Search

In this work, an exhaustive study on post effect processing of three-dimensional (3D) image is carried to solve the problem of nonlinear digital watermarking algorithm. First, through the feature space decomposition method of the host image, the embedded watermark is constructed with the full row or column rank of the matrix, and then the public key is constructed by using the existence of the unitary matrix of the full row rank and column rank matrix, so that the algorithm can embed and extract the watermark in an asymmetric way. Watermark extraction correlation coefficient (ρ) value is 1. When the deformation amplitude of the model is slight and the noise intensity is σ = 0.0001, the watermark can be extracted successfully, and the watermark extraction correlation coefficient (ρ) is 0.92. In addition, the security of the algorithm is analyzed from many angles, the theoretical analysis is given, and verified by the experimental results. The proposed 3D watermarking methods are used to examine the information capacity of various 3D meshes. The 3D watermarking methods’ resistance to noise perturbation and object cropping is also investigated.

AbstractFractures continuously extend and expand along bedding shale formations under the action of drilling fluid and eventually form a complex fracture network, which greatly reduces the strength of the rock. To determine the effect of the drilling fluid action time on the physical and mechanical properties of shale, nuclear magnetic resonance tests are carried out on shale soaked in oil-based drilling fluid for different soaking times. The fluid absorption rate of shale takes the form of a power function. The equations relating the shale mass, porosity, and permeability to soaking time are established. Then, in a sonic time-difference test, the change in the dynamic elastic parameters with the immersion time are observed. According to a triaxial strength test, the failure form and the deterioration degrees of the layered shale in different loading directions with immersion time are analyzed. Numerical simulation of the deterioration degree of shale under different water content conditions is carried out. When the water content increases, the collapse density of the surrounding rock of the well wall increases significantly. Finally, considering the anisotropy of bedding shale, the inclination angle, azimuth angle, and drilling fluid immersion time are substituted into the rock mechanics parameter deterioration model, the three pressure profiles of the formation are corrected, and the safe drilling fluid density window of the target interval is given.

For the impact of underground pressure,the roadway support equipment has poor anti-shock capability and is vulnerable to impact failure. A variable gradient thin-walled cylinder energy-absorbing and anti-shock component for anti-shock bracket is proposed. Design of different wall thickness difference and number of segments of variable gradient thin-walled cylinder energy absorbing members,The impact-crushing experiment of each parameter variable-gradient thin-walled circular tube was carried out,and the relevant energy-absorbing and anti-shock performance parameters were analyzed. The results show that the increase of the number of segments and the difference in thickness of the thin-walled circular pipe members will reduce the initial wall thickness of the thin-walled pipe,and reduce the initial peak force. Under the same average wall thickness,the average supporting reaction force and total energy absorption of the variable gradient thin-walled tubes with different wall thickness differences and number of segments are higher than ordinary thin-walled tubes by 9. 3% ～ 178%. In the variable-thickness thinwalled circular tubes with different parameters,the initial peak force,the absorbed energy,the average supporting force and the supporting force fluctuation performance parameters of the variable-gradient thin-walled circular tube members with four sections and thickness difference of 0. 5 mm are superior,which is ZQ3300 anti-shock bracket ideal anti-shock energy absorbing member,The design of the variable-gradient thin-walled circular pipe member can change the position and quantity of the plastic hinge formed by the ordinary thin-walled circular pipe member,so that the deformation of the thin-walled member tends to be more stable in the diamond mode and the mixed mode,and the energy absorption and anti-shock ability is improved.

The wear resistance of shearer conical pick body affects the service life of pick directly.Based on the analysis and comparison of the existing conical picks wear technology,the wear mechanism of the non-smooth surface with concave in the bionics was analyzed and studied. A kind of pick body surface with a non-smooth shape was designed,and the new structure was conducted a simulated friction and wear tests. The friction and wear tests on the sixteen different parameters of the concave structure show that the wear resistance of the concave-shaped non-smooth surface structure is significantly improved which is compared to the smooth surface,and the bionic non-smooth structure of the concave shape is analyzed through orthogonal test to analyze the effect of the parameters on the wear resistance.

