Al-Mg MMH溶胶和钠土悬浮体的相互作用机理

通过流变参数、电泳淌度和pH值的测定,研究了无机盐(CaCl₂、KCl、NaCl)和pH值对铝镁混合金属氢氧化物与钠土悬浮体间相互作用的影响。发现随着混合金属氢氧化物含量的增加,钠土体系的pH值逐渐降低,而动切力(YP)先上升,经最大值后逐渐下降;当钠土体系为NaCl所饱和时,相同混合金属氢氧化物加量下YP的上升幅度明显减小,在实验混合金属氢氧化物浓度范围内,YP未出现峰值。混合金属氢氧化物/钠土体系的YP随pH值的变化曲线呈抛物线形,加入相同浓度的无机盐,△YP、△pH(绝对值)按CaCl₂KCl～NaCl次序递减。     

On the structures of generating iterated function systems of Cantor sets

A generating IFS of a Cantor set F is an IFS whose attractor is F. For a given Cantor set such as the middle-3rd Cantor set we consider the set of its generating IFSs. We examine the existence of a minimal generating IFS, i.e. every other generating IFS of F is an iterating of that IFS. We also study the structures of the semi-group of homogeneous generating IFSs of a Cantor set F in under the open set condition (OSC). If dim_HF<1 we prove that all generating IFSs of the set must have logarithmically commensurable contraction factors. From this Logarithmic Commensurability Theorem we derive a structure theorem for the semi-group of generating IFSs of F under the OSC. We also examine the impact of geometry on the structures of the semi-groups. Several examples will be given to illustrate the difficulty of the problem we study.     

Multifractal formalism for self-similar measures with weak separation condition

For any self-similar measure μ on satisfying the weak separation condition, we show that there exists an open ball U₀ with μ(U₀)>0 such that the distribution of μ, restricted on U₀, is controlled by the products of a family of non-negative matrices, and hence μ|_U0 satisfies a kind of quasi-product property. Furthermore, the multifractal formalism for μ|_U0 is valid on the whole range of dimension spectrum, regardless of whether there are phase transitions. Moreover the dimension spectra of μ and μ|_U0 coincide for q0. This result unifies and improves many of the recent works on the multifractal structure of self-similar measures with overlaps.     

Lyapunov exponents for products of matrices and multifractal analysis. Part II: General matrices

We continue the study in [15, 18] on the upper Lyapunov exponents for products of matrices. Here we consider general matrices. In general, the variational formula about Lyapunov exponents we obtained in part I does not hold in this setting. In any case, we focus our interest on a special case where the matrix function M(x) takes finite values M ₁, ..., M _m . In this case, we prove the variational formula under an additional irreducibility condition. This extends a previous result of the author and Lau [18]. As an application, we prove a new multifractal formalism for a certain class of self-similar measures on ℝ with overlaps. More precisely, let μ be the self-similar measure on ℝ generated by a family of contractive similitudes {S _j = ρx + b _j } _j=1^ℓ which satisfies the finite type condition. Then we can construct a family (finite or countably infinite) of closed intervals {I _j } _j∈Λ with disjoint interiors, such that μ is supported on ⋃ _j∈Λ I _j and the restricted measure of μ on each interval I _j satisfies the complete multifractal formalism. Moreover, the dimension spectrum dim _H (α) is independent of j. The author was partially supported by the direct grant and RGC grants (Projects 400706, 401008) in CUHK, Fok Ying Tong Education Foundation and NSFC (Grant 10571100).     

Intrinsic Localized Spin-Wave Modes in an Anisotropic Ferromagnet with Dzyaloshinsky-Moriya Interaction

The existence and properties of intrinsic localized spin-wave modes in a ferromagnetic XXZ spin chain with Dzyaloshinsky-Moriya interaction are investigated analytically in the semiclassical limit. The model Hamiltonian is quantized by introducing the Dyson-Maleev transformation and the coherent state representation is chosen as the basic representation of the system. By making use of the method of multiple scales combined with a quasidiscreteness approximation, the equation of motion for the coherent-state amplitude is reduced to the nonlinear Schrödinger equation. It is shown that a bright intrinsic localized spin-wave mode whose eigenfrequency lies below the bottom of the magnon frequency band can exist in the ferromagnetic system. We also show that the system can produce a dark intrinsic localized spin-wave mode, i.e., nonpropagating kink, whose eigenfrequency is below the upper of the magnon frequency band. In addition, we find that the introduction of the Dzyaloshinsky-Moriya interaction changes wave numbers in the Brillouin-zone corresponding to the appearance of intrinsic localized spin-wave modes.     

