Search Results (46)

Fully mechanized mining involves high energy consumption, particularly during cutting and transportation. Scraper conveyors, crucial for coal transport, face energy efficiency challenges due to the lack of accurate dynamic coal flow models, which restricts precise energy estimation and optimization. This study constructs dynamic coal flow and scraper conveyor energy efficiency models to analyze the impact of multiple variables on energy consumption and lump coal rate. A dynamic coal flow model is developed through theoretical derivation and EDEM simulations, validated for parameter settings, boundary conditions, and numerical methods. The multi-objective optimization model for energy consumption is solved using the NSGA-II-ARSBX algorithm, yielding a 33.7% reduction in energy consumption, while the lump coal area is reduced by 27.7%, indicating a trade-off between energy efficiency and coal fragmentation. The analysis shows that increasing traction speed while decreasing scraper chain and drum speeds effectively lowers energy consumption. Conversely, simultaneously increasing both chain and drum speeds helps to maintain lump coal size. The final optimization scheme demonstrates this balance—achieving improved energy efficiency at the cost of increased coal fragmentation. Additional results reveal that decreasing traction speed while increasing chain and drum speeds results in higher energy consumption, while increasing traction speed and reducing chain/drum speeds minimizes energy use but may negatively affect lump coal integrity. Full article

The aim of this study was to examine the functional characteristics of the process of cutting surgical gauze with a drum cutting unit. For this purpose, the authors designed and constructed a test stand on which experimental tests were conducted. As part of this study, the results of the experimental tests are presented, which were conducted for three selected thicknesses of surgical gauze samples, four selected angles of feeding of the material to be cut and nine selected cutting speeds. In order to determine cutting resistance, the specific cutting resistance was used, and the energy consumption was estimated using the specific cutting work related to the cutting surface of the surgical gauze. The conducted experimental studies demonstrated that the highest value of the specific cutting resistance $p_c=78.14 \mathrm{N}\cdot {\mathrm{m}}^{-1}$ occurred during the cutting of eight-layer gauze at a cutting angle $\alpha =0°$ and a cutting speed $V_c=0.66 \mathrm{m}\cdot {\mathrm{s}}^{-1}$. Meanwhile, the highest value of the specific cutting work was approximately $L_{jS}=120.00 \mathrm{J}\cdot {\mathrm{m}}^{-2}$ during the cutting of three-layer gauze, also at a cutting speed $V_c=0.66 \mathrm{m}\cdot {\mathrm{s}}^{-1}$ for cutting angles $\alpha =0°$ and $\alpha =5°$. This study found that $V_c=0.66 \mathrm{m}\cdot {\mathrm{s}}^{-1}$ is the threshold cutting speed at which the material is cut. Below this speed, the cutting drum does not have enough momentum to cut the material. Based on the statistical analysis of the obtained test results, it was concluded that there exists a relationship between the independent and dependent variables. The cutting speed has the greatest impact on the parameters of the surgical gauze cutting process. The test results, which have not been found in the worldwide literature to date, constitute a valuable contribution to the development of the theory of surgical gauze cutting. The experimentally determined specific cutting resistance p_c and specific cutting work of surgical gauze broaden the knowledge of the materials used in medicine and contribute to the expansion of scientific knowledge in this field. Full article

The cryopreservation of ovarian tissues from fish has recently been carried out for several endangered and commercially valuable species. However, previous studies in this context have focused on the cryopreservation of immature ovaries—mainly through slow freezing and vitrification—which requires specialized freezing equipment or higher cryoprotectant concentrations to keep cell viability. Therefore, the aim of this study was to explore a convenient, rapid, efficient and less toxic method for the cryopreservation of ovaries at the stage of vitellogenesis from yellow drum (Nibea albiflora), an economically important marine fish. The ovaries at the stage of vitellogenesis were isolated and cut into blocks of approximately 1 cm³, then cryopreserved with 15% propylene glycol (PG), fetal bovine serum (FBS) and 0.2 M trehalose as cryoprotectants. Finally, the samples were treated using three different freezing procedures, including a −80 °C refrigerator, liquid nitrogen, and their combination. After 7 days, the tissues were thawed and digested, and the cell survival rates and gene expression levels were detected using cell viability assay kits and qRT-PCR, respectively. The results of the viability assay showed that the procedure of ovarian tissue storage at −80 °C in a refrigerator for 1 h, followed by transfer to liquid nitrogen, resulted in the highest cell survival rate (>90%). Furthermore, the germ cells at various phases were of normal size; presented a full, smooth surface and regular shape; and did not show any signs of cell rupture, atrophy, depression, granulation or cavitation. Furthermore, the qRT-PCR results revealed that genes related to reproductive development, such as vasa, foxl2, zp3 and gsdf, were all down-regulated under the optimal protocol, while the expression of the nanos2 gene (which is specifically distributed in oogonia) maintained a higher level, similar to that in the control group. This indicated that the viability of germ stem cells (oogonia) was not weakened after freezing and that oogonia could be isolated from the cryopreserved ovaries for germ cell transplantation. The present study successfully establishes an optimal cryopreservation protocol for ovarian tissues from Nibea albiflora, providing reference for the preservation of ovaries at the stage of vitellogenesis from other species. Full article

