Hydrogenase as the basis for green hydrogen production and utilization

Hydrogenase is a paradigm of highly efficient biocatalyst for H_(2) production and utilization evolved in nature. A dilemma is that despite the high activity and efficiency expected for hydrogenases as promising catalysts for the hydrogen economy, the poor oxygen tolerance and low yield of hydrogenases largely hinder their practical application. In these years, the enigmas surrounding hydrogenases regarding their structures, oxygen tolerance, mechanisms for catalysis, redox intermediates, and proton-coupled electron transfer schemes have been gradually elucidated;the schemes, which can well couple hydrogenases with other highly efficient(in)organic and biological catalysts to build novel reactors and drive valuable reactions, make it possible for hydrogenases to find their niches. To see how scientists put efforts to tackle this issue and design novel reactors in the fields where hydrogenases play crucial roles, in this review,recent advances were summarized, including different strategies for protecting enzyme molecules from oxygen, enzyme-based assembling systems for H_(2) evolution in the photoelectronic catalysis, enzymatic biofuel cells for H_(2) utilization and storage and the efficient electricity-hydrogen-carbohydrate cycle for high-purity hydrogen and biofuel automobiles. Limitations and future perspectives of hydrogenasebased applications in H_(2) production and utilization with great impact are discussed. In addition, this review also provides a new perspective on the use of biohydrogen in healthcare beyond energy.

Epipelagic mesozooplankton communities in the northeastern Indian Ocean off Myanmar during the winter monsoon

The northern Andaman Sea off Myanmar is one of the relatively high productive regions in the Indian Ocean.The abundance,biomass and species composition of mesozooplankton and their relationships with environmental variables in the epipelagic zone(~200 m)were studied for the first time during the Sino-Myanmar joint cruise(February 2020).The mean abundance and biomass of mesozooplankton were(1916.7±1192.9)ind./m3and(17.8±7.9)mg/m3,respectively.A total of 213 species(taxa)were identified from all samples.The omnivorous Cyclopoida Oncaea venusta and Oithona spp.were the top two dominant taxa.Three mesozooplankton communities were determined via cluster analysis:the open ocean in the Andaman Sea and the Bay of Bengal(Group A),the transition zone across the Preparis Channel(Group B),and nearshore water off the Ayeyarwady Delta and along the Tanintharyi Coast(Group C).Variation partitioning analysis revealed that the interaction of physical and biological factors explained 98.8%of mesozooplankton community spatial variation,and redundancy analysis revealed that column mean chlorophyll a concentration(CMCHLA)was the most important explanatory variable(43.1%).The abundance and biomass were significantly higher in Group C,the same as CMCHLA and column mean temperature(CMT)and in contrast to salinity,and CMT was the dominant factor.Significant taxon spatial variations were controlled by CMCHLA,salinity and temperature.This study suggested that mesozooplankton spatial variation was mainly regulated by physical processes through their effects on CMCHLA.The physical processes were simultaneously affected by heat loss differences,freshwater influx,eddies and depth.

A Galaxy Image Augmentation Method Based on Few-shot Learning and Generative Adversarial Networks

Galaxy morphology classifications based on machine learning are a typical technique to handle enormous amounts of astronomical observation data,but the key challenge is how to provide enough training data for the machine learning models.Therefore this article proposes an image data augmentation method that combines few-shot learning and generative adversarial networks.The Galaxy10 DECaLs data set is selected for the experiments with consistency,variance,and augmentation effects being evaluated.Three popular networks,including AlexNet,VGG,and ResNet,are used as examples to study the effectiveness of different augmentation methods on galaxy morphology classifications.Experiment results show that the proposed method can generate galaxy images and can be used for expanding the classification model’s training set.According to comparative studies,the best enhancement effect on model performance is obtained by generating a data set that is 0.5–1 time larger than the original data set.Meanwhile,different augmentation strategies have considerably varied effects on different types of galaxies.FSL-GAN achieved the best classification performance on the ResNet network for In-between Round Smooth Galaxies and Unbarred Loose Spiral Galaxies,with F1 Scores of 89.54%and 63.18%,respectively.Experimental comparison reveals that various data augmentation techniques have varied effects on different categories of galaxy morphology and machine learning models.Finally,the best augmentation strategies for each galaxy category are suggested.

