bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature dependence mechanism of high-temperature oxidation of transition metal silicide MoSi2
Authors: Huang Yang , Zhang Yuhang , Wu Yusong , Yang Zhikang , Wang Na , Fu Tairan
Published: May 2024

Transition metal silicides represented by MoSi2 have excellent oxidation resistance and are widely used as high-temperature anti-oxidation coatings in hot end components of power equipment. However, the mechanism of temperature-dependent growth of MoSi2 oxidation products has not been revealed. Therefore, this study investigated the formation characteristics of oxide film and silicide-poor compound on MoSi2 at temperatures of 1000 °C–1550 °C through high-temperature oxidation experiments, combined with microscopic Raman spectroscopy, scanning electron microscope, and x-ray diffraction (XRD) characterizations. The result showed that MoSi2 underwent high-temperature selective oxidation reactions at 1000 °C–1200 °C, forming MoO2 and SiO2 oxide film on the substrate. As the oxidation temperature increased to 1550 °C, after 100 h of oxidation, along with the disappearance of MoO2 and the phase transformation of SiO2, a continuous Mo5Si3 layer with a thickness of approximately 47 μm was formed at the SiO2–MoSi2 interface. Thermodynamics and kinetic calculations further revealed the mechanism of temperature-dependent growth of oxidation products (MoO2 and Mo5Si3) during high-temperature oxidation process of MoSi2. As the temperature increased, the diffusion flux ratio of O and Si decreased, leading to a decrease in oxygen concentration at the interface and promoting the growth of the Mo5Si3 layer. Its thickness is an important indicator for evaluating the oxidation resistance of MoSi2 coatings during service. This study provides experimental and mechanistic insights into the temperature-dependent growth behavior of Mo5Si3 during the high-temperature oxidation of MoSi2 coating, and provides guidance for predicting the service life and improving the oxidation resistance of silicide coatings.
Signature of excitonic insulators in phosphorene nanoribbons
Authors: Felipe Pereira de Oliveira Andre , Luisa da Rosa Andréia , Cavalheiro Dias Alexandre
Published: May 2024

Phosphorene is a recently developed two-dimensional (2D) material that has attracted tremendous attention because of its unique anisotropic optical properties and quasi-one-dimensional (1D) excitons. We use first-principles calculations combined with the maximally localized Wannier function tight binding Hamiltonian and Bethe–Salpeter equation (BSE) formalism to investigate quasiparticle effects of 2D and quasi-1D blue and black phosphorene nanoribbons. Our electronic structure calculations shows that both blue and black monolayered phases are semiconductors. On the other hand black phosphorene zigzag nanoribbons are metallic. Similar behavior is found for very thin blue phosphorene zig-zag and armchair nanoribbon. As a general behavior, the exciton binding energy decreases as the ribbon width increases, which highlights the importance of quantum confinement effects. The solution of the BSE shows that the blue phosphorene monolayer has an exciton binding energy four times higher than that of the black phosphorene counterpart. Furthermore, both monolayers show a different linear optical response with respect to light polarization, as black phosphorene is highly anisotropic. We find a similar, but less pronounced, optical anisotropy for blue phosphorene monolayer, caused exclusively by the quasi-particle effects. Finally, we show that some of the investigated nanoribbons show a spin-triplet excitonic insulator behavior, thus revealing exciting features of these nanoribbons and therefore provides important advances in the understanding of quasi-one dimensional phosphorus-based materials.
Real time conditioning monitoring of MOSFET using artificial neural network regression
Authors: Choudhary Khilawan , Babu Raja , Christie Latha , Mahto Manpuran
Published: May 2024

The metal–oxide–semiconductor field-effect transistor (MOSFET) is a critical semiconductor device widely used in electrical and electronic systems. The performance of systems depends on the component’s reliability. More than 30% of failures of electronic and electrical systems are due to MOSFET failure. Industries are paying more apprehension towards the improvement of MOSFET reliability. Temperature stress is one of the key parameters to examine the reliability performance of semiconductor devices and to predict the lifetime of the components. This article provides a quick analysis of the MOSFET degradation models. The primary failure precursor metric that reflects the level of degradation is the MOSFET on-resistance R
DS(on). In this paper, a linear, non-linear, and artificial neural network (ANN) deterioration model of MOSFETs is presented with the experimental data. The coefficient of determination (R-square), and root mean square error (RMSE) are used to compare the real data. Finally, it is demonstrated that the proposed model works well with experimental data. More than 500 data were trained for the proposed model. It can therefore predict the real-time conditioning monitoring of MOSFETs to increase the reliability of electrical systems.
The vertical accuracy improvement method considering gravitational anomaly for SINS/GNSS
Authors: Qin Fang-Jun , Qian Lei-Yuan , Li Kai-Long , Zhu Tian-Gao
Published: May 2024

