Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical simulations.The pulsed X-ray technology and a spaced aluminu...Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical simulations.The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used.Three types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and tested.The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over time.Moreover,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact.From simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy cluster.The unique formation structure determines the damage modes of the aluminum plate and the steel plate.Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content.With increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration.However,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.展开更多
Lightweight and efficient carbon-based microwave absorbents are significant in addressing the increasing severity of electromagnetic pollution.In this study,hierarchical NiO/Ni nanosheets with a tuneable phase and mor...Lightweight and efficient carbon-based microwave absorbents are significant in addressing the increasing severity of electromagnetic pollution.In this study,hierarchical NiO/Ni nanosheets with a tuneable phase and morphology supported on a carbon fiber substrate(CF@NiO/Ni)were fabricated using a hydrothermal approach and post-annealing treatment.As the annealing temperature increases,more metallic Ni is formed,and an apparent porosity appears on the sheet surface.Benefiting from the advantages of a three-dimensional(3D)conducting network,hierarchical porous structure,reinforced dipole/interface polarization,multiple scattering,and good impedance matching,the CF@NiO/Ni-500 composite exhibits an excellent microwave absorption performance even at a filling rate of only 3wt%.Specifically,its minimal reflection loss is-43.92 dB,and the qualified bandwidth is up to 5.64 GHz.In addition,the low radar cross-section area of the CF@NiO/Ni composite coating confirms its strong ability to suppress electromagnetic wave scattering.We expect that this work could contribute to a deeper understanding of the phase and morphology evolution in enhancing microwave absorption.展开更多
In recent years,LoRa has been extensively researched in the satellite Internet of Things(IoT).However,the multiple access technology of LoRa is still one of the bottlenecks of satellite IoT.To improve the multiple acc...In recent years,LoRa has been extensively researched in the satellite Internet of Things(IoT).However,the multiple access technology of LoRa is still one of the bottlenecks of satellite IoT.To improve the multiple access performance of LoRa satellite IoT,based on the orthogonality of LoRa symbols in the fractional domain,this paper proposes a low complexity Orthogonal LoRa Multiple Access(OLMA)algorithm for multiple LoRa users occupying the same frequency bandwidth.The algorithm introduces the address code to divide the fractional bandwidth into multiple parts,and the OLMA users with different address codes occupy different parts to transmit the information code,thus avoiding mutual interference caused by collisions in the same frequency bandwidth.The multiple access capability of OLMA can be flexibly configured only by simply adjusting the length of the address code according to the actual application requirements of data transmission.Theoretical analysis and simulation results show that the OLMA algorithm can greatly improve the multiple access capability and the total transmission bit rate of LoRa IoT without changing the existing LoRa modulation parameters and process.展开更多
To detect urea content in milk powder, a nonlinear chemical fingerprint technique was developed. In our study, Belousov-Zhabotinsky oscillatory chemical reaction (B-Z) was performed using milk powder and malonic acid ...To detect urea content in milk powder, a nonlinear chemical fingerprint technique was developed. In our study, Belousov-Zhabotinsky oscillatory chemical reaction (B-Z) was performed using milk powder and malonic acid as main dissipative substances. The same dosage of milk powder with or without artificially added urea was introduced to “H+ + Ce4+ + + malonic acid” oscillating system, respectively, and nonlinear chemical fingerprints of different milk powder were thus obtained. The proposed method was based on a linear relationship between inductive time of non-linear chemical fingerprints and urea content in milk powder, which held when urea content in milk powder was in the range of 0 - 40 mg/g. A detection limit of 7.8 × 10<sup>-3</sup>mg/g was also obtained. Our results showed that the method could be used to certify urea content in milk powder without pretreatment of samples, which was more simple and economical compared with traditional methods.展开更多
Integrating heterogeneous interface through nanostructure design and interfacial modification is essential to realize strengthened interfacial polarization relaxation in electromagnetic wave absorption.However,an in-d...Integrating heterogeneous interface through nanostructure design and interfacial modification is essential to realize strengthened interfacial polarization relaxation in electromagnetic wave absorption.However,an in-depth comprehension of the interfacial polarization behavior at hetero-junction/interface is highly desired but remains a great challenge.Herein,a Mott-Schottky heterojunction consisting of honeycomb-like porous N-doped carbon confined CoP nanoparticles(CoP@HNC)is designed to elevate the interfacial polarization strength.Simultaneously,corresponding electron migration and redistribution between the heterointerface of defective carbon and CoP nanoparticles are revealed.The significant difference in the work function on both sides of heterogeneous interface boosts the interfacial polarization in high frequency region.Furthermore,the relevant spectroscopic characterizations