Actual Shape Research Articles

Three-Dimensional Printing of Bioinspired Hierarchical Structures for Enhanced Fog Collection Efficiency in 3D Space via Vat Photopolymerization

Collecting fog water is crucial for dry areas since natural moisture and fog are significant sources of freshwater. Sustainable and energy-efficient water collection systems can take a page out of the cactus’s playbook by mimicking its native fog gathering process. Inspired by the unique geometric structure of the cactus spine, we fabricated a bioinspired artificial fog collector consisting of cactus spines featuring barbs of different sizes and angles on the surfaces for water collection and a series of microcavities within microchannels inspired by Nepenthes Alata on the bottom to facilitate water flowing to the reservoir. However, replicating the actual shape of the cactus spine using conventional manufacturing techniques is challenging, and research in this area has faced a limitation in enhancing water-collecting efficiency. Here, we turned to 3D printing technology (vat photopolymerization) to create bio-mimetic fog collectors with a variety of geometric shapes that would allow for the most effective conveyance and gathering of water. Various barb sizes, angles between each barb in a single array, spine and barb arrangements, and quantity of barbs were tested experimentally and numeric analysis was carried out to measure the volume of water collected and optimize the mass rate. The result shows that optimal fog collection is with a mass flow rate of 0.7433 g/min, with Li = 900 μm, θ = 45°, ϕ = 90°, Nb = 2, and Ns = 5. This study presents a sustainable and ecologically sound method for efficiently collecting humid air, which is expected to be advantageous for the advancement of future-oriented fog-collection, water-transportation, and separation technologies.

Experimental study on the radiation characteristic of downward turbulent diffusion jet flame

Gaseous fuels are typical clean energy and transported through gas pipelines to household and factories. A downward jet flame occurs when the fuel gas leaks from the bottom of the pipelines, which causes severe damage to the surroundings due to the complicated interaction between flame buoyancy and jet momentum. In order to investigate the combustion characteristics of downward jet flame, a series experiments were carried out to analyze the flame morphology and radiation systematically. The results show that the flame width increased from the upper tip along the centerline to a maximum value, and then decreased till the flame lowest point. The maximum flame width appears at the position of 3/4 flame length near the flame lowest point. A weighted-multi-point source radiation model was employed for prediction of flame radiation of downward jets based on the flame actual shape. The flame radiant fraction was found to be in the range of 0.28∼0.32, which is larger than that of the corresponding upward jets because the luminous downward jet flame generated relatively more soot than upward jet flame. The derived radiant fraction was used to predict radiative heat flux compared with the experimental data, which showed good agreement.

The influence of geometric nonconformance of the SB4 tension clamps on their strength and elasticity characteristics

The paper presents comparative laboratory investigations of tension fastener models that attach rails to concrete sleepers. The aim of the paper was to assess the influence of geometric nonconformity of the actual industrial product that meets the PKP Polskie Linie Kolejowe S.A. requirements on the operation of a tension-fastening clamp under stress. Due to the cost and limited possibility of research of the actual industrial product, an additional objective of the research was to validate the usefulness of it in the comparative assessment of the models. In the research, the authors used models of tension fastening clamps manufactured in incremental engineering technology (3D print) on scale 1:2. The properties of the fastening clamps (in their nominal shape) were compared (described in the PKP Polskie Linie Kolejowe S.A. documentation) with the fastening clamps of the actual shape. In the investigation, the authors have confirmed the negative influence of the non-conformance of the shape of the actual fastening clamps with the nominal ones.

Sensing expectation enables simultaneous proprioception and contact detection in an intelligent soft continuum robot

A high-level perceptual model found in the human brain is essential to guide robotic control when facing perception-intensive interactive tasks. Soft robots with inherent softness may benefit from such mechanisms when interacting with their surroundings. Here, we propose an expected-actual perception-action loop and demonstrate the model on a sensorized soft continuum robot. By sensing and matching expected and actual shape (1.4% estimation error on average), at each perception loop, our robot system rapidly (detection within 0.4 s) and robustly detects contact and distinguishes deformation sources, whether external and internal actions are applied separately or simultaneously. We also show that our soft arm can accurately perceive contact direction in both static and dynamic configurations (error below 10°), even in interactive environments without vision. The potential of our method are demonstrated in two experimental scenarios: learning to autonomously navigate by touching the walls, and teaching and repeating desired configurations of position and force through interaction with human operators.

