bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient token circulation strategies against misers in device‐to‐device relay using token‐based incentive mechanisms
Authors: Wang You‐Chiun , Chang Fu‐Chun
Published: March 2022

Device‐to‐device (D2D) relay not only broadens the service coverage of a base station (BS) but also raises network capacity. When the channel quality of a user equipment (UE) is not good, it requests another UE to relay its data from the BS. Since many UEs are owned by self‐interested users, token‐based incentive (TBI) mechanisms allow UEs selling and buying relay services by exchanging tokens, thereby pricking UEs on to act as relay nodes. However, such mechanisms are vulnerable to the miser problem, where malicious UEs keep collecting tokens from others but never spend tokens. Eventually, negotiable tokens will gradually decrease, so more and more UEs have very few tokens to buy relay services, which restrains D2D relay. To conquer the miser problem, this paper proposes three token circulation strategies, which tax UEs and redistribute the taxed tokens to those UEs in need. Thus, misers can be prevented from hoarding tokens and breaking a TBI mechanism. The proposed strategies need not add tokens to the network, so they will not cause inflation of tokens. Simulation results show that these strategies can keep high D2D throughput with the existence of misers, which protects TBI mechanisms and promotes the performance of D2D relay.
Adaptive filtering method combined with quality map for InSAS interferogram
Authors: Huang Pan , Teng Xiaojie , Zhong Heping
Published: March 2022

The quality of interferogram, which is limited by various phase noise, will greatly influence the subsequent processes of interferometric synthetic aperture sonar (InSAS), such as phase unwrapping and digital elevation model (DEM) estimation. Therefore, phase filtering is an essential step in signal processing for InSAS. In this paper, an adaptive filtering method combined with quality map is proposed to suppress the phase noise while preserving the fringe edges. The main advantage of the new approach is the size of filtering window can be adaptively selected according to the quality map. A function between window size and quality map is established, which controls the strength of filtering. In the area of high quality, the window size is large to remove noise, otherwise, in the low quality area, the window size is small to keep edge details. The effectiveness of the proposed method is validated via some illustrative simulated experiment and the real InSAS data.
Observer based sliding mode control of PMSM speed regulation system with a novel reaching law
Authors: Zou Quan , Li Xiaoxiang , Chen Dong
Published: March 2022

A novel reaching law based sliding mode control of PMSM speed regulation system with uncertainties and unknown external disturbance is proposed in this paper. The proposed reaching law mainly consists of a time‐varying gain and a fractional power term of the sliding variable. And the time‐varying gain is auto‐tuned by the sliding variable such that it is large when the sliding variable is far away from the sliding surface to speed‐up the reaching process, and vice versa. Unlike the existing auto‐tuning power rate reaching law (PRRL), the proposed reaching law provides a guaranteed reaching time independently on initial conditions. Moreover, the reaching time can be effectively reduced by tuning the gains of the reaching law. Based on this new reaching law, a disturbance observer is designed to estimate the unknown total disturbance and a sliding mode controller is designed for the robust control of PMSM speed regulation system based on the estimated disturbance. Simulations and experiments are carried out to verify the effectiveness of the proposed control method.
Soil impulse ionisation model based on dynamic changes of electric field
Authors: Wen Xishan , Li Chun , Chen Jiahao , Tong Xuefang , Mei Hao , Zhou Guangyuan , Xu Bichuan , Lu Hailiang
Published: March 2022

Soil ionisation has an important influence on impulse characteristics of grounding conductor. This paper introduced improvements to an existing soil ionisation model considering the influence of electric field on the change of soil resistivity, while soil resistivity is not directly dependent on soil electric field. The validity of improved soil ionisation model was verified by surge response of vertical conductor in uniform soil and horizontally stratified soil. Furthermore, the impulse experiment was carried out on horizontal conductor in soil with finite volumes. Based on experimental configuration, the corresponding calculation model was built, and calculated results were in good agreement with experimental results.
Review of Various Metaheuristics Techniques for Tuning Parameters of PID/FOPID Controllers
Authors: Nasir Mohannad , Saloumi Majd , Nassif Ali Bou
Published: March 2022

Alongside the rapid advancement of technology, researchers are looking for accurate, flexible, and efficient ways to control systems. One big breakthrough in technology is the PID and its following advancement which is FOPID controller. The PID controller is becoming widely used due to its simplicity and cost-effectiveness, while the latter is more desirable because of its accuracy and flexibility. The parameters of the aforementioned controllers have an enormous effect on the transient responses. For instance, the settling time, rising time, Integral Absolute Error (IAE), and overshooting are greatly influenced by the controller parameters. However, the most difficult problem in delivering the active case of the transient response of any system is the tuning of system parameters. Ziegler-Nicolas (ZN), recursive least squares (RLS) for tuning PID controller, while Pole Placement, and Pole Distribution for tuning FOPID are some examples of classical algorithms that are utilized previously to tackle this problem. Recently, the optimization methods have been employed to tune these parameters in order to have a more stable controller system. This systematic literature review (SLR) will take into consideration various optimization methods that tackled this problem. Methods like PSO, GA and ACO are the most utilized in tackling this problem. This paper will be an introductory guide to other researchers which will immensely help in their metaheuristic method selection.
Feature Selection with a Backtracking Search Optimization Algorithm
Authors: Sikelis Konstantinos , Tsekouras George E.
Published: March 2022

