483 results on '"Ji‐Yong Park"'
Search Results
2. Experimental Study on Performance of a Wave Energy Converter Rotor with a Moving Platform
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Yoon-Jin Ha, Chang-Hyuck Lim, Seung-Ho Shin, and Ji-Yong Park
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WEC rotor ,pitch motion ,efficiency of rotor ,phase ,forced motion ,experiment ,Technology - Abstract
A series of experiments were carried out to investigate the performance of a WEC rotor with platform motion. To achieve platform motion, a forced motion device with a rotor was installed in the Ocean Engineering Basin. In this study, the rotor’s performance was examined at various phase stages between incoming waves at three wave heights, and compared to a rotor without a PTO system. The phase stage where the rotor exhibited the largest pitch motion was identified, and the efficiencies of the rotor with the PTO system were analyzed during this stage. Without the PTO system, the rotor experienced its largest pitch motion when the rotating center was positioned at the zero-up crossing point of the incoming waves at three different wave heights. Furthermore, it was observed that in the optimal phase, the rotor’s efficiency increased with relatively large platform motion. These findings provide fundamental data for rotor design.
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- 2024
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3. Concept Design of a 15 MW TLP-Type Floating Wind Platform for Korean Offshore Installation
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Sung Youn Boo, Yoon-Jin Ha, Steffen Allan Shelley, Ji-Yong Park, Chang-Hyuck Lim, and Kyong-Hwan Kim
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TLP ,floating offshore wind turbine ,FOWT ,tendon ,extreme response analysis ,concept design ,Naval architecture. Shipbuilding. Marine engineering ,VM1-989 ,Oceanography ,GC1-1581 - Abstract
Offshore wind farms on the east offshore of Korea to produce multi-GW power from floating wind platforms are being planned. The objectives of the present study are to develop a new TLP-type floating wind platform with a 15 MW turbine for the planned site and to confirm the feasibility of the TLP design under extreme typhoon environments. The concept design of the 15 MW TLP floating platform was completed for installation at a water depth of 137 m. The platform was vertically moored with highly pretensioned wire rope tendons. The platform and tendons were designed to withstand extreme conditions for up to 50 years. Additionally, a platform with an integrated turbine was designed to be wet-towable from the quayside without dedicated vessels to minimize the pre-service cost and risk. An extreme response analysis was conducted to evaluate the platform motion, acceleration, airgap and tendon tension for wave variation, intact and damaged condition of the tendon, environment heading change, and water level variation. The platform design results were validated using the design criteria from the industry standards and recommendations, and the design was verified to comply with the design requirements for the planned sites.
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- 2024
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4. Effects of Growth Hormone-Releasing Hormone (GHRH) Plasmid Treatment on the Reproductive Productivity of Sows in Primiparous and Multiparous Sow Breeds
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Min Jung Kim, Ji-Yong Park, Chang-Soo Cho, Ye Jin Yang, Ji Woong Heo, Woo H. Kim, Hu-Jang Lee, and Kwang Il Park
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growth hormone-releasing hormone ,insulin-like growth factor-1 ,multiparous sow ,primiparous sow ,Veterinary medicine ,SF600-1100 ,Zoology ,QL1-991 - Abstract
The effect of growth hormone-releasing hormone (GHRH) plasmid treatment on sow reproductive performance was examined. Forty pregnant sows (three-way crossbreed: Landrace × Yorkshire × Duroc) at 85 days of gestation were included in the study and consisted of twenty primiparous and twenty multiparous sows (third parity). Sows were randomly assigned to the control and treatment groups. The treatment group received 5 mg dose of GHRH plasmid injection via electroporation, whereas the control group received a phosphate buffer solution. Reproductive indicators, including serum insulin-like growth factor-1 (IGF-1) concentration and weaned piglet data, were assessed. In the GHRH plasmid-treated group, serum IGF-1 concentration significantly increased compared with that in the control group, a trend observed in primiparous and multiparous sows. The key indicator of reproductive performance, litter size, showed that for control primiparous sows (C-PS), it was 10.90 ± 0.99 kg, while for control multiparous sows (C-MS), it was 14.00 ± 0.67 kg. Furthermore, for primiparous sows treated with GHRH plasmid (G-PS), the litter size was 11.60 ± 0.97 kg, and for multiparous sows treated with GHRH plasmid (G-MS), it was 14.00 ± 0.82 kg. The GHRH plasmid-treated group also exhibited a higher number of total births and surviving piglet numbers, along with a decrease in stillborn piglets; however, there was no significant difference in birth weight. The results suggest that GHRH plasmid treatment can enhance the reproductive performance of sows.
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- 2024
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5. The Consideration of Validation on the Relative Weight Indices Derived from Body Weight and Height
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Ji-Yong Park and Tae-Won Gwon
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body mass index ,relative weight index ,body fat percent ,standard weight ,obesity index ,Nutrition. Foods and food supply ,TX341-641 ,Biochemistry ,QD415-436 - Abstract
PURPOSE This study aimed to consider the validity of relative weight indices, which are used to compare people of different heights. METHODS Cross-sectional analyses were conducted using the 2017-2021 “National Fitness Award” in South Korea. Males (n=77,705) aged 18-65 years and females (n=84,641) were included. Three indices [I1 =kg/m, I2 =kg/m2, and I3 =kg/m3] and I4 [I4 =kg/ m2], which simply reduce the standard error of I1, were analyzed. Pearson's correlation analysis was conducted to determine an index that was highly correlated with weight and was independent of height. Furthermore, an index that was highly correlated with the body fat percentage was considered. The linear relationship between height and the indices was confirmed using regression analysis. The n value of the index (kg/mn), which provides the same value for all height ranges, was derived by regression analysis between weight and height. RESULTS The correlation analysis between height and the indices described I2 (r=-.009, p
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- 2022
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6. Variance-aware weight quantization of multi-level resistive switching devices based on Pt/LaAlO3/SrTiO3 heterostructures
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Sunwoo Lee, Jaeyoung Jeon, Kitae Eom, Chaehwa Jeong, Yongsoo Yang, Ji-Yong Park, Chang-Beom Eom, and Hyungwoo Lee
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Medicine ,Science - Abstract
Abstract Resistive switching devices have been regarded as a promising candidate of multi-bit memristors for synaptic applications. The key functionality of the memristors is to realize multiple non-volatile conductance states with high precision. However, the variation of device conductance inevitably causes the state-overlap issue, limiting the number of available states. The insufficient number of states and the resultant inaccurate weight quantization are bottlenecks in developing practical memristors. Herein, we demonstrate a resistive switching device based on Pt/LaAlO3/SrTiO3 (Pt/LAO/STO) heterostructures, which is suitable for multi-level memristive applications. By redistributing the surface oxygen vacancies, we precisely control the tunneling of two-dimensional electron gas (2DEG) through the ultrathin LAO barrier, achieving multiple and tunable conductance states (over 27) in a non-volatile way. To further improve the multi-level switching performance, we propose a variance-aware weight quantization (VAQ) method. Our simulation studies verify that the VAQ effectively reduces the state-overlap issue of the resistive switching device. We also find that the VAQ states can better represent the normal-like data distribution and, thus, significantly improve the computing accuracy of the device. Our results provide valuable insight into developing high-precision multi-bit memristors based on complex oxide heterostructures for neuromorphic applications.
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- 2022
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7. CFD Study of the Non-Linear Physical Phenomena of the TLP of a 15-MW-Class FOWT under Extreme Waves
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Yoon-Jin Ha, Kyong-Hwan Kim, and Ji-Yong Park
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computational fluid dynamics ,wave impact ,extreme wave ,dynamic tension ,platform motion ,Naval architecture. Shipbuilding. Marine engineering ,VM1-989 ,Oceanography ,GC1-1581 - Abstract
In this study, a numerical simulation was conducted to investigate the non-linear physical phenomena of a tension leg platform (TLP) of a 15-MW-class floating offshore wind turbine (FOWT). Computational fluid dynamics was employed as the numerical tool, and a deforming mesh technique was used to describe the moving body. To examine the non-linear physical phenomena, an irregular wave was generated with a focus on head sea conditions. The springing and ringing responses were calculated from the numerical simulation results, and the relations between the motions and dynamic tensions of the 15-MW-class FOWT TLP were investigated. From the irregular wave impact simulation, it was found that the springing response via the wave sum frequencies and the ringing response occurred at approximately three times the wave peak frequency. Additionally, whipping simulations were conducted under a focused wave. The results show that the response in pitch resonance frequency was caused by the wave impact. The numerical results of this study could be used as fundamental data for FOWT TLP design.
