Structural Components Research Articles

Tracing the origins of Plasmodium vivax resurgence after malaria elimination on Aneityum Island in Vanuatu

BackgroundFive years after successful malaria elimination, Aneityum Island in Vanuatu experienced an outbreak of Plasmodium vivax of unknown origin in 2002. Epidemiological investigations revealed several potential sources of P. vivax. We aimed to identify the genetic origin of P. vivax responsible for the resurgence.MethodsFive P. vivax microsatellite markers were genotyped using DNA extracted from archived blood samples. A total of 69 samples from four P. vivax populations was included: 29 from the outbreak in 2002, seven from Aneityum in 1999 and 2000, 18 from visitors to Aneityum in 2000, and 15 from nearby Tanna Island in 2002. A neighbour-joining phylogenetic tree was constructed to elucidate the relationships among P. vivax isolates. STRUCTURE and principal component analysis were used to assess patterns of genetic structure.ResultsHere we show distinct genetic origins of P. vivax during the outbreak on Aneityum. While the origin of most P. vivax lineages found during the outbreak remains unidentified, limited genetic diversity among these lineages is consistent with a rapid expansion from a recent common ancestor. Contemporaneous P. vivax from neighboring Tanna and potential relapse of P. vivax acquired from other islands in 1999 and 2000 are also identified as minor contributors to the outbreak.ConclusionsMultiple reintroductions of P. vivax after elimination highlight the high receptivity and vulnerability to malaria resurgence in island settings of Vanuatu, despite robust surveillance and high community compliance to control measures.

Assessing bioenergy prospects of algal biomass and yard waste using an integrated hydrothermal carbonization and pyrolysis (HTC–PY): A detailed emission–to–ash characterization via diverse hyphenated analytical techniques and modelling strategies

Hydrothermal carbonization (HTC) presents a promising method for converting carbonaceous waste into renewable fuels, facilitating energy recovery. This study focuses on the HTC pretreatment of microalgae (Chlorella sorokiniana) and yard waste, examining their physicochemical structural changes, component migration, and potential for valorization via integrated HTC and pyrolysis processes. HTC notably enhances the carbon content while reducing oxygen and nitrogen levels in these feedstocks, producing a clean solid fuel with high energy density. The study investigates the pyrolytic behavior of hydrochars and their blends using different analytical techniques, kinetic modeling, and fixed–bed reactor experiments. The blends with 90% and 70% of microalgae hydrochar (CSH) exhibited the most significant synergistic effects during co–pyrolysis, evident in its devolatilization behaviors and reduced activation energies. Integrating artificial neural networks and response surface methodology models facilitated optimization of pyrolysis parameters and accurate prediction of bio–oil, biochar, and gas yields. The analytical techniques enabled characterization of pyrolysis products, revealing notable changes in bio–oil and biochar compositions, suggesting potential enhancements. The study comprehensively evaluates the HTC–pyrolysis approach’s potential for converting microalgae and lignocellulosic biomass into eco–friendly biofuels for industrial applications.

Development of Low-Weight and High-Strength AA6005A Extrudates Intended for Modern Architecture and Design of Innovative Die for Extrusion Process.

In the realm of modern architecture, the demand for materials that combine strength, durability, and aesthetic flexibility is ever-growing. Addressing this need, this paper presents a study on the innovative use of aluminum extrudates in construction. Focusing on the AA6005 alloy, which is known for its excellent balance of strength, corrosion resistance, and weldability, this research delves into the development of an extrusion process that yields thin-walled, lightweight, yet high-strength structural components. Using FEM simulations, a new extrudate of the AA6005A was developed. It is compatible with standard façade systems, with high-strength properties and a weight reduced by 20% compared to that of conventional extrudates made of the AA6063 alloy. Using CAD engineering and FEM simulations of aluminum extrusion process, an innovative die was designed for the extrusion process, ensuring uniform flow of metal from the bearing and minimizing the elastic deflection of the die. This resulted in an increase in the extrusion velocity of thin-walled extrudate from AA6005A by 24% compared to conventional profiles extruded from AA6063. As part of the research, a trial test was carried out in production conditions and the quality of the extrudates was tested by 3D optical scanning, mechanical and structural properties tests, and microstructure observation.

