Synthesis and luminescence property of rare earth complex nanoparticles dispersed within pores of modified mesoporous silica

A rare earth complex, Eu(AA)₃Phen was successfully introduced into the pores of mesoporous silica, which was verified by X-ray photoelectron spectroscopy and nitrogen sorption isotherms. The rare earth complex dispersed in mesoporous silica displayed characteristic fluorescence emission of the pure rare earth complex, and the fluorescence emission was enhanced, especially for that with diamine treated mesoporous silica.     

Band filters: two-material technology versus rugate

We demonstrate theoretically and experimentally a band filter with two reflection and broadband transmission ranges, which was obtained with standard two-material technology. The fabricated filter has transmission and reflectivity characteristics better than those achievable with rugate technology.     

Fluid mixtures in narrow cylindrical pores: Computer simulation and theory

We discuss the simulation results of phase separation of a binary Lennard-Jones mixture in a cylindrical pore induced by a temperature quench. The liquid-vapor phase separation proceeds in two stages involving different time scales. First, following the growth of density fluctuations, mechanical equilibrium is rapidly established when the system splits into a dense and a dilute phase. Material equilibrium, however, is reached via the mutual diffusion of the two components and this proceeds on an appreciably longer time scale. We briefly address the rounding of a first-order phase transition in a cylinder. In particular, we explore the possibility of multiple domains of gas and liquid when the aspect ratio is very large. Finally, we introduce an extension of Tarazona's nonlocal density function to binary mixtures of arbitrary size. The new theory is successfully tested against simulations of an additive hard-sphere mixture against a hard wall.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Molecular pore size characterization within chitosan biopolymer using positron annihilation lifetime spectroscopy

Positron annihilation lifetime spectroscopy has been used to study a chitosan biopolymer, to which nanoclay has been added, and the effect of water absorption and cross-linking on the microporosity. All measurements were conducted at room temperature. The free volume size of the biopolymer samples was obtained based on the ortho-positronium lifetime, and the relative concentration of free volume cavities was measured by the ortho-positronium intensity. Using the PALS technique, effects of hydration were observed as a reduction in the measured pore size. Similarly, the cross-linked samples exhibited an increase in intensity of the smallest pores commensurate with the SEM observations.     

MTL代数的蕴涵滤子与正蕴涵滤子

在MTL代数M上引入了蕴涵滤子、正蕴涵滤子的概念,研究了它们的性质,给出了M的非空子集成为蕴涵滤子及正蕴涵滤子的充要条件和M的蕴涵滤子成为正蕴涵滤子的充要条件.讨论了蕴涵滤子与正蕴涵滤子的关系,得到了M的每一个正蕴涵滤子都是蕴涵滤子,但反之不真.     

Solid-spaced filters: an alternative for narrow-bandpass applications

Solid-spaced filters are composed of one or several thin wafers of excellent optical quality acting as Fabry-Perot spacer layers. We study the different steps of the design and the manufacture of filters following dense-wavelength-division-multiplexing specifications. The design method of such filters requires a tight synergy between numerical simulations and experimental characterizations to correct possible thickness errors. Experimental results of the manufacture and characterization of a three-cavity narrow-bandpass filter and of an interleaver filter are given.     

Microscopic studies of fluids in pores: Computer simulation and mean-field theory

The behavior of a simple model of a fluid confined to a single, infinitely long cylindrical pore is investigated by means of both a grand canonical Monte Carlo computer simulation and a mean-field theory. The theory is used to calculate the density profile of the fluid, as well as the grand potential of the system. The effect of the (size of the) pore radius as well as the temperature and pressure on the phase behavior of the fluid is studied in some detail, and the results are compared to those produced by related work in this field. The preliminary results from the simulation indicate that, in pores whose radii are a few molecular diameters in size, the fluid molecules tend to pack in cylindrically concentric shells about the axis of the pore.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Unconstrained correlation filters

A mathematical analysis of the distortion tolerance in correlation filters is presented. A good measure for distortion performance is shown to be a generalization of the minimum average correlation energy criterion. To optimize the filter's performance, we remove the usual hard constraints on the outputs in the synthetic discriminant function formulation. The resulting filters exhibit superior distortion tolerance while retaining the attractive features of their predecessors such as the minimum average correlation energy filter and the minimum variance synthetic discriminant function filter. The proposed theory also unifies several existing approaches and examines the relationship between different formulations. The proposed filter design algorithm requires only simple statistical parameters and the inversion of diagonal matrices, which makes it attractive from a computational standpoint. Several properties of these filters are discussed with illustrative examples.     

Carbon nanotube filters

Over the past decade of nanotube research, a variety of organized nanotube architectures have been fabricated using chemical vapour deposition. The idea of using nanotube structures in separation technology has been proposed, but building macroscopic structures that have controlled geometric shapes, density and dimensions for specific applications still remains a challenge. Here we report the fabrication of freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimetres. These cylindrical membranes are used as filters to demonstrate their utility in two important settings: the elimination of multiple components of heavy hydrocarbons from petroleum-a crucial step in post-distillation of crude oil-with a single-step filtering process, and the filtration of bacterial contaminants such as Escherichia coli or the nanometre-sized poliovirus ( approximately 25 nm) from water. These macro filters can be cleaned for repeated filtration through ultrasonication and autoclaving. The exceptional thermal and mechanical stability of nanotubes, and the high surface area, ease and cost-effective fabrication of the nanotube membranes may allow them to compete with ceramic- and polymer-based separation membranes used commercially.