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mechanical properties, fracture behavior, creep, and shrinkage of chemically based self-consolidating concrete

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 36-45 doi: 10.1007/s11709-014-0243-0

摘要： This study presents the results of an experimental investigation that compares the mechanical properties, fracture behavior, creep, and shrinkage of a chemically-based self-consolidating concrete (SCC) mix with that of a corresponding conventional concrete (CC) mix. The CC and SCC mix designs followed conventional proportioning in terms of aggregate type and content, cement content, air content, water-cementitiuos materials ( / ) ratio, and workability. Then, using only chemical admixtures, the authors converted the CC mix to an SCC mix with all of the necessary passing, filling, flowability, and stability requirements typically found in SCC. The high fluidity was achieved with a polycarboxylate-based high-range water-reducing admixture, while the enhanced stability was accomplished with an organic, polymer-based viscosity-modifying admixture. The comparison indicated that the SCC and CC mixes had virtually identical tensile splitting strengths, flexural strengths, creep, and shrinkage. However, the SCC mix showed higher compressive strengths and fracture energies than the corresponding CC mix.

关键词： admixture     conventional concrete (CC)     creep     fracture mechanic     mechanical Properties     self-consolidating concrete (SCC)     shrinkage    

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Nonlinear experimental response of non-conventional composite steel and concrete connection

Tobia ZORDAN, Bruno BRISEGHELLA

《结构与土木工程前沿（英文）》 2009年 第3卷 第1期   页码 42-49 doi: 10.1007/s11709-008-0058-y

摘要： An experiment was carried out on a set of full-scale specimens of a non-conventional connection between a concrete column and a composite steel and concrete beam defined on the basis of a number of requirements. The proposed connection, conceived in the ambit of semi-rigid joints, is aimed at combining general ease of construction with a highly simplified assembly procedure with a satisfying transmission of hogging moment at supports in continuous beams. For this purpose, the traditional shear studs used at the interface between the steel beam and the upper concrete slab, are also employed at the ends of the steel profiles welded horizontally to the end plates. The test is aimed at investigating the hogging moment response of the connection under incremental loads until failure.

关键词： composite connections     nonlinear behaviour     hogging moment     monotonic tests    

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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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Experience gained in analyzing severe accidents for WWER RP using CC SOCRAT

《能源前沿（英文）》 2021年 第15卷 第4期   页码 872-886 doi: 10.1007/s11708-021-0796-2

摘要： The current Russian regulatory documents on the safety of nuclear power plant (NPP) specify the requirements regarding design basis accidents (DBAs) and beyond design basis accidents (BDBAs), including severe accidents (SAs) with core meltdown, in NPP design (NP-001-15, NP-082-07, and others). For a rigorous calculational justification of BDBAs and SAs, it is necessary to develop an integral CC that will be in line with the requirements of regulatory documents on verification and certification (RD-03-33-2008, RD-03-34-2000) and will allow for determining the amount of data required to provide information within the scope stipulated by the requirements for the structure of the safety analysis report (SAR) (NP-006-16). The system of codes for realistic analysis of severe accidents (SOCRAT) (formerly, thermohydraulics (RATEG)/coupled physical and chemical processes (SVECHA)/behavior of core materials relocated into the reactor lower plenum (HEFEST)) was developed in Russia to analyze a wide range of SAs at NPP with water-cooled water-moderated power-generating reactor (WWER) at all stages of the accident. Enhancements to the code and broadening of its applicability are continually being pursued by the code developers (Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE RAN)) with OKB Gidropress JSC and other organizations. Currently, the SOCRAT/1 code can be used as a base tool to obtain realistic estimates for all parameters important for computational justification of the reactor plant (RP) safety at the in-vessel stage of SAs with fuel melting. To perform analyses using CC SOCRAT/1, the experience gained during execution of thermohydraulic codes is applied, which allows for minimizing the uncertainties in the results at the early stage of an accident scenario. This study presents the results of the work performed in 2010–2020 in OKB Gidropress JSC using the CC SOCRAT/1. Approaches have been considered to develop calculational models and analyze SAs using CC SOCRAT. This process, which is clearly structured in OKB Gidropress JSC, provides a noticeable reduction in human involvement, and reduces the probability of erroneous results.