Feature selection carries significance in the outcome of any classification or regression task. Exercising evolutionary computation algorithms in feature selection has led to the construction of efficient discrete optimization algorithms. In this paper, a modified backtracking search algorithm is employed to perform wrapper-based feature selection, where two modifications of the standard backtracking search algorithm are adopted. The first one concentrates on utilizing a particle ranking operator regarding the current population. The second one focuses on removing the case of using a single particle on the mutation process. Then, the implementation of the above algorithm in feature selection is carried out in terms of two general frameworks, which originally were developed for the particle swarm optimization. The first framework is based on the binary and the second on the set-based particle swarm optimization. The experimental analysis shows that the above variants of the backtracking search algorithm perform equally well on the classification of several datasets.
Case Study Design of a Stand-Alone Photovoltaic Power System in Gaza-Strip and Genaralizing Aprogram Simulation
Authors: Awad Husam , Harb Naem , Al goboz Ghada abu , Shurrab Shareif
Published: March 2022

This paper considered the design of a stand-alone PV system that would be adequate to power a single residence and estimate the appropriate size of the solar panel. This system converts solar energy directly into electricity using photovoltaic principle in PV panel arrays. The electricity produced can be used to power most ac and dc electrical appliances. Inverter is used to convert the dc generated by the PV panels to ac for most domestic and industrial use. For continuous availability of power during days of autonomy (low insolation or cloudy days), battery storage system and charge controller (for battery charge and discharge control) are required. inverter, charge controller, battery, components interconnection wires. The sizing processes considered the quality of solar irradiation of the geographical location, effect of temperature de-rating, efficiency of components, system voltage selection, days of autonomy and load demand (in watt-hour). A residence in Gaza town was chosen as a case study. The minimum electrical load of 7.875kWh per day, household, Finally excel program simulation was designed to satisfy calculation equations process and generalize the program.
Vector-Valued Nonuniform Multiresolution Associated with Linear Canonical Transform
Authors: Dar Aamir H.
Published: March 2022

A multiresolution analysis associated with linear canonical transform was defined by Shah and Waseem for which the translation set is a discrete set which is not a group. In this paper, we continue the study based on this nonstandard setting and introduce vector-valued nonuniform multiresolution analysis associated with linear canonical transform (LCT-VNUMRA) where the associated subspace vμ0 of L2ℝℂM) has an orthonormal basis of the form ${\left\{ {\Phi (x - \lambda ){e^ - }\frac{{ - \iota \pi A}}{B}({t^2} - {\lambda ^2})} \right\}_{\lambda \in \Lambda }}$ where Λ = {0, r/N} +2ℤ, N ≥ 1 is an integer and r is an odd integer such that r and N are relatively prime. We establish a necessary and sufficient condition for the existence of associated wavelets and derive an algorithm for the construction of vector-valued nonuniform multiresolution analysis on local fields starting from a vector refinement mask with appropriate conditions.
Cause analysis and simulation verification of a 220kV GIS basin insulator along surface discharge
Authors: Li Xin , Chen Peilong , Zeng Huarong , Mao Xianyin , Liu Kai
Published: March 2022

A surface discharge fault of 220kV GIS basin insulator during power transmission has been analyzed. Combined with on-site disassembly inspection, data from previous tests and structural design, the fault point is determined and the fault cause is preliminarily analyzed. In order to verify the correctness of the analysis results, this paper uses the finite element method to mathematically model the accident basin insulator, and formulates the boundary conditions for the calculation of the electric field inside the basin insulator. The simulation results show that there is a distorted electric field on the surface of the basin insulator, which is the main reason for creeping discharge. The preventive measures are summarized for the creeping discharge fault of the basin-type insulator to avoid the occurrence of similar accidents.
Flexural behavior and finite element analysis of waste tires steel fiber reinforced concrete beams with basalt reinforcement
Authors: Ge Teng , Liang Tianfu , Fan Xiaochun
Published: March 2022

Waste Tire Steel Fiber(WTSF) was used in different proportions (0%, 0.5%).1% and 1.5%) were mixed with ordinary concrete to produce WTSF reinforced concrete. Based on basalt fiber reinforced polymer and WTSF concrete, a new structural system, WTSF concrete beam with basalt reinforcement, is proposed. On the basis of the theory test, using the ABAQUS finite element software to simulate basalt rebar waste of the bending properties of steel fiber concrete beam, to obtain the stress nephogram, cracking load, ultimate bearing capacity, load deflection curves and crack location map, comparative tests and fitting results show that WTSF volume content 0% less muscle damage, 0.5% for balance, 1% and 1.5% are superreinforced failure. With the increase of WTSF content, both cracking load and ultimate bearing capacity are improved. Meanwhile, theoretical calculation formulas of relevant components are given to guide engineering practice.
Sporadic non-ampullary duodenal adenoma with low-grade dysplasia: Natural history and clinical management
Authors: Ikenoyama Yohei , Yoshimizu Shoichi , Namikawa Ken , Tokai Yoshitaka , Horiuchi Yusuke , Ishiyama Akiyoshi , Yoshio Toshiyuki , Hirasawa Toshiaki , Fujisaki Junko
Published: March 2022

Background and study aims Management strategies for sporadic non-ampullary duodenal adenoma with low-grade dysplasia (LGD) are not well established. This study aimed to analyze progression factors and determine suitable treatment strategies for LGD lesions.

