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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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Numerical analysis of bearing behaviors of single batter piles under horizontal loads in various directions

《结构与土木工程前沿（英文）》 2023年 第17卷 第2期   页码 224-237 doi: 10.1007/s11709-022-0914-1

摘要： The horizontal bearing behavior of a single batter pile (SBP) is vital to its application in practical engineering; however, the horizontal responses of SBPs change with the directions of horizontal loads, and this phenomenon is rarely investigated. Therefore, the directional differences in the horizontal bearing behaviors of SBPs are investigated in this study. Four model tests are conducted to preliminarily examine the effects of the skew angle of horizontal loads on the horizontal bearing capacities and distributions of the bending moments of the SBPs. Subsequently, the differences in the responses of the SBPs under horizontal loads in various directions at full scale are analyzed comprehensively via finite-element (FE) analysis. The effects of the skew angle on SBP-soil interaction are discussed. Moreover, an empirical design method is proposed based on the FE analysis results to predict the bearing ratios of SBPs in medium-dense and dense sand while considering the effects of the skew angle, batter angle, and pile diameter. The method is confirmed to be effective, as confirmed by the close agreement between the predicting results with the model test (reported in this study) and centrifuge model test results (reported in the literature).

关键词： single batter pile     skew horizontal load     model test     finite-element analysis     empirical design method    

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Reliability design method for steam turbine blades

SHI Jinyuan

《能源前沿（英文）》 2008年 第2卷 第4期   页码 363-368 doi: 10.1007/s11708-008-0073-7

摘要： Based on theories of probability and statistics, and taking static stresses, dynamic stresses, endurance strength, safety ratios, vibration frequencies and exciting force frequencies of blades as random variables, a reliability design method for steam turbine blades is presented. The purport and calculation method for blade reliability are expounded. The distribution parameters of random variables are determined after analysis and numerical calculation of test data. The fatigue strength and the vibration design reliability of turbine blades are determined with the aid of a probabilistic design method and by interference models for stress distribution and strength distribution. Some blade reliability design calculation formulas for a dynamic stress design method, a safety ratio design method for fatigue strength, and a vibration reliability design method for the first and second types of tuned blades and a packet of blades on a disk connected closely, are given together with some practical examples. With these methods, the design reliability of steam turbine blades can be guaranteed in the design stage. This research may provide some scientific basis for reliability design of steam turbine blades.

关键词： design reliability     force     probability     purport     reliability design    

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Prediction of the theoretical and semi-empirical model of ambient temperature

Foued CHABANE,Noureddine MOUMMI,Abdelhafid BRIMA,Abdelhafid MOUMMI

《能源前沿（英文）》 2016年 第10卷 第3期   页码 268-276 doi: 10.1007/s11708-016-0413-y

摘要： It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is often, but not always, based upon experience or knowledge. Although guaranteed accurate information about the future is in many cases impossible, prediction can be useful to assist in making plans about possible developments. As a result, temperature profiles can be developed which accurately represent the expected ambient temperature exposure that this environment experiences during measurement. The ambient temperature over time is modeled based on the previous and data and using a Lagrange interpolation. To observe the comprehensive variation of ambient temperature the profile must be determined numerically. The model proposed in this paper can provide an acceptable way to measure the change in ambient temperature.

关键词： ambient temperature     environment     correlation     theoretical model     semi-empirical    

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Detection of schedule delay risk of empirical construction projects

Tsegay GEBREHIWET, Hanbin LUO

《工程管理前沿（英文）》 2018年 第5卷 第2期   页码 251-267 doi: 10.15302/J-FEM-2018086

摘要： In Ethiopian construction projects, schedule delay risk is a predominant issue because it is not properly addressed. Although several studies have been focused on the various effects of risk in construction projects, limited efforts have been made to investigate the typical and the overall schedule delay risk. In this study, our aim is to detect the typical and overall schedule delay risk throughout the construction project lifecycle, which consists of the pre-construction, construction, and post-construction stages, and compare the stages with each other. Common criteria, sub-criteria, and attributes were developed for all alternatives for the purpose of making a risk decision. The methodology that was followed integrated the multiple-criteria decision-making (MCDM) model of fuzzy analytic hierarchy process comprehensive evaluation (FAHPCE) and the relative important index (RII). Data were collected from 77 participants, who were selected through purposive sampling from different contracting organizations in Ethiopian construction projects by means of questionnaires that were distributed to experienced experts. The findings showed that there is a typical delay risk either in the type or in the level of the different construction activities. Consequently, the most influenced alternative is the construction stage because of the high-risk responsibility, resource, and contract condition related criteria. The post-construction stage was the second most influenced stage because of the high-risk responsibility-related criteria. The pre-constructed stage was the least influenced stage that consist high-risk criteria of responsibility, resource, and contract condition related. These differences provided noteworthy information about risk mitigation in construction projects by identifying the exact risk level on specific activity to make appropriate decision.

