ABSTRACT
Fuel cells offer great promise for portable electricity generation, but their use is currently limited by their low durability, excessive operating temperatures, and expensive precious metal electrodes. It is therefore essential to develop fuel cell systems that can perform effectively using more robust electrolyte materials, at reasonable temperatures, with lower-cost electrodes. Recently, proton exchange membrane fuel cells have attracted attention due to their generally favorable chemical stability and quick start-up times. However, in most membrane materials, water is required for proton conduction, severely limiting operational temperatures. Here, for the first time it is demonstrated that when acidified, PAF-1 can conduct protons at high temperatures, via a unique framework diffusion mechanism. It shows that this acidified PAF-1 material can be pressed into pellets with high proton conduction properties even at high temperatures and pellet thickness, highlighting the processibility, and ease of use of this material. Furthermore, a fuel cell is shown with high power density output is possible using a non-precious metal copper electrode. Acid-doped PAF-1 therefore represents a significant step forward in the potential for a broad-purpose fuel cell due to it being cheap, robust, efficient, and easily processible.
ABSTRACT
X-ray Talbot moiré interferometers can now simultaneously generate two differential phase images of a specimen. The conventional approach to integrating differential phase is unstable and often leads to images with loss of visible detail. We propose a new reconstruction method based on the inverse Riesz transform. The Riesz approach is stable and the final image retains visibility of high resolution detail without directional bias. The outline Riesz theory is developed and an experimentally acquired X-ray differential phase data set is presented for qualitative visual appraisal. The inverse Riesz phase image is compared with two alternatives: the integrated (quantitative) phase and the modulus of the gradient of the phase. The inverse Riesz transform has the computational advantages of a unitary linear operator, and is implemented directly as a complex multiplication in the Fourier domain also known as the spiral phase transform.
ABSTRACT
We present a method for measuring the optical transfer function (OTF) of a camera lens using a tartan test pattern containing sinusoidal functions with multiple frequencies and orientations. The method is designed to optimize measurement accuracy for an adjustable set of sparse spatial frequencies and be reliable and fast in a wide range of measurement conditions. We describe the pattern design and the algorithm for estimating the OTF accurately from a captured image. Simulations show the tartan method is significantly more accurate than the International Organization for Standardization 12233 standard slanted-edge method. Experimental results from the tartan method were reproducible to 0.01 root mean square and in reasonable agreement with the slanted-edge method.
ABSTRACT
We propose a coherent mathematical model for human fingerprint images. Fingerprint structure is represented simply as a hologram - namely a phase modulated fringe pattern. The holographic form unifies analysis, classification, matching, compression, and synthesis of fingerprints in a self-consistent formalism. Hologram phase is at the heart of the method; a phase that uniquely decomposes into two parts via the Helmholtz decomposition theorem. Phase also circumvents the infinite frequency singularities that always occur at minutiae. Reliable analysis is possible using a recently discovered two-dimensional demodulator. The parsimony of this model is demonstrated by the reconstruction of a fingerprint image with an extreme compression factor of 239.
