We consider the waveguide modelled by a n-dimensional infinite tube. The operator we study is the Dirichlet Laplacian perturbed by two distant perturbations. The perturbations are described by arbitrary abstract operators ”localized” in a certain sense, and the distance between their ”supports” tends to infinity. We study the asymptotic behaviour of the discrete spectrum of such system. The mai...

X-ray grating interferometry is a promising imaging technique sensitive to attenuation, refraction and scattering of the radiation. Applications of this technique in the energy range between 80 and 150 keV pose severe technical challenges, and are still mostly unexplored. Phase-contrast X-ray imaging at such high energies is of relevant scientific and industrial interest, in particular for the ...

We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two KaluzaKlein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type u...

Doubly curved crystal X-ray optics provide intense focused monochromatic beams from laboratory X-ray tube sources. These optics are employed in crystallography and X-ray fluorescence systems and may find application to imaging. It is increasingly important to understand how optic defects impact performance for these systems. A simulation model was developed to assess the effects of misalignment...

In this paper, we show that it is possible to synthesize carbon-based three-dimensional networks by adding sulfur, as growth enhancer, during the synthesis process. The obtained material is self-supporting and consists of curved and interconnected carbon nanotubes and to lesser extent of carbon fibers. Studies on the microstructure indicate that the assembly presents a marked variability in the...

We consider the waveguide modelled by n-dimensional tube in which Dirichlet Laplacian is considered perturbed by two distant perturbations. These perturbations are described by two arbitrary abstract operators which are ”localized” in some sense, and the distance between their ”supports” tends to infinity. We study the asymptotic behaviour of the discrete spectrum of such problem. The main resu...

Vortex generation is a potential passive technology for increasing the heat transfer rate in air side of fin and tube exchangers (FTHEs). This study proposes novel configurations curved trapezoidal winglet vortex generator (CTWVG) with without circular holes to improve FTHEs. As per literature, streamlined form demonstrates high enhancement low flow loss pressure drop. But still, different desi...

Many immersive displays developed in previous researches are strongly influenced by the design concept of the CAVE, which is the origin of the immersive displays. In the view of human-scale interactive system for virtual environment (VE), the existing immersive systems are not enough to use the potential of a human sense further extent. The displays require more complicated structure for flexib...

The aim of this study was to determine, using a computerized image analysing system, whether the use of a curved-bristle toothbrush (CBT) alone is more effective than two other toothbrushing protocols on dental plaque elimination in poor-toothbrushing orthodontic patients. The labial surfaces of the maxillary canine-to-canine anterior teeth of 30 patients (12 males and 18 females) were individu...