关键词： system of codes for realistic analysis of severe accidents (SOCRAT)     design basis accidents (DBAs)     severe accidents (SAs)     computer code (CC)     nuclear power plant (NPP) design     water-cooled water-moderated (WWER)     modeling     model     safety requirements    

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Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

《结构与土木工程前沿（英文）》 2022年 第16卷 第5期   页码 600-614 doi: 10.1007/s11709-022-0821-5

摘要： The stress concentration of pipe structure or cavity defect has a great effect on the mechanical properties of the high-performance concrete (HPC) members in deep underground locations. However, the behaviour of HPC with cavities under triaxial compression is not understood, especially when pressurized liquid flows into the fractures from the cavity. This study aims to investigate the effect of the cavity and the confining pressure on the failure mechanisms, strengths, and deformation properties of HPC with a new experimental scheme. In this experiment, the pressurized liquid can only contact the surface of the sample in the cavity, while the other surfaces are isolated from the pressurized liquid. To further explore the effect of the cavity, the same experiments are also conducted on sealed and unsealed intact samples without a cavity. The failure modes and stress-strain curves of all types of the samples are presented. Under various confining pressures, all the samples with a cavity suffer shear failure, and there are always secondary tensile fractures initiating from the cavity sidewall. Additionally, it can be determined from the failure modes and the stress-strain curves that the shear fractures result from the sidewall failure. Based on the different effects of the cavity on the lateral deformations in different directions, the initiation of the sidewall fracture is well predicted. The experimental results show that both the increase of the confining pressure and the decrease of the cavity size are conducive to the initiation of sidewall fracture. Moreover, the cavity weakens the strength of the sample, and this study gives a modified Power-law criterion in which the cavity size is added as an impact factor to predict the strength of the sample.

关键词： high-performance concrete     cavity     conventional triaxial compression     pressurized liquid     modified power-law criterion    

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Telomeric impact of conventional chemotherapy

null

《医学前沿（英文）》 2013年 第7卷 第4期   页码 411-417 doi: 10.1007/s11684-013-0293-z

摘要：

The increased level of chromosome instability in cancer cells, leading to aneuploidy and gross chromosomal rearrangements, is not only a driving force for oncogenesis but also can be the Achille’s heel of the disease since many chemotherapies (CT) kill cells by inducing a non-tolerable rate of DNA damage. A wealth of published evidence showed that telomere stability can be more affected than the bulk of the genome by several conventional antineoplasic drugs. These results raise the interesting possibility that CT with genotoxic drugs preferentially target telomeres. In agreement with this view, accelerated shortening of telomere length has been described in blood lineage cells following high-dose CT (stem cell transplantation) or non-myeloablative CT. However, almost nothing is known on the consequences of this shortening in terms of telomere stability, senescence and on the development of second cancers or post-treatment aging-like syndromes in cancer survivors (cognitive defect, fertility impairment, etc.). In this article, we propose: (1) telomeres of cancer cells are preferential genomic targets of chemotherapies altering chromosome maintenance; (2) telomere functional parameters can be a surrogate marker of chemotherapy sensitivity and toxicity; (3) the use of anti-telomere molecule could greatly enhance the sensitivity to standards chemotherapies.

关键词： telomere     antineoplasic drugs     conventional chemotherapies    

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关于大规模并行处理机系统可扩展性设计

卢锡城

《中国工程科学》 2000年 第2卷 第10期   页码 105-109

摘要：

大规模并行处理系统旨在满足国防和国民经济许多重要应用领域对高性能计算能力的需求。长期以来，结构上的可扩性和编程上的友好性一直是并行计算机系统设计中追求的重要而又互相矛盾的两个目标。文章结合研究实践，对大规模并行处理机系统（MPP)可扩展性设计的若干问题进行探讨。

关键词： 体系结构     大规模并行处理机（MPP)     对称多处理机（SMP)     基于Cache—致性的非一致存储访问（CC-NUMA)     群机（duster)     超结点    

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CC@BCN@PANI core-shell nanoarrays as ultra-high cycle stability cathode for Zn-ion hybrid supercapacitors

