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R²FID: Joint Reranker in Fusion-In-Decoder for Open Domain Question Answering over Tables
Sung-Min Lee, Eunhwan Park, Daeryong Seo, Donghyeon Jeon, Inho Kang, Seung-Hoon Na
http://doi.org/10.5626/JOK.2023.50.10.874
Open Domain Question Answering is a challenging problem that aims to generate an answer where reference documents relevant to a question are not provided. Considering that the importance of the QA system in structured data such as tables has recently gradually increased, this paper presents a method for table open domain question answering of Korean, focusing on tabular contents appearing in Wikipedia. In addition, we extensively apply the Joint Reranker based Fusion-In-Decoder to address limitations entailed in table retrieval, Resulting methods based on Joint Reranker led to improvements of an EM of 3.36 and a F1-Score of 3.25 over open domain question answering tasks.
Early Anomaly Detection of LNG-Carrier Main Engine System based on Multivariate Time-Series Boundary Forecasting and Confidence Evaluation Technique
Donghyun Kim, Taigon Kim, Minji An, Yunju Baek
http://doi.org/10.5626/JOK.2023.50.5.429
Recently, a variety of studies have been conducted to detect abnormal operation of ships and their causes and in the marine and shipbuilding industries. This study proposed a method for early anomaly detection of the main engine system using a multivariate time series sensor data extracted from LNG carriers built at a shipyard. For early anomaly detection, the process of predicting the future value through the sensor data at present is necessary, and in this process, the prediction residual, which is the difference between the actual future value and the predicted value, is generated. Since the generated residual has a significant effect on the early anomaly detection results, a compensating process is necessary. We propose novel loss functions that can learn the upper or lower prediction boundary of a time-series forecasting model. The time-series forecasting model trained with the proposed loss function improves the performance of the early anomaly detection algorithm by compensating the prediction residual. In addition, the real-time confidence of the predicted value is evaluated through the newly proposed confidence model by utilizing the similarity between time-series forecasting residual and confidence residual. With the early anomaly detection algorithm proposed in this study, the prediction model, which learns the upper boundary, outputs the upper limit of the predicted value that can be output by the baseline prediction model learned with the MSE loss function and can predict abnormal behavior that threshold-based anomaly discriminator could not predict because the future prediction of the baseline model is lower than the actual future value. Based on the results of this study, the performance of the proposed method was improved to 0.9532 compared to 0.4001 of the baseline model in Recall. This means that robust early anomaly detection is possible in various operating styles of the actual ship operations.
UHF RFID Tag Identification Method Based on Physical-layer Features of Backscatter Networks
Yoonseo Kim, Hoorin Park, Minwoo Joo, Wonjun Lee
http://doi.org/10.5626/JOK.2021.48.9.1061
Radio-frequency identification (RFID) systems are becoming essential components in Internet of Things (IoT) networks by virtue of their cost and energy efficiency. Especially, in ultra high frequency (UHF) RFID systems, the process of identifying individual tags is crucial because different tags communicate in a passive manner. However, the tag identifiers used in existing systems are vulnerable to be replicated or predicted due to limited tag operation resources and memory, which leads to severe security threats. In this paper, we propose a technology to extract the unique physical-layer characteristics, which are difficult to be forged, and utilize them for tag identification. The proposed method consists of a fingerprint extraction algorithm to obtain the physical-layer features of time interval error and phase by analyzing the backscatter signals of the tags, and a tag identification algorithm to distinguish tags based on their extracted fingerprints. We provide a model of backscatter signals and analyze the identification accuracy of the proposed method with varying signal-to-noise ratios.
