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    Resonant diaphragm pressure measurement system with ZnO on Si excitation

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    The principle of measuring pressure by means of a resonant diaphragm has been studied. An oscillator consisting of an integrated amplifier with a piezoelectrically driven diaphragm in its feedback loop has been built. The oscillator frequency is accurately proportional to the square of the pressure in the range of 60 to 130 Torr.\ud The frequency range is 1324 to 1336 Hz (this range being limited by a spurious mode which could be suppressed by better processing) for a 25 mm diameter diaphragm made of a silicon wafer and with PZT ceramics as driver and receptor. We have made an integrated version (1 × 1 mm2) of a square resonant diaphragm pressure guage by selective etching of (1 0 0) planes with ethylenediamine. The piezoelectric driving materials was sputtered zinc oxide. A driver was deposited midway between the bending point and the point of greatest curvature.\ud A receptor was located at a symmetrical position to give a optimum transfer condition.\ud The integrated current amplifier had a low impedance differential input stage, two gain cells and a high impedance output stage. These electrical conditions ensured maximum elastic freedom of the diaphragm. A digital circuit in I2L technology has been designed and made with eight-bit parallel read out of the frequency. This circuit may be directly connected to a microprocessor. The whole system contains the sensor chip, the analog amplifier chip and the digital chip, all in compatible technology.\ud \u

    Proximity effect in planar superconducting tunnel junctions containing Nb/NiCu superconductor/ferromagnet bilayers

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    We present experimental results concerning both the fabrication and characterization of superconducting tunnel junctions containing superconductor/ferromagnet (S/F) bilayers made by niobium (S) and a weak ferromagnetic Ni0.50Cu0.50 alloy. Josephson junctions have been characterized down to T=1.4 K in terms of current-voltage I-V characteristics and Josephson critical current versus magnetic field. By means of a numerical deconvolution of the I-V data the electronic density of states on both sides of the S/F bilayer has been evaluated at low temperatures. Results have been compared with theoretical predictions from a proximity model for S/F bilayers in the dirty limit in the framework of Usadel equations for the S and F layers, respectively. The main physical parameters characterizing the proximity effect in the Nb/NiCu bilayer, such as the coherence length and the exchange field energy of the F metal, and the S/F interface parameters have been also estimated

    Nonlocal modulation of the energy cascade in broadband-forced turbulence

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    Classically, large-scale forced turbulence is characterized by a transfer of energy from large to small scales via nonlinear interactions. We have investigated the changes in this energy transfer process in broadband forced turbulence where an additional perturbation of flow at smaller scales is introduced. The modulation of the energy dynamics via the introduction of forcing at smaller scales occurs not only in the forced region but also in a broad range of length scales outside the forced bands due to nonlocal triad interactions. Broadband forcing changes the energy distribution and energy transfer function in a characteristic manner leading to a significant modulation of the turbulence. We studied the changes in this transfer of energy when changing the strength and location of the small-scale forcing support. The energy content in the larger scales was observed to decrease, while the energy transport power for scales in between the large and small scale forcing regions was enhanced. This was investigated further in terms of the detailed transfer function between the triad contributions and observing the long-time statistics of the flow. The energy is transferred toward smaller scales not only by wave numbers of similar size as in the case of large-scale forced turbulence, but by a much wider extent of scales that can be externally controlled

    Technology geography: studying the relationships between technology, location and productivity

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    Operations management, international management, public policy and economic geography are scientific areas which come together in the study of international technology transfer. This study shows how each of these areas has its own central issues but also has specific parts that are relevant for research on international technology transfer. It is essential for companies to understand the issues of productivity of production technologies employed by them, and for international companies the relationship of productivity of a specific production line and the environment in which this line operates. Simultaneously, it is essential for governments to understand the productivity of their work force and, therefore, to understand the relationship of their country¿s characteristics and the productivity of specific industries. A recommendation is made to add a new focus to the research on international technology transfer called: Technology Geography. Its primary purpose is to investigate the linkages\ud between technology, location and productivity differences

