PHASE-SPACE DIFFUSION EQUATIONS FOR SINGLE BROWNIAN PARTICLE MOTION NEAR SURFACES

In numerous physical processes involving the motion of micron and submicron sized particles near surfaces, such as the filtration of hydrosols and aerosols, the particle motion is the net result of the combined effects of fluid convection, external forces, particle inertia, Brownian particle motion, and particle-surface fluid dynamic interactions. The most general method of describing particle motion under the combined action of these effects is through the so-called Fokker-Planck equation. In the absence of particle-surface fluid dynamic interactions, the Fokker-Planck equation is well-known, and it has been applied in a general way to problems involving the adsorption or deposition of Brownian particles onto surfaces through a solution technique known as the Brownian dynamics simulation method.

In this study, the Fokker-Planck equation for Brownian particle motion near surfaces is generalized to include particle-surface fluid dynamic interactions. The Fokker-Planck equation is shown to follow from the Liouville equation for the Brownian particle and n-fluid molecules present in the system, thus, establishing a firm theoretical foundation for the Fokker-Planck equation and the various other phase-space diffusion equations that follow from it.

Based on diagonalization of the Fokker-Planck equation, its short-time behavior is also derived here which enables a generalization of the Brownian dynamics method for the study of particle motion near surfaces including fluid dynamic interactions. Additionally, a perturbation solution of the Fokker-Planck equation under the conditions of small, but finite particle Stokes number is also derived. These solutions are shown to agree with previously given representations of the Smoluchowski or convective-diffusion equation for Brownian particle motion near surfaces, as well as with inertial corrections to the Smoluchowski equation available in the literature. This latter equation is also generalized here to include particle-surface fluid dynamic interactions.     

Bench-scale continuous hydrogenation of Australian coals — study of iron catalysts and recycle solvent composition

The inter-relations between iron catalysts, recycle solvent composition and product yield and composition have been investigated in bench-scale (1–2 kg h^?1) continuous hydrogenation of Australian coals at process severity of 21–22 MPa at 400–430°C. Products and recycle solvent are recovered in batch distillation (atmospheric and vacuum) and the distillate solvent is returned to slurry feed without further treatment. Successive samples of recycle solvent are analysed by g.c.-m.s., i.r. and titrimetry. The effect of adding iron catalysts in the form of red mud - sulphur mixtures or compounds after a short period of continuous operation without catalyst is demonstrated. Distillate yields from black coals increase from 24–34 wt% daf under non-catalytic conditions to 35–53 wt% daf by adding iron catalysts. The composition of the almost equilibrated recycle solvent also changes and a new equilibrium is approached after the iron catalyst is added. The effect of solvent composition on distillate yield can not be determined from these data. The ratio of hydroaromatic components to hydroaromatic plus aromatic components in the solvent increases from ≈0.2 at non-catalytic equilibrium to ≈0.5–0.6 at catalysed equilibrium after adding iron. Other compositional parameters in the recycle solvent do not show any clear responses to the addition of iron. Equilibrium solvent composition under constant operating conditions is attained at ≈10 passes at 1 kg ^h?1 throughput with total system holdup of ≈20 kg. Paraffins for the Queensland subbituminous coal equilibrated at 18–24% in the solvent, phenolics at 16–21%, basic nitrogen at ≈0.4% (as N), and the balance a mixture of aromatics and hydroaromatics. The total aromatics neglecting phenolics in the equilibrium recycle solvent consists of ≈40–50% each of two-and three-ring and 5–10% four-ring members.     

Forced intercalation probes (FIT Probes): thiazole orange as a fluorescent base in peptide nucleic acids for homogeneous single-nucleotide-polymorphism detection

Fluorescent base analogues in DNA are versatile probes of nucleic acid-nucleic acid and nucleic acid-protein interactions. New peptide nucleic acid (PNA) based probes are described in which the intercalator dye thiazole orange (TO) serves as a base surrogate. The investigation of six TO derivatives revealed that the linker length and the conjugation site decided whether a base surrogate conveys sequence-selective DNA binding and whether fluorescence is increased or decreased upon single-mismatched hybridization. One TO derivative conferred universal PNA-DNA base pairing while maintaining duplex stability and hybridization selectivity. TO fluorescence increased up to 26-fold upon hybridization. In contrast to most other probes, in which fluorescence is invariant once hybridization had occurred, the emission of TO-containing PNA probes is attenuated when forced to intercalate next to a mismatched base pair. The specificity of DNA detection is therefore not limited by the selectivity of probe-target binding and a DNA target can be distinguished from its single-base mutant under nonstringent hybridization conditions. This property should be of advantage for real-time quantitative PCR and nucleic acid detection within living cells.     

Adsorption of Cationic Dyes by Acrylic Films II—Kinetics of Dyeing

Concentration distributions of basic dyes in a film of acrylic polymer have been determined using a microdensitometric technique. The diffusion coefficients calculated from them are dependent on concentration. An explanation of the dependence is offered based on the ionic transfer of hydrogen (or sodium) ions for dye. From the concentration dependence an average diffusion coefficient was calculated and found to agree with that calculated from rates of dyeing. Rates of dyeing of a binary mixture have demonstrated the competitive effect predicted by the diffusion equation derived for the individual dyes.     

Path‐space Motion Estimation and Decomposition for Robust Animation Filtering

Renderings of animation sequences with physics‐based Monte Carlo light transport simulations are exceedingly costly to generate frame‐by‐frame, yet much of this computation is highly redundant due to the strong coherence in space, time and among samples. A promising approach pursued in prior work entails subsampling the sequence in space, time, and number of samples, followed by image‐based spatio‐temporal upsampling and denoising. These methods can provide significant performance gains, though major issues remain: firstly, in a multiple scattering simulation, the final pixel color is the composite of many different light transport phenomena, and this conflicting information causes artifacts in image‐based methods. Secondly, motion vectors are needed to establish correspondence between the pixels in different frames, but it is unclear how to obtain them for most kinds of light paths (e.g. an object seen through a curved glass panel). To reduce these ambiguities, we propose a general decomposition framework, where the final pixel color is separated into components corresponding to disjoint subsets of the space of light paths. Each component is accompanied by motion vectors and other auxiliary features such as reflectance and surface normals. The motion vectors of specular paths are computed using a temporal extension of manifold exploration and the remaining components use a specialized variant of optical flow. Our experiments show that this decomposition leads to significant improvements in three image‐based applications: denoising, spatial upsampling, and temporal interpolation.     

The Visual Computing of Projector‐Camera Systems

This article focuses on real‐time image correction techniques that enable projector‐camera systems to display images onto screens that are not optimized for projections, such as geometrically complex, coloured and textured surfaces. It reviews hardware‐accelerated methods like pixel‐precise geometric warping, radiometric compensation, multi‐focal projection and the correction of general light modulation effects. Online and offline calibration as well as invisible coding methods are explained. Novel attempts in super‐resolution, high‐dynamic range and high‐speed projection are discussed. These techniques open a variety of new applications for projection displays. Some of them will also be presented in this report.