Showing papers by "University of Ljubljana published in 2004"

Combined Object Categorization and Segmentation With an Implicit Shape Model

Abstract: We present a method for object categorization in real-world scenes. Following a common consensus in the field, we do not assume that a figure- ground segmentation is available prior to recognition. However, in contrast to most standard approaches for object class recognition, our approach automati- cally segments the object as a result of the categorization. This combination of recognition and segmentation into one process is made pos- sible by our use of an Implicit Shape Model, which integrates both into a common probabilistic framework. In addition to the recognition and segmentation result, it also generates a per-pixel confidence measure specifying the area that supports a hypothesis and how much it can be trusted. We use this confidence to derive a nat- ural extension of the approach to handle multiple objects in a scene and resolve ambiguities between overlapping hypotheses with a novel MDL-based criterion. In addition, we present an extensive evaluation of our method on a standard dataset for car detection and compare its performance to existing methods from the literature. Our results show that the proposed method significantly outper- forms previously published methods while needing one order of magnitude less training examples. Finally, we present results for articulated objects, which show that the proposed method can categorize and segment unfamiliar objects in differ- ent articulations and with widely varying texture patterns, even under significant partial occlusion.

Pajek - Analysis and Visualization of Large Networks

Abstract: Pajek (spider, in Slovene) is a program package, for Windows (32 bit), for analysis and visualization of large networks (having thousands of vertices). It is freely available, for noncommercial use, at its home page: http://vlado.fmf.uni-lj.si/pub/networks/pajek/

Orange: from experimental machine learning to interactive data mining

Abstract: Orange (www.ailab.si/orange) is a suite for machine learning and data mining. For researchers in machine learning, Orange offers scripting to easily prototype new algorithms and experimental procedures. For explorative data analysis, it provides a visual programming framework with emphasis on interactions and creative combinations of visual components.

Patterns and Universals of Adult Romantic Attachment Across 62 Cultural Regions Are Models of Self and of Other Pancultural Constructs

Abstract: As part of the International Sexuality Description Project, a total of 17,804 participants from 62 cultural regions completedthe RelationshipQuestionnaire(RQ), a self-reportmeasure of adult romanticattachment. Correlational analyses within each culture suggested that the Model of Self and the Model of Other scales of the RQ were psychometrically valid within most cultures. Contrary to expectations, the Model of Self and Model of Other dimensions of the RQ did not underlie the four-category model of attachment in the same way across all cultures. Analyses of specific attachment styles revealed that secure romantic attachment was normative in 79% of cultures and that preoccupied romantic attachment was particularly prevalent in East Asian cultures. Finally, the romantic attachment profiles of individual nations were correlated with sociocultural indicators in ways that supported evolutionary theories of romantic attachment and basic human mating strategies.

Corporate entrepreneurship contingencies and organizational wealth creation

Abstract: Despite the recognized importance of entrepreneurship for organizational wealth creation, research has devoted minimal attention to investigating this area. This study contributes to a better understanding of the relationship between corporate entrepreneurship and wealth creation by developing and testing a normative model, which clarifies the nature of the influences of corporate entrepreneurship and its environmental and organizational antecedents on organizational performance. The findings of structural equation modeling, based on mail survey data from 477 Slovenian firms, demonstrate that corporate entrepreneurship and some its contingencies make a difference in organizational wealth creation, growth and profitability.

Comparison of logistic regression and linear discriminant analysis : a simulation study

Abstract: Two of the most widely used statistical methods for analyzing categorical outcome variables are linear discrimina nt analysis and logistic regression. While both are appropriate for the deve lopment of linear classification models, linear discriminant analysis makes more assumptions about the underlying data. Hence, it is assumed tha t logistic regression is the more flexible and more robust method in case of violations of these assumptions. In this paper we consider the problem of choosing between the two methods, and set some guidelines for proper cho ice. The comparison between the methods is based on several measures of predictive accuracy. The performance of the methods is studied by simula tions. We start with an example where all the assumptions of the linear dis criminant analysis are satisfied and observe the impact of changes regardi ng the sample size, covariance matrix, Mahalanobis distance and directi on of distance between group means. Next, we compare the robustness of the methods towards categorisation and non-normality of explanatory var iables in a closely controlled way. We show that the results of LDA and LR are close whenever the normality assumptions are not too badl y violated, and set some guidelines for recognizing these situations. W e discuss the inappropriateness of LDA in all other cases.

