Prediction of changes in distribution area of Scopura laminate in response to climate changes of the Odaesan National Park of South Korea

Kwon, Soon Jik,Kim, Tae Geun,Park, Youngjun,Kwon, Ohseok,Cho, Youngho The Ecological Society of Korea 2015 Journal of Ecology and Environment Vol.38 No.4

This study was performed to provide important basic data for the preservation and management of Scopura laminata, a species endemic to Korea, by elucidating the spatial characteristics of its present, potential, and future distribution areas. Currently, this species is found in the Odaesan National Park area of South Korea and has been known to be restricted in its habitat due to its poor mobility, as even fully grown insects do not have wings. Utilizing the MaxEnt model, 20 collection points around Odaesan National Park were assessed to analyze and predict spatial distribution characteristics. The precision of the MaxEnt model was excellent, with an AUC value of 0.833. Variables affecting the potential distribution area of S. laminata by more than 10% included the range of annual temperature, seasonality of precipitation, and precipitation of the driest quarter, in order of greatest to least impact. Compared to the current potential distribution area, no significant difference in the overall habitable area was predicted for the 2050s or 2070s. It was, however, demonstrated that the potential habitable area would be reduced in the 2050s by up to 270.3 km from the current area of 403.9 km; further, no potential habitable area was anticipated by the 2070s according to our predictive model. Taken together, it is anticipated that this endemic species could be significantly affected by climate changes, and hence effective countermeasures are strongly warranted for the preservation of habitats and species management.

Prediction of changes in distribution area of Scopura laminate in response to climate changes of the Odaesan National Park of South Korea

Soon Jik Kwon,Tae Geun Kim,Youngjun Park,Ohseok Kwon,조영호 한국생태학회 2015 Journal of Ecology and Environment Vol.38 No.4

This study was performed to provide important basic data for the preservation and management of Scopura laminata, a species endemic to Korea, by elucidating the spatial characteristics of its present, potential, and future distribution areas. Currently, this species is found in the Odaesan National Park area of South Korea and has been known to be restricted in its habitat due to its poor mobility, as even fully grown insects do not have wings. Utilizing the MaxEnt model, 20 collection points around Odaesan National Park were assessed to analyze and predict spatial distribution characteristics. The precision of the MaxEnt model was excellent, with an AUC value of 0.833. Variables affecting the potential distribution area of S. laminata by more than 10% included the range of annual temperature, seasonality of precipitation, and precipitation of the driest quarter, in order of greatest to least impact. Compared to the current potential distribution area, no significant difference in the overall habitable area was predicted for the 2050s or 2070s. It was, however, demonstrated that the potential habitable area would be reduced in the 2050s by up to 270.3 km from the current area of 403.9 km; further, no potential habitable area was anticipated by the 2070s according to our predictive model. Taken together, it is anticipated that this endemic species could be significantly affected by climate changes, and hence effective countermeasures are strongly warranted for the preservation of habitats and species management.

Carrier Transport Mechanism of Ni/Ag/Pt Contacts to p-Type GaN

Park, Youngjun,Ahn, Kwang-Soon,Kim, Hyunsoo IEEE 2012 IEEE transactions on electron devices Vol.59 No.3

<P>The carrier transport mechanisms of Ni/Ag/Pt contacts to moderately Mg-doped p-GaN (sample A) and highly Mg-doped p-GaN (sample B) were investigated. Depending on the Mg doping concentration, the dominant carrier transport mechanism could be categorized as thermionic field emission for sample A and carrier transport through the deep-level defect (DLD) band for sample B, resulting in different specific contact resistances of <TEX>$\hbox{7.1} \times \hbox{10}^{-2}$</TEX> and <TEX>$\hbox{7.0} \times \hbox{10}^{-4}\ \Omega\hbox{cm}^{2}$</TEX> for samples A and B, respectively. For sample A, the contact parameters, including a Schottky barrier height of 0.94 eV and a tunneling parameter of 0.045 eV, could be observed, yielding the substantial interfacial carriers of <TEX>$\hbox{4.5} \times \hbox{10}^{19}\ \hbox{cm}^{-3}$</TEX> and, hence, field emission through a thin barrier. For sample B, the effective barrier height associated with the DLD band was suggested to be an important parameter since the carrier transport predominantly occurred through the DLD band rather than the valence band. Accordingly, the effective barrier height was calculated to be 0.12 eV, which was low enough to explain the excellent ohmic contact.</P>

Artificial Synapses with Short- and Long-Term Memory for Spiking Neural Networks Based on Renewable Materials

Park, Youngjun,Lee, Jang-Sik American Chemical Society 2017 ACS NANO Vol.11 No.9

<P>Emulation of biological synapses that perform memory and learning functions is an essential step toward realization of bioinspired neuromorphic systems. Artificial synaptic devices have been developed based mostly on inorganic materials and conventional semiconductor device fabrication processes. Here, we propose flexible biomemristor devices based on lignin by a simple solution process. Lignin is one of the most abundant organic polymers on Earth and is biocompatible, biodegradable, as well as environmentally benign. This memristor emulates several essential synaptic behaviors, including analog memory switching, short-term plasticity, long-term plasticity, spike-rate-dependent plasticity, and short-term to long-term transition. A flexible lignin-based artificial synapse device can be operated without noticeable degradation under mechanical bending test. These results suggest lignin can be a promising key component for artificial synapses and flexible electronic devices.</P>

