bluuebunny/crossref_metadata_2025 huggingface dataset:
An in-depth examination of flow structures organization downstream of a delta-winglet pair vortex generator under laminar, transitional, and turbulent flow regimes
Authors: Younes Eliane , Hamidouche Souria , Gautier Rémi , Russeil Serge
Published: February 2024

In the present study, we experimentally investigate the time-averaged and time-evolving flow structures generated downstream of a delta-winglet pair vortex generator in an airflow channel. The Stereoscopic Particle Image Velocimetry technique is used to measure the velocity fields in the cross-sectional planes at various axial positions along the channel. The analysis of time-averaged flow topology shows that the flow is predominantly composed of two main counter-rotating longitudinal vortices under laminar, transitional, and turbulent regimes. While the time-averaged flow behavior might appear simple, the real-time organization of the instantaneous flow structures presents more complex features. The study of the flow's temporal evolution indicates that the transition from laminar to turbulent regime is controlled by a meandering mechanism referred to the motion of the main vortex centers around their axis and the emergence of secondary structures that evolve periodically over time.
The Fokker–Planck–Boltzmann equation in the finite channel
Authors: Lei Yuanjie , Zhang Jing , Zhang Xueying
Published: February 2024

In this paper, we establish the existence of small-amplitude unique solutions near the Maxwellian for the Fokker–Planck–Boltzmann equation in a finite channel with specular reflection boundary conditions. The solution space we consider is denoted as Lk̄1LT∞Lx1,v2, introduced in Duan et al. [Commun. Pure Appl. Math. 74(5), 932–1020 (2021)]. In addition, we investigate the long-time behavior of solutions for both hard and soft potentials.
Chaotic dynamics of two-dimensional flows around a cylinder
Authors: Scott L. Ridgway , Durst Rebecca
Published: February 2024

We study flow around a cylinder from a dynamics perspective, using drag and lift as indicators. We observe that the mean drag coefficient bifurcates from the steady case when the Karman vortex street emerges. We use standard dynamics metrics to analyze the drag/lift phase diagram. We also find a jump in the dimension of the drag/lift attractor just above Reynolds number of 200, indicating a breakdown of periodicity. We compare the simulated drag values with experimental data obtained over the last hundred years. Although there is substantial agreement, we note a Reynolds number range where there is a substantial, unexplained discrepancy with data from over a hundred years ago. Our simulations suggest that a vibrational resonance in the cylinder would be unlikely for Reynolds numbers greater than 1000, where the drag/lift behavior is fully chaotic.
Hot luminescence of two-dimensional electron hole systems in modulation-doped silicon
Authors: Heinz Friedemann D. , Kwapil Wolfram , Glunz Stefan W.
Published: February 2024

Modulation doping of silicon has great potential for miniaturization, surface passivation, and third generation photovoltaics (PV). At a modulation-doped silicon surface, we observe the formation of a 2D hole layer at the silicon surface at low temperatures by means of photoluminescence (PL) measurements. A line shape analysis of band–band and hot luminescence reveals the hole density (which is equal to the modulation-doped acceptor density). A high excitation intensity leads to a Fermi edge singularity of the band–band and hot PL emission. While the 2D layer can be characterized by the observed luminescence, the spectral region of twice the bandgap is fully dominated by emission from this surface layer, impeding the measurement of bulk hot luminescence, e.g., from Auger electrons or from nonthermalized carriers in a hot carrier PV device.
Proximity effects induced exchange bias and perpendicular net moment in SrIrO3
Authors: Shan Zheling , Wang Jianlin , Cui Zhangzhang , Jiang Zhongyuan , Zhu Mo , Zhang Jian , Gong Nanqi , Li Weiwei , Shi Wei , Huang Haoliang , Huang Qiuping , Fu Zhengping , Lu Yalin
Published: February 2024

The magnetic proximity effect enables the incorporation of magnetic properties into non-magnetic materials, thereby achieving high-performance electronic devices. The 5d perovskite-oxide iridates provide a versatile platform for investigating competing electronic states due to their strong spin–orbit coupling. By proximity to conventional 3d transition-metal oxide ferromagnets, originally paramagnetic SrIrO3 is expected to exhibit exotic magnetic phenomena. In this study, we report the emergence of perpendicular net moment and an unprecedented exchange bias effect in SrIrO3 sandwiched between two ferromagnetic LaMnO3 layers. The magnetization measurements clearly demonstrate antiferromagnetic coupling in the heterostructures, resulting in a shift of the magnetic hysteresis loops. Furthermore, magneto-transport measurements provide evidence for the induction of a net moment along the perpendicular direction of the SrIrO3 film plane due to proximity effects. Both the magnetic pinning effect and perpendicular magnetization can be controlled by an external magnetic field. These findings expand the potential applications of iridate-related heterostructures in modern information storage fields such as skyrmions, spin–orbit torques, and antiferromagnet-based spintronics.
On the modification of tip leakage noise sources by over-tip liners
Authors: Palleja-Cabre Sergi , Saraceno Ivan , Chaitanya Paruchuri
Published: February 2024

