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Helsch G.,Clausthal University of Technology | Mos A.,Clausthal University of Technology | Deubener J.,Clausthal University of Technology | Deubener J.,Energie-forschungszentrum Niedersachsen (EFZN) | Holand M.,Interstate University of Applied Sciences and Technology
Solar Energy Materials and Solar Cells | Year: 2010

Quarter-wave anti reflectance (AR) coatings were applied on silica glass by a solgel dip coating process to minimize reflective losses of the receiver cover materials for solar tower power plants. To investigate the thermal resistance of the coatings prepared from silica sols of 20 nm, mean particle sizes, solar transmittance, thickness, and density were determined as a function of isothermal heat treatments using UVvisNIR spectroscopy, profilometry, and X-ray reflectometry, respectively. The initial solar transmittance τ of the AR coated silica glass, cured at 773 K, was 0.973 for a film thickness d=111 nm. Heat treatments in the range from 1273 to 1423 K for 15240 min reduce both film thickness and solar transmittance of the crystal-free films. The isothermal shrinkage rate of the film thickness was described for a relative density >0.634 using MackenzieShuttleworth (MS) model. Viscosity data calculated from the sintering rate constant of the MS model were compared with literature data of silica glasses of known water content prepared by sintering and fusion. This analysis indicates that the sintering kinetics of the nanoporous film were controlled by viscous flow of amorphous silica particles of a water content of ≈1100 ppmw associated with an activation energy of 321 kJ mol-1. © 2010 Elsevier B.V. All rights reserved.


Grant
Agency: Cordis | Branch: FP7 | Program: CP | Phase: ENERGY.2013.4.1.1 | Award Amount: 5.13M | Year: 2013

The FLUIDGLASS project develops a new and innovative concept for multifunctional solar thermal glass faades systems. The FLUIDGLASS approach turns passive glass faades into active transparent solar collectors while at the same time controlling the energy flow through the building envelope. FLUIDGLASS unites four key functionalities in one integrated system: The system firstly acts as a fully transparent solar thermal collector, which enables harvesting of solar energy even in buildings with large glass share. It secondly acts as transparent insulation layer and thirdly controls the solar radiation transmission and inner glass surface temperature thus increasing the thermal user comfort and reducing the demand for heating, cooling and lighting. At the same time FLUIDGLASS substitutes conventional HVAC components such as cooling and heating panels. Replacing four different systems by one, FLUIDGLASS brings a significant cost advantage compared to existing solutions.. FLUIDGLASS increases the thermal performance of the whole building resulting in energy savings potential of 50%-70% for retrofitting and 20%-30% for new low energy buildings while the comfort for the user is significantly improved at the same time. Compared to state-of-the-art solar collectors FLUIDGLASS has the elegant but neutral aesthetics of clear glass. This allows full design freedom for the architect in new built applications and enables retrofits that do not destroy the original look of an existing building. The FLUIDGLASS system will be validated in different climate conditions. The consortium brings together partners experienced in glass architecture, building simulation and energy management but also in experimental testing, HVAC systems, manufacturing of glazing units and construction of faades. It is very well balanced between RTD and industrial sectors covering the whole innovation value chain of the future building skin and gives an important role to participating SMEs.


Andreas E.,Interstate University of Applied Sciences and Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Optical measuring techniques for micro structures are limited by the numerical aperture of the objective. Within these limits different techniques can be used: white light interferometry uses an illumination source with short coherence length to determine the absolute position of the surface while confocal profilometry uses the principle of the defocus of light. As a relatively new technique, digital holography offers the simultaneous measurement of intensity and phase of a wave to generate a 3D image with the acquisition of just one single image. We give some application examples of these techniques to micro structures including deformation measurements. © 2011 SPIE.


