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Reaction kinetics and internal diffusion of Zhundong char gasification with CO

Yun Liu, Jiangyuan Qu, Xuehui Wu, Kai Zhang, Yuan Zhang

《化学科学与工程前沿（英文）》 2021年第15卷第2期页码 373-383 doi: 10.1007/s11705-020-1949-2

摘要： Mass transfer usually affects the rate of chemical reactions in coal. The effect of internal diffusion on char gasification with CO in the temperature range from 1123 K to 1273 K was investigated via thermo-gravimetric analysis and assessment of char morphology features. The results revealed that the effect of internal diffusion on the initial reaction rate was more significant with an increase of particle size, due to the concentration gradient of the gasification agent within the solid particles. In the early stage of gasification, the generation of new micropores and the opening of closed pores led to an increase in specific surface area. As the reaction proceeded, the openings were gradually expanded and the specific surface area continued to increase. However, with further reaction, disappearance of edge pores, melting and collapse of the pore structure led to a decrease in specific surface area. The intrinsic activation energy and reaction order based on the th-order model were 157.67 kJ∙mol and 0.36, respectively. Thus, temperature zones corresponding to chemical reaction and diffusion control were identified. Moreover, the calculated effectiveness factor provided a quantitative estimation of internal diffusion in the initial stage.

关键词： coal char CO₂ gasification internal diffusion pore evolution

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Diffusion process in enzyme–metal hybrid catalysts

《化学科学与工程前沿（英文）》 2022年第16卷第6期页码 921-929 doi: 10.1007/s11705-022-2144-4

摘要： Enzyme–metal hybrid catalysts bridge the gap between enzymatic and heterogeneous catalysis, which is significant for expanding biocatalysis to a broader scope. Previous studies have demonstrated that the enzyme–metal hybrid catalysts exhibited considerably higher catalytic efficiency in cascade reactions, compared with that of the combination of separated enzyme and metal catalysts. However, the precise mechanism of this phenomenon remains unclear. Here, we investigated the diffusion process in enzyme–metal hybrid catalysts using Pd/lipase-Pluronic conjugates and the combination of immobilized lipase (Novozyme 435) and Pd/C as models. With reference to experimental data in previous studies, the Weisz–Prater parameter and efficiency factor of internal diffusion were calculated to evaluate the internal diffusion limitations in these catalysts. Thereafter, a kinetic model was developed and fitted to describe the proximity effect in hybrid catalysts. Results indicated that the enhanced catalytic efficiency of hybrid catalysts may arise from the decreased internal diffusion limitation, size effect of Pd clusters and proximity of the enzyme and metal active sites, which provides a theoretical foundation for the rational design of enzyme–metal hybrid catalysts.

关键词： enzyme–metal hybrid catalyst internal diffusion proximity effect kinetic model

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Cylindrical particulate internal flows: A review

Lizhong HUANG, Xiang GAO, Jianzhong LIN

《机械工程前沿（英文）》 2012年第7卷第4期页码 385-393 doi: 10.1007/s11465-012-0354-z

摘要：

The study of cylindrical particulate internal flows has wide industrial applicability hence received much attention. This article reviews the cylindrical particulate internal flows over the past twenty years. The research is related to the cylindrical particulate flows in the straight channel, curved channel and rotational channel. Finally, several open research issues have been identified.

关键词： cylindrical particulate flow internal flow

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Current progress on internal medicine in China—2006 Part I

YAO Dingkang, ZHU Liang, ZHAO Xue, MEI Changlin

《医学前沿（英文）》 2007年第1卷第3期页码 235-247 doi: 10.1007/s11684-007-0046-y

摘要： The growing interest has been placed in the current state of Chinaºs internal medicine from all over the world. Many data of internal medicine in China were collected by searching through some of the most prominent medical magazines published in China in 2006. Because there are many researches on the field of internal medicine, just some representative reports focusing on this topic were selected in this paper. In part I of this study, a summary of the advances made in cardiology, respiration diseases, and gastroenterology was presented.

