• Structural Engineering and Mechanics
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• 제61권4호
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• pp.497-510
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• 2017

A framed structure may be composed of two sub-structures, which are linked by a hinged joint. One sub-structure is the primary system and the other is the secondary system. The primary system, which is subjected to the periodic external load, can give rise to an auto-parametric resonance of the second system. Considering the geometric-stiffness effect produced by the axially internal force, the element equation of motion is derived by the extended Hamilton's principle. The element equations are then assembled into the global non-homogeneous Mathieu-Hill equations. The Newmark's method is introduced to solve the time-history responses of the non-homogeneous Mathieu-Hill equations. The energy-growth exponent/coefficient (EGE/EGC) and a finite-time Lyapunov exponent (FLE) are proposed for determining the auto-parametric instability boundaries of the structural system. The auto-parametric instabilities are numerically analyzed for the two frames. The influence of relative stiffness between the primary and secondary systems on the auto-parametric instability boundaries is investigated. A phenomenon of the "auto-parametric internal resonance" (the auto-parametric resonance of the second system induced by a normal resonance of the primary system) is predicted through the two numerical examples. The risk of auto-parametric internal resonance is emphasized. An auto-parametric resonance experiment of a ${\Gamma}$-shaped frame is conducted for verifying the theoretical predictions and present calculation method.

• Journal of Gastric Cancer
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• 제4권2호
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• pp.75-81
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• 2004

Recently detection of early gastric cancer (EGC) has been increasing and the treatment strategies for gastric cancer have been changing. The purpose of this study was to compare clinical outcomes between laparoscopically assisted (LADG) and hand-assisted laparoscopic gastrectomy (HALDG) and open distal gastrectomy for early gastric cancer. This review is directed toward providing gastric surgeons with recent advances in the treatment of EGC. We investigated the English language literature for the past 12 years through computer searches which focused on : 1) Patient demographics, 2) Operation time, 3) Intra-operative blood loss, 4) Depth of invasion, 5) CBC, 6)Weight loss, 7) Analgesic requirement, 8)Time NPO, 9) Length of hospital stay, 10) Tumor stage, 11) Lymph node (LN) dissection, 12) Position of LN resected, 13) Complications. Improved operative techniques and surgical instrumentation have facilitated the development of minimally invasive gastric cancer surgery. The short-term benefits of laparoscopic gastrectomy included less surgical trauma, less pain, rapid return of gastrointestinal function, and shorter hospital stay, with no change in operative outcome. Laparoscopic gastrectomy was better accepted by the patients as a good procedure and promptly brought the patients back to their previous lifestyle and activities of daily living. But the advantages of HALDG for gastric cancer, extended lymph node dissection and intracorporeal anastomosis are feasible and easier with the presence of the internal hand. The hand-assisted laparoscopic (HALDG) method reported the best results in lymph node dissection.This method is an alternative to total laparoscopic radical gastrectomy. LADG and HALDG, when compared with conventional open gastrectomy, have several advantages. When performed by a skilled surgeon, LADG and HALDG are safe and useful techniques for patients with early-stage gastric cancer. Their appropriateness for gastric cancer surgery require further study.

• 한국통신학회논문지
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• 제34권7A호
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• pp.554-561
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• 2009

본 논문에서는 통신과 거리측정을 동시에 행하는 대역확산방식을 이용한 VANET에서의 거리측정 시스템에 다중반송파(Multi-Carrier) 변조방식을 적용한 시스템을 제안한다. 기존방식에서는 자기차량이 송신한 PN신호에 상대차량의 정보를 실어서 재송신하고 자기차량은 대역확산에 의해 상대차량 정보를 파악하였으며, 동시에 송수신한 PN신호의 위상차를 탐지허여 차량거리를 정확하게 측정하는 것이 가능했다. 그러나 그 차량거리 측정의 문제점으로서 위상차의 탐지 오차와 분석 능력을 높이기 위해 고속 PN신호가 펼요할 수밖에 없다. 제안 시스템은 이러한 문제점 해결을 위해 다중반송파 변조방식을 적용했다. 다중반송파 변조방식은 단일반송파와 비교해서 Chip rate이 작은 PN신호를 사용함으로 단일반송파와 동일한 주파수 대역에서 복수의 반송파 이용이 가능하다. 복수의 반송파는 등이득 합성법에 의해 합성되기 때문에 다이버시티 효과가 얻어져 위상차의 에러검출을 방지하는 것이 가능하고 정밀 거리측정도 기존방식과 비교해서 우수하게 개선되었다.

