Application Of External Force Research Articles

A Simulation Model for the Analysis of Laser Cutting of Stainless Steel Sheets

In laser cutting processes, the removal of material is achieved without the application of external force, distinguishing it from traditional machining methods. An additional advantage of laser cutting is the ability to achieve desired surface quality in a single step, eliminating the need for additional finishing processes to smoothen and clean the cutting surface. To ensure the quality of the resulting cuts, a comprehensive understanding of the thermal behavior of the cut parts, influenced by the movement of the laser beam, is essential. The article focuses on the numerical simulation of the laser cutting process of the AISI 304 steel sheets with a thickness of 2 mm to investigate the impact of laser cutting parameters on transient thermal fields and the quality of the resulting cuts. A simulation model was developed and verified through temperature measurements during an experimental laser cutting process using the Bystronic Bysprint 3015 CO2 Laser Cutting Machine. Numerical simulations in ANSYS software were used to design a working diagram showing the relationship between laser power and cutting kerf width for three different cutting speeds: 2000 mm.min-1, 4000 mm.min-1, and 5000 mm.min-1.

Piezoelectric ceramics with hierarchical macro- and micro-pore channels for sensing applications

Piezoelectric sensors have attracted increasing attention due to their high sensitivity to forces, pressures and acceleration. The use of porous piezoelectric ceramics with aligned pores formed by freeze casting for sensing application also exhibit advantages due to their combination of a high piezoelectric charge coefficient and low permittivity, which leads to an enhancement in sensor sensitivity compared to dense materials. To fabricate porous materials, the process of direct ink writing (DIW) exhibits superiority in terms of structural design as a result of its ability to provide layer-by-layer and mold-free rapid prototyping. This work provides the first demonstration of the fabrication of lead zirconate titanate (PZT) piezoelectric ceramic scaffolds with sophisticated hierarchical porous structures by simultaneous DIW and freeze casting. The morphology of the porous cells and individual layers of the hierarchical porous PZT ceramic scaffolds were designed by adjusting the rheological properties and optimizing the printing path. The effect of cell structure and number of layers on sensing performance was investigated in detail. Manufactured scaffolds with a sandwich structure exhibited a high output voltage (191 V) under the application of 1 N external force, with a sensitivity of 8.98 V·kPa−1. This work provides a new approach to structural design of piezoelectric sensors to inform future efforts in the fabrication of high-performance piezoelectric ceramics with hierarchical porosity with complex and bespoke geometries.

On the re-evaluation of the clamped members stiffness of bolted joints

To address the structural integrity of bolted joints and verify their capacity to withstand external loads and relaxation resulting from thermal expansion difference and creep, proper evaluation of the axial stiffnesses of bolt and clamped members are of vital importance. A number of finite element (FE) based methods are available for the calculation of the stiffnesses of joint elements, most of which rely on the displacement of arbitrarily selected nodes that has led to the improper evaluation of joint stiffness values. In this paper, the stiffness of clamped members is evaluated by a simple FE methodology using a known bolt stiffness evaluated separately. Two load cases, one based on the application of external force (mechanical loading) and the other on temperature (thermal loading), are conducted using the FE method to validate the obtained results. The proposed methodology is also compared with other FE models and analytical methods obtained from the literature. The new technique is based on axisymmetric FE modeling and is applied to bolted joints with bolts ranging from M6 to M36 having various grip lengths. Finally, the stiffnesses of the bolt and clamped members can be determined accurately, and a general formula is proposed to evaluate the stiffness of clamped members.

