Numerical Analysis of Particle Dispersion Characteristics at the Near Region of Vehicles in a Residential Underground Parking Lot

The study analyzed the transient air flow and particle dispersion at the near region of vehicles under idling conditions in an underground parking lot. It was found that the exhaust jet and particle dispersion behind the vehicles could be treated as a “nearly static” process from 20 seconds after the vehicle started. During the nearly static process, the particle dispersion behind the vehicle could be simplified to be exponentially upward. The particle concentration decreased logarithmically after 0.5 m behind the vehicle. The curvature of the particle streamline behind the vehicle under high exhaust temperature conditions is larger compared with that under low exhaust temperature conditions. When the vehicle exhaust temperature is high enough (318 K or higher in the study), the relationship between time and particle concentration above 3 m remains constant.     

Modeling Focused Beam Reflectance Measurement and its Application to Sizing of Particles of Variable Shape

A model for particle detection in focused beam reflectance measurement is presented in the general case of particles of any convex shape. Shape dependent convolution relationships between measured chord length distribution (CLD), particle size distribution (PSD) and particle mass distribution (PMD) are derived and an explicit formula for the weighting characteristic length is given in terms of particle shape. Based on the derived convolution relationships, equations relating moments of the CLD, PSD and PMD are obtained. Issues related to the definition of particle size of non spherical objects and its connection to the particle sizing technique are discussed. Based on the moment relationships, particle size is defined for focused beam reflectance measurement measurements in terms of a CLD equivalent sphere. CLD and characteristic length for a thin cylinder are obtained analytically and used as simple model in order to illustrate issues in sizing particles of variable shape. General conclusions regarding the role of the weighting characteristic length on the behavior of the measured CLD are drawn.     

Gelatine sizing and discoloration: A comparative study of optical spectra obtained from ancient and artificially aged modern papers

The role of gelatine sizing in ancient paper discoloration is still subject to debate. In this report we have addressed this issue by comparing the optical reflectance of sized and non-sized artificially aged modern papers with reflectance data obtained from a set of ancient specimens. We have used different ageing procedures and prepared the gelatine following methods set down in ancient recipes. Gelatine-sized aged papers showed an optical response comparable with that of ancient paper specimens, while very small reflectance modifications were observed in pure cellulose unsized samples under the same ageing conditions. In addition, measurements carried out on pure gelatine films confirmed that gelatine plays a major role in paper discoloration. Some differences in discoloration effects induced by artificial and natural ageing on sized paper are discussed and a possible explanation is proposed.     

Improved lower bounds for the capacitated lot sizing problem with setup times

We present new lower bounds for the capacitated lot sizing problem, applying decomposition to the network reformulation. The demand constraints are the linking constraints and the problem decomposes into subproblems per period containing the capacity and setup constraints. Computational results and a comparison to other lower bounds are presented.     

Particle sizing by ultrashort laser pulses – numerical simulation

This paper contains the results of our numerical investigations into particle sizing by analysis the time-dependent formation of the scattered light. We use an extended Mie theory for calculation the differences in time between the signals of reflection and higher order of refraction. The corresponding optical path lengths of light rays are computed by the principles of geometrical optics. By using a Debye series expansion it is possible to take into account single orders of scattered light. In detail we demonstrate the pulse-induced generation of scattered light for the refraction of first and second order as function of the detection angle.     

Time-resolved two-color LII: size distributions of nano-particles from gas-to-particle synthesis

A two-color LII technique for in situ measurements of particle size distributions is described. The technique is based on the simultaneous detection of time-resolved LII signals at two different wavelengths with one-dimensional spatial resolution using a newly developed experimental setup. The ratio of both LII signals yields particle temperatures as a function of time and location. Measured particle temperature decays are numerically simulated based on a detailed cooling model for particle ensembles. Particle size distributions are obtained by fitting simulated particle temperature decays to measured ones using multi-dimensional non-linear regression. The two-color LII technique for particle sizing can be applied to a wide range of materials because it is independent of the optical properties of the particle material. Exemplarily, the measuring technique is applied to investigate the synthesis of nanoscaled metal oxide particle in a laser vaporization reactor.     

Fractal Character of Dynamic Light Scattering of Particles

Dynamic light scattering signals from particles, exhibit fractal characteristics. This feature can be used to determine the particle size. The use of the fractal dimension, as a quantitative method to analyze the properties of dynamic light scattering signals from submicron particles, is presented. The analysis is performed directly on the time‐resolved scattered intensity, and the Box Dimensions of light scattering signals of particles with diameters 100, 200, 500 and 1000 nm. The experimental results show that the fractal dimensions of light scattering signals correlate well with particle size. In the submicron size range, the smaller the particles, the larger their fractal dimensions. Compared with the PCS technique, only several hundreds of samples are required in the fractal method. Therefore, the data processing is easily accomplished. However, this method only provides the mean particle size, but not the particle size distribution.     

VLSI Circuit Performance Optimization by Geometric Programming

Delay of VLSI circuit components can be controlled by varying their sizes. In other words, performance of VLSI circuits can be optimized by changing the sizes of the circuit components. In this paper, we define a special type of geometric program called unary geometric program. We show that under the Elmore delay model, several commonly used formulations of the circuit component sizing problem considering delay, chip area and power dissipation can be reduced to unary geometric programs. We present a greedy algorithm to solve unary geometric programs optimally and efficiently. When applied to VLSI circuit component sizing, we prove that the runtime of the greedy algorithm is linear to the number of components in the circuit. In practice, we demonstrate that our unary-geometric-program based approach for circuit sizing is hundreds of times or more faster than other approaches.     

Applications of Defocusing DPIV to Bubbly Flow Measurement

Defocusing digital particle image velocimetry (DDPIV) was used to investigate a bubbly flow in the wake of a hydrofoil. DDPIV is a three component volumetric velocimetry technique that operates at full video rate. Complex, three‐dimensional, and time‐dependent flows can be measured. To measure the bubble sizes, an extension to DDPIV was made to infer bubble sizes from their intensities. Both bubble size distributions and bubble velocity fields were simultaneously measured. Results indicate that DDPIV can reliably measure bubble sizes in the range of 100 microns, as well as resolving their aggregate motion.     

Particle sizing by multiangle light-scattering data using the high-order neural networks

The problem of retrieval of size and refractive index of a spherical particle by angular dependence of scattered light in scanning flow cytometry is considered. For its solution, the high-order neural networks are used. We restricted the range of angles available for measurement from 10° to 60°. The retrieval errors of characteristics of nonabsorbing particles were investigated at the ranges of the radius and relative refractive index 0.6–10.6 μm, and 1.02–1.38, respectively.