基于遗传算法的TOPMODEL参数优化

模型参数的确定是模型研制与应用成功与否的关键．一般采用人工经验率定和自动率定两种方法来确定．遗传算法和一般的优化算法不同,它具有全局寻优能力,是一类优秀的非线性函数优化算法．利用遗传算法来进行TOPMODEL参数优化,并和人工率定的计算结果作了简要的对比,明显地显示该方法的优点．采用遗传算法所得到的精度较高,可以类推到其他水文模型的参数优化中去．     

中国融合降水产品在太行山区的质量评估

山区地形复杂,气象站点稀少导致降水实测资料匮乏,卫星降水产品是实测资料的有效补充。以太行山区为研究区,采用国家气象站点观测降水为基准数据,通过连续评价指标(R、RMSE、RB)和分类统计指标(POD、FAR、CSI)对国家气象信息中心研制的中国区融合降水产品进行质量评估,并探讨海拔、坡度和坡向与产品表现的关系。结果表明:融合降水产品与地面实测数据之间有着良好的相关性(R>0.7),但相比原始产品相对偏差和均方根误差仍较大。在降水探测能力上,融合产品提升明显,全序列站点日降水命中率达到0.65,误报率为0.33,特别是对夏季降水的探测精度更高(POD=0.76,FAR=0.32,CSI=0.56)。海拔对融合前后的产品精度有显著(p<0.05)的影响,回归分析显示,在20°~30°的坡度范围存在产品表现的拐点,融合前后降水产品均在南坡表现较差。融合降水产品在经过地面观测数据的校正之后,降水产品精度和降水捕捉能力都有显著的提升,能够较为准确地反映太行山区的降水分布特征。     

岩石表面形态的各向异性及其摩擦特性研究

岩体的力学性质取决于岩块的强度、岩块的表面形态和岩块的几何组合结构,通过对砂岩、泥岩破裂面及其互层接触的摩擦试验,分析了不同接触面的剪应力一位移变化规律,提取了摩擦试验中样品的表面形态参数,研究了砂岩、泥岩在摩擦前后破裂面表面形态的变化,分析了它们的粗糙度及其起伏特性在摩擦前后的变化规律,研究了岩石表面形态的各向异性和岩石摩擦强度的关系．结果表明：岩石破裂面的力学行为具有各向异性特征,而这种特征不但取决于破裂面的空间形貌,即破裂面形貌自身的各向异性,而且还和摩擦面相对移动的方向有关．     

Manipulating the Level of Sensorimotor Stimulation during LI-rTMS Can Improve Visual Circuit Reorganisation in Adult Ephrin-A2A5-/- Mice

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique that has the potential to treat a variety of neurologic and psychiatric disorders. The extent of rTMS-induced neuroplasticity may be dependent on a subject’s brain state at the time of stimulation. Chronic low intensity rTMS (LI-rTMS) has previously been shown to induce beneficial structural and functional reorganisation within the abnormal visual circuits of ephrin-A2A5^-/- mice in ambient lighting. Here, we administered chronic LI-rTMS in adult ephrin-A2A5^-/- mice either in a dark environment or concurrently with voluntary locomotion. One day after the last stimulation session, optokinetic responses were assessed and fluorescent tracers were injected to map corticotectal and geniculocortical projections. We found that LI-rTMS in either treatment condition refined the geniculocortical map. Corticotectal projections were improved in locomotion+LI-rTMS subjects, but not in dark + LI-rTMS and sham groups. Visuomotor behaviour was not improved in any condition. Our results suggest that the beneficial reorganisation of abnormal visual circuits by rTMS can be significantly influenced by simultaneous, ambient visual input and is enhanced by concomitant physical exercise. Furthermore, the observed pathway-specific effects suggest that regional molecular changes and/or the relative proximity of terminals to the induced electric fields influence the outcomes of LI-rTMS on abnormal circuitry.     

