一种改进的P2P文件共享系统研究

在分层的网络结构基础上构建一种改进的文件共享系统模型,针对改进的模型,引入了移动Agent技术并充分结合了蚁群算法的思想,在该模型的基础上具体实现了一个P2P文件共享系统MAPP并对其进行了测试,结果表明,该方法的搜索性能、搜索的准确性和搜索效率等方面与传统的方法相比具有一定的改善和提高。     

Rheological characterization of PP/jute composite melts

The present article summarizes an experimental study on the molten viscoelastic behavior of PP/jute composites under steady and dynamic mode. Variations in melt viscosity and die swell of the composites with an increase in shear rate, fiber loading, and coupling agent concentration have been investigated using capillary rheometer. It was observed that with the addition of fibers and MAPP, the melt viscosity of the composites increased due to improved fiber‐matrix interfacial adhesion. Further, the dynamic viscoelastic behavior, measured using parallel plate rheometer, revealed an increase in the storage modulus (G′), indicating higher stiffness in case of fiber‐filled composites as compared with the virgin matrix. Time–temperature superposition was applied to generate various viscoelastic master curves. The fiber‐matrix morphology of the extrudates was also examined using scanning electron microscopy, which corroborated the findings of rheological properties. The treated composites displayed uniform distribution of fibers within the PP matrix with lesser surface irregularities. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1476–1484, 2006     

聚丙烯／木粉复合材料的加工成型及其力学性能研究

采用混炼工艺制备了聚丙烯／木粉复合材料（WPC）。研究了木粉、界面增溶剂-马来酸酐接枝聚丙烯（MAPP）的用量对WPC力学性能的影响。采用红外光谱仪对PP、MAPP、木粉及WPC的结构进行了表征和分析。结果表明，聚丙烯中加入木粉后，复合材料的拉伸强度及弯曲强度均比纯PP的要低，拉伸模量和弯曲模量逐渐升高，但复合材料的拉伸断裂伸长率随木粉用量的增加而逐渐下降。随着MAPP用量的增加，木粉用量较低（10％、20％）的WPC的拉伸强度和弯曲强度均先增加，然后逐渐减少，而木粉用量较高的WPC的强度值却在不断增高。当MAPP的质量分数为2％-4％时，复合材料的冲击强度值一般达到最高。红外谱图研究表明，偶联剂的加入可以把木纤维中的羟基酯化，改善木塑界面之间的相容性。     

大型扩声用音箱系统及性能前期预测

由大量音箱组成的大型扩声系统,音箱本身和音箱之间存在大量的干涉,导致音色难于保证,阐述了音箱结构和音箱系统的组成及合理布局,以及多功能声学预测软件对扬声器系统合理性的快速前期预测功能。     

Banana/Glass Fiber-Reinforced Polypropylene Hybrid Composites: Fabrication and Performance Evaluation

Hybrid composites of Polypropylene (PP) reinforced with intimately mixed short banana and glass fibers were fabricated using Haake twin screw extruder followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both the fibers into PP matrix resulted in an increase in tensile, flexural and impact strength with an increasing level of fiber content upto 30 wt% at banana: glass fiber ratio of 15:15 wt% and 2 wt% of MAPP. The rate of water absorption for the hybrid composites decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has also been analyzed to investigate the interfacial properties. An increase in the storage modulus (E′) of the treated composite indicates higher stiffness. The tan δ spectra confirms a strong influence of fiber contents and coupling agent on the α and β relaxation processes of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out employing differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) which indicated a decrease in the crystallization temperature and thermal stability of PP with the incorporation of MAPP treated banana and Glass fiber.     

