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In this study, CO2 and CH4 fluxes were measured in the tundra ecosystem in order to evaluate the potential future sensitivity of the carbon cycle to climate change using chamber systems and eddy covariance methods during summer in 2019 and 2022 in Canada. The study site is located on dry tundra with ponds in high-arctic near Cambridge Bay, Nunavut, Canada (69°7'47.7"N, 105°3'35.3"W). The vegetation cover around the site is mainly covered with dwarf-shrubs, graminoids, and lichens. CO2 and CH4 fluxes were examined to understand the mechanism of the carbon cycle over the tundra ecosystems with the pond. From chamber methods, the variability of net CO2 exchange was more sensitive to grass of wet condition than vegetation of dry condition and the variability and magnitude of CH4 emission near the pond was larger than that of dry condition. The emission CO2 and CH4 fluxes were examined positive relationship at almost bare soil of wet condition and negative relationship at various vegetation at dry condition. Net ecosystem exchange, ecosystem respiration, and gross primary production were measured or calculated using the both methods to investigate the influence of the ecosystem with ponds in the tundra carbon cycle. This study was supported by a National Research Foundation of Korea grant from the Korean government (MSIP) (NRF-2021M1A5A1065679 and NRF-2021R1I1A1A01053870).

A novel series of donor (D)-π-acceptor (A) merocyanine molecules harnessed with intramolecular chalcogen bonding (ChaB) is designed, synthesized, and characterized. ChaB comprises periodic chalcogen atoms, S, Se, and Te, and a neighboring oxygen atom of a carbonyl moiety. Compared to the D-π-A merocyanine dye with nontraditional intramolecular hydrogen bonding, the novel molecules with an intramolecular ChaB exhibit remarkably smaller absorption spectral widths and higher absorption coefficients attributed to their cyanine-like characteristics approaching the resonance parameter (

Accelerated warming and a decline in sea ice coverage in the summertime Arctic Ocean can significantly affect the emissions of marine organic aerosols and biogenic volatile organic compounds. However, how these changes affect the characteristics of atmospheric water-soluble organic carbon (WSOC), which plays an important role in the climate system, remains unclear. Thus, to improve our understanding of WSOC characteristics, including its summertime fluorescence characteristics, in the rapidly changing Arctic Ocean, we simultaneously measured atmospheric concentrations of ionic species and WSOC, fluorescence excitation–emission matrix coupled with parallel factor (EEM–PARAFAC) analysis of WSOC, and marine biological parameters in surface seawaters of the western Arctic Ocean during the summer of 2016. WSOC was predominantly present as fine-mode aerosols (diameter < 2.5 μm) (median = 92 %) with the mean concentration being higher in the coastal water areas (462 ± 130 ngC m−3) than in the sea ice-covered areas (242 ± 88.4 ngC m−3). Moreover, the WSOC in the fine-mode aerosols was positively correlated with the methanesulfonic acid in the fine-mode aerosol samples collected over the sea ice-covered areas (r = 0.88, p < 0.01, n = 10), suggesting high sea–air gas exchange and emissions of aerosol precursor gases due to sea ice retreat and increasing available solar radiation during the Arctic summer. Two fluorescent components, humic-like C1 and protein-like C2, were identified by the PARAFAC modeling of fine-mode atmospheric WSOC. The two components varied regionally between coastal and sea ice-covered areas, with low and high fluorescence intensities observed over the coastal areas and sea ice-covered areas, respectively. Further, the humification index of WSOC was correlated with the fluorescence intensity ratio of the humic-like C1/protein-like C2 (r = 0.89, p < 0.01) and the WSOC concentration in the fine-mode aerosols (r = 0.66, p < 0.05), with the highest values observed in the coastal areas. Additionally, the WSOC concentration in the fine-mode aerosols was positively correlated with the fluorescence intensity ratio of the humic-like C1/protein-like C2 (r = 0.77, p < 0.01), but was negatively correlated to the biological index (r = −0.69, p < 0.01). Overall, these results suggested that the WSOC in the fine-mode aerosols in the coastal areas showed a higher degree of polycondensation and higher aromaticity compared that in the sea ice-covered areas, where WSOC in the fine-mode aerosols was associated with relatively new, less oxygenated, and biologically-derived secondary organic components. The findings can improve our understanding of the chemical and biological linkages of WSOC at the ocean–sea ice–atmosphere interface.

