Mechanical Theory Research Articles

The metaphysics of mechanisms: an ontic structural realist perspective

Existing metaphysical accounts of mechanisms commit to the existence of objects or entities posited in scientific theories, and thus fall within the category of maximal metaphysics. In this paper, I demonstrate the incompatibility of object-based metaphysics of mechanisms with the prevailing trend in the philosophy of physics by discussing the so-called bottoming-out problem. In response, I propose and flesh out a structuralist metaphysics of mechanisms based on Ontic Structural Realism (OSR), which is a kind of minimal metaphysics. I argue that the metaphysical underpinnings of mechanisms are structures, whose metaphysical nature is elaborated through comparison with existing metaphysical theories of mechanisms. After that, I address the concern of whether objects in mechanisms can be accommodated in my account by invoking existing metaphysical theories of objects in special science by structuralists, such as Ladyman, J., & Ross, D. (2007). Every Thing Must Go: Metaphysics Naturalized. Oxford University Press.)’s real pattern account, and suggesting a potential alignment between OSR and processual ontology. Finally, I demonstrate how my view can naturally serve as the metaphysics for Mechanism 2.0 and be applied to systems biology.

A human pluripotent stem cell-based somitogenesis model using microfluidics

Emerging human pluripotent stem cell (hPSC)-based embryo models are useful for studying human embryogenesis. Particularly, there are hPSC-based somitogenesis models using free-floating culture that recapitulate somite formation. Somitogenesis invivo involves intricately orchestrated biochemical and biomechanical events. However, none of the current somitogenesis models controls biochemical gradients or biomechanical signals in the culture, limiting their applicability to untangle complex biochemical-biomechanical interactions that drive somitogenesis. Herein, we develop a human somitogenesis model by confining hPSC-derived presomitic mesoderm (PSM) tissues in microfabricated trenches. Exogenous microfluidic morphogen gradients imposed on the PSM tissues cause axial patterning and trigger spontaneous rostral-to-caudal somite formation. A mechanical theory is developed to explain the size dependency between somites and the PSM. The microfluidic somitogenesis model is further exploited to reveal regulatory roles of cellular and tissue biomechanics in somite formation. This study presents a useful microengineered, hPSC-based model for understanding the biochemical and biomechanical events that guide somite formation.

Finite element data-driven deep learning-based tensile failure analysis of precast bridge slab joint

The joint is a critical component that facilitates force transmission across precast bridge slabs while maintaining structural integrity. Finite Element Analysis (FEA) is commonly used to examine the mechanical properties and load-bearing capacity of joints with different configurations. However, the repetitive process of “modeling-meshing-computing” consumes substantial manpower, time, and expertise. This study proposes an approach consisting of three key steps: (1) predicting strain distributions, (2) determining failure modes, and (3) analyzing interpretability of predicted results. Specifically, DeepLabv3+ is used to map the Finite Element (FE) model to strain distributions. A binary classification model based on VGG-16 predicts the failure state of the specimen. Interpretability analysis, using Gradient-weighted Class Activation Mapping (Grad-CAM), provides insights into the neural network’s decision-making process. The optimized models achieve a Mean Intersection over Union (MIoU) of 0.5691 for strain distribution prediction on the cross-sectional surface and 0.6424 on the front surface. The failure detection model achieves an F1 score of 0.992 in determining failure states. The interpretability results align well with fracture mechanics theory, enhancing confidence in the model’s predictions. This method serves as a surrogate to reduce the workload of finite element analyses, facilitating strain analysis and failure detection.

Real-time imaging of intracellular deformation dynamics in vibrated adherent cell cultures.