To improve the reliability of the shearer output shaft in coal seams with gangue, taking the MG400/951-WD shearer model as the research object, a test system for the physical and mechanical properties of coal seam samples containing gangue was established. Based on the coal breaking theory, the impact load of the spiral drum in a coal seam with gangue was simulated. Combined with rigid-flexible coupling virtual prototype technology, a rigid-flexible coupling virtual prototype model of a shearer with an output shaft as the modal neutral file was established. The output shaft is a typical symmetrical part, and it is of great significance to analyze it by using dynamic theory and mechanical reliability theory. The shearer system modal, the stress distribution of output shaft, and vibration characteristics were obtained by dynamic simulation. Based on resonance failure criterion and combined with a neural network, the output shaft stress reliability, vibration reliability, amplitude reliability, and reliability sensitivity were analyzed under relevant failure modes. The state function of the output shaft reliability optimization design was established, and the structural evolution algorithm obtained the optimal design variables. The results show that the maximum stress of the output shaft is reduced by 14.06%, the natural frequency of the output shaft is increased, the amplitude of the output shaft is reduced by 31.13%, and the reliability of the output shaft is improved. The combination of rigid-flexible coupling virtual prototype technology, reliability sensitivity design theory considering correlated failure modes, and structural evolution algorithm provides a more reliable analysis method for the reliability analysis and design of mechanical equipment transmission mechanisms, which can enhance the reliability of the shearer’s cutting unit and improve safety in fully mechanized coal mining faces. The proposed methodology demonstrates broad applicability in the reliability analysis of critical components for mining machinery, exhibiting universal adaptability across various operational scenarios. Full article

To meet the mining requirements of the ’excavation–backfill–retention’ tunneling method for inter-panel coal pillars, this paper proposes an integrated ‘excavation–backfill–retention’ equipment system centered on a cutting robot. An interactive design method was employed to analyze the interaction between mining conditions and the cutting robot, constructing a ’requirements–functions–structure’ model. The robot integrates a horizontal drum cutting mechanism with a slider shoe walking mechanism, offering enhanced adaptability to various mining conditions. A parameter model was constructed to explore the relationship between the cutting arm length and the robot’s structural parameters under varying mining heights. Using a hierarchical solution method that combines local search and multi−objective genetic algorithms, the robot’s fundamental parameters were determined, enabling the development of a detailed 3D model. A kinematic model based on the modified D–H method was developed to analyze the cutting arm’s swing angle, cylinder extension, propulsion velocity, and cutting velocity in practical mining scenarios. The working range of the height adjustment and feed cylinders at different mining heights was determined through simulation. A dynamics model of the cutting drum was developed, and a coupled simulation using the discrete element method (DEM) was conducted to analyze the relationship between coal/rock hardness, drum load, and cutting depth. The simulation results indicate that as the cutting depth raises the number of cutting teeth in contact with surrounding rock, the cutting depth grows, resulting in a larger reaction force from the coal seam and greater fluctuations in drum load torque. Once the maximum cutting depth is reached, load torque stabilizes within a specific range. Considering cutting efficiency, the robot achieves a maximum cutting velocity of 1 m/min with a cutting depth of 250 mm for rock strength greater than f3. For rock strength f3, the maximum cutting velocity is 1 m/min with a 400 mm depth, and for f2, it is 2 m/min with a 400 mm depth. These findings provide a theoretical foundation for the development of adaptive cutting strategies in mining operations, contributing to improved performance and efficiency in complex mining conditions. Full article

