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.     

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.     

Vehicle detection by means of stereo vision-based obstacles features extraction and monocular pattern analysis.

This paper presents a stereo vision system for the detection and distance computation of a preceding vehicle. It is divided in two major steps. Initially, a stereo vision-based algorithm is used to extract relevant three-dimensional (3-D) features in the scene, these features are investigated further in order to select the ones that belong to vertical objects only and not to the road or background. These 3-D vertical features are then used as a starting point for preceding vehicle detection; by using a symmetry operator, a match against a simplified model of a rear vehicle's shape is performed using a monocular vision-based approach that allows the identification of a preceding vehicle. In addition, using the 3-D information previously extracted, an accurate distance computation is performed.     

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.     

Model study of the crosslinking of polydimethylsiloxanes by peroxides

The decompositions of di-t-butyl peroxide (TBP) and diaroyl peroxides in permethylated silicone oil (47V20) have been studied by differential scanning calorimetry (DSC). Results show the importance of the solubility of the peroxide in the silicone on their rate of disappearance. For the diaroyl peroxides, according to the nature of the substituents on the phenyl ring and the concentration of the peroxide, the decomposition occurs in solution and/or in the solid phase. Decomposition in solution began at a lower temperature than in the solid phase, which took place immediately after melting and was quite instantaneous. Decomposition of these peroxides was also performed in octamethylcyclotetrasiloxane (D₄) and decamethyltetrasiloxane (DMTS). According to DSC results, D₄ seems to be a better model of the silicone than the linear one. Analyses of the products of the decomposition of TBP and dibenzoyl peroxide (BP) in this model showed that the dehydrodimer of D₄ was produced in low yield relative to peroxide. The main compounds obtained were high molecular weight compounds, which were apparently different for the two peroxides. The free radical origin of these products has been proven in the case of TBP by the addition of TEMPO in the reaction medium.     

Nonlinear discrete-time models: state-space vs. I/O representations

This paper compares state-space and input–output realizations for nonlinear discrete-time dynamic models. For linear models, these two realizations are essentially equivalent and their structures are closely related, but these statements do not hold for nonlinear models. We illustrate this point with simple, realistic examples for which only one of the two realizations exists or for which both exist but their structures are profoundly different. Overall, the main point of this paper is the importance of the choice of realization in the development of nonlinear dynamic models.     

Oil yield and compressibility modeling during microscale expression: Criteria for linseed breeding

Seven linseed varieties were harvested at seven times before complete maturity. Microscale oilseed expressions were subsequently carried out on it. A pressure of 10 MPa was applied for 1 h under uniaxial stress. The results were characterized in terms of oil, water and mucilage content, harvest date and oil yield. The piston displacement versus time (creep curves) was described by a four‐Kelvin‐Voigt elements viscoelastic model. Parameters were derived from the model, such as the mechanical properties of seeds (compressibility moduli), showing that the viscoelastic model fits well the experimental data (R² ≈ 0.999). The modeling parameters were combined with some biochemical data in order to predict the kinetics of oil extraction.