聚氨酯应用于缓控释肥料无溶剂包膜的研究进展

精准施肥是当今农业绿色发展的标志性方向,缓控释肥料以可控的方式为植物提供营养的同时,最大限度减少养分损失,降低环境风险.无溶剂聚氨酯包膜材料是当前缓控释肥料研究的重要分支.为更好地掌握研究现状与发展趋势,从材料合成的角度入手,对无溶剂聚氨酯包膜的合成技术、产品种类、改性方法等方面的进展进行了分析、对比和综述.分析表明,...     

无机微粒改性聚丙烯腈纤维的结构和性能

将经过表面修饰的纳米二氧化锑掺杂二氧化锡(ATO)悬浮液加入到预热浴中,对聚丙烯腈(PAN) 纤维进行抗静电改性。讨论了悬浮液ATO含量和添加位置对纤维抗静电性、力学性能等的影响,采用差示扫描量热仪、X射线衍射、透射电镜对改性纤维的结构进行了分析。结果表明:当ATO质量分数为5％以上时,改性PAN纤维的电阻率下降到108 Ω·cm,纤维的断裂强度保持2．7 cN／dtex,改性PAN纤维耐水洗性好,且不同ATO含量的改性PAN纤维的结晶形态和结晶度接近,玻璃化转变温度也没有明显的变化,维持约100℃。     

命名数据网络中的视频传输研究综述

互联网目前已经发展为一个由实时视频和视频点播等内容分发服务主导的网络传统IP网络对于视频分发类任务的支持存在组播的部署复杂且开销大,不能有效利用多路径获取内容、对移动性的支持差和难以同时满足可靠性以及低延时需求等问题命名数据网络(named data networking,NDN)作为新型的下一代互联网体系结构,支持网...     

Frequency and Spectrum of Mutations Induced by Gamma Rays Revealed by Phenotype Screening and Whole-Genome Re-Sequencing in Arabidopsis thaliana

Genetic variations are an important source of germplasm diversity, as it provides an allele resource that contributes to the development of new traits for plant breeding. Gamma rays have been widely used as a physical agent for mutation creation in plants, and their mutagenic effect has attracted extensive attention. However, few studies are available on the comprehensive mutation profile at both the large-scale phenotype mutation screening and whole-genome mutation scanning. In this study, biological effects on M₁ generation, large-scale phenotype screening in M₂ generation, as well as whole-genome re-sequencing of seven M₃ phenotype-visible lines were carried out to comprehensively evaluate the mutagenic effects of gamma rays on Arabidopsis thaliana. A total of 417 plants with visible mutated phenotypes were isolated from 20,502 M₂ plants, and the phenotypic mutation frequency of gamma rays was 2.03% in Arabidopsis thaliana. On average, there were 21.57 single-base substitutions (SBSs) and 11.57 small insertions and deletions (InDels) in each line. Single-base InDels accounts for 66.7% of the small InDels. The genomic mutation frequency was 2.78 × 10⁻¹⁰/bp/Gy. The ratio of transition/transversion was 1.60, and 64.28% of the C > T events exhibited the pyrimidine dinucleotide sequence; 69.14% of the small InDels were located in the sequence with 1 to 4 bp terminal microhomology that was used for DNA end rejoining, while SBSs were less dependent on terminal microhomology. Nine genes, on average, were predicted to suffer from functional alteration in each re-sequenced line. This indicated that a suitable mutation gene density was an advantage of gamma rays when trying to improve elite materials for one certain or a few traits. These results will aid the full understanding of the mutagenic effects and mechanisms of gamma rays and provide a basis for suitable mutagen selection and parameter design, which can further facilitate the development of more controlled mutagenesis methods for plant mutation breeding.     