The Western and Eastern Roots of the Saami—the Story of Genetic “Outliers” Told by Mitochondrial DNA and Y Chromosomes

Abstract: The Saami are regarded as extreme genetic outliers among European populations. In this study, a high-resolution phylogenetic analysis of Saami genetic heritage was undertaken in a comprehensive context, through use of maternally inherited mitochondrial DNA (mtDNA) and paternally inherited Y-chromosomal variation. DNA variants present in the Saami were compared with those found in Europe and Siberia, through use of both new and previously published data from 445 Saami and 17,096 western Eurasian and Siberian mtDNA samples, as well as 127 Saami and 2,840 western Eurasian and Siberian Y-chromosome samples. It was shown that the "Saami motif" variant of mtDNA haplogroup U5b is present in a large area outside Scandinavia. A detailed phylogeographic analysis of one of the predominant Saami mtDNA haplogroups, U5b1b, which also includes the lineages of the "Saami motif," was undertaken in 31 populations. The results indicate that the origin of U5b1b, as for the other predominant Saami haplogroup, V, is most likely in western, rather than eastern, Europe. Furthermore, an additional haplogroup (H1) spread among the Saami was virtually absent in 781 Samoyed and Ob-Ugric Siberians but was present in western and central European populations. The Y-chromosomal variety in the Saami is also consistent with their European ancestry. It suggests that the large genetic separation of the Saami from other Europeans is best explained by assuming that the Saami are descendants of a narrow, distinctive subset of Europeans. In particular, no evidence of a significant directional gene flow from extant aboriginal Siberian populations into the haploid gene pools of the Saami was found.

Mechanistic identification of specific force coefficients for a general end mill

Abstract: The paper presents expressions for semi-empirical mechanistic identification of specific cutting and edge force coefficients for a general helical end mill from milling tests at an arbitrary radial immersion. The expressions are derived for a mechanistic force model in which the total cutting force is described as a sum of the cutting and edge forces. Outer geometry of the end mill is described by a generalized mathematical model valid for a variety of end mill shapes, such as cylindrical, taper, ball, bull nose, etc. The derivations follow a procedure originally proposed for a cylindrical end mill. The procedure itself is improved by including the helix angle in evaluation of the average edge forces. The resulting expressions for the specific force coefficients are verified by simulations and experiments.

Association of BDNF with anorexia, bulimia and age of onset of weight loss in six European populations

Abstract: Several genes with an essential role in the regulation of eating behavior and body weight are considered candidates involved in the etiology of eating disorders (ED), but no relevant susceptibility genes with a major effect on anorexia nervosa (AN) or bulimia nervosa (BN) have been identified. Brain-derived neurotrophic factor (BDNF) has been implicated in the regulation of food intake and body weight in rodents. We previously reported a strong association of the Met66 allele of the Val66Met BDNF variant with restricting AN (ANR) and low minimum body mass index in Spanish patients. Another single nucleotide polymorphism located in the promoter region of the BDNF gene (-270C > T) showed lack of association with any ED phenotype. In order to replicate these findings in a larger sample, we performed a case-control study in 1142 Caucasian patients with ED consecutively recruited in six different centers from five European countries (France, Germany, Italy, Spain and UK) participating in the 'Factors in Healthy Eating' project. We have found that the Met66 variant is strongly associated to all ED subtypes (AN, ANR, binge-eating/purging AN and BN), and that the -270C BDNF variant has an effect on BN and late age at onset of weight loss. These are the first two variants associated with the pathophysiology of ED in different populations and support a role for BDNF in the susceptibility to aberrant eating behaviors.

Inclusive measurement of the photon energy spectrum in b → sγ decays

Abstract: We report a fully inclusive measurement of the flavor changing neutral current decay $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ in the energy range $1.8\text{ }\mathrm{G}\mathrm{e}\mathrm{V}\ensuremath{\le}{E}_{\ensuremath{\gamma}}^{*}\ensuremath{\le}2.8\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$, covering 95% of the total spectrum. Using $140\text{ }\mathrm{f}{\mathrm{b}}^{\mathrm{\ensuremath{-}}\mathrm{1}}$, we obtain $\mathcal{B}(b\ensuremath{\rightarrow}s\ensuremath{\gamma})=(3.55\ifmmode\pm\else\textpm\fi{}{0.32}_{\ensuremath{-}0.31\ensuremath{-}0.07}^{+0.30+0.11})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, where the errors are statistical, systematic, and from theory corrections. We also measure the first and second moments of the photon energy spectrum above $1.8\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ and obtain $\ensuremath{\langle}{E}_{\ensuremath{\gamma}}\ensuremath{\rangle}=2.292\ifmmode\pm\else\textpm\fi{}0.026\ifmmode\pm\else\textpm\fi{}0.034\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ and $\ensuremath{\langle}{E}_{\ensuremath{\gamma}}^{2}\ensuremath{\rangle}\ensuremath{-}\ensuremath{\langle}{E}_{\ensuremath{\gamma}}{\ensuremath{\rangle}}^{2}=0.0305\ifmmode\pm\else\textpm\fi{}0.0074\ifmmode\pm\else\textpm\fi{}0.0063\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}$, where the errors are statistical and systematic.

