Force Method Research Articles

Molecular Insights into the Adsorption of Deposit Control Additives from Hydrocarbon Fuels.

Engine deposits can reduce performance and increase emissions, particularly for modern direct-injection fuel delivery systems. Surfactants known as deposit control additives (DCAs) adsorb and self-assemble on the surface of deposit precursors to keep them suspended in the fuel. Here, we show how molecular simulations can be used to virtually screen the ability of surfactants to bind to polyaromatic hydrocarbons, comprising a major class of carbonaceous deposits. We use molecular dynamics with the adaptive biasing force method to generate the potential of mean force as a function of the vertical distance between the surfactants and deposits in gasoline and diesel fuel surrogates. We find that a zwitterionic surfactant outperforms a conventional polyisobutylene succinimide for binding to these aromatic species. The amine groups in the succinimide headgroup only weakly adsorb on the polyaromatic deposit, while additional functional groups in the zwitterionic surfactant, particularly the quarternary ammonium ion, markedly enhance the binding strength. We decompose the adsorption free energies of the surfactants into their entropic and enthalpic components, to find that the latter dominates the attraction from these non-aqueous solvents. The adsorption free energy of both surfactants is slightly weaker from n-hexadecane (diesel) than iso-octane (gasoline), which is due to the larger steric barrier from stronger molecular layering of the former on the deposit. Density functional theory calculations of the adsorption of DCA fragments validate the force field used in the molecular dynamics simulations and provide further insights into the nature of the intermolecular interactions. The approach introduced here shows considerable promise for accelerating the discovery of novel DCAs to facilitate more advanced fuel formulations to reduce emissions.

A novel technique for precoagulation of blood vessels during saline-immersion colorectal endoscopic submucosal dissection: flushing forced method.

A novel technique for precoagulation of blood vessels during saline-immersion colorectal endoscopic submucosal dissection: flushing forced method.

Characterization of main degradation products from dendrobine under stress conditions by multistage cleavage of UPLC-ESI-IT-TOF.

Dendrobine is a sesquiterpene alkaloid primarily used in the treatment of inflammatory diseases, immune system disorders, and conditions related to oxidative stress. To understand the possible degradation pathways of dendrobine for its quality control, we conducted an in-depth investigation of its degradation products using forced degradation methods. The separation of dendrobine and its degradation products was achieved on a Shim-pack XR-ODS III (75 mm × 2 mm, 1.6 µm) column with a methanol-water mixture as the mobile phase under isocratic conditions, the isolated compounds were examined in positive ion mode with an ion trap-time of flight mass spectrometer (IT-TOF). In order to obtain in-depth structural information about the degradation products, mass spectrometry was performed using a five-stage fragmentation approach. This method allowed for thorough structural clarification via several rounds of selective fragmentation and high-resolution detection. System control and data acquisition were managed using LCMSsolution 3.81 software. The results showed that dendrobine undergoes significant degradation under oxidative, acidic, hydrolytic and thermal conditions, resulting in the formation of several degradation products with notable structural changes. Under oxidative conditions, dendrobine primarily generates two degradation products with mass increases of 16 Da and 32 Da, indicating mono-oxidation and di-oxidation reactions. Acidic degradation led to the identification of three degradation products, including a novel compound with an 18 Da mass increase, suggesting potential hydrolysis or dehydration reactions. Hydrolytic and thermal conditions resulted in the formation of two and three degradation products, respectively, with structural changes indicating possible molecular cleavage and reorganization mechanisms. In contrast, dendrobine exhibited strong stability under alkaline and photolytic conditions, with no significant degradation products detected. Detailed characterization of the degradation products via multi-stage mass spectrometry revealed key reaction pathways and mechanisms involved in dendrobine's degradation, providing critical insights for assessing its chemical stability and optimizing storage conditions.

