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Träfflista för sökning "AMNE:(TECHNOLOGY Other technology Space engineering) "

Sökning: AMNE:(TECHNOLOGY Other technology Space engineering)

  • Resultat 1-10 av 542
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  • Pang, Xiaodan, Dr., et al. (författare)
  • Bridging the Terahertz Gap : Photonics-assisted Free-Space Communications from the Submillimeter-Wave to the Mid-Infrared
  • 2022
  • Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers Inc.. - 0733-8724 .- 1558-2213. ; 40:10, s. 3149-3162
  • Tidskriftsartikel (refereegranskat)abstract
    • Since about one and half centuries ago, at the dawn of modern communications, the radio and the optics have been two separate electromagnetic spectrum regions to carry data. Differentiated by their generation/detection methods and propagation properties, the two paths have evolved almost independently until today. The optical technologies dominate the long-distance and high-speed terrestrial wireline communications through fiber-optic telecom systems, whereas the radio technologies have mainly dominated the short- to medium-range wireless scenarios. Now, these two separate counterparts are both facing a sign of saturation in their respective roadmap horizons, particularly in the segment of free-space communications. The optical technologies are extending into the mid-wave and long-wave infrared (MWIR and LWIR) regimes to achieve better propagation performance through the dynamic atmospheric channels. Radio technologies strive for higher frequencies like the millimeter-wave (MMW) and sub-terahertz (sub-THz) to gain broader bandwidth. The boundary between the two is becoming blurred and intercrossed. During the past few years, we witnessed technological breakthroughs in free-space transmission supporting very high data rates, many achieved with the assistance of photonics. This paper focuses on such photonics-assisted free-space communication technologies in both the lower and upper sides of the THz gap and provides a detailed review of recent research and development activities on some of the key enabling technologies. Our recent experimental demonstrations of high-speed free-space transmissions in both frequency regions are also presented as examples to show the system requirements for device characteristics and digital signal processing (DSP) performance.
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  • Kersten, Anton, 1991, et al. (författare)
  • Output voltage synthesis of a modular battery system based on a cascaded h-bridge multilevel inverter topology for vehicle propulsion: Multilevel pulse width modulation vs. fundamental selective harmonic elimination
  • 2020
  • Ingår i: 2020 IEEE Transportation Electrification Conference and Expo, ITEC 2020. ; , s. 296-302
  • Konferensbidrag (refereegranskat)abstract
    • Lately, the research interest for modular battery systems has increased due to the possibility of a better utilization of individual battery packs/cells and the steadily reducing costs of low voltage power electronics. This paper deals with the output voltage synthesis of a modular battery system based on a seven level Cascaded H-bridge (CHB) inverter topology used in a small passenger vehicle. Two methods are considered, Multilevel Pulse Width Modulation (MPWM) and Fundamental Selective Harmonic Elimination (FSHE). Using simulations, the inverter and battery losses, as well as the current THD, are used to assess the effectiveness of both techniques for the broad operating range of a vehicle's drivetrain. It has been shown that FSHE cannot be applied at a modulation index below 0.25, because of the high current THD (> > 5%). Exceeding a modulation index of 0.25, FSHE reduces the battery and inverter losses in comparison to MPWM, while maintaining an acceptable current THD. Operating at higher speeds, FSHE achieves an even better current THD than MPWM. Consequently, it seems reasonable to use a hybrid modulation technique, using MPWM at low and FSHE at higher speeds, respectively. The exact boundary between MPWM and FSHE can vary in accordance with the individual optimization weightings of current THD and drivetrain efficiency.
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5.
  • Sundin, Maria, 1965, et al. (författare)
  • Space Sports - Sailing in Space
  • 2016
  • Ingår i: Proceedings from icSports 2016, 4th International Conference on Sport Sciences Research and Technology Support, Porto, Portugal, 7-9 november 2016. - : SCITEPRESS - Science and Technology Publications. - 9789897582059 ; , s. 141-146
  • Konferensbidrag (refereegranskat)abstract
    • Titan is the largest moon of Saturn, and apart from the Earth it is the only body in our solar system where a liquid exists on the surface. Within the last ten years a system of lakes and rivers have been discovered. The climate and seasonal cycles of Titan are still not very well known, but the composition and pressure are fairly well established. Perhaps in the future boats will sail the lakes of Titan for research purposes or even sport. The purpose of this paper is to give an overview of the concept of space sports, the conditions of Titan and to calculate important parameters of sailing such as floatability, stability, hull resistance and sail forces. This paper shows that if a sailing yacht on Titan will have twice as large displacement as on Earth, it will be 2.6 times less stable for the same beam. Since friction will be smaller, it will be faster than on Earth at low speed, but significantly slower at high speeds due to the wave generation. The same sail area is required to get the same sail forces if the average wind is 3 m/s, while a 9 times larger sail area is required for if the wind speed is only 1 m/s.
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6.
  • Mellström, Ulf, 1959- (författare)
  • Engineering lives : Technology, time and space in a male-centred world
  • 1995
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis deals with engineers. It is an ethnographic study of the life organisation for seventeen engineers with Master's degrees working at two different workplaces, Automobile Inc. and Microchips Inc. The study is based on participant observation and life-history interviews. It is a study of work, careers and life-paths among thirteen men and four women. Underlying question of this study are what makes sense  to these people  and how meaning is constructed in their lives as engineers.The thesis consists of two parts. In the first part, situated activities and social practices of the two engineering workplaces are focused on. It examines how meaning is produced, reproduced, and socially organised in two engineering microcultures - in short, how technical work is socially constructed under various conditions.In the second part, the lives of the seventeen engineers are presented. Their life-paths are examined through a series of questions such as; Are there any common formative life expedences in the lives of these seventeen engineers? What is their relation to technology and education in the early years of life? How do one relate to family background and "significant others"? How do these engineers present and understand themselves through the reconstruction of their lives in relation to career and gender? What meaning is given to the occupational career in the organisation of life? How are occupational careers in engineering performed?The basic theoretical position in this study is an interactionist one. The most important concepts of the study's first part are microculture, time, space and different forms of everyday interaction. In the study's second part the concepts of perspectives, horizon, socialisation, and career are used to point out individual experiences of culture.
