bluuebunny/crossref_metadata_2025 huggingface dataset:
Recovery of dynamical similarity from lossy representations of collective behavior of midge swarms
Authors: Aung Eighdi , Abaid Nicole , Jantzen Benjamin
Published: October 2023

Understanding emergent collective phenomena in biological systems is a complex challenge due to the high dimensionality of state variables and the inability to directly probe agent-based interaction rules. Therefore, if one wants to model a system for which the underpinnings of the collective process are unknown, common approaches such as using mathematical models to validate experimental data may be misguided. Even more so, if one lacks the ability to experimentally measure all the salient state variables that drive the collective phenomena, a modeling approach may not correctly capture the behavior. This problem motivates the need for model-free methods to characterize or classify observed behavior to glean biological insights for meaningful models. Furthermore, such methods must be robust to low dimensional or lossy data, which are often the only feasible measurements for large collectives. In this paper, we show that a model-free and unsupervised clustering of high dimensional swarming behavior in midges (Chironomus riparius), based on dynamical similarity, can be performed using only two-dimensional video data where the animals are not individually tracked. Moreover, the results of the classification are physically meaningful. This work demonstrates that low dimensional video data of collective motion experiments can be equivalently characterized, which has the potential for wide applications to data describing animal group motion acquired in both the laboratory and the field.
Equality cases in monotonicity of quasi-entropies, Lieb’s concavity and Ando’s convexity
Authors: Hiai Fumio
Published: October 2023

We revisit and improve joint concavity/convexity and monotonicity properties of quasi-entropies due to Petz in a new fashion. Then we characterize equality cases in the monotonicity inequalities (the data-processing inequalities) of quasi-entropies in several ways as follows: Let Φ:B(H)→B(K) be a trace-preserving map such that Φ* is a Schwarz map. When f is an operator monotone or operator convex function on [0, ∞), we present several equivalent conditions for the equality SfK(Φ(ρ)‖Φ(σ))=SfΦ*(K)(ρ‖σ) to hold for given positive operators ρ, σ on H and K∈B(K). The conditions include equality cases in the monotonicity versions of Lieb’s concavity and Ando’s convexity theorems. Specializing the map Φ we have equivalent conditions for equality cases in Lieb’s concavity and Ando’s convexity. Similar equality conditions are discussed also for monotone metrics and χ2-divergences. We further consider some types of linear preserver problems for those quantum information quantities.
Thermal stability study of gallium nitride based magnetic field sensor
Authors: Shetty Satish , Kuchuk Andrian , Zamani-Alavijeh Mohammad , Hassan Ayesha , Eisner Savannah R. , Maia de Oliveira Fernando , Krone Alexis , Harris John , Thompson Josh P. , Eldose Nirosh M. , Mazur Yuriy I. , Huitink David , Senesky Debbie G. , Alan Mantooth H. , Salamo Gregory J.
Published: October 2023

We investigated the thermal stability and performance of AlGaN/AlN/GaN Hall-effect sensors under industry-relevant atmospheric conditions. The thermal stability and performance of Hall sensors are evaluated by monitoring Hall sensitivity, two-dimensional electron gas density, and Ohmic contact resistance during aging at 200 °C for up to 2800 h under atmospheric conditions. This was accomplished by characterizing AlGaN/AlN/GaN micro-Hall sensors, with and without contacts, and before and after being placed under different thermal aging times. Observed electrical performance was correlated with the micro-structural evolution of AlGaN/AlN/GaN Hall sensor heterostructures. Results indicate that the AlGaN/AlN/GaN Hall sensor provides stable performance for as long as 2800 h aging at 200 °C without any significant degradation of (i) Hall sensitivity, (ii) two-dimensional electron gas, and (iii) Ohmic contacts. However, there was a small change in sheet density and mobility, which is due to a decrease in polarization, resulting from local inhomogeneous strain relief at the barrier layer. During the early stage of thermal aging, a decrease in contact resistance was also observed and attributed to (i) out-diffusion of “Ga” at the vicinity of the contact interface, and (ii) a reduction in oxygen concentration and formation of Al–Ti intermediate alloy at the GaN/Ti interface, resulting in a reduced barrier and enhanced electron transport at the contacts. However, despite these small changes, results indicate that the AlGaN/AlN/GaN Hall sensor provides stable performance for as long as 2800 h thermal aging at 200 °C.
Refined composite moving average fluctuation dispersion entropy and its application on rolling bearing fault diagnosis
Authors: Chen Yinsheng , Chen Jiahui , Qiang Yukang , Yuan Zichen , Yang Jingli
Published: October 2023

