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A Copula Based Unsupervised Domain Adaptation for Image Classification
Seungmin Lee(Seungmin Lee),Kyupil Yeon(Kyupil Yeon) 한국자료분석학회 2024 Journal of the Korean Data Analysis Society Vol.26 No.2
In this paper, we present an unsupervised domain adaptation algorithm for image classification using principal component analysis (PCA) and Gaussian copula function alignment. The motivation of the proposed algorithm stems from the idea of CORAL algorithm which extracts domain invariant features by aligning the correlation structure between a source and a target domain. However, it suffers from the fact that highly skewed marginal distributions happen to distort the correlation structure so that it may cause a negative transfer. Therefore we utilize a copula function that enables us to analyze separately the dependency structure and the marginals by Sklar’s theorem. In particular, we propose to align the Gaussian copula correlations in the copula feature spaces instead of aligning the correlation matrices in the original space. Considering the extremely skewed distribution of SURF image features in Office-Caltech10 data set we apply PCA first in order to extract some skewness-mitigated principal features and then derive copula features to align for domain adaptation by using CORAL idea with Gaussian copula correlation matrices. The proposed method showed a good classification accuracy when applied to image classification problem in an unsupervised domain adaptation setting.
Lee, Seungmin,Moon, Byung Joon,Lee, Hyun Jung,Bae, Sukang,Kim, Tae-Wook,Jung, Yong Chae,Park, Jong Hyeok,Lee, Sang Hyun American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.20
<P>In this study, we developed reduced graphene oxide (rGO)-incorporated porous agarose (Ar-rGO) composites that were prepared via a “one-pot” sol-gel method involving a mixing and vacuum freeze-drying process. These composites represent an easy-to-use adsorbent for organic contaminant removal. Ar-rGOs can efficiently adsorb organic molecules, especially aromatic organic compounds from wastewater, because of the synergistic effect between the agarose bundles, which function as a water absorption site, and the rGO sheets, which function as active sites for pollutant binding. The pore structures and morphology of the Ar-rGO composites varied according to the added rGO, resulting in effective water infiltration into the composites. The main adsorption mechanism of the aromatic organic compounds onto Ar-rGOs involved π-π interactions with the rGO sheets. The surface interaction was more effective for adsorbing/desorbing the aromatic pollutants than the electrostatic interaction via the O-containing functional groups. In addition, we confirmed that Ar-rGO is highly stable over the entire pH range (1-13) because of the presence of the rGO sheets.</P> [FIG OMISSION]</BR>
Lee, Seungmin,Lee, Jiyeon,Kim, Wonhee,Kim, Hyeong-Jin,Pak, Chanho,Lee, Jung Tae,Eom, KwangSup Elsevier 2018 Journal of Power Sources Vol.408 No.-
<P><B>Abstract</B></P> <P>A selenium/carbon (Se/C) composite has been suggested as an excellent substitute cathode material due to its high theoretical volumetric capacity. However, it exhibits severe capacity decay, which is caused by the dissolution of active materials as well as s<I>huttle effect</I>. One effective strategy to alleviate this dissolution is to confine the Se within porous carbon frameworks. Here, we report the effects of carbon structure and dopant on the electrochemical performances of Se infiltrated carbon composites with three types carbons; (i) nitrogen-doped ordered mesoporous carbon (NOMC), (ii) sulfur-doped ordered mesoporous carbon (SOMC), and (iii) macroporous spherical carbon, which have different porosities and dopants. The Se/C cathodes are prepared by meting selenium-sulfur compound and then evaporating sulfur from the compound, providing nanoscale space for efficient electrolyte access to the reaction site. Among the three composite cathodes, the Se/NOMC exhibits the highest rate-capability and cyclic stability due to an abundance of cylindrical mesopores (4–5 nm pore diameter) that can provide enough electrolyte diffusion path and effectively impede the dissolution of selenium. As a result, the Se/NOMC has a high volumetric capacity of 1605 mAh cm<SUP>−3</SUP> and excellent capacity retention of 100% during 500 cycles at 0.648 A h cm<SUP>−3</SUP> (C-rate of C/2.5).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three-types of selenium/carbon (Se/C) cathodes for LiSe battery are prepared. </LI> <LI> They have three carbon frameworks with different structure and dopant. </LI> <LI> The ordered mesoporous carbon (OMC) improves rate-capability of Se/C cathode. </LI> <LI> The Se/C cathode with N-doped OMC delivers the excellent cyclic stability. </LI> <LI> The lithiated Si/Gr– Se/NOMC full-cell demonstrates promising cyclic stability. </LI> </UL> </P>
