Comprehensive Mechanical Model Research Articles

A Study of Tennis Score Evaluation Based on Logistic Regression and LSTM Neural Networks

In order to study the performance of athletes in the competition, this paper establishes a comprehensive evaluation mechanism and prediction model through mathematical modeling. Firstly, this paper uses the clustering algorithm to categorize the data and establishes a score evaluation model according to the weights. Then, a momentum evaluation score calculation function was constructed and compared with the results of logistic regression algorithm. Finally, a multi-indicator data system was established to predict the results of the game using the LSTM neural network model. The experimental results show that the model proposed in this paper has a good prediction effect and provides suggestions to the participants.

Ciliary muscles contraction leads to axial length extension--The possible initiating factor for myopia.

This study aimed to investigate the underlying factors driving the onset of myopia, specifically the role of the ciliary muscle's contraction in the elongation of the axial length of the eye. The retrospective study was conducted utilizing data from three ophthalmic centers in Shanghai and Beijing. Both Chinese and Caucasian children were involved. The axial length of the subjects' eyes was measured in both relaxed and contracted state of the ciliary muscle. A comprehensive mechanical model was also developed to observe the influence of ciliary muscle contraction on the axial length. This study included a sample of 198 right eyes of 198 myopic children. Of these, 97 were male and 101 were female, 126 were of Chinese ethnicity and 72 were Caucasian. The age of onset for myopia ranged from 5.9 to 16.9 years old. The axial length of the eye decreased 0.028 ± 0.007mm following dilation, indicating relaxation of the ciliary muscle (t paired student = 15.16, p = 6.72 x 10-35). In contrast, ciliary muscle contraction resulted in an increase in axial length. Considering proportionality, a significant 90.4% (179 eyes) exhibited a reduced axial length, while a minor 9.6% (19 eyes) demonstrated an increase post-mydriasis. Finite element modeling demonstrated that muscle contraction caused a tension force that transmits towards the posterior pole of the eye, causing it to extend posteriorly. The contraction of the ciliary muscle leads to an extension of the axial length. This could potentially be the initiating factor for myopia.

A mechanical model of ocular bulb vibrations and implications for acoustic tonometry.

In this study, we propose a comprehensive mechanical model of ocular bulb vibrations and discuss its implications for acoustic tonometry. The model describes the eye wall as a spherical, pre-stressed elastic shell containing a viscoelastic material and accounts for the interaction between the elastic corneoscleral shell and the viscoelastic vitreous humor. We investigate the natural frequencies of the system and the corresponding vibration modes, expanding the solution in terms of scalar and vector spherical harmonics. From a quantitative point of view, our findings reveal that the eyebulb vibration frequencies significantly depend on IOP. This dependency has two origins: "geometric" stiffening, due to an increase of the pre-stress, and "material" stiffening, due to the nonlinearity of the stress-strain curve of the sclera. The model shows that the second effect is by far dominant. We also find that the oscillation frequencies depend on ocular rigidity, but this dependency is important only at relatively large values of IOP. Thus close to physiological conditions, IOP is the main determinant of ocular vibration frequencies. The vitreous rheological properties are found to mostly influence vibration damping. This study contributes to the understanding of the mechanical behavior of the eye under dynamic conditions and thus has implications for non-contact intraocular pressure measurement techniques, such as acoustic tonometry. The model can also be relevant for other ocular pathological conditions, such as traumatic retinal detachment, which are believed to be influenced by the dynamic behavior of the eye.

