A base-mediated (3 + 2) cycloaddition of trifluoroacetohydrazonoyl chlorides with imidates for the construction of 3-trifluoromethyl-1,2,4-triazoles has been described. This reaction is characterized ...by readily starting materials, simple reaction conditions, good yields, a broad substrate scope, and excellent regioselectivity. The utility of this protocol has been validated by the synthesis of a drug-like molecule.
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IJS, KILJ, NUK, PNG, UL, UM
•Propose of a FRP grid-reinforced UHPC plate and study of its flexural behavior.•26 plates with steel, basalt and PE fibers additions are subjected to four-point bending tests.•Up to 200 % ...enhancement in flexural capacity can be obtained with PE fiber addition.•Increase fiber content for short basalt or PE fibers (<6 mm) has little enhancement in flexural capacity.•Plates with 1 % volume fraction of 12-mm-length PE fibers is the most economical option.
Ultra-high performance concrete (UHPC), which has an excellent compressive strength and an extraordinary durability, has become increasingly popular in structural engineering. However, UHPC has an inferior tensile property to its compressive property, and thus appropriate reinforcing material is necessary in UHPC structures. To this end, fiber-reinforced polymer (FRP) grids have been proposed for UHPC plates as reinforcements (the composite plates are referred to as FRP grid-UHPC composite plates). As the steel fibers in UHPC would still suffer from corrosion problems in aggressive environments, non-metallic fibers can be in UHPC so that steel-free FRP grid-UHPC composite plates are developed. A total of 26 plates (600 mm in length × 120 mm in width × 40 mm in thickness) are prepared for three-point bending tests in this study. The effects of the fiber type, fiber content and the fiber length on the flexural behavior of FRP grid-UHPC composite plates are investigated. Additionally, an analysis into the microstructure based on scanning electron microscope (SEM) of the FRP-UHPC composite plates is conducted. Moreover, a simple evaluation between the costs and the flexural capacities of the FRP grid-UHPC composite plates is conducted. It is economical to adopt 12-mm-length polyethylene (PE) fibers with a 1 % volume fraction to manufacture composite plates. Finally, the ultimate flexural capacities of FRP grid-UHPC plates were predicted using the section analysis approach.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Group decision making is an essential activity in various fields of operations research and management science. This paper focuses on the intuitionistic fuzzy group decision making problem in which ...all the experts use the intuitionistic fuzzy preference relations (IFPRs) to express their preferences. To start our discussion, we first propose the novel framework of intuitionistic fuzzy group decision making and clarify the difficulties in deriving the final result which is accepted by all individuals in the group. Next, a consistency checking method, which is based on the multiplicative consistency, is developed to check the consistency of each IFPR furnished by the group of experts. For those IFPRs that do not have the acceptable consistency, an iterative procedure is proposed to improve the consistency. Furthermore, after introducing a novel consensus measure, an interesting consensus-reaching procedure is developed to help the group to find a solution which is accepted by most members in the group. Finally, in order to make our approaches more applicable, a step-by-step algorithm is given. A numerical example concerning the selection of outstanding Ph.D. students for the China Scholarship Council is given to illustrate and validate the proposed approaches.
Strengthening existing steel beams with externally bonded carbon fiber-reinforced polymer (CFRP) plate has attracted many interests in the research community. Debonding of the CFRP plate is the ...dominant failure mode in a flexurally strengthened steel beam, and the debonding failure is controlled by the interfacial responses between the CFRP plate and the substrate steel beam. Although some experimental investigations have been conducted on CFRP-strengthened steel beams, limited test results on the interfacial stress and strain responses especially in full-scale steel beams, are available to verify the numerical modeling. This paper presents an experimental study on the flexural behavior of full-scale CFRP-strengthened H-section steel beams. The effects of different bond lengths of CFRP plates and the presence of steel stiffeners are investigated. The test results in terms of the failure modes, load-deflection responses, CFRP strains, interfacial shear stress distributions are reported in detail. A three-dimensional finite element model is proposed to predict the flexural performance of full-scale CFRP-strengthened steel beams, and it is then validated extensively by the test results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
A regioselective fluoromethylation by ring‐opening of cyclic sulfamidates and sulfates with α‐fluorocarbanions and subsequent reductive desulfonylation is developed. ...Fluorobis(phenylsulfonyl)methane (FBSM) was explored as fluoromethide equivalent and the reaction was extended to the α‐fluorocarbanion of ethyl 2‐fluoroacetoacetate. This approach allows access to γ‐ and δ‐fluoroamines as well as γ‐ and δ‐fluoroalcohols in high yields.
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BFBNIB, FZAB, GIS, IJS, KILJ, OILJ, SBCE, SBMB, UPUK
Phenylsulfone difluorodiazoethane (PhSO2CF2CHN2), an easy-to-prepare and bench-stable masked CF2-building block, has been developed. The synthetic utility of this reagent is demonstrated by a direct ...regioselective 3 + 2 cycloaddition with electron-deficient alkynes and alkenes. This protocol enables facile construction of an array of difluoromethyl-substituted pyrazoles in good to high yields under mild reaction conditions.