Over-Tip-Rotor (OTR) liners have been investigated over the last decades as a technology to further reduce fan broadband noise in turbofan engines. The suppression of noise with OTR liners is attributed to conventional attenuation of acoustic waves and source modification effects. This paper describes a fundamental experiment to gain a better understanding of the source modification effects and establish whether they are purely due to acoustic back-reactions or also due to hydrodynamic changes on the source. The OTR liner configuration is approximated by a static airfoil with its tip located over a flat plate containing a flush-mounted liner insert and separated from the airfoil tip by a small gap. Synchronous measurements of the far-field noise and wall pressure fluctuations on the airfoil tip have shown that the reduction of wall pressure at the airfoil tip by the liner is the dominant mechanism of noise reduction. The reduction in unsteady pressure fluctuations on the airfoil tip by the liner is mainly caused by back-reaction effects at high frequencies and hydrodynamic modifications at low- and mid-frequencies. Over-tip liners are found to alter the unsteady flow field in the gap region and weaken the flow structures responsible for the generation of tip noise. This study has shown that far-field noise predictions based on analytical models are useful to estimate the performance of over-tip liners, but a complete assessment should also include the impact of the liner on the tip-leakage flow, and, consequently, the sources of tip noise.
Using dimensional analysis to estimate flow resistance for sheet flow subjected to raindrop impact
Authors: Shen Enshuai , Liu Gang , Xia Xiaolin , Liu Dandan , Dan Chenxi , Zhang Qiong , Guo Zhen
Published: February 2024

The impact of raindrops on sheet flow (SF) is a common phenomenon, which plays a vital role in many important nature and engineering fields. The flow resistance of SF is critical for describing flow characteristics and calculating the sediment transport capacity. However, information regarding the theoretical resistance equations of the total resistance of SF subjected to raindrop impact (fr) and the resistance induced by raindrop impact (Δf) is limited. In this study, combination of the π-theorem of dimensional analysis and multiple experimentally simulated rainfalls and inflows was conducted to obtain and verify the deduced predictive flow resistance equations. The results indicated that using dimensionless variables deduced by the π-theorem to calculate the flow resistance equation was appropriate. The main control of fr of SF under rainfall is the ratio of surface roughness to water depth deduced by π-theorem. A newly developed equation [Eq. (24)] can be used to predict fr, with a Nash-Sutcliffe efficiency index (NSE) of 0.91 and a normalized root mean square error (NRMSE) of 0.166. Δf is a very important component to overall SF resistance, accounting for 0.34%–47.79% of fr. The deduced dimensionless variable of the ratio of rainfall intensity to flow velocity is the main controlling factor of Δf. Finally, a new equation [Eq. (26)] was developed to predict Δf, with NSE = 0.673 and NRMSE = 0.445. This study is helpful for understanding the flow resistance subjected to raindrop impact and provides new and scientific equations for flow resistance coefficient prediction.
Effect of the nature of the solid substrate on spatially heterogeneous activated dynamics in glass forming supported films
Authors: Phan Anh D. , Schweizer Kenneth S.
Published: February 2024

We extend the force-level elastically collective nonlinear Langevin equation theory to treat the spatial gradients of the alpha relaxation time and glass transition temperature, and the corresponding film-averaged quantities, to the geometrically asymmetric case of finite thickness supported films with variable fluid–substrate coupling. The latter typically nonuniversally slows down motion near the solid–liquid interface as modeled via modification of the surface dynamic free energy caging constraints that are spatially transferred into the film and which compete with the accelerated relaxation gradient induced by the vapor interface. Quantitative applications to the foundational hard sphere fluid and a polymer melt are presented. The strength of the effective fluid–substrate coupling has very large consequences for the dynamical gradients and film-averaged quantities in a film thickness and thermodynamic state dependent manner. The interference of the dynamical gradients of opposite nature emanating from the vapor and solid interfaces is determined, including the conditions for the disappearance of a bulk-like region in the film center. The relative importance of surface-induced modification of local caging vs the generic truncation of the long range collective elastic component of the activation barrier is studied. The conditions for the accuracy and failure of a simple superposition approximation for dynamical gradients in thin films are also determined. The emergence of near substrate dead layers, large gradient effects on film-averaged response functions, and a weak non-monotonic evolution of dynamic gradients in thick and cold films are briefly discussed. The connection of our theoretical results to simulations and experiments is briefly discussed, as is the extension to treat more complex glass-forming systems under nanoconfinement.
The influence of ring clearance on the performance of a double-suction centrifugal pump
Authors: Lei Lei , Wang Tao , Qiu Bo , Yu He , Liu Yunqi , Dong Yuancheng
Published: February 2024

Due to the complex structure of a double-suction pump's suction chamber, the flow in the pump's cavity is often ignored in numerical simulations because of difficulties in structured hexahedral meshing. However, the wear ring clearance interlinking the pump chamber leads the fluid at the impeller inlet directly to the impeller area. This significantly impacts the pump's internal flow field, so the influence of the clearance on the internal flow of a double-suction pump cannot be ignored. This paper develops four three-dimensional double-suction pump models with different wear ring clearances to investigate their influence on pump performance, and structured hexahedral meshes were used for all the computational domains. The clearances varied from 0.2 to 0.5 mm in 0.1 mm increments. The influences of the clearance on the energy loss, external characteristics, and internal flow field distribution of the pump were simulated via a verified computational fluid dynamics method. The results show that the wear ring leakage decreases with the flow rate and increases with wear ring clearance. The increase in backflow leads to an internal flow disorder inside the impeller, resulting in a decreased head and efficiency. Energy loss is mainly caused by increasing the turbulence entropy production with an increasing wear ring clearance. Also, the low-pressure region in the pump cavity expands to the volute with increasing clearance, and the impeller outlet pressure decreases. This study's research on wear ring clearance provides a reference for the design and application of double-suction centrifugal pumps.
Enhanced flow in deformable carbon nanotubes
Authors: Garg Ashish
Published: February 2024

