bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictor control for non‐linear systems actuated via counter‐convecting transport PDEs
Authors: Cai Xiushan , Lin Cong , Zhan Xisheng , Liu Leibo
Published: December 2020

The authors investigate predictor control for the cascaded system of a non‐linear ordinary differential equation with counter‐convecting transport partial differential equations with propagation velocities dependent on partial differential equations states in this paper. Stability analysis of the closed‐loop system is shown by using the infinite‐dimensional backstepping transformations and an appropriate Lyapunov functional. A predictor control is developed such that the closed‐loop system is asymptotically stable. An example is given to illustrate the validity of the proposed method.
Improved noise‐to‐state stability criteria of random nonlinear systems with stochastic impulses
Authors: Feng Likang , Park Ju H. , Zhang Weihai
Published: December 2020

This paper considers noise‐to‐state stability for random non‐linear systems with stochastic impulses. The impulsive random non‐linear systems contain three random characteristics: the second‐moment processes in continuous dynamics, the sequence of random variables in discrete dynamics, and the number of stochastic impulses obeyed a renewal process. Firstly, the improved criteria of noise‐to‐state stability are established for random non‐linear systems subject to unstable stochastic impulses based on the uniformly asymptotically stable function. Secondly, improved Lyapunov approaches of NSS with unstable stochastic continuous dynamics are accomplished by the uniformly exponentially stable function. Finally, two numerical examples are used to illustrate the feasibility of the proposed methods.
Separation principle for discrete‐time quasi‐one‐sided Lipschitz nonlinear systems
Authors: Dong Wenqiang , Hu Guang‐Da , Cong Yuhao
Published: December 2020

This paper is concerned with output stabilisation for a class of discrete‐time quasi‐one‐sided Lipschitz nonlinear systems. Firstly, an observer is designed for estimating the state of the systems in terms of quasi‐one‐sided Lipschitz condition and quadratic inner‐boundness condition. Then, a state feedback controller is proposed to stabilize the systems. Subsequently, it is shown that the separation principle holds for stabilisation of the discrete‐time nonlinear systems based on the observer‐based controller. Under the quasi‐one‐sided Lipschitz condition, the state observer and feedback controller can be designed separately, even though the parameter of discrete‐time systems is not stabilisable and parameter is not detectable. Finally, two numerical examples are given to indicate the feasibility of the main results.
Probabilistic–proactive distribution network scheduling against a hurricane as a high impact–low probability event considering chaos theory
Authors: Nasri Amirhossein , Abdollahi Amir , Rashidinejad Masoud
Published: December 2020

High impact–low probability (HILP) incidents, such as hurricanes, usually and gravely damage electric distribution networks. A resilient distribution network must have an ability to recover itself with a fast restoration methodology against the effects of HILP events. Due to improve the electric distribution network resiliency against HILP incidents, this paper suggests a probabilistic–proactive distribution network operation model based upon the chaos theory (P‐PDNOMC(. Here, a resilience index based upon operational cost and load shedding cost is employed to decrease the effects of a hurricane as an HILP incident. P‐PDNOMC is formulated as a framework that consists of a novel hurricane modelling and operation scheduling in normal and emergency conditions with uncertainties considering. It should be noted that a prediction approach based on the chaos theory and the least‐squares support vector machine (LS‐SVM) is also designed to consider the provisional and spatial behaviour of the hurricane. Furthermore, this paper proposes a novel optimization framework for damaged lines determination based upon the P‐PDNOM C (DLsP‐PDNOM C) by considering multi‐zone and multi‐period damaged equipment budget constraints. Here, the load shedding cost is applied to present the efficiency of the proposed model. The numerical results indicate the resiliency enhancement of the electric distribution network in the face of HILP incidents.
A pricing strategy based on potential game and bargaining theory in smart grid
Authors: Yang Jie , Dai Yachao , Ma Kai , Liu Hongru , Liu Zhixin
Published: December 2020

In this paper, a two‐stage pricing framework is proposed for the electricity market which is consisted of a generation company (GC), multiple electric utility companies (EUC) and consumers. In the electricity wholesale market, the EUCs will choose an agent to negotiate the wholesale price with GC. An appropriate wholesale price plays an important role in the stable operation of the electricity wholesale market. However, it is challenging to find the optimal wholesale price. Therefore, the Raiffa‐Kalai‐Smorodinsky bargaining solution (RBS) is applied to realize the pricing equilibrium which is . In the electricity retail market, this study designs a retail pricing strategy based on the potential game, which can optimize both social welfare and the benefit of the EUCs. Moreover, the impact of demand disturbance on the benefit of the EUCs and GC is studied in the electricity retail market. Then an iterative pricing algorithm is proposed for the two‐stage pricing model. The simulation results reveal that the demand disturbance has little effect on the benefit of the EUCs and GC, indicating the reliable/promising robustness of the algorithm.
Power transformer fault diagnosis considering data imbalance and data set fusion
Authors: Zhang Yang , Chen Hong Cai , Du Yaping , Chen Min , Liang Jie , Li Jianhong , Fan Xiqing , Yao Xin
Published: December 2020

