With the development of economy,China has gradually begun to pay attention to the protection of the natural environment.Under the concept of"lucid waters and lush mountains are invaluable assets",importance ...With the development of economy,China has gradually begun to pay attention to the protection of the natural environment.Under the concept of"lucid waters and lush mountains are invaluable assets",importance has been attached to the development of forestry economy.The protection of forest resources and the prevention and control of disasters are important contents and necessary components in the construction of China's forestry ecological environment.Through the analysis and research on the types of forest disasters(forest fires,biological disasters,meteorological disasters,geological disasters,deforestation)and disaster-causing factors,some basic countermeasures were put forward with the aim to enhance the production capacity of forest resources,improve the ecological environment of forest resources and prevent forest resource disasters.展开更多
With the continuous development of national economy, the construction of engineering projects in China is also developing rapidly, which makes the safety protection management of construction projects more and more st...With the continuous development of national economy, the construction of engineering projects in China is also developing rapidly, which makes the safety protection management of construction projects more and more stringent. Only such construction project safety protection and management of all aspects of good, constantly summarize the building safety protection and management, strive to explore the experience of building safety. New methods and technologies of protection management can reduce the occurrence of unsafe accidents in construction and protect the lives and property of construction personnel. The safety protection of construction equipment is not only the basic guarantee for the development of construction enterprises, but also the premise for the efficient completion of construction projects. In short, only in this way in the construction safety protection management of a good job, can effectively ensure the construction project quality progress, construction enterprises stable and rapid development, promote the rapid development of the national economy. This research is divided into four main parts: the first part is an overview of the safety protection management theory in the construction process;the second part is the analysis of the current situation of safety protection management in the process of domestic construction;the third part is the detailed analysis of the problems existing in the construction safety protection management in our country;the fourth part is how to improve the safety protection management in the construction process. The countermeasures of strengthening construction safety protection management are summarized in the paper.展开更多
Accurate vector extraction from design drawings is required first to automatically create 3D models from pixel-level engineering design drawings. However, this task faces the challenges of complicated design shapes as...Accurate vector extraction from design drawings is required first to automatically create 3D models from pixel-level engineering design drawings. However, this task faces the challenges of complicated design shapes as well as cumbersome and cluttered annotations on drawings, which interfere with the vector extraction heavily. In this article, the transmission tower containing the most complex structure is taken as the research object, and a semantic segmentation network is constructed to first segment the shape masks from the pixel-level drawings. Preprocessing and postprocessing are also proposed to ensure the stability and accuracy of the shape mask segmentation. Then, based on the obtained shape masks, a vector extraction network guided by heatmaps is designed to extract structural vectors by fusing the features from node heatmap and skeleton heatmap, respectively. Compared with the state-of-the-art methods, experiment results illustrate that the proposed semantic segmentation method can effectively eliminate the interference of many elements on drawings to segment the shape masks effectively, meanwhile, the model trained by the proposed vector extraction network can accurately extract the vectors such as nodes and line connections, avoiding redundant vector detection. The proposed method lays a solid foundation for automatic 3D model reconstruction and contributes to technological advancements in relevant fields.展开更多
The ocean,as one of Earth’s largest natural resources,covers over 70% of the planet’s surface and holds vast water energy potential.Building on this context,this study designs a hybrid generator(WWR-TENG)that integr...The ocean,as one of Earth’s largest natural resources,covers over 70% of the planet’s surface and holds vast water energy potential.Building on this context,this study designs a hybrid generator(WWR-TENG)that integrates a triboelectric nanogenerator(TENG)and an electromagnetic generator(EMG).TENG is a new technology that can capture mechanical energy from the environment and convert it into electrical energy,and is particularly suitable for common natural or man-made power sources such as human movement,wind power,and water flow.EMG is a device that converts mechanical energy into electrical energy through the principle of electromagnetic induction and can usually provide stable power output.The composite design leverages the complementary advantages of both technologies to efficiently capture and convert marine wave energy.By combining the TENG’s high energy conversion efficiency,lowcost,lightweight structure,and simple designwith the EMG’s capabilities,the systemprovides a sustainable solution for marine energy development.Experimental results demonstrate that at a rotational speed of 3.0 r/s,the TENG component of the WWR-TENG achieves an open-circuit voltage of approximately 280 V and a shortcircuit current of 20μA.At the same time,the EMG unit exhibits an open-circuit voltage of 14 V and a short-circuit current of 14 mA.Furthermore,when integrated with a power management circuit,the WWR-TENG charges a 680μF capacitor to 3 V within 10 s at a rotational speed of 3.0 r/s.A simulated wave environment platform was established,enabling the WWR-TENG to maintain the thermo-hygrometer in normal operation under simulated wave conditions.These findings validate the hybrid system’s effectiveness in harnessing and storingwave energy,highlighting its potential for practical marine energy applications.展开更多
