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This study assesses the projected trajectory of Warm Arctic-Cold Continent (WACC) events in East Asia and North America through large ensemble simulation for the upcoming decades. It analyses the evolution of the geographical boundaries of threshold cold temperatures, revealing a significant northward shift as a sign of global warming's impact on the southward advancement of Arctic cold air. While validating the intensification of the WACC phenomenon until the 2020 s, echoing earlier studies, the findings indicate a marked decrease beginning in the 2030s. If warming is not curbed, this shift suggests a critical modification in the WACC pattern, prompting a re-evaluation of existing theories and models for extreme winter weather events. The results have major implications, spurring communities impacted by WACC to anticipate future changes and encouraging the climate forecasting community to update conceptual models for improved adaptation and mitigation approaches. [ABSTRACT FROM AUTHOR]

We present a comprehensive analysis diagnosing the primary factors driving the observed changes in major atmospheric teleconnection patterns in the Northern Hemisphere winter, including the Pacific North American pattern (PNA), North Atlantic Oscillation (NAO), and North American winter dipole (NAWD), with particular focus on their roles in shaping anomalous weather across North America. Our investigation reveals a consistent influence of the NAWD over seven decades, contrasting with fluctuating impacts from PNA and minor impacts from NAO. In particular, an emergent negative correlation between the NAWD and PNA, signaling a shifted phase of teleconnection patterns, is identified. Such a relationship change is traced to enhanced upper-level ridges across western North America, reflecting a reinforced winter stationary wave. Through attribution analysis, we identify greenhouse gas emissions as a probable driver for the northward drift of the Asia-Pacific jet core, which, aided by orographic lifting over the Alaskan Range, subsequently amplifies the winter stationary wave across western North America. This work emphasizes the pronounced effect of human-induced global warming on the structure and teleconnection of large-scale atmospheric circulation in the Northern Hemisphere winter, providing vital perspectives on the dynamics of current climate trends. [ABSTRACT FROM AUTHOR]

Metal halide perovskites (MHPs) have attracted considerable attentions as promising candidates for next-generation optoelectronic devices, such as light-emitting diode (LED), owing to their outstanding photophysical properties. Nanostructuring is considered an essential approach to facilitate the bright emission of MHPs, which entails an increase in the surface domain that can directly affect the carrier dynamics. However, a comprehensive understanding of the surface termination effect on the photodynamic properties of MHPs is still lacking. Herein, we systematically investigate the effect of surface termination on the carrier recombination dynamics of CsPbBr3 using ab-initio non-adiabatic molecular dynamics simulations. We found separate localizations of electron and hole carriers in the vicinity of the more and less coordinated inorganic polyhedral, respectively, which can be explained by the energy level changes associated with the modifications in Pb–Br bond lengths and their anharmonicity. This leads to the spatial separation of charge carriers, which retards the radiative kinetics more than the non-radiative one, reducing the photoluminescence quantum yield (PLQY). We further found that the homogenous linewidth is broadened upon introduction of surface terminations. Thus, our study suggests a possible LED-performance degradation mechanism due to surface termination, and thereby proposes guidelines for enhancing the light-emission properties of nanostructured MHPs. [ABSTRACT FROM AUTHOR]

The Global/Regional Integrated Model system (GRIMs) is upgraded to version 4.0, with the advancement of the moisture advection scheme and physics package, focusing on the global model program (GMP) for seasonal simulation and climate studies. Compared to the original version 3.1, which was frozen in 2013, the new version shows no Gibbs phenomenon in the moisture and tracer fields by implementing the semi-Lagrangian advection scheme with a better computational efficiency at higher resolution. The performance of the seasonal ensemble simulation (June–August 2017 and December 2016–February 2017) is significantly improved by new physics and ancillary data. The advancement is largest in the stratosphere, where the cold bias is dramatically reduced and the wind bias of the polar jets is alleviated, especially for the winter hemisphere. Noticeable improvements are also found in tropospheric zonal mean circulation, eddy transport, precipitation, and surface air temperature. This allows GRIMs version 4.0 to be used not only for long-term climate simulations, but also for subseasonal-to-seasonal climate prediction. [ABSTRACT FROM AUTHOR]

