bluuebunny/crossref_metadata_2025 huggingface dataset:
Training in Sylvian Arachnoid Dissection: The Art of Using Kamiyama Scissors and a Simple Novel Model for Practice Sylvian Arachnoid Dissection Using Cotton Fiber with Brain Model
Authors: Ariyaprakai Chanon , Kusdiansah Muhammad , Degollado-García Javier , Ota Nakao , Noda Kosumo , Kamiyama Hiroyasu , Tanikawa Rokuya
Published: June 2024

Background Transsylvian approach is one of the main approaches for a variety of vascular, tumor, and skull-base lesions. Sylvian fissure harbors a lot of critical structures including the middle cerebral artery and many venous structures. If not done properly, the transsylvian approach could cause several complications. Up to now, there is no simple training model for practicing Sylvian fissure dissection. In this article, we describe the technique of using microscissors for the sharp dissection of arachnoid trabeculae. We also propose a new model for practicing Sylvian arachnoid dissection using a three-dimensional (3D) brain model with cotton fiber.

Materials and Method We inserted cotton fiber into the Sylvian fissure of the brain model (aneurysm box from UpsurgeOn) and covered the Sylvian fissure with a cotton sheet, then sprayed the water over it. We dissected this model under a microscope by using Kamiyama scissors in the right hand and suction in the left hand.

Result Under the microscope, our model appears comparable with the real Sylvian fissure. We can use this model for practicing arachnoid dissection with Kamiyama scissors.

Conclusion The arachnoid dissection model by using a 3D brain model with cotton fiber is a simplified and novel approach for practicing the Sylvian fissure dissection.
Pragmatism and protest: Russia’s communist party through Covid-19 and beyond
Authors: Blackburn Matthew , Hutcheson Derek S.
Published: June 2024

The Covid-19 epidemic came at a sensitive time for Russia’s leadership, which was attempting a political reset and structural reforms, including the removal of President Putin’s presidential term limits. This article examines how issues related to the pandemic provided new opportunities for the systemic opposition, the Communist Party of the Russian Federation, who emerged as the main beneficiaries after capitalising on opportunities created by the epidemic. The underappreciated role of systemic opposition parties in electoral authoritarian systems, which balance “voice” and “loyalty” to benefit both themselves and the regime, is examined in the context of the Covid-19 crisis.
Bitcoin’s bubbly behaviors: does it resemble other financial bubbles of the past?
Authors: Náñez Alonso Sergio Luis , Jorge-Vázquez Javier , Echarte Fernández Miguel Ángel , Sanz-Bas David
Published: June 2024

A number of financial bubbles have occurred throughout history. The objective of this study was to identify the main similarities between Bitcoin price behavior during bubble periods and a number of historical bubbles. Once this had been carried out, we aimed to determine whether the solutions adopted in the past would be effective in the present to reduce investors’ risk in this digital asset. This study brings a new approach, as studies have previously been conducted analyzing the similarity of Bitcoin bubbles to other bubbles individually, but these were not conducted in such a broad manner, addressing different types of bubbles, and over such a broad time period. Starting from a dataset with 9967 records, a combined methodology was used. This consisted of an analysis of the standard deviations, the growth rates of the prices of the assets involved, the percentage increase in asset prices from the origin of the bubble to its peak and its fundamental value, and, finally, the bubble index. Lastly, correlation statistical analysis was performed. The results obtained from the combination of the above methods reveal the existence of certain similarities between the Bitcoin bubbles (2011, 2013, 2017, and 2021) and the tulip bubble (1634–1637) and the Mississippi bubble (1719–1720). We find that the vast majority of the measures taken to avoid past bubbles will not be effective now; this is due to the digital and decentralized nature of Bitcoin. A limitation of the study is the difficulty in making a comparison between bubbles that occurred at different historical points in time. However, the results obtained shed light and provide guidance on the actions to be taken by regulators to ensure the protection of investors in this digital asset.
Insights into the mechanobiology of cancer metastasis via microfluidic technologies
Authors: Liang Lanfeng , Song Xiao , Zhao Hao , Lim Chwee Teck
Published: June 2024

During cancer metastasis, cancer cells will encounter various microenvironments with diverse physical characteristics. Changes in these physical characteristics such as tension, stiffness, viscosity, compression, and fluid shear can generate biomechanical cues that affect cancer cells, dynamically influencing numerous pathophysiological mechanisms. For example, a dense extracellular matrix drives cancer cells to reorganize their cytoskeleton structures, facilitating confined migration, while this dense and restricted space also acts as a physical barrier that potentially results in nuclear rupture. Identifying these pathophysiological processes and understanding their underlying mechanobiological mechanisms can aid in the development of more effective therapeutics targeted to cancer metastasis. In this review, we outline the advances of engineering microfluidic devices in vitro and their role in replicating tumor microenvironment to mimic in vivo settings. We highlight the potential cellular mechanisms that mediate their ability to adapt to different microenvironments. Meanwhile, we also discuss some important mechanical cues that still remain challenging to replicate in current microfluidic devices in future direction. While much remains to be explored about cancer mechanobiology, we believe the developments of microfluidic devices will reveal how these physical cues impact the behaviors of cancer cells. It will be crucial in the understanding of cancer metastasis, and potentially contributing to better drug development and cancer therapy.
Dissolvable photovoltaic cells on hydrogel
Authors: Li Benxuan , Zhan Shijie , Li Zhe , Ming Wenlong , Amaratunga Gehan A. J. , Hou Bo
Published: June 2024

