bluuebunny/crossref_metadata_2025 huggingface dataset:
What might the COVID‐19 pandemic in regard to people with neuromyelitis optica spectrum disorder teach us regarding the future?
Authors: Baba Cavid , Yavas Ipek , Samadzade Ulvi , Ozdogar Asiye Tuba , Ozakbas Serkan
Published: October 2023

Objective

The study aimed to examine the demographic, clinical and therapeutic characteristics of people with neuromyelitis optica spectrum disorders (NMOSD, pwNMOSD) during the coronavirus disease 2019 (COVID‐19) pandemic.

Methods

This was an observational study of pwNMOSD at a tertiary care clinic. Data on COVID‐19 infection were collected between 11 March 2020 and 30 April 2022. Data on COVID‐19 symptoms, severity and death rate were analyzed.

Results

We observed 16 confirmed COVID‐19 cases and three suspected cases. Three (15.8%) patients had severe infections, whereas 16 (84.2%) had mild conditions. Only one person was admitted to the hospital due to pneumonia. COVID‐19 re‐infection was reported by three patients. No pwNMOSD died as a result of COVID‐19 disease. Cough was the most frequently reported symptom. The incidence of COVID‐19 infection in our cohort was 21.1%. Immunosuppressants were taken by 57.9% of pwNMOSD with COVID‐19, and by 84.5% of pwNMOSD without COVID‐19.

Conclusions

Due to the small sample size, there was no predominant difference in infection between infected and uninfected patients with or without immunosuppressant drugs. However, given that immunosuppressants are a risk for infection, patient decision‐making in their selection is important.
An impact evaluation of conservation investments targeting long‐distance migratory species
Authors: Donlan C. Josh , Eusse‐González Diana , Luque Gloria M. , Reiter Matthew E. , Ruiz‐Gutierrez Viviana , Allen Michael C. , Johnston‐González Richard , Robinson Orin J. , Fernández Guillermo , Palacios Eduardo , Valenzuela Jorge
Published: October 2023

We evaluated the impact of a philanthropic program investing in the conservation of sites along the Pacific Americas Flyway, which spans >16,000 km of coastline and is used by millions of shorebirds. Using a quasi‐experimental, mixed methods approach, we estimated what would have happened to shorebird populations at 17 wintering sites without the sustained and additional investment they received. We modeled shorebird populations across the entire flyway and at sites with and without investment. Combining shorebird abundance estimates with a land‐cover classification model, we used the synthetic control method to create counterfactuals for shorebird trends at the treatment sites. We found no evidence of an overall effect across three outcome variables. Species‐ and site‐level treatment effects were heterogeneous, with a few cases showing evidence of a positive effect, including a site with a high level of overall investment. Results suggest six shorebirds declined across the entire flyway, including at many Latin American sites. However, the percentage of flyway populations present at the sites remained stable, and the percentage at the treatment sites was higher (i.e., investment sites) than at control sites. Multiple mechanisms behind our results are possible, including that investments have yet to mitigate impacts and negative impacts at other sites are driving declines at the treatment sites. A limitation of our evaluation is the sole focus on shorebird abundance and the lack of data that prohibits the inclusion of other outcome variables. Monitoring infrastructure is now in place to design a more robust and a priori shorebird evaluation framework across the entire flyway. With this framework, it will prove easier to prioritize limited dollars to result in the most positive conservation outcomes.
Rates of tree cover loss in key biodiversity areas on Indigenous Peoples’ lands
Authors: Simkins Ashley Thomas , Donald Paul F. , Beresford Alison E. , Butchart Stuart H. M. , Fa Julia E. , Fernández‐Llamazares Alvaro Onrubia , Garnett Stephen T. , Buchanan Graeme M.
Published: October 2023

Indigenous Peoples’ lands (IPL) cover at least 38 million km2 (28.1%) of Earth's terrestrial surface. These lands can be important for biodiversity conservation. Around 20.7% of IPL intersect areas protected by government (PAs). Many sites of importance for biodiversity within IPL could make a substantial but hitherto unquantified contribution to global site‐based conservation targets. Key Biodiversity Areas (KBAs) represent the largest global network of systematically identified sites of high importance for biodiversity. We assessed the effectiveness of IPL in slowing biodiversity loss inside and outside PAs by quantifying tree cover loss from 2000 to 2019 in KBAs at international and national levels and comparing it with losses at equivalent sites outside mapped IPL. Based on a matched sample of 1‐km2 cells in KBAs inside and outside mapped IPL, tree cover loss in KBAs outside PAs was lower inside IPL than outside IPL. By contrast, tree cover loss in KBAs inside PAs was lower outside IPL than inside IPL (although the difference was far smaller). National rates of tree cover loss in KBAs varied greatly in relation to their IPL and PA status. In one half of the 44 countries we examined individually, there was no significant difference in the rate of tree cover loss in KBAs inside and outside mapped IPL. The reasons for this intercountry variation could illuminate the importance of IPL in meeting the Convention on Biological Diversity's ambition of conserving 30% of land by 2030. Critical to this will be coordinated action by governments to strengthen and enforce Indigenous Peoples’ rights, secure their collective systems of tenure and governance, and recognize their aspirations for their lands and futures.
Relationship between two pathogens in an amphibian community that experienced mass mortalities
Authors: Thumsová Barbora , Alarcos Gonzalo , Ayres Cesar , Rosa Gonçalo M. , Bosch Jaime
Published: October 2023

