期刊文献+
共找到82,654篇文章
< 1 2 250 >
每页显示 20 50 100
Assessment of challenges and strategies for driving energy transitions in emerging markets:A socio-technological systems perspective 被引量:1
1
作者 Nelson S.Chipangamate Glen T.Nwaila 《Energy Geoscience》 EI 2024年第2期81-100,共20页
The pursuit of improved quality of life standards has significantly influenced the contemporary mining model in the 21st century.This era is witnessing an unprecedented transformation driven by pressing concerns relat... The pursuit of improved quality of life standards has significantly influenced the contemporary mining model in the 21st century.This era is witnessing an unprecedented transformation driven by pressing concerns related to sustainability,climate change,the just energy transition,dynamic operating environments,and complex social challenges.Such transitions present both opportunities and obstacles.The aim of this study is to provide an extensive literature review on energy transition to identify the challenges and strategies associated with navigating transformations in energy systems.Understanding these transformations is particularly critical in the face of the severe consequences of global warming,where an accelerated energy transition is viewed as a universal remedy.Adopting a socio-technological systems perspective,specifically through the application of Actor Network Theory(ANT),this research provides a theoretical foundation while categorising challenges into five distinct domains and outlining strategies across these different dimensions.These insights are specifically tailored for emerging market countries to effectively navigate energy transition while fostering the development of resilient societies.Furthermore,our findings highlight that energy transition encompasses more than a mere technological shift;it entails fundamental changes in various systemic socio-economic imperatives.Through focusing on the role of social structures in transitions,this study makes a significant and innovative contribution to ANT,which has historically been criticised for its limited acknowledgement of social structures.Consequently,we propose an emerging market energy transition framework,which not only addresses technological aspects,but also integrates social considerations.This framework paves the way for future research and exploration of energy transition dynamics.The outcomes of this study offer valuable insights to policymakers,researchers,and practitioners engaged in the mining industry,enabling them to comprehend the multifaceted challenges involved and providing practical strategies for effective resolution.Through incorporating the social dimension into the analysis,we enhance the understanding of the complex nature of energy system transformations,facilitating a more holistic approach towards achieving sustainable and resilient energy transitions in emerging markets and beyond. 展开更多
关键词 Actor network theory Energy transition Social innovation Technology Actor inclusive policy
下载PDF
Crystal structure,phase transitions,and thermodynamic properties of magnesium metavanadate(MgV_(2)O_(6)) 被引量:1
2
作者 Guishang Pei Cheng Pan +2 位作者 Dapeng Zhong Junyi Xiang Xuewei Lv 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2024年第4期1449-1460,共12页
As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile... As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures. 展开更多
关键词 MgV_(2)O_(6) Crystal structure Phase transitions Thermodynamic functions
下载PDF
Structurally Flexible 2D Spacer for Suppressing the Electron-Phonon Coupling Induced Non-Radiative Decay in Perovskite Solar Cells
3
作者 Ruikun Cao Kexuan Sun +8 位作者 Chang Liu Yuhong Mao Wei Guo Ping Ouyang Yuanyuan Meng Ruijia Tian Lisha Xie Xujie Lü Ziyi Ge 《Nano-Micro Letters》 SCIE EI CAS CSCD 2024年第9期325-340,共16页
This study presents experimental evidence of the dependence of non-radiative recombination processes on the electron-phonon coupling of perovskite in perovskite solar cells(PSCs).Via A-site cation engineering,a weaker... This study presents experimental evidence of the dependence of non-radiative recombination processes on the electron-phonon coupling of perovskite in perovskite solar cells(PSCs).Via A-site cation engineering,a weaker electron-phonon coupling in perovskite has been achieved by introducing the structurally soft cyclohexane methylamine(CMA^(+))cation,which could serve as a damper to alleviate the mechanical stress caused by lattice oscillations,compared to the rigid