bluuebunny/crossref_metadata_2025 huggingface dataset:
pyPPG: a Python toolbox for comprehensive photoplethysmography signal analysis
Authors: Goda Márton Á , Charlton Peter H , Behar Joachim A
Published: March 2024

Objective. Photoplethysmography is a non-invasive optical technique that measures changes in blood volume within tissues. It is commonly and being increasingly used for a variety of research and clinical applications to assess vascular dynamics and physiological parameters. Yet, contrary to heart rate variability measures, a field which has seen the development of stable standards and advanced toolboxes and software, no such standards and limited open tools exist for continuous photoplethysmogram (PPG) analysis. Consequently, the primary objective of this research was to identify, standardize, implement and validate key digital PPG biomarkers. Approach. This work describes the creation of a standard Python toolbox, denoted pyPPG, for long-term continuous PPG time-series analysis and demonstrates the detection and computation of a high number of fiducial points and digital biomarkers using a standard fingerbased transmission pulse oximeter. Main results. The improved PPG peak detector had an F1-score of 88.19% for the state-of-the-art benchmark when evaluated on 2054 adult polysomnography recordings totaling over 91 million reference beats. The algorithm outperformed the open-source original Matlab implementation by ∼5% when benchmarked on a subset of 100 randomly selected MESA recordings. More than 3000 fiducial points were manually annotated by two annotators in order to validate the fiducial points detector. The detector consistently demonstrated high performance, with a mean absolute error of less than 10 ms for all fiducial points. Significance. Based on these fiducial points, pyPPG engineered a set of 74 PPG biomarkers. Studying PPG time-series variability using pyPPG can enhance our understanding of the manifestations and etiology of diseases. This toolbox can also be used for biomarker engineering in training data-driven models. pyPPG is available on https://physiozoo.com/.
Design and analysis of Si photonic NaCl sensors based on suspended microdisk resonators
Authors: Moeinimaleki Kaveh , Habibzadeh-Sharif Amir , Ahmadpour Afshin , Bahrami-Chenaghlou Faezeh
Published: March 2024

In this paper, two optical refractive index sensors, respectively based on a suspended microdisk resonator (SMDR) and a sub-wavelength Bragg grating suspended microdisk resonator (SWG-SMDR) have been designed on a silicon on insulator (SOI) platform, and their optical and sensing performances have been analyzed using the three-dimensional finite-difference time-domain method. It has been shown that the Bragg grating increases the optical confinement factor in the sensing region and, consequently, improves the light–matter interaction and sensitivity. Considering concentrations of 0 to 25% for the NaCl dissolved in the deionized water, the enhanced sensitivity and FOM of the SWG-SMDR sensor with the miniaturized optimal geometrical dimensions are 163.77 nm RIU−1 and 10.81 RIU−1, respectively. This compact optical sensor enhances the sensitivity and FOM by combining effects of the Bragg grating and suspension configuration in improving the light–matter interaction.
Quasi-local masses and cosmological coupling of black holes and mimickers
Authors: Cadoni Mariano , Murgia Riccardo , Pitzalis Mirko , Sanna Andrea P.
Published: March 2024

Motivated by the recent heated debate on whether the masses of local objects, such as compact stars or black holes (BHs), may be affected by the large-scale, cosmological dynamics, we analyze the conditions under which, in a general relativity framework, such a coupling small/large scales is allowed. We shed light on some controversial arguments, which have been used to rule out the latter possibility. We find that the cosmological coupling occurs whenever the energy of the central objects is quantified by the quasi-local Misner-Sharp mass (MS). Conversely, the decoupling occurs whenever the MS mass is fully equivalent to the (nonlocal) Arnowitt-Deser-Misner (ADM) mass. Consequently, for singular BHs embedded in cosmological backgrounds, like the Schwarzschild-de Sitter or McVittie solutions, we show that there is no cosmological coupling, confirming previous results in the literature. Furthermore, we show that nonsingular compact objects couple to the cosmological background, as quantified by their MS mass. We conclude that observational evidence of cosmological coupling of astrophysical BHs would be the smoking gun of their nonsingular nature.
XENONnT and LUX-ZEPLIN constraints on DSNB-boosted dark matter
Authors: Romeri Valentina De , Majumdar Anirban , Papoulias Dimitrios K. , Srivastava Rahul
Published: March 2024

We consider a scenario in which dark matter particles are accelerated to semi-relativistic velocities through their scattering with the Diffuse Supernova Neutrino Background. Such a subdominant, but more energetic dark matter component can be then detected via its scattering on the electrons and nucleons inside direct detection experiments. This opens up the possibility to probe the sub-GeV mass range, a region of parameter space that is usually not accessible at such facilities. We analyze current data from the XENONnT and LUX-ZEPLIN experiments and we obtain novel constraints on the scattering cross sections of sub-GeV boosted dark matter with both nucleons and electrons. We also highlight the importance of carefully taking into account Earth's attenuation effects as well as the finite nuclear size into the analysis. By comparing our results to other existing constraints, we show that these effects lead to improved and more robust constraints.
Transition layer of the relativisyic strophotron
Authors: Oganesyan K B , Gevorgyan A H , Miakota D , Kopcansky P
Published: March 2024