Solar energy is potentially the largest source of renewable energy for providing electrical power for human society. However, significant advances are required to make photovoltaic technologies have a low-carbon footprint in manufacture, be environmentally friendly at the end of their lives through recyclability, and be biodegradable. Here we report dissolvable organic photovoltaic devices based on poly(2-hydroxyethyl methacrylate), which show equal power conversion efficiency to their glass substrate-based counterparts. We use a novel method of including smectic liquid crystal (7-dioctyl[1]benzothieno[3,2- b][1]benzothiophene, C8-BTBT) as a crystal phase regulator in the heterojunction donor:acceptor polymer system to maintain the disposable organic solar cell efficiency without pre- or post-thermal annealing. The results show strong promise not only for more sustainable solar-cell fabrication but also as disposable and biocompatible solar cells for self-powered (energy harvesting) wearable and biomedical devices.
Electrodynamic interaction between tumor treating fields and microtubule electrophysiological activities
Authors: Li Xing , Liu Kaida , Fang Haohan , Liu Zirong , Tang Yuchen , Dai Ping
Published: June 2024

Tumor treating fields (TTFields) are a type of sinusoidal alternating current electric field that has proven effective in inhibiting the reproduction of dividing tumor cells. Despite their recognized impact, the precise biophysical mechanisms underlying the unique effects of TTFields remain unknown. Many of the previous studies predominantly attribute the inhibitory effects of TTFields to mitotic disruption, with intracellular microtubules identified as crucial targets. However, this conceptual framework lacks substantiation at the mesoscopic level. This study addresses the existing gap by constructing force models for tubulin and other key subcellular structures involved in microtubule electrophysiological activities under TTFields exposure. The primary objective is to explore whether the electric force or torque exerted by TTFields significantly influences the normal structure and activities of microtubules. Initially, we examine the potential effect on the dynamic stability of microtubule structures by calculating the electric field torque on the tubulin dimer orientation. Furthermore, given the importance of electrostatics in microtubule-associated activities, such as chromosome segregation and substance transport of kinesin during mitosis, we investigate the interaction between TTFields and these electrostatic processes. Our data show that the electrodynamic effects of TTFields are most likely too weak to disrupt normal microtubule electrophysiological activities significantly. Consequently, we posit that the observed cytoskeleton destruction in mitosis is more likely attributable to non-mechanical mechanisms.
A compact quad-square negative-index metamaterial: Design, simulation, and experimental validation for microwave applications
Authors: Khalil Muhammad Amir , Yong Wong Hin , Hoque Ahasanul , Islam Md. Shabiul , Chiong Lo Yew , Chin Leei Cham , Alzamil Ahmed , Islam Mohammad Tariqul
Published: June 2024

This research provides a detailed explanation of the design, simulation, and experimental of quad-square metamaterial-based negative-index unit cells for S-band applications. The Computer Simulation Technology 2022 licensee version was utilized to design and obtain numerical results for the unit cell. The proposed unit cell for the metamaterial has dimensions of 5 × 5 × 1.57 mm3. The substrate chosen was FR-4, resulting in a substantial effective medium ratio value of 19.07. A series of systematic parametric studies were conducted to optimize the quad square metamaterial structure. Key parameters, such as substrate types, unit cell arrays, thicknesses of substrate, and split gaps, were varied to determine their impact on the structure. The validated equivalent circuit result was compared to the simulated results, showing a significant agreement. The demonstrated correlation between simulation and experimental data highlights the dependability of the proposed quad-square metamaterial, positioning it as a viable option for a range of electromagnetic applications, such as communication systems, sensors, and imaging devices.
The electron jet in relativistic laser-plasma with circular magnetic fields
Authors: Zhao ZuYang , Liu Xiaolan , Liu SanQiu , Li XiaoQing , Huang Tao
Published: June 2024

Self-generated magnetic field and electron jet are observed when ultra-intense lasers (>1×1018W/cm2) interact with plasma. It is found that the self-generated magnetic field plays a significant role in the generation of electron jets. The generation mechanism of electron jets under the influence of a self-generated circular magnetic field is examined. It is revealed that magnetic modulation of self-generated magnetic fields can result in the collapse of these fields, consequently leading to the production of electron jets. Furthermore, it has been discovered that the velocity of the electron jets is associated with the maximum growth rate of the modulational instability. As the maximum growth rate of the modulational instability decreases, the velocity of the electron jets is reduced. The present work aids in getting a deeper understanding of the generation of electron jets in relativistic laser plasmas.
Reliability inference based on inverted exponentiated Rayleigh lifetime distribution under unified hybrid censored scheme
Authors: Tashkandy Yusra A. , Hasaballah Mustafa M. , Bakr M. E. , Balogun Oluwafemi Samson , Ramadan Dina A.
Published: June 2024

