Direct photolithographic deforming of organomodified siloxane films for micro-optics fabrication

Direct photolithographic deforming of hybrid glass films is used to fabricate optical structures. The structure is fabricated in polyethylene-oxide-acrylate modified hybrid glass films with (1) binary and gray-scale photomasks using a mercury UV-lamp exposure and (2) maskless UV-laser patterning. Fabrication of isolated lenslets, lens arrays, and gratings is presented, including the associated exposure patterns. The hybrid glass material yields light-induced deformation peak-to-valley (p.v.) heights up to 12.8 microm with mercury UV-lamp exposure and p.v. deformation heights up to 6.8 microm with 365-nm UV-laser exposure. The fabricated lenslets' surface data are presented as Zernike-polynomial fit coefficients. Material synthesis and processing-related aspects are examined to understand and control the material's deformation under exposure. The hybrid glass material exhibits a maximum spectral extinction coefficient of 1.6 x 10(-3) microm(-1) at wavelengths ranging from 450 to 2,200 nm and has a refractive index of 1.52 at 632.8 nm. The fabricated structures exhibit rms surface roughness between 1 and 5 nm.     

Validation of mutual information-based registration of CT and bone SPECT images in dual-isotope studies

The registration of computed tomography (CT) and nuclear medicine (NM) images can substantially enhance patient diagnosis as it allows for the fusion of anatomical and functional information, as well as the attenuation correction of NM images. However, irrespective of the method used, registration accuracy depends heavily on the characteristics of the images that are registered and the degree of similarity between them. This poses a challenge for registering CT and NM images as they have very different characteristics and content. To address the particular problem of registering single photon emission computed tomography (SPECT) oncology studies with corresponding CT, we have proposed to perform a dual-isotope study with simultaneous injection of a tumor tracer and a bone imaging agent to obtain a tumor SPECT and a bone SPECT image that are inherently registered. As bone structures are generally visible in both CT and bone SPECT, performing registration of these images will be more easily attainable than registration of CT and tumor SPECT. By subsequently applying the spatial transformation determined from this registration to the tumor SPECT acquired from the same dual-isotope study, the optimal alignment between the CT and tumor SPECT images can be obtained. In this paper, we present the proof-of-concept of the proposed approach, the MI-based algorithm employed, and the techniques used to select the algorithm's parameters. Our objectives are to show the feasibility of CT and bone SPECT registration using this algorithm and to validate quantitatively the results generated using clinical data.     

Level Set Curve Matching and Particle Image Velocimetry for Resolving Chemistry and Turbulence Interactions in Propagating Flames

We present an imaging, image processing, and image analysis framework for facilitating the separation of flow and chemistry effects on local flame front structures. Image data of combustion processes are obtained by a novel technique that combines simultaneous measurements of distribution evolutions of OH radicals and of instantaneous velocity fields in turbulent flames. High-speed planar laser induced fluorescence (PLIF) of OH radicals is used to track the response of the flame front to the turbulent flow field. Instantaneous velocity field measurements are simultaneously performed using particle image velocimetry (PIV). Image analysis methods are developed to process the experimentally captured data for the quantitative study of turbulence/chemistry interactions. The flame image sequences are smoothed using nonlinear diffusion filtering and flame boundary contours are automatically segmented using active contour models. OH image sequences are analyzed using a curve matching algorithm that incorporates level sets and geodesic path computation to track the propagation of curves representing successive flame contours within a sequence. This makes it possible to calculate local flame front velocities, which are strongly affected by turbulence/chemistry interactions. Since the PIV data resolves the turbulent flow field, the combined technique allows a more detailed investigation of turbulent flame phenomena.     

Priority pollutants in urban stormwater: Part 2 – Case of combined sewers

This study has evaluated the quality of combined sewer overflows (CSOs) in an urban watershed, such as Paris, by providing accurate data on the occurrence of priority pollutants (PPs) and additional substances, as well as on the significance of their concentrations in comparison with wastewater and stormwater. Of the 88 substances monitored, 49 PPs were detected, with most of these also being frequently encountered in wastewater and stormwater, thus confirming their ubiquity in urban settings. For the majority of organic substances, concentrations range between 0.01 and 1 μg l^?1, while metals tend to display concentrations above 10 μg l^?1. Despite this ubiquity, CSO, wastewater and stormwater feature a number of differences in both their concentration ranges and pollutant patterns. For most hydrophobic organic pollutants and some particulate-bound metals, CSOs exhibit higher concentrations than those found in stormwater and wastewater, due to the contribution of in-sewer deposit erosion. For pesticides and Zn, CSOs have shown concentrations close to those of stormwater, suggesting runoff as the major contributor, while wastewater appears to be the main source of volatile organic compounds. Surprisingly, similar concentration ranges have been found for DEHP and tributyltin compounds in CSOs, wastewater and stormwater. The last section of this article identifies substances for which CSO discharges might constitute a major risk of exceeding Environmental Quality Standards in receiving waters and moreover indicates a significant risk for PAHs, tributyltin compounds and chloroalkanes. The data generated during this survey can subsequently be used to identify PPs of potential significance that merit further investigation.     

