bluuebunny/crossref_metadata_2025 huggingface dataset:
Day‐ahead flexibility enhancement via joint optimization for new energy vehicle fleets and electric vehicle charging/hydrogen refuelling stations
Authors: Mo Yuhong , Qin Zhijun , Guo Yi , Zhang Yihui
Published: April 2022

Power systems are striving for the decarbonization goal for long‐term sustainability. As a result, the renewable energy sources (RES) have been playing an increasingly important role in the generation portfolio. Power system flexibility maintaining the power balance under uncertain and variable RES generation has become a major concern during the energy transition. This paper proposes to apply new energy vehicles (NEV) including electric vehicles (EVs) and fuel cell vehicles (FCVs) as day‐ahead flexibility resources to make revenue by providing comprehensive capacity/energy flexibility in the ancillary service market. First, the detailed joint optimized operational strategies of the NEV fleet and the EV charging/hydrogen refuelling stations are formulated. Second, the design and service clearing methodology of the ancillary service market for flexibility enhancement is introduced. A game‐theoretic model is applied to determine the equilibrium price for both the demand and suppliers (namely NEV fleets) of operational flexibility. Third, case studies using IEEE benchmark systems are provided to validate the proposed methods. The results demonstrate that the joint optimization of NEV fleets, charging stations, and hydrogen refuelling stations can improve the power system operational flexibility, reduce the charging expense of NEV owners, and reduce the carbon emission by utilizing the green hydrogen.
Decayless longitudinal oscillations of a solar filament maintained by quasi-periodic jets
Authors: Ni Y. W. , Guo J. H. , Zhang Q. M. , Chen J. L. , Fang C. , Chen P. F.
Published: April 2022

Context. As a ubiquitous phenomenon, large-amplitude longitudinal filament oscillations usually decay in 1–4 periods. Recently, we observed a decayless case of such oscillations in the corona.

Aims. We try to understand the physical process that maintains the decayless oscillation of the filament.

Methods. Multiwavelength imaging observations and magnetograms were collected to study the dynamics of the filament oscillation and its associated phenomena. To explain the decayless oscillations, we also performed one-dimensional hydrodynamic numerical simulations using the code MPI-AMRVAC.

Results. In observations, the filament oscillates without decay with a period of 36.4 ± 0.3 min for almost 4 h before eruption. During oscillations, four quasi-periodic jets emanate from a magnetic cancellation site near the filament. The time interval between neighboring jets is ∼68.9 ± 1.0 min. Numerical simulations constrained by the observations reproduced the decayless longitudinal oscillations. However, it is surprising to find that the period of the decayless oscillations is not consistent with the pendulum model.

Conclusions. We propose that the decayless longitudinal oscillations of the filament are maintained by quasi-periodic jets, which is verified by the hydrodynamic simulations. More importantly, it is found that, when it is driven by quasi-periodic jets, the period of the filament longitudinal oscillations also depends on the driving period of the jets, not on the pendulum period alone. With a parameter survey in simulations, we derived a formula by which the pendulum oscillation period can be derived using the observed period of decayless filament oscillations and the driving periods of jets.
Risikoänderung bei Patienten mit Pulmonaler Arterieller Hypertonie unter medikamentöser Therapie – Ergebnisse aus vier deutschen Zentren
Authors: Stubbe Beate , Halank Michael , Seyfarth Hans-Jürgen , Obst Anne , Desole Susanna , Opitz Christian F. , Ewert Ralf
Published: April 2022

Die Risikobewertung für das abgeschätzte Überleben von PAH-Patienten ist eine wesentliche Grundlage für abgeleitete Therapieentscheidungen. Es existieren verschiedene Modelle für die Einschätzung des Risikos, welche jedoch weitgehend vergleichbar sind.

Es wurden 131 PAH-Patienten aus den Jahren 2016–2018 hinsichtlich des Risikos nach dem ESC-/ERS-Schema ausgewertet. Etwa 2 Drittel der Patienten (mittleres Alter 64 ± 14 Jahre) wiesen ≥ 3 Komorbiditäten bzw. kardiovaskuläre Risikofaktoren auf.

Zu Beginn der Beobachtung waren 13,8 % der Patienten als „low risk“, 76,3 % als „intermediate risk“ und 9,9 % als „high risk“ einzustufen. Zum Zeitpunkt der zweiten Kontrolle (im Mittel nach 12 ± 3 Monaten, Spanne 9–16 Monate) zeigten von den 111/131 (85 %) lebenden Patienten 20,7 % eine „low risk“-, 64,9 % eine „intermediate risk“- und 14,4 % eine „high risk“-Konstellation. Somit konnte lediglich ein geringer Anteil der Patienten durch die Therapie in eine günstigere Risiko-Kategorie überführt werden.

Die von uns beobachteten Patienten mit einem „low risk“-Profil hatten ein Überleben von 100 % über 24 Monate. Die Patienten mit einem „intermediate risk“-Profil zeigten nach 12 Monaten ein Überleben von 96 % und nach 24 Monaten ein Überleben von 82 %. Dagegen lag das Überleben der Patienten mit einer „high risk“-Konstellation nach 12 Monaten bei 89 % und nach 24 Monaten bei nur 51 %.