Many researchers observed enhanced water flow through carbon nanotubes (CNTs) and attributed the reason to large slips. Even after taking significant slip effects into account, there remain unaddressed observations of significant improvements in flow rates. As CNTS are deformable, we represent nanotubes with a deformable-wall using a linear pressure–area relationship. We assume lubrication assumption, and using the properties of nanoconfined water, we derive the model for deformable-nanotubes. We validated our derived model in its limiting cases with the previously reported results in the literature. We compare the predictions by our deformable-wall and rigid-wall model with the experimental results and the MD-simulation predictions by multiple literature studies. Many studies were well-predicted by the rigid-wall model with slips. However, we find that there are many studies with high porosity and thin wall tubes, where elasticity or deformability of the tube is essential in modeling, which is well-predicted by our deformable-wall model with slips. In our study, we focus on investigating the impact of two key factors: the deformability, and the slip length on the flow rate. We find that the flow rate inside the tube increases as the deformability increases or the thickness T and elastic modulus E of the tube-wall decrease). We also find that the flow rate in deformable tubes scales as m˙deformable∼1/α0 for (Δp/αAo)≪1, m˙deformable∼1/α for (Δp/αAo)∼O(10−1) and m˙deformable∼α2 for (Δp/αAo)∼O(1). Further, for a given deformability, the percentage change in flow rate in the smaller diameter of the tube is much larger than the larger diameter. As the tube diameter decreases for the given pressure, Δm˙/m˙ increases. We find that for rigid-tube, the flow rate varies m˙rigid∼Δp, whereas for the deformable-tubes, the flow rate scales as m˙deformable∼Δp2 for (Δp/αAo)∼O(10−1), and finally to m˙deformable∼Δp3 for (Δp/αAo)∼O(1). We further find that slip also significantly increases flow rate, but, deformability has more substantial effect.
Orientational effects in the polarized absorption spectra of molecular aggregates
Authors: Moritaka S. S. , Lebedev V. S.
Published: February 2024

We present a detailed theoretical analysis of polarized absorption spectra and linear dichroism of cyanine dye aggregates whose unit cells contain two molecules. The studied threadlike ordered system with a molecular exciton delocalized along its axis can be treated as two chains of conventional molecular aggregates, rotated relative to each other at a certain angle around the aggregate axis. Our approach is based on the general formulas for the effective cross section of light absorption by a molecular aggregate and key points of the molecular exciton theory. We have developed a self-consistent theory for describing the orientational effects in the absorption and dichroic spectra of such supramolecular structures with nonplanar unit cell. It is shown that the spectral behavior of such systems exhibits considerable distinctions from that of conventional cyanine dye aggregates. They consist in the strong dependence of the relative intensities of the J- and H-type spectral bands of the aggregate with a nonplanar unit cell on the angles determining the mutual orientations of the transition dipole moments of constituting molecules and the aggregate axis as well as on the polarization direction of incident light. The derived formulas are reduced to the well-known analytical expressions in the particular case of aggregates with one molecule in the unit cell. The calculations performed within the framework of our excitonic theory combined with available vibronic theory allow us to quite reasonably explain the experimental data for the pseudoisocyanine bromide dye aggregate.
Customized designs, preparations, and characterizations of high-performance multilayer VO2-based thermochromic smart coatings
Authors: Qin Minhua , Wang Jun , Tian Shouqin , Zhao Xiujian , Liu Baoshun
Published: February 2024

VO2-based thermochromic coatings have gained much attention in temperature-adaptive smart windows, and constructing multilayer film structures is the main way to obtain high thermochromic performances. Based on the self-developed objective-orientated automatic optimization code, the present research realized customized designs of thermochromic multilayer coatings composed of VO2, TiO2, and SiO2 from the objectives of visible luminance (Tlum) and solar light modulation (ΔTsol). The TiO2/VO2/s, VO2/TiO2/s, TiO2/VO2/TiO2/s, and SiO2/TiO2/VO2/TiO2/s (s denotes substrate) multilayer film systems were then prepared by magnetron sputtering and vacuum controllable heating, with their structures, insulator-metallic transition, and thermochromic properties being carefully studied. The result showed that the best trade-off between high Tlum and high ΔTsol was achieved for these film assemblies, and solar light modulation was mainly limited at the near-IR wavelength region of the solar spectrum, with the difference between cool- and hot-state Tlum being greatly reduced. In the case of the four-layer SiO2/TiO2/VO2/TiO2/s, very high average Tlum (60%) and high ΔTsol (14%) were obtained. A 100 × 100 mm2 of the SiO2/TiO2/VO2/TiO2/s was also prepared, and it showed an obvious temperature adjustment, and the service life can last for 14 years under normal weather conditions. Not limited to the prepared multilayer film systems, the methodology used here is also suitable for the fast development of other multilayer film systems.
Off-resonance high-performance surface-enhanced Raman scattering-active substrate by trapping gold nanoparticles using Bessel beam
Authors: Choudhary Riya , Vairagi Kaushal , Mondal Samir Kumar , Srivastava Sachin Kumar
Published: February 2024

