bluuebunny/crossref_metadata_2025 huggingface dataset:
Sign patterns symbolization and its use in improved dependence test for complex network inference
Authors: Yamashita Rios de Sousa Arthur Matsuo , Hlinka Jaroslav
Published: August 2023

Inferring the dependence structure of complex networks from the observation of the non-linear dynamics of its components is among the common, yet far from resolved challenges faced when studying real-world complex systems. While a range of methods using the ordinal patterns framework has been proposed to particularly tackle the problem of dependence inference in the presence of non-linearity, they come with important restrictions in the scope of their application. Hereby, we introduce the sign patterns as an extension of the ordinal patterns, arising from a more flexible symbolization which is able to encode longer sequences with lower number of symbols. After transforming time series into sequences of sign patterns, we derive improved estimates for statistical quantities by considering necessary constraints on the probabilities of occurrence of combinations of symbols in a symbolic process with prohibited transitions. We utilize these to design an asymptotic chi-squared test to evaluate dependence between two time series and then apply it to the construction of climate networks, illustrating that the developed method can capture both linear and non-linear dependences, while avoiding bias present in the naive application of the often used Pearson correlation coefficient or mutual information.
Estimation of cavitation velocity fields based on limited pressure data through improved U-shaped neural network
Authors: Xu Yuhang , Sha Yangyang , Wang Cong , Wei Yingjie
Published: August 2023

In marine applications, estimating velocity fields or other states from limited data are important as it provides a reference for active control. In this work, we propose PVNet (Pressure-Velocity Network), an improved U-shaped neural network (UNet) combined with Transformer Modules and Multi-scale Fusion Modules, to predict velocity fields from pressure on the hydrofoil surface. To improve prediction accuracy, position encodings have been incorporated into the input features. Tests on the cavitation dataset of the NACA66 (National Advisory Committee for Aeronautics) hydrofoil demonstrate that PVNet outperforms traditional models such as shallow neural networks and UNet. In addition, we conducted a quantitative analysis of the impact of input features on prediction performance, providing guidance for the practical arrangement of sampling points. Furthermore, by comparing different positional encodings, we found that reasonable positional encodings can significantly improve prediction accuracy.
Transient responses of the linear and nonlinear gap resonances in the fixed and free-heaving moonpools
Authors: Jing Penglin , He Guanghua , Ghassemi Hassan , Luan Zhengxiao
Published: August 2023

The transient responses in the fixed and free-heaving moonpools under the conditions of linear and nonlinear gap resonance are investigated. A two-dimensional numerical model was established using a constrained interpolation profile method-based in-house code. This paper mainly concentrates on the prediction and quantification of the developing and diminishing processes of the free-surface elevation at gap when encountering both the linear gap resonance and quadratic wave excitation (QWE)-driven gap resonance. The parameter analyses with respect to the distance between the barges and barge draft are considered to derive the variation in the response time and damping time. The continuous wavelet transform (CWT) is introduced to investigate the gap resonances for the first time to obtain the transient characteristics' distribution of the free-surface elevation at gap along time and frequency domains. Numerical results demonstrate that the heave motion has changed the developing patterns of both the linear gap resonance and QWE gap resonance in the free-heaving moonpool rather than those in the fixed moonpool. Nevertheless, the impact caused by heave is little as for the diminishment. By introducing a new hyperbolic-function-type amplification function, the development of the gap resonances for the free-heaving moonpool is well predicted. In addition, the opposite tendency is observed for both the response time and damping time between the fixed and free-heaving moonpools when considering from the linear to QWE gap resonances. According to the transient characteristics obtained from the CWT, it is attributed to the different proportions of the free-surface elevation's second-order component between the fixed and free-heaving moonpools at the QWE resonant point. Moreover, the duration of the damping time is found to be greatly influenced by the phase relation between the free-surface elevation at gap and the heave motion of the moonpool from the linear resonant point to the QWE resonant point.
Efficient approximation of molecular kinetics using random Fourier features
Authors: Nüske Feliks , Klus Stefan
Published: August 2023

Slow kinetic processes in molecular systems can be analyzed by computing the dominant eigenpairs of the Koopman operator or its generator. In this context, the Variational Approach to Markov Processes (VAMP) provides a rigorous way of discerning the quality of different approximate models. Kernel methods have been shown to provide accurate and robust estimates for slow kinetic processes, but they are sensitive to hyper-parameter selection and require the solution of large-scale generalized eigenvalue problems, which can easily become computationally demanding for large data sizes. In this contribution, we employ a stochastic approximation of the kernel based on random Fourier features (RFFs) to derive a small-scale dual eigenvalue problem that can be easily solved. We provide an interpretation of this procedure in terms of a finite, randomly generated basis set. By combining the RFF approach and model selection by means of the VAMP score, we show that kernel parameters can be efficiently tuned and accurate estimates of slow molecular kinetics can be obtained for several benchmarking systems, such as deca alanine and the NTL9 protein.
Numerical investigation on the interaction of an oscillating bubble with the interface of a non-Newtonian fluid
Authors: Tang Hao , Tian Zhao-Li , Ju Xin-Yang , Feng Ji-Tuan , Zhang Shuai , Zhang A-Man
Published: August 2023

