Sung-Soo Kim

Cures for the shock instability: development of a shock-stable Roe scheme

This paper deals with the development of an improved Roe scheme that is free from the shock instability and still preserves the accuracy and efficiency of the original Roes Flux Difference Splitting (FDS). Roes FDS is known to possess good accuracy but to suffer from the shock instability, such as the carbuncle phenomenon. As the first step towards a shock-stable scheme, Roes FDS is compared with the HLLE scheme to identify the source of the shock instability. Through a linear perturbation analysis on the odd-even decoupling problem, damping characteristic is examined and Mach number-based functions f and g are introduced to balance damping and feeding rates, which leads to a shock-stable Roe scheme. In order to satisfy the conservation of total enthalpy, which is crucial in predicting surface heat transfer rate in high-speed steady flows, an analysis of dissipation mechanism in the energy equation is carried out to find out the error source and to make the proposed scheme preserve total enthalpy. By modifying the maximum-minimum wave speed, I the problem of expansion shock and numerical instability in the expansion region is also remedied without sacrificing the exact capturing of contact discontinuity. Various numerical tests concerned with the shock instability are performed to validate the robustness of the proposed scheme. Then, viscous flow test cases ranging from transonic to hypersonic regime are calculated to demonstrate the accuracy, robustness, and other essential features of the proposed scheme.

Rotating composite beam with a breathing crack

A rotating cantilevered beam with a breathing crack was investigated with the material assumed as unidirectional reinforced polyimide. For the numerical analysis, the local flexibility matrix was determined from a fracture mechanics approach by using a crack element model based on the Castiligano theorem. The Newmark time integration method and fast Fourier transform method of analysis were adopted in this study. The effects of various parameters such as crack depths, crack positions, fiber angles, volume fractions, and rotating speeds of the beam were studied in detail.

Large area tunable arrays of graphene nanodots fabricated using diblock copolymer micelles.

Nanostructured graphenes such as nanoribbons, nanomeshes, and nanodots have attracted a great deal of attention in relation to graphene-based semiconductor devices. The block copolymer micellar approach is a promising bottom-up technique for generating large area nanostructures of various materials without using sophisticated electron-beam lithography. Here we demonstrate the fabrication of an array of graphene nanodots with tunable size and inter-distance with the utilization of a monolayer of diblock copolymer micelles. Au nanoparticles were synthesized in the micellar cores and effectively worked as shielding nanostructures in generating graphene nanodots by oxygen plasma etching. We also controlled the radius and inter-distance of graphene nanodots simply through the molecular weight of the copolymers.

COMPLETE NUCLEOTIDE SEQUENCE AND TISSUE-SPECIFIC EXPRESSION OF THE RAT PHENYLETHANOLAMINE N-METHYLTRANSFERASE GENE

Abstract: The rat phenylethanolamine N‐methyltransferase (PNMT) gene was isolated from a genomic library by cross‐hybridization with a bovine PNMT cDNA probe. Complete nucleotide sequence analysis of a genomic clone showed that this gene contained three exons and spanned about 2.8 kb in length. There were the acute‐phase response element, TATA, SP1, and GRE sequences. The physicochemical properties of rat adrenal PNMT were different from those of the brainstem PNMT. However, northern blot and reverse transcription‐polymerase chain reaction analysis showed that the rat PNMT gene may not express the multiple forms of mRNA. These results suggest that the rat PNMT gene might produce a single enzyme protein, whose activity may be differentially modulated by tissue‐specific environment in the central and peripheral systems.

Multigrid Algorithm for Computing Hypersonic, Chemically Reacting Flows

The authorsappreciate nancial supportby theKoreaScienceand nEngineering Foundation (Grant 98-0200-14-01-3) and by the Brain nKorea-21 Program for the Mechanical and Aerospace Engineering nResearch at Seoul National University.

ZnO nanorods and nanowalls directly synthesized on flexible substrates with block copolymer templates

We demonstrated the fabrication of ZnO nanorods and nanowalls directly on flexible substrates by combining a hydrothermal growth technique with nanoporous templates obtained from block copolymers. First, templates with cylindrical nanopores in two sizes and a template with nanogrooves were fabricated on flexible substrates by employing block copolymers with different molecular weights. From these nanotemplates, we synthesized vertically oriented ZnO nanorods with controlled diameters and ZnO nanostructures in a wall shape. Because the ZnO nanostructures were produced without an electrically insulating epitaxial layer, the semiconducting nature of the ZnO nanorods was characterized as synthesized. Thus, this combined method of hydrothermal growth and block copolymer templates for ZnO nanostructures can be directly applied to flexible electronic devices without alteration of the substrate.

