Engineering Archive
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<p>engrXiv (Engineering Archive) is dedicated to the dissemination of engineering knowledge quickly and efficiently. The server is directed by Devin R. Berg and <a href="https://www.openengr.com/" target="_blank" rel="noopener">Open Engineering Inc.</a>, a 501(c)(3) non-profit.</p> <p>Follow us on <a href="https://twitter.com/engrXiv" target="_blank" rel="noopener">Twitter</a>, <a href="https://scicomm.xyz/@engrxiv" target="_blank" rel="noopener">Mastodon</a>, or <a href="https://www.facebook.com/engrXiv" target="_blank" rel="noopener">Facebook</a> or watch the <a href="https://blog.engrxiv.org/" target="_blank" rel="noopener">engrXiv blog</a> for updates.</p>en-USEngineering ArchiveVibration-based Diagnosis of Core Fractures in Composite Insulators
https://engrxiv.org/preprint/view/3640
<p>The most serious condition of a non-ceramic insulator is when the core is damaged, increasing the possibility of a catastrophic failure resulting in the conductor being released. This condition is unacceptable, as it may lead to safety issues both for the public and workers. Furthermore, core damage may occur without any detectable sign on the surface of the insulator. This paper presents a method aiming at the detection of core damages by testing the insulator based on mechanical excitation and measurement of the resulting vibration in the ultrasonic range. The testing arrangement and results on new and damaged insulators are presented in this paper.</p>
Preprintsnon-ceramic insulatorinsulator diagnosticsvibration diagnosticshigh-voltage engineeringpower systemsRichard CselkoDaniel Balogh
Copyright (c) 2024 Richard Cselko, Daniel Balogh
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2024-03-282024-03-2810.31224/3640Are There Photons? - Heterodyning Ultra Low Intensity Electromagnetic Fields
https://engrxiv.org/preprint/view/3639
<p>In exploring the true essence of electromagnetic fields, heterodyning emerges as superior to traditional detection methods. Within heterodyning, a segment of the signal operates independently of field-matter interaction, relying solely on field-field interaction. Consequently, this approach facilitates the statistical elimination of detector influence. Analysis of the gathered data unveils energy levels comparable to those of a few photons, which are fractional and may even descend below the threshold of a single photon, thus evading any quantization effects. This unequivocally falsifies the concept of photons.</p>
PreprintsPhotonsElectromagnetic FieldsHeterodyningPrecision MeasurementsPhotonicAndré Malz
Copyright (c) 2024 André Malz
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2024-03-282024-03-2810.31224/3639Applications of Vedic Computing for Quantum Computing
https://engrxiv.org/preprint/view/3638
<p>This paper investigates the intriguing potential of integrating Vedic Computing—a system of computing principles originating from ancient Indian texts—into the realm of quantum computing. While quantum computing offers unprecedented computational capabilities, leveraging ancient vedic wisdom could pave the way for enhanced efficiency and novel solutions.Through a comprehensive exploration, we examine the application of Vedic computing techniques in various facets of quantum computing. Firstly, we delve into algorithm development, exploring how Vedic sutras and computational methods could inspire the creation of quantum algorithms with improved speed and scalability. Secondly, we investigate the role of Vedic computing in quantum error correction. Given the inherent fragility of quantum states, robust error correction mechanisms are crucial for the reliability of quantum computers. We explore the potential of Vedic principles to contribute to the development of innovative error correction codes and strategies. <br><br>Furthermore, we explore the intersection of Vedic number theory and quantum cryptography. With the advent of quantum computing, conventional cryptographic methods face threats from quantum algorithms like Shor's algorithm. We investigate how Vedic insights into number theory could inform the design of quantum-resistant cryptographic protocols.Additionally, we consider the application of Vedic optimization techniques in quantum computing. Quantum computers excel at solving optimization problems, and incorporating Vedic optimization principles could further enhance their performance in diverse domains such as logistics, finance, and artificial intelligence. <br><br>Through theoretical analysis and computational simulations, we demonstrate the potential synergies between Vedic Computing and quantum computing. This interdisciplinary approach not only enriches the understanding of both fields but also opens new avenues for exploration and innovation at the intersection of ancient wisdom and modern technology.</p>
PreprintsVedic mathematics, Vedic Computing, quantum computing, algorithm development, error correction, cryptography, optimizationCRS KUMAR
Copyright (c) 2024 CRS KUMAR
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2024-03-262024-03-2610.31224/3638Application of Multivariate Statistics to Optimizing Polyolefin Manufacturing
https://engrxiv.org/preprint/view/3637
