Influence of the impaction angle on the triboelectric charging of aerosol nanoparticles

A low pressure impactor is used to measure triboelectric charging behavior of metallic nanoparticles. Ag nanoparticles, produced by spark discharge, were impacted onto Pt sputtered targets. The influence of the impaction angle and impaction velocity on the triboelectric charging was investigated. While for perpendicular impaction the charge transfer behavior of previous work was confirmed, the oblique impaction revealed new phenomena. Additional charge transfer was observable, which increases with obliqueness. The possibility of mass transfer between particle and target due to the high-energy collisions was also investigated. SEM characterization and Auger spectroscopy indicate mass transfer from the particle to the target surface

Interaction of reactive gases with platinum aerosol particles at room temperature: effects on morphology and surface properties

Nanoparticles produced in technical aerosol processes exhibit often dendritic structures, composed of primary particles. Surprisingly, a small but consistent discrepancy was observed between the results of common aggregation models and in situ measurements of structural parameters, such as fractal dimension or mass-mobility exponent. A phenomenon which has received little attention so far is the interaction of agglomerates with admixed gases, which might be responsible for this discrepancy. In this work, we present an analytical series, which underlines the agglomerate morphology depending on the reducing or oxidizing nature of a carrier gas for platinum particles. When hydrogen is added to openly structured particles, as investigated by tandem differential mobility analysis (DMA) and transmission electron microscopy (TEM) analysis, Pt particles compact already at room temperature, resulting in an increased fractal dimension. Aerosol Photoemission Spectroscopy (APES) was also able to demonstrate the interaction of a gas with a nanoscaled platinum surface, resulting in a changed sintering behavior for reducing and oxidizing atmospheres in comparison to nitrogen. The main message of this work is about the structural change of particles exposed to a new environment after complete particle formation. We suspect significant implications for the interpretation of agglomerate formation, as many aerosol processes involve reactive gases or slightly contaminated gases in terms of trace amounts of unintended species

Diurnal Variation in Stretch Shortening Cycle and Non-Stretch Shortening Cycle Jumping Performance

This study assessed the diurnal variations, as well as the subjects’ perceptions of how time of day affects their jumping performance. Eighteen subjects participated in testing sessions at 7 a.m., noon, and 5 p.m., on the same day. Subjects performed squat jumps (SJ) and countermovement jumps (CMJ) on a force platform with peak ground reaction force (GRF), jump height, and reactive strength index-modified (RSImod) obtained for each jump. Diurnal differences for the CMJ were found for GRF (P = 0.048). Diurnal differences for the SJ were found in RSImod (P= 0.04). Subjective assessment of jumping explosiveness was significantly different across time of day (P = 0. 047). Lower body power training such as plyometrics, may be more effective at mid day than early morning or late afternoon

Investigation of particle formation of electrospray flame pyrolysis using a scanning mobility particle sizer

Die elektrohydrodynamische Zerstäubung von flüssigen Präkursoren gekoppelt mit der Flammensprühpyrolyse erlaubt die Synthese von verschiedenartigen, metalloxidischen Nanopartikel. Ein Aufbau bestehend aus einem definiert verfahrbaren Brenner und einer Probennahme in der Flamme eröffnet dabei die Möglichkeit der Erfassung von Partikelgrößenverteilungen entlang der Flammenhöhe. Die Bildung von Eisenoxid- und Siliziumdioxid-Partikel in einer Flamme konnte so mithilfe eines 1nm-SMPS-Aufbaus (Scanning Mobility Particle Sizer) auch in den Frühstadien der Partikelbildung erfasst werden. Hierbei zeigte sich, dass auch für einfache Präkursorlösungen bei hinreichend kleinen Tropfen hochwertige, homogene Nanopulver erzeugt werden können.Electrospray of liquid precursor coupled to flame spray pyrolysis allows for the synthesis of many different metal oxide nanoparticles. A setup consisting of a moveable burner and a static sampling system gives the possibility of characterizing particle size distributions across and along the flame. The particle formation of iron oxide and silica particles in a flame spray was investigated even for early stages using a 1nm scanning mobility particle sizer. Thereby it was found that even for simple precursor solutions high quality nanopowders could be produced as long as the droplet size is sufficiently small

Solving Fuzzy Job-Shop Scheduling Problems with a Multiobjective Optimizer

International audienceIn real-world manufacturing environments, it is common to face a job-shop scheduling problem (JSP) with uncertainty. Among different sources of uncertainty, processing times uncertainty is the most common. In this paper, we investigate the use of a multiobjective genetic algorithm to address JSPs with uncertain durations. Uncertain durations in a JSP are expressed by means of triangular fuzzy numbers (TFNs). Instead of using expected values as in other work, we consider all vertices of the TFN representing the overall completion time. As a consequence, the proposed approach tries to obtain a schedule that optimizes the three component scheduling problems (corresponding to the lowest, most probable, and largest durations) all at the same time. In order to verify the quality of solutions found by the proposed approach, an experimental study was carried out across different benchmark instances. In all experiments, comparisons with previous approaches that are based on a single-objective genetic algorithm were also performed

