Assessment of mechanical properties and microstructure characterizing techniques in their ability to quantify amount of cold work in 316l alloy

Stress corrosion cracking (SCC) behavior is a matter of concern for structural materials, namely, stainless steels and nickel alloys, in nuclear power plants. High levels of cold work (CW) have shown to both reduce crack initiation times and increase crack growth rates. Cold working has numerous effects on a material, including changes in microstructure, mechanical properties, and residual stress state, yet it is typically reported as a simple percent change in geometry. There is need to develop a strategy for quantitative assessment of cold-work level in order to better understand stress corrosion cracking test data. Five assessment techniques, commonly performed alongside stress corrosion cracking testing (optical microscopy (OM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), tensile testing, and hardness testing) are evaluated with respect to their ability to quantify the level of CW in a component. The test material is stainless steel 316L that has been cold-rolled to three conditions: 0%, 20%, and 30% CW. Measurement results for each assessment method include correlation with CW condition and repeatability data. Measured values showed significant spatial variation, illustrating that CW level is not uniform throughout a component. Mechanical properties (tensile testing, hardness) were found to correlate most linearly with the amount of imparted CW

Increasing thermoelectric performance using coherent transport

We show that coherent electron transport through zero-dimensional systems can be used to tailor the shape of the system's transmission function. This quantum-engineering approach can be used to enhance the performance of quantum dots or molecules in thermal-to-electric power conversion. Specifically, we show that electron interference in a two-level system can substantially improve the maximum thermoelectric power and the efficiency at maximum power by suppressing parasitic charge flow near the Fermi energy, and by reducing electronic heat conduction. We discuss possible realizations of this approach in molecular junctions or quantum dots.Comment: 4+ pages, 4 figure

Variation of cloud horizontal sizes and cloud fraction over Europe 1985–2018 in high-resolution satellite data

Aerosol-cloud interactions are a major uncertainty in estimating the anthropogenic climate change. Adjustments of cloud properties to an aerosol perturbation concern among others the cloud fraction, and have been emphasised as particularly complex. Cloud adjustments can generate important responses on the distribution of cloud horizontal sizes. We derive the cloud-size distribution as observational constraint for the cloud-fraction response from high-resolution Landsat satellite data. The goal is to carry out long-term trends in cloud sizes and cloud fraction over Europe during 1985–2018 to investigate the impact of major aerosol reductions during that time. Landsat data with a high spatial resolution of 30m was preprocessed via the web-based platform Google Earth Engine to evade the obstacle of high computational effort and time to handle the comprehensive data archive. The observed multidecadal trends indicate a widespread increase in cloud fraction during 1985–2018. This corresponds to a decrease in the number of small clouds of several 10–100m cloud length, whereas larger clouds (1 km and more), which contribute more to the cloud fraction, became more numerous. We confirm this by showing a largescale decrease of the power-law exponent describing the relative abundance of small and large clouds in the cloud-size distribution. Even though we can interpret the observed changes in cloud properties as significant trends, we do not explicitly identify a clear aerosol signal. Untangling the pure aerosol effect from other confounding factors (e.g., the local meteorology) is therefore left as an outlook for subsequent studies.Aerosol-Wolken-Wechselwirkungen stellen eine große Unsicherheit in der Quantifizierung des anthropogenen Klimawandels dar. Die sekundären Anpassungen von Wolken an eine Veränderung atmosphärischer Aerosolkonzentrationen betreffen beispielsweise denWolken-Bedeckungsgrad und sind besonders komplex. Wolkenanpassungen können sich in der Veränderung der Wolkengrößen-Verteilung widerspiegeln. Wir präsentieren eine Methode, um mittels Beobachtungen der Wolkengrößen- Verteilung zeitliche Veränderungen in Aerosol-Wolken-Wechselwirkungen nachzuweisen. Wolkengrößen-Verteilung und Wolkenbedeckungsgrad wurden mittels hochauflösender Satellitendaten der Landsat-Serie berechnet. Das Ziel ist es, langjährige Trends im Wolkenbedeckungsgrad über Europa im Zeitraum 1985–2018 herzuleiten und ggf. den Einfluss stark rückläufiger Aerosolkonzentrationen während dieser Zeit zu identifizieren. Landsat-Daten haben eine räumliche Auflösung von bis zu 30 Metern. Um die damit verbundenen großen Datenmengen prozessieren zu können, nutzen wir dieWeb-basierte Plattform Google Earth Engine. Unsere langjährigen Trends zeigen eine großskaligen Zunahme im Wolkenbedeckungsgrad zwischen 1985 und 2018. Dies ist zurückzuführen auf einen relativen Rückgang in der Anzahl kleinerer Wolken (einige 10 bis 100 Meter Länge), während größere Wolken (mehrere Kilometer),welche mehr zum Bedeckungsgrad beitragen, häufiger wurden. Dies zeigt sich im negativen Trend des Power-Law-Exponenten der Wolkengrößen- Verteilung, welcher die relative Anzahl kleiner und großer Wolken beschreibt. Auch wenn sich diese Beobachtungen als signifikante Trends herausstellen, identifizieren wir darin kein klares Aerosol-Signal. Die Isolierung des puren Aerosoleffekts von anderen beeinflussenden Faktoren, wie der lokalen Meteorologie, bietet einen Ansatzpunkt für aufbauende Studien