Mechanical vibration has been shown to regulate cell proliferation and differentiation in vitro and in vivo. However, the mechanism of its cellular mechanotransduction remains unclear. Although the measurement of intracellular deformation dynamics under mechanical vibration could reveal more detailed mechanisms, corroborating experimental evidence is lacking due to technical difficulties. In this study, we aimed to propose a real-time imaging method of intracellular structure deformation dynamics in vibrated adherent cell cultures and investigate whether organelles such as actin filaments connected to a nucleus and the nucleus itself show deformation under horizontal mechanical vibration. The proposed real-time imaging was achieved by conducting vibration isolation and making design improvements to the experimental setup; using a high-speed and high-sensitivity camera with a global shutter; and reducing image blur using a stroboscope technique. Using our system, we successfully produced the first experimental report on the existence of the deformation of organelles connected to a nucleus and the nucleus itself under horizontal mechanical vibration. Furthermore, the intracellular deformation difference between HeLa and MC3T3-E1 cells measured under horizontal mechanical vibration agrees with the prediction of their intracellular structure based on the mechanical vibration theory. These results provide new findings about the cellular mechanotransduction mechanism under mechanical vibration.

Study on the damage mechanism and evolution model of preloaded sandstone subjected to freezing–thawing action based on the NMR technology

Abstract Investigating the damage degradation of rock during the freezing and thawing process is more consistent with the actual engineering environment, considering its internal initial damage. In this study, the effects of initial damage from preloading and subzero-temperature freezing–thawing on microscopic and macroscopic mechanical properties of sandstone were studied based on the nuclear magnetic resonance (NMR) technique. The results show that the P-wave velocity of the sample decreased, while the porosity increased as the initial damage level increased. The distribution of T2 signal intensity exposed to the low-temperature freezing–thawing–saturation treatment was rather larger than that under normal temperature conditions for samples with different levels of initial damage from preloading, indicating that the low-temperature freezing–thawing condition would promote the porosity and have an obvious increase in damage. A continuum damage model considering subzero-temperature freezing–thawing damage from different pore sizes was finally introduced to describe the damage evolution mechanism of sandstone. The research results can be used to quantitatively evaluate the damage evolution mechanism of sandstone treated by subzero-temperature freezing–thawing without mechanical tests. Furthermore, the analysis and research results show that the damage variables of sandstone obtained by the NMR theory were lower than those of classical rock mechanics theory.

Micro- and macro- mechanical properties of an Al2O3/Al2O3 ceramic matrix composite after thermal aging at 1400 °C

The evolution mechanism of mechanical properties at elevated temperature is particularly crucial to the oxide/oxide composites. In this work, an Al2O3/Al2O3 ceramic matrix composite was prepared by laminating with high solid content slurry. The microstructure, micro- and macro- mechanical properties of the composites before and after thermal aging at 1400 °C were examined. The density and porosity of the original composite were ∼2.60 g/cm3 and ∼27.2 %, respectively. The sintering phenomenon of matrix in the composite after thermal aging was clearly visible, resulting in the matrix modulus increased by 83.5 % and the interfacial shear strength increased by 154.9 % compared with those of the original composite. The fundamental mechanics theory of composites stated that the significant increase of interfacial shear strength was the main reason that the flexural strength retention ratio of the composite decreased to ∼55 % after thermal aging.

Fatigue driving force of riveted shear joints in bridges — Replacing the net section stress

Many old steel bridges contain hot riveted double strap butt joints. The fatigue life of these joints is subject of growing concern. We collected 629 fatigue tests, showing that the fatigue resistance expressed as the net section stress range is extremely scattered. Based on the theory of mechanics and the finite element method, we developed analytical equations to estimate the hoop stress range in the plate at the rivet hole. Using this stress parameter, the scatter in fatigue resistance reduces significantly. The model also gives insight into how the joint geometry influences the fatigue resistance.