Although the mechanized harvesting rate of maize in China has exceeded 90%, there are still shortcomings in the mechanized harvesting of silage maize. Some areas still rely on manual harvesting, which is not only inefficient but also requires more labor. Therefore, it is extremely important to realize the mechanized harvesting of silo maize. The aim of this paper is to improve the harvesting efficiency of silo maize, ensure the quality of the silage and reduce the loss of nutrients. Aiming at the problems of wide cutting width, difficult access, low operating efficiency, and uneven straw feeding in the process of corn silage harvesting in terraced fields in hilly and mountainous areas. This study creatively designed a single-disk corn silage harvester. The optimal Latin hypercube method and MATLAB R2021 software are used to analyze the influence of various factors on the evaluation index. The ternary quadratic regression prediction model was constructed by using Isight 5.6 software, and the accuracy of the model was verified by variance analysis and field experiments. In addition, the main program was optimized by writing the program of the SMPSO algorithm. The optimal combination of working parameters was determined: the working speed was 1.00 m/s, the cutter rotation speed was 1085.89 rpm, and the drum rotation speed was 30 m/s. At that time, the machine productivity was 38 t·h⁻¹, the average standard grass length rate was 82.15%, and the stubble qualification rate was 91.95%. After two field trials, the results showed that all indicators met the national standards and industry standards, which confirmed the efficiency and practicality of this design. Full article

There are extensive areas of mugwort cultivation in China, making efficient harvesting crucial for the industry’s economic performance. However, the lack of specialized harvesting machinery for hilly and mountainous regions leads to reliance on manual operations, characterized by high labor intensity and low efficiency. To address these issues, a self-propelled mugwort harvester is designed based on mugwort planting patterns and the physical characteristics of mugwort during the harvesting period. Key structural components, such as drum dimensions, tooth shapes, and tine arrangements, are developed, and a defoliation force model is established to identify factors influencing the net rate of mugwort leaf harvesting, impurity rate, and mugwort leaf usability. The harvester employs a fully hydraulic drive system, for which the hydraulic system is designed and components are selected. A quadratic regression orthogonal rotary test determines the optimal parameters: a forward speed of 0.8 m/s, drum speed of 200 r/min, and cutting table height of 50 mm. Field tests show that the harvester achieves a net rate of mugwort leaf harvesting of 93.78%, an impurity rate of 13.96%, a mugwort leaf usability of 86.23%, and an operational efficiency of 0.155 hm²/h, while maintaining stable operation under field conditions. Beyond these performance metrics, the harvester reduces dependency on manual labor, lowers operational costs, and increases profitability for farmers. By improving the sustainability and mechanization of mugwort harvesting, this study provides an efficient solution for mugwort cultivation in hilly and mountainous regions and contributes to the sustainable development of the industry. Full article

With problems of low cutting efficiency, poor forming quality, and low control accuracy in large-section semi-coal rock roadway tunneling, comprehensive coal tunneling seriously lags behind fully mechanized mining. A fuzzy PID control method was proposed, taking the cutting robot in a shield-type tunneling system as the research object. Using mathematical analysis and other methods, a kinematic model of the cutting robot was established, and the pose transformation matrix of the cutting robot during the cutting process was obtained. A limit model for the motion space of the cutting robot cutting drum was established, and the motion relationship between the driving cylinder and the cutting drum was obtained. A fuzzy PID cutting robot control scheme was designed. The feasibility of the model was validated by simulation methods, and the correctness of the model and simulation was verified through on-site experiments. The results indicate that the established cutting robot model is correct, and the proposed fuzzy PID control method for the cutting robot is feasible. The maximum error of the center control of the cutting drum was 5.5 mm, and the average date was 0.89 mm, which was far less than the standard of 50 mm for engineering of the cross-section cutting of the roadway. This study enriches the control theory of shield-type cutting robots by improving control accuracy, enhancing the cutting efficiency of large-section semi-coal rock tunnels, ensuring the quality of section forming, and narrowing the gap between comprehensive coal tunneling and fully mechanized mining. Full article

