A study of the interfacial behavior and internal thermal stress distribution in fiber-reinforced composites is essential to assess their performance and reliability.CNT/carbon fiber(CF)hybrid fibers were constructed u...A study of the interfacial behavior and internal thermal stress distribution in fiber-reinforced composites is essential to assess their performance and reliability.CNT/carbon fiber(CF)hybrid fibers were constructed using electrophoretic deposition.The interfacial properties of CF/epoxy and CNT/CF/epoxy composites were statistically investigated and compared using in-situ thermal Raman mapping by dispersing CNTs as a Raman sensing medium(CNT_(R))in a resin.The associated local thermal stress changes can be simulated by capturing the G'band position distribution of CNT_(R) in the epoxy at different temperatures.It was found that the G'band shifted to lower positions with increasing temperature,reaching a maximum difference of 2.43 cm^(−1) at 100℃.The interfacial bonding between CNT/CF and the matrix and the stress distribution and changes during heat treatment(20-100℃)were investig-ated in detail.This work is important for studying thermal stress in fiber-reinforced composites by in-situ thermal Raman mapping technology.展开更多
TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis(SHS) with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstru...TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis(SHS) with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni+Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC-TiB2-NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.展开更多
The comparative experiments of age forming and artificial aging of 2A12 aluminum alloy were carried out. The effect of the age forming on the microstructure and mechanical properties was investigated. The results demo...The comparative experiments of age forming and artificial aging of 2A12 aluminum alloy were carried out. The effect of the age forming on the microstructure and mechanical properties was investigated. The results demonstrate that the grains are further squashed and elongated compared with artificial aging due to the existence of the applied stress during the age forming. Meanwhile, the precipitated phases change from circle shape with random orientation of age forming to long strip shape with uniform orientation of artificial aging. The dislocation configuration in samples changes from ring dislocation or helical dislocation of the artificial aging to long and straight dislocation of the age forming. Otherwise, age forming slightly reduces the tensile properties and fracture toughness of the alloy and enhances its fatigue crack growth rate.展开更多
In order to reduce the oxidation and volatilization caused by Mg element in the traditional methods for synthesizing Mg2Si compounds,Mg2Si thermoelectric materials were prepared by solid state reaction and microwave r...In order to reduce the oxidation and volatilization caused by Mg element in the traditional methods for synthesizing Mg2Si compounds,Mg2Si thermoelectric materials were prepared by solid state reaction and microwave radiation techniques.Structure and phase composition of the materials were investigated by X-ray diffraction.The electrical conductivity,Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 700 K.It is found that high purity Mg2Si powders can be obtained with excessive content of 8% Mg from the stoichiometric Mg2Si at 853 K and 2.5 kW for 30 min.A maximum dimensionless figure of merit,ZT,of about 0.13 was obtained for Mg2Si at 600 K.展开更多
Changes of ACC and MACC levels, ACC synthase activity as well as ethylene production in the leaves of two spring wheat (Triticum aestivum L.) cultivars 8139 (with relatively low drought-resistance) and 504 (with relat...Changes of ACC and MACC levels, ACC synthase activity as well as ethylene production in the leaves of two spring wheat (Triticum aestivum L.) cultivars 8139 (with relatively low drought-resistance) and 504 (with relatively high drought-resistance) during water stress were determined. The levels of ACC and MACC in both cultivars decreased in the first 24 It of water stress and increased in the second 24 It while the activities of ACC synthase increased continuously throughout the entire period of treatment (48 h), As water stress progressed, ethylene production decreased continuously in cv. 8139 but remarkably increased earlier and decreased later in the cv. 504. Moreover, the decrease in RWC of stressed leaves was greater and the changes in ACC and MACC levels as well as ACC synthase activity were higher in the drought-sensitive cv. 8139 than in the drought-resistant cv, 504 during water stress. The levels of ACC and MACC, activities of ACC synthase and productions of ethylene in the stressed leaves in two cultivars were significantly altered by the application of MGBG (an inhibitor of SAMDC) and AOA (an inhibitor of ACC synthase) where their effects on these items were almost opposite. They were increased by the former inhibitor but reduced by the latter. All of these results suggested that the level of ethylene production in plants did not depend on the level of ACC during water stress. The increase in the level of ethylene in the drought-resistant cultivar during the earlier period of water stress might be a phenomenon of adaptation to water stress and be correlated with the development of the drought-tolerance in plants and playing role in the transduction of stress signal. The role of MACC, however, was primarily in the regulation of ethylene production under water stress.展开更多
