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Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

《结构与土木工程前沿（英文）》 2011年 第5卷 第2期   页码 199-207 doi: 10.1007/s11709-011-0102-1

摘要： Numerical simulations of longitudinal wave propagation in a rock bar with microcracks are conducted by using the numerical manifold method which has great advantages in the simulation of discontinuities. Firstly, validation of the numerical manifold method is carried out by simulations of a longitudinal stress wave propagating through intact and cracked rock bars. The behavior of the stress wave traveling in a one-dimensional rock bar with randomly distributed microcracks is subsequently studied. It is revealed that the highly defected rock bar has significant viscoelasticity to the stress wave propagation. Wave attenuation as well as time delay is affected by the length, quantity, specific stiffness of the distributed microcracks as well as the incident stress wave frequency. The storage and loss moduli of the defected rock are also affected by the microcrack properties; however, they are independent of incident stress wave frequency.

关键词： stress wave propagation     defected rock     numerical manifold method     viscoelastic behavior     storage modulus     loss modulus    

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Empirical models and design codes in prediction of modulus of elasticity of concrete

Behnam VAKHSHOURI, Shami NEJADI

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 38-48 doi: 10.1007/s11709-018-0479-1

摘要： Modulus of Elasticity (MOE) is a key parameter in reinforced concrete design. It represents the stress-strain relationship in the elastic range and is used in the prediction of concrete structures. Out of range estimation of MOE in the existing codes of practice strongly affect the design and performance of the concrete structures. This study includes: (a) evaluation and comparison of the existing analytical models to estimating the MOE in normal strength concrete, and (b) proposing and verifying a new model. In addition, a wide range of experimental databases and empirical models to estimate the MOE from compressive strength and density of concrete are evaluated to verification of the proposed model. The results show underestimation of MOE of conventional concrete in majority of the existing models. Also, considering the consistency between density and mechanical properties of concrete, the predicted MOE in the models including density effect, are more compatible with the experimental results.

关键词： modulus of elasticity     normal strength normal weight concrete     empirical models     design codes     compressive strength     density    

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Elastic modulus and thermal stress in coating during heat cycling with different substrate shapes

Daniel GAONA,Alfredo VALAREZO

《机械工程前沿（英文）》 2015年 第10卷 第3期   页码 294-300 doi: 10.1007/s11465-015-0351-0

摘要：

The elastic modulus of a deposit (Ed) can be obtained by monitoring the temperature (?T) and curvature (?k) of a one-side coated long plate, namely, a one-dimensional (1D) deformation model. The aim of this research is to design an experimental setup that proves whether a 1D deformation model can be scaled for complex geometries. The setup includes a laser displacement sensor mounted on a robotic arm capable of scanning a specimen surface and measuring its deformation. The reproducibility of the results is verified by comparing the present results with Stony Brook University Laboratory’s results. The ?k-?T slope error is less than 8%, and the Ed estimation error is close to 2%. These values reveal the repeatability of the experiments. Several samples fabricated with aluminum as the substrate and 100MXC nanowire (Fe and Cr alloy) as the deposit are analyzed and compared with those in finite element (FE) simulations. The linear elastic behavior of 1D (flat long plate) and 2D (squared plate) specimens during heating/cooling cycles is demonstrated by the high linearity of all ?k-?T curves (over 97%). The Ed values are approximately equal for 1D and 2D analyses, with a median of 96 GPa and standard deviation of 2 GPa. The correspondence between the experimental and simulated results for the 1D and 2D specimens reveals that deformation and thermal stress in coated specimens can be predicted regardless of specimen geometry through FE modeling and by using the experimental value of Ed. An example of a turbine-blade-shaped substrate is presented to validate the approach.

