Acumen : an open-source testbed for cyber-physical systems research

Developing Cyber-Physical Systems requires methods and tools to support simulation and verification of hybrid (both continuous and discrete) models. The Acumen modeling and simulation language is an open source testbed for exploring the design space of what rigorousbut- practical next-generation tools can deliver to developers of Cyber- Physical Systems. Like verification tools, a design goal for Acumen is to provide rigorous results. Like simulation tools, it aims to be intuitive, practical, and scalable. However, it is far from evident whether these two goals can be achieved simultaneously. This paper explains the primary design goals for Acumen, the core challenges that must be addressed in order to achieve these goals, the “agile research method” taken by the project, the steps taken to realize these goals, the key lessons learned, and the emerging language design

An iterative approach to determine the refractive index of 3D printed 60GHz PLA lenses - Mätning och simulering av fokallängd hos 3D-utskriven radarlins

This study is a part of the research project eMC-Hammer. It describes an iterative approach to determine quasi-optical properties of standard 3D printer filament material to, in an inexpensive and fast way, construct focusing lenses for millimetre wave systems. Results from three lenses with different focal lengths are shown and discussed. The real part of the permittivity at 60GHz for polylactic acid (PLA) is in this paper determined to be er=2.74. Purpose: The purpose with the study is to validate an iterative, low cost, method of determining the refractive index of 3D printed lenses, where otherwise expensive equipment would be needed, such as S-parameter measurements using a vector network analyzer. The dataset contains measurements, simulation results and matlab code used for the conference article "An iterative approach to determine the refractive index of 3D printed 60GHz PLA lenses" (doi:10.1049/cp.2018.1480) See the conference article (methods) and lapc2018mainfigure.m (data description - meta data) for details.Den här studien är en del av forskningsprojektet eMC-Hammer. Den beskriver ett iterativt tillvägagångssätt för att bestämma kvasi-optiska egenskaper hos standard 3D-skrivarfilamentmaterial för att, på ett kostnadseffektivt och snabbt sätt, kunna konstruera fokuseringslinser för millimetervågsystem. Resultatet för tre objektiv med olika brännvidd visas och diskuteras. Den verkliga delen av permittiviteten vid 60 GHz för polylaktid (PLA) är här bestämd att vara er = 2,74. Syfte: Syftet med studien är att validera en iterativ, kostnadseffektiv, metod för att bestämma brytningsindex på 3D-utskrivna linser, där annars dyr utrustning skulle behövas, till exempel S-parameter-mätningar med en vektornätverksanalysator. Datasetet innehåller mätningar, simulationer och matlab-kod som användes till konferensartikeln "An iterative approach to determine the refractive index of 3D printed 60GHz PLA lenses" (doi:10.1049/cp.2018.1480). Se konferensartikeln (metoder) och lapc2018mainfigure.m (databeskrivning - metadata) för detaljer

Real-time observation of coherent acoustic phonons generated by an acoustically mismatched optoacoustic transducer using x-ray diffraction

The spectrum of laser-generated acoustic phonons in indium antimonide coated with a thin nickel film has been studied using time-resolved x-ray diffraction. Strain pulses that can be considered to be built up from coherent phonons were generated in the nickel film by absorption of short laser pulses. Acoustic reflections at the Ni-InSb interface leads to interference that strongly modifies the resulting phonon spectrum. The study was performed with high momentum transfer resolution together with high time resolution. This was achieved by using a third-generation synchrotron radiation source that provided a high-brightness beam and an ultrafast x-ray streak camera to obtain a temporal resolution of 10 ps. We also carried out simulations, using commercial finite element software packages and on-line dynamic diffraction tools. Using these tools, it is possible to calculate the time-resolved x-ray reflectivity from these complicated strain shapes. The acoustic pulses have a peak strain amplitude close to 1%, and we investigated the possibility to use this device as an x-ray switch. At a bright source optimized for hard x-ray generation, the low reflectivity may be an acceptable trade-off to obtain a pulse duration that is more than an order of magnitude shorter. (C) 2015 Author(s)

3D Printed Radar Lenses with Anti-Reflective Structures

Background: The purpose of this study was to determine if 3D printed lenses with wavelength specific anti-reflective (AR) surface structures would improve beam intensity and thus radar efficiency for a Printed Circuit Board (PCB)-based 60 GHz radar. This would have potential for improved low-cost radar lenses for the consumer product market. Methods: A hyperbolic lens was designed in 3D Computer Aided Design (CAD) software and was then modified with a wavelength specified AR structure. Electromagnetic computer simulation was performed on both the ‘smooth’ and ‘AR structure’ lenses and compared to actual 60 GHz radar measurements of 3D printed polylactic acid (PLA) lenses. Results: The simulation results showed an increase of 10% in signal intensity of the AR structure lens over the smooth lens. Actual measurement showed an 8% increase in signal of the AR structure lens over the smooth lens. Conclusions: Low cost and readily available Fused Filament Fabrication (FFF) 3D printing has been shown to be capable of printing an AR structure coated hyperbolic lens for millimeter wavelength radar applications. These 3D Printed AR structure lenses are effective in improving radar measurements over non-AR structure lenses. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Time-Resolved X-ray Diffraction Investigation of the Modified Phonon Dispersion in InSb Nanowires.

The modified phonon dispersion is of importance for understanding the origin of the reduced heat conductivity in nanowires. We have measured the phonon dispersion for 50 nm diameter InSb (111) nanowires using time-resolved X-ray diffraction. By comparing the sound speed of the bulk (3880 m/s) and that of a classical thin rod (3600 m/s) to our measurement (2880 m/s), we conclude that the origin of the reduced sound speed and thereby to the reduced heat conductivity is that the C44 elastic constant is reduced by 35% compared to the bulk material

Femtosecond x-ray diffraction reveals a liquid–liquid phase transition in phase-change materials

In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid–liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics