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In view of the problem of poor coupling adaptability and easy rib spalling of coal wall in large mining height comprehensive mining, based on the effective inhibition effect of face guard mechanism on coal wall spalling, the structural characteristics and bearing capacity of different structural forms of the face guard mechanism are compared and analyzed. According to the surrounding rock adaptability of the face guard mechanism, established a numerical analysis model for rigid-flexible coupling of the face guard mechanism under different spalling forms. In order to accurately simulate the stress state of the protective mechanism, a variable stiffness spring damping system is used to replace the hydraulic cylinder. The load-bearing performance and response characteristics of the face guard mechanism under rib spalling coupling conditions were analyzed by applying uniform normal load and impact load to the face guard. The findings indicated that, the integral-type face guard mechanism has a better effect on suppressing rib spalling. When the face guard mechanism bears the static load of the coal wall, the entire response process of the face guard jack can be divided into three stages: initial support, increasing resistance bearing, constant resistance bearing; both the impact load position and the coupling state of the rib spalling will affect the characteristics of force transmission at the face guard mechanism's hinge point, the hinge point between the extensible canopy and the primary face guard is most sensitive to biased load. The research results can provide reference for optimizing the face guard mechanism of large mining height hydraulic support and improving the reliability of coal wall support. [ABSTRACT FROM AUTHOR]

To address the lightweight and real-time issues of coal sorting detection, an intelligent detection method for coal and gangue, Our-v8, was proposed based on improved YOLOv8. Images of coal and gangue with different densities under two diverse lighting environments were collected. Then the Laplacian image enhancement algorithm was proposed to improve the training data quality, sharpening contours and boosting feature extraction; the CBAM attention mechanism was introduced to prioritize crucial features, enhancing more accurate feature extraction ability; and the EIOU loss function was added to refine box regression, further improving detection accuracy. The experimental results showed that Our-v8 for detecting coal and gangue in a halogen lamp lighting environment achieved excellent performance with a mean average precision (mAP) of 99.5%, was lightweight with FLOPs of 29.7, Param of 12.8, and a size of only 22.1 MB. Additionally, Our-v8 can provide accurate location information for coal and gangue, making it ideal for real-time coal sorting applications. [ABSTRACT FROM AUTHOR]

The combined rock breaking method with the saw blade and conical pick is proposed to improve the rock breaking efficiency. The numerical simulation of combined rock breaking with the saw blade and conical pick is established to investigate the rock damage mechanism. And verified and modified the numerical simulation model with the rock breaking comprehensive test bench, the quantitative analysis error is less than 0.05, indicated quantitative analysis system is accuracy. The result indicated that the cutting parameters of the saw blade and conical pick affect the rock damage. And the cutting parameters of conical pick and structural parameters of rock plate have been studied to influence rock breaking volume. The research result could help optimize the cutting parameters of the saw blade and conical pick to improve the rock breaking efficiency. [ABSTRACT FROM AUTHOR]

Top coal caving in fully mechanized caving mining will cause an irregular impact on the caving mechanism of hydraulic support. The vibration response of the caving mechanism varies under different forms of impact. This response difference is a prerequisite for new coal rock identification technology in intelligent mining. Therefore, this work studies the difference in vibration response of the caving mechanism under different forms of impact. An innovative mechanical–hydraulic coupling system model of the caving mechanism impact by coal rock is established. The metal plate impact test proved the significant difference in vibration response of the caving mechanism under coal rock impact of different materials. Afterward, a more improved mechanical–hydraulic co-simulation model analyzed the difference in the vibration response of the caving mechanism under different rock materials, volumes, velocities and impact positions. The results show that the vibration response is more intense under rock impact than under coal impact. A lower position, a faster velocity and a larger volume correspond to a more noticeable response difference in the caving mechanism. The vibration and fault sensitive areas of the caving mechanism are determined. This study has a reference significance for improving the caving mechanism's structural design and failure prevention. The conclusions provide guidance for a new intelligent coal rock identification technology based on vibration signals. [ABSTRACT FROM AUTHOR]

As key supporting equipment in coal mining, hydraulic supports are vulnerable to impact pressure from roof movement and deformation. In this paper, a mechanical-hydraulic co-simulation platform for hydraulic supports is established. Moreover, the rationality of the simulation platform is verified. Based on this platform, the rigid-flexible coupling impact dynamics model of hydraulic support is built. Finally, by delaying the opening time of the relief valve, the energy dissipation problem of the relief valve hysteresis effect on the hydraulic support system under the rotary impact is discussed. The results indicate that the rotary load acting on the hydraulic support decreases gradually with the backward movement of the roof rotary position, which causes the peak pressure in the column to decrease (by 69 MPa). The hinge point load of different parts shows different load transfer laws. The hysteresis effect of the relief valve prolongs the energy release time of the system, increasing the pressure in the column by 23 MPa. The instantaneous opening speed of the relief valve spool reaches 15.7 m/s, and the hinge point between the top beam and the column is most sensitive to the hysteresis effect (impact coefficient increases by 0.63). [ABSTRACT FROM AUTHOR]

Compared with the forward design method through the control of geometric parameters and material types, the inverse design method based on the target stress‐strain curve is helpful for the discovery of new structures. This study proposes an optimization strategy for mechanical metamaterials based on a genetic algorithm and establishes a topology optimization method for energy‐absorbing structures with the desired stress‐strain curves. A series of structural mutation algorithms and design‐domain‐independent mesh generation method are developed to improve the efficiency of finite element analysis and optimization iteration. The algorithm realizes the design of ideal energy‐absorbing structures, which are verified by additive manufacturing and experimental characterization. The error between the stress‐strain curve of the designed structure and the target curve is less than 5%, and the densification strain reaches 0.6. Furthermore, special attention is paid to passive pedestrian protection and occupant protection, and a reasonable solution is given through the design of a multiplatform energy‐absorbing structure. The proposed topology optimization framework provides a new solution path for the elastic‐plastic large deformation problem that is unable to be resolved by using classical gradient algorithms or genetic algorithms, and simplifies the design process of energy‐absorbing mechanical metamaterials. [ABSTRACT FROM AUTHOR]

Circular saw blades are widely used in stone processing. The circular saw blade cutting hard rock numerical simulation model based on ANSYS/LS-DYNA was established to investigate the complex dynamic problem in rock cutting. The failure mechanism of the rock and the influence of cutting parameters on the cutting force and rock fragments were studied by numerical simulation. The results demonstrated that the failure modes of the rock were mainly tensile failure with some shear failure and compressive failure. The cutting force and the number of fragments increased with the feed speed. With the increasing circular saw blade rotational speed, the cutting force and the number of fragments decreased and tended to stabilize. With the distance between the circular saw blades increasing, the cutting force and rock fragments number increase and then maintain basic stability, and when the distance between double circular saw blades reaches 25 mm, it will form a completed rock plate and the interaction of circular saw blades will decrease. The numerical simulation can accurately simulate rock breakage and force when a circular saw blade cuts rock. [ABSTRACT FROM AUTHOR]

