Nowadays,carbon frameworks derived from natural biomaterials have attracted extensive attention for electromagnetic interference(EMI)shielding due to their renewability and affordability.However,it is critical and cha...Nowadays,carbon frameworks derived from natural biomaterials have attracted extensive attention for electromagnetic interference(EMI)shielding due to their renewability and affordability.However,it is critical and challenging to achieve effective regulation of shielding effectiveness(SE)as well as weaken the strong EM reflection of highly conductive biomass-based carbon materials.Herein,commercial cotton pads with oriented structure were selected as carbonaceous precursor to fabricate aligned carbon networks by pyrolysis,and the EMI SE of the samples with increased temperature of 800-1000℃ can be accurately controlled in the effective range of~21.7-29.1,~27.7-37.1 and~32.7-43.3 d B with high reflection coefficient of>0.8 by changing the cross-angle between the electric-field direction of incident EM waves and the fiber-orientation direction due to the occurrence of opposite internal electric field.Moreover,the further construction of Salisbury absorber-liked double-layer structure could result in an ultralow reflection coefficient of only~0.06 but enhanced SE variation range up to~38.7-49.3 d B during the adjustment of cross-angle,possibly due to the destructive interference of EM waves in the double-layer carbon networks.This work would provide a simple and effective way for constructing high-performance biomass carbon materials with adjustable EMI shielding and ultra-low reflectivity.展开更多
In this paper, an efficient multi-conductor simplification technique is proposed to model the electromagnetic immunity on cable bundles within a braid shielding structure over a large frequency range. By grouping toge...In this paper, an efficient multi-conductor simplification technique is proposed to model the electromagnetic immunity on cable bundles within a braid shielding structure over a large frequency range. By grouping together the conductors based on the knowledge of Z-Smith chart, the required computation time is markedly reduced and the complexity of modeling the completely shielding cable bundles is significantly simplified with a good accuracy. After a brief description of the immunity problems in shielding structure, a six-phase procedure is detailed to generate the geometrical characteristics of the reduced cable bundles. Numerical simulation is carried out by using a commercial software CST to validate the efficiency and advantages of the proposed approach. The research addressed in this paper is considered as a simplified modeling technique for the electromagnetic immunity within a shielding structure.展开更多
Cable welding wire（CWW）CO2gas shielded welding is an innovative process arc welding with high efficiency,high quality and low consumption,in which cable wire is used as consumable electrode.CWW CO2gas shielded weldi...Cable welding wire（CWW）CO2gas shielded welding is an innovative process arc welding with high efficiency,high quality and low consumption,in which cable wire is used as consumable electrode.CWW CO2gas shielded welding and submerged arc welding（SAW）are used for contrast studies on processing property of high strength steel A36used in ship structure.The results show that the shapes of weld seam,using CWW CO2gas shielded welding and SAW,are good and no weld defect such as air hole,flaw,slag inclusion,incomplete fusion,lack of penetration and so on are found in the weld seam.Because the rotating of arc during CWW CO2gas shielded welding process has a strong stirring effect on molten pool,the grain in the heat affected zone（HAZ）of the joints,using CWW CO2 gas shielded welding,is small.Tensile failure positions of joints by CWW CO2gas shielded welding and SAW are all in the base metal,but tensile strength of CWW CO2gas shielded welding joint is higher than that of SAW joint by an average of 2.3%.The average impact energy of HAZ,using CWW CO2gas shielded welding and SAW,is almost equal,but the average impact energy of the weld seam using CWW CO2gas shielded welding is increased by 6%,and the average impact energy of the fusion line is increased by 7%.The 180°bending tests for the joints of CWW CO2 gas shielded welding and SAW are all qualified,and the joints hardness is all less than HV 355,but hardness of CWW CO2gas shielded welding wire welding joint near the fusion line is obviously lower.It can be concluded that the properties of CWW CO2gas shielded welding are better than those of the SAW joint,and CWW CO2gas shielded welding is suitable for welding high strength steel A36used in ship structure.展开更多
