Negative resistance state in superconducting NbSe2 induced by surface acoustic waves

We report a negative resistance, namely, a voltage drop along the opposite direction of a current flow, in the superconducting gap of NbSe2 thin films under the irradiation of surface acoustic waves (SAWs). The amplitude of the negative resistance becomes larger by increasing the SAW power and decreasing temperature. As one possible scenario, we propose that soliton-antisoliton pairs in the charge density wave of NbSe2 modulated by the SAW serve as a time-dependent capacitance in the superconducting state, leading to the dc negative resistance. The present experimental result would provide a previously unexplored way to examine nonequilibrium manipulation of the superconductivity.

Impingement of coaxial jet on convex element for confined and unconfined flow

Jet impingement is most effective and active method for cooling and heating of any surface or system. The ability of jet impingement is greatly influenced by nozzle configuration and other dimensional and non-dimensional parameters. Impinging coaxial swirl jet generates interesting flow filed on any test surface and influences both pressure and heat distribution on impinging surfaces. In present study, an experimental investigation is carried to analyze the effects of turbulent coaxial swirl jet on the pressure distribution (PC & PCO) on convex element. For better and acceptable results, the desirable parameters are identified from previous research works. The present experimental result highlights the independency of pressure coefficient (PC) for jet-Reynolds number (Re=70000 to 45000), effect of circumferential angle (θ) or inclination of test element, effect of jet exit to test element distance (Z/dh) and effect of confinement on PC & PCO pattern on a convex test element. The higher pressure coefficient value are obtained at lower Z/dh = 1 & at θ = 15° to 12°and significant drop in the values are seen with increase in the Z/dh & θ. At θ = 20° to 30° the value of PC & PCO reaches to negative magnitude. The use of confinement tube enhancementthe pressure distribution (PC & PCO) by 61% to 64% is seen for the same flow conditions.

Comparison of the Performance of the Calibration Algorithm of Wide-Angle Lens

Fish-eye lens is used in various applications due to wide coverage of scene. In particular, it can be effectively used in visual surveillance and surround monitoring in automotive. It has large radial distortion compared to the conventional lens with small field of view. In this paper, we present comparison results for the calibration of fish-eye lens. We compare two algorithms where one is available in OpenCV [ and the other is Devernay and Faugeras [. Also, we present experimental result according to the number of calibration points, initialization value. We evaluate the accuracy of calibration thorough 3D reconstruction by stereo system. It can give more reliable evaluation than using reprojection eror by single camera.

A thermodynamic prediction on the stability of the nukundamite + chalcopyrite and bornite + pyrite assemblages

A thermodynamic prediction of the Gibbs free energy of formation (ΔGfo) of nukundamite (empirical composition Cu5.5FeS6.5) was made in order to specify whether the nukundamite + chalcopyrite or the bornite + pyrite assemblage is stable in the Cu-Fe-S system. The results of calculations using previously reported data of ΔGfo values of some Cu-Fe-sulphide minerals in equilibrium with nukundamite indicate that the total free energy of the nukundamite + chalcopyrite assemblage is appreciably higher than that of the bornite + pyrite assemblage in the temperature range 250–400°C. This means that nukundamite + chalcopyrite is a metastable assemblage under common ore-forming conditions.The occurrence of nukundamite is not uncommon in the Fijian kuroko deposits in contrast to the Japanese kuroko deposits. A thermochemical treatment for this phenomenon leads to the interpretation that the black ore containing nukundamite in the Fijian deposit was formed under relatively highsulphidation and low-pH conditions. This suggestion is in good agreement with the present experimental result that the bornite + pyrite assemblage was produced in the temperature range 350–250°C by using near-neutral hydrothermal solutions.