Correction to: A comprehensive geometrical, metallurgical, and mechanical characteristic dynamic model of laser beam welding process

Correction to: A comprehensive geometrical, metallurgical, and mechanical characteristic dynamic model of laser beam welding process

A comprehensive critical heat flux mechanism model applicable to narrow rectangular channels

Critical heat flux (CHF) is an essential consideration for the economy and safety of the equipment operation. To understand the CHF triggering mechanism and two-phase evolution characteristics from nucleation boiling until the occurrence of boiling crisis in narrow rectangular channels, a series of CHF visualization experiments were carried out at different gap sizes (1–5 mm), with pressures ranging from 1 to 4 MPa, inlet subcooling ranging from 65 to 120 K, and mass flux ranging from 350 to 2000 kg/(m2·s). Based on the visualization results and energy balance analysis, a comprehensive CHF mechanism model capable of predicting DNB type boiling crisis, Dryout type boiling crisis, and PM (premature) type boiling crisis is proposed. Comparison of the presented CHF mechanism model with the CHF experimental values in one side heated narrow rectangular channels showed that the MRE and RMSE of DNB type boiling crisis are 15.2 % and 21.3 %, of Dryout type boiling crisis are 10.1 % and 12.7 %, and of PM type boiling crisis are 11.8 % and 13.8 %, respectively. The MRE and RMSE of CHF values in double sides heated narrow rectangular channel are about 13.6 % and 15.7 %, respectively, and of non-uniform heated narrow rectangular channel are about 15.9 % and 19.1 %, respectively.

A comprehensive geometrical, metallurgical, and mechanical characteristic dynamic model of laser beam welding process

A comprehensive geometrical, metallurgical, and mechanical characteristic dynamic model of laser beam welding process

Theoretical and experimental research on the mechanical properties of magnetorheological elastomers based on PDMS

Magnetorheological Elastomers (MREs) are smart materials with the ability to modulate their mechanical properties by changing the external magnetic fields, offering extensive potential for applications requiring variable stiffness and damping devices. A comprehensive mechanical model that explains the influence of loading conditions on the performance of MRE is crucial for understanding their intrinsic mechanisms during operation, and for the design, analysis, and improvement of intelligent energy dissipation and vibration control devices based on MRE. In this study, a four-parameter mechanical model was established to reveal the intrinsic mechanisms about the effects of external magnetic fields, loading frequency, and strain amplitude on the storage modulus, loss modulus, equivalent stiffness, and equivalent damping of MRE materials. The dynamic mechanical properties of the MRE materials prepared from carbonyl iron powder and PDMS were tested, and parameter identification of the established model was performed. The comparison results between the theoretical model analysis and the testing results demonstrated that the proposed mechanical model effectively characterizes and predicts the mechanical behavior of MRE materials. Furthermore, based on the prepared MRE materials, a stiffness-controllable energy dissipator operating in shear mode was designed and fabricated, and the mechanical performance of the shear energy dissipator was experimentally evaluated. This research provides a basis and guidance for the design and mechanical performance analysis of devices based on MRE, confirming the feasibility of MRE materials as core components in intelligent energy dissipation devices.

Theoretical modeling and analysis for mechanical properties of deepwater workover riser system

Low-cost midsize workover operation based on deepwater workover riser system is attractive. However, a comprehensive theoretical mechanical model for the complex workover riser system has not been found in present studies. In this paper, a coupled mechanical model of the workover riser system is established based on Euler-Bernoulli beam theory, hydraulic-pneumatic principles and the coupling relationship among workover risers, split tensioner system and workover platform. An analysis method for the coupled mechanical model is proposed based on the finite element method, Newmark-β method and Newton-Raphson method. A mechanical analysis program is finally developed in MATLAB and applied in mechanical property analysis of a deepwater workover riser system. It turns out that the bending moment of the workover riser system near the top part, tension ring and bottom part reaches extremes. Dynamic response envelopes of the workover riser system are obviously larger than static responses due to the dynamic excitation of wave loads and platform motions. It is also found that tension distribution ratio has obvious influence on mechanical properties of workover riser system. Mechanical response of the workover riser system decreases with TDR, whether in static or dynamic analyses.

