Stability of a class of multiplicative nonlinear systems

The problem of input-output stability of a class of systems with multiplicative nonlinearities that arise from a generalization of the Luré problem is considered. Some results are presented that are believed to be new.     

Kinetic study of the solid-state reaction between phthalic anhydride and P-nitroaniline

The addition reaction between the compacted powders of phthalic anhydride and p-nitroaniline was studied. Both the reactants of equal particle size, were mixed in 1-to-1 molar ratio and compacted. Three particle sizes — 0.0065 cm, 0.0178 cm and 0.0376 cm and three compaction pressures — 302.0 kgf/cm², 785.0 kgf/cm² and 1208.0 kgf/cm² were used for the study. Conversions were measured at 80°, 90°, 100°, 110° and 120°C for 1/2, 1, 2, 4, 8, 12, 16, 20 and 24 hours. The reaction rate changed to a constant value, after an initial phase boundary process. The mole percentage conversions increased with decrease in particle size, increase in compaction pressure corresponding to a decrease in the initial porosity of the compact. It was also observed that the final porosity of the compact increased with increase in reaction temperature. Combination of Jander's model and parabolic rate law was used to calculate the values of the reaction rate constant equivalent. The activation energy was calculated to be 14 to 34 kilocalories per gram mole.     

A novel miniature hexagonal shape switched pattern and frequency reconfigurable antenna

This proposed work introduces the structure of frequency and pattern reconfigurable patch antenna. This proposed design comprises of a hexagon patch antenna with four oblique slits, two longitudinal and two latitudinal slits. Four PIN diodes are used to enable frequency and pattern reconfiguration in the longitudinal and latitudinal slits. The operating frequencies of the proposed reconfigurable antenna are 4.25, 5.65, 6.8, and 8.2 GHz and have a pattern slope of ?30°, 0°, +30°, and 180°. The pattern is reconfigurable in four directions without any servo system. The designed antenna is fabricated, and its performance is proved using quantifications. Experimental results have less than 15% error with the simulated results. This antenna is used for C‐band applications.     

Energy-efficient stable multipath routing in MANET

In MANET, node’s battery energy and stability of the links are often affecting the communication activities in the network. These two factors are one of the main reasons which are responsible for the loss of data packets and occurrence of congestion issue that networks are facing today. In order to overcome these issues, we propose an approach known as efficient and stable multipath routing in MANETs with congestion awareness. This approach is an extension work to our previous work where bandwidth and delay are considered during the routing. Here, in this approach, network estimates the residual energy and stability of the links in the network. While estimating the residual energy, it also considers the receiving energy and transmitting energy of the node. Then, stability of the link LET is estimated; this LET is obtained by using motion parameters (i.e. velocity, direction of the nodes). Based on these parameters, the network selects the path to transmit the data packets between the nodes.     

Self-assembly of cerium oxide nanostructures in ice molds

The formation of nanorods, driven by the physicochemical phenomena during the freezing and after the aging of frozen ceria nanoparticle suspensions, is reported. During freezing of a dilute aqueous solution of CeO2 nanocrystals, some nuclei remain in solution while others are trapped inside micro- and nanometer voids formed within the growing ice front. Over time (2-3 weeks) the particles trapped within the nanometer-wide voids in the ice combine by an oriented attachment process to form ceria nanorods. The experimental observations are consistent with molecular dynamics simulations of particle aggregation in constrained environments. These observations suggest a possible strategy for the templated formation of nanostructures through self-assembly by exploiting natural phenomena, such as voids formed during freezing of water. This research suggests a very simple, green chemical route to guide the formation of one- and three-dimensional self-assembled nanostructures.     

Spiral growth of one dimensional titania nanostructures using anodic oxidation

One dimensional spiral titania nanostructures were obtained by anodization of pure titanium from fluoride containing solutions of phosphoric acid. The formation of nanotubes was found to be dependant on current density. Field Emission Scanning Electron Microscopy (FESEM) shows the diameter of tubes around 70-100 nm which is consistent with the High Resolution Transmission Electron Micrographs (HRTEM) and Atomic Force Microscopy (AFM) images. HRTEM showed the one dimensional growth as spiral in nature which was also supported by AFM images. This anisotropic growth is compared with the possible growth mechanisms.     

Optimal machining conditions for turning Ti-6Al-4V using response surface methodology

Machining titanium is one of ever-increasing magnitude problems due to its characteristics such as low thermal conductivity, modulus of elasticity and work
hardening. The efficient titanium alloy machining involves a proper selection of process parameters to minimize the tangential force (F_z) and surface roughness (R_a). In the present work, the performance of PVD/TiAlN coated carbide inserts was investigated using response surface methodology (RSM) for turning Ti-6Al-4V. The effects of process parameters such as speed (v), feed (f), depth of cut (d) and back rake angle (γ_y) on F_z and R_a were investigated.
The experimental plan used for four factors and three levels was designed based on face centered, central composite design (CCD). The experimental results indicated that F_z increased with the increase in d, f and decreased with the increase in v and γ_y, whereas Ra decreased with the increase in v and γ_y, and increased with d and v. The goodness of fit of the regression equations and model fits (R ²) for F_z and R_a were found to be 0.968 and 0.970, which demonstrated that it was an effective model. A confirmation test was also conducted in order to verify the correctness of the model.     

Enhancement of uniform temperature distribution during casting solidification by methoding process

The main purpose of this study was to adapt proper methoding models to improve the cast ability and reduce the defects in casting. According to many researchers, 90% of the defects in casting are due to the wrong design of gating and riser systems and 10% due to casting defects. Here we are improving the runner and riser placement through methoding process. In the present work, to validate the advantages of methoding, we have selected casting model with and without methoding, temperature distribution over various positions have been analysed and it is found that casting model with methoding provides uniform temperature distribution.     

Automated generation of NC part programs for turned parts based on 2-D drawing image files

This paper describes a novel method for automated generation of process plans and numerical control (NC) part programs from 2D drawing image files. Four algorithms are introduced in this paper. First algorithm deals with extraction of geometrical data, second algorithm used to recognise turned features from the extracted geometrical data base. Recognised features are then passed to third and fourth algorithms for generation of process plans and NC part programs respectively. Using proposed system, it is possible to achieve fully automation of recognition of turned features, generation of process plans and NC part programs. Thus, it becomes possible to go from scanned image to finished product in a fully automated fashion. These algorithms have been implemented on mini-computer to process image data, and display recognised turned features, process plans and creates output files containing NC part programs. These NC part programs are verified through CNC train simulation package. The results are satisfactory.