A new method for reducing DNL in nuclear ADCs using an interpolation technique

The paper describes a new method for reducing the DNL associated with nuclear ADCs. The method named the “interpolation technique” is utilized to derive the quantisation steps corresponding to the last n bits of the digital code by dividing quantisation steps due to higher significant bits of the DAC, using a chain of resistors. Using comparators, these quantisation steps are compared with the analog voltage to be digitized, which is applied as a voltage shift at both ends of this chain. The output states of the comparators define the n bit code. The errors due to offset voltages and bias currents of the comparators are statistically neutralized by changing the polarity of quantisation steps as well as the polarity of analog voltage corresponding to last n bits) for alternate A/D conversion. The effect of averaging on the channel profile can be minimized. A 12 bit ADC was constructured using this technique which gives DNL of less than ±1% over most of the channels for conversion time of nearly 4.5 μs. Gatti's sliding scale technique can be implemented for further reduction of DNL. The interpolation technique has a promising potential of improving the resolution of existing 12 bit ADCs to 16 bit, without degrading the percentage DNL significantly.     

Privacy-preserving data mining: why, how, and when

Data mining is under attack from privacy advocates because of a misunderstanding about what it actually is and a valid concern about how it is generally done. This article shows how technology from the security community can change data mining for the better, providing all its benefits while still maintaining privacy.     

FABRICATION OF METALLIC-GLASS RIBBON REINFORCED GLASS-CERAMIC MATRIX COMPOSITES

Metallic-glass ribbon reinforced glass-ceramic matrix composites were fabricated by conventional wet pressing and sintering techniques. Some of the important aspects of composite fabrication are discussed. Variables such as binder content, compaction pressure and specimen size, and their interdependency on one another are discussed. The optimum processing conditions required to obtain the best specimens are described. The sintering temperature was also found to be very important. The sintering temperature not only controls the softening characteristics of the parent glass, but also affects the specimen distortion. Proper selection of the sintering temperature can ensure minimum distortion in the specimens, while at the same time retain the ease and efficiency of fabrication.     

Polyaniline Salts and Complexes as Catalyst in Bisindole Synthesis

Polyaniline salts are prepared by doping of polyaniline base with different Bronsted acids (H₂SO₄, HNO₃ and H₃PO₄), organic acid — p-toluene sulfonic acid (PTSA) and Iodine (I₂). Polyaniline complexes are also prepared using Lewis acids (BF₃, AlCl₃ and SnCl₂). Polyaniline salts and polyaniline complexes are characterized by physical, electrical and spectral methods. Polyaniline salts and polyaniline complexes are used as catalyst for the first time in bisindole synthesis. Bisindole (3,3′-bis(indolyl)phenylmethane) is obtained in excellent yields with simple and more environmental benign procedure. The use of polyaniline catalysts are feasible because of their easy preparation, easy handling, stability, easy recovery, reusability, good activity and eco-friendly.     

Results demonstrating techniques for enhancing electrochemical reactions involving iron oxide in slags and C in liquid iron

Two techniques are described for the enhancement of the kinetics of reduction of iron oxide from slags by carbon in molten iron. Laboratory experiments have shown that the rate of iron oxide reduction by carbon-saturated iron can be increased by 5 to 10 times when the reaction is carried out under a reduced-pressure atmosphere. This effect is thought to be the result of the increased volumetric gas evolution through the slag layer and the associated increase in slag stirring. A model is presented, which relates the mass-transfer coefficient for ferrous ions in the slag to its stirring that is controlled by varying the ambient pressure. Additional laboratory experiments examined the electrochemical nature of iron oxide reduction from slag by carbon in liquid iron. Results indicate that the reduction of iron oxide from slag is increased in the presence of an applied electric field. The external circuit allows for the separation of the half-cell reactions associated with iron oxide reduction and decarburization and increases the reaction area available for the individual reactions. These results have significant implications for several important slag metal reactions, which occur during ironmaking and steelmaking operations.     

Global state considered unnecessary: An introduction to object-based semantics

Semantics of imperative programming languages is traditionally described in terms of functions on global states. We propose here a novel approach based on a notion ofobjects and characterize them in terms of their observable behavior. States are regarded as part of the internal structure of objects and play no role in the observable behavior. It is shown that this leads to considerable accuracy in the semantic modelling of locality and single-threadedness properties of objects.     

Sperm motility and morphology as changing parameters linked to sperm count variations

Variations in semen analyses of 177 males over a 1 year period were assessed. The average means of total counts, motility, morphology, total motile count and non-motile % were determined for 5 classes of patients ranging from azoospermic to normospermic. Positive relationships between a falling sperm count, a decrease in motility and total motile counts were seen. Also, increasingly, abnormal forms were found with lower sperm counts.     

Online pricing for bandwidth provisioning in multi-class networks

We consider the problem of pricing for bandwidth provisioning over a single link, where users arrive according to a known stochastic traffic model. The network administrator controls the resource allocation by setting a price at every epoch, and each user’s response to the price is governed by a demand function. We formulate this problem as a partially observable Markov decision process (POMDP), and explore two novel pricing schemes––reactive pricing and spot pricing––and compare their performance to appropriately tuned flat pricing. We use a gradient-ascent approach in all the three pricing schemes. We provide methods for computing unbiased estimates of the gradient in an online (incremental) fashion. Our simulation results show that our novel schemes take advantage of the known underlying traffic model and significantly outperform the model-free pricing scheme of flat pricing.     

Finite element study of the fibre–matrix interface behaviour of [10°/90°] laminated composites under tensile loading

A three-dimensional unit cell has been developed and modelled using the finite element method to investigate the interface failure behaviour of SiCf/Si3N4 composites under tensile loading at room and elevated temperatures. The model idealizes the composite as a regular rectangular array of fibres in 0° and 90° orientations embedded in the matrix. It introduces three-dimensional contact elements between the fibre and the matrix to simulate the interface conditions between the two phases. Slippage between 0° and 90° layers is also considered by introducing another set of contact elements at the layer separation planes. Two interface conditions, namely, infinitely strong and weakly bonded, are considered to establish the correlation with the experimental data. To simulate the weak interface, the fibre and the matrix are assumed to slide over one another with shear stress through the Coulomb mechanism. The same assumption has been adopted for the layer separation planes. A finite element model utilizing these concepts has been developed. Stress–strain behaviour and the local stress distributions at various ambient temperatures within the unit cell, are presented. The investigation has also been extended to include the effects of residual stresses in the finite element model. It is shown that the model yields results that correlated reasonably well with the experimental data. © 1998 Kluwer Academic Publishers