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Purposes As a coal based solid waste rich in silicon and aluminum oxides, utilization of coal gangue is crucial for the sustainable development of coal industry. Methods Integrated grinding modification of calcined coal gangue and aluminate coupling agent to prepare rubber reinforcement was proposed. The influences of grinding time and the amount of modifier on the surface modification were investigated. Ultrafine particles were obtained through air flow classification, and the influences of modification or not and particle size on the reinforcing and filling properties of rubber were analyzed. Findings The results show that the best comprehensive modification effect is achieved when the duration of ball milling is 30 min and the amount of aluminate coupling agent is 2%. The characteristic functional groups of aluminate coupling agent appear on the surface of coal gangue. Compared with the rubber filled with commercial silica, the rubber filled with the air-flow graded modified filler possesses higher hardness and crosslinking density, its vulcanization performance is better, the tensile strength, elongation at break and permanent deformation at break are reduced, and the fixed extension stress is increased. The particle size distribution of the filler has an obvious effect on the properties of rubber, with the decreases of the particle size of the filler, the vulcanization property is improved, and the tensile property is also improved. The reinforcement performance of modified superfine coal gangue as filler is close to that of silica, which has the potential to replace silica.

To analyze quantitatively various indexes of wire arc additive manufacturing components of 2319 aluminum alloy, the expressions of curved surface between different process parameters, porosity and tensile strength values were fitted, and the "process-structure-property" corresponding rule was established. In addition, a normalized fuzzy evaluation model was developed for process parameters, organizational defects, and mechanical properties using the generalized fuzzy synthesis operation rule. The purpose of this model was to obtain the optimal process parameters. The results show that the porosity generally increases with the wire feeding speed rising.Then the porosity generally decreases with a decrease in scanning speed. When the scanning speed is 0.035 m/s, the correlation between porosity and tensile strength is the lowest, with a correlation coefficient (coefficient of determination, COD) of only 0.6. The comprehensive evaluation score of the expert is the highest when the wire feeding speed is 5.0 m/min and the scanning speed is 0.025 m/s, indicating that this combination of process parameters is optimal.

In order to improve the mechanical and tribological properties of polytetrafluoroethylene (PTFE), carbon nanotubes (CNTs) nano-capsules loaded with the isobutene sulfide (T321) in the internal cavity (CNTs@T321) were proposed as the reinforcing phase of PTFE. T321 can be released from the nano-capsules during friction to make PTFE have better lubrication properties. First, the effects of filling amount on the mechanical and tribological properties of PTFE composites were studied. The existing forms of nano-capsules in PTFE composites were analyzed, and the self-lubrication mechanism during friction was revealed. The results show that the tensile strength of PTFE can be improved when the content of nano-capsules is lower, and the strength of PTFE can be decreased when the mass fraction of nano-capsules exceeds 3%. Under different speeds and loads, the filling of nano-capsules can reduce the friction coefficient and wear rate of PTFE. The anti-friction effect are improved with the increase of load, while the wear rate will be increased. During the friction process, nano-capsules can release T321 with the wear of PTFE, and T321 forms a self-lubricating layer on the wear interface, thus producing anti-friction and anti-wear effects.

Lithium (Li) metal is a potential anode material for high energy density batteries. However, issues such as lithium dendrite growth, interface instability, poor cycling stability and large volume expansion limit the application of lithium metal anode. Aiming at the problem of dendritic growth and volume expansion, a semi-confined hierarchical porous carbon (HPC) material with a large specific surface area was prepared by template method. The high specific area of HPC electrode can reduce the local current density of Li deposition, and the rich pore structure can restrict the Li deposition in it, thus inhibiting the dendritic growth and alleviating the volume expansion. Li‖HPC battery can cycle for more than 250 cycles at a current density of 1.0 mA/cm2 and a deposition capacity of 1.0 mAh/cm2, maintaining a Coulombic efficiency of 97.6%. Li@HPC‖lithium iron phosphate a deposition capacity of (LiFePO4) full cell has a specific capacity of 93.6 mAh/g after 100 cycles at 0.5 C, which is higher than that of Li@Cu‖LiFePO4 full cell (60.8 mAh/g) with an increase of by 32.8 mAh/g.

