Under the background of new engineering,the reform of the comprehensive practical course system for mechanical and electronic engineering majors actively responds to the challenges posed by the new round of technologi...Under the background of new engineering,the reform of the comprehensive practical course system for mechanical and electronic engineering majors actively responds to the challenges posed by the new round of technological revolution and industrial transformation to higher education,cultivating top-notch innovative intellectuals with comprehensive engineering qualities,meeting the requirements of being able to solve complex engineering problems rather than just cognitive capabilities,forming two core courses through reconstructing and reshaping the core courses of the major.The core courses include Drive,Measurement,and Control I and Drive,Measurement,and Control II,which highlight the comprehensive framework of mechanical and electronic engineering professional knowledge,continuing the comprehensive practical course system based on the unity of knowledge and practice,following the trend of new engineering,highlighting the practicality of professional innovation,assisting engineering education reform,and promoting high-quality development of new engineering professionals cultivation.展开更多
With the arrival of the intelligence era of Industry 4.0,social development has shown complex and diversified characteristics,gradually forming an innovation ecological environment constructed by vertical interaction ...With the arrival of the intelligence era of Industry 4.0,social development has shown complex and diversified characteristics,gradually forming an innovation ecological environment constructed by vertical interaction of multi-layer innovation systems and horizontal collaboration of multiple organizations and departments,which has posed extremely challenging requirements for higher engineering education to cultivate engineering talents with comprehensive engineering qualities who can solve complex engineering problems.However,practical engineering problems may involve a complex knowledge chain of interdisciplinary and multi-disciplinary cross-coupling.Therefore,higher engineering education needs to form a new interdisciplinary and multi-disciplinary integrated engineering innovation talent training system.Based on the characteristics of the mechanical and electronic engineering major,we will reshape and reconstruct the core courses of the mechanical and electronic engineering major.Two core courses are formed:Drive and Measurement and Control I and Drive and Measurement and Control II,with information flow and energy flow as the main lines,following up with the comprehensive practical curriculum system based on the unity of knowledge and practice and ability-oriented thinking,supporting teaching objectives,promoting students’individual development,and providing guidelines for relevant curriculum reforms.展开更多
Conventional electronics is planar, hard, and rigid due to the intrinsic brittle nature of inorganic semiconductor materials (e.g., silicon and gallium arsenide). The modern electronic technology has typically been ...Conventional electronics is planar, hard, and rigid due to the intrinsic brittle nature of inorganic semiconductor materials (e.g., silicon and gallium arsenide). The modern electronic technology has typically been concerned with large or small but durable and long-lasting electronics. Recently developed materials and mechanics concepts yield unconventional electronics with unique characteristics (e.g., deformable, degradable, etc.).展开更多
Ceramic materials were investigated as thermal barrier coatings and electrolytes. Electrophoretic deposition(EPD) and physical vapor deposition(PVD) were employed to fabricate samples, and the mechanical propertie...Ceramic materials were investigated as thermal barrier coatings and electrolytes. Electrophoretic deposition(EPD) and physical vapor deposition(PVD) were employed to fabricate samples, and the mechanical properties and microstructure were examined by nanoindentation and microscopy, respectively. Yttria-stabilized zirconia/alumina(YSZ/Al2O3) composite coatings, a candidate for thermal barrier coatings, yield a kinky, rather than smooth, load–displacement curve. Scanning electron microscope(SEM) examination reveals that the kinky curve is because of the porous microstructure and cracks are caused by the compression of the indenter. Li0.34La0.51 Ti O2.94(LLTO) on Si/Sr Ru O3(Si/SRO) substrates, an ionic conductor in nature, demonstrates electronic performance. Although SEM images show a continuous and smooth microstructure, a close examination of the microstructure by transmission electron microscopy(TEM) reveals that the observed spikes indicate electronic performance. Therefore, we can conclude that ceramic coatings could serve multiple purposes but their properties are microstructure-dependent.展开更多
