bluuebunny/crossref_metadata_2025 huggingface dataset:
Extending discrete geometric singular perturbation theory to non-hyperbolic points
Authors: Jelbart S , Kuehn C
Published: September 2024

We extend the recently developed discrete geometric singular perturbation theory to the non-normally hyperbolic regime. Our primary tool is the Takens embedding theorem, which provides a means of approximating the dynamics of particular maps with the time-1 map of a formal vector field. First, we show that the so-called reduced map, which governs the slow dynamics near slow manifolds in the normally hyperbolic regime, can be locally approximated by the time-1 map of the reduced vector field which appears in continuous-time geometric singular perturbation theory. In the non-normally hyperbolic regime, we show that the dynamics of fast-slow maps with a unipotent linear part can be locally approximated by the time-1 map induced by a fast-slow vector field in the same dimension, which has a nilpotent singularity of the corresponding type. The latter result is used to describe (i) the local dynamics of two-dimensional fast-slow maps with non-normally singularities of regular fold, transcritical and pitchfork type, and (ii) dynamics on a (potentially high-dimensional) local center manifold in n-dimensional fast-slow maps with regular contact or fold submanifolds of the critical manifold. In general, our results show that the dynamics near a large and important class of singularities in fast-slow maps can be described via the use of formal embedding theorems which allow for their approximation by the time-1 map of a fast-slow vector field featuring a loss of normal hyperbolicity.
From fractional quantum anomalous Hall smectics to polar smectic metals: nontrivial interplay between electronic liquid crystal order and topological order in correlated topological flat bands
Authors: Lu Hongyu , Wu Han-Qing , Chen Bin-Bin , Sun Kai , Yang Meng Zi
Published: September 2024

Symmetry-breaking orders can not only compete with each other, but also be intertwined, and the intertwined topological and symmetry-breaking orders make the situation more intriguing. This work examines the archetypal correlated flat band model on a checkerboard lattice at filling

ν
=
2

/

3

and we find that the unique interplay between smectic charge order and topological order gives rise to two novel quantum states. As the interaction strength increases, the system first transitions from a Fermi liquid (FL) into FQAH smectic (FQAHS) state, where the topological order coexists cooperatively with smectic charge order with enlarged ground-state degeneracy and interestingly, the Hall conductivity is

σ

x
y

=
ν
=
2

/

3

, different from the band-folding or doping scenarios. Further increasing the interaction strength, the system undergoes another quantum phase transition and evolves into a polar smectic metal (PSM) state. This emergent PSM is an anisotropic non-Fermi liquid, whose interstripe tunneling is irrelevant while it is metallic inside each stripe. Different from the FQAHS and conventional smectic orders, this PSM spontaneously breaks the two-fold rotational symmetry, resulting in a nonzero electric dipole moment and ferroelectric order. In addition to the exotic ground states, large-scale numerical simulations are also used to study low-energy excitations and thermodynamic characteristics. We find that the onset temperature of the incompressible FQAHS state, which also coincides with the onset of non-polar smectic order, is dictated by the magneto-roton modes. Above this onset temperature, the PSM state exists at an intermediate-temperature regime. Although the T = 0 quantum phase transition between PSM and FQAHS is first order, the thermal FQAHS-PSM transition could be continuous. We expect the features of the exotic states and thermal phase transitions could be accessed in future experiments.
Sub-bandgap excited photoluminescence probing of deep defect complexes in GaN doped by Si, Ge and C impurities
Authors: Wang Xiaorui , Vaněk Tomáš , Hájek František , Jarý Vítězslav , Hubáček Tomáš , Hospodková Alice , Ling Francis Chi-Chung , Xu Shijie
Published: September 2024

With the sub-bandgap optical excitation, thermal dynamics of holes among multiple levels in n-type GaN epilayers with different dopants of Si, Ge and C are investigated via measuring and modeling variable-temperature yellow luminescence (YL) band of the samples. In sharp contrast to the case of above-bandgap optical excitation, the variable-temperature YL band of all the studied GaN samples including unintentionally-doped sample exhibit unusual negative thermal quenching (NTQ) behavior, suggesting a possible physical mechanism, namely thermally induced migration of holes from shallower levels to the luminescent deep level. By considering the possible presence of multiple hole levels in the doped GaN samples, a phenomenological model is developed for the thermal transfer of holes among the multi-levels and the interpretation of the observed NTQ phenomenon of the YL band. Different activation energies of 347.9, 520.8 and 348.5 meV are obtained for the Ge-doped, high C-containing, and Si-doped GaN samples, respectively. The results reveal the existence of multiple hole defect levels in the n-type GaN. Possible microstructural origins causing these different hole levels are further argued. The study may shed some light on the nature of various defect complexes in the technologically important GaN epilayers. Combined microstructural and optical investigations need to be further done for elucidating various optically- and electrically-active defect complexes in GaN.
Self-powered Schottky barrier photodetector with high responsivity based on homoepitaxial Ga2O3 films by MOCVD
Authors: Yu Han , Jiao Teng , Dang Xinming , Han Yu , Li Yihan , Li Zhen , Chen Peiran , Dong Xin , Li Guoxing , Zhang Yuantao , Zhang Baolin
Published: September 2024

