ALBERT

Description: Aerosol-assisted CVD synthesis, characterisation and gas-sensing application of gold-functionalised tungsten oxide Journal of Sensors and Sensor Systems, 3, 325-330, 2014 Author(s): F. Di Maggio, M. Ling, A. Tsang, J. Covington, J. Saffell, and C. Blackman Tungsten oxide nanoneedles (NNs) functionalised with gold nanoparticles (NPs) have been integrated with alumina gas-sensor platforms using a simple and effective co-deposition method via aerosol-assisted chemical vapour deposition (AACVD) utilising a novel gold precursor, (NH 4 )AuCl 4 . The gas-sensing results show that gold NP functionalisation of tungsten oxide NNs improves the sensitivity of response to ethanol, with sensitivity increasing and response time decreasing with increasing amount of gold.

Description: Objectifying user attention and emotion evoked by relevant perceived product components Journal of Sensors and Sensor Systems, 3, 315-324, 2014 Author(s): R. Schmitt, M. Köhler, J. V. Durá, and J. Diaz-Pineda A company's aim is to develop products that engage user attention and evoke positive emotions. Customers base their emotional evaluation on product components that are relevant for their perception. This paper presents findings of both identifying relevant product components and measuring emotions evoked by relevant perceived product components. To validate results, the comparison with self-reporting methods identifies similarities and differences between explicit expressed and implicit recorded customer requirements. On the one hand, eye tracking is applied to deduce the attention provoked by perceived product components. In order to link the product strategy with product components, the paper presents results considering the fact that the gaze track is affected by current thoughts. (Köhler et al., 2013, 2014a, b; Köhler and Schmitt, 2012) On the other hand, since self-reporting tools are only useful for obtaining information about the conscious part of customers' emotions, there is a need for measurement methods that measure the changes in physiological signals (bio-signals). Arousal is similar to emotional intensity and is related to the galvanic skin response. Positive or negative emotions are defined by the valence that is measured by facial electromyography. Findings are presented that relate changes in bio-signals on the aesthetical design to the global product impression as well as to emotions and, subsequently, linking changes in physiological signals to the evaluation of semantic concepts and design parameters. The presented approach provides conclusions and valid information about products as well as product components that provoke certain emotions and about product components linked to a certain product concept, which could be part of a product strategy. Consequently, hard facts and special design rules for emotional product design can be deduced.

Description: Equivalent circuit models of two-layer flexure beams with excitation by temperature, humidity, pressure, piezoelectric or piezomagnetic interactions Journal of Sensors and Sensor Systems, 3, 187-211, 2014 Author(s): U. Marschner, G. Gerlach, E. Starke, and A. Lenk Two-layer flexure beams often serve as basic transducers in actuators and sensors. In this paper a generalized description of their stimuli-influenced mechanical behavior is derived. For small deflection angles this description includes a multi-port circuit or network representation with lumped elements for a beam part of finite length. A number of coupled finite beam parts model the dynamic behavior including the first natural frequencies of the beam. For piezoelectric and piezomagnetic interactions, reversible transducer models are developed. The piezomagnetic two-layer beam model is extended to include solenoid and planar coils. Linear network theory is applied in order to determine network parameters and to simplify the circuit representation. The resulting circuit model is the basis for a fast simulation of the dynamic system behavior with advanced circuit simulators and, thus, the optimization of the system. It is also a useful tool for understanding and explaining this multi-domain system through basic principles of general system theory.

Description: A simple method to recover the graphene-based chemi-resistor signal Journal of Sensors and Sensor Systems, 3, 241-244, 2014 Author(s): F. Fedi, F. Ricciardella, M. L. Miglietta, T. Polichetti, E. Massera, and G. Di Francia We present the development of a simple and fast method for restoring exhaust graphene-based chemi-resistors used for NO 2 detection. Repeatedly exposing the devices to gases or to air for more than 2 days, an overall worsening of the sensing signal is observed; we hypothesized that the poisoning effect in both cases is caused by the exposure to NO 2 . Starting from this hypothesis and from the observation that NO 2 is soluble in water, we performed a recovery method consisting in the dipping of exhaust devices into ultrapure water at 100 °C for 60 s. The device performances are compared with those obtained after the restoration is achieved using the typical annealing under vacuum method.

Description: Devices based on series-connected Schottky junctions and β-Ga 2 O 3 /SiC heterojunctions characterized as hydrogen sensors Journal of Sensors and Sensor Systems, 3, 231-239, 2014 Author(s): S. Nakagomi, K. Yokoyama, and Y. Kokubun Field-effect hydrogen gas sensor devices were fabricated with the structure of a series connection between Schottky junctions and β-Ga 2 O 3 /6H-SiC heterojunctions. β-Ga 2 O 3 thin films were deposited on n-type and p-type 6H-SiC substrates by gallium evaporation in oxygen plasma. These devices have rectifying properties and were characterized as hydrogen sensors by a Pt electrode. The hydrogen-sensing properties of both devices were measured in the range of 300–500 °C. The Pt/Ga 2 O 3 /n-SiC device revealed hydrogen-sensing properties as conventional Schottky diode-type devices. The forward current of the Pt/Ga 2 O 3 /p-SiC device was significantly increased under exposure to hydrogen. The behaviors of hydrogen sensing of the devices were explained using band diagrams of the Pt/Ga 2 O 3 /SiC structure biased in the forward and reverse directions.

Description: Catalytic and thermal characterisations of nanosized PdPt / Al 2 O 3 for hydrogen detection Journal of Sensors and Sensor Systems, 3, 273-280, 2014 Author(s): T. Mazingue, M. Lomello-Tafin, M. Passard, C. Hernandez-Rodriguez, L. Goujon, J.-L. Rousset, F. Morfin, and J.-F. Laithier Palladium platinum (PdPt) has been intensively studied these last decades due to high conversion rate in hydrogen oxidation at room temperature with significant exothermic effects. These remarkable properties have been studied by measuring the temperature variations of alumina (Al 2 O 3 ) supported nanosized PdPt nanoparticles exposed to different hydrogen concentrations in dry air. This catalyst is expected to be used as a sensing material for stable and reversible ultrasensitive hydrogen sensors working at room temperature (low power consumption). Structural and gas sensing characterisations and catalytic activity of PdPt / Al 2 O 3 systems synthesised by co-impregnation will be presented. Catalytic characterisations show that the system is already active at room temperature and that this activity sharply increases with rise in temperature. Moreover, the increase of the PdPt proportion in the co-impregnation process improves the activity, and very high conversion can be reached even at room temperature. The thermal response (about 3 °C) of only 1 mg of PdPt / Al 2 O 3 is reversible, and the time response is about 5 s. The integration of PdPt / Al 2 O 3 powder on a flat substrate has been realised by the deposition onto the powder of a thin porous hydrophobic layer of parylene. The possibility of using PdPt in gas sensors will be discussed.

Description: Thermal imaging as a modern form of pyrometry Journal of Sensors and Sensor Systems, 3, 265-271, 2014 Author(s): U. Kienitz Pyrometers and thermography cameras used to be characterized by different specifications and technical definitions. After an analysis of the market situation and the physical basics, the following article describes common methods to determine optical and thermal key parameters. Based on this, aspects of future sensor developments and certain applications of infrared (IR) cameras are discussed. (This article was first published in the journal tm – Technisches Messen, Vol. 81, No. 3, 2014 , a volume which is dedicated to the memory of Prof. Dr.-Ing. habil. Ludwig Walther.)

Description: Selective detection of hazardous VOCs for indoor air quality applications using a virtual gas sensor array Journal of Sensors and Sensor Systems, 3, 253-263, 2014 Author(s): M. Leidinger, T. Sauerwald, W. Reimringer, G. Ventura, and A. Schütze An approach for detecting hazardous volatile organic compounds (VOCs) in ppb and sub-ppb concentrations is presented. Using three types of metal oxide semiconductor (MOS) gas sensors in temperature cycled operation, formaldehyde, benzene and naphthalene in trace concentrations, reflecting threshold limit values as proposed by the WHO and European national health institutions, are successfully identified against a varying ethanol background of up to 2 ppm. For signal processing, linear discriminant analysis is applied to single sensor data and sensor fusion data. Integrated field test sensor systems for monitoring of indoor air quality (IAQ) using the same types of gas sensors were characterized using the same gas measurement setup and data processing. Performance of the systems is reduced due to gas emissions from the hardware components. These contaminations have been investigated using analytical methods. Despite the reduced sensitivity, concentrations of the target VOCs in the ppb range (100 ppb of formaldehyde; 5 ppb of benzene; 20 ppb of naphthalene) are still clearly detectable with the systems, especially when using the sensor fusion method for combining data of the different MOS sensor types.

Description: Aerosol-deposited BaFe 0.7 Ta 0.3 O 3-δ for nitrogen monoxide and temperature-independent oxygen sensing Journal of Sensors and Sensor Systems, 3, 223-229, 2014 Author(s): M. Bektas, D. Hanft, D. Schönauer-Kamin, T. Stöcker, G. Hagen, and R. Moos The gas sensing properties of resistive gas sensors of BaFe 0.7 Ta 0.3 O 3-δ (BFT30) prepared by the so-called aerosol deposition method, a method to manufacture dense ceramic films at room temperature, were investigated. The electrical response of the films was investigated first under various oxygen concentrations and in a wide temperature range between 350 and 900 °C. Between 700 and 900 °C, the conductivity of BaFe 0.7 Ta 0.3 O 3-δ (BFT30) depends on the oxygen concentration with a slope of almost 1/4 in the double-logarithmic plot vs. oxygen partial pressure. In addition, the sensor response is temperature independent. BFT30 responds fast and reproducibly to changing oxygen partial pressures even at 350 °C. The cross-sensitivity has been investigated in environments with various gases (C 3 H 8 , NO, NO 2 , H 2 , CO, CO 2 , and H 2 O) in synthetic air between 350 and 800 °C. BFT30 exhibits good sensing properties to NO between 350 and 400 °C in the range from 1.5 to 2000 ppm with a high selectivity to the other investigated gas species. Thus this semiconducting ceramic material is a good candidate for a temperature-independent oxygen sensor at high temperatures with the application in exhausts and for a selective nitrogen monoxide (NO) sensor at low temperatures for air quality monitoring.

Description: Metal oxide semiconductor gas sensor self-test using Fourier-based impedance spectroscopy Journal of Sensors and Sensor Systems, 3, 213-221, 2014 Author(s): M. Schüler, T. Sauerwald, and A. Schütze For the self-test of semiconductor gas sensors, we combine two multi-signal processes: temperature-cycled operation (TCO) and electrical impedance spectroscopy (EIS). This combination allows one to discriminate between irreversible changes of the sensor, i.e., changes caused by poisoning, as well as changes in the gas atmosphere. To integrate EIS and TCO, impedance spectra should be acquired in a very short time period, in which the sensor can be considered time invariant, i.e., milliseconds or less. For this purpose we developed a Fourier-based high-speed, low-cost impedance spectroscope. It provides a binary excitation signal through an FPGA (field programable gate array), which also acquires the data. To determine impedance spectra, it uses the ETFE (empirical transfer function estimate) method, which calculates the impedance by evaluating the Fourier transformations of current and voltage. With this approach an impedance spectrum over the range from 61 kHz to 100 MHz is acquired in ca. 16 μs. We carried out TCO–EIS measurements with this spectroscope and a commercial impedance analyzer (Agilent 4294A), with a temperature cycle consisting of six equidistant temperature steps between 200 and 450 °C, with lengths of 30 s (200 °C) and 18 s (all others). Discrimination of carbon monoxide (CO) and methane (CH 4 ) is possible by LDA (linear discriminant analysis) using either TCO or EIS data, thus enabling a validation of results by comparison of both methods.