Improving the accuracy of transformer dissolved gas analysis is always an important demand for power companies. However, the requirement for large numbers of fault samples becomes an obstacle to this demand. This article creatively uses a large number of health data, which is much easier to obtain by power companies, to improve diagnosis accuracy. Comprehensive investigations from the view of both data set and methodology to deal with this problem are presented. A data set consists of 9595 health samples and 993 fault samples is used for analysis. The characteristics of the data set and the influence of the health data on diagnostic accuracy are discussed. The performance of many state‐of‐art algorithms that handle the imbalanced problem is evaluated. Meanwhile, an efficient fault diagnosis algorithm named self‐paced ensemble (SPE) is presented. In SPE, classification hardness is proposed to include the data characteristic in the classification. This method can guarantee the diversity of the data set and keep high performance. According to the experiment results, the superior of SPE is confirmed and also proves that involving more health samples can improve transformer diagnosis when fault data are limited.
Micro‐mechanism study on synergistic degradation of the oil‐paper insulation with dibenzyl disulfide, hexadecyl mercaptan and benzothiophene
Authors: Cong Haoxi , Pan Hao , Hu Xuefeng , Zhang Minhao , Li Qingmin
Published: December 2020

In recent years, there have been many cases of transformer failures caused by corrosive sulfides. At present, research mainly focuses on the single sulfide dibenzyl disulphide, but few research on multiple sulphur or the oil‐paper hybrid insulation. In this study, three typical sulfides dibenzyl disulfide, hexadecyl mercaptan and benzothiophene were selected to form seven sulfide‐oil‐paper models. Then relaxation calculations were carried out, and through molecular dynamics simulation, the synergistic effect of different sulfides on the properties of insulating paper and insulating oil was discussed. Results show that the coexistence of the three sulfides has the most severe weakening on the mechanical properties of cellulose, and it also causes great damage to hydrogen bonds. Hexadecyl mercaptan has a weaker effect on hydrogen bond destruction, but it will greatly aggravate the cellulose chain movement. The viscosity of insulating oil is generally increased by the influence of sulfide. Hexadecyl mercaptan is the main factor affecting the viscosity. Thiophene has little effect on the viscosity, ctive protection technology on sulphur corrosion.
Impact of active power recovery rate of DFIG wind farms on first swing rotor angle stability
Authors: Munkhchuluun Enkhtsetseg , Meegahapola Lasantha , Vahidnia Arash
Published: December 2020

The first swing rotor angle stability is still an important stability challenge for modern power systems integrated with a large number of renewable energy‐based sources, such as wind farms and solar‐photovoltaic farms. Therefore, innovative strategies must be developed to exploit the full potential of doubly fed induction generators (DFIGs) to improve the first swing rotor angle stability in the system. This study presents a new active power logic (APL) controller for DFIGs which can reduce the active power during the fault and slowly recover it after the fault to allow synchronous generators to increase the electrical power during and after the fault; thus, enabling synchronous generators to improve the first swing rotor angle stability. The feasibility of the proposed control scheme is investigated via theoretical analysis and simulation studies. The reliability and voltage stability test system is used to demonstrate the effectiveness of the proposed scheme for local and remote faults and increased DFIG penetration conditions. The comparative results show that the proposed APL controller of the DFIG improves the first swing rotor angle stability, specifically when the DFIGs are located near the synchronous generators.
Impact of grid partitioning algorithms on combined distributed AC optimal power flow and parallel dynamic power grid simulation
Authors: Kyesswa Michael , Murray Alexander , Schmurr Philipp , Çakmak Hüseyin , Kühnapfel Uwe , Hagenmeyer Veit
Published: December 2020

The complexity of most power grid simulation algorithms scales with the network size, which corresponds to the number of buses and branches in the grid. Parallel and distributed computing is one approach that can be used to achieve improved scalability. However, the efficiency of these algorithms requires an optimal grid partitioning strategy. To obtain the requisite power grid partitionings, the authors first apply several graph theory based partitioning algorithms, such as the Karlsruhe fast flow partitioner (KaFFPa), spectral clustering, and METIS. The goal of this study is an examination and evaluation of the impact of grid partitioning on power system problems. To this end, the computational performance of AC optimal power flow (OPF) and dynamic power grid simulation are tested. The partitioned OPF‐problem is solved using the augmented Lagrangian based alternating direction inexact Newton method, whose solution is the basis for the initialisation step in the partitioned dynamic simulation problem. The computational performance of the partitioned systems in the implemented parallel and distributed algorithms is tested using various IEEE standard benchmark test networks. KaFFPa not only outperforms other partitioning algorithms for the AC OPF problem, but also for dynamic power grid simulation with respect to computational speed and scalability.
Classification of breast mass in two‐view mammograms via deep learning
Authors: Li Hua , Niu Jing , Li Dengao , Zhang Chen
Published: December 2020