With the development of technology, more and more options are available for insulated cables in power systems. Different cable construction types have different impedance, voltage drop and power losses. In order to ef...With the development of technology, more and more options are available for insulated cables in power systems. Different cable construction types have different impedance, voltage drop and power losses. In order to efficiently design these cable systems and adequately model them for system analysis, </span><span style="font-family:Verdana;">engineers should be able to calculate the parameters of different types of cables. </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Although the methods of parameters calculation are very mature, few types of software are used to calculate all these parameters for different cables</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span></span></span><span><span><span><span style="font-family:""> </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The objective of this paper is to build a user-friendly software to calculate these parameters with greater flexibility even if the users are not familiar with the methods of estimating the parameters of different types of cables. A program that is used to calculate the parameters of different cross-sections of cables is built by combining the method of estimating these parameters with the graphical user interface (GUI). Using this program, users can input or choose any type of cables, and calculate the parameters they need. In the future, more functions can be added to the program and the code could be switched to python or C# and develop a better GUI (Graphical User Interface).展开更多
Thermal aging characteristics of insulation layer and inner semi-conductive shielding layer directly affect the safe operating characteristics of cables.In this work,physical and chemical properties,the evolution of e...Thermal aging characteristics of insulation layer and inner semi-conductive shielding layer directly affect the safe operating characteristics of cables.In this work,physical and chemical properties,the evolution of electrical insulation properties,and interface characteristics are studied.Furthermore,molecular simulation has been used to analyze free volume change and molecular chain motion characteristics induced by temperature to reveal the ageing mechanism.Experimental results show new functional groups are generated in both insulation layer and inner semi-conductive layer.The carbonyl index of insulation layer increases from 0.10 to 0.29,while the degree of crystallinity decreases from 35%to 29.5%.Volume resistivity decreases from 2.93×10^(17)Ω·cm to 2.48×10^(16)Ω·cm,and the breakdown field decreases from 63.83 kV/mm to 51.53 kV/mm.Besides,both dielectric constant and dielectric loss of specimen increase after thermal aging.The degree of crystallinity of semi-conductive shielding layer drops from 9.0%to 3.68%and its volume resistivity also decreases.Simulation results show that the free volume fraction of XLPE molecules increases from 15.3%to 16.5%,and mean square displacement increases from 4.29Å^(2)to 19.10Å^(2)lead to the decrease of breakdown field.This work is instructive for the assessment of the aging state of high-voltage cables.展开更多
Currently,the reinforcement design of shield tunnel secondary linings mainly depends on engineering experience,with a lack of clear guidance from relevant codes and literature.Relying only on experience during constru...Currently,the reinforcement design of shield tunnel secondary linings mainly depends on engineering experience,with a lack of clear guidance from relevant codes and literature.Relying only on experience during construction can cause structural flaws and safety hazards.This study,based on the Guangzhou-Shenzhen-Hong Kong Shiziyang Tunnel project,uses model tests to study shield tunnel double-layer lining structures.It compares and analyzes the mechanical features and interaction mechanisms of reinforced and unreinforced secondary linings.Results show that in such structures,segmental linings bear the main load,and secondary linings offer extra support and adjust deformation.Reinforcement in secondary linings affects the constraint on segmental linings.Reinforcement enhances overall performance significantly.Although it has little impact on ultimate bearing capacity,it prolongs the load-bearing process.Specifically,it increases the ultimate bearing capacity of segmental and secondary linings by 21.2%and 26.1%,respectively.For 10-m-diameter shield tunnels,secondary lining reinforcement design should be adopted when the equivalent overburden thickness at the tunnel crown exceeds three times the tunnel diameter.展开更多
It is vital to study the electromagnetic coupling to shielded cable for improving electromagnetic antiinterference ability of secondary equipment in a substation.As a hybrid of method of moment(MoM)and transmission li...It is vital to study the electromagnetic coupling to shielded cable for improving electromagnetic antiinterference ability of secondary equipment in a substation.As a hybrid of method of moment(MoM)and transmission line method,a frequency domain model is put forward to study the near field coupling to shielded cable due to the switching operation in substation.Compared with the results of EMTP,the proposed method has been proven correct.Furthermore,this method overcomes the disadvantage of EMTP,which is only applicable for transient analysis of parallel conductors.As an example,the presented method is applied to evaluating the electromagnetic interference(EMI)to the shielded cable,whose shield is grounded at both ends,due to the switching operation in 500 kV air insulation substation(AIS).展开更多