Design of a curved surface constant force mechanism

A new curved surface constant force mechanism which mainly consists of a roller and a curved surface has been proposed. The magnitude and the direction of normal force caused by squeezing between the roller and the curved surface satisfy a certain relationship, thus the decomposed force of the normal force keeps constant in a certain direction all the times. According to the envelope theorem, the trajectory of the roller center and the profile of the curved surface are obtained by ignoring friction. Then, the influence of the friction is discussed in detail. In addition, the simulation is performed to verify the theoretical calculation. The simulation results show that the output force is relatively constant and the friction has little effect on the output force.     

Numerical Simulation of Mixing Characteristics and Energy Consumption in Vane Extruders with Different Structure Parameters

Numerical simulation was performed with the Computational Fluid Dynamics (CFD) analysis software POLYFLOW (ANSYS, Inc., USA) to investigate the melt transportation energy consumption and mixing characteristics of vane extruders. By modifying related parameters in the numerical simulation models, the effects of vane arrangement and eccentricity between rotor and stator were studied. The results showed that for different vane arrangements, the vane unit with four vanes distributed uniformly had the lowest energy consumption per unit melt transported in one cycle and the best mixing characteristics. With the increase of eccentricity, the average rotational power transmitted by the vanes to the melt increased, and the rate of increase increased. The same tendency occurred for the maximum shear rate and stretching rate experienced by the particles in the vane extruder. This suggested that the mixing performance of the vane unit increased significantly with the increase of eccentricity.     

高瑞利数下水平自然热对流的幂律关系

采用数值模拟方法，研究了高度和宽度比为1∶10的狭长矩形腔内的水平自然热对流. 根据对瑞利数(Rayleigh数)Ra在10⁴ <Ra<10¹¹内情形的计算结果，将流动分为三个不同的区间：线性区、连续过渡区、1/5次幂律区. 虽然流量和努塞尔数(Nusselt数)Nu随瑞利数的变化都包括了三个参数演化区间，但从一个区间到另外一个参数区间的转变时并不是同步的，其中努塞尔数的转变总是超前流量的转变. 对比前人的研究发现，流量1/3次幂律的结果是由于瑞利数不够高所致. 此外，模拟结果也表明Siggers等的理论分析过高估计了热通量强度，实际的温度边界层内努塞尔数和瑞利数为1/5次幂律关系.     

Facile synthesis of ultra-long Cu microdendrites for the electrochemical detection of glucose

Ultra-long Cu microdendrites (MDs) were prepared by one-step electrodeposition on a glassy carbon electrode. The results demonstrated that the reduction potential, pH, and temperature of the electrolysis solution, as well as the amount of Cu²⁺ and citrate ions, play important roles in the formation of the Cu MDs. Notably, the X-ray diffraction experiments confirmed that the aggregations of the Cu nanocrystals preferred to grow along (111) direction. In addition, the resulting Cu MDs-modified electrode showed good electrochemical performance as a non-enzyme glucose sensor in alkaline media.     

无富集进样原子荧光光谱法测定地表水中的痕量汞

通过增大样品进样量的方式,样品进样量是标准进样量的10-100倍,降低了汞的检出限,从而达到了无富集直接进样测定地表水中痕量汞.其检出限为0.008μg/L;浓度为0.05μg/L和0.10μg/L左右的有证标准物质测定均值分别为0.0483μg/L和0.1016μg/L,加标回收率为92.3％和95.2％.灵敏度高,精密度好,能达到准确定量Ⅰ类和Ⅱ类地表水汞(0.05μg/L以下)的要求.对汉江湖北段水样进行测定,在较洁净的地表水分析中,氧化还原处理后与酸化水样测定结果差异不大,处理后水样结果略微增大.建议对较洁净的地表水样品将氧化还原预处理步骤省略掉,直接进样.