Natural Shape Research Articles

Cognitive, Affective, and Normative Drivers of Pro-Environmental Intentions Among Urban Forest Visitors – The IPMA Approach

This study investigates the cognitive, affective, and normative drivers of pro-environmental intentions among urban forest visitors, applying the Importance-Performance Map Analysis (IPMA) to identify key dimensions influencing sustainable behaviors. Drawing from existing literature, the research examines how environmental awareness, connectedness to nature, environmental empathy, place attachment, social norms, and moral norms shape pro-environmental intentions. Data were collected from 550 respondents in Bangkok using a self-administered online survey. Structural equation modeling was used to evaluate the relationships among these constructs, and IPMA was employed to assess their relative importance and performance. Results revealed that affective components, particularly place attachment and connectedness to nature, and normative factors like social norms, have a significant impact on pro-environmental intentions. Meanwhile, environmental awareness and moral norms showed limited influence. The findings highlight areas for improvement and provide practical implications for enhancing sustainable behaviors in urban forests.

Dynamic characteristics of a horizontal rectangular vessel partially or fully filled with a fluid

A theoretical framework is presented for free vibration of a flexible horizontal rectangular vessel, whether it is partially or fully filled with a fluid. The vibrational modal patterns of the vessel, whether dry or wet, are classified into symmetric and antisymmetric modes. The theoretical model conceptualizes the vessel as an unfolded plate with line supports simulating the vessel's corners. The motion of contained fluid is described using displacement potentials that adhere to the Laplace equation and fluid boundary conditions. Importantly, the proposed analytical approach accounts for the dynamic interaction between the vessel and the fluid, ensuring compatibility along their contacting surfaces. The Rayleigh-Ritz method is employed to formulate an eigenvalue problem, considering entire kinetic and strain energies of the fluid-filled vessel. The accuracy of the theoretical approach is checked by conducting finite element analyses. Remarkably, the natural frequencies obtained through commercial software align closely with the theoretical predictions for both dry and fluid-filled vessels. In instances of fully fluid-filled vessels, we can discern the presence of fluid contact at the vessel's upper plate by examining the natural frequencies and mode shapes. The proposed method offers applicability in dynamically analyzing water-filled spent fuel casks, enhancing safety during transportation.

Study on the dynamic characteristics of the head cover-bolts-stay ring of a variable-speed pump-turbine

Abstract The design and operation of variable-speed pump-turbine units is more difficult than that of conventional units due to their adjustable speed, frequent start stop, and forward and reverse operation. Due to the development of variable-speed pump-turbines towards variable-speed, high head, and large capacity, the vibration instability caused by frequent switching between turbine and pump operating conditions is more prominent. The study on the dynamic characteristics of the head cover-bolts-stay ring system is an important guarantee for the long-term safe and stable operation of the units. This article uses the finite element method to conduct modal analysis on the head cover-bolts-stay ring system of a variable-speed pump-turbine. The natural frequency and mode shape are analyzed, and resonance analysis is carried out in combination with the dynamic and static interference characteristics of the variable-speed unit. The research results show that the dynamic and static interference frequency of the unit during the variable-speed process may be close to the natural frequency of the head cover-bolts-stay ring system, which needs to be paid attention to during operation. The results and findings in this article provide theory and practical basis for the research and design of high head, large capacity, and variable-speed pump-turbine units.

A novel damage index for crack identification of a drilling riser during deployment based on the modal vibration energy flow

Early detection of structural damage especially small cracks in marine deepwater drilling risers is of paramount importance. Small cracks are always hard to detect because of weak vibration signals if using traditional damage indices, such as natural frequencies and mode shapes including modal displacements, cross-section slopes, and curvatures. Especially when the deepwater riser is during deployment, the variable suspension riser length and strong sea environment noise make the small crack identification more difficult. To address this problem, this study formulates a new concept of damage detection by integrating the vibration energy flow theory into the vibration-based damage detection (VDD) technique. A novel damage-sensitive feature (DSF) named modal vibration energy flow (MVEF) is established for detecting and locating the small cracks in deepwater drilling risers. The capability of the approach is verified by using the same riser model and the numerical results in the literature. The sensitivities versus crack positions and depths, variable suspension riser length, and sea noise are studied in detail. Results show that the proposed index MVEF is more sensitive than the classic traditional DSFs, i.e., modal slope, modal strain (or curvature), and modal strain energy. In total, the MVEF approach can accurately identify the small cracks and is robust against noise interference, suitable for detecting and locating small cracks in the deepwater drilling riser during deployment.

