1,632 research outputs found

    Space station structures and dynamics test program

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    The design, construction, and operation of a low-Earth orbit space station poses unique challenges for development and implementation of new technology. The technology arises from the special requirement that the station be built and constructed to function in a weightless environment, where static loads are minimal and secondary to system dynamics and control problems. One specific challenge confronting NASA is the development of a dynamics test program for: (1) defining space station design requirements, and (2) identifying the characterizing phenomena affecting the station's design and development. A general definition of the space station dynamic test program, as proposed by MSFC, forms the subject of this report. The test proposal is a comprehensive structural dynamics program to be launched in support of the space station. The test program will help to define the key issues and/or problems inherent to large space structure analysis, design, and testing. Development of a parametric data base and verification of the math models and analytical analysis tools necessary for engineering support of the station's design, construction, and operation provide the impetus for the dynamics test program. The philosophy is to integrate dynamics into the design phase through extensive ground testing and analytical ground simulations of generic systems, prototype elements, and subassemblies. On-orbit testing of the station will also be used to define its capability

    Space station structures and dynamics test program

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    The design, construction, and operation of a low-Earth orbit space station poses challenges for development and implementation of technology. One specific challenge is the development of a dynamics test program for defining the space station design requirements, and identifying and characterizing phenomena affecting the space station's design and development. The test proposal, as outlined, is a comprehensive structural dynamics program to be launched in support of the space station (SS). Development of a parametric data base and verification of the mathematical models and analytical analysis tools necessary for engineering support of the station's design, construction, and operation provide the impetus for the dynamics test program. The four test phases planned are discussed: testing of SS applicable structural concepts; testing of SS prototypes; testing of actual SS structural hardware; and on-orbit testing of SS construction

    Brain neurons as quantum computers: {\it in vivo} support of background physics

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    The question: whether quantum coherent states can sustain decoherence, heating and dissipation over time scales comparable to the dynamical timescales of the brain neurons, is actively discussed in the last years. Positive answer on this question is crucial, in particular, for consideration of brain neurons as quantum computers. This discussion was mainly based on theoretical arguments. In present paper nonlinear statistical properties of the Ventral Tegmental Area (VTA) of genetically depressive limbic brain are studied {\it in vivo} on the Flinders Sensitive Line of rats (FSL). VTA plays a key role in generation of pleasure and in development of psychological drug addiction. We found that the FSL VTA (dopaminergic) neuron signals exhibit multifractal properties for interspike frequencies on the scales where healthy VTA dopaminergic neurons exhibit bursting activity. For high moments the observed multifractal (generalized dimensions) spectrum coincides with the generalized dimensions spectrum calculated for a spectral measure of a {\it quantum} system (so-called kicked Harper model, actively used as a model of quantum chaos). This observation can be considered as a first experimental ({\it in vivo}) indication in the favour of the quantum (at least partially) nature of the brain neurons activity

    Non-ideality of quantum operations with the electron spin of a 31P donor in a Si crystal due to interaction with a nuclear spin system

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    We examine a 31P donor electron spin in a Si crystal to be used for the purposes of quantum computation. The interaction with an uncontrolled system of 29Si nuclear spins influences the electron spin dynamics appreciably. The hyperfine field at the 29Si nuclei positions is non-collinear with the external magnetic field. Quantum operations with the electron wave function, i.e. using magnetic field pulses or electrical gates, change the orientation of hyperfine field and disturb the nuclear spin system. This disturbance produces a deviation of the electron spin qubit from an ideal state, at a short time scale in comparison with the nuclear spin diffusion time. For H_ext=9 T, the estimated error rate is comparable to the threshold value required by the quantum error correction algorithms. The rate is lower at higher external magnetic fields.Comment: 11 pages, 2 figure