A phase I study of different doses and frequencies of pegylated recombinant human granulocyte-colony stimulating factor(PEG rhG-CSF) in patients with standard-dose chemotherapy-induced neutropenia

Objective： The recommended dose of prophylactic pegylated recombinant human granulocyte-colony stimulating factor（PEG rhG-CSF） is 100 μg/kg once per cycle for patients receiving intense-dose chemotherapy.However, few data are available on the proper dose for patients receiving less-intense chemotherapy. The aim of this phase I study is to explore the proper dose and administration schedule of PEG rhG-CSF for patients receiving standard-dose chemotherapy.Methods：Eligible patients received 3-cycle chemotherapy every 3 weeks.No PEG rhG-CSF was given in the first cycle.Patients experienced grade 3 or 4 neutropenia would then enter the cycle 2 and 3.In cycle 2,patients received a single subcutaneous injection of prophylactic PEG rhG-CSF on d 3,and received half-dose subcutaneous injection in cycle 3 on d 3 and d 5,respectively.Escalating doses（30,60,100 and 200μg/kg）of PEG rhG-CSF were investigated.Results：A total of 26 patients were enrolled and received chemotherapy,in which 24 and 18 patients entered cycle 2 and cycle 3 treatment,respectively.In cycle 2,the incidence of grade 3 or 4 neutropenia for patients receiving single-dose PEG rhG-CSF of 30,60,100 and 200 μg/kg was 66.67%,33.33%,22.22% and 0,respectively,with a median duration less than 1（0–2）d.No grade 3 or higher neutropenia was noted in cycle 3 in all dose cohorts.Conclusions：The pharmacokinetic and pharmacodynamic profiles of PEG rhG-CSF used in cancer patients were similar to those reported,as well as the safety.Double half dose administration model showed better efficacy result than a single dose model in terms of grade 3 neutropenia and above.The single dose of 60 μg/kg,100 μg/kg and double half dose of 30 μg/kg were recommended to the phase Ⅱ study,hoping to find a preferable method for neutropenia treatment.

Partial function prediction of sulfate-reducing bacterial community from the rhizospheres of two typical coastal wetland plants in China

Sulfate-reducing bacteria(SRB)are ubiquitous anaerobic microorganisms that play signifi cant roles in the global biogeochemical cycle.Coastal wetlands,one of the major habitats of SRB,exhibit high sulfate-reducing activity and thus play signifi cant roles in organic carbon remineralization,benthic geochemical action,and plant-microbe interactions.Recent studies have provided credible evidence that the functional rather than the taxonomic composition of microbes responds more closely to environmental factors.Therefore,in this study,functional gene prediction based on PacBio single molecular real-time sequencing of 16S rDNA was applied to determine the sulfate-reducing and organic substrate-decomposing activities of SRB in the rhizospheres of two typical coastal wetland plants in North and South China:Zostera japonica and Scirpus mariqueter.To this end,some physicochemical characteristics of the sediments as well as the phylogenetic structure,community composition,diversity,and proportions of several functional genes of the SRB in the two plant rhizospheres were analyzed.The Z.japonic a meadow had a higher dissimilatory sulfate reduction capability than the S.mariqueter-comprising saltmarsh,owing to its larger proportion of SRB in the microbial community,larger proportions of functional genes involved in dissimilatory sulfate reduction,and the stronger ability of the SRB to degrade organic substrates completely.This study confi rmed the feasibility of applying microbial community function prediction in research on the metabolic features of SRB,which will be helpful for gaining new knowledge of the biogeochemical and ecological roles of these bacteria in coastal wetlands.