Structural, electronic and mechanical properties of the nH-SiC (n = 2, 4, 6, 8 and 10) polytypes are calculated by using the first-principles calculations based on the density-functional theory approach. The optimiz...Structural, electronic and mechanical properties of the nH-SiC (n = 2, 4, 6, 8 and 10) polytypes are calculated by using the first-principles calculations based on the density-functional theory approach. The optimized lattice parameters of nH-SiC are in good agreement with the experimental data. The mechanical properties, including elastic constants, bulk modulus, Young's modulus, shear modulus and Poisson's ratio, are calculated. The analysis of elastic properties indicates that the effects of n on the mechanical properties of the five nil-SiC structures have no difference. The indirect band gap relationship for the live polytypes is Ebg2H 〉 Ebg4H 〉 Ebg6H 〉 Ebg10H 〉 EbgsH.展开更多
The Measures for the Administration of the Import of Mechanical and Electronic' Products co-formulated by the Ministry of Commerce,the General Administration of Customs and the General Administration of Quality Su...The Measures for the Administration of the Import of Mechanical and Electronic' Products co-formulated by the Ministry of Commerce,the General Administration of Customs and the General Administration of Quality Supervision,Inspection and Quarantine,was hereby promul- gated,which entered into force as of May 1,2008.展开更多
Recalcitrance and the inherent heterogeneity of lignin structure are the major bottlenecks to impede the popularization of lignin-based chemicals production processes.Recent works suggested a promising pathway for lig...Recalcitrance and the inherent heterogeneity of lignin structure are the major bottlenecks to impede the popularization of lignin-based chemicals production processes.Recent works suggested a promising pathway for lignin depolymerization and lignin-derived bio-oil upgrading via an electrochemical biorefinery(a process in which lignin valorization is performed via electrochemical oxidation or reduction).This review presents the progress on chemicals synthesis and bio-oil upgrading from lignin by an electrochemical biorefinery,relating to the lignin biosynthesis pathway,reaction pathway of lignin electrochemical conversion,inner-sphere and outer-sphere electron transfer mechanism,basic kinetics and thermodynamics in electrochemistry,and the recent embodiments analysis with the emphasis on the respective feature and limitation for lignin electrochemical oxidative and reductive conversion.Lastly,the challenge and perspective associated with lignin electrochemical biorefinery are discussed.Present-day results indicate that more work should be performed to promote efficiency,selectivity,and stability in pursuing a lignin electrochemical biorefinery.One of the most promising developing directions appears to be integrating various types of lignin electrochemical conversion strategies and other existing or evolving lignin valorization technologies.This review aims to provide more references and discussion on the development for lignin electrochemical biorefinery.展开更多
In the present work, for the first time, the main details of the electronic mechanism of the synergistic antioxidant interaction between different pairs: phenolic food acid and glutathione and the stable radical catio...In the present work, for the first time, the main details of the electronic mechanism of the synergistic antioxidant interaction between different pairs: phenolic food acid and glutathione and the stable radical cation ABTS<sup>+·</sup> were revealed on the basis of a rigorous analysis of the DFT calculated data. It was shown that among all the studied food acids, only caffeic acid exhibits a clear-cut significant synergistic effect with glutathione. It established the electronic and structural factors underlying the mechanism of the synergistic interaction of the mixture caffeic acid and glutathione in its reaction with ABTS<sup>+·</sup>. The main causes of this considered synergistic effect are, firstly, the presence of the 3-OH and 4-OH hydroxyl groups in the structure of caffeic acid, secondly, the greater stability of its anion which contains the deprotonated 4-OH hydroxyl group. All other phenolic food acids under study do not possess the given structural particularity and therefore do not show such synergistic effects with glutathione.展开更多
The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied ...The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries(pores) of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.展开更多
The geometric structure, mechanism of detonation initiation and stability of transition metal carbohydrazide (CHZ) nitrates are investigated via density functional theory. The obtained results show that the Heyd-Scu...The geometric structure, mechanism of detonation initiation and stability of transition metal carbohydrazide (CHZ) nitrates are investigated via density functional theory. The obtained results show that the Heyd-Scuseria-Ernzerhof (HSE) functional yields the most accurate geometry. The initiating reaction of detonation in [Mn(CHZ)3](NO3)2 and [Zn(CHZ)3](NO3)2 is the formation of NO3 radicals. The calculated heat of formation and energy gap predict that the Mn and Zn complexes, which have the half-filled (3d5) and full-filled (3d10) electron configurations for the transition metal ions, respectively are more stable than the Co, Ni and Cu complexes. This indicates that the electron configuration of transition metal ion plays an important role in the stabilities of these energetic complexes.展开更多