In this study, we investigated the Inverted Exponentiated Rayleigh Distribution (IERD), a significant and efficient continuous lifetime distribution commonly applied in lifespan research. Our focus was on estimating unknown parameters for a two-parameter inverted exponentiated Rayleigh distribution using unified hybrid censored data. We considered both maximum likelihood and Bayesian estimation approaches. Specifically, we employed the Gibbs within Metropolis–Hastings samplers method to develop approximate Bayes estimators utilizing informative and non-informative priors, along with symmetric and asymmetric loss functions. In addition, we utilized Markov chain Monte Carlo (MCMC) samples to derive maximum posterior density credible intervals. Simulation experiments were conducted to assess the efficacy of the proposed methodologies, and actual data analysis was performed to validate the proposed estimators.
Multiferroic neuromorphic computation devices
Authors: Lu Guangming , Salje Ekhard K. H.
Published: June 2024

Neuromorphic computation is based on memristors, which function equivalently to neurons in brain structures. These memristors can be made more efficient and tailored to neuromorphic devices by using ferroelastic domain boundaries as fast diffusion paths for ionic conduction, such as of oxygen, sodium, or lithium. In this paper, we show that the local memristor generates a second, unexpected feature, namely, weak magnetic fields that emerge from moving ferroelastic needle domains and vortices. The vortices appear near ferroelastic “junctions” that are common when the external stimulus is a combination of electric fields and structural phase transitions. Many ferroelastic materials show such phase transitions near room temperatures so that device applications display a “multiferroic” scenario where the memristor is driven electrically and read magnetically. Our computer simulation study of an elastic spring model suggests magnetic fields in the order of 10−7 T, which opens the way for a fundamentally new way of running neuromorphic devices. The magnetism in such devices emerges entirely from intrinsic displacement currents and not from any intrinsic magnetism of the material.
Evaluating language models for mathematics through interactions
Authors: Collins Katherine M. , Jiang Albert Q. , Frieder Simon , Wong Lionel , Zilka Miri , Bhatt Umang , Lukasiewicz Thomas , Wu Yuhuai , Tenenbaum Joshua B. , Hart William , Gowers Timothy , Li Wenda , Weller Adrian , Jamnik Mateja
Published: June 2024

There is much excitement about the opportunity to harness the power of large language models (LLMs) when building problem-solving assistants. However, the standard methodology of evaluating LLMs relies on static pairs of inputs and outputs; this is insufficient for making an informed decision about which LLMs are best to use in an interactive setting, and how that varies by setting. Static assessment therefore limits how we understand language model capabilities. We introduce CheckMate, an adaptable prototype platform for humans to interact with and evaluate LLMs. We conduct a study with CheckMate to evaluate three language models (InstructGPT, ChatGPT, and GPT-4) as assistants in proving undergraduate-level mathematics, with a mixed cohort of participants from undergraduate students to professors of mathematics. We release the resulting interaction and rating dataset, MathConverse. By analyzing MathConverse, we derive a taxonomy of human query behaviors and uncover that despite a generally positive correlation, there are notable instances of divergence between correctness and perceived helpfulness in LLM generations, among other findings. Further, we garner a more granular understanding of GPT-4 mathematical problem-solving through a series of case studies, contributed by experienced mathematicians. We conclude with actionable takeaways for ML practitioners and mathematicians: models that communicate uncertainty, respond well to user corrections, and can provide a concise rationale for their recommendations, may constitute better assistants. Humans should inspect LLM output carefully given their current shortcomings and potential for surprising fallibility.
On the co-optation of according to
as an evidential in English
Authors: Ziegeler Debra
Published: June 2024

The use of according to + NP has rarely been the topic of any specialized research in relation to
English evidentiality, although it would probably figure among the most frequent types of reportative evidentials found in written
texts. One of the problems often associated with reportatives has related to the existence of the Reportative Exception (see, e.g.
AnderBois 2014), referring to the fact that the speaker may not always subjectively
endorse the proposition conveyed with the support of the evidential phrase. The present study reviews the history of
according to + NP from Middle English onwards, after which it began to develop evidential functions, and
shows how the tendency to reject the truth of the content of the proposition marked by according to + NP arose in
specific contexts containing alternative information sources, comparison, or adversative clauses. It was shortly after the
diachronic appearance of according to + NP in such contexts that the more periphrastic form, in
accordance with + NP, began to renovate/renew the earlier, non-evidential meanings of according to +
NP. The present study also attributes the development of according to + NP to a process of co-optation (e.g.
Heine 2013) rather than grammaticalization.
“Resident superhero”
Authors: Mullan Kerry
Published: June 2024