Breast cancer is the second deadliest cancer among women. Mammography is an important method for physicians to diagnose breast cancer. The main purpose of this study is to use deep learning to automatically classify breast masses in mammograms into benign and malignant. This study proposes a two‐view mammograms classification model consisting of convolutional neural network (CNN) and recurrent neural network (RNN), which is used to classify benign and malignant breast masses. The model is composed of two branch networks, and two modified ResNet are used to extract breast‐mass features of mammograms from craniocaudal (CC) view and mediolateral oblique (MLO) view, respectively. In order to effectively utilise the spatial relationship of the two‐view mammograms, gate recurrent unit (GRU) structures of RNN is used to fuse the features of the breast mass from the two‐view. The digital database for screening mammography (DDSM) be used for training and testing our model. The experimental results show that the classification accuracy, recall and area under curve (AUC) of our method reach 0.947, 0.941 and 0.968, respectively. Compared with previous studies, our method has significantly improved the performance of benign and malignant classification.
Development of underground coal mine drainage monitoring system based on DSP
Authors: Shi Xiaojuan , Qi Biao , Zhang Xiude
Published: December 2020

Aiming at solving problems such as non‐linear, time‐varying parameters, and weak digital computing capability in the underground drainage system, the monitoring system is built based on a digital signal processor (DSP). Adopting DSP28335 as its control core, the hardware circuit and software program are designed in this monitoring system. The single‐neuron fuzzy proportional, integration, and differential (PID) control algorithm with feedforward proportional and differential compensation is proposed in this study. The simulation results are compared and analysed with a traditional PID algorithm, fuzzy PID algorithm, and single‐neuron fuzzy PID algorithm with feedforward in Matlab/Simulink, and the experimental platform is built to verify the application effect of three control algorithms. The simulation and experiment results show that the single‐neuron fuzzy PID algorithm with feedforward has significant advantages such as shorter adjustment time, good adaptivity, and strong anti‐interference ability, which could effectively improve the work efficiency of an underground mine drainage monitoring system.
Comparison of dynamical behavior between fractional order delayed and discrete conformable fractional order tumor-immune system
Authors: Balci Ercan , Kartal Senol , Ozturk Ilhan
Published: December 2020

In this paper, we analyze the dynamical behavior of the delayed fractional-order tumor model with Caputo sense and discretized conformable fractional-order tumor model. The model is constituted with the group of nonlinear differential equations having effector and tumor cells. First of all, stability and bifurcation analysis of the delayed fractional-order tumor model in the sense of Caputo fractional derivative is studied, and the existence of Hopf bifurcation depending on the time delay parameter is proved by using center manifold and bifurcation theory. Applying the discretization process based on using the piecewise constant arguments to the conformable version of the model gives a two-dimensional discrete system. Stability and Neimark–Sacker bifurcation analysis of the discrete system are demonstrated using the Schur-Cohn criterion and projection method. This study reveals that the delay parameterτin the model with Caputo fractional derivative and the discretization parameterhin the discrete-time conformable fractional-order model have similar effects on the dynamical behavior of corresponding systems. Moreover, the effect of the order of fractional derivative on the dynamical behavior of the systems is discussed. Finally, all results obtained are interpreted biologically, and numerical simulations are presented to illustrate and support theoretical results.
Nierenversagen im Rahmen von autoimmunen Systemerkrankungen
Authors: Weinmann-Menke Julia
Published: December 2020

Nierenfunktionsstörungen bei Patienten mit rheumatischen Erkrankungen sind keine Seltenheit und häufig Prognose-bestimmend. Einige dieser rheumatologischen Erkrankungen werden unter anderem durch ihre Nierenbeteiligung und hier insbesondere durch das Auftreten eines Nierenversagens diagnostiziert. Dies zeigt schon, dass die Nierenbeteiligung bei rheumatologischen Erkrankungen sehr variabel in der Intensität ausfallen kann und von einer leichten Nierenfunktionsstörung (z. B. bei der rheumatoiden Arthritis) bis zum Nierenversagen (z. B. bei den Kleingefäßvaskulitiden, Lupusnephritis, Goodpasture-Syndrom oder der renalen Krise bei der systemischen Sklerose) reichen kann. Wichtig ist es hier, die Differenzierung der Ursache, z. B. chronische Schäden wie Hypertonie/Diabetes versus Manifestation der rheumatologischen Grunderkrankung oder medikamentös toxischen Nebenwirkungen vorzunehmen. Hierbei nimmt die rasche und gezielte Diagnostik einen hohen Stellenwert ein, welche von der gezielten Anamnese, Urindiagnostik (Urinsediment, Proteinurie), serologischen Diagnostik, Sonografie bis hin zur Nierenbiopsie reicht. Das frühe Erkennen sowie die rasche Einleitung einer dann entsprechenden immunsuppressiven Therapie kann bei entzündlichen rheumatologischen Systemerkrankungen die renale Prognose verbessern und damit auch die Mortalität der Patienten maßgeblich beeinflussen.
Screening auf problematischen Alkoholkonsum – Erhebung zur Umsetzung der S3-Leitlinienempfehlungen in der transdisziplinären Versorgung einer Modellregion
Authors: Frischknecht Ulrich , Hoffmann Sabine , Steinhauser Alisa , Lindemann Christina , Buchholz Angela , Manthey Jakob , Schulte Bernd , Rehm Jürgen , Kraus Ludwig , Verthein Uwe , Reimer Jens , Kiefer Falk
Published: December 2020

Ziel Erfassung der Häufigkeit, mit der zentral in die Gesundheitsversorgung der Zielgruppe eingebundene Berufsgruppen auf problematischen Alkoholkonsum screenen. Die S3-Leitlinie „Screening, Diagnose und Behandlung alkoholbezogener Störungen“ empfiehlt „allen Patient/innen in allen Settings“ ein fragebogenbasiertes Screening anzubieten.