Trotz der aktuell verfügbaren therapeutischen Optionen konnte in unserer Analyse aus deutschen PH-Zentren nur ein kleiner Teil der PAH-Patienten während der Beobachtung in eine Niedrig-Risikogruppe mit guter Prognose überführt werden.
Therapie einer chronischen Infektion einer totalen Femurendoprothese bei einem 40-jährigen Patienten
Authors: Lenz Julia Elisabeth , Baumann Florian , Alt Volker
Published: April 2022

Wir berichten über einen Patienten, bei dem 1999 im Alter von 20 Jahren die Implantation eines proximalen Femurersatzes bei einem Ewing-Sarkom notwendig war. Nach mehrfachen
infektionsbedingten Wechseloperationen stellte er sich im August 2019 im Alter von 40 Jahren mit Fistelbildung und chronischer Infektion einer totalen Femurprothese vor. Durch eine
interdisziplinäre Behandlung und 3-zeitige Wechseloperation mit Einsatz einer silberbeschichteten totalen Femurendoprothese konnte die Hüftexartikulation vermieden und reizlose
Weichteilverhältnisse bei voller Belastbarkeit des rechten Beins und Gehfähigkeit ohne Zuhilfenahme von Gehstützen bei einer aktuellen Nachbeobachtungszeit von 2 Jahren erreicht werden.
RCTs in der Pankreaschirurgie der letzten 10 Jahre – ein Update
Authors: Hillebrecht H Christian , Fichtner-Feigl Stefan , Diener Markus
Published: April 2022

Randomisiert kontrollierte Studien (RCT) stellen eine der wichtigsten Quellen neuer Evidenz für die Behandlung insbesondere onkologischer Patienten dar. Insbesondere auf dem Gebiet der
Pankreaschirurgie, wo Komplikationen vergleichsweise häufig und schwerwiegend sind, sind innovative operativ-technische wie auch periinterventionelle Innovationen gefragt, die in der Lage
sind, Morbidität und Mortalität zu reduzieren. Trotz der mannigfaltigen methodischen Herausforderungen bei der Durchführung chirurgischer RCTs konnten in den letzten 10 Jahren große und
wissenschaftlich hochwertige Studien verzeichnet werden.

Dieser Review gibt einen Überblick über wichtige, bereits abgeschlossene und publizierte, aber auch über interessante und wichtige ausstehende RCTs in der Pankreaschirurgie.
Robotisch gestützte Enukleation einer zystischen Neoplasie des Pankreaskopfes
Authors: Litkevych Stanislav , Thomaschewski Michael , Zimmermann Markus , Wellner Ulrich Friedrich , Höppner Jens , Keck Tobias
Published: April 2022

Laut aktuellen revidierten Fukuoka-Leitlinien besteht die Indikation zur Resektion von BD-IPMN des Pankreas mit Worrisome Features, da hier ein Risiko der malignen Entartung von bis zu 30%
besteht. Die Resektion kann bei fehlenden klinischen, bildmorphologischen und laborchemischen Malignitätszeichen als eine nicht anatomische, lokale Exzision durchgeführt werden.

Eine robotische Enukleation bei benignen Raumforderungen der Bauchspeicheldrüse stellt eine sehr gute Alternative zu den resezierenden Verfahren, insbesondere zu denjenigen in offener
Technik, dar. Diese operative Behandlungsoption wird bei einem Mindestabstand bis zum pankreatischen Hauptgang von mindestens 2 mm im „International consensus statement on robotic pancreatic
surgery“ nahegelegt.

Neben den bekannten Vorteilen der minimalinvasiven Chirurgie führt diese parenchymsparende Methode zum Erhalt von endo- und exokriner Funktion (ca. 90%) und zu einem progressfreien
10-Jahres-Überleben von ca. 75% bei etwas erhöhter Morbidität (ca. 60%) verglichen mit den resezierenden Verfahren.

Der folgende Videobeitrag präsentiert das Operationsvideo einer robotischen Zystenenukleation (bei Verdacht auf eine BD-IPMN mit Worrisome Features) im Pankreaskopf und Processus uncinatus
bei einer 62-jährigen Patientin mit besonderer Betonung der wichtigsten vaskulären Landmarken, Besonderheiten der Herangehensweise und Vorteile der robotischen Technik.
Vorstellung und Evaluation des haptisch-visuellen, ohrchirurgischen Trainingssystems „HaptiVisT“
Authors: Sorge Martin , Eixelberger Thomas , Dietz Andreas , Simon Martina , Wittenberg Thomas , Katzky Uwe , Perret Jérôme , Hofer Mathias , Pirlich Markus
Published: April 2022

Hintergrund Operationen am Felsenbein stellen eine besondere Herausforderung für HNO-Chirurgen dar. Ziel des BMBF-geförderten Projektes war die Entwicklung eines realitätsnahen Trainingssystems für Ohroperationen in Form eines „Serious Game“.

Methodik Der vorgestellte Prototyp des HaptiVisT-Systems fungiert als ohrchirurgisches Trainingssystem mit visueller Rückkopplung durch einen brillenlosen 3D-Monitor und haptischer Rückkopplung durch einen den Bohrer simulierenden Haptik-Arm. Eine Vielfalt von Trainingsmöglichkeiten wird durch 3 verfügbare chirurgische Prozeduren (Antrotromie, Mastoidektomie, posteriore Tympanotomie) gewährleistet. Ein gewichtetes Punktesystem ermöglicht die Messbarkeit des Trainingserfolgs. Im Zuge der technischen Entwicklung des Prototyps erfolgte eine prospektive Evaluation durch 8 HNO-Ärzte und 4 Studierende u.a. hinsichtlich der Lerninhalte und Benutzerfreundlichkeit. Zur Anwendung kam ein standardisierter Fragebogen (Ordinalskala: 1=sehr gut bis 5=sehr schlecht).

