Hierarchical Bayesian Approach to a Multi-Site Hidden Markov Model

Kim, Dal Ho,Goh, Gyuhyeong,Kim, Yongku Taylor Francis 2014 Communications in statistics Simulation and comput Vol.43 No.6

Nonparametric Bayesian analysis for multi-site hidden Markov model

Kim, Dal Ho,Jo, Aejung,Kim, Yongku Taylor Francis 2017 Communications in statistics. Simulation and compu Vol.46 No.6

<i>In-situ</i> preparation and unique electrochemical behavior of pore-embedding CoO/Co₃O₄ intermixed composite for Li⁺ rechargeable battery electrodes

Kim, Jin Kyu,Ju, Ji Young,Choi, Seul Ki,Unithrattil, Sanjith,Lee, Sun Sook,Kang, Yongku,Kim, Yongseon,Im, Won Bin,Choi, Sungho Elsevier 2018 Journal of Power Sources Vol.378 No.-

<P><B>Abstract</B></P> <P>Electrochemically active CoO/Co<SUB>3</SUB>O<SUB>4</SUB> co-existing microspheres with morphology-inherited porous particles is successfully synthesized via a simple solvothermal method. The as-prepared intermixed composite undergoes a monoxide CoO-preferred conversion reaction with an extremely enhanced capacity retention, ∼905 mA h g<SUP>−1</SUP> after 250 cycles for discharge state, which is 1.6 times higher than the conventional CoO<SUB>x</SUB>-based anodes. Moreover, stable catalytic behavior of the electrocatalysts in Li-air cathodes of the given composites is also demonstrated. We believe that the extraordinarily enhanced electrode performance might be due to the novel pore-tempered microspheres packed with double electrochemically active centers of the CoO/Co<SUB>3</SUB>O<SUB>4</SUB> composite effectively confine the detrimental volume exchange during the reversible cyclic reactions as well as the preserved multiple reactive sites for a reversible Li<SUP>+</SUP> ⇄ LiO<SUB>x</SUB> reaction, which is advantageous for advanced Li rechargeable battery.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>In-situ</I> growth of electrochemically active CoO/Co<SUB>3</SUB>O<SUB>4</SUB>composite for Li<SUP>+</SUP>ion. </LI> <LI> Unique electrochemical behavior of pore-embedding CoO/Co<SUB>3</SUB>O<SUB>4</SUB>spherical particles. </LI> <LI> Propose conceptual design of metal oxide composites for the novel electrodematerial. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Bootstrap methods for long-memory processes: a review

Kim, Young Min,Kim, Yongku The Korean Statistical Society 2017 Communications for statistical applications and me Vol.24 No.1

This manuscript summarized advances in bootstrap methods for long-range dependent time series data. The stationary linear long-memory process is briefly described, which is a target process for bootstrap methodologies on time-domain and frequency-domain in this review. We illustrate time-domain bootstrap under long-range dependence, moving or non-overlapping block bootstraps, and the autoregressive-sieve bootstrap. In particular, block bootstrap methodologies need an adjustment factor for the distribution estimation of the sample mean in contrast to applications to weak dependent time processes. However, the autoregressive-sieve bootstrap does not need any other modification for application to long-memory. The frequency domain bootstrap for Whittle estimation is provided using parametric spectral density estimates because there is no current nonparametric spectral density estimation method using a kernel function for the linear long-range dependent time process.

Graphene paper with controlled pore structure for high-performance cathodes in Li–O₂ batteries

Kim, Do Youb,Kim, Mokwon,Kim, Dong Wook,Suk, Jungdon,Park, Jung Jin,Park, O Ok,Kang, Yongku Elsevier 2016 Carbon Vol.100 No.-