关键词： fuzzy analytic hierarchy process comprehensive evaluation     construction project     detection of delay risk     relative important index    

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Effect of heat transfer coefficient of steam turbine rotor on thermal stress field under off-design condition

Jie GUO,Danmei XIE,Hengliang ZHANG,Wei JIANG,Yan ZHOU

《能源前沿（英文）》 2016年 第10卷 第1期   页码 57-64 doi: 10.1007/s11708-015-0385-3

摘要： The precise calculation of temperature and thermal stress field of steam turbine rotor under off-design conditions is of paramount significance for safe and economic operation, in which an accurate calculation of heat transfer (HT) coefficient plays a decisive role. HT coefficient changes dramatically along with working conditions. First, a finite element analysis of rotor model, applied with ordinary rotor materials, has been conducted to investigate the temperature and thermal stress difference along with the change of HT coefficient from 20 W/(m ·°C) to 20000 W/(m ·°C). Next, the differentiation between existing empirical formulas has been analyzed from the aspect of physical significance of non-dimension parameters. Finally, a verifying case of the cold startup of a 1000MW unit has been proceeded. The result shows that the accuracy of coefficient calculation when steam parameters are low has a greater influence on that of rotor temperature and thermal stress, which means a precise empirical HT coefficient formula, like the Sarkar formula is strongly recommended. When steam parameters are high and HT coefficient is larger than 10 W/(m ·°C), there will be barely any influence on the calculation of thermal stress. This research plays a constructive role in the calculation and analysis of thermal stress.

关键词： steam turbine     rotor     thermal stress     heat transfer coefficient     empirical formula    

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Relative vibration identification of cutter and workpiece based on improved bidimensional empirical mode

Jiasheng LI, Xingzhan LI, Wei WEI, Pinkuan LIU

《机械工程前沿（英文）》 2020年 第15卷 第2期   页码 227-239 doi: 10.1007/s11465-020-0587-1

摘要： In the process of cutting, the relative vibration between the cutter and the workpiece has an important effect on the surface topography. In this study, the bidimensional empirical mode decomposition (BEMD) method is used to identify such effect. According to Riesz transform theory, a type of isotropic monogenic signal is proposed. The boundary data is extended on the basis of a similarity principle that deals with serious boundary effect problem. The decomposition examples show that the improved BEMD can effectively solve the problem of boundary effect and decompose the original machined surface topography at multiple scales. The characteristic surface topography representing the relative vibration between the cutter and the workpiece through feature identification is selected. In addition, the spatial spectrum analysis of the extracted profile is carried out. The decimal part of the frequency ratio that has an important effect on the shape of the contour can be accurately identified through contour extraction and spatial spectrum analysis. The decomposition results of simulation and experimental surface morphology demonstrate the validity of the improved BEMD algorithm in realizing the relative vibration identification between the cutter and the workpiece.

关键词： bidimensional empirical mode decomposition     spatial spectrum analysis     boundary effect     vibration identification     surface topography    

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Development of mix design method based on statistical analysis of different factors for geopolymer concrete

Paramveer SINGH; Kanish KAPOOR

《结构与土木工程前沿（英文）》 2022年 第16卷 第10期   页码 1315-1335 doi: 10.1007/s11709-022-0853-x

摘要： The present study proposes the mix design method of Fly Ash (FA) based geopolymer concrete using Response Surface Methodology (RSM). In this method, different factors, including binder content, alkali/binder ratio, NS/NH ratio (sodium silicate/sodium hydroxide), NH molarity, and water/solids ratio were considered for the mix design of geopolymer concrete. The 2D contour plots were used to setup the mix design method to achieve the target compressive strength. The proposed mix design method of geopolymer concrete is divided into three categories based on curing regime, specifically one ambient curing (25 °C) and two heat curing (60 and 90 °C). The proposed mix design method of geopolymer concrete was validated through experimentation of M30, M50, and M70 concrete mixes at all curing regimes. The observed experimental compressive strength results validate the mix design method by more than 90% of their target strength. Furthermore, the current study concluded that the required compressive strength can be achieved by varying any factor in the mix design. In addition, the factor analysis revealed that the NS/NH ratio significantly affects the compressive strength of geopolymer concrete.