Situated at the intersection of social media communication and pragmatics of language use online, this article
will examine the social action of community veneration of a local plumber by members of a neighbourhood Facebook group, the vast
majority of whom do not know each other personally (nor necessarily the plumber). Particular attention will be paid to the way in
which this veneration is constructed over time through linguistic creativity and humour, such as limericks, exaggeration, and
various terms of reverence and hero worship. In addition to these linguistic devices, it will be shown how the participants
actively exploit the digital environment to create context-dependent humour through emojis, memes, and other graphics. The
selected examples will illustrate how this collaborative veneration and playfulness also strengthen the sense of belonging in this
group of online strangers.
Cooling of an object by forced convection
Authors: Dutra Mateo , Monteiro Martín , Martí Arturo C
Published: June 2024

We present an experiment on forced convection where a previously heated object is cooled under the effect of a controlled stream of air. We consider a square copper plate in which temperature variations can be considered negligible and we measure the cooling rate as a function of the average velocity of the air stream. We use a thermal camera to measure the temperature field and the cooling curves as a function of time for different conditions. An empirical relation between the characteristic cooling time and the mean velocity of the air stream is reported. The results obtained are discussed in the framework of simple dimensional models and their limits of validity.
Electric-field-controlled electronic structures and quantum transport in monolayer InSe nanoribbons
Authors: Ye Qian , Tang Shunxi , Du Yan , Liu Zhengfang , Wu Qingping , Xiao Xianbo
Published: June 2024

Electronic structures and quantum transport properties of the monolayer InSe nanoribbons are studied by adopting the tight-binding model in combination with the lattice Green function method. Besides the normal bulk and edge electronic states, a unique electronic state dubbed as edge-surface is found in the InSe nanoribbon with zigzag edge type. In contrast to the zigzag InSe nanoribbon, a singular electronic state termed as bulk-surface is observed along with the normal bulk and edge electronic states in the armchair InSe nanoribbons. Moreover, the band gap, the transversal electron probability distributions in the two sublayers, and the electronic state of the topmost valence subband can be manipulated by adding a perpendicular electric field to the InSe nanoribbon. Further study shows that the charge conductance of the two-terminal monolayer InSe nanoribbons can be switched on or off by varying the electric field strength. In addition, the transport of the bulk electronic state is delicate to even a weak disorder strength, however, that of the edge and edge-surface electronic states shows a strong robustness against to the disorders. These findings may be helpful to understand the electronic characteristics of the InSe nanostructures and broaden their potential applications in two-dimensional nanoelectronic devices as well.
The funneling effect in a non-Hermitian Anderson model
Authors: Turker Z , Yuce C
Published: June 2024

The topological funneling effect, i.e., the motion of an arbitrary excitation to a focal point of the lattice no matter where the lattice is excited, is a dynamical effect due to the non-Hermitian skin effect. This effect disappears in the presence of strong disorder where the system is topologically trivial. In Anderson localized regime with complex spectrum, the motion shows jumpy behavior and the focal point can be any point along the lattice as it is not possible to say its exact place in an experiment a priori. We study transport phenomena in a non-Hermitian system, exhibiting both funneling effect and non-Hermitian jumps. We show that the competition between the skin and Anderson localizations may result in the creation of an extended eigenstate. This can lead to disorder-induced dynamical delocalization in topologically nontrivial region.
A generalized analytical viscous model for steady-state atmospheric vortices
Authors: Yadav Kriti , Prasad Maurya Jagdish , Kumar Pandey Sanjay
Published: June 2024

This paper presents a generalised analytical viscous model for atmospheric vortices. All the velocity components are dependent on radial and axial coordinates. The model begins with radial velocity derived by Onishchenko et al (2021). Other components are derived from the governing equations. Rankine (1882) and Burgers (1948) models are used as the boundary condition for imposing cyclostrophic balance. All the velocity components of this model are bounded. The radial pressure is also deduced. Radial profiles of axial, azimuthal velocities and radial pressure are plotted. The azimuthal velocity derived with the Rankine model as the boundary condition shows a sharp turn at the core layer where it is maximum and increases with height, while the changes are smooth near the core and not necessarily maximum at the core for the Burgers boundary condition. The azimuthal component of velocity increases at lower altitudes but declines at higher ones. It shows a reverse trend in the inner and the outer regions close to the core radius. Further, radial velocity reduces in magnitude with height. In both cases, radial pressure is higher in the outer region but lessens gradually in the core to vanish at the axis. It also increases with height.
Cladding-free Fermi arc surface states and topological directional couplers in ideal photonic Weyl metamaterials
Authors: Li Mingzhu , Han Ning , Wang Yiran , Chai Yan , Zhao Rui , Qi Lu , Liu Shutian
Published: June 2024

