Structural System Research Articles

Nontrivial evolution and geometric phase for an orbital angular momentum qutrit

Photonic orbital angular momentum (OAM) offers a promising platform for high-dimensional quantum information processing. While geometric phase (GP) is the crucial tool in enabling intrinsically fault-tolerant quantum computation, the measurement of GP using linear optics remains relatively unexplored in the OAM state space. Here, we propose an experimental scheme to detect GP shifts resulting from the cyclic evolution of OAM qutrit states. Distinguished with the conventional evolution along cyclic path on the Poincaré sphere (PS), the nontrivial evolution in our theoretical scheme is along a cyclic path residing within the SU(3)/U(2) parameter space. By employing a combination of X-gates, dove prisms, and double cylindrical lenses, we achieve the cyclic evolution and analyse the resultant GP through our designed Sagnac interferometer. Our theoretical study may find potential in high-dimensional quantum computation using twisted photons and in exploring the geometric structure of such optical systems.

Designing moiré patterns by strain

Experiments conducted on two-dimensional twisted materials have revealed a plethora of moiré patterns with different forms and shapes. The formation of these patterns is usually attributed to the presence of small strains in the samples, which typically arise during their fabrication. In this paper we find that the superlattice structure of such systems actually depends crucially on the interplay between twist and strain. For systems composed of honeycomb lattices, we show that this can lead to the formation of practically any moiré geometry, even if each lattice is only slightly distorted. As a result, we show that under strain the moiré Brillouin zone is not a stretched irregular hexagon, but rather a primitive cell that changes according to the geometry of the strained moiré vectors. We identify the conditions for the formation of hexagonal moiré patterns arising solely due to shear or biaxial strain, thus opening the possibility of engineering moiré patterns solely by strain. Moreover, we study the electronic properties in such moiré patterns and find that the strain tends to suppress the formation of the flat moiré bands, even in the strain-induced hexagonal patterns analogous to those obtained by the twist only. Our paper explains the plethora of moiré patterns observed in experiments, and provides a solid theoretical foundation from which one can design moiré patterns by strain. Published by the American Physical Society 2024

Chain mail structures in architecture: a systematic, multi-scalar design exploration

Chain mail structures, known for flexibility and adaptability, hold increasing promise for architectural applications, including transportable and reconfigurable systems. However, there is a dearth of knowledge on both systematic methods to design them, and complex behaviours of interlocking modules that comprise the structure. Preliminary studies, in response to this research gap, demonstrate the chain mail’s structural potential as programmable architecture. Nevertheless, to validate our models, we must move from the small scale to recognisably viable structures at an architectural scale.Acknowledging the multiscale prototype’s significance for developing new architectural systems, this study scales up chain mail structures from a small 1:10 scale to larger 1:2 and 1:1 scales. Employing a Research-Through-Design approach, we systematically addressed the challenges, focusing on module fabrication and prototype construction through analogue computation. Fabrication adjustments involve changing materials and modifying designs to suit manufacturing techniques. Additional design elements and process steps are needed to facilitate programming the larger scale structures due to the increased weight during construction. The research culminated in a full-scale saddle-like structure, illustrating the feasibility of direct scaling from smaller to larger scales and the expansive architectural potential of chain mail structures.In conclusion, the study successfully identified and responded to specific challenges related to the fabrication and construction of upscaled chain mail prototypes, aligning solutions with practical contexts. In doing so, this research contributes a set of considerations to enable more systematic design approaches for chain mail structural systems in architecture. At the same time, scaling up uncovers the inherent intelligence of these structures, providing a foundation for both empirical testing through analogue experimentation, and developing a predictive framework for their development and application in the field.