phenethyl methylamine(PEA^(+))analog.It demonstrates a significantly lower non-radiative recombination rate,even though the two types of bulky cations have similar chemical passivation effects on perovskite,which might be explained by the suppressed carrier capture process and improved lattice geometry relaxation.The resulting PSCs achieve an exceptional power conversion efficiency(PCE)of 25.5%with a record-high opencircuit voltage(V_(OC))of 1.20 V for narrow bandgap perovskite(FAPbI_(3)).The established correlations between electron-phonon coupling and non-radiative decay provide design and screening criteria for more effective passivators for highly efficient PSCs approaching the Shockley-Queisser limit. 展开更多
关键词 Electron-phonon coupling A-site cation engineering non-radiative recombination
下载PDF
Pressure-induced structural,electronic,and superconducting phase transitions in TaSe_(3)
4
作者 Yuhang Li Pei Zhou +3 位作者 Chi Ding Qing Lu Xiaomeng Wang Jian Sun 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第10期88-94,共7页
TaSe_(3)has garnered significant research interests due to its unique quasi-one-dimensional crystal structure,which gives rise to distinctive properties.Using crystal structure search and first-principles calculations... TaSe_(3)has garnered significant research interests due to its unique quasi-one-dimensional crystal structure,which gives rise to distinctive properties.Using crystal structure search and first-principles calculations,we systematically investigated the pressure-induced structural and electronic phase transitions of quasi-one-dimensional TaSe_(3)up to 100 GPa.In addition to the ambient pressure phase(P2_(1)/m-I),we identified three high-pressure phases:P2_(1)/m-II,Pnma,and Pmma.For the P2_(1)/m-I phase,the inclusion of spin-orbit coupling(SOC)results in significant SOC splitting and changes in the band inversion characteristics.Furthermore,band structure calculations for the three high-pressure phases indicate metallic natures,and the electron localization function suggests ionic bonding between Ta and Se atoms.Our electron-phonon coupling calculations reveal a superconducting critical temperature of approximately 6.4 K for the Pmma phase at 100 GPa.This study provides valuable insights into the high-pressure electronic behavior of quasi-one-dimensional TaSe_(3). 展开更多
关键词 high pressure transition metal trichalcogenides phase transition SUPERCONDUCTIVITY
下载PDF
Complete Universal Scaling in First-Order Phase Transitions
5
作者 Fan Zhong 《Chinese Physics Letters》 SCIE EI CAS CSCD 2024年第10期8-13,共6页
Phase transitions and critical phenomena are among the most intriguing phenomena in nature and society.They are classified into first-order phase transitions(FOPTs)and continuous ones.While the latter shows marvelous ... Phase transitions and critical phenomena are among the most intriguing phenomena in nature and society.They are classified into first-order phase transitions(FOPTs)and continuous ones.While the latter shows marvelous phenomena of scaling and universality,whether the former behaves similarly is a long-standing controversial issue.Here we definitely demonstrate complete universal scaling in field driven FOPTs for Langevin equations in both zero and two spatial dimensions by rescaling all parameters and subtracting nonuniversal contributions with singular dimensions from an effective temperature and a special field according to an effective theory.This offers a perspective different from the usual nucleation and growth but conforming to continuous phase transitions to study FOPTs. 展开更多
关键词 theory. transitions SCALING
下载PDF
New approach to measuring topological phase transitions utilizing Floquet technology
6
作者 Xue-Ying Yang Wei Wu Ping-Xing Chen 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第9期282-288,共7页
The Floquet technique provides a novel anomalous topological phase for non-equilibrium phase transitions.Based on the high symmetry of the quantum anomalous Hall model,the findings suggest a one-to-one correspondence ... The Floquet technique provides a novel anomalous topological phase for non-equilibrium phase transitions.Based on the high symmetry of the quantum anomalous Hall model,the findings suggest a one-to-one correspondence between the average spin texture and the Floquet quasi-energy spectrum.A new approach is proposed to directly measure the quasienergy spectrum,replacing previous measurements of the average spin texture.Finally,we proposed a reliable experimental scheme based on ion trap platforms.This scheme markedly reduces the measurement workload,improves the measurement fidelity,and is applicable to multiple platforms such as cold atoms and nuclear magnetic resonance. 展开更多
