bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal-bonded perovskite lead hydride with phonon-mediated superconductivity exceeding 46 K under ambient pressure
Authors: He Yong , Du Juan , Liu Shi-ming , Tian Chong , Zhang Min , Zhu Yao-hui , Zhong Hong-xia , Wang Xinqiang , Shi Jun-jie
Published: February 2024

In the search for high-temperature superconductivity in hydrides, a plethora of multi-hydrogen superconductors have been theoretically predicted, and some have been synthesized experimentally under ultrahigh pressures of several hundred GPa. However, the impracticality of these high-pressure methods has been a persistent issue. In response, we propose a new approach to achieve high-temperature superconductivity under ambient pressure by implanting hydrogen into lead to create a stable few-hydrogen binary perovskite, Pb4H. This approach diverges from the popular design methodology of multi-hydrogen covalent high critical temperature (Tc
) superconductors under ultrahigh pressure. By solving the anisotropic Migdal–Eliashberg equations, we demonstrate that perovskite Pb4H presents a phonon-mediated superconductivity exceeding 46 K with inclusion of spin–orbit coupling, which is six times higher than that of bulk Pb (7.22 K) and comparable to that of MgB2, the highest Tc
achieved experimentally at ambient pressure under the Bardeen, Cooper, and Schrieffer framework. The high Tc
can be attributed to the strong electron–phonon coupling strength of 2.45, which arises from hydrogen implantation in lead that induces several high-frequency optical phonon modes with a relatively large phonon linewidth resulting from H atom vibration. The metallic-bonding in perovskite Pb4H not only improves the structural stability but also guarantees better ductility than the widely investigated multi-hydrogen, iron-based and cuprate superconductors. These results suggest that there is potential for the exploration of new high-temperature superconductors under ambient pressure and may reignite interest in their experimental synthesis in the near future.
Anomaly sound detection of industrial devices by using teacher-student incremental continual learning
Authors: Zhou Hao , Wang Kunpeng , Li Hu , Yang Wenhao , Yao Juan , Chai Yi
Published: February 2024

Normal production processes will be substantially impacted by industrial devices in abnormal working conditions. Anomaly sound detection (ASD) model can monitor the working condition of devices by the non-contact and non-invasive way. When new device data is introduced, traditional ASD models are trained using data from all devices, to accommodate every device. However, in real-world settings, the kinds and amounts of devices are constantly changing, which raises difficulties for the current ASD models. This paper proposes a teacher-student incremental learning method for ASD models, aiming to solve ASD model scalability problem. In this paradigm, teacher model has knowledge of all the old devices. The objective of student model is to learn new device knowledge, while avoiding the forgetting of old device knowledge. When student model learns new device data, teacher model transfers the acoustic feature knowledge of old devices to student model via knowledge distillation. Furthermore, the imbalance between old and new knowledge causes challenges, such as knowledge forgetting or lower learning efficiency for student model. This paper presents a dual-teacher-student (DTS) model to solve the problem of knowledge imbalance. Different teacher models for new and old devices in DTS, directing student model to accomplish continuous and deep integration of knowledge. Evaluation for proposed method on the DCASE 2020 Task2 dataset. The results show, the proposed method outperforms other methods in terms of learning capability and robustness during the incremental learning process. Analysis of significance test on the experimental results demonstrates that the method outperforms other methods statistically.
Tomo-PIV in a patient-specific model of human nasal cavities: a methodological approach
Authors: Tauwald Sandra Melina , Erzinger Florian , Quadrio Maurizio , Rütten Markus , Stemmer Christian , Krenkel Lars
Published: February 2024

The human nose serves as the primary gateway for air entering the respiratory system and plays a vital role in breathing. Nasal breathing difficulties are a significant health concern, leading to substantial healthcare costs for patients. Understanding nasal airflow dynamics is crucial for comprehending respiratory mechanisms. This article presents a detailed study using tomo-Particle Image Velocimetry (PIV) to investigate nasal airflow dynamics while addressing its accuracy. Embedded in the OpenNose project, the work described aims to provide a validation basis for different numerical approaches to upper airway flow. The study includes the manufacturing of a transparent silicone model based on a clinical CT scan, refractive index matching to minimize optical distortions, and precise flow rate adjustments based on physiological breathing cycles. This method allows for spatial high-resolution investigations in different regions of interest within the nasopharynx during various phases of the breathing cycle. The results demonstrate the accuracy of the investigations, enabling detailed analysis of flow structures and gradients. This spatial high-resolution tomo-PIV approach provides valuable insights into the complex flow phenomena occurring during the physiological breathing cycle in the nasopharynx. The study’s findings contribute to advancements in non-free-of-sight experimental flow investigation of complex cavities under nearly realistic conditions. Furthermore, reliable and accurate experimental data is crucial for properly validating numerical approaches that compute this patient-specific flow for clinical purposes.
Straightforward method for the electrochemical identification of dopamine in the presence of uric acid and ascorbic acid
Authors: Dung Nguyen Quoc , Toan Tran Quoc , Chuyen Pham Hong , Nang Lam Van , Dang Nguyen Van , Hien Trinh Ngoc , Anh Le Phuoc , Thanh Dang Van
Published: February 2024

