Abstract: Mineral resources provide an importantmaterial basis for a country's economic and social development.After decades of large-scalemining, the shallow-metalmineral resources of China have been reduced annually and the development ofmetal resources has reached the stage of comprehensive promotion of deepmining at present.Based on the investigation of a number ofmines in China and abroad and an extensive review of the relevant literature, this study summarizes the present situation and research progress ofmetalmining by focusing on themain technical engineering problems of deepmining and proposing some strategic recommendations to solve the problems of deepmining from six aspects, including the prediction and prevention of dynamicmining disasters, the control of hightemperature thermal environments and treatment of hazards, deep-well hoisting, deep-wellminingmethod and technology reform, new technology for deepmineral processing, and intelligent unmannedmining.The results include the following: (1) Themedium and long-term strategic research target for the deepmining ofmetals in China will be the depth of 5000m.(2) High efficiency and less restriction are characteristics of the cordless vertical lifting technology, which suggests that China should focus on the research and development of this technology and related equipment.(3) Combining themining of deepmineral resources with that of deep energy resources can effectively reduce the cost of deep cooling and offers a new way to solve the economic challenges of deepmining.(4) Newgenerationmining technologies need to change the original mining models and technologies, and the continuous mechanical cutting and rock breaking technology represent an important development direction for the future construction of ultra-deepmines.(5) The fillingmethod is one of themost effectivemethods for ensuring deep-production safety, and further research is needed on the fillingmaterial and filling process.(6) The conditions necessary for comprehensively promoting remote intelligent unmannedmining in China do notyet exist, andmining progress can be facilitated by university-industry collaboration.
Abstract: Early warning of rock collapse is one of the hot issues in the field of geotechnical engineering.The traditional monitoring and early warning methods of monitoring indicators are relatively uniform, with more attention being paid to the identification of accelerated damage precursors, which means that the early warning of collapse disasters has many inherent difficulties.In fact, rockblock collapse is caused by the dynamic failure of system instability, so it can be more effective to apply kinetic monitoring indicators to realize more scientific early warnings.In this paper, dynamic monitoring indexes were introduced to summarize the dynamic responses of rock and soil failure processes.A dynamic monitoring index based on natural vibration frequency can provide data for detecting damage in a dangerous rock mass.Based on the latest experimental research, it is concluded that the dynamic monitoring index can effectively reflect changes in physical and mechanical characteristics, and thus, can be used to dynamically and quantitatively analyze the damage and stability of a rock mass.A review of the literature on the current development of this field in China and abroad indicates that the early warning method of rock mass collapse disaster based on precursor failure identification in the detachment phase has better timeliness and will also to prove be more useful in future.Meanwhile, the development of an early warning index system of collapse is forecasted.An early monitoring and early warning index system based on dynamic, static, and environmental quantity indexes has greater potential for effective engineering monitoring and disaster warning.However, this new early warning method and its tripartite early warning indicator system offers a foundation for better responses to rock collapse in high-risk regions, and thus can improve the current passive prevention approach of rock-block monitoring and reduce the casualties and property losses that follow instantaneous rock collapse.This paper provides an effective reference for researchers studying early warning systems and the prevention of brittle damage disasters such as collapse.
Abstract: Hydraulic fracturing is a promising technique used in oil and gas reservoirs, enhanced geothermal systems, and coal gas production.Although its use is widespread, many aspects of hydraulic fracturing are still not well understood and need to be further investigated to achieve increases in oil and gas production while mitigating the adverse aspects of hydraulic fracturing.Understanding how hydraulic pressure extends preexisting fractures and forms a complex fracture network is essential for the design and treatment of hydraulic fracturing.Critical water pressure and fracture initiation angle are two important parameters involved in the hydraulic fracture propagation process and production from a well.In the present study, a minimum strain energy density criterion, which considers the effects of T-stress and Poisson's ratio, was proposed to analyze fracture initiation during hydraulic fracturing.The fracture initiation angle for different crack types was investigated using the proposed theoretical method, and the results indicate that the fracture initiation angle is not only related to the stress intensity factor but also affected by the T-stress and Poisson's ratio.The critical water pressure and critical initiation angle for two symmetric radial cracks emanating from a pressurized borehole were investigated, and the theoretical results were consistent with the experimental results.Through the proposed theoretical method, the influence of T-stress, radius of the fracture process zone, Biot's coefficient, lateral pressure coefficient and Poisson's ratio on the hydraulic fracturing behavior was analyzed.Parameter analysis indicates that the radius of the fracture process zone, T-stress, and lateral pressure coefficient play an important role in the critical initiation angle and critical water pressure.The critical water pressure increases with the decrement of Poisson's ratio, whereas the critical initiation angle shows the opposite trend.Biot's coefficient has no effect on the critical initiation angle but has a significant influence on the fracture initiation angle under high water pressure.The theoretical model enables a comprehensive understanding of the characteristics of hydraulic fracturing under complex loading conditions.The results also provided a basis for quantitative investigations of the engineering design of hydraulic fracturing treatments.