Desoxidation von gasgetragenen Pulvern

Metallische Pulver gelten als wichtige Ausgangsmaterialien in vielen Fertigungsprozessen, z. B. bei Fügeverfahren, additiver Fertigung, Beschichtung usw. Bei der Herstellung metallischer Pulver werden die Partikeloberflächen, selbst bei der Handhabung in der Inertgas-Umgebung, infolge von Sauerstoffspuren mit einer Oxidschicht bedeckt, welche für die Weiterverarbeitung und die Qualität der Endprodukte negativ sein kann. Das Projekt zielt darauf ab, die Desoxidation metallischer Pulver durch Wechselwirkung mit aktivierten Wasserstoffspezies zu realisieren. Um dieses Ziel zu erreichen, wurden Pulver in einer Wirbelschicht mit den aktivierten Wasserstoffspezies in Kontakt gebracht. Die Aktivierung wurde mittels dielektrischer Barriere-Entladung (DBD) erzielt und mit den Resultaten der rein thermisch aktivierten Wasserstoffspezies verglichen. Für die Einbringung der DBD-aktivierten Spezies wurden verschiedenen Geometrien untersucht, welche vom konvektiven Transport der DBD-Spezies in die Wirbelschicht bis zu der direkten Erzeugung des Plasmas in der Wirbelschicht reichen. Anhand einer einfachen Analytik basierend auf der Schüttdichte der Pulver konnte gezeigt werden, wie effektiv die verschiedenen Desoxidationsmethoden sind

A new method for deriving aerosol solar radiative forcing and its first application within MILAGRO/INTEX-B

We introduce a method for deriving aerosol spectral radiative forcing along with single scattering albedo, asymmetry parameter, and surface albedo from airborne vertical profile measurements of shortwave spectral irradiance and spectral aerosol optical thickness. The new method complements the traditional, direct measurement of aerosol radiative forcing efficiency from horizontal flight legs below gradients of aerosol optical thickness, and is particularly useful over heterogeneous land surfaces and for homogeneous aerosol layers where the horizontal gradient method is impractical. Using data collected by the Solar Spectral Flux Radiometer (SSFR) and the Ames Airborne Tracking Sunphotometer (AATS-14) during the MILAGRO (Megacity Initiative: Local and Global Research Observations) experiment, we validate an over-ocean spectral aerosol forcing efficiency from the new method by comparing with the traditional method. Retrieved over-land aerosol optical properties are compared with in-situ measurements and AERONET retrievals. The spectral forcing efficiencies over ocean and land are remarkably similar and agree with results from other field experiments

Synthesis of Pure and Fe-Doped TiO2_2 Nanoparticles via Electrospray-Assisted Flame Spray Pyrolysis for Antimicrobial Applications

We report a straightforward aerosol-based approach to synthesizing pure and Fe-doped TiO$_2$ nanoparticles by continuous electrospray-assisted flame spray pyrolysis (EAFSP). Initially, pure TiO$_2$ nanoparticles were prepared by electrospraying titanium diisopropoxide bis(acetylacetonate) (TDIP) at varying concentrations onto a grounded flame. In this regard, various in situ (phase Doppler anemometry, high-speed camera, and scanning mobility particle sizer) and ex situ (small-angle X-ray scattering, transmission electron microscopy, and BET adsorption isotherms) diagnostics were applied for the analysis of the in-flight droplet characteristics in the spray, such as droplet μ-explosions, as well as primary and agglomerate nanoparticle evolution within the process and the particulate product. Moreover, single-particle ICP-MS (inductively coupled plasma–mass spectrometry) in situ measurements have been conducted to get insight into the process that causes various particle morphologies and to open up the option of an in situ determination of the particle formation route. Subsequently, the EAFSP method was utilized to produce Fe-doped TiO$_2$ nanoparticles. The influences of the Fe$^{3+}$ dopant concentration on the particle size, crystal structure, crystallite sizes, phase formation, oxygen vacancy defects, and optical gaps were systematically investigated. The presented EAFSP synthesis, in contrast to conventional flame spray pyrolysis (FSP) with gas atomization of the solvent/precursor, eliminates the need for dispersion gas and complex solvents, making it a more efficient and environmentally friendly method for nanoparticle synthesis. Finally, we studied the application potential of EAFSP-synthesized pure and Fe-doped TiO$_2$ nanoparticles for fighting bacteria resistant to an antibiotic, here spectinomycin-resistant Escherichia coli. A clear inhibitory effect of the Fe-doped TiO$_2$ nanoparticles could be observed during the growth of bacteria in the liquid medium, up to 99.4%. These results point out the high potential of the designed Fe-doped TiO$_2$ nanoparticles to act as antimicrobial agents and treatments against infections

An improved constraint satisfaction adaptive neural network for job-shop scheduling

Copyright @ Springer Science + Business Media, LLC 2009This paper presents an improved constraint satisfaction adaptive neural network for job-shop scheduling problems. The neural network is constructed based on the constraint conditions of a job-shop scheduling problem. Its structure and neuron connections can change adaptively according to the real-time constraint satisfaction situations that arise during the solving process. Several heuristics are also integrated within the neural network to enhance its convergence, accelerate its convergence, and improve the quality of the solutions produced. An experimental study based on a set of benchmark job-shop scheduling problems shows that the improved constraint satisfaction adaptive neural network outperforms the original constraint satisfaction adaptive neural network in terms of computational time and the quality of schedules it produces. The neural network approach is also experimentally validated to outperform three classical heuristic algorithms that are widely used as the basis of many state-of-the-art scheduling systems. Hence, it may also be used to construct advanced job-shop scheduling systems.This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/01 and in part by the National Nature Science Fundation of China under Grant 60821063 and National Basic Research Program of China under Grant 2009CB320601

SEIS: Insight's Seismic Experiment for Internal Structure of Mars.

By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars' surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking's Mars seismic monitoring by a factor of ∼ 2500 at 1 Hz and ∼ 200 000 at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars' surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of M w ∼ 3 at 40 ∘ epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution.Electronic supplementary materialThe online version of this article (10.1007/s11214-018-0574-6) contains supplementary material, which is available to authorized users