Bumshik Lee

Prof. Bumshik Lee

Department of Information and Communication Engineering, Chosun University, Gwangju 61452, Korea
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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7 June 2020 in Sensors
Verified
Journal Article
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NYNagaraj Yamanakkanavar
Nagaraj Yamanakkanavar
JCJaeYoung Choi
JaeYoung Choi
Bumshik LeeBumshik Lee
Bumshik Lee
Many neurological diseases and delineating pathological regions have been analyzed, and the anatomical structure of the brain researched with the aid of magnetic resonance imaging (MRI). It is important to identify patients with Alzheimer’s disease (AD) early so that preventative measures can be taken. A detailed analysis of the tissue structures from segmented MRI leads to a more accurate classification of specific brain disorders. Several segmentation methods to diagnose AD have been proposed with varying complexity. Segmentation of the brain structure and classification of AD using deep learning approaches has gained attention as it can provide effective results over a large set of data. Hence, deep learning methods are now preferred over state-of-the-art machine learning methods. We aim to provide an outline of current deep learning-based segmentation approaches for the quantitative analysis of brain MRI for the diagnosis of AD. Here, we report how convolutional neural network architectures are used to analyze the anatomical brain structure and diagnose AD, discuss how brain MRI segmentation improves AD classification, describe the state-of-the-art approaches, and summarize their results using publicly available datasets. Finally, we provide insight into current issues and discuss possible future research directions in building a computer-aided diagnostic system for AD.

5 August 2018 in Mathematical Problems in Engineering
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Journal Article
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JCJae Young Choi
Jae Young Choi
Bumshik LeeBumshik Lee
Bumshik Lee
Time series forecasting is essential for various engineering applications in finance, geology, and information technology, etc. Long Short-Term Memory (LSTM) networks are nowadays gaining renewed interest and they are replacing many practical implementations of the time series forecasting systems. This paper presents a novel LSTM ensemble forecasting algorithm that effectively combines multiple forecast (prediction) results from a set of individual LSTM networks. The main advantages of our LSTM ensemble method over other state-of-the-art ensemble techniques are summarized as follows: (1) we develop a novel way of dynamically adjusting the combining weights that are used for combining multiple LSTM models to produce the composite prediction output; for this, our method is devised for updating combining weights at each time step in an adaptive and recursive way by using both past prediction errors and forgetting weight factor; (2) our method is capable of well capturing nonlinear statistical properties in the time series, which considerably improves the forecasting accuracy; (3) our method is straightforward to implement and computationally efficient when it comes to runtime performance because it does not require the complex optimization in the process of finding combining weights. Comparative experiments demonstrate that our proposed LSTM ensemble method achieves state-of-the-art forecasting performance on four real-life time series datasets publicly available.

3 August 2020 in PLOS ONE
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Journal Article
Open access
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Bumshik LeeBumshik Lee
Bumshik Lee
NYNagaraj Yamanakkanavar
Nagaraj Yamanakkanavar
JCJaeYoung Choi
JaeYoung Choi
Accurate segmentation of brain magnetic resonance imaging (MRI) is an essential step in quantifying the changes in brain structure. Deep learning in recent years has been extensively used for brain image segmentation with highly promising performance. In particular, the U-net architecture has been widely used for segmentation in various biomedical related fields. In this paper, we propose a patch-wise U-net architecture for the automatic segmentation of brain structures in structural MRI. In the proposed brain segmentation method, the non-overlapping patch-wise U-net is used to overcome the drawbacks of conventional U-net with more retention of local information. In our proposed method, the slices from an MRI scan are divided into non-overlapping patches that are fed into the U-net model along with their corresponding patches of ground truth so as to train the network. The experimental results show that the proposed patch-wise U-net model achieves a Dice similarity coefficient (DSC) score of 0.93 in average and outperforms the conventional U-net and the SegNet-based methods by 3% and 10%, respectively, for on Open Access Series of Imaging Studies (OASIS) and Internet Brain Segmentation Repository (IBSR) dataset.