Eco‐friendly Green Synthesis of Silver Nanoparticles Using Daphne Mucronata Royle Seeds Extract and the Potential Antibacterial, Antifungal, and Scolicidal Activities

AbstractGreen synthesized silver nanoparticles (AgNPs) have received lots of attention due to being used as potential therapeutic agents. For the first time, this research investigated the biosynthesis of silver nanoparticles using the extract of Daphne mucronata seeds, which are rich in phenolic and polyphenolic substances and evaluated their antibacterial, antifungal, and scavenging activities. The process of nanoparticle (NPs) preparation was confirmed using UV–vis spectroscopy with an absorption peak at a wavelength of 440 nm. Dynamic light scattering (DLS) was used to determine the particles' distribution. Fourier‐transform infrared spectroscopy (FTIR) validated the functional groups contributing to the reduction of Ag+ to Ag. Moreover, X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) approved the crystalline nature and spherical shape of the particles with mean and standard deviation of particle size to be 60.25 and 24.88 nm, respectively. The antibacterial, antifungal, and scolicidal activities of AgNPs were studied using disc diffusion against four standard bacteria species and microdilution methods for four Candida strains. The greatest effect of AgNPs with the highest concentration (80 µg/mL) was observed on Staphylococcus aureus (22.26 mm) and the lowest on Pseudomonas aeruginosa (19.07 mm). In the case of Candida fungus, the highest effect of AgNPs was reported for Candida krusei (7.93 µg/mL) and the lowest for Candida albicans (63.49 µg/mL). Also, these nanoparticles were able to register 100% lethality on the Echinococcus granulosus parasite in 15 min at a concentration (80 µg/mL). Therefore, the production of AgNPs as a renewable and cheap material can be effective after performing all the necessary tests as antibacterial, antifungal and antiparasitic agents with the least side effects in biomedical and pharmaceutical sciences.

Development and testing of a novel vibratory compaction instrument considering its natural frequency.

This study aims to develop a novel vibratory compaction instrument designed for the preparation of large triaxial soil specimens, offering an efficient alternative to the traditional manual specimen preparation process. However, when the motor frequency closely aligns with the natural frequency of the structure, severe resonance phenomena may occur. This paper employed finite element modal analysis, experimental modal analysis, and operational modal analysis techniques to conduct a multi-objective optimization of the structure, aiming to improve the dynamic characteristics. First, the natural frequency and mode shapes of the vibratory compaction instrument were determined via finite element technology. Subsequently, the optimization of this instrument was conducted by integrating the Kriging surrogate model with the Non-dominated Sorting Genetic Algorithm II (NSGA-II). Finally, the steel column underwent a modal test using impulse stimulation to ascertain its natural frequency, and the stochastic subspace identification (SSI) approach was employed to conduct an operational modal analysis of the vibratory compaction instrument to determine its modal characteristics. The experimental findings corroborated the conclusions obtained from the finite element analysis, validating the precision of the finite element modal analysis and the rationality of the optimized structure. The research results are of significant importance for improving the preparation efficiency of large triaxial specimen, contributing to advancements in soil mechanics testing.

Machine tool cross beam design, fabrication, and testing using metal big area additive manufacturing

This paper describes the application of metal Big Area Additive Manufacturing (mBAAM) to the fabrication of a machine tool cross beam. The replacement of a traditional box design weldment with a new design printed by wire arc additive manufacturing using the MedUSA system at Oak Ridge National Laboratory (ORNL) is detailed. This requires a new design strategy based on the unique mBAAM capabilities. The intent of the new design is to reduce mass, while maintaining the dynamic stiffness. To compare the two designs, the natural frequencies and mode shapes are measured using impact testing and predicted using finite element analysis. It is confirmed that the printed structure dynamics agreed with the numerical model predictions, which demonstrates that it is feasible to model a large-scale mBAAM part and understand its behavior prior to printing. Another notable outcome of this study is that the significant residual stress and distortion in the print indicate that knowledge gaps remain for widespread implementation of mBAAM.

