Wave dynamics on a thin-liquid film falling down a heated wall

The dynamics of a thin liquid film falling down a uniformly heated wall is studied. The model introduced by Kalliadasis et al. [J. Fluid Mech. 475 (2003) 377] for the same problem is revisited and its deficiencies, namely the prediction of a critical Reynolds number with 20% error, cured. For the energy equation a high-order Galerkin projection in terms of polynomial test functions is developed. It is shown that not only does this more refined formulation correct the critical Reynolds number, but it also gives, with an appropriate expansion close to criticality, the long-wave theory. Bifurcation diagrams for permanent solitary waves are constructed and compared with the solution branches obtained from different models. It is shown that, in all cases, the long-wave theory exhibits limit points and branch multiplicity, while the other models predict the continuing existence of solitary waves. Time-dependent computations show that the free surface and interfacial temperature approach a train of coherent structures that resemble the infinite-domain stationary solitary pulses.     

RF antenna analysis with the ICANT code

The ICANT code computes self-consistently the surface current distribution on a 3D antenna model radiating in a plasma or vacuum and has been used to analyze the coupling properties of various antenna models. In this work it is used to assess near-fields generated by different versions of the TCABR (Tokamak Chauffage Alfvén wave heating experiment in Brazil) antenna as well as coupling properties of the TEXTOR tokamak in Forshungszentrum Jülich. Two different strap models planned for the TCABR antenna are shown to be practically equivalent in terms of maximum electric field. Textor coupling calculations are close to experimental values.     

Electromagnetic Resistive Drift Instability in Current Carrying Low Temperature Tokamak Edges

It is shown that the purely growing electrostatic rippling mode can couple with the shear Alfven wave to give rise to an oscillatory electromagnetic instability in tokamak edge regions. This mechanism can be one of the causes of electromagnetic fluctuations observed near plasma edges. This instability can occur only in the very low temperature regions where resistivity fluctuations can become important due to large electron-ion collision frequency.     

Application of ultrasonic waves in activation of microcrystalline cellulose

In this work, microcrystalline cellulose (MCC) was activated with ultrasonic waves. The influences of ultrasonic treatment on the changes of supramolecular structures and morphology structure were studied by WAXS and SEM. The accessibility of the MCC was characterized by water retention value (WRV) and specific surficial area. The influence of ultrasonic treatment on the reactivity of MCC was investigated through the reaction of MCC being oxidized into 2,3‐diadehyde cellulose (DAC) by periodate sodium. The mechanism of the reactivity change of ultrasonically treated MCC was examined. The results showed that the degree of crystallinity of MCC decreased and the degree of polymerization showed little change after treatment with ultrasonic waves. The morphologial variation of the treated MCC was significant when compared with the untreated MCC, which contribute to the improvement of accessibility. The aldehyde content of DAC prepared from ultrasonically treated MCC was improved from 64.19 to 85.00%, indicating that the regioselective oxidation reactivity of MCC was significantly improved. The aldehyde content was found to first increase with time of ultrasonic treatment to a point, and then decrease as time progressed. In addition, the aldehyde content was found to increase with an increase in ultrasonic power. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A Novel Method Of Transport Barrier Formation

A novel technique is proposed for creating transport barriers by the rf waves. This is that the transport barriers can be created by the rf induced ponderomotive force itself and no rf induced flow shear generation is necessary. It is demonstrated that the ponderomotive force of the rf waves can stabilize the ion temperature gradient (ITG) mode, considered nowadays as the dominant source of anomalous energy losses in the low confinement (L) mode. It is also shown that this stabilization can be achieved for rather modest values of the rf power and hence should be easily obtained in actual experiments.      

An automated tanh-function method for finding solitary wave solutions to non-linear evolution equations

The tanh-function method for finding explicit travelling solitary wave solutions to non-linear evolution equations is described. The method is usually extremely tedious to use by hand. We present a Mathematica package ATFM that deals with the tedious algebra and outputs directly the required solutions. The use of the package is illustrated by applying it to a variety of equations; not only are previously known solutions recovered but in some cases more general forms of solution are obtained.     

Finite-size effects in surface tension: Thermodynamics and the Gaussian interface model

It has been suggested by Kayser that finite-size effects associated with capillary waves might play a significant role in some surface tension measurements; for capillary rise between plates a distance D apart, an effect varying as 1/D and apparently observable in measurements, was proposed. In reconsidering this problem, one must analyze the thermodynamics of finite-size corrections to surface tension. In particular, one sees that capillary rise between plates does not measure the interfacial free energy density but, rather, a derivative of the interfacial free energy with respect to a system dimension. The quantity needed to draw definite conclusions, the finite-size residual free energy, can be calculated within the harmonic or Gaussian capillary wave model in d spatial dimensions with the aid of Poisson summation techniques and should yield the correct leading asymptotic behavior. For d=3 and experimentally relevant parameter values, the results are independent of the short-wavelength cutoff needed in the model and can be checked against the theory of conformai covariance at two-dimensional critical points. It is found that the finite-size effects in capillary-rise measurements of surface tension vary as 1/D ² (with a universal coefficient) but are too small to be seen in current experiments.Invited paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Wigner-Ville变换在抗箔条干扰方法中的研究

在雷达跟踪空中目标时,受箔条干扰信号的影响,会造成雷达探测的数据不完整、不精确、不可靠.针对这一情况,本文应用Wigner-Ville变换理论,给出了一种对雷达回波信号进行滤波的算法.通过仿真实验证明,应用Wigner-Ville变换能较好地抑制箔条干扰信号,可进一步提高雷达系统的跟踪精度和可靠性.     

Langasite based surface acoustic wave sensors for high temperature chemical detection in harsh environment: Design of the transducers and packaging

This work presents the design and the thermal behavior characterization of an innovative self-test portable surface acoustic wave platform for chemical detection under high temperature. Before the forthcoming deposition of the sensitive coating, the thermal behavior of the bare LGS acoustic platform has been focused on. The system includes a (0°, 140°, 25°) crystallographic cut langasite (LGS) piezoelectric substrate, a ceramic heater, and a platform with RF connections for remote measurements. The packaging consists in a hermetic stainless steel cell, which enables safe gas detection. Its thermal behavior was successfully investigated in the temperature range 25-500 °C thanks to the integrated heater, without using an external furnace. Finite element modeling aided the development of this platform structure by predicting the thermal behavior of each of its parts and their cross-influences. The structure of the platform was specifically designed so that 500 °C could be reached on the LGS acoustic device while the temperature on the PCB connections should not exceed 50 °C. Then, the temperature-dependence on the waves generated by the acoustic transducers has been investigated through numerical modeling by resolving the wave propagation equations with several sets of LGS constants. Corresponding simulations showed good agreement with experiments, Thermal cycling up to 350 °C highlighted satisfactory hardiness and response-reproducibility of the system towards thermal stress, after a first burn effect.     

一种新型本征倏逝波型光纤传感器的研究

研究开发了一种新型本征型光纤倏逝波传感器.采用有机玻璃板和大半圆弧高抛光PVC管构成光纤支架,将60/125 μm阶跃多模光纤隔一定距离剥除等长度涂覆层后缠绕于光纤支架上,其无涂覆层部分位于上下两PVC管之间,经化学腐蚀后获得裸芯总长度大于0.5m的新型高灵敏本征型光纤倏逝波传感器.实验结果表明:该传感器对亚甲基蓝的探...