Cutting force model of orbital single-point micromachining tool

This paper presents an analytical, ductile cutting force model of a novel micromachining tool that is based on micro-orbital motion of a single-point tool tip. The single-point tool tip used in this study is a single crystal diamond stylus that consists of a cone section of 50° and a spherical tip with radius less than 1 μm. The tool is actuated by a piezo tube that generates a high frequency micro-orbital motion of a single-point tool tip in a circular trajectory. Unlike conventional micromilling, where the cutting occurs at the edges of the tool flutes, a single-point tool may utilize any point on the circumference surface of the tool tip. Also, due to its extreme negative rake angle at small depths of cut, the technique can machine brittle materials such as silicon in the ductile regime. Experiments were performed on an aluminum alloy (AL2024) to obtain the specific cutting force and the coefficient of friction in order to calculate the cutting forces in all 3 axes and to verify the model.     

Intermittent Switching Between Potential Flow and Turbulence in Superfluid Helium at mK Temperatures

Superfluid flow around an oscillating microsphere is investigated at temperatures down to 25 mK. Stable laminar flow below a critical velocity and turbulence at large drives are found to be separated below 0.5 K by an intermediate range of driving forces where the flow is unstable, intermittently switching between laminar and turbulent phases. We have recorded time series of this switching phenomenon and have made a statistical analysis of the switching probability. The mean lifetime of the turbulent phases grows with increasing drive and becomes infinite at a critical value. Stability of the laminar phases above the critical velocity is limited by natural background radioactivity or cosmic rays.     

Monte Carlo calculation of the small sample reactivity effect

A monte Carlo method for the calculation of the reactivity effect of a small sample in a nuclear reactor is described. Particle histories are started within the sample. Therefore, it is not necessary to enter the sample from outside with a small probability. After leaving the sample, the histories are terminated at some distance from the sample site using pre-calculated results of the unperturbed reference system. The influence of some approximations is diminished because these pre-calculated results are used only far away from the region of interest. Some numerical results show the efficiency of the method. The method is fast and can also be used at rather small and slow computers.     

How tree shrews (Tupaia belangeri) perform in a searching task: Evidence for strategy use.

This study investigated how male tree shrews (Tupaia balngeri) performed in a searching task while in their home cages and assessed whether different food distributions affected their performance. The animals were faced with a holeboard containing 9 food sources arranged in a 3 X 3 matrix or in 3 clusters, each containing 3 sources. Animals tended to start and end the trials from preferred locations, thereafter solving the task by strategically organizing the reward collection according to a minimum-distance principle. In the cluster configuration, they visited the sources hierarchically. Food distribution did not affect the performance. Comparison with data from mice and capuchin monkeys revealed that tree shrews and capuchins solved the task in a similar strategic way, whereas mice did not. These findings attract particular attention because of the phylogenetic position of tree shrews, which are regarded as closely related to primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rheological,microstructural and sensory characterization of low-fat and whole milk set yoghurt as influenced by inulin addition

The effect of inulin addition (0–4%) upon texture and microstructure of set yoghurt with different levels of fat (0.2%–3.5%) was investigated. A two-factor experimental design with four treatments was used for data analysis. Skimmed milk with various inulin and cream concentrations was standardized to 4% protein content, homogenized, heated to 92 °C and fermented at 42 °C until a pH of 4.6 was reached. The chemical composition, pH, consistency and microstructure properties of the yoghurts were analysed after 6 days of storage at 5 °C. The statistical analysis showed that inulin and fat significantly affected the rheological and sensory results. Higher yield stress, “firmness” and “creaminess” values were observed in yoghurt produced with higher inulin additions, whereas the pH value was not affected. A significant correlation was found between yield stress and sensory determined firmness (r = 0.91). The microstructure examined by confocal laser scanning microscopy (CLSM) was only slightly affected by the concentrations of inulin in the range studied, possibly due to weak protein interactions between the inulin and the milk protein network.     

