Historical Origin and Recent Development on Normal Directional Impact Models for Rigid Body Contact Simulation: A Critical Review

The impact is one of the most abundant phenomena in the field of multi-body dynamics when two or more bodies come in close vicinity and depending on the interaction properties and geometry, all the interacting bodies experience certain impulsive force for an infinitesimal duration. Nowadays, impact modelling becomes an intrinsic part in the modelling of structural pounding, granular materials, crash and machinery analysis, robotics and bio-mechatronics applications. Since the time of Newton, numerous literatures have been published on the modelling of both normal and oblique contact phenomena. The scope of this critical review is limited to consolidate the existing knowledge on the computational model of normal directional impact on rigid bodies. The literature related to modelling of oblique impact, soft body impact, impact damage in composites and associated stress wave propagation are excluded from the scope of this critical review. Smooth and non-smooth mechanics are two schools of thought in simulating the normal directional impact. In this review, the shortcomings of all the classes of compliance and non-smooth models are analysed in the unified dimensionless frame-work to compare their response output with the conventional stereo-mechanical model. This review opens a new avenue for future researchers in selecting a proper contact formulation for specific application.     

Structural,magnetic, and magnetotransport properties of LaFe0.5Ni0.5O3

The perovskite-type LaFe_0.5Ni_0.5O₃ belonging to the rhombohedral (space group R-3c) crystal structure has been synthesized for which we have identified a magnetic transition at T₁ =?8?K corresponding to the minimum observed in the derivative of temperature dependent magnetization. A bifurcation in the ZFC and FC curves is observed below T₁ that suggests a frustrated magnetic behavior. The non-zero moment above T₁ hints the possibility of the presence of a high-temperature magnetic transition in the material. The resistivity of LaFe_0.5Ni_0.5O₃ evolves as a function of temperature similar to that of a semiconductor. Mott's variable range hopping governs the conduction mechanism of the material. Presence of various anisotropy terms and inhomogeneous magnetic interactions lead to the presence of antiferromagnetic and ferromagnetic interfaces, which eventually causes a magnetic exchange bias and magnetic hysteresis in resistivity. We have also observed direction dependent magnetoresistance in the material.     

Synthesis and on-line ultrasonic characterisation of bulk and nanocrystalline La0.68Sr0.32MnO3 perovskite manganite

La_0.68Sr_0.32MnO₃ perovskite manganite samples were prepared using sonochemical reactor and solid state reaction technique. The ultrasonic velocity, attenuation and elastic moduli of samples were measured using ultrasonic through transmission method, at a fundamental frequency of 5 MHz over a wide range of temperatures. The temperature dependence of the ultrasonic parameters shows an interesting anomaly in all the compositions. The observed dramatic softening and hardening in sound velocities or attenuation is related to phase transitions. The linear magnetostriction effect is more dominant in the perovskite than volume magnetostriction effect which is evident from the observed anomalous in both longitudinal and shear velocities and attenuation. Further, a decrease in grain size in the sintered sample leads to a shift in the ferromagnetic transition temperature (T_C) from 375 to 370 K.     

Data gathering via mobile sink in WSNs using game theory and enhanced ant colony optimization

Optimal performance and improved lifetime are the most desirable design benchmarks for WSNs and the mechanism for data gathering is a major constituent influencing these standards. Several researchers have provided significant evidence on the advantage of mobile sink (MS) in performing effective gathering of relevant data. However, determining the trajectory for MS is an NP-hard-problem. Especially in delay-inevitable applications, it is challenging to select the best-stops or rendezvous points (RPs) for MS and also to design an efficient route for MS to gather data. To provide a suitable solution to these challenges, we propose in this paper, a game theory and enhanced ant colony based MS route selection and data gathering (GTAC-DG) technique. This is a distributed method of data gathering using MS, combining the optimal decision making skill of game theory in selecting the best RPs and computational swarm intelligence of enhanced ant colony optimization in choosing the best path for MS. GTAC-DG helps to reduce data transfer and management, energy consumption and delay in data delivery. The MS moves in a reliable and intelligent trajectory, extending the lifetime and conserving the energy of WSN. The simulation results prove the effectiveness of GTAC-DG in terms of metrics such as energy and network lifetime.

     

Microstructural analysis and corrosion behaviour of D9 stainless steel - Zirconium metal waste form alloys

Metal waste form (MWF) alloys of D9 stainless steel with 5-20 wt.% zirconium (Zr) were cast and used for the present work. The microstructural analysis by scanning electron microscopy of as-cast MWF alloys showed the presence of two distinctly different phases. Phases identified by X-ray diffraction techniques are mostly iron-based γ-austenite, Fe-Zr and Ni-Zr-type intermetallics. Corrosion properties evaluated by potentiodynamic polarization method in de-mineralized water at pH 1, 5, and 8 showed lower breakdown potential at pH 1 compared to pH 5 and 8. Impedance study showed a single semicircle curve with high polarization resistance indicating stable passive film under all conditions.     

