Evolution of gas permeability for concrete materials under and after uni-axial loading

Under life-cycle service conditions, gas permeability which is usually employed to indicate the durability performance of concrete materials will be changed along with the evolution of microstructure under or after loading. This paper reports an extensive experimental research on the influence of loading condition on the evolution of gas permeability. A cyclic loading scheme under displacement control, which is employed to accelerate the evolution of its microstructure and model the loading condition under real service, is applied on cylinder specimens ϕ37u74mm dried to constant weight at 60°C. Both axial and lateral strains in the whole loading test are recorded by strain gauge to characterize the change of microstructure macroscopically. At the same time, gas permeability measurement is carried out by a well-designed tri-axial permeater at various loading levels in the planned loading history. The relationship between intrinsic gas permeability, Klinkenberg coefficient and residual strains discussed. It is found that intrinsic gas permeability will become great if the uniaxial loading level is beyond about 70% ultimate strength. Moreover, both the klinkenberg coefficient and intrinsic gas permeability are badly linked with elastic and plastic strains. However, the relationship between the Klinkenberg coefficient and intrinsic gas permeability can be approximated by a semi-empirical law, no matter under or after loading

Data-Driven Robust Control of Unknown MIMO Nonlinear System Subject to Input Saturations and Disturbances

This paper presented a new data-driven robust control scheme for unknown nonlinear systems in the presence of input saturation and external disturbances. According to the input and output data of the nonlinear system, a recurrent neural network (RNN) data-driven model is established to reconstruct the dynamics of the nonlinear system. An adaptive output-feedback controller is developed to approximate the unknown disturbances and a novel input saturation compensation method is used to attenuate the effect of the input saturation. Under the proposed adaptive control scheme, the uniformly ultimately bounded convergence of all the signals of the closed-loop nonlinear system is guaranteed via Lyapunov analysis. The simulation results are given to show the effectiveness of the proposed data-driven robust controller

Failure prediction of high-capacity electrode materials in lithium-ion batteries

The large volume change during lithium-ion insertion/extraction leads to huge stress and even failure of active materials. To well understand such a problem, the two-phase lithiation process of film and hollow core-shell electrodes is simulated by using a non-linear diffusion lithiation model. The dynamic evolution of lithium-ion concentration and diffusion-induced stress are obtained. Based on the dimensional analysis, a phase diagram is determined to demonstrate the relationship between critical failure, structure dimensions and mechanical properties. As a case study, the critical state of charge in Sn films are measured and compared with theoretical results

Design of Gas Channels for a Carbon Dioxide Electrochemical Compressor

The fundamental mechanisms behind electrochemical compression have long been understood. However, only now is the electrochemical compressor coming to fruition. The electrochemical compressor offers several key advantages over the traditional mechanical compressor. Its lack of moving parts eliminates energy losses due to friction and reduces noise. Electrochemical compression of hydrogen has already been realized at scale, but its usefulness is generally limited to fuel cell applications. Additionally, electrochemical compression has been performed with ammonia, but its toxicity limits its practicality. A carbon dioxide (CO2) compressor, however, would have potential applications in refrigeration systems that utilize CO2 as an environmentally-friendly refrigerant as well as in carbon capture. A major obstacle in electrochemical CO2 compression lies in the design of the gas distribution and collection channels, which supply to and collect gases from anion exchange membrane surface. The unique design challenge of the gas channel design in the electrochemical compressor is because the mass transfer of CO2 occurs throughout the membrane area, rather than at one specific point. At the same time, the membrane requires mechanical support so that is does not rupture under the pressure developed in the compression cell. Therefore, the gas supply and collection plates are designed with built-in flow channels. Here, we present a method for improving the gas channels using computational fluid dynamics to analyze the distribution of gas for different channel geometries. Several potential designs, including traditional fuel cell configurations as well as nature inspired geometries, were evaluated to determine which design is most effective for the CO2 compressor application. We conducted these analyses assuming baseline performance data determined empirically from previous CO2 compression experiments and the known material properties of the anion exchange membrane. The electrochemical CO2 compressor’s significant advantages show great promise for applications in the HVACR industry if these challenges are addressed