To meet the requirements of shorter synchronization time and higher life for the synchronizer in transmission, mathematical models aiming at synchronization time and synchronizer life were established separately based on Newton’s second law and adhesive wear theory, M-B fractal contact model. The evaluation function was constructed by ideal point method to establish a multi-objective parameter optimization model with the two objectives. Using the AHP to determine weight value of the target in the multi-objective optimization model, and using the improved particle swarm algorithm to optimize the multi-objective parameter optimization model. The results show that the synchronization time is reduced by 8% and the synchronizer life is increased by 9% compared with that before optimization, the two objectives are improved better. The using of the improved particle swarm algorithm improves the performance of the synchronizer, and the application of the ideal point method effectively avoids the problem that the high order of magnitude dominates the multi-objective optimization.

The foamed aluminum filled crash-box with induction grooves on the side wall was made finite element analysis in the impact process by LS-DYNA,and the parameters influence of induction grooves on the energy absorption characteristics of crash-box was studied. The results was dealt with the LS-Prepost, considering the energy absorption, peak impact force, the average impact force and energy absorption ratio, when crash-box was made two radius of 2.5 mm semicircle grooves in the upper 50% part of the side wall, in the impact process of a symmetrical stack the ideal type of shrinkage deformation, depressed peak impact force without affecting energy absorption, higher energy absorption ratio and compression efficiency wound be gotten. The finite element simulation of the impact process was feasible when the crash-box body was made the impact test by the vertical and horizontal hydraulic impact test platform.

In order to realize the protection of broken conveyer belt with different moving direction, the scheme of broken belt protector with bidirectional and arc shaped catching scheme was proposed, and the main parameters were designed taking the GX1000 type conveyer belt as application example. The virtual prototype simulation of the broken belt protector catching process was done, and the velocity characteristic of main components was obtained. The model prototype with 1/2 structure size of the prototype machine was manufactured, and the test of catching process and the catching force were carried out. And the catching force parameters of prototype machine were derived based on small-scale model similarity theory. Consequently, the virtual and model prototype of broken conveyer belt protector with bidirectional and arc shaped catching scheme can carry out catching motion by different directions acorrding to the direction of broken belt motion, and wedge-shaped space for catching is formed and catching brake is finished. The broken belt protector single machine can realizes bidirectional catching. The limit catching force of prototype machine is higher than 56.4 kN, and the limit catching force is higher than theoretical cutting force which is 23.15 kN, and the demand of catching brake safely is met.

To improve the problem that the conventional design results of planetary gear transmission could not guarantee all of objectives were the optimal, aiming at the shortcomings that adaptive particle swarm optimization algorithm easily produced infeasible solution and fell into local optimum, an adaptive particle swarm optimization algorithm based on multi-level penalty function with dynamic change penalty coefficient was proposed. The algorithm set the penalty function as a multi-level penalty function and the penalty coefficient could be adjusted with the iterative process. The reliability and others were taken as the constraint conditions, the volume, the contact ratio and the transmission efficiency as the objective functions. Combined with the ideal point method to construct the evaluation function for multi-objective optimization. The results show that the volume is decreased by 41.87%, the contact ratio is increased by 2.643%, and the transmission efficiency is increased by 0.1563%. The improved particle swarm optimization improves the defects of original algorithm, and each objective is reasonably optimized.

The coal is the basic raw material for energy in China. It has strategic role in national economy,while the problems of roller surface adhesion,belt jitter,falling coal along return trip caused by coal freezing adhesion seriously restrict coal transportation in winter. Prior studies show that surface roughness has an important effect on freezing adhesion,in order to alleviate the freezing adhesive problems of coal by improving the material’s surface shape,our research group designed the freezing adhesive strength test device,under the certain frozen condition,freezing adhesive characteristics of six different roughness steel plates with moisture content 40% of the coal slime were tested. The results show that,the coal freezing adhesive strength with the change of roughness in W curve,appears minimum value when Ra= 9 10 μm,further suggest that appropriate surface roughness can reduce coal freezing adhesive strength. Thesis has guiding significance on mechanism research of freezing adhesion and other anti-freezing adhesive engineering fields.

