Utilisation of time-variant influence functions in the computer controlled polishing

In the computer controlled polishing, a polishing tool moves in a well-defined manner across the workpiece surface in order to individually remove the surface error-profile. The commonly used technique to calculate the moving of the polishing tool is the dwell time method. Based on a constant (time-invariant) removal characteristic of the polishing tool (influence function) the amount of material to be removed is controlled via the dwell time. The longer the polishing tool is in contact with a particular area of the workpiece, the more material is removed at this position.Mathematical basics to calculate dwell time-profiles are shown, and a new approach considering time-variant influence functions for the computer controlled polishing is introduced. The results point out that time-variant influence functions may contribute to further decrease the process time, and thus to make a computer controlled polishing process more efficient. The reduction of the process time was observed to approximately 35% using a combination of the dwell time method with time-variant influence functions.     

Size dependent interactions of nanoparticles with lung surfactant model systems and the significant impact on surface potential

The relationship between a model pulmonary surfactant system and various sized nanoparticles was investigated in this study. Diplamitoylphosphatidylcholine (DPPC) is the main lipid constituent of lung surfactant and has the ability to reach very high surface pressures (around 70 mN/m) upon compression. Due to these properties it was used as a model to simulate the lung surfactant film in vitro. The first objective of this study was to investigate the relationship between DPPC and various sized nanoparticles within the subphase through surface pressure-area isotherms. The second objective was to measure the surface potential of the different preparations (conducted on a mini-Langmuir trough) and to determine if an optimal nanoparticle size exists possessing a greater affinity for the DPPC film compared to other sizes. The results from the pressure area isotherms indicate that the interaction between DPPC and the nanoparticles is stable and that the 235 nm particles may represent an optimal size. Furthermore, the results from the surface potential experiments confirm that an interaction of the nanoparticles with the monolayer exists as indicated by surface-pressure area isotherms. Any even moderate interaction between nanoparticles and lung surfactant film might reduce or increase the surface potential of the surfactant film, and this might impact the deposition of the nanoparticles or other ligands which may be positively or negatively charged drugs within the surfactant film. Thus changes in surface potential due to nanoparticle interactions have to be taken into account for future drug targeting studies using nano-sized drug carriers.     

Thioether–Polyglycidol as Multivalent and Multifunctional Coating System for Gold Nanoparticles

Thiofunctional polymers are the established standard for the coating and biofunctionalization of gold nanoparticles (AuNPs). However, the nucleophilic and oxidative character of thiols provokes polymeric crosslinking and significantly limits the chemical possibilities to introduce biological functions. Thioethers represent a chemically more stable potential alternative to thiols that would offer easier functionalization, yet a few studies in the literature report inconclusive data regarding the efficacy of thioethers to stabilize AuNPs in comparison to thiols. A systematic comparison is presented of mono‐ versus multivalent thiol‐ and thioether‐functional polymers, poly(ethylene glycol) versus side chain functional poly(glycidol) (PG) and it is shown that coating of AuNPs with multivalent thioether‐functional PG leads to superior colloidal stability, even under physiological conditions and after freeze‐drying and resuspension, as compared to thiol analogs at comparable polymer surface coverages. In addition, it is shown that a wide range of functional groups can be introduced in these polymers. Using diazirine functionalization as example, it is demonstrated that proteins can be covalently immobilized, and that conjugation of antibodies via this strategy enables efficient targeting and laser‐irradiation induced killing of cells.     

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.