Search

In this work, numerical modeling techniques were used to determine the thermo-hydraulic flow behavior, heat transfer enhancement, and overall thermal performance of fluid moving inside a corrugated pipe with constant heat flux. The flow patterns, pressure drops, heat transfer coefficients, friction factors, Nusselt numbers, ratios of the Nusselt number to the friction factor, the friction factor for corrugated pipe in comparison with smooth pipe, and the thermal performance factors under various corrugated pipe geometry configurations and ranges of Re number were all predicted numerically. The distance between the corrugated rings of 5, 10, and 15 mm, the ring angles of 120, 240, and 360 degrees, and the diameter of the corrugated rings of 1, 2, and 3 were all modified by numerical calculations. The numerical findings unmistakably demonstrate that the pressure drop increased dramatically as the corrugated patterns took shape. The Nusselt numbers (Nu) values of the designs were about 32.2, 40.5, and 45.6% higher than those of the smooth pipe for a Re of 12,021.9. The smooth pipe's Nu values were 17, 29, and 49.6% less than the value specifications. For the configuration, the Nu were, respectively, around 49.5, 45.7, and 40.9% higher. The results also show that the PEF performs best in the 1.2–1.6 range. Numerous correlation equations were created using Minitab, response surface methodology, and regression analysis for the friction factor (f), Nu, and PEF. These correlation equations' average errors were almost 13%, 9.75%, and 13.33%, respectively. [ABSTRACT FROM AUTHOR]

In this research, a sawing mechanism of a mobile buckling machine was innovatively designed for the forest resources and environmental characteristics of the northeast region of China. The northeast region of China is rich in forest resources, but the climate is cold, which puts high demands on the performance and adaptability of mechanical equipment. In this study, the three-dimensional modeling of the saw-cutting mechanism was completed by Pro/Engineer 5.0 modeling software, and an in-depth dynamics simulation analysis was carried out using dynamics simulation software. The study aims to assess the applicability of this saw-cutting mechanism in the northeast region of China, analyze its design characteristics, and explore possible directions for performance optimization. Through this study, we expect to provide valuable references for future technological innovations, as well as to promote the practical application and development of mobile buckling machines in cold regions. This research not only has regional characteristics, but also reflects the innovative idea of combining mechanical equipment design with environmental adaptability. [ABSTRACT FROM AUTHOR]

Due to manufacturing error and wear, the profiles of bushing and pin in revolute clearance joints are usually non-circular, while traditional kinematic models for revolute clearance joints generally assume a circular profile for the pin or bushing, which may not be able to accurately capture the kinematic behavior of real revolute joints in multibody systems. To this end, a curvature center method was proposed for the kinematic modeling of revolute clearance joints with noncircular bushing and pin. In the proposed method, both the noncircular bushing and pin were discretized, and the curvature center and radius corresponding to each discrete point were then obtained to detect the point of contact between the bushing and pin based on their kinematic constraints. The number of discrete points was determined based on both accuracy and efficiency of the proposed curvature center method, which was then applied to model a revolute clearance joint between the slider and the link of a slider-crank mechanism. Via comparison to the traditional geometric center method and discrete point method, it was validated that the proposed method can achieve a comparable accuracy in modeling revolute joints with a circular pin. The unique advantage of the proposed curvature center method is its ability in modeling revolute joints with noncircular bushing and noncircular pin, which was also demonstrated via a series of simulations. Simulation results show a significant influence of noncircular bushing and noncircular pin on the dynamic response of the multibody system. This implies the promising value of the proposed method in studying the effect of manufacturing error or wear of both bushing and pin on the system's dynamic performance and/or service life. [ABSTRACT FROM AUTHOR]

Candida albicans and Aspergillus fumigatus are recognized as significant fungal pathogens, responsible for various human infections. The rapid emergence of drug-resistant strains among these fungi requires the identification and development of innovative antifungal therapies. We undertook a comprehensive screening of 297 naturally occurring compounds to address this challenge. Using computational docking techniques, we systematically analyzed the binding affinity of each compound to key proteins from Candida albicans (PDB ID: 1EAG) and Aspergillus fumigatus (PDB ID: 3DJE). This rigorous in silico examination aimed to unveil compounds that could potentially inhibit the activity of these fungal infections. This was followed by an ADMET analysis of the top-ranked compound, providing valuable insights into the pharmacokinetic properties and potential toxicological profiles. To further validate our findings, the molecular reactivity and stability were computed using the DFT calculation and molecular dynamics simulation, providing a deeper understanding of the stability and behavior of the top-ranking compounds in a biological environment. The outcomes of our study identified a subset of natural compounds that, based on our analysis, demonstrate notable potential as antifungal candidates. With further experimental validation, these compounds could pave the way for new therapeutic strategies against drug-resistant fungal pathogens. [ABSTRACT FROM AUTHOR]

