共查询到20条相似文献，搜索用时 15 毫秒
1.
介绍纳米、纳米技术和纳米粒子的特征,综述纳米CaCO3制备、表面改性及纳米CaCO3/橡胶复合材料的研究进展. 相似文献
2.
纳米SiO2及纳米SiO2/橡胶复合材料的研究进展 总被引：2，自引：0，他引：2
介绍纳米、纳米技术和纳米粒子的结构特征,综述纳米技术应用于制备纳米Si02及纳米SiO2/橡胶复合材料的研究进展. 相似文献
3.
对马尾松热磨机械浆纤维增强聚丙烯复合材料力学性能进行测试与分析，结果表明：对纤维进行接核处理和偶联处理，可以明显改善纤维与取丙烯基体共混体系的力学性能；纤维与助剂的含量对复合材料力学性能的影响显著，马尾松热磨机械浆含量25％左右时，复合材料可达到的力学性能指标为拉伸强度27MPa以上、弯曲强度40MPa以上、冲击强度（缺口）5kJ/m^2以上。 相似文献
4.
研究利用玉米秸秆粉体作为增强材料与聚乙烯(PE)通过挤出成型制备玉米秸秆粉体/PE复合材料的可行性,并考查了玉米秸秆粉体添加量及其尺寸对复合材料力学性能的影响。结果表明:随玉米秸秆粉体添加量的增加,玉米秸秆粉体/PE复合材料的拉伸强度、拉伸模量呈先升后降趋势,弯曲模量逐渐增大,冲击强度则逐渐减小;当玉米秸秆粉体添加量为50%时,复合材料的综合力学性能最佳。此外,玉米秸秆粉体/PE复合材料的力学性能随玉米秸秆粉体长径比的增大而增强;在考查范围内,添加40目h(粒径)≤60目玉米秸秆粉体复合材料的力学性能最好。电镜结果显示添加20目h≤40目玉米秸秆粉体/PE复合材料粉体在基体中分布不均,断面形貌最差,而添加40目h≤60目玉米秸秆粉体复合材料的断面形貌最佳。 相似文献
5.
Operant conditioning of cortical unit activity 总被引：6，自引：0，他引：6
E E Fetz 《Science (New York, N.Y.)》1969,163(870):955-958
The activity of single neurons in precentral cortex of unanesthetized monkeys (Macaca mulatta) was conditioned by reinforcing high rates of neuronal discharge with delivery of a food pellet. Auditory or visual feedback of unit firing rates was usually provided in addition to food reinforcement. After several training sessions, monkeys could increase the activity of newly isolated cells by 50 to 500 percent above rates before reinforcement. 相似文献
6.
Percolation is a statistical concept that describes the formation of an infinite cluster of connected particles or pathways. Lowering the percolation threshold is a critical issue to achieve light and low-cost conductive composites made of an insulating matrix loaded with conductive particles. This has interest for applications where charge dissipation and electrical conductivity are sought in films, coatings, paints, or composite materials. One route to decreasing the loading required for percolation is to use rod-like particles. Theoretical predictions indicate that this may also be achieved by altering the interaction potential between the particles. Although percolation may not always respond monotonically to interactions, the use of adhesive rods can be expected to be an ideal combination. By using a system made of carbon nanotubes in an aqueous surfactant solution, we find that very small attraction can markedly lower the percolation threshold. The strength of this effect can thereby have direct technological interest and explain the large variability of experimental results in the literature dealing with the electrical behavior of composites loaded with conducting rods. 相似文献
7.
C. Igathinathane L.O. Pordesimo E.P. Columbus W.D. Batchelor S.R. Methuku 《Computers and Electronics in Agriculture》2008,63(2):168-182
Quick and accurate particle size distribution analysis is desirable in various technical fields that handle granular or particulate materials including size reduction. We developed an ImageJ plugin that extracts the dimensions from a digital image of disjoint particles after identifying their shapes and determines their particles size distribution. We established that the major and minor axes of ImageJ fitted ellipse along with the developed correction factors efficiently determined dimensions of particles. This paper describes the plugin development and its application to food grains and ground biomass. Using computer generated geometrical shapes as reference objects, a shape identification strategy that addresses common geometric shapes such as square, inclined square, rectangle, inclined rectangle, circle, ellipse, and inclined ellipse was developed. The strategy used only three newly defined shape parameters to identify objects, such as reciprocal aspect ratio, rectangularity, and feret major axis ratio from the standard outputs generated by ImageJ. Evaluation of effects of the particles shape, size, and orientation on the deviation from the reference particle's length and width indicated that the mean absolute deviations of all these factors were less than 1.3%. Developed plugin was applied successfully to analyze the dimensions and size distribution of food grains and ground Miscanthus particles images. The plugin produced quick and accurate size distribution of particles from digital images and can be applied to variety of particle analysis applications. 相似文献
8.
