Modern Physics Letters B

Historically, although the first indications for the use of lasers in general were in dentistry, coming as a relief from the sound of the drill and mechanical contacts, it still seems somewhat that the entry in various ways of lasers in dentistry has been slower. This is somewhat true for the situation at the continents (e.g. USA much later approved the application relative to Europe). This paper analyzes the potential and existing applications of lasers in dentistry in a wide range of existing types, including interaction with dental tissues, in terms of surgical applications, on living tissue, the prosthetic area of applications and therapeutic doses. There is another special feature that can be recognized is the precise determination of the color of the material (teeth and prosthetics) and in general the determination of the composition of the material including classic, but also modern laser techniques (LIBS, complimentary techniques, tooth tissue, bone) and especially in the case of the first Q switch systems related to pain reduction, because the short pulse favors the intervention rate (ns, ps and fs). Special attention should be paid to modeling of interaction and analysis with the appropriate software support.

In this paper, an enhanced polarization-independent two-layer five-port grating with covering layer is proposed. The rigorous coupled-wave analysis (RCWA) is used to predict grating parameters. In addition, the total efficiency of the polarization-independent five-port grating with covering layer can exceed 80% with the good uniformity of 1.97% for TE and TM polarization. The inherent coupling mechanism and the electric field energy distribution of the gratings are explained well under TE and TM polarization by the simplified mode method (SMM) and the finite element method (FEM). According to the reported five-port gratings, the proposed transmission five-port grating with a covering layer has good uniformity for TE and TM polarization. Moreover, the grating can be protected and the groove of the grating can be kept clean by adding a covering layer during the actual fabrication. At the same time, the fabrication errors of the two-layer five-port diffraction grating are further considered. Therefore, the numerically simulated five-port grating with covering layer has a wide application prospect in precision displacement measurement and holographic projection imaging.

Generating and manipulating valley polarization in a controlled method is significant. The inherently broken centrosymmetry of the buckled honeycomb structures gives it both ferroelectricity and valley degree of freedom, which provides an opportunity to realize electrically controlled valley polarization. In the first step, we explored the origin of buckling. The hexagonal structure is polar due to buckling of the surface, but the degree of buckling and the energy barrier to switching electric polarization are determined not solely by the chemical composition. We combined the electronegativity difference, bond length and the distribution of charge density to describe quantificationally the polarity of chemical bonds. It shows the characteristics of relatively long bond-length but relatively small electronegativity-difference. For exploring the ferroelectricity of buckling structures and the behavior of ferroelectric (FE) control of the valley degree of freedom, the $\beta$-GaP is used as a model system to elucidate the strain effect on FE behavior and the magnetic proximity effect on the polarization and switching of valley. We found that the spontaneous polarization is positively correlated with the electronegativity difference within a certain range, and the compression strain can effectively manipulate spontaneous polarization and switch barrier. A combination of the magnetic proximity effect and the inversion of electric polarization can generate and switch valley polarization effectively.

In this article, three mathematical techniques have been operationalized to discover novel solitary wave solutions of (2+1)-dimensional Maccari system, which also known as soliton equation. This model equation is usually of applicative relevance in hydrodynamics, nonlinear optics and plasma physics. The ${exp}_a$ function, the hyperbolic function and the $exp(-\zeta (\xi ))$-expansion techniques are used to obtain the novel exact solutions of the (2+1)-dimensional Maccari system (arising in nonlinear optics and in plasma physics). Many novel solutions such as periodic wave solutions by ${exp}_a$ function method, singular, combined-singular and periodic solutions by hyperbolic function method, hyperbolic, rational and trigonometric solutions by $exp(-\zeta (\xi ))$-expansion method are obtained. The exact solutions are shown through 3D graphics which present the movement of the obtained solutions.

ZnO–SnO₂ composite nanorods with rough surfaces were synthesized via a coaxially nested needle electrospinning method. The morphology and nanostructure were characterized by scanning electron microscopy, atomic force microscope, EDS mapping, nitrogen physical adsorption, and X-ray diffraction. The synthesis mechanisms of ZnO–SnO₂ nanorods were discussed, which combined the gas sensitivity advantages of different materials. ZnO–SnO₂ nanorods sensor with good ethanol gas sensitivity achieved accurate measurement of continuous ethanol concentration. The sensor exhibited good selectivity to ethanol in the presence of formaldehyde, methanol, acetone, acetic acid, benzene, and xylene at 290${}^{\circ }$C. The response and recovery time to 100 ppm ethanol were about 13 and 35 s, respectively. The energy band, barrier, charge transfer of ZnO–SnO₂ composite material was discussed, and its optimization of gas sensitivity was analyzed in detail.