Description: Characterization of ash particles with a microheater and gas-sensitive SiC field-effect transistors Journal of Sensors and Sensor Systems, 3, 305-313, 2014 Author(s): C. Bur, M. Bastuck, A. Schütze, J. Juuti, A. Lloyd Spetz, and M. Andersson Particle emission from traffic, power plants or, increasingly, stoves and fireplaces poses a serious risk for human health. The harmfulness of the particles depends not only on their size and shape but also on adsorbates. Particle detectors for size and concentration are available on the market; however, determining content and adsorbents is still a challenge. In this work, a measurement setup for the characterization of dust and ash particle content with regard to their adsorbates is presented. For the proof of concept, ammonia-contaminated fly ash samples from a coal-fired power plant equipped with a selective non-catalytic reduction (SNCR) system were used. The fly ash sample was placed on top of a heater substrate situated in a test chamber and heated up to several hundred degrees. A silicon carbide field-effect transistor (SiC-FET) gas sensor was used to detect desorbing species by transporting the headspace above the heater to the gas sensor with a small gas flow. Accumulation of desorbing species in the heater chamber followed by transfer to the gas sensor is also possible. A mass spectrometer was placed downstream of the sensor as a reference. A clear correlation between the SiC-FET response and the ammonia spectra of the mass spectrometer was observed. In addition, different levels of contamination can be distinguished. Thus, with the presented setup, chemical characterization of particles, especially of adsorbates which contribute significantly to the harmfulness of the particles, is possible.

Description: Carbon monoxide gas sensing properties of Ga-doped ZnO film grown by ion plating with DC arc discharge Journal of Sensors and Sensor Systems, 3, 331-334, 2014 Author(s): S. Kishimoto, S. Akamatsu, H. Song, J. Nomoto, H. Makino, and T. Yamamoto The carbon monoxide (CO) gas sensing properties of low-resistance heavily Ga-doped ZnO thin films were evaluated. The ZnO films with a thickness of 50 nm were deposited at 200 °C by ion plating. The electrical properties of the ZnO films were controlled by varying the oxygen assist gas flow rate during deposition. The CO gas sensitivity of ZnO films with Au electrodes was investigated in nitrogen gas at a temperature of 230 to 330 °C. CO gas concentration was varied in the range of 0.6–2.4% in nitrogen gas. Upon exposure to CO gas, the current flowing through the film was found to decrease. This response occurred even at the lowest temperature of 230 °C, and is thought to be the result of a mechanism different than the previously reported chemical reaction.

Description: Electrophoretic deposition of Au NPs on CNT networks for sensitive NO 2 detection Journal of Sensors and Sensor Systems, 3, 245-252, 2014 Author(s): E. Dilonardo, M. Penza, M. Alvisi, C. Di Franco, D. Suriano, R. Rossi, F. Palmisano, L. Torsi, and N. Cioffi In the present study, Au-surfactant core-shell colloidal nanoparticles (NPs) with controlled dimension and composition were synthesized by sacrificial anode electrolysis. Transmission electron microscopy (TEM) revealed that Au NPs core diameter is between 8 and 12 nm, as a function of the electrosynthesis conditions. Moreover, surface spectroscopic characterization by X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of nanosized gold phase. Controlled amounts of Au NPs were then deposited electrophoretically on carbon nanotube (CNT) networked films. The resulting hybrid materials were morphologically and chemically characterized using TEM, SEM (scanning electron microscopy) and XPS analyses, which revealed the presence of nanoscale gold, and its successful deposition on CNTs. Au NP/CNT networked films were tested as active layers in a two-pole resistive NO 2 sensor for sub-ppm detection in the temperature range of 100–200 °C. Au NP/CNT exhibited a p-type response with a decrease in the electrical resistance upon exposure to oxidizing NO 2 gas and an increase in resistance upon exposure to reducing gases (e.g. NH 3 ). It was also demonstrated that the sensitivity of the Au NP/CNT-based sensors depends on Au loading; therefore, the impact of the Au loading on gas sensing performance was investigated as a function of the working temperature, gas concentration and interfering gases.

Description: Principal component analysis for fast and automated thermographic inspection of internal structures in sandwich parts Journal of Sensors and Sensor Systems, 3, 105-111, 2014 Author(s): D. Griefahn, J. Wollnack, and W. Hintze Rising demand and increasing cost pressure for lightweight materials – such as sandwich structures – drives the manufacturing industry to improve automation in production and quality inspection. Quality inspection of honeycomb sandwich components with infrared (IR) thermography can be automated using image classification algorithms. This paper shows how principal component analysis (PCA) via singular value decomposition (SVD) is applied to compress data in an IR-video sequence in order to save processing time in the subsequent step of image classification. According to PCA theory, an orthogonal transformation can project data into a lower dimensional subspace with linearly uncorrelated principal components preserving all original information. The effect of data reduction is confirmed with experimental data from IR-video sequences of simple square-pulsed thermal loadings on aramid honeycomb-sandwich components with CFRP/GFRP (carbon-/glass-fiber-reinforced plastic) facings and GFRP inserts. Hence, processing time for image classification can be saved by reducing the dimension of information used by the classification algorithm without losing accuracy.

Description: Measurement and evaluation of radar cross section for furniture in an indoor propagation channel Advances in Radio Science, 12, 273-278, 2014 Author(s): M. M. Maw, P. Supanakoon, S. Promwong, and J. Takada This paper has attempted to evaluate the radar cross section (RCS) of two furniture items in an indoor environment in a frequency range of 3–7 GHz of the ultra-wideband (UWB) range. The RCS evaluation is achieved through an extended version of the radar equation that incorporates the channel transfer function of scattering. The time-gating method was applied to remove the multipath effect, a phenomenon which typically occurs in the indoor environment. Two double-ridged waveguide horn antennas for both vertical and horizontal polarizations were used to obtain the transfer function of scattering of the furniture prior to analysis in order to derive their bistatic RCS. The RCS results validate the applicability of the proposed extended radar equation to the indoor propagation prediction.

Description: An extended mode-matching model for improved relative permittivity measurements using a split-cylinder resonator Advances in Radio Science, 12, 267-272, 2014 Author(s): S. Zinal and U. Arz In this paper we present an extended mode-matching model for a split-cylinder resonator involving TE and TM resonant modes. The new model enhances the known TE 0np mode-matching model by improving mode identification and distortion analysis and providing better frequency range coverage for relative permittivity estimation. In order to verify the new model, measured spectra of several substrate materials are analyzed and the estimation results are compared with those of the TE 0np mode-matching model.

Description: Ionospheric research in Germany prior to Karl Rawer Advances in Radio Science, 12, 225-230, 2014 Author(s): K. Schlegel This brief historical review summarizes the work and achievements of German researchers on ionospheric problems before Karl Rawer started his scientific career in 1937.

Description: Planetary radio astronomy: Earth, giant planets, and beyond Advances in Radio Science, 12, 211-220, 2014 Author(s): H. O. Rucker, M. Panchenko, and C. Weber The magnetospheric phenomenon of non-thermal radio emission is known since the serendipitous discovery of Jupiter as radio planet in 1955, opening the new field of "Planetary Radio Astronomy". Continuous ground-based observations and, in particular, space-borne measurements have meanwhile produced a comprehensive picture of a fascinating research area. Space missions as the Voyagers to the Giant Planets, specifically Voyager 2 further to Uranus and Neptune, Galileo orbiting Jupiter, and now Cassini in orbit around Saturn since July 2004, provide a huge amount of radio data, well embedded in other experiments monitoring space plasmas and magnetic fields. The present paper as a condensation of a presentation at the Kleinheubacher Tagung 2013 in honour of the 100th anniversary of Prof. Karl Rawer, provides an introduction into the generation mechanism of non-thermal planetary radio waves and highlights some new features of planetary radio emission detected in the recent past. As one of the most sophisticated spacecraft, Cassini, now in space for more than 16 years and still in excellent health, enabled for the first time a seasonal overview of the magnetospheric variations and their implications for the generation of radio emission. Presently most puzzling is the seasonally variable rotational modulation of Saturn kilometric radio emission (SKR) as seen by Cassini, compared with early Voyager observations. The cyclotron maser instability is the fundamental mechanism under which generation and sufficient amplification of non-thermal radio emission is most likely. Considering these physical processes, further theoretical investigations have been started to investigate the conditions and possibilities of non-thermal radio emission from exoplanets, from potential radio planets in extrasolar systems.

Description: Probability of occurrence of planetary ionosphere storms associated with the magnetosphere disturbance storm time events Advances in Radio Science, 12, 261-266, 2014 Author(s): T. L. Gulyaeva, F. Arikan, and I. Stanislawska The ionospheric W index allows to distinguish state of the ionosphere and plasmasphere from quiet conditions ( W = 0 or ±1) to intense storm ( W = ±4) ranging the plasma density enhancements (positive phase) or plasma density depletions (negative phase) regarding the quiet ionosphere. The global W index maps are produced for a period 1999–2014 from Global Ionospheric Maps of Total Electron Content, GIM-TEC, designed by Jet Propulson Laboratory, converted from geographic frame (−87.5:2.5:87.5° in latitude, −180:5:180° in longitude) to geomagnetic frame (−85:5:85° in magnetic latitude, −180:5:180° in magnetic longitude). The probability of occurrence of planetary ionosphere storm during the magnetic disturbance storm time, Dst, event is evaluated with the superposed epoch analysis for 77 intense storms (Dst ≤ −100 nT) and 230 moderate storms (−100 〈 Dst ≤ −50 nT) with start time, t 0 , defined at Dst storm main phase onset. It is found that the intensity of negative storm, iW - , exceeds the intensity of positive storm, iW + , by 1.5–2 times. An empirical formula of iW + and iW - in terms of peak Dst is deduced exhibiting an opposite trends of relation of intensity of ionosphere-plasmasphere storm with regard to intensity of Dst storm.

Description: Extreme ultraviolet (EUV) solar spectral irradiance (SSI) for ionospheric application – history and contemporary state-of-art Advances in Radio Science, 12, 251-260, 2014 Author(s): G. Schmidtke, Ch. Jacobi, B. Nikutowski, and Ch. Erhardt After a historical survey of space related EUV measurements in Germany and the role of Karl Rawer in pursuing this work, we describe present developments in EUV spectroscopy and provide a brief outlook on future activities. The group of Karl Rawer has performed the first scientific space project in Western Europe on 19th October 1954. Then it was decided to include the field of solar EUV spectroscopy in ionospheric investigations. Starting in 1957 an intensified development of instrumentation was going on to explore solar EUV radiation, atmospheric airglow and auroral emissions until the institute had to stop space activities in the early nineteen-eighties. EUV spectroscopy was continued outside of the institute during eight years. This area of work was supported again by the institute developing the Auto-Calibrating Spectrometers (SolACES) for a mission on the International Space Station (ISS). After more than six years in space the instrument is still in operation. Meanwhile the work on the primary task also to validate EUV data available from other space missions has made good progress. The first results of validating those data and combine them into one set of EUV solar spectral irradiance are very promising. It will be recommended for using it by the science and application community. Moreover, a new low-cost type of an EUV spectrometer is presented for monitoring the solar EUV radiation. It shall be further developed for providing EUV-TEC data to be applied in ionospheric models replacing the Covington index F 10.7 . Applying these data for example in the GNSS signal evaluation a more accurate determination of GNSS receiver positions is expected for correcting the propagation delays of navigation signals traveling through the ionosphere from space to earth. – Latest results in the field of solar EUV spectroscopy are discussed, too.

Description: Kleinheubach-U.R.S.I.: 48~years home for the German-Austrian Beacon Satellite Community (BSC) Advances in Radio Science, 12, 237-239, 2014 Author(s): G. K. Hartmann No abstract available.