Vibration signal analysis based on multiscale entropy is one of the important means to realize rotating machinery fault diagnosis. However, the length of the time series will be shortened during the coarse-graining process with the increase of the scale factor, which makes the calculated entropy values unstable. This inherent drawback of the coarse-graining method limits its application in fault feature extraction. This paper presents a novel feature extraction method for vibration signals called refined composite moving average fluctuation dispersion entropy (RCMAFDE). It is verified by simulation experiments that RCMAFDE has high stability of entropy values under different time series lengths as well as different disturbances. The RCMAFDE was applied to the fault diagnosis of rolling bearings, and a new fault diagnosis method of rolling bearings was proposed by combining RCMAFDE and kernel extreme learning machine (KELM) optimized by the chaos sparrow search optimization algorithm (CSSOA). First, the vibration signal is preprocessed to form a sample set, and then, the fault feature vector is calculated by RCMAFDE. Finally, the feature vector set is input into the CSSOA-KELM model for training and testing, and the fault diagnosis result is output. To demonstrate the effectiveness and feasibility of the fault diagnosis method, two publicly available datasets and a self-collected dataset are used for experimental validation. The experimental results show that the proposed fault diagnosis method can extract the nonlinear dynamic complexity information of vibration signals more effectively compared with the comparison methods and obtain the highest fault identification accuracy under different datasets.
Stable standing waves for a Schrödinger system with nonlinearχ3 response
Authors: Colin Mathieu , Watanabe Tatsuya
Published: October 2023

In this paper, we consider standing waves for a nonlinear Schrödinger system which appears in nonlinear optics. This two-component system contains a cubic nonlinear term which is called χ3-interaction, and has a strong coupling on one side only. Oliveira and Pastor [Anal. Math. Phys. 11, 123 (2021)] showed the existence of ground states solutions for the corresponding stationary problems and investigated their stability. In our study, by considering the solvability of a constraint minimization problem, we show the existence of stable standing wave solutions. We also investigate the correspondence between minimizers and ground state solutions.
Spin valve effect in CrN/GaN van der Waals heterostructures
Authors: Xue Junjun , Chen Wei , Tao Tao , Zhi Ting , Shao Pengfei , Cai Qing , Yang Guofeng , Wang Jin , Chen Dunjun , Zhang Rong
Published: October 2023

In the pursuit of developing high-performance low-dimensional spintronic devices, two-dimensional van der Waals heterostructures comprising non-magnetic nitride and ferromagnetic materials have emerged as a crucial area of investigation. This paper proposes a novel structure that employs hexagonal two-dimensional semiconductor GaN flanked by two half-metallic two-dimensional CrN layers. The stability of the proposed structure is verified via first-principles calculations, which indicate good thermodynamic and magnetic stability. The transport characteristics of electrons in the structure are analyzed through the Band structures and density of states. Specifically, the study examines the spin polarizability of parallel and anti-parallel magnetic configurations of the CrN/GaN/CrN vdW heterostructure, and the results demonstrate a significant spin valve effect. Overall, the study establishes the potential of the CrN/GaN/CrN vdW heterostructure as a candidate for the development of innovative spintronic devices.
Diffusion-driven periodic cavitation bubbling from a Harvey-type crevice in shear flows
Authors: Li Zehao , Zuo Zhigang , Qian Zhongdong
Published: October 2023

We experimentally and theoretically study the characteristics of hydrodynamic cavitation bubbles generated from a Harvey-type crevice immersed in near-wall shear flows of a Venturi section. In experiments, the crevice is exposed to flows with well-controlled local liquid pressure, shear rate, and far-field dissolved non-condensable gas content. Using multi-scaled high-speed imaging techniques, we are able to identify cases with and without cavitation. In most cavitation cases, we observe periodic cavitation bubbling originating from the crevice. Furthermore, we find that the frequency of the bubbling is highly sensitive to the far-field dissolved non-condensable gas content, indicating the significant role of gas diffusion in driving the periodic cavitation bubbling. Based on the experimental observations, we summarize the physical process of periodic bubbling from the crevice, which mainly includes diffusion-driven crevice nucleus growth, crevice nucleus destabilization, and cavitation bubble detachment from the crevice. Finally, starting from this physical process, we provide a theoretical explanation that quantitatively accounts for the observed cavitation threshold and frequency of bubbling in the present setup. We believe that our findings can be valuable in predicting and controlling cavitation at surfaces exposed to flows, particularly those with tiny defects such as pinholes on complex structures produced by welding or three-dimensional printing, as well as minor erosion pits on the surfaces of fluid machinery.
Large-eddy simulation of a lean-premixed hydrogen flame in a low-swirl combustor under combustion instability
Authors: Nagao Jun , Pillai Abhishek Lakshman , Shoji Takeshi , Tachibana Shigeru , Yokomori Takeshi , Kurose Ryoichi
Published: October 2023

Large-eddy simulation (LES) of a lean-premixed hydrogen turbulent jet flame with combustion instability (CI) in a low-swirl combustor (LSC) is performed by employing a dynamically thickened flame model with a detailed chemical reaction model with 9 chemical species and 20 reactions, and the LES validity and the CI characteristics are investigated in detail. The results show that the present LES can accurately reproduce the experimentally observed characteristics of the CI such as intensity, frequency, sporadic decay of pressure oscillations, and a flame–flow interaction inducing the periodic transitions of an inverted conical flame structure and a flat flame structure in the LSC. The sporadic decay of pressure oscillations and the flame–flow interaction are caused by the temporal decoupling of pressure and heat release rate and the periodic outward and inward deflections of the inflow, which is associated with the flow behavior in the upstream injector channel, respectively.
Adaptive restoration and reconstruction of incomplete flow fields based on unsupervised learning
Authors: Sha Yangyang , Xu Yuhang , Wei Yingjie , Wang Cong
Published: October 2023

