bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-level Surfel Map Construction for Accurate Localization in Intelligent Vehicles
Authors: Li Yicheng , Ke ChangJing , Cai Yingfeng , Wang Hai 
Published: September 2024

Abstract
The role of mapping in achieving accurate localization in intelligent vehicles is crucial. Accurate maps enable intelligent vehicles to attain accuracy in localization and path planning, ultimately enhancing the safety and overall driving experience. However, the interference of dynamic objects poses a challenge to map updates and subsequent localization. To address this issue, this study proposes a novel algorithm for constructing multi-level semantic surfel maps, along with a corresponding hierarchical localization method. The proposed method divides the map into three levels: semantic level, surfel level, and trajectory level. During the map construction phase, we utilize semantic segmentation technology to accurately distinguish between static and dynamic environments, filter out dynamic point clouds, and focus solely on modeling static scenes. This effectively eliminates the interference of dynamic objects on map updates, ensuring the construction of a precise and reliable static environment model. In the subsequent hierarchical localization phase, a node-level localization method is introduced, which achieves coarse localization by matching perception information with the map.The results of experiments conducted in various scenarios indicate an average absolute trajectory error of 4cm between the transformation matrices of each node in the map. Our algorithm achieves a 92% success rate in node-level localization and an average pose-level localization error of 8.2cm, demonstrating the feasibility and robustness of the proposed algorithm.
Self-calibratable absolute modular rotary encoder: a theoretical feasibility study
Authors: Gurauskis Donatas , Mažeika Dalius , Kilikevičius Artūras 
Published: September 2024

Abstract
This paper introduces a self-calibratable absolute modular rotary encoder based on the equal division average method, designed to significantly enhance measurement accuracy and simplify installation. The proposed design integrates multiple optical sensors into the encoder stator Printed circuit board, enabling precise absolute position measurement through the averaging of sensors data. This multi-sensor approach compensates for alignment and installation inaccuracies, which are common issues in conventional modular encoders. To validate the design and predict encoder behaviour prior to manufacturing, a theoretical modelling of virtual optical sensors is performed. Based on experimentally collected cross-calibration data from a real optical encoder, this modelling framework enables to estimate the efficiency of self-calibration algorithm with sufficient accuracy and optimize the design and performance of the encoder. The obtained results confirm that the proposed measurement system significantly reduces error margin, improving the reliability and precision of position feedback. The initial position deviation of several hundreds of arcseconds might be reduced and kept below 8 arcseconds by using two or more additional optical sensors, even with the 0.5 mm misalignment of the encoder stator.
Dynamic modeling and vibration analysis for motorized spindle with uncertainties
Authors: Feng Wei , Shang Long , Liu Baoguo , Zhang Yun , Zhang Yao , Yang Huaiwen , Li Dongya 
Published: September 2024

Abstract
Uncertainties inevitably exist in motorized spindle and it is difficult to accurately describe its dynamics based on a deterministic model. In this paper, a dynamic model of motorized spindle with uncertainty is proposed. The deterministic dynamic model of the motorized spindle rotor system is built by the finite element method, and the uncertainties are constructed by the polynomial chaos expansion method. The impact of each uncertainty parameter on the critical speed of the system is investigated by adopting the Sobol global sensitivity analysis method. The effects of uncertainties including the bearing stiffness, the material Young’s modulus, the disc mass and the unbalanced excitation on the vibration response of motorized spindle are analyzed. The modal experiments are carried out to verify the effectiveness of the model. The results show that the uncertainties have a great influence on the vibration characteristics of the motorized spindle, in which the bearing stiffness mainly affects the high-order frequency response of the system, while the Young’s modulus affects all the order frequency response of the system. The influence of hybrid uncertainties on the frequency response of the system is more complex. This study provides a guidance to the design of motorized spindle.
A deep learning GNSS spoofing and jamming detection method with dual-frequency C/N0 heatmap
Authors: Wang Xiaoyan , Yang Jingjing , Huang Ming 
Published: September 2024

Abstract
The global navigation satellite system (GNSS) is vulnerable to interference due to the open signal structure and low signal strength, posing a significant threat to the billions of terminals worldwide that rely on GNSS receivers for precise positioning, navigation, and timing services. In this paper, we propose a cloud-edge framwork for GNSS spoofing and jamming monitoring, comprising the data acquisition module, GNSS monitoring module, detecting and reporting module. In this framwork, we design a deep learning (DL) method for detecting GNSS interference through Dual-frequency Carrier-to-Noise density ratio (C/N0
) heatmaps (DD-C/N0). This method involves extracting and correlating features from C/N0 heatmaps of visible navigation satellites operating in the GPS L1 and L2 frequency bands, allowing the identification of anomalous patterns. A U-BLOX receiver was utilized to capture the GNSS satellite signals, while commercial jammers and Software-defined radio (SDR) HackRF One kits were employed to simulate the interference sources. Experimental results demonstrate that the proposed method achieves significantly higher performance, with an accuracy of 99% and 98% on the public dataset and real-time testing data, compared to unsupervised, semi-supervised, and supervised detectors that rely solely on single-channel data (L1 frequency band). Integrated with the DD-C/N0 method, the online GNSS monitoring system will be improved and deployed to automate spoofing and jamming detection tasks in the next step.
Design of hybrid optimized PI controller for power conditioning circuit of piezoelectric energy harvester
Authors: Thulasi V , Lakshmi P , Sangeetha S 
Published: September 2024

Abstract
Piezoelectric energy harvesters (PEHs) are vital in the present day to encourage advancing technology through producing sustainable energy and dealing with economic and ecological issues associated with batteries. The required stable energy production from the PEH is challenging due to its erratic behaviour with input. As such, a power conditioning circuit with an optimized controller is proposed in this paper. The proportional integral (PI) controller is utilized to control the boost converter of the PEH system. The conventional approach of selecting the controller parameters, such as proportional gain (KP
) and integral gain (Ki
), fails to produce optimal outcomes and is time-consuming. Metaheuristic optimization techniques such as Aquila Optimization, African Vulture’s Optimization Algorithm (AVOA) and Hybrid Aquila Optimizer-based AVOA (HAOAVOA) are used to optimize the controller parameter. The different stages of the PEH system (rectifier, boost converter without controller, boost converter with un-optimized controller and boost converter with optimized controller) are simulated and analysed using MATLAB-SIMULINK®software. An experimental study is executed to validate the performance of the PEH system with optimized controller. The experimentally obtained response is compared with the simulation results. In which the HAOAVOA optimized PI controller gives the better response. Furthermore, the power conditioning circuit with a hybrid optimized controller produces an output of 12 V for the input of 6 V.
Extending discrete geometric singular perturbation theory to non-hyperbolic points
Authors: Jelbart S , Kuehn C 
Published: September 2024

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.