关键词 topological phase transition Floquet technique ion trap
下载PDF
Metal-to-insulator transitions in 3d-band correlated oxides containing Fe compositions
7
作者 Yiping Yu Yuchen Cui +2 位作者 Jiangang He Wei Mao Jikun Chen 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CSCD 2024年第1期48-59,共12页
Metal-to-insulator transitions (MITs),which are achieved in 3d-band correlated transitional metal oxides,trigger abrupt variations in electrical,optical,and/or magnetic properties beyond those of conventional semicond... Metal-to-insulator transitions (MITs),which are achieved in 3d-band correlated transitional metal oxides,trigger abrupt variations in electrical,optical,and/or magnetic properties beyond those of conventional semiconductors.Among such material families,iron(Fe:3d^(6)4s^(2))-containing oxides pique interest owing to their widely tunable MIT properties,which are associated with the various valence states of Fe.Their potential electronic applications also show promise,given the large abundance of Fe on Earth.Representative MIT properties triggered by critical temperature (TMIT) were reported for ReFe_(2)O_(4)(Fe^(2.5+)),ReBaFe_(2)O_(5)(Fe^(2.5+)),Fe_(3)O_(4)(Fe^(2.67+)),Re_(1/3)Sr_(2/3)FeO_(3)(Fe^(3.67+)),Re Cu_(3)Fe_(4)O_(12)(Fe^(3.75+)),and Ca_(1-x)Sr_(x)FeO_(3)(Fe^(4+))(where Re represents rare-earth elements).The common feature of MITs of these Fe-containing oxides is that they are usually accompanied by charge ordering transitions or disproportionation associated with the valence states of Fe.Herein,we review the material family of Fe-containing MIT oxides,their MIT functionalities,and their respective mechanisms.From the perspective of potentially correlated electronic applications,the tunability of the TMITand its resultant resistive change in Fe-containing oxides are summarized and further compared with those of other materials exhibiting MIT functionality.In particular,we highlight the abrupt MIT and wide tunability of TMITof Fe-containing quadruple perovskites,such as Re Cu3Fe4O12.However,their effective material synthesis still needs to be further explored to cater to potential applications. 展开更多
关键词 metal-to-insulator transitions Fe-containing oxides charge ordering charge disproportionation
下载PDF
Triple points and phase transitions of D-dimensional dyonic Ad S black holes with quasitopological electromagnetism in Einstein–Gauss–Bonnet gravity
8
作者 牟平辉 蒋青权 +1 位作者 何柯腱 李国平 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第6期272-287,共16页
By considering the negative cosmological constant Λ as a thermodynamic pressure, we study the thermodynamics and phase transitions of the D-dimensional dyonic Ad S black holes(BHs) with quasitopological electromagnet... By considering the negative cosmological constant Λ as a thermodynamic pressure, we study the thermodynamics and phase transitions of the D-dimensional dyonic Ad S black holes(BHs) with quasitopological electromagnetism in Einstein–Gauss–Bonnet(EGB) gravity. The results indicate that the small/large BH phase transition that is similar to the van der Waals(vdW) liquid/gas phase transition always exists for any spacetime dimensions. Interestingly, we then find that this BH system exhibits a more complex phase structure in 6-dimensional case that is missed in other dimensions.Specifically, it shows for D = 6 that we observed the small/intermediate/large BH phase transitions in a specific parameter region with the triple point naturally appeared. Moreover, when the magnetic charge turned off, we still observed the small/intermediate/large BH phase transitions and triple point only in 6-dimensional spacetime, which is consistent with the previous results. However, for the dyonic Ad S BHs with quasitopological electromagnetism in Einstein–Born–Infeld(EBI) gravity, the novel phase structure composed of two separate coexistence curves observed by Li et al. [Phys. Rev. D105 104048(2022)] disappeared in EGB gravity. This implies that this novel phase structure is closely related to gravity theories, and seems to have nothing to do with the effect of quasitopological electromagnetism. In addition, it is also true that the critical exponents calculated near the critical points possess identical values as mean field theory. Finally, we conclude that these findings shall provide some deep insights into the intriguing thermodynamic properties of the dyonic Ad S BHs with quasitopological electromagnetism in EGB gravity. 展开更多
