Automated 360° profilometry of a three-dimensional diffuse object and its reconstruction by use of the shading model

The 360° profilometry of a three-dimensional (3-D) diffuse object by use of the light intersection and its image reconstruction by surface shading are presented. The lack of data in one direction, which was due to occlusion, was compensated by the projection of two lines of light from different directions. Some experiments to profile objects and their reconstruction by computer are shown. The entire surface model was constructed, and a real shading image was obtained by means of computer graphics.     

Examination of scattering at 90° from a cylindrical volume illuminated by polarized light

A comparison is presented of the effects of particle size, concentration, and detector depth on side scattering for linearly and circularly polarized incident light. The scattering medium consists of various concentrations of particles, which are either 1.24, 0.494, 0.36, 0.123, or 0.065 μm in diameter, and which were mixed into filtered, distilled water and serve as the scattering centers. The results indicate that when this scattering medium is irradiated with linearly polarized laser light whose beam has been put through a quarter-wave plate in an effort to produce circularly polarized light, then there are two components scattered 90°, that is, circularly and linearly polarized light. The amount of each component and the ratio to total intensity of scattered light are analyzed for the different particles.     

Contouring of diffused objects using lensless Fourier transform digital moiré holography

A method is proposed for contouring of diffused objects using digital holographic moiré interferometry in lensless Fourier transform configuration. Fringe projection moiré technique combined with digital double-exposure holography produces the contours in this method. Two digital holograms of a 10?mm aluminum alloy cube are recorded by tilting the illumination angle slightly between exposures, and a third one is recorded by translating the detector a little laterally with the final illumination angle unchanged. Upon numerical processing of the first two holograms, a plane parallel fringe system seems to be projected onto the object. This fringe system can be referred to as the modified grid. Processing of the second and the third hologram results in another grid, the reference grid. In effect, processing of the first and the third hologram combines the modified and the reference grids to produce the moiré contour fringes. The range of contour intervals obtained remains between 2.73 and 0.38?mm with seven different contours in between. The present method can measure details of a great variety of sizes on objects of large dimensional range. Deviations in the measured contour intervals from the theoretically calculated values are found to be within 12%-18%. This seems to be because of the deviation in the present experimental geometry from the ideal theoretical configuration, the hologram digitization, and the particular reconstruction algorithm used in the present experimental arrangement.     

The impact of a 360° virtual tour on the reduction of psychological stress caused by COVID-19

The continuous spread of the COVID-19 pandemic is causing people to feel anxiety and stress. This study constructs a four-layer research model to examine how a 360° virtual tour can reduce people's psychological stress through two types of presence (the sense of presence and telepresence) and affective-motivational states (enjoyment and involvement) in this extraordinary period of the COVID-19 pandemic. In order to test the moderating effect of involvement, partial least squares (PLS) analysis is employed to analyse valid data collected from 235 individuals. The results of this study indicate that telepresence has a higher impact in generating affective-motivational states than the sense of presence. Among the factors, enjoyment shows the highest effect on satisfaction with the 360° virtual tour experience and stress reduction; involvement moderates the effect of telepresence on satisfaction with the 360° virtual tour experience. This study also contributes to virtual reality research by distinguishing the concepts of ‘sense of presence’ and ‘telepresence’ as well as demonstrating the mechanisms whereby virtual reality technology influences people's psychological well-being. Timely recommendations are provided for people in order to reduce psychological stress during and after COVID-19 pandemic.     

Switching of ± 360° domain wall states in a nanoring by an azimuthal Oersted field

We demonstrate magnetic switching between two 360° domain wall vortex states in cobalt nanorings, which are candidate magnetic states for robust and low power magnetoresistive random access memory (MRAM) devices. These 360° domain wall (DW) or 'twisted onion' states can have clockwise or counterclockwise circulation, the two states for data storage. Reliable switching between the states is necessary for any realistic device. We accomplish this switching by applying a circular Oersted field created by passing current through a metal atomic force microscope tip placed at the center of the ring. After initializing in an onion state, we rotate the DWs to one side of the ring by passing a current through the center, and can switch between the two twisted states by reversing the current, causing the DWs to split and meet again on the opposite side of the ring. A larger current will annihilate the DWs and create a perfect vortex state in the rings.     

