The physical metallurgy underlying the development of cast microstructures in abrasion resistant high chromium cast irons, and their structural modification by thermal treatments is relatively complex. Structural char...The physical metallurgy underlying the development of cast microstructures in abrasion resistant high chromium cast irons, and their structural modification by thermal treatments is relatively complex. Structural characterisation via electron microscopy therefore has a key role to play in furthering our understanding of the phase transformations that control the microstructures and hence the service performances of these irons as wear parts. This paper shows how both scanning and especially transmission electron microscopy can provide valuable information on the nature of eutectic and secondary carbides and on the matrix structures in these irons. Particular attention is given to current characterisation research on conventionally cast 30%Cr irons that are used for applications involving corrosive wear e.g. slurry pumps and on a semi-solid cast 27%Cr iron that has a potential for applications in industry.展开更多
Phase transformation is one of the essential topics in the studies on high entropy alloys(HEAs).However,characterization of the nucleation behavior in the phase transformation for HEAs is still challenging through exp...Phase transformation is one of the essential topics in the studies on high entropy alloys(HEAs).However,characterization of the nucleation behavior in the phase transformation for HEAs is still challenging through experimental methods.In the present work,HfNbTaTiZr HEA was chosen as the representative material,and molecular dynamics/Monte Carlo(MD/MC)simulations were performed to investigate the nucleation behavior in temperature-induced BCC-to-HCP transformation for this HEA system.The results indicate that Nb–Ta,Ti–Zr,Hf–Zr and Hf–Ti atom pairs are preferred in the BCC solid solution of HfNbTaTiZr HEA and Hf–Ti–Zr-rich atom cluster with chemical short range order acts as the nucleation site for HCP phase.The nucleation process follows the non-classical two-step nucleation model:BCC-like structure with severe lattice distortion forms first and then HCP structure nucleates from the BCC-like structure.Moreover,at low temperature,the BCC-to-HCP nucleation hardly occurs,and the BCC solid solution is stabilized.The present work provides more atomic details of the nucleation behavior in temperature-induced BCC-to-HCP phase transformation for HEA,and can help in deep understanding of the phase stability for HEAs.展开更多
Fast synthesis and screening of materials are vital to the advance of materials science and are an essential component of the Materials Genome Initiative. Here we use copper-oxide superconductors as an example to demo...Fast synthesis and screening of materials are vital to the advance of materials science and are an essential component of the Materials Genome Initiative. Here we use copper-oxide superconductors as an example to demonstrate the power of integrating combinatorial molecular beam epitaxy synthesis with high-throughput electric transport measurements. Leveraging this method, we have generated a phase diagram with more than 800 compositions in order to unravel the doping dependence of interface superconductivity. In another application of the same method, we have studied the superconductorto-insulator quantum phase transition with unprecedented accuracy in tuning the chemical doping level.展开更多
Coal is one of the important energy sources, but it causes serious environmental problems such as air pollution, acid rain and greenhouse effects. Sulfur in coal is one of the responsibilities of these negative effect...Coal is one of the important energy sources, but it causes serious environmental problems such as air pollution, acid rain and greenhouse effects. Sulfur in coal is one of the responsibilities of these negative effects. Coal includes two types of sulfur： organic and inorganic. While inorganic sulfur can be completely removed with physical desulfurization methods, organic sulfur can be removed only by chemical desulfurization methods. But chemical methods are not only expensive but also difficult processes. Firstly in desulfurization, types of the sulfur content in coal should be well characterized. High sulfur Gediz-Turkey coal has been chosen to this study. This coal basin is located in the centre of the Turkey. In this study, characterization and desulfurization possibilities of high sulfur Gediz coal were investigated. For this purpose, several physical and chemical characterization methods such as proximate and ultimate coal analysis （ash, calorific value, volatile matter, moisture and sulfur analysis）, mineralogical and petrographic analysis, fourier transform infrared spectroscopy, scanning electron microscope were used. Results of these analysis are shown that Gediz coals include 3.15% pyritic sulfur and 2.89% organic sulfur. Removing pyritic sulfur from Gediz-Turkey coal with physical methods such as gravity and sink-float separation is not possible because pyrite particle has 1-2 micron liberation size in coal.展开更多
Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other ...Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other is a novel dinuclear V(V,V)complex with an oxo bridge.The conversion between the two complexes had been discussed.展开更多