Patients and methods We retrospectively analyzed consecutive LGD lesions (n = 125) in patients followed up for ≥ 6 months (median, 45 months) and evaluated the changes in clinicopathological features during follow-up. All LGD lesions were classified into two groups: stable LGD (no increase or < 5 mm increase in tumor size, with unchanged histological dysplasia grade) and progressive LGD (≥ 5 mm increase in tumor size and/or progression to high-grade dysplasia or adenocarcinoma).

Results Eighty-six LGD were classified as stable and 39 as progressive. Location on the oral side of the papilla of Vater, large initial tumor size ( ≥ 10 mm), macroscopically complex type, red color, and nodularity were significantly frequent in progressive LGD than in stable LGD. In multivariate analysis, large initial tumor size (odds ratio [OR], 10.2; 95 % confidence interval [CI], 3.3–32.1; P < 0.001) and location on the oral side of the papilla of Vater (OR: 1.8, 95 % CI: 1.4–12.5; P = 0.012) were significant factors for progression. Moreover, initial tumor size < 5 mm rarely progressed (0%–3.9 %); however, initial tumor size ≥ 20 mm and 10–19 mm located on the oral side of the papilla of Vater had a high-risk progression rate (75.0–85.7 %).

Conclusions According to the risk stratification of progression factors by initial tumor size and location, we can determine suitable treatment indications for LGD lesions.
Der Querstromdialysator nach Hoeltzenbein und Hillenbrand
Authors: Sander Ullrich
Published: March 2022

PD Dr. med. Hoeltzenbein war in den 1960er-Jahren Chefarzt der chirurgischen Abteilung des St. Franziskus-Hospitals in Münster. Er hat sich seit den frühen 1950er-Jahren mit der Hämodialyse beschäftigt, zu deren Fortschritt er beigetragen hat.
Die Rolle der Pflege im Entscheidungsprozess des Patienten zwischen HD und PD
Authors: Reichardt Michael
Published: March 2022

Dieser Artikel ist eine Zusammenfassung einer Facharbeit im Rahmen der nephrologischen Fachweiterbildung zur Gesundheits- und Krankenpflegerin in der Nephrologie an der Weiterbildungsstätte nephrologischer Zentren Rhein-Ruhr am AKK in Essen von Svenja Koebe, Porta Westfalica.
The role of a novel self-expanding metal stent in variceal bleeding: a multicenter Australian and New Zealand experience
Authors: Khan Saad , Gilhotra Rajit , Di Jiang Caroline , Rowbotham David , Chong Andre , Majumdar Avik , White Campbell , Huelsen Alex , Brooker Jim , O’Beirne James , Schauer Cameron , Efthymiou Marios , Vaughan Rhys , Chandran Sujievvan
Published: March 2022

Background and study aims Refractory variceal bleeding is associated with high mortality in patients with chronic liver disease. A fully-covered self-expanding metal stent (SEMS) has been reported to have excellent rates of technical success and initial bleeding control; however, studies to date are small and limited to Europe and Asia. Our aim was to evaluate the efficacy and safety of this SEMS for control of refractory variceal bleeding (VB).

Patients and methods A retrospective analysis was undertaken of all patients who received the SX-ELLA Danis SEMS for management of VB at 9 tertiary centers across Australia and New Zealand. A total of 32 SEMS had been deployed in 30 patients (median age 53.3).

Results Technical success of SEMS placement was achieved in 100 % of cases, resulting in immediate control of bleeding across 31 of 32 cases (96.9 %). Re-bleeding with SEMS in situ occurred in three of 32 cases (9.4 %). Mean SEMS in-dwelling time was 6.4 days. Delayed SEMS migration occurred in 6.3 % of cases. Interventional radiological therapy for management of varices within 6 weeks was performed in 12 of 30 patients (40 %). Death with SEMS in situ occurred in seven of 30 patients (23.3 %). Seven-day bleeding-related mortality was 16.7 %, 14-day mortality 23.3 %, and 6-week mortality 33.3 %. Three of 30 patients (10 %) received orthotopic liver transplantation following SEMS insertion, including two patients within 6 weeks.

Conclusions SX-Danis Ella SEMS is highly effective for immediate control of refractory VB and bridging to definitive therapy because it has excellent technical success rates, appears to be relatively easy to use, and has low rates of serious adverse events.
Gehfähigkeit und Mobilität
Authors: Mehrholz Jan , Elsner Bernhard
Published: March 2022

Eines der wichtigsten Rehabilitationsziele nach Schlaganfall ist die Gehfähigkeit. Die Prognosefaktoren sind vielfältig und klinisch leicht zu erheben. Sie umfassen beispielsweise die Gehgeschwindigkeit, die Gangausdauer, die Schrittzahl, die Balance und die Angst vor Stürzen. Zu erleben, wie sich diese Items verbessern, hat womöglich günstige Auswirkungen auf den Langzeitverlauf.
Gesundheitliche Themen von LSBTIQ+Personen in der ärztlichen Ausbildung in Deutschland
Authors: Brandt Gerrit , Prüll Livia , Paslakis Georgios
Published: March 2022

Zielsetzung Lesbische, schwule, bisexuelle, trans, intergeschlechtliche und queere (LSBTIQ+) Personen erfahren auch heutzutage Diskriminierung und Benachteiligung in vielen Lebensbereichen – auch im Bereich der Gesundheitsversorgung. Studien weisen darauf hin, dass LSBTIQ+Personen einerseits hohe Raten an chronischen körperlichen und psychischen Erkrankungen zeigen, andererseits über negative Erfahrungen mit Behandler_Innen im Gesundheitssystem berichten. Das Ziel dieser Arbeit ist es, einerseits auf Barrieren und eine unzureichende gesundheitliche Versorgung von LSBTIQ+Personen hinzuweisen, andererseits aber auch, auf relevante Lücken in der medizinischen Ausbildung in Deutschland aufmerksam zu machen, woraufhin spezifische Aktionen folgen sollen.

