Scalable Successive-Cancellation Hardware Decoder for Polar Codes

Polar codes, discovered by Ar{\i}kan, are the first error-correcting codes with an explicit construction to provably achieve channel capacity, asymptotically. However, their error-correction performance at finite lengths tends to be lower than existing capacity-approaching schemes. Using the successive-cancellation algorithm, polar decoders can be designed for very long codes, with low hardware complexity, leveraging the regular structure of such codes. We present an architecture and an implementation of a scalable hardware decoder based on this algorithm. This design is shown to scale to code lengths of up to N = 2^20 on an Altera Stratix IV FPGA, limited almost exclusively by the amount of available SRAM

A conceptual design methodology for evaluation of alternate propulsion system modifications on small aircraft

Conceptual design is often considered to be the most important step in the design of a new product or the modification of an existing product. The important steps in this conceptual design phase is the synthesis of potential solutions into concepts, the evaluation of these concepts within a repeatable and robust design methodology framework and analysis to identify and characterise the preferred solution concept. This research has arisen from problems associated with developing aircraft-based design modification concepts and predicting the impact of these changes as they propagate or flow down through the various aircraft subsystems, impacting engineering design, and leading to certification and operations challenges. This research problem is particularly evident in highly integrated systems such as high-performance military aircraft, helicopters, and complex civil aircraft. To illustrate this methodology the author has selected two case studies which apply two different alternate propulsion system technologies to small aircraft. These case studies were selected to provide a diverse design modification space encompassing differing aircraft roles and mission types, differing technologies and subsystems integration scope, and different data sources collection and analysis methods. In order to combine the elements of design synthesis, evaluation of concept alternatives and analysis of outputs, this thesis has formulated a matrix-based conceptual design methodology. This methodology extends current knowledge by implementing the concepts of design synthesis, evaluation and analysis as an iterative process, and building and linking together existing techniques. This new methodology combined various techniques and methods such as Quality Function Deployment (QFD), quantified morphological matrices (QMM), Pugh’s decision matrices, change options Multiple-Domain Matrices (MDM), and has adapted the Change Propagation Method (CPM). The second extension to current knowledge in this area was the development of Engineering and Certification Domain Mapping Matrix (DMM) techniques based on Design Structure Matrices (DSM). This extension into engineering and certification domain was undertaken to ensure that important modification-related risks and costs were incorporated into the early stages of design. The extension adopted existing DSM and DMM-based techniques and tools to evaluate the impact of changes to subsystems and hence impact of risks and costs resulting from aircraft modifications using change propagation method analysis techniques. The validation of this conceptual design methodology was achieved by verifying and assessing the adequacy of its application through an analysis process which examined (1) coverage of the design space attributes; (2) validation of the methodology against accepted scientific and industry conceptual design frameworks; and (3) confirmation of the existing techniques, structures and tools applied within the methodology

Resolved shock structure of the Balmer-dominated filaments in Tycho's supernova remnant: Cosmic-ray precursor?

We report on the results from H{\alpha} imaging observations of the eastern limb of Tycho's supernova remnant (SN1572) using the Wide Field Planetary Camera 2 on the Hubble Space Telescope. We resolve the detailed structure of the fast, collisionless shock wave into a delicate structure of nearly edge-on filaments. We find a gradual increase of H{\alpha} intensity just ahead of the shock front, which we interpret as emission from the thin (~1") shock precursor. We find that a significant amount of the H{\alpha} emission comes from the precursor and that this could affect the amount of temperature equilibration derived from the observed flux ratio of the broad and narrow H{\alpha} components. The observed H{\alpha} emission profiles are fit using simple precursor models, and we discuss the relevant parameters. We suggest that the precursor is likely due to cosmic rays and discuss the efficiency of cosmic-ray acceleration at this position.Comment: Prepared with emulateapj.sty (5 pages, 4 figures). Published in ApJL

Some data processing requirements for precision Nap-Of-the-Earth (NOE) guidance and control of rotorcraft