<p>In this chapter, we delve into the sophisticated realm of multivariate statistical methods, focusing on Principal Component Analysis (PCA) and Projection to Latent Structures (PLS), as pivotal tools for unraveling the complexity of process data analytics. By anchoring these statistical techniques within the framework of polyethylene manufacturing processes, we aim to illuminate their exceptional utility and novelty in addressing the multifaceted challenges inherent in process optimization and quality control.</p> <p>The discourse begins by introducing PCA, not merely as a statistical tool, but as a fundamental cornerstone for the analytical examination of process variables. Through a meticulously designed workshop, we demonstrate the application of PCA in dissecting the intricate web of variables influencing the quality and conversion rates of Low-Density Polyethylene (LDPE) production in a two-zone tubular reactor. The integration of Aspen ProMV as a practical tool for PCA applications exemplifies the seamless bridge between statistical theory and industrial application, emphasizing the method's accessibility and relevance to both academia and industry.</p> <p>Transitioning to PLS, the chapter articulates its differentiation from PCA by its ability to simultaneously handle datasets comprising both process variables (X) and product quality variables (Y), offering a holistic view of the manufacturing process. Through pragmatic workshops, we showcase PLS's robustness in application to challenges such as melt index prediction and causal analysis in High-Density Polyethylene (HDPE) manufacturing, underscoring its adaptability to complex industrial datasets, including those with measurement time lags.</p> <p>The exploration extends to the nuanced application of these multivariate statistical methods to batch polymer processes. Here, we introduce a novel batch-wise unfolding approach via multiway PCA and PLS, expanding the frontier of statistical applications in process data analytics.</p> <p>This chapter transcends the conventional boundaries of statistical applications, highlighting the transformative impact of PCA and PLS in the domain of process data analytics. It aspires to foster a deeper understanding and appreciation of these statistical methods, encouraging their broader adoption and adaptation in optimizing manufacturing processes and enhancing product quality. This contribution not only reaffirms the critical role of advanced statistical techniques in the scientific community but also underscores their practical significance in improving industrial operations and outcomes.</p> <p>This is a preprint version of a chapter from our book - <em>Integrated Process Modeling, Advanced Control and Data Analytics for Optimizing Polyolefin Manufacturing</em><em>. Please cite the original work if referenced [31,32]. </em></p>
PreprintsStatistical LearningMachine LearningMultivariate StatisticsNiket Sharma
Copyright (c) 2024 Niket Sharma
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2024-03-262024-03-2610.31224/3637Customized edge cutting of display glass with laser-only machining
https://engrxiv.org/preprint/view/3633
<p>Cleaving of glass substrates with shaped edges using a laser-only concept is presented. In a first laser process shaped ultrashort laser pulses modify in a single pass the entire material thickness with arbitrary edge shape geometries. Afterwards in a second pass CO2 laser radiation is absorbed in the modified area and resulting stresses lead to the separation of the glass. We investigate the quality of the achieved edges and corresponding mechanical properties. The cutting strategy, so far conducted on straight contours, is successfully transferred to curved contours maintaining edge qualities.</p>
PreprintsLaser materials processingGlass processingstructured lightUltrafast opticsBeam shapingMyriam KaiserJonas KleinerJanis WolffDaniel Flamm
Copyright (c) 2024 Myriam Kaiser, Jonas Kleiner, Janis Wolff, Daniel Flamm
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2024-03-252024-03-2510.31224/3633High Velocity Flows Inside Tube Reactors
https://engrxiv.org/preprint/view/3612
<p>Tube reactors used for the chemical vapor deposition of graphene and other 2D films on metal foils are typically operated at ambient pressures or under low vacuum (> 0.1 torr) and at low average flow velocities (< ~1-2 m/s) and Reynolds numbers (< 100). Thus, the flow inside the reactor is laminar and highly diffusive. This report explores what may happen if high velocity flows are instead used, by simulating reactor conditions with the Computational Fluid Dynamics toolbox OpenFOAM. High velocity flows with large Reynolds numbers were found to be turbulent and without any buoyancy driven recirculation. Additionally, a large cooling effect was observed with foil and gas temperatures much lower than the furnace set point. Finally, the temperatures of the 50-100 μm thick metal foils were not uniform but had large temperature gradients sensitive to the system pressure, the total mass flow rate and the process gas composition that increased with decreasing foil thickness. </p>
PreprintsComputational fluid dynamicsheat transferOpenFOAMreactorChemical EngineeringMaterial scienceShahana ChatterjeeThomas AbadieMeihui WangOmar K. MatarRodney S. Ruoff
Copyright (c) 2024 Shahana Chatterjee, Thomas Abadie, Meihui Wang, Omar Matar, Rodney Ruoff
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2024-03-252024-03-2510.31224/3612Distribution-theoretic basis for hidden deltas in frequency-domain structural modelling
https://engrxiv.org/preprint/view/3630
<p>Frequency-domain modelling is a core tool for the analysis of linear time-invariant structures. In a process that has been unclear, additional Dirac delta distributions can arise in the frequencydomain transfer functions of certain structures, beyond those seemingly given by the structural model—for instance, in the mechanical impedance of a linear spring. Previous analyses have manually append these "hidden deltas" to the relevant transfer functions in order to ensure that they remain causal, but questions remain as to their exact origin, and behaviour in in non-causal models. Here, we demonstrate that these hidden deltas arise from the theory of distributions, and the solution of the distributional division equation. We demonstrate a rigorous and reliable method for deriving these hidden deltas in which the role of causality constraints are made clear. Furthermore, we demonstrate that the appropriate frequency-domain conditions for causality in such systems are generalized—not, classical—Hilbert transform relations, and that the process of appending delta distributions is related to the analysis of causality via these generalized relations.</p>
PreprintsApplied MechanicsStructural DynamicsArion Pons
Copyright (c) 2024 Arion Pons