Rats easily discriminate between two types of subcortical brain shock which differ in reinforcing properties. When both stimuli are either neutral or positively reinforcing subjects have difficulty in responding differentially to the two types of electrical stimulation of the brain. Possible implications for a theory concerning a generalized or diffuse reinforcement system are discussed. 相似文献
9.
引入碳纤维作为增强手段,通过设计不同的工艺结构,探究其对木塑复合材力学性能的增强效果。板材结构设计方案有CF313(3 mm表层木塑板+碳布+1 mm芯层木塑板+碳布+3 mm表层木塑板)、CF232(2 mm表层木塑板+碳布+3 mm芯层木塑板+碳布+2 mm表层木塑板)、CF151(1 mm表层木塑板+碳布+5 mm芯层木塑板+碳布+1 mm表层木塑板)、CF070(碳布贴在最外层)、CF7(不添加碳布的空白实验)。研究结果表明,CF070复合材的弯曲强度最大;CF151的弹性模量最大,即碳纤维放在近表层位置时,弯曲性能较好,但拉伸时木塑表层容易拉断;放在靠近中心位置时复合材的拉伸强度和冲击强度提高幅度较大。综合考虑各性能,表层厚度为2 mm时可最大程度发挥碳布优势、增强木塑复合材料力学性能。 相似文献
10.
11.
根据热应力的基本原理,对竹筋混凝土在热、湿变化作用下的热湿应力变化与破坏进行了试验与分析.结果显示,竹材横向热湿膨胀系数大于纵向热湿膨胀系数,且大于混凝土的热湿膨胀系数.热湿同时增大在竹筋内产生的压应力超过竹材料抗压强度时,竹筋内部损坏而降低其抗拉强度,热湿同时减小产生的拉应力大于竹筋与混凝土的表面结合应力时,降低竹筋对构件的加强筋作用.其中温湿度降低是竹筋混凝土在设计工况下运行中产生破坏的重要原因之一. 相似文献
12.
Individual carbocyanine dye molecules in a sub-monolayer spread have been imaged with near-field scanning optical microscopy. Molecules can be repeatedly detected and spatially localized (to approximately lambda/50 where lambda is the wavelength of light) with a sensitivity of at least 0.005 molecules/(Hz)(1/2) and the orientation of each molecular dipole can be determined. This information is exploited to map the electric field distribution in the near-field aperture with molecular spatial resolution. 相似文献
13.
以某机械制造有限公司钢结构厂房加固工程为实例,采取增大截面法和局部补强的方法,使原有承载力不满足的构件达到现有规范抗震承载力的要求,以提高结构整体抗震性能。 相似文献
14.
Corte AE 《Science (New York, N.Y.)》1963,142(3591):499-501
If a hetrogeneous mixture of particles of various sizes is frozen and thawed repeatedly, the particles are sorted into relatively uniformn groups by size. The movement of particles depends on the amount of water between the ice-water interface and the particle, the rate of freezing, the distribution of the particles by size, and the orientation of the freeze-thaw plane. 相似文献
15.
以木屑为基质、真菌菌丝为粘结物质,采用无胶胶合方法制备菌丝-木屑生物质复合材料;参照GB/T17657—2013《人造板及饰面人造板理化性能试验方法》,测试菌丝-木屑生物质复合材料的抗拉强度、静曲强度、内结合强度;采用扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR),分析菌丝-木屑生物质复合材料的微观结构、主要化学成分及材料成型机理。结果表明:制备的菌丝-木屑生物质复合材料,是一种新型可降解木质复合材料;灵芝菌丝-木屑材料、木耳菌丝-木屑材料的密度,分别在为0.64~0.70、0.68~0.78 g/cm~3之间;FTIR分析显示,两种菌丝对纤维素、半纤维素、木质素均有一定的降解,灵芝菌丝对木质素的降解程度略大于木耳菌丝;SEM观察显示,以三维网状结构存在于木屑表面及孔隙中,将散碎的木屑有效的粘结成为整体;力学性能测试显示,菌丝的生长情况对材料的力学强度有一定的影响,但是菌丝-木屑生物质复合材料力学性能仅为中密度纤维板的1/4。 相似文献
16.