关键词： in-plane     Young’s modulus     curvature temperature     thermal stress     coating    

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An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

《结构与土木工程前沿（英文）》 2022年 第16卷 第12期   页码 1653-1653 doi: 10.1007/s11709-019-0578-7

摘要： In recent years, there has been an increased interest in the use of fiber reinforced polymer (FRP) in the construction industry. However, the E-modulus and strength of such members at high service temperatures is still unknown. Modulus and strength of FRP at high service temperatures are highly required parameters for full design. The knowledge and application of this could lead to a cost effective and practical consideration in fire safety design. Thus, this paper proposes design methods for calculating the E-modulus and strength of FRP members at different temperatures. Experimental data from literature were normalized and compared with the results predicted by this method. It was found that the proposed design methods conservatively estimate the E-modulus and strength of FRP structural members. In addition, comparison was also made with direct references to the real behavior of materials. It was found to be satisfactory. Finally, an application is provided.

关键词： concrete     fiber reinforced polymer     E-modulus     strength     temperatures    

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Prediction of falling weight deflectometer parameters using hybrid model of genetic algorithm and adaptive neuro-fuzzy inference system

《结构与土木工程前沿（英文）》   页码 812-826 doi: 10.1007/s11709-023-0940-7

摘要： A falling weight deflectometer is a testing device used in civil engineering to measure and evaluate the physical properties of pavements, such as the modulus of the subgrade reaction (Y1) and the elastic modulus of the slab (Y2), which are crucial for assessing the structural strength of pavements. In this study, we developed a novel hybrid artificial intelligence model, i.e., a genetic algorithm (GA)-optimized adaptive neuro-fuzzy inference system (ANFIS-GA), to predict Y1 and Y2 based on easily determined 13 parameters of rigid pavements. The performance of the novel ANFIS-GA model was compared to that of other benchmark models, namely logistic regression (LR) and radial basis function regression (RBFR) algorithms. These models were validated using standard statistical measures, namely, the coefficient of correlation (R), mean absolute error (MAE), and root mean square error (RMSE). The results indicated that the ANFIS-GA model was the best at predicting Y1 (R = 0.945) and Y2 (R = 0.887) compared to the LR and RBFR models. Therefore, the ANFIS-GA model can be used to accurately predict Y1 and Y2 based on easily measured parameters for the appropriate and rapid assessment of the quality and strength of pavements.

关键词： falling weight deflectometer     modulus of subgrade reaction     elastic modulus     metaheuristic algorithms    

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Energy storage resources management: Planning, operation, and business model

《工程管理前沿（英文）》   页码 373-391 doi: 10.1007/s42524-022-0194-4

摘要： With the acceleration of supply-side renewable energy penetration rate and the increasingly diversified and complex demand-side loads, how to maintain the stable, reliable, and efficient operation of the power system has become a challenging issue requiring investigation. One of the feasible solutions is deploying the energy storage system (ESS) to integrate with the energy system to stabilize it. However, considering the costs and the input/output characteristics of ESS, both the initial configuration process and the actual operation process require efficient management. This study presents a comprehensive review of managing ESS from the perspectives of planning, operation, and business model. First of all, in terms of planning and configuration, it is investigated from capacity planning, location planning, as well as capacity and location combined planning. This process is generally the first step in deploying ESS. Then, it explores operation management of ESS from the perspectives of state assessment and operation optimization. The so-called state assessment refers to the assessment of three aspects: The state of charge (SOC), the state of health (SOH), and the remaining useful life (RUL). The operation optimization includes ESS operation strategy optimization and joint operation optimization. Finally, it discusses the business models of ESS. Traditional business models involve ancillary services and load transfer, while emerging business models include electric vehicle (EV) as energy storage and shared energy storage.

关键词： energy storage system     energy storage resources management     planning configuration     operational management     business model    

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An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

《结构与土木工程前沿（英文）》 2022年 第16卷 第12期   页码 1654-1654 doi: 10.1007/s11709-020-0622-7

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Predicting resilient modulus of recycled concrete and clay masonry blends for pavement applications using

Mosbeh R. KALOOP, Alaa R. GABR, Sherif M. EL-BADAWY, Ali ARISHA, Sayed SHWALLY, Jong WAN HU

