Energetic compounds bearing the trinitromethyl group are garnering broad attraction as potential candidates for a new generation of high energy dense oxidizers.In this work,an effective dual modulation strategy involv...Energetic compounds bearing the trinitromethyl group are garnering broad attraction as potential candidates for a new generation of high energy dense oxidizers.In this work,an effective dual modulation strategy involving both molecular isomerization and crystal morphology control was employed to design and optimize trinitromethyl-oxadiazole with improved comprehensive performance.Utilizing this dual strategy,3,5-bis(trinitromethyl)-1,2,4-oxadiazole(3)was synthesized,resulting in the formation of two distinct crystal morphologies(needle and sheet)corresponding to two crystal forms(3-a and3-b).Encouragingly,while maintaining ultra-high oxygen balance(21.73%),3 achieves impressive densities(1.97-1.98 g/cm^(3)).To our knowledge,the density of 1.98 g/cm^(3)for 3-a sets a new record among that of nitrogen-rich monocyclic compounds.Notably,practical crystal morphology prediction was creatively introduced to guide the experimental crystallization conditions of 3,increasing the impact sensitivity and friction sensitivity from 1 J to 80 N(3-a)to 10 J and 240 N(3-b),respectively.Additionally,the crystal structural analyses and theoretical calculations were conducted to elucidate the reasons of differences between 3-a and 3-b in density and stability.This work provides an efficient strategy to enhance performance of trinitromethyl derivatives,broadening the path and expanding the toolbox for energetic materials.展开更多
A generalized multiple-mode prolate spherical wave functions (PSWFs) multi-carrier with index modulation approach is proposed with the purpose of improving the spectral efficiency of PSWFs multi-carrier systems. The p...A generalized multiple-mode prolate spherical wave functions (PSWFs) multi-carrier with index modulation approach is proposed with the purpose of improving the spectral efficiency of PSWFs multi-carrier systems. The proposed method,based on the optimized multi-index modulation, does not limit the number of signals in the first and second constellations and abandons the concept of limiting the number of signals in different constellations. It successfully increases the spectrum efficiency of the system while expanding the number of modulation symbol combinations and the index dimension of PSWFs signals. The proposed method outperforms the PSWFs multi-carrier index modulation method based on optimized multiple indexes in terms of spectrum efficiency, but at the expense of system computational complexity and bit error performance. For example, with n=10 subcarriers and a bit error rate of 1×10^(-5),spectral efficiency can be raised by roughly 12.4%.展开更多
用于中高压直流电网互联和隔离的模块化多电平直流变压器(modular multilevel DC transformer,MMDCT)在传输功率变化的过程中会出现电流欠阻尼振荡的问题,从而降低了装置的稳定性,因此文中对振荡抑制展开了研究。首先,通过差模和共模电...用于中高压直流电网互联和隔离的模块化多电平直流变压器(modular multilevel DC transformer,MMDCT)在传输功率变化的过程中会出现电流欠阻尼振荡的问题,从而降低了装置的稳定性,因此文中对振荡抑制展开了研究。首先,通过差模和共模电路中的振荡现象分析,并基于状态空间平均法建立数学模型,从而揭示了MMDCT中的电流振荡机理;进一步提出了一种基于共模和差模分离的电流振荡抑制方法,利用变副边交流侧电压占空比的方式实现漏感电流振荡的抑制,同时采用变桥臂电压占空比的方式进行环流电流振荡的抑制,并给出了相应控制器参数设计依据。最后,通过仿真和实验验证了所提控制方法的有效性,结果表明在基于共模和差模分离的振荡抑制方法下,MMDCT可以在功率变化过程中快速实现电流稳定,有利于提升装置稳定性。展开更多
模块化多电平直流变压器(modular multilevel DC transformer, MMDCT)原边侧串联的子模块电容、桥臂电感及寄生电阻之间存在欠阻尼特性,实际运行中易引发频繁且持续的欠阻尼振荡,给系统的安全可靠运行带来挑战。为改善系统的欠阻尼特性...模块化多电平直流变压器(modular multilevel DC transformer, MMDCT)原边侧串联的子模块电容、桥臂电感及寄生电阻之间存在欠阻尼特性,实际运行中易引发频繁且持续的欠阻尼振荡,给系统的安全可靠运行带来挑战。为改善系统的欠阻尼特性,首先,建立了模块化多电平直流变压器原边侧的环流等效模型,揭示系统欠阻尼振荡产生的机理。其次,引入小量修正角实现每隔半个开关周期对环流抑制电压的修正,主动控制环流变化趋势,有效增强系统内部阻尼,从而抑制了暂态过程中的欠阻尼振荡。然后,采用功率前馈-电容电压环流双闭环控制策略,通过合理的参数设计,确保系统在多场景多工况下具备良好的动态响应性能。最后,通过仿真和实验验证了所提控制策略对MMDCT欠阻尼特性的改善作用。展开更多