Cure for Shock Instability: Development of an Improved Roe Scheme

This paper deals with the development of an improved Roe scheme that is free from the shock instability and still preserves the accuracy and efficiency of the original Roes Flux Difference Splitting (EDS). Roes FDS is known to possess good accuracy but to suffer from the shock instability, such as the carbuncle phenomenon. As the first step towards a shockstable scheme, Roes FDS is compared with the HLLE scheme to identify the source of the shock instability. Through a linear perturbation analysis on the odd-even decoupling problem, damping characteristic is examined and control functions / and g are introduced into Roes FDS to cure the shock instability. In order to satisfy the conservation of total enthalpy, which is crucial in predicting surface heat transfer rate in high speed steady flows, an analysis of dissipation mechanism in the energy equation is carried out to find out the error source and to make the proposed scheme preserve total enthalpy. By modifying the maximum-minimum wave speed, the problem of expansion shock and numerical instability in the expansion region is also remedied without sacrificing the exact capturing of contact discontinuity. Various numerical tests concerned with the shock instability are performed to validate the robustness of the proposed scheme. Then, viscous flow test cases ranging from transonic to hypersonic regime are calculated to demonstrate the accuracy, robustness, and other essential features of the proposed scheme. ITRODUCTION It is essential that a numerical representation of inviscid fluxes, namely a numerical flux function, should guarantee the high level of accuracy, efficiency and robustness in computational fluid dynamics (CFD). In the last three decades, numerous numerical flux functions have been developed and much progress has been achieved [2,5,11,14,19]. The Flux Difference Splitting (FDS) framework is one of the most successful groups among the various approaches to design numerical schemes and is Graduate Student f Assistant Professor, Member AIAA, * Professor, Senior Member AIAA 55 Senior Researcher, Member AIAA Copyright

Transferrable superhydrophobic TiO2 nanorods on reduced graphene oxide films using block copolymer templates.

Superhydrophobic surfaces are normally fixed on the chosen materials. Here, we report transferrable superhydrophobicity which was enabled by fabricating TiO2 nanorods on a reduced graphene oxide (rGO) film. Superhydrophobic TiO2 nanorods were first synthesized from a nanoporous template of block copolymers (BCPs). The controllability over the dimension and shape of nanopores of the BCP template allowed for the adjustment of TiO2 nanostructures for superhydrophobicity. Since the rGO film provided effective transferring, TiO2 nanorods were conveyed onto a flexible polymer film and a metal substrate. Thus, the surface of the designated substrate was successfully changed to a superhydrophobic surface without alteration of its inherent characteristics.

Severity-Adjusted LOS Model of AMI patients based on the Korean National Hospital Discharge in-depth Injury Survey Data

This study aims to design a Severity-Adjusted LOS(Length of Stay) Model in order to efficiently manage LOS of AMI(Acute Myocardial Infarction) patients. We designed a Severity-Adjusted LOS Model with using data-mining methods(multiple regression analysis, decision trees, and neural network) which covered 6,074 AMI patients who showed the diagnosis of I21 from 2004-2009 Korean National Hospital Discharge in-depth Injury Survey. A decision tree model was chosen for the final model that produced superior results. This study discovered that the execution of CABG, status at discharge(alive or dead), comorbidity index, etc. were major factors affecting a Sevirity-Adjustment of LOS of AMI patients. The difference between real LOS and adjusted LOS resulted from hospital location and bed size. The efficient management of LOS of AMI patients requires that we need to perform various activities after identifying differentiating factors. These factors can be specified by applying each hospital`s data into this newly designed Severity-Adjusted LOS Model.

Age-related changes of mRNA expression of amyloid precursor protein in the brain of senescence-accelerated mouse

APP695 mRNA is only expressed in the brains of SAM. The expression of APP mRNA in SAM P1 mice brains is more marked than that in SAM R1 mice brain. APP mRNA expression was increased with advancing age in all brain regions of SAM P1 mice compared with SAM R1. Especially, the changes of the amount of APP mRNA in the prosencephalon and the mesencephalon are significant at P value of 0.05. We suggest that overexpression of APP mRNA may be related to accelerated aging phenomenon in the SAM brain. This is the first report of age-related increase in the amount of APP mRNA in the SAM brain.