In the process of coal mining, the canopy and column play an important role in the safety support of hydraulic support. However, due to the complex and changeable coal seam conditions, the hydraulic support is significantly affected by the impact load. This paper aims to reveal the dynamic characteristics of canopy and column under impact load. Firstly, the dynamic model of hydraulic support is established, and the impact response of each hinge point of the canopy is analyzed. Secondly, based on the fluid–structure interaction (FSI) theory, the two-way FSI model of the column is established, and the structural change of the column and the flow field characteristics in the cylinder under the impact load are analyzed. The results show that the front column hinge is more prone to impact failure under impact load. The impact load has a significant impact on the two-level cylinder, the pressure in the cylinder increases, and an eddy current occurs on both sides of the bottom of the cylinder. The research results can provide references for the structural optimization of the hydraulic support with anti-impact load and the strength design of the column. [ABSTRACT FROM AUTHOR]

In the process of top coal caving mining, the caving time and the tail beam swing angle have an important impact on the evolution of the coal gangue boundary, which determines the top coal recovery rate and gangue content rate. Therefore, it is necessary to study the influence of the caving time and the tail beam swing angle on the top coal caving effect. For this purpose, based on Hertz–Mindlin contact theory, this paper established a simulation model of top coal caving and carried out a coal caving simulation with different caving times and tail beam swing angles. In the process of coal caving, under a specific tail beam swing angle and different caving times, this work studied the evolution characteristics of the coal gangue boundary. A simulation model of coal caving with variable time is established, and the influence mechanism of time on the coal caving effect is analyzed. Then, the evolution characteristics of the boundary are studied under different tail beam swing angles and the same caving time. A simulation model of coal caving with variable angles is established, and the influence mechanism of the tail beam swing angle on the coal caving effect is analyzed. Finally, the effects of caving time and tail beam swing angle on coal gangue discharge are studied, and the effect of coal gangue release under different working conditions is analyzed. The boundary data and the discharge data are extracted through the simulation, and contrast curves are drawn. The results show a limit position of the coal gangue boundary under the fixed working condition, which is the middle line position of the coal caving outlet. When the coal gangue boundary does not reach the limit position, there are two characteristics. First, the greater the tail beam swing angle is, the faster the deformation speed of the coal gangue boundary is. At the same caving time, the position of the coal gangue boundary will be closer to the coal caving outlet, which leads to excessive mixing of coal and gangue. Second, the longer the drawing time, the greater the deformation of the coal gangue boundary, and the easier the coal gangue is mixed, resulting in an increase in the gangue content of the discharged coal. When the coal gangue boundary reaches the limit position, the boundary will be basically stable near the top of the coal caving outlet. The limit position and shape of the coal gangue boundary are mainly affected by the density difference of coal gangue particles but not by the coal caving time and the tail beam swing angle. After the end of coal caving, the coal gangue boundary finally presents a double arch structure. The research in this paper has important reference significance for the selection of caving time and tail beam swing angle and further research. [ABSTRACT FROM AUTHOR]

• A leakage flow estimation model based on swashplate position and operating conditions is established by a displacement transducer at actuator piston. • An indirect flow measurement for a bi-tandem axial piston pump is proposed by considering leakage, flow ripple, and compressibility. • The method enables output flow monitoring and feedback without the need for flowmeters in pump-controlled hydraulic systems, avoiding additional energy consumption and cost increase. In pump-controlled hydraulic systems, configuring a flowmeter at a variable piston pump to monitor output flow causes additional losses. A method for indirect flow measurement of the bi-tandem axial piston pump based on flow leakage estimation is proposed to address this problem. The method first installs a displacement transducer at the actuator piston to collect data on the actuator piston position, outlet pressure, and shaft speed, then estimates leakage of key kinematic pairs, and finally considers flow ripple and fluid compressibility to form an indirect measurement for output flow of the pump. The indirect measurement accuracy under various typical operating conditions is analyzed. The results demonstrate that the mean absolute percentage error of the proposed indirect flow measurement method is less than 2.10%, and the method is effective with high measurement accuracy. The indirect measurement method avoids extra costs and energy consumption associated with configuring flowmeters in engineering hydraulic systems. [ABSTRACT FROM AUTHOR]

The research on coal gangue "category" recognition via single classification algorithm for single-channel signal data shows that the classification and recognition capabilities of different algorithms on different channel signals and data types exhibit significant differences. In order to improve coal gangue classification and recognition effect, a coal gangue classification and recognition method of "multi-information fusion" based on the "parallel voting system (PVS)" was proposed in this study. The joint judgment of coal gangue "category" was completed through the combination of multiple algorithms or channel signal data with stronger recognition ability according to the voting principle of "the minority is subordinate to the majority". Based on the signal characteristics data obtained from the impact-slip test between coal gangue and the hydraulic support, three different modes of PVS-based coal gangue classification and recognition, namely, channel signal data PVS (SDPVS), algorithm PVS (APVS), and algorithm and channel signal data combination double PVS (algorithm-data double parallel, A&SDPVS), were respectively investigated herein. The influence of signals combination mode, algorithms matching mode as well as combined mode of signals and algorithms on coal gangue "category" voting recognition accuracy was studied. The research results show that for the SDPVS when a single algorithm with higher recognition accuracy and its corresponding multiple channel signal data with higher recognition accuracy were selected and for the A&SDPVS when the multiple "Recognition combination of single algorithm and single channel signal data" with higher recognition accuracy was selected, coal gangue classification and recognition effect could be improved. PVS-based coal gangue "category" recognition accuracy could reach up to 97.5%, which effectively improved coal gangue classification and recognition ability; moreover, the effectiveness of the multi-information fusion method proposed in this study was proven. [Display omitted] • Proposed three coal gangue "category" voting recognition methods and recognition processes. • Studied influence of signals and algorithms combination modes on voting recognition accuracy. • SDPVS and A&SDPVS can effectively improve recognition accuracy even to more than 97%, but APVS can't. [ABSTRACT FROM AUTHOR]

The conical pick is the most crucial tool of roadheader for breaking rock, establishing the conical pick cutting rock and conical pick fatigue life numerical simulation models to investigate the influence of cutting parameters on rock damage, average peak cutting force, specific cutting energy and the conical pick fatigue life. The research results indicate that the width and depth of rock damage increase with increasing cutting depth and cutting speed. The average peak cutting force and the specific cutting energy have the same changing tendency. The changing trend of conical pick fatigue life and conical pick stress is opposite relationship. The optimum cutting angle of the conical pick cutting rock is 45°. Applying the research results for guiding the optimization of the cutting parameters reduces the specific cutting energy and stress and improves the conical pick fatigue life. [ABSTRACT FROM AUTHOR]

In top coal caving mining, common impact occurs between coal gangue particles and tail beam. Little attention has been paid to the effects of coal gangue particles failure on impact force and tail beam response theoretically, numerically, and experimentally. This paper aims to reveal the influence of coal gangue particles failure on the impact effect of tail beam. First, this paper incorporates the theory of rock failure and energy consumption to assess the impact process of coal gangue particles on the tail beam. A new model to simulate the actual failure conditions of rock particles was developed: the brittle damage-fracture particle model. By comparing damage phenomena and simulation data, the brittle damage-fracture particle model was proved to be correct. Based on this model, a dynamic simulation of brittle coal gangue particles impacting the tail beam was conducted. Then, the dynamic responses of the particles and tail beam were analyzed. The results show that particle failure significantly affects the impact force and dynamic response of the tail beam. The impact effects of coal and gangue particles on the tail beam and their failure energy consumption also differed significantly. This paper stresses the importance of coal gangue particle failure conditions for research on top coal caving mining. Theoretical support is provided for the research of coal gangue identification technology based on the tail beam vibration signal. [ABSTRACT FROM AUTHOR]

