Analysis and direct calculation of the energy migration interaction parameter in high concentration Nd^(3+) doped YAG laser crystal

The energy migration interaction parameter CDD in high concentration Nd3＋ doped YAG laser crystal was estimated using the Yokota-Tanimoto（Y-T） model and the spectral overlap model（SOM） of Kushida, respectively.Firstly, the experimental luminescence decay curves of 4F3/2 state of Nd3＋ ions in YAG laser crystal at room temperature for 2.0at.% and 3.0at.% Nd3＋ concentrations reported by Mao were fitted successfully using the Y-T model, and the parameter CDD was obtained to be 1.50×10-39 cm6/s.Secondly, the parameter CDD was directly calculated using the spectral overlap model（SOM） of Kushida;CDD was calculated to be 2.73×10-39 cm6/s.By comparing the energy migration interaction parameter CDD with the energy transfer interaction parameter CDA（1.794×10-40 cm6/s）, it was concluded that the energy migration rate between Nd3＋ ions in YAG laser crystal was about 11 times larger than the energy transfer rate, and that energy migration played a very important role in high concentration Nd3＋-doped YAG laser crystal.

Revisit of energy transfer upconversion luminescence dynamics—the role of energy migration

Upconversion is a process in which one photon is emitted upon absorption of several photons of lower energy. Potential applications include super resolution spectroscopy, high density data storage, anti-counterfeiting and biological imaging and photo-induced therapy. Upconversion luminescence dynamics has long been believed to be determined solely by the emitting ions and their interactions with neighboring sensitizing ions. Recent research shows that this does not hold for nanostructures.The luminescence time behavior in the nanomaterials is confirmed seriously affected by the migration process of the excitation energy. This new fundamental insight is significant for the design of functional upconversion nanostructures. In this paper we review relevant theoretical and spectroscopic results and demonstrate how to tune the rise and decay profile of upconversion luminescence based on energy migration path modulation.

Boosting the Energy Migration Upconversion through Inter-Shell Energy Transfer in Tb^(3+)-Doped Sandwich Structured Nanocrystals

It remained challenging to fabricate Tb^(3+)-doped lanthanide nanocrystals(NCs)to simultaneously acquire strong energy migration upconversion(EMU)emissions of Tb^(3+)while suppressing the Tm3+UV upconversion emissions that cause background biofluorescence issues in bioapplications based on Tb^(3+)-doped EMU NCs.Herein,we report a novel sandwich structured core@shell@shell scheme for the design of EMU NCs,for example,NaLuF4∶Yb/Gd@NaGdF4∶Tm@NaLuF4∶Tb NCs,wherein Yb^(3+),Tm^(3+),and Tb^(3+)are incorporated separately into the inner core,middle shell,and outer shell,respectively.We found that in the sandwich structured NCs,the effective inter-shell energy transfer from Gd^(3+)in the middle shell to Tb^(3+)in the outer shell accelerated the Yb^(3+)-Tm^(3+)five-photon upconversion and the subsequent Tm^(3+)to Gd^(3+)energy transfer processes,which could eventually lead to almost complete inhibition of Tm^(3+)UV upconversion emissions,concurrent with the strong EMU emissions of Tb^(3+).Our findings might stimulate new concepts for manipulating upconversion emissions of lanthanide NCs.

MEASUREMENT OF VACANCY MIGRATION ENERGY BY ELECTRON IRRADIATION

A method together with a new formula were developed for measuring the vacancy migration energy on HVEM considering the effect of surface sink of specimen on point defects.The va- cancy migration energy may be calculated through the loop growth rate under electron irradiation at various temperatures.

Study on Spectral Overlap Model for Energy Transfer between J-Multiplets in Rare Earth-Doped Crystals

Based on the experimental data of KY 3F 10∶Tm 3+ reported by Diaf, K ushida′s spectral overlap model (SOM) of energy transfer between J-multipl ets was studied. Firstly, with the help of the Inokuti-Hirayama and Yokota-Tan imoto models, the luminescence decay curve of 3H 4 of Tm 3+ ion was fitted, and the fitted values of corresponding interaction parameters C D A of energy transfer and C DD of energy migration were obtained. Seco ndly, by compared with Kushida′s SOM in which the relevant Judd-Ofelt approxim ative transition rates are known, the average overlap integrals of S DD and S DA were obtained. For S DD, how to treat the contributi on of the electronic-dipole (ED) crystal field transition forbidden by C 4v site symmetry in the calculation of S DD was discussed. For S DA we suggested that, by including the contribution of the phonon sideba nds in the analysis of oscillator strength of transition, Kushida′s SOM of ED- ED resonant energy transfer rate can be extended to non-resonant phonon-assist ed D-A energy transfer. The strengths and widths of phonon sidebands in this ex ample were discussed, and the results were reasonably good.

