Enhanced magnetic and thermoelectric properties in epitaxial polycrystalline SrRuO3 thin film

Transition metal oxide thin films show versatile electrical, magnetic, and thermal properties which can be tailored by deliberately introducing macroscopic grain boundaries via polycrystalline solids. In this study, we focus on the modification of the magnetic and thermal transport properties by fabricating single- and polycrystalline epitaxial SrRuO3 thin films using pulsed laser epitaxy. Using epitaxial stabilization technique with atomically flat polycrystalline SrTiO3 substrate, epitaxial polycrystalline SrRuO3 thin film with crystalline quality of each grain comparable to that of single-crystalline counterpart is realized. In particular, alleviated compressive strain near the grain boundaries due to coalescence is evidenced structurally, which induced enhancement of ferromagnetic ordering of the polycrystalline epitaxial thin film. The structural variations associated with the grain boundaries further reduce the thermal conductivity without deteriorating the electronic transport, and lead to enhanced thermoelectric efficiency in the epitaxial polycrystalline thin films, compared with their single-crystalline counterpart.Comment: 24 pages, 5 figure

Enhanced magnetic and thermoelectric properties in epitaxial polycrystalline SrRuO3 thin film

Transition metal oxide thin films show versatile electrical, magnetic, and thermal properties which can be tailored by deliberately introducing macroscopic grain boundaries via polycrystalline solids. In this study, we focus on the modification of the magnetic and thermal transport properties by fabricating single- and polycrystalline epitaxial SrRuO3 thin films using pulsed laser epitaxy. Using epitaxial stabilization technique with atomically flat polycrystalline SrTiO3 substrate, epitaxial polycrystalline SrRuO3 thin film with crystalline quality of each grain comparable to that of single-crystalline counterpart is realized. In particular, alleviated compressive strain near the grain boundaries due to coalescence is evidenced structurally, which induced enhancement of ferromagnetic ordering of the polycrystalline epitaxial thin film. The structural variations associated with the grain boundaries further reduce the thermal conductivity without deteriorating the electronic transport, and lead to enhanced thermoelectric efficiency in the epitaxial polycrystalline thin films, compared with their single-crystalline counterpart.Comment: 24 pages, 5 figure

Age- and cause-specific contributions to increase in life expectancy at birth in Korea, 2000–2019: a descriptive study

Abstract Background Korea’s life expectancy at birth has consistently increased in the 21st century. This study compared the age and cause-specific contribution to the increase in life expectancy at birth in Korea before and after 2010. Methods The population and death numbers by year, sex, 5-year age group, and cause of death from 2000 to 2019 were acquired. Life expectancy at birth was calculated using an abridged life table by sex and year. The annual age-standardized and age-specific mortality by cause of death was also estimated. Lastly, the age and cause-specific contribution to the increase in life expectancy at birth in the two periods were compared using a stepwise replacement algorithm. Results Life expectancy at birth in Korea increased consistently from 2010 to 2019, though slightly slower than from 2000 to 2009. The cause-specific mortality and life expectancy decomposition analysis showed a significant decrease in mortality in chronic diseases, such as neoplasms and diseases of the circulatory system, in the middle and old-aged groups. External causes, such as transport injuries and suicide, mortality in younger age groups also increased life expectancy. However, mortality from diseases of the respiratory system increased in the very old age group during 2010–2019. Conclusions Life expectancy at birth in Korea continued to increase mainly due to decreased mortality from chronic diseases and external causes during the study period. However, the aging of the population structure increased vulnerability to respiratory diseases. The factors behind the higher death rate from respiratory disease should be studied in the future

Fourth-order partial differential equations for effective image denoising

This article concerns mathematical image denoising methods incorporating fourth-order partial differential equations (PDEs). We introduce and analyze piecewise planarity conditions (PPCs) with which unconstrained fourth-order variational models in continuum converge to a piecewise planar image. It has been observed that fourth-order variational models holding PPCs can restore better images than models without PPCs and second-order models. Numerical schemes are presented in detail and various examples in image denoising are provided to verify the claim

A non-convex diffusion model for simultaneous image denoising and edge enhancement

Mathematical restoration models, in particular, total variation-based models can easily lose fine structures during image denoising. In order to overcome the drawback, this article introduces two strategies: the non-convex (NC) diffusion and the texture-free residual (TFR) parameterization. A non-standard numerical procedure is suggested and its stability is analyzed to effectively solve the NC diffusion model which is mathematically unstable. It has been numerically verified that the resulting algorithm incorporating the NC diffusion and TFR parameterization is able to not only reduce the noise satisfactorily but also enhance edges effectively, at the same time

Additional file 1 of Age- and cause-specific contributions to increase in life expectancy at birth in Korea, 2000–2019: a descriptive study

Supplementary Material 1: Supplementary Fig. 1. Life expectancy change by sex in Korea, 2000-2019: Findings from Korea Statistical Information Service (KOSIS). Supplementary Fig. 2. Trends in age-standardized cause-specific mortality by sex during the study period: Findings from the Korean Statistical Information Service (KOSIS

An Improved Alternating-Direction Method For a Viscous Wave Equation

We introduce an accurate and efficient alternating-direction method for solving a viscous wave equation which is based on a three-level, second-order correct implicit algorithm and which has a splitting error not significantly larger than the truncation error of the base method

Oligomerization of Butene Mixture over NiO/Mesoporous Aluminosilicate Catalyst

This study is aimed at preparing C8–C16 alkene through oligomerization of a butene mixture using nickel oxide supported on mesoporous aluminosilicate. Mesoporous aluminosilicate with an ordered structure was successfully synthesized from HZSM-5 zeolite by combining a top-down and a bottom-up method. MMZZSM-5 catalyst showed much higher butene conversion and C8–C16 yield in the butene oligomerization reaction than those with HZSM-5. This is attributed to the pore geometry of MMZZSM-5, which is more beneficial for internal diffusion of reactants, reaction intermediates, and products. The ordered channel-like mesopores were maintained after the nickel-loading on MMZZSM-5. The yield for C8–C16 hydrocarbons over NiO/MMZZSM-5 was higher than that of MMZZSM-5 catalyst, which seemed to be due to higher acid strength from a higher ratio of Lewis acid to Brønsted acid. The present study reveals that a mesoporous NiO/MMZZSM-5 catalyst with a large amount of Lewis acid sites is one of the potential catalysts for efficient generation of aviation fuel through the butene oligomerization

Boundary Engineering for the Thermoelectric Performance of Bulk Alloys Based on Bismuth Telluride

Thermoelectrics, which transports heat for refrigeration or converts heat into electricity directly, is a key technology for renewable energy harvesting and solid-state refrigeration. Despite its importance, the widespread use of thermoelectric devices is constrained because of the low efficiency of thermoelectric bulk alloys. However, boundary engineering has been demonstrated as one of the most effective ways to enhance the thermoelectric performance of conventional thermoelectric materials such as Bi2Te3, PbTe, and SiGe alloys because their thermal and electronic transport properties can be manipulated separately by this approach. We review our recent progress on the enhancement of the thermoelectric figure of merit through boundary engineering together with the processing technologies for boundary engineering developed most recently using Bi2Te3-based bulk alloys. A brief discussion of the principles and current status of boundary-engineered bulk alloys for the enhancement of the thermoelectric figure of merit is presented. We focus mainly on (1) the reduction of the thermal conductivity by grain boundary engineering and (2) the reduction of thermal conductivity without deterioration of the electrical conductivity by phase boundary engineering. We also discuss the next potential approach using two boundary engineering strategies for a breakthrough in the area of bulk thermoelectric alloys. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim120221sciescopu