The aim of "green chemistry" and "atom economy" is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts inclu...The aim of "green chemistry" and "atom economy" is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.展开更多
Effects of four factors on thin sheet metal flow stress were considered, including grain size d, thickness t, grain number across thickness (t/d ratio) and surface property. Surface model was adopted to quantitative...Effects of four factors on thin sheet metal flow stress were considered, including grain size d, thickness t, grain number across thickness (t/d ratio) and surface property. Surface model was adopted to quantitatively describe the effect of t/d ratio on flow stress for pure copper. It is predicted that when t/d ratio is larger than a critical value, effect of t/d ratio on flow stress can be neglected. Existence of critical t/d ratio changes the Hall-Petch relationship and evolution of flow stress with thickness. A criterion was proposed to determine critical t/d ratio. Then a comprehensive constitutive model was developed to consider all the four factors, with parameters determined by fitting experimental data of high purity Ni. The predicted results show the same tendencies with experiment results. Particularly when t/d ratio decreases, Hall-Petch relationship and evolution of true stress show varied slopes with two transition points.展开更多
The chemical constituents, pharmacological activity and traditional uses of 20 species attributed to the genus Elsholtzia (Labiatae) used in China are reviewed and compared. A survey of the literature available show...The chemical constituents, pharmacological activity and traditional uses of 20 species attributed to the genus Elsholtzia (Labiatae) used in China are reviewed and compared. A survey of the literature available shows that these species are used mostly for the treatment of respiratory and gastrointestinal disorders. Additionally, some of these Elsholtzia species show antibacterial, anti-inflammatory, relieving fever, analgesic activities and myocardial ischemia protection. Generally, the essential oils or flavonoids from these plant extracts are assumed to be the active principles.展开更多
Ti(C,N) powders were synthesized by mechanical alloying (MA) from a mixture of pure titanium and graphite under a nitrogen atmosphere in a planetary mill.Effects of arc discharging on phase transformation and micr...Ti(C,N) powders were synthesized by mechanical alloying (MA) from a mixture of pure titanium and graphite under a nitrogen atmosphere in a planetary mill.Effects of arc discharging on phase transformation and microstructure of MA powders milled for 1-7 h were explored.The results show that Ti(C,N) powders were prepared after mechanical milling for 1 h and subsequent arc discharge treatment,whereas the synthesis reaction did not occur in 7 h by mechanical milling alone.The ions produced during arc discharging interacted with powder particles and accelerated the diffusion of atoms and the nucleation on the surface of the as-milled powder,which results in fast synthesis of Ti(C,N) powders.The formation mechanisms of the two synthesis processes are self-propagating reactive synthesis.展开更多
The companion fungus ( Grifola sp.) related to sclerotial formation from hyphae of Grifola umbellata (Pers.) Pilat was isolated from the cavity associated with sclerotia of G. umbellata in natural condition. Experimen...The companion fungus ( Grifola sp.) related to sclerotial formation from hyphae of Grifola umbellata (Pers.) Pilat was isolated from the cavity associated with sclerotia of G. umbellata in natural condition. Experimental results showed that the pure culture of G. umbellata was unable to form sclerotia, whereas sclerotia produced easily in flasks or on trunks when the companion fungus was inoculated together with strain of G. umbellata. The companion fungus is critical for sclerotium formation from hyphae of G. umbellata. Morphological differences were found in cultures of the two fungi. The companion fungus possesses thin-walled narrow hyphae, while G. umbellata is of wider hyphae which are either thick- or thin-walled.展开更多