CNN-based Reduced Complexity Decision Confidence Estimation for Imbalanced Web Application Attack Detection
Seungyoung Park, Hansung Kim, Taejoon Jung
http://doi.org/10.5626/JOK.2020.47.9.842
As web application attacks have been rapidly increasing and their types have been diversified, there are limitations on detecting them with the existing schemes. To resolve this problem, the detection techniques using machine learning such as the convolutional neural network (CNN) have been proposed. However, the confidence on the decision error sample in these techniques has been unreliable. To estimate more reliable decision confidence, the Monte-Carlo batch normalization (MCBN) technique combined with the CNN has been proposed. In particular, the CNN performs multiple decisions on a given evaluation sample using multiple mini-batches containing it. Then, its decision confidence estimate is obtained by averaging the multiple decision results. However, it requires too large of a computational load. The reason is that each mini-batch comprises randomly selected (M-1) training samples and only one evaluation sample, when the mini-batch size is M. In this paper, we propose a reduced complexity decision confidence estimation scheme for imbalanced web application attack detection. Specifically, the proposed scheme reduces the computational load by up to M times compared to the MCBN scheme. Also, at the estimation process, the ratio of normal and attack samples in the mini-batch should be maintained the same as that of the training process. To achieve this, we found which class size was small by performing a temporal decision on the evaluation samples. Then, the small class was over-sampled using the training samples to maintain the ratio. Our experimental results showed that the performance improved, and the reliability estimation performance was not significantly degraded compared to the MCBN scheme.
An Integrated Model of Cybersickness: Understanding User’s Discomfort in Virtual Reality
Eunhee Chang, Daeil Seo, Hyun Taek Kim, Byounghyun Yoo
http://doi.org/10.5626/JOK.2018.45.3.251
Users can experience cybersickness when interacting with virtual reality (VR). The symptoms of cybersickness are similar to those of motion sickness which include eye fatigue, disorientation, and nausea. Despite the longstanding interest of user’s discomfort, inconsistent results have been drawn on the underlying mechanisms and solutions of cybersickness. In this study, we propose an integrated view of cybersickness connecting causes of the symptoms, human perception model, and measurements of cybersickness. Cybersickness-related factors of previous research are reorganized into content, hardware, and human factors as well as analyzed in terms of VR fidelity. Also, pros and cons that measure the degree of cybersickness are discussed.
Confidence Value based Large Scale OWL Horst Ontology Reasoning
Wan-Gon Lee, Hyun-Kyu Park, Batselem Jagvaral, Young-Tack Park
Several machine learning techniques are able to automatically populate ontology data from web sources. Also the interest for large scale ontology reasoning is increasing. However, there is a problem leading to the speculative result to imply uncertainties. Hence, there is a need to consider the reliability problems of various data obtained from the web. Currently, large scale ontology reasoning methods based on the trust value is required because the inference-based reliability of quantitative ontology is insufficient. In this study, we proposed a large scale OWL Horst reasoning method based on a confidence value using spark, a distributed in-memory framework. It describes a method for integrating the confidence value of duplicated data. In addition, it explains a distributed parallel heuristic algorithm to solve the problem of degrading the performance of the inference. In order to evaluate the performance of reasoning methods based on the confidence value, the experiment was conducted using LUBM3000. The experiment results showed that our approach could perform reasoning twice faster than existing reasoning systems like WebPIE.
Spark based Scalable RDFS Ontology Reasoning over Big Triples with Confidence Values
Hyun-Kyu Park, Wan-Gon Lee, Batselem Jagvaral, Young-Tack Park
Recently, due to the development of the Internet and electronic devices, there has been an enormous increase in the amount of available knowledge and information. As this growth has proceeded, studies on large-scale ontological reasoning have been actively carried out. In general, a machine learning program or knowledge engineer measures and provides a degree of confidence for each triple in a large ontology. Yet, the collected ontology data contains specific uncertainty and reasoning such data can cause vagueness in reasoning results. In order to solve the uncertainty issue, we propose an RDFS reasoning approach that utilizes confidence values indicating degrees of uncertainty in the collected data. Unlike conventional reasoning approaches that have not taken into account data uncertainty, by using the in-memory based cluster computing framework Spark, our approach computes confidence values in the data inferred through RDFS-based reasoning by applying methods for uncertainty estimating. As a result, the computed confidence values represent the uncertainty in the inferred data. To evaluate our approach, ontology reasoning was carried out over the LUBM standard benchmark data set with addition arbitrary confidence values to ontology triples. Experimental results indicated that the proposed system is capable of running over the largest data set LUBM3000 in 1179 seconds inferring 350K triples.
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