Improved energy method and agglomeration influence of carbon nanotubes on polymer composites

In this paper, the geometric analysis of carbon nanotubes (CNTs) without external loading is carried out by energy method. Based on the theory of molecular mechanics, an improved mechanical model is proposed to predict the energy of armchair carbon nanotubes under stress-free conditions, and the diameter of CNTs is estimated according to the principle of minimum energy. The results show that the diameter obtained by the improved model is larger, but basically consistent with that obtained by conformal mapping. The inversion energy term is added to the modified model, and the inversion energy term related to atomic curvature is characterized by the conization angle. It can be seen from the error that the inversion energy of carbon nanotubes can not be neglected in the stress-free state, especially in the case of small diameter. The agglomeration of nanotubes is one of the important factors, which affects the effective elastic modulus of nanocomposites. Here, a new micro-mechanics model consisting of both agglomeration of CNTs and pure matrix is also presented to analyze its effect on the effective elastic modulus. It is noted from the results that the stiffness of nanocomposites is very sensitive to the CNTs agglomeration.

Corrosion-Induced Cracking Model of Concrete Considering a Transverse Constraint.

The performance of corrosion-induced cracking of reinforced concrete members under transverse constraints was studied. Based on the theory of elastic-plastic mechanics and the hypothesis of uniform corrosion of a steel bar, a three-layer hollow cylinder model was established to predict the critical corrosion of the steel bar at the time of the cracking of the concrete cover. Taking the constraint of stirrups on surrounding concrete into consideration, it can be used to predict the corrosion rate of members with stirrups at the time of the cracking of the concrete cover, which further expands the application range of the corrosion-induced cracking models of concrete. On this basis, the critical corrosion rate of concrete under different stirrup ratios at the time of cracking was measured. The calculated results of the model are in accordance with experimental data. For corner steel bars, when the stirrup spacing is less than 100 mm, the existence of stirrups can effectively delay the occurrence of rust expansion cracks and enhance the durability of the structure. On the basis of this study, the problem of corrosion expansion and cracking of the concrete cover caused by non-uniform corrosion of steel bars along longitudinal and radial directions needs to be further studied in the future.

The impact of left atrial morphology on thrombosis risk in atrial fibrillation

Atrial fibrillation (AF) is an arrhythmia disease that can disrupt the movement of the left atrium (LA), which will facilitate thromboembolism in LA and further exacerbate the stroke risk. The left atrial appendage (LAA) is a vital site for thrombus formation. The morphology of the LAA is believed to have a profound effect on thrombosis. However, due to the limitation of observation and monitoring methods, the mechanism of this effect is still unrevealed. Virchow's triad is a theory of thrombogenic mechanisms, stating that endothelial injury, blood hypercoagulability, and blood stasis are the three main factors involved in thrombus formation. In this study, we conducted personalized simulation analyses for 12 AF patients and discussed simulation results from the perspective of Virchow's triad. The simulation results indicate the effectiveness of Virchow's triad in elucidating the thrombosis mechanism within the LAA. The LAA is more prone to thrombosis than the other region of LA, because of the lower blood flow velocity and significantly higher endothelial cell activation potential values there, which indicates a higher risk of blood stasis and endothelial injury, respectively. Furthermore, a comprehensive score is proposed to assess the performance of Virchow's triad in the LAA. The morphology of LA has a significant influence on the performance of the three factors in Virchow's triad. Hence, for a quickly assessment of LAA thrombosis risk in AF patients through the lens of Virchow's triad, we need a more refined shape scoring system that can better reflect patient-specific morphological features of the entire LA.

Mechanics equilibrium in Tai-chi diagram

Tai chi culture has a widespread influence on the world. Tai-chi diagrams, as the symbol of Tai chi culture, express the balance between Yin and Yang through the centrosymmetric pattern, but the balance connotation of Tai-chi diagrams needs a comprehensive understanding in more aspects, e.g., the balance in mechanics. In this work, we propose a mechanics theory to investigate the intrinsic mechanism of Yin–Yang equilibrium in ancient and modern Tai-chi diagrams. The model based on the minimum potential energy theory can effectively describe the interface curves of the Yin–Yang equilibrium by modifying boundary conditions, which is proven by experiments. The results show that the balance of Tai-chi diagrams is not only manifested in its symmetrical appearance but also reflected in its intrinsic balance configuration in mechanics. The model presented herein provides a new perspective to understand the balance of Tai-chi diagrams, which may provide useful insights into the applications of Tai-chi diagrams.

