Multi‐flexible‐body Dynamic Analysis of Horizontal Axis Wind Turbines

This article presents a structural dynamic analysis of horizontal axis wind turbines (HAWTs) using a new methodology. The methodology is based on representing a HAWT as a multi‐flexible‐body system with both rigid‐ and flexible‐body subsystems. The rigid‐body subsystems (nacelle, hub) are modelled as interconnected sets of rigid bodies using Kane's method. Kane's method leads to compact equations of motion for rigid‐body mechanisms. The flexible‐body subsystems (blades, tower) are modelled using geometrically exact, non‐linear beam finite elements derived from a mixed variational formulation for the dynamics of moving beams. The use of the mixed formulation allows for the direct determination of constraint forces and moments within the beam finite element and at the boundaries, thus allowing simple connectivity between the finite elements and rigid bodies. The equations for the rigid and flexible subsystems are coupled to obtain a unified framework that models the dynamic behaviour of the complete system. Linearization of the dynamic equations about the steady state solution yields system equations with periodic coefficients that must be solved by Floquet theory to extract the dynamic characteristics. Numerical studies are presented to investigate the natural frequencies and mode shapes for a HAWT with flexible blades and tower. Copyright © 2002 John Wiley & Sons, Ltd.     

Field performance and operation of a flat-glass solar heat collector

A “Base-Line,” flat-glass solar heat collector has been designed and constructed that can be manufactured economically for commercial use. Four of the collectors, 34 by 76 in. (approximately 18 ft²), were installed to provide hot water to a private home in Melbourne, Florida.The details of the collector are described, including coverplates, solar absorber, absorber coating, spacers, seals and glazing.A simple relationship has been established between the collector efficiency, the collector temperature and the rate of insolation for constant rates of flow of circulating fluids.The theoretical and field performance curves have been correlated for collector efficiency, collector temperatures, incident solar radiation and ambient air temperatures. The effect of fluid flow on collector temperatures for various collector parameters has also been presented.     

Bulk resilience of fibers

A theory has been developed for the average bending deformation of fibers in an assembly subjected to compression. It is shown that the maximum average bending deformation of the fibers does not exceed 17°, implying that the method of bulk resilience cannot be used as an indicator of elastic recovery of fibers for any precision measurements.     

An infrared technique for the quick analysis of cotton–polyester blends

The details of an infrared technique standardized to analyze cotton–polyester blends of different compositions are reported. It is observed that particle size plays a very important role in the peak intensity of the 1725 cm^?1 band (C?O stretching) in polyester, the absorption band recommended for analysis of cotton–polyester blends. However, the product of the band width and peak intensity is found to be dependent on particle size to a lesser extent and hence is a more reliable parameter in the measurement of percentage composition. It has further been shown that the method of sample preparation can affect the band width and hence the results. A suitable sample preparation procedure is, therefore, described whereby an accuracy of ±3% in the estimation of polyester content in a given blend can be achieved.     

Compatibility studies between carbamazepine and tablet excipients using thermal and non-thermal methods

Proper formulation is an important aspect of any dosage form design. As a part of preformulation studies, differential scanning calorimetry (DSC) was used to investigate the physicochemical compatibility between Carbamazepine and various excipients commonly used in tablet manufacturing, supported by Fourier transform infrared (FTIR) and x-ray powder diffraction (XRPD) studies. Compatibility studies were conducted on samples kept at room temperature and at an elevated temperature of 55°C for 3 weeks. Carbamazepine was found to be compatible with all lactose-based components, such as Granulac 230®, Flowlac 100®, and Microcelac 100®. Differential scanning calorimetry studies indicated incompatibility with mannitol, microcrystalline cellulose, starch, and stearic acid. However, XRPD and FTIR studies implied that all the above excipients are compatible with Carbamazepine. X-ray powder diffraction demonstrated incompatibility with stearic acid for samples stored at 55°C for 3 weeks, indicative of formation of a solid solution. Thus, DSC being a thermal method of analysis should not be used singly to detect any inherent incompatibility. It has to be supported sufficiently by other non-thermal techniques, such as XRPD and FTIR.     

A new public-domain program for mixed-signal simulation

A new public-domain simulator for mixed-signal circuits is described. The new simulator is very versatile, allowing the user to define new elements easily. The procedure adopted for simulation of circuits with both digital and analog elements is briefly discussed. Several simulation examples are presented to demonstrate the applications of the simulator. The simulator is expected to be particularly useful for engineering teachers in developing countries where access to expensive commercial mixed-signal simulators may be difficult     

Progress towards an international standard for data transfer in rapid prototyping and layered manufacturing

This paper discusses the informational requirements of rapid prototyping and layered manufacturing (RPLM). The study is motivated by the recent decision to embark on the development of a new Application Protocol for the international standard ISO 10303, specifically to handle layered manufacturing information.

The most common industrial use of RPLM today is for rapid prototyping, but a wider view of it as a flexible fabrication technology is taken here, to allow for future developments. Its use in building functional metallic parts under computer control has already been demonstrated, and commercial RPLM machines for building production parts are already being marketed.

The paper includes a survey of current and proposed data formats for communication between the various stages of the RPLM process. In comparing them, particular attention is given to the issue of extensibility to meet future needs. In this last respect, special emphasis is given to materials-related and other non-geometric information needed for fabricating multi-material objects and objects with graded material properties.