Ga2O3 is a fast-developing wide band semiconductor for solar-blind ultraviolet photodetectors (PDs) applications. The heterojunction self-powered PDs fabricated from heteroepitaxial Ga2O3 films currently have low responsivity and response speed. In this work, we fabricated Schottky barrier PDs based on homoepitaxially grown high quality Ga2O3 films, which exhibited high performance with high responsivity at different bias voltages. In particular, the device achieves a responsivity of 90.3 mA W−1, a photo-to-dark current ratio (PDCR) of 3.2 × 104 and a detectivity of 3.8 × 1013 Jones at 0 V. In addition, a response time of superior to 5 ms is achieved. The results demonstrate the advantages of homoepitaxial Ga2O3 films in the field of high-performance devices.
From weak to strong-coupling superconductivity tuned by substrate in TiN films
Authors: Liu Yixin , Liu Yuchuan , Xu Zulei , Yu Aobo , Wang Xiaoni , Peng Wei , Wu Yu , Mu Gang , Lin Zhi-Rong
Published: September 2024

The interplay between substrates and superconducting thin films has attracted increasing attention. Here, we report an in-depth investigation on superconducting properties of the epitaxial TiN thin films grown on three different substrates by dc reactive magnetron sputtering. The TiN films grown on (0001) sapphire exhibit (111) crystal orientation, while that grown on (100) Si and MgO substrates exhibit (100) orientation. Moreover, the samples grown on Si reveal a relatively lower level of disorder, accompanied by the higher critical transition temperature Tc
and smaller magnitude of upper critical field slope near Tc
. Remarkably, we uncovered a rather high value of superconducting gap (with

Δ
0

/

k
B

T
c

= 3.05) in TiN film on Si indicating a very strong coupling superconductivity, in sharp contrast to the case using sapphires and MgO as the substrate which reveals a weak-coupling feature. The comprehensive analysis considering the scenarios of the three substrate shows that the grain size of the thin films may be an important factor influencing the superconductivity.
Thermal quench modeling of REBCO racetrack coils under either alternating current or short-circuit voltage
Authors: Hussain Arif , Dadhich Anang , Pardo Enric
Published: September 2024

Racetrack coils in REBCO High-Temperature Superconductor (HTS) motors help to increase the power-over-weight ratio by raising the magnetic flux density and output power. Nevertheless, HTS motors face thermal quench due to self-heating effects when subjected to alternating or short-circuit onset DC voltage. Additionally, thermal events have been observed due to screening currents when motors operate at high frequencies. Therefore, for the safe operation of HTS motors, quench research is crucial. To accurately simulate and analyze quench events in different scenarios, it is imperative to employ fast and precise software to numerically model the electrothermal behavior in racetrack coils. Our contribution involves the development of a novel and efficient model implemented in C++ that takes screening currents into account. This model is designed to conduct coupled electromagnetic and electrothermal analyses, utilizing variational methods. Specifically, the model incorporates both Minimum Electro-Magnetic Entropy Production and the Finite Difference Method. In this article, we explore the phenomenon of temperature rise within a racetrack coil subjected to either alternating or DC voltages of magnitudes ranging from 0.1 V to 1000 V. The study encompasses conditions of adiabatic operation and heat exchange with liquid nitrogen (LN2). Among other results, we found that in moderate DC voltages like 10 V, non-uniformity in the AC loss causes highly localized quench at the central turns. Then, screening currents play a key role also for DC voltages. The developed model exhibits the potential to comprehensively and swiftly analyze the electromagnetic and electrothermal characteristics of real-world superconducting applications, including high-field rotating machines, such as motors for aviation.
Study on the interstitial oxygen diffusion to understand the reduction of cryogenic RF loss for the superconducting radio-frequency niobium cavities
Authors: Yu Mingming , Huang Shichun , Zhao Yong , Gu Xiangcheng , Peng Long , Lai Jiwei , Zhu Tongtong , Wang Yihan , Wu Andong , Tan Teng , He Yuan , Cao Hongwen , Cao Yunpeng , Zhang Kun
Published: September 2024

Medium-temperature baking (Mid-T baking) is an innovative method employed to enhance the unloaded quality factor Q
0 of superconducting radio-frequency niobium (SRF Nb) cavities at cryogenic temperatures. This study presents an interstitial oxygen diffusion model based on the decomposition of the natural oxide to clarify the improved performance of the Nb cavities after undergoing Mid-T baking. Additionally, the correlation between the interstitial oxygen within the RF penetration depth and the surface resistance of the Nb cavities has been explored. The parameter for the oxide decomposition was determined using in-situ x-ray photoelectron spectroscopy (XPS), where the thickness of the oxide/carbide layer was calculated from the peak fitting of Nb 3d spectra and the attenuation law of the photoelectron beam. The interstitial oxygen diffusion model, validated by the semi-quantitative distribution along the depth determined by time-of-flight secondary ion mass spectrometry, quantifies the oxygen atomic concentration within the RF penetration depth in Mid-T baked Nb material. In the baking temperature range of 300 °C–400 °C, the calculated oxygen concentration from the interstitial oxygen diffusion model demonstrates a more pronounced dependence on the baking temperature than the baking time. This suggests that more precise control of the interstitial oxygen concentration can be achieved by adjusting the baking temperature. Furthermore, it has been observed that maintaining a uniform and moderate oxygen concentration throughout the depth is essential for optimal Bardeen–Cooper–Schrieffer resistance. This study paves the way for more efficient processing optimization and enhancing understanding of the mechanism behind RF loss in Nb cavities.
Enhanced mechanical strength and texture of (Ba,K)Fe2As2 Cu/Ag composite sheathed tapes with Nb barrier layer
Authors: Li Wenchao , Fu Caida , Guo Chen , Huang He , Yao Chao , Zhang Xianping , Ma Yanwei
Published: September 2024