Due to experimental limitations and data transmission constraints, we often encounter situations where we can only obtain incomplete flow field data. However, even with incomplete data, we can still extract valuable information about the main structural characteristics of the flow field. In this study, we propose a novel unsupervised learning reconstruction method to restore the incomplete flow field data. Our method comprises several key steps: First, based on the temporal evolution characteristics of the flow field, we employ the Autoregressive Integrated Moving Average model method to pre-reconstruct the incomplete data. Next, we introduce the Fuzzy Spatial Consistency Index (FSCI), which measures the spatial coherence among neighboring data variations. By utilizing FSCI as a guiding metric, we iteratively optimize and replace missing values using the Proper Orthogonal Decomposition method. Importantly, our reconstruction process does not rely on expensive high-fidelity data fusion or external intervention, making it highly efficient and cost-effective. We focus our research on the classic problem of flow around the hydrofoil and apply the unsupervised learning reconstruction method to restore incomplete flow fields with varying missing rates. We also investigate the impact of flow field stability, snapshot sampling frequency, and missing structure on reconstruction accuracy. Our results indicate that these factors significantly influence the reconstruction of velocity fields with a high missing rate compared with a lower missing rate. Additionally, we observe that the reconstruction performance of the streamwise velocity field is relatively inferior compared to the normal velocity field, and the reconstruction accuracy is higher for relatively stable flow fields. These findings provide valuable insights and further validate the effectiveness and applicability of the unsupervised learning reconstruction method for restoring incomplete flow fields.
Uncovering the substituted-position effect on excited-state evolution of benzophenone-phenothiazine dyads
Authors: Li Jiayu , Yang Sirui , Deng Ziqi , Islam Amjad , Wu Shiqi , He Jiaxing , Ni Shaofei , Dang Li , Li Ming-De
Published: October 2023

Photofunctional materials based on donor-acceptor molecules have drawn intense attention due to their unique optical properties. Importantly, Systematic investigation of substitution effects on excited-state charge transfer dynamics of donor-acceptor molecules is a powerful approach for identifying application-relevant design principles. Here, by coupling phenothiazine (PTZ) at the ortho-, meta-, and para-positions of the benzene ring of benzophenone (BP), three regioisomeric BP-PTZ dyads were designed to understand the relationship between substituted positions and excited-state evolution channels. Ultrafast transient absorption is used to detect and trace the transient species and related evolution channels of BP-PTZ dyads at excited state. In a non-polar solvent, BP-o-PTZ undergoes the through-space charge transfer process to produce a singlet charge-transfer (1CT) state, which subsequently proceeds the intersystem crossing process and transforms into a triplet charge-transfer (3CT) state; BP-m-PTZ experiences intramolecular charge transfer (ICT) process to generate the 1CT state, which subsequently transforms into the 3CT state by the intersystem crossing (ISC) and finally converts into the local-excited triplet (3LE) state; as for BP-p-PTZ, only 3LE states can be detected after the ISC process from the 1CT state. On the other hand, the twisted ICT states are generated via twisted motion between the donor and acceptor for all BP-PTZ dyads or planarization of the PTZ unit in high polar solvents. The excited-state theoretical calculations unveil that the features of ICT and intramolecular interaction between the three dyads play a decisive role in determining the through-bond charge transfer and through-space charge transfer processes. Also, these results demonstrate that the excited-state evolution channels of PTZ derivatives could be modified by tuning the substituted positions of the donor-acceptor dyads. This study provides a deep perspective for the substitute-position effect on donor-acceptor-type PTZ derivatives.
Ensuring fair assessment of solid-state nanopore sensors with reporting baseline current
Authors: Dong Ming , Tang Zifan , Guan Weihua
Published: October 2023

In developing solid-state nanopore sensors for single molecule detection, comprehensive evaluation of the nanopore quality is important. Existing studies typically rely on comparing the noise root mean square or power spectrum density values. Nanopores exhibiting lower noise values are generally considered superior. This evaluation is valid when the single molecule signal remains consistent. However, the signal can vary, as it is strongly related to the solid-state nanopore size, which is hard to control during fabrication consistently. This work emphasized the need to report the baseline current for evaluating solid-state nanopore sensors. The baseline current offers insight into several experimental conditions, particularly the nanopore size. Our experiments show that a nanopore sensor with more noise is not necessarily worse when considering the signal-to-noise ratio (SNR), particularly when the pore size is smaller. Our findings suggest that relying only on noise comparisons can lead to inaccurate evaluations of solid-state nanopore sensors, considering the inherent variability in fabrication and testing setups among labs and measurements. We propose that future studies should include reporting baseline current and sensing conditions. Additionally, using SNR as a primary evaluation tool for nanopore sensors could provide a more comprehensive understanding of their performance.
Efficient calculation of electronic coupling integrals with the dimer projection method via a density matrix tight-binding potential
Authors: Kohn J. T. , Gildemeister N. , Grimme S. , Fazzi D. , Hansen A.
Published: October 2023