The dynamics of an oscillating bubble near a liquid–liquid interface is a complex multiphase flow problem due to the highly nonlinear interaction, such as interface fragmentation and bubble tearing. When one of the liquid mediums is non-Newtonian, its constitution would significantly influence both the bubble motion and the interface evolution. In this study, a numerical model is established based on the Eulerian finite element method with the non-Newtonian fluid described by the Herschel–Bulkley model. The numerical model is validated by comparing with experimental results for a non-spherical pulsating bubble at a water–oil interface and the analytical solution for the laminar flow of non-Newtonian fluids in a circular tube. According to the simulation and analysis with different case parameters, our findings suggest that the non-Newtonian fluid forms a crater when squeezed by the bubble, and the downward jet can penetrate the bubble and further deepen the crater. As the distance parameter increases, the crater gradually disappears or even bulges. Furthermore, the yield shear stress can give non-Newtonian fluid plastic properties similar to a solid, effectively reducing the bubble's pulsation and jet load. Additionally, the flow behavior index n comes from the power-law model for non-Newtonian fluids and significantly impacts the jet's impact process. When n≤1, the crater is likelier to become funnel-shaped, whereas when n > 1, it is likelier to become bullet-head-shaped. In addition to enhancing the bubble's nonsphericity, the reduction in Reynolds number also weakens the crimp deformation of the interface. When the distance parameter is zero, the larger the buoyancy parameter and the less deformable the non-Newtonian fluid, the easier the bubble to split by the annular jet.
Molecular dynamics simulation to reveal the transport mechanism of LiPF6 in ethylene carbonate + dimethylcarbonate binary solvent
Authors: Kiyobayashi Tetsu , Uchida Satoshi , Ozaki Hiroyuki , Kiyohara Kenji
Published: August 2023

This paper presents the molecular dynamics simulation of 1 mol kg−1 LiPF6 in a binary solvent of ethylene carbonate (EC) and dimethylcarbonate, which is a representative electrolyte solution for lithium-ion batteries. The simulation successfully reproduced the diffusion coefficient, ionic conductivity, and shear viscosity as functions of EC content at 300 K, which had been experimentally determined in our previous study. The Yukawa potential was adopted to model intercharge interactions to reduce computational costs, which consequently allowed us to precisely calculate the conductivity and viscosity by directly integrating time-correlation functions without explicitly modeling the molecular polarization. Breaking down microscopic current correlation functions into components revealed that, whereas the cation–anion attractive interaction dominantly impedes the conduction when the EC content is low, it is the cation–cation and anion–anion repulsive interactions that reduce the conductivity at a high EC content. An analysis of the pressure correlations revealed that all components positively contribute to the viscosity in the binary solvent without the electrolyte. On the other hand, negative terms are observed in five out of six cross correlations in the presence of the electrolyte, implying that these correlations negatively contribute to the shear stress and entropy production, both of which are net positive.
Strong pyroelectric enhancement induced by the evolution of PNRs in paraelectric-phase KTN crystals
Authors: Meng Xiangda , Dong Yining , Hu Jianjiang , Jin Song , Liu Mingxuan , Sun Xuejie , Wang Yu , Tian Hao
Published: August 2023

KTa1−xNbxO3 crystals exhibit excellent piezoelectric, ferroelectric, and electro-optical properties near the phase transition point, owing to the evolution of polar nanoregions (PNRs). This paper discusses the physical properties of the PNRs in three characteristic temperature ranges and analyzes the dielectric relaxation properties of the crystals. The effects of different heating rates and initial temperatures on the pyroelectric effect are discussed, and the influence of small electric fields on increasing the pyroelectric coefficient is investigated. The polarization characteristics of the crystal were obtained according to the change in the pyroelectric performance, and the influence of different conditions on the dynamic response of the PNRs was analyzed. It is proposed that the evolution of PNRs, induced by external coupling with an internal electric field, significantly affects macroscopic performance.
The Sociophonetics of Dublin English
Authors: Schulte Marion
Published: August 2023

The Sociophonetics of Dublin English shows how social inequalities and language are connected by the stances speakers take in interaction. It is based on an instrumental phonetic analysis of recorded interviews and broadcasting data and a detailed qualitative account of the same data as well as the socio-cultural context in Ireland. The analysis not only considers macro-social categories but also pragmatic norms and situational, more fluid aspects of communication. Contemporary social meanings and associated phonetic realisations are described and explained as the result of diachronic developments. Since the independence of Ireland local pronunciations have been re-evaluated and realisations connected with the former coloniser have fallen out of use even in formal and powerful domains. This investigation thus highlights the importance of diachronic data to understand contemporary sociolinguistic variation.
A modular experimental system for teaching fluid dynamics with Faraday waves
Authors: Pedersen Henrik B , Abildgaard Albert Freud , Søtang Jacobsen Morten , Juul Henrik
Published: August 2023

