Ammonium-ion hybrid supercapacitors(A-HSCs)have emerged as promising candidates for next-generation energy storage owing to their inherent safety and environmental sustainability.Hexagonal tungsten oxide(h-WO_(3)),wit...Ammonium-ion hybrid supercapacitors(A-HSCs)have emerged as promising candidates for next-generation energy storage owing to their inherent safety and environmental sustainability.Hexagonal tungsten oxide(h-WO_(3)),with its well-defined tunnel structure,holds great promise as a negative electrode material for NH^(4+)storage.However,its practical application is hindered by structural instability and poor intrinsic electrical conductivity.To address these challenges,a dual-regulation strategy is proposed,integrating molybdenum(Mo)doping and NH^(4+)pre-intercalation to concurrently optimize the tunnel structure and electronic environment of h-WO_(3)(Mo-NWO).Comprehensive experimental and theoretical analyses reveal that Mo doping narrows the bandgap of WO_(3)and reduces the diffusion energy barrier,thereby accelerating NH^(4+)adsorption and diffusion.Simultaneously,NH^(4+)pre-intercalation stabilizes the tunnel framework via hydrogen bonding,ensuring structural reversibility.As expected,the Mo-NWO/AC electrode achieves a high areal capacitance of 13.6 F cm^(−2)at 5 mA cm^(−2)and retains 80.14%of its capacitance after 5000 cycles,demonstrating exceptional rate capability and cycling stability.Moreover,the assembled Mn_(3)O_(4)//Mo-NWO/AC device delivers a high energy density of 3.41 mWh cm^(−2)and outstanding long-term stability(85.75%retention after 12,000 cycles).This work provides a viable strategy for designing high-performance NH^(4+)storage materials and advances the development of sustainable energy storage systems.展开更多
Four-dimensional(4D)printing technology is a revolutionary development that produces structures that can adapt in response to external stimuli.However,the responsiveness and printability of smart materials with shape ...Four-dimensional(4D)printing technology is a revolutionary development that produces structures that can adapt in response to external stimuli.However,the responsiveness and printability of smart materials with shape memory properties,which are necessary for 4D printing,remain limited.Biomass materials derived from nature have offered an effective solution due to their various excellent and unique properties.Biomass materials have been abundant in resources and low in carbon content,contributing to the then-current global green energy-saving goals,including carbon peaking and carbon neutrality.This review focused on different sources of biomass materials used in 4D printing,including plant-based,animal-based,and microbial-based biomass materials.It systematically outlined the responsive deformation mechanisms of printed objects that contained biomass materials and delved into the roles and unique advantages of biomass materials in those printed objects.Leveraging these advantages,the review discussed the potential applications of biomass materials in biomedicine,food printing,and other fields to support ongoing development and application efforts.Additionally,it emphasized the crucial role played by bio-fabrication technologies utilizing biomass materials in the integration of biomass materials with 4D printing.Finally,this paper discussed the then-current challenges and potential future directions of biomass materials in 4D printing,aiming to promote the effective development of biomass materials in 4D printing applications.展开更多
A novel process combining oxidation-bonding and sintering was developed to fabricate porous Si3N4 ceramic with high porosity. After sintering at 1800℃, the SiO2 in porous Si3N4 ceramic transforms into Si2N2O because ...A novel process combining oxidation-bonding and sintering was developed to fabricate porous Si3N4 ceramic with high porosity. After sintering at 1800℃, the SiO2 in porous Si3N4 ceramic transforms into Si2N2O because of the reaction of SiO2 and Si3N4 . Due to the reaction of SiO2 and carbon, the porosity of porous Si3N4 ceramic increases obviously from 40.2% to 76.8% with the weight decreasing by 35.6%. As the porosity increases, the dielectric constant and loss of the porous Si3N4 ceramic decrease obviously from 3.08 to 1.61 and from 3.70×10（-3） to 0.74×10（-3） , but due to the production of Si2N2O whose mechanical properties are much higher than SiO2 and the increase of the bonding strength among Si3N4 particles, the flexural strength and the fracture toughness of the porous Si3N4 ceramic decrease from 55 to 39 MPa and from 0.7 to 0.5 MPa·m（1/2） , respectively, but its Vickers hardness increases from 1.2 to 1.3 GPa.展开更多
Hoppressed Si3N4/SiC platelet composites had been investigated with respect to their microstructure and mechanical properties. The results indicate that Vickers hardness, elastic modulus and fracture toughness of the ...Hoppressed Si3N4/SiC platelet composites had been investigated with respect to their microstructure and mechanical properties. The results indicate that Vickers hardness, elastic modulus and fracture toughness of the composites were increased by the addition of SiC platelet until the content up to 20 vol pct. A slight decrease in flexural Strength was measured at room temperature with increasing SiC platelet content. The high temperature flexural strength tests at 1150, 1250, and 1350℃ were conducted. It was found that the flexural strength at elevated temperature was degraded with the rising temperature, and the downward trend of flexural strength for the composite containing 10 vol. pct SiC platelet was less. The results indicate that SiC platelet had a positive influence on the high temperature strength. Effects of SiC platelet reinforcement were presented展开更多