Photons can freely propagate in a vacuum, making it not a simple insulator but rather a conductor for photons. Consequently, in topological photonics, domain wall structures with opposing effective mass terms are used as cladding to confine electromagnetic waves. This approach is necessary to demonstrate topological edge/surface waves and Fermi arc surface states (FASS). Here, we show that the cladding-free FASS with high field localization at the boundary can be achieved using ideal Weyl gyromagnetic metamaterials (GMs). In these GMs, the ideal Weyl semimetal phase exists due to the dispersionless longitudinal modes. At the boundary of the GMs-vacuum system, the cladding-free FASS connects the projections of Weyl nodes with opposite chirality, thanks to the bulk-boundary correspondence principle. We further confirm that chiral boundary modes can propagate without experiencing scattering or backward reflection, i.e., they can advance seamlessly approximately various types of defects. Remarkably, various types of topological directional couplers are achieved by utilizing cladding-free FASS in an ideal gyromagnetic medium. Our theoretical analysis reveals that the underlying operational principle for accomplishing these nonreflecting directional couplers is due to the single coupling channel between the cladding-free FASS and the multi-type scatterers of the continuous media. Furthermore, the controllable propagation and topological directional coupling of cladding-free FASS can be further explored by adjusting the ideal gyromagnetic medium and boundary configurations of the continuous media system. This research offers increased flexibility for the development of cladding-free and directionally coupled topological devices.
Effect of interlayer bonded bilayer graphene on friction
Authors: Li 李 Yao-Long 耀隆 , Tian 田 Zhen-Guo 振国 , Yin 尹 Hai-Feng 海峰 , Zhang 张 Ren-Liang 任良
Published: June 2024

We study the friction properties of interlayer bonded bilayer graphene by simulating the movement of a slider on the surface of bilayer graphene using molecular dynamics. The results show that the presence of the interlayer covalent bonds due to the local sp3 hybridization of carbon atoms in the bilayer graphene seriously reduces the frictional coefficient of the bilayer graphene surface to 30%, depending on the coverage of interlayer sp3 bonds and normal loads. For a certain coverage of interlayer sp3 bonds, when the normal load of the slider reaches a certain value, the surface of this interlayer bonded bilayer graphene will lose the friction reduction effect on the slider. Our findings provide guidance for the regulation and manipulation of the frictional properties of bilayer graphene surfaces through interlayer covalent bonds, which may be useful for applications of friction related graphene based nanodevices.
Stellarators with enhanced tritium confinement and edge radiation control
Authors: Boozer Allen H.
Published: June 2024

A stellarator design is described with the purpose of achieving three goals: (1) enhance the confinement time of tritium. (2) Have a sufficient density of high-Z impurities to radiate the thermal power escaping from the core while having an extremely low impurity density in the core. (3) Maintain a large fraction of the plasma in a burning plasma state with an optimal tritium fraction. Some features of this design could be used in tokamaks. Although having three confinement zones is natural for stellarators, it is not for tokamaks.
ICRH-related impurity source and control across experiments in H, D, T plasmas at JET-ILW
Authors: Chomiczewska A. , Gromelski W. , Ivanova-Stanik I. , Kowalska-Strzęciwilk E. , Wendler N. , Jacquet P. , Meigs A. , Mailloux J. , Menmuir S. , Karhunen J. , Lerche E. , Monakhov I. , Otin R. , Thomas B. , Dumortier P. , Van Eester D. , Barruzo M. , Bobkov V. , Brezinsek S. , Colas L. , Douai D. , Milanesio D. , Pawelec E. , Delabie E. , Lomanowski B. ,   JET Contributors
Published: June 2024

The experimental and theoretical analysis were focused on experiments conducted to assess the effect of plasma isotopes, protium (H), deuterium (D), and tritium (T) on ion cyclotron resonance heating (ICRH) related plasma wall interactions. Comparison of L-mode discharges with N = 1 3He and N = 1 H minority ICRH heating scenarios were done for different isotopes. For the selected pulses, the behaviour of high-Z, mid-Z and low-Z intrinsic impurity and radiated power behaviour was investigated based on data from VUV, visible spectroscopy, and bolometry diagnostic at Joint European Torus. It was found that for N = 1 3He scenario during radiofrequency antennas operation, core W, Ni content, Be source and the radiated power are higher for π/2 in comparison to dipole antenna phasing. Lowest core Ni, W content and radiated power is clearly observed for H plasmas in comparison to D and T, where for this ICRH scenario behaviour was similar. However, lower Be photon flux is observed for T in comparison to D plasmas. Be sputtering by He particles is responsible for such an effect. Additionally, several computer simulations were conducted using the COREDIV code. The difference in the electron temperature was due to the difference in the isotope masses. Increased temperature in the central plasma in the case of T plasmas leads to higher radiation in the central plasma in comparison to H plasmas. As a result, the power across separatrix is lower and the temperature on the divertor plate decreases with the increase of the isotope mass. At these temperatures on the divertor plate, W is not sputtered by the main plasma ions H, D and T and by He. For the N = 1 H ICRH scenario clear difference between D and T plasma was observed with higher metallic impurity content for T plasma in comparison to D. Impurity content in the plasmas is found to be sensitive to the power balance between the antenna straps. Its minimum is observed for the maximum of P
cen/P
tot.
Autonomous Robots Traverse Multi-Terrain Environments via Hierarchical Reinforcement Learning with Skill Discovery
Authors: Wang Yifan , Yao Meibao
Published: June 2024