We describe a modular setup for the observation of Faraday waves on a vibrating bath. The setup will be used as a project exercise on fluid dynamics in a first-year course on experimental physics at Aarhus University as well as for future research on fluids. As a demonstration of the setup, the acceleration threshold for the onset of Faraday waves on a silicone oil bath as a function of the driving frequency is measured and compared to thresholds calculated using different existing models. The possibility to characterize surface waves with the system is demonstrated by recording and analyzing images of Faraday waves, e.g. showing explicitly that the Faraday waves in the present case are subharmonic and establishing the dispersion relation for the waves.
High-efficiency spin and valley filter in a monolayer WSe2 superlattice modulated by an anti-handed off-resonance circularly polarized light
Authors: Guo Y T , Fu X R , Ren B C , Yuan R-Y , Zheng J
Published: August 2023

We have theoretically studied spin and valley transport properties in an optically-controlled electromagnetic superlattice based on monolayer WSe2. Owing to the regulation of the anti-handed off-resonance circularly polarized light, we find that spin- and valley-dependent line-type resonant peaks appear in the transport forbidden region for small incident angles, so that

100
%

high-efficiency spin-valley polarization can be obtained. The result indicates that the high-efficiency spin and valley filter can be more conveniently implemented based on the 2D transition metal dichalcogenides superlattice. In addition, the number of spin- and valley-dependent line-type resonant peaks is tunable using an incident angle, gate voltage and the width of the modulated regions.
Flavor changing neutral current processes and family discrimination in 3-3-1 models
Authors: Oliveira Vinícius , de S Pires C A
Published: August 2023

In 3-3-1 models, anomaly cancellation requires that one of the three families of quarks transforms as triplet by

SU

3

L

, with the other two transforming necessarily as anti-triplet. This is an important feature of the model because, with it, we explain family replication. Thus it is mandatory to discriminate which of the families will transform as triplet by

SU

3

L

because the main consequence of anomaly cancellation in 3-3-1 models is the arising of processes violating flavor at the tree level by means of neutral currents mediated by gauge and scalar fields, and each case leads to different results. In this work, we consider the 3-3-1 model with right-handed neutrinos. Among the spectrum of 3-3-1 particles that contribute to the flavor changing neutral processes, there is a pseudoscalar that may be the lightest of the 3-3-1 particles, and this then should give the main contribution to such processes. We then calculate its contribution to the

K

0

−

K

¯

0

mixing transition and confront it with the current experimental results. We do this for the three cases in which one of the family of quarks transforms as a triplet by

SU

3

L

. According to our findings, each case leads to different constraints on the mass of the pseudoscalar, and the case in which the third family of quarks transforms as triplet seems to be the favoured one. We also obtain the most stringent bounds on the mass of the pseudoscalar of the model.
Nonlinear Hall effect in Rashba systems with hexagonal warping
Authors: Saha Soumadeep , Narayan Awadhesh
Published: August 2023

Rashba spin-orbit coupled systems are an important class of materials noted for diverse fundamental and applied phenomena. Recently, the emergence of non-linear Hall effect under conditions of time-reversal symmetry has been discovered in materials with broken inversion symmetry. In this work, we study the second- and third-order Hall response in Rashba systems with hexagonal warping. Starting with a low-energy model, we obtain the analytic expressions and discover the unique dipole profile in Rashba systems with hexagonal warping. Furthermore, we extend the analysis using a realistic tight-binding model. Next, we predict the existence of a third-order Hall effect in these systems, and calculate the Berry connection polarizability tensor analytically. We also show how the model parameters affect the third-order conductivity. Our predictions can help in the experimental realization of Berry curvature multipole physics in Rashba materials with hexagonal warping, and provide a new platform for engineering the non-linear Hall effects.
Review of material measures for surface topography instrument calibration and performance verification
Authors: Pappas Athanasios , Newton Lewis , Thompson Adam , Leach Richard
Published: August 2023

As the need for the manufacturing of complex surface topographies increases, traceable measurement with known uncertainties can allow a manufacturing process to remain stable. Material measures are the link in the chain that connects the surface topography measurement instrument’s output to the definition of the metre. In this review, the use of material measures is examined for the purposes of instrument calibration and performance verification based on the metrological characteristics framework, as introduced in ISO 25178 part 600. The material measures associated with each metrological characteristic are investigated in terms of fabrication, geometry and functionality. Material measures for metrological characteristics are discussed in a sequential approach, focusing on material measures that have been developed for specific measurement technologies and optical surface topography measurement instruments. There remains a gap in the metrological characteristic framework for the characteristic, topography fidelity, and the review highlights current methods using reference metrology and alternative approaches using virtual instruments to quantify the effects of topography fidelity. The influence of primary instruments is also reviewed in the context of uncertainty propagation. In the conclusion, the current challenges are identified with regards to the scarcity of available material measures in the lower nanometre range, and the limitations in terms of cost, complexity, manufacturing time and industrial applicability.
Domain adaptive networks with limited data for rotating machinery fault diagnosis: a case of study of gears
Authors: Li Xueyi , Yu Tianyu , He Qiushi , Li Daiyou , Xie Zhijie , Kong Xiangwei
Published: August 2023