Methodik Zu diesen Zwecken werden sowohl wissenschaftliche Evidenz für die Benachteiligung von LSBTIQ+Personen im Gesundheitssystem als auch wichtige innovative Interventionen in der Ausbildung von medizinischem Personal vorgestellt und diskutiert.

Ergebnisse Eine Vielzahl von unterschiedlichen – in Bezug auf Umfang, Format und Inhalten – Ausbildungsprogrammen sind bereits erprobt und etabliert, allerdings vor allem in englischsprachigen Regionen der Welt. In der medizinischen Ausbildung in Deutschland fehlen dagegen solche Programme.

Schlussfolgerung Eine Sensibilisierung für und Erweiterung der Ausbildung von Medizinstudierenden um LSBTIQ+Gesundheitsthemen ist in Deutschland von großer Bedeutung.
Stress durch Elternschaft: Psychometrische Evaluation der deutschen
Version der Parental Stress Scale in der
Allgemeinbevölkerung
Authors: Kölch Michael , Lübke Laura , Müller Sascha , Reis Olaf , Brähler Elmar , Lincke Lena , Spitzer Carsten
Published: March 2022

Stress aufgrund von Elternschaft wirkt sich nicht nur negativ auf die Betroffenen
selbst, sondern v. a. auch nachteilig auf die psychische und
körperliche Gesundheit ihrer Kinder aus, was reziprok die Belastung im
Sinne eines Teufelskreises erhöht. Elterlicher Stress scheint ein
negativer Faktor für die psychische Gesundheit auch im Rahmen der
Covid-19 Pandemie zu sein. Daher kommt einer reliablen und validen Erfassung der
elterlichen Stressbelastung sowohl wissenschaftlich als auch klinisch-praktisch
eine hohe Bedeutung zu. Die 18 Items umfassende Parental Stress Scale (PSS) ist
aufgrund ihrer Anwendungsökonomie und soliden psychometrischen Kennwerte
international gut etabliert. In dieser Studie wurde die deutsche Version der PSS
erstmals an Eltern (n=386) von Kindern unter 16 Jahren aus einer
repräsentativen Allgemeinbevölkerungsstichprobe (n=2519)
mit einem Fokus auf der Faktorenstruktur teststatistisch evaluiert. Mittels
konfirmatorischer Faktorenanalyse konnten die in der internationalen Literatur
berichteten Modelle nicht bestätigt werden. Eine explorative
Faktorenanalyse legte unter Ausschluss eines Items eine zweifaktorielle
Lösung mit den Dimensionen ‚Mangel an Zufriedenheit‘
sowie ‚Sorgen und Belastungen‘ nahe. Beide Subskalen zeigten
eine gute interne Konsistenz mit Werten für McDonalds
ω≥0,87. Entgegen den Annahmen fanden sich keine relevanten
Zusammenhänge zwischen der um ein Item gekürzten Gesamtskala
(PSS-17) einschließlich der Subskalen und soziodemographischen
Merkmalen, jedoch hypothesenkonforme Assoziationen mit familiärer
Dysfunktion sowie aktueller Depressivität und Ängstlichkeit.
Obwohl mit der deutschen Version der PSS Stressbelastung durch Elternschaft
anwendungsökonomisch, ausreichend reliabel und valide erfasst werden
kann, legen die Befunde zur faktoriellen Validität nahe, dass das
Verfahren der Multidimensionalität des zugrundeliegenden Konstrukts nur
bedingt gerecht wird. Dieser Aspekt ist bei der klinischen und
wissenschaftlichen Anwendung einschränkend zu
berücksichtigen.
Observation of photo-induced plasmon–phonon coupling in PbTe via ultrafast x-ray scattering
Authors: Jiang M. P. , Fahy S. , Hauber A. , Murray É. D. , Savić I. , Bray C. , Clark J. N. , Henighan T. , Kozina M. , Lindenberg A. M. , Zalden P. , Chollet M. , Glownia J. M. , Hoffmann M. C. , Sato T. , Zhu D. , Delaire O. , May A. F. , Sales B. C. , Merlin R. , Trigo M. , Reis D. A.
Published: March 2022

We report the observation of photo-induced plasmon–phonon coupled modes in the group IV–VI semiconductor PbTe using ultrafast x-ray diffuse scattering at the Linac Coherent Light Source. We measure the near-zone-center excited-state dispersion of the heavily screened longitudinal optical (LO) phonon branch as extracted from differential changes in x-ray diffuse scattering intensity following above bandgap photoexcitation. We suggest that upon photoexcitation, the LO phonon-plasmon coupled (LOPC) modes themselves become coupled to longitudinal acoustic modes that drive electron band shifts via acoustic deformation potentials and possibly to low-energy single-particle excitations within the plasma and that these couplings give rise to displacement-correlations that oscillate in time with a period given effectively by the heavily screened LOPC frequency.
Stochastic sensitivity analysis and early warning signals of critical transitions in a tri-stable prey–predator system with noise
Authors: Garain Koushik , Sarathi Mandal Partha
Published: March 2022

