以棕榈酸为基的复合相变材料的制备和表征   总被引：8，自引：0，他引：8       下载免费PDF全文

张静  丁益民  陈念贻 《盐湖研究》2006,14(1):9-13

采用溶胶—凝胶法,以正硅酸乙酯(TEOS)和棕榈酸(PA)为主原料,制备了一种有机—无机纳米复合相变材料(CPCM)。在研究了加水量、溶剂量、pH值、温度以及PA的百分含量对材料制备影响的基础上,进行了实验条件的优化。用扫描电镜、红外光谱分析、差示扫描量热分析研究了其结构与性能,结果表明,该复合材料为纳米级颗粒的聚集体,具有良好的储热能力和循环热稳定性,有望用于太阳能利用等领域。  相似文献   

莱州浅滩表层沉积物重矿物分布特征及物源识别     

孔庆祥  金秉福  刘春暖 《海洋科学》2014,38(12):86-93

对莱州浅滩80个表层沉积样品进行碎屑矿物分析,主要研究重矿物分布特征,并探讨其物质来源。研究表明:本区优势矿物组合为普通角闪石-绿帘石-黑云母-褐铁矿,可划分成5个矿物区。浅滩滩体(Ⅰ区和Ⅱ区)稳定矿物(以榍石、石榴子石为主)含量高。浅滩北部顶端(Ⅱ区)金属矿物类分布集中,褐铁矿含量近1/3;浅滩两侧(Ⅲ区和Ⅳ区)为云母类高值区。浅滩西侧海域(Ⅳ区)含大量自生黄铁矿,为还原性沉积环境;浅滩西北(Ⅴ区)重矿物含量最高,优势矿物组合为普通角闪石-绿帘石-石榴子石。依据重矿物种类和矿物组合特征,结合陆源近岸河道及黄河沉积物矿物特征,研究显示:浅滩滩体沉积物主要为近岸河流输送,而浅滩两侧沉积物是双重来源,既来自陆地近岸又来自黄河物质向东的输送。矿物区的变化反映了该区水动力的复杂性。重矿物分布特征对研究本区海洋动力环境和探讨浅滩物源都有重要意义。  相似文献   

Study of deposition of fine sediment within the pores of a coarse sediment bed stream     

N.K.KHULLAR  U.C.KOTHYARI  K.G.Ranga RAJU 《国际泥沙研究》2013,28(2):210-219

Elaborate experiments were performed in a 30 m long, 0.5 m deep and 0.2 m wide laboratory flume to study the process of infiltration of fine sediment into the pores of coarse sediment forming the channel bed material. Different concentrations of suspended load of fine sediment of size 0.064 mm were passed over the channel bed made up of three different types of coarse sediments; two uniform and one nonuniform. The proportion of fine sediment infiltrated into the pores of bed material for each equilibrium concentration of suspended load of fine sediment in the flow was studied during several experimental runs. The proportion of fine sediment within the pores of bed material increased with an increase in the equilibrium concentration of suspended load of fine sediment in the flow. This process continued till the pores within the coarse sediment bed were filled up to the capacity with the fine sediment transported by the flow in suspension. The theoretical value was identified for limit for maximum proportion of fine sediment that can be present within the pores of bed material. On further increase in the concentration of suspended load of fine sediment in the flow, deposition of fine sediment occurs on the surface of the flume bed in the form of ripples of the fine sediment. This condition is defined as 'depositional condition'. Experimental observations on these and related aspects are presented herein.  相似文献   

Bedrock versus superficial deposits in the Swiss Jura Mountains: what is the legitimate soil parent material?     

Loraine Martignier  Thierry Adatte  Eric P. Verrecchia 《地球表面变化过程与地形》2013,38(4):331-345

