Italy

In many applications we want to find the number of clusters in a dataset. A common approach is to use a penalized k-means algorithm with an additive penalty term linear in the number of clusters. Obviously, the number of discovered clusters depends critically on the value of the coefficient of the penalty term, and an open problem is estimating the value of the coefficient in a principled manner. In this paper, we derive rigorous bounds for the coefficient of the additive penalty in k-means for ideal clusters. Although in practice clusters typically deviate from the ideal assumption, the ideal case serves as a useful guideline. Furthermore, we investigate
k-means with multiplicative penalty, which generally produces a more reliable signature, compared to additive penalty, for the correct number of clusters in cases where the ideal cluster assumption holds. We also empirically investigate certain types of deviations from ideal cluster assumption. In such cases both types of penalties may suggest multiple, ambiguous solutions. We present a consensus-based approach to resolving these ambiguous solutions by combining the results of additive and multiplicative penalties.

ICPR 2020

Penalized K-Means Algorithms for Finding the Number of Clusters

additive penalty; clustering; multiplicative penalty; number of clusters; penalized k-means; unsupervised learning

ICPR 2020 is the premier international conference on Pattern Recognition, gathering leading researchers from around the world to present their latest achievements in Pattern Analysis and Recognition, applied Artificial Intelligence and Machine Learning. The topic of the year is " Putting Artificial intelligence to work on Patterns". 
For the first time, ICPR has employed a two-round review process similar to journal submissions, with new papers allowed to be submitted in either the first or second round and papers submitted in the first round and not accepted allowed to be revised and re-submitted for second round review. 

In this edition of the **ICPR 2020** Conference, there are 1407 Oral/Poster presentations organized in five Tracks: 
- Artificial Intelligence, Machine Learning for Pattern Analysis; 
- Biometrics, Human Analysis and Behavior Understanding; Computer Vision, Robotics and Intelligent Systems; 
- Document and Media Analysis; and 
- Image and Signal Processing. 

The **ICPR 2020** Main Conference program also includes 7 Keynotes from prominent world-renowned scientists, 8 Tutorials, 28 Demos, 8 Challenges, 2 Panels, as well as an Industry/Sponsor Exhibition. In addition, 41 Workshops on a range of important current and emerging research topics complete the ICPR 2020 program. 


poster

High-order statistics have been proven useful in the framework of Convolutional Neural Networks (CNN) for a variety of computer vision tasks. 
In this paper, we propose to exploit high-order statistics in the framework of Recurrent Neural Networks (RNN) for skeleton-based hand gesture recognition. 
Our method is based on the Statistical Recurrent Units (SRU), an un-gated architecture that has been introduced as an alternative model for Long-Short Term Memory (LSTM) and Gate Recurrent Unit (GRU). 
The SRU captures sequential information by generating recurrent statistics 
that depend on a context of previously seen data and by computing moving averages at different scales. The integration of high-order statistics in the SRU significantly improves the performance of the original one, resulting in a model that is competitive to state-of-the-art methods on the Dynamic Hand Gesture (DHG) dataset,and outperforms them on the First-Person Hand Action (FPHA) dataset.

Learning Recurrent High-order Statistics
for Skeleton-based Hand Gesture Recognition

The ability to detect objects in cultural sites from the egocentric point of view of the user can enable interesting applications for both the visitors and the manager of the site. Unfortunately, current object detection algorithms have to be trained on large amounts of labeled data, the collection of which is costly and time-consuming. While synthetic data generated from the 3D model of the cultural site can be used to train object detection algorithms, a significant drop in performance is generally observed when such algorithms are deployed to work with real images. In this paper, we consider the problem of unsupervised domain adaptation for object detection in cultural sites. Specifically, we assume the availability of synthetic labeled images and real unlabeled images for training. To study the problem, we propose a dataset containing 75244 synthetic and 2190 real images with annotations for 16 different artworks. We hence investigate different domain adaptation techniques based on image-to-image translation and feature alignment. Our analysis points out that such techniques can be useful to address the domain adaptation issue, while there is still plenty of space for improvement on the proposed dataset. We release the dataset at our web page to encourage research on this challenging topic:
https://iplab.dmi.unict.it/EGO-CH-OBJ-ADAPT/.

Unsupervised Domain Adaptation For Object Detection in Cultural Sites

We propose a novel evaluation metric for generating models. We leverage siamese architecture and train our discriminator on the real dataset. We define a loss function that takes advantage of the fact that the discriminator's target features should be close to each other when their input is from the same category.

