공진효과 및 비선형 마찰이 존재하는 서보 시스템의 μ-제어기 설계에 관한 연구

황인휘,임동진 漢陽大學校 工學技術硏究所 1998 工學技術論文集 Vol.7 No.1

공진 효과와 비선형 마찰은 거의 모든 서보 시스템(servo system)에 존재하며, 이를 무시하고 제어기를 설계한 경우 성능 저하를 초래하거나 전체 시스템이 불안정해지는 등, 제어 시스템의 성능에 큰 영향을 주게 된다. 본 논문에서는 이러한 공진 효과와 비선형 마찰이 존재하는 서보 시스템에 대하여 μ-제어기법을 적용하여 제어기를 설계하는 방법을 제시한다. 정상상태 오차 없이 마찰력을 보상할 수 있는 제어기를 설계하기 위하여 원래의 시스템을 적분기로 확장한다. 이렇게 확장된 시스템에 대하여 μ-제어기 설계 방법을 적용하여 제어기를 설계한다. μ-제어기 설계 방법은 부분적으로 H∞ 제어 방법을 사용하는데 일반적으로 적분형 서보 시스템에 H∞ 제어 방법을 적용한 경우 과도응답 특성이 나빠지므로, 과도응답 특성을 개선하기 위하여 제어기를 2-자유도 구조로 변환한다. 때때로 전체 제어 시스템에서 비선형 마찰과 적분기의 상호작용으로 인하여 리미트 사이클이 발생할 수 있으므로 기술 함수법을 사용하여 리미트 사이클의 존재여부를 확인한다. In the designing servo controllers, the most important problems which should be considered are resonance effects and nonlinear frictions. These problems exist in almost all the servo systems, and sometimes cause difficulties in designing controllers. In this thesis, a controller design procedure with employ μ-control method is proposed for the servo systems with these problems. In order to design a controller which is capable of compensating frictions and ensures no steady-state error, the original system is augmented with an integrator and μ-control method is applied. In the course of μ-control method, H∞ control method is partially used. Since a conventional H∞ control problem for integral type servo systems sometimes presents poor control performance in transient response, a control structure is transformed into 2-degree of freedom structure in order to obtain satisfactory control output in transient response. And, sometimes, there is a possibility of limit cycles due to the interaction between the nonlinear friction and integrator. To check the possibility of limit cycles, describing function method is used.

Comparison of Clinical Outcomes among Conventional Scleral Fixation, Retropupillary Iris-claw Intraocular Lens Implantation, and Intrascleral Fixation

Min-Ji Kim(Min-Ji Kim),Gyu Le Han(Gyu Le Han),Tae-Young Chung(Tae-Young Chung),Dong Hui Lim(Dong Hui Lim) 대한안과학회 2022 Korean Journal of Ophthalmology Vol.36 No.5

Purpose: To compare the efficacy and safety of conventional scleral fixation (C-SF), retropupillary iris-claw intraocular lens (RP-IOL) implantation, and intrascleral fixation (ISF). Methods: This retrospective observational study included 58 patients (58 eyes) who underwent C-SF (23 eyes), RP-IOL (23 eyes), and ISF (12 eyes) by a single surgeon at Samsung Medical Center from October 2017 to July 2020 and were followed up for at least 6 months. This study analyzed various clinical outcomes before surgery, and 1 day, 1 week, 1 month, 3 months, and 6 months after surgery. Results: Six months after surgery, best-corrected visual acuity in logarithm of minimum angle of resolution was 0.08 ± 0.10, 0.08 ± 0.16, and 0.03 ± 0.04 in C-SF group, RP-IOL group, and ISF group, respectively, and there was a significant improvement in each group compared to preoperative best-corrected visual acuity. All groups showed a significant increase in astigmatism postoperatively, but no between-group differences were observed. The prediction error was -0.15 ± 0.77, 0.56 ± 0.62, and 0.44 ± 1.00 diopters in the three groups, respectively, indicating RP-IOL group and ISF group for hyperopic shift. The three groups did not differ in terms of absolute prediction error. Six months after surgery, the corneal endothelial cell counts were 2,073 ± 691, 2,014 ± 692, and 1,712 ± 891 cells/mm2, respectively, which were lower than before surgery. IOL dislocation occurred in five eyes only in RP-IOL group, two of which underwent two reoperations, and reenclavation was performed smoothly without complications in all cases. Conclusions: Although the frequency of IOL dislocation in RP-IOL group was higher than that in the other groups, it can be reenclavated relatively easily. As a method of secondary IOL fixation, both RP-IOL implantation and ISF were as effective as conventional scleral fixation.