demonstrate that electron spontaneously migrates from CoP to N-doped carbon at the heterointerface,thereby contributing to the accumulation of electron on defective carbon side and the distribution of hole on CoP side.Impressively,benefitting from the synergistic effects of three-dimensional porous conductive carbon skeleton,foreign N heteroatoms,special CoP nanoparticles,and the resultant CoP/N-doped carbon Mott-Schottky heterojunction,the CoP@HNC exhibits remarkable electromagnetic wave absorption performances with minimum reflection loss up to−60.8 dB and the maximum effective absorption bandwidth of 4.96 GHz,which is superior to most of recently reported transition metal phosphides microwave absorbing composites.The present work opens a new avenue for designing heterogeneous interface to realize strengthened microwave absorption capability and also reveals the in-depth influence of interface structure on electromagnetic wave absorption.展开更多
The ability to sense heat and touch is essential for healthcare,robotics,and human–machine interfaces.By taking advantage of the engineerable waveguiding properties,we design and fabricate a flexible optical microfib...The ability to sense heat and touch is essential for healthcare,robotics,and human–machine interfaces.By taking advantage of the engineerable waveguiding properties,we design and fabricate a flexible optical microfiber sensor for simultaneous temperature and pressure measurement based on theoretical calculation.The sensor exhibits a high temperature sensitivity of 1.2 nm/℃ by measuring the shift of a high-order mode cutoff wavelength in the short-wavelength range.In the case of pressure sensing,the sensor shows a sensitivity of 4.5%per kilopascal with a fast temporal frequency response of 1000 Hz owing to the strong evanescent wave guided outside the microfiber.The cross talk is negligible because the temperature and pressure signals are measured at different wavelengths based on different mechanisms.The properties of fast temporal response,high temperature,and pressure sensitivity enable the sensor for real-time skin temperature and wrist pulse measurements,which is critical to the accurate analysis of pulse waveforms.We believe the sensor will have great potential in wearable optical devices ranging from healthcare to humanoid robots.展开更多
基金the National Natural Science Foundation of China(No.12172052 and No.12132003).
文摘Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical simulations.The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used.Three types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and tested.The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over time.Moreover,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact.From simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy cluster.The unique formation structure determines the damage modes of the aluminum plate and the steel plate.Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content.With increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration.However,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.
基金financially supported by the National Natural Science Foundation of China(Nos.51872002 and 52172174)the key research and development projects in Anhui province,China(No.202004a07020026)。
文摘Lightweight and efficient carbon-based microwave absorbents are significant in addressing the increasing severity of electromagnetic pollution.In this study,hierarchical NiO/Ni nanosheets with a tuneable phase and morphology supported on a carbon fiber substrate(CF@NiO/Ni)were fabricated using a hydrothermal approach and post-annealing treatment.As the annealing temperature increases,more metallic Ni is formed,and an apparent porosity appears on the sheet surface.Benefiting from the advantages of a three-dimensional(3D)conducting network,hierarchical porous structure,reinforced dipole/interface polarization,multiple scattering,and good impedance matching,the CF@NiO/Ni-500 composite exhibits an excellent microwave absorption performance even at a filling rate of only 3wt%.Specifically,its minimal reflection loss is-43.92 dB,and the qualified bandwidth is up to 5.64 GHz.In addition,the low radar cross-section area of the CF@NiO/Ni composite coating confirms its strong ability to suppress electromagnetic wave scattering.We expect that this work could contribute to a deeper understanding of the phase and morphology evolution in enhancing microwave absorption.
基金supported in part by the National Natural Science Foundation of China under Grant 61871153in part by Science and Technology on Communication Networks Laboratory under Grant 6142104200202in part by Science and Technology Project of Ministry of Public Security(2019GABJC35)。
文摘In recent years,LoRa has been extensively researched in the satellite Internet of Things(IoT).However,the multiple access technology of LoRa is still one of the bottlenecks of satellite IoT.To improve the multiple access performance of LoRa satellite IoT,based on the orthogonality of LoRa symbols in the fractional domain,this paper proposes a low complexity Orthogonal LoRa Multiple Access(OLMA)algorithm for multiple LoRa users occupying the same frequency bandwidth.The algorithm introduces the address code to divide the fractional bandwidth into multiple parts,and the OLMA users with different address codes occupy different parts to transmit the information code,thus avoiding mutual interference caused by collisions in the same frequency bandwidth.The multiple access capability of OLMA can be flexibly configured only by simply adjusting the length of the address code according to the actual application requirements of data transmission.Theoretical analysis and simulation results show that the OLMA algorithm can greatly improve the multiple access capability and the total transmission bit rate of LoRa IoT without changing the existing LoRa modulation parameters and process.