Methodik Querschnittsstudie zur Umsetzungshäufigkeit von Screenings auf problematischen Alkoholkonsum durch Fachärzt/innen (Allgemein- und Innere Medizin, Gynäkologie, Psychiatrie und Psychotherapie, Pädiatrie, Kinder- und Jugend- Psychiatrie), Psychotherapeut/innen, Sozialarbeiter/innen und Hebammen/Geburtshelfer in der Modellregion Bremen. Mittels logistischer Regression wurden behandler/innenseitige Einflussfaktoren auf die Umsetzung von Screenings exploriert.

Ergebnisse Mit Rücklaufquoten von etwa 20% berichteten die verschiedenen Berufsgruppen, durchschnittlich bei 6,9% aller behandelten Patient/innen innerhalb der zurückliegenden 4 Wochen ein fragebogenbasiertes Alkoholscreening durchgeführt zu haben. Meist wurden eigene Formulierungen anstatt empfohlener Instrumente (AUDIT, AUDIT-C) genutzt. Höhere Screeningraten wurden für Patient/innen mit neu diagnostiziertem Bluthochdruck (21,2%), alkoholassoziierten Folgeerkrankungen (43,3%) und psychischen Störungen (39,3%) berichtet. Die Kenntnis der S3-Leitlinie war mit einer häufigeren Umsetzung von Screenings verbunden (OR=4,67; 95% KI 1,94–11,25, p<0,001).

Schlussfolgerungen Das von der Leitlinie empfohlene flächendeckende, fragebogenbasierte Screening auf problematischen Alkoholkonsum ist von einer praktischen Umsetzung weit entfernt. Maßnahmen zu einer breiteren Bekanntmachung der S3-Leitlinie erscheinen sinnvoll, um eine häufigere Anwendung von Alkoholscreenings im Gesundheitswesen zu fördern.
Neurologische Notfälle bei rheumatologischen Erkrankungen
Authors: Wolf Joachim
Published: December 2020

Das zentrale und periphere Nervensystem ist ein häufig geschädigtes Organ bei rheumatologischen Erkrankungen. Treten die neurologischen Symptome notfallmäßig auf, sind schwerwiegende und lebensbedrohliche Folgen für den Patienten meist nur durch eine rasche Diagnostik und Therapie abwendbar, weshalb ein enger Austausch zwischen Rheumatologen und Neurologen notwendig ist. Patienten mit einem systemischen Lupus erythematodes, einer rheumatoiden Arthritis oder einer systemischen Vaskulitis sind besonders gefährdet, akute Schädigungen des Nervensystems zu erleiden. Der folgende Artikel stellt relevante neurologische Notfallsyndrome bei rheumatologischen Erkrankungen dar und gibt Ihnen eine Übersicht über diagnostische und therapeutische Optionen.
Differential Uptake of Telehealth for Prenatal Care in a Large New York City Academic Obstetrical Practice during the COVID-19 Pandemic
Authors: Limaye Meghana A. , Lantigua-Martinez Meralis , Trostle Megan E. , Penfield Christina A. , Conroy Erin M. , Roman Ashley S. , Mehta-Lee Shilpi S.
Published: December 2020

During the coronavirus disease 2019 (COVID-19) pandemic in New York City, telehealth was rapidly implemented for obstetric patients. Though telehealth for prenatal care is safe and effective, significant concerns exist regarding equity in access among low-income populations. We performed a retrospective cohort study evaluating utilization of telehealth for prenatal care in a large academic practice in New York City, comparing women with public and private insurance. We found that patients with public insurance were less likely to have at least one telehealth visit than women with private insurance (60.9 vs. 87.3%, p < 0.001). After stratifying by borough, this difference remained significant in Brooklyn, one of the boroughs hardest hit by the pandemic. As COVID-19 continues to spread around the country, obstetric providers must work to ensure that all patients, particularly those with public insurance, have equal access to telehealth.

Key Points
Consistently biased: documented consistency in self-reported holiday healthfulness behaviors and associated social desirability bias
Authors: Bir Courtney , Widmar Nicole Olynk
Published: December 2020

Holiday healthfulness conversations are dominated by overindulgence of consumption and then, largely in reference to resolutions to do better, physical activity, and exercise aspirations. Consistency was found in self-reported agreement with a series of holiday healthfulness statements, across time, holidays (Thanksgiving versus Christmas), and samples of respondents. The largest proportion of respondents displaying social desirability bias (SDB) were found in response to two statements, namely “I will consume more alcohol during the holiday season than at other times of the year” at (63–66%) and “I make it a New Year’s Resolution to lose weight” (60–63%). Cheap talk was tested as a mechanism to reduce SDB in holiday healthfulness reporting, but showed only limited efficacy compared to the control group surveyed simultaneously. Nonetheless, the consistency across time in reporting and SDB are notable in both self-reporting of health-related data and in studying a unique consumption period around the holidays. Healthcare providers and researchers alike seek to improve the accuracy of self-reported data, making understanding of biases in reporting on sensitive topics, such as weight gain and eating over the holiday season, of particular interest.
Heritage and interculturality in EU science diplomacy
Authors: Andersen Casper , Clopot Cristina , Ifversen Jan
Published: December 2020