Electrochemical oxidation of 4-methyl catechol（1a） is investigated in the presence of 1,3-indandione（3）as nucleophile in phosphate buffer solution（0.2 mol/L,pH 6） mixed with ethanol as organic green solvent（50...Electrochemical oxidation of 4-methyl catechol（1a） is investigated in the presence of 1,3-indandione（3）as nucleophile in phosphate buffer solution（0.2 mol/L,pH 6） mixed with ethanol as organic green solvent（50/50） using cyclic voltammetry and controlled-potential coulometry.The results indicated thatquinones derived from electro-oxidation of 1a,participated in a 1,4-Michael addition reaction with1,3-indandione（3） under ECCE mechanism.In this direction,a new bis-quinone was synthesized in high yield and good purity using a facile and convenient electrochemical pathway by carbon anode electrodes in an undivided cell.展开更多
As a new solid state welding,pinless friction stir welding（PFSW） can be used to join thin-wall structures.In this study,four new pinless tools with different groove distributions were designed and manufactured in or...As a new solid state welding,pinless friction stir welding（PFSW） can be used to join thin-wall structures.In this study,four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 alloy.The results show that the small-obliquity tool is detrimental to the transfer of plasticized materials,resulting in the formation of kissing bond defect.For the through-groove tool or the large-curvature tool,bigger flashes form on the joint surface and alclad layer is observed in the nugget zone（NZ）,deteriorating mechanical properties.Compared with the above-mentioned three tools,using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction,but also prevent alclad from flowing into NZ,which has potential to weld thin alclad aluminum alloys.Meanwhile,the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%,up to 85.1% and 64% of BM.展开更多
Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown...Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 ℃-84 ℃ in H2O（g）. The hydration was controlled by diffusion from 24.7 ℃ to 33 ℃. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al4C3 crystals at high temperature. Besides, the matrix changes into the Al4C3 with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al4C3 in situ reaction was immersed in the wax at suitable temperature or storing them below 33 ℃ in a dry place or storing them with paraffin-coating.展开更多
Phspho-olivine Li Fe PO4 was synthesized from the relatively insoluble lithium source Li2CO3, proper iron and phosphorus sources（n（Li）：n（Fe）：n（P）=1：1：1） by a novel hydrothermal method. Afterwards, the opti...Phspho-olivine Li Fe PO4 was synthesized from the relatively insoluble lithium source Li2CO3, proper iron and phosphorus sources（n（Li）：n（Fe）：n（P）=1：1：1） by a novel hydrothermal method. Afterwards, the optimal sample was mixed with glucose and two-step calcinated（500 ℃ and 750 ℃） under high-purity N2 to obtain the Li Fe PO4/C composite. The resultant samples were characterized by X-ray diffraction（XRD）, atomic absorption spectrometry（AAS）, scanning electron microscops（SEM）, transmission electron microscopy（TEM）, energy dispersive spectrometry（EDS）, elementary analysis（EA） and electrochemical tests. The results show that the optimal reaction condition is to set the reactant concentration at 0.5 mol·L^-1, the reaction temperature at 180 ℃ for 16 h duration. During the reaction course, an intermediate product NH4 Fe PO4·H2O was first synthesized, and then it reacted with Li＋ to form Li Fe PO4. The optimized Li Fe PO4 sample with an average particle size（300 to 500 nm） and regular morphology exhibits a relatively high discharge capacity of 84.95 m Ah· g^-1 at the first charge-discharge cycle（0.1C, 1C=170 m A·g^-1）. Moreover, the prepared Li Fe PO4/C composite shows a high discharge capacity of 154.3 m Ah·g^-1 at 0.1C and 128.2 m Ah·g^-1 even at 5C. Besides it has good reversibility and stability in CV test.展开更多
Based on the existing form of Zn2 Si O4 in willemite, the chemical precipitation method was used to synthesize Zn2 Si O4.Through the orthogonal experimentation, the reaction conditions of melten Na OH decomposing Zn2 ...Based on the existing form of Zn2 Si O4 in willemite, the chemical precipitation method was used to synthesize Zn2 Si O4.Through the orthogonal experimentation, the reaction conditions of melten Na OH decomposing Zn2 Si O4 were optimized, and the optimal experimental conditions include reaction temperature of 400 °C, reaction time of 4 h, and alkaline-to-ore molar ratio of 20:1.Based on the optimized experiment, on-line detection for the alkali leaching was made by using Raman spectroscopy; XRD was used to analyze the structure of water leaching residue, to explore the reaction mechanism of Na OH decomposing Zn2 Si O4. The results show that during the reaction process, the Si — O bond in Si O4 is destroyed, and the Na OH inserts itself into the silicate lattice,producing an immediate Na2 Zn Si O4 product. After the alkali leaching process, Zn2+ can be separated from the Si O4 array, which can be released out of the silicate in the form of ZnO.展开更多
