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5 results

  • Signal design and performance analysis for LEO high dynamic navigation application

  • Lei Wang, Jibin Che, Haoyan Chen
  • Journal:
    The Journal of Navigation , First View
    Published online by Cambridge University Press:
    13 May 2024, pp. 1-10
    • Article
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  • With the development of GNSS (Global Navigation Satellite System), LEO (Low Earth Orbit) systems are adopted to enhance the system performance of GNSS. The signal Doppler of the LEO satellite is seven to nine times that of GNSS signals, which benefits positioning performance but leads to high acquisition complexity. This paper proposes the combination of a CSS (Chirp Spread Spectrum) marker and the main body of traditional modulation methods for high dynamic application. The acquisition calculation complexity and mean acquisition time of the proposed signal are analysed and compared with the traditional signal. The result shows that the acquisition calculation complexity is just 26 % of the traditional signal under the parameters considered and the mean acquisition time of the proposed signal is also lower than the traditional signal. Hence, the proposed signal is able to decrease the mean acquisition time of the receiver under the constraint of calculation complexity and should be adopted for LEO high dynamic application.

  • 13 - Lessons and Reflections

  • from Part III - A Focalised View of Sustainable Development
  • Omar A. Guerrero, The Alan Turing Institute, London, Gonzalo Castañeda, Centro de Investigación y Docencia Económicas
  • Book:
    Complexity Economics and Sustainable Development
    Published online:
    04 January 2024
    Print publication:
    25 January 2024, pp 350-369

  • Summary

    This chapter provides the reader with three reflections about the Policy Priority Inference research programme and its potential to make a difference in the real world. First, we synthesise the results found throughout the book and their implications for sustainable development. Second, we elaborate on systematic guidelines for deriving policies from the various analyses presented throughout the book. Third, we discuss the technical capabilities needed to adopt this toolkit and advocate for the training of computational social scientists.

  • 2 - Toward a History of Digital Music: New Technologies, Business Practices and Intellectual Property Regimes

  • Edited by Nicholas Cook, University of Cambridge, Monique M. Ingalls, Baylor University, Texas, David Trippett, University of Cambridge
  • Book:
    The Cambridge Companion to Music in Digital Culture
    Published online:
    30 August 2019
    Print publication:
    19 September 2019, pp 33-57

  • Summary

    The chapter historicises the economics of music in the current age of technological automation – from the invention of intellectual property to the implementation of lock-down technologies at the turn of the twenty-first century. The first section sketches the basic characteristics of music’s technological, legal and political economies. By the late twentieth century, the precarious markets for music – enclosed within large-scale cycles of boom and bust in the nineteenth century – had morphed into a relatively stable set of intersecting industrial networks, including print, radio and phonograph. The second section sketches a transition period for the music industry in the context of distributed digital networks that emerged after the Cold War, producing a disjuncture between practice and policy. The third section traces the dialectics of intellectual property regimes pertaining to digital rights management, arguing that a covert allomorphism of the law effectively disabled both technical and legal functionalities pertaining to music.

Twitter as Data

Twitter as Data
  • Zachary C. Steinert-Threlkeld
  • Published online:
    18 January 2018
    Print publication:
    18 January 2018
  • The rise of the internet and mobile telecommunications has created the possibility of using large datasets to understand behavior at unprecedented levels of temporal and geographic resolution. Online social networks attract the most users, though users of these new technologies provide their data through multiple sources, e.g. call detail records, blog posts, web forums, and content aggregation sites. These data allow scholars to adjudicate between competing theories as well as develop new ones, much as the microscope facilitated the development of the germ theory of disease. Of those networks, Twitter presents an ideal combination of size, international reach, and data accessibility that make it the preferred platform in academic studies. Acquiring, cleaning, and analyzing these data, however, require new tools and processes. This Element introduces these methods to social scientists and provides scripts and examples for downloading, processing, and analyzing Twitter data.

  • Texture-tuned growth of CdTe thin films by closed-space sublimation technique

  • Shang Fei, Ji-kang Jian, Wu Rong, Zheng Yu-feng, Sun Yan-fei
  • Journal:
    Powder Diffraction / Volume 23 / Issue 1 / March 2008
    Published online by Cambridge University Press:
    29 February 2012, pp. 31-34

  • CdTe thin films were grown on indium tin oxide glass substrates by a closed-space sublimation method using a resistor heater. Crystalline structure, morphology, and band gaps of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical absorption, respectively. The XRD analysis showed that the textures of the films were found to depend on the rate of increase in the heating current. The CdTe thin film had an (111) texture when the heating current rate was 2.0 A/min. The SEM analysis revealed that the film is composed of polyhedral grains of microns size. However, the (111) texture of the CdTe thin film observed by XRD decreased with the appearance of (220), (311), (400), (331), (422), and (511) peaks of the fcc CdTe phase when the heating current rate increased to 4.5 A/min. The (111) texture disappeared when the heating current was increased immediately from 0 A to the target current of 70 A. SEM results revealed that the grains in the film are round and the grain size is smaller than 1 μm. Optical absorption analysis showed that there is no distinctive difference in the band gaps of the films.