bluuebunny/crossref_metadata_2025 huggingface dataset:
Classifying Indo-Pacific finless porpoise echolocation clicks
Authors: Shapiro Maura
Published: August 2023

Better understanding of the porpoise echolocation clicks enables passive acoustic monitoring for the threatened species.
Oxidation mechanism of high-volume fraction SiCp/Al composite under laser irradiation and subsequent machining
Authors: Liu Hanliang , Zhao Guolong , Nian Zhiwen , Huang Zhipeng , Yang Kai , Liu Conghua , Wang Peng , Diao Zhenkuan
Published: August 2023

Conventional mechanical machining of a composite material comprising an aluminum matrix reinforced with a high volume fraction of SiC particles (hereinafter referred to as an SiCp/Al composite) faces problems such as rapid tool wear, high specific cutting force, and poor surface integrity. Instead, a promising method for solving these problems is laser-induced oxidation-assisted milling (LOAM): under laser irradiation, the local workpiece material reacts with oxygen, thus forming loose and porous oxides that are easily removed. In the present work, the oxidation mechanism of SiCp/Al irradiated by a nanosecond pulsed laser is studied to better understand the laser-induced oxidation behavior and control the characteristics of the oxides, with laser irradiation experiments performed on a 65% SiCp/Al composite with various laser parameters and auxiliary gases (oxygen, nitrogen, and argon). With increasing laser pulse energy density, both the ablated groove depth and the width of the heat-affected zone increase. When oxygen is used as the auxiliary gas, an oxide layer composed of SiO2 and Al2O3 forms, and CO2 is produced and escapes from the material, thereby forming pores in the oxides. However, when nitrogen or argon is used as the auxiliary gas, a recast layer is produced that is relatively difficult to remove. Under laser irradiation, the sputtered material reacts with oxygen to form oxides on both sides of the ablated groove, and as the laser scanning path advances, the produced oxides accumulate to form an oxide layer. LOAM and conventional milling are compared using the same milling parameters, and LOAM is found to be better for reduced milling force and tool wear and improved machined surface quality.
Droplet microfluidic chip for precise monitoring of dynamic solution changes
Authors: Ma Cong , Gao Zehang , Zhao Jianlong , Feng Shilun
Published: August 2023

In this work, an automated microfluidic chip that uses negative pressure to sample and analyze solutions with high temporal resolution was developed. The chip has a T-shaped channel for mixing the sample with a fluorescent indicator, a flow-focusing channel for generating droplets in oil, and a long storage channel for incubating and detecting the droplets. By monitoring the fluorescence intensity of the droplets, the device could detect changes in solution accurately over time. The chip can generate droplets at frequencies of up to 42 Hz with a mixing ratio of 1:1 and a temporal resolution of 3–6 s. It had excellent linearity in detecting fluorescein solution in the concentration range 1–5 μM. This droplet microfluidic chip provides several advantages over traditional methods, including high temporal resolution, stable droplet generation, and faster flow rates. This approach could be applied to monitoring calcium ions with a dynamic range from 102 to 107 nM and a detection limit of 10 nM.
Field-free spin–orbit torque switching of an antiferromagnet with perpendicular Néel vector
Authors: Xu Zhengde , Ren Jie , Yuan Zhengping , Xin Yue , Zhang Xue , Shi Shuyuan , Yang Yumeng , Zhu Zhifeng
Published: August 2023

The field-free spin–orbit torque induced 180° reorientation of magnetization is beneficial for the high performance magnetic memory. The antiferromagnetic material (AFM) can provide a higher operation speed than the ferromagnetic counterpart. In this paper, we propose a trilayer AFM/insulator/heavy metal structure as the AFM memory device. We show that the field-free switching of the AFM with a perpendicular Néel vector can be achieved by using two orthogonal currents, which provide a uniform damping-like torque and uniform field-like torque, respectively. The reversible switching can be obtained by reversing either current. A current density of 1.79 × 1011 A/m2 is sufficient to induce the switching. In addition, the two magnetic moments become noncollinear during switching. This enables an ultrafast switching within 40 ps. The device and switching mechanism proposed in this work offer a promising approach to deterministically switch the AFM with the perpendicular Néel vector. It can also stimulate the development of an ultrafast AFM-based MRAM.
The magnetocaloric effect of the lanthanide fluorides: Using polarized neutron scattering to probe a magnetocaloric suitable for hydrogen liquefaction
Authors: Dixey Richard J. C. , Wildes Andrew , Doheny Patrick W. , Stenning Gavin B. G. , Saines Paul J.
Published: August 2023

This work reports the competitive magnetocaloric effect of some simple lanthanide fluoride materials with cations with high magnetic anisotropy. Of these, HoF3 is particularly promising due to exhibiting a high magnetocaloric entropy change under modest applied fields at higher temperatures, which only decreases modestly with temperature such that it has the potential for cooling for hydrogen liquefaction. Spin-polarized neutron spectroscopy indicates that its promising conventional magnetocaloric effect is likely due to the presence of ferromagnetic fluctuations of highly anisotropic magnetic moments, while its singlet electronic ground state and low-temperature magnetic ordering lead to a decrease in its magnetocaloric performance below 4 K.
The effect of hydrogen on the properties of Mg0.1Zn0.9O thin film
Authors: Zhang Yufeng , Wu Qiuchen , Zhao Wenxiong , Liu Yuhang , Lin Xinlu , Zhu Ziyao , Huang Kai , Liu Xiangxin
Published: August 2023

