EMPA Media Technology

Publications 2009

Linking socioeconomic classes and land cover data in Lima, Peru: Assessment through the application of remote sensing and GIS

S. Avelar, R. Zah, C. Tavares-Corrêa

The spatial differentiation of socioeconomic classes in a city can deliver insight into the nexus of urban development and the environment. The purpose of this paper is to identify poor and rich regions in large cities according to the predominant physical characteristics of the regions. Meaningful spatial information from urban systems can be derived using remote sensing and GIS tools, especially in large difficult-to-manage cities where the dynamics of development results in rapid changes to urban patterns. We use here very high resolution imagery data for the identification of homogeneous socioeconomic zones in a city. We formulate the categorization task as a GIS analysis of an image classified with conventional techniques. Experiments are conducted using a QuickBird image of a study area in Lima, Peru. We provide accuracy assessment of results compared to ground truth data. Results show an approximated allocation of socioeconomic zones within Lima. The methodology described could also be applied to other urban centers, particularly large cities of Latin America, which have characteristics similar to those of the study area.

International Journal of Applied Earth Observation and Geoinformation

Karte von Lima

Web-based psychometric evaluation of image quality

I. Sprow, Z. Baranczuk, T. Stamm, P. Zolliker

The measurement of image quality requires the judgment by the human visual system. This paper describes a psycho-visual test technique that uses the internet as a test platform to identify image quality in a more time-effective manner, comparing the visual response data with the results from the same test in a lab-based environment and estimate the usefulness of the internet as a platform for scaling studies.

Electronic Imaging 2009


An RGB Color Management Concept based on an Improved Gamut Mapping Algorithm

U. Caluori, K. Simon

In principal, color reproduction on specific devices can be divided into transformation of color coordinates and the adaptation of colors to a device, called gamut mapping. The well established ICC color management neglects the latter aspect. This paper presents a practical implementation addressing both an efficient color transformation and a sophisticated gamut mapping.

Electronic Imaging 2009


Dotgain estimation using linear least squares incorporating neighboring and clustering effects

T. Stamm, K. Simon

This work presents a model for dotgain prediction using repetitive patterns based on the characterization of neighboring and clustering effects of a specific printing device. Estimating dotgain is done nowadays by measuring patches of color patterns realized by a specific printing device. Current models use the information about adjacent dots to predict dotgain. However, research has shown that dotgain is influenced by the neighborhood of a dot which in general is bigger than one dot-size, in particular in connection with laser printers. The presented method predicts the dotgain of a dot considering a larger surrounding based on the observation of two main parameters affecting the luminance of a pattern which can be fitted using linear regression.

Electronic Imaging 2009

Luminances of Patterns

Classification of Paper Images to Predict Substrate Parameters prior to Print

M. Scheller Lichtenauer, S. Mourad, P. Zolliker, K. Simon

An accurate characterization of the substrate is a prerequisite of color management in print. The use of standard ICC profiles in prepress leaves it to the printer to match the fixed substrate characteristics contained in these profiles. This triggers the interest in methods to predict, if a given ink, press and paper combination complies with a given characterization. We present an approach to compare physical and optical characteristics of papers in order to achieve such a prediction of compliance by classification methods. For economical and ecological reasons it is preferable to test paper without printing it. We therefore propose non-destructive methods.

Computational Color Imaging Workshop 2009

Mikroskipische Aufnahme von Papier

Image quality measures for evaluating gamut mapping

Z. Baranczuk, P. Zolliker, J. Giesen

In this paper we compare different image quality measures for the gamut mapping problem, and validate them using psychovisual data from four recent gamut mapping studies. The psychovisual data are choice data of the form: given an original image and two images obtained by applying different gamut mapping algorithms, an observer chooses the one that reproduces the original image better in his/her opinion. The scoring function used to validate the quality measures is the hit rate, i.e., the percentage of correct choice predictions on data from the psycho-visual tests. We also propose a new image quality measure based on the difference in color and local contrast. This measure compares well to the measures from the literature on our psycho-visual data. Some of these measures predict the observer’s preferences equally well as scaling methods like Thurstone’s method or conjoint analysis that are used to evaluate the psycho-visual tests. This is remarkable in the sense that the scaling methods are based on the experimental data, whereas the quality measures are independent of this data.

Gamut mapped images

Stochastic modeling of light scattering with fluorescence using a Monte Carlo-based multiscale approach

M. Sormaz, T. Stamm, S. Mourad, P. Jenny

This work deals with the efficient and accurate modeling of fluorescence in the context of stochastic Monte Carlo methods for which we propose a novel multiscale method. As in other approaches of this category, the transport theory is employed to describe the physics. The new framework was successfully applied for a quantitative assessment of halftone reflectance measurements with three different devices. It could be demonstrated that the described method is faster than classical Monte Carlo by multiple orders of magnitude, and that it is capable of correctly handling the geometrical device differences. It is also shown that optical dot gain is accurately predicted for the whole ink coverage range.

