Torsional Model Research Articles

Encoding dynamical information of protein from normal mode analysis as multigraphs for function prediction by graph neural networks and highlighting functionally-critical residues.

Dynamics of proteins are crucial for its ability to perform its functions, but are often overlooked in the plethora of protein function prediction methods. However, the need for faster screening over sequence-structure-function spaces is ever growing due to the increase in number of known peptide sequences and structures without function annotations. Machine learning methods are commonly implemented to meet the latter need to moderate success, with graph neural networks (GNN) gaining traction in recent years due to its rather intuitive mapping to protein structures. On the other hand, encoding the dynamics of proteins is yet a critical outstanding issue. In our attempt to close this gap, we encode the dynamical information of modal shapes and frequencies, along with the protein contact map, into multigraphs to aid graph neural networks in their prediction. This reduction of mode shapes into graphs is done by calculating the correlation between pairwise residue movements, then weight-averaging the correlation across multiple mode shapes, taking into consideration the equipartition theorem. The anisotropic network model (ANM) and the torsional network model (TNM) are implemented for modal analysis, and the two network models are compared within our framework. The method is tested on various datasets with different sequence similarity cutoffs, and the results compared with existing methods. Furthermore, we are able to extract from our model the dynamically-critical residues, such as hydrogen-binding and ligand-binding sites, for each of the protein's functions. As such, the proposed model provides insight to critical mutation points, facilitating further investigation and understanding of the protein.

Experimental investigation of gear rattle and nonlinear dynamic interaction in a dual-clutch transmission

Dual-clutch transmissions (DCT) having high efficiency and powershift are widely used in passenger cars thanks to the dual-clutch and preselection strategies. However, the dual-clutch transmission gear rattle behaviour still needs to be fully discovered, especially the influence caused by different preselection strategies. In this regard, the gear rattle sensitivity and dynamic evolution of the geartrain in a DCT were experimentally investigated on a rattle test bench and vehicle powertrain. The rattle response and instantaneous speed of all speed gears potentially contributing to the overall rattle are measured. The measured results from the DCT were compared with a similar structure six-speed manual transmission to depict its characteristics. Moreover, a multi-degree-of-freedom nonlinear torsional model was established to gain the nonlinear dynamic response along with the rising torsional irregularities; the model considers the crucial parameters affecting rattle behaviour. Two qualitative criteria were consequently given based on the numerical results and the law of the gear motion.The experimental results on the rattle test bench show that the DCT rattle behaviour varies with different preselected gears and is quite different from the manual transmission. The rattle sensitivity curves disclose an abrupt jump-up phenomenon when the excitation level reaches a certain level. The nominal input speed, preselection gear and lay-shaft configuration considerably determine the excitation level and amplitude increase of the jump-up on the rattle response. Based on the proposed qualitative criteria, a strongly nonlinear dynamic response is observed in the loaded gear pair under preselection conditions and deteriorates the rattle noise. A considerable dynamic interaction between active and passive sub-gearboxes is found. The appearance of the harmonics of the excitation frequency on the active input shaft that generates the high impact amplitude and density contributes to the jump-up and high vibration response on the rattle sensitivity. Finally, vehicle experiments reproduce the rattle jump-up and dynamic torsional interaction in the DCT powertrain are confirmed.

A lateral–torsional buckling demonstration model using 3D printing

It is well-established that beams of relatively narrow cross-section have a tendency to buckle laterally when loaded. This type of lateral–torsional instability, which has considerable practical importance in a variety of thin-walled structures, is a classical buckling situation in which the critical load is related, among other things, to characteristic features of the cross-section. In this short paper, 3D-printing is exploited to provide a parametric study based on a fixed cantilever geometry in which a number of standard cross-sectional forms are compared in terms of their effect on this kind of buckling behavior.