Imaging systems in nature have attracted a lot of research interest due to their superior optical and imaging characteristics, Recent advancements in materials science, mechanics, and stretchable electronics have led ...Imaging systems in nature have attracted a lot of research interest due to their superior optical and imaging characteristics, Recent advancements in materials science, mechanics, and stretchable electronics have led to successful development of bioinspired cameras that resemble the structures and functions of biological light-sensing organs. In this review, we discuss some recent progresses in mechanics of bioinspired imaging systems, including tunable hemispherical eyeball camera and artificial compound eye camera. The mechanics models and results reviewed in this article can provide efficient tools for design and optimization of such systems, as well as other related optoelectronic systems that combine rigid elements with soft substrates.展开更多
On the basis of the fluid theory and the drift-diffusion approximation, a numerical model for dual-frequency atmospheric pressure helium discharge is established, in order to investigate the effects of the high freque...On the basis of the fluid theory and the drift-diffusion approximation, a numerical model for dual-frequency atmospheric pressure helium discharge is established, in order to investigate the effects of the high frequency source (HF) on the characteristics of dual-frequency atmospheric pressure helium discharge. The numerical results showed that the electron heating rate increases with enhancing HF frequency, as well as the particles densities, electron dissipation rate, current density, net electron generation and bulk plasma region. Moreover, it is also observed that the efficient electron heating region moves when the HF frequency has been changed. The plasma parameters are not linear change with the HF frequency linearly increasing.展开更多
The demand and pursuit of chemical entities with UV filtration and antioxidant properties for enhanced photoprotection have been driven in recent times by acute exposure of humans to solar ultraviolet radiations. The ...The demand and pursuit of chemical entities with UV filtration and antioxidant properties for enhanced photoprotection have been driven in recent times by acute exposure of humans to solar ultraviolet radiations. The structural, electronic, antioxidant and UV absorption properties of drometrizole (PBT) and designed ortho-substituted derivatives are reported via DFT and TD-DFT in the gas and aqueous phases. DFT and TD-DFT computations were performed at the M062x-D3Zero/6-311++G(d,p)//B97-3c and PBE0-D3(BJ)/def2-TZVP levels of theory respectively. Reaction enthalpies related to hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were computed and compared with those of phenol. Results show that the presence of -NH2 substituent reduces the O-H bond dissociation enthalpy and ionization potential, while that of -CN increases the proton affinity. The HAT and SPLET mechanisms are the most plausible in the gas and aqueous phases respectively. The molecule with the -NH2 substituent (PBT1) was identified to be the compound with the highest antioxidant activity. The UV spectra of the studied compounds are characterized by two bands in the 280 - 400 nm regions. Results from this study provide a better comprehension antioxidant mechanism of drometrizole and present a new perspective for the design of electron-donor antioxidant molecules with enhanced antioxidant-photoprotective efficiencies for applications in commercial sunscreens.展开更多
We recently proposed a flexible quantum secure direct communication protocol [Chin. Phys. Lett. 23 (2006) 3152]. By analyzing its security in the perfect channel from the aspect of quantum information theory, we fin...We recently proposed a flexible quantum secure direct communication protocol [Chin. Phys. Lett. 23 (2006) 3152]. By analyzing its security in the perfect channel from the aspect of quantum information theory, we find that an eavesdropper is capable of stealing all the information without being detected. Two typical attacks are presented to illustrate this point. A solution to this loophole is also suggested and we show its powerfulness against the most general individual attack in the ideal case. We also discuss the security in the imperfect case when there is noise and loss.展开更多
Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of rubidium metal hydrides RbMH4(M = B, Al, Ga) for five different crystal structures, nam...Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of rubidium metal hydrides RbMH4(M = B, Al, Ga) for five different crystal structures, namely hexagonal(P63mc), tetragonal(P42/nmc), tetragonal(P421c), orthorhombic(Pnma) and monoclinic(P21/c). Among the considered structures, tetragonal(P421c) phase is found to be the most stable one for these metal hydrides at normal pressure. A pressure-induced structural phase transition from tetragonal(P421c) to monoclinic(P21/c) phase is observed in all the three metal hydrides. The electronic structure reveals that these hydrides are wide band gap semiconductors. The calculated elastic constants indicate that these alkali metal tetrahydrides are mechanically stable at normal pressure.展开更多
Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we s...Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol(4-BP) by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH(6.1–10) and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8 kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.展开更多
Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant e...Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant efficiency and improved safety.It is found that with the increasing dosage of NGPs into AP,the two exothermal peaks of AP merge into one intense exothermal peak,indicating that an "energy stacking" has been achieved.Meanwhile,the unique delay of the first exothermal peak of AP is conducive to the safety of AP in application process.Furthermore,the dependence of decomposition heat of AP on dosage and calcination temperature is more evident than on the surface areas of NGPs,suggesting that the promotion effect of NGPs on the thermal decomposition of AP does not only rely on the surface interaction.Therefore,an electron transfer mechanism is proposed to illustrate the decomposition process of AP tuned by NGPs.展开更多
Size reduction can generally enhance the surface reactivity of inorganic nanomaterials.The origin of this nano-effect has been ascribed to ultrasmall size,large specific surface area,or abundant defects,but the most i...Size reduction can generally enhance the surface reactivity of inorganic nanomaterials.The origin of this nano-effect has been ascribed to ultrasmall size,large specific surface area,or abundant defects,but the most intrinsic electronic-level principles are still not fully understood yet.By combining experimental explorations and mathematical modeling,herein we propose an electronic-level model to reveal the physicochemical nature of size-dependent nanomaterial surface reactivity.Experimentally,we reveal that competitive redistribution of surface atomic orbitals from extended energy band states into localized surface chemical bonds is the critical electronic process of surface chemical interactions,using H_(2)O_(2)-TiO_(2)chemisorption as a model reaction.Theoretically,we define a concept,orbital potential(G),to describe the electronic feature determining the tendency of orbital redistribution,and deduce a mathematical model to reveal how size modulates surface reactivity.We expose the dual roles of size reduction in enhancing nanomaterial surface reactivity-inversely correlating to orbital potential and amplifying the effects of other structural factors on surface reactivity.展开更多
The cyclic extrusion compression (CEC) was applied to severely deform the as-extruded GW102K (Mg- 10.0Gd-2.0Y-0.5Zr, wt%) alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundar...The cyclic extrusion compression (CEC) was applied to severely deform the as-extruded GW102K (Mg- 10.0Gd-2.0Y-0.5Zr, wt%) alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechan- ical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning elec- tron microscopy (SEM). The result shows that the microstructure was dramatically refined by dynamic recrystallization (DRX). The initial fiber texture was disintegrated and obviously weakened. The 8-passes/ 350 ℃ CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 ℃ CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initi- ated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In ad- dition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall-Petch relationships have been obtained for the CECed GW102K alloy.展开更多
Electron beam melting (EBM) has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features (i.e. smooth strut surfaces, fewer ...Electron beam melting (EBM) has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features (i.e. smooth strut surfaces, fewer defects) and an (α + β)-type microstructure, similar to that subjected to aging treat- ment. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti- 6A1-4V components having the same porosity. The processing-microstructure-property relationship and deformation behavior of EBM-produced components are discussed in detail. Such porous titanium com- ponents composed of non-toxic elements and having high strength-to-modulus ratio are highly attractive for biomedical applications.展开更多
文摘Under the background of new engineering,the reform of the comprehensive practical course system for mechanical and electronic engineering majors actively responds to the challenges posed by the new round of technological revolution and industrial transformation to higher education,cultivating top-notch innovative intellectuals with comprehensive engineering qualities,meeting the requirements of being able to solve complex engineering problems rather than just cognitive capabilities,forming two core courses through reconstructing and reshaping the core courses of the major.The core courses include Drive,Measurement,and Control I and Drive,Measurement,and Control II,which highlight the comprehensive framework of mechanical and electronic engineering professional knowledge,continuing the comprehensive practical course system based on the unity of knowledge and practice,following the trend of new engineering,highlighting the practicality of professional innovation,assisting engineering education reform,and promoting high-quality development of new engineering professionals cultivation.