The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial thr...The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial threat to public health because of a high mortality rate. In this study, we sequenced whole genomes of eight H5N1 avian influenza viruses isolated from domestic poultry in eastern China and compared them with those of typical influenza virus strains. Phylogenetic analyses showed that all eight genomes belonged to clade 2.3.2.1 and clade 7.2, the two main circulating clades in China. Viruses that clustered in clade 2.3.2.1 shared a high degree of homology with H5N1 isolates located in eastern Asian. Isolates that clustered in clade 7.2 were found to circulate throughout China, with an east-to-west density gradient. Pathogenicity studies in mice showed that these isolates replicate in the lungs, and clade 2.3.2.1 viruses exhibit a notably higher degree of virulence compared to clade 7.2 viruses. Our results contribute to the elucidation of the biological characterization and pathogenicity of HPAI H5N1 viruses.展开更多
The dissimilar material resistance spot welding of galvanized high strength steel and aluminum alloy had been conducted. The welded joint exhibited a thin reaction layer composed of Fe2Al5 and Fe4Al13 phases at steel/...The dissimilar material resistance spot welding of galvanized high strength steel and aluminum alloy had been conducted. The welded joint exhibited a thin reaction layer composed of Fe2Al5 and Fe4Al13 phases at steel/aluminum interface. The welded joint presented a tensile shear load of 3.3 kN with an aluminum alloy nugget diameter of 5.7 mm. The interfacial failure mode was observed for the tensile shear specimen and fracture occurred at reaction layer and aluminum alloy fusion zone beside the interface. The reaction layer with compounds was the main reason for reduction of the welded joint mechanical property.展开更多
We report on the single crystal growth and superconducting properties of PbTaSe2 with the non-centrosymmetric crystal structure. By using the chemicM vapor transport technique, centimeter-size single crystals are succ...We report on the single crystal growth and superconducting properties of PbTaSe2 with the non-centrosymmetric crystal structure. By using the chemicM vapor transport technique, centimeter-size single crystals are success- fully obtained. The measurement of temperature dependence of electricaJ resistivity p（T） in both normal and superconducting states indicates a quasi-two-dimensional electronic state in contrast to that of polycrystalline samples. Specific heat C（T） measurement reveals a bulk superconductivity with Tc ≈ 3.75K and a specific heat jump ratio of 1.42. All these results are in agreement with a moderately electron-phonon coupled, type-g Bardeen-Cooper-Schrieffer superconductor.展开更多
Grain boundary engineering（GBE） is a practice of improving resistance to grain boundary failure of the material through increasing the proportion of low Σ coincidence site lattice（CSL） grain boundaries（special g...Grain boundary engineering（GBE） is a practice of improving resistance to grain boundary failure of the material through increasing the proportion of low Σ coincidence site lattice（CSL） grain boundaries（special grain boundaries） in the grain boundary character distribution（GBCD）. The GBCD in a cold rolled and annealed Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel was analyzed by electron back scatter difraction（EBSD）. The results show that the optimization process of GBE in the conventional austenitic stainless steel cannot be well applied to this high-nitrogen austenitic stainless steel. The percentage of low ΣCSL grain boundaries could increase from 47.3% for the solid solution treated high-nitrogen austenitic stainless steel specimen to 82.0% for the specimen after 5% cold rolling reduction and then annealing at 1423 K for 10 min.These special boundaries of high proportion efectively interrupt the connectivity of conventional high angle grain boundary network and thus achieve the GBCD optimization for the high-nitrogen austenitic stainless steel.展开更多
The {111} fiND plane texture, grain boundary characterization and grain boundary segregation of phos- phorus are investigated for the phosphorus added high strength interstitial free （IF） steel annealed at 810℃ for...The {111} fiND plane texture, grain boundary characterization and grain boundary segregation of phos- phorus are investigated for the phosphorus added high strength interstitial free （IF） steel annealed at 810℃ for 60 s to 180 s. The results show that the maximum volume fraction of {111} fiND plane texture is about 85% and the grain boundary Segregation peak of phosphorus is about 14 at. % for the steel annealed at 810℃ for 120 s. The ∑3 and other low-∑CSL （coincident site lattice） boundaries are lowest for the steel annealed for 120 s. Segregation of phosphorus is also found at low angle grain boundaries.展开更多
