Finite difference analysis of unsteady natural convection flow along an inclined plate with variable surface temperature and mass diffusion

An analysis is performed to study the transient laminar natural convection flows along an inclined semi-infinite flat plate in which the wall temperatureT _w ^′ and species concentration on the wallC _w ^′ vary as the power of the axial co-ordinate in the formT _w ^′ (x)=T _∞ ^′ +ax ⁿ andC _w ^′ =C _∞ ^′ +bx ^m respectively. The dimensionless governing equations considered here are unsteady, two-dimensional, coupled and non-linear integro-differential equations. A finite difference scheme of Crank-Nicolson type is employed to solve the problem. The velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number are studied in detail for various sets of values of parameters. Correlation equations are also established for Nusselt number and Sherwood number in terms of parameters.     

Investigation of in-plane stresses on bolted flange joints using digital speckle pattern interferometry

Digital Speckle Pattern Interferometry (DSPI) is a promising field for a wide range of applications such as measurement of displacements/deformations, contouring, nondestructive testing, etc. It has holographic sensitivity and circumvents delays in photographic processing/filtering. Speckle correlation interferometry can be made sensitive to only one of the components of in-plane displacement by illuminating the object with two beams symmetric about the viewing axis and imaging along this axis using a viction. This configuration allows measurement of in-plane displacements independent of out-of-plane displacements.

In this paper, the in-plane deformation/stress distribution has been studied for a typical bolted flange joint of a pressure vessel using two beam illumination DSPI. The information obtained can be very useful in predicting the leakage behaviour of such joints employed in pressure vessels. Experimental investigations along with theoretical predictions are presented.     

The electronic structure,spectra, and reactivity of nitrophenols

The all-valence-electron CNDO /2 calculations were performed for the three isomeric nitrophenols. Using the newly derived σ-core charges and subsequently revising the valence-state ionization potentials and one-center two-electron repulsion integrals, Pariser–Parr–Pople (PPP ) CI calculations were performed on the title compounds following the Nishimoto–Forster scheme. A better agreement between theory and experiment has been observed in spectral assignments compared to the conventional PPP approach. Information from the CNDO /2 calculations was used to obtain useful electronic structural parameters and to get a quantitative insight into the chemical reactivity of these molecules. All the results were compared with the basic compounds, phenol and nitrobenzene. The electronic spectra of these isomers were recorded in both polar and nonpolar solvents.     

Synthetic studies on indolocarbazoles: total synthesis of staurosporine aglycon

A synthesis of staurosporine aglycon and its analogs was achieved in a 28-36% overall yield starting from 2-methylindole. The prominent key steps for the synthesis of the indolocarbazole alkaloids involved electrocyclization and nitrene insertion reactions.     

Search for a light neutral particle in the decay of the 3.68 MeV state in C

A search is made for a short lived neutral particle, ø, in the decay of the 3.68 MeV (3/2^-) state in ¹³C. No evidence for such a particle with a rest mass in the region of 1.7–2.0 MeV/c² is found with a limit on the branching ratio Γ _ø/Γ_γ7×10 ⁻⁵. An upper limit of 10⁻⁶ is placed for the coupling of such a particle to proton/neutron.     

Ion transport mechanisms in salt-doped polymerized zwitterionic electrolytes

Polyzwitterions (polyZIs), macromolecules with repeating ampholytic monomers, are a novel class of materials with attractive properties for battery electrolytes. In this study, we probe the ion transport characteristics and underlying mechanisms in two salt-doped (Li⁺-TFSI⁻) polyZIs of similar composition with contrasting zwitterion (ZI) ionic organization: pendant monomers organized via backbone-anion-cation (B-ZI⁻-ZI⁺, Motif B) and backbone-cation-anion (B-ZI⁺-ZI⁻, Motif C). Within both Motifs B and C, the counterion of the pendant-end ZI moiety shows higher mobility. Similarly, when comparing Li⁺ or TFSI⁻ across motifs, it is seen that the respective pendant-end counterion possesses higher mobility than its backbone-adjacent counterpart. Furthermore, when comparing counterions to same-position ZI moieties, TFSI⁻ is seen to possess higher mobility than Li⁺ in each case, a result rationalized by invoking the lower interaction strength between the TFSI⁻ and ZI⁺. Analysis of ion-transport mechanisms demonstrate that the mobility of countercharges to the pendant-end ZI moiety correlates with the ion-association relaxation timescale, similar to ideas noted in polymerized ionic liquids in past studies. However, the mobility of countercharges to the backbone-adjacent ZI moiety is shown to be correlated with a cage relaxation time, which incorporates the combined effects of frustrated motion due to the presence of the polymer backbone and pendant-end ZI moiety and the higher mobility in a population of lightly ZI-coordinated ions. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 578–588     

Dense energetic compounds of carbon,hydrogen, nitrogen,and oxygen atoms. V. 1,2,7,8-bisfuroxano-3,4,9,10-tetranitro-5, 11-dehydro-5H, 11H-benzotriazolo[2, 1-a]benzotriazole (BTBB)

A reaction between 2, 8-dichloro-4, 10-dinitro-5, 11-dehydro-5H, 11H-benzotriazolo[2, 1-a]-benzotriazole 8 and sodium azide in dimethyl sulfoxide produced 3, 9-diazido-4, 10-dinitro-5, 11-dehydro-5H, 11H-benzotriazolo [2, 1-a]benzotriazole 10 rather than the 2.8-diazido isomer 9 expected by direct displacement. Thermolytic elimination of nitrogen (2 moles) converted the dinitro diazide 10 to 3,4,9,10-bisfuroxano-5, 11-dehydro-5H, 11H-benzotriazolo[2, 1-a]benzotriazole 11 that was subsequently nitrated to give the 2,8-dinitro derivative 12 . Similar nitration converted the dinitro diazide 9 to the trinitro 15 and tetranitro 14 derivatives: thermolysis of the latter gave 1,2,7,8-bisfuroxano-4, 10-dinitro-5, 11-dehydro-5H, 11H-benzotriazolo[2, 1-a]-benzotriazole 16 . Nitration (100% HNO₃, CF₃SO₃H) converted compound 16 to the 3,4,10-trinitro derivative 17 , whereas a similar nitration (100% HNO₃, FSO₃H) gave the title compound BTBB, an insensitive high-energy, high-density (d 2.03 g/cc) molecule. © 1995 John Wiley & Sons, Inc.