To study the occurrence mechanism of rock burst during mining the irregular working face,the study took irregular panel 7447 near fault tectonic as an engineering background.The spatial fracture characteristic of over...To study the occurrence mechanism of rock burst during mining the irregular working face,the study took irregular panel 7447 near fault tectonic as an engineering background.The spatial fracture characteristic of overlying strata was analyzed by Winkler elastic foundation beam theory.Furthermore,the influence law of panel width to suspended width and limit breaking span of key strata were also analyzed by thin plate theory.Through micro-seismic monitoring,theoretical analysis,numerical simulation and working resistance of support of field measurement,this study investigated the fracture characteristic of overlying strata and mechanism of rock burst in irregular working face.The results show that the fracture characteristic of overlying strata shows a spatial trapezoid structure,with the main roof being as an undersurface.The fracture form changes from vertical‘‘O-X"type to transverse‘‘O-X"type with the increase of trapezoidal height.From the narrow mining face to the wide mining face,the suspended width of key strata is greater than its limit breaking width,and a strong dynamic load is produced by the fracture of key strata.The numerical simulation and micro-seismic monitoring results show that the initial fracture position of key strata is close to tailgate 7447.Also there is a high static load caused by fault tectonic.The dynamic and static combined load induce rock burst.Accordingly,a cooperative control technology was proposed,which can weaken dynamic load by hard roof directional hydraulic fracture and enhance surrounding rock by supporting system.展开更多
Magnesium hydride(MgH_(2)) is a candidate material for hydrogen storage.MgH_(2)-AlH_(3) composite shows superior hydrogen desorption properties than pure MgH_(2).However,this composite still suffers from poor cycling ...Magnesium hydride(MgH_(2)) is a candidate material for hydrogen storage.MgH_(2)-AlH_(3) composite shows superior hydrogen desorption properties than pure MgH_(2).However,this composite still suffers from poor cycling performance.In this work,NbF_(5) was utilized to improve the cycling properties of the MgH_(2)-AlH_(3) composite.Cycling hydrogen desorption studies show that NbF_(5) significantly improves the cycling stability of MgH_(2)-AlH_(3).The MgH_(2)-AlH_(3)-NbF_(5) composite can release about 2.7 wt% of hydrogen at 300℃ for 1 h and the hydrogen desorption capacity can maintain at 2.7 wt% for more than100 cycles.In comparison,the hydrogen desorption capacity of the MgH_(2)-AlH_(3) composite is decreasing with the cycle number increasing.The capacity is reduced from a maximum value of 3.3 wt% to about 1.0 wt% after 40 cycles.Brunauer-Emmett-Teller(BET) surface area measurements show that the particle size of MgH_(2)-AlH_(3) composite decreases after cycling,which means pulverization of the composite.NbF_(5) can to some extent suppress the pulverization of the composite during cycling,which partially contributes to the improvement of the cycling hydrogen desorption properties of the material.展开更多
Water conveyance tunnels usually experience high internal water pressures and complex soil conditions.Therefore,shield tunnels with double-lining structure have been adopted because of their high bearing capacity.The ...Water conveyance tunnels usually experience high internal water pressures and complex soil conditions.Therefore,shield tunnels with double-lining structure have been adopted because of their high bearing capacity.The effect of the interface between the segmental and inner linings on the bearing capacity has been widely investigated;however,the effect of soil on the internal water pressure bearing capacity has not been emphasized enough.Therefore,in this study,model tests and an analytical solution are presented to elucidate the effect of soil on the internal water pressure bearing capacity.First,model tests are conducted on double-lining models under sandy soil and highly weathered argillaceous siltstone conditions.The internal force and earth pressure under these different soil conditions are then compared to reveal the contribution of soil to the internal water pressure bearing capacity.Following this,an analytical solution,considering the soil–double-lining interaction,is proposed to further investigate the contribution of the soil.The analytical solution is verified with model tests.The analytical solution is in good agreement with the model test results and can be used to evaluate the mechanical behavior of the double-lining and soil contribution.The effect of soil on the bearing capacity is found to be related with the elastic modulus of the soil and the deformation state of the double-lining.Before the double-lining cracks,the sandy soil contributes 3.7%of the internal water pressure but the contribution of the soil rises to 10.4%when it is the highly weathered argillaceous siltstone.After the double-lining cracks,the soil plays an important role in bearing internal water pressure.The soil contributions of sandy soil and highly weathered argillaceous siltstones are 10.5%and 27.8%,respectively.The effect of soil should be considered in tunnel design with the internal water pressure.展开更多
In China,Beishan granite is chosen as a potential host surrounding rock of a high-level radioactive waste(HLW)repository.For this research,Beishan granite specimens were heated up to 300℃,400℃ and 500℃,respectively...In China,Beishan granite is chosen as a potential host surrounding rock of a high-level radioactive waste(HLW)repository.For this research,Beishan granite specimens were heated up to 300℃,400℃ and 500℃,respectively.And conventional triaxial compression tests were conducted after cooling down the samples.The results show that after 300℃,400℃ and 500℃ heating treatment,the diameter of samples increases by 0.066%,0.143%and 0.409%,respectively,which is a little larger than the axial length changes.Mechanical tests show that peak strength increases slightly with increasing temperature.However,the dilatancy threshold is lower than that observed for samples which have not experienced heating treatment.Peak strain and dilatancy threshold strain show a strong temperature dependence.The higher the temperature,the greater the strain.Furthermore,increasing temperature has negative influence on threshold elastic modulus E_(c) and tangent elastic modulus E_(t).Poisson ratio decreases when temperature increases from 300℃ to 500℃,but it is still larger than that observed for samples which have not experienced heating treatment.In addition,AE monitoring shows a quiet period in the initial loading stage,which proves that the micro cracks are closed during heating and contribute to the increase of peak strength.展开更多