关键词 AdS black hole phase transition triple point
下载PDF
Farm buildings and agri-food transitions in Southern France:Mapping dynamics using a stakeholder-based diagnosis
9
作者 Orlane Rouquier Coline Perrin +1 位作者 Michaël Pouzenc Valérie Olivier-Salvagnac 《Geography and Sustainability》 CSCD 2024年第1期108-120,共13页
This study's goal is to present a dynamic portrait of the farm-buildings environment in Occitania,in Southern France,in order to better identify the transitions underway in agri-food chains.To this end,we undertoo... This study's goal is to present a dynamic portrait of the farm-buildings environment in Occitania,in Southern France,in order to better identify the transitions underway in agri-food chains.To this end,we undertook a ter-ritorial diagnosis based on actor statements,using 28 semi-structured interviews across Occitania.This diagnosis was enriched by graphic modelling,which enabled the spatialization of the dynamics described.We show that the process of standardisation of farm buildings prevails in the majority of the territories studied.This phenomenon has intensified in recent years with the development of vast photovoltaic-roofed sheds,accentuating the farm-land conversion and soil sealing.At the same time,in areas with strong environmental,landscape and heritage contexts,a'new adventure in farm buildings'(2022 survey)is taking shape.It is primarily driven by local short food chains,which rely on self-construction,repurposing and refurbishment,the sharing of tools and equipment,and which favour the use and reuse of local resources.This study shows that farm-buildings dynamics crystallise many challenges confronting the reterritorialisation of agriculture and food production. 展开更多
关键词 Farm buildings transitION Local food systems Occitania Cartographic modelling
下载PDF
Water Photomolecular Evaporation Due to Light-Mediated Ortho-Para Spin Transitions
10
作者 Sergey Pershin Irina Bjørnø Michael Grishin 《Open Journal of Applied Sciences》 2024年第8期2201-2206,共6页
Recent discoveries have revealed a groundbreaking phenomenon where light alone, without any thermal input, can induce water evaporation, termed the “photomolecular effect”. This study explores a novel hypothesis tha... Recent discoveries have revealed a groundbreaking phenomenon where light alone, without any thermal input, can induce water evaporation, termed the “photomolecular effect”. This study explores a novel hypothesis that this effect can be explained by ortho-para magnetic spin interactions in water molecules within the water-air interface layer. Water molecules, consisting of hydrogen and oxygen, exhibit different nuclear spin states: ortho-(triplet) and para-(singlet). The interaction of polarized light with these spin states may induce transitions between the rotational levels of ortho- and para-forms due to catalysts like triplet oxygen (O2) in its inhomogeneous magnetic field. Resonance pumping at 532 nm (~18,797 cm−1) due to the transition v1-v2-v3 ~ 0-8-2 (~18,796 cm−1) results in an increase in molecular energy sufficient to overcome intermolecular forces at the water surface, thereby causing evaporation. The proposed ortho-para conversion mechanism involves spin-orbit coupling and specific resonance conditions. This theory provides a quantum mechanical perspective on the photomolecular effect, potentially offering insights into natural processes such as cloud formation and climate modeling, as well as practical applications in solar desalination and industrial drying. Further experimental validation is required to confirm the role of spin interactions in light-induced water evaporation. 展开更多
关键词 Ortho-Para Spin transition Water Structure Evaporation Theory Photo Molecular Effect
下载PDF
Bearing Fault Diagnosis Based on the Markov Transition Field and SE-IShufflenetV2 Model
11
作者 Chaozhi Cai Tiexin Xu +1 位作者 Jianhua Ren Yingfang Xue 《Structural Durability & Health Monitoring》 EI 2025年第1期125-144,共20页