Mechanical behavior of entangled metallic wire materials-polyurethane interpenetrating composites

Composite materials exhibit the impressive mechanical properties of high damping and stiffness, which cannot be attained by employing conventional single materials. Along these lines, a novel material architecture is presented in this work in order to fabricate composites with enhanced mechanical characteristics. More specifically, entangled metallic wire materials were used as the active matrix, whereas polyurethane was employed as the reinforcement elements. As a result, an entangled metallic wire material-polyurethane composite with high damping and stiffness was prepared by enforcing the vacuum infiltration method. On top of that, the mechanical properties (loss factor, energy consumption, and average stiffness) of the proposed composite materials were characterized by performing dynamic tests, and its fatigue characteristics were verified by the micro-interface bonding, as well as the macro-damage factor. The impact of the density, preloading spacing, loading amplitude, and exciting frequency on the mechanical properties of the composites were also thoroughly analyzed. The extracted results indicate that the mechanical properties of the composites were significantly enhanced than those of the pure materials due to the introduction of interface friction. Moreover, the average stiffness of the composites was about 10 times the respective value of the entangled metallic wire material. Interestingly, a rise in the loading period leads to some failure between the composite interfaces, which reduces the stiffness property but enhances the damping dissipation properties. Finally, a comprehensive dynamic mechanical model of the composites was established, while it was experimentally verified. The proposed composites possess higher damping features, i.e., stiffness characteristics, and maintain better fatigue characteristics, which can broaden the application range of the composites. In addition, we provide a theoretical and experimental framework for the research and applications in the field of metal matrix composites.

Application of Semi-Mechanistic Pharmacokinetic and Pharmacodynamic Model in Antimicrobial Resistance.

Antimicrobial resistance is a major public health issue. The pharmacokinetic/pharmacodynamic (PK/PD) model is an essential tool to optimize dosage regimens and alleviate the emergence of resistance. The semi-mechanistic PK/PD model is a mathematical quantitative tool to capture the relationship between dose, exposure, and response, in terms of the mechanism. Understanding the different resistant mechanisms of bacteria to various antibacterials and presenting this as mathematical equations, the semi-mechanistic PK/PD model can capture and simulate the progress of bacterial growth and the variation in susceptibility. In this review, we outline the bacterial growth model and antibacterial effect model, including different resistant mechanisms, such as persisting resistance, adaptive resistance, and pre-existing resistance, of antibacterials against bacteria. The application of the semi-mechanistic PK/PD model, such as the determination of PK/PD breakpoints, combination therapy, and dosage optimization, are also summarized. Additionally, it is important to integrate the PD effect, such as the inoculum effect and host response, in order to develop a comprehensive mechanism model. In conclusion, with the semi-mechanistic PK/PD model, the dosage regimen can be reasonably determined, which can suppress bacterial growth and resistance development.

China actively promotes CO2 capture, utilization and storage research to achieve carbon peak and carbon neutrality

China actively promotes CO2 capture, utilization and storage research to achieve carbon peak and carbon neutrality

Faceting and Flattening of Emulsion Droplets: A Mechanical Model.

When cooled down, emulsion droplets stabilized by a frozen interface of alkane molecules and surfactants have been observed to undergo a spectacular sequence of morphological transformations: from spheres to faceted liquid icosahedra, down to flattened liquid platelets. While generally ascribed to the interplay between the elasticity of the frozen interface and surface tension, the physical mechanisms underpinning these transitions have remained elusive, despite different theoretical pictures having been proposed in recent years. In this Letter, we introduce a comprehensive mechanical model of morphing emulsion droplets, which quantitatively accounts for various experimental observations, including the size scaling behavior of the faceting transition. Our analysis highlights the role of gravity and the spontaneous curvature of the frozen interface in determining the specific transition pathway.

