Material Constraints Research Articles

Comparison of Immersion and Portable Ultrasonic Housing to Quantify the Adhesive Bond Thickness and Sizing of Foreign Objects.

High-performance materials, such as carbon fiber laminates, are costly to manufacture and are often used in demanding environments requiring the use of high-resolution non-destructive testing (NDT) methods to confirm the integrity of the parts. One NDT method that has shown promise for qualifying carbon fiber laminates is the use of immersion ultrasound with spherically focused probes. However, many parts may not be submersible in an immersion tank due to size or material constraints. These parts must be scanned with contact transducers with inferior resolutions or with expensive and messy systems such as bubblers. This research presents the use of a novel housing system that allows for the use of focused immersion transducers in an out-of-tank portable ultrasonic scanning application. This work presents a comparison between scans taken using a custom high-resolution immersion system and scans taken using the presented housing. There are a wide variety of potential inspection applications for this novel system, and the present work focused on two specific applications: the quantification of the spatially varying adhesive thickness in bonded carbon fiber laminates and the quantification of foreign object inclusions in carbon fiber laminates. The results presented show that scans using the portable housing are comparable in quality to scans performed using an immersion system. Specifically, both inspection approaches had an average error of 0.04 mm when quantifying the adhesive thickness of a bonded composite, and for the foreign object detection, the error in quantifying the dimensions of the embedded foreign object was 0.1 mm and 0.2 mm for the immersion system and the portable inspection system, respectively. The demonstration was performed in a laboratory setting, but a discussion is provided for the necessary improvements needed to extend the system for use in field applications.

Designing metasurface optical interfaces for solid-state qubits using many-body adjoint shape optimization

We present a general strategy for the inverse design of metasurfaces composed of elementary shapes. We use it to design a structure that collects and collimates light from nitrogen-vacancy centers in diamond. Such metasurfaces constitute scalable optical interfaces for solid-state qubits, enabling efficient photon coupling into optical fibers and eliminating free-space collection optics. The many-body shape optimization strategy is a practical alternative to topology optimization that explicitly enforces material and fabrication constraints throughout the optimization, while still achieving high performance. The metasurface is easily adaptable to other solid-state qubits, and the optimization method is broadly applicable to fabrication-constrained photonic design problems.

Flexible and Large‐Scale Liquid Metal Frequency‐Selective Surfaces: Enhanced Tuning through Mechanical Reconfiguration

The tuning capability is crucial for broadening the application possibilities of frequency‐selective surfaces (FSSs). Flexible and stretchable FSSs have attracted widespread research interest due to their ability for adhering to curved surfaces conformally and reconfiguring electromagnetic (EM) wave transmission performance mechanically. However, conventional metal FSSs lack sufficient flexibility and deformability due to material constraints, resulting in diminished durability and limited EM tuning range. In this article, a design approach for flexible liquid metal FSS (LMFSS), which can conform to curved structures and achieve a wide range of EM wave tuning via mechanical stretching without structural damage, is presented. The fabrication of LMFSS is simplified using silicone elastomer curing and liquid metal inkjet printing, avoiding the complexities of traditional microchannel techniques. In the experimental results, it is demonstrated that the designed LMFSS achieves a tuning range of up to 16% under biaxial stretch strains not more than 25%. The tuning mechanism is explored through mechanical–EM simulations and equivalent circuit analyses. Additionally, the tuning phenomenon observed in another flexible LMFSS in this study underscores the portability of the design approach and tuning mechanism. In this research, a promising direction for tunable flexible LMFSS applications is offered.