Opto-electrical properties of MgxZn1−xO can be tuned by adjusting the value of x, but phase separation occurs when x is greater than 0.4. Hydrogen acts as a shallow donor in MgxZn1−xO and can play an important role in tuning the opto-electrical properties in a way that avoids phase separation. Mg0.1Zn0.9O (MZO) films were prepared at different hydrogen partial pressures and their structures and properties were studied. XRD results show that the MZO film has a wurtzite structure with a preferential orientation along the c-axis, but the crystallinity declines with increasing hydrogen partial pressure. Stress in the MZO film changes from tensile to compressive as the hydrogen partial pressure increases. Increasing the hydrogen partial pressure improves the conductivity and increases the optical bandgap, but the electronic affinity of MZO decreases, according to ultraviolet photoelectron spectroscopy results. These key parameters were used to simulate a device with a TCO/MZO/CdTe/ZnTe:Cu type structure, in which TCO is the transparent conductive oxide. The highest efficiency of 17.37% was achieved when the electron affinity of the MZO film was 3.71 eV, corresponding to a spark-like band offset of 0.29 eV at the MZO/CdTe interface. These results suggest that the electron affinity of MZO can be tuned to achieve an optimal band alignment in the device.
Design of the shattered pellet injection system for ASDEX Upgrade
Authors: Dibon M. , de Marne P. , Papp G. , Vinyar I. , Lukin A. , Jachmich S. , Kruezi U. , Muir A. , Rohde V. , Lehnen M. , Heinrich P. , Peherstorfer T. , Podymskii D. ,   ASDEX Upgrade Team
Published: August 2023

A new shattered pellet injection system was designed and built to perform disruption mitigation experiments on ASDEX Upgrade. The system can inject pellets with diameters of 1, 2, 4, or 8 mm with variable lengths over a range of L/D ratios of ∼0.5–1.5. By using helium or deuterium as propellant gas, the pellets can be accelerated to speeds between 60 and 750 m/s. The velocity range slightly depends on the pellet mass. The injection system is capable of preparing three pellets in separate barrels at the same time. Once accelerated by the propellant gas pulse, the pellets travel through one of three parallel flight tubes. Each flight tube is separated into three sections with increasing diameters of 12, 14, and 16 mm. Two gaps between the sections allow for removal of the propellant gas by expansion into two separate expansions tanks (0.3 and 0.035 m3), pellet observation in the first gap and the torus gate valve in the second. Each flight tube end is equipped with an exchangeable shatter head with different shatter angles, square or circular cross-section, and different lengths. The gas preparation and control systems allow highly automated pellet generation for precision of the pellet composition and an excellent reproducibility of shattered pellet experiments.
Low temperature tetragonal polymorph of CaZrF6
Authors: Bodine Daniel L. , Wilkinson Angus P.
Published: August 2023

A new tetragonal polymorph of CaZrF6 can be prepared by high energy ball milling of a CaF2/ZrF4 mixture, followed by heat treatment at 325 °C. This polymorph is thermodynamically stable with respect to the well-known cubic form at low temperatures. However, it readily transforms to the cubic form on heating above ∼400 °C. The tetragonal (β) CaZrF6 is not isostructural with any previously known alkaline earth AZrF6 phase. Unlike the cubic form, which shows strong negative thermal expansion over a wide temperature range, the tetragonal form displays positive thermal expansion in all directions (100–400 K: αl ∼ +17 × 10−6 K−1 and +13 × 10−6 K−1 along the a- and c-axes, respectively).
Optimal control of a Wilson–Cowan model of neural population dynamics
Authors: Salfenmoser Lena , Obermayer Klaus
Published: August 2023

Nonlinear dynamical systems describe neural activity at various scales and are frequently used to study brain functions and the impact of external perturbations. Here, we explore methods from optimal control theory (OCT) to study efficient, stimulating “control” signals designed to make the neural activity match desired targets. Efficiency is quantified by a cost functional, which trades control strength against closeness to the target activity. Pontryagin’s principle then enables to compute the cost-minimizing control signal. We then apply OCT to a Wilson–Cowan model of coupled excitatory and inhibitory neural populations. The model exhibits an oscillatory regime, low- and high-activity fixed points, and a bistable regime where low- and high-activity states coexist. We compute an optimal control for a state-switching (bistable regime) and a phase-shifting task (oscillatory regime) and allow for a finite transition period before penalizing the deviation from the target state. For the state-switching task, pulses of limited input strength push the activity minimally into the target basin of attraction. Pulse shapes do not change qualitatively when varying the duration of the transition period. For the phase-shifting task, periodic control signals cover the whole transition period. Amplitudes decrease when transition periods are extended, and their shapes are related to the phase sensitivity profile of the model to pulsed perturbations. Penalizing control strength via the integrated 1-norm yields control inputs targeting only one population for both tasks. Whether control inputs drive the excitatory or inhibitory population depends on the state-space location.
Recent progress in understanding the microscopic origin of triboelectricity from mechanochemistry to thermoelectricity
Authors: Shin Eui-Cheol , Mun Ji-Ho , Baek Seungil , Jung Jaegwan , Kim Yong-Hyun
Published: August 2023