To analyze the effect of single grain deformation behaviors on microforming process, a crystal plasticity model was developed considering grains at free surface layer as single grains. Based on the rate-dependent crys...To analyze the effect of single grain deformation behaviors on microforming process, a crystal plasticity model was developed considering grains at free surface layer as single grains. Based on the rate-dependent crystal plasticity theory, the analysis of the scale effect mechanism on upsetting deformation of micro rods was performed with respect to specimen dimension, original grain orientation and its distribution. The results show that flow stress decreases significantly with the scaling down of the specimen. The distribution of the grain orientation has an evident effect on flow stress of the micro specimen, and the effect becomes smaller with the progress of plastic deformation. For the anisotropy of single grains, inhomogeneous deformation occurs at the surface layer, which leads to the increase of surface roughness, especially for small specimens. The effect of grain anisotropy on the surface topography can be decreased by the transition grains. The simulation results are validated by upsetting deformation experiments. This indicates that the developed model is suitable for the analysis of microforming processes with characteristics, such as scale dependency, scatter of flow stress and inhomogeneous deformation.展开更多
To find a reasonable way to prepare the designed CPP32 inhibitors. Method Ugifour-component condensation reaction was used to synthesize peptide mimic CPP32 inhibitors; ResultsA key isocyanide component (aspartate-der...To find a reasonable way to prepare the designed CPP32 inhibitors. Method Ugifour-component condensation reaction was used to synthesize peptide mimic CPP32 inhibitors; ResultsA key isocyanide component (aspartate-derived isocyanide 3) and one of the designed CPP32inhibitors 4 (as a template) were synthesized; Conclusion The CPP32 inhibitor 4 was synthesized bythe newly developed procedure, which is an Ugi four-component condensation reaction based onaspartate-derived isocyanide 3. This method can be used to build up the CPP32 inhibitor library.展开更多
A new polycrystal model was presented from the viewpoint of polycrystal structure of the billets considering free surface effects.In the model,the billet was divided into three portions,such as free surface portion,tr...A new polycrystal model was presented from the viewpoint of polycrystal structure of the billets considering free surface effects.In the model,the billet was divided into three portions,such as free surface portion,transition portion and internal portion.The grains in free surface portion were considered the single grains,and the anisotropy of the grains was taken into account by introducing grain orientation to explain the inhomogeneous deformation.In the transition portion,the effects of the neighbouring grains were adopted in the model.The grains in the internal portion were considered the polycrystalline material.With the developed model,the upsetting deformation process was simulated by the MSC Superform software.The scatter of the flow stress and inhomogeneous deformation was observed by analysis of the model.The comparisons show that the computational results are good agreed with the experimental results.This means that the presented model is effective.展开更多
文摘A study of the interfacial behavior and internal thermal stress distribution in fiber-reinforced composites is essential to assess their performance and reliability.CNT/carbon fiber(CF)hybrid fibers were constructed using electrophoretic deposition.The interfacial properties of CF/epoxy and CNT/CF/epoxy composites were statistically investigated and compared using in-situ thermal Raman mapping by dispersing CNTs as a Raman sensing medium(CNT_(R))in a resin.The associated local thermal stress changes can be simulated by capturing the G'band position distribution of CNT_(R) in the epoxy at different temperatures.It was found that the G'band shifted to lower positions with increasing temperature,reaching a maximum difference of 2.43 cm^(−1) at 100℃.The interfacial bonding between CNT/CF and the matrix and the stress distribution and changes during heat treatment(20-100℃)were investig-ated in detail.This work is important for studying thermal stress in fiber-reinforced composites by in-situ thermal Raman mapping technology.
基金Projects(51072104,51272141)supported by the National Natural Science Foundation of ChinaProject(ts20110828)supported by Taishan Scholars Project of Shandong,China
文摘TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis(SHS) with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni+Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC-TiB2-NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.
基金Project (NCET-10-0278) supported by the Program for New Century Excellent Talents in University, ChinaProject (20102024) supported by the Natural Science Foundation of Liaoning Province, China
文摘The comparative experiments of age forming and artificial aging of 2A12 aluminum alloy were carried out. The effect of the age forming on the microstructure and mechanical properties was investigated. The results demonstrate that the grains are further squashed and elongated compared with artificial aging due to the existence of the applied stress during the age forming. Meanwhile, the precipitated phases change from circle shape with random orientation of age forming to long strip shape with uniform orientation of artificial aging. The dislocation configuration in samples changes from ring dislocation or helical dislocation of the artificial aging to long and straight dislocation of the age forming. Otherwise, age forming slightly reduces the tensile properties and fracture toughness of the alloy and enhances its fatigue crack growth rate.
