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A high-frequency and high-power quasi-class-E amplifier design using a finite bias feed inductor
Van, Ju-Ho,Kim, Min-Su,Jung, Sung-Chan,Park, Hyun-Chul,Ahn, Gunhyun,Park, Cheon-Seok,Kim, Byung-Sung,Yang, Youngoo Wiley Subscription Services, Inc., A Wiley Company 2007 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.49 No.5
<P>This paper presents a design method for a compact high-efficiency quasi-class-E amplifier, using a finite bias feed inductor. It is very difficult to achieve proper class-E operation from high-power transistors operating in the high-frequency region because of their internal parasitic components. To mitigate the effects of internal parasitic components on class-E operation, a finite DC feed inductance is introduced to resonate out the capacitive parasitic components. A quasi-class-E amplifier with a finite DC feed inductor was designed and implemented at 1.2 GHz using a high-power laterally diffused metal-oxide-semiconductor field-effect transistor (LDMOSFET). We compared simulated time domain current and voltage waveforms with ideal ones. As the test results indicated, power-added efficiency as high as 70.4% was achieved, at high output power of 39.55 dBm, without losing the circuits' simplicity, one of the most important advantages of class-E operation. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1114–1118, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22368</P>
Ju-Il Sung,Ngoc Van Thi Nguyen,Min-Jung Park,Seung-Beom Lee,Yong-Jae Lee,Seung-Ho Choi,김경호 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.9
Stereoisomers of nadolol were derivatized with S-(-)-menthyl chloroformate((-)-MCF) forming their diastereomers, RSR-nadolol-(-)-MCF, SRS-nadolol-(-)-MCF, RRS-nadolol-(-)-MCF and SSRnadolol-(-)-MCF. Diastereomeric mixture were then chromatographically resolved by preparative HPLC (JAIGEL-ODS-BP-L, 500 × 25 mm column) eluted with methanol-water (84:16, v/v) at flow rate 2.5 mL/min. RSR-nadolol-(-)-MCF diastereomer was hydrolyzed with 5% LiOH at 80oC for 48 h, and the decomposed mixture was further purified by semi-preparative HPLC. The purity and final yield of RSR-nadolol were 99.97% and 12.95%, respectively.
Ni Van,Ned Ahlberg,Byung Chul Jung,Min Ho Lee,Seung Ju Ahn,In-soo Lee,Yoon Suk Kim,Ki-Jong Rhee 대한의생명과학회 2012 Biomedical Science Letters Vol.18 No.4
Enterotoxigenic Bacteroides fragilis (ETBF) is an intestinal commensal bacterium implicated as a risk factor for colon cancer. The key virulence factor is a secreted toxin called B. fragilis toxin (BFT). In this study we used an in vitro bioassay to examine the prevalence of ETBF in colonic washings from patients with colorectal polyps and normal control patients. We found that 9.3% of polyp patients and 10.9% of non-polyp patients harbored ETBF, respectively. A total of nine ETBF clinical isolates were isolated and confirmed to be positive for the BFT gene by PCR analysis and the ability to induce IL-8 secretion in the colonic epithelial cell line HT29/c1. Two of the ETBF clinical strains were characterized further in vitro and in vivo. We found that the two ETBF clinical isolates induced E-cadherin cleavage in HT29/c1 cells and promoted colonic inflammation in C57BL/6 mice. Our results indicate that the prevalence of ETBF in polyp patients were similar in non-polyp patients suggesting that ETBF carriage does not positively correlate to polyp incidence.
Kyung-Ho Lee,Keun-Hyeok Yang,Ju-Hyun Mun,Nguyen Van Tuan 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.1
The objective of this study is to examine the workability and various mechanical properties of concrete using artificial lightweight aggregates produced from expanded bottom ash and dredged soil. Fifteen concrete mixes were classified into three groups with regard to the designed compressive strengths corresponding to 18 MPa, 24 MPa, and 35 MPa. In each group, lightweight fine aggregates were replaced by using natural sand from 0 to 100% at an interval of 25%. Thus, the density of concrete ranged between 1455 and 1860 kg/㎥. Based on the regression analysis using test data, a reliable model was proposed to clarify lower early-age strength and higher long-term strength gains of lightweight aggregate concrete (LWAC) when compared with the predictions of the fib model. The proposed model also indicates that a lower water-to-cement ratio is required with the decrease in the natural sand content to achieve the designed compressive strength of concrete. The partial use natural sand is favorable for enhancing the tensile resistance capacity, shear friction strength, and bond behavior with a reinforcing bar of LWAC. The fib model overestimates direct tensile strength, bond strength and the amount of slip at the peak bond stress of LWAC. Therefore, it is necessary to consider the density of concrete as a critical factor in conjunction with its compressive strength to rationally evaluate the various mechanical properties of LWAC.