Due to the limited availability of fault samples and the expensive nature of marking fault samples in Electric Multiple Unit (EMU) gearbox monitoring data, a study was conducted to simulate the degradation process of key components in the CRH5 gearbox using rigid–flexible coupling dynamics. Vibration acceleration data from the simulation were utilized to create a six-dimensional hybrid feature domain representing the degradation process. By leveraging the capabilities of the Hidden Markov Model (HMM) for handling hidden transitive probabilities in temporal data and Gated Recurrent Unit (GRU) for addressing long-distance and high-dependence temporal data, a GRU-HMM fault prediction model was developed. This model was validated using monitoring data and the six-dimensional hybrid feature domain from the CRH5 gearbox and compared against actual maintenance records. The findings indicated that the GRU-HMM fault prediction model can effectively recognize the degradation patterns of multiple components, offering higher accuracy in fault prediction compared to traditional models. These research outcomes are expected to optimize EMU maintenance schedules based on usage conditions, enhance EMU utilization rates, and reduce operational and maintenance costs, thereby providing valuable theoretical support. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the spindle system of the new disc chipper for forestry residues such as branch wood, tending timber and thinning timber was studied, and the installation structure of the cutter head and spindle of the chipper was different from the current mainstream installation form, and it was necessary to verify whether the spindle system met the structural design requirements in the process of cutting logs. ADAMS software and ANSYS software were used to establish the rigid-flexible coupling model of the flexible spindle, the law of the periodic variation of cutting force was added to the model, and the axial and radial amplitudes of the spindle at the connection point between the spindle and the cutter head were simulated and extracted, and the maximum vibration amplitude of the cutter head in the radial direction was 175μm, which met the long-term operation standard of the rotating shaft stipulated in the Chinese national standard. This study provides a verification of the rationality of the new chipper spindle system, and provides a theoretical basis for the structural improvement of the chipper spindle system. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The experiments involving protein denaturation and refolding serve as the foundation for predicting the three-dimensional spatial structures of proteins based on their amino acid sequences. Despite significant progress in protein structure engineering, exemplified by AlphaFold2 and OmegaFold, there remains a gap in understanding the folding pathways of polypeptide chains leading to their final structures. We developed a lightweight tool for protein unfolding visualization called PUV whose graphics design is mainly implemented by OpenGL. PUV leverages principles from molecular biology and physics, and achieves rapid visual dynamics simulation of protein polypeptide chain unfolding through mechanical force and atom-level collision detection and elimination. After a series of experimental validations, we believe that this method can provide essential support for investigating protein folding mechanisms and pathways.

Abstract This paper aims to reduce friction pair erosion of the clutch in the case of continuous shift; the dynamic separation process of the friction pair is investigated. The temperature of the friction pair, friction torque, and separation speed in the separation process are taken as the research objects, and the dynamics simulation model and finite element thermal coupling simulation model of the clutch separation process are established. The nonlinear dynamic separation characteristics of the friction pair are investigated by comparing and analyzing the effects of control parameters such as rotational speed difference, damping ratio, and lubricant viscosity on the friction torque, friction pair separation speed, separation gap, and contact stress during the separation process. The gap recovery coefficient is proposed as a response indicator for observing the separation process in response to the inability to observe the nonlinear dynamic motion of the friction pair during the separation process and to measure the end time of the separation. Finally, the clutch was subjected to a separation test. The results show that the proposed gap recovery coefficient accurately describes the separation process. The simulation model can simulate the clutch's separation and predict the trend of separation parameters.

In order to solve the problem of waste lithium-ion battery recycling, a robot end-effector is designed to carry the battery weight and adapt to different sizes in the process of sorting. In this study, each mechanism of the end-effector is introduced. The kinematic model of the six-bar mechanism is established by further checking the toe-bar six-bar mechanism. The rod length and position parameters of six-bar mechanism are optimized by genetic algorithm-BFGS （GA-BFGS） quasi-Newton method and particle swarm optimization-BFGS (PSO-BFGS) quasi-Newton method, and the dynamics model of the six-bar mechanism is established. The driving force required by no load and the radial force in the handling process under the limit condition are calculated and simulated. This study provides a new idea of the six-bar drive mechanism, and provides reference for the research and development of the waste lithium-ion battery sorting equipment.