Description: Remote sensing and modeling of lightning caused long recovery events within the lower ionosphere using VLF/LF radio wave propagation Advances in Radio Science, 12, 241-250, 2014 Author(s): E. D. Schmitter On the 4 November 2012 at 3:04:27 UT a strong lightning in the midst of the North Sea affected the propagation conditions of VLF/LF transmitter radio signals from NRK (Iceland, 37.5 kHz) and GBZ (UK, 19.58 kHz) received at 5246° N 8° E (NW Germany). The amplitude and phase dips show a recovery time of 6–12 min pointing to a LOng Recovery Early VLF (LORE) event. Clear assignment of the causative return stroke in space and time was possible with data from the WWLLN (Worldwide Lightning Location Network). Based on a return stroke current model the electric field is calculated and an excess electron density distribution which decays over time in the lower ionosphere is derived. Ionization, attachment and recombination processes are modeled in detail. Entering the electron density distribution in VLF/LF radio wave propagation calculations using the LWPC (Long Wavelength Propagation Capability) code allows to model the VLF/LF amplitude and phase behavior by adjusting the return stroke current moment. The results endorse and quantify the conception of lower ionosphere EMP heating by strong – but not necessarily extremely strong – return strokes of both polarities.

Description: Karl Rawer: space research and international cooperation – Laudation on the occasion of the 100 th birthday of Professor Karl Rawer Advances in Radio Science, 12, 221-223, 2014 Author(s): B. W. Reinisch This laudation is given in honor of the 100 th birthday of Prof. Karl Rawer which happens to coincide with the 45th anniversary of the International Reference Ionosphere (IRI). The ionosphere was discovered during Karl Rawer's lifetime, and he has dedicated his professional life to its exploration. World Wars I and II shaped his early life, but they also launched his career as one of the eminent geophysical scientists of the twentieth century. The paper looks back at Karl Rawer's life and his pioneering work and leadership in advancing and shaping the exploration of the ionosphere.

Description: The International Reference Ionosphere: Rawer's IRI and its status today Advances in Radio Science, 12, 231-236, 2014 Author(s): D. Bilitza When the Committee on Space Research (COSPAR) initiated the International Reference Ionosphere (IRI) project in 1968 it wisely selected K. Rawer as its first Chairperson. With a solid footing and good contacts in both the ground-based and space-based ionospheric communities he was ideally suited to pull together colleagues and data from both communities to help build the first version of the IRI. He assembled a team of 20+ international ionospheric experts in the IRI Working Group and chaired and directed the group from 1968 to 1984. The working group has now grown to 63 members and the IRI model has undergone many revisions as new data became available and new modeling techniques were applied. This paper was presented during a special session of the Kleinheubach Tagung 2013 in honor of K. Rawer's 100th birthday. It will review the current status of the IRI model and project and the international recognition it has achieved. It is quite fitting that this year we not only celebrate K. Rawer's 100th birthday but also the exciting news that his favorite science endeavor, IRI, has been internationally recognized as an ISO (International Standardization Organization) standard. The IRI homepage is at http://irimodel.org .

Description: Compensation for the influence of temperature and humidity on oxygen diffusion in a reactive polymer matrix Journal of Sensors and Sensor Systems, 3, 291-303, 2014 Author(s): P. Marek, J. J. Velasco-Veléz, T. Doll, and G. Sadowski In a previous work (Marek et al., 2013) a time-monitoring oxygen sensor was proposed. This sensor is based on a diffusion-controlled oxygen reaction of the indicator system methylene blue (MB)/leuco methylene blue (LMB) and riboflavin embedded in a water-loaded poly(vinyl alcohol) (PVA) matrix. It can be used in packaging, sensors, and biotechnology applications. Since the oxygen diffusion coefficient in the PVA matrix strongly depends on temperature and humidity, two different approaches were developed within this work to compensate for these two effects. To compensate for faster oxygen diffusion at higher temperatures, iron particles were added to the PVA matrix, resulting in a novel PVA/iron composite matrix. Adding silicone particles allows compensating the influence of humidity. Both temperature and humidity compensation were modeled using the finite-element method in good accordance with the experimental data. This allows tuning the sensor for application at different conditions of temperature and humidity and therewith in different environments.

Description: Data fusion of surface normals and point coordinates for deflectometric measurements Journal of Sensors and Sensor Systems, 3, 281-290, 2014 Author(s): B. Komander, D. Lorenz, M. Fischer, M. Petz, and R. Tutsch Measuring specular surfaces can be realized by means of deflectometric measurement systems with at least two reference planes as proposed proposed by Petz and Tutsch (2004). The results are the point coordinates and the normal direction of each valid measurement point. The typical evaluation strategy for continuous surfaces involves an integration or regularization of the measured normals. This method yields smooth results of the surface with deviations in the nanometer range but it is sensitive to systematic deviations. The measured point coordinates are robust against systematic deviations but the noise level is in the order of micrometers. As an alternative evaluation strategy a data-fusion process that combines both the normal direction and the point coordinates has been developed. A linear fitting technique is proposed to increase the accuracy of the point coordinate measurements by forming an objective functional as the mean squared misfit of the gradients with respect to the point coordinates on the one hand and to the normals on the other hand. Moreover, a constraint on the maximal change of the coordinate measurements is added to the optimization problem. To minimize to objective under the constraint a projected gradient method is used. The results show that the proposed method is able to adjust the point coordinate measurement to the measured normals and hence decrease the spatial noise level by more than an order of magnitude.

Description: Encapsulation of implantable integrated MEMS pressure sensors using polyimide epoxy composite and atomic layer deposition Journal of Sensors and Sensor Systems, 3, 335-347, 2014 Author(s): P. Gembaczka, M. Görtz, Y. Celik, A. Jupe, M. Stühlmeyer, A. Goehlich, H. Vogt, W. Mokwa, and M. Kraft Implantable MEMS sensors are an enabling technology for diagnostic analysis and therapy in medicine. The encapsulation of such miniaturized implants remains a largely unsolved problem. Medically approved encapsulation materials include titanium or ceramics; however, these result in bulky and thick-walled encapsulations which are not suitable for MEMS sensors. In particular, for MEMS pressure sensors the chip surface comprising the pressure membranes must be free of rigid encapsulation material and in direct contact with tissue or body fluids. This work describes a new kind of encapsulation approach for a capacitive pressure sensor module consisting of two integrated circuits. The micromechanical membrane of the pressure sensor may be covered only by very thin layers, to ensure high pressure sensitivity. A suitable passivation method for the high topography of the pressure sensor is atomic layer deposition (ALD) of aluminium oxide (Al 2 O 3 ) and tantalum pentoxide (Ta 2 O 5 ). It provides a hermetic passivation with a high conformity. Prior to ALD coating, a high-temperature resistant polyimide–epoxy composite was evaluated as a die attach material and sealing compound for bond wires and the chip surface. This can sustain the ALD deposition temperature of 275 °C for several hours without any measurable decomposition. Tests indicated that the ALD can be deposited on top of the polyimide–epoxy composite covering the entire sensor module. The encapsulated pressure sensor module was calibrated and tested in an environmental chamber at accelerated aging conditions. An accelerated life test at 60 °C indicated a maximum drift of 5% full scale after 1482 h. From accelerated life time testing at 120 °C a maximum stable life time of 3.3 years could be extrapolated.

Description: Humidity measurement with capacitive humidity sensors between −70°C and 25°C in low vacuum Journal of Sensors and Sensor Systems, 3, 177-185, 2014 Author(s): A. Lorek At the German Aerospace Center (DLR), capacitive humidity sensors are used to measure relative humidity in experiments under extreme atmospheric conditions such as on Mars or in the coldest regions on Earth. This raises the question whether such experiments can be performed using low-cost humidity sensors with a tolerable measurement uncertainty. As part of the standardizing project SMADLUSEA (project no. SF11021A), nine capacitive humidity sensors (Sensirion SHT75) were investigated for pressure ranging from 10 to 1000 hPa (low vacuum) and temperatures from −70 to 25 °C. It has been shown that these sensors worked reliably and with reproducibly measured values over the entire investigated pressure and temperature range. There was no aging of the sensors observable. In addition to the known strong temperature dependency, the SHT75 also shows a pressure dependency below −10 °C. A characteristic curve for the SHT75 was calculated with an expanded uncertainty of 7% of the measured values. In conclusion, low-cost capacitive humidity sensors offer the option to obtain reliably measured values even under extreme conditions with comparatively little effort.

Description: Fabrication and characterization of a piezoresistive humidity sensor with a stress-free package Journal of Sensors and Sensor Systems, 3, 167-175, 2014 Author(s): T. Waber, M. Sax, W. Pahl, S. Stufler, A. Leidl, M. Günther, and G. Feiertag A highly miniaturized piezoresistive humidity sensor has been developed. The starting point of the development was a 1 × 1 mm 2 piezoresistive pressure sensor chip. As sensing material, a polyimide was used that swells with increasing adsorption of water molecules. To convert the swelling into an electrical signal, a thin layer of the polyimide was deposited onto the bending plate of the pressure sensor. The humidity sensor was characterized in a climate chamber. The measurements show a sensitivity of 0.25 mV per percent relative humidity (%RH) and a non-linearity of 3.1% full scale (FS) in the range of 30–80% RH. A high cross-sensitivity to temperature of around 0.5 mV °C −1 was measured, so temperature compensation is necessary. For stress-free packaging of the sensor chip, a novel packaging technology was developed.

Description: A novel horizontal to vertical spectral ratio approach in a wired structural health monitoring system Journal of Sensors and Sensor Systems, 3, 145-165, 2014 Author(s): F. P. Pentaris This work studies the effect ambient seismic noise can have on building constructions, in comparison with the traditional study of strong seismic motion in buildings, for the purpose of structural health monitoring. Traditionally, engineers have observed the effect of earthquakes on buildings by usage of seismometers at various levels. A new approach is proposed in which acceleration recordings of ambient seismic noise are used and horizontal to vertical spectra ratio (HVSR) process is applied, in order to determine the resonance frequency of movement due to excitation of the building from a strong seismic event. The HVSR technique is widely used by geophysicists to study the resonance frequency of sediments over bedrock, while its usage inside buildings is limited. This study applies the recordings inside two university buildings attached to each other, but with different construction materials and different years of construction. Also there is HVSR application in another much older building, with visible cracks in its structure. Sensors have been installed on every floor of the two university buildings, and recordings have been acquired both of ambient seismic noise and earthquakes. Resonance frequencies for every floor of every building are calculated, from both noise and earthquake records, using the HVSR technique for the ambient noise data and the receiver function (RF) for the earthquake data. Differential acceleration drift for every building is also calculated, and there is correlation with the vulnerability of the buildings. Results indicate that HVSR process on acceleration data proves to be an easy, fast, economical method for estimation of fundamental frequency of structures as well as an assessment method for building vulnerability estimation. Comparison between HVSR and RF technique shows an agreement at the change of resonance frequency as we move to higher floors.

Description: Work area monitoring in dynamic environments using multiple auto-aligning 3-D sensors Journal of Sensors and Sensor Systems, 3, 113-120, 2014 Author(s): Y. Wang, D. Ewert, T. Meisen, D. Schilberg, and S. Jeschke Compared to current industry standards future production systems will be more flexible and robust and will adapt to unforeseen states and events. Industrial robots will interact with each other as well as with human coworkers. To be able to act in such a dynamic environment, each acting entity ideally needs complete knowledge of its surroundings, concerning working materials as well as other working entities. Therefore new monitoring methods providing complete coverage for complex and changing working areas are needed. While single 3-D sensors already provide detailed information within their field of view, complete coverage of a complete work area can only be achieved by relying on a multitude of these sensors. However, to provide useful information all data of each sensor must be aligned to each other and fused into an overall world picture. To be able to align the data correctly, the position and orientation of each sensor must be known with sufficient exactness. In a quickly changing dynamic environment, the positions of sensors are not fixed, but must be adjusted to maintain optimal coverage. Therefore, the sensors need to autonomously align themselves in real time. This can be achieved by adding defined markers with given geometrical patterns to the environment which can be used for calibration and localization of each sensor. As soon as two sensors detect the same markers, their relative position to each other can be calculated. Additional anchor markers at fixed positions serve as global reference points for the base coordinate system. In this paper we present a prototype for a self-aligning monitoring system based on a robot operating system (ROS) and Microsoft Kinect. This system is capable of autonomous real-time calibration relative to and with respect to a global coordinate system as well as to detect and track defined objects within the working area.