In recent decades, the interior regions of Eurasia and North America have experienced several unprecedentedly cold winters despite the global surface air temperature increases. One possible explanation of these increasing extreme cold winters comes from the so-called Warm Arctic Cold Continent (WACC) pattern, reflecting the effects of the amplified Arctic warming in driving the circulation change over surrounding continents. This study analyzed reanalysis data and model experiments forced by different levels of anthropogenic forcing. It is found that WACC exists on synoptic scales in observations, model's historical and even future runs. In the future, the analysis suggests a continued presence of WACC but with a slightly weakened cold extreme due to the overall warming. Warm Arctic events under the warmer climate will be associated with not only a colder continent in East Asia but also a warmer continent, depending on the teleconnection process that is also complicated by the warmer Arctic. Such an increasingly association suggests a reduction in potential predictability of the midlatitude winter anomalies. [ABSTRACT FROM AUTHOR]

Capacitors based on ABO3-type perovskite oxides show considerable promise for overcoming the limitations of nanoscale integration with dynamic random access memory (DRAM) devices. Among the thermodynamically stable perovskite oxides, titanates (ATiO3) exhibit high dielectric permittivity in metal–insulator–metal (MIM) configurations. However, their performance in mitigating the large leakage current caused by their narrow bandgap (3 eV) remain under scrutiny. Herein, substantially enhanced dielectric properties of an epitaxial SrRuO3/Ba0.5Sr0.5TiO3/SrRuO3 MIM capacitor with a thin dielectric layer (10 nm) are reported. The dielectric/electrode heterointerface was engineered to realize a capacitor with a low leakage current and high dielectric permittivity. A pit-free and stoichiometric SrRuO3 bottom electrode with an atomically smooth surface was exploited to suppress defect formation at the heterointerface. The critical roles of oxygen vacancies and substituted transition-metal atoms in determining the leakage current were assessed, and a strategy for reducing the leakage current via interface engineering was established. Consequently, a dielectric permittivity of 861 and a leakage current density of 5.15 × 10−6 A/cm2 at 1 V were obtained with the thinnest dielectric layer ever reported. Our work paves the way for the development of perovskite-oxide-based capacitors in next-generation DRAM memories. In this work, we demonstrated the critical roles of oxygen vacancies and substituted transition-metal atoms in determining the leakage current of epitaxial all-perovskite oxide capacitor, and established a strategy for reducing the leakage current via interface engineering. [ABSTRACT FROM AUTHOR]

Hydrogen (H) spillover in nonreducible oxides such as zeolites and Al2O3 has been a highly controversial phenomenon in heterogeneous catalysis. Since industrial catalysts are predominantly prepared using these materials as supports, it is important to understand the mechanism and catalytic functions of H spillover on their surfaces. In the past decade, fundamental studies on zeolite-encapsulated metal catalysts have revealed that H spillover and reverse spillover can be utilized in the design of hydrogenation and dehydrogenation catalysts with improved properties. Both experimental and theoretical studies have indicated that H spillover can occur in nonreducible oxides when they possess substantial acid sites that aid the surface migration of active H. In the present review, we will discuss the possible mechanisms of H spillover in nonreducible oxides and the unique opportunities of using this phenomenon for the design of advanced hydroprocessing catalysts. [ABSTRACT FROM AUTHOR]

The chalcogenides of platinum-group metals (PGMs) have been known to be present in minerals and the intermediate products of refining. Over recent years, their applications in various fields, including catalysis, have been explored. Given that certain PGM chalcogenides behave as compound semiconductors, they can be used as materials for photodetectors. In this study, RuS2, featuring a bandgap suitable for near-infrared photodetectors, was prepared by forming Ru on a SiO2/Si substrate via the atomic layer deposition method using [Ru(TMM)(CO)3] as the precursor. Annealing was conducted at 800 °C for 1 h under H2S flow. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis clearly confirmed that the as-deposited hexagonal close-packed (hcp) Ru transformed to cubic RuS2 after post-annealing. The surface morphologies, chemical states, and electrical and optical properties of RuS2 were investigated. The influence of the metallic Ru surface morphology prior to sulfurization on the reaction between Ru and H2S was also discussed. To evaluate the potential of using RuS2 as a photodetector, a photodetector was fabricated by forming electrodes on RuS2 to measure its photocurrent under near-infrared light. Thus, RuS2 was proven to exhibit a short response time (59 μs) and generate a photocurrent of 84 nA under near-infrared light at 940 nm. [ABSTRACT FROM AUTHOR]

