External Forces Research Articles (Page 1)

With advancements in digital technology and construction techniques in modern times, buildings of diverse geometries are now being constructed. Many of these structures feature curved surfaces and are of large scale, and they are referred to as free-form architecture. Among the exterior panels of such free-form buildings, those made of concrete are termed Free-form Concrete Panels(FCPs). Since these panels are exposed to external environments, they are subjected to various external forces, and thus must exhibit resistance according to their specific geometries. Accordingly, this study aims to measure the bending behavior of FCPs among the various external forces acting upon them. A testing method for flexural strength test measurement will be proposed, and, if necessary, testing equipment will be developed to conduct the experiments. Through this research, differences in strength arising from variations in curved geometries can be identified, and it will also be possible to determine which shapes are most vulnerable to bending loads.

ABSTRACT The urban identity recognition of China’s returned sent-down youth is not simply determined by social structures. Instead, it is produced intermittently, driven by events, and characterised by its constructed and uncertain nature. The process of recognising the social roles of returned educated youth occurs through the interaction of internal and external forces. In the self-defining system, institutionalised social roles shape their ‘cognitive social identity’, whereas cultural experiences in the emotional realm influence their ‘affective social identity’. The external-defining system serves as a tool for self-cognition and provides an orientation system to define individuals’ positions within society.

Millimeter cable-driven continuum robots exhibit shape conforming, dexterous manipulation capabilities in constrained environments. They are increasingly used for narrow space and endoluminal intervention. For delicate manipulation, quantifying the force interaction between the robot and its surrounding environment is important for both shape adjustment and avoiding damages to luminal structures. In this work, we propose a real-time, whole-body contact estimation framework for small-scale continuum robots, based on actuation fibers and model-informed neural networks. The physical relationship among external body contact, internal actuation, and shape sensing of the continuum robot is formulated based on rod theory, and body contact estimation is treated as an inverse problem given the actuation tension profile and robot shape as inputs. The contact position and force are estimated using a neural network, and a generative adversarial network-based data augmentation strategy is proposed to reduce the need for large amounts of real data from the continuum robot under external forces. In addition, an automatic data acquisition platform is developed to efficiently collect the small amount of required data. Experiments with notched continuum robots were conducted to demonstrate the general applicability and accuracy of the proposed approach. The results show that the mean estimation errors for the three-dimensional (3D) contact position and contact force magnitude are 1.7 mm (2.3%) and 8.7 mN (5.8%), respectively, with an estimation frequency of 25 Hz. It paves the way for embodied integration using multiplexed fibers for the simultaneous actuation and sensing of millimeter-scale continuum robots, enabling their safer operation in confined spaces through machine intelligence.

Abstract In scientific machine learning (SciML), a key challenge is learning unknown, evolving physical processes and making predictions across spatio-temporal scales. For example, in real-world manufacturing problems like additive manufacturing, users adjust known machine settings while unknown environmental parameters simultaneously fluctuate. To make reliable predictions, it is desired for a model to not only capture long-range spatio-temporal interactions from data but also adapt to new and unknown environments; traditional machine learning models excel at the first task but often lack physical interpretability and struggle to generalize under varying environmental conditions. To tackle these challenges, we propose the attention-based spatio-temporal neural operator (ASNO), a novel architecture that combines separable attention mechanisms for spatial and temporal interactions and adapts to unseen physical parameters. Inspired by the backward differentiation formula, ASNO learns a transformer for temporal prediction and extrapolation and an attention-based neural operator for handling varying external loads, enhancing interpretability by isolating historical state contributions and external forces, enabling the discovery of underlying physical laws and generalizability to unseen physical environments. Empirical results on SciML benchmarks demonstrate that ASNO outperforms existing models, establishing its potential for engineering applications, physics discovery, and interpretable machine learning.

The development of layered structures represents a viable and promising avenue in the field of construction, as their utilization has the potential to significantly enhance strength characteristics, resistance against external forces, as well as enhance the thermal and acoustic insulation properties of buildings and structures. The aim of this study is to investigate the diversity and benefits of utilizing multilayer building components as an alternative to conventional structures, as well as to analyze the characteristics of their operation. Based on the findings of the study, it can be inferred that multilayered structures offer enhanced thermal and acoustic insulation characteristics, which contribute to the creation of a more comfortable living and working environment. Additionally, these structures can significantly decrease the weight of buildings, leading to potential savings in foundation and other structural components.