Because host species tend to harbor multiple parasitic species, coinfection in a host is common. The chytrid fungus Batrachochytrium dendrobatidis (Bd) and the viruses in the genus Ranavirus (Rv) are responsible for the decline of amphibians worldwide. Despite wide geographical co‐occurrence and the serious conservation problem that coinfection with these pathogens could represent, little is known about their possible synergistic interactions and effects in a host community. We investigated the occurrence and associations between these two pathogens in an amphibian community after Rv‐driven disease outbreaks were detected in four populations of the Iberian ribbed newt (Pleurodeles waltl) in northwestern Spain. We collected tissue samples from amphibians and fish and estimated Bd and Rv infection loads by qPCR. A few months after the most recent mass mortality event, Rv infection parameters at the affected sites decreased significantly or were lower than such registered at the sites where no outbreaks were recorded. Both pathogens were simultaneously present in almost all sites, but coinfection in a single host was rare. Our findings suggest that the co‐occurrence of Bd and Rv does not predict adverse outcomes (e.g., enhanced susceptibility of hosts to one pathogen due to the presence or infection intensity of the other) following an outbreak. Other variables (such as species identity or site) were more important than infection with a pathogen in predicting the infection status and severity of infection with the other pathogen. Our results highlight the importance of host‐specific and environmental characteristics in the dynamics of infections, coinfection patterns, and their impacts.
New Law for Old Trees in Romania: lessons and opportunities
Authors: Hartel Tibor , Arghiuș Viorel , Stoican Florin , Réti Kinga Olga , Bouriaud Laura
Published: October 2023

Large Old Trees (LOT) are keystone ecological structures and have high cultural and economic importance. Still, LOT are only exceptionally targeted specifically by National Laws and are absent from powerful nature conservation policies (e.g., the Natura 2000 protected area policies of the European Union). Romania recently adopted a Law for its LOT. As persons who contributed to the scientific premisses and the first draft of this Law as well as in the advocacy for Romanian LOT, we present the Law (its weaknesses and opportunities) and provide insights into encourage other countries for adopting the Law specifically for LOT.
Fusion to the sacrum or pelvis increases survival in patients with Duchenne muscular dystrophy
Authors: Cho Robert
Published: October 2023

This commentary is on the original article by Arshad and Tsirikos on pages 187–194 of this issue.
High importance of indirect evolutionary rescue in a small food web
Authors: van Velzen Ellen
Published: October 2023

Evolutionary rescue may allow species to survive environmental change, but how this mechanism operates in food webs is poorly understood. Here, the evolutionary rescue was investigated in a small model food web, systematically allowing the evolution of each single species in order to reveal how its adaptation affects the persistence of itself and others. The impact of evolution was highly species‐specific and not necessarily positive: only one species, the specialist predator, consistently had a positive impact on overall persistence. Most strikingly, evolution overwhelmingly affected other species: rescue of others (indirect rescue) was far more frequent than self‐rescue, and negative effects were nearly always indirect. This demonstrates that evolutionary rescue in food webs is inextricably bound up with species interactions, as the effects of evolution in one species ripple through the entire community. It is therefore critically important to consider the food web context in efforts to understand how species may survive global change.
S‐acylation: an orchestrator of the life cycle and function of membrane proteins
Authors: Mesquita Francisco S. , Abrami Laurence , Samurkas Arthur , van der Goot F. Gisou
Published: October 2023

S‐acylation is a covalent post‐translational modification of proteins with fatty acids, achieved by enzymatic attachment via a labile thioester bond. This modification allows for dynamic control of protein properties and functions in association with cell membranes. This lipid modification regulates a substantial portion of the human proteome and plays an increasingly recognized role throughout the lifespan of affected proteins. Recent technical advancements have propelled the S‐acylation field into a ‘molecular era’, unveiling new insights into its mechanistic intricacies and far‐reaching implications. With a striking increase in the number of studies on this modification, new concepts are indeed emerging on the roles of S‐acylation in specific cell biology processes and features. After a brief overview of the enzymes involved in S‐acylation, this viewpoint focuses on the importance of S‐acylation in the homeostasis, function, and coordination of integral membrane proteins. In particular, we put forward the hypotheses that S‐acylation is a gatekeeper of membrane protein folding and turnover and a regulator of the formation and dynamics of membrane contact sites.
How Does the Bible Refer to Christ? Interacting with Augustine the Allegorist
Authors: Boone Mark J.
Published: October 2023