Enhanced Oil Recovery for ASP Flooding Based on Biorthogonal Spatial-Temporal Wiener Modeling and Iterative Dynamic Programming

Because of the mechanism complexity, coupling, and time-space characteristic of alkali-surfactant-polymer (ASP) flooding, common methods are very hard to be implemented directly. In this paper, an iterative dynamic programming (IDP) based on a biorthogonal spatial-temporal Wiener modeling method is developed to solve the enhanced oil recovery for ASP flooding. At first, a comprehensive mechanism model for the enhanced oil recovery of ASP flooding is introduced. Then the biorthogonal spatial-temporal Wiener model is presented to build the relation between inputs and states, in which the Wiener model is expanded on a set of spatial basis functions and temporal basis functions. After inferring the necessary condition of solutions, these basis functions are determined by the snapshot method. Furthermore, a theorem is proved to identify parameters in the Wiener model. Combined with the least square estimation (LSE), all unknown parameters are determined. In addition, the ARMA model is applied to build the model between states and outputs, whose parameters are identified by recursive least squares (RLS). Thus, the whole modeling process for ASP flooding is finished. At last, the IDP algorithm is applied to solve the enhanced oil recovery problem for ASP flooding based on the identification model to obtain the optimal injection strategy. Simulations on the ASP flooding with four injection wells and nine production wells show the accuracy and effectiveness of the proposed method.

Parametric Studies of Mechanical Power Loss for Helical Gear Pair Using a Thermal Elastohydrodynamic Lubrication Model

In this study, a comprehensive mechanical efficiency model based on the thermal elastohydrodynamic lubrication (TEHL) is developed for a helical gear pair. The tribological performance of the helical gear pair is evaluated in terms of the average film thickness, friction coefficient, mechanical power loss, mechanical efficiency, etc. The influence of basic design parameters, working conditions, thermal effect, and surface roughness are studied under various transmission ratios. Results show that the contribution of thermal effect on the tribological performance is remarkable. Meanwhile, the rolling power loss constitutes an important portion of the total mechanical power loss, especially around the meshing position where the pitch point is located in the middle of contact line and the full elastohydrodynamic lubrication (EHL) state with the friction coefficient less than 0.005. The proper increase of normal pressure angle and number of tooth can improve the tribological performance. The influence of helix angle on the mechanical efficiency is less significant. A positive addendum modification coefficient for pinion and a negative addendum modification coefficient for wheel are good for improving the mechanical efficiency. The results provide the tribological guidance for design of a helical gear pair in engineering.

System identification and robust stabilization using structured controller for a novel ducted fan flying robot

This paper proposes complete procedures for system identification and control of a novel ducted fan flying robot on near hover flight condition. A control-oriented model structure is derived from a comprehensive mechanism model and identified by ground tests and flight experiments. In order to achieve state decoupling and reference tracking, a two-loop control architecture is employed. Non-smooth optimization algorithm is applied to efficiently tune controller parameters against multiple control requirements. Experimental results show that designed structured controller can provide better performance than classical proportional -integral -derivative (PID) controller.

Comprehensive critical mechanical model of covered karst collapse under the effects of positive and negative pressure

Three different processes of karst collapse under the effects of positive and negative pressure are discussed in this paper. The aim is to evaluate mechanisms of karst collapse. Critical mechanical models are established for each of three specific stages: arched holes in soil, vertical collapse of columns, and surface funnel-shaped collapse. Then, a comprehensive critical mechanical model of covered karst collapse under the effect of positive and negative pressure is developed. This was created based on Boyle’s law of gases. A method has been developed that provides a theoretical reference for quantifying early warnings of karst collapse. This procedure is based on fundamental coincidences between the physical situation and a check analysis. This is made by integrating the monitored results of an established karst water and gas pressure monitoring system into the output of a comprehensive critical mechanical model of covered karst collapse, which is affected by positive and negative pressures.

