a-Si:H based two-dimensional photonic crystals

We describe the fabrication processes of silicon-based two-dimensional photonic crystals (2D-PCs) with a photonic band gap in the near-IR range. The procedures involve electron beam lithography followed by an anisotropic etching step of hydrogenated amorphous silicon thin films deposited by plasma enhanced chemical vapor deposition. Micrometric and submicrometric arrays of cylindrical holes are transferred using a poly-methylmethacrylate resist layer as a mask. A careful comparison between standard parallel plate reactive ion etching and inductively coupled plasma etching techniques is performed, aimed at obtaining periodic structures with high aspect ratio and good profile sharpness.     

Management of Vocal Fold Scar with Autologous Fat Implantation: Perceptual Results

Vocal fold scar disrupts the mucosal wave and interferes with glottic closure. Treatment involves a multidisciplinary approach that includes voice therapy, medical management, and sometimes surgery. We reviewed the records of the first eight patients who underwent autologous fat implantation for vocal fold scar. Information on the etiology of scar, physical findings, and prior interventions were collected. Videotapes of videostroboscopic findings and perceptual voice ratings [Grade, Roughness, Breathiness, Asthenia, Strain (GRBAS)] were randomized and analyzed independently by four blinded observers. Etiology of scar included mass excision (7), vocal fold stripping (3), congenital sulcus (2), and hemorrhage (1). Prior surgical procedures performed included thyroplasty (1), autologous fat injection (9), excision of scar (2), and lysis of adhesions (2). Strobovideolaryngoscopy: Statistically significant improvement was found in glottic closure, mucosal wave, and stiffness (P = 0.05). Perceptual ratings (GRBAS): Statistically significant improvement was found in all five parameters, including overall Grade, Roughness, Breathiness, Asthenia, and Strain (P = 0.05). Patients appear to have improved vocal fold function and quality of voice after autologous fat implantation in the vocal fold. Autologous fat implantation is an important adjunctive procedure in the management of vocal fold scar, and a useful addition to the armamentarium of the experienced phonomicrosurgeon.     

Investigation of structural and optical properties of UHV deposited titanium thin films under thermal oxidation

Titanium dioxide thin layers were prepared by annealing method, on glass substrate at different temperatures, 150, 250 and 350 °C, in presence of 5 cm³/s uniform oxygen flow. The structural investigations were performed by means of atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. Roughness of the films changed due to annealing process. The optical constants of the layers were obtained by Kramers–Kronig analysis of the reflectivity curves. There was a good agreement between structural and optical properties of the layers. Annealing temperature can play an important role in nanostructures of the films.     

Characterization of Agglomerated and Aggregated Aerosol Particles Using Image Analysis

Accurate particle size characterization of aggregated and agglomerated particles is only possible by analysis of photographs. Both the primary particle size and the morphology of the aggregate are important experimental results. Since standard image analysis techniques for particle size analysis usually recognize only single particles, a new programme, called here Sparse Hough Transformation, was developed for the automated recognition of spherical particles within an aggregate. The method is shown to perform well, even for images with many overlapping particles. The structure of the aggregate is analysed using the fractal dimension, determined from the density-density correlation function. Finite size effects, important when dealing with aggregates containing few primary particles, are taken into account by including a cut-off function.     

粗糙表面对微尺度流动影响的数值分析

本文利用表面规则突起来模拟粗糙元,通过对平板间微尺度层流流动的数值计算,研究了粗糙表面对微尺度层 流流动阻力的影响。对数值计算结果的分析表明,壁面处由于粗糙元存在可引起逆压梯度,从而导致层流流动阻力系数的 增加。     

Ein Verfahren zur Messung der Rauhigkeitsautokorrelationsfunktion von polierten Glasoberflächen mittels Streubildscherung

A Possibility for Measuring the Autocorrelation Function of Surface Roughness by Means of Stray Light Shearing A method for measuring the autocorrelation function of polished surfaces is presented, utilizing interference of two laterally shifted projections of the scattering sample. The systematic error due to the spread function of the optical image is estimated. BK 7 and BaK 4 samples polished by different techniques are investigated.     

Wetting modifications of uhmwpe surfaces induced by ion implantation

Ultra-high-molecular-weight-polyethylene (UHMWPE) surfaces are characterized in terms of roughness and wetting. Changes in the surface morphology of the polymer were induced macroscopically by mechanical friction and microscopically by ion implantation. The ion irradiation was obtained by using 300?keV Xe⁺ beams with doses ranging between 10¹⁴ and 10¹⁵?ions/cm².

Roughness and wetting measurements were performed in order to investigate the UHMWPE surface properties before and after the surface treatments. The wetting angle of the polymeric surface increases with the decrease of the roughness and with the increase of the absorbed dose. Results are discussed from the point of view of the biological reactions that could degrade the UHMWPE biocompatible surfaces employed in different mobile prostheses.     