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2024-03-242024-03-2410.31224/3630Transformer tricks: Removing weights for skipless transformers
https://engrxiv.org/preprint/view/3629
<div class="page" title="Page 1"> <div class="section"> <div class="layoutArea"> <div class="column"> <p>He and Hofmann [1] detailed a skipless transformer without the V and P (post-attention projection) linear layers, which reduces the total number of weights. However, this scheme is only applicable to MHA (multi-head attention), but not for MQA (multi-query attention) and GQA (grouped- query attention). The latter schemes are used by many popular LLMs such as Llama 2, Mistral, Mixtral, PaLM, and Gemma. Therefore, this micro-paper proposes mathematically equivalent versions that are suitable for MQA and GQA. For example, removing Q and P from a skipless version of Mistral-7B would remove 15% of its weights (and thus reduce its compute and memory complexity).</p> </div> </div> </div> </div>
PreprintsMachine Learningartificial neural networkArtificial IntelligenceNatural Language ProcessingComputer ScienceNils Graef
Copyright (c) 2024 Nils Graef
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2024-03-242024-03-2410.31224/3629Resilient Operations in Space with Digital Twin Integration for Solar PV and Energy Storage
https://engrxiv.org/preprint/view/3628
<p>Space missions would not be possible without an available, reliable, autonomous, and resilient power system. Space-based power systems are different than Earth’s grid in terms of generation sources, needs, structure, and controllability. This research paper introduces a groundbreaking approach employing digital twin technology to emulate and enhance the performance of a physical nanogrid plant representing such a space-based power system. The proposed system encompasses three DC converters, a DC source, and a modular battery storage unit feeding a variable load. Rigorous testing across diverse operating points establishes the digital twin’s high-fidelity real-time representation, with root mean square error (RMSE) values consistently below 5%. The principal innovation lies in leveraging this digital twin to fortify system resilience against unforeseen events, beyond the capabilities of existing controllers and autonomy levels. By simulating scenarios that the current system may not be primed for, the digital twin provides operators with the tools to proactively respond to disruptions. Importantly, the approach offers an invaluable tool for scenarios where physical access to components is limited. This research introduces a modular battery storage solution as a key augmentation, capable of seamlessly compensating for power shortages at the source end that might arise from the dust effect on the Lunar surface or unexpected faults in the system. The proposed holistic approach not only validates the fidelity of the digital twin but also underscores its potential to revolutionize system operation, safeguard against uncertainties, and expedite response strategies in the face of unexpected contingencies. The proposed approach also paves the way for future development.</p>
PreprintsDigital Twinspace systems engineeringPower SystemsShayan EbrahimiMohammad SeyediSM Safayet UllahFarzad Ferdowsi
Copyright (c) 2024 Shayan Ebrahimi, Mohammad Seyedi, SM Safayet Ullah, Farzad Ferdowsi
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2024-03-212024-03-2110.31224/3628Finite Element Analysis of Custom Shoulder Implants Provides Accurate Prediction of Initial Stability
https://engrxiv.org/preprint/view/3626
<p>Custom reverse shoulder implants represent a valuable solution for patients with large bone defects. Since each implant has unique patient-specific features, finite element (FE) analysis has the potential to guide the design process by virtually comparing the stability of multiple configurations without the need of a mechanical test. The aim of this study was to develop an automated virtual bench test to evaluate the initial stability of custom shoulder implants during the design phase, by simulating a fixation experiment as defined by ASTM F2028-14. Three-dimensional (3D) FE models were generated to simulate the stability test and the predictions were compared to experimental measurements. Good agreement was found between the baseplate displacement measured experimentally and determined from the FE analysis (Spearman’s rank test, <span class="html-italic">p</span> < 0.05, correlation coefficient ρs = 0.81). Interface micromotion analysis predicted good initial fixation (micromotion <150 µm, commonly used as bone ingrowth threshold). In conclusion, the finite element model presented in this study was able to replicate the mechanical condition of a standard test for a custom shoulder implants.</p>
PreprintsFinite element analysisshoulder implant stabilityimplant designreverse shoulder arthroplastymicromotionJonathan PitocchiMariska WesselingG. Harry van LentheMaría Ángeles Pérez
Copyright (c) 2024 Jonathan Pitocchi, Mariska Wesseling, G. Harry van Lenthe, María Ángeles Pérez
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2024-03-212024-03-2110.31224/3626Automated muscle elongation measurement during reverse shoulder arthroplasty planning
https://engrxiv.org/preprint/view/3625