In recent years, culture and heritage have explicitly entered into science diplomacy debates and initiatives within the EU system and in EU’s foreign policy. For EU’s external relations heritage offers opportunities for developing partnerships based on shared, entangled histories but also challenges posed by dealing with difficult pasts of domination and colonialism. The paper, therefore, presents a new conceptual model for European science diplomacy that can enable more equitable ways of dealing with colonial heritage in relations between EU countries and partners outside Europe. It does so by combining recent literature on science diplomacy, heritage diplomacy, decolonial thinking, and on the concepts of interculturality. We argue that to engage successfully with colonial legacies and heritage, the concept of science diplomacy needs to be developed from a traditional “diffusionist” understanding towards a dialogical approach, which is epismologically open and acknowledges the inequalities in global knowledge production. In the second part of the paper, the practical implications of the theoretical framework are fleshed out in a discussion of three cases involving colonial heritage: The Tendaguru Fossil Collection, the Royal Museum for Central Africa in Brussels, and the work of Canadian indigenous artist Sonny Assu.
Morphology driven spatial dependence of wetting, evaporation, and unidirectional spreading of water on hexagonally patterned gold microstructure arrays
Authors: S. Brindhu Malani , P. Viswanath
Published: December 2020

We report here our investigations on the wettability, evaporation, and unidirectional spreading behavior of water on a patterned substrate. Using colloidal lithography, hexagonally ordered gold microstructure arrays with varying morphologies were fabricated along the length of the substrate. Three different regions of the substrate exhibiting different morphologies (R1: microshells, R2: microshells with interstice, and R3: microholes) and their transition positions were identified using a field emission scanning electron microscope. Spatial dependence of wetting and the influence of surface functionalization were investigated in these regions. In R1 and R2, wetting studies show hydrophobic behavior for both the as-prepared (θ=116°−120°) and octadecanethiol (ODT, θ=128°–132°) functionalized substrates. In contrast, R3 exhibits hydrophilicity (θ=84°), which transforms to hydrophobicity (θ=102°) post ODT-functionalization. Interestingly, underwater wettability investigations of the same substrate using oil (air bubble) show superoleophobicity (superaerophobicity) that after functionalization transforms to oleophilicity (aerophobicity) for all regions. Furthermore, the evaporation of the water droplet has been studied for different regions. It shows clear distinction in the modes of evaporation for the as-prepared and functionalized substrates. Taking into account geometrical parameters, we calculated theoretical contact angles for different wetting states and compared them with our experimental results. We have found evidence for the occurrence of the penetrating Cassie–Baxter state for both as-prepared (water penetration angle, δ=50° for all regions) and ODT-functionalized substrates (δ=56° for R1 and R2 and δ=0° for R3). Unidirectional spreading of water against gravity is observed for different inclinations of the substrate at the transition positions (e.g., at 10 mm, droplet velocity = 0.83 mm/s). Our study has potential implications in microfluidic devices, biosensors, and water transportation.
Quasi-geometric integration of guiding-center orbits in piecewise linear toroidal fields
Authors: Eder M. , Albert C. G. , Bauer L. M. P. , Kasilov S. V. , Kernbichler W.
Published: December 2020

A numerical integration method for guiding-center orbits of charged particles in toroidal fusion devices with three-dimensional field geometry is described. Here, high order interpolation of electromagnetic fields in space is replaced by a special linear interpolation, leading to locally linear Hamiltonian equations of motion with piecewise constant coefficients. This approach reduces computational effort and noise sensitivity, while the conservation of total energy, magnetic moment and phase space volume is retained. The underlying formulation treats motion in piecewise linear fields exactly and, thus, preserves the non-canonical symplectic form. The algorithm itself is only quasi-geometric due to a series expansion in the orbit parameter. For practical purposes, an expansion to the fourth order retains geometric properties down to computer accuracy in typical examples. When applied to collisionless guiding-center orbits in an axisymmetric tokamak and a realistic three-dimensional stellarator configuration, the method demonstrates stable long-term orbit dynamics conserving invariants. In Monte Carlo evaluation of transport coefficients, the computational efficiency of quasi-geometric integration is an order of magnitude higher than with a standard fourth order Runge–Kutta integrator.
Long-wavelength dielectric properties and infrared active optical phonon modes of molecular beam epitaxy ScxAl1−xN determined by infrared spectroscopic ellipsometry
Authors: Mock Alyssa L. , Jacobs Alan G. , Jin Eric N. , Hardy Matthew T. , Tadjer Marko J.
Published: December 2020