Dye arrays from dimers up to larger oligomers constitute the functional units of natural light harvesting systems as well as organic photonic and photovoltaic materials. Whilst in the past decades many photophysical studies were devoted to molecular dimers for deriving structure-property relationship to unravel the design principles for ideal optoelectronic materials, they fail to accomplish the subsequent processes of charge carrier generation or the detachment of two triplet species in singlet fission (SF). Here, we present a slip-stacked perylene bisimide trimer, which constitutes a bridge between hitherto studied dimer and solid-state materials, to investigate SF mechanisms. This work showcases multiple pathways towards the multiexciton state through direct or excimer-mediated mechanisms by depending upon interchromophoric interaction. These results suggest the comprehensive role of the exciton coupling, exciton delocalization, and excimer state to facilitate the SF process. In this regard, our observations expand the fundamental understanding the structure-property relationship in dye arrays. Understanding structure-property relationship of dye arrays is of great importance for designing organic photonic and photovoltaic materials. Here, authors present a slip-stacked perylene bisimide array as a model system to investigate singlet fission mechanisms by depending upon interchromophoric interaction. [ABSTRACT FROM AUTHOR]

Droughts that exceed the magnitudes of historical variation ranges could occur increasingly frequently under future climate conditions. However, the time of the emergence of unprecedented drought conditions under climate change has rarely been examined. Here, using multimodel hydrological simulations, we investigate the changes in the frequency of hydrological drought (defined as abnormally low river discharge) under high and low greenhouse gas concentration scenarios and existing water resource management measures and estimate the time of the first emergence of unprecedented regional drought conditions centered on the low-flow season. The times are detected for several subcontinental-scale regions, and three regions, namely, Southwestern South America, Mediterranean Europe, and Northern Africa, exhibit particularly robust results under the high-emission scenario. These three regions are expected to confront unprecedented conditions within the next 30 years with a high likelihood regardless of the emission scenarios. In addition, the results obtained herein demonstrate the benefits of the lower-emission pathway in reducing the likelihood of emergence. The Paris Agreement goals are shown to be effective in reducing the likelihood to the unlikely level in most regions. However, appropriate and prior adaptation measures are considered indispensable when facing unprecedented drought conditions. The results of this study underscore the importance of improving drought preparedness within the considered time horizons. Significant regional disparities exist in the time left to prepare for unprecedented drought and how much we can buy time depending on climate scenarios. Specific regions pass this timing by the middle of 21st century even with stringent mitigation. [ABSTRACT FROM AUTHOR]

This paper proposes a traffic monitoring system that detects, tracks, and classifies multiple vehicles on the road in real time using various digital image processing techniques and the process of machine learning based on a convolutional neural network (CNN). With this system, a video camera is installed on the road, and calibration is used to obtain the projection equation of the actual road on the image plane. Several image processing techniques, such as background modeling, background extraction, edge detection, and object tracking, are used to develop and implement a prototype system. The proposed system also uses a transfer learning process that is more efficient than starting CNN from scratch. This maximizes training efficiency and increases prediction accuracy in vehicle classification. Preliminary experimental results demonstrate that multiple vehicle tracking and classification are possible while calculating vehicle speed. The ultimate goal of this study is to develop a single digital video camera system with embedded machine learning process that can monitor and distinguish multiple vehicles simultaneously in multiple lanes. [ABSTRACT FROM AUTHOR]

Future projections of global mean precipitation change (ΔP) based on Earth-system models have larger uncertainties than projections of global mean temperature changes (ΔT)1. Although many observational constraints on ΔT have been proposed, constraints on ΔP have not been well studied2–5 and are often complicated by the large influence of aerosols on precipitation4. Here we show that the upper bound (95th percentile) of ΔP (2051–2100 minus 1851–1900, percentage of the 1980–2014 mean) is lowered from 6.2 per cent to 5.2–5.7 per cent (minimum–maximum range of sensitivity analyses) under a medium greenhouse gas concentration scenario. Our results come from the Coupled Model Intercomparison Project phase 5 and phase 6 ensembles6–8, in which ΔP for 2051–2100 is well correlated with the global mean temperature trends during recent decades after 1980 when global anthropogenic aerosol emissions were nearly constant. ΔP is also significantly correlated with the recent past trends in precipitation when we exclude the tropical land areas with few rain-gauge observations. On the basis of these significant correlations and observed trends, the variance of ΔP is reduced by 8–30 per cent. The observationally constrained ranges of ΔP should provide further reliable information for impact assessments.Model simulations show that the historical relationship between global temperature and precipitation under a medium greenhouse gas concentration scenario lowers the projected high end of future precipitation change. [ABSTRACT FROM AUTHOR]