Iron-based superconductors with ultra-high upper critical fields and low anisotropy have attracted much attention for superconducting mechanisms and high-field applications. In practical applications, improving the mechanical strength and heat treatment temperature of superconducting tapes is of great significance for the improvement of transport current as well as stability. In this paper, (Ba, K)Fe2As2(Ba-122) superconducting tapes with Cu/Nb/Ag composite sheaths were successfully fabricated using a pre-composite process, which provides a feasible method for the fabrication of high-strength superconducting wires and tapes. It is shown that Cu/Nb/Ag composite sheathed tapes can be sintered at 880 °C, and tapes sintered at 880 °C have the highest transport properties as well as excellent superconductivity of the superconducting cores, as demonstrated by a series of characterizations. In addition, other superconducting properties of the tapes sintered at 880 °C, including grain orientation, flux pinning, upper critical field and irreversible field, were also studied. It was found that none of the three sheaths fractured after sintering and the superconducting core had a high c-axis texture and densities. The high mechanical strength of the Cu/Nb/Ag composite sheathed tape was also demonstrated by comparative tensile experiments. The results indicate that the low-cost Ba-122 tapes with Cu/Nb/Ag composite sheaths hold great promise for future practical applications.
Local plastic deformation effects on the critical current of high-Jc Nb3Sn strands under uniaxial strain
Authors: Liu Yunhao , Sun Yi , Gao Peng , Nijhuis Arend , Devred Arnaud , Guo Zichuan , Zhu Huajin , Xu Peng , Shi Yi , Liu Fang , Dai Chao , Wu Yu , Qin Jinggang
Published: September 2024

In order to meet the target operating parameters of the toroidal field coils (TFCs) for the next-generation Chinese compact burning plasma tokamak, high critical current density (J
c) Nb3Sn strand will be applied to the high-field winding-package of the TFC. To improve the transverse stiffness of the cable in withstanding the huge Lorentz force and avoiding conductor performance degradation, the short-twist-pitch and copper-wound-strand cable patterns were taken into consideration. In the processes of cabling and compaction of the conductor, the tight cable configurations lead to severe local plastic deformation (LPD) within the strands. The strands in the conductor are subjected to strain caused by thermal contraction and Lorentz force during conductor cooling down and operation. So far it is unknown, whether the LPD could impact the critical current (I
c) versus uniaxial applied strain behavior of high-J
c Nb3Sn strand. Aiming to investigate the effect of LPD on the I
c of strands under uniaxial strain, three types of high J
c Nb3Sn strand with different indentation depths were tested on a U-shaped bending spring. The axial strain ranges from −0.9% to +0.4% at 14 T and 4.2 K. The three types of strands showed more strain sensitivity and lower tensile irreversible strain limit with increasing LPD, while even irreversible degradation of the I
c could be observed in the compressive strain region. The sample preparation, test process, test results and analysis are reported.
Valley-polarized edge plasmons in graphene p–n junctions with pseudomagnetic fields
Authors: Zhang Ya , Zhai Feng , Jiang Wei
Published: September 2024

Owing to the inherent characteristics of collective excitations in graphene, electrical control of edge plasmons is highly desirable for nanoplasmonic applications. This study investigates valley-polarized edge pseudomagnetoplasmons in a graphene p–n junction subjected to a strain-induced pseudomagnetic field. A four-component hydrodynamic model is employed and solved via the Wiener–Hopf method, revealing the coexistence of three plasmon modes, including counterpropagating acoustic edge modes, gapless topological edge states, and zero modes. The valley polarization, as determined from the numerically exact solution, is stronger than that predicted by the approximate models. Notably, the confinement of edge plasmons at the graphene p–n junction significantly exceeds that at the graphene/vacuum interface, possibly because of the electron–hole attraction. Furthermore, gate-controlled subwavelength confinement is successfully achieved by applying an appropriate gate voltage, thereby highlighting a unique and promising attribute of edge pseudomagnetoplasmons in graphene p–n junctions.
Enhancing quantum time transfer security: detecting intercept-resend attacks with energy-time entanglement
Authors: Quan Runai , Hong Huibo , Xiang Xiao , Cao Mingtao , Li Xinghua , Li Baihong , Dong Ruifang , Liu Tao , Zhang Shougang
Published: September 2024

