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Biomechanical surface roughness analysis of ramie-low melt polyester nonwovens exposed to plasma
Get PDFThis study aims to characterize ramie-low melt polyester nonwoven fabrics treated with low-temperature plasma and to analyze 3-D images based on object-depth mapping (ODM) using the MATLAB® R2022a software. We examined the low-temperature plasma treatment of nonwoven ramie fabrics using a plasma generator with 30 kV output power, six-minute treatment times, and a 4.5 cm distance between electrodes. The fabric’s chemical properties and surface topography were investigated using scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). An analysis of the SEM images was performed using a statistical approach and image processing to determine the level of surface roughness. FTIR analysis revealed that fabrics exposed for six minutes differed from those that were not. Our findings indicated that plasma treatment caused the following: 1) Ramie fabrics to become more hydrophilic, as shown by their increased T% in the FTIR of hydrophilic functional groups such as hydroxyl (O-H), carboxyl (-COOH), and carbonyl (C=O); 2) A higher surface roughness was observed in nonwoven fabric during SEM testing and image processing; 3) Plasma treatment of fabrics resulted in a higher coefficient of variation (CV) than untreated fabrics; 4) Nonwoven fabric mass reduction. Based on this study, we found the relationship between plasma-treated ramie fabric and textiles in biomechanics. Plasma treatment reduced the mass of ramie fabric by 0.11 %, according to our findings. We found that the greater the mass reduction, the greater the surface roughness value. The novelty of this study is the use of 3-D images based on object-depth mapping (ODM) using the MATLAB® R2022a software in SEM to observe surface roughness to the physical properties of ramie fabric for the first time
Analysis of vibration characteristics of ship propeller spindle
Get PDFIn order to obtain the vibration response characteristics of the propeller spindle system effectively and accurately, and provide the basis for the subsequent fault diagnosis, the modal simulation and test of the spindle model were carried out. With the propeller set as eccentric mass, the amplitude and torsion angle of the spindle model were simulated under the condition of excited vibration and unexcited vibration respectively, and the frequency response of bending and torsion under the coupled condition was obtained. The newmark-β method was used to solve the transient response of the bent-torsional coupling model. The results shows that when the propeller spindle system undergoes rotation at a specific frequency and experiences bending vibration excitation force, the latter will induce torsional vibration response. Moreover, the amplitude of the torsional vibration response varies with changes in the frequency of the bending vibration excitation force
Application of ultrasonic vibration in magnesium alloy lap welding
Get PDFIn order to enhance the performance of magnesium alloy and galvanized steel welds, ultrasonic vibration was applied to the laser welding process, and the effect of ultrasonic on mechanical properties was verified through experimental methods. The laser welding system for the lap weld seam was designed, and the ultrasonic vibration module and image detection module were added, which can obtain the influence of ultrasonic vibration on the molten pool area. Under the conditions of ultrasonic vibration power of 1000 W and 0 W, the characteristics of the weld pool area, metallographic structure, tensile strength, fracture morphology, hardness, residual stress, wear resistance, and corrosion resistance of the weld specimen were compared. The image data acquisition structure indicated that ultrasonic vibration can effectively reduce the ineffective area of the molten pool and make the energy in the molten pool more concentrated. Under the influence of ultrasonic vibration, the maximum molten pool area decreased to 5.38 mm2, with a variation range of 3.9 %, and the proportion of pores was greatly reduced. Research found that ultrasonic vibration can significantly improve the microstructure characteristics of the fusion welding zone, with an average grain size reduced to 23 μm. The reduction of grain size and refinement of microstructure were beneficial to the improvement of mechanical properties of magnesium alloy joints, with a yield strength increase of 6.5 %. Ultrasonic vibration had little effect on the hardness of the heat affected zone, it can increase the average hardness of the weld zone by more than 5 % and reduce the maximum residual stress by more than 50 %. Under different pressure and friction speed conditions, the maximum wear amount can be reduced by more than 25 %. At the same time, the resistance to oxidation corrosion and electrochemical corrosion also can be improved to a certain extent
Contributions of jaw functional orthopedics in temporomandibular joint ankylosis (TMA) – clinical case report
Get PDFTemporomandibular joint (TMJ) ankylosis is one of the most disabling pathological conditions that can occur in the maxillofacial region, often occurring at an early age, limiting growth and causing facial deformity, which significantly affects the quality of life of the individual. The objective of the study was to evaluate the contribution of Jaw Functional Orthopedics (JFO) in TMJ ankylosis after the surgical phase. The case of a 7-year-old female patient diagnosed with bilateral condylar ankylosis (fibrous ankylosis on the right side and bony ankylosis on the left side) is presented. On clinical examination, facial asymmetry, retrognathia, muscle contraction and opening limitation were observed. Treatment consisted of temporalis muscle flap rotation surgery with condylectomy and coronoidectomy, physical therapy, and functional therapy with OFM. The clinical results at 4 months of follow-up suggest significant progress in oral opening and protrusion. The patient showed a high degree of satisfaction with the results obtained. She is currently continuing with the use of orthopedic appliances to correct the sequelae of ankylosis and improve mandibular kinematics
Testing the effect of functional orthopedic appliance Simões network 6 (SN6) through surface electromyography on rest mandibular position – a pilot study
Get PDFThe maintenance of the lower level of muscle contraction is fundamental for the development and health of the stomatognathic system (SS). Malocclusion leads to unbalance muscle activity, since Class II treatment is not the most prevalent malocclusion in the general population but is the more frequent to search for treatment in dental offices and the most prevalent skeletal component in the class II malocclusion is the retrognathia this pilot investigation aims to study the effect of rest electric activity of bilateral anterior temporal, masseter and suprahyoid muscle in individuals undergoing class II treatment with functional orthopedic appliance Simões Network 6 (SN6). Surface electromyography recordings of bilateral anterior temporal, masseter and suprahyoid muscle in rest position was obtained before and 8 minutes after the functional appliance insertion in mouth. Results showed improvement of electric muscle activity in rest position and balance of bilateral muscle electric activity in all muscle. Based on the preliminary results it can be conclude that jaw functional orthopedics (JFO) provides alteration of the resting records in the mandibular rest position of the studied muscles, indicating relaxation of the muscles studied and a more symmetrical electric activity. Further studies are necessary for a better understanding of the effects of functional orthopedic appliances in the electric activity of stomatognathic muscle in the mandibular rest position