To design electrochemical interfaces for efficient electric-chemical energy interconversion, it is critical to reveal the electric double layer (EDL) structure and relate it with electrochemical activity; nonetheless, this has been a long-standing challenge. Of particular, no molecular-level theories have fully explained the characteristic two peaks arising in the potential-dependence of the EDL capacitance, which is sensitively dependent on the EDL structure. We herein demonstrate that our first-principles-based molecular simulation reproduces the experimental capacitance peaks. The origin of two peaks emerging at anodic and cathodic potentials is unveiled to be an electrosorption of ions and a structural phase transition, respectively. We further find a cation complexation gradually modifies the EDL structure and the field strength, which linearly scales the carbon dioxide reduction activity. This study deciphers the complex structural response of the EDL and highlights its catalytic importance, which bridges the mechanistic gap between the EDL structure and electrocatalysis. The structure of the electric double layer (EDL) has been a long-standing question since the 19th century. Here, the authors simulate EDL structures and highlight their importance in catalysis through comparison of atomic simulations and experiment. [ABSTRACT FROM AUTHOR]

Highlights: A three single-phase Cu, Cu2O, and CuO monolithic nanowire network was successfully fabricated by reversible selective laser-induced redox (rSLIR) Monolithic metal–semiconductor–metal multispectral photodetectors with Cu nanowire (CuNW) as an electrode and Cu2ONW/CuONW having different bandgaps were suggested.Active electronics are usually composed of semiconductor and metal electrodes which are connected by multiple vacuum deposition steps and photolithography patterning. However, the presence of interface of dissimilar material between semiconductor and metal electrode makes various problems in electrical contacts and mechanical failure. The ideal electronics should not have defective interfaces of dissimilar materials. In this study, we developed a novel method to fabricate active electronic components in a monolithic seamless fashion where both metal and semiconductor can be prepared from the same monolith material without creating a semiconductor–metal interface by reversible selective laser-induced redox (rSLIR) method. Furthermore, rSLIR can control the oxidation state of transition metal (Cu) to yield semiconductors with two different bandgap states (Cu2O and CuO with bandgaps of 2.1 and 1.2 eV, respectively), which may allow multifunctional sensors with multiple bandgaps from the same materials. This novel method enables the seamless integration of single-phase Cu, Cu2O, and CuO, simultaneously while allowing reversible, selective conversion between oxidation states by simply shining laser light. Moreover, we fabricated a flexible monolithic metal–semiconductor–metal multispectral photodetector that can detect multiple wavelengths. The unique monolithic characteristics of rSLIR process can provide next-generation electronics fabrication method overcoming the limitation of conventional photolithography methods. [ABSTRACT FROM AUTHOR]

In CO2 transformation catalysis, the synthesis of cyclic carbonates using two classes of MOF catalysts viz., zeolitic imidazolate frameworks (ZIF) and MOFs with carboxylate-capped SBUs have gained large attention. Herein we propose the strategy of employing a unified multifunctional framework formed in the metal-centered assembly of imidazole and amino-carboxylates for CO2 transformation, such as propylene carbonate (PC) by the cycloaddition of CO2 with propylene oxide. The framework {[Cu(L-asp)(1,4-bix)0.5]·3H2O}n (CuAspBix) comprises of the amino acid building units, L-aspartic acid (L-Asp) and the flexible ligand, 1,4-bis(imidazole-1-yl methyl)benzene [1,4-Bix]. The 1,4-Bix ligand with imidazole terminals renders elongated M-M distances and flexibility in comparison with pristine ZIF materials. The cumbersome synthesis procedure poor phase purity of the bulk catalyst in solvothermal conditions were improved by a microwave-assisted synthesis, preserving the structural and physicochemical properties. Minimal energy input or room temperatures for the catalysis occurred via the synergistic participation of CuAspBix and quaternary ammonium bromide salt, demonstrated by density-functional theory computational studies to propose mechanistic pathway of the reaction. Reaction conditions were optimized by altering the parameters. The heterogeneous catalyst was reused four times without a significant change in activity. [ABSTRACT FROM AUTHOR]

