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In the last decade, the possibility to use liquid crystal droplets as optical micro-cavities and lasers has attracted much attention since it paves the way for many applications in the field of sen...

Using an interdisciplinary law and computer science approach, this article argues that quantum computing must push lawmakers to implement more dynamic privacy regulation to cushion quantum computing's impact on data protection and privacy. This article highlights the EU GDPR position as the global standard for data protection and privacy regulation. The GDPR has ignited a legal standardization phenomenon, whereby many jurisdictions are shaping their privacy regulation based on the GDPR. A move by EU lawmakers to amend the GDPR to embed post-quantum encryption requirements dynamically would ignite a global paradigm shift. This would result in forward-looking protection of data subjects' rights that extends beyond quantum computing perils. It would also signal that lawmakers' intention to making privacy regulation dynamic, thus enabling it to cope with future threats by being ahead of the technological disruption curve.

The ability to produce distributed sensors by tailoring materials readily available on the market is becoming an emerging strategy for Internet of Things applications. Embedding sensors into functional substrates allows one to reduce costs and improve integration and gives unique functionalities inaccessible to silicon or other conventional materials used in microelectronics. In this paper, we demonstrate the functionalization of a commercial polyurethane (PU) foam with the conductive polymer PEDOT:PSS: the resulting material is a modified all-polymeric foam where the internal network of pores is uniformly coated with a continuous layer of PEDOT:PSS acting as a mechanical transducer. When an external force causes a modification of the foam microstructure, the conductivity of the device varies accordingly, enabling the conversion of a mechanical pressure into an electric signal. The sensor provides a nearly linear response when stimulated by an external pressure in the range between 0.1 and 20 kPa. Frequency-dependent measurements show a useful frequency range up to 20 Hz. A simple micromechanical model has been proposed to predict the device performance based on the characteristics of the system, including geometrical constrains, the microstructure of the polymeric foam, and its elastic modulus. By taking advantage of the simulation output, a flexible shoe in sole prototype has been developed by embedding eight pressure sensors into a commercial PU foam. The proposed device may provide critical information to medical teams, such as the real-time bodyweight distribution and a detailed representation of the walking dynamic.

We developed and optimized a custom dynamic Electronic Speckle Pattern Interferometer (d-ESPI) for measuring time-dependent three-dimensional (3D) surface displacements during inflation testing of ocular tissues. The 3D displacement field was resolved under dynamic loading conditions for a simplified test case of a rubber phantom and a real-world test case of the posterior sclera of a human eye. We present the optical layout and calibration procedure of the d-ESPI, and demonstrate how the displacement field can be accurately resolved for specimen deformation rates up to 6 μm/s.

In the present paper the author describes the potential offered by the combined use of the Confocal Microscopy (CM) and Digital Image Correlation (DIC) to resolve the whole displacement vector in full-field fashion and with nanometric accuracy. By means of two different configurations of the same portion of the area under investigation, the surface profile retrieved at microscopic level by the CM functioned as a carrier for the DIC algorithm, both for a polished surface and an engineering standard roughness. The in-plane displacement components obtained by DIC were then used to extract the out-of-plane component from the profile information. After describing all steps that are necessary for applying the procedure, preliminary results of an indentation tests carried out on a polished steel specimen are reported and discussed.

Specific features of biological materials, such as microstructure, heterogeneities or hybrid compositions, already inspired the fabrication of several architected materials. More recently, special emphasis has been placed on the development of damage tolerant interfaces by introducing tailored surface heterogeneities. However, thanks to the current developments in the area of additive manufacturing, the mating substrates can be now fashioned into complex shapes to confer the desired joint behavior. By taking inspiration from the base plate of the Balanus Amphitrite, we recently employed 3D printing to fabricate bio-inspired structural interfaces and adhesive bonded Double Cantilever Beam (DCB) fracture specimens. The results of DCB tests have shown a remarkable increase in the total dissipated energy with respect to baseline samples. In this work we supplement our previous study by performing finite element simulations in order to ascertain the variation of the driving force as a function of crack advance. The obtained results, which are analyzed in conjunction with high resolution imaging of the crack propagation process, allow to further elucidate the mechanics of debonding. It is shown that the sub-surface channels can modulate the driving force available for crack growth, introducing a crack trapping ability which depends on the specific geometry of the interfacial region.