Natural gas hydrate(NGH)holds great promise as a source of clean energy.It is critical for acquiring the largest possible in situ NGH core for NGH eigen features and resource assessment.However,the existing NGH coring...Natural gas hydrate(NGH)holds great promise as a source of clean energy.It is critical for acquiring the largest possible in situ NGH core for NGH eigen features and resource assessment.However,the existing NGH coring technology has limitations,such as temperature increments,limited coring diameters,low coring rates,and complex coring structures.Therefore,this study designs and proposes an NGH freezing coring(NGHFC)method and verifies the freezing and coring capacities of the NGHFC method in laboratories and experimental wells.Results suggest that NGHFC shows good freezing and heat-retention properties.A freezing core heat transfer model is developed.According to the actual air temperature and operating time,the optimum initial temperature of the cold source can be determined using this model.The average coring rate of NGHFC can reach 77.86%.The research results will provide a new idea of coring gas hydrates.展开更多
Starting from the historical evolution of China s regional coordinated development policy and practice,three stages of"enlightenment stage","development stage"and"maturity stage",as well ...Starting from the historical evolution of China s regional coordinated development policy and practice,three stages of"enlightenment stage","development stage"and"maturity stage",as well as the connotation,characteristics and content of implementing regional coordinated development strategy were analyzed.On this basis,from different aspects of industrial distribution,pollutant characteristics and regional environmental protection policy,the existing ecological and environmental protection problems in China s regional coordinated development in the new era were analyzed,and some suggestions for the next step were put forward.It is necessary to follow the"four ones"concept from the overall point of view,implement"three lines and one list"from the perspective of the width of the access red line,strengthen"joint prevention and control"from the perspective of the depth of regional regulation,deepen the"planning environmental impact assessment"from the perspective of the breadth of industrial distribution,and promote the"green-way model"from the perspective of ecological low carbon.展开更多
The compression and creep characteristics of moraine soil are important mechanical properties of geomaterials to be analyzed during the construction process of engineering projects.However,related references about the...The compression and creep characteristics of moraine soil are important mechanical properties of geomaterials to be analyzed during the construction process of engineering projects.However,related references about these characteristics through large-size in-situ tests have rarely been reported.In this study,in-situ tests of particle size distribution,compression deformation,and compression creep were conducted at the Xingkang Bridge,West Sichuan,China.The results show that the uniformity coefficient of moraine soil ranges from 12.1 to 183.3,and gradation coefficient ranges from 0.4 to 2.8.The total compression deformations of moraine samples during the conventional compression deformation test are 4.70,4.07,and 0.47 mm,and their residual deformations are 2.81,2.45,and 0.22 mm,respectively.The deformation modulus ranges from 127.3 to 676.4 MPa,and elastic modulus ranges from 316.3 to 765.7 MPa.During compression creep tests,moraine soil enters the steady creep stage after 3.8 h of loading pressure at 445 k Pa,and it keeps steady after 14 h of loading pressure at 900 k Pa.The Burgers model and generalized Kelvin model predict the deformation well in transient,deceleration and steady creep stages.Results provide a valuable reference for the analysis of the compression deformation and creep behavior of moraine soil during engineering construction and management.展开更多
The Fe-0.21C 2.2Mn 0.49Si-1.77A1 transformation induced plasticity （TRIP） aided steel was heat trea- ted at various austenitizing temperatures under both TRiP-aided polygonal ferrite type （TPF） and an- nealed mart...The Fe-0.21C 2.2Mn 0.49Si-1.77A1 transformation induced plasticity （TRIP） aided steel was heat trea- ted at various austenitizing temperatures under both TRiP-aided polygonal ferrite type （TPF） and an- nealed martensite matrix （TAM） processes. The microstructure evolution and their effects on mechanical properties were systematically investigated through the microstructure observation and dilatometric analysis. The microstructure homogeneity is improved in TPF steel heated at a high temperature due to the reduced banded martensite and the increased bainite. Compared with the mechanical properties of the TPF steels, the yield strength and elongation of the TAM steels are much higher, while the tensile strength is lower than that of TPF steels. The stability of intercritical austenite is affected by the heating tempera- ture, and thus the following phase transformation influences the mechanical properties, such as the bain- ite transformation and the precipitation of polygonal ferrite. Obvious dynamic bainite transformation occurs at TAM850, TAM900 and TAM950, More proportion of polygonal ferrite is found in the sample heated at 950 ℃. The bainite transformation beginning at a higher temperature results in the wider bainitic ferrite laths. The more proportion of polygonal ferrite and wide bainitic ferrite laths commonly contribute to the lower strength and better elongation. The uniform microstructure with lath-like morphology and retained austenite with high average carbon content ensures a good mechanical property in TAM850 with the product of strength and elongation of about 28 GPa ·%,展开更多