Magnetic properties of Mn54Al46C2.44/Sm2Fe17N3 and Mn54Al46C2.44/Fe65Co35 composites

Hui-Dong Qian,Ping-Zhan Si,Jung Tae Lim,Jong-Woo Kim,박지훈,Chuljin Choi 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.11

Ferromagnetic -phase Mn54Al46C2:44 particles were synthesized, and its composites with com- mercial Sm2Fe17N3 and synthesized Fe65Co35 powders were fabricated. Smaller grain size than the single domain size of the Mn54Al46C2:44 without obvious grain boundaries and secondary phases is the origin for the low intrinsic coercivity. It was confirmed that the magnetic properties of the Mn54Al46C2:44 can be enhanced by magnetic exchange coupling with the hard magnetic Sm2Fe17N3 and soft magnetic Fe65Co35. The high degrees of the exchange coupling were verified by calculat- ing first derivative curves. Thermo-magnetic stabilities of the composites from 100 to 400 K were measured and compared. It was demonstrated that the Mn54Al46C2:44 based composites containing Sm2Fe17N3 and Fe65Co35 could be promising candidates for future permanent magnetic materials with the proper control of purity, magnetic properties, etc.

Measurement of Heavy Metal Ions Using a Personal Glucose Meter

Dong-yeon SONG,Ju-hui LEE,Hye-jin LIM,Dong-myung KIM 한국생물공학회 2022 한국생물공학회 학술대회 Vol.2022 No.9

Fabrication and magnetic properties of Fe rich compound with a tetragonal ThMn<SUB>12</SUB> structure

Hui-Dong Qian,Jung Tae Lim,Yang Yang,Jong-Woo Kim,Kyung Mox Cho,Jihoon Park,Chul-Jin Choi 한국자기학회 2019 한국자기학회 학술연구발표회 논문개요집 Vol.29 No.2

Fabrication and magnetic properties of Iron-rich intermetallic compounds with ThMn<SUB>12</SUB> structure

Hui-Dong Qian,Jung Tae Lim,Yang Yang,Jong-Woo Kim,Tian Hong Zhou,Su Yeon Ahn,Hankuk-Jeon,Kyung Mox Cho,Jihoon Park,Chul-Jin Choi 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2

Rare-earth intermetallic compounds of R(Fe,M)12 (R = rare earth elements, M = transition metals) with ThMn12 structure have been known to be promising permanent magnetic materials since the 1980s. Recently, increasing rare earth price has pushed the industry to seek ways to reduce the R-content in the hard magnetic materials. In case, strong magnets with the ThMn12 type of structure received much attention. However, during the several tens of years, the research about ThMn12 magnetic materials was not made a breakthrough. As a turning point of the ThMn12-type Fe-rich compounds research, ThMn12-type Sm(Fe1-xCox)12 compound films with a saturation magnetization of 1.78 T, an anisotropy field of 12 T, and a Curie temperature of 586 °C, all of which are superior to those for Nd₂Fe14B, were successfully produced. However, it still has difficulty in stabilizing the unstable ThMn12 phase in magnetic powders and bulks. In previous research, the ThMn12 structure is also unstable and partial Fe atoms must be substituted with phase stabilizing element(s), such as Ti, V, Cr, Mn, Mo, W, Al, and Si, which results in magnetization reduction. So, decreasing magnetization or coercivity with the non-magnetic elements substitution is a new challenge for the ThMn12-type Sm(Fe1-xCox)12 compound research. Therefore, we have developed a new fabrication method to produce a high-density Sm(Fe0.8Co0.2)11Ti bulk with high purity and magnetic properties and investigated Si substitution or doping effects on this work"s magnetic and physical properties. The purity of the hard magnetic ThMn12 phase in the bulk magnet reached higher than 97 wt.%. The remanent magnetization and maximum energy product of the prepared Sm(Fe0.8Co0.2)11Ti bulk reached high values of 96.0 emu/g and 12.22 MGOe, respectively. The phase transformation behavior from amorphous to ThMn12 phase during heat treatment was systematically investigated by transmission electron microscopy. The magnetic properties and grain sizes of Sm(Fe0.8Co0.2)11Ti bulk magnets with different annealing times were shown in Fig. 1 (a). To investigate the effect of substituted elements in the ThMn12-type Fe-rich compounds and compare with the Ti substitution, Si was selected to dop into the ThMn12-type Fe-rich compounds. Sm(Fe0.8Co0.2)10Si₂ and Sm(Fe0.8Co0.2)11Ti+Six (x = 0, 0.5, and 1) ribbons were produced using a melt spinning method. The magnetic properties of the Sm(Fe0.8Co0.2)10Si₂ ribbons with different melt spinning speeds and the Sm(Fe0.8Co0.2)11Ti+Six ribbons with melt spinning speed of 39 m/s are shown in Fig. 1 (b). The maximum coercivity of the Sm(Fe0.8Co0.2)10Si₂ and Sm(Fe0.8Co0.2)11Ti+Six ribbons reached 1745 and 3140 Oe, respectively. The details of the fabrication procedure, microstructure, and magnetic properties of as mentioned compounds will be discussed. 〈그림 본문참조〉

