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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 chain drive system, being one of the core subsystems of the scraper conveyor, greatly influences the coal-conveying efficiency due to its dynamic characteristics. Therefore, this paper employed an experimental method to compare the dynamic characteristics of the chain rings at various positions within the chain drive system. This article simulated the three most common working conditions. The results indicated that the chain speed, load, and surface undulation had a stimulating effect on chain vibration, with the most significant impact observed on the chain ring located in the middle of the adjacent scraper. The scraper exerted an inhibitory effect on the vibration of the chain ring. Among the factors studied, the load had the most significant influence on the transverse direction. When there was surface undulation, the vibration of the chain ring in the running direction formed an 'N' shape. This condition intensified the vibration during uphill and downhill stages while suppressing vibration at the slope peak. This research holds great significance in enhancing operation stability. [ABSTRACT FROM AUTHOR]

In longwall top coal caving (LTCC), due to the fracture and migration of top coal, the roof will break and collapse, which causes serious impact damage to hydraulic support. Therefore, we aimed to reveal the relationship between the roof instability effect and the bearing characteristics of hydraulic support in the LTCC face. Based on the occurrence conditions of the 08 mining area in the Shilawusu Coal Mine, the instability model of the upper immediate roof was established, and the working resistance of hydraulic support was derived. Secondly, the dynamic coupling model of roof-top coal-hydraulic support was established in LS-DYNA, and the crushing degree of top coal and the bearing characteristics of the hydraulic support in different roof instability fields were analyzed. The results show that the main factors affecting the working resistance of hydraulic support are the fracture position of the upper immediate roof, the acting force of the lower immediate roof, and the distribution of the gangue in the goaf. The rotary instability of the upper immediate roof at the coal wall brings serious impact effects, resulting in fractures in front of the coal wall and a large amount of crushed coal concentrated at the front end of the canopy. The crushing degree of top coal significantly impacts the canopy, especially the back end of the canopy and the hinged pin shaft, which is prone to bending fracture. The research results can provide references and experience for the stability control of roof strata and the structural optimization of hydraulic support. [ABSTRACT FROM AUTHOR]

The bi-tandem axial piston pump is an indispensable powerhouse in high-pressure and high-power engineering hydraulic systems, with its output flow response characteristics under pressure disturbance exerting a significant influence on the working process of double pumps. Unfortunately, the stability of the original single-loop mechanical–hydraulic servo control system is sensitive to unpredictable interference. To alleviate this quandary, this paper proposes a dual-loop positive flow control method for the flow control of the bi-tandem axial piston pump, establishes a mathematical model of the bi-tandem axial piston pump with dual-loop positive flow control, and establishes a simulation model based on Simulink. The validity of the model is verified by experiments. The performance advantages of the dual-loop positive flow control method relative to the single-loop positive flow control method are analyzed. The results show a faster response speed and smaller steady-state error with the dual-loop method, which performs better than the original single-loop positive flow control. Furthermore, the study examines the influence of different forms, degrees, and directions of pressure disturbance on the dynamic response characteristics of the bi-tandem axial piston pump. Symmetric pressure disturbance results in an increase in the maximum relative error of the output flow proportional to its degree. Notably, the influence of asymmetric pressure disturbance on the output flow of the double pumps possesses characteristics of a superimposable nature, and the steady-state value of the output flow is highly dependent on superimposed pressure disturbance and less affected by the action time point of asymmetric pressure disturbance. Further, the unloading pressure disturbance exerts less influence on the system compared to the loading pressure disturbance. This paper provides valuable insights into improving the response speed and control accuracy of bi-tandem axial piston pumps equipped with positive flow control. [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]