Galaxy Morphology Classification Using a Semi-supervised Learning Algorithm Based on Dynamic Threshold

Machine learning has become a crucial technique for classifying the morphology of galaxies as a result of the meteoric development of galactic data.Unfortunately,traditional supervised learning has significant learning costs since it needs a lot of labeled data to be effective.FixMatch,a semi-supervised learning algorithm that serves as a good method,is now a key tool for using large amounts of unlabeled data.Nevertheless,the performance degrades significantly when dealing with large,imbalanced data sets since FixMatch relies on a fixed threshold to filter pseudo-labels.Therefore,this study proposes a dynamic threshold alignment algorithm based on the FixMatch model.First,the class with the highest amount has its reliable pseudo-label ratio determined,and the remaining classes'reliable pseudo-label ratios are approximated in accordance.Second,based on the predicted reliable pseudo-label ratio for each category,it dynamically calculates the threshold for choosing pseudo-labels.By employing this dynamic threshold,the accuracy bias of each category is decreased and the learning of classes with less samples is improved.Experimental results show that in galaxy morphology classification tasks,compared with supervised learning,the proposed algorithm significantly improves performance.When the amount of labeled data is 100,the accuracy and F1-score are improved by 12.8%and 12.6%,respectively.Compared with popular semisupervised algorithms such as FixMatch and MixMatch,the proposed algorithm has better classification performance,greatly reducing the accuracy bias of each category.When the amount of labeled data is 1000,the accuracy of cigar-shaped smooth galaxies with the smallest sample is improved by 37.94%compared to FixMatch.

简易离体猪胃模型在内镜黏膜下剥离术培训中的应用效果

目的设计一种简易离体猪胃模型,通过举办8期胃内镜黏膜下剥离术(ESD)培训班来评估其应用效果。方法前瞻性研究2018年12月-2020年10月重庆医科大学附属第一医院消化内科设计的一种简易离体猪胃模型,探讨其在ESD学员培训中的应用效果。共举办8期猪胃ESD手把手教学培训班,选用12个猪胃,共培训学员72例,其中公立医院46例、私立医院26例。将当天新鲜购买未经冷冻的重量在0.6~0.9 kg的猪胃洗净后,用民用缝衣针线或医用外科缝合针线将猪胃缝合完整,仅保留食管入口,再将猪胃固定于厚度为2 cm的珍珠棉泡沫板上(长60 cm,宽40 cm),每个猪胃需要固定5个点,猪胃与泡沫板之间预先放置手术电刀所需的电极板,胃镜通过食管入口后,用外科止血钳夹闭食管入口处,防止漏气。将上述装置平放于手术平台上,尽量防止移动。ESD手术流程参照传统ESD操作流程进行,通过评估手术操作时间、完整切除率、完成率、成功率和后期能否独立开展ESD工作等来判断该模型的应用效果。结果所有学员在培训当天使用该模型独立完成1例ESD操作,多采用口袋法完成ESD,完成时间为30~50 min,平均(38.6±5.3)min,完整切除率为95%,完成率为98%,成功率为98%,整个过程中医生和助手均不需要对模型进行按压或校正,胃腔始终能保持扩张状态。部分学员熟练操作后,甚至可以在没有助手辅助的情况下独立完成整个ESD。通过培训,学员返回自己医院后,可以独立制作该模型进行反复的ESD练习,有3名医生通过培训后,能独立进行临床ESD工作。结论简易离体猪胃模型设计简单,所需材料容易获得,缝合方式可靠,基本不会漏气,视野清晰,手术操作流畅,可以良好地模拟ESD操作,值得临床推广应用。

Study on the effect of RDX content on the properties of nitramine propellant

Four kinds of nitroamine propellants with different RDX contents(10%,20%,30%and 40%)were prepared to study the effect of RDX content on the mechanical properties and combustion properties of nitroamine propellant.The mechanical properties and combustion properties of nitroamine propellant at the normal temperature(20C)and low temperature(à40C)were test by using impact testing machine,drop hammer impact test machine and closed bomb vessel.The test results show that the impact strength of30%RDX-contained nitramine propellant is maximum,but 40%RDX-contained nitramine propellant has the minimum impact strength.And the crushing height of propellant with 20%RDX-contained was the highest,but the crushing height of propellant with 40%RDX-contained the lowest.With the increase in RDX content in nitramine propellant,the energy of nitramine propellant increases and its burning rate reduces,but 40%RDX-contained nitramine propellant did not meet this trend at the low temperature because of its poor mechanical properties.

