Density Profile Characteristics Research Articles

Chemical surface densification of hardwood through lateral monomer impregnation and in situ electron beam polymerization, Part I: density profile and surface hardness of three hardwood species

Filling wood cells with polymeric materials offers great opportunities to improve wood strength. Some applications, such as flooring, may require densification on one side of the material only. Yellow birch (Betula alleghaniensis Britt.), sugar maple (Acer saccharum Marsh.) and red oak (Quercus rubra L.) were surface densified through lateral chemical impregnation of monomers under vacuum followed by in situ electron beam polymerization. Lateral impregnation led to low mean chemical retention of 4% for sugar maple, 11% for red oak and 12% for yellow birch. X-ray densitometry and microtomography revealed an asymmetric density profile comparable to mechanically surface densified wood due to polymer-filled vessels. Scanning electron microscopy images showed presence of polymer-filled fibers beneath the surface. Brinell hardness of all species increased significantly compared to untreated wood. Low chemical retention significantly improved hardness due to localized polymer beneath the surface. Density profile characteristics were extracted from densitometry curves and correlated to hardness. Deep monomer penetration was more favorable to hardness than high surface density peak.

Uncertainty Quantification of Density and Stratification Estimates with Implications for Predicting Ocean Dynamics

AbstractWe present a statistical method for reconstructing continuous background density profiles that embeds incomplete measurements and a physically intuitive density stratification model within a Bayesian hierarchal framework. A double hyperbolic tangent function is used as a parametric density stratification model that captures various pycnocline structures in the upper ocean and offers insight into several density profile characteristics (e.g., pycnocline depth). The posterior distribution is used to quantify uncertainty and is estimated using recent advances in Markov chain Monte Carlo sampling. Temporally evolving posterior distributions of density profile characteristics, isopycnal heights, and nonlinear ocean process models for internal gravity waves are presented as examples of how uncertainty propagates through models dependent on the density stratification. The results show 0.95 posterior interval widths that ranged from 2.5% to 4% of the expected values for the linear internal wave phase speed and 15%–40% for the nonlinear internal wave steepening parameter. The data, collected over a year from a through-the-column mooring, and code, implemented in the software package Stan, accompany the article.

Effect of hot pressing temperature on the density profile of compressed solid wood

To expand the applications of low-density wood, solid white poplar (Populus tomentosa) wood with a moisture content of 10.6% was compressed 5 mm radially at 90 °C, 120 °C, 150 °C, 180 °C, and 210 °C, and the density profile characteristics were analyzed. It was found that compressed wood with a non-uniform density profile contributed to the peak density and average density of the compressed layer, where the highest values were 0.87 g/cm3 and 0.72 g/cm3, respectively. The density peak and compressed layer were formed at various distances from the wood surface according to the pressing temperatures tested. It was concluded that the pressing temperature had a great effect on the density profile of the compressed wood and the pressing temperature effectively controlled the shape of the density profile.

Analysing density profile characteristics of surface densified solid wood using computational approach

In this study, solid Scots pine was surface densified in an open press using different moisture contents (9·6 and 12·4%), temperatures (150 and 200°C), press closing times (0·5 and 5 min), holding times (1 and 10 min) and compression ratios (6·7 and 25%). The characteristics of the formed density profiles were defined and their correlations to the process parameters and Brinell hardness and elastic recovery were analysed. Compression ratio and closing time had the strongest effect on the formation of the density profile, as well as the hardness and elastic recovery. The amount of localised deformation (peak area) did not have significant effect on the Brinell hardness or elastic recovery, whereas, the highest density achieved (peak density) and its location (peak distance) dominated the effect. Brinell hardness and elastic recovery were found to correlate well with each other.