PENGUJIAN AKARAKTERISTIK PASIR PANTAI KABUPATEN KOLAKA SEBAGAI MATERIAL ALTERNATIF PEMBUATAN BETON (Pasir Pantai Kec. Tanggetada, Kec. Watubangga dan Kec. Toari)

The quality characteristics of the concrete produced are greatly influenced by the quality of the fine aggregate used as a structural component, because fine aggregate has a large influence on the volume of concrete. So, the use of beach sand as a construction material must meet the specified requirements. The aim of this research is to determine the characteristics of beach sand in 3 (three) sub-districts in Kolaka district, whether it can be used in making concrete or not. The research method used was a detailed experiment carried out at the Concrete Laboratory of Sembilanbelas November University Kolaka with samples of Tanggetada Beach Sand, Watubangga Beach Sand and Toari Beach Sand. The results of testing the characteristics of the three beach sands used were obtained by testing data that met the requirements specified in SNI 03-1971-1990, except for the sieve analysis examination at No. 50 for all sand locations and No. 100 for Tanggetada and Toari Beach sand locations. Meanwhile, the specific gravity and water absorption, bulk weight, water content and passing sieve No. 200 have met the specifications. From the results obtained, the use of Watubangga Beach Sand can be used as sand material for normal concrete construction.

Investigation of Non-Uniform Inflow Effects on Impeller Forces in Axial-Flow Pumps Operating as Turbines

Due to the existence of an inlet elbow, transmission shaft, and other structural components, the inflow of axial-flow pumps as turbines (PATs) becomes non-uniform, resulting in the complexity of internal flow and adverse effects such as structural vibration. In this paper, numerical methods were employed to explore the non-uniform inflow effects on impeller forces and internal flow field characteristics within an axial-flow PAT. The study results indicated that non-uniform inflow caused uneven pressure distribution inside the impeller, which leads to an imbalance in radial forces and offsetting the center of radial forces. With an increasing flow rate, the asymmetry of radial forces as well as the amplitude of their fluctuations increased. Non-uniform inflow was found to induce unstable flow structures inside the impeller, leading to low-frequency, high-amplitude pressure fluctuations near the hub. Using the enstrophy transport equation, it was shown that the relative vortex generation term played a major part in the spatiotemporal evolution of vortices, with minimal viscous effects.

Energy flexibility in aerospace manufacturing: The case of low carbon intensity production

In this paper, the prospects of energy flexibility in mitigating the environmental impact of aerospace manufacturing are explored. In collaboration with a UK-based aerospace manufacturing enterprise, demand response, in particular production time, is explored under different stochastic scenarios. This is done through a decision-support framework that consists of a stochastic discrete-event simulation model that tests different scenarios under a full factorial design of experiments framework. The simulation model tests various improvement strategies pertaining to prioritisation rules, production start-up rules, and operating hours. The model aids in scheduling energy-intensive processes, so the time of performing such processes can coincide with times of the day when the energy’s carbon intensity is at its lowest. The use case constitutes a family of aluminium structural aerospace components that are characterised by high production rate. Results demonstrate promising potential of the proposed approach, with the best-case scenario resulting in a 7% reduction in CO2e emissions. Analysis of the results demonstrate that operational decisions that do not require infrastructural changes or capital expenditures can contribute favourably to achieving net-zero targets. This research offers useful insights on leveraging operational short-term decisions to meet the aerospace manufacturing’s sector decarbonisation targets.

Fast computational approach with prior dimension reduction for three-dimensional chemical component analysis using CT data of spectral imaging.

