상용 에어컨의 원심팬 주위의 비정상 유동 특성 분석 및 제어

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 2. 최해천.In this study, unsteady flow characteristics of a centrifugal fan in a commercial air conditioner are investigated and flow control ideas are suggested to develop a low noise fan. The experiment is conducted at the operation condition where the fan rotational speed is 580 rpm and the Reynolds number is 167,000 based on the blade tip velocity and chord length. The instantaneous velocity fields are acquired using a particle image velocimetry. Fluctuating flow appears at the leading edge showing intermittent separation, whereas vortex shedding occurs at the trailing edge. Particularly, intermittent reverse flow appear near the shroud having a high Reynolds stress level. To control these flow structures, we modify the shapes of the blade leading edge and shroud of the centrifugal fan, which results in noise reduction. The flow fields of the base and modified fans are compared and discussed.Chapter 1 Introduction 1 Chapter 2 Experimental Setup 6 2.1 Air conditioner indoor unit 6 2.2 PIV setup 6 2.3 Noise and flow-rate measurement 7 Chapter 3 Flow Characteristics 12 3.1 Mean fields 12 3.2 Instantaneous fields near leading edge 13 3.3 Instantaneous fields near trailing edge 13 Chapter 4 Flow Control 27 4.1 Control ideas 27 4.2 Modified fan 1 – wavy leading edge 28 4.3 Modified fan 2 – junction cut & blade profile modification 28 Chapter 5 Summary and Conclusions 37 Bibliography 38 요약 40Maste

Distribution and Kinematics of H I through Raman He II Spectroscopy of NGC 6302

The young planetary nebula NGC 6302 is known to exhibit Raman-scattered He II features at 6545 and 4851 Angstrom. These features are formed through inelastic scattering of He II$\lambda\lambda$ 1025 and 972 with hydrogen atoms in the ground state, for which the cross sections are $1.2 \times 10^{-21}$ and $1.4\times 10^{-22} {\rm\ cm^2}$, respectively. We investigate the spectrum of NGC 6302 archived in the ESO Science Portal. Our Gaussian line fitting analysis shows that the Raman-scattered He II features are broader and more redshifted than the hypothetical model Raman features that would be formed in a cold static H I medium. We adopt a simple scattering geometry consisting of a compact He II emission region surrounded by a H I medium to perform Monte Carlo simulations using the radiative transfer code ${\it STaRS}$. Our simulations show that the H I region is characterized by the H I column density $N_{\rm HI}=3\times 10^{21}{\rm\ cm^{-2}}$ with the random speed component $v_{\rm ran}=10{\rm\ km\ s^{-1}}$ expanding with a speed $v_{\rm exp}= 13{\rm\ km\ s^{-1}}$from the He II emission region. Based on our best fit parameters, we estimate the H I mass of the neutral medium$M_{\rm HI} \simeq 1.0\times 10^{-2}\ {\rm M_\odot}$, pointing out the usefulness of Raman He II spectroscopy as a tool to trace H I components.Comment: 12 pages, 8 figures, accepted for publication in Ap

Liquid Biopsy Transcriptomics of Extracellular Vesicles (EV) in Plasma of Pancreatic Ductal Adenocarcinoma (PDAC)

https://openworks.mdanderson.org/sumexp22/1089/thumbnail.jp

Enhanced expression of microrna-1273g-3p contributes to alzheimer’s disease pathogenesis by regulating the expression of mitochondrial genes

Alzheimer’s disease (AD) is the most common form of dementia in the elderly population, but its underlying cause has not been fully elucidated. Recent studies have shown that microRNAs (miRNAs) play important roles in regulating the expression levels of genes associated with AD development. In this study, we analyzed miRNAs in plasma and cerebrospinal fluid (CSF) from AD patients and cognitively normal (including amyloid positive) individuals. miR-1273g-3p was identified as an AD-associated miRNA and found to be elevated in the CSF of early-stage AD patients. The overexpression of miR-1273g-3p enhanced amyloid beta (Aβ) production by inducing oxidative stress and mitochondrial impairments in AD model cell lines. A biotin-streptavidin pull-down assay demonstrated that miR-1273g-3p primarily interacts with mitochondrial genes, and that their expression is downregulated by miR-1273g-3p. In particular, the miR-1273g-3p-target gene TIMM13 showed reduced expression in brain tissues from human AD patients. These results suggest that miR1273g-3p expression in an early stage of AD notably contributes to Aβ production and mitochondrial impairments. Thus, miR-1273g-3p might be a biomarker for early diagnosis of AD and a potential therapeutic target to prevent AD progression

Ruthenium-catalyzed direct C-H amidation of arenes including weakly coordinating aromatic ketones

C-H activation: The ruthenium-catalyzed direct sp2 C-H amidation of arenes by using sulfonyl azides as the amino source is presented (see scheme). A wide range of substrates were readily amidated including arenes bearing weakly coordinating groups. Synthetic utility of the thus obtained products was demonstrated in the preparation of biologically active heterocycles. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.11211201sciescopu

Approximate ML Detection with the Best Channel Matrix Selection for MIMO Systems

In this paper, a best channel matrix selection scheme (BCMS) is proposed to approximate maximum likelihood (ML) detection for a multiple-input multiple-output system. For a one stage BCMS scheme, one of the transmitted symbols is selected to perform ML detection and the other symbols are detected by zero forcing (ZF). To increase the diversity of the symbols that are detected by ZF, multi-stage BCMS detection scheme is used to further improve the system performance. Simulation results show that the performance of the proposed BCMS scheme can approach that of ML detection with a significant reduction in complexity.This work is partly supported by Brain Korea 21 Project and Seoul R&BD program (10544)

Estimated bivariate power distributions P(l,s) × 1,000 of the 7 methods for cluster model A (RR = 1.5).

<p>Estimated bivariate power distributions P(l,s) × 1,000 of the 7 methods for cluster model A (RR = 1.5).</p

Number of clusters and districts in the clusters of simulated cluster models A–G.

<p>Number of clusters and districts in the clusters of simulated cluster models A–G.</p