The primary goal of this study is to provide an efficient numerical tool to analyze the seismic performance of nailed walls.Modeling such excavation supports involves complexities due partly to the interaction of supp...The primary goal of this study is to provide an efficient numerical tool to analyze the seismic performance of nailed walls.Modeling such excavation supports involves complexities due partly to the interaction of support with soil and partly because of the amplification of seismic waves through an excavation wall.Consequently,innovative modeling is suggested herein,incorporating the calibration of the soil constitutive model in a targeted range of stress and strain,and the detection of a natural period of complex systems,including soil and structure,while benefiting from Rayleigh damping to filter unwanted noises.The numerical model was achieved by simulating a previous centrifuge test of the excavation wall,manifested at the pre-failure state.Notably,the calibration of the soil constitutive model through empirical relations,which replaces the numerical reproduction of an element test,more accurately simulated the soil-nail-wall interaction.Two factors were crucial to a successful result.First,probing the natural period of the complicated geometry of the model by applying white noises.Second,considering Rayleigh damping to withdraw unwanted noises and thus assess their permanent effects on the model.Rayleigh damping was applied instead of filtering the obtained results.展开更多
Autism spectrum disorder is a developmental disorder impacting a child’s social interactions,behaviors,and communication skills.One of the crucial aspects of autism care,which is often overlooked,is the parent’s men...Autism spectrum disorder is a developmental disorder impacting a child’s social interactions,behaviors,and communication skills.One of the crucial aspects of autism care,which is often overlooked,is the parent’s mental health status while trying to improve and overcome challenges faced by their child.A study by Lu et al examined the effectiveness of remote family psychological support courses on the mental health status of parents having children with autism spectrum disorder.It was found that the integration of these remote psychological courses with conventional care had a positive impact on the parents by reducing their stress levels,leading to an increase in their competence,and hence they could engage effectively in child therapy.However,a long-term study is necessary to assess whether these interventions have a sustained effect.The study emphasizes the need for developing such culturally sensitive intervention models on a global scale,making them accessible to all and improving autism care support.展开更多
The major aim of stroke therapy is to stimulate brain repair and improve behavioral recovery after cerebral ischemia.One option is to stimulate endogenous neurogenesis in the subventricular zone and direct the newly f...The major aim of stroke therapy is to stimulate brain repair and improve behavioral recovery after cerebral ischemia.One option is to stimulate endogenous neurogenesis in the subventricular zone and direct the newly formed neurons to the damaged area.However,only a small percentage of these neurons survive,and many do not reach the damaged area,possibly because the corpus callosum impedes the migration of subventricular zone-derived stem cells into the lesioned cortex.A second major obstacle to stem cell therapy is the strong inflammatory reaction induced by cerebral ischemia,whereby the associated phagocytic activity of brain macrophages removes both therapeutic cells and/or cell-based drug carriers.To address these issues,neurogenesis was electrically stimulated in the subventricular zone,followed by isolation of proliferating cells,including newly formed neurons,which were subsequently mixed with a nutritional hydrogel.This mixture was then transferred to the stroke cavity of day 14 post-stroke mice.We found that the performance of the treated animals improved in behavioral tests,including novel object,open field,hole board,grooming,and“time-to-feel”adhesive tape tests.Furthermore,immunostaining revealed that the stem cell marker nestin,the neuroepithelial marker Mash1,and the immature neuronal marker doublecortin-positive cells survived in the transplanted area for 2 weeks,possibly due to reduced phagocytic activity and supportive angiogenesis.These results clearly indicate that the transplantation of committed subventricular zone stem cells combined with a protective nutritional gel directly into the infarct cavity after the peak of stroke-induced neuroinflammation represents a feasible approach to improve neurorestoration after cerebral ischemia.展开更多
Parkinson’s disease(PD)is a debilitating neurological disorder affecting over 10 million people worldwide.PD classification models using voice signals as input are common in the literature.It is believed that using d...Parkinson’s disease(PD)is a debilitating neurological disorder affecting over 10 million people worldwide.PD classification models using voice signals as input are common in the literature.It is believed that using deep learning algorithms further enhances performance;nevertheless,it is challenging due to the nature of small-scale and imbalanced PD datasets.This paper proposed a convolutional neural network-based deep support vector machine(CNN-DSVM)to automate the feature extraction process using CNN and extend the conventional SVM to a DSVM for better classification performance in small-scale PD datasets.A customized kernel function reduces the impact of biased classification towards the majority class(healthy candidates in our consideration).An improved generative adversarial network(IGAN)was designed to generate additional training data to enhance the model’s performance.For performance evaluation,the proposed algorithm achieves a sensitivity of 97.6%and a specificity of 97.3%.The performance comparison is evaluated from five perspectives,including comparisons with different data generation algorithms,feature extraction techniques,kernel functions,and existing works.Results reveal the effectiveness of the IGAN algorithm,which improves the sensitivity and specificity by 4.05%–4.72%and 4.96%–5.86%,respectively;and the effectiveness of the CNN-DSVM algorithm,which improves the sensitivity by 1.24%–57.4%and specificity by 1.04%–163%and reduces biased detection towards the majority class.The ablation experiments confirm the effectiveness of individual components.Two future research directions have also been suggested.展开更多