Spectral image (SI) measurement techniques, such as X-ray absorption fine structure (XAFS) imaging and scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS), are useful for identifying chemical structures in composite materials. Machine-learning techniques have been developed for automatic analysis of SI data, and their usefulness has been proven. Recently, an extended measurement technique combining SI with a computed tomography (CT) technique (CT-SI), such as CT-XAFS and STEM-EDS/EELS tomography, was developed to identify the three-dimensional (3D) structures of chemical components. CT-SI analysis can be conducted by combining CT reconstruction algorithms and chemical component analysis based on machine learning techniques. However, this analysis incurs high computational costs owing to the size of the CT-SI datasets. To address this problem, this study proposed a fast computational approach for 3D chemical component analysis in an unsupervised learning setting. The primary idea for reducing the computational cost involved compressing the CT-SI data prior to CT computation and performing 3D reconstruction and chemical component analysis on the compressed data. The proposed approach significantly reduced the computational cost without losing information about the 3D structure and chemical components. We experimentally evaluated the proposed approach using synthetic and real CT-XAFS data, which demonstrated that our approach achieved a significantly faster computational speed than the conventional approach while maintaining analysis performance. As the proposed procedure can be implemented with any CT algorithm, it is expected to accelerate 3D analyses with sparse regularized CT algorithms in noisy and sparse CT-SI datasets.

Deterioration and imperfection of the ship structural components and its effects on the structural integrity: A review

Abstract The design of ship structural safety is crucial to ensure the ship’s survivability during the operation. Extensive research has been conducted on ship structural components, including box girders, stiffened panels, and plates, beyond the ideal conditions by considering the implication of manufacturing processes, vessel usage, and aging in the form of defects like cracks, corrosion, and imperfections, both locally and globally. Previous research has also explored various methodologies, conditions, and parameters to understand the impact of damages and imperfections on ship structure and strength. However, there is a significant need to bridge the gap in prior research to advance technology and ship structural strength analysis. A comprehensive benchmark study specifically focused on improving ship structural component needs, identifying differences and gaps among existing studies as challenging. This article thoroughly reviews ship structural components, such as box girders, stiffened panels, and plates, while examining the effects of structural defects like corrosion, cracks, and imperfections on ship structural integrity. It synthesizes the influence of various defect parameters, including crack length, angle, position, corrosion severity, pit corrosion, pit diameter, and pit models, using finite element modeling and experimental investigations, particularly emphasizing ship structural components. The comparative analysis of methods and parameters presented in this review will serve as a valuable reference for future investigations and studies related to ship structural strength and design. The article’s contribution is expected to enhance the understanding of ship structural strength, contributing to the sustainability and effectiveness of vessel design in the global maritime industry.

Microstructure and abnormal mechanical properties under the coupling effect of strain and temperature for friction-stir-welded joints of Al-Mg-Si alloy

In the fields of automotive engineering and shipbuilding, friction stir welding (FSW) is utilized for joining aluminum alloy structural components. However, the nugget zone (NZ) in FSW joints often exhibits anomalous mechanical properties, consequently diminishing the stability of the welded joints. Here, an NZ was subdivided into a high-strain nugget zone (HS-NZ) and a high-temperature nugget zone (HT-NZ). The anomalous mechanical properties of the Al-Mg-Si alloy HS-NZ were systematically investigated at welding speeds of 100 mm/min and 200 mm/min and rotational speeds of 600 rpm and 900 rpm. Compared to the HT-NZ, the average grain size of the HS-NZ reduced by a maximum of 3 μm, the density of geometrically necessary dislocations (GNDs) increased by a maximum of 0.26 ×1014 m−2, and the microhardness showed a maximum increase of 15 HV. However, its shear strength is lower than that of the HT-NZ, with a maximum decrease of 15 MPa, exhibiting an abnormal mechanical performance. The increase in the "soft-oriented" grains in the HS-NZ results in more localized stress concentration between "soft-oriented" and "hard-oriented" grains during the deformation, thereby providing a reasonable explanation for the observed reduction in shear strength in HS-NZ under severe loading conditions. The increase of "soft-oriented" grains is primarily attributed to the promotion of discontinuous dynamic recrystallization (DDRX) facilitated by the coupled effects of high temperature and high strain. The constructed mathematical model also illustrated the effect of the coupled temperature and strain fields on the abnormal shear strength.