关键词： internal medicine Chinaºs internal respiration gastroenterology cardiology

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A comprehensive assessment on the durability of gas diffusion electrode materials in PEM fuel cell stack

Arunkumar JAYAKUMAR

《能源前沿（英文）》 2019年第13卷第2期页码 325-338 doi: 10.1007/s11708-019-0618-y

摘要： Polymer electrolyte membrane (PEM) fuel cell is the most promising among the various types of fuel cells. Though it has found its applications in numerous fields, the cost and durability are key barriers impeding the commercialization of PEM fuel cell stack. The crucial and expensive component involved in it is the gas diffusion electrode (GDE) and its degradation, which limits the performance and life of the fuel cell stack. A critical analysis and comprehensive understanding of the structural and functional properties of various materials involved in the GDE can help us to address the related durability and cost issues. This paper reviews the key GDE components, and in specific, the root causes influencing the durability. It also envisages the role of novel materials and provides a critical recommendation to improve the GDE durability.

关键词： PEM fuel cell gas diffusion electrode(GDE) gas diffusion layer(GDL) membrane electrode assembly durability fuel cell catalyst

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Unified cycle model of a class of internal combustion engines and their optimum performance characteristics

Shiyan ZHENG

《能源前沿（英文）》 2011年第5卷第4期页码 367-375 doi: 10.1007/s11708-011-0170-x

摘要： The unified cycle model of a class of internal combustion engines is presented, in which the influence of the multi-irreversibilities mainly resulting from the adiabatic processes, finite-time processes and heat leak loss through the cylinder wall on the performance of the cycle are taken into account. Based on the thermodynamic analysis method, the mathematical expressions of the power output and efficiency of the cycle are calculated and some important characteristic curves are given. The influence of the various design parameters such as the high-low pressure ratio, the high-low temperature ratio, the compression and expansion isentropic efficiencies etc. on the performance of the cycle is analyzed. The optimum criteria of some important parameters such as the power output, efficiency and pressure ratio are derived. The results obtained from this unified cycle model are very general and useful, from which the optimal performance of the Atkinson, Otto, Diesel, Dual and Miller heat engines and some new heat engines can be directly derived.

关键词： internal combustion engine irreversibility power output efficiency optimization

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Coupled diffusion of chloride and other ions in saturated concrete

Nattapong DAMRONGWIRIYANUPAP, Linyuan LI, Yunping XI

《结构与土木工程前沿（英文）》 2011年第5卷第3期页码 267-277 doi: 10.1007/s11709-011-0112-z

摘要： Corrosion of reinforcing steel due to chloride ions is one of the severe deterioration problems in long-term performance of reinforced concrete structures. The deterioration process is frequently found in marine concrete structures, highway pavements, and bridges exposed to deicing salts. The diffusion of chloride ions is associated and strongly affected by other ions in the pore solution in concrete. In this paper, chloride penetration into concrete structures was mathematically characterized by the Nernst-Planck equation which considered not only diffusion mechanism of the chloride ions but also ionic interaction among other ions coming from externally applied deicers and within the Portland cement paste. Electroneutrality was used to determine the electrostatic potential induced by the ionic interaction. The material models of chloride binding capacity and chloride diffusion coefficient were incorporated in the governing equations. The governing equations were solved by using finite element method. A numerical example was used to illustrate the coupling effect of multi-ionic interactions and the effect of influential parameters. The numerical results obtained from the present model agreed very well with available test data.

关键词： diffusion chloride concrete Nernst-Planck equation durability

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An Empirical Study on the Internal Control Efficiency of Listed Engineering Companies

Zhi-wen Wang,Jing Tong

《工程管理前沿（英文）》 2015年第2卷第2期页码 159-164 doi: 10.15302/J-FEM-2015026

摘要： The authors carried out an empirical study on the internal control efficiency of publically listed engineering companies in China. This study presents an exploration of the relationship of independent director ratios, audit committee quality and auditor independence with the internal control efficiency of publically listed engineering companies and forward suggestions and recommendations on raising the internal control efficiency of publically listed engineering companies.