Influence of friction between wood and support elements in the design of timber structures for roofing

Throughout history, wood has played a crucial role in all phases of building construction. Despite existing prejudices in Brazil regarding its use in structural systems, primarily due to the lack of dissemination of technical information, wood is gradually gaining more space in the market as a viable and environmentally sustainable alternative. With exceptional mechanical properties, wood is compatible with other widely used construction materials in the Brazilian structural market, such as concrete and steel. In this context, this research aims to analyze the influence of considering the friction coefficient caused by the sliding of the support with free horizontal displacements in isostatic trusses, investigating its impact on the design of the components that make up the truss. Such sliding generates a lateral friction force that promotes a restraining effect on the structure, potentially relieving stresses on the lower chord members. For this purpose, the Finite Element Method (FEM) is used as an analytical tool, supported by the iTruss verification software to validate the obtained results. By considering the frictional force generated on the support links of the analyzed trusses, the numerical results revealed changes in the design of structural profiles for all existing wood strength classes (D20, D30, D40, D50, and D60) in situations of friction between wood and wood, and between wood and concrete. A reduction in the volume of wooden pieces was observed, ranging from 5.88% to 8.54%, suggesting that the inclusion of the friction coefficient during structural calculations can result in savings, not only from a financial standpoint but also promoting environmental benefits by encouraging a more responsible use of wood in civil construction.

Unlocking the potential of epoxy binders for efficient reclaimed asphalt pavement recycling: an experimental and molecular simulation study

ABSTRACT The efficient utilisation of reclaimed asphalt pavement (RAP) has emerged as a critical focal point within pavement recycling technology. High-performance epoxy binders show promise in achieving this objective. This study investigates the interaction mechanisms between epoxy systems and aged asphalt from three perspectives: macroscopic properties, microscopic phase structures, and molecular structure of the asphalt-epoxy system. Results reveal that the aged asphalt-epoxy system has increased elongation at break and decreased tensile strength. Microscopic assessments show that the phase structure of the aged asphalt-epoxy system is denser compared to neat asphalt-epoxy systems. The looser structure of neat asphalt-epoxy systems provides more space for epoxy system chemical reactions, leading to higher crosslinking compared to both pure epoxy and aged asphalt-epoxy systems. Additionally, the epoxy system exhibits better compatibility with aged asphalt than neat asphalt. At the molecular level, the epoxy system strongly adsorbs onto asphalt components, especially aged resin molecules. These findings contribute to the scientific application of epoxy binder in pavement recycling technology.

Investigation of additively manufactured lattice structures for refractive optical systems based on auxetic properties

This paper reports on a novel concept of thermally stable lattice structures for next-generation refractive optical systems. The aim is to develop a metallic mount for optical lenses based on auxetic structures fabricated by additive manufacturing. Auxetic structures exhibit an effective negative Poisson ratio at the macroscopic level. This property is used to develop a mounting structure that compensates for thermal defocus between refractive optical elements. Numerical and experimental studies of the mechanical behavior of additively manufactured body-centered cubic cells provide the basis for the development of this application-specific mounting structure. Several static load cases are analyzed and deviations between numerical and experimental data are examined to quantify differences in dependence of element type, element size, and manufacturing-related geometrical inaccuracies. These results are used to compare the numerical analysis of the Poisson ratio of an auxetic unit cell with the analytical descriptions. This comparison is then applied to two-dimensional auxetic unit cell compounds. These studies provide the basis for the further development process of an auxetic mounting structure.

Uncoupling of Damped Linear Potential Multi-degree-of-freedom Structural and Mechanical Systems

Abstract This paper provides the necessary and sufficient conditions for a multi-degree-of-freedom linear potential system with an arbitrary damping matrix to be uncoupled into independent subsystems of at most two degrees-of-freedom using a real orthogonal transformation. The incorporation of additional information about the matrices, which many structural and mechanical systems commonly possess, shows a reduction in the number of these conditions to three. Several new results are obtained and are illustrated through examples. A useful general form for the damping matrix is developed that guarantees uncoupling of such systems when they satisfy just two conditions. The results provided herein lead to new physical insights into the dynamical behavior of potential systems with general damping matrices and to robust computational procedures. It is shown that the dynamics of a damped potential system in which the damping matrix may be arbitrary is identical to that of a damped gyroscopic potential system with a symmetric damping matrix. This brings, for the first time, these two systems, which are seen today as belonging to different categories of dynamical systems, under a unified framework.

