• 전자공학회논문지
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• 제49권10호
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• pp.47-53
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• 2012

시간 반전 (time-reversal, TR) 전처리 기법은 유효 채널의 전력을 특정 시간으로 집중시키는 역할을 하며, 이를 통해 단일 탭 수신기의 수신 성능을 향상시킬 수 있다. 선형 블록 전처리 형태를 가지는 주파수 영역 동일 이득 결합 (frequency-domain equal-gain-combining, FD-EGC) TR 기법은 기존의 TR 기법에 비해 temporal focusing 성능이 뛰어나다. 또한, FD-EGC는 분산 안테나 시스템 (distributed antenna systems, DAS)에서 minimum mean square error 수신기의 수신 성능을 향상시킨다. 본 논문에서는 이러한 FD-EGC의 수신 성능 분석에 그치지 않고, capacity 성능을 분석하는 것에 중점을 두었다. 우선, DAS에서 FD-EGC의 capacity를 유도하였으며, 안테나 수에 따라 capacity가 증가함을 보였다. 이어 정보 이론적 보안 측면에서 secrecy rate를 유도하였으며, 이를 통해 FD-EGC가 다른 사용자에게 보안을 유지하면서도 목표 사용자에게는 많은 양의 정보를 전송할 수 있음을 보였다.

• Journal of Applied Biological Chemistry
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• 제60권3호
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• pp.199-205
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• 2017

To investigate the anti-inflammatory activity of natural products, we determined the anti-inflammatory activity of purified epigallocatechin (EGC) from Camellia sinensis leaves. In the present study, we found that EGC inhibited the production of proinflammatory mediators (IL-6, TNF-${\alpha}$, NO, and $PGE_2$) in lipopolysaccharide (LPS)-stimulated Raw 264.7 cells. Suppression of IL-6 seems to be at least partly attributable to the inhibitory effect of EGC. TNF-${\alpha}$ is a major cytokine produced by LPS-induced macrophages, and they have a wide variety of biological functions including regulation of inflammation. The inhibition of IL-6 and TNF-${\alpha}$ production by EGC may downregulate the acute-phase response to LPS, thereby reducing LPS-induced inflammation. In addition to IL-6 and TNF-${\alpha}$, EGC effectively reduced the production of other key inflammatory mediators, including NO and $PGE_2$. The inhibitory effect of EGC on NO and $PGE_2$ production was supported by the suppression of inducible nitric oxide synthase and COX-2 at protein levels. These results support the traditional use of EGC in the alleviation of various inflammation-associated diseases and suggest that EGC might be useful in the development of new functional foods for inflammatory diseases.

• 한국콘텐츠학회논문지
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• 제12권11호
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• pp.278-285
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• 2012

녹차를 천일염과 혼합하여 발효시킨 후 항균활성을 가지고 있고 셀룰라제가 없는 균종을 첨가하여 발효시킨 실험에서 녹차만을 발효시켰을 경우보다 천일염을 첨가하여 발효시킨 모든 시료에서 카테킨류인 EGC, EC, EGCG, ECG의 추출량이 증가하였고, 발효 일에 따른 분석에서는 EGC(epigallocatechin), ECG(epicatechin gallate), EC(epicatechin), EGCG(epigallocatechin gallate)모두에서 2일째와 3일째 높은 추출량이 검출되었다. 또한 발효균을 첨가하여 발효시켰을 경우 Paenibacillus spp에서는 모든 카테킨류(EGC, EC, EGCG, ECG)의 추출량이 증가하였고, Bacillus amyloliquefaciens에서는 EGC와 EC는 감소하고 EGCG와 ECG는 증가하였으며, Bacillus pumilus, Bacillus subtilis는 모든 카테킨류(EGC, EC, EGCG, ECG)에서 감소하였다. 위와 같은 실험의 결과에서 녹차에 천일염과 Paenibacillus spp를 함께 3일 동안 발효시킨 결과에서 가장 많은 카테킨류가 추출되었다.