Tuning the optical, electronic, and long-wavelength properties of group-III nitride alloys can be achieved by alloying AlN with ScN. We report here on the infrared dielectric functions determined from spectroscopic ellipsometry of (0001) wurtzite ScxAl1−xN with compositions of 0≤x≤0.20 grown by molecular beam epitaxy on c-plane sapphire substrates. We also report the optical phonons and their parameters determined in our analysis and compare with those in the previous literature. We find that all phonons shift to a lower wavenumber as a function of scandium incorporation, and we also see evidence of a decrease in crystal quality. Further, we report the high frequency and static dielectric constants and the Born effective charge as well as their evolution with the scandium content.
A monochromatic confocal micro-x-ray fluorescence (μXRF) spectrometer for the lab
Authors: Ingerle D. , Swies J. , Iro M. , Wobrauschek P. , Streli C. , Hradil K.
Published: December 2020

Confocal micro-x-ray fluorescence (μXRF) is a powerful tool to analyze the spatial distribution of major, minor, and trace elements in three dimensions. Typical (confocal) μXRF measurements in the lab use polychromatic excitation, complicating quantification and fundamental parameter-based corrections and furthermore deteriorating peak-to-background ratios due to scattered bremsstrahlung. The goal for the new setup was to remedy these problems, without sacrificing spatial resolution, and keep it flexible for different excitation energies and transportation to other sources. The source assembly consists of a water-cooled fine-focus x-ray diffraction tube and a parallel beam-mirror, which produces a quasi-parallel, monochromatic beam. The presented results were obtained using a 2 kW molybdenum tube and a mirror for Mo-Kα. The confocal setup itself consists of two polycapillary half-lenses, one for the source side and the other for the detector side, where a 50 mm2 silicon drift detector is mounted. Both polycapillaries have a focus size of ∼15 μm for Mo-Kα. The second polycapillary can also be exchanged for a custom-designed collimator in order to perform non-confocal μXRF. Details of the technical setup and results from technical and biological samples are presented. Detection limits for selected elements from Ca to Pb in the confocal and non-confocal mode were established (e.g., 1 μg/g non-confocal and 20 μg/g confocal for As) using the NIST standard reference materials (SRMs) 621 and 1412. Furthermore, the results of the measurements of SRM 621 were evaluated using the fundamental parameter based quantification software ATI-QUANT. The results are compared with the certified values and generally are in good agreement.
Enhancement of the Seebeck coefficient and power factor in gated silicene superlattices induced by aperiodicity
Authors: Guzmán E. J. , Molina-Valdovinos S. , Oubram O. , Rodríguez-Vargas I.
Published: December 2020

This paper theoretically investigates the impact of aperiodic sequences in the ballistic transport and thermoelectric effect in silicene gated superlattices. In our analysis, we have implemented the well-known Fibonacci, Thue–Morse, and triadic Cantor type sequences. The transfer matrix technique and the Landauer–Bütikker formalism are used to calculate the transmission probability and the conductance, respectively. The Cutler–Mott formula is employed to estimate the Seebeck coefficient, and the thermoelectric power factor is then obtained. We found that the transmission minibands of aperiodic superlattices exhibit a much more fragmented structure in comparison to that reported in the periodic case. Consequently, the conductance curve presents a more pronounced oscillating shape, which improves the thermoelectric properties. In particular, the Seebeck coefficient has reached values up to 78.2 mV/K for Fibonacci, 233.0 mV/K for Thue–Morse, and 436.3 mV/K for Cantor. In addition, the power factor has been substantially increased, reaching peaks of approximately 8.2, 50.2, and 2.1 nW/K2 for the mentioned sequences, respectively. The best results were obtained for spindown (spinup) charge carriers in the K (K′) valley. Besides, an additional improvement is obtained by considering superior generations of the aperiodic sequences. Finally, our findings are supported through the redistribution of the density of the states, which is induced by the aperiodicity of the nanostructure as well as by the low-dimensionality of the thermoelectric device.
Effect of crystal orientation on droplet wetting behavior on single-crystal Al2O3 substrates: An experimental study
Authors: He Chengyu , Liu Tie , Tian Lei , Xiao Yubao , Yuan Shang , Wang Qiang
Published: December 2020

The wetting property of liquids on a solid surface is of key relevance to many areas ranging from biological systems to industrial applications. The wetting behavior of water, glycerin, and castor oil (featuring varying viscosities and surface energies) on single-crystal α-Al2O3 substrates with various crystal orientations of (0001), (112¯0), (101¯0), and (011¯2) was studied using the improved sessile drop method at room temperature and a closed environment. The effects of substrate crystal orientation on the liquid wetting behavior and its dependence on the liquid type were investigated. The contact angle of all three liquids on the (0001)-orientated substrates was obviously smaller than those of the other substrate orientations. The effects of α-Al2O3 substrate crystal orientation on the liquid wetting behavior on the substrates can be attributed to the liquid and substrate surface energies, the liquid viscosity, and the substrate atomic arrangement. The wetting process of water on α-Al2O3 could be divided into two stages. The contact angle was basically unchanged in stage I, and evaporation of droplets causes stepwise decreases of the contact angle in stage II. The height and contact angle of glycerin and castor oil on the substrates change very slowly in 1800 s. The findings of this study help provide a better understanding of the wetting behavior of liquids on solids and its mechanism.
Stimulated Raman scattering and defect-based photoconductivity in mixtures of CdS/TiO2
Authors: Nila Andreea , Baibarac Mihaela
Published: December 2020