Vertical information (vertical velocity and altitude) is important in three-dimensional navigation. In order to improve the vertical accuracy of strapdown inertial navigation system/global navigation satellite system integrated navigation (SINS/GNSS) while reducing costs, firstly, the propagation laws of vertical error sources in two types of SINS/GNSS (vertical velocity set to 0 and not set to 0) are systematically analyzed. Furthermore, a vertical accuracy improvement method considering the gravitational anomaly is proposed. In this method, the gravitational anomaly is considered as one of the vertical error sources. Then, the processing method of error sources in integrated navigation is referenced, and two processing modes of gravitational anomaly are designed. The first method is to represent the gravitational anomaly as one of the system states of SINS/GNSS. The number of dimensions for the system is expanded from 15 to 16. The corresponding mathematical model is derived to ‘absorb’ the vertical errors caused by the gravitational anomaly. The second is to represent the gravitational anomaly as one of the vertical system noises. Thereby, the Kalman filter is adjusted in real time using the above adaptive method to improve the accuracy of the estimated state. The corresponding errors are then suppressed. Field experiments show that both modes of the proposed method can effectively improve the vertical accuracy.
Introduction and application of a new approach for model-based optical bidirectional measurements
Authors: Krüger Jan , Manley Phillip , Bergmann Detlef , Köning Rainer , Bodermann Bernd , Eder Christian , Heinrich Andreas , Schneider Philipp-Immanuel , Hammerschmidt Martin , Zschiedrich Lin , Manske Eberhard
Published: May 2024

Accurate measurements of micro- and nanoscale features in optical microscopy demand comprehensive modelling approaches. In this study, we introduce an enhanced evaluation method, utilizing rigorous simulations based on a finite element method algorithm within an advanced Bayesian optimization framework. We provide an in-depth explanation of the measurement process, including the dimension reduction techniques applied to the acquired measurement data. Additionally, we employ Hopkins’ approximation or also referred to as local Hopkins’ methods for an efficient microscopic image simulation, resulting in a significant reduction of the computing time. We applied this method to measure the linewidths of six different chrome lines, nominally 300 nm–1000 nm wide, on a glass substrate. Our results show an excellent agreement with previous investigations conducted using various measurement systems, including atomic force microscopy, scanning electron microscopy, and optical microscopy in combination with different measurement evaluation techniques.
Ultra-long-term spatiotemporal feature fusion network for bearing remaining life prediction under strong interference
Authors: Yin Zhongxi , Tan Jinbiao , Wan Jiafu
Published: May 2024

Under high noise conditions and random impacts, which constitute strong interference, models often exhibit limited capability in capturing long-term dependencies, leading to lower accuracy in predicting the remaining useful life (RUL) of bearings. To address this issue, a spatiotemporal fusion network capable of ultra-long-term feature analysis is proposed to enhance the accuracy of bearing RUL prediction under substantial interference. This network utilizes a dilated convolution-based lightweight vision transformer encoder to extract spatial features reflecting the short-term degradation state of the bearing. Then, these features are sequentially fed into an adaptive tiered memory unit, based on the multiple attention mechanism and the neuron layering mechanism, to analyze temporal features indicative of long-term degradation. Subsequently, short-term spatial and long-term temporal features are fused for RUL prediction. To validate the robustness and predictive accuracy of the proposed approach under strong interference, a gearbox-rolling bearing accelerated platform is constructed, simulating high noise and random impact conditions. Experiments confirm the high robustness and predictive accuracy of the proposed method under strong interference conditions.
Crystal plasticity based constitutive model for deformation in metastable β titanium alloys
Authors: Christie P , Siddiq M A , Asim U B , McMeeking R M , Kartal M E
Published: May 2024

Due to attractive mechanical properties, metastable β titanium alloys have become very popular in many industries including aerospace, marine, biomedical, and many more. It is often the complex interplay among the different deformation mechanisms that produces many of the sought-after properties, such as enhanced ductility, super-elasticity, and shape memory effects. Stress induced martensitic transformation is an important deformation mechanism for these alloys. Understanding of it and the influence it has on the microstructural evolution of materials is of great importance. To this end we have developed a crystal plasticity based constitutive model which accounts for both martensitic phase transformation and slip based plasticity simultaneously in metastable

β

titanium alloys. We present a new formulation for the evolution of martensite transformation, based on physical principles and crystal plasticity theory. To understand and demonstrate this feature of the model, a parametric assessment of the newly developed constitutive model is conducted. This is followed by first of its kind analyses of stress induced martensitic transformation in metastable

β

titanium alloys. We firstly present validations against uniaxial loading experiments for different metastable

β

titanium alloys exhibiting stress induced martensite transformation. As part of this, single crystal simulations in metastable

β

titanium alloys are used for the first time to investigate the interaction of individual transformation systems during unconstrained transformation. This study shows good agreement between the experimental and simulated responses during all stages of deformation in which elastic, transformation and finally the slip stage are exhibited. Relatively ‘strong’ and ‘weak’ orientations for transformation are observed, consistent with experimental studies. The work done here demonstrates the ability of this crystal plasticity finite element method to capture physical mechanisms while bringing new insight about the interaction of different deformation mechanisms in metastable

β

titanium alloys.
A parylene/graphene UV photodetector with ultrahigh responsivity and long term stability
Authors: Huang Liting , Zhu Zhaowei , Cheng Chuantong , Gao Y
Published: May 2024