ObjectiveTo solve the problem of the autonomous and safe landing of multi-rotor unmanned aerial vehicles (UAVs) in the application of unmanned platforms at sea, this paper studies multi-rotor UAV landing devices and their safety boundary assessment methods.MethodBased on the idea of the "Harpoon-Grid" rapid securing system, a new type of "V-foot–net" landing device is designed for multi-rotor UAVs. Multi-rigid body dynamic models of the UAV and deck are established, and simulations of the landing process are carried out using ADAMS under different rolling amplitudes and period conditions to obtain the attitude change process, landing critical period and attitude stabilization time of the UAV. ResultsThe simulation results show that the proposed "V-foot–net" device has higher docking redundancy under a smaller rolling period and larger rolling amplitude, and achieves attitude stability faster than ordinary landing devices.ConclusionThe results show that this device has superior safety compared to ordinary devices, and its safety boundary obtained through simulation can provide valuable references for improving the reliability of the autonomous landing of UAVs on offshore platforms.

Copyright of Rolling Stock (1002-7602) is the property of Rolling Stock Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, an outdoor automated guided vehicle (AGV) with an absorbent vibration system was designed, and a 7-degrees of freedom (DOF) model was established for this system. We built a simulation model in Simulink software that serves as the 7-DOF model. The three indicators for evaluating the stability of the AGV are simulated and analyzed in the simulation model when one side of the AGV crosses a sloping obstacle. A vibration absorptive property experiment of the AGV was performed, and the average maximum displacement of the AGV sprung mass was 13.42 mm. The maximum predicted amplitude of sprung mass in the Simulink simulation model is 12.8 mm, and its prediction error is about 4.6%. The prediction accuracy of the Simulink model is higher than that of the Adams simulation method. According to the efficiency comparison experiment of the AGV obstacle crossing simulation method, the obstacle crossing simulation method based on Simulink designed in this paper saves about 28% of the working time of the designer compared with the traditional Adams simulation method, which provides a new idea for the simulation method of outdoor AGV obstacle crossing before the 3D model is established. [ABSTRACT FROM AUTHOR]

