In this paper,a modified single-degree-of-freedom(SDOF)model of reinforced concrete(RC)beams under close-in explosion is proposed by developing the specific impulse equivalent method and flexural resistance calculatio...In this paper,a modified single-degree-of-freedom(SDOF)model of reinforced concrete(RC)beams under close-in explosion is proposed by developing the specific impulse equivalent method and flexural resistance calculation method.The equivalent uniform specific impulse was obtained based on the local conservation of momentum and global conservation of kinetic energy.Additionally,the influence of load uniformity,boundary condition and complex material behaviors(e.g.strain rate effect,hardening/softening and hoop-confined effect)was considered in the resistance calculation process by establishing a novel relationship between external force,bending moment,curvature and deflection successively.The accuracy of the proposed model was verified by carrying out field explosion tests on four RC beams with the scaled distances of 0.5 m/kg~(1/3)and 0.75 m/kg~(1/3).The test data in other literatures were also used for validation.As a result,the equivalent load implies that the blast load near the mid-span of beams would contribute more to the maximum displacement,which was also observed in the tests.Moreover,both the resistance model and test results declare that when the blast load becomes more concentrated,the ultimate resistance would become lower,and the compressive concrete would be more prone to softening and crushing.Finally,based on the modified SDOF model,the calculated maximum displacements agreed well with the test data in this paper and other literatures.This work fully proves the rationality of the modified SDOF method,which will contribute to a more accurate damage assessment of RC structures under close-in explosion.展开更多
Polyurea is an elastomeric material that can be applied to enhance the protection ability of structures under blast and impact loading.In order to study the compressive mechanical properties of SiC/polyurea nanocompos...Polyurea is an elastomeric material that can be applied to enhance the protection ability of structures under blast and impact loading.In order to study the compressive mechanical properties of SiC/polyurea nanocomposites under quasi-static and dynamic loading,a universal testing machine and split Hopkinson pressure bar(SHPB)apparatus were used respectively.The stress-strain curves were obtained on polyurea and its composites at strain rates of 0.001e8000 s1.The results of the experiment suggested that increase in the strain rates led to the rise of the flow stress,compressive strength,strain rate sensitivity and strain energy.This indicates that all of the presented materials were dependent on strain rate.Moreover,these mechanical characters were enhanced by incorporating a small amount of SiC into polyurea matrix.The relation between yield stress and strain rates were established using the power law functions.Finally,in order to investigate the fracture surfaces and inside information of failed specimens,scanning electron microscopy(SEM)and micro X-ray computed tomography(micro-CT)were used respectively.Multiple voids,crazes,micro-cracks and cracking were observed in fracture surfaces.On the other hand,the cracking propagation was found in the micro-CT slice images.It is essential to understand the deformation and failure mechanisms in all the polyurea materials.展开更多
To improve the accuracy and usability of the superconducting electron cyclotron resonance ion source with advanced design in Lanzhou(SECRAL), an upgraded version of the control system was designed and tested. This pap...To improve the accuracy and usability of the superconducting electron cyclotron resonance ion source with advanced design in Lanzhou(SECRAL), an upgraded version of the control system was designed and tested. This paper details the architecture of the optimized control system and presents the results of its use in the long-term operation of the accelerator. The control system software, based on Visual C++, was developed following the model-view-controller architecture design pattern. The data acquisition system was based on a field-programmable gate array integrated circuit. In addition, control strategies were optimized for higher operational stability. The upgraded control system was tested with a U^(33+) ion beam at SECRAL, where it provided a data acquisition time of less than 1 ms. The fast reaction time and highprecision data processing during beam tuning verified the stability and maintainability of the control system.展开更多