Advancing the Coupling of III–V Quantum Dots to Photonic Structures to Shape Their Emission Diagram

AbstractThe development of optoelectronic devices based on III–V semiconductor colloidal quantum dots (CQDs) is highly sought after due to their reduced toxicity. While devices based on conventional CQDs (II–VI semiconductors, halide perovskites) have achieved impressive technological leaps since their discovery, the most mature of these compounds contain toxic heavy metal elements (Cd, Hg, or Pb), which are highly undesirable for safe industrial scale applications. The strong covalent bonds of III–V compounds like InP, InAs, or InSb prevent the release of their toxic atoms, making them safer. However, these same bonds create severe material constraints. Namely, their harsher reaction conditions and increased sensitivity to oxidation have kept most of the research focused on material development. Meanwhile, their integration into devices and their coupling to photonic structures lag behind. Here, the integration of InAs/ZnSe core‐shell CQDs is advanced. First, the material parameters necessary to design plasmonic gratings coupled to the CQDs are elucidated and those gratings are fabricated. Angle‐resolved spectroscopy shows that the plasmon modes successfully couple to the CQD layer's emission leading to a tunable directivity with a 15° linewidth. A 3‐fold increase of the PL signal is achieved at normal incidence, thus advancing toward the goal of efficient outcoupling in LEDs.

An Actualistic Experimental Study of Giant Quartzite Core Reduction Strategies: Implications for Large Flake Blank Production and Handaxe Manufacture at Amanzi Springs, South Africa

ABSTRACT The later Acheulian assemblages (ca. 534–< 390 ka) from Amanzi Springs in South Africa show a preferential selection for large flake blanks when undertaking large cutting tool manufacture. However, due to the small number of giant cores from the site, we have limited insight into the technical preparation of quartzite raw material packages for large flake production. Here, we present an actualistic experimental study to better understand these procedures at the site and to gain perspective on how knappers may have reduced quartzite boulders of differing internal qualities. Our results highlight the influence of raw material constraints and how the overall morphology of quartzite boulders in turn impacts giant core reduction sequences and large flake blank morphologies. Finally, the experimental study exemplifies the need for high levels of knapping expertise to deal with tough, heterogeneous quartzite varieties.

Design and practice of human-machine cooperative international Chinese character teaching in ChatGPT application

The incorporation of artificial intelligence (AI) into language education has created new opportunities for improving the instruction and acquisition of Chinese characters. Nevertheless, the cognitive difficulties linked to the acquisition of Chinese characters, such as their intricate visual features and lack of clear meaning, necessitate thoughtful deliberation when developing AI-supported learning interventions. The objective of this project is to explore the capacity of a collaborative method between humans and machines in teaching Chinese characters, utilising the advantages of both human expertise and AI technology. We specifically investigate the utilisation of ChatGPT, a substantial language model, for the creation of instructional materials and evaluation methods aimed at teaching Chinese characters to individuals who are not native speakers. The study utilises a mixed-methods approach, which involves both qualitative examination of lesson plans created by ChatGPT and quantitative evaluation of student learning outcomes. The results indicate that the suggested framework for human-machine collaboration can successfully tackle the cognitive difficulties associated with learning Chinese characters, resulting in enhanced learner involvement and performance. Nevertheless, the research also emphasises the constraints of AI-generated material and the significance of human involvement in guaranteeing the accuracy and dependability of educational interventions. This research adds to the expanding collection of literature on AI-assisted language learning and offers practical insights for educators and instructional designers who aim to use AI tools into Chinese language curriculum. The results emphasise the necessity of employing a multi-disciplinary strategy in AI-supported language learning, incorporating knowledge from cognitive psychology, educational technology, and second language acquisition.

Engaging in Transnational Feminist Praxis

In this reflective article, I focus on the meanings and implications of conducting feminist ethnographic research during the COVID-19 pandemic with women participants of an educational project supported by the non-governmental sector in India. This research aimed to provide the space for women to organically present and provide insight into the multiplicity of factors that influence their decision-making authority and ability, illuminating the connections between education, agency, and empowerment during the COVID-19 pandemic. I discuss the nuances as well as on-the-ground limitations of developing collaborative and relational research in contexts with significant material and structural constraints. In this article, I seek to underscore the need to examine closely what collective belonging, duty, and responsibility looks like for researchers in the development and implementation of transnational feminist projects during crisis.