Long term stability, high responsivity, and fast response speed are essential for the commercialization of graphene photodetectors (GPDs). In this work, a parylene/graphene UV photodetector with long term stability, ultrahigh responsivity and fast response speed, is demonstrated. Parylene as a stable physical and chemical insulating layer reduces the environmental sensitivity of graphene, and enhances the performances of GPDs. In addition, utilizing bilayer electrodes reduces the buckling and damage of graphene after transferring. The parylene/graphene UV photodetector exhibits an ultrahigh responsivity of 5.82 × 105 AW−1 under 325 nm light irradiation at 1 V bias. Additionally, it shows a fast response speed with a rise time of 80 μs and a fall time of 17 μs, and a long term stability at 405 nm wavelength which is absent in the device without parylene. The parylene/graphene UV photodetector possesses superior performances. This paves the way for the commercial application of the high-performance graphene hybrid photodetectors, and provides a practical method for maintaining the long term stability of two dimensional (2D) materials.
Remarks on the smoothness of the

C

1
,
α

asymptotically self-similar singularity in the 3D Euler and 2D Boussinesq equations
Authors: Chen Jiajie
Published: May 2024

We show that the constructions of

C

1
,
α

asymptotically self-similar singularities for the three-dimensional (3D) Euler equations by Elgindi, and for the 3D Euler equations with large swirl and 2D Boussinesq equations with boundary by Chen-Hou can be extended to construct singularity with velocity

u

∈

C

1
,
α

that is not smooth at only one point. The proof is based on a carefully designed small initial perturbation to the blowup profile, and a BKM-type continuation criterion for the one-point nonsmoothness. We establish the criterion using weighted Hölder estimates with weights vanishing near the singular point. Our results are inspired by the recent work of Cordoba, Martinez-Zoroa and Zheng that it is possible to construct a

C

1
,
α

singularity for the 3D axisymmetric Euler equations without swirl and with velocity

u

∈

C

∞

(

R

3

∖
{
0
}
)

.
Human-like intelligent automatic treatment planning of head and neck cancer radiation therapy
Authors: Gao Yin , Kyun Park Yang , Jia Xun
Published: May 2024

Objective. Automatic treatment planning of radiation therapy (RT) is desired to ensure plan quality, improve planning efficiency, and reduce human errors. We have proposed an Intelligent Automatic Treatment Planning framework with a virtual treatment planner (VTP), an artificial intelligence robot built using deep reinforcement learning, autonomously operating a treatment planning system (TPS). This study extends our previous successes in relatively simple prostate cancer RT planning to head-and-neck (H&N) cancer, a more challenging context even for human planners due to multiple prescription levels, proximity of targets to critical organs, and tight dosimetric constraints. Approach. We integrated VTP with a real clinical TPS to establish a fully automated planning workflow guided by VTP. This integration allowed direct model training and evaluation using the clinical TPS. We designed the VTP network structure to approach the decision-making process in RT planning in a hierarchical manner that mirrors human planners. The VTP network was trained via the Q-learning framework. To assess the effectiveness of VTP, we conducted a prospective evaluation in the 2023 Planning Challenge organized by the American Association of Medical Dosimetrists (AAMD). We extended our evaluation to include 20 clinical H&N cancer patients, comparing the plans generated by VTP against their clinical plans. Main results. In the prospective evaluation for the AAMD Planning Challenge, VTP achieved a plan score of 139.08 in the initial phase evaluating plan quality, and 15 min of planning time with the first place ranking in the adaptive phase competing for planning efficiency while meeting all plan quality requirements. For clinical cases, VTP-generated plans achieved an average VTP score of

125.33
±
11.12

, which outperformed the corresponding clinical plans with an average score of

117.76
±
13.56

. Significance. We successfully integrated VTP with the clinical TPS to achieve a fully automated treatment planning workflow. The compelling performance of VTP demonstrated its potential in automating H&N cancer RT planning.
Innovations in dedicated PET instrumentation: from the operating room to specimen imaging
Authors: Arabi Hossein , Manesh Abdollah Saberi , Zaidi Habib
Published: May 2024

This review casts a spotlight on intraoperative positron emission tomography (PET) scanners and the distinctive challenges they confront. Specifically, these systems contend with the necessity of partial coverage geometry, essential for ensuring adequate access to the patient. This inherently leans them towards limited-angle PET imaging, bringing along its array of reconstruction and geometrical sensitivity challenges. Compounding this, the need for real-time imaging in navigation systems mandates rapid acquisition and reconstruction times. For these systems, the emphasis is on dependable PET image reconstruction (without significant artefacts) while rapid processing takes precedence over the spatial resolution of the system. In contrast, specimen PET imagers are unburdened by the geometrical sensitivity challenges, thanks to their ability to leverage full coverage PET imaging geometries. For these devices, the focus shifts: high spatial resolution imaging takes precedence over rapid image reconstruction. This review concurrently probes into the technical complexities of both intraoperative and specimen PET imaging, shedding light on their recent designs, inherent challenges, and technological advancements.
Modeling and analysis of a hydraulic electric energy harvesting suspension
Authors: Liu Xujin , Kang Shuangyuan , Wu Zhifei
Published: May 2024

