The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism, The numerical results demonstrate that as the radius of the curvatur...The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism, The numerical results demonstrate that as the radius of the curvature decreases, detonation fails near the inner wall due to the strong expansion effect. As the radius of the curvature increases, the detonation front near the inner wall can sustain an underdriven detonation. In the case where deto- nation fails, a transverse detonation downstream forms and re-initiates the quenched detonation as it propagates toward the inner wall. Two kinds of propagation modes exist as the detonation is propagating in the curved channel. One is that the detonation fails first, and then a following transverse detonation initiates the quenched detonation and this process repeats itself. The other one is that without detonation failure and re-initiation, a steady detonation exists which consists of an underdriven detonation front near the inner wall subject to the diffraction and an overdriven detonation near the outer wall subject to the compression.展开更多
For the superconductors(Rb_xK_(1-x))_3C_(60)(x=0.1),according to BCS theory and assuming that the virtual phonon acting on electron-pair is corresponding to the intrasolecular vibration in the bnckminnterfullerene C_(...For the superconductors(Rb_xK_(1-x))_3C_(60)(x=0.1),according to BCS theory and assuming that the virtual phonon acting on electron-pair is corresponding to the intrasolecular vibration in the bnckminnterfullerene C_(60),a linear relationship of the superconducting transition temperature T_c with x has been derived,which is in agreement with the experimentals,展开更多
ESR measurements using spin trapping technique were carried out for β-carotene-halobenzene system under UV light irradiation.The ESR spectra observed in the presence and in the absence of β-carotene are markedly dif...ESR measurements using spin trapping technique were carried out for β-carotene-halobenzene system under UV light irradiation.The ESR spectra observed in the presence and in the absence of β-carotene are markedly different.The possible scheme of β-carotene interacting with halogen atom was proposed.展开更多
In the presence of alkali nitrite and carbonate,some nitrobenzenes subs- tituted by strongly electron withdrawing group undergo a self condensation in an aprotic polar sotvent to give symmetrical disubstituted dipheny...In the presence of alkali nitrite and carbonate,some nitrobenzenes subs- tituted by strongly electron withdrawing group undergo a self condensation in an aprotic polar sotvent to give symmetrical disubstituted diphenyl ethers in good yields.A possible mechanism is discussed,the nucteophilic aromatic substitution S_NAr and S_(Ru)Ar may occur simultaneously.展开更多
When criminal suspects are being investigated for criminal responsibil- ity, they are the most vulnerable to infringement by public power. Thus, they need more special attention and protection. It is the in- evitable ...When criminal suspects are being investigated for criminal responsibil- ity, they are the most vulnerable to infringement by public power. Thus, they need more special attention and protection. It is the in- evitable requirement of the modern democratic rule of law, and also the inevitable historic choice of respecting and protecting human rights.展开更多
The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting challenge.Although Na_(4)MnCr(PO_(4))_(3)has emerged as one of...The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting challenge.Although Na_(4)MnCr(PO_(4))_(3)has emerged as one of the most promising high-energy-density cathode materials owing to its three-electron reactions,it still suffers from serious structural distortion upon repetitive charge/discharge processes caused by the Jahn-Teller active Mn^(3+).Herein,the selective substitution of Cr by Zr in Na_(4)MnCr(PO_(4))_(3)was explored to enhance the structural stability,due to the pinning effect of Zr ions and the≈2.9-electron reactions,as-prepared Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C delivers a high capacity retention of 85.94%over 500 cycles at 5 C and an ultrahigh capacity of 156.4 mAh g^(-1)at 0.1 C,enabling the stable energy output as high as 555.2 Wh kg^(-1).Moreover,during the whole charge/discharge process,a small volume change of only 6.7%was verified by in situ X-ray diffraction,and the reversible reactions of Cr^(3+)/Cr^(4+),Mn^(3+)/Mn^(4+),and Mn^(2+)/Mn^(3+)redox couples were identified via ex situ X-ray photoelectron spectroscopy analyses.Galvanostatic intermittent titration technique tests and density functional theory calculations further demonstrated the fast reaction kinetics of the Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C electrode.This work offers new opportunities for designing high-energy and high-stability NASICON cathodes by ion doping.展开更多
