• 한국통신학회논문지
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• 제24권6A호
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• pp.767-774
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• 1999

본 논문에서는 서로 다른 대역폭을 갖는 비동기 W-CDMA 시스템의 성능을 비교하였다. 채널은 이산적인 다중 경로 성분으로 구성되어 있는 광대역 다중경로 환경을 고려하였고, 이 다중경로 성분의 각각의 크기는 레일리 분포를 갖는 것으로 가정하였다. W-CDMA 시스템의 대역폭에 따라 1칩 구간 내의 다중경로의 수가 다르기 때문에, 다른 대역폭을 갖는 각각의W-CDMA 시스템은 서로 다른 다중경로의 영향을 겪게 된다. 시스템의 용량에 따른 평균 에러확률을 유도하였고, DS-CDMA 시스템에서 EGC(Equal Gain Combining) 다이버시티를 채용한 레이크 수신기를 사용하여 시스템의 대역폭에 따른 용량을 비교하였다.

• Journal of Gastric Cancer
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• 제15권2호
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• pp.139-142
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• 2015

Hepatic metastasis of early gastric cancer (EGC) following subtotal gastrectomy with lymphadenectomy is rare. We report the case of a 61-year-old male patient who was diagnosed with EGC that was initially treated using endoscopic submucosal dissection (ESD) and subsequently underwent laparoscopic subtotal gastrectomy. Histopathological examination of the patient's ESD specimen showed a moderately differentiated tubular adenocarcinoma invading the submucosa without lymphatic invasion. The deep margin of the specimen was positive for adenocarcinoma, and he subsequently underwent laparoscopic distal gastrectomy. The patient developed liver metastasis 15 months after the operation and then underwent liver resection. Histology of the resected specimen confirmed the diagnosis of two foci of metastatic adenocarcinoma originating from stomach cancer. Immunohistochemical analysis of the specimen demonstrated overexpression of human epidermal growth factor receptor 2. The patient was treated with trastuzumab in combination with chemotherapy consisting of capecitabine and cisplatin. Twenty-four months after the operation, the patient remained free of recurrence.

• 한국초등과학교육학회지:초등과학교육
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• 제19권2호
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• pp.93-105
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• 2000

The purpose of the study is to find out students' misconceptions and the stability of misconceptions in the domain of mechanics. According to the incorrect choices by grades, three different kinds of conceptual change were identified ; (1) easily overcome misconceptions, (2) stable misconceptions, and (3) reinforced misconceptions. The analyses of the results showed that easily overcome misconceptions occurred in simple or visual concepts, stable misconceptions occurred in the concepts involving EGC(experiential gestalt of causation) or in the concepts overgeneralized in school teaming, and finally, reinforced misconceptions as grade level increases occurred in the concepts EGC with scientific logical procedures. The results on the type of conceptual changes may provide significant cognitive theoretic evidences on the sources of misconceptions.

• 한국전자파학회논문지
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• 제12권3호
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• pp.470-477
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• 2001

Multucarrier code-division multiple access(MC-CDMA) is one of the promising technique for high capacity wireless communication. Hower the carrier phase error and frequency offest cause the performance degradation of MC-CDMA due to the inter-carrier interference. In this work, downlink performance of the partially coherent MC-CDMA is analytically derived in Rayleigh fading channels. The bit error rate sensitivity by combining method, Maxiaml ratio combining (MRC)and Equal gain combining(EGC), is compared as functions of phase errors. multi-user interference, and received signal-to-noise ratio. The results show that the susceptibility for the performance degradation of EGc and MRC is negligible for loop SNR's of above 15 dB and above 10 dB, respectivtely.

• Journal of Communications and Networks
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• 제15권1호
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• pp.25-30
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• 2013

Uplink multicarrier code-division multiple-access (MC-CDMA) with equal gain combining (EGC) over Nakagami fading channels is considered. An improved expression which is a feasible alternative for the bit error rate (BER) performance evaluation of MC-CDMA signals is proposed. Simulated annealing algorithm is employed to obtain the optimum value of the coefficients belonging to the proposed expression. Numerical examples show that the performance curves computed by the improved expression are in good agreement with the results obtained by the exact expression. Thus, the proposed expression can improve the accuracy of BER performance evaluation that has been realized by the approximate expression.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.30-34
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• 2008

In this paper, we analyze the performance of pulse position modulation-time hopping ultra wide band (PPM-TH UWB) systems with antenna diversity technique in indoor wireless channel. A modified Saleh and Valenzuela (SV) model is adopted as a UWB indoor channel model. Perfect synchronization between a transmitter and a receiver is assumed. Therefore, coherent equal gain combining (EGC) scheme to collect the energy available in the multipath components is investigated. It is shown that the performance is improved by increasing the number of antennas at the receiver. The results of this paper can be applied to the applications of UWB.