Formation mechanism of AlNbTiVZr high entropy alloy/Ti multi-principal element alloy by laser direct energy deposition: Microstructure evaluation and mechanical properties

A novel refractory multi-principal element alloy with high strength and toughness matching characteristics was successfully prepared by mixing TA15 alloy with AlNbTiVZr high-entropy alloy. The effects of the composition ratio of the high-entropy alloy on the microstructure evolution and its influence on properties were investigated in this study. The tensile strength of the 70 wt % AlNbTiVZr HEA/Ti multi-principal element alloy is 1.18 times more than that of TA15 alloy, which has a value of 1068.0 ± 2.1 MPa. The increase in strength is mainly due to the production of equiaxed fine grains and the development of a robust and resilient body-centered cubic (BCC) phase in the alloy following the introduction of the high-entropy alloy. The attainment of the acceptable tensile strain is the result of the combined influence of the BCC matrix phase and the dispersed second-phase particles. The exceptional mechanical capabilities of the 70 wt % AlNbTiVZr/Ti multi-principal element alloy undeniably enhance its potential for use as a structural component in aerospace load-bearing constructions.

Global Experience in the Use of Unmanned Aviation Technologies in Public Administration: a Review

TUnmanned Aerial Systems (UAS), despite their relative novelty, are already an integral component of the general aviation structure, and, based on a number of complex and sophisticated solutions, including those related to artificial intelligence, are part of the spectrum of high technologies. UAS find application not only in the sphere of commerce, but also in the realisation of specific tasks of public administration, such as territory management, healthcare, emergency prevention and elimination, ensuring environmental safety and law and order, nature management. The purpose of the study, the results of which are presented in this publication, is to assess the current state and potential of the use of UAS in these areas based on a review of literature sources on the practice of their application in order to solve the tasks of public administration in different countries of the world. The main conclusion drawn from the analysis and characterising the general scientific novelty of the study is that, despite a significant number of specific examples, the breadth of UAS use range can be characterised as imaginary. The main and the only really significant application is various types of aerial survey in the interests of state control and supervision bodies. In the course of the work, a number of promising directions for the use of UAS have been identified. It is also noted that their wider implementation in the practice of public administration is hindered by the lack and/or imperfection of the relevant legal framework, typical for most legislative systems of the world, and postulates the need to actively address these issues in relation to the classification and certification of UAS, requirements for their operators and software, the procedure and rules of operation, the integration of unmanned aircraft (UAS) into the existing air traffic management system.

Optimization of Formic Acid-Formalin-Based Decalcification Protocol for Rat Calvarial Bone Histology

Decalcification is crucial in histological processing, particularly for studying mineralized tissues like bone. The choice of decalcification method can significantly impact the quality of histological sections and the preservation of tissue morphology. This study aims to establish a standardized protocol for decalcifying rat calvarial bone using a formic acid-formalin-based decalcification solution. The protocol was systematically optimized and evaluated based on various parameters, including decalcification time, formic acid concentration, and tissue integrity preservation. The decalcification process was evaluated through comprehensive assessments, including gross physical examination, chemical analysis, and radiographic imaging techniques. Our result demonstrated that the 10% formic acid concentration proved most effective for decalcifying rat calvarial bone samples within eight days, excelling in mineral content removal while preserving specimen structural integrity. In contrast, the 5% concentration failed to complete decalcification within ten days, and the 15% compromised sample quality within eight days. Histological analyses confirmed the efficacy of the 10% formic acid concentration in maintaining tissue integrity and achieving optimal staining quality. The standardized protocol presented in this study provides an effective and reliable approach for achieving consistent and high-quality histological sections of rat calvarial bone. An ideal decalcification agent should effectively remove calcium salts, preserve structural integrity and molecular components, facilitate rapid yet minimally damaging decalcification, and ensure ease of handling for laboratory personnel. Further exploration of its applicability to different bone types or species is recommended to broaden its research utility.