UTILITY OF ULTRASOUND ELASTOGRAPHY IN DIFFERENTIATING BENIGN FROM MALIGNANT THYROID NODULES

Background: Ultrasound elastography is an imaging technique used for the evaluation of tissue stiffness by measuring the degree of tissue deformation in response to the application of external force. Methodology: In this prospective comparative study, a total of 52 thyroid nodules from 44 euthyroid patients undergoing fine needle aspiration cytology (FNAC) were assessed. Elastography was performed by a single experienced sonologist, wherein the nodules were graded as per elastography scoring (ES), and the strain ratio (SR) for each nodule was computed. Final histopathology findings of the patients undergoing surgery were compared to elastography findings, and measures of diagnostic accuracy to differentiate between benign and malignant nodules were determined. Results: Thirty (68.2%) females and 14 (31.8%) males, with a mean age of 45.18±11.23 years, were assessed. Fourteen (31.8%) patients underwent thyroidectomy, and histopathology was reported for 18 (34.6%) nodules. In all, nine (17.3%) nodules were malignant, and 43 (82.7%) nodules were considered benign. ES demonstrated a sensitivity of 88.9%, specificity of 88.3%, PPV of 61.5% and NPV of 97.4% to identify benign thyroid nodules. The mean SR for benign nodules was significantly lower as compared to malignant nodules (2.72±0.62 vs. 4.52±0.75, P<0.0001). The optimal cut-point value for SR to differentiate benign and malignant thyroid nodules was determined to be 3.8, with the sensitivity, specificity, PPV, and NPV being 88.9%, 95.4%, 80%, and 94.6%, respectively. Of the six nodules classified as Bethesda category-III or IV on FNAC, histopathological diagnosis was follicular carcinoma in one nodule (Bethesda category-IV), four were diagnosed with follicular adenoma, and one with colloid goitre. The ES of the nodule with follicular carcinoma was malignant, while amongst the rest, two nodules were classified as benign, and three nodules as malignant. The SR of the follicular carcinoma was 4.3, while the mean strain ratio in remaining nodules was 3.48 (P=0.001). Conclusion: Ultrasound elastography has good diagnostic efficacy for the differentiation of benign from malignant thyroid nodules. It can potentially reduce the rates of unnecessary fine needle-aspiration biopsy. However, whether elastography score or strain ratio will be useful in diagnosis of nodules which are indeterminate on FNAC is open to further studies.

Validating the Mechanism Underlying the Slacking of the Gate-Opening Behavior in Flexible Metal-Organic Frameworks Arising from the Application of External Force.

Flexible metal-organic frameworks (MOFs) are innovative adsorbents expected to revolutionize conventional separation systems as they exhibit stepwise adsorption arising from structural transitions, commonly known as "gate opening." However, because MOFs are typically obtained in powder form, they require shaping for industrial applications. In our previous study, we reported that the stepwise uptake observed in the CO2 gate opening of ELM-11 ([Cu(BF4)2(4,4'-bipyridine)2]) became less distinct when molded with polymer binders and found that this slacking phenomenon could be caused by the polymer binder inhibiting the structural change of the ELM-11 particles. In this study, we aimed to fully validate and generalize the mechanism behind the slacking of gate adsorption from both theoretical and experimental perspectives. First, we conducted grand canonical molecular dynamics simulations for a simplified MOF model to directly calculate free energy profiles of the particle to validate the slacking theory without any assumptions. The results confirmed the fundamental assumption made in our previous study that the deformation of the flexible motifs within the MOF particles occurs sequentially, which is a key factor contributing to the slacking phenomenon. The second part of the study focused on the relationship between the volume expansion ratio of MOFs and the degree of slacking. The relationship predicted by the theory was experimentally validated by comparing ELM-11, which exhibits 30% volume expansion, to another MOF with a mutually interpenetrating jungle-gym structure, which exhibits 10% volume expansion. These findings strengthened and generalized the understanding of the mechanism underlying the slacking of gate adsorption induced upon the application of external force, which could guide the fabrication of molded MOFs while maintaining a high adsorption efficiency for various industrial applications.

