A practical Equivalent Electrical Circuit model for Proton Exchange Membrane Fuel Cell (PEMFC) systems

An alternative Equivalent Electrical Circuit for Proton Exchange Membrane Fuel Cells is modelled in this study. Both I–V characteristics and H₂ consumptions corresponding to generated power under load and no-load conditions are investigated. For this purpose, H₂ consumptions and I–V characteristics of three different sized PEMFCs are tested. There is a very good harmony between the model results and measured values (relative error %0.7, %6.4 and %2.5 for FC-A, FC-B and FC-C respectively). In the proposed model current passes only on parallel resistance and not on serial resistance at no-load condition. Thus, a FC with higher parallel resistance should be preferred. Another key output of this study is that based on the proposed model, performance comparison of FCs can be performed with the parameters defined in this work. Proposals made in this study can easily be used for performance analysis of FCs under for both steady state and transient analysis.     

Automated classification of simulated wind field patterns from multiphysics ensemble forecasts

In this study, we have proposed an automated classification approach to identify meaningful patterns in wind field data. Utilizing an extensive simulated wind database, we have demonstrated that the proposed approach can identify low‐level jets, near‐uniform profiles, and other patterns in a reliable manner. We have studied the dependence of these wind profile patterns on locations (eg, offshore vs onshore), seasons, and diurnal cycles. Furthermore, we have found that the probability distributions of some of the patterns depend on the underlying planetary boundary layer schemes in a significant way. The future potential of the proposed approach in wind resource assessment and, more generally, in mesoscale model parameterization improvement is touched upon in this paper.     

Partitioning of predominant lipophilic bioactives (squalene, α-tocopherol and β-sitosterol) during olive oil processing

The partitioning of predominant lipophilic olive bioactives (squalene, β-sitosterol and α-tocopherol) in olive oil processing was studied for the first time using common integrated olive milling plant. 7% of the oil and 5% of the squalene present in the olives was lost in the last pomace. β-sitosterol and α-tocopherol, which are mainly concentrated in the seed of the olive fruit, was recovered in virgin olive oil to a lesser extent (66%, 67%) while 10% were lost in last pomace. Thus, the loss of β-sitosterol and α-tocopherol was higher than that of squalene and oil, due to nonrecovered bound forms. 19% of the α-tocopherol and 21% of the β-sitosterol loss was unaccounted for, which can be attributed to degradation of α-tocopherol and incomplete recovery of sterols from the olive and pomace matrices. This study provides a basis for process development studies.     

Gebrauchsgegenst?nde

Ohne Zusammenfassung     

Optimal design of elastic beams with segmentwise constant height in the case of dynamic loading

A shape optimization method for elastic beams with segmentwise constant height is proposed. The ends of the beam are simply supported, clamped or free. Two problems are discussed; (i) a beam is loaded by lateral pressure, (ii) a beam is struck by an attached mass. External loads and volume of the beam are prescribed and the deflection in a given cross-section is to be minimized. For solving this problem, the deflections are expanded into a Fourier series by eigenfunctions. Numerical results are given for two-, three- and four-stepped beams.     

Über die Anwendung von Ionensensitiven Feldeffekttransistoren zur Untersuchung von Korrosionsvorgängen

On the application of ion sensitive field-effect transistors for the investigation of corrosion phenomena Ion sensitive field-effect transistors (ISFET) are chemical sensors based on semiconductor technology. They exhibit small dimensions, a plane measuring surface and have short response times. Thus, they are very suitable for the determination of local changes of the pH value at electrochemical corrosion studies. The described in this paper experimental set-up allows in situ measurements of the pH value by means of ISFET sensors in amounts of liquids below 1 mm³; the active surface area of the material under test may be below 1 mm². In model tests preferably changes of the pH value of dist. water due to the corrosion of steel St 38 have been investigated. After an initial short-time rise caused by oxygen reduction a decay of the pH value to pH = 3 ?4 was obseved. Furthermore, ISFET sensors have been used as a potential probe for electrochemical polarization measurements in low conductive media. It was shown, that the dynamic behaviour of potentiostatic control circuits may be influenced favourably by the low output resistance of the ISFET.     

Microwave cavity perturbation technique: Part I: Principles

This report reviews the analysis used to extract the complex conductivity of a compound from a microwave cavity perturbation measurement. We intend to present a generalized treatment valid for any spheroidally shaped sample of arbitrary conductivity which is placed at either the electric or magnetic field antinode of the cavity. To begin with, we establish the relationship between the measured parameters and the conductivity for a spherical sample. Next, we extend these results to the case of spheroids; and for the first time, we cover all different configurations that one can possibly use to study an arbitrary conducting sample inside a cavity: in particular, all possible orientations of the sample with respect to the applied field are solved.     

Milch und K?se

Ohne Zusammenfassung