To enhance the performance of the hydraulic electric energy harvesting suspension, several steps were taken. Firstly, a resistance feedback control strategy was proposed in this paper based on the controllable damping characteristics. Subsequently, a model of the suspension was established based on its structure and working principle. And a simulation model was created, the tracking effect of current as well as the enhancement of suspension performance, were investigated to preliminarily validate the effectiveness of the control strategy. Finally, a bench test was conducted to verify the proposed strategy. Experimental results demonstrated that the peak harvesting can reach about300 W, and the average is 190.3 W. The vertical acceleration of the body in the hydraulic electric energy harvesting suspension decreased by 18.01% when employing the control strategy compared to the passive suspension.
Decoding trust: a reinforcement learning perspective
Authors: Zheng Guozhong , Zhang Jiqiang , Zhang Jing , Cai Weiran , Chen Li
Published: May 2024

Behavioral experiments on the trust game have shown that trust and trustworthiness are commonly seen among human beings, contradicting the prediction by assuming Homo economicus in orthodox Economics. This means some mechanism must be at work that favors their emergence. Most previous explanations, however, need to resort to some exogenous factors based upon imitative learning, a simple version of social learning. Here, we turn to the paradigm of reinforcement learning, where individuals revise their strategies by evaluating the long-term return through accumulated experience. Specifically, we investigate the trust game with the Q-learning algorithm, where each participant is associated with two evolving Q-tables that guide one’s decision-making as trustor and trustee, respectively. In the pairwise scenario, we reveal that high levels of trust and trustworthiness emerge when individuals appreciate both their historical experience and returns in the future. Mechanistically, the evolution of the Q-tables shows a crossover that resembles human psychological changes. We also provide the phase diagram for the game parameters, where the boundary analysis is conducted. These findings are robust when the scenario is extended to a latticed population. Our results thus provide a natural explanation for the emergence of trust and trustworthiness, and indicate that the long-ignored endogenous factors alone are sufficient to drive. More importantly, the proposed paradigm shows the potential to decipher many puzzles in human behaviors.
Formation of solitary waves solutions and dynamic visualization of the nonlinear schrödinger equation with efficient techniques
Authors: Majid Sheikh Zain , Asjad Muhammad Imran , Faridi Waqas Ali
Published: May 2024

This article investigates the non-linear generalized geophysical KdV equation, which describes shallow water waves in an ocean. The proposed generalized projective Riccati equation method and modified auxiliary equation method extract a more efficient and broad range of soliton solutions. These include U-shaped, W-shaped, singular, periodic, bright, dark, kink-type, breather soliton, multi-singular soliton, singular soliton with high amplitude, multiple periodic, multiple lump wave soliton, and flat kink-type soliton solutions. The travelling wave patterns of the model are graphically presented with suitable parameter values using the modern software Maple and Wolfram Mathematica. The visual representation of the solutions in 3D, 2D, and contour surfaces enhances understanding of parameter impact. Sensitivity and modulation instability analyses were performed to offer insights into the dynamics of the examined model. The observed dynamics of the proposed model were presented, revealing quasi-periodic chaotic, periodic systems, and quasi-periodic behaviour. This analysis confirms the effectiveness and reliability of the method employed, demonstrating its applicability in discovering travelling wave solitons for a wide range of nonlinear evolution equations.
Two-photon absorption in quantum dots with Hellmann potential
Authors: Hieu Nguyen N , Dinh Le , Poklonski N A , Phan Thi Hai Ha , Phuc Huynh V
Published: May 2024

We study the nonlinear optical absorption properties of a spherical quantum dot (SQD) with Hellmann potential, focusing on the two-photon absorption (TPA) process, using GaAs/AlGaAs material as an example. The radial Schrödinger equation is solved using the Nikiforov-Uvarov method, while the two-photon absorption coefficient is determined through second-order perturbation theory concerning the electron-photon interaction. Our study shows that the intraband transition has a smaller energy transition than the interband transition, leading to TPA spectra for the intraband transition that is restricted within a smaller energy range and exhibits a higher peak value than those for the interband transition. The peak corresponding to the orbital quantum number of electrons in SQD ℓ = 2 consistently appears to the left of the peak corresponding to ℓ = 1 in both intraband and interband transition cases. Additionally, the dependence of the absorption peak position on the order of transition, n, differs between intra- and inter-band transitions. We also observe blue shift behavior in the TPA spectra as all three parameters, r
0, V
0e
, and η, increase. Our investigation has the potential to enable the design of novel photonic devices, ultra-fast optical switches, and highly efficient solar cells through the optimization of quantum dot material properties.
Simulation investigation of effects of substrate and thermal boundary resistance on performances of AlGaN/GaN HEMTs
Authors: Wang Kang , Hu Wenbo , Wu Shengli , Wang Hongxing , Padhiar Muhammad Amin , Ji Yongqiang
Published: May 2024

The temperature distributions and thermal resistances of the GaN HEMTs fabricated on different substrates (sapphire, Si, SiC and diamond) with Mo/Au interlayers were calculated and analyzed by numerical simulation. The results show that the GaN HEMT on the diamond substrate exhibits the lowest channel temperature and thermal resistance, and the thermal resistance rises with the increase of the thermal boundary resistance (TBR) for all the GaN HEMTs with the different substrate materials. Meanwhile, the high TBR (2 × 10−7 m2·K/W) severely hinders the heat exchange between the GaN layer and the substrate, which makes it difficult for the heat flux to pass through the barrier. Even diamond with high thermal conductivity can hardly reduce the channel temperature of the device. Therefore, TBR must be reduced so that the heat flux can be dissipated through a high thermal conductivity substrate. In addition, the Mo/Au interlayer generates a lower thermal boundary resistance, which has little effect on the channel temperature, thermal resistance and interfacial temperature discontinuity of GaN HEMTs.
A new co-infection model for HBV and HIV with vaccination and asymptomatic transmission using actual data from Taiwan
Authors: Ullah Muhammad Asad , Raza Nauman , Omame Andrew , Alqarni M S
Published: May 2024