IPv4 and IPv6 will coexist for many years during the transition period from the traditional IPv4-based Internet to an IPv6-based Internet.DHTLayer,a novel IPv4/IPv6 transition mechanism based on Distributed Hash Table...IPv4 and IPv6 will coexist for many years during the transition period from the traditional IPv4-based Internet to an IPv6-based Internet.DHTLayer,a novel IPv4/IPv6 transition mechanism based on Distributed Hash Table(DHT) is presented in this paper.It can fully support IPv4 and IPv6 inter-operation.DHTLayer employs a DHT overlay to maintain the routing information between IPv4 and IPv6.It decouples path selection from packet delivery.In DHTLayer,the Looking-Up Route Path is responsible for selecting paths,and then the Delivering Process takes charge of delivering IP packets along the path selected above.Simulation results show that it is very effective and efficient.展开更多
A novel proton exchange membrane(PEM) was designed and prepared from a polymer containing calix[4]arene as the functional unit to transport proton.The proton-conductivity of this membrane is about the same order of ma...A novel proton exchange membrane(PEM) was designed and prepared from a polymer containing calix[4]arene as the functional unit to transport proton.The proton-conductivity of this membrane is about the same order of magnitude as that of Nation~■ 112 membrane.It is of interest to note that very different from most of the currently known PEMs,this membrane can transport proton without the help of water or other solvents.It is deduced that the protons are transported via an ion tunneling model.This opens up a n...展开更多
BACKGROUND ： To summarize the metabolic pathway of 1-methyl-4-phenyl-1,2,3,6-tetradropyridine （MPTP） and its mechanism in inducing Parkinson disease. DATA SOURCES： A computer-based online search of Medline databas...BACKGROUND ： To summarize the metabolic pathway of 1-methyl-4-phenyl-1,2,3,6-tetradropyridine （MPTP） and its mechanism in inducing Parkinson disease. DATA SOURCES： A computer-based online search of Medline database was undertaken to identify articles about the metabolic pathway of MPTP and its mechanism in inducing Parkinson disease published in English between January 1996 and August 2004, the keywords were ＂MPTP, Parkinson disease＂. Meanwhile, Chinese relevant articles published between January 2000 and August 2004 were searched in Wanfang database with the keywords of ＂MPTP, Parkinson disease＂. STUDY SELECTION： More than 300 relevant literatures were retrieved, and the full-texts were further searched, those about the establishment of animal models, molecular mechanism of MPTP neurotoxicity and the metabolism were selected, and the obviously repetitive ones, case report and reviews were excluded, finally 18 of them were selected for summarization. DATA EXTRACTION： The 18 literatures were categorized according to MPTP induced animal models of Parkinson disease, mechanism of MPTP in inducing apoptosis in models of Parkinson disease, role of dopamine in the neurotoxic mechanism of MPTP, the role of reactive oxygen species and nitric oxide in the neurotoxicity of MPTP. DATA SYNTHESIS： Animal models of Parkinson disease induced by MPTP can not only produce the clinical characters of Parkinson disease, also duplicate the main biochemical and pathological changes of Parkinson disease. The metabolic pathway of MPTP and its mechanism in inducing Parkinson disease included producing free oxygen and nitric oxide, damaging mitochondrial respiratory chain, and inducing apoptosis, etc. which could all lead to the degeneration and loss of dopaminergic neurons. CONCLUSION ： Although some aspects of the models of Parkinson disease are different from that in human beings, we can still know the neurodegeneration of Parkinson disease through studying the molecular mechanism of MPTP.展开更多
Most current biped robots are equipped with two feet arranged in the right and left which inspired by the human body system. Different from the existing configurations, a novel biped robot with inner and outer feet ba...Most current biped robots are equipped with two feet arranged in the right and left which inspired by the human body system. Different from the existing configurations, a novel biped robot with inner and outer feet based on a spatial six-bar 4R2C（R and C denote revolute and cylindric joints, respectively） mechanism is proposed. It can move along a line or a curve by three walking modes that are dwell adjustment mode, limit position adjustment mode and any position adjustment mode. Kinematic, gait planning and stability analyses are performed respectively, and a prototype is developed. Lastly, a potential application is considered and two manipulating modes（sphere and cylinder manipulating modes） are carried out. This interesting mechanism feathering its single dosed-chain structure and unique work performance is expected to motivate the configuration creation of biped robots.展开更多
