有序抖动半调图像的无损压缩算法

在分析不同有序抖动模板对所生成抖动半调图像的影响因素基础上,设计了尺度变化的分块及块间异或预处理策略,大大提高了二值游程长度.进而使用游程和哈夫曼相结合的编码思想提出了一种新的有序抖动半调图像无损压缩算法.仿真实验表明,该算法在编码效率上具有较大优势.     

Influence of mesoporous structure type on the controlled delivery of drugs: release of ibuprofen from MCM-48, SBA-15 and functionalized SBA-15

Ordered mesoporous materials exhibit potential features to be used as controlled drug delivery systems, including their wide range of chemical compositions and their outstanding textural and structural properties. Therefore, it is possible to control the drug release kinetics by tailoring such parameters. In this paper, mesoporous materials such as MCM-48 and SBA-15, which present different pore sizes (3.7 and 8.8 nm) and structural characteristics (3D-bicontinuous cubic and 2D-hexagonal, respectively) have been synthesized to evaluate their application as drug delivery system and to determine their influence on release kinetic of ibuprofen. Moreover, a chemical modification of the SBA-15 mesoporous material with octadecyltrimethoxysilane has also been performed to study its influence on the release rate of ibuprofen. The structural characteristics (3D cubic and 2D hexagonal pore system) do not affect the release kinetic profiles of ibuprofen. On the contrary, the pore size affects highly to the release kinetic profiles from first-order kinetic to zero-order kinetic for MCM-48 and SBA-15, respectively. Moreover, the importance of surface functionalization was demonstrate through the very fast delivery of ibuprofen from SBA-15 mesoporous materials functionalized with octadecyl chains.     

Synthesis, structure and adsorption properties of nanoporous SBA-15 materials with framework and surface functionalities

Highly ordered SBA-15 nanoporous silica containing ethylene, phenylene bridges or/and amine, thiol, vinyl and phenyl surface groups were synthesized by using amphiphilic block copolymer as the structure-directing agent. The XRD data shows high degree of the order of the final structures. Obtained materials have well-developed porous structure—values of specific surface area are in the range 700–1050 m²/g and the sizes of cylindrical mesopores are in the range 6.5–9.5 nm. It was determined that size of the mesopores strongly depends even on small amounts of co-monomers co-condensing with TEOS. A new technique to introduce some amount of pendant amine groups by co-condensation of proper monomers has been proposed. Tetragonal structure was obtained when small amount of vinyl groups was introduced to the system. A new approach of determining pore size based only on the XRD measurements was compared with KJS method, confirming full usefulness of the former for calculation of the size of mesopores in SBA-15 materials. Dedicated to Professor Mietek Jaroniec on the occasion of his 60th birthday.     

Improved compositional analysis of block copolymers using Diffusion Ordered NMR Spectroscopy

Block copolymers constitute a fascinating class of polymeric materials that are used in a broad range of applications. The performance of these materials is highly coupled to the physical and chemical properties of the constituting block copolymers. Traditionally, the composition of block copolymers is obtained by ¹H NMR spectroscopy on purified copolymer fractions. Specifically, the integrals of a properly selected set of ¹H resonances are compared and used to infer the number average molecular weight (M_n) of one of the block from the (typically known) M_n value of the other. As a corollary, compositional determinations achieved on imperfectly purified samples lead to serious errors, especially when isolation of the block copolymer from the initial macro initiator is tedious. This investigation shows that Diffusion Ordered NMR Spectroscopy (DOSY) can be used to provide a way to assess the advancement degree of the copolymerization purification/reaction, in order to optimize it and hence contribute to an improved compositional analysis of the resulting copolymer. To this purpose, a series of amphiphilic polystyrene-b-poly(ethylene oxide) block copolymers, obtained by controlled free-radical nitroxide mediated polymerization, were analyzed and it is shown that, under proper experimental conditions, DOSY allows for an improved compositional analysis of these block copolymers.     

Graft polymerization from pore wall of three-dimensionally ordered macroporous cross-linked polystyrene via atom transfer radical polymerization

The surface-initiated atom-transfer radical polymerization (ATRP) technique was applied to the graft polymerization of methyl methacrylate (MMA) and N-isopropylacrylamide (NIPAm) from three-dimensionally ordered macroporous cross-linked polystyrene (3DOM CLPS) on which the initiator, halogen atom was immobilized onto the pore wall of 3DOM CLPS by chloromethylation. FT-IR and TG-DWA analyses confirm that the graft polymerization of MMA and NIPAm via ATRP had been taken place at the pore wall of 3DOM CLPS. The initiating efficiency of chloromethyl groups was calculated according to the data of TGA-titration, revealed that the benzyl chloride is not only distributed on the surface of the pore walls but also must be present throughout the inner of the cross-linked polystyrene matrix. SEM analyses show that the grafted layers are smooth and homogeneous, and the ordered structure is well preserved after polymerization. By the adjustment of the graft polymerization time, the thickness of grafted polymer layers can be controlled. The max thickness of grafted PMMA layer is 85 nm and the max thickness of grafted PNIPAm layer is 35 nm.     