Model uncertainties are usually unavoidable in the control systems, which are caused by imperfect system modeling, disturbances, and nonsmooth dynamics. This paper presents a novel method to address the robust control problem for uncertain systems. The original robust control problem of the uncertain system is first transformed into an optimal control of nominal system via selecting the appropriate cost function. Then, we develop an adaptive critic leaning algorithm to learn online the optimal control solution, where only the critic neural network (NN) is used, and the actor NN widely used in the existing methods is removed. Finally, the feasibility analysis of the control algorithm is given in the paper. Simulation results are given to show the availability of the presented control method. [ABSTRACT FROM AUTHOR]

Advancing of the intelligent fully mechanized caving mining technology (IFMCMT) is the fundamental method to improve the output of coal resources. Accurate identification of coal gangue is the necessary condition for the realization of IFMCMT. To achieve coal gangue recognition, Internet of Things (IoT) technology and impact-slip contact characteristics based method for coal gangue "category" recognition is proposed in this paper. An IoT recognition system is constructed, then impact-slip test bed between coal gangue mixture and the hydraulic support is designed. Secondly, coal gangue "category" recognition parameters are discussed, hereby multi-dimensional contact characteristic information acquisition system is constructed. After that, impact-slip tests were carried out to extract and process the multi-source and multi-azimuth signals, and three kinds of data samples were obtained. Finally, 10 kinds of classification algorithms were selected for random classification recognition of coal gangue "caving category" and "shut down category". Coal gangue "category" recognition ability by algorithms, signal types and data types is compared, which provides the theoretical basis for further classification recognition effect improving research. Research show that coal gangue "category" random recognition accuracy can reach to 0.935 (Define the range of recognition accuracy as 1), which proves the effectiveness of "category" by IoT system and impact-slip contact characteristics. Coal gangue "category" recognition. [Display omitted] • Proposed a coal gangue recognition method based on impact-slip contact tests and IoT system. • Impact-slip test equipment between coal gangue mixture and the hydraulic support is put forward. • Multi-dimensional effective contact characteristic parameters for recognition are determined. • A multi-source and multi-azimuth information acquisition system is constructed. • Formulated coal gangue recognition procedure and realize coal gangue recognition. [ABSTRACT FROM AUTHOR]

The diamond sawblade has been widely used in the field of rock mining and processing. This article, through the establishment of a numerical simulation model of diamond sawblade cutting rock, studies the influence of the distance between the diamond sawblade and free surface on cutting performance. In the process of diamond sawblade cutting rock, with the increase of the distance from the sawblade to the free surface, the average cutting force, normal force, and tangential force of the sawblade increase at first and then stabilize, and the axial force gradually decreases and tends to be stable. In the process of cutting rock with fixed depth, cutting force and rock damage are positively related to feed speed and cutting depth of the diamond sawblade. Through the statistical analysis of rock damage by image recognition program statistics, it is concluded that the feed speed and cutting depth of the sawblade have a significant impact on the rock damage value. When the distance increases to 12 mm, there is a relatively complete rock plate between the sawblade and free surface. The rock free surface damage disappears when distance reaches 16 mm. The research results provide a theoretical basis for the sawblade processing rock plate. [ABSTRACT FROM AUTHOR]

Impact contact behaviors with different velocities, direction and contact states occurred in the process of coal drawing between coal gangue particles and the hydraulic support greatly increase the difficulty of coal gangue recognition in top coal caving. In order to finally realize coal gangue recognition in top coal caving, this paper studied the impact behavior of a single particle coal gangue and the metal plate at any position and the problem of the identification of coal gangue particles. First, the any position impacting test bench and test system is constructed, in which multipoint acceleration information acquisition space is built. Second, 2400 groups of random impact tests between coal gangue particle and the metal plate are conducted. Third, while each impact test was going on, acceleration signals in the seven different positions of the metal plate were collected. Forth, after all the impact tests are completed, signals are processed by segmentation and re-sorted by randomization. Then, the method of signals serial splicing is proposed to process the different position standardized signals obtained in each group of impact test, and coal gangue recognition is proposed based on processed signal data and SVM algorithm. After that, the effect of parameters on coal gangue recognition accuracy of SVM algorithm is studied, and the corresponding parameter settings of SVM are accordingly determined. Finally, coal gangue recognition was conducted by using SVM based on different data samples, the influence law of the training set data set expansion method and the test set data matching relationship, the number of tandem sensors and matching relationship, and the number of training set samples on coal gangue recognition accuracy were studied. The study will serve as the research basis for the application of SVM and signals serial splicing method in coal gangue recognition. [ABSTRACT FROM AUTHOR]

• The force on the surface unit of the crankpin exhibits consistency within the cycle. • There is a law of force variation at each crank pin of the crankshaft. • There is a correlation between crankshaft force and load condition with flow rate. The stability and safety of emulsion pumps are significantly influenced by crankshafts. However, the crankshaft of the emulsion pump bears complex torsional and bending stresses during operation; thus, it is prone to failure. The purpose of this paper is to determine the dynamic response of the crankshaft under various working conditions. The mechanical model of the power end of the emulsion pump is constructed, and the dynamic model is established by LS-DYNA. The stress distribution characteristics of the surface element of the crankpin in the pulsating impact cycle are analysed, and the dynamic response of the crankpin under multiple working conditions is studied. The results show that under the action of pulsating impact, the edge position of the crankpin is more likely to fail, especially at the second crankpin, and the maximum stress can reach 213 MPa. The dynamic impact of the connecting rod on the crankpin is positively correlated with the flow of the emulsion pump and the hydraulic pressure on the plunger, and the crankshaft vibration becomes more noticeable as the flow rate rises. Doubling the flow rate increases the vibration by 73.9 %. Our research results provide a reference for avoiding the failure of the crankshaft and optimizing the design. [ABSTRACT FROM AUTHOR]

The conical pick is the most crucial tool of roadheader for breaking rock, establishing the conical pick cutting rock and conical pick fatigue life numerical simulation models to investigate the influence of cutting parameters on rock damage, average peak cutting force, specific cutting energy and the conical pick fatigue life. The research results indicate that the width and depth of rock damage increase with increasing cutting depth and cutting speed. The average peak cutting force and the specific cutting energy have the same changing tendency. The changing trend of conical pick fatigue life and conical pick stress is opposite relationship. The optimum cutting angle of the conical pick cutting rock is 45°. Applying the research results for guiding the optimization of the cutting parameters reduces the specific cutting energy and stress and improves the conical pick fatigue life. [ABSTRACT FROM AUTHOR]

