The voltage-pulsing effects in AC plasma display panel

The effect of the voltage pulsing is simulated in AC plasma display panel using various two-dimensional simulation codes. The volume-averaged density increases rapidly because of the large electric field in the AC-plasma display panel cell as the peak voltage is raised. The ignition time and the decaying time of the discharge are related to the external voltage. The space and time variations of the charged particle densities and the potential profile are described for various voltage forms. The ion energy distribution near the cathode-side dielectric which plays an important role in the MgO lifetime and the secondary electron emission coefficient is concentrated to much lower energies than the applied voltage     

Macroscopic cell experiments and three-dimensionalmodelling on electrode-shaping plasma display cell

A macroscopic cell and three-dimensional fluid model have been used to investigate the discharge characteristics in ac plasma display panel cells of electrode-shaping configurations. Four kinds of non-standard geometries (i.e. $D$-, ${\it\del}$-, $W$- and $U$-shape electrodes) have been considered. The characteristics of the discharge current, the operating voltage and the discharge efficiency of different configurations have been discussed. It is found that the discharge efficiency can be improved by about 10\%--30\% compared with the standard geometry, while the operating voltage increases slightly in the non-standard geometries. There is a trade-off between improving the discharge efficiency and lowering the sustaining voltage in design of plasma display cells by electrode shaping.     

Design and development of driving waveforms for AC plasma display panels

This paper presents design and development of driving waveforms to improve efficacy, contrast, and resolution for ac plasma display panels (PDPs). In the paper, the conventional driving waveforms are first reviewed, and the proposed driving waveforms are then discussed. The driving of PDPs in each subframe is divided into three periods: the reset period, scan period, and sustain period. During the reset period, the proposed ramp-like reset waveforms can enhance the contrast and resolution, and can lower the scan voltage while still sustaining a reliable wall-charge control. Additionally, a square sustain waveform stacked with the ramp-like waveform can induce self-erasing discharges which will improve efficacy during the sustain period. Operation of a PDP and comparison among various driving waveforms are also presented. Experimental results measured from a 46-in PDP system have verified the feasibility of the proposed driving waveforms.     

Two-dimensional simulations of plasma flow and charge spreadingacross barrier pixels in AC plasma displays

Two-dimensional multispecies simulations of adjacent pixels separated by a barrier height 80% the gap height in a plasma display pixel cell are performed. The fill gas pressure is 400 torr with 2% xenon in helium. The simulations using a minimum number of excited states of helium and xenon are performed for different cell widths representing different display resolutions. The simulations show plasma transport through the gap to the adjacent pixel which is in the sustained off state. In a sustained off state, there is no discharge in the pixel at the sustained voltage. The simulations show that for low-resolution displays, the plasma overflow does not cause a discharge in the adjacent pixel that is in the sustained off mode, while for a high-resolution display a 20% gap in the barrier height could result in a breakdown in the adjacent off pixel. A higher pixel resolution, or equivalently smaller pixel pitch. requires higher firing and sustained voltages due primarily to increased particle losses as a result of the reduced particle transit times. Finally, using a larger number of excited xenon atomic states including the xenon [6s, j=1] and [6s', j=1] radiative states and the molecular xenon dimer, an isolated single pixel is simulated to model the transport of excited states including the radiative states. The model shows that the density profiles peak in the cathode fall region spreading out to the side walls with decreasing intensity     

Experimental observation of image sticking phenomenon in AC plasma display panel

The itinerant strong sustain discharge that occurs during a sustain period over a few minutes causes image sticking, which means a ghost image remains in the subsequent image when the previous image was continuously displayed over a few minutes. Accordingly, this paper investigates whether the dominant factor in image sticking is the MgO surface or phosphor layer by testing the effects of image sticking in subsequent dark and bright images using a 42-in plasma display panel. When the subsequent image was dark, the image sticking was found to produce a brighter ghost image than the background. Thus, since the luminance of a dark image is produced by the weak discharge that occurs during the reset-period, the higher luminance of the ghost image was mainly due to the activation of the MgO surface. Conversely, when the subsequent image was bright, the image sticking was found to produce a darker ghost image than the background. Thus, since the luminance of a bright image is predominantly produced by the strong discharge that occurs during the sustain period, the lower luminance of the ghost image was mainly due to the deterioration of the phosphor layer.     

Granular Rayleigh-Taylor instability: experiments and simulations

A granular instability driven by gravity is studied experimentally and numerically. The instability arises as grains fall in a closed Hele-Shaw cell where a layer of dense granular material is positioned above a layer of air. The initially flat front defined by the grains subsequently develops into a pattern of falling granular fingers separated by rising bubbles of air. A transient coarsening of the front is observed right from the start by a finger merging process. The coarsening is later stabilized by new fingers growing from the center of the rising bubbles. The structures are quantified by means of Fourier analysis and quantitative agreement between experiment and computation is shown. This analysis also reveals scale invariance of the flow structures under overall change of spatial scale.     

