In this paper, the effect of the spatial electric field on the hydrogenic impurity self-polarization and binding energy in a GaAs/AlAs tetragonal quantum dot are calculated by the variational method ...based on the effective mass approximation. We have shown that the self-polarization and binding energy of a hydrogenic impurity in a tetragonal quantum dot depends strongly on the
θ
angle of the spatial electric field, the size effect (L
z
/L ratio (M)), the volume of the dot, and impurity position. Furthermore, we define the angle
θ
max
, which aligns the spatial electric field vector with the position vector of the hydrogenic impurity on the diagonal axis. It has been noted that self-polarization reaches its peak at this particular angle.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Using the variational method within the effective-mass approximation, the effects of geometrical shape and impurity position on the ground-state self-polarization and binding energy of a donor ...impurity are theoretically studied for the infinite GaAs/AlAs tetragonal quantum dot. We have found that the ground-state self-polarization and binding energy depend on geometrical shape and impurity-AlAs layer distance.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Background
The aim of this study was to compare the flexural strength and Vickers hardness of tooth‐coloured restorative materials with and without applying a self‐adhesive coating for up to 6 ...months.
Methods
Specimens were prepared from three resin composites (RC), two resin‐modified glass‐ionomer cements (RM‐GIC) and two conventional glass‐ionomer cements (CGIC). All materials were tested both with and without applying G‐Coat Plus (GCP). Specimens were conditioned in 37 °C distilled deionized water for 24 h, and 1, 3 and 6 months. The specimens were strength tested using a four‐point bend test jig in a universal testing machine. The broken specimen's halves were used for Vickers hardness testing. Representative specimens were examined under an environmental scanning electron microscope.
Results
Data analysis showed that regardless of time and materials, generally the surface coating was associated with a significant increase in the flexural strength of the materials. Applying the GCP decreased the hardness of almost all materials significantly (P < 0.05) and effect of time intervals on hardness was material dependent.
Conclusions
The load‐bearing capacity of the restorative materials was affected by applying self‐adhesive coating and ageing. The CGIC had significantly higher hardness but lower flexural strength than the RM‐GIC and RC.
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BFBNIB, CMK, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This study evaluated the effect of conventional versus ultrasonic cementation techniques on the fracture strength of resin composite laminates. In addition, the failure modes were assessed. ...Window-type preparations 1 mm above the cemento-enamel junction were made on intact human maxillary central incisors (N=60) of similar size with a depth cutting bur. All the prepared teeth were randomly assigned to six experimental groups (10/per group). Using a highly filled polymeric material (Estenia), laminates were produced and finished. The standard thickness of laminates in original tooth form was achieved using the impression molds made prior to tooth preparation. A three-step bonding procedure and dual polymerized resin composite cement (Panavia F 2.0) was employed. The cementation surfaces of the laminates were conditioned (CoJet-Sand, 30 microm SiO2) and silanized (ESPE-Sil). Laminates in Groups 1, 2, 3, 4 and 5 were cemented by five different operators under finger pressure and Group 6 was cemented ultrasonically (Amdent). After excess removal, the laminates were light polymerized. The specimens were stored in water at 37 degrees C for one month prior to the fracture test (universal testing machine, 1 mm/minute). Failure types were classified as: a) Cohesive failure within the composite laminate (Type A), b) Adhesive failure between the tooth and laminate (Type B) and c) Chipping of the laminate with enamel exposure (Type C). No significant difference was found among the mean fracture strength values of the laminates in all the experimental groups (ANOVA, p=0.251). The mean fracture strength values in descending order were: 513 +/- 197, 439 +/- 125, 423 +/- 163, 411 +/- 126, 390 +/- 94, 352 +/- 117 N for Groups 2, 5, 4, 3, 1 and 6, respectively. The majority of failure types was Type A (30/60). While Type B failure was not observed in Group 6 (0/10), Group 1 presented a more frequent incidence of this failure (6/10). The two cementation techniques did not effect the fracture strength of composite laminates, but failure types varied between groups, being more favorable for the ultrasonically cemented group.
In this study, the self-polarization and binding energy of the donor impurity atom in the laser field applied Ga1−xAlxAs/GaAs quantum well are investigated under the combined influence of hydrostatic ...pressure and temperature. Variation of self-polarization and binding energy depending on temperature, hydrostatic pressure, impurity position, well width and laser field parameters are shown. Using the effective mass approximation, subband energy has been found by finite difference method and impurity energy has been found by variation method. Our results showed that hydrostatic pressure and temperature have a noticeable effect on the calculated self-polarization and binding energy in a quantum well under the effect of the laser field. We think that the results obtained will be useful in determining the physical properties of the quantum well under the influence of laser field, hydrostatic pressure and temperature.
•The square quantum well is considered.•The effects of hydrostatic pressure and temperature on self-polarization have been calculated under laser field.•The variational and finite differences calculations have been performed.•Laser field parameter, hydrostatic pressure and temperature are important factor.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, the edge physics of an Aharonov–Bohm interferometer (ABI) defined on a two dimensional electron gas, subject to strong perpendicular magnetic field
B, is investigated. We solve the ...three dimensional Poisson equation using numerical techniques starting from the crystal growth parameters and surface image of the sample. The potential profiles of etched and gate defined geometries are compared and it is found that the etching yields a steeper landscape. The spatial distribution of the incompressible strips is investigated as a function of the gate voltage and applied magnetic field, where the imposed current is confined to. AB interference is investigated due to scattering processes between two incompressible “edge-states”.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this study, we examine the effect of the laser field on normalized self-polarization, self-polarization, and binding energy in square quantum wells made of four different materials under effective ...mass approximation. The effects of well width, laser field, and impurity position on normalized self-polarization, self-polarization, and binding energies are shown in detail. The subband energies are obtained by the finite difference method, and the impurity energies are calculated by the variational method. The laser field significantly affects binding energy, self-polarization, and normalized self-polarization. The term normalized self-polarization is defined for the first time in this study. This allows a more detailed examination of the self-polarization change depending on the impurity position. Examining the laser field effect, especially in square quantum wells made of different materials, will provide researchers with helpful information about the importance of material selection in calculating binding energy, self-polarization, and normalized self-polarization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We exploit rotational-symmetry breaking in the one-body density to examine the formation of structures in systems of N strongly coupled charged bosons with logarithmic repulsions inside isotropic ...two-dimensional harmonic traps, with N in the range from 2 to 7. The results serve as a map for ordered arrangements of vortices in a trapped Bose-Einstein condensate. Two types of N-body wavefunctions are assumed: (i) a permanent of N identical Gaussian orbitals centred at variationally determined sites, and (ii) a permanent of N orthogonal orbitals built from harmonic-oscillator energy eigenstates. With increasing coupling strength, the bosons in the orbitals localize into polygonal-ringlike crystalline patterns ('Wigner molecules'), whereas the wavefunctions describe low energy excited states containing delocalized bosons as in supersolid crystallites ('supermolecules'). For N = 2 at strong coupling both states describe a Wigner dimer.
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