• Journal of Gastric Cancer
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• 제23권1호
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• pp.146-158
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• 2023

Endoscopic resection (ER) is widely performed for early gastric cancer (EGC) with a negligible risk of lymph node metastasis (LNM) in Eastern Asian countries. In particular, endoscopic submucosal dissection (ESD) leads to a high en bloc resection rate, enabling accurate pathological evaluation. As undifferentiated EGC (UD-EGC) is known to result in a higher incidence of LNM and infiltrative growth than differentiated EGC (D-EGC), the indications for ER are limited compared with those for D-EGC. Previously, clinical staging as intramucosal UD-EGC ≤2 cm, without ulceration, was presented as 'weakly recommended' or 'expanded indications' for ER in the guidelines of the United States, Europe, Korea, and Japan. Based on promising long-term outcomes from a prospective multicenter study by the Japan Clinical Oncology Group (JCOG) 1009/1010, the status of this indication has expanded and is now considered 'absolute indications' in the latest Japanese guidelines published in 2021. In this study, which comprised 275 patients with UD-EGC (cT1a, ≤2 cm, without ulceration) treated with ESD, the 5-year overall survival (OS) was 99.3% (95% confidence interval, 97.1%-99.8%), which was higher than the threshold 5-year OS (89.9%). Currently, the levels of evidence grades and recommendations for ER of UD-EGC differ among Japan, Korea, and Western countries. Therefore, a further discussion is warranted to generalize the indications for ER of UD-EGC in countries besides Japan.

• Journal of Gastric Cancer
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• 제17권4호
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• pp.331-341
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• 2017

Purpose: This study aimed to evaluate the clinical significance of microscopic invasion to determine the adequate resection margin in early gastric cancer (EGC). Materials and Methods: A retrospective review was performed that included patients who underwent gastrectomy for clinical early gastric cancer (cEGC) at Seoul National University Hospital between January 2007 and December 2010. After subtracting the microscopic resection margin from the gross resection margin for each proximal or distal resection margin, microscopic invasion was represented by the larger value. Microscopic invasion and its risk factors were analyzed according to the clinicopathologic characteristics. Results: In total, 861 patients were enrolled in the study. Microscopic invasion of cEGC was $6.0{\pm}12.8mm$, and the proportion of patients with microscopic invasion ${\geq}0mm$ was 78.4%. In the risk group, tumor location, pT stage, and differentiation did not significantly discriminate the presence of microscopic invasion. The microscopic invasion of EGC-IIb was $13.9{\pm}16.8mm$, which was significantly greater than that of EGC-I. No linear correlation was observed between the overall tumor size and microscopic invasion (R=0.030). The independent risk factors for microscopic invasion ${\geq}20mm$ were EGC-IIb vs. EGC-I/IIa/IIc/III (odds ratio [OR], 3.103; 95% confidence interval [CI], 1.533-6.282; P=0.002) and male vs. female sex (OR, 1.655; 95% CI, 1.012-2.705; P=0.045). Conclusions: Male sex and EGC-IIb were independent risk factors for microscopic invasion ${\geq}20mm$. Examination of intraoperative frozen sections is highly recommended to avoid resection margin involvement, especially in cases of EGC-IIb.

• Journal of Gastric Cancer
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• 제11권3호
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• pp.146-154
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• 2011

Endoscopic resection has been accepted as a curative modality for early gastric cancer (EGC). Since conventional endoscopic mucosal resection (EMR) has been introduced, many improvements in endoscopic accessories and techniques have been achieved. Recently, endoscopic submucosal dissection (ESD) using various electrosurgical knives has been performed for complete resection of EGC and enables complete resection of EGC, which is difficult to completely resect in the era of conventional EMR. Currently, ESD is accepted as the standard method for endoscopic resection of EGC in indicated cases. In this review, the history of endoscopic treatment for EGC, overall ESD procedures, and indications and clinical results of endoscopic treatment will be presented.

• 한국위성정보통신학회논문지
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• 제12권2호
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• pp.38-41
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• 2017

이동형 위성단말의 운용 환경에서는 장애물로 수신 성능이 감소한다. 하나의 방법으로 Diversity를 적용하여 수신 성능을 향상시킬 수 있다. 본 논문에서는 Diversity방법 중 Equal Gain Combining(EGC)방식과 Selective Combining(SC)방식을 적용하여 성능을 분석한다. 분석을 위해 이동형 위성단말로 측정한 결과를 활용한다. 분석결과 SC방식을 사용 시 성능향상을 확인할 수 있었다. 하지만 EGC방식은 rural지역에선 성능향상을 보이지만, urban지역에서는 성능이 나빠지는 결과를 확인할 수 있었다.