《能源前沿（英文）》 2023年 第17卷 第4期   页码 555-566 doi: 10.1007/s11708-023-0882-8

摘要： Exploring cathode materials that combine excellent cycling stability and high energy density poses a challenge to aqueous Zn-ion hybrid supercapacitors (ZHSCs). Herein, polyaniline (PANI) coated boron-carbon-nitrogen (BCN) nanoarray on carbon cloth surface is prepared as advanced cathode materials via simple high-temperature calcination and electrochemical deposition methods. Because of the excellent specific capacity and conductivity of PANI, the CC@BCN@PANI core-shell nanoarrays cathode shows an excellent ion storage capability. Moreover, the 3D nanoarray structure can provide enough space for the volume expansion and contraction of PANI in the charging/discharging cycles, which effectively avoids the collapse of the microstructure and greatly improves the electrochemical stability of PANI. Therefore, the CC@BCN@PANI-based ZHSCs exhibit superior electrochemical performances showing a specific capacity of 145.8 mAh/g, a high energy density of 116.78 Wh/kg, an excellent power density of 12 kW/kg, and a capacity retention rate of 86.2% after 8000 charge/discharge cycles at a current density of 2 A/g. In addition, the flexible ZHSCs (FZHSCs) also show a capacity retention rate of 87.7% at the current density of 2 A/g after 450 cycles.

关键词： CC@BCN@PANI cathode     Zn-ion hybrid supercapacitor     core-shell nanoarrays     high energy density     ultra-high cycle stability    

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Oxygen reduction electrocatalysis: From conventional to single-atomic platinum-based catalysts for proton

《能源前沿（英文）》 doi: 10.1007/s11708-023-0907-3

摘要： Platinum (Pt)-based materials are still the most efficient and practical catalysts to drive the sluggish kinetics of cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, their catalysis and stability performance still need to be further improved in terms of corrosion of both carbon support and Pt catalyst particles as well as Pt loading reduction. Based on the developed synthetic strategies of alloying/nanostructuring Pt particles and modifying/innovating supports in developing conventional Pt-based catalysts, Pt single-atom catalysts (Pt SACs) as the recently burgeoning hot materials with a potential to achieve the maximum utilization of Pt are comprehensively reviewed in this paper. The design thoughts and synthesis of various isolated, alloyed, and nanoparticle-contained Pt SACs are summarized. The single-atomic Pt coordinating with non-metals and alloying with metals as well as the metal-support interactions of Pt single-atoms with carbon/non-carbon supports are emphasized in terms of the ORR activity and stability of the catalysts. To advance further research and development of Pt SACs for viable implementation in PEMFCs, various technical challenges and several potential research directions are outlined.

关键词： oxygen reduction electrocatalysis     Pt single-atom catalysts     conventional Pt-based catalysts     design thoughts and synthesis     metal-support interactions    

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Esophageal pulse oximetry is more accurate and detects hypoxemia earlier than conventional pulse oximetry

null

《医学前沿（英文）》 2012年 第6卷 第4期   页码 406-410 doi: 10.1007/s11684-012-0217-3

摘要：

The esophagus is perfused directly by prominent arteries and may provide a more consistent tissue source for pulse oximetry. The goal of this study was to evaluate the sensitivity and accuracy of an esophageal pulse oximetry probe on patients during controlled hypoxemia in comparison to measurements obtained with conventional pulse oximetry (SpulseO2). Forty-five ASA I–II adult patients were included in this prospective observational study. Nellcor digital oximetric probes were placed on finger tips for SpulseO2 before anesthesia. After tracheal intubation, an esophageal probe was placed in the lower segment of the esophagus for esophageal oximetric monitoring (SoesO2). All patients were disconnected from the breathing circuit to establish a controlled hypoxemia, and were re-connected to the breathing circuit and ventilated with 100% oxygen immediately when SoesO2 dropped to 90%. Matched SoesO2 and SpulseO2 readings were recorded when SoesO2measurements were at 100%, 95%, 90% and the lowest reading. The time for SoesO2 and SpulseO2 to drop from 100% to 95%, 90% and return to 100% was recorded. Oxygen saturation from arterial blood samples (SartO2) was also measured at each time point respectively. The linear correlation coefficient of the regression analysis between SartO2 and SoesO2 was 0.954. The mean±2SD of the difference was 0.3%±4.3% for SoesO2vs. SartO2 and 6.8%±5.6% for SpulseO2vs. SartO2 (P<0.001). The 95% confidence interval for the absolute difference between SoesO2 and SartO2 was 0.3% to 0.7% and 6.2% to 7.4% between SpulseO2 and SartO2. The time to reach 90% saturation measured with SoesO2 was approximately 94 seconds earlier than the SpulseO2 (P<0.001). In conclusion, SoesO2 is more accurate and enables earlier detection of hypoxemia when compared to conventional pulse oximetry during hypoxemia for patients undergoing general anesthesia.