<div id="abssec0010"> <h3 id="sectitle0010" class="u-h4 u-margin-m-top u-margin-xs-bottom">Background</h3> <p id="abspara0015">Adequate deltoid and rotator cuff elongation in reverse shoulder arthroplasty is crucial to maximize postoperative functional outcomes and to avoid complications. Measurements of deltoid and rotator cuff elongation during preoperative planning can support surgeons in selecting a suitable implant design and position. Therefore, this study presented and evaluated a fully automated method for measuring deltoid and rotator cuff elongation.</p> </div> <div id="abssec0015"> <h3 id="sectitle0015" class="u-h4 u-margin-m-top u-margin-xs-bottom">Methods</h3> <p id="abspara0020">Complete scapular and humeral models were extracted from computed tomography scans of 40 subjects. First, a statistical shape model of the complete humerus was created and evaluated to identify the muscle attachment points. Next, a muscle wrapping algorithm was developed to identify the muscle paths and to compute muscle lengths and elongations after reverse shoulder arthroplasty implantation. The accuracy of the muscle attachment points and the muscle elongation measurements was evaluated for the 40 subjects by use of both complete and artificially created partial humeral models. Additionally, the muscle elongation measurements were evaluated for a set of 50 arthritic shoulder joints. Finally, a sensitivity analysis was performed to evaluate the impact of implant positioning on deltoid and rotator cuff elongation.</p> </div> <div id="abssec0020"> <h3 id="sectitle0020" class="u-h4 u-margin-m-top u-margin-xs-bottom">Results</h3> <p id="abspara0025">For the complete humeral models, all muscle attachment points were identified with a median error < 3.5 mm. For the partial humeral models, the errors on the deltoid attachment point largely increased. Furthermore, all muscle elongation measurements showed an error < 1 mm for 75% of the subjects for both the complete and partial humeral models. For the arthritic shoulder joints, the errors on the muscle elongation measurements were <2 mm for 75% of the subjects. Finally, the sensitivity analysis showed that muscle elongations were affected by implant positioning.</p> </div> <div id="abssec0025"> <h3 id="sectitle0025" class="u-h4 u-margin-m-top u-margin-xs-bottom">Discussion</h3> <p id="abspara0030">This study presents an automated method for accurately measuring muscle elongations during preoperative planning of shoulder arthroplasty. The results show that the accuracy in measuring muscle elongations is higher than the accuracy in indicating the muscle attachment points. Hence, muscle elongation measurements are insensitive to the observed errors on the muscle attachment points. Related to this finding, muscle elongations can be accurately measured for both a complete humeral model and a partial humeral model. Because the presented method also showed accurate results for arthritic shoulder joints, it can be used during preoperative shoulder arthroplasty planning, in which typically only the proximal humerus is present in the scan and in which bone arthropathy can be present. As the muscle elongations are sensitive to implant positioning, surgeons can use the muscle elongation measurements to refine their surgical plan.</p> </div>
PreprintsStatistical shape modelreverse shoulder arthroplastyshoulder planningmuscle elongationimplant positioningautomatizationJonathan PitocchiKatrien PlessersRoel Wirix-SpeetjensPhilippe DebeerG. Harry van LentheIlse JonkersMaría Ángeles PérezJos Vander Sloten
Copyright (c) 2024 Jonathan Pitocchi, Katrien Plessers, Roel Wirix-Speetjens, Philippe Debeer, G. Harry van Lenthe, Ilse Jonkers, María Ángeles Pérez, Jos Vander Sloten
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2024-03-212024-03-2110.31224/3625Biomechanical evaluation of syndesmotic fixation techniques via finite element analysis: Screw vs. suture button
https://engrxiv.org/preprint/view/3624
<div id="abss0003"> <h3 id="cesectitle0003" class="u-h4 u-margin-m-top u-margin-xs-bottom">Background and Objective</h3> <p id="spara008">Tibiofibular syndesmotic injuries may cause degenerative changes, reduction in ankle function and compromising ankle stability. Different fixation techniques try to restore its functionality. Screw-fixation is the gold-standard. Recently, suture-button fixation has aroused the attention because it allows for physiologic micromotion while maintaining an accurate reduction. The aim of this study is to compare the biomechanical behaviour of both fixation techniques using the finite element method.</p> </div> <div id="abss0004"> <h3 id="cesectitle0004" class="u-h4 u-margin-m-top u-margin-xs-bottom">Methods</h3> <p id="spara009">A three-dimensional finite element model of the tibiofibular joint was reconstructed simulating the intact ankle and the injured syndesmosis. Then, different methods of syndesmosis fixation were analysed: screws (number of cortices, number of screws and distance between screws) and suture buttons (single, double parallel and double divergent with a sensitivity analysis on the pretension forces) configuration. Ligaments and cartilages were included and simulated as spring elements. Physiological loads during stance phase were simulated.</p> </div> <div id="abss0005"> <h3 id="cesectitle0005" class="u-h4 u-margin-m-top u-margin-xs-bottom">Results</h3> <p id="spara010">Syndesmosis widening and von Mises stresses were computed. Syndesmosis widening in the injured configuration compromised joint stability (2.06 mm), whereas using a single quadricortical screw (0.18 mm) stiffened the joint. Syndesmosis widening using suture-buttons were closer to syndesmosis widening of the intact ankle configuration (0.97 mm). Von Mises stresses were higher for the titanium screws than for the suture buttons.</p> </div> <div id="abss0006"> <h3 id="cesectitle0006" class="u-h4 u-margin-m-top u-margin-xs-bottom">Conclusions</h3> <p id="spara011">A detailed biomechanical comparison among different syndesmotic fixation was performed. Suture buttons have advantages with regard to syndesmosis widening in comparison to screw fixation. This fact supports the good long-term clinical results obtained with suture buttons fixation. The proposed methodology could be an efficient tool for preoperative planning.</p> </div>
PreprintsSyndesmotic injuriesFinite element analysisScrewSuture buttonbiomechanical behavioursyndesmotic wideningDiego Alastruey-LópezBelen SeralMaría Ángeles Pérez
Copyright (c) 2024 Diego Alastruey-López, Belen Seral, María Ángeles Pérez
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2024-03-212024-03-2110.31224/3624Decellularization of tumours: A new frontier in tissue engineering
https://engrxiv.org/preprint/view/3623