Electromagnetic analysis on conceptual design of the EU DEMO EC equatorial laucher

The EU DEMO Tokamak is foreseen to be equipped with Electron Cyclotron (EC) launching systems for plasma heating, MHD control and thermal instability suppression. Up to six launchers will be installed into equatorial ports with the aim to inject a maximum of 130 MW millimeter wave power at dedicated positions into the plasma. The integrated design of the EC launcher is made of two equatorial port plug modules mounted into the equatorial port extensions of the vacuum vessel that mainly serve as housing for the eight optical system´s mirrors.To guarantee reliable operation of the launcher, in the latest year, a structural system has been designed which provides secure fastening and alignment of the optical components, sufficient heat dissipation and protection of sensitive areas against nuclear loads from neutrons by adequate shielding capability.To prove the fastening concept of the port plug modules and mirrors, a set of mechanical loads acting on these components is essential. EM loads caused by plasma instabilities are major contributions of mechanical load set for components close to the plasma.The present paper describes the EM analysis carried out to support the assessment of the pre-conceptual design solution. A dedicated Finite Element (FE) model was developed using ANSYS® solid236 element type (edge-based formation). Transient electromagnetic analysis was performed under centered plasma disruption event. Total force and moment due to Lorentz and ferromagnetic loads on the EC launcher port plugs and mirrors were computed. The resulting EM loads can be used for the preliminary design assessment.

Review and analysis of the failure risk mitigation via monitoring for monopile offshore wind structures

Structural health monitoring systems are gaining more attention in the offshore wind industry as they offer valuable insights into the integrity status of operating assets. Whilst most Class Society Rules and International Standards recognise the importance of implementing a condition-based maintenance strategy, they only provide theoretical guidance. Ultimately, it is the asset owner’s responsibility to determine how to integrate this strategy into their broader operation and maintenance planning, including identifying which components to monitor and which monitoring techniques to employ. The present paper applies the Failure Mode, Effects, and Criticality methodology to identify the most critical failure modes to prioritise for monopile offshore wind structures. Hence, the potential benefits of incorporating structural health monitoring systems within a condition-based maintenance strategy and exploiting lifetime extension possibilities are assessed. To achieve this, a novel 4-step methodology is introduced, involving understanding failure mechanisms (time-dependent behaviour and pattern), current regime (inspections at intervals), monitoring options (both direct and indirect), improvement potential evaluation through 5 key performance indicators relevant for optimal O&M, which is more comprehensive and realistic than considering only monetary consequence of failure. The study addressed the prevailing failure modes in 5 categories, namely fatigue, corrosion, deformation, buckling and displacement, and connection failure, aiming to demonstrate potential improvement in terms of risk mitigation against these failure modes. The results of this study can significantly help offshore wind developers optimise where and how to allocate their resources for structural health monitoring, resulting in long-term cost reduction opportunities.

The Microstructure and Mechanical Properties of Si3N4f/BN/SiBCN Microcomposites Fabricated by the PIP Process.

SiBCN ceramics based on SiC, BN and Si3N4 structures have good comprehensive properties such as high-temperature resistance, oxidation resistance, creep resistance and long life, which makes it one of the very promising ceramic material systems in military and aerospace fields, etc. In this study, SiBCN ceramics, as well as Si3N4f/BN/SiBCN microcomposites, were prepared by a polymer infiltration pyrolysis method using PBSZ as the polymer precursor. The PBSZ was completely ceramized by pyrolysis at 900 °C. The weight loss and elemental bonding forms of the products after the pyrolysis of the precursors hardly changed from 600 °C to 900 °C. After pyrolysis at 600 °C for 4 h and using the BN coating obtained from twice deposition as the interfacial phase, a more desirable weak interface of fiber/matrix with a binding strength of 21.96 ± 2.01 MPa can be obtained. Si3N4f/BN/SiBCN ceramic matrix microcomposites prepared under the same pyrolysis conditions have a relatively good tensile strength of 111.10 MPa while retaining a weak interface between the fibers and the matrix. The results of the study provide more theoretical and methodological support for the application of new composite structural ceramic material systems.

