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Two-scale modeling of granular materials: A FEM-FEM approach

Yun-Zhu CAI, Yu-Ching WU

《结构与土木工程前沿（英文）》 2013年第7卷第3期页码 304-315 doi: 10.1007/s11709-013-0213-y

摘要： In the present paper, a homogenization-based two-scale FEM-FEM model is developed to simulate compactions of visco-plastic granular assemblies. The granular structure consisting of two-dimensional grains is modeled by the microscopic finite element method at the small-scale level, and the homogenized viscous assembly is analyzed by the macroscopic finite element method at large-scale level. The link between scales is made using a computational homogenization method. The two-scale FEM-FEM model is developed in which each particle is treated individually with the appropriate constitutive relations obtained from a representative volume element, kinematic conditions, contact constraints, and elimination of overlap satisfied for every particle. The method could be used in a variety of problems that can be represented using granular media.

关键词： homogenization two-scale representative volume element compaction granular assembly finite element method

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Numerical simulation of sudden-expansion two-phase flows with two-scale second-order moment particle

ZENG Zhuoxiong, HAN Shoulei, ZHOU Lixing

《能源前沿（英文）》 2007年第1卷第2期页码 202-206 doi: 10.1007/s11708-007-0026-6

摘要： A two-scale second-order moment particle turbulence model is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. The model is employed to simulate gas-particle flows in a sudden-expansion chamber. Simulation results are compared with the experimental results and with those obtained by the single-scale second-order moment two-phase turbulence model. It is shown that the two-scale model is with higher calculating accuracy than the single-scale model.

关键词： gas-particle single-scale second-order large-scale fluctuation second-order sudden-expansion

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Remediation of 2,4-dichlorophenol-contaminated groundwater using nano-sized CaO in a two-dimensionalscale tank

《环境科学与工程前沿（英文）》 2020年第15卷第5期 doi: 10.1007/s11783-020-1381-3

摘要：

• Nano CaO₂ is evaluated as a remediation agent for 2,4-DCP contaminated groundwater.

关键词： Calcium peroxide 2 4-DCP Reaction zone Fenton reaction

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A full-scale integrated-bioreactor with two zones treating odours from sludge thickening tank and dewatering

Jianwei Liu, Kaixiong Yang, Lin Li, Jingying Zhang

《环境科学与工程前沿（英文）》 2017年第11卷第4期 doi: 10.1007/s11783-017-0932-8

摘要： A full-scale integrated-bioreactor consisting of a suspended zone and an immobilized zone was employed to treat the ordours emitted from a wastewater treatment plant. The inlet concentrations of H S and NH were 1.6–38.6 mg·m and 0.1–6.7 mg·m , respectively, while the steady-state outlet concentrations were reduced to 0–2.8 mg·m for H S and 0–0.5 mg·m for NH . Both H S and NH were eliminated effectively by the integrated bioreactor. The removal efficiencies of H S and NH differed between the two zones. Four species of microorganisms related to the degradation of H S and NH were isolated. The characteristics and distributions of the microbes in the bioreactor depended on the inlet concentration of substrates and the micro-environmental conditions in the individual zones. Product analysis indicated that most of the H S was oxidized into sulfate in the immobilized zone but was dissolved into the liquid phase in the suspended zone. A large amount of NH was converted into nitrate and nitrite by nitration in the suspended zone, whereas only a small amount of NH was transferred to the aqueous phase mainly by absorption or chemical neutralization in the immobilized zone. Different microbial populations dominated the individual zones, and the major biodegradation products varied accordingly.