The whole process of turbulence formation was quantitatively studied by the catastrophe method. The change law of the production of turbulent kinetic energy and its spectral distribution with the transformation of wave number and time factor are mainly studied. In addition, the distribution and production of turbulent kinetic energy in Karman vortex street model are studied by numerical simulation. The results show that the production of turbulent kinetic energy first increases and then decreases with the time factor, and the spectrum at different wave numbers follows this trend. When the time factor $g(t)=-1.8$, the maximum value appears. In the Karman vortex street model, the simulation results are consistent with our derived values.

The ferromagnetism induced by an external magnetic field (EMF), in (3+1) dimensions, is governed by Kraenkel–Manna–Merle system (KMMS). A (1+1) dimension model equation was derived in the literature. The magnetic moments are parallel to the magnetic field in ferromagnetism as they are aligning in the same direction of the external field. Here, it is shown that the KMMS supports the presence of internal magnetic field. This may be argued to medium characteristics. The objective of this work is to mind multiple soliton solutions, which are obtained via the generalized together with extended unified methods. Graphical representation of the results are carried. They describe infinite soliton shapes, which arise from the multiple variation of the arbitrary functions in the solutions. It is, also, shown that internal magnetic field decays, asymptotically, to zero with time.

The polycrystalline samples of manganites perovskite ${\mathrm{\text{La}}}_{0.67}{\mathrm{\text{Sr}}}_{0.33}{\mathrm{\text{Mn}}}_{1-x}{({\mathrm{\text{V}}}_{\mathrm{\text{Mn}}})}_x{\mathrm{\text{O}}}_3(0.00\le x\le 0.065)$ with B-sites vacancies were synthesized using the conventional solid-state reaction method. The results based on the X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses show that the samples with $x\ge 0.05$ have a secondary phase of lanthanum oxides. It indicates there is a maximum vacancy content at the B-sites with $0.03\le V_{max}<0.05$. By X-ray Photoelectron Spectra (XPS), the ionicities of oxygen were determined to be 0.762, 0.842, and 0.886, corresponding to $x=0.00$, 0.03, and 0.05, respectively. The B-sites vacancy plays an important role in magnetic performances: (i) B-sites vacancy changes the contents and the average cant angle of Mn cations, and makes the specific saturation magnetization at 100 K and 300 K increase, and then decrease rapidly. (ii) The Curie temperature changes in a small range from 363.93 K to 366.00 K, resulting from both the double exchange interaction increasing and the double exchange path destroyed by the vacancies. (iii) The magnetoresistance (MR) at room temperature achieves 6.97% in the ${\mathrm{\text{La}}}_{0.67}{\mathrm{\text{Sr}}}_{0.33}{\mathrm{\text{Mn}}}_{0.95}{({\mathrm{\text{V}}}_{\mathrm{\text{Mn}}})}_{0.05}{\mathrm{\text{O}}}_3$ sample, whose value is larger than that of ${\mathrm{\text{La}}}_{0.67}{\mathrm{\text{Sr}}}_{0.33}{\mathrm{\text{MnO}}}_3$ sample.

In this paper, we study a coupled system of the nonlinear Schrödinger (NLS) equation and the Maxwell–Bloch (MB) equation with nonzero boundary conditions by Riemann–Hilbert (RH) method. We obtain the formulae of the simple-pole and the multi-pole solutions via a matrix Riemann–Hilbert problem (RHP). The explicit form of the soliton solutions for the NLS-MB equations is obtained. The soliton interaction is also given. Furthermore, we show that the multi-pole solutions can be viewed as some proper limits of the soliton solutions with simple poles, and the multi-pole solutions constitute a novel analytical viewpoint in nonlinear complex phenomena. The advantage of this way is that it avoids solving the complex symmetric relations and repeatedly solving residue conditions.