Sodium silicate activated slag‐fly ash binders: Part I – Processing,microstructure, and mechanical properties

Alkali silicate activated slag and class F fly ash‐based binders are ambient curing, structural materials that are feasible replacements for ordinary Portland cement (OPC). They exhibit advantageous mechanical properties and less environmental impact than OPC. In this work, five sodium silicate activated slag‐fly ash binder mixtures were developed and their compressive and flexural strengths were studied as a function of curing temperature and time. It was found that the strongest mixture sets at ambient temperature and had a Weibull average flexural strength of 5.7 ± 1.5 MPa and Weibull average compressive strength of 60 ± 8 MPa at 28 days. While increasing the slag/fly ash ratio accelerated the strength development, the cure time was decreased due to the formation of calcium silicate hydrate (C–S–H), calcium aluminum silicate hydrate (C–A–S–H), and (Ca,Na) based geopolymer. The density, microstructure, and phase evolution of ambient‐cured, heat‐cured, and heat‐treated binders were studied using pycnometry, scanning electron microscopy, energy dispersive X‐ray spectroscopy (SEM‐EDS), and X‐ray diffraction (XRD). Heat‐cured binders were more dense than ambient‐cured binder. No new crystalline phases evolved through 28 days in ambient‐ or heat‐cured binders.     

Watershed segmentation using prior shape and appearance knowledge

Watershed transformation is a common technique for image segmentation. However, its use for automatic medical image segmentation has been limited particularly due to oversegmentation and sensitivity to noise. Employing prior shape knowledge has demonstrated robust improvements to medical image segmentation algorithms. We propose a novel method for enhancing watershed segmentation by utilizing prior shape and appearance knowledge. Our method iteratively aligns a shape histogram with the result of an improved k-means clustering algorithm of the watershed segments. Quantitative validation of magnetic resonance imaging segmentation results supports the robust nature of our method.     

Viscoelastoplastic Damage Characterization of Asphalt–Aggregate Mixtures Using Digital Image Correlation

This paper presents the research effort in which the viscoelastoplastic continuum damage (VEPCD) model is developed and calibrated for the behavioral prediction of asphalt–aggregate mixtures subjected to tensile stresses in pavement structures. It is found that the formation of strains in the mixtures becomes highly localized as microcracks densify, coalesce, and further grow to develop into macrocracks. However, conventional linear variable differential transformers (LVDTs) used in most laboratory tests are unable to capture the localized process zone strains [or fracture process zone (FPZ) strains] due to various limitations. Consequently, the VEPCD model, calibrated using LVDT measurements, ceases to accurately predict the performance of asphalt–aggregate mixtures after the strain localization. This study explores the use of a digital image correlation (DIC) technique for measuring the FPZ strains in an aim to extend the validity of the VEPCD model beyond localization. An experimental/analytical methodology that requires transfer from LVDT strains to DIC strains after strain localization for model calibration and validation is presented for a range of loading and temperature conditions.     

On the effect of time-dependent deformations on the behaviour of patch-repaired reinforced concrete short columns

This paper reports the results of an experimental study of the effect of time-dependent deformations (such as shrinkage and creep) of concrete repair materials on the ability of patch repairs to contribute to the structural function of reinforced concrete short columns. Prior to repair, strain measurements were taken from loaded columns with preformed cavities; cavity depths varied between columns. One polymeric and one polymer-modified concrete repair material were used for repair, all repairs being performed under zero load. After repair, the distribution of strain was measured from columns subjected to axial service load and from similar columns observed under zero load. Test results indicate that in the short term both the repair materials assist the repaired column to carry load, but in the long term the contribution of the polymer-modified material is reduced substantially while that of the polymeric material is sustained. It is observed that shrinkage of the repair material can induce bending in the repaired column and that this bending increases with patch repair cavity depth. Within the repaired zone, bending strain distributions were linear which would suggest that conventional methods of structural analysis are appropriate for such members.     

Solar adsorption refrigeration (SAR) system modeling

The solar adsorption refrigeration (SAR) system has economical and environmental aspects that motivate many researches to investigate its capability in cooling system design. In this study, multi-dimensional mathematical models have been generated to predict the coefficient of performance (COP) value of the SAR system as function of the evaporator, condenser, and generator temperatures. Fuzzy logic and regression analysis approaches were implemented to construct a mathematical model for this purpose from one-dimensional collected data that relates COP value separately to condensation, evaporation, and generation temperatures, respectively. The results of COP calculation from the two models were agreed quite well with the measured values. However, the fuzzy logic technique showed excellent accuracy than the regression model when compared to the calculated COP value, as its steps have the optimum nature in constructing the required model.