Regulating the interfacial charge transfer is pivotal for elucidating the kinetics of engineering the interface between the light-harvesting semiconductor and the substrate/catalyst for photoelectrocatalytic water spl...Regulating the interfacial charge transfer is pivotal for elucidating the kinetics of engineering the interface between the light-harvesting semiconductor and the substrate/catalyst for photoelectrocatalytic water splitting.In this study,we constructed a superior Ti-doped hematite photoanode(TiFeO)by employing SnOx as an electron transfer mediator,partially oxidized graphene(pGO)as a hole transfer mediator,and molecular Co cubane as a water oxidation catalyst.The Co/pGO/TiFeO/SnO_(x)integrated system achieves a photocurrent density of 2.52 mA cm^(-2) at 1.23 VRHE,which is 2.4 times higher than bare photoanode(1.04 mA cm^(-2)),with operational stability up to 100 h.Kinetic measurements indicate that pGO can promote charge transfer from TiFeO to the Co cubane catalyst.In contrast,SnOx reduces charge recombination at the interface between TiFeO and the fluorinated tin oxide substrate.In-situ infrared spectroscopy shows the formation of an O–O bonded intermediate during water oxidation.This study highlights the crucial role of incorporating dual charge-transfer mediators into photoelectrodes for efficient solar energy conversion.展开更多
The monkeypox virus(MPXV)has triggered a current outbreak globally.Genome sequencing of MPXV and rapid tracing of genetic variants will benefit disease diagnosis and control.It is a significant challenge but necessary...The monkeypox virus(MPXV)has triggered a current outbreak globally.Genome sequencing of MPXV and rapid tracing of genetic variants will benefit disease diagnosis and control.It is a significant challenge but necessary to optimize the strategy and application of rapid full-length genome identification and to track variations of MPXV in clinical specimens with low viral loads,as it is one of the DNA viruses with the largest genome and the most AT-biased,and has a significant number of tandem repeats.Here we evaluated the performance of metagenomic and amplicon sequencing techniques,and three sequencing platforms in MPXV genome sequencing based on multiple clinical specimens of five mpox cases in Chinese mainland.We rapidly identified the full-length genome of MPXV with the assembly of accurate tandem repeats in multiple clinical specimens.Amplicon sequencing enables cost-effective and rapid sequencing of clinical specimens to obtain high-quality MPXV genomes.Third-generation sequencing facilitates the assembly of the terminal tandem repeat regions in the monkeypox virus genome and corrects a common misassembly in published sequences.Besides,several intra-host single nucleotide variations were identified in the first imported mpox case.This study offers an evaluation of various strategies aimed at identifying the complete genome of MPXV in clinical specimens.The findings of this study will significantly enhance the surveillance of MPXV.展开更多
Thin-walled torispherical heads under internal pressure can fail by plastic buckling because of compressive circumferential stresses in the head knuckle.However,existing formulas still have limitations,such as complic...Thin-walled torispherical heads under internal pressure can fail by plastic buckling because of compressive circumferential stresses in the head knuckle.However,existing formulas still have limitations,such as complicated expressions and low accuracy,in determining buckling pressure.In this paper,we propose a new formula for calculating the buckling pressure of torispherical heads based on elastic-plastic analysis and experimental results.First,a finite element(FE)method based on the arc-length method is established to calculate the plastic buckling pressure of torispherical heads,considering the effects of material strain hardening and geometrical nonlinearity.The buckling pressure results calculated by the FE method in this paper have good consistency with those of BOSOR5,which is a program for calculating the elastic-plastic bifurcation buckling pressure based on the finite difference energy method.Second,the effects of geometric parameters,material parameters,and restraint form of head edge on buckling pressure are investigated.Third,a new formula for calculating plastic buckling pressure is developed by fitting the curve of FE results and introducing a reduction factor determined from experimental data.Finally,based on the experimental results,we compare the predictions of the new formula with those of existing formulas.It is shown that the new formula has a higher accuracy than the existing ones.展开更多