Fourth-Order Accurate Strain-Parameterized Shape Representation of Beam Elements for Modeling Continuum Robots and Robotic Manipulation of Slender Objects

Abstract Soft rods and tubular elements are the main building blocks of continuum robots. Kinetostatic models along with a geometrically exact description of the kinematics on SE(3) are now an established foundation for simulation and control. A key aspect is the reconstruction of the actual shape of a soft slender element. This involves numerically solving nonlinear differential equations on SE(3), which is problematic, in particular for real-time applications. To circumvent this, shape functions are used to approximate the deformation. A widely used approach is based on the constant curvature assumption. This has limited accuracy, however. In this article, an interpolation is presented that leads to a fourth-order accurate approximation of the deformation of a Cosserat beam. This serves as a strain-parameterized shape function. Either the strain at the two ends of the beam or the strain and its derivative at one end are specified. The presented interpolation is relevant also for shape control when handling flexible slender objects with robotic manipulators.

AFM Nanoindentation of Stiff Inhomogeneous Layer onPolymeric Substrate.

Analysis of indentation data of heterogeneous material, in particular, layer on an elastic substrate requires information about the contact area that is essential for calculating mechanical properties. The actual shape of the AFM-tip is not described by simple body of revolution. In this work, the indentation of a stiff layer on a hyperelastic substrate by a truncated conical tip is studied using finite element methods. The size of the tip, elastic modulus, and thickness of the layer are varied. The obtained model dependences of loading and contact area versus the depth of indentation are used in analysis of the experimental data of AFM indentation of stiff inhomogeneous nanolayers of polyurethane surface. Thickness and elastic modulus of the layers, fracture properties of the surface are studied. The obtained results can find application in the study of mechanical properties and fracture toughness of thin flexible films on an elastic substrate.

Multi-label feature selection based on adaptive label enhancement and class-imbalance-aware fuzzy information entropy

Multi-label feature selection can select representative features to reduce the dimension of data. Since existing multi-label feature selection methods usually suppose that the significance of all labels is consistent, the relationships between samples in the entire label space are generated straightforwardly such that the shape of label distribution and the property of class-imbalance are ignored. To address these issues, we propose a novel multi-label feature selection approach. Based on non-negative matrix factorization (NMF), the similarities between the logical label and label distribution are constrained, which ensures that the shape of label distribution does not deviate from the underlying actual shape to some extent. Further, the relationships between samples in label space and feature space are restricted by graph embedding. Finally, we leverage the properties of label distribution and class-imbalance to generate the relationships between samples in label space and propose a multi-label feature selection approach based on fuzzy information entropy. Eight state-of-the-art methods are compared with the proposed method to validate the effectiveness of our method.

Simulation-Based Design for Inlet Nozzle of Vortex Tube to Enhance Energy Separation Effect

The vortex tube, also known as the Ranque–Hilsch vortex tube, is a mechanical device that separates compressed gas into hot and cold streams. It offers a reliable and cost-effective solution to a wide range of cooling applications, as it operates without moving parts, electricity, or refrigerants. Research on vortex tubes has primarily focused on understanding the mechanisms of energy separation and optimizing cooling performance by altering geometric operational parameters. In this study, a Computation Fluid Dynamics (CFD) analysis was conducted to enhance the prediction of energy separation performance and improve the overall energy efficiency of the vortex tube. First, the geometry of the experimental device was modeled to closely match its actual shape, unlike the simplified geometries commonly used in previous CFD studies. Simulations were then carried out with variation in grid systems and turbulence models, and the results demonstrated improved agreement with experimental data compared to those reported in previous studies. Finally, simulations with a modified shape of the inlet nozzle shape were performed, revealing that the energy separation effect of the vortex tube could be enhanced by approximately 15% with an increased inlet expansion ratio (ϵ) while maintaining a constant nozzle length.

