Ohmic contact and transport properties of II–VI Green/Blue laser diodes

The employment of the Zn(Se,Te) pseudo-graded contacting scheme to p-type ZnSe-based alloys contributes directly to the recent demonstration of room temperature continuous-wave operation of II– VI green-blue laser diodes. Contact ohmicity is maintained down to cryogenic temperatures which enabled the investigation of electrical transport properties associated with the p-type nitrogen-doped ZnSe, Zn(S,Se), and (Zn,Mg)(S,Se). The observation of both persistent photoconductivity and a metastable population of holes which are in thermodynamic equilibrium with hydrogenic acceptors having reduced activation energy suggests the presence of a DX-like behavior for holes in p-type (Zn,Mg)(S,Se).     

Performance of TZCD-MBOK watermarking scheme in T-DMB systems

Recently, watermarking based data transmission techniques using terrestrial digital TV signal have been proposed since they are also cost-free and can overcome the limitations of GPS. However, in the previous watermarking based methods, the detection accuracy is low and additional data rate is too low. Thus, we propose the throughput enhancement method by employing the TZCD-MBOK watermarking technique in T-DMB system. By applying the proposed scheme to T-DMB, it allows additional data transmission for disaster broadcasting and improves efficiency of data transmission in shadow region and indoor to mobile environment through watermarking spread code. From the simulation results, we confirm the proposed watermarking scheme affected on the existing T-DMB signal. Moreover, it was also confirmed that the system capacity increases as the power of additional watermarking signal rose. The results of the paper can be applied to wireless multimedia digital broadcasting systems.     

Effects of intermetallic compound on the electrical and mechanical properties of friction welded Cu/Al bimetallic joints during annealing

Al/Cu metal joints applied for the electrical connector was joined by the friction welding method to limit the formation of intermetallic compound under optimum friction welding condition. To guarantee the reliability of the Al/Cu joints in service requirement, the effects of the intermetallic compound layer on the electrical and mechanical properties have been investigated under various annealing conditions. Two kinds of intermetallic compounds layer were formed in the joints interface and identified by AlCu and Al₂Cu. The growth kinetic of these intermetallics during the annealing can be followed by volume diffusion process. The activation energy of Al₂Cu, AlCu and total intermetallic compound (AlCu + Al₂Cu) represented 107.5, 98.42 and 110.22 kJ/mol, respectively. A thicker intermetallic compound layers could seriously degrade the electrical resistivity and tensile strength. The electrical resistivity with 21 μm thickness of intermetallic compound was 45 μΩ cm and increased to be 85 μΩ cm with 107 μm of intermetallic compound. Tensile strength remarkably decreased from 85 MPa to near zero at the annealing condition of 773 K and 129.6 ks and fracture occurred through the intermetallic compound layers.     

Blends of chlorinated isotactic polypropylene with poly(ethylene-co-vinyl acetate) II. Phase studies of the miscible blends

By measuring T_g, T_m and T_c (cloud point) phase diagrams for the four miscible blends of chlorinated isotactic polypropylenes (chlorine content 39.2 (CPP-40) and 49.8 wt.-% (CP-50)) with Poly(ethylene-co-vinyl acetate)s (vinyl acetate contents 40 (EVA-40) and 45 wt.-% (EVA-45)) were investigated. The blend of CPP-50 with EVA-40 was the most compatible of the four blend pairs.     

Bücherschau

Ohne Zusammenfassung VDI     

Preparation of ketoprofen‐loaded high‐molecular‐weight poly(vinyl alcohol) gels

High‐molecular‐weight atactic poly(vinyl alcohol) (a‐PVA) gels loaded with (R,S)‐2‐(3‐benzoylphenyl)propionic acid (ketoprofen) were prepared from 5, 6, 7, and 8 g/dL solutions of a‐PVA with a number‐average degree of polymerization of 4000 in an ethylene glycol/water mixture with an aging method to identify the effect of the initial polymer concentration on the swelling behavior, morphology, and thermal properties of a‐PVA gels. Then, the release behavior of ketoprofen from a‐PVA gels was investigated. As the polymer concentration decreased, the ability for network formation decreased, and the degree of swelling of the a‐PVA gels increased. In addition, the enthalpy increased with an increase in the a‐PVA concentration, but the melting temperatures of the gels prepared at different initial polymer concentrations were the same; this indicated that tighter gel networks would be formed by a higher polymer chain density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Performance of fluorine-added CoMoS/Al2O3 prepared by sonochemical and chemical vapor deposition methods in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

The performance of a new type of CoMoS/Al₂O₃ catalyst, with added fluorine and prepared by sonochemical and chemical vapor deposition (CVD) methods, was investigated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The catalyst, which was designed to contain optimum amounts of fluorine and cobalt, exhibited a higher activity, ca. 4.6 times higher activity particularly in the HDS of 4,6-DMDBT, than a fluorine-free catalyst prepared by a conventional impregnation method. The enhanced activity of the new catalyst can be attributed to the cumulative effects of individual factors involved in the catalyst preparation. That is, the use of a sonochemical synthesis led to a high dispersion of small MoS₂ crystallites on the alumina, and the addition of the Co species to the catalyst by CVD caused a close interaction between the Co species and the MoS₂ crystallites to produce numerous CoMoS species, which are the catalytically active species for HDS. The addition of fluorine increased the amounts of acidic sites in the catalyst, which promoted hydrogenation (HYD) route to a greater extent than the direct desulfurization (DDS) route in DBT HDS and both HYD and DDS routes to similar extents in the case of 4,6-DMDBT HDS. Accordingly, the addition of fluorine led to a greater increase in catalytic activity for 4,6-DMDBT HDS than for DBT HDS.