A hybrid M-algorithm/sequential decoder for convolutional and trellis codes

The Viterbi Algorithm (VA) is optimum in the sense of being maximum likelihood for decoding codes with a trellis structure. However, since the VA is in fact an exhaustive search of the code trellis, the complexity of the VA grows exponentially with the constraint length upsilon. This limits its application to codes with small values of upsilon and relatively modest coding gains. The M-Algorithm (MA) is a limited search scheme which carries forward M paths in the trellis, all of the same length. All successors of the M paths are extended at the next trellis depth, and all but the best M of these are dropped. Since a limited search convolutional decoder will flounder indefinitely if one of the paths in storage is not the correct one, the data are usually transmitted in blocks. It has been shown that the performance of the MA approaches the VA at high signal to noise ratios (SNR's) with an M which is far less than the 2 sup upsilon states in the full trellis. Thus the MA can be used with larger values of upsilon, making larger coding gains possible at high SNR's. However, it still requires a relatively large fixed computational effort to achieve good performance

Bandwidth efficient CCSDS coding standard proposals

The basic concatenated coding system for the space telemetry channel consists of a Reed-Solomon (RS) outer code, a symbol interleaver/deinterleaver, and a bandwidth efficient trellis inner code. A block diagram of this configuration is shown. The system may operate with or without the outer code and interleaver. In this recommendation, the outer code remains the (255,223) RS code over GF(2 exp 8) with an error correcting capability of t = 16 eight bit symbols. This code's excellent performance and the existence of fast, cost effective, decoders justify its continued use. The purpose of the interleaver/deinterleaver is to distribute burst errors out of the inner decoder over multiple codewords of the outer code. This utilizes the error correcting capability of the outer code more efficiently and reduces the probability of an RS decoder failure. Since the space telemetry channel is not considered bursty, the required interleaving depth is primarily a function of the inner decoding method. A diagram of an interleaver with depth 4 that is compatible with the (255,223) RS code is shown. Specific interleaver requirements are discussed after the inner code recommendations

Evaluation of Decentralized Event-Triggered Control Strategies for Cyber-Physical Systems

Energy constraint long-range wireless sensor/ actuator based solutions are theoretically the perfect choice to support the next generation of city-scale cyber-physical systems. Traditional systems adopt periodic control which increases network congestion and actuations while burdens the energy consumption. Recent control theory studies overcome these problems by introducing aperiodic strategies, such as event trigger control. In spite of the potential savings, these strategies assume actuator continuous listening while ignoring the sensing energy costs. In this paper, we fill this gap, by enabling sensing and actuator listening duty-cycling and proposing two innovative MAC protocols for three decentralized event trigger contro l approaches. A laboratory experimental testbed, which emulates a smart water network, was modelled and extended to evaluate the impact of system parameters and the performance of each approach. Experimental results reveal the predominance of the decentralized event-triggered control against the classic periodic control either in terms of communication or actuation by promising significant system lifetime extension

Investigation of a Resistive-Gate MESFET Contiguous Domain Oscillator

The goal of this research is to investigate a novel microwave oscillator — the MESFET version contiguous domain oscillator. By combining the transferred electron effect in GaAs material with the two dimensional electrostatics in the device, a series of contiguous electron packets can be generated in the channel of a resistive gate MESFET. Therefore this novel device can eliminate some restraints which are suffered by the presently existing oscillators, and provides unique new features for oscillators: a wide range of oscillation frequency (from a few tens of GHz to a hundred GHz), an ideal current source, instantaneous frequency tuning, compatibility with the presently existing planar semiconductor integration technology, etc. This investigation is composed of two parts. The first pa rt is to use various semiconductor processing technologies to fabricate the devices which can supply an ideal electrostatic condition for the electrons in the channel; the second part is the device characterization; which includes power output, frequency tunability, and the relationship between device performance and device parameters

Single atom catalyst having a two dimensional support material.

A method for forming a single atom catalyst on a two-dimensional support material involves providing the two-dimensional support material. The two-dimensional support material is combined with at least two heteroatoms and a metal to form a solution. Liquid is removed from the solution to form a material that includes the two-dimensional support material, the at least two heteroatoms, and the metal. The material including the two-dimensional support material, the at least two heteroatoms, and the metal is heated to form the single atom catalyst that includes single atoms of the metal. The at least two heteroatoms bind the single atoms of the metal to, and stabilize the single atoms of the metal on, the two-dimensional support material

Exponential and Laguerre Squeezed States for su(1,1) Algebra and Calogero-Sutherland Model

A class of squeezed states for the su(1,1) algebra is found and expressed by the exponential and Laguerre-polynomial operators acting on the vacuum states. As a special case it is proved that the Perelomov's coherent state is a ladder-operator squeezed state and therefore a minimum uncertainty state. The theory is applied to the two-particle Calogero-Sutherland model. We find some new squeezed states and compared them with the classical trajectories. The connection with some su(1,1) quantum optical systems (amplitude-squared realization, Holstein-Primakoff realization, the two mode realization and a four mode realization) is also discussed.Comment: 18 pages, Six figures (in two pages), LaTeX, Accepted for publication in Phys.Rev.

Solar cell with MXene electrode.

A solar cell (100) includes a p-type silicon layer (105) having a first side and a second side and an n-type silicon layer (110) having a first side and a second side. The first side of the n-type silicon layer is arranged on the second side of the p-type silicon layer. The solar cell also includes a first metal electrode (115) arranged on the first side of the p-type silicon layer and a second metal electrode (120) arranged on the second side of the n-type silicon layer. The second metal electrode includes an MXene

Carbon and Hydrogen Isotope Measurements of Alcohols and Organic Acids by Online Pyroprobe-GC-IRMS

The detection of methane in the atmosphere of Mars, combined with evidence showing widespread water-rock interaction during martian history, suggests that the production of methane on Mars may be the result of mineral surface-catalyzed CO2 and or CO reduction during Fisher-Tropsch Type (FTT) reactions. A better understanding of these reaction pathways and corresponding C and H isotope fractionations is critical to deciphering the synthesis of organic compounds produced under abiotic hydrothermal conditions. Described here is a technique for the extraction and analysis of both C and H isotopes from alcohols (C1-C4) and organic acids (C1-C6). This work is meant to provide a "proof of concept" for making meaningful isotope measurements on complex mixtures of solid-phase hydrocarbons and other intermediary products produced during high-temperature and high-pressure synthesis on mineral-catalyzed surfaces. These analyses are conducted entirely "on-line" utilizing a CDS model 5000 Pyroprobe connected to a Thermo Trace GC Ultra that is interfaced with a Thermo MAT 253 isotope ratio mass spectrometer operating in continuous flow mode. Also, this technique is designed to carry a split of the GC-separated product to a DSQ II quadrupole mass spectrometer as a means of making semi-quantitative compositional measurements. Therefore, both chemical and isotopic measurements can be carried out on the same sample