Pore network,pore connectivity,and the resulting effective adsorbate pore diffusivity within an adsorbent are critical physical considerations in mass transport modeling of aqueous adsorption.Tied to these three adsorbent features are the adsorbent tortuosity and tortuosity factor concepts.These concepts encompass the collective hindrance to intra-adsorbent adsorbate transport arising because of a disorderly adsorbent porous topology.It is crucial for materials scientists,chemists,chemical engineers,and water treatment specialists to understand the complex and variable connections among adsorbate chemistry,adsorbent chemistry,adsorbent porosity,pore shape,size,and tortuosity,pore wall effect,adsorbate-adsorbent interactions,and adsorbate-adsorbate interactions in competitively contaminated aqueous environments.Adsorbent tortuosity has been sporadically studied in aqueous adsorption models.Despite the small population of these studies,insightful observations and inferences have been reported.However,as it appears,no review has been published to compile,compare,and contrast these aspects.Hence,this review concisely brings up those observations and interpretations around adsorbent tortuosity for aqueous adsorption systems.The notion of an adsorbent's tortuosity being single-valued is argued to be imprecise.Finally,perspectives are aired on possible research and development directions for elucidating the dynamic attributes of adsorbent tortuosity and applying them in real-scale adsorption-oriented water purification.The data acquired by filling in these research gaps can enable the design of adsorbents more adapted for real-scale water purification.
Water evaporation-induced electricity generation is a promising technology for renewable energy harvesting.However,the output power of some reported two-dimensional(2D)nanofluidic films is still restricted by the relatively weak water–solid interactions within the tortuous nanochannels.To further enhance the comprehension and utilization of water–solid interactions,it is of utmost importance to conduct an in-depth investigation and propose a regulatory concept encompassing ion transport.Herein,we propose tortuosity regulation of 2D nanofluidic titanium oxide(Ti_(0.87)O_(2))films to optimize the ion transport within the interlayer nanochannel for enhanced efficiency in water evaporation-induced electricity generation for the first time.The significance of tortuosity in ion transport is elucidated by designing three 2D nanofluidic films with different tortuosity.Tortuosity analysis and in situ Raman measurement demonstrate that low tortuosity can facilitate the formation of efficient pathways for hydrated proton transport and promote water–solid interactions.Consequently,devices fabricated with the optimized 2D nanofluidic films exhibited a significantly enhanced output power density of approximately 204.01μW·cm^(−2),far exceeding those prepared by the high-tortuosity 2D nanofluidic films.This work highlights the significance of the construction of low tortuosity channels for 2D nanofluidic films with excellent performance.
Effective thermal conductivity and thermal tortuosity are crucial parameters for evaluating the effectiveness of heat conduction within porous media.The direct pore-scale numerical simulation method is applied to investigate the heat conduction processes inside porous structures with different morphologies.The thermal conduction performances of idealized porous structures are directly compared with real foams across a wide range of porosity.Real foam structures are reconstructed using X-ray computed tomography and image processing techniques,while Kelvin and Weaire-Phelan structures are generated through periodic unit cell reconstruction.The detailed temperature fields inside the porous structures are determined by solving the heat conduction equation at the pore scale.The results present that the equivalent thermal conductivity of Kelvin and Weaire-Phelan structures is similar to and greater than that of the real foam structure with the same strut porosity.The thermal tortuosity of real foam structure is relatively larger and the heat conduction path becomes straighter by adopting the anisotropic design.The thermal tortuosity of the fluid channels for Kelvin,Weaire-Phelan,and real foam structures is close to one.The thermal conductivity of porous structures with heat transfer fluid increases as the thermal conductivity ratio of fluid to solid becomes larger.A small porosity of porous media leads to a larger equivalent thermal conductivity due to the dominant contribution of porous skeleton in the heat conduction process.Correlations derived from parallel and series models,as well as the Maxwell-Eucken models,provide decent predictions of effective thermal conductivity,with an average error of less than 8%in the entire range of thermal conductivity ratio.
The microstructure of granular media, including grain's shape- and size-polydispersities, orientation, and area fraction can potentially affect its permeability. However, few studies consider the coupling effects of these features. This work employs geometrical probability and stereology to establish quantitative relationships between the above microstructural features and the geometric tortuosity of the two-dimensional granular media containing superellipse, superoval, and polygon grains. Then the lattice Boltzmann method (LBM) is used to determine the permeabilities of these granular media. By combining the tortuosity model and the LBM-derived permeabilities, modified K–C equations are formulated to predict the permeability and the shape factor, considering the grain's shape- and size-polydispersities, orientation, and area fraction. The reliability of these methods can be verified by comparing them with both our simulations and available experimental, theoretical, and numerical data reported in the literature. The findings implicate that the tortuosity and permeability of the granular media are strongly correlated with the grain's shape, orientation, and area fraction but unaffected by the size polydispersity and spatial arrangement of grains. Only circularity is not enough to derive a unified formula for considering the impact of grain shape on tortuosity and permeability, other shape parameters need to be explored in the future.
Ke CaoHuisu ChenMohammad Iqbal KhanMingqi LiLin Liu
目的 探讨椎-基底动脉迂曲与老年血管源性头晕/眩晕脑梗死的关系。方法 选取2022年1月至2023年10月太原西山医院神经内科住院的老年血管源性头晕/眩晕脑梗死患者160例,根据头颅磁共振血管成像检查是否存在椎-基底动脉异常将其分为迂曲组和非迂曲组,每组各80例。比较两组患者的一般临床资料、血管病危险因素、美国国立卫生研究院卒中量表扩展版(expanded-National Institutes of Health stroke scale,e-NIHSS)评分。迂曲组根据椎-基底动脉形态又分为单纯异常组和混合异常组,分析对相关脑梗死的影响程度。结果 迂曲组患者的高血压、椎动脉优势、吸烟史的比例和e-NIHSS评分均显著高于非迂曲组(P<0.05)。多因素Logistic回归分析结果显示,高血压病史、椎动脉优势、吸烟史均是伴有椎-基底动脉异常老年血管源性头晕/眩晕脑梗死患者的独立危险因素(P<0.05)。单纯异常组中54.3%为中重度脑卒中患者,混合异常组中58.8%为中重度脑卒中患者,两组比较差异无统计学意义(χ^(2)=0.029,P=0.864)。结论 高血压病史、椎动脉优势、吸烟史是伴有椎-基底动脉迂曲的老年血管源性头晕/眩晕脑梗死的独立危险因素,此类患者神经功能缺损评分更高。