The new method of rock breaking based on the combination of circular sawblade and conical pick was proposed to improve the effectiveness of hard rock breaking. The numerical simulation method was applied to research the conical pick cutting arc rock plate by ANSYS/LS-DYNA. The conical pick cutting arc rock plate numerical simulation model was established to research the influence of arc rock plate structural parameters and cutting parameters on cracks formation and propagation of the arc rock plate and the cutting force in the process of conical pick cutting arc rock plate. The amount of cracks is positively correlated with arc rock plate thickness, the cutting speed, and distance of cutting point to arc rock plate central axis and negatively correlated with the cutting angle. The mean peak cutting force is positively correlated with the thickness of arc rock plate and the distance of cutting point to arc rock plate central axis; however, it is negatively correlated with the arc rock plate height and width and cutting angle of conical pick. The simulation results can be used to predict the conical pick work performance with various cutting parameters and structural parameters. [ABSTRACT FROM AUTHOR]

A simple and effective mechanical parts maintenance approach with lower cost is urgently needed by the cost-sensitive manufactures for traditional excavators (HE). This paper proposes maintenance strategy for hydraulic cylinders (HC) of HE with energy regeneration and recovery system (ERRS). Reliability analysis and FMEA of historical failure data are applied to make maintenance strategy. In this study, the failure data required for reliability analysis are collected from the manufacturers and users over two and a half years, Excel is used as statistical tool, Minitab is used for parameter estimation, and Kolmogorov–Smirnov test is used to reject or accept the hypothesis of the distribution model. The reliability parameters R(t), Rset, and R∗(t) are determined and parameter β∗ is the reference value for making countermeasures and maintenance policies properly for the failure modes of the new HC of HE with ERRS. The purpose of this paper is to make proper maintenance policies and to maintain a high availability level and fulfill the user's needs for HC, which also paves the way for further reliability study about ERRS. [ABSTRACT FROM AUTHOR]

Conical pick wear is an urgent problem in the roadway excavation caused by hard rock difficult to break. The traditional method of increasing cutting power to improve cutting performance of conical pick significantly increases pick wear. In the paper, a saw blade and conical pick combined cutting method is proposed based on increased free surface. To research the fracture morphology and cutting force of rock plate, theoretical, numerical, and experimental methods are used. By theoretical research, the bending mechanical model of rock plate bending is established. The cutting position and the junction between the free sides and fixed sides are preferentially broken. A numerical model combining the erosion and damage constitutive model is built, and the cutting process of rock plate was presented. According to rock plate experiment, the peak cutting force increases with the increasing uniaxial compressive strength, thickness of rock plate, and cutting depth of conical pick and decreases with the increasing width and height of rock plate. Exponential relationships exist between peak cutting force and thickness, width and height of rock plate, and cutting depth of conical pick. Linear relationship exists between peak cutting force and uniaxial compressive strength. The size of rock fragments increases with uniaxial compressive strength, width, and height of rock plate. [ABSTRACT FROM AUTHOR]

The rock cutting process with a circular sawblade and the rock breaking mechanism of rock are studied with a numerical simulation method in this paper. The influence of cutting parameters of the circular sawblade on cutting force, rock damage, and specific cutting energy in the process of circular sawblade cutting rock is researched. The cutting force increases with the feed speed and an increase in cutting depth and decline in rotation speed. Cutting rock with double circular sawblades can reduce cutting force. However, the specific cutting energy declines with the increase in cutting depth and the decline in the distance between the double circular sawblades. Cutting parameters have a great influence on the damage range of rock. The research results can be applied to rock processing with a circular sawblade. [ABSTRACT FROM AUTHOR]

Conical pick is a rock cutting tool that is commonly used in roadway driving. Pick wear frequently happens in the course of breaking hard rock. The current paper shows a new method to solve the problem of pick wear. The rock is preslit with the saw blade and then broken by the conical pick. In order to study the cutting force and features of rock fragment, the numerical model is built between rock plate and conical pick. And element erosion is added in the code to obtain the fracture result. The rock plate cutting testbed is made to testify the correctness of numerical simulation. The width, height, and thickness of the rock plate, as well as cutting angle and cutting position, which influence cutting force and rock fracture are studied. According to the results, there exist exponential relationships between cutting force and width and thickness of rock plate. In addition, a linear relationship is found between the cutting force and the height of rock plate. Furthermore, both the cutting angle and cutting depth have an influence on cutting force. In particular, the factors of thickness and height or rock plate have the most obvious influence on cutting force. It is proven that what is beneficial to rock fracture is higher height and lower thickness of rock plate. [ABSTRACT FROM AUTHOR]

Conical pick is a diffusely applied cutting tool in rock excavation in the coal-mining industry. In order to enhance the capability of conical pick, a new rock cutting method based on increased free surface is proposed. To research the peak cutting force and fracture morphology, ANSYS/LS-DYNA is used to establish the conical pick and rock interaction model. To obtain the fracture morphology of rock plate, eroding contact, erosion element failure, and damage constitutive are considered in the numerical model. Mechanical properties test and rock plate cutting experiment are carried out to guarantee and verify the correctness of the numerical model. The width and height of rock plate influencing peak cutting force and fracture morphology are studied, and the stable peak cutting force is defined. Lower width and height contribute to more fragments in smaller dimension produced during the rock plate cutting process. Besides, higher skew angle leads to more fragments. The peak cutting force decreases with the increasing width and height of rock plate while reaching stable peak cutting force, and it reduces and then remains stable with the increasing cutting position and symmetrical with skew angle of zero degree. [ABSTRACT FROM AUTHOR]

In the rock cutting process, conical pick wear is often encountered. In order to restrain this condition, a saw blades and conical pick combined cutting method was put forward. Saw blades were employed to slit the rock for increasing the free surface, and then the conical pick was used to break the rock. To research the cutting performance of the new cutting method, the corresponding experimental device and a three-dimensional finite element model are established. In order to obtain crack propagation and fragment separation and to study the fracture process of the rock plate, a damage constative model and failure mechanism were combined in the numerical model. The mechanical tests were carried out to achieve the mechanical parameters of the rock. To investigate different parameters affecting rock plate cutting performance, experiments with different compressive strengths, physical parameters, and cutting depths were carried out. Moreover, the confining pressures affecting the cutting performance were adopted to simulate deep mining conditions. The experimental results demonstrated that the peak cutting force shows the exponential positive correlation with compressive strength, thickness of the rock plate, and cutting depth of the conical pick, and exhibits the exponential positive correlation with rock plate height and width. Besides, the numerical simulation results show that peak cutting force and confining pressure have a binomial relationship. [ABSTRACT FROM AUTHOR]

Aiming at the complex nonlinear dynamic problem of cutting hard rock with diamond sawblades, the process of hard rock cutting with a diamond sawblade was studied based on ANSYS/LS-DYNA. A numerical simulation model of a diamond sawblade cutting hard rock with different rotation speeds, feed speeds, and cutting depths was established to study the effects of the cutting parameters on the cutting force and specific cutting energy consumption and on the damage to the rock. The numerical simulation results demonstrated that the feed speed and cutting depth of the diamond saw are quadratically correlated with the cutting force, but the rotation speed is negatively linearly correlated. The damage region of the rock is positively correlated with the feed speed and cutting depth of the diamond sawblade and has a negative correlation with the rotation velocity. The cutting parameters have a great influence on specific cutting energy consumption. Analysis of the relationship among the cutting parameters and the specific cutting energy with multivariate linear fitting indicated that the cutting speed and cutting depth have a great influence on the cutting energy. [ABSTRACT FROM AUTHOR]

