• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.2
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• pp.149-155
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• 2023

Photovoltaic power generation is the most familiar power generation facility among new and renewable energies, and its supply began to expand about 10 years ago, and at this point, interest in solutions and technologies for system maintenance management is increasing. In particular, it is necessary to take measures to maximize the overall efficiency of the solar power generation system, whether or not there is an abnormality in the solar power generation system, and when to replace parts. The PV inverter, one element of the photovoltaic power generation system, is a power conversion system that relies on power switching devices, and DC-Link capacitors are used according to the configuration of DC/DC converters and DC-AC inverters. These DC capacitors also affect system safety (Safety) through renewable energy facilities due to the decrease in power generation of PV inverters, power loss, and increase in harmonics (THD, total distortion of AC output current) due to aging and deterioration due to long-term use. factors can be analyzed. Therefore, in this paper, the PV inverter operating characteristics according to the DC capacitor capacity state currently operating in the photovoltaic power generation system were considered, and research contents were proposed to secure the safety and reliability of renewable energy facilities.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.129-132
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• 2008

The generally six-port phase correlator is comprised of a wilkinson power divider and three $90^{\circ}$ hybrid coupler, got bandwidth performance of less than 10%. in this paper, the six-port phase correlator using two section power divider has 33% bandwidth and external matching hybrid coupler has 15% bandwidth was designed with the center frequency of 2.5GHz. Analysis of the simulation result indicates that RF port and LO port got frequency bandwidth of 13%. Insert loss performance of fabricated six-port phase correlator is incremented, but bandwidth resembles simulation result. And phase tolerance within bandwidth is less than $90^{\circ}$.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.5
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• pp.706-711
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• 2009

This study was carried out to compare the growth performance and quality properties of pork from finishing pigs fed different levels of betaine. A total 120 female pigs (Landrace${\times}$Yorkshire${\times}$Duroc) were fed either a control commercial diet or the control diet supplemented with 2, 4 and 6% betaine for 31 days. The average daily feed intake (ADFI) of the 2% diet was lower than of the other treatment groups. The average daily gain (ADG) for pigs fed betaine diets was significantly higher (p<0.05) compared with nonsupplemented diets. Feed conversion ratio (FCR) of pigs fed betaine diets was significantly lower (p<0.05) compared with nonsupplemented diets. pH of loin and ham samples were not significantly different between dietary groups, whereas CIE a* (redness) of pork loin was increased by dietary betaine. Also, the shear force value of loin was significantly higher (p<0.05) in pigs given dietary betaine compared with non-supplemented diets, but no significant differences were found in cooking loss by the loin among diets with different levels of betaine (p>0.05). Dietary supplementation with betaine decreased total cholesterol concentrations in blood, and increased saturated fatty acid and decreased unsaturated fatty acid levels in muscle. Pigs supplemented with betaine had increased betaine concentrations in the loin muscle. It was concluded that dietary betaine supplementation of finishing pigs can improve growth performance and reduce blood cholesterol concentrations. It was also concluded that dietary betaine produced detectable betaine concentrations in the lion muscle.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.621-626
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• 2010

In this study, imidazole-based ionic liquid on polystyrene was prepared and its catalytic performance in the cycloaddition of $CO_2$ with allyl glycidyl ether(AGE) to produce allyl glycidyl carbonate was investigated. The ionic liquid was generated on the polystyrene-based polymer through the immobilization of imidazole. The prepared catalyst was characterized using a number of instrumental analysis including EA, FT-IR, TGA and SEM. The immobilized ionic liquid showed very good catalytic activity for the cycloaddition of $CO_2$ with AGE, having 80% of AGE conversion with over 96% of the carbonate selectivity at $120^{\circ}C$ under 1.48 MPa $CO_2$ pressure. The immobilized ionic liquid can be used for the reaction up to four consecutive runs without significant loss of its catalytic activity.