Three-dimensional amino acid backbone Cu-aspartate metal organic frameworks {[Cu(l-asp)(1,4-bpy)0.5].H2O}n (CuAspBpy) were prepared from copper salt, l-aspartic acid linker, and 4,4′-bipyridyl cross-linker by solvothermal and microwave methods. The synthesized CuAspBpy was characterized and used as a catalyst for the synthesis of propylene carbonate (PC) by the cycloaddition of CO2 with propylene oxide (PO). An efficient catalytic process for PC synthesis was developed via the synergistic role of CuAspBpy and the quaternary ammonium bromide co-catalyst. Computational studies based on density-functional theory (DFT) were utilized to propose a mechanistic pathway for the reaction. The heterogeneous catalyst was reused four times without any considerable loss in the activity. [ABSTRACT FROM AUTHOR]

Electrocatalytic conversion of nitrogen oxides to value-added chemicals is a promising strategy for mitigating the human-caused unbalance of the global nitrogen-cycle, but controlling product selectivity remains a great challenge. Here we show iron–nitrogen-doped carbon as an efficient and durable electrocatalyst for selective nitric oxide reduction into hydroxylamine. Using in operando spectroscopic techniques, the catalytic site is identified as isolated ferrous moieties, at which the rate for hydroxylamine production increases in a super-Nernstian way upon pH decrease. Computational multiscale modelling attributes the origin of unconventional pH dependence to the redox active (non-innocent) property of NO. This makes the rate-limiting NO adsorbate state more sensitive to surface charge which varies with the pH-dependent overpotential. Guided by these fundamental insights, we achieve a Faradaic efficiency of 71% and an unprecedented production rate of 215 μmol cm−2 h−1 at a short-circuit mode in a flow-type fuel cell without significant catalytic deactivation over 50 h operation. Electrocatalytic conversion of nitrogen oxides to value-added chemicals is a promising strategy for mitigating the imbalance in the global nitrogen cycle. Here, the authors present iron–nitrogen-doped carbon as an efficient and durable electrocatalyst for selective nitric oxide reduction to hydroxylamine. [ABSTRACT FROM AUTHOR]

Neural network constitutive models (NNCMs) for crystal structures are proposed based on computationally generated high-fidelity data. Stress, and tangent modulus data are generated under various strain states using empirical potentials and first-principles calculations. Strain–stress artificial neural network and strain-tangent modulus ANN are constructed. The symmetry conditions are considered for cubic, tetragonal, and hexagonal structures. The NNCMs of six face-centered cubic materials (Cu, Ni, Pd, Pt, Ag, and Au), two diamond cubic materials (Si, Ge), two tetragonal crystal materials (TiO2, ZnO), and two hexagonal crystal materials (ZnO, GaN) are constructed and tested under the untrained strain state. In particular, the performance of NNCM for cubic structure is better compared with that of the classical model. The suggested NNCM can be embedded into a nonlinear finite element method, and numerical examples are performed to verify the proposed NNCM. [ABSTRACT FROM AUTHOR]

High-valent metal-oxo moieties have been implicated as key intermediates preceding various oxidation processes. The critical O–O bond formation step in the Kok cycle that is presumed to generate molecular oxygen occurs through the high-valent Mn-oxo species of the water oxidation complex, i.e., the Mn4Ca cluster in photosystem II. Here, we report the spectroscopic characterization of new intermediates during the water oxidation reaction of manganese-based heterogeneous catalysts and assign them as low-spin Mn(IV)-oxo species. Recently, the effects of the spin state in transition metal catalysts on catalytic reactivity have been intensely studied; however, no detailed characterization of a low-spin Mn(IV)-oxo intermediate species currently exists. We demonstrate that a low-spin configuration of Mn(IV), S = 1/2, is stably present in a heterogeneous electrocatalyst of Ni-doped monodisperse 10-nm Mn3O4 nanoparticles via oxo-ligand field engineering. An unprecedented signal (g = 1.83) is found to evolve in the electron paramagnetic resonance spectrum during the stepwise transition from the Jahn–Teller-distorted Mn(III). In-situ Raman analysis directly provides the evidence for Mn(IV)-oxo species as the active intermediate species. Computational analysis confirmed that the substituted nickel species induces the formation of a z-axis-compressed octahedral C4v crystal field that stabilizes the low-spin Mn(IV)-oxo intermediates. Understanding reaction intermediates provides a foundation for active electrocatalysts' design, but it remains elusive for heterogeneous electrocatalysts. Here, the authors report the spectroscopic characterization of low-spin Mn(IV)-oxo as the active intermediates during electrochemical water oxidation. [ABSTRACT FROM AUTHOR]

