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The process of the power conversion increases harmonics and losses and reduces the stability of the power. New technology of multilevel inverter can be used to overcome disadvantages of traditional inverters. Multilevel inverter technologies have recently gained popularity as a cost-effective alternative for a variety of industrial applications. This topology has a few noteworthy properties, including lower component, lower switching losses, and better output voltage/current waveform. The reduction of harmonic components in the inverter output voltage/current is the most important requirement in multilevel inverters. The system suggested in this study is made up of four separate renewable energy sources. Three PV solar systems with voltages of (1:3:4)E values and wind-turbine of 2E value are recommended. The total dc sources were combined are (1:2:3:4)E to produce a 21-level output voltage. Also the system is designed to produce 17-level in the case of absence wind. The system is designed using MATLAB program. [ABSTRACT FROM AUTHOR]

We emphasize the potential of soft-modeling multivariate curve resolution method to extract pure difference spectra and kinetic profiles from data sets obtained by femtosecond transient absorption experiments. The example of the photo-switching of photochromic salicylidene aniline after 266 nm excitation will be detailed. [ABSTRACT FROM AUTHOR]

In this presentation we report a theoretical study on the performance of diarylethene photoswitches. We start with a comparison between the electronic structures of different substituted diarylethene cores. Using a NEGF-DFT formalism we compute self-consistently transmission and IV curves with a focus on the impact of the substituents usually introduced for various synthetic and functional reasons. We find that the conductance properties of the diarylethene photoswitches are rather insensitive to these substitutions in the core. In the interpretation of our results, we make a connection between transmission spectra and molecular electronic properties. [ABSTRACT FROM AUTHOR]

The details of metal-molecule coupling play a pivotal role in the functionality of molecular junctions. Molecules that have intrinsic switchable properties may lose this capability after coupling to electrodes. On the other hand, connecting passive molecules to electrodes may lead to a switchable molecular device ('extrinsic switching'). Here, we first discuss this general matter, and then focus on two specific cases, one of intrinsic switching (for photochromic diarylethenes) and one of extrinsic switching (for hydrogen molecules) in gold-molecule-gold structures. [ABSTRACT FROM AUTHOR]

The β contrast in molecular switches has been evaluated at different levels of approximation to assess the performance of typical DFT methods, employing GGA, hybrid, and long-range corrected exchange-correlation functionals. It appears that both the BLYP and B3LYP XC functionals behave poorly and either strongly underestimate or overestimate the β contrasts. On the other hand, the performance of the LC-BLYP functional is better, though the improvement over HF is not systematic. [ABSTRACT FROM AUTHOR]

We investigate the effects of a static electric field on the third-order nonlinear optical (NLO) properties - static second hyperpolarizabilities y - of symmetric singlet diradical molecules using the valence configuration interaction scheme. It is found that the application of the field strongly (~ two - three order) enhances the component of y along the axis joining the two radical sites of symmetric diradicals having intermediate diradical characters as compared to those of closed-shell and pure diradical molecules in absence of a field. These results are expected to open a new path to realize an electric field control NLO switch based on open-shell singlet molecular systems. [ABSTRACT FROM AUTHOR]

Electromagnetically induced transparency (EIT), which is known as an efficient control method of optical absorption property, is investigated using the polarizability spectra and population dynamics obtained by solving the quantum Liouville equation. In order to clarify the intermolecular interaction effect on EIT, we examine several molecular aggregate models composed of three-state monomers with the dipole-dipole coupling. On the basis of the present results, we discuss the applicability of EIT in molecular aggregate systems to a new type of optical switch. [ABSTRACT FROM AUTHOR]

Substituent and solvent effects on tautomeric equilibria of isomeric phenylazo naphthols and the analogous Schiff bases are calculated by various quantum chemical methods and solvation models. Special emphasis is put on the reliability of the computational procedures used. The results obtained should aid in resolving discrepancies of experimental data resulting from UV/Vis and NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Bianthrone is a sterically hindered compound that exists in the form of two non-planar isomers. Our experimental study of single-molecule junctions with bianthrone reveals persistent switching of electric conductance at low temperatures, which can be reasonably associated to molecular isomerization events. Temperature dependence of the switching rate allows for an estimate of the activation energy of the process, on the order of 35-90 meV. Quantumchemical calculations of the potential surface of neutral bianthrone and its anion, including identification of transition states, yields the isolated molecule isomerization barriers too high vs. the previous estimate, though in perfect agreement with previous experimental studies in solution. Nevertheless, we show that the attraction of the anion in the vicinity of the metal surface by its image charge can significantly alter the energetic landscape, in particular, by reducing the barrier to the values compatible with the observed switching behavior. [ABSTRACT FROM AUTHOR]

Organometallic complexes associated with an appropriate choice of ancillary ligands reveal to have a wide range of physical properties leading to promising applications when incorporated in nano-size devices. The challenge is to design innovative multifunctional compounds based on redox active carbon-rich organometallics associated with spin carriers and/or photochromic units. A multidisciplinary approach in this area has proved to be efficient in a series a systems combining carbon-rich bridging ligands and redox metallic moieties. In this domain, the role of theoretical investigations based on quantum mechanics tools have a crucial role in rationalizing and in helping designing systems possessing target properties. [ABSTRACT FROM AUTHOR]

This paper focuses on a few of the intricacies when relating theoretical calculations of first hyperpolarizabilities to experimental observables in second-order nonlinear optics. This is important for both theoreticians and experimentalists, as it provides for a better understanding of what the level of sophistication should be for the theory versus the experimental precision attainable in nonlinear optical experiments with pulsed lasers, but also to appreciate that there are limitations and assumptions that are imposed by the nature of the experiment. [ABSTRACT FROM AUTHOR]

The use of three tautomeric azocompounds (4-phenylazo-1-phenol, 4-phenylazo-1-naphthol and 4-phenylazoanthracen-1-ol) as a skeleton of tautomeric switches is considered in respect to provide structural conditions (implementation of nitrogen containing antenna) for controlled shift of the tautomeric equilibrium to the pure tautomers. [ABSTRACT FROM AUTHOR]

Rotary and translational motion of synthetic molecular systems can be achieved by photochemical, chemical or electrical energy input based on molecular different hierarchical levels is discussed. [ABSTRACT FROM AUTHOR]

The dynamics of a water soluble spiropyran is investigated by means of femtosecond transient absorption spectroscopy in the visible and infrared spectral range revealing an ultrafast reversible switching behavior under aqueous conditions with a high fatigue resistance. [ABSTRACT FROM AUTHOR]

Ultrafast transient absorption spectroscopy reveals the effect of chemical substitutions on the photoreaction kinetics of biomimetic photoswitches displaying coherent dynamics. Ground state vibrational coherences are no longer observed when the excited state lifetime exceeds 300fs. [ABSTRACT FROM AUTHOR]

We use pump-repump-probe transient absorption spectroscopy to investigate the role of higher-lying electronic states in the photochemistry of a molecular switch. Moreover, replacing the pump pulse by a pulse-shaper-generated phase-stable double pulse, triggered-exchange two-dimensional (TE2D) electronic spectroscopy is established in the visible regime. [ABSTRACT FROM AUTHOR]