Molybdenum carbide(Mo_(2)C)is a promising non-noble metal electrocatalyst with electronic structures similar to Pt for hydrogen evolution reaction(HER).However,strong H^(*)adsorption at the Mo sites hinders the improv...Molybdenum carbide(Mo_(2)C)is a promising non-noble metal electrocatalyst with electronic structures similar to Pt for hydrogen evolution reaction(HER).However,strong H^(*)adsorption at the Mo sites hinders the improvement of HER performance.Here,we synthesized monodisperse hollow Mo_(2)C nanoreactors,in which the carbon dots(CD)were in situ formed onto the surface of Mo_(2)C through carburization reactions.According to finite element simulation and analysis,the CD@Mo_(2)C possesses better mesoscale diffusion properties than Mo_(2)C alone.The optimized CD@Mo_(2)C nanoreactor demonstrates superior HER performance in alkaline electrolyte with a low overpotential of 57 mV at 10 mA cm^(−2),which is better than most Mo_(2)C-based electrocatalysts.Moreover,CD@Mo_(2)C exhibits excellent electrochemical stability during 240 h,confirmed by operando Raman and X-ray diffraction(XRD).Density functional theory(DFT)calculations show that carbon dots cause the d-band center of CD@Mo_(2)C to shift away from Fermi level,promoting water dissociation and the desorption of H^(*).This study provides a reasonable strategy towards high-activity Mo-based HER eletrocatalysts by modulating the strength of Mo–H bonds.展开更多
针对多重同步挤压变换及其改进算法存在的未重排点问题,提出了一种基于最大系数的多重同步挤压变换(maximum coefficient based multi-synchrosqueezing transform,简称MCMSST)方法来识别时变结构非平稳响应信号的瞬时频率(instantaneou...针对多重同步挤压变换及其改进算法存在的未重排点问题,提出了一种基于最大系数的多重同步挤压变换(maximum coefficient based multi-synchrosqueezing transform,简称MCMSST)方法来识别时变结构非平稳响应信号的瞬时频率(instantaneous frequency,简称IF)。首先,引入傅里叶频谱来辅助多分量响应信号选取截止频率;其次,对响应信号进行短时傅里叶变换(short time fourier transform,简称STFT),针对短时傅里叶变换系数求取针对时间的偏导,从而获得估算的瞬时频率;然后,在对瞬时频率的估算值进行多次迭代的基础上,仅保留时频系数模值最大处所对应的估算瞬时频率,并将其余位置的瞬时频率值归零;最后,对时频系数模值最大处所对应的瞬时频率进行时频重排即可得到细化后的瞬时频带。由于基于MCMSST方法提取的是瞬时频带,故采用时频系数模极大值法在限定的频带范围内提取瞬时频率曲线。通过2组数值算例和1个铝合金悬臂梁质量突变试验,验证了所提方法的有效性。研究结果表明,MCMSST方法不仅彻底解决了未重排点问题,而且提高了瞬时频率的识别精度和抗噪能力。展开更多
文摘Regulating the interfacial charge transfer is pivotal for elucidating the kinetics of engineering the interface between the light-harvesting semiconductor and the substrate/catalyst for photoelectrocatalytic water splitting.In this study,we constructed a superior Ti-doped hematite photoanode(TiFeO)by employing SnOx as an electron transfer mediator,partially oxidized graphene(pGO)as a hole transfer mediator,and molecular Co cubane as a water oxidation catalyst.The Co/pGO/TiFeO/SnO_(x)integrated system achieves a photocurrent density of 2.52 mA cm^(-2) at 1.23 VRHE,which is 2.4 times higher than bare photoanode(1.04 mA cm^(-2)),with operational stability up to 100 h.Kinetic measurements indicate that pGO can promote charge transfer from TiFeO to the Co cubane catalyst.In contrast,SnOx reduces charge recombination at the interface between TiFeO and the fluorinated tin oxide substrate.In-situ infrared spectroscopy shows the formation of an O–O bonded intermediate during water oxidation.This study highlights the crucial role of incorporating dual charge-transfer mediators into photoelectrodes for efficient solar energy conversion.
基金supported by the National Key Research and Development Program of China(2022YFC2303401,2022YFC2304100,2016YFD0500301,2021YFC0863300)the Beijing Science and Technology Plan(Z211100002521017)the National Natural Science Foundation of China(82241080)。
文摘The monkeypox virus(MPXV)has triggered a current outbreak globally.Genome sequencing of MPXV and rapid tracing of genetic variants will benefit disease diagnosis and control.It is a significant challenge but necessary to optimize the strategy and application of rapid full-length genome identification and to track variations of MPXV in clinical specimens with low viral loads,as it is one of the DNA viruses with the largest genome and the most AT-biased,and has a significant number of tandem repeats.Here we evaluated the performance of metagenomic and amplicon sequencing techniques,and three sequencing platforms in MPXV genome sequencing based on multiple clinical specimens of five mpox cases in Chinese mainland.We rapidly identified the full-length genome of MPXV with the assembly of accurate tandem repeats in multiple clinical specimens.Amplicon sequencing enables cost-effective and rapid sequencing of clinical specimens to obtain high-quality MPXV genomes.Third-generation sequencing facilitates the assembly of the terminal tandem repeat regions in the monkeypox virus genome and corrects a common misassembly in published sequences.Besides,several intra-host single nucleotide variations were identified in the first imported mpox case.This study offers an evaluation of various strategies aimed at identifying the complete genome of MPXV in clinical specimens.The findings of this study will significantly enhance the surveillance of MPXV.