Simultaneous CO₂ Utilization and Rare Earth Elements Recovery by Novel Aqueous Carbon Mineralization of Industrial Wastes

Youngjune Park 한국신재생에너지학회 2022 AFORE Vol.2022 No.9

Arginine Deiminase Enhances MCF-7 Cell Radiosensitivity by Inducing Changes in the Expression of Cell Cycle-related Proteins

Park, Hwan,Lee, Junbeom,Shim, Youngjun,Shin, Yongjae,Jeong, Seongyun,Oh, Junseo,Park, Gilhong,Lee, Keeho,Min, Bonhong Korean Society for Molecular Biology 2008 Molecules and cells Vol.25 No.2

After successful clinical application, arginine deiminase (ADI) has been proposed to be a new cancer therapeutic. In the present study, we examined the effect of ADI in combination with ionizing radiation (IR) on MCF-7 cell growth and clonogenic cell death. Cell growth was inhibited by IR in a dose-dependent manner and ADI enhanced the radiosensitivity. ADI itself did not suppress the growth of MCF-7 cells due to the high level of expression of argininosuccinate synthetase (ASS), which convert citrulline, a product of arginine degradation by ADI, to arginine. Previously, it was suggested that ammonia, another product of arginine degradation by ADI, is the main cause of the growth inhibition of irradiated hepatoma cells contaminated with ADI-expressing mycoplasma [van Rijn et al. (2003)]. However, we found that ammonia is not the only factor that enhances radiosensitivity, as enhancement was also observed in the absence of ammonia. In order to identify the enhancing effect, levels of ASS and proteins related to the cell cycle were examined. ASS was unchanged by ADI plus IR, but p21 (a CDK inhibitor) was upregulated and c-Myc downregulated. These findings indicate that changes in the expressions of cell cycle proteins are involved in the enhancement of radiosensitivity by ADI. We suggest that ADI is a potential adjunct to cancer therapy.

A Wide Frequency Range LLC Resonant Controller IC with a Phase-Domain Resonance Deviation Prevention Circuit for LED Backlight Units

YoungJun Park,Hongjin Kim,Joo-Young Chun,JooYoung Lee,YoungGun Pu,Kang-Yoon Lee 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4

This paper presents a wide frequency range LLC resonant controller IC for LED backlight units. In this paper a new phase-domain resonance deviation prevention circuit (RDPC), which covers a wide frequency and input voltage range, is proposed. In addition, a wide range gate clock generator and an automatic dead time generator are proposed. The chip is fabricated using 0.35 μm BCD technology. The die size is 2 x 2 mm2. The frequency of the clock generator ranges from 38 kHz to 400 kHz, and the dead time ranges from 300 ns to 2 μs. The current consumption of the LLC resonant controller IC is 4 mA for a 100 kHz operation frequency using a supply voltage of 15 V.

a Masai

Youngjune Park(박영준) 한국디자인학회 2015 한국디자인학회 국제초대전도록 Vol.2015 No.5

Denoise of Astronomical Images with Deep Learning

Youngjun Park,Yun-Young Choi,Yong-Jae Moon,Eunsu Park,Beomdu Lim,Taeyoung Kim 한국천문학회 2019 天文學會報 Vol.44 No.1

Sequestering carbon dioxide into complex structures of naturally occurring gas hydrates.

Park, Youngjune,Kim, Do-Youn,Lee, Jong-Won,Huh, Dae-Gee,Park, Keun-Pil,Lee, Jaehyoung,Lee, Huen National Academy of Sciences 2006 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.103 No.34

<P>Large amounts of CH4 in the form of solid hydrates are stored on continental margins and in permafrost regions. If these CH4 hydrates could be converted into CO2 hydrates, they would serve double duty as CH4 sources and CO2 storage sites. We explore here the swapping phenomenon occurring in structure I (sI) and structure II (sII) CH4 hydrate deposits through spectroscopic analyses and its potential application to CO2 sequestration at the preliminary phase. The present 85% CH4 recovery rate in sI CH4 hydrate achieved by the direct use of binary N2+CO2 guests is surprising when compared with the rate of 64% for a pure CO2 guest attained in the previous approach. The direct use of a mixture of N2+CO2 eliminates the requirement of a CO2 separation/purification process. In addition, the simultaneously occurring dual mechanism of CO2 sequestration and CH4 recovery is expected to provide the physicochemical background required for developing a promising large-scale approach with economic feasibility. In the case of sII CH4 hydrates, we observe a spontaneous structure transition of sII to sI during the replacement and a cage-specific distribution of guest molecules. A significant change of the lattice dimension caused by structure transformation induces a relative number of small cage sites to reduce, resulting in the considerable increase of CH4 recovery rate. The mutually interactive pattern of targeted guest-cage conjugates possesses important implications for the diverse hydrate-based inclusion phenomena as illustrated in the swapping process between CO2 stream and complex CH4 hydrate structure.</P>