16,968 research outputs found

    Slowly decaying classical fields, unitarity, and gauge invariance

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    In classical external gauge fields that fall off less fast than the inverse of the evolution parameter (time) of the system the implementability of a unitary perturbative scattering operator (SS-matrix) is not guaranteed, although the field goes to zero. The importance of this point is exposed for the counter-example of low-dimensionally expanding systems. The issues of gauge invariance and of the interpretation of the evolution at intermediate times are also intricately linked to that point.Comment: 8 pages, no figure

    Tracking system study

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    A digital computer program was generated which mathematically describes an optimal estimator-controller technique as applied to the control of antenna tracking systems used by NASA. Simulation studies utilizing this program were conducted using the IBM 360/91 computer. The basic ideas of applying optimal estimator-controller techniques to antenna tracking systems are discussed. A survey of existing tracking methods is given along with shortcomings and inherent errors. It is explained how these errors can be considerably reduced if optimal estimation and control are used. The modified programs generated in this project are described and the simulation results are summarized. The new algorithms for direct synthesis and stabilization of the systems including nonlinearities, are presented

    Results of a study of the stability of cointegrating relations comprised of broad monetary aggregates

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    There is strong evidence of a stable “money demand” relationship for MZM and M2 through the 1990s. Though the M2 relationship breaks down somewhere around 1990, evidence has been accumulating that the disturbance is well characterized as a permanent upward shift in M2 velocity that began around 1990 and was largely over by 1994. This paper’s results support the hypothesis that households permanently reallocated a portion of their wealth from time deposits to mutual funds. This reallocation may have been induced by depository restructuring, but it could also be explained by appropriately measured opportunity cost.Demand for money

    Short-term studies underestimate 30-generation changes in a butterfly metapopulation

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    Most studies of rare and endangered species are based on work carried out within one generation, or over one to a few generations of the study organism. We report the results of a study that spans 30 generations (years) of the entire natural range of a butterfly race that is endemic to 35 km2 of north Wales, UK. Short-term studies (surveys in single years and dynamics over 4 years) of this system led to the prediction that the regional distribution would be quite stable, and that colonization and extinction dynamics would be relatively unimportant. However, a longer-term study revealed unexpectedly high levels of population turnover (local extinction and colonization), affecting 18 out of the 20 patches that were occupied at any time during the period. Modelling the system (using the 'incidence function model' (IFM) for metapopulations) also showed higher levels of colonization and extinction with increasing duration of the study. The longer-term dynamics observed in this system can be compared, at a metapopulation level, with the increased levels of variation observed with increasing time that have been observed in single populations. Long-term changes may arise from local changes in the environment that make individual patches more or less suitable for the butterfly, or from unusual colonization or extinction events that take metapopulations into alternative states. One implication is that metapopulation and population viability analyses based on studies that cover only a few animal or plant generations may underestimate extinction threats

    Unangan past and present: the contrasts between observed and inferred histories

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    Journal ArticleAbstract Academic research focusing on the population and culture history of the Aleut (Unangan) people began in the late 19th century and continues to the present. The papers in this special issue of Human Biology summarize the latest results from archaeological, linguistic, genetic, and morphometric research approaches that bear on our current understanding of Unangan history and prehistory. Although these new analyses have provided a level of description and resolution previously unattainable, explanatory models and mechanisms for the patterned variation observed over time in the biological and cultural record of the Aleutian region remains elusive. Bringing the diverse data sets into concordance to represent an integrated synthesis of Aleut population and culture history and of Unangan origins and their relationships with other groups in the region remains a goal for future investigators