The Klein–Gordon equation of motion in the transition layer of a free-electron laser of the relativistic strophotron type is studied. The condition of suddenly switching-on interaction is found: a smallness of the transition layer at the entrance compared to the distance traveled by the electron in longitudinal direction in one period of transverse oscillations in strophotron. The results are correspond to the results of classical description. It is shown, that in an electric strophotron, under the assumption of a suddenly switching-on interaction, the transverse energy of an electron at the moment t = 0 undergoes a jump. However, the total energy is conserved, because at the same moment t = 0, the longitudinal energy of the electron has the same jump with opposite sign.
A personalized earbud for non-invasive long-term EEG monitoring
Authors: Zeydabadinezhad Mahmoud , Jowers Jon , Buhl Derek , Cabaniss Brian , Mahmoudi Babak
Published: March 2024

Objective. The primary objective of this study was to evaluate the reliability, comfort, and performance of a custom-fit, non-invasive long-term electrophysiologic headphone, known as Aware Hearable, for the ambulatory recording of brain activities. These recordings play a crucial role in diagnosing neurological disorders such as epilepsy and in studying neural dynamics during daily activities. Approach. The study uses commercial manufacturing processes common to the hearing aid industry, such as 3D scanning, computer-aided design modeling, and 3D printing. These processes enable the creation of the Aware Hearable with a personalized, custom-fit, thereby ensuring complete and consistent contact with the inner surfaces of the ear for high-quality data recordings. Additionally, the study employs a machine learning data analysis approach to validate the recordings produced by Aware Hearable, by comparing them to the gold standard intracranial electroencephalography recordings in epilepsy patients. Main results. The results indicate the potential of Aware Hearable to expedite the diagnosis of epilepsy by enabling extended periods of ambulatory recording. Significance. This offers significant reductions in burden to patients and their families. Furthermore, the device’s utility may extend to a broader spectrum, making it suitable for other applications involving neurophysiological recordings in real-world settings.
Brain connectivity patterns derived from aging-related alterations in dynamic brain functional networks and their potential as features for brain age classification
Authors: Han Hongfang , Jiang Jiuchuan , Gu Lingyun , Gan John Q , Wang Haixian
Published: March 2024

Objective. Recent studies have demonstrated that the analysis of brain functional networks (BFNs) is a powerful tool for exploring brain aging and age-related neurodegenerative diseases. However, investigating the mechanism of brain aging associated with dynamic BFN is still limited. The purpose of this study is to develop a novel scheme to explore brain aging patterns by constructing dynamic BFN using resting-state functional magnetic resonance imaging data. Approach. A dynamic sliding-windowed non-negative block-diagonal representation (dNBDR) method is proposed for constructing dynamic BFN, based on which a collection of dynamic BFN measures are suggested for examining age-related differences at the group level and used as features for brain age classification at the individual level. Results. The experimental results reveal that the dNBDR method is superior to the sliding time window with Pearson correlation method in terms of dynamic network structure quality. Additionally, significant alterations in dynamic BFN structures exist across the human lifespan. Specifically, average node flexibility and integration coefficient increase with age, while the recruitment coefficient shows a decreased trend. The proposed feature extraction scheme based on dynamic BFN achieved the highest accuracy of 78.7% in classifying three brain age groups. Significance. These findings suggest that dynamic BFN measures, dynamic community structure metrics in particular, play an important role in quantitatively assessing brain aging.
Effect of Binder Content on Properties of Cordierite-Mullite Porous Ceramics
Authors: Dai Xinchao , Xue RiDong , Qiu Shuang , Deng Xiangyun
Published: March 2024

In this paper, 70-80 mesh SiC particles were used as the base, and 2.5%MgO was added on the basis of quartz, kaolin and potassium feldspar as the binder. Meanwhile, graphite and activated carbon were added as pore-making agents for SiC porous ceramic supports. At the same time, the amount of binder added was changed under the condition of keeping SiC: pore-making agent 8:1 unchanged. The effects of binder content on flexural strength, filtration pressure drop and porosity of porous SiC ceramics were investigated. The results indicated that the comprehensive properties of SiC porous ceramics can be improved by adding proper amount of MgO. When the content of MgO in the binder was controlled at 2.5% and the amount of binder was 6%, the comprehensive performance of the sample was the best under the conditions of 1300 °C, holding time for 90 minutes and forming pressure of 4/10MPa, respectively. In this case, the flexural strength was 48mpa, the porosity was 25% and the filtration pressure drop was good.
Research on the Material Performance and Forming Process of Lunar Regolith Simulant
Authors: Zuo Yang , Shao Heng , Bao Charun , Yang Shaobo , Qi Junfeng , Liu Minying , Zhang Daobo , Feng Peng
Published: March 2024

