Parallel Surface Research Articles

Laser-induced surface alloying in nanosized Ni/Ti multilayer structures

Laser-induced alloying effects on the composition and structure of different Ni/Ti multilayer structures were studied. Thin films composed of one, five, and ten (Ni/Ti) bilayers were deposited by DC ion sputtering on (100) Si wafers. Laser irradiations were performed by 150ps pulses of a Nd:YAG laser operating at 1064nm. The samples were characterized by Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). At a laser fluence of 0.9Jcm−2, interaction between Ni and Ti layers was initiated, and NiTi alloy formed in 5- and 10-bilayered samples. Progressed alloying was achieved at a laser fluence of 1.2Jcm−2. The alloy was formed mostly within the heat affected zone (HAZ) of the sample. Surface segregation of titanium was followed by formation of a 25nm thin TiO2 film on the surface of the multilayered structures. In addition, parallel periodic surface structures on the surfaces of the 5- and 10-bilayered samples were clearly recorded. Their period in the case of the 5-bilayered system (0.77μm) agrees very well with the predictions of the common theory, whereas, in the case of the 10-bilayered system, two periods of such structures are observed (1.43μm and 0.4μm), and none of them coincides with the prediction.

Multi-tube parallel surface discharge plasma reactor for wastewater treatment

A multi-tube parallel surface discharge plasma reactor has been designed to investigate its mineralization potential for organic wastewater. p-Nitrophenol (PNP) was used as the target pollutant. The effects of some operational parameters such as solution pH value, discharge voltage, air flow rate and air moisture on COD removal were investigated. Ozone utilization and biodegradability (BOD5/COD) of wastewater were evaluated. The results indicated that this discharge system presented a great potential for COD removal. For 40L of PNP wastewater, complete PNP removal and 97% of COD removal efficiency were achieved after 1h of discharge treatment with energy yield of 27.4gCODkWh−1, and correspondingly, the ozone consumption and ozone utilization efficiency were 80% and 1.3gCODgO3−1. Increasing solution pH value and increasing discharge voltage were both beneficial for COD removal. The optimal air flow rate was observed as 1.5m3h−1. Dry air contributed to a greater COD removal efficiency, due to more O3 generation. The biodegradability of PNP wastewater increased up to 0.42 after 1h of treatment.

Oscillating plasma bubbles. IV. Grids, geometry, and gradients

Plasma bubbles are created in an ambient plasma. The bubble is formed inside a cavity bounded by a negatively biased grid. Ions are injected through the grid and neutralized by electrons from either the background plasma or an internal electron emitter. The external electron supply is controlled by the grid bias relative to the external plasma potential. When the electron flux is restricted to the ion flux, the sheath of the bubble becomes unstable and causes the plasma potential to oscillate near the ion plasma frequency. The exact frequency depends on the net space charge density in the bubble sheath. The frequency increases with density and grid voltage, provided the grid forms a parallel equipotential surface. The present investigation shows that when the Debye length becomes smaller than the grid openings the electron flux cannot be controlled by the grid voltage. The frequency dependence on grid voltage and density is modified creating frequency and amplitude jumps. Low frequency sheath oscillations modulate the high frequency normal oscillations. Harmonics and subharmonics are excited by electrons in an ion-rich sheath. When the plasma parameters vary over the bubble surface, the sheath may oscillate at different frequencies. A cavity with two isolated grids has been used to investigate anisotropies of the energetic electron flux in a discharge plasma. The frequency dependence on grid voltage is entirely different when the grid controls the energetic electrons or the bulk electrons. These observations are important to several fields of basic plasma physics, such as sheaths, sheath instabilities, diagnostic probes, current, and space charge neutralization of ion beams.

Fluctuation pressure on a bio-membrane confined within a parabolic potential well

A compliant bio-membrane with a nominally flat reference configuration is prone to random transverse deflections when placed in water, due primarily to the Brownian motion of the water molecules. On the average, these fluctuations result in a state of thermodynamic equilibrium between the entropic energy of the water and the total free energy of the membrane. When the membrane is in close proximity to a parallel surface, that surface restricts the fluctuations of the membrane which, in turn, results in an increase in its free energy. The amount of that increase depends on the degree of confinement, and the resulting gradient in free energy with degree of confinement implies the existence of a confining pressure. In the present study, we assume that the confinement is in the form of a continuous parabolic potential well resisting fluctuation. Analysis leads to a closed form expression for the mean pressure resulting from this confinement, and the results are discussed within the broader context of results in this area. In particular, the results provide insights into the roles of membrane stiffness, number of degrees of freedom in the model of the membrane and other system parameters.

