Morse set classification and hierarchical refinement using Conley index

Morse decomposition provides a numerically stable topological representation of vector fields that is crucial for their rigorous interpretation. However, Morse decomposition is not unique, and its granularity directly impacts its computational cost. In this paper, we propose an automatic refinement scheme to construct the Morse Connection Graph (MCG) of a given vector field in a hierarchical fashion. Our framework allows a Morse set to be refined through a local update of the flow combinatorialization graph, as well as the connection regions between Morse sets. The computation is fast because the most expensive computation is concentrated on a small portion of the domain. Furthermore, the present work allows the generation of a topologically consistent hierarchy of MCGs, which cannot be obtained using a global method. The classification of the extracted Morse sets is a crucial step for the construction of the MCG, for which the Poincare′ index is inadequate. We make use of an upper bound for the Conley index, provided by the Betti numbers of an index pair for a translation along the flow, to classify the Morse sets. This upper bound is sufficiently accurate for Morse set classification and provides supportive information for the automatic refinement process. An improved visualization technique for MCG is developed to incorporate the Conley indices. Finally, we apply the proposed techniques to a number of synthetic and realworld simulation data to demonstrate their utility.     

On delay adjustment for dynamic load balancing in distributed virtual environments

Distributed virtual environments (DVEs) are becoming very popular in recent years, due to the rapid growing of applications, such as massive multiplayer online games (MMOGs). As the number of concurrent users increases, scalability becomes one of the major challenges in designing an interactive DVE system. One solution to address this scalability problem is to adopt a multi-server architecture. While some methods focus on the quality of partitioning the load among the servers, others focus on the efficiency of the partitioning process itself. However, all these methods neglect the effect of network delay among the servers on the accuracy of the load balancing solutions. As we show in this paper, the change in the load of the servers due to network delay would affect the performance of the load balancing algorithm. In this work, we conduct a formal analysis of this problem and discuss two efficient delay adjustment schemes to address the problem. Our experimental results show that our proposed schemes can significantly improve the performance of the load balancing algorithm with neglectable computation overhead.     

稀土元素对钯室温电学性能的影响

研究了稀浓度(0.6at％以下)稀土元素(La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Er、Yb)对钯的室温电学性能的影响。所有稀土元素均提高钯的电阻率(p)、降低电阻温度系数(α),实验结果与理论分析证明(p·α)_((?)d-RE)d=(p·α)_(Pd)。Gd以前的稀土元素降低钯的对铜热电势(ε),其余重稀土元素增大钯的对铜热电势。按0.1at％RE归一化处理的实验数据表明,轻稀土元素对钯电阻率的影响稍大于重稀土,但Ce、Eu、Yb呈反常影响,化合价和尺寸因素是影响电学性能的主要因素。     

CdZnTe Crystal Growth by Vertical Gradient Freezing Method

ＣｄＺｎＴｅＣｒｙｓｔａｌＧｒｏｗｔｈｂｙＶｅｒｔｉｃａｌＧｒａｄｉｅｎｔＦｒｅｅｚｉｎｇＭｅｔｈｏｄＨｏｕＱｉｎｇｒｕｎ；ＷａｎｇＪｉｎｙｉ；ＤｅｎｇＪｉｎｃｈｅｎｇ；ＤｕＢｉｎｇ，（侯清润）（王金义）（邓金诚）（杜冰）；ＬｉＭｅｉｒｏｎｇａｎｄＣ...     

结晶性高聚物作为相变材料的应用

本文研究了结晶性高聚物聚乙烯及其共混物作为相变材料对模拟发热体铜片热量的吸收作用，由于相变的吸热，铜片的温度在一定时间范围内保持在一个定值。选择不同的相变材料，可使这种温度平台出现在不同的温度范围，不共晶的共混物可有两个以上的温度平台，提高了降温效果。     

Comprehensive Benefit Evaluation System for Low-Impact Development of Urban Stormwater Management Measures

In recent years, plenty of simulation research about the low impact development(LID) control effect has emerged, but studies on scheme comparison and evaluation are lacking. In this study, a comprehensive benefit evaluation system for LID, including environmental, economic, and social benefits, was established on the basis of Analytic Hierarchy Process(AHP) and urban storm water model. Above all, benefit identification, quantitative evaluation and scheme comparison of single LID measures were obtained according to site investigation, simulated calculation and theoretical analysis. Whereafter, LID combination plans were designed based on single LID measures with high comprehensive benefit values, and their comprehensive benefits were evaluated to obtain the optimal plan. Then, based on well-founded system combined with Storm Water Management Model (SWMM), the design and optimization of LID were conducted, with a case in Xi’an, China. It turned out that the preferential order of the LID single measures according to the comprehensive benefit was: bio-retention > rain barrels > low-elevation greenbelt > green roofs > permeable pavement. Five LID combination plans were designed based on bio-retention, rain barrels, low-elevation greenbelt, and green roofs. Evaluation results showed that plan I (bio-retention and green roofs) was the optimal LID combination plan.     

Modeling and global trajectory tracking control for an over-actuated MAV

This paper deals with an original micro aerial vehicle (MAV) design, the Omnicopter MAV. It has two central coaxial rotors with fixed-pitch propellers and three perimeter mounted ducted fans with servo motors performing thrust vectoring. Compared with traditional rotary wing MAVs that have inherent underactuation, the Omnicopter possesses some advantages in mobility, for example, lateral translation with zero attitude and hover with nonzero attitude. The trajectory tracking control design, global stability analysis, and control allocation are demonstrated through numerical simulation. The advantage of zero attitude translation is illustrated through experimental results.     

Video background modeling: recent approaches,issues and our proposed techniques

Effective and efficient background subtraction is important to a number of computer vision tasks. We introduce several new techniques to address key challenges for background modeling using a Gaussian mixture model (GMM) for moving objects detection in a video acquired by a static camera. The novel features of our proposed model are that it automatically learns dynamics of a scene and adapts its parameters accordingly, suppresses ghosts in the foreground mask using a SURF features matching algorithm, and introduces a new spatio-temporal filter to further refine the foreground detection results. Detection of abrupt illumination changes in the scene is dealt with by a model shifting-based scheme to reuse already learned models and spatio-temporal history of foreground blobs is used to detect and handle paused objects. The proposed model is rigorously tested and compared with several previous models and has shown significant performance improvements.     

顺酐化SBS的钠离聚体形式与丙烯酰胺的乳液接枝共聚

研究了顺酐化SBS的钠离聚体与丙烯酸胺以过氧化苯甲酰为引发剂的乳液聚合,得到了共聚的较佳条件.并以IR及DSC表征了试样的组成和多相结构.     

锤头用中锰耐磨铸钢的生产与应用

含碳含硅较高的中锰铸钢是一种可用于制造锤头的耐磨铸钢，破碎白云石时，此种钢制作的锤头的单耗为７．１ｇ／ｔ，而高锰钢制作的锤头单耗为１７．４ｇ／ｔ。中锰耐磨铸钢属脆性材料，在非强烈冲击条件下使用，是高锰钢耐磨性的２．４５倍，适用于破碎中低硬度的矿石。文中介绍了中锰铸钢的成分、生产工艺、热处理过程和机械性能。