关键词： Shear deformation  

摘要： Viscous environments are ubiquitous in nature and in engineering applications, from mucus in lungs to oil recovery strategies in the earth's subsurface - and in all these environments, bacteria also thrive. The behavior of bacteria in viscous environments has been investigated for a single bacterium, but not for active suspensions. Dense populations of pusher-type bacteria are known to create superfluidic regimes where the effective viscosity of the entire suspension is reduced through collective motion, and the main purpose of this study is to investigate how a viscous environment will affect this behavior. Using a Couette rheometer, we measure shear stress as a function of the applied shear rate to define the effective viscosity of suspensions of Escherichia coli (E. coli), while varying both the bacterial density within the suspension and the viscosity of the suspending fluid. We document the remarkable observation that E. coli decreases the effective suspension viscosity to near-zero (superfluidic regime) for all solvent viscosities tested (1-17 mPa s). Specifically, we observe that the bacterial density needed to trigger this superfluidic regime and the maximum shear rate under which this regime can be sustained both decrease with increasing solvent viscosity. We find that the resulting rheograms can be well approximated by the Carreau-Yasuda law. Using this, we propose a constitutive model as a function of the solvent viscosity and the bacterial concentration only. This model captures the onset of the superfluidic regime and offers promising avenues for the modelling of flow of bacterial suspensions in viscous environments.

关键词： 课堂教学   心流体验   精细化管理   开放式教学环境  

摘要： 面对教学方式不断变革、线上教学发展迅猛的新形势,如何提升原有课堂教学质量成为教育研究重点。为此提出一种面向心流体验的精细化开放式教学模式。首先在原有课堂教学理论基础上,引入心流理论,进行课堂提升需求分析。然后充分结合线上教学方式优势,设计课堂教学辅助分析系统,在信息化技术支撑下实现课堂精细化管理。在理论支撑与系统需求指导下,打造开放式教学环境,构建“以学生学习为主体、信息分析为辅助、心流体验为目标”的课堂环境,增强学生主动学习的积极性,提高学生各方面综合能力。

关键词： 增殖过程   生理条件   激活机制   肿瘤细胞   黏附细胞   流动腔   增殖影响   B细胞  

摘要： 目的生理条件下,布鲁顿酪氨酸激酶(BTK)在淋巴B细胞的增殖、发育和归巢过程起到重要的作用。病理条件下,BTK也影响了多发性骨髓瘤细胞在骨髓区域的黏附和增殖。然而该过程中BTK扮演的角色尚未明了。探明BTK对B细胞瘤黏附和随后增殖影响的力学调控机制。方法使用流动腔和分子动力学模拟技术,研究力条件下由BTK参与的肿瘤细胞的黏附和增殖过程,并寻求其中的激活机制。结果抑制BTK活性能明显降低细胞的滚动速度和减少滚动黏附细胞的数目。

关键词： 铁素体   铁磁性   矩形管   匀强磁场   磁感应强度  

摘要： 用Ansys静磁模块数值模拟了在外加强磁场环境下铁素体矩形通道管中心磁感应强度分布。与文献结果、解析解及实验数据的对比表明,模拟结果与它们基本一致。进一步的数值模拟还表明,铁素体矩形管对其内部的整体磁场分布影响较大,不同区域内产生不同程度的磁力线扭曲及非均匀的磁感应强度分布效应。该分布可能对管道内磁流体动力学效应产生较大影响。

关键词： Attrition rate   Bituminous coal   Ash composition   Fluidized bed  

摘要： While fluidized bed coal combustion technology has advanced significantly, attrition and its impact on combustion remains a problem. Using a bench scale fluidized bed unit, we examined the experimental attrition data for batches of coal ash particles. Experiments were carried out in the presence of bed material (sand) by adding coal particle to the hot riser, which has a height of 500 mm and internal diameter of 25.4 mm. Combustion of coal particles with high ash content was carried out in both O-2/N-2 and O-2/CO2 environments. Coal particles with sizes of 0.4-0.8 mm and 0.8-1.4 mm were prepared by sieving and examined in this work. Using this data, the effect of critical factors on attrition such as gas velocity, particle size, and combustion environments were analyzed. In addition, the composition of ash particles was analyzed by SEM/EDX and XRF. The sizes of ash particles were less than 0.2 mm after combustion. A higher attrition rate was determined at higher gas velocity, regardless of the combustion environment. The ash composition analysis showed high concentration of silicon and aluminum oxide in the ash, and this possibly was increased due to kaolinite decomposition.

关键词： Redox reactions   Atmospheric chemistry   Environmental pollution   Coal   Power  

摘要： Oxy-coal combustion with circulating fluidized bed (OCFB) is a promising technology for CO2 capture and sequestration. However, its development is highly hindered by the high price of electricity and CO2 capture. In this work, a comprehensive life-cycle environmental and economic assessment of OCFB power plants with a pressurized combustor (POCFB) and a supercritical CO2 Brayton cycle is conducted using a specific life-cycle assessment (LCA) method. There are four processes evaluated in this work, including construction material production, transport, raw material mining, and power plant operation. Both environmental midpoint and endpoint impacts are derived and compared. The results show that compared to the oxy-coal combustion power plant, systems with a pressurized combustor and a S-CO2 Brayton cycle have less damage (6-12%) to the human health and the environment. Meanwhile, compared to the OCFB power plant, POCFB has relatively lower costs of electricity, CO2 capture, and CO2 avoidance, which are 58.1 USD/MWh, 15.5 USD/t, and 33.4 USD/t, respectively. The results from the Analytic Hierarchy Process-Technique for Order Preference by Similarity to Ideal Solution methodology show that comprehensively considering the economy, resource, and environment, the POCFB power plant is the best option among the cases from the perspective of residents and the government. The influence of several parameters including net electricity efficiency, CO2 capture rate, boiler investment, coal price, and CO2 tax on the economic indicators is also discussed.