Establishing a safe and sustainable lunar base on the moon is the foundation for human exploration and development activities. Due to the high transportation costs of the Earth Moon space, a large amount of construction materials are difficult to obtain from Earth. Therefore, how to utilize lunar resources for in-situ construction on the lunar surface has become the key challenge for the construction and operation of lunar base. Faced with special lunar simulant materials and extreme lunar environments, lunar construction faces a series of problems and challenges. This article conducted research on lunar regolith simulant and forming process, providing guidance for lunar surface construction.
Design Reliability Analysis and Quality Control of Nuclear Pressure Reducing Valve
Authors: Lv Yanxin , Luo Lusheng , Wei Dong , Shi Hong , Li Haitao
Published: March 2024

In order to improve the localization level of nuclear power and solve the “neck” problem of nuclear pressure reducing valve in CAP1400 project, the design reliability analysis and quality control requirements of domestic prototype of nuclear pressure reducing valve was studied. Through the analysis and application of the technical requirements of the pressure reducing valve, the control was strengthened from the reliability requirements of seismic analysis, identification test and quality control points, which provided a strong technical support for the localization of nuclear grade pressure reducing valve. The seismic analysis required that the stress, resonance frequency and deformation analysis on the dangerous section of the main parts of nuclear pressure reducing valve met the requirements of regulations and standards. The reliability control was carried out from three aspects: the selection of test medium, the stability control of pressure behind the valve and the requirements of failure operation performance. Quality point control taked quality control measures from three aspects: tooling design, standard application and test bench management. All measurements ensured that the design quality of nuclear pressure reducing valve meets the requirements. The successful development of the domestic prototype of nuclear grade pressure reducing valve shows the effectiveness of the design reliability analysis and quality control method, which provides a reference for the localization of equipment in the future.
Strength Analysis and Research of Composite Material Bridge Deck
Authors: Zhu Kunning
Published: March 2024

The strength of each layer of composite bridge deck under different load conditions is analyzed and studied by Tsai-Wu tensor theory. The results indicate that, the characteristic strength values calculated in the predetermined reinforcement fabric are significantly smaller than those in the E-glass fiber layer, and the damage will first occur in E-glass fiber layer. Under various operating conditions, the characteristic strength values in each layer of FRP bridge panel are smaller than 1, and have a certain safety factor. The weak positions of each layer are related to the configuration of bridge panel. Tsai-Wu tensor theory can accurately evaluate the status of each layer, and supervise the design work of GFRP bridge panel.
Study on Welding Parameter Model of Resistance Spot Welding of Body-in-white Al Alloy Plate
Authors: Han Lijun , Yu Wenchao , Jia Lei
Published: March 2024

In this paper, the welding parameter model of resistance spot welding (RSW) of body-in-white(BIW) Al alloy plate was studied in details, and the key welding parameters that influence the RSW quality are analysed in-depth. Based on the concept of equivalent plate thickness (SV
), simplification of nugget volume and thermodynamic theories, combined with the properties of Al alloy, the mathematical models of welding current, pressure, time were established through production data and test verification. These models reflect the relationship between key welding parameters and equivalent plate thickness. The welding current and pressure are linear with SV
, and the expressions are different when SV
is greater than 2. For welding pressure, there exist two critical curves according to the different yield strength of welding materials. The yield of the material lies in between and pressure can be chosen between two critical curves. The welding time is directly linear to the actual thickness of the plate. Actual welding parameters can be obtained by the models and least test, which is very important for decision of welding parameters rapidly.
Health Factor Experimental Testing and SOH Estimation for Nickel Cadmium Batteries
Authors: Zhang Yin , Cui Jie , Yuan Hao , Dai Chaohua
Published: March 2024

Based on the fact that the working characteristics of Nickel–cadmium battery are significantly different from lithium batteries, and in view of the complex discharge conditions of Nickel–cadmium battery in Multiple Unit, a SOH estimation method of Nickel–cadmium battery based on charging health factors was proposed. Firstly, aging experiments were conducted on individual nickel cadmium batteries using an experimental platform; Secondly, health factors such as total charging time, constant voltage charging time at the end of constant current charging, and average current during a specific time period of constant voltage charging were selected as health factors at different aging stages. The rationality of the health factors was verified through correlation analysis; Then, principal component analysis was used to reduce the dimensionality of the health factor data matrix as input to the support vector regression model, and cross validation was used to optimize the model parameters; Finally, the proposed method was validated based on experimental data.
Development and Research of non-alkali FGD Gypsum Products
Authors: Lu Guozhong , Wang Zhaojia , He Guangming , Ma Guoru , Shao Lushan
Published: March 2024

