VHF command system study

Solutions are provided to specific problems arising in the GSFC VHF-PSK and VHF-FSK Command Systems in support of establishment and maintenance of Data Systems Standards. Signal structures which incorporate transmission on the uplink of a clock along with the PSK or FSK data are considered. Strategies are developed for allocating power between the clock and data, and spectral analyses are performed. Bit error probability and other probabilities pertinent to correct transmission of command messages are calculated. Biphase PCM/PM and PCM/FM are considered as candidate modulation techniques on the telemetry downlink, with application to command verification. Comparative performance of PCM/PM and PSK systems is given special attention, including implementation considerations. Gain in bit error performance due to coding is also considered

Development of optical data processing techniques applicable to detection and study of meteor trails

Development of coherent optical data processing techniques applicable to detection of meteor trails and examination of propertie

Chemical reactivity of hydrogen, nitrogen and oxygen atoms at temperatures below 100 deg K Fifth semiannual technical report

Chemical reactivity of hydrogen, nitrogen, and oxygen atoms at temperatures below 100 deg

Nanoscale junctions for single molecule electronics fabricated using bilayer nanoimprint lithography combined with feedback controlled electromigration

Nanoimprint lithography (NIL) is a fast, simple and high throughput technique that allows fabrication of structures with nanometre precision features at low cost. We present an advanced bilayer nanoimprint lithography approach to fabricate four terminal nanojunction devices for use in single molecule electronic studies. In the first part of this work, we demonstrate a NIL lift-off process using a bilayer resist technique that negates problems associated with metal side-wall tearing during lift-off. In addition to precise nanoscale feature replication, we show that it is possible to imprint micron-sized features while still maintaining a bilayer structure enabling an undercut resist structure to be formed. This is accomplished by choosing suitable imprint parameters as well as residual layer etching depth and development time. We then use a feedback controlled electromigration procedure, to produce room-temperature stable nanogap electrodes with sizes below 2 nm. This approach facilitates the integration of molecules in stable, solid-state molecular electronic devices as demonstrated by incorporating benzenethiol as molecular bridges between the electrodes and characterizing its electronics properties through current-voltage measurements. The observation of molecular transport signatures, showing current suppression in the I-V behaviour at low voltage, which is then lifted at high voltage, signifying on- and off-resonant transport through molecular levels as a function of voltage, is confirmed in repeated I-V sweeps. The large conductance, symmetry of the I-V sweep and small value of the voltage minimum in transition voltage spectroscopy indicates the bridging of the two benzenethiol molecules is by π-stacking

Multivariate Normalization with Symmetric Diffeomorphisms for Multivariate Studies

Current clinical and research neuroimaging protocols acquire images using multiple modalities, for instance, T1, T2, diffusion tensor and cerebral blood flow magnetic resonance images (MRI). These multivariate datasets provide unique and often complementary anatomical and physiological information about the subject of interest. We present a method that uses fused multiple modality (scalar and tensor) datasets to perform intersubject spatial normalization. Our multivariate approach has the potential to eliminate inconsistencies that occur when normalization is performed on each modality separately. Furthermore, the multivariate approach uses a much richer anatomical and physiological image signature to infer image correspondences and perform multivariate statistical tests. In this initial study, we develop the theory for Multivariate Symmetric Normalization (MVSyN), establish its feasibility and discuss preliminary results on a multivariate statistical study of 22q deletion syndrome

Large dopant dependence of the current limiting properties of intrinsic conducting polymer surge protection devices

New two terminal surge protection devices based on intrinsic conducting polymers are demonstrated to be strongly affected by the dopant molecule type. Thermogravimetric analysis combined with current–voltage studies show a causal link between the dopant molecule, moisture content and the current limiting capability of the devices. Polyaniline thin-films with high moisture content produce devices with current saturation and foldback effects at high applied voltages while low moisture content films exhibit no current rectification and instead demonstrate decreasing resistivity with increasing voltage. Polyaniline doped with sulfuric acid (H2SO4) exhibited the largest moisture content and surge protection devices built with this material produced for the first time negative differential resistance under ambient conditions. A further improvement was made upon this through surface engineering of the interface between the polymer and electrodes using self-assembled monolayers

