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The design of plasmonic metasurfaces is often based on solving the Maxwell electromagnetic equations, which can be a time-consuming and expensive process considering many geometrical parameters that can limit design flexibility. To speed up the design flow, a model based on the classical transmission line theory is presented. The proposed equivalent circuit model can predict the plasmon resonance wavelength based on various geometrical parameters including dielectric thickness and disk diameter. In addition, unlike other reported circuit models, the developed model considers the nanostructure array pitch size, which is crucial in metasurface design. Comparison between the results obtained from circuit model and full wavelength simulation showed that the circuit parameters accurately determine the response of the structure. Finally, as a metasurface design demonstration, we utilized our model to simulate aluminum-based gap-plasmon nanodisk arrays for optimizing their optical response to maximize structural color saturation. • The equivalent circuit model for the plasmonic MIM structure composed of Al-nanodisk and Al-oxide was developed. • The optimal geometric parameters for color generation were determined using circuit modeling. • The results showed that the response of the structure to the wave were accurately determined by the circuit parameters. • Changing the diameter of the nanodisks and their pitch size in a certain range lead to the generation of a wide color spectrum. [ABSTRACT FROM AUTHOR]

In this work we propose a finite-difference scheme based circuit model of a general spintronic device and benchmark it with other models proposed for spintronic switching devices. Our model is based on the four-component spin circuit theory and utilizes the widely used coupled stochastic magnetization dynamics/spin transport framework. In addition to the steady-state analysis, this work offers a transient analysis of carrier transport. By discretizing the temporal and spatial derivatives to generate a linear system of equations, we derive new and simple finite-difference conductance matrices that can, to the first order, capture both static and dynamic behaviors of a spintronic device. We also discuss an extension of the spin modified nodal analysis (SMNA) for time-dependent situations based on the proposed scheme. [ABSTRACT FROM AUTHOR]

Effectively alleviating the urban thermal environment is an important problem faced by modern urban environment optimization. This paper predicts the land surface temperature (LST) of Guangzhou based on the whale intelligence optimization algorithm. The circuit model is used to analyze the urban ventilation distribution, and the contribution of wind resistance and ventilation effect to LST is examined. We attempt to explore the relationship between the two in combination with urban functional zoning. Results showed that the temperature range of >34 °C in winter in Guangzhou increased by 49.13% from 1990 to 2030. Guangzhou has four main wind resistances in the ventilation direction, and the areas with large wind resistance are located in high-rise buildings or densely-built areas. The pearl river basin is the main urban ventilation corridor in Guangzhou. The ventilation coefficient is between 0.560 and 1.605, due to the poor ventilation in the central city. Interestingly, the overall contribution rate of urban ventilation and wind resistance to LST reaches 11.09%. Urban functional areas have a significant influence on LST. We found that the temperature in commercial land and transportation land is high, and the proportion of temperature ranges above 34 °C in the functional areas reaches 57% and 22%. This research can provide new insights into the mitigation of the urban thermal environment. • Improve LSTM model by using whale intelligent optimization algorithm to predict LST in 2030; • Calculate the frontal area index (FAI) of four wind directions in Guangzhou; • The ventilation distribution in Guangzhou is analyzed based on the circuit model; • Explore the relationship between urban function and LST, and the contribution of FAI and urban ventilation to LST. [ABSTRACT FROM AUTHOR]

In this work, an efficient circuit model of functional thin-film graphene-assisted metamaterial devices with exploiting transmission line theory is presented. The design is done by the usage of a MATLAB code analytically and the numerical results are obtained by the Finite Element Method (FEM) to verify the accuracy and validity of the circuit model approach. This paper proposes two new broadband graphene metasurface absorbers at terahertz frequencies. At first, a metasurface absorber consisting of pyramid graphene patches separated by dielectric layers is introduced. For most absorber applications, the bandwidth of the absorber is one of the most remarkable metrics. The obtained normalized absorption bandwidth for this absorber is 83.85 % for 90 % absorption with a bandwidth of 4.57 THz. To attain broad frequency bandwidth, we design the metasurface absorber consisting of disk graphene and extract its circuit model. There is good agreement between the results of the circuit model and those of the full-wave simulations. Also, the obtained normalized absorption bandwidth is 82.57 % for 90 % absorption with a bandwidth of 4.74 THz. The suggested method is easy and general, so we can apply it to the design and the simulation of other subwavelength structures in the wide frequency range from terahertz (THz) to visible regions. • This paper proposes two new broadband graphene metasurface absorbers at terahertz frequencies. • At first, a metasurface absorber consisting of pyramid graphene patches separated by dielectric layers is introduced. Also, simulation results of the proposed structure with its circuit model are verified. • To achieve broad bandwidth, we design the disk graphene metasurface absorber and obtain its circuit model. There is good agreement between the results of the circuit model and those of the full-wave simulations. • The proposed method is simple and general and can be applied to the design and the simulation of other subwavelength structures in the broad frequency range from terahertz (THz) to visible regions. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator-driven electroluminescence (TDEL) that can convert human kinetic energy into visible light has attracted extensive attention in wearable electronics. However, the brightness is usually low due to the low electric field strength on the phosphors caused by impedance mismatch. In this work, a TDEL system with optimal brightness has been proposed by adjusting the dielectric constant of nanocomposite and matching impedance. The circuit model of the TDEL system is established and the voltage of the EL layer is predicted through simulation with an error below 4.7%. Finite element simulation is used to simulate the optimal field strength of phosphors under the dual effects of voltage drop and polarization enhancement of the EL layer caused by the increase of dielectric constant of nanocomposites. When the volume ratio of ZnS:Cu is 40% and the dielectric constant of the composite increases from 12 to 22.8, the optimal brightness value increases by 172%. Finally, a patterned TDEL system driven by walking or running to realize night alarm and information exchange is demonstrated. This study opens the window to improve the brightness of TDEL system through permittivity manipulation and impedance matching, which applies to different types of TENG, luminescent particles, and dielectric nanocomposites. A triboelectric nanogenerator-driven electroluminescence system with optimal brightness has been proposed by adjusting the dielectric constant of nanocomposite and matching impedance with TENG. The equivalent circuit model of the system is constructed and voltage of EL layer can be predicted. The finite element simulation is used to simulate the best field strength of phosphors under the dual effects of voltage drop and polarization enhancement of EL layer caused by the increase of dielectric constant of nanocomposites in TDEL system. This study opens the window to improve the brightness of TDEL system through permittivity manipulation and impedance matching, which is applicable to different types of TENG, luminescent particles and dielectric nanocomposites. [Display omitted] • Brightness-enhanced electroluminescence has been proposed by adjusting the dielectric constant and impedance matching. • The equivalent circuit model of the system is constructed and voltage of EL layer can be predicted. • Finite element simulation is used to simulate the best field strength of phosphors in TDEL system. [ABSTRACT FROM AUTHOR]