<p>Cancer is one of the leading causes of death worldwide. The tumour extracellular matrix (ECM) has unique features in terms of composition and mechanical properties, resulting in a structurally and chemically different ECM to that of native, healthy tissues. This paper reviews to date the efforts into decellularization of tumours, which in the authors’ view represents a new frontier in the ever evolving field of tumour tissue engineering. An overview of the ECM and its importance in cancer is given, ending with examples of research using decellularized tumours, which has already indicated potential therapeutic targets, unravelled malignancy mechanisms or response to chemotherapy agents. The review highlights that more research is needed in this area, which can answer important questions related to tumour formation and progression to ultimately identify new and effective therapeutic targets. Within the near-future of personalized medicine, this research can create patient-specific tumour models and therapeutic regimes.</p>
PreprintsCancertumourextracellular matrixdecellularizationdecellularized tumourElena Garcia-GaretaMaría Ángeles PérezJosé Manuel García-Aznar
Copyright (c) 2024 Elena Garcia-Gareta, María Ángeles Pérez, José Manuel García-Aznar
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2024-03-212024-03-2110.31224/3623The Correlation between Bone Density and Mechanical Variables in Bone Remodelling Models: Insights from a Case Study Corresponding to the Femur of a Healthy Adult
https://engrxiv.org/preprint/view/3622
<p>Bone remodelling models (BRM) are often used to estimate the density distribution in bones from the loads they are subjected to. BRM define a relationship between a certain variable measuring the mechanical stimulus at each bone site and either the local density or the local variation of density. This agrees with the Mechanostat Theory, which establishes that overloaded bones increase their density, while disused bones tend to decrease their density. Many variables have been proposed as mechanical stimuli, with stress or strain energy density (SED) being some of the most common. Yet, no compelling reason has been given to justify the choice of any of these variables. This work proposes a set of variables derived from the local stress and strain tensors as candidates for mechanical stimuli; then, this work correlates them to the density in the femur of one individual. The stress and strain tensors were obtained from a FE model and the density was obtained from a CT-scan, both belonging to the same individual. The variables that best correlate with density are the stresses. Strains are quite uniform across the femur and very poorly correlated with density, as is the SED, which is, therefore, not a good variable to measure the mechanical stimulus.</p>
PreprintsBone remodellingmechanical stimuluscorrelationbone density distributionstrain energy densityabsolute maximum principal stressfluctuation of stressesJosé Luis Calvo-GallegoFernando Gutiérrez-MillánJoaquín Ojeda María Ángeles PérezJavier Martínez-Reina
Copyright (c) 2024 José Luis Calvo-Gallego, Fernando Gutiérrez-Millán, Joaquín Ojeda , María Ángeles Pérez, Javier Martínez-Reina
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2024-03-212024-03-2110.31224/3622Hydrocolloids of Egg White and Gelatin as a Platform for Hydrogel-Based Tissue Engineering
https://engrxiv.org/preprint/view/3621
<p>Innovative materials are needed to produce scaffolds for various tissue engineering and regenerative medicine (TERM) applications, including tissue models. Materials derived from natural sources that offer low production costs, easy availability, and high bioactivity are highly preferred. Chicken egg white (EW) is an overlooked protein-based material. Whilst its combination with the biopolymer gelatin has been investigated in the food technology industry, mixed hydrocolloids of EW and gelatin have not been reported in TERM. This paper investigates these hydrocolloids as a suitable platform for hydrogel-based tissue engineering, including 2D coating films, miniaturized 3D hydrogels in microfluidic devices, and 3D hydrogel scaffolds. Rheological assessment of the hydrocolloid solutions suggested that temperature and EW concentration can be used to fine-tune the viscosity of the ensuing gels. Fabricated thin 2D hydrocolloid films presented globular nano-topography and in vitro cell work showed that the mixed hydrocolloids had increased cell growth compared with EW films. Results showed that hydrocolloids of EW and gelatin can be used for creating a 3D hydrogel environment for cell studies inside microfluidic devices. Finally, 3D hydrogel scaffolds were fabricated by sequential temperature-dependent gelation followed by chemical cross-linking of the polymeric network of the hydrogel for added mechanical strength and stability. These 3D hydrogel scaffolds displayed pores, lamellae, globular nano-topography, tunable mechanical properties, high affinity for water, and cell proliferation and penetration properties. In conclusion, the large range of properties and characteristics of these materials provide a strong potential for a large variety of TERM applications, including cancer models, organoid growth, compatibility with bioprinting, or implantable devices.</p>
PreprintsHydrocolloidsEgg whitegelatinhydrogelstissue engineeringmicrofluidicsKarinna Georgiana Pele Hippolyte Amaveda Mario MoraCarlos MarcuelloAnabel Lostao Pilar Alamán-DíezSalvador Pérez-HuertasMaría Ángeles PérezJosé Manuel García-AznarGarcia-Gareta Elena
Copyright (c) 2024 Karinna Georgiana Pele , Hippolyte Amaveda , Mario Mora, Carlos Marcuello, Anabel Lostao , Pilar Alamán-Díez, Salvador Pérez-Huertas, María Ángeles Pérez, José Manuel García-Aznar, Garcia-Gareta Elena
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2024-03-202024-03-2010.31224/3621Collagen-Laponite Nanoclay Hydrogels for Tumor Spheroid Growth
https://engrxiv.org/preprint/view/3620