Soils are generally considered to be the result of in situ weathered products of geological substrata. Nevertheless, the Earth's surface is mainly composed of superficial deposits made of sediments reworked during periods of climate instability (glaciation, aridification, flooding, etc.). But to what extent do these deposits influence present‐day soil development and/or lessen the contribution of the geological substratum? In the Swiss Jura Mountains, characterization and distribution of superficial deposits along a toposequence are used in order to decipher the polygenic sources of soil parent materials and question the importance of lithodependence in soil development. The in situ weathering material and the allochtonous deposits are discriminated through analysis of mineralogical composition, grain size distribution of the soil mineral fraction, and multivariate statistical treatment. As expected, calcite is dominant in the autochonous mineral phase, leading to high pH values in deep soil layers. However, the mineralogical composition of the surficial deposits is made of local mineral components mixed with allochtonous aeolian deposits. This exogenous material is dominated by quartz and phyllosilicates, and is reflected by low pH values in soil surficial horizons. The grain size distribution curves of the insoluble residue from bedrocks are unimodal and dominated by fine loam and clays. In contrast, surficial deposits display polymodal curves, demonstrating the contribution of various aeolian episodes and/or sources. Analysis of the surface texture of quartz sand grains shows glacial marks intersected by aeolian shock marks, indicating the posteriority of wind transportation. Loess material originates from Alpine moraines of the Swiss Plateau and is mixed with deposits originating from more proximal Jura moraines, diluting the Alpine signature. Consequently, the soil development does not follow the expected and conventional decalcification process, but is directly influenced by the origin of the primary sediments (even when present only in small amounts) and their evolution. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Quantifying rainfall controls on catchment‐scale landslide erosion in Taiwan     

Yi‐Chin Chen  Kang‐tsung Chang  Yu‐Jia Chiu  Sze‐Man Lau  Hong‐Yuan Lee 《地球表面变化过程与地形》2013,38(4):372-382

Landslide erosion is a dominant hillslope process and the main source of stream sediment in tropical, tectonically active mountain belts. In this study, we quantified landslide erosion triggered by 24 rainfall events from 2001 to 2009 in three mountainous watersheds in Taiwan and investigated relationships between landslide erosion and rainfall variables. The results show positive power‐law relations between landslide erosion and rainfall intensity and cumulative rainfall, with scaling exponents ranging from 2·94 to 5·03. Additionally, landslide erosion caused by Typhoon Morakot is of comparable magnitude to landslide erosion caused by the Chi‐Chi Earthquake (M_W = 7·6) or 22–24 years of basin‐averaged erosion. Comparison of the three watersheds indicates that deeper landslides that mobilize soil and bedrock are triggered by long‐duration rainfall, whereas shallow landslides are triggered by short‐duration rainfall. These results suggest that rainfall intensity and watershed characteristics are important controls on rainfall‐triggered landslide erosion and that severe typhoons, like high‐magnitude earthquakes, can generate high rates of landslide erosion in Taiwan. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Effects of material variability on the ductility of composite beams and overstrength coefficients     

Srour Nofal  Hugues Somja  Mohammed Hjiaj  Quang Huy Nguyen 《地震工程与结构动力学》2013,42(7):953-972

The aim of this paper is to investigate the plastic rotation capacity of composite beams as well as the overstrength factors for composite joints considering the actual European steel production. It relies on the statistical data of the mechanical properties of steel profiles and reinforcement bars produced in several European steel mills that have been collected during the European research project OPUS. Several steel and composite structures have been designed following the EN 1998 rules, and the effect of the statistical distribution of the steel properties on the design has been analyzed. In such structures, the first attainment of the rotation capacity is expected to happen in the hogging region. The plastic rotation capacity was evaluated using the so‐called standard beam concept. The moment–rotation curve was constructed by joining together the pre‐buckling branch, determined using a fiber model, and the post‐buckling part derived by considering the local plastic failure mechanism as suggested by Gioncu. A program in MATLAB (MATLAB version 7.10.0. Natick, Massachusetts: The MathWorks Inc., 2010) was developed to establish such curve for arbitrary composite beams. The predictions of the model compare favorably against the experimental results. On the basis of the probabilistic model for the mechanical properties of steel, we derive the statistical distribution of the maximum rotation defined at the intersection of the pre‐buckling and post‐buckling curves. Next, we estimate the so‐called overstrength factors. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Constitutive modeling of inherent anisotropy in a strain space multiple mechanism model for granular materials     