On the Evaluation of Generative Adversarial Networks By Discriminative Models

We propose Fast Direction-Search-Based Subspace Clustering (Fast DiSC), a scalable and robust framework for large scale clustering that rests upon representations derived from projections on computed data-dependent directions. To advance scalability, a Direction Search in Data Partitions (DiSPart) procedure performs direction-search in small partitions of sampled data, followed by retrieval using Retrieval using Direction-based Projections (ReDiP) to cluster out-of-sample data using projections on the computed directions and the associated clustering. A theoretical study establishes the correctness of the direction-based clustering framework and that of direction-search in small partitions. In turn, Fast DiSC can provably realize substantial speedups while maintaining high accuracy.

Scalable Direction-Search-Based Approach to Subspace Clustering


This paper studies the problem of Person Re-Identification (ReID)
for large-scale applications. Recent research efforts have been devoted
to building complicated part models, which introduce considerably
high computational cost and memory consumption, inhibiting its practicability
in large-scale applications. This paper aims to develop a novel learning
strategy to find efficient feature embeddings while maintaining the
balance of accuracy and model complexity. More specifically, we find
by enhancing the classical triplet loss together with cross-entropy
loss, our method can explore the hard examples and build a discriminant
feature embedding yet compact enough for large-scale applications.
Our method is carried out progressively using Bayesian optimization,
and we call it the Progressive Learning Algorithm (PLA). Extensive
experiments on three large-scale datasets show that our PLA is comparable
or better than the state-of-the-arts. Especially, on the challenging
Market-1501 dataset, we achieve Rank-1=94.7%/mAP=89.4% while saving
at least 30\% parameters than strong part models.

Efficient Online Subclass Knowledge Distillation for Image Classification

Fourier Domain Pruning of MobileNet-V2 with Application to Video Based Wildfire Detection

We propose a novel network initialization method using Perlin noise for training image classification networks with a limited amount of data. Our main idea is to initialize the network parameters by solving an artificial noise classification problem, where the aim is to classify Perlin noise samples into their noise categories. Specifically, the proposed method consists of two steps. First, it generates Perlin noise samples with category labels defined based on noise complexity. Second, it solves a classification problem, in which network parameters are optimized to classify the generated noise samples. This method produces a reasonable set of initial weights (filters) for image classification. To the best of our knowledge, this is the first work to initialize networks by solving an artificial optimization problem without using any real-world images. Our experiments show that the proposed method outperforms conventional initialization methods on four image classification datasets.

Initialization Using Perlin Noise for Training Networks with a Limited Amount of Data


Accurate segmentation for lung nodules in lung computed tomography (CT) scans plays a key role in the early diagnosis of lung cancer. In this work, we propose a novel Mask and Texture-driven Generative Adversarial Network (MTGAN) with a joint multi-scale L1 loss for lung nodule segmentation, which takes full advantages of U-Net and adversarial training. The proposed MTGAN leverages adversarial learning strategy guided by the boundary and texture information of lung nodules to generate more accurate segmentation results with lesser false positives.

MTGAN: Mask and Texture-driven Generative Adversarial Network for Lung Nodule Segmentation

Since the poor performance of Faster R-CNN in dense scenes. We propose a straightforward sampling method, which helps to elevate the ratio of positive samples. By assigning a positive label to more anchors in three steps according to different rules, we increase the number of positive samples and reduce the waste of ground-truth. The experiments prove that the performance of our method reaches nearly the existing state-of-the-art with faster inference speed.

Multiple-step Sampling for Dense Object Detection and Counting


In an ECG record, the PQRST waves are of important medical significance which provide ample information reflecting heartbeat activities. In this paper, we propose a novel arrhythmia classification method namely EasiECG, characterized by simplicity and accuracy. Compared with other works, the EasiECG takes the configuration of these five key waves into account and does not require complicated feature engineering. Meanwhile, an additional encoding of the extracted features makes the EasiECG applicable even on samples with missing waves. To automatically capture interactions that contribute to the classification among the processed features, a novel adapted classification model named Attention-based Convolution Factorization Machines (ACFM) is proposed. Extensive experiments show that our method is competitive compared with other state-of-the-arts.

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Penalized K-Means Algorithms for Finding the Number of Clusters

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Learning Recurrent High-order Statistics for Skeleton-based Hand Gesture Recognition

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