基金supported by the National Natural Science Foundation of China(No.22375021,22235003,22261132516&22205021)the BIT Research and Innovation 265 Promoting Project(Grant No.2023YCXZ017)。
文摘Energetic compounds bearing the trinitromethyl group are garnering broad attraction as potential candidates for a new generation of high energy dense oxidizers.In this work,an effective dual modulation strategy involving both molecular isomerization and crystal morphology control was employed to design and optimize trinitromethyl-oxadiazole with improved comprehensive performance.Utilizing this dual strategy,3,5-bis(trinitromethyl)-1,2,4-oxadiazole(3)was synthesized,resulting in the formation of two distinct crystal morphologies(needle and sheet)corresponding to two crystal forms(3-a and3-b).Encouragingly,while maintaining ultra-high oxygen balance(21.73%),3 achieves impressive densities(1.97-1.98 g/cm^(3)).To our knowledge,the density of 1.98 g/cm^(3)for 3-a sets a new record among that of nitrogen-rich monocyclic compounds.Notably,practical crystal morphology prediction was creatively introduced to guide the experimental crystallization conditions of 3,increasing the impact sensitivity and friction sensitivity from 1 J to 80 N(3-a)to 10 J and 240 N(3-b),respectively.Additionally,the crystal structural analyses and theoretical calculations were conducted to elucidate the reasons of differences between 3-a and 3-b in density and stability.This work provides an efficient strategy to enhance performance of trinitromethyl derivatives,broadening the path and expanding the toolbox for energetic materials.
基金supported by the China National Postdoctoral Program for Innovative Talents(BX20200039)the Special Fund Project of“Mount Taishan Scholars”Construction Project in Shandong Province(ts20081130).
文摘A generalized multiple-mode prolate spherical wave functions (PSWFs) multi-carrier with index modulation approach is proposed with the purpose of improving the spectral efficiency of PSWFs multi-carrier systems. The proposed method,based on the optimized multi-index modulation, does not limit the number of signals in the first and second constellations and abandons the concept of limiting the number of signals in different constellations. It successfully increases the spectrum efficiency of the system while expanding the number of modulation symbol combinations and the index dimension of PSWFs signals. The proposed method outperforms the PSWFs multi-carrier index modulation method based on optimized multiple indexes in terms of spectrum efficiency, but at the expense of system computational complexity and bit error performance. For example, with n=10 subcarriers and a bit error rate of 1×10^(-5),spectral efficiency can be raised by roughly 12.4%.
文摘用于中高压直流电网互联和隔离的模块化多电平直流变压器(modular multilevel DC transformer,MMDCT)在传输功率变化的过程中会出现电流欠阻尼振荡的问题,从而降低了装置的稳定性,因此文中对振荡抑制展开了研究。首先,通过差模和共模电路中的振荡现象分析,并基于状态空间平均法建立数学模型,从而揭示了MMDCT中的电流振荡机理;进一步提出了一种基于共模和差模分离的电流振荡抑制方法,利用变副边交流侧电压占空比的方式实现漏感电流振荡的抑制,同时采用变桥臂电压占空比的方式进行环流电流振荡的抑制,并给出了相应控制器参数设计依据。最后,通过仿真和实验验证了所提控制方法的有效性,结果表明在基于共模和差模分离的振荡抑制方法下,MMDCT可以在功率变化过程中快速实现电流稳定,有利于提升装置稳定性。
文摘模块化多电平直流变压器(modular multilevel DC transformer, MMDCT)原边侧串联的子模块电容、桥臂电感及寄生电阻之间存在欠阻尼特性,实际运行中易引发频繁且持续的欠阻尼振荡,给系统的安全可靠运行带来挑战。为改善系统的欠阻尼特性,首先,建立了模块化多电平直流变压器原边侧的环流等效模型,揭示系统欠阻尼振荡产生的机理。其次,引入小量修正角实现每隔半个开关周期对环流抑制电压的修正,主动控制环流变化趋势,有效增强系统内部阻尼,从而抑制了暂态过程中的欠阻尼振荡。然后,采用功率前馈-电容电压环流双闭环控制策略,通过合理的参数设计,确保系统在多场景多工况下具备良好的动态响应性能。最后,通过仿真和实验验证了所提控制策略对MMDCT欠阻尼特性的改善作用。