The roadway support in many places of Jiulongkou Colliery, Fengfeng Mining Bureau, such as in the Permanent transportation roadway, was failed or locally caved, which seriously affected the colliery’s coal production...The roadway support in many places of Jiulongkou Colliery, Fengfeng Mining Bureau, such as in the Permanent transportation roadway, was failed or locally caved, which seriously affected the colliery’s coal production performance and safety. Based on analysis of supporting objects for roadway repairing, this paper proposes the supporting parameters and condruction technics. The industrial ted of 70m long roadway repairing shows that the proposed parameters and technics of bolt shotcrete and mesh support for roadway repairing are reasouable, bring good technical and economic results for the colliery, and the repairing is successful.展开更多
Soft rock surrounding deep roadway has poor stability and long-term rheological effect. More and larger deformation problems of surrounding rock occur due to adverse supporting measures for such roadways, which not on...Soft rock surrounding deep roadway has poor stability and long-term rheological effect. More and larger deformation problems of surrounding rock occur due to adverse supporting measures for such roadways, which not only affects the engineering safety critically but also improves the maintenance costs. This paper takes the main rail roadway with severely deformation in China＇s Zaoquan coal mine as an example to study the long-term deformation tendency and damage zone by means of in-situ deformation monitoring and acoustic wave testing technique. A three-dimensional finite element model reflecting the engineering geological condition and initial design scheme is established by ABAQUS. Then, on the basis of field monitoring deformation data, the surrounding rock geotechnical and theological parameters of the roadway are obtained by back analysis. A combined supporting technology with U-shaped steel support and anchor-grouting is proposed for the surrounding soft rock. The numerical simulation of the combined supporting technology and in-situ deformation monitoring results show that the soft rock surrounding the roadway has been held effectively.展开更多
Linear failure criterion is widely used in calculation of earth pressure acting on shallow tunnels. However, experimental evidence shows that nonlinear failure criterion is able to represent fairly well the failure of...Linear failure criterion is widely used in calculation of earth pressure acting on shallow tunnels. However, experimental evidence shows that nonlinear failure criterion is able to represent fairly well the failure of almost all types of rocks, A nonlinear Hock-Brown failure criterion is employed to estimate the supporting pressures of shallow tunnels in limit analysis framework. Two failure mechanisms are proposed for calculating the work rate of extemal force and the internal energy dissipation. A tangential line to the nonlinear failure criterion is used to formulate the supporting pressure problem as a nonlinear programming problem. The objective function formulated in this way is minimized with respect to the failure mechanism and the location of tangency point. In order to assess the validity, the supporting pressures for the proposed failure mechanisms are calculated and compared with each other, and the present results are compared with previously published solutions when the nonlinear criterion is reduced to linear criterion. The agreement supports the validity of the proposed failure mechanisms. An experiment is conducted to investigate the influences of the nonlinear criterion on collapse shape and supporting pressures of shallow tunnels.展开更多
In deep underground engineering,rock burst and other dynamic disasters are prone to occur due to stress concentration and energy accumulation in surrounding rock.The control of dynamic disasters requires bolts and cab...In deep underground engineering,rock burst and other dynamic disasters are prone to occur due to stress concentration and energy accumulation in surrounding rock.The control of dynamic disasters requires bolts and cables with high strength,high elongation,and high energy-absorbing capacity.Therefore,a constant resistance energy-absorbing(CREA)material is developed.In this study,the dynamic characteristics of the new material are obtained via the drop hammer tests and the Split Hopkinson Pressure Bar(SHPB)tests of the new material and two common bolt(CB)materials widely used in the field.The test results of drop hammer test and SHPB test show that the percentage elongation of CREA material is more than 2.64 and 3.22 times those of the CB material,and the total impact energy acting on CREA material is more than 18.50 and 21.84 times,respectively,indicating that the new material has high elongation and high energy-absorbing capacity.Subsequently,the CREA bolts and cables using the new material are developed,which are applied in roadways with high stress and strong dynamic disturbance.The field monitoring results show that CREA bolts and cables can effectively control the surrounding rock deformation and ensure engineering safety.展开更多
Thin-walled parts are widely used in the aerospace industry owing to their light weight and high specific strength.However,due to the low rigidity of thin-walled parts,elastic deformation and chatter easily occur,whic...Thin-walled parts are widely used in the aerospace industry owing to their light weight and high specific strength.However,due to the low rigidity of thin-walled parts,elastic deformation and chatter easily occur,which seriously affect the machining accuracy and workpiece surface quality.To solve this problem,several supporting technologies have been reported in recent years.This paper reviews the recent research progress of flexible supporting technologies in the aerospace field by classifying them based on different principles and characteristics.The principle,progress,advantages,and limitations of the technologies are expounded by systematic comparison and summarized.Finally,the challenges and future development trends of flexible supporting technology,which will provide guidelines for further research,are discussed.展开更多
A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large d...A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation（CRLD） bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt（rebar） using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson＇s ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson＇s ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.展开更多
To analyze the stability of a shallow square tunnel, a new curved failure mechanism, representing the mechanical characteristics and collapsing form of this type of tunnel, is constructed. Based on the upper bound the...To analyze the stability of a shallow square tunnel, a new curved failure mechanism, representing the mechanical characteristics and collapsing form of this type of tunnel, is constructed. Based on the upper bound theorem of limit analysis and the Hoek-Brown nonlinear failure criterion, the supporting pressure derived from the virtual work rate equation is regarded as an objective function to achieve optimal calculation. By employing variational calculation to optimize the objective function, an upper bound solution for the supporting pressure and the collapsing block shape of a shallow square tunnel are obtained. To evaluate the validity of the failure mechanism proposed in this paper, the solutions computed by the curved failure mechanism are compared with the results calculated by the linear multiple blocks failure mechanism when the Hoek-Brown nonlinear failure criterion is converted into the Mohr-Coulomb linear criterion. The influences of rock mass parameters on the supporting pressure and collapsing block shape are discussed.展开更多