PURPOSE. To determine if in vivo strain response of the Optic Nerve Head (ONH) to IOP elevation visualized using Optical Coherence Tomography (OCT) video imaging and quantified using novel virtual extensometers was able to be provided repeatable measurements of tissue specific deformations. METHODS. The ONHs of 5 eyes from 5 non-human primates (NHPs) were imaged by Spectralis OCT. A vertical and a horizontal B-scan of the ONH were continuously recorded for 60 seconds at 9Hz (video imaging mode) during IOP elevation from 10 to 30 mmHg. Imaging was repeated over three imaging sessions. The 2D normal strain was computed by template-matching digital image correlation using virtual extensometers. ANOVA F-test (F) was used to compare inter-eye, inter-session, and inter-tissue variability for the prelaminar, Bruch’s membrane opening (BMO), lamina cribrosa (LC) and choroidal regions (against variance the error term). F-test of the ratio between inter-eye to inter-session variability was used to test for strain repeatability across imaging sessions (F(IS)). RESULTS. Variability of strain across imaging session (F=0.7263, p=0.4855) and scan orientation was not significant (F=1.053, p=0.3066). Inter session variability of strain was significantly lower than inter-eye variability (F(IS)=22.63, p=0.0428) and inter-tissue variability (F(IS)=99.33 p=0.00998). After IOP elevation, strain was highest in the choroid (−18.11%, p

A WiFi-based landmark (LM) is a unique point in the physical space that has a repeatable and identifiable WiFi signature as sensed by a mobile device. We present Lighthouse, a new class of WiFi landmarks based on concepts from computational geometry theory that can be leveraged to provide worldwide robust and accurate location based services (LBSs). The proposed Lighthouse landmarks have the nice properties of being abundant in space, hardware-and carry position-independent, can be computed efficiently from a single scan, are confined to a small area of space, do not restrict the user movement path, and do not require any calibration. We show that the positioning error of the Lighthouse landmarks is bounded and present the different extensions that allow it to handle practical situations including the noisy wireless channel, different AP transmit powers, obstacles in the environment, among others. We further present efficient algorithms for extracting them from WiFi scans. We have implemented and evaluated Lighthouse using thousands of surveys collected from different cities worldwide over a six months period. Our results show that Lighthouse's landmarks are one order of magnitude more frequent in the environment compared to the other state-of-the-art WiFi-based landmarks. In addition, the median accuracy of determining the LMs location is less than 3.6 meters. This accuracy is robust over time, different phones hardware, phone carrying positions, and parameters configurations; highlighting the promise of Lighthouse landmarks for enabling the next generation LBSs on a worldwide scale.

Changes in the biomechanical properties of the connective tissue of the eye occur with age and underlie the development of several ocular diseases, such as glaucoma, myopia, and keratoconus. The biomechanical dynamics of ocular connective tissue are measured by ex vivo inflation testing, in which intraocular pressure (IOP) is varied and optical methods are used to produce maps of corneal and scleral displacement. Current optical methods are limited by acquisition rate, occlusions, poor spatial resolution, and insufficient 3D mapping. We developed an interferometric optical method integrates four-camera electronic speckle pattern interferometry (ESPI) and a novel three-dimensional (3D) shape reconstruction process to measure shape and full-field mechanical deformations of corneal and scleral shells during ex vivo inflation testing. Each camera provides accurate measurements of the laser beam phase related to deformations of the specimen surface; a multi-view stereovision method generates the shape of the specimen and a functional form that links every pixel of a given camera to 3D points on the specimen's visible surface. In this way, dynamic deformations of the specimen are localized, with quantification of the time-dependent 3D displacements of the specimen at nanometric accuracy. The ESPI-3D system is suitable for analyzing scleral deformation and morphological changes caused by time-varying IOP.

PURPOSE: To compare the three-dimensional (3D) morphology of the deep load-bearing structures of the human optic nerve head (ONH) as revealed in vivo by spectral domain optical coherence tomography (SDOCT) with ex vivo quantitative 3D histology. METHODS: SDOCT imaging of the ONH was performed in six eyes from three brain-dead organ donors on life-support equipment awaiting organ procurement (in vivo conditions). Following organ procurement (ex vivo conditions), the eyes were enucleated and underwent a pars plana vitrectomy followed by pressurization to physiologic IOP and immersion fixation. Ex vivo ONH morphology was obtained from high-fidelity episcopic fluorescent 3D reconstruction. Morphologic parameters of the observed ONH canal geometry and peripapillary choroid, as well as the shape, visibility and depth of the lamina cribrosa were compared between ex vivo and in vivo measurements using custom software to align, scale, and manually delineate the different regions of the ONH. RESULTS: There was significant correspondence between in vivo and ex vivo measurements of the depth and shape of the lamina cribrosa, along with the size and shape of Bruch’s membrane opening (BMO) and anterior scleral canal opening (ASCO). Weaker correspondence was observed for choroidal thickness; as expected, a thinner choroid was seen ex vivo due to loss of blood volume upon enucleation (−79.9 %, p