Thinking diegetically

In the process of thinking diegetically, the videographic practitioner is guided by the diegetic (story world) logic of the films or media works under scrutiny. As opposed to videographic approaches that extract audiovisual segments from a narrative and spatiotemporal logic, this form of videographic work engages with the constraints of the source materials’ diegetic tethers to (re)construct a story world in meaningful and productive ways. This essay seeks to explore the ramifications of such diegetic argumentation through an analysis of several videographic works: the author’s “Imagining Orphée | Orphée imaginé” (Oyallon-Koloski 2023), Catherine Grant’s “Fated to be Mated: An Architectural Promenade” (2018), Dayna McLeod’s “Speculative Queer Autoethnography: Desert Hearts” (2023), and Liz Greene’s “Spencer Bell, Nobody Knows My Name” (2022). These examples embrace the intrinsic form of their source material’s diegesis, prioritize the rhetorical impact of spatiotemporal construction, and deliberately balance the pulls between original and videographic diegetic logic through the application of precise videographic techniques. Video essayists use the formal, performative, and nonverbal options afforded by centering diegetic principles in powerful ways to shape their rhetoric.

Metode Flipped Classroom dalam Pembelajaran Maharoh Istima': Studi Kasus dan Hasil

This article deals with the application of flipped classroom methods in learning istima' maharoh (listening skills) through case studies. Maharoh istima' is an important aspect of language skills that enables students to understand intonation, pronunciation, and meaning in oral texts. However, traditional teaching methods are often inadequate due to challenges such as lack of authentic material and time constraints in the classroom. Flipped classroom offers solutions by moving the delivery of basic material outside the classroom, through video and online tasks, so that class time can be focused on interactive activities and in-depth practice. This study revealed positive results from the application of this method, with an average increase in listening test scores of 20% after students followed the flipped classroom method. Students showed more active participation and greater confidence in classroom discussions, as well as improved understanding of the material. The findings suggest that the flipped classroom method can significantly improve the effectiveness of istima maharoh learning, by providing additional advantages in the development of self-learning skills. Further research is needed to evaluate other factors that affect the effectiveness of this method and how its application can be adapted in different educational contexts.

Experimental and numerical study on the material constraint effect in pipeline steel welded joint

An in-depth analysis of the material constraint effect is crucial for accurately determining the constitutive relationship and safety evaluation of pipeline steel welded joint. Therefore, this work combines experiments and finite element simulations to study the constraint effect. Through the welding method, the weld specimens with different sizes and strength mismatch conditions are prepared. The microstructure and hardness distribution of the specimens are measured, and tensile tests based on the digital image correlation (DIC) technology are conducted. Finite element models of the weld specimens with different sizes and material parameters are established, followed by tensile simulations and detailed analysis. Based on the experiments and numerical simulations, the tensile strain responses, stress-strain curves, and material parameters of different weld specimens are obtained. The results show that the smaller the weld width, the more significant the effect of the material constraint. For undermatched welds, the calculated stress of the weld metal (WM) increases with the decrease of the weld width. Additionally, the calculated stress of WM also increases with the decrease of the mismatch coefficient, where the mismatch coefficient refers to the ratio of the yield strength of WM to that of the base metal (BM). Conversely, for overmatched welds, the calculated stress of WM decreases with the decrease of the weld width. The material constraint effect is also influenced by the mismatch condition of the weld. An increase in the mismatch coefficient reduces the effective range of the stress-strain curve obtainable for WM. To analyze the effect of the mismatch condition, it is necessary to comprehensively compare the yield strength and strain hardening capacity of each material. The width-to-thickness ratio of the weld specimen has little effect on the calculated stress of WM. The finite element simulation method can be used to correct the stress-strain curves obtained from the tests to achieve accurate constitutive relationships.

