Wetting Properties of Steel Surfaces Modified by Laser Interference Metallurgy

The wetting properties of 100Cr6 bearing steel surfaces modified using laser interference metallurgy (LIMET) are analyzed. The steel surfaces are structured with line‐like patterns with line‐spacing. The topography of the ridged surface is analyzed by means of white light interferometry and scanning electron microscopy and surface chemistry of the different topographic regions by Raman spectroscopy. Contact angle (CA) measurements are performed on modified and non‐irradiated surfaces, using bi‐distilled water and FVA2 industrial oil. The angles are measured parallel and perpendicular to the line‐pattern orientation. The topographical analysis shows steep line‐pattern produced by laser. Raman analysis indicates that the laser irradiation does not significantly change the chemical species of the modified surfaces. The CA measurements elucidates that the parallel orientation provides a better wetting of the surface, because the laser line‐pattern acts as capillary flow channels, whereas the perpendicular orientation imposes energy barrier thus preventing wetting. As expected, the wetting coverage is more effective for larger than for smaller periodic structures, due to the larger area of flat contact. These novel results highlight the relevant use of LIMET to tailor the wetting properties of steel surfaces.     

The Effect of Seasonal Variations,Covariations with Minerals and Forage Value on Itchgrass’ Foliar Silicification from Sudanian Benin

Silica (SiO ₂) in forage grasses has been found in reducing cell-wall digestibility. This study investigates whether: (i) the seasonal variability affects the silica and minerals accumulation and forage values of leaves of R. cochinchinensis and (ii) silica concentration is correlated with minerals and fodder value. In an itchgrass population selected in the W Biosphere Reserve, leaves were collected on 90 marked plants from May to October 2003 and 2004, at 15 days intervals except May, June and October. Some 300 g of fresh blades from the 3 ^rd most recently expanded leaves were oven dried and analyzed for dry mass, SiO ₂, ash, N, Na, Ca, P, K, and Mg. Digestible Nitrogen Matter (DNM) and Fodder Energetic Value (FEV) were calculated using the Demarquilly formula. Apart from SiO ₂, ash and forage value, data were log-transformed to restore homoscedasticity before statistical analyses. SiO ₂ ranges from 5.69 % to 9.95 %, i.e. varying 1.4 fold between May and October, reaching 1.75 fold at mid-September. SiO ₂ is positively related to Ca but negatively to K, P, N, DNM and FEV. The negative correlations suggest that SiO ₂ concentration in R. cochinchinensis could be reduced with a significant increase in energy and accumulation of important nutrients such as N, P and K. Therefore, leaf silicification and nutritive value relationship should be conclusive in the case of itchgrass.     

Investigation of elastic constants of polymer/nanoparticles composites using the brillouin spectroscopy and the mechanical homogenization modeling

A numerical model using homogenization techniques is proposed to simulate the evolution of elastic properties of nanocomposite polymer‐nanoparticles, depending on the concentration of nanoparticles and the rigidity of the particle–matrix interface. To validate this model, it was confronted to several physical systems having different interface behavior, the nanocomposite systems: poly(vinylidene fluoride trifluoroethylene)/Al₂O₃ (alumina nanoparticles incorporated into copolymer of vinylidene difluoride and trifluoroethylene to form nanocomposite), PMMA/CNT (carbon nanotube/poly(methyl methacrylate) composite) and PMMA/SiO₂ with nanoparticles with or without surface treatment of silanization. For all these systems, the Young's modulus (nanoparticles and matrix) has been obtained experimentally from the elastic modulus C₁₁ obtained by Brillouin spectroscopy. These macroscopic measurements coupled with the theoretical model allow a multiscale approach of the elastic behavior of nanocomposite systems, providing information on the global elastic properties of polymer‐nanoparticle material, and also indications about the strength of physical and chemical bonds between the nanoparticles and the matrix. Our results validate the hypothesis of the crucial role of the interface module, provided by numerical simulation which shows that incorporation of nanoparticles may lead to a strengthening or a weakening of the matrix. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.     

Life cycle analysis of 4.5 MW and 250 W wind turbines

Electric generation by wind turbine is growing very strongly. However, the environmental impact of wind energy is still a matter of controversy. This paper uses Life Cycle Assessment, comparing two systems: a 4.5 MW and a 250 W wind turbines, to evaluate their environmental impact. All stages of life cycle (manufacturing, transports, installation, maintenance, disassembly and disposal) have been analysed and sensitivity tests have been performed. According to the indexes (PEPBT (primary energy pay back time), CO₂ emissions, etc.), the results show that wind energy is an excellent environmental solution provided first, the turbines are high efficiency ones and implemented on sites where the wind resource is good, second, components transportation should not spend too much energy and, third, recycling during decommissioning should be performed correctly. This study proves that wind energy should become one of the best ways to mitigate climate change and to provide electricity in rural zones not connected to the grid.     