A hydraulic support is one of the key pieces of equipment in a fully mechanized coal-mining face. The shaft is seriously worn due to repeated support shifting in coal-mining operations, and the hydraulic support bears a large amount of impact load in the support process, leading to a threat to its dynamic stability. In order to study the impact load on the posture and dynamics of a hydraulic support, and considering the joint clearance of the hydraulic-support hinge point, based on the dynamics software Adams, the equivalent variable-stiffness damping system is used to replace the column, and the impact analysis model of the hydraulic support with joint clearance is established. The roof pressure is vertically applied to the load balance area of the top beam by static load, and the impact load is vertically applied to the top beam downward. Based on the above model, considering the different distributions of joint clearance, research about the influence of joint clearance on the posture and dynamic characteristics of the hydraulic support is carried out. The results show that when there is joint clearance on both sides of the hydraulic support, when the top beam bears the impact load, the X-axis PMR (position movement ratio) at different positions of the top beam is more than 80%, and the forward-tilt posture is obvious. When the hydraulic support has only unilateral clearance, the front end of the top beam bears the impact load, and the front end of the top beam moves laterally, while the rear end of the top beam mainly moves longitudinally. When the end of the top beam bears the impact load, the vertical PMR of the top beam is less than 1%. When the impact load acts on the side with joint clearance, the top beam has a certain degree of lateral offset, and the offset directions on both sides of the top beam are inconsistent. At this time, the top beam presents a torsional-bearing posture. When the front end of the top beam is loaded, the mechanical curve of each hinge point is higher than the rear-end load. For the hinge point on the side without clearance, the maximum load-fluctuation coefficient reaches 1.04, while for the hinge point on the side with clearance, the minimum load is 0 kN, which will mean some hinge points cannot to play a supporting role. The analysis results will be helpful to research hydraulic supports considering joint clearance. [ABSTRACT FROM AUTHOR]

In the study of coal mining, the position and posture, the working status, and the straightness of the hydraulic support are critical to the safety of the coal mine. To detect and control the position of a hydraulic support, a model for solving the self-position and posture and a model for solving the relative position and pose of a hydraulic support based on the principle of three points determining a plane in space were established. Then, with the help of particle swarm optimization algorithm and Bang-Bang control algorithm, the hydraulic support position and the posture detection and control system are constructed. Finally, according to the requirements of sensor data collection and online monitoring of the position and posture of hydraulic support, a hydraulic support posture detection and control system is developed, and the simulation experiments of hydraulic support cylinder movement sample collecting, hydraulic support following motion and hydraulic support independent following machine are carried out on the self-developed three-machine intelligent control simulation experiment platform of the working face. However, the test under this simulation platform did not add the load of the top beam. The results show that the self-pose solution model and the relative-pose solution model of the hydraulic support can be used to quickly monitor the position and posture of the hydraulic support group. In the hydraulic support cylinder following motion movement, the largest following error of each cylinder is the balance cylinder, and its maximum error is 2.6 mm. In the hydraulic support independent following machine simulation, the maximum motion error of the support base is 2.2 mm. The position and posture detection and control system developed for hydraulic support can realize accurate detecting and control the position and posture of hydraulic support, as well as meet the requirements for industrial applications. [ABSTRACT FROM AUTHOR]

The complement system is composed of a complex protein network and is pivotal to innate immunity. Complement 3 (C3) is a critical protein in the complement cascade and participates in complement activation and immune defense. In this study, C3 from Nile tilapia (Oreochromis niloticus) was cloned and its function in resisting pathogen infection was characterized. The full length of OnC3 open reading frame is 4974 bp, encoding 1657 aa, and the predicted protein mass weight is 185.93 kDa. The OnC3 amino acid sequence contains macroglobulin domains. The expression pattern of OnC3 mRNA in the tissues of healthy fish was detected, with the highest in the liver and the lowest in the muscle. After challenged with Streptococcus agalactiae and Aeromonas hydrophila, the expression of OnC3 mRNA was significantly up-regulated in the liver, spleen, and head kidney. Further, the recombinant OnC3 protein alleviated the inflammatory response and pathological damage of tissues after infected with S. agalactiae. Moreover, the OnC3 promoted the phagocytosis of monocytes/macrophages to S. agalactiae. The data obtained in this study provide a theoretical reference for in-depth understanding of C3 in host defense against bacterial infection and the immunomodulatory roles in teleost fish. [ABSTRACT FROM AUTHOR]

Conical picks are applied to rock breaking, and the cutting parameters greatly influence cutting performance and rock damage. A conical pick rock-cutting numerical simulation model and software to provide a quantitative analysis of rock damage are established to research the influence of cutting parameters on cutting force and rock damage. The research results indicated that the average peak cutting force decreases with an increased cutting angle, and the average peak cutting force increases with a decreased cutting speed. The average peak cutting force of the second conical pick increases as the distance between double conical picks increases in the process of rock-cutting with double conical picks. There is a positive correlation between the volume of rock damage, the volume of rock breaking, and the cutting force of the conical pick. The research results provide a reference for optimizing the cutting parameters of conical picks. [ABSTRACT FROM AUTHOR]

