A non-invasive form finding method with application to metal forming

Inverse form finding aims in determining the optimal material configuration of a workpiece for a specific forming process. A gradient- and parameter-free (nodal-based) form finding approach has recently been developed, which can be coupled non-invasively as a black box to arbitrary finite element software. Additionally the algorithm is independent from the constitutive behavior. Consequently, the user has not to struggle with the underlying optimization theory behind. Benchmark tests showed already that the approach works robustly and efficiently. This contribution demonstrates that the optimization algorithm is also applicable to more sophisticated forming processes including orthotropic large strain plasticity, combined hardening and frictional contact. A cup deep drawing process with solid-shell elements and a combined deep drawing and upsetting process to form a functional component with external teeth are investigated.     

Metamer density estimated color correction

Color correction is the transformation of response values of scanners or digital cameras into a device- independent color space. In general, the transformation is not unique due to different acquisition and viewing illuminants and non-satisfaction of the Luther–Ives condition by a majority of devices. In this paper we propose a method that approximates the optimal color correction in the sense of a minimal mean error. The method is based on a representative set of reflectance spectra that is used to calculate a special basic collection of device metameric blacks and an appropriate fundamental metamer for each sensor response. Combining the fundamental metamer and the basic collection results in a set of reflectances that follows the density distribution of metameric reflectances if calculated by Bayesian inference. Transforming only positive and bounded spectra of the set into an observer’s perceptually uniform color space results in a point cloud that follows the density distribution of device metamers within the metamer mismatch space of acqcuisition system and human observer. The mean value of this set is selected for color correction, since this is the point with a minimal mean color distance to all other points in the cloud. We present the results of various simulation experiments considering different acquisition and viewing illuminants, sensor types, noise levels, and existing methods for comparison.     

Quantification of polycyclic aromatic hydrocarbons in the NIST standard reference material (SRM1649A) urban dust using thermal desorption GC/MS

A thermal desorption GC/MS technique has been developed for the quantification of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter using the NIST Standard Reference Material (SRM1649a) Urban Dust. The technique was developed using standard linearity tests in order to establish optimum sample weights and optimum desorption and chromatographic parameters. This direct analysis technique eliminates the use of solvents in the sample preparation (reducing volatile component losses) and also significantly reduces the sample preparation time (no extraction procedure). The technique has been shown to give linearity in terms of the overall TIC response as well as for a prominent series of n-alkanes (C20-C33) and 10 NIST priority PAHs, 8 of which have been quantified. The technique is reported to be uniquely sensitive (PAH concentrations 2-6 mg kg(-1)) and reproducible (MW = 178-228 SD < or =0.228 mg kg(-1), < or =7%; MW = 252 SD < or =0.922 mg kg(-1), < or =33%) over the range of sample weights (1-5 mg). Such sample weights illustrate that the technique can be equally applied to the analysis of airborne particulate samples collected over short time periods (24-48 h) using only commonly used low-volume collection devices.     

Power spectral density analysis of optical substrates for gravitational-wave interferometry

The power spectral density of surface-relief variations on polished optical surfaces across microscopic through to macroscopic spatial scales is calculated from measurements on substrates that are being produced for the Laser Interferometer Gravitational-Wave Observatory (LIGO). These spectra give a guide to the scattering properties of the surface, which in turn critically influence the performance of LIGO. Measurements obtained by use of a full-aperture interferometer and an interference microscope with two different objectives are combined to produce one-dimensional power spectral density representations of the surfaces across spatial frequencies ranging from 0.1 to 8000 cm(-1). These measurements from different instruments are in good agreement with an analytic power spectrum that varies as nu(-1.5), where nu is the spatial frequency. Some anomalies in the power spectral density spectra can be related to aspects of the polishing process.     

Potential mycotoxin problems in mould-fermented sausage

Summary A considerable proportion of the sausage consumed in many European countries is produced by a mould-fermentation process that does not involve pure culture technics.422Penicillium cultures isolated from mould-ripened sausages produced in II European countries were analyzed for their ability to produce the following nine mycotoxins: aflatoxin B₁ and G₁ ochratoxin A, penicillic acid, patulin, citrinin, tremortin A, zearalenone, rubratoxin B; 88 isolates were found capable of toxin synthesis (20.9%). 44 of these cultures produced penicillic acid, 17 ochratoxin A, 11 tremortin A, 10 citrinin, and 6 patulin. 3 cultures produced both patulin and citrinin.Sausages were ripened with 6 moulds producing penicillic acid, 17 producing ochratoxin, 5 producing citrinin and 3 each producing patulin or tremortin. No mycotoxins were detected up to 70 days of ripening.Direct addition of penicillic acid to raw sausage resulted in disappearance of the mycotoxin. Amino acids normally occuring in meat were found capable of rapidly reacting with penicillic acid to produce adducts that were nontoxic to laboratory animals.Although our data indicate that consumption of mould ripened sausage is not a health hazard with respect to the 9 mycotoxins analyzed for, it is recommended that manufacturers of these products adopt pure culture technics using moulds known to be toxicologically safe.