Automation of machines working equip-ment calculation using graph theory

Problem. The paper presents an example of using a methodology for automated calculation of working equipment for construction machines, which are represented by hinge-lever mechanisms. The approach employed in the methodology is based on graph theory and provides semi-automatic generation of the mechanism's structure description and automatic formation of systems of equations for its static calculation. Based on the methodology, software has been developed that automates the performance of force calculations in arbitrary positions of the mechanism for different loading schemes. Methodology. To automate the force calculation, an incidence matrix describing the structure of the mechanism is formed and used. Results. The developed software not only provides results in numerical form but also generates images of the mechanism's diagram. Additionally, the software includes exporting capabilities for results to a separate file that can be further used for selecting hydraulic cylinders and pumps, calculating hydraulic systems, and assessing the strength of working equipment components. Originality. Certain rules for numbering mechanism links and joints, as well as methods for indicating the coordinates of the joints and points of application of external forces, have been developed. These rules and methods not only ensure the automatic formation and solution of systems of equations for the mechanism's static equilibrium but also automate the construction of the incidence matrix. Practical value. The developed software and the data representation method proposed by the authors automate the majority of stages in the force calculation of hinge-lever mechanisms for construction machinery. It can be applied not only in the design stage but also before the use of new types of variable working equipment.

Facilitation of Osteogenic Differentiation of hASCs on PEDOT:PSS/MXene Composite Sponge with Electrical Stimulation

Innovations in biomedical tissue engineering are on the increase as many researchers look for ways to develop biological scaffolds for cells. Studies have shown that the application of external force and electrical stimulation (ES) promotes stem cell chondrogenic and osteogenic differentiation. Therefore, bioscaffolds sensitive to external stimuli can not only influence the cell behavior with their native physical and biochemical properties but also act as a mediator receiving an outside-in signal to alter the cellular activities under specific conditions. For the first time, the synthetic polymer poly(3,4-ethylene dioxythiophene):polystyrene sulfonate) (PEDOT:PSS) was combined with a two-dimensional, nanoconducting material, titanium carbide (MXene, Ti3C2X3), to prepare three-dimensional (3D) conductive scaffolds. Some studies have shown that MXene has good biocompatibility, osteoinductivity, and bone regeneration activity. The PEDOT:PSS/MXene scaffold was applied to the osteogenic differentiation of hASCs, and ES was used to enhance the osteogenic differentiation. The results showed that the conductive scaffold had low cytotoxicity to hASCs, which could grow and migrate in the 3D scaffold. In addition, osteogenic-specific gene expression significantly differed when the ES was applied. We propose that this PEDOT:PSS/MXene scaffold may serve as a platform for the study of osteogenic differentiation of stem cells with ES and may potentially be ex vivo fabricated as a tissue engineering construct for studying other modes of other ESs such as direct current, capacitive, or inductive coupling in a 3D environment.

A LITERARY REVIEW OF SIDDHA TREATMENT FOR MECHANICAL TRAUMA

Siddha is one of the oldest traditional medical systems followed in the Southern part of India. Herbal medicines and their preparation for the wound healing in mechanical trauma are found in Siddha texts. Mechanical trauma is an injury or wound to a living body caused by the application of external force or violence. Both internal and external medications used for the treatment of mechanical trauma were collected and compiled from this work. The treatment for specific wounds such as abrasion, burns and scalds, contusion, incision, and lacerated wounds in mechanical trauma is briefly discussed in this work. Of these, even simple herbs were used to arrest bleeding from wounds and also cures severe wounds are noteworthy. From the literary evidences, it is clear that ancient people used the medicinal plants and their resources in the treatment and management of mechanical trauma as the first hand medicine. This work paves the way for the future researchers to concentrate on mechanism of action of these medications for its specific role in wound healing will strengthen our Siddha system.

