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Preparation and lithium storage performances of g-C

Zhengxu BIAN, Zehua TANG, Jinfeng XIE, Junhao ZHANG, Xingmei GUO, Yuanjun LIU, Aihua YUAN, Feng ZHANG, Qinghong KONG

《能源前沿(英文)》 2020年 第14卷 第4期   页码 759-766 doi: 10.1007/s11708-020-0810-0

摘要: As the anode material of lithium-ion battery, silicon-based materials have a high theoretical capacity, but their volume changes greatly in the charging and discharging process. To ameliorate the volume expansion issue of silicon-based anode materials, g-C N /Si nanocomposites are prepared by using the magnesium thermal reduction technique. It is well known that g-C N /Si nanocomposites can not only improve the electronic transmission ability, but also ameliorate the physical properties of the material for adapting the stress and strain caused by the volume expansion of silicon in the lithiation and delithiation process. When g-C N /Si electrode is evaluated, the initial discharge capacity of g-C N /Si nanocomposites is as high as 1033.3 mAh/g at 0.1 A/g, and its reversible capacity is maintained at 548 mAh/g after 400 cycles. Meanwhile, the improved rate capability is achieved with a relatively high reversible specific capacity of 218 mAh/g at 2.0 A/g. The superior lithium storage performances benefit from the unique g-C N /Si nanostructure, which improves electroconductivity, reduces volume expansion, and accelerates lithium-ion transmission compared to pure silicon.

关键词: magnesium thermal reduction     g-C3N4/Si nanocomposites     volume expansion     electroconductivity     lithium-ion battery    

Assessment of liver volume variation to evaluate liver function

null

《医学前沿(英文)》 2012年 第6卷 第4期   页码 421-427 doi: 10.1007/s11684-012-0223-5

摘要:

In order to assess the value of liver volumetry in cirrhosis and acute liver failure (ALF) patients, we explored the correlation between hepatic volume and severity of the hepatic diseases. The clinical data of 48 cirrhosis patients with 60 normal controls and 39 ALF patients were collected. Computed tomography-derived liver volume (CTLV) and body surface area (BSA) of normal controls were calculated to get a regression formula for standard liver volume (SLV) and BSA. Then CTLV and SLV of all patients were calculated and grouped by Child-Turcotte-Pugh classification for cirrhosis patients and assigned according to prognosis of ALF patients for further comparison. It turned out that the mean liver volume of the control group was 1 058±337 cm3. SLV was correlated with BSA according to the regression formula. The hepatic volume of cirrhosis patients in Child A, B level was not reduced, but in Child C level it was significantly reduced with the lowest liver volume index (CTLV/SLV). Likewise, in the death group of ALF patients, the volume index was significantly lower than that of the survival group. Based on volumetric study, we proposed an ROC (receiver operating characteristic) analysis to predict the prognosis of ALF patients that CTLV/SLV<83.9% indicates a poor prognosis. In conclusion, the CTLV/SLV ratio, which reflects liver volume variations, correlates well with the liver function and progression of cirrhosis and ALF. It is also a very useful marker for predicting the prognosis of ALF.

关键词: liver volume variation     cirrhosis     acute liver failure (ALF)    

Destructive and non-destructive evaluation of concrete for optimum sand to aggregate volume ratio

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1400-1414 doi: 10.1007/s11709-021-0779-8

摘要: Aggregates are the biggest contributor to concrete volume and are a crucial parameter in dictating its mechanical properties. As such, a detailed experimental investigation was carried out to evaluate the effect of sand-to-aggregate volume ratio (s/a) on the mechanical properties of concrete utilizing both destructive and non-destructive testing (employing UPV (ultrasonic pulse velocity) measurements). For investigation, standard cylindrical concrete samples were made with different s/a (0.36, 0.40, 0.44, 0.48, 0.52, and 0.56), cement content (340 and 450 kg/m3), water-to-cement ratio (0.45 and 0.50), and maximum aggregate size (12 and 19 mm). The effect of these design parameters on the 7, 14, and 28 d compressive strength, tensile strength, elastic modulus, and UPV of concrete were assessed. The careful analysis demonstrates that aggregate proportions and size need to be optimized for formulating mix designs; optimum ratios of s/a were found to be 0.40 and 0.44 for the maximum aggregate size of 12 and 19 mm, respectively, irrespective of the W/C (water-to-cement) and cement content.