Mediating role of self-esteem on university students’ physical activity attitude and frequency

Background and Study Aim. The health benefits of physical activity are well-known. Despite this, there is an ongoing decline in total physical activity (PA), especially among adolescents and young women. This decline points to the need to find more effective solutions. This study aimed to determine the relationship between physical activity and attitudes toward physical activity, and also between self-esteem body image (as subjective variables) and body mass index (as an objective variable). Material and Methods. This cross-sectional study measured and investigated 152 female students from various faculties in their first and second years of study at the Bucharest University of Economic Studies. The research utilized direct anthropometrical measurements and several self-reported instruments. These included questionnaires on self-esteem body image, physical activity attitude, and a report on the frequency of physical activity. Self-esteem was assessed using the Rosenberg Self-Esteem Scale. Body dissatisfaction was evaluated using the Contour Drawing Rating Scale. Results. The mean Body Mass Index (BMI) value of 20.89 kg/m² indicates a healthy, normal BMI. The mean self-esteem score (31.48) falls within the normal range, but 60% of respondents could not match their actual body shape with their ideal or desired body image. 54% of respondents reported engaging in 30 minutes of physical activity, three times a week, outside the university program. As a result, the mean value of the attitude towards physical activity is slightly positive. 33% of young women's self-esteem is related to physical factors such as body image, frequency of physical activity, and attitude towards physical activity. Conclusions. The study indicates that targeted physical education programs and consistent, independent physical activity can mitigate the challenges associated with the investigated variables. Moreover, self-esteem significantly mediates the relationship between body image and physical activity frequency, as well as students’ attitudes toward physical activity.

Assessing the Efficacy of Cognitive-Behavioral Therapy on Body Image in Adolescent Scoliosis Patients Using Virtual Reality.

Background/Objectives: Adolescents with idiopathic scoliosis require emotional support to change their experience of their desired body shape and to feel optimistic about the cosmetic results of surgical treatment. Recently, the use of virtual reality in psychological assessment and treatment has given specialists a technology that appears particularly well-suited for addressing body image disorders. The study objectives were two-fold. Firstly, we aimed to evaluate changes within the body image of scoliosis patients pre- and postoperatively. Secondly, we aimed to investigate if differences in body image exist in scoliosis females after implementing cognitive-behavioral therapy. Methods: Thirty-six total scoliosis patients participated in the 1st and 2nd study phases. The psychotherapy took place before and after surgery and during the patient's stay in the hospital. Body image was assessed using a virtual reality-based application, "Avatar Scoliosis 3D". Results: Regarding body image dissatisfaction evaluated via virtual tasks, the difference between the desired by patients and actual (based on the radiographic parameters) body shape is significant preoperatively in both scoliosis samples: with and without therapy (p < 0.000001 and p < 0.000001, respectively). Conclusions: The results of the present study may have important implications for developing standards for body image disorder treatments in scoliosis patients. We revealed that irrespective of received therapeutic support, scoliosis patients accurately estimate their body shape pre- and postoperatively, and they feel dissatisfied with their body preoperatively but not postoperatively.

Research on Non-Destructive Testing of Log Knot Resistance Based on Improved Inverse-Distance-Weighted Interpolation Algorithm

The objective of this paper is to propose a non-destructive resistance detection imaging algorithm for log knots based on improved inverse-distance-weighted interpolation algorithm, i.e., the eccentric circle-based inverse-distance-weighted (ECIDW) method, to predict the size, shape, and position of internal knots of logs; evaluate its precision and accuracy; and both lay a theoretical foundation and provide a scientific basis for predicting and assessing knots in standing trees. Six sample logs with natural knots were selected for this study. Resistance measurements were performed on the log cross-sections using a digital bridge, and resistance tomography was conducted using the improved ECIDW algorithm, which combines the azimuth search method with the eccentric circle search method. The results indicated that both the conventional inverse-distance-weighted (IDW) algorithm and the ECIDW algorithm accurately predicted the positions of the knots. However, neither algorithm was able to predict the shape of the knots with high precision, leading to some discrepancies between the predicted and actual knot shapes. The relative error (Dt1) between the knot areas measured by the IDW algorithm and the actual knot areas ranged from 18.97% to 88.34%. The relative error (Dt2) for the knot areas predicted by the ECIDW algorithm ranged from 1.82% to 74.16%. The average prediction accuracy for the knot areas using the IDW algorithm was 51.58%, compared to 72.90% using the ECIDW algorithm. This indicates that the ECIDW algorithm has higher accuracy in predicting knot areas compared to the conventional IDW algorithm. The ECIDW algorithm proposed in this paper provides a more reasonable and accurate prediction and evaluation of knots inside logs. Compared to the conventional IDW algorithm, the ECIDW algorithm demonstrates greater precision and accuracy in predicting the shape and size of knots. While the resistance method shows significant potential for predicting internal knots in logs and standing trees, further improvements to the algorithm were needed to enhance the imaging effects and the precision and accuracy of knot area and shape predictions.