关键词： Biological deodorization Microbial characteristics Ammonia Hydrogen sulfide Wastewater treatment plant

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New form of geodetic coordinate system taking two length quantity as coordinate parameters

Yimin SHI, Ziyang ZHU, Yeming FAN

《结构与土木工程前沿（英文）》 2009年第3卷第1期页码 105-110 doi: 10.1007/s11709-009-0014-5

摘要： A new form of geodetic coordinate system based on geodesic coordinates instead of geodetic longitude and latitude was proposed. The vertical and horizontal geodesic coordinates measured with length were defined as coordinate parameters, but the two families of coordinate curves were still meridians and parallel circles. The first fundamental form on the ellipsoidal surface and its three coefficients were deduced by the geodesic coordinate. The formula for the latitudinal scale factor of length for geodetic parallel lines was derived, by which the obtained result conformed to that standard value calculated from geodetic latitude, and it is applicable in the range of 400 km from north to south. Therefore, it lays the foundation for establishing the differential equation and differential relationship based on this type of coordinate parameters; and consequently, it is convenient and accurate enough to operate on the ellipsoidal surface in this new form of geodetic coordinate system.

关键词： geodetic coordinate system meridian and parallel circle coordinate parameter the first fundamental form on the ellipsoidal surface latitudinal scale factor of length

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图像边缘检测二维小波算法研究与实现

张红岩,张登攀

《中国工程科学》 2003年第5卷第4期页码 61-64

摘要：

边沿作为图像视觉的最主要特征，成为图像信息获取的重要内容。小波变换具有检测局域突变的能力，而且可以结合多尺度信息进行检测，因此成为图像信息边缘检测的优良工具。根据二维小波变换的特点,分析了利用二维小波进行图像边缘检测的基本原理，并设计了利用二维小波变换进行多尺度边缘匹配的检测算法。基于研究结果，编写了计算机应用程序，进行实例分析。

关键词：小波变换多尺度边缘检测

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Carbon dots-based fluorescence sensor for two-photon imaging of pH in diabetic mice

《化学科学与工程前沿（英文）》 2023年第17卷第3期页码 298-306 doi: 10.1007/s11705-022-2212-9

摘要： Herein, a reversible pH fluorescent sensor was developed using caffeic acid as the precursor by one-step solvothermal synthesis method. The carbon dots-based sensor (CA-CDs) exhibited pH-dependent increase in fluorescence intensity and showed linear relationship in the range of pH 6.60 and 8.00. Notably, the fluorescence sensor has a reversible response to pH change. Finally, the CA-CDs has been successfully applied for two-photon imaging of the pH in liver and kidney of diabetic mice. Imaging results showed that the pH value in kidney of diabetic mice was lower than that of the normal mice, while the pH value in liver of diabetic mice was almost the same as that of the normal mice. The present study provides a simple analytical method for pH detection suitable for in vivo.

关键词： carbon dots two-photon imaging pH diabetic mice

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New medical risks affecting obstetrics after implementation of the two-child policy in China

null

《医学前沿（英文）》 2017年第11卷第4期页码 570-575 doi: 10.1007/s11684-017-0552-5

摘要：

China recently instituted a two-child policy in response to its aging population, declining workforce and demographic dividend, and the need to develop asocial economy. Additionally, women generally delay having a second child because of the overwhelming pressure in their lives. With the improvements in assisted fertility technologies in recent years, the number of elderly women attempting to bear children has increased. The quality of woman’s eggs and a man’s sperm declined dramatically with increasing age, leading to an increased risk of pregnancy-related complications among older women. Therefore, the types of fertility problems experienced by elderly females must be provided with considerable attention by obstetricians. This commentary article focuses on the medical problems faced by older second-child pregnant women. This work discusses their increased rates of infertility, spontaneous abortion, fetal malformation, gestational diabetes, cesarean section, placenta previa, postpartum hemorrhage, postpartum depression, and hypertensive disorders, which complicate pregnancy.

