Won-Du Chang

Pukyong National University · Department of Computer Engineering

Automatic age estimation using panoramic dental radiographic images is an important procedure for forensics and personal oral healthcare. The accuracies of the age estimation have increased recently with the advances in deep neural networks (DNN), but DNN requires large sizes of the labeled dataset which is not always available. This study examined...

Oral health plays an important role in people’s quality of life as it is related to eating, talking, and smiling. In recent years, many studies have utilized artificial intelligence for oral health care. Many studies have been published on tooth identification or recognition of dental diseases using X-ray images, but studies with RGB images are rar...

Hand gestures are a common means of communication in daily life, and many attempts have been made to recognize them automatically. Developing systems and algorithms to recognize hand gestures is expected to enhance the experience of human–computer interfaces, especially when there are difficulties in communicating vocally. A popular system for reco...

Speech recognition technology is a promising hands-free interfacing modality for virtual reality (VR) applications. However, it has several drawbacks, such as limited usability in a noisy environment or a public place and limited accessibility to those who cannot generate loud and clear voices. These limitations may be overcome by employing a silen...

Developing a hum–computer interface (HCI) is essential, especially for those that have spinal cord injuries or paralysis, because of the difficulties associated with the application of conventional devices and systems. Eye-writing is an HCI that uses eye movements for writing characters such that the gaze movements form letters. In addition, it is...

Eye writing is a human–computer interaction tool that translates eye movements into characters using automatic recognition by computers. Eye-written characters are similar in form to handwritten ones, but their shapes are often distorted because of the biosignal’s instability or user mistakes. Various conventional methods have been used to overcome...

As a representative concept of the fourth industrial revolution era where everything is digitized, digital twin means analyzing and optimizing a complex system using a simulation model synchronized with the system. In this paper, we propose a digital twin simulation model for the efficient operation of urban railways in Busan. Due to the geopolitic...

Unexpected loads are commonly applied in cargo ships when workers fail to comply with applicable regulations while loading and unloading cargo. This important factor can shorten the design life of a ship by increasing the possibility of structural damage. One way to improve the reliability of the fatigue life of a ship is to check for fatigue damag...

Background: The digits-in-noise (DiN) test is a speech-in-noise test to measure speech recognition threshold in noise adaptively. Herein, we aimed to develop the Korean version of the DiN test to provide a useful hearing screening tool for clinical as well as research purposes. Method: Spoken monosyllabic digits from 0 to 9 were recorded by a fe...

The most popular way of learning oriental calligraphy has been by practicing the calligraphy under the supervision of a human teacher, but finding a good instructor can be difficult. There are a number of studies in the literature that have evaluated calligraphic characters in holistic ways, but such systems do not support detailed supervision of s...

Eye movements generate electric signals, which a user can employ to control his/her environment and communicate with others. This paper presents a review of previous studies on such electric signals, that is, electrooculograms (EOGs), from the perspective of human–computer interaction (HCI). EOGs represent one of the easiest means to estimate eye m...

The increase in the number of adolescents with internet gaming disorder (IGD), a type of behavioral addiction is becoming an issue of public concern. Teaching adolescents to suppress their craving for gaming in daily life situations is one of the core strategies for treating IGD. Recent studies have demonstrated that computer-aided treatment method...

Background Electrooculogram (EOG) can be used to continuously track eye movements and can thus be considered as an alternative to conventional camera-based eye trackers. Although many EOG-based eye tracking systems have been studied with the ultimate goal of providing a new way of communication for individuals with amyotrophic lateral sclerosis (AL...

In traditional brain-computer interface (BCI) studies, binary communication systems have generally been implemented using two mental tasks arbitrarily assigned to "yes" or "no" intentions (e.g., mental arithmetic calculation for "yes"). A recent pilot study performed with one paralyzed patient showed the possibility of a more intuitive paradigm for...