Description: Chain of refined perception in self-optimizing assembly of micro-optical systems Journal of Sensors and Sensor Systems, 3, 87-95, 2014 Author(s): S. Haag, D. Zontar, J. Schleupen, T. Müller, and C. Brecher Today, the assembly of laser systems requires a large share of manual operations due to its complexity regarding the optimal alignment of optics. Although the feasibility of automated alignment of laser optics has been shown in research labs, the development effort for the automation of assembly does not meet economic requirements – especially for low-volume laser production. This paper presents a model-based and sensor-integrated assembly execution approach for flexible assembly cells consisting of a macro-positioner covering a large workspace and a compact micromanipulator with camera attached to the positioner. In order to make full use of available models from computer-aided design (CAD) and optical simulation, sensor systems at different levels of accuracy are used for matching perceived information with model data. This approach is named "chain of refined perception", and it allows for automated planning of complex assembly tasks along all major phases of assembly such as collision-free path planning, part feeding, and active and passive alignment. The focus of the paper is put on the in-process image-based metrology and information extraction used for identifying and calibrating local coordinate systems as well as the exploitation of that information for a part feeding process for micro-optics. Results will be presented regarding the processes of automated calibration of the robot camera as well as the local coordinate systems of part feeding area and robot base.

Description: Capacitive strain gauges on flexible polymer substrates for wireless, intelligent systems Journal of Sensors and Sensor Systems, 3, 77-86, 2014 Author(s): R. Zeiser, T. Fellner, and J. Wilde This paper presents a novel capacitive strain gauge with interdigital electrodes, which was processed on polyimide and LCP (liquid crystal polymer) foil substrates. The metallization is deposited and patterned using thin-film technology with structure sizes down to 15 μm. We determined linear strain sensitivities for our sensor configuration and identified the most influencing parameters on the output signal by means of an analytical approach. Finite-element method (FEM) simulations of the strain gauge indicated the complex interaction of mechanical strains within the sensitive structure and their effect on the capacitance. The influence of geometry and material parameters on the strain sensitivity was investigated and optimized. We implemented thin films on 50 μm thick standard polymer foils by means of a temporary bonding process of the foils on carrier wafers. The characterization of the strain sensors after fabrication revealed the gauge factor as well as the cross sensitivities on temperatures up to 100 °C and relative humidity up to 100%. The gauge factor of a sensor with an electrode width of 45 μm and a clearance of 15 μm was −1.38 at a capacitance of 48 pF. Furthermore, we achieved a substantial reduction of the cross sensitivity against humidity from 1435 to 55 ppm % −1 RH when LCP was used for the sensor substrate and the encapsulation instead of polyimide. The gauge factor of a sensor half-bridge consisting of two orthogonal capacitors was 2.3 and the cross sensitivity on temperature was reduced to 240 ppm K −1 . Finally, a sensor system was presented that utilizes a special instrumentation Integrated Circuit (IC). For this system, performance data comprising cross sensitivities and power consumption are given.

Description: Towards assessing online uncertainty for three-phase flow metering in the oil and gas industry Journal of Sensors and Sensor Systems, 3, 97-103, 2014 Author(s): M. P. Henry, M. S. Tombs, and F. B. Zhou A new three-phase (oil/water/gas) flow metering system has been developed for use in the oil and gas industries, based on Coriolis mass flow metering. To obtain certification for use in the Russian oil and gas industries, trials have taken place at the UK and Russian national flow laboratories, NEL in Glasgow and VNIIR in Kazan, respectively. The metrology of three-phase flow is complex, and the uncertainty of each measurement varies dynamically with the operating point, as well as the metering technology, and other aspects. To a limited extent this is reflected in the error limits allowed in national standards, which may vary with operating point. For example, the GOST standard allows errors in the oil flow rate of ±6% for water cuts of less than 70%, which is increased to ±15% for water cuts between 70 and 95%. The provision of online uncertainty for each measurement, for example in accordance with the British Standard BS-7986, would be highly desirable, allowing the user to observe in real time variations in measurement quality. This paper will discuss how an online uncertainty assessment could be implemented in the Coriolis meter-based system.

Description: A micro optical probe for edge contour evaluation of diamond cutting tools Journal of Sensors and Sensor Systems, 3, 69-76, 2014 Author(s): S. H. Jang, Y. Shimizu, S. Ito, and W. Gao This paper presents a micro optical probe, which is employed to evaluate edge contours of single point diamond tools with a size in a range of several millimetres. The micro optical probe consists of a laser source with a wavelength of 405 nm, an objective lens with a numerical aperture of 0.25, a photodiode for measurement, and a compensating optical system including another photodiode for compensation of laser intensity. A collimated laser beam, which is divided by a beam splitter in the compensating optical system, is focused by the objective lens so that the focused spot can be used as the micro optical probe. The micro optical probe traces over an edge contour of an objective tool while the signals of both the two photodiodes are monitored. The output of the photodiode for measurement is compensated by using that of the photodiode for laser intensity compensation to eliminate the influence of the laser instability. The signal of the photodiode for measurement is used to define the deviation of edge contour within the diameter of the micro optical probe. To verify the feasibility of the developed optical probe, the optical system was mounted on a diamond turning machine, and some experiments were carried out. Two types of edge contours of the diamond tools having a straight cutting edge and a round cutting edge were measured on the machine.

Description: Multi-channel IR sensor system for determination of oil degradation Journal of Sensors and Sensor Systems, 3, 121-132, 2014 Author(s): T. Bley, E. Pignanelli, and A. Schütze A miniaturized infrared (IR) multi-channel sensor system was realized to determine chemical oil degradation, e.g., oxidation, increasing water content. Different artificially aged oil samples (synthetic motor oil, mineral hydraulic oil and ester-based hydraulic fluid) were prepared by oxidative degradation at elevated temperatures or addition of water, and characteristic degradation features in the IR spectrum were detected using FTIR spectroscopy. In addition, the absorption behavior of water contaminated synthetic motor oil was analyzed with increasing temperature. To determine the influence of different degradation effects on the measurement results the sensor system was characterized with the various oil samples. The system uses a reference channel to suppress the effect of decreasing transmission over the entire spectrum caused, e.g., by increasing soot content in the oil or contamination of the optical path.

Description: Electrochemical analysis of water and suds by impedance spectroscopy and cyclic voltammetry Journal of Sensors and Sensor Systems, 3, 133-140, 2014 Author(s): R. Gruden, A. Buchholz, and O. Kanoun Optimum detergent dosage during a washing process depends on water quality, degree of pollution and quantity of laundry. Particularly, water quality is an important factor. Other parameters like carbonate- or non-carbonate hardness and calcium / magnesium (Ca / Mg) ratio in addition to total hardness of water have an impact on the amount of detergent. This work discusses the possibilities realizing a detergent sensor that measures important parameters for the washing process and assess the ideal necessary amount of detergent during the washing process. The approach is to combine impedance spectroscopy with cyclic voltammetry in order to determine both water quality and concentration of detergent in the suds which build up the basis for an optimum detergent dosage. The results of cyclic voltammetry show that it is possible to identify the Ca / Mg ratio and the carbonate hardness separately, which is necessary for the optimization of the washing process. Impedance measurements identify total hardness and detergent concentrations.

Description: A catalytic combustion-type CO gas sensor incorporating aluminum nitride as an intermediate heat transfer layer for accelerated response time Journal of Sensors and Sensor Systems, 3, 141-144, 2014 Author(s): A. Hosoya, S. Tamura, and N. Imanaka A catalytic combustion-type carbon monoxide gas sensor exhibiting good sensing performance even at moderate temperatures was previously developed by employing a Pt loaded CeO 2 –ZrO 2 –SnO 2 solid solution as the CO oxidizing catalyst. The addition of aluminum nitride as an intermediate heat transfer layer between the Pt coil and the CO oxidizing catalyst drastically accelerated the response of this device to CO at temperatures as low as 70 °C.

Description: Room temperature carbon nanotube based sensor for carbon monoxide detection Journal of Sensors and Sensor Systems, 3, 349-354, 2014 Author(s): A. Hannon, Y. Lu, J. Li, and M. Meyyappan Sulfonated single-walled carbon nanotubes have been used in an integrated electrode structure for the detection of carbon monoxide. The sensor responds to 0.5 ppm of CO in air at room temperature. All eight sensors with this material in a 32-sensor array showed good repeatability and reproducibility, with response and recovery times of about 10 s. Pristine nanotubes generally do not respond to carbon monoxide and the results here confirm sulfonated nanotubes to be a potential candidate for the construction of an electronic nose that requires at least a few materials for the selective detection of CO.

Description: Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements Journal of Sensors and Sensor Systems, 3, 355-367, 2014 Author(s): F. Vita, C. Kern, and S. Inguaggiato Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and power-inefficient, making their application to remote environments extremely challenging. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used to measure sulfur dioxide (SO 2 ) emissions from La Fossa crater, Vulcano, Italy, where column densities of up to 1.2 × 10 18 molec cm −2 (~ 500 ppmm) were detected along open paths of up to 400 m in total length. The instrument's SO 2 detection limit was determined to be 2 × 10 16 molec cm −2 (~ 8 ppmm), thereby making quantitative detection of even trace amounts of SO 2 possible. The instrument is capable of measuring other volcanic volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide (ClO) and carbon disulfide (CS 2 ) were both below the instrument's detection limits during the experiment, the upper limits for the X / SO 2 ratio (X = ClO, CS 2 ) could be derived, and yielded 2 × 10 −3 and 0.1, respectively. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.

Description: A company's aim is to develop products that engage user attention and evoke positive emotions. Customers base their emotional evaluation on product components that are relevant for their perception. This paper presents findings of both identifying relevant product components and measuring emotions evoked by relevant perceived product components. To validate results, the comparison with self-reporting methods identifies similarities and differences between explicit expressed and implicit recorded customer requirements. On the one hand, eye tracking is applied to deduce the attention provoked by perceived product components. In order to link the product strategy with product components, the paper presents results considering the fact that the gaze track is affected by current thoughts. (Köhler et al., 2013, 2014a, b; Köhler and Schmitt, 2012) On the other hand, since self-reporting tools are only useful for obtaining information about the conscious part of customers' emotions, there is a need for measurement methods that measure the changes in physiological signals (bio-signals). Arousal is similar to emotional intensity and is related to the galvanic skin response. Positive or negative emotions are defined by the valence that is measured by facial electromyography. Findings are presented that relate changes in bio-signals on the aesthetical design to the global product impression as well as to emotions and, subsequently, linking changes in physiological signals to the evaluation of semantic concepts and design parameters. The presented approach provides conclusions and valid information about products as well as product components that provoke certain emotions and about product components linked to a certain product concept, which could be part of a product strategy. Consequently, hard facts and special design rules for emotional product design can be deduced.

Description: An approach for detecting hazardous volatile organic compounds (VOCs) in ppb and sub-ppb concentrations is presented. Using three types of metal oxide semiconductor (MOS) gas sensors in temperature cycled operation, formaldehyde, benzene and naphthalene in trace concentrations, reflecting threshold limit values as proposed by the WHO and European national health institutions, are successfully identified against a varying ethanol background of up to 2 ppm. For signal processing, linear discriminant analysis is applied to single sensor data and sensor fusion data. Integrated field test sensor systems for monitoring of indoor air quality (IAQ) using the same types of gas sensors were characterized using the same gas measurement setup and data processing. Performance of the systems is reduced due to gas emissions from the hardware components. These contaminations have been investigated using analytical methods. Despite the reduced sensitivity, concentrations of the target VOCs in the ppb range (100 ppb of formaldehyde; 5 ppb of benzene; 20 ppb of naphthalene) are still clearly detectable with the systems, especially when using the sensor fusion method for combining data of the different MOS sensor types.