Triboelectricity has long been discussed from ancient Greece to modern times in daily life experiences as well as in the earliest stages of planet formation and the cutting-edge triboelectric nanogenerator technology. Despite the numerous efforts from scientists and engineers, fundamental understanding of the friction-driven static electrification has remained elusive. Here, we review recent progress in understanding the microscopic origin of triboelectricity, directly associated with frictional energy dissipation at the interface, from mechanochemistry, strain-driven polarization, and tribo-tunneling to thermoelectricity. Noticeably, we note that the microscopic thermoelectric charging mechanism due to interfacial frictional heat offers a generally applicable, but exactly solvable triboelectric model in the weakly interacting regime, implying many opportunities in triboelectric based science and technology in the future.
Estimates of the wavenumber wavelet power spectrum of magnetic fluctuations during magnetic reconnection
Authors: Titus J. B. , Almagri A. F. , DeHaas T.
Published: August 2023

Fluctuation analyses of experimental observations generally lack high temporal resolution and are in frequency-space f, contrary to theoretical efforts in wavenumber-space k. This is due to the inherent limits of the Fourier transform, though it is prominent due to the ease of diagnostic implementation. Advances in wavelet-based analysis have provided relief due to its temporal resolution, but in its common use, is still hard to compare to theoretical models. By using the two-point correlation technique in conjunction with large data sets, a wavelet power spectrum in wavenumber-space can be created. Dubbed the wavenumber wavelet power spectrum, this spectrum relates wavenumber to power in time. This analysis technique more closely connects characterizations of experimentally observed fluctuations with other system parameters and theoretical predictions. In this article, we develop the wavenumber wavelet power spectrum using magnetic fluctuations caused by tearing instability driven magnetic reconnection in reproducible, high temperature laboratory plasmas. These dynamic magnetic fluctuations generated in reversed field pinch plasmas are broadband, ranging from the low frequency, 10's of kHz, up to the ion gyroradii frequencies, 100's of kHz. The dominant fluctuations have poloidal and toroidal mode numbers (m,n)=(1,6−10) and can grow to 2%–3% of the mean magnetic field. During these reconnection events, ions, and electrons are energized, magnetic fluctuation amplitudes increase, plasma flow is halted, and the toroidal magnetic flux increases, all on a semi-periodic basis. The newly developed spectrum provides better temporal resolution of spectrum characteristics to correlate with these particle energization phenomena.
Whistler modes guided by a nonuniform cylindrical duct in a magnetoplasma below the lower hybrid frequency
Authors: Kudrin Alexander V. , Ostafiychuk Oleg M. , Zaboronkova Tatyana M.
Published: August 2023

Guided propagation of whistler waves and their excitation by a loop antenna in the presence of a field-aligned cylindrical duct with enhanced density in a magnetoplasma are studied below the lower hybrid resonance frequency. The emphasis is placed on the case where the duct is transversely nonuniform such that the plasma density in it decreases monotonically from a constant value in the near-axis inner region to the lower background value in the outer medium. Conditions are determined under which the dispersion characteristics and field structures of the modes guided by such a duct allow an approximate description within the framework of perturbation theory. The approximate results are shown to be in good agreement with the numerical results obtained using a full-wave approach. It is also found that the radiation resistance of a loop antenna located in the smooth-walled enhanced density duct can be notably greater than that of the same antenna immersed in the background magnetoplasma due to the excitation of the modes guided by the duct. The reported results extend previous analyses performed for sharp-walled uniform ducts to the case of a more realistic plasma density profile in the duct and can be useful in understanding the basic features of whistler wave guidance and excitation as well as in planning the related experiments.
Deformation insensitive thermal conductance of the designed Si metamaterial
Authors: Yang Lina , Zhang Quan , Hu Gengkai , Yang Nuo
Published: August 2023

The thermal management has been widely focused due to its broad applications. Generally, the deformation can largely tune the thermal transport. The main challenge of flexible electronics/materials is to maintain thermal conductance under large deformation. This work investigates the thermal conductance of a nano-designed Si metamaterial constructed with curved nanobeams by molecular dynamics simulation. Interestingly, it shows that the thermal conductance of the nano-designed Si metamaterial is insensitive under a large deformation (strain ∼ −41%). The new feature comes from the designed curved nanobeams, which exhibit a quasi-zero stiffness. Further calculations show that, when under large deformation, the average stress in nanobeam is ultra-small (<151 MPa), and its phonon density of states are little changed. This work provides valuable insight on the multifunction, such as both stable thermal and mechanical properties, of nano-designed metamaterials.
Instability of Langmuir-beam waves: Kappa-distributed electrons
Authors: Lazar M. , López R. A. , Poedts S. , Shaaban S. M.
Published: August 2023