Serum amyloid P component (SAP), an ancient short pentraxin of the pentraxin family, plays an essential role in resistance to bacterial infection. In this study, the expression and functional characterization of SAP (OnSAP) in Nile tilapia (Oreochromis niloticus), a primary vertebrate, are investigated. The open reading frame of OnSAP is 645 bp of a nucleotide sequence encoding a polypeptide of 214 amino acids. As a calcium-binding protein, the structure and relative motif of OnSAP is highly similar to those of humans, containing amino acid residues Asn, Glu, Gln and Asp. In healthy fish, OnSAP mRNA is extensively distributed in all eleven tissues examined, with the highest level in spleen. The mRNA expression of OnSAP was significantly up-regulated after being challenged with gram-positive bacterium Streptococcus agalactiae and gram-negative bacterium Aeromonas hydrophila in vivo. In addition, recombinant OnSAP ((r)OnSAP) protein had capacities of binding S. agalactiae or A. hydrophila in the presence of Ca2+. Further, (r)OnSAP helped monocytes/macrophages to efficiently phagocytize bacteria. Moreover, the (r)OnSAP was able to enhance the complement-mediated lysis of the chicken red blood cells. Collectively, the evidence of SAP in tilapia, based on the results including its evolutionary conserved protein structure, bacterial binding and agglutination, opsonophagocytosis of macrophage and hemolysis enhancement, enriches a better understanding of the biological functions of the pentraxin family. [ABSTRACT FROM AUTHOR]

Coal resources perform an important role in China's energy structure. Hydraulic support is the main supporting equipment of fully mechanized mining face in coal mines. Because the hydraulic support frequently bears the impact pressure from the working face, it is very easy to cause failure of the balance jack. In order to solve the problem that the balance jack easily damaged by impact and improve the impact resistance of the hydraulic support, an improved fast response balance jack with multiple adaptive buffers was proposed in this paper. The energy dissipation characteristics of the balance jack were analyzed by establishing the mathematical model of the multiple buffering process of it. Based on ADAMS, the dynamic simulation model of the hydraulic support was constructed, and the mechanical response characteristics of the proposed balance jack and the traditional balance jack under different impact loads were compared and analyzed. By changing the equivalent stiffness of the novel balance jack system, the influence of different initial inflation pressure and length of the buffer cavity on the dynamic performance of the novel balance jack was discussed. The results show that compared with the traditional balance jack, the multi-adaptive response balance jack proposed in this paper can reduce the peak force of the hinge point by about 24.6% and the fluctuation frequency was also significantly reduced under the ultimate load condition at the front end of the top beam, which has better impact resistance. When the initial inflation pressure of the buffer cavity is 40~45 MPa and the initial length is less than 105 mm, a better buffer effect can be achieved. This study provides a new solution to solve the failure problem of the balance jack under the underground impact pressure and improve the safety and reliability of hydraulic support. [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]

A scraper conveyor is important in coal mining. During operation, its working performance is affected by chain speed fluctuations, terrain fluctuations, and load changes. Thus, evaluating the influence of these factors on the dynamic properties of a scraper conveyor is important. This study first built a dynamic property test bench. Then, the vibration signals of the reducer output shaft were measured under various chain speed, terrain, and load conditions. Finally, the dynamic properties of a scraper conveyor were evaluated by conducting a frequency domain analysis of the measured vibration signals. The results show that the output shaft of the motor, the second shaft, and the second-stage meshing gear of the reducer are sensitive to external factors. Under the terrain conditions of "horizontal + vertical" bending, the middle chute was the most sensitive to the meshing frequency of the sprocket chain. This type of condition had a significant influence on the scraping phenomenon of the scraper and the middle chute. Under various load conditions, the amplitude of each shaft of the reducer decreased, especially the amplitude of the motor output shaft, but the scraping amplitude of the scraper and middle chute greatly increased. This study is of great significance for improving the dynamic properties and structural optimization of scraper conveyors. [ABSTRACT FROM AUTHOR]