关键词： internal control efficiency board of directors independent directors audit committee

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Embankment dam foundation analysis for the decrease of internal erosion likelihood

Marc SMITH

《结构与土木工程前沿（英文）》 2012年第6卷第4期页码 431-436 doi: 10.1007/s11709-012-0183-5

摘要： A zoned embankment dam is founded on clay underlain by a sand deposit. Major seepage phenomena were noticed in the foundation downstream from the dam where the vertical seepage forces in the sand layer were expected to exceed the downward forces due to the overlying clay. Modern technologies were applied to delineate critical zones to help design optimal rehabilitation measures. A global electromagnetic survey was carried out to detect and map the main sources, pathways and exits of seepage. Based on these global findings, a more detailed analysis was then conducted to identify zones where thickness of the foundation clay is minimal, pore pressures in sand are higher and thus where the factor of safety against uplift is lower and internal erosion is more likely to occur. Clay thickness evaluation required the determination of land surface as well as clay-sand contact elevations. A laser airborne survey was performed to model the land surface elevation. Data concerning the clay-sand contact elevation came from the interpreted stratigraphy based on a series of boreholes and cone penetration tests. This data was combined in a geostatistical model along with the measured piezometric levels in the foundation. This resulted in a contour map showing factors of safety against uplift over the entire downstream area. The use of modern technologies, namely electromagnetic and laser surveys as well as geostatistical tools, was instrumental in defining the limits of an otherwise spread-out problem and to provide an optimal solution, in terms of costs and effectiveness, for the long-term stabilization of the foundation.

关键词： seepage detection geostatistical analysis dam monitoring internal erosion LIDAR survey

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Experimental study of humid air reverse diffusion combustion in a turbulent flow field

GE Bing, ZANG Shusheng, GU Xin

《能源前沿（英文）》 2007年第1卷第4期页码 428-434 doi: 10.1007/s11708-007-0062-6

摘要： Experiments were performed to investigate the differences between the propane/air turbulent diffusion reactive flows past bluff-body and the propane/humid air turbulent diffusion reactive flows in the same conditions. The velocity

关键词： propane/humid propane/air turbulent bluff-body turbulent diffusion

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Preparation of a Pb loaded gas diffusion electrode and its application to CO

Ang LI, Hua WANG, Jinyu HAN, Li LIU

《化学科学与工程前沿（英文）》 2012年第6卷第4期页码 381-388 doi: 10.1007/s11705-012-1216-2

摘要： A Pb loaded gas diffusion electrode was fabricated and used for the electroreduction of CO to formic acid. The Pb/C catalyst was prepared by isometric impregnation. The crystal structure and morphology of the Pb/C catalyst were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The preparation conditions of the gas diffusion electrode were optimized by adjusting the amounts of polytetrafluoroethylene (PTFE) in the gas diffusion layer and acetylene black in the catalytic layer. The electrochemical performance of the as-prepared gas diffusion electrode was studied by chronoamperometry and cyclic voltammetry. The optimized gas diffusion electrode showed good catalytic performance for the electroreduction of CO . The current efficiency of formic acid after 1 h of operation reached a maximum of 22% at -2.0 V versus saturated calomel electrode (SCE).

关键词： electroreduction carbon dioxide lead catalyst gas diffusion electrode formic acid

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evaluation of renal function using diffusion weighted imaging and diffusion tensor imaging in type 2

null

《医学前沿（英文）》 2014年第8卷第4期页码 471-476 doi: 10.1007/s11684-014-0365-8

摘要：

This work aims to estimate the value of diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) in detecting early-stage kidney injury in type 2 diabetic patients with normoalbuminuria (NAU) versus microalbuminuria (MAU) prospectively. A total of 30 T2DM patients with normal kidney function were recruited and assigned to the NAU group (n = 14) or MAU group (n= 16) according to 8 h overnight urinary albuminuria excretion rate (AER) results. A contemporary cohort of health check-up recipients were included as controls (n = 12). DWI and DTI scans were performed on bilateral kidney using SE single-shot EPI, and apparent diffusion coefficient (ADC) and fractional anisotropy (FA) of the renal parenchyma was determined from ADC and FA maps of the three groups. ADC and FA values were compared among the three groups. According to DWI with a b value of 400 s/mm², the MAU and NAU groups showed significantly lowered mean ADC values compared with the healthy controls (P<0.01). The mean ADC in the MAU group [(2.22±0.07)×10^–3 mm²/s] was slightly lower than that of the NAU group [(2.31±0.22)×10^–3 mm²/s], but this difference was not statistically significant (P>0.05). The FA value in the MAU group was higher than that in the control group (0.45±0.07 vs. 0.39±0.03, P = 0.004) but did not differ from that in the NAU group (0.42±0.03) (P>0.05). ADC and FA values may be more sensitive than urine AER in reflecting early-stage kidney injury and, hence, may facilitate earlier detection and quantitative evaluation of kidney injury in T2DM patients. Combined evaluation of ADC and FA values may provide a better quantitative approach for identifying diabetic nephropathy at early disease stages.