Evaluating the progress of e-government development: A critical analysis

Abstract: The development of e-government in most countries is still primarily aimed at developing electronic services that customers can access via the internet. This has been matched by the methods for monitoring e-government development, which fall far short of providing a true overall assessment. Such a narrow focus on e-government has led to a significant slowdown of development in most countries. Countries have used "quick fix, quick win" solutions, while continued development require above all the development of an integrated government portal and reengineering of back-office processes. The more developed countries are therefore increasingly tailoring their e-government strategies in the direction of customer-orientation and instead of persisting with rigid organisational structures are working on integrating services and processes across individual administrative bodies and institutions and even include private businesses. The development of e-government therefore demands a holistic strategic approach that encompasses the entire public administration and is not limited to individual bodies and institutions, or individual sectors and levels of administration. The methods of monitoring, evaluating and benchmarking e-government development will have to follow the same principles. Based on critical analyses of existing approaches, this paper attempts to define the areas and aspects that must be included within the integrated approach in order to facilitate the progress of e-government towards its strategic objectives, that is the development of services based on user's needs and problems, i.e. integrated services or life-events.

Improving random forests

Abstract: Random forests are one of the most successful ensemble methods which exhibits performance on the level of boosting and support vector machines. The method is fast, robust to noise, does not overfit and offers possibilities for explanation and visualization of its output. We investigate some possibilities to increase strength or decrease correlation of individual trees in the forest. Using several attribute evaluation measures instead of just one gives promising results. On the other hand replacement of ordinary voting with voting weighted with margin achieved on most similar instances gives improvements which are statistically highly significant over several data sets.

Study of B-→D**0π-(D**0→D(*)+π-) decays

Abstract: We report the results of a study of charged B decays to the D(+/-)pi(-/+)pi(-/+) and D(*+/-)pi(-/+)pi(-/+) final states using complete D-(*) reconstruction. The contributions of two-body B-->D**pi decays with narrow (j=3/2) and broad (j=1/2) D** states have been determined and the masses and widths of four D** states have been measured. This is the first observation of the broad P-wave D-0*(0) and D'(0)(1) mesons. The analysis is based on a data sample of 65 million B(B) over bar pairs collected in the Belle experiment.

Properties of Ca2+‐dependent exocytosis in cultured astrocytes

Abstract: Astrocytes, a subtype of glial cells, have numerous characteristics that were previously considered exclusive for neurons. One of these characteristics is a cytosolic [Ca2+] oscillation that controls the release of the chemical transmitter glutamate and atrial natriuretic peptide. These chemical messengers appear to be released from astrocytes via Ca(2+)-dependent exocytosis. In the present study, patch-clamp membrane capacitance measurements were used to monitor changes in the membrane area of a single astrocyte, while the photolysis of caged calcium compounds by a UV flash was used to elicit steps in [Ca2+]i to determine the exocytotic properties of astrocytes. Experiments show that astrocytes exhibit Ca(2+)-dependent increases in membrane capacitance, with an apparent Kd value of approximately 20 microM [Ca2+]i. The delay between the flash delivery and the peak rate in membrane capacitance increase is in the range of tens to hundreds of milliseconds. The pretreatment of astrocytes by the tetanus neurotoxin, which specifically cleaves the neuronal/neuroendocrine type of SNARE protein synaptobrevin, abolished flash-induced membrane capacitance increases, suggesting that Ca(2+)-dependent membrane capacitance changes involve tetanus neurotoxin-sensitive SNARE-mediated vesicular exocytosis. Immunocytochemical experiments show distinct populations of vesicles containing glutamate and atrial natriuretic peptide in astrocytes. We conclude that the recorded Ca(2+)-dependent changes in membrane capacitance represent regulated exocytosis from multiple types of vesicles, about 100 times slower than the exocytotic response in neurons.