The periodic flow and pressure pulsation of the axial piston pump can lead to periodic vibration, noise, and even damage to various components in the hydraulic system. Therefore, the dynamic characteristics analysis of the axial piston pump in the hydraulic system is of great significance for reducing vibration and noise in the hydraulic system and improving efficiency. The double-compound axial piston pump is the key component of a high power and large flow hydraulic power system, which has a special power control mode. In this paper, the working and control principles of the double-compound axial piston pump are analyzed, the numerical model of the double-compound axial piston pump is established, and the effectiveness of the model is verified through experimental tests. The constant power control characteristics of the double-compound axial piston pump under different power settings and the variable power control characteristics under the rated load pressure are analyzed. By analyzing the dynamic characteristics of the double-compound axial piston pump, the influence of different working conditions on the dynamic characteristics is investigated. The results show that the output efficiency of the double-compound axial piston pump is higher when the output flow is larger. When the piston chamber works in the closed pre-compression pressure zone and the closed pre-release pressure zone, oil backflow occurs. The oil backflow in the piston chamber seriously intensifies the outlet flow pulsation of the double-compound axial piston pump. The flow pulsation rate is positively correlated with load pressure and power control pilot pressure, while negatively correlated with spindle speed. The paper provides a basis for the analysis and optimization of power control, flow pulsation, fluid vibration, and noise of the double-compound axial piston pump. [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]

Thin-coal-seam shearer mining efficiency is seriously restricted by the poor loading performance of the drum. The loading of the drum to the cracked coal lumps is based on a screw-conveying mechanism, and its loading performance is influenced by many structural parameters, including drum width, helical angle, axial tilt angle, number of blades and form and diameter of the barrel. The barrel diameter directly influences the drum envelope zone's capacity, and its influence on loading performance is not yet clear. Therefore, this work first compared the drum-loading results between experiments and numerical modeling, and the results proved that the application of the discrete element method (DEM) to the modeling drum loading process is feasible and the results are reliable. Secondly, the influence of barrel diameter on particles' axial velocity, loading rate and web depth was studied using the ejection and pushing modes. The results showed that the particles' axial velocity has a noticeable impact on loading rate under ejection loading conditions, and the loading rate first increases and then decreases with the increase in barrel diameter. When the diameter is less than 700 mm in drum-pushing modes, the particles' axial velocity plays an important role on drum loading; the filling level has an obvious impact on loading performance when the barrel diameter is larger than 700 mm. The drum loading ejection rate is 25% higher than that of pushing mode, which is due to the loading rate of particles located in a web depth from 300 to 600 mm. The influence of barrel diameter on loading performance using drum ejection is more obvious than that in pushing mode. The results provide a reference for drum structural design to some extent. [ABSTRACT FROM AUTHOR]

Energy-saving and emission reduction has become the theme of the world. The wheel loader has a harsh working environment, complicated working conditions, and drastic changes in load, and the performance of the engine cannot be fully utilized. Therefore, the variable speed transmission of vehicles plays a vital role in improving the efficiency and performance of the vehicle. This paper establishes the general characteristic equations for the input coupling type of hydro-mechanical continuously variable transmission (HMCVT) based on the wheel loader and determines reasonable structural forms for connection of working conditions. It establishes the general efficiency equation for the reasonable structural form for efficiency analysis and presents a method of co-validation of the simulation and test for making the results of efficiency more accurate. Through this method, the transmission performance is more accurately analyzed, which provides an important guiding role and validation for the early design of HMCVT. Eventually, it gets reasonably optimized products and reduces the design cost and cycle. [ABSTRACT FROM AUTHOR]

Top coal caving is an important way of thick coal seam mining. The current coal gangue identification technology is not mature, resulting in a low degree of automation of coal caving. The current numerical simulation pays little attention to the real shape of rocks. This paper aims to reveal the vibration response of the tail beam under the action of real shape coal gangue particles. First, the real shape rock and hydraulic support model are established, and the relationship between the Rock Mixed Ratio (RMR) and the vibration signal characteristics during the impact process are studied. The influence of falling velocity and coal strength on this relationship are analyzed. Finally, the influence of motion mode on this relationship is analyzed and discussed. The numerical results show that the increase of the RMR can significantly enhance the velocity and acceleration signals of the tail beam, and the signals caused by different RMR are still different under different velocities and strengths. The best recognition effect can be obtained when the coal gangue particles slip on the hydraulic support, and the effect is the the worst when the coal gangue particles impact upon and roll on the hydraulic support. The conclusion provides directions for further study of coal gangue identification based on vibration. [ABSTRACT FROM AUTHOR]