Abstract: In light of the serious environmental pollution caused by the conventional roasting processes and the corresponding low comprehensive utilization of rubidium resources, a novel acid leaching and solvent extraction process was developed to extract rubidium from rubidium mica ore.The effects of leaching temperature, sulfuric acid concentration, and time on the leaching of rubidium were investigated, and the phase transformations during the leaching were analyzed through X-ray diffraction(XRD), scanning electron microscope(SEM), and energy dispersive spectrometry(EDS).The experimental results show that the optimum conditions of acid leaching for rubidium mica ore are as follows: leaching temperature of 250 ℃, H2SO4 concentration of 200 g·L－1, and leaching time of 1 h.Under these conditions, the leaching ratio of rubidium increases up to 85. 2%.The XRD patterns of the raw ore indicate that quartz, biotite, muscovite, orthoclase, and albite are the major phases.Further SEM-EDS analysis shows that the Rb is scatted in biotite and muscovite in the form of isomorphism.Furthermore, the main reaction in the leaching process was the dissolution of the rubidium-rich micas.The countercurrent extraction experiment was conducted under the following conditions: extractant concentration of 1 mol·L－1, phase ratio(O/A)of 3:1, and extraction stage 3.The concentration of rubidium in the raffinate was 0. 003 g·L－1, and the extraction ratio of rubidium was 98%.After performing the 2-stage countercurrent stripping with 1 mol·L－1 HCl at a phase ratio(O/A)of 4:1, the stripping ratio of rubidium reached 99%.Silica white was prepared via alkali melting leaching residue and neutralization precipitation; thus, the comprehensive utilization of rubidium resource was achieved.XRD and Fourier transform infrared spectroscopy were used to characterize the silica white product.The corresponding results show that the product comprises hydrated silica, thus meeting the characteristics of the amorphous silica white.Finally, the chemical quantitative analysis results show that the silica white product comprises 91. 65% of SiO2, which is in accordance with the national chemical industry standard.
Abstract: Solar energy is an ideal renewable energy, and how to use solar energy efficiently is a hot topic for many researchers. So far, the development of solar cells has gone through three generations. The first generation used crystalline silicon cells; the second generation used thin-filmsolar cells. At present, the third generation utilizes new-type solar cells. As a part of the third-generation solar cells, perovskite solar cells have developed rapidly in recent years, making thema subject of a very vital research area. Lead iodide is a key raw material for organic-inorganic hybrid perovskite solar cells, and it is used by dissolving in dimethylformamide(DMF), thereby forming a film. Experimental results show that the reason for poor solubility of lead iodide in DMF is that oxides, such as H2O, PbO, and PbO2, tend to formoxide films on the surface of lead iodide crystals, which hinder its dissolution. Within a certain range, the solubility of lead iodide in DMF depends on the pH of the reaction solution during the synthesis process. After performing scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and other analytical tests, the optimal synthesis pH of lead iodide for the organic-inorganic hybrid perovskite solar cells is 2. Within a certain range, the pH value, dropping speed, and solution concentration of the reaction solution do not affect the microscopic morphology of lead iodide and its solubility in DMF. Simultaneously, results indicate that the recrystallization, thermal reaction, and low dropping speed reaction conditions led to the preferential growth of lead iodide on the(001)surface.
