Structural, electrical and thermodynamical aspects of hydrogenated La-Ni-Si alloy

The structural, electrical and thermodynamic properties of a La-Ni-Si [La = 28.9%, Ni = 67.5%, Si = 3.6%] alloy have been investigated. Powder XRD results show that the lattice constants and unit cell volume of the alloy increase after hydrogen storage. It was also found that the resistance of the alloy increased with dissolved hydrogen concentration. Hydrogen absorption pressure composition isotherms have also been investigated which show the presence of two single a and β regions and one mixed (α + β) phase. The thermo-dynamic parameters viz. the relative partial molar enthalpy (ΔH) and relative partial molar entropy (ΔS) of dissolved hydrogen, are found to be in the range 8–18 kJ (mol H)^-1 and 25–63 JK^-1 (mol H)^-1. From the dependence of ΔH on the hydrogen concentration,X, the different phases [α, α + β, β] and phase boundaries of the alloy-H system are identified. Thermal conductivity and diffusivity of La-Ni-Si and its hydride have been measured at room temperature by using TPS technique. Thermal conductivity was found to decrease due to absorbed hydrogen in the alloy.     

Processing, microstructure, and mechanical properties of cast In-Situ Al(Mg, Ti)-Al2O3(TiO2) composite

In-situ particle-reinforced aluminum alloy-based cast composites have been synthesized by solidification of the slurry obtained by dispersion of externally added titanium dioxide (TiO₂) particles in molten aluminum at different processing temperatures. Alumina particles (Al₂O₃) form in situ through chemical reaction of TiO₂ particles with molten aluminum. Simultaneously, the chemical reaction also releases titanium, which dissolves into molten aluminum and results in the formation of intermetallic phase Ti(Al_1−x ,Fe _x )₃ during solidification. Increasing the processing temperature increases (1) the amount of elongated as well as blocky intermetallic phase Ti(Al_1−x ,Fe _x )₃, (2) the proportion of alumina particles in the reinforcing oxides, and (3) the porosity content in the resulting cast in-situ composite. The difference in particle content and porosity between the top and the bottom of the cast ingot increases with increasing processing temperature. The hardness of the cast in-situ composite is significantly more than that of the matrix alloy due to the presence of reinforcing particles, but the hardness is greatly impaired by the presence of porosity at the top of the cast ingot. The percent elongation of the cast in-situ composite decreases with increasing processing temperature possibly due to increasing porosity as well as an increasing amount of elongated intermetallic phase, which affects the percent elongation of the matrix alloy. The tensile and yield stresses of the cast in-situ composite decreases with increasing processing temperature again due to increasing porosity, which affects the ultimate tensile stress more than the yield stress. In the cast in-situ composite containing 3.31 ± 0.77 vol pct of porosity, the Brinell hardness is about 6 times its yield stress. The estimated yield stress of the cast in-situ composite at zero porosity as given by the linear least-squares fit appears to increase with particle content at a significantly higher rate than that predicted by the shear-lag model.     

A novel converter topology for multiple individually regulated outputs

Power supply voltages in digital systems have reduced considerably in recent years, and often digital components requiring different voltages are present on the same board. This has increased the demand for multiple output power distribution systems with tight individual load voltage regulation. This paper presents a power distribution system having a central power supply that acts as a controlled current source whose output is connected to individual loads on a time shared basis. All the magnetics are concentrated in the converter acting as the current source. The current source can be realized by a current controlled buck, buck-boost, or single-ended primary inductance converter (SEPIC). First, a comparative analysis of buck, buck-boost, and SEPIC based implementation of the current source is carried out. Next, a buck-based current source implementation with constant frequency pulse-width modulation control for the output voltages is described. Detailed component and control design, simulations, and experimental results for a 100-W prototype are presented.     