<p>The extracellular matrix (ECM) plays an important regulatory role in the development and progression of tumoral tissue. Its functions and properties are crucial in determining tumor cell behavior such as invasion, migration, and malignancy development. Our study explores the role of collagen type I in cancer development and spread using engineered tumor models like multicellular spheroids grown in collagen-based hydrogels to simulate early tumor formation. We employ microfluidic techniques to test the hypothesis that (i) adding Laponite nanoclay to collagen hydrogels modifies mechanical and rheological properties and (ii) changing the stiffness of the collagen microenvironment affects tumor spheroid growth. Our findings support our theories and suggest the use of ECM components and engineered tumor models in cancer research, offering a biocompatible and biomimetic method to tailor the mechanical properties of conventional collagen hydrogels.</p>
PreprintsPilar Alamán-DíezCarlos Borau-ZamoraPedro Enrique GuerreroHippolyte Amaveda Mario MoraJosé María FraileElena Garcia-GaretaJosé Manuel García-AznarMaría Ángeles Pérez
Copyright (c) 2024 Pilar Alamán-Díez, Carlos Borau-Zamora, Pedro Enrique Guerrero, Hippolyte Amaveda , Mario Mora, José María Fraile, Elena Garcia-Gareta, José Manuel García-Aznar, María Ángeles Pérez
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2024-03-202024-03-2010.31224/3620Simultaneous Multicomponent Topology Optimization using Unilateral Contact-Constraints
https://engrxiv.org/preprint/view/3619
<p>In this paper, the framework for topology optimization considering unilateral contact-constraints of Strömberg and Klarbring is extended to assemblies. Here, an assembly consists of two or more components that are connected via joints. The unilateral characteristic of the contact inside each joint is considered, and the topology of all components of the assembly are optimized simultaneously. Therefore, linear-elastic material is considered and the augmented Lagrangian approach is used to model the unilateral contact. For topology optimization, the SIMP-approach is applied to all members of the assembly and different filtering techniques such as sensitivity filtering, density filtering or projection filtering can be applied on each member independently. In consequence, the global design space of the optimization consists of the normalized densities of all members of the assembly. Using the proposed approach, one can optimize a topology for the whole assembly instead of optimizing all members of the assembly independently. This is of major importance, since changes in the topology of any member will lead to changes in the force transfer at the joints, which in consequence influences the optimization of all members of the assembly.</p>
PreprintsTopology OptimizationcontactSimultaneous optimizationjoint optimizationTimo Hendrik SchmidtRobert Seifried
Copyright (c) 2024 Timo Hendrik Schmidt, Robert Seifried
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2024-03-202024-03-2010.31224/3619The rise of mechanical metamaterials: Auxetic constructs for skin wound healing
https://engrxiv.org/preprint/view/3618
<p>Auxetic materials are known for their unique ability to expand/contract in multiple directions when stretched/compressed. In other words, they exhibit a negative Poisson’s ratio, which is usually positive for most of materials. This behavior appears in some biological tissues such as human skin, where it promotes wound healing by providing an enhanced mechanical support and facilitating cell migration. Skin tissue engineering has been a growing research topic in recent years, largely thanks to the rapid development of 3D printing techniques and technologies. The combination of computational studies with rapid manufacturing and tailored designs presents a huge potential for the future of personalized medicine. Overall, this review article provides a comprehensive overview of the current state of research on auxetic constructs for skin healing applications, highlighting the potential of auxetics as a promising treatment option for skin wounds. The article also identifies gaps in the current knowledge and suggests areas for future research. In particular, we discuss the designs, materials, manufacturing techniques, and also the computational and experimental studies on this topic.</p>
PreprintsSkin tissue engineeringauxetic materialsadditive manufacturingOscar Lecina-TejeroMaría Ángeles PérezElena Garcia-GaretaCarlos Borau
Copyright (c) 2024 Oscar Lecina-Tejero, María Ángeles Pérez, Elena Garcia-Gareta, Carlos Borau
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2024-03-202024-03-2010.31224/3618In silico assessment of the bone regeneration potential of complex porous scaffolds
https://engrxiv.org/preprint/view/3617
<p>Mechanical environment plays a crucial role in regulating bone regeneration in bone defects. Assessing the mechanobiological behavior of patient-specific orthopedic scaffolds in-silico could help guide optimal scaffold designs, as well as intra- and post-operative strategies to enhance bone regeneration and improve implant longevity. Additively manufactured porous scaffolds, and specifically triply periodic minimal surfaces (TPMS), have shown promising structural properties to act as bone substitutes, yet their ability to induce mechanobiologially-driven bone regeneration has not been elucidated. The aim of this study is to i) explore the bone regeneration potential of TPMS scaffolds made of different stiffness biocompatible materials, to ii) analyze the influence of pre-seeding the scaffolds and increasing the post-operative resting period, and to iii) assess the influence of patient-specific parameters, such as age and mechanosensitivity, on outcomes. To perform this study, an in silico model of a goat tibia is used. The bone ingrowth within the scaffold pores was simulated with a mechano-driven model of bone regeneration. Results showed that the scaffold’s architectural properties affect cellular diffusion and strain distribution, resulting in variations in the regenerated bone volume and distribution. The softer material improved the bone ingrowth. An initial resting period improved the bone ingrowth but not enough to reach the scaffold’s core. However, this was achieved with the implantation of a pre-seeded scaffold. Physiological parameters like age and health of the patient also influence the bone regeneration outcome, though to a lesser extent than the scaffold design. This analysis demonstrates the importance of the scaffold’s geometry and its material, and highlights the potential of using mechanobiological patient-specific models in the design process for bone substitutes.</p>