To improve the segmentation accuracy and timeliness of raw cotton mixed impurity images, a new improved UNet model of raw cotton impurity segmentation algorithm was proposed. A new coding module was designed based on the ResNet50 structure, and one convolutional layer was used to replace the last three residual modules and the fully connected layer to implement optimization of the model parametric quantities and improve the extraction of image feature information. The loss function of CEloss and Dice loss was designed to optimize the imbalance between positive and negative samples and improve the segmentation ability of the model for fine impurities. Finally, the migration learning method was applied to pre-train the encoder for the initialization of the backbone network weights based on the VOC dataset to further optimize the slow convergence of the model due to the small amount of image data. The experimental validation shows that the MPA value of the method is improved by 24.52%, the accuracy rate reaches 88.24%, and the processing time of a single image is shortened to 21.9 ms, which is 49.42% higher than that of the traditional method. The improved method described is effective in improving the accuracy and timeliness of image segmentation of raw cotton impurities.

In order to study the strength performance of the airship envelope and the influence of overpressure bearing on its residual strength, the sample forms and experiments plans for the uniaxial and biaxial tensile of the envelope material were designed, and the tearing situation of the airship was analyzed with the help of a high-speed camera. Based on the experimental data, fitted the uniaxial tensile strength curve when the airship bears air pressure, and the longitudinal and latitudinal strength envelope line of the material when it was biaxially stretched. The experimental results demonstrate that there is a negative correlation between the residual strength of the envelope and the airship bearing air pressure when uniaxially stretched, the bearing strength of the envelope is comprehensively affected by the longitudinal and latitudinal strengths when biaxially stretched. This experiment also analyzes the failure situation of the airship envelope, which can provide an experimental guidance for its strength prediction.

Dural defects and subsequent leakage of cerebrospinal fluid (CSF) after neurosurgery are often associated with serious complications or even death. The associated surgical suture or sealant repair is often followed by pinhole leakage or a loose seal. Thus, pressure-resistant, high-viscosity dural repair is highly desired. In this study, a chitosan-based hydrogel sealant with the benefits of easy handling, high safety, rapid setting time, simple injection, excellent mechanical strength, and strong tissue adhesiveness was created to accomplish efficient sutureless dural closure during operation. This sealant may successfully prevent or stop intraoperative CSF leaking and provide sutureless dural closure. In conclusion, this sutureless chitosan-based hydrogel sealant could be a very promising candidate with high practical value for dural repair.

In order to explore the influence of the size effect on the fracture strength of unidirectional continuous glass fiber reinforced polypropylene composites（unidirectional GF/PP composites）, the Zwick/Roell Z005 universal material testing machine was used to test different gauge lengths through orthogonal test methods.（60 mm, 100 mm, 200 mm）, unidirectional GF/PP composites with different widths（10 mm, 15 mm, 20 mm） are subjected to tensile test. The test results show that as the test size increases, the breaking strength of unidirectional GF/PP composites gradually decreases. Because the fracture strength of unidirectional GF/PP composites has a large dispersion, the distribution law of the strength of unidirectional GF/PP composites under different size conditions is obtained through the classic two-parameter Weibull strength statistical model, and the improved generalized The two-parameter weakest chain strength statistical model introduces the exponential parameterβto modify the influence of the spatial distribution of defects. The fracture strength data under different sizes are processed in a unified manner. The resulting failure function comprehensively reflects the size effect on the unidirectional GF/PP composite The effect of material breaking strength.

