Correlation between central receiver size and solar field using flat heliostats

In Central Receiver Systems (CRSs), thousands of heliostats track the sunrays and reflect beam radiation on to a receiver surface. The size of the reflected image and the extent of reflection from the heliostats are one of the important criteria that need to be taken into account while designing a receiver, since spillage losses may vary from 2 to 16% of the total losses. The present study aims to determine the size of an external cylindrical receiver, such that the rays reflected from all the heliostats in the field are intercepted. A dimensionless correlation with respect to tower height and receiver size (diameter and height) as a function of heliostat size and its position is discussed in the paper. This correlation could be used as a first-order approximation to estimate the receiver dimensions. When applied to the Ivanpah Solar Electricity Generating Station (ISEGS) plant, the correlation yields satisfactory estimation of receiver dimensions.     

A Controlled Agitation Process for Improving Quality of Canned Green Beans during Agitation Thermal Processing

This work introduces the concept of a controlled agitation thermal process to reduce quality damage in liquid‐particulate products during agitation thermal processing. Reciprocating agitation thermal processing (RA‐TP) was used as the agitation thermal process. In order to reduce the impact of agitation, a new concept of “stopping agitations after sufficient development of cold‐spot temperature” was proposed. Green beans were processed in No. 2 (307×409) cans filled with liquids of various consistency (0% to 2% CMC) at various frequencies (1 to 3 Hz) of RA‐TP using a full‐factorial design and heat penetration results were collected. Corresponding operator's process time to impart a 10‐min process lethality (F_o) and agitation time (AT) were calculated using heat penetration results. Accordingly, products were processed again by stopping agitations as per 3 agitation regimes, namely; full time agitation, equilibration time agitation, and partial time agitation. Processed products were photographed and tested for visual quality, color, texture, breakage of green beans, turbidity, and percentage of insoluble solids in can liquid. Results showed that stopping agitations after sufficient development of cold‐spot temperatures is an effective way of reducing product damages caused by agitation (for example, breakage of beans and its leaching into liquid). Agitations till one‐log temperature difference gave best color, texture and visual product quality for low‐viscosity liquid‐particulate mixture and extended agitations till equilibration time was best for high‐viscosity products. Thus, it was shown that a controlled agitation thermal process is more effective in obtaining high product quality as compared to a regular agitation thermal process.     

Design and material analysis for prototyping of four arm mechanical microgripper with self-locking and anti-slipping capability

Microsystem Technologies - In this work, a mechanically actuated microgripper is designed with the COMSOL Multiphysics and its analysis is discussed. The mechanical microgripper is having a...     

Modelling of Chevron electrothermal actuator and its performance analysis

Microsystem Technologies - In this work, a Chevron electrothermal actuator is designed and its analytical model is developed. Chevron actuator works on the principle of Joules heating effect and...     

Thermal barrier coating application of zircon sand

Naturally occurring zircon sand was plasma spray coated on steel substrates previously coated with NiCrAlY bond coat. The coatings were characterized for their microstructure, chemical composition, thermal shock resistance, and the nature of structural phases present. The as-sprayed coatings consisted of t-ZrO₂ (major phase), m-ZrO₂, ZrSiO₄ (minor phases), and amorphous SiO₂. These coatings, when annealed at 1200 °C/1.44 × 10⁴s yielded a ZrSiO₄ phase as a result of the reaction between ZrO₂ and SiO₂. Dramatic changes occurred in the characteristics of the coatings when a mixture of zircon sand and Y₂O₃ was plasma spray coated and annealed at 1400 °C/1.44 × 10⁴s. The t-ZrO₂ phase was completely stabilized, and these coatings were found to have considerable potential for thermal barrier applications.     

Effect of elastomer modification on the adhesive characteristics of maleimide‐functional phenolic resins

The effect of addition of elastomeric modifiers on the adhesive properties like lap shear strength and T‐peel strength of an addition curable, maleimide functional novolac phenolic resin (PMF), self‐cured and cocured with a novolac epoxy resin, was studied using aluminium adherends. The modifiers used were (1) two grades of carboxyl terminated butadiene acrylonitrile copolymer (CTBN) of different molecular weights, (2) a low molecular weight, epoxidized hydroxyl‐terminated polybutadiene, and (3) a high molecular weight acrylate terpolymer containing pendant epoxy functionality. The adhesive properties, when examined as a function of the varying concentrations of the additives, ranging from 10 to 30 parts per hundred parts (phr) of the resin, were found to depend on the nature of the matrix being modified as well as on the nature and concentration of the elastomer. The adhesive properties at ambient temperature of the self‐cured, highly brittle PMF resin were dramatically improved by the inclusion of all the elastomers, the increase being substantial in the case of high molecular weight CTBN. For the more rigid, less ductile, epoxy‐cured PMF system, the adhesive properties were marginally improved by the high molecular weight CTBN, whereas the other elastomers were practically ineffective. For both self‐cured and epoxy‐cured PMF systems, the inclusion of these elastomers generally decreased the high‐temperature adhesive properties, implying impairment of thermal characteristics, evidenced also from their dynamic mechanical spectra. The presence of phase‐separated elastomer particles in the modified systems has been evidenced from scanning electron micrographs. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2321–2332, 1999     

Simplified design and analysis method for a waveguide iris filter

A simplified method for design and analysis of a direct coupled waveguide iris filter suitable for computer aided design implementation is presented. A curve fit formula for calculating the aperture dimensions of an iris as a function of normalized shunt inductor values is given. The analysis of the entire filter response is calculated using ABCD parameters. Using proposed equations a five section iris filter at X band has been designed and tested. Comparison between measured and theoretical results is shown. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 150–154, 1999     

Influence of Load and Sliding Speed on Friction and Interface Temperature of Hypereutectic Alloyed Gray Cast Iron

The influence of incremental sliding speeds and normal loads on friction, wear and interface temperature have been investigated on a series of hypereutectic alloyed gray cast irons. Mass loss and friction coefficient values show inverse trend with sliding speeds. The interfacial temperature increases with incremental speeds and loads while the friction coefficient decrease with the same. The alloys with higher volume of graphite show slightly lower interfacial temperature due to higher thermal transport capacity. The conjoint interaction of asperities and debris possibly predominates at lower speeds and higher mass loss predominates at higher sliding speeds.     

An Object-Oriented Modeling and Simulation Environment for Reactive Systems Development

An environment to support the modeling, analysis, simulation, and development of state transition models, SMOOCHES (State Machines for Object-Oriented Concurrent Hierarchical Engineering Specifications), is presented. SMOOCHES allows the hierarchical construction, analysis, and simulation of state transition models in an object-oriented distributed environment. Statecharts (see Harel 1987b), a powerful mechanism for state transition specification, are fundamental to the development of SMOOCHES. To assist in the specification of hierarchical state transition models for distributed and reactive systems, statecharts are extended by introducing the concept of exit-safe states. SMOOCHES allows the specification of objects in the system with hierarchical state transition models and the derivation of new classes of objects through inheritance. A graphical monitoring system has been developed to represent and simulate the object state life cycles and monitor event generations. The example presented illustrates the modeling and simulation of different state life cycles of an assembly robot.