PA6短纤维对水泥基材料塑性开裂的影响及其工程应用

采用PA6短纤维在不同掺量情况下对水泥基材料抗塑性干缩开裂性能的影响进行了研究 ,并与Nycon纤维进行对比。结果表明PA6短纤维可明显提高水泥基材料的抗塑性干缩开裂性能 ,其效果可达到国外同类产品水平 ,且在实际工程中应用效果较好     

基于分布式振动传感的车辆轴载感知方法

提出了基于分布式振动传感的车辆轴载感知方法。采用分布式光纤感知路面振动,建立光纤信号与路面振动位移映射关系及车辆轴载反演解析模型。利用足尺试验对所提车辆轴载反演解析模型进行拟合优度验证,并通过自然车辆称重试验验证所提车辆轴载感知算法有效性。结果表明：车辆轴载感知系统对单轴最大估计误差为0.98%,对车辆总重预估精度达到0.34%,且系统精度受车辆速度影响小,符合国家对于单轴2%、总重5%的精度标准。     

树冠空间占用对不同高宽比街道行人热环境的影响

在深浅有别的街谷内部,针对树冠大小差异如何影响行人小气候,并在多大程度上产生影响的问题,本文构建了NE-WS和N-S走向的浅、中、深三种不同AR特征的街道,开展了不同大小的树冠对行人气温影响的数值计算,结果表明：（1）无论街谷深浅,植树总是减弱街谷内部行人高度的平均风速,并引起上午行人气温的小幅升高;但是,植树可降低中午和下午的行人气温;（2）树木对行人小气候的影响程度随着街谷深度的增加而减弱,故,行道树绿化差异所致的深街谷行人小气候差异微乎其微;（3）行道树对行人小气候的调节作用很有限,并受来流方向的影响,平行来流下植树阻风而增强的局地湍流有助于树木发挥冷却降温作用。建议NE-WS和N-S走向的街道,种植带有小空隙率（0.125）的行道树,而不是让树冠形成连续树荫,以获得更好的降温和通风。     

NaHCO3胁迫下白桦四倍体表型及生理分析

采用Na HCO3胁迫处理白桦四倍体苗木,测定其表型特征及生理特性.结果表明:在Na HCO3胁迫下,白桦四倍体叶片受盐害程度明显低于二倍体,苗高和地径生长明显高于二倍体;白桦四倍体净光合速率、可溶性糖含量、可溶性蛋白含量、脯氨酸含量、超氧化物歧化酶活性和过氧化物酶活性始终显著高于二倍体.     

Molecular basis of xeroderma pigmentosum group C DNA recognition by engineered meganucleases

Xeroderma pigmentosum is a monogenic disease characterized by hypersensitivity to ultraviolet light. The cells of xeroderma pigmentosum patients are defective in nucleotide excision repair, limiting their capacity to eliminate ultraviolet-induced DNA damage, and resulting in a strong predisposition to develop skin cancers. The use of rare cutting DNA endonucleases-such as homing endonucleases, also known as meganucleases-constitutes one possible strategy for repairing DNA lesions. Homing endonucleases have emerged as highly specific molecular scalpels that recognize and cleave DNA sites, promoting efficient homologous gene targeting through double-strand-break-induced homologous recombination. Here we describe two engineered heterodimeric derivatives of the homing endonuclease I-CreI, produced by a semi-rational approach. These two molecules-Amel3-Amel4 and Ini3-Ini4-cleave DNA from the human XPC gene (xeroderma pigmentosum group C), in vitro and in vivo. Crystal structures of the I-CreI variants complexed with intact and cleaved XPC target DNA suggest that the mechanism of DNA recognition and cleavage by the engineered homing endonucleases is similar to that of the wild-type I-CreI. Furthermore, these derivatives induced high levels of specific gene targeting in mammalian cells while displaying no obvious genotoxicity. Thus, homing endonucleases can be designed to recognize and cleave the DNA sequences of specific genes, opening up new possibilities for genome engineering and gene therapy in xeroderma pigmentosum patients whose illness can be treated ex vivo.     

里氏木霉制备木聚糖酶的产酶历程

以玉米芯木聚糖为原料,里氏木霉（Ｔｒｉｃｈｏｄｅｒｍａｒｅｓｅｉ）ＲｕｔＣ３０为菌种,采用改进的Ｍａｎｄｅｌｓ配方制备木聚糖酶,产酶历程与制备纤维素酶时有较大差异。具体表现在产酶周期短,ｐＨ值基本无下降的趋势,酶液中可溶性蛋白质浓度较低。底物浓度为７ｇ／Ｌ时,木聚糖酶活力达１２５６ＩＵ／ｍＬ,比活力、酶得率及酶产率分别为８１９０ＩＵ／ｍｇ蛋白质、１７９４３ＩＵ／ｇ木聚糖和４１８６．７ＩＵ／Ｌ·ｄ。产酶最终ｐＨ应控制在６～７较为适宜,酶活力最高。ｐＨ超过７．０,酶可能失活。酶解结果表明,木聚糖酶对木聚糖干粉具有很高的降解效率,当每克底物的酶用量为０．１克木聚糖干粉产的酶液量时,酶解得率一般可达９０％左右。     

建设用地地质灾害危险性评估的意义和作用

根据国家有关政策和法规要求,综合阐述了地质灾害危险性评估工作的目的、意义和作用.     

论黑客的攻击技术及防御策略

讨论了计算机网络上常见的黑客行为的危害 ,对黑客的拒绝服务攻击技术进行了分析 ,并对防范黑客的拒绝服务攻击 ,保证网络安全提出了相应的策略。     

哲学视野中的虚拟现实(VP)--兼评戈登·格雷厄姆VP技术哲学思想

文章首先简介了虚拟现实技术的概念、发展历史、特点及应用领域 ,分析了虚拟现实技术与网络虚拟性的关系。在此基础上 ,评述了戈登·格雷厄姆对虚拟现实的本体论分析。之后 ,以本体论为前提 ,评述了格雷厄姆对虚拟现实在认识论、实践论层面的理论贡献     

Application of nonlinear optimization method to sensitivity analysis of numerical model

A nonlinear optimization method is applied to sensitivity analysis of a numerical model. Theoretical analysis and numerical experiments indicate that this method can give not only a quantitative assessment whether the numerical model is able to simulate the observations or not, but also the initial field that yields the optimal simulation. In particular, when the simulation results are apparently satisfactory, and sometimes both model error and initial error are considerably large, the nonlinear optimization method, under some conditions, can identify the error that plays a dominant role.