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IJS, KILJ, NUK, PNG, UL, UM
•Raw material, characteristic and applications of ECCs and UHPFRCCs are reviewed.•Comprehensive reviews on structural members strengthened with ECCs/UHPFRCCs are presented.•Behavior and applications ...of FRP-reinforced ECC/UHPFRCC composites are reviewed.•Existing data and theoretical models for FRP-ECC/UHPFRCC strengthened structures are summarized.•Future research needs on ECC/UHPFRCC with and without FRP reinforcement are identified.
High-performance cementitious composites, such as engineered cementitious composites (ECCs) with strong tensile strain-hardening behavior or ultra-high performance fiber-reinforced cementitious composites (UHPFRCCs) with excellent compressive behavior, have been widely used in civil engineering. In cases that UHPFRCC strengthening layer without internal reinforcement has an inferior average ultimate tensile stress to UHPFRCC strengthening layer with internal reinforcement, fiber-reinforced polymer (FRP) bar/grid can be adopted as internal tension reinforcement. This paper presents a state-of-the-art comprehensive review on the characteristics and application of high-performance cementitious composites with and without FRP grid reinforcement. This review discusses the feasibility of application of ECC/UHPFRCC to structural strengthening/repairing, and concludes that FRP grid-reinforced ECC/UHPFRCC exhibits better potential than ECC/UHPFRCC in improving mechanical performance of composite structures. Finally, the application prospect and future research on FRP grid-reinforced ECC/UHPFRCC are identified.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Typical three-segment axial stress-strain curves of FRP-confined UHPC are defined.•Stress reduction and the actual confinement ratio threshold reduce with the content of steel fibers.•Addition of ...steel fibers compromises effects of specimen size.•Performances of existing axial stress-strain models for FRP-confined concrete are verified.
Ultra-high performance concrete (UHPC) usually exhibits a weak ductility under axial compression. However, the ductility can be enhanced by implementing confining devices such as fiber-reinforced polymer (FRP) wraps. In order to gain in-depth understandings on the compressive behavior of FRP-confined UHPC, axial compression tests on 52 FRP-confined and 12 unconfined UHPC cylinders were carried out in this study. The failure modes, stress-strain behaviors, confinement efficiency, and the influences of crucial variables (steel fiber contents, specimen sizes, FRP fiber types, and FRP thickness) on the compressive behavior of FRP-confined UHPC were investigated and discussed. Results show that the increase in steel fiber content could increase the first peak stress and its corresponding strain, hoop strain efficiency, avoid the abrupt stress reduction after the first peak stress, as well as alleviating the effect of specimen sizes. Addition of steel fibers also alters the actual confinement ratio threshold for sufficient confinement. Comparisons suggest that FRP confinement fiber types have limited influence on the normalized stress-strain behavior of specimens with similar level of actual confinement ratio. Additionally, performances of four existing axial stress-strain models for FRP-confined concrete are verified and the results reveal that Teng et al.’s model performs the best although this model is incapable in capturing the strain softening behavior after the first peak stress.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Using large rupture strain (LRS) fiber-reinforced polymer (FRP) composites as confining material has become increasingly prominent in structural repair or retrofitting, owing to their ...advantageous high deformation capacity. Economic and rational usage of LRS FRP relies on displacement-based design, which requires calculation of the ultimate deformation of a member. However, prediction of the ultimate strain of LRS FRP–confined concrete is more complex and can be more inaccurate than prediction of strength, especially for structural elements under large deformation or severe damage conditions. This study proposes a unified ultimate strain model for LRS FRP–confined concrete based on an energy balance method. A unified expression form is derived using this method, providing an ultimate strain model with no restrictions on column cross section, in terms of circular, square, or oblong columns. The proposed ultimate strain model has a wider application and a better performance than other models. Furthermore, according to this paper’s updated database, the characteristic points on the whole stress–strain curve can also be accurately determined. Using the new ultimate strain model for LRS FRP–confined concrete and its characteristic points, the whole entire stress–strain curve of LRS FRP–confined concrete is accurately derived.
Long-term straw return is an important carbon source for improving soil organic carbon (SOC) stocks in croplands, and straw removal through burning is also a common practice in open fields in South ...China. However, the specific effects of long-term rice straw management on SOC fractions, the related enzyme activities and their relationships, and whether these effects differ between crop growing seasons remain unknown. Three treatments with equal nitrogen, phosphorus, and potassium nutrient inputs, including straw/ash and chemical nutrients, were established to compare the effects of straw removal (CK), straw return (SR), and straw burned return (SBR). Compared to CK, long-term SR tended to improve the yield of early season rice (P=0.057), and significantly increased total organic carbon (TOC) and microbial biomass carbon (MBC) in double-cropped rice paddies. While SBR had no effect on TOC, it decreased light fraction organic carbon (LFOC) in early rice and easily oxidizable organic carbon (EOC) in late rice, significantly increased dissolved organic carbon (DOC), and significantly decreased soil pH. These results showed that MBC was the most sensitive indicator for assessing changes of SOC in the double-cropped rice system due to long-term straw return. In addition, the different effects on SOC fraction sizes between SR and SBR were attributed to the divergent trends in most of the soil enzyme activities in the early and late rice that mainly altered DOC, while DOC was positively affected by β-xylosidase in both early and late rice. We concluded that straw return was superior to straw burned return for improving SOC fractions, but the negative effects on soil enzyme activities in late rice require further research.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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