Preparation and characterization of solidified oleanolic acid–phospholipid complex aiming to improve the dissolution of oleanolic acid

The purpose of this study was to prepare the oleanolic acid–phospholipid complex (OAPC) and then solidify it employing fumed silica by simple solvent evaporation technique to improve dissolution rate of oleanolic acid and oleanolic acid–phospholipid complex. The process of OA-PC was optimized and the type and proportion of fumed silica were studied by dissolution text. The structures of the phospholipid complex and solidified powder were also characterized by differential scanning calorimetry, X-ray diffraction, and scanning electron microscope. In the dissolution tests, OA from solidified powder was further released compared with that from pure OA and OA-PC in different kinds of dissolution media. These results suggest that the method of preparing solidified powder of oleanolic acid–phospholipid complex is suitable for enhancing the dissolution rate of OA and OA-PC.

Rates and risk factors for suicidal ideation,suicide attempts and suicide deaths in persons with HIV:a systematic review and meta-analysis

Background People living with HIV/AIDS(PLWHA)must contend with a significant burden of disease.However,current studies of this demographic have yielded wide variations in the incidence of suicidality(defined as suicidal ideation,suicide attempt and suicide deaths).Aims This systematic review and meta-analysis aimed to assess the lifetime incidence and prevalence of suicidality in PLWHA.Methods Publications were identified from PubMed(MEDLINE),SCOPUS,OVID(MEDLINE),Joanna Briggs Institute EBP and Cochrane Library databases(from inception to before 1 February 2020).The search strategy included a combination of Medical Subject Headings associated with suicide and HIV.Researchers independently screened records,extracted outcome measures and assessed study quality.Data were pooled using a random-effects model.Subgroup and meta-regression analyses were conducted to explore the associated risk factors and to identify the sources of heterogeneity.Main outcomes were lifetime incidence of suicide completion and lifetime incidence and prevalence of suicidal ideation and suicide attempt.Results A total of 185199 PLWHA were identified from 40 studies(12 cohorts,27 cross-sectional and 1 nested case-control).The overall incidence of suicide completion in PLWHA was 10.2/1000 persons(95%CI:4.5 to 23.1),translating to 100-fold higher suicide deaths than the global general population rate of 0.11/1000 persons.The lifetime prevalence of suicide attempts was 158.3/1000 persons(95%CI:106.9 to 228.2)and of suicidal ideation was 228.3/1000 persons(95%CI:150.8 to 330.1).Meta-regression revealed that for every 10-percentage point increase in the proportion of people living with HIV with advanced disease(AIDS),the risk of suicide completion increased by 34 per 1000 persons.The quality of evidence by Grading of Recommendations,Assessment,Development and Evaluations for the suicide deaths was graded as‘moderate’quality.Conclusions The risk of suicide death is 100-fold higher in people living with HIV than in the general population.Lifetime incidence of suicidal ideation and attempts are substantially high.Suicide risk assessments should be a priority in PLWHA,especially for those with more advanced disease.

Distinct root system acclimation patterns of seagrass Zostera japonica in sediments of different trophic status:a research by X-ray computed tomography

Conspecific seagrass living in differing environments may develop different root system acclimation patterns.We applied X-ray computed tomography(CT)for imaging and quantifying roots systems of Zostera japonica collected from typical oligotrophic and eutrophic sediments in two coastal sites of northern China,and determined sediment physicochemical properties that might influence root system morphology,density,and distribution.The trophic status of sediments had little influence on the Z.japonica root length,and diameters of root and rhizome.However,Z.japonica in oligotrophic sediment developed the root system with longer rhizome node,deeper rhizome distribution,and larger allocation to below-ground tissues in order to acquire more nutrients and relieve the N deficiency.And the lower root and rhizome densities of Z.japonica in eutrophic sediment were mainly caused by fewer shoots and shorter longevity,which was resulted from the more serious sulfide inhibition.Our results systematically revealed the effect of sediment trophic status on the phenotypic plasticity,quantity,and distribution of Z.japonica root system,and demonstrated the feasibly of X-ray CT in seagrass root system research.