Lee, Seungmin,Lee, Youngjun,Park, Sungwon,Kim, Yunju,Lee, Ju Dong,Seo, Yongwon American Chemical Society 2012 The Journal of physical chemistry B Vol.116 No.30
<P>The precise nature and unique pattern of the double tetra-<I>n</I>-butylammonium fluoride (TBAF) semiclathrates with a guest gas (CH<SUB>4</SUB> or CO<SUB>2</SUB>) was closely investigated through thermodynamic and spectroscopic analyses. The three-phase equilibria of semiclathrate (H), liquid water (L<SUB>W</SUB>), and vapor (V) for the ternary CH<SUB>4</SUB> + TBAF + water and CO<SUB>2</SUB> + TBAF + water mixtures with various TBAF concentrations were experimentally measured in order to determine the stability conditions of the double TBAF semiclathrates. The double CH<SUB>4</SUB> (or CO<SUB>2</SUB>) + TBAF semiclathrates showed remarkably enhanced thermal stability when compared with pure CH<SUB>4</SUB> (or CO<SUB>2</SUB>) hydrate. The highest stabilization effect was observed at the stoichiometric concentration of pure TBAF semiclathrate, which is 3.3 mol %. Gas uptake measurements were undertaken in order to estimate the amount of gas consumed during double semiclathrate formation. CH<SUB>4</SUB> was found to be a relatively more favorable guest for the 5<SUP>12</SUP> cages of the double TBAF semiclathrate than CO<SUB>2</SUB>. From the results of the NMR and Raman spectroscopic analyses it was identified that the guest gas molecules (CH<SUB>4</SUB> or CO<SUB>2</SUB>) were enclathrated in the 5<SUP>12</SUP> cages of the double TBAF semiclathrates. The overall results given in this study are useful for understanding the fundamental guest gas enclathration behavior in the double semiclathrates.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2012/jpcbfk.2012.116.issue-30/jp302647c/production/images/medium/jp-2012-02647c_0001.gif'></P>
Lee, Seungmin,Lee, Yohan,Lee, Jaehyoung,Lee, Huen,Seo, Yongwon American Chemical Society 2013 Environmental science & technology Vol.47 No.22
<P>The methane (CH<SUB>4</SUB>) – carbon dioxide (CO<SUB>2</SUB>) swapping phenomenon in naturally occurring gas hydrates is regarded as an attractive method of CO<SUB>2</SUB> sequestration and CH<SUB>4</SUB> recovery. In this study, a high pressure microdifferential scanning calorimeter (HP μ-DSC) was used to monitor and quantify the CH<SUB>4</SUB> – CO<SUB>2</SUB> replacement in the gas hydrate structure. The HP μ-DSC provided reliable measurements of the hydrate dissociation equilibrium and hydrate heat of dissociation for the pure and mixed gas hydrates. The hydrate dissociation equilibrium data obtained from the endothermic thermograms of the replaced gas hydrates indicate that at least 60% of CH<SUB>4</SUB> is recoverable after reaction with CO<SUB>2</SUB>, which is consistent with the result obtained via direct dissociation of the replaced gas hydrates. The heat of dissociation values of the CH<SUB>4</SUB> + CO<SUB>2</SUB> hydrates were between that of the pure CH<SUB>4</SUB> hydrate and that of the pure CO<SUB>2</SUB> hydrate, and the values increased as the CO<SUB>2</SUB> compositions in the hydrate phase increased. By monitoring the heat flows from the HP μ-DSC, it was found that the noticeable dissociation or formation of a gas hydrate was not detected during the CH<SUB>4</SUB> – CO<SUB>2</SUB> replacement process, which indicates that a substantial portion of CH<SUB>4</SUB> hydrate does not dissociate into liquid water or ice and then forms the CH<SUB>4</SUB> + CO<SUB>2</SUB> hydrate. This study provides the first experimental evidence using a DSC to reveal that the conversion of the CH<SUB>4</SUB> hydrate to the CH<SUB>4</SUB> + CO<SUB>2</SUB> hydrate occurs without significant hydrate dissociation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2013/esthag.2013.47.issue-22/es403542z/production/images/medium/es-2013-03542z_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es403542z'>ACS Electronic Supporting Info</A></P>