A few-layer graphene/Pt (FGP) electrode and a novel electrochemical technique were used in determining dopamine and simultaneously detecting uric acid (UA), ascorbic acid (AA), and dopamine (DA) in a buffered phosphate-saline solution at pH 7.4. The FGP electrode effectively separated the oxidation peaks of UA, DA, and AA in the positive scan. Interestingly, during the negative scan, the FGP electrode selectively responded to DA while showing negligible response to UA and AA, thus allowing the accurate quantification of small amounts of DA in the presence of considerable UA and AA interferences. The sensors for AA, DA, and UA exhibited successful detection in the positive scan. The linear ranges were 10–1800 (AA), 1–300 (DA), and 5–800 (UA) µM, the sensitivity was 109.27 (AA), 754.19 (DA), and 493.03 (UA) µA cm–2 mM–1, and the detection limits were 4.2 µM (AA), 0.42 µM (DA), and 2.2 µM (UA). Furthermore, DA quantification was achieved in the negative scan, demonstrating a linear range of 1–100 µM, sensitivity of 2235.7 µA cm–2 mM–1, and detection limit of 0.14 µM. This study presents a novel and efficient electrochemical technique for the rapid and straightforward detection of dopamine.
Tailoring optical and photocatalytic properties of sulfur-doped boron nitride quantum dots via ligand functionalization
Authors: Cui Peng , Wu Qiulan
Published: February 2024

Boron nitride quantum dots (BNQDs) have emerged as promising photocatalysts due to their excellent physicochemical properties. This study investigates strategies to enhance the photocatalytic performance of BNQDs through sulfur-doping (S-BNQDs) and edge-functionalization with ligands (urea, thiourea, p-phenyl-enediamine (PPD)). To analyze the geometry, electronic structure, optical absorption, charge transfer, and photocatalytic parameters of pristine and functionalized S-BNQDs, we performed density functional theory calculations. The results showed that S-doping and ligand functionalization tune the bandgap, band energies, and introduce mid-gap states to facilitate light absorption, charge separation, and optimized energetics for photocatalytic redox reactions. Notably, the PPD ligand induced the most substantial bandgap narrowing and absorption edge red-shift by over 1 electron volt (eV) compared to pristine S-BNQD, significantly expanding light harvesting. Additionally, urea and PPD functionalization increased the charge transfer length by up to 2.5 times, effectively reducing recombination. On the other hand, thiourea functionalization yielded the most favorable electron injection energetics. The energy conversion efficiency followed the order: PPD (15.0%) > thiourea (12.0%) > urea (11.0%) > pristine (10.0%). Moreover, urea functionalization maximized the first-order hyperpolarizability, enhancing light absorption. These findings provide valuable insights into tailoring S-BNQDs through strategic doping and functionalization to develop highly efficient, customized photocatalysts for sustainable applications.
The wave mode transition of argon helicon plasma
Authors: Cui Ruilin , Zhang Tianliang , He Feng , Zheng Bocong , Ouyang Jiting
Published: February 2024

In this paper, multiple wave modes and transitions of argon helicon plasma excited by a half right-helical antenna in a system without any reflection endplate are investigated experimentally and theoretically at increasing radio frequency (RF) powers and external magnetic fields. Experiments show that above a critical magnetic field strength and pressure (about 250 G and 0.3 Pa in this work), two to four distinct wave-coupled modes and transitions were observed at increasing RF powers and/or magnetic fields. Theoretical analysis based on the dispersion relationship shows that in a high magnetic field, the helicon wave of the lowest order of axial eigenmode is always excited first, then the higher-order axial or radial mode; hence, the plasma density increases after mode jumping. There are two mechanisms responsible for the wave mode transitions in the present system, i.e. axial and radial mode transitions due to the change of axial and radial wavenumbers from a lower eigenmode to a higher one. A higher plasma density and magnetic field are helpful for achieving more higher-order modes of helicon waves.
Electrical characterization and imaging of discharge morphology in a small-scale packed bed dielectric barrier discharge
Authors: Rad Rezvan Hosseini , Brüser Volker , Brandenburg Ronny
Published: February 2024

Packed bed dielectric barrier discharges (DBDs) exhibit an improved energy efficiency and selectivity in nonthermal plasma based gas conversion. They enable the direct interaction between plasma and catalyst. In this contribution a compact coaxial DBD reactor enabling the end-on imaging of the discharge with and without packed beds is studied. The discharge morphology is correlated with electrical measurements such as voltage-charge (V-Q) plots. The studies are performed for different packed bed materials, binary gas compositions of argon and carbon dioxide, voltage amplitudes, average powers, and pressures. The analysis points outs the role of parasitic capacitances and parasitic discharges as often overlooked aspects. The introduction of the packed bed material into the coaxial barrier discharge arrangement increases the total capacitance, but the barrier of the outer glass tube mostly determines the maximum effective dielectric capacitance. The choice of the packed bed material determines the voltage threshold and the average discharge power. The investigations leads to a revision of the equivalent circuit for packed bed barrier discharge reactors, which also accounts the properties of different filling materials.
Nucleon-nucleon correlations inside atomic nuclei: synergies, observations and theoretical models
Authors: Dalal Ranjeet , Douglas MacGregor I J
Published: February 2024

