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[IEEE 2019 IEEE 3rd International Electrical and Energy Conference (CIEEC) - Beijing, China (2019.9.7-2019.9.9)] 2019 IEEE 3rd International Electrical and Energy Conference (CIEEC) - Coordinated Control of Active and Reactive Power of Distribution Network with Distributed Photovoltaic Based On Scene Analysis
摘要： Variables such as distributed generation (DG) output and load demand have randomness and volatility, brings large challenges to operation and control of distribution network. In order to solve this problem, this paper generates multiple scene samples through Latin hypercube sampling (LHS) based on mathematical distribution model of variables, then reduces the scene samples by K-means clustering, typical scenes and the probability of each typical scene are obtained. Considering the adjustable capabilities of distributed photovoltaic (PV) and energy storage system (ESS), a multi-objective optimization model based on scene analysis for coordinated control of active and reactive power in distribution network is established, and the mixed integer nonlinear programming model is solved by second- order cone relaxation (SOCR) technique. Finally, the improved IEEE 33-node system is taken as an example for simulation with results confirming accuracy and rationality of the proposed algorithm.
关键词： coordinated control of active and reactive power,distributed generation,scene analysis,second-order cone relaxation
更新于2025-09-23 15:21:01
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Self-assembled InAs/InGaAsP/InP quantum dots: Intraband relaxation impacted by ultrathin GaP sublayer
摘要： The influence of an ultrathin GaP (or GaAs) sublayer on the nonradiative intraband relaxation in InAs/InGaAsP/InP quantum dots (QDs) is investigated. It is found that, based on our studies, the QDs with some heights (e.g., 1.5 nm) and GaP sublayer thicknesses (e.g., 1.03 monolayers) present the first excited state (ES) with higher state degeneracy with respect to ground state (GS), which suggests that the Auger relaxation is triggered more easily. We also find that the energy difference of the ES and GS decreases with increasing sublayer thickness, which suggests that the electron–phonon interaction is affected. This work further presents a study of intraband relaxation for an InAs/InP QD with a GaP or GaAs sublayer. It is found that there is a critical thickness of the GaP sublayer: When the sublayer is less than the critical thickness, the intraband relaxation is only determined by one-longitudinal optical (LO) phonon or two-LO phonons, which is dependent on QD heights. However, with the GaAs sublayer, QDs do not have the above feature. This finding may be helpful for designing and optimizing high-speed QD devices.
关键词： quantum dots,electron–phonon interaction,InAs/InGaAsP/InP,intraband relaxation,GaP sublayer
更新于2025-09-23 15:21:01
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Dual-comb-based asynchronous pump-probe measurement with an ultrawide temporal dynamic range for characterization of photo-excited InAs quantum dots
摘要： A dual-comb-based asynchronous optical sampling (ASOPS) pump-probe measurement system is demonstrated for characterizing the relaxation dynamics in a photo-excited self-assembled InAs quantum dot (QD) semiconductor. Although the photo-excited QD material has multiple complex relaxation processes, the transient transmittance responses (from femtoseconds to nanoseconds) are successfully obtained within a sub-second short acquisition time by using the ASOPS system. This is achieved with high stability and an extremely wide temporal dynamic range of approximately 105. The utility of the developed system is demonstrated as a powerful and easy-to-use measurement tool for studying the complex photo-excited dynamics of QD materials.
关键词： dual-comb,asynchronous optical sampling,InAs quantum dots,pump-probe measurement,relaxation dynamics
更新于2025-09-23 15:21:01
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Dielectric and electro-optic studies of a ferroelectric liquid crystal dispersed with different sizes of silica nanoparticles
摘要： The impact of the size of silica nanoparticles (SNPs) on the properties of ferroelectric liquid crystals (KCFLC 10R) has been investigated by electro-optical and dielectric techniques. We have found that the doping of silica nanoparticles in the host ferroelectric liquid crystal strongly affects the various properties of doped systems. Doping of silica nanoparticles shows a small decrease in spontaneous polarisation and faster switching time. An improvement in permittivity and conductivity with the temperature at a constant frequency was also noticed after dispersion. This dependence is stronger for large size particles (,40 nm) and weaker for small size particles (~12 nm). The Goldstone mode (GM) shifts towards the higher relaxation frequency. These results would be useful to manufacture better optical and electronic devices for display, switching and beam steering applications.
关键词： relaxation frequency,Ferroelectric liquid crystals,spontaneous polarisation,silica nanoparticles,goldstone mode,electro-optical,switching time
更新于2025-09-23 15:21:01
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Ionic relaxation of electrospun nanocomposite polymer-blend quasi-solid electrolyte for high photovoltaic performance of Dye-sensitized solar cells
摘要： New quasi-solid electrolytes were developed by blending PVDF-HFP and PMMA with dispersed TiO2 nanoparticles as fillers and electrospun as, nanofibrous porous membranes activated in electrolyte solutions with various redox couples. Among them, PVDF-HFP/ PMMA 6 wt% TiO2 with LiI based redox electrolyte have achieved highest conductivity of 2.26 × 10?2 Scm-1 and power conversion efficiency (PCE) of 7.081% for its fabricated DSSC. The dynamics of the ionic transport of charge carriers of the developed electrolyte membranes were studied using Random barrier model. The relaxation mechanisms of ionic charge carriers were analysed by Havriliak–Negami formulation. It is inferred that the conductivity is dominated by electrode-polarization and ionic charges exhibit non-debye behaviour in conducting mechanism.
