两种溃坝模型在唐家山堰塞湖溃决模拟中的对比

基于唐家山堰塞坝溃决的实测数据,使用BREACH模型及中国水科院DB-IWHR模型,对唐家山堰塞坝溃决过程进行了反演分析,并对两种模型进行参数敏感性分析。研究结果表明:使用针对唐家山的参数,两种模型均可较好地反演唐家山溃决洪水的过程,BREACH模型的下游坡比和孔隙率是对结果影响比较敏感的输入参数;DB-IWHR模型在冲刷参数和下游水深计算两方面做了改善,较好地解决了这一问题;DB-IWHR提供了一个Excel格式的计算软件,数值分析稳定性好,使用简洁客观,可供类似堰塞湖应急处置时参考。     

Probabilistic pseudo-morphology for grayscale and color images

Mathematical morphology offers popular image processing tools, successfully used for binary and grayscale images. Recently, its extension to color images has become of interest and several approaches were proposed. Due to various issues arising from the vectorial nature of the data, none of them imposed as a generally valid solution. We propose a probabilistic pseudo-morphological approach, by estimating two pseudo-extrema based on Chebyshev inequality. The framework embeds a parameter which allows controlling the linear versus non-linear behavior of the probabilistic pseudo-morphological operators. We compare our approach for grayscale images with the classical morphology and we emphasize the impact of this parameter on the results. Then, we extend the approach to color images, using principal component analysis. As validation criteria, we use the estimation of the color fractal dimension, color textured image segmentation and color texture classification. Furthermore, we compare our proposed method against two widely used approaches, one morphological and one pseudo-morphological.     

Manipulating the phase morphology in PPS/PA66 blends using clay

By adding a small amount of clay into poly(p‐phenylene sulfide) (PPS)/polyamide 66 blends, the morphology was found to change gradually from sea–island into cocontinuity and lamellar supramolecular structure, as increasing of clay content. Clay was selectively located in the PA66 phase, and the exfoliated clay layers formed an edge‐contacted network. The change of morphology is not caused by the change of volume ratio and viscosity ratio but can be well explained by the dynamic interplay of phase separation between PPS and PA66 through preferential adsorption of PA66 onto the clay layers and through layer–layer repulsion. This provides a means of manipulating the phase morphology for the immiscible polymer blends. The mechanical and tribological properties of PPS/PA66 blends with different phase morphologies (different clay contents) were studied. Both tensile and impact strength of the blends were found obviously increased by the addition of clay. The antiwear property was greatly improved for the blends with cocontinuous phase form. Our work indicates that the phase‐separating behavior of polymer blends contained interacting clay can be exploited to create a rich diversity of new structures and useful nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Morphology evolution of immiscible LDPE/PVC blends in the presence of compatibilizer and phase dispersant

Phase dispersion and coalescence in low‐density polyethylene (LDPE)/polyvinyl chloride (PVC) (70/30) blends influenced by compatibilizer and phase dispersant was studied. It was found that the morphology evolution of blends is sensitive to not only processing conditions (shear strength and mixing time) but also the added compatibilizer or phase dispersant. In our conditions, the stable phase morphology of each blend is obtained after mixing 15–25 min. In addition, the dispersed PVC phase in blends is easy to aggregate when the mixing rotor speed changed from high to low for the binary blends. As a compatibilizer, chlorided polyethylene (CPE) or nitrile rubber (NBR) can stabilize the morphology and hinder the coalescence of the dispersed PVC phase when added to the blends. However, the phase dispersant butadiene rubber (BR) or styrene butadiene rubber (SBR) could not stabilize the phase structure, although it could accelerate phase dispersion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 763–772, 2004     

Influence of composition and molecular mass on the morphology,crystallization and melting behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends

Results are reported on the influence of composition and molecular mass of components on the isothermal growth rate of spherulites, on the overall kinetic rate constant, on the primary nucleation and on the thermal behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends. The growth rate of PEO spherulites as well as the observed equilibrium melting temperatures decrease, for a given T_c or ΔT, with the increase of PMMA content.Such observations are interpreted by assuming that the polymers are compatible in the undercooled melt, at least in the range of crystallization temperatures investigated. Thermodynamic quantities such as the surface free energy of folding σ_e and the Flory-Huggins parameter χ₁₂ have been obtained by studying the dependence of the radial growth rate G and of the overall kinetic rate constant K from temperature and composition and the dependence of the equilibrium melting temperature depression ΔT_m upon composition, respectively.     

