Micro-friction of diazoresin/polyacrylic acid self-assembly films in water with atomic force microscopy

Ultrathin films composed of diazoresin（DR）and polyacrylic acid（PAA）were fabricated.The surface morphology of the films in water was measured using an atomic force microscopy（AFM）.The self-assembly technique makes the surface rather flat and uniform.The friction force and its dependence on the velocity differ from the surface charge of the thin films.The friction force of repulsive DR/PAA film increases linearly with velocity and has lower values than that of attractive DR film over the full range of velocity.As the velocity increases,the attractive friction of DR film first decreases to a minimum at a velocity of 2 line/s and then increases all the way.When the surface is repulsive to the friction substrate,the friction of thin films that is determined by hydrated lubrication of polymer chains that is ultralubricated;when it is adhesive to the friction substrate,the friction is mainly contributed from the elastic deformation of adsorbed polymer chains in the low velocity region and from viscous sliding in the presence of hydrated-layer lubrication of the polymer chains in the higher velocity region.     

基于气候和土壤要素的中国耕地适宜性指数构建

中国历史土地利用的重建工作主要分为数据重建和空间重建,而建立具有空间指示作用的参数对于历史土地利用的空间重建具有举足轻重的指示意义.本文基于此想法,参考前人经验,构建了一套耕地适宜性指数,作为历史土地利用空间重建的基础.首先通过分析影响耕地时空分布的多种自然要素和人文因素,从中厘定土壤和气候这2个关键要素,然后基于此构建了一套计算耕地适宜性指数的方法.通过获取的气候适宜性与土壤适宜性的空间分布图与实际土地利用的相关性分析验证了这2个要素的一定代表性.本文最终的结果代表自然状态下耕地分布的最初可能性,具体特征有:1)对耕地分布起影响的气候适宜性分为4个等级的块状分布;2)对耕地分布有影响的土壤适宜性比较零散,但是大体还是以秦岭-淮河一线为分界线,呈现北高南低的分布;3)对于不同地区耕地分布,影响的主导因素有区别,西北为土壤要素,东南为气候要素;4)耕地适宜性最高的地区基本集中在华北平原、长江中下游平原区域,而青藏高原地区的适宜性最低.结合人口、经济等因素,这样一套耕地适宜性分布图对历史土地利用空间分布有重要的空间指示作用.     

Formation mechanism of the graphite-rich protective layer in blast furnace hearths

A long campaign life of blast furnaces is heavily linked to the existence of a protective layer in their hearths. In this work, we conducted dissection studies and investigated damage in blast furnace hearths to estimate the formation mechanism of the protective layer. The results illustrate that a significant amount of graphite phase was trapped within the hearth protective layer. Furthermore, on the basis of the thermodynamic and kinetic calculations of the graphite precipitation process, a precipitation potential index related to the formation of the graphite-rich protective layer was proposed to characterize the formation ability of this layer. We determined that, under normal operating conditions, the precipitation of graphite phase from hot metal was thermodynamically possible. Among elements that exist in hot metal, C, Si, and P favor graphite precipitation, whereas Mn and Cr inhibit this process. Moreover, at the same hot-face temperature, an increase of carbon concentration in hot metal can shorten the precipitation time. Finally, the results suggest that measures such as reducing the hot-face temperature and increasing the degree of carbon saturation in hot metal are critically important to improve the precipitation potential index.     

程潮铁矿联合开采时回采顺序的数值模拟优化

程潮铁矿的矿体随着开采深度的增加而逐渐西移,导致选矿车间下保安矿柱所占矿量不断增多,故拟采用联合开采方法回收-430~-500m阶段矿体:充填法回收选矿车间下预留保安矿柱;无底柱分段崩落法开采保安矿柱以外的其他矿体。为了研究联合开采时回采顺序对地表稳定性的影响,采用数值模拟方法得到不同回采顺序下地表监测点的垂直位移,确定地表沉降最小且施工组织容易的回采顺序组合为最优方案,即充填法采用"中-左-右"以及无底柱分段崩落法采用"左-右-中"的回采顺序。模拟开采结果表明,在该回采顺序方案下,选矿车间区域的地表稳定性、充填采场及隔离矿柱的安全性均满足要求。     

面向CIM的组合机床CAD系统的研究开发

报道了一种新近研究开发的面向ＣＩＭ新型组合机床不ＣＡＤ系统,该系统基于产品装配模型进行开发,采用了面向对象的软件开发技术,支持自上而下的设计过程,提供了与下游生产活动的产品数据接口,可以方便与下游生产活动的集成。     

伊犁河谷绿洲的形成演化与开发利用研究

伊犁绿洲是新疆非常独特,光热水土诸环境因子搭配最好的一片绿洲。本文通过系统地分析其形成演化过程与特点,划分出绿洲发展的四个阶段。本文认为,现今的伊犁绿洲正处于向现代绿洲演进的过渡阶段。基于以上分析,提出了开发该绿洲的原则与思路。     

有限单元法在露天矿高边坡岩体稳定性研究中的应用

以厂坝铅锌矿为例,通过实地调查及室内与野外实验,综合分析了该矿北帮边坡岩体的岩性分布特征、断层与节理发育状况等工程地质条件．在充分考虑到该矿为山坡型露天矿这一显著特点,以及当地地应力特征的基础上,选择最具代表性的剖面,建立了适当的力学模型．依照这一模型,利用有限单元法模拟边坡开挖卸荷的动态过程,依次计算了边坡现阶段和设计开采后期的位移场、破坏场．计算结果较好地解释了该边坡局部塌滑多发点的形成机制与过程．最后,对边坡在开采后期的整体稳定性进行了探讨,并提出了适当的防患措施,     

带非精确线搜索的改进Dixon方法的下降性质及其全局收敛性

在推广Ｄｉｘｏｎ公式的基础上,对于无约束最优化问题,提出了一类改进的Ｄｉｘｏｎ共轭下降算法,其中搜索方向迭代公式ｄｋ＋１＝－ｇｋ＋１βｋｄｋ中的参数βｋ可以取负值并结合一类非精确线搜索,证明了新算法的全局收敛性。最后给出了改进的Ｄｉｘｏｎ公式的一个重要应用－自校正近似重新开始共轭下降算法。     

Anomalous dielectric behavior in nanocrystalline γ-Fe_2O_3

The measurements of electric capacities and dielectric loss angles for nanocrystalline γ-Fe₂O₃, under air and vacuum atmospheres have been conducted by using ac LRC method, and the conductivity and the polarization relaxation time have also been calculated from the frequency spectra of real and imaginary parts of the dielectric constants. The anomalous dielectric behavior implies the existence of two kinds of polarization mechanisms with different relaxation times, which are caused by the defects and the dangling bonds in the interfaces, respectively. The experimental and calculated results indicated that the polarization loss and the conductance loss are dominant in air atmosphere and vacuum, respectively.     

一种组织细胞图象的分割

自动、时实、计算机视学细胞追踪系统需要一种非常有效的细胞图象分割方式．通常一些文献介绍的分割算法在运用于未染色活细胞图象分析时,由于灰度变化和不均匀的光照等,显得非常虚弱．我们研究了分割的两步策略即：（１）选出含有细胞和一部分细胞周围背景的近似区域;（２）从这个区域内的背景中分割出细胞．这种方式能有效降低周围背景灰度和细胞区域上纹理的影响．实验结果表明这种方法作为细胞图象的分割时既快又省力．