Contact force measurement using acoustic emission analysis and system identification methods

Acoustic emission (AE) signals were used to investigate the contact force occurring at the head/disk interface of a computer hard drive. The AE sensor was calibrated directly using the “ball drop method” and indirectly using system identification. For the indirect calibration, a high bandwidth laser Doppler vibrometer (LDV) was used. The transfer function was established from the harmonic response derived at different vibration modes and frequencies. A finite element method based transient response simulation of impact was used to estimate the velocity and stress response of the slider. In our experiments, contact forces were found to be in the range of 5–25 mN for nano sliders and 2–10 mN for pico sliders.     

Cavitation erosion of electroplated nickel composite coatings

The cavitational wear resistance of electroplated nickel composite layers was tested following ASTM G32. Particles of different hardness (titania and silicon carbide) and different sizes from micro-scale to nano-scale were incorporated up to 30 vol.% into a nickel matrix. Martens hardness is improved by grain refinement via particle incorporation. Compared to pure electroplated nickel films the composite layers strengthened by submicro-scale silicon carbide particles exhibit a decreased mass loss of one order of magnitude after 8 h testing time. Remarkably, layers with nano-scaled titania particles show a similar performance.

Apart from particle adherence failures, reduced mass loss of the composite layers correlate with improved hardness of the composite due to grain refinement of the matrix and dispersion hardening effects.     

Parkhaus “Am Gericht” in Frankfurt am Main – Eine Sanierung mit kathodischem Korrosionsschutz

Parking garage “Am Gericht” in Frankfurt am Main – a refurbishment with cathodic corrosion protection. After several decades in use a refurbishment is often necessary for the bearing structure of reinforced concrete parking garages due to chlorides, which have been brought into concrete by road salt, and the resulting corrosion of the reinforcement, which may lead to a serious decrease of the bearing capacity. With the system of the cathodic protection of the reinforcement exists a cost‐effective and reliable technique as an alternative to common solutions. An intensive investigation of the structure, the knowledge of the reasonable limits of the system, excellent design and execution of the construction work and the monitoring of the working system are nevertheless required, which is illustrated by the example of the parking garage “Am Gericht” in Frankfurt am Main.     

Surface potentials of magnetron sputtered transparent conducting oxides

Work functions, ionization potentials (electron affinities) and Fermi level positions measured in-situ by photoelectron spectroscopy at surfaces of transparent conducting oxides are presented. Thin films of ZnO, ZnO:Al, SnO₂, SnO₂:Sb, In₂O₃, In₂O₃:Sn, and In₂O₃:(Zn,Sn) are prepared by magnetron sputtering. The Fermi level position is strongly affected by the oxygen content in the sputter gas. The ionization potential and work function of ZnO are strongly affected by surface orientation. In contrast, SnO₂-based and In₂O₃-based materials show pronounced changes of ionization potential and work function induced by surface oxidation and reduction. Unlike SnO₂, the oxidation of the In₂O₃-based TCO surfaces does not occur during deposition but can be induced by post-deposition treatments.     

Characterization of the Melt Quality and Impurity Content of an Lm25 Alloy

The melt quality of an LM25 aluminum casting alloy has been examined using reduced pressure test (RPT) measurements, porous disc filtration analysis (PoDFA), and fatigue and tensile tests. The aim of this study was to determine the existing melt quality and thus to evaluate methods used with respect to monitoring and improving melt cleanliness. Special emphasis was given to the influence of oxides. It was found that the melt quality has varying degrees of effect on the tests used. The results indicate in particular that it was necessary to distinguish between “new” oxides (bifilms) and “hard” inclusions in the melt, as new oxides impact on porosity, whereas hard inclusions impact on ductility. Based on the results of this study, suggestions for the measurement of the melt quality have been proposed.     

