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Projector-based renormalization approach to electron-hole-photon systems in their nonequilibrium steady state
摘要： We present an extended version of the projector-based renormalization method that can be used to address not only equilibrium but also nonequilibrium situations in coupled fermion-boson systems. The theory is applied to interacting electrons, holes, and photons in a semiconductor microcavity, where the loss of cavity photons into vacuum is of particular importance. The method incorporates correlation and fluctuation processes beyond mean-field theory in a wide parameter range of detuning, Coulomb interaction, light-matter coupling, and damping, even in the case when the number of quasiparticle excitations is large. This enables the description of exciton and polariton formation and their possible condensation through spontaneous phase symmetry breaking by analyzing the ground-state, steady-state, and spectral properties of a rather generic electron-hole-photon Hamiltonian, which also includes the coupling to two fermionic baths and a free-space photon reservoir. Thereby, the steady-state behavior of the system is obtained by evaluating expectation values in the long-time limit by means of the Mori-Zwanzig projection technique. Tracking and tracing different order parameters, the fully renormalized single-particle spectra and the steady-state luminescence, we demonstrate the Bose-Einstein condensation of excitons and polaritons and its smooth transition when the excitation density is increased.
关键词： exciton condensation,nonequilibrium steady state,semiconductor microcavity,projector-based renormalization method,electron-hole-photon systems,Bose-Einstein condensation,polariton condensation
更新于2025-09-23 15:23:52
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Variational Solution of Steady-Structure in Exciton-Polariton Condensates with a Modified Lagrangian Approach
摘要： Exciton-polariton condensate is a new kind of system exhibiting spontaneous coherence, which is a new quantum dissipation system. Numerical simulation and analytical methods can be used to study the static and dynamical properties of exciton-polariton condensate. In this paper, A modified Lagrangian method is developed for exciton-polariton system to find the steady-state structure and regimes among the parameters of the system, and two new forms of trial wave function are proposed. The modified Lagrangian method is successfully applied to the exciton-polariton system described by the open-dissipative Gross-Pitaevskii equation for the first time. Furthermore, static version of the modified Lagrangian method provides stationary shape of the steady-state structure, while the time-dependent version can be used to study small amplitude oscillations around stationary states. On the one hand, comparison of the profiles for steady-state structure, predicted by the modified Lagrangian and those found from numerical solution of the open-dissipative Gross-Pitaevskii(dGP) equation shows good agreement, thereby proving the accuracy of the trial wave function and validating the proposed approach. Particularly, this new method promotes the deeper cognition and understanding for the dissipative exciton-polariton system and is helpful to explore the mechanism of the gain and dissipation effect on the steady-state structure of the system.
关键词： dissipative,Lagrangian method,trial wave function,exciton-polariton condensate,steady-state structure
更新于2025-09-23 15:22:29
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A spatiotemporal probabilistic model-based temperature-augmented probabilistic load flow considering PV generations
摘要： The probabilistic steady‐state forecasting of a PV‐integrated power system requires a suitable forecasting model capable of accurately characterizing the uncertainties and correlations among multivariate inputs. The critical and foremost difficulties in the development of such a model include the accurate representation of the characterizing features such as complex nonstationary pattern, non‐Gaussianity, and spatial and temporal correlations. This paper aims at developing an improved high‐dimensional multivariate spatiotemporal model through enhanced preprocessing, transformation techniques, principal component analysis, and a suitable time series model that is capable of accurately modeling the trend in the variance of uncertain inputs. The proposed model is applied to the probabilistic load flow carried out on the modified Indian utility 62‐bus transmission system using temperature‐augmented system model for an operational planning study. A detailed discussion of various results has indicated the effectiveness of the proposed model in capturing the aforesaid characterizing features of uncertain inputs.
关键词： PV generation,probabilistic load flow,operational planning,spatiotemporal correlation,steady‐state forecasting
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Intelligence and Safety for Robotics (ISR) - Shenyang, China (2018.8.24-2018.8.27)] 2018 IEEE International Conference on Intelligence and Safety for Robotics (ISR) - Experimental study on operator-based integral sliding mode robust nonlinear control for WPT systems
摘要： In our previous research on wireless power transfer systems, an operator-based sliding mode control design was proposed to regulate the output voltage. However, the steady-state error exists in the nonlinear control system. In this paper, an operator-based integral sliding mode robust nonlinear control design scheme is proposed to eliminate the steady-state error in the wireless power transfer system. Besides, the robust stability is guaranteed by using robust right coprime factorization approach. Results of simulations and experiments are presented to prove the effectiveness of the proposed control design scheme.
