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111.
112.
Seung-Mook Baek Jung-Wook Park Hiskens I.A. 《Industry Applications, IEEE Transactions on》2009,45(1):87-97
This paper focuses on the systematic optimal tuning of the power system stabilizer (PSS), which can improve the system damping performance immediately following a large disturbance. As the PSS consists of both linear parameters (such as the gain and time constant) and nonsmooth nonlinear parameters (such as saturation limits of the PSS), two methods are applied for the optimal tuning of all parameters. One is to use the optimization technique based on the Hessian matrix estimated by the feedforward neural network, which identifies the first-order derivatives obtained by the trajectory sensitivities, for the nonlinear parameters. Moreover, the other is to use the eigenvalue analysis for the linear parameters. The performances of parameters optimized by the proposed method are evaluated by the case studies based on time-domain simulation and real-time hardware implementation. 相似文献
113.
B.-M.?HanEmail author H.-J.?Kim S.-T.?Baek 《Electrical Engineering (Archiv fur Elektrotechnik)》2004,86(5):285-291
This paper proposes a soft-switching CSI for a photovoltaic power system which has an H-type switched-capacitor module composed of two semiconductor switches, two diodes and an L-C resonant circuit. The operation of the proposed system was analyzed using a theoretical approach with equivalent circuits and verified by computer simulations using a simulation program with integrated circuit emphasis and experimental work with a hardware prototype. The proposed system could be effectively applied to the power converter of a photovoltaic power system interconnected with an a.c. power system. 相似文献
114.
Changhyun Cho 《International Journal of Control, Automation and Systems》2010,8(6):1250-1256
This paper presents a passivity condition of a haptic interface with the multirate wave transform (MWT). Although rate transitions at the wave communication line are achieved passively, the sample-and-hold for the continuous system still generates energy. Since the update rates of the sample-and-hold are high (or assumed to be high) in most cases, its effects are often ignored. However, as the update rate of the sample-and-hold decreases, more energy is generated and the whole haptic interface consequently becomes active. A passivity condition is derived for a system consisting of the sample-and-hold, MWT, and virtual environment (VE). An example study has shown that the minimum update rate of the sample-and-hold can be obtained by investigating the passivity condition. Experiments also have shown that stable force displays can be achieved with the proposed update rates. 相似文献
115.
Se-Jin Joo Hee-Jung Park Ji-Hae Park Jin-Gyeong Cho Ji-Hyun Kang Tae-Sook Jeong Hee Cheol Kang Dae-Young Lee Hack-Soo Kim Sang-Yo Byun Nam-In Baek 《International journal of molecular sciences》2014,15(9):16418-16429
Stems of Machilus japonica were extracted with 80% aqueous methanol (MeOH) and the concentrated extract was successively extracted with ethyl acetate (EtOAc), normal butanol (n-BuOH), and water. Six flavonoids were isolated from the EtOAc fraction: (+)-taxifolin, afzelin, (−)-epicatechin, 5,3''-di-O-methyl-(−)-epicatechin, 5,7,3''-tri-O-methyl-(−)-epicatechin, and 5,7-di-O-methyl-3'',4''-methylenedioxyflavan-3-ol. The chemical structures were identified using spectroscopic data including NMR, mass spectrometry and infrared spectroscopy. This is the first report of isolation of these six compounds from M. japonica. The compounds were evaluated for their diphenyl picryl hydrazinyl scavenging activity and inhibitory effects on low-density lipoprotein oxidation. Compounds 1 and 3–6 exhibited DPPH antioxidant activity equivalent with that of ascorbic acid, with half maximal inhibitory concentration (IC50) values of 0.16, 0.21, 0.17, 0.15 and 0.07 mM, respectively. The activity of compound 1 was similar to the positive control butylated hydroxytoluene, which had an IC50 value of 1.9 µM, while compounds 3 and 5 showed little activity. Compounds 1, 3, and 5 exhibited LDL antioxidant activity with IC50 values of 2.8, 7.1, and 4.6 µM, respectively. 相似文献
116.