There have been substantial conflicts in the human-water relationship in the Huaihe River Basin （HRB）. To achieve sustainable economic development without degrading the water environment in the HRB, we develop a thr...There have been substantial conflicts in the human-water relationship in the Huaihe River Basin （HRB）. To achieve sustainable economic development without degrading the water environment in the HRB, we develop a three-dimensional water environmental sup- porting capacity （WESC） model based on water environmental carrying capacity （WECC）, water environmental pressure （WEP）, and water pollution prevention and control capacity （WPPC）. Geographic information systems spatial analysis with the analytical hierarchy process method and dynamic weighted summation is applied. Several proposals for suitable locations for industry and environmental protection strategies for water were presented. The following results were obtained. （1） The spatial differences in WECC are substantial; areas with high-value WECC zones are mainly located along the main stream of the Huaihe River on the south side. WEP is generally high, with an overall low level of pollution prevention and control in the whole HRB. WPPC and WEP show high spatial overlapping due to the fact that areas with higher environmental pollution usually have high level of economic development, and thus have a strong capacity for pollution control. （2） Overall, WESC is moderate in the HRB. In particular, areas with a high WESC value only account for 56.24% of the HRB in 2010 Distinct differences in WESC also exist between areas located in the south compared with in the north of the basin, and areas alongside the downstream region compared with alongside the upstream and midstream regions. （3） Consequently, according to the guidance for indus- try zoning in the HRB, the areas in the south and alongside the downstream and sub-streams with a low WEP value and high WECC and WPPC, traditional industries should be developed based on strict environmental access and pollution emission standards. While for the areas along the midstream of the HRB and along the whole Yishusi River Basin, which have a high WEP value, industrial restructuring and technological upgrading are suggested. Action should be taken to limit development and protect the environment in the upstream region of the basin which is a key source of drinking water, in the eastern route along the line of the South-toNorth Water Diversion Project, and in the ecologically fragile region alongside the basin. This will ensure good environmental functionality including subsistent provision of clean water, while at the same time satisfying the urgent need to adjust, transform, and upgrade the industrial structure.展开更多
Tunnels deeply buried have high crustal stress and are prone to large deformation disasters when encountering soft rock.The large deformation phenomenon during the construction process of the Maoxian Tunnel on the Che...Tunnels deeply buried have high crustal stress and are prone to large deformation disasters when encountering soft rock.The large deformation phenomenon during the construction process of the Maoxian Tunnel on the Chengdu-Lanzhou Railway is particularly evident.This article focuses on the large deformation problem of the No.1 inclined shaft of the Maoxian Tunnel,and uses on-site monitoring methods to explore the reasons for tunnel structure failure,and analyzes the mechanical behavior of the tunnel structure.By using numerical simulation methods,the effectiveness of the second-layer support in resisting creep loads in tunnels was studied,and the influence of the construction time of the secondlayer support on the mechanical properties of the tunnel was discussed.The results indicate that the first-layer support in the tunnel is a structural failure caused by asymmetric deformation caused by creep,while the second-layer support has a good effect on resisting creep loads.The research results can provide a technical reference for deformation control of squeezing tunnels.展开更多
More accurate forecasting of rock burst might be possible from observations of electromagnetic radiation emitted in the mine.We analyzed experimental observations and field data from the Muchengjian coal mine to study...More accurate forecasting of rock burst might be possible from observations of electromagnetic radiation emitted in the mine.We analyzed experimental observations and field data from the Muchengjian coal mine to study the relationship between electromagnetic radiation signal intensity and stress during the fracturing of coal, or rock, and samples under load.The results show that the signal intensity is positively correlated with stress.In addition, we investigated the change in the electromagnetic radiation intensity, the supporting resistance in a real coal mine environment, and the coal or rock stress in the mining area.The data analysis indicates that:1) electromagnetic radiation intensity can accurately reflect the distribution of stress in the mining area;and, 2) there is a correlation between electromagnetic radiation intensity and supporting resistance.The research has some practical guiding significance for rock burst forecasting and for the prevention of accidents in coal mines.展开更多
Based on the active failure mechanism generated by a spatial discretization technique, the stability of tunnel face was studied. With the help of the spatial discretization technique, not only the anisotropy and inhom...Based on the active failure mechanism generated by a spatial discretization technique, the stability of tunnel face was studied. With the help of the spatial discretization technique, not only the anisotropy and inhomogeneity of the cohesion but also the inhomogeneity of the internal friction angle was taken into account in the analysis of the supporting forces. From the perspective of upper bound theorem, the upper bound solutions of supporting pressure were derived. The influence of the anisotropy and heterogeneity on the supporting forces as well as the failure mechanisms was discussed. The results show that the spatial discretization characteristics of cohesion and internal frictional angle impose a significant effect on the supporting pressure, which indicates that above factors should be considered in the actual engineering.展开更多
