Search results

This paper aims to report the modelling and simulation work that predicts the behaviours of both a Josephson junction (JJ) and a dc superconducting quantum interference device (SQUID). It is pertinent to predict the SQUID magnetometers’ behaviours via simulations, before subjecting them to real experiments because they are quite expensive to acquire, and can be easily damaged during test analysis.

To achieve this, power simulation (PSIM) was used to model and simulate a JJ, using the basic equation that describes the effective current through it. A dc SQUID magnetometer, which is composed of two JJs, was then modelled and simulated using the modelled JJ. Thermal noise simulation is also included, to observe its effects on the magnetometer’s output. A directly coupled flux-locked loop circuit was later included in the simulation to amplify and linearise the SQUID’s output, which is usually sinusoidal.

When steady bias currents were applied to the JJ, the resulting voltage across it was seen to oscillate. The JJ’s and SQUID’s voltage–current characteristics, and voltage–flux characteristics were also observed in the simulations, and the results respectively agree with the behaviours of a typical JJ and dc SQUID magnetometer.

A way of simulating SQUIDs, without a superconducting simulation tool, is presented. The work provides a much simpler way of studying the behaviour of dc SQUID magnetometers, due to the easy accessibility and fast simulation capability of the software used, with an added advantage of being able to simulate the thermal noise effects, without having to import this facility from secondary software.

The increase in seafood trade in recent years motivates more detailed studies of different species, as well as evaluation of the nutritional quality of their lipid content. Thus, the purpose of this paper is to evaluate the fatty acid composition, especially the concentrations and fractionation of omega‐3 essential fatty acid in classes of mussels (male and female), oysters, squid, and octopus captured on the south coast of Brazil.

Fatty acid methyl esters were prepared by methylation of total lipids and were separated by gas chromatography. Quantification of LNA, AA, EPA, and DHA was done against tricosanoic acid methyl ester as an internal standard. Total lipids were fractionated into neutral lipids and polar lipids by classical column chromatography.

The results of this study were as follows: the female mussel had the highest lipid content (3.52 per cent), followed by the male mussel (2.70 per cent), squid (1.05 per cent), octopus (0.79 per cent), and oyster (0.62 per cent). The samples that had the highest percentages of EPA and DHA in their lipid fraction were the female mussel and squid, respectively. The species belonging to the Bivalvia class (mussels and oysters) showed a predominance of PL, while those belonging to the cephalopods class (octopus and squid), showed a predominance of NL. The n‐6/n‐3 and polyunsaturated fatty acid/saturated fatty acids ratios of all samples analyzed were in accordance with the recommendations. The female mussel had the highest concentration of EPA+DHA omega‐3 fatty acids, corresponding to 1,064.63 mg EPA+DHA 100 g⁻¹ of the sample. So, the consumption of mussels caught off the southern coast of Brazil provides the omega‐3 essential fatty acids.

This paper provides important data concerning lipid quality of seafood caught off on the south coast of Brazil.

Many electronic journals are licensed on the basis that allowing connections from a specified IP address range is “good enough” as a mechanism for identifying authorised users. This is inadequate when legitimate users wish to connect from home via a commercial ISP. This paper discusses a novel approach to allowing this in a secure fashion, using Squid on Unix.

Josephson junctions act as active elements in superconducting electronics. The behavior of this nonlinear element is characterized by the relation between current and the quantum mechanical phase‐difference. For an accurate device modeling, detailed knowledge about this relation is necessary. This paper aims to discuss these issues.

To obtain detailed information, a method for DC measurement of the current‐phase relation suitable for all kinds of superconducting circuit elements was accomplished.

The authors developed a linear transformation algorithm to calculate the current‐phase relation from the measured data.

It turns out that in future designs additional connections and special test structures are required to gain more knowledge about inductance values required for the algorithm.

Based on the inverse calculation of that algorithm, the authors found a 7 percent deviation of the current‐phase relation of a standard superconductor/insulator/superconductor Josephson junction from the predicted sine‐wave behavior. Furthermore, the paper suggests to use this method to evaluate the current‐phase relation of new Josephson elements such as a superconductor/ferromagnet/superconductor junction. Therefore, the authors will deposit the new element directly on the chip with the test setup fabricated with standard Nb‐technology.

The purpose of this paper is to evaluate the proximate composition, amino acid and mineral profiles of seafood for human consumption.

A total of 21 seafood species (eight seawater, one fresh water fish, six crustacean and six mollusc species) of commercial importance were chosen and purchased from the Istanbul local fish market. The sample to amino acids analyze was prepared in accordance with the hydrolysis technique described by Waters AccQ.Tag Chemistry Package Method (HPLC). Determination of iron (Fe), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), selenium (Se), phosphorus (P) and iodine (I) was performed with thermo electron X7 inductively coupled plasma mass spectrometry (ICP‐MS).

The lipid contents of species were found to be very low and considered as lean. The highest total amino acid values of fishes, crustaceans and molluscs were determined in John Dory, hake, red scorpion fish, spiny lobster, Norway lobster, sea snail and pecten. The mineral content of seafood species were found to be 9.3‐157.11 mg/kg Fe, 558.13‐6095.89 mg/kg Na, 253.25‐1032.29 mg/kg Mg, 125.43‐17174.76 mg/kg Ca, 0.18‐7.76 mg/kg Se, 1586.45‐5811.16 mg/kg P and 0.086‐2.630 mg/kg I.

This paper is helpful to consumers and academics concerning the proximate, amino acid and mineral composition of 21 estimable seafood species (nine fish, six crustacean and six mollusc species).

The World Wide Web (WWW) has become an extremely popular information service. Large HTTP packets result in network congestion. Proxy cache servers are widely deployed on the Internet to overcome this obstacle. However, the approach yields an undesirable phenomenon – a small set of users misuse proxy servers to mirror the entire contents of Web sites. This behavior wastes network resources, increases WWW servers’ loads, increases users’ waiting time, and violates copyrights. Approaches to designing a proxy server with WWW usage control and to making the proxy server effective on local area networks are proposed to prevent such abnormal WWW access and to prioritize WWW usage. Finally, a system, ProxyBreaker, is implemented to demonstrate the approaches. The implementation reveals that the proposed approaches are effective, such that the abnormal Web access does not reoccur.