Abstract: Traditional Christianity teaches that the Bible's primary referent is Jesus Christ, the Messiah, and Christians have long looked for ways to connect every passage in the Bible to the Christ. One venerable strategy is the allegorical or figurative approach of creatively interpreting any unit of biblical meaning, sometimes down to the individual words, as referencing Christ. Alternatively, we might take the biblical narrative itself as referencing Christ and find the connection of smaller units of meaning to Christ through their place in that narrative. My article clarifies this topic through interaction with an exemplary practitioner of the strategy of figurative reading, the Church Father Augustine. I will first explain Augustine's reasons for his hermeneutics, which stem largely from his focus on smaller units of reference such as the word and the sentence. Then I will argue that his reasons are not persuasive if indeed the Bible does refer to Christ at a broader level, the level of narrative.
THE TWILIGHT OF THE GODS? GENOMIC HISTORY AND THE RETURN OF RACE IN THE STUDY OF THE ANCIENT MEDITERRANEAN
Authors: Parmenter Christopher Stedman
Published: October 2023

This article discusses the impact of genomic history, a subdiscipline that emerged in the study of the ancient Mediterranean in the 2010s. In 2014, scientists first published a method for extracting genetic material, which they christened aDNA (ancient DNA), from ancient human remains in hot climates. After a decade of research, genomic history is now poised to transform our understanding of Mediterranean premodernity, centering migration and conflict as the key mechanisms for cultural change. Despite years of critique, aDNA researchers have failed to seriously examine the bioessentialist assumptions implicit in their work—a failure that has led many to deploy language that is strikingly evocative of pre‐World War II racialism. Even worse, some genomic historians continue to make troubling overtures toward the ethnonationalist Right, which has been ascendant across Europe and North America since the 2010s. This article traces the intellectual genealogy of genomic history from World War II to the present, examines recent attempts to answer criticism from the humanities and social sciences, and suggests paths for responsible use of aDNA in historical and prehistorical scholarship.
Bictegravir/emtricitabine/tenofovir alafenamide in paediatrics: Real‐life experience from a French cohort (2019–2023)
Authors: Frange P. , Veber F. , Burgard M. , Blanche S. , Avettand‐Fenoel V.
Published: October 2023

Objectives

Although widely recommended, data on bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) efficacy in HIV‐1‐infected children/adolescents are mainly extrapolated from studies in adults and one paediatric trial in which subjects have good treatment adherence. This study aimed to provide data about the risk of virological failure (VF) and acquired genotypic resistance in children and adolescents receiving BIC/FTC/TAF in a real‐world setting.

Methods

This retrospective monocentric study included 74 paediatric patients who received BIC/FTC/TAF during ≥6 months in 2019–2023. VF was defined as not achieving a plasma viral load <50 copies/mL within 6 months of BIC/FTC/TAF initiation or as experiencing virological rebound ≥50 copies/mL.

Results

Most patients were antiretroviral therapy (ART)‐experienced (93.2%), previously exposed to integrase inhibitors (85.1%) and displayed viral suppression at baseline (67.6%). Their median age was 11.2 years [interquartile range (IQR): 8.8–15.2]. BIC/FTC/TAF introduction reduced treatment burden in most ART‐experienced subjects. Genotypic susceptibility score of BIC/FTC/TAF was ≥2 in all cases. Median follow‐up was 40 months (IQR: 21–46). VF occurred in 28 people (37.8%), more frequently in the case of VF versus viral suppression at baseline (68% vs. 26%, P = 0.02). BIC/FTC/TAF was interrupted for suspected intolerance in only one case (1.4%). Nucleoside reverse transcriptase inhibitor (NRTI) mutation (T69D/N) emerged in one patient (3.6% of VF) after 47 months of continuous detectable viraemia while on ART. No acquisition of mutations in the integrase gene was observed.

Conclusion

Because of its high genetic barrier to resistance, BIC/FTC/TAF could be especially useful in the paediatric population, in which the risk of poor treatment adherence and VF is high.
LBBB and heart failure—Relationships among QRS amplitude, duration, height, LV mass, and sex
Authors: Manne Mahesh , Niebauer Mark , Tchou Patrick , Varma Niraj
Published: October 2023

Background

Height, left ventricular (LV) size, and sex were proposed as additional criteria for patient selection for cardiac resynchronization therapy (CRT) but their connections with the QRS complex in left bundle branch block (LBBB) are little investigated. We evaluated these.

Methods

Among patients with “true” LBBB, QRS duration (QRSd) and amplitude, and LV hypertrophy indices, were correlated with patient's height and LV mass, and compared between sexes.

Results

In this study cohort (n = 220; 60 ± 12 years; left ventricular ejection fraction [LVEF] 21 ± 7%; mostly New York Heart Association II–III, QRSd 165 ± 19 ms; 57% female; 70% responders [LVEF increased ≥5%]), LV mass was increased in all patients. QRS amplitude did not correlate with LV mass or height in any individual lead or with Sokolow‐Lyon or Cornell‐Lyon indices. QRSd did not correlate with height. In contrast, QRSd correlated strongly with LV mass (r = .51). CRT response rate was greater in women versus men (84% vs. 58%, p < .001) despite shorter QRSd [7% shorter (p < .0001)]. QRSd normalized for height resulted in a 2.7% and for LV mass 24% greater index in women.