A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poo... A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poor generalization of rolling bearing.Firstly,MTF is used to encode one-dimensional time series vibration sig-nals and convert them into time-dependent and unique two-dimensional feature images.Then,the generated two-dimensional dataset is fed into the SE-IShufflenetV2 model for training to achieve fault feature extraction and classification.This paper selects the bearing fault datasets from Case Western Reserve University and Paderborn University to experimentally verify the effectiveness and superiority of the proposed method.The generalization performance of the proposed method is tested under the variable load condition and different signal-to-noise ratios(SNRs).The experimental results show that the average accuracy of the proposed method under different working conditions is 99.2%without adding noise.The accuracy under different working conditions from 0 to 1 HP is 100%.When the SNR is 0 dB,the average accuracy of the proposed method can still reach 98.7%under varying working conditions.Therefore,the bearing fault diagnosis method proposed in this paper is characterized by high accuracy,strong anti-noise ability,and generalization.Moreover,the proposed method can also overcome the influence of variable working conditions on diagnosis accuracy,providing method support for the accurate diagnosis of bearing faults under strong noise and variable working conditions. 展开更多
关键词 Bearings Markov transitionfield SE-IShufflenetV2
下载PDF
Phase transitions, micro-morphology and its oxidation mechanism in oxidation of ilmenite (FeTiO_3) powder 被引量:5
12
作者 肖玮 鲁雄刚 +2 位作者 邹星礼 危雪梅 丁伟中 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第8期2439-2445,共7页
Phase transitions, morphology changes, and oxidation mechanism of the ilmenite oxidation process were investigated. FeTi03 transforms to hematite and rutile when oxidation at 700-800 ℃, and pseudobrookite is formed w... Phase transitions, morphology changes, and oxidation mechanism of the ilmenite oxidation process were investigated. FeTi03 transforms to hematite and rutile when oxidation at 700-800 ℃, and pseudobrookite is formed when the oxidation temperature reaches 900 ℃. The initial ilmenite powder exhibits paramagnetism; however, after being oxidized at the intermediate temperature (800-850 ℃), the oxidation product exhibits weak ferromagnetism. The oxidation mechanism was discussed. The microstructure observations show that a lot of micro-pores emerge on the surfaces of ilmenite particles at the intermediate temperature, which is deemed to be caoable ofenhancin~ the mass transfer ofoxgen during oxidation. 展开更多
关键词 ILMENITE phase transitions MICRO-MORPHOLOGY oxidation mechanism
下载PDF
Magnesium vapor nucleation in phase transitions and condensation under vacuum conditions 被引量:4
13
作者 杨成博 田阳 +3 位作者 曲涛 杨斌 徐宝强 戴永年 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第2期561-569,共9页
Recent findings related to coagulable magnesium vapor nucleation and growth in vacuum were assessed critically, with emphasis on understanding these processes at a fundamental molecular level. The effects of magnesium... Recent findings related to coagulable magnesium vapor nucleation and growth in vacuum were assessed critically, with emphasis on understanding these processes at a fundamental molecular level. The effects of magnesium vapor pressure, condensation temperature, and condensation zone temperature gradient on magnesium vapor nucleation in phase transitions and condensation from atomic collision and coacervation with collision under vacuum conditions were discussed. Magnesium powder and magnesium lump condensates were produced under different conditions and characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The right condensation zone temperature approach to the liquid transition primarily improved the magnesium vapor concentration rate. The gas-solid phase transition was primarily inhibited by setting a small condenser temperature gradient. Under the right condensation temperature and temperature gradients, increasing magnesium vapor partial pressure improved crystallization and reduced the oxidation rate. 展开更多
关键词 magnesium vapor VACUUM phase transition CONDENSATION NUCLEATION
下载PDF
Dielectric properties and phase transitions of La_2O_3- and Sb_2O_3-doped barium strontium titanate ceramics 被引量:4
14
作者 张晨 曲远方 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2012年第11期2742-2748,共7页
