Design of cylindrical plastic pipe linings to resist buckling due to collapse pressures

Flexible (non-bonded) polymeric sewer linings are used extensively to renovate both gravity and pressure pipes. Linings for both types of pipe are subject to collapse pressures, and in the case of gravity pipes this is the dominant source of loading; the efficient design of linings to sustain collapse pressures is therefore an important problem. In this paper, the buckling of an ideal thinwalled elastic lining in a rigid cylindrical cavity is first presented as a simple closed form solution, and The effect of a representative small imperfection shown to be significant. The different types of imperfection that can be encountered in practical lined pipe systems are identified, and the situations in which each can arise are discussed. A generalised procedure for obtaining the structural imperfections in, and hence buckling capacities of, practical systems is then presented and two example applications are used to illustrate its application in specific situations

Improved linings for integrating spheres

Sphere surface is covered with plain weave of glass fibers coated with polytetrafluoroethylene and one or two layers of magnesium oxide vapor. The resultant lining is suitable for measurement of radiation in the ultraviolet, visible, and near-infrared wavelengths, is not damage prone, and is easily cleaned

Why ban sex hormones in the nursery?

Canada leads the world with new regulations to prohibit the importation, sale and advertising of polycarbonate baby bottles that contain bisphenol A (BPA). The world production of BPA is currently 3.3 billion kilograms per year, half a kilogram per person. The estrogenic activity of BPA has been known at least since 1936. Estrogens have biological effects at parts per billion. BPA is used in food and beverage containers, including baby bottles, some drink bottles, and food container linings, in particular can linings. A recent study in the USA reported that all the adult subjects tested had bisphenol A in their urine. Canada has just declared bisphenol A to be a toxic substance. Canada has responded to the accumulating evidence that BPA leaches from polycarbonate baby bottles and behaves like an estrogen. An extra dose of female sex hormones is not the best of dietary supplements for babies, either male or female; or for teenagers, or even adults. Canada is the first country in the world to act to banish bisphenol A from the nursery

Sustainability based-approach to determine the concrete type and reinforcement configuration of TBM tunnels linings. Case study: Extension line to Barcelona Airport T1

Fibre-reinforced concrete (FRC) is a suitable alternative to the traditional reinforced concrete used in the manufacture of precast segments used to line tunnels excavated with a tunnel boring machine (TBM). Moreover, its use as a structural material has been approved by several national codes and by the current fib Model Code (2010). The use of FRC in segmental linings confers several technical and economic advantages, evidenced by the fact that structural fibres have been used to partially or entirely replace reinforcing bars in many TBM tunnels built over the past 20 years or currently under construction. FRC could also have been used in other tunnels, which are currently in the planning stage or under construction. However, despite its technical suitability and approval in current codes, the use of FRC was not possible in some cases. The impediment has sometimes been an incomplete understanding of the structural behaviour of the material, but a more general motive has been that comparisons of materials have taken into account only direct material costs and have not considered indirect costs or social and environmental factors. The aim of the present research is to develop a method for analysing the sustainability of different concrete and reinforcement configurations for segmental linings of TBM tunnels using the MIVES method (a multi-criteria decision making approach for assessing sustainability). This MCDM method allows minimising subjectivity in decision making while integrating economic, environmental and social factors. The model has been used to assess the sustainability of different alternatives proposed for manufacturing the segmental tunnel lining for the extension of the rail line of Ferrocarrils de la Generalitat de Catalunya (FGC) to Terminal 1 of El Prat Airport in Barcelona.Peer ReviewedPostprint (author's final draft

Determination of the parameters of semiconducting CdF2:In with Schottky barriers from radio-frequency measurements