While the main features of atomic nuclei are well described by nuclear mean-field models, there is a large and growing body of evidence which indicates an important additional role played by spatially-correlated nucleon–nucleon structures. The role of nucleonic structures was first suggested by Heidmann in 1950 to explain the pick-up reactions of energetic nucleons. Since then, a steady flux of new experimental evidence has confirmed the presence of similar structures inside atomic nuclei, dominated by correlations between pairs of nucleons. The role of these internal nucleon–nucleon correlations has been established using various energetic probes like photons, pions, leptons and hadrons. These correlated structures are essential for understanding the interaction of particles with nuclei and their presence provides an explanation of many specific nuclear phenomena, including backscattered protons, copious deuteron production, sub-threshold particle production, neutrino interactions with nuclei and the European Muon Collaboration effect. On the theoretical side, these measurements have stimulated a large number of phenomenological models specifically devised to address these enigmatic observations. While reviews exist for specific interactions, there is currently no published commentary which systematically encompasses the wide range of experimental signatures and theoretical frameworks developed thus far. The present review draws together the synergies between a wide range of different experimental and theoretical studies, summarizes progress in this area and highlights outstanding issues for further study.
Enhancing sparse regression modeling of hysteresis with optimized PIO algorithm in piezo actuator
Authors: Jin Yu , Yu Jianbo , Xu Yunlang , Lu Qiaodan , Yang Xiaofeng
Published: February 2024

The extensive application of piezo actuators is attributed to their high responsiveness and ability to achieve nanoscale steps. However, the accuracy and stability of motion are seriously affected by hysteresis caused by nonlinear characteristics. In this paper, a pigeon-inspired optimization (PIO) algorithm based on dynamic opposite learning (DOL) is proposed to address the issue of nonlinear modeling accuracy in piezo actuators by integrating the sparse identification of nonlinear dynamics (SINDy) method. Firstly, the DOL strategy is employed to introduce reverse pigeon flock into the PIO algorithm, thereby enhancing population diversity and optimization performance. Secondly, through combining the DOLPIO algorithm with the SINDy algorithm, sparse optimization for the penalty process in SINDy algorithm is conducted and the sparse coefficient is optimized based on modeling accuracy. Thirdly, the DOLPIO algorithm is utilized again to optimize the framework of optimized sparse penalty model in order to improve overall modeling accuracy. Finally, experiments are conducted on an established platform to validate the effectiveness of this algorithm.
Dynamic measurement of ballistic impact using an optical fibre sensor
Authors: Velasco Ivann , Seng Frederick , Hodges Greyson , Peters Kara , Pankow Mark , Schultz Stephen
Published: February 2024

An optical fibre-based sensor is developed for measuring the dynamics of the back face deformation of soft body armor. The measurement system consists of embedding an optical fibre into a thin silicone mat to increase survivability. The silicone sensor mat is placed between the soft body armor and the backing material. The optical fibre experiences times of sticking and slipping. The portions of the impact with the optical fibre stuck are reconstructed into slipping-equivalent strain using exponential extrapolation from adjacent slipping portions. The strain on the optical fibre is related to the projectile acceleration when the optical fibre is slipping. The strain is measured with the optical fibre sensor using a fibre Bragg grating. The system is characterized using a gas gun in combination with high-speed imaging. The system is experimentally demonstrated at the Army Test Center in Aberdeen, MD. Of the 23 shots 17 had an error less than 10%.
Generalization of Gisin’s theorem to quantum fields
Authors: Schlichtholz Konrad , Markiewicz Marcin
Published: February 2024

We generalize Gisin’s theorem on the relation between the entanglement of pure states and Bell non-classicality to the case of mode entanglement of separated groups of modes of quantum fields extending the theorem to cover also states with undefined particle number. We show that any pure state of the field which contains entanglement between two groups of separated modes violates some Clauser–Horne (CH) inequality. In order to construct the observables leading to a violation in the first step, we show an isomorphism between the Fock space built from a single-particle space involving two separated groups of modes and a tensor product of two abstract separable Hilbert spaces spanned by formal monomials of creation operators. In the second step, we perform a Schmidt decomposition of a given entangled state mapped to this tensor product space and then we map back the obtained Schmidt decomposition to the original Fock space of the system under consideration. Such obtained Schmidt decomposition in Fock space allows for construction of observables leading to a violation of the CH inequality. We also show that our generalization of Gisin’s theorem holds for the case of states on non-separable Hilbert spaces, which physically represent states with actually infinite number of particles. Such states emerge, for example, in the discussion of quantum phase transitions. Finally, we discuss the experimental feasibility of constructed Bell test and provide a necessary condition for realizability of this test within the realm of passive linear optics.
A step towards the diagnostic of the ITER first wall: in-situ LIBS measurements in the WEST tokamak
Authors: Favre Aurélien , Bultel Arnaud , Lamine Sankhe Mamadou , Vartanian Stéphane , Bruno Vincent , Morel Vincent , L’Hermite Daniel , Sirven Jean-Baptiste , Diez Mathilde , Missirlian Marc , Magaud Philippe , Grisolia Christian
Published: February 2024