Designing organic semiconductors for practical applications in organic solar cells, organic field-effect transistors, and organic light-emitting diodes requires understanding charge transfer mechanisms across different length and time scales. The underlying electron transfer mechanisms can be efficiently explored using semiempirical quantum mechanical (SQM) methods. The dimer projection (DIPRO) method combined with the recently introduced non-self-consistent density matrix tight-binding potential (PTB) [Grimme et al., J. Chem. Phys. 158, 124111 (2023)] is used in this study to evaluate charge transfer integrals important for understanding charge transport mechanisms. PTB, parameterized for the entire Periodic Table up to Z = 86, incorporates approximate non-local exchange, allowing for efficient and accurate calculations for large hetero-organic compounds. Benchmarking against established databases, such as Blumberger’s HAB sets, or our newly introduced JAB69 set and comparing with high-level reference data from ωB97X-D4 calculations confirm that DIPRO@PTB consistently performs well among the tested SQM approaches for calculating coupling integrals. DIPRO@PTB yields reasonably accurate results at low computational cost, making it suitable for screening purposes and applications to large systems, such as metal-organic frameworks and cyanine-based molecular aggregates further discussed in this work.
Bilayer vanadium dioxide thin film with elevated transition temperatures and high resistance switching
Authors: Dutta Achintya , Ashok P. , Verma Amit
Published: October 2023

Despite widespread interest in the phase-change applications of vanadium dioxide (VO2), the fabrication of high-quality VO2 thin films with elevated transition temperatures (TIMT) and high insulator–metal-transition resistance switching still remains a challenge. This study introduces a two-step atmospheric oxidation approach to fabricate bilayer VO2−x/VO2 films on a c-plane sapphire substrate. To quantify the impact of the VO2 buffer layer, a single-layer VO2 film of the same thickness was also fabricated. The bilayer VO2−x/VO2 films, wherein the top VO2−x film was under-oxidized, demonstrated an elevation in TIMT reaching ∼97 °C, one of the highest reported to date for VO2 films and is achieved in a doping-free manner. Our results also reveal a one-order increase in resistance switching, with the optimum bilayer VO2/VO2 film exhibiting ∼3.6 orders of switching from 25 to 110 °C, compared to the optimum single-layer VO2 reference film. This is accompanied by a one-order decrease in the on-state resistance in its metallic phase. The elevation in TIMT, coupled with increased strain extracted from the XRD characterization of the bilayer film, suggests the possibility of compressive strain along the c-axis. These VO2−x/VO2 films also demonstrate a significant change in the slope of their resistance vs temperature curves contrary to the conventional smooth transition. This feature was ascribed to the rutile/monoclinic quasi-heterostructure formed due to the top VO2−x film having a reduced TIMT. Our findings carry significant implications for both the lucid fabrication of VO2 thin film devices as well as the study of phase transitions in correlated oxides.
In situ observation of indium filament growth dynamics in ITO electrode-based memristor
Authors: Ye Caiyang , Xu Yimeng , Li Yang , Qian Kai
Published: October 2023

Indium tin oxide (ITO) electrode is commonly used in integrated transparent electronics, including memristor, solar cell, light emitting diode, and photodetector. However, the lack of appropriate understanding of indium (In) ions motion from ITO is the major roadblock to disclose the mechanism of ITO electrode-based memristors. Revealing the filaments growth dynamics is of critical importance to continued devices optimization. Here, we show direct evidence of In filament growth dynamics by in situ transmission electron microscopy, where the In–O bond in ITO would dissociate at high electric field, leading to the In ions transport and cone-like filament formation in the dielectric layer. The In filament formation and melt are responsible for the resistive switching, which can both commence growth toward active ITO and inert Au electrodes, respectively, by controlling the ion mobility. This study can provide a generalized guideline for high performance electronics design and modeling with transparent ITO electrodes.
Numerical investigations of activation energy on the peristaltic transport of Carreau nanofluid through a curved asymmetric channel
Authors: Magesh A. , Pushparaj V. , Srinivas S. , Tamizharasi P.
Published: October 2023

Nanometric particles with base liquids cause the production of nanofluids, which are distinguished by their outstanding thermally conductive fluid properties and the expansion of electrical and mechanical devices. Based on these considerations, we devised a study to investigate the effect of activation energy on the peristaltic motion of Carreau nanofluid inside a curved asymmetric channel under the influence of a magnetic field. The governing equations for the curved channel of non-Newtonian fluid flow are formulated. The nonlinear partial differential equations system has been reduced to ordinary differential equations by the assumptions of low Reynolds number and long wavelength approximations. The resulting nonlinear coupled differential equations are numerically solved directly using NDSolve (numerical differential equation solver) coding of computational mathematical software Mathematica, and velocity, temperature, concentration, and streamlines are plotted. With graphical demonstrations, the influence of essential parameters on velocity, temperature, concentration, and streamlines is explained in detail. The dimensionless temperature distribution grows as the activation energy parameter grows. In reality, the number of energetic particles (with energies equal to or greater than activation energy) increases, resulting in improved temperature distribution.
Choi matrices revisited. II
Authors: Han Kyung Hoon , Kye Seung-Hyeok
Published: October 2023