Description: We present the development of a simple and fast method for restoring exhaust graphene-based chemi-resistors used for NO2 detection. Repeatedly exposing the devices to gases or to air for more than 2 days, an overall worsening of the sensing signal is observed; we hypothesized that the poisoning effect in both cases is caused by the exposure to NO2. Starting from this hypothesis and from the observation that NO2 is soluble in water, we performed a recovery method consisting in the dipping of exhaust devices into ultrapure water at 100 °C for 60 s. The device performances are compared with those obtained after the restoration is achieved using the typical annealing under vacuum method.

Description: For the self-test of semiconductor gas sensors, we combine two multi-signal processes: temperature-cycled operation (TCO) and electrical impedance spectroscopy (EIS). This combination allows one to discriminate between irreversible changes of the sensor, i.e., changes caused by poisoning, as well as changes in the gas atmosphere. To integrate EIS and TCO, impedance spectra should be acquired in a very short time period, in which the sensor can be considered time invariant, i.e., milliseconds or less. For this purpose we developed a Fourier-based high-speed, low-cost impedance spectroscope. It provides a binary excitation signal through an FPGA (field programable gate array), which also acquires the data. To determine impedance spectra, it uses the ETFE (empirical transfer function estimate) method, which calculates the impedance by evaluating the Fourier transformations of current and voltage. With this approach an impedance spectrum over the range from 61 kHz to 100 MHz is acquired in ca. 16 μs. We carried out TCO–EIS measurements with this spectroscope and a commercial impedance analyzer (Agilent 4294A), with a temperature cycle consisting of six equidistant temperature steps between 200 and 450 °C, with lengths of 30 s (200 °C) and 18 s (all others). Discrimination of carbon monoxide (CO) and methane (CH4) is possible by LDA (linear discriminant analysis) using either TCO or EIS data, thus enabling a validation of results by comparison of both methods.

Description: Implantable MEMS sensors are an enabling technology for diagnostic analysis and therapy in medicine. The encapsulation of such miniaturized implants remains a largely unsolved problem. Medically approved encapsulation materials include titanium or ceramics; however, these result in bulky and thick-walled encapsulations which are not suitable for MEMS sensors. In particular, for MEMS pressure sensors the chip surface comprising the pressure membranes must be free of rigid encapsulation material and in direct contact with tissue or body fluids. This work describes a new kind of encapsulation approach for a capacitive pressure sensor module consisting of two integrated circuits. The micromechanical membrane of the pressure sensor may be covered only by very thin layers, to ensure high pressure sensitivity. A suitable passivation method for the high topography of the pressure sensor is atomic layer deposition (ALD) of aluminium oxide (Al2O3) and tantalum pentoxide (Ta2O5). It provides a hermetic passivation with a high conformity. Prior to ALD coating, a high-temperature resistant polyimide–epoxy composite was evaluated as a die attach material and sealing compound for bond wires and the chip surface. This can sustain the ALD deposition temperature of 275 °C for several hours without any measurable decomposition. Tests indicated that the ALD can be deposited on top of the polyimide–epoxy composite covering the entire sensor module. The encapsulated pressure sensor module was calibrated and tested in an environmental chamber at accelerated aging conditions. An accelerated life test at 60 °C indicated a maximum drift of 5% full scale after 1482 h. From accelerated life time testing at 120 °C a maximum stable life time of 3.3 years could be extrapolated.

Description: Measuring specular surfaces can be realized by means of deflectometric measurement systems with at least two reference planes as proposed proposed by Petz and Tutsch (2004). The results are the point coordinates and the normal direction of each valid measurement point. The typical evaluation strategy for continuous surfaces involves an integration or regularization of the measured normals. This method yields smooth results of the surface with deviations in the nanometer range but it is sensitive to systematic deviations. The measured point coordinates are robust against systematic deviations but the noise level is in the order of micrometers. As an alternative evaluation strategy a data-fusion process that combines both the normal direction and the point coordinates has been developed. A linear fitting technique is proposed to increase the accuracy of the point coordinate measurements by forming an objective functional as the mean squared misfit of the gradients with respect to the point coordinates on the one hand and to the normals on the other hand. Moreover, a constraint on the maximal change of the coordinate measurements is added to the optimization problem. To minimize to objective under the constraint a projected gradient method is used. The results show that the proposed method is able to adjust the point coordinate measurement to the measured normals and hence decrease the spatial noise level by more than an order of magnitude.

Description: Field-effect hydrogen gas sensor devices were fabricated with the structure of a series connection between Schottky junctions and β-Ga2O3/6H-SiC heterojunctions. β-Ga2O3 thin films were deposited on n-type and p-type 6H-SiC substrates by gallium evaporation in oxygen plasma. These devices have rectifying properties and were characterized as hydrogen sensors by a Pt electrode. The hydrogen-sensing properties of both devices were measured in the range of 300–500 °C. The Pt/Ga2O3/n-SiC device revealed hydrogen-sensing properties as conventional Schottky diode-type devices. The forward current of the Pt/Ga2O3/p-SiC device was significantly increased under exposure to hydrogen. The behaviors of hydrogen sensing of the devices were explained using band diagrams of the Pt/Ga2O3/SiC structure biased in the forward and reverse directions.

Description: A catalytic combustion-type carbon monoxide gas sensor exhibiting good sensing performance even at moderate temperatures was previously developed by employing a Pt loaded CeO2–ZrO2–SnO2 solid solution as the CO oxidizing catalyst. The addition of aluminum nitride as an intermediate heat transfer layer between the Pt coil and the CO oxidizing catalyst drastically accelerated the response of this device to CO at temperatures as low as 70 °C.

Description: Two-layer flexure beams often serve as basic transducers in actuators and sensors. In this paper a generalized description of their stimuli-influenced mechanical behavior is derived. For small deflection angles this description includes a multi-port circuit or network representation with lumped elements for a beam part of finite length. A number of coupled finite beam parts model the dynamic behavior including the first natural frequencies of the beam. For piezoelectric and piezomagnetic interactions, reversible transducer models are developed. The piezomagnetic two-layer beam model is extended to include solenoid and planar coils. Linear network theory is applied in order to determine network parameters and to simplify the circuit representation. The resulting circuit model is the basis for a fast simulation of the dynamic system behavior with advanced circuit simulators and, thus, the optimization of the system. It is also a useful tool for understanding and explaining this multi-domain system through basic principles of general system theory.

Description: Compared to current industry standards future production systems will be more flexible and robust and will adapt to unforeseen states and events. Industrial robots will interact with each other as well as with human coworkers. To be able to act in such a dynamic environment, each acting entity ideally needs complete knowledge of its surroundings, concerning working materials as well as other working entities. Therefore new monitoring methods providing complete coverage for complex and changing working areas are needed. While single 3-D sensors already provide detailed information within their field of view, complete coverage of a complete work area can only be achieved by relying on a multitude of these sensors. However, to provide useful information all data of each sensor must be aligned to each other and fused into an overall world picture. To be able to align the data correctly, the position and orientation of each sensor must be known with sufficient exactness. In a quickly changing dynamic environment, the positions of sensors are not fixed, but must be adjusted to maintain optimal coverage. Therefore, the sensors need to autonomously align themselves in real time. This can be achieved by adding defined markers with given geometrical patterns to the environment which can be used for calibration and localization of each sensor. As soon as two sensors detect the same markers, their relative position to each other can be calculated. Additional anchor markers at fixed positions serve as global reference points for the base coordinate system. In this paper we present a prototype for a self-aligning monitoring system based on a robot operating system (ROS) and Microsoft Kinect. This system is capable of autonomous real-time calibration relative to and with respect to a global coordinate system as well as to detect and track defined objects within the working area.

Description: Knowledge of temperature fluctuations in fast reactor subassembly is very important from a safety point of view. The time constant of thermocouples which are used for measuring coolant temperature in a fast reactor varies owing to various factors. Hence, it becomes necessary to investigate the effect of change in the time constant on sensed fluctuations. This paper investigates the dependence of temperature fluctuations on thermocouple time constants. A Scilab model consisting of source temperature profile, second-order thermocouple and histogram calculation is designed. Simulation is performed for various levels of fluctuations, fixed and variable thermocouple time constants. Kurtosis for each condition is calculated with the help of a histogram. It is found that the effect of true source fluctuations on sensor output is very large compared to that of a similar percentage of time-constant variations. Hence in systems like fast reactors, where the degree of source fluctuations (fluid enthalpy) is large in comparison to that of time-constant variations, the overall effect can be considered with great confidence to be the outcome of coolant temperature rather than thermocouple time-constant variations.

Description: This paper presents a micro optical probe, which is employed to evaluate edge contours of single point diamond tools with a size in a range of several millimetres. The micro optical probe consists of a laser source with a wavelength of 405 nm, an objective lens with a numerical aperture of 0.25, a photodiode for measurement, and a compensating optical system including another photodiode for compensation of laser intensity. A collimated laser beam, which is divided by a beam splitter in the compensating optical system, is focused by the objective lens so that the focused spot can be used as the micro optical probe. The micro optical probe traces over an edge contour of an objective tool while the signals of both the two photodiodes are monitored. The output of the photodiode for measurement is compensated by using that of the photodiode for laser intensity compensation to eliminate the influence of the laser instability. The signal of the photodiode for measurement is used to define the deviation of edge contour within the diameter of the micro optical probe. To verify the feasibility of the developed optical probe, the optical system was mounted on a diamond turning machine, and some experiments were carried out. Two types of edge contours of the diamond tools having a straight cutting edge and a round cutting edge were measured on the machine.

Description: Induction sensors are used in a wide range of scientific and industrial applications. One way to improve these is rigorous modelling of the sensor combined with a low voltage and current input noise preamplifier aiming to optimize the whole induction magnetometer. In this paper, we explore another way, which consists in the use of original ferromagnetic core shapes of induction sensors, which bring substantial improvements. These new configurations are the cubic, orthogonal and coiled-core induction sensors. For each of them we give modelling elements and discuss their benefits and drawbacks with respect to a given noise-equivalent magnetic induction goal. Our discussion is supported by experimental results for the cubic and orthogonal configurations, while the coiled-core configuration remains open to experimental validation. The transposition of these induction sensor configurations to other magnetic sensors (fluxgate and giant magneto-impedance) is an exciting prospect of this work.

Description: This paper presents a semi-active broadband vibrational-energy harvesting system. Based on a non-resonant rotational generator, electronic circuitry was used to overcome the physical start-up restrictions. Due to the functional design it remains an energy harvester suitable for battery-less devices. For the first time a vibrational energy harvester is presented that allows standardization and thus higher volume production. A system layout, simulation, and measurement data will be shown.

Description: Pyrometers and thermography cameras used to be characterized by different specifications and technical definitions. After an analysis of the market situation and the physical basics, the following article describes common methods to determine optical and thermal key parameters. Based on this, aspects of future sensor developments and certain applications of infrared (IR) cameras are discussed. (This article was first published in the journal tm – Technisches Messen, Vol. 81, No. 3, 2014, a volume which is dedicated to the memory of Prof. Dr.-Ing. habil. Ludwig Walther.)

Description: This work studies the effect ambient seismic noise can have on building constructions, in comparison with the traditional study of strong seismic motion in buildings, for the purpose of structural health monitoring. Traditionally, engineers have observed the effect of earthquakes on buildings by usage of seismometers at various levels. A new approach is proposed in which acceleration recordings of ambient seismic noise are used and horizontal to vertical spectra ratio (HVSR) process is applied, in order to determine the resonance frequency of movement due to excitation of the building from a strong seismic event. The HVSR technique is widely used by geophysicists to study the resonance frequency of sediments over bedrock, while its usage inside buildings is limited. This study applies the recordings inside two university buildings attached to each other, but with different construction materials and different years of construction. Also there is HVSR application in another much older building, with visible cracks in its structure. Sensors have been installed on every floor of the two university buildings, and recordings have been acquired both of ambient seismic noise and earthquakes. Resonance frequencies for every floor of every building are calculated, from both noise and earthquake records, using the HVSR technique for the ambient noise data and the receiver function (RF) for the earthquake data. Differential acceleration drift for every building is also calculated, and there is correlation with the vulnerability of the buildings. Results indicate that HVSR process on acceleration data proves to be an easy, fast, economical method for estimation of fundamental frequency of structures as well as an assessment method for building vulnerability estimation. Comparison between HVSR and RF technique shows an agreement at the change of resonance frequency as we move to higher floors.