文摘With the arrival of the intelligence era of Industry 4.0,social development has shown complex and diversified characteristics,gradually forming an innovation ecological environment constructed by vertical interaction of multi-layer innovation systems and horizontal collaboration of multiple organizations and departments,which has posed extremely challenging requirements for higher engineering education to cultivate engineering talents with comprehensive engineering qualities who can solve complex engineering problems.However,practical engineering problems may involve a complex knowledge chain of interdisciplinary and multi-disciplinary cross-coupling.Therefore,higher engineering education needs to form a new interdisciplinary and multi-disciplinary integrated engineering innovation talent training system.Based on the characteristics of the mechanical and electronic engineering major,we will reshape and reconstruct the core courses of the mechanical and electronic engineering major.Two core courses are formed:Drive and Measurement and Control I and Drive and Measurement and Control II,with information flow and energy flow as the main lines,following up with the comprehensive practical curriculum system based on the unity of knowledge and practice and ability-oriented thinking,supporting teaching objectives,promoting students’individual development,and providing guidelines for relevant curriculum reforms.
文摘Conventional electronics is planar, hard, and rigid due to the intrinsic brittle nature of inorganic semiconductor materials (e.g., silicon and gallium arsenide). The modern electronic technology has typically been concerned with large or small but durable and long-lasting electronics. Recently developed materials and mechanics concepts yield unconventional electronics with unique characteristics (e.g., deformable, degradable, etc.).
基金financially supported by the Natural Science Foundation of Hebei Province,China(No.E2013502272)
文摘Ceramic materials were investigated as thermal barrier coatings and electrolytes. Electrophoretic deposition(EPD) and physical vapor deposition(PVD) were employed to fabricate samples, and the mechanical properties and microstructure were examined by nanoindentation and microscopy, respectively. Yttria-stabilized zirconia/alumina(YSZ/Al2O3) composite coatings, a candidate for thermal barrier coatings, yield a kinky, rather than smooth, load–displacement curve. Scanning electron microscope(SEM) examination reveals that the kinky curve is because of the porous microstructure and cracks are caused by the compression of the indenter. Li0.34La0.51 Ti O2.94(LLTO) on Si/Sr Ru O3(Si/SRO) substrates, an ionic conductor in nature, demonstrates electronic performance. Although SEM images show a continuous and smooth microstructure, a close examination of the microstructure by transmission electron microscopy(TEM) reveals that the observed spikes indicate electronic performance. Therefore, we can conclude that ceramic coatings could serve multiple purposes but their properties are microstructure-dependent.
