273 research outputs found
Preparation of highly visible-light active N-doped TiO<sub>2</sub> photocatalyst
No full textA series of N-doped anatase TiO2 samples have been prepared using a solvothermal method in an organic amine/ethanol–water reaction system. The effects of different starting N:Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated. The photocatalytic activity and stability of the N-doped TiO2 samples were evaluated through using the decomposition of Methylene blue (MB) and Methyl orange (MO) as model reaction under visible light irradiation. Characterization results show that the nitrogen dopant has a significant effect on the crystallite size and optical absorption of TiO2. It was found that the N-doped TiO2 catalysts have enhanced absorption in the visible light region, and exhibit higher activity for photocatalytic degradation of model dyes (e.g. MB and MO). The catalyst with the highest performance was the one prepared using N:Ti molar ratio of 1.0. Electron paramagnetic resonance (EPR) measurement suggests the materials contain Ti3+ ions, with both the degree of N doping and oxygen vacancies make contributions to the visible light absorption of TON. The presence of superoxide radicals (O•-) and hydroxyl radicals (•OH) on the surface of TON were found to be responsible for MB and MO solution decoloration under visible light. Based on the results of the present study, a visible light induced photocatalytic mechanism has been proposed for N-doped anatase TiO2
Influence of trimethylsilane flow on the microstructure, mechanical and tribological properties of CrSiCN coatings in water lubrication
No full textCrSiCN coatings with different silicon and carbon contents were deposited on silicon wafers and 316L stainless steels using unbalanced magnetron sputtering via adjusting trimethylsilane (TMS) flow, and their microstructure and mechanical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectrons spectroscopy (XPS) and nano-indenter, respectively. The tribological properties of CrSiCN coatings sliding against SiC balls in water were investigated using ball-on-disk tribometer. The results showed that the CrSiCN coatings had fine composite microstructure consisting of nanocrystallites of Cr(C, N) crystal and amorphous phases such as a-Si3N4 and a-C(a-CNx). The typical columnar structures changed from fine cluster to coarse ones when the Si content was beyond 3.4 at.%. With an increase in the TMS flow, the hardness and Young's modulus of Corsican coatings all first increased, and then rapidly decreased, but the compressive stress in the coatings varied in the range of 2.8–4.8 GPa. When the TMS flow was 10 sccm, the CrSiCN coatings exhibited the highest hardness of 21.3 GPa and the lowest friction coefficient (0.11) and wear rate (8.4 × 10-8 mm3/N m). But when the TMS flow was beyond 15 sccm, the tribological properties of CrSiCN coatings in water became poor
Examining the effect of the aging state on strength and plasticity of wrought aluminum alloys
No full textA general rule of strength and plasticity is proposed for three typical wrought Al alloys (2xxx, 6xxx, and 7xxx) subjected to different aging times. Investigations of the work-hardening processes and dislocation configurations in tensile and compressive testing reveal that this general rule arises because there is a common mechanism for these three kinds of wrought alloys whereby the tendency for cross-slip increases monotonously with aging time. By analyzing the strain hardening exponent and the stacking fault energy, it is demonstrated that the change in the dislocation slip mode is attributed mainly to the formation of second phases rather than to the matrix composition. Accordingly, a new work-hardening model is proposed for wrought Al alloys containing second phases and this explains the interaction between dislocations and second phases and other relevant experimental phenomena. This study is therefore beneficial for quantitatively investigating and optimizing the strength and plasticity of wrought aluminum alloys
Study on the photocatalysis of F-S co-doped TiO2 prepared using solvothermal method
No full textFluorine–sulfur (F–S) co-doped TiO2 materials have been prepared using low-temperature solvothermal method, and tested for catalytic activity by the visible light photocatalytic degradation of the Methylene Blue. For comparison, the mono-elemental doped samples, e.g., S- and F-doped TiO2 have also been prepared and tested under the same conditions. The characterization results showed that F–S co-doped TiO2 has a higher photocatalytic activity than that of mono-doped F- and S-doped samples under visible light irradiation. It is believed that the co-doping gives rise to a localized state in the band gap of the oxide and creates active surface oxygen vacancies, both which are responsible for visible light absorption and the promotion of electrons from the localized states to the conduction band. Characterization by electron paramagnetic resonance revealed the presence of a superoxide radical (O2?) which may be mainly responsible for photodegradation of Methylene Blue under visible light
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No full text[No abstract available][Anonymous], 12 MONTH MONT BLANC; [Anonymous], VERTEPORFIN COMBINAT; Bashshur ZF, 2011, RETINA-J RET VIT DIS, V31, P636, DOI 10.1097-IAE.0b013e3181fe54ab0
Necessity of paracentesis before or after intravitreal injection of bevacizumab - Reply
No full text[No abstract available]Bashshur ZF, 2007, ARCH OPHTHALMOL-CHIC, V125, P1357, DOI 10.1001-archopht.125.10.13571
The Modular VZ window