Self-sustained phase-shift modulated resonant converters: modeling, design, and performance

This paper presents an improved control technique for the full bridge series, parallel, and series-parallel resonant converters. This control technique combines a self-sustained oscillation mode with a phase shift modulation technique that can significantly reduce the range of frequency variation necessary for obtaining zero voltage switching in the resonant converters. This frequency reduction provides optimized component ratings and operating frequency. A simple and accurate low order mathematical model based on the sampled data technique that fully describes the steady-state, and dynamic performance of the resonant converters, has been developed. A refinement algorithm is developed to enhance the accuracy of the modeling technique and the converter design. The improved converter performance and the feasibility of the developed dynamic model have been investigated using the series-parallel resonant converter topology with a capacitive output filter. Finally, MATLAB numerical solutions, PSIM simulation results, and experimental results are given to highlight the merits of the proposed work.     

Information assimilation framework for event detection in multimedia surveillance systems

Most multimedia surveillance and monitoring systems nowadays utilize multiple types of sensors to detect events of interest as and when they occur in the environment. However, due to the asynchrony among and diversity of sensors, information assimilation – how to combine the information obtained from asynchronous and multifarious sources is an important and challenging research problem. In this paper, we propose a framework for information assimilation that addresses the issues – “when”, “what” and “how” to assimilate the information obtained from different media sources in order to detect events in multimedia surveillance systems. The proposed framework adopts a hierarchical probabilistic assimilation approach to detect atomic and compound events. To detect an event, our framework uses not only the media streams available at the current instant but it also utilizes their two important properties – first, accumulated past history of whether they have been providing concurring or contradictory evidences, and – second, the system designer’s confidence in them. The experimental results show the utility of the proposed framework.     

Characterization and identification of forming features for 3-D sheet metal components

This paper presents a new classification system for forming operations, and concepts for extracting and recognizing forming feature from the 3-D sheet metal component created in a wireframe model. A set of principles is developed for characterizing forming features geometrically and topologically. Forming features are extracted by identifying 3-D component graph and subgraphs by vector normal method and vertex fusion methodology. Further, various planes and their type in the component graph are identified, and adjacency plane relationship between them is determined. Cross bend features are extracted by identifying common edges. Pattern recognition is then done using isomorphism principle and a set of characterization principles developed for forming features. A flat pattern is developed for the 3-D component and shearing features are identified. Recognized pressworking features help in the integration of Computer Aided Process Planning (CAPP), codification system, mapping of tools, inspection of tools, etc. The system has been tested for live components.     

Development of an air recirculating tray dryer for high moisture biological materials

Fruits and vegetables are highly perishable and deterioration in quality and quantity occurs due to poor storage and processing facilities at the production site in developing countries like India. Dehydration of vegetables using a recirculatory dryer is possible but limited, in practice. The recirculatory dryers so far developed have a drawback of non-uniform drying along the length of the trays. Hence an effort was made to solve this problem. A recirculatory cabinet dryer of capacity 5 kg/batch using a central air distribution system was designed and developed. The dryer was tested with blanched potato chips. At a constant air flow rate of 1.5 m³/min and 65°C temperature, it took about 3 h time to reduce the moisture content from 856.94% (dry basis) to 9.98% (dry basis). The heat utilization factor (HUF) and thermal heat efficiency (THE) of the developed dryer were found to be 18.94% and 22.16%, respectively.     

Universal Single-Stage Grid-Connected Inverter

A new single-stage grid-connected inverter, suitable for distributed generation applications, is proposed. The inverter is universal in the sense that it can be switched between buck, boost, and buck--boost configurations by appropriately altering the pulse width modular (PWM) control. Discontinuous current mode (DCM) operation is implemented to facilitate shuffling between configurations during the converter operation. Such flexibility ensures maximum benefit of the buck, boost, and the buck--boost operations (e.g., low device stresses, higher efficiency, higher boosting capability, etc.). The PWM is achieved by comparing a high frequency carrier (triangular) waveform with a suitable reference waveform, which is not necessarily sinusoidal, but has a shape specific to the individual configuration and is derived by equating the power fed into the grid with that extracted from the source during each switching cycle. The values of the components (inductors and capacitors) need to be optimized so that DCM is maintained and the required amount of energy is transferred to the grid in all the three configurations during their respective operation. All the design expressions have been derived. A salient feature of this inverter is its compatibility with various types of sources (PV array, fuel cell, etc.) with varying voltage levels and control requirements. Being single-stage, the proposed topology offers additional advantages like modularity, compactness, and low cost. All the details of simulation and experimental work are presented.