SYNCHRONIZATION OF SLOWLY ROTATING PENDULUMS

We study synchronization of a number of rotating pendulums mounted on a horizontal beam which can roll on the parallel surface. It has been shown that after the initial transient, different states of pendulums synchronization occur. We derive the analytical equations for the estimation of the phase differences between phase synchronized pendulums. After the study of the basins of attraction of different synchronization states, we argue that the observed phenomena are robust as they occur for a wide range of both initial conditions and system parameters.

Parallel Surface Reconstruction for Particle‐Based Fluids

AbstractThis paper presents a novel method that improves the efficiency of high‐quality surface reconstructions for particle‐based fluids using Marching Cubes. By constructing the scalar field only in a narrow band around the surface, the computational complexity and the memory consumption scale with the fluid surface instead of the volume. Furthermore, a parallel implementation of the method is proposed. The presented method works with various scalar field construction approaches. Experiments show that our method reconstructs high‐quality surface meshes efficiently even on single‐core CPUs. It scales nearly linearly on multi‐core CPUs and runs up to fifty times faster on GPUs compared to the original scalar field construction approaches.

Synchronization of pendula rotating in different directions

We study the synchronization of a number of pendula mounted on a horizontal beam which can roll on the parallel surface. Under the driving moment, the pendula rotate in different directions: one of them rotates counterclockwise, the rest rotate clockwise. It has been shown that after a transient different types of phase synchronization between pendula can be observed, despite opposite directions of rotations.

Macroscopy Lattice Deformation of Martensitic Transformation in Fe-Based Shape Memory Alloy

Macroscopic lattice deformation of martensitic transformation and shape memory effect (SME) were studied by atom force microscopy (AFM), X-ray diffraction and so on. The results showed that stress induced martensitic surface relief was “N”-shaped. The surface relief was parallel distribution when deformation was less than 6%. When relief became to intercross, its height and width were far less than parallel relief in same deformation. Superior heat-recovery was discovered in parallel surface relief. The recovery ratio was very low in intercrossed relief. The macroscopic lattice deformation descends in virtue of relief intercrossed, then recovery process was forbidden, so that recovery ratio was descent.

27 Monitoring the levels of the reactive oxygen species on the whole heart and in single cardiomyocytes during ischaemia-reperfusion

ROS production during ischaemia-reperfusion induces mitochondrial permeability transition pore opening and so mediates reperfusion injury. Several groups have used real-time fluorescence to determine ROS production by isolated cardiomyocytes during simulated...

Investigation of Tribological Properties of PI/FEP Laminated Composites Under Dry Sliding, Water- and Oil-Lubricated Conditions

Polyimide/fluorinated ethylene propylene (PI/FEP) laminated composites were fabricated by means of hot-press molding. The friction and wear behavior of high performance PI/FEP laminated composites has been comparatively evaluated under dry sliding, water- and oil-lubricated conditions. The worn surface morphologies of samples under different lubrication conditions were examined by scanning electron microscope and the wear mechanisms were comparatively discussed. As the results, PI/FEP laminated composites sliding against stainless steel under water lubrication registered lower friction coefficients, but higher wear rates than those under dry sliding. The friction coefficients and wear rates of samples under liquid paraffin-lubricated condition were lowest in three sliding conditions. The lateral surface of samples exhibited better wear resistance than parallel surface did under dry sliding.

Monolithic design of a compliant template orientation stage for step imprint lithography

The parallel surface contact between a template and a wafer is of critical importance for pattern fidelity in step imprint lithography. The passive compliant stage, which has a much simpler structure than an active control one, is an effective orientation-adjusting mechanism. For a perfect passive compliant stage, the orientation-adjusting process should bring about the smallest possible additional lateral motion to maintain the overlay precision. In the present paper, based on the analysis of a compliant wafer stage and the influence of the rotation axis on position shift, a monolithic template orientation stage with four groups of passive compliant mechanisms is proposed to satisfy the above requirements. This compliant template orientation stage can be regarded as two four-bar linkages that interfere with each other, with the connecting line of two flexible hinges in each group passing through the centre of the template, ensuring that the rotation axis is located in the centre of the template during the whole orientation-adjusting process. The performance of the designed compliant template orientation stage is researched using the finite element analysis method and experiments. The results indicate that this compliant template stage can ensure the parallel surface contact between a template and a wafer while minimizing relative lateral motion during the imprinting process.