In order to verify the bending effect of quartz wafer,a special elastic ring clamping structure was designed to install and position the sensitive element. According to elastic mechanics and piezoelectricity,the calculation formula of bending stress and polarization of quartz wafer were deduced and the stress analysis of the elastic ring wafer clamping structure was carried out. In order to reduce the influence of structural deformation on sensor application performance,using the energy principle of elastic mechanics the static stiffness formula of the elastic ring wafer clamping structure under load was calculated. Using the finite element method the strength and stiffness of the elastic ring wafer clamping structure was verified. The theoretical calculation,finite element analysis and experimental measurement results show that the rigidity of the elastic ring wafer clamping structure is more than 10 kgf/um,which meets the requirements of sensor design. The research can provide technical support for the structural design of the new cantilever force sensor and micro actuator.

According to the structure orthogonal anisotropic periodic raised structure plate,the equivalent stiffness of the arc periodic raised structure plate is investigated. Based on the classical theory of elastic thin plate and the homogeneous distribution characteristics of the plate,the analytic equation of the equivalent stiffness of the arc periodic raised structure plate is derived.The finite element method is used to simulate the numerical results of arc periodic raised structure plate with simply supported on Four Sides under the concentrated load. The rationality and accuracy of equivalent stiffness is verified. Then the natural frequency of the arc periodic raised structure plate under simply supported on four sides is calculated by using the analytic method. The calculation results are in agreement with the finite element simulation results,and the correctness of the analytical equation of the equivalent stiffness is verified again. The present new method can be used to calculate the equivalent stiffness of the periodic raised structure plate accurately. Moreover,the calculation is directly performed with the geometric parameters of the typical unit.This method is intuitive and concise,and improves the efficiency of solution. The results have important guiding significance for studying the static and dynamic characteristics of the periodic raised structure plate and engineering applications.

The main drive system of rolling mill is a complicated electromechanical system,as the main device of transmitting motion and torque. The factor of electromechanical coupling is one of the important reasons for the abnormal variation of torsional vibration. The paper mainly researched that the dynamic analyses of the torsional vibration of main drive system of rolling mill. Comparative analysis the torsional vibration of main drive system is obtained between considering electromechanical coupling and not considering electromechanical coupling. Then,the mechanical and mathematical models of the main drive torsional vibration system are established. Based on Matlab/Simulink simulation,the unstable state of the main drive torsional vibration system is used to be studied,and then the influences of the uncertain parameters on the torsional vibration of main drive system are analyzed. The results could be revealed the oscillation law for the torsional vibration of main drive system of rolling mill and provided a theoretical foundation for the formulation of control strategy.

Strip steel vibrations is inevitable in the rolling process of tandem mill, and the coupled model between elastoplastic body of strip steel and main drive system directly affects the overall dynamic performance of rolling mill. According to the movement mechanism of strip steel and main drive system, the main drive system was simplified to a two-degree-of-freedom discrete model and the strip steel was simplified to an axially moving Euler beam, the coupled vibration mechanical model of transverse and longitudinal vibrations of strip steel and torsional vibration of main drive system was established. Then, the nonlinear vibration differential equations of the coupled model were derived with Hamilton’s principle. The modified iteration method and the Kantorovich averaging method were used to solve the differential equations. Finally, by using the Matlab simulation, the influence of torsional vibration fundamental frequency of main drive system on strip steel vibration characteristics was discussed. The results can enrich the theoretical achievements on vibration of rolling mill, and it is valuable for transforming theoretical results into engineering applications.

The surface roughness data of test-pieces with transverse profiles were firstly measured by a roughness profile measuring analyzer. With the help of the Fourier nonlinear approximation the measured data was used to form a roughness function which was superimposed to film thickness equation and a mixed thermal elastohydrodynamic lubrication model for the rolling bearing was then established. Based on the model,45 sets of numerical calculations were carried out by changing the roughness values under other conditions of the rolling bearing were fixed. Then the two quantitative relationships between the average oil film at the contact point and the roughness as well as the maximum subsurface principal stress and the roughness are respectively established through the regression analysis of the calculation results.