Zeptonewton and attotesla per centimeter metrology with coupled oscillators.

We present the coupled oscillator: A new mechanism for signal amplification with widespread application in metrology. We introduce the mechanical theory of this framework and support it by way of simulations. We present a particular implementation of coupled oscillators: A microelectromechanical system (MEMS) that uses one large (∼100mm) N52 magnet coupled magnetically to a small (∼0.25mm), oscillating N52 magnet, providing a force resolution of 200zN measured over 1s in a noiseless environment. We show that the same system is able to resolve magnetic gradients of 130aT/cm at a single point (within 500μm). This technology, therefore, has the potential to revolutionize force and magnetic gradient sensing, including high-impact areas such cardiac and brain imaging.

Identification and Characterization of High-Molecular-Weight Proteins Secreted by Plasmodiophora brassicae That Suppress Plant Immunity.

Plasmodiophora brassicae is an obligate intracellular parasitic protist that causes clubroot disease on cruciferous plants. So far, some low-molecular-weight secreted proteins from P. brassicae have been reported to play an important role in plant immunity regulation, but there are few reports on its high-molecular-weight secreted proteins. In this study, 35 putative high-molecular-weight secreted proteins (>300 amino acids) of P. brassicae (PbHMWSP) genes that are highly expressed during the infection stage were identified using transcriptome analysis and bioinformatics prediction. Then, the secretory activity of 30 putative PbHMWSPs was confirmed using the yeast signal sequence trap system. Furthermore, the genes encoding 24 PbHMWSPs were successfully cloned and their functions in plant immunity were studied. The results showed that ten PbHMWSPs could inhibit flg22-induced reactive oxygen burst, and ten PbHMWSPs significantly inhibited the expression of the SA signaling pathway marker gene PR1a. In addition, nine PbHMWSPs could inhibit the expression of a marker gene of the JA signaling pathway. Therefore, a total of 19 of the 24 tested PbHMWSPs played roles in suppressing the immune response of plants. Of these, it is worth noting that PbHMWSP34 can inhibit the expression of JA, ET, and several SA signaling pathway marker genes. The present study is the first to report the function of the high-molecular-weight secreted proteins of P. brassicae in plant immunity, which will enrich the theory of interaction mechanisms between the pathogens and plants.

Innovative Ecofriendly Coconut Husk Brushes

AIM : To reduce the time, energy and labours to cleaning the floor and bathroom by using the of innovative ecofriendly cocnut husk brushes. INTRODUCTION : The outer of almost houses are made by favors, interlocks or tiles or cement. Those are made dirty due to walking or by own vehicles or green algae of thallophytes are grown on the outside floor due to rain and also bathroom become dirty due to daily use. We can easily clean the floor and bathroom by using of the innovative ecofriendly cocnut husk brushes (Innovative Indigenous Floor And Bathroom Cleanig Brushes) in very less time which is made by coir husk. This is eco friendly brush. This brush worked on the principle of Simple Mechanism Theory. METHODS: Take two plates of 1.5x5 inches size of metal plate and these are bent as an arc. 4-5 holes are made on those plates equally for screw nuts. 3 pieces of desirable size of coir husk are cut at one end which becomes a brush. Each coir husk has a hole at another end as shown in the figure. Now, these coir husks are inserted between arc plates and fixed by the help of bolts tightly. Half feet of bent pipe is welded to this one with 60 degree angle as shown in the figure. And then two feet length wooden handle is fixated to this pipe as a handle. Now we can easily clean by rubbing it against the bathroom tiles or outside floor with the help of water. It takes only one minute to clean 1 sq mt area. Comparatively with plastic brush takes three to four minutes. So we can save plenty of time along with being eco friendly. It costs 100 rupees only.

