7,196 research outputs found

    User manual of the CATSS system (version 1.0) communication analysis tool for space station

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    The Communication Analysis Tool for the Space Station (CATSS) is a FORTRAN language software package capable of predicting the communications links performance for the Space Station (SS) communication and tracking (C & T) system. An interactive software package was currently developed to run on the DEC/VAX computers. The CATSS models and evaluates the various C & T links of the SS, which includes the modulation schemes such as Binary-Phase-Shift-Keying (BPSK), BPSK with Direct Sequence Spread Spectrum (PN/BPSK), and M-ary Frequency-Shift-Keying with Frequency Hopping (FH/MFSK). Optical Space Communication link is also included. CATSS is a C & T system engineering tool used to predict and analyze the system performance for different link environment. Identification of system weaknesses is achieved through evaluation of performance with varying system parameters. System tradeoff for different values of system parameters are made based on the performance prediction

    Developing a predictive tool for psychological well-being among Chinese adolescents in the presence of missing data

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    <p>Abstract</p> <p>Background</p> <p>Multi-dimensional behavioral rating scales like the CBCL and YSR are available for diagnosing psychosocial maladjustment in adolescents, but these are unsuitable for large-scale usage since they are time-consuming and their many sensitive questions often lead to missing data. This research applies multiple imputation to tackle the effects of missing data in order to develop a simple questionnaire-based predictive instrument for psychosocial maladjustment.</p> <p>Methods</p> <p>Questionnaires from 2919 Chinese sixth graders in 21 schools were collected, but 86% of the students were missing one or more of the variables for analysis. Fifteen (10 training, 5 validation) samples were imputed using multivariate imputation chain equations. A ten-variable instrument was constructed by applying stepwise variable selection algorithms to the training samples, and its predictive performance was evaluated on the validation samples.</p> <p>Results</p> <p>The instrument had an AUC of 0.75 (95% CI: 0.73 to 0.78) and a calibration slope of 0.98 (95% CI: 0.86 to 1.09). The prevalence of psychosocial maladjustment was 18%. If a score of > 1 was used to define a negative test, then 80% of the students would be classified as negative. The resulting test had a diagnostic odds ratio of 5.64 (95% CI: 4.39 to 7.24), with negative and positive predictive values of 88% and 43%, and negative and positive likelihood ratios of 0.61 and 3.41, respectively.</p> <p>Conclusions</p> <p>Multiple imputation together with internal validation provided a simple method for deriving a predictive instrument in the presence of missing data. The instrument's high negative predictive value implies that in populations with similar prevalences of psychosocial maladjustment test-negative students can be confidently excluded as being normal, thus saving 80% of the resources for confirmatory psychological testing.</p

    Long-range surface plasmon polariton excitation at the quantum level

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    We provide the quantum mechanical description of the excitation of long-range surface plasmon polaritons (LRSPPs) on thin metallic strips. The excitation process consists of an attenuated-reflection setup, where efficient photon-to-LRSPP wavepacket-transfer is shown to be achievable. For calculating the coupling, we derive the first quantization of LRSPPs in the polaritonic regime. We study quantum statistics during propagation and characterize the performance of photon-to-LRSPP quantum state transfer for single-photons, photon-number states and photonic coherent superposition states.Comment: 9 pages, 6 figures, RevTeX4; Accepted versio

    Space Shuttle/TDRSS communication and tracking systems analysis

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    In order to evaluate the technical and operational problem areas and provide a recommendation, the enhancements to the Tracking and Data Delay Satellite System (TDRSS) and Shuttle must be evaluated through simulation and analysis. These enhancement techniques must first be characterized, then modeled mathematically, and finally updated into LinCsim (analytical simulation package). The LinCsim package can then be used as an evaluation tool. Three areas of potential enhancements were identified: shuttle payload accommodations, TDRSS SSA and KSA services, and shuttle tracking system and navigation sensors. Recommendations for each area were discussed

    O assistente social como mediador cultural em escolas públicas dos bairros de Guamá e Terra firme