The methods combined by test, field monitoring and theoretical analysis were adopted to do the systemic research on the rock mass from micro-structure to macro-deformation, and rheological model of Jinchuan rock mass ...The methods combined by test, field monitoring and theoretical analysis were adopted to do the systemic research on the rock mass from micro-structure to macro-deformation, and rheological model of Jinchuan rock mass was established to discuss the reasonable supporting time. Resuhs show that supporting after suitable stress and displacement release can benefit for the long-term stability of surrounding rock.展开更多
A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjac...A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjacent steel structural units are jointed with fasteners, and each steel structural unit has a certain radian and is welded by two steel tubes and one piece of steel disc. In order to test and verify the reliability of the new supporting structure, the field tests are designed. The main monitoring programs include the hoop stress of supporting structure, lateral earth pressure, and soil deformation. The monitoring data of the field tests show that the new supporting structure is convenient, reliable and safe.展开更多
In order to solve the large deformation controlling problem for surrounding rock of gob-side entry driving under common cable anchor support in deep mine, site survey, physical modeling experiment, numerical simulatio...In order to solve the large deformation controlling problem for surrounding rock of gob-side entry driving under common cable anchor support in deep mine, site survey, physical modeling experiment, numerical simulation and field measurement were synthetically used to analyze the deformation and failure characteristics of surrounding rock. Besides, applicability analysis, prestress field distribution characteristics of surrounding rock and the control effect on large deformation of surrounding rock were also further studied for the gob-side entry driving in deep mine using the cable-truss supporting system. The results show that, first, compared with no support and traditional bolt anchor support, roof cable-truss system can effectively restrain the initiation and propagation of tensile cracks in the roof surrounding rock and arc shear cracks in the two sides, moreover, the broken development of surrounding rock, roof separation and extrusion deformation between the two sides of the roadway are all controlled; second, a prestressed belt of trapezoidal shape is generated in the surrounding rock by the cable-truss supporting system, and the prestress field range is wide. Especially, the prestress concentration belt in the shallow surrounding rock can greatly improve the anchoring strength and deformation resisting capability of the rock stratum;third, an optimized support system of ‘‘roof and side anchor net beam, roof cable-truss supporting system and anchor cable of the narrow coal pillar" was put forward, and the support optimization design and field industrial test were conducted for the gob-side entry driving of the working face 5302 in Tangkou Mine, from which a good supporting effect was obtained.展开更多
To improve the diagnosis accuracy and self-adaptability of fatigue crack in ulterior place of the supporting shaft, time series and neural network are attempted to be applied in research on diag-nosing the fatigue cr...To improve the diagnosis accuracy and self-adaptability of fatigue crack in ulterior place of the supporting shaft, time series and neural network are attempted to be applied in research on diag-nosing the fatigue crack’s degree based on analyzing the vibration characteristics of the supporting shaft. By analyzing the characteristic parameter which is easy to be detected from the supporting shaft’s exterior, the time series model parameter which is hypersensitive to the situation of fatigue crack in ulterior place of the supporting shaft is the target input of neural network, and the fatigue crack’s degree value of supporting shaft is the output. The BP network model can be built and net-work can be trained after the structural parameters of network are selected. Furthermore, choosing the other two different group data can test the network. The test result will verify the validity of the BP network model. The result of experiment shows that the method of time series and neural network are effective to diagnose the occurrence and the development of the fatigue crack’s degree in ulterior place of the supporting shaft.展开更多
Aiming at the characteristics of the poor steady ability, the short stable time and severe deformation behavior of weakly cemented soft surrounding rock around extraction roadway, a bolt–cable combined supporting tec...Aiming at the characteristics of the poor steady ability, the short stable time and severe deformation behavior of weakly cemented soft surrounding rock around extraction roadway, a bolt–cable combined supporting technology was proposed. Numerical simulation was performed by using FLAC3 D software to study the effects of different supporting systems. The simulation result proves that those supporting systems have good practical values. Based on real-time monitoring and analysis of the deformation of surrounding rock and the stress of supporting structure, real time information of deformation of surrounding rock and stress state of supporting structure of extraction roadway within weakly cemented strata was obtained. Monitoring results show that large deformation and failure of surrounding rock of extraction roadway within weakly cemented strata can be effectively controlled by the bolt–cable combined supporting technology, which ensures the long-term stability and safety of surrounding rock and supporting structure.展开更多
基金supported by the International Institute of Earthquake Engineering and Seismology(IIEES) as technical project No.760
文摘The primary goal of this study is to provide an efficient numerical tool to analyze the seismic performance of nailed walls.Modeling such excavation supports involves complexities due partly to the interaction of support with soil and partly because of the amplification of seismic waves through an excavation wall.Consequently,innovative modeling is suggested herein,incorporating the calibration of the soil constitutive model in a targeted range of stress and strain,and the detection of a natural period of complex systems,including soil and structure,while benefiting from Rayleigh damping to filter unwanted noises.The numerical model was achieved by simulating a previous centrifuge test of the excavation wall,manifested at the pre-failure state.Notably,the calibration of the soil constitutive model through empirical relations,which replaces the numerical reproduction of an element test,more accurately simulated the soil-nail-wall interaction.Two factors were crucial to a successful result.First,probing the natural period of the complicated geometry of the model by applying white noises.Second,considering Rayleigh damping to withdraw unwanted noises and thus assess their permanent effects on the model.Rayleigh damping was applied instead of filtering the obtained results.
