Search results for: Jiwon Jeong

Items from 1 to 16 out of 16 results

article

Controlled Doping of Electrocatalysts through Engineering Impurities

Se‐Ho Kim, Su‐Hyun Yoo, Sangyong Shin, Ayman A. El‐Zoka, more

Advanced Materials > 34 > 28 > n/a - n/a

Fuel cells recombine water from H₂ and O₂ thereby can power, for example, cars or houses with no direct carbon emission. In anion‐exchange membrane fuel cells (AEMFCs), to reach high power densities, operating at high pH is an alternative to using large volumes of noble metals catalysts at the cathode, where the oxygen‐reduction reaction occurs. However, the sluggish kinetics of the hydrogen‐oxidation...

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In-situ TEM observation of {101¯2} twin-dominated deformation of Mg pillars: Twinning mechanism, size effects and rate dependency

Jiwon Jeong, Markus Alfreider, Ruth Konetschnik, Daniel Kiener, more

Acta Materialia > 2018 > 158 > C > 407-421

To investigate the mechanism of {101¯2} twinning in magnesium (Mg) single crystal and its influence on mechanical size effects and strain rate dependent deformation behavior, in-situ microcompression of Mg [21¯1¯0] pillars of various sizes from 0.5 μm to 4 μm was carried out in a scanning electron microscope (SEM) and also in a transmission electron microscope (TEM), covering strain rates from 10⁻⁴...

article

Anti-osteoarthritic effects of ChondroT in a rat model of collagenase-induced osteoarthritis

Jiwon Jeong, Kiljoon Bae, Sun-Gil Kim, Dongwook Kwak, more

BMC Complementary and Alternative Medicine > 2018 > 18 > 1 > 1-10

Background Previously, we reported that ChondorT showed significant anti-arthritis and anti-inflammatory effects. ChondroT, a new herbal medication, consists of the water extracts of Osterici Radix, Lonicerae Folium, Angelicae Gigantis Radix, Clematidis Radix, and Phellodendri Cortex (6:4:4:4:3). The objective of this study was to investigate the effects of ChondroT in collagenase-induced osteoarthritis...

article

Rheological Analysis of Live and Dead Microalgae Suspensions

Young Seok Song, Chul Kang, Jiwon Jeong, Kyu-Oh Kim, more

Journal of the Korean Physical Society > 2018 > 72 > 8 > 858-862

We investigate the rheological properties of microalgae suspensions that are currently being used in various applications. Two kinds of microalgae, chlorella and Synechococcus, were used for preparation of the suspensions, and their rheological characteristics were analyzed experimentally. In order to evaluate the viability of algae, we performed live and dead tests using trypan blue staining assays...

article

FIB-induced dislocations in Al submicron pillars: Annihilation by thermal annealing and effects on deformation behavior

Subin Lee, Jiwon Jeong, Youbin Kim, Seung Min Han, more

Acta Materialia > 2016 > 110 > C > 283-294

In-situ transmission electron microscopy (TEM) annealing of submicron Al pillars (∼300–450 nm in diameter) fabricated by focused ion beam (FIB) shows that the dislocation loops formed by the high energy Ga⁺ ion beam impact near the material surface can be removed by annealing at around half of the melting point (T_m). Quantitative analysis of real-time TEM data reveals that the dislocation loops first...

article

Microstructural evolution and strain-hardening behavior of multi-pass caliber-rolled Ti–13Nb–13Zr

Taekyung Lee, Kyung-Tae Park, Dong Jun Lee, Jiwon Jeong, more

Materials Science and Engineering: A > 2015 > 648 > C > 359-366

The multi-pass caliber-rolling (MPCR) process is a rod-manufacturing process that has recently proven capable of fabricating ultrafine-grained bulk rods with superior mechanical performance for biomedical uses. There have rarely been studies which focused on MPCR-processed nonferrous alloys in spite of the great potential of doing so. The present work elucidates the metallurgical phenomena which occur...

article

Microstructural evolution of a focused ion beam fabricated Mg nanopillar at high temperatures: Defect annihilation and sublimation

Jiwon Jeong, Subin Lee, Youbin Kim, Seung Min Han, more

Scripta Materialia > 2014 > 86 > Complete > 44-47

Microstructural evolution of focused ion beam machined Mg nanopillars was investigated by in situ heating experiments in a transmission electron microscope. The dislocation loops generated by a Ga ⁺ ion beam were annihilated at around half of the melting point of Mg. At a higher temperature (673K), the sublimation of Mg occurred due to the reduced stability of Mg under the vacuum environment...