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    I Congresso Internacional América Latina e Interculturalidade: América Latina e Caribe: cenários linguístico-culturais contemporâneos, 07, 08 e 09 de novembro de 2013 - UNILAA intervenção do Assistente Social nas atividades de arte e cultura nas instituições de ensino fundamental e médio nos bairros do Guamá e da Terra Firme. Estudos anteriores constatam que estes não são apenas espaços de violência, como registra a mídia. São espaços multiculturais e agregadores de cultura antiviolência, onde os sujeitos artistas utilizam a arte como meio de transformação social, através do método fenomenológico busco contribuir para a sistematização da intervenção do assistente social na área da educação e cultura, identificando as atividades de arte e cultura nas instituições de ensino fundamental e médio, importância nas instituições em que são desenvolvidas e habilidades requeridas ao profissional de Serviço Social. A metodologia conduziu a investigação nos respectivos bairros com os alunos que estudam nas instituições de ensino fundamental e médio nos bairros, por meio de aplicação de questionários sócio­econômico­cultural que ao definir cultura identificaram as manifestações culturais que estavam ocorrendo no mês (junho/2013) em que o questionário foi aplicado, quanto ao fazer profissional do Serviço Social, a maioria dos alunos da escola pública estadual relacionam o trabalho do assistente social com a prestação de ajuda e auxílio. Os alunos da escola pública federal demonstraram maior efetividade e segurança na resposta, em consonância com o Código de Ética do Assistente Social, também foi realizada entrevista semi­estruturada com a Assistente Social das instituições de ensino. Segundo a pesquisa identifica­se a sobrecarga do profissional do serviço social com as demandas postas pelos alunos no processo de ensino e aprendizagem, de tal modo que não possa acompanhar atividades de arte e cultura desenvolvidas nas instituições de ensino, e por meio de levantamentos bibliográficos e visitas de observação ao local de pesquisa foi possível identificar as atividades, projetos de extensão de arte e cultura nas instituições de ensino

    Familial Clustering For Weakly-labeled Android Malware Using Hybrid Representation Learning

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    IEEE Labeling malware or malware clustering is important for identifying new security threats, triaging and building reference datasets. The state-of-the-art Android malware clustering approaches rely heavily on the raw labels from commercial AntiVirus (AV) vendors, which causes misclustering for a substantial number of weakly-labeled malware due to the inconsistent, incomplete and overly generic labels reported by these closed-source AV engines, whose capabilities vary greatly and whose internal mechanisms are opaque (i.e., intermediate detection results are unavailable for clustering). The raw labels are thus often used as the only important source of information for clustering. To address the limitations of the existing approaches, this paper presents ANDRE, a new ANDroid Hybrid REpresentation Learning approach to clustering weakly-labeled Android malware by preserving heterogeneous information from multiple sources (including the results of static code analysis, the metainformation of an app, and the raw-labels of the AV vendors) to jointly learn a hybrid representation for accurate clustering. The learned representation is then fed into our outlieraware clustering to partition the weakly-labeled malware into known and unknown families. The malware whose malicious behaviours are close to those of the existing families on the network, are further classified using a three-layer Deep Neural Network (DNN). The unknown malware are clustered using a standard density-based clustering algorithm. We have evaluated our approach using 5,416 ground-truth malware from Drebin and 9,000 malware from VIRUSSHARE (uploaded between Mar. 2017 and Feb. 2018), consisting of 3324 weakly-labeled malware. The evaluation shows that ANDRE effectively clusters weaklylabeled malware which cannot be clustered by the state-of-theart approaches, while achieving comparable accuracy with those approaches for clustering ground-truth samples

    Coupled thermal-hydrological-mechanical analyses of the Yucca Mountain Drift Scale Test-Comparison of field measurements to predictions of four different numerical models