Additive manufacturing (AM) technology such as selective laser melting (SLM) often produces a high refection phenomenon that makes defect detection and information extraction challenging. Meanwhile, it is essential to...Additive manufacturing (AM) technology such as selective laser melting (SLM) often produces a high refection phenomenon that makes defect detection and information extraction challenging. Meanwhile, it is essential to establish a characterization method for defect analysis to provide sufcient information for process diagnosis and optimization. However, there is still a lack of universal standards for the characterization of defects in SLM parts. In this study, a polarization-based imaging system was proposed, and a set of characterization parameters for SLM defects was established. The contrast, defect contour information, and high refection suppression efect of the SLM part defects were analyzed. Comparative analysis was conducted on defect characterization parameters, including geometric and texture parameters. The experimental results demonstrated the efects of the polarization imaging system and verifed the feasibility of the defect feature extraction and characterization method. The research work provides an efective solution for defect detection and helps to establish a universal standard for defect characterization in additive manufacturing.展开更多
AIM： To study the relation between acoustic parameters and histological structure of biological tissue and to provide the basis for high-resolution image of biological tissues and quantitative ultrasonic diagnosis of...AIM： To study the relation between acoustic parameters and histological structure of biological tissue and to provide the basis for high-resolution image of biological tissues and quantitative ultrasonic diagnosis of liver disease. METHODS： Ultrasonic imaging and tissue characterization of four normal porcine liver and five cirrhotic liver tissue samples were performed using a high frequency imaging system. RESULTS： The acoustic parameters of cirrhotic liver tissue were larger than those of normal liver tissue. The sound velocity was 1577 m/s in normal liver tissue and 1631 m/s in cirrhotic liver tissue. At 35 MHz, the attenuation coefficient was 3.0 dB/mm in normal liver tissue and 4.1 dB/mm in cirrhotic liver tissue. The backscatter coefficient was 0.00431 dB/Srmm in cirrhotic liver tissue and 0.00303 dB/Srmm in normal liver tissue. The backscatter coefficient increased with the frequency. The high frequency images coincided with their histological features. CONCLUSION： The acoustic parameters, especially the sound backscatter coefficient, are sensitive to the changes of liver tissues and can be used to differentiate between the normal and pathological liver tissues. High frequency image system is a useful device for highresolution image and tissue characterization.展开更多
Evolution and fractal character of the phase morphology of high impact polystyrene/poly（cis-butadiene） rubber （HIPS/PcBR） blends during melting and mixing were investigated using scanning electron microscopy （SEM...Evolution and fractal character of the phase morphology of high impact polystyrene/poly（cis-butadiene） rubber （HIPS/PcBR） blends during melting and mixing were investigated using scanning electron microscopy （SEM）. The characteristic length L was defined as the size of particles of the dispersed phase in blends. Different fractal dimensions, Df and Din, were introduced to study the distribution width of phase dimensions in the dimensionless region and the uniformity of the spatial distribution of particles, respectively. The results showed that the average characteristic length Lm and Df increase as the volume fraction of the dispersed phase increases, when the volume fraction of the dispersed phase is lower than 50%. In other words, the size of particles increases and their distribution in the dimensionless region becomes more uniform. Meanwhile, the uniformity of the spatial distribution becomes more perfect as the volume fraction increases. At a certain composition, Lm decreases in the initial stage of the mixing and levels off in the late stage. In the initial stage, Df becomes large rapidly with the process of blending, which means that the distribution of L in the dimensionless region becomes more uniform. Meanwhile, the spatial distribution tends to be ideal rapidly in the early stage and fluctuates in a definite range in the late stage of the mixing.展开更多
The present study aimed to examine the mediating effect of strengths use between character strengths and mental health in high school students. Totally 508 China high school students completed questionnaires measuring...The present study aimed to examine the mediating effect of strengths use between character strengths and mental health in high school students. Totally 508 China high school students completed questionnaires measuring character strengths, strengths use and mental health for middle school students＇ inventory. The correlations between character strength, strengths use and mental health were all significantly positive, 0.41 -0.65, P 〈 0.01. Character strengths significantly positively predicted mental health, and standard regression coefficient was 0.65, P 〈 0.01. Strengths use mediated partially the relationship between character strengths and mental health in high school students and the value of mediating effect was 11.3%. Strengths use played a moderated mediating role in the relationship between character strengths and mental health.展开更多
NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with...NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with scanning electron microscopy （SEM）, X-ray diffraction （XRD） and specific surface area （BET）. The characterization result showed that the NaY Zeolite had a particle size of approximately 200 rim, n（SiO2）/n（Al203） ratio of 5.03, crystallinity of 96% and specific surface area of 714 m2/g. The experimental results indicated that the structure of NaY Zeolite was related to the synthesis conditions （such as reactors, crystallization time and so on）. The micromixing efficiency was proven to be the most important factor for synthesis of NaY Zeolite in the high-gravity environment in RPB.展开更多
Herein, the effect of high chloride ion(Cl^-) concentration on the corrosion behavior and passive film breakdown of 13Cr martensitic stainless steel under CO_2 environment was demonstrated. The Cl^- concentration was ...Herein, the effect of high chloride ion(Cl^-) concentration on the corrosion behavior and passive film breakdown of 13Cr martensitic stainless steel under CO_2 environment was demonstrated. The Cl^- concentration was varied from 30 to 150 g/L and cyclic potentiodynamic polarization was conducted to investigate the influence of the Cl^- concentration on the corrosion potential(E_(corr)), passive breakdown potential(E_(pit)), and repassivation potential(E_(rep)). The results of the polarization curves revealed that 13Cr stainless steel is susceptible to pitting under high Cl^- concentration. The passive breakdown potential and repassivation potential decreased with the increase of Cl-concentration. The semiconducting behavior of the passive film was investigated by Mott-Schottky analysis and the point defect model(PDM). It was observed that the iron cation vacancies and oxygen vacancies were continuously generated by autocatalytic reactions and the higher Cl^- concentration resulted in higher vacancies in the passive film. Once the excess vacancies condensed at the metal/film interface, the passive film became locally detached from the metal, which led to the breakdown of the passive film.展开更多
With the advancement of Materials Genome Initiative,there is an urgent need for nondestructive,rapid characterization methods for obtaining electrical transport properties and phonon information of materials.In this a...With the advancement of Materials Genome Initiative,there is an urgent need for nondestructive,rapid characterization methods for obtaining electrical transport properties and phonon information of materials.In this article,we develop a method using the dielectric resonant spectroscopies of materials to derive critical parameters such as conduction electron frequency,quantum relaxation time,and phonon frequency for metals and semiconductors.As a typical example,based on the new approaches,we realized simultaneous extraction of carrier concentration n and electron-phonon relaxation timeτ_(e−p),and establish a new relationship ofτ_(e−p)=C^(∗)⋅T^(−1)⋅n^(−1/3)for n-type doped silicon,where the true electron-phonon coupling constant C^(∗)is proposed for the first time.This innovative methodology offers significant potential for high-throughput screening of materials,expediting the development of next-generation electronic devices.展开更多
The non-stationary behavior, caused by the train rmverrent, is the rmin factor for the variation of high speed railway channel. To measure the tirce-variant effect, the parameter of stationarity interval, in which the...The non-stationary behavior, caused by the train rmverrent, is the rmin factor for the variation of high speed railway channel. To measure the tirce-variant effect, the parameter of stationarity interval, in which the channel keeps constant or has no great change, is adopted based on Zhengzfiou- Xi＇an （Zhengxi） passenger dedicated line measurement with different train speeds. The stationarity interval is calculated through the definition of Local Region of Stationarity （LRS） under three train ve- locities. Furthermore, the time non-stationary characteristic of high speed pared with five standard railway channel is corn- Multiple-Input MultipleOutput （MIMO） channel models, i.e. Spatial Channel Model （SCM）, extended version of SCM （SCME）, Wireless World Initiative New Radio Phase II （WINNERII）, International Mobile Teleconmnications-Advanced （IMT-Advanced） and WiMAX models which contain the high speed moving scenario. The stationarity interval of real channel is 9 ms in 80% of the cases, which is shorter than those of the standard models. Hence the real channel of high speed railway changes more rapidly. The stationarity intervals of standard models are different due to different modeling methods and scenario def- initions. And the compared results are instructive for wireless system design in high speed railway.展开更多
文摘The physical metallurgy underlying the development of cast microstructures in abrasion resistant high chromium cast irons, and their structural modification by thermal treatments is relatively complex. Structural characterisation via electron microscopy therefore has a key role to play in furthering our understanding of the phase transformations that control the microstructures and hence the service performances of these irons as wear parts. This paper shows how both scanning and especially transmission electron microscopy can provide valuable information on the nature of eutectic and secondary carbides and on the matrix structures in these irons. Particular attention is given to current characterisation research on conventionally cast 30%Cr irons that are used for applications involving corrosive wear e.g. slurry pumps and on a semi-solid cast 27%Cr iron that has a potential for applications in industry.
