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The small and remote households in Northern regions demand thermal energy rather than electricity. Wind turbine in such places can be used to convert wind energy into thermal energy directly using a heat generator based on the principle of the Joule machine. The heat generator driven by a wind turbine can reduce the cost of energy for heating system. However the optimal performance of the system depends on the torque-speed characteristics of the wind turbine and the heat generator. To achieve maximum efficiency of operation both characteristics should be matched. In the article the condition of optimal performance is developed and an example of the system operating at maximum efficiency is simulated.
Superconducting heterodyne receiver has played a vital role in the high resolution spectroscopy applications for astronomy and atmospheric research up to 2THz. NbN hot electron bolometer (HEB) mixer, as the most sensitive mixer above 1.5THz, has been used in the Herschel space telescope for 1.4-1.9THz and has also shown an ultra-high sensitivity up to 5.3THz. Combined a HEB mixer with a novel THz quantum cascade laser (QCL) as local oscillator (LO), such an all solid-state heterodyne receiver provides the technology which can be used for any balloon-, air- and space-borne heterodyne instruments above 2THz. Here we report the first high-resolution heterodyne spectroscopy measurement using a gas cell and using such a HEB-QCL receiver. The receiver employs a 2.9THz metal-metal waveguide QCL as LO and a NbN HEB as a mixer. By using a gas cell filled with methanol (CH3OH) gas in combination with hot/cold blackbody loads as signal source, we successfully recorded the methanol emission line around 2.918THz. Spectral lines at different pressures and also different frequency of the QCL are studied.
Based on our reconfigurable FPGA spectrometer technology, we have developed a read-out system, operating in the frequency domain, for arrays of Microwave Kinetic Inductance Detectors (MKIDs). The readout consists of a combination of two digital boards: A programmable DAC-/FPGA-board (tone-generator) to stimulate the MKIDs detectors and an ADC-/FPGA-unit to analyze the detectors response. Laboratory measurement show no deterioration of the noise performance compared to low noise analog mixing. Thus, this technique allows capturing several hundreds of detector signals with just one pair of coaxial cables.
This paper picks up on one of the ways reported in the literature to represent hybrid models of engineering systems by bond graphs with static causalities. The representation of a switching device by means of a modulated transformer (MTF) controlled by a Boolean variable in conjunction with a resistor has been used so far to build a model for simulation. In this paper, it is shown that it can also constitute an approach to bond graph based quantitative fault detection and isolation in hybrid system models. Advantages are that Analytical Redundancy Relations (ARRs) do not need to be derived again after a switch state has changed. ARRs obtained from the bond graph are valid for all system modes. Furthermore, no adaption of the standard sequential causality assignment procedure (SCAP) with respect to fault detection and isolation (FDI) is needed.
The Anomalous X‐ray Pulsar 4U 0142+61 is the only neutron star where it is believed that one of the long searched‐for ‘fallback’ disks has been detected in the mid‐IR by Wang et al. [1] using Spitzer. Such a disk originates from material falling back to the NS after the supernova. We search for cold circumstellar material in the 90 GHz continuum using the Plateau de Bure Interferometer. No millimeter flux is detected at the position of 4U 0142+61, the upper flux limit is 150 μJy corresponding to the 3σ noise rms level. The re‐processed Spitzer MIPS 24μm data presented previously by Wang et al. [2] show some indication of flux enhancement at the position of the neutron star, albeit below the 3σ statistical significance limit. At far infrared wavelengths the source flux densities are probably below the Herschel confusion limits.
Spectral surveys provide the only way to determine the full molecular inventory of an object and hence build a comprehensive view of the state of the molecular gas and its role in star formation and the structure and evolution of the ISM. Of course spectral surveys also provide the most efficient method of identifying new and unexpected species that have to be include in the chemical networks. The most extensive and complete survey of an extragalactic system has been the continuous spectral survey from 129 GHz to 175 GHz carried out by Martín et al. (2006) toward NGC253. This first spectral line surveys at 2 mm towards the prototypical starbursts galaxies NGC253 have shown an unexpected chemical richness.
Providing Mobile Phone Access in Rural Areas via Heterogeneous Meshed Wireless Back-Haul Networks
(2011)
The Web has become an indispensable prerequisite of everyday live and the Web browser is the most used application on a variety of distinct devices. The content delivered by the Web has changed drastically from static pages to media-rich and interactive Web applications offering nearly the same functionality as native applications, a trend which is further pushed by the Cloud and more specifically the Cloud’s SaaS layer. In the light of this development, security and performance of Web browsing has become a crucial issue.
Despite perfect functioning of its internal components, a robot can be unsuccessful in performing its tasks because of unforeseen situations. These situations occur when the behavior of the objects in the robot’s environment deviates from its expected values. For robots, such deviations are exhibited in the form of unknown external faults which prohibit them from performing their tasks successfully. In this work we propose to use naive physics knowledge to reason about such faults in the robotics domain. We propose an approach that uses naive physics concepts to find information about the situations which result in a detected unknown fault. The naive physics knowledge is represented by the physical properties of objects which are formalized in a logical framework. The proposed approach applies a qualitative version of physical laws to these properties for reasoning about the detected fault. By interpreting the reasoning results the robot finds the information about the situations which can cause the fault. We apply the proposed approach to the scenarios in which a robot performs manipulation tasks of picking and placing objects. Results of this application show that naive physics holds great promise for reasoning about unknown ex- ternal faults in robotics.
This paper addresses special skills, learners in Internet-based learning scenarios need. In self-directed learning scenarios, as most Internet-based learning scenarios are designed, learners bear the responsibility for their learning progress. To ease this task, institutions could prime the learners for the situation which may be quite different to their previous learning experiences. Basing on a Delphi-study, conducted with experts from the e-Learning sector in Germany, Austria, and Switzerland, the basic requirements have been determined.