As part of the development of proven diagnostics allowing the characterization of ITER’s PFUs (Plasma Facing Units) without dismantling, LIBS (Laser-Induced Breakdown Spectroscopy) is a serious candidate for determining the multi-elemental composition. In this article, we report a measurement campaign carried out within the WEST tokamak using an original device based on the following technological choices. (1) The laser source and the spectrometer are placed outside the tokamak. (2) The laser pulses are conveyed by an optical fiber. (3) The signals are collected by a second optical fiber. (4) The optical focusing and collection device is placed in the desired location by a remote handling arm (AIA, Articulated Inspection Arm). The processed signals allow the measurement of the composition of the irradiated material. The technological choices are discussed in the light of their implementation and proposals are made for a more efficient future version of the system.
Galaxy bias in the era of LSST: perturbative bias expansions
Authors: Nicola Andrina , Hadzhiyska Boryana , Findlay Nathan , García-García Carlos , Alonso David , Slosar Anže , Guo Zhiyuan , Kokron Nickolas , Angulo Raúl , Aviles Alejandro , Blazek Jonathan , Dunkley Jo , Jain Bhuvnesh , Pellejero Marcos , Sullivan James , Walter Christopher W. , Zennaro Matteo ,   The LSST Dark Energy Science collaboration
Published: February 2024

Upcoming imaging surveys will allow for high signal-to-noise measurements of galaxy clustering at small scales. In this work, we present the results of the Rubin Observatory Legacy Survey of Space and Time (LSST) bias challenge, the goal of which is to compare the performance of different nonlinear galaxy bias models in the context of LSST Year 10 (Y10) data. Specifically, we compare two perturbative approaches, Lagrangian perturbation theory (LPT) and Eulerian perturbation theory (EPT) to two variants of Hybrid Effective Field Theory (HEFT), with our fiducial implementation of these models including terms up to second order in the bias expansion as well as nonlocal bias and deviations from Poissonian stochasticity. We consider a variety of different simulated galaxy samples and test the performance of the bias models in a tomographic joint analysis of LSST-Y10-like galaxy clustering, galaxy-galaxy-lensing and cosmic shear. We find both HEFT methods as well as LPT and EPT combined with non-perturbative predictions for the matter power spectrum to yield unbiased constraints on cosmological parameters up to at least a maximal scale of k
max = 0.4 Mpc-1 for all samples considered, even in the presence of assembly bias. While we find that we can reduce the complexity of the bias model for HEFT without compromising fit accuracy, this is not generally the case for the perturbative models. We find significant detections of non-Poissonian stochasticity in all cases considered, and our analysis shows evidence that small-scale galaxy clustering predominantly improves constraints on galaxy bias rather than cosmological parameters. These results therefore suggest that the systematic uncertainties associated with current nonlinear bias models are likely to be subdominant compared to other sources of error for tomographic analyses of upcoming photometric surveys, which bodes well for future galaxy clustering analyses using these high signal-to-noise data.
Primordial Black Holes and loops in single-field inflation
Authors: Firouzjahi Hassan , Riotto Antonio
Published: February 2024

Using the δN formalism we calculate the one-loop correction to the large-scale
power spectrum of the curvature perturbation in the standard scenario where primordial black holes
are formed in the early universe thanks to a phase of ultra-slow-roll in single-field
inflation. We explicitly show that one-loop corrections are negligible when the transition from
the ultra-slow-roll to the slow-roll phase is smooth. We conclude that the PBH formation scenario
through a ultra-slow-roll phase is viable.
Mechanism of hydrogen isotope exchange for tritium removal in plasma-facing materials: a multi-scale investigation
Authors: Sun F. , Hao C. , Chen D.Y. , Zhou H.S. , Oya Y. , Zhu J.P. , Tang J. , Zong H. , Luo L.M. , Wu Y.C.
Published: February 2024