Joint-task learning framework with scale adaptive and position guidance modules for improved household rooftop photovoltaic segmentation in remote sensing image

Inaccurate edge detection is a common challenge in the segmentation of household rooftop photovoltaic (PV) systems from remote sensing images, which hinders the accurate retrieval of PV distribution information critical for planning and managing PV development. A widely adopted solution is to incorporate an additional edge detection task into a joint-task learning framework to enhance edge perception. However, existing joint-task learning methods often struggle to accurately detect PV edges and lack effective mechanisms for distinguishing PV edges from those of similar objects. To address the above challenges, we develop a novel joint-task learning framework. This framework introduces a Scale Adaptive Module (SAM) that dynamically adjusts the receptive field of edge features based on the PV actual size and shape, enabling precise detection of PV edges with varying shapes and sizes. In addition, a Position Guidance Module (PGM) is proposed based on the intrinsic relationship between the PV segmentation task and the edge detection task. The PGM not only guides the edge detection task to focus on identifying the semantic edges of PVs using the distribution information from the segmentation task but also enhances the ability of the segmentation task to accurately locate PVs in complex backgrounds by utilizing the backward gradient from the edge detection task. Multiple rounds of repeated experiments on the Duke and IGN datasets demonstrate the framework's superior performance. Compared to other models, the proposed framework significantly improves the detection accuracy of various PV edges, achieving the best performance in household rooftop PV segmentation with an Intersection over Union (IoU) of 77.4 %. This study provides valuable insights into the accurate acquisition of household rooftop PV information and offers a promising solution for object segmentation tasks facing the challenge of inaccurate edge extraction.

Numerical Study on the Unsteady Behavior of the Solid-Fuel Scramjet

The unsteady evolution of the flowfield in a solid-fuel scramjet is investigated. The researchers approximate the continuous working of the solid-fuel scramjet via stand-alone geometries. These directly correspond to the actual shapes of the combustor recorded during experimental tests of the engine. The flow is modeled using the compressible Navier–Stokes and species transport equations and the shear stress transport k−ω turbulence model. A two-dimensional axisymmetric formulation is employed. The fuel is the polymer polymethyl methacrylate. The integral parameters of the combustor are computed in the simulations using nonvarying geometries at discrete instants. These values are then compared with measurements taken at the same instant during the continuous working of the engine in experimental tests. The good agreement during the whole process demonstrates the permanent quasi-steadiness nature of the fluid flow in relation to the varying combustor shape. The discussion analyzes the evolution of critical combustor parameters, including thrust, fuel regression rate, and various efficiencies, and correlates them with the underlying flow variables. The findings provide valuable insights into the unsteady development of the flow physics within the combustor of a solid-fuel scramjet, contributing to a better understanding of this complex system.

Improving the roller screen efficiency to classify green iron pellets using DEM simulation, novel roll design and implementing banana configuration

Roller screens play a decisive character in the efficiency of pelletizing circuits and induration furnaces. Unlike vibrating screens, there have been no studies on roller screens to determine their capacity and dimensions. Most studies have utilized the discrete element method (DEM) simulation to assess roller screen performance by employing a spherical shape and the Hertz-Mindlin elastic model. However, this approach is unsuitable due to green pellets’ non-spherical shape and elastic–plastic properties. This study introduces the incorporation of the actual shape of green pellets and a hysteretic spring elastoplastic contact model. In this research work, a novel design of rolls with a grooved surface was recommended for the first time, resulting in a Total Screening Efficiency (TSE) of 96.4% compared to 87.1% for rolls with a smooth surface. Additionally, while exploring the impact of the decks number on the roller screen, a new design, known as the banana roller screen, was introduced. Under similar conditions, the TSE increased by 1.22% compared to the general roller screen type. It was also found that the roller screen’s capacity is directly related to the diameter, speed of rotation, and the number of rolls, while it has a reverse relationship with TSE and deck angle.