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    The Yucca Mountain Drift Scale Test (DST) is a multiyear, large-scale underground heating test designed to study coupled thermal&ndash;hydrological&ndash;mechanical&ndash;chemical behavior in unsaturated fractured and welded tuff. As part of the international cooperative code-comparison project DEvelopment of COupled models and their VALidation against EXperiments, four research teams used four different numerical models to simulate and predict coupled thermal&ndash;hydrological&ndash;mechanical (THM) processes at the DST. The simulated processes included heat transfer, liquid and vapor water movements, rock-mass stress and displacement, and stress-induced changes in fracture permeability. Model predictions were evaluated by comparison to measurements of temperature, water saturation, displacement, and air permeability. The generally good agreement between simulated and measured THM data shows that adopted continuum model approaches are adequate for simulating relevant coupled THM processes at the DST. Moreover, thermal-mechanically induced rock-mass deformations were reasonably well predicted using elastic models, although some individual displacements appeared to be better captured using an elasto-plastic model. It is concluded that fracture closure/opening caused by change in normal stress across fractures is the dominant mechanism for thermal-stress-induced changes in intrinsic fracture permeability at the DST, whereas fracture shear dilation appears to be less significant. This indicates that such changes in intrinsic permeability at the DST, which are within one order of magnitude, are likely to be mostly reversible

    Percutaneous pulmonary valve implantation in humans - Results in 59 consecutive patients

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    Background - Right ventricular outflow tract (RVOT) reconstruction with valved conduits in infancy and childhood leads to reintervention for pulmonary regurgitation and stenosis in later life.Methods and Results - Patients with pulmonary regurgitation with or without stenosis after repair of congenital heart disease had percutaneous pulmonary valve implantation (PPVI). Mortality, hemodynamic improvement, freedom from explantation, and subjective and objective changes in exercise tolerance were end points. PPVI was performed successfully in 58 patients, 32 male, with a median age of 16 years and median weight of 56 kg. The majority had a variant of tetralogy of Fallot (n = 36), or transposition of the great arteries, ventricular septal defect with pulmonary stenosis (n = 8). The right ventricular (RV) pressure (64.4 +/- 17.2 to 50.4 +/- 14 mm Hg, P < 0.001), RVOT gradient (33 +/- 24.6 to 19.5 +/- 15.3, P < 0.001), and pulmonary regurgitation ( PR) (grade 2 of greater before, none greater than grade 2 after, P < 0.001) decreased significantly after PPVI. MRI showed significant reduction in PR fraction (21 +/- 13% versus 3 +/- 4%, P < 0.001) and in RV end-diastolic volume (EDV) (94 +/- 28 versus 82 +/- 24 mL (.) beat(-1) (.) m(-2), P < 0.001) and a significant increase in left ventricular EDV ( 64 +/- 12 versus 71 +/- 13 mL (.) beat(-1.) m(-2), P = 0.005) and effective RV stroke volume ( 37 +/- 7 versus 42 +/- 9 mL (.) beat(-1) (.) m(-2), P = 0.006) in 28 patients (age 19 +/- 8 years). A further 16 subjects, on metabolic exercise testing, showed significant improvement in V(O2)max (26 +/- 7 versus 29 +/- 6 mL (.) kg(-1) (.) min(-1), P < 0.001). There was no mortality.Conclusions - PPVI is feasible at low risk, with quantifiable improvement in MRI-defined ventricular parameters and pulmonary regurgitation, and results in subjective and objective improvement in exercise capacity

    Interdiffusion: A probe of vacancy diffusion in III-V materials

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    Copyright 1997 by the American Physical Society. Article is available at

    Charge carrier induced barrier height reduction at organic heterojunctions

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    In order to provide an accurate theoretical description of current density voltage (J-V) characteristics of an organic heterojunction device over a wide range of electric fields at various temperatures, it is proposed that an accumulation of charge carriers at the heterojunction will lead to a reduction in the barrier height across the heterojunction. Two well-known hole transporting materials, 4,4,4-Tris(N-3-methylphenyl-N-phenyl-amino) triphenylamine (MTDATA) and N,N-diphenyl-N,N-bis(1-naphthyl)(1,1-biphenyl)-4,4diamine (NPB) were used to fabricate unipolar heterojunction devices. It is found that the J-V characteristics depends strongly on applied bias. The simulated J-V characteristics of the heterojunction device, with the modified injection model, are found to be in excellent agreement with the experimental data.Comment: 4 pages, 4 figures, published in Phys. Rev. B Vol. 78, No. 8, http://link.aps.org/abstract/PRB/v78/e08130
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