Search results

The phenomenon of superconductivity has been studied for 90 years, with the latest surge in popularity occurring in the late 1980s, when high‐temperature superconductors were first created. In this time much progress has been made to create commercially viable applications of the technology and understand the theory behind the phenomenon. Furthermore, at a time when national science policy was undergoing close scrutiny, the high‐temperature superconductor boom served as a high‐profile case study of the role of government in spurring the acceptance of new technologies. This bibliography provides resources that chronicle the technological and scientific developments in the field since its discovery and the policy decisions and issues that governments and society made when faced with a possible scientific revolution.

Develops an original 12‐step management of technology protocol and applies it to 51 applications which range from Du Pont’s failure in Nylon to the Single Online Trade Exchange for Auto Parts procurement by GM, Ford, Daimler‐Chrysler and Renault‐Nissan. Provides many case studies with regards to the adoption of technology and describes seven chief technology officer characteristics. Discusses common errors when companies invest in technology and considers the probabilities of success. Provides 175 questions and answers to reinforce the concepts introduced. States that this substantial journal is aimed primarily at the present and potential chief technology officer to assist their survival and success in national and international markets.

Briefly reviews previous literature by the author before presenting an original 12 step system integration protocol designed to ensure the success of companies or countries in their efforts to develop and market new products. Looks at the issues from different strategic levels such as corporate, international, military and economic. Presents 31 case studies, including the success of Japan in microchips to the failure of Xerox to sell its invention of the Alto personal computer 3 years before Apple: from the success in DNA and Superconductor research to the success of Sunbeam in inventing and marketing food processors: and from the daring invention and production of atomic energy for survival to the successes of sewing machine inventor Howe in co‐operating on patents to compete in markets. Includes 306 questions and answers in order to qualify concepts introduced.

The thermal stability of superconductor is numerically investigated under the effect of a two‐dimensional hyperbolic heat conduction model. Two types of superconductor wires are considered, Types II and I. The thermal stability of superconductor wires under the effect of different design, geometrical and operating conditions is studied. The Effect of the time rate of change of the disturbance and the disturbance duration time is investigated. Generally, it is found that wave model predicts a wider stability region as compared to the predictions of the classical diffusion model.

The objectives of this study are to assess the utility of the high‐Tc superconductor, yttrium barium copper oxide (YBCO), as a gate material in two‐ and three‐terminal superconductor‐insulator‐semiconductor (SulS) devices, and to study the electrical properties of the insulator and the insulator/Si interface. The YBCO and yttria‐stabilised‐zirconia (YSZ) layers were epitaxially grown on Si by pulsed‐laser deposition. The SulS diodes were fabricated using standard lithographic techniques, with evaporated gold providing the gate and substrate contacts. Electrical characterisation of these superconducting devices is performed using current vs. voltage and capacitance vs. voltage (C‐V) measurements under bias‐temperature cycling. It is found that deposition of thicker YBCO films (≥ 1500 A) minimises the leakage current of the devices, resulting in electrically stable capacitors, especially at superconducting temperatures. A thermally activated process in the temperature range 80–295 K, as determined from flat‐band shifts of C‐V curves, is attributed to trapping/detrapping mechanisms in the SiOx interfacial layer between YSZ and Si. The mobile ions present in YSZ, which affect the room‐temperature C‐V behaviour, give rise to adjustable threshold voltages at superconducting temperatures. These findings will have a significant impact on future transistors using this capacitor as the gate structure.

Ceramic superconductors experience losses when carrying alternating currents. A first step in an attempt to macroscopically model the loss mechanism is to consider the ac transport current in a ribbon that has a cross‐section of width much greater than thickness. To some extent high‐temperature superconductors behave in a way similar to type II superconductors in which the loss mechanism is described by the critical state model, where the current is assumed to flow with a constant critical density Jc and is independent of the magnetic flux density B and ∂B/∂t. The dominant mechanism is the irreversible motion of fluxoids due to their interaction with the pinning sites, resulting in a form of hysteretic loss that can be represented in macroscopic terms (in a system with only one component of magnetic field) as proportional to ∫HsdBa/T over a complete cycle of period T, where Hs is the surface magnetic field strength and Ba is the space average value of flux density. However, it is found that the high‐temperature materials exhibit strong flux creep effects, and so the critical state model may not provide a sufficient description. To find an alternative formulation it is necessary to consider the flux creep E‐J characteristic of the ceramic material. If a highly nonlinear expression for the resistivity ? can be found, it may be possible to model the flux and current behaviour as a diffusion process.

The purpose of the paper is to provide a comparison of first‐ and second‐order two dimensional finite element models for evaluating the electromagnetic properties and calculating AC loss in high‐temperature superconductor (HTS) coated conductors.

The models are based on the two‐dimensional (2D) H formulation, which is based on directly solving the magnetic field components in 2D. Two models – one with a minimum symmetric triangular mesh and one with a single‐layer square mesh – are compared based on different types of mesh elements: first‐order (Lagrange – linear) and second‐order (Lagrange – quadratic) mesh elements, and edge elements.

The number and type of mesh elements are critically important to obtain the minimum level of discretization to achieve accurate results. Artificially increasing the superconductor layer and choosing a minimum symmetric mesh with triangular edge elements can provide a sufficiently accurate estimation of the hysteretic superconductor loss for a transport current.

This paper describes how the selection of mesh type and number of elements affects the computation speed and convergence properties of the finite element model using two different types of meshing. It offers an insight into the different factors modelers must consider when modeling HTS coated conductors and the methods that may be applied when extending the model to complex device geometries, such as wound coils.

Specially formulated frit materials have been applied in thick film superconductors similar to the standard thick film materials in order to achieve processing parameters closely compatible with conventional thick film technology and alumina substrates. The applied frits have improved the adhesion and superconductor properties at the same time due to a superconductor bridge formation between the grains. Both YBCO and BSCCO systems have been analyzed. The results are promising.

Thick film superconductors with the nominal composition Bi2Pb0.5Sr2Ca2.5Cu3.5Ox were fired on stainless steel substrates and on alumina substrates covered with silver or gold thick film conductors. Films on stainless steel substrates were semiconducting due to reaction between the superconducting film and oxidised chromium and iron from the steel. Tc(R=0) of films on silver was between 80 K and 90 K while Tc (R=0) on gold was below 60 K. The low Tc (R=0) of films on gold is attributed to the interaction between the gold layer and copper from the superconductor.

In the paper is analyzed the influence of Josephson's junctions array on the transport current and magnetic properties of the high temperature ceramical, granular superconductors. It has been considered the influence of vortices penetrating the Junctions on the macroscopic current flowing through the sample. For the case of absence transport current the existence of vortices modifies magnetic field dependence of the screening currents and then such magnetic properties, as the shape of magnetization curves, while when the transport current is flowing the existence of vortices may lead to new critical state approach and in the consequence to the anomalies of current‐voltage characteristics. Comparison of the model with experimental data and possible application of phenomenon as high Tc superconducting sensor is also briefly reviewed.