Evaluation of selectivity for l-glutamide-derived highly ordered assemblies in reversed-phase high-performance liquid chromatography

Two dioctadecyl l-glutamic acid derivatives with amide and ester type bondings have been synthesized and immobilized from 3-aminopropyltrimethoxysilane (APS) grafted silica (Sil-APS) to be used in reversed-phase high-performance liquid chromatography (RP-HPLC). Subsequent studies showed that dioctadecyl-l-glutamide derivative (GLN) can self-assemble into highly ordered structures by forming three-dimensional fibrillar aggregates as observed in scanning and transmission electron microscopes (SEM and TEM). Variable temperature ¹H NMR and FT-IR spectra of organogel revealed that the special aggregation morphology shown by GLN was stabilized by inter and or intra molecular hydrogen bonding among amide moieties. However, such ordered aggregated or self-assembled structures were not observed for the dioctadecyl-l-glutamate (GLU) derivative. The stationary phases Sil-GLN and Sil-GLU were characterized by DRIFT, elemental analysis, TGA, and ¹³C and ²⁹Si CP-MAS NMR spectroscopic measurements. The chromatographic selectivity for both stationary phases was evaluated from the retention studies of different size and shape polycyclic aromatic hydrocarbons (PAHs). The chromatographic experiment for PAHs and geometrical isomers in RP-HPLC showed that Sil-GLN demonstrated extremely enhanced selectivity than Sil-GLU. The higher selectivity attributed by Sil-GLN has been brought by multiple π-π interactions among the π-electrons of the grafted organic phase and π-electrons of the guest PAHs molecules. Thermodynamic studies for linear and nonlinear PAHs revealed that the retention behavior does not change over a temperature range from 10 to 60 °C for both stationary phases.     

Revising the OWA operator for multi criteria decision making problems under uncertainty

Multi criteria decision making (MCDM) problems are usually under uncertainty. One of these uncertain parameters is the decision maker (DM)’s degree of optimism, which has an important effect on the results. Fuzzy linguistic quantifiers are used to obtain the assessments of this parameter from DM and then, because of its uncertainty it is assumed to have stochastic nature. A new approach, entitled FSROWA, is introduced to combine the Fuzzy and Stochastic features into a Revised OWA operator.     

On ordered categories as a framework for fuzzification of algebraic and topological structures

Using the framework of ordered categories, the paper considers a generalization of the fuzzification machinery of algebraic structures introduced by Rosenfeld as well as provides a new approach to fuzzification of topological structures, which amounts to fuzzifying the underlying “set” of a structure in a suitably compatible way, leaving the structure itself crisp. The latter machinery allows the so-called “double fuzzification”, i.e., a fuzzification of something that is already fuzzified.     

The actual structure of K6(VO)2(V2O3)2(PO4)4(P2O7): Ordered distribution of P2O7 groups and charge ordering of vanadium

The actual structure of the vanadium phosphate K₆(VO)₂(V₂O₃)₂(PO₄)₄(P₂O₇) has been determined, using a much larger single crystal than previously used for the isostructural Rb-phase. The actual supercell is four times larger than the corresponding orthorhombic subcell with , , , α=β=γ=90°. The structure resolution, performed in the triclinic space group C-1, shows that the P₂O₇ groups alone are responsible for the superstructure, all the other atoms keeping the atomic positions of the orthorhombic subcell. This structural study shows a perfect ordering of the P₂O₇ groups in the actual structure, in contrast to the results obtained from the subcell. Concomitantly, the V⁴⁺ and V⁵⁺ are found to be ordered in the form of [110] stripes.     

Influence of Preparation Conditions on Structural Stability of Ordered Mesoporous Carbons Synthesized by Evaporation-induced Triconstituent Co-assembly Method

Various ordered mesoporous carbons (OMCs) have been prepared by evaporation-induced triconstituent co-assembly method. Their mesostructural stability under different carbon content, aging time and acidity were conveniently monitored by X-ray diffraction, transmis-sion electron microscopy, and N₂ sorption isotherms techniques. The results show mesostruc-tural stability of OMCs is enhanced as the carbon content increases from 36% to 46%, further increasing carbon content deteriorates the mesostructural stability. Increasing aging time from 0.5 h to 5.0 h make the mesostructural stability go through an optimum (2.0 h) and gradually reduce framework shrinkage of the OMCs. Highly OMCs can only be obtained in the acidity range of 0.2～1.2 mol/L HCl, when the acidity is near the isoelectric point of silica, the resulting OMCs have the best mesostructure stability. Under the optimum condi-tion, the carbon content of 46%, aging time of 2.0 h, and 0.2 mol/L HCl, the resulting OMCs have the best mesostructure stability and the highest BET surface areas of 2281 m²/g.