关键词： geopolymer concrete     mix design     fly ash     response surface methodology     compressive strength     stress−strain    

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Estimation of relations among hysteretic response measures and design parameters for RC rectangular shear

A. ARAB, Ma. R. BANAN, Mo. R. BANAN, S. FARHADI

《结构与土木工程前沿（英文）》 2018年 第12卷 第1期   页码 3-15 doi: 10.1007/s11709-017-0418-6

摘要： Seismic design of RC structures requires estimation of structural member behavioral measures as functions of design parameters. In this study, the relations among cyclic behavioral measures and design parameters have been investigated for rectangular RC shear walls using numerical simulations calibrated based on the published laboratory tests. The OpenSEES numerical simulations modeling of plastic hinge hysteretic behavior of RC shear walls and estimation of empirical relations among wall hysteretic indices and design parameters are presented. The principal design parameters considered were wall dimensions, axial force, reinforcement ratios, and end-element design parameters. The estimated hysteretic response measures are wall effective stiffness, yield and ultimate curvatures, plastic moment capacity, yield and ultimate displacements, flexural shear capacity, and dissipated energy. Using results of numerous analyses, the empirical relations among wall cyclic behavioral measures and design parameters are developed and their accuracy is investigated.

关键词： RC wall hysteretic measures     RC wall design parameters     empirical relations     numerical simulations     RC rectangular wall plastic hinge    

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The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 456-477 doi: 10.1007/s11709-019-0519-5

摘要：

The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects; 2) upper-bound solutions; 3) accurate solutions and higher convergence rates; 4) insensitivity to mesh distortion; 5) Jacobian-free; 6) volumetric-locking-free; and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on AI-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model on-demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided.

关键词： computational method     finite element method     smoothed finite element method     strain smoothing technique     smoothing domain     weakened weak form     solid mechanics     softening effect     upper bound solution    

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Changes in public trust in physicians: empirical evidence from China

Dahai Zhao, Zhiruo Zhang

《医学前沿（英文）》 2019年 第13卷 第4期   页码 504-510 doi: 10.1007/s11684-018-0666-4

摘要： Studies examining the trends in public trust in physicians have provided a considerable amount of valuable policy implications for policymakers compared with cross-sectional studies on this topic in many countries. This study investigated changes in public trust in physicians in China based on two cross-sectional national surveys conducted in 2011 and 2016 and identified the determinants of these changes. The results indicated 83.4% of respondents in 2011 reported trust or strong trust in physicians in China, which decreased to 64.2% by 2016. The results of ordinal logistic regression demonstrated that public trust in physicians in China had decreased significantly from 2011 to 2016 ( <0.001) after adjusting for other independent variables. Self-reported health status, self-rated happiness, and self-identified social class were all associated positively with public trust in physicians in China. The results also confirmed that decreasing public satisfaction with the most recent treatment experience was the major determinant of decreasing public trust in physicians in China. The findings of this study suggest that decreasing public trust in physicians deserves considerable attention from national policymakers and that improving satisfaction with treatment experiences would be the most effective strategy for enhancing public trust in physicians in China.

关键词： trust in physicians     public trust     physician-patient relationship     health system performance    

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Overall HIEs deconstruction method and its application

Li LIN, Chengqi XUE,

《机械工程前沿（英文）》 2009年 第4卷 第4期   页码 466-471 doi: 10.1007/s11465-009-0076-z

摘要： Based on the human interface elements (HIEs) as the emotional carriers, this paper researches the general analysis steps of hierarchical HIEs and puts forward a new systematical deconstruction method for Kansei engineering fields. A mobile phone is taken as the research subject, the emotional design rules are inferred based on the multiple-orientation information of human interfaces, and the emotional change law is grasped from a new perspective. The research on the deconstruction method promotes the study of Kansei engineering and is a significant guide and reference for the theory and practice of related product design fields.

