201 research outputs found
Influence of wettability on liquid water transport in gas diffusion layer of proton exchange membrane fuel cells (PEMFC)
Water management is a key factor that limits PEFC's performance. We show how
insights into this problem can be gained from pore-scale simulations of water
invasion in a model fibrous medium. We explore the influence of contact angle
on the water invasion pattern and water saturation at breakthrough and show
that a dramatic change in the invasion pattern, from fractal to compact, occurs
as the system changes from hydrophobic to hydrophilic. Then, we explore the
case of a system of mixed wettability, i.e. containing both hydrophilic and
hydrophobic pores. The saturation at breakthrough is studied as a function of
the fraction of hydrophilic pores. The results are discussed in relation with
the water management problem, the optimal design of a GDL and the fuel cell
performance degradation mechanisms. We outline how the study could be extended
to 3D systems, notably from binarised images of GDLs obtained by X ray
microtomography
Quantitative validation of PEDFLOW for description of unidirectional pedestrian dynamics
The results of a systematic quantitative validation of PEDFLOW based on the
experimental data from FZJ are presented. Unidirectional flow experiments,
totaling 28 different combinations with varying entry, corridor and exit
widths, were considered. The condition imposed on PEDFLOW was that all the
cases should be run with the same input parameters. The exit times and
fundamental diagrams for the measuring region were evaluated and compared. This
validation process led to modifications and enhancements of the model
underlying PEDFLOW. The preliminary conclusions indicate that the results agree
well for densities smaller than 3 m-2 and a good agreement is observed even at
high densities for the corridors with bcor = 2.4 m, and bcor = 3.0 m. For
densities between 1 and 2 m-2 the specific flow and velocities are
underpredicted by PEDFLOW.Comment: 6 pages, 3 figures, 1 Table, conference PED201
Die Bedeutung der arabischen NGOs für die Stärkung der Zivilgesellschaft:eine empirische Untersuchung am Beispiel Jemen
Diese Dissertation untersucht, inwieweit arabische Non-Governmental Organizations (NGOs) einen
entwicklungspolitischen Beitrag zur Stärkung der Zivilgesellschaft leisten können. Was können
diese NGOs zum Demokratisierungsprozess in der arabischen Welt beisteuern?
Es wird am Beispiel von Zielsetzungen und Aktivitäten drei ausgesuchter lokaler
entwicklungspolitischer NGOs im Jemen untersucht, die mit ihrer Arbeit die Zivilgesellschaft
stärken können.
Die NGOs der arabischen Welt wollen nicht nur eine Verbesserung ihrer unmittelbaren
ökonomischen Situation, sondern sie streben darüber hinaus nach mehr Kontrolle des politischen
Geschehens, nehmen Einfluss auf gesellschaftliche Entscheidungsprozesse und streben nach einer
Veränderung der politischen und sozioökonomischen Rahmenbedingungen; dafür sind sie bereit,
sich einzusetzen
Generalized Centrifugal Force Model for Pedestrian Dynamics
A spatially continuous force-based model for simulating pedestrian dynamics
is introduced which includes an elliptical volume exclusion of pedestrians. We
discuss the phenomena of oscillations and overlapping which occur for certain
choices of the forces. The main intention of this work is the quantitative
description of pedestrian movement in several geometries. Measurements of the
fundamental diagram in narrow and wide corridors are performed. The results of
the proposed model show good agreement with empirical data obtained in
controlled experiments.Comment: 10 pages, 14 figures, accepted for publication as a Regular Article
in Physical Review E. This version contains minor change
Modeling the desired direction in a force-based model for pedestrian dynamics
We introduce an enhanced model based on the generalized centrifugal force
model. Furthermore, the desired direction of pedestrians is investigated. A new
approach leaning on the well-known concept of static and dynamic floor-fields
in cellular automata is presented. Numerical results of the model are presented
and compared with empirical data.Comment: 14 pages 11 figures, submitted to TGF'1
ONE STEP ELECTRODEPOSITION OF CuInSe2 THIN FILMS
Formation of CuInSe2 (CIS) thin films from aqueous solution containing citrate as complexing agent is reported. The surface morphology and the composition of the deposited films are characterized by scanning electron microscopy (SEM). The texture of the deposits and their compositions are analyzed by X-ray diffraction and transmission electron microscopy (TEM). Annealing of the films at 350°C in flowing argon electrodeposited at potentials in the range [-0.24, -0.4 (V vs Ag/AgCl)] resulted in the formation of alpha-Cu 2 Se (JCPDS 24-1131) and CuSe (JCPDS 6-0427). On the contrary, annealing in the same conditions of the films electrodeposited between -0.4 and -0.6 V vs Ag/AgCl led to the formation of chalcopyrite CuInSe 2 (JCPDS 23-209) with alpha-Cu 2 Se (JCPDS 24-1131) as secondary phase. The formation of CuInSe 2 films with a chalcopyrite structure and good stoichiometry is observed.Formation of CuInSe2 (CIS) thin films from aqueous solution containing citrate as complexing agent is reported. The surface morphology and the composition of the deposited films are characterized by scanning electron microscopy (SEM). The texture of the deposits and their compositions are analyzed by X-ray diffraction and transmission electron microscopy (TEM). Annealing of the films at 350°C in flowing argon electrodeposited at potentials in the range [-0.24, -0.4 (V vs Ag/AgCl)] resulted in the formation of alpha-Cu 2 Se (JCPDS 24-1131) and CuSe (JCPDS 6-0427). On the contrary, annealing in the same conditions of the films electrodeposited between -0.4 and -0.6 V vs Ag/AgCl led to the formation of chalcopyrite CuInSe 2 (JCPDS 23-209) with alpha-Cu 2 Se (JCPDS 24-1131) as secondary phase. The formation of CuInSe 2 films with a chalcopyrite structure and good stoichiometry is observed