[60]Fullerene derivatives with high thermal stability can be used for vacuum deposition under heating to fabricate thin films for organic electronic devices. Here, we investigated the thermal stability of [60]fullerene derivatives with various bulky substituents for thermal evaporation under vacuum by means of thermogravimetric analysis under reduced and normal pressure. We found sterically bulky groups such as tert-butyl groups of [60]fullerene derivatives lowered the vacuum deposition temperature. Also, we performed isothermal thermogravimetric analysis to examine the long-term thermal stability of the designed compounds under heating conditions. Furthermore, we investigated the UV-Vis absorption patterns of the deposited films. Absorption in the blue wavelength range, which was attributed to intermolecular HOMO-LUMO transitions among the molecular orbitals of adjacent [60]fullerenes, was dramatically modified. These results were associated with the prevention of aggregation among neighboring [60]fullerene by the sterically bulky groups. This concept could contribute to expanding the use of evaporable [60]fullerene derivatives in organic thin-film electronics research fields.

Stacked structures employing wavelength-selective organic photodiodes (OPDs) have been studied as promising alternatives to the conventional Si-based image sensors because of their color constancy. Herein, novel donor (D)-π-acceptor (A) molecules are designed, synthesized, and characterized as green-light-selective absorbers for application in organic-on-Si hybrid complementary metal-oxide-semiconductor (CMOS) color image sensors. The p-type molecules, combined with two fused-type heterocyclic donors and an electron-accepting unit, exhibit cyanine-like properties that are characterized by intense and sharp absorption. This molecular design leads to improved absorption properties, thermal stability, and higher photoelectric conversion compared to those of a molecular design based on a nonfused ring. A maximum external quantum efficiency of 66% (λ

In this article, flip chip assembly using nonconductive films (NCFs) was evaluated for chip-on-board (COB) packages using Cu/Sn–Ag hybrid bumps. In general, significant thermomechanical stress can be induced at the Cu-pillar/Sn–Ag solder joint because of a large coefficient of thermal expansion (CTE) mismatch between the Si chip and printed circuit board (PCB). If a concave-shaped solder joint morphology is generated at the solder joint, thermomechanical stress could be concentrated at the solder joint, resulting in an early failure of T/C reliability. To obtain the solder joint morphology without a concave-shaped solder joint, NCFs’ curing properties and viscosity should be controlled. In particular, the NCFs’ viscosity at the solder melting temperature, at which metallurgical bonding between molten solder and Cu pads occurs, will significantly affect the solder joint morphology. For this reason, solder joint formation was investigated at each viscosity of NCFs and bonding temperature during the thermo compression (TC) flip chip bonding process. In addition, specific viscosities at certain bonding temperatures during the flip chip bonding process were obtained from measured degrees of cure and viscosity approximation. Finally, the material properties of NCFs were optimized without NCF traps at the solder joint and concave-shaped solder joint, and T/C reliability was evaluated for each silica powder content. As a result, it was confirmed that the COB packages using Cu/Sn–Ag hybrid bumps and optimized NCFs show stable resistance changes within 10% of the initial resistance after the T/C reliability test.

The western Korean Peninsula preserves evidence for multiple Proterozoic to Phanerozoic orogenic processes along the convergent continental margins. After the Late Palaeozoic to Early Mesozoic coll...

The TAROGE-M radio observatory is a self-triggered antenna array on top of the ∼2700 m high Mt. Melbourne in Antarctica, designed to detect impulsive geomagnetic emission from extensive air showers induced by ultra-high energy (UHE) particles beyond 1017 eV, including cosmic rays, Earth-skimming tau neutrinos, and particularly, the “ANITA anomalous events” (AAE) from near and below the horizon. The six AAE discovered by the ANITA experiment have signal features similar to tau neutrinos but that hypothesis is in tension either with the interaction length predicted by Standard Model or with the flux limits set by other experiments. Their origin remains uncertain, requiring more experimental inputs for clarification. The detection concept of TAROGE-M takes advantage of a high altitude with synoptic view toward the horizon as an efficient signal collector, and the radio quietness as well as strong and near vertical geomagnetic field in Antarctica, enhancing the relative radio signal strength. This approach has a low energy threshold, high duty cycle, and is easy to extend for quickly enlarging statistics. Here we report experimental results from the first TAROGE-M station deployed in January 2020, corresponding to approximately one month of livetime. The station consists of six receiving antennas operating at 180–450 MHz, and can reconstruct source directions of impulsive events with an angular resolution of ∼0.3°, calibrated in situ with a drone-borne pulser system. To demonstrate TAROGE-M's ability to detect UHE air showers, a search for cosmic ray signals in 25.3-days of data together with the detection simulation were conducted, resulting in seven identified candidates. The detected events have a mean reconstructed energy of 0.95-0.31 +0.46 EeV and zenith angles ranging from 25° to 82°, with both distributions agreeing with the simulations, indicating an energy threshold at about 0.3 EeV. The estimated cosmic ray flux at that energy is 1.2-0.9 +0.7 × 10-16 eV-1 km-2 yr-1 sr-1, also consistent with results of other experiments. The TAROGE-M sensitivity to AAEs is approximated by the tau neutrino exposure with simulations, which suggests comparable sensitivity as ANITA's at around 1 EeV energy with a few station-years of operation. These first results verified the station design and performance in a polar and high-altitude environment, and are promising for further discovery of tau neutrinos and AAEs after an extension in the near future.

