Search

[Objective] Compared with conventional gas fuel, hydrogen is more susceptible to explosion. Meanwhile, the existence of obstacles notably stimulates hydrogen combustion and accelerates flame propagation, causing more serious consequences of accidents. To reduce destructive damage caused by hydrogen combustion under obstacle conditions, it is particularly important to reveal the influences of different obstacle conditions on the characteristics of flame propagation of hydrogen. [Methods] Based on large eddy simulation, the hydrogen/air combustion and explosion processes under different obstacle shapes and blockage rate conditions were numerically simulated.Focus was given to the research on different flame propagation velocities caused by different obstacle shapes and the sensitivity to blockage rate changes. [Results] Under low blockage rate, grid-type obstacles had a stronger destructive effect on the regular flow field at the flame front than single-side obstacles, and as the number of voids in grid-type obstacles increased, their destructive effect on the flow field motion further intensified, making it difficult for the flame front to recover to a regular state. When the blockage rate went up, the difference of the shapes of obstacles became insignificant in causing damage to the regular flow field, and the flame front was continuously distorted under all obstacle conditions. As the blockage rate continued to increase, single-side obstacles brought higher peak flame propagation velocity than grid-type obstacles. At the same blockage rate, the mechanism of flame acceleration by grid-type obstacles can be changed by adjusting the single void area to enhance the acceleration effect. [Conclusion] The shape and blockage rate of obstacles are the key factors influencing the state of flame front behind obstacles.The single-side obstacle is more sensitive to the blockage rate,while the grid-type obstacle has higher acceleration potential.The research results provide basic reference data for the prevention and control of hydrogen fire accidents and serve as a reference for the design of hydrogen power systems.

[Objective] Girth welds are known to be vulnerable locations along high-pressure transmission pipelines due to their susceptibility to cracking accidents under the combined action of internal and external loads, as well as defects and stress concentration. Considering the significant safety hazards associated with root beads around girth welds in high-grade steel pipelines, comprehending the failure mechanisms of girth welds becomes essential in ensuring operational safety. [Methods] This study investigated the mechanical properties of materials in different zones of root beads around girth welds along pipelines, using impact and tensile tests on small-size specimens, with a focus on microzones. Since cracking failures of girth welds predominantly occur at root beads in high-grade steel pipelines, this study explored the causes of crack initiation and propagation at these specific locations, examining mechanical properties within micro-zones, strain concentration across the weld's wall thickness, and characteristics of plastic strain aging within micro-zones. Optical full-field strain tests based on Digital Image Correlation(DIC) were performed to quantitatively analyze local strain concentration in welds under three different strength matching conditions during the tensile process. [Results] The micro-zone mechanical properties at root beads round girth welds exhibited significant variation depending on the welding procedures and strength matching conditions. When subjected to tension across the wall thickness, the root beads experienced substantial local strain concentration, especially in the presence of defects such as incomplete fusion, slag inclusion, porosity, and poor formation. These defects contributed to conditions conducive to cracking at the root beads. Moreover, the toughness at the root beads was significantly reduced during the strain aging process,ranging from 42.6%to 52.1%,thereby increasing the risk of brittle cracking. [Conclusion] In pipeline design and construction,managing the upper limit of base metal strength is crucial to ensure equal-matching or over-matching welds.By reducing the risk of weld cracking,the inherent safety of high-grade steel pipelines can be enhanced.

Based on field investigation, InSAR, GNSS monitoring, and deep displacement monitoring, a deformed loess landslide in Lingwan Village, Yujiaping Town, West-East Gas Pipeline Project was analyzed to understand its deformation characteristics and landslide formation mechanism from 2017 to 2022. The analysis shows that the groundwater level of the landslide has reached the toe of the slope, and numerous soil slips have been formed at the front edge of the landslide. The surface of the landslide exhibits vertical subsurface erosion cracks, while the penetrating cracks can be seen at the trailing edge. InSAR data shows that the landslide has been slowly deformed, with an annual deformation rate between 2.0 - 4.0 cm. GNSS deformation and crack deformation show that since August 2020, the surface deformation rate has increased significantly, with a deformation rate between 4.0 - 10.0 cm. The variation of deep deformation monitoring data is minimal, between 0.05 to 1.36 mm. Analysis of rainfall and soil moisture data shows that the landslide has displacement deformation after rainstorm. The comprehensive analysis of monitoring data reveals that the landslide in Lingwan Village is a shallow landslide induced by rainfall. Natural heavy rainfall and human engineering economic activities in the region are the primary inducing factors for the occurrence and development of landslide. Combined with pipeline strain monitoring data, the risk of landslide disasters in Shaanxi Province section of West-East Gas Pipeline Project is controllable.