• Journal of Digestive Cancer Research
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• 제7권2호
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• pp.31-39
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• 2019

The early detection of early gastric cancer (EGC) is important. However, the sensitivity of conventional white light imaging (WLI) in detecting EGC had been reported to range only from 77% to 84%. Although the resolution of endoscopes has been remarkably developed, precancerous lesions such as adenomas and microscopic early cancers are difficult to diagnose with general endoscopy. Linked Color Imaging (LCI) magnifies the differences in color for easy detection. Therefore, it produces a bright image from a distance and is performed for screening endoscopy. The 410 nm wavelength of BLI (Blue Light Imaging) helps to detect cancer by showing microstructure and microvessels in the mucosal superficial layer. This review will focus on the utility of Image enhanced endoscopy (IEE) techniques in diagnosis of gastrointestinal cancer.

• Journal of Gastric Cancer
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• 제14권2호
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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.

• Journal of Gastric Cancer
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• 제20권3호
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• pp.245-255
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• 2020

Purpose: Recently, non-exposure simple suturing endoscopic full-thickness resection (NESS-EFTR) was developed to prevent tumor exposure to the peritoneal cavity. This study aimed to evaluate the feasibility of NESS-EFTR with sentinel basin dissection for early gastric cancer (EGC). Materials and Methods: This was the prospective SENORITA 3 pilot. From July 2017 to January 2018, 20 patients with EGC smaller than 3 cm without an absolute indication for endoscopic submucosal dissection were enrolled. The sentinel basin was detected using Tc^99m-phytate and indocyanine green, and the NESS-EFTR procedure was performed when all sentinel basin nodes were tumor-free on frozen pathologic examination. We evaluated the complete resection and intraoperative perforation rates as well as the incidence of postoperative complications. Results: Among the 20 enrolled patients, one dropped out due to large tumor size, while another underwent conventional laparoscopic gastrectomy due to metastatic sentinel lymph nodes. All NESS-EFTR procedures were performed in 17 of the 18 other patients (94.4%) without conversion, and the complete resection rate was 83.3% (15/18). The intraoperative perforation rate was 27.8% (5/18), and endoscopic clipping or laparoscopic suturing or stapling was performed at the perforation site. There was one case of postoperative complications treated with endoscopic clipping; the others were discharged without any event. Conclusions: NESS-EFTR with sentinel basin dissection is a technically challenging procedure that obtains safe margins, prevents intraoperative perforation, and may be a treatment option for EGC after additional experience.

• Journal of Preventive Medicine and Public Health
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• 제49권4호
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• pp.197-204
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• 2016

Objectives: In the context of the global decrease in mortality due to gastric cancer, previous studies have reported that the effect of chronic Helicobacter pylori (H. pylori) infection on the incidence of gastric cancer varies among regions. This systematic review was conducted to investigate H. pylori as a risk factor for gastric cancer in Korea, where the incidence of gastric cancer is among the highest in the world. Methods: A search strategy was established to identify articles published in Korean as well as in English. Ultimately, we included observational studies conducted among Korean patients that designed with an age-matched and sex-matched control group that reported the odds ratio associated with H. pylori. Gastric cancer cases were subdivided into overall (OGC), cardia (CGC), non-cardia (NGC), early (EGC), advanced, intestinal (IGC), and diffuse forms of gastric cancer. Summary odds ratios (SORs) with 95% confidence intervals (CIs) were calculated in the meta-analysis using a random-effect model. Results: Eleven case-control studies were ultimately selected. H. pylori was associated with an SOR of 1.81 (95% CI, 1.29 to 2.54) for OGC. Additionally, statistically significant risks were observed for CGC, NGC, EGC, and IGC. Conclusions: Chronic H. pylori infection was found to raise the risk of gastric cancer among Koreans, with the highest risk observed for CGC and EGC (SOR=2.88 for both). Follow-up clinical epidemiologic studies are needed to assess the effects of current treatments aimed at eradicating H. pylori infections.