A WiFi-based landmark (LM) is a unique point in the physical space that has a repeatable and identifiable WiFi signature as sensed by a mobile device. We present Lighthouse, a new class of WiFi landmarks based on concepts from computational geometry theory that can be leveraged to provide robust and accurate location based services (LBSs). Our experimental results show that Lighthouse's landmarks are one order of magnitude more frequent in the environment compared to the other state-of-the-art WiFi-based landmarks. In addition, the median accuracy of determining the LMs location is 3.4 meters which is robust under different conditions; highlighting the promise of Lighthouse landmarks for enabling the next generation LBSs.

This study presents a quantification method for the assessment of the optic nerve head (ONH) deformations of the living human eye under acute intraocular pressure (IOP) elevation and change of cerebrospinal fluid pressure (CSFP) with body position. One eye from a brain-dead organ donor with open-angle glaucoma was imaged by optical coherence tomography angiography during an acute IOP and CSFP elevation test. Volumetric 3D strain was computed by digital volume correlation. With increase in IOP the shear strain consistently increased in both sitting and supine position (p

PURPOSE We tested the hypothesis that there are age- and race-related differences in posterior scleral material properties, using eyes from human donors of European (20-90 years old, n = 40 eyes) and African (23-74 years old, n = 22 eyes) descent. METHODS Inflation tests on posterior scleral shells were performed while full-field, three-dimensional displacements were recorded using laser speckle interferometry. Scleral material properties were fit to each eye using a microstructure-based constitutive formulation that incorporates the collagen fibril crimp and the local anisotropic collagen architecture. The effects of age and race were estimated using Generalized Estimating Equations, while accounting for intradonor correlations. RESULTS The shear modulus significantly increased (P = 0.038) and collagen fibril crimp angle significantly decreased with age (P = 0.002). Donors of African descent exhibited a significantly higher shear modulus (P = 0.019) and showed evidence of a smaller collagen fibril crimp angle (P = 0.057) compared to donors of European descent. The in-plane strains in the peripapillary sclera were significantly lower with age (P < 0.015) and African ancestry (P < 0.015). CONCLUSIONS The age- and race-related differences in scleral material properties result in a loss of scleral compliance due to a higher shear stiffness and a lower level of stretch at which the collagen fibrils uncrimp. The loss of compliance should lead to larger high frequency IOP fluctuations and changes in the optic nerve head (ONH) biomechanical response in the elderly and in persons of African ancestry, and may contribute to the higher susceptibility to glaucoma in these at-risk populations.

Crack tip stress-induced phase transformation mechanisms in nickel–titanium alloys (NiTi), subjected to fatigue mechanical loads, have been analyzed by full field measurement techniques. In particular, Infrared thermography (IR) and Digital Image Correlation (DIC), have been applied to analyze the cyclic temperature and displacement evolutions in the crack tip region of a commercial pseudoelastic alloy, together with the associated thermal and mechanical hysteresis, by using Single Edge Crack (SEC) specimens. IR investigations revealed a global temperature variation of the specimen due to crack formation and propagation mechanisms, which is similar to common engineering metals, i.e. surface temperature rises quickly in an initial phase, then it reaches an almost constant value, and finally it increases rapidly as a consequence of the fatigue crack growth. In addition, cyclic thermal variation in the crack tip region and related hysteresis (temperature vs load) has been measured, which can been directly related to the thermal effects of the reversible stress-induced phase transformations. Furthermore, a proper experimental setup has been made, based on a reflection microscope, for direct measurements of the crack tip displacement field by the DIC technique. Furthermore, a fitting procedure has been developed to calculate the mode I Stress Intensity Factor (SIF), starting from the displacement field, and the related mechanical hysteresis (SIF vs load).

In this work, we demonstrate micro resonators made of liquid crystal blue phase (BP) microspheres, embedded in a polymer/water matrix. The omnidirectional 3D lasing from BPII and BPI microspheres and the temperature-controlled laser tuning within the range of 55 nm from the BPI microspheres were observed for the first time. The potential applications of BPs microlasers range from temperature-controllable, omnidirectional, coherent light micro sources to informational displays and micro sensing devices.

