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  • Books  (132)
  • Articles  (11,029)
  • Physics  (11,148)
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  • 1
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-14
    Description: The exchange of orbit information is becoming more important in view of the increasing population of objects in space as well as the increase in parties involved in space operations. The aim of this thesis was to investigate how orbit information maintained by a space surveillance system can be provided to its users. Services like collision avoidance require very accurate information, while other services might be less stringent. An approach was studied, which allows to derive orbit and covariance information of predetermined accuracy from a reference orbit. Using Chebyshev polynomials, continuous state vector and covariance matrix information can be provided. The major advantage is that no inter- or extrapolation on the user's side is required. A method to reduce the data amount by interpolating the variance envelope functions was also studied. The proposed method in this thesis gives access to highly accurate information from the catalogue, where this information is required. On the other hand it can also provide less accurate information, where requirements are less restrictive, thereby allowing for a significantly reduced amount of data to be transferred and stored.
    Keywords: Computers ; Computer Science ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::U Computing and Information Technology::UY Computer science ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 2
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-14
    Description: Orbital debris is becoming an increasing problem for space flight missions. New satellite launches, explosions, collisions and other events cause a steady rise in the number of objects orbiting the Earth. It is therefore important to determine the future development of the object population, as well as the effectiveness of debris mitigation measures, in long-term simulations. Orbital propagation, the calculation of an object's movement in its orbit, poses a challenge for this research due to the high computation times of the complex perturbation models involved. With populations consisting of hundreds of thousands of objects as well as simulation time frames of up to 200 years, these calculations can take up hours of computation time. To speed up this process, the analytical propagator Ikebana is introduced in this work of applied computer science in engineering. The program runs on graphics processing units, hardware designed for massively parallel execution of up to thousands of concurrent threads. This reduces the overall run time for large object populations from hours to minutes. Porting software from a conventional CPU is not a trivial task and involves a number of potential pitfalls and optimization opportunities which are detailed in this work. The propagator is integrated into other applications via a generic, multi-platform interface specifically designed for this task. It allows to develop the propagator separately and integrate it into other tools as a plugin at run time. The interface's architecture serves as a design template for analytical propagation software.
    Keywords: Computers ; Computer Science ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::U Computing and Information Technology::UY Computer science ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 3
    Publication Date: 2024-04-14
    Description: Limiting climate change will require transformation of energy and other systems. This report presents an agent-based, game theoretic model designed to compare the long-term sustainability of alternative carbon emission reduction policies. The model tracks the co-evolution of an industry sector, its technology base, and political coalitions that influence government policy. It uses robust decision making methods to compare alternative policies.
    Keywords: Physics ; Mathematics ; Technology ; thema EDItEUR::U Computing and Information Technology::UN Databases::UNA Database design and theory ; thema EDItEUR::P Mathematics and Science::PB Mathematics::PBU Optimization::PBUD Game theory ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RB Earth sciences::RBP Meteorology and climatology
    Language: English
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  • 4
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-11
    Description: While binaural technology applications gained in popularity in recent years, the majority of applications still use non-individual Head-Related Transfer Functions (HRTFs) from artificial heads. However, certain applications, for example research of spatial hearing or hearing attention, require an physically exact and realistic binaural signal. The limiting factor that prohibits the widespread use of individual HRTFs is the acquisition time of such data. This time requirement has recently been reduced by the use of parallelization in the measurement signal which lead to the development of fast measurement systems capable of acquiring individual and spatially dense HRTF. This thesis provides a objective and subjective evaluation of such a system that is designed with the goal of little disturbance of the measurements in mind. The construction is detailed, followed by both an objective and subjective evaluation. A detailed investigation into additional distortion of the sound field introduced by the system itself is presented and it is shown that the system performs comparably to a conventional system in terms of sound source localization. Furthermore, a method is introduced and evaluated to further reduce the measurement time by using continuous rotation during the measurement. This method is used to reduced the measurement duration from eight minutes to three minutes without audible differences.
