Defect-induced strong ferromagnetism in Cr-doped In2O3 from first-principles theory

We demonstrate by means of first-principles calculations that the high Curie temperature observed in Cr-doped In₂O₃ is mediated by intrinsic p-type defects, namely In vacancies or O interstitials. Charge transfer from Cr 3d states to the hole states formed by these defects makes Cr ions in the mixed valence state, giving rise to a strong ferromagnetic coupling. Calculated formation energies of various defects also show that doping Cr in In₂O₃ could greatly lower the formation energies of p-type intrinsic defects even in oxygen-deficient growth conditions. These results advance our understanding of the underlying physics of diluted magnetic oxides.     

On the Representation of Functions with Gaussian Wave Packets

We introduce Gaussian wave packets in pursuit of representations of functions, in which the representation is invariant under translation, modulation, scale, rotation and anisotropic dilation. Properties of both continuous and discrete representations are discussed. For the discrete (two-dimensional) case, we develop fast algorithms for the application of the analysis and synthesis operators. A main objective for using Gaussian wave packets is to obtain sparse approximations of functions. However, due to the many invariance properties, the representations will have a high degree of redundancy. Therefore, we also introduce sparse methods for highly redundant representations, that employ some of the analytic properties of Gaussian wave packet for gaining computational efficiency.     

Parallel algorithm of 3D wave-packet decomposition of seismic data: Implementation and optimization for GPU

In this paper, we consider 3D wave-packet transform that is useful in 3D data processing. This transform is computationally intensive even though it has a computational complexity of O(N³ log N). Here we present its implementation on GPUs using NVIDIA CUDA technology. The code was tested on different types of graphical processors achieving the average speedup up to 46 times on Tesla M2050 compared to CPU sequential code. Also, we analyzed its scalability for several GPUs. The code was tested for processing synthetic seismic data set: data compression, de-noising, and interpolation.     

A practical synthesis of [C4] N-benzylpiperazine from [C2] glycine

A high yielding gram-scale synthesis of [¹³C₄] N-benzylpiperazine for use as a convenient and versatile building block in isotope labeling studies of clinical drug candidates is reported.     

Acoustical and perceptual influence of duplex stringing in grand pianos

This study investigates the acoustical and perceptual influence of the string parts outside the speaking length in grand pianos (front and rear duplex strings). Acoustical measurements on a grand piano in concert condition were conducted, measuring the fundamental frequencies of all main and duplex strings in the four octaves D4-C8. Considerable deviations from the nominal harmonic relations between the rear duplex and main string frequencies, as described by the manufacturer in a patent, were observed. Generally the rear duplex strings were tuned higher than the nominal harmonic relations with average and median deviations approaching +50 cent. Single keys reached +190 and -100 cent. The spread in deviation from harmonic relations within trichords was also substantial with average and median values around 25 cent, occasionally reaching 60 cent. Contributions from both front and rear duplex strings were observed in the bridge motion and sound. The audibility of the duplex strings was studied in an ABX listening test. Complete dampening of the front duplex was clearly perceptible both for an experiment group consisting of musicians and a control group with naive subjects. The contribution from the rear duplex could also be perceived, but less pronounced.     

On the uncertainty of building acoustic measurements – Case study of a cross-laminated timber construction

If variations and uncertainty in building acoustic measurements can be controlled, construction costs can potentially be reduced since the building will not have to be acoustically over-designed. Field measurements of impact and airborne sound insulation were carried out for an industrially prefabricated cross-laminated timber (CLT) system of plate elements. The results from 18 rooms, forming three groups with respect to size, were compared to a similar study dealing with a prefabricated Volume Based Building (VBB) system. Large variations were found at frequencies below 100 Hz which is crucial for the low frequency adaptation terms connected to the weighted sound insulation indices. The measurement uncertainty was investigated by analysing the repeatability, measurement direction and the time dependence of the sound source. The variations due to the measurement procedure were found to be small compared to the total variations. It was also indicated that the variations in sound insulation are smaller with a prefabricated system compared to on-site production, since less work is required at the building site.     

Comparative PL study of individual ZnO nanorods,grown by APMOCVD and CBD techniques

The photoluminescence properties of individual ZnO nanorods, grown by atmospheric pressure metalorganic chemical vapor deposition (APMOCV) and chemical bath deposition (CBD) are investigated by means of temperature dependent micro-PL. It was found that the low temperature PL spectra are driven by neutral donor bound exciton emission D⁰X, peaked at 3.359 and 3.363 eV for APMOCVD and CBD ZnO nanorods, respectively. The temperature increase causes a red energy shift of the peaks and enhancement of the free excitonic emission (FX). The FX was found to dominate after 150 K for both samples. It was observed that while APMOCVD ZnO nanorods possess a constant low signal of visible deep level emission with temperature, the ZnO nanorods grown by CBD revealed the thermal activation of deep level emission (DLE) after 130 K. The resulting room temperature DLE was a wide band located at 420–550 nm. The PL properties of individual ZnO nanorods can be of importance for their forthcoming application in future optoelectronics and photonics.     

Computing the Lambert W function in arbitrary-precision complex interval arithmetic

Numerical Algorithms - We describe an algorithm to evaluate all the complex branches of the Lambert W function with rigorous error bounds in arbitrary-precision interval arithmetic or ball...     

Surface state on the SiC(0001)-(√3 × √3) surface

An angle resolved photoemission study of a surface state on the SiC(0001)-(√3 × √3) surface is reported. Experiments carried out on the 6H and 4H polytypes give essentially identical results. A surface state band with semiconducting occupation is observed, centered around 1.0 eV above the valence band maximum (VBM) and with a width of about 0.2 eV. Recently calculated results for a Si-adatom-induced √3 × √3 reconstruction give a metallic surface state band centered about 1.2 eV above the VBM and with a width of 0.35 eV. The dispersion determined experimentally is smaller than calculated but exhibits the same trend, the surface state disperses downwards towards the VBM with increasing parallel wavevector component along both the qG--- and qG--- directions of the √3 × √3 surface Brillouin zone. The VBM is determined to be located at about 2.3(±0.2) eV below the Fermi level. The results indicate that Si adatoms on top of an outermost Si---C bilayer may be an inadequate structural model for explaining recent experimental findings for the SiC(0001)-(√3 × √3) surface.