Power generation quality analysis and geometric optimization for solar chimney power plants

Solar chimney power plant (SCPP) is one of the promising power generation approaches for future applications of solar energy. An unsteady comprehensive mechanism model and a streamlined unsteady mechanism model of SCPPs are derived to analyze the energy conversion and transmission of the system in this paper. The streamlined unsteady mechanism model with concise expressions clearly indicates the correlations among the power output and geometric parameters. Both of the two models are verified by the experimental data from the Spain Manzanares demonstration plant. Moreover, a power quality factor is defined to evaluate the power generation quality of SCPPs both from the points of generation efficiency and power stability. The suitability of the geometric optimization of SCPPs based on the streamlined unsteady mechanism model is finally verified by an example. The coupling optimization results show that there are a strong positive correlation between the chimney height and the power quality factor, as well as a negative correlation between the solar collector radius and the power quality factor. Furthermore, the optimal solar collector height is a quadratic function relation with the chimney diameter, while the optimal thickness of the heat storage layer is little associated with other geometric parameters.

Mechanotransduction mechanisms for coordinating uterine contractions in human labor.

This review presents evolving concepts of how the human uterus contracts in pregnancy, with emphasis on the mechanisms of long-distance signaling. Action potential propagation has historically been assumed to be the sole mechanism for signaling and tissue recruitment over both short and long distances. However, data in animals and humans indicate that a single action potential does not travel distances greater than a few centimeters. To address this enigma, a long-distance signaling mechanism based on hydraulic signaling and mechanotransduction is developed. By combining this mechanism for long-distance signaling with the action potential propagation mechanism for signaling over short distances, a comprehensive dual mechanism model (or 'dual model') of uterine function is formulated. Mechanotransduction is an accepted phenomenon of myometrium, but the dual model identifies mechanotransduction as relevant to normal labor. For hydraulic signaling, a local contraction slightly increases intrauterine pressure, which globally increases wall tension. Increased wall tension then mechanically induces additional local contractions that further raise pressure. This leads to robust, positive feedback recruitment that explains the emergence of consistently strong contractions of human labor. Three key components of the dual model - rapid long-distance signaling, mechanical triggering, and electrical activity - converge with the concept of mechanically sensitive electrogenic pacemakers distributed throughout the wall. The dual model retains excitation-contraction coupling and action potential propagation for signaling over short distances (<10cm) and hence is an extension of the action potential model rather than a replacement.

Pathways of allosteric regulation in Hsp70 chaperones.

Central to the protein folding activity of Hsp70 chaperones is their ability to interact with protein substrates in an ATP-controlled manner, which relies on allosteric regulation between their nucleotide-binding (NBD) and substrate-binding domains (SBD). Here we dissect this mechanism by analysing mutant variants of the Escherichia coli Hsp70 DnaK blocked at distinct steps of allosteric communication. We show that the SBD inhibits ATPase activity by interacting with the NBD through a highly conserved hydrogen bond network, and define the signal transduction pathway that allows bound substrates to trigger ATP hydrolysis. We identify variants deficient in only one direction of allosteric control and demonstrate that ATP-induced substrate release is more important for chaperone activity than substrate-stimulated ATP hydrolysis. These findings provide evidence of an unexpected dichotomic allostery mechanism in Hsp70 chaperones and provide the basis for a comprehensive mechanical model of allostery in Hsp70s.

One to One Nonlinear Internal Resonance of Sensor Diaphragm Under Initial Tension

In this paper, investigations into the nonlinear asymmetric vibrations of a pressure sensor diaphragm under initial tension are presented. A comprehensive mechanics model based on a plate with in-plane tension is presented and the effect of cubic nonlinearity is studied. Specifically, the nonlinear asymmetric response is investigated when the excitation frequency is close to the natural frequency of an asymmetric mode of the plate. The obtained results show that in the presence of an internal resonance, depending on the initial tension, the response can have not only the form of a standing wave but also the form of a traveling wave. In addition, damping can be used to reduce the nonlinear effect and avoid the nonlinear interactions. The results of this work will benefit the design of diaphragm-type structures used in microscale sensors including pressure sensors.