Ergebnisse Hinsichtlich der Lerninhalte ergaben die Aspekte „Festigung Anatomie (Mittelwert=1,58)“, „Training Hand-Augen-Koordination (1,67)“, „Übertragbarkeit in die Praxis (1,83)“ und „Nützlichkeit für die Praxis (1,33)“ gute bis sehr gute Werte. Die Benutzerfreundlichkeit zeigte für die Aspekte „Realitätsnähe (2,29)“, „Zusammenspiel Haptik und Optik (2,33)“ sowie „Immersion in das Trainingssystem (1,89)“ ebenfalls gute Werte. Der „Motivationsfaktor“ war bei allen Testpersonen sehr hoch (1,2).

Schlussfolgerung Das ohrchirurgische Trainingssystem HaptiVisT bietet die Möglichkeit des immersiven Trainings von Ohroperationen. Eine Integration in den klinischen Alltag und insbesondere in die ärztliche Weiterbildung zum HNO-Facharzt erscheint daher sinnvoll.
Synthesis and C60 Binding of Aza[10]CPP and N-Methylaza[10]CPP
Authors: Schwer Fabian , Zank Simon , Freiberger Markus , Kaur Ramandeep , Frühwald Stefan , Robertson Craig C. , Görling Andreas , Drewello Thomas , Guldi Dirk M. , von Delius Max
Published: April 2022

Within the growing family of strained carbon nanohoops and nanobelts, [10]CPP arguably offers the best compromise between synthetic accessibility and strong binding affinity for C60. In this work, we report the synthesis of two nitrogen-containing analogues of [10]CPP and we systematically compare the structure, optoelectronic properties and C60 binding affinities of this small set of structurally similar macrocycles. While Aza[10]CPP outcompetes the parent compound by approximately one order of magnitude with respect to C60 binding, we found that the reverse was true for the methylaza analogue. Transient absorption studies showed that photo-induced electron transfer occurred readily from [10]CPP and its aza-analogue to an encapsulated C60 guest. Formation of a charge-separated complex was not observed however for the N-methylated derivative. These insights will prove useful for further applications of strained nanohoops in supramolecular chemistry and organic electronics.
Copper-Catalyzed Alkylation of Quinoxalin-2(1H)-ones with Styrenes and tert-Butyl Peroxybenzoate
Authors: Zhong Xiaoyang , Li Xinying , Yao Hua , Lin Sen , Yan Zhaohua , Guo Hui , Min Li
Published: April 2022

A simple strategy for the synthesis of 3-substituted quinoxalin-2(1H)-ones containing ether units is proposed. The method is realized by the three-component synthesis of quinoxalin-2(1H)-ones, styrenes, and tert-butyl peroxybenzoate (TBPB). This reaction has good functional group tolerance and may involve a free-radical process.
Patient Safety, Clinical Microbiology, and Collaborative Healthcare
Authors: Chugh Tulsi Das , Duggal Ashish Kumar , Duggal Shalini Dewan
Published: April 2022

“Right to health” is a universal right inclusive of a culture of safety. This review aims to highlight how clinical microbiology laboratories can contribute to patient safety. They can bring down medical errors through clinical collaboration and quality control. Timely and accurate inputs from microbiology laboratory help in clinical correlation and aid in safe patient care. Through internet search, using keywords such as “medical errors” and “quality assurance,” global burden of medical errors has been compiled. References have been taken from guidelines and documents of standard national and international agencies, systematic reviews, observational studies, retrospective analyses, meta-analyses, health bulletins and reports, and personal views. Safety in healthcare should lay emphasis on prevention, reporting, analysis, and correction of medical errors. If not recorded, medical errors are regarded as occasional or chance events. Global data show adverse events are as high as 10% among hospitalized patients, and approximately two-thirds of these are reported from low- to middle-income countries (LMICs). This includes errors in laboratories as well. Clinical microbiology can impact patient safety when practiced properly with an aim to detect, control, and prevent infections at the earliest. It is a science that integrates a tripartite relationship between the patient, clinician, and a microbiology specialist. Through collaborative healthcare, all stakeholders benefit by understanding common errors and mitigate them through quality management. However, errors tend to happen despite standardization and streamlining all processes. The aim should be to minimize them, have fair documentation, and learn from mistakes to avoid repetition. Local targets should be set and then extended to meet national and global benchmarks.
On the extension of the FKG inequality to n functions
Authors: Lieb Elliott H. , Sahi Siddhartha
Published: April 2022

The 1971 Fortuin–Kasteleyn–Ginibre inequality for two monotone functions on a distributive lattice is well known and has seen many applications in statistical mechanics and other fields of mathematics. In 2008, one of us (Sahi) conjectured an extended version of this inequality for all n > 2 monotone functions on a distributive lattice. Here, we prove the conjecture for two special cases: for monotone functions on the unit square in Rk whose upper level sets are k-dimensional rectangles and, more significantly, for arbitrary monotone functions on the unit square in R2. The general case for Rk,k>2, remains open.
Higher-order topological states in locally resonant elastic metamaterials
Authors: Zheng Zhoufu , Yin Jianfei , Wen Jihong , Yu Dianlong
Published: April 2022