Conclusion

True LBBB criteria do not exclude HF patients with increased LV mass. QRS amplitudes do not correlate with height or LV mass. Height does not affect QRSd. However, QRSd correlates with LV size. QRSd normalized for LV mass results in 24% greater value in women in the direction of sex‐specific responses. LV mass may be a significant nonelectrical modifier of QRSd for CRT.
Rescue method for a stranded giant manta ray (Mobula birostris)
Authors: Chupil Henrique , Medeiros Andrielli Maryan , Dopona Alisson Peter Brito , Treza Carolina de Castro , Pessi Caroline Freitas , Pereira Eduardo Roberto
Published: October 2023

An opportunistic rescue of a stranded 6 m giant manta ray off Ilha Comprida, in São Paulo, southeastern Brazil, revealed a new technique for returning large bodied mobulid rays to the water once beached. The technique, adapted from protocols to move stranded cetaceans, was modified to suit the dorso‐ventrally compressed shape of mobulid rays and reduce damage to the animal while being pulled back into deeper water. The method and suggestions for its improvement have been described with the intention of assisting in the rescue of other stranded large mobulids.
Globalization: Migrant nurses' acculturation and their healthcare encounters as consumers of healthcare
Authors: Zlotnick Cheryl , Patel Harshida , Ali Parveen Azam , Odewusi Temitayo , Luiking Marie‐Louise
Published: October 2023

Globally, one of every eight nurses is a migrant, but few studies have focused on the healthcare experiences of migrant nurses (MNs) as consumers or recipients of healthcare. We address this gap by examining MNs and their acculturation, barriers to healthcare access, and perceptions of healthcare encounters as consumers. For this mixed‐methods study, a convenience sample of MNs working in Europe and Israel was recruited. The quantitative component's methods included testing the reliability of scales contained within the questionnaire and using Hayes Process Model #4 to test for mediation. The qualitative component's methods included analyzing interviews with iterative inductive thematic analysis. Quantitative findings on MNs (n = 73) indicated that the association between acculturation and perception of the healthcare encounter, which MNs experienced as healthcare consumers, was mediated by barriers to healthcare access, even after adjusting for age and gender (p = 0.03). Qualitative interviews with MNs (n = 13) provided possible explanations for the quantitative findings. Even after working in the host country's healthcare system for several years, MNs reported difficulties with their healthcare encounters as healthcare consumers, not only due to their limited knowledge about the culture and healthcare resources but also due to the biased responses they received.
Authigenic‐cemented pebbles formed during Pleisto–Holocene transgression of gently inclined coastal plains
Authors: Wetzel Andreas , Niemann Helge
Published: October 2023

From numerous modern gently inclined coastal areas and deltas around the world carbonate‐cemented sandstone slabs and pebbles have been reported. Such sandstones collected at the coast of the German North Sea and the Mediterranean Sea (Rhône Delta) are cemented by calcite derived from the anaerobic oxidation of methane, as evidenced by biomarkers and δ13C isotope values <−35‰ typical of anaerobic oxidation of methane. The methane originated from peat, which formed in coastal lowlands, deltas and channels during the Pleisto–Holocene transgression due to the concomitant rise of the groundwater level. During ongoing transgression, the peat became overlain by marginal‐marine mud, acting as a seal, and finally by marine sand. In shallow‐marine settings, wave‐pumping effects during storms led to seal failure and methane could migrate upward. This scenario matches recent observations in the German North Sea where a pockmark field formed during the winter storm season. The emanating methane was eventually oxidized aerobically or anaerobically by anaerobic oxidation of methane in the sand cover. The CH4 generated in the peat underneath contains ‘old’ carbon that becomes, in the case of anaerobic oxidation of methane, incorporated into bicarbonate, which in turn facilitates cementation of sand and, thus, causes the peculiar situation that the C‐14 age of the cement is older than the bioclasts embedded in the sandstone. Such authigenically cemented sandstones have environmental significance for flooding of gently inclined coastal plains.
Cover crops and soil loosening are key components for managing P and C stocks in agricultural soils
Authors: Mattila Tuomas J.
Published: October 2023

Agricultural soils have accumulated phosphorus (P) and lost carbon (C) in the recent decades. Simultaneously, soil structure has been degraded by the large increase in machinery weight. High wheel loads compact the subsoil, resulting in reduced root growth, decreased yields, and hence decreased C inputs and P removals. To reduce the accumulated excess P stock, the P balance should be kept strongly negative for decades, which requires high biomass production. P accumulation in poorly yielding field parts has created local hotspots, often characterized by soil compaction and poor drainage. They may be only 1%–6% of the agricultural landscape area but present a high risk for waterbodies. Identifying and targeting these hotspots for P removal can be a key strategy for mitigating P emissions. Achieving the P removal is most likely to require soil loosening to repair the damage caused by compaction and use of cover crops to mine out the accumulated P. This soil improvement strategy can also be beneficial for C sequestration and crop productivity. This commentary highlights the current status and recent developments in the interactions between compaction, cover crops and P loss to provide a research basis for developing landscape‐level strategies.
An Invariant Representation of Coupler Curves Using a Variational AutoEncoder: Application to Path Synthesis of Four-Bar Mechanisms
Authors: Nurizada Anar , Purwar Anurag
Published: October 2023

