Linearizer for pulse-shaping of received pulse in ultra-wideband radio systems

This paper presents a novel concept of pulse-shaping in an ultra-wide band radio system. Instead of attempting to design an antenna with flat group delay, the emphasis has been shifted to the signal processing aspect of pulse shaping. The received pulse which has broadened due to non-linear phase response of the propagating channel is shaped back closer to the ideal pulse using a linearizer. The block schematic of the linearizer is presented along with simulated results. Though only a Rayleigh first order pulse has been used for simulation purpose, the method can easily be generalized to incorporate other pulse shapes.     

Multi-objective optimization for optimum tolerance synthesis with process and machine selection using a genetic algorithm

This paper presents a new approach to the tolerance synthesis of the component parts of assemblies by simultaneously optimizing three manufacturing parameters: manufacturing cost, including tolerance cost and quality loss cost; machining time; and machine overhead/idle time cost. A methodology has been developed using the genetic algorithm technique to solve this multi-objective optimization problem. The effectiveness of the proposed methodology has been demonstrated by solving a wheel mounting assembly problem consisting of five components, two subassemblies, two critical dimensions, two functional tolerances, and eight operations. Significant cost saving can be achieved by employing this methodology.     

Assessment of the performance of different compost models to manage urban household organic solid wastes

The environmental, cultural, socio-economic and political conditions of each community greatly affect the municipality’s effort and decision-making in managing household wastes. Composting at home can be used as a sound method of SWM, can manage the waste at source itself thereby can increase their recycling. And vermicomposting is a viable and completely feasible option at household level, provided it is acceptable to family members to handle the worms and to remove worm-casts subsequently. In this regard, the present paper gives a methodological framework for assessing the management of urban household organic wastes using different compost models to influence the actual efficiency and effectiveness of a municipality’s collection and management services. The current study also deals with the challenges of solid waste management with a focus on the segregation of compostable wastes from the non-compostable ones and their composting, recycling or disposal. The non-compostable wastes can be left for recycling and re-use by the concerned authorities. The composting behavior and the efficiency of different compost models have been dealt with, and it is concluded that vermicomposting model is the best option. Urban residents can be educated to vermicompost not only their entire kitchen wastes but also garden wastes to reduce the burden on the municipal councils.     

Effect of grinding aids on the grinding energy consumed during grinding of calcite in a stirred ball mill

A series of wet-grinding experiments has been carried out on inorganic powders by a stirred ball mill to systematically investigate the grinding characteristics. The grinding power consumed for a given grinding time was considered, as well as the effect of grinding aids on particle size. The grinding energy consumed, defined as the integral of the grinding power over time, was also investigated. The grinding aids were found to influence the product size and decrease the grinding energy. This is attributed to the prevention of agglomeration and coating of the sample powder onto the ball and grinding chamber wall. The grinding process seemed to be controlled by the force of agglomeration of the ground products. It was demonstrated that the particle size and grinding consumption energy could be decreased by the addition of grinding aids.     

Simplified Impedance Model for Adhesively Bonded Piezo-Impedance Transducers

The electromechanical impedance technique employs surface-bonded lead zirconate titanate piezoelectric ceramic patches as impedance transducers for structural health monitoring and nondestructive evaluation. The patches are bonded to the monitored structures using finitely thick adhesive bond layer, which introduces shear lag effect, thus invariably influencing the electromechanical admittance signatures. This paper presents a new simplified impedance model to incorporate shear lag effect into electromechanical admittance formulations, both one-dimensional and two-dimensional. This provides a closed-form analytical solution of the inverse problem, i.e. to derive the true structural impedance from the measured conductance and susceptance signatures, thus an improvement over the existing models. The influence of various parameters (associated with the bond layer) on admittance signatures is investigated using the proposed model and the results compared with existing models. The results show that the new model, which is far simpler than the existing models, models the shear lag phenomenon reasonably well besides providing direct solution of a complex inverse problem.     

Simulation of optical model parameters with reduced model deficiency by D-optimal criterion

The nucleon optical model is widely used to calculate the elastic scattering cross-sections and polarizations. The only requirement, in using the optical model for a reliable prediction of the nuclear data is the unique set of optical model parameters (OMP). The uncertainties in the OMP lead to uncertainties in calculated cross-sections and thus the deficiency in the model itself. To our knowledge, there is no technique, to estimate the limits of variation of OMP to establish good fits with consequent reduction of optical model deficiency between these limits. In this paper, we propose D-optimal criterion and the technique of Determinant Inequalities developed by us to simulate OMP with reduced optical model deficiency. Our technique enables one to simulate the limits of variation of the OMP with the existing covariance data. The simulation of these limits would aid to establish good fits among the OMP. Further, the variation in the range of deficiency in the optical model can be ascertained well in advance. We demonstrate the utility of our technique to the OMP of ²³⁹Pu.     

A computationally efficient approach for NN based system identification of a rotary wing UAV

Neural Network (NN) models based on autoregressive structures have long been used for nonlinear system identification problems. Their application for on-line implementations, however require them to be trained within a prescribed time span, which is often related to the sampling time of the system. In this paper, we introduce a NN model that is embedded with a dimensionality reduction mechanism in order to reduce the size of the network. The dimensionality reduction is based on Principal Component Analysis (PCA) and the resulting smaller NN trains faster. The longitudinal and lateral dynamics of a rotary wing Unmanned Aerial Vehicle (UAV) is modelled using flight test data. The results of system identification, error statistics and training times are provided to highlight the benefits of the proposed approach for NN based system identification models.     

Comparative study of microwave and conventional methods for the preparation and optical properties of novel MgO-micro and nano-structures

Magnesium oxide (MgO) was synthesised by a simple microwave-assisted combustion route without using any template, catalyst or surfactant. For the purpose of comparison, it was also prepared using conventional method. The as-synthesized MgO was characterized by powder X-ray diffraction (XRD), Fourier Transform infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), Energy Dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The XRD results confirmed the formation of cubic phase MgO. FT-IR was used to investigate the adsorption of water and CO₂ on MgO surface and confirm the formation of Mg-O phase. The formation of MgO micro cubes structures was confirmed by HR-SEM. The formation of MgO nanosheets was confirmed by HR-SEM and TEM and their possible formation mechanisms were also proposed. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra respectively. An attempt has been made to compare the lattice parameter and the PL intensity.