文摘To detect urea content in milk powder, a nonlinear chemical fingerprint technique was developed. In our study, Belousov-Zhabotinsky oscillatory chemical reaction (B-Z) was performed using milk powder and malonic acid as main dissipative substances. The same dosage of milk powder with or without artificially added urea was introduced to “H+ + Ce4+ + + malonic acid” oscillating system, respectively, and nonlinear chemical fingerprints of different milk powder were thus obtained. The proposed method was based on a linear relationship between inductive time of non-linear chemical fingerprints and urea content in milk powder, which held when urea content in milk powder was in the range of 0 - 40 mg/g. A detection limit of 7.8 × 10<sup>-3</sup>mg/g was also obtained. Our results showed that the method could be used to certify urea content in milk powder without pretreatment of samples, which was more simple and economical compared with traditional methods.
基金supported by the National Natural Science Foundation of China(Nos.51872002 and 52172174)Open Project of Provincial and Ministerial Scientific Research Platform,and Fuyang Normal University(No.FSKFKT009D).
文摘Integrating heterogeneous interface through nanostructure design and interfacial modification is essential to realize strengthened interfacial polarization relaxation in electromagnetic wave absorption.However,an in-depth comprehension of the interfacial polarization behavior at hetero-junction/interface is highly desired but remains a great challenge.Herein,a Mott-Schottky heterojunction consisting of honeycomb-like porous N-doped carbon confined CoP nanoparticles(CoP@HNC)is designed to elevate the interfacial polarization strength.Simultaneously,corresponding electron migration and redistribution between the heterointerface of defective carbon and CoP nanoparticles are revealed.The significant difference in the work function on both sides of heterogeneous interface boosts the interfacial polarization in high frequency region.Furthermore,the relevant spectroscopic characterizations demonstrate that electron spontaneously migrates from CoP to N-doped carbon at the heterointerface,thereby contributing to the accumulation of electron on defective carbon side and the distribution of hole on CoP side.Impressively,benefitting from the synergistic effects of three-dimensional porous conductive carbon skeleton,foreign N heteroatoms,special CoP nanoparticles,and the resultant CoP/N-doped carbon Mott-Schottky heterojunction,the CoP@HNC exhibits remarkable electromagnetic wave absorption performances with minimum reflection loss up to−60.8 dB and the maximum effective absorption bandwidth of 4.96 GHz,which is superior to most of recently reported transition metal phosphides microwave absorbing composites.The present work opens a new avenue for designing heterogeneous interface to realize strengthened microwave absorption capability and also reveals the in-depth influence of interface structure on electromagnetic wave absorption.
基金Acknowledgements We thank Dr. Jian Wang, Dr. Pengxin Chen, Dr. Xiaowei Guan, Dr. Fei Lou, Prof. Lech Wosinski, Dr. Di Liang, Prof. John Bowers, Dr. Yaocheng Shi, Prof. Sailing He, et al for their contributions and the support from the National Natural Science Foundation of China （NSFC） （Grant Nos. 11374263, 6141101056, 61422510）, the Doctoral Fund of Ministry of Education of China （No. 20120101110094）, and the Fundamental Research Funds for the Central Universities.
基金National Key Research and Development Program of China(2018YFB2200400)National Natural Science Foundation of China(61975173,62075192)+2 种基金Natural Science Foundation of Zhejiang Province(LQ21F050001,LQ22F050021)Major Scientific Research Project of Zhejiang Lab(2019MC0AD01)Key Research and Development Project of Zhejiang Province(2021C05003)。
文摘The ability to sense heat and touch is essential for healthcare,robotics,and human–machine interfaces.By taking advantage of the engineerable waveguiding properties,we design and fabricate a flexible optical microfiber sensor for simultaneous temperature and pressure measurement based on theoretical calculation.The sensor exhibits a high temperature sensitivity of 1.2 nm/℃ by measuring the shift of a high-order mode cutoff wavelength in the short-wavelength range.In the case of pressure sensing,the sensor shows a sensitivity of 4.5%per kilopascal with a fast temporal frequency response of 1000 Hz owing to the strong evanescent wave guided outside the microfiber.The cross talk is negligible because the temperature and pressure signals are measured at different wavelengths based on different mechanisms.The properties of fast temporal response,high temperature,and pressure sensitivity enable the sensor for real-time skin temperature and wrist pulse measurements,which is critical to the accurate analysis of pulse waveforms.We believe the sensor will have great potential in wearable optical devices ranging from healthcare to humanoid robots.