    Big Data Sustainability: An Environmental Management Systems Analogy

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    Today, organizations globally wrestle with how to extract valuable insights from diverse data sets without invading privacy, causing discrimination, harming their brand, or otherwise undermining the sustainability of their big data projects. Leaders in these organizations are thus asking: What management approach should businesses employ sustainably to achieve the tremendous benefits of big data analytics, while minimizing the potential negative externalities? This Paper argues that leaders can learn from environmental management practices developed to manage the negative externalities of the industrial revolution. First, it shows that, along with its many benefits, big data can create negative externalities that are structurally similar to environmental pollution. This suggests that management strategies to enhance environmental performance could provide a useful model for businesses seeking sustainably to develop their personal data assets. Second, this Paper chronicles environmental management’s historical progression from a back-end, siloed approach to a more proactive and collaborative “environmental management system” method. An approach modeled after environmental management systems—a Big Data Management System approach—offers an effective model for managing data analytics operations to prevent negative externalities. Finally, this Paper shows that a Big Data Management System approach aligns with: (A) Agile software development and DevOps practices that companies use to develop and maintain big data applications, (B) best practices in Privacy by Design and Privacy Engineering, and (C) emerging trends in organizational management theory. At this critical, formative moment when organizations begin to leverage personal data to revolutionary ends, we can readily learn from environmental management systems to embrace sustainable big data management from the outset

    Pengaruh Persepsi Nilai Pada Intensi Pembelian Produk Virtual Yang Dimediasi Oleh Kepuasan

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    . This study investigates online game consumer intention to purchase virtualproduct offered during the playing period. Satisfaction of the game was predicted asmediating variable in the influence of perceived value to purchase intention.Hypotheses testing were done by using mediation analysis in IBM SPSS Statisticssoftware version 21 and macro Hayes (2013) model 4. Results showed that in bothgroups, MMORPG (Massively Multiplayer Online Role Playing Games) and MMOBA(Massively Multiplayer Online Battle Arena), online games satisfaction mediates theinfluence of perceived value to virtual product purchase intention. This study extendsconsumer behavior literature, particularly in perceived value, satisfaction and purchaseintentions of online game consumers. Practical implication of this research can be usedspecifically by online games developer, where satisfaction with the game being playedis one determinant of the players intention to purchase virtual products offered duringthe playing period

    Building Health Equity One Institution at a Time: The Research Infrastructure in Minority Institutions Project

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    Developing a well-trained workforce interested in, and prepared for, conducting health equity research is an important national priority. Scientists from Minority-Serving Institutions (MSIs) bring unique perspectives and experiences with racial, ethnic and social inequities in health and health status but often lack access to training and mentoring opportunities, which is crucial for increasing the diverse pool of investigators who are adequately prepared to conduct health disparities research and to compete for National Institutes of Health research funding. The focus of the California State University, Long Beach (CSULB) Research Infrastructure in Minority Institutions (RIMI) Project was to: (a) enhance CSULB’s infrastructure and research capacity, (b) conduct applied community health research on health conditions disproportionately affecting disadvantaged populations, and (c) support faculty to embark on careers in reducing health disparities. Faculty received training, mentorship, and release time support to participate in research-related activities. Select faculty also received funding to conduct a two-year health disparities research project. Within a relatively short period of time, the RIMI Project made important strides toward strengthening the research infrastructure at CSULB by enhancing faculty capacity, improving research utilization to address health disparities, and strengthening campus and community collaborations. MSIs are encouraged to apply for opportunities to build their institution’s research capacity. The lessons learned from this project may be used as a guide for other teaching institutions that have the goal to develop minority faculty researchers

    Presenting in Virtual Worlds: An Architecture for a 3D Anthropomorphic Presenter

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    Multiparty-interaction technology is changing entertainment, education, and training. Deployed examples of such technology include embodied agents and robots that act as a museum guide, a news presenter, a teacher, a receptionist, or someone trying to sell you insurance, homes, or tickets. In all these cases, the embodied agent needs to explain and describe. This article describes the design of a 3D virtual presenter that uses different output channels (including speech and animation of posture, pointing, and involuntary movements) to present and explain. The behavior is scripted and synchronized with a 2D display containing associated text and regions (slides, drawings, and paintings) at which the presenter can point. This article is part of a special issue on interactive entertainment
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