Although deep reinforcement learning (DRL) has been widely used in robotic mapless navigation tasks, most of the current research focuses on structured environments such as indoor or maze scenes, and little is targeted on outdoor environments. Unlike indoor environments and mazes, outdoor fields tend to be unstructured with complex landforms and sparse rewards for robotic navigation. The performance of most DRL-based strategies is directly affected by the design of the reward function, which greatly deteriorates its generalizability to outdoor environments. To this end, here we propose a two-stage learning paradigm based on skill discovery and hierarchical reinforcement learning (HRL) to cope with this challenge. Specifically, we implement skill discovery through a pre-training stage to acquire diverse skills with terrain-adaptive exploration strategies; then we select multiple skills using HRL to cope with more complex scenarios. We carry out the robotic multi-terrain traverse task based on a high-fidelity robotic simulation platform, Webots, and implement extensive comparative experiments and ablation studies to demonstrate the effectiveness of our approach.
Situation Awareness of Mars helicopter based on YOLOv7
Authors: Qi Yifan , Xiao Xueming , Yao Meibao , Zhang Lei , Fu Yuegang
Published: June 2024

Situation awareness on Mars is indispensable for various downstream applications such as navigation and path planning, mapping and scientific discover. However, current Mars rover platform suffered from the absence of global information, leading to mission reduction and the failure of global planning. Compared to the rover, Mars helicopter is a new type of attempt for Mars exploration, which can provide a wide range view of scenes to well support the above missions. To this end, in this paper we proposed a novel learning-based situation awareness model for Mars helicopter. We modified the Yolov7 model by embedding a new channel attention on its head to improve the accuracy of detection. Besides, we designed a Tiny-Scale Detection Module (TSDM) to capture small or hidden rocks in complex Martian surface. To achieve further refinement and validate our proposal, we built an open-source synthetic dataset in air view. After extensive experiments, our model achieved excellent outperforms than the baseline model in our Mars dataset.
Manipulator Control System Based on Gesture Recognition for Space Operation
Authors: Yang Kaiyu , Xiao Xueming , Lin Boyu , Zhang Lei , Fu Yuegang
Published: June 2024

In the scenario of on-orbit servicing, the complex space environment and the strict limitation of spacesuits made the manual control of manipulator extremely inconvenient. Current remote-control methods such as voice control, are commonly affected by the signal ratio, especially in the case of solar wind. Therefore, in this paper, we proposed a gesture-based remote-control system for real-time manipulation of the space manipulator in order to accomplish the onboard tasks. Gesture-based control strategy is more friendly on human-machine interaction than voice control or manual control. The proposed method: utilized gesture recognition technique to perform scheduled tasks according to the preset gestures. For preset missions, specific gestures are recognized and matched through KNN algorithm, and then manipulator is driven to execute the scheduled tasks. To validate the efficiency of the proposed method, extensive experiments are carried out on simulation platforms and compared with the traditional method of gesture recognition using rotation angle and gesture recognition using CNN. Results demonstrated that our method outperforms the other two solutions in terms of accuracy and speed.
Kinematic accuracy reliability evaluation method of space deployable mechanism based on dynamic model
Authors: Liu Chang , Zhuang Xinchen , Sun Zhongchao , Yu Tianxiang
Published: June 2024

Space deployable mechanisms are widely used in aerospace missions. The uncertainties in the geometric or physical parameters seriously affect the kinematic accuracy of the mechanism during the deployment process. In this paper, a kinematic accuracy reliability evaluation method of the space deployable mechanism based on dynamic model and adaptive hybrid surrogate models is presented. Firstly, the dynamic model of the space deployable mechanism is established based on the Lagrange method, and the motion error function considering the factors such as the mass, dimension and load is established. In order to improve the efficiency, an adaptive hybrid surrogate model reliability evaluation method based on improved weight measurement method is further proposed. The weight measurement method considers the global errors and local errors of the models. Finally, the Monte Carlo method is used to verify the accuracy of the hybrid surrogate model method. The relative error of the failure probability calculated by the proposed method is within 2.5 %, indicating that the proposed method has high calculation accuracy and efficiency.
Sparse linear parameter-varying autoregressive moving average modelling of non-stationary gearbox vibration signals
Authors: Li Zihan , Liu Xuemei , Chen Yuejian
Published: June 2024

Gearboxes frequently operate under variable speed conditions, leading to the non-stationarity of collected monitoring signals. This paper proposes a sparse linear parameter-varying autoregressive moving average (Spa LPV-ARMA) model for fault detection of gearboxes under variable speed conditions. The Spa LPV-ARMA model integrates the advantages of LPV concepts, sparse models, and ARMA models. The proposed model has a more compact structure compared to the reported Spa LPV-AR model, which results in a lower ratio of parameter number to data amount, and the compact model structure also allows the Spa LPV-ARMA model to have higher computational efficiency during the testing phase. A simulation study was conducted to validate the performance of the proposed method. The results demonstrate that the Spa LPV-ARMA model exhibits superior modeling accuracy compared to the reported Spa LPV-AR model. Additionally, the fault detection method based on the Spa LPV-ARMA model achieves a higher fault detection rate when contrasted with a model that solely considers the autoregressive component.
Analysis and Experimental Study on Vibration Isolation Performance of Full-scale Turbofan Engine Mounting
Authors: Wang Jian-Qiang , Nie Yan-Ping , Chen Yong-Hui , Qun Yan , Chen Chun-Lan , Dong Wan-Yuan
Published: June 2024

