Fachbereich Elektrotechnik, Maschinenbau, Technikjournalismus
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Solar energy plants are one of the key options to serve the rising global energy need with low environmental impact. Aerosols reduce global solar radiation due to absorption and scattering and therewith solar energy yields. Depending on the aerosol composition and size distribution they reduce the direct component of the solar radiation and modify the direction of the diffuse component compared to standard atmospheric conditions without aerosols.
Solar energy is one option to serve the rising global energy demand with low environmental impact. Building an energy system with a considerable share of solar power requires long-term investment and a careful investigation of potential sites. Therefore, understanding the impacts from varying regionally and locally determined meteorological conditions on solar energy production will influence energy yield projections.
Reliable and regional differentiated power forecasts are required to guarantee an efficient and economic energy transition towards renewable energies. Amongst other renewable energy technologies, e.g. wind mills, photovoltaic (PV) systems are an essential component of this transition being cost-efficient and simply to install. Reliable power forecasts are however required for a grid integration of photovoltaic systems, which among other data requires high-resolution spatio-temporal global irradiance data.
Journalistinnen und Journalisten, die in Publikumsmedien über Technik berichten, müssen Komplexität in besonders starkem Maße reduzieren: Es gilt, komplizierte Themen für ein Publikum ohne Fachwissen verständlich und ansprechend aufzubereiten. Der vorliegende Beitrag geht der Frage auf den Grund, wie dies im Redaktionsalltag gelingt.
Gleichlaufgelenke als Teil der Antriebswellen (Seitenwellen und Längswellen) sind in allen maßgeblichen Triebstrangkonfigurationen im direkten Leistungsfluss angeordnet. Ihre Hauptfunktion ist die Übertragung einer Antriebsleistung unter Ermöglichung von Abbeugung und Axialverschiebung. Dieser Beitrag soll einen Überblick zu den wesentlichen, auf dem heutigen Markt verbreiteten Bauweisen und ihren jeweiligen Einsatzgebieten geben. Besonders berücksichtigt werden hierbei neue Gelenkkonzepte, die sich aufgrund ihrer besonderen Gestaltung durch deutlich höhere Wirkungsgrade auszeichnen. Der Einfluss auf den Energieverbrauch soll quantifiziert werden, hierzu wird ein neuartiger Berechnungsansatz vorgestellt, der eine einfache Abschätzung des Einflusses von Wirkungsgradverbesserungen auf den Energieverbrauch für verschiedener Antriebskonzepte (ICE / Hybrid / E-Fahrzeuge) erlaubt.
This paper discusses the analysis of mechanical power flow in an electric motor drive operating under variation of conditions. The drive system vibration generates the oscillation in the supplied active power which can reduce performance of the system and increase the actual load on the shaft. It is shown that the vibration damper installation significantly decreases the oscillations in mechanical power flow on the motor shaft and improves characteristics of the system operation. The paper provide analysis of two models of the electric drive installed on the platform - the system which is quipped with vibration dampers and without.
We present the performance of the upGREAT heterodyne array receivers on the SOFIA telescope after several years of operations. This instrument is a multi-pixel high resolution (R≳10 7 R≳107) spectrometer for the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA). The receivers use 7-pixel subarrays configured in a hexagonal layout around a central pixel. The low frequency array receiver (LFA) has 2×7 2×7 pixels (dual polarization), and presently covers the 1.83–2.07 THz frequency range, which allows to observe the [CII] and [OI] lines at 158 μ μm and 145 μ μm wavelengths. The high frequency array (HFA) covers the [OI] line at 63 μ μm and is equipped with one polarization at the moment (7 pixels, which can be upgraded in the near future with a second polarization array). The 4.7 THz array has successfully flown using two separate quantum-cascade laser local oscillators from two different groups. NASA completed the development, integration and testing of a dual-channel closed-cycle cryocooler system, with two independently operable He compressors, aboard SOFIA in early 2017 and since then, both arrays can be operated in parallel using a frequency separating dichroic mirror. This configuration is now the prime GREAT configuration and has been added to SOFIA’s instrument suite since observing cycle 6.
Differential-Algebraic Equations and Beyond: From Smooth to Nonsmooth Constrained Dynamical Systems
(2018)
In light of emobility, the development of efficiency improved drivetrain components will also have a high priority. Whereas for conventional vehicle propulsion systems (i.e. combustion type engines) the avoidance of CO2 penalty was in strong focus, for electrified vehicles it is the impact on vehicle range. For GKN Driveline as the world's leading supplier of driveline components and systems, the prediction of energy savings is of particular importance in order to quantify the benefit of efficiency optimizations on the energy consumption of the vehicles. This paper gives an introduction to a simplified and transparent method of modelling to provide a basic understanding of the impact of efficiency improvements. Hereby it is shown, that with the increasing electrification of the drivetrain, the optimization of the efficiency in the mechanical path of power transmission will become even more important.
The paper is about finding the global optimum for a wheel loader work cycle in a gravel application. This includes simulating the gravel and extracting the trajectories for the main actuators; propulsion, lift and tilt, during the work cycle. The optimal control method is dynamic programming and the optimum is calculated with regard to fuel efficiency [ton/l] but can be weighted towards productivity [ton/h].
