某电站坝区碎粒型结构面特征及成因机制分析

水电工程建设中,工程地质体中软弱结构面的正确认识和评价对大坝建基面选取及抗滑稳定问题影响重大。本文在大量现场调查和试验的基础上,分析了坝区碎粒型结构面的主要工程地质特征,包括空间分布、优势方向、形态及物质组成、物理性质、声波波速和地球化学特征;并通过初始建造和后期改造两个阶段的地质过程机制分析,对碎粒型结构面的成因机制进行了初步探讨。

碎粒型结构面特征及物理力学参数优化分析

某水电站坝区两岸的勘探平洞揭示了百余条挤压破碎带,兼具挤压错动和风化蚀变双重特征,其组成以碎粒岩为主,空间分布不均。作为一种软弱结构面,其工程地质特征及物理力学参数对坝区岩体利用和枢纽建筑物布置具有重要影响。通过现场调查及物理试验,分析统计了其发育分布特征、物理性质;结合现场碎粒型结构面的抗剪强度试验,获得了抗剪强度参数,根据点群趋势,分别按优定斜率法和最小二乘法取值。为避免因某些薄弱单元的累进性破坏而危及工程岩体的整体安全,建议使用优定斜率法成果的下限值作为试验成果标准值。

6种非常规动物皮革种类的鉴别分析

本文简要介绍了真假皮革常用的鉴别方法,以6种动物皮革为试验材料,对于皮革外观形态进行观察并分析显微镜下皮革粒面结构及横截面的结构特征,为6种动物皮革种类鉴别提供参考。

Microstructures and mechanical properties of BP/7A04 Al matrix composites

The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compared with those of BP/7A04 Al matrix composites. The results show that the basalt particles are dispersed in the Al matrix and form a strong bonding interface with the Al matrix. SiO2 at the edge of the basalt particles is continuously replaced by Al2O3 formed in the reaction, forming a high-temperature reaction layer with a thickness of several tens of nanometers, and Al2O3 strengthens the bonding interface between basalt particles and Al matrix. The dispersed basalt particles promote the dislocation multiplication, vacancy formation and precipitation of the matrix, and the precipitated phases mainly consist of plate-like η(MgZn2) phase and bright white band-shaped or ellipsoidal T (Al2Mg3Zn3) phase. The bonding interface, high dislocation density and dispersion strengthening phase significantly improve the mechanical properties of the composites. The yield strength and ultimate tensile strength of BP/7A04 Al matrix composites are up to 665 and 699 MPa, which increase by 11.4% and 10.9% respectively compared with 7A04 Al alloy without basalt particles.

Electronic and geometric structure of the copper-ceria interface on Cu/CeO2 catalysts

The atomic structure of the active sites in Cu/CeO2 catalysts is intimately associated with the copper-ceria interaction. Both the shape of ceria and the loading of copper affect the chemical bonding of copper species on ceria surfaces and the electronic and geometric character of the relevant interfaces. Nanostructured ceria, including particles(polyhedra), rods, and cubes, provides anchoring sites for the copper species. The atomic arrangements and chemical properties of the(111),(110) and(100) facets, preferentially exposed depending on the shape of ceria, govern the copper-ceria interactions and in turn determine their catalytic properties. Also, the metal loading significantly influences the dispersion of copper species on ceria with a specific shape, forming copper layers, clusters, and nanoparticles. Lower copper contents result in copper monolayers and/or bilayers while higher copper loadings lead to multi-layered clusters and faceted particles. The active sites are usually generated via interactions between the copper atoms in the metal species and the oxygen vacancies on ceria, which is closely linked to the number and density of surface oxygen vacancies dominated by the shape of ceria.

