V

Meglumine catalyzed one-pot green synthesis of novel 4,7-dihydro-1H-pyrazolo3,4-bpyridin-6-amines

Meglumine efficiently catalyzes the one-pot, five-component reaction of hydrazine, ethyl acetoacetate, aryl aldehydes, substituted phenylacetonitriles and ammonium acetate in ethanol at room temperature to afford novel 4,7-dihydro-1H-pyrazolo3,4-bpyridin-6-amine derivatives. The present approach offers several advantages such as shorter reaction durations, low cost, excellent yields, milder reaction conditions, simple workup procedure and is environment friendly. All the synthesized derivatives are characterized by IR,1H NMR,13C NMR, HRMS and CHN analysis. � 2016 Mohamed Afzal Pash

Stumbling Blocks of Online Learning During COVID 19 Pandemic – Perspectives of Students of Selected Universities in London

COVID 19 Pandemic has led to mayhem across the Planet. Educational institutions are the worst affected arena. There is a paradigm shift from conventional classroom teaching to online methods. But it has its own obstructions. Thus, this research is undertaken to study the impediments of online learning faced by the students of selected universities of London. The questionnaire was administered among 200 students out of which 196 responded. The results of the Study reveal that the major obstructions which hindered online learning were lack of computer skills, internet connectivity issues, difficulty in operating the software, absence of social bonding between teachers and students, difficulty in recording lectures, difficulty in grasping practical courses such as mathematics, finance, accounting, engineering etc. To cope up with the Stumbling Blocks, the Study advocates some of the most innovative and creative ways such as application of Bloom’s Digital Taxonomy, VARK Model, 5/5/5 rule etc

Characterisation of gas-atomised metal powders used in binder jet 3D printing

A comprehensive characterisation study has been undertaken to examine the flowability and spreadability of two distinct types of gas-atomised metal powders used in Binder Jet 3D printing technology. The experimental characterisation encompasses an analysis of the physical properties of individual particles as well as the flow behaviour of bulk powder. The data gathered from individual particle analysis are subsequently employed in numerical simulations of roller spreading by Discrete Element Method (DEM) to gain valuable insights into the intricate interplay between powder attributes and its spreading characteristics. The findings reveal that employing bulk characterisation tests, such as shear cell tests and compressibility indices, results in contradictory outcomes. Moreover, the spreadability data derived from the DEM simulations do not exhibit a strong correlation with the results obtained from the characterisation of the bulk powder. These results underscore that the flowability of the powder may not necessarily serve as an accurate measure of its spreadability when applied in thin layers for additive manufacturing. This study further establishes a crucial connection between the intrinsic properties of individual particles and the collective behaviour of particles within the bulk material

Interactive 4-D Visualization of Stereographic Images From the Double Orthogonal Projection

The double orthogonal projection of the 4-space onto two mutually perpendicular 3-spaces is a method of visualization of four-dimensional objects in a three-dimensional space. We present an interactive animation of the stereographic projection of a hyperspherical hexahedron on a 3-sphere embedded in the 4-space. Described are synthetic constructions of stereographic images of a point, hyperspherical tetrahedron, and 2-sphere on a 3-sphere from their double orthogonal projections. Consequently, the double-orthogonal projection of a freehand curve on a 3-sphere is created inversely from its stereographic image. Furthermore, we show an application to a synthetic construction of a spherical inversion and visualizations of double orthogonal projections and stereographic images of Hopf tori on a 3-sphere generated from Clelia curves on a 2-sphere.Comment: ICGG 2020 submissio

Analysis of the dynamics of the FT4 powder rheometer

Traditional powder flow measurement devices, such as shear cells, operate in the quasi-static regime of shear strain rate. The FT4 powder rheometer of Freeman Technology, developed over the last two decades, has provided a clearer differentiation of powder flowability in some instances. This has been attributed to the instrument operating in the dynamic regime of shear strain rates, a feature that has yet to be established. We report an analysis of the dynamic behaviour of a bed of glass beads made cohesive by silanisation and subjected to standard FT4 testing procedure, where a rotating blade is driven into a cylindrical bed, using a combination of experimental measurements and numerical simulations by the Distinct Element Method. The DEM analysis underestimates the flow energy measured experimentally, although the agreement is improved when sliding friction is increased. The shear stress of the powder in front of the blade is shown to be roughly constant along the radial direction and increasing as the impeller penetrates the bed, suggesting a characteristic shear stress can be determined for a powder under a given test conditions in the FT4. For ease of simulations large beads were used (1.7 – 2.1 mm). Future work will investigate the influence of particle properties and operational conditions on the prevailing stresses and strain rates