Stimulated Raman scattering (SRS) is studied in polycrystalline CdS/TiO2 mixtures based on laser power and temperature dependences in Raman investigation. Our Raman analysis reveals several features of nonlinear behavior, such as nonlinear laser power dependencies or high enhancement of Raman lines at a low temperature due to the intrinsic nonlinear nature of CdS, a high light scattering inside the matter, and a trap-based diffusive medium in a grain-boundary system. In particular, building up experimental evidence of conductivity at various temperatures, it is shown that the samples exhibit thermally activated conductivity due to potential local barriers revealed by a considerable fraction of the grain-boundaries in a diffusive medium. Taking into account the defect-based conductivity, a double Poole–Frenkel barrier is established within the grain-boundaries of CdS/TiO2 mixtures, and their barrier energies are investigated considering the temperature-dependent dark current of the grain-boundary model. We thus demonstrate that diffusive medium-based defects in a grain-boundary model makes CdS/TiO2 mixtures behave efficiently in nonlinear processes such as SRS. These features are of particular interest for optical communication technology, and the fundamental application of the SRS effect is semiconductor optical amplifiers.
Physical interpretation of a pulsed atmospheric pressure plasma jet following parametric study of the UV–to–NIR emission
Authors: Gazeli K. , Svarnas P. , Lazarou C. , Anastassiou C. , Georghiou G. E. , Papadopoulos P. K. , Clément F.
Published: December 2020

In the present report, an atmospheric pressure plasma jet is sustained in a helium channel by high square wave unipolar voltage. The gas flow rate and the square wave features (amplitude, frequency, and duty cycle) are varied over a wide range, while the plasma ultraviolet to near infrared emission is recorded. The plasma emission pattern, the propagation dynamics of the involved ionization fronts, the relative density of critical excited species, and the rotational and vibrational temperatures of neutral and ionic species are measured. An optimum operational window is found corresponding to a helium flow rate of 2 slm, a pulse amplitude of 7.5 kV, a pulse repetition rate of 10 kHz, and a pulse duty cycle of 5%–7%. Under these conditions, a plasma jet length close to 45 mm and a gas temperature close to 325 K are obtained, while a high yield of OH, N2(SPS), N2+(FNS), N2(FPS), He*, O*, and NOγ is achieved. The results are found to be in good agreement with the bibliography and motivate a consideration on the involved physical mechanisms. The plasma jet propagation with respect to the reactive species production is discussed based on the local electric field variation over the high voltage pulse width.
Numerical study and buoyancy–drag modeling of bubble and spike distances in three-dimensional spherical implosions
Authors: El Rafei M. , Thornber B.
Published: December 2020

High-resolution three-dimensional implicit large eddy simulations of implosion in spherical geometries are presented. The growth of perturbations is due to Rayleigh–Taylor (RT) and Richtmyer–Meshkov (RM) instabilities and also to geometric convergence and compression effects. RM and RT instabilities have been studied extensively in planar configurations, but there are comparatively few studies on spherical geometries. Planar geometries lack the effect of convergence that changes the morphology and growth of perturbations in spherical geometries. This paper presents a study of turbulent mixing in spherical geometries considering different narrowband (NB) and broadband multimode initial perturbations and examines several quantities including the evolution of the integral mixing layer width and integral bubble and spike heights using novel integral definitions. The growth of the bubble and spike is modeled using a Buoyancy–Drag (BD) approach that is based on simple ordinary differential equations to model the growth of the turbulent mixing layer. In a recent study, Youngs and Thornber [“Buoyancy-drag modelling of bubble and spike distances for single-shock Richtmyer-Meshkov mixing,” Physica D 410, 132517 (2020)] constructed modifications to the BD equations to take into account the early stages of the mixing process that are dependent on the initial conditions. Those modifications are shown to be important to obtain correct results. The current study adopted the same modifications and adapted the BD equations to the spherical implosion case. The results of the BD model are compared with those of different initial NB cases that include different initial amplitudes and wavelengths of the perturbations, for validation purposes. The predictions from the new BD model are in very good agreement with the numerical results; however, there exist some limitations in the accuracy of the model, in particular the use of the interface position and fluid velocity from one-dimensional data.
Fast-ion-induced secondary ion emission from submicron droplet surfaces studied using a new coincidence technique with forward-scattered projectiles
Authors: Majima T. , Mizutani S. , Mizunami Y. , Kitajima K. , Tsuchida H. , Saito M.
Published: December 2020