The collision between the coal–gangue and the metal plate of the hydraulic support is a typical mechanical contact behavior in the surface coal mining, which will cause vibration in the tail beam and even in the whole hydraulic support. This paper presents a contact analysis of coal–gangue impact on the metal plate to discover how vibration signals are generated and propagated in the collision process. We build a dynamic model for rock impact on the metal plate based on the elastoplastic contact theory, the Drucker–Prager criterion and the Tavares and King particle impact damage model. We establish a finite element model of the impact system between the coal–gangue and the metal plate, conduct contact simulation using the software LS-DYNA and study the stress transfer process on the metal plate contact surface. We compare the parameters of coal and gangue impact on the metal plate and discuss how they are different by calculating the stress and displacement created in the metal plate, kinetic energy of the coal–gangue particles and the total energy of the metal plate. In addition, we study the effect of impact velocity on the vibration response of the metal plate. Results show that the stress wave diffuses outward from the center of the metal plate. The collision frequency, contact position of the rock sphere and re-collision time are random. As the impact velocity increases, the contact responses all increase. This study provides guidance for the analysis of vibration response of coal–gangue impact on tail beam. [ABSTRACT FROM AUTHOR]

Scraper conveyor is the most important transportation equipment in the comprehensive mining equipment, and the chain drive system is its core subsystem, its dynamic characteristics will significantly affect the efficiency of coal transportation in the comprehensive mining face. In this paper, the dynamic characteristics of chain drive system when impacted by falling coal are investigated by means of test. The impact test bench of scraper conveyor was set up to analyze the effects of chain speed, impact height and impact load mass on the dynamic characteristics of the chain drive system of scraper conveyor under the working conditions of unloaded and loaded. The results show that the longitudinal vibration of the scraper conveyor is most obvious when it is impacted by the falling coal, and the chain speed, impact height and impact load mass of the scraper conveyor all play an excitation role on the vibration of the chain drive system, and the vibration of the chain ring is the most intense in the chain drive system, and the loaded coal pile conveyed on the scraper conveyor plays an inhibiting role on the vibration of the chain drive system. This study can help to identify the location where the scraper conveyor fails first in the impact condition, so as to provide a basis for its structural design and improvement, which is of great significance for the stable operation and structural optimization of the scraper conveyor. [ABSTRACT FROM AUTHOR]

It is important to allocate a reliability goal for the hydraulic excavator in the early design stage of the new system. There are some effective methods for setting reliability target and allocating its constituent subsystems in the field of aerospace, electric, vehicles, railways, or chemical system, but until now there is no effective method for the hydraulic excavator or engineering machinery. In this paper, an approach is proposed which combines with the conventional reliability allocation methods for setting reliability goals and allocating the subsystem and parts useful in the early design stage of the hydraulic excavator newly developed. It includes Weibull analysis method, modified Aeronautical Radio Inc. (ARINC) method, and modified systematic failure mode and effect analysis (FMEA) method. After completing reliability allocation, it is necessary to organize the designers and experts to evaluate the rationality of the reliability target through FEMA analysis considering feasibility of the improvement technically for the part which was new developed or had fault in its predecessor. The proposed approach provides an easy methodology for allocate a practical reliability goal for the hydraulic excavator capturing the real life behavior of the product. It proposes a simple and unique way to capture the improvement of the subsystems or components of the hydraulic excavator. The proposed approach could be extended to consider other construction machinery equipment and have practicality value to research excellent mechanical product. [ABSTRACT FROM AUTHOR]

It is important to allocate a reliability goal for the hydraulic excavator in the early design stage of the new system. There are some effective methods for setting reliability target and allocating its constituent subsystems in the field of aerospace, electric, vehicles, railways, or chemical system, but until now there is no effective method for the hydraulic excavator or engineering machinery. In this paper, an approach is proposed which combines with the conventional reliability allocation methods for setting reliability goals and allocating the subsystem and parts useful in the early design stage of the hydraulic excavator newly developed. It includes Weibull analysis method, modified Aeronautical Radio Inc. (ARINC) method, and modified systematic failure mode and effect analysis (FMEA) method. After completing reliability allocation, it is necessary to organize the designers and experts to evaluate the rationality of the reliability target through FEMA analysis considering feasibility of the improvement technically for the part which was new developed or had fault in its predecessor. The proposed approach provides an easy methodology for allocate a practical reliability goal for the hydraulic excavator capturing the real life behavior of the product. It proposes a simple and unique way to capture the improvement of the subsystems or components of the hydraulic excavator. The proposed approach could be extended to consider other construction machinery equipment and have practicality value to research excellent mechanical product. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to reveal the cavitation characteristics of three oil wedges sleeve bearing and set the theoretical and experimental basis for defining the oil film boundary condition.Design/methodology/approach Computational fluid dynamics model of three oil wedges sleeve bearings based on the Navier–Stokes equation is set using Fluent considering turbulent situation and two-phase flow theory. The cavitation characteristics of bearing is investigated by taking pictures of experiment.Findings The rupture region of oil film and the contours of air volume fraction increase distinctly with the increase of rotating speed and the decrease of input pressure. The critical rotating speed of cavitation occurrence and oil film pressure increases with the increase of input pressure. The change trend of experiment cavitation with the rotating speed and input pressure is consistent with theoretical cavitation in general.Originality/value The finite element model of three oil wedges sleeve bearings is established based on the Navier-Stokes calculation equation of the fluid, two-phase flow theory and turbulent model. Sleeve bearing is transparent, the pictures of cavitation can be easily taken by high-speed camera, the cavitation characteristics of bearing is studied by experiment. The cavitation performance of three oil wedges bearings is studied with the change of input pressure and rotating speed, the change trend is basically consistent for theory and experiment. The study on critical rotating speed of cavitation occurrence is benefit for defining the oil film boundary condition. [ABSTRACT FROM AUTHOR]

Highlights • Based on the Flores contact model, we establish the dynamic model of spherical rocks vertical impact on the metal plate with the considering the energy absorbed and consumed by the compression of the rock and energy absorbed by the bending deformation of the metal plate. • Based on the Drucker–Prager criterion, we obtain the function of maximum comprehensive stress ε 0 (α, μ 1) and deduced the initial yield stress and initial yield impact velocity for the consideration of principal stress σ2. • We propose the approximate theoretical formula of the maximum contact compression of spherical rocks based on recursive solution. Influence law of impact velocity, material parameters and structure size on the dynamic response of the impact system is obtained. • The combining simulation based on ADAMS and Hypermesh was used to verify the correctness of the theoretical model. Abstract In the process of top coal caving mining, the metal sheet of the tail beam of the hydraulic support will vibrate when coal and rock particles start to impact the tail beam. In the impact between the particles and the metal plate of finite dimension, there are many complicated problems such as short duration of impact, rapid enhancement of transient stress, local large deformation of particles and macroscopic deflection of the metal plate are involved. However, the analysis of the contact force between the spherical particles and other objects is still simplified to the ideal Hertz contact problem. In order to study the real contact states of coal and rock particles impact on the metal plate, we simplified the working conditions from the coal and rock particles impact the tail beam in top coal caving mining to the system that spherical particles have similar properties to coal or rocks impact vertically on the metal plate. Based on the Flores contact theory and the energy absorbed by the bending deformation of the metal plate, the contact model of spherical rock at the compression stage was established. At the same time, we researched the initial yield stress and initial yield impact velocity of spherical rock that obeys the Drucker–Prager (D–P) criterion and proposed the approximate theoretical calculation method of maximum contact compression of spherical rocks. In the range of elastic impact velocity, the influence of impact velocity, restitution coefficient, material parameters and structure sizes on the dynamic response of the system were also analyzed. Finally, the correctness of the theoretical model has been verified by the virtual prototype simulation combined by ADAMS and Hypermesh. The research will provide the basic theory reference for the recognition technology of a single particle of coal or rock that based on the impact vibration of the tail beam. [ABSTRACT FROM AUTHOR]

