On the thermal impact during drilling operations in guided dental surgery: An experimental and numerical investigation

In recent years, a major development in dental implantology has been the introduction of patient-specific 3D-printed surgical guides. The utilization of dental guides offers advantages such as enhanced accuracy in locating the implant sites, greater simplicity, and reliability in performing bone drilling operations. However, it is important to note that the presence of such guides may contribute to a rise in cutting temperature, hence increasing the potential hazards of thermal injury to the patient's bone. The aim of this study is to examine the drilling temperature evolution in two distinct methods for 3D-printed surgical dental guides, one utilizing an internal metal bushing system and the other using external metal reducers. Cutting tests are done on synthetic polyurethane bone jaw models using a lab-scale automated Computer Numeric Control (CNC) machine to find out the temperature reached by different drilling techniques and compare them to traditional free cutting configurations. Thermal imaging and thermocouples, as well as the development of numerical simulations using finite element modeling, are used for the aim. The temperature of the tools' shanks experienced an average rise of 2.4 °C and 4.8 °C, but the tooltips exhibited an average increase of around 17 °C and 24 °C during traditional and guided dental surgery, respectively. This finding provides confirmation that both guided technologies have the capability to maintain temperatures below the critical limit for potential harm to bone and tissue. Numerical models were employed to validate and corroborate the findings, which exhibited identical outcomes when applied to genuine bone samples with distinct thermal characteristics

Comparing and Connecting: Comacchio and the Early Medieval Trading Towns

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Numerical simulation of a complete charging-discharging phase of a shell and tube thermal energy storage with phase change material

Abstract Numerical simulations of a shell and tube energy storage device based on a phase change material (PCM) in vertical position are performed. The heat transfer fluid (HTF) is a diathermic oil and the PCM, made by molten salts, is confined within a closed shell surrounding the tube where the HTF flows. The energy loss through the external wall is included. The test has been carried out within the experimental activity performed by ENEA. A complete cycle is considered: the initial stabilization, the charging phase and the discharging phase. Details of flow behavior within the molten PCM are described highlighting its influence on the device performance

Effects of particle settling on Rayleigh-Bénard convection

The effect of particles falling under gravity in a weakly turbulent Rayleigh-Bénard gas flow is studied numerically. The particle Stokes number is varied between 0.01 and 1 and their temperature is held fixed at the temperature of the cold plate, of the hot plate, or the mean between these values. Mechanical, thermal, and combined mechanical and thermal couplings between the particles and the fluid are studied separately. It is shown that the mechanical coupling plays a greater and greater role in the increase of the Nusselt number with increasing particle size. A rather unexpected result is an unusual kind of reverse one-way coupling, in the sense that the fluid is found to be strongly influenced by the particles, while the particles themselves appear to be little affected by the fluid, despite the relative smallness of the Stokes numbers. It is shown that this result derives from the very strong constraint on the fluid behavior imposed by the vanishing of the mean fluid vertical velocity over the cross sections of the cell demanded by continuity

Transitional regimes and rotation effects in Rayleigh–Bénard convection in a slender cylindrical cell

In this paper we analyze transitional regimes and mean flow structures for the thermally driven convective flow in a cylindrical cell of aspect-ratio (diameter over cell height) Γ=1/2. The investigation is carried out through the numerical integration of the three-dimensional unsteady Navier–Stokes equations with the Boussinesq approximation. In particular the critical Rayleigh numbers for the onset of convection, for the unsteady, chaotic and turbulent regimes are computed for two values of the Prandtl number and comparisons with cylindrical cells of larger aspect-ratio are performed. The effect of the background rotation on the flow dynamics is also described showing that the heat transfer increase, already evidenced in the literature, is only obtained for a range of rotation rates. The rotation can enhance or inhibit the heat transfer and, at low Rayleigh numbers, it is a very effective way to inhibit vertical motions and to prevent horizontal thermal gradients. This is highly desirable in solidification and crystal growth processes where thermally induced motions cause material defects and crystal inhomogeneities

Multiphase Rayleigh-Bénard convection

Numerical simulations of two-phase Rayleigh-Bénard convection in a cylindrical cell with particles or vapor bubbles suspended in the fluid are described. The particles or bubbles are modeled as points, the Rayleigh number is 2×106 and the fluids considered are air, for the particle case, and saturated water for bubbles. It is shown that the presence of a second phase has a profound effect on the flow and heat transfer in the cell. The heat capacity of the particles and the latent heat of the liquid are used, in dimensionless form, as control parameters to modulate these effects. It is shown that, as these parameters are varied, the nature of the flow in the cell changes substantially, in some cases with adverse and in others beneficial effects on the Nusselt number. By the analysis of several aspects of the numerical results, a physical discussion of several mechanisms is provided

Investigation of a pressure compensated vane pump

Variable displacement hydraulic machines offer a very promising alternative and energy saving solution for many applications in mobile machines, robots and other applications. In the present paper a vane pump will be theoretically analyzed using the software AMESim and/or MATLAB/Simulink, in order to estimate the friction forces and volumetric efficiency loss without hardworking experimental tests. The friction forces taken into account by our model are the friction between vanes and rotor slots and that between vanes and eccentric pump stator. The same design parameters affect the volumetric and mechanical efficiency, whose behavior has been reported and discussed. The behavior of the machine is analyzed and discussed at different angular velocities and pressure regimes