Near a tipping point, small changes in a certain parameter cause an irreversible shift in the behavior of a system, called critical transitions. Critical transitions can be observed in a variety of complex dynamical systems, ranging from ecology to financial markets, climate change, molecular bio-systems, health, and disease. As critical transitions can occur suddenly and are hard to manage, it is important to predict their occurrence. Although it is very tough to predict such critical transitions, various recent works suggest that generic early warning signals can detect the situation when systems approach a critical point. The most important indicator that predicts the risk of an upcoming critical transition is critical slowing down (CSD). CSD indicates a slow recovery rate from external perturbations of the stable state close to a bifurcation point. In this contribution, we study a two dimensional prey–predator model. Without any noise, the prey–predator model shows bistability and tri-stability due to the Allee effect in predators. We explore the critical transitions when external noise is added to the prey–predator system. We investigate early warning indicators, e.g., recovery rate, lag-1 autocorrelation, variance, and skewness to predict the critical transition. We explore the confidence domain method using the stochastic sensitivity function (SSF) technique near a stable equilibrium point to find a threshold value of noise intensity for a transition. The SSF technique in a two stage transition through confidence ellipse is described. We also show that the possibility of a transition to the predator-free state is independent of initial conditions. Our result may serve as a paradigm to understand and predict the critical transition in a two dimensional system.
An innovative eye-tracker: Main features and demonstrative tests
Authors: Bellizzi Lorenzo , Bevilacqua Giuseppe , Biancalana Valerio , Carucci Mario , Cecchi Roberto , Chessa Piero , Donniacuo Aniello , Mandalà Marco , Stiaccini Leonardo
Published: March 2022

We present a set of results obtained with an innovative eye-tracker based on magnetic dipole localization by means of an array of magnetoresistive sensors. The system tracks both head and eye movements with a high rate (100–200 Sa/s) and in real time. A simple setup is arranged to simulate head and eye motions and to test the tracker performance under realistic conditions. Multimedia material is provided to substantiate and exemplify the results. A comparison with other available technologies for eye-tracking is drawn, discussing advantages (e.g., precision) and disadvantages (e.g., invasivity) of the diverse approaches, with the presented method standing out for low cost, robustness, and relatively low invasivity.
Temperature-dependent thermal resistance of phase change memory
Authors: Stern Keren , Keller Yair , Neumann Christopher M. , Pop Eric , Yalon Eilam
Published: March 2022

One of the key challenges of phase change memory (PCM) is its high power consumption during the reset operation, when the phase change material (typically Ge2Sb2Te5, i.e., GST) heats up to ∼900 K or more in order to melt. Here, we study the temperature-dependent behavior of PCM devices by probing the reset power at ambient temperatures from 80 to 400 K. We find that different device structures exhibit contrasting temperature-dependent behavior. The reset power in our confined-type PCM is nearly unchanged with ambient temperature, corresponding to a temperature-dependent thermal resistance, whereas results for mushroom-type PCM from the literature show a linear relation between power and temperature, suggesting a more constant thermal resistance. This discrepancy is ascribed to different temperature distributions and thermal properties of the dominant components of the PCM cell thermal resistance, as shown by electro-thermal modeling. In the confined cell, the thermal boundary resistance of the GST and the thermal conductivity of the bottom electrode dominate the thermal resistance, while for the mushroom cell, the GST thermal conductivity plays a greater role. These findings can help to design more power- and energy-efficient PCM devices by better focusing thermal management efforts on the key components of the device.
Effect of grain size on damage and failure in two-phase materials: Homogenized CuPb
Authors: Fensin Saryu J. , Jones David R. , Martinez Daniel T. , Patterson Brian , Gray George T.
Published: March 2022

It is well known that spall failure strongly depends on the microstructure of a material. There have been numerous studies to study the effect of grain size on the overall spall strength and the total amount of damage in single element metals like copper. However, such systematic studies remain rare in two-phase materials and alloys. In this work, two incipient spall experiments were performed on a Cu–1%Pb alloy to understand the effect of grain size on the damage and failure in a two-phase material. Overall, these results showed that even though the spall strength did not change as a function of grain size, there were significant differences in the total amount of damage as a function of grain size. A clear increase in the total damage present in the material was seen as the grain size was increased from 32 to either 70 or 75 μm in either of the experiments. This difference was attributed to variations in the void growth rate as the grain size was increased.
Single-step rapid trench filling with poly-Si using concentration dependence of deposition rate under a SiHCl3–H2 system
Authors: Yamamoto Takanori , Nakashima Kenji , Kamijo Takuma
Published: March 2022

A single-step rapid trench filling with poly-Si was demonstrated using SiHCl3, which advantageously has a high decomposition temperature and contains an etching gas. Through elementary reaction rate analysis, we found a unique condition in which the film deposition rate decreased as the source concentration increased. This negative correlation between the concentration and deposition rate is referred to in this study as NCCR. Through cross-sectional observation, we confirmed that under the NCCR condition, the trench was filled without clogging at a rate that was 60 times faster than conventional low-pressure chemical vapor deposition.
Linear stability of flow in a 90° bend
Authors: Proskurin Alexander
Published: March 2022