Properties and sorption studies of polyethylene oxide–starch blended films

A series of polyethylene oxide (PEO) and starch blends were prepared by extrusion and their films prepared by compression molding. The mechanical, barrier, optical, thermal properties and surface morphology characteristics of PEO–starch blended films were studied. The tensile strength of the blended films decreased whereas the haze values increased with an enhanced starch concentration in PEO–starch blends. The inter-molecular interaction between PEO–starch blends were investigated with FTIR. The thermal properties were also analyzed by differential scanning calorimetric (DSC) and thermo-gravimetric analysis (TGA) techniques. Moisture-sorption characteristics of PEO–starch blended films were carried out at 27 °C for water activity (a_w) ranged from 0.1 to 0.9. The sorption data at different a_w were used to fit different sorption isotherm models as proposed in the literatures. The model constants were determined by linear fitting of the sorption equations. The high coefficient of determination R² (ranged from 0.7 to 1) confirms the applicability of the equations employed. The study on the application of such water activity data of PEO/starch blended films on different model equations will be helpful in prediction of durability and functional behavior of moisture sensitive biopolymeric films.     

Formation and Surface Structural Features of Crystalline Ceramic Nanocomposite Coatings on Aluminium Using Lithium Sulphate with Silicate Additive

We have synthesized a series of the ceramic coatings by anodization of aluminium using lithium sulphate and sodium silicate additive.Our experiments show that the present coatings are nanocomposites in nature,consisting of a mixture of nanocrystalline alumina,silica,aluminium silicate and mullite; the formation of alumina was similar to conventional anodizing technology,while the formation of mullite was attributed to an addition of sodium silicate.The microhardness of the coatings progressively increased with the increasing current density up to 0.2 A/cm2,which could mainly be attributed to the decrease of porosity in the interfacial region of the oxides up to the range.From the performance of the coatings against corrosion(Tafel/Nyquist plots),it was inferred that the coatings fabricated by lithium sulphate–sodium silicate bath have enhanced corrosion resistance(Rp=3.12 kΩ),as well as better microhardness value than that of the lithium sulphate bath alone(Rp=660.96 Ω) which confirm the perception that the silica particles included in the anodized alumina matrices randomly.Presence of Al,Si and O indicated that the electrolyte components had been intensively incorporated into the coatings.     

Multiwall carbon nanotube supported poly(3,4-ethylenedioxythiophene)/manganese oxide nano-composite electrode for super-capacitors

MWCNT-PSS/PEDOT/MnO₂ nano-composite electrodes were fabricated by generating pseudo-capacitive poly(3,4-ethylenedioxythiophene) (PEDOT)/MnO₂ nano-structures on poly(styrene sulfonate) (PSS) dispersed multiwalled carbon nanotubes (MWCNTs). PSS dispersed MWCNTs (MWCNT-PSS) facilitated the growth of PEDOT and MnO₂ into nano-rods with large active surface area and good electrical conductivity. The ternary MWCNT-PSS/PEDOT/MnO₂ nano-composite electrode was studied for the application in super-capacitors, and exhibited excellent capacitive behavior between −0.2 V and 0.8 V (vs. saturated Ag/AgCl electrode) with high reversibility. Specific capacitance of the nano-composite electrode was found as high as 375 F g⁻¹. In contrast, specific capacitance of MWCNT-PSS/MnO₂ and MWCNT-PSS nano-composite electrodes is 175 F g⁻¹ and 15 F g⁻¹, respectively. Based on cyclic voltammetric studies and cycle-life tests, the MWCNT-PSS/PEDOT/MnO₂ nano-composite electrode gave a highly stable and reversible performance up to 2000 cycles. Our studies demonstrate that the synergistic combination of MWCNT-PSS, PEDOT and MnO₂ has advantages over the sum of the individual components.     

Enhanced forward osmosis from chemically modified polybenzimidazole (PBI) nanofiltration hollow fiber membranes with a thin wall

To develop high-flux and high-rejection forward osmosis (FO) membranes for water reuses and seawater desalination, we have fabricated polybenzimidazole (PBI) nanofiltration (NF) hollow fiber membranes with a thin wall and a desired pore size via non-solvent induced phase inversion and chemically cross-linking modification. The cross-linking by p-xylylene dichloride can finely tune the mean pore size and enhance the salt selectivity. High water permeation flux and improved salt selectivity for water reuses were achieved by using the 2-h modified PBI NF membrane which has a narrow pore size distribution. Cross-linking at a longer time produces even a lower salt permeation flux potentially suitable for desalination but at the expense of permeation flux due to tightened pore sizes. It is found that draw solution concentration and membrane orientations are main factors determining the water permeation flux. In addition, effects of membrane morphology and operation conditions on water and salt transport through membrane have been investigated.