In order to solve the heat damages in deep mines, a cool-wall cooling technology and its working model are proposed based on the principles of heat absorption and insulation in this paper. During this process, the dif...In order to solve the heat damages in deep mines, a cool-wall cooling technology and its working model are proposed based on the principles of heat absorption and insulation in this paper. During this process, the differential equation of thermal equilibrium for roadway control unit is built, and the heat adsorption control equation of cool-wall cooling system is derived by an integral method, so as to obtain the quantitative relationship among the heat absorption capacity of cooling system, the heat dissipating capacity of surrounding rock and air temperature change. Then, the heat absorption capacity required by air temperature less than the standard value for safety is figured out by section iterative method with the simultaneous solution of heat absorption control equation and the heat dissipation density equation of surrounding rock. Finally, the results show that as the air temperature at the inlet of roadway is 25 ℃, the roadway wall is covered by heat-absorbing plate up to 39% of the area, as well as the cold water is injected into the heat-absorbing plate with a temperature of 20 ℃ and a mass flow of 113.6 kg/s, the air flow temperature rise per kilometer in the roadway can be less than 3 ℃.展开更多
Chemical vapor deposition(CVD)has emerged as a promising approach for the controlled growth of graphene films with appealing scalability,controllability,and uniformity.However,the synthesis of high-quality graphene fi...Chemical vapor deposition(CVD)has emerged as a promising approach for the controlled growth of graphene films with appealing scalability,controllability,and uniformity.However,the synthesis of high-quality graphene films still suffers from low production capacity and high energy consumption in the conventional hot-wall CVD system.In contrast,owing to the different heating mode,cold-wall CVD(CW-CVD)system exhibits promising potential for the industrial-scale production,but the quality of as-received graphene remains inferior with limited domain size and high defect density.Herein,we demonstrated an efficient method for the batch synthesis of high-quality graphene films with millimeter-sized domains based on CW-CVD system.With reduced defect density and improved properties,the as-received graphene was proven to be promising candidate material for electronics and anti-corrosion application.This study provides a new insight into the quality improvement of graphene derived from CW-CVD system,and paves a new avenue for the industrial production of high-quality graphene films for potential commercial applications.展开更多
A new method and devices for the electromagnetic levitation melting of metallic samples with greater weights and axisymmetrically stabilized positions is presented in this paper.The new method is applying two homogene...A new method and devices for the electromagnetic levitation melting of metallic samples with greater weights and axisymmetrically stabilized positions is presented in this paper.The new method is applying two homogeneous magnetic fields of different frequencies,whose field lines are in absence of a charge horizontally and reciprocally normal in order to exert electromagnetic lift forces also on the axis of the levitated sample.Therefore the weight of the charge can be increased and the charge can be drip- and leakage-free melted.The method can be used in a melting furnace with or without a cold protective wall,as well as for the coreless induction valves applied for flow rate control,e.g.in the continuous casting of molten metals.The applicability of the method was experimentally examined and proved by tests conducted with three types of laboratory setups.展开更多
基金Project(2018CXNL08) supported by the Fundamental Research Funds for the Central Universities,China。
文摘In order to solve the heat damages in deep mines, a cool-wall cooling technology and its working model are proposed based on the principles of heat absorption and insulation in this paper. During this process, the differential equation of thermal equilibrium for roadway control unit is built, and the heat adsorption control equation of cool-wall cooling system is derived by an integral method, so as to obtain the quantitative relationship among the heat absorption capacity of cooling system, the heat dissipating capacity of surrounding rock and air temperature change. Then, the heat absorption capacity required by air temperature less than the standard value for safety is figured out by section iterative method with the simultaneous solution of heat absorption control equation and the heat dissipation density equation of surrounding rock. Finally, the results show that as the air temperature at the inlet of roadway is 25 ℃, the roadway wall is covered by heat-absorbing plate up to 39% of the area, as well as the cold water is injected into the heat-absorbing plate with a temperature of 20 ℃ and a mass flow of 113.6 kg/s, the air flow temperature rise per kilometer in the roadway can be less than 3 ℃.
基金financially supported by the National Natural Science Foundation of China(Nos.T2188101,21525310,and 52072042)the National Key R&D Program of China(No.2018YFA0703502)+1 种基金Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXTD-202001)Beijing Municipal Science&Technology Commission(Nos.Z181100004818001,Z18110300480001,Z18110300480002,Z191100000819005,Z191100000819007,and Z201100008720005)。
文摘Chemical vapor deposition(CVD)has emerged as a promising approach for the controlled growth of graphene films with appealing scalability,controllability,and uniformity.However,the synthesis of high-quality graphene films still suffers from low production capacity and high energy consumption in the conventional hot-wall CVD system.In contrast,owing to the different heating mode,cold-wall CVD(CW-CVD)system exhibits promising potential for the industrial-scale production,but the quality of as-received graphene remains inferior with limited domain size and high defect density.Herein,we demonstrated an efficient method for the batch synthesis of high-quality graphene films with millimeter-sized domains based on CW-CVD system.With reduced defect density and improved properties,the as-received graphene was proven to be promising candidate material for electronics and anti-corrosion application.This study provides a new insight into the quality improvement of graphene derived from CW-CVD system,and paves a new avenue for the industrial production of high-quality graphene films for potential commercial applications.
基金Item Sponsored by the German Research Association(DFG)under the Grant No.BA 3565/3-1
文摘A new method and devices for the electromagnetic levitation melting of metallic samples with greater weights and axisymmetrically stabilized positions is presented in this paper.The new method is applying two homogeneous magnetic fields of different frequencies,whose field lines are in absence of a charge horizontally and reciprocally normal in order to exert electromagnetic lift forces also on the axis of the levitated sample.Therefore the weight of the charge can be increased and the charge can be drip- and leakage-free melted.The method can be used in a melting furnace with or without a cold protective wall,as well as for the coreless induction valves applied for flow rate control,e.g.in the continuous casting of molten metals.The applicability of the method was experimentally examined and proved by tests conducted with three types of laboratory setups.
