To achieve efficient catalytic hydrogenation of CO_(2)to formate,we employed a transmetallation strategy to develop three novel iridium(Ⅰ)complexes,which feature N‑heterocyclic carbene‑nitrogen‑phosphine ligands(CNP)...To achieve efficient catalytic hydrogenation of CO_(2)to formate,we employed a transmetallation strategy to develop three novel iridium(Ⅰ)complexes,which feature N‑heterocyclic carbene‑nitrogen‑phosphine ligands(CNP)and a 1,5‑cyclooctadiene(cod)molecule:[Ir(cod)(κ^(3)‑CN^(im)P)]Cl(1⁃Cl),[Ir(cod)(κ^(3)‑CN^(im)P)]PF6(1⁃PF_(6)),and[Ir(cod)(κ^(3)‑CNHP)]Cl(2).The^(1)H NMR spectra,^(31)P NMR spectra,and high‑resolution mass spectra verify the successful synthesis of these three Ir(Ⅰ)‑CNP complexes.Furthermore,single‑crystal X‑ray diffraction analysis confirms the coordination geometry of 1⁃PF_(6).The strong Ir—C(NHC)bond suggests that the carbene carbon plays an enhanced anchoring role to iridium due to its strongσ‑donating ability,which helps stabilize the active metal species during CO_(2)hydrogenation.As a result,the Ir(Ⅰ)‑CNP complex exhibits remarkable activity and long catalytic lifetime for the hydrogenation of CO_(2)to formate,reaching a turnover number(TON)of 1.16×10^(6)after 150 h at a high temperature of 170℃,which was a relatively high value among all the Ir complexes.CCDC:2384071,1⁃PF_(6).展开更多
The digital transformation in Cameroon presents critical cybersecurity challenges that demand immediate attention and strategic intervention. This comprehensive analysis examines the evolving cybersecurity landscape i...The digital transformation in Cameroon presents critical cybersecurity challenges that demand immediate attention and strategic intervention. This comprehensive analysis examines the evolving cybersecurity landscape in Cameroon from 2020 to 2023, during which cyber-attacks increased by 156% and financial losses from digital fraud exceeded $45 million. This research identifies significant vulnerabilities in Cameroon’s cybersecurity ecosystem through a rigorous assessment of national infrastructure, policy frameworks, and institutional capacities. Recent data indicates that while digital service adoption has grown exponentially, with internet penetration reaching 35.2% in 2023, cybersecurity measures have lagged significantly behind international standards. This analysis draws on comprehensive data from multiple sectors, including financial services, government institutions, and telecommunications, incorporating findings from the National Cybersecurity Assessment Program and the Digital Infrastructure Security Report. The research reveals that 73% of organizations lack dedicated security teams, while response times to cyber incidents average 72 hours—three times than the global standard. Based on these findings, this paper proposes evidence-based solutions for enhancing digital resilience, including policy modernization, capacity-building initiatives, and technical infrastructure development. The recommendations encompass short-term tactical responses, medium-term strategic improvements, and long-term structural changes, providing a comprehensive roadmap for strengthening Cameroon’s national cybersecurity frameworks.展开更多