Seong-Joong Kim Yeojin Ahn Jeong F. Kim Seung-Eun Nam Hosik Park Young Hoon Cho Kyung-youl Baek You-In Park 《应用聚合物科学杂志》2021,138(7):49860
To overcome the plasticization effect in polyimide membranes, many researchers have proposed crosslinking method. This can reduce an inter-segmental mobility by tightening and rigidifying the polymer chains. However, it is difficult to modify the whole polymer chains throughout the membrane because the reaction can be hindered by the diffusion rate of the crosslinker. In particular, it is hard for bulky crosslinker to penetrate a dense membrane with a small d-spacing. This study investigated the effect of crosslinking a dense Matrimid membrane with p-phenylenediamine (p-PDA) via two different crosslinking methods (i.e., methanol-swelling crosslinking process [M-SCP] and liquid-phase crosslinking process [L-PCP]). Most of the crosslinking reaction in M-SCP occurs on the membrane surface due to difficulty in penetration of the bulky p-PDA into the Matrimid dense membrane. In contrast, the L-PCP allows uniform crosslinking across the membrane. The membranes crosslinked using L-PCP showed excellent chemical resistance. Furthermore, the plasticization phenomenon was not observed in the membranes crosslinked using L-PCP with p-PDA more than 15%. Meanwhile, the membrane crosslinked using M-SCP exhibited poor plasticization and chemical resistance properties. These results showed that the L-PCP method can be more effective for the crosslinking of dense membrane to deliver both high plasticization and chemical resistance. 相似文献
117.
Myung-Sun Kim Kyunggon Kim Su Kyung Oh Gidae Lee Jin-Ock Kim Lan Li Jung-Hyun Park Kwang-Hyun Baek 《International journal of molecular sciences》2021,22(12)
To increase the half-life of growth hormones, we proposed its long-lasting regulation through the ubiquitin-proteasome system (UPS). We identified lysine residues (K67, K141, and K166) that are involved in the ubiquitination of human growth hormone (hGH) using ubiquitination site prediction programs to validate the ubiquitination sites, and then substituted these lysine residues with arginine residues. We identified the most effective substituent (K141R) to prevent ubiquitination and named it AUT-hGH. hGH was expressed and purified in the form of hGH-His, and ubiquitination was first verified at sites containing K141 in the blood stream. Through the study, we propose that AUT-hGH with an increased half-life could be used as a long-lasting hGH in the blood stream. 相似文献
118.
119.
Hye Jin Hwang Sang Woo Kim Yu Mi Baek Sung Hak Lee Hee Sun Hwang Jong Won Yun 《Korean Journal of Chemical Engineering》2009,26(1):115-126
We established the gene expression profiling in streptozotocin (STZ)-induced diabetic rat liver in response to hypoglycemic
fungal polysaccharides (EPS), using oligonucleotide microarray analysis. Differentially regulated genes showing higher fold
change than 2 were identified and categorized through hierarchical clustering analysis. Among the 835 genes analyzed, 244
were up-regulated, while 321 were down-regulated after diabetes induction. Interestingly, many gene expressions altered after
STZ-treatment mimicked a normal rat liver by EPS therapy. Most of these genes included genes involving cell structure and
motility, immunity and defense, lipid, fatty acid and steroid metabolism, protein metabolism and modification, and signal
transduction. More importantly, we found a total of 36 genes that showed significant fold changes in their expression that
have not previously been examined in the context of diabetes. To validate the microarray results, we further confirmed the
gene expression patterns by RT-PCR using four genes of interest (carboxylesterase 2, stearoyl-coenzyme A desaturase 1, insulin-like
growth factor 1, and insulin-like growth factor binding protein 2). Taken together, EPS acted as a potent regulator of gene
expression for a wide variety of genes in diabetic rat liver. 相似文献
120.
Sung-Chan Kim Baek-Seok Ko Tae-Jong Baek Byeong-Ok Lim An D. Dong-Hoon Shin Jin-Koo Rhee 《Microwave and Wireless Components Letters, IEEE》2005,15(10):652-654
The hybrid ring coupler was designed and fabricated on a GaAs substrate using surface micromachining techniques, which adopted dielectric-supported air-gapped microstrip line (DAML) structure. The fabrication process of DAML is compatible with the standard monolithic microwave integrated circuit (MMIC) techniques, and the hybrid ring coupler can be simply integrated into a plane-structural MMIC. The fabricated hybrid ring coupler shows wideband characteristics of the coupling loss of 3.57 /spl plusmn/ 0.22dB and the transmission loss of 3.80 /spl plusmn/ 0.08dB across the measured frequency range of 85 to 105GHz. The isolation characteristics and output phase differences are -34dB and 180/spl plusmn/1/spl deg/, at 94GHz, respectively. 相似文献