Hybrid Methods for Detection and Identification of Faults in Dynamic Systems

Since the 1960s, when automation became essential to productivity, methods for the detection and identification of faults have been proposed. Physical systems are diversified and can be mechanical, electrical, pneumatic, electronic, or a combination of these. In addition, real plants have a large number of these devices, which are for its own operation, sensoring or control. Therefore the solutions given for detection of faults are generally very specific or particular. This paper aims to describe and analyze two hybrid methods of detection and fault identification based on residue and to check whether their inclusion with other methods, combining different techniques, can produce a better fault detection and identification system. The methods use the state observers for the generation of residues, which serve for the detection and identification and the set called the bank of signatures to identify the faults. Thereafter, the methods use different approaches to diagnose the fault: the first uses the approach of the mean square error, and the second uses a decision tree.     

Novel carbon nanosheets as support for ultrahigh-resolution structural analysis of nanoparticles

The resolution in transmission electron microscopy (TEM) has reached values as low as 0.08 nm. However, these values are not accessible for very small objects in the size range of a few nanometers or lower, as they have to be placed on some support, which contributes to the overall electron-scattering signal, thereby blurring the contrast. Here, we report on the use of nanosheets made from cross-linked aromatic self-assembled monolayers as TEM sample supports. When transferred onto a copper grid, a single 1.6-nm-thick nanosheet can cover the grid and is free standing within the micron-sized openings. Despite its thinness, the sheet is stable under the impact of the electron beam. Micrographs taken from nanoclusters onto these nanosheets show highly increased contrast in comparison to the images taken from amorphous carbon supports. In scanning transmission electron microscopy with nanosheet support, a size analysis of sub-nanometer Au clusters was performed and single Au atoms were resolved.     

Effect of a desk attachment board on posture and muscle activity in women during computer work

Working at a computer is part of a large number of jobs and has been associated with upper extremity musculoskeletal disorders and back pain. The study evaluated the effects of a board attachment on upper extremity and back. The findings are mixed in that the board may have a positive effect in preventing back pain, but may be detrimental to upper extremities. Effect of a desk attachment board on upper extremity and trunk posture, and muscle activity was assessed in women video display terminal users. Participants completed a standard 20-min computer task under two conditions: 1) using a standard desk; 2) using a desk attachment board designed to support the forearms. Bilateral electromyography of the trapezius, multifidus and longissimus muscles and the right anterior deltoid and forearm extensor muscles was recorded. 3-D trunk and upper extremity posture was monitored. Participants were tested before and after 2 weeks of familiarisation with the board in their workplace. Perceived tension and discomfort were recorded before and after use of the board. Use of the board tended to increase muscle activity in the right trapezius and forearm extensor and to decrease muscle activity in the back. Perceived tension in the low back decreased slightly with the board. The board may be useful in reducing tension in the low back during computer work, but may adversely affect the upper extremities.     

Too much computer and Internet use is bad for your grades, especially if you are young and poor: Results from the 2001 Brazilian SAEB

This work presents the analysis of the 2001 Brazilian Basic Education Evaluation System (SAEB) achievement exam. The SAEB tested 4th, 8th, and 11th grade students, in mathematics and reading (Portuguese). We classified the students into seven socioeconomic classes, and for each class, compared the test results according to frequency of computer use, computer ownership, Internet access at home, and whether the teachers used computers and Internet as pedagogical tools. Frequency of computer use had, in general, a negative effect on the test results, and the negative effect increased for younger and poorer students. Computer ownership had, in general, a small positive effect on the test results for older students, and no effect for 4th graders. Internet access had a negative effect for younger and poorer students, and a positive effect for 11th graders. Finally, whether the teacher used computers or Internet as pedagogical tools had no effect on the student’s test results for all social economic classes and grades.     

Nanomicrobiology

Recent advances in atomic force microscopy (AFM) are revolutionizing our views of microbial surfaces. While AFM imaging is very useful for visualizing the surface of hydrated cells and membranes on the nanoscale, force spectroscopy enables researchers to locally probe biomolecular forces and physical properties. These unique capabilities allow us to address a number of questions that were inaccessible before, such as how does the surface architecture of microbes change as they grow or interact with drugs, and what are the molecular forces driving their interaction with antibiotics and host cells? Here, we provide a flavor of recent achievements brought by AFM imaging and single molecule force spectroscopy in microbiology.     

Synthesis and characterization of ultraviolet‐curable fluorinated polydimethylsiloxanes as ultraviolet‐transparent coatings for optical fiber gratings

Synthesis of photocrosslinkable fluorinated polydimethylsiloxane (PDMS) was carried out through the direct hydrosilylation of allyl 2‐(perfluorohexyl)ethyl ether with copoly(dimethyl methyl hydro siloxane). The hydrosilylation of the fluorinated allyl ether allowed the introduction of fluorinated groups onto the polysiloxane backbone. Then, a second hydrosilylation of allyl methacrylate led to PDMS bearing both fluorinated and photocrosslinkable groups. The ratio between fluorinated groups and allyl methacrylate groups allowed us to tune the refractive index of the resin without changing thermal properties. Formulations containing fluorinated PDMS were ultraviolet‐cured, and their ultraviolet transparency and Yttrium Aluminium Garnet (YAG) laser resistance were investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2021–2026, 2003     

Irrigation and crop diversification in the 25 de Setembro irrigation scheme,Mozambique

Abstract

Crop diversification is one way of improving the profitability of small-scale irrigation schemes. The 25 de Setembro scheme is an ideal site to analyze diversification, as it is influenced by the markets in Maputo and South Africa. This study uses information gathered from observations, discussions with irrigators and an irrigator survey. Results identified seven irrigator types with different crop diversification strategies predominantly influenced by resource constraints. Most irrigators produce traditional crops, although there are opportunities for growing crops that are more profitable. Improved extension services, to identify cropping strategies that better align with market demand, would improve profitability.     

Contract signing, optimism, and advantage

A contract signing protocol lets two parties exchange digital signatures on a pre-agreed text. Optimistic contract signing protocols enable the signers to do so without invoking a trusted third party. However, an adjudicating third party remains available should one or both signers seek timely resolution. We analyze optimistic contract signing protocols using a game-theoretic approach and prove a fundamental impossibility result: in any fair, optimistic, timely protocol, an optimistic player yields an advantage to the opponent. The proof relies on a careful characterization of optimistic play that postpones communication to the third party.     

SAR imagery to estimate roughness parameters when modelling runoff risk

The influence of the roughness of agricultural soil on runoff and erosion is a proven fact. Synthetic aperture radar (SAR) sensors should enable discrimination between plots with different cropping patterns. A study of Mediterranean vineyards in southern France was made, with the aim of obtaining a better understanding of the potential for using radar satellite data from ERS-1 when estimating roughness parameters. Roughness measurements enabled modelling of the backscattering coefficient (sigma0) of known surfaces, using the electromagnetic Integral Equation Model (IEM). The good correlation between ERS-1 and IEM data indicated the feasibility of extracting roughness parameters by means of remote sensing methods. Seven ERS-1 images were examined, corresponding to different stages in the development of vegetation and roughness. Two images were finally selected as they offered the possibility of discriminating between two factors: (1) the orientation of mechanical labour, which can be related toa periodic and stable roughness over time, and (2) cropping practices, corresponding to a random roughness pattern that changes with season. Both roughness parameters derived from SAR satellite data contribute additional data to runoff models a preferred runoff direction as defined by furrow direction, as well as the intensity of this runoff under the influence of random roughness. A rule for the behaviour of sigma0 in terms of furrow orientation is presented.