Superachromatic lens combinations

Achromatic objectives are constructed by combining two or more lenses with properly chosen powers made of materials with different dispersions. We present a new approach that simplifies the design of multilens achromatic combinations as well as the choice of materials for them and show how this method can be applied to the design of a four-lens superachromatic combination.     

Measuring techniques in industrial applications of electrostatic forces: Plenary Lecture at Electrostatics 2005, Helsinki,Finland

Considering the vast field of Electrostatic Industries, this paper describes only some chosen special measuring techniques that have been used for powders, solids, liquids, and gases in the chosen industrial activities listed below: Electrostatic; Precipitation; Corona and Tribocoating; Beneficiation and separation of minerals; Aerial spraying of vegetations; Filters and Microphones with dielectret materials.     

Two-dimensional microwave band-gap structures of different dielectric materials

We report the use of low dielectric constant materials to form two-dimensional microwave band-gap structures for achieving high gap-to-midgap ratio. The variable parameters chosen are the lattice spacing and the geometric structure. The selected geometries are square and triangular and the materials chosen are PTFE (ε = 2.1), PVC (ε = 2.38) and glass (ε = 5.5). Using the plane-wave expansion method, proper lattice spacing is selected for each structure and material. The observed experimental results are analyzed with the help of the theoretical prediction     

Metal-supported ultrathin oxide film systems as designable catalysts and catalyst supports

Thin oxide films lend themselves as model supports for studies in heterogeneous catalysis, for example, to study the growth and reaction of metal deposits (atoms, clusters and nanoparticles). If the thickness of the film is chosen appropriately these thin films are reasonable models to mimic the situation of bulk materials. If thin films below a critical thickness are studied these materials exhibit properties in their own right. Their structural properties may be tuned to control their functional characteristics. Possible implications for heterogeneous catalysis are discussed.     

Apochromatic lens combinations: a novel design approach

Apochromatic objectives are constructed by combining three lenses made of different materials with properly chosen powers and dispersions. This paper presents a novel approach to the design of such apochromatic combinations which automatically minimizes the residual chromatic aberration over a specific wavelength range.     

A prototype of a high-voltage platform for the KRION ion source

A high-voltage platform that has been developed for the KRION ion source is described. The platform design concept is explained. The calculations that have been performed of the influence of the design and materials on the source magnetic field make it possible to define a range of materials suitable for manufacturing the platform. The major components of the high-voltage platform, such as a high-voltage power supplier, and decoupling insulators of the high-voltage power source, and the main and supplementary platforms, are chosen and described. It is determined that, to exclude electric breakdowns and corona discharges, one should use an electrically shielded channel with a cryocooler and power supplies for the KRION-source coupling cables.     

材料性质和燃料特性对浸没在多孔介质中的液体燃料燃烧特性影响

本文研究了浸没在沙、钢珠和氟石等不同材料的多孔介质床中的液体燃料的燃烧特性.探讨了燃料性质对火焰特性、床层温度分布、离表面最近测点处蒸气区的下边界到达时间以及燃料消耗的影响.实验结果揭示了浸没在多孔床中的液体燃料燃烧的特殊规律.     

Theory of thin-film, narrowband, linear-polarization rejection filters with superlattice structure

A device to be obtained by depositing a columnar thin-film on a transparent substrate decorated periodically by an array of rectangular grooves is proposed as a narrowband, linear-polarization rejection filter. The rigorous coupled-wave approach is harnessed to calculate the reflectances and transmittances. High-quality filters of chosen materials and with less than 2 nm bandwidths can be designed with a vapor flux angle for deposition of the columnar thin-film as the controlling parameter.     