A mass spectrometric study of secondary ions emitted from droplet surfaces by MeV-energy heavy ion impact was performed to investigate fast-ion-induced molecular reaction processes on liquid surfaces. Herein, a new coincidence technique was developed between secondary ions and scattered projectile ions at a small forward angle. The advantages of this technique were demonstrated by measurement of the collision between 4-MeV C3+ and ethanol droplets. Secondary ion emission probabilities were obtained directly from the coincidence data. Notably, this technique enabled positive fragment ions that had not been identified in previous measurements to be observed by suppressing the strong background originating from gas-phase molecules more than 104-fold. H+, H3O+, C2H5+, and C2H5O+ were found to be produced as major positive fragment ions, in addition to minor fragments H2+, C2H3+, and CH2OH+. Production of these ions suggests that competition between rapid hydrogen ion emission from multiply ionized states and intermolecular proton transfer accompanied by fragmentation through protonated ethanol occurs after fast heavy-ion collisions. Clarification of the positive fragment ions also revealed the characteristic features of negative ions. Negative ions were realized to exhibit higher degrees of fragmentation and reactivity compared with positive ions. Furthermore, the energy loss by forward-scattered ions during droplet penetration was used to evaluate the target thickness at a submicron level. Variations in secondary ion yield, mass distribution, and kinetic energies depending on the penetration length were observed below 1 µm. These results highlight the unknown mechanism of these “submicron effects” observed in secondary ion emission processes as a new phenomenon.
In Neotropical savannas, altitude affects the diversity of the Anisoptera but not the Zygoptera (Insecta: Odonata)
Authors: Palacino-Rodríguez Fredy , Brito Joás da Silva , Batista Calvão Lenize , Sabogal Gonzalez Alexander , Juen Leandro
Published: December 2020

Lentic and lotic habitats, combined with varying altitudes, may have differential effects on communities of the Order Odonata. We sampled adult odonates at 94 waterbodies of the Orinoquía region of eastern Colombia. Our hypothesis was that species composition and richness, as well as abundance, would be affected by both altitude and habitat. Overall, 70 of the 100 species recorded in the study were sampled in both lotic and lentic environments, with 16 species (5 in the Suborder Zygoptera and 11 in the Suborder Anisoptera) occurring only in lentic habitats and 14 occurring exclusively in lotic habitats (13 Zygoptera, 1 Anisoptera). The results of the analysis indicated that the species richness and abundance of anisopterans were affected by altitude, whereas the diversity of zygopterans was not affected in any way. Despite these mixed findings, the results for anisopterans were consistent with the results of previous studies, which have indicated altitude as a primary determinant of the Odonata diversity through its effect on the dynamics of water flow and the shift from lentic to more lotic environments. Further studies over a more ample altitudinal gradient should provide more conclusive evidence, particularly regarding the role played by both altitude and habitat on the local diversity of odonates.
Papatuanuku, Earth Mother: indigenous knowledge in 21st century soil management
Authors: McGowan Robert
Published: December 2020

On 20 March 2017 the New Zealand parliament passed the Te Awa Tupua (Whanganui River Claims Settlement) Bill which established the Whanganui River as a legal ‘person’ with all of the rights, powers, duties, and liabilities of the same. The Act endorses and illustrates how Māori perceive their relationship to the natural world. The passing of the Act challenged the river people to restore their ancestral river to good health. Changes in land use beginning in the later part of the 19th century had seen soil fertility decline, water quality deteriorate and the soils that sustained life in its catchment increasingly washed out to sea. These impacts profoundly changed the lifestyles of the people that belonged to it. Describing the issues facing the river iwi (tribes) and their response to them will help illustrate traditional understandings relating to the river, the whenua (the land) and the life sustaining capacity of the soil. It also serves to demonstrate the relevance of traditional knowledge to addressing the current ecological crisis. This viewpoint focuses on key concepts from Māori understandings of the natural world that relate to the primary themes of this conference and suggest how they can contribute towards deepening and broadening our knowledge of soils and what needs to be done to sustain them. In particular the concept of ‘mauri’ will be explored and how that relates to the capacity of soils to support the life that belongs there. Māori, and many traditional peoples, regard the whole landscape as essentially interdependent and consider that the wellness of any part of it, be it soils, vegetation, water quality, etc., can only be understood within the context of the whole network of connections that sustain life. The challenge for researchers, from an indigenous perspective, is to be mindful of the ‘whole’ while focusing on the areas of their particular expertise.
Vamos en Palma ‘we are going to Palma’
Authors: Enrique-Arias Andrés
Published: December 2020

This study analyzes historical and contemporary data of
Spanish produced by Catalan-dominant bilinguals in Majorca to
explore the origin and historical evolution of a contact feature of
Majorcan Spanish: the preposition en to express
direction of movement. The transgenerational survival of this
feature of Majorcan Spanish for over three centuries points to a
scenario of intra-community recycling of a structure that emerged as
the result of incomplete grammatical competence in Spanish and was
then perpetuated by limited contact with monolingual Spanish
speakers. The changing linguistic ecology of Majorca, however, with
wider access to canonical varieties of Spanish in the last half
century, has facilitated the demise of this trait among younger
urban generations.
Anthroponymic perseverance of Spanish vestigial 〈x〉
Authors: Parada Maryann
Published: December 2020

Until the early 19th century, the letter 〈x〉 was a common representation of the voiceless velar fricative /x/ (Quixote, brúxula). Despite the Royal Spanish Academy’s (RAE) 1815 elimination of 〈x〉 for /x/, it has survived in a number of Mexican indigenous toponyms and their derivatives as well as in a handful of Spanish anthroponymic variants. Drawing on diatopic, diachronic demographic data, this paper traces the retention of vestigial 〈x〉 in six anthroponymic variants: the given name Ximena and the surnames Ximénez/Ximenes, Mexía/s, and Roxas. These forms can be attributed to the often exceptional orthography of proper nouns from a normative perspective. In the case of Ximena, a powerful resurgence of the feature is linked to robust indexicalities of 〈x〉 in Mexican society.