Pebble bed-oil thermal energy storage for solar thermo-electric power systems

Results of a study to examine the operating characteristics of a 100 kWh thermal energy storage (TES) system suitable for solar thermo electric applications is described. The system chosen consisted of a pebble bed as the primary storage medium and oil as the heat transfer cum storage medium. The operating temperatures considered were between 230 and 250°C with a 20 deg C swing. A full-size unit consisting of a steel tank of volume 10 m³ with 50 mm pebbles, suitable instrumentation and facility for heating the oil was built. The important operating variables and characteristics of the system studied included the transient behaviour of the bed, namely the thermal wave front characteristics. Results of the theoretical analysis of the transient bed behaviour were compared with the experimental data on the wave front propogation characteristics and the comparisons are discussed. The uniformity of flow distribution is also examined.     

SignText: a web-based tool for providing accessible text book contents for Deaf learners

Universal Access in the Information Society - Lack of Sign Language-based learning tools is a hindrance in acquiring knowledge for deaf students. Technology-based tools have introduced innovative...     

Optimum difference mode excitations for monopulse arrays

A technique has been developed to obtain optimum difference mode excitations for monopulse arrays. In addition, a direct interpolation scheme has been devised for situations where near-optimum results would suffice. A parameter designated asu_{0}is identified with every optimum difference pattern. The choice of this parameteru_{0}determines the sidelobe level of the optimum pattern. The problem of obtaining the optimum excitations has been shown to be reducible to one of finding out the best approximation that minimizes the maximum deviation (minimax) from the real line (u = betad cos varpaxis), over a range determined byu_{0}. This latter problem has been solved using a modified Remez exchange algorithm. An extensive set of design curves has also been presented.     

Pervasive pose-aware applications and infrastructure

Pose-aware devices, in concert with functional geometric models describing architectural spaces, enable a new class of indoor applications, including resource location, route finding, direct population and annotation of world models, and direct information overlay. The article describes these applications along with the device infrastructure and algorithms required to support them. We demonstrate a few prototype devices and applications now underway and point to future directions in which these techniques might evolve.     

Thermal radiation by combustion gasesRayonnement thermique dans les gaz de combustionThermische strahlung von verbrennungsgasenTeплoвoe излyчeниe тoпoчныч гaзoв

Generalized expressions for the calculation of the emissivity, absorptivity, and other relevant radiation properties of molecular gases are given. New rational correlations for the properties of H₂O, CO₂, CO, NO, SO₂ and CH₄ are shown to be readily applicable to combustion gas radiation problems. Hand calculations are shown to be easily made for any arbitrary mixture of the above gases, and a simple computer routine for high-speed computation is described. Tabular and graphical aids giving the engineer physical insight into the radiation heat-transfer characteristics of the gases considered are presented and explained.     

Reliability modeling of degradation of products with multiple performance characteristics based on gamma processes

Many highly reliable products usually have complex structure, with their reliability being evaluated by two or more performance characteristics. In certain physical situations, the degradation of these performance characteristics would be always positive and strictly increasing. In such a case, the gamma process is usually considered as a degradation process due to its independent and non-negative increments properties. In this paper, we suppose that a product has two dependent performance characteristics and that their degradation can be modeled by gamma processes. For such a bivariate degradation involving two performance characteristics, we propose to use a bivariate Birnbaum-Saunders distribution and its marginal distributions to approximate the reliability function. Inferential method for the corresponding model parameters is then developed. Finally, for an illustration of the proposed model and method, a numerical example about fatigue cracks is discussed and some computational results are presented.