The microstructure and mechanical properties of NANOBAIN steel treated at different isothermal temperatures were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,uniaxial ten...The microstructure and mechanical properties of NANOBAIN steel treated at different isothermal temperatures were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,uniaxial tensile tests and X-ray diffraction（XRD）.It was found that bainitic ferrite（BF）plate was made of basic shear transformation units arranged in the same direction of subunits.The existence of defects,such as nanoscale twinning and dislocation,suggested that the growth of transformation units was controlled by the surrounding defect plane with dislocation,which was consistent with the moving direction of BF/austenite interface parallel to the twinning plane.The behavior of work hardening indicated that mechanical stability of microstructures obtained at 250 ℃ and 300 ℃ was much more stable than that obtained at 210℃.The evolution of carbon partitioning in retained austenite and bainitic ferrite also indicated that austenite was enriched in carbon at the initial stage step by step;after the formation of BF,the austenite did not seem to be greatly enriched in carbon and the carbon content showed a little decrease instead;subsequently,aphenomenon of little decarburization of supersaturated bainitic ferrite has also been found.展开更多
The reservoir thickness of sub-member of Lower Permain in the south of the eastern margin of Ordos Basin is thin and large variable i laterally. And the seismic response characteristics of sandstone reservoir are doub...The reservoir thickness of sub-member of Lower Permain in the south of the eastern margin of Ordos Basin is thin and large variable i laterally. And the seismic response characteristics of sandstone reservoir are doubly interfered by the strong reflection sidelobes of overlying 5# coal seam and underlying 8# coal seam. In view of this situation, in order to better eliminate the influence of upper and lower coal seams and improve the accuracy of reservoir prediction, the strategy of de-strong seismic reflection and de-logging (curve) interference is adopted to carry out the matching of logging and seismic, and on this basis, uses the seismic waveform indication inversion to predict the thin sandstone. The steps are as follows: firstly, by using wavelet decomposition and reconstruction technology, select the seismic wavelet component that can better characterize the reservoir or oil & gas to reasonablely reconstruct seismic data, weaken the influence of the strong reflection from overlying 5# coal seam and underlying 8# coal seam, and highlight the response of weak seismic reflection of tight sandstone in Shan 2<sup>3</sup> sub-member;Then, the acoustic value of coal seam is corrected to that of mudstone on the logging curve to maintain the consistency of logseismic data. This method realizes the effective identification of sandstone reservoir in Shan 2<sup>3</sup> sub-member, and greatly improves the target-penetrated rate and sandstone-penetrated rate of horizontal wells.展开更多
The article introduces the composition and working principle of the batching and weighing system underneath the blast furnace hearth.Besides,the shortcomings of the batching and weighing system during installation,deb...The article introduces the composition and working principle of the batching and weighing system underneath the blast furnace hearth.Besides,the shortcomings of the batching and weighing system during installation,debugging,and calibration,as well as the dynamic errors in the batching process are also analyzed.Corresponding solutions are then provided.展开更多
Introduction The Annual Meeting of the Rural Planning Practice Committee of the Universities Alliance for Rural Development,along with the 2024 Rural Planning Practice Forum was successfully held at the Wang Zesheng L...Introduction The Annual Meeting of the Rural Planning Practice Committee of the Universities Alliance for Rural Development,along with the 2024 Rural Planning Practice Forum was successfully held at the Wang Zesheng Lecture Hall of the School of Architecture,Tsinghua University on Dec.15,2024.The annual theme“New Era,New Village,and New Planning”has brought together experts and scholars from 96 universities and research institutions across China.The discussions focused on rural planning practices and case studies in three distinct regions:metropolitan areas,major producing areas for agricultural products,and ecological conservation areas,in the context of national policies and socio-economic transformations in the new era.China City Planning Review(CCPR)has compiled the 11 distinguished experts'presentations to foster further discussions on these critical topics.展开更多
The distributed generation (DG) plays an important role in the context of the environmental problems and sustain- able development throughout the world. This paper proposes a DG siting and sizing model in an active di...The distributed generation (DG) plays an important role in the context of the environmental problems and sustain- able development throughout the world. This paper proposes a DG siting and sizing model in an active distribution network (ADN). The objective is to minimize the total cost, including investment, operation and maintenance costs. The proposed model is transferred to a Mixed Integer Second-Order Cone Programming (MISOCP) model based on a distribution network forward backward-sweep power flow and constraint relaxation. The CVX platform and GUROBI solver are used for the solution. The scenario analysis is used for the uncertainties of load and DG. Different numbers of operational scenarios are considered in order to analyze the effect of a non-network solution to the final planning result and total investment. The planning results with and without consideration of active managements, and the planning results with and without taking environmental profits into consideration, are compared and analyzed. The proposed methodology is verified with a modified IEEE 33 example.展开更多
基金Supported by National Natural Science Foundation of China(41671283)。
文摘With the development of economy,China has gradually begun to pay attention to the protection of the natural environment.Under the concept of"lucid waters and lush mountains are invaluable assets",importance has been attached to the development of forestry economy.The protection of forest resources and the prevention and control of disasters are important contents and necessary components in the construction of China's forestry ecological environment.Through the analysis and research on the types of forest disasters(forest fires,biological disasters,meteorological disasters,geological disasters,deforestation)and disaster-causing factors,some basic countermeasures were put forward with the aim to enhance the production capacity of forest resources,improve the ecological environment of forest resources and prevent forest resource disasters.
