Preserving mapping consistency under schema changes

In dynamic environments like the Web, data sources may change not only their data but also their schemas, their semantics, and their query capabilities. When a mapping is left inconsistent by a schema change, it has to be detected and updated. We present a novel framework and a tool (ToMAS) for automatically adapting (rewriting) mappings as schemas evolve. Our approach considers not only local changes to a schema but also changes that may affect and transform many components of a schema. Our algorithm detects mappings affected by structural or constraint changes and generates all the rewritings that are consistent with the semantics of the changed schemas. Our approach explicitly models mapping choices made by a user and maintains these choices, whenever possible, as the schemas and mappings evolve. When there is more than one candidate rewriting, the algorithm may rank them based on how close they are to the semantics of the existing mappings.Received: 13 January 2004, Accepted: 26 March 2004, Published online: 12 August 2004Edited by: M. Carey     

Studies on the electronic transport properties of some organic semiconductors in thin films

The investigated compounds are some derivatives of orthotolidin-N,N-bis (4-aminobenzene-2-sulphonic) acid. The temperature dependences of the electrical conductivity and Seebeck coefficient are studied on the thin films deposited from dimethylformamide solution onto glass substrates. It is known that the investigated compounds have typical semiconducting properties. The values of some important parameters of the films (thermal activation energy of electrical conduction, concentrations and mobilities of charge carriers) have been determined. The correlations between some of these parameters and molecular structure of the respective compounds are discussed.     

From Quantum to Classical Effects in Interactions Between Electrons and Very Intense Laser Beams

We prove that the Schrodinger equation, written for a closed system composed of an electron and electromagnetic field, has a solution at the classical limit if the dipole approximation is fulfilled and the magnetic potential vector enters in classical form in the Schrodinger equation. Though the above property is valid generally in the case of laser beams, its potential importance is increased for the domain of the very high intensities of the electrical field, where it is in agreement with a lot of recent classical models and experimental results from literature. This result leads to a simplified computational model for the interaction between electrons and laser beams.     

Capillary rise properties of porous mullite ceramics prepared by an extrusion method with various diameters of fiber pore formers

Porous mullite ceramics with unidirectionally oriented pores were prepared by an extrusion method using rayon fibers as the pore formers. Rayon fibers of 8.1, 9.6, 16.8, and 37.6 μm in diameter were used as the pore formers and were kneaded with alumina powder, kaolin clay, China earthen clay, and water to form pastes. These pastes were extruded into cylindrical tubes, dried, and fired at 1500 °C for 4 h. The apparent porosities ranged from 45.7 to 48.2 %. The pore size distributions showed a sharp peak at 9.4, 10.0, 15.6, and 30 μm with increasing fiber diameters. The height of the capillary rise was 1780, 1670, 1320, and 950 mm with increasing fiber diameter. The maximum capillary rise is much higher than previously reported. The contact angle and effective pore radius that determine the capillary rise ability were calculated by fitting the capillary rise curves using the Fries and Dreyer’s equation.     

Bioactive polymers LVII. A novel drug delivery system based on 5-nitro-2-furaldehyde-semicarbazone and poly(acrylic acid-co-vinyl alcohol)

The coupling of 5-nitro-2-furaldehyde-semicarbazone on to poly(acrylic acid-co-vinyl alcohol) copolymer by the use of dicyclohexylcarbodiimide as activator has been studied. On the basis of an experimental design, the influence of different parameters is studied (activator/support, drug/support, reaction time, solvent volume) in order to determine the optimum conditions for obtaining the maximum amount of the coupled drug on the support.     

Secondary data — the Poor Relative of Business Continuity

Cable & Wireless Plc acquired Exodus on the 1st February 2002.You think you’ve got BCP covered because you take regular backups and store them safely off site and perhaps even encrypt them … Think again. There is a whole plethora of devices and programs that facilitate your users accessing that data after you have dutifully restored it from your backup medium of choice. These facilitators contain secondary data and this data needs backing up and security measures as well, otherwise your primary data will resemble a newly restored vintage car: great looks, but no leaded gasoline available to run on.     