In order to increase the exhaust-gas temperature of austenitic stainless cast steels used for turbo-charger-housings up to 1050 °C, the more excellent high-temperature strength should be obtained because it works for keeping a sustainability of the housing shape. Three austenitic stainless cast steels were fabricated in this study by adding Nb into the Ni/Mn-replaced conventional ASTM HK40 steel, and their high-temperature strength was investigated in relation with the carbide formation and matrix strengthening. The 1-wt%-Nb-added steel showed the enhancement in high-temperature strength over the non-Nb-added steel. This indicated that the Nb addition was effective on the strength improvement because it raised both the fraction of thermally-stable hard MC-type carbides and the austenite-matrix hardness. However, the 1.5-wt%-Nb-added steel showed the lower high-temperature strength than the 1-wt%-Nb-added steel, although it contained the more MC carbides. The more MC carbides reduced the matrix hardness, enlarged the hardness difference between carbides and matrix, and deteriorated the high-temperature strength. Our results demonstrate that the strengthened matrix as well as populated carbides due to the Nb addition are desirable for further improving the high-temperature strength. [ABSTRACT FROM AUTHOR]

We report the hydrogen barrier performance of sputtered La2O3 thin films for the device stability of amorphous indium–gallium–zinc–oxide (a-IGZO) thin-film transistors (TFTs). Hydrogen acts as a shallow donor in a-IGZO films, which makes TFTs conductive, resulting in degradation of their on/off properties. Since hydrogen can be easily incorporated by external environments or post-processing, an appropriate hydrogen barrier is essential for enhancing device stability. La2O3, with its extreme electronegativity, can provide excellent hygroscopic characteristics. Because hydrogen exists in the form of –OH groups inside a-IGZO films, La2O3 is expected to be a promising barrier material for preventing hydrogen incorporation. Therefore, we investigate the growth characteristics of sputtered La2O3 thin films as hydrogen barrier layers, focusing on variations in growth rate, refractive index, and film stress, which depend on various process parameters, such as radio-frequency (RF) power, O2 partial pressure, and substrate temperature during reactive magnetron sputtering. The effects of these parameters on hydrogen barrier properties are systematically investigated and correlated with the microstructures of La2O3 films. The results demonstrate that La2O3 films grown with low RF power and low O2 partial pressure have an amorphous phase and provide excellent hydrogen barrier performance. We anticipate that these experimental results will help improve the environmental stability of a-IGZO TFTs. [ABSTRACT FROM AUTHOR]

High-Ni austenitic cast steels were fabricated by replacing the expensive Ni content by inexpensive Mn in a commercial DIN 1.4849 steel (0.4C-2.0Mn-1.5Si-20Cr-38Ni-1.5Nb (wt pct)), and their high-temperature tensile properties were enhanced by controlling the volume fraction and distribution of carbides. The 14-pct-Ni-containing steel showed the highest total fraction and most homogeneous distribution of carbides due to the smallest cell size, which played a role in improving high-temperature properties far better than those of the DIN 1.4849 steel. [ABSTRACT FROM AUTHOR]

For maintaining high-performance turbo-charger housings at higher exhaust-gas temperatures, e.g., 1050 °C, a high-Ni(20 wt%)-containing austenitic steel (ASTM HK40 steel) has been actively modified. As a promising method, the solid-solution hardening obtained from the V or Cu addition was utilized in this study. Five austenitic cast steels were made by adding V or Cu in the modified HK40 steel (N16 steel; 4%-Ni replacement by 4.6%-Mn), and the high-temperature property improvement was explained by detailed microstructural evolutions coupled with thermodynamically calculated phase diagrams. The V- or Cu-added steels showed improvements in high-temperature properties over the N16 steel because the addition of V or Cu raised both austenite matrix hardness and volume fraction of M7C3 carbide. Considering that only 3.6-4.8 vol% of M7C3 was present in the five austenitic cast steels, the strengths were affected more by the matrix hardness. When the V or Cu content was quite high, however, the ferrite or Cu-coring is formed, thereby leading to the serious deterioration of high-temperature properties. The V- or Cu-added steels within proper contents are applicable well to automotive turbo-charger housings requiring or emphasizing high-temperature tensile properties. [ABSTRACT FROM AUTHOR]