Structural entropy in detecting background patterns of AFM images

Structural entropy was developed for detecting the type of localization in charge distributions on a finite grid, especially in mesoscopic electronic systems. However, it is possible to detect and analyze superstructures, i.e., topologies consisting of more structures with different types of localization properties. In the definition of the structural entropy, the von Neumann entropy of the system is divided into two parts: first, the extension entropy, which is simply the logarithm of the occupation number; the second part is the structural entropy. On a structural entropy versus logarithm of the spatial filling factor map, the different types of localizations follow different, well-characterized curves. Spatial filling factor measures the percentage of the “filled” (i.e., high intensity) pixels of the image.An atomic force microscopy (AFM) image can be interpreted as some kind of charge distribution on a grid: after normalization, the darkness (or lightness) of the pixels fulfills all the necessary conditions. AFM image artifacts can be detected by plotting the structural entropy versus the logarithm of the spatial filling factor maps of the images. Not only the type of an added large-scale Gaussian, parabolic, exponential, or other function can be identified, but also by careful study of the curves belonging to the structures, the parameters can be detected, too.     

隐退的岗丘(一)

本文从一张大连的旧照片说起,通过描绘和分析人们对于高差与坡度的感觉改变,讲述了在大连城市开发中自然地貌特征的逐渐隐退。     

Numerical modelling of wind flow over a complex topography

Numerical modelling of wind flow over complex dune topography is an ambitious prospect. There is an increasing need to understand wind flow over complex topography for land planning purposes to enable prediction of sediment transport at a particular site. New surveying techniques permit the rapid development of digital terrain models, however a stumbling block is the ability of Computational Fluid Dynamics (CFD) to emulate the wind flow over such a landscape. To overcome these difficulties, it is important to establish the parameters within which such simulations can operate. This paper details an initial two-dimensional numerical model developed in order to test various modelling assumptions against experimental field wind data. Mason Bay, Stewart Island, New Zealand was chosen as an undisturbed but accessible experimental site with a prevalent on-shore wind perpendicular to a simple foredune and a complex down-wind parabolic dune system. A complex topographical two-dimensional model with vegetation represented as a roughness was compared against field data along a transect dissecting a dune system.This paper establishes that:

* Replicating the roughness patterns at the surface is important

* The inlet profile should be duplicated with care

* Modelling only a portion of the domain can have an effect on the flow patterns due to outflow effects

* There is a modelling decision to be made between the complexity of the topography and the sophistication of the turbulence model and degree to which vegetation and sand transportation are modelled.

The long-term aim is to instil confidence in numerical techniques so that such technology can be used for predictive purposes.     

Effect of chemical and heat treatment on the interfacial contact resistance and corrosion resistance of 446M ferritic stainless steel as a bipolar plate for polymer electrolyte membrane fuel cells

The bipolar plate is an important component of the polymer electrolyte membrane fuel cell (PEMFC) because it supplies the pathway of the electron flow between each unit cell. The ferritic stainless steel is considered a good candidate material for bipolar plate, but it is limited to use as a bipolar plate due to its corrosion problem and high interfacial contact resistance (ICR). To explore a cost-effective method of surface modification, various chemical and heat treatments are performed with 446M ferritic stainless steel to understand the effect of the surface modifications on the ICR and the corrosion resistance. The ICR and corrosion resistance of 446M stainless steel can be effectively controlled by a proper surface modification with combined treatment of immersion in the acidic solution, followed by heat treatment. The combined chemical and heat treatment not only improves the corrosion resistance but also reduces the ICR value.     

“先前小组”辅助指导方式在测绘学科专业课程实习中的应用研究

教师少与实习任务重是测绘专业课程实习长期面临的一个突出矛盾,严重影响了学生实习的效果."先前小组"辅助指导方式能锻炼学生各项能力,调动学生学习兴趣,辅助教师高效指导全体学生完成实习任务,在较好地解决教师少与实习任务重矛盾的同时,亦体现了教育以学生为本的根本要求.