Cupping behaviour of surface densified Scots pine wood: the effect of process parameters and correlation with density profile characteristics

Surface densification is a process by which the mechanical properties of the wood surface can be improved, increasing the attractiveness of low density wood for applications such as flooring. The purpose of this study was to investigate the development of undesired cupping deformations in surface densified solid wood. The effects of process parameters (compression ratio, temperature, holding time, closing time, and initial moisture content) on cupping were studied, and correlation analysis was used to determine the strength of association. Correlation analysis was also performed to explore the potential dependence of cupping on the density profile characteristics of surface densified wood. Correlations of moderate strength were found between cupping and the process parameters, as well as between cupping and the density profile characteristics. Compression ratio was found to be the most influential process parameter: samples with a high compression ratio showed distinctly different cupping behaviour than samples with a low compression ratio. Density profile characteristics were considered a probable contributor to cupping, but the influence of other effects was also considered likely. Interestingly, certain combinations of parameters were found to result in very small cupping deformations. Therefore, the results of this study indicate that cupping can be minimised by optimisation of process parameters.

ICRH antenna coupling physics and optimum plasma edge density profile. Application to ITER

The performance of an ICRH system depends on the coupling capabilities of the antenna to the inhomogeneous plasma profile in front of it. The aim of this study is to understand the key physics phenomena contributing to the coupling. It is shown that the following plasma density profile characteristics are decisive: (i) distance between the antenna and the wave cutoff density, (ii) position of an optimum density with respect to the cutoff one and (iii) the density gradient leading from this optimum density to the plasma bulk. At each step of the analysis approximate relations are derived and the loading due to the plasma is compared with that of an isotropic dielectric medium in view of the application for modelling or dummy load testing. Examples are taken starting from the case of the projected ITER antenna array with its different phasing cases in front of the plasma edge profile used in the conceptual design phase. It is shown that, for the same antenna–cutoff distance, slight profile modifications can lead to substantial coupling and therefore power capability variations. Stronger profile modifications and some critically shaped resonant edge profiles are also analysed. The usefulness of a dielectric medium to simulate plasma loading is discussed in an appendix.

Automatic evaluation of edge profile characteristics in ASDEX Upgrade H-mode density limit discharges with FM-CW reflectometry

The set of data processing techniques used on ASDEX Upgrade to automatically evaluate edge density profile characteristics from broadband data, obtained with the frequency-modulated continuous-wave reflectometer, has recently been upgraded to include (i) an adaptive algorithm that automatically optimizes the length of the window used in the spectrogram analysis of broadband signals and (ii) a new method to estimate the edge pedestal density based on the evolution of the local derivative of the group delay curve, removing the need for user supplied parameters. These tools are especially important in cases where the group delay of the reflected signals varies significantly in a short probing frequency range, such as when the profile exhibits a density shoulder at the edge. The application of these techniques in ASDEX Upgrade H-mode density limit discharges, to automatically obtain the time evolution of the edge pedestal parameters, namely, its density, position, and width, shows a clear improvement both on the time-frequency resolution of the group delay characteristic and on the detection of the density shoulder.

Surface Tension Prediction Using Characteristics of the Density Profile Through the Interfacial Region

A simple surface tension estimation technique is described that is based solely upon the characteristics of the density profile in the interfacial region and the physical properties of the molecules in the fluid. This method, denoted free energy integration (FEI), links interfacial tension to known interfacial region density profile characteristics obtained via experiment or simulation. The general FEI methodology is provided here, and specific relations are derived for a methodology that incorporates the Redlich–Kwong fluid model. The Redlich–Kwong based FEI method was used to predict interfacial tension using the density profile characteristics of molecular dynamics (MD) simulations of argon using the Lennard–Jones potential, diatomic nitrogen using the two-center Lennard–Jones potential, and water using the extended simple point-charge (SPC/E) model. These results for argon compare favorably to values calculated by the traditional virial approach, known values from the literature using the finite-size scaling technique, and ASHRAE recommended values. In addition, the FEI predictions agree well with ASHRAE values and predictions using the virial method for nitrogen for the simulated range of temperatures in this study, and for water for reduced temperatures above 0.7. In addition, the FEI method results agree well with other established theoretical techniques for predictions of the surface tension of sulfur hexafluoride close to the critical point.