Analysis of longitudinal and torsional vibration of mining scraper conveyor under the over bending section working condition

Considering that the scraper will produce longitudinal and torsional pendulum vibration when passing through the bending section, and have a great influence on the motion characteristics of the scraper conveyor, this paper studies the longitudinal and torsional pendulum coupling vibration characteristics of the scraper conveyor under the working condition of over-bending section for the first time. Firstly, the simplified model of torsional pendulum vibration of scraper chain system is established based on Voigt model and point-by-point tension method. Then, the change law of scraper group vibration and chain tension under the condition of scraper bending is studied. Thirdly, through the influence area and attenuation characteristics of torsional pendulum vibration, the thumbnail model of torsional pendulum vibration is constructed. Finally, the longitudinal and torsional pendulum coupling vibration dynamic model of the scraper chain system is constructed based on the torsional pendulum vibration abbreviation model, and the overall longitudinal and torsional pendulum vibration characteristics of the scraper conveyor are studied when the scraper is over the bending section. The conclusion of this paper provides a theoretical basis for better understanding the operation characteristics of scraper conveyor in coal mine.

Three-dimensional Newtonian gravity with cosmological constant and torsion

In this paper we present an alternative cosmological extension of the three-dimensional extended Newtonian Chern–Simons gravity by switching on the torsion. The theory is obtained as a non-relativistic limit of an enhancement and U(1)-enlargement of the so-called teleparallel algebra and can be seen as the teleparallel analogue of the Newtonian gravity theory. The infinite-dimensional extension of our result is also explored through the Lie algebra expansion method. An infinite-dimensional torsional Galilean gravity model is presented which in the vanishing cosmological constant limit reproduces the infinite-dimensional extension of the Galilean gravity theory.

An Empirical Torsional Spring Model for the Inclined Crack in a 3D-Printed Acrylonitrile Butadiene Styrene (ABS) Cantilever Beam.

This paper presents an empirical torsional spring model for the inclined crack on a 3D-printed ABS cantilever beam. The work outlined deals mainly with our previous research about an improved torsional spring model (Khan-He model), which can represent the deep vertical (90°) crack in the structure. This study used an experimental approach to investigate the relationships between the crack angle and torsional spring stiffness. ABS cantilever beams with different crack depths (1, 1.3 and 1.6 mm) and angles (30, 45, 60, 75 and 90°) were manufactured by fused deposition modelling (FDM). The impact tests were performed to obtain the dynamic response of cracked beams. The equivalent spring stiffness was calculated based on the specimen's fundamental frequency. The results suggested that an increased crack incline angle yielded higher fundamental frequency and vibration amplitude, representing higher spring stiffness. The authors then developed an empirical spring stiffness model for inclined cracks based on the test data. These results extended the Khan-He model's application from vertical to inclined crack prediction in FDM ABS structures.

A Modeling and Calibration Method of Heavy-Duty Automated Fiber Placement Robot Considering Compliance and Joint-Dependent Errors

Abstract The accuracy of industrial robots is critical in many manufacturing applications. In this case, a self-developed automated fiber placement heavy-duty robot is used for the lay-up of carbon fiber composite prepregs, which requires high positioning accuracy. The mass of the robot body and end-effector exceeds 3 tons and 1 ton, respectively, resulting in considerable deformation and other errors due to the huge size and mass. Paradoxically, the work that our robot engaged in requires high precision, and the positioning accuracy needs to be less than 0.5 mm. This paper conducts a comprehensive analysis of the robot joint error, so as to improve the accuracy of the robot. A torsional and capsize deformation model for joints is established. In addition, the capsize torque and capsize axis of joint deformation are derived to determine the transformation relationship between joint frames. Chebyshev polynomials are used to describe joint-dependent errors. The Levenberg–Marquarelt (L–M) algorithm was used to identify the error model parameters. The effects of different error factors on the positioning accuracy were compared and analyzed. The validation result shows that the proposed model describes 88.11% of the positioning error, and the average residual error of the calibration can reach 0.132 mm. The identified joint-dependent error and the compliance error are 0.296 mm and 0.240 mm, accounting for 26.67% and 21.62% of the positioning error, respectively.