基金funded by the China Postdoctoral Science Foundation(No.2020M672787)the National Natural Science Foundation of China(Nos.51701125,51801128,52001123)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515012278)。
文摘Phase transformation is one of the essential topics in the studies on high entropy alloys(HEAs).However,characterization of the nucleation behavior in the phase transformation for HEAs is still challenging through experimental methods.In the present work,HfNbTaTiZr HEA was chosen as the representative material,and molecular dynamics/Monte Carlo(MD/MC)simulations were performed to investigate the nucleation behavior in temperature-induced BCC-to-HCP transformation for this HEA system.The results indicate that Nb–Ta,Ti–Zr,Hf–Zr and Hf–Ti atom pairs are preferred in the BCC solid solution of HfNbTaTiZr HEA and Hf–Ti–Zr-rich atom cluster with chemical short range order acts as the nucleation site for HCP phase.The nucleation process follows the non-classical two-step nucleation model:BCC-like structure with severe lattice distortion forms first and then HCP structure nucleates from the BCC-like structure.Moreover,at low temperature,the BCC-to-HCP nucleation hardly occurs,and the BCC solid solution is stabilized.The present work provides more atomic details of the nucleation behavior in temperature-induced BCC-to-HCP phase transformation for HEA,and can help in deep understanding of the phase stability for HEAs.
文摘Fast synthesis and screening of materials are vital to the advance of materials science and are an essential component of the Materials Genome Initiative. Here we use copper-oxide superconductors as an example to demonstrate the power of integrating combinatorial molecular beam epitaxy synthesis with high-throughput electric transport measurements. Leveraging this method, we have generated a phase diagram with more than 800 compositions in order to unravel the doping dependence of interface superconductivity. In another application of the same method, we have studied the superconductorto-insulator quantum phase transition with unprecedented accuracy in tuning the chemical doping level.
文摘Coal is one of the important energy sources, but it causes serious environmental problems such as air pollution, acid rain and greenhouse effects. Sulfur in coal is one of the responsibilities of these negative effects. Coal includes two types of sulfur： organic and inorganic. While inorganic sulfur can be completely removed with physical desulfurization methods, organic sulfur can be removed only by chemical desulfurization methods. But chemical methods are not only expensive but also difficult processes. Firstly in desulfurization, types of the sulfur content in coal should be well characterized. High sulfur Gediz-Turkey coal has been chosen to this study. This coal basin is located in the centre of the Turkey. In this study, characterization and desulfurization possibilities of high sulfur Gediz coal were investigated. For this purpose, several physical and chemical characterization methods such as proximate and ultimate coal analysis （ash, calorific value, volatile matter, moisture and sulfur analysis）, mineralogical and petrographic analysis, fourier transform infrared spectroscopy, scanning electron microscope were used. Results of these analysis are shown that Gediz coals include 3.15% pyritic sulfur and 2.89% organic sulfur. Removing pyritic sulfur from Gediz-Turkey coal with physical methods such as gravity and sink-float separation is not possible because pyrite particle has 1-2 micron liberation size in coal.
文摘Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other is a novel dinuclear V(V,V)complex with an oxo bridge.The conversion between the two complexes had been discussed.