关键词: aggregates     non-destructive testing     sand-to-aggregate volume ratio (s/a)     maximum aggregate size (MAS)    

A MATLAB code for the material-field series-expansion topology optimization method

《机械工程前沿(英文)》 2021年 第16卷 第3期   页码 607-622 doi: 10.1007/s11465-021-0637-3

摘要: This paper presents a MATLAB implementation of the material-field series-expansion (MFSE) topo-logy optimization method. The MFSE method uses a bounded material field with specified spatial correlation to represent the structural topology. With the series-expansion method for bounded fields, this material field is described with the characteristic base functions and the corresponding coefficients. Compared with the conventional density-based method, the MFSE method decouples the topological description and the finite element discretization, and greatly reduces the number of design variables after dimensionality reduction. Other features of this method include inherent control on structural topological complexity, crisp structural boundary description, mesh independence, and being free from the checkerboard pattern. With the focus on the implementation of the MFSE method, the present MATLAB code uses the maximum stiffness optimization problems solved with a gradient-based optimizer as examples. The MATLAB code consists of three parts, namely, the main program and two subroutines (one for aggregating the optimization constraints and the other about the method of moving asymptotes optimizer). The implementation of the code and its extensions to topology optimization problems with multiple load cases and passive elements are discussed in detail. The code is intended for researchers who are interested in this method and want to get started with it quickly. It can also be used as a basis for handling complex engineering optimization problems by combining the MFSE topology optimization method with non-gradient optimization algorithms without sensitivity information because only a few design variables are required to describe relatively complex structural topology and smooth structural boundaries using the MFSE method.

关键词: MATLAB implementation     topology optimization     material-field series-expansion method     bounded material field     dimensionality reduction    

Assessment of bridge expansion joints using long-term displacement measurement under changing environmental

Youliang DING, Aiqun LI

《结构与土木工程前沿(英文)》 2011年 第5卷 第3期   页码 374-380 doi: 10.1007/s11709-011-0122-x

摘要: This paper addresses the problem of condition assessment of bridge expansion joints using long-term measurement data under changing environmental conditions. The effects of temperature, traffic loading and wind on the expansion joint displacements are analyzed and interpreted, which reveal that measured displacements are observed to increase with an increase in temperature and to decrease with increased traffic loading, while the correlation between displacement and wind speed is very weak. Two regression models are developed to simulate the varying displacements under the changes in temperature and traffic loadings. Based on these models, the effects of the environmental conditions are removed to obtain the normalized displacement. Statistical process control using mean value control charts is further used to detect damage to the bridge expansion joints. The results reveal that the proposed method had a good capability for detecting the damage-induced 1.0% variances of the annual changes in the expansion joint displacements.

关键词: structural health monitoring     displacement     expansion joint     temperature effect     wind effect     traffic loading     statistical process control     suspension bridge    

An approach for evaluating the impact of an intermittent renewable energy source on transmission expansion

Rongrit CHATTHAWORN,Surachai CHAITUSANEY

《信息与电子工程前沿(英文)》 2015年 第16卷 第10期   页码 871-882 doi: 10.1631/FITEE.1500049

摘要: We propose a new robust optimization approach to evaluate the impact of an intermittent renewable energy source on transmission expansion planning (TEP). The objective function of TEP is composed of the investment cost of the transmission line and the operating cost of conventional generators. A method to select suitable scenarios representing the intermittent renewable energy generation and loads is proposed to obtain robust expansion planning for all possible scenarios. A meta-heuristic algorithm called adaptive tabu search (ATS) is employed in the proposed TEP. ATS iterates between the main problem, which minimizes the investment and operating costs, and the subproblem, which minimizes the cost of power generation from conventional generators and curtailments of renewable energy generation and loads. The subproblem is solved by nonlinear programming (NLP) based on an interior point method. Moreover, the impact of an intermittent renewable energy source on TEP was evaluated by comparing expansion planning with and without consideration of a renewable energy source. The IEEE Reliability Test System 79 (RTS 79) was used for testing the proposed method and evaluating the impact of an intermittent renewable energy source on TEP. The results show that the proposed robust optimization approach provides a more robust solution than other methods and that the impact of an intermittent renewable energy source on TEP should be considered.

关键词: Adaptive tabu search     Renewable energy generation     Robust optimization     Transmission expansion planning    

Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

《机械工程前沿(英文)》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0758-y

摘要: Accurately controlling the nodal lines of vibrating structures with topology optimization is a highly challenging task. The major difficulties in this type of problem include a large number of design variables, the highly nonlinear and multi-peak characteristics of iteration, and the changeable orders of eigenmodes. In this study, an effective material-field series-expansion (MFSE)-based topology optimization design strategy for precisely controlling nodal lines is proposed. Here, two typical optimization targets are established: (1) minimizing the difference between structural nodal lines and their desired positions, and (2) keeping the position of nodal lines within the specified range while optimizing certain dynamic performance. To solve this complex optimization problem, the structural topology of structures is first represented by a few design variables on the basis of the MFSE model. Then, the problems are effectively solved using a sequence Kriging-based optimization algorithm without requiring design sensitivity analysis. The proposed design strategy inherently circumvents various numerical difficulties and can effectively obtain the desired vibration modes and nodal lines. Numerical examples are provided to validate the proposed topology optimization models and the corresponding solution strategy.