In space plasmas, electron populations exhibit non-equilibrium velocity distributions with high-energy tails that are reproduced by the Kappa power-laws and contrast with the Maxwellian distributions often used in theoretical and numerical analyses. In this work, we investigate typical electron beam-plasma systems and show the influence of Kappa tails on the linear dispersion and stability spectra of Langmuir-beam waves. The most common scenarios invoke instabilities of Langmuir waves at the origin of radio emissions in solar flares and interplanetary shocks. However, the parametric domain of these instabilities is narrow (i.e., energetic beams but with very low density, nb/ne≲10−3), making their analytical and numerical characterization not straightforward, while the approximations used may lead to inconclusive results. Here, we provide exact numerical solutions of the Langmuir-beam mode, which distinguish from the classical ones (unaffected by the beam), and also from electron beam modes destabilized by more energetic and/or denser beams. Langmuir-beam solutions are only slightly modified by the Kappa distribution of the beam component, due to its very low density. However, if the main (core) population is Kappa distributed, the instability of the Langmuir-beam mode is strongly inhibited, if not suppressed. New analytical solutions are derived taking into account the more or less resonant involvement of the electron core and beam populations. As a result, the analytical solutions show an improved match with the exact solutions, making them applicable in advanced modeling of weak (weakly nonlinear) turbulence.
Turbulence characterization of instantaneous airflow above passengers with different air distribution systems in a commercial airliner cabin
Authors: Liu Mingxin , Li Jiayu , Liu Junjie , Hassan Muhammad Azher
Published: August 2023

The environment inside airliner cabins has attracted increasing attention. Instantaneous airflow, as one of the fundamental parameters of airflow field, affects aspects of the airliner cabin environment such as occupant comfort and airborne disease transmission. This study evaluated the characteristics of instantaneous airflow in airliner cabins with different ventilation systems (mixing ventilation and displacement ventilation) and focused on the region above passengers' heads, where complex turbulence characteristics are found. This investigation used ultrasonic anemometers for measurements at ten selected points above passengers' heads. The energy ratio on the low-frequency scale with mixing ventilation was greater than that with displacement ventilation. The instantaneous airflow with mixing ventilation was close to that of natural wind, while the instantaneous airflow with displacement ventilation was close to that of mechanical wind. Compared with mixing ventilation, displacement ventilation produced a smaller vortex length and a shorter residence time. Moreover, there was no long-term vortex in the flow field under displacement ventilation, and therefore, pollutants would be discharged more quickly from the cabin. In addition, this paper distinguishes the spatial and temporal turbulence scales of mixing and displacement ventilation, thus providing a reference for the selection of grid size and time steps in computational fluid dynamics simulations.
Effects of moving endwall on the unsteadiness of tip leakage flow in compressor cascades
Authors: Qiang Xiaoqing , Deng Hefang , Xia Kailong , Teng Jinfang , Zhu Mingmin , Lu Shaopeng
Published: August 2023

The influence of the moving endwall on the behavior of the tip leakage flow in compressors holds substantial significance. This work investigates the unsteadiness of the compressor's tip leakage flow under the impact of the moving endwall, employing both experimental methods and unsteady Reynolds-averaged Navier–Stokes (URANS) simulations. First, a numerical decomposition technique is proposed to isolate the tip leakage flow within a controlled diffusion airfoil (CDA) cascade. Subsequently, URANS simulations based on the CDA cascade are conducted at various incidence angles (−6° to +7°), tip clearances (clearance to chord: 0.83% to 3.33%), and flow coefficients (0.4 to 0.6), and additional URANS simulations based on the Virginia Tech cascade are also performed. The results indicate that the moving endwall induces a greater inclination of the tip leakage flow in the pitchwise direction, allowing it to impinge upon the pressure side of the adjacent blade. The impingement, if sufficiently intense, leads to the periodic generation of unsteady tip leakage flow by altering the blade loading. Moreover, the degree of unsteadiness diminishes significantly as the endwall speed and clearance height decrease. Additionally, it is observed that the breakdown of the tip leakage vortex does not serve as the root cause of the periodic unsteadiness. These findings underscore the critical role played by the moving endwall in the unsteadiness of the compressor's tip leakage flow.
Human-animal interactions from an evolutionary perspective: Symbioses as extended ultrasociality
Authors: Steklis H. Dieter , Steklis Netzin G. , Peñaherrera-Aguirre Mateo , Figueredo Aurelio J.
Published: August 2023

The field of human-animal interactions (HAI) is focused primarily on human-companion animal relationships, especially the impact of such relationships on human health. Here, we demonstrate how a wider, integrative approach, consisting of an evolutionary framework, provides new insights into the varieties of HAIs and their emergence and significance during human evolution. Along with other HAI researchers, we show that those HAIs which develop into interrelationships can best be treated as ecological symbioses that involve fitness interdependence among the symbionts and entail the evolution of phenotypic traits that support the adaptive features of the symbionts. We present the novel idea that the formation of mutualistic symbiotic relationships through the process of domestication depended on the prior evolution of hominin hypersociality and ultrasociality in modern humans. Hypersociality was characterized by high levels of social cooperation and social tolerance that became increasingly important for human social life and cooperative hunting. The further development of ultrasociality in modern humans consisted of the development of large-scale (i.e., beyond the hunting band) cooperative social networks of genetically unrelated individuals. This depended on the evolution of further enhancements in socio-cognitive skills, especially representational abilities (e.g., theory of mind), symbolic capacities, and formation of tribal societies with complex social institutions. These modern cognitive and socio-cultural features were made possible by significant brain reorganization during the past 60,000 years. Tribal social institutions were founded on normative moral sentiments and behavior and regulated and ultimately reduced levels of lethal violence. The extension of fitness interdependent, cooperative relationships to large networks of unrelated individuals (i.e., ultrasociality), we argue, was foundational in modern humans to the formation of mutualistic symbioses (i.e., process of domestication) with other animals. Because they are an outgrowth of ultrasociality, we suggest that the term “extended ultrasociality” appropriately describes human interrelationships with domesticated animals. We further suggest that these human-animal interrelationships are unique in that they become imbued with and immersed in our symbolic world, as is demonstrated by the earliest representational art in caves after 50,000 years when enhanced modern human representational and symbolic capacities were evolving. An evolutionary framework invites new questions and avenues for research.
The Role of Technology in Promoting Environmental Conservation and Cross-Cultural Understanding: Lessons From Ridgeline Wanaka
Authors: Dold Pippa , Finkler Wiebke , Walker Lloyd , Carr Neil , Lee Craig
Published: August 2023