基金supported in part by the funding from the National Natural Scientific Foundation(81370518)the National High Technology Research and Development Program of China(2015AA020924 and 2013ZX10004003)supported by a grant from the Beijing Nova Program(No.Z141107001814054)
文摘The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial threat to public health because of a high mortality rate. In this study, we sequenced whole genomes of eight H5N1 avian influenza viruses isolated from domestic poultry in eastern China and compared them with those of typical influenza virus strains. Phylogenetic analyses showed that all eight genomes belonged to clade 2.3.2.1 and clade 7.2, the two main circulating clades in China. Viruses that clustered in clade 2.3.2.1 shared a high degree of homology with H5N1 isolates located in eastern Asian. Isolates that clustered in clade 7.2 were found to circulate throughout China, with an east-to-west density gradient. Pathogenicity studies in mice showed that these isolates replicate in the lungs, and clade 2.3.2.1 viruses exhibit a notably higher degree of virulence compared to clade 7.2 viruses. Our results contribute to the elucidation of the biological characterization and pathogenicity of HPAI H5N1 viruses.
文摘The dissimilar material resistance spot welding of galvanized high strength steel and aluminum alloy had been conducted. The welded joint exhibited a thin reaction layer composed of Fe2Al5 and Fe4Al13 phases at steel/aluminum interface. The welded joint presented a tensile shear load of 3.3 kN with an aluminum alloy nugget diameter of 5.7 mm. The interfacial failure mode was observed for the tensile shear specimen and fracture occurred at reaction layer and aluminum alloy fusion zone beside the interface. The reaction layer with compounds was the main reason for reduction of the welded joint mechanical property.
基金Supported by the National Basic Research Program of China under Grant Nos 2015CB921303,2011CBA00100 and 2012CB821404the Strategic Priority Research Program(B) of Chinese Academy of Sciences under Grant Nos XDB07020100and XDB07020200the National Natural Science Foundation of China under Grant No 11174350
文摘We report on the single crystal growth and superconducting properties of PbTaSe2 with the non-centrosymmetric crystal structure. By using the chemicM vapor transport technique, centimeter-size single crystals are success- fully obtained. The measurement of temperature dependence of electricaJ resistivity p（T） in both normal and superconducting states indicates a quasi-two-dimensional electronic state in contrast to that of polycrystalline samples. Specific heat C（T） measurement reveals a bulk superconductivity with Tc ≈ 3.75K and a specific heat jump ratio of 1.42. All these results are in agreement with a moderately electron-phonon coupled, type-g Bardeen-Cooper-Schrieffer superconductor.
基金supported by National Natural Science Foundation of China(Nos.51201027 and 51271054)Fundamental Research Funds for the Central Universities of China(Nos.N110105001,N120405001 and N120505001)
文摘Grain boundary engineering（GBE） is a practice of improving resistance to grain boundary failure of the material through increasing the proportion of low Σ coincidence site lattice（CSL） grain boundaries（special grain boundaries） in the grain boundary character distribution（GBCD）. The GBCD in a cold rolled and annealed Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel was analyzed by electron back scatter difraction（EBSD）. The results show that the optimization process of GBE in the conventional austenitic stainless steel cannot be well applied to this high-nitrogen austenitic stainless steel. The percentage of low ΣCSL grain boundaries could increase from 47.3% for the solid solution treated high-nitrogen austenitic stainless steel specimen to 82.0% for the specimen after 5% cold rolling reduction and then annealing at 1423 K for 10 min.These special boundaries of high proportion efectively interrupt the connectivity of conventional high angle grain boundary network and thus achieve the GBCD optimization for the high-nitrogen austenitic stainless steel.
基金Item Sponsored by National Natural Science Foundation of China(51101114,50901054)
文摘The {111} fiND plane texture, grain boundary characterization and grain boundary segregation of phos- phorus are investigated for the phosphorus added high strength interstitial free （IF） steel annealed at 810℃ for 60 s to 180 s. The results show that the maximum volume fraction of {111} fiND plane texture is about 85% and the grain boundary Segregation peak of phosphorus is about 14 at. % for the steel annealed at 810℃ for 120 s. The ∑3 and other low-∑CSL （coincident site lattice） boundaries are lowest for the steel annealed for 120 s. Segregation of phosphorus is also found at low angle grain boundaries.
基金Supported by National Natural Science Foundation of China(Grant No.52075100)Shanghai Municipal Science and Technology Committee Innovation Program(Grant No.23ZR1404200).