<P>In non-aqueous Li-O-2 batteries, relatively large amounts of discharge products are formed on air cathodes. As such, the expansion of air cathodes is a critical issue that remains to be solved. Here, we report the fabrication of highly porous free-standing graphene paper by introducing macropores within the paper using polystyrene colloidal particles as a sacrificial template. The as-prepared macroporous graphene paper (mp-GP) have a large BrunauereEmmetteTeller (BET) surface area (ca. 373 m(2) g(-1)), a large pore volume (ca. 10.9 cm(3) g(-1)), and a high porosity (91.6%). Owing to the high surface area and large pore volume, the mp-GPs exhibit a high specific capacity of ca. 12,200 mAh g(-1) at a current density of 200 mA g(-1), as well as good rate capability, when used as an air cathode in a non-aqueous Li-O-2 battery. Moreover, the mp-GP shows good stability up to 100 and 78 cycles at a current density of 500 mA g(-1) and 2000 mA g(-1) respectively, with a limiting capacity of 1000 mAh g(-1). It is found that formation and decomposition of the discharge product, Li2O2, occur within the macropores, and thus, the mp-GP maintains its original structure without considerable expansion during cycling. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Noninformative priors for the between-group variance in the unbalanced one-way random effects model with heterogeneous error variances

Kim, Dal Ho,Lee, Woo Dong,Kang, Sang Gil,Kim, Yongku Informa UK (Taylor Francis) 2019 JOURNAL OF STATISTICAL COMPUTATION AND SIMULATION Vol.89 No.10

Neuroprotection in Schizophrenia and Its Therapeutic Implications

YongKu Kim,KyoungSae Na 대한신경정신의학회 2017 PSYCHIATRY INVESTIGATION Vol.14 No.4

Schizophrenia is a chronic and debilitating mental disorder. The persisting negative and cognitive symptoms that are unresponsive to pharmacotherapy reveal the impairment of neuroprotective aspects of schizophrenia. In this review, of the several neuroprotective factors, we mainly focused on neuroinflammation, neurogenesis, and oxidative stress. We conducted a narrative and selective review. Neuroinflammation is mainly mediated by pro-inflammatory cytokines and microglia. Unlike peripheral inflammatory responses, neuroinflammation has a role in various neuronal activities such as neurotransmission neurogenesis. The cross-talk between neuroinflammation and neurogenesis usually has beneficial effects in the CNS under physiological conditions. However, uncontrolled and chronic neuroinflammation exert detrimental effects such as neuronal loss, inhibited neurogenesis, and excessive oxidative stress. Neurogenesis is also a major component of neuroprotection. Adult neurogenesis mainly occurs in the hippocampal region, which has an important role in memory formation and processing. Impaired neurogenesis and an ineffective response to antipsychotics may be thought to indicate a deteriorating course of schizophrenia. Oxidative stress and excessive dopaminergic neurotransmission may create a vicious cycle and consequently disturb NMDA receptor-mediated glutamatergic neurotransmission. Based on the current evidences, several neuroprotective therapeutic approaches have been reported to be efficacious for improving psychopathology, but further longitudinal and large-sample based studies are needed.

Improved electrochemical performance of ordered mesoporous carbon by incorporating macropores for Li‒O₂ battery cathode

Kim, Do Youb,Jin, Xing,Lee, Chang Hyun,Kim, Dong Wook,Suk, Jungdon,Shon, Jeong Kuk,Kim, Ji Man,Kang, Yongku Elsevier 2018 Carbon Vol.133 No.-

<P><B>Abstract</B></P> <P>Optimized porous structure is a prerequisite for high performance Li‒O<SUB>2</SUB> battery cathode. Macroporous-mesoporous carbon (MMC) is fabricated <I>via</I> a nano-replication method using mesoporous SiO<SUB>2</SUB> (KIT-6) containing NiO as the template. By varying the amount of NiO in the KIT-6/NiO composite template, the amount of macropores inside MMC is easily controlled. The as-prepared MMC exhibits a highly porous structure with abundant ordered mesopores along with macropores that are larger than 200 nm in size. When the MMC is applied as the cathode material in a Li‒O<SUB>2</SUB> battery, the cell exhibits greatly improved electrochemical performance in comparison to a cell using conventional ordered mesoporous carbon (OMC) without macropores. Systematic studies indicate that while mesopores in the OMC are clogged with Li<SUB>2</SUB>O<SUB>2</SUB> formed during the early stage of discharge, the MMC sufficiently accommodates a large amount of Li<SUB>2</SUB>O<SUB>2</SUB> in the pores. In addition, Li<SUB>2</SUB>O<SUB>2</SUB> with poor crystallinity forms on the cathode containing MMC during subsequent discharge processes, which can be due to the accumulated side product and the limited size of pores. The formation of amorphous Li<SUB>2</SUB>O<SUB>2</SUB> and the expedited mass transport through the interconnected meso- and macropores of MMC can attribute to the improved electrochemical performance of the MMC cathode material.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Two-Dimensional Phosphorene-Derived Protective Layers on a Lithium Metal Anode for Lithium-Oxygen Batteries

