Electrostatic fields of an infinite medium containing arbitrarily positioned coated cylinders

We propose a framework for evaluation of the electrostatic fields in an unbounded isotropic medium containing a number of arbitrarily dispersed circular cylinders or coated cylinders subjected to a remotely prescribed potential field. The cylinders or coated cylinders could be at most cylindrically orthotropic, and may have different radii with different conductivities. The approach is based on a multipole expansion formalism, together with a construction of consistency conditions and translation operators. This main procedure is inspired from an ingenious concept of the classic work of Lord Rayleigh [1], in which the effective conductivity of a periodic array of circular disks or spheres is considered. In the present formulation, we expand the potential field versus various local coordinates with origins positioned at the inclusions’ centers. The key step is to link the potential data with the outer applied field, which is accomplished by the use of Green’s second identity in the matrix domain. We show that the coefficients of field expansions are governed by an infinite set of linear algebraic equations. Numerical results are presented for a few different configurations. We have verified our numerical solutions for a simplified configuration with those obtained from the bipolar coordinate transformation.     

Phosphorus removal from aqueous solution using iron coated natural and engineered sorbents

New filtration materials covered with metallic oxides are good adsorbents for both cation and anion forms of pollutants. Sfax is one of the most important industrial towns in Tunisia. Its phosphate manufacture in particular is causing considerable amounts of water pollution. Therefore, there is a need to find out a new way of getting rid of this excessive phosphate from water. This work is aimed to examining the potential of three sorbent materials (synthetic iron oxide coated sand (SCS), naturally iron oxide coated sand (NCS) and iron oxide coated crushed brick (CB)) for removing phosphate ions from aqueous solutions. According to our literature survey CB was not used as adsorbent previously. Phosphate ions are used here as species model for the elimination of other similar pollutants (arsenates, antimonates). Optical microscope and scanning electron microscope (SEM) analyses were used to investigate the surface properties and morphology of the coated sorbents. Infra-red spectroscopy and X-ray diffraction techniques were also used to characterize the sorbent structures. Results showed that iron coated crushed brick possess more micro pores and a higher surface area owing to its clay nature. The comparative sorption of PO4(3-) from aqueous solutions by SCS, CB and NCS was investigated by batch experiments. The estimated optimum pH of phosphate ion retention for the considered sorbents was 5. The equilibrium data were analysed using the Langmuir and Freundlich isotherms. The sorption capacities of PO(4)3- at pH 5 were 1.5 mg/g for SCS, 1.8 mg/g for CB and 0.88 mg/g for NCS. The effect of temperature on sorption phenomenon was also investigated. The results indicated that adsorption is an endothermic process for phosphate ions removal. This study demonstrates that all the considered sorbents can be used as an alternative emerging technology for water treatment without any side effect or treatment process alteration.     

彩色双层复合镀膜玻璃的在线制备与性能

分别采用电化学方法和化学气相沉积法对生产线锡槽和退火窑内的浮法玻璃两次镀膜,制备出具有阳光控制功能的双层彩色浮法玻璃,采用分光光度计、扫描电镜、能谱仪、透射电镜、原子力显微镜和二次离子质谱等方法分析了复合镀膜样品的形貌．结构,研究了不同深度的膜层成分和性能．结果表明,可见光透射比与硅烷浓度和电流强度之间有强烈依赖性;上层的硅膜表面均匀平整,表面粗糙度约9．66nm,团粒尺寸约100nm,其厚度约70-78nm,且沿厚度方向呈梯度化氧化;底层膜中铜和铋的扩散深度约10μm．     

低频率振动对液体表面流动的影响

以Al粉为示踪粒子,对甘油+水的混合液施加一个连续可调的振动振幅;利用CCD摄像头采集流场信号,首次观察到了不同振幅下液体表面不同的谐振现象;并测量了不同谐振点时液体表面流动的速度;用实验现象清晰的反映了液体表面行为随振幅的变化.     

A review of factors influencing defect detection in infrared thermography: Applications to coated materials

Infrared thermography is a technique that is used to nondestructively inspect parts for the presence of subsurface defects. The technique normally consists of applying heat to one surface of the part and observing the thermal response, using heat-sensing devices such as infrared cameras, as the part cools. Internal defects such as voids modify the thermal response and produce local hot or cold spots on the specimen surface. For the detection of subsurface defects, the sensitivity of the technique to different parameters such as defect depth, material properties, and heating methods has not been established due in part to the complex nature of the heat/flaw interaction. A finite element model is used here to examine the influence of these parameters on defect dectability. The model shows that the defect detectability decreases with increasing defect depth beneath the surface, and that the technique is most sensitive to the inspection of low thermal diffusivity coatings bonded to high thermal diffusivity substrates. The results also show that the heat pulse duration should be made as short as possible to maximize defect detectability.     