Rotating machinery is one of the most common components in the industry. Therefore, timely and accurate fault diagnosis of rotating machinery is essential for the regular operation of equipment. At present, some achievements have been made in rotating machinery fault diagnosis based on a large number of marked fault data. However, most of the machines are in a normal state in actuality. Especially, the machines run under different loads, so it is costly to collect a large number of labeled fault data under different load distributions. To solve rotating machinery fault diagnosis in different load conditions with limited samples, a domain adaptive group convolutional neural network is proposed. Firstly, the least squares generative adversarial networks were used to expand the limited target sample data. By changing the objective function, the two defects of the low quality of the vibration signal generated by the traditional generative adversarial networks and the unstable training process are optimized. Secondly, the raw vibration signals in the source domain are pre-trained by the group convolutional neural network, and the group training network effectively reduces network parameters. Finally, the source domain signals and target domain signals were trained in domain adversarial networks to diagnose different distributed data in target domains. The proposed method is validated by collecting the raw vibration signals of gears under different loads and different health states, and the effectiveness of the proposed method is proved. Experimental validation shows that the method proposed in this paper achieves an average accuracy improvement of more than 12% compared to other existing methods.
A method for compensation of permanent magnetic field perturbation (PMFP) testing signal based on lift-off measurement
Authors: Hu Yu , Wang Shenghan , Duan Zhaoqi , Gao Yiming
Published: August 2023

This paper proposes a novel composite measurement method for defect detection, which integrates PMFP (permanent magnetic field perturbation) testing and lift-off measurement. The PMFP method is used to detect defects, while the permanent magnet is utilized to construct a magnetic bridge for lift-off measurement. In PMFP testing, the variation of lift-off can significantly affect the signal. To mitigate this effect, the proposed method compensates for the defect signal using the measured lift-off information, which effectively reduces the impact of lift-off variation during the testing. Therefore, this paper constructs a magnetic dipole model based on the PMFP method and analyzes the numerical relationship between the defect signal and lift-off. Based on this, a composite lift-off measurement method for PMFP with a signal compensation function is proposed. This multifunctional sensing method has a compact structure, which significantly reduces the impact of lift-off on the defect signal. The experimental results demonstrate that the confidence level can reach 93% after compensating for the amplitude of the defect signal. The proposed method exhibits excellent performance in practical applications.
Additive manufacturing materials for structural optimisation and cooling enhancement of superconducting motors in cryo-electric aircraft
Authors: Lumsden Grant , Ludbrook Bart , Rogers Rehn Nic , Solis Fernandez Fernando , Davies Mike , Chamritski Vadim , Signamneni Sarat , Badcock Rod
Published: August 2023

Superconducting electric motors offer the potential for low weight and high power in applications such as electric aircraft and high speed marine transport. Combined with renewably-sourced cryogenic fuels and advanced fuel cells they offer a path to zero-carbon mass transport. The proposed architectures of these extreme machines, operating at temperatures around 20 K–50 K and employing very high alternating magnetic fields, require materials for the stator that are not electrically conducting and at the same time have good cryogenic structural performance. Additively manufactured (AM) materials can play a key role in these designs, and a collaboration between the Robinson Research Institute and Auckland University of Technology is studying the performance of a range of composite polymers in superconducting machine applications. There are significant challenges to be met, including understanding the effect of the build process on material properties at low temperatures, and also the effect of formulation changes on thermal properties. AM metals can be employed in the rotor components, where the magnetic field fluctuations are very small for our synchronous designs. In this usage case, we can achieve dramatic reductions in the weight of the rotor assembly by minimising the number of joints and facilitating the design of multi-functional components in our helium cooled, vacuum cryostat architecture. Novel design solutions have been developed for several key components in our prototype machines and these are discussed, along with cryogenic testing results for selected AM polymers and composites.
Strong-field vacuum polarisation with high energy lasers
Authors: Macleod A J , Edwards J P , Heinzl T , King B , Bulanov S V
Published: August 2023

When photons propagate in vacuum they may fluctuate into matter pairs thus allowing the vacuum to be polarised. Thislineareffect leads to charge screening and renormalisation. When exposed to an intense background field anonlineareffect can arise when the vacuum is polarised by higher powers of the background. This nonlinearity breaks the superposition principle of classical electrodynamics, allowing for light-by-light scattering of probe and background photons mediated through virtual pairs dressed by the background. Vacuum polarisation is astrong-fieldeffect when all orders of interaction between the virtual pair and the background must be taken into account. In this investigation we show that multiple scattering processes of this type may be observed by utilising high-energy laser pulses with long pulse duration, such as are available at facilities like ELI Beamlines. In combination with appropriate sources of high-energy probe photons, multiple probe-background light-by-light scattering allows for testing the genuine nonlinear regime of strong-field quantum electrodynamics. This provides access to the uncharted non-perturbative regime beyond the weak-field limit.
Manipulation of phonon states in ion traps by shortcuts to adiabaticity
Authors: Yang Xueying , Xie Yi , Zhang Jie , Zhang Manchao , Wu Chunwang , Wu Wei , Chen Ting , Chen Ping-Xing
Published: August 2023