Multi-Stage Reinforcement Learning for Non-Prehensile Manipulation

Manipulating objects without grasping them enables more complex tasks, known as non-prehensile manipulation. Most previous methods only learn one manipulation skill, such as reach or push, and cannot achieve flexible object manipulation.In this work, we introduce MRLM, a Multi-stage Reinforcement Learning approach for non-prehensile Manipulation of objects.MRLM divides the task into multiple stages according to the switching of object poses and contact points.At each stage, the policy takes the point cloud-based state-goal fusion representation as input, and proposes a spatially-continuous action that including the motion of the parallel gripper pose and opening width.To fully unlock the potential of MRLM, we propose a set of technical contributions including the state-goal fusion representation, spatially-reachable distance metric, and automatic buffer compaction.We evaluate MRLM on an Occluded Grasping task which aims to grasp the object in configurations that are initially occluded.Compared with the baselines, the proposed technical contributions improve the success rate by at least 40\% and maximum 100\%, and avoids falling into local optimum.Our method demonstrates strong generalization to unseen object with shapes outside the training distribution.Moreover, MRLM can be transferred to real world with zero-shot transfer, achieving a 95\% success rate.Code and videos can be found at https://sites.google.com/view/mrlm

Power generation expansion optimization model considering multi-scenario electricity demand constraints: a case study of Zhejiang Province, China

Reasonable and effective power planning contributes a lot to energy efficiency improvement, as well as the formulation of future economic and energy policies for a region. Since only a few provinces in China have nuclear power plants so far, nuclear power plants were not considered in many provincial-level power planning models. As an extremely important source of power generation in the future, the role of nuclear power plants can never be overlooked. In this paper, a comprehensive and detailed optimization model of provincial-level power generation expansion considering biomass and nuclear power plants is established from the perspective of electricity demand uncertainty. This model has been successfully applied to the case study of Zhejiang Province. The findings suggest that the nuclear power plants will contribute 9.56% of the total installed capacity, and it will become the second stable electricity source. The lowest total discounted cost is 1033.28 billion RMB and the fuel cost accounts for a large part of the total cost (about 69%). Different key performance indicators (KPI) differentiate electricity demand in scenarios that are used to test the model. Low electricity demand in the development mode of the comprehensive adjustment scenario (COML) produces the optimal power development path, as it provides the lowest discounted cost

Alibaba Grupo, presente, pasado y futuro

El contenido de este artículo trata sobre el gigante de Internet de China—— Alibaba Grupo. El artículo se divide en cuatro direcciones generales. La primera parte: presenta la historia de Alibaba Grupo. El negocio de Alibaba incluye: compras en línea, servicios de entrega de alimentos, servicios de logística y otras industrias. La segunda parte: analiza el modelo comercial principal de Alibaba, enumera algunas de las secciones del modelo comercial de Alibaba y tiene un modelo comercial para Alibaba Grupo. La tercera parte presenta a los competidores de Alibaba. Tiene dos competidores fuertes, uno es JINGDONG, que es una gran empresa que también es una empresa de comercio electrónico; el otro es Tencent, que es una empresa de Internet. La cuarta parte analiza las áreas de negocio de Alibaba y las tendencias de desarrollo futuras.Grado en Comerci

Bending behavior test and assessment for full-scale PC box girder reinforced by prestressed CFRP plate

This paper focuses on behavior of full scale prestressed concrete (PC) box girder with difference degrees of damage derived from service stage. According to typical structural damage, strengthening measures are proposed, including gluing steel plate, gluing prestressed CFRP plate and so on. In order to testify the effectiveness of reinforced method, bending behavior test are conducted for full scale PC box girder both before and after strengthening. After the test, the bending behaviors of test girder are comparatively analyzed, and the failure mechanism of test girder reinforced by prestressed CFRP plate is studied. What’s more, the strengthening method of gluing prestressed CFRP plate is applied in in-situ prestressed concrete box girder bridge with obvious damage. The static and dynamic testing of this reinforced bridge shows the feasibility and effectiveness of gluing prestressed CFRP plate strengthening method. Studies in this paper provide reliable guidance for engineering application

The Mechanism Study of Vortex Tools Drainage Gas Recovery of Gas Well

The liquid loading of gas well is an important issue in deep exploitation of natural gas. The technic of vortex drainage has good prospects because the tool construction and construction work is simple, the technic is environmental and efficient. Currently, the mechanism for the vortex drainage and the theory of fluid motion are still missing. Therefore, in order to further understand the downhole flow field, verify drainage mechanism and select best working conditions, based on computational fluid dynamics and mixture model of multiphase flow through Fluent, the study established a three-dimensional structural model of vortex tools and the numerical simulation has been done. By monitoring the wellhead and the radial distribution of the liquid content and observing the state of the gas-liquid flow and the path line, the study analyzed the influence on gas well flow field by vortex tool. The study revealed the working mechanism of vortex tools to facilitate understanding the nature of the vortex drainage process, guide how to select the preferred process conditions and provide theoretical basis for the application and the dynamics simulation of vortex drainage technology.Key words: The liquid loading of gas well; Vortex drainage; Multiphase flow; Numerical simulatio