Quantum time transfer has emerged as a powerful technique, offering sub-picosecond precision and inherent security through the nonlocal temporal correlation property of energy-time entangled biphoton sources. In this paper, we demonstrate the inherent security advantage of quantum time transfer, and the utilization in detecting potential intercept-resend attacks. By investigating the impact of these attacks on the nonlocality identifier associated with nonlocal dispersion cancellation of energy-time entanglement, we establish a security threshold model for detecting intercept-resend attacks. Experimental verification on a 102 km fiber-optic link confirms that even a malicious delay as small as 25 ps can be identified. This investigation serves as a compelling illustration of secure two-way time transfer, safeguarding against intercept-resend attacks, and showcasing its potential applications in fields reliant on authentic time distribution between remote parties.
Room-temperature spontaneous perpendicular exchange bias in IrMn/[Co/Pt]3 multilayers
Authors: Wang Jiabin , Bao Xilai , Chen Jinxia , Zou Mengting , Xie Yali , Li Run-Wei , Li Xiaoguang , Cao Yanwei , Wang Baomin
Published: September 2024

Perpendicular exchange bias (PEB) is highly desirable for the development of advanced nanoscale spintronics devices. The attainment of conventional PEB typically involves a field-cooling process through the Néel temperature of antiferromagnetic materials. In this study, we demonstrated the realization of spontaneous PEB (SPEB) in IrMn/[Co/Pt]3 multilayers utilizing isothermal crystallization of IrMn at room temperature (RT). And the SPEB generated isothermally at IrMn/Co interface does not destroy the perpendicular magnetic anisotropy of the multilayers. The magnetic domains of the multilayers captured by Kerr microscopy after different magnetization time also indicate the generation of SPEB. The magnitude of SPEB can be controllable by varying the isothermal magnetization time and the annealing temperature of IrMn. The relationship between magnetization waiting time and SPEB reveals that even slight isothermal crystallization can generate substantial SPEB. Our results provide an alternative approach to isothermally generate PEB in IrMn/[Co/Pt]3 multilayers at RT.
Multi-polarized four-mode wideband vortex electromagnetic beams generation through reflective metasurface in Ka-band
Authors: Tian Lu , Zhang Rui , Wang Yong , Xie Bingchuan , Li Haixuan , Ren Yueyan
Published: September 2024

Orbital angular momentum (OAM) is a new dimension for improving channel capacity and has been widely studied by scientists. In recent years, there has been an increasing amount of research on antennas and electromagnetic (EM) beams containing OAM, demonstrating its excellent ability in communication. This article proposes a Ka-band multi-mode orbital angular momentum reflectarray antenna (RA) capable of generating four vortex EM beams with four modes (l = −1, 0, +1, +2). The proposed unit cell can cover a 360-degree reflection phase range with a magnitude above 0.88, achieved through a combination of variable-sized and delay-line units. Furthermore, the unit cell’s mirror configuration allows for cross-polarization rejection. Based on these unit cells, a square reflectarray antenna (25 × 25 elements) is designed, fabricated, and measured. The measured results demonstrate that the 1 dB bandwidths for four modes are 25.81% (27–35 GHz, l = −1), 31.25% (27–37 GHz, l = 0), 28.57% (27–36 GHz, l = +1), and 20.69% (26–32 GHz, l = +2), respectively. Notably, the 3 dB gain bandwidths of all modes exceed 40%, with the maximum 3 dB bandwidth reaching 47.62% at mode l = +1. Furthermore, all vortex EM beams of this proposed RA maintain mode purities exceeding 70% within 3 dB bandwidths.
Influence of sulfurization temperature on grain growth in Cu2ZnSnS4 thin films synthesized for solar cell applications
Authors: Gupta Indu , Singla Shivani , Kanjariya Prakash , Jain Rahul , Mohanty Bhaskar Chandra , Nayak Manas
Published: September 2024

Copper-zinc-tin-sulfur (CZTS) thin films, prepared through a dip-coating solution method, present a highly attractive option as absorber materials for thin-film solar cells. This is due to their affordability, environmentally friendly composition, and abundant availability of raw materials. Although films processed with hydrazine-based solutions have achieved the highest efficiency of approximately 12.6%, the toxic and carcinogenic nature of hydrazine negates these advantages. In the ongoing global research on solution-based processing methods, the size of the grains has emerged as a critical factor in the fabrication of efficient solar cells. In our study, we have successfully prepared CZTS thin films with a pure kesterite phase, characterized by large micro-sized grains, using a dip-coating process with an ethanol-based precursor solution, followed by sulfurization. We investigated how the grain size evolves with varying sulfurization temperatures. Notably, we observed that increasing the temperature led to larger and more uniform grain growth. These results underscore the potential of our approach for the straightforward production of high-quality films with sizable grains, ultimately enhancing their photosensitivity and making them a promising candidate for efficient solar cell applications.
Dynamics of memristive circuit driven by Josephson junction
Authors: Jiang Cuimei , Gu Xuejing , Zhang Fangfang , Liu Jian , Liu Pengfei
Published: September 2024