Novel Approach for Solving an Assignment Problem using Brute Force Method

Novel Approach for Solving an Assignment Problem using Brute Force Method

An analytical solution for internal forces of shallow circular low-to-vacuum tunnel linings in soft soils

This paper presents an analytical solution derived with force method for the internal forces in the ring lining of maglev train tunnels, which are typically in a circular section and shallowly buried with low vacuum air pressure in the lining. The model incorporates the vacuum pressure induced by the differences in air pressures outside and inside the lining, and the vacuum pressure is assumed to be the active load exerting to the outside of the lining. The model assumes the vertical overburden acting on the lining is proportional to the soil depth at every particular point along the tunnel lining circumference. The lining-ground interaction, represented by tangential and normal resistance to the lining, is combined into the model and is comprehensively evaluated. The Mohr-Coulomb theory is used to estimate the interaction between tangential and normal resistance. The comparison with other models and case histories implies that the proposed model fits well for the field measurement data and results predicted with other models. Analyses based on the proposed model indicated that the vacuum pressure has a negligible effect on the bending moments acting on the lining, but its effect on the normal forces is significant. Parametric studies show that a higher cohesion and internal angle of friction of soils can induce a lower maximum bending moment and higher normal force, indicating that the better the soil conditions the thinner the lining. The cover-to-diameter ratio C/D impacts the maximum bending moment and the optimum C/D is approximately 0.20 in this study, a generally soft soil case.

Numerical study on the back slope effect of trapezoidal canyon slope under oblique incidence of P-SV waves

The incident angle of seismic waves influences the dynamic response of rock slopes. However, the relationship between the back-slope effect in strong earthquake areas and the incident angle has not been well-explained. Based on the equivalent nodal force method and the viscoelastic artificial boundary theory, the oblique incidence of seismic P-wave and SV-wave are carried out in FLAC3D software. The accuracy of the proposed method is verified by comparing it with the results of the theoretical solution and another numerical result. The dynamic response of trapezoidal canyon slope under oblique incidence of P-waves and SV-waves was studied, and the effects of different slope angles and canyon widths were analyzed. The study reveals a pronounced back-slope effect under the action of the P-wave and SV-wave, and the slope’s horizontal direction dynamic response plays an important role. At the same location on the slope surface, the relative horizontal acceleration of the slope increases with the incident angle of P-waves and SV-waves, and the maximum value on the back-slope side is approximately 19 times and 6.8 times that of the front-slope side, respectively. Slope angle significantly affects the back-slope side’s dynamic response, showing an increase with increasing slope angle, while canyon width has a limited impact.

The Influence of Rubber Hysteresis on the Sliding Friction Coefficient During Contact Between Viscoelastic Bodies and a Hard Substrate

This paper describes research aimed at the experimental determination of the influence of rubber hysteresis on the friction coefficient between rubber samples for making soles and granite tiles. In the experiments, four types of shoe rubber with similar hardness and different hysteresis properties and two granite tiles with different roughnesses (smooth and anti-slip) were used. The determination of rubber hysteresis was carried out experimentally on a uniaxial testing machine. The friction coefficient was measured using a device specially developed for this type of test, which was based on the pulling force method, while the measurement conditions were based on the EN 13893:2011 standard. The friction coefficient was measured at two different speeds, 50 mm/s and 300 mm/s, with different surface conditions. Using regression analysis and the Taguchi method, the data obtained from the experiments were analyzed to determine the influence of parameters on the friction coefficient. The experimental research shows that different rubber mixtures with the same or similar hardness could have different hysteresis properties but also different friction properties.

Ultimate limit-state design of textile-reinforced concrete folded floor panels

Purpose of reseach. The main goal of this study is to evaluate the effectiveness of using non-metallic meshes made of high-strength fibres in the reinforcement of folded elements. For this purpose, methods for calculating folded structures made of concrete composites are investigated, and a comparative calculation of the structure with various reinforcement parameters is performed.Methods. The study analyzes an algorithm for calculating reinforced cement structures using the limit force method with the transition from the original folded section to the reduced section. Using the method under study, we calculated a thin folded panel reinforced with meshes of various materials with a constant mesh reinforcement coefficient. Welded steel mesh, high-strength glass fiber textile mesh and carbon fiber textile mesh were considered as reinforcement. Simultaneously, the inverse problem was solved, within the framework of which the reinforcement coefficient necessary to ensure the same load-bearing capacity of the section when using different reinforcing materials was selected.Results. Sample of section reinforced with carbon fiber mesh exhibit the greatest ultimate load of 14.5 kNm . Sample of section reinforced with glass fiber and welded steel mesh exhibit ultimate load of 6.4 kNm and 1.72 kNm, respectively. Inverse problem was also solved. The reinforcement ratio necessary to ensure equal load-bearing capacity of the panel reinforced with different materials was determined. The reinforcement ratios of steel mesh (S), AR-glass textile (G) and carbon textile (C) were found as S:G:C=1:0.26:0.12.Conclusion. Reinforcement of concrete composites with non-metallic meshes has significant potential for the design of lightweight spatial structures for roofing buildings and structures. The use of high-strength reinforcing textile meshes makes it possible to achieve panel strength comparable to that of traditional reinforced concrete products. It is necessary to consider other strength calculations of folded panels reinforced with non-metallic meshes and experimentally confirm the results of analytical calculations.