文摘With the continuous development of national economy, the construction of engineering projects in China is also developing rapidly, which makes the safety protection management of construction projects more and more stringent. Only such construction project safety protection and management of all aspects of good, constantly summarize the building safety protection and management, strive to explore the experience of building safety. New methods and technologies of protection management can reduce the occurrence of unsafe accidents in construction and protect the lives and property of construction personnel. The safety protection of construction equipment is not only the basic guarantee for the development of construction enterprises, but also the premise for the efficient completion of construction projects. In short, only in this way in the construction safety protection management of a good job, can effectively ensure the construction project quality progress, construction enterprises stable and rapid development, promote the rapid development of the national economy. This research is divided into four main parts: the first part is an overview of the safety protection management theory in the construction process;the second part is the analysis of the current situation of safety protection management in the process of domestic construction;the third part is the detailed analysis of the problems existing in the construction safety protection management in our country;the fourth part is how to improve the safety protection management in the construction process. The countermeasures of strengthening construction safety protection management are summarized in the paper.
基金funded by the Chinese State Grid Jiangsu Electric Power Co.,Ltd.Science and Technology Project Funding,Grant Number J2023031.
文摘Accurate vector extraction from design drawings is required first to automatically create 3D models from pixel-level engineering design drawings. However, this task faces the challenges of complicated design shapes as well as cumbersome and cluttered annotations on drawings, which interfere with the vector extraction heavily. In this article, the transmission tower containing the most complex structure is taken as the research object, and a semantic segmentation network is constructed to first segment the shape masks from the pixel-level drawings. Preprocessing and postprocessing are also proposed to ensure the stability and accuracy of the shape mask segmentation. Then, based on the obtained shape masks, a vector extraction network guided by heatmaps is designed to extract structural vectors by fusing the features from node heatmap and skeleton heatmap, respectively. Compared with the state-of-the-art methods, experiment results illustrate that the proposed semantic segmentation method can effectively eliminate the interference of many elements on drawings to segment the shape masks effectively, meanwhile, the model trained by the proposed vector extraction network can accurately extract the vectors such as nodes and line connections, avoiding redundant vector detection. The proposed method lays a solid foundation for automatic 3D model reconstruction and contributes to technological advancements in relevant fields.
文摘The ocean,as one of Earth’s largest natural resources,covers over 70% of the planet’s surface and holds vast water energy potential.Building on this context,this study designs a hybrid generator(WWR-TENG)that integrates a triboelectric nanogenerator(TENG)and an electromagnetic generator(EMG).TENG is a new technology that can capture mechanical energy from the environment and convert it into electrical energy,and is particularly suitable for common natural or man-made power sources such as human movement,wind power,and water flow.EMG is a device that converts mechanical energy into electrical energy through the principle of electromagnetic induction and can usually provide stable power output.The composite design leverages the complementary advantages of both technologies to efficiently capture and convert marine wave energy.By combining the TENG’s high energy conversion efficiency,lowcost,lightweight structure,and simple designwith the EMG’s capabilities,the systemprovides a sustainable solution for marine energy development.Experimental results demonstrate that at a rotational speed of 3.0 r/s,the TENG component of the WWR-TENG achieves an open-circuit voltage of approximately 280 V and a shortcircuit current of 20μA.At the same time,the EMG unit exhibits an open-circuit voltage of 14 V and a short-circuit current of 14 mA.Furthermore,when integrated with a power management circuit,the WWR-TENG charges a 680μF capacitor to 3 V within 10 s at a rotational speed of 3.0 r/s.A simulated wave environment platform was established,enabling the WWR-TENG to maintain the thermo-hygrometer in normal operation under simulated wave conditions.These findings validate the hybrid system’s effectiveness in harnessing and storingwave energy,highlighting its potential for practical marine energy applications.