The nonlinear circuit with charge-controlled memristor (CCM) can capture the external electric field effect. The nonlinear circuit with Josephson junction (JJ) can estimate the external magnetic field effect. Therefore, we propose an enhanced functional circuit by connecting a CCM and a JJ into a simple RLC nonlinear circuit. This enchanced circuit can estimate the external electromagnetic fields concurrently. The dynamical equations of the new memristive circuit and its Hamilton energy function are obtained by using the Kirchhoff’s law and the Helmholtz’s theorem. Furthermore, the complex dynamics of memristive circuit are investigated by applying bifurcation diagrams, Lyapunov exponents and time sampled series. The simulation experiment results indicate that the electromagnetic field has a great influence on complex dynamics of memristive circuit. In fact, this new nonlinear circuit is also a functional neural circuit, and it can be used to study the collective dynamic of functional neural network under the condition of an external electromagnetic fields.
A multifunctional interlayer between mesoporous TiO2 and perovskite for perovskite solar cells with high efficiency and stability
Authors: Huang Wen-Jie , Zhang Zhen-Long , Liu Yue-Feng , Gao Hui-Ping , Mao Yan-Li
Published: September 2024

The industrialization of the perovskite solar cells (PSCs) requires further lifting their power conversion efficiency (PCE). There are some important factors to hinder the PCE improvement, such as interface defects and energy level mismatching betwee electron transport layer (ETL) and perovskite layer, and solar energy loss due to no absorption of near infrared (NIR) for the perovsktie. Thus in this study, a multifunctional material of W-Er-Yb doped TiO2 (W-UC-TiO2) was prepared and applied to PSCs as an interlayer between mesoporous TiO2 and perovskite. The experimental results demonstrate that the interlayer of W-UC-TiO2 has the functions of improving NIR absorption for PSCs, passivating inerface defects and improving energy level matching between TiO2 and perovskite. A high efficiency of 21.32% was acquired for the PSCs with W-UC-TiO2 interlayer from 19.26% for the control device. Moreover, stability of the PSCs was improved by the insertion of W-UC-TiO2 interlayer.
Tidal Love numbers from EFT of black hole perturbations with timelike scalar profile
Authors: Barura Chams Gharib Ali , Kobayashi Hajime , Mukohyama Shinji , Oshita Naritaka , Takahashi Kazufumi , Yingcharoenrat Vicharit
Published: September 2024

We study static tidal Love numbers (TLNs) of a static and spherically symmetric black hole for odd-parity metric perturbations.
We describe black hole perturbations using the effective field theory (EFT), formulated on an arbitrary background with a timelike scalar profile in the context of scalar-tensor theories.
In particular, we obtain a static solution for the generalized Regge-Wheeler equation order by order in a modified-gravity parameter and extract the TLNs uniquely by analytic continuation of the multipole index ℓ to non-integer values.
For a stealth Schwarzschild black hole, the TLNs are vanishing as in the case of Schwarzschild solution in general relativity.
We also study the case of Hayward black hole as an example of non-stealth background, where we find that the TLNs are non-zero (or there is a logarithmic running).
This result suggests that our EFT allows for non-vanishing TLNs and can in principle leave a detectable imprint on gravitational waves from inspiralling binary systems, which opens a new window for testing gravity in the strong-field regime.
Metrological non-classical correlations and quantum coherence in hybrid

(
1

/

2
,
1
)

system under decoherence channels
Authors: Chhieb Abdessamie , Oumennana Mansoura , Bouafia Zakaria , Chouiba Aicha , Mansour Mostafa , Ouchrif Mohamed
Published: September 2024

Our research focuses on the interplay between thermal noise and decoherence channels on quantum coherence and nonclassical correlations in a hybrid

(
1

/

2
,
1
)

Heisenberg model. This hybrid system integrates the Dzyaloshinsky–Moriya interaction (DMI) and operates under the influence of an external magnetic field. We use local quantum Fisher information (LQFI) for correlation estimation and relative entropy of coherence for coherence measurement in the considered system. Our investigation encompasses various parameters of the hybrid system, the strength of the DMI and the intensity of the external magnetic field. Our findings underscore that elevated temperature compromises both nonclassical correlations and coherence. On the other hand, the robustness of the DMI mitigates the impact of thermal noise on quantum Fisher information correlations and relative entropy of coherence in the hybrid system. Additionally, we inspect the impact of decohering channels-specifically, dephasing, phase flip, and bit- and trit-flip channels-on thermal coherence and quantum correlations. The introduction of various decoherence processes into the hybrid qubit-qutrit system leads to a competition with thermal fluctuations, thereby giving rise to out-of-equilibrium states. Our results indicate that as the decoherence strength parameter (p) increases, both LQFI and relative entropy of coherence exhibit similar behaviors in the dephasing and phase flip channels. These resources gradually diminish, eventually disappearing entirely at p = 1. In the context of the bit- and trit-flip channels, quantum coherence displays notable distinctions compared to what is observed under dephasing and phase flip channels, revealing that coherence can be preserved if the DMI is strong and the intensity of the external magnetic field is reduced. These findings are important since it is crucial to first understand the decoherence process, arising from the interaction with the environment, and then to find ways to hinder this decoherence in order to avoid the complete loss of the quantum resources necessary to quantum information processing.
Identification of hidden danger discharges in transmission lines based on multi-scale convolutional neural network
Authors: Huang Zhidu , Huang Wei , Liu Yinglong , Chen Yajuan , Li Shengdong
Published: September 2024