• 한국통신학회논문지
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• 제39C권9호
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• pp.757-766
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• 2014

본 논문에서는 차기 군 위성통신체계 환경에서 OTM(On-The-Move) 위성단말의 채널 blockage 신호 손실 보상을 위한 협업통신 기법을 제안하였다. 제안하는 협업기법은 인접 OTM 위성단말과 지상 무전기 체계를 통해 데이터를 공유하고 직교확산코드를 이용하여 대역확산 후 동시에 전송한다. 중첩되어 전송된 확산열은 EGC(Equal Gain Combining) 방식으로 결합한다. 성능 분석을 위해 OTM 위성단말의 blockage 채널을 2-state Markov chain으로 모델링하였으며, 이를 기반으로 협업단말들의 blockage 채널 상태에 따른 비트오류율을 도출하였다. 성능분석 결과 채널 조건이 더 나은 인접 OTM 위성단말의 협업으로 비트오류율 성능이 향상됨을 확인할 수 있었다. 특히 blockage 확률이 높을수록 협업을 통해 더욱 우수한 성능을 확인할 수 있었다. 그러나 서로 다른 지연을 갖는 확산 열 간 중첩으로 인해 협업단말 수 증가 시 다중접속간섭으로 인한 성능상의 제약이 있음을 확인하였다.

• 한국통신학회논문지
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• 제36권3A호
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• pp.198-204
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• 2011

음향 통신 시스템은 오디오와 데이터를 동시에 전송하는 기술이다. 음향 통신 시스템은 데이터 신호의 파워를 높게 할수록 데이터 신호가 소리로 들리는 문제점을 가진다. 데이터 신호의 송신 파워가 낮아질수록 전송 가능한 거리는 감소된다. 따라서 음향 통신 시스템에서 전송 거리를 증가시킬 수 있는 방법에 대한 연구가 필요하다. 본 논문에서는 데이터 전송 효율을 높이기 위해 사용되는 수신 다이버시티 기법을 음향 통신 시스템에 적용하여 송신 거리를 향상 시키고자 한다. 동일한 송신 파워로 전송될 때 제안된 시스템과 기존 시스템의 수신 성능을 거리에 따라 측정 하였다. Single Input Sing Output (SISO) 시스템에서 $7{\times}10^{-3}$의 Bit Error Rate (BER) 성능을 만족 시키는 거리가 약 2m 일 경우, Selection Combining (SC) 기법을 적용하게 되면 약 3m로 거리가 증가하고, Equal Gain Combining (EGC) 기법을 적용하면 약 4m 에서도 수신 성능을 만족 시킬 수 있다.

• Preventive Nutrition and Food Science
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• 제15권3호
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• pp.229-232
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• 2010

Caffeine and catechins from the Yabukita, Yutakamidori, Saemidori, Okumidori, and Fushun varieties of tea leaves picked during different harvesting seasons from April to October were evaluated using HPLC. Total content of catechins increased greatly with the later harvesting time of tea leaves (i.e., picking the leaves in September versus in April) and decreased slightly after September. Yabukita tea leaves picked in August contained 43.1 mg% catechins including EGC, EC, ECG, and EGCG, with the ECGC levels constituting greater than 50% of those four compounds. Yutakamidori and Okumidori varieties picked in September contained the highest catechin values, at 43.6 mg% and 31.0 mg%, respectively. Fushun and Saemidori varieties contained lower catechin concentrations of 14.5 mg% (July) and 11.7 mg% (August) compared to other varieties. The EGCG levels gradually decreased in the late harvesting season, while levels of the other catechins, EC, EGC, and ECG, gradually increased. All varieties of green tea showed a gradual decrease in caffeine content toward the end of our harvesting efforts in October, with levels of 58～68 mg% in April and 28～57 mg% in October. Yabukita, Saemidori, and Okumidori varieties reached their highest caffeine levels in late spring/early summer, with Yabukita and Okumidori varieties reaching a high of 73.4% and 63.5% caffeine, respectively, in May, and Saemidori at 64.0% in June. In particular, Fushun still contained high caffeine of 66.8 mg% (September) during the late harvesting season.

• Journal of Gastric Cancer
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• 제19권1호
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• pp.102-110
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• 2019

Purpose: Despite an increased acceptance of laparoscopic gastrectomy (LG) in early gastric cancer (EGC), there is insufficient evidence for its oncological safety in advanced gastric cancer (AGC). This is a prospective phase II clinical trial to evaluate the feasibility of LG with D2 lymph node dissection (LND) in AGC. Materials and Methods: The primary endpoint was set as 3-year disease-free survival (DFS). The eligibility criteria were as follows: 20-80 years of age, cT2N0-cT4aN3, American Society of Anesthesiologists score of 3 or less, and no other malignancy. Patients were enrolled in this single-arm study between November 2008 and May 2012. Exclusion criteria included cT4b or M1, or having final pathologic results as EGC. All patients underwent D2 lymphadenectomy. Three-year DFS rates were estimated by the Kaplan-Meier method. Results: A total of 157 patients were enrolled. The overall local complication rate was 10.2%. Conversion to open surgery occurred in 11 patients (7.0%). The mean follow-up period was $55.0{\pm}20.4months$ (1-81 months). The cumulative 3-year DFS rates were 76.3% for all stages, and 100%, 89.3%, 100%, 88.0%, 71.4%, and 35.3% for stage IB, IIA, IIB, IIIA, IIIB, and IIIC, respectively. Recurrence was observed in 37 patients (23.6%), including hematogenous (n=6), peritoneal (n=13), locoregional (n=1), distant node (n=8), and mixed recurrence (n=9). Conclusions: In addition to being technically feasible for treatment of AGC in terms of morbidity, LG with D2 LND for locally advanced gastric cancer showed acceptable 3-year DFS outcomes.

