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The connection between two submarine pipelines is usually made by welding. In the process of welding, the incomplete penetration, incomplete fusion, porosity, cracks and other welding defects are hardly preventable. The incomplete penetration defects at the root of pipeline girth welds can greatly reduce the safety of submarine pipelines and increase the risk of pipeline failure. In this paper, the safety assessment of incomplete penetration defects at the root of pipeline girth welds are studied. Firstly, a novel model of incomplete penetration defects at the root of girth weld pipelines is provided. Then, an analytical solution of the novel model is obtained according to stress function method. Next, the residual strength equation of the incomplete penetration defects at the root of pipeline girth welds is derived based on the analytical solution. In the end, the calculated results of the residual strength equation are verified by finite element method (FEM) and experiment. The results indicate that the calculated values are in good agreement with the FEM and experiment. In addition, the results indicate that the safety assessment method of incomplete penetration defects at the root of pipeline girth welds is feasible. It is beneficial for the safety assessment of pipelines with incomplete penetration defects.

This paper introduces a practical and cross-platform virtual electrical experimental tool (VEET) based on an off the shelf game engine called Unity3D which is powerful and flexible to develop Virtual and Augmented Reality (VR/AR) applications. Taking the electrical experiments of technological university as examples, the well designed virtual experimental system has the characteristics of lifelike three dimensional (3D) experimental environments, AR interactive interface on mobile devices, intelligent detecting mechanism and cross-platform. We described VEET’?s flexible design and demonstrate its use in teaching where 120 students from three classes conducted electrical experiments with it. The experiments in VEET were presented on desktop, mobile and web browser using low cost common devices (personal computer, android handheld device, Chrome browser). Evaluating the main performance parameters, the well practicability was confirmed.

In this paper, we improved the home-made EL experimental set-up, have increased the function of TSC, enable the joint measurement of EL and TSC to measure the trap of shallow and deep. It is significant to study material properties. through the Labview8.6 software programming, the data of temperature and current could be collected, then we can get the curve that the current changes with temperature, it is the TSC curve. Experiment result proved the reliability of laboratory equipment.

The electronic structural and optical properties of Polyimide (PI) are studied by first principle method of density theory. It is shown that molecules orbit contribution of PI is derived from carbon 2p orbital and oxygen 2p orbital, respectively,and the band gap from the energy band structure is much smaller than that of the experimental value. It is also found that the band gap calculated from the absorption edge of absorption spectra is in agreement with the result of the energy band structure. Furthermore, the relationship between the formation of dielectric function peaks and other spectral characteristics is interpreted.

The Electroluminescence (EL) intensity and the spectrum of the of the PET films under different temperatures (77K, 296K, 353K) is tested, it is found that the pre-breakdown field under the low normal and high temperature of PET films is about 3.0MV/cm, 3.2MV/cm, 3.4MV/cm, respectively, and the formation of hot electron is not the main reason that cause aging and breakdown of PET films.

The EL intensity and the spectrum of the PET films were tested under the low temperature by home-made experimental set-up on the conditions of DC high electric fields and irradiated by xenon lamp. The result shows that there are emission peaks at about 350~450nm, 500~600nm and 750nm in the EL spectrum of the PET films. The intensity of light emission increases with the applied electric fields; the pre-breakdown field is about 3.3MV/cm, this threshold value is no significant change which compares with the normal temperature.

A new microwave imidization method was used to prepare polyimide (PI) film in this paper. FT-IR spectrum and ultraviolet absorption spectrum are measured to study the chemical structure and optical properties of this film. The FT-IR spectrum shows that the characteristic imide groups are observed at the peaks of 727.18 cm-1, 1379.67 cm-1 and 1776.51 cm-1, which confirmed imide formation. The ultraviolet absorption spectrum reveals that optical band gap of the PI is about 2.64 eV.