Tailoring the surface structures of iron oxide nanorods to support Au nanoparticles for CO oxidation

Iron oxide supported Au nanomaterials are one of the most studied catalysts for low-temperature CO oxidation.Catalytic performance not only critically depends on the size of the supported Au nanoparticles(NPs)but also strongly on the chemical nature of the iron oxide.In this study,Au NPs supported on iron oxide nanorods with different surface properties throughβ-FeOOH annealing,at varying temperatures,were synthesized,and applied in the CO oxidation.Detailed characterizations of the interactions between Au NPs and iron oxides were obtained by X-ray diffraction,transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy.The results indicate that the surface hydroxyl group on the Au/FeOOH catalyst,before calcination(Au/FeOOH-fresh),could facilitate the oxygen adsorption and dissociation on positively charged Au,thereby contributing to the low-temperature CO oxidation reactivity.After calcination at 200℃,under air exposure,the chemical state of the supported Au NP on varied iron oxides partly changed from metal cation to Au0,along with the disappearance of the surface OH species.Au/FeOOH with the highest Au0 content exhibits the highest activity in CO oxidation,among the as-synthesized catalysts.Furthermore,good durability in CO oxidation was achieved over the Au/FeOOH catalyst for 12 h without observable deactivation.In addition,the advanced identical-location TEM method was applied to the gas phase reaction to probe the structure evolution of the Au/iron oxide series of the catalysts and support structure.A Au NP size-dependent Ostwald ripening process mediated by the transport of Au(CO)x mobile species under certain reaction conditions is proposed,which offers a new insight into the validity of the structure-performance relationship.

Effective Thermal Conductivity with Convection and Radiation in Packed Bed

Effective thermal conductivity with convection and radiation is analyzed by the homogenization method. This method can precisely represent the microstructure of a packed bed. In this study, the effects of parameters such as the radiation emissivity, temperature, contact area and particle size of the packed bed on the conductivity have been estimated. For example, heat transfer by radiation does not dominate if the material has voids of less than l mm in size. Moreover, the effects of contact area and pressure on effective thermal conductivity are negligible for thermal radiation. By considering the microscopic behavior of a packed bed, the homogenization method is thus a powerful tool for estimating the bed＇s effective thermal conductivity.

Octahedral PtNi nanoparticles with controlled surface structure and composition for oxygen reduction reaction

Controlling the surface structure and composi- tion at the atomic level is an effective way to tune the cat- alytic properties of bimetallic catalysts. Herein, we demon- strate a generalized strategy to synthesize highly monodis- perse, surfactant-free octahedral PtxNi1-x nanoparticles with tunable surface structure and composition. With increasing the Ni content in the bulk composition, the degree of concave- ness of the octahedral PtxNi1-x nanoparticles increases. We systematically studied the correlation between their surface structure/composition and their observed oxygen reduction activity. Electrochemical studies have shown that all the octa- hedral PtxNi1-x nanoparticles exhibit enhanced oxygen reduc- tion activity relative to the state-of-the-art commercial Pt/C catalyst. More importantly, we find that the surface struc- ture and composition of the octahedral PtxNi1-x nanoparti- cles have significant effect on their oxygen reduction activ- ity. Among the studied PtxNi1-x nanoparticles, the octahedral PtlNi1 nauoparticles with slight concaveness in its （111） facet show the highest activity. At 0.90 V vs. RHE, the Pt mass and specific activity of the octahedral PhNil nanoparticles are 7.0 and 7.5-fold higher than that of commercial Pt/C catalyst, re- spectively. The present work not only provides a generalized strategy to synthesize highly monodisperse, surfactant-free octahedral PtxNi1-x nanoparticles with tunable surface struc- ture and composition, but also provides insights to the struc- ture-activity correlation.

Aggregate Development and Organic Matter Storage in Mediterranean Mountain Soils

Soil aggregation and organic matter of soils from the pre-Pyrenean range in Catalonia (NE Spain) were studied,in order to assess their quality as carbon sinks and also to select the best soil management practices to preserve their quality.Aggregate stability,organic carbon and micromorphology were investigated.The highest amount of organic carbon was found in alluvial,deep soils (228 Mg C ha -1 ),and the lowest was in a shallow,stony soil with a low plant cover (78 Mg C ha -1 ).Subsurface horizons of degraded soils under pastures were the ones with smaller and less-stable aggregates.Fresh residues of organic matter (OM) were found mostly in interaggregate spaces.Within the aggregates there were some organic remains that were beginning to decompose,and also impregnative nodules of amorphous OM.Although OM was evenly distributed among the aggregate fractions,the larger blocky peds had more specific surface,contained less decomposed OM and had a lower organic/mineral interphase than smaller crumb aggregates,which were also more stable.Soil carbon storage was affected primarily by the OM inputs in the surface horizons.In order to store organic carbon over the mid- and long-term periods,the mechanisms favouring structuration through biological activity and creating small aggregates with intrapedal stable microporosities seemed to be the most effective.