    Superconducting weak links in YBa2Cu3O7-δ an AC magnetic susceptibility study

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    AC magnetic susceptibility, X' and X'', and ac resistivity, ρ, of two different samples of superconducting YBa2Cu3O7-δ have been measured. The results show a strong non-linear behaviour and are very sensitive to the exciting amplitudes. From the analysis of the data and comparison with appropriate models and other superconducting compounds, evidence for the existence of weak superconducting links is inferred. Finally, the utility of acX measurements for detection of different superconducting phases is made evident. \u

    Selffield losses and selffield stability of superconducting wires with low conductivity matrix material

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    The influence of the normal material in a superconducting wire on the selffield losses has been investigated. The results show that the contribution of the normal material is considerable in the case of a highly conductive material like Cu. Measurements on wires with CuNi-material show no significant contribution of the normal material to the losses. In the latter case, however, special attention should be paid to stability. Measurements show that the obtainable maximum current under a.c. conditions obeys the adiabatic stability criterion rather well. The dependence of the maximum current amplitude on the critical current density and the diameter of the wire has been obtained. Wires with Al cores inside the NbTi filaments for better stabilization have also been investigated regarding maximum current and selffield losses

    Correlation between anisotropy direction and pulse shape for metal evaporated tape

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    Measured replay pulses, recorded on metal evaporated tape, show a strong asymmetry and dependence on the direction of tape movement. It is found that pulse height and pulse width are unequal for both directions of tape movement. This is attributed to the nonlongitudinal easy-axis direction which causes differences in head-tape geometry for both directions, resulting in a different transition width. A simulation model is proposed. The differences in pulse asymmetry and pulse width between both directions of tape movement are very well reproduced by this mode. From X-ray diffraction measurements and the results of the simulations, it is concluded that not the columns but the crystallites act as magnetic entities for this kind of tape

    The critical current of Nb3Sn wires for ITER as a function of the axial tension and compression

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    The influence of compressive and tensile axial strains on the critical current of various Nb3Sn conductors is investigated. The investigated multifilamentary wires are especially developed for the ITER project. The critical current is determined as a function of an axial tension in a standard pull set-up. These results are compared with the results that are obtained on a bending spring-type strain device. In this second device an axial compression larger than the integral thermal shrinkage of the matrix, can be achieved. A study of the field dependence of the critical current yields the strain dependence of the extrapolated upper-critical field versus the axial strain. A good correlation is found between the two different strain devices in the tensile strain regime. There is a difference in the (limited) compressive strain regime where such a comparison can be mad

    iButton Enrolment and Verification Requirements for the Pressure Sequence Smartcard Biometric

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    With the growing number of smartcard applications there comes an increasing need to restrict access to the card itself. In previous work we proposed the pressure sequence biometric, within which a biometric sensor is integrated onto the card in a low-cost and mechanically compliant manner. Using an off-card verifier we demonstrated reasonable discrimination between users. In this paper we consider a number of on-card verification schemes, the best of which offers an equal error rate of 2.3%. On-card computational time requirements were found to be 3.1 seconds for enrolment and 0.12 seconds for verification. Incorporating our implementation into an existing applet used 684 bytes of program space. Whilst data memory requirements are estimated to be 1400 and 300 bytes for enrolment and verification, respectively. These time and size requirements demonstrate our biometric as a practical proposition for the protection of smart cards. Experiments were performed with the iButton's Java Card platform

    Tools for Integration of Ecosystem Studies towards the Development of Management Strategies

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    The seventh session of the bilateral workshop showed a\ud broad variety of oral presentations and posters on\ud approaches to integration for evaluating ecosystem\ud management strategies and on concrete tools for or\ud contributions to these approaches. Presentations from the\ud programs WAVES and MADAM dominated the session.\ud The explicit attention for integration appears to have an ever more central role in interdisciplinary research, outgrowing the traditional `trivial serial linkage of disciplinary contributions. Within the programs SHIFT, MADAM and WAVES, integration plays different roles, varying from being a method to connect the multiple aspects of ecosystem functioning, thus improving ecosystem understanding, to being the central research goal
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