Most of the biomass of cereal straw is chopped and left on the field as organic fertilizer, but its conversion into fertilizer depends on the quality of chopping, which is influenced by the wear of the chopping blades. The aim of the study was to determine the influence of the contamination of the cereal straw on the wear of the combine chopper blades. The study was conducted during the harvest in 2022, when 30 ± 1% of the grain was lodged and contaminated with abrasive soil particles (poor conditions), and in 2023, when the straw was unlodged and clean (excellent conditions). Six sets of blades with different mechanical and geometric properties were selected. The results showed that the wear ranges were very different: 1.47–2.99 g/100 ha in 2022 and 0.72–2.14 g/100 ha in 2023. For micro-abrasive wear, the hardness of the blades (349–568 HV) and the cutting edge angle (20°–29°) were important factors of their wear resistance. When the clean straw was chopped, the influence of the blade hardness and cutting edge angle on wear was not significant, and the wear was less. The wear of the blades had a sinusoidal character, which was related to the position of the blades on the chopping drum. This character depends on the design of the chopper and not on the straw quality. Full article

Accurately obtaining the geological characteristic digital model of a coal seam and surrounding rock in front of a fully mechanized mining face is one of the key technologies for automatic and continuous coal mining operation to realize an intelligent unmanned working face. The research on how to establish accurate and reliable coal seam digital models is a hot topic and technical bottleneck in the field of intelligent coal mining. This paper puts forward a construction method and dynamic update mechanism for a digital model of coal seam autonomous cutting by a coal mining machine, and verifies its effectiveness in experiments. Based on the interpolation model of drilling data, a fine coal seam digital model was established according to the results of geological statistical inversion, which overcomes the shortcomings of an insufficient lateral resolution of lithology and physical properties in a traditional geological model and can accurately depict the distribution trend of coal seams. By utilizing the numerical derivation of surrounding rock mining and geological SLAM advanced exploration, the coal seam digital model was modified to achieve a dynamic updating and optimization of the model, providing an accurate geological information guarantee for intelligent unmanned coal mining. Based on the model, it is possible to obtain the boundary and inclination information of the coal seam profile, and provide strategies for adjusting the height of the coal mining machine drum at the current position, achieving precise control of the automatic height adjustment of the coal mining machine. Full article

Cereal grain crops are used as main food and raw feed materials all over the world. Among cereal crops, wheat occupies a leading place as the most valuable crop. Harvesting is the most energy-intensive stage in wheat cultivation. Therefore, improving technologies and tools to reduce energy costs in this process is an urgent task. A new stripping and threshing unit for harvesting cereal crops has been developed, allowing the harvesting of grain at both full maturity and in the early stages of maturity, when the grain has an increased content of protein and amino acids and is a valuable raw feed material. The new unit consists of a stripping and threshing unit. The stripping unit consists of a stripping drum and stripping combs. The threshing unit contains replaceable decks that collide with the grain, separating it from the ear; an auger for transporting the heap to the unloading device; and a blade beater with a cut-off shield. Wheat grain in the early stages of maturity has a strong connection with the ear, as a result of which harvesting such grain can be energy-intensive and impractical. In this regard, the purpose of this research was to study the dynamics of changes in the energy intensity of the wheat grain harvesting process during ripening and to compare the energy intensity of the harvesting process with the new unit with the energy intensity of a combine harvester. The methodology is based on measuring torque on the shaft of the stripping and threshing unit. The results show that the power required for stripping by the new unit is reduced from 8–10 kW to 2–4 kW, which is 2.5–4 times lower. The difference in power values between harvesting at the hard wax ripeness stage and full ripeness is only 1–1.5 kW, indicating the feasibility of harvesting grain at this stage. Full article

This study presents an advanced simulated shearer machine cutting experiment system enhanced with digital twin technology. Central to this system is a simulated shearer drum, designed based on similarity theory to accurately mirror the operational dynamics of actual mining cutters. The setup incorporates a modified machining center equipped with sophisticated sensors that monitor various parameters such as cutting states, forces, torque, vibration, temperature, and sound. These sensors are crucial for precisely simulating the shearer cutting actions. The integration of digital twin technology is pivotal, featuring a real-time data management layer, a dynamic simulation mechanism model layer, and an application service layer that facilitates virtual experiments and algorithm refinement. This multifaceted approach allows for in-depth analysis of simulated coal cutting, utilizing sensor data to comprehensively evaluate the shearer’s performance. The study also includes tests on simulated coal samples. The system effectively conducts experiments and captures cutting condition signals via the sensors. Through time domain analysis of these signals, gathered while cutting materials of varying strengths, it is determined that the cutting force signal characteristics are particularly distinct. By isolating the cutting force signal as a key feature, the system can effectively distinguish between different cutting modes. This capability provides a robust experimental basis for coal rock identification research, offering significant insights into the nuances of shearer operation. Full article