In order to solve the freezing adhesive problem on roller and belt during coal transportation process in winter,on the basis of referring to relevant freezing adhesive theory,inspired by bionics,we did the theoretical analysis and experimental research about the application of bionic convex hull geometry structure on the roller and belt. In theory,it is verified bionic convex hull geometry structure can increase the the water contact angle,to a certain extent,it can reduce the freezing adhesive strength. We referred to the existing anti-freezing adhesive experimental study,used the UHMW-PE,designed and processed a bionic convex hull template,the height is 1. 0 mm,projected radius is 1. 0 mm,the center distance is 6. 4 mm,and another same material smooth template,by homemade freezing adhesive strength test device,under conditions of-25℃ temperature and3 h freezing time,we tested the freezing adhesive characteristics of two kinds of templates with moisture content 40% of the coal slime. The results showed that the normal freezing adhesive strength and tangential freezing adhesive strength of bionic convex hull template reduced about 8% and 12% respectively,we verified the bionic geometric convex hull indeed had certain antifreezing ability from the experiment aspect,hope can be used in anti-freezing adhesive field.

In order to enhance the competitiveness of the domestic hydraulic support. It is imperative to carry out reliability engineering. The reliability evaluation of the hydraulic support in service can effectively provide reference for the development and improvement of the product. It can also provide a reference for development of new type of reliability test. Based on support vector machine has great advantages in small sample data processing,Putting forward using support vector regression machine estimate weibull distribution parameter of hydraulic support failure time,when the failure date is small sample. The accuracy of the results obtained by different empirical formulas is compared. The reliability of the model is evaluated and predicted by the highest accuracy. Research shows that: support vector machine can be used to evaluate the reliability of hydraulic support under small sample maintenance data. Shape parameter of some commonly used hydraulic support reliability Weibull distribution is3. 0157,the scale parameter is 61728.

In order to analyze the influence of the related factors on the body temperature of high-speed gear in the meshing process,taking the standard involute gear as study object,based on the finite element analysis of temperature field and using the control variable method,the influence law of related factors on gear temperature is analyzed quantificationally. The results show that,the body temperature on tooth surface increase as rotation rate or torque increases,and the temperature increase amplitude decrease as rotation rate or torque increases. The temperature on tooth surface uniformly increase when tooth width increases,the change of modulus cause the changes of multiple factors and temperature on tooth surface decrease and then increase as modulus decreases. When rotation rate or torque is higher,the influence of rotation rate,torque,tooth width,modulus on gear temperature become bigger. The maximal body temperature increases or decreases as air and lube oil temperature,and the change has nothing with rotation rate or torque. The influence of heat transfer coefficients of gear end and meshing surface on gear temperature is relatively small,and temperature decreases as heat transfer coefficients increase. A reference for reducing the risk of gear high-temperature failure is provided.

In order to study the turnabout roller coal slime freezing adhesion problem in the process of open-pit mine during winter,experimental apparatus was designed by ourselves,simulated the production site,studied the change of freezing adhesive characteristics of different material in different temperature and different freezing time condition. The results show that different materials and dry basis moisture content 40% of the coal slime have different freezing adhesive strength,among them PTFE material in normal and tangential freezing adhesive strength is lower than other materials,2. 5hours at- 25℃,normal freezing adhesive coefficient is 0. 037 MPa,tangential freezing adhesive coefficient is 0. 076 MPa,it is about 1 /3 of UHMW-PE material ’s normal freezing adhesive coefficient,and about 1 /6 of it’s tangential freezing adhesive coefficient; it is about 1 /44 of Q235 material’s normal freezing adhesive coefficient,and about 1 /19 of it’s tangential freezing adhesive coefficient,It illustrates PTFE has good antifreezing adhesive ability. Tests also show that temperature of freezing adhesive strength has a certain influence,but is not a linear relation; After 3 hours freezing adhesive strength change is small; Material of tangential freezing adhesive coefficient is usually larger than normal freezing adhesive coefficient; Surface freezing adhesive strength is independent of how much coal sample.

Coal is the important basic energy in China,while the coal freezing adhesion seriously restricts with coal mine safe and efficient production in winter. Pressure as a secondary factor of coal freeze condition,it has an important influence on coal freezing adhesive strength. Through the freezing adhesive strength test device designed by ourselves,under conditions of- 25 ℃temperature and 3h freezing time,freezing adhesive characteristic of six different materials with moisture content 40% of the coal slime were tested. Studies have shown that pressure usually makes the coal freezing adhesive strength increase,such as Q235,normal freezing adhesive strength of under prepressure is 6. 2 times bigger than under no pressure’s,tangential freezing adhesive strength of under prepressure is 5. 9 times bigger than under no pressure’s. But only PTFE’s normal and tangential freezing adhesive strength under the condition of pressure both do not increase among six materials. In a sense,pressure will increase the hydrophilic material freezing adhesive strength,instead it will reduce the hydrophobic material freezing adhesive strength. The excellent characteristic of PTFE material shows wide application prospect in cold area of coal transportation,it deserves further study.