文摘Autism spectrum disorder is a developmental disorder impacting a child’s social interactions,behaviors,and communication skills.One of the crucial aspects of autism care,which is often overlooked,is the parent’s mental health status while trying to improve and overcome challenges faced by their child.A study by Lu et al examined the effectiveness of remote family psychological support courses on the mental health status of parents having children with autism spectrum disorder.It was found that the integration of these remote psychological courses with conventional care had a positive impact on the parents by reducing their stress levels,leading to an increase in their competence,and hence they could engage effectively in child therapy.However,a long-term study is necessary to assess whether these interventions have a sustained effect.The study emphasizes the need for developing such culturally sensitive intervention models on a global scale,making them accessible to all and improving autism care support.
基金supported by European Union Funding Programme,PNRR,No. 760058(to DMH)the UEFISCDI Project,No. PN-III-P4-IDPCE-2020-059(to APW)
文摘The major aim of stroke therapy is to stimulate brain repair and improve behavioral recovery after cerebral ischemia.One option is to stimulate endogenous neurogenesis in the subventricular zone and direct the newly formed neurons to the damaged area.However,only a small percentage of these neurons survive,and many do not reach the damaged area,possibly because the corpus callosum impedes the migration of subventricular zone-derived stem cells into the lesioned cortex.A second major obstacle to stem cell therapy is the strong inflammatory reaction induced by cerebral ischemia,whereby the associated phagocytic activity of brain macrophages removes both therapeutic cells and/or cell-based drug carriers.To address these issues,neurogenesis was electrically stimulated in the subventricular zone,followed by isolation of proliferating cells,including newly formed neurons,which were subsequently mixed with a nutritional hydrogel.This mixture was then transferred to the stroke cavity of day 14 post-stroke mice.We found that the performance of the treated animals improved in behavioral tests,including novel object,open field,hole board,grooming,and“time-to-feel”adhesive tape tests.Furthermore,immunostaining revealed that the stem cell marker nestin,the neuroepithelial marker Mash1,and the immature neuronal marker doublecortin-positive cells survived in the transplanted area for 2 weeks,possibly due to reduced phagocytic activity and supportive angiogenesis.These results clearly indicate that the transplantation of committed subventricular zone stem cells combined with a protective nutritional gel directly into the infarct cavity after the peak of stroke-induced neuroinflammation represents a feasible approach to improve neurorestoration after cerebral ischemia.
基金The work described in this paper was fully supported by a grant from Hong Kong Metropolitan University(RIF/2021/05).
文摘Parkinson’s disease(PD)is a debilitating neurological disorder affecting over 10 million people worldwide.PD classification models using voice signals as input are common in the literature.It is believed that using deep learning algorithms further enhances performance;nevertheless,it is challenging due to the nature of small-scale and imbalanced PD datasets.This paper proposed a convolutional neural network-based deep support vector machine(CNN-DSVM)to automate the feature extraction process using CNN and extend the conventional SVM to a DSVM for better classification performance in small-scale PD datasets.A customized kernel function reduces the impact of biased classification towards the majority class(healthy candidates in our consideration).An improved generative adversarial network(IGAN)was designed to generate additional training data to enhance the model’s performance.For performance evaluation,the proposed algorithm achieves a sensitivity of 97.6%and a specificity of 97.3%.The performance comparison is evaluated from five perspectives,including comparisons with different data generation algorithms,feature extraction techniques,kernel functions,and existing works.Results reveal the effectiveness of the IGAN algorithm,which improves the sensitivity and specificity by 4.05%–4.72%and 4.96%–5.86%,respectively;and the effectiveness of the CNN-DSVM algorithm,which improves the sensitivity by 1.24%–57.4%and specificity by 1.04%–163%and reduces biased detection towards the majority class.The ablation experiments confirm the effectiveness of individual components.Two future research directions have also been suggested.
文摘The roadway support in many places of Jiulongkou Colliery, Fengfeng Mining Bureau, such as in the Permanent transportation roadway, was failed or locally caved, which seriously affected the colliery’s coal production performance and safety. Based on analysis of supporting objects for roadway repairing, this paper proposes the supporting parameters and condruction technics. The industrial ted of 70m long roadway repairing shows that the proposed parameters and technics of bolt shotcrete and mesh support for roadway repairing are reasouable, bring good technical and economic results for the colliery, and the repairing is successful.