Higher-order topological insulators (HOTIs), capable of hosting topological states over multiple dimensionalities, have received considerable attention recently, providing unprecedented platforms for robust wave manipulation. Aiming at applications of HOTIs for integrated sensing, energy harvesting, or control of structural vibration propagation, challenges remain in achieving topological states at low frequencies with ample flexibility and tunability. Here, we report the theoretical modeling and experimental realization of HOTIs in elastic locally resonant metamaterials (LRMs). By exploring the interplay between local resonance couplings and nontrivial band topology, a variety of higher-order topological corner states (TCSs) are constructed in deep sub-wavelength regime with high efficiency in energy confinement. More importantly, we reveal that the TCSs are dependent on localization mechanisms of interacting sites at interfaces, which endows our HOTIs with unique frequency-selective and dimension-switching abilities. We further design complex domain walls to demonstrate the TCSs can be selectively switched on at desired frequencies or geometric corners. Our findings not only offer effective routes for the design of deep sub-wavelength topological devices but also enrich the understandings of higher-order topological physics that can be extended to other classic systems.
Reaction-path statistical mechanics of enzymatic kinetics
Authors: Lim Hyuntae , Jung YounJoon
Published: April 2022

We introduce a reaction-path statistical mechanics formalism based on the principle of large deviations to quantify the kinetics of single-molecule enzymatic reaction processes under the Michaelis–Menten mechanism, which exemplifies an out-of-equilibrium process in the living system. Our theoretical approach begins with the principle of equal a priori probabilities and defines the reaction path entropy to construct a new nonequilibrium ensemble as a collection of possible chemical reaction paths. As a result, we evaluate a variety of path-based partition functions and free energies by using the formalism of statistical mechanics. They allow us to calculate the timescales of a given enzymatic reaction, even in the absence of an explicit boundary condition that is necessary for the equilibrium ensemble. We also consider the large deviation theory under a closed-boundary condition of the fixed observation time to quantify the enzyme–substrate unbinding rates. The result demonstrates the presence of a phase-separation-like, bimodal behavior in unbinding events at a finite timescale, and the behavior vanishes as its rate function converges to a single phase in the long-time limit.
Calorimeter with Bayesian unfolding of spectra of high-flux broadband x rays
Authors: Laso Garcia A. , Hannasch A. , Molodtsova M. , Ferrari A. , Couperus Cadabağ J. P. , Downer M. C. , Irman A. , Kraft S. D. , Metzkes-Ng J. , Naumann L. , Prencipe I. , Schramm U. , Zeil K. , Zgadzaj R. , Ziegler T. , Cowan T. E.
Published: April 2022

We report the development of a multipurpose differential x-ray calorimeter with a broad energy bandwidth. The absorber architecture is combined with a Bayesian unfolding algorithm to unfold high energy x-ray spectra generated in high-intensity laser–matter interactions. Particularly, we show how to extract absolute energy spectra and how our unfolding algorithm can reconstruct features not included in the initial guess. The performance of the calorimeter is evaluated via Monte Carlo generated data. The method accuracy to reconstruct electron temperatures from bremsstrahlung is shown to be 5% for electron temperatures from 1 to 50 MeV. We study bremsstrahlung generated in solid target interaction showing an electron temperature of 0.56 ± 0.04 MeV for a 700 μm Ti titanium target and 0.53 ± 0.03 MeV for a 50 μm target. We investigate bremsstrahlung from a target irradiated by laser-wakefield accelerated electrons showing an endpoint energy of 551 ± 5 MeV, inverse Compton generated x rays with a peak energy of 1.1 MeV, and calibrated radioactive sources. The total energy range covered by all these sources ranges from 10 keV to 551 MeV.
Nanoscale multiply charged focused ion beam platform for surface modification, implantation, and analysis
Authors: Lalande Mathieu , Salou Pierre , Houel Arnaud , Been Thierry , Birou Thierry , Bourin Charles , Cassimi Amine , Keizer Arthur , Mellier Jean-Baptiste , Ramillon Jean-Marc , Sineau Anthony , Delobbe Anne , Guillous Stéphane
Published: April 2022

The PELIICAEN (Platform for the Study of Ion Implantation Controlled and Analyzed at the Nanometric Scale) setup is a unique device, both for all of its in situ ultra-high vacuum equipment (focused ion beam column, secondary electron microscope, atomic force microscope, and scanning tunneling microscope) and for its nanostructuration performances on materials. The setup has been recently equipped with its own electron cyclotron resonance ion sources, a new position-controlled platform using pneumatic vibration insulators, and a fast pulsing device. Its performances were then deeply improved, providing access to a large choice of ions, an adjustable ion implantation depth up to a few hundred nanometers, an image resolution down to 25 nm, and an ion beam size on the sample down to 100 nm. With all this equipment, the PELIICAEN setup is in the international foreground to perform and analyze ion implantation and surface modification.
Filter bubble effect in the multistate voter model
Authors: Iannelli Giulio , De Marzo Giordano , Castellano Claudio
Published: April 2022

Social media influence online activity by recommending to users content strongly correlated with what they have preferred in the past. In this way, they constrain users within filter bubbles strongly limiting their exposure to new or alternative content. We investigate this type of dynamics by considering a multistate voter model where, with a given probability λ, a user interacts with “personalized information,” suggesting the opinion most frequently held in the past. By means of theoretical arguments and numerical simulations, we show the existence of a nontrivial transition between a region (for small λ) where a consensus is reached and a region (above a threshold λc) where the system gets polarized and clusters of users with different opinions persist indefinitely. The threshold always vanishes for large system size N, showing that a consensus becomes impossible for a large number of users. This finding opens new questions about the side effects of the widespread use of personalized recommendation algorithms.
Effect of laser preheat in magnetized liner inertial fusion at OMEGA
Authors: Leal L. S. , Maximov A. V. , Hansen E. C. , Davies J. R. , Barnak D. H. , Peebles J. L. , Woo K. M. , Heuer P. V. , Sefkow A. B. , Betti R.
Published: April 2022