基金supported by the National Natural Science Foundation of China(No.52105161).
文摘Thin-walled torispherical heads under internal pressure can fail by plastic buckling because of compressive circumferential stresses in the head knuckle.However,existing formulas still have limitations,such as complicated expressions and low accuracy,in determining buckling pressure.In this paper,we propose a new formula for calculating the buckling pressure of torispherical heads based on elastic-plastic analysis and experimental results.First,a finite element(FE)method based on the arc-length method is established to calculate the plastic buckling pressure of torispherical heads,considering the effects of material strain hardening and geometrical nonlinearity.The buckling pressure results calculated by the FE method in this paper have good consistency with those of BOSOR5,which is a program for calculating the elastic-plastic bifurcation buckling pressure based on the finite difference energy method.Second,the effects of geometric parameters,material parameters,and restraint form of head edge on buckling pressure are investigated.Third,a new formula for calculating plastic buckling pressure is developed by fitting the curve of FE results and introducing a reduction factor determined from experimental data.Finally,based on the experimental results,we compare the predictions of the new formula with those of existing formulas.It is shown that the new formula has a higher accuracy than the existing ones.
基金financially supported by the National Natural Science Foundation of China (22372001)Starting Fund for Scientific Research of High-Level Talents, Anhui Agricultural University (rc382108)+1 种基金Anhui Provincial Key Research and Development Plan (2022e07020037)Innovation and Entrepreneurship Training Program for College Students (X202310364204, S202210364046, X202310364209)
文摘Molybdenum carbide(Mo_(2)C)is a promising non-noble metal electrocatalyst with electronic structures similar to Pt for hydrogen evolution reaction(HER).However,strong H^(*)adsorption at the Mo sites hinders the improvement of HER performance.Here,we synthesized monodisperse hollow Mo_(2)C nanoreactors,in which the carbon dots(CD)were in situ formed onto the surface of Mo_(2)C through carburization reactions.According to finite element simulation and analysis,the CD@Mo_(2)C possesses better mesoscale diffusion properties than Mo_(2)C alone.The optimized CD@Mo_(2)C nanoreactor demonstrates superior HER performance in alkaline electrolyte with a low overpotential of 57 mV at 10 mA cm^(−2),which is better than most Mo_(2)C-based electrocatalysts.Moreover,CD@Mo_(2)C exhibits excellent electrochemical stability during 240 h,confirmed by operando Raman and X-ray diffraction(XRD).Density functional theory(DFT)calculations show that carbon dots cause the d-band center of CD@Mo_(2)C to shift away from Fermi level,promoting water dissociation and the desorption of H^(*).This study provides a reasonable strategy towards high-activity Mo-based HER eletrocatalysts by modulating the strength of Mo–H bonds.
文摘针对多重同步挤压变换及其改进算法存在的未重排点问题,提出了一种基于最大系数的多重同步挤压变换(maximum coefficient based multi-synchrosqueezing transform,简称MCMSST)方法来识别时变结构非平稳响应信号的瞬时频率(instantaneous frequency,简称IF)。首先,引入傅里叶频谱来辅助多分量响应信号选取截止频率;其次,对响应信号进行短时傅里叶变换(short time fourier transform,简称STFT),针对短时傅里叶变换系数求取针对时间的偏导,从而获得估算的瞬时频率;然后,在对瞬时频率的估算值进行多次迭代的基础上,仅保留时频系数模值最大处所对应的估算瞬时频率,并将其余位置的瞬时频率值归零;最后,对时频系数模值最大处所对应的瞬时频率进行时频重排即可得到细化后的瞬时频带。由于基于MCMSST方法提取的是瞬时频带,故采用时频系数模极大值法在限定的频带范围内提取瞬时频率曲线。通过2组数值算例和1个铝合金悬臂梁质量突变试验,验证了所提方法的有效性。研究结果表明,MCMSST方法不仅彻底解决了未重排点问题,而且提高了瞬时频率的识别精度和抗噪能力。