This paper presents a method for fabricating a low-cost,highly reproducible miniature optical fiber Fabry-Perot(FP)sensor based on a polydimethylsiloxane(PDMS)end-cap structure.The FP cavity end-cap is formed by the o...This paper presents a method for fabricating a low-cost,highly reproducible miniature optical fiber Fabry-Perot(FP)sensor based on a polydimethylsiloxane(PDMS)end-cap structure.The FP cavity end-cap is formed by the optical fiber end-face and a PDMS droplet deposited onto it.The PDMS deposition is achieved by immersing the fiber end into pre-cured PDMS at a fixed speed,a process requiring careful control of PDMS viscosity and surface tension.By leveraging PDMS’s excellent thermal expansion coefficient,Poisson’s ratio,and other parameters,this method achieves high reproducibility via viscosity-optimized pre-curing,enhanced sensitivity for temperature measurements,and significant cost reduction versus commercial counterparts.Fiber FP sensors are increasingly widely used in biomedical and precision detection fields owing to their significant advantages,including small size,light weight,high sensitivity,and immunity to electromagnetic interference.In the fabrication of fiber FP sensors,using polymer materials is an effective technical approach.These polymers can be applied as coatings on the optical fiber end-face or as interlayer materials embedded between fibers to form the FP cavity structure,which not only significantly improves the overall sensor performance,but also enhances its sensitivity to changes in temperature,pressure,and refractive index.In the final part of this study,we successfully validated the exceptional performance of the PDMS end-cap based fiber FP sensor in detecting different temperatures conditions.Experimental results demonstrate a temperature sensitivity of 0.752 nm/℃for sensors with a 60-μm PDMS end-cap,further confirming the sensor’s reliability and efficiency in practical applications.展开更多
A task allocation problem for the heterogeneous unmanned aerial vehicle (UAV) swarm in unknown environments is studied in this paper.Considering that the actual mission environment information may be unknown,the UAV s...A task allocation problem for the heterogeneous unmanned aerial vehicle (UAV) swarm in unknown environments is studied in this paper.Considering that the actual mission environment information may be unknown,the UAV swarm needs to detect the environment first and then attack the detected targets.The heterogeneity of UAVs,multiple types of tasks,and the dynamic nature of task environment lead to uneven load and time sequence problems.This paper proposes an improved contract net protocol (CNP) based task allocation scheme,which effectively balances the load of UAVs and improves the task efficiency.Firstly,two types of task models are established,including regional reconnaissance tasks and target attack tasks.Secondly,for regional reconnaissance tasks,an improved CNP algorithm using the uncertain contract is developed.Through uncertain contracts,the area size of the regional reconnaissance task is determined adaptively after this task assignment,which can improve reconnaissance efficiency and resource utilization.Thirdly,for target attack tasks,an improved CNP algorithm using the fuzzy integrated evaluation and the double-layer negotiation is presented to enhance collaborative attack efficiency through adjusting the assignment sequence adaptively and multi-layer allocation.Finally,the effectiveness and advantages of the improved method are verified through comparison simulations.展开更多