Integrated magnetized liner inertial fusion (MagLIF) experiments on the OMEGA laser system are modeled to investigate the effects of laser preheat on implosion performance. In both simulations and experiments, preheating the fuel with a laser enhances the neutron yield, with the maximum yield occurring at an optimal preheat laser energy. Increasing the preheat energy past the optimal value reduces the neutron yield. In simulations, the rate of the drop in neutron yield depends on the inclusion of the Nernst effect. The Nernst effect advects the magnetic field away from the center of the fuel region during the preheat stage of MagLIF on OMEGA and weakens magnetic-flux compression. If the Nernst effect is not included, the simulated drop in yield past the optimal preheat laser energy is more gradual as opposed to the sharper drop seen in experiments. Simulations are able to model trend in measured ion temperatures seen in experiments. A mix model is used to show that including mix from the wall in the simulated fuel region further degrades the yield and lowers the optimal preheat laser energy. Simulations with mix predict that increasing the initial axial magnetic field may still enhance yield performance in integrated implosions.
Work hardening in Ti48Zr29Ni6Ta1Be16 metallic glass matrix composites at cryogenic temperature
Authors: Zhu R. T. , Wang Z. , Shi X. H. , Yang H. J. , Guo X. T. , Qiao J. W.
Published: April 2022

A Ti-based metallic glass matrix composite (MGMC), which contains abundant primary α′ and ω phases in dendrites, has a strong work-hardening ability. A significant martensitic transformation occurred during plastic deformation at 298 K, and deformation twins were produced at 77 K. Transformation-induced plasticity and twinning-induced plasticity enable MGMC to achieve prominent strength–plasticity synergy. At 298 K, the alloy exhibits a yield strength (YS) of 1140 MPa and a uniform elongation (UE) of 8.1%, while at 77 K, the YS increases to 1520 MPa, still maintaining a UE of 4.6%. The prediction models of the temperature dependent YS and martensite trigger stress (σSIM) in MGMC were established. The strengthening and toughening mechanisms provide a great theoretical guidance for the development of low-temperature high-performance MGMCs.
Absence of pure voltage instabilities in the third-order model of power grid dynamics
Authors: Thümler Moritz , Zhang Xiaozhu , Timme Marc
Published: April 2022

Secure operation of electric power grids fundamentally relies on their dynamical stability properties. For the third-order model, a paradigmatic model that captures voltage dynamics, three routes to instability are established in the literature: a pure rotor angle instability, a pure voltage instability, and one instability induced by the interplay of both. Here, we demonstrate that one of these routes, the pure voltage instability, requires infinite voltage amplitudes and is, thus, nonphysical. We show that voltage collapse dynamics nevertheless exist in the absence of any voltage instabilities.
Analytical model of a short DC glow discharge in the presence of significant radial ambipolar diffusion losses
Authors: Eliseev S.
Published: April 2022

We present a simple analytical model of a short direct-current glow discharge (without positive column) that is applicable for the case of narrow discharge tubes when radial losses of charged particles due to ambipolar diffusion significantly influence discharge properties. The model is based on the analytical parameterization of the non-local ionization produced by fast electrons, which allows obtaining an exact solution of the ambipolar diffusion equation with radial particle losses written in the τ-approximation. Analysis of the spatial distribution of electron density in the near-cathode plasma regions of a discharge allow obtaining an explicit expression for the position of electric field reversal in the negative glow that is independent of electron temperature and interelectrode distance. The latter fact makes the model viable for description of near-cathode plasma regions in the general case of a discharge with a positive column. The procedure for obtaining quantitative estimates and interpretation of experimental data on discharge properties using the proposed model is presented and discussed in detail.
The dimensional evolution of structure and dynamics in hard sphere liquids
Authors: Charbonneau Patrick , Hu Yi , Kundu Joyjit , Morse Peter K.
Published: April 2022

The formulation of the mean-field infinite-dimensional solution of hard sphere glasses is a significant milestone for theoretical physics. How relevant this description might be for understanding low-dimensional glass-forming liquids, however, remains unclear. These liquids indeed exhibit a complex interplay between structure and dynamics, and the importance of this interplay might only slowly diminish as dimension d increases. A careful numerical assessment of the matter has long been hindered by the exponential increase in computational costs with d. By revisiting a once common simulation technique involving the use of periodic boundary conditions modeled on Dd lattices, we here partly sidestep this difficulty, thus allowing the study of hard sphere liquids up to d = 13. Parallel efforts by Mangeat and Zamponi [Phys. Rev. E 93, 012609 (2016)] have expanded the mean-field description of glasses to finite d by leveraging the standard liquid–state theory and, thus, help bridge the gap from the other direction. The relatively smooth evolution of both the structure and dynamics across the d gap allows us to relate the two approaches and to identify some of the missing features that a finite-d theory of glasses might hope to include to achieve near quantitative agreement.
Spin transport properties of highly lattice-matched all-Heusler-alloy magnetic tunnel junction
Authors: Feng Yu , Ding Haonan , Li Xiaohua , Wu Bo , Chen Hong
Published: April 2022