The safety of future fusion reactors is critically dependent on the tritium (T) retention in plasma-facing materials. Hydrogen isotope (HI) exchange offers a method to redistribute HIs within solid materials, presenting a feasible approach for removing T from bulk materials and trapped by strong trapping sites. Nonetheless, unraveling the intricate mechanism behind HI exchange remains an urgent yet formidable challenge. This study undertakes a comprehensive investigation into the mechanism of HI exchange in tungsten materials across multiple scales. First, we developed a multi-component hydrogen isotope transport and exchange model (HIDTX) based on classical rate theory. The model validation was further carried out, demonstrating good consistency with the well-controlled laboratory experiments. From the results of different comparative models in HIDTX, it is found that the reduction in deuterium retention due to HI exchange was primarily driven by three synergistic effects: competitive re-trapping, collision, and swapping effects. Through molecular dynamics (MD) and first-principles calculations, the microscopic mechanism of HI exchange was revealed to be that the presence of hydrogen atoms in the interstitial sites surrounding a vacancy in tungsten decreased the binding energy between the vacancy and hydrogen. Meanwhile, we discovered that the combination of thermal desorption and HI exchange can significantly lower the temperature required for the hydrogen removal and enhance the removal rate. Particularly, the hydrogen removal time can be shortened by approximately 95% with simultaneous HI exchange compared to that with only thermal desorption. This work provides a practical guideline for comprehending and subsequently designing for efficient T removal in future nuclear fusion materials.
Simulation of the degraded (steel - concrete) bond strength due to corrosion via modeling pull out tests
Authors: Koulouris Konstantinos , Charalampopoulos Alkiviadis , Apostolopoulos Charis
Published: February 2024

Steel corrosion is recognised as major degradation factor of structural capacity and durability of reinforced concrete (RC) structures, especially in marine environment. RC structures with corroded reinforcement present reduced performance due to loss of the cross-sectional area of reinforcement, cracks in concrete and loss of bond between steel and the surrounding concrete. In the present study, simulation of the degraded bond strength on corroded RC elements was elaborated developing a three-dimensional (3D) model through finite element analysis (FEA) in ABAQUS, taking into account the recommendations of fib Model Code 2010. As a basis for the model validation, an existing experimental study on the effect of corrosion and stirrups spacing on bond behavior was considered. In the abovementioned study the bond mechanism of two groups of corroded RC specimens in confined (stirrups Φ8/120mm) and unconfined (without stirrups) conditions were examined upon the completion of eccentric pull-out tests. In order to model the complex conditions of the corroded steel-concrete interface, the cohesive behavior was adopted by appropriately modificated parameters, for each corrosion level. The bond-slip curves extracted from the developed model were shown to be in a good agreement with the relevant experimental results. In particular, the bond strength of confined RC specimens deviates at about 10% among the analytical and experimental outcomes, for both uncorroded and corroded conditions up to 8.3% corrosion level. In case of the unconfined specimens, the bond strength prediction was satisfactory up to 5% corrosion level, whereas for greater corrosion level, large deviation was observed. Regarding the prediction of the relative slip between steel and concrete, further investigation is required as the development of slip is influenced by a plethora of factors.
Thick Film Sensor Manufacturing Techniques for Realization of Smart Components via Low Pressure Die Casting
Authors: Lehmhus Dirk , Cen Marco , Struss Adrian , Rijk Tim de , Pille Christoph , Lang Walter
Published: February 2024

Recent developments like autonomous driving have increased the interest of the automotive industry in structural health and condition monitoring of safety-relevant components often manufactured via High or Low Pressure Die Casting (HPDC, LPDC). Specifically the latter process is important in this field as the improved quality of castings produced facilitates T6 heat treatments aimed at optimizing mechanical performance of such components. The specific challenge associated with this approach is that it produces critical thermal loads which may compromise the characteristics of the integrated sensor. The present study shows the results obtained by LPDC on thick film sensor systems prepared by means of screen printing on aluminum substrates. The response of the sensor systems to the thermal loads associated with the casting process is evaluated in casting experiments, with temperatures reached during casting checked by means of thermocouples attached to the inserts. The focus is on the influence on general properties of the piezoresistive sensors as well as on their response to thermal and mechanical stimuli. The results show that in contrast to HPDC, in the case of LPDC, the former provides stimuli for thermally induced processes which can compromise sensor layers. The respective trends have been studied via resistance measurements on samples subjected to repeated firing cycles and actual casting experiments.
Morphological and functional characterization of electroplated Ni-graphene composite coatings
Authors: Almonti Daniele , Baiocco Gabriele , Millia Massimiliano Della , Mingione Emanuele , Menna Erica , Rubino Gianluca , Salvi Daniel , Stamopoulos Antonios , Ucciardello Nadia
Published: February 2024

Composite coatings (CECs) are providing a unique technological advantage for improving mechanical and tribological surface properties. Among different methods, electrodeposition is one of the most exploited to produce composite surface coatings on metal substrates. However, the process parameters affect graphene distribution, coating morphology and performance. This paper investigates how different deposition conditions influence the inclusion of large Graphene nanoplates (GnPs) in a Nickel matrix and the coating morphology and tribological performance. Set the process condition such as electrical parameters and the galvanic bath, the work focuses on the stirring rate effect. To this end, Ni-GnP coatings were obtained by a laboratory setup and evaluated through surface profilometry, SEM characterization and a dry-sliding linear reciprocating wear test. The results highlight the influence of stirring on coating uniformity. The low stirring rate allows larger particles to be embedded, which are not thoroughly covered; however, they act as a solid lubricant and reduce the friction coefficient.
Ageing Behavior of Rubber Compounds Prepared with Different ZnO Types
Authors: Börüban Bingöl C , Polat Ş , Atapek Ş H
Published: February 2024