Eye movements can be used as alternative inputs for human-computer interface (HCI) systems such as virtual or augmented reality systems as well as new communication ways for patients with locked-in syndrome. In this study, we developed a real-time electrooculogram (EOG)-based eye-writing recognition system, with which users can write predefined sym...

Electroencephalogram (EEG) is easily contaminated by unwanted physiological artifacts, among which electrooculogram (EOG) artifacts due to eye blinking are known to be most dominant. The eye blink artifacts are reported to affect theta and alpha rhythms of frontal EEG signals, and hard to be accurately detected in an unsupervised way due to large i...

This paper introduces a method to remove the unwanted interdependency between vertical and horizontal eye-movement components in electrooculograms (EOGs). EOGs have been widely used to estimate eye movements without a camera in a variety of human-computer interaction (HCI) applications using pairs of electrodes generally attached either above and b...

Ictal epileptiform discharges (EDs) are characteristic signal patterns of scalp electroencephalogram (EEG) or intracranial EEG (iEEG) recorded from patients with epilepsy, which assist with the diagnosis and characterization of various types of epilepsy. The EEG signal, however, is often recorded from patients with epilepsy for a long period of tim...

Eye blinks are one of the most influential artifact sources in electroencephalogram (EEG) recorded from frontal channels, and thereby detecting and rejecting eye blink artifacts is regarded as an essential procedure for improving the quality of EEG data. In this paper, a novel method to detect eye blink artifacts from a single-channel frontal EEG s...

Human eye blinking is cognitively suppressed to minimize loss of visual information for important real-world events. Despite the relationship between eye blinking and cognitive state, the effect of eye blinks on cognition in real-world environments has received limited research attention. In this study, we focused on the temporal pattern of inter-e...

Neurocinematics is an emerging research discipline that studies audiences’ cognitive and affective responses to cinematic stimuli. To date, functional magnetic resonance imaging (fMRI) has been the most widely used research tool for neurocinematics studies; however, recent studies have shown that electroencephalography (EEG) can also be a promising...

Template matching is an approach for signal pattern recognition, often used for biomedical signals including electroencephalogram (EEG). Since EEG is often severely contaminated by various physiological or pathological artifacts, identification and rejection of these artifacts with improved template matching algorithms would enhance the overall qua...

This paper proposes a text-independent writer verification scheme by using character level features. Four character features are introduced in the context of handwritten string, which mainly represent a character's relative position in its string. The scheme is implemented by comparing character shapes and relative features of characters in the con...

Synthesizing handwritten-style characters is an interesting issue in today’s handwriting analysis field. The purpose of this study is to artificially generate training data, foster a deep understanding of human handwriting, and promote the use of the handwritten-style computer fonts, in which the individuality or variety of the synthesized characte...

This paper addresses the problem of dynamic time warping (DTW) causing unintended matching correspondences when it is employed for online two-dimensional (2D) handwriting signals, and proposes the concept of dynamic positional warping (DPW) in conjunction with DTW for online handwriting matching problems. The proposed DPW allows subsignal translati...

A lot of image data has been digitized and preserved in computers. In order to search for an image, an efficient and accurate retrieval method is needed. This paper is concerned with shape retrieval which is one of the searching methods for finding similar images in a database. Shape, the outer form of a picture, is considered the most promising fe...

In this paper, we present object detection using Histogram of Oriented Gradients. The method of the person detection is a matching of the source image and the template image. In step one, the brightness inclination is calculated from the image, 5x5 pixels become a cell, and 3x3 cells become a block. In step two, processing compares a source image a...

This paper proposes a text-independent writer verification scheme by using character level features. Four character features are introduced in the context of handwritten string, which mainly represent a character's relative position in its string. The scheme is implemented by comparing character shapes and relative features of characters in the con...

In this paper, the features that have personal characteristic using pen inclination and pressure information are discussed. Forging a pen inclination and pressure information is difficult because it is not visible. Four features using invisible information are proposed and their characteristics are discussed. Proposed features calculated by physica...