Auflösungsverhalten von Dolomit in Stahlwerksschlacken sowie Grenzen der Löslichkeit und Folgen für den Feuerfestverschleiß

Das Auflösungsverhalten von gebranntem Dolomit wurde durch Schmelzversuche ermittelt, bei denen stahlwerksähnliche Schlakken mit einem Dolomittiegel reagierten. Die Auflösung des Tiegelmaterials in der Schlacke wurde dabei sowohl unter dem Aspekt des Schlackenbildners Dolomit als auch aus der Sicht MgO-haltigen Feuerfestmaterials ausgewertet. Es konnte verfolgt werden, wie die beiden unverbunden nebeneinander vorliegenden Hauptkomponenten des Dolomitkalks, CaO und MgO, entsprechend ihren jeweils treibenden Kräften, den Abständen zur Sättigung, unterschiedlich schnell in Lösung gehen. Trotz bevorzugter Auflösung des CaO erreicht das MgO wegen eines geringeren Abstandes zur Sättigung eher die Löslichkeitsgrenze, unterstützt durch den Effekt, daß bereits gelöstes CaO die MgO-Sättigungsgehalte erniedrigt, während umgekehrt MgO die CaO-Löslichkeit zunächst durch Zurückdrängen der Dicalciumsilikat-Ausscheidung (?C₂S-Nase”) deutlich, dann an der eigentlichen Kalksättigung noch leicht erhöht. Die Auflösung kommt durch eine rasche Sättigung an MgO zwar nicht völlig zum Stillstand, wird aber stark verlangsamt, so daß die metallurgisch wichtige Kalksättigung bei alleinigem Einsatz von Dolomitkalk als Schlackenbildner nicht erreicht werden kann. Darüberhinaus wird die Schlacke infolge der Übersättigung an MgO heterogen und viskos. Die Auflösung von magnesitischem Feuerfestmaterial konnte simuliert werden, indem nur das Verhalten der MgO-Komponente des Dolomits zu Beginn des Versuchs betrachtet wurde. Die verschleißmindernde Wirkung von MgO-Vorgaben zur angreifenden Schlacke wurde nachgewiesen. Ferner konnten durch Annahme einer diffusionsgesteuerten Auflösung in der ersten Phase des Versuchs Stoffübergangskoeffizienten des CaO und des MgO gewonnen werden.     

Microbial Abundance in the Schwertmannite Formed in a Mine Water Treatment Plant

Treatment of acidic iron- and sulfate-rich mine waters in a pilot plant at the opencast lignite mining pit Nochten (Lusatia, Germany) involves microbial iron oxidation and subsequent precipitation of the iron-oxyhydroxysulfate schwertmannite. To determine if recirculation of schwertmannite can stabilize and optimize the oxidation process, cell number, viability, and diversity of the bacterial community in schwertmannite precipitated on carrier material and stored schwertmannite were analyzed. In schwertmannite on carrier material, the total cell number decreased slightly with increasing mineral depth, whereas the percentage of viable cells decreased significantly. The microbial community, investigated by fluorescence-in-situ-hybridization (FISH) and terminal restriction fragment length polymorphism (T-RFLP), revealed the presence of the iron-oxidizing bacterium “Ferrovum” sp. and relatives of Gallionella, independent of mineral depth. Analysis of the viability of microorganism in stored schwertmannite indicated an almost constant percentage of viable cells over 42 days.     

Etching of Laminates with Hydrogen Peroxide in Sulphuric Acid Solution

Three types of nuclear reaction have been applied to study chromium conversion coatings on zinc electroplate. The 1005keV resonance in the ⁵²Crlp, Y)⁵³Mn reaction has been used to determine the depth versus concentration profile of chromium in the coatings, while the ¹⁵O(d,α) ¹⁴N reaction has been used to profile oxygen content, or particle induced elastic forward scattering of protons (proton recoil) was used to determine the hydrogen profile in the samples. The results suggest that the newly introduced trivalent type treatments produce coatings containing comparable water/hydroxide contents to the establishedhexavalent type treatments.     

New statistical method for detection and quantification ofrespiratory sinus arrhythmia

A statistical method with the advantages of 1) enabling graphical representation of within-respiratory cycle heart rate variations, 2) detecting the presence of respiratory sinus arrhythmia (RSA) in a moving window, and 3) providing breath-by-breath RSA amplitude and phase obtained from the fitting of a sinusoid to the instantaneous relative heart rate is presented.