Zinc oxide is considered as the most widely used activator that influences curing reaction kinetics and promotes short sulphide crosslinks to achieve higher crosslink density in rubber compounds. Besides its effect on curing process, it has beneficial effects on the physical and mechanical properties of rubber as well. However, its level should be minimized in rubber compounds because of its toxicity for human health and environment, especially on aquatic wildlife. One of the potential routes for decreasing ZnO level is to use composite ZnO materials where ZnO particles are coated. In this study, composite ZnO materials having ZnO:CaCO3 ratio as 40:60, 60:40 and 90:10 are used in SBR/BR compounds and their effects on mechanical properties under ageing conditions are investigated and compared with the conventional white seal ZnO and active ZnO types. The findings have shown that all composite materials have no negative effect on mechanical properties under ageing conditions, thus they can be used as alternative materials to conventional activators.
Improving the mechanical properties of Glass Reinforced Plastics by slight mechanical compression
Authors: Iakovidis I , Dimitrellou S , Orfanos G , Vlachogiannis M
Published: February 2024

Glass reinforced plastics (GRPs) are composite materials that have been used widely in engineering. Mechanical properties of fabricated GRP products depend on the type and arrangement of reinforcement, the type of the plastic as well as the reinforcement to plastic ratio. Some of these factors are interdepended in determining the quality of the final product. In the present study, the influence of applying mechanically a slight pressure during fabrication on the properties of GRP specimens, was investigated. Specimens were fabricated using the hand lay-up method and were further processed either by a vacuum bag compression or a mechanically applied pressure. The properties of the produced composite specimens were then determined experimentally. The application of mechanical compression was found to improve their properties. The effect of the mechanically applied compression or vacuum was evident as a reduction of the specimens’ internal void volume compared to the non-compressed ones, resulting in an increase in the density by 9–12% and a reduction in the thickness of the specimens by 15–20%. Additionally, the tensile and flexural strength of the specimens were increased by more than 15% and 5% respectively when pressure was applied mechanically, reflecting an improvement in GRPs’ mechanical properties.
Development and experimental validation of a prototype system for Machine Learning based SHM in composite aerostructures
Authors: Spiliotopoulos P E , Fera F T , Saramantas I E , Sakellariou J S , Fassois S D , Ofir Y , Kressel I , Tur M , Papadopoulos P , Giannopoulos F , Spandonidis C
Published: February 2024

The development and experimental validation of a Machine Learning (ML) vibration based Structural Health Monitoring (SHM) prototype system for composite aerostructures operating under uncertainty is presented. Following initial training, it is intended to operate autonomously, in almost real-time, without interrupting normal operation, relying on a limited number of acceleration and strain measurements from properly selected locations on the aerostructure. It is equipped with a multi-level information fusion methodology comprising multiple sensor technologies and diagnostic algorithms for optimized SHM performance in terms of damage detection and characterization. Through its flexible software, the system provides multiple options of ML based SHM methods targeting wide applicability to various types of structures. The system is validated based on numerous experiments with healthy and damaged full-scale composite bonded spars operating under multiple uncertainty factors. Its diagnostic performance indicates that the current progress in hardware and robust vibration-based Machine Learning algorithms may lead to compact, effective, and low cost SHM systems for composite aerostructures under normal operating conditions.
Fatigue Life Assessment of Automotive Leaf Springs
Authors: Giannakis E , Savaidis G
Published: February 2024

The creation of a new mechanical component, such as a high-performance leaf spring, is a very challenging procedure that consists of many stages over a long timeframe from concept to production. High performance leaf springs are components with high complexity at the areas of failure. This complexity is derived from the multiple manufacturing processes that the raw material undergoes to reach its final geometrical and microstructural form. The paper shows the assessment of fatigue life of high-performance leaf springs, from different manufacturers with different geometrical and loading parameters. The assessment uses the fatigue life calculations which are described at the FKM Guideline as a basis. Limitations of the FKM Guideline, concerning the material’s ultimate tensile strength and the exclusion of the stress shot peening process, are restricting the fatigue life calculations of such components, therefore, a new theoretical tool is needed for more accurate calculations.
NAVMAT: an AI-powered pathway to knowledge sharing on material failures
Authors: Melanitis N , Giannakopoulos G , Stamatakis K
Published: February 2024