Kim, Youngjin,Koo, Dongho,Ha, Seongmin,Jung, Sung Chul,Yim, Taeeun,Kim, Hanseul,Oh, Seung Kyo,Kim, Dong-Min,Choi, Aram,Kang, Yongku,Ryu, Kyoung Han,Jang, Minchul,Han, Young-Kyu,Oh, Seung M.,Lee, Kyu T American Chemical Society 2018 ACS NANO Vol.12 No.5

<P>Lithium-oxygen (Li-O<SUB>2</SUB>) batteries are desirable for electric vehicles because of their high energy density. Li dendrite growth and severe electrolyte decomposition on Li metal are, however, challenging issues for the practical application of these batteries. In this connection, an electrochemically active two-dimensional phosphorene-derived lithium phosphide is introduced as a Li metal protective layer, where the nanosized protective layer on Li metal suppresses electrolyte decomposition and Li dendrite growth. This suppression is attributed to thermodynamic properties of the electrochemically active lithium phosphide protective layer. The electrolyte decomposition is suppressed on the protective layer because the redox potential of lithium phosphide layer is higher than that of electrolyte decomposition. Li plating is thermodynamically unfavorable on lithium phosphide layers, which hinders Li dendrite growth during cycling. As a result, the nanosized lithium phosphide protective layer improves the cycle performance of Li symmetric cells and Li-O<SUB>2</SUB> batteries with various electrolytes including lithium bis(trifluoromethanesulfonyl)imide in <I>N,N</I>-dimethylacetamide. A variety of <I>ex situ</I> analyses and theoretical calculations support these behaviors of the phosphorene-derived lithium phosphide protective layer.</P> [FIG OMISSION]</BR>

Exploration of Biological Markers of Suicidal Behavior in Major Depressive Disorder

YongKu Kim,SungDoo Won,JiWon Hur,BunHee Lee,HwaYoung Lee,SeHoon Shim,SangWoo Han,SoHyun Choi 대한신경정신의학회 2007 PSYCHIATRY INVESTIGATION Vol.4 No.1

Objective-Most suicides occur in the context of depressive disorders. In this study, new candidate biological markers for suicide were explored. Methods-The suicidal subjects consisted of 48 depressed patients (18 males and 30 females) admitted to emergency rooms following suicide attempts. The levels of nitric oxide, brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), beta-nerve growth factor (β-NGF), and transforming growth factor-beta 1 (TGF-β1) were measured in the plasma of these 48 patients and 50 normal controls. The levels of tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), interleukin-2 (IL-2), interleukin-4 (IL-4), and interleukin-6 (IL-6) were measured in the culture supernatant after mitogen stimulation of whole blood from both groups. The lethality of the suicide attempt was measured using the Lethality Suicide Attempt Rating Scale (LSARS), and the Risk-Rescue Rating (RRR). Results-The suicidal depressed patients had significantly higher IL-6, TGF-β1, and nitric oxide (NO) levels compared with the normal controls after controlling for body mass. On the other hand, the BDNF, IL-2, IL-4 and IFN-γ levels were lower in the suicidal depressed patients than in the normal controls. The NO levels in the suicidal depressed patients were negatively significantly correlated with the LSARS and RRR scores. The IFN-γ levels in the suicidal depressed patients were positively correlated with the LSARS scores, but their TGF-β1 levels were negatively correlated with the LSARS scores. When the suicidal behaviors were divided into violent or nonviolent, the IL-6 and IFN-γ levels of the violent suicidal patients were significantly higher than those of the nonviolent suicidal patients. Conclusions-These results suggest that BDNF, NO, and cytokines could be useful as biological markers of suicidal behavior in major depression.