Towards an approximate solution of highly viscous electro-osmotic flows in inclined Channel: Applications in petroleum and gas engineering

Electro-osmotic flows (EoF) through an inclined channel are investigated in this article. Differential type non-Newtonian fluid model has been used to form highly viscous bi-phase fluid flows. Two different kinds of metallic particles are considered for disperse phase. The application of external electric fields and gravitational force are the main sources of multiphase flows under the magnetic environment. Nonlinear differential equations are formulated taking the stress tensor of fourth-grade fluid, Poisson equation, and Debye length approximation into account, respectively. An approximate solution is obtained for the nonlinear flow problems. Comparative analyses have also been performed with the previous investigations via tables and graphs and, were found to be in great agreement. A comprehensive parametric study is carried out, as well, which reveals that there is a definite difference between the momentum of the fluid phase and the particles phase. The contribution of the Helmholtz–Smoluchowski parameter in each phase is quite supportive. However, the effects of the transverse magnetic field and electro-osmotic parameter are in full coherence. Moreover, traditional multiphase flows can be derived for the limiting case. Finally, this theoretical study explicitly describes the applications in petroleum and gas engineering.

Transparent Piezoelectric Nanogenerator for Self-Powered Force Sensing Applications

Piezoelectric materials have been widely used as dynamic force sensors, accelerometers, and energy harvesters. Herein, we report the poly(vinylidene fluoride-co-tetrafluoroethylene) (P(VDF-TrFE)) based transparent piezoelectric nanogenerator (PENG) as a self-powered force sensor. The 2 × 2 array of PENGs was fabricated by sandwiching the P(VDF-TrFE) film between two indium tin oxide-based electrodes. The device demonstrated good stable and repeatable piezoelectric response (sensitivity of 0.3 V N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> ), which increased linearly with externally applied compressive force. The output voltage of the devices varied with the frequency of the external force application, and they showed a sensitivity of 0.25 V Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> between 2 and 10 Hz frequency. The excellent dynamic force sensing response, transparency, and self-power feature make presented devices ideally suited for applications such as see-through smart plaster that allow wound healing monitoring without removing the plaster.

Применение топологической оптимизации при проектировании элементов грузозахватных устройств

The article provides guidelines for the implementation of conceptual topology optimization. By «conceptual» is meant optimization, the result of which is not a specific design solution, but a rational topology – a structure that best transmits the given force flows. In accordance with the above recommendations, it is proposed to carry out optimization in the following sequence: determining the object of study, searching for points of application of external forces to the object and substantiating (if necessary) their most rational relative location, determining the nature of external forces at the points of their application, applying connections, taking into account other factors and analysis of the results with their possible refinement. Particular attention is paid to the issue of constructing a loading diagram for topology optimization, which, in the author’s opinion, largely determines the success of solving the problem. A correctly prepared loading diagram should take into account all the most unfavorable combinations of loads. Recommendations on the most rational construction of loading diagrams are given. The recommendations given in the article are tested on a practical example, which considers the procedure for optimizing the load grip lever. Such a grip has a complex nature of loading, and therefore its most rational structure is not obvious. Therefore, in order to search for a rational design of its elements, it is advisable to use conceptual topology optimization. Optimization made it possible to reduce the mass of the lever of such a grip by 42%. At the same time, the strength of the new solution increased by 15%, and the stiffness increased by 49%.

Contact-impact events with friction in multibody dynamics: Back to basics

Multibody dynamics deals with the study of mechanical systems composed of multiple bodies, whose motion interactions are governed by the presence of kinematic constraints and by the application of external forces. Frictional contact-impact events are among the most complex and important phenomena that can be modeled under the umbrella of multibody systems, since their behavior depend on critical factors, including geometry of the contacting surfaces, material properties of the colliding bodies, and constitutive laws utilized to mimic the contact response. This paper is aimed to present a comprehensive description of the most relevant aspects and the state-of-the-art techniques concerning the modeling collisions in multibody dynamics. For that purpose, the contact geometry, contact detection and contact resolution procedures are subjected to a critical analysis. Particular attention is given to the regularized or continuous models to treat frictional contacts in dynamical systems. Moreover, relevant numerical ingredients associated with contact-impact events in multibody systems are examined with the intent to discuss the computational accuracy and efficiency. Application examples are provided whose results allow to highlight the key features related to the modeling process of frictional contacts and impacts in multibody systems.