Kyohei Ueda  Susumu Iai 《国际地质力学数值与分析法杂志》2019,43(3):708-737

Consideration of fabric anisotropy is crucial to gaining an improved understanding of the behavior of granular materials. This paper presents a constitutive model to describe the sand behavior associated with fabric anisotropy within a framework of a strain space multiple mechanism model. In the proposed model, a second-order fabric tensor is extended by incorporating a new function that represents the effect of inherent (or initial fabric) anisotropy, along with three additional parameters: two of them, a₁ and a₂ , control the degree of anisotropy, and the second mode of inherent anisotropy can be expressed by introducing the parameter a₂ as well as the first mode by the parameter a₁ . The third parameter, θ₀ , expresses the principal direction of inherent anisotropy (eg, the normal vector direction of bedding planes relative to horizontal axis). The formulation of the dilative component of dilatancy (ie, positive dilatancy) is also extended to consider the effect of inherent anisotropy based on the interlocking mechanism. Experimental data on the complex anisotropic responses of Fraser River sand and Toyoura sand under monotonic loading is used to validate this model. The proposed model is shown to successfully capture anisotropic responses, which become contractive or dilative depending on different principal-stress directions, with a single set of anisotropy parameters; thus, the model is considered to possess the capability to simulate the anisotropic behaviors of granular materials. In addition to different loadings on the same fabric, the effects of different fabric anisotropies upon the sand behavior under the same loadings are also investigated.  相似文献   

Stiffness pathologies in discrete granular systems: Bifurcation,neutral equilibrium,and instability in the presence of kinematic constraints     

Matthew R. Kuhn  Florent Prunier  Ali Daouadji 《国际地质力学数值与分析法杂志》2019,43(5):888-918

The paper develops the stiffness relationship between the movements and forces among a system of discrete interacting grains. The approach is similar to that used in structural analysis, but the stiffness matrix of granular material is inherently nonsymmetric because of the geometrics of particle interactions and of the frictional behavior of the contacts. Internal geometric constraints are imposed by the particles' shapes, in particular, by the surface curvatures of the particles at their points of contact. Moreover, the stiffness relationship is incrementally nonlinear, and even small assemblies require the analysis of multiple stiffness branches, with each branch region being a pointed convex cone in displacement space. These aspects of the particle-level stiffness relationship give rise to three types of microscale failure: neutral equilibrium, bifurcation and path instability, and instability of equilibrium. These three pathologies are defined in the context of four types of displacement constraints, which can be readily analyzed with certain generalized inverses. That is, instability and nonuniqueness are investigated in the presence of kinematic constraints. Bifurcation paths can be either stable or unstable, as determined with the Hill–Bažant–Petryk criterion. Examples of simple granular systems of three, 16, and 64 disks are analyzed. With each system, multiple contacts were assumed to be at the friction limit. Even with these small systems, microscale failure is expressed in many different forms, with some systems having hundreds of microscale failure modes. The examples suggest that microscale failure is pervasive within granular materials, with particle arrangements being in a nearly continual state of instability.  相似文献   

紫外辐照条件下二维填料对聚丙烯耐老化行为的影响          下载免费PDF全文

郭凡  刘志启  李娜  王庭胜  李丽娟 《盐湖研究》2020,28(3):54-60

采用水热法合成了二维层状材料——镁镍铁水滑石(MgNiFe-LDH),考察不同水热时间和水热温度对MgNiFe-LDH合成的影响,通过X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)和热分析(TG/DTG)等测试方法,对样品的结构、形貌及热性能进行表征。将合成的MgNiFe-LDH添加至聚丙烯(PP)制备MgNiFe-LDH/PP复合材料,通过对材料加速老化测其力学性能,研究了添加MgNiFe-LDH前后材料机械性能变化。结果表明,当Mg~(2+):Ni~(2+):Fe~(3+)=2∶1∶1,水热温度140℃、水热时间24 h时,合成的MgNiFe-LDH为片状,形貌较为规整,颗粒粒径约为2μm。MgNiFe-LDH/PP复合材料经加速老化后,填充MgNiFe-LDH复合材料的抗老化性能优于纯PP,当MgNiFe-LDH的填充量为6 wt%复合材料拉伸强度不变,可明显提高PP的抗老化性能。  相似文献   

海洋环境微生物腐蚀机理研究进展   总被引：5，自引：0，他引：5  

张盾  吴佳佳 《海洋与湖沼》2020,51(4):821-828

微生物腐蚀(microbiologically influenced corrosion, MIC)是海洋环境中一种非常重要的腐蚀形式,其是微生物、环境、材料共同作用的结果,本文自MIC对海洋环境、菌株、材料性质的依赖性三个方面概述其机理的研究进展。在MIC对海洋环境的依赖性方面,突出溶解氧浓度和营养水平的影响规律与机制。在MIC对菌株的依赖性方面,首先介绍典型单菌株的腐蚀影响机制,然后分析混合菌株间不同菌株的腐蚀协同与拮抗作用,最后阐述复杂微生物群落的影响。在MIC对材料性质的依赖性方面,在总结基体化学成分与结构影响的基础上,介绍对MIC有抑制作用的典型表面的特性及其作用机制。  相似文献