nils-herrmann/clean_scirepeval huggingface dataset:
Clustering ensembles: models of consensus and weak partitions

Clustering ensembles have emerged as a powerful method for improving both the robustness as well as the stability of unsupervised classification solutions. However, finding a consensus clustering from multiple partitions is a difficult problem that can be approached from graph-based, combinatorial, or statistical perspectives. This study extends previous research on clustering ensembles in several respects. First, we introduce a unified representation for multiple clusterings and formulate the corresponding categorical clustering problem. Second, we propose a probabilistic model of consensus using a finite mixture of multinomial distributions in a space of clusterings. A combined partition is found as a solution to the corresponding maximum-likelihood problem using the EM algorithm. Third, we define a new consensus function that is related to the classical intraclass variance criterion using the generalized mutual information definition. Finally, we demonstrate the efficacy of combining partitions generated by weak clustering algorithms that use data projections and random data splits. A simple explanatory model is offered for the behavior of combinations of such weak clustering components. Combination accuracy is analyzed as a function of several parameters that control the power and resolution of component partitions as well as the number of partitions. We also analyze clustering ensembles with incomplete information and the effect of missing cluster labels on the quality of overall consensus. Experimental results demonstrate the effectiveness of the proposed methods on several real-world data sets.
3D Face Reconstruction from Stereo Video

Face processing in video is receiving substantial attention due to its importance in many securityrelated applications. A video provides rich information about a face (multiple frames and temporal coherence) that can be utilized in conjunction with 3D face models, if available, to establish a subject’s identity. We propose a 3D face modeling method that reconstructs a user-specific model derived from a generic 3D face model and two video frames of the user. The user-specific 3D face model can be enrolled into the 3D face database at the enrollment stage to be used in later identification process. The reconstruction process can also be used for the probe data in recognition stage, where the reconstructed 3D face model using probe face is used to generate an optimal view and lighting for the recognition process. The advantage of utilizing reconstructed 3D face model is demonstrated by conducting face recognition experiments for 15 probe subjects against a gallery database containing 100 subjects.
Dental biometrics: alignment and matching of dental radiographs

Dental biometrics utilizes dental radiographs for human identification. The dental radiographs provide information about teeth, including tooth contours, relative positions of neighboring teeth, and shapes of the dental work (e.g., crowns, fillings, and bridges). The proposed system has two main stages: feature extraction and matching. The feature extraction stage uses anisotropic diffusion to enhance the images and a mixture of Gaussians model to segment the dental work. The matching stage has three sequential steps: tooth-level matching, computation of image distances, and subject identification. In the tooth-level matching step, tooth contours are matched using a shape registration method and the dental work is matched on overlapping areas. The distance between the tooth contours and the distance between the dental works are then combined using posterior probabilities. In the second step, the tooth correspondences between the given query (postmortem) radiograph and the database (antemortem) radiograph are established. A distance based on the corresponding teeth is then used to measure the similarity between the two radiographs. Finally, all the distances between the given postmortem radiographs and the antemortem radiographs that provide candidate identities are combined to establish the identity of the subject associated with the postmortem radiographs.
Unsupervised texture segmentation using Gabor filters

A texture segmentation algorithm inspired by the multichannel filtering theory for visual information processing in the early stages of the human visual system is presented. The channels are characterized by a bank of Gabor filters that nearly uniformly covers the spatial-frequency domain. A systematic filter selection scheme based on reconstruction of the input image from the filtered images is proposed. Texture features are obtained by subjecting each (selected) filtered image to a nonlinear transformation and computing a measure of energy in a window around each pixel. An unsupervised square-error clustering algorithm is then used to integrate the feature images and produce a segmentation. A simple procedure to incorporate spatial adjacency information in the clustering process is proposed. Experiments on images with natural textures as well as artificial textures with identical second and third-order statistics are reported. The algorithm appears to perform as predicted by preattentive texture discrimination by a human.<<ETX>>
3D face texture modeling from uncalibrated frontal and profile images

