Improving the performance of perovskite solar cells via addition of poly(3-dodecylthiophene)-grafted multi-walled carbon nanotubes

Multi-walled carbon nanotubes grafted with poly(3-dodecylthiophene) (MWCNT-g-PDDT) and pure MWCNT were embedded into the active layer to investigate the optical, morphological, and photovoltaic properties of CH₃NH₃PbI₃ perovskite solar cells. Using an optimized concentration of MWCNT-g-PDDT (0.01%) improved photoresponse of perovskite structure in the wavelength range of 400?800 nm. Field emission scanning electron microscopy revealed that addition of 0.01% MWCNT-g-PDDT reduced the pin-holes and empty spaces. The grafted MWCNT enhanced the J_sc as well as PCE by reduction in series resistance and impressive charge transfer from perovskite active layer to the contact transport layers.

     

A study of principle stress rotation on granular soils using DEM simulation of hollow cylinder test

This study presents the numerical modeling of a hollow cylinder test (HCT) on granular soils by modifying the TRUBAL code. The discrete element method (DEM) was employed for this purpose. Owing to the significant expenditure of the HCT, a verified numerical modeling for this test was developed. The introduced numerical model (HCTBALL) defines plane and cylindrical walls for the boundary conditions to be applied. In addition, the article presents an efficient method to apply the torque. The displacements of the inner and outer walls are interdependent while torsion was applied to control the intermediate principal stress parameter (b). To verify the model, the paper employs results from experimental HCTs on Firoozkooh sand under both monotonic loading and drained conditions. A comparison of the presented model and the experimental results shows that both are closely concordant.It was shown that the deviatoric stress decreases as the principal stress angle (α) increases. In addition, it was observed that by increasing the confining pressure, the internal friction angle (φ′) decreases; however, at higher confining pressures, this reduction is insignificant. Furthermore, this study investigates the coordination number and its relationship to volumetric strain variations.     

A hybrid GA–SQP optimization technique for determination of kinetic parameters of hydrogenation reactions

A hybrid optimization technique, GA–SQP, is developed in which the genetic algorithm (GA) which is a stochastic method is combined with the sequential quadratic programming (SQP) method which is a deterministic method. This method was used to determine the kinetic parameters of the set of highly nonlinear hydrogenation reactions. Catalyst deactivation was also taken into account. The ability of GA and SQP in solving this type of problem was investigated. It was shown that although the SQP is fast, it is not able to solve this problem properly and is very sensitive to the choice of initial point. The GA was able to solve the problem after a large number of generations. It was shown that the new GA–SQP hybrid method is able to determine the final solution considerably faster than the GA while it is not sensitive to the initial point.     

Application of pressure-cycle purge (PCP) in dry-down of ultra-high-purity gas distribution systems

The existence of trace amounts of moisture in process gases could adversely affect the fabrication of semiconductor devices. One important and practical challenge in transporting ultra-high-purity (UHP) gases from the point-of-storage (POS) to the point-of-use (POU) is the susceptibility of the gas distribution systems to molecular contaminants, especially moisture. In modern micro/nanoelectronic manufacturing plants, the moisture content at the POU has to satisfy very stringent specifications. Once a distribution system is contaminated, a significant amount of purge time is required to recover the system background due to the strong interactions between moisture molecules and the inner surfaces of the components in a gas distribution system. Because of the very high cost of UHP gases and factory downtime, it is critical for high-volume semiconductor manufacturers to reduce purge gas usage as well as purge time during the dry-down process. In the present work, a combination of experimental investigation and process simulations is used to compare the traditional steady-state purge (SSP), which typically is operated at constant pressure and flow rate, with the pressure-cycle purge (PCP) process in which the pressure and flow rate are cycled at a controlled frequency and interval. The results show that under certain conditions the new PCP process has significant advantages over the SSP process; for example, it reduces the purge time and gas usage when the gas purity at POU is the principal concern. This conclusion was confirmed by the experimental investigation on lab-scale gas distribution test beds as well as by the simulation of industrial scale systems. The process model developed and used in this work couples gas phase transport processes with surface adsorption/desorption and the purge schedule introduced by pressure variation in the system. This model is then validated using experimental results under various operating conditions. The process simulator is a useful tool for industrial applications in parametric studies and purge process optimization. The effect of key operational parameters, such as start time of PCP process as well as choice of PCP patterns in the PCP process, are presented.     

Mitigating Socio-Economic-Environmental Impacts During Drought Periods by Optimizing the Conjunctive Management of Water Resources

Multi-period optimization of conjunctive water management can utilize reservoirs and aquifer carry-over to alleviate drought impacts. Stakeholders’ socio-economic and environmental indices can be used to minimize the socio-economic and environmental costs associated with water shortages in drought periods. The knowledge gap here is the evaluation and inclusion of the socio-economic and environmental value of conjunctive water management in terms of its drought mitigation capability. In this paper, an integrated water quantity-quality optimization model that considers socio-economic and environmental indices is developed. The model considers and integrates reservoir and aquifer carry-over, river-aquifer interaction and water quality with stakeholders’ socio-economic indices of production, net income and labor force employment to evaluate the socio-economic and environmental value of conjunctive water management. Total dissolved solid (TDS) is used as the water quality index for environmental assessments. The model is formulated as a multi-period nonlinear optimization model, with analysis determining the optimal decisions for reservoir release and withdrawal from the river and aquifer in different months to maximize the socio-economic indices of stakeholders within the environmental constraints. The proposed model is used in Zayandehrood water resource system in Iran, which suffers from water supply and pollution problems. Model analysis results show that conjunctive water use in the Zayandehrood water basin reduces salinity by 50 % in the wetland and keeps water supply reduction during a drought under 10 % of irrigation demand.