We investigate theγ-ray and X-ray properties of the flat spectrum radio quasar（FSRQ）4C 50.11 at redshift z=1.517.The Fermi-LAT data indicate that this source was in an active state since July 2013.During this activ...We investigate theγ-ray and X-ray properties of the flat spectrum radio quasar（FSRQ）4C 50.11 at redshift z=1.517.The Fermi-LAT data indicate that this source was in an active state since July 2013.During this active period,the source’s emission appeared harder inγ-rays,with the flux having increased by more than a factor of three.We analyze two distinct flares seen in the active state and find that the variability is as short as several hours.The Swift-XRT data show that the source was variable at X-ray energies,but no evidence is found for flux or spectral changes related to theγ-ray activity.The broad-band X-ray spectrum obtained with Swift-XRT and Nu STAR is described well by a broken power law model,with an extremely flat spectrum（Γ_1~0.1）below the break energy,E_（break）~2.1 keV,and Γ_2~1.5 above the break energy.The spectral flattening below^3 keV is likely due to the low energy cut-off in the energy distribution of the photon-emitting electron population.We fit the broad-band spectral energy distribution of the source during both the active and quiescent states.The X-ray andγ-ray emission from the jet is mainly due to the inverse-Compton scattering process,with seed photons provided from the broad line region,and the jet is estimated to be larger than the accretion power if the jet is mainly composed of electron-proton pairs.展开更多
In this study,a reduced-order crystal plasticity finite element(CPFE)model was developed to study the effects of the microstructural morphology and crystallographic texture on the mechanical anisotropy of selective la...In this study,a reduced-order crystal plasticity finite element(CPFE)model was developed to study the effects of the microstructural morphology and crystallographic texture on the mechanical anisotropy of selective laser melted(SLMed)Ti-6Al-4V.First,both hierarchical and equiaxed microstructures in columnar prior grains were modeled to examine the influence of the microstructural morphology on mechanical anisotropy.Second,the effects of crystallographic anisotropy and textural variability on mechanical anisotropy were investigated at the granular and representative volume element(RVE)scales,respectively.The results show that hierarchical and equiaxed CPFE models with the same crystallographic texture exhibit the same mechanical anisotropy.At the granular scale,the significance of crystallographic anisotropy varies with different crystal orientations.This indicates that the present SLMed Ti-6Al-4V sample with weak mechanical anisotropy resulted from the synthetic effect of crystallographic anisotropies at the granular scale.Therefore,combinations of various crystallographic textures were applied to the reduced-order CPFE model to design SLMed Ti-6Al-4V with different mechanical anisotropies.Thus,the crystallographic texture is considered the main controlling variable for the mechanical anisotropy of SLMed Ti-6Al-4V in this study.展开更多
Objective To investigate the inhibitory effect of Tripterygium wilfordii polycoride（TWP） towards the pro-inflammatory factors（TNF-α and IL-1β） on the inflammatory reaction in macrophages induced by LPS and its r...Objective To investigate the inhibitory effect of Tripterygium wilfordii polycoride（TWP） towards the pro-inflammatory factors（TNF-α and IL-1β） on the inflammatory reaction in macrophages induced by LPS and its regulatory effect and influence on the inflammation via TLR4/NF-k B. Methods The MTT method was adopted to test the effect of drugs, TWP, dexamethasone（DXM） and azathioprine（AZA） on cell growth and to select the appropriate concentration. LPS was used to induce the inflammatory reaction in RAW264.7 cell line of mice. Elisa kit was adopted to test the levels of TNF-α and IL-1β. Western blotting was adopted to test the protein expression of TNF-α and IL-1β. RT-PCR was adopted to test the expression of TLR4 and NF-κB. Results The inhibiting effect of TWP on the release of TNF-α and IL-1β in a dose dependent manner. The inhibitory effect of three different TWP dose groups is weaker than that in DXM group. However, TWP in high dose is better than AZA on TNF-α and is as strong as AZA on IL-1β. The dose dependent manner also exits in the effect on the expression of TLR4 and NF-κB, the effect is not weaker, but even stronger than that of DXM and AZA. Conclusion The research shows that down regulation of TLR4 and NF-k B p65 may be one of the mechanisms about the TWP inhibitory effect on TNF-α and IL-1β.展开更多
The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were an...The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were analyzed with advanced tools. The results showed that the CN-U has a porous structure, a high specific surface area and a wide band gap in comparison with CN-T. The in situ FT-IR technique was used to monitor the adsorption and reaction process of visible photocatalytic NO oxidation on g-C_3N_4. The corresponding reaction mechanism was proposed based on the results of reaction intermediate observation and electron paramagnetic resonance(EPR) radical scavenging. It was revealed that(1) the presence of defective sites favored the adsorption of gas molecules and electronically compensated it leading to promoted formation of the final products;(2) the high separation efficiency of photogenerated electron-hole pairs enhanced the production of radicals during the photocatalytic reaction;(3) the hydroxyl radicals(-OH) are not selective for the decomposition of pollutants, which are favorable to the complete oxidation of the reaction intermediates. The above three aspects are the main reasons for the CN-U possessing the efficient visible light photocatalytic activity. The present work could provide new insights and methods for understanding the mechanism of photocatalysis.展开更多
基金supported by the National Natural Science Foundation of Guangxi Province(2024GXNSFBA010033)the Special Fund for Science and Technology Development of Guangxi(Grant No.AD25069078).
