基于刚体-弹簧元法的全级配混凝土本构特性模拟

在细观层次上把混凝土看作是由粗骨料、硬化水泥砂浆基体组成的两相非均质复合材料,采用适宜极限分析及处理微裂纹行为的刚体－弹簧元法,研究了不同的组成成分对材料的影响,建立起混凝土的细观结构以观性能之间的关系。     

共轨蓄压式电控泵喷嘴系统的实验研究

研究共轨蓄压式电控泵喷吡系统的喷射特性,取代传统的泵－油管－喷嘴系统,利用研制的实验装置对共轨蓄压式电控泵喷嘴的流量特性、喷油压力特性及喷油定时进行实验,由此分析影响喷射特性的各种因素,实验结果表明,共轨蓄压式电控泵喷嘴的特性不仅受共轨压力、增压时间的影响,转速对其也有一定的影响,而在喷射特性调节的灵活性方面,共轨蓄压式电控泵喷嘴较传统的泵－油管－喷嘴系统有明显改善。     

MAS NMR studies of modified HY zeolites

The variations in structure and acidity on the internal and external surfaces of HY zeolites modified by MgO and SiO₂ have been studied by MAS NMR, together with the selective adsorption of perfluorotributyl-amine.²⁷Al and²⁹Si MAS NMR spectra revealed that the modifications led to significant changes of the framework owing to the migration of some non-framework Si and Al into the framework in the course of the modifications.¹H MAS NMR spectra showed that the modifications decreased the acidity of the zeolite surfaces. With an increasing of the loading of the oxides, the acidity of the surface decreased further. Both of the two kinds of Brönsted acidity of the MgO-modified HY zeolites decreased, particularly those in the supercages, while those of the SiO₂-modified HY zeolites decreased less, and this result is consistent with that of NH₃-TPD. From the adsorption of perfluorotributyl-amine, it was found that the acidic sites on the external surface of the HY zeolite can be completely covered by SiO₂ after being modified by the chemical liquid deposition (CLD) method.     

Measuring radial Young’s modulus of DNA by tapping mode AFM

Based on tapping mode AFM imaging, a method was demonstrated to evaluate compression elasticity of single double-stranded DNA （dsDNA） molecules in the force region. With images under ambient conditions, Young＇s moduli of dsDNA in compression were calculated. Results demonstrated that Young＇s moduli of dsDNA can be simply deduced according to the proposed model. The method can also be used to evaluate the compression elasticity of similar soft nanomaterials.     

分担值与正规定则

设F为单位圆盘上的一个亚纯函数族，a，b为两个判别的有穷复数，b≠0，如果A↓f∈F，f的零点至少是重级的，且E（a／f^（k））包含E（a,f），E（b,f^（k））包含E（b,f），则F在单位圆盘上正规．     

与分担值有关的正规定则

设F为单位圆盘上的一族亚纯函数,a非零有穷复数,k为任一正整数,若对每一f∈F,f零点的重数≥k 1(k≥2),极点重数≥2,′f和f(k)IM分担值a,则F在单位圆盘上正规。     

Neuroglobin mutation associated with hypoxia adaptation in Tibet chicken

Globin protein family plays an important role in storing and transporting oxygen. As a newly reported globin, the revealed function of neuroglobin includes binding and storing oxygen as well as facilitating the utilization of oxygen in neuronal cells. In the present study, mutations in exons of chicken Ngb gene were identified with the method of sequencing and created restriction site PCR in Tibet chicken and other four lowland chicken breeds. The mutations of Lys-2224(E4)-Asn and Ser-2279(E4)-Gly were identified in exon 4 of the gene. The Lys-2224(E4)-Asn mutation existed only in Tibet chicken and the mutation frequencies increased with increasing altitude. Analysis of the haplotype and diplotype of the two mutations in Tibet chicken populations of different altitudes showed that the frequencies of TG haplotype and TTGG diplotype also increased with increasing altitude, while the reverse tendency was found on GGAA diplotype. Under the hypoxic simulation incubation, the main haplotype was TG in living embryos and GA in dead embryos. The results showed that the Lys-2224(E4)-Asn mutation may be a specific mutation associated with hypoxia adaptation in Tibet chicken.     

Neuroglobin mutation associated with hypoxia adaptation in Tibet chicken

Globin protein family plays an important role in storing and transporting oxygen. As a newly reported globin, the revealed function of neuroglobin includes binding and storing oxygen as well as facilitating the utilization of oxygen in neuronal cells. In the present study, mutations in exons of chicken Ngb gene were identified with the method of sequencing and created restriction site PCR in Tibet chicken and other four lowland chicken breeds. The mutations of Lys-2224(E4)-Asn and Ser-2279(E4)-Gly were identified in exon 4 of the gene. The Lys-2224(E4)-Asn mutation existed only in Tibet chicken and the mutation frequencies increased with increasing altitude. Analysis of the haplotype and diplotype of the two mutations in Tibet chicken populations of different altitudes showed that the frequencies of TG haplotype and TTGG diplotype also increased with increasing altitude, while the reverse tendency was found on GGAA diplotype. Under the hypoxic simulation incubation, the main haplotype was TG in living embryos and GA in dead embryos. The results showed that the Lys-2224(E4)-Asn mutation may be a specific mutation associated with hypoxia adaptation in Tibet chicken.     

加碳方式对磷酸铁锂动力学及电化学性能的影响

以FeSO4.7H2O和NH4H2PO4为原料,以H2O2为氧化剂,通过液相沉淀法制得前驱体FePO4,然后通过碳热还原反应制得LiFePO4。采用2种加碳方式:方法一是先制得FePO4,然后加入乙炔黑混合后高温合成LiFePO4;方法二是先把乙炔黑分散在液相中,然后通过液相沉淀制得含碳的FePO4,再高温合成LiFePO4。研究结果表明:采用方法二合成的LiFePO4动力学及电化学性能比方法一合成的优。采用方法二所制备的LiFePO4样品以0.1C的倍率放电,其比容量达149 mA.h/g;当放电倍率为1C时,其比容量为124 mA.h/g,且循环性能良好。     

道路交通事故黑点鉴别及改善对策研究综述

本文介绍了道路交通事故黑点的定义和黑点鉴别的方法,提出了改善事故黑点的对策.