COVID-19 impact in sourcing in Global Value Chains

This study explores the impact of COVID-19 on Global Value Chains (GVCs) using the Eurostat dataset, focusing on trade barriers and the difficulty of sourcing raw materials or intermediate goods from local and international suppliers. Using a contingency table grouped by country, we can see how raw material constraints and COVID-19’s GVCs affect many countries. The study uses Chi-square test to determine if these factors have a significant association. The data imply that foreign sourcing presents less challenges for suppliers than domestic sourcing, stressing the need of examining the consumer behaviour under uncertainties to develop GVCs resilience. The findings show a statistically significant link between barriers related to raw material and the effect level of COVID-19 in global value chains across all countries analysed. Suggesting that it is unlikely to have happened by random chance alone, highlighting the importance of addressing trade barriers and adapting to the impact of COVID-19 within global value chains.

Free-space direct nanoscale 3D printing of metals and alloys enabled by two-photon decomposition and ultrafast optical trapping.

Nanoscale three-dimensional (3D) printing of metals and alloys has faced challenges in speed, miniaturization and deficiency in material properties. Traditional nanomanufacturing relies on lithographic methods with material constraints, limited resolution and slow layer-by-layer processing. This work introduces polymer-free techniques using two-photon decomposition and optical force trapping for free-space direct 3D printing of metals, metal oxides and multimetallic alloys with resolutions beyond optical limits. This method involves the two-photon decomposition of metal atoms from precursors, rapid assembly into nanoclusters via optical forces and ultrafast laser sintering, yielding dense, smooth nanostructures. Enhanced near-field optical forces from laser-induced localized surface plasmon resonance facilitate nanocluster aggregation. Our approach eliminates the need for organic materials, layer-by-layer printing and complex post-processing. Printed Mo nanowires show an excellent mechanical performance, closely resembling the behaviour of single crystals, while Mo-Co-W alloy nanowires outperform Mo nanowires. This innovation promises the customizable 3D nanoprinting of high-quality metals and metal oxides, impacting nanoelectronics, nanorobotics and advanced chip manufacturing.

Freecycling Markets as Sustainable Materialist Movements?

This paper seeks to redress the over-emphasis on state-driven circular policies in public and academic discourses by attending to two physical community-based freecycling markets at the emerging frontiers of circular waste/resource management in Singapore. Freecycling markets that close short reuse loops are a counterpoint to policies that close long recycling loops. Drawing primarily on empirical data from ethnographic fieldwork, we argue that freecycling markets exemplify a sustainable materialist movement concerned about the sustainability of material resources vis-à-vis the closing/shortening of material circularity loops. This is achieved through the reconfiguration of (a) material flows and (b) material relations. The redirection of unwanted but reusable household objects away from the incinerator and towards potential reusers animates a shift from a linear to circular material flow. We contend that this redirection of material resources for reuse is augmented by rescue and recirculation, which are relatively neglected within the scholarship on circular R-behaviours. Additionally, freecycling markets seek to transform material relations by encouraging care and stewardship, instead of use and disposal. Crucially, we highlight how freecycling markets may be plagued with material constraints that render them not-so-sustainable-and-scalable, thereby shedding light on the practical limits of sustainable materialist action. Taken together, this paper extends the scholarship on circular economies by bringing work on sustainable materialism into a productive dialogue with that on circular activisms and R-behaviours.