《结构与土木工程前沿（英文）》 2019年 第13卷 第6期   页码 1379-1392 doi: 10.1007/s11709-019-0562-2

摘要： To date, very few researchers employed the Least Square Support Vector Machine (LSSVM) in predicting the resilient modulus ( ) of Unbound Granular Materials (UGMs). This paper focused on the development of a LSSVM model to predict the of recycled materials for pavement applications and comparison with other different models such as Regression, and Artificial Neural Network (ANN). Blends of Recycled Concrete Aggregate (RCA) with Recycled Clay Masonry (RCM) with proportions of 100/0, 90/10, 80/20, 70/30, 55/45, 40/60, 20/80, and 0/100 by the total aggregate mass were evaluated for use as UGMs. RCA/RCM materials were collected from dumps on the sides of roads around Mansoura city, Egypt. The investigated blends were evaluated experimentally by routine and advanced tests and the values were determined by Repeated Load Triaxial Test (RLTT). Regression, ANN, and LSSVM models were utilized and compared in predicting the of the investigated blends optimizing the best design model. Results showed that the ’s of the investigated RCA/RCM blends were generally increased with the decrease in RCM proportion. Statistical analyses were utilized for evaluating the performance of the developed models and the inputs sensitivity parameters. Eventually, the results approved that the LSSVM model can be used as a novel tool to estimate the of the investigated RCA/RCM blends.

关键词： Least Square Support Vector Machine     Artificial Neural Network     resilient modulus     Recycled Concrete Aggregate     Recycled Clay Masonry    

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Assessing artificial neural network performance for predicting interlayer conditions and layer modulus

Lingyun YOU, Kezhen YAN, Nengyuan LIU

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 487-500 doi: 10.1007/s11709-020-0609-4

摘要： The objective of this study is to evaluate the performance of the artificial neural network (ANN) approach for predicting interlayer conditions and layer modulus of a multi-layered flexible pavement structure. To achieve this goal, two ANN based back-calculation models were proposed to predict the interlayer conditions and layer modulus of the pavement structure. The corresponding database built with ANSYS based finite element method computations for four types of a structure subjected to falling weight deflectometer load. In addition, two proposed ANN models were verified by comparing the results of ANN models with the results of PADAL and double multiple regression models. The measured pavement deflection basin data was used for the verifications. The comparing results concluded that there are no significant differences between the results estimated by ANN and double multiple regression models. PADAL modeling results were not accurate due to the inability to reflect the real pavement structure because pavement structure was not completely continuous. The prediction and verification results concluded that the proposed back-calculation model developed with ANN could be used to accurately predict layer modulus and interlayer conditions. In addition, the back-calculation model avoided the back-calculation errors by considering the interlayer condition, which was barely considered by former models reported in the published studies.

关键词： asphalt pavement     interlayer conditions     finite element method     artificial neural network     back-calculation    

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Encapsulation of polyethylene glycol in cellulose-based porous capsules for latent heat storage and light-to-thermal

《化学科学与工程前沿（英文）》 2023年 第17卷 第8期   页码 1038-1050 doi: 10.1007/s11705-022-2279-3

摘要： Phase change materials are potential candidates for the application of latent heat storage. Herein, we fabricated porous capsules as shape-stable materials from cellulose-based polyelectrolyte complex, which were first prepared using cellulose 6-(N-pyridinium)hexanoyl ester as the cationic polyelectrolyte and carboxymethyl cellulose as the anionic polyelectrolyte to encapsulate polyethylene glycol by the vacuum impregnation method. Furthermore, the multi-walled carbon nanotube or graphene oxide, which were separately composited into the polyelectrolytes complex capsules to enhance thermal conductivity and light-to-thermal conversion efficiency. These capsules owned a typical core–shell structure, with an extremely high polyethylene glycol loading up to 34.33 g∙g‒1. After loading of polyethylene glycol, the resulted cellulose-based composite phase change materials exhibited high thermal energy storage ability with the latent heat up to 142.2 J∙g‒1, which was 98.5% of pure polyethylene glycol. Further results showed that the composite phase change materials demonstrated good form-stable property and thermal stability. Moreover, studies involving light-to-thermal conversion determined that composite phase change materials exhibited outstanding light-to-thermal conversion performance. Considering their exceptional comprehensive features, innovative composite phase change materials generated from cellulose presented a highly interesting choice for thermal management and renewable thermal energy storage.

