- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2018
- Solar Photovoltaic (SPV)
- Fuzzy Logic Control (FLC)
- MATLAB/Simulink
- Simulation
- Variable Step Size Incremental Conductance (VSS InC)
- Maximum Power Point Tracking (MPPT)
- Electrical Engineering and Automation
- Cochin University College of Engineering
- T.K.M College of Engineering
-
Effect of thioglycolic acid molecules on luminescence properties of $$\hbox {Ag}_2$$Ag2S quantum dots
摘要： For monoclinic Ag2S nanocrystals (quantum dots, Ag2S/TGA QDs), the correlation between their luminescence properties and aspects of their passivation by thioglycolic acid (TGA) molecules is considered. The features of quantum confinement effect in the QDs absorption and photoluminescence spectra are analyzed for Ag2S QDs with an average size of 1.7–3.1 nm. We show that, in various conditions of passivation of QDs interfaces, the luminescence mechanism of Ag2S/TGA QDs is switched from recombination luminescence in the 870–1000 nm region to exciton luminescence with a band maximum at 620 nm. By means of FTIR spectra, two major types of interactions between TGA molecules and Ag2S QDs, arising due to changing the [Ag+]:[S2?] ratio from 1:0.9 to 1:1.43, are determined. Exciton luminescence (620 nm) occurs in case of using TGA as the sulfur source in Ag2S crystallization and the interface passivation agent, with [Ag+]:[S2?] = 1:1. The analysis of the FTIR spectra indicates bonding of TGA with the Ag2S surface by both thiol and carboxylic groups in this case. With increasing the sulfur concentration in the synthesis of Ag2S/TGA QDs, the exciton luminescence is suppressed. The employment of Na2S as the sulfur source in Ag2S crystallization with TGA acting as the surface passivation agent promotes the formation of recombination centers for IR luminescence. In this case, analysis of the FTIR spectra indicates passivation of Ag2S QDs by TGA molecules due to adsorption of thiol groups. It is found that the photodegradation or IR luminescence of Ag2S/TGA QDs upon exposure to exciting radiation is due to the photolysis of Ag2S nanocrystals with formation of luminescence quenching centers as well as due to photodestruction of TGA molecules.
关键词： Size dependence,Thioglycolic acid,Interaction mechanism,FTIR spectra,Trap state luminescence,Silver sulfide,Luminescence properties
更新于2025-09-23 15:19:57
-
Effect of processing parameters on the size of molten pool in GH3536 alloy during selective laser melting
摘要： A combination of the finite element simulation and experimental measurement is proposed to study the influence of laser power and scanning velocity on the molten pool size in the selective laser melting (SLM) of GH3536 alloy. The results show that line energy density and molten pool size exhibit linear growth relationship within the scope of the study parameters. In addition, several GH3536 alloy samples are fabricated by SLM technology with different parameters. All SLM samples are used for metallographic experiment to measure the molten pool size. The result shows that experimental measurements are in good agreement with the simulation predictions.
关键词： molten pool size,experimental measurement,finite element simulation,GH3536 alloy,selective laser melting
更新于2025-09-23 15:19:57
-
[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Low-voltage Si-Ge Avalanche Photodiodes for Datacom
摘要： Vector linear network coding (LNC) is a generalization of the conventional scalar LNC, such that the data unit transmitted on every edge is an L-dimensional vector of data symbols over a base field GF(q). Vector LNC enriches the choices of coding operations at intermediate nodes, and there is a popular conjecture on the benefit of vector LNC over scalar LNC in terms of alphabet size of data units: there exist (single-source) multicast networks that are vector linearly solvable of dimension L over GF(q) but not scalar linearly solvable over any field of size q' ≤ q^L. This paper introduces a systematic way to construct such multicast networks, and subsequently establish explicit instances to affirm the positive answer of this conjecture for infinitely many alphabet sizes p^L with respect to an arbitrary prime p. On the other hand, this paper also presents explicit instances with the special property that they do not have a vector linear solution of dimension L over GF(2) but have scalar linear solutions over GF(q') for some q' < 2^L, where q' can be odd or even. This discovery also unveils that over a given base field, a multicast network that has a vector linear solution of dimension L does not necessarily have a vector linear solution of dimension L' > L.