Magnetohydrodynamics streamwise and cross flow of hybrid nanofluid along the viscous dissipation effect: Duality and stability

One of the most pressing issues in contemporary applied mathematics is the regulation of energy transfer via the application of external forces. The processes of heat transfer are affected by magnetic force, which has many practical uses in industry, engineering, and medicine. This research explores the magnetohydrodynamics (MHD) three-dimensional stable axisymmetric boundary layer over a permeable moving plate, which consists of water as a base liquid and binary distinct nanoparticles to generate a hybrid nanofluid. In all of these, flow beyond the boundary layer area might be calculated by a small crosswise velocity. As a result of its high thermal conductivity, a pair of distinct kinds of nanoparticles have been considered, namely alumina and copper, which are integrated into the base water. The mathematical model is built within a boundary of specified geometry and then converted into a set of ordinary differential equations (ODEs). Resultant ODEs are solved numerically using the technique of three-stage Lobatto IIIa in bvp4c solver in 2017, MATLAB software. Results revealed that two branches exist in certain ranges of moving parameter. The impacts of an increasing physical parameter on profiles of velocities and temperature with skin friction as well as with heat transfer rate are represented in graphs. Furthermore, as the volume fraction of copper increases, so does the skin friction coefficient in the positive direction of λ. The effect of viscous dissipation on the temperature profile in the z-direction has the same rising results as observed in the x-direction. According to the results of the temporal stability analysis, the upper branch is realizable and stable.

Host-Guest Doping in Flexible Organic Crystals for Room-Temperature Phosphorescence.

Organic single crystals (OSCs) with excellent flexibility and unique optical properties are of great importance due to their broad applicability in optical/optoelectronic devices and sensors. Nevertheless, fabricating flexible OSCs with room-temperature phosphorescence (RTP) remains a great challenge. Herein, we propose a host-guest doping strategy to achieve both RTP and flexibility of OSCs. The single-stranded crystal is highly bendable upon external force application and can immediately return to its original straight shape after removal of the stress, impressively emitting bright deep-red phosphorescence. The theoretical and experimental results demonstrate that the bright RTP arises from Förster resonance energy transfer (FRET) from the triphenylene molecules to the dopants. This strategy is both conceptually and synthetically simple and offers a universal approach for the preparation of flexible OSCs with RTP.

Host–Guest Doping in Flexible Organic Crystals for Room‐Temperature Phosphorescence

AbstractOrganic single crystals (OSCs) with excellent flexibility and unique optical properties are of great importance due to their broad applicability in optical/optoelectronic devices and sensors. Nevertheless, fabricating flexible OSCs with room‐temperature phosphorescence (RTP) remains a great challenge. Herein, we propose a host–guest doping strategy to achieve both RTP and flexibility of OSCs. The single‐stranded crystal is highly bendable upon external force application and can immediately return to its original straight shape after removal of the stress, impressively emitting bright deep‐red phosphorescence. The theoretical and experimental results demonstrate that the bright RTP arises from Förster resonance energy transfer (FRET) from the triphenylene molecules to the dopants. This strategy is both conceptually and synthetically simple and offers a universal approach for the preparation of flexible OSCs with RTP.

Salivary peptidome analysis and protease prediction during orthodontic treatment with fixed appliances

