Large area ZnO films optimized for graded band-gap Cu(InGa)Se2-based thin-film mini-modules

In this study, two deposition methods (i.e. MOCVD and sputtering methods) to prepare n-type ZnO window layers for CIGS-based thin-film solar cells are discussed. In order to make ZnO : Al transparent conductive oxide (TCO) films prepared by DC magnetron sputtering comparable to ZnO : B TCO prepared by MOCVD, a new ZnO sputtering process is proposed by introducing a multilayer structure. Using these films, CIGS thin-film solar cells with efficiencies of greater than 14% have been fabricated with an active area of 3.2 cm². This structure was adapted to fabricate CIGS thin-film mini-modules with efficiencies around 11% having aperture area of 50 cm².     

A molecular orbital study on the chemical interaction across the indomethacin/silica interparticle boundary due to mechanical stressing

A discrete variational-Xα (DV-Xα) method was applied to elucidate the formation of C-O-Si bridging bonds, produced when a silanol group of SiO₂ comes close enough to react with a carboxyl group of indomethacin (IM). A decrease in the coordination number (CN) of oxygen atoms per silicon atom at the SiO₂ surface increased the net charge (NC) of the silanolic hydrogen atom and decreased the bond overlap population (BOP) between the silanolic oxygen and hydrogen atoms. These changes favored the formation and stabilization of C-O-Si bridging bonds with simultaneous dehydration. The computational results agreed well with our previous experimental study of a ground indomethacin-SiO₂ mixture to obtain a better solid dispersion of the drug.     

On Efficient Traffic Distribution for Disaster Area Communication Using Wireless Mesh Networks

In recent time, a great deal of research effort has been directed toward promptly facilitating post-disaster communication by using wireless mesh networks (WMNs). WMN technology has been considered to be effectively exploited for this purpose as it provides multi-hop communication through an access network comprising wireless mesh routers, which are connected to the Internet through gateways (GWs). One of the critical challenges in using WMNs for establishing disaster-recovery networks is the issue of distributing traffic among the users in a balanced manner in order to avoid congestion at the GWs. To overcome this issue, we envision a disaster zone WMN comprising a network management center. First, we thoroughly investigate the problem of traffic load balancing amongst the GWs in our considered disaster zone WMN. Then, we develop traffic load distribution techniques from two perspectives. Our proposal from the first perspective hinges upon a balanced distribution of the bandwidth to be allocated per user. On the other hand, our second perspective considers the dynamic (i.e., varying) bandwidth demands from the disaster zone users that requires a more practical and refined distribution of the available bandwidth by following an intelligent forecasting method. The effectiveness of our proposals is evaluated through computer-based simulations.     

Reactive and selective redox system of Ni(II)-ferrite for a two-step CO and H2 production cycle from carbon and water

A number of redox systems composed of carbon and bivalent metal-ferrites, MFe₂O₄(M = bivalent metal ions), were studied to find the most reactive and selective working materials for a thermochemical water-decomposition cycle combined with CO production from a carbon compound. Magnetite and Mg(II)-, Mn(II)-, Co(II)-, Ni(II)-, and Zn(II)-ferrites mixed with carbon powder have been screened for reactivity and selectivity in the CO-production step (first step) and subsequent water-decomposition step (second step). The Ni(II)-ferrite showed the most reactivity and selectivity for CO formation from carbon in the first step at temperatures above 700°C. The Ni(II)-ferrite could be completely reduced with carbon to the metallic phase of the Ni---Fe alloy and Ni in the first step although only a small portion of magnetite was reduced to wustite under similar conditions. The ferrites reduced in the first step were oxidized with water vapor to generate H₂ in the second step. The highest conversion of H₂O to H₂ was obtained using the Ni(II)-ferrite. The total amount of evolved H₂ using Ni(II)-ferrite was 10 times larger than for the magnetite at 500°C. The processes could be repeated using the phase transition between Ni(II)-ferrite and Ni---Fe alloy in the temperature range 700–800°C, with the highly efficient net reaction H₂O + C → H₂ + CO.     