The set-up of desulphurization units in domestic coal-fired power plants has brought increasing output of FGD gypsum, which results in a wide application of FGD gypsum products. During the application of such products, people found that they are prone to alkalization, i.e., a phenomenon significantly affecting the appearance and performance of the products. In this study, fly ash, another kind of waste from coal-fired power plants, was introduced to inhibit the alkalization of FGD gypsum products under the action of the alkali-activator for better utilization of waste resources.
Design and Analysis of a Micro Displacement Actuator Based on Stick-slip Principle Using Piezoelectric Ceramic
Authors: Wang Liang , Wang Heran , Zhang Yaxun , Su Donghao
Published: March 2024

This work introduces a triangular shape piezoelectric actuator using the principle of piezoelectric ceramic bending vibration and stick-slip motion. The lateral displacement of the driving foot is used to press the slider, while the vertical displacement is used to drive the slider. The structural dimensions are determined by simulation considering the required parameters. Finite element software is used to analyze the static performance. The dynamic performance of the actuator are simulated and analyzed, including its response to different input voltages and frequencies. Dynamic model provides a comprehensive understanding of the behaviour of the actuator during operation and further reveals the principle. The actuator combines piezoelectric bending vibration and stick-slip motion with the merits of compactness, high accuracy and fast response.
Research Overview on Rectangular Tube Cross-Section Deformation in Rotary-Draw Bending Process
Authors: Liu Yixian , Zhang Ranyang , Guo Zhenghua , Cheng Hui
Published: March 2024

Rectangular tube bending process forming quality is not only affected by the tube material but also geometric dimensions will also be affected by bending mold and related process parameters. Cross-section deformation produced by the tube during the forming process becomes a major constraint to heightening the quality of the tube. The research work and process of cross-section deformation in the rotary-draw bending process (RDBP) of rectangular tubes in theory analysis, experiment research, and finite-element (FE) simulation in recent years is reviewed in this paper. The development trend of research in this field is also proposed.
Research Progress on Occurrence, Removal and Fate of Microplastics in WWTPs
Authors: Li Mengmeng , Hong Lei , Wu Ke , Zhang Jie , Wang Qun , Li Xu , Jin Jie
Published: March 2024

WWTPs are considered to be a major indirect source of MPs discharged into the environment. Characteristics of MPs in the influent and effluent water and sludge of WWTPs were analysed, including abundance, type, shape and size. Detailed comparisons were made to summarise the removal efficiency of each treatment process on MPs and the analysis of the factors affecting them, and to analyse the trend of MPs attribution in WWTPs. It is also concluded that the main shapes of MPs in the influent and effluent water of sewage plants are fibres and fragments, in which fibres account for an increased proportion in the outlet water, and the main polymer types are PP, PE, PA and PET; the shapes of MPs in sludge are mainly fibres, and the main polymer types are PP, PE and PET; and the removal of MPs mainly relies on the physical effects of adsorption, interception, flocculation, filtration, precipitation, and so on.
Exploration of Ecological Function and Restoration of Small and Micro Wetlands
Authors: Chen Junlin , Zhang Weihua
Published: March 2024

Due to their unique ecological functions, small and micro wetlands have received more extensive attention and recognition from the international community, and have become an important part of China’s ecological civilization construction. In this paper, the concept, characteristics and classification of small and micro wetlands are described, and the ecological functions and services of small and micro wetlands are discussed. On this basis, the principles of ecological restoration of small and micro wetlands were analyzed, and suggestions for the protection and management of small and micro wetlands were put forward, in order to provide reference for the protection and restoration of small and micro wetlands in China.
Influence of Xinjiang Saline Soil on Corrosion of X80 Pipeline Steel
Authors: Xu Shuailing
Published: March 2024

A large-scale gas transmission pipeline project will pass through typical saline soil areas in Xinjiang, China, to find out the influence of the saline soil on the long-distance pipeline in this area, this paper investigates the corrosive behavior of X80 pipeline steel embedded in saline soil with multiple corrosion intensities. Firstly, NaCl, Na2SO4, NaHCO3, and deionized water were used to simulate the saline soil with different corrosion intensities, and then the corrosion test of X80 steel was carried out. A scanning electron microscope was used to observe the X80 steel before and after corrosion. Finally, the weight loss method was used to calculate the corrosion rate, and the corrosive behavior of X80 pipeline steel in Xinjiang saline soil environment was analyzed. The results show that: (1) X80 steel is susceptible to pitting corrosion in the saline soil environment; (2) the rate and level of corrosion were mainly related to the content of Cl− and SO4
2−. The greater the content, the stronger the pipeline is corroded; (3) the rate and level of corrosion were positively correlated with the corrosion intensities of saline soils.
Explosion Cracking Analysis of Sulfur Resistance Induction Heat Bend Pipe
Authors: Liu Yangqin , Li Xiaolong , Li Na , Lin Weiping
Published: March 2024

