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International Powder Metallurgy Congress and Exhibition, Euro PM 2013

作者： Poetschke, Johannes Grasso, Salvatore Richter, Volkmar Michaelis, Alexander Fraunhofer Institute for Ceramic Technologies and Systems Winterbergstraße 28 Dresden01277 Germany School of Engineering and Materials Science and Nanoforce Technology Ltd. Queen Mary University of London Mile End Road LondonE14NS United Kingdom

ISBN: (纸本)9781899072408

Pure tungsten carbide is a very hard and corrosion resistant material. Its various applications, such as wear parts, water-jet nozzles or pressing tools for forming glass lenses attract toolmakers and scientists alike. Due to the absence of any metallic binder or sintering aides, sintering of pure binderless tungsten carbide is normally done at high temperatures at around 2000 °C. In order to limit grain growth, sintering at lower temperatures is preferable. Two different pressurized sintering techniques were used to densify a nanoscaled tungsten carbide powder (DBET=60 nm) at low temperatures: a conventional SinterHIP furnace with an Ar pressure of 10 MPa (100 bar) and a special high pressure SPS furnace, enabling a pressure of 300 MPa. Sintering temperature was between 1200 °C and 1400 °C. The development of density and microstructure was correlated with the chemical processes occurring during sintering. Grain growth was studied using XRD and Rietveld techniques.

关键词： Sintering

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A 2.4-µA 868-MHz low latency wake-up receiver for strong interference channels

A 2.4-µA 868-MHz low latency wake-up receiver for strong in...

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European (Formerly European Gallium Arsenide and Other Semiconductors Application Symposium - EGASS) Microwave Integrated Circuit Conference (EuMIC)

作者： Heinrich Milosiu Frank Oehler Robert Weigel Integrated Circuits and Systems Department Fraunhofer Institute for Integrated Circuits IIS Erlangen Germany Institute for Electronics Engineering University of Erlangen-Nuremberg Erlangen Germany

This paper describes an innovative approach for integrated ultra-low current wireless receivers for UHF bands in a 180-nm CMOS technology. The classical method of slow periodic switching off of the receiver was picked up, essentially enhanced and applied to a superheterodyne receiver topology. A novel fast sampling pulse operation method for ultra low power integrated receivers is presented meeting both short reaction time and very low power consumption requirements. In addition, the receiver was designed for radio channels with strong interferers. The presented ASIC comprises both an analogue front-end and two digital 31 bit correlating decoders. The current consumption of the fabricated prototype is 2.4 μA at 3 volts supply voltage with a reaction time of 485 ms.

关键词： Receivers Switches Power demand Batteries Sampling methods Application specific integrated circuits Sensitivity

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Dynamical model of ball juggling Delta robots using reflection laws

Dynamical model of ball juggling Delta robots using reflecti...

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International Conference on Advanced Robotics (ICAR)

作者： Zeeshan Shareef Viktor Just Heinrich Teichrieb Christopher Lankeit Ansgar Trächtler Department of Mechanical Engineering Heinz Nixdorf Institute Paderborn Germany Project Group Mechatronic Systems Design Fraunhofer Institute for Production Technology IPT Paderborn Germany

In this paper, the dynamical model of the ball juggling robot is presented. The dynamical model takes advantage of the fact that instead of using the camera or vision system, this dynamical model can be used to continuously calculate ball velocity and position during juggling or playing between two robots. In ball juggling or playing robot experiments the most difficult task is to get the position and velocity of the ball during play. This paper deals with calculating the position and velocity of the ball continuously during juggling or playing with the rigid racket. Basic physics reflection laws are used to calculate the outgoing velocity of the ball after each hit. The hitting of the ball on the racket is detected by measuring the distance between the ball contact point and the rigid racket surface. To get the velocity and position of the ball throughout the juggling, the gravitational effect is also incorporated. An overall structure of the stand alone model is also proposed to get the position and velocity continuously. This model is computationally less expensive and gives better insight of the juggling. To validate this dynamical model, experiments are performed on the test bench. The results of this dynamical model are compared and analysed with the results obtained from the RecurDyn simulation and test bench experiment.