Shortcuts to adiabaticity (STA) provides the possibility of high accuracy manipulation of phonon states in ion traps. We propose a scheme realized experimentally for manipulating phonon states using STA and confirmed its effectiveness through generating Fock states. Our results show that the duration of the STA manipulation of phonon states is 16 times faster than that of the adiabatic evolution, and the non-resonant excitation can be suppressed by laser bias frequency, which are confirmed by experimental results. Moreover, we also carried out an experimental research on the robustness of STA, showing good robustness respect to the pulse shape deformation, bias noises and stochastic noise. This might lead to a useful step toward realizing fast and noise-resistant quantum manipulation within current experimental capacity.
Structural and topological phase transitions in Se doping-controlled intrinsic magnetic topological material FeBi2Te4
Authors: Guo Wen-Ti , Huang Zhigao , Zhang Jian-Min
Published: August 2023

Defects profoundly affect the magnetic, electronic structure and topological behaviour of intrinsic magnetic topological insulators. Here, we investigate the magnetic, structural stability and topological properties of different Te atomic sites in the intrinsic magnetic topological insulator FeBi2Te4 with Se substitution of the FM-z magnetic order. When Se replaces the outermost site of the septuple layer (the Te atomic layer connected by van der Waals bonds), the Se–Bi bond length formed with its nearest neighbour Bi is drastically shortened and the lattice constant and volume contract accordingly. We speculate that this defect-induced chemical bond enhancement is related to the strong electronegativity of Se over Te. In contrast, the system has lower formation energy, a more stable structure, and enhanced magnetic moment when Se replaces the Te atomic layer inside the septuple layer. Also, we reveal a variety of topological phase transitions due to substitution defects. FeBi2Te4 is considered to belong to the

z

2

×

z

4

topological classification of higher-order topological insulators with z
4 = 2. The system after Se substitution can be transformed into Weyl semimetals, strong 3D topological insulators, and unknown topological materials without symmetry-base indicators, respectively.
Study of single electron capture in O6+ + He collisions
Authors: Meng T , Ma M X , Tu B , Ma P , Zhang Y W , Liu L , Xiao J , Yao K , Zou Y , Wu Y , Wang J G , Wei B
Published: August 2023

Research on electron capture (EC) process are undoubtedly helpful for maturing theoretical models on ion-induced collision especially for low-energy region. In this work, a two-active-electron semiclassical asymptotic-state close-coupling method was used to calculate the total and l-solved state-selective single EC cross sections of O6+ + He collisions in the energy range of 0.3–100 keV u−1, accompanied with experimental measurements in the energy range of 2.63–37.5 keV u−1 with an uncertainty of 11% in good agreement. Above 4.5 keV u−1, the state-selective cross section of n = 5 was reported experimentally for the first time. Calculations with multiple theoretical methods were gathered and compared with present calculations. The importance of two-active-electrons correlation and large basis sets in theoretical calculations was found, and discrepancies between previous theoretical and experimental results can be explained by the present results.
Numerical study of MoSe2-based dual-heterojunction with In2Te3 BSF layer toward high-efficiency photovoltaics
Authors: Sultana Basra , Islam A T M Saiful , Haque Md. Dulal , Kuddus Abdul , Ali Md. Hasan , Rahman Md. Ferdous
Published: August 2023

In this study, molybdenum diselenide (MoSe2)-based dual-heterojunction with Indium Telluride (In2Te3) as an absorber and a back surface field (BSF) layers with Al/ITO/CdS/MoSe2/In2Te3/Ni heterostructure has been studied by SCAPS-1D simulator. To explore the potentiality of layered materials in photovoltaic devices, a detailed investigation has been executed on the CdS window, MoSe2 absorber, and In2Te3 BSF layers at varied layer thicknesses, carrier concentrations, interface and defect densities, resistances, and operating temperatures. The photoconversion efficiency (PCE) of 24.78% with short circuit current J
sc of 30.55 mA cm−2, open circuit voltage V
oc of 0.95 V, and fill factor FF of 85.5% were obtained in the reference cell (without the In2Te3 BSF layer), while a notably improved PCE of 29.94% (5.16% higher) with J
sc of 31.06 mA cm−2, V
oc of 1.10 V, and FF of 87.28% was achieved by inserting the In2Te3 BSF layer. With a favorable band alignment and almost similar chemical and physical properties as transitional metal dichalcogenides (TMDCs) materials, the proposed dual heterostructure with CdS, MoSe2, and In2Te3 exhibits huge potential as a photoactive material and paves a pathway for the fabrication of uniquely layered material-based thin, flexible high-efficiency solar cells.
Microwave assisted switching in two-phase nanowires
Authors: Thanos Christos , Panagiotopoulos Ioannis
Published: August 2023