This case study offers valuable insights into the field of tourism business studies through the analysis of three interviews with Mark Orbell, the founder of Ridgeline Wanaka. With a focus on connecting individuals with nature through private walks, off-road safaris, and photography tours, the business simultaneously emphasizes the importance of conservation and cross-cultural understanding through technology. Mark Orbell’s commitment to preserving the Wanaka region’s natural beauty and biodiversity serves as the fundamental cornerstone of Ridgeline Wanaka’s overarching business strategy. By conducting interviews that spanned the periods prior to, during, and after the COVID-19 pandemic, this study sheds light on the challenges encountered by the business and showcases the implementation of innovative cross-cultural strategies. In conjunction with advancements in technology and an emphasis on conservation tourism, cross-cultural understanding emerges as a pivotal element within Ridgeline Wanaka’s business strategy, playing a critical role in elevating the quality of tourism service delivery and cultivating authentic and meaningful visitor experiences.

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© The Authors 2023
The velocity of resistance exercise does not accurately assess repetitions‐in‐reserve
Authors: Mansfield Sean K. , Peiffer Jeremiah J. , Galna Brook , Scott Brendan R.
Published: August 2023

This study assessed the reliability of mean concentric bar velocity from 3‐ to 0‐repetitions in reserve (RIR) across four sets in different exercises (bench press and prone row) and with different loads (60 and 80% 1‐repetition maximum; 1RM). Whether velocity values from set one could be used to predict RIR in subsequent sets was also examined. Twenty recreationally active males performed baseline 1RM testing before two randomised sessions of four sets to failure with 60 or 80% 1RM. A linear position transducer measured mean concentric velocity of repetitions, and the velocity associated with each RIR value up to 0‐RIR. For both exercises, velocity decreased between each repetition from 3‐ to 0‐RIR (p ≤ 0.010). Mean concentric velocity of RIR values was not reliable across sets in the bench press (mean intraclass correlation coefficient [ICC] = 0.40, mean coefficient of variation [CV] = 21.3%), despite no significant between‐set differences (p = 0.530). Better reliability was noted in the prone row (mean ICC = 0.80, mean CV = 6.1%), but velocity declined by 0.019–0.027 m·s−1 (p = 0.032) between sets. Mean concentric velocity was 0.050–0.058 m·s−1 faster in both exercises with 60% than 80% 1RM with (p < 0.001). At the individual level, the velocity of specific RIR values from set one accurately predicted RIR from 5‐ to 0‐RIR for 30.9% of repetitions in subsequent sets. These findings suggest that velocity of specific RIR values vary across exercises, loads and sets. As velocity‐based RIR estimates were not accurate for 69.1% of repetitions, alternative methods to should be considered for autoregulating of resistance exercise in recreationally active individuals.
Theoretical Predictions on Superconducting Phase above Room Temperature in Lutetium-Beryllium Hydrides at High Pressures
Authors: Li Bin , Yang Yeqian , Fan Yuxiang , Zhu Cong , Liu Shengli , Shi Zhixiang
Published: August 2023

High-pressure structural search was performed on the hydrogen-rich compound LuBeH8 at pressures up to 200 GPa. We found an

F
m

3
¯

m

structure that exhibits stability and superconductivity above 100 GPa. Our phonon dispersion, electronic band structure, and superconductivity analyses in the 100–200 GPa pressure range reveal a strong electron–phonon coupling in LuBeH8, while the superconducting critical temperature T
c shows a decreasing trend as the pressure increases, with T
c = 255 K at 200 GPa and maximal T
c = 355 K at 100 GPa. This study demonstrated the room-temperature superconductivity in

F
m

3
¯

m

-LuBeH8, thus enriching the family of ternary hydrides. These findings provide valuable guidance for identifying new high-temperature superconducting hydrides.
Double buffer of MAPbBr3 QDs using a bulk crystal source by the LARP method and MABr modifier for CsPbBr3 perovskite light-emitting diodes
Authors: Chen Lung-Chien , Wei You-Siang , Zhang Meng
Published: August 2023

In this work, we employed MAPbBr3 quantum dots (QDs) and MABr salt as buffer layers to boost the optoelectronic characteristics of CsPbBr3 perovskite light-emitting diodes (PeLEDs). The MAPbBr3 QDs were prepared by ligand-assisted reprecipitation method and using MAPbBr3 bulk single crystals as source material, but traditional powder source. The MAPbBr3 bulk single crystals were obtained by inverse temperature crystallization method. The purification cycles of bulk-crystal source MAPbBr3 quantum dots (bc-MAPbBr3 QDs) were studied. The bc-MAPbBr3 QDs and MABr salt were applied into the PeLED structures. The best brightness reached 7555 cd m−2, and the external quantum efficiency reached 0.318%.
Tuning the spin of Dirac fermions on the surface of topological insulators in proximity to a helical spin density wave
Authors: Yar Abdullah , Taif Usman Muhammad , Sabeeh Kashif
Published: August 2023