Seasonal and regional diff erences in long-term changes in large mesozooplankton(>505μm)biomass and abundance in a semi-enclosed subtropical bay

Obvious spatiotemporal heterogeneity is a distinct characteristic of ecosystems in subtropical bays.To aid targeted management and ecological restoration in long and narrow semi-enclosed subtropical bays,we analyzed seasonal and regional differences in long-term changes(1980-2019)in the biomass and abundance of large mesozooplankton(LMZ;>505μm)in Xiangshan Bay,Zhejiang,China.We found spatiotemporal heterogeneity in the historical changes of LMZ.Significant negative trends in LMZ biomass were found in the inner and middle bay during the warm season(summer and autumn),when the nutrient concentration(especially dissolved inorganic nitrogen)and temperature increased simultaneously.Nutrient changes in Xiangshan Bay began in the late 1980s or early 1990s,coinciding with large-scale fish cage development.A rapid decline in LMZ biomass occurred after 2005 when power plants commenced operation,accelerating the warming trend.Therefore,the joint stress of eutrophication and warming likely precipitated the decline in LMZ biomass.Conversely,a significant increase in LMZ biomass was found in the outer bay in spring.This trend was consistent with the trend of LMZ biomass near the Changjiang(Yangtze)River estuary,which indicates that the pelagic ecosystem in the outer bay was aff ected by water from the Changjiang River estuary during spring.Based on our results,ecosystem management and restoration in semi-enclosed subtropical bays should focus on internal waters,which have a poor capacity for water exchange.For Xiangshan Bay,the changes in the Changjiang River estuary ecosystem during the cold season(winter and spring)should also be considered.

Path Analysis of Rural Social Work Intervention in Precision Poverty Alleviation in Sichuan Province

The targeted poverty alleviation policy isone of the important methods to solve the problemof poverty in China. After the implementation of thetargeted poverty alleviation policy in China, someresults have shown positive. However, due to theshortage of resources and talents for poverty alleviation,there are still some shortcomings in the targeted povertyalleviation work. In the process of targeted povertyalleviation, if we can promote social work to participatein targeted poverty alleviation and use a wider rangeof social forces to provide more professional andtargeted assistance work for the poor, we will achievethe final sprint for the success of targeted povertyalleviation in China and a well-off society. Based onthe actual situation of China’s current targeted povertyalleviation work, this article takes the relationship andcontent of rural social work in Sichuan Province aspart of the targeted poverty alleviation as well as thedifficulties it faces. The analysis focuses on the pathof rural social work in Sichuan Province to targetedpoverty alleviation and aims to provide more referencesuggestions for targeted poverty alleviation in China.

Analysis on the Path of Local Universities’Intervention in the Sustainable Development of Poor Rural Areas in the Era of Post-Poverty Alleviation:Taking Sichuan University of Science and Engineering as an Example

China has entered the era of post-poverty alleviation,which effectively links poverty alleviation achievements with rural revitalization strategies.In the era of post-poverty alleviation,in order to effectively promote the sustainable development of poor rural areas,local colleges and universities should actively nurture the self-development skills of the needy.Local colleges and universities should guide the transformation of ideas and concepts,scientifically optimize the allocation of poverty alleviation resources,improve the interest linkage mechanism between colleges and universities,strengthen the investigation and analysis of poverty alleviation projects,improve the convergence of assistance and practice,actively create a good spiritual and cultural environment,uphold the mission of helping cadres,attach importance to the support for the development of characteristic industries,and lastly,promote the convergence of rural revitalization strategies.