Nap-Of-the-Earth (NOE) flight in a conventional helicopter is extremely taxing for two pilots under visual conditions. Developing a single pilot all-weather NOE capability will require a fully automatic NOE navigation and flight control capability for which innovative guidance and control concepts were examined. Constrained time-optimality provides a validated criterion for automatically controlled NOE maneuvers if the pilot is to have confidence in the automated maneuvering technique. A second focus was to organize the storage and real-time updating of NOE terrain profiles and obstacles in course-oriented coordinates indexed to the mission flight plan. A method is presented for using pre-flight geodetic parameter identification to establish guidance commands for planned flight profiles and alternates. A method is then suggested for interpolating this guidance command information with the aid of forward and side looking sensors within the resolution of the stored data base, enriching the data content with real-time display, guidance, and control purposes. A third focus defined a class of automatic anticipative guidance algorithms and necessary data preview requirements to follow the vertical, lateral, and longitudinal guidance commands dictated by the updated flight profiles and to address the effects of processing delays in digital guidance and control system candidates. The results of this three-fold research effort offer promising alternatives designed to gain pilot acceptance for automatic guidance and control of rotorcraft in NOE operations

Pathways to Success at Four-Year Institutions as Perceived by Black First-Generation College Students

The purpose of this study was to examine the pathways to success at 4-year institutions from the perspective of Black first-generation college students (FGCS). This study was designed as a response to the large body of research that highlights the disparity between enrollment and degree attainment for Black first-generation college students. Specifically, Black FGCS are 4 times more likely to drop out after their first year at a 4-year institution compared to their non-first-generation college student (non-FGCS) counterparts. The research sought enlightening insights and lived experiences of Black FGCS who persisted to their junior and senior years of college at a 4-year college. A hermeneutic, phenomenological approach was employed to examine the factors that contribute to persistence, the factors that are most impactful upon persistence, and the strategies that are employed by persistent students that increase the likelihood of degree completion. A purposeful and convenient sample of six participants who attended 4-year institutions in the Northeast United States was utilized. A semi-structured interview protocol with open-ended questions was used to collect data. The data were analyzed and the emergent themes were categorized under three categories: contributors to persistence, impact on persistence, and persistence strategies. Recommendations included creating a college-readiness environment in high school and establishing a supportive campus environment within the institution

Interfacing High Performance Liquid Chromatography with Inductively Coupled Plasma Mass Spectrometry for Speciation Studies

A novel interface for the coupling of high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) for the speciation of organometallic compounds has been developed and utilised for a number of diverse applications. Desolvation of the sample prior to reaching the plasma is shown to facilitate a more versatile coupling of the two instrumental techniques. This has been achieved by first volatilising the aerosol after nebulisation of the sample in a heated cyclone spray chamber. The resulting vapour is removed using a membrane drier and a thermoelectrically cooled condenser. The apparatus developed has been fully optimised to facilitate the introduction of a range of organic solvents, particularly those used as mobile phases for HPLC separations such as acetonitrile and methanol. This interface also facilitates gradient elutions to be used with ICP-MS for the first time. The interface developed has enabled the use of HPLC-ICP-MS to speciate the metabolites of a novel platinum based chemotherapy drug, JM-216, in human plasma ultrafiltrate. This approach offers a number of advantages over existing techniques especially in terms of speed of analysis and sensitivity. The platinum containing metabolites derived from this drug have been separated, identified, and compared to those arising from the breakdown of cisplatin and carboplatin in both plasma ultrafiltrate and an aqueous solution. A detection limit of 119 pg of Pt has been achieved for real samples. The interface has also been used for the speciation of organotin and organolead compounds in environmental samples, and to investigate the speciation of metals in tea liquors. It was found that although the apparatus proved beneficial for both the determination of organotins and the identification of metal containing species in tea, its use adversely affected the analysis of organolead compounds. The results of these latter studies are critically assessed and discussed with respect to HPLC-ICP-MS interface design.Fisons Instruments Elemental, Ion Path Road 3, Winsford, Cheshire, CW7 3BX and Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading, RG4 9N