基金Project (2009BB4228) supported by the Natural Science Foundation Project of Chongqing Science and Technology Commission,ChinaProject (CK2010Z09) supported by the Research Foundation of Chongqing University of Science and Technology,China
文摘In order to reduce the oxidation and volatilization caused by Mg element in the traditional methods for synthesizing Mg2Si compounds,Mg2Si thermoelectric materials were prepared by solid state reaction and microwave radiation techniques.Structure and phase composition of the materials were investigated by X-ray diffraction.The electrical conductivity,Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 700 K.It is found that high purity Mg2Si powders can be obtained with excessive content of 8% Mg from the stoichiometric Mg2Si at 853 K and 2.5 kW for 30 min.A maximum dimensionless figure of merit,ZT,of about 0.13 was obtained for Mg2Si at 600 K.
文摘Changes of ACC and MACC levels, ACC synthase activity as well as ethylene production in the leaves of two spring wheat (Triticum aestivum L.) cultivars 8139 (with relatively low drought-resistance) and 504 (with relatively high drought-resistance) during water stress were determined. The levels of ACC and MACC in both cultivars decreased in the first 24 It of water stress and increased in the second 24 It while the activities of ACC synthase increased continuously throughout the entire period of treatment (48 h), As water stress progressed, ethylene production decreased continuously in cv. 8139 but remarkably increased earlier and decreased later in the cv. 504. Moreover, the decrease in RWC of stressed leaves was greater and the changes in ACC and MACC levels as well as ACC synthase activity were higher in the drought-sensitive cv. 8139 than in the drought-resistant cv, 504 during water stress. The levels of ACC and MACC, activities of ACC synthase and productions of ethylene in the stressed leaves in two cultivars were significantly altered by the application of MGBG (an inhibitor of SAMDC) and AOA (an inhibitor of ACC synthase) where their effects on these items were almost opposite. They were increased by the former inhibitor but reduced by the latter. All of these results suggested that the level of ethylene production in plants did not depend on the level of ACC during water stress. The increase in the level of ethylene in the drought-resistant cultivar during the earlier period of water stress might be a phenomenon of adaptation to water stress and be correlated with the development of the drought-tolerance in plants and playing role in the transduction of stress signal. The role of MACC, however, was primarily in the regulation of ethylene production under water stress.
基金supported by the National Science and Technology Support Project of China(2013BAC11B03)the National Natural Science Foundation of China(21401054,21476065,21273067)the Graduate Student Scientific Research Innovation Fund Project of Hunan Province(CX2015B082)~~
文摘The aim of "green chemistry" and "atom economy" is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.
基金Projects(50835002,50975174,50821003)supported by the National Natural Science Foundation of ChinaProjects(200802480053,20100073110044)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Effects of four factors on thin sheet metal flow stress were considered, including grain size d, thickness t, grain number across thickness (t/d ratio) and surface property. Surface model was adopted to quantitatively describe the effect of t/d ratio on flow stress for pure copper. It is predicted that when t/d ratio is larger than a critical value, effect of t/d ratio on flow stress can be neglected. Existence of critical t/d ratio changes the Hall-Petch relationship and evolution of flow stress with thickness. A criterion was proposed to determine critical t/d ratio. Then a comprehensive constitutive model was developed to consider all the four factors, with parameters determined by fitting experimental data of high purity Ni. The predicted results show the same tendencies with experiment results. Particularly when t/d ratio decreases, Hall-Petch relationship and evolution of true stress show varied slopes with two transition points.
文摘The chemical constituents, pharmacological activity and traditional uses of 20 species attributed to the genus Elsholtzia (Labiatae) used in China are reviewed and compared. A survey of the literature available shows that these species are used mostly for the treatment of respiratory and gastrointestinal disorders. Additionally, some of these Elsholtzia species show antibacterial, anti-inflammatory, relieving fever, analgesic activities and myocardial ischemia protection. Generally, the essential oils or flavonoids from these plant extracts are assumed to be the active principles.