The present work describes the development of an organic photodiode (OPD) receiver for high-speed optical wireless communication. To determine the optimal communication design, two different types of photoelectric conversion layers, bulk heterojunction (BHJ) and planar heterojunction (PHJ), are compared. The BHJ-OPD device has a -3 dB bandwidth of 0.65 MHz (at zero bias) and a maximum of 1.4 MHz (at -4 V bias). A 150 Mbps single-channel visible light communication (VLC) data rate using this device by combining preequalization and machine learning (ML)-based digital signal processing (DSP) is demonstrated. To the best of the authors' knowledge, this is the highest data rate ever achieved on an OPD-based VLC system by a factor of 40 over the previous fastest reported. Additionally, the proposed OPD receiver achieves orders of magnitude higher spectral efficiency than the previously reported organic photovoltaic (OPV)-based receivers.

We examined the seasonal cycle of radon concentration observed at King Sejong Station (KSG, 62°S), Antarctic Peninsula, during the period 2013-2016. The distribution of monthly radon concentration was found to be highly positively skewed from March through October (austral autumn to spring) due to large numbers of short-lived periods of high radon concentration. The global atmospheric chemistry model (CAM-Chem), which includes all global terrestrial sources of radon except for those in Antarctica, well reproduces the observed seasonal cycle of monthly-mean radon concentration at KSG. Further offline experiments suggest that uncertainties in radon emissions over South America and the Southern Ocean should be improved for the simulations of radon in Antarctica. The results demonstrate that seasonally varying transport of radon in the boundary layer from South America substantially affects the seasonality of monthly mean radon concentration at KSG. The composite analyses further reveal that high radon events at KSG are the result of a distinct east-west dipole-like structure associated with surface cyclonic circulation over the Bellingshausen Sea and anticyclonic circulation in the Weddell Sea. This atmospheric pattern provides favorable conditions for radon transport into KSG from the northwest. The relationship between radon concentration at KSG and climate variability is also discussed in this study.

Several nonmarine basins were formed in SW Korea under an extensional or transtensional tectonic regime during the Cretaceous. The Neungju Basin is one of these basins, filled by alluvial to lacustrine deposits interbedded with thick, amalgamated tuff beds. Facies analysis in the northern part of the basin shows that the basin fill is composed of four facies associations, representing (1) alluvial fan, (2) alluvial plain, (3) sandflat, and (4) marginal playa lake environments. The basin fill can be subdivided into four stratigraphic units by interbedded thick amalgamated tuff beds. The lowermost unit (unit I) is composed of alluvial plain deposits. The lack of any vertical depositional trend indicates a balance between basin subsidence and sediment supply. The middle unit (units II and III) show regional variations. The extensive lake formed in the central to northern parts of the basin, which are later partly filled by proximal sediments from surrounding areas. In contrast, only alluvial plain to sandflat environments occurred in the southern part. The uppermost unit (unit IV) shows a transition from alluvial fan to sandflat, comprising a fining-upward trend that reflects a gradual decrease in sediment supply and slope-gradient during denudation of uplifted source areas. The variations in depositional patterns were possibly caused by the relationship between volcanism-driven sediment supply and basin subsidence. Basin subsidence may have been sufficient to compensate the volcanism-driven sediment supply prior to the deposition of units II and III, resulting in the conformable deposition of lake sediments over thick amalgamated tuff beds. In contrast, volcanism-driven sediment supply may have reduced the generation of accommodation prior to the deposition of unit IV, resulting in the deposition of conglomerates over thick tuff beds. The traditional depositional model composed of syn-eruption aggradation and inter-eruption degradation may not sufficiently explain the development of sedimentary succession, in which the balance between volcanism-driven sediment supply versus basin subsidence coeval to volcanism is variable.