• Journal of Gastric Cancer
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• 제21권3호
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• pp.246-257
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• 2021

Purpose: It is unclear whether high-definition (HD) imaging improves visibility and diagnostic ability in early gastric cancer (EGC) compared with standard-definition (SD) imaging. We aimed to compare the diagnostic performance and visibility scores of HD and SD ultraslim endoscopes in EGC. Materials and Methods: We used HD and SD ultraslim endoscopes to obtain 60 images with similar compositions of gastric environments. Of the 60 images, 30 showed EGC (15 images for each modality) and 30 showed no EGC (15 images for each modality). Seventeen endoscopists evaluated the presence and location of the lesions in each image. Diagnostic ability was compared between modalities. The color difference between a lesion and the surrounding mucosa (ΔE) was measured and compared between the modalities. Results: The ability of HD to detect EGC was significantly higher than that of SD (accuracy: 80.8% vs. 71.6%, P=0.017; sensitivity: 94.9% vs. 76.5%, P<0.001; positive predictive value, 76.2% vs. 55.3%, P<0.001; and negative predictive value (NPV), 94.1% vs. 73.5%, P<0.001). The ability of HD to determine the horizontal extent of EGC was significantly higher than that of SD (accuracy: 71.0% vs. 57.8%, P=0.004; sensitivity: 75.3% vs. 49.0%, P<0.001; NPV, 72.9% vs. 55.9%, P<0.001; and area under the curve: 0.891 vs. 0.631, P=0.038). The mean ΔE was significantly higher for HD than for SD (10.3 vs. 5.9, P=0.011). Conclusions: The HD ultraslim endoscope showed a higher diagnostic performance in EGC than the SD endoscope because it provided good color contrast.

• Journal of Gastric Cancer
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• 제18권2호
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• pp.152-160
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• 2018

Purpose: Totally laparoscopic gastrectomy (TLG) for advanced gastric cancer (AGC) is a technically and oncologically challenging procedure for surgeons. This study aimed to compare the oncologic feasibility and technical safety of TLG for AGC versus early gastric cancer (EGC). Materials and Methods: Between 2011 and 2016, 535 patients (EGC, 375; AGC, 160) underwent curative TLG for gastric cancer. Clinicopathologic characteristics and surgical outcomes of both patient groups were analyzed and compared. Results: Patients with AGC required a longer operation time and experienced more intraoperative blood loss than those with EGC did. However, patients from both the AGC and EGC groups demonstrated similar short-term surgical outcomes such as postoperative morbidity (14.4% vs. 13.3%, P=0.626), mortality (0% vs. 0.5%, P=0.879), time-to-first oral intake (2.7 days for both groups, P=0.830), and postoperative hospital stay (10.2 days vs. 10.1 days, P=0.886). D2 lymph node dissection could be achieved in the AGC group (95%), with an adequate number of lymph nodes being dissected ($36.0{\pm}14.9$). In the AGC group, the 3-year overall and disease-free survival rates were 80.5% and 73.7%, respectively. Conclusions: TLG is as safe and effective for AGC as it is for EGC.

• 한국컴퓨터정보학회논문지
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• 제11권5호
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• pp.195-201
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• 2006

MC-CDMA의 전체 시스템 대역폭은 부대역으로 분할되며, 각 부대역은 직접시권스확산을 사용하고 각 부대역 신호는 부캐리어 주파수를 사용하여 전송한다. 본 논문에서는 주파수 선택적 나까카미-m 페인팅 채널에서 동이득 합성법과 최대비 합성법을 사용한 MC-CDMA시스템 성능을 분석한다. 본 논문에서 제안된 시스템은 데이터 스트림을 직렬에서 병렬로 변환하여, 각 병렬 데이터 스트림을 MC-CDMA시스템에 사용한다. 데이터 스트림은 송신기에서 칩 레벨과 심볼 프락션 레벨을 확산시킨다. 본 논문에서는 동 이득 합성과 최대비 합성 두가지 다이버시티 합성법을 비교분석하였다. 동이득 합성법 보다 최대비 합성법을 사용한 시스템 성능이 우월하였다.