The size of suspended particulate matter in air 总被引：2，自引：0，他引：2
R E Lee 《Science (New York, N.Y.)》1972,178(61):567-575
By means of the NASN cascade impactor the particle sizes of ambient aerosols can be measured by fractionating the particles according to their aerodynamic dimensions, and the fractions can be quantified gravimetrically. Data obtained with this instrument show that particulate matter suspended in urban air in the United States and Great Britain is remarkably uniform in distribution and that the particles are predominantly less than 1 microm in diameter. In Ankara, Turkey, the high proportion of particles larger than 1 microm in diameter are associated with the incomplete combustion of lignite; particulate concentrations in Ankara, however, are considerably higher than those measured elsewhere. The growth of particles in air during temperature inversions occurs in Cincinnati; the greater proportion of large particles found there during inversion periods can account for the reduction in visibility. Aerosols in the vicinity of highways are composed of particles larger than those found some distance away because of the reentrainment of debris by the traffic-induced turbulence. On the other hand, highway configuration and traffic volume have little effect on the size distribution of aerosols in samples collected away from the turbulence area of the roadway. Aerosols measured inside buildings are predominantly smaller in size and exhibit a narrower range of sizes than aerosols outside buildings. 相似文献
17.
铺装结构及密度对玉米秸秆轻质复合板性能的影响 总被引：1，自引：1，他引：0
为充分利用玉米秸秆并制备性能优越的轻质复合材料,通过对玉米秸秆内外表面特性的分析,采用机械疏解重组其胶合结构单元,以脲醛树脂为胶黏剂,制备定向和均向2种玉米秸秆轻质复合板。本文研究了不同铺装方式和密度对板材静曲强度(MOR)、弯曲弹性模量(MOE)、内结合强度(IB)、吸水厚度膨胀率(TS)、吸水率(WA)的影响。结果表明:定向铺装结构可以增强复合板材的MOR、MOE、IB,相同密度下定向玉米秸秆复合板(OCSB)的纵向静曲强度(MOR∥)和纵向弹性模量(MOE∥)约为均向玉米秸秆复合板(HCSB)的3倍,IB约为4~5倍。OCSB的MOR∥、MOE∥明显大于横向静曲强度(MOR#x22A5;)、横向弹性模量(MOE#x22A5;);OCSB密度为0.3 g/cm3时,MOR∥约为MOR#x22A5;的3.5倍,MOE∥约为MOE#x22A5;的5倍。OCSB的MOR#x22A5;均大于HCSB的MOR(密度0.3 g/cm3除外),OCSB的MOE#x22A5;均小于HCSB。OCSB和HCSB的MOR、MOE在试验范围内都随着密度的增加而增加;当OCSB密度为0.6 g/cm3时,MOR∥为25.24 MPa,MOE∥达到4 216 MPa,其物理力学性能够满足在民用建筑中的使用。此外,OCSB的TS、WA均小于HCSB。 相似文献
18.
采用碳纤维布和玻璃纤维布与中密度纤维板复合,研究纤维布种类、胶粘剂品种、涂胶量及纤维板基材厚度等因素对纤维增强聚合物／MDF复合板性能的影响。结果表明：对于复合板静曲强度和弹性模量的提高,碳纤维布的效果优于玻璃纤维布;酚醛胶单面涂胶量为180g／m2时,复合板的MOR、MOE和他分别达到3633．8、62．5、1．046MPa;环氧胶单面涂胶量为120g／m2时,复合板的MOR和MOE分别为3900．5、49．58MPa;中密度纤维板厚度不同,其静曲强度和弹性模量提高量也不同,FRP对薄板的增强效果优于厚板。 相似文献
19.
Bunker BC Rieke PC Tarasevich BJ Campbell AA Fryxell GE Graff GL Song L Liu J Virden JW McVay GL 《Science (New York, N.Y.)》1994,264(5155):48-55
Processing routes have been developed for the production of thin ceramic films through precipitation from aqueous solutions. The techniques are based on crystal nucleation and growth onto functionalized interfaces. Surface functionalization routes have been developed by the mimicking of schemes used by organisms to produce complex ceramic composites such as teeth, bones, and shells. High-quality, dense polycrystalline films of oxides, hydroxides, and sulfides have now been prepared from "biomimetic" synthesis techniques. Ceramic films can be synthesized on plastics and other materials at temperatures below 100 degrees C. As a low-temperature process in which water rather than organic solvents is used, this synthesis is environmentally benign. Nanocrystalline ceramics can be produced, sometimes with preferred crystallite orientation. The direct deposition of high-resolution patterned films has also been demonstrated. The process is well suited to the production of organic-inorganic composites. 相似文献
20.
林区不同结构类型的桥梁,由于设计、施工、维修养护等诸原因,经过长期的车辆运行,存在着不同程度的破坏和损伤,承载能力及通过能力难以满足现行荷载和日益增长交通量的需要,迫切需要改建或加固补强。本文阐述了林区桥梁改建加固的实用价值和经济效果,并根据其特点介绍了几种可行方案。同时据丰林大桥静、动荷载试验及外观检查结果,提出了加固补强的具体方法。 相似文献