Comparative analysis of automotive paints by laser induced breakdown spectroscopy and nonparametric permutation tests

Laser-induced breakdown spectroscopy (LIBS) has been investigated for the discrimination of automobile paint samples. Paint samples from automobiles of different makes, models, and years were collected and separated into sets based on the color, presence or absence of effect pigments and the number of paint layers. Twelve LIBS spectra were obtained for each paint sample, each an average of a five single shot “drill down” spectra from consecutive laser ablations in the same spot on the sample. Analyses by a nonparametric permutation test and a parametric Wald test were performed to determine the extent of discrimination within each set of paint samples. The discrimination power and Type I error were assessed for each data analysis method. Conversion of the spectral intensity to a log-scale (base 10) resulted in a higher overall discrimination power while observing the same significance level. Working on the log-scale, the nonparametric permutation tests gave an overall 89.83% discrimination power with a size of Type I error being 4.44% at the nominal significance level of 5%. White paint samples, as a group, were the most difficult to differentiate with the power being only 86.56% followed by 95.83% for black paint samples. Parametric analysis of the data set produced lower discrimination (85.17%) with 3.33% Type I errors, which is not recommended for both theoretical and practical considerations. The nonparametric testing method is applicable across many analytical comparisons, with the specific application described here being the pairwise comparison of automotive paint samples.     

The Mathematics of Internet Search Engines

This article presents a survey of techniques for ranking results in search engines, with emphasis on link-based ranking methods and the PageRank algorithm. The problem of selecting, in relation to a user search query, the most relevant documents from an unstructured source such as the WWW is discussed in detail. The need for extending classical information retrieval techniques such as boolean searching and vector space models with link-based ranking methods is demonstrated. The PageRank algorithm is introduced, and its numerical and spectral properties are discussed. The article concludes with an alternative means of computing PageRank, along with some example applications of this new method.     

Thermal roots of correlation‐based complexity

Bayesian maxent lets one integrate thermal physics and information theory points of view in the quantitative study of complex systems. Since net surprisal (a free energy analog for measuring “departures from expected”) allows one to place second law constraints on mutual information (a multimoment measure of correlations), it makes a quantitative case for the role of reversible thermalization in the natural history of invention, and suggests multiscale strategies to monitor standing crop as well. It prompts one to track evolved complexity starting from live astrophysically observed processes, rather than only from evidence of past events. Various gradients and boundaries that play a role in availability flow, ranging from the edge of a wave‐packet to the boundary between idea‐pools, allow one to frame wide‐ranging correlations (including that between a phenomenon and its explanation) as delocalized physical structures. © 2007 Wiley Periodicals, Inc. Complexity, 2008     

Absorption of external thermal radiation in asymmetrically illuminated droplets

A theoretical model of thermal radiation absorption in semi-transparent droplets at the surface and inside a fuel spray is presented. Asymmetry of droplet illumination is taken into account. Results of Mie calculations of thermal radiation absorption inside large spherical droplets illuminated from a hemisphere are presented. Simple approximations for the angular and radial dependencies of the absorbed radiation power are suggested. These approximations are generalisations of the approximations suggested earlier by the authors for the case of symmetric illumination of droplets. They predict the results close to those which follow from the Mie calculations. Results of approximate calculations for a typical diesel fuel droplet at the periphery of the spray are presented. As in the case of symmetrical droplet illumination, an increased absorption of thermal radiation in the central area of the droplet is predicted. Also, at the illuminated side of the droplet, the absorption of radiation in a thin layer near the surface of the droplet is predicted, as in the case of symmetrical droplet illumination. Absorption of radiation in the central area of the droplet is related to the contribution of radiation in the spectral ranges of semi-transparency. The maximum of radiation absorption near the droplet surface is linked to the contribution of radiation in the vicinity of the diesel fuel absorption peak .     

The Fire/Heat Concept and Its Journey from Prehistoric Time into the Third Millennium

The notion of fire/light/heat/energy is recognized as an integrating element in the pathway of ordering matter and society, and its historical aspects are thoroughly reviewed. Fire is argued to be a philosophical archetype and its role in the early concept of four elements is discussed. The Indian, Arabic and Greek historical bases are mentioned. Alchemy is briefly reviewed as a source of the wider adoption of fire. The era of renaissance and the new age are also included. The message of fire/heat is nowadays focused on the progress of civilization, with the assumption of engines as information transducers based on the conscious exploitation of fire. The role of chaos is emphasized. Overall, a condensed but consistent view is given of the various concepts that emerged during the historical progress of the understanding of heat (noting 61 references). This revised version was published online in July 2006 with corrections to the Cover Date.     