The surface-enhanced Raman scattering (SERS) technique provides outstanding molecular fingerprint identification and high sensitivity of analytes. Herein, colloidal sphere-shaped gold nanoparticles (Au-NPs) trapped in concentric rings of the Bessel beam generated from the optical fiber-based negative axicon has been reported as a SERS substrate. With the trapping of Au-NPs, the SERS ability of colloidal Au-NPs improved, and the average enhancement factor (AEF) of the rhodamine-6G (R6G) and 4-aminothiophenol (4-ATP) molecules can reach up to the order of 107. Control experiments were also carried out with the trapping of Au-NPs by Gaussian beam illumination, without any illumination of the light and with the trapping of Au-NPs by the Bessel beam illumination on a silver (Ag)-coated silicon (Si) substrate with a self-assembled monolayer (SAM) of 4-ATP. Theoretical studies were also carried out using the finite element method (FEM) to identify the hotspots generated in the gaps formed between the Au-NPs, leading to an enhancement in the SERS signal of the molecules, and the results were consistent with the experimentally determined AEFs. The obtained results demonstrate that the proposed SERS technique is stable. This study has significant potential applications in clinical diagnosis, food safety, environment safety, chemical sensing, and biosensing.
X-ray reciprocal space mapping analysis of ferromagnetic GdN films grown by pulsed laser epitaxy
Authors: Tanaka Yusuke , Krockenberger Yoshiharu , Kunihashi Yoji , Gotoh Hideki , Nitta Junsaku , Sanada Haruki
Published: February 2024

Epitaxial thin films of ferromagnetic rare-earth nitride, GdN, were synthesized using pulsed laser deposition (PLD) on (001) MgO, pseudo-cubic (001) YAlO3, and (001) TiN buffered (001) MgO substrates. X-ray high-resolution reciprocal space mappings confirmed the epitaxial relationship between GdN and the substrates. The use of a TiN buffer layer changed the growth direction of the GdN films from (001) to (111). The ferromagnetic behavior of the films was characterized, and it was found that the magnetic easy axis could be tuned according to the crystal growth direction. These results suggest that PLD is a viable method for synthesizing epitaxial GdN films with tunable magnetic properties. The ability to control the crystal growth direction and magnetic easy axis of GdN films could be useful for developing spintronic devices.
Ion transport through short nanopores modulated by charged exterior surfaces
Authors: Ma Long , Liu Zhe , Ai Bowen , Man Jia , Li Jianyong , Wu Kechen , Qiu Yinghua
Published: February 2024

Short nanopores find extensive applications, capitalizing on their high throughput and detection resolution. Ionic behaviors through long nanopores are mainly determined by charged inner-pore walls. When pore lengths decrease to sub-200 nm, charged exterior surfaces provide considerable modulation to ion current. We find that the charge status of inner-pore walls affects the modulation of ion current from charged exterior surfaces. For 50-nm-long nanopores with neutral inner-pore walls, the charged exterior surfaces on the voltage (surfaceV) and ground (surfaceG) sides enhance and inhibit the ion transport by forming ion enrichment and depletion zones inside nanopores, respectively. For nanopores with both charged inner-pore and exterior surfaces, continuous electric double layers enhance the ion transport through nanopores significantly. The charged surfaceV results in higher ion current by simultaneously weakening the ion depletion at pore entrances and enhancing the intra-pore ion enrichment. The charged surfaceG expedites the exit of ions from nanopores, resulting in a decrease in ion enrichment at pore exits. Through adjustment in the width of charged-ring regions near pore boundaries, the effective charged width of the charged exterior is explored at ∼20 nm. Our results may provide a theoretical guide for further optimizing the performance of nanopore-based applications, such as seawater desalination, biosensing, and osmotic energy conversion.
Numerical study of roll wave development for non-uniform initial conditions using steep slope shallow water equations
Authors: Dai Shubing , Liu Xinyuan , Zhang Kuandi , Ma Yulei , Liu Hansheng , Jin Sheng
Published: February 2024

Periodic shock waves of roll waves may cause the flow to jump over the canal bank, increase soil erosion, and enhance the destructive power of debris flow. This paper focuses on the spatiotemporal changes in waveform, velocity, discharge, shear stress, and Froude number during the development process of roll waves, taking the non-uniform flow as the initial condition. This work studied numerically the influence mechanism of different variables on the development process of roll waves based on steep slope shallow water equations. The roll wave is unstable when the disturbance amplitude is too large. By reducing the inlet velocity, increasing the disturbance wavelength, and reducing the roughness coefficient, it can make the roll wave stable. Reducing the inlet velocity not only reduces the frequency of the shock wave but also keeps the wave crest from rising. Under different boundary conditions of disturbance amplitude, the crest growth rate (crest water depth difference/crest distance difference) of the roll wave development segment at a certain time is almost consistent. For different initial water depths, there is overlap in the roll wave development segment at a certain time. Under the initial condition of non-uniform flow, the congestion at the inlet means that the initial water depth is less than the normal water depth, and the decline of the water depth at the inlet means that the initial water depth is greater than the uniform water depth.
Realization of Hadamard gate with twisted magnon modes in synthetic antiferromagnets
Authors: Wang Xuan , Yuan Shaohua , Sui Chaowei , Wang Yan , Jia Chenglong
Published: February 2024