Control of Integrated Circuits Crystals' Surface Microrelief and Defects of Heteroand Submicrostructures by the Atomic Force Microscopy Method

The aim of the work was to study the structure and defects of a channel transistor with two types of conductivity (p and n), the submicrostructures based on nickel silicide films, and the seed layers based on AlN using atomic force microscopy (including conductive or electric force method, which allow one to study the electrical conductivity of the material surface). The influence of the manufacturing technology and local oxide formation on the relief and structure of the pand n-type transistor was established. The local oxide is necessary for the electrical isolation of the transistors from each other. The surface roughness is higher on the surface and outside the p-channel transistor than on the n-channel transistor. When examining the AlN layers both in the topography mode and in the adhesion mode, defects in the form of pores were revealed, which are places of electrical breakdowns, which worsens the properties of the such heterostructures. With an increase in the temperature and time of nitriding, the defects of the AlN layers significantly decrease. The conductive areas on the surface of the nickel silicides after rapid thermal treatment at 300 and 400 °C using electric force microscopy were detected, which shows incomplete formation of nickel silicide during the treatment. Thus, the efficiency of the atomic force microscopy method using a specialized conductive technique as a method for monitoring microelectronic components was demonstrated.

Strength of bending concrete filled steel elements of improved design

An improved design of concrete filled steel tube element of rectangular cross-section subjected to bending has been proposed, which has greater strength and requires significantly greater energy consumption for destruction compared to known analogues. To test the effectiveness of the proposed design, experimental studies were carried out on the strength of normal sections and the beam rigidity of concrete filled steel tube beams under four-point bending. Research has shown that by simultaneously strengthening the compressed and tensile zones, it was possible to increase the strength of normal sections of beams. The increase in strength of beams of the improved design averaged 42%. The rigidity of non-reinforced concrete filled steel tube beams turned out to be significantly higher compared to beams without filling the steel pipe with concrete. In the improved beams, the stiffness was still approximately 20% higher. The results of comparing the calculated strength of concrete filled steel tube beams using the limit force method with experimental data indicate their satisfactory agreement.

A novel approach for risk assessment optimization in big data platforms using SMT solvers

Big Data platforms store vast amounts of information, necessitating robust security measures, including risk-based approaches. Risk assessment, a key part of Information Security Management Systems (ISMS), involves evaluating threats, vulnerabilities, and documenting risks through risk registers. Organizations face the challenge of allocating resources effectively to implement controls that mitigate these risks. This involves calculating risk scores before and after control implementation and prioritizing them—an NP-Complete (Nondeterministic Polynomial-time Complete) problem. This paper presents a mathematical model for solving this using the Z3 Satisfiability Modulo Theories (SMT) solver. The model enables risk-based planning for security implementation in big data platforms. The results demonstrate the feasibility of the approach, with the system processing up to 11 risks (almost 40 million permutations) efficiently, compared to brute force methods, which struggle beyond six risks (720 permutations).

