Seismic Strength and Stiffness for Recycled Aggregate Concrete-Filled Steel Tube Frame

To study the seismic strength and stiffness for recycled aggregate concrete-filled steel tube (RACFST) frame, two-frame specimens made up of RACFST column and reinforced recycled aggregate concrete (RAC) beam were used for a seismic test under reversed low-cycle loading. The failure mechanism, hysteresis curve, strength attenuation, and stiffness degradation were determined for the specimens. The design methods for the story shear bearing capacity and stiffness for the single-layer single-span RACFST frame were discussed. It is shown that the seismic design requirements including “strong column weak beam” and “strong shear weak bending” can be met. The hysteresis curves are symmetric and the strength attenuation and rigidity degeneration change significantly, then change a little, and then significantly again under the same displacement. It is possible that the methods including elastic bending moment at the column end, plastic hinge at the column end, and plastic hinge at the column bottom can all be applied to the design calculation of the story shear bearing capacity for the single-layer single-span RACFST frame. The method adopted in this paper can be used to estimate the original elastic layer stiffness of the RACFST frame

Discovery of host defence genes in the Japanese scallop Mizuhopecten yessoensis Jay by expressed sequence tag analysis of kidney tissue

The Japanese scallop Mizuhopecten yessoensis is one of the most important aquaculture mollusca in Japan and China. In the present study, a high-quality cDNA library of the Japanese scallop was constructed from the kidney tissue. A total of 2919 expressed sequence tags longer than 100 bp were generated from this library. A cluster of 1440 unique sequences, which consisted of 258 contigs and 1182 singletons, was revealed. Based on blast searches, 882 (61.3%) genes had significant (E-value 70 genes were involved in stress response, immunity and apoptosis. These results expanded our knowledge of the genetics and physiology of the Japanese scallop, and provided a useful resource for gene discovery for further research of this species

Shale high pressure isothermal adsorption curve and the production dynamic experiments of gas well

The high pressure static adsorption curves of shale samples from Silurian Changning-Weiyuan Longmaxi Formation were tested by using high pressure isothermal adsorption equipment. The physical modeling of depletion production was tested on single cores and multi-core series by using self-developed shale gas fluid-solid coupling experiment system. The adsorption and desorption laws were summarized and a high pressure isothermal adsorption model was established. The calculation formula of gas content was corrected, and the producing law of adsorption gas was determined. The study results show that the isothermal adsorption law of the shale reservoir under high pressure was different from the conventional low pressure. The high pressure isothermal adsorption curve had the maximum value in excess adsorption with pressure change, and the corresponding pressure was the critical desorption pressure. The high pressure isothermal curve can be used to evaluate the amount of adsorbed gas and the producing degree of adsorption gas. The high pressure isothermal adsorption model can fit and characterize the high pressure isothermal adsorption law of shale. The modified gas content calculation method can evaluate the gas content and the proportion of adsorbed gas more objectively, and is the theoretical basis of reserve assessment and production decline analysis. The producing degree of adsorption gas is closely related to the pressure, only when the reservoir pressure is lower than the critical desorption pressure, the adsorption gas can be produced effectively. In the process of gas well production, the pressure drop in the near-well area is large, the production of adsorption gas is high; away from the wellbore, the adsorption gas is low in production, or no production. Key words: shale, high pressure isothermal adsorption, excess adsorption, critical desorption pressure, shale gas, adsorption curv

Experimental and numerical study on gas production decline trend under ultralong-production-cycle from shale gas wells

Abstract It is of engineering interest to explore recovered shale gas composition and its effects on total gas production trend over a long-term extraction period. However, there are previous experimental studies mostly focused on short term development for small scaled cores, which is less convincing to mimic reservoir-scaled shale production process. In addition, the previous production models mostly failed to account for comprehensive gas nonlinear effects. As a result, in this paper, to illustrate the full-life-cycle production decline phenomenon for shale gas reservoir, dynamic physical simulation was performed for more than 3433 days to simulate shale gas transport out of the formations over a relatively long production period. Moreover, a five-region seepage mathematical model was then developed and was subsequently validated by the experimental results and shale well production data. Our findings show that for physical simulation, both the pressure and production declined steadily at an annual rate of less than 5%, and 67% of the total gas in the core was recovered. These test data supported earlier finding that shale gas is of low flow ability and slow pressure decline in the shale matrices. The production model indicated that free gas accounts for the majority of recovered shale gas at the initial stage. Based on a shale gas well example, free gas extraction makes up 90% of produced total gas. The adsorbed gas constitutes a primary gas source during the later stage. Adsorbed gas contributes more than 50% of the gas produced in the seventh year. The 20-year-cumulative adsorbed gas makes up 21% of the EUR for a single shale gas well. The results of this study can provide a reference for optimizing production systems and adjusting development techniques for shale gas wells throughout the combinations of mathematical modeling and experimental approaches

Facile Morphology Modulation to Enhance Stability and Fast Kinetics of Anionic Redox for Li-Rich Layered Oxides Cathodes

Li-rich layered oxide cathodes (LLOs) have been regarded as promising high-energy-density cathode materials for lithium-ion batteries due to exceptional specific capacity and eco-friendly nature. However, issues such as irreversible oxygen evolution and severe structural degradation have led to low initial Coulombic efficiency (ICE), poor cycling stability, voltage decay, and unfavorable rate performance. In this work, we have systematically manipulated the morphologies and structures of low cobalt-containing LLOs, specifically Li1.08Mn0.54Ni0.21Co0.07O2, to stabilize anionic redox chemistry and enhance the rapid kinetic performance of LLOs, resulting in optimized electrochemical properties. Electrochemical testing has demonstrated that LLOs with radial shapes exhibit superior performance, achieving a high ICE of 88.74% with reversible discharging capacity of 285.1 mAh/g and excellent capacity retention of 85.35% at 1 C after 100 cycles. Furthermore, even at 5 C, these LLOs maintain a high discharge capacity of 165.8 mAh/g, indicating significantly improved rate performance due to modulation of their morphology and structure. This work provides valuable insight into the design of high-energy-density LLOs via morphology and structure modulation, laying the groundwork for large-scale production of lithium-ion batteries in the near future