Slip ratio estimation of electric wheels based on tire force and road conditions

The independently controlled electric wheels of distributed drive vehicles provide faster and more accurate actuators for vehicle slip ratio control. Meanwhile, the estimation of the slip ratio of electric wheels has been of vital importance for the dynamics control of distributed drive electric vehicles. However, the conventional slip ratio estimation method is hard to accurately estimate the slip ratio under steering conditions without multiple observations, increasing the cost and introducing errors. Considering that the output torque and motor rotation rate of electric wheels can be accurately collected, the novel slip ratio estimation method takes advantage of the signals of the electric wheels and requires fewer vehicle sensors. Based on the torsional vibration model of electric wheel, the slip ratio estimation method was proposed and validated by simulations and experiments. With the drum dynamometer, the slip ratio estimation method was applied to a single electric wheel for testing, proving the feasibility and accuracy of the proposed method. The slip ratio estimation was finally applied to a fuel cell heavy truck for road tests, of which the results show that the error index is reduced from 0.0152 to 0.0064 compared to the conventional slip ratio estimation method, confirming the good estimation performance achievable via the proposed method.

First-principles study of torsional single-walled carbon nanotubes

The controllable band gap of single-walled carbon nanotube (SWCNT) has become a research hotspot. This study introduces a torsional model that involves each rotating carbon atom along the axial direction of SWCNT, and a detailed description of the model creation process. Two guidelines for constructing the model are proposed, and the self-consistency of the torsion model is established through first-principles density functional theory. Initially, the band gap map of SWCNTs under torsion is present. As the twist strength increases, the band gap of SWCNT undergoes several phase transitions, including semiconductor-metal transition and metal-semiconductor transition. Moreover, we investigate the variations in the average bond length, average bond angle, and diameter of SWCNT under torsion. Furthermore, this work turns to the analysis of carbon atomic energy statistics, revealing distinct energy changes for different types of single-walled carbon nanotubes under identical torsion intensity. The findings shed light on the controllable band gap of SWCNTs, offering a theoretical foundation for the development of nanoelectronic devices and microintegrated circuits utilizing single-walled carbon nanotubes. In conclusion, this research presents a novel approach for exploring the controllable band gap of single-walled carbon nanotube through torsional manipulation. Theoretical insights into the behavior of SWCNTs under torsion provide valuable contributions to the field and pave the way for potential applications in nanoelectronics and microintegrated circuits.

Protective effects of propolis on ischemia-reperfusion injury in a rat testicular torsion and detorsion model.

The torsion model of testis in a rat was adopted for evaluation of possible effects of propolis (Prop) on ischemia-reperfusion (IS/REP) injury. The healthy male Wistar rats (totally 24 animals) were randomized into four groups (n = 6) and animals experienced bilateral testicular torsions as follows: In sham group just, laparotomy was performed and in IS group, animals experienced a 3 hr period testicular IS. In IS/REP group, a 3 hr period of IS followed by a 3 hr period of testicular REP for left testis and a one-week testicular REP for right testis were done. In this group animals were gavaged by 1.00 mL normal saline 1 hr before the onset of IS. In IS/REP/ Prop group, the same procedures for IS/REP animals were followed as well as gavage of 1.00 mL Prop extract solution 1 hr before the onset of IS. Analyses of biochemistry, histology, inflammatory biomarkers and sperm parameters were carried out. In IS/REP/Prop group, nitric oxide synthase malondialdehyde, myeloperoxidase and 8-hydroxy-2 deoxyguanine in IS/REP/Prop group were significantly decreased and, superoxide dismutase, total glutathione, glutathione peroxidase, glutathione reductase and glutathione S-transferase were significantly increased compared to the other animals. In IS/REP/Prop group, seminiferous tubules (with normal spermatogenesis) showed all stages of spermatogenic cells with plentiful spermatozoa. Tubular deterioration and atrophy and spermatogenic cell loss in were seen in a limited extent. The mean concentrations of Interleukin-1 beta and tumor necrosis factor alpha in IS/REP/Prop were significantly decreased. Sperm quality was significantly improved by Prop in IS/REP/Prop group. It was concluded that Prop could be supportive in diminishing IS/REP injury in testicular tissue exposed to ischemia.