机场行李分拣系统中异构数据库迁移的实现

文章描述了首都机场行李自动分拣系统中异构数据库系统DECRDB与Oracle间数据迁移的设计和实现。基于异构数据库的数据迁移思想,系统采用OracleRDBODBC、OracleRDBWorkbench建立DECRDB数据库与Oracle数据库的物理连接,运用PowerBuilder提供的数据管道技术编程实现数据的自动迁移。     

Study on surface magnetization recover ilmenite from titanaugite using surfactant sodium oleate

ABSTRACT

Separation of ilmenite from titanaugite was investigated by magnetic coating. By enlarging magnetic difference between ilmenite and titanaugite, ilmenite was efficiently recovered. Scanning electron microscope and vibrating sample magnetometer results indicated that magnetite selectively coated onto ilmenite surface and increased its magnetism, which resulted in different magnetic separation behavior between ilmenite and titanaugite. FTIR and contact angle measurements confirmed that the adsorption difference of sodium oleate resulted in a stronger hydrophobicity on magnetite and ilmenite than titanaugite. Interaction energy analysis illustrated that hydrophobic association interaction on ilmenite was stronger than that on titanaugite, and which led to the selective coating of magnetite onto ilmenite.     

静电纺丝法制备ZnO构建酪氨酸酶生物传感器检测邻苯二酚

电化学生物传感器在环境监测、生物与食品分析等领域应用广泛。本文采用静电纺丝法制备了氧化锌微纳米纤维材料,并负载酪氨酸酶（Tyr）构建了检测邻苯二酚的生物传感电极。利用X射线粉末衍射（XRD）、扫描电子显微镜（SEM）表征了氧化锌微纳米纤维的形貌结构,采用循环伏安法（CV）和计时电流法（IT）优化了检测邻苯二酚的工作条件。结果表明,制备的Tyr/ZnO/CS/GCE生物传感电极具有良好的电化学性能,在反应过程中为扩散控制,对邻苯二酚的检测在5～50μmol/L的浓度范围内具有较好的线性关系,最低检测限为1.9041μmol/L,灵敏度为376.31μA/(mmol·L·cm²),氧化锌的加入可增强酪氨酸酶的稳定性,在尿素、多巴胺和葡萄糖3种电化学活性相近物质存在的情况下仍对邻苯二酚的检测有较好的选择性,且具有良好的循环稳定性。     

应用于钠冷快堆的超临界二氧化碳动力转换系统研究

超临界二氧化碳（SCO₂）布雷顿循环由于高效、紧凑和可避免钠水反应等特性而成为钠冷快堆的理想动力转换系统。本文以1 200 MWe大型池式钠冷快堆为系统热源,钠回路温度及热负荷为循环系统运行边界,对比研究了不同SCO₂布雷顿循环系统性能和关键设备性能的变化规律。研究发现,级间冷却再压缩循环与钠冷快堆热源特性匹配性最佳,且循环效率最高（40.7%）。进而研究了不同运行参数对级间冷却再压缩循环效率的影响规律,给出了循环系统效率对各关键影响因素的敏感度,发现循环系统效率对冷端参数的敏感度最强,其次为分流比和透平入口参数,对主压缩机级间压比的敏感度最弱。     

工艺参数对注塑制品沉降斑的影响分析及优化

采用最大沉降斑指数表征注塑制品的沉降斑,结合CAE和Taguch i DOE技术研究了工艺参数对(丙烯腈/丁二烯/苯乙烯)共聚物、高密度聚乙烯、聚丙烯注塑制品沉降斑的影响。对实验结果进行方差分析,估计选用3种不同形态的材料时各个工艺参数对制品最大沉降斑指数的影响度,同时对工艺参数进行优化并通过实验验证使制品的最大沉降斑指数降低。     

绿色生态城区指标体系研究与实践

本文研究绿色生态城区指标体系的构建思路和核心内容,并通过实际案例,说明指标体系在城区绿色生态发展过程中的引领作用,分析绿色生态指标体系发展趋势,提出指标提升和优化的具体建议.