3D face modeling from 2D face images is of significant importance for face analysis, animation and recognition. Previous research on this topic mainly focused on 3D face modeling from a single 2D face image; however, a single face image can only provide a limited description of a 3D face. In many applications, for example, law enforcement, multi-view face images are usually captured for a subject during enrollment, which makes it desirable to build a 3D face texture model, given a pair of frontal and profile face images. We first determine the correspondence between un-calibrated frontal and profile face images through facial landmark alignment. An initial 3D face shape is then reconstructed from the frontal face image, followed by shape refinement utilizing the depth information provided by the profile image. Finally, face texture is extracted by mapping the frontal face image on the recovered 3D face shape. The proposed method is utilized for 2D face recognition in two scenarios: (i) normalization of probe image, and (ii) enhancing the representation capability of gallery set. Experimental results comparing the proposed method with a state-of-the-art commercial face matcher and densely sampled LBP on a subset of the FERET database show the effectiveness of the proposed 3D face texture model.
Suspect identification based on descriptive facial attributes

We present a method for using human describable face attributes to perform face identification in criminal investigations. To enable this approach, a set of 46 facial attributes were carefully defined with the goal of capturing all describable and persistent facial features. Using crowd sourced labor, a large corpus of face images were manually annotated with the proposed attributes. In turn, we train an automated attribute extraction algorithm to encode target repositories with the attribute information. Attribute extraction is performed using localized face components to improve the extraction accuracy. Experiments are conducted to compare the use of attribute feature information, derived from crowd workers, to face sketch information, drawn by expert artists. In addition to removing the dependence on expert artists, the proposed method complements sketchbased face recognition by allowing investigators to immediately search face repositories without the time delay that is incurred due to sketch generation.
Learning texture discrimination masks

Texture segmentation using multichannel filtering involves applying a set of masks to an input image, and then grouping the pixels based on the responses to these masks. We solve the problem of finding an optimal set of masks by designing a neural network which is trained to maximize a relevant function. Two algorithms, the centroid algorithm and the gradient descent algorithm, are used to train the network. Experimental results on segmenting two natural textures and extracting barcodes in an image are reported, and the error rates compared for both the algorithms with different network configurations. The centroid algorithm gives better results in small parameter spaces, whereas the gradient descent algorithm works better with more parameters. Our method of automatically generating texture discrimination masks not only results in a good segmentation performance, but also reduces the dimensionality of the feature space compared to previously published multichannel filtering methods.<<ETX>>
A Test to Determine the Multivariate Normality of a Data Set

A test is described for multivariate normality that is useful in pattern recognition. The test is based on the Friedman-Rafsky (1979) multivariate extension of the Wald-Wolfowitz runs test. The test data are combined with a multivariate swarm of points following the normal distribution generated with mean vector and covariance matrix estimated from the test data. The minimal spanning tree of this resultant ensemble of points is computed and the count of the interpopulation edges in the minimal spanning tree is used as a test statistic. The simulation studied both the null case of the test and one simple deviation from normality. Two conclusions are made from this study. First, the test can be conservatively applied by using the asymptotic normality of the test statistic, even for small sample sizes. Second, the power of the test appears reasonable, especially in high dimensions. Monte Carlo experiments were performed to determine if the test is reliable in high dimensions with moderate sample size. The method is compared to other such tests available in the literature.
A Fast and Accurate Unconstrained Face Detector

We propose a method to address challenges in unconstrained face detection, such as arbitrary pose variations and occlusions. First, a new image feature called Normalized Pixel Difference (NPD) is proposed. NPD feature is computed as the difference to sum ratio between two pixel values, inspired by the Weber Fraction in experimental psychology. The new feature is scale invariant, bounded, and is able to reconstruct the original image. Second, we propose a deep quadratic tree to learn the optimal subset of NPD features and their combinations, so that complex face manifolds can be partitioned by the learned rules. This way, only a single soft-cascade classifier is needed to handle unconstrained face detection. Furthermore, we show that the NPD features can be efficiently obtained from a look up table, and the detection template can be easily scaled, making the proposed face detector very fast. Experimental results on three public face datasets (FDDB, GENKI, and CMU-MIT) show that the proposed method achieves state-of-the-art performance in detecting unconstrained faces with arbitrary pose variations and occlusions in cluttered scenes.
Learning user-specific parameters in a multibiometric system

Biometric systems that use a single biometric trait have to contend with noisy data, restricted degrees of freedom, failure-to-enroll problems, spoof attacks, and unacceptable error rates. Multibiometric systems that use multiple traits of an individual for authentication, alleviate some of these problems while improving verification performance. We demonstrate that the performance of multibiometric systems can be further improved by learning user-specific parameters. Two types of parameters are considered here. (i) Thresholds that are used to decide if a matching score indicates a genuine user or an impostor, and (ii) weights that are used to indicate the importance of matching scores output by each biometric trait. User-specific thresholds are computed using the cumulative histogram of impostor matching scores corresponding to each user. The user-specific weights associated with each biometric are estimated by searching for that set of weights which minimizes the total verification error. The tests were conducted on a database of 50 users who provided fingerprint, face and hand geometry data, with 10 of these users providing data over a period of two months. We observed that user-specific thresholds improved system performance by /spl sim/ 2%, while user-specific weights improved performance by /spl sim/ 3%.
Adaptive clustering ensembles