A nonlinear optimisation considering axle load transfer for enhancing adhesion utilisation of a locomotive with an oblique traction rod

Locomotives are susceptible to wheel slip when passing through the low adhesion sections. Wheel slip is more likely to occur on wheelsets with reduced axle load due to axle load transfer (ALT). To address this problem, we propose a nonlinear optimisation method for traction forces to improve the locomotive adhesion utilisation under the rail adhesion limitation. Firstly, we established an improved ALT model considering the rotation of the traction rod and verified its effectiveness through a field test. Then, we applied a sequential quadratic programming algorithm to optimise the traction forces with the constraints of the adhesion and ALT. Based on the proposed method, we analysed the impact of static axle load, traction force limitations, and coupler pitch angle on the optimisation results. The results indicate that the optimisation method can effectively utilize the axle load and adhesion of all wheelsets under different factors. A train dynamics model incorporating the optimisation module is further developed to investigate the method's effectiveness in improving the adhesion utilisation of locomotives. Simulation results demonstrate that the proposed optimisation method can enhance the maximum traction force of the locomotive, effectively preventing the wheelset with reduced axle load from slipping.

Implementation of Gaussian quadrature in Python program for grillages with curved elements

This paper demonstrates the development of a Python program for linear-elastic structural analysis of grillages featuring circumferential arc-shaped and regular straight elements subjected to concentrated and distributed loads. The algorithm is based on the Finite Element Method. The force method was employed to compute the flexibility matrix, followed by the determination of the stiffness matrix and load vectors through inversion. A Gauss-Legendre Quadrature was incorporated in order to have a better control on accuracy for displacements, rotations, forces and moments. Results were validated through comparisons with literature data and similar software where curved structures are simulated using numerous straight elements. It was demonstrated that the Python-based program yields results closer to the exact solution with simplified input data, highlighting the effectiveness of both programming language and Gauss quadrature technique in structural analysis.

Translational joint in a Finite Element Analysis program of 2D frames with straight and curved elements

This paper describes the development of an algorithm for the structural analysis of bidimensional frames with straight and curved elements that include a translational joint which can be set to any specified angle. The code was written in Fortran following a Finite Element Method-based structure. Three elements were considered: a circumferential arc-shaped; a straight bar with cross-sectional height varying according to a linear polynomial function; and the traditional straight element with constant inertia. All Stiffness matrices and load vectors were derived from the inversion of their corresponding Flexibility matrices obtained using the Force Method. In a few cases, a Gaussian Quadrature was needed in order to calculate the integral. The resulting program was validated against solutions found in the scientific literature in addition to structures created and solved by the authors using the Virtual Work Method, and it is shown to give very accurate predictions for displacements and rotations as well as reactions and internal forces (axial, shear and bending).

A non-destructive measurement method for axial force using torque in connecting bar with joint bearing ends

ABSTRACT The measurement of axial force in connecting bar is widely used in scenarios such as condition monitoring, motion controlling and fatigue analysing of mechanisms. By measuring the torque applied to the bar, this paper proposes an innovative method for non-destructive obtaining axial force in connecting bar with joint bearing ends. A mechanical analysis of joint bearing is conducted, and a theoretical model of axial force and torque is established. An experimental setup for measuring axial force and torque is constructed, and then the theoretical model is refined. The bar axial force and torque formula is calibrated at different torsional speeds, and the method correctness and reliability are verified experimentally. In summary, in a non-destructive way, this method is innovative and practical, addressing issues like inaccuracies in measuring bars with variable cross-section, even unknown material and inside structure, achieving relatively accurate measurement of axial force in connecting bar without damage.

Video2Haptics: Converting Video Motion to Dynamic Haptic Feedback with Bio-Inspired Event Processing.

In cinematic VR applications, haptic feedback can significantly enhance the sense of reality and immersion for users. The increasing availability of emerging haptic devices opens up possibilities for future cinematic VR applications that allow users to receive haptic feedback while they are watching videos. However, automatically rendering haptic cues from real-time video content, particularly from video motion, is a technically challenging task. In this article, we propose a novel framework called "Video2Haptics" that leverages the emerging bio-inspired event camera to capture event signals as a lightweight representation of video motion. We then propose efficient event-based visual processing methods to estimate force or intensity from video motion in the event domain, rather than the pixel domain. To demonstrate the application of Video2Haptics, we convert the estimated force or intensity to dynamic vibrotactile feedback on emerging haptic gloves, synchronized with the corresponding video motion. As a result, Video2Haptics allows users not only to view the video but also to perceive the video motion concurrently. Our experimental results show that the proposed event-based processing methods for force and intensity estimation are one to two orders of magnitude faster than conventional methods. Our user study results confirm that the proposed Video2Haptics framework can considerably enhance the users' video experience.