文摘Ammonium-ion hybrid supercapacitors(A-HSCs)have emerged as promising candidates for next-generation energy storage owing to their inherent safety and environmental sustainability.Hexagonal tungsten oxide(h-WO_(3)),with its well-defined tunnel structure,holds great promise as a negative electrode material for NH^(4+)storage.However,its practical application is hindered by structural instability and poor intrinsic electrical conductivity.To address these challenges,a dual-regulation strategy is proposed,integrating molybdenum(Mo)doping and NH^(4+)pre-intercalation to concurrently optimize the tunnel structure and electronic environment of h-WO_(3)(Mo-NWO).Comprehensive experimental and theoretical analyses reveal that Mo doping narrows the bandgap of WO_(3)and reduces the diffusion energy barrier,thereby accelerating NH^(4+)adsorption and diffusion.Simultaneously,NH^(4+)pre-intercalation stabilizes the tunnel framework via hydrogen bonding,ensuring structural reversibility.As expected,the Mo-NWO/AC electrode achieves a high areal capacitance of 13.6 F cm^(−2)at 5 mA cm^(−2)and retains 80.14%of its capacitance after 5000 cycles,demonstrating exceptional rate capability and cycling stability.Moreover,the assembled Mn_(3)O_(4)//Mo-NWO/AC device delivers a high energy density of 3.41 mWh cm^(−2)and outstanding long-term stability(85.75%retention after 12,000 cycles).This work provides a viable strategy for designing high-performance NH^(4+)storage materials and advances the development of sustainable energy storage systems.
基金the support by National Natural Science Foundation of China(No.52375314,12472147,U23A20412)the National Key R&D Program of China(No.2024YFB4710205,2024YFD2200700)Heilongjiang Provincial Natural Science Foundation of China(No.2022ZX02C25).
文摘Four-dimensional(4D)printing technology is a revolutionary development that produces structures that can adapt in response to external stimuli.However,the responsiveness and printability of smart materials with shape memory properties,which are necessary for 4D printing,remain limited.Biomass materials derived from nature have offered an effective solution due to their various excellent and unique properties.Biomass materials have been abundant in resources and low in carbon content,contributing to the then-current global green energy-saving goals,including carbon peaking and carbon neutrality.This review focused on different sources of biomass materials used in 4D printing,including plant-based,animal-based,and microbial-based biomass materials.It systematically outlined the responsive deformation mechanisms of printed objects that contained biomass materials and delved into the roles and unique advantages of biomass materials in those printed objects.Leveraging these advantages,the review discussed the potential applications of biomass materials in biomedicine,food printing,and other fields to support ongoing development and application efforts.Additionally,it emphasized the crucial role played by bio-fabrication technologies utilizing biomass materials in the integration of biomass materials with 4D printing.Finally,this paper discussed the then-current challenges and potential future directions of biomass materials in 4D printing,aiming to promote the effective development of biomass materials in 4D printing applications.
基金support from the National Natural Science Foundation of China (No. 51209177)the Basic Research Fund of Northwest Agriculture and Forestry University (No.Z109021203)
文摘A novel process combining oxidation-bonding and sintering was developed to fabricate porous Si3N4 ceramic with high porosity. After sintering at 1800℃, the SiO2 in porous Si3N4 ceramic transforms into Si2N2O because of the reaction of SiO2 and Si3N4 . Due to the reaction of SiO2 and carbon, the porosity of porous Si3N4 ceramic increases obviously from 40.2% to 76.8% with the weight decreasing by 35.6%. As the porosity increases, the dielectric constant and loss of the porous Si3N4 ceramic decrease obviously from 3.08 to 1.61 and from 3.70×10（-3） to 0.74×10（-3） , but due to the production of Si2N2O whose mechanical properties are much higher than SiO2 and the increase of the bonding strength among Si3N4 particles, the flexural strength and the fracture toughness of the porous Si3N4 ceramic decrease from 55 to 39 MPa and from 0.7 to 0.5 MPa·m（1/2） , respectively, but its Vickers hardness increases from 1.2 to 1.3 GPa.