关键词： alphabet size,direct sum,scalar network coding,multicast networks,Vector network coding
更新于2025-09-23 15:19:57
-
Coherent Exciton Dynamics in Ensembles of Size-Dispersed CdSe Quantum Dot Dimers Probed via Ultrafast Spectroscopy: A Quantum Computational Study
摘要： Interdot coherent excitonic dynamics in nanometric colloidal CdSe quantum dots (QD) dimers lead to interdot charge migration and energy transfer. We show by electronic quantum dynamical simulations that the interdot coherent response to ultrashort fs laser pulses can be characterized by pump-probe transient absorption spectroscopy in spite of the inevitable inherent size dispersion of colloidal QDs. The latter, leading to a broadening of the excitonic bands, induce accidental resonances that actually increase the efficiency of the interdot coupling. The optical electronic response is computed by solving the time-dependent Schrodinger equation including the interaction with the oscillating electric field of the pulses for an ensemble of dimers that differ by their size. The excitonic Hamiltonian of each dimer is parameterized by the QD size and interdot distance, using an effective mass approximation. Local and charge transfer excitons are included in the dimer basis set. By tailoring the QD size, the excitonic bands can be tuned to overlap and thus favor interdot coupling. Computed pump-probe transient absorption maps averaged over the ensemble show that the coherence of excitons in QD dimers that lead to interdot charge migration can survive size disorder and could be observed in fs pump-probe, four-wave mixing, or covariance spectroscopy.
关键词： coherent electronic dynamics,pump-probe transient absorption spectroscopy,CdSe quantum dots dimers,exciton dynamics,size dispersion effects
更新于2025-09-23 15:19:57
-
Effects of different complexing agents on the physical properties of ZnO nanoparticles
摘要： ZnO nanoparticles have been synthesised via a co-precipitation method using different complexing agents. X-ray diffraction (XRD) analysis revealed that ZnO nanoparticles were composed of a single hexagonal wurtzite phase. Transmission electron microscopy (TEM) analysis indicates that the samples prepared without any complexing agent have slight agglomeration characteristics presenting a prismatic morphology and a wider size distribution from 22 to 72 nm, which provides good material packing density. However, samples synthesised using urea and glycine are similar and show spherical-like morphology. XRD and TEM analyses indicate that complexing agents also have an important role in the size of the ZnO nanoparticles, where the average particle size of 47 and 22 nm were obtained using urea and glycine, respectively.
关键词： size distribution,glycine,ZnO,complexing agents,co-precipitation,urea,morphology,nanoparticles
更新于2025-09-23 15:19:57
-
Examining Storm Asymmetries in Hurricane Irma (2017) Using Polarimetric Radar Observations
摘要： Dual-polarization radar observations of Hurricane Irma (2017) provide new insight into the microphysical structure of a mature tropical cyclone that can be tied to the cyclone dynamics. The primary eyewall exhibited a radar signature of hydrometeor size sorting, which implied that large drops fell out near persistent upward motion in the front-right quadrant of the storm, while smaller drops were advected downstream. In the outer rainbands, convective initiation was also preferred in the front-right quadrant, whereas stratiform precipitation was predominant downwind. For both the primary eyewall and outer rainbands, the preferred quadrant for convective initiation was consistent with the expected kinematic asymmetry of a tropical cyclone in weak environmental wind shear but with moderate translation speed. The developing secondary eyewall exhibited a different asymmetry that indicated a stratiform-to-convective transition associated with heavy precipitation in the rear quadrants. This transition is consistent with hypothesized dynamical theories for secondary eyewall formation.