关键词： cellulose     polyelectrolytes     phase change materials     thermal energy storage     light-to-thermal conversion    

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Can energy storage make off-grid photovoltaic hydrogen production system more economical?

《工程管理前沿（英文）》   页码 672-694 doi: 10.1007/s42524-022-0245-x

摘要： Under the ambitious goal of carbon neutralization, photovoltaic (PV)-driven electrolytic hydrogen (PVEH) production is emerging as a promising approach to reduce carbon emission. Considering the intermittence and variability of PV power generation, the deployment of battery energy storage can smoothen the power output. However, the investment cost of battery energy storage is pertinent to non-negligible expenses. Thus, the installation of energy-storage equipment in a PVEH system is a complex trade-off problem. The primary goals of this study are to compare the engineering economics of PVEH systems with and without energy storage, and to explore time nodes when the cost of the former scenario can compete with the latter by factoring the technology learning curve. The levelized cost of hydrogen (LCOH) is a widely used economic indicator. Represented by seven areas in seven regions of China, results show that the LCOH with and without energy storage is approximately 22.23 and 20.59 yuan/kg in 2020, respectively. In addition, as technology costs drop, the LCOH of a PVEH system with energy storage will be less than that without energy storage in 2030.

关键词： hydrogen     off-grid photovoltaic     energy storage     LCOH     engineering economics    

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Analysis of flow and heat transfer characteristics of porous heat-storage wall in greenhouse

OUYANG Li, LIU Wei

《能源前沿（英文）》 2008年 第2卷 第4期   页码 406-409 doi: 10.1007/s11708-008-0094-2

摘要： The flow and heat transfer characteristics of porous heat-storage wall in greenhouse are studied by using the one-dimensional steady energy two-equation model for saturated porous medium. The results show that the heat exchange between the air and the solid matrix of the porous heat-storage wall depends upon the inlet air velocity, the porosity and the permeability of porous medium, and the thermal conductivity of the solid matrix. Because the incidence of solar radiation on the porous heat-storage wall is not uniform, the new composite porous solar wall with different porosity is proposed to reduce the disadvantageous effect.

关键词： incidence     thermal conductivity     heat-storage     exchange     composite    

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Machine perfusion versus cold storage of livers: a meta-analysis

null

《医学前沿（英文）》 2016年 第10卷 第4期   页码 451-464 doi: 10.1007/s11684-016-0474-7

摘要：

Different organ preservation methods are key factors influencing the results of liver transplantation. In this study, the outcomes of experimental models receiving donation after cardiac death (DCD) livers preserved through machine perfusion (MP) or static cold storage (CS) were compared by conducting a meta-analysis. Standardized mean difference (SMD) and 95% confidence interval (CI) were calculated to compare pooled data from two animal species. Twenty-four studies involving MP preservation were included in the meta-analysis. Compared with CS preservation, MP can reduce the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and hyaluronic acid (HA) and the changes in liver weight. By contrast, MP can enhance bile production and portal vein flow (PVF). Alkaline phosphatase (ALP) levels and histological changes significantly differed between the two preservation methods. In conclusion, MP of DCD livers is superior to CS in experimental animals.

关键词： machine perfusion     cold storage     DCD     meta-analysis    

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The stress relaxation of cement clinkers under high temperature