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- 2023
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8. Top-emitting 940-nm thin-film VCSELs transferred onto aluminum heatsinks
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Sunghyun Moon, Yeojun Yun, Minhyung Lee, Donghwan Kim, Wonjin Choi, Ji-Yong Park, and Jaejin Lee
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Medicine ,Science - Abstract
Abstract Thin-film vertical cavity surface emitting lasers (VCSELs) mounted onto heatsinks open up the way toward low-power consumption and high-power operation, enabling them to be widely used for energy saving high-speed optical data communication and three-dimensional sensor applications. There are two conventional VCSEL polarity structures: p-on-n and n-on-p polarity. The former is more preferably used owing to the reduced series resistance of n-type bottom distributed Bragg reflection (DBR) as well as the lower defect densities of n-type GaAs substrates. In this study, the p-on-n structures of thin-film VCSELs, including an etch stop layer and a highly n-doped GaAs ohmic layer, were epitaxially grown in upright order by using low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The p-on-n structures of thin-film VCSELs were transferred onto an aluminum heatsink via a double-transfer technique, allowing the top-emitting thin-film VCSELs to keep the p-on-n polarity with the removal of the GaAs substrate. The threshold current (I th ) and voltage (V th ) of the fabricated top-emitting thin-film VCSELs were 1 mA and 2.8 V, respectively. The optical power was 7.7 mW at a rollover point of 16.1 mA.
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- 2022
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9. Thru‐Hole Epitaxy: A Highway for Controllable and Transferable Epitaxial Growth
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Dongsoo Jang, Chulwoo Ahn, Youngjun Lee, Seungjun Lee, Hyunkyu Lee, Donghoi Kim, Yongsun Kim, Ji‐Yong Park, Young‐Kyun Kwon, Jaewu Choi, and Chinkyo Kim
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crystallographic alignment ,density functional theory ,gallium nitride ,hexagonal boron nitride ,thru‐hole epitaxy ,transferability ,Physics ,QC1-999 ,Technology - Abstract
Abstract Controllable growth and facile transferability of a crystalline film with desired characteristics, acquired by tuning composition and crystallographic orientation, become highly demanded for advanced flexible devices. Here the desired crystallographic orientations and facile transferability of a crystalline film can be achieved by “thru‐hole epitaxy” in a straightforward and undemanding manner with no limitation on the layer number and polarity of a 2D space layer and the surface characteristics. The crystallographic alignment can be established by the connectedness of the grown material to the substrate through a small net cross‐sectional area of thru‐holes, which also allows the straightforward detachment of the grown material. Thru‐hole epitaxy can be adopted for the realization of advanced flexible devices on large scale with desired crystallographic orientation and facile transferability.
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- 2023
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10. Light intensity dependence of organic solar cell operation and dominance switching between Shockley–Read–Hall and bimolecular recombination losses
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Shinyoung Ryu, Na Young Ha, Y. H. Ahn, Ji-Yong Park, and Soonil Lee
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Medicine ,Science - Abstract
Abstract We investigated the variation of current density–voltage (J–V) characteristics of an organic solar cell (OSC) in the dark and at 9 different light intensities ranging from 0.01 to 1 sun of the AM1.5G spectrum. All three conventional parameters, short-circuit currents (J sc), open-circuit voltage (V oc), and Fill factor (FF), representing OSC performance evolved systematically in response to light intensity increase. Unlike J sc that showed quasi-linear monotonic increase, V oc and FF showed distinctive non-monotonic variations. To elucidate the origin of such variations, we performed extensive simulation studies including Shockley–Read–Hall (SRH) recombination losses. Simulation results were sensitive to defect densities, and simultaneous agreement to 10 measured J–V curves was possible only with the defect density of $$5 \times 10^{12} {\text{ cm}}^{ - 3}$$ 5 × 10 12 cm - 3 . Based on analyses of simulation results, we were able to separate current losses into SRH- and bimolecular-recombination components and, moreover, identify that the competition between SRH- and bimolecular-loss currents were responsible for the aforementioned variations in J sc, V oc, and FF. In particular, we verified that apparent demarcation in V oc, and FF variations, which seemed to appear at different light intensities, originated from the same mechanism of dominance switching between recombination losses.
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- 2021
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11. Enhanced third-harmonic generation by manipulating the twist angle of bilayer graphene
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Seongju Ha, Nam Hun Park, Hyeonkyeong Kim, Jiseon Shin, Jungseok Choi, Sungmin Park, Ji-Yun Moon, Kwanbyung Chae, Jeil Jung, Jae-Hyun Lee, Youngdong Yoo, Ji-Yong Park, Kwang Jun Ahn, and Dong-Il Yeom
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Applied optics. Photonics ,TA1501-1820 ,Optics. Light ,QC350-467 - Abstract
Nonlinear optics: When graphene ‘does the twist’ Modifying the angle between the two layers of twisted bilayer graphene can considerably improve how photons interact with it to generate higher-energy photons. Dong-Il Yeom of Ajou University and colleagues in Korea shined laser light onto twisted bilayer graphene stacked at various angles, and measured the outcoming optical signals. Twisted bilayer graphene is made by stacking two monolayer graphenes at an angle. The interlayer interaction in this material leads to intriguing properties. The scientists found that changing the angle could enhance a nonlinear optical property, called third-harmonic generation, by 60 times compared to monolayer graphene. The team then conducted Raman measurements and modeling calculations to understand how this process occurs. They say their findings could pave the way towards novel designs for enhancing optical nonlinearity in two-dimensional stacked materials.
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- 2021
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12. Conceptual Design Study Based on Reliability Assessment of Secondary Energy Conversion Mechanical System in Movable Object Type Wave Power Generator
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Tae-Wook Kim, Ji-Yong Park, Jae-Won Oh, Kyong-Hwan Kim, Jung-Hee Lee, and Hyung-Woo Kim
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movable object type wave power generator ,secondary energy conversion system ,conceptual design ,reliability assessment ,system analysis ,IDEF0 ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Movable object type wave power generators produce energy through the process of primary energy conversion, which converts the potential and kinetic energy of the waves into mechanical energy, secondary energy conversion that converts it into energy for generator operation using a mechanical system or hydraulic system, and final energy conversion, the last step in power generation. The secondary energy conversion system that transmits and amplifies energy according to the primary energy conversion needs to secure durability while power generation performance varies greatly depending on how the secondary energy conversion system is built. As a result, reliability assessment of systems based on system engineering are a very important issue. Therefore, in this study, for the conceptual design based on reliability assessment of the secondary energy conversion system, the system concept was established using the integrated computer-aided manufacturing (ICAM) definition for function modeling (IDEF0), a system analysis method, while necessary equipment and process flow diagrams (PFD) were derived. In addition, the database (DB) and formula of the secondary energy conversion system were constructed, and reliability assessment algorithms and programs were developed. Finally, the PFD and reliability assessment program were verified by applying them to a representative movable object type wave power generator.
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- 2022
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13. High-Speed Imaging of Second-Harmonic Generation in MoS2 Bilayer under Femtosecond Laser Ablation
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Young Chul Kim, Hoseong Yoo, Van Tu Nguyen, Soonil Lee, Ji-Yong Park, and Yeong Hwan Ahn
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second-harmonic generation ,transition-metal dichalcogenides ,twisted bilayer ,laser ablation ,Chemistry ,QD1-999 - Abstract
We report an in situ characterization of transition-metal dichalcogenide (TMD) monolayers and twisted bilayers using a high-speed second-harmonic generation (SHG) imaging technique. High-frequency laser modulation and galvano scanning in the SHG imaging enabled a rapid identification of the crystallinity in the TMD, including the orientation and homogeneity with a speed of 1 frame/s. For a twisted bilayer MoS2, we studied the SHG peak intensity and angles as a function of the twist angle under a strong interlayer coupling. In addition, rapid SHG imaging can be used to visualize laser-induced ablation of monolayer and bilayer MoS2 in situ under illumination by a strong femtosecond laser. Importantly, we observed a characteristic threshold behavior; the ablation process occurred for a very short time duration once the preheating condition was reached. We investigated the laser thinning of the bilayer MoS2 with different twist angles. When the twist angle was 0°, the SHG decreased by approximately one-fourth of the initial intensity when one layer was removed. Conversely, when the twist angle was approximately 60° (the SHG intensity was suppressed), the SHG increased abruptly close to that of the nearby monolayer when one layer was removed. Precise layer-by-layer control was possible because of the unique threshold behavior of the laser-induced ablation.