6 January 2020 in IEEE Signal Processing Letters
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Journal Article
Closed access
JCJaeYoung Choi
JaeYoung Choi
Bumshik LeeBumshik Lee
Bumshik Lee
This letter proposes a novel way of using an ensemble of multiple deep convolutional neural networks (DCNNs) for Alzheimer's disease classification, based on magnetic resonance imaging (MRI) images. To create this ensemble of DCNNs, we propose to combine the use of multiple MRI projections (as input) with that of different DCNN architectures to increase the deep ensemble diversity. In particular, to find the optimal fusion weights of the DCNN members, we designed a novel deep ensemble generalization loss, which accounts for interaction and cooperation during the optimal weight search. The optimization framework, equipped with our ensemble generalization loss, was formulated and solved using the sequential quadratic programming. Through this method, we achieved optimal DCNN weights (i.e., a high generalization performance). The experimental results showed that our proposed DCNN ensemble outperforms current deep learning-based methods: it is able to produce state-of-the-art results on the Alzheimer's disease neuroimaging initiative (ADNI) dataset.

1 July 2019 in IEEE Transactions on Multimedia
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Journal Article
Closed access
SGSarala Ghimire
Sarala Ghimire
JCJaeYoung Choi
JaeYoung Choi
Bumshik LeeBumshik Lee
Bumshik Lee
A video record plays a crucial role in providing evidence for crime scenes or road accidents. However, the main problem with the video record is that it is often vulnerable to various video tampering attacks. Although visual evidence is required to conduct an integrity verification before investigations, it is still difficult for human vision to detect a forgery. In this paper, we propose a novel video integrity verification method (IVM) that takes advantage of a blockchain framework. The proposed method employs an effective blockchain model in centralized video data, by combining a hash-based message authentication code (HMAC) and elliptic curve cryptography (ECC) to verify the integrity of a video. In our method, video content with a predetermined size (segments) is key-hashed in a real-time manner and stored in a chronologically-chained fashion, thus establishing an irrefutable database. The verification process applies the same procedure to the video segment, and generates a hash value that can be compared with the hash in the blockchain. The proposed IVM is implemented on a PC environment, as well as on an accident data recorder (ADR)-embedded system for verification. The experimental results show that the proposed method has better detection capabilities and robustness towards various kinds of tampering such as copy-move, insert, and delete, as compared to other state-of-the-art methods. An analysis based on execution time along with an increase in the number of blocks within the blockchain shows a minimal overhead in the proposed method.

18 December 2019 in IEEE Transactions on Image Processing
Verified
Journal Article
Closed access
JCJaeYoung Choi
JaeYoung Choi
Bumshik LeeBumshik Lee
Bumshik Lee
Most DCNN-based FR approaches typically employ grayscale or RGB color images as input representations of DCNN architectures. However, other effective face representation methods have been developed and incorporated into current practical FR systems. In light of this fact, the focus of our study is to employ Gabor face representations in the design of DCNN-based FR frameworks to improve FR performance. To this end, we develop a novel “Gabor DCNN (GDCNN)” ensemble method that effectively applies different and multiple Gabor face representations as inputs during the training and testing phases of a DCNN for FR applications. The proposed GDCNN ensemble method primarily consists of two parts: 1) GDCNN ensemble construction and 2) GDCNN ensemble combination. The goal of the former part is to build an ensemble of GDCNN members (i.e., base models), each learned with a particular type of Gabor face representation. The objective of the latter part is to adaptively combine multiple FR outputs of individual GDCNN members. We perform extensive experiments to evaluate our proposed method on four public face databases (DBs) using the associated standard evaluation protocols. Experimental results demonstrate that our approach exhibits significantly better FR performance than typical DCNN-based approaches that rely only on grayscale or color face images as input representations. In addition, the feasibility of our proposed GDCNN ensemble has been successfully demonstrated by making comparisons with other state-of-the-art DCNN-based FR methods.