Accurate emulation of steady-state and dynamic performances of PEM fuel cells using simplified models.

The current effort addresses a novel attempt to extract the seven ungiven parameters of PEMFCs stack. The sum of squared deviations (SSDs) among the measured and the relevant model-based calculated datasets is adopted to define the cost function. A Kepler Optimization Algorithm (KOA) is employed to decide the best values of these parameters within viable ranges. Initially, the KOA-based methodology is applied to assess the steady-state performance for four practical study cases under several operating conditions. The results of the KOA are appraised against four newly challenging algorithms and the other recently reported optimizers in the literature under fair comparisons, to prove its superiority. Particularly, the minimum values of the SSDs for Ballard Mark, BCS 0.5 kW, NedStack PS6, and Temasek 1 kW PEMFCs stacks are 0.810578 V2, 0.0116952 V2, 2.10847 V2, and 0.590467 V2, respectively. Furthermore, the performance measures are evaluated on various metrics. Lastly, a simplified trial to upgrade Amphlett's model to include the PEMFCs' electrical dynamic response is introduced. The KOA appears to be viable and may be extended in real-time conditions according to the presented scenarios (steady-state and transient conditions).

Integration of Capacitive Pressure Sensor-on-Chip with Lead-Free Perovskite Solar Cells for Continuous Health Monitoring.

The increasing prevalence of hypertension necessitates continuous blood pressure monitoring. This can be safely and painlessly achieved using non-invasive wearable electronic devices. However, the integration of analog, digital, and power electronics into a single system poses significant challenges. Therefore, we demonstrated a comprehensive multi-scale simulation of a sensor-on-chip that was based on a capacitive pressure sensor. Two analog interfacing circuits were proposed for a full-scale operation ranging from 0 V to 5 V, enabling efficient digital data processing. We also demonstrated the integration of lead-free perovskite solar cells as a mechanism for self-powering the sensor. The proposed system exhibits varying sensitivity from 1.4 × 10-3 to 0.095 (kPa)-1, depending on the pressure range of measurement. In the most optimal configuration, the system consumed 50.5 mW, encompassing a 6.487 mm2 area for the perovskite cell and a CMOS layout area of 1.78 × 1.232 mm2. These results underline the potential for such sensor-on-chip designs in future wearable health-monitoring technologies. Overall, this paper contributes to the field of wearable health-monitoring technologies by presenting a novel approach to self-powered blood pressure monitoring through the integration of capacitive pressure sensors, analog interfacing circuits, and lead-free perovskite solar cells.

Optical investigation and computational modelling of BaTiO3 for optoelectronic devices applications.

ABX3 perovskite-based materials have attracted research attention in various electronic and optoelectronic applications. The ability to tune the energy band gap through various dopants makes perovskites a potential candidate in many implementations. Among various perovskite materials, BaTiO3 has shown great applicability as a robust UV absorber with an energy band gap of around 3.2 eV. Herein, we provide a new sonochemical-assisted solid-phase method for preparing BaTiO3 thin films that optoelectronic devices can typically be used. BaTiO3 nano-powder and the thin film deposited on a glass substrate were characterized using physicochemical and optical techniques. In addition, the work demonstrated a computational attempt to optically model the BaTiO3 from the atomistic level using density functional theory to the thin film level using finite difference time domain Maxwell's equation solver. Seeking repeatability, the dispersion and the extinction behavior of the BaTiO3 thin film have been modeled using Lorentz-Dude (LD) coefficients, where all fitting parameters are listed. A numerical model has been experimentally verified using the experimental UV-Vis spectrometer measurements, recording an average root-mean-square error of 1.44%.

Analytical model for transmission dips in self-assembled two-dimensional colloidal crystals.

Self-assembled two-dimensional (2D) colloidal crystals (CCs) are utilized in various optical devices, lasers, biosensors, and light harvesting applications. Optical design tuning capabilities, in terms of sphere refractive index and diameter size, can influence the optical characteristics for the close-packed single-layer or multilayer structures. Often transmission dips in 2D CCs are observed, which cannot be explained by Bragg diffraction as it does for 3D photonic crystals. In this work, an analytical attempt to accurately model the transmission dips observed in the 2D CCs optical spectra is presented, aiming to explain the origin of these dips. The formation of a broad dip was studied experimentally as well. A less than 1% mismatching error was found between experiment and theory for the two blaze peak positions as well as for the transmission intensity ratio. Finally, the 2D CCs were integrated in mesostructured solar cells as light trapping structures.

Investigating the UV absorption capabilities in novel Ag@RGO/ZnO ternary nanocomposite for optoelectronic devices.

A facile one-pot method was utilized at room-temperature for the synthesis of novel ternary nanocomposite of Ag@RGO/ZnO, which is introduced as a low cost, efficient and reliable UV absorber. The crystalline, morphological, structural, and optical characteristics of the as-synthesized samples were investigated by various techniques such as XRD, FE-SEM, HR-TEM, XPS, and DRS. The measurements confirm the successful fabrication of the Ag@RGO/ZnO ternary nanocomposite. Optical characterization showed the synergetic role of Ag NPs and RGO NSs in the enhancement of the light absorption of the ternary nanocomposite in the UV portion compared to the bare ZnO NPs. Additionally, band-gap narrowing was observed due to the Ag-doping impact where potential applications for the proposed nanocomposite have been suggested.

Modeling disorder in two-dimensional colloidal crystals based on electron microscope measurements.

Self-assembled two-dimensional colloidal crystals (CCs) are critical components in many optical and optoelectronic devices. Such structures usually exhibit various types of disorder, which sometimes can be beneficial for the desired applications. However, disorder poses challenges to the modeling of two-dimensional structures. In this work, two-dimensional CCs employed in optoelectronic devices, especially dye-sensitized solar cells, are investigated. scanning electron microscope (SEM) images were used to quantify the disorder in the studied structures. As a basis for simulations, disordered model patterns were generated with properties extracted from the SEM images of prepared samples. Optical modeling was performed with a finite-difference time-domain simulator. The simulated transmission data are consistent with the experimentally measured spectra.

Thermoelectric Energy Harvesters: A Review of Recent Developments in Materials and Devices for Different Potential Applications.

The thermoelectric effect encompasses three different effects, i.e. Seebeck effect, Peltier effect, and Thomson effect, which are considered as thermally activated materials that alter directions in smart materials. It is currently considered one of the most challenging green energy harvesting mechanisms among researchers. The ability to utilize waste thermal energy that is generated by different applications promotes the use of thermoelectric harvesters across a wide range of applications. This review illustrates the different attempts to fabricate efficient, robust and sustainable thermoelectric harvesters, considering the material selection, characterization, device fabrication and potential applications. Thermoelectric harvesters with a wide range of output power generated reaching the milliwatt range have been considered in this work, with a special focus on the main advantages and disadvantages in these devices. Additionally, this review presents various studies reported in the literature on the design and fabrication of thermoelectric harvesters and highlights their potential applications. In order to increase the efficiency of equipment and processes, the generation of thermoelectricity via thermoelectric materials is achieved through the harvesting of residual energy. The review discusses the main challenges in the fabrication process associated with thermoelectric harvester implementation, as well as the considerable advantages of the proposed devices. The use of thermoelectric harvesters in a wide range of applications where waste thermal energy is used and the impact of the thermoelectric harvesters is also highlighted in this review.