We investigate the spin tunability of Dirac fermions on the surface of a 3D topological insulator in proximity to a helical spin density wave, acting as an applied one-dimensional periodic potential for spins produced by spiral multiferroic oxide. It is observed that the spin mean values of Dirac fermion undergo oscillations under the influence of such a periodic potential created by the exchange field of magnetization. The tunability of spin is strongly affected by the strength, orientation and period of the exchange field. In particular, the mean values of spin are anisotropic around the Dirac point, depending strongly on the amplitude and spatial period of the periodic potential. We also find that the spin expectation values change significantly by changing the plane of magnetization. Interestingly, the in-plane components of spin mean values perform pronounced oscillations, whereas the out of plane component does not oscillate at all. The oscillations of planar components of spin are originated from the spin-momentum locking on the surface of topological insulator.
Defining optimal thickness for maximal self-field
Jc
in YBCO/CeO2 multilayers grown on buffered metal
Authors: Tuomola A , Rivasto E , Aye M M , Zhao Y , Huhtinen H , Paturi P
Published: August 2023

The effect of multilayering YBa2Cu3O

6
+
x

(YBCO) thin films with sequentially deposited CeO2 layers between YBCO layers grown on buffered metallic template is investigated to optimize the self-field critical current density

J

c

(
0
)

. We have obtained that the improvement in

J

c

(
0
)

clearly depends on the YBCO layer thickness and temperature, where at high temperature

J

c

(
0
)

can be increased even 50% when compared with the single layer YBCO films. Based on our experimental results and theoretical approach to the growth mechanism during multilayer deposition, we have defined a critical thickness for the YBCO layer, where the maximal self-field

J

c

(
0
)

is strongly related to the competing issues between the uniform and nonuniform strain relaxation and the formation of dislocations and other defects during the film growth. Our results can be directly utilized in the future coated conductor technology, when maximizing the overall in-field

J

c

(
B
)

by combining both the optimal crystalline quality and flux pinning properties typically in bilayer film structures.
BEG spin-1 model with random exchange magnetic interactions for spin-crossover solids
Authors: Ogou Saliou Bolarinwa , Oke Toussaint Djidjoho , Karimou Mounirou , Hontinfinde Félix , Boukheddaden Kamel
Published: August 2023

We have investigated magnetic phase diagrams of spin-crossover (SCO) solids throughout the Blume–Emery–Griffiths spin-1 model where the spin states ±1 and 0 are associated to high-spin state and low-spin states respectively. In the present work, the quadrupolar interaction, K, parameter depends linearly on temperature and accounts for the role of the lattice phonons in the elastic interactions between the SCO units. Magnetic interactions are randomly distributed in the system and are controlled by a factor

γ
=

J

i
j

/

K

such that for γ = 0 (

J

i
j

=
0

), magnetic ordering is not expected. The crystal-field that acts on SCO sites depends both on the ligand-field strength and the degeneracy ratio between HS and LS states as in some previous works. The system is also under the effect of a random local magnetic field hi
acting on each site i. The model is solved using a homogeneous mean field theory. Our investigations reveal the occurrence of thermally-induced gradual, and first-order spin-transitions by varying the model parameters. At vicinity of first-order transition, various types of isothermal magnetic hysteresis loops are obtained and their corresponding coercive field and loop patterns are discussed as function of temperature.
Deep learning algorithm for visual quality assessment of the spirograms
Authors: Waląg Damian , Soliński Mateusz , Kołtowski Łukasz , Górska Katarzyna , Korczyński Piotr , Kuźnar-Kamińska Barbara , Grabicki Marcin , Basza Mikołaj , Łepek Michał
Published: August 2023

Objective. The quality of spirometry manoeuvres is crucial for correctly interpreting the values of spirometry parameters. A fundamental guideline for proper quality assessment is the American Thoracic Society and European Respiratory Society (ATS/ERS) Standards for spirometry, updated in 2019, which describe several start-of-test and end-of-test criteria which can be assessed automatically. However, the spirometry standards also require a visual evaluation of the spirometry curve to determine the spirograms’ acceptability or usability. In this study, we present an automatic algorithm based on a convolutional neural network (CNN) for quality assessment of the spirometry curves as an alternative to manual verification performed by specialists.Approach. The algorithm for automatic assessment of spirometry measurements was created using a set of randomly selected 1998 spirograms which met all quantitative criteria defined by ATS/ERS Standards. Each spirogram was annotated as ‘confirm’ (remaining acceptable or usable status) or ‘reject’ (change the status to unacceptable) by four pulmonologists, separately for FEV1 and FVC parameters. The database was split into a training (80%) and test set (20%) for developing the CNN classification algorithm. The algorithm was optimised using a cross-validation method.Main results. The accuracy, sensitivity and specificity obtained for the algorithm were 92.6%, 93.1% and 90.0% for FEV1 and 94.1%, 95.6% and 88.3% for FVC, respectively.Significance.The algorithm provides an opportunity to significantly improve the quality of spirometry tests, especially during unsupervised spirometry. It can also serve as an additional tool in clinical trials to quickly assess the quality of a large group of tests.
Electron kinetics in a positive column of AC discharges in a dynamic regime
Authors: Humphrey Nathan A , Kolobov Vladimir I
Published: August 2023