The co-infection of Human Immunodeficiency Virus (HIV) and Hepatitis B virus (HBV) poses a major threat to public health due to their combined negative impacts on health and increased risk of complications. A novel fractional mathematical model of the dynamics of co-infection between HBV and HIV for Taiwan is presented in this paper. Detailed analyses are conducted on the possible impact of HBV vaccination on the dynamics of HBV and HIV co-infection. The next-generation matrix technique is used to calculate the fundamental reproduction number R
0 = max{R
1, R
2}, where R
1 and R
2 are the reproduction numbers for HBV and HIV, respectively. The disease-free and endemic equilibria of the co-infection model are calculated. An extensive investigation is carried out to determine the local and global stability of the disease-free equilibrium point through Rough Hurtwiz criteria and the construction of Lyapunov function, respectively. We demonstrate that when R
1 < 1 < R
2, HBV infection is eradicated, but HIV remains prevalent. If R
2 < 1 < R
1, the opposite outcome occurs. The real data from 2000-2023 for Taiwan is used to fit the model. The fitting results show how effectively our model handles the data. In addition, numerical simulations are run for different scenarios to observe how the vaccine and fractional parameters changed the model state variables, as well as how the solutions behaved and how quickly they reached the model’s equilibrium points. According to the model’s numerical analysis, greater vaccination efforts against HBV have a positive effect on the propagation of co-infection.
Facile fabrication of MgAl2O4/MWCNT nanocomposite for efficient and stable solar-driven degradation of organic dye
Authors: Ahmad Sajjad , Hussain Tousif , Shuaib Urooj , Mubarik Farrukh Ehtesham , Yasin Amna , Shakir Imran
Published: May 2024

This work reports the synthesis and characterization of Magnesium Aluminate (MgAl2O4) and Magnesium Aluminate/Multi Walled Carbon Nanotube (MgAl2O4/MWCNT) nanocomposite by facile chemical co-precipitation method for the dye degradation application. MgAl2O4 and MgAl2O4/MWCNT nanocomposite are characterized by Scanning Electron Microscopy (SEM), x-ray Diffractometry (XRD), Raman Spectrometry, UV–vis Spectrophotometry (UV–vis), Fourier Transform Infrared Spectroscopy(FTIR), and x-ray Photoelectron Spectroscopy (XPS). Surface morphology of MgAl2O4/MWCNT nanocomposite exhibits entangled needle-like structures while MgAl2O4 spinel comprises agglomerated nanoparticles of different sizes. XRD confirms the formation of MgAl2O4. XPS identifies the chemical states and binding energies of constituent elements present in the sample. Optical properties reveal that addition of MWCNTs in MgAl2O4 decreases the optical bandgap energy from 3.02 eV to 2.78 eV. MgAl2O4/MWCNT nanocomposite shows reduced bandgap compared to pristine MgAl2O4 due to increased chemical defects or vacancies in intergranular regions and chemical interaction between MgAl2O4 and MWCNT, leading to the formation of new energy levels in MgAl2O4/MWCNT nanocomposite. Addition of MWCNTs provides a large surface area, more active sites, and enhances electron mobility between energy levels. MgAl2O4/MWCNT nanocomposite proves itself a better photocatalyst due to the fast degradation of Methyl Blue (MB) in 65 min as compared to MgAl2O4 which degrades the dye in 90 min. MgAl2O4/MWCNT nanocomposite also shows good stability and reusability even after performing the six cycles of dye degradation.
Broadband spin-decoupled metasurface for independent wavefront manipulations of orthogonal circularly-polarized waves
Authors: Chen Wenqiong , Zhang Jingwei , Feng Junlang , Niu Tiaoming , Mei Zhonglei
Published: May 2024

Metasurfaces endowed with spin-decoupled functionalities offer the capability to meticulously customize the electromagnetic wavefronts of incident dual orthogonal circularly-polarized (CP) waves in a desirable manner, that holds immense potential for broadening their application fields. Nevertheless, a major lack that persists in most spin-decoupled metasurfaces is the limited bandwidth or the intricate design requirements. Herein, we propose a broadband spin-decoupled metasurface, consisted of weak-resonant mirror-symmetry unit structures, that enables independent and distinct wavefront manipulations under the incidence of orthogonal CP waves. As a demonstration, we present a dual-channel metasurface that integrates geometric and propagation phases to generate vortex waves with two distinct modes in a wide frequency range from 10 GHz to 16 GHz. Both simulated and experimental results are consistent and collectively confirm the validity of our proposed metasurface. The research provides a practical and efficient avenue for constructing spin-decoupled metasurface within a broad frequency band.
Spectral distortion signatures of step-like inflationary potential
Authors: Mastache Jorge , Barrera Wilson , Henríquez-Ortiz Raúl
Published: May 2024