文摘Hoppressed Si3N4/SiC platelet composites had been investigated with respect to their microstructure and mechanical properties. The results indicate that Vickers hardness, elastic modulus and fracture toughness of the composites were increased by the addition of SiC platelet until the content up to 20 vol pct. A slight decrease in flexural Strength was measured at room temperature with increasing SiC platelet content. The high temperature flexural strength tests at 1150, 1250, and 1350℃ were conducted. It was found that the flexural strength at elevated temperature was degraded with the rising temperature, and the downward trend of flexural strength for the composite containing 10 vol. pct SiC platelet was less. The results indicate that SiC platelet had a positive influence on the high temperature strength. Effects of SiC platelet reinforcement were presented
基金Semnan University Research Council,Semnan,Iran for financial supports to this work
文摘Electrochemical oxidation of 4-methyl catechol（1a） is investigated in the presence of 1,3-indandione（3）as nucleophile in phosphate buffer solution（0.2 mol/L,pH 6） mixed with ethanol as organic green solvent（50/50） using cyclic voltammetry and controlled-potential coulometry.The results indicated thatquinones derived from electro-oxidation of 1a,participated in a 1,4-Michael addition reaction with1,3-indandione（3） under ECCE mechanism.In this direction,a new bis-quinone was synthesized in high yield and good purity using a facile and convenient electrochemical pathway by carbon anode electrodes in an undivided cell.
基金supported by the National Natural Science Foundation of China(No.51204111)the Natural Science Foundation of Liaoning Province(No.2014024008)the Aeronautical Science Foundation of China(No.2014ZE54021)
文摘As a new solid state welding,pinless friction stir welding（PFSW） can be used to join thin-wall structures.In this study,four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 alloy.The results show that the small-obliquity tool is detrimental to the transfer of plasticized materials,resulting in the formation of kissing bond defect.For the through-groove tool or the large-curvature tool,bigger flashes form on the joint surface and alclad layer is observed in the nugget zone（NZ）,deteriorating mechanical properties.Compared with the above-mentioned three tools,using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction,but also prevent alclad from flowing into NZ,which has potential to weld thin alclad aluminum alloys.Meanwhile,the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%,up to 85.1% and 64% of BM.
基金Funded by the National Torch Plan of China(No.2005EB031110)the Key Scientific and Technical Innovation Project of Xi’an University of Architecture and Technology(No.zx 0402)
文摘Hydration mechanism of tabular alumina carbon composites reinforced by Al4C3 in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 ℃ to 85 ℃. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 ℃-84 ℃ in H2O（g）. The hydration was controlled by diffusion from 24.7 ℃ to 33 ℃. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al4C3 crystals at high temperature. Besides, the matrix changes into the Al4C3 with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al4C3 in situ reaction was immersed in the wax at suitable temperature or storing them below 33 ℃ in a dry place or storing them with paraffin-coating.
基金Funded by the National Natural Science Foundation of China(No.51004074)
文摘Phspho-olivine Li Fe PO4 was synthesized from the relatively insoluble lithium source Li2CO3, proper iron and phosphorus sources（n（Li）：n（Fe）：n（P）=1：1：1） by a novel hydrothermal method. Afterwards, the optimal sample was mixed with glucose and two-step calcinated（500 ℃ and 750 ℃） under high-purity N2 to obtain the Li Fe PO4/C composite. The resultant samples were characterized by X-ray diffraction（XRD）, atomic absorption spectrometry（AAS）, scanning electron microscops（SEM）, transmission electron microscopy（TEM）, energy dispersive spectrometry（EDS）, elementary analysis（EA） and electrochemical tests. The results show that the optimal reaction condition is to set the reactant concentration at 0.5 mol·L^-1, the reaction temperature at 180 ℃ for 16 h duration. During the reaction course, an intermediate product NH4 Fe PO4·H2O was first synthesized, and then it reacted with Li＋ to form Li Fe PO4. The optimized Li Fe PO4 sample with an average particle size（300 to 500 nm） and regular morphology exhibits a relatively high discharge capacity of 84.95 m Ah· g^-1 at the first charge-discharge cycle（0.1C, 1C=170 m A·g^-1）. Moreover, the prepared Li Fe PO4/C composite shows a high discharge capacity of 154.3 m Ah·g^-1 at 0.1C and 128.2 m Ah·g^-1 even at 5C. Besides it has good reversibility and stability in CV test.
基金Project(2007CB613603)supported by the National Basic Research Program of ChinaProject(51204037)supported by the National Natural Science Foundation of China
文摘Based on the existing form of Zn2 Si O4 in willemite, the chemical precipitation method was used to synthesize Zn2 Si O4.Through the orthogonal experimentation, the reaction conditions of melten Na OH decomposing Zn2 Si O4 were optimized, and the optimal experimental conditions include reaction temperature of 400 °C, reaction time of 4 h, and alkaline-to-ore molar ratio of 20:1.Based on the optimized experiment, on-line detection for the alkali leaching was made by using Raman spectroscopy; XRD was used to analyze the structure of water leaching residue, to explore the reaction mechanism of Na OH decomposing Zn2 Si O4. The results show that during the reaction process, the Si — O bond in Si O4 is destroyed, and the Na OH inserts itself into the silicate lattice,producing an immediate Na2 Zn Si O4 product. After the alkali leaching process, Zn2+ can be separated from the Si O4 array, which can be released out of the silicate in the form of ZnO.