Surface states and their possible role in the superconductivity of MgB2

We report layer-Korringa-Kohn-Rostocker calculations for bulk and surface states as well as the corresponding angle resolved photoemission (ARPES) intensities of MgB2. Our theoretical results reproduce very well the recent ARPES data by Uchiyama et al., cond-mat/0111152. At least two surface states are assigned. Consequences of SFS on the anisotropy of the upper critical fields and other properties in the superconducting state of small grains in micropowder samples are briefly discussed.Comment: 4pages, 6figures, corrected typos, references adde

Reading Videogames as (authorless) Literature

This article presents the outcomes of research, funded by the Arts and Humanities Research Council in England and informed by work in the fields of new literacy research, gaming studies and the socio-cultural framing of education, for which the videogame L.A. Noire (Rockstar Games, 2011) was studied within the orthodox framing of the English Literature curriculum at A Level (pre-University) and Undergraduate (degree level). There is a plethora of published research into the kinds of literacy practices evident in videogame play, virtual world engagement and related forms of digital reading and writing (Gee, 2003; Juul, 2005; Merchant, Gillen, Marsh and Davies, 2012; Apperley and Walsh, 2012; Bazalgette and Buckingham, 2012) as well as the implications of such for home / school learning (Dowdall, 2006; Jenkins, 2006; Potter, 2012) and for teachers’ own digital lives (Graham, 2012). Such studies have tended to focus on younger children and this research is also distinct from such work in the field in its exploration of the potential for certain kinds of videogame to be understood as 'digital transformations' of conventional ‘schooled’ literature. The outcomes of this project raise implications of such a conception for a further implementation of a ‘reframed’ literacy (Marsh, 2007) within the contemporary curriculum of a traditional and conservative ‘subject’. A mixed methods approach was adopted. Firstly, students contributing to a gamplay blog requiring them to discuss their in-game experience through the ‘language game’ of English Literature, culminating in answering a question constructed with the idioms of the subject’s set text ‘final examination’. Secondly, students taught their teachers to play L.A. Noire, with free choice over the context for this collaboration. Thirdly, participants returned to traditional roles in order to work through a set of study materials provided, designed to reproduce the conventions of the ‘study guide’ for literature education. Interviews were conducted after each phase and the outcomes informed a redrafting of the study materials which are now available online for teachers – this being the ‘practical’ outcome of the research (Berger and McDougall, 2012). In the act of inserting the study of L.A. Noire into the English Literature curriculum as currently framed, this research moves, through a practical ‘implementation’ beyond longstanding debates around narratology and ludology (Frasca, 2003; Juul, 2005) in the field of game studies (Leaning, 2012) through a direct connection to new literacy studies and raises epistemological questions about ‘subject identity’, informed by Bernstein (1996) and Bourdieu (1986) and the implications for digital transformations of texts for both ideas about cultural value in schooled literacy (Kendall and McDougall, 2011) and the politics of ‘expertise’ in pedagogic relations (Ranciere, 2009, Bennett, Kendall and McDougall, 2012a)

A Chip Architecture for Compressive Sensing Based Detection of IC Trojans

We present a chip architecture for a compressive sensing based method that can be used in conjunction with the JTAG standard to detect IC Trojans. The proposed architecture compresses chip output resulting from a large number of test vectors applied to a circuit under test (CUT). We describe our designs in sensing leakage power, computing random linear combinations under compressive sensing, and piggybacking these new functionalities on JTAG. Our architecture achieves approximately a 10× speedup and 1000× reduction in output bandwidth while incurring a small area overhead.Engineering and Applied Science