关键词： Circulating fluidized bed boiler   Cost-benefit analysis   PSO-ELM   Environmental benefits  

摘要： In this paper, the environmental cost and environmental benefit evaluation system of circulating fluidized bed (CFB) technology is established by analyzing the environmental damage caused by coal-fired power generation and comparing circulating fluidized bed boilers with ordinary coal-fired boilers. Among them, the environmental cost is mainly the cost of desulfurization equipment and sellout equipment. Environmental benefits include internal environmental benefits and external environmental benefits. The internal environmental benefits mainly include the cost savings from desulfurization and denitrification to reduce the emission of polluting gases and the benefits from the comprehensive utilization of the ash from the circulating fluidized bed boiler. The external environmental benefits mainly include the reduction of occupied farmland, the emission of waste gas caused by spontaneous combustion of coal gangue and the pollution of water resources. After measuring the environmental costs and benefits of CFB technology, this paper further estimated its value. On this basis, particle swarm optimization (PSO) with extreme learning machine (ELM) intelligent algorithm was used to predict the scenario of thermal power generation and evaluate the environmental benefits of CFB units in the future through further calculation. (c) 2020 Elsevier Ltd. All rights reserved.

关键词： 近红外光谱   地层测试   油基钻井液   污染率   油藏流体分布   西湖凹陷  

摘要： 油基钻井液在储层保护方面具有较大的优势。然而,油基钻井液在钻进过程中滤失到近井筒周围,影响了电缆地层测试中取样的代表性及对井下油藏流体的识别。文中利用井下近红外光谱分析,区分油藏流体和油基钻井液滤液的特征,实时监测油藏流体的污染率。同时,利用流体方程进行去污染率的校正,以更好地确定油藏流体的性质。通过多井对比分析,认识了油藏流体的分布规律。通过实时分析油藏流体来准确判断污染率,不仅为后期的作业决策及完井计划提供了重要依据,而且对认识油藏的充注成藏机理及地质构造特点具有较大帮助。

摘要： Movement of skeletal-muscle fibres is generated by the locomotion circuit, in which many cells play a different role. Failures in any part of the circuit can cause or define the severity of neuromuscular diseases (NMD), such as amyotrophic lateral sclerosis (ALS). Conventional in vitro study models are based on cocultures of motoneurons and skeletal muscle cells from animal origin in 2D. These models have proved to be quite limited for the understanding of neuromuscular connection and NMD. They do not consider that: i) neural somas and muscles or peripheral glia are physically separated in vivo and have different microenvironment requirements; ii) both sensory and motor neurons can be altered in particular NMD; iii) glial cells are also affected and involved in several neuromuscular pathologies; iv) 2D cultures do not mimic physiological conditions; v) rodent models offer limited benefit translated into clinic research, as they do not carry human genetic background. Later progresses in neuromuscular-mimicking in vitro systems, have been achieved incorporating increasingly evolving technologies, such as 3D cell-culture techniques, human induced pluripotent stem cells (hiPSC) and compartmentalised microfluidic culture systems (cµFCS). The later ones are microfluidic devices for 2D or 3D cell- cultures, with several interconnected compartments, each mimicking different microenvironments or functional units in organ or tissue level. 3D cell culture techniques make cells acquire more in vivo like phenotype and genotype patterns. And finally, hiPSC serve to create study models that mimic the human physiology in both healthy and pathological conditions. This thesis, entitled "Compartmentalised microfluidic culture systems for in vitro modelling of neurological and neuromuscular microenvironments", aims to study the neuromuscular context in vitro through cµFCS and to create physiologically relevant models. It offers an evolving prospective of in vitro models, moving from mi

关键词： Computational fluid dynamics   Multiphase particle-in-cell   CFD-MPPIC   Gasification   Fluidized bed   Single bubble   Biomass  

摘要： Biomass gasification can be performed in dense phase sand fluidized beds. The proposed model involves Computational Fluid Dynamics Multiphase Particle-In-Cell (CFD-MPPIC) simulations, allowing the evaluation of bubble dynamics and bubble drag correlations. The proposed model accounts for a single bubble injection into a unit loaded with 520-mu m sand particles and 2.7 cm x 0.7 cm cylindrical wood pellets. Model development also includes the selection of an adequate number of computational cells, the sizing of the particle-in-cell population, and the cell distribution throughout the column. Predictions of the proposed CFD-MPPIC Model were compared with bubbles measured by the HESC Model (Torres Brauer et al., 2020). This data was obtained in a 0.44 m diameter Plexiglas unit, using CREC-Optiprobes and a spherical cap bubble assumption. It is anticipated that the CFD-MPPIC Model could have significant value for the design of scaled-up biomass units operated under dense phase fluidization conditions. (C) 2020 Elsevier Ltd. All rights reserved.