Local Hall effect in hybrid ferromagnetic/semiconductor devices

We have investigated the magnetoresistance of ferromagnet-semiconductor devices in an InAs two-dimensional electron gas system in which the magnetic field has a sinusoidal profile. The magnetoresistance of our device is large. The longitudinal resistance has an additional contribution which is odd in applied magnetic field. It becomes even negative at low temperature where the transport is ballistic. Based on the numerical analysis, we confirmed that our data can be explained in terms of the local Hall effect due to the profile of negative and positive field regions. This device may be useful for future spintronic applications.Comment: 4 pages with 4 fugures. Accepted for publication in Applied Physics Letter

Field-induced confinement in (TMTSF)2ClO4 under accurately aligned magnetic fields

We present transport measurements along the least conducting c direction of the organic superconductor (TMTSF)2ClO4, performed under an accurately aligned magnetic field in the low temperature regime. The experimental results reveal a two-dimensional confinement of the carriers in the (a,b) planes which is governed by the magnetic field component along the b' direction. This 2-D confinement is accompanied by a metal-insulator transition for the c axis resistivity. These data are supported by a quantum mechanical calculation of the transverse transport taking into account in self consistent treatment the effect of the field on the interplane Green function and on the intraplane scattering time

Temperature dependence of nonlinear auto-oscillator linewidths: Application to spin-torque nano-oscillators

The temperature dependence of the generation linewidth for an auto-oscillator with a nonlinear frequency shift is calculated. It is shown that the frequency nonlinearity creates a finite correlation time, tau, for the phase fluctuations. In the low-temperature limit in which the spectral linewidth is smaller than 1/tau, the line shape is approximately Lorentzian and the linewidth is linear in temperature. In the opposite high-temperature limit in which the linewidth is larger than 1/tau, the nonlinearity leads to an apparent "inhomogeneous broadening" of the line, which becomes Gaussian in shape and has a square-root dependence on temperature. The results are illustrated for the spin-torque nano-oscillator.Comment: 4 pages, 1 figur

Electronic properties of quantum dots formed by magnetic double barriers in quantum wires

The transport through a quantum wire exposed to two magnetic spikes in series is modeled. We demonstrate that quantum dots can be formed this way which couple to the leads via magnetic barriers. Conceptually, all quantum dot states are accessible by transport experiments. The simulations show Breit-Wigner resonances in the closed regime, while Fano resonances appear as soon as one open transmission channel is present. The system allows to tune the dot's confinement potential from sub-parabolic to superparabolic by experimentally accessible parameters.Comment: 5 pages, 5 figure

Quantitative Kinetic Energy Estimated from Disdrometer Signal

The kinetic energy of the rain drops was predicted in a relation between the rain rate and rain quantity, derived directly from the rain drop size distribution (DSD), which had been measured by a disdrometer located in the eastern state of Alagoas-Brazil. The equation in the form of exponential form suppressed the effects of large drops at low rainfall intensity observed at the beginning and end of the rainfall. The kinetic energy of the raindrop was underestimated in almost rain intensity ranges and was considered acceptable by the performance indicators such as coefficient of determination, average absolute error, percent relative error, mean absolute error, root mean square error, Willmott's concordance index and confidence index

Protecting Internet Users with Epilepsy or Chronic Migraine from Graphic-Based Attacks

Flagging graphics interchangeable formats (GIFs) on personal devices are essential to protect users with epilepsy or chronic migraine. The research broke GIFs into frames and compared consecutive frames in pairs with three conditions: the ratio of average intensity, percentage of dangerous pixels, and hertz value. First, the average intensity of each frame is calculated using the formula: 0.299 * red + 0.587 * green + 0.114 * blue (Sedgewick & Wayne, 2017), for each pixel in the frame. Next, to obtain the percentage of dangerous pixels, each pixel of the same location from the two frames is compared. The absolute value of the difference between intensities of the pixels is found. A value less than 128.0 (Sedgewick & Wayne, 2017) is incompatible. Then, the ratio of incompatible and different pixels is obtained, which is multiplied by the ratio of different and total pixels. Finally, if the hertz value, inverse of the duration of each frame divided by 1000, falls within 3 to 30 (Wirrell & Hernandez), the GIF can be potentially dangerous. Thus, three threat levels, risky, dangerous, and extreme, have been established if one, two, or three conditions are met, respectively. After taking these results, viewers can be notified so that they can be protected from potential graphic-based attacks. Keywords: epilepsy; chronic migraine; graphics interchangeable format; Sedgewick, R., & Wayne, K. (2017). Object-Oriented Programming. Computer science an interdisciplinary approach. Addison-Wesley Professional. (pp. 330-381). Boston: Addision-Wesley. Wirrell, E., & Hernandez, A. (Eds.). (2019). Photosensitivity and Seizures. Epilepsy. https://www.epilepsy.com/learn/triggers-seizures/photosensitivity-and-seizur