Random gas mixtures for efficient gas sensor calibration

Applications like air quality, fire detection and detection of explosives require selective and quantitative measurements in an ever-changing background of interfering gases. One main issue hindering the successful implementation of gas sensors in real-world applications is the lack of appropriate calibration procedures for advanced gas sensor systems. This article presents a calibration scheme for gas sensors based on statistically distributed gas profiles with unique randomized gas mixtures. This enables a more realistic gas sensor calibration including masking effects and other gas interactions which are not considered in classical sequential calibration. The calibration scheme is tested with two different metal oxide semiconductor sensors in temperature-cycled operation using indoor air quality as an example use case. The results are compared to a classical calibration strategy with sequentially increasing gas concentrations. While a model trained with data from the sequential calibration performs poorly on the more realistic mixtures, our randomized calibration achieves significantly better results for the prediction of both sequential and randomized measurements for, for example, acetone, benzene and hydrogen. Its statistical nature makes it robust against overfitting and well suited for machine learning algorithms. Our novel method is a promising approach for the successful transfer of gas sensor systems from the laboratory into the field. Due to the generic approach using concentration distributions the resulting performance tests are versatile for various applications

UV-Assisted Gate Bias Cycling in Gas-Sensitive Field-Effect Transistors

Static and dynamic responses of a silicon carbide field-effect transistor gas sensor have been investigated at two different gate biases in several test gases. Especially the dynamic effects are gas dependent and can be used for gas identification. The addition of ultraviolet light reduces internal electrical relaxation effects, but also introduces new, temperature-dependent effects

Simultaneous Detection of Longitudinal and Transverse Bunch Signals at a Storage Ring

To understand and control the dynamics in the longitudinal phase space, time-resolved measurements of different bunch parameters are required. For a reconstruction of this phase space, the detector systems have to be synchronized. This reconstruction can be used e.g. for studies of the micro-bunching instability. It occurs if the interaction of the bunch with its own radiation leads to the formation of sub-structures on the longitudinal bunch profile. These sub-structures can grow rapidly -- leading to a sawtooth-like behaviour of the bunch. At KARA, we use a fast-gated intensified camera for energy spread studies, Schottky diodes for coherent synchrotron radiation studies as well as electro-optical spectral decoding for longitudinal bunch profile measurements. For a synchronization, a hardware synchronization scheme is used which compensates for eventual hardware delays. In this paper, the different experimental setups and their synchronization are discussed and first results of synchronous measurements are presented

Advances and perspectives from a decade of collaborative efforts on zeolites for selective catalytic reduction of NOx

[EN] Nitrogen oxides (NOx) is a major air pollutant and its release is regulated by increasingly stringent legislation. Selective catalytic reduction using ammonia as a reductant (NH3-SCR) is the most widely applied method to reduce NOx from diesel vehicle exhaust. Significant technological achievements have been developed in the last 10-15 years to minimize NOx by NH3-SCR, particularly using Cu-containing small-pore zeolites as active and stable catalysts. In the present perspective, we highlight some of the most noteworthy advances achieved by industry and academia on the understanding of the unique reaction mechanism of NH3-SCR over Cu-zeolites. With the increased understanding, researchers have been able to rationalize the design and realization of new Cu-zeolite catalysts. Although light-duty diesel vehicles will be electrified in the near future, heavy-duty diesel vehicles will continue to play a large role in future powertrain solutions even beyond 2030. Hence, we highlight some of the challenges and perspectives moving forward.This work has been supported by Umicore and by the Spanish Government through PID2021-122755OB-I00 funded by MCIN/AEI/10.13039/501100011033 and TED2021-130739B-I00 funded by MCIN/AEI/10.13039/501100011033/EU/PRTR, and by Generalitat Valenciana through AICO/2021/201.Vennestrøm, PN.; Thogersen, JR.; Gabrielsson, PLT.; Van Tendeloo, L.; Schütze, FW.; Moliner Marin, M. (2022). Advances and perspectives from a decade of collaborative efforts on zeolites for selective catalytic reduction of NOx. Microporous and Mesoporous Materials. 358:1-12. https://doi.org/10.1016/j.micromeso.2022.11233611235