Description: A miniaturized infrared (IR) multi-channel sensor system was realized to determine chemical oil degradation, e.g., oxidation, increasing water content. Different artificially aged oil samples (synthetic motor oil, mineral hydraulic oil and ester-based hydraulic fluid) were prepared by oxidative degradation at elevated temperatures or addition of water, and characteristic degradation features in the IR spectrum were detected using FTIR spectroscopy. In addition, the absorption behavior of water contaminated synthetic motor oil was analyzed with increasing temperature. To determine the influence of different degradation effects on the measurement results the sensor system was characterized with the various oil samples. The system uses a reference channel to suppress the effect of decreasing transmission over the entire spectrum caused, e.g., by increasing soot content in the oil or contamination of the optical path.

Description: We approached the problem of sensing gaseous pollutants and malodors originating as a result of decomposition of organic compounds via chemoresistive sensors. A set of four screen-printed films based on two types of mixed tin and titanium oxides, mixed tungsten and tin oxides, and zinc oxide has been tested vs. the main gaseous components of malodors. N-butanol was also considered because of its importance as a reference gas in the odorimetric intensity scale. We found that, under proper working conditions, the films can sensitively detect such gases either in dry or in wet environments, within the range of concentrations of interest for their monitoring. We also demonstrated that the array is robust under solicitation by harmful interference gases such as CO, C6H6, NO2 and NO.

Description: The aim of this article is to introduce the operation principles of conductometric solid-state dosimeter-type gas sensors, which have found increased attention in the past few years, and to give a literature overview on promising materials for this purpose. Contrary to common gas sensors, gas dosimeters are suitable for directly detecting the dose (also called amount or cumulated or integrated exposure of analyte gases) rather than the actual analyte concentration. Therefore, gas dosimeters are especially suited for low level applications with the main interest on mean values. The applied materials are able to change their electrical properties by selective accumulation of analyte molecules in the sensitive layer. The accumulating or dosimeter-type sensing principle is a promising method for reliable, fast, and long-term detection of low analyte levels. In contrast to common gas sensors, few devices relying on the accumulation principle are described in the literature. Most of the dosimeter-type devices are optical, mass sensitive (quartz microbalance/QMB, surface acoustic wave/SAW), or field-effect transistors. The prevalent focus of this article is, however, on solid-state gas dosimeters that allow a direct readout by measuring the conductance or the impedance, which are both based on materials that change (selectively in ideal materials) their conductivity or dielectric properties with gas loading. This overview also includes different operation modes for the accumulative sensing principle and its unique features.

Description: This paper presents a novel capacitive strain gauge with interdigital electrodes, which was processed on polyimide and LCP (liquid crystal polymer) foil substrates. The metallization is deposited and patterned using thin-film technology with structure sizes down to 15 μm. We determined linear strain sensitivities for our sensor configuration and identified the most influencing parameters on the output signal by means of an analytical approach. Finite-element method (FEM) simulations of the strain gauge indicated the complex interaction of mechanical strains within the sensitive structure and their effect on the capacitance. The influence of geometry and material parameters on the strain sensitivity was investigated and optimized. We implemented thin films on 50 μm thick standard polymer foils by means of a temporary bonding process of the foils on carrier wafers. The characterization of the strain sensors after fabrication revealed the gauge factor as well as the cross sensitivities on temperatures up to 100 °C and relative humidity up to 100%. The gauge factor of a sensor with an electrode width of 45 μm and a clearance of 15 μm was −1.38 at a capacitance of 48 pF. Furthermore, we achieved a substantial reduction of the cross sensitivity against humidity from 1435 to 55 ppm %−1 RH when LCP was used for the sensor substrate and the encapsulation instead of polyimide. The gauge factor of a sensor half-bridge consisting of two orthogonal capacitors was 2.3 and the cross sensitivity on temperature was reduced to 240 ppm K−1. Finally, a sensor system was presented that utilizes a special instrumentation Integrated Circuit (IC). For this system, performance data comprising cross sensitivities and power consumption are given.

Description: A new three-phase (oil/water/gas) flow metering system has been developed for use in the oil and gas industries, based on Coriolis mass flow metering. To obtain certification for use in the Russian oil and gas industries, trials have taken place at the UK and Russian national flow laboratories, NEL in Glasgow and VNIIR in Kazan, respectively. The metrology of three-phase flow is complex, and the uncertainty of each measurement varies dynamically with the operating point, as well as the metering technology, and other aspects. To a limited extent this is reflected in the error limits allowed in national standards, which may vary with operating point. For example, the GOST standard allows errors in the oil flow rate of ±6% for water cuts of less than 70%, which is increased to ±15% for water cuts between 70 and 95%. The provision of online uncertainty for each measurement, for example in accordance with the British Standard BS-7986, would be highly desirable, allowing the user to observe in real time variations in measurement quality. This paper will discuss how an online uncertainty assessment could be implemented in the Coriolis meter-based system.

Description: In this work dynamic variation of gate bias is used on a gas-sensitive SiC field effect transistor ("GasFET") to optimize its sensitivity and increase its selectivity. Gate bias ramps introduce strong hysteresis in the sensor signal. The shape of this hysteresis is shown to be an appropriate feature both for the discrimination of various gases (ammonia, carbon monoxide, nitrogen monoxide and methane) as well as for different gas concentrations (250 and 500 ppm). The shape is very sensitive to ambient conditions as well as to the bias sweep rate. Thus, the influences of oxygen concentration, relative humidity, sensor temperature and cycle duration, i.e., sweep rate, are investigated and reasons for the observed signal changes, most importantly the existence of at least two different and competing processes taking place simultaneously, are discussed. Furthermore, it is shown that even for very fast cycles, in the range of seconds, the gas-induced shape change in the signal is strong enough to achieve a reliable separation of gases using gate bias cycled operation and linear discriminant analysis (LDA) making this approach suitable for practical application.

Description: Sulfonated single-walled carbon nanotubes have been used in an integrated electrode structure for the detection of carbon monoxide. The sensor responds to 0.5 ppm of CO in air at room temperature. All eight sensors with this material in a 32-sensor array showed good repeatability and reproducibility, with response and recovery times of about 10 s. Pristine nanotubes generally do not respond to carbon monoxide and the results here confirm sulfonated nanotubes to be a potential candidate for the construction of an electronic nose that requires at least a few materials for the selective detection of CO.

Description: A new induction-heated fixed-point device was developed for calibration of temperature measurement devices typically used in laser heat treatment for the temperature range 1000–1500 °C. To define the requirements for the calibration method, selected measurement setups were compared as well as process data and results of industrial processes were analyzed. Computer simulation with finite element method (FEM) and finite difference method (FDM) was used to optimize the system components and processing parameters of the induction heating of fixed-point cells. The prototype of the fixed-point device was tested successfully, and the first measuring results are presented here. The new calibration method is expected to improve the quality and reproducibility of industrial heat treatment processes with temperature control.

Description: Palladium platinum (PdPt) has been intensively studied these last decades due to high conversion rate in hydrogen oxidation at room temperature with significant exothermic effects. These remarkable properties have been studied by measuring the temperature variations of alumina (Al2O3) supported nanosized PdPt nanoparticles exposed to different hydrogen concentrations in dry air. This catalyst is expected to be used as a sensing material for stable and reversible ultrasensitive hydrogen sensors working at room temperature (low power consumption). Structural and gas sensing characterisations and catalytic activity of PdPt / Al2O3 systems synthesised by co-impregnation will be presented. Catalytic characterisations show that the system is already active at room temperature and that this activity sharply increases with rise in temperature. Moreover, the increase of the PdPt proportion in the co-impregnation process improves the activity, and very high conversion can be reached even at room temperature. The thermal response (about 3 °C) of only 1 mg of PdPt / Al2O3 is reversible, and the time response is about 5 s. The integration of PdPt / Al2O3 powder on a flat substrate has been realised by the deposition onto the powder of a thin porous hydrophobic layer of parylene. The possibility of using PdPt in gas sensors will be discussed.

Description: Optimum detergent dosage during a washing process depends on water quality, degree of pollution and quantity of laundry. Particularly, water quality is an important factor. Other parameters like carbonate- or non-carbonate hardness and calcium / magnesium (Ca / Mg) ratio in addition to total hardness of water have an impact on the amount of detergent. This work discusses the possibilities realizing a detergent sensor that measures important parameters for the washing process and assess the ideal necessary amount of detergent during the washing process. The approach is to combine impedance spectroscopy with cyclic voltammetry in order to determine both water quality and concentration of detergent in the suds which build up the basis for an optimum detergent dosage. The results of cyclic voltammetry show that it is possible to identify the Ca / Mg ratio and the carbonate hardness separately, which is necessary for the optimization of the washing process. Impedance measurements identify total hardness and detergent concentrations.

Description: Particle emission from traffic, power plants or, increasingly, stoves and fireplaces poses a serious risk for human health. The harmfulness of the particles depends not only on their size and shape but also on adsorbates. Particle detectors for size and concentration are available on the market; however, determining content and adsorbents is still a challenge. In this work, a measurement setup for the characterization of dust and ash particle content with regard to their adsorbates is presented. For the proof of concept, ammonia-contaminated fly ash samples from a coal-fired power plant equipped with a selective non-catalytic reduction (SNCR) system were used. The fly ash sample was placed on top of a heater substrate situated in a test chamber and heated up to several hundred degrees. A silicon carbide field-effect transistor (SiC-FET) gas sensor was used to detect desorbing species by transporting the headspace above the heater to the gas sensor with a small gas flow. Accumulation of desorbing species in the heater chamber followed by transfer to the gas sensor is also possible. A mass spectrometer was placed downstream of the sensor as a reference. A clear correlation between the SiC-FET response and the ammonia spectra of the mass spectrometer was observed. In addition, different levels of contamination can be distinguished. Thus, with the presented setup, chemical characterization of particles, especially of adsorbates which contribute significantly to the harmfulness of the particles, is possible.

Description: Tungsten oxide nanoneedles (NNs) functionalised with gold nanoparticles (NPs) have been integrated with alumina gas-sensor platforms using a simple and effective co-deposition method via aerosol-assisted chemical vapour deposition (AACVD) utilising a novel gold precursor, (NH4)AuCl4. The gas-sensing results show that gold NP functionalisation of tungsten oxide NNs improves the sensitivity of response to ethanol, with sensitivity increasing and response time decreasing with increasing amount of gold.

Description: In a previous work (Marek et al., 2013) a time-monitoring oxygen sensor was proposed. This sensor is based on a diffusion-controlled oxygen reaction of the indicator system methylene blue (MB)/leuco methylene blue (LMB) and riboflavin embedded in a water-loaded poly(vinyl alcohol) (PVA) matrix. It can be used in packaging, sensors, and biotechnology applications. Since the oxygen diffusion coefficient in the PVA matrix strongly depends on temperature and humidity, two different approaches were developed within this work to compensate for these two effects. To compensate for faster oxygen diffusion at higher temperatures, iron particles were added to the PVA matrix, resulting in a novel PVA/iron composite matrix. Adding silicone particles allows compensating the influence of humidity. Both temperature and humidity compensation were modeled using the finite-element method in good accordance with the experimental data. This allows tuning the sensor for application at different conditions of temperature and humidity and therewith in different environments.