The presence of hidden dangers in transmission lines poses a significant threat to the safe and stable operation of the power grid. Timely identification of these hidden dangers is crucial to simplify maintenance tasks for the operation department. This paper introduces a model based on a Multi-Scale Convolutional Neural Network (MSCNN) to identify the discharge types of hidden dangers in transmission lines. Initially, the Intrinsic Mode Functions (IMFs) of the hidden danger discharge signal measured from the transmission line are obtained through Variational Mode Decomposition (VMD). Subsequently, multi-scale time-frequency features within the IMFs are extracted by MSCNN. Finally, a Softmax classifier completes the task of identifying the type of hidden danger discharge. The training and testing results of the model demonstrate that its accuracy in identifying the four types of hidden dangers researched in this paper can reach 90.38%.
Research on photovoltaic grid-connected inverters with source filtering function
Authors: Wei Junqiu , Chen Qigong , Li Ao
Published: September 2024

To suppress the current harmonics caused by the nonlinear load connected to the grid when the photovoltaic system is connected to the grid for power generation, this paper adopts a composite control strategy based on the PI-RC controller to realize the synthesis of the command current signal in different modes. According to the different command current signals, the system can work in three modes: photovoltaic grid-connected harmonic compensation control, photovoltaic grid-connected control, and harmonic compensation unified control. Under the composite control strategy, the system realizes the active output of the photovoltaic grid-connected system with the function of source filtering, compensates for the harmonics caused by nonlinear loads, successfully reduces the harmonic distortion rate of grid current, and then realizes the function expansion of photovoltaic grid-connected inverter. Finally, the feasibility and rationality of the unified control strategy designed in this study are verified by simulation experiments.
Design and research of high-frequency electromagnetic wave detection antenna for discharge of transmission lines
Authors: Yang Jie , Xia Yunfeng , Liang Qishuai , Xia Zhongchen , Tao Xi
Published: September 2024

Overhead lines have a wide range of applications in power systems. When early insulation faults occur in the long-term operation of overhead lines, corona discharge may occur. Timely detection of corona discharge can guide maintenance personnel to discover and eliminate faults in a timely manner. The height and distribution of overhead lines are relatively high, and close-range detection cannot quickly locate the discharge area. Using radio frequency antennas to measure the electromagnetic wave signals generated by corona discharge can achieve long-distance positioning detection of corona discharge. This article uses a log-periodic antenna as the detection antenna and simulates the antenna structure to prove that its directionality, gain, and measurement frequency band meet the design requirements. Finally, the discharge detection performance of the antenna is verified through experiments.
Abatement of ionizing radiation for superconducting quantum devices
Authors: Loer B. , Harrington P.M. , Archambault B. , Fuller E. , Pierson B. , Arnquist I.J. , Harouaka K. , Schlieder T.D. , Kim D.K. , Melville A.J. , Niedzielski B.M. , Yoder J.L. , Serniak K. , Oliver W.D. , Orrell J.L. , Bunker R. , VanDevender B.A. , Warner M.
Published: September 2024

Ionizing radiation has been shown to reduce the performance
of superconducting quantum circuits. In this report, we evaluate the
expected contributions of different sources of ambient radioactivity
for typical superconducting qubit experiment platforms. Our
assessment of radioactivity inside a typical cryostat highlights the
importance of selecting appropriate materials for the experiment
components nearest to qubit devices, such as packaging and
electrical interconnects. We present a shallow underground facility
(30-meter water equivalent) to reduce the flux of cosmic rays and a
lead shielded cryostat to abate the naturally occurring radiogenic
gamma-ray flux in the laboratory environment. We predict that
superconducting qubit devices operated in this facility could
experience a reduced rate of correlated multi-qubit errors by a
factor of approximately 20 relative to the rate in a typical
above-ground, unshielded facility. Finally, we outline overall
design improvements that would be required to further reduce the
residual ionizing radiation rate, down to the limit of current
generation direct detection dark matter experiments.
Digital input requirements for global carbon emission reduction
Authors: Jiang Meihui , Cai Wenlin
Published: September 2024

To answer the question of whether the growth of digital inputs can be beneficial for carbon neutrality, we thoroughly explore the impacts of digital inputs on carbon emission reduction in this work. We propose a combined framework of panel regression model and multi-objective optimization model to identify the key digital sectors and obtain their optimal total outputs. First, the results show that digital inputs continue to increase in most countries (regions) from 2000 to 2021, especially in the USA, EU countries and China. Digital equipment inputs in China are the most significant, while digital service inputs in the USA and EU countries are relatively important. Second, the regression results show that digital service inputs have significantly negative influence on carbon emissions, which means that the growth of digital service inputs will decrease carbon emissions. This result indicates that the key point of industrial digitalization for carbon emission reduction may be increasing the digital service inputs. Third, the optimization results show that the digital-input-oriented optimization model, which encourages an increase in digital service inputs, could achieve greater targets of economic growth and carbon emission reduction. The total outputs of Telecommunication Services and Computer Services should increase globally by 10.24% and 8.89%, respectively.
Comparison of the risks and drivers of compound hot-dry and hot-wet extremes in a warming world
Authors: Zeng Jianxin , Zhang Shulei , Zhou Sha , Obulkasim Omarjan , Zhang Han , Lu Xingjie , Dai Yongjiu
Published: September 2024