This paper focuses on the representation and synthesis of coupler curves of planar mechanisms using a deep neural network. While the path synthesis of planar mechanisms is not a new problem, the effective representation of coupler curves in the context of neural networks has not been fully explored. This study compares four commonly used features or representations of four-bar coupler curves: Fourier descriptors, wavelets, point coordinates, and images. The results demonstrate that these diverse representations can be unified using a generative AI framework called variational autoencoder (VAE). This study shows that a VAE can provide a standalone representation of a coupler curve, regardless of the input representation, and that the compact latent dimensions of the VAE can be used to describe coupler curves of four-bar linkages. Additionally, a new approach that utilizes a VAE in conjunction with a fully connected neural network to generate dimensional parameters of four-bar linkage mechanisms is proposed. This research presents a novel opportunity for the automated conceptual design of mechanisms for robots and machines.
Buckling Load Optimization of Variable Thickness and Stiffness Composite Plate Using Semi-Analytical Method: Aerospace Structures
Authors: Vallabhbhai Patel Jeegar , Amgai Sandesh , Davidson Paul
Published: October 2023

Optimized structures with lightweight designs are an essential requirement for aerospace structures. Thin skin composites are utilized in such structures owing to their strength-to-weight benefits. Additionally, varying the fiber angle in the composite structures allows for design with localized stiffness variation. Stiffness variation, especially in bending can also be achieved by varying local thickness. In this study, we attempt to improve the buckling performance of the thin skin structures by combining the fiber angle variation and thickness variation spatially across a panel. The semi-analytical approach was used to calculate the buckling load of the panel was calculated with the objective to increase the buckling load while maintaining the weight of the uni-axially loaded panels. The optimized buckling value was observed to be increased up to 0.5308 N/mm from a quasi-isotropic stack up ([−45/45/45/−45]2s) of constant thickness plies (0.125 mm each), by varying the fiber angles of the laminate stack, with a further increase up to 1.49 N/mm by inducing thickness variation along with the varied fiber angles.
A Micro-Scale Numerical Investigation of Internal and Interfacial Void Defects in Adhesive on Failure Behavior of Adhesively-Bonded Materials With Rough Surfaces
Authors: Qiao Yao , Ko Seunghyun , Samanta Avik , Merkel Daniel R. , Shin Yongsoon , Guzman Anthony , Nickerson Ethan K. , Ramos Jose L. , Simmons Kevin L.
Published: October 2023

This paper studied the effects of air void defects on the failure behavior of adhesively-bonded materials under global shear via micro-scale computational modeling. The numerical results indicated that interfacial void defects can largely facilitate interfacial debonding of a weaker adherend/adhesive interface under shear. However, this is not the case for a stronger adherend/adhesive interface, showing the reduction on the nominal shear strength of an adhesive joint is mainly due to internal void defects. The reduced bonding performance due to voids can be improved by leveraging an appropriate surface roughness. This preliminary investigation is a first step to better understand the micro-mechanics of inter-facial failure in the adhesion of a roughened/patterned adherend via surface modification(s) and an adhesive, and also shows the importance of minimizing interfacial void defects in particular at a weaker adherend/adhesive interface via different techniques.
Quantification of Material and Geometric Defects Variability in Fiber-Reinforced Composites With Ply Waviness Defects
Authors: Díaz-Montiel Paulina , González Ayala Gabriela , Rivera Adrian , Mauk Rebekah , Reiner Coleman , Venkataraman Satchi
Published: October 2023

This article presents the findings of defects in fiber-reinforced polymeric composite laminates manufactured with artificially-induced ply waviness features. The design of the ply waviness mimics defects seen in composites at ply drops and in regions of tow overlaps and gaps. Detailed imaging of the composite microstructure after curing is conducted via optical microscopy, and material and defect variability are quantified.

Results confirm that manufacturing of composites with artificially-induced ply waviness causes additional defects at lower material scales, including fiber volume fraction variations, voids/porosity, and ply thickness variations. The consolidation during debulking, flow of the resin, and deformation of the fibers at regions of gaps or overlaps cause these additional defects during the curing. Efforts to understand strength knockdowns in composites due to ply waviness, therefore, must also include such associated defects or look for process improvements that minimize them.
Enhancement of NX NASTRAN Flutter Prediction Capabilities and Use of Experimental Parameters in Aeroelastic Calculations
Authors: Gagliardi Giuseppe Maurizio , Kulkarni Mandar D. , Marulo Francesco
Published: October 2023

This work introduces a novel methodology to improve the flutter calculation capabilities of NX NASTRAN software. The developed methodology, named Master of Modes (MoM), further enhances its capabilities to exceptionally increase the accuracy of the structural model. MoM approach allows for smarter numerical models where each vibration mode can be individually selected and included in the analysis. The investigation of the behavior of each mode alone and the study of how it interacts with each of the other modes enables an improved investigation of the Velocity-damping-frequency (Vgf) plots, solving the tedious problem of roots sorting. Furthermore, MoM allows a partial or complete utilization of experimental data to improve flutter calculations. Until now, data coming from Ground Vibration Testing (GVT) are merely used to tune the numerical flutter model trying to obtain the best correspondence for modal parameters. With MoM, it is possible to go beyond this tuning procedure and use experimental data in a more direct and massive way, allowing the highest possible fidelity of the structural model. The procedure has been applied and validated on a wide variety of models including full-aircraft aeroelastic models.
Finite Element Modeling on F.R.E.T. for Origami-Inspired CubeSat Applications
Authors: Troise Andrea , Buscicchio Alessandro , Netti Vittorio , Cinefra Maria
Published: October 2023