This study addresses the issue of quality consistency in the extrusion process of energetic materials using multi-channel dies. To improve the extrusion efficiency of single-base energetic materials, a multi-channel die approach is utilized to yield more products in one extrusion. However, this method may compromise quality consistency during the process. Consequently, the finite element method (FEM) was employed for dynamics simulation of the extrusion process in the multi-channel die and further analysed the impact of critical parameters, such as extrusion speed and channel position, on product quality consistency. A strong linear relationship between flow parameters and d c , the average distance from each channel to the center of the die outlet plane, was reveal from simulation results. An optimization method based on channel distribution was proposed, and the product quality consistency ratio was calculated by averaging the shape consistency ratio, surface quality consistency ratio, and density consistency ratio. Simulation results indicate that this method effectively improves product quality consistency without significantly compromising extrusion efficiency. However, while increasing piston speed can also enhance product quality consistency, it will raise the extrusion pressure, thus increasing the risk of energetic material burning. Overall, this research provides new theoretical underpinnings and practical methods for optimizing the extrusion process of energetic materials. The basic theory, formula, algorithm, and simulation will be presented to validate the correctness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Context: Adipose triglyceride lipase (ATGL), a key enzyme responsible for lipolysis, catalyzes the first step of lipolysis and converts triglycerides to diacylglycerols and free fatty acids (FFA). Our previous work suggested that phillyrin treatment improves insulin resistance in HFD-fed mice, which was associated with ATGL inhibition. In this study, using docking simulation, we explored the binding pose of phillyrin and atglistatin (a mouse ATGL inhibitor) to ATGL in mouse. From the docking results, the interactions with Ser47 and Asp166 were speculated to have caused phillyrin to inhibit ATGL in mice. Further, molecular dynamics simulation of 100 ns and MM-GBSA were conducted for the protein–ligand complex, which indicated that the system was stable and that phillyrin displayed a better affinity to ATGL than did atglistatin throughout the simulation period. Moreover, the results of pharmacological validation were consistent with those of the in silico simulations. In summary, our study illustrates the potential of molecular docking to accurately predict the binding protein produced by AlphaFold and suggests that phillyrin is a potential small molecule that targets and inhibits ATGL enzymatic activity. Methods: The ATGL-predicted protein structure, verified by PROCHECK, was determined using AlphaFold. Molecular docking, molecular dynamics simulation, and prime molecular mechanic–generalized born surface area were performed using LigPrep, Desmond, and prime MM-GBSA modules of Schrödinger software release 2021-2, respectively. For pharmacological validation, immunoblotting was performed to assess ATGL protein expression. The fluorescence intensity and glycerol concentration were quantified to evaluate the efficiency of phillyrin in inhibiting ATGL. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In response to the increasing prevalence of diabetes mellitus and the limitations associated with the current treatments, there is a growing need to develop novel medications for this disease. This study is focused on creating new compounds that exhibit a strong inhibition of alpha-glucosidase, which is a pivotal enzyme in diabetes control. A set of 33 triazole derivatives underwent an extensive QSAR analysis, aiming to identify the key factors influencing their inhibitory activity against α-glucosidase. Using the multiple linear regression (MLR) model, seven promising compounds were designed as potential drugs. Molecular docking and dynamics simulations were employed to shed light on the mode of interaction between the ligands and the target, and the stability of the obtained complexes. Furthermore, the pharmacokinetic properties of the designed compounds were assessed to predict their behavior in the human body. The binding free energy was also calculated using MMGBSA method and revealed favorable thermodynamic properties. The results highlighted three novel compounds with high biological activity, strong binding affinity to the target enzyme, and suitability for oral administration. These results offer interesting prospects for the development of effective and well-tolerated medications against diabetes mellitus. Dataset License: License under which the dataset is made available (CC0, CC-BY, CC-BY-SA, CC-BY-NC, etc.) [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The 4′-(4-chlorobenzoyl)-3,-(2,6-dichlorophenyl)-1′-methylspiro(indole-3,2′-pyrrolidin)-2(1H)-one (SOD1) compound has been synthesized and the single crystals are grown by the slow evaporation method using ethanol. Initially, FT-IR and NMR (1H and 13C NMR) spectroscopic studies were used to confirm the structure of the compound. Single crystal X-ray diffraction data were used to determine the solid state structure of the grown single crystals. The title compound SOD1 crystallizes in the orthorhombic space group Pbca. The crystal packing analysis of the compound shows that distinct hydrogen bonding intermolecular interactions construct the R22(12), R22(8), and R12(8), supramolecular synthons to stabilize the packing modes. The propensity of intermolecular interactions is quantified by the Hirshfeld surface analysis, 2-D fingerprint plots and enrichment ratio analysis. Further, the 3-D packing topology of the molecular fragments is visualized through energy frameworks, which reveal the predominance of dispersion energy over other interaction energies. The optimized structure's geometric parameters were computed using DFT calculations using B3LYP/6–311+G(d,p) basis set and compared with the crystal structure parameters obtained by the X-ray diffraction studies. To explore the anticancer activity of the spiro compound, molecular docking with the 6FS1 protein was performed and the binding score of -7.7 kcal/mol was observed. Further, the binding interaction was explored by the dynamics simulation studies.

In view of the impact and fatigue failure caused by the chain transmission system of a bending machine, the dynamic characteristics of the chain drive and the modification of the sprocket are analyzed and studied. First of all, the operation characteristics of the chain drive are analyzed theoretically.Then the simulation model of the bending machine chain drive system is established by using the RecurDyn software, and the dynamic simulation analysis and gear tooth static strength analysis are carried out. Finally, by using the method of tooth tip circle modification, the simulation models of short-modification and long-modification are established, and the variation curves of force, meshing force, transmission error and static strength of sprocket teeth are obtained. The research results show that the short-modification effectively reduces the meshing impact force in the meshing process of the bending machine chain transmission, the peak meshing force between the sprocket chains is reduced by 43.64%, and the maximum equivalent stress of the gear teeth is reduced by 14.69%. It effectively improves the tooth surface strength, increases the service life of the sprocket, and is more suitable for the chain transmission system of the bending machine than the long-modification.