基金financial supports from Natural Science Foundation of Ningbo(202003N4026)S&T Innovation 2025 Major Special Programme of Ningbo(2018B10054)National Natural Science Foundation of China(62001065 and 51603218)。
文摘Nowadays,carbon frameworks derived from natural biomaterials have attracted extensive attention for electromagnetic interference(EMI)shielding due to their renewability and affordability.However,it is critical and challenging to achieve effective regulation of shielding effectiveness(SE)as well as weaken the strong EM reflection of highly conductive biomass-based carbon materials.Herein,commercial cotton pads with oriented structure were selected as carbonaceous precursor to fabricate aligned carbon networks by pyrolysis,and the EMI SE of the samples with increased temperature of 800-1000℃ can be accurately controlled in the effective range of~21.7-29.1,~27.7-37.1 and~32.7-43.3 d B with high reflection coefficient of>0.8 by changing the cross-angle between the electric-field direction of incident EM waves and the fiber-orientation direction due to the occurrence of opposite internal electric field.Moreover,the further construction of Salisbury absorber-liked double-layer structure could result in an ultralow reflection coefficient of only~0.06 but enhanced SE variation range up to~38.7-49.3 d B during the adjustment of cross-angle,possibly due to the destructive interference of EM waves in the double-layer carbon networks.This work would provide a simple and effective way for constructing high-performance biomass carbon materials with adjustable EMI shielding and ultra-low reflectivity.
基金Project supported by the National Natural Science Foundation of China(Grant No.51675086)the National Defense Pre-Research Foundation of China(Grant No.6140758010116DZ02002)
文摘In this paper, an efficient multi-conductor simplification technique is proposed to model the electromagnetic immunity on cable bundles within a braid shielding structure over a large frequency range. By grouping together the conductors based on the knowledge of Z-Smith chart, the required computation time is markedly reduced and the complexity of modeling the completely shielding cable bundles is significantly simplified with a good accuracy. After a brief description of the immunity problems in shielding structure, a six-phase procedure is detailed to generate the geometrical characteristics of the reduced cable bundles. Numerical simulation is carried out by using a commercial software CST to validate the efficiency and advantages of the proposed approach. The research addressed in this paper is considered as a simplified modeling technique for the electromagnetic immunity within a shielding structure.
基金Sponsored by National Natural Science Foundation of China(51275224,51005106)Prospective Joint Research Project ofJiangsu Province of China(BY2012184)
文摘Cable welding wire（CWW）CO2gas shielded welding is an innovative process arc welding with high efficiency,high quality and low consumption,in which cable wire is used as consumable electrode.CWW CO2gas shielded welding and submerged arc welding（SAW）are used for contrast studies on processing property of high strength steel A36used in ship structure.The results show that the shapes of weld seam,using CWW CO2gas shielded welding and SAW,are good and no weld defect such as air hole,flaw,slag inclusion,incomplete fusion,lack of penetration and so on are found in the weld seam.Because the rotating of arc during CWW CO2gas shielded welding process has a strong stirring effect on molten pool,the grain in the heat affected zone（HAZ）of the joints,using CWW CO2 gas shielded welding,is small.Tensile failure positions of joints by CWW CO2gas shielded welding and SAW are all in the base metal,but tensile strength of CWW CO2gas shielded welding joint is higher than that of SAW joint by an average of 2.3%.The average impact energy of HAZ,using CWW CO2gas shielded welding and SAW,is almost equal,but the average impact energy of the weld seam using CWW CO2gas shielded welding is increased by 6%,and the average impact energy of the fusion line is increased by 7%.The 180°bending tests for the joints of CWW CO2 gas shielded welding and SAW are all qualified,and the joints hardness is all less than HV 355,but hardness of CWW CO2gas shielded welding wire welding joint near the fusion line is obviously lower.It can be concluded that the properties of CWW CO2gas shielded welding are better than those of the SAW joint,and CWW CO2gas shielded welding is suitable for welding high strength steel A36used in ship structure.