This paper proposes a system which can detect the effect of alcohol consumption from handwritten signatures for the purpose of strengthening on-line signature verification systems. In spite of the popularity of the signature verification; the influence of alcohol has not been covered very much in literature. As the preliminarily step of this resear...

This paper considers the unsupervised classification of handwritten character strokes in regards to speed, since handwritten strokes prove challenging with their high and variable dimensions for classification problems. Our approach employs a robust feature detection method for brief classification. The dimension is reduced by selecting feature poi...

This paper proposes a stochastic stroke model which synthesizes variable handwritten characters preserving one's writing style. Our fundamental concept of the stochastic model is thinking a stroke as consecutive state changes of segments. After clustering segments into several states, a number of characters are presented as a directed graph with pr...

In this paper, we present novel model to find the contour of an image in phases. The model was designed by modelling physical motion of a real elastic band. This is applied to top of any existing shape representation methods in order to offer additional information. The model makes us deal with global and local shape characteristics at once and res...

In this paper, we refer a phenomenon of relatively high error rates against random forgeries in online signature verification. Though human can easily distinguish random forgeries from genuine signatures, the most published research results during last decades have reported high error rates against them, compared to the error rates against skilled...

Dynamic time warping (DTW) is one of the most widely been used method to match and compare the dissimilarity of two signals’ shapes. Though it is frequently used for two-dimensional signals in many researches, applying DTW directly to the 2D shape signal involves matching problems. Through our researches, the most of the previous approaches on 2D s...

In the stroke-based signature verification system, it is important to find correct points of a testing signature to be spilt according to its template signature. In this paper, we propose a modified dynamic time warping algorithm (DTW) for the problem. Proposed method has two differences to the conventional approaches. First, the stroke information...

In spite of the importance of natural drawing with input device, the interface between the device and virtual brush’s status has been dealt less in literatures. Through this paper, we present a natural interface between pen-tablet device and virtual brush. Proposed system uses pressure instead of z-coordinate of pen to allow drawing with the simila...

Oriental ink writing consists of simple strokes intended to convey an artist¿s deep feelings that makes it to be regarded as a painting. Scratchiness in Japanese Kasure is one of the techniques which can express writer¿s emotion remarkably in calligraphy. A novel method to express Kasure focused on the change of the energy is proposed in this pap...

Multi layer perceptron with back propagation algorithm is popular in various fields of investigation as a non-linear predictor. Though MLP can solve complex and non-linear estimation problems, it cannot use incomplete data patterns for training directly. The estimation of macroinvertbrates is important issue in ecological informatics, and data miss...

In recent years, biometrics is attracting attention and Signature verification is one of the easiest methods to implement among biometrics. There have been many researches on it and the error rate is getting decreases. However, as error rate reduces making performance higher cost more efforts and is getting difficult and some fusion methods have be...

The background subtraction algorithm is one of two main methods of extracting the object from the image sequence. It has a merit of being able to detect much region of objects region clearly even when the object is paused where the back ground im­ age is known to the computer , whi le the method based on frame difference algorithm can detect moving...

As reported in many researches, the performance of signature verification is quite high in these days. However, as error rate reduces making performance higher cost more efforts and is getting difficult. This paper proposes a new global feature for on-line signature verification, which can be used in addition to the other system. The proposed featu...

Multi layer perceptron with back propagation algorithm is popular and more used than other neural network types in various fields of investigation as a non-linear predictor. Though MLP can solve complex and non-linear problems, it cannot use missing data for training directly. We propose a training algorithm with incomplete pattern data using conve...

The classification error of 'ᄆ', 'ᄋ' is one of the main causes of incorrect recognition in Korean characters, but there haven't been enough researches to solve this problem. In this paper, a new feature extraction method from Korean grapheme is proposed to recognize 'ᄆ', 'ᄋ'effectively. First, we defined an optimal neighbor-distance selection measu...