A Criterion for Combination Rule in Flaw Assessment of Parallel Surface Cracks

When multiple cracks approach one another, the stress intensity factor and J-integral value change due to the interaction of the stress field. Since the changes in these parameters are not always conservative in structural reliability evaluations, the interaction between multiple cracks should be taken into account. Section XI of the ASME Boiler and Pressure Vessel Code provides a flaw characterization rule for interacting multiple cracks. In Section XI, adjacent cracks are replaced with a coalesced single crack when the distance between the cracks is less than half of the crack depth. However, the criterion for the offset distance is given as an absolute value, although the magnitude of the interaction depends on the crack size. In the current study, an alternative criterion for the offset distance was examined. Linear-elastic and elastic–plastic analyses were performed for interacting semicircular and semi-elliptical surface cracks by the finite element method under a tensile or bending load. The change in the stress intensity factors and J-integral values due to the relative spacing of cracks was investigated. Based on the relationship between the magnitude of the interaction and the relative position of the cracks, the allowable ctriterion for the offset distance was discussed.

An efficient two-step solution for vision-based pose determination of a parallel manipulator

A vision sensor for the direct pose determination of a parallel manipulator can extend the manipulators capabilities in many aspects. The existing approaches to a solution to the pose problem fall into two distinct categories: analytical solutions and iterative solutions. In this paper, we present an efficient two-step solution for the pose determination of a parallel manipulator by combining the advantages of the above two methods. Four points in an image, vertices of a parallelogram in object space, and the correspondences among these four coplanar points are utilized in the proposed method. In the first step, four coplanar vertices of a parallelogram, which locate the parallel manipulator's surface, are detected, Subsequently, the pose of the parallel manipulator can be determined with two affine invariants. In the second step, an iterative method is introduced, and the results of the first step are passed to the current step being used as initial values of the iterative process. Also, an error matrix is established through seven error functions, that are produced by the depth estimation and the co-planarity of the four vertices. The proposed method has been experimentally validated by a calibration board and the Pan and Tilt platform, which is a parallel manipulator developed by Googol Technology Ltd. The proposed method is then compared with three other existing methods. Experimental results demonstrate that the proposed method has the advantage of lower computational cost. The accuracy and stability, which are the main concerns during the real-time applications, are also improved.

Femtosecond laser modification of multilayered TiAlN/TiN coating

A target of multilayered TiAlN/TiN coating deposited on steel was irradiated by 200fs pulses of a Ti:Sapphire laser, operating at 775nm. Laser fluences of 1.16Jcm−2 to 116Jcm−2 produced a range of modifications, from well defined parallel surface structures on the coating, to deep craters in the substrate. Parameters for coating ablation were determined in terms of laser fluence and pulse count. A single-pulse damage threshold was found to be 0.66Jcm−2 and the damage incubation factor 0.642. At lower laser fluences formation of laser induced parallel surface structures was evident, beginning from the first pulse, with a periodicity of about 580nm. These structures remained and were pronounced at the rim of the damage spot even when the coating was completely ablated in the centre.

Parallel and adaptive surface reconstruction based on implicit PHT-splines

We present a new surface reconstruction framework, which uses the implicit PHT-spline for shape representation and allows us to efficiently reconstruct surface models from very large sets of points. A PHT-spline is a piecewise tri-cubic polynomial over a 3D hierarchical T-mesh, the basis functions of which have good properties such as nonnegativity, compact support and partition of unity. Given a point cloud, an implicit PHT-spline surface is constructed by interpolating the Hermitian information at the basis vertices of the T-mesh, and the Hermitian information is obtained by estimating the geometric quantities on the underlying surface of the point cloud. We take full advantage of the natural hierarchical structure of PHT-splines to reconstruct surfaces adaptively, with simple error-guided local refinements that adapt to the regional geometric details of the target object. Examples show that our approach can produce high quality reconstruction surfaces very efficiently. We also present the multi-threaded algorithm of our approach and show its parallel scalability.