Xiufang WANG,Yiwang BAO,Xiaogen LIU,Yan QIU

《机械工程前沿（英文）》 2015年 第10卷 第4期   页码 413-417 doi: 10.1007/s11465-015-0357-7

摘要：

The energy consumption of crushing is directly affected by the mechanical properties of cement materials. This research provides a theoretical proof for the mechanism of the stress relaxation of cement clinkers under high temperature. Compression stress relaxation under various high temperatures is discussed using a specially developed load cell, which can measure stress and displacement under high temperatures inside an autoclave. The cell shows that stress relaxation dramatically increases and that the remaining stress rapidly decreases with an increase in temperature. Mechanical experiments are conducted under various temperatures during the cooling process to study the changes in the grinding resistance of the cement clinker with temperature. The effects of high temperature on the load-displacement curve, compressive strength, and elastic modulus of cement clinkers are systematically studied. Results show that the hardening phenomenon of the clinker becomes apparent with a decrease in temperature and that post-peak behaviors manifest characteristics of the transformation from plasticity to brittleness. The elastic modulus and compressive strength of cement clinkers increase with a decrease in temperature. The elastic modulus increases greatly when the temperature is lower than 1000 °C. The compressive strength of clinkers increases by 73.4% when the temperature drops from 1100 to 800 °C.

关键词： stress relaxation     high temperature     cement clinker     compression     elastic modulus    

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Experimental study and assessment of thermal energy storage mortar with paraffin/recycled brick powder

Luchen HAO; Jianzhuang XIAO; Wanzhi CAO; Jingting SUN

《结构与土木工程前沿（英文）》 2022年 第16卷 第10期   页码 1301-1314 doi: 10.1007/s11709-022-0883-4

摘要： Thermal energy storage recycled powder mortar (TESRM) was developed in this study by incorporating paraffin/recycled brick powder (paraffin/BP) composite phase change materials (PCM). Fourier transform infrared and thermogravimetric analysis results showed that paraffin/BP composite PCM had good chemical and thermal stability. The onset melting temperature and latent heat of the composite PCM were 46.49 °C and 30.1 J·g−1. The fresh mortar properties and hardened properties were also investigated in this study. Paraffin/BP composite PCM with replacement ratio of 0%, 10%, 20%, and 30% by weight of cement were studied. The results showed that the static and dynamic yield stresses of TESRM were 699.4% and 172.9% higher than those of normal mortar, respectively. The addition of paraffin/BP composite PCM had a positive impact on the mechanical properties of mortar at later ages, and could also reduce the dry shrinkage of mortar. The dry shrinkage of TESRM had a maximum reduction about 26.15% at 120 d. The thermal properties of TESRM were better than those of normal mortar. The thermal conductivity of TESRM was 36.3% less than that of normal mortar and the heating test results showed that TESRM had good thermal energy storage performance.

关键词： recycled powder mortar     recycled brick powder     thermal energy storage     paraffin     phase change material    

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标题 作者 时间 类型 操作

Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

期刊论文

Empirical models and design codes in prediction of modulus of elasticity of concrete

Behnam VAKHSHOURI, Shami NEJADI

期刊论文

Elastic modulus and thermal stress in coating during heat cycling with different substrate shapes

Daniel GAONA,Alfredo VALAREZO

期刊论文

An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

期刊论文

Prediction of falling weight deflectometer parameters using hybrid model of genetic algorithm and adaptive neuro-fuzzy inference system

期刊论文

Energy storage resources management: Planning, operation, and business model

期刊论文

An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

期刊论文

Predicting resilient modulus of recycled concrete and clay masonry blends for pavement applications using

Mosbeh R. KALOOP, Alaa R. GABR, Sherif M. EL-BADAWY, Ali ARISHA, Sayed SHWALLY, Jong WAN HU

期刊论文

Assessing artificial neural network performance for predicting interlayer conditions and layer modulus

Lingyun YOU, Kezhen YAN, Nengyuan LIU

期刊论文

Encapsulation of polyethylene glycol in cellulose-based porous capsules for latent heat storage and light-to-thermal

期刊论文

Can energy storage make off-grid photovoltaic hydrogen production system more economical?

期刊论文

Analysis of flow and heat transfer characteristics of porous heat-storage wall in greenhouse

OUYANG Li, LIU Wei

期刊论文

Machine perfusion versus cold storage of livers: a meta-analysis

null

期刊论文

The stress relaxation of cement clinkers under high temperature

Xiufang WANG,Yiwang BAO,Xiaogen LIU,Yan QIU

期刊论文

Experimental study and assessment of thermal energy storage mortar with paraffin/recycled brick powder

Luchen HAO; Jianzhuang XIAO; Wanzhi CAO; Jingting SUN

期刊论文