Enhancing the dielectric constant (k) of conventional gate dielectric materials such as HfO2 and ZrO2 is one of the important requirements for further scaling down of devices in future years. One promising approach for achieving this is to incorporate a specific element in the high-k host material for stabilizing a particular higher-k crystalline phase. Although Ge has been theoretically suggested as a stabilizer for ZrO2, there are no experimental studies correlating the structure of ZrO2 films fabricated by atomic layer deposition (ALD) with their electrical properties. In this work, we systematically investigated the structural and electrical properties of Ge-doped ZrO2 films prepared by ALD. We used germanium butoxide (Ge(OnBu)4) and Zr tris(dimethylamino)cyclopentadienyl zirconium as the Ge and Zr precursors, respectively, with O3 as a reactant. We controlled the ALD cycle ratio using a supercycle process (GeO2/ZrO2 = 1:128, 1:64, 1:32, 1:16, 1:8, 1:4, and 1:2) to produce the alloy films. Electrical properties of these samples were evaluated by measuring the electrical characteristics of metal-oxide-semiconductor (MOS) capacitors based on them, and the results are discussed together with crystallographic analysis. The results revealed that Ge incorporation into ZrO2 induced the stabilization of the cubic/tetragonal phase of the ZrO2 film at low temperatures and improved its dielectric properties. Consequently, this is a systematic and facile method to optimize the dielectric properties of Ge-doped ZrO2 prepared by varying the ALD cycle ratio, and these films could be applied in future nanoscale devices. [ABSTRACT FROM AUTHOR]

We investigate the energetics involved in the 101¯21¯011 tension and 101¯11¯012 compression twinning deformation processes in magnesium via first-principles studies. Through identification of structural changes associated with each deformation process, we study the energetics of each deformation process and the local instability in the twin boundary region. We observe that the energy barrier in the 101¯11¯012 compression twinning deformation pathway is higher than that in the 101¯21¯011 tension twinning deformation pathway, even though the 101¯1 compression twin boundary is more stable than the 101¯2 tension twin boundary. We extend our study to examine the effects of Y and Li as alloying elements on each twinning deformation process. Our calculations predict that the addition of Y causes a reduction in the probability of fracture by an order of magnitude when the twinning deformation occurs and weakening of the resistivity to twinning deformation. However, the effect of Li addition on the twinning deformations is weaker than that of Y addition. [ABSTRACT FROM AUTHOR]

A novel, rational, and efficient way to explore high-performance electrocatalysts was developed by controlling the reaction kinetics of the rate-determining step (RDS). Density functional theory (DFT) calculations demonstrate that the RDS for the oxygen evolution reaction driven by transition metal hydroxides/oxides, i.e., surface adsorption of OH−/OOH• species, can be significantly promoted by increasing the electrophilicity of electrocatalysts via hybridization with electron-withdrawing inorganic nanosheets. As predicted by DFT calculation, the hybridization of Ni-Fe-layered double hydroxide (LDH)/Ni-Co-LDH, with RuO2 nanosheets (1.0 wt%) leads to significant lowering of the overpotentials to 207/276 mV at 10 mA cm−2, i.e., one of the smallest overpotentials for LDH-based materials, with the increase in the current density. The necessity of a very small amount of RuO2 nanosheets (1.0 wt%) to optimize the electrocatalyst activity highlights the remarkably high efficiency of the RuO2 addition. The present study underscores the importance of kinetic control of the RDS via hybridization with electron-withdrawing species for exploring novel efficient electrocatalysts. Platinum and other precious metals currently used in fuel cells may ultimately be replaced by nanostructured catalysts designed with the help of computers. Catalysts are essential for speeding up the oxygen evolution reaction in fuel cells, a normally slow extraction of electrons and protons from water molecules. A team led by Hyungjun Kim from the Korea Advanced Institute of Science and Technology in Daejon and Seong-Ju Hwang from Ewha Womans University in Seoul have now used computer simulations to optimize inexpensive oxygen evolution catalysts made from transition metal hydroxides. Their calculations predicted that these normally multilayered catalysts could split water faster if exfoliated into individual sheets and attached to a ruthenium nanostructure. Fabrication of these materials revealed they had significantly higher active surface areas and improved energy efficiency compared to typical metal hydroxide catalysts. A rational way to explore economically feasible high-performance electrocatalyst for OER is developed by improving the reaction kinetics of rate-determining step via the hybridization with electron-withdrawing RuO2 nanosheet. Even with very low RuO2 content, self-assembled Ni-Fe-/Ni-Co-layered double hydroxide (LDH)-RuO2 nanohybrids show very small overpotentials of 207/276 mV at 10 mA cm−2 for oxygen evolution reaction with greatly improved current densities. [ABSTRACT FROM AUTHOR]

