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result(s) for
"Seo, Dong-Hyun"
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Melt-quenched carboxylate metal–organic framework glasses
2024
Although carboxylate-based frameworks are commonly used architectures in metal-organic frameworks (MOFs), liquid/glass MOFs have thus far mainly been obtained from azole- or weakly coordinating ligand-based frameworks. This is because strong coordination bonds of carboxylate ligands to metals block the thermal vitrification pathways of carboxylate-based MOFs. In this study, we present the example of carboxylate-based melt-quenched MOF glasses comprising Mg
2+
or Mn
2+
with an aliphatic carboxylate ligand, adipate. These MOFs have a low melting temperature (
T
m
) of 284 °C and 238 °C, respectively, compared to zeolitic-imidazolate framework (ZIF) glasses, and superior mechanical properties in terms of hardness and elastic modulus. The low
T
m
may be attributed to the flexibility and low symmetry of the aliphatic carboxylate ligand, which raises the entropy of fusion (Δ
S
fus
), and the lack of crystal field stabilization energy on metal ions, reducing enthalpy of fusion (Δ
H
fus
). This research will serve as a cornerstone for the integration of numerous carboxylate-based MOFs into MOF glasses.
Many MOFs feature carboxylate ligands with strong coordination bonds, hindering thermal melting. Here, authors present a meltable carboxylate MOF designed with a thermodynamically favored component.
Journal Article
Detailed Building Energy Impact Analysis of XPS Insulation Degradation Using Existing Long-Term Experimental Data
by
Seo, Dong-Hyun
,
Kim, Seok-Ho
,
Jeong, Ju-Yeon
in
Aging
,
Analysis
,
Architecture and energy conservation
2025
This study investigates the long-term impact of insulation degradation on building heating energy consumption, with a focus on extruded polystyrene (XPS) insulation. Year-by-year degradation in thermal transmittance was derived from long-term experimental data and applied to prototypical energy models of multifamily apartment buildings and office buildings. Simulations were performed using both Actual Meteorological Year (AMY) and Typical Meteorological Year (TMY) data for six cities representing Korea’s major climate zones. The results showed that insulation degradation led to a significant increase in heating energy consumption from 23.2% to 34.9% in AMY simulations and 23.5% to 36.2% in TMY simulations for multifamily apartment buildings over 15 years. The difference between the AMY and TMY estimates was within 4%, demonstrating the reliability of TMY for long-term performance assessments. Notably, the southern and Jeju zones exhibited higher sensitivity to degradation due to their relaxed insulation standards and lower initial thermal performance. Office buildings were less affected, with increases below 8%, attributed to smaller envelope areas and higher internal heat gains. These findings highlight the need for zone-specific insulation standards and differentiated energy-saving design strategies by building type to ensure long-term energy efficiency.
Journal Article
Manufacturing of stretchable substrate with biaxial strain control for highly-efficient stretchable solar cells and displays
2023
There has been significant research focused on the development of stretchable materials that can provide a large area with minimal material usage for use in solar cells and displays. However, most materials exhibit perpendicular shrinkage when stretched, which is particularly problematic for polymer-based substrates commonly used in stretchable devices. To address this issue, biaxial strain-controlled substrates have been proposed as a solution to increase device efficiency and conserve material resources. In this study, we present the design and fabrication of a biaxial strain-controlled substrate with a re-entrant honeycomb structure and a negative Poisson’s ratio. Using a precisely machined mold with a shape error of less than 0.15%, we successfully fabricated polydimethylsiloxane substrates with a 500 μm thick re-entrant honeycomb structure, resulting in a 19.1% reduction in perpendicular shrinkage. This improvement translates to a potential increase in device efficiency by 9.44% and an 8.60% reduction in material usage for substrate fabrication. We demonstrate that this design and manufacturing method can be applied to the fabrication of efficient stretchable devices, such as solar cells and displays.
