An effective authentication mechanism for ubiquitous collaboration in heterogeneous computing environment

With the advent of new generation of mobile access devices such as smartphone and tablet PC, there is coming a need for ubiquitous collaboration which allows people to access information systems with their disparate access devices and to communicate with others in anytime and in anywhere. As the number of collaborators with a large number of disparate access devices increases in ubiquitous collaboration environment, the difficulties for protecting secured resources from unauthorized users as well as unsecured access devices will increase since the resources can be compromised by inadequately secured human and devices. Therfore, authentication mechanism for access of legitimate participants is essential in ubiquitous collaboration environment. In this paper we present an efficient authentication mechanism in ubiquitous collaboration environment. We show that proposed scheme is secure through security analysis and is efficient through the experimental results obtained from the practical evaluation of the scheme in ubiquitous collaboration environment.     

Synthesis of TiC, TiC-Cu Composites, and TiC-Cu Functionally Graded Materials by Electrothermal Combustion

Titanium carbide and composites and functionally graded materials (FGMs) of TiC– x Cu were synthesized by an electrothermal combustion (ETC) method. TiC synthesized by ETC showed small amounts of porosity relative to those synthesized by ignition using radiative heating. Composites and FGMs with higher copper content can be synthesized by ETC. In the FGM products a nearly linear change in composition in the graded region was observed in samples with 0 ≤ x (wt%) ≤ 75.     

Optical and Magnetic Properties of Ten-Period InGaMnAs/GaAs Quantum Wells

Ten layers of InGaMnAs/GaAs multiquantum wells (MQWs) structure were grown on high resistivity (100) p-type GaAs substrates by molecular beam epitaxy (MBE). A presence of the ferromagnetic structure was confirmed in the InGaMnAs/GaAs MQWs structure, and have ferromagnetic ordering with a Curie temperature, T _C=50 K. It is likely that the ferromagnetic exchange coupling of the sample with T _C=50 K is hole-mediated resulting in Mn substituting In or Ga sites. PL emission spectra of the InGaMnAs MQWs sample grown at a temperature of 170 °C show that an activation energy of the Mn ion on the first quantum confinement level in InGaAs QW is 32 meV and impurity Mn is partly ionized. The fact that the activation energy of 32 meV of Mn ion in the QW is lower than an activation energy of 110 meV for a substitutional Mn impurity in GaAs, indicating an impurity band existing in the bandgap due to substitutional Mn ions.     

Simultaneous synthesis and consolidation of nanocrystalline Fe2Al5 and Fe2Al5-Al2O3 by pulsed current activated sintering and their mechanical properties

Nanopowders of Fe, Al and Fe₂O₃ are fabricated by high energy ball milling. Using the pulsed current activated sintering method, the densification of nanocrystalline Fe₂Al₅ and Al₂O₃ reinforced Fe₂Al₅ composites were simultaneously synthesized and consolidated within two minutes from mechanically activated powders. The advantage of this process is that it allows very quick densification to near theoretical density and prohibition of grain growth in nanostuctured materials. Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties. As nanomaterials possess high strength, high hardness, excellent ductility and toughness, undoubtedly, more attention has been paid to the application of nanomaterials. Not only the hardness but also the fracture toughness of the Fe₂Al₅-Al₂O₃ composite was higher than that of monolithic Fe₂Al₅ due to the addition of the hard phase of Al₂O₃ and the crack deflection by Al₂O₃.     

Properties and pulsed current activated consolidation of nanostuctured MgSiO3-MgAl2O4 composites

Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties. As nanomaterials possess high strength, high hardness, excellent ductility and toughness, undoubtedly, more attention has been paid for the application of nanomaterials. Nanopowders of MgO, Al₂O₃ and SiO₂ were made by high energy ball milling. The simultaneous synthesis and consolidation of nanostuctured MgAl₂O₄-MgSiO₃ composites from milled 2MgO, Al₂O₃ and SiO₂ powders was investigated by the pulsed current activated sintering process. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition of grain growth. Highly dense nanostructured MgAl₂O₄-MgSiO₃ composites were produced with a simultaneous application of 80 MPa pressure and a pulsed current of 2000A within 1min. The fracture toughness of MgAl₂O₄-Mg₂SiO₄ composites sintered from 60 mol%MgO-20 mol%Al₂O₃-20mol%SiO₂ powders milled for 4 h was 3.2MPa·m^1/2. The fracture toughness of MgAl₂O₄-MgSiO₃ composite is higher than that of monolithic MgAl₂O₄.     

Simultaneous pulsed current activated combustion synthesis and densification of NbSi2–SiC composite

Dense ultrafine NbSi₂–SiC composite was synthesized by the pulsed current activated combustion synthesis (PCACS) method within 3 min in one step from mechanically activated powders of NbC and 3Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense NbSi₂–SiC composite with relative density of up to 97% was produced under simultaneous application of a 60 MPa pressure and the electric current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated.     

Sintering of binderless WC–Mo2C hard materials by rapid sintering process

High-frequency induction heated sintering (HFIHS) is a new rapid sintering method which was developed recently for the fabrication of ceramics and composites. This method combines a short time high-temperature exposure with pressure application. In this work, we reported results on the sintering of binderless WC–x wt.%Mo₂C (0 ≤ x ≤ 6) hard materials using ultra fine powders of WC and Mo₂C. A complete densification of the materials was achieved within 1 min. The relative densities of the composites were about 99% for an applied pressure of 60 MPa and an induced current for 90% output of total capacity. The Vickers hardness decreased and the fracture toughness increased with increasing the Mo₂C content.     

Development of an oral immunoadjuvant from cheonggukjang that is efficacious for both mucosal and systemic immunity

Immunological properties of a 50% ethanol/aqueous extract of cheonggukjang (CGJ), a fermented soybean product, were investigated as a potent, orallyavailable, and cost-effective immunoadjuvant. Different from cholera toxin, a widely used experimental oral adjuvant with effects limited to mucosal immunity in the gut, oraladministration of the CGJ extract had positive effects on both mucosal and systemic immunity. Administration of keyhole limpet hemocyanin (KLH) with the CGJ extract resulted in hyper-production of KLH-specific IgA in the gut and KLH-specific IgG in the serum. Oral-administration of the CGJ extract resulted in promotion of both Th1 and Th2 immune responses, thus eliminating concerns over an imbalanced Th1 and Th2 immune bias that is often observed upon administration of other commonly used immunoadjuvants. Ethanol/aqueous extraction of CGJ resulted in enrichment of polyphenolic compounds, including flavonoids, providing a potential extra health benefit.