Extension of the RBD-FAST method to the computation of global sensitivity indices

This paper deals with the sensitivity analysis method named Fourier amplitude sensitivity test (FAST). This method is known to be very robust for the computation of global sensitivity indices but their computational cost remains prohibitive for complex and large dimensional models. Recent developments in the implementation of FAST by use of the random balance designs (RBD) technique have allowed significant reduction of the computational cost. The method is now called RBD-FAST. The drawback of this improvement is that only individual first-order sensitivity indices can be computed. In this article, an extension of RBD is derived for the estimation of any global sensitivity indices of individual factor or group of factors. Several tests are proposed to compare the performances of classical FAST and RBD-FAST.     

Motion planning for cooperative unicycle-type mobile robots with limited sensing ranges: A distributed receding horizon approach

This paper presents a decentralized motion planner for a team of nonholonomic mobile robots subject to constraints imposed by sensors and the communication network. The motion planning scheme consists of decentralized receding horizon planners that reside on each vehicle to achieve coordination among flocking agents. The advantage of the proposed algorithm is that each vehicle only requires local knowledge of its neighboring vehicles. The main requirement for designing an optimal conflict-free trajectory in a decentralized way is that each robot does not deviate too far from its presumed trajectory designed without taking the coupling constraints into account. A comparative study between the proposed algorithm and other existing algorithms is provided in order to show the advantages, especially in terms of computing time. Finally, experiments are performed on a team of three mobile robots to demonstrate the validity of the proposed approach.     

Tailoring of elastomeric grafted coating via sol–gel chemistry of crosslinked polymethylhydrosiloxane

Thin coating of crosslinked polymethylhydrosiloxane are grafted on silica using sol–gel process that leads to polymer layers tailored in term of thickness and elasticity. The degree of crosslinking is tuned by sol–gel polycondensation of a mixture of methyldiethoxysilane(DH) HSi(CH₃)(OCH₂CH₃)₂ and triethoxysilane (TH) HSi(OCH₂CH₃)₃, yielding triethoxysilane‐based networks. Samples with well‐defined thicknesses from nanometer to micrometer range are prepared by sol–gel dip‐coating method on silicon surface. Homogeneous or gradient‐thickness coating can be produced in this way. It results in surface‐attached networks bearing Si? H functionalities covalently anchored to the substrate. Powdered gels of DH/TH composition from 50/50 to 95/5 (mol %) were also prepared for a comparison purpose. The structure of the gels was investigated by NMR and FTIR, showing that DH/TH mixtures react totally to yield homogeneous matrix. The surface‐attached polymer films are very stable and present high hydrophobicity as evidenced by contact angle measurements. Their surface and mechanical properties have been qualitatively studied using the atomic force microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1504–1516, 2007     

Synthesis and applications of XAD-4-DAN chelate resin for the separation and determination of Se(IV)

Solid-phase extraction for cationic elements is a promising approach for water treatment or for analysis applications. However, supports that allow the selective extraction and/or preconcentration of metalloid species are still not widespread. A new chelating sorbent has been prepared by grafting 2,3-diaminonaphtalene (DAN) on Amberlite^® XAD-4 resin beads via a diazo bridge. The synthesis was first carried out at a molecular level to optimise experimental conditions and to facilitate characterisation of solid sorbent by FTIR. TGA, Py-GC/MS experiments and back titration of amine functions showed that the sorbent was grafted. Se(IV) was retained by grafted Amberlite^® XAD-4 with a rate of 88% at pH 2 and 80 °C. This paper presents a convenient way of grafting DAN on polystyrene-like resins and the first applications of these supports in solid-phase extraction of Se(IV).     

满足对背板连接器在信号速率和密度方面的更高要求

对电信和数据通信系统的设计者来说，高达12Gb／s的数据速率已经成为满足当前与未来市场要求的最新基准。但是，只要还使用背板连接，速度就不是唯一一个需要解决的问题。芯片设计师、参考设计单位、系统设计师们认为更高的信号密度具有同等重要性。     

EEG-based synchronized brain-computer interfaces: a model for optimizing the number of mental tasks.