At present, the contact problem between the particle and the plane plate is generally equivalent to the rigid sphere impacting the elastic half space or the elastic sphere impacting the rigid surface. However, in the actual contact process, there will be no rigid body, and both contact and contacted object will deform and absorb energy. The research results obtained from the equivalent of the contact material to the rigid body are less accurate. In order to obtain the accurate mechanical relation and contact response, we took the research of impact between particles and the metal plate as a breakthrough in which the particle is equivalent to an elastic sphere and the metal plate is equivalent to an elastic half space and established the theory of vertical impact contact between elastic sphere and elastic half space by the Hertz contact theory. Through the dynamic simulation of an elastic sphere which has similar properties with rock impacting target in elastic half space in LS-DYNA, the correctness of the established theory and the feasibility of the contact process simulated by LS-DYNA are verified. Based on the established theory and 3D simulation, we studied the influence law of material parameters on the contact response and analyzed the differences of the collision vibration signals caused by the different contact objects. From the above research results, we obtain that the theoretical model is more accurate to predict the maximum contact force and contact displacement in this paper than traditional Hertz theory. And the sphere radius and both contact objects’ elastic modulus have larger influence on the contact response than sphere density, while the Poisson’s ratio has the smallest influence on the contact response results. Different material properties will cause the different contact response. The conclusions of this paper provide a theoretical calculation method for contact and a 3D simulation method for elastic half space and provide theoretical guidance for the differences analysis of the vibration signal. [ABSTRACT FROM AUTHOR]

In order to study the support failure mechanism of a super-large mining height powered support, a mathematical model of the load carrying capability area (LCCA) under various loading conditions for the support was established. A certain type of support was considered as an example, and the distribution characteristics of the LCCA were analyzed. According to the results of theoretical analysis, a dynamics numerical simulation model based on the ADAMS software was developed. The response of the support was observed under conditions of various loading intensities and positions. The simulation results demonstrated that deviation of the roof load from the optimal equilibrium area (OEA) was the key reason for the support failure. Subsequently, the factors affecting the OEA of the support were analyzed and the analysis result appraisal was executed by the load carrying capability theory. The results demonstrated that optimization of the structural parameters of the powered support was reasonably conducive to the range expansion of the OEA. Therefore, the support failure tendency could be reduced. The research results were useful in the structure optimization of the powered support, thus improving the corresponding reliability and stability. [ABSTRACT FROM AUTHOR]

To improve the safety and the stability of the support under mines and reduce the cost, we design a new slipper-type hydraulic support with energy-efficiency and high reliability. To study its dynamics, we build a reverse kinematics model. We analyze the motion and the force for each component of the new support with a simulation in Matlab/Simulink. The results show that it has appropriate structures with the required four-bar linkages. To compare the performance between the new slipper-type support and the traditional support, we design their mechanics models, deduce their mechanics relations and obtain the force curves for each component of both supports under the same loads. The results prove that the new slipper-type support has less demand on oil pressure for the hydraulic cylinder when working at middle and high positions and it has a larger supporting force and a higher supporting stability which would be more energy-efficient. [ABSTRACT FROM AUTHOR]

The problems of insufficient recognition accuracy, poor real‐time performance and lack of consideration of actual working conditions in the process of intelligent construction of coal mines make this technology still in the research stage and not applied in practical engineering. The purpose of this paper is to establish an accurate and real‐time recognition model, which can quickly distinguish the vibration acceleration signals of coal and gangue under the influence of external factors such as impact position, velocity, and direction by using the different physical properties of coal and gangue particles. Therefore, the accuracy and real‐time of coal gangue recognition model established by different convolutional neural networks (CNN) structures and different position signal input are studied. First, to meet the real‐time requirements, an original CNN recognition model composed of single convolution layer and single pooling layer is established, and the data collected by seven sensors are input in the form of two‐dimensional matrix. However, the stability of the training and test results is insufficient. To solve this problem, once improved CNN (OI‐CNN) recognition model with multiconvolution layers and multipooling layers is built by deepening the network. The experimental results show that the stability and accuracy are improved, but the real‐time performance is poor. Furthermore, through parameter adjustment, the OI‐CNN is changed to the twice improved CNN (TI‐CNN), and the sensor data at different positions are input in the form of one‐dimensional vectors. The results show that the accuracy and real‐time performance of the TI‐CNN coal gangue recognition model are further improved. Finally, according to the research purpose of this paper, the weights of CNN indexes are given, and a multi‐index comprehensive evaluation system (MICES) is established. With the original CNN recognition model as the control, the OI‐CNN recognition model and the TI‐CNN recognition model at different positions are quantitatively compared to obtain the comprehensive evaluation scores of each model. The results show that the MICES of the coal gangue recognition model established based on the TI‐CNN structure and the data input of a single position sensor is the highest, while the sensor position has little effect on the recognition results. [ABSTRACT FROM AUTHOR]

• A topology optimization design of the stiffness-tunable structure is proposed. • The proposed deep learning metastructure design method is faster than optimization. • Multi-scale design based on neural network is realized. • Bionic structure design with gradient characteristics, applied to the structural design of hip joint. Mechanical metamaterials with unique micro-architectures possess excellent physical properties in terms of stiffness, toughness, vibration isolation, and thermal expansion. Meanwhile, meta-structures in organisms or geography operate efficiently under complex service conditions thanks to their heterogeneous and gradient distribution of naturally evolved micro-architectures that are difficult to obtain by forward design. In this paper a multi-network deep learning system that satisfies the different design property requirements of microstructures is proposed, and the network predicts the configuration with 99.09% accuracy. The analogy between color space and mechanical parameter space is used to transform parametric design into pixel matching. The microstructures are prepared by AM (additive manufacturing) and their properties are verified by DIC (Digital Image Correlation) experiments (the property error of the structures was less than 2%). Multiscale inverse design of multifunctional and gradient mechanical metamaterials is realized, with special attention payed to the automatic customization of biomimetic structures. The design flow takes only 2 s and the geometric connectivity between microstructure units is considered to ensure compatibility between adjacent microstructures for AM. The proposed design strategy accelerates the emergence of high-performance structures, and provides a reference for topology optimization design of mechanical metamaterials. [Display omitted] [ABSTRACT FROM AUTHOR]