Study of dynamic hydrophobicity of micro-structured hydrophobic surfaces and lotus leaves

The dynamic wetting characteristics of water droplets on silicon wafers with microscale regular pillars structures and fresh lotus leaves are investigated experimentally.We measured the static contact angle,contact angle hysteresis,and roll-off angle of water droplets on both of these superhydrophobic surfaces with a high speed contact angle meter.The dynamic contact angles and internal velocity distribution of water droplets on superhydrophobic surfaces were studied with a high-speed camera system and a particle image velocimetry (PIV) system,respectively.We found that the acceleration of water droplets when they slide off lotus leaves is greater than that of water droplets sliding off the silicon wafers with microscale pillar structures although the static contact angles of water droplets on lotus leaves are slightly smaller than those on the silicon wafers.The reason is that water droplets sliding off lotus leaves have smaller contact angle hysteresis and larger slip velocities.These results indicate that the dynamic contact angle hysteresis and sliding acceleration of liquid droplets are more suitable for reflecting the hydrophobicity of material surfaces compared with static contact angles.Our experiments also show that lotus leaves with multiscale micro/nanostructures have stronger hydrophobicity and self-cleaning properties compared with the micro-structured superhydrophobic surfaces.

Soil Microbial Responses to Biochars Varying in Particle Size,Surface and Pore Properties

Biochars are known for their heterogeneity, especially in pore and surface structure associated with pyrolysis processes and sources of feedstocks. The surface area of biochar is likely to be an important determinant of the extent of soil microbial attachment, whereas the porous structure of biochar is expected to provide protection for soil microorganisms. Potential interactions between biochars from different sources and with different particle sizes were investigated in relation to soil microbial properties in a short-term incubation study. Three particle size （sieved） fractions （0.5-1.0, 1.0-2.0 and 2.0-4.0 mm） from three woody biochars produced from jarrah wood, jarrah and wandoo wood and Australian wattle branches, respectively, were incubated in soil at 25 ℃ for 56 d. Observation by scanning electron microscopy （SEM） and characterisation of pore and surface area showed that all three woody biochars provided potential habitats for soil microorganisms due to their high porosity and surface areas. The biochars were structurally heterogeneous, varying in porosity and surface structure both within and between the biochar sources. After the 56-d incubation, hyphal colonisation was observed on biochar surfaces and in larger biochar pores. Soil clumping occurred on biochar particles, cementing and covering exposed biochar pores. This may have altered surface area and pore availability for microbial colonisation. Transient changes in soil microbial biomass, without a consistent trend, were observed among biochars during the 56-d incubation.

Study on swelling model and thermodynamic structure of native konjac glucomannan

We investigated the higher structure of konjac glucomannan (KGM) in the amorphous state and solution using a laser particle size analyzer and a water activity meter. The results show that the thermodynamic structures of native KGM were primarily composed of the lamella structure units, which involve both granular crystalline and amorphous regions, and that the connection zones of such units contained both loose and tight aggregation regions. The value of surface tension (σ) of native KGM, resting with the density of its hydroxyl groups' self-association, was an important parameter to analyze the higher structures of native KGM in the thermodynamic swelling model of native KGM.

Spherical Kadomtsev-Petviashvili Solitons in a Suprathermal Complex Plasma

The nonlinear aspects of nonplanar dust acoustic (DA) solitary waves are investigated in an unmagnetized complex plasma comprising of cold dust grains,kappa-distributed ions as well as electrons.The nonplanar DA solitons are studied based on the reductive perturbation technique.It is shown that the evolution of DA solitons is governed by a spherical Kadomtsev-Petviashvili (sKP) equation and then the impact of suprathermality on the spatial structure as well as the nature of DA soliton is studied.It seems that the properties of DA solitons in nonplanar geometry are quite different from that of the planar solitons.