Optimal parameter estimation for uncertain structural systems under unknown random excitations

An optimal parameter estimation method for uncertain structural systems under unknown random excitations is proposed, which combines the Bayesian inference and stochastic dynamics using geometrically averaged likelihood and optimal response estimation. The general description of optimal parameter estimation problems for uncertain dynamic systems under only stochastic responses measured is presented. The posterior probability density conditional on measured responses is expressed by the likelihood function conditional on system parameters based on Bayes’ theorem. For finite time processes, the parameter estimation problem as the probability integral of conditional means is converted into the optimization problem expressed as maximizing the posterior probability density. A geometrically averaged likelihood function is defined and used for calculating the logarithmic posterior probability density. This estimation can avoid the numerical singularity of the likelihood function and reduce the effects of incomplete posterior probability density and inaccurate prior statistics of unknown random excitations, and then it will be more reasonable and effective. Furthermore, the differential equations for system response means and covariances are derived and solved based on stochastic dynamics theory. The means and covariances conditional on responses at the present instant are expressed by the previous statistics based on optimal response estimation. By combining two results, the analytical expressions of the averaged likelihood function and logarithmic posterior probability density are obtained which will be more reliable and accurate. The proposed optimal estimation method is verified by numerical results for a five-storey frame structure under base random excitation. The estimated results are not affected by the prior statistics errors of random excitation as a factor. For noisy observation, the Kalman filtering is incorporated in the estimation method and hence the estimation is more accurate and robust even for low signal noise ratios. The optimal estimation method has the potential for application to general uncertain systems.

The Management of Patients at High Risk of Serious COVID-19 Disease: Optimising the Patient Pathway in the Middle East, Africa, and Eastern Europe.

Introduction For patients at high risk of severe COVID-19 disease, antiviral therapeutic options are available to reduce the risk of hospitalization or death. Although many countries have developed national guidelines for COVID-19 management that include use of antiviral agents, it is unclear how these guidelines are used in daily clinical practice. This study aims to assess the management of high-risk COVID-19 patients in the Middle East, Africa, and Eastern Europe, with a focus on understanding current practices, challenges, and potential strategies for improvement. Methods Healthcare professionals (HCPs) from the Middle East, Africa, and Eastern Europe came together at a regional summit in February 2023 to share perspectives on the therapeutic management of patients at high risk of serious COVID-19 disease in the community. Summit participants represented diverse medical specialties, geographical regions, and healthcare settings. Key insights gathered during the summit were supplemented with evidence from the published literature via a non-systematic literature search of MEDLINE and online sources such as government reports since the start of 2020 to identify articles on disease burden, unmet needs, treatment access, antiviral therapy, guidelines related to individuals with COVID-19 at high-risk for poor outcomes in low- and middle-income countries (LMICs). Together, these sources were used by the authors to generate their recommendations for future priorities and optimal care pathways globally. Results Specific insights gathered from the summit were that participants reported that primary care is the first point of contact for high-risk patients, but the role of primary care physicians (PCPs) in treatment is uncertain. Additionally, participants highlighted that between-country differences in the care pathway for high-risk patients are due to variations in local treatment practices, healthcare system structures, and resourcing. In line with the published literature, participants agreed that HCP education is needed to support the identification, counseling, and appropriate management of high-risk patients and that pharmacists have a critical role to play in identifying clinically important potential interactions with antiviral treatment and recommending appropriate adjustments. Furthermore, patient hesitancy can result in late presentation, delayed treatment, and potential progression of symptoms. HCPs should proactively counsel high-risk patients, so they are aware of their risk and its implications and understand what to do if they experience symptoms of COVID-19. Targeted educational initiatives for patients are needed to mitigate reluctance to undergo COVID-19 testing and counter COVID-19 misinformation. Conclusion Collaboration among stakeholders is essential to optimize COVID-19 management for high-risk patients globally, ensuring effective implementation of guidelines and improving outcomes.