Physical properties of CdSexTe1-x thin films prepared by electrodeposition
The cadmium chalcogenides CdSexTe1-x (0≤x ≤1 ) thin films have been electrodeposited onto ITO coated glass substrates from an acid sulphate solution at 90 °C. The structure, the composition and the morphology have been studied as a function of the x coefficient by XRD, EDAX, optical absorbance and AFM techniques. All deposits have a cubic structure with a preferred orientation along the (111) direction. The composition in the films is found to vary linearly with the composition in the solution. The increase of the amount of tellurium in the CdSexTe1-x films decreases the band gap down to 1.35 eV and increases the lattice constant. The photoelectrochemical studies in a polysulfide electrolyte show that CdSexTe1-x thin films behave as n-type semiconductors.The cadmium chalcogenides CdSexTe1-x (0≤x ≤1 ) thin films have been electrodeposited onto ITO coated glass substrates from an acid sulphate solution at 90 °C. The structure, the composition and the morphology have been studied as a function of the x coefficient by XRD, EDAX, optical absorbance and AFM techniques. All deposits have a cubic structure with a preferred orientation along the (111) direction. The composition in the films is found to vary linearly with the composition in the solution. The increase of the amount of tellurium in the CdSexTe1-x films decreases the band gap down to 1.35 eV and increases the lattice constant. The photoelectrochemical studies in a polysulfide electrolyte show that CdSexTe1-x thin films behave as n-type semiconductors
Effect of heat treatment with CdCl2 on the electrodeposited CdTe/CdS heterojunction
CdS/CdTe heterojunction was subjected to chemical treatment commonly used in photovoltaic device fabrication to determine the resulting microscopic effect on the morphology and structure. CdS and CdTe thin films were electrodeposited successively onto indium tin oxide (ITO) from aqueous solution. Containing CdCl2 and Na2S2O3 for the deposition of thin film windows, the ITO/CdS resulting substrates was then used for the deposition of CdTe thin film absorber using aqueous solution of CdSO4 and TeO2. Next CdCl2 dip followed by 400°C heat treatment was used to modify the CdTe/CdS surface and interface. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) were used to evaluate the resulting surface morphology. X-ray diffraction analysis reveals that the heat treatment enhances the recrystallisation and shifts the CdTe peaks towards a smaller lattice parameter.CdS/CdTe heterojunction was subjected to chemical treatment commonly used in photovoltaic device fabrication to determine the resulting microscopic effect on the morphology and structure. CdS and CdTe thin films were electrodeposited successively onto indium tin oxide (ITO) from aqueous solution. Containing CdCl2 and Na2S2O3 for the deposition of thin film windows, the ITO/CdS resulting substrates was then used for the deposition of CdTe thin film absorber using aqueous solution of CdSO4 and TeO2. Next CdCl2 dip followed by 400°C heat treatment was used to modify the CdTe/CdS surface and interface. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) were used to evaluate the resulting surface morphology. X-ray diffraction analysis reveals that the heat treatment enhances the recrystallisation and shifts the CdTe peaks towards a smaller lattice parameter
Argan Oil Exerts an Antiatherogenic Effect by Improving Lipids and Susceptibility of LDL to Oxidation in Type 2 Diabetes Patients
In this study, we investigate the effect of argan oil consumption on serum lipids, apolipoproteins (AI and B), CRP, and LDL susceptibility to oxidation in type 2 diabetic patients which are known to have a high level of cardiovascular risk due to lipid abnormalities and lipid peroxidation. For that, 86 type 2 diabetic patients with dyslipidemia were randomized to one group consuming 25 mL/day of argan oil during 3 weeks and control group consuming 20 g/day of butter in breakfast. After argan oil intervention, serum triglycerides decreased by 11.84%, (P = 0.001), total chol by 9.13%, (P = 0.01), and LDL-chol by 11.81%, (P = 0.02). However, HDL-chol and Apo AI increased (10.51%, P = 0.01 and 9.40%, P = 0.045, resp.). Susceptibility of LDL to lipid peroxidation was significantly reduced by increasing of 20.95%, (P = 0.038) in lag phase after argan oil consumption. In conclusion, we show for the first time that consumption of argan oil may have an antiatherogenic effect by improving lipids, and the susceptibility of LDL to oxidation in type 2 diabetes patients with dyslipidemia, and can therefore be recommended in the nutritional management of type 2 diabetes
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