Active damping of laminated thin cylindrical composite panels using vertically/obliquely reinforced 1–3 piezoelectric composites

This paper deals with the analysis of active constrained layer damping (ACLD) of laminated thin composite panels using vertically and obliquely reinforced 1–3 piezoelectric composite materials as the material of the constraining layer of the ACLD treatment. A finite element model has been developed for analyzing the ACLD of laminated antisymmetric cross-ply and antisymmetric angle-ply thin composite panels integrated with the patches of such ACLD treatment. Both in-plane and out-of-plane actuations of the constraining layer of the ACLD treatment have been utilized for deriving the finite element model. The analysis revealed that the vertical actuation dominates over the in-plane actuation. Particular emphasis has been placed on investigating the performance of the patches when the orientation angle of the piezoelectric fibers of the constraining layer is varied in the two mutually orthogonal vertical planes. The analysis revealed that the vertically reinforced 1–3 piezoelectric composites which are in general being used for the distributed sensors can be potentially used for the distributed actuators of high performance light-weight smart thin composite panels.     

Dynamic emission of dislocations from a crack tip — a computer simulation

The behavior of dynamic emission of dislocations from the tip of a stationary crack under mode II or mode III loading is examined. A critical stress intensity factor, K _D is assumed for dislocation emission. After emission, the dislocation moves with a velocity which varies with the effective shear stress to the third power. The effective shear stress is due to the applied stress , modified by the presence of the crack and all other dislocations minus the lattice friction stress, ^F. The effects of K _D, , and ^F on the rate of emission, the plastic zone strain rate, the plastic zone size, the dislocation distribution, and the dislocation-free zone are reported.

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Résumé On a examiné le comportement d'une émission dynamique de dislocations depuis l'extrémité d'une fissure stationnaire. On suppose que l'émission de dislocations est caractérisée par un facteur critique d'intensité de constrainte K _D. Après son émission, la dislocation se meut avec une vitesse qui varie avec le cube de la constrainte effective de cisaillement. Celle-ci résulte de la constrainte appliquée , modifiée par la présence de la fissure et de toutes les autres dislocations, et sous déduction de la contrainte de friction du réseau, ^F.On étudie les effects de K _D, et ^F sur la vitesse d'émission des dislocations, la vitesse de déformation plastique, la taille de la zone plastique, la distribution des dislocations, et sur la zone qui en est dépourvue.

     

Dynamic buckling of a laminated composite stringer–stiffened cylindrical panel

The present study deals with the “dynamic buckling” of a laminated composite stringer–stiffened curved panel. The “dynamic buckling”, in the present study, is concerned with the unbounded lateral response of the panel, which is subjected to an axial impact load.In reinforced panels with widely spaced adequately stiff stringers, the structure may pass through two major states before its total collapse: buckling of the panel skin between stiffeners and buckling of the stiffeners themselves. This study focuses on the lowest buckling load of the stringer–stiffened panel, which is, buckling of the panel skin between stiffeners.The analysis of the laminated composite stringer–stiffened cylindrical panel was performed by using the commercial ANSYS finite element software. The model simulates the structure and its associated boundary conditions. The boundary conditions simulate the stringer–stiffened cylindrical panel as a part of a fuselage. The static buckling analysis was performed using the eigenvalue buckling approach to determine the static critical load. Modal analysis was used to calculate the first natural frequency and corresponding mode shape of the structure. Nonlinear transient dynamic analysis was used to determine the dynamic critical load. In the transient dynamic analysis the Newmark method with the Newton–Raphson scheme were used.In the present study, the equation of motion approach was applied. By this approach, the equations of motion were numerically solved for various load parameter values (loading amplitude and loading duration) to obtain the system response. Special attention was given to the neighborhood of loading durations corresponding to the period of the lowest bending frequency of the skin.For each load duration, the dynamic buckling load was calculated using a load versus lateral displacement curve generated by the ANSYS code.The results were plotted on a dynamic load amplification factor (DLF) graph. The DLF is defined, as the ratio of the dynamic buckling to the static buckling of the panel. For loading periods in the neighborhood of the lowest natural frequency of the panel, the DLF was less than unity. It means that, for those particular loading periods, the dynamic buckling load is lower than the static one.     