Modelling of multi-layer rigid-flex printed circuit boards (PCB) for origami structures can be carried out with several different strategies, often resorting to models that either require a considerable amount of computational power, resulting excessively complex, or descending to oversimplifications that do not grasp the structural dynamics. Among these strategies, finite element modelling results the most convenient because it seizes the behaviour of the system with an eye on computational efficiency. This study shows a new finite element analysis approach to model the dynamics of FRET (Flexible Reinforced Electronics with Textile), a novel technology enabler for aerospace structures, applied on a COTS solar panel for small CubeSats (Solarcube). Solar-cube is a deployable solar panel prototype system based on the flasher origami pattern, which possesses a large ratio of stowed-to-deployed area. Two finite element analyses are carried out, The first one is a launch forces modal analysis of the undeployed prototype, during which vibrations and impact shocks become relevant. The second analysis was performed on the fully-deployed model to investigate the response of the solar panel substructure to the various solicitations relevant to the working phase. The results allow to evaluate the effectiveness of the finite element technique in this specific scenario and also to explore the possibilities of the FRET technology, applied to deployable space structures.
An Optimization Strategy Based on Machine Learning and Layer-Wise Models to Minimize Process-Induced Deformations in CFRP Parts
Authors: Zobeiry Navid , Zappino Enrico , Schoenholz Caleb , Masia Rebecca , Petrolo Marco
Published: October 2023

Virtual manufacturing of composites has become increasingly important over the last two decades as a tool to improve the quality and sustainability of composite structures. However, the manufacturing process simulation is complex and multidisciplinary and may require high computational overheads. This paper aims to the virtual curing of composite parts and use machine learning techniques to optimize the stacking sequence and minimize process-induced deformations. Such a methodology combines 1D finite element (FE) models, experimental testing, and machine learning models. The FE model exploits higher-order layer-wise theories to compute accurate through-the-thickness distributions of shear and peeling stresses. 1D elements lead to better efficiency by requiring a fraction of the computational cost usually needed by 3D finite element models. DSC and DMA tests characterize relevant material properties, e.g., the degree of cure, viscoelastic moduli, and free strains. Furthermore, a cure-hardening instantaneously linear elastic (CHILE) constitutive model is adopted. The FE model allows the rapid evaluation of residual stresses, spring-in angles, and warpage. Due to its numerical efficiency, various lay-up combinations can be evaluated, and the results can feed a dataset to train an Artificial Intelligence system. This study uses Gaussian process regression (GPR) to fit probabilistic response surfaces to numerical deformation predictions, explore the design space, and find optimal lay-ups minimizing defects. Furthermore, mitigation strategies are developed using specific lay-ups around geometry transition points such as sharp corners. Finally, optimal lay-ups are validated by fabricating L-shaped parts with similar conditions.
A Theory-Guided Machine Learning and Reduced-Order Finite Element Modeling Framework to Accelerate Process Simulation of Aerospace Composite Parts
Authors: Fu Huilong , Zobeiry Navid
Published: October 2023

Finite Element (FE) analysis is widely used for process simulation of advanced composites in aerospace applications. However, as the fidelity of FE models improves, the cost and time to calibrate, setup and perform simulations also increases significantly. To speed-up process simulation, reduced-order FE can be used. Reduced-order FE and Machine Learning (ML) can be combined to further speed-up the process simulation and enable process optimization. However, theory-agnostic ML usually requires large datasets which may not be feasible in industry. This can be mitigated by integrating the underlying physics into ML to develop Theory-Guided Machine Learning (TGML) models. In this study, for process simulation and optimization of a composite stringer on a wing skin, three modeling approaches are compared: 1) high-fidelity FE modeling, 2) surrogate ML modeling based on high-fidelity FE results, and 3) surrogate TGML modeling based on both high-fidelity and low-fidelity FE results. It is shown that TGML, with the guidance of underlying physics of composites curing, can improve prediction accuracy and significantly reduce the amount of data needed for training compared to theory-agnostic ML.
Equivalent Modeling Scheme of Cellular Structure Under Extreme Loading Using Finite Element Method
Authors: Verma Praveen Kr. , Sankrityayan Rohit , Chawla Anoop , Mukherjee Sudipto , Dubey Devendra K.
Published: October 2023