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- 2021
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14. Electronic Band Alignment at Complex Oxide Interfaces Measured by Scanning Photocurrent Microscopy
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J. H. Yoon, H. J. Jung, J. T. Hong, Ji-Yong Park, Soonil Lee, S. W. Lee, and Y. H. Ahn
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Medicine ,Science - Abstract
Abstract The band alignment at an Al2O3/SrTiO3 heterointerface forming a two-dimensional electron gas (2DEG) was investigated using scanning photocurrent microscopy (SPCM) in an electrolyte-gated environment. We used a focused UV laser source for above-the-bandgap illumination on the SrTiO3 layer, creating electron-hole pairs that contributed to the photocurrent through migration towards the metal electrodes. The polarity of the SPCM signals of a bare SrTiO3 device shows typical p-type behavior at zero gate bias, in which the photogenerated electrons are collected by the electrodes. In contrast, the SPCM polarity of 2DEG device indicates that the hole carriers were collected by the metal electrodes. Careful transport measurements revealed that the gate-dependent conductance of the 2DEG devices exhibits n-type switching behavior. More importantly, the SPCM signals in 2DEG devices demonstrated very unique gate-responses that cannot be found in conventional semiconducting devices, based on which we were able to perform detailed investigation into the electronic band alignment of the 2DEG devices and obtain the valence band offset at the heterointerface.
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- 2017
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15. Imaging Hydrogen Sulfide in Hypoxic Tissue with [99mTc]Tc-Gluconate
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Yongkyoung Kweon, Ji-Yong Park, Young-Joo Kim, Yun-Sang Lee, and Jae-Min Jeong
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H2S ,technetium-99m ,hypoxia ,gluconate ,Organic chemistry ,QD241-441 - Abstract
Hydrogen sulfide (H2S) is the third gasotransmitter and is generated endogenously in hypoxic or inflammatory tissues and various cancers. We have recently demonstrated that endogenous H2S can be imaged with [99mTc]Tc-gluconate. In the present study, we detected H2S generated in hypoxic tissue, both in vitro and in vivo, using [99mTc]Tc-gluconate. In vitro uptake of [99mTc]Tc-gluconate was measured under hypoxic and normoxic conditions, using the colon carcinoma cell line CT26, and was higher in hypoxic cells than that in normoxic cells. An acute hindlimb ischemia-reperfusion model was established in BALB/c mice by exposing the animals to 3 h of ischemia and 3 h of reperfusion prior to in vivo imaging. [99mTc]Tc-gluconate (12.5 MBq) was intravenously injected through the tail vein, and uptake in the lower limb was analyzed by single-photon emission computed tomography/computed tomography (SPECT/CT). SPECT/CT images showed five times higher uptake in the ischemic limb than that in the normal limb. The standard uptake value (SUVmean) of the ischemic limb was 0.39 ± 0.03, while that of the normal limb was 0.07 ± 0.01. [99mTc]Tc-gluconate is a novel imaging agent that can be used both in vitro and in vivo for the detection of endogenous H2S generated in hypoxic tissue.
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- 2020
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16. Power Performance Analysis According to the Configuration and Load Control Algorithm of Power Take-Off System for Oscillating Water Column Type Wave Energy Converters
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Roh Chan, Kil-Won Kim, Ji-Yong Park, Se-Wan Park, Kyong-Hwan Kim, and Sang-Shin Kwak
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oscillating water column ,wave energy converter ,turbine efficiency ,power converter topology ,load control ,maximum power point control ,Technology - Abstract
A power take-off (PTO) system for an oscillating water column (OWC) wave energy converter comprises a turbine-generator-power converter. In this study, only the topologies of the power converter that affect the load control algorithm are compared. A power converter for renewable energy is composed of a diode-dc/dc converter and a pulse-width modulation (PWM) converter operating at small and large capacities, respectively. However, selecting a power converter according to the capacity based on the characteristics of the wave energy converter, in which the input energy is highly fluctuating, can significantly reduce the power performance. Thus, to verify load control characteristics according to the topology of the power converter, the turbine-generator-power converter was incorporated in the modeling, and the power performance based on the power converter topology under various wave conditions was analyzed. Further, torque control to obtain the maximum power among load control algorithms was applied under irregular wave conditions, and the power performance and PTO system characteristics according to the torque coefficient were analyzed. The results of this study suggested an increase in the torque coefficient of the maximum power control for the operational stability of the OWC-WEC, and it was confirmed that the RPM characteristics of the PTO system were reduced.
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- 2020
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17. Ultrasound-guided femoral and popliteal sciatic nerve blocks for below knee surgery in patients with severe cardiac disease
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Yun Suk Choi, Hyeon Ju Shin, Ji-Yong Park, Hyun Jung Kim, and So-Hui Yun
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Anesthesiology ,RD78.3-87.3 - Published
- 2015
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18. Diffusion length in nanoporous TiO2 films under above-band-gap illumination
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J. D. Park, B. H. Son, J. K. Park, Sang Yong Kim, Ji-Yong Park, Soonil Lee, and Y. H. Ahn
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Physics ,QC1-999 - Abstract
We determined the carrier diffusion lengths in TiO2 nanoporous layers of dye-sensitized solar cells by using scanning photocurrent microscopy using an ultraviolet laser. Here, we excited the carrier directly in the nanoporous layers where the diffusion lengths were found to 140 μm as compared to that of visible illumination measured at 90 μm. The diffusion length decreased with increasing laser modulation frequency, in which we determined the electron lifetimes and the diffusion coefficients for both visible and UV illuminations. The diffusion lengths have been studied in terms of the sintering temperatures for both cells with and without binding molecules. We found a strong correlation between the diffusion length and the overall light-to-current conversion efficiency, proving that improving the diffusion length and hence the interparticle connections, is key to improving cell efficiency.
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- 2014
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19. Posterior auricular pain caused by the trigger points in the sternocleidomastoid muscle aggravated by psychological factors -A case report
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Sam Hong Min, Seong-Ho Chang, Se Keun Jeon, Seung Zhoo Yoon, Ji-Yong Park, and Hye Won Shin
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myofascial pain syndrome ,posterior auricular pain ,psycological factor ,sternocleidomastoid muscle ,trigger point injection ,Anesthesiology ,RD78.3-87.3 - Abstract
Psychological factors play a significant role in the pain mechanism, and psychological approaches may be useful complements to traditional medical and surgical treatments in pain management. The authors report a case of recurrent severe posterior auricular pain caused by trigger points in the right sternocleidomastoid muscle and influenced by stressful psychological situations (e.g., family affairs, job loss) in a 50-year-old man.
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- 2010
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20. Central pontine myelinolysis in a patient with persistent mild hypernatremia following cadaver donor liver transplantation
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Sang Hoon Yoon, Ji-Yong Park, Sung-Uk Choi, Seung Zhoo Yoon, and Hye Won Lee
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Anesthesiology ,RD78.3-87.3 - Published
- 2013
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21. Predictive Auto-scaler for Kubernetes Cloud.
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Simon Shim, Ankit Dhokariya, Devangi Doshi, Sarvesh Upadhye, Varun Patwari, and Ji-Yong Park
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- 2023
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22. Predictors of lateral lymph node metastasis and skip metastasis in patients with papillary thyroid microcarcinoma.