Energy-Efficient Framework for Virtual Machine Consolidation in Cloud Data Centers

With the advent of the era of cloud computing, the high energy consumption of cloud computing data centers has become a prominent problem, and how to reduce the energy consumption of cloud computing data center and improve the efficiency of data center has become the research focus of researchers all the world. In a cloud environment, virtual machine consolidation(VMC) is an effective strategy that can improve the energy efficiency. However, at the same time, in the process of virtual machine consolidation, we need to deal with the tradeoff between energy consumption and excellent service performance to meet service level agreement(SLA). In this paper, we propose a new virtual machine consolidation framework for achieving better energy efficiency-Improved Underloaded Decision(IUD) algorithm and Minimum Average Utilization Difference(MAUD) algorithm. Finally, based on real workload data on Planet Lab, experiments have been done with the cloud simulation platform Cloud Sim. The experimental result shows that the proposed algorithm can reduce the energy consumption and SLA violation of data centers compared with existing algorithms, improving the energy efficiency of data centers.

Oxygen vacancy formation and migration in Sr- and Mg-doped LaGaO_3:a density functional theory study

Oxygen vacancy formation and migration in La0.9Sr0.1Ga0.8Mg0.2O3-5 （LSGM） with various crystal symmetries （cubic, rhombohedral, orthorhombic, and monoclinic） are studied by employing first-principles calculations based on density functional theory （DFT）. It is shown that the cubic LSGM has the smallest band gap, oxygen vacancy formation energy, and migration barrier, while the other three structures give rise to much larger values for these quantities, implying the best oxygen ion conductivity of the cubic LSGM among the four crystal structures. In out calculations, one oxygen vacancy migration pathway is considered in the cubic and rhombohedral structures due to all the oxygen sites being equivalent in them, while two vacancy migration pathways with different migration barriers are found in the orthorhombic and monoclinic symmetries owing to the existence of nonequivalent O1 and 02 oxygen sites. The migration energies along the migration pathway linking the two 02 sites are obviously lower than those along the pathway linking the O1 and 02 sites. Considering the phase transitions at high temperatures, the results obtained in this paper can not only explain the experimentally observed different behaviours of the oxygen ionic conductivity of LSGM with different symmetries, but also predict the rational crystal structures of LSGM for solid oxide fuel cell applications.

THE PIGMENT-PROTEIN COMPLEXES OF HIGHER PLANTS MIGRATION IN THYLAKOID AND THE REGULATION OF LIGHT ENERGY DISTRIBUTION BETWEEN PHOTOSYSTEMS

Appressed and non-appressed lamella membranes of Castor bean leaf chloroplasts were separated by non-ionic detergent Triton-X 100.Appressed membranes showed a high oxygen-evolving activity and low chl a/b ratio. Examining with SDS-PTGE and liquid nitrogen temperature fluorescence measurement showed that they contained only PSII and light-harvesting pigment-protein complexes (LHCP),and there was no detectable amount of PSI. Freeze-fracture electromicroscopic observation confirmed that this part was really an appressed lamella membrane. Through divalent cation Mg^(++), the thylakoid membranes were induced to unstack and restack.With the addition of Mg^(++), the fluorescence intensity was changed instantly. We realized that there existed two processes:One was a rapid process which was accomplished within 30 s. The other was a slow process of which the time duration was about 60 min. This dual effects of Mg^(++) had not been reported before.We had analyzed the change of F685/F730 and discussed the possible rneehanis ms of light energy distribution between photosystems.

Integrated Railway Smart Grid Architecture Based on Energy Routers

Railway power system is an inseparable part of the power system,therefore,the intelligent architecture of the railway power system should also be focused on.The unique power supply characteristics of the railway power system are analyzed and integrated railway smart grid architecture based on energy routers is proposed.Importantly,three corresponding resilient mode control methods are suggested for the proposed architecture.In the fourth section,a simulation model corresponding to the resilient control mode is built and the simulation results prove the feasibility of the proposed control mode.Equally,for the novel network-connected backbone router(NCBR),a 1000 kVA,27.5/10 kV NCBR engineering prototype is used to prove its effectiveness in practical applications.Finally,a differentiation analysis is given,followed by conclusions regarding the traditional power system and proposed system.