An Attempt to Analyze a Human Nervous System Algorithm for Sensing Earthquake Precursors

We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a prediction accuracy higher than 70% and a confidence level of 95% over a 12-year period. Since the reliable earthquake precursor signals described by Ada and the characteristics of Alfvén waves match quite well, this paper proposes a hypothesis on how earthquakes are triggered based on the Alfvén (Q G) torsional wave model of Gillette et al. When the plume of the upper mantle column intrudes into the magma and lithosphere of the soft flow layer during the exchange of hot and cold molten material masses deep inside the Earth’s interior during ascent and descent, it is possible to form body and surface plasma sheets under certain conditions to form Alfven nonlinear isolated waves, and Alfven waves often perturb the geomagnetic field, releasing huge heat and kinetic energy thus triggering earthquakes. To explain the complex phenomenon of how Ada senses Alvfen waves and how to locate epicenters, we venture to speculate that special magnetosensory cells in a few human bodies can sense earthquake precursors and attempt to hypothesize an algorithm that analyzes how the human biological nervous system encodes and decodes earthquake precursors and explains how human magnetosensory cells can solve complex problems such as predicting earthquake magnitude and locating epicenters.

Study on Active Control of Stick-slip Vibration of Drill String System

The stick-slip vibration phenomenon of drill string widely exists in the drilling process, which has a great negative impact on drilling equipment, efficiency, cost and safety. In order to effectively suppress the stick-slip vibration of the drill string system, a two-degree-of-freedom torsional vibration model of the drill string system is established considering the nonlinear friction between the drill bit and rock. Based on this model, an optimal LQR controller is designed to suppress the stick-slip vibration of drill string, and the driving torque is fed back in real time through the state error. The effectiveness of the controller under parameter perturbation is verified by simulation analysis. The results show that the controller can effectively suppress the stick-slip vibration of drill string system under the desired speed, feedforward torque, start time and bit weight parameter perturbation, achieve real-time feedback of driving torque, and ensure that the angular velocity of rotary table and BHA can be tracked and maintained at the desired speed in a short time. The control effect shows good steady-state error and dynamic performance. The research results have a certain reference significance for suppressing stick-slip vibration of drill string system and improving drilling efficiency.

The effect of protocatechuic acid on ovarian histopathology and reserve in rat ovarian torsion model.

The aim of the study is to investigate the effects of Protocatechuic Acid (PCA), which is an antioxidant, anti-inflammatory and anti-apoptotic agent, on ovarian tissue and ovarian reserve against ischemia-reperfusion (IR) injury in a rat ovarian torsion model. Reactive oxygen radicals cause histopathological changes in the ovarian tissue during the reperfusion phase. PCA may have protective effects on ovarian tissue and reserve due to its antioxidant and antiapoptotic properties. A total of 24 Wistar adult female rats were divided into 3 groups as the control (sham operation, n = 8), IR (Ischemia-Reperfusion, n = 8), and IR+PCA (Ischemia-Reperfusion + 80 mg/kg protocatechuic acid, n = 8). The IR and IR + PCA groups underwent 3 hours of ischemia followed by 3 hours of ovarian reperfusion. Protocatechuic acid (80 mg/kg) was administered to the IR+PCA group 30 minutes before reperfusion. After reperfusion, the ovaries were removed for histopathological and biochemical examination. Histopathological score and TUNEL+ cell count were significantly lower and AMH expression level was significantly higher in the IR+PCA group when compared to the IR group (p <0.05). However, in the comparison of the follicle counts, there was no statistically significant difference between all groups. Due to the increase in antioxidant activity, the MDA levels were found to be significantly lower in the IR+PCA group compared to the IR group (p < 0.05). Protocatechuic acid may be an effective antioxidant in protecting ovarian tissue and follicle reserve against IR injury of the ovary (Tab. 1, Fig. 4, Ref. 36).

