A computational fluid dynamics study of two-phase flows in the presence of surfactants

Drop formation in co-flowing fluids and drops rising in a tube are important in applications such as microencapsulation and enhanced oil recovery. A hybrid volume-of-fluid method with a front-tracking scheme is developed to study two-phase flows in the presence of surfactants at finite Reynolds numbers. Both fluids can be Newtonian or shear-thinning, and surfactants are soluble in the adsorption-desorption limit. A drop in the co-flowing geometry typically breaks up at the primary neck. The drop breaks faster with smaller volumes as the outer flow rate increases or the drop viscosity decreases. When surfactants are present, they accumulate in the neck region resulting in Marangoni stresses that slow down the neck thinning rate. This results in longer breakup times with larger drop volumes. At high surfactant coverages, the primary neck formation slows down enough and breakup occurs at the secondary neck. Increasing outer co-flowing flow weakens the retarding effect of the high surfactant coverage leading to breakup again at the primary neck. The adsorption-desorption kinetics also affects the neck breakup position, and the primary drop volume and breakup time depend non-linearly on the Biot number. The presence of a confining wall may lower the value of the critical equilibrium fractional coverage required for the drop to enter the no-necking regime. As the drop becomes more shear-thinning, the drop breaks up faster with a shorter remnant drop length. Multiple satellite drops are observed at breakup with strongly shear-thinning drop fluid at high coverage of soluble surfacants. The buoyancy-driven motion of drops in a tube is investigated by determining the steady shapes and velocities of the drops as a function of the drop size. Higher buoyancy force leads to larger deformation of drops and increased terminal velocities. Higher inertia increases the terminal velocity of drops and results in the development of negative curvatures at the rear of the drop. The non-uniform distribution of surfactants at the interface gives rise to Marangoni stresses that retard the drop motion though the drop shapes remain unaffected

A Study of EFL Classroom Discourse from the Perspectives of both DA and CA

In order to get the deeper understanding of EFL classroomdiscourse, the researcher displays the process of EFLclassroom discourse through the analytical instrumentsof both DA and CA. It is found that there are severaldiscourse structures in the EFL classroom discourse fromthe perspective of DA, it is more complex than the singleIRF structure which also including the IRFR structure,theIR [I1R1 … (InRn)] F structure and the IR1F1R2F2 …RnFnstructure. From the perspective of CA, the researchshows that quite a few conversational skills are usedin the EFL classroom discourse, such as turn-taking,conversation repair, interruption and repetition. It isconcluded that the students generally play a passive roleinEFL classroom discourse, especially in teacher-studentinteraction. Itshould be the joint effort of teacher andstudents to increase students’ contributionin classroomdiscourse and interaction.Key words: Discourse analysis; Conversationanalysis; IRF model; Turn-taking; ESL classroo

Selective disruption of high sensitivity heat activation but not capsaicin activation of TRPV1 channels by pore turret mutations.

The capsaicin receptor transient receptor potential vanilloid (TRPV)1 is a highly heat-sensitive ion channel. Although chemical activation and heat activation of TRPV1 elicit similar pungent, painful sensation, the molecular mechanism underlying synergistic activation remains mysterious. In particular, where the temperature sensor is located and whether heat and capsaicin share a common activation pathway are debated. To address these fundamental issues, we searched for channel mutations that selectively affected one form of activation. We found that deletion of the first 10 amino acids of the pore turret significantly reduced the heat response amplitude and shifted the heat activation threshold, whereas capsaicin activation remained unchanged. Removing larger portions of the turret disrupted channel function. Introducing an artificial sequence to replace the deleted region restored sensitive capsaicin activation in these nonfunctional channels. The heat activation, however, remained significantly impaired, with the current exhibiting diminishing heat sensitivity to a level indistinguishable from that of a voltage-gated potassium channel, Kv7.4. Our results demonstrate that heat and capsaicin activation of TRPV1 are structurally and mechanistically distinct processes, and the pore turret is an indispensible channel structure involved in the heat activation process but is not part of the capsaicin activation pathway. Synergistic effect of heat and capsaicin on TRPV1 activation may originate from convergence of the two pathways on a common activation gate

Multivariate Supply Model of Small-Scale Irrigation and Water Conservancy Facilities in China Rural Area

The supply of small-scale irrigation and water conservancy facilities has received wide attentions from the academic circles. In China,the deficiency of providing public goods in rural areas have hindered rural and agricultural development, and restricted the modernization of governance in China to some extent.It is urgent to seek a way to solve these issues.Through history and comparative analysis, this paper first divides the supply model of small-scale irrigation and water conservancy facilities into three categories on the basis of existing research, which are state centralized supply, self-financing farmers and multivariate supply; Secondly, we focus on launching a further research and refinement on multivariate supply model which is under way in current practice, and we proposed that four main actors and four stages constitute the multivariate supply model. Four main actors are government, farmers, NGOs and private sector and four stages refer to investment, construction, management and maintenance and usage; Thirdly , through the investigation and research of Z county in Anhui Province, we found that the small-scale irrigation and water conservancy in Z county is in general accord with the multivariate supply model. Specific performance is in the aspects of increasingly diverse investment channels, increasingly flexible construction ways and constant innovation of management and maintenance models, these characteristics verify the rationality and feasibility of multivariate supply model. Finally, we point out the matters needed to pay special attention when using multivariate supply model to effectively solve the problem in the process of supply of small-scale irrigation and water conservancy facilities in Rural China. Keywords: Small-scale Irrigation And Water Conservancy, Public Governance, Multi-participation, Supply Mode