关键词： esophageal pulse oximetry     conventional pulse oximetry     hypoxemia    

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Techno-economic characteristics of wastewater treatment plants retrofitted from the conventional activated

《环境科学与工程前沿（英文）》 doi: 10.1007/s11783-021-1483-6

摘要：

While a growing number of wastewater treatment plants (WWTPs) are being retrofitted from the conventional activated sludge (CAS) process to the membrane bioreactor (MBR) process, the debate on the techno-economy of MBR vs. CAS has continued and calls for a thorough assessment based on techno-economic valuation.

关键词： Membrane bioreactor (MBR)     Conventional activated sludge (CAS)     Cost-benefit analysis     Data envelopment analysis     Net profit    

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Innovative hybrid reinforcement constituting conventional longitudinal steel and FRP stirrups for improved

Mostafa FAKHARIFAR,Ahmad DALVAND,Mohammad K. SHARBATDAR,Genda CHEN,Lesley SNEED

《结构与土木工程前沿（英文）》 2016年 第10卷 第1期   页码 44-62 doi: 10.1007/s11709-015-0295-9

摘要： The use of fiber reinforced polymer (FRP) reinforcement is becoming increasingly attractive in construction of new structures. However, the inherent linear elastic behavior of FRP materials up to rupture is considered as a major drawback under seismic attacks when significant material inelasticity is required to dissipate the input energy through hysteretic cycles. Besides, cost considerations, including FRP material and construction of pre-fabricated FRP configurations, especially for stirrups, and probable damage to epoxy coated fibers when transported to the field are noticeable issues. The current research has proposed a novel economical hybrid reinforcement scheme for the next generation of infrastructures implementing on-site fabricated FRP stirrups comprised of FRP sheets. The hybrid reinforcement consists of conventional longitudinal steel reinforcement and FRP stirrups. The key feature of the proposed hybrid reinforcement is the enhanced strength and ductility owing to the considerable confining pressure provided by the FRP stirrups to the longitudinal steel reinforcement and core concrete. Reinforced concrete beam specimens and beam-column joint specimens were tested implementing the proposed hybrid reinforcement. The proposed hybrid reinforcement, when compared with conventional steel stirrups, is found to have higher strength, stiffness, and energy dissipation. Design methods, structural behavior, and applicability of the proposed hybrid reinforcement are discussed in detail in this paper.

关键词： FRP     ductility     confinement     seismic     shear    

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AGRI-ENVIRONMENTAL ASSESSMENT OF CONVENTIONAL AND ALTERNATIVE BIOENERGY CROPPING SYSTEMS PROMOTING BIOMASS

《农业科学与工程前沿（英文）》 2022年 第9卷 第2期   页码 284-294 doi: 10.15302/J-FASE-2021435

摘要：

Bioenergy, currently the largest renewable energy source in the EU (64% of the total renewable energy consumption), has sparked great interest to meet the 32% renewable resources for the 2030 bioeconomy goal. The design of innovative cropping systems informed by bioeconomy imperatives requires the evaluate of the effects of introducing crops for bioenergy into conventional crop rotations. This study aimed to assess the impacts of changes in conventional cropping systems in mixed dairy cattle farms redesigned to introduce bioenergy crops either by increasing the biomass production through an increase of cover crops, while keeping main feed/food crops, or by substituting food crops with an increase of the crop rotation length. The assessment is based on the comparison between conventional and innovative systems oriented to feed and biogas production, with and without tillage, to evaluate their agri-environmental performances (biomass production, nitrogen fertilization autonomy, greenhouse gas emissions and biogas production). The result showed higher values in the biogas cropping system than in the conventional and feed ones for all indicators, biomass productivity (27% and 20% higher, respectively), nitrogen fertilization autonomy (26% and 73% higher, respectively), methanogenic potential (77% and 41% higher, respectively) and greenhouse gas emissions (15% and 3% higher, respectively). There were no negative impacts of no-till compared to the tillage practice, for all tested variables. The biogas cropping system showed a better potential in terms of agri-environmental performance, although its greenhouse gas emissions were higher. Consequently, it would be appropriate to undertake a multicriteria assessment integrating agri-environmental, economic and social performances.

