In situ sounding of radiative flux profiles through the Arctic lower troposphere

In situ profiles and fixed-altitude time series of all four components of net radiation were obtained at Ny-Ålesund, Svalbard (78.9° N, 11.9° E), in the period May 04–21, 2015. Measurements were performed using adapted high-quality instrumentation classified as “secondary standard” carried by a tethered balloon system. Balloon-lifted measurements of albedo under clear-sky conditions demonstrate the local dependence on altitude and on the surface inhomogeneity of this parameter over coastal terrain of Ny-Ålesund. Depending on the surface composition within the sensor’s footprint near the coastline, the albedo over predominantly snow-covered surfaces was found to decrease to 0.548 and 0.452 at 494 m and 881 m altitude compared with 0.731 and 0.788 measured with near-surface references, respectively. Albedo profiles show an all-sky maximum at 150 m above surface level due to local surface inhomogeneity, and an averaged vertical change rate of − 0.040/100 up to 750 m aboveground level (clear sky) and − 0.034/100 m (overcast). Profiling of arctic low-level clouds reveals distinct vertical gradients in all radiative fluxes but longwave upward at the cloud top. Observed radiative cooling at the top of a partly dissolving stratus cloud with heating rates of − 40.4 to − 62.1 Kd−1 in subsequent observations is exemplified

Electrical Properties of Thin ZrSe3 Films for Device Applications

Measurements of key properties of the two-dimensional transition metal trichalcogenide ZrSe3are reported. The bulk material was created by chemical vapor deposition and subsequently exfoliated to obtain thin films of varying thicknesses. The samples were then characterized by atomic force microscopy measurements and Raman spectroscopy and contacted by e-beam lithography. Electrical measurements give values for the band gap energy of 0.6 eV increasing for thinner samples. Transistor measurements show ZrSe3to be an n-type semiconductor. By looking at several samples with varying thicknesses, it was possible to determine a mean free path of 103 nm for the bulk material which opens the possibility for new electronic devices

Locally controlled MOF growth on functionalized carbon nanotubes

Metal-organic frameworks (MOFs) are highly versatile materials because of their tunable properties. However, the typically poor electrical conductivity of MOFs presents challenges for their integration into electrical devices. By adding carbon nanotubes to MOF synthesis, a highly intergrown material with increased conductivity and chemiresistive sensing properties can be obtained. Here, we present a patterning technique to control MOF growth on predefined areas of one particular carbon nanotube. We found that electron beam pretreatment of -COOH functionalized multi-walled carbon nanotubes inhibits the growth of UiO-66 MOF on these multi-walled carbon nanotubes. By irradiating individual multi-walled carbon nanotubes, we show that MOF growth can be inhibited in predefined tube areas, creating MOF-free spaces on the nanotube. In this way, our method shows a possibility to pattern MOF growth on individual nanotubes

Long-Persistent Photoconductivity in Transistor Structures Made from Thin ZrS3-Films

In the search for two-dimensional (2D) materials, transition-metal trichalcogenides (TMTCs) have emerged as promising candidates for optoelectronic applications. Here, we show a very long-lasting persistent photoconductivity (PPC) over several hours in thin films of the TMTC zirconium trisulfide (ZrS3) at room temperature when illuminated with a 470 nm LED. ZrS3 crystals were grown using chemical vapor transport. UV-vis spectroscopy showed an indirect band gap of 1.81 eV and an Urbach energy of 83 meV, indicating that the system has a large number of defects. Transistor measurements on thin layers with thicknesses varying between 19 and 50 nm showed ZrS3 to be an n-type semiconductor. The conductivity increases under illumination, and it only reaches the original state several hours after switching off the illumination. This PPC can be described by using a stretched exponential function. On top of that, the sum of three exponential functions with tree different relaxation times fits the observed PPC nearly equally well. This shows that three processes dominate the relaxation. The three observed processes can be differentiated with respect to their origin by their dependence on the thickness of the thin layers

Experimental determination of Lamb wave dispersion diagrams over large frequency ranges in fiber metal laminates

Fiber metal laminates (FML) are of high interest for lightweight structures as they combine the advantageous material properties of metals and fiber-reinforced polymers. However, low-velocity impacts can lead to complex internal damage. Therefore, structural health monitoring with guided ultrasonic waves (GUW) is a methodology to identify such damage. Numerical simulations form the basis for corresponding investigations, but experimental validation of dispersion diagrams over a wide frequency range is hardly found in the literature. In this work the dispersive relation of GUWs is experimentally determined for an FML made of carbon fiber-reinforced polymer and steel. For this purpose, multi-frequency excitation signals are used to generate GUWs and the resulting wave field is measured via laser scanning vibrometry. The data are processed by means of a non-uniform discrete 2d Fourier transform and analyzed in the frequency-wavenumber domain. The experimental data are in excellent agreement with data from a numerical solution of the analytical framework. In conclusion, this work presents a highly automatable method to experimentally determine dispersion diagrams of GUWs in FML over large frequency ranges with high accuracy

Personal Dosimetry in Pulsed Photon Fields with the Dosepix Detector

First investigations regarding dosimetric properties of the hybrid, pixelated, photon-counting Dosepix detector in a pulsed photon field (RQR8) for the personal dose equivalent $H\mathrm{_p(10)}$ are presented. The influence quantities such as pulse duration and dose rate were varied, and their responses were compared to the legal limits provided in PTB-A 23.2. The variation of pulse duration at a nearly constant dose rate of 3.7$\,$Sv/h shows a flat response around 1.0 from 3.6$\,$s down to 2$\,$ms. A response close to 1.0 is achieved for dose rates from 0.07$\,$mSv/h to 35$\,$Sv/h for both pixel sizes. Above this dose rate, the large pixels (220$\,\mathrm{\mu}$m edge length) are below the lower limit. The small pixels (55$\,\mathrm{\mu}$m edge length) stay within limits up to 704$\,$Sv/h. The count rate linearity is compared to previous results, confirming the saturating count rate for high dose rates.Comment: 6 pages, 3 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Schnelle Leit- und Sicherungstechnik für mehr Fahrwegkapazität

Nach durchwachsenen Erfahrungen mit den Laufzeiten der Leit- und Sicherungstechnik (LST) rückten diese frühzeitig in den Fokus der im Digitalen Knoten Stuttgart (DKS) verfolgten LST-Optimierung für "maximale Leistungsfähigkeit". Dazu wurde ein Verfahren entwickelt, bei dem die Laufzeiten von sechs für die Leistungsfähigkeit des Gesamtprojekts reprä- sentativen Szenarien durch die Bieter im Zuge des Vergabeverfahrens zu benennen und zu plausibilisieren waren. Letztlich können die Laufzeiten damit erheblich verkürzt und somit merkliche Spielräume für Kapazitäts- und Qualitätsverbesserungen geschaffen werden

Melting, bubble-like expansion and explosion of superheated plasmonic nanoparticles

We report on time-resolved coherent diffraction imaging of gas-phase silver nanoparticles, strongly heated via their plasmon resonance. The x-ray diffraction images reveal a broad range of phenomena for different excitation strengths, from simple melting over strong cavitation to explosive disintegration. Molecular dynamics simulations fully reproduce this behavior and show that the heating induces rather similar trajectories through the phase diagram in all cases, with the very different outcomes being due only to whether and where the stability limit of the metastable superheated liquid is crossed.Comment: 17 pages, 8 figures (including supplemental material