The dielectric properties and phase transition characteristics of La2O3- and Sb2O3-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray d... The dielectric properties and phase transition characteristics of La2O3- and Sb2O3-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray diffraction method and scanning electron microscope was also employed to observe the surface morphologies. It is found that (La,Sb)-codoped barium strontium titanate ceramics exhibit typical perovskite structure and the average grain size decreases dramatically with increasing the content of Sb2O3. Both La3+ ions and Sb3+ ions occupy the A-sites in perovskite lattice. The dielectric constant and dielectric loss of barium strontium titanate based ceramics are obviously influenced by La2O3 as well as Sb2O3 addition content. The tetragonal-cubic phase transition of La2O3 modified barium strontium titanate ceramics is of second order and the Curie temperature shifts to lower value with increasing the La2O3 doping content. The phase transition of (La,Sb)-codoped barium strontium titanate ceramics diffuses and the deviation from Curie-Weiss law becomes more obvious with the increase in Sb2O3 concentration. The temperature corresponding to the dielectric constant maximum of (La,Sb)-codoped barium strontium titanate ceramics decreases with increasing the Sb2O3 content, which is attributed to the replacement of host ions by the Sb3+ ions. 展开更多
关键词 barium strontium titanate LA2O3 SB2O3 PEROVSKITE CERAMICS dielectric properties phase transition
下载PDF
Transitions of Normal Universities and Strategies of Talents Cultivation 被引量:1
15
作者 李旸 马建辉 贾砚萍 《Sino-US English Teaching》 2006年第6期60-63,共4页
Transitions of normal universities in our country are inexorable trends with the development of the times. In this process, normal universities should actively reform models of talents cultivation, establish teachers... Transitions of normal universities in our country are inexorable trends with the development of the times. In this process, normal universities should actively reform models of talents cultivation, establish teachers' profession with distinguishing features, construct new strategies of talents cultivation so as to improve all-round capacities of normal universities in running schools. 展开更多
关键词 normal universities transitions MODELS strategies of talents cultivation
下载PDF
Rovibrational State-Selectivity in Photoassociation through Multi-photon Transitions
16
作者 王荣 邱明辉 修俊玲 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2014年第5期497-502,I0003,共7页
The rovibrational state-selectivity in photoassociation (PA) is investigated for the ground electronic state of OH radical. The calculated results show that population can be transferred from continuum state to the ... The rovibrational state-selectivity in photoassociation (PA) is investigated for the ground electronic state of OH radical. The calculated results show that population can be transferred from continuum state to the target states through three-, four-, and nine-photon transitions by choosing suitable pulse parameters and initial collision energy. To control population transfer to a lower rovibrational state, a shorter pulse frequency has to be chosen and the photon number transferred to target state should be increased. In PA process, some associated OH radicals can be dissociated via intermediate and background states, which decreases the nal population of the target state. 展开更多
关键词 PHOTOASSOCIATION Multi-photon transition State-selectivity Intermediate state
下载PDF
以人为本,全人教育——评广东外语外贸大学英语教材《Transitions》
17
作者 杨贝 《洛阳师范学院学报》 2009年第1期139-141,共3页
经过高考拼搏而跨入大学校门的一年级学生,既对大学生活充满憧憬,对自己充满自信,又对大学生活感到陌生和茫然。广东外语外贸大学英语教材Transitions采用了人本主义课程编写理念,强调"以人为本,全人教育",选取贴近大学新生... 经过高考拼搏而跨入大学校门的一年级学生,既对大学生活充满憧憬,对自己充满自信,又对大学生活感到陌生和茫然。广东外语外贸大学英语教材Transitions采用了人本主义课程编写理念,强调"以人为本,全人教育",选取贴近大学新生学习和生活的主题,以帮助新生顺利地实现由中学学习到大学学习的过渡,学会学习,学会生活,学会做人。 展开更多
关键词 人本主义 英语教材transitions 大学新生
下载PDF
Influence of Polarization-Induced Electric Fields on Optical Properties of Intersubband Transitions in Al_xGa_(1-x)N/GaN Double Quantum Wells 被引量:1
18
作者 雷双英 沈波 +3 位作者 许福军 杨志坚 徐柯 张国义 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2006年第3期403-408,共6页
The influence of polarization-induced electric fields on the electron distribution and the optical properties of intersubband transitions (ISBT) in AlxGa(1-x)N/GaN coupled double quantum wells (DQWs) is investig... The influence of polarization-induced electric fields on the electron distribution and the optical properties of intersubband transitions (ISBT) in AlxGa(1-x)N/GaN coupled double quantum wells (DQWs) is investigated by self-consistent calculation. It is found that the polarization-induced potential drop leads to an asymmetric potential profile of AlxGa(1-x)N/GaN DQWs even though the two wells have the same width and depth. The polarization effects result in a very large Stark shift between the odd and even order subbands,thus shortening the wavelength of the ISBT between the first odd order and the second even order (1odd-2 ) subbands. Meanwhile, the electron distribution becomes asymmetric due to the polarization effects, and the absorption coefficient of the 1odd-2 ISBT decreases with increasing polarization field discontinuity. 展开更多