基金Projects(51409154,41772299)supported by the National Natural Science Foundation of ChinaProject(J16LG03)supported by the Shandong Province Higher Educational Science and Technology Program,China+1 种基金Projects(2015JQJH106,2014TDJH103)supported by the SDUST Research Fund,ChinaProject(201630576)supported by the Tai’an Scientific and Technologic Development Project,China
文摘Soft rock surrounding deep roadway has poor stability and long-term rheological effect. More and larger deformation problems of surrounding rock occur due to adverse supporting measures for such roadways, which not only affects the engineering safety critically but also improves the maintenance costs. This paper takes the main rail roadway with severely deformation in China＇s Zaoquan coal mine as an example to study the long-term deformation tendency and damage zone by means of in-situ deformation monitoring and acoustic wave testing technique. A three-dimensional finite element model reflecting the engineering geological condition and initial design scheme is established by ABAQUS. Then, on the basis of field monitoring deformation data, the surrounding rock geotechnical and theological parameters of the roadway are obtained by back analysis. A combined supporting technology with U-shaped steel support and anchor-grouting is proposed for the surrounding soft rock. The numerical simulation of the combined supporting technology and in-situ deformation monitoring results show that the soft rock surrounding the roadway has been held effectively.
基金Foundation item： Project（2013CB036004） supported by the National Basic Research Program of China Project（51178468） supported by the National Natural Science Foundation of China
文摘Linear failure criterion is widely used in calculation of earth pressure acting on shallow tunnels. However, experimental evidence shows that nonlinear failure criterion is able to represent fairly well the failure of almost all types of rocks, A nonlinear Hock-Brown failure criterion is employed to estimate the supporting pressures of shallow tunnels in limit analysis framework. Two failure mechanisms are proposed for calculating the work rate of extemal force and the internal energy dissipation. A tangential line to the nonlinear failure criterion is used to formulate the supporting pressure problem as a nonlinear programming problem. The objective function formulated in this way is minimized with respect to the failure mechanism and the location of tangency point. In order to assess the validity, the supporting pressures for the proposed failure mechanisms are calculated and compared with each other, and the present results are compared with previously published solutions when the nonlinear criterion is reduced to linear criterion. The agreement supports the validity of the proposed failure mechanisms. An experiment is conducted to investigate the influences of the nonlinear criterion on collapse shape and supporting pressures of shallow tunnels.
基金This work was supported by the National Natural Science Foundation of China(Nos.41941018,52074164,and 42077267);the Natural Science Foundation of Shandong Province,China(Nos.2019SDZY04 and ZR2020JQ23)the Project of Shandong Province Higher Educational Youth Innovation Science and Technology Program,China(No.2019KJG013).
文摘In deep underground engineering,rock burst and other dynamic disasters are prone to occur due to stress concentration and energy accumulation in surrounding rock.The control of dynamic disasters requires bolts and cables with high strength,high elongation,and high energy-absorbing capacity.Therefore,a constant resistance energy-absorbing(CREA)material is developed.In this study,the dynamic characteristics of the new material are obtained via the drop hammer tests and the Split Hopkinson Pressure Bar(SHPB)tests of the new material and two common bolt(CB)materials widely used in the field.The test results of drop hammer test and SHPB test show that the percentage elongation of CREA material is more than 2.64 and 3.22 times those of the CB material,and the total impact energy acting on CREA material is more than 18.50 and 21.84 times,respectively,indicating that the new material has high elongation and high energy-absorbing capacity.Subsequently,the CREA bolts and cables using the new material are developed,which are applied in roadways with high stress and strong dynamic disturbance.The field monitoring results show that CREA bolts and cables can effectively control the surrounding rock deformation and ensure engineering safety.
基金supported by National Natural Science Foundation of China(No.51975096,No.51905075)China Postdoctoral Science Foundation(No.2019M661090)Liao Ning Revitalization Talents Program(No.XLYC1807230)。
文摘Thin-walled parts are widely used in the aerospace industry owing to their light weight and high specific strength.However,due to the low rigidity of thin-walled parts,elastic deformation and chatter easily occur,which seriously affect the machining accuracy and workpiece surface quality.To solve this problem,several supporting technologies have been reported in recent years.This paper reviews the recent research progress of flexible supporting technologies in the aerospace field by classifying them based on different principles and characteristics.The principle,progress,advantages,and limitations of the technologies are expounded by systematic comparison and summarized.Finally,the challenges and future development trends of flexible supporting technology,which will provide guidelines for further research,are discussed.
基金supported by National Key Research and Development Program(2016YFC0600901)the National Natural Science Foundation of China(Grant Nos.51374214,51134005 and 51574248)+1 种基金the Special Fund of Basic Research and Operating of China University of Mining&Technology,Beijing(Grant Nos.2009QL03)the State Scholarship Fund of China
文摘A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation（CRLD） bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt（rebar） using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson＇s ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson＇s ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.
