Invar 36 alloy is increasingly used as a structural material for manufacture of liquefied natural gas (LNG) transporters and storage tanks. However, the conventional arc welding of Invar 36 alloy has high susceptibility of hot-cracking. As a high-energy-beam welding process, laser welding could be effective for producing defect-free Invar 36 weld. In the present study, defect-free Invar 36 weld was successfully produced by Nd:YAG laser welding. The microstructure and mechanical properties of weld were also tested.
To compare the stochastic autoregressive integrated moving average (ARIMA) model and the grey system GM(1,1) model to predict the hepatitis B incidence in Qianan. Considering the Box-Jenkins modeling and GM(1,1) model approach, hepatitis B incidence was collected monthly from 2004 to 2011, a SARIMA model and a gray system GM(1,1) model were fit. Then, these models were used for calculating hepatitis B incidence for the last 6 observations compared with observed data. The constructed models were performed to predict the monthly incidence rate in 2013. The model SARIMA(0,1,1)(0,1,1)12 and was established finally and the residual sequence was a white noise sequence. Using Excel 2003 to establish the gray system GM(1,1) model of hepatitis B incidence and evaluating the accuracy of the mode as well as forecasting. By posterior-error-test (C=0.435, p=0.821) and residual test, the model accuracy was qualified. It was necessary and practical to apply the approach of ARIMA model in fitting time series to predict hepatitis within a short lead time. The prediction results showed that the hepatitis B incidence in 2013 had a slight upward trend.
The effects of welding residual stress (WRS) would be harmful to safety and intensity of pressure vessel. X-ray stress analyzer (XRSA) can be used to non-destructively quantitative analyze WRS. In this study, stress changes of constant stress beam in loading process were tested using strain gauge (SG), strain rosette (SR) and XRSA, and their test results were compared to analyze measurement errors of XRSA. It was found that the property of XRSA meets the experimental requirement. The machining stress in surface of welding test plate could be completely removed after 4 min electrolytic polishing under 1 A current and 100% NaCl electrolyte. The WRS of welding test plate was tested by XRSA after machining stress completely removed, and its distribution along vertical welding seam direction corresponded with theory calculation. Furthermore, XRSA as a non-destructive method will be more used to study WRS of pressure vessel, so these results can provide scientific basis for the studying.
To improve the joining efficiency of Bi-Sr-Ca-Cu-O ( BSCCO) superconducting tapes, a
new diffusion bonding technology with a direct uniaxial pressing at high temperature was
developed to join 61-filament tapes. It was observed that bonding parameters such as bonding
pressure and holding time, significantly affected the critical current ratio (CCRo). A peak CCRo
value of 89 % for the lap-joined tapes was achieved at 3 MPa for 2 h when bonding temperature
was 800 °C. Compared with the conventional diffusion bonding technology, this new technology
remarkably shortened the fabrication period and improved the superconductivity of the joints. The
bonding interface and microstructures of the joints were evaluated and correlated to the CCRo. An
uniaxial pressing at high temperature was beneficial to interface bonding, and there was an optimal
pressure value for the CCRo.
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