In order to enhance heat transfer performance of plate-fin radiator,multi-objective optimization was carried out to the structural parameters of the serrated fin based on the genetic algorithm. According to the result of optimization,threedimensional physical model of the channel was built. The temperature field was investigated by the method of CFD. The heat transfer factor,friction factor and comprehensive performance evaluation factor of fin were obtained. The simulation results show that the heat transfer performance of the optimized fin was improved. Heat transfer performance of copper fin is better than that of aluminum fin. The validity of the simulation result is verified by wind tunnel test.

The fatigue life scatter factor is an important reliability index of the assessment of aircraft fatigue life. At present,the safe-life of a fleet is gotten by using the total test hours and the fatigue scatter factor. Usually,the environment scatter factor caused by the different service environments is not considered,and the fatigue scatter factor mainly includes two parts,one is the load scatter factor caused by the load spectrum difference of fleets; the other is the structure scatter factor caused by the difference of material and manufacturing quality. The expressions of scatter factor of fatigue life obeying the log-normal distribution and Weibull distribution are introduced and analyzed. To the situation that the structure fatigue life of the same aircraft model under different load spectrums obeys the log-normal distribution,the condition that the fatigue scatter factor is the product of the load scatter factor and the structure scatter factor is deduced. To the situation that the structure fatigue life obeys the different distributions,the service flying hours can be converted into the equivalent flying hours under the same test load spectrum based on the equal damage principle,the structure scatter factor under this spectrum can be calculated and can be taken as the fatigue life scatter factor,the safe-life calculated by this scatter factor can be seen as the reference value for the management of individual aircraft life.

The surface roughness data of test-pieces with transverse profiles were firstly measured by a roughness profile measuring analyzer. With the help of the Fourier nonlinear approximation the measured data were used to form a roughness function which was superimposed to film thickness equation and a mixed thermal elastohydrodynamic lubrication model was then established. Based on the model,280 sets of numerical calculations were carried for both medium and heavy duty transmissions through changing the roughness values. The results show that the contact stress τmax,rfor rough teeth surfaces is increased by 5%compared with the contact stress τmax,sfor smooth teeth surfaces when the root mean square roughness of tooth surface σ≤0. 3μm; While the τmax,ris increased by 15- 20% compared with the τmax,swhen σ ≥ 0. 5 μm. At the end,several theoretical formulas for determining the roughness factors are created based on the multiple regression analysis of the above calculated results.

In order to discuss theoretically the effects of surface roughness on gearing contact fatigue stress,a mixed Elastohydrodynamic Lubrication（ EHL） model for heavy-duty gear transmission was established based on the transverse roughness features simulated by the fractal function,which were superimposed to the film equation. Applied the multi-grid method,40 groups of numerical calculations were completed. The results show that the average film thickness is almost linearly increased with an increment of the roughness value. But it is not simply the case that the less the roughness value,the better. When the roughness is less than a critical value,however,increasing roughness value is found to reduce the maximum principal shear stress on pinion subsurface. At the end,the quantitative relation between the maximum principal shear stress and the roughness is acquired based on the regression analysis of the calculation results.

A three-dimensional sliding model of micro-scale was established between two rough surfaces exhibiting fractal behavior,and the thermo-mechanical coupling factor in the process of contact was considered. The surface temperature in sliding processes was analysed using the finite element analysis taking into account Ti-6Al-4V elastic-plastic properties with material failure. The transient surface temperature distribution of the rough surface was presented. The numerical results showed that the surface temperature in initial time rise sharply and then tend to be temporarily stable until a new contacted asperity coming into interaction. With the increase of friction slide distance the surface temperature was to present the state of fluctuating. The values of highest temperature at contact zones were different,while the highest temperature at contact zone was higher relative to the greater interface shear strength. Compared with the experimental data of the literatures,it was concluded that the rationality of the simulation,these results also deepened understanding the reason of the friction and wear.