Strain rate effects on the mechanical behavior of two Dual Phase steels in tension

This paper presents an experimental investigation on the strain rate sensitivity of Dual Phase steel 1200 (DP1200) and Dual Phase steel 1400 (DP1400) under uni-axial tensile loads in the strain rate range from 0.001?s^?1 to 600?s^?1. These materials are advanced high strength steels (AHSS) having high strength, high capacity to dissipate crash energy and high formability. Flat sheet specimens of the materials having gauge length 10?mm, width 4?mm and thickness 2?mm (DP1200) and 1.25?mm (DP1400), are tested at room temperature (20^°C) on electromechanical universal testing machine to obtain their stress-strain relation under quasi-static condition (0.001?s^?1), and on Hydro-Pneumatic machine and modified Hopkinson bar to study their mechanical behavior at medium (3?s^?1, and 18?s^?1) and high strain rates (200?s^?1, 400?s^?1, and 600?s^?1) respectively. Tests under quasi-static condition are performed at high temperature (200^°C) also, and found that tensile flow stress is a increasing function of temperature. The stress-strain data has been analysed to determine the material parameters of the Cowper-Symonds and the Johnson-Cook models. A simple modification of the Johnson-Cook model has been proposed in order to obtain a better fit of tests at high temperatures. Finally, the fractographs of the broken specimens are taken by scanning electron microscope (SEM) to understand the fracture mechanism of these advanced high strength steels at different strain rates.     

Study of Molecular Interactions in Binary Mixtures of Aniline with Carboxylic Acids at 293.15 K, 303.15 K and 313.15 K

Ultrasonic velocity, density, refractive index and viscosity of binary mixtures of aniline with acetic acid (AA) and propionic acid (PA) have been measured at 293.15, 303.15 and 313.15 K over the entire composition range. Further, the specific heat ratio, heat capacity, effective Debye temperature and pseudo-Gruensisen parameter and non-linearity parameter have been evaluated using ultrasonic absorption data. The deviation in isentropic compressibility, excess molar volume, excess intermolecular free length, deviation in molar refraction, deviation in viscosity, relaxation time, enthalpy, entropy and Gibbs energy of activation have been calculated from the experimental data and fitted with the Redlich-Kister polynomial equation. A comparative study has also been made between experimental and theoretically calculated values of densities using the HBT and Rackett density models. Mixing rules for the prediction of refractive index, e.g. Lorentz-Lorenz (L-L), Eykmen (Eyk), Weiner (W), Heller (H), Gladstone-Dale (G-D), Arago-Biot (A-B) and Newton (N) have been applied to these binary mixtures.     

Current perspectives on quinazolines with potent biological activities: A review

Quinazoline is a heterocyclic compound having biological activities. It is aromatic in nature having bicyclic structure containing benzene ring and pyrimidine ring. Quinazoline and its derivatives are found to have wide range of biological activities that is anticancer, analgesic, antimicrobial, antihypertensive, anticonvulsant, antimalarial, antitumor, and anti-tubercular activities. The purpose of this review is to highlight the recent researches made by researchers on various biological activities of quinazoline derivatives on different targets.     

Selective oxidation of benzyl alcohol to benzaldehyde, 1‐phenylethanol to acetophenone and fluorene to fluorenol catalysed by iron (II) complexes supported by pincer‐type ligands: Studies on rapid degradation of organic dyes

Hexacoordinated non‐heme iron complexes [Fe^II(L¹)₂](ClO₄)₂ ( 1 ) and [Fe^II(L²)₂](PF₆)₂ ( 2 ) have been synthesized using ligands L¹ = (E)‐2‐chloro‐6‐(2‐(pyridin‐2ylmethylene) hydrazinyl)pyridine and L² = (E)‐2‐chloro‐6‐(2‐(1‐(pyridin‐2‐yl)ethylidene)hydrazinyl) pyridine]. These complexes are highly active non‐heme iron catalysts to catalyze the C (sp³)?H bonds of alkanes. These iron complexes have been characterized using ESI?MS analysis and molecular structures were determined by X‐ray crystallography. ESI ? MS analysis also helped to understand the generation of intermediate species like Fe^III?OOH and Fe^IV=O. DFT and TD?DFT calculations revealed that the oxidation reactions were performed through high‐valent iron center and a probable reaction mechanism was proposed. These complexes were also utilized for the degradation of orange II and methylene blue dyes.     

