DC and ac Josephson effects observed in high-temperature superconductor YBaCuO

We report the observation of the dc and ac Josephson effect and quasiparticle tunnelling in the high-temperature superconductor YBaCuO. The observation is made at 4.2 K. These effects were observed in a junction made by a niobium tip pressed against a high-T _c sample of YBaCuO ceramic. We observed a clean dc Josephson effect with a critical currentI _c 2 A and the ac effect with Shapiro steps corresponding toV=(hf/2e)n. The nature of the junction is not clear; however, we suggest that all observed effects can be explained by assuming a singlet pairing state in the ceramic. We have also observed a very peculiar noise behavior along theV-I characteristic.     

An algorithm for solving sparse Nonlinear Least Squares problems

We introduce a new method for solving Nonlinear Least Squares problems when the Jacobian matrix of the system is large and sparse. The main features of the new method are the following:

1. The Gauss-Newton equation is “partially” solved at each iteration using a preconditioned Conjugate Gradient algorithm.
2. The new point is obtained using a two-dimensional trust region scheme, similar to the one introduced by Bulteau and Vial.

We prove global and local convergence results and we present some numerical experiments.     

Current oscillations in austenitic stainless steel induced by the presence of chloride ions

The conditions for current oscillations in austenitic stainless steel (AISI Type 303) in 1M H₂SO₄ containing Cl^? ions are given. The periodic oscillations are produced in a close potential range determined at the active-passive transition region. It requires a non-homogeneous distribution of inclusions and carbides at the metal surface and a concentration range of Cl^? ion where active and passive areas coexist on the metal surface. The constraints at the surface determining these two regions are related to the Cl^? ion competitive adsorption and the local accumulation of corrosion products. Electrochemical data and SEM observations are correlated.     

Surface Areas of Nitrated Hydrotalcites

Hydrotalcites in the nitrate form were prepared using microwave irradiation in the hydrotreatment step. The surface area (BET) of nitrated hydrotalcites was evaluated. Solids were characterized by atomic absorption, X-ray diffraction and BET analysis. Thermal pretreatment temperature determined the surface area of the hydrotalcites.     

Hydrolysis of fish oils containing polymers of triacylglycerols by pancreatic lipasein vitro

Fish oils containing different levels of polymers of triacylglycerols formed during autoxidation were incubated with pancreatic lipase to establish whether these polymers are substrates for lipase hydrolysis. With oils containing low amounts (less than 4%) of triacylglycerol polymers as substrates, both triacylglycerols and polymers of triacylglycerols were almost completely hydrolyzed, and fatty acid monomers and monoacylglycerols were the major lipid products. Under the same incubation conditions, some triacylglycerols remained intact when highly oxidized oils containing 20 or 30% triacylglycerol polymers were the substrate. The fatty acid composition of these residual triacylglycerols was almost identical to that of triacylglycerols present at the start of the assay. When fish oil containing 30% triacylglycerol polymers was incubated with the lipase, the component triacylglycerols and polymers of triacylglycerols were hydrolyzed at similar rates, and fatty acid dimers were detected as a product. It is concluded that the high molecular weight polymers of triacylglycerols present in oxidized fish oils can be hydrolyzed by pancreatic lipasein vitro.     

Gaussian,Lobatto and Radau positive quadrature rules with a prescribed abscissa

For a given $\theta \in (a,b)$ , we investigate the question whether there exists a positive quadrature formula with maximal degree of precision which has the prescribed abscissa $\theta $ plus possibly $a$ and/or $b$ , the endpoints of the interval of integration. This study relies on recent results on the location of roots of quasi-orthogonal polynomials. The above positive quadrature formulae are useful in studying problems in one-sided polynomial $L_1$ approximation.     

Application of the classical levels of intelligence to structuring the control system in an automated distribution centre

Traditional management and control models can benefit from added levels of intelligence to increase their capability to adapt to the continuous changes in global markets. After reviewing the classical definition of intelligence and its levels, this paper provides a new approach to help increase the responsiveness of management and control to changes and disturbances in the manufacturing supply chain. The ancient concept of the “Tertium Quid” has inspired a three-level community of agents (MAS-TRIO) that is proposed to improve the coordination of all actors involved. The proposed model combines Multi-Agent Systems (MAS) with Radio-Frequency Identification (RFID) to make possible a certain level of Autonomous Intelligence in the decision-taking process. This paper analyses how these levels of intelligence can be applied to management and control, and the performance of the proposed model has been tested at low and mid-levels on an experimental platform representing the facilities of a distribution centre controlled by a network of programmable logic controllers (PLCs).     

A genetic tango attack against the David–Prasad RFID ultra‐lightweight authentication protocol

Radio frequency identification (RFID) is a powerful technology that enables wireless information storage and control in an economical way. These properties have generated a wide range of applications in different areas. Due to economic and technological constrains, RFID devices are seriously limited, having small or even tiny computational capabilities. This issue is particularly challenging from the security point of view. Security protocols in RFID environments have to deal with strong computational limitations, and classical protocols cannot be used in this context. There have been several attempts to overcome these limitations in the form of new lightweight security protocols designed to be used in very constrained (sometimes called ultra‐lightweight) RFID environments. One of these proposals is the David–Prasad ultra‐lightweight authentication protocol. This protocol was successfully attacked using a cryptanalysis technique named Tango attack. The capacity of the attack depends on a set of boolean approximations. In this paper, we present an enhanced version of the Tango attack, named Genetic Tango attack, that uses Genetic Programming to design those approximations, easing the generation of automatic cryptanalysis and improving its power compared to a manually designed attack. Experimental results are given to illustrate the effectiveness of this new attack.     

A 2D algorithm with asymmetric workload for the UPC conjugate gradient method

This paper examines four different strategies, each one with its own data distribution, for implementing the parallel conjugate gradient (CG) method and how they impact communication and overall performance. Firstly, typical 1D and 2D distributions of the matrix involved in CG computations are considered. Then, a new 2D version of the CG method with asymmetric workload, based on leaving some threads idle during part of the computation to reduce communication, is proposed. The four strategies are independent of sparse storage schemes and are implemented using Unified Parallel C (UPC), a Partitioned Global Address Space (PGAS) language. The strategies are evaluated on two different platforms through a set of matrices that exhibit distinct sparse patterns, demonstrating that our asymmetric proposal outperforms the others except for one matrix on one platform.