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Dual Long Memory Properties in Marine Freight Rates
Sang Hoon Kang(강상훈),Seong-Min Yoon(윤성민) 한국경제통상학회 2010 경제연구 Vol.28 No.4
This paper examines the long memory properties in three indices of the marine freight transportation market. In particular, the existence of the long memory property in the level of returns and volatility is the focus of the study. For this purpose, the ARFIMA, ARFIMA-GARCH, and ARFIMA-FIGARCH models were estimated under the assumption of normal and skewed Student-t distributions. The empirical analysis of this study provides some interesting results: First, the results of the ARFIMA model indicate the existence of long memory, implying possible inefficiencies in the Baltic freight transportation market. Second, the results of the ARFIMA-GARCH model indicate strong persistence in the volatility and a weakening presence of long memory in the returns. Third, the results of the ARFIMA FIGARCH model show a strong long memory in the volatility of the indices examined. Only the Baltic Dry Index (BDI) case exhibits the dual long memory property in the level of returns and volatility. Fourth, a skewed Student-t distribution may be appropriate to capture the tendency of residual distributions referring to asymmetry and leptokurtosis. We think that the models proposed in this study and the empirical results are useful to predict the dynamics of the marine freight rates. 본 연구는 국제해운운송시장의 세 가지 운임지수 움직임에 내재된 장기기억 특성을 분석하였다. 특히 수익률과 변동성에 장기기억 특성이 존재하는지에 분석의 초점을 맞추었다. 이를 위하여 정구분포와 편향된 Student-t 분포 가정 하에서 ARFIMA, ARFIMA-GARCH 및 ARFIMA-FIGARCH 모형을 추정하였다. 실증분석을 통하여 몇 가지 흥미로운 분석결과를 얻었는데, 그 내용은 다음과 같다. 첫째, ARFIMA 모형의 추정 결과 장기기억 특성이 존재하는 것으로 나타났는데, 이는 발틱 해운운송시장이 효율적이지 못할 가능성이 있다는 것을 의미한다. 둘째, ARFIMA-GARCH 모형의 추정 결과 변동성에는 지속성이 강하지만 수익률에는 장기기억 특성이 상대적으로 약한 것으로 나타났다. 셋째, ARFIMA-FIGARCH 모형의 추정 결과에 의하면 역시 운임지수들의 변동성에 장기기억 특성이 강한 것으로 나타났다. 그리고 Baltic Dry Index (BDI) 에서는 이원적 장기기억 특성이 존재하는 것이 발견되었다. 넷째, 편향된 Student-t 분포가 변동성의 비대칭성과 첨예성을 포착하는데 적절한 것으로 나타났다. 본 연구에서 제안된 모형들과 추정 결과들은 국제해운운임의 변화를 예측하는데 유용하게 활용될 수 있을 것으로 기대된다.
( Sung Hwa Sohn ),( Sang Yeon Lee ),( Jun Choi ),( Ho Hee Jang ),( Tae Hoon Kang ),( Jong Keun Kim ),( In Kyoung Kim ),( Deuk Ki Lee ),( Seulgi Choi ),( Il Sub Yoon ),( Ji Woo Chung ),( Jae Hwan Nam ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.12
Apios americana Medik (hereinafter Apios) has been reported to treat diseases, including cancer, hypertension, obesity, and diabetes. The therapeutic effect of Apios is likely to be associated with its anti-inflammatory activity. This study was conducted to evaluate the protective effects of Apios in animal models of acute lung injury induced by lipopolysaccharide (LPS) or pandemic H1N1 2009 influenza A virus (H1N1). Mice were exposed to LPS or H1N1 for 2-4 days to induce acute lung injury. The treatment groups were administered Apios extracts via oral injection for 8 weeks before LPS treatment or H1N1 infection. To investigate the effects of Apios, we assessed the mice for in vivo effects of Apios on immune cell infiltration and the level of pro-inflammatory cytokines in the bronchoalveolar lavage (BAL) fluid, and histopathological changes in the lung. After induction of acute lung injury, the numbers of neutrophils and total cells were lower in the Apios-treated groups than in the non-Apios-treated LPS and H1N1 groups. The Apios groups tended to have lower levels of tumor necrosis factor-a and interleukin-6 in BAL fluid. In addition, the histopathological changes in the lungs were markedly reduced in the Apios-treated groups. These data suggest that Apios treatment reduces LPS- and H1N1-induced lung inflammation. These protective effects of Apios suggest that it may have therapeutic potential in acute lung injury.
