Conventional density functional theory (DFT) fails to describe accurately the London dispersion essential for describing molecular interactions in soft matter (biological systems, polymers, nucleic acids) and molecular crystals. This has led to several methods in which atom-dependent potentials are added into the Kohn-Sham DFT energy. Some of these corrections were fitted to accurate quantum me...

This paper proposes an efficient frequency estimator based on Chinese Remainder Theorem for undersampled waveforms. Due to the emphasis on frequency offset recognition (i.e., frequency shift and compensation) of small-point DFT remainders, compared to estimators using large-point DFT remainders, it can achieve higher noise robustness in low signal-to-noise ratio (SNR) cases and higher accuracy ...

In a recent paper, Bourchard et al. [1] proposed the block sum transformation, a method intended as an alternative to the discrete Fourier transform (DFT), with application to the analysis of excited vibrations of linear systems. In this note, we mention the existence of a number of alternative algorithms for the computation of the DFT, and show that the block sum transformation is equivalent t...

In this paper, we propose a nonuniform DFT based on nonequispaced sampling in the frequency domain. It is useful to detect some specific frequencies such as in DTMF which is composed on two different frequencies, main (fundamental) frequency component among lots of harmonics, and feature detection from noisy signals. Some trials for nonuniform data processing via DFT are discussed and resamplin...

In this paper, a pass-band optimal reconstruction technique is adapted to the Body-Centered Cubic (BCC) lattice. In order to perform the frequencydomain preprocessing, we derive a practical Discrete Fourier Transform (DFT) for BCC-sampled data. In the discrete frequency domain our DFT provides a natural isotropic periodicity on a FaceCentered Cubic (FCC) pattern, unlike the previous method, whi...

The Kohn-Sham equation in first-principles density functional theory (DFT) calculations is a nonlinear eigenvalue problem. Solving the nonlinear eigenproblem is usually the most expensive part in DFT calculations. Sparse iterative diagonalization methods that compute explicit eigenvectors can quickly become prohibitive for large scale problems. The Chebyshevfiltered subspace iteration (CheFSI) ...

In this paper an estimator for speech enhancement based on Laplacian Mixture Model has been proposed. The proposed method, estimates the complex DFT coefficients of clean speech from noisy speech using the MMSE  estimator, when the clean speech DFT coefficients are supposed mixture of Laplacians and the DFT coefficients of  noise are assumed zero-mean Gaussian distribution. Furthermore, the MMS...

The implementation of OFDM transmitters typically consists of a discrete DFT matrix and a digital-to-analog (DAC) converter. Many existing results on the analysis of OFDM systems, e.g., spectral roll-off, are based on a convenient analog representation. In this paper, we show that the analog representation and the DFT-based OFDM transmitters are equivalent only in special cases. Using the analo...

Iron oxides are materials of wide interest that exhibit diverse electric, magnetic, optical, and catalytic properties; therefore, many studies to gain complete understanding of their polytypic phase boundary have been pursued. However, firstprinciples investigations of iron oxides using conventional density functional theory (DFT) calculations often yield a gross error due to the strong electro...

quantum chemical calculations, based on density functional theory (dft) method, were performed on calix[4]arene and polychlorinated dibenzo-p-dioxins (pcdds) in gas and liquid phases for comparison purposes. the simulation results show the 1,2,3,4, 6,7,8,9-octachlorodibenzo-p-dioxin (ocdd) is quite a reactive dioxin. this paper attempts to examine the possibility of dioxin adsorption by calix[n...