University of Architecture, Civil Engineering and Geodesy

About: University of Architecture, Civil Engineering and Geodesy is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Finite element method & Beam (structure). The organization has 3808 authors who have published 3822 publications receiving 30736 citations. The organization is also known as: Sofia Polytechnic.

Characterization of Graphene Nanosheets as Electrode Material and Their Performances for Electric Double-Layer Capacitors

Abstract: In this work, graphene nanosheets were prepared using the Hummers-Offeman method. We prepared the resultant graphene electrode with kneading type. The prepared graphene nanosheets were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy, Fourier transform infrared spectroscopy instrument and Raman spectra. Finally, the electrochemical performances of graphene nanosheets in an electrolyte solution of tetraethylammonium tetrafluoroborate ((C2H5)4NBF4, TEABF4) in propylene carbonate (C4H6O3, PC) were examined.

Ratchet motion and current reversal of coupled Brownian motors in pulsating symmetric potentials

Abstract: In this study, we investigate the collective directed transport of coupled Brownian particles in spatially symmetric periodic potentials under time-periodic pulsating modulations. We find that the coupling between two particles can induce symmetry breaking and consequently collective directed motion. Moreover, the direction of motion can be reversed under certain conditions. The dependence of directed current on various parameters is systematically studied. reverse motion can be achieved by modulating the coupling free length and the phase shift of the pulsating potential. The dynamical mechanism of these transport properties is understood in terms of the effective-potential theory and the space-time transformation invariance. The directed transport of coupled Brownian motors can be manipulated and optimized by adjusting the coupling strength, pulsating frequency, or noise intensity.

The influence of GC/AT composition on intercalating and semi-intercalating binding of ethidium bromide to DNA

Abstract: The binding parameters of ethidium bromide (EtBr) with DNA of various GC/AT ratios were determined using absorption and fluorescence spectroscopy. Our experimental data clearly demonstrate the co-existence of fluorescing and non-fluorescing types of “strong” binding at low concentration of EtBr. The fluorescent complex corresponds to the ordinary intercalative model. The non-fluorescent complex is referred to semi-intercalative binding of EtBr. The binding constant (K) and the number of base pairs corresponding to a binding site (n) of the fluorescent (K f and n f ) and non-fluorescent (K nf, nnf) types of interactions were determined. The average size of binding site (n) is equal to 1.5 bp (absorption spectroscopy), and nf ca. 2 bp (fluorescence spectroscopy). It was shown that nnf is dependent on GC-content and total n is independent of it.

Various uncertainties self-correction method for the supervisory control of a hybrid cooling system in data centers

Abstract: The uncertainties of the crucial parameters have a considerable influence on the supervisory control performance of the water side free cooling system in data centers, especially for the model-based optimal control. To reduce the uncertainty of the key parameters in an operational data center hybrid cooling system, this study proposed an uncertainties self-correction method based on Bayesian Inference and Markov Chain Monte Carlo (BI-MCMC) theory. Four novel enhanced self-correction strategies, including the benchmarks extended, adding sensitivity coefficient , local correction and prior distribution updated, were developed to handle the negative impacts caused by the various uncertain working conditions and complex relationships between parameters. The performance of the proposed method was fully investigated under the cases with single/multiple uncertain parameters with different degrees of uncertainty and deviation. For the uncertainties problem with single parameter error scenario, the basic BI-MCMC method reduced the error by at least 92.5%. For the multiple parameter uncertain scenarios, the designed enhanced strategies can significantly reduce the degree of the uncertainty, i.e. the correction accuracy is up to 98% and the absolute correction deviations are not more than 0.02. Therefore, the proposed method could provide a solution to the current challenges in handling the uncertainties and establishing a reliable model for the supervisory control.

Influence of the stark effect on the resonance excitation transfer between quantum dots

Abstract: The resonance energy transfer between exciton states in a system comprised of two semiconductor quantum dots is studied theoretically. A model Hamiltonian is constructed to describe the influence of the laser pulse, Coulomb interaction, the static Stark effect, and the relaxation of exciton states on the dynamics of the system. Specific calculations of the efficiency of energy transfer under different excitation conditions and different positions of energy levels are exemplified. It is shown that the transfer process can be controlled by shifting the levels in a constant electric field.