The scattering of electro-elastic waves by a spherical piezoelectric particle in a polymer matrix

This paper is devoted to the study of scattering of plane harmonic waves by a piezoelectric sphere with spherical isotropy embedded in an unbounded isotropic polymer matrix. The scattered displacement field and the electric potential in the matrix are expressed in terms of spherical vector wave functions and spherical harmonic functions, respectively. For the field points inside the inhomogeneity, new displacement functions are introduced. Expansion of the new displacement functions and the electric potential in terms of spherical harmonic functions, the equations of motion and electrostatic lead to four second order ordinary differential equations (odes), where three of them are coupled. The coupled system of odes is solved by the generalized Frobenius series. This approach is readily used to handle low and high frequencies. Three different types of piezoelectric inhomogeneities, PZT-4, PZT-5H, and BaTiO₃ are considered and the associated piezoelectric effects on the electro-mechanical fields, differential and total scattering cross-sections are addressed.     

低频振动对塑性成形表面微观形貌的影响

目的 通过对塑性成形界面施加纵向和法向低频振动,探究不同振动参数对成形过程中表面质量的影响规律。方法 采用自主设计的低频振动发生器完成纵向振动作用下的摩擦实验和法向振动作用下的压缩实验,统计材料表面变形区域的平均粗糙度,评价成形质量。结果 在干摩擦条件下,不同频率（0～50 Hz）的纵向小振幅（0.1mm）振动有利于提高成形界面的表面质量,变形区域的表面粗糙度与频率成反比,但是较大振幅（0.4 mm）的纵向振动会增加接触面的材料磨损,降低表面质量;不同频率（0～50 Hz）和不同振幅（0～0.4 mm）的法向振动均有利于提高干摩擦成形界面的表面质量,在0.2 mm振幅条件下表面粗糙度下降最为明显,振幅超过0.2mm后,增加振幅对提升表面质量的影响不明显。结论 低频振动对成形界面微观形貌影响较大,合理优化低频振动工艺参数可显著提高成形界面的表面质量。     

The application of freestanding titanate nanofiber paper for scattering layers in dye-sensitized solar cells

A titanate nanofiber paper with robust and good flexible property was successfully prepared by alkali hydrothermal synthesis with simple paper-making method. These nanofibers were about 80 nm in diameter and had a typical length in the range of tens of micrometers. Despite the transformation from titanate to TiO₂-B phase was initially started, such nanofiber paper still kept its original shape and good flexibility after calcinations at 450 °C for 30 min. A solar cell with titanate nanofiber paper as scattering layer yielded an overall conversion efficiency of 4.90% under an incident solar energy of 100 mW/cm², about 27.5% higher than that without nanofiber paper.     

封闭空间低频气流调制器喉道的声波特性

采用流体力学和声学相关原理,分析圆孔转动型气流调制器气室压力、喷口流量和喉道声波特性。理论计算与实验结果进行了对,并给出喉道声波的声压级随供气压力、供气流量和工作频率改变的变化规律。结果表明理论计算与实验结果基本符合,增大供气压力和流量可提高喉道声波强度。该分析方法对气流调制器设计有一定的指导意义。     

KTV包间低频噪声控制

KTV包间内的噪声污染主要在低频63 Hz～125 Hz,噪声级一般可以超过105 dB,其噪声源边界排放噪声也超出了相应的限值,针对KTV包间的噪声污染,介绍了目前比较成熟的噪声处理方案。首先KTV包间内的墙壁、顶棚、门和地板隔声处理;其次是介绍包间采取的吸声材料和广泛应用的吸声结构;包间音箱设备的隔振处理;包间内减少声波的泄露;以及新型局域共振声子晶体的理论及应用。     

碳包覆铁碳化合物的爆轰合成及表征

以Fe（NO3）3，CO（NH2）2和萘为原料，掺入一定量黑索金（RDX），在真空的爆炸容器中引爆，从而制备出碳包覆铁碳化合物的纳米材料。通过XRD，TEM以及Raman等检测手段对所得爆轰产物进行表征。结果表明，产物由碳包覆Fe2.5C以及富勒烯组成，其中，包覆结构以无定型碳作为外壳，将Fe2.5C内核完全包覆起来。利用爆轰法制备碳包覆材料，方法简单、迅速，节省能源。     

银铜包覆粉末的制备与表征

采用液相还原法制备银包铜超细粉末。以抗坏血酸为还原剂采用葡萄糖预还原法制备铜粉末,以水合肼为还原剂制备银包铜粉末,引入不同的分散剂来制备超细铜粉末。并对样品进行SEM、TEM-EDS和XRD等检测。结果表明,通过条件控制可得粒度均匀、球形度好的包覆粉末。该方法设备简单,且易于操作,适合工业生产。     

Nonlocal effective parameters of a coated sphere medium

An analytical theory has been developed to find the general effective parameters of a nonlocal medium. The medium is nonlocal due to presence of spatial dispersion. The proposed theory is based upon the dipolar scattering model of the inclusions comprising the medium. The bianisotropy stemming from the magnetoelectric coupling at the inclusion and lattice level has been discussed. The developed theory is then applied to a medium which consists of coated spheres with realistic materials. Effects of different values of wavevector upon the effective permittivity, effective permeability, and magnetoelectric coefficient stemming from lattice effects have been studied for a coated sphere medium. It is shown that a coated sphere medium with a weak spatial dispersion gives rise to a broader range of frequencies, where real parts of the effective permittivity and permeability are negative. On the other hand, this range of frequencies becomes smaller when the spatial dispersion of the medium is not weak.     