Multi-scale variations of subglacial hydro-mechanical conditions at Kongsvegen glacier, Svalbard

Abstract. The flow of glaciers is largely controlled by changes at the ice–bed interface, where basal slip and sediment deformation drive basal glacier motion. Determining subglacial conditions and their responses to hydraulic forcing remains challenging due to the difficulty of accessing the glacier bed. Here, we monitor the interplay between surface runoff and hydro-mechanical conditions at the base of the Kongsvegen glacier in Svalbard. From July 2021 to August 2022, we measured both subglacial water pressure and till strength. Additionally, we derived median values of subglacial hydraulic gradient and radius of channelized subglacial drainage system from seismic power, recorded at the glacier surface. To characterize the variations in the subglacial conditions caused by changes in surface runoff, we investigate the variations of the following hydro-mechanical properties: measured water pressure, measured sediment ploughing forces, and derived hydraulic gradient and radius, over seasonal, multi-day, and diurnal timescales. We discuss our results in light of existing theories of subglacial hydrology and till mechanics to describe subglacial conditions. We find that during the short, low-melt-rate season in 2021, the subglacial drainage system evolved at equilibrium with runoff, increasing its capacity as the melt season progressed. In contrast, during the long and high-melt-rate season in 2022, the subglacial drainage system evolved transiently to respond to the abrupt and large water supply. We suggest that in the latter configuration, the drainage capacity of the preferential drainage axis was exceeded, promoting the expansion of hydraulically connected regions and local weakening of ice–bed coupling and, hence, enhanced sliding.

Determining the Cohesive Length of Rock Materials by Roughness Analysis

In this research, the cohesive length of various rock types is measured using quantitative fractography alongside a recently developed multifractal analysis. This length is then utilized to gauge material cohesive stress through the theory of critical distances. Furthermore, the fracture process zone length of different rings sourced from identical rocks is assessed as a function of ring dimensions and experimental measurements of fracture toughness, in accordance with the energy criterion of the finite fracture mechanics theory. Subsequently, employing the stress criterion within coupled finite fracture mechanics, the failure stress corresponding to the fracture process zone is determined for various rings. Ultimately, through interpolation, the critical stress corresponding to the cohesive length, quantified via quantitative fractography, is approximated. Remarkably, the cohesive stress values derived from both methodologies exhibit perfect alignment, indicating the successful determination of cohesive length for the analyzed rock materials. The study also delves into the significant implications of these findings, including the quantification of intrinsic tensile strength in quasi-brittle materials and the understanding of tensile strength variations under diverse stress concentrations and loading conditions.

Quantitative Assessment of Bed-Separation Dynamic Development Caused by Inclined Coal Seam Longwall Mining

Coal mining under the Quaternary thick loose layer affects key strata breakage, Bed-separations development, ground subsidence, and other studies. This paper presents a method for solving the deflection of a large-deflection inclined thin plate under a thick loose-layer cover with additional lateral loads and midplane forces. The methods presented are based on the principle of large-deflection of thin-plate, energy method, and fracture mechanics theory. The 7225 work face in Anhui Province, China, was studied. Combined with the large-deflection inclined thin plate model, the initial breakage distance within the main roof plate was calculated to be 33 m with the initial breakage angle of 61.2°, and the period breakage distance was calculated to be 21 m with the period breakage angle of 55.4°. The distribution range of “Vertical Three Zones” from 7225 working face to the ground, including the height of the caved zone is 38.07 m, the height of the fractured zone is 41.13 m, and the height of the curved zone with the thick loose layer removed is 187.56 m. During the dynamic development of the principal key strata (PKS), the deflection value develops from 0 mm to 2714 mm with 7225 working face mining, and the maximum value of the spatial volume is 56,485 m3, which is verified by Three-dimensional Discrete Element Code (3DEC) numerical simulation. The dynamic development of Bed-separation within the overlying strata, with a maximum development height of 545.2 mm and a maximum volume of 11,228.1 m3 of the Bed-separation cavity. The dynamic development of the Bed-separation height and the cavity under different mining length and width conditions of the working face are also discussed. The large-deflection inclined thin plate model proposed in this paper effectively explores the dynamic deflection and fragmentation law of the overlying strata induced by the inclined working face of Longwall mining and provides a theoretical basis and computational model for quantitatively evaluating the dynamic development of the Bed-separation cavity.

