Meeting stricter legal emission limits and the simultaneous introduction of new synthetic fuels are key challenges for current and future research in the field of engine combustion. A deep knowledge of spray behavior ...
详细信息
Meeting stricter legal emission limits and the simultaneous introduction of new synthetic fuels are key challenges for current and future research in the field of engine combustion. A deep knowledge of spray behavior is mandatory to address these problems, as air‐fuel mixture and spray propagation in gasoline direct injection (GDI) are essential processes to achieve a highly efficient and clean combustion. Thus, a lot of effort is put into the identification of air‐fuel spray distributions. Most of them use lasers or X‐ray sources, which are accompanied by a high experimental complexity and further drawbacks. In this work, the measurement technique application of high speed diffuse back illumination extinction imaging (DBIEI) is used to obtain quantitative information in the form of projected liquid volume fraction (PLV). The DBIEI setup is simplified to enable an easier and quicker application for different experimental environments, using a LED-Panel as light source, which fulfills diffuse back illumination (DBI) criteria. Measurements are done in a constant volume chamber, allowing easy optical access with up to 200 mm in diameter and enabling measurements at real world ambient engine conditions. An engine combustion network (ECN) Spray G injector is used. ECN ambient conditions G1 (3.5 kg/m3 ambient density at 300°C), G2 (0.5 kg/m3 ambient density at 60°C) and G3 (1.01 kg/m3 ambient density at 60°C) are chosen. Isooctane is used as fuel. The injector is mounted in a motorized rotational system, enabling measurements of the spray at defined and exact angles. The DBIEI measurement technique suppresses the effect of beam steering at elevated ambient conditions, allowing the measurement of scattering based light attenuation by spray droplets. This requires a light source radiating uniformly over a certain angle‐range. Nevertheless, an inherent error in the quantification of liquid phase results from the detection of multiple scattered photons. The error is even more
diffuse optical tomography (DOT) is one of the ways to probe highlyscattering media such as tissue using low-energy near infra-red light (NIR) to reconstruct a map of the optical property distribution. The interactio...
详细信息
ISBN:
(纸本)9780819489623
diffuse optical tomography (DOT) is one of the ways to probe highlyscattering media such as tissue using low-energy near infra-red light (NIR) to reconstruct a map of the optical property distribution. The interaction of the photons in biological tissue is a non-linear process and the phton transport through the tissue is modelled using diffusion theory. The inversion problem is often solved through iterative methods based on nonlinear optimization for the minimization of a data-model misfit function. The solution of the non-linear problem can be improved by modeling and optimizing the cost functional. The cost functional is f(x) = x(T)Ax - b(T)x + c and after minimization, the cost functional reduces to Ax = b. The spatial distribution of optical parameter can be obtained by solving the above equation iteratively for x. As the problem is non-linear, ill-posed and ill-conditioned, there will be an error or correction term for x at each iteration. A linearization strategy is proposed for the solution of the nonlinear ill-posed inverse problem by linear combination of system matrix and error in solution. By propagating the error (e) information (obtained from previous iteration) to the minimization function f(x), we can rewrite the minimization function as f(x;e) = (x + e)(T) A(x + e) - b(T)(x + e) + c. The revised cost functional is f(x;e) = f(x) + e(T)Ae. The self guided spatial weighted prior (e(T)Ae) error (e, error in estimating x) information along the principal nodes facilitates a well resolved dominant solution over the region of interest. The local minimization reduces the spreading of inclusion and removes the side lobes, thereby improving the contrast, localization and resolution of reconstructed image which has not been possible with conventional linear and regularization algorithm.
In the last few years, the propagation of diffusephotons in scattering media has become an important field of interest. This is mainly due to the possibility offered by the low absorption of light in the range 700 to...
详细信息
In the last few years, the propagation of diffusephotons in scattering media has become an important field of interest. This is mainly due to the possibility offered by the low absorption of light in the range 700 to...