文摘With the development of technology, more and more options are available for insulated cables in power systems. Different cable construction types have different impedance, voltage drop and power losses. In order to efficiently design these cable systems and adequately model them for system analysis, </span><span style="font-family:Verdana;">engineers should be able to calculate the parameters of different types of cables. </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Although the methods of parameters calculation are very mature, few types of software are used to calculate all these parameters for different cables</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span></span></span><span><span><span><span style="font-family:""> </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The objective of this paper is to build a user-friendly software to calculate these parameters with greater flexibility even if the users are not familiar with the methods of estimating the parameters of different types of cables. A program that is used to calculate the parameters of different cross-sections of cables is built by combining the method of estimating these parameters with the graphical user interface (GUI). Using this program, users can input or choose any type of cables, and calculate the parameters they need. In the future, more functions can be added to the program and the code could be switched to python or C# and develop a better GUI (Graphical User Interface).
基金supported by National Natural Science Foundation of China(52107154)Youth Innovation Technology Support Plan of Shandong Province Universities(2021KJ023)Science and Technology project of State Grid Shandong Electric Power Company(52062621N003)。
文摘Thermal aging characteristics of insulation layer and inner semi-conductive shielding layer directly affect the safe operating characteristics of cables.In this work,physical and chemical properties,the evolution of electrical insulation properties,and interface characteristics are studied.Furthermore,molecular simulation has been used to analyze free volume change and molecular chain motion characteristics induced by temperature to reveal the ageing mechanism.Experimental results show new functional groups are generated in both insulation layer and inner semi-conductive layer.The carbonyl index of insulation layer increases from 0.10 to 0.29,while the degree of crystallinity decreases from 35%to 29.5%.Volume resistivity decreases from 2.93×10^(17)Ω·cm to 2.48×10^(16)Ω·cm,and the breakdown field decreases from 63.83 kV/mm to 51.53 kV/mm.Besides,both dielectric constant and dielectric loss of specimen increase after thermal aging.The degree of crystallinity of semi-conductive shielding layer drops from 9.0%to 3.68%and its volume resistivity also decreases.Simulation results show that the free volume fraction of XLPE molecules increases from 15.3%to 16.5%,and mean square displacement increases from 4.29Å^(2)to 19.10Å^(2)lead to the decrease of breakdown field.This work is instructive for the assessment of the aging state of high-voltage cables.
基金supported by the National Natural Science Foundation of China(Grant Nos.52178398 and 51991394).
文摘Currently,the reinforcement design of shield tunnel secondary linings mainly depends on engineering experience,with a lack of clear guidance from relevant codes and literature.Relying only on experience during construction can cause structural flaws and safety hazards.This study,based on the Guangzhou-Shenzhen-Hong Kong Shiziyang Tunnel project,uses model tests to study shield tunnel double-layer lining structures.It compares and analyzes the mechanical features and interaction mechanisms of reinforced and unreinforced secondary linings.Results show that in such structures,segmental linings bear the main load,and secondary linings offer extra support and adjust deformation.Reinforcement in secondary linings affects the constraint on segmental linings.Reinforcement enhances overall performance significantly.Although it has little impact on ultimate bearing capacity,it prolongs the load-bearing process.Specifically,it increases the ultimate bearing capacity of segmental and secondary linings by 21.2%and 26.1%,respectively.For 10-m-diameter shield tunnels,secondary lining reinforcement design should be adopted when the equivalent overburden thickness at the tunnel crown exceeds three times the tunnel diameter.
基金supported by the Scientific Funds for Outstanding Young Scientists of China (No.50325723)the Program for Changjiang Scholars and Innovative Research Team in University in China (No.IRT0515).
文摘It is vital to study the electromagnetic coupling to shielded cable for improving electromagnetic antiinterference ability of secondary equipment in a substation.As a hybrid of method of moment(MoM)and transmission line method,a frequency domain model is put forward to study the near field coupling to shielded cable due to the switching operation in substation.Compared with the results of EMTP,the proposed method has been proven correct.Furthermore,this method overcomes the disadvantage of EMTP,which is only applicable for transient analysis of parallel conductors.As an example,the presented method is applied to evaluating the electromagnetic interference(EMI)to the shielded cable,whose shield is grounded at both ends,due to the switching operation in 500 kV air insulation substation(AIS).