In this paper, we consider all possible variants of Choi matrices of linear maps, and show that they are determined by non-degenerate bilinear forms on the domain space. We will do this in the setting of finite dimensional vector spaces. In case of matrix algebras, we characterize all variants of Choi matrices which retain the usual correspondences between k-superpositivity and Schmidt number ≤k as well as k-positivity and k-block-positivity. We also compare de Pillis’ definition [Pac. J. Math. 23, 129–137 (1967)] and Choi’s definition [Linear Algebra Appl. 10, 285–290 (1975)], which arise from different bilinear forms.
Conformational effects in the vibrational and electronic spectra of propionaldehyde: Experimental and theoretical studies
Authors: Sharma Neha , Shastri Aparna , Das Asim Kumar , Rajasekhar B. N.
Published: October 2023

We report here investigations on conformational effects in the vibrational and electronic spectra of the propionaldehyde (propanal) molecule using FTIR (600–3200 cm−1) and vacuum ultraviolet (VUV) synchrotron radiation photoabsorption (52 500–85 000 cm−1) spectroscopy respectively. Detailed theoretical calculations (using DFT and TDDFT methodologies) on ground and excited states of the cis and gauche conformers of propanal are performed; a comprehensive spectral analysis of the IR and VUV spectra is presented. A reinvestigation of the IR spectrum reveals several new bands assigned to the gauche conformer based on theoretical calculations. The VUV spectrum exhibits rich Rydberg series structure assigned to ns, np and nd series converging to the first ionization potentials of the two conformers. Earlier assignments of the 3s cis and gauche origins are revised in addition to extending Rydberg series analysis to several higher members. Vibronic bands accompanying the 3s, 4s and 4p Rydberg states are assigned using estimated vibrational frequencies of cis and gauche conformers in the cationic ground state. Simulated potential energy curves of the first few excited states (singlets and triplets) of cis and gauche conformers of propanal help in gaining insights into photodissociation mechanisms and possible conformational effects therein.
Three-dimensional shape optimization of a submerged body under wave diffraction
Authors: Lu Chenyu , Liu Jiabin , Guo Anxin
Published: October 2023

This study explores the use of shape optimization to reduce wave forces on a submerged floating body subjected to wave diffraction. To this end, gradient-based shape optimization is adopted, in which dimensionless wave excitation forces are the optimization objective. A shape parameterization method based on the Fourier-series expansion is developed that permits the representation of an arbitrary three-dimensional floating body. The discrete adjoint method is utilized to calculate the gradient of the objective function with respect to the shape parameters. Using three-dimensional shape optimization, taking the initial shape to be a hemisphere, a significant reduction in surge, heave, and pitch wave forces is achieved, with a maximum reduction of 48.40%, 68.43%, and 46.22%, respectively. Furthermore, optimization effectively suppresses wave run-up, with a maximum reduction of 15.62%. A comprehensive analysis of parameters is performed to reveal the effects of wave number, incident angle, and shape parameters on the final optimized shape and wave load characteristics. This study provides a solid guide to the optimization of floating offshore platforms and the development of innovative structural systems.
Public–private partnership in the UK fusion program
Authors: Chapman I. T. , Bestwick T. , Methven P.
Published: October 2023

Fusion power could be one of a few sustainable options in a portfolio required to replace fossil fuels as the world's primary energy source. The attractive properties of fusion combined with the imperative to address climate change has resulted in a burgeoning interest in the field with a dramatic growth in privately funded fusion ventures in recent years. Historically, fusion has been developed by governments globally, including through ITER, the largest scientific collaborative project ever undertaken. The result is that the majority of people working in fusion today as well as most of the intellectual property reside within the public sector. However, there is equally a recognition that the private sector plays a vital role in delivering large-scale infrastructure projects, especially at the pace and agility required in the case of fusion and because it is the private sector that ultimately will deliver a fleet of fusion plants. Therefore, many countries are increasingly pursuing variants of public–private partnerships in the delivery of fusion. In this paper, we provide the perspective of expedient delivery of fusion through public–private partnership as presently intended in the UK fusion program.
Evolution of unsteady secondary flow structures near the onset of stall in a tip-critical transonic axial flow compressor stage
Authors: Kumar Lakshya , Alone Dilipkumar Bhanudasji , Pradeep A. M.
Published: October 2023