Abstract Two different work-energy theorems can be used to describe the work done on an extended object if it rotates and/or compresses when an external force is applied to the object. An example is presented where a force is applied to a flexible rod that simultaneously translates, rotates and compresses.

In the last half century, the approach that identifies the influence of the Enlightenment in the academic and public activities of the ecclesiastical intellectuals has taken root in the history of ideas, including in Central and Eastern Europe. One of the aims of this trend is to identify the reform ideas that emerged among the leaders of Christian churches and non-Christian religious communities to modernize pastoral practice. As one of the most important results, the changes that took place in the second half of the 18th century are no longer seen as the inevitable consequence of external forces, primarily from the state, but also as the derivative of internal aspirations in dialog with the ‘Zeitgeist’. Previous scholarly work, however, rarely examined the theoretical considerations behind the reform of religious practice, which can in fact be explained by changes in the image of the church among the ecclesiastical intelligentsia. The study aims to illustrate these changes in the ecclesiastical image by means of three contemporary texts, focused on the episcopal oath and the reform of the clergy.

Plane unsteady potential flows of an ideal incompressible fluid with a free boundary are considered in the absence of external forces and surface tension. At the initial time, the flow occupy a wedge with an angle at the apex. For different initial flow velocities and values of the angle at the vertex, a family of exact solutions is found. A method for finding solutions based on reducing the boundary-value problems to systems of ordinary differential equations.

Mechanoresponsive molecular devices are capable of exhibiting dynamic responses to external mechanical stimuli, enabling applications in smart materials, nano-devices, and flexible electronics. However, energy conversion induced by mechanical stimuli requires efficient energy dissipation mechanisms. Traditional methods often involve bond breaking or incomplete energy release, which can lead to device failure during continuous operations. Therefore, ensuring the mechanical stability of molecular devices under cyclic external forces remains a significant challenge. Here, we introduce a pillar[6]arene-like cyclophane (PLC) as an energy-dissipative structure to construct a programmable multistate mechanoswitching at the single-molecule level. We observed that, compared to rigid molecules with low energy dissipation, PLC-based macrocyclic molecular devices not only withstand mechanical stretching up to 6Å but also exhibit three stable states during the mechanical stretching/compressing processes. Combined with theoretical calculations, we confirm that these three distinct states are related to the charge transport pathways and the strength of the electrode-molecule interface coupling. This work establishes energy dissipation as a core design principle for multistate mechanoelectronic devices.

The subject of the research is a mathematical model of the equilibrium of a solid body of satisfactory spatial shape under external load. The development of solid mechanics is largely related to practical goals — calculations of the strength of structural elements and machine parts, the violation of which is usually understood as reaching a state where the structural properties of the product change, rendering it unsuitable for use. Many years of research into the system of differential equations in partial derivatives of the laws of equilibrium in mechanics, known as the Navier-Lame system of equations, has not yet, due to its complexity, achieved the level of development that would guarantee the possibility of obtaining analytical solutions. This raises many questions and misunderstandings regarding the solutions of boundary value problems using widely available application packages based on finite difference approaches. The purpose of this article is to present the results of the development of an alternative method of boundary integral equations, which, due to the boundary conditions of deformation of a continuous medium, leads to a system of linear boundary integral equations with the existing set of solutions. Task: to construct integral representations of solutions to the system of differential equations of equilibrium laws of a solid deformable body using the generalized potential theory method for differential operator forms of the corresponding equations. Scientific novelty. The differential operations of vector-tensor analysis are developed and generalized. The generalized integral theorems for differential operators of the second order adequate to the equilibrium laws of a deformable solid are proved. The results obtained. On the basis of the created generalized apparatus of vector-tensor analysis, analytical solutions in the form of integral representations of the main kinematic characteristics of the problem of deformation of a solid of satisfactory spatial form are constructed. Conclusions. The boundary value problem of the equilibrium of a deformed solid in the presence of an external force is reduced to a system of linear boundary integral equations with respect to the kinematic characteristics of the problem. In addition, it is proved for the first time that all the obtained characteristics are related to the vector momentum potential, which greatly simplifies the integral representation of solutions and numerical implementation of solutions of the corresponding integral equations.