Measurements of electron density profile characteristics in various kinds of plasma configurations in the TS‐3 plasma merging device

AbstractMeasurements and a comparative study have been performed on electron density profiles, focusing on the electron density gradient near the magnetic separatrix in various kinds of plasma confinements such as the ST, spheromak, and RFP in the TS‐3 device. A CO2 laser interferometer using a glass tube to clear the path for the laser was introduced in order to measure the electron density profile with time resolution. It was shown that ST with a high q value at the plasma edge (q: safety factor) has a larger electron density gradient than low‐q plasma confinements such as the spheromak and RFP. In particular, the ST with edge q value greater than about 2 showed a large electron density gradient at the edge. The idea that the j×B force profile of the higher‐q ST could sustain the higher thermal pressure supports these results. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 35–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10158

Application of the drilling resistance method for annual ring characteristics: evaluation of Taiwania (Taiwania cryptomerioides) trees grown with different thinning and pruning treatments

The effects of various thinning and pruning methods on the density profile and annual ring characteristics of Taiwania (Taiwania cryptomerioides Hay.) using the drilling resistance technique were investigated. The results showed that thinning caused wider annual rings than medium thinning or no thinning, and pruning caused narrower annual rings than no pruning. Moreover, the thinning treatment affected annual rings more effectively than the pruning treatment. The average ring density after the thinning treatments showed a trend as follows: no thinning > medium > heavy. This indicates that thinning reduces the average ring density. The average ring density after the pruning treatments showed a trend as follows: medium > no pruning > heavy. However, the differences between thinning and no thinning were not statistically significant. The percentage of latewood in Taiwania after these three thinning and pruning treatments are shown. The results with silvicultural treatments have the order: medium > not treated > heavy, but there are no statistically significant differences among thinning, pruning, and thinning where pruning interactions were observed. Moreover, there were highly significant negative relations between the average ring width and the various ring densities for Taiwania, but the determination coefficients were small. In addition, there was a highly positively significant relation between the latewood percentage and latewood width.

コンパクトトーラス合体実験装置TS-3における各種プラズマ配位の電子密度分布特性の計測

コンパクトトーラス合体実験装置TS-3における各種プラズマ配位の電子密度分布特性の計測

A three-wave heterodyne correlation reflectometer developed in the T-10 tokamak

A three-wave heterodyne O-mode reflectometer was developed and tested in experiments on the T-10 tokamak. Three launched waves are obtained by frequency splitting due to amplitude modulation with a p-i-n diode. Source frequencies from 36 to 78 GHz were used in the experiments. The ability of the reflectometer to measure simultaneously density profile characteristics, such as the time evolution of the relative phase and the unambiguous time delay of the reflected wave together with small-scale density fluctuation characteristics such as the radial and poloidal correlation lengths, was demonstrated with T-10 experimental data. The reflectometer can provide important information about fine changes in the density profile during sawteeth and low-m magnetohydrodynamics oscillations. Poloidal correlation measurements make it possible to measure transverse turbulence velocities and velocity shear. It was shown that both types of correlation measurements enable one to distinguish different types of turbulence according to the values of their correlation lengths, and that probing the plasma from several poloidal directions simultaneously greatly enhances the potential of reflectometry for the investigation of turbulence physics. In particular, it was found that different turbulence types may be either poloidally symmetrical or have much higher amplitude on the low field side of the discharge. Probing with several poloidal directions also enables one to make toroidal correlation measurements over long distances at certain resonant q values after one or two turns of magnetic field line around the major tokamak axis. In fact, correlations near 40% were observed experimentally. Such measurements may give additional information about turbulence characteristics on the one hand and allow radial q profile measurements on the other hand. In addition, the capabilities of reflectometry may be enhanced with the application of a proposed holography approach.

Helium clusters at finite temperature

An analysis of helium cluster properties at finite temperature using a phenomenological free energy density has been carried out. We have studied in detail the energetics and the density profile characteristics of hot drops of both helium isotopes containing 70, 112, 168, 240 and 330 atoms. A finite temperature mass formula including volume, surface and curvature terms has been derived.