Leonardo Chang

Dr. Leonardo Chang

orcid

Research Focus & Metrics

Academic Career Length

19Years (2008-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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6 August 2022 in Medical Image Analysis
Verified
Journal Article
Open access
JCJuan Carlos Ángeles Cerón
Juan Carlos Ángeles Cerón
GRGilberto Ruiz
Gilberto Ruiz
LCLeonardo Chang
Leonardo Chang
Sharib AliSharib Ali
Sharib Ali
Precise instrument segmentation aids surgeons to navigate the body more easily and increases patient safety. While accurate tracking of surgical instruments in real-time plays a crucial role in minimally invasive computer-assisted surgeries, it is a challenging task to achieve, mainly due to: (1) a complex surgical environment, and (2) model design trade-off in terms of both optimal accuracy and speed. Deep learning gives us the opportunity to learn complex environment from large surgery scene environments and placements of these instruments in real world scenarios. The Robust Medical Instrument Segmentation 2019 challenge (ROBUST-MIS) provides more than 10,000 frames with surgical tools in different clinical settings. In this paper, we propose a light-weight single stage instance segmentation model complemented with a convolutional block attention module for achieving both faster and accurate inference. We further improve accuracy through data augmentation and optimal anchor localization strategies. To our knowledge, this is the first work that explicitly focuses on both real-time performance and improved accuracy. Our approach out-performed top team performances in the most recent edition of ROBUST-MIS challenge with over 44% improvement on area-based multi-instance dice metric MI_DSC and 39% on distance-based multi-instance normalized surface dice MI_NSD. We also demonstrate real-time performance (>60 frames-per-second) with different but competitive variants of our final approach.

1 January 2021 in IEEE Access
Verified
Journal Article
Open access
LGLazaro Janier Gonzalez-Soler
Lazaro Janier Gonzalez-Soler
MGMarta Gomez-Barrero
Marta Gomez-Barrero
LCLeonardo Chang
Leonardo Chang
APAirel Perez-Suarez
Airel Perez-Suarez
CBChristoph Busch
Christoph Busch
Fingerprint-based biometric systems have experienced a large development in the past. In spite of many advantages, they are still vulnerable to attack presentations (APs). Therefore, the task of determining whether a sample stems from a live subject (i.e., bona fide) or from an artificial replica is a mandatory requirement which has recently received a considerable attention. Nowadays, when the materials for the fabrication of the Presentation Attack Instruments (PAIs) have been used to train the Presentation Attack Detection (PAD) methods, the PAIs can be successfully identified in most cases. However, current PAD methods still face difficulties detecting PAIs built from unknown materials and/or unknown recepies, or acquired using different capture devices. To tackle this issue, we propose a new PAD technique based on three image representation approaches combining local and global information of the fingerprint. By transforming these representations into a common feature space, we can correctly discriminate bona fide from attack presentations in the aforementioned scenarios. The experimental evaluation of our proposal over the LivDet 2011 to 2019 databases, yielded error rates outperforming the top state-of-the-art results by up to 72% in the most challenging scenarios. In addition, the best representation achieved the best results in the LivDet 2019 competition (overall accuracy of 96.17%).

30 May 2012 in Machine Vision and Applications
Verified
Journal Article
Closed access
PDF file
LCLeonardo Chang
Leonardo Chang
JHJosé Hernández-Palancar
José Hernández-Palancar
Luis Enrique SucarLuis Enrique Sucar
Luis Enrique Sucar
MAMiguel Arias-Estrada
Miguel Arias-Estrada

13 December 2021 in IEEE Access
Verified
Journal Article
Open access
YMYoanna Martinez-Diaz
Yoanna Martinez-Diaz
HMHeydi Mendez-Vazquez
Heydi Mendez-Vazquez
LLLuis S. Luevano
Luis S. Luevano
MNMiguel Nicolas-Diaz
Miguel Nicolas-Diaz
LCLeonardo Chang
Leonardo Chang
MGMiguel Gonzalez-Mendoza
Miguel Gonzalez-Mendoza
Given the current COVID-19 pandemic, most people wear a mask to effectively prevent the spread of the contagious disease. This sanitary measure has caused a significant drop in the effectiveness of current face recognition methods when handling masked faces on practical applications such as face access control, face attendance, and face authentication-based mobile payment. Under this situation, recent efforts have been focused on boosting the performance of the existing face recognition technology on masked faces. Some solutions trying to tackle this issue fine-tune the existing deep learning face recognition models on synthetic masked images, while others use the periocular region as a naive manner to eliminate the adverse effect of COVID-19 masks. Although the accuracy of masked face recognition remains an important issue, in the last few years, the development of efficient and lightweight face recognition methods has received an increased attention in the research community. In this paper, we study the effectiveness of three state-of-the-art lightweight face recognition models for addressing accurate and efficient masked face recognition, considering both fine-tuning on masked faces and periocular images. For the experimental evaluation, we create both real and simulated masked face databases as well as periocular datasets. Extensive experiments are conducted to determine the most effective solution and state further steps for the research community. The obtained results disclose that fine-tuning existing state-of-the-art face models on masked images achieve better performance than using periocular-based models. Besides, we evaluate and analyze the effectiveness of the trained masked-based models on well-established unmasked benchmarks for face recognition and assess the efficiency of the used lightweight architectures in comparison with state-of-the-art face models.

1 February 2012 in Expert Systems with Applications
Verified
Journal Article
Closed access
LCLeonardo Chang
Leonardo Chang
MDMiriam M. Duarte
Miriam M. Duarte
Luis Enrique SucarLuis Enrique Sucar
Luis Enrique Sucar
EMEduardo Morales
Eduardo Morales

Verified
Journal Article
Open access
PDF file
FCFernando Camarena
Fernando Camarena
Miguel Gonzalez-MendozaMiguel Gonzalez-Mendoza
Miguel Gonzalez-Mendoza
LCLeonardo Chang
Leonardo Chang
RCRicardo Cuevas-Ascencio
Ricardo Cuevas-Ascencio
Artificial intelligence’s rapid advancement has enabled various applications, including intelligent video surveillance systems, assisted living, and human–computer interaction. These applications often require one core task: video-based human action recognition. Research in human video-based human action recognition is vast and ongoing, making it difficult to assess the full scope of available methods and current trends. This survey concisely explores the vision-based human action recognition field and defines core concepts, including definitions and explanations of the common challenges and most used datasets. Additionally, we provide in an easy-to-understand manner the literature approaches and their evolution over time, emphasizing intuitive notions. Finally, we explore current research directions and potential future paths. The core goal of this work is to provide future works with a shared understanding of fundamental ideas and clear intuitions about current works and find new research opportunities.