Bio-inspired cellular structures are being used for armor design for human safety. During highly dynamic phenomena such as impact and shock loading, these structures absorb energy by plastic deformation, hence minimizing injuries. Numerical approach employed for impact and ballistic simulations is well established for medium-range strain rates between 400 and 700 per second. However, under shock loading, the structure undergoes deformation with strain rates ranging 1000 to 5000 per second as it involves rampant interaction of shock waves with structures. For numerical modelling of such phenomenon, ConWep and MM-ALE simulation techniques are used effectively. In ConWep, the shock loads applied on structures are empirically derived and extrapolated from the experiment which is suited for higher scaled distances. The interaction between eulerian and lagrangian mesh is defined using MM-ALE approach by using FSI (Fluid-structure interaction) coupling. Intuitively, these methodology are stable for a far-field analysis but have shown inconsistency in predicting the behaviour for close to contact detonation scenarios. Current study investigates a deformable hybrid sandwich structure (such as cellular sandwich structures) subjected to such close-range scenario using non-cellular modelling techniques. The cellular structure is defined using an equivalent material model by implementing continuum orthotropic properties, considering lagrangian mesh to ameliorate the computational time. Hydrocodes based finite element scheme employed in LS-DYNA for investigating specific energy absorption (SEA) and force transmission through the structure during the deformation. Study aids in minimizing computational time and modelling complexities particularly in case of near-field detonation scenario. It is observed that the compression pattern in cellular structure is different for a near-field scenario when compared with the far-field scenarios.
Lightweight Composites With 3D Printed Sensors for Real-Time Damage Detection
Authors: Fitzpatrick Daniel , Billings Christopher , Liu Yingtao
Published: October 2023

Although composites are widely used and accepted across various industries, concerns still remain about the structural integrity of composite materials that are subject to fatigue and possible impact loading. The goal of this paper is to describe the design, development, manufacture, and characterization of a novel type of fiber-reinforced composite laminates with embedded nanocomposite-based strain sensors for potential real-time load monitoring and damage detection. The fiber reinforced composite laminates are composed of Kevlar fiber and an epoxy mixture, with a nanocomposite of carbon nanotubes (CNTs) and the same epoxy mixture. The CNT-based nanocomposite is 3D printed onto a strip of Kevlar fiber at a speed of 1 mm/s in a strain sensor pattern. Then, high-quality structural composites are manufactured by wet layup of 6 layers of Kevlar fiber, with the sensor embedded within. The manufactured composite laminates with embedded nanocomposite sensors are characterized under uniaxial-tension load to understand their in-situ sensing capability. To quantify the piezoresistive behavior, relative resistance change ΔR/R0 (where R0 is the initial resistance at the unloaded condition) is recorded while applying quasi-static tension at different strains in a cyclic manner. The mechanical properties and piezoresistive functionality of the composites will be determined as the samples undergo deformation. The corresponding piezoresistive change happening simultaneously can be used as a damage identification feature. This research can assist in the development of reliable and accurate damage detection technologies to improve the structural durability and operational safety of lightweight composite laminates for industry applications.
Design of In-Plane and Thickness-Wise Functionally Graded Shells
Authors: Serhat Gokhan
Published: October 2023

Functionally graded material (FGM) designs can outperform structures made of conventional materials due to the improved internal load distribution. However, the actual potency of FGM highly depends on the parametrization of the material distribution. Hence, the determination of the effective grading approaches suitable for different scenarios is highly important. This study compares the in-plane and thickness-wise grading strategies for the design of FGM shells. The considered structures comprise two materials, one that is relatively stiffer-heavier and another being softer-lighter. The proportion of the denser material is constrained not to exceed half of the total volume. The design task concerns maximizing the fundamental frequency as the objective. The analyses were performed for different combinations of shell thickness and boundary conditions. The results show that the effectiveness of the grading type notably depends on the analyzed case. The findings of this study can serve as a guideline for future studies investigating similar problems.
Healing Efficiency Evaluation of CFRP Composite Wing After Bird Strike
Authors: Brezetić Dominik , Ivančević Darko , Smojver Ivica
Published: October 2023

This work presents results of the research assessing application advantages of intrinsically self-healing FRP composites over conventional FRP composite materials in typical airframe structures. The previously developed multiscale constitutive model for intrinsically self-healing FRP composites has been validated for the cases of static loading conditions (3PB test) in [1], and dynamic loading conditions (LVI) in [2]. The model is implemented in Abaqus/Explicit and Abaqus/Standard user material subroutines VUMAT and UMAT, respectively. Experimental and numerical analysis results of bird strike in FRP composite wing are taken from [3] and used as a reference. Inhere, for analysis purposes, the conventional epoxy resin is replaced with a self-healing polymer blend of Epon™ 828EL epoxy resin with 25vol% of PCL, poly(ε-caprolactone) and it is combined with T700 UD fibres to obtain intrinsically self-healing FRP composite. In the conclusions, the critical assessment of the obtained results is performed, and advantages of the new material systems are validated.
Slope-Inertia Model for Rotating Timoshenko-Ehrenfest Beams
Authors: Rangari Apurva Sunil , Elishakoff Isaac , Sarkar Korak
Published: October 2023

Rotating beams are used to model various aerospace and mechanical structures like helicopter blades, wind turbines, gas turbine, propeller blades, etc. The long and slender beams are modelled using the Euler-Bernoulli beam theory (EBT). Whereas the short and thicker beams are usually modelled using the Timoshenko beam theory (TBT) in order to incorporate the effects of rotary inertia and shear deformation. This paper focuses on the free vibration analysis of axially inhomogeneous and nonuniform rotating beams considering the Timoshenko-Ehrenfest slope-inertia model (TESIM) as the governing equation. The TESIM governing equation is obtained by modifying the rotational term in the kinetic energy expression of the original Timoshenko beam theory. To solve the TESIM equation finite element method has been used. Natural frequencies are then calculated for different material and geometric non-uniformities along the beam axis, and for various boundary conditions.
A Variable Camber Piezocomposite Rotor: Aerodynamic Analysis
Authors: Shah Bharg , Bilgen Onur
Published: October 2023