Comparison of hyperbaric oxygen and ozone treatment for ischemia/re-perfusion injury in an experimental testicular torsion model.

This study aims to compare the effects of medical ozone (MO) therapy and hyperbaric oxygen (HBO) therapy in an experimental testicular torsion model by measuring the oxidant and antioxidant markers and examining the histopathological tissue damage findings. Thirty-two Wistar rats are used and are divided into four groups; (1) sham group (SG), (2) only ischemia/reperfusion (I/R) by testicular torsion, (3) HBO administered group, and (4) MO administered group. No torsion was conducted in the SG. In all other groups, rats underwent testicular torsion followed by detorsion to create an I/R model. After I/R, HBO was injected in the HBO group, and in the MO group, intraperitoneal ozone was applied. At the end of 1 week, testicular tissues were obtained for biochemical analyzes and histopathological examinations. Biochemically, malondialdehyde (MDA) levels were measured for oxidant activity, and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels were measured for antioxidant activity. Furthermore, the testicles were evaluated histopathologically. Both HBO and MO have significantly decreased MDA levels, compared with sham and I/R groups, resulting in decreased oxidation effects. The antioxidant GSH-Px levels in the HBO and MO groups were significantly higher than in the sham and I/R groups. In addition, the antioxidant SOD levels in the HBO group were significantly higher than sham, I/R, and MO groups. Therefore, the antioxidant effect of HBO was observed to be superior to MO, specifically considering SOD levels. Histopathologically, there was no significant difference between the groups (p>0.05). The study may extrapolate that both HBO and MO are antioxidant agents that can be used in testicular torsion. HBO treatment might improve the cellular antioxidant capacity due to increased antioxidant marker levels more than MO therapy. However, further studies are needed with a larger sample size.

Torsion among Women with Acute Lower Abdominal Pain: A Retrospective Cross-Sectional Study.

Background: Lower abdominal or pelvic pain is a common complaint among women and one of the most challenging findings to evaluate. We performed the present study to construct a new algorithm for predicting the chance of ovarian torsion among women with acute lower abdominal pain. Methods: This diagnostic retrospective cross-sectional study was performed on all female individuals who were referred to Imam Hossein Medical Center, Tehran, Iran, with the chief complaint of acute lower abdominal pain, and underwent laparotomy between 2010 and 2016. Clinical and paraclinical findings were evaluated to construct a predictive model for ovarian torsion. The variables were compared in 2 groups. The first group included individuals with a final diagnosis of ovarian torsion and the second group included those individuals with any diagnosis other than ovarian torsion. All data were compared between these 2 groups using SPSS software Version 21 to find the related findings with a predictive value for ovarian torsion. Results: A total of 372 participants were evaluated, of whom 116 participants (31.2%) had ovarian torsion (case group) and 256 participants had other diagnoses for their lower abdominal pain (control group). Nausea and vomiting (p < 0.001), tenderness (p < 0.001), the size of ovarian mass (p = 0.004), and the percentage of polymorphonuclear (p < 0.001) showed significant relationships with ovarian torsion as the final diagnosis. Multiple logistic regression models were constructed to predict the factors affecting ovarian torsion, and a scoring system was designed to predict ovarian torsion, with a sensitivity of 77.59% (68.9%- 84.8%) and specificity of 74.61% (68.8% 79.8%). Conclusion: The proposed model is suitable for predicting ovarian torsion and its necessary information is readily available from individuals' history, examination findings, laboratory results, and an ultrasound exam.