[Objective] Under unpredictable complex conditions such as natural disasters, failures of vehicle/track key components, or external impacts, metro train derailment is still highly prone to occurrence. Therefore, research on train passive derailment protection device schemes is essential. [Method] A dynamics nonlinear simulation model of metro train multi-body system is established. The typical shapes of both the wheel tread and the steel rail are matched. Based on the characteristics of metro train operating routes, three schemes for metro train derailment protection devices are proposed, and the derailment condition for each scheme is simulated under low-speed operating conditions. Regarding the simulation results, the effectiveness of preventing secondary rail climbing/derailment, the strength of the installation position, and the damage to vehicle caused by collision between rail and derailment protection device after derailment are taking into consideration comprehensively, a scheme of installing lateral anti-derailment stops at framework lower end as the derailment protection device is proposed. A dynamics simulation analysis is conducted on the metro train derailment protection device and the result is compared with the non-protection device working condition. [Result & Conclusion] The metro train derailment protection device exhibits a significant anti-derailment effect with certain feasibility. The dynamic envelope of the above device meets the clearance requirements of the metro line and does not affect train normal operation, making it suitable for engineering applications.

In this research, a sawing mechanism of a mobile buckling machine was innovatively designed for the forest resources and environmental characteristics of the northeast region of China. The northeast region of China is rich in forest resources, but the climate is cold, which puts high demands on the performance and adaptability of mechanical equipment. In this study, the three-dimensional modeling of the saw-cutting mechanism was completed by Pro/Engineer 5.0 modeling software, and an in-depth dynamics simulation analysis was carried out using dynamics simulation software. The study aims to assess the applicability of this saw-cutting mechanism in the northeast region of China, analyze its design characteristics, and explore possible directions for performance optimization. Through this study, we expect to provide valuable references for future technological innovations, as well as to promote the practical application and development of mobile buckling machines in cold regions. This research not only has regional characteristics, but also reflects the innovative idea of combining mechanical equipment design with environmental adaptability.

In the large-scale production of Diethyl Oxalate (DEO), numerous control and optimization challenges are faced. These issues are targeted in this study by implementing a gain scheduling approach to control a catalytic fixed bed multi-tubular reactor designed for DEO production. A novel inferential modeling method, developed using Python and response surface methodology, was applied to simulate the dynamics of the reactor, and the inlet coolant temperature was identified as the most influential parameter. An inferential control system was implemented that utilized gain scheduling for Proportional Integral Derivative (PID) controllers. The results showed that the proposed PID controller gains offered fast and stable responses, even at high conversion setpoints. However, minimization of response overshoot at high amplitudes of step changes proved challenging, leading to a decrease in conversion estimator accuracy. The use of a quadratic model from response surface methodology for the regression of the inferential estimator was proposed, showing improved prediction accuracy over the linear model. These findings provide valuable insights and guide future optimization in the design and operation of reactors for large-scale DEO production. [Display omitted] • Reactor Modeling : Deep insights into the coupling reactor dynamics via Simulink. • Most Effective Parameter : Coolant temperature identified through statistical analysis. • Novel Estimation Method : Python-based approach for inferential control's estimator. • Enhanced Prediction Accuracy : Quadratic model improves estimator precision. • Gain Scheduling Control: Implemented gains ensured stability and speed of responses. [ABSTRACT FROM AUTHOR]

This paper addresses the issues caused by traditional tractors during seeding operations, such as soil compaction, decreased soil fertility, use of unclean fuel leading to environmental pollution, and the disruption of sustainable development. In response, the study designs a compact and lightweight electric four-wheel-drive chassis for a seeding robot suitable for strip planting of soybeans and corn. Using RecurDyn(V9R2) software and MATLAB/Simulink(2020a) modules, the paper conducts simulation and analysis of the straight-line driving process of the electric four-wheel-drive chassis on hilly terrain in field conditions. The simulation results demonstrate that when the suspension stiffness is 14.4 kN/m and the damping is 900 N·s/m, the chassis achieves optimal vibration reduction and straight-line driving performance. Experimental results based on the simulation findings indicate a high consistency between the simulation and actual models, confirming that optimizing the suspension damping parameters effectively improves chassis smoothness and enhances operational quality. [ABSTRACT FROM AUTHOR]