Strain engineering of ion migration in LiCoO_(2)

Strain engineering is a powerful approach for tuning various properties of functional materials. The influences of lattice strain on the Li-ion migration energy barrier of lithium-ions in layered LiCoO_(2) have been systemically studied using lattice dynamics simulations, analytical function and neural network method. We have identified two Li-ion migration paths, oxygen dumbbell hop (ODH), and tetrahedral site hop (TSH) with different concentrations of local defects. We found that Li-ion migration energy barriers increased with the increase of pressure for both ODH and TSH cases, while decreased significantly with applied tensile uniaxial c-axis strain for ODH and TSH cases or compressive in-plane strain for TSH case. Our work provides the complete strain-map for enhancing the diffusivity of Li-ion in LiCoO_(2), and therefore, indicates a new way to achieve better rate performance through strain engineering.

Low-carbon transition in smart city with sustainable airport energy ecosystems and hydrogen-based renewable-grid-storage-flexibility

Hybrid renewable integration,electrification,hydrogenation,spatiotemporal energy sharing and migration,and optimisations are necessary roadmaps for the transition towards low-carbon airport transportation systems.In this study,a comprehensive review on sustainable airport energy ecosystems with hydrogen-based renewable-gridstorage-flexibility,has been conducted,from perspectives of airport energy ecosystem constitutions,renewable supported power supply chain,novel spatiotemporal energy migration paradigms,single and multi-objective optimisations,together with multi-criteria decision-making approaches.Hydrogenation in jet aircraft systems has various advantages,such as lightweight with low fuel transportation load,high specific energy,zero CO_(2) emissions,and low NOx emissions,reduced air pollution,and environmental sustainability.Depending on different energy sources,liquid hydrogen(LH2)can be produced by solar energy,wind energy,coastal ocean energy,and bioenergy,through chemical technologies and water electrolysis from renewable power.Synergistic operation between land and air transportation systems can promote net-zero emissions.Novel energy interaction frameworks have been formulated,for inter-city/inter-country energy sharing and trading,spatiotemporal compensation on uneven distributed renewable energy resources,and high penetration of renewables.Results showed that power characteristics in airport energy systems include lightweight,high-energy density,energyintensive,fast power response,safety,stochastic,nonlinear,and dynamics.Coastal energy resources are full of huge potentials to support airport energy systems,through off-shore wind turbines,floating PV panels,current turbines,wave energy converters,tidal stream generators,and ocean thermo-electric generators.Research results can provide conceptional frameworks,prospects,and technical challenges,on electrification and hydrogenation in both land and air transportation sectors,paving path for transition towards sustainability and carbon neutrality.

Predicting the Transition between Upper and Lower Bainite via a Gibbs Energy Balance Approach

The transition temperature between upper bainite and lower bainite is calculated with an extended Gibbs energy balance model, which is able to quantitatively describe the evolution of carbon supersaturation within bainitic ferrite sheaves during the entire thickening process. The nucleation rate of intra-lath cementite precipitation on a dislocation is calculated based on of the degree of carbon supersaturation.Upper bainite and lower bainite are thus distinguished by the effective nucleation density and therefore a numerical criterion can be set to define the transition. The model is applied to Fe-xC-1Mn/2Mn/1 Mo ternary alloys. Results show that the transition temperature increases with bulk carbon content at lower carbon concentration but decreases in the higher carbon region. This prediction agrees very well with the experimental observations in Mn and Mo alloyed systems. Moreover, the highest transition temperature and the carbon content at which it occurs in the Fe-xC-2Mn system are in good agreement with reported experimental data. The inverse ＂V＂ shaped character of the carbon concentration-transition temperature curve indicates two opposite physical mechanisms operating at the same time. An analysis is carried out to provide an explanation.

Flexible and free-standing La_(0.33)Ti_(2)(PO_(4))_(3)/C nanofibers film as a novel high-performance anode for sodium-and potassium-ion batteries

Na superionic conductor(NASICON)-type La_(0.33)Ti_(2)(PO_(4))_(3)(LaTP) is firstly proposed as sodium/potassium storage materials.The density functional theory(DFT) calculations show that LaTP has good electronic character and low Na^(+)/K^(+)migration barriers.The flexible La_(0.33)Ti_(2)(PO_(4))_(3)/C nanofiber film is synthesized via electrostatic spinning and investigated as free-standing electrode applied to sodium-ion batteries(SIBs) and potassiumion batteries(PIBs) in this work.The low band gap and Na^(+)/K^(+) migration barriers of LaTP,unique morphology,and complete conductive carbon net allow the La_(0.33)Ti_(2)(PO_(4))_(3)/C nanofibers film to deliver high capacity(296.3 mAh·g^(-1) for SIBs and 235.8 mAh·g^(-1) for PIBs),excellent rate performance(142.5 mAh·g^(-1) for SIBs and50.5 mAh·g^(-1) for PIBs at 1.00 A·g^(-1)),and superior cyclability above 1000 cycles.The full-cell tests show that the material has a good application prospect,indicating a promising flexible anode material for SIBs and PIBs.