New color-enhancing discharge mode using self-erasing discharge in AC plasma display panel

A new color-enhancing discharge mode using a self-erasing discharge is proposed based on an analysis of the Ne emission mechanism in a Ne-Xe gas mixture. The effects of the new color-enhancing discharge mode produced by a ramped-square sustain waveform on improving the color reproducibility are examined in an alternate current plasma display panel (ac-PDP) filled with a Ne-Xe gas mixture. When the ramped-square sustain pulses are applied at 150 kHz, the color purities of the blue and green visible emissions are both improved, thereby expanding the color gamut area by about 5.4% without reducing the luminance.     

一种合成显示超声反射CT三维图像的方法

针对超声反射ＣＴ在无损检测中的应用，本文提出了一种先投影被测物体轮廓作为背景，然后在投影内部缺陷的过程中合成显示三维图像的方法，对模拟３Ｄ数据作处理，实例表明，该方法实用有效。     

Oxygen K-edge in vanadium oxides: simulations and experiments

Band-structure (BS) calculations of the density of states (DOS) using the full potential augmented plane waves code WIEN97 were performed on the four single-valence vanadium oxides VO, V₂O₃, VO₂ and V₂O₅. The DOS are discussed with respect to the distortions of the VO₆ octahedra, the oxidation states of vanadium and the orbital hybridisations of oxygen atoms. The simulated oxygen K-edge fine structures (ELNES) calculated with the TELNES program were compared with experimental results obtained by electron energy-loss spectrometry (EELS), showing good agreement. We show that changes in the fine structures of the investigated vanadium oxides mainly result from changes in the O-p DOS and not from the shift of the DOS according to a rigid band model. Received 17 December 2001 / Received in final form 19 June 2002 Published online 13 August 2002     

Condensation in disordered lasers: theory, 3D+1 simulations, and experiments

The complex processes underlying the generation of a coherent emission from the multiple scattering of photons and wave localization in the presence of structural disorder are still mostly unexplored. Here we show that a single nonlinear Schr?dinger equation, playing the role of the Schwalow-Townes law for standard lasers, quantitatively reproduces experimental results and three-dimensional time-domain parallel simulations of a colloidal laser system.     

Bridging simulations and experiments in microstructure evolution

We demonstrate the importance of anisotropic interface properties in microstructure evolution by comparing computed evolved microstructures to final experimental microstructures of 5170 grains in 19 thin aluminum foil samples. This is the first time that a direct experimental validation of simulation has been performed at the level of individual grains. We observe that simulated microstructures using curvature-driven grain boundary motion and anisotropic interface properties agree well with experimentally evolved microstructures, whereas agreement is poor when isotropic properties are used.     

Rate processes on fractals: Theory,simulations, and experiments

Heterogeneous kinetics are shown to differ drastically from homogeneous kinetics. For the elementary reaction A + A products we show that the diffusion-limited reaction rate is proportional tot ^– h[A]² or to [A]^x, whereh=1- d _s/2, X=1+2/d _s =(h-2)(h-1), andd _s is the effective spectral dimension. We note that ford = d _s =1, h =1/2 andX = 3, for percolating clustersd _s = 4/3,h = 1/3 andX = 5/2, while for dust ds <1, 1 >h > 1/2 and >X > 3. Scaling arguments, supercomputer simulations and experiments give a consistent picture. The interplay of energetic and geometric heterogeneity results in fractal-like kinetics and is relevant to excitation fusion experiments in porous membranes, films, and polymeric glasses. However, in isotopic mixed crystals, the geometric fractal nature (percolation clusters) dominates.     

Virtual experiments: Combining realistic neutron scattering instrument and sample simulations

A new sample component is presented for the Monte Carlo, ray-tracing program, McStas, which is widely used to simulate neutron scattering instruments. The new component allows the sample to be described by its material dynamic structure factor, which is separated into coherent and incoherent contributions. The effects of absorption and multiple scattering are treated and results from simulations and previous experiments are compared.     

Catalytic ignition and extinction of hydrogen: comparison of simulations and experiments

Surface ignition and extinction of hydrogen/air mixtures on platinum surfaces are modeled using a detailed surface kinetic mechanism and transport phenomena. It is shown that the platinum surface can be poisoned by different adsorbates, and the dynamic process of catalytic ignition and extinction is associated with a phase transition from one poisoning species to another. For certain temperatures, multiple poisoned states of the surface coexist. Comparison of simulations with experiments is conducted, and it is shown that the self-inhibition of hydrogen catalytic ignition is caused by poisoning of platinum by atomic hydrogen.     

