Efficient Ray Tracing Through Aspheric Lenses and Imperfect Bokeh Synthesis

We present an efficient ray‐tracing technique to render bokeh effects produced by parametric aspheric lenses. Contrary to conventional spherical lenses, aspheric lenses do generally not permit a simple closed‐form solution of ray‐surface intersections. We propose a numerical root‐finding approach, which uses tight proxy surfaces to ensure a good initialization and convergence behavior. Additionally, we simulate mechanical imperfections resulting from the lens fabrication via a texture‐based approach. Fractional Fourier transform and spectral dispersion add additional realism to the synthesized bokeh effect. Our approach is well‐suited for execution on graphics processing units (GPUs) and we demonstrate complex defocus‐blur and lens‐flare effects.     

Tool Support for Continuous Quality Control

Over time, software systems suffer gradual quality decay and therefore costs can rise if organizations fail to take proactive countermeasures. Quality control is the first step to avoiding this cost trap. Continuous quality assessments help users identify quality problems early, when their removal is still inexpensive; they also aid decision making by providing an integrated view of a software system's current status. As a side effect, continuous and timely feedback helps developers and maintenance personnel improve their skills and thereby decreases the likelihood of future quality defects. To make regular quality control feasible, it must be highly automated, and assessment results must be presented in an aggregated manner to avoid overwhelming users with data. This article offers an overview of tools that aim to address these issues. The authors also discuss their own flexible, open-source toolkit, which supports the creation of dashboards for quality control.     

Simulation of a complex optical polishing process using a neural network

 Most modern manufacturing processes change their set of parameters during machining in order to work at the optimum state. But in some cases, like computer-controlled polishing, it is not possible to change these parameters during the machining. Then usually a standard set of parameters is chosen which is not adjusted to the specific conditions. To gather the optimum set of parameters anyway simulation of the process prior to manufacturing is a possibility. This research illustrates the successful implementation of a neural network to accomplish such a simulation. The characteristic of this neural network is described along with the decision of the used inputs and outputs. Results are shown and the further usage of the neural network within an automation framework is discussed. The ability to simulate these advanced manufacturing processes is an important contribution to extend automation further and thus increase cost effectiveness.     

Filter algorithm for influence functions in the computer controlled polishing of high-quality optical lenses

Computer controlled polishing (CCP) is widely used in the production of high-quality optical lenses. CCP enables surface error-profile-dependent calculation of polishing sequences prior to processing, and facilitates the cost-effective manufacture of high-quality optical surfaces. Calculation of an individual polishing sequence requires knowledge of the surface error-profile in addition to knowledge of the material removal characteristic (influence function) of the polishing tool. Measurement errors during both determination of the surface error-profile, and the influence function, may lead to an incorrect polishing sequence calculation, which in turn may result in an inadequate product quality. A new method has been developed which minimises the effects of measurement errors on the influence function. The resulting algorithm renders an influence function symmetrical and filters noisy data. Practical polishing tests with magnetorheological finishing have been performed to verify this new technique. The improvement of the peak-valley (PV) value of the surfaces polished with the symmetrical rendered influence function was observed to average 14% greater than that which related to the PV value improvement of those surfaces which were polished with the unmodified influence function. The algorithm developed is based on software and is easily implemented. Thus, artificial enhancement of an influence function is a straightforward technique to improve the result of the polishing process.     

Engineering the Mechanics of Heterogeneous Soft Crystals

This work demonstrates how the geometric and topological characteristics of substructures within heterogeneous materials can be employed to tailor the mechanical responses of soft crystals under large strains. The large deformation mechanical behaviors of elastomeric composites possessing long‐range crystalline order are examined using both experiments on 3D‐printed prototype materials and precisely matched numerical simulations. The deformation mechanisms at small and large strains are elucidated for six sets of morphologies: dispersed particles on each of the simple cubic, body‐centered cubic or face‐centered cubic lattices, and their bi‐continuous counterparts. Comparison of results for the six types of morphologies reveals that the topological connectivity of dissimilar domains is of critical importance for tailoring the macroscopic mechanical properties and the mechanical anisotropy.     

Cultural Entrepreneurship: The Impact of Social Networking on Success

Because of the complex structures characteristic of the arts sector and creative industries, it is often thought that external network ties of leading managers are critical to the success of their cultural enterprises. Based on research into entrepreneurship and promoters' activity, this study examines the influence of social network relationships on the success of cultural establishments in Germany. The regression analysis of data from 121 private arts and culture ventures presented here clearly shows that founders as well as managers can overcome numerous barriers through their engagement and activity in social networks, and thereby exercise to a significant degree a positive influence on establishing their enterprise. As expected, this effect is even stronger in cases of low sponsorship of cultural activities on the part of cities and communities. Contrary to expectations, the positive effect of intensive networking activities is not increased by a high intensity of competition; it is worth noting that the effect is strongest in situations of low competitive pressure. The results of this study demonstrate that successful networking expertise, as postulated by research into promoters' activity, is of great importance for overcoming significant barriers in the cultural sector, but that its effectiveness also has limits.     

Resistance variation in donor-doped PZT stacks with Cu inner electrodes under high field stress

Changes of the resistance of donor-doped lead zirconate titanate (PZT) under high voltages were investigated at temperatures from 350 to 500°C in different gas atmospheres. Measurements on individual ceramic layers (about 75 μm thickness) of PZT multilayer stacks with Cu inner electrodes allowed numerous experiments on nominally identical PZT material. Under high fields, the conductivity decreased significantly on time scales much longer than needed for capacitor charging. At 350°C, for example, decay times of several 1000 s were found. The time constant of this conductivity decay depends exponentially on temperature with activation energies of about 1.3 eV in air. After interrupting the field stress, thermally activated (ca. 1.1 eV) relaxation of the conductivity was found on an even longer time scale. The results are interpreted in terms of oxygen vacancy motion under high fields (stoichiometry polarization) and diffusive relaxation. The importance of oxygen migration despite donor doping is attributed to the high PbO volatility of PZT which readily leads to significant oxygen deficiency. Oxygen diffusion coefficients are estimated.     

Piezoelectric properties and conductivity of Pb(Zr,Ti)O<Subscript>3</Subscript> with SrO–WO<Subscript>3</Subscript> additive

The influence of SrO–WO₃ additive on the piezoelectric properties and electric conductivity of lead zirconate–titanate (PZT) near the morphotropic phase boundary was investigated. Starting from the composition 0.995 Pb(Zr_0.525Ti_0.475)O₃ + 0.015 SrO + 0.005 WO₃ (corresponding to 0.5 mol% of Sr₃WO₆) the fraction of WO₃ was increased until Sr:W = 1:1. These samples were compared to a set of samples of PZT with WO₃ addition but without SrO. Sr₃WO₆ has pseudocubic K₂NaAlF₆ structure with part of the strontium being octahedrally coordinated. In a solid solution with PZT this opens the possibility of realizing Sr on a B-site adjacent to a B-site occupied by W. Piezoelectric properties were measured on sintered disc samples under high field conditions. Impedance spectroscopy was used to investigate the conductivity and dielectric properties of the ceramics at various temperatures. The combined addition of SrO and WO₃ increases the piezoelectric strain compared to samples of PZT with WO₃ addition only. The results in polarization and conductivity indicate that the donor effect of WO₃ is counteracted by the addition of SrO.