Diffusion of a passive impurity through a porous media: fractal model in an unsaturated medium

The theory of fractal sets is used to describe convective diffusion of a passive impurity in a partly-saturated porous medium.     

On the Modified Resonance Theory of Waveguide Circulator with Various Ferrite Specimens

A modified resonance theory of waveguide circulator with ferrite specimen is presented. The kernal of this theory is a two-step analysis method of an H-plane Y-junction waveguide circulator. For the first step, the ferrite specimens of Y-junction waveguide circulators are treated as if it were dielectric resonators with no magnetic bias. This simplistic approach is used to design the ferrite specimens of the circulators. Simple formulas are developed for determining the center frequency of the circulators. For the second step, wave circulation is made possible when a pair of degenerate resonance modes experiences different changes when the ferrite specimens are being magnetized. A modified analysis of joint resonance theory and simple field theory is advanced to evaluate the performances of the circulators. Good agreements between the analytically obtained performance and experimental result of various MMW waveguide circulators are observed.     

Synthesis and characterization of new blue‐greenish electroluminescent materials based on 1,3,4‐oxadiazole‐triazolopyridinone hybrids

New functionalized oxadiazole‐triazolopyridinone derivatives were synthesized via arcycloaddition. With the chromophores of triazolopyridinone, the photoluminescence spectra of these compounds in dichloromethane solution showed emission peaks between 430 and 520 nm. Following the spectroscopic studies, and the measurements of cyclic voltammogram, 1,3,4‐oxadiazole‐triazolopyridinone hybrids possess a great potential as highly efficient, blue‐greenish, organic light‐emitting devices materials. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:212–219, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20285     

Two-level chaos-based video cryptosystem on H.263 codec

Chaos-based video encryption algorithms are designed based on selective encryption method. Different from many prevailing MPEG-based video encryption designs, this paper lays out a scheme for a two-level H.263-based video cryptosystem, which skillfully combines the traditional selective encryption algorithm with permutation and subsequent masking operation of the coded H.263-based stream. Lastly, the implementation of the proposed cryptosystem on a local area network (LAN) strongly illustrates the efficiency and feasibility of the two-level chaos-based cryptosystem for practical use in many respects, including processing speed, compression ratio, quality of reconstructed image and security level.     

The Decomposition Reaction of 4‐Acetylsydnones Arylhydrazones

The acidic decomposition of 4‐acetylsydnones arylhydrazones 2 results in the formation of 4‐arylhydrazo‐1,2‐pyrazolin‐5‐ones 3 and 4‐arylamino‐1,2,3‐triazoles 4 , respectively. The reactions of 4‐acetylsydnones 1 with arylhydrazines 5 afford compounds 3 as the only products in the absence of solvent.     

Synthesis and characterization of new electroluminescent materials of 1,3,4‐oxadiazole–1,2,3‐triazole hybrids and 1,3,4‐oxadiazole–1,2,3‐triazole–pyridine derivatives

New electroluminescent materials of 1,3,4‐oxadiazole–1,2,3‐triazole and 1,3,4‐oxadiazole–1,2,3‐triazole–pyridine hybrid derivatives were synthesized and characterized. Following spectroscopic studies and characterization of their electronic properties, 1,3,4‐oxadiazole–1,2,3‐triazole hybrids and 1,3,4‐oxadiazole–1,2,3‐triazole–pyridine derivatives were found to be potentially efficient blue electroluminescent materials. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:322–328, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20210     

Application of the Severity Factor and HMF Removal of Red Macroalgae Gracilaria verrucosa to Production of Bioethanol by Pichia stipitis and Kluyveromyces marxianus with Adaptive Evolution

Applied Biochemistry and Biotechnology - Gracilaria verrucosa, red seaweed, is a promising biomass for bioethanol production due to its high carbohydrate content. The optimal hyper thermal (HT)...