This paper considers two-dimensional flow in a channel that consists of straight inlet and outlet branches and a circular 90° curved bend. An incompressible viscous fluid flows through the elbow under the action of a constant pressure gradient between the inlet and outlet. Navier–Stokes equations were solved numerically using a high-fidelity spectral/hp element method. In a range of Reynolds numbers, an adaptive selective frequency damping method was used to obtain steady-state flow. It was found that three separation bubbles and vortex shedding can exist in the bend. The modal stability of two- and three-dimensional perturbations was investigated. The critical Reynolds number of two-dimensional disturbances was found by extrapolation from lower Reynolds number results. It is much greater than the three-dimensional one, but the two-dimensional flow could be subcritically unstable with respect to the externally imposed small-amplitude white noise. For three-dimensional perturbations, the dependence of critical Reynolds numbers on the bending radius was obtained. For the case of a moderate bending radius, a neutral curve is provided and eigenfunctions are studied in detail. Three-dimensional instability can be caused by a periodic or monotonically growing mode, and these unstable modes relate to recirculation bubbles that occur after the bend.
Preparation of a series of new buffer materials for coated conductors
Authors: Zhu Yiqin , Zhang Xin , Huang Jie , Xia Yudong , Cheng C. H. , Zhao Yong
Published: March 2022

New buffer layer materials RESbO3 (RE = Y, Sm, Dy, and Ho), Gd1−xCaxBiO3, Gd1−xPbxBiO3, and Eu1−xCaxBiO3 for coated conductors were deposited on a single crystal LaAlO3 substrate through the self-developed polymer-assisted chemical solution deposition method, and YSbO3 was also deposited on CeO2/NiW. Then, the results of x-ray diffraction patterns and SEM indicate high c-axis oriented, smooth, compact, and seamless properties of fabricated new buffer layers, which satisfied the subsequent growth of the superconducting layer. This work offers an effective method to prepare new buffer layers for coated conductors and may provide a new way to search materials with minimal mismatched lattice.
Effect of dust grains on the parametric coupling of a lower hybrid wave driven ion cyclotron wave in a tokamak plasma
Authors: Kumar Amit , Gupta Ruby , Sharma Jyotsna
Published: March 2022

In this article, the effect of dust charge fluctuations on the parametric upconversion of a lower hybrid wave into an ion cyclotron wave and a side band wave in a two-ion species tokamak plasma is studied. When the oscillatory velocity of plasma electrons is a few percent of the sound velocity, the lower hybrid wave becomes unstable and decays into two modes: an ion cyclotron wave mode and a low frequency lower hybrid side band wave. Furthermore, a ponderomotive force by a lower hybrid pump and a side band wave is exerted on the existing electrons, which drives the ion cyclotron decay mode. The presence of negatively charged dust grains and their shape, size, radius, and density influence the instability. The growth rate of instability is calculated by considering typical existing D–T (Deuterium–Tritium) dusty plasma parameters, and it is observed that the growth rate increases with the relative density of dust grains, number density of dust grains, oscillatory velocity of electrons, and amplitude of pump waves. However, the normalized growth rate increases with the unstable wave frequency, and it also increases as we increase the ratio of deuterium to tritium density. Here, the growth rate decreases with the increase in the size of dust grains and electron cyclotron frequency. The theoretical results summarized in the present study are able to efficiently elaborate the complexity produced in plasma properties in a tokamak due to the dust–plasma interactions, which are briefly discussed here.
Effect of micro-explosion of biodiesel and ethanol droplets on evaporation: A three-stage mixed fuel droplet evaporation model
Authors: Meng Kesheng , Huang Zhiyong , Zhang Xiaolei , Li Lan , Li Rui , Lin Qizhao
Published: March 2022

The ejection and micro-explosion of a mixed fuel droplet group affected the evaporation and combustion rate of fuel. In order to explore the evaporation, micro-explosion, and interaction rules of the biodiesel and ethanol droplet group with different component proportions and volumes during heating, a set of multiparameter tubular furnace experimental equipment was designed. By setting the experimental parameters of the tubular furnace, the heating sequence pictures of the biodiesel and ethanol droplet group were obtained by high-speed photography, and the droplet parameters were analyzed and processed by Image-Proplus. In the experiment, not only the phenomena of ejection, micro-explosion, and white fog but also the interactions of collision, interweaving, and fusion of droplets were observed, which affected the micro-explosion and evaporation of individual droplets in the droplet group. When the ratio of biodiesel to ethanol was 40:60 (40% biodiesel and 60% ethanol), the micro-explosion intensity was the highest. For the same type of droplet, the higher the micro-explosion intensity, the higher the evaporation rate, and the super micro-explosion made the droplet evaporate almost instantaneously. The modified equation for calculating the micro-explosion intensity was established, and the micro-explosion intensity of the mixed droplet was calculated. By integrating the droplet micro-explosion intensity equation and evaporation equation, a three-stage evaporation model of the mixed droplet was established, and the average evaporation rate of the second-stage BD30E70 (30% biodiesel and 70% ethanol) droplet was nearly 28 times the first stage, which was nearly 32 times the third stage.
Enhancing ultrasound transmission and focusing through a stiff plate with inversely optimized auxiliary meta-lens
Authors: Gao He , Gu Zhongming , Liang Shanjun , Liu Tuo , Zhu Jie , Su Zhongqing
Published: March 2022