Manipulating the polarization of spin waves highlights the potential of antiferromagnetic magnonics in encoding and handling magnon information with high fidelity. Here, we propose a flexible approach to mutually convert polarization states (i.e., Hadamard gate) by incorporating a topological degree of freedom, intrinsic orbital angular momentum (OAM), into twisted spin wave modes within synthetic antiferromagnetic nanodisks. The polarization states of spin waves and the implementation of magnonic logic operations can be electrically read out through combined spin pumping and inverse spin Hall effect, as demonstrated by numerical micromagnetic simulations for CoFeB-based synthetic antiferromagnets. Our findings present an exciting possibility of parallel magnonic computing utilizing topologically protected and magnetic damping-resistance OAM of twisted magnons.
Modeling of vapor bubble dynamics considering the metastable fluid state
Authors: Yi Qihao , Guo Pengcheng , Zuo Zhigang , Liu Shuhong
Published: February 2024

This study investigates the dynamic modeling of a spherical vapor bubble in an infinite liquid. Initially, the liquid is in a state of saturation, but then, there is a change in ambient pressure. Unlike previous studies that assumed vapor saturation, our model fully considers the metastable fluid state of subcooled vapor and superheated liquid. The theoretical model is based on the state equation of vapor and the kinetic theory of gases, allowing the visualization of the effects of superheating and subcooling on the bubble pressure and the phase transition rate. The accuracy of the numerical solutions for the bubble collapse and growth is confirmed by experimental results using water as the working fluid. Two approaches of heat transfer simplification are validated in the numerical solution, and an adhesion coefficient within the range of 0.1–1 is recommended for the calculation. Additionally, this study provides insights into how the metastable fluid state affects the bubble pressure and phase transition, especially in the early stages of bubble collapse. Furthermore, the conservation of vapor mass inside the bubble is also demonstrated.
Dangling bonds, the charge neutrality level, and band alignment in semiconductors
Authors: Varley J. B. , Weber J. R. , Janotti A. , Van de Walle C. G.
Published: February 2024

We present a systematic study of the electronic properties of dangling bonds (DBs) in a variety of semiconductors and examine the relationship between DBs and the charge neutrality level (CNL) in the context of band alignments of semiconductors. We use first-principles calculations based on density functional theory to assess the energetics of DBs in a set of diamond-structure group-IV and III–V or II–VI zinc-blende-structure semiconductors, considering both cation and anion-derived states. We examine the charge-state transition levels of DBs to assess whether they can serve as a CNL to align band structures, by comparing with offsets calculated from interface calculations. Our results show that this approach for evaluating the CNL yields quantitative results for band offsets and provides useful insights. We discuss the relation with alternative approaches for determination of CNLs based on branch-point energies or transition levels of interstitial hydrogen.
A versatile beamline for soft x-ray reflectivity, absorption, and fluorescence measurements at Indus-2 synchrotron source
Authors: Modi Mohammed H. , Gupta Rajkumar , Gupta Shruti , Yadav Praveen Kumar , Kant Chander , Lal Sohan , Raghuvanshi V. K. , Kane S. R.
Published: February 2024

A versatile beamline for performing reflectivity, fluorescence, and absorption experiments in the soft x-ray region of 100–1500 eV is commissioned on a bending magnet port of the Indus-2 synchrotron source. A high vacuum 2-axis reflectometer with x, y, and z sample scanning stages is installed. This reflectometer is used to measure the reflectivity of large samples up to 300 mm in length and 5 kg in weight. This feature is useful for characterizing x-ray optical elements, such as mirrors, gratings, and multilayers. A flange mounted silicon drift detector is installed in the downstream of the reflectometer for soft x-ray fluorescence measurements. The soft x-ray absorption measurements are carried out in the total electron yield and partial fluorescence yield modes. Integration of three different experimental techniques in the experimental station makes the beamline versatile for materials science applications as it provides structural, chemical, and electronic state information by performing the required experiments in an identical environment. The beamline uses a varied line spacing plane grating monochromator and gives a high flux (∼109 to 1011 photon/s) with a moderate resolution (λ/Δλ ~1000–5000). A three-mirror-based higher harmonic setup is incorporated to get rid of harmonics and to get a high spectral purity monochromatic beam with less than 0.1% harmonic content. In the present article, the beamline optical scheme, mechanical configuration, and details of the experimental setups are presented, along with a few representative results of each experimental mode.
Significant enhancement of spin-orbit torque efficiency by optimizing the interlayer thickness in [Pt/Ru]n/Pt multilayers
Authors: Zhan Xiang , Wang Haozhe , Li Zishuang , Liu Ronghua
Published: February 2024