The explosion cracking reason on induction heat bend pipe was analyzed through macroscopic analysis, chemical composition analysis, mechanical properties testing, metallographic analysis, scanning electron microscopy and XRD. The results showed that the chemical composition, tensile test, Vickers hardness results of the straight section of the bent pipe met the requirements of the technical specifications, and the metallographic structure of the straight section of the bent pipe was pearlite and ferrite. The Charpy impact test in the neutral zone of the bend section had a low shear fracture ratio, and the Vickers hardness test results were on the high side. The metallographic structure was granular bainite. The fracture surface of the failed bent pipe exhibited brittle fracture characteristics on the macro level. The metallographic analysis and hardness test results of the crack source area showed that the fracture surface had typical intergranular propagation characteristics and high hardness values. Energy spectrum analysis of the crack source area revealed the presence of S element. The XRD analysis of the product on the inner wall of the pipe contained sulfides. The comprehensive results indicated that the failed bend pipe undergoes stress corrosion and initiates corrosion cracks on the surface under the combined action of operating pressure, additional bending stress, residual stress, etc. in a sulfide corrosive medium, the cracks continued to propagate along the grain boundaries and ultimately caused the bend pipe to explode.
Propeller wake impact on transition location
Authors: Russo Serena , Giannetti Flavio
Published: March 2024

This work has been carried out within ESTRO Clean Sky 2 CfP project, whose goal was to develop an innovative future green regional aircraft configuration based on several new technologies able to match the very demanding and challenging objectives ACARE 2020 in terms of environmental impact. In details, an automatic numerical procedure for the evaluation of the detrimental effect of the propeller on transition location of a laminar turbo-prop wing is proposed here. The evaluation of transition location is based on a well-known procedure, based on the use of eN method implemented in a Linear Stability (LST) solver. The input data for the LST solver are represented by the pressure distribution as derived from high-fidelity Reynolds-Averaged Navier–Stoke (RANS) solutions and the velocity profiles in the boundary layer derived from a conical formulation of the boundary layer equations.
Model-based approach for the automatic inclusion of production considerations in the conceptual design of aircraft structures
Authors: Bruggeman A M R M , Bansal D , La Rocca G , van der Laan T , van den Berg T
Published: March 2024

Including production considerations in the early design stages of aircraft structures is challenging. Production information is mostly known by experts and rarely formally documented such that it can be effectively used during the design process. Producibility is mostly considered after completing the design, resulting in increased cost and development time due to the late discovery of production issues. This paper presents a new model, called the Manufacturing Information Model (MIM), which supports the automatic inclusion of production considerations into the design process. The MIM provides a single source of truth and a generic structure to capture and organize production-related information in a product system. Furthermore, it provides compatibility analyses to automatically warn for or exclude infeasible designs. Analysis tools use the information stored within the MIM to calculate the mass, costs, and production rate of the product. To show the functionalities of the MIM, it has been applied to the conceptual design of a wing box at a Tier 1 company. This use case shows how the MIM supports trade-off decisions, as it allows for the identification of trends and the ranking of different manufacturing concepts. Overall, the MIM provides a structured and formal approach to include production information in the conceptual design, improving the decision-making process.
A pre-screening of the solvolysis recycling process for CFRPs based on the mechanical properties of the recovered fibers.
Authors: Vogiantzi Christina , Tserpes Konstantinos
Published: March 2024

Over the past few decades, composite materials, and specifically carbon fiber reinforced plastics (CFRPs), are finding increasing use in the automotive, aerospace, and aeronautics industries. As a result, the production of CFRPs has been significantly increased, thus leading to a corresponding increase in waste production. In the near future, landfill and incineration disposal of waste will likely be prevented due to legislation, thereby bringing forward the need to develop efficient recycling processes for CFRPs. However, recycling of CFRPs is very challenging, mainly due to the difficulty in removing the thermosetting matrix. This paper reports a pre-screening of the solvolysis recycling process for CFRPs on the basis of the mechanical properties of the recovered fibers. To this end, solvolysis tests were conducted on unidirectional CFRP samples under supercritical and subcritical conditions using acetone and water. The solvolysis tests were conducted for various conditions of temperature, pressure, and reaction time. The efficiency of the recycling processes has been evaluated by means of single-fiber tension tests on the recovered fibers, which were conducted according to the ASTM C 1557-14 standard. In most cases, the decomposition efficiency of the epoxy resin in the CFRP, measured in terms of mass, ranged between 90 and 100%. Moreover, the mechanical tests showed that the recovered fibers retained more than 58% of their initial Young’s modulus and tensile strength.
Structural sizing of a hydrogen tank for a commercial aircraft
Authors: Parello R , Gourinat Y , Benard E , Defoort S
Published: March 2024