Journal Article
Single-Frame-Based Data Compression for CAN Security
2024
To authenticate a controller area network (CAN) data frame, a message authentication code (MAC) must be sent along with the CAN frame, but there is no space reserved for the MAC in the CAN frame. Recently, difference-based compression (DBC) algorithms have been used to create a space inside the frame. DBC has the advantage of being very efficient, but its drawback is that, if an error occurs in one frame, the effects of that error propagate to subsequent frames. In this paper, a CAN data compression algorithm is proposed that compresses the current frame without relying on previous frames. Therefore, an error generated in one frame cannot be propagated to subsequent frames. In addition, a CAN signal grouping technique is proposed based on entropy analysis. To efficiently authenticate CAN frames, the length of the compressed data must be 4 bytes or less (4BL). Simulation shows that the 4BL-compression ratio of a Kia Sorento vehicle is 99.36% in the DBC method, but 100% in the proposed method. In an LS Mtron tractor, the 4BL-compression ratio is 98.58% in the DBC method, but 100% in the proposed method. In addition, the execution time of the proposed compression algorithm is only 27.39% of that of the DBC algorithm. The results show that the proposed algorithm has better compression characteristics for CAN security than the DBC algorithms.
Journal Article
MAC-Based Compression Ratio Improvement for CAN Security
2023
Information security in a controller area network (CAN) is becoming more important as the connections between a vehicle’s internal and external networks increase. Encryption and authentication techniques can be applied to CAN data frames to enhance security. To authenticate a data frame, a message authentication code (MAC) needs to be transmitted with the CAN data frame. Therefore, space for transmitting the MAC is required within the CAN frame. Recently, the Triple ID algorithm has been proposed to create additional space in the data field of the CAN frame. The Triple ID algorithm ensures every CAN frame is authenticated by at least 4 bytes of MAC without changing the original CAN protocol. However, since the Triple ID algorithm uses six header bits, there is a problem associated with low data compression efficiency. In this paper, we propose an algorithm that can remove up to 15 bits from frames compressed with the Triple ID algorithm. Through simulation using CAN signals of a Kia Sorento vehicle and an LS Mtron tractor, we show that the generation of frames containing compressed messages of 4 bytes or more is reduced by up to 99.57% compared to the Triple ID method.
Journal Article
Apomorphine is a novel necroptosis inhibitor targeting mixed lineage kinase domain-like protein oligomerization
2025
Necroptosis, a form of programmed cell death, has emerged as a promising therapeutic target. Although several RIPK1 inhibitors have demonstrated favorable safety profiles in clinical trials, clinical translation of necroptosis-targeted therapies remains limited by modest efficacy, limited specificity, and species-specific activity of compounds such as necrosulfonamide (NSA). To resolve these challenges, this study identified a potential necroptosis inhibitor from a clinical drug library. Apomorphine (APO), a non-addictive morphine derivative used to treat Parkinson’s disease, was found to inhibit necroptosis by sterically blocking key residues involved in mixed lineage kinase domain-like protein (MLKL) activation and oligomerization, as confirmed by nuclear magnetic resonance analysis. APO is redox sensitive and prone to auto-oxidation. The oxidized form of APO (Ox-APO) showed stronger binding to MLKL than the reduced form of APO (Re-APO), as demonstrated by surface plasmon resonance analysis. Ox-APO significantly ameliorated tissue damage in two murine necroptosis models: dextran sulfate sodium (DSS)-induced colitis and acetaminophen (APAP)-induced liver injury. Collectively, these data highlight the therapeutic potential of APO as a necroptosis-specific inhibitor in necroptosis-related diseases in both humans and mice.
Journal Article
Preparation and in vivo evaluation of an orally available enteric-microencapsulated parathyroid hormone (1-34)-deoxycholic acid nanocomplex
by
Seo, Dong-Hyun
,
Hwang, Seung Rim
,
Park, Jin Woo
in
Administration, Oral
,
Amino acids
,
Analysis
2016
The N-terminal 34-amino-acid peptide fragment of human parathyroid hormone PTH (1-34), is used clinically to treat osteoporosis; however, it is currently administered by a once-daily subcutaneous injection, resulting in poor patient compliance. We have developed enteric microcapsules containing an ionic nanocomplex between PTH (1-34) and lysine-linked deoxycholic acid (LysDOCA) for the oral delivery of PTH (1-34). We measured the particle size of the PTH/LysDOCA complex and assessed its biological activity by determining the cAMP content in MC3T3-E1 cells. We also assessed its permeability across a Caco-2 cell monolayer and the bioavailability of the intrajejunally administered PTH/LysDOCA complex compared with PTH (1-34) in rats. In addition, the antiosteoporotic activity of the PTH/LysDOCA complex, encapsulated in an enteric carrier by coaxial ultrasonic atomization, was evaluated after it was orally administered to ovariectomized (OVX) rats. The formation of an ionic complex between PTH (1-34) and LysDOCA produced nanoparticles of diameter 33.0±3.36 nm, and the bioactivity of the complex was comparable with that of PTH (1-34). The Caco-2 cell permeability and AUClast value of the PTH/LysDOCA (1:10) nanocomplex increased by 2.87- and 16.3-fold, respectively, compared with PTH (1-34) alone. Furthermore, the OVX rats treated with oral PTH/LysDOCA-loaded enteric microcapsules showed an increase in bone mineral density (159%), bone volume fraction (175%), and trabecular number (174%) compared with those in the OVX control group. Therefore, the PTH/LysDOCA nanocomplex oral delivery system is a promising treatment modality for osteoporosis because it improves osteogenesis and trabecular connectivity.