基金supported by the Key Project of National Natural Science Foundation of China (No. 51634001)the National Natural Science Foundation of China (Nos. 51404269 and 51674253)+1 种基金the State Key Research Development Program of China (No. 2016YFC0801403)the Key Research Development Program of Jiangsu Province, China (No. BE2015040)
文摘To study the occurrence mechanism of rock burst during mining the irregular working face,the study took irregular panel 7447 near fault tectonic as an engineering background.The spatial fracture characteristic of overlying strata was analyzed by Winkler elastic foundation beam theory.Furthermore,the influence law of panel width to suspended width and limit breaking span of key strata were also analyzed by thin plate theory.Through micro-seismic monitoring,theoretical analysis,numerical simulation and working resistance of support of field measurement,this study investigated the fracture characteristic of overlying strata and mechanism of rock burst in irregular working face.The results show that the fracture characteristic of overlying strata shows a spatial trapezoid structure,with the main roof being as an undersurface.The fracture form changes from vertical‘‘O-X"type to transverse‘‘O-X"type with the increase of trapezoidal height.From the narrow mining face to the wide mining face,the suspended width of key strata is greater than its limit breaking width,and a strong dynamic load is produced by the fracture of key strata.The numerical simulation and micro-seismic monitoring results show that the initial fracture position of key strata is close to tailgate 7447.Also there is a high static load caused by fault tectonic.The dynamic and static combined load induce rock burst.Accordingly,a cooperative control technology was proposed,which can weaken dynamic load by hard roof directional hydraulic fracture and enhance surrounding rock by supporting system.
基金financially supported by the National Natural Science Foundation of China(Nos.51771171 and 51971199)the Natural Science Foundation of Guangxi Province(Nos.2019GXNSFBA185004 and 2018GXNSFAA281308)the Basic Ability Improvement Project for Young and Middle-Aged Teachers in Colleges and Universities in Guangxi(No.2019KY0021)。
文摘Magnesium hydride(MgH_(2)) is a candidate material for hydrogen storage.MgH_(2)-AlH_(3) composite shows superior hydrogen desorption properties than pure MgH_(2).However,this composite still suffers from poor cycling performance.In this work,NbF_(5) was utilized to improve the cycling properties of the MgH_(2)-AlH_(3) composite.Cycling hydrogen desorption studies show that NbF_(5) significantly improves the cycling stability of MgH_(2)-AlH_(3).The MgH_(2)-AlH_(3)-NbF_(5) composite can release about 2.7 wt% of hydrogen at 300℃ for 1 h and the hydrogen desorption capacity can maintain at 2.7 wt% for more than100 cycles.In comparison,the hydrogen desorption capacity of the MgH_(2)-AlH_(3) composite is decreasing with the cycle number increasing.The capacity is reduced from a maximum value of 3.3 wt% to about 1.0 wt% after 40 cycles.Brunauer-Emmett-Teller(BET) surface area measurements show that the particle size of MgH_(2)-AlH_(3) composite decreases after cycling,which means pulverization of the composite.NbF_(5) can to some extent suppress the pulverization of the composite during cycling,which partially contributes to the improvement of the cycling hydrogen desorption properties of the material.
基金the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-0700-07-456 E00051)the National Natural Science Foundation of China(Nos.51978517,52090082,and 52108381)the Shanghai Science and Technology Committee Program(Nos.21DZ1200601 and 20DZ1201404)。
文摘Water conveyance tunnels usually experience high internal water pressures and complex soil conditions.Therefore,shield tunnels with double-lining structure have been adopted because of their high bearing capacity.The effect of the interface between the segmental and inner linings on the bearing capacity has been widely investigated;however,the effect of soil on the internal water pressure bearing capacity has not been emphasized enough.Therefore,in this study,model tests and an analytical solution are presented to elucidate the effect of soil on the internal water pressure bearing capacity.First,model tests are conducted on double-lining models under sandy soil and highly weathered argillaceous siltstone conditions.The internal force and earth pressure under these different soil conditions are then compared to reveal the contribution of soil to the internal water pressure bearing capacity.Following this,an analytical solution,considering the soil–double-lining interaction,is proposed to further investigate the contribution of the soil.The analytical solution is verified with model tests.The analytical solution is in good agreement with the model test results and can be used to evaluate the mechanical behavior of the double-lining and soil contribution.The effect of soil on the bearing capacity is found to be related with the elastic modulus of the soil and the deformation state of the double-lining.Before the double-lining cracks,the sandy soil contributes 3.7%of the internal water pressure but the contribution of the soil rises to 10.4%when it is the highly weathered argillaceous siltstone.After the double-lining cracks,the soil plays an important role in bearing internal water pressure.The soil contributions of sandy soil and highly weathered argillaceous siltstones are 10.5%and 27.8%,respectively.The effect of soil should be considered in tunnel design with the internal water pressure.