A connectionist approach to automatic transcription of polyphonic piano music

Abstract: In this paper, we present a connectionist approach to automatic transcription of polyphonic piano music. We first compare the performance of several neural network models on the task of recognizing tones from time-frequency representation of a musical signal. We then propose a new partial tracking technique, based on a combination of an auditory model and adaptive oscillator networks. We show how synchronization of adaptive oscillators can be exploited to track partials in a musical signal. We also present an extension of our technique for tracking individual partials to a method for tracking groups of partials by joining adaptive oscillators into networks. We show that oscillator networks improve the accuracy of transcription with neural networks. We also provide a short overview of our entire transcription system and present its performance on transcriptions of several synthesized and real piano recordings. Results show that our approach represents a viable alternative to existing transcription systems.

Mineral magnetic properties of loess/paleosol couplets of the central loess plateau of China over the last 1.2 Myr

Abstract: [1] We have conducted a multiparameter investigation of 15 loess-paleosol couplets (S0/L1 to S14/L15) from the Jiaodao section in the central loess plateau of China using environmental magnetic approaches coupled with soil science techniques. The magnetic parameters display systematic variations that seem to be closely related to paleoclimate variations and intensity of pedogenesis. High-temperature susceptibility curves of paleosols show a generally decreasing trend in reversibility from the base of the Lishi Formation to the Holocene black loam, possibly indicating a decrease in weathering intensity. This may reflect a long-term increase in aridity and/or a general long-term cooling trend of the interior of the Asian continent from 1.2 Ma to the present. Several samples display wasp-waisted hysteresis loops. These are most pronounced in moderately enhanced paleosols, less pronounced in the practically unaltered loess, and subdued in the well-developed paleosols, but wasp waistedness reappears in the most developed paleosols. This wasp-waistedness sequence suggests that the composition, concentration, and grain size of magnetic minerals all contribute to the hysteresis behavior of samples from the studied loess-paleosol sequence, but each factor has a different effect at different stages of pedogenesis.

Salt-induced changes in lipid composition and membrane fluidity of halophilic yeast-like melanized fungi.

Abstract: The halophilic melanized yeast-like fungi Hortaea werneckii, Phaeotheca triangularis, and the halotolerant Aureobasidium pullulans, isolated from salterns as their natural environment, were grown at different NaCl concentrations and their membrane lipid composition and fluidity were examined. Among sterols, besides ergosterol, which was the predominant one, 23 additional sterols were identified. Their total content did not change consistently or significantly in response to raised NaCl concentrations in studied melanized fungi. The major phospholipid classes were phosphatidylcholine and phosphatidylethanolamine, followed by anionic phospholipids. The most abundant fatty acids in phospholipids contained C16 and C18 chain lengths with a high percentage of C18:2Δ9,12. Salt stress caused an increase in the fatty acid unsaturation in the halophilic H. werneckii and halotolerant A. pullulans but a slight decrease in halophilic P. triangularis. All the halophilic fungi maintained their sterol-to-phospholipid ratio at a significantly lower level than did the salt-sensitive Saccharomyces cerevisiae and halotolerant A. pullulans. Electron paramagnetic resonance (EPR) spectroscopy measurements showed that the membranes of all halophilic fungi were more fluid than those of the halotolerant A. pullulans and salt-sensitive S. cerevisiae, which is in good agreement with the lipid composition observed in this study.

Wavelet Phase Coherence Analysis: Application to Skin Temperature and Blood Flow

Abstract: The technique of wavelet phase coherence analysis is introduced and used to explore relationships between oscillations on blood flow and temperature in the skin of 10 healthy subjects. Their skin temperature and blood flow were continuously recorded: under basal conditions for 30 min; during local cooling of the skin with an ice-pack for 20 min: and 30 min thereafter. The group mean basal skin temperature of 33.4°C was decreased to 29.2°C during the cooling period, and had recovered to 32.1°C by the end of the recording. The wavelet transform was used to obtain the time–frequency content of the two signals, and their coherence. It is shown that cooling increases coherence to a statistically significant extent in two frequency intervals, around 0.007 and 0.1 Hz, suggesting that these oscillatory components are involved in the regulation of skin temperature when cold is applied as a stress.

Nomograms for visualization of naive Bayesian classifier

Abstract: Besides good predictive performance, the naive Bayesian classifier can also offer a valuable insight into the structure of the training data and effects of the attributes on the class probabilities. This structure may be effectively revealed through visualization of the classifier. We propose a new way to visualize the naive Bayesian model in the form of a nomogram. The advantages of the proposed method are simplicity of presentation, clear display of the effects of individual attribute values, and visualization of confidence intervals. Nomograms are intuitive and when used for decision support can provide a visual explanation of predicted probabilities. And finally, with a nomogram, a naive Bayesian model can be printed out and used for probability prediction without the use of computer or calculator.