Portugueses na China: um exame da situação atual

Dissertação de mestrado em Estudos Interculturais Português/Chinês (área de especialização em Tradução, Formação e Comunicação Empresarial)Com o rápido desenvolvimento da globalização e a crescente cooperação entre a China e Portugal, cada vez mais portugueses rumam à China para estudar ou trabalhar. Pretende-se com este trabalho apresentar vários aspetos relevantes relacionados com a comunidade portuguesa na China, incluindo o contexto e as razões da sua migração, os seus olhares sobre o país e a sua situação atual. Estes migrantes portugueses são pontes entre duas sociedades muito diferentes. A aplicação de inquéritos e a respetiva análise de dados permitirá, assim, obter um retrato da sua vida quotidiana, a fim de melhorar o conhecimento do “outro” e de nós próprios. Um outro objetivo deste trabalho é o de contribuir para o melhorar da integração social da comunidade portuguesa na China, aprofundando de forma concomitante o conhecimento mútuo entre os dois países. Neste sentido, à descrição objetiva soma-se uma visão pessoal da autora em relação ao assunto tratado.With the rapid development of Globalization and the increased cooperation between China and Portugal, more and more Portuguese have chosen China to study or work. The aim of this dissertation is to explore several relevant aspects related to the Portuguese community in China, including the context and reasons for their migration, their views about the country and their current situation. These Portuguese migrants help bridging two very different societies. The conduct of inquiries and consequent data analysis will allow to understand their life circumstances, in order to improve the understanding of the "others" and "ourselves". Another aim of this work is to work as a contribution to improve the social integration of the Portuguese community in China and, at the same time, to deepen the mutual understanding between the two countries. Therefore, besides the objective description, we also present the author’s personal vision on this subject.近年来，随着全球化的快速发展以及中葡间经贸往来的不断增多，越来越 多的葡萄牙人选择去中国学习、工作和生活。本论文旨在从不同方面介绍在中 国生活的葡萄牙人这一特殊群体，包括移民背景、移民原因、对中国的具体看 法以及目前生活的现状。 本文中使用的主要数据和信息都来源于对目前正在中国生活的葡萄牙移民 进行的问卷采访和调查，他们的生活现状以及对目前生活的看法不仅影响着葡 萄牙社会对中国的认识和态度，也为中国社会提供了一个深入了解自我的视角。 除了具体的客观论述，本文还尝试在不同文化背景下为葡萄牙移民群体在 中国社会的深层次融入提出一些可行性建议，以期为中葡关系的深层次研究做 一些微小的贡献

Defining Next Generation Supply Chain Sustainability

The importance of understanding supply chain sustainability is being realized by increasingly more people, including corporate managers, investors, policy makers, customers and other stakeholders. A lot of practitioners and academic researchers have addressed this issue in past few years. However, most of their studies lack systematic thinking and are not quantifiable. Thus, a systematic and quantifiable model which incorporates economic, environmental and social factors is needed. In our study, a systematic and quantifiable risk assessment model based on the concept of “Triple Bottom Line” is developed in order to solve supply chain sustainability problem from risk assessment perspectiveMaster of ScienceNatural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/110983/1/276-Defining Next Generation Supply Chain Sustainability_2015.pd

Structured Neural-PI Control with End-to-End Stability and Output Tracking Guarantees

We study the optimal control of multiple-input and multiple-output dynamical systems via the design of neural network-based controllers with stability and output tracking guarantees. While neural network-based nonlinear controllers have shown superior performance in various applications, their lack of provable guarantees has restricted their adoption in high-stake real-world applications. This paper bridges the gap between neural network-based controllers and the need for stabilization guarantees. Using equilibrium-independent passivity, a property present in a wide range of physical systems, we propose neural Proportional-Integral (PI) controllers that have provable guarantees of stability and zero steady-state output tracking error. The key structure is the strict monotonicity on proportional and integral terms, which is parameterized as gradients of strictly convex neural networks (SCNN). We construct SCNN with tunable softplus-$\beta$ activations, which yields universal approximation capability and is also useful in incorporating communication constraints. In addition, the SCNNs serve as Lyapunov functions, giving us end-to-end performance guarantees. Experiments on traffic and power networks demonstrate that the proposed approach improves both transient and steady-state performances, while unstructured neural networks lead to unstable behaviors.Comment: arXiv admin note: text overlap with arXiv:2206.0026

Bridging Transient and Steady-State Performance in Voltage Control: A Reinforcement Learning Approach with Safe Gradient Flow

Deep reinforcement learning approaches are becoming appealing for the design of nonlinear controllers for voltage control problems, but the lack of stability guarantees hinders their deployment in real-world scenarios. This paper constructs a decentralized RL-based controller featuring two components: a transient control policy and a steady-state performance optimizer. The transient policy is parameterized as a neural network, and the steady-state optimizer represents the gradient of the long-term operating cost function. The two parts are synthesized through a safe gradient flow framework, which prevents the violation of reactive power capacity constraints. We prove that if the output of the transient controller is bounded and monotonically decreasing with respect to its input, then the closed-loop system is asymptotically stable and converges to the optimal steady-state solution. We demonstrate the effectiveness of our method by conducting experiments with IEEE 13-bus and 123-bus distribution system test feeders.Comment: Published in IEEE Control Systems Letters, vol. 7, pp. 2845-2850, 2023 with CDC presentatio