基金Project(50674057) supported by the National Natural Science Foundation of China
文摘Ti(C,N) powders were synthesized by mechanical alloying (MA) from a mixture of pure titanium and graphite under a nitrogen atmosphere in a planetary mill.Effects of arc discharging on phase transformation and microstructure of MA powders milled for 1-7 h were explored.The results show that Ti(C,N) powders were prepared after mechanical milling for 1 h and subsequent arc discharge treatment,whereas the synthesis reaction did not occur in 7 h by mechanical milling alone.The ions produced during arc discharging interacted with powder particles and accelerated the diffusion of atoms and the nucleation on the surface of the as-milled powder,which results in fast synthesis of Ti(C,N) powders.The formation mechanisms of the two synthesis processes are self-propagating reactive synthesis.
文摘The companion fungus ( Grifola sp.) related to sclerotial formation from hyphae of Grifola umbellata (Pers.) Pilat was isolated from the cavity associated with sclerotia of G. umbellata in natural condition. Experimental results showed that the pure culture of G. umbellata was unable to form sclerotia, whereas sclerotia produced easily in flasks or on trunks when the companion fungus was inoculated together with strain of G. umbellata. The companion fungus is critical for sclerotium formation from hyphae of G. umbellata. Morphological differences were found in cultures of the two fungi. The companion fungus possesses thin-walled narrow hyphae, while G. umbellata is of wider hyphae which are either thick- or thin-walled.
基金Project (50835002) supported by the National Natural Science Foundation of ChinaProject (QC08C55) supported by the Natural Science Foundation of Heilongjiang Province, China Project (200802131031) supported by the PhD. Programs Foundation of Ministry of Education of China for Young Scholars
文摘To analyze the effect of single grain deformation behaviors on microforming process, a crystal plasticity model was developed considering grains at free surface layer as single grains. Based on the rate-dependent crystal plasticity theory, the analysis of the scale effect mechanism on upsetting deformation of micro rods was performed with respect to specimen dimension, original grain orientation and its distribution. The results show that flow stress decreases significantly with the scaling down of the specimen. The distribution of the grain orientation has an evident effect on flow stress of the micro specimen, and the effect becomes smaller with the progress of plastic deformation. For the anisotropy of single grains, inhomogeneous deformation occurs at the surface layer, which leads to the increase of surface roughness, especially for small specimens. The effect of grain anisotropy on the surface topography can be decreased by the transition grains. The simulation results are validated by upsetting deformation experiments. This indicates that the developed model is suitable for the analysis of microforming processes with characteristics, such as scale dependency, scatter of flow stress and inhomogeneous deformation.
文摘To find a reasonable way to prepare the designed CPP32 inhibitors. Method Ugifour-component condensation reaction was used to synthesize peptide mimic CPP32 inhibitors; ResultsA key isocyanide component (aspartate-derived isocyanide 3) and one of the designed CPP32inhibitors 4 (as a template) were synthesized; Conclusion The CPP32 inhibitor 4 was synthesized bythe newly developed procedure, which is an Ugi four-component condensation reaction based onaspartate-derived isocyanide 3. This method can be used to build up the CPP32 inhibitor library.
基金Projects(50835002,50805035)support by the National Natural Science Foundation of ChinaProject(QC08C55)supported by the Natural Science Foundation of Heilongjiang Province,ChinaProject(200802131031)supported by the PhD Programs Foundation of Ministry of Education of China for Young Scholars
文摘A new polycrystal model was presented from the viewpoint of polycrystal structure of the billets considering free surface effects.In the model,the billet was divided into three portions,such as free surface portion,transition portion and internal portion.The grains in free surface portion were considered the single grains,and the anisotropy of the grains was taken into account by introducing grain orientation to explain the inhomogeneous deformation.In the transition portion,the effects of the neighbouring grains were adopted in the model.The grains in the internal portion were considered the polycrystalline material.With the developed model,the upsetting deformation process was simulated by the MSC Superform software.The scatter of the flow stress and inhomogeneous deformation was observed by analysis of the model.The comparisons show that the computational results are good agreed with the experimental results.This means that the presented model is effective.