Micromagnetic simulations are used to study the resonances and the microwave assisted magnetic switching (MAS) in two-phase Co/CoPt nanowires. This is chosen as an interesting model system in which the processes of nucleation, interfacial domain wall pinning, and propagation are well distinguished and can all come into play. The coupling strength is varied to cover both smooth (strong coupling) and stepped (weak coupling) hysteresis curves. At intermediate coupling strengths interfacial resonances play an important role in MAS and enable to find optimal conditions combining both low MAS frequencies and dc applied fields. There is always a tradeoff between using low fields and achieving short reversal time.
Monotonic and cyclic axial compressive responses of concrete specimens externally confined with different types of FRP composites: experimental and analytical investigations
Authors: Rodsin Kittipoom , Hussain Qudeer , Parichatprecha Rattapoohm
Published: August 2023

The main objective of this study was to investigate the monotonic and cyclic axial stress versus strain response of the concrete confined with different types of fiber reinforced polymer (FRP) composites such as cotton fiber rope reinforced polymer (CFRRP), glass fiber reinforced polymer (GFRP) composites and carbon fiber reinforced polymer (CFRP) composites. Another objective was to investigate the applicability of existing ultimate strength models to predict the ultimate strength of concrete confined with CFRRP, GFRP and CFRP composites. For this, a total number of 28 concrete cylinders were cast, strengthened and tested under pure axial compression. The concrete cylinders were strengthened with two and four layers of FRPs. The experimental results indicate that all kinds of FRPs are very useful to alter the ultimate strength and strain of the confined concrete. The highest increase in ultimate strength was recorded for CFRP composite confined specimens and the highest increase in ultimate strain was observed for CFRRP composite confined specimens. Further, both ultimate strength and ultimate strains are found higher in the case of cyclic loads compared with the monotonic load. In general, the stress versus strain curves of cotton fiber rope and glass FRPs are found trilinear. Whereas, stress versus strain curves of CFRP confined specimens are observed to be bilinear. Existing ultimate strength models developed for CFRRP and CFRP composites are found well accurate to predict the ultimate strengths of CFRRP and CFRP confined concrete specimens tested in this study.
Inference and physics applications of the logistic-exponential parameters using adaptive progressively hybrid censoring
Authors: Nassar Mazen , Alotaibi Refah , Elshahhat Ahmed
Published: August 2023

To save test time and costs and to improve the efficiency of the experiments, an adaptive Type-II progressively hybrid censored technique has been developed. Besides two standard methods of parameter inference, namely, likelihood and product of spacing approaches, the Bayesian method is further used in this study to explore the issue of estimating model parameters, reliability, and hazard rate functions of the logistic-exponential distribution via the adaptive Type-II progressively hybrid censored mechanism. The relevant approximate confidence intervals for unknown parameters of life are also acquired using the normal approximations of the frequentist estimators. Under the squared error loss function, Bayesian estimators are obtained using independent gamma priors. Because of the complicated form of the posterior distributions, the Bayes estimators and associated credible intervals cannot be computed analytically, but they can be examined by employing Monte Carlo Markov Chain methodologies. The actual performance of the offered estimation procedures is examined using Monte Carlo simulations. Four optimality criteria are also utilized to select the optimum censoring scheme. Two physical applications are considered to show the operability and applicability of the various methods. The numerical findings show that our proposed methodologies perform well and demonstrate that the offered estimates are satisfactory in practice.
Image encryption algorithm based on ElGamal cryptography and selective random diffusion
Authors: Guo Liming , He Jianqing , Ye Guodong
Published: August 2023

Some current image encryption schemes are independent of the plaintext, leading to a vulnerability to the chosen-plaintext attack under symmetric structure. To address this issue, an asymmetric image encryption algorithm with plaintext correlation is suggested, after analyzing various image encryption schemes using chaotic systems. First, a three-dimensional New Logistic-Sine Map (NewLSM) is designed by coupling Logistic map and Sine map, considering them as seed maps. Analyses prove that the NewLSM has a wider continuous chaotic interval and more complex chaotic behavior than seed maps. Secondly, to enhance the keystream associated with plaintext, a new key acquisition model is constructed, i.e., NewMKG, by combining the hash function SHA-3 with the public key ElGamal cryptography. Then, employing the NewLSM and the NewMKG, a new image encryption algorithm with asymmetric structure is presented using classical framework of confusion-diffusion. In particular, a new diffusion method is proposed after confusion, namely, selective random diffusion (NewSRD). Moreover, experiments and analyses indicate that a good performance can be reached for the proposed algorithm. For example, the value of information entropy for the obtained cipher image is close to eight.
Mechanical and metallurgical characterization of B4C and SiC reinforced stir casted AA6061 hybrid MMC
Authors: Balasubramani Veerappan , Pandiarajan R , Stalin Balasubramanian , Kavimani Vijayananth
Published: August 2023