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7.
  • Borgue, Olivia, 1989 (författare)
  • Affordable identification and modelling of uncertain design specifications when introducing new technologies in space applications
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • When introducing new technologies in space products, both the uncertainties regarding technology feasibility and the way in which the technology affects the product development process hinder the early establishment of appropriate engineering specifications. Failing to establish product specifications during conceptual stages leads to problems discovered during later phases of the product development process, when design and process changes are the most expensive. This thesis proposes a digital holistic design platform and a method of constraints replacement for a cost- and time-efficient identification of specification uncertainties when designing space products with new technologies. The digital platform and methods have been developed and tested through industrial case studies featuring the introduction of new technologies for on-orbit applications. Most of these studies were performed in the context of, but are not limited to, the introduction of additive manufacturing. The platform and proposed constraints replacement method are based on function modeling strategies (for modeling product architecture and requirements during conceptual design phases), coupled with activity modeling strategies (for modeling the impact of product architecture on product development schedules and costs). The platform and method enable the identification and assessment of unknown uncertainties, thereby reducing the likelihood of expensive redesign processes during later development phases. Moreover, they enable the inclusion of multidisciplinary design trade-offs during conceptual stages and encourage the establishment of a culture of uncertainty seeking and effective data documentation and transfer.
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8.
  • Klintberg, Jacob, 1994, et al. (författare)
  • Mitigation of Ground Clutter in Airborne Bistatic Radar Systems
  • 2020
  • Ingår i: Proceedings of the IEEE Sensor Array and Multichannel Signal Processing Workshop. - 2151-870X. ; 2020-June
  • Konferensbidrag (refereegranskat)abstract
    • Space-Time Adaptive Processing is a commonly used technique to mitigate ground clutter reflections from an airborne radar system. It estimates a covariance matrix based on spatial and temporal information, and the estimate is thereafter used to suppress the ground clutter. In a side-looking monostatic radar system, the estimate is rather straight forward based on radar observations. However, in this paper, we consider bistatic systems where the power of adaptivity is limited due to nonstationarity of the ground clutter reflections over the range dimension. To overcome this, scenario dependent transformations are commonly used when forming the sample covariance matrix. In this contribution we instead investigate a detector where the clutter covariance matrix is determined from the geometry of the bistatic scenario. Using a Monte-Carlo simulation, we investigate how sensitive the detector is to errors in the assumed geometry, and compare this with state-of-the-art adaptive methods. The results indicates that a good clutter rejection is obtained for errors of order 103 m for assumed transmitter position and 100km/h for assumed transmitter velocity.
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9.
  • Bin, Jiang, 1965-, et al. (författare)
  • Automatic generation of the axial lines of urban environments to capture what we perceive
  • 2010
  • Ingår i: International Journal of Geographical Information Science. - London : Taylor & Francis Group. - 1365-8816 .- 1365-8824 .- 1362-3087. ; 24:4, s. 545-558
  • Tidskriftsartikel (refereegranskat)abstract
    • Based on the concepts of isovists and medial axes, we developed a set of algorithms that can automatically generate axial lines for representing individual linearly stretched parts of open space of an urban environment. Open space is the space between buildings, where people can freely move around. The generation of the axial lines has been a key aspect of space syntax research, conventionally relying on hand-drawn axial lines of an urban environment, often called axial map, for urban morphological analysis. Although various attempts have been made towards an automatic solution, few of them can produce the axial map that consists of the least number of longest visibility lines, and none of them really works for different urban environments. Our algorithms provide a better solution than existing ones. Throughout this paper, we have also argued and demonstrated that the axial lines constitute a true skeleton, superior to medial axes, in capturing what we perceive about the urban environment. 
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10.
  • Petersson, Jesper, 1974 (författare)
  • Technospatialities and telehealthcare: Unfolding new spaces of visibility
  • 2016
  • Ingår i: Information, Communication & Society. - 1369-118X .- 1468-4462. ; 19:6, s. 824-842
  • Tidskriftsartikel (refereegranskat)abstract
    • The umbrella term ‘telehealthcare’ denotes an array of information and communication technology-based solutions for digitally connecting citizens with healthcare services. Guided by the conviction that bodies can be translated into digital data which may serve as the basis for clinical decisions made elsewhere, these designs are widely assumed to enable a mode of healthcare delivery which is independent of space and time. Addressing the increasing use of telehealthcare for personalized health monitoring targeting the growing populations of elderly and chronic-care patients, this paper suggests that such designs invariably unfold new spaces of visibility. Based on an analysis of articles published in a leading telehealthcare journal, I argue that these new visibilities do not provide a window onto something that is already there. Instead, such visibilities are shaped by the way techno-medical practices and knowledge production processes are intertwined with a specific politico-economic agenda. The paper explores differences with respect to the positioning of older people and chronic-care patients in relation to two versions of health monitoring. While each version represents an attempt to promote individual freedom, improve health outcomes and ensure a functioning healthcare system, contrasting rationales are involved and different types of spaces are being unfolded.
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