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A 1.5 V High-Cain High-Frequency CMOS Complementary Operational Amplifier
Park, Kwangmin The Korean Institute of Electrical and Electronic 2001 Transactions on Electrical and Electronic Material Vol.2 No.4
In this paper, a 1.5 V high-gain high-frequency CMOS complementary operational amplifier is presented. The input stage of op-amp is designed for supporting the constant transconductance on the Input stage by consisting of the parallel-connected rail-to-rail complementary differential pairs. And consisting of the class-AB rail-to-rail output stage using the concept of elementary shunt stage and the grounded-gate cascode compensation technique for improving the low PSRR which was a disadvantage in the general CMOS complementary input stage, the load dependence of open loop gain and the stability of op- amp on the output load are improved, and the high-gain high-frequency operation can be achieved. The designed op-amp operates perfectly on the complementary mode with the 180° phase conversion for a 1.5 V supply voltage, and shows the DC open loop gain of 84 dB, the phase margin of 65°, and the unity gain frequency of 20 MHz. In addition, the amplifier shows the 0.1 % settling time of .179 ㎲ for the positive step and 0.154 ㎲ for the negative step on the 100 mV small-signal step, respectively, and shows the total power dissipation of 8.93 mW.
Park, Sae Hume,Kwak, Jaesung,Shin, Kwangmin,Ryu, Jaeyune,Park, Yoonsu,Chang, Sukbok American Chemical Society 2014 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.136 No.6
<P>Direct C–H amination of arenes offers a straightforward route to aniline compounds without necessitating aryl (pseudo)halides as the starting materials. The recent development in this area, in particular in the metal-mediated transformations, is significant with regard to substrate scope and reaction conditions. Described herein are the mechanistic details on the Rh-catalyzed direct C–H amination reaction using organic azides as the amino source. The most important two stages were investigated especially in detail: (i) the formation of metal nitrenoid species and its subsequent insertion into a rhodacycle intermediate, and (ii) the regeneration of catalyst with concomitant release of products. It was revealed that a stepwise pathway involving a key Rh(V)–nitrenoid species that subsequently undergoes amido insertion is favored over a concerted C–N bond formation pathway. DFT calculations and kinetic studies suggest that the rate-limiting step in the current C–H amination reaction is more closely related to the formation of Rh–nitrenoid intermediate rather than the presupposed C–H activation process. The present study provides mechanistic details of the direct C–H amination reaction, which bears both aspects of the inner- and outer-sphere paths within a catalytic cycle.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2014/jacsat.2014.136.issue-6/ja411072a/production/images/medium/ja-2013-11072a_0019.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja411072a'>ACS Electronic Supporting Info</A></P>
The Firm Growth Pattern in the Restaurant Industry : Does Gibrat's Law Hold?
Kwangmin Park,Jinhoo Kim 한국관광학회 2010 International Journal of Tourism Sciences Vol.10 No.3
This study tests the relationship between firm size and rate of growth, based on Gibrat's Law. The core idea of Gibrat's Law is that firm growth rates should be independent of firm size. The minimum efficient scale (MES) of level of output and merger and acquisition (M&A) are also considered in analyzing the relationship. Overall, this study shows that Gibrat's Law does not hold in the restaurant industry. Firm growth patterns reveal that small firms are expected to grow faster than their larger competitors. However, larger firms grow faster when they remain below MES, whereas smaller firms show higher growth rates when they are operated at a point above MES. Firms executing M&A show that firm growth rate is independent of firm size, supporting Gibrat's Law. This study does not evidence persistent growth after M&A for those firms above MES. Nevertheless, M&A is still an effective growth strategy for those who are below MES.
A CMOS Bridge Rectifier for HF and Microwave RFID Systems
Park Kwangmin The Korean Institute of Electrical and Electronic 2004 Transactions on Electrical and Electronic Material Vol.5 No.6
In this paper, a CMOS bridge rectifier for HF and microwave RFID systems is presented. The proposed RFID CMOS bridge rectifier is designed with two NMOSs and two PMOSs whose gates are connected to the antenna, and it is operated as a full wave bridge rectifier. The simulation results obtained with SPICE show the well rectified and high enough DC output voltages for the operating frequencies of 13.56 MHz, 915 MHz, and 2.45 GHz which are used in various RFID systems. The obtained DC output voltages are sufficiently high for driving the low power microchip in RFID transponder for the frequency range of HF and microwave.
Kim Kwangmin,Veerappan Karpagam,Woo Nahyun,Park Bohyeon,Natarajan Sathishkumar,Chung Hoyong,김철민,Park Junhyung 한국미생물학회 2021 The journal of microbiology Vol.59 No.12
The stem and root bark of Ulmus macrocarpa Hance has been used as traditional pharmacological agent against inflammation related disorders. The objective of this study was to explore the impact of Ulmus macrocarpa Hance extract (UME) on human gut microbiota. A randomized placebo-controlled clinical study was conducted in healthy adults. The study subjects were given 500 mg/day of UME or placebo orally for 4 weeks. Eighty fecal samples were collected at baseline and 4 weeks of UME or placebo intervention. The gut microbiota variation was evaluated by 16S rRNA profiling. The microbial response was highly personalized, and no statistically significant differences was observed in both species richness and abundance. The number of bacterial species identified in study subjects ranged from 86 to 182 species. The analysis for taxonomical changes revealed an increase in Eubacterium ventriosum, Blautia faecis, Ruminococcus gnavus in the UME group. Functional enrichment of bacterial genes showed an increase in primary and secondary bile acid biosynthesis in UME group. Having known from previous studies Eubacterium regulated bile acid homeostasis in protecting gut microbial architecture and immunity, we suggest that UME supplementation might enhance host immunity by modulating gut microbiota. This is the first stage study and forthcoming clinical studies with larger participants are needed to confirm these findings.
부유형 해양 광생물반응기의 선택적 투과막의 술폰화 반응을 통한 Biofouling 억제 및 미세조류 생산성 향상
김광민(Kwangmin Kim),이윤우(Yunwoo Lee),김지훈(Z-Hun Kim),박한울(Hanwool Park),정인재(Injae Jung),박재훈(Jaehoon Park),임상민(Sang-Min Lim),이철균(Choul-Gyun Lee) 한국해양바이오학회 2017 한국해양바이오학회지 Vol.9 No.1
The purpose of this study was to inhibit biofouling on a selectively permeable membrane (SPM) and increase biomass productivity in marine photobioreactors (PBRs) for microalgal cultivation by chemical treatment. Surfaces of a SPM, composed of polyethylene terephthalate (PET), was sulfonated to decrease hydrophobicity through attaching negatively charged sulfonic groups. Reaction time of sulfonation was varied from 0 min to 60 min. As the reaction time increased, the water contact angle value of SPM surface was decreased from 75.5o to 44.5o, indicating decrease of surface hydrophobicity. Furthermore, the water permeability of sulfonated SPM was increased from 5.42 mL/㎡/s to 10.58 mL/㎡/s, which reflects higher nutrients transfer rates through the membranes, due to decreased hydrophobicity. When cultivating Tetraselmis sp. using 100-mL floating PBRs with sulfonated SPMs, biomass productivity was improved by 34% compared with the control group (non-reacted SPMs). In addition, scanning electron microscopic observation of SPMs used for cultivation clearly revealed lower degree of cell attachment on the sulfonated SPMs. These results suggest that sulfornation of a PET SPM could improve microalgal biomass productivity by increasing nutrients transfer rates and inhibiting biofouling by algal cells.