    Keywords: Technology & Engineering ; Electronics ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TJ Electronics and communications engineering::TJF Electronics engineering ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 5
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-11
    Description: Our world today is becoming increasingly complex, and technical devices are getting ever smaller and more powerful. The high density of electronic components together with high clock frequencies leads to unwanted side-effects like crosstalk, delayed signals and substrate noise, which are no longer negligible in chip design and can only insufficiently be represented by simple lumped circuit models. As a result, different physical phenomena have to be taken into consideration since they have an increasing influence on the signal propagation in integrated circuits. Computer-based simulation methods play thereby a key role. The modelling and analysis of complex multi-physics problems typically leads to coupled systems of partial differential equations and differential-algebraic equations (DAEs). Dynamic iteration and model order reduction are two numerical tools for efficient and fast simulation of coupled systems. Formodelling of low frequency electromagnetic field, we use magneto-quasistatic (MQS) systems which can be considered as an approximation to Maxwells equations. A spatial discretization by using the finite element method leads to a DAE system. We analyze the structural and physical properties of this system and develop passivity-preserving model reduction methods. A special block structure of the MQS model is exploited to to improve the performance of the model reduction algorithms.
    Keywords: Technology & Engineering ; Electronics ; Mathematics ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TJ Electronics and communications engineering::TJF Electronics engineering ; thema EDItEUR::P Mathematics and Science::PB Mathematics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 6
    Publication Date: 2024-04-11
    Description: In einem Solarturmkraftwerk werden hunderte bis tausende Spiegel (sogenannte Heliostate) einzeln der Sonne nachgeführt, sodass das Sonnenlicht auf die Spitze eines Turmes konzentriert wird. Dort befindet sich der Receiver, der die Solarstrahlung absorbiert und an das Wärmeträgermedium weitergibt. Große thermische Energiespeicher erlauben die ganztägige Stromproduktion (auch Nachts). In aktuellen Solarturmkraftwerken kommen als Wärmeträger- und Speichermedium häufig flüssige Nitratsalze wie Solar Salt zum Einsatz. Aufgrund ihrer hohen Wärmekapazität und den geringen Kosten eignen sie sich sehr gut zur thermischen Energiespeicherung, jedoch bringen sie auch einige Nachteile mit sich. Flüssigmetalle weisen in vielen Punkten Vorteile gegenüber den Flüssigsalzen auf. In der vorliegenden Arbeit werden die Eigenschaften von Flüssigmetallen detailliert analysiert und mit Solar Salt verglichen. Zur Bewertung werden die Jahreserträge bzw. die Stromgestehungskosten (LCOE) herangezogen. Die Ergebnisse zeigen ein Potenzial zur Reduktion der Stromgestehungskosten mit Flüssigmetallen um bis zu 16 % gegenüber dem Referenzsystem mit Solar Salt, ohne dabei den Kraftwerksblock und den thermischen Speicher zu verändern.
    Keywords: Technology & Engineering ; Construction ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TN Civil engineering, surveying and building::TNK Building construction and materials ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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  • 7
    Publication Date: 2024-04-11
    Description: Die Optimierung dynamischer Dichtsysteme ist eine kostengünstige Methode zur Erhöhung der Wirkungsgrade, Lebensdauer und Betriebssicherheit von Turbomaschinen. Zuverlässige und effiziente Dichtsysteme lassen sich nur realisieren, wenn die Anstreifvorgänge zwischen rotierenden und statischen Komponenten sowie ihre Folgen schon bei der Auslegung berücksichtigt und im Betrieb beherrscht werden können. Bis heute sind die physikalischen Vorgänge beim Anstreifen jedoch nur unzureichend verstanden und es fehlen zuverlässige Modellierungsansätze für ihre Vorhersage. Die vorliegende Arbeit liefert einen essentiellen Beitrag zum Verständnis des Anstreifverhaltens und somit zur Optimierung einlaufender dynamischer Dichtsysteme mit Fokus auf Labyrinthdichtungen mit Einlaufbelägen aus Hohlkörperstrukturen. Mit Hilfe aufwändiger experimenteller Untersuchungen wird in dieser Arbeit ein tiefergreifendes physikalisches Verständnis der Anstreifvorgänge bereitgestellt. Die experimentell gewonnenen Erkenntnisse bilden schließlich die Grundlage für die Entwicklung eines Modellierungsansatzes, der erstmals unter Berücksichtigung aller Einflussparameter die zuverlässige Vorhersage des Anstreifverhaltens einlaufender Labyrinthdichtungen ermöglicht.