In order to utilize the properties of jumping noise for health monitoring of expansion joints, a simulation model was established for GQF-C type expansion joints, considering both healthy and damaged states. The damage was characterized by steel bar exposure resulting from pavement damage. By conducting dynamics simulation, the acceleration experienced during the jumping contact process between wheels and expansion joints was obtained. Subsequently, the acceleration field was transformed into sound pressure through acoustic simulation. The study focused on analyzing the sound pressure distribution recorded by microphones at various points under different jump heights, comparing the differences in noise characteristics between healthy and damaged expansion joints. The results indicate that the sound pressure amplitude is key in distinguishing between healthy and damaged expansion joints. Furthermore, while the height of the jump does influence the sound pressure amplitude, its impact is relatively small compared to the change caused by damage to the expansion joints. Interestingly, the proximity of the microphone measuring point to the expansion joint has minimal effect on the health status of the joint. Therefore, by utilizing jumping noise, it is possible to effectively monitor the health condition of expansion joints. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The impact of novel coronavirus (SARS-CoV-2) is very high; its mutant variants provide a higher transmission rate. Due to many mutations in the omicron-variant, it can evade previously available neutralizing antibodies. The inhibitory effect of the novel compound “Ignaciomycin” was investigated using various computational analyses against the RBD of the SARS-CoV-2 wild-type, Delta, and omicron-variants. Molecular docking revealed the potentially stable interaction of Ignaciomycin with an energy value of −8.65 kcal/mol for the omicron-variant. DFT and Hirshfeld surface calculations showed higher efficiency and reactivity with strong electrostatic potential values. In-silico toxicity studies revealed a significant drug-likeness score (7.5912) with non-toxic properties. MD simulation studies confirmed the stability of Ignaciomycin during ∼ 100 ns simulation. Covariance, PCA, and FEL analyses revealed significant fluctuations in residues and atom mobility in all variants based on the strong interaction of Ignaciomycin. Mutations in the Delta and omicron-variants increased the binding efficiency of the RBD of the SARS-CoV-2 S-glycoprotein with human ACE2. Ignaciomycin had high efficiency in interacting with mutated sites in the RBD, thereby blocking the interaction of the RBD with ACE2. Our findings provide a strong hypothesis for preclinical validation of Ignaciomycin as a potential drug against SARS-CoV-2 and its mutant variants.

Modern planetary gear transmissions are often made with flexible components and operated at high or varying speed. Despite advances in understanding their dynamic performance, they remain vulnerable to problems leading—in some cases—to subsequent system failure. In this study, using angular and translational displacements as generalized coordinates, we establish lumped-parameter dynamic sub-models of the sun and planet gears that accurately consider gear-tooth dynamic behavior; we also develop reduced-order finite-element sub-models that fully consider the flexibility of the housing and carrier. Investigating the coupling between these sub-models in depth enables us to construct a complete hybrid dynamic model that can be used for coupling-dynamics analysis of flexible planetary gears under high- and variable-speed conditions. The accuracy of our planetary-gear-dynamics model is verified by comparing simulation data in the time and frequency domains to the results of experiments conducted on a planetary gear transmission system test bench specially built for this purpose. Finally, the dynamic characteristics of high-speed flexible planetary gears are studied at low speed, high speed, and high acceleration.

Candida albicans and Aspergillus fumigatus are recognized as significant fungal pathogens, responsible for various human infections. The rapid emergence of drug-resistant strains among these fungi requires the identification and development of innovative antifungal therapies. We undertook a comprehensive screening of 297 naturally occurring compounds to address this challenge. Using computational docking techniques, we systematically analyzed the binding affinity of each compound to key proteins from Candida albicans (PDB ID: 1EAG) and Aspergillus fumigatus (PDB ID: 3DJE). This rigorous in silico examination aimed to unveil compounds that could potentially inhibit the activity of these fungal infections. This was followed by an ADMET analysis of the top-ranked compound, providing valuable insights into the pharmacokinetic properties and potential toxicological profiles. To further validate our findings, the molecular reactivity and stability were computed using the DFT calculation and molecular dynamics simulation, providing a deeper understanding of the stability and behavior of the top-ranking compounds in a biological environment. The outcomes of our study identified a subset of natural compounds that, based on our analysis, demonstrate notable potential as antifungal candidates. With further experimental validation, these compounds could pave the way for new therapeutic strategies against drug-resistant fungal pathogens.