Decomposition of the Heusler alloy Cu2MnAl at 360°C

During thermomagnetic studies, the as-quenched Heusler alloy Cu_2.00 Mn_1.00 Al_1.01 exhibits two Curie temperatures \(\theta _{C_I } \) and \(\theta _{C_{II} } \) . After 98 h at 360° C, above the Curie point, X-ray diffraction patterns indicate two ferromagnetic phases: Cu₂MnAl (I) witha _I=5.8707 Å and \(\theta _{C_I } \) = 151 ± 10° C; Cu₂MnAl (II) witha _II=5.9656 Å and \(\theta _{C_{II} } \) = 332 ± 4° C, whereas the 850° C as-quenched alloy exhibitsa=5.9612 Å andθ _c=341±5° C. The results are discussed in terms of the early stages of the decomposition of the Heusler phase. A mechanism, involving mainly the atomic migration of manganese, is suggested in order to reach the equilibrium phases of the ternary Cu-Mn-Al diagram. The kinetics of the decomposition should be ruled by the nucleation and the growth of the Cu₃Mn₂Al intermetallic compound.     

Image reconstruction using a photonic crystal based flat lens operating at 1.55 μm

We used an optimized photonic crystal based flat lens for target detection and image reconstruction of micrometer sized objects for an operating wavelength of 1.55 μm. Using numerical retrieval procedures inspired from tomography, the ability to detect subwavelength sized targets and to image metallic objects of complex shapes is shown. The relation between the reconstructed image quality and lens resolution is investigated.     

Stiffness control of cylindrical shells under axial compression using piezocomposite actuators—An experimental investigation

The present study explores the modification and control of prebuckling stiffness of cylindrical shells for their potential use in smart structures. The effects of surface-bonded microfiber composite actuator patches on cylindrical shells subjected to axial compression are studied experimentally. The actuators are placed such that the distance separating them is less than the observed axial and circumferential buckling wavelengths. Strain gauge sensors are used to measure the axial strains at discrete locations on the cylindrical shell. Experimental results indicate that the actuation effect can reduce the local strains as well as improve the overall stiffness of the structure. The results obtained in this study potentially have a significant impact in space applications.     

Is 3D Printing of Pharmaceuticals a Disruptor or Enabler?

Additive manufacturing (AM) is a fast‐growing manufacturing approach that comes with the promise of delivering personalized medicine to treat individual patients. However, large‐scale commercial applications in the pharmaceutical industry have been limited. Here, some of the challenges are discussed along with some pharmaceutical products where AM has the potential to make a tangible impact and pave the way for more rapid adoption are highlighted.     

CFD study of forced convective heat transfer enhancement in a 90° bend duct of square cross section using nanofluid

In this paper, the forced convective heat transfer enhancement with nanofluids in a 90° pipe bend has been presented. Numerical investigation is carried out for the turbulent flow through the pipe employing finite volume method. The governing differential equations are discretized using hexahedral cells, and the resulting algebraic equations are solved using Commercial solver Fluent 6.3. In order to close the time averaged Navier–Stokes equations, the two-equation k–? turbulence model with a standard wall function have been used. The duct Reynolds number is varied in the range of 2,500–6,000. It is observed that the heat transfer is enhanced significantly by varying the volume fraction of the nanofluid. It is also found that the heat transfer is increased with Reynolds number. A strong secondary flow is observed due to the presence of the wall. Turbulent kinetic energy near outer wall is found to be higher than the inner wall of the bend. A comparative assessment for the heat transfer enhancement with different types of nanofluids is also presented. The computed results of area weighted average Nusselt numbers are validated with some of the existing literature.     

Design of a novel dielectric resonator antenna using MgTiO3–CoTiO3 for wideband applications

In this work, a novel low profile design of a cylindrical dielectric resonator (DR) antenna with two different permittivity materials is proposed for wideband applications. The multi-permittivity cylindrical DR (MPCDR) was formed by combining four 90° sectors whereby sectors with the same permittivity were positioned in opposite quadrants. Simulation of the antenna was performed in the time domain using computer simulation technology (CST 2014). A systematic analysis was carried out to optimize the antenna's sector size and permittivity. The prototype was fabricated using MgTiO₃ (MTO) and CoTiO₃ (CTO) dielectric materials prepared via solid state reaction. MTO and CTO were sintered at 950 °C (4 h) and subsequently analyzed by XRD to confirm the presence of a single phase. The dielectric properties of MTO and CTO were studied by electrical characterization; it was found that MTO and CTO have permittivity values of 15.72 and 9.85, respectively. The antenna performance was analyzed by placing the MPCDR on top of a microstrip line with an angular position (θ) of 27.5° with respect to the longitudinal axis of the feed-line. An impedance bandwidth up to 56% with stable broadside radiation pattern was achieved in both the simulation and measured.     