Description: At the German Aerospace Center (DLR), capacitive humidity sensors are used to measure relative humidity in experiments under extreme atmospheric conditions such as on Mars or in the coldest regions on Earth. This raises the question whether such experiments can be performed using low-cost humidity sensors with a tolerable measurement uncertainty. As part of the standardizing project SMADLUSEA (project no. SF11021A), nine capacitive humidity sensors (Sensirion SHT75) were investigated for pressure ranging from 10 to 1000 hPa (low vacuum) and temperatures from −70 to 25 °C. It has been shown that these sensors worked reliably and with reproducibly measured values over the entire investigated pressure and temperature range. There was no aging of the sensors observable. In addition to the known strong temperature dependency, the SHT75 also shows a pressure dependency below −10 °C. A characteristic curve for the SHT75 was calculated with an expanded uncertainty of 7% of the measured values. In conclusion, low-cost capacitive humidity sensors offer the option to obtain reliably measured values even under extreme conditions with comparatively little effort.

Description: In the present study, Au-surfactant core-shell colloidal nanoparticles (NPs) with controlled dimension and composition were synthesized by sacrificial anode electrolysis. Transmission electron microscopy (TEM) revealed that Au NPs core diameter is between 8 and 12 nm, as a function of the electrosynthesis conditions. Moreover, surface spectroscopic characterization by X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of nanosized gold phase. Controlled amounts of Au NPs were then deposited electrophoretically on carbon nanotube (CNT) networked films. The resulting hybrid materials were morphologically and chemically characterized using TEM, SEM (scanning electron microscopy) and XPS analyses, which revealed the presence of nanoscale gold, and its successful deposition on CNTs. Au NP/CNT networked films were tested as active layers in a two-pole resistive NO2 sensor for sub-ppm detection in the temperature range of 100–200 °C. Au NP/CNT exhibited a p-type response with a decrease in the electrical resistance upon exposure to oxidizing NO2 gas and an increase in resistance upon exposure to reducing gases (e.g. NH3). It was also demonstrated that the sensitivity of the Au NP/CNT-based sensors depends on Au loading; therefore, the impact of the Au loading on gas sensing performance was investigated as a function of the working temperature, gas concentration and interfering gases.

Description: A highly miniaturized piezoresistive humidity sensor has been developed. The starting point of the development was a 1 × 1 mm2 piezoresistive pressure sensor chip. As sensing material, a polyimide was used that swells with increasing adsorption of water molecules. To convert the swelling into an electrical signal, a thin layer of the polyimide was deposited onto the bending plate of the pressure sensor. The humidity sensor was characterized in a climate chamber. The measurements show a sensitivity of 0.25 mV per percent relative humidity (%RH) and a non-linearity of 3.1% full scale (FS) in the range of 30–80% RH. A high cross-sensitivity to temperature of around 0.5 mV °C−1 was measured, so temperature compensation is necessary. For stress-free packaging of the sensor chip, a novel packaging technology was developed.

Description: Rising demand and increasing cost pressure for lightweight materials – such as sandwich structures – drives the manufacturing industry to improve automation in production and quality inspection. Quality inspection of honeycomb sandwich components with infrared (IR) thermography can be automated using image classification algorithms. This paper shows how principal component analysis (PCA) via singular value decomposition (SVD) is applied to compress data in an IR-video sequence in order to save processing time in the subsequent step of image classification. According to PCA theory, an orthogonal transformation can project data into a lower dimensional subspace with linearly uncorrelated principal components preserving all original information. The effect of data reduction is confirmed with experimental data from IR-video sequences of simple square-pulsed thermal loadings on aramid honeycomb-sandwich components with CFRP/GFRP (carbon-/glass-fiber-reinforced plastic) facings and GFRP inserts. Hence, processing time for image classification can be saved by reducing the dimension of information used by the classification algorithm without losing accuracy.

Description: Today, the assembly of laser systems requires a large share of manual operations due to its complexity regarding the optimal alignment of optics. Although the feasibility of automated alignment of laser optics has been shown in research labs, the development effort for the automation of assembly does not meet economic requirements – especially for low-volume laser production. This paper presents a model-based and sensor-integrated assembly execution approach for flexible assembly cells consisting of a macro-positioner covering a large workspace and a compact micromanipulator with camera attached to the positioner. In order to make full use of available models from computer-aided design (CAD) and optical simulation, sensor systems at different levels of accuracy are used for matching perceived information with model data. This approach is named "chain of refined perception", and it allows for automated planning of complex assembly tasks along all major phases of assembly such as collision-free path planning, part feeding, and active and passive alignment. The focus of the paper is put on the in-process image-based metrology and information extraction used for identifying and calibrating local coordinate systems as well as the exploitation of that information for a part feeding process for micro-optics. Results will be presented regarding the processes of automated calibration of the robot camera as well as the local coordinate systems of part feeding area and robot base.

Description: Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and power-inefficient, making their application to remote environments extremely challenging. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used to measure sulfur dioxide (SO2) emissions from La Fossa crater, Vulcano, Italy, where column densities of up to 1.2 × 1018 molec cm−2 (~ 500 ppmm) were detected along open paths of up to 400 m in total length. The instrument's SO2 detection limit was determined to be 2 × 1016 molec cm−2 (~ 8 ppmm), thereby making quantitative detection of even trace amounts of SO2 possible. The instrument is capable of measuring other volcanic volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide (ClO) and carbon disulfide (CS2) were both below the instrument's detection limits during the experiment, the upper limits for the X / SO2 ratio (X = ClO, CS2) could be derived, and yielded 2 × 10−3 and 0.1, respectively. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.

Description: The carbon monoxide (CO) gas sensing properties of low-resistance heavily Ga-doped ZnO thin films were evaluated. The ZnO films with a thickness of 50 nm were deposited at 200 °C by ion plating. The electrical properties of the ZnO films were controlled by varying the oxygen assist gas flow rate during deposition. The CO gas sensitivity of ZnO films with Au electrodes was investigated in nitrogen gas at a temperature of 230 to 330 °C. CO gas concentration was varied in the range of 0.6–2.4% in nitrogen gas. Upon exposure to CO gas, the current flowing through the film was found to decrease. This response occurred even at the lowest temperature of 230 °C, and is thought to be the result of a mechanism different than the previously reported chemical reaction.

Description: The gas sensing properties of resistive gas sensors of BaFe0.7Ta0.3O3-δ (BFT30) prepared by the so-called aerosol deposition method, a method to manufacture dense ceramic films at room temperature, were investigated. The electrical response of the films was investigated first under various oxygen concentrations and in a wide temperature range between 350 and 900 °C. Between 700 and 900 °C, the conductivity of BaFe0.7Ta0.3O3-δ (BFT30) depends on the oxygen concentration with a slope of almost 1/4 in the double-logarithmic plot vs. oxygen partial pressure. In addition, the sensor response is temperature independent. BFT30 responds fast and reproducibly to changing oxygen partial pressures even at 350 °C. The cross-sensitivity has been investigated in environments with various gases (C3H8, NO, NO2, H2, CO, CO2, and H2O) in synthetic air between 350 and 800 °C. BFT30 exhibits good sensing properties to NO between 350 and 400 °C in the range from 1.5 to 2000 ppm with a high selectivity to the other investigated gas species. Thus this semiconducting ceramic material is a good candidate for a temperature-independent oxygen sensor at high temperatures with the application in exhausts and for a selective nitrogen monoxide (NO) sensor at low temperatures for air quality monitoring.

Description: The ionospheric W index allows to distinguish state of the ionosphere and plasmasphere from quiet conditions (W = 0 or ±1) to intense storm (W = ±4) ranging the plasma density enhancements (positive phase) or plasma density depletions (negative phase) regarding the quiet ionosphere. The global W index maps are produced for a period 1999–2014 from Global Ionospheric Maps of Total Electron Content, GIM-TEC, designed by Jet Propulson Laboratory, converted from geographic frame (−87.5:2.5:87.5° in latitude, −180:5:180° in longitude) to geomagnetic frame (−85:5:85° in magnetic latitude, −180:5:180° in magnetic longitude). The probability of occurrence of planetary ionosphere storm during the magnetic disturbance storm time, Dst, event is evaluated with the superposed epoch analysis for 77 intense storms (Dst ≤ −100 nT) and 230 moderate storms (−100 〈 Dst ≤ −50 nT) with start time, t0, defined at Dst storm main phase onset. It is found that the intensity of negative storm, iW-, exceeds the intensity of positive storm, iW+, by 1.5–2 times. An empirical formula of iW+ and iW- in terms of peak Dst is deduced exhibiting an opposite trends of relation of intensity of ionosphere-plasmasphere storm with regard to intensity of Dst storm.

Description: This paper investigates the impact of an error-prone buffer memory on a channel decoder as employed in modern digital communication systems. On one hand this work is motivated by the fact that energy efficient decoder implementations may not only be achieved by optimizations on algorithmic level, but also by chip-level modifications. One of such modifications is so called aggressive voltage scaling of buffer memories, which, while achieving reduced power consumption, also injects errors into the likelihood values used during the decoding process. On the other hand, it has been recognized that the ongoing increase of integration density with smaller structures makes integrated circuits more sensitive to process variations during manufacturing, and to voltage and temperature variations. This may lead to a paradigm shift from 100 %-reliable operation to fault tolerant signal processing. Both reasons are the motivation to discuss the required co-design of algorithms and underlying circuits. For an error-prone receive buffer of a Turbo decoder the influence of quantizer design and index assignment on the error resilience of the decoding algorithm is discussed. It is shown that a suitable design of both enables a compensation of hardware induced bits errors with rates up to 1 % without increasing the computational complexity of the decoder.

Description: The quasi 2 day wave (QTDW) over Collm (51° N, 13° E) has been studied between September 2004 and September 2013 using a VHF meteor radar. The 9 year mean amplitudes show a strong summer maximum with several irregular bursts and much weaker winter maxima. In summer, the meridional amplitude is slightly larger than the zonal one with about 15 m s−1 at 91 km height. Phase differences are slightly higher than 90°, which indicates a polarization that is nearly circular. On an average the QTDW is amplified after a maximum of zonal wind shear. This can be realized in the summer mesospheric jet where the zonal wind component has its minimum or, in other words, the easterly jet maximizes. Thus, instability is found as a likely forcing mechanism. QTDW amplitudes exhibit considerable inter-annual variability. In particular, there is a possible relation between the QTDW amplitude and the 11-year solar cycle in winter but not in summer.

Description: On the 4 November 2012 at 3:04:27 UT a strong lightning in the midst of the North Sea affected the propagation conditions of VLF/LF transmitter radio signals from NRK (Iceland, 37.5 kHz) and GBZ (UK, 19.58 kHz) received at 5246° N 8° E (NW Germany). The amplitude and phase dips show a recovery time of 6–12 min pointing to a LOng Recovery Early VLF (LORE) event. Clear assignment of the causative return stroke in space and time was possible with data from the WWLLN (Worldwide Lightning Location Network). Based on a return stroke current model the electric field is calculated and an excess electron density distribution which decays over time in the lower ionosphere is derived. Ionization, attachment and recombination processes are modeled in detail. Entering the electron density distribution in VLF/LF radio wave propagation calculations using the LWPC (Long Wavelength Propagation Capability) code allows to model the VLF/LF amplitude and phase behavior by adjusting the return stroke current moment. The results endorse and quantify the conception of lower ionosphere EMP heating by strong – but not necessarily extremely strong – return strokes of both polarities.

Description: In this paper we present an extended mode-matching model for a split-cylinder resonator involving TE and TM resonant modes. The new model enhances the known TE0np mode-matching model by improving mode identification and distortion analysis and providing better frequency range coverage for relative permittivity estimation. In order to verify the new model, measured spectra of several substrate materials are analyzed and the estimation results are compared with those of the TE0np mode-matching model.