Based on the particularities of gas outbursts,i.e.,low gas bearing capacity and low gas pressure in the "Three Soft" coal seam in western Henan,we applied the theories of plate tectonics and regional structu...Based on the particularities of gas outbursts,i.e.,low gas bearing capacity and low gas pressure in the "Three Soft" coal seam in western Henan,we applied the theories of plate tectonics and regional structural evolution to investigate the mechanism of this seam and its impact on the coal seam gas formation.Our investigation revealed that coal and gas outbursts are distributed in a strip in a NW direction,with a number of high-penetration mines scattered towards the south side and low-gas mines largely located on the north side.We analyzed the statistics of 38 gas explosions and the rock-coal sturdiness number coefficient f of 167 sampling sites in the region and found the gas outburst mechanism that features a "low indicator outburst phenomenon".The mechanism is characterized by structural coal as its core,a low gas bearing capacity,low gas pressure and sturdiness coefficient f mostly less than 0.3.Our research results provide a theoretical foundation for effective control of gas disasters.展开更多
Hypoxia is a common pathological process in various clinical diseases and is characterized by abnormal changes in metabolism, function, and morphological structure of tissues resulting from insufficient oxygen supply ...Hypoxia is a common pathological process in various clinical diseases and is characterized by abnormal changes in metabolism, function, and morphological structure of tissues resulting from insufficient oxygen supply or oxygen barriers in tissues. In particular, hypoxia in vital organs such as the brain and heart is an important cause of death;. The prevention of tissue hypoxia and the展开更多
Effect of mechanical stress on magnetic properties of an exchange-biased ferromagnetic/antiferromagnetic bilayer deposited on a flexible substrate is investigated. The hysteresis loops with different magnitudes and or...Effect of mechanical stress on magnetic properties of an exchange-biased ferromagnetic/antiferromagnetic bilayer deposited on a flexible substrate is investigated. The hysteresis loops with different magnitudes and orientations of the stress can be classified into three types. The corresponding physical conditions for each type of the loop are deduced based on the principle of minimal energy. The equation of the critical stress is derived, which can judge whether the loops show hysteresis or not. Numerical calculations suggest that except for the magnitude of the mechanical stress, the relative orientation of the stress is also an important factor to tune the exchange bias effect.展开更多
The question of possible teleconnections between the middle latitude general circulation and the Indian south-west monsoon was investigated in this paper. Within the framework of a simple model it was shown that there...The question of possible teleconnections between the middle latitude general circulation and the Indian south-west monsoon was investigated in this paper. Within the framework of a simple model it was shown that there can exist such an interaction via the ultra-long Rossby waves.展开更多
Production of’renewable Methane’has attracted renewed research interest as a fundamental probe reaction and process for CO_(2)utilization through potential use in Cl fuel production and even for future space explora...Production of’renewable Methane’has attracted renewed research interest as a fundamental probe reaction and process for CO_(2)utilization through potential use in Cl fuel production and even for future space exploration technologies.CO_(2)methanation is a structure sensitive reaction on Ni/CeO_(2)catalysts.To precisely elucidate the size effect of the Ni metal center on the CO_(2)methanation performance,we prepared2%Ni/CeO_(2)catalysts with pre-synthesized uniform Ni particles(2,4 and 8 nm)on a high surface area CeO_(2)support.Transmission electron microscopy(TEM)and ambient pressure X-ray photo spectroscopy(AP-XPS)characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions.The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts,and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts,respectively.The DRIFTS studies revealed that the larger Ni(8 nm particles)over CeO_(2)efficiently facilitated the hydrogenation of the surface formate intermediates,which is proposed as the rate determining step accounting for the excellent CO_(2)methanation performance.展开更多