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Jee Hee Yoon, Ji Yong Park, A Ram Hong, Hee Kyung Kim, and Ho-Cheol Kang
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LYMPHATIC metastasis ,PAPILLARY carcinoma ,WATCHFUL waiting ,THYROID gland ,METASTASIS - Abstract
Background: Papillary thyroid microcarcinoma (PTMC) is characterized by its favorable prognosis and potential for active surveillance (AS) as a management option. However, the presence of cervical lymph node (LN) metastasis, especially lateral LN metastasis, significantly impacts management and prognosis. Previous studies have focused on post-surgery risk factors for cervical LN metastasis. This study aims to identify predictors of lateral LN metastasis by analyzing pre)operative ultrasonographic findings alongside clinicopathological factors. Methods: A retrospective review of medical records was conducted for patients with PTMC who underwent surgery at Chonnam National University Hwasun Hospital between 2004 and 2013. This is a case–control study that compares patients with lateral LN metastasis (N1b) to age- and sex-matched patients without LN metastasis (N0). Subgroup analysis was performed to evaluate risk factors of skip metastasis. Results: The study included 90 patients with PTMC with lateral LN metastasis (N1b) and 268 age- and sex-matched patients without LN metastasis (N0). The mean age was 49.3 years, and female patients were dominant in both groups. Structural recurrences of 4.4% (4/90) were observed only in the N1b group. The N1b group exhibited a higher frequency of upper lobe tumor location compared to the N0 group (38.9% vs. 16.0%, p < 0.001). There was no significant difference in the locations with the presence of invasion to adjacent organs. A higher proportion of non-parallel shape was observed in the N1b group than the N0 group (80.0% vs. 66.0%, p = 0.013). There were no differences in echogenicity, sonographic feature, margin, and AP diameter of the thyroid gland between the two groups. In multivariate analysis, independent risk factors for lateral LN metastasis included extrathyroidal extension, multiplicity, upper lobe tumor location, and non-parallel shape. Skip metastasis in patients with PTMC was associated with upper lobe tumor location. Conclusion: Detailed ultrasound examinations, evaluating tumor location, number, orientation, and the presence of ETE, are crucial in accurately predicting lateral LN metastasis especially when primary tumor was in the upper lobe to avoid missing skip metastasis. These evaluations can help guide the decision between AS and immediate surgery in patients with PTMC. [ABSTRACT FROM AUTHOR]
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- 2024
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23. A Study on the Regional Type and Characteristics of Greenhouse Gas Emissions by Region
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Sangwon Oh, Ji-yong park, and Juchul Jung
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- 2023
24. High-Level Spectral Method for the Fully Nonlinear Waves
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Jang Kim, Sewan Park, Zhirong Shen, Johyun Kyoung, Aldric Baquet, Hyungtae Lee, Yoon-Jin Ha, Ji-Yong Park, and Kyong-Hwan Kim
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Mechanical Engineering ,Ocean Engineering - Published
- 2023
25. A Comprehensive Assessment of the Harms of Fine-Needle Aspiration Biopsy for Thyroid Nodules: A Systematic Review
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Ji Yong Park, Wonsuk Choi, A Ram Hong, Jee Hee Yoon, Hee Kyung Kim, and Ho-Cheol Kang
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Endocrinology ,Endocrinology, Diabetes and Metabolism - Abstract
Background: There have concerns related with the potential harms of fine-needle aspiration biopsy (FNAB). We aimed to summarize the clinical complications and evaluate the safety of FNAB.Methods: Studies related with the harms of FNAB were searched on MEDLINE, Embase, Cochrane library, and KoreaMed from 2012 to 2022. Also, studies reviewed in the previous systematic reviews were evaluated. Included clinical complications were postprocedural pain, bleeding events, neurological symptoms, tracheal puncture, infections, post-FNAB thyrotoxicosis, and needle tract implantation of thyroid cancers.Results: Twenty-three cohort studies were included in this review. Nine studies which were related with FNAB-related pain showed that most of the subjects had no or mild discomfort. The 0% to 6.4% of the patients had hematoma or hemorrhage after FNAB, according to 15 studies. Vasovagal reaction, vocal cord palsy, and tracheal puncture have rarely described in the included studies. Needle tract implantation of thyroid malignancies was described in three studies reporting 0.02% to 0.19% of the incidence rate.Conclusion: FNAB is considered to be a safe diagnostic procedure with rare complications, which are mainly minor events. Thorough assessement of the patients’ medical condition when deciding to perform FNABs would be advisable to lower potential complications.
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- 2023
26. Circulation Time-Optimized Albumin Nanoplatform for Quantitative Visualization of Lung Metastasis via Targeting of Macrophages
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Hyewon Chung, Ji Yong Park, Kyuwan Kim, Ran Ji Yoo, Minseok Suh, Gyo Jeong Gu, Jin Sil Kim, Tae Hyeon Choi, Jung Woo Byun, Young Wook Ju, Wonshik Han, Han Suk Ryu, Gehoon Chung, Do Won Hwang, Yujin Kim, Hye-Ryun Kang, Yi Rang Na, Hongyoon Choi, Hyung-Jun Im, Yun-Sang Lee, and Seung Hyeok Seok
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Blood Circulation Time ,Lung Neoplasms ,Macrophages ,General Engineering ,Humans ,General Physics and Astronomy ,General Materials Science ,Mannose ,Serum Albumin - Abstract
The development of molecular imaging probes to identify key cellular changes within lung metastases may lead to noninvasive detection of metastatic lesions in the lung. In this study, we constructed a macrophage-targeted clickable albumin nanoplatform (CAN) decorated with mannose as the targeting ligand using a click reaction to maintain the intrinsic properties of albumin
- Published
- 2022
27. Highly Resilient Dual-Crosslinked Hydrogel Adhesives Based on a Dopamine-Modified Crosslinker
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Gi-Yeon Han, Ji Yong Park, Tae-Hyung Lee, Mo-Beom Yi, and Hyun-Joong Kim
- Subjects
Adhesives ,Dopamine ,Humans ,Hydrogels ,Tissue Adhesions ,Tissue Adhesives ,General Materials Science ,Bandages - Abstract
Hydrogels are promising material for wound dressing and tissue engineering. However, owing to their low tissue adhesion in a moist environment and lack of flexibility, hydrogels are still not widely applied in movable parts, such as joints. Herein, we report a dual-crosslinked hydrogel adhesive using a dopamine-modified and acrylate-terminated crosslinker, tri(ethylene glycol) diacrylate-dopamine crosslinker (TDC). The covalent crosslinking was formed by photopolymerization between acrylic acid (AA) and TDC, and the noncovalent crosslinking was formed by intermolecular dopamine-dopamine and dopamine-AA interactions. Our resultant hydrogel demonstrated strong tissue adhesion in a moist environment (approximately 71 kPa) and high mechanical resilience (approximately 94%) with immediate recovery at a 200% strain rate. Moreover, it accelerated wound healing upon dressing the wound site properly. Our study provides the potential for advanced polymer synthesis by introducing a functional crosslinking agent.