Durager C.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Heinzelmann A.,Interstate University of Applied Sciences and Technology | Riederer D.,Interstate University of Applied Sciences and Technology
Structure and Infrastructure Engineering | Year: 2013

Piezoelectric transducers are widely used for structural health monitoring (SHM) applications. Low weight and small dimensions are only two of the several advantages of piezoelectric transducers. However, these advantages are weakened by using wired connections for supplying the piezoelectric transducers. Besides the additional weight, a long wire connection can have an influence on the measured capacitance. Due to the aforementioned disadvantages, researchers developed different wireless solutions for SHM applications in the last 10 years. In this paper, we present a wireless SHM system, which is designed for SHM applications with piezoelectric transducers and guided ultrasonic waves (GUW). The first part in this paper describes the different parts of the wireless SHM system. One novelty ofthe proposed wireless system is that every wireless signal-processing unit (SPU) in the network can be used for exciting the piezoelectric transducer and also for measuring the voltage signals coming from the piezoelectric transducer. Finally, the paper presents a laboratory test on an aluminium/hardfoam sandwich plate with a removable artificial defect to accurately assess the performance merits and weaknesses of the wireless sensor network. © 2013 Copyright Taylor and Francis Group, LLC.


Schoch A.,Interstate University of Applied Sciences and Technology | Bach C.,Interstate University of Applied Sciences and Technology | Ettemeyer A.,Interstate University of Applied Sciences and Technology | Linz-Dittrich S.,Interstate University of Applied Sciences and Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The trend towards computers with multiple processing units keeps going with no end in sight. Modern consumer computers come with 2 - 6 processing units. Programming methods have been unable to keep up with this fast development. In this paper we present a framework that uses a dataflow model for parallel processing: the Generic Parallel Rapid Development Toolkit, GePaRDT. This intuitive programming model eases the concurrent usage of many processing units without specialized knowledge about parallel programming methods and it's pitfalls. © 2012 SPIE.


Ettemeyer A.,Interstate University of Applied Sciences and Technology
Optical Engineering | Year: 2012

Increasing manufacturing accuracy requirements enforce the development of innovative and highly sensitive measuring tools. Especially for measurement with submicrometer accuracy, the sensor principle has to bechosenappropriately foreachmeasurementsurface.Modernmultisensor coordinatemeasurement systemsallow automatic selection of different sensor heads to measure different areas or properties of a sample. As an example, different types of optical sensors as well as tactile sensors can be used within the same measuring system. I describe different principles of optical sensors used in multisensor coordinate measurement systems as well as a newapproach for tactilemeasurement with submicrometer accuracy.Aspecial fiber probe has been developed. The tip of the fiber probe is formed as a sphere.Thelateral position of this sphereisobservedbyamicroscope objective and can be determined within a fraction of a micrometer. Additionally, a novel optical setup now allows the determination of the z-position of the fiber tipwith submicrometer accuracy. For this purpose, an interferometer setup is used. The laser light is coupled into the optical fiber. The light exiting the fiber tip is collected by themicroscope objective and superposed with a reference wave, generated directly from the laser. The result is an interference signal that is recorded by the cameraandprocessed bya computer.With this setup, thez-displacement of thefiberspherecanbemeasuredwithanaccuracyofa fraction of the laser wavelength used. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).


Ghiotti A.,University of Padua | Schoch A.,University of Padua | Schoch A.,Interstate University of Applied Sciences and Technology | Salvadori A.,University of Padua | And 2 more authors.
CIRP Annals - Manufacturing Technology | Year: 2015

Geometrical distortions due to inappropriate setting of process parameters are one of the main causes of variability in manufacturing hot forged thin parts. Their identification and measurement at the earliest steps of the process chain may permit significant benefit especially in case of small batch production. The paper presents a coordinate measuring system for fast inspection of freeform parts at elevated temperatures through high-speed laser triangulation. Main error sources are discussed, including a new method for the correction of systematic errors due to imperfect laser planes alignment. A procedure for testing the metrological performances at elevated temperature is also presented. © 2015 CIRP.


Ettemeyer A.,Interstate University of Applied Sciences and Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Increasing manufacturing accuracy requirements enforce the development of innovative and highly sensitive measuring tools. Especially for measurement with sub micrometer accuracy, the sensor principle has to be chosen appropriately for each measurement surface. Modern multi sensor coordinate measurements systems allow automatic selection of different sensor heads to measure different areas or properties of a sample. As example, different types of optical sensors as well as tactile sensors can be used with the same machine. In this paper we describe different principles of optical sensors used in multi sensor coordinate measurement systems as well as a new approach for tactile measurement with sub micrometer accuracy. A special fiber probe has been developed. The tip of the fiber probe is formed as a sphere. The lateral position of this sphere is observed by a microscope optics and can be determined to a fraction of a micrometer. Additionally, a novel optical set-up now even allows the determination of the z-position of the fiber tip with sub micrometer accuracy. For this purpose we use an interferometric set-up. The light of laser is coupled into the optical fiber. The light, exiting the fiber tip is collected by a microscope optics and superposed with a reference wave, generated directly from the laser. The result is an interferometric signal which is recorded by the camera and processed by a computer. With this set-up, the zdisplacement of the fiber sphere can be measured with an accuracy of a fraction of the used laser wavelength. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).