Multi-rotor vehicles use complex mechanisms and/or mechanical components and varying rotor speeds to attain stability, control, and maneuverability. This research proposes variable camber shape morphing blades for thrust generation. The goal is to use minimum number of mechanical components and produce varying thrust levels without varying the rotor speeds. This mechanism-free concept is referred to as the Solid-State Rotor by the authors. The concept employs morphing blades with strain-inducing actuators such as the Macro-Fiber Composite device. This concept uses onboard electronics powered by an electromagnetic generator attached to the rotor. The excitation of the strain-inducing actuators on the rotor blades changes the camber of the rotor blades, which leads to a change in thrust. In this paper, first, the concept is described. Next, aerodynamic analyses are conducted using a theoretical model based on the XROTOR software to predict the aerodynamic performance of variable camber piezocomposite rotors for various geometric and flow properties.
Hierarchical Modelling of Variable Stiffness Composite Plates Through Carrera’s Unified Formulation
Authors: Iannotta Domenico Andrea , Giunta Gaetano , Montemurro Marco
Published: October 2023

Variable Stiffness Composites (VSCs) have been lately proposed as a promising alternative to classical straight fibres composites where the variation of fibres orientation angle within the plane of the structure allows for a more general design of composite structures and consequent performances. Nevertheless, this new class of materials calls for new modelling techniques due to a higher complexity in their analysis related to an increased amount of design variables that is usually considered. In order to overcome these difficulties, Carrera’s Unified Formulation has been used in previous works investigating buckling, vibrational and stress analyses on VSCs. Usually, one-dimensional Carrera’s Unified Formulation beam models are used, while two-dimensional plate models are obtained as a particular case of shells by considering a null curvature. In most cases, a linear law is considered to describe the variation of fibres orientation in the main plane of the structure. The purpose of this article is developing a Carrera’s Unified Formulation two-dimensional plate finite element family for the mechanical analysis of composite laminated plate structures with curvilinear fibres using, besides the Principle of Virtual Displacements (PVD), Reissner’s Mixed Variational Theorem (RMVT). The outcomes of the proposed approach when investigating VSC plates is compared with the results present in the literature or obtained via commercial software tools in order to assess the effectiveness of the proposed models.
Machine Learning Assisted Composite Rotor Blade Planform Design
Authors: Tao Fei , Tian Su , Du Haodong , Yu Wenbin
Published: October 2023

Composite materials are increasingly used in the design of rotor blades due to their high stiffness-to-weight ratio and excellent fatigue life. Currently, the composite rotor blade planform design intensively focuses on optimizing planform parameters to achieve higher performance. However, the strength of the material is rarely considered in the planform design. One issue is that the failure analysis of the rotor blade is usually performed by an expensive multiscale analysis which requires calculating the sectional properties, computing the rotor blade global response, and reproducing local stress for each layer of the composite blade. This process is inefficient when applied to an optimization framework, as whenever there is a new structural load, this analysis procedure needs to be performed again. Unfortunately, millions of load cases can be accumulated during the blade design optimization. The ignoring of strength analysis may result in the blade working in an unsafe or low safety factor region, as composite materials are anisotropic and susceptible to various failure mechanisms. In this paper, we propose to optimize the composite rotor blade planform design with strength consideration. The optimized design can improve the performance of the aircraft and ensure the structure is within the safety margin. To reduce the computational cost of the cross-sectional failure analysis, we will use machine learning model to construct a beam-level failure criterion surrogate model to replace the physics-based cross-sectional failure analysis. The surrogate model is constructed based on the Timoshenko beam model via Artificial neural networks (ANN), where the mapping will be between blade loads and the strength ratios of the cross-section.
Improved impedance matching speed with gradient descent for advanced RF plasma system
Authors: Shin Dongwon , Hong Sang Jeen
Published: October 2023

Plasma processes are widely used in the fabrication of integrated circuits for the smaller, faster, more powerful circuits demanded by new technology. High-performance semiconductor equipment is required for dynamic random-access memory and three-dimensional NAND flash memory in semiconductor manufacturing. To enhance the speed of RF impedance matching, this paper proposes a method for calculating the load impedance of the plasma chamber. To calculate the target value of the variable components, we employ the input impedance of the impedance-matching unit and the complex impedances of the variable components. In addition, the internal parameters are automatically tuned through the gradient-descent method of machine learning, which improves the accuracy of impedance matching. The new matching method achieved a fast matching time and high efficiency of the matching trajectories. Moreover, it avoids the increase of the reflected power during the matching process, which causes plasma instability, and prohibits significant matching delay in a specific area, which disadvantages the conventional matching algorithm. These advantages are expected to significantly expand the development of new plasma processes from that of conventional impedance matching.