To respond to the current climate crisis, hydrogen-powered aircraft are seen as a promising solution in the aviation sector to cut down CO
2 emissions. Hydrogen-fueled aircraft present however huge challenges, especially due to the complex storage of hydrogen. To achieve a reasonable fuel energy density for medium- to long-range missions, hydrogen must indeed be stored in liquid form in big and heavy pressurized tanks. Tank design must so be included in conceptual design, which now has an important impact on the aircraft. This study proposes a structural sizing methodology for a liquid hydrogen tank for a commercial aircraft. A parametric model of a cylindrical cryogenic tank placed at the back of the cabin in a conventional aircraft is created and sized to withstand pressure, bending, torsion and shear loads. The process integrates sizing standards for pressurized structures of the current CS-25 regulation in its methodology and remains general enough to consider both integral and non-integral tanks of any dimensions or materials. Initial analyses show a clear dependency of the tank’s performance as well as the optimal stiffening structure configuration on the design pressure.
Graphene Devices for Aerial Wireless Communications at THz
Authors: Mura Monica La , Cassioli Dajana , Shundalau Maksim , Cianca Ernestina , Lamberti Patrizia
Published: March 2024

This paper investigates the state-of-the-art of graphene-based technologies for the prospective use cases of end-to-end terahertz (THz) communication systems, such as industrial Internet of Things (IoT) applications and unmanned aerial vehicles (UAVs). THz communications offer ultra-high throughput and enhanced sensing capabilities, enabling advanced applications like UAV swarms and integrated sensing, localization, and mapping. The potential of wireless THz communication can be unlocked by graphene technology. Graphene, owing to its remarkable electrical, thermal, and mechanical properties, emerges as a promising candidate for a multitude of applications in aerial wireless communications in the THz band, including high-speed electronic devices, tunable metamaterials, and innovative antennas. However, reliable tools for the simulation-based design of graphene components, able to account for the fabrication-related uncertainties, are still missing. This paper presents the envisaged possibilities of wireless communications in THz bands, overviews graphene devices for RF applications at THz, and discusses the open issues of modelling THz devices and THz channel.
A System of Systems Framework for Strategic Cargo Airlift Using Agent-Based Modelling
Authors: Kalliatakis Nikolaos , Dietl Tobias , Prakasha Prajwal Shiva , Zill Thomaz , Nagel Björn
Published: March 2024

The effective transport of cargo across the globe by aircraft, termed strategic airlift, is foundational to the success of humanitarian aid/disaster relief (HA/DR) missions and even military operations. Due to the variable extremity of these events, it is essential for aircraft and operations to be designed with a high resilience, factoring in performance in a plethora is scenarios. This work aims to provide a framework that enables the coupling of aircraft, fleet and concepts of operations (CONOPS) design to a mission effectiveness in a strategic cargo airlift. Through agent-based modelling, the complex interaction and emergent behaviors of the different systems in the dynamic airlift environment is better captured and evaluated. Unexpected events, such as cargo requirement reformulation, aircraft servicing and changing airbase accessibility, are employed to emulate the dynamic and spontaneous nature of rapid cargo airlift missions. The impact of these events is stochastically modelled, promoting an analysis of a variety of scenarios. By creating a theoretical disaster relief mission, a trade-space exploration is conducted so that aircraft designs and operational objectives can be evaluated for their mission effect. The framework demonstrates the ability to evaluate aircraft and operational performance holistically, enabling a more robust design procedure for a variety of potential design scenarios and metrics.
Manufacturing, development and control of a two-way 3D printed soft actuator actuated with SMAs
Authors: Acevedo-Velazquez Aline Iobana , Wang Zhenbi , Winkler Anja , Modler Niels , Röbenack Klaus
Published: March 2024

In this contribution, the development of a novel two-way 3D printed soft actuator actuated with shape memory alloys (SMAs) is presented, considering all the stages from the design, manufacturing, control, and implementation. The SMAs are integrated into the 3D printed composite using thermoplastic polyurethane (TPU). In order to measure the deflection of the soft actuator a computer vision system was implemented. With these measures and using system identification techniques, a mathematical model was developed, which describes the dynamics of the prototype and helps to design of a controller. However, precise control of deflection in systems actuated by SMAs is challenging due to their inherent nonlinearities and hysteretic behavior. To face this challenge, a proportional-integral (PI) controller was designed based on robust stability conditions. The effectiveness of the designed PI controller was validated through experimental results.
On the design of a cup anemometer performance simulator. From the wind speed to the output data.
Authors: Alfonso-Corcuera Daniel , Curea Octavian , Ogueta-Gutiérrez Mikel , Sanz-Andrés Ángel , Pindado Santiago
Published: March 2024