基金supported in part by National High Technical Research and Development Program of China(863 Program)under Grant No.2009AA01Z210National Key Basic Research Program of China(973 Program)under Grant No.2009CB320504+1 种基金Guangdong Ministry of Education Industry-Academia-Research project under Grant No.2009B090300315supported by the special program for joint construction project of Beijing
文摘IPv4 and IPv6 will coexist for many years during the transition period from the traditional IPv4-based Internet to an IPv6-based Internet.DHTLayer,a novel IPv4/IPv6 transition mechanism based on Distributed Hash Table(DHT) is presented in this paper.It can fully support IPv4 and IPv6 inter-operation.DHTLayer employs a DHT overlay to maintain the routing information between IPv4 and IPv6.It decouples path selection from packet delivery.In DHTLayer,the Looking-Up Route Path is responsible for selecting paths,and then the Delivering Process takes charge of delivering IP packets along the path selected above.Simulation results show that it is very effective and efficient.
文摘A novel proton exchange membrane(PEM) was designed and prepared from a polymer containing calix[4]arene as the functional unit to transport proton.The proton-conductivity of this membrane is about the same order of magnitude as that of Nation~■ 112 membrane.It is of interest to note that very different from most of the currently known PEMs,this membrane can transport proton without the help of water or other solvents.It is deduced that the protons are transported via an ion tunneling model.This opens up a n...
基金the National Nat-ural Science Foundation of Chi-na, No. 30270433 a grant fromTechnological DevelopmentPlanning of Beijing Committeeof Education, No.KM200310025092*
文摘BACKGROUND ： To summarize the metabolic pathway of 1-methyl-4-phenyl-1,2,3,6-tetradropyridine （MPTP） and its mechanism in inducing Parkinson disease. DATA SOURCES： A computer-based online search of Medline database was undertaken to identify articles about the metabolic pathway of MPTP and its mechanism in inducing Parkinson disease published in English between January 1996 and August 2004, the keywords were ＂MPTP, Parkinson disease＂. Meanwhile, Chinese relevant articles published between January 2000 and August 2004 were searched in Wanfang database with the keywords of ＂MPTP, Parkinson disease＂. STUDY SELECTION： More than 300 relevant literatures were retrieved, and the full-texts were further searched, those about the establishment of animal models, molecular mechanism of MPTP neurotoxicity and the metabolism were selected, and the obviously repetitive ones, case report and reviews were excluded, finally 18 of them were selected for summarization. DATA EXTRACTION： The 18 literatures were categorized according to MPTP induced animal models of Parkinson disease, mechanism of MPTP in inducing apoptosis in models of Parkinson disease, role of dopamine in the neurotoxic mechanism of MPTP, the role of reactive oxygen species and nitric oxide in the neurotoxicity of MPTP. DATA SYNTHESIS： Animal models of Parkinson disease induced by MPTP can not only produce the clinical characters of Parkinson disease, also duplicate the main biochemical and pathological changes of Parkinson disease. The metabolic pathway of MPTP and its mechanism in inducing Parkinson disease included producing free oxygen and nitric oxide, damaging mitochondrial respiratory chain, and inducing apoptosis, etc. which could all lead to the degeneration and loss of dopaminergic neurons. CONCLUSION ： Although some aspects of the models of Parkinson disease are different from that in human beings, we can still know the neurodegeneration of Parkinson disease through studying the molecular mechanism of MPTP.
基金Supported by National Natural Science Foundation of China(Grant Nos.51175030,51505022)Foundation of Talents of Beijing Jiaotong University,China(Grant No.2015RC047)+1 种基金China Postdoctoral Science Foundation(Grant No.2013M531168)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20130009110030)
文摘Most current biped robots are equipped with two feet arranged in the right and left which inspired by the human body system. Different from the existing configurations, a novel biped robot with inner and outer feet based on a spatial six-bar 4R2C（R and C denote revolute and cylindric joints, respectively） mechanism is proposed. It can move along a line or a curve by three walking modes that are dwell adjustment mode, limit position adjustment mode and any position adjustment mode. Kinematic, gait planning and stability analyses are performed respectively, and a prototype is developed. Lastly, a potential application is considered and two manipulating modes（sphere and cylinder manipulating modes） are carried out. This interesting mechanism feathering its single dosed-chain structure and unique work performance is expected to motivate the configuration creation of biped robots.