Shearer is an essential equipment in mechanized coal mining process. Roof cutting often turns up for shearer during working process, leading to extra vibration on shearer and reducing its service life. Coal and rock interface recognition is a fundamental technical way for shearer to avoid continuous roof cutting. In this paper, an effective method for coal and rock interface is proposed and it is mainly based on the cutting loads on shearer drum in three different kinds of working states. The constitutions of cutting force on shearer drum are analyzed under conditions of different proportions of rock thickness in the cutting range and then model for calculation of cutting force in the coal–rock mixed seam are proposed which is a function of rock proportion in the cutting range. To verify the model, hard roof with different material strengths and different interfaces are established with the numerical method and rock proportions in the cutting range are derived based on the mentioned method. In terms of the situations where rock material properties are close to coal and the results are obtained with lower accuracy, enlarging the difference of rock proportions in the second and third states is proposed and the relations between the recognition accuracy and the differences of rock proportions in different states are explored as well. The results show that the estimation method works well with qualititative analysis of coal and roof interface even if coal and rock material properties are various and not able to be known in advance. In addition, the adjustment height of shearer drum is the important factors highly related with the estimation accuracy and it would be helpful for accuracy improvement in conditions where the material properties of coal and roof are closer to each other or larger roof cutting thickness happens in coal mining. The method provides the possibility for qualititative analysis of coal and roof interface with easy accessibility and wide adaptability. [ABSTRACT FROM AUTHOR]

• Classify image inpainting methods based on deep learning from a new perspective. • Summarizes the current research status in the field of image inpainting. • Select some representative image inpainting methods for comparison and analysis. • The research direction and development trend of image inpainting are prospected. Image inpainting aims to restore the pixel features of damaged parts in incomplete image and plays a key role in many computer vision tasks. Image inpainting technology based on deep learning is a major current research hotspot. To deeply understand related methods and technologies, this article combs and summarizes the latest research status in this field. Firstly, we summarize inpainting methods of different types of neural network structure based on deep learning, then analyze and study important technical improvement mechanisms. In addition, various algorithms are comprehensively reviewed from the aspects of model network structure and restoration methods. And we select some representative image inpainting methods for comparison and analysis. Finally, the current problems of image inpainting are summarized, and the future development trend and research direction are prospected. [ABSTRACT FROM AUTHOR]

Three dopant-free hole-transporting materials (HTMs) M1−3 containing dithieno[3′,2':3,4;2″,3'':5,6]benzo[1,2-d]imidazole (DTBI) or phenanthro[9,10-d]imidazole (PTI) were designed, synthesized and applied in perovskite solar cells (PSCs), where DTBI and PTI were first introduced as a core structure in the HTMs. Different steric groups (4-methoxybenzene and 4,4′-dimethoxytriphenylamine) were introduced as the periphery groups connected at carbon-2 (C-2) position of imidazole moiety. Accordingly, the relationship between chemical structure and function was systematically investigated with respect to the fused cores and periphery groups, by the measurements of the energy levels, hole mobility, film-forming morphology, extraction and transfer of photo-generated holes, and photovoltaic performances. It was found that M1−2 with DTBI as a core structure exhibited suitable energy levels, higher hole mobility and uniform film-forming morphology, as well as efficient extraction and transfer of photo-generated holes at the perovskite/HTM interfaces. The PSCs using M2 as dopant-free HTM exhibited an impressive power conversion efficiency (PCE) of 16.9% with a negligible hysteresis, surpassing that of the doped spiro-OMeTAD-based standard device (16.4%) under the same testing conditions. Importantly, the unencapsulated PSCs based on dopant-free M2 presented much higher stability than that of doped spiro-OMeTAD. This work provides a promising strategy to construct dopant-free HTMs with both high efficiency and high stability by using DTBI as a core structure. Image 1 • HTM with dithieno[3′,2':3,4;2″,3'':5,6]benzo[1,2-d]imidazole as core is designed. • They are applied in PSCs as dopant-free hole-transporting materials (HTMs). • They exhibit suitable energy levels and high hole mobility. • They exhibit much higher stability over the doped spiro-OMeTAD in the ambient air. [ABSTRACT FROM AUTHOR]

The volume detection of medical mice feed is crucial to understand the food intake requirements of mice at different growth stages and to grasp their growth, development, and health status. Aiming at the problem of volume calculation in the way of feed bulk in mice, a method for detecting the bulk volume of feed in mice based on binocular stereo vision was proposed. Firstly, the three-dimensional point coordinates of the feed's surface were calculated using the binocular stereo vision three-dimensional reconstruction technology. The coordinates of these dense points formed a point cloud, and then the projection method was used to calculate the volume of the point cloud; and finally, the volume of the mice feed was obtained. We use the stereo matching data set provided by the Middlebury evaluation platform to conduct experimental verification. The results show that our method effectively improves the matching degree of stereo matching and makes the three-dimensional point coordinates of the obtained feed's surface more accurate. The point cloud is then denoised and Delaunay triangulated, and the volume of the tetrahedron obtained after the triangulation is calculated and summed to obtain the total volume. We used different sizes of wood instead of feed for multiple volume calculations, and the average error between the calculated volume and the real volume was 7.12%. The experimental results show that the volume of the remaining feed of mice can be calculated by binocular stereo vision. [ABSTRACT FROM AUTHOR]

In the process of top coal caving, coal gangue particles may impact on various parts of the hydraulic support. However, at present, the contact mechanism between coal gangue and hydraulic support is not entirely clear. Therefore, this paper first constructed the accurate mathematical model of the hydraulic cylinder equivalent spring stiffness forming by the equivalent series of different parts of emulsion and hydraulic cylinder, and then built the mesh model of the coal gangue particles and the support's force transmission components; on this basis, the rigid–flexible coupling impact contact dynamic model between coal gangue and hydraulic support was established. After deducing contact parameters and setting impact mode, contact simulations were carried out for coal particles impacting at the different parts of the support and coal/gangue particles impacting at the same component of the support, and the contact response difference in the support induced by the difference in impacted component and coal/gangue properties was compared and studied. The results show that the number of collisions, contact force, velocity and acceleration of impacted part are different when the same single coal particle impact different parts of the support. Various contact responses during gangue impact are more than 40% larger than that of coal, and the difference ratio can even reach 190%. [ABSTRACT FROM AUTHOR]

The investigation on the effect of defects on the mechanical properties of composites is vital to explain the failure mechanism of materials. A computer tomography (CT) scanning in-situ shear test is designed to obtain u-CT images of plain weave glass-fiber reinforced composites. The images are then applied to reconstruct the samples by using image processing techniques. Damage evolution characterization of the plain weave glass-fiber composites under in-situ shear experiment are realized by visualizing damages in three dimension. The damage evolution process is compared with the numerical simulation results to verify the materials failure mode. [ABSTRACT FROM AUTHOR]

