A Normalized Terzaghi Model and Time-Step FEA for Predicting the Adsorption of a Cylindrical Object in Subsea Salvage

This paper proposes a normalized Terzaghi model modified based on finite element analysis to predict the adsorption force of a cylindrical object for salvage from the seabed. The maximum relative error is less than 5% compared with finite element analysis. Furthermore, the time-step finite element method is adopted to analyze the effects of the lifting force and bury depth. With increased lifting force, the critical displacement is reduced slightly, soil separation on the bottom of the object occurs earlier, and the velocity increases more quickly at the same burial depth. In addition, the soil displacement on the bottom stops increasing earlier, and the off-mud process is completed earlier. With increased burial depth, soil separation takes considerably longer, velocity increases more slowly, the maximum soil displacement is increased, and the off-mud process takes longer to complete

A Normalized Terzaghi Model and Time-Step FEA for Predicting the Adsorption of a Cylindrical Object in Subsea Salvage

This paper proposes a normalized Terzaghi model modified based on finite element analysis to predict the adsorption force of a cylindrical object for salvage from the seabed. The maximum relative error is less than 5% compared with finite element analysis. Furthermore, the time-step finite element method is adopted to analyze the effects of the lifting force and bury depth. With increased lifting force, the critical displacement is reduced slightly, soil separation on the bottom of the object occurs earlier, and the velocity increases more quickly at the same burial depth. In addition, the soil displacement on the bottom stops increasing earlier, and the off-mud process is completed earlier. With increased burial depth, soil separation takes considerably longer, velocity increases more slowly, the maximum soil displacement is increased, and the off-mud process takes longer to complete

An improved carbon fixation management strategy into the crop-soil ecosystem by using biomass ash as the medium

Returning the carbonated biomass ash into the soil can enhance the carbon fixation capacity of crop-soil ecosystem, contributing to the achievement of "4 per mille Soils for Food Security and Climate' goal launched at COP21. The CO2 sequestration of crop- soil ecosystem induced by biomass ash, however, highly depended on the soil pH and crops growth, which have not been elucidated. Here, we explored the effects of different management strategies (watering, chemical fertilizer, and CO2-rich biogas slurry on the CO2 fixation performance of tomato ecosystem (Tom-E) containing one tomato plant, biomass ash, and soil, and evaluated the impact of tomato cultivation concerning carbon fixation. Results showed that when burying biomass ash into the soil, biomass ash did not cause physiological stress on tomato growth, and even improved the tomato qualities. Furthermore, through sequestrating CO2 from biomass ash, CO2 fixation capacity of the tomato ecosystem reached about 8.8 +/- 1.10, 13.7 +/- 0.74, and 20.7 +/- 0.53 mmol-CO2/Tom-E for watering, chemical fertilizer, and CO2-rich biogas slurry management strategies, respectively. However, due to the influence of fertilization management strategy, about 57.4% +/- 0.09 and 27.3% +/- 0.09 of CO2 sequestrated in the biomass ash returned to the atmosphere (i.e, CO2 loss) for only watering treatment and conventional fertilization (chemical fertilizer) treatment, respectively. Comparatively, as a pH buffering fertilizer, CO2-rich biogas slurry application improved the bicarbonate assimilation environment of tomato, which contributed to reducing the CO2 loss to only 12.5% +/- 0.01. Clearly, adopting the carbonated biomass ash and CO2-rich biogas slurry as fertilizer provides a suitable and potential strategy for the enhancement of soil carbon sink. (C) 2022 The Author(s). Published by Elsevier B.V

A Fuzzy Markov Model for Risk and Reliability Prediction of Engineering Systems: A Case Study of a Subsea Wellhead Connector

In production environments, failure data of a complex system are difficult to obtain due to the high cost of experiments; furthermore, using a single model to analyze risk, reliability, availability and uncertainty is a big challenge. Based on the fault tree, fuzzy comprehensive evaluation and Markov method, this paper proposed a fuzzy Markov method that takes the full advantages of the three methods and makes the analysis of risk, reliability, availability and uncertainty all in one. This method uses the fault tree and fuzzy theory to preprocess the input failure data to improve the reliability of the input failure data, and then input the preprocessed failure data into the Markov model; after that iterate and adjust the model when uncertainty events occur, until the data of all events have been processed by the model and the updated model obtained, which best reflects the system state. The wellhead connector of a subsea production system was used as a case study to demonstrate the above method. The obtained reliability index (mean time to failure) of the connector is basically consistent with the failure statistical data from the offshore and onshore reliability database, which verified the accuracy of the proposed method

Synthesis of hierarchical structured porous MoS2/SiO2 microspheres by ultrasonic spray pyrolysis

Hierarchical structure porous MoS2/SiO2 microspheres were prepared by ultrasonic pyrolysis technique. The nanostructured MoS2/SiO2 materials were characterised by scanning electron micrograph (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), as well as nitrogen isotherm. The MoS2/SiO2 microspheres, synthesised using polystyrene latex spheres as a template, showed two pore sizes: 5.8 and 68 nm. The micro-, meso- and macropore volume was also calculated. Effect of PSL:SiO2 ratio on the hierarchical structure was also investigated.Peer reviewed: YesNRC publication: Ye

