1,626,804 research outputs found
The Anti-Inflammatory Actions of Lcy-2-Cho, a Carbazole Analogue, in Vascular Smooth Muscle Cells
No full textLCY-2-CHO has anti-infl amm atory actions on macrophages. To understand its therapeutic implication in atherosclerosis, we examined its effects on the expressions of antiinflammatory and inflammatory proteins in cultured rat aortic vascular smooth muscle cells (VSMC). LCY-2-CHO is able to induce heme oxygenase-1 (HO-1) protein expression through a transcriptional action. The HO-1 inducting effect of LCY-2-CHO was inhibited by SB203580, N (G)-nitro-L- arginine methylester (L-NAME), and wortmannin, but was not affected by U0126 or SP600125. In accordance LCY-2 -CHO increased protein phosphorylation of p38, Akt, and eNOS. Nrf 2 is a transcription factor essential for HO-1 gene induction and we showed that LCY-2-CHO is able to cause Nrf2 nuclear translocation and this action depends on p38, Akt and eNOS. in addition to induce anti-inflammatory HO-1 , LCY- 2-CHO reduced interleukin-lp (IL-1 beta)-induced inflammatory mediators, inducible nitric oxide synthase ( iNOS), cyclooxygenase-2 (COX- 2), growth-related oncogene protein-alpha (GRO-alpha), and interleukin-8 ( IL-8). Inhibitory effect on IL-lp-mediated NF-KB activation was evidenced by the diminishment of I kappa B kinase (IKK) phosphorylation and I kappa B alpha degradation. In contrast , IL-1 beta-mediated ERK and JNK activations were not changed by LCY-2-CHO, while p38 activation by IL-1 beta and LCY-2-CHO displayed the nonadditivity. Taken together, given the overall anti-inflammatory properties of LCY-2-CHO in VSMC, in terms to induce HO-1 gene expression and inhibit inflammatory gene expression, these results highlight the therapeutic potential of LCY-2-CHO in atherosclerosis. (C) 2007 Elsevier Inc. All rights reserved
Raw Training Data (NCP 2020).xlsx
No full textCitation: 1. Qiang Li, In Ho Cho, Rana Biswas, and Jaeyoun Kim, 2019. Nanoscale Modulation of Friction and ContactElectrification via Surface Nanotexturing, Nano Letters 19, 850-856. [10.1021/acs.nanolett.8b04038].2. In Ho Cho, Qiang Li, Rana Biswas, and Jaeyoun Kim, 2020. Nature Communications Physics (under review).</div
새로운 고효율 멀티레벨 하프브릿지 컨버터
No full text학위논문(석사) - 한국과학기술원 : 전기및전자공학전공, 2009.2, [ iii, 42 p. ]Nowadays, power supply market needs the server power supply with high power density and high efficiency. To meet this trend, many researches are conducted in power companies and many of them are focused on the DC/DC converting part in a server power supply. There are two types of converter topologies which are widely used in middle power application, conventional half-bridge converter and asymmetric half-bridge converter. However, these two types of converters have critical problems. Symmetric half-bridge converters operate under hard switching condition, which cause severe EMI problem and heat problem. In asymmetric converters, DC offset current which degraded transformer utilization is existed. The proposed A ZVS four level half-bridge converter with small output filter inductor overcome those problems which are showed in symmetric and asymmetric half-bridge converters by employing auxiliary transformer and auxiliary switches. Also the proposed converters have less stress on power switching components and have smaller output inductor. The operational principle, ZVS condition and output filter analysis are presented. Experimental results are demonstrated to verify the feasibility and advantages of the new topologies.한국과학기술원 : 전기및전자공학전공
Performance evaluation of data link protocol with adaptive frame length in satellite networks
No full textWe propose a new data link protocol with an adaptive frame length control scheme for satellite networks. The wireless communication channel in satellite networks is subject to errors that occur with time variance. The frame length of the data link layer is another important factor that affects throughput performance in dynamic channel environments. If the frame length could be chosen adaptively in response to changes in the dynamically varying satellite channel, maximum throughput could be achieved under both noisy and non-noisy error conditions. So, we propose a frame length control scheme that acts adaptively to counter errors that occur with time variance. We model the satellite channel as a two-state Markov block interference (BI) model. The estimation of the channel error status is based on the short-term bit error rate and the duty cycle of noise bursts. Numerical and computer simulation results show that the proposed scheme can achieve high throughput for both dense and diffuse burst noise channels.