This paper describes some important aspects of the development of a cup anemometer performance simulator. This tool aims to simulate the different phenomena which affect the different subsystems of the anemometer, in order to develop different strategies to improve the accuracy of the data obtained through post-processing or design changes. Bearing in mind that the cup anemometer is the most widely used wind speed sensor in the wind energy sector (to control wind generators and to analyse the future economic revenue of wind farms in certain locations), the relevance of the present study should be highlighted. The software is designed in Simulink® and is divided in 4 modules representing the different subsystems of an anemometer from the actual wind speed to the output data. The first two modules of the simulator are detailed in this paper, which consist of the Rotation Rate Module and the Pulse Generating Module. The first module outputs the anemometer’s rotor angular position with time, which depends on the wind speed of the anemometer. Oscillations of the rotation rate caused by steady state harmonic accelerations are taken into account. The Pulse Generating Module simulates the optoelectronic system of the anemometer and creates the pulse train signal based on the rotor’s angular position, taking into account the manufacturing and eccentricity errors of the system. The architecture of the modules is detailed, and related with the phenomena which is intended to simulate.
Increasing predictability in the response of an AI-assisted stall recovery system in complex stall conditions by expanding the knowledge-base of AI
Authors: Koopman C , Zammit-Mangion D
Published: March 2024

The environment in the cockpit of commercial aircraft is becoming increasingly complex due to the introduction of automation systems. This complexity is especially evident when malfunctions take place, making it difficult for pilots to comprehend the interconnectedness of the systems and potentially leading to loss of control. This paper investigates a novel method for creating an Artificial Intelligence-based stall recovery assistant using Reinforcement Learning by training the agent to generate a stall and subsequently recover from it. This enables training in a large training space with a simple reward function, where the agent has the ability to develop a deep understanding of the environment. Tests show that the agent is able to recover from stall at a variety of altitudes while experiencing unreliable airspeed information originating from a blocked Pitot tube system and with a better response than all baseline agents. The results indicate that restricting AI is not always necessary and, further, that too many restrictions can lead to a system that learns only shallow features, causing it to be unreliable in unforeseen circumstances.
Drone intrusion management systems in airports: assessment of ASPRID solution
Authors: Pascarella D , Bieber P , Cioffi M , Dubot T , Ippolito M , Jiménez Roncero F J , Martinavarro Armengol E , Pellegrino P , Remiro Bellostas A , Sodano M , Vozella A
Published: March 2024

Drone intrusions pose a growing threat for the airports as their expansion is sponsored by the widespread availability of their technology and by the ongoing U-space implementation. Counter-drone systems traditionally employ a reactive policy, which implies the closure of the overall airport following an intrusion, penalizing the continuity and the resilience of airport operations. Instead, a drone intrusion management system shall ensure a resilient behaviour against drone intrusions with a proactive policy, supported by specific procedures to mitigate the impacts of intrusions. ASPRID (Airport System PRotection from Intruding Drones) is an exploratory research project to develop an innovative operational concept for managing both careless and malicious drone intrusions in airports. This work demonstrates the positive impact of the ASPRID solution for the resilient protection of airport operations against drone intrusions. Such impact is assessed by means of real-time simulations, including a gaming exercise with experts representing aerodrome stakeholders and Law Enforcement Agencies. We present here the main results of the quantitative assessment and the main feedbacks received by the experts.
Operational pressure and the SHP framework: Connecting the dots for safety
Authors: Marsman L A , Vlasblom J I D , Minnema M F
Published: March 2024

Operational pressure refers to pressure, whether induced or self-induced, that can affect the (flight) operation and may also impact safety. It is a hot topic in many sectors, being an important reason for multiple personnel strikes - the aviation sector is no exception here. Given the rapid evolution of these different operational pressures as the world adapts, continuous attention will be necessary for addressing the concept of operational pressure and discovering new mitigation strategies. Therefore, this paper delves deeper into both current and future factors influencing operational pressure, as well as mentioning some potential mitigating measures. Moreover, the case of operational pressure is structured and visualised using NLR’s Safety & Human Performance (SHP) framework. The result provides a structured overview of the impacts of different operational pressures on safety, which can aid in developing mitigations to lessen the effect of such pressures.
Preliminary study of pilot stress and mental workload monitoring through physiological signals
Authors: Luzzani G , Buraioli I , Demarchi D , Guglieri G
Published: March 2024

The aviation industry is moving towards single-pilot operations due to increased operating expenses and a shortage of pilots. The necessity of developing a digital cockpit assistant leads to discovering methods to assess the stress and mental workload of pilots. This study used twenty-eight healthy volunteers to conduct preliminary computerised cognitive tasks while recording their physiological data for PPG, EDA, and temperature under four different stress and workload situations. The results highlight how they are sensible to a binary classification between a relaxed and more cognitively demanding condition.
Safety and Resilience Bayesian Belief Network (SR-BBN) for ATM
Authors: Jurado Raquel Delgado-Aguilera , Comendador Víctor Fernando Gómez , Suárez María Zamarreño , Moreno Francisco Pérez , Gallego Christian Eduardo Verdonk , Valdés Rosa María Arnaldo
Published: March 2024