Technische Innovationen verändern den Alltag enorm – auch den von Journalisten. Technik-Fachjournalisten sind daher gefragt wie nie. Was sie können müssen, wie in den Medien über Digitalisierung berichtet wird und inwiefern künstliche Intelligenz (KI) Journalisten in Zukunft überflüssig machen wird, beantwortet der Medienwissenschaftler Andreas Schümchen im Gespräch mit dem "Fachjournalist".
The lattice Boltzmann method is a modern approach to simulate fluid flow. In its original formulation, it is restricted to regular grids, second-order discretizations, and a unity CFL number. This paper describes our new off-lattice Boltzmann solver NATriuM, an extensible and parallel C++ code to perform lattice Boltzmann simulations on irregular grids. NATriuM also allows high-order spatial discretizations and non-unity CFL numbers to be used. We demonstrate how these features can efficiently decrease the number of grid points required in a simulation and thus reduce the computational time, compared to the standard lattice Boltzmann method. We detail the implementation of a recently proposed semi-Lagrangian lattice Boltzmann method and prove its efficiency in comparisons to other state-of-the-art off-lattice Boltzmann schemes.
Umwelt: Technologien, um die Folgen des Klimawandels zu begrenzen, gibt es. Die soziale und politische Dimension ist der Hemmschuh, so dass sie teils nur zögernd zum Einsatz kommen.
Die Redaktion der VDI nachrichten betreute drei Studierende, die aktuell von jedem Vortrag einen Artikel für unser Ingenieurportal www.ingenieur.de schrieben sowie eine Meldung für die VDI-nachrichten-E-Paper-App. Dieser Artikel ist das Resümee der drei zur Ringvorlesung, aber keine inhaltlich komplette Zusammenfassung. Alle Artikel lesen Sie online unter: www.ingenieur.de/Ringvorlesung2018
The main requirements of efficient steganographic systems are transparency, robustness and security. In this work, the proposed system is designed to achieve these requirements, as follows: to increase the transparency and robustness, the proposed system uses the transform domain technique, in this case the wavelet domain technique to embed the color secret image into the color cover image. To achieve high security, chaotic systems are used to accomplish the following two purposes: firstly to scramble the secret color image before hiding it into the color cover image, secondly to randomly select the embedding positions in the cover image. Three chaotic systems with many combinations are used for the scrambling and the embedding process. Experimental results including Mean Square Error (MSE), Peak Signal to Noise Ratio (PSNR), Correlation, Signal to Noise Ratio (SNR) and embedding capacity demonstrate that the proposed system has good performance as compared with other existing methods without attack and under different types of attacks such as filtering and noise attacks. Simulation results show that the combination of chaotic systems providing the best performance include the use of Logistic and Hénon maps for the embedding process and Arnold's cat map for the encryption process. The MSE, PSNR, correlation, SNR and embedding capacity obtained in this case reach up to 0.0010, 78.1dB, 0.9999, 67.2dB and 0.39% respectively when the secret image is Airplane with 32×32 pixels and the cover image is Girl with 512×512 pixels. For the extracted secret image, the chaotic system set that provides the best performance includes the use of Arnold's cat map for the encryption process. The MSE, PSNR, correlation and SNR obtained in this case reach up to 0.0846, 58.9dB, 1 and 56.1dB respectively. As compared with other methods, the proposed method achieves gains without any attack of 8.2dB for the stego image and 32.4dB for the extracted secret image in PSNR when the secret image is Airplane with 256×256 pixels and the cover image is Girl with 512×512 pixels.
The paper presents the design of a baseband pi/4-DQPSK complex wavelet packet modulation CWPM transceiver and the results of its FPGA implementation. The design uses 8-point Discrete Wavelet Packet Transform (DWPT) and its inverse as core processing modules. All modules have been designed using VHDL programming language together with the Altera software tools Quartus II 9.1 and ModelSim 6.5b. The transceiver was implemented on a Cyclone III board.
The requirements of an efficient communication scheme for wireless sensing applications have been investigated. The noncoherent direct chaotic communication scheme called chaos on-off keying (COOK) has presented itself as a promising candidate. This paper proposes a modified version of the COOK scheme to improve its performance in noisy and fading environments. The proposed scheme is designed to increase the signal space of the decision variable by using the concept of differential correlation keeping implementation requirements simple. The results show that the proposed modified version of the COOK scheme achieves less bit-error probability in noisy and fading channels at moderate signal-to-noise ratio values and almost constant detection threshold as compared with the original version.
High peak to average power ratio (PAPR) of a transmitted signal is one of the major drawbacks of the complex wavelet packet modulation (CWPM) as usual in any multicarrier communication system. Utilizing the advantage of concentrating the energy to certain subspaces of the discrete wavelet transform, many PAPR reduction techniques are proposed to solve this problem like threshold and clipping methods. In this paper a novel hybrid PAPR reduction method for CWPM called Threshold-Clipping (TC) method has been proposed. The simulation results in Rayleigh multipath fading channel show that the proposed scheme has achieved 4.5 dB and 3 dB reduction in PAPR over the traditional threshold and clipping methods respectively with less than 0.5 dB degradation in bit error probability.
Low Cost Displays
(2010)