Laser metrology — a diagnostic tool in automotive development processes

Laser measurement techniques are widely used in automotive development processes. Applications at Volkswagen are presented where laser metrology works as a diagnostic tool for analysing and optimising complex coupled processes inside and between automotive components and structures such as the reduction of a vehicle's interior or outer acoustic noise, including brake noise, and the combustion analysis for diesel and gasoline engines to further reduce fuel consumption and pollution. Pulsed electronic speckle pattern interferometry (ESPI) and holographic interferometry are used for analysing the knocking behaviour of modern engines and for correct positioning of knocking sensors. Holographic interferometry shows up the vibrational behaviour of brake components and their interaction during braking, and allows optimisation for noise-free brake systems. Scanning laser vibrometry analyses structure-born noise of a whole car body for the optimisation of its interior acoustical behaviour.Modern engine combustion concepts such as in direct-injection (DI) gasoline and diesel engines benefit from laser diagnostic tools which permit deeper insight into the in-cylinder processes such as flow generation, fuel injection and spray formation, atomisation and mixing, ignition and combustion, and formation and reduction of pollutants. The necessary optical access inside a cylinder is realised by so-called ‘transparent engines’ allowing measurements nearly during the whole engine cycle. Measurement techniques and results on double-pulse particle image velocimetry (PIV) with a frequency-doubled YAG laser for in-cylinder flow analysis are presented, as well as Mie-scattering on droplets using a copper vapour laser combined with high-speed filming, and laser-induced fluorescence (LIF) with an excimer laser for spray and fuel vapour analysis.     

Multi-location laser ignition using a spatial light modulator towards improving automotive gasoline engine performance

We report on a study into multi-location laser ignition (LI) with a Spatial Light Modulator (SLM), to improve the performance of a single cylinder automotive gasoline engine. Three questions are addressed: i/ How to deliver a multi-beam diffracted pattern into an engine cylinder, through a small opening, while avoiding clipping? ii/ How much incident energy can a SLM handle (optical damage threshold) and how many simultaneous beam foci could thus be created? ; iii/ Would the multi-location sparks created be sufficiently intense and stable to ignite an engine and, if so, what would be their effect on engine performance compared to single-location LI? Answers to these questions were determined as follows. Multi-beam diffracted patterns were created by applying computer generated holograms (CGHs) to the SLM. An optical system for the SLM was developed via modelling in ZEMAX, to cleanly deliver the multi-beam patterns into the combustion chamber without clipping. Optical damage experiments were carried out on Liquid Crystal on Silicon (LCoS) samples provided by the SLM manufacturer and the maximum safe pulse energy to avoid SLM damage found to be 60 mJ. Working within this limit, analysis of the multi-location laser induced sparks showed that diffracting into three identical beams gave slightly insufficient energy to guarantee 100% sparking, so subsequent engine experiments used 2 equal energy beams laterally spaced by 4 mm. The results showed that dual-location LI gave more stable combustion and higher engine power output than single-location LI, for increasingly lean air-fuel mixtures. The paper concludes by a discussion of how these results may be exploited.     

Fault Detection and Diagnosis of Components of the Vehicle Vertical Dynamics

In this paper, model and signal-based methods for supervision ofsuspension elements of a car are presented. A model-based approach usingparameter estimation is used to determine the current parameters of avehicle suspension. Exploiting the analytical redundancy, different faults,like weak dampers or sensor faults, can be distinguished. For faultdetection the use of parity equations is shown. In addition, a signal-basedapproach is presented which makes a detection of tire pressure losspossible. All presented results were drawn from a test rig or from a drivingcar.     

Absorption of thermal radiation in a semi-transparent spherical droplet: a simplified model

The boundary-value problem for calculation of differential absorption of thermal radiation is formulated based on the modified DP₀ approximation. The solution of this problem is supplemented by simple analytical approximations for the normalised absorbed radiation power. The latter is used together with the analytical approximation for the efficiency factor of absorption, suggested earlier. The resulting simplified model is applied to the specific problem of absorption of thermal radiation by a diesel fuel droplet. Two types of diesel fuel have been considered. It is pointed out that the radial distribution of absorbed thermal radiation power is non-monotonic. The power absorbed in the droplet core is shown to be rather large and almost homogeneous. Also, the absorbed power is large in the vicinity of the droplet surface, but is minimal in the intermediate region. It is pointed out that the variations of the refractive index of diesel fuel with wavelengths can smooth the predicted radial dependence of the thermal radiation power, absorbed in diesel fuel droplets.