Considering spurious timeout in proxy for improving TCP performance in wireless networks
No full textIn this paper, we introduce a new proxy that effectively prevents unnecessary retransmissions of Transmission Control Protocol data segments from flowing over a wireless link on a path with sudden delay. The proposed Spurious Timeout Detection (STD) algorithm detects spurious timeout based on the data and acknowledge sequence number. It responses to spurious timeout by filtering unnecessary data transmissions that can cause spurious fast retransmission. Simulation result shows that proposed STD algorithm performs better than, or as well as, other end-to-end mechanisms in a certain range of data rate. (C) 2003 Published by Elsevier B.V.
CHO microRNA engineering is growing up : recent successes and future challenges
No full textmicroRNAs with their ability to regulate complex pathways that control cellular behavior and phenotype have been proposed as potential targets for cell engineering in the context of optimization of biopharmaceutical production cell lines, specifically of Chinese Hamster Ovary cells. However, until recently, research was limited by a lack of genomic sequence information on this industrially important cell line. With the publication of the genomic sequence and other relevant data sets for CHO cells since 2011, the doors have been opened for an improved understanding of CHO cell physiology and for the development of the necessary tools for novel engineering strategies. In the present review we discuss both knowledge on the regulatory mechanisms of microRNAs obtained from other biological models and proof of concepts already performed on CHO cells, thus providing an outlook of potential applications of microRNA engineering in production cell lines
Cho, Jun-Ho
No full text학위논문(석사)--아주대학교 일반대학원 일반대학원 :산업공학과,2007. 8주성분분석을 이용한 Hotelling T² 관리도는 지금껏 다변량 공정 모니터링으로 가장 널리 사용되어왔다. 그러나 최근 독립성분분석이라는 기법이 제안되고, 이를 이용한 공정 모니터링이 나오면서 PCA를 이용한 공정 모니터링을 대체하고 있다. 하지만 아직 두 공정 모니터링을 체계적으로 비교 분석하여 성능을 비교한 연구는 이루어지지 않았다.
본 연구에서는 공정 데이터를 생성하여 여러 상황을 설정한 후 각상황 하에서 어떤 공정 모니터링이 더 나은 성능을 보이는지 모의실험을 통해 비교, 분석한다.
본 연구에서 사용한 데이터는 실제 공정 데이터와 비슷한 다변량 자기상관이 존재하는 데이터와 이론적으로 많이 사용되는 다변량 정규분포를 따르는 데이터를 생성한다. 각 데이터는 2단계로 이루어진 공정 데이터로 3개의 원인 변수와 2개의 결과 변수로 이루어진다.
각 공정 변수에 이상 상황을 가정하여 2종 과오를 측정한다. 각 상황은 1)모든 변수가 변하였을 때, 2)변수 일부가 변하였을 때, 3)데이터에 갑자기 이상치가 주어졌을 때, 4)데이터의 분산이 변하였을 때 이렇게 4가지의 이상상황을 가정한다. 각 상황의 공정 변화는 3수준으로 10회 반복하여 각 데이터마다 총 120회 실험을 실시한다.