Orthodontic tooth movement (OTM) occurs through proteolytic remodelling within the periodontium following the application of external force to the tooth. This study describes the first characterization of the salivary peptidome and protease profile during the alignment stage of fixed appliance orthodontic treatment. Unstimulated whole mouth saliva from 16 orthodontic patients (10 males, 6 females, mean (SD) age 15.2 (1.6) years) was collected prior to fixed appliance placement (T1), 1-h (T2), 1-week (T3) following fixed appliance placement and on completion of mandibular arch alignment (T4). Salivary peptides were extracted using filtration followed by mass spectrometry to identify amino acid sequences. Protease prediction was carried out in silico using Proteasix and validated with gelatin zymography and enzyme-linked immunosorbent assay. A total of 2852 naturally-occurring peptides were detected, originating from 436 different proteins. Both collagen and statherin-derived peptide levels were increased at T2. Proteasix predicted 73 proteases potentially involved in generating these peptides, including metalloproteinases, calpains and cathepsins. Changes in predicted activity of proteases over time were also observed, with most metalloproteinases showing increased predicted activity at T2–T3. Increased gelatinolytic activity and MMP8/MMP9 levels were detected at T3. Collectively, multiple protein targets and changes in protease-predicted activity during OTM have been identified.

Effects of scCO2 foaming process and post‐vulcanization method on cellular structure, mechanical properties, and thermal stability of PMVQ foams

AbstractIn this paper, the microcellular foam materials of methyl vinyl phenyl silicone rubber (PVMQ) were prepared by supercritical foaming technology (SFT) and high temperature compression molding. The effect of supercritical carbon dioxide (scCO2) on the vulcanizing properties of PVMQ composite was investigated because vulcanization of microcellular PVMQ foams played an important role on the cellular structure and mechanical properties. It was found that the sulfurization reaction of PVMQ composite was inhibited by scCO2, which led to reduction of apparent activation energy (Ea) of PVMQ composite. Compared with the existing post‐vulcanization process, the introduction of the high temperature molding can effectively improve the degree of vulcanization of microcellular PVMQ foams, which can solve the problem that the cellular structure will be destroyed during the application of external force. What's more, the mechanical properties of microcellular PVMQ foam were obviously improved. The maximum value of tensile strength and the compressive strength of microcellular PVMQ foam with the high temperature molding respectively increase by 34.7% and 133.3% compared with that of microcellular PVMQ foams with existing post‐vulcanization.

Functional Instability of the Second to Fifth Metacarpophalangeal Joints.

Clinically, functional instability (FI) of metacarpophalangeal joints (MCPJ) is not considered to represent a pathology. This excessive mobility can be detected by the application of external forces to a MCPJ at different angles. Our study aimed to measure the FI of 2nd to 5th MCPJ. A group of 36 healthy right-handed individuals were enrolled. The value of FI was measured in millimeters and verified by a CT scan. Statistical calculations was made in Statistica v.10.0. The largest values of the right and left-hand finger posterior displacement (FI) in the second to fifth MCPJ were obtained in the neutral position 0° (p&lt;0.05). Measurements of volar displacement of the proximal phalanx second to fifth MCPJs in both hands revealed higher values at position 0° (p&lt;0.05). 1. FI of the second to fifth MCPJs is determined by anatomical configuration and dynamic stabilizers. 2. Instability measurements show that posterior displacement of the proximal phalanges is greater by at least 1 mm in the 0° neutral position.

Evaluation of the mechanical behaviour of confectionery with porous structure under the application of external forces

Evaluation of the mechanical behaviour of confectionery with porous structure under the application of external forces

LINC complex independent perinuclear actin organization and cell migration

The link of the metazoan nucleus to the actin cytoskeleton is highly important for actin polymerization and migration of multiple cell types as well as for mechanotransduction and even affects the cellular transcriptome. Several mechanisms of organization of actin filaments next to the nuclear envelope have been identified. Among these mechanisms the most studied one is the Linker of nucleoskeleton and cytoskeleton (LINC) complex-dependent perinuclear actin organization. However, recently additional mechanisms have been identified: an Actin-related protein-2/3 (Arp2/3)-dependent perinuclear actin polymerization during migration of dendritic cells and a perinuclear actin rim that is formed in response to external force application or migration cues. In parallel, there are also reports on cancer cells that migrate in a LINC complex independent manner and on cancers with reduced expression of the LINC complex components. Thus, suggesting that LINC complex independent migration may be associated with tumour formation.