The aerodynamic stability of an axial compressor stage depends on the rotor and stator. However, due to the specific design requirements, the evolving flow field and the resulting secondary flow structures are different in both components. This study investigates the evolution of dominant secondary flow structures occurring in the rotor and stator of a tip-critical transonic compressor stage at the near-stall condition using unsteady numerical analysis and validates performance characteristics with the experimental data. The investigation reveals that the presence of rotor tip shock creates a large difference in the pressure gradient across the pressure surface and the suction surface, intensifying tip leakage flow and shock-induced boundary layer separation. The higher incidence angle near the hub leading edge creates a local separation and reattachment zone. The radial pressure gradient causes the low momentum flow from this local separation zone to migrate radially upward. This migrated flow interacts with the tip leakage flow and separated blade boundary layer, eventually creating a colossal recirculation zone and subsequent rotor blockage of around 46%. The increasing streamwise adverse pressure gradient pushes the tip shock upstream, and at the onset of the stall, the flow directly separates from the rotor leading edge avoiding the shock formation. The stator flow field is dominated by the asymmetric hub corner separation induced by the streamwise adverse pressure gradient and the tip corner separation caused by the vortex structures convected downstream from the rotor tip region leading to stator blockage of around 48%. Along with the blade passing frequency, four other dominating frequencies (0.06×BPF, 0.12×BPF, 0.44×BPF, and 0.84×BPF) related to the aerodynamic instabilities are observed at the inception of stall.
Two-phase flow structures in a helically coiled microchannel: An experimental investigation
Authors: Saisorn Sira , Benjawun Phakkhanan , Suriyawong Adirek , Asirvatham Lazarus Godson , Mondal Pranab Kumar , Wongwises Somchai
Published: October 2023

At the microfluidic scale, the utilization of helically coiled channels (HCCs), also known as a spiral channel, for two-phase flow offers numerous advantages in various applications. Existing articles mainly focus on the macro-scale transport, examining secondary flows induced in curved channels. The increasing demand, however, for innovative miniature equipment for thermal energy management emphasizes the importance of comprehending gas–liquid micro-scale flow in curved channels. Unfortunately, despite a vast body of literature on this paradigm, there is still a lack of systematic investigations into the underlying facets of two-phase micro-scale transport in HCCs. To address this gap, our study conducted experiments on adiabatic two-phase air–water flow inside an up-flow helical micro-scale tube. The tube had a hydraulic diameter of 0.87 mm, a coil diameter of 50 mm, and a helical pitch of 20 mm. The primary aim was to explore the impact of centrifugal force on flow pattern, void fraction, and frictional pressure drop characteristics. Additionally, we carefully examined the phase separation phenomenon influenced by the secondary flows induced by the curved channel. In particular, we compared the gas-core flow pattern (either throat-annular flow or annular flow), void fraction, and frictional pressure drop obtained from our experiments on the helical tube with corresponding results based on straight micro-scale channel configurations for an Eötvös number of approximately 0.01. In summary, this study delves deep into the crucial aspects of two-phase micro-scale transport in HCCs, contributing to a better understanding of these systems for future advancements in micro-channel applications.
Conditions for EPR detection of chirality-induced spin selectivity in spin-polarized radical pairs in isotropic solution
Authors: Ren Yi , Hore P. J.
Published: October 2023

Chiral molecules can act as spin filters, preferentially transmitting electrons with spins polarized along their direction of travel, an effect known as chirality-induced spin selectivity (CISS). In a typical experiment, injected electrons tunnel coherently through a layer of chiral material and emerge spin-polarized. It is also possible that spin polarization arises in radical pairs formed photochemically when electrons hop incoherently between donor and acceptor sites. Here we aim to identify the magnetic properties that would optimise the visibility of CISS polarization in time-resolved electron paramagnetic resonance (EPR) spectra of transient radical pairs without the need to orient or align their precursors. By simulating spectra of actual and model systems, we find that CISS contributions to the polarization should be most obvious when at least one of the radicals has small g-anisotropy and an inhomogeneous linewidth larger than the dipolar coupling of the two radicals. Under these conditions there is extensive cancellation of absorptive and emissive enhancements making the spectrum sensitive to small changes in the individual EPR line intensities. Although these cancellation effects are more pronounced at lower spectrometer frequencies, the spectral changes are easier to appreciate with the enhanced resolution afforded by high-frequency EPR. Consideration of published spectra of light-induced radical pairs in photosynthetic bacterial reaction centres reveals no significant CISS component in the polarization generated by the conventional spin-correlated radical pair mechanism.
Measuring response functions of active materials from data
Authors: Molaei Mehdi , Redford Steven A. , Chou Wen-Hung , Scheff Danielle , de Pablo Juan J. , Oakes Patrick W. , Gardel Margaret L.
Published: October 2023

From flocks of birds to biomolecular assemblies, systems in which many individual components independently consume energy to perform mechanical work exhibit a wide array of striking behaviors. Methods to quantify the dynamics of these so-called active systems generally aim to extract important length or time scales from experimental fields. Because such methods focus on extracting scalar values, they do not wring maximal information from experimental data. We introduce a method to overcome these limitations. We extend the framework of correlation functions by taking into account the internal headings of displacement fields. The functions we construct represent the material response to specific types of active perturbation within the system. Utilizing these response functions we query the material response of disparate active systems composed of actin filaments and myosin motors, from model fluids to living cells. We show we can extract critical length scales from the turbulent flows of an active nematic, anticipate contractility in an active gel, distinguish viscous from viscoelastic dissipation, and even differentiate modes of contractility in living cells. These examples underscore the vast utility of this method which measures response functions from experimental observations of complex active systems.
Sequence-independent activity of a predicted long disordered segment of the human papillomavirus type 16 L2 capsid protein during virus entry
Authors: Oh Changin , Buckley Patrick M. , Choi Jeongjoon , Hierro Aitor , DiMaio Daniel
Published: October 2023