Process-based reconstruction of digital rock based on discrete element method considering thermal-mechanical coupling effect and actual particle shape

The digital rock is a crucial platform for numerical simulations of pore-scale flow in various fields such as geo-energy, carbon (CO2) sequestration, and hydrogen (H2) storage. Under these conditions, rocks deform, and pore structures change due to temperature and stress effects. However, existing methods for reconstructing digital rocks, such as physical experimental, stochastic simulation, and machine learning, can not consider the influence of high temperature and stress. Therefore, a process-based reconstruction method based on the discrete element method (DEM) considering the thermal-mechanical coupling effect is proposed in this paper. Initially, the computed tomography (CT) images are segmented based on the watershed algorithm, and a contour database is established using the spherical harmonic analysis method. A clump template library is then constructed in PFC3D (Particle Flow Code in 3 Dimensions). Subsequently, the DEM model is established using clumps from the template library according to porosity and particle radius distribution, and the model's accuracy is evaluated based on two-point and linear path correlation functions. Micro-mechanical and thermal parameters between particles are calibrated, and different temperature and stress boundary conditions are applied to obtain digital rocks under varying conditions. Finally, digital rocks' geometric and topological structures under different conditions are analyzed, and permeability and relative permeability are calculated. Using Bentheim sandstone as an example, digital rocks are constructed under various temperature and stress conditions. The research findings indicate that high temperatures and stress result in decreased pore and throat radii, elongated throats, deteriorated connectivity, reduced porosity, and permeability, making the digital rocks more water-wet. This study provides theoretical guidance for the accurate pore-scale flow simulation of geo-energy fluids, CO2, and H2.

Digital twin technology facilitates precision improvement in complex product assembly: A progressive deduction method of data-driven tolerance allocation

Advancements in aerospace technology have significantly increased the demands on assembly precision, particularly for large aircraft models. These developments require sub-millimeter precision to be achieved in assembly, posing new challenges for conventional tolerance allocation methods, which rely heavily on theoretical models and static simulations. To address these limitations, this paper proposes a digital twin system for online deduction of assembly tolerances (DTS-ODTA) using point cloud registration and free-form deformation (FFD). The proposed method includes three key innovations. First, a digital twin (DT)-based assembly process control framework supports the simulation of assembly deviations by integrating virtual and actual data. Second, a data-driven method models the actual surface shapes, ensuring synchronization between physical and digital states. Third, a progressive deduction strategy for tolerance allocation combines virtual and actual information, providing effective inputs for real-time assembly process control. This approach was validated through an industrial case study, achieving a prediction accuracy of 91.64 % for assembly precision and effectively preventing out-of-tolerance issues during product assembly. By promptly identifying and addressing potential assembly discrepancies, this method enhances the overall assembly quality and provides critical support for design decisions. In summary, this paper introduces a novel DT-based tolerance allocation method that shifts from traditional open-loop design to closed-loop control, thereby meeting the high precision demands of modern aerospace manufacturing.

Energy dissipation damage constitutive relation of CFRP passively confined coal sample

