Microwave heating-induced DC magnetic flux penetration in YBa2_{2}Cu3_{3}O7−δ_{7-\delta} superconducting thin films

The magneto-optical imaging technique is used to visualize the penetration of the magnetic induction in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films during surface resistance measurements. The in-situ surface resistance measurements were performed at 7 GHz using the dielectric resonator method. When only the microwave magnetic field $H_{rf}$ is applied to the superconductor, no $H_{rf}$-induced vortex penetration is observed, even at high rf power. In contrast, in the presence of a constant magnetic field superimposed on $H_{rf}$ we observe a progression of the flux front as $H_{rf}$ is increased. A local thermometry method based on the measurement of the resonant frequency of the dielectric resonator placed on the YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin film shows that the $H_{rf}$--induced flux penetration is due to the increase of the film temperature.Comment: 6 pages, Journal of Applied Physic

Heating and high frequency nonlinearities in the surface impedance of high Tc superconductors

Using the dielectric resonator method, we have investigated nonlinearities in surface impedance Zs = Rs + jXs of YBa2Cu3O7-delta thin films at 10 GHz as a function of the incident microwave power level and temperature. The use of a rutile dielectric resonator allows us to measure the precise temperature of the films. We conclusively show that the usually observed increase of the surface resistance of YBa2Cu3O7-delta thin film as function of microwave power is due to local heating

Mechanical Characterization of Timber Structural Elements Using Integral Mechanical Attachments

Automation is increasingly present in the construction industry, whether at the design, manufacturing or assembly stage. Thanks to new technologies, such as robotics, new ways of designing structural elements can be imagined and implemented. Complex methods and sequences of assembly can be set up quickly as well. Numerous studies have been carried out in this direction at the laboratory for timber constructions IBOIS (EPFL) especially on wood-wood connections called Integral Mechanical Attachments (IMA). This paper is focused on the mechanical characterization of a prefabricated structural element entirely made of Oriented Strand Board (OSB) panels produced by a fully robotized line. In order to avoid bonding process due to cost, ecological and time reasons, IMA using OSB have been chosen to connect each prefabricated element. Experimental tests and numerical models have been developed to determine the mechanical response of such structural elements