成都电视台1200平米演播室有源线阵列扬声器扩声系统的设计安装调试

介绍了如何利用声学分析软件设计演播室的扩声系统,使得覆盖范围,声场不均匀度、最大声压级等各项指标通过软件预测做到设计者心中有数;同时说明了安装完成以后,如何使用实时频谱分析仪分步骤调整音箱处理器的各项参数,使得演播室的观众区有令人满意的传输频率特性。如何对这样一个复杂的扩声系统做好音箱处理器的参数竭整是本文的核心。     

苎麻布/聚丙烯复合材料的力学性能

利用聚丙烯及苎麻布作原料、马来酸酐接枝聚丙烯 (MAPP) 作界面增容剂, 采用模压工艺, 在175℃, 5、10、15及20 MPa四种压力下成型复合材料, 研究了MAPP质量分数、苎麻布质量分数及成型压力对复合材料力学性能的影响。复合材料的拉伸强度和弯曲强度在MAPP加入量为 3 %和 5 %时分别达最大值 46.72 MPa和 68. 43 MPa , 较无MAPP的复合材料的强度值分别提高 50. 95 %和 61. 81 %; 拉伸模量及弯曲模量因使用MAPP而增加, 但拉伸断裂伸长率却会下降。随着苎麻布质量分数增加, 复合材料拉伸强度、 拉伸模量、弯曲模量均逐渐增加; 苎麻布质量分数10 %、20 %的复合材料在较低的压力 (5、10 MPa) 下成型时 , 其拉伸强度和弯曲强度值相对更高, 当苎麻布质量分数超过20 %后, 成型压力对力学性能的影响无明显的规律。      

Creep behavior and manufacturing parameters of wood flour filled polypropylene composites

The influence of wood flour content, coupling agent and stress loading level on the creep behavior of wood flour–polypropylene composites was investigated. Maleated polypropylene (MAPP; Epolene G-3003™) was used as the coupling agent to treat the wood flour used as reinforcing filler for polypropylene composite. The tensile strength and modulus of various wood flour–polypropylene composites (WPCs), manufactured using the melt blending, extrusion, and palletizing methods, were measured before performing the creep test. The residual tensile strength, creep strain, and fractional deflection of the resultant wood flour–polypropylene composites were measured by means of the creep test. It was shown that the tensile strength decreased with increasing wood flour level in the composites. The creep strain also decreased as the wood flour level increased. The presence of the coupling agent increased the tensile strength of the wood flour–polypropylene composites, compared with the specimens made of pure polypropylene. For those composites containing the coupling agent, the creep deflection was significantly lower than those made without any coupling agent. The creep strains of the WPC specimens observed during the creep test fitted perfectly with the four-element burger creep model. Further investigation is required of the effects of combined mechanical and environmental loading in varying proportions.     

Mechanical properties and morphology of impact modified polypropylene–wood flour composites

The mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. Two different ethylene/propylene/diene terpolymers (EPDM) and one maleated styrene–ethylene/butylene–styrene triblock copolymer (SEBS–MA) have been used as impact modifiers in the PP/WF systems. All three elastomers increased the impact strength of the PP/WF composites but the addition of maleated EPDM and SEBS gave the greatest improvements in impact strength. Addition of MAPP did not affect the impact properties of the composites but had a positive effect on the composite unnotched impact strength when used together with elastomers. Tensile tests showed that MAPP had a negative effect on the elongation at break and a positive effect on tensile strength. The impact modifiers were found to decrease the stiffness of the composites. Scanning electron microscopy showed that maleated EPDM and SEBS had a stronger affinity for the wood surfaces than did the unmodified EPDM. The maleated elastomers are, therefore, expected to form a flexible interphase around the wood particles giving the composites better impact strength. MAPP further enhanced adhesion between WF and impact-modified PP systems. EPDM and EPDM–MA rubber domains were homogeneously dispersed in the PP matrix, the diameter of domains being between 0.1–1 μm. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1503–1513, 1998     

多智能体路径规划研究进展

多智能体路径规划是一类寻找多个智能体从起始位置到目标位置且无冲突的最优路径集合的问题,针对该问题的研究在物流、军事和安防等领域有着大量的应用场景.对国内外关于多智能体路径规划问题的研究进展进行系统整理和分类,按照结果最优性的不同,多智能体路径规划算法被分为最优算法和近似算法2类.最优的多智能体路径规划算法主要分为基于A*搜索、基于代价增长树、基于冲突搜索和基于规约的4种算法.近似的多智能体路径规划算法主要分为无边界次优的算法和有边界次优的算法2类.基于上述分类,分析各种算法的特点,介绍近年来具有代表性的研究成果,并对多智能体路径规划问题未来的研究方向进行展望.