Improved Accuracy Pseudo-Exponential Function Generator With Applications in Analog Signal Processing

A new CMOS current-mode pseudo-exponential circuit based on the n-order Taylor series expansion will be presented. The most important advantage of the circuit with respect to the previously reported similar ones is the smaller value of the total computing error (under 0.3 dB), for a maximal output range of the proposed function generator greater than 40 dB. The total error could be very easily reduced by increasing the number of terms considered in the Taylor expansion. The circuit also presents the advantage of the independence of the output current on technological parameters. The frequency response is improved due to the strong inversion operation of all MOS transistors and to the current-mode operation of the circuit. The circuit area is relatively small due to the exclusively utilization of MOS transistors. The SPICE simulations confirm the theoretical estimated results. The proposed exponential function generator is designed in 0.12-mum CMOS technology and it consumes a reasonable power (less than 0.3 mW) for obtaining the previous mentioned computing error and has a low-voltage operation (a minimal accepted supply voltage under 1.2 V). The total silicon occupied area of the exponential function generator with third-order approximation is about 5.9 mum times 7.9 mum.     

Impact of Some Properties of Quaternized Polysulfone/Poly(Vinylidene Fluoride) Blend on the Potential Biomedical Applications

Blends of quaternized polysulfones with triphenylphosphonium pendant groups/poly(vinylidene fluoride) were analyzed to establish their impact on the rheological, morphological and surface properties, as well as their interactions with some blood compounds. The rheological functions reflect the influence of both polymers’ chemical structures. Blend compositions of the corresponding films influence the surface tension parameters, increase blend hydrophobicity and, implicitly, decrease the polar surface tension parameters. The specific surface characteristics of polymer blends are related to their interactions with some blood constituents and plasma proteins. Also, the specific microarchitecture of the blend represents an excellent scaffold for medical applications.     

Increase of regression speed of combustion through oxidizer doping

This paper presents an innovative method to increase the regression speed of a solid fuel grain by using oxidizer doping. The results obtained on a propulsion application showing the performance parameters as an output of a numerical model are provided. Two models are given that predict the regression speed increase for embedding wires and for oxidizer doping with a factor of ～2 to 3. Also, it is shown that this increase of the regression speed by using a low oxidizer doping percentage, which is based on the assumption that at a higher doping rate the combustion instabilities, can lead to detonations. Next, a thermochemical model for the combustion within the oxidizer doping model is afforded. For this model, the burn is assumed to take place around the surface of each of the oxidizer particles, being composed of two different burning processes: one is the burning on the surface of the solid fuel grain and the other is the burning between the solid fuel and the solid oxidizer. For a non-doped fuel grain, the burning takes place only on the surface of the fuel grain. Finally, a potential application of such propulsion units to small satellite launchers is presented, and a case study of such a vehicle intended to place a 50 kg payload on a low earth orbit (300 to 500 km altitude) is described. The modelling proposed is based on the assumption that the use of solid methane makes this launcher environmentally friendly.     

Microstructure,mechanical properties,and corrosion resistance of Ti-20Zr alloy in undoped and NaF doped artificial saliva

The corrosion behavior of a new, advanced Ti-20Zr alloy with α+β microstructure (determined by optical microscopy, XRD, and SEM) and very good mechanical properties (obtained from the stress-strain curve) is studied in this paper. The composition of the alloy native passive film was determined from a XPS analysis and the long-term corrosion resistance in undoped and doped states with 0.05M NaF artificial Carter-Brugirard saliva of different pH values, simulating the severe functional conditions of a dental implant, was analyzed by electrochemical methods. This alloy possesses an advantageous balance between good mechanical resistance and plasticity and Young’s modulus and exhibits more favorable electrochemical parameters and corrosion resistance than CP Ti due to its more resistant passive layer containing Ti₂O₃, TiO₂, and ZrO₂ protective oxides. After 1000 h of immersion in saliva, the protective properties of the alloy were enhanced due to the deposited surface layer that incorporated protective phosphates (shown by SEM and XPS).