NH3-SCR catalysts for heavy-duty diesel vehicles: Preparation of CHA-type zeolites with low-cost templates

Computer-assistance allows selecting the most adequate low-cost organic structure directing agents (OSDAs) for the crystallization of Al-rich CHA-type zeolites. The host-guest stabilization energies of tetraethylammonium (TEA), methyltriethylammonium (MTEA) and dimethyldiethylammonium (DMDEA), in combination with Na, were first theoretically evaluated. This “ab-initio” analysis reveals that two TEA show a serious steric hindrance in a cha cavity, whereas two MTEA would present excellent host-guest confinements. The synthesis of Al-rich CHA-type zeolites has been accomplished using TEA and MTEA. Electron diffraction and high-resolution transmission electron microscopy reveal large CHA-domains with narrow faulted GME-domains in the CHA-type material synthesized with TEA, confirming the better OSDA-directing roles of MTEA cations towards the cha cavity, in good agreement with DFT calculations. Cu-exchanged Al-rich CHA-type samples achieved with MTEA and TEA show excellent catalytic activity and hydrothermal stability for the selective catalytic reduction (SCR) of NOx with ammonia under conditions relevant for future heavy duty diesel conditions.This work has been supported by Umicore and by the Spanish Government-MCIU through RTI2018-101033-B-I00 (MCIU/AEI/FEDER, UE) and PID2020-112590GB-C21 (AEI/FEDER, UE). T.W. acknowledges financial support by the Swedish Research Council (Grant No. 2019-05465). E.B. acknowledges the Spanish Government-MCIU for a FPI scholarship (PRE2019-088360). P.F. thanks ITQ for a contract. The Electron Microscopy Service of the UPV is acknowledged for their help in sample characterization. The computations were performed on the Tirant III cluster of the Servei d'Informàtica of the University of Valencia

Developing a Monolithic Silicon Sensor in a 65 nm CMOS Imaging Technology for Future Lepton Collider Vertex Detectors

Monolithic CMOS sensors in a 65 nm imaging technology are being investigated by the CERN EP Strategic R&D Programme on Technologies for Future Experiments for an application in particle physics. The appeal of monolithic detectors lies in the fact that both sensor volume and readout electronics are integrated in the same silicon wafer, providing a reduction in production effort, costs and scattering material. The Tangerine Project WP1 at DESY participates in the Strategic R&D Programme and is focused on the development of a monolithic active pixel sensor with a time and spatial resolution compatible with the requirements for a future lepton collider vertex detector. By fulfilling these requirements, the Tangerine detector is suitable as well to be used as telescope planes for the DESY-II Test Beam facility. The project comprises all aspects of sensor development, from the electronics engineering and the sensor design using simulations, to laboratory and test beam investigations of prototypes. Generic TCAD Device and Monte-Carlo simulations are used to establish an understanding of the technology and provide important insight into performance parameters of the sensor. Testing prototypes in laboratory and test beam facilities allows for the characterization of their response to different conditions. By combining results from all these studies it is possible to optimize the sensor layout. This contribution presents results from generic TCAD and Monte-Carlo simulations, and measurements performed with test chips of the first sensor submission.Comment: 7 pages, 8 figures, submitted to IEEE Xplore as conference record for 2022 IEEE NSS/MIC/RTS

Syntactic microvariation and methodology: problems and perspectives

Variation in empirical data has been a perseverant problem for theoretical linguistics, especially syntax. Data inconsistencies among authors allegedly analyzing the same phenomenon are ubiquitous in the syntactic literature (e.g., literature on focus-raising in Hungarian; É. Kiss 1987 vs. Lipták 1998), and partly result from the highly informal methodology of data collection. However, even if adequate controls are used to exclude potential biases, variation might remain. The general practice in syntactic research has been to ignore these „microvariations”-mainly in the lack of any systematic empirical method to detect them. The present paper shows that this practice leads to serious theoretical problems and proposes a new empirical method, cluster analysis, to discover, explore and systematize these variations. It also illustrates how this richer empirical basis gives rise to a more fine-grained theoretical analysis