Abstract: ND steel is a low alloy steel that resists the dew point corrosion of sulfuric acid.To improve the special performance of ND steel, the chemical composition of ND steel not only contains conventional elements but also adds corrosion-resistant elements, such as Cu, Cr, and Ni.During the solidification process, the molten steel will undergo a phase change reaction.Owing to the differences in the distribution coefficients and diffusion coefficients of solute elements in different phases, solute elements will be redistributed in the solid-liquid two-phase region during solidification, which will lead to microsegregation of solute elements.The microsegregation of solute element makes the zero strength temperature and zero plasticity temperature (ZDT) of steel decrease, which makes the temperature range of brittleness expand and deteriorates the mechanical property of high temperature of the continuous casting billet, and finally increases the probability of inducing surface cracks.This paper takes the microsegregation of solute elements as the research background.Herein, a microsegregation model for the solute in the solidified two-phase region of an ND steel continuous casting billet was established.In the model, the effects of elements C, S, and P on high-temperature mechanical parameters and solute redistribution of steel in its solid-liquid two-phase region were studied, and the variation law of the segregation ratio of elemental P with cooling rate (CR) was also explored.According to the analysis of the model results, when the initial C content was between 0.075%and 0.125%, with an increase in the initial C content, segregation of P and S elements intensified, and the temperature drop at the solidification end became larger, leading to the increase in the brittle temperature range.According to the analysis of the model results, increasing the initial content of P and S will decrease the segregation ratio of P and S elements but will increase the enrichment content of P and S elements in the residual liquid phase between dendrites, directly leading to the decline of ZDT.Analysis of the model results shows that the Cu content in ND steel is lower than the critical content that significantly increases the crack sensitivity, and the segregation ratio of Cu element is at a low level during solidification.Therefore, elemental Cu cannot dominate the induced crack in ND steel during solidification.Finally, within a certain range of cooling rate fluctuation, the segregation ratio of P will decrease slightly with increasing CR.
Abstract: With the rapid development of global economy, problems in energy production and environmental protection are becoming severe, and the automotive industry is under increasing pressure to reduce the weight of vehicles and improve crash performance. Due to the demand for reduced vehicle weight as well as improved safety and crashworthiness, hot-stamped components from ultra-high strength steels have been utilized for automobile manufacturing. Currently, the most widely used hot-stamped steel plate is 22MnB5. Its tensile strength is 1500 MPa and yield strength is 1200 MPa. In contrast, as the demands for steel strength have increased, the demand for high strength grades of steel has been quickly put on the production agenda. In recent years, a novel hot-stamped steel, 38MnB5 has been developed, with a tensile strength exceeding 2000 MPa. The high temperature deformation behavior of 38MnB5 steel was investigated by the Gleeble-3500 thermal-mechanical simulator. The isothermal uniaxial tensile tests of the steel were performed within deformation temperature range of 650-950℃ under strain rates of 0. 01, 0. 1, 1, and 10 s-1, and the typical true stress-strain curves of 38MnB5 at relative conditions were analyzed. The experimental results show that the flow stress rises with decreasing deformation temperature under the same strain rate, and with an increasing strain rate. When the strain rate gradually increased, dynamic recovery and dynamical recrystallization exhibited an apparent effect on the hot deformation process, while the inconspicuous impact receded with rising temperature. In consideration of the multiple influences on deformation temperature, strain rate and strain, a phenomenological, constitutive relationship was developed to depict the hot deformation process of 38MnB5. In the established equation, the material constants dependent on the deformation temperature, strain rate, and strain were obtained using regression analysis of the experimental data for flow stress, strain, strain rate, etc. The comparison between the calculated data and the experimental data show that the calculated data derived from the constitutive models are found to be in satisfactory agreement with the experimental results.
Abstract: Nickel-base superalloy 617B is one of the most promising candidates for superheater and reheater pipes of advanced ultra-supercritical (AUSC) power plants.Hot extrusion is a key process during the manufacturing of superalloy 617B pipes.However, the high content of alloying elements in superalloy 617B makes microstructure control difficult during the hot extrusion process.Furthermore, to date, no systematical theoretical investigation has been conducted in the hot extrusion process control of superalloy 617B.Hence, in this work, the hot extrusion process of superalloy 617B tube was studied by finite element simulation using DEFORM-2D finite element software.The microstructure evolution during hot extrusion was considered by combining the microstructure evolution model of superalloy 617B and finite element simulation software.The microstructure evolution model was programmed using FORTRAN language and was developed using the finite element simulation software.The hot extrusion characteristics of superalloy 617B were systematically analyzed by the simulation.As a result, the evolution of temperature, grain size, and loading could be predicted quantitatively.At the same time, to optimize the hot extrusion parameters, microstructure-based hot extrusion control principles, including temperature principle, loading principle, precise microstructure control principle, were proposed considering practical hot extrusion process.Moreover, the control mechanism and application process of these principles were elaborated in detail in this paper.The hot extrusion parameters of superalloy 617B tube were optimized based on the proposed microstructure-based hot extrusion control principles.Under the guidance of the microstructure-based hot extrusion control principles, superalloy 617B tube with uniform axial dimension and good surface quality was extruded successfully in the factory.The practical extrusion result agrees well with the simulated one.Therefore, the establishment and validation of the simulation method and microstructure-based hot extrusion control principles can provide theoretical guidance for the hot extrusion process optimization of nickel-base superalloy tube in practical applications.