In this work, we analyze a power-law inflationary potential enhanced with a step that can introduce features in the primordial power spectrum. We focus on the computation of the Spectral Distortions (SD) induced by these features obtained from the inflationary dynamics. In this scenario, we explore the potential of upcoming experimental missions like PIXIE to detect the SD of the model within a power of n = 2/3, a power that agrees with recent tensor-to-scalar ratio constraints. The model offers insights into models with cosmological phases and different scalar field dynamics. Introducing a step in the inflaton potential leads to distinct features in the primordial power spectrum, such as oscillations and localized enhancements/suppressions at specific scales. We analyze the impact of three primary parameters — β, δ, and ϕ
step — on the amplitude and characteristics of the SD. The ϕ
step places the onset of the oscillations in the primordial power spectrum. The β parameter significantly influences the magnitude of the μ-SD, with its increase leading to larger SD and vice versa. Similarly, the δ parameter affects the smoothness of the step in the potential, with larger values resulting in smaller SD. Our findings indicate a distinct parameter space defined by 0.02 < δ/Mpl ≲ 0.026, 0.10 ≲ β < 0.23, and 7.53 ≲ ϕ
step/ Mpl ≲ 7.55, which produces SD potentially detectable by PIXIE. This region also corresponds to the maximum observed values of μ and y SD, which in special cases are an order of magnitude larger than the expected for ΛCDM. However, we also identify parameter ranges where μ and y SD may not be detectable due to the limitations of current observational technology. This comprehensive analysis of SD provides constraints of step-like inflationary models and their implications on its dynamics.
Quantum gravity effects on fermionic dark matter and gravitational waves
Authors: King Stephen F. , Roshan Rishav , Wang Xin , White Graham , Yamazaki Masahito
Published: May 2024

We explore the phenomenological consequences of breaking discrete global symmetries in
quantum gravity (QG). We extend a previous scenario where discrete global symmetries are
responsible for scalar dark matter (DM) and domain walls (DWs), to the case of fermionic DM,
considered as a feebly interacting massive particle, which achieves the correct DM relic density
via the freeze-in mechanism. Due to the mixing between DM and the standard model neutrinos,
various indirect DM detection methods can be employed to constrain the QG scale, the scale of
freeze-in, and the reheating temperature simultaneously. Since such QG symmetry breaking leads to
DW annihilation, this may generate the characteristic gravitational wave background, and hence
explain the recent observations of the gravitational wave spectrum by pulsar timing arrays. This
work therefore highlights a tantalizing possibility of probing the effective scale of QG
from observations.
How robust are gravitational wave predictions from cosmological phase transitions?
Authors: Athron Peter , Morris Lachlan , Xu Zhongxiu
Published: May 2024

Gravitational wave (GW) predictions of cosmological phase transitions are almost invariably evaluated at either the nucleation or percolation temperature. We investigate the effect of the transition temperature choice on GW predictions, for phase transitions with weak, intermediate and strong supercooling. We find that the peak amplitude of the GW signal varies by a factor of a few for weakly supercooled phase transitions, and by an order of magnitude for strongly supercooled phase transitions. The variation in amplitude for even weakly supercooled phase transitions can be several orders of magnitude if one uses the mean bubble separation, while the variation is milder if one uses the mean bubble radius instead. We also investigate the impact of various approximations used in GW predictions. Many of these approximations introduce at least a 10% error in the GW signal, with others introducing an error of over an order of magnitude.
Wide binaries and modified gravity (MOG)
Authors: Moffat J.W.
Published: May 2024

Wide binary stars are used to test the modified gravity called Scalar-Tensor-Vector Gravity or MOG. This theory is based on the additional gravitational degrees of freedom, the scalar field G = GN
(1+α), where GN
is Newton's constant, and the massive (spin-1 graviton) vector field ϕμ
. The wide binaries have separations of 2–30 kAU. The MOG acceleration law, derived from the MOG field equations and equations of motion of a massive test particle for weak gravitational fields, depends on the enhanced gravitational constant G = GN
(1+α) and the effective running mass μ. The magnitude of α depends on the physical length scale or averaging scale ℓ of the system. The modified MOG acceleration law for weak gravitational fields predicts that for the solar system and for the wide binary star systems gravitational dynamics follows Newton's law.
Féeton (B-L gauge boson) dark matter for the 511-keV gamma-ray excess and the prediction of low-energy neutrino flux*
Authors: Sheng 盛 Jie 杰 , Cheng 程 Yu 昱 , Lin 林 Weikang 伟康 , Yanagida Tsutomu T.
Published: May 2024