Modern manufacturing places increasing demands on assembly accuracy, revealing the limitations of conventional tolerance-based methods and studies that oversimplify multi-surface constraints into single-surface problems. To address this challenge, it is crucial to account for geometric distribution errors on multiple surfaces and constraints from multiple mating surfaces, analyzing their coupling effects in assembly. This paper presents a model that incorporates the effects of machining-induced geometric distribution errors and the constraints arising from multiple mating surfaces. The model determines contact points between two pairs of mating surfaces and calculates the spatial pose of the assembled part to predict assembly accuracy. The model validation was conducted in two stages: initial verification of fundamental principles through a two-dimensional simulation, followed by experimental validation. The experimental study involved mating surfaces with distinct geometric distribution errors manufactured by different machine tools. Assembly tests were performed under two distinct orientations of applied external forces. Results show close agreement between predicted and measured values, with a root mean square error (RMSE) below 2%, confirming the method’s effectiveness. The proposed method offers a solution to the assembly registration problem involving coupled multi-constraints and geometric distribution errors.

ABSTRACT Small and medium-sized enterprises (SMEs) in emerging economies face increasing pressure to meet sustainability goals while staying competitive. This study explores how external forces and internal practices shape sustainable tourism management among technology-based SMEs in Bangladesh. Using the Stimulus–Organism–Response (SOR) framework, we examine how institutional requirements, market competition, and green human resource management influence the adoption of environmental, social, and governance (ESG) practices and business analytics capability. These, in turn, affect sustainable tourism management performance. The analysis is based on 760 SMEs using structural equation modeling (SEM), propensity score matching (PSM), and fuzzy-set qualitative-comparative analysis (fsQCA). The results show that institutional pressure, market competition, and green human resource management all play an important role in encouraging SMEs to adopt ESG practices and develop business analytics capability. Both ESG adoption and analytics, in turn, make a strong contribution to sustainable tourism performance. The PSM analysis, which compares firms with high and low levels of ESG and analytics, confirms these findings: SMEs that adopt ESG practices achieve about 19% higher sustainability scores, while those with strong analytics capability perform about 17% better than others. The fsQCA results further reveal that there is no single path to achieving sustainability. Instead, different combinations of ESG practices, analytics capability, and competitive conditions can all lead to strong outcomes, highlighting the diverse strategies SMEs can follow. This research demonstrates the importance of ESG and data-driven decision-making for SME sustainability and offers practical guidance for entrepreneurs and policymakers working to strengthen tourism in emerging markets.

Physiologically constrained neuromuscular synergy extraction using a deep off-policy dynamic neuro-fuzzy system in wheelchair propulsion.

Hydrogel-based tactile sensors, typically featuring a sandwiched structure of electrode/hydrogel/electrode with charges (electrons and ions) accumulated at both interfaces forming electrical double layers (EDLs), are considered promising candidates as human-machine interfaces (HMIs); however, the continuous dense structure limits the deformability of bulk hydrogels, hindering the achievement of high-sensitivity and wide detectable range. Moreover, the state-of-the-art strategies for enhancing sensitivity predominantly focus on enlarging the changes of hydrogel/electrode contact area upon external force, while overlooking the design of interfacial properties and ion transport kinetics. Herein, polyacrylamide/chitosan/MXene (PAM/CS/MXene, PCM) hydrogels with gradient porosity and tailorable softness are developed following the phase-transition-induced foaming mechanism. Ti3C2TX MXene plays critical roles in promoting rapid gelation, stabilizing bubbles, regulating ion transport kinetics, and modulating charge accumulation/dissipation at the hydrogel/electrode interfaces. As a consequence, the obtained PCM foam (PCMF) tactile sensor exhibits an optimal sensitivity of 4267 kPa-1 together with a wide detectable pressure range up to 100 kPa. Proof-of-concept applications are demonstrated for acquiring and identifying gesture commands to control a robotic arm for swab sampling and the movement of an electric car in a maze game by integrating PCMF sensors with a digital camera for visual feedback and machine learning for accurate recognition, respectively.

Impact of gravitational forces on Red Blood Cell dynamics in biofluid suspension.

Local and global effects of inertial force components producing brain strain during head impacts.

Freezing of a spreading droplet.

Influence of suture and fontanelle morphological variabilities on infant head injury biomechanics.

Ti3C2 quantum dots/hydroxypropyl methylcellulose modified Bi2WO6 for enhancing piezo-photocatalytic degradation of tetracycline.

Aeration-driven peroxymonosulfate piezoactivation by PVDF-BTO composite membrane for the effective elimination of antibiotic resistance genes.