Study on 3-D arc plasma fields with holographic interferometry

In this paper,serveral temperature(refractive index)fields which are de-scribed by different kinds of functions are reconstructed by computer simulations based onholographic tomography theory.The obtained results are compared and analyzed.We de-signed a special multibeam holographic system in which the disturbance from the intense arclight can be filtered.With the system multidirectional holographic interferograms of arc fieldscan be taken simultaneously.We also calculate the quantitative distributions of temperature,the number density of particles and ionicity at a typical section of the argon arc field from theexperimeantal data.     

Hydrophobic/hydrophilic solvation: inferences from Monte Carlo simulations and experiments

In this study Monte Carlo simulations are used to determine the solvation properties of model hydrophobic (xenon and hard sphere) and hydrophilic (dimethyl ether) solutes in SPC/E water. Various contributions to the experimental solvation entropy, including the solvent reorganization entropy, have been determined. The main conclusion drawn, which is in accord with solubility data, is that poor solubility correlates with poor solute-water interaction. At room temperature, energy dominates the aqueous solubility of both hydrophobic and hydrophilic solutes, rather than entropy. However, at higher temperatures the solubility can pass through a minimum, and then entropy becomes dominant. Another interesting finding is the presence of larger than expected cavities in water. Two different simulation results support this finding. This unexpected hollow structure in water explains why a hard sphere solute is more soluble in water than in a comparable hard sphere or Lennard-Jones solvent. Hydrogen bonding causes water to aggregate into clusters that produce a few large cavities rather than many smaller cavities. The propensity for clustering also explains why water gives the illusion of being a low density liquid. Sufficient theoretical apparatus is developed to connect theoretical solvation properties to those measured by simulation and experiment. Finally, based on gas solubility, an intuitive hydrophobic/hydrophilic scale is developed.     

The acoustical influence of balcony depth and parapet form: experiments and simulations

The influence of balcony depth and parapet form on the acoustical performance of building facades close to roadways have been investigated. Various depths and two inclinations of parapet have been modeled on an eight floor building. Pyramid ray-tracing simulations and scale model measurements have been carried out. The predicted and measured A-weighted sound pressure level reductions over the balcony back wall and in free field conditions have been compared. The results have been used to derive empirical equations for predicting protection as a function of geometrical parameters. The protection obtained by various parapet depths ranges between 4 and 8 dB(A), while an additional protection of between 0.5 and 4 dB(A) can be obtained by inclining the parapets.     

Multispectral 3D phase-encoded turbo spin-echo for imaging near metal: Limitations and possibilities demonstrated by simulations and phantom experiments

To see improvements in the imaging performance near biomaterial implants we assessed a multispectral fully phase-encoded turbo spin-echo (ms3D-PE-TSE) sequence for artifact reduction capabilities and scan time efficiency in simulation and phantom experiments.For this purpose, ms3D-PE-TSE and ms3D-TSE sequences were implemented to obtain multispectral images (± 20 kHz) of a cobalt-chromium (CoCr) knee implant embedded in agarose. In addition, a knee implant computer model and the acquired ms3D-PE-TSE images were used to investigate the possibilities for scan time acceleration using field-of-view (FOV) reduction for off-resonance frequency bins and compressed sensing reconstructions of undersampled data. Both acceleration methods were combined to acquire a + 10 kHz frequency bin in a second experiment.The obtained ms3D-PE-TSE images showed no susceptibility related artifacts, while ms3D-TSE images suffered from hyper-intensity artifacts. The limitations of ms3D-TSE were apparent in the far off-resonance regions (±[10–20] kHz) located close to the implant. The scan time calculations showed that ms3D-PE-TSE can be applied in a clinically relevant timeframe (~ 12 min), when omitting the three central frequency bins. The feasibility of CS acceleration for ms3D-PE-TSE was demonstrated using retrospective reconstructions before combining CS and rFOV imaging to decrease the scan time for the + 10 kHz frequency bin from ~ 10.9 min to ~ 3.5 min, while also increasing the spatial resolution fourfold. The temporally resolved signal of ms3D-PE-TSE proved to be useful to decrease the intensity ripples after sum-of-squares reconstructions and increase the signal-to-noise ratio.The presented results suggest that the scan time limitations of ms3D-PE-TSE can be sufficiently addressed when focusing on signal acquisitions in the direct vicinity of metal implants. Because these regions cannot be measured with existing multispectral methods, the presented ms3D-PE-TSE method may enable the detection of inflammation or (pseudo-)tumors in locations close to the implant.     

Coalescence in 2 dimensions: experiments on thin copolymer films and numerical simulations

This paper presents on one hand the experimental study of the coalescence kinetics of two closed bidimensional fluid domains at the surface of a multilayered dibloc copolymer film, and on the other hand a numerical simulation of the same evolution. The latter is based on ”diffusive” phenomenological equations which are surface conservative and which neglect the 2-dimensional viscosity of the layers. The successive shapes observed in the experiments and obtained from the simulation are very close. It would not be the case if the 2D viscosity was significant. Received : 17 march 1997 / Revised : 11 september 1997 / Accepted : 2 december 1997