Spin–orbit torque (SOT) is a promising strategy for switching magnetization for magnetic random access memory and maintaining magnetization coherent precession for magnetic nano-oscillator or magnon-based logic device applications. Thus, the enhancement of SOT efficiency is the crucial point for the implementation of high-performance SOT devices. Here, we demonstrate that the effective damping-like SOT efficiency ξDL in the periodic [Pt(2 nm)/Ru(1 nm)]nPt(2 nm) multilayers with a low resistivity of ∼40 μΩ cm (comparable to 23 μΩ cm of the pure Pt film) exhibits an over 100% enhancement compared to that of the pure 12 nm thick Pt (ξDL = 0.055) at the periodic number n = 3, even reaches 0.257 (∼360% enhancement) determined by damping dc modulation method at [Pt/Ru] total thickness of 32 nm with n = 10. Our findings will benefit various SOT devices by significantly reducing energy consumption.
Research on the electromagnetic characteristics of metasurfaces based on air dielectric substrates
Authors: Ni Chun , Li Yixuan , Zhang Liang
Published: February 2024

Electromagnetic metasurfaces can achieve effective control of electromagnetic waves and achieve effects such as blocking, enhancing, reflecting, transmitting, or deflecting electromagnetic waves, possessing electromagnetic properties that go beyond traditional materials. Existing research indicates that the dielectric substrate of metasurfaces has a significant impact on their electromagnetic properties. Increasing the substrate thickness will be beneficial for expanding the impedance bandwidth of the metasurface, and changes in dielectric constant will also have some impact on the operating frequency and bandwidth of the metasurface. A metasurface based on an air substrate was proposed through the research of dielectric materials. In addition, an ultrawideband, miniaturized, and high-gain metasurface antenna based on an air substrate is designed. The overall size of the designed antenna is 0.5λL × 0.5λL (where λL represents the wavelength at the lowest working frequency in free space). The measured results indicate that the proposed antenna exhibits a −10 dB impedance bandwidth of 74.3% (2.53–5.52 GHz) and a peak boresight gain of 10.1 dBi.
Understanding the importance of four-phonon scattering in low-symmetry monolayer 1T′-ReS2 using machine learning potential
Authors: Yang Xiao , Chen Yong-Sen , Zheng Yu-Hao , Wu Cheng-Wei , Xie Guo-Feng , Zeng Yu-Jia , Zhou Wu-Xing
Published: February 2024

The importance of higher-order anharmonic effects on thermal transport has recently been demonstrated in highly symmetrical 2D materials with large acoustic–phonon (A–O) gap. However, the phonon scattering and the thermal transport properties in low-symmetry structures remain ambiguous. In this work, we employed moment tensor potential and Boltzmann transport equation to investigate phonon thermal transport properties of 1T′-ReS2 and 2H-WS2. We show that the mechanism of four-phonon scattering in 1T′-ReS2 is quite different from that in 2H-WS2. In 1T′-ReS2, the four-phonon scattering can reduce the thermal conductivity by up to 40.29%, even in the absence of an acoustic-optical phonon bandgap. The strong four-phonon scattering in 1T′-ReS2 is attributed to A–O phonon scattering mediated by abundant flattening optical phonon modes. However, in 2H-WS2, the strong four-phonon scattering is attributed to the presence of a large A–O phonon bandgap. Our work suggests that considering the four-phonon scattering is essential for calculating the thermal conductivity of 2D materials, even in the absence of an A–O phonon gap.
Carrier trapping in diamond Schottky barrier diode
Authors: Nunomura Shota , Sakata Isao , Nishida Taiki , Ohmagari Shinya
Published: February 2024

Carrier trapping in a diamond Schottky barrier diode, consisting of a stack of a p− drift and p+ contact layer, is experimentally studied via subgap photocurrent measurements. In the measurements, trapped carriers are detected as an increment of the diode current under a probe light illumination in a near infrared range of 2.0 μm (0.62 eV). The density of trapped carriers is examined, and it is found to be sufficiently low, compared with that of free carriers, by an order of 105. Interestingly, the trapped carriers are observed only for the forward bias of the diode; they are not observed for the reverse bias. This suggests that the carrier trapping, yielding trapped carriers, originates from the valence band offset at the p−/p+ interface.
Induced out-of-plane piezoelectricity and giant Rashba spin splitting in Janus WSiZ3H (Z = N, P, As) monolayers toward next-generation electronic devices
Authors: Vu Tuan V. , Hoi Bui D. , Kartamyshev A. I. , Hieu Nguyen N.
Published: February 2024

