The objective of the present work is to analyze influence of temperature boundary conditions on the solidification process of NiTi alloy. Alloy is taken as an incompressible fluid where the heat is transferred by conduction and convection, including the thermal phase change phenomenon. The last one is modelled by the improvement procedure, so-called enthalpy-porosity formulation, where the liquid-solid mushy zone is treated as a porous zone with porosity equal to the liquid fraction. The numerical model is based on the finite volume method in body fitted coordinates with a SIMPLER scheme to couple the pressure and velocity fields. Simulation presents solidification for two cooling cases on the cylindrical part, where in the first case the adiabatic boundary condition is considered and in the second case the convective cooling over the wall is present. The results are presented for the velocity and temperature field as well as for the NiTi mass fraction during the solidification process. Results shows that velocity and temperature field is strongly affected by the different cooling condition on the cylindrical wall and therefore the solidification process of the alloy. Analysis shows that cooling on the cylindrical part is one of the major parameters for alloy solidification and therefore should not be neglected.

In the article, we discuss the influence of the locally perturbed order parameter in austenitic-martensitic phase transformation on the character of the phase transformation. We choose Landau type mean field approximation which covers the most important features of the proposed theoretical description.

We study meniscus driven locking of point defects of nematic liquid crystals confined within a cylindrical tube with free ends. Curvilinear coordinate system is introduced in order to focus on the phenomena of both (convex and concave) types of menisci. Frank's description in terms of the nematic director field is used. The resulting Euler-Lagrange differential equation is solved numerically. We determine conditions for the defects to be trapped by the meniscus.

The development of high-frequency printed electronics requires simulation methodologies that represent the electrical behaviour of nanoparticle-based conductive materials accurately. Conventional electromagnetic simulations typically assume ideal bulk material properties, neglecting the influence of nanoparticle synthesis, printing and thermal processing. This work presents a simulation-driven design methodology for microwave components based on experimentally characterised plasma-printed gold nanoparticle (AuNPs) conductors. The experimentally determined material properties, including electrical conductivity and conductor thickness, obtained from previously developed plasma-printed AuNP structures, were incorporated directly into the electromagnetic model to provide realistic simulation conditions. The proposed workflow integrates equivalent-circuit synthesis, distributed transmission-line implementation and full-wave electromagnetic simulation using the AXIEM Method of Moments solver, numerical optimisation and a sensitivity analysis. The methodology was demonstrated through the design of a third-order edge-coupled microstrip band-pass filter operating at 15 GHz on a 96% alumina substrate (Al2O3). The optimised design satisfied the target electrical specifications, while accounting for the realistic material properties and manufacturing constraints associated with plasma printing. The sensitivity analysis identified the transmission-line length as the most influential geometrical parameter, while the transmission-line width, coupling gaps and substrate dielectric constant exhibited comparatively lower sensitivity. The proposed methodology provides a practical framework for the design of additively manufactured microwave and millimetre-wave components.

We study the influence of random anisotropy type quenched disorder on the phase behavior of the system, which exhibits in undistorted case the 2nd order continuous symmetry breaking phase transition. Invoking the central limit theorem we express the free energy of the system in terms of the order parameter η and the characteristic length ξ of the gauge field ϕ. The latter exhibits the Goldstone fluctuation mode and is consequently extremely susceptible to the imposed disorder. In case of negligible distribution width ΔT of the local transition temperatures the disorder converts the 2nd order transition into a discontinuous one for W0. We demonstrate that for large enough values of ΔT the system behavior is dominated by the distribution of temperatures, while the details of the random field interaction term play a secondary role. The influence of distribution of local (quasi) phase transitions is in most theoretical approaches dealing with randomly perturbed systems neglected from the outset.

The integration of advanced materials, additive manufacturing processes, and simulation-driven design is becoming increasingly important in the development of high-frequency electronic and machinery components. In this work, a simulation-driven design methodology is presented for gold nanoparticles-based (AuNPs) conductive structures intended for implementation on low-temperature co-fired ceramic (LTCC) substrates. The approach incorporates both electromagnetic performance requirements and manufacturing constraints associated with already developed printed conductive materials. As a representative application, a microstrip coupled-line band-pass filter operating in the Ku-band frequency range is designed using full-wave electromagnetic simulations. The geometry is optimized while considering realistic limitations related to conductor thickness, minimum feature size, and effective electrical conductivity of AuNPs based conductive layers. The AuNPs are produced via ultrasonic spray pyrolysis (USP), liophilizied, dispered in a solvent, plasma printed on a Al2O3 substrate and sintered. The resulting properties thus deviate from bulk gold. The optimized structure of the AuNPs LTCC filter exhibits a center frequency of approximately 15 GHz with a bandwidth of about 1 GHz. Simulated S-parameter results demonstrate efficient signal transmission within the passband and strong attenuation outside the operating frequency range.