Experimental Investigation of the Hydrodynamic Stability of Flow in Rotating Pipes Using Thermistors

The hydrodynamic stability of flow in a rotating pipe Is investigated experimentally using thermistors. The experimental apparatus consists of a rotating pipe made of lucite, 3-1/4 inch inside diameter, six feet long, equipped with porous plugs at the ends to minimize recirculation. The working fluid is water and a range of axial and tangential Reynolds numbers up to 7,000 and 20,000, respectively, is covered. Thermistors were chosen for this study since their high electrical resistivity yields strong signals which permit the use of inexpensive and convenient electronics. They also have a high temperature coefficient of electrical resistance which minimizes the problem of noise due to brushes and slip rings. The intensity of the signal and the signal to noise ratio are better by an order of magnitude than those attainable with platinum film probes. The probes are rugged, inexpensive and are commercially available. The major problem encountered is their low frequency response. This, however, does not limit their usefulness in determining transition from laminar to turbulent flow regimes, as can be seen from the results of the present investigation, which were verified by visual diagnostic techniques utilizing dye streaks and hydrogen bubbles

Predicting organic acid concentration from UV/vis spectrometry measurements – A comparison of machine learning techniques

The concentration of organic acids in anaerobic digesters is one of the most critical parameters for monitoring and advanced control of anaerobic digestion processes. Thus, a reliable online-measurement system is absolutely necessary. A novel approach to obtaining these measurements indirectly and online using UV/vis spectroscopic probes, in conjunction with powerful pattern recognition methods, is presented in this paper. An UV/vis spectroscopic probe from S::CAN is used in combination with a custom-built dilution system to monitor the absorption of fully fermented sludge at a spectrum from 200 to 750 nm. Advanced pattern recognition methods are then used to map the non-linear relationship between measured absorption spectra to laboratory measurements of organic acid concentrations. Linear discriminant analysis, generalized discriminant analysis (GerDA), support vector machines (SVM), relevance vector machines, random forest and neural networks are investigated for this purpose and their performance compared. To validate the approach, online measurements have been taken at a full-scale 1.3-MW industrial biogas plant. Results show that whereas some of the methods considered do not yield satisfactory results, accurate prediction of organic acid concentration ranges can be obtained with both GerDA and SVM-based classifiers, with classification rates in excess of 87% achieved on test data

Conflicts of interest in medicine and their management: current challenges and initiatives in Germany

Conflicts of interest (COI) in healthcare have increasingly gained attention in the lay press as well as among healthcare professionals. COIs increase the risk of undue influence on professional decision making and may have far-reaching consequences in healthcare. Therefore, it is essential to develop strategies to deal with such risk situations in order to prevent negative outcomes for patients and the health care system. This article describes recent research on COIs in Germany as well as initiatives aiming at more transparency and better management of COIs in Germany

Predicting organic acid concentration from UV/vis spectrometry measurements – A comparison of machine learning techniques

The concentration of organic acids in anaerobic digesters is one of the most critical parameters for monitoring and advanced control of anaerobic digestion processes. Thus, a reliable online-measurement system is absolutely necessary. A novel approach to obtaining these measurements indirectly and online using UV/vis spectroscopic probes, in conjunction with powerful pattern recognition methods, is presented in this paper. An UV/vis spectroscopic probe from S::CAN is used in combination with a custom-built dilution system to monitor the absorption of fully fermented sludge at a spectrum from 200 to 750 nm. Advanced pattern recognition methods are then used to map the non-linear relationship between measured absorption spectra to laboratory measurements of organic acid concentrations. Linear discriminant analysis, generalized discriminant analysis (GerDA), support vector machines (SVM), relevance vector machines, random forest and neural networks are investigated for this purpose and their performance compared. To validate the approach, online measurements have been taken at a full-scale 1.3-MW industrial biogas plant. Results show that whereas some of the methods considered do not yield satisfactory results, accurate prediction of organic acid concentration ranges can be obtained with both GerDA and SVM-based classifiers, with classification rates in excess of 87% achieved on test data

Nonequilibrium valley polarization in graphene nanoconstrictions

We recently shown, using tight-binding calculations, that nonequilibrium valley polarization can be realized in graphene, when the current is injected through "valley filter": a ballistic point contact with zigzag edges. Here we demonstrate, that the effect is surprisingly robust against changing the crystallographic orientation of the filter axis. Namely, the output current remains polarized unless a point contact has perfect armchair edges, at which two subblattices are equally represented. The polarization is inverted when the filter orientation crosses the amchair line and, subsequently, dominating subblattice index of terminal atoms changes. In a bended graphene strip, the valley-polarized current can be directed towards one edge providing a theoretical possibility to observe a zero-magnetic-field analogue of the well-known Hall effect. For the valley valve, build of two valley filters in series and controlled elecrostatically by a gate voltage, the conductance-to-gate characteristic is inverted when $\pi/3$ vertex is placed between two filters.Comment: 10 pages, 7+1 figures, presented on the conference TNT2007 "Trends in Nanotechnology", San Sebastian (Spain), September 3-7, 2007. Submitted to special edition of phys. stat. sol. (a

Zu den Beschäftigungspotentialen einer Entkoppelung von Arbeits- und Betriebszeiten

"Die Untersuchung ist ein Beitrag zur Diskussion um die grundsätzliche Problematik, die sich zwischen der Forderung nach kürzeren Arbeitszeiten einerseits und dem Interesse an einer möglichst langen Nutzungsdauer der immer aufwendigeren Produktionsanlagen andererseits auftut. Als Einstieg in dieses Problembild hat das IAB zusammen mit dem ifo-Institut eine Betriebsbefragung im Verarbeitenden Gewerbe und im Handel durchgeführt. Sie allein erlaubt freilich noch keine umfassende Einschätzung der hier angeschnittenen Fragen; hierzu müßten vor allem auch die diesbezüglichen Arbeitnehmerpräferenzen genutzt werden. Im Zentrum stehen folgende Fragen: Wie groß und wie elastisch ist das gegenwärtige Arbeitplatzpotential, das - im Falle einer wie auch immer gearteten und erklärbaren Nachfragebelebung - ohne zusätzlichen Investitionsaufwand genutzt werden könnte? Lassen sich konsensfähige Arbeitszeit-/Betriebszeit-Modelle finden, die zugleich die arbeitsmarktpolitisch gebotene, weitere Verkürzung der effektiven Jahres-Arbeitszeit erlauben, dabei den Arbeitszeitwünschen und den Interessenlagen der Arbeitnehmer entgegenkommen und auch den betrieblichen Rentabilitätsbelangen entsprechen?" (Autorenreferat)Beschäftigung, Arbeitszeit, Betriebszeit, verarbeitendes Gewerbe, Großhandel, Einzelhandel, Schichtarbeit