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Critical evaluation and thermodynamic optimization of Mg–Ga system and effect of low pressure on phase equilibria

Youn-Bae Kang, Jiwon Jeong, Sang Ho Oh

Calphad > 2014 > 46 > C > 168-175

A complete literature review and critical evaluation of the Mg–Ga binary system are presented. All stable phases known in this system were thermodynamically modeled in the framework of CALPHAD. Liquid phase was modeled using the Modified Quasichemical Model in the pair approximation which takes into account short-range ordering. α-(Mg) solid solution of hcp structure was modeled as a substitutional...

article

Space-holder effect on designing pore structure and determining mechanical properties in porous titanium

Byounggab Lee, Taekyung Lee, Yongmoon Lee, Dong Jun Lee, more

Materials and Design > 2014 > 57 > Complete > 712-718

The present work studied the effect of space holders on pore structure and mechanical properties in porous titanium. Four types of space holders (sodium chloride, starch, and urea with different size and morphology) were utilized to fabricate porous titanium. The space holders played a key role in the pore structure as confirmed by microstructural observations and three-dimensional computed tomography...

article

Characterizations of furfuryl alcohol oligomer/polymerization catalyzed by homogeneous and heterogeneous acid catalysts

Taejin Kim, Jiwon Jeong, Mohammed Rahman, Elaine Zhu, more

Korean Journal of Chemical Engineering > 2014 > 31 > 12 > 2124-2129

The liquid-phase oligomer/polymerization of furfuryl alcohol (FA) catalyzed by homogeneous and heterogeneous acid catalysts was investigated by Infrared (IR) spectroscopy. At room temperature and 100 °C, FA was not decomposed with metal oxide catalysts except for tungsten oxide, whereas amberlyst and sulfuric acid converted a furfuryl alcohol monomer into oligomer/polymer even at a room temperature...

article

Unexpected angular or rotational deformity after corrective osteotomy

Seung Yeol Lee, Jiwon Jeong, Kyungho Lee, Chin Youb Chung, more

BMC Musculoskeletal Disorders > 2014 > 15 > 1 > 1-7

Background Codman’s paradox reveals a misunderstanding of geometry in orthopedic practice. Physicians often encounter situations that cannot be understood intuitively during orthopedic interventions such as corrective osteotomy. Occasionally, unexpected angular or rotational deformity occurs during surgery. This study aimed to draw the attention of orthopedic surgeons toward the concepts of...

article

Transmission electron microscopy and thermodynamic studies of CaO-added AZ31 Mg alloys

Jiwon Jeong, Jiseong Im, Kyung Song, Minhyeok Kwon, more

Acta Materialia > 2013 > 61 > 9 > 3267-3277

We investigated the microstructural evolution of Mg–3Al–1Zn (AZ31) alloy systems, with Ca or CaO added, by carrying out microstructural characterizations in conjunction with thermodynamic calculations. A calculated phase diagram of the Mg–Ca–O ternary system showed that CaO can be dissolved in liquid Mg so as to have 12.6wt.% Ca content in the liquid Mg at 700°C. Therefore, for a 0.3wt.% CaO-added...

article

Influence of trace element fluxes from submarine groundwater discharge (SGD) on their inventories in coastal waters off volcanic island, Jeju, Korea

Jiwon Jeong, Guebuem Kim, Seunghee Han

Applied Geochemistry > 2012 > 27 > 1 > 37-43

The concentrations of trace elements in groundwater and seawater were measured in a coastal embayment (Bangdu Bay) of a volcanic island (Jeju) off the southernmost coast of Korea in August and December of 2009. The concentrations of trace elements (Al, Mn, Fe, Co, Ni, and Cu) in the groundwater in summer were approximately 20-fold higher than those in winter, with good correlation to each other. Overall,...

article

Physiology of fresh-cut ‘Galia’ (Cucumis melo var. reticulatus) from ripe fruit treated with 1-methylcyclopropene

Muharrem Ergun, Jiwon Jeong, Donald J. Huber, Daniel J. Cantliffe

Postharvest Biology and Technology > 2007 > 44 > 3 > 286-292

‘Galia’ (Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit were harvested at the three-quarter slip stage and treated with 1μLL ⁻¹ 1-methylcyclopropene (1-MCP) at 20°C for 24h. The fruit were processed and stored as fresh-cut cubes and intact fruit for 10d at 5°C. Ethylene production of fresh-cut cubes was approximately 4–5-fold higher than intact fruit at day 1. Afterward, the ethylene...

article

Delay of avocado (Persea americana) fruit ripening by 1-methylcyclopropene and wax treatments

Jiwon Jeong, Donald J. Huber, Steven A. Sargent

Postharvest Biology and Technology > 2003 > 28 > 2 > 247 - 257

1-Methylcyclopropene (1-MCP), an inhibitor of ethylene action, has been shown to extend the postharvest storage period of avocado fruit. Waxing is also known to extend the storage life of avocado by reducing water loss and modifying the fruit internal atmosphere. In this study, 1-MCP and waxing were used to investigate their combined effects on ripening characteristics of avocado fruit. Preclimacteric...

article

Influence of 1-methylcyclopropene (1-MCP) on ripening and cell-wall matrix polysaccharides of avocado (Persea americana) fruit

Jiwon Jeong, Donald J. Huber, Steven A. Sargent

Postharvest Biology and Technology > 2002 > 25 > 3 > 241 - 256

West Indian-type avocado (Persea americana Mill. cv. 'Simmonds') fruit were treated with two different concentrations (0.09 and 0.45 μll ^- ¹ ) of 1-methylcyclopropene (1-MCP) for three exposure times (6, 12, and 24 h) at 20 ^o C. The fruit were then stored at 20 ^o C in ethylene-free air for ripening assessment. Firmness, weight loss, respiration and C ₂ H ₄ ...

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