JOSA A, Vol. 26, No. 6, June 2009


Optical effects by fiber surface microstructuring

M. Halbeisen, R. Hufenus, P. Zolliker, W. Shi

It is well known that some colors of natural objects are produced by periodic structures for example in animals and in minerals. The colors of these objects depend on the angle of observation and originate from interference of light at thin layers or diffraction at periodic structures. When light is diffracted by an object, interference occurs when the incoming wave is superimposed with the diffracted waves. A diffraction grating is a structure with a repeating pattern. Micro- and nanoscaled gratings rendering spectral separation of light are widely used for securing documents, credit cards or bank notes. A challenging idea is to extend fiber coloring beyond the possibilities of dye colors using interference effects of photonic structures. The potential to use such color effects as a fashion element is not yet widely investigated. Structurally colored fibers, based on alternating thin layers of polyester and polyamide, are commercially available.

The Fiber Society

Fiber structuring

Enhanced acoustic damping in flexible polyurethane foams filled with carbon nanotubes

R. Verdejo, R. Stämpfli, M. Alvarez-Lainez, S. Mourad, M.A. Rodriguez-Perez, P.A. Brühwiler, M. Shaffer

Flexible polyurethane (PU) foams, with loading fractions of up to 0.2 wt% carbon nanotubes (CNTs), were made by free-rising foaming using water as blowing agent. Electron microscopy revealed an open cellular structure and a homogeneous dispersion of CNTs, although the incorporation of nanofiller affected the foaming process and thus the final foam density and cellular structure. The compressive response of the foams did not show an unambiguous improvement with CNT content due to the variable foam structure. However, dense films generated by hot pressing the foams indicated a significant intrinsic reinforcement of the polymer, even at low loadings of CNTs. Most significantly, CNTs were found to increase the acoustic activity monotonically at concentrations up to 0.1 wt%.

Composites Science and Technology


Ecophysiological responses of the biocontrol agent Trichoderma atroviride (T-15603.1) to combined environmental parameters

M. Schubert, S. Mourad, S. Fink, F.W.M.R Schwarze

The effects of temperature, water activity (aw), and nutritional status, and their interactions, on the radial growth rate (mm day−1) and lag phase of Trichoderma atroviride (T-15603.1), a strain with high biocontrol potential against wood-decay fungi, was monitored for 20 days on nutrient-rich (MEA) and nutrient-poor (LNA) media. Five levels of aw (0.998, 0.982, 0.955, 0.928, 0.892) were combined with five incubation temperatures (10, 15, 20, 25, and 30 °C). The growth rate dropped and the lag prior to growth increased as the temperature, aw and nutrient status of the medium decreased. T-15603.1 appeared to be more sensitive to aw reduction than to temperature or nutrient status. The use of response surface methodology to model the combined effects of these environmental factors on the radial growth rate of T. atroviride completed the experimental results and showed that the radial growth rate was particularly limited at low aw values on the nutrient-rich medium (MEA) and at incubation temperatures 25 °C. Internal and external mathematical evaluations (RMSE,%SEP, Af, Bf, pRE) demonstrated that the model provides a useful and accurate method for predicting the growth rate of T-15603.1. This study should contribute towards a better understanding of the biocontrol efficacy of T-15603.1 in urban tree management.

Biological control/p>

Ecophysiological responses

Determination of optimal growth parameters for the bioincising fungus Physisporinus vitreus by means of response surface methodology

M. Schubert, V. Dengler, S. Mourad, F.W.M.R Schwarze

Aim: To evaluate the influence of water activity (aw), temperature and pH on the radial growth and lag phase of Physisporinus vitreus (E-642), a basidiomycete was used in the biotechnological process of bioincising.

Methods and results: Radial growth was monitored for 20 days on malt extract agar medium. Five levels of aw (0·998, 0·982, 0·955, 0·928, 0·892) were combined with three incubation temperatures (10, 15, 20°C) and three pH values (4, 5, 6). Data analyses showed a highly significant effect of aw and temperature (P < 0·0001) and a significant effect of pH (P < 0·05). The radial growth rate and lag phase of P. vitreus were very sensitive to aw reduction. Although P. vitreus was able to grow at all the selected temperatures and pH values, the lag phase increased with decreasing aw and growth became inhibited at aw = 0·955. Optimal conditions for growth of P. vitreus were aw = 0·998, 20°C and pH 5. The response surface model provided reliable estimates of these growth parameters and confirmed a greater dependence on aw than on temperature or pH under in vitro conditions.

Conclusions: Low levels of aw can prevent growth of P. vitreus, so wood moisture content should be adjusted accordingly.

Significance and impact of the study: Implementation of these results should contribute towards the optimization and efficiency of bioincising.

Journal of Applied Microbiology

Growth rates