In view of the stability problem of coal pillars left over during coal resource mining, (Carbon Fiber Reinforced Polymer) CFRP sheet is applied in coal pillar reinforcement. Uniaxial compression tests of CFRP passively confined coal samples are carried out to explore the mechanical response mechanism of passively confined coal samples under different layers, and the energy dissipation damage constitutive relationship of CFRP passively confined coal samples is established based on the energy dissipation principle. The conclusions are: As CFRP layers increased, the local damage of coal samples before the peak evolved from a 'cliff-like jagged' to a 'capillary jagged', with post-peak instability marked by a shift to more 'cliff-like' characteristics. The tests revealed improvements in peak strength and elastic modulus, with a defined functional relationship between these properties and CFRP layers. The energy storage capacity of passively confined coal samples improved with CFRP layers, requiring less axial deformation to achieve equivalent energy levels. The energy dissipation rate showed an initial decrease followed by an increase, with a minimum inflection point, the elastic energy consumption ratio tends to decrease slowly and then rapidly during post-peak instability. A damage constitutive relationship and evolution equation were developed, highlighting that the CFRP sheet significantly inhibits damage, with diminishing effectiveness beyond two layers. The study concludes that three-layer CFRP sheets provide optimal confinement, offering a novel strategy for the reinforcement of coal pillars and the prevention and control of rock burst, without considering the actual coal pillar dimensions and shape. To sum up, the use of CFRP sheet to strengthen coal pillar has considerable potential research value in strengthening coal pillar and improving the recovery rate of coal resources.

Experimental and numerical investigations of bending mechanical properties and fracture characteristics of cemented tailings-waste rock backfill under three-point bending

The bending mechanical properties and fracture characteristics of cemented tailings-waste rock backfill (CT-WRB) have a significant impact on efficient mine production. In this study, the effects of waste rock content (WRC) and waste rock size (WRS) on the bending mechanical properties and macroscopic failure characteristics of CT-WRB were investigated through experiments. Concurrently, PFC3D numerical simulation software was used to establish a three-point bending numerical model of CT-WRB with actual waste rock shapes to explore the crack evolution law and microscopic damage characteristics. Results showed that adding appropriate waste rock improved the initial stiffness, flexural strength, and modulus of the backfill, with optimal WRC and WRS at 40 % and 4–6 mm, respectively. Simulations indicated that under load, the displacement field of CT-WRB formed a vortex, with tensile stress in the middle and lower parts and compressive stress in an upper arch. Cracks started at the bottom and extended upward, leading to failure. Compared to OCTB (without waste rock incorporation), CT-WRB had more total cracks and tension-shear composite failure of internal particles. Waste rock altered stress distribution and crack paths, resulting in curved, bifurcated, and discontinuous main cracks. These findings provide a reference for efficiently recycling tailings, waste rock and ensuring safe mine production.

Pathogen shape: Implication on pathogenicity via respiratory deposition

The shape of environmental aerosols contributes to the discrepancy in their dynamic behavior compared to spherical particles, which have received inadequate consideration. We reported deposition patterns of aerosols and aerosol-transmissible pathogens in real human respiratory systems, taking into account their actual shape, using a validated computational-based model. We found that the shape of the aerosols significantly influenced its deposits and accessibility within the respiratory system, significantly in the tracheobronchial region. As an example, we estimated that over 180 % of differences in deposits in the trachea and bronchi were attributable to pathogens shape, inferring the underlying pathogenicity difference of these regions. These findings, capturing the spatial heterogeneity of pathogens and aerosols deposition in human respiratory system, have major implication for understanding the evolution of aerosol-related disease.

Predicting and optimizing the dimensions of rod in lattice structures fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is a highly effective method for manufacturing complex parts and is widely used in industry for creating lattice structures. However, during the manufacturing process, the actual dimensions and shapes of the lattice structure rod often deviate significantly from the design model due to limited understanding of the structure-process-property relationship in LPBF. This makes it difficult to carry out targeted structural design and process planning based on the technical characteristics of LPBF. This paper investigates the relationship between melt pool dimensions and lattice structure rod dimensions through theoretical analyses. Based on melt pool dimensions obtained with the help of numerical simulation, a prediction model for the actual dimensions of lattice structure rod is established. We design experiments to validate the accuracy of the predictive model, using LPBF to fabricate rods with varying inclinations, dimensions, and cross-sectional shapes. The actual dimensions are measured under a microscope and compared with the predicted dimensions. The results indicate a difference of no more than 0.1 mm. Furthermore, the experiments reveal a correlation between scan path curvature and actual dimensions. Based on this correlation, the dimensional prediction model is corrected, resulting in an improved generalization performance of the model for parts with varying scan paths. Based on the dimension prediction model, we propose an optimization method to modify the CAD dimensions of the rod to ensure the consistency between the actual and designed dimensions of the rod.