Vibration control of high-speed trains self-excitation under-chassis equipment by HSLDS vibration isolators

Yu Sun,Jinsong Zhou,Dao Gong,Wenjing Sun,Zhanghui Xia 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

To minimize the self-excitation effects of the equipment on the carbody, a high static and low dynamic stiffness (HSLDS) vibration isolator is proposed by connecting a negative stiffness unit and a positive linear stiffness spring in parallel. The nonlinear stiffness of the HSLDS isolator can be designed according to the needs of any target stiffness curve. A vibration test is applied to obtain the vibration acceleration of the under-chassis equipment. A rigid-flexible coupling multi-body dynamic model of a high-speed train is established which considers the elastic vibration of the carbody and the self-excitation of the under-chassis equipment based on the tested result. Different connection methods of the under-chassis equipment including rigid hanging, vibration isolation theory (VIT) hanging, dynamic vibration absorber (DVA) hanging and HSLDS hanging are applied and their effects on the carbody vibration and ride quality are investigated. The simulation results reveal that the proposed HSLDS vibration isolator can effectively isolate the self-excitation of the under-chassis equipment from the carbody and enhance the ride quality of the high-speed train.

Overview of Real-Time Java Computing

Yu Sun,Wei Zhang 한국정보과학회 2013 Journal of Computing Science and Engineering Vol.7 No.2

This paper presents a complete survey of recent techniques that are applied in the field of real-time Java computing. It focuses on the issues that are especially important for hard real-time applications, which include time predictable garbage collection, worst-case execution time analysis of Java programs, real-time Java threads scheduling and compiler techniques designed for real-time purpose. It also evaluates experimental frameworks that can be used for researching real-time Java. This overview is expected to help researchers understand the state-of-the-art and advance the research in real-time Java computing.

A Case of Computed Tomography Angiography Imaging of Chronic Thromboembolic Pulmonary Hypertension Secondary to Patent Ductus Arteriosus

Yu Sun,Jie Hou,Benqiang Yang 아시아심장혈관영상의학회 2023 Cardiovascular Imaging Asia Vol.7 No.2

Patent ductus arteriosus (PDA) is a relatively common congenital heart disease in which the ductus arteriosus fails to close after birth. PDA’s primary complications include left cardiac insufficiency, pulmonary hypertension, and right heart volume overload. Detection and evaluation of pulmonary hypertension level is a routine clinical concern, as it benefits treatment of PDA. However, few cases PDA with chronic thromboembolic pulmonary hypertension (CTEPH) have been reported. This study presents a 66-year-old male patient with PDA and CTEPH detected using computed tomography angiography (CTA). The main CTA imaging features include a PDA 3 cm in diameter, right pulmonary embolism with partial thrombosis calcification, pulmonary artery dilatation and pulmonary hypertension, and right ventricular enlargement.

On-line Trace Based Automatic Parallelization of Java Programs on Multicore Platforms

Yu Sun,Wei Zhang 한국정보과학회 2012 Journal of Computing Science and Engineering Vol.6 No.2

We propose two new approaches that automatically parallelize Java programs at runtime. These approaches, which rely on run-time trace information collected during program execution, dynamically recompile Java byte code that can be executed in parallel. One approach utilizes trace information to improve traditional loop parallelization, and the other parallelizes traces instead of loop iterations. We also describe a cost/benefit model that makes intelligent parallelization decisions, as well as a parallel execution environment to execute parallelized programs. These techniques are based on Jikes RVM. Our approach is evaluated by parallelizing sequential Java programs, and its performance is compared to that of the manually parallelized code. According to the experimental results, our approach has low overheads and achieves competitive speedups compared to the manually parallelizing code. Moreover, trace parallelization can exploit parallelism beyond loop iterations.

Time-Predictable Java Dynamic Compilation on Multicore Processors

Yu Sun,Wei Zhang 한국정보과학회 2012 Journal of Computing Science and Engineering Vol.6 No.1

Java has been increasingly used in programming for real-time systems. However, some of Java’s features such as automatic memory management and dynamic compilation are harmful to time predictability. If these problems are not solved properly then it can fundamentally limit the usage of Java for real-time systems, especially for hard real-time systems that require very high time predictability. In this paper, we propose to exploit multicore computing in order to reduce the timing unpredictability that is caused by dynamic compilation and adaptive optimization. Our goal is to retain high performance comparable to that of traditional dynamic compilation, while at the same time, obtain better time predictability for Java virtual machine (JVM). We have studied pre-compilation techniques to utilize another core more efficiently, preoptimization on another core (PoAC) scheme to replace the adaptive optimization system (AOS) in Jikes JVM and the counter based optimization (CBO). Our evaluation reveals that the proposed approaches are able to attain high performance while greatly reducing the variation of the execution time for Java applications.