---

Zusammenfassung In zahlreichen Ländern Europas werden seit altersher mit Schimmelpilzen gereifte Rohwürste hergestellt. Es handelt sich hierbei um traditionelle Produktionsverfahren, bei denen jedoch keine Schimmelpilz-Reinkulturen verwendet werden.Wir untersuchten das Toxinbildungsvermögen von 422Penicillium-Stämmen, die von schimmelpilzgereiften Rohwürsten isoliert worden waren, die aus II verschiedenen Ländern stammten. Insbesondere interessierten uns die Mykotoxine Aflatoxin B₁ und G₁, Ochratoxin A, Penicillinsäure, Patulin, Citrinin, Tremortin A, Zearalenon und Rubratoxin B. Bei 88 Stämmen (20,9%) war eine Toxinbildung nachweisbar. 44 dieser Kulturen bildeten Penicillinsäure, 17 Ochratoxin A, 11 Tremortin A, 10 Citrinin und 6 Patulin. Von drei Stämmen wurde sowohl Patulin als auch Citrinin gebildet.Wurden frisch hergestellte Rohwürste mit Schimmelpilzen, die die genannten Toxine bilden, beimpft, so konnten während der 70 Tage dauernden Reifung keine Mykotoxine in der Wurst nachgewiesen werden.Den Rohwürsten direkt zugesetzte Penicillinsäure wurde inaktiviert, da dieses Mykotoxin sehr rasch mit Aminosäuren reagiert, die im Fleisch vorhanden sind.Obwohldiese Untersuchungen darauf hinweisen, daß sehimmelpilzgereifte Rohwürste, zumindest bezüglich der 9 genannten Mykotoxine, keine potentielle Gefahr für den Verbraucher darstellen, sollte man dennoch dazu übergehen als Starterkultur nur technologisch und toxikologisch geprüfte Schimmelpilz-Stämme in Reinkultur einzusetzen.

     

A Rank Encoder: Adaptive Analog to Digital Conversion Exploiting Time Domain Spike Signal Processing

An electronic circuit is presented that encodes an array of analog input signals into a digital number. The digital output is a rank order code that reflects the relative strength of the inputs, but is independent of the absolute input intensities. In that sense, the circuit performs an adaptive analog to digital conversion, adapting to the average intensity of the inputs (i.e. effectively normalizing) and adapting the quantization levels to the spread of the inputs. Thus, it can convey essential information with a minimal amount of output bits over a huge range of input signals.As a first processing step the analog inputs are projected into the time domain, i.e. into voltage spikes. The latency of those spikes encodes the strength of the input. This conversion enables the circuit to conduct further analog processing steps by asynchronous logic.     

Some observations of the effects of intertrial interval and delay on delayed matching to sample in pigeons.

Accuracy of delayed matching to sample was studied in 12 Silver King pigeons at different combinations of length of intertrial interval (ITI) and length of delay. When ITI and delay were varied between sessions in Exps I and II, accuracy increased monotonically with ITI and decreased monotonically with delay. Evidence was found for constancy of performance at equivalent ratios of ITI to delay, and percentage of correct choices was linearly related to the log of this ratio. In Exps III and IV, ITI was manipulated as a within-sessions variable. In contrast to the effect of this variable when manipulated between sessions, accuracy improved only from the shortest interval to the next shortest interval and remained constant at all longer intervals. In Exp IV, it was found that performance improved as a direct function of the mean ITI for sessions and that this relation was not affected by the degree of ITI variability within sessions. Findings resemble the effects of temporal variables on autoshaping, and the possibility that some common processes are involved in delayed matching and autoshaping is discussed. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Femtosecond broadband stimulated Raman: a new approach for high-performance vibrational spectroscopy

Femtosecond stimulated Raman spectroscopy (FSRS) is a new technique that produces high-quality vibrational spectra free from background fluorescence. FSRS combines a narrow-bandwidth picosecond Raman pump pulse with an approximately 80 fs continuum probe pulse to produce stimulated Raman spectra from the pump-induced gain in the probe spectrum. The high intensity of the Raman pump combined with the broad bandwidth of the probe produces high signal-to-noise vibrational spectra with very short data acquisition times. FSRS spectra of standard solutions and solvents such as aqueous Na2SO4, aqueous KNO3, methanol, isopropanol, and cyclohexane are collected in seconds. Furthermore, stimulated Raman spectra can be obtained using just a single pump-probe pulse pair that illuminates the sample for only approximately 1 ps. Fluorescence rejection is demonstrated by collecting FSRS spectra of dyes (rhodamine 6G, chlorophyll a, and DTTCI) with varying degrees of fluorescence background and resonance enhancement. The high signal-to-noise, short data acquisition time, fluorescence rejection, and high spectral and temporal resolution of femtosecond stimulated Raman spectroscopy make it a valuable new vibrational spectroscopic technique.