Clustering ensembles combine multiple partitions of the given data into a single clustering solution of better quality. Inspired by the success of supervised boosting algorithms, we devise an adaptive scheme for integration of multiple non-independent clusterings. Individual partitions in the ensemble are sequentially generated by clustering specially selected subsamples of the given data set. The sampling probability for each data point dynamically depends on the consistency of its previous assignments in the ensemble. New subsamples are drawn to increasingly focus on the problematic regions of the input feature space. A measure of a data point's clustering consistency is defined to guide this adaptation. An empirical study compares the performance of adaptive and regular clustering ensembles using different consensus functions on a number of data sets. Experimental results demonstrate improved accuracy for some clustering structures.
Quality-based Score Level Fusion in Multibiometric Systems

The quality of biometric samples has a significant impact on the accuracy of a matcher. Poor quality biometric samples often lead to incorrect matching results because the features extracted from these samples are not reliable. Therefore, dynamically assigning weights to the outputs of individual matchers based on the quality of the samples presented at the input of the matchers can improve the overall recognition performance of a multibiometric system. We propose a likelihood ratio-based fusion scheme that takes into account the quality of the biometric samples while combining the match scores provided by the matchers. Instead of estimating the quality of the template and query images individually, we estimate a single quality metric for each template-query pair based on the local image quality measures. Experiments on a database of 320 users with iris and fingerprint modalities demonstrate the advantages of utilizing the quality information in multibiometric systems
Boundary detection using multiscale Markov random fields

The basic difficulty encountered in filtering-based multiscale boundary detection methods is the elimination of noise and insignificant edges while preserving positional accuracy at the image discontinuities. In this paper, a nonlinear multiscale boundary detection method which prevents the conflict between the detection and localization goals is introduced. The method uses multiscale representations of coupled Markov random fields and applies a stochastic regularization scheme based on the Bayesian approach. This allows the integration of boundary information extracted at multiple scales simultaneously resulting in robust integration of the information at a variety of spatial scales. The scheme is applicable to intensity images as well as to range images and eliminates the dependency on edge operator size which is the main difficulty in filtering-based multiscale techniques.
Incremental learning for Bayesian classification of images

Grouping images into (semantically) meaningful categories using low-level visual features is a challenging and important problem in content-based image retrieval. In this paper, we develop an incremental learning paradigm for Bayesian classification of images. Under the Bayesian paradigm, the class-conditional densities are represented in terms of codebook vectors. Learning is thus incrementally updating these codebook vectors as new training data become available. The proposed learning scheme estimates the already learnt training samples from the existing codebook vectors and augments these to the new training set for re-training the classifier. The above paradigm is shown to yield good results on three complex image classification problems. A classifier trained incrementally has comparable accuracies to the one which is trained using the true training samples.
Heterogeneous Face Recognition Using Kernel Prototype Similarities

Heterogeneous face recognition (HFR) involves matching two face images from alternate imaging modalities, such as an infrared image to a photograph or a sketch to a photograph. Accurate HFR systems are of great value in various applications (e.g., forensics and surveillance), where the gallery databases are populated with photographs (e.g., mug shot or passport photographs) but the probe images are often limited to some alternate modality. A generic HFR framework is proposed in which both probe and gallery images are represented in terms of nonlinear similarities to a collection of prototype face images. The prototype subjects (i.e., the training set) have an image in each modality (probe and gallery), and the similarity of an image is measured against the prototype images from the corresponding modality. The accuracy of this nonlinear prototype representation is improved by projecting the features into a linear discriminant subspace. Random sampling is introduced into the HFR framework to better handle challenges arising from the small sample size problem. The merits of the proposed approach, called prototype random subspace (P-RS), are demonstrated on four different heterogeneous scenarios: 1) near infrared (NIR) to photograph, 2) thermal to photograph, 3) viewed sketch to photograph, and 4) forensic sketch to photograph.
Online script recognition