In order to solve the problem of poor antiimpact ability of hydraulic support under rock bursting, a kind of thin-walled cylinder crushing component used in the composite spiral antiimpact device was developed, and different structural models were proposed and simulated. On this basis, the model was verified by experiments. The results show that the arrangement of the hollow structure can restrain the ring mode deformation and Euler instability of the tube member in the crushing yield and can carry out the buckling deformation according to the expected crushing force during the compression deformation process and effectively reduce the initial peak force. The arrangement of guide grooves can make the buckling deformation more stable and regular, which can effectively reduce the initial peak force and elastic displacement. With the smaller wall thickness and the smaller wall thickness of the induced groove, the effective deformation yield stroke of the crushing member increases, and the initial peak force, total energy absorption, average reaction force, and elastic displacement decrease. The simulation results are consistent with the experimental results which will be used in the future works. [ABSTRACT FROM AUTHOR]

In order to solve the problem of poor antiimpact ability of hydraulic support under rock bursting, a kind of thin-walled cylinder crushing component used in the composite spiral antiimpact device was developed, and different structural models were proposed and simulated. On this basis, the model was verified by experiments. The results show that the arrangement of the hollow structure can restrain the ring mode deformation and Euler instability of the tube member in the crushing yield and can carry out the buckling deformation according to the expected crushing force during the compression deformation process and effectively reduce the initial peak force. The arrangement of guide grooves can make the buckling deformation more stable and regular, which can effectively reduce the initial peak force and elastic displacement. With the smaller wall thickness and the smaller wall thickness of the induced groove, the effective deformation yield stroke of the crushing member increases, and the initial peak force, total energy absorption, average reaction force, and elastic displacement decrease. The simulation results are consistent with the experimental results which will be used in the future works. [ABSTRACT FROM AUTHOR]

• Three SFX-based dopant-free HTMs with different donor units were synthesized. • The effects of the donor units of HTMs on photophysical properties were systematically investigated. • The SFX-2CZ based PSCs exhibited a high efficiency of 15.83% without dopants. Three spiro[fluorene-9,9′-xanthene] (SFX)-based organic molecules with different donor units were synthesized and used as dopant-free hole-transport materials (HTMs) in perovskite solar cells (PSCs). The end-capping donor units on the SFX core are two methoxydiphenylamine-substituted diphenylamine (MDDPA), two and four methoxydiphenylamine-substituted carbazole (MDCZ) for SFX-2DPA , SFX-2CZ and SFX-4CZ , respectively. The structure-function relationship is systematically investigated as the impact of the different donor units upon the optical, electrochemical and photophysical properties of SFX-based HTMs. The PSCs based on SFX-2CZ attain the higher power conversion efficiency (PCE) of 15.83% than that based on SFX-2DPA (14.25%), due to higher molecular planarity of SFX-2CZ with enhanced hole transporting ability and the downshifted HOMO level. On other hands, SFX-4CZ has the lowest efficiency (12.19%) among three HTMs mainly due to its inferior film-forming ability. The results provide not only the new molecular design of dopant-free organic HTMs based on SFX core, but also a promising strategy to develop efficient HTMs with both the molecular planarity and number of donor groups being considered. [ABSTRACT FROM AUTHOR]

Cu/SSZ-13 catalysts not only exhibit superior SCR performance but also possess excellent selective catalytic oxidation (SCO) ability to remove NH 3 escaped from engine exhaust gas fueled by NH 3. To elucidate the effect of Cu loading on Cu/SSZ-13 catalysts, a series of Cu/SSZ-13 catalysts were prepared through wet impregnation method to remove high-concentration NH 3 (5000 ppm). The SCO activity test results showed that when Cu loading increased from 1% to 10%, there was an obvious improvement effect on NH 3 conversion performance at low temperature. Cu 10 /SSZ-13 catalyst reached a high NH 3 conversion of 96% at 250 °C, and N 2 selectivity was higher than 86% in the whole temperature range. However, when further increasing Cu loading from 10% to 20%, there was no distinctive difference in NH 3 conversion and N 2 selectivity. The characterization results indicated that there were abundant active species, adsorbed oxygen species, and acid sites on the surface of Cu 10 /SSZ-13 catalyst. The [Cu(OH)]+ and isolated Cu2+ species in zeolite channels of Cu 10 /SSZ-13 catalyst rather than CuO species on the surface played a key role in NH 3 -SCO reactions. Since 20% Cu loading would result in a significant decrease in isolated Cu2+ species, it resulted in both [Cu(OH)]+ species in zeolite channels and superfluous Cu species on zeolite surface being main active species in NH 3 -SCO reactions. In-situ DRIFTS experiments suggested that NH 3 -SCO reactions over Cu/SSZ-13 catalysts followed the internal selective catalytic reduction (i-SCR) mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

AbstractSpherical and flaky particles are mixed during hard rock tunneling. In particular, flakey particles are difficult to load, resulting in conveying machines that have difficultly operating efficiently. Based on the characteristics of flakey particles and the present conveying structures, such as star wheels, three new conveying structures are introduced in this paper, and the parameters related to the conveying ability are evaluated with theoretical analysis. Then, the flow and trajectory of particles under different conveying structures and the difference in their working capabilities were investigated with the help of the discrete element method (DEM). Finally, conveying machines with different conveying structures are made with 3D printing technology and experiments for validation of the conveying ability are performed. The results show that the conveying structures can be divided into two categories: those with a rotational speed proportional to the loading rate and those with the opposite condition. The propulsion status has a stable loading phase with a long time period relative to the non-propulsion status. The findings can be used to guide conveying machine designs, and they can be helpful for the enhancement of the working ability in conveying particles with flakey shapes. [ABSTRACT FROM AUTHOR]

There are various forms of clearance at the connection of various parts of the hydraulic support. However, the influence of clearance has been ignored in various related research studies of the hydraulic support. In order to clearly grasp the accurate impact contact response law between coal gangue and the hydraulic support, the radial clearance in the pin shaft connection structure of the tail beam is considered for the first time in this paper. By constructing the theoretical contact model of the pin shaft connection, the difficulty of studying the interaction between coal gangue and the hydraulic support through theoretical solution is proved. On this basis, the finite element contact simulation analysis method is proposed to study the impact contact behavior between coal gangue and the tail beam. This paper constructed the finite element impacting simulation model between coal gangue and the radial clearance-contained tail beam structure and carried out impact contact simulation between coal gangue and the multiple clearance-contained tail beam structure as well as the changing clearance-contained tail beam structure, respectively, and contact responses of the tail beam structure such as the spring stress, the pin shaft test point stress, acceleration, and velocity of the tail beam test point under different working conditions are obtained. The influence law of clearance on different contact responses is studied, and the differences of contact responses after coal gangue impact between two clearance-contained tail beam structures and three clearance-contained tail beam structures are compared and analyzed. Research results show that, in the condition of multiclearance, the amplitude of each contact response when gangue is impacted is greater than that of coal. When the radial clearance of the connection unit increases from 0 to 0.25 mm, the overall fluctuation amplitude of the contact responses decreases. In 3-clearance state, increase of the radial clearance size of the connection unit will lead to the increase of the spring stress, the stress of the pin shaft test point, and the velocity of the tail beam test point gradually and the decrease of the acceleration of the tail beam test point. Throughout the research, the vibration response of the pin shaft can be taken as coal gangue recognition parameter. The work provides a theoretical basis for the study of the influence law of clearance on hydraulic support and provides a reference for the study of contact behavior between coal gangue and the hydraulic support. [ABSTRACT FROM AUTHOR]