Mechanical coupling in flashing ratchets

We consider the transport of rigid objects with internal structure in a flashing ratchet potential by investigating the overdamped behavior of a rod-like chain of evenly spaced point particles. In 1D, analytical arguments show that the velocity can reverse direction multiple times in response to changing the size of the chain or the temperature of the heat bath. The physical reason is that the effective potential experienced by the mechanically coupled objects can have a different symmetry than that of individual objects. All analytical predictions are confirmed by Brownian dynamics simulations. These results may provide a route to simple, coarse-grained models of molecular motor transport that incorporate an object's size and rotational degrees of freedom into the mechanism of transport.Comment: 9 pages, 10 figure

Multi-directional sorting modes in deterministic lateral displacement devices

Deterministic lateral displacement (DLD) devices separate micrometer-scale particles in solution based on their size using a laminar microfluidic flow in an array of obstacles. We investigate array geometries with rational row-shift fractions in DLD devices by use of a simple model including both advection and diffusion. Our model predicts novel multi-directional sorting modes that could be experimentally tested in high-throughput DLD devices containing obstacles that are much smaller than the separation between obstacles

Inhomogeneous soliton ratchets under two ac forces

We extend our previous work on soliton ratchet devices [L. Morales-Molina et al., Eur. Phys. J. B 37, 79 (2004)] to consider the joint effect of two ac forces including non-harmonic drivings, as proposed for particle ratchets by Savele'v et al. [Europhys. Lett. 67}, 179 (2004); Phys. Rev. E {\bf 70} 066109 (2004)]. Current reversals due to the interplay between the phases, frequencies and amplitudes of the harmonics are obtained. An analysis of the effect of the damping coefficient on the dynamics is presented. We show that solitons give rise to non-trivial differences in the phenomenology reported for particle systems that arise from their extended character. A comparison with soliton ratchets in homogeneous systems with biharmonic forces is also presented. This ratchet device may be an ideal candidate for Josephson junction ratchets with intrinsic large damping

Analytical model of brittle destruction based on hypothesis of scale similarity

The size distribution of dust particles in nuclear fusion devices is close to the power function. A function of this kind can be the result of brittle destruction. From the similarity assumption it follows that the size distribution obeys the power law with the exponent between -4 and -1. The model of destruction has much in common with the fractal theory. The power exponent can be expressed in terms of the fractal dimension. Reasonable assumptions on the shape of fragments concretize the power exponent, and vice versa possible destruction laws can be inferred on the basis of measured size distributions.Comment: 10 pages, 3 figure

Implementing an Insect Brain Computational Circuit Using III–V Nanowire Components in a Single Shared Waveguide Optical Network

Recent developments in photonics include efficient nanoscale optoelectronic components and novel methods for sub-wavelength light manipulation. Here, we explore the potential offered by such devices as a substrate for neuromorphic computing. We propose an artificial neural network in which the weighted connectivity between nodes is achieved by emitting and receiving overlapping light signals inside a shared quasi 2D waveguide. This decreases the circuit footprint by at least an order of magnitude compared to existing optical solutions. The reception, evaluation and emission of the optical signals are performed by a neuron-like node constructed from known, highly efficient III-V nanowire optoelectronics. This minimizes power consumption of the network. To demonstrate the concept, we build a computational model based on an anatomically correct, functioning model of the central-complex navigation circuit of the insect brain. We simulate in detail the optical and electronic parts required to reproduce the connectivity of the central part of this network, using experimentally derived parameters. The results are used as input in the full model and we demonstrate that the functionality is preserved. Our approach points to a general method for drastically reducing the footprint and improving power efficiency of optoelectronic neural networks, leveraging the superior speed and energy efficiency of light as a carrier of information.Comment: 28 pages, 6 figures; supplementary information 15 pages, 8 figure

Eine „dienende Rolle“ für den Finanzsektor? Nicht dienen, sondern funktionieren!

The image is undisputed in the political debate that the function of the financial sector is to "play servant" to the real economy, but the consequences derived from this debate are controversial. Clearer is the academic concept to restrict the functions of the financial sector deliberately. But such restriction is hardly convincing from the different persepectives of functionality. Because of this indetermination and, respectively, restriction, a "servant role" is apparently inappropriate as a useful yardstick for reorienting the financial sector. In line with this image, it would certainly be possible to improve crisis prevention, but at the price of cuts in important functions so that a "sevant role" as a concept of crisis prevention would not be desirable either

Molecular motor that never steps backwards

We investigate the dynamics of a classical particle in a one-dimensional two-wave potential composed of two periodic potentials, that are time-independent and of the same amplitude and periodicity. One of the periodic potentials is externally driven and performs a translational motion with respect to the other. It is shown that if one of the potentials is of the ratchet type, translation of the potential in a given direction leads to motion of the particle in the same direction, whereas translation in the opposite direction leaves the particle localized at its original location. Moreover, even if the translation is random, but still has a finite velocity, an efficient directed transport of the particle occurs.Comment: 4 pages, 5 figures, Phys. Rev. Lett. (in print