Abstract: Pyrite (FeS2) is considered to be an excellent electrode material candidate for energy storage devices because of its abundant resources, cost effectiveness, environmental friendliness and high theoretical capacity of 894 mA·h·g-1 based on conversiontype reactions.However, transition metal sulfides (TMSs), includingFeS2, suffer from low electronic conductivity, sluggish Li ion transfer kinetics, and severe volume change while charging and discharging, which contribute to the sharp decline in capacity as well as limit its application as electrode material for secondary batteries.Downsizing TMS powders to the nanoscale becomes a common strategy to mitigate the volume change and maximize the proportion of active material involved in the electrochemical process.However, nanostructures lead to a serious interphase detrimental reaction, dissolution of the polysulfide intermediates, and low volumetric energy density.Therefore, micron particles are critical to the design of high energy density active material in view of industrial applications.In this study, a facile hydrothermal method has been successfully developed to synthesize a novel mesoporous composite of core-shell FeS2 micron spheres with multi-walled carbon nanotubes (C-S-FeS2@ MWCNT).The protective layer is constructed on FeS2 micron spheres consisting of the approximately 350 nm-thickness shell stacked by nanosheet FeS2 particles and the reticular MWCNTs anchored via chemical binding.The FeS2 content is determined using thermogravimetric analysis to be 73.4% of the C-S-FeS2@ MWCNT composite, which is higher than the value of the reported compound material with nanopowder.The unique architecture with abundant functional groups and pore structures not only provides the Li+ ion diffusion pathway but also buffers volume expansion during cycling.The galvanostatic circulation tests indicate that the C-S-FeS2@ MWCNT electrode delivers a high reversible capacity of 638 mA·h·g-1 in 250 cycles at a current density of 200 mA·g-1 and exhibits a significantly improved rate performance.This work demonstrates a new method to develop TMSmicron electrode material with high volumetric energy density.
Abstract: The binary Zr-Cu system is a paradigm for studying the atomistic structure-property relationships and glass transition due to its outstanding glass formation ability (GFA). Metallic glass (MG) thin films are mainly prepared using magnetron sputtering deposition methods. The outstanding mechanical properties of these MG thin films have gained the attention of the industry. In this study, molecular dynamic (MD) simulations were employed to investigate the growth of ZrxCu100-x(x=50, 70, and 90), with initial conditions similar to the experimental operating ones. The deposition process of the Zr-Cu system was performed on the Si (100) substrate. The simulated radial distribution functions (RDF) and X-ray diffraction (XRD) were adopted to analyze the phase of Zr-Cu films. Additionally, the correlation between GFA and five-fold local symmetry (FFLS) was discussed in depth. The mechanical properties of the deposited films and the effect of film thickness on the tensile process were also analyzed. The results show that the structure is composition-dependent. Both Zr50Cu50 and Zr70Cu30-deposited films exhibited amorphous properties with strong short range orders, whereas Zr90Cu10 -deposited film showed a perfect crystal characteristic. The positive correlation exists between GFA and degree of FFLS in binary Zr-Cu systems. Zr90Cu10 -deposited film has a Young's modulus of 100 GPa, which is larger than that of the other two deposited films. Deposited Zr-Cu MG films exhibited better ductility than crystalline ones. Herein, the failure strain of Zr-Cu MG films exceeded 40%. The correlation existed between GFA and mechanical strength. Deposited films with higher GFAs had greater strength at the same box size. Moreover, the Zr50Cu50 -deposited glass film had greater ultimate tensile strength than the near-eutectic glass film (Zr70Cu30). This study also shows that the deposited film exhibited a certain size effect. The size effect was detected, and when the thickness of the film was smaller, the tensile strength was greater. This study provides new ideas for the preparation of MG films with perfect mechanical properties.