Automatic identification of handwritten script facilitates many important applications such as automatic transcription of multi-lingual documents and search for documents on the Internet containing a particular script. The increase in usage of handheld devices which accept handwritten input is creating a huge volume of handwritten data. We propose a method to classify words and lines in an online handwritten document into Arabic, Cyrillic, Devnagari, Han, Hebrew and Roman scripts. The proposed classification system, based on spatial and temporal features of the strokes, attained an overall classification accuracy of 86.5% at the word level on a dataset containing 13,379 words. The classification accuracy improves to 95% as the number of words in the test sample is increased to five and to 95.1% for complete text lines.
Statistical Models for Assessing the Individuality of Fingerprints

Following the Daubert ruling in 1993, forensic evidence based on fingerprints was first challenged in the 1999 case of the U.S. versus Byron C. Mitchell and, subsequently, in 20 other cases involving fingerprint evidence. The main concern with the admissibility of fingerprint evidence is the problem of individualization, namely, that the fundamental premise for asserting the uniqueness of fingerprints has not been objectively tested and matching error rates are unknown. In order to assess the error rates, we require quantifying the variability of fingerprint features, namely, minutiae in the target population. A family of finite mixture models has been developed in this paper to represent the distribution of minutiae in fingerprint images, including minutiae clustering tendencies and dependencies in different regions of the fingerprint image domain. A mathematical model that computes the probability of a random correspondence (PRC) is derived based on the mixture models. A PRC of 2.25 times10-6 corresponding to 12 minutiae matches was computed for the NIST4 Special Database, when the numbers of query and template minutiae both equal 46. This is also the estimate of the PRC for a target population with a similar composition as that of NIST4.
Analysis of facial features in identical twins

A study of the distinctiveness of different facial features (MLBP, SIFT, and facial marks) with respect to distinguishing identical twins is presented. The accuracy of distinguishing between identical twin pairs is measured using the entire face, as well as each facial component (eyes, eyebrows, nose, and mouth). The impact of discriminant learning methods on twin face recognition is investigated. Experimental results indicate that features that perform well in distinguishing identical twins are not always consistent with the features that best distinguish two non-twin faces.
A unified DCT/IDCT architecture for VLSI implementation

A unified discrete cosine transform/inverse discrete cosine transform (DCT/IDCT) architecture suitable for VLSI implementation is presented. A single VLSI NMOS chip design and layout for realizing this architecture is described. Algorithm simulations and experimental performance of integrated test subcircuits indicate that this chip would be capable of real-time processing of 10-MHz video signals. It is considered that circuits of this type could be very useful in real-time image data compression.<<ETX>>
An improved coupled spectral regression for heterogeneous face recognition

Coupled spectral regression (CSR) is an effective framework for heterogeneous face recognition (e.g., visual light (VIS) vs. near infrared (NIR)). CSR aims to learn different projections for different face modalities respectively to find a common subspace where the samples of different modalities from the same class are as close as possible. In original CSR, the projection for one modality is supposed to be represented by the data from the same modality. In this paper, we show that not only the samples of the same modality, but also all samples from different modalities are useful to learn the projection. Based on this assumption, we propose an improved coupled spectral regression (ICSR) approach which assumes the projections are linearly represented by all samples. Moreover, in order to improve the generalization capability, the locality information among samples is considered during the ICSR learning. Experiments on PIE, Multi-PIE and CASIA-HFB face database show that the proposed ICSR enhances the heterogeneous face recognition performance compared with the original CSR and validates the effectiveness of the proposed method.
Face Recognition in the Virtual World: Recognizing Avatar Faces

Criminal activity in virtual worlds is becoming a major problem for law enforcement agencies. Forensic investigators are becoming interested in being able to accurately and automatically track people in virtual communities. In this paper a set of algorithms capable of verification and recognition of avatar faces with high degree of accuracy are described. Results of experiments aimed at within-virtual-world avatar authentication and inter-reality-based scenarios of tracking a person between real and virtual worlds are reported. In the FERET-to-Avatar face dataset, where an avatar face was generated from every photo in the FERET database, a COTS FR algorithm achieved a near perfect 99.58% accuracy on 725 subjects. On a dataset of avatars from Second Life, the proposed avatar-to-avatar matching algorithm (which uses a fusion of local structural and appearance descriptors) achieved average true accept rates of (i) 96.33% using manual eye detection, and (ii) 86.5% in a fully automated mode at a false accept rate of 1.0%. A combination of the proposed face matcher and a state-of-the art commercial matcher (FaceVACS) resulted in further improvement on the inter-reality-based scenario.