Stope Dimension Analysis Based on Geomechanical Properties Using Brute Force Algorithm

Abstract Mining operations play a crucial role in meeting global resource demands, emphasizing the importance of determining optimal stope dimensions for safe and efficient ore extraction. However, the complexity arising from multiple geomechanical factors affecting stope stability poses challenges in identifying ideal dimensions. Traditionally, engineers use an iterative process for stability analysis, but its limited scope and time-consuming nature call for more efficient algorithms. This research proposes a series of algorithms based on the brute force method using Potvin’s empirical stability criterion. The algorithm efficiently generates and evaluates stope dimension scenarios, enabling comprehensive stability analysis. Testing on case studies demonstrates its remarkable speed and effectiveness, making it a valuable tool for mine planning and optimization.

Stratified Ocean Currents with Constant Vorticity

We analyze vertically stratified three-dimensional oceanic flows under the assumption of constant vorticity. More precisely, these flows are governed by the f-plane approximation for the divergence-free incompressible Euler equations at arbitrary off-equatorial latitudes. A discontinuous stratification gives rise to a freely moving impermeable interface, which separates the two fluid layers of different constant densities; the fluid domain is bounded by a flat ocean bed and a free surface. It turns out that the constant vorticity assumption enforces almost trivial bounded solutions: the vertical fluid velocity vanishes everywhere; the horizontal velocity components are simple harmonic oscillators with Coriolis frequency f and independent of the spatial variables; the pressure is hydrostatic apart from sinusoidal oscillations in time; both the surface and interface are flat. To enable larger classes of solutions, we discuss a forcing method, which yields a characterization of steady stratified purely zonal currents with nonzero constant vorticity. Finally, we discuss the related viscous problem, which has no nontrivial bounded solutions.

Advanced heave control of a hydrofoil-based autonomous surface vehicle: CFD modeling with integrated variable propeller revolution control

An innovative control strategy employing the Proportional-Integral-Derivative (PID) algorithm is proposed to address the heave stability challenges in the in-house developed hydrofoil-based Autonomous Surface Vehicle (HASV). This method regulates the HASV's heave motion by adjusting the propeller's revolution speed. After confirming that the aerodynamic load on the superstructure contributes less than 2% compared to the hydrodynamic load, a detailed numerical simulation study and recirculating water tunnel test were conducted to validate the reliability of the established Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD model for the HASV substructure. The integration of the PD controller for propeller revolutions into the CFD free-running model, which incorporates fully nonlinear and viscous effects, was achieved using the ‘Region-Moving’ method for the background domain and the Body Force Method (BFM) for the propeller domain. By analyzing the impact of various PD coefficients on heave control, optimal settings for the HASV were determined. Subsequent studies examined the vehicle's capability in draft correction and draft maintenance under wave conditions. The results of direct CFD-PD simulations demonstrate that the proposed heave control method effectively stabilizes the HASV under complex nonlinear environmental conditions, offering valuable insights for addressing similar heave control challenges in hydrofoil-based vehicles.

Solution of Internal Forces in Statically Indeterminate Structures Under Localized Distributed Moments

Classical methods for manually solving internal forces in statically indeterminate structures mainly include force and displacement methods. While the force method involves substantial work when solving the internal forces of structures with higher degrees of indeterminacy, the displacement method offers a fixed and easily understood approach. However, the displacement method requires prior knowledge of load constant formulas. Common methods for deriving load constant formulas include the force method, virtual beam method, and energy method. Nevertheless, deriving load constant formulas for localized distributed moments using these methods proves to be highly challenging. This study aims to derive load constant formulas for localized distributed moments. Firstly, the load constant formula for a single concentrated moment is derived using the formula for a single concentrated force. Then, the load constant formulas for localized uniform moments and localized linearly distributed moments are derived via the integral method, leveraging the load constant formula for a single concentrated moment. This approach addresses the problem of solving internal forces in statically indeterminate structures under distributed moments via the displacement method. Finally, the proposed approach is verified using three typical examples. The promotion of the research results in this article in teaching can deepen students’ understanding of load constants and the displacement method, enrich teaching content, and have certain engineering applications and teaching practical significance.