No full textCurrently the building construction industry is still using its traditional way to make buildings and leads to several issues, high energy consumption, more waste than needed, less profit, not optimized and high failure cost. This is because each and every building is unique and the wheel is reinvented for every designed building. The reason of traditional building is rooted in the process of thinking in the building construction industry, because the client wants to have a building designed according to his wishes. However the client lacks knowledge to make a building. This knowledge has to be giving by advisors who will give advice each of them in the flow of the process. This will lead to an accumulation of knowledge instead of an integration of it. This design is then delivered to the contractor who tries to build the design in the cheapest way possible. Whereas the subcontractor needs to deliver the best price for his services. So the manufacturer need to focus on marketing to make profit and their main focus is on selling their own product. When we are looking at the different kind of production industries like car, computer, airplane industry. They keep improving their products while keeping the structure of their products the same. This process need to be introduced to give the building industry more standardization, flexibility and integration while keeping each building unique. The building are kept up to date whereas the buildings that are built now, are already older than the current technical level. The next problem is the energy consumption of the current building stock and the future created buildings. The building sector is using 40% of the energy generated and can be potentially reduced by combining the different expertise’s together in one product. That is why the following window product is developed to answer the needs of these occurring problems. A usual building construction process follows the following scheme: A problem needs to be solved -> solutions are developed -> a product is designed and produced. However looking at different other industries e.g. the mobile phone. An idea is created by doing a research on what the market wants. With this information the demands are made to specify the scope of the design and through an elimination of concepts, a design is created that will satisfy the need of the market. Currently the architect search for all these different product and combine these together. This makes every product unique and the change of failure is higher than when an integrated product can be used. When it does fail, the different product manufactures start blaming each other about who caused the problems instead finding the solution. This change of process is introduced in the modular window product whereas the architect has the freedom to design, form, specify his own preferences while the product is tested and the chance of failing will be limited. By introducing this product, the building construction industry will be able to improve the building while reducing the amount of waste and impact to the environment. Through this integrated approach, there will be more user satisfaction, flexibility in the façade and more profit for all the stakeholders involved in the process. The modular window concept integrates sun shading and ventilation as modular elements in the window. This is done by creating a functional gap on top of the standard window. So the window stays free for the architect to play with in an aesthetic way, while the functions can be attached directly or on a later stage of the life cycles. The advantages lies that sun shading will not interfere with the ventilation system when placed later and the product is adaptable.Building TechnologyArchitecture and The Built Environmen
Catalytic ammonia decomposition over CMK-3 supported Ru catalysts: Effects of surface treatments of supports
No full textCMK-3 carbon was used as a catalyst support for Ru catalyst for ammonia decomposition. The supports were treated with acid, and the effects of treatment on the properties of CMK-3 supports were studied by N2 adsorption, XRD, XPS and mass titration. The chemical treatment of carbon support cause significant changes in carbon surface chemistry and in turn had significant effects on both catalyst dispersion and catalytic activity. It is found that the as-synthesized CMK-3 carbon is not a good catalyst support for this reaction. However, surface functional groups produced by acid treatments led to larger Ru catalyst particles, while alkali treatments made the Ru catalyst dispersion even worse due to the residue alkali or earth alkali metals. Interestingly, relatively larger Ru catalyst particles but still well dispersed in the channel of the mesoporous structures of the carbon improves NH3 conversion into H2. This is determined by the chemical reaction rate-limiting step of ammonia decomposition. The catalytic activity follows the order: Ru-K/CMK-3 > Ru-Na/CMK-3 > Ru-Ca/CMK-3 > Ru-Cl/CMK-3 > Ru-SO4/CMK-3 > Ru-PO4/CMK-3 > Ru/CMK-3 > Ru-Li/CMK-3. CMK-3 is not a good carbon catalyst support due to its amorphous structure resulting in the poor electron conductivity. © 2006 Elsevier Ltd. All rights reserved.L. Li, Z.H. Zhu, G.Q. Lu, Z.F. Yan, S.Z. Qia
Fuzzy Analytic Hierarchy Process for Risk Assessment to General-assembling of Satellite
No full textAbstractWith a fuzzy analytic hierarchy process, the hierarchy of risk factors in satellite general-assembling process is established, based on which, the weights of various risk factors are determined one by one. Furthermore, the risk factors are quantitatively analyzed, and the comprehensive risk assessment model is established in the end. Taking a satellite model as an example, the risks in the satellite general-assembling process are assessed comprehensively, and the risk levels are quantitatively measured. The factors are sorted according to their impact capabilities to the overall risk level, and the key points of risk control for satellite general-assembling process is clarified. Results obtained from the analysis to risk sub-factors suggested that experience and techniques, narrow space and production rhythm are more detrimental to process risk than any other sub-factors. The results also show that the risk could be mitigated, provided that the effectiveness of engineering measures against deficiencies in the most influential (sub-)factors is maintained. The rationality and feasibility of the proposed method model is proved by the engineering application, which provide the effective technical support for the risk control in satellite general-assembling process
Robust Observer Design for a Class of Nonlinear Systems Using the System Internal Dynamics Structure
No full textIn this paper, an observer design strategy is presented for a class of nonlinear systems with structural uncertainty. The modern geometric approach is exploited to simplify the system structure. Then, based on the Lyapunov direct method, a robust observer is proposed using the system internal dynamics structure and the distribution of the uncertainty structure. The bound on the uncertainty, which is employed in the observer design, is allowed to be nonlinear and have a more general form. Simulation shows that the proposed approach is effective
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