关键词： Robots Mathematical model Cameras Machine vision Computational modeling Vectors Equations

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Optimizing Fine Line Dispensed Contact Grids

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Energy Procedia 2014年 55卷 693-701页

作者： Maximilian Pospischil Tobias Fellmeth Andreas Brand Sebastian Nold Martin Kuchler Markus Klawitter Harald Gentischer Markus König Matthias Hörteis Lars Wende Oliver Doll Roland Zengerle Florian Clement Daniel Biro Fraunhofer Institute for Solar Energy Systems (ISE) Heidenhofstr. 2 D-79110 Freiburg Germany Heraeus Precious Metals GmbH & Co. KG Electronic Materials Division Business Unit Photovoltaics Heraeusstr. 12-14 D-63450 Hanau Germany ASYS Automatisierungssysteme GmbH Solar & New Technologies Benzstr. 10 D-89160 Dornstadt Germany Merck KGaA Performance Materials Division Postcode Q004/001 Frankfurter Str. 250 D-64293 Darmstadt Germany Department of Microsystems Engineering – IMTEK University of Freiburg Georges-Köhler-Allee 103 D-79110 Freiburg Germany

Previous studies on dispensing as an alternative front side metallization process in crystalline silicon photovoltaics demonstrated, how an adaption of paste rheology allows for a precise adjustment of contact finger geometry in a wide range. In order to demonstrate the benefit of this advantage, the analytical simulation tool Gridmaster was extended to observe the effect of various geometrical parameters on solar cell results and manufacturing costs. In addition, respective geometrical parameters of thick film printed contact fingers were determined using a special in house developed tool based on MATLAB. As a result, contact geometries as achievable by means of ultrafine line dispensing are ideally suited for contacting silicon solar cells. Compared with standard fine line single screen printed finger geometries, an efficiency increase of up to Δη = 0.4%abs. as well as a reduction of manufacturing costs of 1 €ct./W p on module level can be achieved using dispensing technology. In order to obtain suitable data, simulation results were compared with solar cell results on industrial pre-processed Cz-Si p-type wafer material applying the novel ten nozzle parallel fine line dispensing unit. Therefore, a new dispensing paste was developed combining optimum optical finger aspect ratios of AR o =0.7 with excellent contacting behavior. A successful first test of applicability already led to a maximum cell efficiency of η = 18.7%, demonstrated on an industrial emitter with a sheet resistance of around R sh = 90 Ω/sq.

关键词： silicon solar cells printing metallization dispensing contact geometries economic evaluation analytic simulation

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Analytical Models for Channel Aging and Synchronization Errors for Base Station Cooperation

Analytical Models for Channel Aging and Synchronization Erro...

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European Signal Processing Conference

作者： Konstantinos Manolakis Christian Oberli Lurys Herrera Volker Jungnickel Technische Universitat Berlin Department of Telecommunication Systems Pontificia Universidad Catolica de Chile Department of Electrical Engineering Fraunhofer Heinrich Hertz Institute

Base station cooperation is a powerful technique for eliminating inter-cell interference and enhancing spectral efficiency in cellular networks. However, impairment effects due to channel time variance, channel estimation, feedback quantization and imperfect synchronization among base stations are limiting the potential gains. In this paper, we present a comprehensive signal model for multi-user multi-cellular systems with cooperating base stations, which includes those essential impairments. The effect of each impairment is captured by its mean square error (MSE), for which exact analytical expressions and accurate approximations are derived and numerically verified. Those MSE expressions can be used for link-layer abstraction, system-level evaluation and signal to interference ratio (SIR) analysis. We evaluate the spectral efficiency of cooperative networks considering a real-world scenario and find that channel aging has the largest impact on performance degradation.

关键词： Synchronization Downlink Aging Numerical models Speech

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Efficiency of dense-array CPVT module with front-side interconnected cells

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AIP Conference Proceedings 2013年第1期1556卷 180-184页

作者： G. Polonsky G. Shelef Y. Flitsanov M. Wiesenfarth M. Steiner H. Helmers A. W. Bett A. Kribus School of Mechanical Engineering Tel Aviv University Tel Aviv 69978 Israel Fraunhofer Institute for Solar Energy Systems ISE Heidenhofstr. 2 79110 Freiburg Germany

Dense array concentrating photovoltaic collectors can be used as cogeneration systems, CPV and thermal (CPVT), producing both electricity and heat, leading to high overall system efficiency. Triple-junction metamorphic III-V cells with front side interconnections were developed to minimize the spacing among the cells and maximize the active area that intercepts the concentrated radiation. Modules with front interconnected cells and active cooling were fabricated and tested outdoors in a parabolic dish under a range of temperatures. Performance of the modules and the dependence on operating temperatures are reported.

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Energy-efficient multi-hop transmission for machine-to-machine communications

Energy-efficient multi-hop transmission for machine-to-machi...

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International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt)

作者： Christian Dombrowski Neda Petreska Simon Görtzen Anke Schmeink James Gross UMIC Research Centre RWTH Aachen University Germany Fraunhofer Institute for Communication Systems ESK Munich Germany School of Electrical Engineering Royal Institute of Technology Sweden

ISBN: (纸本)9781479922390

Emerging machine-to-machine communication scenarios are envisioned to deal with more stringent quality-of-service demands. This relates mainly to outage and latency requirements, which are for example for safety-critical messages quite different than for traditional applications. On the other hand, it is widely accepted that machine-to-machine communication systems need to be energy-efficient because of the widespread use of battery-powered devices, but also due to their huge deployment numbers. In this paper, we address these issues with respect to multi-hop transmissions. Specifically, we deal with minimizing the consumed energy of transmitting a packet with end-to-end outage and latency requirements. We account for the cases in which the system can utilize solely average channel state information, or in addition obtain and profit from instantaneous channel state information. The developed solution is based on convex optimization. It is shown numerically that despite accounting for the energy consumption of acquiring instantaneous channel state information, especially as the outage and latency requirements become tough, it is by up to 100 times more energy efficient to convey a packet with instantaneous than with average channel state information.