Park, Cheon-Ho,Van Duong, Quang,Moon, Yong-Ju,Ha, Kanglyeol,Choi, Seung Tae Elsevier 2018 Sensors and actuators. A, Physical Vol.279 No.-
<P><B>Abstract</B></P> <P>In this study, the fabrication process of a piezoelectric poly[(vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)] film was optimized to maximize its crystallinity and piezoelectric properties and to improve its thermal stability. The effect of purification of P(VDF-TrFE) solution dissolved in methyl ethyl ketone [MEK] and uniaxial stretching on the properties and performance of P(VDF-TrFE) film was studied. In the purification process, the solution was filtered with a syringe filter with 2.7 μm pores. X-ray diffraction measurements showed that the stretching and purification processes increased the crystallinity of the P(VDF-TrFE) films by approximately 16.2% and 2.2%, respectively. A high-temperature storage test showed that the unstretched P(VDF-TrFE) films lose most of their polarization after 1-h storage at 70 °C. The stretching process greatly increased the thermal stability of the films so that the purified and stretched P(VDF-TrFE) films exhibited a small variation within 6% in the piezoelectric strain constant (d<SUB>33</SUB>) for 96 h at 70 °C. Ultrasonic transducers (UTs) were also fabricated with the purified and stretched P(VDF-TrFE) films. The pulse-echo measurement showed that the sensitivity and bandwidth of the UTs increased by 4.5 dB and decreased by 24.3%, respectively, compared to UTs fabricated with the purified P(VDF-TrFE) film without stretching.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly crystalline P(VDF-TrFE) films were fabricated by introducing purification and uniaxial stretching processes. </LI> <LI> The stretching and purification processes increase the crystallinity of the P(VDF-TrFE) films by about 16.2% and 2.2%, respectively. </LI> <LI> The purified and stretched films exhibit a variation within 6% in the piezoelectric constant (d<SUB>33</SUB>) during the storage test at 70 °C for 96 h. </LI> <LI> UTs were also fabricated with the purified P(VDF-TrFE) films. </LI> <LI> The sensitivity and bandwidth of the UTs with the purified and stretched film has a 4.5 dB increase and 24.3% decrease, respectively. </LI> </UL> </P>
Soybean cultivars screening for resistance to Phomopsis seed decay in Korea
Suli Sun,Kyujung Van,Moon Young Kim,Yeong-Ho Lee,Ahra Bae,Hyun Ju Jang,Suk-Ha Lee 한국육종학회 2012 한국육종학회 심포지엄 Vol.2012 No.07
Phomopsis seed decay (PSD), primarily caused by Phomopsis longicolla, is a major contributor to poor soybean seed quality and significant yield loss, particularly in early maturing soybean genotypes. However, it is not yet known whether PSD resistance is associated with early maturity. This study was conducted to identify quantitative trait loci (QTLs) for resistance to PSD and maturity time using a recombinant inbred line (RIL) population derived from a cross between the PSD-resistant Taekwangkong and the PSD-susceptible SS2-2. Based on a genetic linkage map incorporating 117 simple sequence repeat markers, QTL analysis revealed two and three QTLs conferring PSD resistance and maturity time, respectively, in the RIL population. Two QTLs (PSD-6-1 and PSD-10-2) for PSD resistance were identified in the intervals of Satt100-Satt460 and Sat_038-Satt243 on chromosomes (Chrs) 6 and 10, respectively. These QTLs do not overlap with any previously reported loci for PSD resistance in other soybean genotypes. Two QTLs explained phenotypic variances in PSD resistance of 46.3% and 14.1%, respectively. Among three QTLs for maturity time, two (Mat-6-2 and Mat-10-3) were located at positions similar to the PSD resistance QTLs. The identification of the QTLs linked to both PSD resistance and maturity time indicates a biological correlation between these two traits. The newly identified QTLs for resistance to PSD associated with maturity time in Taekwangkong will help improve soybean resistance to P. longicolla.