Two-dimensional (2D) piezoelectric nanomaterials have widely been studied recently due to their promise for various applications in technology. Investigation of vertical piezoelectricity will contribute to a deeper understanding of the intrinsic mechanism of piezoelectric effects in the 2D structures. In this paper, we report a first-principle study for the structural, electronic, piezoelectric, and transport properties of new-designed Janus WSiZ3H (Z= N, P, and As) monolayers. The structural stability of WSiZ3H is theoretically confirmed based on the energetic, phonon dispersion, and also elastic analyses. At the ground state, while WSiN3H is an indirect semiconductor, both WSiP3H and WSiAs3H are predicted to be direct semiconductors with smaller bandgaps. When the spin-orbit coupling effects are taken into account, a large valley spin splitting is observed at the K point of WSiZ3H materials. Interestingly, a giant Rashba spin splitting is found in WSiP3H and WSiAs3H with Rashba constant αR up to 770.91 meV Å. Additionally, our first-principles study indicates that Janus WSiZ3H monolayers are piezoelectric semiconductors with high out-of-plane piezoelectric coefficient |d31|, up to 0.15 pm/V, due to the broken mirror symmetry. Besides, with high electron mobilities and also possessing direct band gaps, WSiP3H and WSiAs3H monolayers are favorable for applications in optoelectronics.
Suspension and transportation of sediments in submarine canyon induced by internal solitary waves
Authors: Tian Zhuangcai , Huang Jinjian , Xiang Jiaming , Zhang Shaotong
Published: February 2024

The submarine canyon was the main channel for the transport of sediment to the deep sea, but the transport process in submarine canyon induced by internal solitary waves (ISWs) had not yet been conducted. Based on computational fluid dynamics, this study investigated sediment resuspension and transport induced by the interaction between ISWs and submarine canyon. The simulations showed that sediment particles near the canyon were resuspended due to the propagation of ISWs. The sediment of slope section experienced higher resuspension rates compared to the horizontal section. Sediments on the slope were suspended before the trough of ISW and then transported into the canyon. Sediment resuspension induced by ISWs was more significant in the slope section compared to the horizontal sections and contained 45% more sediment particles than the horizontal section within the canyon. The sediment concentration within the canyon gradually increased in both the horizontal and slope sections, with a particularly pronounced increase at the junction between the horizontal and slope section. The concentration of particles in the canyon was significantly higher than in the horizontal section, with an increase in 2.73 times. Furthermore, the sediment concentration within the canyon was 1.73 times higher than outside the canyon. A sediment water column with higher suspended matter concentration, known as the bottom nepheloid layer, was formed above the submarine canyon. However, these sediment particles could not cross the pycnocline and accumulated in the upper region of the lower water. The sediment distribution of the canyon was much greater than outside the canyon within the transverse section, with three times more sediment particles within the canyon compared to outside. The sediment distribution of slope section was significant more than the horizontal section. Sediment suspended above the canyon gradually moved downstream along the submarine canyon and primarily deposit at the junction between the horizontal and slope sections. Sediment movement also occurred along the submarine canyon in the horizontal section. The interaction between ISWs and submarine canyons intensified sediment resuspension and significantly affected the spatial distribution of sediment particles. This interaction could transport resuspended sediments from the continental shelf to the deep-sea basin, thereby influencing the deep-sea environment.
Enhanced SLF radiation efficiency in a piezoelectrically driven magnetic pendulum transmitter
Authors: Chu Zhaoqiang , Yu Chenyuan , Dan Wei , Jiang Shizhan , Ren Yuzhu , Dong Kewen , Dong Shuxiang
Published: February 2024

Long-wave radio station based on an electrically small antenna and mechanical transmitter based on a rotating permanent antenna are commonly used for super low frequency (SLF, 30–300 Hz) communication. The current challenge is the difficulty in developing both an efficient and a miniaturized SLF transmitter. Enlightened by the advantages of piezoelectric motor over conventional electromagnetic motor in terms of efficiency and the output torque in low frequency band, we propose a piezoelectrically driven magnetic pendulum transmitter by combining a magneto-mechano-electric (MME) cantilever and a swinging magnet in this work. The magnetic force coupling between the MME cantilever and the swinging magnet is optimized by changing the thickness and the attached position of the used Metglas laminates. The experimental results show that the piezoelectrically driven magnetic pendulum transmitter has a working frequency of 57 Hz, and a flux density of 149 f Tpk at 100 m distance could be expected with a low power consumption of 40.64 mW. When driving the same magnet with an electromagnetic motor, however, the required power consumption reaches 4.2 W for 57 Hz magnetic field radiation. By dividing the induced magnetic moment over the consumed power, the effective radiation efficiency of our proposed piezoelectrically driven SLF magnetic pendulum transmitter significantly increased from 0.55 to 17.4. This proof-of-concept work is believed to open a dimension for the design and the application of efficient SLF mechanical transmitter in the future.
Shaping the laser control landscape of a hydrogen transfer reaction by vibrational strong coupling. A direct optimal control approach
Authors: Ramos Ramos A. R. , Fischer E. W. , Saalfrank P. , Kühn O.
Published: February 2024

Controlling molecular reactivity by shaped laser pulses is a long-standing goal in chemistry. Here, we suggest a direct optimal control approach that combines external pulse optimization with other control parameters arising in the upcoming field of vibro-polaritonic chemistry for enhanced controllability. The direct optimal control approach is characterized by a simultaneous simulation and optimization paradigm, meaning that the equations of motion are discretized and converted into a set of holonomic constraints for a nonlinear optimization problem given by the control functional. Compared with indirect optimal control, this procedure offers great flexibility, such as final time or Hamiltonian parameter optimization. A simultaneous direct optimal control theory will be applied to a model system describing H-atom transfer in a lossy Fabry–Pérot cavity under vibrational strong coupling conditions. Specifically, optimization of the cavity coupling strength and, thus, of the control landscape will be demonstrated.
On the clustering of triacylglycerols in the molten state
Authors: Mazzanti G. , De Nicola A. , Pink D. , Pizzirusso A. , Fuhrmann P. , Green N. L. , Liu R. , Adams C. , Milano G. , Rousseau D. , Marangoni A. G.
Published: February 2024