Improving seismic performance of structural systems via reinforcing column bases

Improving seismic performance of structural systems via reinforcing column bases

The structurally‐controlled polyphase Au mineralization in the southern Youjiang Basin: Insights from magnetotelluric imaging

The Youjiang Basin, located on the southwestern margin of the Yangtze Craton, hosts significant Upper Triassic and Lower Cretaceous gold (Au) deposits. Isotope studies suggest that the polyphase Au mineralization in the Youjiang Basin is derived from Indosinian and Yanshanian magmatic events, but the structural plumbing system beneath the basin remains poorly understood. We collected 32 magnetotelluric (MT) stations extending from the southern margin of the Youjiang Basin which hosts the Zhesang, Badu, and Jinya Au deposits at the western margin of the Jiangnan Orogenic (JNO) belt. The full impedance tensor of MT data is utilized to generate a high-precision lithospheric resistivity model by three-dimensional (3-D) inversion. Importantly, our MT data reveals several crustal conductors (<30 Ω·m) underlying major structures in the northwestern part of the study area. These crustal conductive anomalies spatially overlap with high-magnetic anomalies and polymetallic Au-Sn deposits. We interpret these anomalies as solid conductive materials such as graphite and/or sulfides related to the structurally controlled Mesozoic Au mineralization. Additionally, we interpret these conductive anomalies beneath the known Au deposits as the conduits of magmas and solidified paleo-magma chambers that were emplaced along deep-seated northwestern faults and likely documenting the genetic relationship between Au mineralization and Mesozoic magmatism. The synthesis of the electrical resistivity structure and metallogenic considerations is presented in a schematic sketch model illustrating that the deep-seated northwest-trending structures likely acted as a plumbing system controlling both the migration and emplacement of magmas and related oxidizing fluids that subsequently precipitated the polyphase Au deposits.

Flexural wave propagation characteristics of advanced nanocomposites reinforced sandwich structure via 3D-flexibility-deep neural networks approaches

The propagation of flexural waves in advanced nanocomposites reinforced sandwich structures is a topic of paramount importance in the field of structural engineering and materials science. This study investigates the dynamic behavior of such structures, focusing on the wave propagation characteristics along with longitude and lateral directions and their influence on structural performance. Advanced nanocomposites, with their unique material properties and enhanced mechanical properties, offer promising opportunities for the development of lightweight and high-strength sandwich structures. For this important aim, first, a mathematical modeling using three-dimensional flexibility theory and an analytical solution procedure, the results are collected. After that using the datasets of the mathematical modeling section, the hybrid deep neural networks are trained, tested, and validated. Through comprehensive analytical simulations and machine network validations, this research elucidates the complex interplay between material composition, structural geometry, and wave propagation phenomena. Key parameters, such as wave velocity, dispersion, and geometry conditions are analyzed to gain insights into the dynamic response of the sandwich structure. The findings contribute to a deeper understanding of the underlying physics governing flexural wave propagation in nanocomposite-reinforced sandwich structures, thereby facilitating the design and optimization of lightweight and resilient structural systems for diverse engineering applications.