Compound hot-dry (CHD) and compound hot-wet (CHW) extremes have both intensified under global warming, posing exacerbated socio-economic threats compared to univariate extremes. This study presents a comprehensive assessment and comparison of the historical changes and driving factors behind CHD and CHW using observational data and climate model simulations. Findings indicate a notable surge in CHD and CHW occurrences, with CHW experiencing a higher increasing rate. Our investigation further reveals that anthropogenic climate change predominantly drives the increase in both types of compound extremes, especially for CHW. In contrast, land-atmosphere feedbacks have a limited impact on CHW at a global scale, but substantially contributes to the rise in CHD by reinforcing the negative precipitation-temperature coupling. This influence even surpasses that of anthropogenic climate change in specific regions. Understanding these variations and underlying causes is crucial for improving prediction accuracy and mitigating the impacts of compound extremes.
Divergent changes in crop yield loss risk due to droughts over time in the US
Authors: Rathore Lokendra S , Kumar Mukesh , Moftakhari Hamed , Ganguli Poulomi
Published: September 2024

Drought poses a major threat to agricultural production and food security. This study evaluates the changes in drought-induced crop yield loss risk for six crops (alfalfa, barley, corn, soybean, spring wheat, and winter wheat) between 1971–2000 and 1991–2020 across the contiguous US. Using a copula-based probabilistic framework, our results reveal a spatially heterogeneous change in yield risk to meteorological droughts, which varies with crop types. Regional analyses identify the largest temporal decline in yield risk in the Southeast and Upper Midwest, while the Northwest and South show an increase in risk. Among the considered anthropogenic and climatic drivers of crop productivity, changes in climatic variables such as high temperatures (e.g., killing degree days), vapor pressure deficit and precipitation show significantly stronger associations with changes in yield risk than irrigated area and nitrogen fertilizer application. Among the counties that observe drier drought events, only 55% exhibit an increase in crop yield loss risk due to drier droughts. The rest 45% show a decrease in yield loss risk due to mediation of favorable climatic and anthropogenic factors. Alarmingly, more than half (for barley and spring wheat), and one-third (for alfalfa, corn, soybean and winter wheat) of that the risk increasing regions have outsized influence on destabilizing national crop production. The findings provide valuable insights for policymakers, agricultural stakeholders, and decision-makers in terms of the potential ways and locations to be prioritized for enhancing local and national agricultural resilience and ensuring food security.
Increasing the strength of potato digger elevator rods
Authors: Bayboboyev N , Toshtillayev Sh , Akbarov Sh , Umirzokov J
Published: September 2024

Currently, high-quality steels are used to increase the reliability of potato digging machines and the durability of elevator rods. Recently, new materials, new technologies and non-metallic materials that are not inferior in strength to steel have been used in agricultural machines. Such materials significantly reduce the mass of the working parts. This article examines the deformation of a new elevator rod design due to the action of soil and tuber-bearing mass. The rods, covered with double-cavity rubber profiles, vibrate the component of the potato heap. During vibrations, in addition to static deformations, dynamic deformations occur, depending on the magnitude of the impact force. As a result, it was found that to eliminate the loss of tubers between the bars of the separating elevator, given the maximum deflection value of 0.03 m and the weight of the soil-tuber-bearing mass, the rubber bar must have the following parameters: elasticity model E = 50 N/mm2; rod perimeter 11x11 mm; the maximum jump height of a mass weighing 130 kg is no more than 0.6 m.
Research of ultrasonic sensors for measuring water flow in hydromelioration objects
Authors: Djalilov A , Nazarov O , Sobirov E , Gayipov I , Abdunabiev D , Urolov S
Published: September 2024

Currently, many countries are experiencing water shortages, which requires efficient use of available water resources. Therefore, there is an increasing need for simple, reliable and inexpensive water flow measurement devices with high measurement accuracy. This article researched an ultrasonic device for measuring water flow, operating on the basis of the time-pulse method. The device was based on an STM32 microcontroller, and a high-precision TDC-GP22 converter was used to generate ultrasonic signals and subsequently collect the difference in their propagation time. The main advantages of the proposed device are ease of use and low power consumption. The experiment’s findings indicate that the water flow meter being examined can be effectively utilized at hydromelioration sites.
From consumption to context: assessing poverty and inequality across diverse socio-ecological systems in Ghana
Authors: Cavanaugh Alicia C , Bixby Honor R , Mangwani Saeesh , Agyei-Mensah Samuel , Awuni Cynthia Azochiman , Baumgartner Jill C , Owusu George , Robinson Brian E
Published: September 2024