    Keywords: Technology & Engineering ; Construction ; Technology & Engineering ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TN Civil engineering, surveying and building::TNK Building construction and materials ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: German
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  • 8
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-11
    Description: Human sound localization helps to pay attention to spatially separated speakers using interaural level and time differences as well as angle-dependent monaural spectral cues. In a monophonic teleconference, for instance, it is much more difficult to distinguish between different speakers due to missing binaural cues. Spatial positioning of the speakers by means of binaural reproduction methods using head-related transfer functions (HRTFs) enhances speech comprehension. These HRTFs are influenced by the torso, head and ear geometry as they describe the propagation path of the sound from a source to the ear canal entrance. Through this geometry-dependency, the HRTF is directional and subject-dependent. To enable a sufficient reproduction, individual HRTFs should be used. However, it is tremendously difficult to measure these HRTFs. For this reason this thesis proposes approaches to adapt the HRTFs applying individual anthropometric dimensions of a user. Since localization at low frequencies is mainly influenced by the interaural time difference, two models to adapt this difference are developed and compared with existing models. Furthermore, two approaches to adapt the spectral cues at higher frequencies are studied, improved and compared. Although the localization performance with individualized HRTFs is slightly worse than with individual HRTFs, it is nevertheless still better than with non-individual HRTFs, taking into account the measurement effort.
    Keywords: Technology & Engineering ; Electronics ; Science ; Physics ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TJ Electronics and communications engineering::TJF Electronics engineering ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 9
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publication Date: 2024-04-11
    Description: This reprint focuses on recent progress on hydrothermal carbonization (HTC) to upcycle wet waste biomass like sewage sludge and corn stover into valuable energy and materials like carbon quantum dots (CQDs). The reprint also reports fundamentals of HTC and compares with vapothermal carbonization.
    Keywords: &nbsp ; Waste biomass ; Hydrothermal Carbonization ; Hydrochar ; Energy ; Materials ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues::TBX History of engineering and technology ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TQ Environmental science, engineering and technology
    Language: English
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  • 10
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    Springer Nature
    Publication Date: 2024-04-08
    Description: This open access book chronicles the rise of a new scientific paradigm offering novel insights into the age-old enigmas of existence. Over 300 years ago, the human mind discovered the machine code of reality: mathematics. By utilizing abstract thought systems, humans began to decode the workings of the cosmos. From this understanding, the current scientific paradigm emerged, ultimately discovering the gift of technology. Today, however, our island of knowledge is surrounded by ever longer shores of ignorance. Science appears to have hit a dead end when confronted with the nature of reality and consciousness. In this fascinating and accessible volume, James Glattfelder explores a radical paradigm shift uncovering the ontology of reality. It is found to be information-theoretic and participatory, yielding a computational and programmable universe.
    Keywords: Popular works ; Physics ; Epistemology ; Physics ; Statistical physics ; Dynamical systems ; Philosophy and science ; Philosophy ; thema EDItEUR::Q Philosophy and Religion::QD Philosophy::QDT Topics in philosophy::QDTK Philosophy: epistemology and theory of knowledge ; thema EDItEUR::Q Philosophy and Religion::QD Philosophy::QDX Popular philosophy ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDA Philosophy of science ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDX History of science ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDZ Popular science ; thema EDItEUR::P Mathematics and Science::PH Physics::PHS Statistical physics ; thema EDItEUR::Q Philosophy and Religion::QD Philosophy::QDT Topics in philosophy::QDTK Philosophy: epistemology and theory of knowledge ; thema EDItEUR::Q Philosophy and Religion::QD Philosophy::QDX Popular philosophy ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDA Philosophy of science ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDX History of science ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDZ Popular science ; thema EDItEUR::P Mathematics and Science::PH Physics::PHS Statistical physics
    Language: English
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