关键词: nodal line     topology optimization     structural dynamics design     material-field series-expansion    

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    

Integration of molecular dynamic simulation and free volume theory for modeling membrane VOC/gas separation

Bo Chen, Yan Dai, Xuehua Ruan, Yuan Xi, Gaohong He

《化学科学与工程前沿(英文)》 2018年 第12卷 第2期   页码 296-305 doi: 10.1007/s11705-018-1701-3

摘要: Gas membrane separation process is highly unpredictable due to interacting non-ideal factors, such as composition/pressure-dependent permeabilities and real gas behavior. Although molecular dynamic (MD) simulation can mimic those complex effects, it cannot precisely predict bulk properties due to scale limitations of calculation algorithm. This work proposes a method for modeling a membrane separation process for volatile organic compounds by combining the MD simulation with the free volume theory. This method can avoid the scale-up problems of the MD method and accurately simulate the performance of membranes. Small scale MD simulation and pure gas permeation data are employed to correlate pressure-irrelevant parameters for the free volume theory; by this approach, the microscopic effects can be directly linked to bulk properties (non-ideal permeability), instead of being fitted by a statistical approach. A lab-scale hollow fiber membrane module was prepared for the model validation and evaluation. The comparison of model predictions with experimental results shows that the deviations of product purity are reduced from 10% to less than 1%, and the deviations of the permeate and residue flow rates are significantly reduced from 40% to 4%, indicating the reliability of the model. The proposed method provides an efficient tool for process engineering to simulate the membrane recovery process.

关键词: membrane vapor separation     membrane process modeling     process engineering     free volume theory     volatile organic compound    

硝酸铵膨化理论研究

吕春绪

《中国工程科学》 2001年 第3卷 第9期   页码 58-63

摘要:

描述了硝酸铵膨化过程,计算与测定了其物理化学参数,研究了膨化过程的影响因素,并给出了膨化过程可能的机理。

关键词: 膨化硝酸铵     膨化理论     物理化学参数     影响因素    

Modelling autogenous expansion for magnesia concrete in arch dams

JIN Feng, LUO Xiaoqing, ZHANG Chuhan, ZHANG Guoxin

《结构与土木工程前沿(英文)》 2008年 第2卷 第3期   页码 211-218 doi: 10.1007/s11709-008-0025-7

摘要: Magnesia Concrete is a kind of expansive concrete used in Chinese hydraulic engineering more and more widely. To evaluate the effects of autogenous expansion on the stresses of arch dams, a simple model of autogenous expansion for Magnesia Concrete in dam engineering is presented. This model is based on three assumptions: 1) the total amount of autogenous expansion of Magnesia Concrete is related only to the properties of materials and mixing of concrete; 2) the autogenous expansion of Magnesia Concrete is irreversible due to the irreversibility of hydration reaction of Magnesia in the concrete; 3) the autogenous expansion strain rates of Magnesia Concrete bear a relation between temperature and residual Magnesia per unit volume of concrete. The model is verified by some experimental data of autogenous expansion of Magnesia Concrete and field-measured data of an arch dam in China. Embedded into finite element arch dam simulation software, this model is employed to simulate the effects of autogenous expansion of Magnesia Concrete in hydraulic engineering.

关键词: field-measured     irreversibility     temperature     irreversible     element arch    

燕山石化公司乙烯装置66×104t/a扩能改造方案的研究与决策

曹湘洪

《中国工程科学》 2003年 第5卷 第11期   页码 34-46

摘要:

燕山石化公司30×104t/a乙烯装置1994年完成第一次扩能至45×104t/a的改造后,仍存在原料灵活性差、能耗高、与同期建设的乙烯装置比规模偏小等问题。以全面提高技术水平、降低能耗、增加原料灵活性、尽可能扩大生产能力为目标,充分考虑方案的可实施性、实施时的安全性、实施后的可操作性及方案的先进性和经济性,对装置技术改造的方案进行了比选研究。经改造,实现了生产能力扩大到66×104t/a的目标,实际可达71×104t/a,装置能耗明显下降,石脑油、轻柴油、重柴油、加氢裂化尾油均可作为乙烯原料。在世界上,首次在乙烯装置中采用混合冷剂制冷技术和碳三催化精馏加氢技术并获得成功,对世界乙烯工业技术进步有推动作用。

关键词: 乙烯     装置     扩能     方案     研究    

Lagrangian simulation of deposition of CO gas-solid sudden expansion flow

HUANG Dongping, DING Guoliang, QUACK Hans

《能源前沿(英文)》 2008年 第2卷 第2期   页码 216-221 doi: 10.1007/s11708-008-0032-3

摘要: Freezing and blockage resulting from the deposition of solid CO formed because of sudden expansion of the downstream pipe during the release of CO through safety valves, will endanger the protected equipment. To overcome this problem, the characteristics of the CO gas-solid sudden expansion flow are studied by using the disperse Lagrangian model. A comparison of the calculated deposition of the solid CO with the experimental results shows that they are in reasonable agreement. The simulation results show that the size of the solid CO formed should not be in the range of 0.04–0.07 mm ( number 3.2–9.8). This can be achieved by using an appropriate flow cross section of the safety valve.