Research on the Flow-Induced Vibration of Cylindrical Structures Using Lagrangian-Based Dynamic Mode Decomposition

An oscillating flow past a structure represents a complex, high-dimensional, and nonlinear flow phenomenon, which can lead to the failure of structures due to material fatigue or constraint relaxation. In order to better understand flow-induced vibration (FIV) and coupled flow fields, a numerical simulation of a two-degrees-of-freedom FIV in a cylinder was conducted. Based on the Lagrangian-based dynamic mode decomposition (L-DMD) method, the vorticity field and motion characteristics of a cylinder were decomposed, reconstructed, and predicted. A comparison was made to the traditional Eulerian-based dynamic mode decomposition (E-DMD) method. The research results show that the first-order mode in the stable phase represents the mean flow field, showcasing the slander tail vortex structure during the vortex-shedding period and the average displacement in the in-line direction. The second mode predominantly captures the crossflow displacement, with a frequency of approximately 0.43 Hz, closely matching the corresponding frequency observed in the CFD results. The higher dominant modes mainly capture outward-spreading, smaller-scale vortex structures with detail displacement characteristics. The motion of the cylinder in the in-line direction was accompanied by symmetric vortex structures, while the motion of the cylinder in the crossflow direction was associated with anti-symmetric vortex structures. Additionally, crossflow displacement will cause a symmetrical vortex structure that spreads laterally along the axis behind the cylinder. Finally, when compared with E-DMD, the L-DMD method demonstrates a notable advantage in analyzing the nonlinear characteristics of FIV.

DNN-Based Resource Recommendation for Ideology Theory Courses Online

Revamped IPE confronts static material constraints and outdated pedagogy, warranting integration of web resources and big data analytics for instructional innovation. Digital IPE adoption in vocational education optimizes online resource use, enhancing teaching effectiveness. Introducing CUPMF, a personalized learning model, we conduct empirical assessments on a large dataset (364,617+ entries) from Smart Classroom's cloud platform and public datasets, reflecting varied IPE scenarios. Comparative experiments against association rule, content-, tag-based, and collaborative filtering algorithms show CUPMF's superiority. It achieves a 11.61% F1 score boost over four alternatives for basic recommendations and outperforms Que Rec by 1.975%. Complexity-wise, CUPMF registers an 11.52% mean F1 score increment over four methods and 1.875% over Que Rec. Proven, CUPMF markedly improves IPE resource recommendation accuracy and efficacy, poised to transform personalized online vocational learning.

Topology optimization of periodic cellular materials employing the finite-volume theory

Topology optimization is a technique used in engineering to determine the optimal distribution of material within a defined design domain. This technique has been applied to the design of cellular materials to create an efficient microstructural arrangement that meets the necessary performance criteria and minimizes the weight of the material. This article presents an innovative approach that combines topology optimization, a homogenization method based on the unit cell concept and finite-volume theory to design highly efficient periodic cellular materials with optimized macroscopic elastic properties. To determine the optimal microstructural topology, specific linear combinations of components of the homogenized elastic matrix are considered to obtain optimized elastic properties, such as maximum shear/bulk moduli, considering a prescribed volume fraction constraint of solid material. Numerical examples are analysed, and the results demonstrate the exceptional performance of this approach in achieving optimal designs of cellular materials characterized by chequerboard-free patterns without filtering techniques.

Optimizing MSME Profits using the Simplex Method

This research aims to calculate the maximum profit from selling spinach chips, onion cakes and steak cakes at Guna Asih MSMEs and to determine the use of the simplex method for raw material constraints faced by Guna Asih MSMEs. In addition, this research uses POM-QM for Windows software to estimate the maximum profit obtained from each production of spinach chips, onion cakes and sistik cakes at Guna Asih UMKM so as to have an accurate estimate. This research method involves problem identification, selection of problem-solving models, data collection, data processing and analysis, model implementation, and evaluation of results. The research results show that the simplex method can be used to determine maximum profits in Guna Asih MSMEs. The maximum profit obtained by MSMEs is IDR. 1,277,778 per day when only producing spinach chips (X1) 1.12 times more than previous production or 336 pcs and producing onion cakes (X2) 5 times more than previous production or 500 pcs. This profit is greater than the profit before optimization which only earned IDR. 900,000 from 300 pcs of spinach chips, 100 pcs of onion cakes and 60 pcs of steak cakes. Apart from that, the use of POM-QM for Windows software is very relevant in solving linear programming problems using the simplex method because it can help in completing maximum profit level calculations quickly, precisely and accurately.