We have performed hybrid kinetic-fluid simulations of a positive column in alternating current (AC) argon discharges over a range of driving frequencies f and gas pressure p for the conditions when the spatial nonlocality of the electron energy distribution function (EEDF) is substantial. Our simulations confirmed that the most efficient conditions of plasma maintenance are observed in the dynamic regime when time modulations of mean electron energy (temperature) are substantial. The minimal values of the root mean square electric field and the electron temperature have been observed at f/p values of about 3 kHz Torr−1 in a tube of radius R = 1 cm. The ionization rate and plasma density reached maximal values under these conditions. The numerical solution of a kinetic equation allowed accounting for the kinetic effects associated with spatial and temporal nonlocality of the EEDF. Using the kinetic energy of electrons as an independent variable, we solved an anisotropic tensor diffusion equation in phase space. We clarified the role of different flux components during electron diffusion in phase space over surfaces of constant total energy. We have shown that the kinetic theory uncovers a more exciting and rich physics than the classical ambipolar diffusion (Schottky) model. Non-monotonic radial distributions of excitation rates, metastable densities, and plasma density have been observed in our simulations at pR > 6 Torr cm. The predicted off-axis plasma density peak in the dynamic regime has never been observed in experiments so far. We hope our results stimulate further experimental studies of the AC positive column. The kinetic analysis could help uncover new physics even for such a well-known plasma object as a positive column in noble gases.
A novel negative stiffness metamaterials: discrete assembly and enhanced design capabilities
Authors: Sun Min , Zhang Kun , Guo Xinzheng , Zhang Zheng , Chen Yiji , Zhang Guang , Jiang Shaofei
Published: August 2023

In this study, a new negative stiffness metamaterial is designed using laminates with independent negative stiffness properties as the functional component and a discrete assembly method. In this paper, the metamaterial is designed by a mathematical model, which has been verified and analyzed systematically by experiment and finite element method. The influence of each laminate parameter on the design of metamaterials under uniform distribution and gradient distribution was investigated, and based on this, the load-bearing capacity enhancement strategy of metamaterials was further explored. The metamaterial has the advantages of discrete assembly and designability, which solves the defects of the previous performance constrained by the structure and enhances usability.
A deep learning approach for anomaly identification in PZT sensors using point contact method
Authors: Kalimullah Nur M M , Shelke Amit , Habib Anowarul
Published: August 2023

The implementation of piezoelectric sensors is degraded due to surface defects, delamination, and extreme weathering conditions, to mention a few. Hence, the sensor needs to be diagnosed before the efficacious implementation in the structural health monitoring (SHM) framework. To rescue the problem, a novel experimental method based on Coulomb coupling is utilised to visualise the evolution of elastic waves and interaction with the surface anomaly in the lead zirconate titanate (PZT) substrate. Recently, machine learning (ML) has been expeditiously becoming an essential technology for scientific computing, with several possibilities to advance the field of SHM. This study employs a deep learning-based autoencoder neural network in conjunction with image registration and peak signal-to-noise ratio (PSNR) to diagnose the surface anomaly in the PZT substrate. The autoencoder extracts the significant damage-sensitive features from the complex waveform big data. Further, it provides a nonlinear input–output model that is well suited for the non-linear interaction of the wave with the surface anomaly and boundary of the substrate. The measured time-series waveform data is provided as input into the autoencoder network. The mean absolute error (MAE) between the input and output of the deep learning model is evaluated to detect the anomaly. The MAEs are sensitive to the anomaly that lies in the PZT substrate. Further, the challenge arising from offset and distortion is addressed with ad hoc image registration technique. Finally, the localisation and quantification of the anomaly are performed by computing PSNR values. This work proposes an advanced, efficient damage detection algorithm in the scenario of big data that is ubiquitous in SHM.
Two-dimensional Superconductivity in Misfit Layered Compound (BiSe)1.10NbSe2
Authors: Matsuzawa S , Kitano H , Pyon S , Tamegai T
Published: August 2023

Novel two-dimensional superconductivity in a misfit layered compound (BiSe)1.10NbSe2 with a critical temperature T
c of 2.7 K is reported. The temperature dependence of H
c2 is linear close to T
c for both H ∥ c-axis and H ∥ ab-plane, suggesting that the superconductivity is three-dimensional with some anisotropy. However, the angular dependence of H
c2 clearly reveals a cusp-like behavior, which can be explained by Tinkham model, indicating that the system is two-dimensional. In order to clarify the relationship between stripe structures on the surface and the two-dimensional superconductivity, we also performed the same measurement on a uniform microbridge sample. We found similar two-dimensional behavior even in a microbridge without linear defects, indicating that the origin of two-dimensional superconductivity in (BiSe)1.10NbSe2 is not related to the stripe structure.
Unusual Transport Properties with In-plane Magnetic Field in SrxBi2Se3 Single Crystals
Authors: Zu Y. , Matsumae T. , Pyon S. , Tamegai T.
Published: August 2023