According to the structural characteristics of Hydro-mechanical continuously variable transmission (HMCVT), a multi-functional test bench was developed, and the basic structure, working principle, and test functions of the test bench were introduced. The test bench has the following characteristics: To analyze the impact of mechanical transmission and hydraulic transmission on the HMCVT transmission system, the performance can be tested separately by using a test bench; the coupling characteristics of the hydraulic transmission and mechanical transmission can also be tested; it can also test and verify the performance of the HMCVT transmission system and the control system; the test bench has a simple structure, diverse functions, and convenient operation. Using the multi-functional test bench, this paper proposes a method of multi-level test and verification. Through this method, the simulation models are revised and improved many times, and the accuracy of the models is improved, which are consistent with the physical model, and eventually, the accuracy of the simulation result is improved. This method is used to test and verify the hydraulic transmission system, analyze the characteristics of the hydraulic transmission system, and verify the feasibility and practicability of the multi-level verification method. [ABSTRACT FROM AUTHOR]

Based on the background of a mine, this study aimed to improve underground wireless communication. The study selected Zigbee technology from many wireless technologies as the basis, expounded the technical advantages and disadvantages, and addressed its disadvantages. First, the modulation technology of Zigbee was improved. This article selects and describes O-QPSK technology from three modulation technologies, thereby addressing the synchronization difficulties caused by inherent technical reasons, and proposes a modulation method based on feedforward timing. Moreover, excellent performance was achieved in the follow-up simulation experiment. For networking problems, a series of mechanisms are proposed to address several problems in large-scale networking: node offline, energy waste, signal delay, etc. This article proposes five main mechanisms and an improved protocol from two significant perspectives. The problem of node disconnection is divided into two parts. Considering the different status of edge nodes and important nodes in the network, three mechanisms are proposed for edge nodes for disconnection detection and self-repair, and two mechanisms are proposed for essential nodes. This can compensate for the loss caused by the disconnection of essential nodes at a specific time. For network energy waste, an Improved-LEACH protocol is proposed to alleviate the signal delay problem. The performance of the five mechanisms and one protocol was verified in a simulation test, and the performance was reasonable and in line with expectations. [ABSTRACT FROM AUTHOR]

The poor loading performance of shearer drums restricts the development and production efficiency of coal in thin coal seams. Changing operation and structural parameters can improve the drum's loading performance to some extent, but the effect is not obvious. A two-segment differential rotational speed drum (TDRSD) was proposed after analyzing the drum's influence mechanism on coal particles. To further reveal the drum's coal loading principle, the velocity, particles distribution, and loading rate were analyzed. The effect of the matching relationship of the rotational speed and helix angle between the front and rear drum are also discussed. The results show that a lower front drum rotational speed had a positive impact on improving the loading performance, and the loading rate first increases and then decreases with the increase in rear drum rotational speed. The optimal loading performance was obtained in the range 60–67.5 rpm. The front drum's helix angle had no evident effect on loading performance, and the loading rate increase with the increase in the rear drum's helix angle. The results provide a reference and guidance for operation parameters selection, structure design, and drum optimization. [ABSTRACT FROM AUTHOR]

Shearer traction failure occurs frequently, which seriously restricts the safe and efficient mining of coal. However, the influence of the shearer's posture on traction has not been fully considered in the existing research. To improve traction reliability: the dynamic model of the traction unit is established considering longitudinal swing; the walking characteristics of the shearer and the dynamics of the traction unit are analyzed; and the influences of traction velocity, drum load cutting arm angle, and depression angle are discussed. The results show that the longitudinal swing is reciprocating and the positive swing is more serious. With the increase of the traction velocity, the walking stability of the shearer decreases while the contact force increases, especially the support slipper. The longitudinal swing increases with the increase of lateral load, but the supporting force of the support slipper decreases with the increase of cutting load. The forces of the walking wheel and the support slipper show an increasing trend with the increase of cutting arm angle. When the depression angle is 5–10°, the load distribution of the contact components of the traction unit is more balanced. The results provide a reference for the structure optimization of the shearer and the layout of coalface. [ABSTRACT FROM AUTHOR]