Dynamic Modelling and Performance Analysis of Deployable Telescopic Tubular Mast

AbstractThis work presents the longitudinal and transverse coupling vibrations of a deployable Telescopic Tubular Mast (TTM), a multi-stepped structure integrated into a spacecraft system, while considering the rigid-flexible coupling phenomenon. The model is derived using the principle of virtual work and discretized via the variable separation method. The von Kármán strain is employed to incorporate geometric nonlinear effects. Semi-analytical results for the shape functions and natural frequencies of the quasi-static multi-stepped boom are obtained using the extended transfer matrix method (ETMM). These natural frequencies are validated against results from Nastran, confirming the ETMM's accuracy. In addition, the model accounts for the continuously changing natural frequencies and shape functions during the deployment phase. Finally, the dynamic phenomena of the longitudinal and transverse displacements are analyzed at various deploying states, including locking and restart behaviors. The influence of the structural damping on the vibration evolution is also contained in the numerical analysis.

Pittosporum tobira Japanese Pittosporum, Japanese Cheesewood

This document provides an overview of Pittosporum tobira, commonly known as Japanese pittosporum or Japanese cheesewood. It details the plant’s characteristics, including its glossy, dark green leaves, creamy white flowers, and natural mounding shape. The document highlights its uses in landscaping, such as for screens, hedges, and container planting, and discusses its growth requirements and maintenance needs. Additionally, it addresses potential issues like pest sensitivity and soil preferences, emphasizing the importance of proper drainage to prevent root rot. The document also mentions different cultivars and their suitability for residential landscapes. Original publication date October, 1999.

Free vibration analysis of Euler-Bernoulli beams modeled by spatial-fractional differential equation

In this article, a more accurate dynamic model of Euler-Bernoulli beam is proposed, based on the spatial-fractional derivatives. Firstly, the governing differential equation is derived. After that, this equation is solved by two different methods: the first method uses only the left fractional derivative, while the second method tends to use both the left and right fractional derivatives, simultaneously. In the second method, the location of the "switching point" which connects the left and right derivatives is treated as a variable parameter. The effect of this parameter is investigated by analyzing several beams. As numerical results, the natural frequencies and mode shapes of beams with different boundary conditions are presented.

Thermoelastic damping properties in hemi-ellipsoidal shells with variable thickness

Thermoelastic damping (TED) is a fundamental dissipation mechanism that inevitably exists in shell resonators with high quality factors. Based on the thermal energy method, this paper demonstrates an effective method for the TED characterization of the hemi-ellipsoidal shells with variable thickness which manifest lower TED compared with the hemispherical shells. The equation of motion of the hemi-ellipsoidal shell under clamped-free boundary conditions is established by Hamilton's principle and the assumed mode method, and the natural frequencies and mode shape functions of the hemi-ellipsoidal shell with variable thickness are obtained by solving the eigenvalue problem. The temperature field is acquired by solving the heat conduction equation along the radial direction, and an analytical model for the TED of the hemi-ellipsoidal shell with variable thickness is presented by calculating the maximum elastic potential energy and the work lost per cycle of vibration due to irreversible heat conduction. Analysis on TED at the vibration patterns of meridional wave number m = 1 and the circumferential wave number n = 2 or 3 where the shell resonators typically operate is carried out. The analytically calculated TED results are compared with those of the finite element method (FEM) to verify the feasibility and correctness of the present method. The influences of the geometrical parameters on the TED characteristics of the hemi-ellipsoidal shells with variable thickness are analyzed in detail. A meaningful discovery is that compared with the hemispherical shell, the hemi-ellipsoidal shell with variable thickness has a smaller TED when its semiminor axis is shorter than the semimajor axis, which is particularly significant for optimizing the design of the shell resonators with high quality factors.