关键词： hydrometeor size sorting,stratiform precipitation,microphysical structure,Hurricane Irma,tropical cyclone,convective initiation,dual-polarization radar,secondary eyewall formation
更新于2025-09-23 15:19:57
-
Hybrid spherical particle field measurement based on interference technology
摘要： Interferometric particle imaging is widely used in particle size measurement. Conventional algorithms, which focus on single size particle fields, have difficulties in extracting each interference fringe in a hybrid spherical particle field due to the noise. To solve this problem, an iterative mean filter (IMF) algorithm is proposed. Instead of the specific mean filter template coefficient, the noise is reduced by iterating the calculation results under different template coefficients. The average value of the calculation results excluding the gross error is output as the final result. The effect of different template coefficients are simulated, furthermore, the value range of template coefficients has been analyzed. The interferogram of the hybrid spherical particle field from 21.3 μm to 57.9 μm is processed by the conventional algorithms with specific template coefficients of 2, 8, 12 and the IMF algorithm. The corresponding measurement errors are 17.22%, 10.69%, 9.04% and 5.11%. The experimental results show that the IMF algorithm would reduce measurement error, and could be potentially applied in particle field measurement.
关键词： interferometric particle imaging,particle size measurement,hybrid spherical particle field,gross error elimination
更新于2025-09-23 15:19:57
-
Fractal Analysis - Applications in Physics, Engineering and Technology || Fractals in Antennas and Metamaterials Applications
摘要： Recently, telecommunications systems have been requiring more advanced features in the design and operation. Among others a smaller size of devices, which can be integrated for multiple mobile communications systems, applied in one user's device board, such as PDA or smartphone. Moreover, the cost of mass production should be minimized as much as possible. To meet part of that request, the antennas of these devices should have small size, lower weight, operating in multiple frequency bands and/or be broadband. There are many research methods to achieve this goal, one of which is using the fractal geometries for the shape of antenna elements. In recent years, there are many fractal shapes that have been proposed for such applications, and the designed antennas have significantly improved antenna features such as smaller size, operating in multi-frequency bands, with improved power gain and efficiency. In recent years, the new approach for modern antenna the metamaterials, MTM, is adopted, and sometimes that based on the fractal geometry is adopted.
关键词： fractal geometries,fractal antenna,antenna array,efficiency,fractal dimension,IFS,metamaterials,power gain,MTM,multiband,antenna elements,compact size
更新于2025-09-19 17:15:36
-
Atomic layer deposition for membrane interface engineering
摘要： In many applications, interfaces govern the performance of membranes. Structure, chemistry, electrostatics, and other properties of interfaces can dominate the selectivity, flux, fouling resistance, and other critical aspects of membrane functionality. Control over membrane interfacial properties, therefore, is a powerful means of tailoring performance. In this Minireview, we discuss the application of atomic layer deposition (ALD) and related techniques in the design of novel membrane interfaces. We discuss recent literature in which ALD is used to (1) modify the surface chemistry and interfacial properties of membranes, (2) tailor the pore sizes and separation characteristics of membranes, and (3) enable novel advanced functional membranes.
关键词： membrane interface engineering,pore size tuning,surface modification,functional membranes,atomic layer deposition
更新于2025-09-19 17:15:36
-
Calculations of defect states in various sizes of InN nanowires
摘要： InN has received considerable attentions due to its small band-gap and unique properties in the III-nitride family. Understanding the effects of defects on optoelectronic properties of InN nanowire is essential for exploring its applications in future nanodevices. In this work, we have systematically calculated defect states in InN nanowires based on density-functional theory. Hydrogen passivation and several potential intrinsic point defects are considered in various sizes of nanowires, as well as charged defect states. For small-sized hexagonal nanowires, VN at N-poor condition or NIn at N-rich condition is the most stable defect. Whereas for larger-sized nanowires, VN and InN defects are competing when the N chemical potential changes, showing obvious size effect of the defect stability on the nanowire surface. Those defect states change the electronic structure of the nanowires drastically by introducing empty bands or deep level and provide possibility to tailor the optical properties in terms of forming different stable defects.
关键词： InN,nanowires,size effect,first-principals calculations,electronic structure,defects
更新于2025-09-19 17:15:36