Dongyun Lee

Bio: Dongyun Lee is an academic researcher from Pusan National University. The author has contributed to research in topics: Thin film & Nanoindentation. The author has an hindex of 25, co-authored 106 publications receiving 2080 citations. Previous affiliations of Dongyun Lee include Korea Institute of Science and Technology & Oak Ridge National Laboratory.

Microstructure and local brittle zone phenomena in high-strength low-alloy steel welds

Abstract: This study is concerned with a correlation between the microstructure and the local brittle zone (LBZ) phenomena in high-strength low-alloy (HSLA) steel welds The influence of the LBZ on toughness was investigated by means of simulated heat-affected zone (HAZ) tests as well as welded joint tests Micromechanical processes involved in microvoid and cleavage microcrack formation were also identified using notched round tensile tests and subsequent scanning electron microscopy (SEM) analyses The LBZ in the HAZ of a mUltipass welded joint is the intercritically reheated coarse-grained HAZ whose properties are strongly influenced by metallurgical factors such as an effective grain size and high-carbon martensitic islands: The experimental results indicated that Charpy energy was found to decrease monotonically with increasing the amount of martensitic islands, confirming that the martensitic island is the major microstructural factor controlling the HAZ toughness In addition, microvoids and microcracks were found to initiate at the interface between the martensitic island and the ferrite matrix, thereby causing the reduction in toughness These findings suggest that the LBZ phenomena in the coarse-grained HAZ can be explained by the morphology and the amount of martensitic islands

Piezoelectric two-dimensional nanosheets/anionic layer heterojunction for efficient direct current power generation.

Abstract: Direct current (DC) piezoelectric power generator is promising for the miniaturization of a power package and self-powering of nanorobots and body-implanted devices. Hence, we report the first use of two-dimensional (2D) zinc oxide (ZnO) nanostructure and an anionic nanoclay layer to generate piezoelectric DC output power. The device, made from 2D nanosheets and an anionic nanoclay layer heterojunction, has potential to be the smallest size power package, and could be used to charge wireless nano/micro scale systems without the use of rectifier circuits to convert alternating current into DC to store the generated power. The combined effect of buckling behaviour of the ZnO nanosheets, a self-formed anionic nanoclay layer, and coupled semiconducting and piezoelectric properties of ZnO nanosheets contributes to efficient DC power generation. The networked ZnO nanosheets proved to be structurally stable under huge external mechanical loads.

Electrical Power Generation by Mechanically Modulating Electrical Double Layers

Abstract: Since Michael Faraday and Joseph Henry made their great discovery of electromagnetic induction, there have been continuous developments in electrical power generation. Most people today get electricity from thermal, hydroelectric, or nuclear power generation systems, which use this electromagnetic induction phenomenon. Here we propose a new method for electrical power generation, without using electromagnetic induction, by mechanically modulating the electrical double layers at the interfacial areas of a water bridge between two conducting plates. We find that when the height of the water bridge is mechanically modulated, the electrical double layer capacitors formed on the two interfacial areas are continuously charged and discharged at different phases from each other, thus generating an AC electric current across the plates. We use a resistor-capacitor circuit model to explain the results of this experiment. This observation could be useful for constructing a micro-fluidic power generation system in the near future.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

American Society for Testing and Materials

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

Large Scale Growth and Characterization of Atomic Hexagonal Boron Nitride Layers

Abstract: Hexagonal boron nitride (h-BN), a layered material similar to graphite, is a promising dielectric. Monolayer h-BN, so-called "white graphene", has been isolated from bulk BN and could be useful as a complementary two-dimensional dielectric substrate for graphene electronics. Here we report the large area synthesis of h-BN films consisting of two to five atomic layers, using chemical vapor deposition. These atomic films show a large optical energy band gap of 5.5 eV and are highly transparent over a broad wavelength range. The mechanical properties of the h-BN films, measured by nanoindentation, show 2D elastic modulus in the range of 200-500 N/m, which is corroborated by corresponding theoretical calculations.