基金supported by the National Program on Key Research and Development Project(Grant No.2016YFA0400804)the National Natural Science Foundation of China for Youth(11603059)+3 种基金the National Natural Science Foundation of China(11373055,11633007,11233006 and U1431123)the CAS grant(QYZDJ-SSW-SYS023)financial support from Chinese Academy of Sciences through the President’s International Fellowship Initiative(CAS PIFI,Grant No.2015PM059)support by the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘We investigate theγ-ray and X-ray properties of the flat spectrum radio quasar（FSRQ）4C 50.11 at redshift z=1.517.The Fermi-LAT data indicate that this source was in an active state since July 2013.During this active period,the source’s emission appeared harder inγ-rays,with the flux having increased by more than a factor of three.We analyze two distinct flares seen in the active state and find that the variability is as short as several hours.The Swift-XRT data show that the source was variable at X-ray energies,but no evidence is found for flux or spectral changes related to theγ-ray activity.The broad-band X-ray spectrum obtained with Swift-XRT and Nu STAR is described well by a broken power law model,with an extremely flat spectrum（Γ_1~0.1）below the break energy,E_（break）~2.1 keV,and Γ_2~1.5 above the break energy.The spectral flattening below^3 keV is likely due to the low energy cut-off in the energy distribution of the photon-emitting electron population.We fit the broad-band spectral energy distribution of the source during both the active and quiescent states.The X-ray andγ-ray emission from the jet is mainly due to the inverse-Compton scattering process,with seed photons provided from the broad line region,and the jet is estimated to be larger than the accretion power if the jet is mainly composed of electron-proton pairs.
基金supported by National Natural Science Founda-tion of China(Grant Nos.51971113,51905279,11972202)Zhe-jiang Provincial Natural Science Foundation of China(Grant No.LY21A020002).
文摘In this study,a reduced-order crystal plasticity finite element(CPFE)model was developed to study the effects of the microstructural morphology and crystallographic texture on the mechanical anisotropy of selective laser melted(SLMed)Ti-6Al-4V.First,both hierarchical and equiaxed microstructures in columnar prior grains were modeled to examine the influence of the microstructural morphology on mechanical anisotropy.Second,the effects of crystallographic anisotropy and textural variability on mechanical anisotropy were investigated at the granular and representative volume element(RVE)scales,respectively.The results show that hierarchical and equiaxed CPFE models with the same crystallographic texture exhibit the same mechanical anisotropy.At the granular scale,the significance of crystallographic anisotropy varies with different crystal orientations.This indicates that the present SLMed Ti-6Al-4V sample with weak mechanical anisotropy resulted from the synthetic effect of crystallographic anisotropies at the granular scale.Therefore,combinations of various crystallographic textures were applied to the reduced-order CPFE model to design SLMed Ti-6Al-4V with different mechanical anisotropies.Thus,the crystallographic texture is considered the main controlling variable for the mechanical anisotropy of SLMed Ti-6Al-4V in this study.
基金National Natural Science Foundation of China Granted Project(81273903)
文摘Objective To investigate the inhibitory effect of Tripterygium wilfordii polycoride（TWP） towards the pro-inflammatory factors（TNF-α and IL-1β） on the inflammatory reaction in macrophages induced by LPS and its regulatory effect and influence on the inflammation via TLR4/NF-k B. Methods The MTT method was adopted to test the effect of drugs, TWP, dexamethasone（DXM） and azathioprine（AZA） on cell growth and to select the appropriate concentration. LPS was used to induce the inflammatory reaction in RAW264.7 cell line of mice. Elisa kit was adopted to test the levels of TNF-α and IL-1β. Western blotting was adopted to test the protein expression of TNF-α and IL-1β. RT-PCR was adopted to test the expression of TLR4 and NF-κB. Results The inhibiting effect of TWP on the release of TNF-α and IL-1β in a dose dependent manner. The inhibitory effect of three different TWP dose groups is weaker than that in DXM group. However, TWP in high dose is better than AZA on TNF-α and is as strong as AZA on IL-1β. The dose dependent manner also exits in the effect on the expression of TLR4 and NF-κB, the effect is not weaker, but even stronger than that of DXM and AZA. Conclusion The research shows that down regulation of TLR4 and NF-k B p65 may be one of the mechanisms about the TWP inhibitory effect on TNF-α and IL-1β.
基金supported by the National Key Research and Development Plan (2016YFC02047)the National Natural Science Foundation of China (51478070, 21777011 and 21501016)+1 种基金the Innovative Research Team of Chongqing (CXTDG201602014)the Natural Science Foundation of Chongqing (cstc2017jcyj BX0052, cstc2016jcyj A0481)
文摘The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were analyzed with advanced tools. The results showed that the CN-U has a porous structure, a high specific surface area and a wide band gap in comparison with CN-T. The in situ FT-IR technique was used to monitor the adsorption and reaction process of visible photocatalytic NO oxidation on g-C_3N_4. The corresponding reaction mechanism was proposed based on the results of reaction intermediate observation and electron paramagnetic resonance(EPR) radical scavenging. It was revealed that(1) the presence of defective sites favored the adsorption of gas molecules and electronically compensated it leading to promoted formation of the final products;(2) the high separation efficiency of photogenerated electron-hole pairs enhanced the production of radicals during the photocatalytic reaction;(3) the hydroxyl radicals(-OH) are not selective for the decomposition of pollutants, which are favorable to the complete oxidation of the reaction intermediates. The above three aspects are the main reasons for the CN-U possessing the efficient visible light photocatalytic activity. The present work could provide new insights and methods for understanding the mechanism of photocatalysis.