The present work was the novel investigation of mechanical and metallurgical characteristics of stir casted AA6061 based metal matrix composites (MMC) and hybrid MMCs. The reinforcements utilized in the investigation were silicon carbide and boron carbide. The thirteen stir casted MMC and hybrid MMC samples were tested for ultimate tensile strength, microhardness, fractography and wear performance. The stir casting process had enhanced the reinforcement distribution within the aluminium matrix. The enhancement in ultimate tensile strength was observed due to the addition of reinforcements in increasing weight percentages with the hybrid MMC exhibiting peak ultimate strength which was a 32.17% improvement against the non-reinforced AA6061 alloy. The formation of reinforcement particulates had enhanced microhardness of the specimens with the peak microhardness observed for boron carbide reinforced MMC exhibiting microhardness 25.41% higher than the base alloy. The hybrid MMC exhibited ductile fracture with highest elongation corresponding to the highest ultimate tensile strength. The wear performance analysis revealed reduced wear rates for the particulate reinforced specimen with highest weight percentage of reinforcements.
Time-domain supersymmetry for massless scalar and electromagnetic fields in anisotropic cosmologies
Authors: Asenjo Felipe A , Hojman Sergio A
Published: August 2023

It is shown that any cosmological anisotropic model produces supersymmetric theories for both massless scalar and electromagnetic (abelian) fields. This supersymmetric theory is the time-domain analogue of a supersymmetric quantum mechanics algebra theory. In this case, the variations of the anisotropic scale factors of the Universe are responsible for triggering the supersymmetry. For scalar fields, the superpartner fields evolve in two different cosmological scenarios (Universes). On the other hand, for propagating electromagnetic fields, supersymmetry is manifested through its polarization degrees of freedom in one Universe. In this case, polarization degrees of freedom of electromagnetic waves, which are orthogonal to its propagation direction, become superpartners from each other. This behavior can be measured, for example, through the rotation of the plane of polarization of cosmological light.
Relativistic matter bispectrum of cosmic structures on the light cone
Authors: Montandon Thomas , Adamek Julian , Hahn Oliver , Noreña Jorge , Rampf Cornelius , Stahl Clément , van Tent Bartjan
Published: August 2023

Upcoming surveys of cosmic structures will probe scales close to the cosmological horizon, which opens up new opportunities for testing the cosmological concordance model to high accuracy. In particular, constraints on the squeezed bispectrum could rule out the single-field hypothesis during inflation. However, the squeezed bispectrum is also sensitive to dynamical effects of general relativity as well as interactions of matter with residual radiation from the early Universe. In this paper, we present a relativistic simulation pipeline that includes these relativistic effects consistently. We produce light cones and calculate the observed number counts of cold dark matter for five redshift bins betweenz= 0.55-2.25. We compare the relativistic results against reference Newtonian simulations by means of angular power- and bispectra. We find that the dynamical relativistic effects scale roughly inversely proportional to the multipole in the angular power spectrum, with a maximum amplitude of 10% forℓ≲ 5. By using a smoothing method applied to the binned bispectrum we detect the Newtonian bispectrum with very high significance. The purely relativistic part of the matter bispectrum, obtained by subtracting the Newtonian bispectrum from the relativistic one, is detected with a significance of ∼ 3σ, mostly limited by cosmic variance. We find that the pure dynamical relativistic effects accounts for up to 3% and 10% of the total amplitude, respectively in the squeezed and equilateral limits. Our relativistic pipeline for modelling ultra-large scales yields gauge-independent results as we compute observables consistently on the past light cone, while the Newtonian treatment employs approximations that leave some residual gauge dependence. A gauge-invariant approach is required in order to meet the expected level of precision of forthcoming probes of cosmic structures on ultra-large scales.
The AIMS Site Survey
Authors: Bao Xing-Ming , Wang Jian , Jing Shuai , Deng Yuan-Yong , Wang Dong-Guang
Published: August 2023

This paper reports site survey results for the Infrared System for the Accurate Measurement of Solar Magnetic Field, especially in Saishiteng Mountain, Qinghai, China. Since 2017, we have installed a weather station, spectrometers for precipitable water vapor, and Solar Differential Image Motion Monitor, and have carried out observations on weather elements, precipitable water vapor, and daytime seeing conditions for more than one year in almost all candidates. At Mt. Saishiteng, the median value of daytime precipitable water vapor is 5.25 mm and its median value in winter season is 2.1 mm. The median value of the Fried parameter of daytime seeing observation at Saishiteng Mountain is 3.42 cm. Its solar direct radiation data show that solar average observable time is 446 minutes per day and premium time is 401 minutes per day in 2019 August.
Three novel methods for determining motor threshold with transcranial magnetic stimulation outperform conventional procedures
Authors: Wang Boshuo , Peterchev Angel V , Goetz Stefan M
Published: August 2023