Coal is the important basic energy in China,however due to the problems of conveyor belt running deviation and avultion caused by freezing adhesive turnabout roller surface,it seriously restricts with coal mine safe and efficient production in cold regions during winter and brings huge economic losses to the company,although existing solutions have a certain ease of coal freezing adhesion but can not fundamentally solve the problem. Through the freezing adhesive strength test device designed by ourselves,under conditions of- 25℃ temperature and 3h freezing time,freezing adhesive characteristic of four different materials with moisture content 40% of the coal slime were tested. Experimental studies have found that with the decrease of material waterlubricating coefficient of kinetic friction coal normal and tangential freezing adhesive strength decrease,it shows a certain linear relation,the results indicate that improving the water-lubricating performance can reduce the freezing adhesive strength,the discovery has important guiding significance to the selection and preparation of anti-freezing adhesive coating in engineering field,it deserves further explore and study.

According to the freezing adhesion problem which exists between the coal and the belt conveyor turnabout roller surface,the freezing adhesive strength test device is created. To simulate the belt conveyor turnabout roller surface environment,- 30℃ temperature and 3h freezing time of stress conditions,several different materials are studied with moisture content 30% of the coal slime,each of the freezing adhesive characteristic. Comparative tests have proved that UHMW-PE material in normal,tangential freezing adhesive strength is lower than test of other materials,which proves that it is provided with good anti-freezing adhesive capability. According to UHMW-PE package roller based on the actual application situation can further illustrate that the UHMW-PE can be used as roller coating in order to achieve anti-freezing adhesive effect.

In order to optimize the layout of the large vibrating screen side panel stiffeners,Topology optimization design was applied in structural design of the side panel stiffeners. The topology optimization model of side panel stiffeners which were based on the goal of maximizing the lateral stiffness of side panel stiffeners was established. According to the pseudo density distribution of the topology optimization,the stiffeners would be rewired. The modal analysis and the harmonic response analysis were done for the panels before and after optimization. Compared with the original side panel structure,the new side panel’s dynamic stress was reduced by 56. 5%,Vibration displacement was reduced by 55. 3%. In addition,the first natural frequency was improved by 72. 03%,the natural frequency was far from working frequency effectively.

The finite element model of belt conveyor drum is established.And the stress and deformation of with and without reinforcement ring and different structures of reinforcing ring are analyzed by using finite element analysis software ANSYS.The corresponding relation between the different structures of reinforcing ring and the maximum deformation of drive drum is obtained after modeling and calculation.And the function relation between different structures of reinforcing ring and maximum displacement is fitted by using MATLAB,and the structure of reinforcing ring with minimum displacement can be selected according to the function.The theoretical basis and thought are provided for the standardized design of reinforcing ring of belt conveyor drive drum.

For analyzing the influence of related factors on gear thermo- elastic coupling deformation,based on the response surface method and the sample- point test method,the function relation between the gear thermo- elastic coupling deformation and related factor is constructed,gained by analyzing,the influence factors of tooth width,rotational speed,torque,boundary temperature on gear maximum thermo- elastic coupling deformation are- 0. 207,0. 273,0. 321 and 0. 199. According to the size and the positive and negative of these influence factors,the boundary temperature,tooth width,speed and torque have larger and larger influence on maximum deformation. The maximum deformation increased with the rotational speed,torque and boundary temperature,and decreased with the tooth width.

The chain used in embedded type stereo carport sustain the main weight during the process of lifting stereo carport. The chain plate is the main part of the chain,and lifting the carport repeatedly leads to fatigue failure. The traction mode of 28 A and 20 A,two types of the single and double row of chain are chosen,the chain plate model is established by using the ANSYS software,the force analysis is carried out and the fatigue analysis is carried out through the finite element software Workbench. By comparing the two kinds of force distribution regularity of the chain plate,the optimal chain mode is selected. And the more about life and fatigue failure about the chain can be known,which is convenient for maintenance and replacement of chain in timely.