Material‐Constrained Optimization of Liquid Crystal‐Based Holograms

AbstractA novel material‐constrained method for the design of liquid crystal optical devices – computer‐generated liquid crystal‐based holograms – and their manufacture using photo‐patterning is demonstrated. The developed topology optimization method is compared to the Gerchberg‐Saxton algorithm, and key advantages and disadvantages are outlined. The key novelties and advantages of the method are that it accounts for the natural relaxation and material properties of the liquid crystal and that it can account for different material or manufacturing constraints, such as maximum optical axis gradients. The viability of the method is applied for different binary and greyscale target images of varying complexity, target image sizes, and algorithms that account for the material properties of the liquid crystal. Finally, with the topology optimization design approach and photo‐patterning, it is possible to produce high‐accuracy and high‐contrast liquid crystal‐based computer‐generated holograms.

Timeliness and quality of peripartum care provision during a health system strengthening initiative in rural Guinea-Bissau: a qualitative situation analysis

Guinea-Bissau has among the world’s highest maternal and perinatal mortality rates. To improve access to quality maternal and child health (MCH) services and thereby reduce mortality, a national health system strengthening initiative has been implemented. However, despite improved coverage of MCH services, perinatal mortality remained high. Using a systems-thinking lens, we conducted a situation analysis to explore factors shaping timeliness and quality of facility-based care during labour, childbirth, and the immediate postpartum period in rural Guinea-Bissau. We implemented in-depth interviews with eight peripartum care providers and participant observations at two health facilities (192 h) in 2021-22, and analysed interview transcripts and field notes using thematic network analysis. While providers considered health facilities as the only reasonable place of birth and promoted facility birth uptake, timeliness and quality of care were severely compromised by geographical, material and human-resource constraints. Providers especially experienced a lack of human resources and materials (e.g., essential medicines, consumables, appropriate equipment), and explained material constraints by discontinued donor supplies. In response, providers applied several adaptation strategies including prescribing materials for private purchase, omitting tests, and delegating tasks to birth companions. Consequences included financial barriers to care, compromised patient and occupational safety, delays, and diffusion of health worker responsibilities. Further, providers explained that in response to persisting access barriers, women conditioned care seeking on their perceived risk of developing birthing complications. Our findings highlight the need for continuous monitoring of factors constraining timeliness and quality of essential MCH services during the implementation of health system strengthening initiatives.

Chemically reactive non-Newtonian fluid flow through a vertical microchannel with activation energy impacts: A numerical investigation

This work examines the second law analysis of an electrically conducting reactive third-grade fluid flow embedded with the porous medium in a microchannel with the influence of variable thermal conductivity, activation energy, viscous dissipation, joule heating, and radiative heat flux. A suitable non-dimensional variable is included into the governing equations to transform them into an ensemble of equations that are devoid of dimensions. The acquired equations are then tackled using the Runge Kutta Felhberg 4th and 5th order (RKF-45) approach in conjunction with the shooting methodology. Through comparison with the current results, the numerical results are verified, which provides a good agreement. From the present outcomes, it is established that the entropy generation is supreme for the viscous heating constraint, variable thermal conductivity, Frank Kameneski, heat source ratio parameter and third-grade fluid material constraint. The Bejan number boosts up with larger values of activation energy, and Frank Kameneski constraint and the decreasing nature is noticed for increasing third-grade material parameter, viscous heating parameter. With magnetism, the fluid’s velocity slows down because of a resistive force. A similar impact in the channel on velocity is noticed for larger third-grade fluid, activation energy parameter, and Frank-Kameniski parameters and increasing behavior is noticed for variable thermal conductivity, and permeability parameter. Further, it is cleared that the variable thermal conductivity assumption in the channel plate leads to a significant under prediction of the irreversibility rate.