纳米氧化锌表面包覆改性及其表征

采用液相沉积法对纳米氧化锌进行表面包覆SiO2和SiO2/Al2O3改性,并用XRD、TEM、TG-DSC对其表面结构进行了表征,借助Zeta电位测定仪、静态沉降实验等分析手段考察了改性前后纳米氧化锌在水体系中的分散稳定性.结果表明,在ZnO表面形成的包覆物是以非晶态形式存在的,通过表面包覆SiO2和SiO2/Al2O3改性后明显提高了氧化锌的表面羟基含量,有效改变了氧化锌的等电点,显著提高了纳米氧化锌在水中的分散稳定性.     

氟碳涂料及其在彩钢材料中的应用

对氟碳涂料的制备技术、应用领域及发展前景进行了综述。环保型全氟碳涂料由于各项性能均很优越,必将成为该类涂料未来发展的主流。     

Defects analysis for bright spots on surface of electro-zinc coated sheet

The painting effect of products would be affected if the bright spots happen on the surface of electro-zinc coated sheet. The defects of bright spots are researched by macroscopical observation, scanning electronic microscope, X-ray energy spectrometer, metallography microscope and the electron back-scatter diffraction (EBSD). The result shows that the defects of bright spots are inherited by mixed-grains on the surface of primary steel sheet. It could be solved by controlling the annealing temperature of cold-rolled steel sheets, increasing the rolling reduction or strain rate when the sheets are rolled and uniform heat treatment to the original austenite grains in the continuous metal casting blank.Electro-zinc coated steel sheets are widely used in automobile and apparatus industry. The appearance is more instruct besides its mechanical and corrosion resistant property. Some tiny defects would affect the painting effect of products. Once the bright spot defects were found on the surface of electro-zinc coated steel sheet in some steel works and the appearance of electro-zinc coated steel sheets become bad. In order to finding how the bright spots happened and how to eliminate the defects in the end, rounded analysis is made by some inspections.     

低辐射隔热复合镀膜玻璃的制备

采用溶胶-凝胶法成功制备了SnO2∶F/SiO2气凝胶复合镀膜玻璃,并采用扫描电子显微镜(SEM)、导热系数仪、红外光谱仪,紫外-可见光谱仪等对镀膜玻璃的微观结构、热导率、辐射率、透光率等进行了表征。结果表明,镀膜玻璃的透过率最高在75%左右;辐射率为0.53,复合镀膜玻璃与FTO玻璃相比,其热导率从3.615W/(m·K)降低到3.368W/(m·K),所得复合镀膜玻璃兼具低热导性和低辐射性。     

A model for the screen-printing of Newtonian fluids

A preliminary investigation into aspects of the off-contact screen-printing process is presented. A mathematical model for the printing of a thin film of Newtonian fluid is proposed, in which the screen is modelled as a permeable membrane, and the entire region above and below the screen is flooded. By drawing upon widely used industrial circuit printing practices, the distinguished limit of greatest interest to this industry is identified. Numerical and asymptotic solutions of this distinguished limit are presented that reproduce many of the features observed in industrial screen-printing     

AC loss characteristics of copper-stabilized YBCO coated conductor

Influence of copper layer and mechanical stress-strain on AC losses in copper-stabilized YBCO coated conductor (CC) was investigated. The uni-axial tensile stress-strain was applied to the sample CC in liquid nitrogen at atmospheric pressure, and the AC losses (transport, magnetization and total AC losses) were measured by an electric method. Experimental results showed that the stress-strain dependence of the AC losses can be estimated by knowing stress dependent critical current and magnetization losses in the non-stressed CC. Influence of the copper layer was investigated by measuring frequency dependence of the AC losses. The experimental results showed that there are some influences of the copper layer. However, the influence of the copper layer was not significant from the stand point of practice applications.     

Stress singularities in 2D orthotropic corners

A new technique for analysis of two-dimensional linear elastostatic solutions with stress singularities at orthotropic corners is developed. An explicit and general representation of the associated eigenequation given as ‘zero determinant condition’ of a matrix with half dimension in comparison with the current approach is derived by application of Stroh relations of anisotropic elasticity. The technique is directly applicable to anisotropic corners. Analytical formulae for stress singularity exponents, roots of the associated eigenequations, at orthotropic half-plane and semiinfinite crack problems for all combinations of basic homogeneous boundary conditions, including slip with friction, are derived. it is noteworthy that the singularity exponents are invariant with respect to the relative orientation of boundary edges and orthotropic material for nine of these combinations. Numerical analysis of singularity exponents for some configurations typical in the modelization of material tests of fiber-matrix composite materials is presented. This revised version was published online in July 2006 with corrections to the Cover Date.