A highly lattice-matched all-Heusler-alloy magnetic tunnel junction (MTJ) is proposed by associating half metallic CoFeTiSi electrode and non-magnetic semiconductor Fe2TiSi barrier. Based on the non-equilibrium Green's function combined with first-principles calculations, spin transport mechanism is studied by analyzing the transmission coefficient, local density of states, and scattering states. The calculated equilibrium tunnel magnetoresistance (TMR) ratio in CoFeTiSi/Fe2TiSi/CoFeTiSi reaches up to about 3.30 × 108%, which is much higher than in CoFeTiSi/MgO/CoFeTiSi. The calculated scattering states reveal that CoFeTiSi/Fe2TiSi/CoFeTiSi MTJ possesses two transport channels, and the contribution of channel I to the total transport is about 80%, which plays a dominate role. The analyses on non-equilibrium spin transport properties reveal that CoFeTiSi/MgO/CoFeTiSi MTJ can output a high intensity transport current with complete spin polarization, and it can output a stable and highly efficient signal. The TMR ratio possesses an extremely large value of about 2.4 × 108% and even the bias voltage increases to 0.2 V, exhibiting a robust current-driven stability.
Thermal model for time-domain thermoreflectance experiments in a laser-flash geometry
Authors: Peng Wanyue , Wilson Richard B.
Published: April 2022

Time-domain thermoreflectance (TDTR) is a well-established pump–probe method for measuring thermal conductivity and interface conductance of multilayers. Interpreting signals in a TDTR experiment requires a thermal model. In standard front/front TDTR experiments, both pump and probe beams typically irradiate the surface of a multilayer. As a result, existing thermal models for interpreting thermoreflectance experiments assume that the pump and probe beams both interact with the surface layer. Here, we present a frequency-domain solution to the heat-diffusion equation of a multilayer in response to nonhomogeneous laser heating. This model allows analysis of experiments where the pump and probe beams irradiate opposite sides of a multilayer. We call such a geometry a front/back experiment to differentiate such experiments from standard TDTR experiments. As an example, we consider a 60nm amorphous Si film. We consider how signals differ in a front/front vs front/back geometry and compare thermal model predictions to experimental data.
A three-dimensional multiphase numerical model for the influence of Marangoni convection on Marangoni self-driven object
Authors: Chen Shuai , Zhang Zhi , Zhang Yu , Sha Yong
Published: April 2022

By means of coordinate transformation and the volume-of-fluid-level set multiphase flow method, a three-dimensional multiphase numerical model is established to simulate a Marangoni self-driven object. The forces on the Marangoni self-driven object are discussed as the driving force, viscous resistance, and pressure resistance. A typical disk-shaped, Marangoni self-driven object driven by the diffusion of camphor from its tail to water is utilized to perform a numerical study. Its motion evolution and force change in the whole process are represented quantitatively alongside the flow field and camphor concentration distribution in the flow domain. Meanwhile, the influence of Marangoni convection, which is induced by camphor diffusion at the moving gas–liquid interface, on surfer motion is surveyed. The results presented in this work can improve understanding of self-driven Marangoni propulsion since self-driven object motion and fluid movement details are difficult to acquire experimentally.
Investigation on the arc root characteristics of vacuum arc between the iron-core cup-shaped transverse magnetic field contacts
Authors: Jiang Yuzi , Xiu Shixin , Yang Jinwang , Tan Tao , Liu Zhanpeng , Chu Bo
Published: April 2022

The severity of the contact surface ablation determines the breaking capacity of the vacuum circuit breaker, and the interaction between the arc root and the electrode is the main cause of the contact surface ablation. The characteristics of the arc root determine the magnitude of the electromagnetic force received by the arc during the movement stage as well as the shape and speed of the arc movement. It will eventually affect the temperature of the contact surface and the ablation situation. This paper studied the arc root characteristics of high-current constricted vacuum arcs between the iron-core cup-shaped transverse magnetic field contacts and put forward the idea of using the ratio of cathode and anode arc root areas to quantitatively analyze the concentration of vacuum arc. The research on the arc root characteristics of the vacuum arc can help to improve the arc characteristics and arcing mechanism, and the proposition of the ratio can provide a new method for the study of constricted arc. This can provide a basis for improving the arc extinction performance of the switch, reducing the ablation of the contact material, and improving the contact life.
Quantitative assessment of fitting errors associated with streak camera noise in Thomson scattering data analysis
Authors: Swadling G. F. , Bruulsema C. , Rozmus W. , Katz J.
Published: April 2022

Thomson scattering measurements in high energy density experiments are often recorded using optical streak cameras. In the low-signal regime, noise introduced by the streak camera can become an important and sometimes the dominant source of measurement uncertainty. In this paper, we present a formal method of accounting for the presence of streak camera noise in our measurements. We present a phenomenological description of the noise generation mechanisms and present a statistical model that may be used to construct the covariance matrix associated with a given measurement. This model is benchmarked against simulations of streak camera images. We demonstrate how this covariance may then be used to weight fitting of the data and provide quantitative assessments of the uncertainty in the fitting parameters determined by the best fit to the data and build confidence in the ability to make statistically significant measurements in the low-signal regime, where spatial correlations in the noise become apparent. These methods will have general applicability to other measurements made using optical streak cameras.
Dimerization of dehydrogenated polycyclic aromatic hydrocarbons on graphene
Authors: Tang Zeyuan , Hammer Bjørk
Published: April 2022