关键词： product design     relationship model     human interface     design rules     emotion    

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Function-oriented optimization design method for underactuated tendon-driven humanoid prosthetic hand

《机械工程前沿（英文）》 2022年 第17卷 第3期 doi: 10.1007/s11465-022-0696-0

摘要： The loss of hand functions in upper limb amputees severely restricts their mobility in daily life. Wearing a humanoid prosthetic hand would be an effective way of restoring lost hand functions. In a prosthetic hand design, replicating the natural and dexterous grasping functions with a few actuators remains a big challenge. In this study, a function-oriented optimization design (FOD) method is proposed for the design of a tendon-driven humanoid prosthetic hand. An optimization function of different functional conditions of full-phalanx contact, total contact force, and force isotropy was constructed based on the kinetostatic model of a prosthetic finger for the evaluation of grasping performance. Using a genetic algorithm, the optimal geometric parameters of the prosthetic finger could be determined for specific functional requirements. Optimal results reveal that the structure of the prosthetic finger is significantly different when designed for different functional requirements and grasping target sizes. A prosthetic finger was fabricated and tested with grasping experiments. The mean absolute percentage error between the theoretical value and the experimental result is less than 10%, demonstrating that the kinetostatic model of the prosthetic finger is effective and makes the FOD method possible. This study suggests that the FOD method enables the systematic evaluation of grasping performance for prosthetic hands in the design stage, which could improve the design efficiency and help prosthetic hands meet the design requirements.

关键词： function-oriented     tendon driven     prosthetic hand     optimization     humanoid     underactuated    

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relationship of industrial agglomeration and low-carbon economy considering spatiotemporal differentiation: An empirical

《工程管理前沿（英文）》 2023年 第10卷 第2期   页码 285-299 doi: 10.1007/s42524-022-0197-1

摘要： Although China’s construction machinery thrives to meet the needs of construction, a number of challenges still remain to be overcome, such as lack of thorough knowledge of regional disparities and several limitations in terms of carbon emissions and economic development. Meanwhile, a low-carbon economy was proposed and implemented in China. This research aims to investigate the differences in industrial agglomeration of construction machineries and further explore the relationship between industrial agglomeration and low-carbon economy. On this basis, spatiotemporal analysis was performed to evaluate the levels of industrial agglomeration in different regions based on the situations of China’s construction machinery industry. Furthermore, this study explored the interaction between industrial agglomeration and low-carbon economy utilizing the coupling coordination analysis method. Results showed that the coupling coordination of the two subsystems was extremely unbalanced in 2006, and it maintained an increasing trend, reaching a relatively high level in 2018. Finally, suggestions, such as establishing a policy guarantee system and implementing variable policies in different regions, were proposed to provide guidelines for the government decision-making and promote the sustainable development of China’s construction machinery industry.

关键词： spatiotemporal differentiation     industrial agglomeration     low-carbon economy     construction machinery industry     empirical study    

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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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标题 作者 时间 类型 操作

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

Behnam VAKHSHOURI, Shami NEJADI

期刊论文

Numerical analysis of bearing behaviors of single batter piles under horizontal loads in various directions

期刊论文

Reliability design method for steam turbine blades

SHI Jinyuan

期刊论文

Prediction of the theoretical and semi-empirical model of ambient temperature

Foued CHABANE,Noureddine MOUMMI,Abdelhafid BRIMA,Abdelhafid MOUMMI

期刊论文

Detection of schedule delay risk of empirical construction projects

Tsegay GEBREHIWET, Hanbin LUO

期刊论文

Effect of heat transfer coefficient of steam turbine rotor on thermal stress field under off-design condition

Jie GUO,Danmei XIE,Hengliang ZHANG,Wei JIANG,Yan ZHOU

期刊论文

Relative vibration identification of cutter and workpiece based on improved bidimensional empirical mode

Jiasheng LI, Xingzhan LI, Wei WEI, Pinkuan LIU

期刊论文

Development of mix design method based on statistical analysis of different factors for geopolymer concrete

Paramveer SINGH; Kanish KAPOOR

期刊论文

Estimation of relations among hysteretic response measures and design parameters for RC rectangular shear

A. ARAB, Ma. R. BANAN, Mo. R. BANAN, S. FARHADI

期刊论文

The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

期刊论文

Changes in public trust in physicians: empirical evidence from China

Dahai Zhao, Zhiruo Zhang

期刊论文

Overall HIEs deconstruction method and its application

Li LIN, Chengqi XUE,

期刊论文

Function-oriented optimization design method for underactuated tendon-driven humanoid prosthetic hand

期刊论文

relationship of industrial agglomeration and low-carbon economy considering spatiotemporal differentiation: An empirical

期刊论文

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

Zhi-wen Wang,Jing Tong

期刊论文