Solar radiation visibility testing algorithm for precise shadow distribution for spatial steel structural thermal analysis under sunlight

As a large-span spatial steel structure, the radio telescope, characterized by its extensive span and numerous structural components, is sensitive to temperature gradients and susceptible to localized deformations induced by non-uniform temperature filed under sunlight, thereby affecting the operational performance. In order to calculate the shadow distribution of the structure, this study proposes a solar radiation visibility testing algorithm based on the depth buffer. To validate the accuracy of the proposed algorithm, the shadow distribution of a shading device is calculated employing the new algorithm, theoretical methods, and Ladybug tools. The results show that the shadow distribution obtained by the three methods is consistent. The thermal numerical simulation of the grid structure using the direct solar radiation calculated by the proposed algorithm is compared with the experiment results, and the error is below 5 %. Taking a radio telescope as an engineering application, the temperature distribution and pointing accuracy under solar are calculated. 9:00 and 16:00 have the worst pointing accuracy, while 11:00–13:00 has the best pointing accuracy. This study can provide a reference for the calculation of temperature field of spatial steel structure which is sensitive to sunlight temperature.

Multiscale 3D displacement field measurement using stereo digital image correlation on a fractal speckle pattern

AbstractEven though the simulations used to predict failure are becoming increasingly predictive, complex multiaxial loading tests are still required to validate the design of structural components in a wide range of industries. Large specimen testing often requires two different scales. A global Far Field to obtain boundary conditions and a local Near Field to evaluate strain gradients around discontinuities such as bolts, notches… The main goal of this study is to provide a continuous displacement over the whole specimen surface integrating data from multiple cameras. In this paper, we propose a new methodology that generates 3D displacements determined by finite‐element stereo digital image correlation in the Near Field and in the Far Field using a unique fractal speckle pattern and an off‐line determined texture. The displacements are obtained in the same coordinate system and on the same mesh. Satisfactory data fusion from both Near Field and Far Field images of a biaxial test on a notched laminate composite was obtained with a refined mesh at the notch tip. This methodology can be applied to any tests requiring multiple camera systems and will support the use of the finite‐element digital image correlation framework as an experimental‐numerical efficient technique.

High-performance hybrid glass fibre epoxy composites reinforced with amine functionalised graphene oxide for structural applications

Glass fibre-reinforced epoxy (GFRE) composites have had limited use as structural components in industrial applications (e.g., oil and gas, aerospace and civil infrastructure). The use of nanomaterials, such as graphene, has been explored recently to enhance the mechanical and long-term properties of GFRE to realise their full potential and increase their usage. This study evaluated the tensile, creep, and fatigue behaviour of amine-functionalised graphene oxide (fGO) modified glass fibre/epoxy laminate composites. A spray coating technique was used to coat the fGO particles onto the glass fibre surface, and epoxy composite laminates were manufactured using the vacuum resin infusion method. Creep and fatigue testing was performed under a load-controlled mode in tension. Adding fGO within the composites significantly improves the static, creep, and fatigue properties of the fGO-GFRE composites at both room and elevated temperatures. It is shown that fGO acts as a barrier to microcrack initiation and restrains the macrocrack propagation during cyclic loading under elevated temperatures in the GFRE composites. These factors, therefore, prevent the early delamination of the matrix and fibre interface during cyclic loading, which explains the fatigue life extension observed in the fGO-modified composites. With 0.05 wt% fGO, the fatigue life of the fGO-GFRE composites was extended by 8× and 30× at a maximum stress of 124 and 151 MPa respectively, in a 90 °C environment compared to the control GFRE composites. While the creep life compared to the control increased by 63×, 103× and 159× with 0.25 wt%, 0.5 wt% and 1 wt% fGO, respectively. These enhancements are attributed to the large surface area, high stiffness, and functional groups present, which provide a stronger bond between the composite phases. These features help restrict the mobility of the polymer chain during the creeping load and act as barriers to fatigue crack propagation, enhancing the composite’s durability. The nanocomposites produced display attractive properties for many possible industrial applications where improved performance is needed while maintaining a minimum cost.