文摘Additive manufacturing (AM) technology such as selective laser melting (SLM) often produces a high refection phenomenon that makes defect detection and information extraction challenging. Meanwhile, it is essential to establish a characterization method for defect analysis to provide sufcient information for process diagnosis and optimization. However, there is still a lack of universal standards for the characterization of defects in SLM parts. In this study, a polarization-based imaging system was proposed, and a set of characterization parameters for SLM defects was established. The contrast, defect contour information, and high refection suppression efect of the SLM part defects were analyzed. Comparative analysis was conducted on defect characterization parameters, including geometric and texture parameters. The experimental results demonstrated the efects of the polarization imaging system and verifed the feasibility of the defect feature extraction and characterization method. The research work provides an efective solution for defect detection and helps to establish a universal standard for defect characterization in additive manufacturing.
基金Supported by the National Natural Science Foundation of China, No. 10204014
文摘AIM： To study the relation between acoustic parameters and histological structure of biological tissue and to provide the basis for high-resolution image of biological tissues and quantitative ultrasonic diagnosis of liver disease. METHODS： Ultrasonic imaging and tissue characterization of four normal porcine liver and five cirrhotic liver tissue samples were performed using a high frequency imaging system. RESULTS： The acoustic parameters of cirrhotic liver tissue were larger than those of normal liver tissue. The sound velocity was 1577 m/s in normal liver tissue and 1631 m/s in cirrhotic liver tissue. At 35 MHz, the attenuation coefficient was 3.0 dB/mm in normal liver tissue and 4.1 dB/mm in cirrhotic liver tissue. The backscatter coefficient was 0.00431 dB/Srmm in cirrhotic liver tissue and 0.00303 dB/Srmm in normal liver tissue. The backscatter coefficient increased with the frequency. The high frequency images coincided with their histological features. CONCLUSION： The acoustic parameters, especially the sound backscatter coefficient, are sensitive to the changes of liver tissues and can be used to differentiate between the normal and pathological liver tissues. High frequency image system is a useful device for highresolution image and tissue characterization.
基金This work was supported by the National Natural Science Foundation of China (No. 50390090).
文摘Evolution and fractal character of the phase morphology of high impact polystyrene/poly（cis-butadiene） rubber （HIPS/PcBR） blends during melting and mixing were investigated using scanning electron microscopy （SEM）. The characteristic length L was defined as the size of particles of the dispersed phase in blends. Different fractal dimensions, Df and Din, were introduced to study the distribution width of phase dimensions in the dimensionless region and the uniformity of the spatial distribution of particles, respectively. The results showed that the average characteristic length Lm and Df increase as the volume fraction of the dispersed phase increases, when the volume fraction of the dispersed phase is lower than 50%. In other words, the size of particles increases and their distribution in the dimensionless region becomes more uniform. Meanwhile, the uniformity of the spatial distribution becomes more perfect as the volume fraction increases. At a certain composition, Lm decreases in the initial stage of the mixing and levels off in the late stage. In the initial stage, Df becomes large rapidly with the process of blending, which means that the distribution of L in the dimensionless region becomes more uniform. Meanwhile, the spatial distribution tends to be ideal rapidly in the early stage and fluctuates in a definite range in the late stage of the mixing.
文摘The present study aimed to examine the mediating effect of strengths use between character strengths and mental health in high school students. Totally 508 China high school students completed questionnaires measuring character strengths, strengths use and mental health for middle school students＇ inventory. The correlations between character strength, strengths use and mental health were all significantly positive, 0.41 -0.65, P 〈 0.01. Character strengths significantly positively predicted mental health, and standard regression coefficient was 0.65, P 〈 0.01. Strengths use mediated partially the relationship between character strengths and mental health in high school students and the value of mediating effect was 11.3%. Strengths use played a moderated mediating role in the relationship between character strengths and mental health.
基金supported by the National Basic Research Program of China (973 Program)(No. 2004CB217804)the Science and Technology Development Project of PetroChina (050203-01-06)
文摘NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with scanning electron microscopy （SEM）, X-ray diffraction （XRD） and specific surface area （BET）. The characterization result showed that the NaY Zeolite had a particle size of approximately 200 rim, n（SiO2）/n（Al203） ratio of 5.03, crystallinity of 96% and specific surface area of 714 m2/g. The experimental results indicated that the structure of NaY Zeolite was related to the synthesis conditions （such as reactors, crystallization time and so on）. The micromixing efficiency was proven to be the most important factor for synthesis of NaY Zeolite in the high-gravity environment in RPB.