Laser-induced graphene(LIG)has been exploited in various fields,such as batteries,water treatment,and flexible actuators and sensors,with the advantages of ease in patternable fabrication and graphene/metal hybrid pre...Laser-induced graphene(LIG)has been exploited in various fields,such as batteries,water treatment,and flexible actuators and sensors,with the advantages of ease in patternable fabrication and graphene/metal hybrid preparation.The in situ method which includes a single lase step and the ex situ method which uses two lase steps are both widely implemented to synthesize graphene/metal hybrids.However,the differences in the structures and properties of the resulting hybrids are not fully understood.Here,we investigate the advantages of ex situ and in situ methods for preparing LIG hybrids using NiFe/LIG as an example.The morphology,elemental composition,resistance to strong acid,and application in electrocatalysis and dye adsorption of ex situ and in situ NiFe/LIG hybrids were systematically studied and compared.Energy-dispersive X-ray spectrometry(EDS)and vibrating sample magnetometry(VSM)results confirmed the structural differences between the NiFe/LIG hybrids.Metal nanoparticles are mostly wrapped by carbon layers in the in situ NiFe/LIG hybrid,while the ex situ NiFe/LIG hybrid largely exposes the metal nanoparticles.These structural differences are significant for tailoring performance in applications,such as wastewater treatment and electrocatalysis.This work provides insights into the synthesis and properties of LIGs and has important implications for future applications.展开更多
Background The control system for ion source is based on distributed architecture.The hardware structure,working principle,interlock design and graphics interface design are introduced and stated in this paper.Purpose...Background The control system for ion source is based on distributed architecture.The hardware structure,working principle,interlock design and graphics interface design are introduced and stated in this paper.Purpose To improve the accuracy and usability of the electron cyclotron resonance ion source with advanced design for HIMM.Methods The data acquisition system is based on PLC and FPGA integrated circuit.Interlock protection is designed for vacuum system,power supplies system and cooling water system.Results The control system is tested with C5+ion beam,where fast reaction time and high-precision data processing during beam tuning have verified the stability and maintainability of the control system.Conclusion The latest results and the reliable long-term operation of the accelerator demonstrate that the performance has been continually improved with the development of the optimized control system.展开更多
基金National Natural Science Foundation of China(Grant No.12102337)to provide fund for conducting experiments。
文摘In this paper,a modified single-degree-of-freedom(SDOF)model of reinforced concrete(RC)beams under close-in explosion is proposed by developing the specific impulse equivalent method and flexural resistance calculation method.The equivalent uniform specific impulse was obtained based on the local conservation of momentum and global conservation of kinetic energy.Additionally,the influence of load uniformity,boundary condition and complex material behaviors(e.g.strain rate effect,hardening/softening and hoop-confined effect)was considered in the resistance calculation process by establishing a novel relationship between external force,bending moment,curvature and deflection successively.The accuracy of the proposed model was verified by carrying out field explosion tests on four RC beams with the scaled distances of 0.5 m/kg~(1/3)and 0.75 m/kg~(1/3).The test data in other literatures were also used for validation.As a result,the equivalent load implies that the blast load near the mid-span of beams would contribute more to the maximum displacement,which was also observed in the tests.Moreover,both the resistance model and test results declare that when the blast load becomes more concentrated,the ultimate resistance would become lower,and the compressive concrete would be more prone to softening and crushing.Finally,based on the modified SDOF model,the calculated maximum displacements agreed well with the test data in this paper and other literatures.This work fully proves the rationality of the modified SDOF method,which will contribute to a more accurate damage assessment of RC structures under close-in explosion.
基金The authors would like to thank the State Administration of Science,Technology and Industry for National Defense of China(Grant No.WDZCKYXM20190503)Xi’an Modern Chemistry Institute for the financial support.Beijing Institute of Technology and Northwestern Polytechnical University are thanked for providing experimental equipments for this work.