关键词： type 2 diabetes mellitus microalbuminuria diffusion weighted imaging diffusion tensor imaging early-stage kidney injury

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Magnetohydrodynamic slip flow and diffusion of a reactive solute past a permeable flat plate with suction

Krishnendu BHATTACHARYYA, G. C. LAYEK

《化学科学与工程前沿（英文）》 2011年第5卷第4期页码 471-476 doi: 10.1007/s11705-011-1130-z

摘要： The magnetohydrodynamic (MHD) boundary layer slip flow and solute transfer over a porous plate in the presence of a chemical reaction are investigated. The governing equations were transformed into self-similar ordinary differential equations by adopting the similarity transformation technique. Then the numerical solutions are obtained by a shooting technique using the fourth order Runge-Kutta method. The study reveals that due to the increase in the boundary slip, the concentration decreases and the velocity increases. On the other hand, with an increase in the magnetic field and mass suction, both boundary layer thicknesses decreased. As the Schmidt number and the reaction rate parameter increases, the concentration decreases and the mass transfer increases.

关键词： slip flow MHD boundary layer reactive solute diffusion flat plate suction/injection

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Advances in polishing of internal structures on parts made by laser-based powder bed fusion

《机械工程前沿（英文）》 2023年第18卷第1期 doi: 10.1007/s11465-022-0724-0

摘要： The internal structures of metallic products are important in realizing functional applications. Considering the manufacturing of inner structures, laser-based powder bed fusion (L-PBF) is an attractive approach because its layering principle enables the fabrication of parts with customized interior structures. However, the inferior surface quality of L-PBF components hinders its productization progress seriously. In this article, process, basic forms, and applications relevant to L-PBF internal structures are reviewed comprehensively. The causes of poor surface quality and differences in the microstructure and property of the surface features of L-PBF inner structures are presented to provide a perspective of their surface characteristics. Various polishing technologies for L-PBF components with inner structures are presented, whereas their strengths and weaknesses are summarized along with a discussion on the challenges and prospects for improving the interior surface quality of L-PBF parts.

关键词： laser-based powder bed fusion polishing internal structures surface quality surface features post process additive manufacturing

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Molecular diffusion in ternary poly(vinyl alcohol) solutions

《化学科学与工程前沿（英文）》 2022年第16卷第6期页码 1003-1016 doi: 10.1007/s11705-021-2121-3

摘要： The diffusion kinetics of a molecular probe—rhodamine B—in ternary aqueous solutions containing poly(vinyl alcohol), glycerol, and surfactants was investigated using fluorescence correlation spectroscopy and dynamic light scattering. We show that the diffusion characteristics of rhodamine B in such complex systems is determined by a synergistic effect of molecular crowding and intermolecular interactions between chemical species. The presence of glycerol has no noticeable impact on rhodamine B diffusion at low concentration, but significantly slows down the diffusion of rhodamine B above 3.9% (w/v) due to a dominating steric inhibition effect. Furthermore, introducing surfactants (cationic/nonionic/anionic) to the system results in a decreased diffusion coefficient of the molecular probe. In solutions containing nonionic surfactant, this can be explained by an increased crowding effect. For ternary poly(vinyl alcohol) solutions containing cationic or anionic surfactant, surfactant–polymer and surfactant–rhodamine B interactions alongside the crowding effect of the molecules slow down the overall diffusivity of rhodamine B. The results advance our insight of molecular migration in a broad range of industrial complex formulations that incorporate multiple compounds, and highlight the importance of selecting the appropriate additives and surfactants in formulated products.

关键词： fluorescence correlation spectroscopy poly(vinyl alcohol) anomalous diffusion crowding effects dynamic light scattering binding effects rhodamine B