Physical properties of semiconducting CdF_2 crystals doped with In are determined from measurements of the radio-frequency response of a sample with Schottky barriers at frequencies 10 - 10^6 Hz. The dc conductivity, the activation energy of the amphoteric impurity, and the total concentration of the active In ions in CdF_2 are found through an equivalent-circuit analysis of the frequency dependencies of the sample complex impedance at temperatures from 20 K to 300 K. Kinetic coefficients determining the thermally induced transitions between the deep and the shallow states of the In impurity and the barrier height between these states are obtained from the time-dependent radio-frequency response after illumination of the material. The results on the low-frequency conductivity in CdF_2:In are compared with submillimeter (10^{11} - 10^{12} Hz) measurements and with room-temperature infrared measurements of undoped CdF_2. The low-frequency impedance measurements of semiconductor samples with Schottky barriers are shown to be a good tool for investigation of the physical properties of semiconductors.Comment: 9 pages, 7 figure

Analysis of a thaumasite attack in a railway tunnel

Concrete linings failed before the acceptance of a railway tunnel in a north mountain area of China. A series of experiments were done to analyze the cause of this case. Thaumasite, ettringite, gypsum and calcite were found in the deteriorated concrete linings. The composition of on-situ soil and water samples were also analyzed. Though the sulfate concentration soil behind the linings are not very high, the underground water bring plenty of sulfate after its upsteam flow through a gypsum stratum. It is the external sulfate that induce the deterioration in a low temperature environment which is suitable for thaumasite formation

Developmental design, fabrication, and test of acoustic suppressors for fans of high bypass turbofan engines

An analysis procedure was developed for design of acoustically treated nacelles for high bypass turbofan engines. The plan was applied to the conceptual design of a nacelle for the quiet engine typical of a 707/DC-8 airplane installation. The resultant design was modified to a test nacelle design for the NASA Lewis quiet fan. The acoustic design goal was a 10 db reduction in effective perceived fan noise levels during takoff and approach. Detailed nacelle designs were subsequently developed for both the quiet engine and the quiet fan. The acoustic design goal for each nacelle was 15 db reductions in perceived fan noise levels from the inlet and fan duct. Acoustically treated nacelles were fabricated for the quiet engine and quiet fan for testing. Performance of selected inlet and fan duct lining configurations was experimentally evaluated in a flow duct. Results of the tests show that the linings perform as designed

The importance of the diffusive permeability of animal burrow linings in determining marine sediment chemistry

Many of the abundant burrows formed by animals in marine sediments are lined with thin layers of organic material. The permeability of these linings to solute diffusion can be an important determinant of the chemical composition of surrounding sediment and the burrow habitat. Measurement of the diffusive permeability of burrow linings from 8 species of marine invertebrates indicates that the diffusion coefficients of small inorganic solutes within linings are ∼ 10-40% that in free solution. The diffusion of anions, represented by Br−, is hindered somewhat relative to cations, represented by NH4+, indicating that linings have negatively charged regions at the pH of natural waters. The time dependence of diffusion through linings is affected by simple ion exchange within the lining material. Adsorption constants for solutes like NH4+ and Si(OH)4, are in the range of K ∼ 2-8 (relative to pore water volume). Silica shows evidence of interaction other than reversible ion exchange in some cases. The permeability of linings can affect sedimentary solute distributions differently depending on the types of reactions controlling a particular solute in surrounding sediment. The concentrations of solutes subject to zeroth-order reactions are greatly influenced by lining permeability but net fluxes (at steady state) across the lining are not. The opposite is true for solutes subject to first or higher order concentration-dependent reactions. Assuming burrow linings can act as molecular sieves, then some classes of solutes will be strongly influenced by the presence of irrigated burrows while others will be distributed in a deposit as though burrows were completely absent. This may greatly complicate sedimentary solute distributions

Effect of the concrete´s component on the heat shock bearing capacity of tunnel linings

During the last decades, the increasing number of incidents in road and railway tunnels have attracted public attention to the danger of tunnel fires. These incidents established that quickly accumulating, huge amount of evolved heat impairs the reinforced concrete structures of tunnel linings. Designing of fire-bearing linings, it is necessary to understand the behaviour of the linings impacted by bumping heat load. In this paper, the results of our heat load examinations of residual strength (compressive strength and split-tensile strength) parameters on different mixtures of concrete were summarised