关键词： two-child policy birth defects cesarean delivery placenta previa

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Structure controlling and process scale-up in the fabrication of nanomaterials

Chunzhong LI,

《化学科学与工程前沿（英文）》 2010年第4卷第1期页码 18-25 doi: 10.1007/s11705-009-0305-3

摘要： Nanotechnology is already having a significant commercial impact, and will very certainly have a much greater impact in the future. The research on process engineering and scale-up will be very important for the commercial production and application of nanomaterials, because the properties and structure of nanomaterials are not only determined by the nucleation and growth process, but also strongly affected by the engineering properties, such as the mixing, the heat and mass transfer, and also the distribution of temperature, concentration, etc. This paper will present some research work in our laboratory on the fabrication of nanomaterials. Based on the chemical engineering principle and methods, many kinds of novel nanomaterials can be synthesized and their structure can be easily controlled through adjusting the parameters of the fluid mixing, and the distribution of temperature, residence time and concentration, etc. By using the micro-mixing, heat and mass transfer and reaction control methods, the host-guest nanocomposites have been assembled and assumed as the novel electroanalytical sensing nanobiocomposite materials. Based on the principles of chemical engineering, the manufacturing technologies for magnetic powders, calcium carbonate, and titanium dioxide have been developed for commercial-scale production, and the largest production scale has reached 15 kt/year.

关键词： scale-up significant commercial electroanalytical engineering laboratory

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Large-scale App privacy governance

《工程管理前沿（英文）》页码 640-652 doi: 10.1007/s42524-022-0228-y

摘要： Recently, the problem of mobile applications (Apps) leaking users’ private information has aroused wide concern. As the number of Apps continuously increases, effective large-scale App governance is a major challenge. Currently, the government mainly filters out Apps with potential privacy problems manually. Such approach is inefficient with limited searching scope. In this regard, we propose a quantitative method to filter out problematic Apps on a large scale. We introduce Privacy Level (P-Level) to measure an App’s probability of leaking privacy. P-Level is calculated on the basis of Permission-based Privacy Value (P-Privacy) and Usage-based Privacy Value (U-Privacy). The former considers App permission setting, whereas the latter considers App usage. We first illustrate the privacy value model and computation results of both values based on real-world dataset. Subsequently, we introduce the P-Level computing model. We also define the P-Level computed on our dataset as the PL standard. We analyze the distribution of average usage and number of Apps under the levels given in the PL standard, which may provoke insights into the large-scale App governance. Through P-Privacy, U-Privacy, and P-Level, potentially problematic Apps can be filtered out efficiently, thereby making up for the shortcoming of being manual.

关键词： privacy risk Privacy Level quantification large-scale App governance

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Extended two-fluid model applied to analysis of bubbly flow in multiphase rotodynamic pump impeller

Zhiyi YU, Guoyu WANG, Shuliang CAO

《机械工程前沿（英文）》 2009年第4卷第1期页码 53-59 doi: 10.1007/s11465-009-0006-0

摘要： This paper presents an extended two-fluid model based on the Navier-Stokes equations and the standard turbulence model, to simulate the three-dimensional air-water bubbly flow in turbo machinery. In the governing equations, the drag force and added mass force are added and the additional source terms arising from fluctuations of gas volume fraction are considered. The discrete equations are solved using a developed two-phase semi-implicit method for pressure-linked equations, consistent (SIMPLEC) algorithm in body-fitted coordinates with a staggered grid system. Simulation is then carried out for the pure liquid flow and air-water two-phase flow with the inlet gas volume fraction being 15% in a multiphase rotodynamic pump impeller and the pump head performance is predicted. Comparison with experimental results shows the reliability and commonality of the numerical model.

关键词： two-fluid model multiphase rotodynamic pump SIMPLEC algorithm numerical simulation

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Feasible workspace regions for general two-revolute manipulator

Conghui LIANG, Marco CECCARELLI

《机械工程前沿（英文）》 2011年第6卷第4期页码 397-408 doi: 10.1007/s11465-011-0228-9

摘要：

In this paper, a topology is presented for feasible workspace regions in general two-revolute manipulators. The design problem and concept of feasible workspace regions have been discussed as linked to each other. Design equations are formulated by arbitrarily prescribing four workspace boundary points. The so-called feasible workspace regions are the intersection of three different sub-regions, which are given by constraint curves as function of the relative positions of three workspace boundary points. By using a parametric study, all topologies for three sub-regions are figured out. Corresponding areas in cross section plane are determined for prescribing the position of a feasible workspace point as function of the topology for sub-regions. A classification has been proposed to determine and to characterize the combination of the topologies for those sub-regions. All topologies for feasible workspace regions are figured out and they are discussed as a design tool. Three general cases are analyzed in details to characterize workspace design capabilities for general two-revolute manipulators.