This study delves into the realm of Air Traffic Management (ATM) and its criticality in ensuring the safety and resilience of aviation systems. Traditionally, safety has been approached reactively (Safety I), but with the complexities of socio-technical systems like ATM, a shift towards proactive measures is essential. This research explores Resilience Engineering (RE) and Safety II, emphasizing learning from a system’s adaptability in everyday situations. ATM, a multifaceted system, relies on technology, organization, and human interactions, striving to maintain equilibrium among these pillars for safe and efficient operations. Any changes to these elements can disrupt this balance, necessitating a systemic perspective. Safety in ATM depends on resource availability, timeliness, and coordination among organizations and humans, while resilient performance extends safety beyond the expected operating conditions. To unify safety and resilience, this study introduces the Safety Resilience-Bayesian Network (SR-BBN) model. This model integrates data-driven and knowledge-based approaches, categorizing variables into separations, external factors, nominal conditions, and Air Traffic Controller (ATCO) strategies. The SR-BBN model aids in predicting safety outcomes and identifies influential variables.
Enhancing Development of Modular Application-Specific Configurable Space Robots
Authors: Wiedemann H. , Schilling M. , Chowdhury P. , Brinkmann W. , Kien I. , Li J. , Langosz M. , Michelson E.
Published: March 2024

In many space activities, existing robotic systems are highly mission-specific and cannot be reused. On the other hand, there are several highly modular system designs, that lack the specialized hardware, yet. The MODKOM (Modular Components as Building Blocks for Application-specific Configurable Space Robots) project, aims to create a toolbox that allows to configure and recombine a robot for certain tasks, out of specialized and standardized building blocks; this also includes commercial off-the-shelf components. Therefore, MODKOM also focuses on providing a software framework to compose and configure such systems. Based on the proposed system modeling, all entities (hard- & software) can be represented, handled, and also be stored to reuse sub-systems. By providing adequate (graphical) user interfaces and thereby lowering the need for manually-typed files, this process is simplified benefiting accessibility to non-experts. First tests in parallel projects show already the reduced necessity for manual configuration work and thus, a decrease in mistakes in formerly error-prone tasks. MODKOM also provides a set of modular hardware building blocks, which will be used in the upcoming final demonstration scenario to evaluate the advances made.
Context-attentive robot reconfiguration for human-machine space missions
Authors: Kien I. , Meder M. , Sharma P.
Published: March 2024

With humankind’s aspiration of extraterrestrial inhabitation, the need for robotic support is eminent. To master the emerging challenge of providing astronauts with assistive space robots possessing the required adaptability to new situations and tasks under the constraints of severely limited supply chains in extraterrestrial missions, the utilization of existing hardware to its fullest is required. We propose the combination of a concept with an architecture to jointly support context-aware collaboration between humans and robotic systems for implementing effective resource utilization in space missions. The underlying framework is an implementation of a flexible architecture that enables context awareness for robotic systems. It supports processing nodes for retrieval of context information from the raw sensor values as well as further inferences using the output of nodes. Context information spans across three entities and describes the current state of the environment, the astronaut, and the robot itself. This information then can be used to infer the human’s current intention as well as influence the behaviour to be executed next. Additionally, dynamic changes in the data processing chains are handled by the framework to facilitate an adequate adaptation of the system to situational events. We combine this architecture with the concept of space robots as a composition from building blocks, which are supported and made accessible by a software toolkit. The modular design approach enables online self-reconfiguration of robotic hardware and software components. In combination with dynamic mission planning, based on ontological descriptions of available resources and functionalities, robots are able to adapt their physical and computational appearance dynamically during a mission according to different tasks and goals. By incorporating these two developments in a joint deployment we envision raising the efficiency of robotic systems in human-machine interaction through the usage of self-reconfiguration as a reactive behavior in order to adapt to a specific task, recognized or derived from a human’s intention. Transfer of the proposed idea back to Earth may help to abate resource dissipation caused by deploying specialized monolithic systems with a narrow range of capabilities through utilizing the adaptivity of reconfigurable robots.
Study on the influence of thermal aging on the mechanical and magnetic properties of ferritic steel
Authors: Jia Wenqing , Fan Minyu , Wan Jing , Qi Shuang , Liu Xiangbing , Xu Chaoliang , Li Yuanfei , Qian Wangjie , Quan Qiwei , Yin Jian
Published: March 2024

Due to the extensive use of ferrite in nuclear power plants, the thermal aging issues of ferritic alloys have attracted significant attention. The present study investigates thermally aged FeCr binary ferritic alloys with different Cr contents using various mechanical and magnetic properties tests. The result indicates that the increase in Cr element content and prolonged thermal aging significantly enhances the strength of alloy materials, along with an important reduction in toughness. Meanwhile, the magnetic characteristic shows a considerable difference in different ferritic alloys with varying Cr contents under the influence of thermal aging. As a potential characterization method, magnetic measurement can be used to determine the thermal aging degree in ferritic alloys and the Cr concentration should be considered.