The féeton is the gauge boson of the

gauge theory. If the gauge coupling constant is extremely small, the féeton becomes a candidate for dark matter. We show that its decay to a pair of an electron and a positron explains the observed Galactic 511-keV gamma-ray excess in a consistent manner. This féeton dark matter decays mainly into pairs neutrino and anti-neutrino. Future low-energy experiments with improved directional capability will enable capturing these neutrino signals. The seesaw-motivated parameter space predicts a relatively short féeton lifetime that is comparable to the current cosmological constraint.
Analysis of fusion alphas interaction with RF waves in D-T plasma at JET
Authors: Kirov K.K. , Auriemma F. , Bonofiglo P.J. , Challis C.D. , De la Luna E. , Eriksson J. , Gallart D. , Garcia J. , Gorelenkova M. , Hobirk J. , Jacquet P. , Kappatou A. , Kazakov Y. , Keeling D. , King D. , Kiptily V. , Lerche E. , Maggi C. , Mailloux J. , Mantica P. , Mantsinen M. , Maslov M. , Menmuir S. , Sharma R. , Siren P. , Stancar Z. , Van Eester D. ,   JET Contributors
Published: May 2024

This work studies the influence of radio frequency (RF) waves in the ion cyclotron resonance heating (ICRH) range of frequencies on fusion alphas during the recent JET D-T campaign. Fusion alphas from D-T reactions are created with energies of about 3.5 MeV and therefore have significant Doppler shifts enabling synergistic interactions between them and RF waves at a broad range of frequencies, including the ones foreseen for future fusion machines in ITER (Schneider et al 2021 Nucl. Fusion
61 126058) and SPARC (Creely et al 2020 J. Plasma Phys.
86 865860502). Resonant interactions between RF waves and alphas, also called synergistic effects, will modify the alpha distribution and ultimately will have an impact on alpha orbit losses and heating. Data from JET 3.43 T/2.3 MA pulses based on the hybrid scenario (Hobirk et al 2023 Nucl. Fusion; Hobirk et al 29th IAEA FEC23 Conf. (16–21 October 2023); Challis et al 48th EPS Conf. on Plasma Physics (27 June–1 July 2022) during the DTE2 campaign (Maggi et al 2023 Nucl. Fusion)) were used for the analysis in this study. The impact of synergistic effects on alpha orbit losses and alpha heating are assessed. The conclusions are based on the analysis of experimental data for fast alpha losses, i.e. measurements from neutral particle analyser (NPA), fast ion losses scintillator detector, Faraday cups (FCs), and TRANSP (Hawryluk et al 1980 Physics of Plasmas Close to Thermonuclear Conditions vol 1 (CEC) pp 19–46) simulations. Experimental data and TRANSP analysis indicates that there are indeed changes in the alpha distribution function (DF) due to interaction with RF waves. Data from the NPA show increased 4He flux in the range from a few hundred keV up to 800 keV for pulses with RF power, while TRANSP clearly shows modifications in the fast alpha DF for these energies. Data from the scintillator detector and the FCs were compared for pulses with and without ICRH power and versus cases with enhanced alpha losses due to MHD activity. The trends from these diagnostics consistently show no additional alpha losses due to interaction with RF waves. TRANSP predictions for the impact of ynergistic effects on alpha heating show up to a 42% increase in alpha electron heating and up to a 25% increase in alpha ion heating. These effects, however, become negligibly small, less than 1%, when alpha heating is compared to the total auxiliary heating power in the investigated JET pulses.
Beam dynamics design and error study of the coupled structure with ladder RFQ and IH-DTL
Authors: Li H.P. , Su H.Q. , Kong G.Q. , Pan W.L. , Lin J.R.L. , Lu Y.R. , Wang S.
Published: May 2024

The coupled structure with ladder radio-frequency quadrupole
(RFQ) and interdigital H-type drift tube linac (IH DTL) has been
proposed to accelerate the proton beam to several MeV with high
acceleration gradient and one RF feed-in system. A ladder RFQ-IH DTL
coupled structure was designed to accelerate a proton beam 2.5 MeV
with a peak current of 15 mA. Detailed dynamics optimization and
error study were performed to achieve high transmission efficiency
and small emittance growth, including ladder RFQ, coupling section
and IH DTL section. The Kombinierte Null Grad Struktur (KONUS)
dynamics scheme with two quadrupole doublets (QDs) was adopted in
the IH-DTL section. Start-to-end beam tracking results showed that
the proton beam can be accelerated to the final energy with a length
of 2.11 m and a transmission efficiency above 98.5%. In addition,
we performed error sensitivity analysis and the combined error study
to evaluate the error tolerance limits of the ladder RFQ-IH DTL
coupled structure.
Performance of the mass testing setup for arrays of silicon photomultipliers in the TAO experiment.
Authors: Rybnikov A. , Anfimov N. , Qu M. , Chetverikov A. , Cao G. , Fedoseev D. , Wang H. , Kozhukalov V. , Sharov V. , Sokolov S. , Sotnikov A.
Published: May 2024

Modern neutrino physics detectors often employ thousands,
and sometimes even hundreds of thousands, of Silicon
Photomultipliers (SiPMs). The TAO experiment [1] is a
notable example that utilizes a spherical scintillator barrel with a
diameter of 1.8 meters, housing approximately 130,000 SiPMs
organized into 4,100 tiles. Each tile with size of
5×5 cm2 consists of a 32-SiPM array functioning as a
single detector unit. To achieve an unparalleled energy resolution
of 2% at 1 MeV within this volume, the SiPMs must possess
cutting-edge parameters, including a photon detection efficiency
(PDE) exceeding 50%, cross-talk of approximately 10%, and an
extremely low dark count rate (DCR) below
50 Hz/mm2. Maintaining the setup at a negative temperature of
-50°C is necessary to achieve the desired DCR. This article
presents the setup and methods employed to individually characterize
the mass of SiPMs across all 4,100 tiles at the specified negative
temperature.
Rapid high-latitude cooling in the southeastern Pacific sector driven by North Atlantic warming during 1979–2013 in CESM1
Authors: Yao Shuai-Lei , Wu Renguang , Wang Pengfei , Chen Shangfeng
Published: May 2024