关键词： Electrolyte intake,Nanocomposite,Electrospinning,Relaxation
更新于2025-09-23 15:21:01
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Impact of transition metal ion doping on electron spin relaxation time in CdSe/ZnSe quantum dots
摘要： Theoretical calculations of spin relaxation time (SRT) of conduction electrons have been carried out considering the relaxation mediated by acoustic phonons using k.p perturbation theory and envelope function approximation in a transition metal doped II-VI semiconductor quantum dot under the strong con?nement regime. In this calculation, we are considering the transitions in the Zeeman sublevels arising due to magnetic impurity doping and applied magnetic ?eld in a Mn doped CdSe/ZnSe quantum dots. The occurrence of spin polarization switching at moderately low applied magnetic ?eld is established in Cd1(cid:1)xMnxSe/ZnSe quantum dots. The spin relaxation times have been found to be considerably longer with a higher dopant concentration in small magnetic ?elds (B < 2T) and at very low temperature (T < 50 K) regime. The results may help to demonstrate that, such small quantum dots can successfully be used as polarization switch in different spintronic nano-device.
关键词： Quantum dot,Electronic structure,Spin relaxation,Spintronics,Semiconductor
更新于2025-09-23 15:21:01
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Analyzing role of relaxation time on second harmonic generation and optical dielectric function of impurity doped quantum dots under the aegis of noise
摘要： Present study monitors the influence of relaxation time (τ) on second harmonic generation (SHG) and total optical dielectric function (TODF) of impurity containing quantum dot (QD) under the stewardship of Gaussian white noise. Two distinct roadways viz. ‘additive’ and ‘multiplicative’ have been exploited for the entrance of noise to the system. Both in absence and presence of noise the SHG and TODF peak positions do not exhibit any shift with increase in τ. The SHG peak values display monotonic behavior with the variation of τ. However, the TODF peak values delicately depend on variation of τ being guided by the presence of noise and also on its mode of introduction. Presence of additive (multiplicative) noise causes enhancement (suppression) of SHG and TODF peak values as τ varies over a range. The findings appear to be crucial in the fabrication of QD-based opto-electronic devices where role of noise deserves to be properly addressed.
关键词： Quantum dot,Gaussian white noise,Impurity,Total optical dielectric function,Relaxation time,Second harmonic generation
更新于2025-09-23 15:21:01
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-type PbTe from first principles
摘要： We present an ab initio study that identifies the main electron-phonon scattering channels in n-type PbTe. We develop an electronic transport model based on the Boltzmann transport equation within the transport relaxation time approximation, fully parametrized from first-principles calculations that accurately describe the dispersion of the electronic bands near the band gap. Our computed electronic mobility as a function of temperature and carrier concentration is in good agreement with experiments. We show that longitudinal optical phonon scattering dominates electronic transport in n-type PbTe, while acoustic phonon scattering is relatively weak. We find that scattering due to soft transverse optical phonons is by far the weakest scattering mechanism, due to the symmetry-forbidden scattering between the conduction band minima and the zone center soft modes. Soft phonons thus play the key role in the high thermoelectric figure of merit of n-type PbTe: they do not degrade its electronic transport properties although they strongly suppress the lattice thermal conductivity. Our results suggest that materials like PbTe with soft modes that are weakly coupled with the electronic states relevant for transport may be promising candidates for efficient thermoelectric materials.
关键词： electron-phonon scattering,transport relaxation time approximation,thermoelectric materials,Boltzmann transport equation,n-type PbTe
更新于2025-09-23 15:21:01
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Electrical transport properties and complex impedance investigation of Fe3+ and La3+ co-doping (Pb,Sr)TiO3 thin films
摘要： This work investigates the impact of Fe3+ and La3+ co-doping on the structural, electrical transport and dielectric relaxation properties of PST thin films. XRD and Raman spectroscopy data show that the Fe3+ and La3+ doping induce a pseudocubic to tetragonal structural phase transformation. Schottky barrier heights calculated from temperature-dependent current–voltage plots for the PST, PSTF and PSLTF films decreased to 1.20, 0.59, and 0.36 eV, respectively. This behavior was directly assigned to the increase in oxygen vacancies. The frequency dependence of sample’s impedance revealed the presence of the typical electrical relaxation phenomenon in all films. Activation energies calculated from the imaginary part of the impedance are 1.73 and 0.57 eV: the high value (1.73 eV, PST films) suggests the presence of long-range oxygen vacancy diffusion, while the lower one (0.57 eV PSLTF films) should be associated to the short-range oxygen vacancy diffusion.
关键词： Dielectric relaxation,Thin films,Electrical transport,Impedance spectroscopy
更新于2025-09-23 15:21:01
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Non-linear relaxation of interacting bosons coherently driven on a narrow optical transition
摘要： We study the dynamics of a two-component Bose-Einstein condensate (BEC) of 174Yb atoms coherently driven on a narrow optical transition. The excitation transfers the BEC to a superposition of states with di?erent internal and momentum quantum numbers. We observe a crossover with decreasing driving strength between a regime of damped oscillations, where coherent driving prevails, and an incoherent regime, where relaxation takes over. Several relaxation mechanisms are involved: inelastic losses involving two excited atoms, leading to a non-exponential decay of populations; Doppler broadening due to the ?nite momentum width of the BEC and inhomogeneous elastic interactions, both leading to dephasing and to damping of the oscillations. We compare our observations to a two-component Gross-Pitaevskii (GP) model that fully includes these e?ects. For small or moderate densities, the damping of the oscillations is mostly due to Doppler broadening. In this regime, we ?nd excellent agreement between the model and the experimental results. For higher densities, the role of interactions increases and so does the damping rate of the oscillations. The damping in the GP model is less pronounced than in the experiment, possibly a hint for many-body e?ects not captured by the mean-?eld description.
关键词： coherent driving,Bose-Einstein condensate,narrow optical transition,Gross-Pitaevskii model,relaxation mechanisms
更新于2025-09-23 15:21:01