基金Supported by the National Natural Science Foundation of China under Grant No 51372203the National Basic Research Program of China under Grant No 2011CB605806+1 种基金the Basic Research Foundation of Northwestern Polytechnical University under Grant Nos JCY20130114 and JCY20110248the Foreign Talents Introduction and Academic Exchange Program under Grant No B08040
文摘Structural, electronic and mechanical properties of the nH-SiC (n = 2, 4, 6, 8 and 10) polytypes are calculated by using the first-principles calculations based on the density-functional theory approach. The optimized lattice parameters of nH-SiC are in good agreement with the experimental data. The mechanical properties, including elastic constants, bulk modulus, Young's modulus, shear modulus and Poisson's ratio, are calculated. The analysis of elastic properties indicates that the effects of n on the mechanical properties of the five nil-SiC structures have no difference. The indirect band gap relationship for the live polytypes is Ebg2H 〉 Ebg4H 〉 Ebg6H 〉 Ebg10H 〉 EbgsH.
文摘The Measures for the Administration of the Import of Mechanical and Electronic' Products co-formulated by the Ministry of Commerce,the General Administration of Customs and the General Administration of Quality Supervision,Inspection and Quarantine,was hereby promul- gated,which entered into force as of May 1,2008.
基金supported by the National Natural Science Foundation of China(21876030)the International Cooperation Project of Science and Technology Commission of Shanghai Municipality(18230710700)。
文摘Recalcitrance and the inherent heterogeneity of lignin structure are the major bottlenecks to impede the popularization of lignin-based chemicals production processes.Recent works suggested a promising pathway for lignin depolymerization and lignin-derived bio-oil upgrading via an electrochemical biorefinery(a process in which lignin valorization is performed via electrochemical oxidation or reduction).This review presents the progress on chemicals synthesis and bio-oil upgrading from lignin by an electrochemical biorefinery,relating to the lignin biosynthesis pathway,reaction pathway of lignin electrochemical conversion,inner-sphere and outer-sphere electron transfer mechanism,basic kinetics and thermodynamics in electrochemistry,and the recent embodiments analysis with the emphasis on the respective feature and limitation for lignin electrochemical oxidative and reductive conversion.Lastly,the challenge and perspective associated with lignin electrochemical biorefinery are discussed.Present-day results indicate that more work should be performed to promote efficiency,selectivity,and stability in pursuing a lignin electrochemical biorefinery.One of the most promising developing directions appears to be integrating various types of lignin electrochemical conversion strategies and other existing or evolving lignin valorization technologies.This review aims to provide more references and discussion on the development for lignin electrochemical biorefinery.
文摘In the present work, for the first time, the main details of the electronic mechanism of the synergistic antioxidant interaction between different pairs: phenolic food acid and glutathione and the stable radical cation ABTS<sup>+·</sup> were revealed on the basis of a rigorous analysis of the DFT calculated data. It was shown that among all the studied food acids, only caffeic acid exhibits a clear-cut significant synergistic effect with glutathione. It established the electronic and structural factors underlying the mechanism of the synergistic interaction of the mixture caffeic acid and glutathione in its reaction with ABTS<sup>+·</sup>. The main causes of this considered synergistic effect are, firstly, the presence of the 3-OH and 4-OH hydroxyl groups in the structure of caffeic acid, secondly, the greater stability of its anion which contains the deprotonated 4-OH hydroxyl group. All other phenolic food acids under study do not possess the given structural particularity and therefore do not show such synergistic effects with glutathione.
基金funded by the National Natural Science Foundation of China(51372193)the Natural Science Basic Research Plan in the Shaanxi Province of China(2014JM6224)
文摘The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries(pores) of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.
基金supported by the National Natural Science Foundation of China(No.20471008)the Natural Science Foundation of Chongqing(No.cstc2011jjA50013)the Chongqing Municipal Commission of Education(No.KJ111310)
文摘The geometric structure, mechanism of detonation initiation and stability of transition metal carbohydrazide (CHZ) nitrates are investigated via density functional theory. The obtained results show that the Heyd-Scuseria-Ernzerhof (HSE) functional yields the most accurate geometry. The initiating reaction of detonation in [Mn(CHZ)3](NO3)2 and [Zn(CHZ)3](NO3)2 is the formation of NO3 radicals. The calculated heat of formation and energy gap predict that the Mn and Zn complexes, which have the half-filled (3d5) and full-filled (3d10) electron configurations for the transition metal ions, respectively are more stable than the Co, Ni and Cu complexes. This indicates that the electron configuration of transition metal ion plays an important role in the stabilities of these energetic complexes.