Tutorial on Describing, Classifying, and Visualizing Common Crystal Structures in Nanoscale Materials Systems

Tutorial on Describing, Classifying, and Visualizing Common Crystal Structures in Nanoscale Materials Systems

Ediacaran marine animal forests and the ventilation of the oceans

The rise of animals across the Ediacaran-Cambrian transition marked a step-change in the history of life, from a microbially dominated world to the complex macroscopic biosphere we see today.1,2,3 While the importance of bioturbation and swimming in altering the structure and function of Earth systems is well established,4,5,6 the influence of epifaunal animals on the hydrodynamics of marine environments is not well understood. Of particular interest are the oldest "marine animal forests,"7 which comprise a diversity of sessile soft-bodied organisms dominated by the fractally branching rangeomorphs.8,9 Typified by fossil assemblages from the Ediacaran of Mistaken Point, Newfoundland,8,10,11 these ancient communities might have played a pivotal role in structuring marine environments, similar to modern ecosystems,7,12,13 but our understanding of how they impacted fluid flow in the water column is limited. Here, we use ecological modeling and computational flow simulations to explore how Ediacaran marine animal forests influenced their surrounding environment. Our results reveal how organism morphology and community structure and composition combined to impact vertical mixing of the surrounding water. We find that Mistaken Point communities were capable of generating high-mixing conditions, thereby likely promoting gas and nutrient transport within the "canopy." This mixing could have served to enhance local-scale oxygen concentrations and redistribute resources like dissolved organic carbon. Our work suggests that Ediacaran marine animal forests may have contributed to the ventilation of the oceans over 560 million years ago, well before the Cambrian explosion of animals.

Excellent Persistent Near-Infrared Room Temperature Phosphorescence from Highly Efficient Host-Guest Systems.

Organic near-infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal-to-background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy-gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten-folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host-guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs.

Passive Shunted Piezoelectric Systems for Vibration Control of Wind Turbine Towers: A Feasibility Study

Many countries have a variety of offshore and onshore wind turbines that face extreme aging challenges. Issues with harmful vibrations that must be minimized are addressed in this paper. A new method of wind turbine tower vibration control using piezoelectricity and shunt circuits is proposed in this paper. The passive vibration control method is shown to improve the tower’s structural performance under various environmental loads, like wind and seismic excitations. To examine the effectiveness of the suggested shunted piezoelectric system, a simple surrogate finite element model of a wind turbine tower is considered, and various investigations at the second eigenfrequency are carried out. An alternative way of modeling the studied structure is considered and the results demonstrate better performance. The advantages of setting up structural damping systems for decreasing tower vibrational loads and boosting their structural stability and resilience against extreme events are highlighted throughout this work.

Overcoming Challenges of Education: Effects of Structural Violence and Advances in Quality Education in Colombia and Pakistan

Far from solely direct, structural violence moves stealthily within the very frameworks of society, injuring in ways not seen. Its harms manifest not in physical blows but through the architecture of injustice, through inequities etched into policies, laws, norms. Having this in mind, the main goal of this paper is to present how structural violence takes place in the sustainable development goal of Quality Education (SDG4) in Colombia and Pakistan. To make it possible, structural violence will be defined, as well as the sustainable development goals, and in particular its goal 4 about quality of education. Likewise, it will be analyzed how SDG-4 correlates with other sustainable development goals. This study adopts a cyclical and exploratory approach to theory development as its scaffolding, specifically Grounded Theory methodology. data collection and analysis techniques follow the mixed method with a transformative theoretical design prioritizing qualitative interviews findings. Results highlight the current status of SDG 4 in Colombia and Pakistan, illuminating how ingrained systemic biases and discrimination undermine equitable quality education. Experts outline interlinked recommendations such as sustained investment in education systems, building societal recognition of education as a human right, engaging communities to shift discriminatory beliefs and norms, and centering marginalized groups' agency in political and social reform efforts. A multifaceted approach combining top-down resource provision and bottom-up consciousness-raising is advocated among other recommendations. Overcoming structural violence requires transforming systemic structures while simultaneously shifting societal mindsets perpetuating discrimination in education.