新型筒状双层闪络板等离子体枪

提出了新型筒状双层闪络板等离子体枪及其驱动电路的设计方案。枪内层接脉冲高压,均布160个电弧点,每个电弧点由中心焊盘及填充TiH2粉末的外围凹槽组成,TiH2粉末用硅酸钠粘接于凹槽中;通过100Ω电阻连接每个高压焊盘与接地端,电极间隙中产生等离子体。通过放电实验得出:当由3 kV,20μF电容器驱动时,脉宽为1.5μs、幅值约150 A的电流通过枪,产生的等离子体密度为1013~1014cm-3,存在时间0.5μs,等离子体定向速率达到5 cm/μs。实验证明:该闪络板等离子体枪可靠性强,可重复产生均匀等离子体。     

不同原料DKDP晶体的生长和损伤阈值

 采用传统降温法,利用不同原料从氘化程度为85%的溶液生长了四方相磷酸二氘钾(DKDP)晶体,并选取部分样品进行三倍频光损伤阈值测试。实验结果表明：不同纯度原料对DKDP晶体的损伤阈值以及DKDP晶体的生长溶液稳定性的影响效果相反,即由于原料中杂质金属离子含量的差别,高纯原料生长的晶体较一般原料生长的晶体损伤阈值可提高1.5倍,但其生长溶液的稳定性比一般原料低。     

Materials with on-demand refractive indices in the terahertz range

We demonstrate the possibility to create materials with chosen refractive indices and a strong birefringence in the terahertz range by etching of patterns with appropriate filling factors in a dielectric substrate. We show that by using deep inductive plasma etching of silicon wafers, it is possible to achieve a birefringence as high as 1.2 in an 80 microm thick layer. The resulting stacks were used as building blocks for a photonic crystal displaying sharp defect mode peaks in transmittance.     

Development of electrochemical oxygen meter for liquid sodium

The development of an electrochemical oxygen meter for liquid sodium is briefly accounted. The current design, based on a solid electrolyte crucible machined out of a sintered pellet is described along with some technological details. Present experience with testing in sodium loops and post-exposure analysis has shown that the chosen assembly is capable of achieving approximately the Nernst voltage. The service period was limited mainly by corrosion and by some incompatibilities in reference electrode compartment materials.     

Perpendicular magnetocrystalline anisotropy in tetragonally distorted Fe-Co alloys

We report on the experimental realization of tetragonal Fe-Co alloys as a constituent of Fe0.36Co0.64/Pt superlattices with huge perpendicular magnetocrystalline anisotropy energy, reaching 210 microeV/atom, and a saturation magnetization of 2.5 microB/atom at 40 K, in qualitative agreement with theoretical predictions. At room temperature the corresponding values and are achieved. This suggests that Fe-Co alloys with carefully chosen combinations of composition and distortion are good candidates for high-density perpendicular storage materials.     

Quasiparticle relaxation in optically excited high-Q superconducting resonators

The quasiparticle relaxation time in superconducting films has been measured as a function of temperature using the response of the complex conductivity to photon flux. For tantalum and aluminum, chosen for their difference in electron-phonon coupling strength, we find that at high temperatures the relaxation time increases with decreasing temperature, as expected for electron-phonon interaction. At low temperatures we find in both superconducting materials a saturation of the relaxation time, suggesting the presence of a second relaxation channel not due to electron-phonon interaction.     

A Preliminary Study of the Relationship between Lewis Acid–Base Parameters and Structure of Polymers

Acid–base theory is an important method to describe the interaction between materials. The inverse gas chromatography (IGC) technique can be used to measure the surface Lewis acid–base parameters of materials. Compared with the solubility parameter method, the merit of the IGC technique is that it can give the surface acid–base properties of many undissolvable materials, such as inorganic materials, metal‐oxides, and thermosetting polymers. In this paper, six polymers are chosen to discuss the rationality of their Lewis acid–base parameters from the molecular structure viewpoint. Compared with some small molecules, the values of these polymers are reasonable. However, endowing each group with a set of acid–base parameters is impossible at this stage because of the lack of sufficient data. Thus more characterization work is needed to develop the IGC method.     