Objective. Thresholding of neural responses is central to many applications of transcranial magnetic stimulation (TMS), but the stochastic aspect of neuronal activity and motor evoked potentials (MEPs) challenges thresholding techniques. We analyzed existing methods for obtaining TMS motor threshold and their variations, introduced new methods from other fields, and compared their accuracy and speed. Approach. In addition to existing relative-frequency methods, such as the five-out-of-ten method, we examined adaptive methods based on a probabilistic motor threshold model using maximum-likelihood (ML) or maximum a-posteriori (MAP) estimation. To improve the performance of these adaptive estimation methods, we explored variations in the estimation procedure and inclusion of population-level prior information. We adapted a Bayesian estimation method which iteratively incorporated information of the TMS responses into the probability density function. A family of non-parametric stochastic root-finding methods with different convergence criteria and stepping rules were explored as well. The performance of the thresholding methods was evaluated with an independent stochastic MEP model. Main Results. The conventional relative-frequency methods required a large number of stimuli, were inherently biased on the population level, and had wide error distributions for individual subjects. The parametric estimation methods obtained the thresholds much faster and their accuracy depended on the estimation method, with performance significantly improved when population-level prior information was included. Stochastic root-finding methods were comparable to adaptive estimation methods but were much simpler to implement and did not rely on a potentially inaccurate underlying estimation model. Significance. Two-parameter MAP estimation, Bayesian estimation, and stochastic root-finding methods have better error convergence compared to conventional single-parameter ML estimation, and all these methods require significantly fewer TMS pulses for accurate estimation than conventional relative-frequency methods. Stochastic root-finding appears particularly attractive due to the low computational requirements, simplicity of the algorithmic implementation, and independence from potential model flaws in the parametric estimators.
Spontaneous formation of a transport barrier in helium plasma in a tokamak with circular configuration
Authors: Macha P. , Adamek J. , Seidl J. , Stockel J. , Svoboda V. , Van Oost G. , Lobko L. , Krbec J.
Published: August 2023

We report on the first experimental observation of a spontaneously formed transport barrier in the tokamak with a circular configuration in helium plasmas. There was no external polarization of the plasma by electric field or other technique to form the barrier as it is typically used in tokamaks with circular plasma. In general, the transport barriers play an important role in plasma confinement especially in tokamaks with divertor configuration. In our experiments, we clearly observe distinct characteristics of a transport barrier, including a steep gradient of the electron temperature and an enhanced radial electric field along with the change in the plasma potential, floating potential, and electron temperature fluctuation. The electron temperature and the plasma potential are obtained by a combination of the ball-pen and Langmuir probe measurements with high temporal resolution on a shot-to-shot basis. This first experimental observation of the spontaneously formed transport barrier might bring new possibilities to obtain a fusion-relevant study of the edge plasma parameters and transport in helium plasmas even on small tokamaks.
Gaussian process-based quasi-coherent noise suppression in magnetic confinement devices with superconductors
Authors: Kim Jaewook , Kim Jayhyun , Ghim Y.-c. , Jang Juhyeok
Published: August 2023

Gaussian process (GP)-based technique suppressing quasi-coherent noises, i.e. structured noises, is developed which is more effective than conventional denoising techniques such as using frequency-domain filters. Superconducting devices like KSTAR, EAST, JT-60SA and ITER require separate sets of normal conducting magnetic coils inside the tokamak vacuum vessels to achieve a prompt control of fusion-grade plasmas in response to various fast and abrupt plasma activities such as vertical displacement events. Hence, these in-vessel control coils are typically operated with high-frequency switching power supplies which generate quasi-coherent noises. Semi-conductor based bolometers in KSTAR, for instance, are vulnerable to the quasi-coherent noise that makes a tomographic reconstruction for the 2D poloidal radiation map with the noise-contaminated signals flawed. By modeling the quasi-coherent properties of the noise as multivariate Gaussian distribution and generating the kernel function for the GP solely based on the measurements, the proposed method is able to suppress the noise whose performance is superior to the conventional filtering schemes. The method not only suggests an estimate of the denoised signal but also informs the consistent (with the measurements) uncertainty of the estimate at a level smaller than the standard deviation of the quasi-coherent noise. Performance of the method is confirmed with synthetic data containing the quasi-coherent noises, and it is applied to the measured data obtained by the KSTAR bolometers.
Microstructure and Properties of U75V 60 kg/m Heavy Rail at Different Cooling Rates of Heat Treatment
Authors: Kang Hao , Feng Gangzhen , Liu Ning
Published: August 2023

Considering the U75V 60 kg/m heavy rail as the research object, compressed air was selected as the cooling medium, and the temperature fields of the rail surface before and after heat treatment were recorded by using a thermal imager. Pearlite in the hardened layer was examined for its morphology by using a scanning electron microscope, and Rockwell hardness was tested. Important basic data for the formulation and optimization of the heat treatment process of the U75V 60 kg/m heavy rail is determined by analyzing the correlation between the cooling rates of the rail head surface, the microstructure, and the properties of the hardened layer.