文摘Polyurea is an elastomeric material that can be applied to enhance the protection ability of structures under blast and impact loading.In order to study the compressive mechanical properties of SiC/polyurea nanocomposites under quasi-static and dynamic loading,a universal testing machine and split Hopkinson pressure bar(SHPB)apparatus were used respectively.The stress-strain curves were obtained on polyurea and its composites at strain rates of 0.001e8000 s1.The results of the experiment suggested that increase in the strain rates led to the rise of the flow stress,compressive strength,strain rate sensitivity and strain energy.This indicates that all of the presented materials were dependent on strain rate.Moreover,these mechanical characters were enhanced by incorporating a small amount of SiC into polyurea matrix.The relation between yield stress and strain rates were established using the power law functions.Finally,in order to investigate the fracture surfaces and inside information of failed specimens,scanning electron microscopy(SEM)and micro X-ray computed tomography(micro-CT)were used respectively.Multiple voids,crazes,micro-cracks and cracking were observed in fracture surfaces.On the other hand,the cracking propagation was found in the micro-CT slice images.It is essential to understand the deformation and failure mechanisms in all the polyurea materials.
基金supported by the National Natural Science Foundation of China(No.u1232123)
文摘To improve the accuracy and usability of the superconducting electron cyclotron resonance ion source with advanced design in Lanzhou(SECRAL), an upgraded version of the control system was designed and tested. This paper details the architecture of the optimized control system and presents the results of its use in the long-term operation of the accelerator. The control system software, based on Visual C++, was developed following the model-view-controller architecture design pattern. The data acquisition system was based on a field-programmable gate array integrated circuit. In addition, control strategies were optimized for higher operational stability. The upgraded control system was tested with a U^(33+) ion beam at SECRAL, where it provided a data acquisition time of less than 1 ms. The fast reaction time and highprecision data processing during beam tuning verified the stability and maintainability of the control system.
基金financially supported by the State Key Laboratory of Marine Pollution(SKLMP)Seed Collaborative Research Fund(No.SKLMP/IRF/0029)support from the Chow Sang Sang Group Research Fund(No.9229060)sponsored by Chow Sang Sang Holdings International Ltd and the CityU Applied Research Grant(No.9667224)。
文摘Laser-induced graphene(LIG)has been exploited in various fields,such as batteries,water treatment,and flexible actuators and sensors,with the advantages of ease in patternable fabrication and graphene/metal hybrid preparation.The in situ method which includes a single lase step and the ex situ method which uses two lase steps are both widely implemented to synthesize graphene/metal hybrids.However,the differences in the structures and properties of the resulting hybrids are not fully understood.Here,we investigate the advantages of ex situ and in situ methods for preparing LIG hybrids using NiFe/LIG as an example.The morphology,elemental composition,resistance to strong acid,and application in electrocatalysis and dye adsorption of ex situ and in situ NiFe/LIG hybrids were systematically studied and compared.Energy-dispersive X-ray spectrometry(EDS)and vibrating sample magnetometry(VSM)results confirmed the structural differences between the NiFe/LIG hybrids.Metal nanoparticles are mostly wrapped by carbon layers in the in situ NiFe/LIG hybrid,while the ex situ NiFe/LIG hybrid largely exposes the metal nanoparticles.These structural differences are significant for tailoring performance in applications,such as wastewater treatment and electrocatalysis.This work provides insights into the synthesis and properties of LIGs and has important implications for future applications.
基金the National Natural Science Foundation of China(Grant No.U1632141).
文摘Background The control system for ion source is based on distributed architecture.The hardware structure,working principle,interlock design and graphics interface design are introduced and stated in this paper.Purpose To improve the accuracy and usability of the electron cyclotron resonance ion source with advanced design for HIMM.Methods The data acquisition system is based on PLC and FPGA integrated circuit.Interlock protection is designed for vacuum system,power supplies system and cooling water system.Results The control system is tested with C5+ion beam,where fast reaction time and high-precision data processing during beam tuning have verified the stability and maintainability of the control system.Conclusion The latest results and the reliable long-term operation of the accelerator demonstrate that the performance has been continually improved with the development of the optimized control system.