Continuous mining is one of the development goals for metal mines, and the application of coal mining equipment represented by shearers provides a reference for continuous mining. However, rock in metal mines is generally harder than coal, making cutting difficult. Improving the surrounding rock conditions is an important way to improve the applicability of the drum for hard rock cutting. Therefore, this article explores the correlation between drum-cutting performance and surrounding rock boundary conditions, aiming to obtain surrounding rock boundary conditions that can help improve drum-cutting performance. To achieve the goal, a model of a shearer drum and hard rock is established using finite element software. With the model, hard rock cutting was simulated and the stress distribution on rock mass, deformation of rock mass, and drum cutting force during the cutting process under different confining pressures were analyzed. Relations between drum cutting force and confining pressure on rock mass were obtained. Then, drum cutting force under different free surfaces of rock mass are studied and the positions of free surface on rock mass that help to reduce the drum cutting force were summarized. According to the research, when the rock mass is under uniaxial compression, drum cutting force increases with the confining pressure on the rock mass; In addition, the free surfaces on the rock mass are proved to be helpful to reduce the drum cutting force. The research content lays the foundation for the boundary conditions required to reduce drum-cutting force in metal mining. Full article

The main focus of this work is the design and development of a three-dimensional force sensor for the cutting pick of a coal mining shearer’s simulated drum. This sensor is capable of simultaneously measuring the magnitude of force along three directions of the cutting pick during the cutting sample process. The three-dimensional force sensor is built based on the strain theory of material mechanics, and reasonable structural design is implemented to improve its sensitivity and reduce inter-axis coupling errors. The strain distribution of the sensor is analyzed using finite element analysis software, and the distribution of the strain gauges is determined based on the analysis results. In addition, a calibration test system is designed for the sensor, and the sensitivity, linearity, and inter-axis coupling errors of the sensor are calibrated and tested using loading experiments in three mutually perpendicular directions. Modal simulation analysis and actual cutting pick testing of the coal mining machine’s simulated drum are conducted to study the dynamic characteristics and functionality of the sensor in practical applications. The experimental results depict sensitivities of 0.748 mV/V, 2.367 mV/V, and 2.83 mV/V for the newly developed sensor, respectively. Furthermore, the cross-sensitivity error was lower than 5.02%. These findings validate that the sensor’s structure satisfies the measurement requirements for pick-cutting forces. Full article

In this paper, we propose an ultrasonically coupled mechanical rock-breaking technology, creatively design an ultrasonically coupled mechanical rock-breaking drum, concurrently develop an ultrasonic cracking simulation method based on test coordination, and study the cracking mechanism and characteristics of ultrasonically pre-broken rock in order to increase the rock-breaking efficiency of shearer drums and lengthen pickaxe service life. To further understand the theory behind ultrasonic-coupled mechanical rock breaking, the operation of a fusion drum and the implications of ultrasonic field theory in a solid medium are first examined. Second, the impact and mechanism of the ultrasonic pre-crushing of the target red sandstone are investigated in conjunction with conducting a rock uniaxial compression test and RFPA^2D modeling. Furthermore, an ultrasonic pre-crushing fracturing mechanism test of the target red sandstone further reveals the effect and mechanism of ultrasonic fracturing. The efficacy of ultrasonic-coupled mechanical single-cutter cutting is then investigated using the discrete element cutting model (PFC^2D) of red sandstone. The results show that under the action of ultrasonic waves with an excitation frequency of 41 kHz, cracks can effectively be produced inside the rock mass of the target red sandstone, and the cumulative amount of acoustic emission is as high as 513, which reduces the strength of the rock mass and disintegrates its internal structure; the average cut-off force of the purely mechanical rock-breaking mode is 6374 N, and that of ultrasonically coupled rock breaking is 4185 N, which is a reduction of 34.34%, and can be attributed to the fact that ultrasonic waves can loosen the structure of the rock mass. This is explained by the ability of ultrasonic vibrations to weaken the structure of rock. The coupled rock-breaking technology not only simplifies mechanical cutting and rock breaking but the lower force can also reduce a pick-shaped trunnion’s wear failure cycle. This improves the environment for subsequent pick-shaped trunnion cutting and rock breaking and prevents the pick-shaped trunnion from being subjected to high-stress loads for an extended period of time so as to prolong its working life. Full article