    Metatranscriptome of human faecal microbial communities in a cohort of adult men

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    The gut microbiome is intimately related to human health, but it is not yet known which functional activities are driven by specific microorganisms\u27 ecological configurations or transcription. We report a large-scale investigation of 372 human faecal metatranscriptomes and 929 metagenomes from a subset of 308 men in the Health Professionals Follow-Up Study. We identified a metatranscriptomic \u27core\u27 universally transcribed over time and across participants, often by different microorganisms. In contrast to the housekeeping functions enriched in this core, a \u27variable\u27 metatranscriptome included specialized pathways that were differentially expressed both across participants and among microorganisms. Finally, longitudinal metagenomic profiles allowed ecological interaction network reconstruction, which remained stable over the six-month timespan, as did strain tracking within and between participants. These results provide an initial characterization of human faecal microbial ecology into core, subject-specific, microorganism-specific and temporally variable transcription, and they differentiate metagenomically versus metatranscriptomically informative aspects of the human faecal microbiome

    Impact of freight traffic on school walking decisions in urban environments

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    In light of the decline in social acceptance of walking and biking to school, there is a critical need to examine issues impacting school transportation decisions and to identify strategies to promote healthier behavior. In urban areas with high volume freight corridors, factors affecting school walking decisions can be complicated by increased truck and rail traffic. This paper presents findings from a study of urban neighborhoods in a major southeastern city, including those that are adjacent to freight corridors. Perceptions of neighborhood residents are compared in the context of existing infrastructure and network characteristics (urban vs. urban freight-centric). The results provide insight into factors influencing school transportation decisions in urban environments, and highlight discrepancies between perceptions and actual issues relevant to child pedestrian safety

    Consumers’ adoption of mobile payment: comparison between China and Malaysia / S-C Chuah … [et al.]

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    Mobile payment services has emerged as one of the prominent transaction payment methods. China is leading in mobile payment globally while mobile payment in Malaysia still in its infancy. This paper compares the factors in adoption of mobile payment among consumers’ in Zuhai, China and Kuala Lumpur, Malaysia. The factors included in the study were perceived usefulness, perceived ease of use, subjective norms and perceived security risk. A cross-sectional, descriptive study was undertaken on 96 smartphone users from China and 51 users from Malaysia. Inferential statistics Mann-Whitney U test was applied to compare between study variables. Spearman’s ho correlation was used to identify the association between the study variables and behavioral intention to adopt mobile payment services. The study found significant different between users’ perception on subjective norms and perceived security risk in these two city. There was no significant different for perceived usefulness and perceived ease of use between users in Zuhai and Kuala Lumpur. Significant negative linear correlations between perceived security risk and behavioral intention, and significant positive correlations between perceived usefulness, perceived ease of use and subjective norms and behavioral intention were observed from the study. The findings of this study indicate that the consumers in Kuala Lumpur have higher concern on mobile payment services security and greater social influences to adopt mobile payments

    Consumers’ adoption of mobile payment: comparison between China and Malaysia / Soo Cheng Chuah … [et al.]

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    Mobile payment services has emerged as one of the prominent transaction payment methods. China is leading in mobile payment globally while mobile payment in Malaysia still in its infancy. This paper compares the factors in adoption of mobile payment among consumers’ in Zuhai, China and Kuala Lumpur, Malaysia. The factors included in the study were perceived usefulness, perceived ease of use, subjective norms and perceived security risk. A cross-sectional, descriptive study was undertaken on 96 smartphone users from China and 51 users from Malaysia. Inferential statistics Mann-Whitney U test was applied to compare between study variables. Spearman’s ho correlation was used to identify the association between the study variables and behavioral intention to adopt mobile payment services. The study found significant different between users’ perception on subjective norms and perceived security risk in these two city. There was no significant different for perceived usefulness and perceived ease of use between users in Zuhai and Kuala Lumpur. Significant negative linear correlations between perceived security risk and behavioral intention, and significant positive correlations between perceived usefulness, perceived ease of use and subjective norms and behavioral intention were observed from the study. The findings of this study indicate that the consumers in Kuala Lumpur have higher concern on mobile payment services security and greater social influences to adopt mobile payments
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