Effect of ZnO doping on morphology and electrochemical properties of sub-micron RuO2 sensing electrode of DO sensor

Thick-film 20 mol% ZnO-doped RuO₂ sensing electrodes (SEs) were fabricated by screen-printing technique on the platinised alumina substrate of the planar electrochemical dissolved oxygen (DO) sensor. The effect of ZnO doping on morphology, electrochemical properties and sensing characteristics of the sensor was investigated. It was found that ZnO doping has not only improved the SE structure, but has also enhanced selectivity of the DO sensor. Selectivity testing exhibited that the presence of Cl⁻, Li⁺, SO₄²⁻, NO³⁻, Ca²⁺, PO₄³⁻, Mg²⁺, Na⁺ and K⁺ with a concentration range of 10⁻⁷ to 10⁻¹ mol/L in the solution had practically no effect on the sensor's emf. The reason in enhancement of the sensor characteristics could be related to the establishment of the better structured SE as more advanced crystallization is achieved for the doped RuO₂-SE.     

Nano-strip grating lines self-organized by a high speed scanning CW laser

After a laser annealing experiment on Si wafer, we found an asymmetric sheet resistance on the surface of the wafer. Periodic nano-strip grating lines (nano-SGLs) were self-organized along the trace of one-time scanning of the continuous wave (CW) laser. Depending on laser power, the nano-trench formed with a period ranging from 500 to 800 nm with a flat trough between trench structures. This simple method of combining the scanning laser with high scanning speed of 300 m min(-1) promises a large area of nanostructure fabrication with a high output. As a demonstration of the versatile method, concentric circles were drawn on silicon substrate rotated by a personal computer (PC) cooling fan. Even with such a simple system, the nano-SGL showed iridescence from the concentric circles.     

Bubble behavior in vertical tube banks installed in a fluidized bed

Fluidized bed combustion is one of the advantageous technologies for coal and/or incineration firing especially with respect to the environmental protection of emissions, such as NO_x/SO_x. Bed material movement in such a fluidized bed has a prime importance in the heat transfer process. Thus, quantitative measurement of the bed material movement and the void fraction are indispensable for better understanding of the fluidized bed. In this investigation, neutron radiography is applied to visualize the bed material movement in a simulated fluidized bed heat exchanger installed with vertical tubes. Bubble behavior and void fraction profile are obtained by the image processing technique. Bubble movement is highly restrained by these vertical tubes, so that the bubbles rise up along the tube. The bubble diameter is well correlated by the modified Mori and Wen's correlation taking into account the pitch of the tube arrangement. The bubble rise velocity and void fraction are well correlated by applying the drift‐flux model. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 727–739, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10127     

Bradykinin stimulates type II alveolar cells to release neutrophil and monocyte chemotactic activity and inflammatory cytokines

In the present study, we evaluated the potential of bradykinin (BK) to induce the release of neutrophil and monocyte chemotactic activity (NCA and MCA) and cytokines from an alveolar type II epithelial cell line, A549 cells. BK stimulated A549 cells to release NCA and MCA in a dose- and time-dependent manner (P < 0.001). Checkerboard analysis revealed that both NCA and MCA involved chemotactic and chemokinetic activity. Molecular sieve column chromatography showed three molecular weight masses (near 19 kd, 8 kd, and 400 d) for NCA and several molecular weight peaks (near 66 kd, 25 kd, 19 kd, 16 kd, and 400 d) for MCA. The release of NCA and MCA was inhibited by cycloheximide and lipoxygenase inhibitors (P < 0.01). The NCA and MCA were inhibited by leukotriene B4 (LTB4) receptor antagonist (P < 0.01), and the concentration of LTB4 was high enough for NCA and MCA. Antibodies to interleukin (IL)-8 and granulocyte colony-stimulating factor (G-CSF) attenuated NCA (P < 0.01), and antibodies to monocyte chemotactic protein-1 (MCP-1), G-CSF, and transforming growth factor (TGF)-beta attenuated MCA (P < 0.01). The levels of IL-8, G-CSF, MCP-1, and TGF-beta increased time dependently (P < 0.01). BK also stimulated the release of ILeukin-6 from A549 cells (P < 0.001). The receptors responsible for the release of NCA, MCA, and individual chemokines involved both BKB1 and BKB2 receptors. These data suggest that BK may stimulate alveolar type II pneumocytes to release inflammatory cytokines, which then may modulate the lung inflammation.