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Eunsong Kim,Minseon Kim,Juo Kim,Joonchul Kim,Jung-Hwan Park,Kyoung-Tak Kim,Joung-Hu Park,Taesic Kim,Kyoungmin Min 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.7
Lithium-ion batteries are widely used in electric vehicles, electronic devices, and energy storage systems owing to their high energy density, long life, and outstanding performance. However, various internal and external factors affect the battery performance, leading to deterioration and ageing. Accurately estimating the state of health (SOH), state of charge (SOC), and remaining useful life (RUL) of batteries is challenging owing to complex operating characteristics and changing internal physical parameters. With the increasing availability of shared battery data and improved computer performance, the use of data-driven methods for battery health estimations and RUL predictions has gained popularity. We provide a comprehensive review of several studies in which data-driven methods were used for SOC and SOH estimation and RUL prediction. Specifically, we focus on the importance of open battery-cycling databases, various prediction methods used, and results obtained using each of these methods. Moreover, we aim to facilitate further research by providing a comprehensive description of the current state-of-the-art methods employed in battery health estimation and RUL prediction using open databases and machine-learning algorithms. Thus, we hope that this review will help researchers to develop accurate and reliable predictive models for battery health assessment in the future.
열교환기 휜에서의 서리층 두께와 서리층 표면온도의 실험 상관식
김경민(Kyoungmin Kim),김정수(Jung-Soo Kim),김장현(Janghyun Kim),이관수(Kwan-Soo Lee) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
In this study, dimensionless correlations of frost properties (i.e. the thickness and surface temperature of frost) on heat exchanger fin with nonuniform temperature distribution are proposed from frosting experiments. We analyzed the local fin temperature distribution, frost thickness and frost surface temperature on a 2D fin; in the airflow direction and the direction perpendicular to airflow. As a result, the frost growth on the fin had a close relation with fin heat conduction. The dimensionless correlations for the average frost properties were expressed as a function of dimensionless temperature, humidity ratio, Reynolds number, and Fourier number. These correlations agreed well with experimental data with the error less than 14%.
The number of representations of squares by integral ternary quadratic forms (II)
Kim, Kyoungmin,Oh, Byeong-Kweon Elsevier 2017 Journal of number theory Vol.173 No.-
<P><B>Abstract</B></P> <P>Let <I>f</I> be a positive definite ternary quadratic form. We assume that <I>f</I> is non-classic integral, that is, the norm ideal of <I>f</I> is Z . We say <I>f</I> is <I>strongly s-regular</I> if the number of representations of squares of integers by <I>f</I> satisfies the condition in Cooper and Lam's conjecture in . In this article, we prove that there are only finitely many strongly <I>s</I>-regular ternary forms up to isometry if the minimum of the nonzero squares that are represented by the form is fixed. In particular, we show that there are exactly 207 non-classic integral strongly <I>s</I>-regular ternary forms that represent one (see Tables 1 and 2). This result might be considered as a complete answer to a natural extension of Cooper and Lam's conjecture.</P>
Action Recognition Model to Monitor Illegal Dumping using Zoom-In Image Sequence Data
Kyoungmin Ko,Hyunmin Gwak,Eunseok Lee,Gunhwi Kim,Donghyeon Moon,Youngjoo Cho,SungHwan Kim 계명대학교 자연과학연구소 2021 Quantitative Bio-Science Vol.40 No.2
In this study, we propose an action recognition model that provides generalized performance regardless of camera location and distance between the camera and human. The proposed model consists of two-stage networks, namely, human detection and action recognition. The proposed method operates on video frames that are resized by a new zoom-in method using pretrained Yolo v3. To use temporal information, which is regarded as a critical factor in action recognition, we adopt the R(2+1)D model, which is a factorized model capable of representing more complex networks. The proposed Zoom-In method yields generalized performance regardless of distance. In an experiment, the proposed method exhibited accuracies of 96.07%, 96.61%, and 94.55% in the short, medium, and long ranges in which our datasets were employed, respectively.
Kyoungmin Kim,Jung-Hoon Kim,Yongsub Yoon,신동욱 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.1
Li0.33La0.55TiO3 solid electrolytes with a pure phase were synthesized by the citric acid-supported sol-gelmethod and then sintered under controlled redox atmospheres of air, argon and hydrogen. Although ofsimilar morphology and relative density, Li0.33La0.55TiO3 samples sintered under reduction atmosphere suchas argon and hydrogen exhibited a tetragonal structure with lattice distortion. The distortion and volumeexpansion of the crystal lattice was identified as originating from the transformation of the Ti valence state,and this was more clearly observed under sintering of the hydrogen atmosphere. The qualitative analysisof the Ti valence state using an X-ray Photoelectron Spectroscopy experiment was performed and indi-cated that the largest amount of Ti3+(18.6%) was formed in the Li0.33La0.55TiO3 samples sintered underhydrogen atmosphere. The relationship between the lattice distortion and the lithium ion conductivity of theLi0.33La0.55TiO3 sintered under different atmospheres is also discussed on the basis of the lattice distortion.
The number of representations of squares by integral ternary quadratic forms
Kim, Kyoungmin,Oh, Byeong-Kweon Elsevier 2017 Journal of number theory Vol.180 No.-
<P><B>Abstract</B></P> <P>Let <I>f</I> be a positive definite integral ternary quadratic form and let r ( k , f ) be the number of representations of an integer <I>k</I> by <I>f</I>. In this article we study the number of representations of squares by <I>f</I>. We say the genus of <I>f</I>, denoted by gen ( f ) , is indistinguishable by squares if for every integer <I>n</I>, r ( <SUP> n 2 </SUP> , f ) = r ( <SUP> n 2 </SUP> , <SUP> f ′ </SUP> ) for every quadratic form <SUP> f ′ </SUP> ∈ gen ( f ) . We find some non-trivial genera of ternary quadratic forms which are indistinguishable by squares. We also give some relation between indistinguishable genera by squares and the conjecture given by Cooper and Lam, and we resolve their conjecture completely.</P>