Pareto analysis evolutionary and learning systems

This paper attempts to argue that most adaptive systems, such as evolutionary or learning systems, have inherently multiple objectives to deal with. Very often, there is no single solution that can optimize all the objectives. In this case, the concept of Pareto optimality is key to analyzing these systems. To support this argument, we first present an example that considers the robustness and evolvability trade-off in a redundant genetic representation for simulated evolution. It is well known that robustness is critical for biological evolution, since without a sufficient degree of mutational robustness, it is impossible for evolution to create new functionalities. On the other hand, the genetic representation should also provide the chance to find new phenotypes, i.e., the ability to innovate. This example shows quantitatively that a trade-off between robustness and innovation does exist in the studied redundant representation. Interesting results will also be given to show that new insights into learning problems can be gained when the concept of Pareto optimality is applied to machine learning. In the first example, a Pareto-based multi-objective approach is employed to alleviate catastrophic forgetting in neural network learning. We show that learning new information and memorizing learned knowledge are two conflicting objectives, and a major part of both information can be memorized when the multi-objective learning approach is adopted. In the second example, we demonstrate that a Pareto-based approach can address neural network regularizationmore elegantly. By analyzing the Pareto-optimal solutions, it is possible to identifying interesting solutions on the Pareto front.     

Recreational use of cocaine eliminates inhibition of return.

Chronic and recreational use of cocaine has been shown to impair inhibitory output control (response inhibition) but whether input control is also affected is an open question. For the first time, this study compared the ability to perform a cued target-discrimination task that measured inhibition of return (IOR), a reflexive inhibitory mechanism that delays attention from returning to a previously attended location, in adult recreational users and in a cocaine-free-matched sample controlled for age, race, gender distribution, and level of intelligence. Results show that the recreational use of cocaine eliminates IOR, suggesting that input control is strongly impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Glashäuser im Osten Deutschlands

Houses of glass in East Germany. Beginning with a short summary about important english trends on the field of glasshouses, the focus shifts to existing plant houses from the 19. and beginning 20. century in Berlin and Dresden. Afterwards the fast development in building of tranparent roofs, facades and halls with steel and glass are described on the basis of projects the from of East Germany.     

Visualization of active biomass distribution in a BGAC fluidized bed reactor using GFP tagged Pseudomonas putida F1

A favorable microenvironment for biofilm growth on GAC particles was shown using green fluorescent protein (GFP) as a marker for a phenol degrading bacterium, Pseudomonas putida F1. The dispersion of P. putida F1 in a biofilm covering granulated activated carbon (GAC) particles was monitored and compared to a biofilm on non-activated granular carbon particles. Laser scanning confocal microscopy (LSCM) micrographs of the biofilms taken from two fluidized bed reactors operating under identical conditions, showed higher fluorescent green areas in the GAC biofilm, especially close to the GAC surface. Quantitative analysis of the biofilm by COMSTAT, a three-dimensional biofilm structure analysis program, showed higher biomass concentration and higher viability in the GAC covered biofilm vs. the non-activated carbon biofilm. In addition, better effluent quality was measured for the BGAC reactor, which strongly suggests a significantly larger biofilm surface area available to the substrate, as opposed to that of the non-activated carbon carrier reactor.     

The fate of experimentally deposited nitrogen in mesocosms from two Canadian peatlands

In large regions of Europe and North America, peatlands have been exposed to elevated rates of atmospheric nitrogen (N) deposition. We investigated the fate of experimentally added N (NH(4)(15)NO3) at two different N loads (1.2 and 4.7 g N m(-2) yr(-1)) and water tables (1 and 32 cm) in intact cores from two peatlands, located in Central and Eastern Canada. The sites receive an estimated total N load of 0.6 g m(-2) a(-1) and 1.5 g m(-2) yr(-1), excluding nitrogen fixation. In all treatments, experimentally added nitrate (NO(3-)) was fully (96-99%) and ammonium (NH(4+)) mostly (81-97%) retained by the plant cover, mainly consisting of Sphagnum mosses, or in the unsaturated zone below. However, on average only 48% of the (15)N were recovered from the plant cover, and substantial amounts were found in depth layers of 2-6 cm (21-46%) and 8-12 cm (1.4-10.8%) below the moss surface. The amount of (15)N retained also significantly decreased with a lower water table from 56+/-9% to 40+/-10%. These findings document a substantial mobility of N, particularly during water table drawdown. Analysis of (15)N by a sequential diffusion procedure revealed a transfer of (15)N from NO(3-) into NH(4+) and dissolved organic N (DON), but the contents of (15)N in these pools accounted for less than 1% of the total N, natural background subtracted. The mass flux of dissolved (15)N into the peat was small compared to the total mass flux of (15)N. The accumulation of (15)N in the bulk peat must have been caused by a mechanism that was not investigated, possibly by transport of particulate organic N.