关键词： operator-based control,robust nonlinear control,steady-state error,sliding mode control,wireless power transfer
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - On the impact of the metal work function on the recombination in passivating contacts using quasi-steady-state photoluminescence
摘要： Understanding the impact of metal contacts on the recombination within a passivated silicon wafer is crucial for the optimization of various photovoltaic devices such as passivating-contact-based solar cells. To investigate the effect of the metal work function, a selection of metals is applied to aluminum-oxide-passivated n-type crystalline silicon wafers. The saturation current density of the metalized contact (J0m) is determined using the quasi-steady-state photoluminescence method and used as a figure of merit to quantify the effect. We find that J0m increases with the metal work function and that this effect is modulated with the passivation layer thickness. It is more pronounced for thinner passivation layers, which can be attributed to a significant change in the populations of electrons and holes near the silicon surface induced by the metal. Meanwhile thicker layers prevent the charge transfer between the silicon and metal more efficiently leading to insignificant changes in J0m. Based on these findings, we suggest a suitable metal work function range to optimize contact recombination in silicon-based solar cells.
关键词： passivating contacts,surface recombination,saturation current density,quasi-steady-state photoluminescence,work function,Effective lifetime,silicon solar cells
更新于2025-09-23 15:21:01
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Design of an Ultra-Wideband Tightly Coupled Dipole Array
摘要： The superconducting stellarator Wendelstein 7-X is currently being commissioned. First plasmas are expected for the second half of 2015. W7-X is designed to overcome the main drawbacks of the stellarator concept and simultaneously demonstrate its intrinsic advantages relative to the tokamak—i.e., steady-state operation without the requirement of current drive or stability control. An elaborate optimization procedure was used to avoid excessive neoclassical transport losses at high plasma temperature, while simultaneously achieving satisfactory equilibrium and stability properties at high β in combination with a viable divertor concept. In addition, fast-ion confinement must be consistent with the requirements of alpha-heating in a power plant. Plasma operation of Wendelstein 7-X follows a staged approach following the successive completion of the in-vessel components. The main objective of Wendelstein 7-X is the demonstration of steady-state plasma at fusion relevant plasma parameters. Wendelstein 7-X will address major questions for the extrapolation of the concept to a power plant. These include divertor operation at high densities, plasma fueling at high central temperatures, avoiding impurity accumulation, and an assessment of the effect of neoclassical optimization on turbulent transport and fast-ion confinement. A power plant concept based on an extrapolation from Wendelstein 7-X, the helical advanced stellarator, has been developed.
关键词： Fusion power plant,steady-state magnetic confinement,stellarator
更新于2025-09-23 15:21:01
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Degradation of InGaN-based LEDs: Demonstration of a recombination-dependent defect-generation process
摘要： This paper provides insights into the degradation of InGaN-based LEDs by presenting a comprehensive analysis carried out on devices having two quantum wells (QWs) with different emission wavelengths (495 nm and 405 nm). Two different configurations are considered: one with the 495 nm QW closer to the p-side and one with the 495 nm QW closer to the n-side. The original results collected within this work indicate that (i) during stress, the devices show an increase in defect-related leakage both in reverse and low-forward voltage ranges: current increases with the square-root of stress time, indicating the presence of a diffusion process; (ii) stress induces a decrease in the luminescence signal emitted by both quantum wells: the drop in luminescence is stronger when measurements are carried out at low current levels, indicating that degradation is due to the generation of Shockley–Read–Hall recombination centers; (iii) remarkably, the degradation rate is linearly dependent on the luminescence signal emitted before stress by the well, indicating that carrier density impacts on degradation; and (iv) the optical degradation rate has a linear dependence on the stress current density. The results strongly suggest the existence of a recombination-driven degradation process: the possible role of Shockley–Read–Hall and Auger recombination is discussed. The properties of the defects involved in the degradation process are described through steady-state photocapacitance measurements.
