Determination of flexibility factors in curved pipes with end restraints using a semi-analytic formulation

Piping systems are structural sets used in the chemical industry, conventional or nuclear power plants and fluid transport in general-purpose process equipment. They include curved elements built as parts of toroidal thin-walled structures. The mechanical behaviour of such structural assemblies is of leading importance for satisfactory performance and safety standards of the installations. This paper presents a semi-analytic formulation based on Fourier trigonometric series for solving the pure bending problem in curved pipes. A pipe element is considered as a part of a toroidal shell. A displacement formulation pipe element was developed with Fourier series. The solution of this problem is solved from a system of differential equations using mathematical software. To build-up the solution, a simple but efficient deformation model, from a semi-membrane behaviour, was followed here, given the geometry and thin shell assumption. The flexibility factors are compared with the ASME code for some elbow dimensions adopted from ISO 1127. The stress field distribution was also calculated.     

Modeling of sporicidal effect of hydrogen peroxide in the sterilization of low density polyethylene film inoculated with Bacillus subtilis spores

The sporicidal effect of hydrogen peroxide (H₂O₂) in the sterilization of low density polyethylene film (LDPE) was evaluated using a Central Composite Design (CCD). The effects of contact time (5-19s), bath temperature (23–70 °C) and concentration of H₂O₂ (0–35%) in an immersion bath were investigated. A 16 cm² film surface was evenly inoculated with 100 μL of the test microorganism Bacillus subtilis var. globigii ATCC9372 spores. The effective H₂O₂ sporicidal activity was demonstrated at concentrations from 18 to 35% and in a temperature range from 46 to 70 °C, resulting in 2–7 decimal reductions of B. subtilis spores. A quadratic mathematical model representative of the action of H₂O₂ on the B. subtilis spores was developed as a function of concentration, time and temperature. Test specimens sanitized with 28% H₂O₂ at 60 °C for 8 s showed 4 decimal reductions. In the same sterilization procedure, but extending the time to 16 s, this value increased to 7 decimal reductions, demonstrating the efficiency of H₂O₂ as a function of contact time. The sterilization system tested showed satisfactory performance in the sterilization of LDPE films, being capable of reaching up to 7 decimal reductions of the bacterial spore population.     

Sub-5 keV electron-beam lithography in hydrogen silsesquioxane resist

We fabricated 9-30 nm half-pitch nested Ls and 13-15 nm half-pitch dot arrays, using 2 keV electron-beam lithography with hydrogen silsesquioxane (HSQ) as the resist. All structures with 15 nm half-pitch and above were fully resolved. We observed that the 9 and 10-nm half-pitch nested Ls and the 13-nm-half-pitch dot array contained some resist residues. We obtained good agreement between experimental and Monte-Carlo-simulated point-spread functions at energies of 1.5, 2, and 3 keV. The long-range proximity effect was minimal, as indicated by simulated and patterned 30 nm holes in negative-tone resist.     

Comparison between power line communication multipath model and coaxial cable interferometer theory

The authors have studied a new method to find parameters of broadband power line communication channel model. Lossless power line communication channel model is compared with classical interferometers approach to develop this model. The authors also used coaxial cables to simulate a multipath channel, because it can behave like a lossless power line communication channel. Thus, measurements were carried out with a network analyzer to find S parameters. The modeling parameters, for the multipath model were found after using MATLAB software and classical interferometers approach. Then, theoretical and experimental results are presented and compared. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of a Near Net Shape Processing Method for Rhenium Using Directed Light Fabrication

Directed Light Fabrication (DLF) is a direct metal deposition process that fuses gas delivered powder, in the focal zone of a high powered laser beam to form fully fused near net shaped components. The near net shape processing of rhenium and refractory metals is currently in development and may offer significant cost savings compared with conventional processing. A full y associative 3D design through manufacturing model is presented for the application of DLF for the fabrication of a near net shaped nozzle part. This study describes the ability to move from a parametric 3D model integrated into a manufacturing model, creating a control file which can run on the DLF machine to produce a near net shaped metal component. Examples of DLF deposited rheniurn and iridium show a continuously solidified microstructure in rod and tube shapes. Entrapped porosity indicates the required direction for continued process development. These results demonstrate a new methodology for fabricating complex near net shaped components using rhenium.     

The relationship between advisors and students

Considering the influence of graduation courses on the scientific productivity in Brazil, fifty productive Brazilian scientists working in life sciences were interviewed about their relationship with their advisors and their own experience with their students. Admired by freedom and intellectual qualities, by their love and dedication for science, advisors seem to have had a deep influence on their students. This bond is not free from either an idealized frame or from some complaints and conflicts. Interviewed scientists see in themselves lesser qualities and faults but the same respect for freedom. Some students are thought to be specially important to the interviewed's productivity. Eldest and most productive scientists seem to be intellectually more impressed by their advisors than the other groups. The emotional and sometimes strong and idealized bond between advisor and students lead us to believe that the stated frequencies of conflicts might be underestimated.     

Une nouvelle architecture de gestion de réseaux DiffServ basée sur la technologie de réseau actif et la gestion à base de règles

The objective of this work is to propose an architectural solution to the very complex problem of DiffServ network management and control. Despite the fact that DiffServ offers a scalable QoS provisioning solution, it introduces a high complexity in term of its deployment due to the number of complex configurations to perform in the highly distributed and heterogeneous network environment. The proposed solution aims to take benefit from the scalability and flexibility properties of Active Network technology for distributing the control in large scale as well as the autonomic property of Policy Based Management to automate the distribution of these tasks in the operator network. This solution constitutes an alternative to the client/server approach generally used.     

Competition between FWM dynamics and modulational instability indispersion shifted fibers

In this letter, we analyze the relationship between four-wave mixing (FWM) and modulational instability (MI), using numerical simulations. Our results suggest that FWM dynamics interfere on MI process, shifting its maximum frequency gain. This relation may affect the performance of highly nonlinear fibers, which are being proposed to implement wavelength-conversion devices to be used in all-optical networks