The paper describes the product development methodology, the architecture, the modules and features of the operating prototype, as well as future challenges of NAVMAT, a naval materials failure management system. The fundamental compound of the knowledge management platform is the recording and classification of a failure incident. NAVMAT supports different types of users, from the first Reporter to the Analyst and Forensic Engineer through appropriate workflows. In these workflows the incident-related information can be provided as text, files, images and videos, which can be easily associated to the incident and provide structured information. NAVMAT provides a number of Artificial Intelligence (AI)-enabled helpers. During the incident recording, NAVMAT brings into play reactive real-time search which suggests related incidents and literature to facilitate the editor. It also speeds up the classification of incidents by providing AI-suggested labels, chosen from the (multi-lingual) concepts contained in the system Ontology. On the other hand, the intelligent indexing and search infrastructure of the system supports easy identification and retrieval of past incidents, reports and publications, by applying Natural Language Processing. The prototype of the described system has been embedded as a web application validated by potential Users and is being prepared for Operation in a fleet environment.
A structural-thermal coupled modeling approach on the formation of adiabatic shear bands in steel sheet blanking process
Authors: Karantza Konstantina D. , Vaxevanidis Nikolaos M. , Manolakos Dimitrios E.
Published: February 2024

Adiabatic shear banding reflects an unstable and dynamic plastic deformation mechanism occurring at high strain and strain rates which is strongly conjugated to fracture. Current work carries out a numerical study on the initiation and development of adiabatic shear bands (ASBs) in blanking process of AISI 4340 steel sheet. A structural-thermal coupled finite element analysis is developed in LS-DYNA software by implementing a thermo-viscoplastic flow rule for material plasticity and a damage criterion considering dynamic failure. The numerical simulations are focused on capturing ASB genesis through intense shear localization by evincing strain instability. Also, the evolution of ASB mechanism is investigated, aiming to contribute a stage-by-stage propagation and highlight its connection to dynamic failure. Further, the effect of ASB temperature and strain field on fracture is analysed, while the influence of strain/strain rate hardening and thermal softening on strain instability, peak force and the blanked surface is studied. The results revealed an S-shaped ASB due to severe shear localization and significant temperature increase, leading to dynamic recrystallization around punch-die corners and reacting to strain instability and dynamic. Finally, high magnitude thermal softening during ASB development resulted in earlier ASB generation and reduction of the peak blanking force, while further it decreased shear zone expansion and increased fractured length in the blanked surface.
Investigation of bio-based and recycled printing materials for additive manufacturing
Authors: Junk S , Vögele P
Published: February 2024

Additive manufacturing (AM) processes are becoming increasingly important alongside conventional processes. As a result, the consumption of materials is also increasing. The most widespread process in polymer AM is Fused Layer Modelling (FLM). Today, the FDM process often uses synthetically produced materials based on petrochemical processes. However, there is little knowledge about which bio-based and recycled polymer materials are suitable for sustainable polymer AM. The aim of this paper is to carry out investigations of eight selected materials, which are already commercially available, to gain insights into their suitability as materials for polymer AM. These materials are divided into four categories: conventional, recycled, bio-based and fibre-reinforced thermoplastics. The evaluation model consists of a point system in which the materials are evaluated according to various weighted criteria. For technical, economic and ecological evaluation meaningful criterions were developed and applied. Based on the evaluations, three two-dimensional strength diagrams were developed, from which the results of the materials, on two of the evaluations in each case, can be read. These results are combined in a three-dimensional diagram. This representation provides the ability to make a precise selection of bio-based or recycled materials for polymer AM.
Liquid Hydrogen Storage Tank Virtual Crashworthiness Design Exploration for Civil Aircraft
Authors: Gallois A , Giannopoulos I K , Theotokoglou E E
Published: February 2024

Civil aviation industry is researching for alternative fuel energy sources to substitute current hydrocarbon-based aviation fuels. Carbon free emissions flights could be achieved with fuels like Hydrogen either through combustion or via electricity producing fuel cells. It is of great importance to explore the airframe designs to house Hydrogen in its cryogenic liquified state. The objective of the study herein was to provide a conceptual qualitative analysis related to the crashworthiness behaviour of civil aircraft carrying liquid Hydrogen fuel storage tanks. The design parameters of interest were the storage tank location in the airframe, the structural energy absorption following crash landing scenarios and the structural deformation of the structure surrounding the tanks, penetrating the survival space of the occupants. Several structural design arrangements were proposed and compared. Simulation results indicated that the optimal location for the fuel storage greatly depends on the actual aircraft layout as well as on the future civil aircraft airworthiness requirements that are still under development for that type of fuel energy source.
Dissipation closure of fluid turbulence from energy spectrum
Authors: Balonishnikov A M , Kruchkova J V
Published: February 2024

Direct method of the turbulence closure consists of obtaining expression for small-scale velocity and inserting this expression in the Reynolds tensor and in the transport equations for turbulent energy, dissipation, eddy and so on, implementing some averaging. Previously such approaches were used for Burgers-Lundgren vortex. Here we used ‘naïve’ perturbation method for the transport equation for small-scale velocity incompressible fluid - the equation suggested by one of the authors earlier. It is assumed that the energy spectrum of turbulence is given.
Photoconductivity and bandgap of binary impurity - doped crystalline silicon
Authors: Sh Mavlyanov A , Khakkulov M K , Sattarov O E , Akbarova N A , Yakubov D Z
Published: February 2024