Three-dimensional-ordered Yb/Er co-doped Bi2Ti207 inverse opal, powder, and disordered reference sam- ples are prepared and their upconversion （UC） emission properties and mechanisms are investigated. Sig- nificant ...Three-dimensional-ordered Yb/Er co-doped Bi2Ti207 inverse opal, powder, and disordered reference sam- ples are prepared and their upconversion （UC） emission properties and mechanisms are investigated. Sig- nificant suppression of UC emission is detected when the photonic band-gaps overlap with Er3＋ UC green emission bands. Interestingly, green and red UC emissions follow a two-photon process in the powder sample but a three-photon one in the inverse opal.展开更多
The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied. Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi- tive trigonometrica...The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied. Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi- tive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is 5.0 ×10^(-6) mol/L and the linear calibration range extends up to 1.0 ×10^(-2) mol/L; the relative standard deviation for 1.0 ×10^(-5) mol / L chloride is 5%. The influencing factors for chloride determination are also discussed. The possible mechanism for the electrochemiluminescence reaction may be due to the oxidation of chloride ion in the solution to ClO^-, and the latter acts on luminol and then gives out luminescence. The method has been applied to determine the total chloride in tap water with satisfactory results.展开更多
Nickel-CeO_(2)-based materials are commonly used for the thermal catalytic hydrogenation of CO_(2).However,high Ni loadings and low CO selectivity restrict their use in the reverse water–gas shift(RWGS)reaction.Herei...Nickel-CeO_(2)-based materials are commonly used for the thermal catalytic hydrogenation of CO_(2).However,high Ni loadings and low CO selectivity restrict their use in the reverse water–gas shift(RWGS)reaction.Herein,we demonstrate a highly active,robust,and low-Ni-doped(1.1 wt.%)CeO_(2) catalyst(1.0-Ni-CeO_(2)).The Ni-based-mass-specific CO formation rate reaches up to 1,542 mmol·gNi^(−1)·h^(−1) with 100%CO selectivity at 300°C for 100 h,among the best values reported in the literature.Density functional theory(DFT)and diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)results reveal that the enhanced catalytic activity is attributed to the abundant Ce–H species,while the high selectivity results from low CO affinity.More importantly,a new reaction mechanism is proposed,which involves the reduction of bicarbonate to generate formate intermediate and CO by the H−released from Ce–H species.The new findings in this work will benefit the design of economic,efficient,and robust catalysts for low-temperature RWGS reactions.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11390363 and 11325209
文摘The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism, The numerical results demonstrate that as the radius of the curvature decreases, detonation fails near the inner wall due to the strong expansion effect. As the radius of the curvature increases, the detonation front near the inner wall can sustain an underdriven detonation. In the case where deto- nation fails, a transverse detonation downstream forms and re-initiates the quenched detonation as it propagates toward the inner wall. Two kinds of propagation modes exist as the detonation is propagating in the curved channel. One is that the detonation fails first, and then a following transverse detonation initiates the quenched detonation and this process repeats itself. The other one is that without detonation failure and re-initiation, a steady detonation exists which consists of an underdriven detonation front near the inner wall subject to the diffraction and an overdriven detonation near the outer wall subject to the compression.
文摘For the superconductors(Rb_xK_(1-x))_3C_(60)(x=0.1),according to BCS theory and assuming that the virtual phonon acting on electron-pair is corresponding to the intrasolecular vibration in the bnckminnterfullerene C_(60),a linear relationship of the superconducting transition temperature T_c with x has been derived,which is in agreement with the experimentals,
文摘ESR measurements using spin trapping technique were carried out for β-carotene-halobenzene system under UV light irradiation.The ESR spectra observed in the presence and in the absence of β-carotene are markedly different.The possible scheme of β-carotene interacting with halogen atom was proposed.
基金Supported by the Education Department of Ministry of Metatturgical Industry of PRC.
文摘In the presence of alkali nitrite and carbonate,some nitrobenzenes subs- tituted by strongly electron withdrawing group undergo a self condensation in an aprotic polar sotvent to give symmetrical disubstituted diphenyl ethers in good yields.A possible mechanism is discussed,the nucteophilic aromatic substitution S_NAr and S_(Ru)Ar may occur simultaneously.