A topological insulator Bi2Se3 becomes a topological superconductor by doping Cu or Sr. Due to the nematicity of these Ax
Bi2Se3 (A = Cu, Sr) materials, physical quantities show two-fold rotational symmetry as a function of in-plane magnetic field angle φ despite their three-fold structural symmetry in the plane. In this study, single crystals of Sr
x
Bi2Se3 (0.0 ≤ x ≤ 0.17) were grown by the self-flux method. Using these crystals, extensive measurements of the magnetoresistivity as a function of φ (ρ(φ)) were performed. Angular dependence of magnetoresistance shows an unusual cos(φ) term, which can be related to the c-axis current as well as higher harmonics components. Origins of higher harmonics components of ρ(φ) are discussed.
Turbulent Structure and Characterization of ‘11’-type Iron-based Superconductors by Magneto-optical Imaging
Authors: Ren T , Sun Y , Pyon S , Tamegai T
Published: August 2023

Magneto-optical imaging is employed to investigate the vortex penetration modes in ‘11’-type iron-based superconductors (IBSs) Fe(Te0.6Se0.4) and FeSe single crystals. In Fe(Te0.6Se0.4), vortices penetrate mostly homogeneously from all edges, forming an unstable turbulent interface with pre-existing anti-vortices, where ‘Meissner hole’ emerges as those have been reported in ‘122’-type IBSs. In FeSe, however, the penetration is restricted to numerous mesoscopic stripe-like regions. Further experiments revealed an inhomogeneous vortex propagation pattern, where vortices are most likely to be channeled along the twin boundaries.
Current-voltage characteristics of 100-pixel 200-μm-square superconducting tunnel junction X-ray detector array
Authors: Shiki Shigetomo , Fujii Go
Published: August 2023

The superconducting tunnel junction (STJ) X-ray detector is an important tool for materials analysis because of its high energy resolution and high counting rate. In this work, the current-voltage (I-V) characteristics were investigated for a 100-pixel STJ array with a pixel size of 200 μm having a layer structure of Nb-Al/AlO
x
/Al-Nb and working at 0.3 K. The fabrication yield of the 200-μm STJ reached approximately 90%. A series of I-V curves for a single pixel in different cooling runs showed a discrete excess current, possibly due to the trapping of single fluxoids. With a reduction of the ambient magnetic field during cooling, larger STJ pixels can be used.
Thermal Characteristic Analysis of Fully Superconducting Motors Employing Dilute Gas Rotor Cooling Structure
Authors: Akasaka Kazuki , Terao Yutaka , Ohsaki Hiroyuki , Okai Keiichi , Taguchi Hideyuki
Published: August 2023

We have proposed a rotor cooling structure using dilute gas for a fully superconducting motor for aircraft application. Numerical analysis was performed to investigate the feasibility of the proposed cooling method and structure, which can make a fully superconducting motor lighter and more compact than a partially superconducting motor. The helium gas pressure in the gap, the rotor rotational speed, and the rotor loss are key parameters of the cooling, and thermal analysis was performed to clarify the dependence of the field winding temperature on these parameters. In the analysis, the motor model has the maximum output of 5.5 MW and the maximum speed of 5000 rpm. The superconducting armature windings are cooled down to 20 K by conduction cooling with liquid hydrogen, and the superconducting field winding is cooled down to about 50 K indirectly using helium gas in the gap. Numerical analysis results indicate that the helium gas pressure should be increased when the rotor loss is larger, but if the pressure is increased too much, the temperature of the field winding becomes higher due to wind loss. When the rotor loss is several hundred watts, the helium gas pressure should be in the range of 104 to 105 Pa.
Enhanced bone regeneration using Antheraea mylitta silk fibroin and chitosan based scaffold: in-vivo and in-vitro study
Authors: Ray Sambit , Nandi Samit Kumar , Dasgupta Sudip
Published: August 2023

In this study, highly interconnected porous scaffolds from Antheraea mylitta silk fibroin (SF) and chitosan (CH) were fabricated using the freeze-drying method. The weight ratios of SF to CH were varied from 90:10 (SF90/CH10) to 50:50 (SF50/CH50) to prepare the scaffolds from the aqueous suspension of the protein-polysaccharide mix. From the initial optimization of scaffold composition with respect to their microstructure, porosity, and mechanical properties, the SF80/CH20 scaffold exhibited the most suitable properties for bone tissue engineering application as compared to others compositions. Hence in-vitro hemocompatibility, protein adsorption, and MG-63 cell culture studies were carried out for SF80/CH20 scaffold. The fabricated SF80/CH20 scaffold showed a more controlled swelling percentage of 42.8%, with high BSA protein adsorption of 0.39 mg of BSA per gm of the scaffold at 24 h incubation period. Furthermore, in-vitro MG-63 cell culture study onto the fabricated SF80/CH20 scaffold elicited excellent MG-63 cell attachment with better biocompatibility and cell viability with increased F-action production from day 3 to day 7 of the cell culture period. In vivo bone defect healing in a rabbit tibia model revealed excellent bone healing capacity in SF80/CH20 scaffold implanted specimens compared to control ones, as evident from histology and fluorochrome labeling analysis.
Symmetric hypergraph states: entanglement quantification and robust Bell nonlocality
Authors: Nöller Jan , Gühne Otfried , Gachechiladze Mariami
Published: August 2023

Quantum hypergraph states are the natural generalization of graph states. Here we investigate and analytically quantify entanglement and nonlocality for large classes of quantum hypergraph states. More specifically, we connect the geometric measure of entanglement of symmetric hypergraphs to their local Pauli stabilizers. As a result we recognize the resemblance between symmetric graph states and symmetric hypergraph states. This explains both the exponentially increasing violation of local realism for infinitely many classes of hypergraph states and robustness towards particle loss.