Experimental and numerical investigation of the modal parameters for thin laminated composite plates

In the present work, glass fiber-reinforced (GFR) composite specimens were fabricated using the vacuum-bag molding process. The properties related to the vibrational response of the fabricated composite plates, such as natural frequency, modal density, and damping loss factor (DLF), were investigated through both experimental and numerical approaches. The effects of different parameters, including boundary conditions (BCs), fiber orientations, laminate layer numbers, and aspect ratios, were comprehensively studied. It was found that the experimental and numerical results were in close agreement. For each case, finite element analysis was performed to determine the natural frequencies and mode shapes. Regarding the various BCs, the DLF was observed to be highest (0.47) for fully clamped BC and lowest (0.12) for free-free BC, whereas the modal density was highest (0.068) for cantilever BC and lowest (0.037) for fully clamped BC. In terms of different lamination schemes, the DLF was highest (0.42) for a plate with quasi-isotropic fibers and lowest (0.25) for a plate with unidirectional fibers, while the modal density was highest (0.068) for quasi-isotropic fibers and lowest (0.047) for unidirectional fibers. Regarding the plates with different laminate layers, the highest DLF (0.47) was observed for a plate with 16 layers, while the lowest DLF (0.33) was found in a plate with 8 layers. Conversely, the highest modal density (0.067) was observed for a plate with 8 layers, and the lowest (0.057) was noted for a plate with 16 layers. Lastly, considering aspect ratios, the highest DLF (0.48) was observed for an aspect ratio of 0.5, and the lowest (0.26) for an aspect ratio of 1.5. The highest modal density (0.09) was also observed for an aspect ratio of 0.5, while the lowest modal density (0.045) was for an aspect ratio of 1.5.

Investigation of the tissue displacement through textile pressure on soft avatar in Browzwear’s VStitcher software

Nowadays, soft avatars are used in various fields to simulate the behavior of human soft tissues in different applications. Likewise, they are also utilized in the garment industry in order to achieve a realistic testing of the fit and functionality of tight-fitting clothing. Therefore it is important that avatars in CAD programs for clothing conform to the mechanical properties of human soft tissue. The accuracy of the avatars' properties in simulating the change in shape of human tissue is crucial here, which is caused by the contact pressure that compressive or tight-fitting garments exert onto the body. In this study, Browzwear’s VStitcher soft avatar Sofia was investigated and different body shapes resulting from being influenced by a legging with different levels of negative ease values were compared with non-affected natural avatar body shape. The examination of the soft avatar simulation shows that although a fast estimation of the tissue displacement can be predicted, there are some shape changes limitations compared to the natural behavior of human soft tissue.

Morphogens in the evolution of size, shape and patterning.

Much of the striking diversity of life on Earth has arisen from variations in the way that the same molecules and networks operate during development to shape and pattern tissues and organs into different morphologies. However, we still understand very little about the potential for diversification exhibited by different, highly conserved mechanisms during evolution, or, conversely, the constraints that they place on evolution. With the aim of steering the field in new directions, we focus on morphogen-mediated patterning and growth as a case study to demonstrate how conserved developmental mechanisms can adapt during evolution to drive morphological diversification and optimise functionality, and to illustrate how evolution algorithms and computational tools can be used alongside experiments to provide insights into how these conserved mechanisms can evolve. We first introduce key conserved properties of morphogen-driven patterning mechanisms, before summarising comparative studies that exemplify how changes in the spatiotemporal expression and signalling levels of morphogens impact the diversification of organ size, shape and patterning in nature. Finally, we detail how theoretical frameworks can be used in conjunction with experiments to probe the role of morphogen-driven patterning mechanisms in evolution. We conclude that morphogen-mediated patterning is an excellent model system and offers a generally applicable framework to investigate the evolution of developmental mechanisms.