Journal Article
Characteristics of metal contact to GaS films and photodetector applications
by
Bae, Hagyoul
,
Park, Joo Hyung
,
Kim, Ju Won
in
Atomic layer epitaxy
,
Electrical measurement
,
Electrodes
2024
Group-III monochalcogenides, particularly gallium sulfide (GaS), have garnered attention for visible–UV range optoelectronic applications owing to their wide bandgap, which can reach approximately 3 eV. The interplay between group-III monochalcogenides and metal electrodes needs to be understood to optimize the device performance. In this study, we explored the Schottky barrier height between GaS deposited through atomic layer deposition and commonly employed Ti/Au electrodes through low-temperature current–voltage measurements. The GaS photodetector exhibited p-type transport characteristics with a mobility of 7.71 × 10
–1
cm
2
V
−1
s
−1
and a photoresponsivity of 547 A W
−1
.
Journal Article
Sirtuin 3 (SIRT3) maintains bone homeostasis by regulating AMPK-PGC-1β axis in mice
2016
The mitochondrial sirtuin 3 (SIRT3) is involved in suppressing the onset of multiple pathologies, including cardiovascular disease, fatty liver, age-related hearing loss, and breast cancer. But a physiological role of SIRT3 in bone metabolism is not known. Here we show that SIRT3 is a key regulatory molecule to maintain bone homeostasis. Mice deficient in SIRT3 exhibited severe osteopenia owing to increased numbers of osteoclasts. Osteoclast precursors from
Sirt3
−/− mice underwent increased osteoclastogenesis in response to receptor activator of nuclear factor-κB ligand (RANKL), an essential cytokine for osteoclast differentiation. SIRT3 expression from RANKL induction depended on the transcription coactivator PGC-1β (peroxisome proliferator-activated receptor-γ co-activator-1β) and the nuclear receptor ERRα (estrogen receptor-related receptor α), and that SIRT3 inhibited the differentiation by interfering with the RANKL-induced expression of PGC-1β. Thus an auto-regulatory feedback mechanism operates to induce its own inhibitor SIRT3 by PGC-1β. Moreover,
Sirt3
−/− osteoclast precursors reduced AMP-activated protein kinase (AMPK) phosphorylation through down-regulating the expression of AMPK. Our results suggest that a mitochondrial SIRT3 is an intrinsic inhibitor for RANKL-mediated osteoclastogenesis.
Journal Article
Fabrication and characterization of controllable micro wavy pattern on cylindrical surface using ultra-precision diamond turning system
by
Seo, Dong-Hyun
,
Gwak, Eun-Ji
,
Choi, Doo-Sun
in
Controllability
,
Cutting tool paths
,
Cutting tools
2024
The study investigated the fabrication and characterization of a controllable wavy patterned mold using an ultra-precision diamond machining system. The design method of cutting tool path for controllable wavy pattern on a cylindrical surface, considering the tool radius, was discussed. The target was designed as periodic sine wave and random amplitude wave to develop components for next-generation displays. The effectiveness of the designed tool path was confirmed by comparing the machined surface profiles. The compensated tool path was able to reduce the machined shape error by approximately 50%. The optical characteristics of the machined pattern were analyzed by the luminance distribution of the transmitted laser through the replicated optical film for each machined tool path. When the compensated tool path was applied, a symmetrical distribution line with two spots of higher luminance concentration was observed. Finally, an investigation was conducted on the machinability of controllable randomness for next-generation display components, and their optical characteristics were evaluated.
Journal Article