Smoke Particle-Source Prediction Model Based on Multiple Optical Wavelengths Using Deep Learning

Yusun Ahn(Yusun Ahn),Kyuwon Han(Kyuwon Han),Hoesung Yang(Hoesung Yang),Soocheol Kim(Soocheol Kim),Jin Hwa Ryu(Jin Hwa Ryu),Kangbok Lee(Kangbok Lee) 한국화재소방학회 2023 International Journal of Fire Science and Engineer Vol.37 No.2

Recently, installing smoke detectors has become crucial owing to the risk of fatal human damage that may be caused by inhaling smoke during a fire. Smoke detectors have been reported as highly efficient in detecting smoke particles from fire; however, they may generate false alarms because of their limitation in distinguishing the fire smoke from the smoke generated by daily activities. Despite the frequent occurrence of these false alarms, research on predicting the types of sources through smoke particles remains insufficient. This study involved the development process of an intelligent smoke detector for false alarm reduction that aims to predict the occurrence and type of fire and the evaluation of its performance using the light-scattering characteristics for fire/non-fire sources. First, a previous experimental dataset of fire-related conditions was collected from three fire sources and three non-fire sources to train the model with the light-scattering characteristics of the smoke generated from each source. In addition, to reduce the computing power, data preprocessing was performed on the collected dataset using the median and RobustScaler. Finally, we evaluated the prediction performance of the three deep learning models using three networks: RNN, LSTM, and CNN-LSTM. As a result, we confirmed that the scattering intensity of smoke particles has unique characteristics for each source. When the data preprocessing and prediction models were applied, all three models achieved an accuracy of 0.90 or higher. However, some errors occurred that appeared at similar scattering intensities. The proposed method differs from existing methods in that it presents the possibility of predicting fire and non-fire sources and can be used as an alternative for improving false alarms in the future.

The small welfare states: rethinking welfare in the US, Japan, and South Korea

Yusun Cho 한국행정학회 2021 International Review of Public Administration Vol.26 No.3

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Korean EFL Learners’ Referential Ability and Their L2 Proficiency in Oral Narrative Discourse

Yusun Kang,Sookbin Han,Juyeon Kim 한국응용언어학회 2010 응용 언어학 Vol.26 No.2

Referencing plays an essential role in achieving discourse competence. Making appropriate referential choices in diverse contexts reflects language learners’ pragmatic competence that takes the listeners into account as well as linguistic competence which marks the connectivity and coherence among sentences. However, there is little research that looks at the Korean EFL students’ reference management. The present study aims to assess Korean EFL learners’ discourse competence by analyzing their reference management in oral narrative discourse production. In addition, the potential relationship between their overall English proficiency and reference management at discourse level was examined in order to investigate whether general language ability tested on KPSAT is related to discourse competence. Our findings indicate that Korean high school EFL learners generally lacked full control over making appropriate referential choices, especially with those that involve articles. Moreover, their English KPSAT scores did not necessarily correspond to their referential skills reflected in producing extended oral discourse in English.

A Study of Viewers' Responses to Luxury Haul Videos on YouTube

( Yusun Her ),( Jaehoon Chun ) 한국의류학회 2020 한국의류학회지 Vol.44 No.4

This study examined how viewers perceived luxury haul videos, what factors made them experience vicarious pleasure and gain relative deprivation when watching them. This study conducted an interview with 20 viewers of luxury haul videos. The content obtained from the interview was analyzed by classifying it into academic terms. Cases of vicarious pleasure arose when viewers had sufficient empathy when watching videos, which was intensified by YouTubers' behavior and visual stimulation in videos. A person's relative deprivation due to her financial capabilities or appearance occurred when she compared herself with YouTubers. The more viewers perceived luxury haul as a source of information, the more they felt relative deprivation; in addition, the more they perceived it as entertainment, the more they felt vicarious pleasure. Viewers who had a high level of involvement in luxury goods tended to feel vicarious pleasure; however, viewers with a high level of involvement in YouTubers tended to feel relative deprivation. This study helps luxury brands and YouTubers understand viewers' perception of their products and programs as well as helps in the development of fashion haul videos that are beneficial to viewers.

Relative Contribution of Reading Fluency and Vocabulary Knowledge in Predicting Korean EFL Learners’ Reading Comprehension

Yusun Kang 아시아영어교육학회 2020 The Journal of Asia TEFL Vol.17 No.3

Despite the growing body of research evidence validating the Simple View of Reading (SVR) which highlights decoding and listening comprehension abilities as the prominent contributors of reading comprehension, there have been concerns regarding the need to augment it to consider other relevant variables. For advanced readers whose decoding skills are fully developed, an alternate code-related skill such as reading fluency needs to be considered. This is especially pertinent for second language readers whose phonics skills tend to be superior to their language abilities. Another concern has not only been with the need to consider vocabulary knowledge as an independent predictor, but also with the need to discern the contribution of both quantity and quality of vocabulary knowledge. Although there have been numerous studies showing the significant relationship between reading comprehension and both vocabulary breadth and depth, these have been rarely looked at discretely in the SVR framework. This study investigated the relative contribution of vocabulary breadth, vocabulary depth, and reading fluency to secondary Korean EFL learners’ reading comprehension within an augmented SVR model. The findings indicated that although all of the considered predictors were significantly related to their reading comprehension, only listening comprehension and vocabulary depth demonstrated significant unique contribution.