A study on preparation and properties of carbon materials/myristic acid composite phase change thermal energy storage materials

Microscale graphite (Gr) and nanoscale multi-walled carbon nanotubes (MWCNTs) were chosen to modify the organic phase change material (PCM) of myristic acid (MA). The Gr/MA and MWCNTs/MA composite PCMs were prepared by adding the carbon materials at different mass fractions into MA. The experimental results indicated that both Gr and MWCNTs could enhance the thermal conductivity of MA. For the 3?wt% loading, the solid thermal conductivity of MA increased by 37.42% with Gr and 62.26% with MWCNTs. The FT-IR spectra showed that the reactions between carbon materials and MA were physical. The DSC results illustrated that the phase change latent heats of the composite PCMs decreased gradually with the additives increasing. Gr and MWCNTs strengthened the thermal stability of MA. The heat release rates of the composite PCMs accelerated. Three hundred thermal cycles of the chosen composite PCMs revealed that the prepared composite PCMs presented good thermal cycling stability.     

Stability of rod-shaped nanoparticles embedded in an elastic matrix

In many biological tissues as well as in some technical materials we find nano-sized rod-shaped particles embedded in a relatively soft matrix. Loss of stability of equilibrium, i.e. buckling, is one of the possible failure modes of such materials. In the present paper different kinds of load transfer between matrix and reinforcing particles, which are typical for rod-shaped nanostructures in biological tissues, are considered with respect to stability of equilibrium. Two regimes of matrix stiffnesses leading to different modes of buckling, and a transition regime in between, have been found: soft matrix materials leading to the so-called ‘flip mode’ (also called ‘tilt mode’) and hard matrix materials resulting in ‘bending mode’ buckling. The transition regime is of particular interest for biological tissues. Numerical and semi-analytical as well as asymptotic concepts are employed leading to results for estimating the critical load intensities both in the form of closed form solutions and diagrams. The analytical solutions are compared with results of finite element analyses. From these comparisons indications are gained for deciding which of the different analytical approaches should be chosen for a particular nanostructure configuration in terms of the associated buckling modes.     

3D reconstruction of grains in polycrystalline materials using a tessellation model with curved grain boundaries

A compact and tractable representation of the grain structure of a material is an extremely valuable tool when carrying out an empirical analysis of the material’s microstructure. Tessellations have proven to be very good choices for such representations. Most widely used tessellation models have convex cells with planar boundaries. Recently, however, a new tessellation model — called the generalised balanced power diagram (GBPD) — has been developed that is very flexible and can incorporate features such as curved boundaries and non-convexity of cells. In order to use a GBPD to describe the grain structure observed in empirical image data, the parameters of the model must be chosen appropriately. This typically involves solving a difficult optimisation problem. In this paper, we describe a method for fitting GBPDs to tomographic image data. This method uses simulated annealing to solve a suitably chosen optimisation problem. We then apply this method to both artificial data and experimental 3D electron backscatter diffraction (3D EBSD) data obtained in order to study the properties of fine-grained materials with superplastic behaviour. The 3D EBSD data required new alignment and segmentation procedures, which we also briefly describe. Our numerical experiments demonstrate the effectiveness of the simulated annealing approach (compared to heuristic fitting methods) and show that GBPDs are able to describe the structures of polycrystalline materials very well.     

On the use of perforations to improve the sound absorption of porous materials

The concept of meso-perforations in appropriately chosen porous media can help enhance their sound absorption performance. The meso-perforated materials are also referred to as “double porosity materials” since they are made up of two interconnected networks of pores of different characteristic size. Several theoretical, numerical and experimental works have been accomplished on the subject by the authors. The purpose of this paper is to give a synthetic review of these works and establish practical design rules to develop optimized noise control solutions based on this concept. The paper presents two complementary models to deal with this kind of materials: an analytical model based on homogenization techniques and a numerical model relying on a finite element discretization of the domains. The limits of these models are discussed. The choice of the design parameters is then been investigated in order to provide practical design rules. This choice relies on a criterion which is evaluated from the knowledge of the resistivity, porosity and tortuosity of the micropous medium, and the calculation of a geometrical parameter defined from the chosen mesoscopic structure. Experimental and numerical results regarding the influence of the mesopore profile along the thickness performed in a appropriately chosen substrate microporous medium are presented. The agreement between the models and the experiments is satisfactory. Results show that significant enhancements of the absorption properties can be obtained over a selected frequency band by adjusting the mesopore profile. It is also shown that interesting absorbing properties can be obtained when coating a double porosity medium with an impervious screen.