• Journal of Gastric Cancer
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• 제21권1호
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• pp.38-48
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• 2021

Purpose: As the number of gastric cancer survivors is increasing and their quality of life after surgery is being emphasized, single-port surgery is emerging as an alternative to conventional gastrectomy. A novel multi-degree-of-freedom (DOF) articulating device, the ArtiSential® device (LivsMed, Seongnam, Korea), was designed to allow more intuitive and meticulous control for surgeons facing ergonomic difficulties with conventional tools. In this study, we evaluated the feasibility of this new device during single-port laparoscopic distal gastrectomy (SP-LDG) for early gastric cancer (EGC) patients. Materials and Methods: Consecutive patients diagnosed with EGC who underwent SP-LDG with ArtiSential® (LivsMed) graspers between April 2018 and August 2020 were enrolled in the study. The clinical outcomes were compared with those of a control group, in which prebent graspers (Olympus Medical Systems Corp) were used for the same procedures. Results: Seventeen patients were enrolled in the ArtiSential® group. There was no significant difference in operative time (205.4±6.0 vs. 218.1±9.9 minutes, P= 0.270) or the quality of surgery, in terms of the number of retrieved lymph nodes (49.5±3.5 vs. 45.9±4.0, P=0.473), length of hospital stay (15.4±2.0 vs. 12.4±1.3 days, P=0.588), and postoperative complications (40.0% vs. 41.2%, P=0.595), between the ArtiSential® group and the control group. Conclusions: The new multi-DOF articulating grasper is feasible and can be used as an alternative for prebent graspers during SP-LDG.

• Journal of Gastric Cancer
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• 제22권4호
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• pp.339-347
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• 2022

Purpose: Lymphovascular invasion is a criterion for non-curative resection in patients who have undergone endoscopic submucosal dissection (ESD) for early gastric cancer (EGC). We aimed to determine the rate of extragastric metastasis (EGM) and identify the predictors of EGM in patients with negative resection margins (R0 resection) and lymphovascular invasion in post-ESD pathology. Materials and Methods: A total of 2,983 patients underwent ESD for EGC. Among them, 110 had a pathology of R0 resection and positive lymphovascular invasion. Patients underwent additional gastrectomy (n=63) or further follow-up without gastrectomy (n=47). Results: The 110 patients were assigned to one of the 3 groups according to ESD indications based on post-ESD pathology. The first group satisfied the absolute indication for ESD (n=18), the second group satisfied the expanded indications for ESD (n=34), and the last group satisfied the beyond indication (n=58). The number of occurrences of EGM in each group was 1 (5.6%), 3 (8.8%), and 3 (5.2%), respectively. The logistic regression analysis adjusted for age, sex, tumor size, and indication for ESD, showed that larger tumor size was associated with EGM (odds ratio, 1.76; 95% confidence interval, 1.00-3.10; P=0.048). In contrast, ESD indication criteria did not affect EGM (P=0.349). Conclusions: Tumor size was the only predictive indicator for EGM in patients who underwent R0 resection and lymphovascular invasion on post-ESD pathology. Even patients with pathology corresponding to the absolute indication criteria of ESD had lymphovascular invasion, which means that they require additional gastrectomy due to the risk of EGM.

• Journal of Gastric Cancer
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• 제23권3호
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• pp.375-387
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• 2023

Stomach cancer has a high annual mortality rate worldwide necessitating early detection and accurate treatment. Even experienced specialists can make erroneous judgments based on several factors. Artificial intelligence (AI) technologies are being developed rapidly to assist in this field. Here, we aimed to determine how AI technology is used in gastric cancer diagnosis and analyze how it helps patients and surgeons. Early detection and correct treatment of early gastric cancer (EGC) can greatly increase survival rates. To determine this, it is important to accurately determine the diagnosis and depth of the lesion and the presence or absence of metastasis to the lymph nodes, and suggest an appropriate treatment method. The deep learning algorithm, which has learned gastric lesion endoscopyimages, morphological characteristics, and patient clinical information, detects gastric lesions with high accuracy, sensitivity, and specificity, and predicts morphological characteristics. Through this, AI assists the judgment of specialists to help select the correct treatment method among endoscopic procedures and radical resections and helps to predict the resection margins of lesions. Additionally, AI technology has increased the diagnostic rate of both relatively inexperienced and skilled endoscopic diagnosticians. However, there were limitations in the data used for learning, such as the amount of quantitatively insufficient data, retrospective study design, single-center design, and cases of non-various lesions. Nevertheless, this assisted endoscopic diagnosis technology that incorporates deep learning technology is sufficiently practical and future-oriented and can play an important role in suggesting accurate treatment plans to surgeons for resection of lesions in the treatment of EGC.