Description: We present observations of polar mesospheric summer echoes (PMSE) using the Middle Atmosphere Alomar Radar System in Northern Norway (69.30° N, 16.04° E). The radar is able to resolve PMSE at high spatial and temporal resolution and to perform pulse-to-pulse beam steering. In this experiment, 81 oblique beam directions were used with off-zenith angles up to 25°. For each beam pointing direction and range gate, coherent radar imaging was applied to determine the mean backscatter location. The location of the mean scatterer in the beam volume was calculated by the deviation from the nominal off-zenith angle of the brightest pixel. It shows that in tilted beams with an off-zenith angle greater than 5°, structures appear at the altitudinal edges of the PMSE layer. Our results indicate that the mean influence of the location of the maximum depends on the tilt of the beam and on the observed area of the PMSE layer. At the upper/lower edge of the PMSE layer, the mean backscatter has a greater/smaller off-zenith angle than the nominal off-zenith angle. This effect intensifies with greater off-zenith beam pointing direction, so the beam filling factor plays an important role in the observation of PMSE layers for oblique beams.

Description: The scattering and diffraction of a complex-source beam (CSB) by an acoustically soft or hard plane angular sector is treated by a rigorous spherical-multipole analysis in sphero-conal coordinates. By assigning a complex-valued radial source coordinate to the corresponding Green's function, the CSB is directed exactly towards the corner of the sector. Since the CSB can be interpreted as a localized plane wave, its interaction with the corner in the presence of the semi-infinite structure can be analyzed in detail. In opposite to the classical case of a non-localized incident plane wave, the resulting multipole series is strongly convergent and no summation techniques are necessary to obtain meaningful results. The numerical results include a convergence analysis, total near fields as well as scattered far fields and prove the applicability of this new approach.

Description: The characterization of antenna radiation patterns by transformed near-field measurements requires accurate amplitude and phase data. This represents a problem since expensive measurement equipment is required, especially at millimeter and submillimeter wavelengths (Isernia et al., 1996). Amplitude-only antenna field measurements are theoretically sufficient for the unique determination of antenna far-fields. Therefore, phaseless techniques are of special interest. However, the required field transformations are extremely challenging, since they are nonlinear and strongly ill-posed. In this work, the amplitude-only or phaseless near-field far-field transformation problem is formulated as a nonlinear optimization problem. The linear radiation operator within the nonlinear formulation is evaluated using the fast irregular antenna field transformation algorithm (FIAFTA). A hybrid solution procedure is described which combines a genetic algorithm with an iterative conjugate gradient (CG) search method. Numerical results prove the efficiency and flexibility of the formulation and it is shown that the algorithm remains stable when the noise level in the measurements is moderate. Nevertheless, regularization techniques might be beneficial to further improve the robustness of the algorithm.

Description: Powerful compute clusters and multi-core systems have become widely available in research and industry nowadays. This boost in utilizable computational power tempts people to run compute-intensive tasks on those clusters, either for speed or accuracy reasons. Especially Monte Carlo simulations with their inherent parallelism promise very high speedups. Nevertheless, the quality of Monte Carlo simulations strongly depends on the quality of the employed random numbers. In this work we present a comprehensive analysis of state-of-the-art pseudo random number generators like the MT19937 or the WELL generator used for parallel stream generation in different settings. These random number generators can be realized in hardware as well as in software and help to accelerate the analysis (or simulation) of communications systems. We show that it is possible to generate high-quality parallel random number streams with both generators, as long as some configuration constraints are met. We furthermore depict that distributed simulations with those generator types are viable even to very high degrees of parallelism.

Description: We study solar Type III radio bursts simultaneously observed by RPWS/Cassini, URAP/Ulysses and WAVES/Wind experiments. The observations allows us to cover a large frequency bandwidth from 16 MHz down to a few kHz. We consider the onset time of each burst, and estimate the corresponding intensity level. Also we measure the Langmuir frequency as observed on the dynamic spectra recorded by the Ulysses spacecraft. The distances of Wind, Ulysses and Cassini spacecraft, with regard to the Sun, were in the order of 1 AU, 2.4 AU and 4.5 AU, respectively. The spacecraft trajectories were localized in the ecliptic plane in the case of Wind and Cassini, and for Ulysses in the southern hemisphere (i.e. heliocentric latitude higher than −50°). Despite the different locations, the spectral patterns of the selected solar bursts are found to be similar between 10 MHz and 2 MHz but unalike at lower frequency. We discuss the variation of the intensity level as recorded by the three spacecraft. We show that the reception system of each experiment affected the way the Type III burst intensity is measured. Also we attempt to estimate the electron beam along the interplanetary magnetic field where the trajectory is an Archimedean spiral. This leads us to infer on the visibility of the source location with regard to the spacecraft position.

Description: Microwave induced selective heating outmatches conventional mold heating by convective heat transfer in means of energy efficiency and cycle time. Moreover, it provides the opportunity of a local manipulation of solidification and cooling processes within the sand casting mold. In this paper, we investigate the suitability of different highly absorbing materials to indirectly heat up the mostly microwave transparent sand mold. The temperature-dependent permittivity of the involved materials is determined by resonator experiments and subsequently used to simulate the electromagnetic field and the thermodynamic response of the sand mold prior to a metal casting process. Experimental results are presented and compared with the outcome of the coupled electromagnetic-thermodynamic simulations and the influence of local microwave heating on the solidification and cooling of the cast is studied.

Description: This paper presents an improved finite-element formulation for axially uniform electromagnetic waveguides. It allows for both dielectric and conduction losses and covers the entire range from optics down to the static limit. Propagation coefficients of small magnitude, particularly those of transmission line modes in the low-frequency regime, are computed much more accurately than with previous approaches.

Description: This laudation is given in honor of the 100th birthday of Prof. Karl Rawer which happens to coincide with the 45th anniversary of the International Reference Ionosphere (IRI). The ionosphere was discovered during Karl Rawer's lifetime, and he has dedicated his professional life to its exploration. World Wars I and II shaped his early life, but they also launched his career as one of the eminent geophysical scientists of the twentieth century. The paper looks back at Karl Rawer's life and his pioneering work and leadership in advancing and shaping the exploration of the ionosphere.

Description: This brief historical review summarizes the work and achievements of German researchers on ionospheric problems before Karl Rawer started his scientific career in 1937.

Description: When the Committee on Space Research (COSPAR) initiated the International Reference Ionosphere (IRI) project in 1968 it wisely selected K. Rawer as its first Chairperson. With a solid footing and good contacts in both the ground-based and space-based ionospheric communities he was ideally suited to pull together colleagues and data from both communities to help build the first version of the IRI. He assembled a team of 20+ international ionospheric experts in the IRI Working Group and chaired and directed the group from 1968 to 1984. The working group has now grown to 63 members and the IRI model has undergone many revisions as new data became available and new modeling techniques were applied. This paper was presented during a special session of the Kleinheubach Tagung 2013 in honor of K. Rawer's 100th birthday. It will review the current status of the IRI model and project and the international recognition it has achieved. It is quite fitting that this year we not only celebrate K. Rawer's 100th birthday but also the exciting news that his favorite science endeavor, IRI, has been internationally recognized as an ISO (International Standardization Organization) standard. The IRI homepage is at http://irimodel.org.

Description: This contribution provides an approach for emulating the behaviour of an ASIC temperature monitoring system (TMon) during run-time for a tightly-coupled processor array (TCPA) of a heterogeneous invasive multi-tile architecture to be used for FPGA prototyping. It is based on a thermal RC modeling approach. Also different usage scenarios of TCPA are analyzed and compared.

Description: Due to the increasing electrification of modern aircraft, as a result of the More Electric Aircraft concept, new strategies and approaches are required to fulfil the strict EMC aircraft standards (DO-160/ED-14–Sec. 20). Common mode chokes are a key component of electromagnetic filters and often oversized because of the unknown impedance of the surrounding power electronic system. This oversizing results in an increase of weight and volume. It has to be avoided as far as possible for mobile applications. In this context, an advanced method is presented to measure these impedances under operating conditions. Furthermore, the different parameters of the inductance design is explained and an optimisation for weight and volume is introduced.

Description: In this paper an FPGA-based test system for high-speed transmission experiments with integrated photonic receivers is presented. Pseudorandom binary sequences are generated inside the FPGA and encoded as either differential quadrature phase shift keying (DQPSK) or quadrature phase shift keying (QPSK) signals. The DQPSK encoder uses a 64-fold parallel-prefix-layers architecture for real-time operation which allows for a maximum internal encoder data rate of 64 Gbit/s. Two-fold parallel data streams of I and Q signals suitable for driving an optical IQ-modulator can be transmitted and received by four 12.5 Gbit/s transceivers. Integrated bit error testers are used to determine bit error rates in real-time.

Description: This paper has attempted to evaluate the radar cross section (RCS) of two furniture items in an indoor environment in a frequency range of 3–7 GHz of the ultra-wideband (UWB) range. The RCS evaluation is achieved through an extended version of the radar equation that incorporates the channel transfer function of scattering. The time-gating method was applied to remove the multipath effect, a phenomenon which typically occurs in the indoor environment. Two double-ridged waveguide horn antennas for both vertical and horizontal polarizations were used to obtain the transfer function of scattering of the furniture prior to analysis in order to derive their bistatic RCS. The RCS results validate the applicability of the proposed extended radar equation to the indoor propagation prediction.

Description: After a historical survey of space related EUV measurements in Germany and the role of Karl Rawer in pursuing this work, we describe present developments in EUV spectroscopy and provide a brief outlook on future activities. The group of Karl Rawer has performed the first scientific space project in Western Europe on 19th October 1954. Then it was decided to include the field of solar EUV spectroscopy in ionospheric investigations. Starting in 1957 an intensified development of instrumentation was going on to explore solar EUV radiation, atmospheric airglow and auroral emissions until the institute had to stop space activities in the early nineteen-eighties. EUV spectroscopy was continued outside of the institute during eight years. This area of work was supported again by the institute developing the Auto-Calibrating Spectrometers (SolACES) for a mission on the International Space Station (ISS). After more than six years in space the instrument is still in operation. Meanwhile the work on the primary task also to validate EUV data available from other space missions has made good progress. The first results of validating those data and combine them into one set of EUV solar spectral irradiance are very promising. It will be recommended for using it by the science and application community. Moreover, a new low-cost type of an EUV spectrometer is presented for monitoring the solar EUV radiation. It shall be further developed for providing EUV-TEC data to be applied in ionospheric models replacing the Covington index F10.7. Applying these data for example in the GNSS signal evaluation a more accurate determination of GNSS receiver positions is expected for correcting the propagation delays of navigation signals traveling through the ionosphere from space to earth. – Latest results in the field of solar EUV spectroscopy are discussed, too.

Description: The magnetospheric phenomenon of non-thermal radio emission is known since the serendipitous discovery of Jupiter as radio planet in 1955, opening the new field of "Planetary Radio Astronomy". Continuous ground-based observations and, in particular, space-borne measurements have meanwhile produced a comprehensive picture of a fascinating research area. Space missions as the Voyagers to the Giant Planets, specifically Voyager 2 further to Uranus and Neptune, Galileo orbiting Jupiter, and now Cassini in orbit around Saturn since July 2004, provide a huge amount of radio data, well embedded in other experiments monitoring space plasmas and magnetic fields. The present paper as a condensation of a presentation at the Kleinheubacher Tagung 2013 in honour of the 100th anniversary of Prof. Karl Rawer, provides an introduction into the generation mechanism of non-thermal planetary radio waves and highlights some new features of planetary radio emission detected in the recent past. As one of the most sophisticated spacecraft, Cassini, now in space for more than 16 years and still in excellent health, enabled for the first time a seasonal overview of the magnetospheric variations and their implications for the generation of radio emission. Presently most puzzling is the seasonally variable rotational modulation of Saturn kilometric radio emission (SKR) as seen by Cassini, compared with early Voyager observations. The cyclotron maser instability is the fundamental mechanism under which generation and sufficient amplification of non-thermal radio emission is most likely. Considering these physical processes, further theoretical investigations have been started to investigate the conditions and possibilities of non-thermal radio emission from exoplanets, from potential radio planets in extrasolar systems.