关键词: comparison     gas-solid     downstream     blockage     Lagrangian    

V-shaped substrate for surface and volume enhanced Raman spectroscopic analysis of microplastics

《环境科学与工程前沿(英文)》 2022年 第16卷 第11期 doi: 10.1007/s11783-022-1578-8

摘要:

● V-shaped substrate was obtained for SERS analysis of microplastics (diameter ≈ 1 μm).

关键词: SERS     V-shaped     AAO     Microplastic     Atmospheric aerosol    

Modeling limit force capacities of high force to volume lead extrusion dampers

《结构与土木工程前沿(英文)》 2021年 第15卷 第3期   页码 609-622 doi: 10.1007/s11709-021-0724-x

摘要: Lead extrusion dampers are supplemental energy-dissipation devices that are used to mitigate seismic structural damage. Small volumetric sizes and high force capacities define high-force-to-volume (HF2V) devices, which can absorb significant response energy without sacrificial damage. However, the design of such devices for specific force capacities has proven difficult based on the complexities of their internal reaction mechanisms, leading to the adoption of empirical approaches. This study developed upper- and lower-bound force capacity estimates from analytical mechanics based on direct and indirect metal extrusion for guiding design. The derived equations are strictly functions of HF2V device geometric parameters, lead material properties, and extrusion mechanics. The upper-bound estimates from direct and indirect extrusion are denoted as (FUB,1, FUB,2) and (FUB,3, FUB,4), respectively, and the lower-bound estimates are denoted as (FLB, FLB,1) based on the combination of extrusion and friction forces. The proposed models were validated by comparing the predicted bounds to experimental force capacity data from 15 experimental HF2V device tests. The experimental device forces all lie above the lower-bound estimates (FLB, FLB,1) and below the upper-bound estimates (FUB,1, FUB,2, FUB,4). Overall, the (FLB, FUB,2) pair provides wider bounds and the (FLB,1, FUB,4/FUB,1) pair provides narrower bounds. The (FLB,1, FUB,1) pair has a mean lower-bound gap of 36%, meaning the lower bound was 74% of the actual device force on average. The mean upper-bound gap was 33%. The bulge area and cylinder diameter of HF2V devices are key parameters affecting device forces. These relatively tight bounds provide useful mechanics-based predictive design guides for ensuring that device forces are within the targeted design range after manufacturing.

关键词: extrusion     lead dampers     upper and lower bound     analytical modelling     limit force    

标题 作者 时间 类型 操作

Preparation and lithium storage performances of g-C

Zhengxu BIAN, Zehua TANG, Jinfeng XIE, Junhao ZHANG, Xingmei GUO, Yuanjun LIU, Aihua YUAN, Feng ZHANG, Qinghong KONG

期刊论文

Assessment of liver volume variation to evaluate liver function

null

期刊论文

Destructive and non-destructive evaluation of concrete for optimum sand to aggregate volume ratio

期刊论文

A MATLAB code for the material-field series-expansion topology optimization method

期刊论文

Assessment of bridge expansion joints using long-term displacement measurement under changing environmental

Youliang DING, Aiqun LI

期刊论文

An approach for evaluating the impact of an intermittent renewable energy source on transmission expansion

Rongrit CHATTHAWORN,Surachai CHAITUSANEY

期刊论文

Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

期刊论文

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

ZENG Zhuoxiong, HAN Shoulei, ZHOU Lixing

期刊论文

Integration of molecular dynamic simulation and free volume theory for modeling membrane VOC/gas separation

Bo Chen, Yan Dai, Xuehua Ruan, Yuan Xi, Gaohong He

期刊论文

硝酸铵膨化理论研究

吕春绪

期刊论文

Modelling autogenous expansion for magnesia concrete in arch dams

JIN Feng, LUO Xiaoqing, ZHANG Chuhan, ZHANG Guoxin

期刊论文

燕山石化公司乙烯装置66×104t/a扩能改造方案的研究与决策

曹湘洪

期刊论文

Lagrangian simulation of deposition of CO gas-solid sudden expansion flow

HUANG Dongping, DING Guoliang, QUACK Hans

期刊论文

V-shaped substrate for surface and volume enhanced Raman spectroscopic analysis of microplastics

期刊论文

Modeling limit force capacities of high force to volume lead extrusion dampers

期刊论文