Experimental study of noise emitted by circular cylinders with large roughness

The aerodynamic noise generated by high Reynolds number flow around a bluff body with large surface roughness was investigated. This is a relevant problem in many applications, in particular aircraft landing gear noise. A circular cylinder in cross-flow and a zero-pressure-gradient turbulent boundary layer with various types of roughness was tested in a series of wind tunnel experiments. It has been shown that distributed roughness covering a circular cylinder affects the spectra over the entire frequency range. Roughness noise is dominant at high frequencies, and the peak frequency is well described by Howe?s roughness noise model when scaled with the maximum outer velocity. There are differences between hemispherical and cylindrical roughness elements for both the circular cylinder and the zero-pressure-gradient turbulent boundary layer cases, indicating a dependence on roughness shape, not described by the considered roughness noise models. Cylindrical roughness generates higher noise levels at the highest frequencies, especially for the zero-pressure-gradient turbulent boundary layer case. Cable-type roughness aligned with the mean flow does not generate roughness noise, and its spectrum has been found to collapse with the smooth cylinder at medium and high frequencies. At low and medium frequencies the noise spectra have the same features as the smooth cylinder, but with higher shedding peak levels and fall-off levels, despite the decrease in spanwise correlation length. Roughness induces early separation, and thus a shift of the spectra to lower frequencies.     

Perceptual evaluation of voice quality and its correlation with acoustic measurements

To determine whether a correlation exists between the Grade, Roughness, Breathiness, Aesthenia, Strain (GRBAS) scale (a subjective measure of voice) and the Multi-Dimensional Voice Program (MDVP) scale (an objective measure of voice). A retrospective review of 37 voice patients (12 male/25 female) was conducted. Each voice was perceptually evaluated using the GRBAS scale by an experienced speech pathologist and acoustically analyzed using the MDVP scale. Statistical analysis using a multivariate regression model identified a significant correlation between the noise-related parameters of MDVP and the components of the GRBAS scale. Grade correlated with voice turbulence index (VTI), noise harmonic ratio (NHR), and soft phonation index (SPI). Roughness correlated with NHR only. Breathiness correlated with SPI only. Aesthenia also correlated with SPI only. Of the 19 acoustic variables measured by the MDVP system, only three noise parameters significantly correlated with the GRBAS perceptual voice analysis. Perhaps "noise" is the perceived acoustical quality of the dysphonic voice. A voice quantifying measure such as a "voice index score" could be proposed using the GRBAS scoring and the three clinically relevant MDVP values following further studies.     

Biochemical and anisotropical properties of tendons

Tendons are formed by dense connective tissue composed of an abundant extracellular matrix (ECM) that is constituted mainly of collagen molecules, which are organized into fibrils, fibers, fiber bundles and fascicles helicoidally arranged along the largest axis of the tendon. The biomechanical properties of tendons are directly related to the organization of the collagen molecules that aggregate to become a super-twisted cord. In addition to collagen, the ECM of tendons is composed of non-fibrillar components, such as proteoglycans and non-collagenous glycoproteins. The capacity of tendons to resist mechanical stress is directly related to the structural organization of the ECM. Collagen is a biopolymer and presents optical anisotropies, such as birefringence and linear dichroism, that are important optical properties in the characterization of the supramolecular organization of the fibers. The objective of this study was to present a review of the composition and organization of the ECM of tendons and to highlight the importance of the anisotropic optical properties in the study of alterations in the ECM.     

Compressive behaviour of dam concrete at higher strain rates

The mechanical behaviour of concrete when subjected to impact or blast has still many aspects requiring further study. Dam concrete is characterized by large coarse aggregates, hence large specimen sizes are needed in order to study a representative volume of the material. Exploiting an innovative equipment, based on Hopkinson bar techniques, the dynamic behaviour of concrete of 64?mm maximum aggregate size has been investigated. Direct dynamic compression tests have been performed on medium and large size cylindrical samples. Full stress-strain curves have been obtained, which have allowed the estimation of fracturing energies and of the relevant dynamic increase factor. The experimental campaign has also included a reference standard concrete in order to highlight the peculiarity of the dam concrete at high strain rates and to validate the transition of this type of testing to very large specimens.     

Brownian dynamics simulations of a cubic haematite particle suspension with a more effective treatment of steric layer interactions

We have proposed a new repulsive layer model for describing the interaction between steric layers of coated cubic particles. This approach is an effective technique applicable to particle-based simulations such as a Brownian dynamics simulation of a suspension composed of cubic particles. 3D Brownian dynamics simulations employing this repulsive interaction model have been performed in order to investigate the equilibrium aggregate structures of a suspension composed of cubic haematite particles. It has been verified that Brownian dynamics employing the present steric interaction model are in good agreement with Monte Carlo results with respect to particle aggregate structures and particle orientational characteristics. From the viewpoint of developing a surface modification technology, we have also investigated a regime change in the aggregate structure of cubic particle in a quasi-2D system by means of Brownian dynamics simulations. If the magnetic particle–particle interaction strength is relatively strong, in zero applied magnetic field the particles aggregate in an offset face-to-face configuration. As the magnetic field strength is increased, the offset face-to-face structure is transformed into a more direct face-to-face contact configuration that extends throughout the whole simulation region.     

