EFFECT OF RADIATIVE TRANSFER ON THE THERMOPHORETIC PARTICLE DEPOSITION AROUND A CIRCULAR CYLINDER IN A UNIFORM CROSS FLOW

We investigated the effects of radiative transfer on the particle deposition around a circular cylinder in a cross flow. The fluid is transparent to radiation, and radiating particles are suspended in flow. The finite volume method was applied to analyze radiative transfer in the flow utilizing the nonorthogonal coordinate system. The radiative transfer coupled with convection and mass transfer is reasonably predicted by the method. The results are in good agreement with those of boundary layer analysis and available experimental data. We discuss the effects of the conduction-to-radiation parameter, optical thickness, scattering albedo, and wall emissivity on the heat transfer and particle deposition.     

A Study of Plastic Deformation Behavior of AA1050 Aluminum Alloy during Pure Shear Extrusion with Back Pressure

In the present study, the effects of back pressure on the filling fraction of die and the effective strain distribution throughout severely deformed material during pure shear extrusion, a novel severe plastic deformation process, are investigated by finite element analysis. A pure shear extrusion process found in the literature is employed and the predicted forming load is compared with experiments. A good agreement is observed between the results of the simulation with Coulomb friction of 0.12 and experiments. Various back pressures are applied to plunger at the exit channel of the die, and their influence on the filling fraction of the die and the effective strain in severely deformed billets are studied, indicating that the homogeneity of the effective strain on the cross-section of the deformed billet is decreased slightly. It is also found that the filling fraction of the die exit channel as well as average strain on the cross-section of the billet are increased.     

Laser induced transition from soot generation to shell shaped carbon nanoparticles in an acetylene flow: aerosol characterization

Shell shaped carbon nanoparticles were synthesized from acetylene flow injected inside an oxygen-hydrogen diffusion flame when it was irradiated with a focused beam of a CW CO₂ laser above a certain laser power and at a certain position [1]. In the present study, the evolution of carbon nanoparticles generated under laser irradiation has been investigated together with a study on the visualization of particle generating flames. The size distributions of carbon shell nanoparticles and soots have been determined by examining the images of TEM grid on which particles were captured by local thermophoretic sampling. The variations of radii of gyration and fractal dimensions of soot and shell shaped particulate aggregates are obtained at different laser powers.     

A flame metal combustion method for production of nanoparticles

We propose a flame metal combustion method for continuously synthesizing metal oxide nanoparticles. Micro-sized metal powder precursors were injected into a hydrogen-oxygen flame through a newly designed feeder system in order to be completely converted into metal oxide nanoparticles with good crystallinity. There is no limitation in the selection of precursors including metal, metal chloride and metal organic powders to synthesize nanoparticles. Various oxides such as magnesia, iron oxides and zinc oxide were demonstrated to be successfully generated by using this method. The sizes of oxide nanoparticles were controlled by varying flame temperatures and residence times.     

Frequency‐Temporal Filtering for a Robust Audio Fingerprinting Scheme in Real‐Noise Environments

In a real environment, sound recordings are commonly distorted by channel and background noise, and the performance of audio identification is mainly degraded by them. Recently, Philips introduced a robust and efficient audio fingerprinting scheme applying a differential (high‐pass filtering) to the frequency‐time sequence of the perceptual filter‐bank energies. In practice, however, the robustness of the audio fingerprinting scheme is still important in a real environment. In this letter, we introduce alternatives to the frequency‐temporal filtering combination for an extension method of Philips’ audio fingerprinting scheme to achieve robustness to channel and background noise under the conditions of a real situation. Our experimental results show that the proposed filtering combination improves noise robustness in audio identification.     

Determination of particle temperatures in a silica-generating counterflow flame via flame emission measurements

We propose a simple technique to measure particle temperatures in a particle generating counterflow flame. The silica particle temperature was derived from flame light emission measurements. This technique allows the non-intrusive measurement of particle temperatures over 2000 K. In addition, the OH concentration distribution in the hydrogen–oxygen flame was estimated from flame emission spectra in the ultraviolet region. A numerical model of the combustion processes, which included the reactions of SiCl₄ leading to the formation of silica particles, verified that the measured particle temperatures and OH concentration were close to the theoretical values.     

A novel hybrid carbon material

Both fullerenes and single-walled carbon nanotubes (SWNTs) exhibit many advantageous properties. Despite the similarities between these two forms of carbon, there have been very few attempts to physically merge them. We have discovered a novel hybrid material that combines fullerenes and SWNTs into a single structure in which the fullerenes are covalently bonded to the outer surface of the SWNTs. These fullerene-functionalized SWNTs, which we have termed NanoBuds, were selectively synthesized in two different one-step continuous methods, during which fullerenes were formed on iron-catalyst particles together with SWNTs during CO disproportionation. The field-emission characteristics of NanoBuds suggest that they may possess advantageous properties compared with single-walled nanotubes or fullerenes alone, or in their non-bonded configurations.     

Speaker Adaptation Using ICA‐Based Feature Transformation

Speaker adaptation techniques are generally used to reduce speaker differences in speech recognition. In this work, we focus on the features fitted to a linear regression‐based speaker adaptation. These are obtained by feature transformation based on independent component analysis (ICA), and the feature transformation matrices are estimated from the training data and adaptation data. Since the adaptation data is not sufficient to reliably estimate the ICA‐based feature transformation matrix, it is necessary to adjust the ICA‐based feature transformation matrix estimated from a new speaker utterance. To cope with this problem, we propose a smoothing method through a linear interpolation between the speaker‐independent (SI) feature transformation matrix and the speaker‐dependent (SD) feature transformation matrix. From our experiments, we observed that the proposed method is more effective in the mismatched case. In the mismatched case, the adaptation performance is improved because the smoothed feature transformation matrix makes speaker adaptation using noisy speech more robust.