- Published
- 2022
28. Effects of Oxygen Vacancies in a Zinc Oxide Electron Transport Layer on Long-Term Degradation and Short-Term Photo-Induced Changes in the Operation Characteristics of Organic Solar Cells
- Author
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Shin Young Ryu, Na Young Ha, Yeong Hwan. Ahn, Ji-Yong Park, and Soonil Lee
- Subjects
Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering - Published
- 2022
29. Enhanced Optical Third-Harmonic Generation in Phase-Engineered MoTe2 Thin Films
- Author
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Seongju Ha, Hyeonkyeong Kim, Hyunjun Nam, Jungseok Choi, Kwanbyung Chae, Jae-Ung Lee, Ji-Yong Park, Youngdong Yoo, and Dong-Il Yeom
- Subjects
Electrical and Electronic Engineering ,Atomic and Molecular Physics, and Optics ,Biotechnology ,Electronic, Optical and Magnetic Materials - Published
- 2022
30. Development of finely tuned liposome nanoplatform for macrophage depletion
- Author
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Tae Hyeon Choi, Ran Ji Yoo, Ji Yong Park, Ji Yoon Kim, Young Chan Ann, Jeongbin Park, Jin Sil Kim, Kyuwan Kim, Yu Jin Shin, Yong Jin Lee, Kyo Chul Lee, Hyewon Chung, Seung Hyeok Seok, Hyung-Jun Im, and Yun-Sang Lee
- Abstract
Background Immunotherapy with clodronate-encapsulated liposomes, which induce macrophage depletion, has been studied extensively. However, previously reported liposomal formulation-based drugs (Clodrosome® and m-Clodrosome®) are limited by their inconsistent size and therapeutic efficacy. Thus, we aimed to achieve consistent therapeutic effects by effectively depleting macrophages with uniform-sized liposomes.Results We developed four types of click chemistry-based liposome nanoplatforms that were uniformly sized and encapsulated with clodronate, for effective macrophage depletion, followed by conjugation with Man-N3 and radiolabeling. Functionalization with Man-N3 improves the specific targeting of M2 macrophages, and radioisotope labeling enables in vivo imaging of the liposome nanoplatforms. The functionalized liposome nanoplatforms are stable under physiological conditions. The difference in the biodistribution of the four liposome nanoplatforms in vivo were recorded using positron emission tomography imaging. Among the four platforms, the clodronate-encapsulated mannosylated liposome effectively depleted M2 macrophages in the normal liver and tumor microenvironment ex vivo compared to that by Clodrosome® and m-Clodrosome®.Conclusion The newly-developed liposome nanoplatform, with finely tuned size control, high in vivo stability, and excellent ex vivo M2 macrophage targeting and depletion effects, is a promising macrophage-depleting agent.
- Published
- 2023
31. The Consideration of Validation on the Relative Weight Indices Derived from Body Weight and Height
- Author
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Tae-Won Kwon and Ji Yong Park
- Subjects
Physiology (medical) ,Public Health, Environmental and Occupational Health ,Physical Therapy, Sports Therapy and Rehabilitation - Abstract
PURPOSE: This study aimed to consider the validity of relative weight indices, which are used to compare people of different heights.METHODS: Cross-sectional analyses were conducted using the 2017-2021 “National Fitness Award” in South Korea. Males (n=77,705) aged 18-65 years and females (n=84,641) were included. Three indices [I1=kg/m, I2=kg/m2/sup>, and I3=kg/m3] and I4 [I4=kg/ m2], which simply reduce the standard error of I1, were analyzed. Pearson's correlation analysis was conducted to determine an index that was highly correlated with weight and was independent of height. Furthermore, an index that was highly correlated with the body fat percentage was considered. The linear relationship between height and the indices was confirmed using regression analysis. The n value of the index (kg/mn), which provides the same value for all height ranges, was derived by regression analysis between weight and height.RESULTS: The correlation analysis between height and the indices described I2 (r=-.009, p
- Published
- 2022
32. Imaging Spatial Distribution of Photogenerated Carriers in Monolayer MoS2 with Kelvin Probe Force Microscopy
- Author
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Woongbin Yim, Van Tu Nguyen, Quynh Thi Phung, Hwan Sik Kim, Yeong Hwan Ahn, Soonil Lee, and Ji-Yong Park
- Subjects
General Materials Science - Published
- 2022
33. [64Cu]Cu-Albumin Clearance Imaging to Evaluate Lymphatic Efflux of Cerebrospinal Space Fluid in Mouse Model
- Author
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Azmal Sarker, Minseok Suh, Yoori Choi, Ji Yong Park, Seokjun Kwon, Hyun Kim, Eunji Lee, Hyeyeon Seo, Yun-Sang Lee, and Dong Soo Lee
- Subjects
Original Article ,Radiology, Nuclear Medicine and imaging - Abstract
PURPOSE: Clearance of brain waste in the cerebrospinal fluid (CSF) through the meningeal lymphatic vessels (mLV) has been evaluated mostly through the fluorescent imaging which has inherent limitations in the context of animal physiology and clinical translatability. The study aimed to establish molecular imaging for the evaluation of mLV clearance function. METHODS: Radionuclide imaging after intrathecal (IT) injection was acquired in C57BL/6 mice of 2–9 months. The distribution of [(99m)Tc]Tc-diethylenetriamine pentaacetate (DTPA) and [(64)Cu]Cu-human serum albumin (HSA) was comparatively evaluated. Evans Blue and [(64)Cu]Cu-HSA were used to evaluate the distribution of tracer under various speed and volume conditions. RESULTS: [(99m)Tc]Tc-DTPA is not a suitable tracer for evaluation of CSF clearance via mLV as no cervical lymph node uptake was observed while it was cleared from the body. A total volume of 3 to 9 μL at an infusion rate of 300 to 500 nL/min was not sufficient for the tracer to reach the cranial subarachnoid space and clear throughout the mLV. As a result, whole-body positron emission tomography imaging using [(64)Cu]Cu-HSA at 700 nL/min, to deliver 6 μL of injected volume, was set for characterization of the CSF to mLV clearance. Through this protocol, the mean terminal CSF clearance half-life was measured to be 123.6 min (range 117.0–135.0) in normal mice. CONCLUSIONS: We established molecular imaging to evaluate CSF drainage through mLV using [(64)Cu]Cu-HSA. This imaging method is expected to be extended in animal models of dysfunctional meningeal lymphatic clearance and translational research for disease-modifying therapeutic approaches. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13139-022-00746-6.
- Published
- 2022
34. Growth of bilayer MoS2 flakes by reverse flow chemical vapor deposition
- Author
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Van Tu Nguyen, Van Chuc Nguyen, Van Hau Tran, and Ji-Yong Park
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2023
35. Nanoscale visualization of hot carrier generation and transfer at non-noble metal and oxide interface
- Author
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Ji-Yong Park, Hyungtak Seo, Qadeer Akbar Sial, Ranveer Singh, Sanghee Nah, and Seung-Ik Han
- Subjects
Photocurrent ,Kelvin probe force microscope ,Materials science ,Polymers and Plastics ,Passivation ,business.industry ,Mechanical Engineering ,Electrostatic force microscope ,Energy conversion efficiency ,Metals and Alloys ,chemistry.chemical_element ,Conductive atomic force microscopy ,chemistry ,Mechanics of Materials ,Materials Chemistry ,Ceramics and Composites ,Optoelectronics ,business ,Tin ,Surface states - Abstract
The conversion efficiency of energy-harvesting devices can be increased by utilizing hot-carriers (HCs). However, due to ultrafast carrier-carrier scattering and the lack of carrier injection dynamics, HC-based devices have low efficiencies. In the present work, we report the effective utilization of HCs at the nanoscale and their transfer dynamics from a non-noble metal to a metal oxide interface by means of real-space photocurrent mapping by using local probe techniques and conducting femtosecond transient absorption (TA) measurements. The photocurrent maps obtained under white light unambiguously show that the HCs are injected into the metal oxide layer from the TiN layer, as also confirmed by conductive atomic force microscopy. In addition, the increased photocurrent in the bilayer structure indicates the injection of HCs from both layers due to the broadband absorption efficiency of TiN layer, passivation of the surface states by the top TiN layer, and smaller barrier height of the interfaces. Furthermore, electrostatic force microscopy and Kelvin probe force microscopy provide direct evidence of charge injection from TiN to the MoOx film at the nanoscale. The TA absorption spectra show a strong photo-bleaching signal over wide spectral range and ultrafast decaying behavior at the picosecond time scale, which indicate efficient electron transfer from TiN to MoOx. Thus, our simple and effective approach can facilitate HC collection under white light, thereby achieving high conversion efficiency for optoelectronic devices.