Phosphate-induced differences in stabilization efficiency for soils contaminated with lead, zinc, and cadmium

Phosphates can cost-effectively decrease the mobility of Pb in contaminated soils. However, Pb always coexists with other metals in soil, their competitive reactions with phosphates have not been tested. In this study, the abilities of KHzPO4, K2HPO4, and K3PO4 to stabilize Pb, Zn, and Cd in soils contaminated with a single metal or a ternary metal for different phosphorus/metal molar ratios were investigated. Results indicated that the stabilization efficiency of KH2PO4, K2HPO4, and K3PO4 for Pb, Zn, and Cd in single metal contaminated soil （P/M ratio 0.6） was 96.00%-98.74%, 33.76%-47.81%, and 9.50%-55.79%, respectively. Competitive stabilization occurred in the ternary system, Pb exhibited a strong competition, the stabilization efficiency of Zn and Cd reduced by 23.50%- 31.64%, and 7.10%--39.26%, respectively. Pyromorphite and amorphous lead phosphate formed with excess KH2PO4 or K2HPO4 addition, while K3PO4 resulted in the formation of a hydroxypyr- omorphite precipitate. Amorphous Zn and Cd phosphates and hydroxides were the primary products. The immobilization rate of Zn and Cd depends on pH, and increased significantly in response to the excess phosphate application. This approach provides insight into phosphate-induced differences in stabilization efficiency in soils contaminated with multiple metals, which is of theoretical and engineering significance.

Salinity fronts shape spatial patterns in zooplankton distribution in Hangzhou Bay

Ocean fronts play important roles in nutrient transport and in the shaping ecological patterns.Frontal zones in small bays are typically small in scale,have a complex structure,and they are spatially and temporally variable,but there are limited data on how biological communities respond to this variation.Hangzhou Bay,a mediumsized estuary in China,is an ideal place in which to study the response of plankton to small-scale ocean fronts,because three water masses(Qiantang River Diluted Water,Changjiang River Diluted Water,and the East China Sea current) converge here and form dynamic salinity fronts throughout the year.We investigate zooplankton communities,and temperature,salinity and chlorophyll a(Chl a) in Hangzhou Bay in June(wet perio d) and December(dry period) of 2022 and examine the dominant environmental factors that affect zooplankton community spatial variability.We then match the spatial distributions of zooplankton communities with those of salinity fronts.S alinity is the most important explanatory variable to affect zooplankton community spatial variability during both wet and dry periods,in that it contributes>60% of the variability in community structure.Furthermore,the spatial distributions of zooplankton match well with salinity fronts.During December,with weaker Qiantang River Diluted Water and a stronger secondary Changjiang River Plume,zooplankton communities occur in moderate salinity(MS,salinity range 15.6±2.2) and high salinity(HS,22.4±1.7) regions,and their ecological boundaries closely match the Qiantang River Diluted Water front.In June,different zooplankton communities occur in low salinity(LS,3.9±1.0),MS(11.7±3.6) and HS(21.3±1.9) regions.Although the LS region occurs abnormally in the central bay rather than its apex because of the anomalous influence of rising and falling tides during the sampling perio d,the ecological boundaries still match salinity interfaces.Low-salinity or brackish-water zooplankter taxa are relatively more abundant in LS or MS regions,and the biomass and abundance of zooplankton is higher in the MS region.

Multifaceted Insight into Sensitivity Analysis and Environmental Impact on Human Health of Soil Contamination Risk Assessment