关键词： Quality of service Energy consumption Channel state information Payloads Resource management Minimization Signal to noise ratio

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Evaluation of Industrially Relevant Parameters for Contact Firing of Screen Printed Front Side Silver Contacts

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Energy Procedia 2013年 38卷 737-744页

作者： Rene Hoenig Daniel Voessing Florian Clement Daniel Biro Ralf Preu Juergen Wilde Fraunhofer Institute for Solar Energy Systems ISE Heidenhofstr. 2 79110 Freiburg Germany Department of Microsystems Engineering IMTEK Albert-Ludwigs-University Georges-Koehler-Allee 103 79110 Freiburg Germany

To evaluate the impact of industrially relevant contact firing parameters on the contact resistance of screen printed front side silver contacts to the n-type emitter of crystalline silicon solar cells, contact firing is performed using design of experiments. Therefore, H-pattern aluminum back surface field solar cells processed on boron-doped Czochralski silicon are contact fired by rapid thermal firing in an industrial conveyor belt furnace as well as in a single wafer reactor. Current-voltage data as well as contact resistance values of 36 parameter sets are analyzed and evaluated regarding the significance of several contact firing parameters. Further aspects of the current transport mechanisms and performance of front side silver contacts in correlation with their microstructure are revealed. Comprehensive macroscopical characterization as well as microstructural analysis is done. An efficiency gain of ≥ 0.1% abs only due to optimization of contact firing parameters is shown.

关键词： contact formation rapid thermal firing screen printing crystalline silicon solar cells

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Autonomously driven railway cabin convoys — Communication, control design and experimentation

Autonomously driven railway cabin convoys — Communication, ...

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International Conference on Connected Vehicles and Expo (ICCVE)

作者： Christian Henke Ansgar Trächtler Project Group Mechatronic Systems Design Fraunhofer Institute for Production Technology IPT Paderborn Germany Control Engineering and Mechatronics (RtM) University of Paderborn Paderborn Germany

The subject of the RailCab project is the development of autonomous railway cabins, which can dynamically group to convoys without mechanical coupling. This enables an on-demand use of these vehicles while retaining the cost and ecological advantages of public transport. In this paper, we present (1) the system concept with focus on the convoy operation mode. Furthermore we explain (2) the system and communication architecture, which is the basis for the coordination and organization of locally distributed systems. The main contribution of this paper is the convoy control system (3). The proposed methods allow automatic and dynamic operation of vehicle convoys. Experimental results from real-life tests (4) validate the system, the communication structure and the control synthesis, thereby ensuring safe and reliable operation.

关键词： Vehicles Vehicle dynamics Merging Stability analysis Control systems Acceleration Aerodynamics

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Performance comparison of H.265/MPEG-HEVC, VP9, and H.264/MPEG-AVC encoders

Performance comparison of H.265/MPEG-HEVC, VP9, and H.264/MP...

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Picture Coding Symposium, PCS

作者： Dan Grois Detlev Marpe Amit Mulayoff Benaya Itzhaky Ofer Hadar Image Processing Department Fraunhofer Heinrich-Hertz-Institute (HHI) Berlin Germany Communication Systems Engineering Department Ben-Gurion University of the Negev Beer-Sheva Israel

This work presents a performance comparison of the two latest video coding standards H.264/MPEG-AVC and H.265/MPEG-HEVC (High-Efficiency Video Coding) as well as the recently published proprietary video coding scheme VP9. According to the experimental results, which were obtained for a whole test set of video sequences by using similar encoding configurations for all three examined representative encoders, H.265/MPEG-HEVC provides significant average bit-rate savings of 43.3% and 39.3% relative to VP9 and H.264/MPEG-AVC, respectively. As a particular aspect of the conducted experiments, it turned out that the VP9 encoder produces an average bit-rate overhead of 8.4% at the same objective quality, when compared to an open H.264/MPEG-AVC encoder implementation - the x264 encoder. On the other hand, the typical encoding times of the VP9 encoder are more than 100 times higher than those measured for the x264 encoder. When compared to the full-fledged H.265/MPEG-HEVC reference software encoder implementation, the VP9 encoding times are lower by a factor of 7.35, on average.

关键词： Transform coding Video coding Encoding Software Standards Image coding Codecs

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