Observation of Slow Relaxation and Single‐Molecule Toroidal Behavior in a Family of Butterfly‐Shaped Ln4 Complexes

A family of five isostructural butterfly complexes with a tetranuclear [Ln₄] core of the general formula [Ln₄(LH)₂(μ₂‐η¹η¹Piv)(η²‐Piv)(μ₃‐OH)₂]?x H₂O?y MeOH?z CHCl₃ ( 1 : Ln=Dy^III, x=2, y=2, z=0; 2 : Ln=Tb^III, x=0, y=0, z=6; 3 : Ln=Er^III, x=2, y=2, z=0; 4 : Ln=Ho^III, x=2, y=2, z=0; 5 : Ln=Yb^III, x=2, y=2, z=0; LH₄=6‐{[bis(2‐hydroxyethyl)amino]methyl}‐N′‐(2‐hydroxy‐3‐methoxybenzylidene)picolinohydrazide; PivH=pivalic acid) was isolated and characterized both structurally and magnetically. Complexes 1 – 5 were probed by direct and alternating current (dc and ac) magnetic susceptibility measurements and, except for 1 , they did not display single‐molecule magnetism (SMM) behavior. The ac magnetic susceptibility measurements show frequency‐dependent out‐of‐phase signals with one relaxation process for complex 1 and the estimated effective energy barrier for the relaxation process was found to be 49 K. We have carried out extensive ab initio (CASSCF+RASSI‐SO+SINGLE_ANISO+POLY_ANISO) calculations on all the five complexes to gain deeper insights into the nature of magnetic anisotropy and the presence and absence of slow relaxation in these complexes. Our calculations yield three different exchange coupling for these Ln₄ complexes and all the extracted J values are found to be weakly ferro/antiferromagentic in nature (J₁=+2.35, J₂=?0.58, and J₃=?0.29 cm^?1 for 1 ; J₁=+0.45, J₂=?0.68, and J₃=?0.29 cm^?1 for 2 ; J₁=+0.03, J₂=?0.98, and J₃=?0.19 cm^?1 for 3 ; J₁=+4.15, J₂=?0.23, and J₃=?0.54 cm^?1 for 4 and J₁=+0.15, J₂=?0.28, and J₃=?1.18 cm^?1 for 5 ). Our calculations reveal the presence of very large mixed toroidal moment in complex 1 and this is essentially due to the specific exchange topology present in this cluster. Our calculations also suggest presence of single‐molecule toroics (SMTs) in complex 2 . For complexes 3 – 5 on the other hand, the transverse anisotropy was computed to be large, leading to the absence of slow relaxation of magnetization. As the magnetic field produced by SMTs decays faster than the normal spin moments, the concept of SMTs can be exploited to build qubits in which less interference and dense packing are possible. Our systematic study on these series of Ln₄ complexes suggest how the ligand design can help to bring forth such SMT characteristics in lanthanide complexes.     

Normal vibrations and their dispersion in syndiotactic polystyrene

Normal modes and their dispersion are obtained for syndiotactic polystyrene (sPS) in the planar zigzag and s(2/1)2 helical conformations. Comparison is made with the spectra of isotactic polystyrene (ips) to identify the conformation-sensitive modes; for example, the 1221 cm^?1 mode is identified as a skeletal mode sensitive to chain structure and it also shows maximum dispersion. Bunching of dispersion curves and their intersection are among the characteristic features which are discussed. A check on the dispersion curves below 400 cm^?1 is made from the spectra of polystyrene oligomers.