PreprintsMechanobiologybone regenerationscaffoldstriply periodic minimal surfacesmechanical stimulusFE-based modelMaría Ángeles PérezReduan Asbai-GhoudanGabriele NaselloStefaan W. VerbruggenSergio Ruiz de GalarretaNaiara Rodriguez-Florez
Copyright (c) 2024 María Ángeles Pérez, Reduan Asbai-Ghoudan, Gabriele Nasello, Stefaan W. Verbruggen, Sergio Ruiz de Galarreta, Naiara Rodriguez-Florez
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2024-03-202024-03-2010.31224/3617Evaluation of economic disruptions from the 2016 Kumamoto Earthquake using a refined adaptive regional input-output model
https://engrxiv.org/preprint/view/3616
<p>The Adaptive Regional Input-Output (ARIO) model is popular for quantifying indirect economic losses, which stem from business and supply chain interruption. However, refining this model to study new contexts is challenging in its basic form due to low-resolution modeling of behavioral parameters and temporally static reconstruction rates. This paper presents a refined ARIO, or R-ARIO model that incorporates dynamic reconstruction rates, sector-level modeling of behavioral parameters, and explicit modeling of housing losses separately from productive capital losses. We perform a global variance-based sensitivity analysis to identify the most influential parameters on predicted indirect loss from the R-ARIO model. A case study application to the 2016 Kumamoto Earthquake Sequence isolates trends in housing and economic recovery, capturing temporal differences in reconstruction demand and uncertainty across economic indicators.</p>
PreprintsDisaster recoveryARIOEconomic recoveryBusiness adaptationKumamotoearthquake resilienceOmar IssaTinger ZhuMaryia MarkhvidaRodrigo CostaJack W. Baker
Copyright (c) 2024 Omar Issa, Tinger Zhu, Maryia Markhvida, Rodrigo Costa, Jack W. Baker
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2024-03-202024-03-2010.31224/3616Symmetry Heuristics for Stable Reinforcement Learning Design Agents
https://engrxiv.org/preprint/view/3615
<p>Deep Reinforcement Learning (RL) has emerged as a promising technique for automating configuration design because of its capacity for sequential decision-making. However, it faces challenges in learning stability when complex engineering simulations compose the reward function. This diminishes the practicality of deep RL for configuration design. To address this challenge, this work integrates configuration design heuristics in a deep RL framework to enhance stability and efficiently converge to high performance solutions. Specifically, we shape the reward based on symmetry, a deep-rooted heuristic that is widely applicable and frequently used in engineering design practice. This approach is empirically tested on a truss design problem wherein the RL agent employs a symmetry detection method during the design process. The results reveal that the proposed symmetry-guided approach consistently yields high-performance symmetric configurations, outperforming a naïve approach in terms of stability while also demonstrating an alignment with intuitive human design principles.</p>
PreprintsAkash AgrawalChristopher McComb
Copyright (c) 2024 Akash Agrawal, Christopher McComb
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2024-03-202024-03-2010.31224/3615Smart Investment Framework for Energy Resilience: A Case Study of a Campus Microgrid Research Facility
https://engrxiv.org/preprint/view/3614
<p>Energy resilience is a vital consideration for ensuring the survivability of modern infrastructure systems. Achieving 100% resilience, however, is often impractical and economically burdensome. In this paper, we propose a smart investment framework that enables decision-makers to determine optimal investments in energy resilience based on available resources and desired levels of resilience. To illustrate the effectiveness of this framework, we present a case study of a campus microgrid research and testing facility. Using a real-time simulation approach conducted with Typhoon HIL, we evaluate the performance of the microgrid system over 24 hours following four historically significant hurricanes that have affected Louisiana in the past few years. The microgrid is designed to power local loads during outages, providing an effective solution for enhancing energy resilience. Real solar data collected from our 1.1 Megawatt (MW) solar facility on the University of Louisiana at Lafayette campus is integrated into the simulation, enabling a realistic evaluation of the system's performance under hurricane-induced disruptions. By employing the proposed smart investment framework, decision-makers can better identify and address resilience challenges. The framework facilitates informed investment decisions by considering available resources and aligning them with the desired level of resilience. This approach avoids over-investment in unnecessary redundancy while ensuring critical systems are adequately protected. Our research contributes to the field by demonstrating the practicality and benefits of a smart investment framework for energy resilience in a real-world scenario. The case study of the campus microgrid research facility provides valuable insights for decision-makers in similar contexts, highlighting the potential of this framework to guide resilient energy infrastructure planning and investment strategies.</p>
Preprintsenergy resilienceAC MicrogridsRenewable energyBattery Energy Storage SystemEnergy Resilience Power Systems, Electrical EngineeringSM Safayet UllahSamuel YanksonShayan EbrahimiFarzad FerdowsiTerrence Chambers