The paper presents a simple and straightforward procedure for determining the phase of an interferogram by exploiting the specific behavior of laser diodes—i.e., the small variation of the operating wavelength attainable by varying the forward current of the diode. The proposed procedure was developed by using a laser diode for feeding a quasi-balanced Michelson interferometer, by which the optimal operating conditions were investigated—i.e., the proper unbalancing and the proper variation of the supply voltage of the diode. The selected operating conditions were then used for evaluating the phase-steps by a simple algorithm developed on purpose for the present application. The phase measurements carried out by the proposed method have shown a very good accordance with those obtained by a conventional temporal phase-shifting procedure performed by a high-end commercial PZT actuator with quasi-nanometric accuracy.

In the present paper the authors propose a portable and low-cost speckle interferometer for evaluating 3D deformation fields. The interferometer was designed and realized with the aim of carrying out measurements on small areas, hence it can be used to approach problems characterized by displacement field with highly localized gradients, such as the strain relief occurring in residual stress evaluation or the displacements which arise around notches or crack tips. The costs of the experimental equipment were reduced by employing laser diodes as light sources, a PZT actuator designed and calibrated by the authors and a control electronics realized on purpose. Moreover the configuration which was adopted allows further saving on optical components. The experimental results reported at the end of the paper, and obtained by a specimen subjected to 3D rigid body motions, show a high repeatability and accuracy. Furthermore the experimental results have shown that the geometry of the optical setup implies the variation of the sensitivity vectors on the inspected area, but this effect can be evaluated (analytically and/or experimentally) and taken into account in order to increase the accuracy of the measurements.

The paper presents an inverse procedure for identifying elastic properties of isotropic or orthotropic materials from the full-field measurement of the surface displacements of plates under flexural loading configurations. The procedure is based on a numerical–experimental optimisation process which minimizes an error function defined by subtracting the experimental data from the outputs of the numerical analysis. In each iteration the optimisation process updates the values of the elastic constants in a finite element model of the specimen used in the experimental tests. The unknown parameters are simultaneously identified by a single test and without damaging the structural integrity of the specimen. The possibility of using the methodology for characterizing any-shaped plates was investigated. The applicability and the robustness of the procedure were carried out on aluminum and unidirectional Graphite/PEEK laminate specimens. Phase-shifting speckle interferometry was employed to detect the out-of-plane displacement field of a portion of the observed surface of the specimen.

In the present paper a piezoelectric actuator realized for interferometric applications is described, together with a numerical model to simulate its electro-mechanical behavior. The actuator is an open-loop device made up of three piezoelectric ceramics glued into a stainless steel case and connected directly to the parallel port of a personal computer by control electronics developed on purpose. It consists of a 16 bit digital-to-analog converter whose voltage is fixed by the parallel port, a charge amplifier which provides the voltage to the piezoelectric ceramics and a current divider for the control of the voltage on each channel. The layout based on three active elements has allowed to obtain a device which is able to perform a straight expansion with a negligible tilting, a desirable feature for an actuator used for interferometric applications. The hysteretic behavior, a typical characteristic of this kind of actuator, was simulated by a numerical model, based on the Prandtl–Ishlinskii hysteresis operator, which shows a high capability to predict the input–output response at any level of the input signal, and it is efficient enough for use in real-time applications.

The present work reports a possible solution for a low-cost piezoelectric actuator available for interferometric applications. In the paper the design, the assembly and the calibration of the actuator are described in detail. The solution adopted consists of a machined stainless steel case deformed by three low-voltage multilayer plumbum zirconate titanate (PZT) ceramic blocks. In the proposed arrangement a three degree of freedom device is obtained, by which a translation and two rotations can be performed. The PZTs are driven by a supply voltage provided by a 16 bit D/A converter directly connected to the parallel port of a personal computer which guarantees a very accurate output. This voltage is applied on each ceramic by means of a variable resistor, by which it is possible to adjust the maximum driving voltage for the single block. This electrical solution allows to match up the strokes of the ceramics in order to obtain a straight expansion of the whole actuator. After the mechanical and electrical set-up of the actuator, a static calibration was carried out by inserting it along one arm of a Michelson speckle interferometer. The calibration procedure had emphasized the hysteresis loop and the non-linearity of the electromechanical behaviour of the actuator.