基金financially supported by the National Science and Technology Major Project of China (No. 2016ZX05028-004)
文摘Herein, the effect of high chloride ion(Cl^-) concentration on the corrosion behavior and passive film breakdown of 13Cr martensitic stainless steel under CO_2 environment was demonstrated. The Cl^- concentration was varied from 30 to 150 g/L and cyclic potentiodynamic polarization was conducted to investigate the influence of the Cl^- concentration on the corrosion potential(E_(corr)), passive breakdown potential(E_(pit)), and repassivation potential(E_(rep)). The results of the polarization curves revealed that 13Cr stainless steel is susceptible to pitting under high Cl^- concentration. The passive breakdown potential and repassivation potential decreased with the increase of Cl-concentration. The semiconducting behavior of the passive film was investigated by Mott-Schottky analysis and the point defect model(PDM). It was observed that the iron cation vacancies and oxygen vacancies were continuously generated by autocatalytic reactions and the higher Cl^- concentration resulted in higher vacancies in the passive film. Once the excess vacancies condensed at the metal/film interface, the passive film became locally detached from the metal, which led to the breakdown of the passive film.
基金supported by the Natural Science Foundation of China(12204220)supported by Shenzhen Basic Research Fund(Grant No.JCYJ20220818100612027,JCYJ20220530112816038)+1 种基金The authors thank Guangdong Provincial Key Laboratory of Sustainable Biomimetic Materials and Green Energy(2024B1212010003)the Major Science and Technology Infrastructure Project of Material Genome Big-science Facilities Platform supported by the Municipal Development and Reform Commission of Shenzhen。
文摘With the advancement of Materials Genome Initiative,there is an urgent need for nondestructive,rapid characterization methods for obtaining electrical transport properties and phonon information of materials.In this article,we develop a method using the dielectric resonant spectroscopies of materials to derive critical parameters such as conduction electron frequency,quantum relaxation time,and phonon frequency for metals and semiconductors.As a typical example,based on the new approaches,we realized simultaneous extraction of carrier concentration n and electron-phonon relaxation timeτ_(e−p),and establish a new relationship ofτ_(e−p)=C^(∗)⋅T^(−1)⋅n^(−1/3)for n-type doped silicon,where the true electron-phonon coupling constant C^(∗)is proposed for the first time.This innovative methodology offers significant potential for high-throughput screening of materials,expediting the development of next-generation electronic devices.
基金Acknowledgements This work was supported partially by the Beijing Natural Science Foundation under Crant No. 4112048 the Program for New Century Excellent Talents in University under Gant No. NCET-09-0206+4 种基金 the National Natural Science Foundation of China under Crant No. 60830001 the Key Project of State Key Laboratory of Rail Traffic Control and Safety under Crants No. RCS2008ZZ006, No. RCS2011ZZ008 the Program for Changjiang Scholars and Innovative Research Team in University under Crant No. IRT0949 the Project of State Key kab. of Rail Traffic Control and Safety under C~ants No. RCS2008ZT005, No. RCS2010ZT012 the Fundamental Research Funds for the Central Universities under Crants No. 2010JBZ（~8, No. 2011YJS010.
文摘The non-stationary behavior, caused by the train rmverrent, is the rmin factor for the variation of high speed railway channel. To measure the tirce-variant effect, the parameter of stationarity interval, in which the channel keeps constant or has no great change, is adopted based on Zhengzfiou- Xi＇an （Zhengxi） passenger dedicated line measurement with different train speeds. The stationarity interval is calculated through the definition of Local Region of Stationarity （LRS） under three train ve- locities. Furthermore, the time non-stationary characteristic of high speed pared with five standard railway channel is corn- Multiple-Input MultipleOutput （MIMO） channel models, i.e. Spatial Channel Model （SCM）, extended version of SCM （SCME）, Wireless World Initiative New Radio Phase II （WINNERII）, International Mobile Teleconmnications-Advanced （IMT-Advanced） and WiMAX models which contain the high speed moving scenario. The stationarity interval of real channel is 9 ms in 80% of the cases, which is shorter than those of the standard models. Hence the real channel of high speed railway changes more rapidly. The stationarity intervals of standard models are different due to different modeling methods and scenario def- initions. And the compared results are instructive for wireless system design in high speed railway.