TE modes in parallel cylindrical surface waveguides

Dispersion equations for TE and TM modes in width-limited waveguides formed by parallel cylindrical surfaces are derived in adiabatic approximation. It is shown that the dominant TE01 mode is strongly localized in the waveguide center.

Bioactive glass microspheres as osteopromotive inlays in macrotextured surfaces of Ti and CoCr alloy bone implants: Trapezoidal surface grooves without inlay most efficient in resisting torsional forces

We have tested the efficacy of porous bioactive glass (BG) inlays in enhancement of implant osseointegration. A total of 24 sheep underwent bilateral surgical implantation of three parallel implants on the anteromedial cortical surface of each tibia. The disc-shaped implants made of Ti6Al4V or cobalt chromium (CoCr) alloys had two parallel surface grooves (trapezoidal space with bottom widening) filled with sintered 100% bioactive glass microspheres or a selected mixture of bioactive and biocompatible glass microspheres. The surface of uncoated control implants was smooth, grit-blasted or had unfilled grooves. A subgroup of control smooth CoCr implants was coated with two or three BG layers. Implant incorporation with bone was evaluated using torque testing to failure, scanning electron microscopy and morphometry at 12 and 25 weeks. A total of 144 in vivo implants and 16 ex vivo cemented control implants were analyzed. Control Ti6Al4V implants with unfilled trapezoidal grooves showed highest torsional failure loads with excellent ingrowth of new bone and remodeling of ingrown bone into lamellar bone. Implants with BG inlays and microroughened control Ti6Al4V implants showed significantly lower torsional failure loads than control Ti6Al4V implants with unfilled grooves. In conclusion, BG inlays failed to enhance biological implant fixation. Macrotextured surface was more effective than grit-blasting in promotion of mechanical incorporation.

Study of interference in a double-slit without walls by plasmon tomography techniques

We investigate the free propagation of two parallel surface plasmon polaritons (SPP) beams using plasmon tomography. In the Fourier-plane images, we observed interference features that are not in correspondence with the images of SPPs on the sample's surface. We clearly observed that the interference maxima and minima are distributed over an arc of a circle. We explain the characteristics of the observed interference patterns assuming that each SPP beam can be considered as a “slit without walls”. We discuss important implications of this work for SPP tomography and interferometric plasmonic sensors.

Dry reforming of methane over Pt/PrCeZrO catalyst: Kinetic and mechanistic features by transient studies and their modeling

The effect of pretreatment and Pt content on the catalytic properties as well as mechanistic features of DR were investigated for structured catalysts comprised of Pt supported on CeO 2–ZrO 2 oxide doped by Pr. Progressive reduction of cationic Pt species by the reaction feed lowers the activity in CH 4 dry reforming while accelerating the reverse water gas shift reaction catalyzed only by Pt 0, which then decreases progressively the H 2/CO ratio in the effluent. This process is counteracted by the mobility of surface oxygen supplying oxygen atoms to reduced Pt centers thus ensuring their reoxidation and generating in parallel surface oxygen vacancies for the dissociation of CO 2. A mathematical model and software were developed for numerically studying the transients of the complex catalytic reactions. The processing of experimental data was fulfilled taking into account the importance of cationic forms of Pt, reactivity of carbonate complexes coordinated to these cations and oxygen surface/bulk diffusion. A quantitative evaluation of the density of catalyst's active sites and their coverage by reactive species was accomplished and the rates both of the lattice oxygen diffusion and main stages of the catalytic reaction were estimated.

Parallel implementation and optimization of the Sebvhos algorithm

In this paper, a parallel Surface Extraction from Binary Volumes with Higher-Order Smoothness (SEBVHOS) algorithm is proposed to accelerate the SEBVHOS execution. The original SEBVHOS algorithm is parallelized first, and then several performance optimization techniques which are loop optimization, cache optimization, false sharing optimization, synchronization overhead optimization, and thread affinity optimization, are used to improve the implementation’s performance on multi-core systems. The performance of the parallel SEBVHOS algorithm is analyzed on a dual-core system. The experimental results show that the parallel SEBVHOS algorithm achieves an average of 1.86x speedup. More importantly, our method does not come with additional aliasing artifacts, comparing to the original SEBVHOS algorithm.