Effective sound energy transmission and beam manipulation through stiff and dense materials such as metal remain daunting tasks. It is in part attributable to the vast impedance mismatch between those materials and ambient media. Adding openings may facilitate to better bridge energy over, yet ineffective in many applications and may also damage the structural integrity. Here, we present an auxiliary ultrasound focusing meta-lens for stiff and dense materials. It offers significantly enhanced ultrasound transmission and focusing through a stiff metal plate yet without enforcing any through holes or openings. The simple, one-sided only meta-structures are designed and optimized by an inverse strategy based on the genetic algorithm. We numerically and experimentally demonstrate the much enhanced ultrasound transmission when the meta-lens is added to a flat brass plate, along with the capability to offer simultaneous ultrasound focusing. This design methodology can be easily extended to deal with more complex shaped target in a straightforward manner, offering a practical solution to the efficient tunneling of ultrasound energy through stiff and dense materials. With simple grating structures, the meta-lens can be easily fabricated, showing great application prospects in medical imaging and disease treatment.
Terahertz solid immersion microscopy: Recent achievements and challenges
Authors: Chernomyrdin N. V. , Skorobogatiy M. , Ponomarev D. S. , Bukin V. V. , Tuchin V. V. , Zaytsev K. I.
Published: March 2022

Unique effects of terahertz (THz)-wave–matter interaction push rapid progress in THz optoelectronics aimed at bridging the problematic THz gap. However, majority of modern methods of THz spectroscopy and imaging are still hampered by low spatial resolution. Common lens/mirror-based THz optics fails to overcome the Abbe barrier and usually provides resolution larger than a free-space wavelength λ (i.e., hundreds of micrometers or even few millimeters). To mitigate this difficulty, supperresolution THz imaging modalities were introduced recently, among which we particularly underline different methods of THz scanning-probe near-field microscopy. They not only rely on strong light confinement on sub-wavelength probes and provide resolution down to ∼10−1–10−3λ but also suffer from small energy efficiency or presume an interplay among imaging resolution, signal-to-noise ratio, and performance. In this paper, we consider reflection-mode THz solid immersion (SI) microscopy that offers some compromise between the high imaging resolution of 0.15λ and high energy efficiency, which is due to the absence of any subwavelength probe in an optical scheme. Recent achievements, challenging problems, and prospects of SI microscopy are overviewed with an emphasis on resolving the inverse problem and applications in THz biophotonics.
Simulation of the lubricant flow in thin slot channels with a moving wall under slip boundary conditions
Authors: Avramenko A. A. , Shevchuk I. V. , Tyrinov A. I. , Kovetskaya M. M. , Dmitrenko N. P.
Published: March 2022

The article presents the results of studying the flow of a Newtonian fluid in a narrow wedge-shaped slot with a moving wall. A solution to the problem with slip boundary conditions on the channel walls is obtained. The influence of the slip conditions on the walls on the flow parameters is shown. In diverging and converging sections of the channel, different types of flow take place. In the region of the diverging flow near the stationary wall, a reverse flow zone is formed, the width of which increases with an increase in the Knudsen number, which is due to an increase in the flow velocity on the stationary wall due to the slip condition. Calculations elucidated the effect of slippage on the variation of the hydrostatic lifting force and hydraulic resistance in the slot channel. The dependence of the relative hydrostatic lifting force on the Knudsen number and the opening angle of the channel were revealed. It has been determined that with an increase in the Knudsen number, the magnitude of the hydrostatic lifting force decreases, since in this case the influence of the flow on the wall weakens. With an increase in the opening angle of the channel, slip effect weakens.
Spatially heterogeneous dynamics and locally arrested density fluctuations from first principles
Authors: Lira-Escobedo J. , Vélez-Cordero J. R. , Ramírez-González Pedro E.
Published: March 2022

We present a first-principles formalism for studying dynamical heterogeneities in glass-forming liquids. Based on the non-equilibrium self-consistent generalized Langevin equation theory, we were able to describe the time-dependent local density profile during the particle interchange among small regions of the fluid. The final form of the diffusion equation contains both the contribution of the chemical potential gradient written in terms of a coarse-grained density and a collective diffusion coefficient as well as the effect of a history-dependent mobility factor. With this diffusion equation, we captured interesting phenomena in glass-forming liquids such as the cases when a strong density gradient is accompanied by a very low mobility factor attributable to the denser part: in such circumstances, the density profile falls into an arrested state even in the presence of a density gradient. On the other hand, we also show that above a certain critical temperature, which depends on the volume fraction, any density heterogeneity relaxes to a uniform state in a finite time, known as equilibration time. We further show that such equilibration time varies little with the temperature in diluted systems but can change drastically with temperature in concentrated systems.
Evaluation of three-dimensional electromagnetic properties of a soft magnetic composite containing amorphous Fe–Co–B–Si magnetic flakes with magnetic anisotropy
Authors: Kinouchi Hiroaki , Sanada Naoyuki , Suetsuna Tomohiro
Published: March 2022

We investigated electromagnetic properties in a previously developed soft magnetic composite (SMC) containing amorphous Fe-Co-B-Si magnetic flakes with magnetic anisotropy. Magnetic permeability, core loss, and electrical resistivity in three axial directions were measured. These measurements revealed that magnetic permeability differed between the three axial directions, whereas core loss was larger in the direction perpendicular to the flattened plane of the interior flakes than in the other two directions, although it was still expected to be acceptable for applications due to the relatively high electrical resistivity. This paper is the first direct evidence that such an SMC would have three-dimensional magnetic anisotropy and low core loss.
Skyrmion velocities in FIB irradiated W/CoFeB/MgO thin films
Authors: Ahrens Valentin , Gnoli Luca , Giuliano Domenico , Mendisch Simon , Kiechle Martina , Riente Fabrizio , Becherer Markus
Published: March 2022