- Published
- 2022
36. Melatonin-mediated FKBP4 downregulation protects against stress-induced neuronal mitochondria dysfunctions by blocking nuclear translocation of GR
- Author
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Min Jeong Kim, Gee Euhn Choi, Chang Woo Chae, Jae Ryong Lim, Young Hyun Jung, Jee Hyeon Yoon, Ji Yong Park, and Ho Jae Han
- Subjects
Cancer Research ,Cellular and Molecular Neuroscience ,Immunology ,Cell Biology - Abstract
The physiological crosstalk between glucocorticoid and melatonin maintains neuronal homeostasis in regulating circadian rhythms. However, the stress-inducing level of glucocorticoid triggers mitochondrial dysfunction including defective mitophagy by increasing the activity of glucocorticoid receptors (GRs), leading to neuronal cell death. Melatonin then suppresses glucocorticoid-induced stress-responsive neurodegeneration; however, the regulatory mechanism of melatonin, i.e., associated proteins involved in GR activity, has not been elucidated. Therefore, we investigated how melatonin regulates chaperone proteins related to GR trafficking into the nucleus to suppress glucocorticoid action. In this study, the effects of glucocorticoid on suppressing NIX-mediated mitophagy, followed by mitochondrial dysfunction, neuronal cell apoptosis, and cognitive deficits were reversed by melatonin treatment by inhibiting the nuclear translocation of GRs in both SH-SY5Y cells and mouse hippocampal tissue. Moreover, melatonin selectively suppressed the expression of FKBP prolyl isomerase 4 (FKBP4), which is a co-chaperone protein that works with dynein, to reduce the nuclear translocation of GRs among the chaperone proteins and nuclear trafficking proteins. In both cells and hippocampal tissue, melatonin upregulated melatonin receptor 1 (MT1) bound to Gαq, which triggered the phosphorylation of ERK1. The activated ERK then enhanced DNA methyltransferase 1 (DNMT1)-mediated hypermethylation of FKBP52 promoter, reducing GR-mediated mitochondrial dysfunction and cell apoptosis, the effects of which were reversed by knocking down DNMT1. Taken together, melatonin has a protective effect against glucocorticoid-induced defective mitophagy and neurodegeneration by enhancing DNMT1-mediated FKBP4 downregulation that reduced the nuclear translocation of GRs.
- Published
- 2023
37. Mannosylated-serum albumin nanoparticle imaging to monitor tumor-associated macrophages under anti-PD1 treatment
- Author
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Gyo Jeong Gu, Hyewon Chung, Ji Yong Park, Ranji Yoo, Hyung-Jun Im, Hongyoon Choi, Yun-Sang Lee, and Seung Hyeok Seok
- Subjects
Biomedical Engineering ,Pharmaceutical Science ,Molecular Medicine ,Medicine (miscellaneous) ,Bioengineering ,Applied Microbiology and Biotechnology - Abstract
Background Immune checkpoint inhibitors such as anti-programmed cell death protein 1 (PD1) block tumor growth by reinvigorating the immune system; however, determining their efficacy only by the changes in tumor size may prove inaccurate. As the immune cells including macrophages in the tumor microenvironment (TME) are associated with the response to anti-PD1 therapy, tumor-associated macrophages (TAMs) imaging using nanoparticles can noninvasively provide the immune enrichment status of TME. Herein, the mannosylated-serum albumin (MSA) nanoparticle was labeled with radioactive isotope 68Ga to target the mannose receptors on macrophages for noninvasive monitoring of the TME according to anti-PD1 therapy. Results B16F10-Luc and MC38-Luc tumor-bearing mice were treated with anti-PD1, and the response to anti-PD1 was determined by the tumor volume. According to the flow cytometry, the responders to anti-PD1 showed an increased proportion of TAMs, as well as lymphocytes, and the most enriched immune cell population in the TME was also TAMs. For noninvasive imaging of TAMs as a surrogate of immune cell augmentation in the TME via anti-PD1, we acquired [68Ga] Ga-MSA positron emission tomography. According to the imaging study, an increased number of TAMs in responders at the early phase of anti-PD1 treatment was observed in both B16F10-Luc and MC38-Luc tumor-bearing mice models. Conclusion As representative immune cells in the TME, non-invasive imaging of TAMs using MSA nanoparticles can reflect the immune cell enrichment status in the TME closely associated with the response to anti-PD1. As non-invasive imaging using MSA nanoparticles, this approach shows a potential to monitor and evaluate anti-tumor response to immune checkpoint inhibitors.
- Published
- 2023
38. Intrathecal [64Cu]Cu-albumin PET reveals age-related decline of cerebrospinal fluid (CSF)-lymphatic efflux
- Author
-
Azmal Sarker, Minseok Suh, Yoori Choi, Ji Yong Park, Yun-Sang Lee, and Dong Soo Lee
- Abstract
Age-related cognitive decline is associated with dysfunctional lymphatic efflux of cerebrospinal fluid (CSF) through meningeal lymphatic vessels. Intrathecal [64Cu]Cu-albumin positron emission tomography (PET) was applied in mice for the evaluation of lymphatic efflux of CSF and its age-related variation. [64Cu]Cu-albumin PET was done at multiple time points after intrathecal injection of [64Cu]Cu-albumin with the infusion speed of 700 nl/min in the adult and aged mice of 15–25 months old age. CSF clearance and paravertebral lymph nodes were quantified after injection and at later stationary phase. Representing perturbed state by 6 μl (1/7 of CSF volume with twice the production rate for 9 minutes of intrathecal injection) and at the next day of stationary return of CSF dynamics in mice, CSF clearance half-time from the subarachnoid space was 93.4 ± 19.7 in adult and 123.3 ± 15.6 minutes in aged mice (p = 0.01). The % injected dose at 4, 6 and 24 hours were higher in aged mice than in the adult mice (p < 0.05) and the visualized paravertebral lymph node activity tended to be lower in the aged, which was different from [64Cu]Cu-NOTA or [64Cu]Cu-ESION PET. [64Cu]Cu-albumin PET enabled quantification of CSF-lymphatic efflux over all the levels of brain spinal cords and visualization with quantifiability of lymph node activity. [64Cu]Cu-albumin PET revealed an age-related decrease in CSF-lymphatic efflux due to less efflux from the subarachnoid space, especially at stationary phase in the aged mice.
- Published
- 2023
39. Flexoelectric effect driven colossal triboelectricity with multilayer graphene
- Author
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Jaeseong Lim, Hyungtak Seo, Mohit Kumar, and Ji-Yong Park
- Subjects
Coupling ,Materials science ,Graphene ,business.industry ,Direct current ,General Physics and Astronomy ,Engineering physics ,Piezoelectricity ,law.invention ,Semiconductor ,law ,General Materials Science ,business ,Energy harvesting ,Triboelectric effect ,Voltage - Abstract
Converting mechanical deformation from surrounding environment into detectable electrical signals remains one of the most attractive fields due to its potential applications in sustainable energy harvesting, self-powered sensors, and others. Presently, deformation energy is harvested by generating voltage/current through bending/twisting of piezoelectric materials, but its recyclability is limited in number. In contrast, polarization is generated in all known insulators/semiconductors due to elastic strain gradient, which offers unique electromechanical coupling and in turn, could generate significant potential differences to drive charge transfer. Here, we demonstrate that extremely high direct current with density of 28 × 106 A m−2 is generated without need of any external power supply by applying pointed force using conductive-atomic force microscope (cAFM) tip on multilayer graphene/substrate (SiO2, Si, glass). Further, the ramp-dependent time-resolved current is measured at a localized point, which indicates that pointed force-induced flexoelectric potential differences are the main driving factor to utilize mechanoelectrical coupling and in turn generate high current density. This research work provides a new strategy to utilize the flexoelectric effect to utilize electromechanical coupling to generate giant energy harvesting, which will have a potential impact on the various multiple fields including smart devices, materials, and even a fundamental understanding of physics.
- Published
- 2021
40. Engineering Silk Protein to Modulate Polymorphic Transitions for Green Lithography Resists
- Author
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Soon-Chun Chung, Joon-Song Park, Rakesh Kumar Jha, Jieun Kim, Jinha Kim, Muyoung Kim, Juwan Choi, Hongdeok Kim, Da-Hye Park, Narendar Gogurla, Tae-Yun Lee, Heonsu Jeon, Ji-Yong Park, Joonmyung Choi, Ginam Kim, and Sunghwan Kim
- Subjects
General Materials Science - Abstract
Silk protein is being increasingly introduced as a prospective material for biomedical devices. However, a limited locus to intervene in nature-oriented silk protein makes it challenging to implement on-demand functions to silk. Here, we report how polymorphic transitions are related with molecular structures of artificially synthesized silk protein and design principles to construct a green-lithographic and high-performative protein resist. The repetition number and ratio of two major building blocks in synthesized silk protein are essential to determine the size and content of β-sheet crystallites, and radicals resulting from tyrosine cleavages by the 193 nm laser irradiation induce the β-sheet to α-helix transition. Synthesized silk is designed to exclusively comprise homogeneous building blocks and exhibit high crystallization and tyrosine-richness, thus constituting an excellent basis for developing a high-performance deep-UV photoresist. Additionally, our findings can be conjugated to design an electron-beam resist governed by the different irradiation-protein interaction mechanisms. All synthesis and lithography processes are fully water-based, promising green lithography. Using the engineered silk, a nanopatterned planar color filter showing the reduced angle dependence can be obtained. Our study provides insights into the industrial scale production of silk protein with on-demand functions.
