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61.
Ethylene–propylene–diene terpolymer (EPDM) was modified by bromination reaction. Blending the resulting brominated EPDM with natural rubber (STR5L) and blending the unmodified EPDM with STR5L at various compositions were carried out. The rheological properties of the blends were investigated using a capillary extrusion. Shear flow curves of the pure rubbers and their blends illustrated the pseudoplastic property as shear thinning behavior with a power law index n < 1. True shear viscosity of all blends showed the negative deviation in relation to their additive values. Rheological behavior and two Tg's found from the DSC thermograms at all blend compositions indicated blend incompatibility for both sets of blends. The incompatibility of the vulcanized blends was also found by measuring the spin–spin relaxation time T2 by pulsed NMR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 837–847, 2003 相似文献
62.
P.L. Lin P.Y. Huang P.W. Huang H.C. Hsu C.C. Chen 《Computer methods and programs in biomedicine》2014
Teeth segmentation for periapical raidographs is one of the most critical tasks for effective periapical lesion or periodontitis detection, as both types of anomalies usually occur around tooth boundaries and dental radiographs are often subject to noise, low contrast, and uneven illumination. In this paper, we propose an effective scheme to segment each tooth in periapical radiographs. The method consists of four stages: image enhancement using adaptive power law transformation, local singularity analysis using Hölder exponent, tooth recognition using Otsu's thresholding and connected component analysis, and tooth delineation using snake boundary tracking and morphological operations. Experimental results of 28 periapical radiographs containing 106 teeth in total and 75 useful for dental examination demonstrate that 105 teeth are successfully isolated and segmented, and the overall mean segmentation accuracy of all 75 useful teeth in terms of (TP, FP) is (0.8959, 0.0093) with standard deviation (0.0737, 0.0096), respectively. 相似文献
63.
64.
Pramod Kandanarachchi Andrew Guo Dmytro Demydov Zoran Petrovic 《Journal of the American Oil Chemists' Society》2002,79(12):1221-1225
The kinetics and mechanism of the hydroformylation of soybean oil by homogeneous ligand-modified rhodium catalysts were investigated
at 70–130°C and 4000–11,000 kPa. The effects of reaction rates on systematic variations in reaction parameters were evaluated
in order to develop an industrial process to convert vegetable oils to polyaldehydes. The activation energies in the presence
of triphenylphosphine (Ph3P) (61.1±0.8 kJ/mol) (mean±SD) and triphenyl phosphite [(PhO)3P] (77.4±5.0 kJ/mol) were determined. The catalyst was deactivated at temperatures higher than 100°C. An evaluation of the
effects of the reaction parameters on initial rates yielded the rate laws for Ph3P {rate=k [olefin][Rh(CO)2Acac]1.1 [Ph3P]−0.5 (pH2+pCO)1.4, where Rh(CO)2Acac is (acetylacetonato)dicarbonylrhodium (I)} and (PhO)3P {rate=[olefin] [Rh(CO)2Acac]1.2 [(PhO)3P]−0.8 (pH2+pCO)0.9 at total pressures lower than 7000 kPa, and rate =[olefin] [Rh(CO)2Acac]1.2 [(PhO)3P]−0.8(pH2+pCO)1.7 at total pressures higher than 7000 kPa}. 相似文献
65.
泽朗准 《自动化与仪器仪表》2014,(7):105-106
牛顿第二定律是经典力学的基本定律之一,为了形象、直观、准确地验证牛顿第二定律,本文利用数字实验系统生动地展示F=ma的关系。通过本实验可以使学生获得更直观的教学感受。 相似文献
66.
为研究火药的实际燃烧规律,建立了定容条件下火药燃烧的修正数学模型,分析了火药实际弧厚的分布及变化、点火不同步和燃速系数变化等因素对火药实际燃烧规律的影响。在此基础上,用考虑综合因素的修正数学模型对定容条件下火药的实际燃烧过程进行了模拟,计算值与实验结果具有较好的一致性,说明修正模型所建立的假设及处理方案是合理的。 相似文献
67.
The forced convective heat transfer characteristics for incompressible power-law fluids past a bundle of circular cylinders have been investigated numerically. The cylinder-to-cylinder hydrodynamic interactions have been approximated via a simple cell model. The momentum and energy equations have been solved using a finite difference based numerical method for a range of physical and kinematic conditions. The role of the two commonly used thermal boundary conditions, namely, constant temperature or constant heat flux, on heat transfer characteristics has also been studied. Extensive numerical results elucidating the effect of shear-thinning viscosity on the values of Nusselt number have been obtained for Peclet numbers ranging from 1 to 5000, Reynolds number in the range 1-500, flow behaviour index 1?n?0.5 and three values of voidages, namely, 0.4, 0.5 and 0.6, typical of tubular heat exchangers and tube banks. Under all conditions, varying levels of enhancement in Nusselt number are observed due to shear-thinning behaviour. The surface averaged Nusselt number shows strong dependence on the values of voidage, power-law index, Reynolds and Peclet numbers. The paper is concluded by presenting comparisons with the scant experimental results available in the literature. 相似文献
68.
69.
为探究过度开采对地下水水化学特征的影响,通过对比分析研究区1997年和2010年的地下水水位与水质资料,研究了过度开采条件下地下水水位与水化学特征的动态规律及两者之间的联系。研究结果表明:1997年和2010年研究区地下水水位与水化学特征的空间变化规律具有很高的一致性,表现为地下水水位降幅较大的区域对应的镁离子、硫酸盐含量增幅也相对较大,地下水水化学特征受地下水水位变化的影响较大。空间叠加分析结果表明:镁离子、硫酸盐与地下水水位变化较大的区域空间重合率分别为72.2%,53.1%。过度开采通过改变地下水补径排条件及饱和带、非饱和带的水环境变化对地下水水化学特征产生影响,因此对于地下水不可盲目、过度开采。 相似文献
70.
《Information Processing Letters》2014,114(6):317-321
We propose an output-sensitive algorithm for the enumeration of all maximal bicliques in a bipartite graph, tailored to the case when the degree distribution in one partite set is very skewed. We accomplish a worst-case bound better than previously known general bounds if, e.g., the degree sequence follows a power law. 相似文献