浅海海底界面混响平均强度特性仿真

海底粗糙界面是产生混响的主要因素之一。本文通过理论分析和数值仿真的方法,根据浅海全波动混响模型对不同海底粗糙界面所引起浅海混响平均强度特性进行研究,主要考虑Goff-Jordan谱、Gauss谱和指数谱三种不同粗糙界面条件下的海底反向散射强度和混响平均强度特性。计算结果表明:海底粗糙界面会引起海底反向散射强度的频率特性的差异,进而导致海底平均混响强度的频率特性的差异,但随入射角度的变化不大。即使界面起伏的方差和相关长度相同,不同的粗糙度谱也会引起平均混响强度的差异。     

New type of domain walls: Domain walls caused by frustrations in multilayer magnetic nanostructures

Roughness of the interfaces between layers in a multilayer magnetic structure causes frustration of the exchange interaction between spins. Under certain conditions, frustration brings about the formation of domain walls (DWs) of a new type, whose parameters are determined by the competition between different exchange interactions rather than between the exchange and anisotropy energies as is the case with conventional DWs. Such DWs are much sharper than conventional DWs. The conditions under which micro-(nano-) domains arise are considered, and magnetic phase diagrams for ferromagnet-nonmagnetic metal-ferromagnet and ferromagnet-antiferromagnet nanostructures are discussed.     

蒸养再生骨料混凝土断裂声发射特征*

为研究蒸汽养护对再生骨料混凝土断裂过程损伤特征的影响,开展了再生骨料混凝土三点弯断裂试验,并采用声发射技术对损伤过程进行了监测分析。结果表明,蒸养降低了再生骨料混凝土断裂峰值荷载,断裂过程中声发射信号强度低于标准养护试件。声发射振铃计数、撞击数、b值等参数能够准确反映再生骨料混凝土断裂过程损伤演变规律。加载上升阶段,声发射信号活动性很低,试件内以微裂纹的形成为主,加载至荷载峰值,声发射振铃计数累计值增长呈现平缓阶段,混凝土内微裂缝的聚合会持续一段时间。峰值后荷载迅速降低阶段声发射信号最活跃,为裂缝迅速发展的过程。峰后荷载缓慢降低的过程,声发射信号活跃性降低,裂缝扩展至试件顶部区域,主要是宏观裂缝的开展,不再产生新的裂缝。     

Application of improved Speckle contouring technique to surface roughness measurements

One of the well known drawbacks in Electronic Speckle Pattern Interferometry (ESPI) is the poor fringe density due to electronic and speckle noise and decreasing fringe visibility with increasing speckle decorrelation. As recently reported we suggested improving the fringe density and enlarging the measurement range by the incremental addition of phase images. The technique has already been successfully applied to in-plane and out-of-plane displacement field measurements of carbon-fibre reinforced composites. This paper demonstrates how the technique can be used to improve the sensitivity and to extend the measurement range for speckle contouring applications. The angular correlation of the speckle phase images is used to get the desired 3D information of the investigated object surface. It is demonstrated how the angular speckle contouring techinque can easily be automated with respect, for example, to possible industrial applications. Roughness measurements are carried out on milled Rugo test surfaces. All measurements are performed without the usual vibration isolation, and of course, without the treatment of the surface with fine, white powder for contrast enhancement, which would falsify the results.     

The effect of blending granular aggregates of different origin on the strength of concrete

This work correlates the resistance of concrete cores with the physical properties of the granular material forming it. A basic physical characterization is conducted, taking into account the origin of the grains involved in the concrete mixture; that is, if they come from natural degradation (natural granular aggregates) or from a grinding process (crushed granular aggregates). Apparent and real densities, shape factors, packing densities, and specific surface areas of the grains are measured. The results are discussed as a function of size and origin of the grains. Several mixtures are prepared following a standard protocol and using different ratios of natural and crushed aggregates. For each ratio, six cores are prepared and uniaxial compression tests are performed. A non-monotonic relation between the resistance of concrete and the percentage of crushed aggregate present in it is obtained, with an optimum ratio depending on the physical properties of the grains.     

A self-adapting image encryption algorithm based on spatiotemporal chaos and ergodic matrix

To ensure the security of a digital image, a new self-adapting encryption algorithm based on the spatiotemporal chaos and ergodic matrix is proposed in this paper. First, the plain-image is divided into different blocks of the same size, and each block is sorted in ascending order to obtain the corresponding standard ergodic matrix. Then each block is encrypted by the spatiotemporal chaotic system and shuffled according to the standard ergodic matrix. Finally, all modules are rearranged to acquire the final encrypted image. In particular, the plain-image information is used in the initial conditions of the spatiotemporal chaos and the ergodic matrices, so different plain-images will be encrypted to obtain different cipherimages. Theoretical analysis and simulation results indicate that the performance and security of the proposed encryption scheme can encrypt the image effectively and resist various typical attacks.