文摘When criminal suspects are being investigated for criminal responsibil- ity, they are the most vulnerable to infringement by public power. Thus, they need more special attention and protection. It is the in- evitable requirement of the modern democratic rule of law, and also the inevitable historic choice of respecting and protecting human rights.
基金Financial support from the National Natural Science Foundation of China(22075016 and 22103057)Fundamental Research Funds for the Central Universities(FRF-TP-20-020A3 and QNXM20220060)+1 种基金Interdisciplinary Research Project for Young Teachers of USTB(FRF-IDRY-21-011)111 Project(B170003 and B12015)
文摘The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting challenge.Although Na_(4)MnCr(PO_(4))_(3)has emerged as one of the most promising high-energy-density cathode materials owing to its three-electron reactions,it still suffers from serious structural distortion upon repetitive charge/discharge processes caused by the Jahn-Teller active Mn^(3+).Herein,the selective substitution of Cr by Zr in Na_(4)MnCr(PO_(4))_(3)was explored to enhance the structural stability,due to the pinning effect of Zr ions and the≈2.9-electron reactions,as-prepared Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C delivers a high capacity retention of 85.94%over 500 cycles at 5 C and an ultrahigh capacity of 156.4 mAh g^(-1)at 0.1 C,enabling the stable energy output as high as 555.2 Wh kg^(-1).Moreover,during the whole charge/discharge process,a small volume change of only 6.7%was verified by in situ X-ray diffraction,and the reversible reactions of Cr^(3+)/Cr^(4+),Mn^(3+)/Mn^(4+),and Mn^(2+)/Mn^(3+)redox couples were identified via ex situ X-ray photoelectron spectroscopy analyses.Galvanostatic intermittent titration technique tests and density functional theory calculations further demonstrated the fast reaction kinetics of the Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C electrode.This work offers new opportunities for designing high-energy and high-stability NASICON cathodes by ion doping.
基金support for this work,provided by the National Natural Science Foundation of China (No.50834005)
文摘Based on the particularities of gas outbursts,i.e.,low gas bearing capacity and low gas pressure in the "Three Soft" coal seam in western Henan,we applied the theories of plate tectonics and regional structural evolution to investigate the mechanism of this seam and its impact on the coal seam gas formation.Our investigation revealed that coal and gas outbursts are distributed in a strip in a NW direction,with a number of high-penetration mines scattered towards the south side and low-gas mines largely located on the north side.We analyzed the statistics of 38 gas explosions and the rock-coal sturdiness number coefficient f of 167 sampling sites in the region and found the gas outburst mechanism that features a "low indicator outburst phenomenon".The mechanism is characterized by structural coal as its core,a low gas bearing capacity,low gas pressure and sturdiness coefficient f mostly less than 0.3.Our research results provide a theoretical foundation for effective control of gas disasters.
基金financially supported by 1226 major project [Grant no.AWS16J018]
文摘Hypoxia is a common pathological process in various clinical diseases and is characterized by abnormal changes in metabolism, function, and morphological structure of tissues resulting from insufficient oxygen supply or oxygen barriers in tissues. In particular, hypoxia in vital organs such as the brain and heart is an important cause of death;. The prevention of tissue hypoxia and the
基金Supported by the Youth Science Foundation of Shanxi Province under Grant No 2013021010-3the National Natural Science Foundation of China under Grant Nos 61434002 and 11404202
文摘Effect of mechanical stress on magnetic properties of an exchange-biased ferromagnetic/antiferromagnetic bilayer deposited on a flexible substrate is investigated. The hysteresis loops with different magnitudes and orientations of the stress can be classified into three types. The corresponding physical conditions for each type of the loop are deduced based on the principle of minimal energy. The equation of the critical stress is derived, which can judge whether the loops show hysteresis or not. Numerical calculations suggest that except for the magnitude of the mechanical stress, the relative orientation of the stress is also an important factor to tune the exchange bias effect.
