Self-adaptation of mutation distribution in evolutionary algorithms

This paper is posted here with permission from IEEE - Copyright @ 2007 IEEEThis paper proposes a self-adaptation method to control not only the mutation strength parameter, but also the mutation distribution for evolutionary algorithms. For this purpose, the isotropic g-Gaussian distribution is employed in the mutation operator. The g-Gaussian distribution allows to control the shape of the distribution by setting a real parameter g and can reproduce either finite second moment distributions or infinite second moment distributions. In the proposed method, the real parameter q of the g-Gaussian distribution is encoded in the chromosome of an individual and is allowed to evolve. An evolutionary programming algorithm with the proposed idea is presented. Experiments were carried out to study the performance of the proposed algorithm

Enhancing MB-OFDM throughput with dual circular 32-QAM

Quadrature Phase Shift Keying (QPSK) and Dual Carrier Modulation (DCM) are currently used as the modulation schemes for Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) in the ECMA-368 defined Ultra-Wideband (UWB) radio platform. ECMA-368 has been chosen as the physical radio platform for many systems including Wireless USB (W-USB), Bluetooth 3.0 and Wireless HDMI; hence ECMA-368 is an important issue to consumer electronics and the users experience of these products. To enable the transport of high-rate USB, ECMA-368 offers up to 480 Mb/s instantaneous bit rate to the Medium Access Control (MAC) layer, but depending on radio channel conditions dropped packets unfortunately result in a lower throughput. This paper presents an alternative high data rate modulation scheme that fits within the configuration of the current standard increasing system throughput by achieving 600 Mb/s (reliable to 3.1 meters) thus maintaining the high rate USB throughput even with a moderate level of dropped packets. The modulation system is termed Dual Circular 32-QAM (DC 32-QAM). The system performance for DC 32-QAM modulation is presented and compared with 16-QAM and DCM1

Energy Dependent Contrast in Atomic-Scale Spin-Polarized Scanning Tunneling Microscopy ofMn3N2(010): Experiment and First-Principles Theory

The technique of spin-polarized scanning tunneling microscopy is investigated for its use in determining fine details of surface magnetic structure down to the atomic scale. As a model sample, the row-wise anti-ferromagnetic Mn3N2(010) surface is studied. It is shown that the magnetic contrast in atomic-scale images is a strong function of the bias voltage around the Fermi level. Inversion of the magnetic contrast is also demonstrated. The experimental SP-STM images and height profiles are compared with simulated SP-STM images and height profiles based on spin-polarized density functional theory. The success of different tip models in reproducing the non-magnetic and magnetic STM data is explored.Comment: 15 pages, 7 figure

Fighting covid-19 outbreaks in prisons

Improving prison health services is critical for fighting epidemics such as covid-19. Prisoners are at much higher risk of infectious diseases than communities outside. Eruption of covid-19 in prisons emphasises the need to improve prison healthcare. Health education for inmates and prison staff must be intensified, and better treatment and prevention measures require increased funding. More non-custodial sentences would decongest prisons, reducing the potential for the outbreaks. Links between prison and national health services should be strengthened

Generation of Large Moments in a Spin-1 Chain with Random Antiferromagnetic Couplings

We study the spin-1 chain with nearest neighbor couplings that are rotationally invariant, but include both Heisenberg and biquadratic exchange, with random strengths. We demonstrate, using perturbative renormalization group methods as well as exact diagonalization of clusters, that the system generates ferromagnetic couplings under certain circumstances even when all the bare couplings are antiferromagnetic. This disorder induced instability leads to formation of large magnetic moments at low temperatures, and is a purely quantum mechanical effect that does not have a classical counterpart. The physical origin of this instability, as well as its consequences, are discussed.Comment: 4 pages, 4 eps figure

Comment on "Fock-Darwin States of Dirac Electrons in Graphene-Based Artificial Atoms"

Chen, Apalkov, and Chakraborty (Phys. Rev. Lett. 98, 186803 (2007)) have computed Fock-Darwin levels of a graphene dot by including only basis states with energies larger than or equal to zero. We show that their results violate the Hellman-Feynman theorem. A correct treatment must include both positive and negative energy basis states. Additional basis states lead to new energy levels in the optical spectrum and anticrossings between optical transition lines.Comment: 1 page, 1 figure, accepted for publication in PR