Dimerization of polycyclic aromatic hydrocarbons (PAHs) is an important, yet poorly understood, step in the on-surface synthesis of graphene (nanoribbon), soot formation, and growth of carbonaceous dust grains in the interstellar medium (ISM). The on-surface synthesis of graphene and the growth of carbonaceous dust grains in the ISM require the chemical dimerization in which chemical bonds are formed between PAH monomers. An accurate and cheap method of exploring structure rearrangements is needed to reveal the mechanism of chemical dimerization on surfaces. This work has investigated the chemical dimerization of two dehydrogenated PAHs (coronene and pentacene) on graphene via an evolutionary algorithm augmented by machine learning surrogate potentials and a set of customized structure operators. Different dimer structures on surfaces have been successfully located by our structure search methods. Their binding energies are within the experimental errors of temperature programmed desorption measurements. The mechanism of coronene dimer formation on graphene is further studied and discussed.
An automated method for the identification of interaction tone noise sources on the beamforming maps of counter-rotating rotors
Authors: Fenyvesi B. , Kriegseis J. , Horváth Cs.
Published: April 2022

Counter-rotating rotor configurations are considered more efficient than their single rotor counterparts. Consequently, the coaxially aligned rotors have appeared in the fixed-wing aircraft sector and are appearing in the quickly developing unmanned aerial vehicle sector, where they are expected to play a significant role, especially for long haul and heavy load configurations. As their noise levels have proven to be rather significant, the localization and reduction of the noise of such counter-rotating blade sets is a relevant topic of interest. One of the dominant contributors to counter-rotating rotor noise is interaction tones. Interaction tones appear at combinations of the harmonics of the blade passing frequencies of the two rotors and are significant throughout the spectra. In this paper, an automated method is presented that analyzes an entire series of beamforming noise source maps using principal component analysis-based methods in order to identify the dominant noise generation mechanisms in frequency bins that are associated with interaction tones. The processing technique is presented herein through the investigation of counter-rotating open rotor datasets developed for a fixed-wing aircraft configuration. With the proposed method, an objective mean has been provided for separating apart contributions from various noise sources, which can be automated, making the processing and investigation of large sets of measurement data rather quick and easy. The method has been developed such that the results of the analysis are easy to comprehend even without specialized prior knowledge in the area of counter-rotating rotor noise.
Extended bounce-kinetic model for trapped electron mode turbulence
Authors: Kim Y. J. , Kwon J. M. , Qi Lei , Hahm T. S.
Published: April 2022

The bounce-kinetic model based on the modern nonlinear bounce-kinetic theory [Fong and Hahm, Phys. Plasmas 6, 188 (1999)] has been developed and used for simulations previously. This work reports on an extension of the bounce-kinetic model including more accurate treatment of barely trapped particles and its implementation in the Gyro-Kinetic Plasma Simulation Program gyrokinetic code [Kwon et al., Comp. Phys. Commun. 215, 81 (2017)]. This leads to more accurate gyrokinetic simulations of the collisionless trapped electron mode at low magnetic shear.
Modeling of the bilayer piezoelectric microbeam based on the strain gradient effect
Authors: Fu Jie , Zhang Zhenjie
Published: April 2022

In this paper, a size-dependent bilayer piezoelectric microbeam model is established based on the modified piezoelectric theory, which considers the strain gradient effect. The hypothesis of the Euler–Bernoulli beam is taken for the size-dependent bilayer piezoelectric microbeam model. The governing equations and boundary conditions are obtained from the variational principle. The electromechanical coupling performance for two boundary value problems of a cantilever beam and a simply supported beam is assessed. The size dependence of a bilayer piezoelectric microbeam electromechanical coupling property under the direct piezoelectric effect and converse piezoelectric effect is investigated. Results reveal that, for the piezoelectric mircobeam, the electromechanical coupling responses have been restrained by the size effect. The induced charge and deflection predicted by the size-dependent model is smaller than that of the classical model. However, the influence of the size effect is weakened with the increase in the beam thickness. The size effect can be neglected when the beam thickness is far greater than the material length-scale parameter. Because the structural stiffness of the cantilever beam is higher than that of the simply supported beam, the electromechanical coupling responses of the bilayer piezoelectric cantilever microbeam are greater than that of the bilayer piezoelectric simply supported microbeam.
On the dynamic behaviors of freely falling annular disks at different Reynolds numbers
Authors: Bi Dianfang , Sun Tiezhi , Wei Yingjie , Huang Xudong
Published: April 2022

Freely falling or rising objects in quiescent Newtonian fluid have been frequently encountered in nature or industry, such as the spreading of seeds from a tree or the movement of ores in deep sea mining. The dynamic behaviors of freely moving objects can provide a significant understanding of the evolution of the body wake and the resulting path instability. In this study, we present numerical simulations of freely falling annular disks released from quiescent water for relatively low Reynolds numbers from 10 to 500 while keeping the non-dimensional moment of inertia I* and inner to outer diameter ratio η constant. The falling stage experiences a variation from quasi-one-dimensional mode, steady oblique motion (SO motion), to the fully three-dimensional mode, helical motion. The stage diagram is plotted to show the variation tendency with the increment of Reynolds numbers. The detailed characteristics of the trajectories and orientation of the annular disks for different motions are analyzed. The corresponding vortical structures are presented, and an analog of the wingtip vortex is found at the outer rim of the disk for transitional and helical motion. A steady recirculation region of SO motion is observed, which is similar to that of a stationary disk but with complex multilayer structures formed by the combined effects of both the inner and outer rims. The limit streamline and pressure coefficient are investigated, demonstrating that the asymmetrical pressure distribution that exerts fluid forces and torques on the disk plays a crucial role in the dynamic response of the disk. Furthermore, combining the flow fields and fluid forces, the physical mechanism responsible for the diverse falling patterns is explored in detail.
New magnetic intermediate state, “B-phase,” in the cubic chiral magnet MnSi
Authors: Ohkuma M. , Mito M. , Pardo M. , Kousaka Y. , Iwasaki S. , Ohishi K. , Akimitsu J. , Inoue K. , Laliena V. , Campo J.
Published: April 2022