Heeb P.,Interstate University of Applied Sciences and Technology | Tschanun W.,MicroTech | Buser R.,Interstate University of Applied Sciences and Technology
Journal of Micromechanics and Microengineering | Year: 2012

A comprehensive and completely parameterized model is proposed to determine the related electrical and mechanical dynamic system response of a voltage-driven capacitive coupled micromechanical switch. As an advantage over existing parameterized models, the model presented in this paper returns within few seconds all relevant system quantities necessary to design the desired switching cycle. Moreover, a sophisticated and detailed guideline is given on how to engineer a MEMS switch. An analytical approach is used throughout the modelling, providing representative coefficients in a set of two coupled time-dependent differential equations. This paper uses an equivalent mass moving along the axis of acceleration and a momentum absorption coefficient. The model describes all the energies transferred: the energy dissipated in the series resistor that models the signal attenuation of the bias line, the energy dissipated in the squeezed film, the stored energy in the series capacitor that represents a fixed separation in the bias line and stops the dc power in the event of a short circuit between the RF and dc path, the energy stored in the spring mechanism, and the energy absorbed by mechanical interaction at the switch contacts. Further, the model determines the electrical power fed back to the bias line. The calculated switching dynamics are confirmed by the electrical characterization of the developed RF switch. The fabricated RF switch performs well, in good agreement with the modelled data, showing a transition time of 7 μs followed by a sequence of bounces. Moreover, the scattering parameters exhibit an isolation in the off-state of >8 dB and an insertion loss in the on-state of <0.6 dB up to frequencies of 50 GHz. The presented model is intended to be integrated into standard circuit simulation software, allowing circuit engineers to design the switch bias line, to minimize induced currents and cross actuation, as well as to find the mechanical structure dimensions necessary for the desired switching time and actuation voltage waveform. Moreover, process related design rules can be automatically verified. © 2012 IOP Publishing Ltd.


Durager C.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Heinzelmann A.,Interstate University of Applied Sciences and Technology | Riederer D.,Interstate University of Applied Sciences and Technology
Structural Health Monitoring 2011: Condition-Based Maintenance and Intelligent Structures - Proceedings of the 8th International Workshop on Structural Health Monitoring | Year: 2011

Guided waves are widely used for structural health monitoring (SHM) applications especially for the observing of width structures. For exciting guided waves into structures piezoelectric transducers are common used. But for an effective observing of structures a network of piezoelectric transducers is needed and normally the connection between the different transducers is done with wires. For short distances between the nodes (e.g. 5 to 10 cm) this works well, but for longer distances the influence of the cables capacitance is quiet high. Also the more on weight is a drawback of wired sensor networks. Because of the above mentioned disadvantages of such wired sensor networks, researchers developed wireless sensor network systems for SHM. In this paper we present a wireless sensor network system which is designed for SHM application with piezoelectric transducers and guided waves. First, the different hardware components of the wireless sensor network system are described in detail. The hardware mainly consists of a PC connected via USB hub which remotely controls wireless the actuator - sensor nodes. Each node in the sensor network can be used as actuator with an excitation voltage of about 60 V peak-to-peak, as well as sensor with a variable amplification to measure signals in the range between 0.5 and 100 mV. The frequency range covers 30 - 300 kHz. Powered by the integrated battery, the nodes operate completely autonomously. The main novelty of this system is its simple handling because of the Graphical User Interface (GUI). The GUI enables the choice between the actuator or sensor mode for each device in few seconds. Also the number of active nodes in the network (up to 8 nodes) or the excitation frequency can be selected by a mouse click. After every measurement cycle the measured data from each sensor node is diagramed on the screen. Finally, the paper presents a laboratory test on an aluminum/foam sandwich plate with a removable artificial defect to accurately assess the performance merits and weaknesses of the integrated hardware and software.

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