Abstract: This work presents the design of an estimator-based on equivalent circuit for the state of charge of battery in order to some batteries behavior. In order to achieve the goal we present in the first stage the different batteries and some equivalents circuits treated in literature. In the second stage we design the Adaptive Sliding Mode Observer-based (ASMO) on a third order state space mode. two phases is considered: in the first one we identify the parameters of the equivalent circuit chosen, the second one treat the ASMO design taking into a count the variation of capacitor and an adaptation law is considered for this. The ASMO robust observers are developed and compared in some simulations to emphasize the observer performance. [Copyright &y& Elsevier]

Abstract: An electrical equivalent circuit model is developed to study the thermal effects in capacitive MEMS accelerometer. The mechanical system of the MEMS is implemented as an analogous electrical system and analyzed under different temperature conditions in the range of 100K to 400K. The variation in elongation, spring constant, damping coefficient of the MEMS cantilever are incorporated in the model. The entire analysis is carried at a constant pressure of 30Pa. The transient and frequency response is determined by simulating the equivalent circuit using PSpice® circuit simulator. [Copyright &y& Elsevier]

Abstract: Superconducting passive microwave devices unlike routine normal conductor ones, due to dependence of superfluid density (ns) to current distribution, have a nonlinear behavior called Nonlinear Meissner Effect (NME). In this paper, a nonlinear distributed circuit model for HTS transmission lines with sub-wavelength longitudinal non-uniformity in the case of weak nonlinearity is proposed. This model is based on the quasi-TEM approximation of sub-wavelength non-uniform transmission lines (SW-NUTLs) that proposes closed form formulas for effective characteristic impedance and complex propagation constant of SW-NUTLs. Any NUTLs can be modeled with the mentioned method through dividing it into adequately small subsections to fulfill sub-wavelength condition. Regarding these propagation parameters relations, some effective equations for RLGC parameters are inferred. Because of dependence of the penetration depth and the real part of conductivity on ns, the proposed effective resistance and inductance depend on current distribution that in case of weak nonlinearity, follow a square-law form. As such the nonlinear microwave effects such as Intermodulation distortion (IMD) and harmonic generation can be calculated with harmonic balance (HB) Analysis. This semi-analytical approach shows great accuracy in different test cases. [Copyright &y& Elsevier]

A complete high-frequency small-signal circuit model of a 40 Gb/s butterfly electroabsorption modulator integrated laser module is presented for the first time to analyze and optimize its electro-optic (E/O) response and reflection characteristics. An agreement between measured and simulated results demonstrates the accuracy and validity of the procedures. By optimizing the bonding wire length and the impedance of the coplanar waveguide transmission lines, the E/O response increases approximately 5% to 15% from 20 GHz to 33 GHz, while the signal injection efficiency increases from approximately 15% to 25% over 18 GHz to 35 GHz. [ABSTRACT FROM AUTHOR]

• A developed circuit model approach is exploited to model multi-layers structures. • A reconfigurable device is designed, can works as both wide-band and multi-band absorber. • A multiple-bias scheme is introduced to provide more degree of adjustability. • A developed algorithm is used to optimize design parameters. The terahertz frequency band becomes a growth platform of various applications from medical imaging to indoor communications. Emerging new materials such as graphene and developing reliable models paved the design way for graphene-based microstructures. This paper proposes a relatively comprehensive design methodology for graphene-based multi-layers structures. The procedure includes forming device geometry, finding graphene patterns, material types, and optimizing control parameters. In this way, a reconfigurable THz wave absorber is introduced. Exploiting a multi bias scheme for a single graphene layer provide opportunity to affect device reaction via bias itself and patterns period simultaneously which increase adjustability of device response. Also using two different graphene patterns turns the device complex regarding design optimizations and simulations. So a well-known and simple circuit representation is used to design the proposed methodology and the proposed device. Knowing equivalent circuit models for the device elements triggers developing an evolutionary algorithm to search for a desirable response. In this context, the paper suggests using a weighted binary matrix in the design process. The matrix determines bias schemes for each layer. Then an evolutionary algorithm optimizes whole biases values. The expectation is more in-depth control over the device behavior via biases values. This is verified by exploited circuit model formulations and Finite Element Method (FEM) as numerical simulation for a unique three layers device. [ABSTRACT FROM AUTHOR]