Alignment Error Modelling, Analysis and Experiment of the Deep-Water Bolt Flange Automatic Connection Tool

A deep-water bolt flange automatic connection tool plays a very important role in the process of offshore oil exploitation and transportation. In the connection process, the alignment error of bolts and nuts is the key factor to ensure the connection process is successful. Using the kinematics modeling method, this paper created the alignment error model of the deep-water bolt flange automatic connection tool and analyzed the influence of manufacturing accuracy on the alignment error of bolts and nuts through computer simulation software. Based on the error matching design method, the manufacturing accuracy of parts were optimized with a part-size-based priority sequence to ensure the bolt–nut alignment error was within the allowable limits. The land tests, the pool tests and the sea test were carried out. The test results showed that the bolt and nut can be connected in the subsea environment reliably

An Arm-Claw-Type Manipulator for Rapid Deep Water Salvage with a General Support Vessel, Part A: Prototype and Test

This paper proposed a concept prototype of the arm-claw-type manipulator with a general purpose support vessel for the rapid salvage of deep submergence vehicles, aircraft, satellites, etc. The key functions were realized, including object clamping, claw butting and locking, position and posture adjustment, awareness, positioning, and navigation. The prototype was successfully tested in a lake environment on a hollow and cylindrical object. The arm-claw-type manipulator is suitable for the rapid salvage of cylindrical objects in an underwater environment to minimize the clamping force and possible clamping damage on the object being salvaged. Four propeller thrusters with a symmetrical arrangement can be used for the adjustment of position and posture in underwater environments, to match the orientation of the object. Cameras capture the profile images of the underwater salvage object and can be used for posture adjustment, but in dark, deep-water environments, sonar can be used in the place of underwater cameras

Thickness-tunable growth of ultra-large, continuous and high-dielectric h-BN thin films

The outstanding thermal properties, mechanical properties and large optical bandgap of hexagonal boron nitride (h-BN) make it very attractive for various applications in ultrathin 2D microelectronics. However, the synthesis of large lateral size and uniform h-BN thin films with a high breakdown strength still remains a great challenge. Here, we comprehensively investigated the effect of growth conditions on the thickness of h-BN films via low pressure chemical vapor deposition (LPCVD). By optimizing the LPCVD growth parameters with electropolished Cu foils as the deposition substrates and developing customized `` enclosure'' quartz-boat reactors, we achieved thickness-tunable (1.50-10.30 nm) growth of h-BN thin films with a smooth surface (RMS roughness is 0.26 nm) and an ultra-large area (1.0 cm x 1.0 cm), meanwhile, the as-grown h-BN films exhibited an ultra-high breakdown strength of similar to 10.0 MV cm(-1), which is highly promising for the development of electrically reliable 2D microelectronic devices with an ultrathin feature.This work was supported by the China Postdoctoral Science Foundation (Grant No. 2016M602820), the National Natural Science Foundation of China (Grant No. 51607138), the Youth Innovation Foundation of State Key Laboratory of Electrical Insulation and Power Equipment (Grant No. EIPE17312), the Research Foundation of State Key Laboratory of Intense Pulsed Radiation Simulation and Effect (Grant No. SKLIPR.1512) and the Innovative Research Group of National Natural Science Foundation of China (Grant No. 51521065)

Alignment Error Modelling, Analysis and Experiment of the Deep-Water Bolt Flange Automatic Connection Tool

A deep-water bolt flange automatic connection tool plays a very important role in the process of offshore oil exploitation and transportation. In the connection process, the alignment error of bolts and nuts is the key factor to ensure the connection process is successful. Using the kinematics modeling method, this paper created the alignment error model of the deep-water bolt flange automatic connection tool and analyzed the influence of manufacturing accuracy on the alignment error of bolts and nuts through computer simulation software. Based on the error matching design method, the manufacturing accuracy of parts were optimized with a part-size-based priority sequence to ensure the bolt–nut alignment error was within the allowable limits. The land tests, the pool tests and the sea test were carried out. The test results showed that the bolt and nut can be connected in the subsea environment reliably

Structure, ordering, and surfaces of Pt\u2013Fe alloy catalytic nanoparticles from quantitative electron microscopy and X-ray diffraction

The current challenge in catalyst development is to produce highly active and economical catalysts. This challenge cannot be overcome without an accurate understanding of catalyst structure, surfaces and morphology as the catalytic reactions occur on the surface active sites. Transmission Electron Microscopy (TEM) is an excellent tool for understanding the structures of the nanoparticles down to the atomic level in determining the relationship with the catalyst's performance in fuel cell applications. This paper describes a detailed structural characterization of Pt\u2013Fe nanoparticles using aberration corrected TEM. Detailed analysis regarding the morphology, structural ordering, facets, nature of the surfaces, atomic displacements and compositions was carried out and presented in the context of their electrochemical performances. In addition, the effects of electrochemical cycling in terms of morphology and composition evolution of the nanoparticles were analyzed. Lastly, along with data from X-ray diffractometry, two different crystallographic models of the unknown Pt3Fe2 nanoparticle phase are proposed. The detailed characterization by TEM provides useful insights into the nanoparticle chemistry and structure that contributes to catalyst development for next generation fuel cells.Peer reviewed: YesNRC publication: Ye