基金Projects(52104135, 51674266) supported by the National Natural Science Foundation of ChinaProject supported by the Qingdao Postdoctoral Applied Research Project Foundation,China。
文摘In China,Beishan granite is chosen as a potential host surrounding rock of a high-level radioactive waste(HLW)repository.For this research,Beishan granite specimens were heated up to 300℃,400℃ and 500℃,respectively.And conventional triaxial compression tests were conducted after cooling down the samples.The results show that after 300℃,400℃ and 500℃ heating treatment,the diameter of samples increases by 0.066%,0.143%and 0.409%,respectively,which is a little larger than the axial length changes.Mechanical tests show that peak strength increases slightly with increasing temperature.However,the dilatancy threshold is lower than that observed for samples which have not experienced heating treatment.Peak strain and dilatancy threshold strain show a strong temperature dependence.The higher the temperature,the greater the strain.Furthermore,increasing temperature has negative influence on threshold elastic modulus E_(c) and tangent elastic modulus E_(t).Poisson ratio decreases when temperature increases from 300℃ to 500℃,but it is still larger than that observed for samples which have not experienced heating treatment.In addition,AE monitoring shows a quiet period in the initial loading stage,which proves that the micro cracks are closed during heating and contribute to the increase of peak strength.
基金supported by the Program for Guangdong Introducing Innovative and Entrepreneurial Teams(No.2019ZT08G315)National Natural Science Foundation of China No.51827901 and U2013603Shenzhen Basic Research Project(JCYJ20190808153416970)
文摘Natural gas hydrate(NGH)holds great promise as a source of clean energy.It is critical for acquiring the largest possible in situ NGH core for NGH eigen features and resource assessment.However,the existing NGH coring technology has limitations,such as temperature increments,limited coring diameters,low coring rates,and complex coring structures.Therefore,this study designs and proposes an NGH freezing coring(NGHFC)method and verifies the freezing and coring capacities of the NGHFC method in laboratories and experimental wells.Results suggest that NGHFC shows good freezing and heat-retention properties.A freezing core heat transfer model is developed.According to the actual air temperature and operating time,the optimum initial temperature of the cold source can be determined using this model.The average coring rate of NGHFC can reach 77.86%.The research results will provide a new idea of coring gas hydrates.
基金Supported by Special Project for Prevention and Control of Air Pollution from Fixed Sources of Ministry of Ecology and Environment,China(2020A060).
文摘Starting from the historical evolution of China s regional coordinated development policy and practice,three stages of"enlightenment stage","development stage"and"maturity stage",as well as the connotation,characteristics and content of implementing regional coordinated development strategy were analyzed.On this basis,from different aspects of industrial distribution,pollutant characteristics and regional environmental protection policy,the existing ecological and environmental protection problems in China s regional coordinated development in the new era were analyzed,and some suggestions for the next step were put forward.It is necessary to follow the"four ones"concept from the overall point of view,implement"three lines and one list"from the perspective of the width of the access red line,strengthen"joint prevention and control"from the perspective of the depth of regional regulation,deepen the"planning environmental impact assessment"from the perspective of the breadth of industrial distribution,and promote the"green-way model"from the perspective of ecological low carbon.
基金supported by the Engineering Research Center of Rock-Soil Drilling&Excavation and Protection,Ministry of Education (No.202202)the National Natural Science Foundation of China (Nos.42107180,42162023 and 42162025)the Construction S&T Project of Department of Transportation of Sichuan Province of China (No.2020A01)。
文摘The compression and creep characteristics of moraine soil are important mechanical properties of geomaterials to be analyzed during the construction process of engineering projects.However,related references about these characteristics through large-size in-situ tests have rarely been reported.In this study,in-situ tests of particle size distribution,compression deformation,and compression creep were conducted at the Xingkang Bridge,West Sichuan,China.The results show that the uniformity coefficient of moraine soil ranges from 12.1 to 183.3,and gradation coefficient ranges from 0.4 to 2.8.The total compression deformations of moraine samples during the conventional compression deformation test are 4.70,4.07,and 0.47 mm,and their residual deformations are 2.81,2.45,and 0.22 mm,respectively.The deformation modulus ranges from 127.3 to 676.4 MPa,and elastic modulus ranges from 316.3 to 765.7 MPa.During compression creep tests,moraine soil enters the steady creep stage after 3.8 h of loading pressure at 445 k Pa,and it keeps steady after 14 h of loading pressure at 900 k Pa.The Burgers model and generalized Kelvin model predict the deformation well in transient,deceleration and steady creep stages.Results provide a valuable reference for the analysis of the compression deformation and creep behavior of moraine soil during engineering construction and management.