基金supported by the National Natural Science Foundation of China (No. 51178468)the National Basic Research Program (973) of China (No. 2011CB013800)
文摘To analyze the stability of a shallow square tunnel, a new curved failure mechanism, representing the mechanical characteristics and collapsing form of this type of tunnel, is constructed. Based on the upper bound theorem of limit analysis and the Hoek-Brown nonlinear failure criterion, the supporting pressure derived from the virtual work rate equation is regarded as an objective function to achieve optimal calculation. By employing variational calculation to optimize the objective function, an upper bound solution for the supporting pressure and the collapsing block shape of a shallow square tunnel are obtained. To evaluate the validity of the failure mechanism proposed in this paper, the solutions computed by the curved failure mechanism are compared with the results calculated by the linear multiple blocks failure mechanism when the Hoek-Brown nonlinear failure criterion is converted into the Mohr-Coulomb linear criterion. The influences of rock mass parameters on the supporting pressure and collapsing block shape are discussed.
基金National Science and Technology Major Project,No.2009ZX07210-010Supported by Program B for Outstanding Ph D Candidate of Nanjing University
文摘There have been substantial conflicts in the human-water relationship in the Huaihe River Basin （HRB）. To achieve sustainable economic development without degrading the water environment in the HRB, we develop a three-dimensional water environmental sup- porting capacity （WESC） model based on water environmental carrying capacity （WECC）, water environmental pressure （WEP）, and water pollution prevention and control capacity （WPPC）. Geographic information systems spatial analysis with the analytical hierarchy process method and dynamic weighted summation is applied. Several proposals for suitable locations for industry and environmental protection strategies for water were presented. The following results were obtained. （1） The spatial differences in WECC are substantial; areas with high-value WECC zones are mainly located along the main stream of the Huaihe River on the south side. WEP is generally high, with an overall low level of pollution prevention and control in the whole HRB. WPPC and WEP show high spatial overlapping due to the fact that areas with higher environmental pollution usually have high level of economic development, and thus have a strong capacity for pollution control. （2） Overall, WESC is moderate in the HRB. In particular, areas with a high WESC value only account for 56.24% of the HRB in 2010 Distinct differences in WESC also exist between areas located in the south compared with in the north of the basin, and areas alongside the downstream region compared with alongside the upstream and midstream regions. （3） Consequently, according to the guidance for indus- try zoning in the HRB, the areas in the south and alongside the downstream and sub-streams with a low WEP value and high WECC and WPPC, traditional industries should be developed based on strict environmental access and pollution emission standards. While for the areas along the midstream of the HRB and along the whole Yishusi River Basin, which have a high WEP value, industrial restructuring and technological upgrading are suggested. Action should be taken to limit development and protect the environment in the upstream region of the basin which is a key source of drinking water, in the eastern route along the line of the South-toNorth Water Diversion Project, and in the ecologically fragile region alongside the basin. This will ensure good environmental functionality including subsistent provision of clean water, while at the same time satisfying the urgent need to adjust, transform, and upgrade the industrial structure.
基金the National Natural Science Foundation of China(Grant No.51978041)。
文摘Tunnels deeply buried have high crustal stress and are prone to large deformation disasters when encountering soft rock.The large deformation phenomenon during the construction process of the Maoxian Tunnel on the Chengdu-Lanzhou Railway is particularly evident.This article focuses on the large deformation problem of the No.1 inclined shaft of the Maoxian Tunnel,and uses on-site monitoring methods to explore the reasons for tunnel structure failure,and analyzes the mechanical behavior of the tunnel structure.By using numerical simulation methods,the effectiveness of the second-layer support in resisting creep loads in tunnels was studied,and the influence of the construction time of the secondlayer support on the mechanical properties of the tunnel was discussed.The results indicate that the first-layer support in the tunnel is a structural failure caused by asymmetric deformation caused by creep,while the second-layer support has a good effect on resisting creep loads.The research results can provide a technical reference for deformation control of squeezing tunnels.
基金Projects 50427401 supported by the National Natural Science Foundation of China2006AA06Z119 by the Hi-tech Research and Development Program of China+2 种基金NCET-06-0477 by the New Century Excellent Talent Plan of Ministry of Education2007A002 by the Science & Research Foundation for Youth of China University of Mining and Technologythe Na-tional Basic Research Program of China (2005cb221505)
文摘More accurate forecasting of rock burst might be possible from observations of electromagnetic radiation emitted in the mine.We analyzed experimental observations and field data from the Muchengjian coal mine to study the relationship between electromagnetic radiation signal intensity and stress during the fracturing of coal, or rock, and samples under load.The results show that the signal intensity is positively correlated with stress.In addition, we investigated the change in the electromagnetic radiation intensity, the supporting resistance in a real coal mine environment, and the coal or rock stress in the mining area.The data analysis indicates that:1) electromagnetic radiation intensity can accurately reflect the distribution of stress in the mining area;and, 2) there is a correlation between electromagnetic radiation intensity and supporting resistance.The research has some practical guiding significance for rock burst forecasting and for the prevention of accidents in coal mines.