Dürer’s pentagon is known to the artist Albrecht Dürer, whose work has produced an effect on modern telecommunication. In this paper, we consider directed networks generated by Dürer-type polygons, which is based on an $M$-sided polygon where $M=4m$ and $m\ge 2$. This object is quite different from what we previously studied when $M$ is not a multiple of 4. We aim to study some properties of these networks, such as degree distribution, clustering coefficient and average path length. We show that such networks have the scale-free effect, but do not have the small-world effect. It is expected that our results will provide certain theoretical support to further applications in modern telecommunication.

To address the closure problem of Reynolds-averaged Navier–Stokes in numerical simulations of turbulence, the method of solving Reynolds-averaged Navier–Stokes equations based on artificial neural network is introduced in this paper. We establish the nonlinear mapping relationship between the average flow field and the steady-state eddy viscosity field. The machine learning (ML) surrogate model for the shear stress transport turbulence model is constructed. The solution process of replacing the original turbulence model equations with the predicted field variables is realized by coupling the ML algorithm with the CFD solver. The classical backward facing step problem is selected in our study to verify the simulation accuracy of the surrogate model. The comparative analysis is carried out on the six backward facing step flows simulations at different Reynolds numbers. The results of simulations show that the testing flows with the Reynolds numbers closest training datasets Reynolds numbers can obtain the best simulation accuracy. Then for the Reynolds number that is lower than the training datasets, the simulation accuracy will decrease as the Reynolds number decreases. On the contrary, the simulation accuracy of the test flow will increase as the Reynolds number increases. These results indicate the feasibility of the ML surrogate model to simulate at higher Reynolds number. It shows the great potential of applying ML algorithms to Reynolds-averaged Navier–Stokes simulation (RANS) turbulence model and also provides a new idea for industrial simulations of turbulent flows.

This paper introduces a gyro control system with the quadrature control circuit. The control system realizes the automatic decoupling of driving mode and sensing mode. The quadrature control circuit eliminates the quadrature signal in the sensitive mode by applying a voltage to the quadrature control electrode. The time needed to adjust the voltage can be changed by adjusting the parameters of the controller. The control system is realized by a digital circuit. The feasibility of the design is verified by the test.

This paper investigates the problem of exponential passive filter design for switched neural networks with time-delay and reaction-diffusion terms. With the aid of a suitable Lyapunov–Krasovskii functional and some inequalities, a linear matrix inequality-based design method is developed that not only makes the filtering error system exponentially stable but also forces it to be passive from external interference to output error. Then, the filter design is extended to the complex-valued case via separating the system into real-valued and complex-valued parts. Finally, a numerical example is utilized to illustrate the effectiveness of the filter design methods for the real-valued and complex-valued cases, respectively.

This paper constructs and numerically analyzes a theoretical model of three-dimensional few cycle optical pulse dynamics in semiconductor carbon nanotube-based spatially-modulated refractive index medium. It takes into account external deformation in terms of the gauge theory. It identifies the stable propagation of that kind of pulses in photonic crystal. The paper also reveals the dependence of pulse dynamics on photonic crystal characteristics (refractive index depth and modulation period in particular).

In this paper, we discussed the local preparation methods of two types of multi-qubit logical GHZ-type states using controlled quantum gates, and drew the corresponding quantum circuits. Subsequently, we investigated the measurement-related properties of logical GHZ-type state and thus proposed two multi-party quantum secret sharing schemes against collective-dephasing and collective-rotation noise, respectively. Further, we demonstrated that the schemes can effectively resist some familiar attack strategies. Finally, we analyzed the quantum efficiency of our schemes and made a comprehensive comparison with previous similar schemes.

In this work, a generalized $(G^{\prime }/G)$-expansion method has been used for solving the nonlinear Chen–Lee–Liu equation. This method is a more common, general, and powerful mathematical algorithm for finding the exact solutions of nonlinear partial differential equations (NPDEs), where $G=G(\tau )$ follows the Jacobi elliptic equation ${[G^{\prime }(\tau )]}^2=H(G)$, and we let $H(G)$ be a fourth-order polynomial. Many new exact solutions such as the hyperbolic, rational, and trigonometric solutions with different parameters in terms of the Jacobi elliptic functions are obtained. The distinct solutions obtained in this paper clearly explain the importance of some physical structures in the field of nonlinear phenomena. Also, this method deals very well with higher-order nonlinear equations in the field of science. The numerical results described in the plots were obtained by using Maple.