The liquid–solid phase transition of triacylglycerols (TAGs), the main components of edible fats and oils is central to the production and sensory properties of many processed foods. While there has been extensive research on the nucleation and growth of fats, there remains a dearth of knowledge regarding the structural organization of TAGs in the liquid state. From a molecular perspective, TAGs consist of three alkyl chains esterified to a glycerol backbone. Several models based on experiment and simulation have helped to unveil TAG organization in the molten state. However, more evidence for their structural organization is necessary. Here, we provide simulation and experimental insights on the structural organization of molten tripalmitin using small-angle neutron and x-ray scattering, and wide-angle x-ray scattering. In agreement with recent work, we also propose a model in which TAGs associate as clusters via glycerol-glycerol interactions, with their alkyl chains extending outwards in a loose shell. Our model, however, highlights and demonstrates the dynamic nature of clusters, where TAGs can transfer from one cluster to another via diffusion. The average number of TAG molecules per cluster varies from 5 to 9 and decreases with increasing temperature, which results in a smaller average distance between clusters. Overall, this study strongly suggests that prior to the onset of nucleation, TAGs are associated as dynamic clusters formed via intermolecular interactions between neighboring glycerol cores.
Numerical study of a novel cooling protection scheme with rail crown holes for the squealer tip in a turbine blade
Authors: Zhou Haimeng , Luo Lei , Du Wei , Yan Han , Wang Songtao
Published: February 2024

The squealer tip is acknowledged as an effective and dependable design for minimizing leakage loss and reducing thermal load in high-pressure turbine blades. After confirming the numerical approach, this study explored the cooling and aerodynamic characteristics of a novel cooling protection scheme with rail crown holes in a squealer tip. The rail crown hole parameters including the hole number, size, and distribution are research variable. Evaluation indexes of cooling and aerodynamic performance are the tip surface adiabatic film cooling efficiency (η) and clearance leakage flow rate (LFR). In cooling aspects, increasing the hole number or the hole size can improve the coolant attachment to the rail crown surface under the same coolant mass flow rate (Q). The coolant distribution within the cavity is substantially improved by concentrating the film holes at the leading-edge rail, which enhances the cooling protection of the cavity floor. In aerodynamic aspects, at low Q conditions, the total LFR correlates only with Q and is less sensitive to hole parameters. At high Q conditions, enlarging the hole size proves more effective in suppressing total LFR. Additionally, three cases with optimal cooling effects are chosen to investigate the impact of Q. These three cases are the scheme with an increasing hole number (case 1), the scheme with an enlarging hole size (case 4), and the scheme with concentrated holes at the leading edge (case 5). The results show that case 5 consistently exhibits superior cooling protection for the cavity floor in all Q conditions. For average η of the rail crown surface, cases 1 and 5 reach the peak value of average η at Q = 1.0Q0, while case 4 attains its peak value at Q = 1.5Q0.
β-Ga2O3 Schottky barrier height improvement using Ar/O2 plasma and HF surface treatments
Authors: Sharma Pooja , Lodha Saurabh
Published: February 2024

In this report, we show that Ar/O2 plasma exposure followed by HF treatment improves the Schottky barrier height (SBH) in β-Ga2O3 Schottky barrier diodes (SBDs) by nearly 0.3 eV, resulting in a breakdown voltage (VBR) gain of over 100 V on 2 × 1016 cm−3 doped substrates, without compromising the specific on-resistance. The SBH and VBR enhancement is observed on (2¯01) as well as (001) surfaces. Through extensive surface characterization, the Ar/O2 plasma exposure is shown to amorphize and increase surface oxygen vacancy concentration. HF treatment cleans the surface damage and passivates the surface through fluorine adsorption, leading to Fermi-level de-pinning and SBH improvement. Remarkably, however, the Ar/O2 plasma exposure enhances fluorine adsorption when compared to fluorine treatment alone, resulting in a more substantial improvement in SBH and VBR. Surface clean/treatment plays a critical and fundamental role in determining the quality of the metal/β-Ga2O3 interface. The improved surface treatment process demonstrated in this work can be easily integrated with various field termination methods that can help further improve the β-Ga2O3 SBD performance.
Model selection over partially ordered sets
Authors: Taeb Armeen , Bühlmann Peter , Chandrasekaran Venkat
Published: February 2024

In problems such as variable selection and graph estimation, models are characterized by Boolean logical structure such as the presence or absence of a variable or an edge. Consequently, false-positive error or false-negative error can be specified as the number of variables/edges that are incorrectly included or excluded in an estimated model. However, there are several other problems such as ranking, clustering, and causal inference in which the associated model classes do not admit transparent notions of false-positive and false-negative errors due to the lack of an underlying Boolean logical structure. In this paper, we present a generic approach to endow a collection of models with partial order structure, which leads to a hierarchical organization of model classes as well as natural analogs of false-positive and false-negative errors. We describe model selection procedures that provide false-positive error control in our general setting, and we illustrate their utility with numerical experiments.