Photon Management for Thin-Film Quantum Dot Solar Cells

L'abstract è presente nell'allegato / the abstract is in the attachmen

Evaluation and implementation of a 5-level hybrid DC-DC converter

In this work, a hybrid voltage regulator topology is analyzed, implemented, and evaluated. The common topologies of DC-DC converters have proven to be lacking in some aspects, such as integrability for buck converters, or maximum efficiency for switched-capacitor regulators. The hybrid topology tackles these shortcomings by combining the advantages of switched-capacitor and inductor-based voltage regulators. A 5-level buck converter is evaluated, implemented, and compared to other converter implementations using the same components. The 5-Level Buck converter can achieve 5 different levels, allowing it to cover 4 operation regions, each between 2 levels. Accordingly, it covers a wide range of output voltages. By reducing the voltage difference at the inductor input, the 5-level buck converter can use smaller inductor compared to both 3-level and conventional buck converters which makes it cheaper, smaller in size, and much more efficient. Simulations show proper functionality of the 5-Level topology, while putting restrictions on the inductor size, efficiency, and component footprint (or total converter area). A test PCB is implemented for verification of the functionality and experimental measurements show that for the same switching frequency and inductor size, the 5-level buck converter achieves up to 15% efficiency improvement over a conventional buck converter and a 3-level buck converter at certain output voltage ranges. Peak efficiency of 94% has been achieved by the 5-Level hybrid converter, which includes all external switching and conduction losses. The proposed hybrid topology proved to yield high conversion efficiency even in the face of component size limitations, which indicates potential benefit in using multilevel converters for several off-chip as well as on-chip applications

Experimental and Theoretical Study on Reverse Osmosis Based Water Desalination

Freshwater availability has dropped due to population growth, inefficient use, climate change, and industrial pollution. Although the reverse osmosis, RO, system is one of the most effective desalination technologies worldwide, spiral wound membranes still need deeper theoretical and experimental investigations for removing salts under low energy consumption. In this study, the performance of a commercial pilot RO plant that utilizes a spiral wound seawater membrane module is experimentally investigated under a wide range of operating parameters. In addition, a Mathematical model is developed based on the solution-diffusion model theory and then solved using an in-house MATLAB algorithm to analyze its performance. The theoretical and experimental results were then compared. The present results revealed that the mathematical model’s predictions were highly consistent with the actual experimental results, achieving an average accuracy of about 98%. The average deviation was 4.0578% when predicting water productivity and just 0.2755% when estimating the salt rejection coefficient. The findings of this study could assist designers in predicting the membrane’s performance and selecting the most advantageous operational parameters for supplying water to the RO system

Experimental and Theoretical Study on Reverse Osmosis Based Water Desalination

Freshwater availability has dropped due to population growth, inefficient use, climate change, and industrial pollution. Although the reverse osmosis, RO, system is one of the most effective desalination technologies worldwide, spiral wound membranes still need deeper theoretical and experimental investigations for removing salts under low energy consumption. In this study, the performance of a commercial pilot RO plant that utilizes a spiral wound seawater membrane module is experimentally investigated under a wide range of operating parameters. In addition, a Mathematical model is developed based on the solution-diffusion model theory and then solved using an in-house MATLAB algorithm to analyze its performance. The theoretical and experimental results were then compared. The present results revealed that the mathematical model’s predictions were highly consistent with the actual experimental results, achieving an average accuracy of about 98%. The average deviation was 4.0578% when predicting water productivity and just 0.2755% when estimating the salt rejection coefficient. The findings of this study could assist designers in predicting the membrane’s performance and selecting the most advantageous operational parameters for supplying water to the RO system

Work Environment And Corporate Culture Influence On The Performance Of Employees Of Pt. Tiga Serangkai Pustaka Mandiri

The purpose of this study are: first, to Determine the influence of the work environment on the performance of employees in the company; second, to Determine the influence of corporate culture on the performance of employees in the company; third, to Determine the influence of the working environment and corporate culture on the performance of employees in the company. This research is quantitative, by taking samples at PT. Tiga Serangkai Pustaka Mandiri, Surakarta, Indonesia. The study population and sample as many as 268 employees were taken by 100 employees. The technique of collecting data using questionnaires. The data analysis technique used is multiple linear regression analysis. The results obtained showed that: first, there is a positive and significant contribution of the work environment on employee performance at PT. Tiga Serangkai Pustaka Mandiri; second, there is a positive and significant contribution of the corporate culture on employee performance at PT. Tiga Serangkai Pustaka Mandiri; third, there is a positive and significant contribution of the work environment and corporate culture on employee performance at PT. Tiga Serangkai Pustaka Mandiri

Catalytic behavior and antibacterial/antifungal activities of new MNPs/zeolite@alginate composite beads

In this paper, a new family of composite materials was prepared based on calcium alginate and metal nanoparticle-loaded zeolite omega. Different types of metal nanoparticles (NPs), namely Cu, Co and Fe, were loaded onto zeolite omega to test the performance of the resulting metal/zeolite@alginate composites towards the catalytic reduction of methylene blue dye. To examine their application field as broadly as possible, these composite beads were also tested as antibacterial and antifungal agents against several types of bacteria. Several techniques such as XRD, XRF, FTIR, XPS, SEM and TGA were used to characterize the samples. The obtained results showed that all the composite bead samples were effective in the reduction of MB dye. The composite Co/Zeolite@ALG with relatively low Co nanoparticle (NP) content was selected as the best performing catalyst due to its reduction of MB dye being completely achieved in 3 min with a rate constant of 0.02 min-1, which was attributed to its highly porous structure. The reuse tests conducted on the best-performing catalyst showed good results which persisted through five successive cycles. For antibacterial and antifungal activities, the Cu/Zeolite@ALG and Fe/Zeolite@ALG composites showed good activity with significant inhibition zones

The effect of compliance on the impact of mass drug administration for elimination of lymphatic filariasis in Egypt

We studied effects of compliance on the impact of mass drug administration (MDA) with diethylcarbamazine and albendazole for lymphatic filariasis (LF) in an Egyptian village. Baseline microfilaremia (mf) and filarial antigenemia rates were 11.5% and 19.0%, respectively. The MDA compliance rates were excellent (> 85%). However, individual compliance was highly variable; 7.4% of those surveyed after five rounds of MDA denied having ever taken the medications and 52.4% reported that they had taken all five doses. The mf and antigenemia rates were 0.2% and 2.7% in those who reported five doses of MDA and 8.3% and 13.8% in those who reported zero doses. There was no significant difference in residual infection rates among those who had taken two or more doses. These results underscore the importance of compliance for LF elimination programs based on MDA and suggest that two ingested doses of MDA are as effective as five doses for reducing filariasis infection rates

Enabling high-efficiency InAs/GaAs Quantum Dot Solar Cells by Epitaxial Lift-Off and Light Management

We report thin-film InAs/GaAs QD solar cells fabricated by epitaxial lift-off of 3-inch wafers containing QD epi-structures with high in-plane QD density. External quantum efficiency measurements demonstrate enhanced QD harvesting in the thin-film configuration. Numerical simulations show that remarkably high increase of the QD photocurrent may be achieved by replacing the planar rear mirror with micro-structured photonic gratings. Measurements of diffraction efficiency of grating prototypes realized on GaAs wafers by nanoimprint lithography are presented