Copyright Protection of 3D Digitized Artistic Sculptures by Adding Unique Local Inconspicuous Errors by Sculptors

In recent years, digitization of cultural heritage objects, for the purpose of creating virtual museums, is becoming increasingly popular. Moreover, cultural institutions use modern digitization methods to create three-dimensional (3D) models of objects of historical significance to form digital libraries and archives. This research aims to suggest a method for protecting these 3D models from abuse while making them available on the Internet. The proposed method was applied to a sculpture, an object of cultural heritage. It is based on the digitization of the sculpture altered by adding local clay details proposed by the sculptor and on sharing on the Internet a 3D model obtained by digitizing the sculpture with a built-in error. The clay details embedded in the sculpture are asymmetrical and discreet to be unnoticeable to an average observer. The original sculpture was also digitized and its 3D model created. The obtained 3D models were compared and the geometry deviation was measured to determine that the embedded error was invisible to an average observer and that the watermark can be extracted. The proposed method simultaneously protects the digitized image of the artwork while preserving its visual experience. Other methods cannot guarantee this.

Geometry deviation effects of railway catenaries on pantograph–catenary interaction: a case study in Norwegian Railway System

This paper presents a non-contact measurement of the realistic catenary geometry deviation in the Norwegian railway network through a laser rangefinder. The random geometry deviation is included in the catenary model to investigate its effect on the pantograph–catenary interaction. The dispersion of the longitudinal deviation is assumed to follow a Gaussian distribution. A power spectrum density represents the vertical deviation in the contact wire. Based on the Monte Carlo method, several geometry deviation samples are generated and included in the catenary model. A lumped mass pantograph with flexible collectors is employed to reproduce the high-frequency behaviours. The stochastic analysis results indicate that the catenary geometry deviation causes a significant dispersion of the pantograph–catenary interaction response. The contact force standard deviations measured by the inspection vehicle are within the scope of the simulation results. A critical cut-off frequency that covers 1/16 of the dropper interval is suggested to fully describe the effect of the catenary geometry deviation on the contact force. The statistical minimum contact force is recommended to be modified according to the tolerant contact loss rate at high frequency. An unpleasant interaction performance of the pantograph–catenary can be expected at the catenary top speed when the random catenary geometry deviation is included.

Prefabricated Concrete Component Geometry Deviation Statistical Analysis

The research objects of this paper were the prefabricated concrete components produced by four enterprises in China, and the dimension deviation data of more than 1400 prefabricated concrete components are measured with high-precision 3D photogrammetry technology. The nonparametric Kruskal–Wallis test was carried out for the size deviation of the same type of components produced by different enterprises. The distribution characteristics of geometric parameters of typical components of prefabricated structures in China, such as beams, columns, wall boards, and composite slabs, were analyzed by using the probability statistical method. The Kolmogorov–Smirnov goodness-of-fit method was used to test the cumulative distribution function of dimension deviation, and the size distribution of fabricated components was studied. The results showed that there was no significant difference in the size deviation of the same-type component produced by different enterprises, and the range of geometric parameter uncertainty random variables was small, which was between 0.99 and 1.02. Also, the fluctuation was small, the coefficient of variation was below 0.0093, and the variability of component size deviation was small. The transverse dimension of the component shows a positive deviation, the vertical dimension of component shows a negative deviation, and the dimension deviation of prefabricated concrete components follows the normal distribution.

Position, momentum, and wave spreading in curved space

The effect of the geometry (deviation from the flat space) on the quantum evolution of the momentum and position of a free particle is discussed. It is shown that beginning with a wave-packet of minimum uncertainty (a Gaussian wave), there is a usual increase in the product of the volume uncertainties in the momentum and position space, as seen in the quantum mechanics on a flat spaces. But there is also a contribution from geometry. The leading order of this contribution is calculated.