详细信息
ISBN:
(纸本)9780819467720
In the last few years, the propagation of diffusephotons in scattering media has become an important field of interest. This is mainly due to the possibility offered by the low absorption of light in the range 700 to 900nm. Indeed, this property leads to a potential deep penetration. But a non negligible limitation appears: the scattering processes strongly reduce both the contrast and the resolution. In this paper, the time-dependent light propagation in highlyscattering media containing an inclusion is. solved by means of a finite element method, tacking into account Robin type air-tissue boundary conditions. This study is devoted to the depth localization of a tumor enclosed into a breast-like slab. The tissue is modeled by a rectangular meshed domain that mimics a breast compressed between two transparent plates. Cartesian coordinates are used in order to solve the time-dependent diffusion approximation. A short laser pulse of 1ps is considered. The transillumination technique is able to laterally detect the object when the source and detector are moved together on the same axis. In order to perform the localization of the inclusion in this study, the optical properties of the object were varied. Knowing the lateral position of the inclusion, we derive interesting temporal contrast functions based on the mean time of flight of photons. These functions allow to localize in depth the inclusion under the assumption that the object is very diffusing. To conclude, our study demonstrates the possibility to detect laterally and axially a tumor-like inclusion enclosed in breast-like tissues.
The proceedings contain 38 papers. The topics discussed include: time-resolved breast transillumination: comparison of theoretical and experimental image-resolution;experimental study of spatial resolution for time-re...
The proceedings contain 38 papers. The topics discussed include: time-resolved breast transillumination: comparison of theoretical and experimental image-resolution;experimental study of spatial resolution for time-resolved near-infrared imaging;anisotropic and spectral properties of biological scattering objects with the ordered particle orientation;in vivo experimental technique for one-line absorption measurements in scattering biotissues;experimental study of continuous wave coherent techniques for optical transillumination;and optical transfer function and resolution of transillumination processes calculated by Monte Carlo simulations and diffusion theory.
The computer simulation of light propagation in homogeneous and heterogeneous biotissues accounting for absorption and scattering radiation energy by pigmented granules and diffraction is made.
ISBN:
(纸本)0819413496
The computer simulation of light propagation in homogeneous and heterogeneous biotissues accounting for absorption and scattering radiation energy by pigmented granules and diffraction is made.
A model of the calculation of the diffuse reflection of the living tissue based on Kubelka-Munk theory is presented. The equation describing the relationship between backscattering of the living tissue and radiation p...
详细信息
ISBN:
(纸本)0819413496
A model of the calculation of the diffuse reflection of the living tissue based on Kubelka-Munk theory is presented. The equation describing the relationship between backscattering of the living tissue and radiation parameters, inanimate tissue optical characteristics, and chromophores concentration is outlined. The use of the method in clinical dosimetry is given.
The suitability and limits of time-resolved transillumination to determine inner details of biological tissues are investigated by phantom experiments. The achievable improvement is demonstrated by using different pha...
详细信息
ISBN:
(纸本)0819413496
The suitability and limits of time-resolved transillumination to determine inner details of biological tissues are investigated by phantom experiments. The achievable improvement is demonstrated by using different phantoms (absorbing objects embedded in a turbid medium). By means of line-scans across a sharp edge the spatial resolution and its dependence on temporal resolution can be determined. To demonstrate the physical resolution according to the Rayleigh-criterion, measurements were performed on blackened bead pairs. Investigations with partially transparent beads demonstrate the high sensitivity of time-resolving techniques with respect to variations in scattering or absorption coefficients.
The results of goniometric measurements of the intensity of laser light scattered by bone samples are presented. The experiment was performed on macerated, full-thickness skull samples. The angular dependencies of the...
详细信息
ISBN:
(纸本)0819413496
The results of goniometric measurements of the intensity of laser light scattered by bone samples are presented. The experiment was performed on macerated, full-thickness skull samples. The angular dependencies of the intensity of laser light scattered by the samples was measured. The transmission of light through the samples was calculated and is shown as a function of sample thickness for various wavelengths of the incident radiation. The contribution of the fluorescent light in the scattered radiation is taken into account.
A method of measuring the sphere equivalent hydrodynamic radius in highly concentrated suspensions is reported. Results showing the system to be concentration independent are given. The effects of polarization and the...
详细信息
ISBN:
(纸本)0819413496
A method of measuring the sphere equivalent hydrodynamic radius in highly concentrated suspensions is reported. Results showing the system to be concentration independent are given. The effects of polarization and the use of high birefringence fibers are discussed and shown to be important. The possibility of independence to fluid flow and the monitoring of the enhanced backscatter cone to given information on structure are considered. The equipment allows the use of a dip in probe and laser powers of only 1 mW are required.
暂无评论