Abstract: In the current inversion process of variable-polarity arc welding of aluminum alloy, drastic changes in electron and ion concentrations in arc space may lead to the failure of current commutation and arc reignition, thus affecting the arc burning stability and weld formation quality. The novel reverse arc reignition voltage-generating circuit will produce a stable reverse voltage during the current polarity inversion process. In this circuit, the value of the reverse voltage remains unchanged with the variation in the base welding current, and thus can better meet the requirement of reverse arc reignition voltage for current inversion. Through the use of the variablepolarity welding power supply with novel reverse arc reignition voltage-generating circuit as the experimental platform, the influence of the power equipment and its control parameters, the parasitic inductance of the cable in the output welding loop, and the welding process parameters on the current commutation process of variable-polarity arc welding was investigated. The experimental results show that increasing the value of the reverse arc reignition voltage can increase the current variation rate in the polarity inversion process. Contrastingly, a large parasitic inductance of the cable in the output welding loop will reduce the current variation rate and the current value at the end of the polarity inversion process, which is detrimental by the reliable arc reignition and stable arc burning in the polarity inversion process. The lower the initial welding current is, the lower the current value at the end of the polarity inversion process. Increasing the common conduction time can increase the current value at the end of the polarity inversion process, but decrease the current value at the beginning of this process. Therefore, to improve the arc stability in the polarity inversion process, a large value of the reverse arc reignition voltage and an appropriate increase in common conduction time can be used in low-current variable-polarity welding. All of the conclusions previously presented can provide reference and basis for the selection and adjustmentof the power equipment and its control parameters for variable-polarity arc welding under various process parameters.
Abstract: A 3D printing photosensitive resin structure has many advantages, such as good corrosion resistance, flexibility, low yield, and superior deformability; thus, it has been widely used in several fields.In this study, a new photosensitive resin structure was designed and built using 3D printing method.The new photosensitive resin structure is mainly used as a damping element in shockabsorbing and -isolating composite structures.First, load-displacement curves were obtained by compression experiments using the universal testing machine controlled via a microcomputer, and the equivalent elastic modulus of the specific points in the structure was calculated.Dynamic loading tests were conducted using the fatigue machine.Moreover, the hysteresis loops under different frequencies between 5 Hz and 20 Hz were obtained.The equivalent damping ratio was calculated on the basis of the hysteresis loops.The static and dynamic calculation models were built on the basis of the finite element method.After the calculations, the numerical results and the test data under the same conditions were compared.The numerical results agreed well with the test data, thereby verifying the feasibility of the finite element models.Furthermore, the influences of different geometric parameters, such as slot width, inner arc, outer arc, and thickness, on the equivalent elastic modulus of the specific location and equivalent damping ratio of photosensitive resin were investigated by the finite element method.When the 3D printing photosensitive resin structure is subjected to force, it maintains a stiffness output and small deformation along the longitudinal direction; however, the lateral displacement can be enlarged.The 3D printing photosensitive resin structure has a good capability to reduce vibration and resist deformation.The results provide references for the future research of the static and dynamic characteristics and engineering application of the 3D printing photosensitive resin structure.
Abstract: An important part of the iron-and-steel production process, converter steelmaking is the most widely used and efficient method of steelmaking in the world. Under the requirements of"China Manufacturing 2025, "ensuring intelligent steelmaking, improving smelting production efficiency, and reducing production cost are major concerns that should be addressed urgently in converter steelmaking. Owing to the complex thermodynamic and dynamic reactions in the converter smelting process, sublance control and traditional flue-gas analysis models have limitations that result in low prediction accuracy of the end-point carbon in converter smelting, thereby causing the main technical bottleneck in intelligent steelmaking. Therefore, a functional digital twin model of the steelmaking process based on flue-gas analysis was proposed. First, continuously monitored real-time data were obtained by flue gas analysis to observe the carbon and oxygen reaction state of molten steel in the converter. Then, according to various stages of the converter reaction, the functional data analysis method was used to establish the functional prediction models for the early and late stages of blowing. The greatest advantage of the method is that the model can automatically adjust the coefficient function according to the measured off-gas data by using a continuous functional curve to fit the complex dynamic reaction process. Therefore, the proposed model can accurately predict not only the normal smelting process but also the decarburization and carbon drawing process for the secondary scraping slag. An industrial experiment on a 260 t converter was conducted to prove that the functional digital twin model of the converter smelting process has good self-learning and self-adaptive ability and is robust to the abnormal smelting state. Furthermore, the model can predict the carbon content of the converter dynamically in the entire process and the end-point carbon content can reach 95% at ± 0. 02%. Using the predicted value of the carbon content to control the final blowing point through the functional digital twin model can effectively prevent overblowing or underblowing. More importantly, on the premise of guaranteeing the stability of raw material composition, temperature, weight, and other parameters, the model is expected to cancel the blown-off sampling step based on sublance. This feature can reduce the production cost while improving the product quality and production efficiency for a wide range of industrial applications.