Finite time thermodynamics study and exergetic analysis of ammonia–water absorption systems

This paper presents an optimization study of a single stage absorption machine operating with an ammonia–water mixture under steady state conditions. The power in the evaporator, the temperatures of the external fluids entering the four external heat exchangers as well as the effectiveness of these heat exchangers and the efficiency of the pump are assumed fixed. The results include the minimum value of the total thermal conductance UA_tot as well as the corresponding mean internal temperatures, overall irreversibility and exergetic efficiency for a range of values of the coefficient of performance (COP). They show the existence of three optimum values of the COP: the first minimises UA_tot, the second minimises the overall irreversibility and the third maximises the exergetic efficiency. They also show that these three COP values are lower than the maximum COP which corresponds to the convergence of the internal and external temperatures towards a common value. The influence of various parameters on the minimum thermal conductance of the heat exchangers and on the corresponding exergy efficiency has also been evaluated. From an exergetic viewpoint it is interesting to reduce the temperature at the desorber and at the evaporator and to raise the values of that parameter at the condenser and the absorber. However these changes must be accompanied by an important increase in the total UA if it is desired to conserve a constant COP. The internal heat exchangers between the working fluid and the solution improve both the overall exergy efficiency and the coefficient of performance of the absorption apparatus.     

Electrospray micromixer chip for on-line derivatization and kinetic studies

An electrospray microchip for mass spectrometry comprising an integrated passive mixer to carry out on-chip chemical derivatizations is described. The microchip fabricated using UV-photoablation is composed of two microchannels linked together by a liquid junction. Downstream of this liquid junction, a mixing unit made of parallel oblique grooves is integrated to the microchannel in order to create flow perturbations. Several mixer designs are evaluated. The mixer efficiency is investigated both by fluorescence study and mass spectrometric monitoring of the tagging reaction of cysteinyl peptides with 1,4-benzoquinone. The comparisons with a microchip without a mixing unit and a kinetic model are used to assess the efficiency of the mixer showing tagging kinetics close to that of bulk reactions in an ideally mixed reactor. As an ultimate application, the electrospray micromixer is implemented in a LC-MS workflow. On-line derivatization of albumin tryptic peptides after a reversed-phase separation and counting of their cysteines drastically enhance the protein identification.     

TCPST allocation using optimal power flow and Genetic Algorithms

This work presents an optimization model to allocate TCPST at congested transmission systems. The problem was resolved by the Genetic Algorithms (GA) together with an optimal power flow (OPF). The proposed strategy used the GA to make the allocation of the TCPST and the OPF to obtain the load flow solution and optimal adjustments of the phase shifter’s taps. The mathematical formulation of the methodology is based on installation’s costs of the equipment and total system overload minimization. In order to diminish the search field a methodology to elect the most favorable substations to the devices allocation was considered. This methodology was tested at a 291 bus system that is equivalent, in heavy load, to the electric network of the State of Paraná in Brazil.     

Infrared detection of hot spots in energized transmission and distribution equipment

An important facet of transmission and substation operation is preventive maintenance of energized electrical apparatus. Problems in energized equipment often appear as hot spots due to local thermal overloads or bad electrical connections. An excellent method of locating these hot spots is remote detection of the infrared radiation emitted. This paper is a survey of infrared detection systems suitable for this application. The first part of the paper is a brief tutorial introduction to infrared detection and imaging systems. Following this introduction, a survey of commercially available systems suitable for remote detection of hot spots is presented. Finally, the highlights of new developments in infrared technology are briefly discussed and the results of the investigation are summarized.     

Mitigating the imitation of aggressive behaviors by changing children's attitudes about media violence.

In 2 experiments, 169 1st- and 3rd-graders selected because of their high exposure to TV violence, were randomly divided into an experimental and a control group. Over 2 yrs, the experimental Ss were exposed to 2 treatments designed to reduce the likelihood of their imitating the aggressive behaviors they observed on TV. The treatments involved teaching the Ss that (a) TV violence is an unrealistic portrayal of the real world, (b) aggressive behaviors are not as acceptable in the real world as they appear on TV, and (c) one should not behave like the aggressive characters seen on TV. The control group received comparable neutral treatments. By the end of the 2nd yr, the experimental Ss were rated as significantly less aggressive by their peers, and the relation between violence viewing and aggressiveness was diminished in the experimental group. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)