Due to the limited availability of fault samples and the expensive nature of marking fault samples in Electric Multiple Unit (EMU) gearbox monitoring data, a study was conducted to simulate the degradation process of key components in the CRH5 gearbox using rigid–flexible coupling dynamics. Vibration acceleration data from the simulation were utilized to create a six-dimensional hybrid feature domain representing the degradation process. By leveraging the capabilities of the Hidden Markov Model (HMM) for handling hidden transitive probabilities in temporal data and Gated Recurrent Unit (GRU) for addressing long-distance and high-dependence temporal data, a GRU-HMM fault prediction model was developed. This model was validated using monitoring data and the six-dimensional hybrid feature domain from the CRH5 gearbox and compared against actual maintenance records. The findings indicated that the GRU-HMM fault prediction model can effectively recognize the degradation patterns of multiple components, offering higher accuracy in fault prediction compared to traditional models. These research outcomes are expected to optimize EMU maintenance schedules based on usage conditions, enhance EMU utilization rates, and reduce operational and maintenance costs, thereby providing valuable theoretical support.

Momordica charantia, Nigella sativa, and Anethum graveolens are established medicinal plants possessing noted anti-diabetic and anti-obesity properties. However, the molecular mechanisms underscoring their inhibitory effects on pancreatic lipase, α-glucosidase, and HMG-CoA reductase remain unexplored. This study aimed to elucidate the efficacy of various NS, MC, and AG blends in modulating the enzymatic activity of pancreatic lipase, HMG-CoA reductase, and a-glucosidase, utilizing an integrative approach combining in vitro assessments and molecular modeling techniques. A factorial design matrix generated eight distinct concentration combinations of NS, MC, and AG, subsequently subjected to in vitro enzyme inhibition assays. Molecular docking analyses using AutoDock Vina, molecular dynamics simulations, MMPBSA calculations, and principal component analysis, were executed with Gromacs to discern the interaction dynamics between the compounds and target enzymes. A formulation comprising NS:MC:AG at a 215:50:35 μg/mL ratio yielded significant inhibition of pancreatic lipase (IC50: 74.26 ± 4.27 μg/mL). Moreover, a concentration combination of 215:80:35 μg/mL effectively inhibited both α-glucosidase (IC50: 66.09 ± 3.98 μg/mL) and HMGCR (IC50: 129.03 μg/mL). Notably, MC-derived compounds exhibited superior binding affinity towards all three enzymes, compared to their reference molecules, with diosgenin, Momordicoside I, and diosgenin displaying binding affinities of −11.0, −8.8, and −7.9 kcal/mol with active site residues of pancreatic lipase, α-glucosidase, and HMGCR, respectively. Further, 100 ns molecular dynamics simulations revealed the formation and stabilization of non-bonded interactions between the compounds and the enzymes’ active site residues. Through a synergistic application of in vitro and molecular modeling methodologies, this study substantiated the potent inhibitory activity of the NS:MC:AG blend (at a ratio of 215:80:35 μg/mL) and specific MC compounds against pancreatic lipase, α-glucosidase, and HMGCR. These findings provide invaluable insights into the molecular underpinnings of these medicinal plants' anti-diabetic and anti-obesity effects and may guide future therapeutic development.

Understanding the dynamics of precariously balanced rocks (PBRs) is important for seismic hazard analysis and rockfall prediction. Utilizing a physics engine and robotic tools, we develop a virtual shake robot (VSR) to simulate the dynamics of PBRs during overturning and large-displacement processes. We present the background of physics engines and technical details of the VSR, including software architecture, mechanical structure, control system, and implementation procedures. Validation experiments show the median fragility contour from VSR simulation is within the 95% prediction intervals from previous physical experiments, when PGV/PGA is greater than 0.08 s. Using a physical mini shake robot, we validate the qualitative consistency of fragility anisotropy between the VSR and physical experiments. By overturning cuboids on flat terrain, the VSR reveals the relationship between fragility and geometric dimensions (e.g., aspect and scaling ratios). The ground motion orientation and lateral pedestal support affect PBR fragility. Large-displacement experiments estimate rock trajectories for different ground motions, which is useful for understanding the fate of toppled PBRs. Ground motions positively correlate with large displacement statistics such as mean trajectory length, mean largest velocity, and mean terminal distance. The overturning and large displacement processes of PBRs provide complementary methods of ground motion estimation.