The paper presents the results of study of the photoconductivity spectra of sulfur- and -doped samples of silicon (Si, Si) under dark conditions and while samples were subjected to constant light in forward and reverse switching modes. The paper also presents the calculation results of the value of the band gap (Eg
) of  -doped silicon samples (Si). Spatial analogues of generally accepted GaAs structure such as Si2Mn2S and Si2Zn2S are hypothesized to be brought up in the result of above mixed dopings. Tentative investigations of the short-circuit current and open-circuit voltage of p-n-structures, as well as the photoconductivity of such structures, together with the analysis of their lux-ampere characteristic might serve for proposing potential varying band structures for solar cells.
Corrosion resistance of the modified surface of AISI 316L steel
Authors: Dasaev M R , Kalakutskaya O V , Ryzhenkov O V , Tkhabisimov A B
Published: February 2024

The paper is devoted to the study of the effect of laser processing on the wettability and corrosion resistance of the surface of experimental samples made of AISI 316L sheet steel and samples made by printing from AISI 316L steel powder using selective laser melting technology. As a result of the studies, it was established that laser texturing of the relief with the subsequent formation of molecular layers of surfactants on a steel surface helps to achieve higher contact angle values, however, such treatment leads to a decrease in corrosion resistance.
Theoretical study of the influence of gas phase turbulent disturbances on the kinetics of ultrasonic coagulation of PM2.5
Authors: Khmelev Vladimir , Nesterov Viktor , Bochenkov Alexander
Published: February 2024

A numerical model of ultrasonic coagulation of PM2.5 aerosol particles in three-dimensional vortex and turbulent acoustic flows is proposed in the article. The model is intended to identify the possibility of increasing the efficiency of the process. A numerical analysis of the model using the example of PM2.5 aerosol made it possible to establish that the presence of three-dimensional turbulent disturbances leads to the fact that the coagulation efficiency of PM2.5 reaches almost 100% at a sound pressure level of no more than 165 dB.
Simulation of light scattering on a deformed gas bubble
Authors: Gordeeva Varvara
Published: February 2024

The paper describes simulating light scattering of an electromagnetic field on a deformed gas bubble suspended in a liquid. The field intensity distributions around the deformed bubble were obtained. It turned out that field scattering increases with bubble deformation up to a certain limit of the deformation coefficient A (relative deformation amplitude). At A = 0.7 and higher, the scattering remains independent of the magnitude of the deformation.
Application of sand mold casting modelling for casting pump volute
Authors: Aripov A R , Vokhidov B R , Asrorov A A , Sayfullaev F I , Kurbonov M N
Published: February 2024

This work details the development of a gating system for sand mold casting utilizing advanced computer technologies in the casting industry. The study employs advanced methods to manufacture a component referred to as the pump volute. Made from the EN-GJN-HV600(XCr23) alloy, this component displays superior technological characteristics, notably for the production of sand mold gravity castings. SolidWorks software is utilized to generate 3D models of the component and the fill system based on predetermined dimensions. Subsequently, the component is imported into Pro-CAST software to conduct a simulation. Various time parameters were inputted during the study. Post-simulation, defects were scrutinized, and the casting system underwent modification to eliminate them. The process was iterated on the software and its efficacy was verified to be faultless.
Simulation and control of ball mills under uncertainty conditions
Authors: Mukhitdinov Djalolitdin , Kadirov Yorkin , Boybutayev Sanjar , Boeva Okila , Babakhonova Umida
Published: February 2024

The article considers a model for monitoring the grinding process in a ball mill, where the ground material itself is involved in grinding. The constructed model takes into account the uncertainties associated with the quality indicators of the processed ore at the beginning and in the process of grinding, the influence of the quality indicators of the ore in terms of particle size and their hardness on the kinetics of grinding. The non-linearity of the technological process and uncertainties are taken into account in the control system aimed at stabilizing the system. The model is presented in the form of four blocks describing the main links of the mill plant. At the output of the model, the participation of the mill, the volume of the sump are determined, and the particle size at the outlet of the hydrocyclone is estimated. The operation of the hydrocyclone control system is demonstrated, which controls the loading density and particle size depending on the change in ore quality.
A multiparameter mathematical model for the problem of nonlinear filtration of fluids in two-layer media
Authors: Kayumov Shukur , Arzikulov Golib , Bekchanov Sherzad , Zuyadullayeva Shohida
Published: February 2024

In the realm of fluid dynamics and porous media, the nonlinear filtration of fluids in two-layer media presents a complex and intriguing challenge that demands a comprehensive mathematical framework for accurate representation and analysis. This paper introduces a multiparameter mathematical model designed to elucidate the intricacies of fluid filtration in heterogeneous environments, specifically focusing on two-layer media. The authors research the construction of a multiparameter mathematical model and numerical solution of nonlinear problems of the theory of filtration of unstructured and structured fluids in hydrodynamically connected multilayer formations with different characteristics. The developed models and solution algorithms were tested on hypothetical data.