Local social and ecological contexts influence the experience of poverty and inequality in a number of ways that include shaping livelihood opportunities and determining the available infrastructure, services and environmental resources, as well as people’s capacity to use them. The metrics used to define poverty and inequality function to guide local and international development policy but how these interact with the local ecological contexts is not well explored. We use a social-ecological systems (SES) lens to empirically examine how context relates to various measures of human well-being at a national scale in Ghana. Using a novel dataset constructed from the 100% Ghanian Census, we examine poverty and inequality at a fine population level across and within multiple dimensions of well-being. First, we describe how well-being varies within different Ghanian SES contexts. Second, we ask whether monetary consumption acts a good indicator for well-being across these contexts. Third, we examine measures of inequality in various metrics across SES types. We find consumption distributions differ across SES types and are markedly distinct from regional distributions based on political boundaries. Rates of improved well-being are positively correlated with consumption levels in all SES types, but correlations are weaker in less-developed contexts like, rangelands and wildlands. Finally, while consumption inequality is quite consistent across SES types, inequality in other measures of living standards (housing, water, sanitation, etc) increases dramatically in SES types as population density and infrastructural development decreases. We advocate that SES types should be recognized as distinct contexts in which actions to mitigate poverty and inequality should better incorporate the challenges unique to each.
Deciphering the degradation of sulfonamides by UV/chlorination in aqueous solution: kinetics, reaction pathways, and toxicological evolution
Authors: Bano Shah , Shad Asam , Alqhtani Haifa A , Bin-Jumah May , Altoom Naif G , Allam Ahmed A
Published: September 2024

UV/Cl is a cost-effective process and is often used in municipal water treatment plants as well as in industrial applications. UV/Cl method is found highly effective in degrading contaminants, including pathogens, The conventional methods for water treatment have been proven inefficient for the complete elimination of pollutants and generate harmful by-products in the environment. This study evaluated the efficacy of three different treatment methods, chlorination alone, UV photolysis, and UV/Cl, for the degradation of sulfonamides (SAs) in water. The results highlighted that UV/Cl treatment was an efficient method for enhancing the degradation of sulfisoxazole (SFX), sulfadimethoxine (SAT), and sulfaguanidine (SG), with substrates degrading in 5, 6.5, and 4 min. The study also investigated the reactive species generated in the UV/Cl system and found that ·OH was the species responsible for the elimination of SFX. Additionally, the study explored the intermediate products generated during the degradation of SFX under the UV/Cl system, identifying VI distinct degradation pathways. The presence of ·OH radicals significantly enhanced the degradation of SFX, while some chlorine species also contributed to the degradation. The study predicted the toxicity of degradation products from the UV/Cl system using the ECOSAR (Ecological Structure Activity Relationships) program and found that the final degradation products of SFX were non-toxic, but concerns were raised about acute toxicity.
Evaluating D-InSAR performance to detect small water level fluctuations in two small lakes in Sweden
Authors: Aminjafari Saeid , Brown Ian A , Jaramillo Fernando
Published: September 2024

Monitoring lake water level fluctuations is critical for managing water resources, predicting the impacts of climatic change, and preserving ecosystem services lakes provide. However, traditional gauging stations are insufficient to monitor all lakes worldwide due to the large number of existing lakes, the challenges of installation and maintenance, and the remote locations of some. Although satellite altimetry is an alternative for measuring water levels, it cannot monitor small lakes effectively. This study evaluates the potential of Differential Interferometric Synthetic Aperture Radar (D-InSAR) for tracking minor water level changes in small lakes, a method more typically used in wetland studies. We investigate two Swedish lakes using Sentinel-1A and Sentinel-1B data from 2019, generating six-day interferograms and filtering out those with in situ water level changes exceeding one phase cycle. Our results show that D-InSAR can detect small water level changes with Lin’s correlations up to 0.63 and 0.89 and RMSE values of approximately 9 and 4 mm, respectively. These results evidence the potential of future L-band SAR missions with larger wavelengths, such as the NASA-ISRO SAR (NISAR) of the National Aeronautics and Space Administration (NASA) and the Indian Space Research Organisation (ISRO), to track water level changes in lakes and aid water tracking missions such as the SWOT (Surface Water and Ocean Topography).
Water structures and anisotropic dynamics at Pt(211)/water interface revealed by machine learning molecular dynamics
Authors: Wang Fei-Teng , Liu Xiandong , Cheng Jun
Published: September 2024

Water molecules at solid–liquid interfaces play a pivotal role in governing interfacial phenomena that underpin electrochemical and catalytic processes. The organization and behavior of these interfacial water molecules can significantly influence the solvation of ions, the adsorption of reactants, and the kinetics of electrochemical reactions. The stepped structure of Pt surfaces can alter the properties of the interfacial water, thereby modulating the interfacial environment and the resulting surface reactivity. Revealing the in situ details of water structures at these stepped Pt/water interfaces is crucial for understanding the fundamental mechanisms that drive diverse applications in energy conversion and material science. In this work, we have developed a machine learning potential for the Pt(211)/water interface and performed machine learning molecular dynamics simulations. Our findings reveal distinct types of chemisorbed and physisorbed water molecules within the adsorbed layer. Importantly, we identified three unique water pairs that were not observed in the basal plane/water interfaces, which may serve as key precursors for water dissociation. These interfacial water structures contribute to the anisotropic dynamics of the adsorbed water layer. Our study provides molecular-level insights into the anisotropic nature of water behavior at stepped Pt/water interfaces, which can influence the reorientation and distribution of intermediates, molecules, and ions—crucial aspects for understanding electrochemical and catalytic processes.