The Impact of User Effects on the Performance of Dual Receive Antenna Diversity Systems in Flat Rayleigh Fading Channels

In this paper we study the impact of user effects on the performance of receive antenna diversity systems in flat Rayleigh fading channels. Three diversity combining techniques are compared: maximal ratio combining (MRC), equal gain combining (EGC), and selection combining (SC). User effects are considered in two scenarios: 1) body loss (the reduction of effective antenna gain due to user effects) on a single antenna, and 2) equal body loss on both antennas. The system performance is assessed in terms of mean SNR, link reliability, bit error rate of BPSK, diversity order and ergodic capacity. Our results show that body loss on a single antenna has limited (bounded) impact on system performance. In comparison, body loss on both antennas has unlimited (unbounded) impact and can severely degrade system performance. Our results also show that with increasing body loss on a single antenna the performance of EGC drops faster than that of MRC and SC. When body loss on a single antenna is larger than a certain level, EGC is not a “sub-optimal” method anymore and has worse performance than SC

A broadband microwave Corbino spectrometer at 3^3He temperatures and high magnetic fields

We present the technical details of a broadband microwave spectrometer for measuring the complex conductance of thin films covering the range from 50 MHz up to 16 GHz in the temperature range 300 mK to 6 K and at applied magnetic fields up to 8 Tesla. We measure the complex reflection from a sample terminating a coaxial transmission line and calibrate the signals with three standards with known reflection coefficients. Thermal isolation of the heat load from the inner conductor is accomplished by including a section of NbTi superconducting cable (transition temperature around 8 $-$ 9 K) and hermetic seal glass bead adapters. This enables us to stabilize the base temperature of the sample stage at 300 mK. However, the inclusion of this superconducting cable complicates the calibration procedure. We document the effects of the superconducting cable on our calibration procedure and the effects of applied magnetic fields and how we control the temperature with great repeatability for each measurement. We have successfully extracted reliable data in this frequency, temperature and field range for thin superconducting films and highly resistive graphene samples

Taste or Addiction?: Using Play Logs to Infer Song Selection Motivation

Online music services are increasing in popularity. They enable us to analyze people's music listening behavior based on play logs. Although it is known that people listen to music based on topic (e.g., rock or jazz), we assume that when a user is addicted to an artist, s/he chooses the artist's songs regardless of topic. Based on this assumption, in this paper, we propose a probabilistic model to analyze people's music listening behavior. Our main contributions are three-fold. First, to the best of our knowledge, this is the first study modeling music listening behavior by taking into account the influence of addiction to artists. Second, by using real-world datasets of play logs, we showed the effectiveness of our proposed model. Third, we carried out qualitative experiments and showed that taking addiction into account enables us to analyze music listening behavior from a new viewpoint in terms of how people listen to music according to the time of day, how an artist's songs are listened to by people, etc. We also discuss the possibility of applying the analysis results to applications such as artist similarity computation and song recommendation.Comment: Accepted by The 21st Pacific-Asia Conference on Knowledge Discovery and Data Mining (PAKDD 2017

Resonant versus anti-resonant tunneling at carbon nanotube A-B-A heterostructures

Narrow antiresonances going to zero transmission are found to occur for general (2n,0)(n,n)(2n,0) carbon nanotube heterostructures, whereas the complementary configuration, (n,n)(2n,0)(n,n), displays simple resonant tunneling behaviour. We compute examples for different cases, and give a simple explanation for the appearance of antiresonances in one case but not in the other. Conditions and ranges for the occurence of these different behaviors are stated. The phenomenon of anti-resonant tunneling, which has passed unnoticed in previous studies of nanotube heterostructures, adds up to the rich set of behaviors available to nanotube based quantum effect devices.Comment: Published in phys. stat. sol. (b); 6 pages, 4 figure

Pulsar-black hole binaries: prospects for new gravity tests with future radio telescopes

The anticipated discovery of a pulsar in orbit with a black hole is expected to provide a unique laboratory for black hole physics and gravity. In this context, the next generation of radio telescopes, like the Five-hundred-metre Aperture Spherical radio Telescope (FAST) and the Square Kilometre Array (SKA), with their unprecedented sensitivity, will play a key role. In this paper, we investigate the capability of future radio telescopes to probe the spacetime of a black hole and test gravity theories, by timing a pulsar orbiting a stellar-mass-black-hole (SBH). Based on mock data simulations, we show that a few years of timing observations of a sufficiently compact pulsar-SBH (PSR-SBH) system with future radio telescopes would allow precise measurements of the black hole mass and spin. A measurement precision of one per cent can be expected for the spin. Measuring the quadrupole moment of the black hole, needed to test GR's no-hair theorem, requires extreme system configurations with compact orbits and a large SBH mass. Additionally, we show that a PSR-SBH system can lead to greatly improved constraints on alternative gravity theories even if they predict black holes (practically) identical to GR's. This is demonstrated for a specific class of scalar-tensor theories. Finally, we investigate the requirements for searching for PSR-SBH systems. It is shown that the high sensitivity of the next generation of radio telescopes is key for discovering compact PSR-SBH systems, as it will allow for sufficiently short survey integration times.Comment: 20 pages, 11 figures, 1 table, accepted for publication in MNRA

Interface states and anomalous quantum oscillations in graphene hybrid structures

One- and two-layer graphene have recently been shown to feature new physical phenomena such as unconventional quantum Hall effects and prospects of supporting a non-silicon technological platform using epitaxial graphene. While both one- and two-layer graphene have been studied extensively, continuous sheets of graphene possessing both parts have not yet been explored. Here we report a study of such graphene hybrid structures. In a bulk hybrid featuring two large-area one- and two-layer graphene and an interface between them, two sets of Landau levels and features related to the interface were found. In edge hybrids featuring a large two-layer graphene with narrow one-layer graphene edges, we observed an anomalous suppression in quantum oscillation amplitude due to the locking of one- and two-layer graphene Fermi energies and emergent chiral interface states. These findings demonstrate the importance of these hybrid structures whose unique interface states and related phenomena deserve further studies.Comment: 4 pages, 4 figure

Brane Formation and Cosmological Constraint on the Number of Extra Dimensions

Special relativity is generalized to extra dimensions and quantized energy levels of particles are obtained. By calculating the probability of particles' motion in extra dimensions at high temperature of the early universe, it is proposed that the branes may have not existed since the very beginning of the universe, but formed later. Meanwhile, before the formation, particles of the universe may have filled in the whole bulk, not just on the branes. This scenario differs from that in the standard big bang cosmology in which all particles are assumed to be in the 4D spacetime. So, in brane models, whether our universe began from a 4D big bang singularity is questionable. A cosmological constraint on the number of extra dimensions is also given which favors $N\geq 7$.Comment: 11 pages, no figures. To appear in IJT