It is well known that the archetype chiral magnet MnSi stabilizes a skyrmion lattice, termed “A-phase,” in a narrow temperature range in the vicinity of the paramagnetic boundary around Tc ∼ 29 K and Hc ∼ 2 kOe. Recently, it has been predicted that at much lower temperatures below Tc, the conical helicoid and the forced ferromagnetic (FFM) states could be separated by a new “unknown state.” In order to detect this “unknown state,” we explored the phase diagram of MnSi oriented single crystals as a function of the d.c. magnetic field (H⃗dc) and the temperature (T) by using a.c. magnetization measurements. For H⃗dc∥ 〈111〉, we observed a new region, termed “B-phase,” in the magnetic phase diagram, characterized by a flat-valley-like anomaly on the in-phase component of the a.c. magnetization (m′), over 3.5 ≤ Hdc ≤ 6.2 kOe just below the low temperature (T < 6 K) FFM boundary. The observed frequency independence over 0.3–1000 Hz and the absence of any measurable absorption in the a.c. magnetization (m″) in the “B-phase” suggest a static nature. The “B-phase” was not observed for either H⃗dc∥ 〈100〉 or 〈110〉, revealing that the magnetic anisotropy could play a role in the stabilization of the phase. The “B-phase” could be compatible with the theoretical predictions if the new magnetic state is supposedly related with a relative reorientation of the four helices in MnSi.
Theory and simulations of field strengths in magnetosonic shock waves in finite beta plasmas
Authors: Toida Mieko , Ohsawa Yukiharu
Published: April 2022

Field strengths in an oblique magnetosonic shock wave in a collisionless, finite beta plasma are studied with theory and simulations. With the use of the warm, two-fluid model, the maximum values of the magnetic field, the transverse electric field, and the electric potential in a shock wave are analytically obtained as functions of the shock speed. One-dimensional, electromagnetic particle simulations are then carried out to measure the field strengths in shock waves. The theory and the simulation results are found to be consistent.
Dispersion corrected r2SCAN based global hybrid functionals: r2SCANh, r2SCAN0, and r2SCAN50
Authors: Bursch Markus , Neugebauer Hagen , Ehlert Sebastian , Grimme Stefan
Published: April 2022

The regularized and restored semilocal meta-generalized gradient approximation (meta-GGA) exchange–correlation functional r2SCAN [Furness et al., J. Phys. Chem. Lett. 11, 8208–8215 (2020)] is used to create three global hybrid functionals with varying admixtures of Hartree–Fock “exact” exchange (HFX). The resulting functionals r2SCANh (10% HFX), r2SCAN0 (25% HFX), and r2SCAN50 (50% HFX) are combined with the semi-classical D4 London dispersion correction. The new functionals are assessed for the calculation of molecular geometries, main-group, and metalorganic thermochemistry at 26 comprehensive benchmark sets. These include the extensive GMTKN55 database, ROST61, and IONPI19 sets. It is shown that a moderate admixture of HFX leads to relative improvements of the mean absolute deviations for thermochemistry of 11% (r2SCANh-D4), 16% (r2SCAN0-D4), and 1% (r2SCAN50-D4) compared to the parental semi-local meta-GGA. For organometallic reaction energies and barriers, r2SCAN0-D4 yields an even larger mean improvement of 35%. The computation of structural parameters (geometry optimization) does not systematically profit from the HFX admixture. Overall, the best variant r2SCAN0-D4 performs well for both main-group and organometallic thermochemistry and is better or on par with well-established global hybrid functionals, such as PW6B95-D4 or PBE0-D4. Regarding systems prone to self-interaction errors (SIE4x4), r2SCAN0-D4 shows reasonable performance, reaching the quality of the range-separated ωB97X-V functional. Accordingly, r2SCAN0-D4 in combination with a sufficiently converged basis set [def2-QZVP(P)] represents a robust and reliable choice for general use in the calculation of thermochemical properties of both main-group and organometallic chemistry.
Analysis of self-excited transverse combustion instability in a rectangular model rocket combustor
Authors: Guo Kangkang , Ren Yongjie , Tong Yiheng , Lin Wei , Nie Wansheng
Published: April 2022

A methane/oxygen mixture is considered to be an appropriate propellant for many future rocket engines due to its practicality and low cost. To better understand the combustion instability in methane/oxygen-fed rocket engines, the spontaneous transverse combustion instability in a rectangular multi-element combustor (RMC) was analyzed both experimentally and numerically. Severe combustion instabilities occurred in the RMC during repeatable hot-fire tests. The physical mechanisms were systematically investigated through numerical simulations based on the stress-blended eddy simulation and flamelet-generated manifolds method with detailed chemical mechanisms (GRI Mech 3.0). The numerical results for the frequency spectrum and spatial modes agree well with the theoretical analysis and experimental data. The driven regions of the combustion instability were identified on both sides of the combustion chamber through a Rayleigh index analysis. The longitudinal pressure oscillations in the oxidizer post were found to be coupled with the transverse pressure waves in the combustion chamber and led to periodic oscillations of the mass flow rate of propellant. Moreover, the mixing was highly enhanced when the pressure wave interacted with walls of the combustion chamber. Therefore, a sudden release of heat occurred. The pressure oscillations were enhanced by pulsated heat release. A closed-loop system with positive feedback associated with periodic oscillations mass flow rate of the propellant, and sudden heat release, was believed to account for the present combustion instability.