基金funded by National Natural Science Foundation of China(51574028)
文摘The Fe-0.21C 2.2Mn 0.49Si-1.77A1 transformation induced plasticity （TRIP） aided steel was heat trea- ted at various austenitizing temperatures under both TRiP-aided polygonal ferrite type （TPF） and an- nealed martensite matrix （TAM） processes. The microstructure evolution and their effects on mechanical properties were systematically investigated through the microstructure observation and dilatometric analysis. The microstructure homogeneity is improved in TPF steel heated at a high temperature due to the reduced banded martensite and the increased bainite. Compared with the mechanical properties of the TPF steels, the yield strength and elongation of the TAM steels are much higher, while the tensile strength is lower than that of TPF steels. The stability of intercritical austenite is affected by the heating tempera- ture, and thus the following phase transformation influences the mechanical properties, such as the bain- ite transformation and the precipitation of polygonal ferrite. Obvious dynamic bainite transformation occurs at TAM850, TAM900 and TAM950, More proportion of polygonal ferrite is found in the sample heated at 950 ℃. The bainite transformation beginning at a higher temperature results in the wider bainitic ferrite laths. The more proportion of polygonal ferrite and wide bainitic ferrite laths commonly contribute to the lower strength and better elongation. The uniform microstructure with lath-like morphology and retained austenite with high average carbon content ensures a good mechanical property in TAM850 with the product of strength and elongation of about 28 GPa ·%,
基金Item Sponsored by National Natural Science Foundation of China(51271035)
文摘The microstructure and mechanical properties of NANOBAIN steel treated at different isothermal temperatures were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,uniaxial tensile tests and X-ray diffraction（XRD）.It was found that bainitic ferrite（BF）plate was made of basic shear transformation units arranged in the same direction of subunits.The existence of defects,such as nanoscale twinning and dislocation,suggested that the growth of transformation units was controlled by the surrounding defect plane with dislocation,which was consistent with the moving direction of BF/austenite interface parallel to the twinning plane.The behavior of work hardening indicated that mechanical stability of microstructures obtained at 250 ℃ and 300 ℃ was much more stable than that obtained at 210℃.The evolution of carbon partitioning in retained austenite and bainitic ferrite also indicated that austenite was enriched in carbon at the initial stage step by step;after the formation of BF,the austenite did not seem to be greatly enriched in carbon and the carbon content showed a little decrease instead;subsequently,aphenomenon of little decarburization of supersaturated bainitic ferrite has also been found.
文摘The reservoir thickness of sub-member of Lower Permain in the south of the eastern margin of Ordos Basin is thin and large variable i laterally. And the seismic response characteristics of sandstone reservoir are doubly interfered by the strong reflection sidelobes of overlying 5# coal seam and underlying 8# coal seam. In view of this situation, in order to better eliminate the influence of upper and lower coal seams and improve the accuracy of reservoir prediction, the strategy of de-strong seismic reflection and de-logging (curve) interference is adopted to carry out the matching of logging and seismic, and on this basis, uses the seismic waveform indication inversion to predict the thin sandstone. The steps are as follows: firstly, by using wavelet decomposition and reconstruction technology, select the seismic wavelet component that can better characterize the reservoir or oil & gas to reasonablely reconstruct seismic data, weaken the influence of the strong reflection from overlying 5# coal seam and underlying 8# coal seam, and highlight the response of weak seismic reflection of tight sandstone in Shan 2<sup>3</sup> sub-member;Then, the acoustic value of coal seam is corrected to that of mudstone on the logging curve to maintain the consistency of logseismic data. This method realizes the effective identification of sandstone reservoir in Shan 2<sup>3</sup> sub-member, and greatly improves the target-penetrated rate and sandstone-penetrated rate of horizontal wells.
文摘The article introduces the composition and working principle of the batching and weighing system underneath the blast furnace hearth.Besides,the shortcomings of the batching and weighing system during installation,debugging,and calibration,as well as the dynamic errors in the batching process are also analyzed.Corresponding solutions are then provided.
基金funded by Shaanxi Provincial Natural Science Basic Research Program(No.2024JC-YBMS-289)Shaanxi Provincial Key Research and Development Plan:Research and Promotion of Common Technologies for Model Villages Under Shaanxi’s Green Rural Revival Program(No.2025NCYBXM-323)。
文摘Introduction The Annual Meeting of the Rural Planning Practice Committee of the Universities Alliance for Rural Development,along with the 2024 Rural Planning Practice Forum was successfully held at the Wang Zesheng Lecture Hall of the School of Architecture,Tsinghua University on Dec.15,2024.The annual theme“New Era,New Village,and New Planning”has brought together experts and scholars from 96 universities and research institutions across China.The discussions focused on rural planning practices and case studies in three distinct regions:metropolitan areas,major producing areas for agricultural products,and ecological conservation areas,in the context of national policies and socio-economic transformations in the new era.China City Planning Review(CCPR)has compiled the 11 distinguished experts'presentations to foster further discussions on these critical topics.
基金This work was supported in part by the Shanghai Engineering Re-search Center of Green Energy Grid-Connected Technology under Grant 13DZ2251900the Key Laboratory of Control of Power Transmission and Conversion(SJTU),Ministry of Education(2016AA01,2016AA03).
文摘The distributed generation (DG) plays an important role in the context of the environmental problems and sustain- able development throughout the world. This paper proposes a DG siting and sizing model in an active distribution network (ADN). The objective is to minimize the total cost, including investment, operation and maintenance costs. The proposed model is transferred to a Mixed Integer Second-Order Cone Programming (MISOCP) model based on a distribution network forward backward-sweep power flow and constraint relaxation. The CVX platform and GUROBI solver are used for the solution. The scenario analysis is used for the uncertainties of load and DG. Different numbers of operational scenarios are considered in order to analyze the effect of a non-network solution to the final planning result and total investment. The planning results with and without consideration of active managements, and the planning results with and without taking environmental profits into consideration, are compared and analyzed. The proposed methodology is verified with a modified IEEE 33 example.