Sensitivity analysis is a valuable method for evaluating the impact of model parameters on health risk characterization,thereby supporting the prediction of critical uncertainty factors.However,limitations arise in terms of cross-disciplinary discussions and in-depth analyses of previous research.To overcome these limitations,a systematic and multifaceted approach was introduced for analyzing the parameter sensitivities in soil contamination risk assessment.This approach specifically targeted the 12 main parameters associated with 65 soil contaminants for health risk assessment,employing detailed authoritative statistics for risk assessment.Screening analysis revealed that identified heavy metals and organics were influenced by key parameters,such as PM_(10),body weight of adults(BW_(a)),daily air inhalation rate of adults(DAIR_(a)),air exchange rate(ER),and typical soil parameters.PM_(10) showed a positive 100%correlation with inorganics and metals,but BW_(a) and DAIR_(a) exhibited different impacts on different chemicals,with an increase in potential risk observed with higher BW_(a) and lower DAIR_(a).Furthermore,incorporating soil parameters in the analysis showed that compact soil could improve the protection against vapor organic compounds for human health.This refined study presents a comprehensive strategy for sensitivity analysis in health risk assessment of soil contamination,thereby offering substantial support for the protection and preservation of human health.A logical framework also was provided for addressing the limitations of sensitivity analysis and facilitating an understanding of the complex relationships between model parameters and the health risk of soil contamination.

嵌合型口蹄疫病毒样颗粒构建、表达及鉴定

为提高口蹄疫病毒(Foot-and-mouthdiseasevirus,FMDV)病毒样颗粒(Virus-likeparticles,VLPs)的特异性识别和递呈,为靶向疫苗研究奠定基础,利用反向PCR技术,将卵清蛋白(Ovalbumin,OVA)第257–264位氨基酸(Amino acids,aa)的短肽嵌入FMDV结构蛋白VP3第171–172位aa或第173–174位aa,通过大肠杆菌表达FMDV结构蛋白VP0、VP1和嵌合型VP3,体外组装得到嵌合OVA257-264肽的病毒样颗粒(VLPOVA)。用动态光散射、透射电镜检测VLPOVA大小和形态,免疫印迹、酶联免疫吸附试验和激光共聚焦显微镜检测短肽的嵌入情况。结果显示在VP3的第173–174位aa嵌入OVA,不影响蛋白表达和VLPs的组装且OVA位于VLPOVA的表面,VLPOVA粒径比VLPs稍大。

显微组织对460MPa级抗震耐火建筑钢性能影响的研究

为研究不同组织对于建筑用抗震耐火钢的性能影响,设计一种节钼(Mo)型含量的试验钢,其组织由铁素体+贝氏体组成。研究发现,采用不同的轧制工艺,可获得具有不同贝氏体体积分数的建筑钢。由于奥氏体变形促进了铁素体相变,二阶段轧制相较于一阶段轧制会获得更多体积分数的铁素体组织,经过铁素体相变后,保留的未转变奥氏体体积分数会减少,因而会获得更多体积分数的贝氏体组织。通过对显微组织、室温及高温力学性能进行分析研究,发现包括一阶段轧制和二阶段轧制的两种轧制工艺都能获得建筑钢原型,其室温性能优异,符合460 MPa级钢的强度标准,屈强比小于0.80,表明钢种具有优异的抗震性能。高温力学性能测试及分析结果表明,具有较多贝氏体体积分数的试验钢具有更优异的耐火性能,一阶段轧制钢的高温屈服强度约为402.5 MPa,二阶段轧制钢的高温屈服强度约为294.1 MPa,前者比后者高约108.4 MPa。在600℃高温下,生成大量的大尺寸合金渗碳体。同时通过高温应力-应变曲线可以测量出,一阶段轧制试验钢的高温弹性模量约为104.6 GPa,明显高于二阶段轧制试验钢的87.5 GPa。通过对600℃3 h后试验钢的几何必须位错密度进行统计,可以看出,贝氏体体积分数更高的一阶段轧制试验钢的位错密度明显高于二阶段轧制试验钢的。通过强度贡献计算可以看出,一阶段轧制试验钢在600℃时的位错强化贡献值约为141.7 MPa,而二阶段轧制试验钢只有约91.7 MPa,表明贝氏体具有更高的高温稳定性。更高贝氏体体积分数的钢具有更加优异的耐火性能,其在耐火试验中位错密度和高温弹性模量仍保持较高,位错强化带来的强度贡献是其耐火性能差异的最重要原因。