Segmentation algorithm for diesel spray image analysis

An algorithm for segmentation of diesel spray images has been developed. Its most important feature is robustness against experimental setups that fail to guarantee images whose histograms show two distinct peaks. According to the approach presented, only the peak from the background is used, and it is assumed that the background peak is narrow enough not to include too much of the spray. The algorithm has proved successful for evaluation of images from a pressurized vessel as well as from an engine with optical access, with no need for adjusting the tuning parameters. By adjusting them, one may tune the noise sensitivity.     

Pure rotational coherent anti-Stokes Raman spectroscopy in mixtures of CO and N2

We present a model for quantitative measurements in binary mixtures of nitrogen and carbon monoxide by the use of dual-broadband rotational coherent anti-Stokes Raman spectroscopy. The model has been compared with experimental rotational coherent anti-Stokes Raman scattering spectra recorded within the temperature range of 294-702 K. Temperatures and concentrations were evaluated by spectral fits using libraries of theoretically calculated spectra. The relative error of the temperature measurements was 1-2%, and the absolute error of the CO concentration measurements was <0.5% for temperatures < or =600 K. For higher temperatures, the gas composition was not chemically stable, and we observed a conversion of CO to CO2. The influence of important spectroscopic parameters such as the anisotropic polarizability and Raman line-broadening coefficients are discussed in terms of concentration measurements. In particular, it is shown that the CO concentration measurement was more accurate if N2-CO and CO-N2 line-broadening coefficients were included in the calculation. The applicability of the model for quantitative flame measurements is demonstrated by measuring CO concentrations in ethylene/air flames.     

Globally Optimal Estimates for Geometric Reconstruction Problems

We introduce a framework for computing statistically optimal estimates of geometric reconstruction problems. While traditional algorithms often suffer from either local minima or non-optimality—or a combination of both—we pursue the goal of achieving global solutions of the statistically optimal cost-function. Our approach is based on a hierarchy of convex relaxations to solve non-convex optimization problems with polynomials. These convex relaxations generate a monotone sequence of lower bounds and we show how one can detect whether the global optimum is attained at a given relaxation. The technique is applied to a number of classical vision problems: triangulation, camera pose, homography estimation and last, but not least, epipolar geometry estimation. Experimental validation on both synthetic and real data is provided. In practice, only a few relaxations are needed for attaining the global optimum.     

Influence of wettability on the properties of thin porous platinum films as gates of metal-oxide-semiconductor devices in electrolytes

Thin discontinuous (4 and 35 nm thick) platinum films were used as the gate metal of metal-oxide-semiconductor capacitors. It was observed that the metal film acts as a gas permeable structure in electrolyte solutions when the surface was hydrophobic and sufficiently rough. The probable explanation to this is that the electrolyte does not penetrate into the voids of the metal film. The geometry of the surface was investigated by transsion electron microscopy and profilometer measurements. Surfaces with different contact angles were studied in order to determine whether the electrolyte penetrates into the voids in the platinum film when the surface is sufficiently hydrophilic.     

Influence of molecular tilt angle on the SHG response of pyroelectric liquid crystal polymers

Second harmonic generation in novel pyroelectric liquid crystal polymers (PLCP) made from a series binary mixtures, was studied using 1100 nm as the fundamental wavelength. The PLCPs were prepared by photo-polymerization of binary mixtures of two monomers which exhibit a smectic C^* phase, A2c (4″-(R)-(−)-2-[(10-acrylo-yloxy)decyl]oxy-3-nitrophenyl 4-{4′-[(11-acryloyloxy)-undecyloxy]phenyl}benzoate) and Alb (4″-((R)-(+)-2-octyloxy)-3″-nitrophenyl 4-(4′-(11-acryloyloxy)undecyloxy)-phenyl)-benzoate). The highest d₁₆ and d₂₃ coefficients were found to be in the range 0.65–0.8 pm/V, and differed depending on the detailed preparation of the sample. All cases of polymers formed from the chiral smectic C* phase showed an SHG-signal with no external field present, indicating that polar order became fixed. The SHG-signal was found to increase with the tilt angle of the FLC molecules.     

On-line monitoring of fuel moisture-content in biomass-fired furnaces by measuring relative humidity of the flue gases

Combustion of biomass for heat and power production is continuously growing in importance, because of incentives for replacing fossil energy resources with renewable ones. In biomass combustion, the moisture content of the fuel is an essential operation parameter, which often fluctuates for biomass fuels. Variation in moisture content complicates the operation of the furnaces and results in an uncertainty in the energy content of the fuel delivered to a plant. The fuel moisture-content in a furnace may be determined either by direct measurement on the entering fuel or by measuring the moisture and oxygen contents of the flue gases deriving the moisture content of the fuel. However, reliable methods of a motivated cost for the small to medium-scale furnaces are today not available. An exception is if the furnace is equipped with flue-gas condenser, which can be used to estimate the moisture content of the flue gases. A limitation of this method is, though, that not all furnaces have flue-gas condensers and that the measured signal has an inherent time delay.In this work, measurement of the relative humidity (RH) of the flue gases from a furnace is investigated as the central component in the on-line monitoring of the moisture content of the fuel in a furnace. The method was analysed with humid air in a laboratory environment and tested for accuracy and dynamical behaviour in two biomass-fired heat-production units, one circulating fluidised-bed boiler (CFB) and one grate furnace. The results show that the method, which is easy to calibrate on site, can be used to predict the moisture content of the biomass fuel in the grate furnace with very good precision (<4% error). Furthermore, the method detects variations in moisture content of the furnace flue gases due to changes in the moisture content of the combusted fuel within the order of seconds. Since the transport time of the flue gases from the furnace to the measurement position is of the same order of magnitude, the total time for detection of a change in the moisture content of the fuel is small enough for the signal to be used to control both the fuel feed and the combustion air in a grate furnace.     

High resolution experimental measurement of turbulent flow field in a high pressure homogenizer model and its implications on turbulent drop fragmentation

Particle image velocimetry is performed on a model of a high pressure homogenizer, scaled for qualitative similarity of the one phase turbulent flow field in a production scale homogenizer. Flow fields in gap entrance, gap and gap outlet chamber are obtained with high resolution. The measurements show gap flow development and formation of a turbulent wall adherent jet when exiting into the outlet chamber. Turbulent kinetic energy spectra show how the turbulent energy available for fragmentation is transported over distance along the jet centre axis.The high resolution images are also used together with a Kolmogorov–Hinze theory framework for discussing drop fragmentation together with a direct evaluation of disruptive stresses from measurements. For the turbulent inertial mechanism large drops experience high fragmenting force close to eight gap heights downstream of the gap exit whereas this occurs closer to 20 gap heights for smaller drops. The turbulent viscous mechanism is most efficient at a downstream distance of eight gap heights into the outlet chamber for all drops sizes.     

On the stability of delamination growth at scratching of thin film structures

Scratching of thin film/substrate structures is studied theoretically and numerically. The results are discussed in connection to delamination initiation and in particular subsequent growth at scratching. The material behavior of the film is described by classical elastoplasticity accounting for large deformations. The deformation of the substrate is neglected indicating that the results are pertinent to soft thin films. The numerical investigation is performed using the finite element method (FEM) and the numerical strategy is discussed in some detail. The results from this study show that delamination growth at thin film scratching is a stable feature with crack arrest occurring at a decreasing load.