In the present study, SiO2 was deposited using the atomic layer deposition (ALD) with a 1,2-bis(diisopropylamino)disilane (BDIPADS) precursor. The use of this precursor exhibited a higher growth rate and lower initial growth temperature than the use of diisopropylaminosilane (DIPAS) did. The ALD reaction using BDIPADS produced SiO2 with excellent quality owing to the self-catalytic reaction between the amine ligand and O3; therefore, the SiO2 film has no impurities. When the growth temperature was increased gradually, the stoichiometry and density of SiO2 were improved also because the reaction between surface adsorbate species was nearly complete. ALD SiO2 exhibited a higher dielectric constant than the bulk SiO2 did, from the metal-oxide-semiconductor capacitor, because of the incorporated hydroxyl groups in the film. Furthermore, the etching characteristics were modulated by changing the growth temperature to ensure that the film can be used as a hard mask for lithography. From the DFT calculation, high reaction energy between the BDIPADS and Si–OH was observed. Moreover, the Si–Si cleavage results in the existence additional reaction sites, such as amine group, allowing low-temperature growth and enhanced productivity. Therefore, the number of Si atoms in a molecule affects the growth rate and initial growth temperature to ensure that BDIPADS is a highly excellent precursor for the SiO2 deposition; therefore, its use can lead to a remarkably high productivity.

Cu-pillar/SnAg microbumps have been used for the latest 3-D through silicon via chip stacking. This microbumps flip-chip interconnection method can significantly further reduce the dimensions of the package and enhance the electrical performance by reducing interconnection path. As the pitch of the Cu-pillar/SnAg microbumps becomes extremely smaller, nonconductive films (NCFs) have recently been introduced to solve interconnection problems induced by the fine size microbumps. However, the applied pressure and heat during the thermo-compression (TC) bonding processes deform the SnAg solder and cause SnAg solder wetting on the sidewall of the Cu-pillar. The SnAg solder sidewall wetting causes rapid Sn consumption at the interface between the Cu-pillar and solder and decreases the joint gap heights of the SnAg solder joints. In this paper, the effects of the new double-layer NCFs (D-NCFs) were investigated for 40- $\mu \text{m}$ pitch chip-on-chip interconnection. The D-NCFs consisted of two NCF layers. The bottom NCF layer behaves as a conventional single NCF layer, and the top NCF layer, covering the Cu-pillar, prevents the movement of molten SnAg solder to the sidewall of Cu-pillar during the TC bonding process. As a result, the gap height of SnAg solder joints was doubled without SnAg solder sidewall wetting of Cu-pillar using the D-NCFs. SnAg solder joints using D-NCFs showed excellent reliability during thermal cycle tests up to 3000 cycles and pressure cooker test up to 72 h because of the significantly remaining Sn at the SnAg solder joint interface and increased joint gap height.

Nonconductive films (NCFs) have been introduced for 3-D through-silicon via chip stacking interconnection using reliable fine pitch Cu-pillar/Ni/SnAg microbumps. In this paper, four NCF materials with various elastic modulus and coefficient of thermal expansion (CTE) values were used to investigate the effect of the thermomechanical properties of the NCFs on the thermal cycle reliability of fine pitch Cu-pillar/Ni/SnAg/Cu-pad interconnections. The NCFs’ materials properties were adjusted by changing the ratio of epoxy resins and the curing accelerators. Compared with the borate curing accelerator, the use of the imidazole curing accelerator resulted in better thermomechanical properties on NCFs. And, NCFs containing higher ratio of solid epoxy resins showed higher elastic modulus and higher Tg values when using imidazole curing accelerator. After thermocompression bonding using four different types of NCFs, a thermal cycle reliability test (−40 °C–125 °C) was performed to investigate the effects of the NCFs’ thermomechanical properties on the reliability of Cu-pillar/Ni/SnAg/Cu-pad joints. Due to the CTE mismatch of chips and printed circuit board (PCB) substrates, the SnAg solder joint interconnections were damaged during the thermal cycling. Compared with the four types of NCFs, NCFs with higher elastic modulus at 30 °C showed better thermal cycle reliability. And among the NCFs with similar CTE values, those with higher Tg and higher elastic modulus at 30 °C value showed better thermal cycle reliability. In summary, the NCFs with lower CTE and higher elastic modulus at 30 °C were suitable for highly thermal cycle reliable Cu-pillar/Ni/SnAg/Cu-pad bump joints.