• Journal of Gastric Cancer
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• v.14 no.2
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• pp.105-110
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• 2014

Purpose: The advantages of totally laparoscopic surgery in early gastric cancer (EGC) are unproven, and some concerns remain regarding the oncologic safety and technical difficulty. This study aimed to evaluate the technical feasibility and clinical benefits of totally laparoscopic distal gastrectomy (TLDG) for the treatment of gastric cancer compared with laparoscopy-assisted distal gastrectomy (LADG). Materials and Methods: A retrospective review of 211 patients who underwent either TLDG (n=134; 63.5%) or LADG (n=77; 36.5%) for EGC between April 2005 and October 2013 was performed. Clinicopathologic features and surgical outcomes were analyzed and compared between the groups. Results: The operative time in the TLDG group was significantly shorter than that in the LADG group (193 [range, 160~230] vs. 215 minutes [range, 170~255]) (P=0.021). The amount of blood loss during TLDG was estimated at 200 ml (range, 100~350 ml), which was significantly less than that during LADG, which was estimated at 400 ml (range, 400~700 ml) (P<0.001). The hospital stay in the TLDG group was shorter than that in the LADG group (7 vs. 8 days, P<0.001). One patient from each group underwent laparotomic conversion. Two patients in the TLDG group required reoperation: one for hemostasis after intraabdominal bleeding and 1 for repair of wound dehiscence at the umbilical port site. Conclusions: TLDG for distal EGC is a technically feasible and safe procedure when performed by a surgeon with sufficient experience in laparoscopic gastrectomy and might provide the benefits of reduced operating time and intraoperative blood lossand shorter convalescence compared with LADG.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.10
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• pp.1452-1458
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• 2004

An experiment was conducted to examine the effects of sex and market weight on performance, carcass characteristics and pork quality. A total of 224 crossbred pigs (initially 26.64 kg BW) were allotted in a $2{\times}4$ factorial arrangement in a randomized complete block (RCB) design. The variables were sex (gilts and barrows) and different market weights (100, 110, 120 and 130 kg). Average daily gain (ADG) and average daily feed intake (ADFI) were significantly higher (p<0.01) in barrows than gilts, ADFI and feed conversion ratio (FCR) increased as body weight increased (p<0.05). Gender differences were observed in carcass characteristics. Backfat thickness and drip loss were greater in barrows (p<0.01), while loin eye area (p<0.01), flavor score (p<0.05) and lean content (p<0.001) were higher in gilts. Carcass grade and water holding capacity were the highest in 110 kg market weight pigs. The 100 kg arket weight pigs showed lower juiciness, tenderness, shear forces and total palatability than the other market weights (p<0.01). Hunter values (L*, a* and b*) were increased as market weight increased (p<0.05). Hunter a* value was greater in gilts (p<0.01) but L* value and b* value were not affected by sex of pigs. Net profit [(carcass weight${\times}$price by carcass grade)-(total feed cost+cost of purchased pig)] was higher in gilts than barrows (p<0.01), and was higher (p<0.05) in the pigs marketed at 110 and 120 kg market weight compared with 100 kg market weight. These results demonstrated that gilts showed higher carcass characteristics, pork quality, feed cost per kg body weight gain and net profit compared with barrows. Moreover, 110 or 120 kg body weight would be the recommended market weight based on pork quality and net profit for swine producers.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1449-1454
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• 2014

The co-sensitization of N719 with a cyclic thiourea functionalized organic dye, coded AZ5, for dye-sensitized solar cells (DSSCs) was demonstrated. Due to its intensive absorption in ultraviolet region, AZ5 could compensate the loss of light harvest induced by triiodide, thereby the short-circuit photocurrent density ($J_{sc}$) was increased for co-sensitized (N719+AZ5) DSSC. Moreover, the electron recombination and dye aggregation were retarded upon N719 cocktail co-sensitized with AZ5, thus the open-circuit voltage ($V_{oc}$) of co-sensitized device was enhanced as well. The increased $J_{sc}$ (17.9 $mA{\cdot}cm^{-2}$) combined with the enhanced $V_{oc}$ (698 mV) ultimately resulted in an improved power conversion efficiency (PCE) of 7.91% for co-sensitized DSSC, which was raised by 8.6% in comparison with that of N719 (PCE = 7.28%) sensitized alone. In addition, co-sensitized DSSC exhibited a better stability than that of N719 sensitized device probably due to the depression of dye desorption.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.339-342
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• 2004