At present, speckle interferometry is a well-assessed experimental technique for investigating on deformations of specimen and real object in static and dynamic loading configurations. Its operating principle has made feasible the development of computer-aided methods for full-field non-contact measurements of in-plane and out-of-plane displacements or their (approximated) derivatives with interferometric sensitivity. Due to these facts, speckle interferometry comes up as a more versatile technique with respect to its ancestor, the holographic interferometry. Mainly devoted, at its early stage of development, to semi-quantitative non-destructive testing, the progress in electronic imaging and computer hardware and the use of novel techniques for phase measurement, boosted the performance of speckle interferometers which, when using appropriate software, can now straightforwardly produce accurate whole field phase maps by which the detected physical quantities can be obtained by an unwrapping procedure.

A method for measuring the axial residual stress profile in axisymmetric optical fibers is presented. The procedure is based on integrated photoelasticity and a fringe shifting technique is used to measure the optical retardation. The radial distribution of the axial residual stress is reconstructed using the inverse Abel transform. The paper describes the operating principle, the experimental setup and the results obtained on a multimode fiber are also reported. The influence of the measurement errors is finally discussed.

The present paper describes an experimental procedure for the measurement of the displacement field around a spherical indentation. The measurements were performed by a speckle interferometer designed for the detection on small areas of one or more oblique components of displacement; the indentations were made by a standard durometer used for metals. The experiments were carried out on a hardened and tempered steel, previously characterized by a standard tensile test; the results are in accordance with the numerical results obtained by an elasto-plastic FEM analysis.

The random noise of the laser speckle field which develops at the focusing plane of an imaging system, is, by now, efficiently used in several interferometric techniques as an information carrier of the macroscopic wavefront distortion induced by the surface displacement field of the object under investigation. The actual noise in this kind of techniques is represented by the speckle decorrelation at the image plane — i.e. the destruction of the carrier — which may be caused by the modification of the texture surface (e.g. by yielding under a severe stress state), but it is inherently produced by the same displacement field under measurement. In the paper the phenomenon of laser speckle decorrelation is numerically simulated and experimentally investigated with the aim of estimating its sensitivity to local deformation and assessing a possible field of application. Satisfactory results in the field of NDT of multilayer fiber-reinforced composites were obtained by reducing the diaphragm of the lens to increase the sensitivity of the imaging system to speckle decorrelation induced by local deformation; unfortunately this simple approach requires a considerable amount of laser power for illuminating the object. Different aperture shapes were therefore numerically simulated which provided improved efficiency and sensitivity and whereby a semi-quantitative analysis of the displacement field could be experimented.

We present a Simultaneous Localization and Mapping (SLAM) algorithm based on measurements of the ambient magnetic field strength (MagSLAM) that allows quasi-real-time mapping and localization in buildings, where pedestrians with foot-mounted sensors are the subjects to be localized. We assume two components to be present: firstly a source of odometry (human step measurements), and secondly a sensor of the local magnetic field intensity. Our implementation follows the FastSLAM factorization using a particle filter. We augment the hexagonal transition map used in the pre-existing FootSLAM algorithm with local maps of the magnetic field strength, binned in a hierarchical hexagonal structure. We performed extensive experiments in a number of different buildings and present the results for five data sets for which we have ground truth location information. We consider the results obtained using MagSLAM to be strong evidence that scalable and accurate localization is possible without an a priori map.

Indoor positioning by means of received signal strengths has been gathering much interest since the massive presence of wireless local area networks (WLANs) in buildings. Theoretical approaches rely on the perfect knowledge of the APs' positions and propagation conditions; since this is unrealistic in real world, we estimate such knowledge as well as the building map from data by applying Simultaneous Localization and Mapping (SLAM). In this paper we address the joint estimation of the path loss parameters, namely the transmitted power and the path loss exponent, this latter being usually approximated in the literature by the free space value. We provide examples that show the relevance of estimating both parameters and analyze observability issues from the point of view of estimation theory. The integration of the parameter estimation in a WLAN based SLAM algorithm - WiSLAM - has been carried out and the results are discussed.

Received signal strengths have been widely exploited in indoor positioning due to the massive presence of wireless local networks in buildings. Theoretical propagation models such as the path-loss model can be used in order to avoid long training phases as in fingerprinting approaches. The main issue concerning the employiment of the path-loss model is that the values of some parameters, i.e., the transmit power and the decay exponent, depend on many factors, such as the device, building structure and other environmental features. In this paper, we propose a Bayesian positioning algorithm based on the Rao-Blackwellized particle filter, where the parameters of the path-loss model are estimated independently for each AP in addition to localizing the user. Both parameters are described by discrete random variables with uniform priors. We validate ou proposal by means of simulations and two different experiments; finally, some remarks on complexity are also given.