Rückführung von Messergebnissen in den Konstruktionsprozess/Partially automated mould correction for plastic injection moulding – Feedback of measurement results into the design process

Die Geometrie von Kunststoffspritzgußwerkstücken wird durch Abkühlung der Schmelze bei der Fertigung beeinflusst. Die hieraus resultierende Geometrieabweichung wird mittels Simulation abgeschätzt und bei der Konstruktion berücksichtigt. Trotz der eingesetzten Verfahren sind Abweichungen zwischen Soll- und Ist-Geometrie häufig zu groß. Durch Rückführung von Messergebnissen in den Konstruktionsprozess werden systematische Abweichungen reduziert. Aufwendige manuelle Verfahren können so entfallen.   The geometry of plastic injection molded workpieces is influenced by cooling of the melt during production. The resulting geometry deviation is estimated by means of simulation and taken into account in the design. Despite the methods used, deviations between nominal and actual geometry are often too high. Systematic deviations are reduced by feeding measurement results back into the design process. Time-consuming manual procedures can thus be eliminated.

Section Based Profile Tolerance Assessment of 3D Scanned Compressor Airfoils

This paper presents two turbomachinery-specific methods for profile tolerance assessment of compressor airfoils that process 3D scan data. This optical inspection technology digitizes the entire surface of the part into a triangulated mesh, which is aligned to nominal geometry and then processed to extract densely arranged profile sections. For the reverse engineering method, the profile sections are decomposed into thickness and camber distributions. These distributions and the camber line are used to identify the profile parameter vector of the reverse engineering model. The deviation of the actual geometry is obtained by subtracting its parameters from those of the nominal geometry. Parameter-span graphs reveal airfoil shape deviation and allow for quantification of blisk scatter. The design-like parameters are meaningful and enable an intuitive engineering judgement of the actual geometry deviation. The profile tolerance assessment method utilizes the camber line from the reverse engineering method to elegantly check against variable profile tolerance limits. The actual section is best-fitted to its nominal counterpart and assessed regarding its deviation relative to the allowed local tolerance. This ratio is plotted in a developed view summarizing the result of the profile tolerance assessment for the whole airfoil in a single graph. Thus, the condensed results allow for effective utilization of the high-resolution in airfoil sections. Ultimately, the paper widens the view from one airfoil towards the assessment of the entire blisk. The blisk data is presented by statistical processing of deviation fields of all airfoils, in terms of mean and standard deviation. These statistical quantities are plotted onto the airfoil contour to e.g. represent the average airfoil thickness of the blisk. The standard deviation plot points to airfoil sections of larger geometric scatter and reveals areas of a non-robust manufacturing process.

Uncertainty quantification of the effects of squealer tip geometry deviation on aerothermal performance

The first-stage rotor squealer tip is a key area in gas turbine for both aerodynamic performance and blade cooling tasks, which should be carefully designed. However, harsh operating conditions near the rotor squealer tip can cause the geometry of the squealer tip to degrade, and manufacturing inaccuracies can also cause the squealer tip geometry to deviate from the ideal design. These geometry deviations would change the flow field near the blade tip, which will influence the thermal and aerodynamic performance. Thus, it is important to quantitatively investigate the effects of squealer tip geometry deviation on the aerothermal performance. In this paper, a typical transonic first-stage turbine is employed, and three important geometric features of squealer tip, the tip clearance height (H), the squealer depth (D), and the squealer edge chamfer (R), are selected. An uncertainty quantification process is performed to study the effect of deviation of H, D, and R on the aerothermal performance. Many cases with different geometry features are checked in the current study using 3D Reynolds-averaged Navier–Stokes simulations. A parameter sensitivity analysis using Sobol Indice method is carried out to identify the key parameters to aerothermal performance of the squealer tip. The uncertainty quantification results show that the existence of the tip chamfer reduces the size of separation bubble and the dwelling range of the scraping vortex, thus, the blockage effect of the leakage flow is weakened, which results in larger amount of leakage flow and more mixing loss of squealer tips with edge chamfer than those without edge chamfer. The results of the parameter sensitivity analysis show that the height of tip clearance is the main factor that affects the aerodynamic performance of the squealer tip. This work provides a certain guiding direction for the optimization design of the turbine groove tip.