Interconnection of Subsystem Reduced-Order Models in the Electrothermal Analysis of Large Systems

Heat conduction in an electronic device is commonly modeled as a discretized thermal system (e.g., finite element or finite difference models) that typically uses large matrices for solving complex problems. The large size of electronic-system heat transfer models can be reduced using model reduction methods and the resulting reduced-order models can yield accurate results with far less computational costs. Electronic devices are typically composed of components, like chips, printed circuit boards, and heat sinks that are coupled together. There are two ways of creating reduced-order models for devices that have many coupled components. The first way is to create a single reduced-order model of the entire device. The second way is to interconnect reduced-order models of the components that constitute the device. The second choice (which we call the "reduce then interconnect" approach) allows the heat transfer specialist to perform quick simulations of different architectures of the device by using a library of reduced-order models of the different components that make up the device. However, interconnecting reduced-order models in a straightforward manner can result in unstable behavior. The purpose of this paper is two-fold: creating reduced-order models of the components using a Krylov subspace algorithm and interconnecting the reduced-order models in a stable manner using concepts from control theory. In this paper, we explain the logic behind the "reduce then interconnect" approach, formulate a control-theoretic method for it, and finally exhibit the whole process numerically, by applying it to an example heat conduction problem     

Structural, electrical and optical properties of Bi2Se3 and Bi2Se(3−x)Tex thin films

Thin films of Bi₂Se₃, Bi₂Se_2.9Te_0.1, Bi₂Se_2.7Te_0.3 and Bi₂Se_2.6Te_0.4 are prepared by compound evaporation. Micro structural, optical and electrical measurements are carried out on these films. X-ray diffraction pattern indicates that the as-prepared films are polycrystalline in nature with exact matching of standard pattern. The composition and morphology are determined using energy dispersive X-ray analysis and scanning electron microscopy (SEM). The optical band gap, which is direct allowed, is 0.67 eV for Bi₂Se₃ thin films and the activation energy is 53 meV. Tellurium doped thin films also show strong optical absorption corresponding to a band gap of 0.70-0.78 eV. Absolute value of electrical conductivity in the case of tellurium doped thin film shows a decreasing trend with respect to parent structure.     

Verification of schedulability for real-time programs

Assume that a real-time programP ^T consisting of a number of parallel processes is executed on a system having a setPr of processors which are shared between the processes by a real-time schedulerS ^T. Assume that P^T must meet some timing deadlines. We show that such an implementation ofP ^T can be represented as a transformationL(P ^T) and that the deadlines ofP ^T will be met if they are satisfied by the timing properties of the transformed program. The condition for feasibility of a real-time program executed under a scheduler is formalized and rules are provided for verification. The schedulerS ^T can be specifiedgenerically and applied to different programs, making it unnecessary to introduce low-level operations such as scheduling primitives into the programming language. Thus real-time program specification and Schedulability can be considered in the same framework and the timing properties of a program can be determined at the specification level. By separating the specification of the scheduler from that of the program, the feasibility of an implementation can be proved by considering a scheduling policy rather than its implementation details.     

Residual aluminium in water defluoridated using activated alumina adsorption - Modeling and simulation studies

The removal of fluoride from drinking water by the method of adsorption on activated alumina is found superior than other defluoridation techniques mostly due to the strong affinity between aluminium and fluoride. Dissolution of aluminium from the alumina surfaces into its free and hydroxide ions in the aqueous medium is reported to be very low, but the presence of high fluoride concentrations may increase its solubility due to the formation of monomeric aluminium fluoride and aluminium hydroxyl fluoride complexes. An Activated Alumina Defluoridation Model Simulator (AAD) has been developed to represent fluoride adsorption on the basis of the surface complexation theory incorporating aspects of aluminium solubility in presence of high fluoride concentrations and pH variations. Model validations were carried out for residual aluminium concentrations in alumina treated water, by conducting a series of batch fluoride adsorption experiments using activated alumina (grade FB101) treating fluoride concentrations of 1-10 mg/L, at varying pH conditions. The total residual aluminium in the defluoridated water is due to presence of both dissolved and precipitated Al-F complexed forms. The Freundlich adsorption isotherm was found fit for fluoride adsorption capacity versus residual fluoride concentrations for pH = 7.5, and the relationship is given by the linearised equation log (x/m) = log k + (1/n) log C_e with values of k = 0.15 mg/g and 1/n = 0.45 indicating favorable adsorption. The relationship is linear in the region of low fluoride concentrations, but as concentrations of fluoride increased, the formation of the dissolved AlF₃⁰ complexes was favored than adsorption on alumina, and hence makes the isotherm nonlinear. The AAD simulations can predict for operating fluoride uptake capacity in order to keep the residual aluminium within permissible limits in the alumina treated water.     

Direct observation of Frank-Read sources in stoichiometric bismuth telluride crystals

Stoichiometric crystals of bismuth telluride have been grown from the melt by the horizontal zone levelling technique. The multiplication of dislocations and dislocation density was studied by using chemical etching. Dislocation spirals and loops due to Frank-Read sources have been observed on the basal plane.     

Photocatalytic degradation of pesticide contaminants in water

Photocatalysis has been proved to be an effective and inexpensive tool for the removal of organic and inorganic pollutants from water. Of particular interest in this context, in recent years, has been the complete photocatalytic mineralisation of a variety of pesticides into harmless products. The technique is now reaching the pre-industrial level, with several pilot plants and prototypes being operational in various countries. This paper reviews the major developments in the area, with special reference to the mechanism of the process involved, nature of the reactive intermediates and final products.     

Compatibility problems after intravenous immunoglobulin--a case report

The purpose of this study was to determine whether there are changes in anterior and posterior glenohumeral translation after arthroscopic, nonablative, thermal capsuloplasty with a laser. Two anteriorly and two posteriorly directed loads were sequentially applied to the humerus of nine cadaveric glenohumeral joints, and anterior and posterior translation of the humerus on the glenoid was measured. The glenoid was rigidly fixed, and the glenohumeral joint was positioned simulating 90 degrees of shoulder abduction and 90 degrees of external rotation. Using the holmium:yttrium-aluminum-garnet laser, thermal energy was then applied to the anterior capsuloligamentous structures and anterior and posterior translation measurements were then repeated. The results showed a significant reduction in anterior and posterior translation after laser anterior capsuloplasty. Anterior translation decreased from 10.9 +/- 2.0 mm (mean +/- SEM) to 6.4 +/- 1.5 mm with the 15-N load; and from 13.4 +/- 2.1 mm to 8.9 +/- 1.8 mm with the 20-N load. Posterior translation decreased from 7.2 +/- 1.2 mm to 4.4 +/- 0.6 mm with the 15-N load and from 10.4 +/- 1.4 mm to 6.5 +/- 0.9 mm with the 20-N load. These results indicate that the holmium:yttrium-aluminum-garnet laser can be used to decrease glenohumeral joint translation and may be an effective treatment for glenohumeral joint instability.     

VISTECH contrast sensitivity testing in primary open angle glaucoma

DOT ELISA was compared with RT-PCR and tissue culture to detect RSV from nasopharyngeal aspirates. DOT ELISA had diagnostic sensitivity and specificity of 65.62% and 93.92%, respectively. The results indicate that DOT ELISA can be used for screening detection of RSV from clinical specimens and is suitable for small laboratories in the provincial areas of developing countries.