The activity of proteins is thought to be invariably determined by their amino acid sequence or composition, but we show that a long segment of a viral protein can support infection independent of its sequence or composition. During virus entry, the papillomavirus L2 capsid protein protrudes through the endosome membrane into the cytoplasm to bind cellular factors such as retromer required for intracellular virus trafficking. Here, we show that an ~110 amino acid segment of L2 is predicted to be disordered and that large deletions in this segment abolish infectivity of HPV16 pseudoviruses by inhibiting cytoplasmic protrusion of L2, association with retromer, and proper virus trafficking. The activity of these mutants can be restored by insertion of protein segments with diverse sequences, compositions, and chemical properties, including scrambled amino acid sequences, a tandem array of a short sequence, and the intrinsically disordered region of an unrelated cellular protein. The infectivity of mutants with small in-frame deletions in this segment directly correlates with the size of the segment. These results indicate that the length of the disordered segment, not its sequence or composition, determines its activity during HPV16 pseudovirus infection. We propose that a minimal length of L2 is required for it to protrude far enough into the cytoplasm to bind cytoplasmic trafficking factors, but the sequence of this segment is largely irrelevant. Thus, protein segments can carry out complex biological functions such as Human papillomavirus pseudovirus infection in a sequence-independent manner. This finding has important implications for protein function and evolution.
Auxiliary Selection in Italo-Romance
Authors: Amato Irene
Published: October 2023

This book proposes a new solution to the long-standing puzzle of auxiliary selection in Romance languages, in particular Italian. The following questions are addressed: why the perfect auxiliary appears in the two forms be and have within a single language, what drives this distribution, and how cross-linguistic data can be accounted for. The solution to these issues consists of an Agreebased analysis that accounts for auxiliary selection in root clauses and restructuring in Standard Italian and in Italo-Romance varieties, which is also compatible with participle agreement. By answering these questions, the book also touches upon more theoretical and foundational problems, such as the distribution of labor between syntax, morphology and the lexicon, and the conditions on the operation Agree (in particular, multiple probing, locality, and minimality). This work contributes to the discussion in the fields of formal morpho-syntax, theoretical linguistics, and Romance linguistics.
A SINS/DVL navigation method based on hierarchical water velocity estimation*
Authors: Wang Di , Wang Bing , Huang Haoqian , Zhang Haixu
Published: October 2023

Aiming at the problem that Doppler velocity log (DVL) cannot measure the velocity of the vehicle in the middle water environment, a Strap-down Inertial Navigation System (SINS)/DVL integrated navigation method based on hierarchical water velocity assistance is proposed. Firstly, according to the principle of DVL water layer flow measurement, the paper gives a hierarchical water recurrence principle. On this basis, a water velocity estimation method based on average weighted recurrence is proposed. The carrier depth information is introduced in this method, and the carrier velocity information is obtained by means of average value. This method can prevent the carrier velocity anomaly caused by the large error of single-layer water velocity measurement. Secondly, in view of the problem that the DVL water velocity measurement is easily disturbed in the middle water environment, a sliding window and a Chebyshev polynomial fitting function are introduced to realize the robust treatment of the water velocity. On this basis, combined with the Huber M robust filter algorithm, a hierarchical water velocity assisted integrated navigation algorithm based on the improved Huber M robust estimation is proposed to further improve the autonomous navigation accuracy in the middle water environment. Finally, the method proposed in this paper is verified by simulation. The results show that the hierarchical water velocity estimation method proposed in this paper can effectively estimate the water flow velocity, and its robust filtering algorithm can further improve the SINS/DVL integrated navigation accuracy in the middle water environment.
Finite element model correction method based on surrogate model with multiple working conditions and multiple measurement points
Authors: Song Mingchang , Shi Quan , You Zhifeng , Bai Yongsheng
Published: October 2023

The finite element model inversion method has been widely used in recent years for iterative adjustment of finite element model parameters. However, the models constructed in the existing literature are weak and time consuming to adapt to the environment, which makes it difficult to adapt to the current needs of numerical simulations. To address the problem of large uncertainty in the material parameters of real objects and the difficulty of constructing finite element simulation models, a surrogate-based model correction method was proposed for multi-condition and multi-measurement point finite element models. The innovative use of the working condition parameter as one of the training parameters of the surrogate model to construct the optimal mathematical model for parameter correction of the finite element model to variable working conditions. To reduce the number of finite element model calls and speed up the convergence process, an Minimizing Prediction-CV-Voronoi parallel infill sampling method for the surrogate model was proposed to overcome the problems of easily falling into local optima and slow convergence when solving after constructing the surrogate model. The proposed parallel infill sampling method was tested using the test functions. The finite element model correction method with multiple working conditions and multiple measurement points was applied for material parameter correction and identification of aluminum alloys. The superiority of the proposed parallel point addition method in terms of the solution accuracy and speed was demonstrated. The results show that the multi-measurement points have a significant effect on improving the model correction effect, and the constructed multi-condition surrogate model can make fast predictions for arbitrary conditions and has strong environmental adaptability. The finite element model correction method proposed in this paper, with strong environmental adaptability, high accuracy and fast iteration, has been tested to be very effective.
Uniform zinc-ion deposition regulated by thin sulfonated poly(ether ketone) layer for Stabilizing Zn anodes
Authors: Song Binxin , Wang Xinyu , Gao Hang , Gao Wenlong , Ma Xiangkun
Published: October 2023