基金Project(2013CB036004) supported by the National Basic Research Program of ChinaProjects(51178468,51378510) supported by the National Natural Science Foundation of China
文摘Based on the active failure mechanism generated by a spatial discretization technique, the stability of tunnel face was studied. With the help of the spatial discretization technique, not only the anisotropy and inhomogeneity of the cohesion but also the inhomogeneity of the internal friction angle was taken into account in the analysis of the supporting forces. From the perspective of upper bound theorem, the upper bound solutions of supporting pressure were derived. The influence of the anisotropy and heterogeneity on the supporting forces as well as the failure mechanisms was discussed. The results show that the spatial discretization characteristics of cohesion and internal frictional angle impose a significant effect on the supporting pressure, which indicates that above factors should be considered in the actual engineering.
文摘The methods combined by test, field monitoring and theoretical analysis were adopted to do the systemic research on the rock mass from micro-structure to macro-deformation, and rheological model of Jinchuan rock mass was established to discuss the reasonable supporting time. Resuhs show that supporting after suitable stress and displacement release can benefit for the long-term stability of surrounding rock.
基金Project(41202220) supported by the National Natural Science Foundation of ChinaProject(20120022120003) supported by the Research Fund for the Doctoral Program of Higher Education, China+1 种基金Project(2-9-2012-65) supported by the Fundamental Research Funds for the Central Universities, ChinaProject(2013006) supported by the Research Fund for Key Laboratory on Deep GeoDrilling Technology, Ministry of Land and Resources, China
文摘A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjacent steel structural units are jointed with fasteners, and each steel structural unit has a certain radian and is welded by two steel tubes and one piece of steel disc. In order to test and verify the reliability of the new supporting structure, the field tests are designed. The main monitoring programs include the hoop stress of supporting structure, lateral earth pressure, and soil deformation. The monitoring data of the field tests show that the new supporting structure is convenient, reliable and safe.
基金provided by the National Basic Research 973 Program of China (No. 2013CB036003)the National Natural Science Foundation of China (No. 51374198)the Annual College Graduate Research and Innovation Projects of Jiangsu Province of China (No. KYLX15_1402)
文摘In order to solve the large deformation controlling problem for surrounding rock of gob-side entry driving under common cable anchor support in deep mine, site survey, physical modeling experiment, numerical simulation and field measurement were synthetically used to analyze the deformation and failure characteristics of surrounding rock. Besides, applicability analysis, prestress field distribution characteristics of surrounding rock and the control effect on large deformation of surrounding rock were also further studied for the gob-side entry driving in deep mine using the cable-truss supporting system. The results show that, first, compared with no support and traditional bolt anchor support, roof cable-truss system can effectively restrain the initiation and propagation of tensile cracks in the roof surrounding rock and arc shear cracks in the two sides, moreover, the broken development of surrounding rock, roof separation and extrusion deformation between the two sides of the roadway are all controlled; second, a prestressed belt of trapezoidal shape is generated in the surrounding rock by the cable-truss supporting system, and the prestress field range is wide. Especially, the prestress concentration belt in the shallow surrounding rock can greatly improve the anchoring strength and deformation resisting capability of the rock stratum;third, an optimized support system of ‘‘roof and side anchor net beam, roof cable-truss supporting system and anchor cable of the narrow coal pillar" was put forward, and the support optimization design and field industrial test were conducted for the gob-side entry driving of the working face 5302 in Tangkou Mine, from which a good supporting effect was obtained.
基金This project is supported by National Natural Science Fundation of China (No. 50675066)Provincial Key Technologies R&D of Hunan, China (No. 05FJ2001)China Postdoctoral Science Foundation (No. 2005038006).
文摘To improve the diagnosis accuracy and self-adaptability of fatigue crack in ulterior place of the supporting shaft, time series and neural network are attempted to be applied in research on diag-nosing the fatigue crack’s degree based on analyzing the vibration characteristics of the supporting shaft. By analyzing the characteristic parameter which is easy to be detected from the supporting shaft’s exterior, the time series model parameter which is hypersensitive to the situation of fatigue crack in ulterior place of the supporting shaft is the target input of neural network, and the fatigue crack’s degree value of supporting shaft is the output. The BP network model can be built and net-work can be trained after the structural parameters of network are selected. Furthermore, choosing the other two different group data can test the network. The test result will verify the validity of the BP network model. The result of experiment shows that the method of time series and neural network are effective to diagnose the occurrence and the development of the fatigue crack’s degree in ulterior place of the supporting shaft.
基金financially supported by the National Natural Science Foundation of China (Nos. 51174196, 51204168, 51109209 and 51309222)the Youth Fund Project of Jiangsu Province Natural Science Foundation (No. BK20130193)
文摘Aiming at the characteristics of the poor steady ability, the short stable time and severe deformation behavior of weakly cemented soft surrounding rock around extraction roadway, a bolt–cable combined supporting technology was proposed. Numerical simulation was performed by using FLAC3 D software to study the effects of different supporting systems. The simulation result proves that those supporting systems have good practical values. Based on real-time monitoring and analysis of the deformation of surrounding rock and the stress of supporting structure, real time information of deformation of surrounding rock and stress state of supporting structure of extraction roadway within weakly cemented strata was obtained. Monitoring results show that large deformation and failure of surrounding rock of extraction roadway within weakly cemented strata can be effectively controlled by the bolt–cable combined supporting technology, which ensures the long-term stability and safety of surrounding rock and supporting structure.