Finite Element Modelling for the Dynamic Behaviour Analysis of a Structure with Hi-Lok Fasteners

The number of Hi-Lok fasteners used in the assembly of aircraft structures is very high. For this reason, an efficient modelling technique is required to accurately analyse the dynamic behaviour of the structures. In this study, a modelling technique with special emphasis on Hi-Lok modelling is proposed to analyse the dynamic behaviour of a test structure with Hi-Lok fasteners. Four different finite element (FE) models to represent the test structure with the Hi-Lok fasteners were developed using MSC Software packages. The natural frequencies and mode shapes obtained from the FE models are compared with those of the Experimental Modal Analysis (EMA) in terms of total error, computational time and memory disk usage. It was found that the model D with the simplified beams representing Hi-Lok predicts the dynamic behaviour of the test structure with an accuracy of 96.6% and with comparatively low computational time and memory disk usage. This proposed modelling scheme may provide useful approaches to aircraft researchers and engineers for the dynamic analysis of the structures.

Geotourism and Geoeducation: A Holistic Approach for Socioeconomic Development in Rural Areas of Los Santos Municipality, Santander, Colombia

This study emphasizes the untapped geotourism and geoeducation potential in the Mesa de Los Santos region, situated within the Chicamocha Canyon in Colombia, renowned for its abundant geoheritage. Despite the region's geological richness, geotourism development opportunities have been overlooked, leaving its geoheritage largely unexplored for tourism. Focused on the georoute Refugio La Roca—Los Santos, the study identifies key geosites with significant potential for future geotourism endeavors. The Mesa de Los Santos region boasts a complex geological history and diverse geodiversity shaped by various natural phenomena. However, its full geotourism potential remains undiscovered. The georoute, incorporating natural and cultural heritage, is strategically designed for geotourism and geoeducation, aiming at fostering geoconservation in rural areas. Educational and interpretive panels are employed as didactic resources to enlighten tourists about the natural phenomena shaping the landscape, enhancing their overall experience and understanding. By integrating geoethical considerations into geosite management, the study proposes achieving sustainable geoconservation in the Chicamocha Canyon territory. This approach not only contributes to preserving the region's geological uniqueness but also provides a platform for socio-economic development in rural areas. The study envisions creating meaningful experiences that attract tourists while benefiting local communities, thereby promoting holistic and sustainable rural development.

Fine classification of rice fields in high-resolution remote sensing images

Fine-grained management of rice fields can enhance the yield and quality of rice crops. Challenges in achieving fine classification include interference from similar vegetation, the irregularity of natural field shapes, and complex scale variations. This paper introduces Rice Attention Cascade Network (RACNet), for the fine classification of rice fields in high-resolution satellite remote sensing imagery. The network employs the Hybrid Task Cascade network as the base framework and uses spectral and indices mixed multimodal data as input to reinforce the feature differentiation of similar vegetation. Initially, a Channel Attention Deformable-ResNet (CAD-ResNet) was designed to enhance the feature representation of rice on different channels. Deformable convolution improves the ability of CAD-ResNet to capture irregular field shapes. Then, to address the issue of complex scale changes, the multi-scale features extracted by the CAD-ResNet are progressively fused using an Asymptotic Feature Pyramid, reducing the loss of scale information between non-adjacent layers. Experiments on the Meishan rice dataset show that the proposed method is capable of accurate instance segmentation for fragmented or irregularly shaped rice fields. The evaluation metric AP50 of RACNet reaches 50.8%.

Natural Transposable Element Insertions Contribute to Host Fitness in Model Yeasts.

Transposable elements (TEs) are ubiquitous in the eukaryote genomes, but their evolutionary and functional significance remains largely obscure and contentious. Here, we explore the evolution and functional impact of TEs in two model unicellular eukaryotes, the fission yeast Schizosaccharomyces pombe and the budding yeast Saccharomyces cerevisiae, which diverged around 330 to 420 million years ago. We analyze the distribution of LTR retrotransposons (LTR-RTs, the only TE order identified in both species) and their solo-LTR derivatives in 35 strains of S. pombe and 128 strains of S. cerevisiae. We find that natural LTR-RT and solo-LTR insertions exhibit high presence-absence polymorphism among individuals in both species. Population genetics analyses show that solo-LTR insertions experienced functional constraints similar to synonymous sites of host genes in both species, indicating a majority of solo-LTR insertions might have evolved in a neutral manner. When knocking out nine representative solo-LTR insertions separately in the S. pombe strain 972h- and 12 representative solo-LTR insertions separately in the S. cerevisiae strain S288C, we find that one solo-LTR insertion in S. pombe has a significant effect on the fitness and transcriptome of its host. Together, our findings indicate that a fraction of natural TE insertions likely shape their host transcriptomes and thereby contribute to their host fitness, with implications for understanding the functional significance of TEs in eukaryotes.