基金support from ACS Petroleum Research Fund(Grant No.53780-DNI7)NSF(Grant No.CMMI-1405355)
文摘Imaging systems in nature have attracted a lot of research interest due to their superior optical and imaging characteristics, Recent advancements in materials science, mechanics, and stretchable electronics have led to successful development of bioinspired cameras that resemble the structures and functions of biological light-sensing organs. In this review, we discuss some recent progresses in mechanics of bioinspired imaging systems, including tunable hemispherical eyeball camera and artificial compound eye camera. The mechanics models and results reviewed in this article can provide efficient tools for design and optimization of such systems, as well as other related optoelectronic systems that combine rigid elements with soft substrates.
基金financially supported by National Natural Science Foundation of China (Grant No. 11505089)the Doctoral Scientific Research Foundation of Liaoning Province (Grant No. 20170520381)
文摘On the basis of the fluid theory and the drift-diffusion approximation, a numerical model for dual-frequency atmospheric pressure helium discharge is established, in order to investigate the effects of the high frequency source (HF) on the characteristics of dual-frequency atmospheric pressure helium discharge. The numerical results showed that the electron heating rate increases with enhancing HF frequency, as well as the particles densities, electron dissipation rate, current density, net electron generation and bulk plasma region. Moreover, it is also observed that the efficient electron heating region moves when the HF frequency has been changed. The plasma parameters are not linear change with the HF frequency linearly increasing.
文摘The demand and pursuit of chemical entities with UV filtration and antioxidant properties for enhanced photoprotection have been driven in recent times by acute exposure of humans to solar ultraviolet radiations. The structural, electronic, antioxidant and UV absorption properties of drometrizole (PBT) and designed ortho-substituted derivatives are reported via DFT and TD-DFT in the gas and aqueous phases. DFT and TD-DFT computations were performed at the M062x-D3Zero/6-311++G(d,p)//B97-3c and PBE0-D3(BJ)/def2-TZVP levels of theory respectively. Reaction enthalpies related to hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were computed and compared with those of phenol. Results show that the presence of -NH2 substituent reduces the O-H bond dissociation enthalpy and ionization potential, while that of -CN increases the proton affinity. The HAT and SPLET mechanisms are the most plausible in the gas and aqueous phases respectively. The molecule with the -NH2 substituent (PBT1) was identified to be the compound with the highest antioxidant activity. The UV spectra of the studied compounds are characterized by two bands in the 280 - 400 nm regions. Results from this study provide a better comprehension antioxidant mechanism of drometrizole and present a new perspective for the design of electron-donor antioxidant molecules with enhanced antioxidant-photoprotective efficiencies for applications in commercial sunscreens.
文摘We recently proposed a flexible quantum secure direct communication protocol [Chin. Phys. Lett. 23 (2006) 3152]. By analyzing its security in the perfect channel from the aspect of quantum information theory, we find that an eavesdropper is capable of stealing all the information without being detected. Two typical attacks are presented to illustrate this point. A solution to this loophole is also suggested and we show its powerfulness against the most general individual attack in the ideal case. We also discuss the security in the imperfect case when there is noise and loss.
文摘Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of rubidium metal hydrides RbMH4(M = B, Al, Ga) for five different crystal structures, namely hexagonal(P63mc), tetragonal(P42/nmc), tetragonal(P421c), orthorhombic(Pnma) and monoclinic(P21/c). Among the considered structures, tetragonal(P421c) phase is found to be the most stable one for these metal hydrides at normal pressure. A pressure-induced structural phase transition from tetragonal(P421c) to monoclinic(P21/c) phase is observed in all the three metal hydrides. The electronic structure reveals that these hydrides are wide band gap semiconductors. The calculated elastic constants indicate that these alkali metal tetrahydrides are mechanically stable at normal pressure.