Modern planetary gear transmissions are often made with flexible components and operated at high or varying speed. Despite advances in understanding their dynamic performance, they remain vulnerable to problems leading—in some cases—to subsequent system failure. In this study, using angular and translational displacements as generalized coordinates, we establish lumped-parameter dynamic sub-models of the sun and planet gears that accurately consider gear-tooth dynamic behavior; we also develop reduced-order finite-element sub-models that fully consider the flexibility of the housing and carrier. Investigating the coupling between these sub-models in depth enables us to construct a complete hybrid dynamic model that can be used for coupling-dynamics analysis of flexible planetary gears under high- and variable-speed conditions. The accuracy of our planetary-gear-dynamics model is verified by comparing simulation data in the time and frequency domains to the results of experiments conducted on a planetary gear transmission system test bench specially built for this purpose. Finally, the dynamic characteristics of high-speed flexible planetary gears are studied at low speed, high speed, and high acceleration. [ABSTRACT FROM AUTHOR]

It is a new application of the high-altitude balloon system to launch multiple small folding wing unmanned aerial vehicles (UAVs). Based on the design of the launching system, we conduct numerical simulations of the ejection process from the balloon platform and the subsequent UAV wing deployment with trajectory leveling operation. We use the Kane method to establish the dynamic model of the balloon launching platform in the inertial coordinate system (ICS). By introducing the degree of freedom of UAV sliding along the sliding track, we realize the dynamic simulation of eight UAV launching processes and obtain the instantaneous separated states. The folding wing UAV first deploys its wings after ejection, which has the coupling characteristics between structural deformation and attitude adjustment. It is regarded as a multi-rigid body connecting structure composed of the fuselage and four wings. We establish the dynamic simulation model by the Kane method in the UAV body coordinate system (BCS). The Radau pseudo-spectral method is used to calculate the flight trajectory of each UAV. This paper is an engineering application research and can provide a simulation reference for the launching test of the balloon-borne folding wing UAV program. [ABSTRACT FROM AUTHOR]

To address the problem of insufficient real-world data on planetary gearboxes, which makes it difficult to diagnose faults using deep learning methods, it is possible to obtain sufficient simulation fault data through dynamic simulation models and then reduce the difference between simulation data and real data using transfer learning methods, thereby applying diagnostic knowledge from simulation data to real planetary gearboxes. However, the label space of real data may be a subset of the label space of simulation data. In this case, existing transfer learning methods are susceptible to interference from outlier label spaces in simulation data, resulting in mismatching. To address this issue, this paper introduces multiple domain classifiers and a weighted learning scheme on the basis of existing domain adversarial transfer learning methods to evaluate the transferability of simulation data and adaptively measure their contribution to label predictor and domain classifiers, filter the interference of unrelated categories of simulation data, and achieve accurate matching of real data. Finally, partial transfer experiments are conducted to verify the effectiveness of the proposed method, and the experimental results show that the diagnostic accuracy of this method is higher than existing transfer learning methods. [ABSTRACT FROM AUTHOR]

A kind of clearance elimination and vibration reduction structure of cylindrical gear slot holes is proposed. The vibration acceleration of slotted and backlash gears with different sizes is simulated using the dynamics software Adams. The vibration acceleration spectrum and power spectrum are obtained by Fourier transform and correlation power spectrum estimation method. A three-factor and three-level orthogonal test table is designed. Taking the amplitude of angular acceleration of meshing frequency as the evaluation index of orthogonal tests, the relatively optimal parameter design scheme is obtained. The effectiveness of the proposed damping structure design is verified by vibration tests. The slot structure can reduce the gear vibration acceleration by about 20%-33%, and the test results are similar to the simulation results. Under the constraint of slot relaxation, the negative backlash has an obvious inhibitory effect on the vibration.

In response to the increasing prevalence of diabetes mellitus and the limitations associated with the current treatments, there is a growing need to develop novel medications for this disease. This study is focused on creating new compounds that exhibit a strong inhibition of alpha-glucosidase, which is a pivotal enzyme in diabetes control. A set of 33 triazole derivatives underwent an extensive QSAR analysis, aiming to identify the key factors influencing their inhibitory activity against α-glucosidase. Using the multiple linear regression (MLR) model, seven promising compounds were designed as potential drugs. Molecular docking and dynamics simulations were employed to shed light on the mode of interaction between the ligands and the target, and the stability of the obtained complexes. Furthermore, the pharmacokinetic properties of the designed compounds were assessed to predict their behavior in the human body. The binding free energy was also calculated using MMGBSA method and revealed favorable thermodynamic properties. The results highlighted three novel compounds with high biological activity, strong binding affinity to the target enzyme, and suitability for oral administration. These results offer interesting prospects for the development of effective and well-tolerated medications against diabetes mellitus.