The foundation settlement of the natural gas station can cause stress concentration and deformation of the pipeline, and in severe cases, the pipeline may even be subjected to cracking damage. To accurately and effectively assess the hidden risk of foundation settlement in natural gas station, a set of monitoring and alarm system of foundation settlement in natural gas station based on the IOT cloud platform was designed through the on-site investigation of a new natural gas station. Then, the system was used to collect, transmit and analyze the multidimensional data such as pipe strain and foundation settlement. The arrangement of monitoring points was optimized in combination with the finite element numerical simulation. On this basis, a set of three-level early warning scheme was proposed for the foundation settlement in natural gas station, and the alarm function was realized through the early warning threshold configuration of the alarm system. The results show that the system has stable and efficient data acquisition and transmission capabilities, the complex pipeline systems and foundation settlement in natural gas stations is monitored comprehensively, and the early warning ability for potential foundation settlement risks in the stations is improved, which is of great significance to the safe operation and maintenance of natural gas station.

In recent years, the "Room Escape" industry in China is booming, and this real live game has become popular. However, health threatening events such as fire, trauma, coma, and lung infection in the game venues have been reported at home and abroad. If these venues are not supervised in time, there will be great potential public safety and health hazards. In this review, we summarized the hidden dangers of public safety and health in such venues, including fire and safety hazards, persistent stress state, indoor ventilation problems, risk of contagious infection, non-player characters’ health risk, special film effects of 4D cinemas, mosquito problems, light pollution and noise, and food safety. Meanwhile, health management recommendations for the game venues were proposed from the aspects of formulating health management standards, improving health security measures, and strengthening related health education to players, so as to improve the hygiene levels of such venues and protect players and staff from injuries or diseases.

Click-through rate(CTR) prediction is an important task in the recommendation system.Its goal is to predict the pro-bability of a user clicking on an advertisement or item.Feature embedding and feature interacting are critical for prediction performance.Therefore,the ideas of many click-through rate prediction models are optimized based on these two aspects.However,most of the work only focus on one of the aspects,and almost all models do not distinguish features in feature interacting.The same embedding and interacting method are used when crossing the same feature with other features,which hinders the improvement of model performance.In order to solve this problem,the automatic super-field-aware feature embedding and interacting(Auto-SEI) model is proposed.Firstly,it assigns each sub-field to a super-field,and obtains the feature embedding according to the grouping,then selects appropriate interacting method for the feature pair to obtain the cross feature,and finally makes prediction.In Auto-SEI model,the division of sub-field and the selection of interacting methods are parameterized as an architecture search problem,and the neural architecture search(NAS) algorithm is used to compress the search space and make selections.A large number of experiments are conducted on three real large-scale data sets and the results show the excellent performance of the Auto-SEI model on the task of click-through rate prediction.

Using data of regional radar mosaic products, MICAPS, 6-hourly reanalysis data of CFSR with horizontal resolution of 0.5°×0.5°, and data of national meteorological observatories and regional automatic stations in Guangdong Province, the train effect features of an extremely severe rainfall event in Guangdong with a record-breaking rainfall of 1 056.7 mm within 24 hours in Gaotan of Huidong from 30 to 31 August 2018 is analyzed. The result is shown as follows. The train effect took place in the environment of a favorable atmospheric circulation induced by slowly moving monsoon depression. The most remarkable characteristic was that the high value of vapor flux divergence and potential pseudo-equivalent temperature mainly appeared in the boundary layer below 925 hPa. The wind direction in the boundary layer near Shanwei gradually shifts from southwest to south. The air current produced an upward movement of convergence around the central region of Shanwei. The storm cells of the severe rainfall moved along with southwest monsoon and the Lianhua Moutain from southwest to northeast. Surface mesoscale convergence line, the pulses of southwest-south airflows and the special terrain distribution triggered the generation and development of the train effect. The conditions presented above have resulted in the extremely severe precipitation breaking historical records in Gaotan.