基金supported by the National Natural Science Foundation of China(No.21307057)the Natural Science Foundation of Jiangsu Province(No.BK20130577)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(SRFDP,No.20130091120014)the Fundamental Research Funds for the Central Universities(No.20620140128)
文摘Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol(4-BP) by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH(6.1–10) and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8 kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.
基金Project supported by the National Natural Science Foundation of China(51864033,51274123,21761020)the National Key Basic Research Program of China(973 Program,2012CBA01204)Jiangxi Provincial Scientific&Technological Support Project of China(20132BBE500041)
文摘Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant efficiency and improved safety.It is found that with the increasing dosage of NGPs into AP,the two exothermal peaks of AP merge into one intense exothermal peak,indicating that an "energy stacking" has been achieved.Meanwhile,the unique delay of the first exothermal peak of AP is conducive to the safety of AP in application process.Furthermore,the dependence of decomposition heat of AP on dosage and calcination temperature is more evident than on the surface areas of NGPs,suggesting that the promotion effect of NGPs on the thermal decomposition of AP does not only rely on the surface interaction.Therefore,an electron transfer mechanism is proposed to illustrate the decomposition process of AP tuned by NGPs.
基金This research was supported by the National Natural Science Foundation of China(No.21801012).
文摘Size reduction can generally enhance the surface reactivity of inorganic nanomaterials.The origin of this nano-effect has been ascribed to ultrasmall size,large specific surface area,or abundant defects,but the most intrinsic electronic-level principles are still not fully understood yet.By combining experimental explorations and mathematical modeling,herein we propose an electronic-level model to reveal the physicochemical nature of size-dependent nanomaterial surface reactivity.Experimentally,we reveal that competitive redistribution of surface atomic orbitals from extended energy band states into localized surface chemical bonds is the critical electronic process of surface chemical interactions,using H_(2)O_(2)-TiO_(2)chemisorption as a model reaction.Theoretically,we define a concept,orbital potential(G),to describe the electronic feature determining the tendency of orbital redistribution,and deduce a mathematical model to reveal how size modulates surface reactivity.We expose the dual roles of size reduction in enhancing nanomaterial surface reactivity-inversely correlating to orbital potential and amplifying the effects of other structural factors on surface reactivity.
基金supported by the National Natural Science Foundation of China (No. 51204117)Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxithe Natural Science Foundation of Shanxi province (No. 2015021017)
文摘The cyclic extrusion compression (CEC) was applied to severely deform the as-extruded GW102K (Mg- 10.0Gd-2.0Y-0.5Zr, wt%) alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechan- ical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning elec- tron microscopy (SEM). The result shows that the microstructure was dramatically refined by dynamic recrystallization (DRX). The initial fiber texture was disintegrated and obviously weakened. The 8-passes/ 350 ℃ CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 ℃ CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initi- ated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In ad- dition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall-Petch relationships have been obtained for the CECed GW102K alloy.
基金supported partially by the National High-Tech R&D Program of China(863 Program,No.2015AA033702)the National Basic Research Program of China(Nos.2012CB619103 and 2012CB933901)+1 种基金the National Natural Science Foundation of China(Nos.51271182 and 51501200)the Australian Research Council Discovery Project(Nos.DP110101653 and DP130103592)
文摘Electron beam melting (EBM) has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features (i.e. smooth strut surfaces, fewer defects) and an (α + β)-type microstructure, similar to that subjected to aging treat- ment. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti- 6A1-4V components having the same porosity. The processing-microstructure-property relationship and deformation behavior of EBM-produced components are discussed in detail. Such porous titanium com- ponents composed of non-toxic elements and having high strength-to-modulus ratio are highly attractive for biomedical applications.