Comparison of cohesive powder flowability measured by Schulze Shear Cell, Raining Bed Method, Sevilla Powder Tester and new Ball Indentation Method

Poor powder flow leads to many problems during manufacturing and can lead to inaccurate dosing and off-specification products. Powder flowability is commonly assessed under relatively high applied loads using shear cells by characterising the unconfined yield strength at a range of applied loads. For applied stresses below 1 kPa, it becomes increasingly difficult to obtain reliable values of the unconfined yield strength. The bulk cohesion and tensile strength of the powder are then obtained by extrapolating the yield locus to zero and negative loads, respectively. However, the reliability of this approximation for a given material is not known. To overcome this limitation, techniques such as the Raining Bed Method, Sevilla Powder Tester and the newly-developed Ball Indentation Method may be used. In this paper, we report our measurement results of the tensile strength of glass beads, α-lactose monohydrate and various sizes of fluid catalytic cracking powders determined by the Sevilla Powder Tester and Raining Bed Method and compare them with those inferred from the Schulze Shear Cell. The results of the latter are also compared with those of the Ball Indentation Method. The outcome suggests that in the case of shear cell tests, the extrapolation of the yield locus to lower or negative loads is unsafe. The ball indentation method enables the characterisation of highly cohesive powders at very low compressive loads; however extrapolation to negative loads is still not reliable. In contrast, the Sevilla Powder Tester and Raining Bed Methods are able to characterise the tensile strength directly, but high bulk cohesion poses difficulties as the internal bed failure needs to be analysed in order to reliably estimate the tensile strength. These methods provide a better understanding of powder flow behaviour at low stresses, thus enabling a greater control of manufacturing processes

Characterisation of gas-atomised metal powders used in binder jet 3D printing

A comprehensive characterisation study has been undertaken to examine the flowability and spreadability of two distinct types of gas-atomised metal powders used in Binder Jet 3D printing technology. The experimental characterisation encompasses an analysis of the physical properties of individual particles as well as the flow behaviour of bulk powder. The data gathered from individual particle analysis are subsequently employed in numerical simulations of roller spreading by Discrete Element Method (DEM) to gain valuable insights into the intricate interplay between powder attributes and its spreading characteristics. The findings reveal that employing bulk characterisation tests, such as shear cell tests and compressibility indices, results in contradictory outcomes. Moreover, the spreadability data derived from the DEM simulations do not exhibit a strong correlation with the results obtained from the characterisation of the bulk powder. These results underscore that the flowability of the powder may not necessarily serve as an accurate measure of its spreadability when applied in thin layers for additive manufacturing. This study further establishes a crucial connection between the intrinsic properties of individual particles and the collective behaviour of particles within the bulk material

Jamming during particle spreading in additive manufacturing

Additive manufacturing (AM) is going through an exponential growth, due to its enormous potential for rapid manufacturing of complex shapes. One of the manufacturing methods is based on powder processing, but its major bottleneck is associated with powder spreading, as mechanical arching adversely affects both product quality and speed of production. Here we analyse transient jamming of gas-atomised metal powders during spreading. These particles are highly frictional, as they have asperities and multiple spheres and are prone to jamming in narrow gaps. Therefore their detailed characterisations of mechanical properties are critical to be able to reliably predict the jamming frequency as influenced by powder properties and process conditions. Special methods have been used to determine the physical and mechanical properties of gas-atomised stainless steel powders. These properties are then used in numerical simulations of powder spreading by the Discrete Element Method. Particle shape is reconstructed for the simulations as a function of particle size. The characteristic size D₉₀ by number (i.e. the particle size, based on the projected-area diameter, for which 90% of particles by number are smaller than this value) is used as the particle dimension accountable for jamming. Jamming is manifested by empty patches over the work surface. Its frequency and period have been characterised as a function of the spreader gap height, expressed as multiple of D₉₀. The probability of formation of empty patches and their mean length, the latter indicating jamming duration, increase sharply with the decrease of the gap height. The collapse of the mechanical arches leads to particle bursts after the blade. The frequency of jamming for a given survival time decreases exponentially as the survival time increases