Comparison of nature‐inspired algorithms in finite element‐based metaheuristic optimisation of laminated shells

AbstractThis work presents a unique technique for optimising composite laminates used as structural components, which is critical for situations where failure might result in disastrous effects. Unlike traditional surrogate‐based optimisation approaches, this methodology combines the accurate modelling capabilities of finite element (FE) analysis with the iterative refining capacity of metaheuristic algorithms. By combining these two methodologies, our method intends to improve the design process of laminated shell structures, assuring robustness and dependability is crucial. Compared to existing benchmark solutions, the current FE shows a <1% error for cylindrical and spherical shells. The prime objective of this study is to identify the optimum ply angles for attaining a high fundamental frequency. The problem is NP‐hard because the possible ply angles span a wide range (±90°), making it difficult for optimisation algorithms to find a solution. Seven popular metaheuristic algorithms, namely the genetic algorithm (GA), the ant lion optimisation (ALO), the arithmetic optimisation algorithm (AOA), the dragonfly algorithm (DA), the grey wolf optimisation (GWO), the salp swarm optimisation (SSO), and the whale optimisation algorithm (WOA), are applied to and compared on a wide range of shell design problems. It assesses parameter sensitivity, discovering significant design elements that influence dynamic behaviour. Convergence studies demonstrate the superior performance of AOA, GWO, and WOA optimisers. Rigorous statistical comparisons assist practitioners in picking the best optimisation technique. FE‐GWO, FE‐DA, and FE‐SSA methods surpass the other techniques as well as the layerwise optimisation strategy. The findings obtained, employing the GWO, DA, and SSA optimisers, demonstrate ~3% improvement over the existing literature. With respect to conventional layup designs (cross‐ply and angle‐ply), the current optimised designs are better by at least 0.43% and as much as 48.91%.

Magnetically modified-mitoxantrone mesoporous organosilica drugs: an emergent multimodal nanochemotherapy for breast cancer

BackgroundChemotherapy, the mainstay treatment for metastatic cancer, presents serious side effects due to off-target exposure. In addition to the negative impact on patients’ quality of life, side effects limit the dose that can be administered and thus the efficacy of the drug. Encapsulation of chemotherapeutic drugs in nanocarriers is a promising strategy to mitigate these issues. However, avoiding premature drug release from the nanocarriers and selectively targeting the tumour remains a challenge.ResultsIn this study, we present a pioneering method for drug integration into nanoparticles known as mesoporous organosilica drugs (MODs), a distinctive variant of periodic mesoporous organosilica nanoparticles (PMOs) in which the drug is an inherent component of the silica nanoparticle structure. This groundbreaking approach involves the chemical modification of drugs to produce bis-organosilane prodrugs, which act as silica precursors for MOD synthesis. Mitoxantrone (MTO), a drug used to treat metastatic breast cancer, was selected for the development of MTO@MOD nanomedicines, which demonstrated a significant reduction in breast cancer cell viability. Several MODs with different amounts of MTO were synthesised and found to be efficient nanoplatforms for the sustained delivery of MTO after biodegradation. In addition, Fe3O4 NPs were incorporated into the MODs to generate magnetic MODs to actively target the tumour and further enhance drug efficacy. Importantly, magnetic MTO@MODs underwent a Fenton reaction, which increased cancer cell death twofold compared to non-magnetic MODs.ConclusionsA new PMO-based material, MOD nanomedicines, was synthesised using the chemotherapeutic drug MTO as a silica precursor. MTO@MOD nanomedicines demonstrated their efficacy in significantly reducing the viability of breast cancer cells. In addition, we incorporated Fe3O4 into MODs to generate magnetic MODs for active tumour targeting and enhanced drug efficacy by ROS generation. These findings pave the way for the designing of silica-based multitherapeutic nanomedicines for cancer treatment with improved drug delivery, reduced side effects and enhanced efficacy.

