Phosphoric Acid Invasion in High Temperature PEM Fuel Cell Gas Diffusion Layers

In this work, liquid phosphoric acid was injected into polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs) to visualize the invasion patterns developed at breakthrough. Three-dimensional (3D) images of the GDLs were obtained through X-ray computed tomography, and equivalent pore networks were generated as the basis for pore network simulations using OpenPNM. Strong qualitative agreement was obtained between the simulated and experimentally observed liquid phosphoric acid invasion patterns, which provided validation for the numerical modeling. Different GDL materials were evaluated by examining the effects of a micro porous layer (MPL) and pore size distribution on the saturation and distribution of phosphoric acid. The MPL was shown to restrict liquid phosphoric acid from entering the carbon fiber substrate. The overall phosphoric acid saturation at breakthrough was found to decrease significantly for samples containing an MPL due to the smaller pore sizes. Further, the influence of cracks in an MPL on overall saturation at breakthrough was investigated. It was observed that a crack-free MPL provided a more effective physical barrier to restrict the undesired leaching of liquid phosphoric acid through the GDL

Optical coherence tomography- a non-invasive technique applied to conservation of paintings

It is current practice to take tiny samples from a painting to mount and examine in cross-section under a microscope. However, since conservation practice and ethics limit sampling to a minimum and to areas along cracks and edges of paintings, which are often unrepresentative of the whole painting, results from such analyses cannot be taken as representative of a painting as a whole. Recently in a preliminary study, we have demonstrated that near-infrared Optical Coherence Tomography (OCT) can be used directly on paintings to examine the cross-section of paint and varnish layers without contact and the need to take samples. OCT is an optical interferometric technique developed for in vivo imaging of the eye and biological tissues; it is essentially a scanning Michelson’s interferometer with a ‘broadband’ source that has the spatial coherence of a laser. The low temporal coherence and high spatial concentration of the source are the keys to high depth resolution and high sensitivity 3D imaging. The technique is non-invasive and noncontact with a typical working distance of 2 cm. This non-invasive technique enables cross-sections to be examined anywhere on a painting. In this paper, we will report new results on applying near-infrared en-face OCT to paintings conservation and extend the application to the examination of underdrawings, drying processes, and quantitative measurements of optical properties of paint and varnish layers

Patterning functional materials using channel diffused plasma-etched self-assembled monolayer templates

A simple and cost-effective methodology for large-area micrometer-scale patterning of a wide range of metallic and oxidic functional materials is presented. Self-assembled monolayers (SAM) of alkyl thiols on Au were micropatterned by channel-diffused oxygen plasma etching, a method in which selected areas of SAM were protected from plasma oxidation via a soft lithographic stamp. The patterned SAMs were used as templates for site-selective electrodeposition, electroless deposition and solution-phase deposition of functional materials such as ZnO, Ni, Ag thin films, and ZnO nanowires. The patterned SAMs and functional materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and tunneling AFM (TUNA).\u

Testing moderation effects using non-parametric regressions

Testing moderation effects is highly common in the hospitality literature. Most theories in the field depend on variables that alter the nature and direction of the relationship between two variables. While moderation continues to be heavily used, methods for testing moderation effects are not always robust. One common problem that researchers often face is the need to pre-assign a particular functional form. The aim of this note is to address this problem. We describe three different non-parametric models that offer more flexibility in testing moderating effects without a need to pre-impose a specific functional form. We test the three models on an interesting application involving the moderating role of corporate social responsibility (CSR) on the relationship between advertising and firm value. The results revealed interesting moderating effects that go beyond the simple linear moderation

Nanopatterning of functional materials by gas phase pattern deposition of self assembled molecular thin films in combination with electrodeposition

We present a general methodology to pattern functional materials on the nanometer scale using self-assembled molecular templates on conducting substrates. A soft lithographic gas phase edge patterning process using poly(dimethylsiloxane) molds was employed to form electrically isolating organosilane patterns of a few nanometer thickness and a line width that could be tuned by varying the time of deposition. Electrodeposition was employed to deposit patterns of Ni and ZnO on these prepatterned substrates. Deposition occurred only on patches of the substrate where no organosilane monolayer was present. The process is simple, inexpensive, and scalable to large areas. We achieved formation of metallic and oxide material patterns with a lateral resolution of 80 n

Transient magnetic domain wall ac dynamics by means of magneto-optical Kerr effect microscopy

The domain wall response under constant external magnetic fields reveals a complex behavior where sample disorder plays a key role. Furthermore, the response to alternating magnetic fields has only been explored in limited cases and analyzed in terms of the constant field solution. Here we unveil phenomena in the evolution of magnetic domain walls under the application of alternating magnetic fields within the creep regime, well beyond a small fuctuation limit of the domain wall position. Magnetic field pulses were applied in ultra-thin ferromagnetic films with perpendicular anisotropy, and the resulting domain wall evolution was characterized by polar magneto-optical Kerr effect microscopy. Whereas the DC characterization is well predicted by the elastic interface model, striking unexpected features are observed under the application of alternating square pulses: magneto-optical images show that after a transient number of cycles, domain walls evolve toward strongly distorted shapes concomitantly with a modification of domain area. The morphology of domain walls is characterized with a roughness exponent when possible and contrasted with alternative observables which result to be more suitable for the characterization of this transient evolution. The final stationary convergence as well as the underlying physics is discussed.Comment: 9 pages, 8 figure

A continuous time random walk model for financial distributions

We apply the formalism of the continuous time random walk to the study of financial data. The entire distribution of prices can be obtained once two auxiliary densities are known. These are the probability densities for the pausing time between successive jumps and the corresponding probability density for the magnitude of a jump. We have applied the formalism to data on the US dollar/Deutsche Mark future exchange, finding good agreement between theory and the observed data.Comment: 14 pages, 5 figures, revtex4, submitted for publicatio

Optical transmission losses in materials due to repeated impacts of liquid droplets

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76812/1/AIAA-7018-720.pd

Cellular Automata Applications in Shortest Path Problem

Cellular Automata (CAs) are computational models that can capture the essential features of systems in which global behavior emerges from the collective effect of simple components, which interact locally. During the last decades, CAs have been extensively used for mimicking several natural processes and systems to find fine solutions in many complex hard to solve computer science and engineering problems. Among them, the shortest path problem is one of the most pronounced and highly studied problems that scientists have been trying to tackle by using a plethora of methodologies and even unconventional approaches. The proposed solutions are mainly justified by their ability to provide a correct solution in a better time complexity than the renowned Dijkstra's algorithm. Although there is a wide variety regarding the algorithmic complexity of the algorithms suggested, spanning from simplistic graph traversal algorithms to complex nature inspired and bio-mimicking algorithms, in this chapter we focus on the successful application of CAs to shortest path problem as found in various diverse disciplines like computer science, swarm robotics, computer networks, decision science and biomimicking of biological organisms' behaviour. In particular, an introduction on the first CA-based algorithm tackling the shortest path problem is provided in detail. After the short presentation of shortest path algorithms arriving from the relaxization of the CAs principles, the application of the CA-based shortest path definition on the coordinated motion of swarm robotics is also introduced. Moreover, the CA based application of shortest path finding in computer networks is presented in brief. Finally, a CA that models exactly the behavior of a biological organism, namely the Physarum's behavior, finding the minimum-length path between two points in a labyrinth is given.Comment: To appear in the book: Adamatzky, A (Ed.) Shortest path solvers. From software to wetware. Springer, 201