关键词： quantum wells,Shockley–Read–Hall recombination,Auger recombination,degradation,steady-state photocapacitance,InGaN-based LEDs
更新于2025-09-23 15:21:01
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Understanding the mechanisms of a conjugated polymer electrolyte for interfacial modification in solution-processed organic-inorganic hybrid perovskite photodetectors
摘要： Interfacial modification is an effective strategy to suppress the dark current in photodetectors for performance improvements. Here, solution-processed conjugated polymer electrolyte poly[(9,9-bis(3’-(N,N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN), widely used for interface engineering in organic and perovskite solar cells, is introduced to the photovoltaic photodetectors based on α-phase formamidinium lead iodide (α-FAPbI3) perovskite at cathode interfaces. The PFN layer has both positive and negative impacts on the overall device performances. The steady-state device parameters including external quantum efficiency, photoresponsivity, and detectivity are enhanced because the dark current is effectively suppressed due to the hindered hole injection by the PFN layer. However, the incorporation of PFN leads to different transient photocurrent dynamics with a peak after turn-on and a long-lived tail after turn-off, increasing the fall time, although it has little impact on the rise time. The proposed mechanisms involve the trapping and detrapping effects of accumulated photogenerated electrons at the electron-transporting layer/PFN interface, which are proved by capacitance-voltage measurements and impedance spectroscopy analysis. Our results have important significance for understanding the different effects and mechanisms of conjugated polymer electrolytes for interfacial engineering in photodetectors and solar cells and selecting suitable interfacial materials for electrode modification in photodetectors.
关键词： Conjugated polymer electrolyte,Transient photocurrent dynamics,Steady-state device parameters,α-FAPbI3 perovskite photodetectors,Interfacial modification
更新于2025-09-23 15:21:01
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Graphite Supported Stainless-Steel Electrode for the Degradation of Azo Dye Orange G by Fenton Reactions: Effect of Photo-Irradiation
摘要： An electrode, stainless steel supported on graphite, was used for the degradation of hazardous organic compounds, azo dye Orange G (OG), using the photoelectro- Fenton (PEF) process. Results showed that the applied current controlled the electrogeneration rate of both ferrous ion and hydrogen peroxide, which in turn affected the dye degradation kinetics. At an applied current density of 45 μA cm?2, the SS-graphite electrode yielded a molar ?H2O2(cid:2)=?Fe2t(cid:2) ratio of 3.6, which was optimal for dye degradation. Under otherwise identical conditions, UV irradiation significantly enhanced OG degradation, i.e., PEF is more effective than electro-Fenton (EF) process. At the optimal applied current density of 45 μA cm?2, or optimal molar ?H2O2(cid:2)=?Fe2t(cid:2) of 3.6, OG decolorization and total organic carbon removal were 83% (in 3 h) and 55% (in 7 h), versus 75% (in 3 h) and 20% (in 7 h) by PEF and EF, respectively. OG degradation by both PEF and EF processes followed the pseudo first-order kinetics, which suggested the major role of OH radical in OG decolorization.
关键词： Stainless steel,Graphite,Orange G,Photo-electro-Fenton (FEF),Steady-state approximation,Decolorization
更新于2025-09-23 15:21:01
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Additive Value of 3T 3D CISS Imaging to Conventional MRI for Assessing the Abnormal Vessels of Spinal Dural Arteriovenous Fistulae
摘要： We investigated the additive value of the 3T 3D constructive interference in steady state (CISS) sequence to conventional MRI for the evaluation of spinal dural arteriovenous fistulae (SDAVF). We included 16 consecutive patients (15 men, 1 woman; age range 42–81 years; mean 64 years) with SDAVF who underwent 3T MRI and digital subtraction angiography (DSA) before treatment. Two neuroradiologists independently evaluated the presence of abnormal vessels on 3D CISS-, T2- and T1-weighted images (T1WI, T2WI), and contrast-enhanced T1WI using a 3-point grading system. Interobserver agreement was assessed by calculating the κ coefficient. The SDAVF site was the cervical region in one patient, the thoracic region in 12 patients, the lumbar region in two, and the sacral region in one. For the visualization of abnormal vessels, the mean score was significantly higher for 3D CISS than the other sequences (P < 0.05). In 12 of 16 cases (75%) both readers made definite positive findings on additional 3D-CISS images. Interobserver agreement was excellent for 3D CISS images (κ = 1.0), good for T1WI (κ = 0.78; 95% confidence interval [CI] 0.54–1.00) and T2WI (κ = 0.74; 95% CI 0.48–1.00) and moderate for contrast-enhanced T1WI (CET1WI) (κ = 0.50; 95% CI 0.21–0.80). Conclusion: For the assessment of abnormal vessels of SDAVF, the 3T 3D CISS sequence adds value to conventional MRI.
关键词： arteriovenous fistulae,spinal dural arteriovenous fistulae,abnormal vessels,constructive interference in steady state,magnetic resonance imaging
更新于2025-09-23 15:21:01