关键词： workspace two-revolute manipulators topology analysis design

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Offline motion planning and simulation of two-robot welding coordination

Tie ZHANG, Fan OUYANG

《机械工程前沿（英文）》 2012年第7卷第1期页码 81-92 doi: 10.1007/s11465-012-0309-4

摘要：

This paper focuses on the two-robot welding coordination of complex curve seam which means one robot grasp the workpiece, the other hold the torch, the two robots work on the same workpiece simultaneously. This paper builds the dual-robot coordinate system at the beginning, and three point calibration method of two robots’ relative base coordinate system is presented. After that, the non master/slave scheme is chosen for the motion planning, the non master/slave scheme sets the poses versus time function of the point u on the workpiece, and calculates the two robot end effecter trajectories through the constrained relationship matrix automatically. Moreover, downhand welding is employed which can guarantee the torch and the seam keep in good contact condition all the time during the welding. Finally, a Solidworks-SimMechanics simulation platform is established, and a simulation of curved steel pipe welding is conducted. The results of the simulation illustrate the welding process can meet the requirements of downhand welding, the joint displacement curves are smooth and continuous and no joint velocities are out of working scope.

关键词： complex curve seam two robots coordinated welding motion planning

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On the added value of multi-scale modeling of concrete

《结构与土木工程前沿（英文）》 2022年第16卷第1期页码 1-23 doi: 10.1007/s11709-021-0790-0

摘要： This review of the added value of multi-scale modeling of concrete is based on three representative examples. The first one is concerned with the analysis of experimental data, taken from four high-dynamic tests. The structural nature of the high-dynamic strength increase can be explained by using a multi-scale model. It accounts for the microstructure of the specimens. The second example refers to multi-scale thermoelastic analysis of concrete pavements, subjected to solar heating. A sensitivity analysis with respect to the internal relative humidity (RH) of concrete has underlined the great importance of the RH for an assessment of the risk of microcracking of concrete. The third example deals with multi-scale structural analysis of a real-scale test of a segmental tunnel ring. It has turned out that multi-scale modeling of concrete enables more reliable predictions of crack opening displacements in tunnel segments than macroscopic models taken from codes of practice. Overall, it is concluded that multi-scale models have indeed a significant added value. However, its degree varies with these examples. In any case, it can be assessed by means of a comparison of the results from three sources, namely, multi-scale structural analysis, conventional structural analysis, and experiments.

关键词： experiments multi-scale analysis conventional structural analysis concrete reinforced concrete

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Large Scale Infrastructure Projects: The Art of Project or Change Management?

Geert Letens,Kurt Verweire,Peter De Prins

《工程管理前沿（英文）》 2016年第3卷第3期页码 197-202 doi: 10.15302/J-FEM-2016033

摘要： Although it is generally understood that change is a fundamental component of managing projects in the construction industry in general and an inevitable challenge for large scale infrastructure project in particular, there has been little to no attention in the literature to understand change in this context from a more holistic perspective. For this purpose, this work looks at change through the eyes of a framework of six batteries of change that seem essential to charge an organization’s capabilities for change. The framework brings together the expertise of four specialists that all have developed their insights over many years of study and practice, and has been validated through an extensive review of the management literature on organization development and change. Reflections on the application of this model in the construction industry and in large scale infrastructure projects demonstrate that energizing organizations to successfully deal with change goes beyond the traditional techniques of managing change from a program or project management perspective. Assessing the six batteries of change in this context can help organizations to develop capabilities for change that build change energy by balancing formal/rational methods with informal/emotional interventions at both a local (department/subproject) and global (business) level.

关键词： large scale project management organization development and change batteries of change model