During the 1979–2013 satellite observation period, the sea surface temperature (SST) has cooled substantially in the high-latitude Southern Ocean, with the most pronounced cooling tendency centered in the southeastern Pacific domain. Previous hypotheses have commonly ascribed the recent Southern Ocean cooling to either the tropical eastern Pacific cooling or North Atlantic and tropical Indian Ocean SST warming. However, the mechanisms underpinning significant cooling in the southeastern Pacific sector remain debatable. By diagnosing three pacemaker experiments with a state-of-the-art global climate model in which SSTs in the North Atlantic, tropical central-eastern Pacific, and tropical Indian Ocean-western Pacific are individually nudged to mimic the observed trajectory, we show that the North Atlantic dominates in the cold SST response of the southeastern Pacific sector during 1979–2013. Anomalous North Atlantic warming initiates a quasi-stationary Rossby wave response to a south-to-north cross-equatorial Hadley circulation strengthening, leading to an enhanced Amundsen Sea Low. As a result, due primarily to the increased low-level marine cloud cover, the net surface shortwave radiation reduction triggers rapid SST cooling in the southeastern Pacific domain. The southeastern Pacific cold SST anomalies are further maintained via the shortwave radiation-low-cloud-SST positive feedback on decadal timescales. Our results suggest that the shortwave radiation-low-cloud SST feedback is fundamental to the observed long-term cooling of the high-latitude Southern Ocean, with profound climate consequences worldwide.
Pillar electrodes embedded in the skeletal muscle tissue for selective stimulation of biohybrid actuators with increased contractile distance
Authors: Li Tingyu , Nie Minghao , Morimoto Yuya , Takeuchi Shoji
Published: May 2024

Electrodes are crucial for controlling the movements of biohybrid robots, but their external placement outside muscle tissue often leads to inefficient and non-selective stimulation of nearby biohybrid actuators. To address this, we propose embedding pillar electrodes within the skeletal muscle tissue, resulting in enhanced contraction of the target muscle without affecting the neighbor tissue with a 4 mm distance. We use finite element method simulations to establish a selectivity model, correlating the VIE (volume integration of electric field intensity within muscle tissue) with actual contractile distances under different amplitudes of electrical pulses. The simulated selective index closely aligns with experimental results, showing the potential of pillar electrodes for effective and selective biohybrid actuator stimulation. In experiments, we validated that the contractile distance and selectivity achieved with these pillar electrodes exceed conventional Au rod electrodes. This innovation has promising implications for building biohybrid robots with densely arranged muscle tissue, ultimately achieving more human-like movements. Additionally, our selectivity model offers valuable predictive tools for assessing electrical stimulation effects with different electrode designs.
On-chip tunable quantum interference in a lithium niobate-on-insulator photonic integrated circuit
Authors: Maeder Andreas , Finco Giovanni , Kaufmann Fabian , Sabatti Alessandra , Kellner Jost , Chapman Robert J , Grange Rachel
Published: May 2024

Programmable interferometric circuits are at the heart of integrated quantum photonic processors. While the lithium niobate-on-insulator platform has the potential to advance integrated quantum photonics due to its strong nonlinearity and tight mode confinement, the demonstration of reconfigurable two-photon interference has not yet been achieved. Here, we design, fabricate and characterize the building block of such interferometric networks in the form of a 2 × 2 Mach–Zehnder Interferometer. We use a thermo-optic phase shifter to achieve stable performance with a power consumption of

P
π

=
44.4

mW and sub-microsecond switching times. We demonstrate the effectiveness of our device for quantum applications by measuring single-photon routing with up to 34 dB extinction ratio. We show Hong-Ou-Mandel interference with fully tunable visibilities reaching a maximum value of

97.4
±
1.0
%

. As part of large scale quantum photonic circuits, this building block will facilitate reconfigurable and tunable photonic processing units integrated alongside non-classical light sources.
Exploratory data science on supercomputers for quantum mechanical calculations
Authors: Dawson William , Beal Louis , Ratcliff Laura E , Stella Martina , Nakajima Takahito , Genovese Luigi
Published: May 2024

Literate programming—the bringing together of program code and natural language narratives—has become a ubiquitous approach in the realm of data science. This methodology is appealing as well for the domain of Density Functional Theory (DFT) calculations, particularly for interactively developing new methodologies and workflows. However, effective use of literate programming is hampered by old programming paradigms and the difficulties associated with using high performance computing (HPC) resources. Here we present two Python libraries that aim to remove these hurdles. First, we describe the PyBigDFT library, which can be used to setup materials or molecular systems and provides high-level access to the wavelet based BigDFT code. We then present the related remotemanager library, which is able to serialize and execute arbitrary Python functions on remote supercomputers. We show how together these libraries enable transparent access to HPC based DFT calculations and can serve as building blocks for rapid prototyping and data exploration.