Fracture toughness of the + 45° / – 45° interface of a laminate composite

Experiments are carried out to determine the delamination toughness for a crack along the interface between two transversely isotropic materials. The material chosen for study consists of carbon fibers embedded within an epoxy matrix. A crack is introduced between two layers of this material, with fibers in the upper layer along the + 45°-direction and those in the lower layer along the − 45°-direction both with respect to the crack plane. The Brazilian disk specimen is employed in the testing. To calibrate the specimens, stress intensity factors are obtained which result from the applied load, as well as residual curing stresses. It may be noted that all three modes are coupled, leading to a three-dimensional problem. The finite element method and a mechanical M-integral are employed to determine the stress intensity factors arising from the applied load. For the residual stresses, a three-dimensional conservative thermal M-integral is presented for stress intensity factor determination. The stress intensity factors found for the applied load and residual stresses are superposed to obtain a local energy release rate, together with two phase angles. From the load at fracture, the critical interface energy release rate or interface toughness as a function of phase angles ψ and ϕ is determined. Results are compared to a fracture criterion.     

Compression of a 0°-ply/acrylic sandwich

The compressive behaviour of a 0°-ply (AS4/PPS) inserted between two acrylic layers is studied experimentally, and results are compared with existing theoretical predictions. A transparent acrylic is chosen so that kink formation in the 0°-ply may be directly observed. Experiments show that failure occurs by catastrophic formation of an in-plane kink band with a kink band angle of 20° to the horizontal axis. Then, as the compression strain is further increased, several additional kink bands appear. The load corresponding to the formation of the first kink is in agreement with theoretical predictions. These experiments confirm that failure initiates by in-plane kinking, and shed light upon the behaviour of an internal 0°-ply inside a multidirectional laminate, especially the propensity for in-plane kinking versus out-of-plane kinking.     

Starting solutions for oscillating motions of a generalized Burgers’ fluid in cylindrical domains

Exact solutions for the motions of a generalized Burgers’ fluid due to longitudinal and torsional oscillations of a circular cylinder are obtained using Hankel transform and Laplace transform. These solutions are expressed as sum of steady-state and transient solutions. They describe the motion of the fluid for some time after its initiation. After that time, when the transients disappear, the motion is described by the steady-state solution which is periodic in time and independent of the initial conditions. Finally, by means of graphical illustrations, the velocity field is determined for sine and cosine combined oscillations of the boundary.     

Axisymmetric natural damped frequencies of a viscous liquid in a circular cylindrical Container — An alternative semi-analytical solution

For axisymmetric liquid motion (m=0) in a circular cylindrical Container nlled with an incompressible and viscous liquid the natural damped frequencies are determined. The analysis satisfies the side wall conditions exactly while only the normal Container bottom condition could be satisfied. This restricts the Solution results to liquid height flllings h/a to larger values (h/a>1). It was found that with increase of the liquid height ratio h/a the oscillation frequency and decay magnitude are both increasing.     

Acquisition of customer’s tailor measurements for 3D clothing design using virtual reality devices

Over recent years, various virtual prototyping technologies have been developed to innovate apparel industry. For each step of the garment design process one can find dedicated tools (from body acquisition to garment modelling and simulation) with the aim of making the process easier and faster. However, most of them are based on expensive solutions both for hardware and software systems. In this paper, we focus the attention on the first step of the made-to-measure garment design, i.e. customer’s measures acquisition. We present a plug-in, named Tailor Tracking, which permits to get the measurements by interacting with the customer’s avatar using hands as in the traditional way. Tailor Tracking has been developed using low cost devices, such as Microsoft Kinect sensor, Leap motion device and Oculus Rift, and open source libraries, such as Visualisation Toolkit (VTK) and Qt. The proposed approach is based on the use of multiple Kinect v2 to simultaneously acquire both customer’s body and motion. This permits to emulate the customer’s postures required to take the correct measurements. In addition, a virtual measuring tape is made available to replicate the one commonly used by the tailor. A men shirt has been considered as case study and a tailor and 14 people with no skills in garment design and different levels of experience in virtual reality technology have been involved to preliminary test Tailor tracking. Finally, tests as well as results reached so far are presented and discussed. Results have been considered quite good; however, some critical measures have been identified as well as future developments. Anyway, Tailor Tracking can represent an alternative solution to the existing approaches that automatically extract anthropometric measures from the customer’s avatar.