The information-transfer rate (ITR) is commonly used to assess the performance of brain-computer interfaces (BCIs). Various studies have shown that the optimal number of mental tasks to be used is fairly low, around 3 or 4. We propose an experimental validation as well as a formal approach to demonstrate and confirm that this optimum is user and BCI design dependent. Even if increasing the number of mental tasks to the optimum indeed leads to an increase of the ITR, the gain remains small. This might not justify the added complexity in terms of protocol design.     

Effect of cations on corrosion of zinc and carbon steel covered with chloride deposits under atmospheric conditions

The effect of sodium, calcium, and magnesium chlorides deposited on zinc and carbon steel surfaces was studied under atmospheric conditions. The cations strongly affected the corrosion rate of zinc, whereas they had a significantly lower impact on the corrosion of carbon steel. The corrosivity of cations of chloride salts for zinc increased in order of Mg²⁺ < Ca²⁺ < Na⁺. The higher corrosion resistance of zinc treated with calcium and magnesium chlorides was connected to prevention of formation of hydrozincite during zinc exposure in wet air. It was observed that zinc weight loss and the carbonate to simonkolleite ratio in corrosion products were correlating. The principal protective effect of bivalent cations can be seen in the decrease of pH of the surface electrolyte, which was caused by hydrolysis of such cations and subsequent formation of simonkolleite that blocked the cathodic sites.     

In situ studies of the corrosion during drying of confined zinc surfaces

The corrosion process during the drying out of zinc surfaces confined in crevices was studied using real time photograpy and in situ FTIR microspectroscopy. A pH‐indicator was used to visualise differences in the pH during the drying process. The distribution and the composition of the corrosion products after several wetting and drying cycles were studied with FTIR microspectroscopy and SEM‐EDS. An area with high pH formed during the drying process at the border of the electrolyte, with a zone of white corrosion products that contained zinc hydroxycarbonate in the electrolyte inside this area. A differential aeration cell is present at the border of the electrolyte, and the cathodic oxygen reduction reaction takes place close to the border of the electrolyte during the drying process. The corrosion attack and the distribution and composition of the corrosion products on the surface depend strongly on the drying process of the surface. The corrosion attack of confined surfaces was localised, with a significantly higher corrosion attack in some areas. Outside the drying front a thin layer of electrolyte formed as a result of surface tension driven flow of electrolyte from the electrolyte border. This effect was attributed to the alkaline pH of the electrolyte due to the oxygen reduction reaction at the border. A galvanic element was formed between the local cathodes in the area outside the drying front and the anode in the area with bulk electrolyte. The main corrosion products detected after several wet dry cycles were ZnO, Zn₅(OH)₆(CO₃)₂ and Zn₅(OH)₈Cl₂ · H₂O, but Na₂CO₃ · 10H₂O was also detected. The corrosion products were non‐homogeneously distributed on the surface and the distribution was related to the anodic and cathodic processes that took place in different regions on the surface during the corrosion process.     

Electrodeposition of Inorganic/Organic Hybrid Thin Films

Electrodeposition of inorganic compound thin films in the presence of certain organic molecules results in self‐assembly of various hybrid thin films with new properties. Examples of new discoveries by the authors are reviewed, taking cathodic formation of a ZnO/dye hybrid as the leading example. Hybridization of eosinY leads to the formation of highly oriented porous crystalline ZnO as the consequence of dye loading. The hybrid formation is a highly complicated process involving complex chemistry of many molecular and ionic constituents. However, electrochemical analyses of the relevant phenomena indicate the possibility of reaching a comprehensive understanding of the mechanism, giving us the chance to further develop them into industrial technologies. The porous crystals are ideal for photoelectrodes in dye‐sensitized solar cells. As the process also permits the use of non‐heat‐resistant substrates, the technology can be applied for the development of colorful and light‐weight plastic solar cells.