Copyright (c) 2024 SM Safayet Ullah, Samuel Yankson, Shayan Ebrahimi, Farzad Ferdowsi, Terrence Chambers
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2024-03-202024-03-2010.31224/3614Neural Architecture Transfer 2
https://engrxiv.org/preprint/view/3613
<p>The advent of deep learning has had a significant impact on various sectors of modern society, with artificial neural networks becoming the leading models for tackling a wide range of challenges. The innovation of Neural Architecture Search (NAS) methods, which facilitate the automated creation of optimal neural networks, marks a significant step forward in this field. However, the large computational resources and time required for NAS processes are significant limitations. To address these challenges, Once-For-All (OFA) and its advanced version, Once-For-All-2 (OFAv2), were introduced to develop a single, comprehensive super-network capable of efficiently deriving specific sub-networks without the need for retraining, thereby maintaining stellar performance under varying constraints. Building on this, Neural Architecture Transfer (NAT) was developed to improve the efficiency of extracting such sub-networks from the overarching super-network. This study introduces Neural Architecture Transfer 2 (NAT2), an evolution of NAT that refines the multi-objective search mechanisms within dynamic super-networks to further improve the performance-complexity trade-off for the searched architectures. Leveraging the advances of OFAv2, NAT2 introduces significant qualitative improvements in the sub-networks that can be extracted by incorporating novel policies for network initialisation, pre-processing, and archive updates, as well as a fine-tuning based post-processing pipeline. The empirical evidence presented here highlights the effectiveness of NAT2 over its predecessor, particularly in the development of high-performance architectures with a reduced number of parameters and multiply-accumulate operations.</p>
PreprintsNeural Architecture Transfer 2Neural Architecture SearchSuper-NetworkSub-NetworkMulti-Objective OptimisationEugenio LomurnoMatteo MatteucciSimone Sarti
Copyright (c) 2024 Eugenio Lomurno, Matteo Matteucci, Simone Sarti
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2024-03-182024-03-1810.31224/3613Hard data on hard drugs? - Assessing illicit drug loads in sewers
https://engrxiv.org/preprint/view/3611
<p>The monitoring of illicit drugs in wastewater is an appealing idea within an emerging field. Objective, evidence-based data on drug-use can be obtained from urban drainage systems in real-time and without the limitations of population surveys. While current analytical techniques are sensitive enough to quantify arrays of substances in wastewater, current models to assess community consumption figures from substance loads are too simplistic and neglect relevant influence factors, such as sewer transport and transformation. In a case study of community cocaine use, observed substance loads show significant hourly variations, which demonstrates the need to consider the effect of short-time variations in the assessment of community drug use. Although the results from an integrated stochastic model are in general agreement with population surveys, further work is needed regarding the conceptualisation of drug use epidemiology, sewer processes and parameter estimation procedures.</p>
Preprintswastewater based epidemiologymodellingsewer water quality monitoringCivil and Environmental Engineeringenvironmental chemistryJörg Rieckermann
Copyright (c) 2024 Jörg Rieckermann
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2024-03-182024-03-1810.31224/3611Pyramid of Thought: Enhancing the Chain of Thought with the Fibonacci Sequence and the Inner Thought Journal
https://engrxiv.org/preprint/view/3610
<div class="page" title="Page 1"> <div class="section"> <div class="layoutArea"> <div class="column"> <p>Recent advances in large language models (LLMs) have demonstrated their remarkable abilities in complex language tasks. However, achieving the depth and flexibility of human reasoning remains a challenge. Inspired by the power of step-by-step reasoning highlighted in "Chain-of-Thought Prompting Elicits Reasoning in Large Language Models," this paper introduces the "Pyramid of Thought" framework. This framework leverages principles of Euclidean geometry, the Fibonacci sequence, and psychological engagement to create structured, adaptable AI responses while promoting transparent and intuitive communication.</p> <p>The "Pyramid of Thought" uses a dynamic layer mechanism, adjustable via linear, logarithmic, or Fibonacci-based scaling. This aligns the AI's thought process with natural mathematical patterns. Mirroring psychological principles, this approach aims to promote user engagement. Each layer builds on the previous one, starting with foundational facts ("Five Ws") and progressing through reasoning steps ("How," "Then"), culminating in an "Apex" of analysis or insight. An inner thought journal maintains contextual richness.</p> <p>The flexible and iterative nature of the "Pyramid of Thought" reflects the emphasis on refinement and evolution found in conceptual modeling. Experiments will evaluate its effectiveness against traditional AI response methods. Metrics will include user engagement, response coherence, satisfaction, and the model's ability to communicate its reasoning process transparently. We anticipate that the "Pyramid of Thought" will produce more intuitive, meaningful, and thought-provoking interactions, aligning with the goals of conceptual modeling in simulation. This work contributes to the development of AI systems that better emulate human reasoning patterns and foster clearer communication.</p> </div> </div> </div> </div>
PreprintsArtificial General IntelligenceApplication of Artificial IntelligenceSoftwarePrompt EngineeringArtificial IntelligenceComputer and Systems ArchitectureSoftwareFritz Nkwindjeu Fabo
Copyright (c) 2024 Fritz Nkwindjeu Fabo
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2024-03-182024-03-1810.31224/3610