At present, most of the turbofan engine use the articulated link mount to connect the engine to the wing, and the analysis and experimental research of articulated link mount are important means in the development of engine mount. In this paper, the vibration isolation performance analysis of a certain turbofan engine mounting was carried out, and a full-scale turbofan engine mounting vibration isolation test platform was established based on the four-terminal parameter method, and the engine simulation device - eccentric rotation excitation tester was developed, which simulates the real engine vibration through rotor imbalance, and the vibration isolation efficiency of a certain type of engine mount at the high and low pressure rotor frequency was obtained. The results show that the simulation and test results are very close, the error is within 15% at the low-frequency, and the error is within 5% at the high-frequency. The research of this paper can provide test evaluation means for my country to independently carry out the design and improvement for large passenger aircraft engine installation devices, and provide test basis for its design and finalization.
Modal analysis of honeycomb panel satellite structure based on MSC Apex
Authors: Sun Risi , Liu Xuefeng , He Ningbo
Published: June 2024

Modal analysis plays an important role in the process of Satellite structure development. In this paper, the honeycomb sandwich plate and the satellite structure are taken as the research objects, and the corresponding finite element models are established. The analysis results of the actual modeling of honeycomb plate and the equivalent modeling of sandwich sandwich plate are obtained, and the fundamental frequency deviation of the whole satellite structure is discussed when the equivalent correction coefficient γ of honeycomb plate is different. The results show that the maximum relative error of the modal frequency between the equivalent method of sandwich sandwich plate and the actual modeling is 2.8%. Therefore, the equivalent method can be applied to large-scale finite element analysis and calculation, and the calculation efficiency can be improved. When the value of γ is 0.4∼0.6, the vibration modes of the whole satellite structure are basically consistent, and the maximum fundamental frequency difference is 10%. The results can evaluate the accuracy of the sandwich sandwich plate equivalent method for satellite mechanical analysis.
Dynamic Load Identification at Natural Frequencies for Aircraft via Attention Based 1D-CNN
Authors: He Wenbo , Li Baoqing , Feng Zhenyu , Zhang Xiaoqiang , Sun Hanyu
Published: June 2024

Since the frequency response function is ill-conditioned at the natural frequency of the system, the traditional load identification method based on the system parameters is no longer applicable. Aiming at the difficulty of dynamic load identification at the natural frequency of the structural system, a dynamic load identification method at the natural frequency of the structure based on one-dimensional convolutional neural network(1D-CNN) with attention mechanism is proposed. Specifically, the high-level features in the vibration response signal are first extracted through the convolution layer. Then the weight matrix of the network is updated by backpropagation algorithm, which represents the importance of different features. The mapping relationship between response and load is established to realize the task of load identification. From the trained data, the attention module learns the contribution of features according to the different contribution of different features to load prediction. The important components in the response signal are highlighted and noise pollution is suppressed. Excitation and response signals at the natural frequency of the system were acquired using exciters and an accelerometer mounted on the GARTEUR aircraft model. Excitation and response signals at the natural frequencies of the system are obtained by an exciter and accelerometer mounted on the GARTEUR aircraft model. The responses of the model at the first three natural frequencies of 6.4Hz,35.8Hz and 48.5Hz were obtained respectively. Experimental results show that compared with the traditional TSVD load identification method, the maximum error of this method is only 3.19%. Compared with the 1D-CNN method, the proposed method has stronger robustness under 20%, 50% and 80% noise levels.
Determining the start to degradation time of bearings using the improved diversity entropy
Authors: Zhang Jingyi , Bai Rui
Published: June 2024

Rolling element bearing is an essential part of rotating components. If the rolling element bearing is broken, it may cause damage to the system and even pose a threat to life health, and property safety. Therefore, the rolling element bearing’s health condition needs to be monitored and forecasted, thereby reducing unplanned downtime and improving bearing productivity. It is also important to determine the start to degradation time (SDT) when monitoring and predicting the condition of rolling bearings. Determining the SDT can help monitor the degradation process of the bearing so that it can be repaired or replaced in time. To facilitate the determination of the SDT of the bearing, a new method is proposed to adaptively determine the SDT of rolling element bearings by using the improved diversity entropy. In this way, early warning signs can be provided on time by determining the SDT. The run to failure experimental results show that the proposed improved diversity entropy method based determination of rolling bearing’s SDT has broad application prospects.
A novel feature mode decomposition method and its application for gear fault detection
Authors: Shi Huifang , Miao Yonghao , Lin Jing
Published: June 2024