Effect and mechanism of wheel–rail adhesion on torsional vibration and stability of the braking system

A high-speed train braking system with the disc–pad sliding friction pair and the wheel–rail rolling friction pair is a classic torsional system. By adopting a developed braking system torsional dynamics model, the influences of dry and wet rail surface conditions on system dynamic responses were investigated. Further, the system stability under different disc–pad friction and wheel–rail adhesion characteristics was explored and the interaction mechanism between the disc–pad and the wheel–rail sub-systems was revealed. The results indicated that the wheel–disc torsional vibration was more complicated under the wet rail surface condition. Moreover, the braking system had worse stability when the negative slope characteristics of disc–pad friction and wheel–rail adhesion were interacted.

Torsion models for tensor-triangulated categories: the one-step case

Given a suitable stable monoidal model category $\mathscr{C}$ and a specialization closed subset $V$ of its Balmer spectrum one can produce a Tate square for decomposing objects into the part supported over $V$ and the part supported over $V^c$ spliced with the Tate object. Using this one can show that $\mathscr{C}$ is Quillen equivalent to a model built from the data of local torsion objects, and the splicing data lies in a rather rich category. As an application, we promote the torsion model for the homotopy category of rational circle-equivariant spectra from [18] to a Quillen equivalence. In addition, a close analysis of the one step case highlights important features needed for general torsion models which we will return to in future work.

Rational torus-equivariant stable homotopy V: The torsion Adams spectral sequence

We provide a calculational method for rational stable equivariant homotopy theory for a torus G based on the homology of the Borel construction on fixed points. More precisely we define an abelian torsion model, At(G) of finite injective dimension, a homology theory π⁎At(⋅) taking values in At(G) based on the homology of the Borel construction, and a finite Adams spectral sequenceExtAt(G)⁎,⁎(π⁎At(X),π⁎At(Y))⇒[X,Y]⁎G for rational G-spectra X and Y.

Improved Mesh Stiffness Method and Vibration Analysis of a Planetary Gear System with a Spatial Tooth Crack

Dynamic modeling and analysis are generally regarded as effective tools to investigate the vibration characteristics and fault mechanisms of planetary gear systems with a tooth crack fault. In actual gearboxes, the tooth crack is always a three-dimensional spatial surface, but it was usually simplified as a two-dimensional domain in most previous studies. In this paper, the tooth crack is modeled as a spatial shape that propagates along the crack depth, length and height directions simultaneously. Based on the potential energy principle, an improved analytical method is proposed to calculate the time-varying mesh stiffness (TVMS) of a planetary gear system with a spatial tooth crack. Furthermore, a coupled translational–torsional dynamic model is established for a planetary gear system including time-varying parameters and nonlinear factors. Numerical simulations are conducted to reveal the influences of the spatial crack propagation on the TVMS and vibration responses. In addition, an experimental study is carried out on a gear transmission test rig to verify the proposed analytical method and dynamic model. The mesh stiffness calculation method of the spatial cracked tooth and corresponding analysis results in this study might provide references to detect tooth crack faults in planetary gear systems.

Torsional vibration of open-ended pipe piles in saturated soil considering the construction disturbance

A soil-pipe pile-inner soil torsional dynamic interaction model is developed accounting for the radial inhomogeneity of the outer saturated soil as well as the soil plug (inner soil) due to the construction disturbance. Both the outer and inner saturated soils are divided into a series of annular zones in the radial direction with linearly varying soil properties from zone to zone. The governing equation of motion for each soil zone is established based on the Biot's two-phase linear theory and is solved to derive the circumferential shear stress at the pipe pile-soil interface in conjunction with the continuous conditions at the interface of adjacent soil zones. Further, the governing equation for the open-ended pipe pile is established and is solved to derive an analytical solution for the torsional vibration of the pile in the frequency domain. The developed solution is validated against the results of available analytical solutions. The validated solution is then used to examine the torsional vibration characteristics of the open-ended pipe pile under different saturated soil parameters and construction disturbance conditions. The results show that: (1) The pile resistance to torsional dynamic load is enhanced as the soil strengthening range or degree increases, while is reduced as the soil porosity, soil weakening range or degree increases; (2) The inner soil contributes a lot to the enhancement of pile torsional resistance.