Research on dynamic characteristics of wind turbine’s transmission system considering gear tooth lubrication
Get PDFTo improve wind turbines’ reliability and lifespan, taking the two-stage fixed shaft gearbox of wind turbines as study object. The oil stiffness and meshing stiffness of the transmission system are calculated, and the composite stiffness is obtained with the consideration of lubricating film. Then analyzed the dynamic characteristics of wind turbines’ transmission system before and after consider the oil stiffness in different operating conditions. The findings indicate that after considering the gear lubrication effect, the composite stiffness gradually decreases as rotational speed increase; within a certain rotational speed range, the tooth-surface load can be reduced, making the system run more smoothly. Therefore, the presence of oil film and its impact on its stiffness cannot be ignored. This study has certain guiding significance in improving the transmission efficiency and reducing noise of wind turbines
Identification of modal parameters of soil specimen based on impact force
Get PDFThis study used vibration testing signals of soil samples under external loading to identify modal parameters (including natural frequencies and damping ratios) with different compaction degrees. Based on these parameters, a novel approach was proposed for reliable roadbed vibration compaction control and compaction process optimization. The experimental section utilized six soil samples with varying compaction degrees as experimental subjects, using the hammering method as the excitation mode. Subsequently, the frequency response function and modal parameters of the sample system were obtained through the acquisition, analysis, and parameter identification of samples’ acceleration signals. Firstly, samples with compaction degrees ranging from 88 % to 97 % primarily exhibited three modes, with the second modal frequency response displaying the weakest amplitude, and the fundamental mode being the dominant one. Additionally, parameter identification results revealed that the fundamental modal frequency exhibited a significant negative exponential growth with increasing compaction degree, while the second and third modal frequencies showed significant linear growth. Furthermore, the average damping ratio also demonstrated a tendency toward linear change with increasing compaction degree. Finally, the feasibility of modal parameters being actively used in practical engineering is discussed. Consequently, this study aimed to propose an indicator system for accurately assessing the bearing level of compacted soils from a modal dynamics perspective and to integrate modal dynamic indicators with density-class indicators into further optimization design work on road compaction processes
Fault diagnosis of rolling bearing based on hierarchical discrete entropy and semi-supervised local Fisher discriminant analysis
Get PDFThis paper addresses challenges in extracting effective information from rolling bearing fault signals and handling strong correlations and information redundancy in high-dimensional feature samples post-extraction. A rolling bearing fault diagnosis method is proposed on the basis of hierarchical discrete entropy (HDE) combined with semi-supervised local Fisher discriminant analysis (SELF). Firstly, hierarchical discrete entropy is extracted from signals preprocessed via variational mode decomposition. We assess entropy stability under different parameters using the coefficient of variation and select optimal parameters accordingly. Secondly, we employ the SELF method to remap the multidimensional feature sample set extracted, performing dimensionality reduction. Finally, a fault diagnosis model classifies the dimensionality-reduced feature samples for fault identification. Experimental results demonstrate that entropy samples extracted via HDE achieve higher diagnostic accuracy after dimensionality reduction with the SELF method. Specifically, accuracy rates of 100 % and 98.2 % are achieved for two types of fault samples, respectively, validating the feasibility and effectiveness of our approach
Optimization of lubrication characteristics of wind turbine’s transmission system based on Newton Raphson method
Get PDFTo improve the reliability and lifespan of wind turbines, this paper takes the two-stage fixed shaft gearbox experimental platform of wind turbines as the research object. Based on Hertz contact theory, the oil film pressure and thickness in the contact area are solved by combining the equations of elastohydrodynamic lubrication and the Newton Raphson method; And the lubrication characteristics of the transmission system were analyzed to verify the correctness of the method; At the same time, in response to partial load phenomenon caused by system coupling deformation, genetic algorithm was selected to modify the gear teeth. The results show that the max unit load on the tooth face and the maximum stress of tooth root decreased by up to 26.48 % and up to 20.35 % respectively after modification which can improve the uneven distribution of oil film and the lubrication performance of the tooth surface
Statistical review of literature sources on carbon emissions during the CSPB based on knowledge graphs
Get PDFThe construction industry, a significant contributor to global carbon emissions, is pivotal in implementing carbon reduction strategies. This study delves into the carbon emissions associated with the construction stage of prefabricated buildings (CSPB), a burgeoning field of research. Utilizing the CiteSpace knowledge graph visualization software, we comprehensively analyzed literature from the Web of Science (WoS) database. Our study encompasses several vital dimensions: academic paper publication volume, keyword co-occurrence network, keyword co-occurrence network clustering, and citation burst visualization and analysis. The findings indicate that the topic of carbon emissions in prefabricated building construction is gaining increasing attention globally. Over the past decade, related literature has surged by an average annual growth rate of 41.42 %. Key research themes have emerged around the quantification of carbon emissions, construction methodologies, influencing factors, mitigation strategies, the use of prefabricated components, and predictive studies on emissions. These insights underscore the evolving focus and critical importance of this field in global sustainability efforts