본 논문은 밀리미터파 대역 무선통신 시스템 송신부의 응용을 위해 CPW 구조를 이용하여 V-band용 상향 주파수 혼합기와 2단 구동증폭기를 설계$\cdot$제작하였다. 능동소자는 본 연구실에서 제작한 $0.1{\mu}m$ 게이트 GaAs Pseudomorphic HEMTs(PHEMTs)를 사용하였으며 입$\cdot$출력단은 CPW를 사용해 정합 회로를 설계하였다. 제작된 상향 주파수 혼합기는 LO power 5.4 dBm, 2.4 GHz IF 신호를 -10.25 dBm으로 입력하였을 때 Conversion Loss 1.25 dB, LO-to-RF Isolation은 58 GHz에서 13.2 dB의 특성을 나타내었다 2단 구동 증폭기는 측정결과 60 GHz에서 S21 이득 13 dB, $58\;GHz\;\~\;64\;GHz$ 대역에서 S21 이득 12 dB 이상을 유지하는 광대역 특성을 얻었고 증폭기의 Pl dB는 3.8 dBm, 최대 출력전력은 6.5 dBm의 특성을 얻었다.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.765-768
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• 2005

In this paper, high LO-RF isolation 94 GHz MMIC single-balanced mixer was designed and fabricated using a branch line coupler and a ${\lambda}/4$ transmission line. The 94 GHz MMIC single-balanced mixer was designed using the 0.1 ${\mu}m$ InGaAs/InAlAs/GaAs Metamorphic HEMT(MHEMT) diode. The fabricated MHEMT was obtained the cut-off frequency($f_T$) of 189 GHz and the maximum oscillation frequency($f_{max}$) of 334 GHz. The designed MMIC single-balanced mixer was fabricated using 0.1 ${\mu}m$ MHEMT MMIC process. From the measurement, the conversion loss of the single-balanced mixer was 23.1 dB at an LO power of 10 dBm. The LO-RF isolations of single-balanced mixer was obtained 45.5 dB at 94.19 GHz. We obtained in this study a higher LO-RF isolation compared to some other balanced mixers in millimeter-wave frequencies.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.5
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• pp.2475-2478
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• 2016

Background: Laparoscopic partial nephrectomy is one of the major surgical techniques for small renal masses. However, it is difficult to manage cutting and suturing procedures within acceptable time periods. To overcome this difficulty, we applied a three-dimensional (3D) video system with laparoscopic partial nephrectomy, and evaluated its utility. Materials and Methods: We retrospectively enrolled 31 patients who underwent laparoscopic partial nephrectomy between November 2009 and June 2014. A conventional two-dimensional (2D) video system was used in 20 patients, and a 3D video system in 11. Patient characteristics and video system type (2D or 3D) were recorded, and correlations with perioperative outcomes were analyzed. Results: Mean age of the patients was $55.8{\pm}12.4$, mean body mass index was $25.7{\pm}3.9kg/m^2$, mean tumor size was $2.0{\pm}0.8cm$, mean R.E.N.A.L nephrometry score was $6.9{\pm}1.9$, and clinical stage was T1a in all patients. There were no significant differences in operative time (p=0.348), pneumoperitoneum time (p=0.322), cutting time (p=0.493), estimated blood loss (p=0.335), and Clavien grade of >II complication rate (p=0.719) between the two groups. However, warm ischemic time was significantly shorter in the 3D group than the 2D group (16.1 min vs. 21.2min, p=0.021), which resulted from short suturing time (9.1 min vs. 15.2 min, p=0.008). No open conversion occurred in either group. Conclusions: A 3D video system allows the shortening of warm ischemic time in laparoscopic partial nephrectomy and thus may be useful in improving the procedure.