Fault detection can promptly reveal the potential hazards of mechanical equipment, guaranteeing the safety, stability, and reliability of their operation. Although many advanced fault detection methods, such as spectral kurtosis, deconvolution and decomposition, have been developed, most of them still suffer from insufficient utilization of fault features and incomplete extraction of diagnostic information. Given this, we propose a novel method named feature mode decomposition (FMD). Firstly, to coarsely steer the decomposition direction, a finite impulse response (FIR) filter bank is set up with a window initialization. The, correlated kurtosis (CK) is taken to evaluate the latent fault-related information in mode signals, thereby guides the updating process of all adaptive filters, assisted with period estimation. Ultimately, the unnecessary and intermingled modes are weeded out by mode selection. Experimental cases verified that the proposed FMD can adaptively decompose the fault mode of gear fault signal with excellent inspection ability. Comparison between the results and those of the classical variational mode decomposition (VMD) further highlights that FMD is more robust to other interference and noise.
Research on non-contact dynamic stress calibration method of fan blade on simulation
Authors: Zhang Qiangbo , Dong Jiang , Zhang Shuai
Published: June 2024

In order to establish the non-contact measurement method of fan blade dynamic stress, the most important thing is to establish the method of fan blade dynamic stress calibration. In this paper, the static virtual loading and harmonious response analysis of fan blades in the simulation platform, and the calibration equation between the blade tip displacement and the blade dynamic stress is established. Finally, the calibration equation is verified and the error analysis is carried out by simultaneously carrying out contact and non-contact dynamic stress measurement tests on the rotor test bench.
Research on structural damage identification method of aircraft aluminium alloy skin based on power spectral entropy
Authors: Zhou Qiting , Sun Dingyi , Shen Ao , Xu Jianhao , Li Yongbo
Published: June 2024

Skin is an important structural component which covers the surface of aircraft widely, the structural health of skin has a great impact on the overall safety of aircraft. Due to the harsh operating environment, complex and changing working conditions, and high-intensity service process of aircraft, it is easy to cause damage to the skin. Thus, the in-situ health monitoring for aircraft skin is an effective approach to ensure its safety and reliability. Thanks to the ability of Lamb waves to propagate over long distances and recognize small-scale defects, they have shown great potential in the health monitoring of thin-walled structures and have received widespread attention. However, the traditional Lamb wave-based damage identification methods generally suffer from the problems of large number of sensors and low efficiency. Therefore, a skin damage identification method based on power spectral entropy is proposed in this paper, which can estimate the damage extent by extracting the nonlinear component increase caused by damage, and the experiments validate that the proposed method has higher sensitivity and computational efficiency than the existing other entropy-based methods.
Effects of viscosity and launch pressure on variations of the maximum impact acceleration in cross media water-entry process
Authors: Han Xiangdong , Li Chao , Wang Xiquan , Li Junzhi , Yun Kang , Li Zhe , Liu Baowei
Published: June 2024

The aim of the investigation was to experimentally discuss effects of viscosity and launch pressure on variations of the maximum impact acceleration in cross media water-entry process. For different launch pressures, they reflected effects of motion peculiarity. They were 2.5MPa, 2.75MPa, and 3.0MPa. Variations of viscosity explained influences of property of operating environment. Via the change of lithium bromide solution mass fraction, various viscosities were got. The mass fractions employed were 1%, 2%, and 3%. Results indicated that the maximum impact acceleration grew steadily with the increment of lithium bromide solution viscosity. When launch pressure grew, the maximum impact acceleration increased gradually. Comprehensively, effect degree of viscosity was more intense than that of the launch pressure.
Experimental investigation on effects of temperature and launch pressure on variations of the impact acceleration in cross media water-entry process
Authors: Han Xiangdong , Wang Xiquan , Li Chao , Chen Junbiao , He Lei , Yu Fangyan , Hu Xin
Published: June 2024

In the paper, effects of temperature and launch pressure on variations of the maximum impact acceleration in cross media water-entry process are systematically investigated via experiments. Results indicated that under the water entry angle of 25°, the maximum impact acceleration increased gradually with the growing of launch pressure from 2.5MPa to 3.0MPa when the temperature is 30°C, 40°C, and 50°C. The maximum impact acceleration decreased constantly with the increase of the temperature from 30°C to 50°C when launch pressure is the constant. According to the comprehensive analysis, effect degrees of variations of the launch pressure on the maximum impact acceleration are more significant than that of the variations of temperature.
Research on dynamic sealing performance of sealer structure under the influence of temperature
Authors: Lu Rende , Cheng Wenjia , Wei Ruitao , Li Liangqing , Lu Daosheng , Ren Xiaoyang
Published: June 2024

Affected by the extreme environment of high temperature and high pressure downhole, the mechanical behavior of the sealer rubber sleeve undergoes significant changes during service, leading to a sharp decline in the mechanical properties of the rubber material within the high-temperature environment. To address the issue of seal failure in the sealer rubber barrel under high-temperature loads, experimental investigations were conducted to analyze the compression properties of rubber materials at various temperatures. The constitutive parameters of the rubber were then fitted using the Reduce-Polynomial model. Subsequently, a finite element model was employed to study the sealing performance and mechanical response of the three-compartment rubber-tube structure sealer at different temperatures. The findings demonstrate that temperature fluctuations have a substantial impact on the sealing performance and bearing strength of the sealer. Consequently, this research holds crucial guiding significance for the structural design of the sealer rubber cylinder under high-temperature conditions.