Systematic dissection of tumor-normal single-cell ecosystems across a thousand tumors of 30 cancer types

The complexity of the tumor microenvironment poses significant challenges in cancer therapy. Here, to comprehensively investigate the tumor-normal ecosystems, we perform an integrative analysis of 4.9 million single-cell transcriptomes from 1070 tumor and 493 normal samples in combination with pan-cancer 137 spatial transcriptomics, 8887 TCGA, and 1261 checkpoint inhibitor-treated bulk tumors. We define a myriad of cell states constituting the tumor-normal ecosystems and also identify hallmark gene signatures across different cell types and organs. Our atlas characterizes distinctions between inflammatory fibroblasts marked by AKR1C1 or WNT5A in terms of cellular interactions and spatial co-localization patterns. Co-occurrence analysis reveals interferon-enriched community states including tertiary lymphoid structure (TLS) components, which exhibit differential rewiring between tumor, adjacent normal, and healthy normal tissues. The favorable response of interferon-enriched community states to immunotherapy is validated using immunotherapy-treated cancers (n = 1261) including our lung cancer cohort (n = 497). Deconvolution of spatial transcriptomes discriminates TLS-enriched from non-enriched cell types among immunotherapy-favorable components. Our systematic dissection of tumor-normal ecosystems provides a deeper understanding of inter- and intra-tumoral heterogeneity.

Non-Contact Blood Pressure Estimation from Radar Signals by a Stacked Deformable Convolution Network.

This study introduces a contactless blood pressure monitoring approach that combines conventional radar signal processing with novel deep learning architectures. During the preprocessing phase, datasets suitable for synchronization are created by integrating Kalman filtering, multiscale bandpass filters, and a periodic extraction method in the time domain. These data comprise data on chest micro variations, encapsulating a complex array of physiological and biomedical information reflective of cardiac micromotions. The Radar-based Stacked Deformable convolution Network (RSD-Net) integrates channel and spatial self attention mechanisms within a deformable convolutional framework to enhance feature extraction from radar signals. The network architecture systematically employs deformable convolutions for initial deep feature extraction from individual signals. Subsequently, continuous blood pressure estimation is conducted using self attention mechanisms on feature map from single source coupled with multi-feature map channel attention. The performance of model is corroborated via the open-source dataset procured using a non-invasive 24GHz six-port continuous wave radar system. The dataset, encompassing readings from 30 healthy individuals subjected to diverse conditions including rest, the Valsalva maneuver, apnea, and tilt-table examinations. It serves to substantiate the validity and resilience of the proposed method in the non-contact assessment of continuous blood pressure. Evaluation metrics reveal Pearson correlation coefficients of 0.838 for systolic and 0.797 for diastolic blood pressure predictions. The Mean Error (ME) and Standard Deviation (SD) for systolic and diastolic blood pressure measurements are -0.32 ±6.14mmHg and -0.20 ±5.50mmHg, respectively. The ablation study assesses the contribution of different structural components of the RSD-Net, validating their significance in the overall of model performance.

Simplifying algebraic expressions with brackets: Insights into Grade 10 learners’ structure sense through a study of their errors

Developing structure sense is an important part of learning algebra. We investigated learners’ structure sense of algebraic expressions involving brackets. This led us to propose the constructs surface structure sense and systemic structure sense. Using a random sample of 58 Grade 10 learners scoring above 40% in a test, we coded incorrect responses for surface and systemic structure errors. The initial analysis revealed that the presence of more brackets supports surface structure sense. However, learners overgeneralised the presence of brackets to represent multiplication in situations involving subtraction. The arrangement of brackets also led to errors in the order of operations. Further analysis suggested that regular application of procedures on familiar algebraic structures may give the illusion of systemic structure sense. We recommend that the teaching of algebraic expressions must emphasise what the arrangement of an expression means before focusing on how to operate on the expression.Contribution: The research contributes to mathematics teaching by suggesting teaching strategies to improve on learners’ understanding of the role of brackets in algebraic expressions, by considering the arrangement of the components in structures.