关键词： alternative cropping systems / bioeconomy / biogas / biomass production / fertilization autonomy / greenhouse gas assessment    

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Robotic distal pancreatectomy versus conventional laparoscopic distal pancreatectomy: a comparative study

null

《医学前沿（英文）》 2015年 第9卷 第3期   页码 356-360 doi: 10.1007/s11684-015-0404-0

摘要：

Robotic system has been increasingly used in pancreatectomy. However, the effectiveness of this method remains uncertain. This study compared the surgical outcomes between robot-assisted laparoscopic distal pancreatectomy and conventional laparoscopic distal pancreatectomy. During a 15-year period, 35 patients underwent minimally invasive approach of distal pancreatectomy in our center. Seventeen of these patients had robot-assisted laparoscopic approach, and the remaining 18 had conventional laparoscopic approach. Their operative parameters and perioperative outcomes were analyzed retrospectively in a prospective database. The mean operating time in the robotic group (221.4 min) was significantly longer than that in the laparoscopic group (173.6 min) (P = 0.026). Both robotic and conventional laparoscopic groups presented no significant difference in spleen-preservation rate (52.9% vs. 38.9%) (P = 0.505), operative blood loss (100.3 ml vs. 268.3 ml) (P = 0.29), overall morbidity rate (47.1% vs. 38.9%) (P = 0.73), and post-operative hospital stay (11.4 days vs. 14.2 days) (P = 0.46). Both groups also showed no perioperative mortality. Similar outcomes were observed in robotic distal pancreatectomy and conventional laparoscopic approach. However, robotic approach tended to have the advantages of less blood loss and shorter hospital stay. Further studies are necessary to determine the clinical position of robotic distal pancreatectomy.

关键词： distal pancreatectomy     pancreatic neoplasm     robotic surgery    

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Liquefaction assessment using microtremor measurement, conventional method and artificial neural network

Sadegh REZAEI,Asskar Janalizadeh CHOOBBASTI

《结构与土木工程前沿（英文）》 2014年 第8卷 第3期   页码 292-307 doi: 10.1007/s11709-014-0256-8

摘要： Recent researchers have discovered microtremor applications for evaluating the liquefaction potential. Microtremor measurement is a fast, applicable and cost-effective method with extensive applications. In the present research the liquefaction potential has been reviewed by utilization of microtremor measurement results in Babol city. For this purpose microtremor measurements were performed at 60 measurement stations and the data were analyzed by suing Nakmaura’s method. By using the fundamental frequency and amplification factor, the value of vulnerability index ( ) was calculated and the liquefaction potential has been evaluated. To control the accuracy of this method, its output has been compared with the results of Seed and Idriss [ ] method in 30 excavated boreholes within the study area. Also, the results obtained by the artificial neural network (ANN) were compared with microtremor measurement. Regarding the results of these three methods, it was concluded that the threshold value of liquefaction potential is . On the basis of the analysis performed in this research it is concluded that microtremors have the capability of assessing the liquefaction potential with desirable accuracy.

关键词： liquefaction     microtremor     vulnerability index     artificial neural networks (ANN)     microzonation    

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标题 作者 时间 类型 操作

mechanical properties, fracture behavior, creep, and shrinkage of chemically based self-consolidating concrete

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

期刊论文

Nonlinear experimental response of non-conventional composite steel and concrete connection

Tobia ZORDAN, Bruno BRISEGHELLA

期刊论文

On the added value of multi-scale modeling of concrete

期刊论文

Experience gained in analyzing severe accidents for WWER RP using CC SOCRAT

期刊论文

Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

期刊论文

Telomeric impact of conventional chemotherapy

null

期刊论文

关于大规模并行处理机系统可扩展性设计

卢锡城

期刊论文

CC@BCN@PANI core-shell nanoarrays as ultra-high cycle stability cathode for Zn-ion hybrid supercapacitors

期刊论文

Oxygen reduction electrocatalysis: From conventional to single-atomic platinum-based catalysts for proton

期刊论文

Esophageal pulse oximetry is more accurate and detects hypoxemia earlier than conventional pulse oximetry

null

期刊论文

Techno-economic characteristics of wastewater treatment plants retrofitted from the conventional activated

期刊论文

Innovative hybrid reinforcement constituting conventional longitudinal steel and FRP stirrups for improved

Mostafa FAKHARIFAR,Ahmad DALVAND,Mohammad K. SHARBATDAR,Genda CHEN,Lesley SNEED

期刊论文

AGRI-ENVIRONMENTAL ASSESSMENT OF CONVENTIONAL AND ALTERNATIVE BIOENERGY CROPPING SYSTEMS PROMOTING BIOMASS

期刊论文

Robotic distal pancreatectomy versus conventional laparoscopic distal pancreatectomy: a comparative study

null

期刊论文

Liquefaction assessment using microtremor measurement, conventional method and artificial neural network

Sadegh REZAEI,Asskar Janalizadeh CHOOBBASTI

期刊论文