Abstract: Integration of order acceptance and scheduling on unrelated parallel machines is a joint decision problem, and arise from the multi-variety customized production environment, which usually has the following characteristics. First, there are a number of parallel machines (production lines), each of which can only produce a limited variety of products referred as the machine-eligibility constraint. Second, the processing technologies of various machines differ; thus, these parallel machines are unrelated. Third, because the machines are unrelated, the setup time of an order is related not only to the order sequence but also to the machine used, which is called a sequence-and machine-dependent setup time. To minimize total cost, this study investigates the scheduling problems posed by order acceptance and unrelated parallel machines with setup time and machine-eligibility constraints. In this problem, an order has two options, rejection or acceptance. If an order is rejected, it generates a rejection cost. Otherwise, the order process must be completed before the due date, or there will be a tardiness cost. Therefore, the total cost spent is calculated as the sum of the total rejection cost of rejected orders and total weighted tardiness cost of accepted orders. To solve this problem, the effect of rejecting an order on the total cost was analyzed, and a list of rejecting methods and rejection rules were proposed. Furthermore, a cooperative coevolving genetic algorithm (CCGA) was developed. In this CCGA, an encoding scheme was proposed that divides chromosomes into two subsets corresponding to the order list and order assignment. Moreover, a list-rejecting-based decoding procedure was presented for deciding rejection for a chromosome. As the two subsets are independent of each other and their evolutionary constraints are essentially different, a cooperative coevolution strategy was applied to evolve the subpopulations of these subsets using partheno-genetic and traditional genetic operators. Computational experiments on a large set of randomly generated instances were performed to verify the effectiveness and efficiency of this algorithm. Additionally, the impacts of problem size and rejection cost were studied experimentally. The results reveal that in the majority of cases characterized by various problem sizes and rejection costs, the proposed algorithm performs effectively and efficiently.
Abstract: Optical coherence tomography (OCT) is an indispensable tool used for the diagnosis and identification of ocular fundus disease and nondestructive, rapid, and high-resolution imaging of the living retinas. The attendant research focuses on the development of computer-aided methods to help ophthalmologists make judgments regarding the morphological changes of retinal tissue and acquire tissue characteristic parameters. Realizing the segmentation of retinal tissue in OCT images is the key aspect of this kind of research. Mathematical morphology, which has been widely used in the fields of image detection, shape analysis, pattern recognition, and computer vision, uses different structural elements to measure, extract, analyze, and identify image targets. However, traditional morphological structure elements cannot be adaptively changed on the basis of the structural characteristics of the images. In this study, an algorithm for generating morphological adaptive structural elements was proposed on the basis of an immune genetic algorithm, which the detection of retinal tissue edges in optical coherence tomography (OCT) images was applied. First, the image is preprocessed by denoising and coarse segmentation and then the image is divided into several sub-images. Second, the adaptive structure elements are computed using an immune genetic algorithm for each sub-image. A string of binary numbers of fixed length is initially randomly generated as an antibody and then converted into a format of structural element. The fitness of an antibody is defined by the two-dimensional entropy of the image and the optimal antibody and structural elements are identified according to the structural characteristics of the subimage itself. Finally, with these optimal structural elements, morphological edge detection is performed to obtain the segmentation results of each sub-image combined with those of each sub-graph to realize the extraction of the target boundary of the whole image. The experimental results show the proposed method to be effective in the boundary extraction of images.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