设置模拟氮沉降的控制试验,以NH4NO3作为外加氮源,设计CK(0 kg N hm-2·a-1)、LN(50 kg N hm-2·a-1)、MN(100 kgN hm-2·a-1)、HN(150 kg N hm-2·a-1)4个处理,历时9个月,测定木荷(Schima superba)幼苗的光合特性、生...设置模拟氮沉降的控制试验,以NH4NO3作为外加氮源,设计CK(0 kg N hm-2·a-1)、LN(50 kg N hm-2·a-1)、MN(100 kgN hm-2·a-1)、HN(150 kg N hm-2·a-1)4个处理,历时9个月,测定木荷(Schima superba)幼苗的光合特性、生物量和C、N、P含量及其分配格局对氮沉降的响应。结果表明:(1)木荷幼苗的最大净光合速率和光饱和点随着氮处理水平增加呈先增加后减小的特点,在中氮处理下极显著增加(P<0.01)。氮处理降低了幼苗的光补偿点和暗呼吸速率,光补偿点在低氮处理下显著降低(P<0.05),暗呼吸速率在低中氮处理下极显著降低(P<0.01),高氮处理下显著降低(P<0.05)。未见氮处理对表观量子效率产生显著影响。(2)氮处理促进了木荷的全株生物量以及各部分生物量的增长。随着氮处理水平的增加,叶重比呈升高的趋势,而根重比和根冠比呈降低的趋势,在高氮处理下叶重比的增加和根重比、根冠比的降低都达到了显著水平(P<0.05)。(3)氮沉降促进各器官N含量的增加,在高氮处理下根和茎中N含量极显著增加(P<0.01),叶中N含量显著增加(P<0.05)。而各器官C含量随着氮沉降程度的增加呈先增加后降低的趋势,在中氮处理下根和茎中C含量极显著增加(P<0.01),叶中C含量显著增加(P<0.05)。但各器官P含量变化趋势各不相同,随着氮的增加,根中P含量是呈先增加后降低的趋势,而茎和叶中P含量是呈降低的趋势。氮沉降一定程度上降低了木荷各器官的C/N比值而增加了N/P比值。展开更多
文摘To achieve efficient catalytic hydrogenation of CO_(2)to formate,we employed a transmetallation strategy to develop three novel iridium(Ⅰ)complexes,which feature N‑heterocyclic carbene‑nitrogen‑phosphine ligands(CNP)and a 1,5‑cyclooctadiene(cod)molecule:[Ir(cod)(κ^(3)‑CN^(im)P)]Cl(1⁃Cl),[Ir(cod)(κ^(3)‑CN^(im)P)]PF6(1⁃PF_(6)),and[Ir(cod)(κ^(3)‑CNHP)]Cl(2).The^(1)H NMR spectra,^(31)P NMR spectra,and high‑resolution mass spectra verify the successful synthesis of these three Ir(Ⅰ)‑CNP complexes.Furthermore,single‑crystal X‑ray diffraction analysis confirms the coordination geometry of 1⁃PF_(6).The strong Ir—C(NHC)bond suggests that the carbene carbon plays an enhanced anchoring role to iridium due to its strongσ‑donating ability,which helps stabilize the active metal species during CO_(2)hydrogenation.As a result,the Ir(Ⅰ)‑CNP complex exhibits remarkable activity and long catalytic lifetime for the hydrogenation of CO_(2)to formate,reaching a turnover number(TON)of 1.16×10^(6)after 150 h at a high temperature of 170℃,which was a relatively high value among all the Ir complexes.CCDC:2384071,1⁃PF_(6).
文摘The digital transformation in Cameroon presents critical cybersecurity challenges that demand immediate attention and strategic intervention. This comprehensive analysis examines the evolving cybersecurity landscape in Cameroon from 2020 to 2023, during which cyber-attacks increased by 156% and financial losses from digital fraud exceeded $45 million. This research identifies significant vulnerabilities in Cameroon’s cybersecurity ecosystem through a rigorous assessment of national infrastructure, policy frameworks, and institutional capacities. Recent data indicates that while digital service adoption has grown exponentially, with internet penetration reaching 35.2% in 2023, cybersecurity measures have lagged significantly behind international standards. This analysis draws on comprehensive data from multiple sectors, including financial services, government institutions, and telecommunications, incorporating findings from the National Cybersecurity Assessment Program and the Digital Infrastructure Security Report. The research reveals that 73% of organizations lack dedicated security teams, while response times to cyber incidents average 72 hours—three times than the global standard. Based on these findings, this paper proposes evidence-based solutions for enhancing digital resilience, including policy modernization, capacity-building initiatives, and technical infrastructure development. The recommendations encompass short-term tactical responses, medium-term strategic improvements, and long-term structural changes, providing a comprehensive roadmap for strengthening Cameroon’s national cybersecurity frameworks.