The Influence of Diphenyl Siloxane on Morphology and Physical Properties in the Poly(Imide Siloxane)(PIS) Copolymer

Various numbers of diphenyl-siloxane groups were incorporated in α,ω-bis(aminopropyl)polydimethylsiloxane (APPS) to prepare α,ω-bis(aminopropyl)-polydimethyldiphenylsiloxane (APPPS) oligomers of three different number-average molecular weights(Mn = 547,772,1210 g mol⁻¹).These APPPS oligomers were than used, together with 3,3′,4,4′-bezonphenone tetracarboxylic dianhydride (BTDA) and 2-2′-bis[4-(3-aminophenoxy)phenyl] sulfone (m-BAPS), to synthesize a series of APPPS containing poly(imide siloxane) (PIS) copolymers. Microstructural studies showed that at certain APPPS content, a critical microphase separation point existed, beyond which, microphase separation began to develop. This critical point of microphase separation was found to be affected by the Mn of the APPPS oligomers (8.0, 4.3 and 2.1 mol% for Mn of 547, 772 and 1,210 g mol⁻¹, respectively). Diphenyl-siloxane significantly improved compatibility between polyimide and polysiloxane segments. Physical studies showed that the introduction of diphenyl siloxane changed the thermal stabilities and mechanical properties of the PIS copolymers. These findings have potential applications for design purposes in engineering polymers.     

Preparation,morphology, and mechanical properties of elastomers based on α,ω‐dihydroxy‐polydimethylsiloxane/polystyrene blends

α,ω‐Dihydroxy‐polydimethylsiloxane/polystyrene (PDMS/PS) blends were prepared by the solution polymerization of styrene (St) in the presence of α,ω ‐dihydroxy‐polydimethylsiloxane (PDMS), using toluene as solvent and benzoyl peroxide (BPO) as initiator. The PDMS/PS blends obtained by this method are a series of stable, white gums, which were vulcanized to elastomers at room temperature with methyl‐triethoxysilicane (MTES). The use level of MTES was far more than the necessary amount used to end‐link hydroxy‐terminated chains of PDMS, with the excess being hydrolyzed to crosslinked networks, which were similar to SiO₂ and acted as filler. Investigations were carried out on the elastomeric materials by extraction measurement, swelling measurement, and scanning electron microscopy. The extraction data show that at each composition the amount of soluble fraction is less than expected and the difference between experimental and theoretical values becomes more and more significant as PS content increases. This is mainly due to the grafting of PS onto PDMS and the entanglement of PS in the interpenetrating polymer network (IPN), which consists of either directly linked PDMS chains or chains linked via PS grafts and is formed by free radical crosslinking of PDMS during the radical polymerization of St. PS grafted on PDMS is insoluble and PS entangled in the IPN is difficult to extract. Both render the soluble fraction to be less than expected. As the St content in preparing PDMS/PS blends increases, the probability of grafting PS onto PDMS also increases, which may subsequently produce a higher crosslinking level of PDMS networks that linked via PS grafts by radical crosslinking. As a result, not only the amount of insoluble PS increases but also PS entangled in the IPN is more difficult to extract. Scanning electron microscopy demonstrates that the elastomer system has a microphase‐separated structure and a certain amount of PS remains in the PDMS networks after extraction, which is in accordance with the extraction data. Moreover, the mechanical properties of the elastormeric materials have been studied in detail. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3542–3548, 2004     

Reactive Compatibilizer Precursors for LDPE/PA6 Blends, 4

Summary: The effectiveness of some thermoplastic elastomers grafted with maleic anhydride (MA) or with glycidyl methacrylate (GMA) as compatibilizer precursors (CPs) for blends of low density polyethylene (LDPE) with polyamide‐6 (PA) has been studied. The CPs were produced by grafting different amounts of MA or GMA onto a styrene‐block‐(ethylene‐co‐1‐butene)‐block‐styrene copolymer (SEBS) (KRATON G 1652), either in the melt or in solution. A commercially available SEBS‐g‐MA copolymer with 1.7 wt.‐% MA (KRATON FG 1901X) was also used. The effect of the MA concentration and of other characteristics of the SEBS‐g‐MA CPs was also studied. The specific interactions between the CPs and the blends components were investigated through characterizations of the binary LDPE/CP and PA/CP blends, in the whole composition range. It was demonstrated that the SEBS‐g‐GMA copolymers display poor compatibilizing effectiveness due to cross‐linking resulting from reactions of the epoxy rings of these CPs with both the amine and the carboxyl end groups of PA. On the contrary, the compatibilizing efficiency of the MA‐grafted elastomers, as revealed by the thermal properties and the morphology of the compatibilized blends, was shown to be excellent. The results of this study confirm that the anhydride functional groups possess considerably higher efficiency, for the reactive compatibilization of LDPE/PA blends, than those of the ethylene‐acrylic acid and ethylene‐glycidyl methacrylate copolymers investigated in previous works.

SEM micrograph of the 75/25 LD08/PA blend (with 2 phr SEBSMA1).     

不同形貌ZnO气敏材料的制备及影响气敏性因素分析

以锌盐和碱为原料,采用水热和溶剂热法合成了三种形貌的氧化锌粉体,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)对产物的结构和形貌及表面化学状态进行了表征,并将粉体制备成厚膜型气敏元件,测试了其对几种还原性气体的气敏性能,结果表明:在工作温度为395℃时,三种形貌氧化锌对相同浓度的同种测试气体的灵敏度大小顺序为:菜花状氧化锌﹥棒状氧化锌﹥六棱柱状氧化锌。并对影响氧化锌材料气敏性的各种因素进行了分析。