We investigated the characteristics of the total ozone column (TOC) around West Antarctica (near the Weddell Sea) compared with ambient meteorological factors. For this analysis, we used ground-based and satellite TOC measurements as well as meteorology (air temperature, potential vorticity and wind field) from reanalysis data. Long-term patterns of TOC show the large year-to-year variation (e.g., maximumly ∼200 DU at King Sejong) but a steady recovering trend recently. Despite a generally consistent pattern, the TOC around West Antarctica did not correlate well between high- and low-latitude regions during austral spring; this result implies that the ozone hole area had a spatial variation over West Antarctica. The TOC pattern around West Antarctica correlated well with air temperature but showed a vertical difference; high positive correlations appeared in the lower stratosphere (maximumly R > 0.9 at ∼50–100 hPa height) showing enhanced ozone depletion in colder conditions, but negative correlations appeared in the upper stratosphere (minimum R 0.9 at ∼500–600 K height) during the austral spring but a moderately negative correlation in the lower stratosphere (minimum R

The ground-based ozone observation instrument, Brewer spectrophotometer (Brewer), was used to evaluate the quality of the total ozone column (TOC) produced by multiple polar-orbit satellite measurements at three stations in Antarctica (King Sejong, Jang Bogo, and Zhongshan stations). While all satellite TOCs showed high correlations with Brewer TOCs (R = ~0.8 to 0.9), there are some TOC differences among satellite data in austral spring, which is mainly attributed to the bias of Atmospheric Infrared Sounder (AIRS) TOC. The quality of satellite TOCs is consistent between Level 2 and 3 data, implying that “which satellite TOC is used” can induce larger uncertainty than “which spatial resolution is used” for the investigation of the Antarctic TOC pattern. Additionally, the quality of satellite TOC is regionally different (e.g., OMI TOC is a little higher at the King Sejong station, but lower at the Zhongshan station than the Brewer TOC). Thus, it seems necessary to consider the difference of multiple satellite data for better assessing the spatiotemporal pattern of Antarctic TOC.

To test the previous hypothesis that upper Paleozoic sediments in the eastern Sino-Korean Block were mostly derived from the paleo-orogen located to the east, we compared published and new U&ndash, Pb age data of detrital zircons from Pennsylvanian strata distributed in the Sino-Korean Block (SKB). The age distributions of detrital zircons from different localities of Pennsylvanian strata in North China reflect varying contributions from the Inner Mongolia Paleo-uplift in the north and the Central China Orogenic Belt in the south. The supply of detritus from the northern source to distant areas, however, appears to have been limited during the Pennsylvanian times. The age distributions of detrital zircons from Korean Pennsylvanian strata located in the east of the SKB are characterized by a dense cluster of 1.84&ndash, 1.90 Ga and differ from those of North China. The Korean age characteristic is best explained by strong influences of the detritus derived from the Paleoproterozoic Yeongnam Massif in southeastern Korea. Along with the significant number of zircons that record syn- to near-depositional magmatic activities, this observation supports the hypothesis of the existence of an active continental margin setting in the east of the SKB.

In response to orogenic cycles, the ductile shear zone records a complex crustal deformation history. In this study, we conducted a microstructural analysis of two NW&ndash, SE trending ductile shear zones (Deokjeok Shear Zone (DSZ) and Soya Shear Zone (SSZ)) in the Late Triassic post-collisional granites along the western Gyeonggi Massif in the Korean Peninsula. The DSZ, overlain by the Late Triassic to the Early Jurassic post-collisional basin fill (Deokjeok Formation), has asymmetric microstructures indicative of a top-down-to-the-northeast shear. Depending on the structural position, the SSZ, which structurally overlies the Deokjeok Formation, exhibits two contrasting styles of deformation. The lower portion of the SSZ preserves evidence of top-up-to-the-southwest shearing after top-down-to-the-northeast shearing, on the other hand, the upper portion only indicates a top-up movement. Given the primary deformation mechanisms of both quartz and feldspar, the deformation temperatures of DSZ and SSZ were estimated at ~300&ndash, 350 &deg, C and ~350&ndash, 400 &deg, C, respectively, indicative of the mid-crustal condition. New zircon U-Pb isotopic ages from mylonitic granite in the SSZ and volcanic rocks in the Deokjeok Formation, combined with previously published geochronological data, indicate that the post-collisional granites and volcano-sedimentary sequence were nearly contemporaneous (ca. 223&ndash, 217 Ma) and juxtaposed because of the Late Triassic orogenic collapse and subsequent new orogenic event. In this study, we highlight the role of the extensional DSZ as a detachment propagated into the middle crust during the Late Triassic orogenic collapse. Our results report a deformational response to a transition from the collisional Songrim Orogeny to the subduction-related Daebo Orogeny in the western Gyeonggi Massif. This, in turn, provides essential insight into cyclic mountain building/collapse in the East Asian continental margin during the Mesozoic time.