In glaucoma, the optic nerve head (ONH) is the site of damage to the retinal ganglion cell axons that transmit the visual information from the eye to the brain. Results of several randomized prospective trials showed that intraocular pressure (IOP), age1, increased optic disc cupping, corneal thickness, and African ancestry2 are independently associated with glaucomatous progression. All of these risk factors have a biologically plausible association with either the level of IOP, the severity of disease, or biomechanical properties of the ONH. Importantly, age is the only risk factor other than IOP that is independently associated with the onset and progression of glaucoma across all of the major prospective clinical trials conducted over the past twenty years. In addition, every population-based survey conducted to date has demonstrated a strong relationship between the prevalence of glaucoma with advancing age, despite almost no studies showing IOP changes with age. These findings indicate that the aging ONH becomes increasingly vulnerable to glaucomatous injury at similar levels of IOP.Copyright © 2013 by ASME

The retinal ganglion cell axons carry visual information, and pass through the optic nerve head (ONH) as they traverse from inside the eye to the brain. The ONH is the site of axonal damage in glaucoma, the second leading cause of blindness in the world, and ONH biomechanics is hypothesized to play a crucial role in the development and progression of the disease. The load bearing tissues of the ONH insert into the surrounding sclera, which provides the boundary conditions for this important structure. It is therefore important to develop accurate experimental techniques to measure scleral shell deformations under intraocular pressure (IOP) loading that can be used to drive constitutive and computational models of scleral biomechanics. The overall goal of this project is to better understand the role of ocular biomechanics in the development of glaucoma by constructing eye-specific finite element models of the posterior pole and ONH.

Location based services, as well as security issues, require the knowledge of the user's position within an indoor area. Here, we address the problem of how the location service based on a WLAN can profit of the Received Signal Strengths (RSSs) collected from those Access Points (APs) whose position is not available. For this task, we develop two different algorithms, both relying on a dual estimation approach, in which RSS measures from ‘unknown’ APs are used along with RSS from ‘known’ APs. Simulative and experimental analyses, both corroborating the effectiveness of our solutions, are carried out.

We address Simultaneous Localization and Mapping (SLAM) for pedestrians by means of WiFi signal strength measurements. In our system odometric data from foot mounted Inertial Measurements Units are fused with received signal strength (RSS) measurements of IEEE 802.11. To do this, we assign a probabilistic model to RSS measurements, and adopt the Bayesian framework on which FootSLAM and PlaceSLAM are based. Computational aspects are also accounted in order to provide a practical implementation of the algorithm. Simulative and experimental examples of WiSLAM are shown to underline the effectiveness of our proposal.

In the paper the authors present an experimental equipment for elasto-plastic characterization of engineering materials by tensile tests. The stress state is imposed to a dog bone shaped specimen by a testing machine fixed on the optical table and designed for optimizing the performance of a speckle interferometer. All three displacement components are measured by a portable speckle interferometer fed by three laser diodes of 50 mW, by which the deformations of a surface of about 6×8 mm 2 can be fully analyzed in details. All the equipment is driven by control electronics designed and realized on purpose, by which it is possible to accurately modify the intensity of the illumination sources, the position of a PZT actuator necessary for applying phase-shifting procedure, and the overall displacement applied to the specimen. The experiments were carried out in National Instrument LabVIEW environment, while the processing of the experimental data in Wolfram Mathematica environment. The paper reports the results of the elasto-plastic characterization of a high strength steel specimen.

Wireless location of a User Equipment (UE) has received growing attention in recent years. The first step for the design of a wireless location system consists in choosing the system architecture and the localization algorithm that match the requirements of the working scenario. In this paper the area of interest is represented by an indoor parking lot, in which the variable occupancy of motor vehicles alters the electromagnetic propagation and causes large errors in vehicle location estimation. The proposed strategy to deal with this problem is the use of a server-based architecture, that ensures security and scalability and accounts for the system state in terms of number and positions of already present vehicles. This concept of state is shown to be useful to design suitable algorithms, based on simplified electromagnetic models, to improve the localization performance.

The present paper describes in details the operating principle of a completely new family of speckle interferometers: the double-focusing. This type of interferometer is sensitive to the same components of displacement given by holographic interferometry, i.e. the component along the bisector of the angle identified by the illumination and the observation directions. In addition, no external reference beam is necessary, with a consequent reduction of the complexity of the experimental setup. The only requirement for the correct functioning of this family of interferometers is that only a portion of the illuminated area undergoes a sensible deformation. The implementation can be indifferently carried out by adopting the classical Michelson or Mach-Zender configurations, but also a particularly compact in-line implementation can be realized.