文摘This paper presents a method for fabricating a low-cost,highly reproducible miniature optical fiber Fabry-Perot(FP)sensor based on a polydimethylsiloxane(PDMS)end-cap structure.The FP cavity end-cap is formed by the optical fiber end-face and a PDMS droplet deposited onto it.The PDMS deposition is achieved by immersing the fiber end into pre-cured PDMS at a fixed speed,a process requiring careful control of PDMS viscosity and surface tension.By leveraging PDMS’s excellent thermal expansion coefficient,Poisson’s ratio,and other parameters,this method achieves high reproducibility via viscosity-optimized pre-curing,enhanced sensitivity for temperature measurements,and significant cost reduction versus commercial counterparts.Fiber FP sensors are increasingly widely used in biomedical and precision detection fields owing to their significant advantages,including small size,light weight,high sensitivity,and immunity to electromagnetic interference.In the fabrication of fiber FP sensors,using polymer materials is an effective technical approach.These polymers can be applied as coatings on the optical fiber end-face or as interlayer materials embedded between fibers to form the FP cavity structure,which not only significantly improves the overall sensor performance,but also enhances its sensitivity to changes in temperature,pressure,and refractive index.In the final part of this study,we successfully validated the exceptional performance of the PDMS end-cap based fiber FP sensor in detecting different temperatures conditions.Experimental results demonstrate a temperature sensitivity of 0.752 nm/℃for sensors with a 60-μm PDMS end-cap,further confirming the sensor’s reliability and efficiency in practical applications.
基金National Natural Science Foundation of China (12202293)Sichuan Science and Technology Program (2023NSFSC0393,2022NSFSC1952)。
文摘A task allocation problem for the heterogeneous unmanned aerial vehicle (UAV) swarm in unknown environments is studied in this paper.Considering that the actual mission environment information may be unknown,the UAV swarm needs to detect the environment first and then attack the detected targets.The heterogeneity of UAVs,multiple types of tasks,and the dynamic nature of task environment lead to uneven load and time sequence problems.This paper proposes an improved contract net protocol (CNP) based task allocation scheme,which effectively balances the load of UAVs and improves the task efficiency.Firstly,two types of task models are established,including regional reconnaissance tasks and target attack tasks.Secondly,for regional reconnaissance tasks,an improved CNP algorithm using the uncertain contract is developed.Through uncertain contracts,the area size of the regional reconnaissance task is determined adaptively after this task assignment,which can improve reconnaissance efficiency and resource utilization.Thirdly,for target attack tasks,an improved CNP algorithm using the fuzzy integrated evaluation and the double-layer negotiation is presented to enhance collaborative attack efficiency through adjusting the assignment sequence adaptively and multi-layer allocation.Finally,the effectiveness and advantages of the improved method are verified through comparison simulations.
文摘设置模拟氮沉降的控制试验,以NH4NO3作为外加氮源,设计CK(0 kg N hm-2·a-1)、LN(50 kg N hm-2·a-1)、MN(100 kgN hm-2·a-1)、HN(150 kg N hm-2·a-1)4个处理,历时9个月,测定木荷(Schima superba)幼苗的光合特性、生物量和C、N、P含量及其分配格局对氮沉降的响应。结果表明:(1)木荷幼苗的最大净光合速率和光饱和点随着氮处理水平增加呈先增加后减小的特点,在中氮处理下极显著增加(P<0.01)。氮处理降低了幼苗的光补偿点和暗呼吸速率,光补偿点在低氮处理下显著降低(P<0.05),暗呼吸速率在低中氮处理下极显著降低(P<0.01),高氮处理下显著降低(P<0.05)。未见氮处理对表观量子效率产生显著影响。(2)氮处理促进了木荷的全株生物量以及各部分生物量的增长。随着氮处理水平的增加,叶重比呈升高的趋势,而根重比和根冠比呈降低的趋势,在高氮处理下叶重比的增加和根重比、根冠比的降低都达到了显著水平(P<0.05)。(3)氮沉降促进各器官N含量的增加,在高氮处理下根和茎中N含量极显著增加(P<0.01),叶中N含量显著增加(P<0.05)。而各器官C含量随着氮沉降程度的增加呈先增加后降低的趋势,在中氮处理下根和茎中C含量极显著增加(P<0.01),叶中C含量显著增加(P<0.05)。但各器官P含量变化趋势各不相同,随着氮的增加,根中P含量是呈先增加后降低的趋势,而茎和叶中P含量是呈降低的趋势。氮沉降一定程度上降低了木荷各器官的C/N比值而增加了N/P比值。