The effect of alpha lipoic acid in a porcine in-stent restenosis model

Lim, Sang Yup,Bae, Eun Hui,Jeong, Myung Ho,Kim, Ju Han,Hong, Young Joon,Sim, Doo Sun,Kim, Yong Sook,Park, In Kyu,Ahn, Youngkeun,Song, Sun-Jung,Cho, Dong Lyun,Kim, Kyoung Seok,Kang, Jung Chaee Elsevier 2009 Journal of cardiology Vol.54 No.3

<P><B>Summary</B></P><P><B>Background</B></P><P>The aim of this study was to investigate the effect of alpha lipoic acid (α-LA) on a porcine in-stent restenosis (ISR) model.</P><P><B>Methods</B></P><P>In protocol 1, porcine vascular smooth muscle cells (PVSMC) were stimulated by granulocyte-colony stimulating factor (G-CSF) in the presence or absence of α-LA. MTT (3-[4,5-dimethylthiazole-2-yl] 2,5-diphenyl tetrazolium bromide) assay and western blotting were used to determine the cell growth inhibitory rate and anti-inflammatory effect associated with nuclear factor-κb (NF-κb) and extracellular signal-regulated kinase (ERK). In protocol 2, 28 days after balloon overdilation injuries, 24 bare metal stents were placed in coronary artery of 12 pigs. The pigs were randomly divided to receive control diet with or without α-LA (100mg/kg). In protocol 3, 8 control stents and 8 α-LA coated stents were randomly implanted in 2 coronary arteries of 8 pigs and follow-up coronary angiogram and histopathologic assessment were performed 4 weeks after stenting.</P><P><B>Results</B></P><P>Protocol 1. The proliferation of PVSMC was inhibited and protein expression of NF-κb and ERK were attenuated by α-LA pretreatment. Protocol 2<I>.</I> On histopathologic analysis, the neointimal area (4.0±1.0mm<SUP>2</SUP> vs. 1.5±0.7mm<SUP>2</SUP>, <I>p</I><0.001) and histopathologic area of stenosis (66.7±10.7% vs. 24.2±9.7%, <I>p</I><0.001) were reduced in the α-LA feeding group compared to controls. Protocol 3. On histopathologic analysis, the neointimal area (3.9±0.8mm<SUP>2</SUP> vs. 1.0±0.4mm<SUP>2</SUP>, <I>p</I><0.001), and the histopathologic area of stenosis (67.1±8.8% vs. 17.4±10.0%, <I>p</I><0.001) were reduced in the α-LA coated stent group compared to the control stent group.</P><P><B>Conclusions</B></P><P>α-LA feeding and α-LA coated stents inhibit neointimal hyperplasia in porcine ISR, possibly through inhibiting the activation of NF-κb pathway and proliferation of PVSMC.</P>

Application of high-strength biodegradable polyurethanes containing different ratios of biobased isomannide and poly (ϵ-caprolactone) diol

Lim, Dong-In,Park, Hyung-Seok,Park, Jeong-Hui,Knowles, Jonathan C,Gong, Myoung-Seon SAGE Publications 2013 Journal of bioactive and compatible polymers Vol.28 No.3

<P>Biodegradable–biocompatible polyurethanes were prepared with fixed hexamethylene diisocyanate and varying ratios of isomannide and poly(ϵ-caprolactone) diol using a simple one-step polymerization without a catalyst. The polyurethane structures were confirmed by <SUP>1</SUP>H-nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. The glass transition temperatures were determined by thermal analysis to be between 25°C and 30°C. Degradation tests performed at 37°C in phosphate buffer produced mass losses of 5%–10% after 8 weeks. After 5 days of culture, using osteoblastic cells, the relative cell number on all the polyurethane films was only slightly lower than that of an optimized tissue culture plastic. These polymers offer significant promise with a simplistic synthesis and controlled degradation.</P>

Structure and magnetic properties of Fe-rich permanent magnetic materials prepared by melt spinning

Hui-Dong Qian,Jung Tae Lim,Yang Yang,Ping-Zhan Si,Jong-Woo Kim,Kyung Mox Cho,Jihoon Park,Chul-Jin Choi 한국자기학회 2018 한국자기학회 학술연구발표회 논문개요집 Vol.2018 No.11

Phase transformation and magnetic properties of Sm(Fe<SUB>0.8</SUB>Co<SUB>0.2</SUB>)<SUB>11</SUB>Ti bulk magnets

Hui-Dong Qian,Jung Tae Lim,Yang Yang,Jong-Woo Kim,Su Yeon Ahn,Hankuk-Jeon,Tian Hong Zhou,Kyung Mox Cho,Jihoon Park,Chul-Jin Choi 한국자기학회 2020 한국자기학회 학술연구발표회 논문개요집 Vol.30 No.2