Highly efficient phosphorus removal by a novel prolonged stirring pelleting coagulation for sludge water treatment

Sludge water with high total phosphorus (TP) and suspended solids (SS) easily causes the effluent quality to be substandard in wastewater treatment plants. Although the conventional coagulation process can achieve TP removal, higher sludge production occurred due to loose flocs generation. The prolonged stirring pelleting coagulation (PSPC) process, based on one-by-one agglomeration and mechanical syneresis theories, was proposed to achieve compact flocs and reduced sludge production. Compared with the conventional coagulation process, the removal efficiency of TP was improved by >20 %, settling volume was reduced by about 30 %, and the dosages of polyaluminum chloride (PAC) and polyacrylamide (PAM) were saved by 50 % and 30 %, respectively in the PSPC process. The PSPC process produced pellet-like flocs with the d50 of 6.27 mm, settling velocity of 21.07 mm/s, effective density of 0.1411 g/cm3, and three-dimensional fractal dimension (D3) of 2.094 under the optimal conditions of 50 mg/L PAC and 10 mg/L PAM. With the d50 decreased from 38.38 μm to 21.81 μm, fragmentation of primary particles was realized by high-intensity stirring. Therefore, the mechanism of the PSPC process involves reducing voids in primary particles, achieving regular combination of microflocs under appropriate PAC, PAM, and hydraulic control. The PSPC process shows promising prospects for treating high SS wastewater and may have practical implications for enhancing coagulation.

Clinical phenotype and management of sound-induced pain: Insights from adults with pain hyperacusis.

Pain hyperacusis, also known as noxacusis, causes physical pain in response to everyday sounds that do not bother most people. How sound causes excruciating pain that can last for weeks or months in otherwise healthy individuals is not well understood, resulting in a lack of effective treatments. To address this gap, we identified the most salient physical and psychosocial consequences of debilitating sound-induced pain and reviewed the interventions that sufferers have sought for pain relief to gain insights into the underlying mechanisms of the condition. Adults (n = 32) with pain hyperacusis attended a virtual focus group to describe their sound-induced pain. They completed three surveys to identify common symptoms and themes that defined their condition and to describe their use of pharmaceutical and non-pharmaceutical therapies for pain relief. All participants endorsed negative effects of pain hyperacusis on psychosocial and physical function. Most reported sound-induced burning (80.77%), stabbing (76.92%), throbbing (73.08%), and pinching (53.85%) that occurs either in the ear or elsewhere in the body (i.e., referred pain). Participants reported using numerous pharmaceutical and non-pharmaceutical interventions to alleviate their pain with varying degrees of pain relief. Benzodiazepines and nerve blockers emerged as the most effective analgesic options while non-pharmaceutical therapies were largely ineffective. Symptoms of pain hyperacusis and therapeutic approaches are largely consistent with peripheral mechanistic theories of pain hyperacusis (e.g., trigeminal nerve involvement). An interdisciplinary approach to clinical studies and the development of animal models is needed to identify, validate, and treat the pathological mechanisms of pain hyperacusis.

A Critical Review of Constitutive Models Applied to Ice-Crushing Simulations

In marine engineering, understanding the compressive behaviour of ice is crucial for accurately modelling ice loads on ships and offshore structures in ice-prone waters. Over the past few decades, numerous studies have focused on numerically simulating the ice-crushing process using various material models. A significant source of contention among these models lies in the representation of ice strength envelopes and their evolution with pressure and strain rate. Moreover, there is ongoing debate regarding whether plasticity or viscoelasticity more effectively captures the rheology of ice. Additionally, various flow rules have been implemented in plasticity models and different damage models have been used in viscoelasticity models, all of which play a critical role in simulating ice loads. This critical review aims to shed light on the reasons behind these disagreements and to evaluate the advantages and limitations of the most commonly used models, based on established theories in ice mechanics and empirical evidence.