In recent years magnetic skyrmions attracted great attention for the possibility to move them with low current density, their intrinsic stability and their robustness against defects and edge roughness compared to other magnetic textures. For applications, it is very important to be able to influence the behaviour of skyrmions locally. In this article, we present an evaluation on the effects of FIB Ga+ irradiation on skyrmion motion in W/CoFeB/MgO thin films. The influence of FIB irradiation is evaluated both, in terms of modification of the skyrmion Hall angle and the skyrmion velocity. An overview of the effects of the pulsing parameters on the skyrmion motion, shows low influence of the pulses rise-time and an external magnetic field. In addition the analysis after the irradiation shows that it influences notably the dynamics of skyrmions. In the irradiated zone the speed and angle of motion of these magnetic textures are strongly reduced.
Shape effect of Co nanoparticles on the electric and magnetic properties of Co–SiO2 nanogranular films
Authors: Kijima-Aoki Hanae , Endo Yasushi , Miyazaki Takamichi , Nojima Tsutomu , Ikeda Kenji , Kobayashi Nobukiyo , Ohnuma Shigehiro , Masumoto Hiroshi
Published: March 2022

Controlling the magnetic anisotropy of nanoparticles is a crucial but challenging step for developing new magnetic functions. Here, we demonstrate a simple approach to controlling the shape of Co nanoparticles in a Co-SiO2 nanogranular film from oblate to prolate spheroid by varying the substrate rotation speed during the tandem fabrication process without changing the film composition (Co:SiO2 = 3:7). Changing the nanoparticles from oblate to prolate, increasing perpendicular length of ellipsoidal nanoparticles, changes the magnetic anisotropy axis of Co–SiO2 nanogranular films from in-plane to out-of-plane, which indicates that the shape anisotropy profoundly affects the magnetic properties. Despite the small tunneling current of a few tens of nanoamperes, a maximum tunneling magnetoresistance effect of up to 2.8 % was realized under an applied magnetic field of 12 kOe in the film plane. Achieving both in-plane and perpendicular spin-dependent tunneling, the anisotropic nanogranular films imply direction controllable tunneling materials as future topological nanoarchitecture. Such high-resistivity nanogranular films with a controllable magnetic nanoparticle shape facilitate the design of new magneto-optical devices with high withstand voltages.
Domain wall propagation in Fe-rich magnetic microwires with graded magnetic anisotropy
Authors: Corte-Leon P. , Zhukova V. , Blanco J. M. , Ipatov M. , Fert A. , Gonzalez J. , Zhukov A.
Published: March 2022

We observed that stress-annealing of Fe75B9Si12C4 magnetic microwire at variable annealing temperature allows to create graded magnetic anisotropy. We have found that single domain wall (DW) propagation in a media with graded magnetic anisotropy is essentially non-uniform: faster DW propagation is observed in the region with moderate stress-annealing induced magnetic anisotropy. Higher DW velocity in the region with induced magnetic anisotropy is explained by the transverse character of stress-annealing induced magnetic anisotropy which affects the travelling DW in a similar way as application of transversal bias magnetic field. Obtained graded magnetic anisotropy allows engineering the DW dynamics of Fe-rich microwires.
Inducing Fe moment in LaFeSi with p-block element substitution
Authors: Chouhan Rajiv K. , Del Rose Tyler J. , Mudryk Yaroslav , Pecharsky Vitalij K.
Published: March 2022

We studied the LaFeSi phase using density functional theory based full-potential linearized augmented plane wave (FP-LAPW) method. Specifically we examined the effect of p-element substitution on the stability and magnetic properties focusing on pathways to induce Fe magnetic moments. We demonstrate that either partial or complete substitutions at the Si 2c-site by several p-block elements lead to non-zero Fe moments. Our theoretical study shows that partially substituted LaFeSi1-yGay and LaFeSi1-yAly are more thermodynamically stable than the fully substituted LaFeGa and LaFeAl. We also found that the P substitutions, either partial or complete, have the most negative formation energies, however the compounds containing phosphorus are non-magnetic. Our work highlights a pathway toward manipulations of the otherwise quenched Fe-moments in LaFeSi-related compounds and help in advancing the potential magnetic functionalities of LaFeX compounds.
Depth-resolved magnetization profile of MgO/CoFeB/W perpendicular half magnetic tunnel junctions
Authors: Bansal V. , Tonnerre J.-M. , Mossang E. , Ortega L. , Fettar F. , Chatterjee J. , Auffret S. , Prejbeanu I.-L. , Dieny B.
Published: March 2022

In this work, we used the soft X-ray resonant magnetic reflectivity to study the depth-resolved out-of-plane (oop) magnetization profile of a CoFeB/MgO sample with W/Ta cap layer after annealing at 400°C. It is a powerful technique to probe buried magnetic interfaces of ultra-thin films by combining the depth-resolved information of X-ray reflectivity with the species selectivity of X-ray magnetic circular dichroism. It allowed us to resolve the oop magnetization within a 1.36 nm thick CoFeB layer by the measurement of angle-dependent specular reflectivity at large scattering angles (up to 80°). We determined a graded magnetic distribution for both Fe and Co with a 20% increase at the interface with MgO, decreasing slightly over a thickness of 0.7 nm from MgO before it rapidly decreases to 50% at the interface with W. After applying a non-saturating magnetic field in the plane of the sample, we also quantified a similar magnetization profile with an inclined moment configuration. This indicates that the magnetization gradient is a robust property of the CoFeB layer in the studied sample.