Performance of Hybrid ARQ Schemes with ML Code Combining over a Block-Fading Rayleigh Channel

This paper considers two well-known selective-repeat retransmission schemes, namely, hybrid type-I ARQ and hybrid type-II ARQ, using convolutional coding, in conjunction with maximum-likelihood code combining. Our theoretical analysis, based upon the concept of generalized weight distribution, shows that the use of code combining yields a significant throughput at very high channel error rates not only in constant AWGN channels but also in fading channels. To demonstrate this, we consider a widely-used block-fading Rayleigh channel model, in which the channel is assumed to be constant during each block of data and the fading is assumed to be independent from block to block. A key parameter in designing retransmission protocols for delay-limited applications in such channels is the minimum number of retransmissions, needed to achieve error-free decoding at almost all channel conditions (low outage probability). This number can be reduced significantly when code combining is employed.     

On‐Surface Synthesis of Ethynylene‐Bridged Anthracene Polymers

Engineering low‐band‐gap π‐conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on‐surface synthesis protocol to overcome such difficulties and produce poly(p‐anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr₂ moieties is deposited and annealed to 400 K, resulting in anthracene‐based polymers. High‐resolution nc‐AFM measurements confirm the nature of the ethynylene‐bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface‐stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design π‐conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on‐surface synthesis.     

Decoding Reed-Solomon codes generated by any generator polynomial

A Reed-Solomon code can be generated by n=2/sup m/-1 different generator polynomials, where 2/sup m/ is the size of the field. In the letter a structure for a Reed-Solomon decoder is introduced which can decode a Reed-Solomon code generated by any generator polynomial.<>     

Nonparaxial spatial solitons and propagation-invariant pattern solutions in optical Kerr media

We investigate nonlinear propagation in the presence of the optical Kerr effect by relying on a rigorous generalization of the standard parabolic equation that includes nonparaxial and vectorial terms. We show that, in the (1 + 1)-D case, both soliton and propagation-invariant pattern solutions exist (while the standard hyperbolic-secant function is not a solution).     

Mode cycling in microring optical resonators

Electromagnetic resonators are important not only as realizable models of fundamental concepts in classical and quantum physics, based on the existence and properties of eigenmodes, but also in the practical design of lasers, amplifiers, sensors, filters, and delay lines. Coupled-eigenmode systems may be realized via the multiple eigenmodes of a single resonator or by the coupling of a mode across multiple resonators. Mode cycling is demonstrated as a distinct concept of sequential population transfer in coupled multiple-eigenvalue resonators. Based on this principle, a coupled polymeric microring resonator interferometer is fabricated and characterized; the device achieves greater than 30 dB extinction and (loaded) Q approximately 5.5 x 10(3).     

Design of Reed-Solomon (16,12) codec for North American AdvancedTrain Control System

The design of the codec for the ATCS radio data link is considered. The code is defined. The encoding algorithm, the decoding algorithm, and Galois field arithmetic are discussed. Implementation of the Reed-Solomon codec as a stand-alone system in order to provide a possibility of real-time bit-rate measurement is discussed. The implementation of this codec using three different 8-b and 16-b microprocessors/microcomputers is described. Their complexity and throughput are discussed     

Implementing EPR Dosimetry for Life-Threatening Incidents: Factors Beyond Technical Performance

Starting with the assumption that a device to detect unplanned radiation exposures is technically superior to current technology, we examine the additional stakeholders and processes that must be considered to move the device from the lab into use. The use is to provide reliable information to triage people for early treatment of exposure to ionizing radiation that could lead to the Acute Radiation Syndrome. The scenario is a major accident or terrorist event that leaves a large number of people potentially exposed, with the resulting need to identify those to treat promptly or not. In vivo EPR dosimetry is the exemplar of such a technique.Three major areas are reviewed: policy considerations, regulatory clearance, and production of the device. Our analysis of policy-making indicates that the current system is very complex, with multiple significant decision-makers who may have conflicting agendas. Adoption of new technologies by policy-makers is further complicated because many sources of expert input already have made public stances or have reasons to prefer current solutions, e.g., some may have conflicts of interest in approving new devices because they are involved with the development or adoption of competing techniques. Regulatory clearance is complicated by not being able to collect evidence via clinical trials of its intended use, but pathways for approval for emergency use are under development by the FDA. The production of the new device could be problematical if the perceived market is too limited, particularly for private manufacturers; for in vivo EPR dosimetry the potential for other uses may be a mitigating factor.Overall we conclude that technical superiority of a technique does not in itself assure its rapid and effective adoption, even where the need is great and the alternatives are not satisfactory for large populations. Many important steps remain to achieve the goals of approval and adoption for use.     

Low-power continuous-wave four-wave mixing in silicon coupled-resonator optical waveguides

We demonstrate four-wave mixing in silicon-on-insulator coupled-resonator optical waveguides consisting of 35 and 65 microring resonators, using a cw pump with coupled power below 20 mW and observed parametric conversion across more than 10 THz. The conversion efficiency is enhanced by +16 dB relative to a silicon straight waveguide of equivalent length, due to the slowing factor of the coupled-resonator structure.     

Self-assembling of Prussian blue nanocubic particles on nanoporous glassy carbon and its use in the electrocatalytic reduction of hydrogen peroxide

In this paper, self-assembled Prussian blue nanocubic particles on nanoporous glassy carbon was developed. The morphology of the PBNP-modified porous glassy carbon was characterized by scanning electron microscopy. The PBNP-GCE-red film-modified electrode was used for the sensitive detection of hydrogen peroxide. The electrochemical behavior of the resulting sensor was investigated using cyclic voltammetry and chronoamperometry. The value of α, k _cat, and D was calculated as 0.35, 1.7 × 10⁵ cm³ mol^?1 s^?1, and 2.6 × 10^?5 cm² s^?1, respectively. The calibration curve for hydrogen peroxide determination was linear over 0–600 μM with a detection limit (S/N = 3) of 0.51 μM.