Cytotoxic and Apoptotic Effects of Green Synthesized Silver Nanoparticles via Reactive Oxygen Species-Mediated Mitochondrial Pathway in Human Breast Cancer Cells.

Due to their exceptional physicochemical features, green synthesized silver nanoparticles (AgNPs) have been of considerable interest in cancer treatment. In the present study, for the first time, we aimed to green synthesize AgNPs from Euphorbia retusa and explore their anticancer potential on human breast cancer (MCF-7) cells. First, the green synthesized AgNPs (EU-AgNPs) were well characterized by UV-visible spectroscopy, Fourier transmission infrared (FTIR) spectrum, XRD, scanning and transmission electron microscopy (SEM and TEM), and EDX techniques. The characterization data exhibited that EU-AgNPs were spherical in shape and crystalline in nature with an average size of 17.8 nm. FTIR results established the presence of active metabolites in EU-AgNPs. Second, the anticancer effect of EU-AgNPs was evaluated against MCF-7 cells by MTT and neutral red uptake (NRU) assays. Moreover, morphological changes, ROS production, MMP, and apoptotic marker genes were also studied upon exposure to cytotoxic doses of EU-AgNPs. Our results showed that EU-AgNPs induce cytotoxicity in a concentration-dependent manner, with an IC50 value of 40 μg/mL. Morphological changes in MCF-7 cells exposed to EU-AgNPs also confirm their cytotoxic effects. Increased ROS and decreased MMP levels revealed that EU-AgNPs induced oxidative stress and mitochondrial membrane dysfunction. Moreover, ROS-mediated apoptosis was confirmed by elevated levels of proapoptotic marker genes (p53, Bax, caspase-3, and caspase-9) and reduced levels of an antiapoptotic gene (Bcl-2). Altogether, these findings suggested that EU-AgNPs could induce potential anticancer effects through ROS-mediated apoptosis in MCF-7 cells.

Experimental and numerical analyses on the modal behaviour of an aluminium alloy sheet

Abstract The study of modal behaviour for vehicle body panels represents a field of interest for automotive engineering, having a major influence on automotive comfort, with respect to vehicle noise, vibration and harshness, but also concerning the durability of vehicle body. The investigation of natural frequencies and vibration mode shapes is crucial in the design phase, because essential information can be obtained concerning the behaviour of the components in dynamic conditions. The current paper focuses on the investigation of vibration modes and frequency response function on an aluminium alloy sheet. The aim of the paper is to perform the study of modal behaviour both experimentally and theoretically, through measurements using the impact hammer method and respectively through finite element analysis. The CAD model of the aluminium alloy sheet has been developed in Catia V5 environment in view of elaborating the finite element model, which has been used for investigation of modal behaviour, taking into account the case of free vibrations. Through the modal finite element analysis performed in Ansys Workbench, the natural frequencies of the aluminium alloy sheet, as well as the corresponding mode shapes have been obtained. Experiments have been performed on an aluminium alloy sheet, mounted on an elastic support with low natural frequency. The impact hammer method has been used for obtaining the natural frequencies, through frequency analysis of accelerations measured with two piezoelectric accelerometers mounted on the aluminium alloy sheet. The frequency response function has been computed from the response acceleration measured on the aluminium alloy sheet and the impact force measured using the force transducer of the impact hammer. Virtual instruments have been developed in LabVIEW environment for data acquisition, time domain and frequency analysis, as well as for determining the frequency response function using the measured signals. The natural frequencies obtained from the finite element analyses have been compared to the results of measurements and very good similarities have been ascertained. The experimental investigation of modal behaviour contributed to the validation of the finite element model, but further research is required to investigate the possibilities of improving the modal behaviour of the aluminium alloy sheet.