文摘The question of possible teleconnections between the middle latitude general circulation and the Indian south-west monsoon was investigated in this paper. Within the framework of a simple model it was shown that there can exist such an interaction via the ultra-long Rossby waves.
基金supported by the U.S.Department of Energy under contract no.DE-SC0012704supported by a U.S.Department of Energy Early Career Award+2 种基金ICREA Academia program and projects MICINN/FEDER RTI2018093996-B-C31 and GC 2017 SGR 128financial support from the Natural Science Foundation of China(22002140)Young Elite Scientist Sponsorship Program by CAST,NO.2019QNRC001。
文摘Production of’renewable Methane’has attracted renewed research interest as a fundamental probe reaction and process for CO_(2)utilization through potential use in Cl fuel production and even for future space exploration technologies.CO_(2)methanation is a structure sensitive reaction on Ni/CeO_(2)catalysts.To precisely elucidate the size effect of the Ni metal center on the CO_(2)methanation performance,we prepared2%Ni/CeO_(2)catalysts with pre-synthesized uniform Ni particles(2,4 and 8 nm)on a high surface area CeO_(2)support.Transmission electron microscopy(TEM)and ambient pressure X-ray photo spectroscopy(AP-XPS)characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions.The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts,and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts,respectively.The DRIFTS studies revealed that the larger Ni(8 nm particles)over CeO_(2)efficiently facilitated the hydrogenation of the surface formate intermediates,which is proposed as the rate determining step accounting for the excellent CO_(2)methanation performance.
基金supported by the Natural Science Foundation of Yunnan Province(No.2010ZC038)the Open Foundation of Key Laboratory of Advanced Materialsin Rare,Precious and Non-ferrous Metals,Ministry of Education,and the Open Foundation of Key Laboratory of Advanced Materials of Yunnan Province(No.ZDS2010011B)
文摘Three-dimensional-ordered Yb/Er co-doped Bi2Ti207 inverse opal, powder, and disordered reference sam- ples are prepared and their upconversion （UC） emission properties and mechanisms are investigated. Sig- nificant suppression of UC emission is detected when the photonic band-gaps overlap with Er3＋ UC green emission bands. Interestingly, green and red UC emissions follow a two-photon process in the powder sample but a three-photon one in the inverse opal.
基金the National Natural Science Foundation of China.
文摘The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied. Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi- tive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is 5.0 ×10^(-6) mol/L and the linear calibration range extends up to 1.0 ×10^(-2) mol/L; the relative standard deviation for 1.0 ×10^(-5) mol / L chloride is 5%. The influencing factors for chloride determination are also discussed. The possible mechanism for the electrochemiluminescence reaction may be due to the oxidation of chloride ion in the solution to ClO^-, and the latter acts on luminol and then gives out luminescence. The method has been applied to determine the total chloride in tap water with satisfactory results.
基金the Science and Technology Project of Shenzhen(No.JCYJ20190806155814624)the National Natural Science Foundation of China(No.22002120)the Fundamental Research Funds for the Central Universities(No.3102017jc01001).
文摘Nickel-CeO_(2)-based materials are commonly used for the thermal catalytic hydrogenation of CO_(2).However,high Ni loadings and low CO selectivity restrict their use in the reverse water–gas shift(RWGS)reaction.Herein,we demonstrate a highly active,robust,and low-Ni-doped(1.1 wt.%)CeO_(2) catalyst(1.0-Ni-CeO_(2)).The Ni-based-mass-specific CO formation rate reaches up to 1,542 mmol·gNi^(−1)·h^(−1) with 100%CO selectivity at 300°C for 100 h,among the best values reported in the literature.Density functional theory(DFT)and diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)results reveal that the enhanced catalytic activity is attributed to the abundant Ce–H species,while the high selectivity results from low CO affinity.More importantly,a new reaction mechanism is proposed,which involves the reduction of bicarbonate to generate formate intermediate and CO by the H−released from Ce–H species.The new findings in this work will benefit the design of economic,efficient,and robust catalysts for low-temperature RWGS reactions.