- Published
- 2022
41. Improved growth control of atomically thin WSe2 flakes using pre-deposited W source
- Author
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Ji-Yong Park, Ngoc Minh Phan, and Van Tu Nguyen
- Subjects
Electron mobility ,Yield (engineering) ,Materials science ,Graphene ,Bilayer ,Heterojunction ,Substrate (electronics) ,Carbon nanotube ,Chemical vapor deposition ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Chemical engineering ,law ,Electrical and Electronic Engineering - Abstract
The improvement in the growth yield and control of atomically thin WSe2 flakes by chemical vapor deposition (CVD) using pre-deposited WO3 nanopowders as a W source is demonstrated. WO3 nanopowders are pre-deposited on the growth substrate and utilized as a W source instead of separate W sources in the CVD system. In this way, mostly mono or bilayer WSe2 flakes are grown on the growth substrate with high density and an average size of around 20 μm. The devices based on the as-grown WSe2 flakes show p-type behaviors with a high on/off ratio of ~ 105 and carrier mobility of ~ 0.5 cm2 V− 1 s−1 as well as a large positive photoresponse. The density and size of WSe2 flakes can be controlled by adjusting the amount of pre-deposited WO3 nanopowders. This approach can be used to grow W-based two-dimensional materials as well as their heterostructures with other materials such as graphene and carbon nanotubes.
- Published
- 2021
42. Mannosylated-Serum Albumin Nanoparticle Imaging to Monitor Tumor-Associated Macrophages under Anti- PD1 Treatment
- Author
-
Gyo Jeong Gu, Hyewon Chung, Ji Yong Park, Ran ji Yoo, Hyung Jun Im, Hongyoon Choi, Yun-Sang Lee, and Seung Hyeok Seok
- Abstract
Background Immune checkpoint inhibitors such as anti-programmed cell death protein 1 (PD1) block tumor growth by reinvigorating the immune system; however, determining their efficacy only by the changes in tumor size may prove inaccurate. As the immune cells including macrophages in the tumor microenvironment (TME) are associated with the response to anti-PD1 therapy, tumor-associated macrophages (TAMs) imaging using nanoparticles can noninvasively provide the immune enrichment status of TME. Herein, the mannosylated-serum albumin (MSA) nanoparticle was labeled with radioactive isotope 68Ga to target the mannose receptors on macrophages for noninvasive monitoring of the TME according to anti-PD1 therapy. Results B16F10 tumor-bearing mice were treated with anti-PD1, and the response to anti-PD1 was determined by the tumor volume. According to the flow cytometry, the responders to anti-PD1 showed an increased proportion of TAMs, as well as lymphocytes, and the most enriched immune cell population in the TME was also TAMs. For noninvasive imaging of TAMs as a surrogate of immune cell augmentation in the TME via anti-PD1, we acquired [68Ga]Ga-MSA positron emission tomography. According to the imaging study, an increased number of TAMs in responders at the early phase of anti-PD1 treatment was observed in both B16F10 and MC38 tumor-bearing mice models. Conclusion As representative immune cells in the TME, non-invasive imaging of TAMs using MSA nanoparticles can reflect the immune cell enrichment status in the TME closely associated with the response to anti-PD1. As non-invasive imaging using MSA nanoparticles, this approach shows a potential to monitor and evaluate anti-tumor response to immune checkpoint inhibitors.
- Published
- 2022
43. Study of phase-dependent third-harmonic generation in MoTe2 thin films
- Author
-
Seongju Ha, Hyeonkyeong Kim, Hyunjun Nam, Jungseok Choi, Kwan Byung Chae, Ji-Yong Park, Youngdong Yoo, and Dong-Il Yeom
- Published
- 2022
44. Light intensity dependence of organic solar cell operation and dominance switching between Shockley–Read–Hall and bimolecular recombination losses
- Author
-
Na Young Ha, Yeong Hwan Ahn, Soonil Lee, Ji-Yong Park, and Shinyoung Ryu
- Subjects
Multidisciplinary ,Materials science ,Organic solar cell ,Energy science and technology ,Science ,Article ,Light intensity ,Nanoscience and technology ,Medicine ,Fill factor ,Atomic physics ,Recombination ,Voltage - Abstract
We investigated the variation of current density–voltage (J–V) characteristics of an organic solar cell (OSC) in the dark and at 9 different light intensities ranging from 0.01 to 1 sun of the AM1.5G spectrum. All three conventional parameters, short-circuit currents (Jsc), open-circuit voltage (Voc), and Fill factor (FF), representing OSC performance evolved systematically in response to light intensity increase. Unlike Jsc that showed quasi-linear monotonic increase, Voc and FF showed distinctive non-monotonic variations. To elucidate the origin of such variations, we performed extensive simulation studies including Shockley–Read–Hall (SRH) recombination losses. Simulation results were sensitive to defect densities, and simultaneous agreement to 10 measured J–V curves was possible only with the defect density of $$5 \times 10^{12} {\text{ cm}}^{ - 3}$$ 5 × 10 12 cm - 3 . Based on analyses of simulation results, we were able to separate current losses into SRH- and bimolecular-recombination components and, moreover, identify that the competition between SRH- and bimolecular-loss currents were responsible for the aforementioned variations in Jsc, Voc, and FF. In particular, we verified that apparent demarcation in Voc, and FF variations, which seemed to appear at different light intensities, originated from the same mechanism of dominance switching between recombination losses.
- Published
- 2021
45. Response of wave energy to tidal currents in the western sea of Jeju Island, Korea
- Author
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Il-Hyoung Cho, Taekyun Kim, Jong-Su Choi, Ji-Seok Hong, Ji Yong Park, and Jae-Hong Moon
- Subjects
060102 archaeology ,Renewable Energy, Sustainability and the Environment ,Wave propagation ,020209 energy ,Magnitude (mathematics) ,06 humanities and the arts ,02 engineering and technology ,Atmospheric sciences ,Current (stream) ,Wave height ,0202 electrical engineering, electronic engineering, information engineering ,Energy condition ,0601 history and archaeology ,Wave–current interaction ,Geology ,Energy (signal processing) ,Wave power - Abstract
This study focuses on the changes in wave energy in response to tidal currents in the western sea of Jeju Island where high-energy wave conditions along with strong tidal currents are usual. Here, an ocean-wave coupled modeling system was used to investigate the effect of tidal currents on the wave energy condition. A comparative experiment with and without tidal currents shows that the current largely affects wave energy in terms of the wave spectrum as a response to the relative direction between waves and currents. When the direction of the tidal current is the same as that of wave propagation, the magnitude of wave height is reduced with energy transfer from shorter periods of 7–9 s to longer periods of 10–12 s, resulting in a decrease (increase) of shorter (longer) wave energy. This reaction is reversed when the tidal current flows in a direction opposite to that of wave propagation. The uncoupled model tends to overestimate/underestimate the wave energy during the ebb/flood tides when the waves follow/oppose the currents by approximately 25%. This study demonstrates that ocean-wave coupling is capable of improving model wave conditions, and therefore, this model is useful for estimating potential wave energy resource and candidate sites.
