三峡工程三期截流三维施工仿真研究

三峡工程三期截流提前到 2 0 0 2年 11月上旬进行 ,截流难度显著增大。为了使截流工程顺利进行 ,以先进的计算机可视化技术为基础 ,采用IMAGIS软件生成三维地形图 ,用Creator建模形成导流明渠、纵向围堰及三期围堰等三维实体模型 ,最后通过运用虚拟现实技术 ,开发出三峡工程三期截流施工实时动态演示、查询系统。该系统能根据需要实现漫游 ,可以随意定位到感兴趣的区域作细部观察 ,且具有良好的交互性。通过施工仿真研究 ,将三期截流施工过程生动地显示在屏幕上 ,用以指导施工组织管理 ,为三期截流的决策和控制提供了有效的工具     

Fundamental solutions for half plane with an oblique edge crack

An elastic half plane with an oblique edge crack is considered in this paper. A pair of concentrated forces or point dislocations is assumed to act at an arbitrary point in the half plane. The half plane with an edge crack is first mapped into a unit circle by a rational mapping function so that the following analysis can be carried out on the mapped plane analytically. Then the complex stress functions are derived by separating the whole problem into two parts; one is the principal part corresponding to the infinite plane acted on by concentrated forces or dislocations, the other is the holomorphic part, which can be determined by making use of the property of regularity of complex stress functions. The stress intensity factors of the crack can be calculated with different inclined angles of the crack, and the displacement and stress components at an arbitrary position in the half plane can be expressed explicitly.     

Interactive image segmentation based on level sets of probabilities

In this paper, we present a robust and accurate algorithm for interactive image segmentation. The level set method is clearly advantageous for image objects with a complex topology and fragmented appearance. Our method integrates discriminative classification models and distance transforms with the level set method to avoid local minima and better snap to true object boundaries. The level set function approximates a transformed version of pixelwise posterior probabilities of being part of a target object. The evolution of its zero level set is driven by three force terms, region force, edge field force, and curvature force. These forces are based on a probabilistic classifier and an unsigned distance transform of salient edges. We further propose a technique that improves the performance of both the probabilistic classifier and the level set method over multiple passes. It makes the final object segmentation less sensitive to user interactions. Experiments and comparisons demonstrate the effectiveness of our method.     

基于深度学习的电子鼻食品新鲜度检测与识别技术研究

实际生活中,食品储存情况复杂,对食品新鲜度的准确检测十分重要.将常见食品分为水果、蔬菜、肉类三个类别,并根据实际情况,对不同食品储存情况设计相应实验,利用设计的电子鼻系统对食品样本进行检测,将测试得到的样本数据用于建立线性判别分析(Linear Discriminant Analysis,LDA)、支持向量机(Support Vector Machine,SVM)、卷积神经网络(Convolutional Neural Network,CNN)模型,最终利用不同模型对食品样本的状态:新鲜、水果腐败、蔬菜腐败、肉类腐败,作出分类识别.对于实际测试样本,LDA、SVM、CNN识别准确率分别为:45.00％、85.00％、90.00％,结果证明基于深度学习的电子鼻系统可对不同储存情况下的食品新鲜状态作出有效判断,可在一定程度上为受主观因素影响的感官评价提供客观参考,提高食品新鲜度判断准确性.     

紫外光引发聚合P(AM-MAPTAC)及其响应面优化制备

以丙烯酰胺（AM）与甲基丙烯酰胺丙基三甲基氯化铵（MAPTAC）为共聚单体,通过紫外光引发聚合法制备阳离子聚丙烯酰胺絮凝剂P（AM-MAPTAC）。通过红外光谱（IR）与差热热重分析（TG/DSC）分别对P（AM-MAPTAC）进行结构表征与热稳定性分析,并采用响应曲面法得到优化制备条件：反应体系pH为4.75,引发剂v-044质量分数为0.07%,EDTA-2Na质量分数为0.20%,n（MATPAC）/n（AM）为0.33,光照时间为60 min。在优化条件下制备P（AM-MAPTAC）絮凝剂,特性粘度可达14.72 dL/g,通过污泥脱水实验可验证该特性粘度下的污泥脱水效果最好,滤饼含水率（FCMC）达70%,污泥比阻（SRF）达6.94×10¹²m/kg,上清液剩余浊度达9.70 NTU,污泥脱水效果优于市售常用絮凝剂。     

Robust Feature-Preserving Mesh Denoising Based on Consistent Subneighborhoods

In this paper, we introduce a feature-preserving denoising algorithm. It is built on the premise that the underlying surface of a noisy mesh is piecewise smooth, and a sharp feature lies on the intersection of multiple smooth surface regions. A vertex close to a sharp feature is likely to have a neighborhood that includes distinct smooth segments. By defining the consistent subneighborhood as the segment whose geometry and normal orientation most consistent with those of the vertex, we can completely remove the influence from neighbors lying on other segments during denoising. Our method identifies piecewise smooth subneighborhoods using a robust density-based clustering algorithm based on shared nearest neighbors. In our method, we obtain an initial estimate of vertex normals and curvature tensors by robustly fitting a local quadric model. An anisotropic filter based on optimal estimation theory is further applied to smooth the normal field and the curvature tensor field. This is followed by second-order bilateral filtering, which better preserves curvature details and alleviates volume shrinkage during denoising. The support of these filters is defined by the consistent subneighborhood of a vertex. We have applied this algorithm to both generic and CAD models, and sharp features, such as edges and corners, are very well preserved.     

Effect of Solidifcation Rate on Grain Structure Evolution During Directional Solidifcation of a Ni-based Superalloy

The effect of solidification rate on grain structure evolution during directional solidification(DS) of a Ni-based superalloy was explored.It was found that a high solidification rate led to sharper <001> texture and smaller grain size in the DS samples.One of the most important findings in this work was that such result was not in accordance with the general concept,and the sharper <001> texture was accompanied by the larger grain size.To explain the contradiction,the modeling samples with five grains were produced and the effect of solidification rate on the evolution of grain texture was illustrated based on the modeling samples.     

新型清垢剂清除碳酸钙垢的试验研究

采用失重法研究了清垢剂SCB和PVT在碱性条件下对碳酸钙垢的清除效果。结果表明,影响清垢剂SCB和清垢剂PVT清垢效果的因素有温度、pH值、清垢剂的用量,通过比较得出清垢剂SCB的清垢效果优于PVT。设计3因素5水平正交试验,得到清垢剂SCB的最佳使用条件为:清垢温度80℃,体系pH值为9,DMA的使用质量8.000g,清垢时间24h。该条件下其清垢效率为52.61%。