PVC pipes in gas distribution: still going strong!

In the Netherlands (impact-modified) PVC is the preferred material for low-pressure (30 and 100 mbar) gas distribution systems. More than 50% of the total length (about 122,000 km) of this system is rigid PVC or impact-modified PVC. The installation of rigid PVC (uPVC) pipelines started about 50 years ago. Presently, about 22,500 km of rigid PVC is still in operation. In this paper the good experiences with rigid PVC gas distribution systems in the Netherlands will be illustrated by results of regular leak surveys and test results on pipe samples taken from the gas grid. It will be shown that the leakage rate of uPVC pipe systems is very low and about equal to that of PE and steel pipe systems. Impact tests show no significant decrease in ductility with respect to time of use. Furthermore, the ductility of the PVC pipeline materials which have been in use for many years is shown to be mainly dependent on the (initial) quality (degree of gelation). The good performance of PVC gas pipeline systems is also proven by modelling studies. It will be shown that the long-term failure behaviour of uPVC is determined by the ability to yield. Failure will occur if a certain critical value of the plastic strain is surpassed. Using this model the long-term behaviour under internal pressure of rigid PVC pipes can be predicted quantitatively

An attempt to use scratch tests to predict the residual lifetime of unplasticised poly(vinyl chloride) pipes,

This paper reports on a procedure that can potentially predict the residual lifetime of low-pressure uPVC pipes in a non-destructive way. Ageing of these materials is characterised by a change in yield stress and fracture behaviour. The search for a method being able to non-destructively evaluate the yield stress and the fracture behaviour led to the study of scratching of the polymer surface. According to an extensive study by Atkins and Liu, the scratching behaviour is a function of yield stress, fracture toughness and the attack angle of the cutting tool. Experiments reported in this paper give an evaluation of the scratched area as a function of the attack angle for uPVC samples having different ageing times. Existing analyses for metals are adapted for polymer specific properties, such as the pronounced strain rate dependence of yield stress and visco-elastic recovery. The suggested adaptations are successful in the sense that the resulting analysis is capable of describing the forces during scratching and the resulting cross-sectional area of the groove. Although the scratching technique was not able to discriminate between differences in the scratch force or cross-sectional area of the groove of the different ageing times, it was possible to get an estimate of the fracture toughness from the analysis. Therefore, scratching is a promising technique to determine the fracture toughness for ductile materials for which it is difficult to obtain accurate results with conventional techniques

Fabrication and mechanical characterisation of inkjet printed strain gauges

The present study focuses on printing strain sensors directly on tensile test specimens using inkjet printing technology. This type of strain gauges has the advantage over conventional strain gauges that no glue or carrying platelet is present between the sensor and the surface that should be measured. Therefore, strains in thin foils can possibly be measured with printed strain gauges. First, proof of principle is given in this paper by successfully printing strain gauges on FR4. The printed strain gauges prove to behave linearly up to strains of 0.2% and can measure the strains within 3.5% accuracy

A comparative study of heating elements used for the development of textile heaters

The focus of this paper is to make a comparison between five different types of conductive, heatable samples. These textile samples have been produced according to the five most important implementation techniques such as knitting, weaving, embroidery, printing and nonwoven padding. The idea is to identify a conductive option best suitable for a heating application. This study was divided into four major steps: choosing the adequate materials, swatch production, conductivity measurements and heating behaviour assessment. The first three methods use electro conductive wires as heating elements, the fourth uses conductive ink and the fifth uses carbon black coating. For all of them, resistance, current and heat distribution was measured. The results show that the best options for the development of a wearable textile heating system are the embroidered and the woven techniques, as their mechanical strength and elasticity, is sufficiently high and the fabric/substrate structure allows the insertion/deposition of different types of heating element

A Study on SPICE Modeling of Non-Resonant Plasmonic Terahertz Detector

Department Of Electrical EngineeringThe terahertz (sub-millimeter wave) is the frequency resource, ranging from 100 GHz ~ 10 THz band, located in the middle region of the infrared and millimeter waves in the electromagnetic spectrum. Terahertz waves has unique physical characteristics, which is transparency of radio waves and straightness of light waves, simultaneously. The terahertz wave is applied to the basic science, such as device, spectroscopy, and imaging technology. And also adjust in the applied science, such as biomedical engineering, security, environment, information and communication. Which importance already verified. In the new shape of future market is expected to be formed broadly. For this application, operating in the THz frequency detecting device essential. Recently, Current elements operating in terahertz are present, such as compound semiconductor (???-???HBT, HEMT). But, there are disadvantage to use as a high price. Therefore, research have been made of silicon based THz detector in many research groups. Silicon-based nano-technology utilizes a plasma wave transistor technology. Which is using the space-time change of the channel charge density. That causes plasma wave oscillation in the MOSFET (Metal oxide semiconductor field effect transistor) channel and this effect available MOSET operating terahertz regime beyond MOSFET cut-off frequency. So, PWT (plasma wave transistor) is available terahertz detection and oscillation. For integrated possible post processing circuit development in these of terahertz applications system, silicon based PWT compact model is essential thing. For this compact model for spice simulation beyond cut-off frequency, we consider charge time variance model which is NQS (non-quasi-static) model, not quasi-static model. For NQS model two kinds of model exist, first is RC ladder model. That is seral connect MOSFET get rid of parasitic elements. And these complex circuit making the equivalent circuit model, it called New Elmore model. For post processing circuit simulation, fast simulation speed is essential, RC ladder model has a disadvantage (for simulating each segment). In this thesis we using New Elmore model based on Non-resonant plasmonic THz detector modeling, And verified physical validity of our NQS model using the our TCAD model based on Quasi-plasma 2DEG. And we propose fast and accurate compact modelingope

Critical properties of spherically symmetric accretion in a fractal medium

Spherically symmetric transonic accretion of a fractal medium has been studied in both the stationary and the dynamic regimes. The stationary transonic solution is greatly sensitive to infinitesimal deviations in the outer boundary condition, but the flow becomes transonic and stable, when its evolution is followed through time. The evolution towards transonicity is more pronounced for a fractal medium than what is it for a continuum. The dynamic approach also shows that there is a remarkable closeness between an equation of motion for a perturbation in the flow, and the metric of an analogue acoustic black hole. The stationary inflow solutions of a fractal medium are as much stable under the influence of linearised perturbations, as they are for the fluid continuum.Comment: 9 pages, 4 figures. Accepted for publication in MNRAS. The definitive version is available at http://www.blackwell-synergy.co