- Published
- 2021
46. Programmed Cell Death-Ligand 1 (PD-L1) gene Single Nucleotide Polymorphism in Graves’ Disease and Hashimoto’s Thyroiditis in Korean Patients
- Author
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Hee Nam Kim, Wonsuk Choi, Jee Hee Yoon, Ho-Cheol Kang, A Ram Hong, Hee Kyung Kim, Min-Ho Shin, and Ji Yong Park
- Subjects
single nucleotide ,medicine.medical_specialty ,Endocrinology, Diabetes and Metabolism ,Graves' disease ,immune checkpoint inhibitor ,030209 endocrinology & metabolism ,Single-nucleotide polymorphism ,Apoptosis ,Ligands ,Gastroenterology ,Polymorphism, Single Nucleotide ,programmed cell death 1 ligand ,Thyroiditis ,B7-H1 Antigen ,Diseases of the endocrine glands. Clinical endocrinology ,polymorphism ,hashimoto disease ,03 medical and health sciences ,0302 clinical medicine ,Endocrinology ,Gene Frequency ,Polymorphism (computer science) ,Internal medicine ,Genotype ,Republic of Korea ,medicine ,Humans ,Hashimoto Disease ,Genetic Predisposition to Disease ,Thyroid ,biology ,business.industry ,medicine.disease ,RC648-665 ,graves disease ,Genotype frequency ,030220 oncology & carcinogenesis ,biology.protein ,Original Article ,Antibody ,business - Abstract
Background Programmed cell death-ligand 1 (PD-L1) has an important role in regulating immune reactions by binding to programmed death 1 (PD-1) on immune cells, which could prevent the exacerbation of autoimmune thyroid disease (AITD). The aim of this study was to evaluate the association of PD-L1 polymorphism with AITD, including Graves' disease (GD) and Hashimoto's thyroiditis (HT). Methods A total of 189 GD patients, 234 HT patients, and 846 healthy age- and sex-matched controls were enrolled in this study. We analyzed PD-L1 single nucleotide polymorphism (SNP) (rs822339) and investigated the associations with clinical disease course and outcome. Results Genotype frequency at the PD-L1 marker RS822339 in GD (P=0.219) and HT (P=0.764) patients did not differ from that among healthy controls. In patients with GD, the A/G or G/G genotype group demonstrated higher TBII titer (20.6±20.5 vs. 28.0± 25.8, P=0.044) and longer treatment duration (39.0±40.4 months vs. 62.4±65.0 months, P=0.003) compared to the A/A genotype group. Among patients in whom anti-thyroid peroxidase (TPO) antibody was measured after treatment of GD, post-treatment antiTPO positivity was higher in the A/G or G/G genotype group compared to the A/A genotype group (48.1% vs. 69.9%, P=0.045). Among patients with HT, there was no significant difference of anti-TPO antibody positivity (79.4% vs. 68.6%, P=0.121), anti-thyroglobulin antibody positivity (80.9% vs. 84.7%, P=0.661), or development to overt hypothyroidism (68.0% vs. 71.1%, P=0.632) between the A/A genotype group and the A/G or G/G genotype group. Conclusion The genotype frequency of PD-L1 (rs822339) is not different in patients with AITD compared with healthy controls. The intact PD-1/PD-L1 pathway in GD and HT might be important to maintain chronicity of AITD by protecting immune tolerance. However, the PD-L1 SNP could be associated with difficulty in achieving remission in patients with GD, which may be helpful to predict the possibility of longer treatment. Further studies are required to investigate the complex immune tolerance system in patients with AITD.
- Published
- 2021
47. Spurious Thyroid Function Test Results due to Biotin Interference: a Report of Three Cases and a Literature Review
- Author
-
Ji Yong Park, Wonsuk Choi, Jee Hee Yoon, and Ho-Cheol Kang
- Subjects
Vitamin ,Streptavidin ,medicine.diagnostic_test ,business.industry ,Thyroid ,General Engineering ,Bioinformatics ,medicine.disease ,Thyroid function tests ,Excessive biotin intake ,Papillary thyroid cancer ,chemistry.chemical_compound ,medicine.anatomical_structure ,chemistry ,Biotin ,General Earth and Planetary Sciences ,Medicine ,Medical history ,business ,General Environmental Science - Abstract
Biotin (vitamin B7) is a water-soluble vitamin used as a co-enzyme for carboxylases essential for human metabolism. The high affinity to streptavidin makes biotin an important substance in immunoassays. Excessive biotin intake due to over-the counter supplements has become problematic because of the effects on laboratory test results. There have been no reports of biotin-induced thyroid immunoassay interference in Korea. We report three patients with papillary thyroid cancer who showed false thyrotoxicosis on follow-up laboratory examinations with a literature review. The patients’ medical history should be thoroughly questioned and patients should be informed to curtail consuming biotin before laboratory tests to avoid assay interference. Non-biotinylated assays can be considered if it is impossible to withhold the supplements. These methods will prevent physicians from making incorrect decisions that could result in an inappropriate treatment for their patients.
- Published
- 2021
48. Performance Evaluation of SimPET-X, a PET Insert for Simultaneous Mouse Total-Body PET/MR Imaging
- Author
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K.-W. Kim, Ji-Yong Park, Guen Bae Ko, Jeong-Whan Son, Yina Chung, Kyeong Yun Kim, Yun Sang Lee, and Jae Sung Lee
- Subjects
Cancer Research ,Materials science ,Pixel ,Instrumentation ,Detector ,Imaging phantom ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Silicon photomultiplier ,Oncology ,Radiology, Nuclear Medicine and imaging ,Molecular imaging ,Sensitivity (electronics) ,Image resolution ,Biomedical engineering - Abstract
In this study, a small animal PET insert (SimPET-X, Brightonix Imaging Inc.) for simultaneous PET/MR imaging studies is presented. This insert covers an 11-cm-long axial field-of-view (FOV) and enables imaging of mouse total-bodies and rat heads. SimPET-X comprises 16 detector modules to yield a ring diameter of 63 mm and an axial FOV of 110 mm. The detector module supports four detector blocks, each comprising two 4 × 4 SiPM arrays coupled with a 20 × 9 array of LSO crystals (1.2 × 1.2 × 10 mm3). The physical characteristics of SimPET-X were measured in accordance with the NEMA NU4-2008 standard protocol. In addition, we assessed the compatibility of SimPET-X with a small animal-dedicated MRI (M7, Aspect Imaging) and conducted phantom and animal studies. The radial spatial resolutions at the center based on 3D OSEM without and with the warm background were 0.73 mm and 0.99 mm, respectively. The absolute peak sensitivity of the system was 10.44% with an energy window of 100–900 keV and 8.27% with an energy window of 250–750 keV. The peak NECR and scatter fraction for the mouse phantom were 348 kcps at 26.2 MBq and 22.1% with an energy window of 250–750 keV, respectively. The standard deviation of pixel value in the uniform region of an NEMA IQ phantom was 4.57%. The spillover ratios for air- and water-filled chambers were 9.0% and 11.0%, respectively. In the hot-rod phantom image reconstructed using 3D OSEM-PSF, all small rods were resolved owing to the high spatial resolution of the SimPET-X system. There was no notable interference between SimPET-X and M7 MRI. SimPET-X provided high-quality mouse images with superior spatial resolution, sensitivity, and counting rate performance. SimPET-X yielded a remarkably improved sensitivity and NECR compared with SimPETTM.
- Published
- 2021
49. High-Performance and Self-Powered Alternating Current Ultraviolet Photodetector for Digital Communication
- Author
-
Hyungtak Seo, Mohit Kumar, and Ji-Yong Park
- Subjects
Materials science ,business.industry ,Electrical engineering ,Optical communication ,Photodetector ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease_cause ,01 natural sciences ,Space exploration ,0104 chemical sciences ,law.invention ,law ,medicine ,General Materials Science ,0210 nano-technology ,business ,Alternating current ,Sensitivity (electronics) ,Ultraviolet - Abstract
Self-powered ultraviolet photodetectors offer great potential in the field of optical communication, smart security, space exploration, and others; however, achieving high sensitivity with maintaining fast response speed has remained a daunting challenge. Here, we develop a titanium dioxide-based self-powered ultraviolet photodetector with high detectivity (≈1.8 × 10
- Published
- 2021
50. Development of hybrid model test technique for performance evaluation of a 10 MW class floating offshore wind turbine considering asymmetrical thrust
- Author
-
Yoon-Jin Ha, Hyeonjeong Ahn, Sewan Park, Ji-Yong Park, and Kyong-Hwan Kim
- Subjects
Environmental Engineering ,Ocean Engineering - Published
- 2023
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