Radial flow rapid pressure swing adsorption

A new PSA process has been proposed and experimentally verified. This process was operated with a radial flow geometry under a cycle time less than 30 seconds. It has been showed that enriched oxygen could be produced when air was fed inward. The same system showed virtually no separation effect if the feed direction was reversed. The change of separation efficiency upon flow reversal was most significant when small adsorbent particles were employed. A ø 200×75 mm annular packing with 3 µm particles of zeolite 5A was able to produce 60% purity oxygen from air. The effect of flow direction on system performance confirmed the importance of flow resistance distribution. In radial flow geometry, most of the flow resistance was located near the center of the disk. The relative small pressure gradient at the feed end enabled a better absorbent utilization during the inward feed step, and a more effective desorption during the vent step. The same principle could be extended to other geometric configurations.     

Quantum oscillations in the layer structure of thin metal films

Understanding the underlying physical principles that determine the internal structure of objects at the atomic scale is critical for the advancement of nanoscale science. We have performed synchrotron x-ray diffraction studies to determine the structural properties of smooth Pb films with varying thicknesses of 6 to 18 monolayers deposited on a Si(111) substrate at 110 K. We observe quasibilayer variations in the atomic interlayer spacings of the films consistent with charge density oscillations due to quantum confinement of conduction electrons and surface-interface interference effects. Quantum oscillations in atomic step height are also deduced.     

Quantum melting of the charge-density-wave state in 1T-TiSe2

We report a Raman scattering study of low-temperature, pressure-induced melting of the charge-density-wave (CDW) phase of 1T-TiSe2. Our measurements reveal that the collapse of the CDW state occurs in three stages: (i) For P<5 kbar, the pressure dependence of the CDW amplitude mode energies and intensities are indicative of a "crystalline" CDW regime; (ii) for 525 kbar, the absence of amplitude modes reveals a metallic regime in which the CDW has melted.     

Atomistics of Ge deposition on Si(100) by atomic layer epitaxy

Chlorine termination of mixed Ge/Si(100) surfaces substantially enhances the contrast between Ge and Si sites in scanning tunneling microscopy observations. This finding enables a detailed investigation of the spatial distribution of Ge atoms deposited on Si(100) by atomic layer epitaxy. The results are corroborated by photoemission measurements aided by an unusually large chemical shift between Cl adsorbed on Si and Ge. Adsorbate-substrate atomic exchange during growth is shown to be important. The resulting interface is thus graded, but characterized by a very short length scale of about one monolayer.     

Diphenylamino group as an effective handle to conjugated donor-acceptor polymers through electropolymerization

[reaction: see text] The diphenylamino group is an effective handle for electropolymerization to give electron donor-acceptor conjugated polymers. In addition, interesting electrochromic and photoresponsive behavior of 13 has been investigated.     

Process Algorithms for Resolution Improvement and Contrast Enhancement in Optical Coherence Tomography

We proposed two process algorithms for resolution improvement and contrast enhancement in the images of optical coherence tomography (OCT). An OCT system with a non-Gaussian light source spectrum or dispersion mismatch usually results in sidelobes in the interference fringe envelope that may produce artifacts and reduce image contrast. Based on the concept of deconvolution, we proposed two different process algorithms and demonstrated their effectiveness in retrieving sample structures. The effects of the process algorithms were examined by numerical simulations and real OCT scanning images. After processing with the proposed procedures, the effects of sidelobes were tremendously suppressed and the image qualities were improved.