关键词 AlxGa(1-x)N/GaN DQWs intersubband transition polarization field discontinuity
下载PDF
Nonlinear Feature of the Abrupt Transitions between Multiple Equilibria States of an Ecosystem Model 被引量:9
19
作者 孙国栋 穆穆 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2009年第2期293-304,共12页
Based on a five-variable theoretical ecosystem model, the stability of equilibrium state and the nonlinear feature of the transition between a grassland state and a desert state are investigated. The approach of the c... Based on a five-variable theoretical ecosystem model, the stability of equilibrium state and the nonlinear feature of the transition between a grassland state and a desert state are investigated. The approach of the conditional nonlinear optimal perturbations (CNOPs), which are the nonlinear generalization of the linear singular vectors (LSVs), is adopted. The numerical results indicate that the linearly stable grassland and desert states are nonlinearly unstable to large enough initial perturbations on the condition that the moisture index # satisfies 0.3126 〈 μ 〈 0.3504. The perturbations represent some kind of anthropogenic influence and natural factors. The results obtained by CNOPs, LSVs and Lyapunov vectors (LVs) are compared to analyze the nonlinear feature of the transition between the grassland state and the desert state. Besides this, it is shown that the five-variable model is superior to the three-variable model in providing more visible signals when the transitions occur. 展开更多
关键词 nonlinear feature abrupt transition grassland and desert ecosystem shading effect
下载PDF
Epithelial-to-mesenchymal and mesenchymal-to-epithelial transitions in the colon 被引量:16
20
作者 Ferenc Sipos Orsolya Galamb 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第7期601-608,共8页
Epithelial-to-mesenchymal and mesenchymal-to-epi- thelial transitions are well established biological events which have an important role in not just normal tissue and organ development, but in the pathogenesis of dis... Epithelial-to-mesenchymal and mesenchymal-to-epi- thelial transitions are well established biological events which have an important role in not just normal tissue and organ development, but in the pathogenesis of diseases. Increasing evidence has established their presence in the human colon during colorectal carcinogenesis and cancer invasion, chronic inflammation-related fibrosis and in the course of mucosal healing. A large body of evidence supports the role for transforming growth factor-13 and its downstream Smad signaling, the phosphatidylinositol 3'-kinase/Akt/mTOR axis, the Ras-mitogen-activated protein kinase/Snail/Slug and FOXC2 pathway, and Hedgehog signaling and microR- NAs in the development of colorectal cancers via epi- thelial-to-mesenchymal transition. C-met and Frizzled-7, among others, seem to be the principle effectors of mesenchymal-to-epithelial transition, hence have a role not just in mucosal regeneration but in the progression of colonic wall fibrosis. Here we discuss a role for these pathways in the initiation and development of the transition events. A better understanding of their induction and regulation may lead to the identification of pathways and factors that could be potent therapeu- tic targets. The inhibition of epithelial-to-mesenchymal transition using mTOR kinase inhibitors targeting theATP binding pocket and which inhibit both mTORC1 and mTORC2, RNA aptamers or peptide mimetics, such as a Wnt5A-mimetic, may all be useful in both cancer treatment and delaying fibrosis, while the induction of mesenchymal-to-epithelial transition in induced pluripotent stem cells may enhance epithelial healing in the case of severe mucosal damage. The preliminary results of the current studies are promising, but more clinical investigations are needed to develop new and safe therapeutic strategies for diseases of the colon. 展开更多
关键词 Epithelial-to-mesenchymal transition Mesen-chymal-to-epithelial transition Colorectal cancer FIBROSIS Mucosal healing
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部