The present paper describes a fitting procedure capable of providing a smooth approximation of experimental data distributed on a bi-dimensional domain, e.g. the typical output of an interferometric technique. The procedure is based on the optimization of an analytical model defined on the whole domain by the B-spline formulation. In the paper rectangular, circular and polygonal convex domains are considered in details, but, according to the need of the operating conditions, the procedure can be extended to domains of different shapes. The proposed procedure was initially calibrated by an analytical case study: a thin square plate simply supported along the edges and loaded by a uniform pressure. Subsequently, by the operative parameters defined by the analyses carried out on the analytic data, the fitting procedure was applied on experimental data obtained by phase shifting speckle interferometry.

The paper presents an algorithm able to retrieve the phase in speckle interferometry by a single intensity pattern acquired in a deformed state, provided that the integrated speckle field is resolved in the reference condition in terms of mean intensity, modulation amplitude and phase. The proposed approach, called throughout the paper "one-step", can be applied for studying phenomena whose rapid evolution does not allow the application of a standard phase-shifting procedure, which, on the other hand, must be applied at the beginning of the experiment. The approach was proved by an experimental test reported at the end of the paper.

Despite the variety of speckle interferometric setups dedicated to the detection of mechanical deformations which have been reported in the literature since the early 70’s, sometimes with various misleading acronyms, the operating principle of speckle interferometry has been till now essentially applied by two basically different approaches.

The paper deals with the calibration error of unequal phase changes across the interferogram in phase shifting interferometry, i.e., tilt-shift error. For its detection the lattice-site representation of phase shift angles is used. The error can be readily discerned using (N+1) algorithms. Four and five frame algorithms are considered. The influence of experimental parameters on the error detection sensitivity is discussed. Numerical studies are complemented by experimental results.

The present paper describes a hybrid method which combines finite element analyses and genetic algorithms (GAs) for determining the elastic properties of isotropic and anisotropic materials from the full-field measurement of the displacements of plates under flexural loads. An optimized procedure based on GAs updates iteratively the elastic constants in a numerical model until the displacements obtained by numerical analysis fit the experimental data. The unknown parameters are identified simultaneously by a single test and without damaging the structure. The procedure was applied to both isotropic (aluminum) and anisotropic (Graphite/PEEK unidirectional laminate) specimens.

The paper describes a simple low-cost open-loop PZT actuator and the procedures which have been developed for its calibration and alignment in order to obtain a device dedicated to phase-shifting speckle interferometry. A low-voltage multilayer PZT ceramic block was inserted between a mirror and a cube beamsplitter of a Michelson interferometer to be used in a shearometer assembled on a cube 40x40x40 mm. The PZT was driven by a supply voltage output by a 16 bit D/A converter directly connected to the parallel port of a personal computer which guarantees a very accurate output. By the analysis of the interference pattern produced by the Michelson interferometer the calibration curves (for ascending and descending input voltage) were obtained. When the whole hysteresis loop has been identified, a fairly linear working range can be chosen. The device is equipped with three setscrews acting on a leaf-spring for the compensation of the mirror tilting produced by the non uniform expansion of the PZT block. The calibration can be performed using either the interference between two smooth wavefronts (in presence of a sufficiently fine fringe pattern) or the interference between two speckle patterns. The calibration procedure can be consequently carried out directly on any speckle interferometer at the beginning of the measuring session, in this way the environmental sensitivity of the actuator can be overcome.

PURPOSE We tested the hypothesis that the variation of peripapillary scleral structural stiffness with age is different in donors of European (ED) and African (AD) descent. METHODS Posterior scleral shells from normal eyes from donors of European (n = 20 pairs; previously reported) and African (n = 9 pairs) descent aged 0 and 90 years old were inflation tested within 48 hours post mortem. Scleral shells were pressurized from 5 to 45 mm Hg and the full-field, 3-dimensional (3D) deformation of the outer surface was recorded at submicrometric accuracy using speckle interferometry (ESPI). Mean maximum principal (tensile) strain of the peripapillary and midperipheral regions surrounding the optic nerve head (ONH) were fit using a functional mixed effects model that accounts for intradonor variability, same-race correlation, and spatial autocorrelation to estimate the effect of race on the age-related changes in mechanical scleral strain. RESULTS Mechanical tensile strain significantly decreased with age in the peripapillary sclera in the African and European descent groups (P < 0.001), but the age-related stiffening was significantly greater in the African descent group (P < 0.05). Maximum principal strain in the peripapillary sclera was significantly higher than in the midperipheral sclera for both ethnic groups. CONCLUSIONS The sclera surrounding the ONH stiffens more rapidly with age in the African descent group compared to the European group. Stiffening of the peripapillary sclera with age may be related to the higher prevalence of glaucoma in the elderly and persons of African descent.

