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Hwang, Sunwook,Kim, Dong-Hui,Shin, Jeong Hee,Jang, Jae Eun,Ahn, Kyoung Ho,Lee, Chulhaeng,Lee, Hochun American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.34
<P>Expanding the performance limit of current Li-ion batteries requires ion-ion and ion-solvent interaction, which governs the ion transport behavior of the electrolytes, to be fully understood as a matter of crucial importance. We herein examine the ionic speciation and conduction behavior of propylene carbonate (PC) electrolytes of 0.1-3.0 M LiPF<SUB>6</SUB> and LiBF<SUB>4</SUB> using Raman spectroscopy, dielectric relaxation spectroscopy (DRS), and pulsed-field gradient NMR (PFG-NMR) spectroscopy. In both LiPF<SUB>6</SUB>-PC and LiBF<SUB>4</SUB>-PC, free ions and a solvent-shared ion pair (SIP) are dominant species at dilute salt concentrations (<0.8 M), and SIP becomes dominant at intermediate concentrations (0.8-1.5 M). At higher concentrations (1.5-3.0 M), the solvent-shared dimer (SSD) and contact dimer (CD) are dominant in LiPF<SUB>6</SUB>-PC, whereas the contact ion pair (CIP), CD, and agglomerate (AGG) prevail in LiBF<SUB>4</SUB>-PC. Ionic conduction in 0.1-1.5 M LiPF<SUB>6</SUB>-PC and LiBF<SUB>4</SUB>-PC is governed by the migration of free ions and SIP. Notably, above 1.5 M of the two PC electrolytes, SSD participates in ionic conduction via the migration mode as well. Furthermore, it is suggested that the large number of CIPs present in LiBF<SUB>4</SUB>-PC may contribute to ionic conduction via a Grotthuss-type mechanism.</P> [FIG OMISSION]</BR>
ON UNIFORMLY ULTRASEPARATING FAMILY OF FUNCTION ALGEBRAS
Hwang, Sunwook Korean Mathematical Society 1993 대한수학회보 Vol.30 No.1
Let X be a compact Hausdorff space, and let C(X) (resp. $C_{R}$(X)) be the complex (resp. real) Banach algebra of all continuous complex-valued(resp. real-valued) functions on X with the pointwise operations and the supremum norm x. A Banach function algebra on X is a Banach algebra lying in C(X) which separates the points of X and contains the constants. A Banach function algebra on X equipped with the supremum norm is called a uniform algebra on X, that is, a uniformly closed subalgebra of C(X) which separates the points of X and contains the constants.s.
중학생의 학년별 및 성별에 따른 수학불안과 수학성취와의 관계
황선욱 ( Hwang Sunwook ),유경훈 ( Lew Kyounghoon ) 한국수학교육학회 2018 수학교육논문집 Vol.32 No.2
이 연구의 목적은 대학 진학 준비의 심리적 부담을 현실적으로 느끼기 시작하는 중학생을 대상으로 수학불안과 수학성취 정도가 학년 및 성별에 따라 어떻게 다른지 분석하고 수학불안과 수학성취 요인 간의 상관관계 및 수학불안 요인이 수학성취에 미치는 설명력을 알아보기 위한 것이다. 이를 위해 서울지역의 중학생 587명을 대상으로 수학불안검사와 수학 성적을 조사하였으며 수집된 자료는 spss 24.0 프로그램을 활용하여 t-검증, Pearson 상관계수, 회귀 분석(stepwise multiple regression) 등을 실시하였다. 연구 결과에 의하면 성별에 따른 수학 점수 및 수학 불안도에서 의미 있는 차이가 있는 것으로 나타났으며, 학년별로도 수학 점수 및 수학 불안도에 있어 의미 있는 차이가 있었다. 수학불안과 수학성취 간의 관계는 모두 높은 상관이 있었으며 학년별, 성별로도 상관이 있는 것을 알 수 있었다. 중학생들의 수학성취 정도를 가장 잘 설명해주는 요인으로는 흥미와 관심도, 수학교과요인, 교사요인 순으로 의미 있는 설명력을 나타냈다. 이러한 결과로부터 수학불안 요인 중에서 흥미도, 수학교과요인, 교사요인이 중학생들의 수학성취를 증진시키는 데 중요함을 알 수 있었다. The purpose of this paper is to investigate the differences of the mathematics anxiety and mathematical achievement of middle school students according to gender and grade, and to find out which mathematics anxiety causes have more influence on mathematical achievement and how much it is. For this purposes, the problem of this study as follows: firstly, are there any differences in the mathematics anxiety and mathematical achievement according to gender and grade? secondly, are there any relationship between mathematics anxiety and mathematical achievement according to gender and grade? lastly, are there any mathematics anxiety predict to mathematical achievement according to gender and grade? The subjects of this study consist of 171(1st graders), 144(2nd graders), 272(3rd graders) students selected for a class of unit, in middle schools located in Seoul, Korea. In this study, for children's mathematics anxiety, Huh(1996)'s Mathematics Anxiety Scale was used. The collected data were analyzed by using the 24.0 SPSS program. The data were also tested by using the t-test, correlation and multiple regression. The major results of this study were as follows: firstly, mathematics anxiety and mathematical achievement have significant differences depending on gender and grade, secondly, mathematics anxiety and mathematical achievement have significantly related each other depending on gender and grade, lastly, the multiple regression analyses demonstrated that sub factors of mathematics anxiety were the significant predictors of mathematical achievement according to gender and grade.
황선욱,윤현주,정진강,Hwang, Sunwook,Yoon, Hyun-Ju,Chong, Chin-Kang 한국수학사학회 2014 Journal for history of mathematics Vol.27 No.1
The book Su Hak Ip Mun(數學入門, Introduction to Mathematics) is one part of 5 sections of the book Seung Aeh Ill Chan(升厓日簒), which is a hand written manuscript in Chinese characters and the author and the date of writing is unknown. The book Seung Aeh Ill Chan begins with the song of division table so called Guguiga(九歸歌). We first investigate and compare the writing pattern of this with other old Korean mathematical books. Next, we investigate typical expression and calculation methods of mathematical contents and terminologies used in Su Hak Ip Mun and also figure out oddities of writing pattern of mathematical expression and cultural circumference of several problems dealt in the book. From these analysis and investigation, we estimate the writing date of Su Hak Ip Mun later than the year 1723 on which Su Ri Jeong On(數理精蘊) was first published. And we presumably guess that Guguiga and Su Hak Ip Mun are made not for practical use or theoretical purpose but for text to teach students.
Federated Learning 의 통신효율 향상을 위한 기술의 연구 동향
김영석(Youngseok Kim),황선욱(Sunwook Hwang),박세웅(Saewoong Bahk) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
본 논문은 FL(Federated Learing) 에서의 통신효율성을 향상시키기 위한 기술의 연구 동향을 파악하는 것을 목표로 한다. 먼저 기본적인 모델 양자화부터 업링크 MU-MIMO 를 활용한 OTA(over-the-air) 모델 병합기법을 살펴보고, 모델학습을 어렵게 만드는 non-i.i.d.(independent and identically distributed) 데이터 분포 하에서 성능을 높이기 위한 연구들을 소개하고자 한다.