Aqueous zinc-ion batteries (AZIBs) have been getting lots of attention in the field of large scale energy storage owing to their low cost, large capacity and excellent safety. However, Zn anodes have serious dendritic growth and corrosion hydrogen evolution issues, which hinder their further application. Herein, a simple drop-coating technique was used to build a thin sulfate poly(ether ketone) (SPEEK) solid-electrolyte interphase (SEI) on the surface of the Zn anode to address these issues. The sulfonated group (−SO3
−） in SPEEK can provide rich coordination sites for Zn2+, controlling the uniform deposition of Zn2+. Therefore, the polymer SEI can block electrolytes and homogenize the Zn2+ flux, resulting that the modified Zn (SPEEK@Zn) anode could effectively limit the formation of dendrites and side reactions. At a current density of 0.5 mA cm−2, SPEEK@Zn electrodes can maintain an ultra-long plating/stripping cycle life of 1000 h. Full batteries based on SPEEK@Zn have more superior cycle stability than the bare ones. This approach offers a straightforward and scalable remedy for high-performance Zn anode batteries.
Modulation of spin and charge currents through functionalized 2D diamond devices
Authors: Pinto Alysson A , de Moraes Elizane E , Chacham Helio , Batista Ronaldo J C
Published: October 2023

In this study, we explore the potential of functionalized two-dimensional (2D) diamond for spin-dependent electronic devices using first-principles calculations. Specifically, we investigate functionalizations with either hydroxyl (−OH) or fluorine (−F) groups. In the case of an isolated layer, we observe that the quantity and distribution of (−OH) or (−F) on the 2D diamond surface significantly influence the sp
2/sp
3 ratio of the carbon atoms in the layer. As the coverage is reduced, both the band gap and magnetic moment decrease. When the 2D diamond is placed between gold contacts and functionalized with (−OH), it results in a device with lower resistance compared to the (−F) functionalization. We predict that the maximum current achieved in the device increases with decreasing (−OH) surface coverage, while the opposite behavior occurs for (−F). Additionally, the surface coverage alone can alter the direction of current rectification in (−F) functionalized 2D diamonds. For all studied systems, a single spin component contributes to the total current for certain values of applied bias, indicating a spin filter behavior.
Modeling the co-assembly of binary nanoparticles
Authors: Mohanty Saurav , Chen Timothy , Chen I-Te , So Franky , Chang Chih-Hao
Published: October 2023

In this work, we present a binary assembly model that can predict the co-assembly structure and spatial frequency spectra of monodispersed nanoparticles with two different particle sizes. The approach relies on an iterative algorithm based on geometric constraints, which can simulate the assembly patterns of particles with two distinct diameters, size distributions, and at various mixture ratios on a planar surface. The two-dimensional spatial-frequency spectra of the modeled assembles can be analyzed using fast Fourier transform analysis to examine their frequency content. The simulated co-assembly structures and spectra are compared with assembled nanoparticles fabricated using transfer coating method are in qualitative agreement with the experimental results. The co-assembly model can also be used to predict the peak spatial frequency and the full-width at half-maximum bandwidth, which can lead to the design of the structure spectra by selection of different monodispersed particles. This work can find applications in fabrication of non-periodic nanostructures for functional surfaces, light extraction structures, and broadband nanophotonics.
Engineering microcracks in MWCNT/elastomer bilayers for high-performance stretchable sensor development
Authors: Wang Fei , Zhou Boran , Wang Rui , Jenkinson Jim , Zhu Weihang , Zhong Jing , Fan Zheng , Sun Li
Published: October 2023

Stretchable strain sensors in motion detection, health monitoring, and human-machine interfaces are limited by device sensitivity, linearity, hysteresis, stability, and reproducibility in addition to stretchability. Engineering defect structures in sensing material is an effective approach in modulating the material's physical properties, particularly those associated with mechanical responses. Here, we demonstrate that bilayers of carbon nanotubes deposited on an elastomer substrate are mechanically coupled. The microcrack size, density, and distribution in the nanotube thin film can be engineered through uniaxial tensile training to exhibit highly tunable and stable piezoresistive responses with sensitivity, linearity, range, and reproducibility. These responses far exceeding those in uniform metallic films, patterned structures, and composites. In addition, numerical analyses performed on a two-dimensional network model of the cracked nanotube film provide quantitative explanations of how crack configuration, and evolvement under strain, lead to the significant enhancements in stretchable sensor performance using current bilayer structures.