The improved electrical properties of Cu-gate thin-film transistors (TFTs) using an ink-synthesizing process were studied; this technology enables a low-cost and large area process for the display industry. We investigated the film properties and the effects of the ink-synthesized Cu layer in detail with respect to device characteristics. The mobility and reliability of the devices were significantly improved by applying a diffusion barrier at the interface between the Cu gate and the gate insulator. By using a TaN diffusion barrier layer, considerably improved and stabilized ink-Cu gated TFTs could be realized, comparable to sputtered-Cu gated TFTs under positive bias temperature stress measurements. [ABSTRACT FROM AUTHOR]

The deposition of high-quality SiO films has been achieved through the use of both plasma-enhanced chemical vapor deposition (PE-CVD) and plasma-enhanced atomic layer deposition (PE-ALD) methods using HSi[N(CH)] as a Si precursor. We systematically investigated growth characteristics, chemical compositions, and electrical properties of PE-CVD SiO prepared under various deposition conditions. The SiO films prepared using PE-CVD showed high purity and good stoichiometry with a dielectric constant of ~4. In addition, the PE-ALD process of the SiO films exhibited well-saturated and almost linear growth characteristics of ~1.3 Å cycle without notable incubation cycles, producing pure SiO films. Electrical characterization of metal-oxide silicon capacitor structures prepared with each SiO film showed that PE-ALD SiO films had relatively lower leakage currents than PE-CVD SiO films. This might be a result of the saturated surface reaction mechanism of PE-ALD, which allows a smooth surface in comparison with PE-CVD method. In addition, the dielectric properties of both SiO films were further evaluated in the structures of In-Ga-Zn-O thin-film transistors, and they both showed good device performances in terms of high I − I ratios (>10) and low off-currents (<10 A). However, based on the negative bias stress reliability test, it was found that PE-ALD SiO showed better reliability against a negative V shift than PE-CVD SiO, which might also be understood from its smoother channel/insulator interface generation at the interface. [ABSTRACT FROM AUTHOR]

A highly efficient n-Si/ p-CuO core-shell (C-S) nanowire (NW) photodiode was fabricated using CuO grown by atomic layer deposition (ALD) on a well-ordered Si NW array. Ordered Si nanowires arrays were fabricated by nano-sphere lithography to pattern metal catalysts for the metal-assisted etching of silicon, resulting in a Si NW arrays with a good arrangement, smooth surface and small diameter distribution. The ALD-CuO thin films were grown using a new non-fluorinated Cu precursor, bis(1-dimethylamino-2-methyl-2-butoxy)copper (CHNOCu), and water vapor (HO) at 140°C. Transmission electron microscopy equipped with an energy dispersive spectrometer confirmed that p-CuO thin films had been coated over arrayed Si NWs with a diameter of 150 nm (aspect ratio of ∼7.6). The C-S NW photodiode exhibited more sensitive photodetection performance under ultraviolet illumination as well as an enhanced photocurrent density in the forward biasing region than the planar structure diode. The superior performance of C-S NWs photodiode was explained by the lower reflectance of light and the effective carrier separation and collection originating from the C-S NWs structure. [ABSTRACT FROM AUTHOR]

A warmer climate would increase the risk of floods. So far, only a few studies have projected changes in floods on a global scale. None of these studies relied on multiple climate models. A few global studies have started to estimate the exposure to flooding (population in potential inundation areas) as a proxy of risk, but none of them has estimated it in a warmer future climate. Here we present global flood risk for the end of this century based on the outputs of 11 climate models. A state-of-the-art global river routing model with an inundation scheme was employed to compute river discharge and inundation area. An ensemble of projections under a new high-concentration scenario demonstrates a large increase in flood frequency in Southeast Asia, Peninsular India, eastern Africa and the northern half of the Andes, with small uncertainty in the direction of change. In certain areas of the world, however, flood frequency is projected to decrease. Another larger ensemble of projections under four new concentration scenarios reveals that the global exposure to floods would increase depending on the degree of warming, but interannual variability of the exposure may imply the necessity of adaptation before significant warming. [ABSTRACT FROM AUTHOR]