1종 과오의 경우 PCA가 약간 좋은 결과를 보였다. 2종 과오의 경우 변수 일부가 변하였을 때에는 ICA가 모델에 관계없이 좋은 성능을 보였고 모든 변수가 변하였을 때와 산포가 변화했을 때에는 AR모델에서는 ICA가 약가 좋은 성능을 보였고 정규분포에서는 PCA가 좋은 성능을 보였다. 이상치가 주어졌을 경우는 AR모델은 PCA, 정규분포는 ICA가 좋은 성능을 보였다.제1장 서론 = 1
1.1 연구의 목적 및 배경 = 1
1.2 기존 연구 고찰 = 2
1.3 연구 범위 및 내용 = 3
1.4 연구의 구성 = 4
제2장 PCA를 이용한 다변량 공정 모니터링 = 5
2.1 T² 관리도 = 5
2.2 PCA를 이용한 다변량 공정 모니터링 = 10
제3장 ICA를 이용한 다변량 공정 모니터링 = 15
3.1 독립성분분석 = 15
3.1.1 개요 = 16
3.1.2 ICA의 기본원리 = 17
3.1.3 비정규성 척도 = 19
3.1.4 Centering & Whitening = 20
3.1.5 Fast ICA = 21
3.2 ICA를 이용한 다변량 공정 모니터링 = 22
제4장 모의실험 = 25
4.1 데이터 생성 = 25
4.1.1 VAR(Vector Autoregressive) 가정 = 25
4.1.2 다변량 정규분포 가정 = 26
4.2 성능비교 = 28
4.2.1 제 1종 과오 = 28
4.2.2 제 2종 과오 = 30
4.3 모의실험 결과 = 35
4.3.1 모의실험 결과 비교 분석 = 35
4.3.2 ICA, PCA의 정성적 비교 = 47
제5장 결과 및 향후 연구과제 = 49
참고문헌 = 51
Abstract = 56MasterThe objective of this research is to compare and analyze performance of PCA and ICA process monitoring techniques. Formerly, Hotelling's T2 control chart based on PCA has been used for multivariate statistical process monitoring. Recently, ICA based monitoring is introduced for process control monitoring, especially for chemical processes. However, there have been no researches conducted to compare the performance of PCA and ICA process monitoring.
In this research, simulation is carried out to generate process data and analyze the behaviors of two monitoring techniques. Two different cases are considered: in first case, data are generated by AR model and in second case, by multivariate normal distribution. The process is assumed to have three input (control) variables and two output characteristics. To find out type II error in the given process, four out-of-control cases are considered: a) all variables are changed b) some variables are changed c) sudden change in data, and d) change in variance.
The results are obtained after ten simulation test in the range of three degrees: small change, standard change, and huge change. Which shows performance of ICA is better than PCA in both AR and normal model, in case a). Similarly, in case b) and d) ICA little outperform PCA in AR model, whereas, PCA is better than ICA in normal model. As in case (c), ICA is more preferable to PCA in normal model; however, PCA is superior to ICA in AR model
High efficient multi-level half-bridge converter
No full textA new high efficient multi-level half-bridge converter is proposed in this paper. The proposed converter regulate the output voltage by adjusting additional voltage on a main transformer with an auxiliary circuit while main switches are operated at fixed duty ratio and switching frequency. Therefore, no magnetizing dc offset current is existed in the main transformer and all switches can realize zero voltage switching (ZVS). Furthermore, a multi-level voltage shown at the output filter reduces the output inductance significantly. To verify these features of the proposed circuit, operational principles, and experimental results will be presented with a 700 W prototype
A novel transformer winding for phase shift full bridge converter
No full textA phase-shift full-bridge (PSFB) converter with additional resonant inductor and clamping diodes is attractive topology in high power applications. The additional resonant inductor is used for improving zero voltage switching (ZVS) range and clamping voltage oscillation of the secondary rectifiers. However, since the high input voltage with small duty ratio is applied to the additional resonant inductor, it has very fast flux swing As a result, high eddy current loss and excess eddy current loss are occurred on magnetic core. To overcome this drawback, a new separated resonant inductor winding (SRW) is proposed. It can implement the additional resonant inductor and transformer using only one magnetic. Therefore, it can reduce the size, cost and core loss due to the additional resonant inductor. The experimental results shows that the proposed winding method can achieve high efficiency and high power density in a 1200 W (12 V,100 A) prototype converter
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