The paper shows how, in speckle interferometry, the phase information can be retrieved from a single intensity pattern provided that the speckle field captured from the object at the reference conditions is fully resolved in its components of mean intensity, modulation and phase. The “one-step” approach proposed can be applied to the study of transient phenomena if a phase stepping technique can be used to resolve the speckle pattern at the reference conditions. The performance of the procedure has been evaluated and compared with that of the conventional four-step procedure by numerically simulating the diffraction process which occurs in a generic speckle interferometer. Experimental results are reported for a shearing interferometer.

We proposed and validated a compensation method that accounts for the optical distortion inherent in measuring displacements on specimens immersed in aqueous solution. A spherically-shaped rubber specimen was mounted and pressurized on a custom apparatus, with the resulting surface displacements recorded using electronic speckle pattern interferometry (ESPI). Point-to-point light direction computation is achieved by a ray-tracing strategy coupled with customized B-spline-based analytical representation of the specimen shape. The compensation method reduced the mean magnitude of the displacement error induced by the optical distortion from 35% to 3%, and ESPI displacement measurement repeatability showed a mean variance of 16 nm at the 95% confidence level for immersed specimens. The ESPI interferometer and numerical data analysis procedure presented herein provide reliable, accurate, and repeatable measurement of sub-micrometer deformations obtained from pressurization tests of spherically-shaped specimens immersed in aqueous salt solution. This method can be used to quantify small deformations in biological tissue samples under load, while maintaining the hydration necessary to ensure accurate material property assessment.

Temporal phase shifting in automatic interferogram analysis offers very high accuracy of phase retrieval providing that several experimental conditions are met. The paper is focused on the calibration error of unequal phase changes across the interferogram field, i.e., tilt-shift error. For its detection the lattice-site representation of phase shift angles is proposed. The error can be readily discerned using (N+1) algorithms with the last frame overlapping the first one. Four and five frame algorithms are considered. The influence of experimental parameters on the error detection sensitivity is discussed. Numerical studies are complemented by experimental results.

The behavior and analysis of bolted flange plate connections in rectangular hollow section tension members is considered, with the bolts along only two opposite sides of the rectangular hollow section. Sixteen tension tests on such connections are described, and it is shown that one can, by selecting specific connection parameters, fully develop the tensile resistance of the member by bolting along only two sides of the tube. The application of traditional prying models developed for T-stubs is found to not correlate well with the test results, so analytical models based on plastic theory are consequently proposed, and these are found to predict the failure mode and the joint ultimate strength to within 6%.

In the paper a procedure is described whereby the characterization of isotropic and anisotropic laminae is carried out by full-field measurement of the surface rotations under proper flexural loads. The analytic formulation does not necessarily imply a numerical calibration and the elastic constants are determined by integrating the whole experimental data on the surface of the specimen. Measurements were carried out by phase-stepped speckle interferometry using a shearometer based on Michelson design. The experimental instrumentation, including the loading device, and the procedures for the manipulation of experimental data are detailedly described; experimental results obtained on a steel specimen and a composite laminate are also reported.

This paper describes the application of active pulsed Thermography (PT) as a Non-Destructive Test (NDT) method for the investigation of CFRP aeronautical components. The analyzed specimens include T-shaped stringers, previously monitored by ultrasonic analysis, and laminated flat plates with internal production defects. Several set-up tests allowed to identify optimal configurations for the defect detection, according to specimen geometry and defect location. A custom post-processing algorithm has been developed to improve thermographic data for more precise defect characterization, whilst a successive full-field contrast mapping allows to achieve a reliable defect distribution map and a better definition on larger areas. Detection of defects was studied with a specific thermal contrast evaluation, with a suitable choice of undamaged reference area during the transient cooling phase. The influence of heating time and experimental set-up on the thermal contrast results has also been studied; moreover, the ability of thermographic technique to detect real small production defects with accuracy and reliability is verified for CFRP aeronautical components.