Radiation field modeling of multi-lamp, homogeneous photoreactors

For modeling and optimization of photoreactors, knowing radiation distribution inside the reactor is essential because the kinetics of photochemical and photocatalytic reactions are strongly dependent on the local incident radiation. In this work, a Monte Carlo multi-lamp radiation model is proposed. The model takes into account the reflection on the surface of the lamps, the refraction in the quartz lamp envelope, as well as the adsorption and the isotropic re-emission of radiation in the mercury vapor of the lamp. To quantify the shadowing effect among the lamps, the effective transmittance through a UV-lamp turned on, a lamp turned off, and a lamp quartz envelope have been measured. For validation purposes, experimental measurements have been performed using one, two, and three lamps. The model predictions show good agreement with the experimental results. Finally, in order to simplify the numerical solution of the model, the validity of assuming the lamps 100% opaque and 100% transparent have been analyzed.     

Classical and generalized coupled thermoelasticity analysis in one-dimensional layered media

The behavior of thermoelastic waves at the interface of layered medium and distributions of these waves through the domain are examined by applying the direct finite element method to obtain the field variables directly within the spatial and temporal domains. The analysis is performed in a one-dimensional domain with two different layers to provide a means to follow the behavior of the reflected thermoelastic waves at the interface. It appears that the distributions of thermoelastic waves in an isotropic slab with one layer are significantly different from those in multilayered slabs. For instance, the negative displacement waves, several stresses with positive or negative signs and temperature distributions produced in the multilayered domains, are quite different from those in a single layer. This method may be generalized to simulate the propagation of thermoelastic waves in various multilayered regions and analyze the behavior of the layered composite structures under the mechanical or thermal impact loads.     

Synthesis of new polyaryl-substituted imidazoles bridged on enamine or urea moieties and evaluation of their optical and electrochemical properties

Research on Chemical Intermediates - The reaction of the free amine group in polyaryl-substituted imidazole structures with phenyl isocyanate or dimethyl acetylenedicarboxylate gave two new series...     

Athermal performance in high-Q polymer-clad silicon microdisk resonators

We present a method for eliminating the temperature dependence of the resonance wavelength in high-Q silicon-based microdisk resonators by using a polymer cladding with a negative thermo-optic coefficient. Design requirements for athermal performance are derived based on theory and simulation, and their validity is experimentally verified.     

Time-dependent density functional theory benchmarking for the calculations of atomic spectra: efficiency of exc-ETDZ basis set

We present a time-dependent density functional theory (TD-DFT) benchmarking of recently constructed basis set, namely exc-ETDZ (Guevara et al. in J Chem Phys 131: 064104, 2009) for predicting the atomic spectra of the first-row atoms. A systematic testing with 31 density functional methods has been performed to see whether convincing performance of this basis set carries over the TD-DFT formalism. The efficiency of exc-ETDZ basis set for reproducing atomic spectra has been compared with Pople- and Dunning-style basis sets. We focused on the atomic low-lying valence excited states with single excitation character for our benchmarking, and the calculated excitation energies were compared to experimental data. On average, the functionals providing the best match with exc-ETDZ basis are BMK, BH&HLYP and ωB97. Moreover, on the basis of comparison between the results of these superior functionals with CIS(D) estimates, it turned out that TD-DFT and CIS(D) errors are of the same order of magnitude, once the exc-ETDZ basis set is used. Finally, the results of present study indicate that different functionals show results that are highly dependent on the atomic configuration as well as the basis set.     

Nanocrystalline TiO_2 as an efficient and reusable catalyst for the chemoselective trimethylsilylation of primary and secondary alcohols and phenols

Nanocrystalline TiO₂ was used as an efficient and recyclable catalyst for the chemoselective trimethylsilylation of primary and less hindered secondary alcohols and phenols with hexamethyldisilazane（HMDS）.All reactions were performed under mild and completely heterogeneous conditions in good to excellent yields.