Diffraction Behaviors of New Photopolymers and their Diffuser Properties
Yoon, Hyuk,Kim, Jae-Hong,Lee, Seung-Hwan,Paek, Sang-Hyon,Choi, Dong-Hoon The Korean Infomation Display Society 2004 Journal of information display Vol.5 No.1
Photopolymers are quite promising candidates for holographic data storage and diffusers because of their high sensitivity and high refractive index modulation. New photopolymers were prepared using the cellulose ester binder bearing different kinds of monomer. The holographic gratings were elaborated successfully in these photopolymer samples by conventional optical interference method. We investigated the dynamic behavior of the diffraction efficiency and the effect of the functionality of the monomer doped into the polymer binder. Triacrylate monomer doped photopolymer showed the highest diffraction efficiency of around 80-90 %, even under low intensity of writing beam (I=2 mW/$cm^2$). We inscribed the gratings of the glass diffuser on the surface of the photopolymer and investigated their diffusion properties.
대설특성을 통한 잠재적 위험도 분석 - 충청북도 11개 시·군을 중심으로 -
Sang Hoon Yoon,Keun Oh Park,Geun Young Kim 한국재난정보학회 2015 한국재난정보학회 논문집 Vol.11 No.1
본 연구에서는 충청북도 내 각 지자체를 대상으로 지역별 대설특성을 통한 잠재적 위험요인을 분석하였다. 분석결과, 35년 평균적설량으로 인한 잠재적 위험도는 제천시와 보은군이 가장 높았으며 35년 최대적설량을 통한 잠재적 위험요인에서는 다른 결과가 도출되는 것을 알 수 있었다. 잠재적 위험요인에 대한 지역의 빈도수를 살펴보면 가장 높은 지역은 보은군, 제천시, 괴산군, 영동군, 청주시 순으로 도출되었다. 본 연구는 일반적인 대설특성뿐만 아니라 잠재적인 위험요인들을 도출하고 그에 대한 위험도를 제시하였다는 점에서 그 의의를 가진다. 본 연구의 결과는 향후 충청북도 각 지자체들의 제설대응체계 및 방안 마련에 기초자료로 활용할 수 있을 것이다. This Study analyzed heavy snow properties according to the area that was based by winter weather properties and the damage data by the heavy snow among each local government of Chungcheongbuk-do. The result of analysis, Jecheon-si and Boeun-gun are represented the highest dangerous regions by potential degree of risk by average amount of snowfall for 35 years. But, the potential degree of risk by maximum amount of snowfall for 35 years is different with it. Cheongju-si and Youngdong-gun, Goesan-gun, Boeun-gun are represented the highest dangerous regions. Examining the frequency of regions with potential danger factors according to the characteristics of heavy snowfall, Boeun-gun and Jecheon-si, Goesan-gun, Youngdong-gun, Cheongju-si is derived the highest dangerous regions in Chungcheongbuk-do.
Efficacy evaluation of SurgiGuard<SUP>®</SUP> in partially hepatectomized pigs
Sung Hyun Kim,Hye Sung Yoon,Chang Hoon In,Kyung Sik Kim 한국간담췌외과학회 2016 한국간담췌외과학회지 Vol.20 No.3
Backgrounds/Aims: This study evaluated the hemostatic effects of a novel oxidized regenerated cellulose, SurgiGuard<SUP>®</SUP>, during liver surgery, using a reproducible and clinically relevant animal model. Methods: Fifteen mini-pigs underwent left partial hepatectomy. They were randomized to treatment of the resected surface with SurgiGuard<SUP>®</SUP> (Group C [test], n=5), Surgicel<SUP>®</SUP> (Group B [reference], n=5), or nothing (Group A [control], n=5). Blood loss was measured 5, 7 and 9 min after resection. Time to hemostasis was recorded. Mini-pigs were necropsied 4 or 6 weeks postoperatively to evaluate toxicity changes and material dissolution. Results: The median resected liver weight was 2.13 g (2.02-2.20) in control group, 2.04 g (2.01-2.13) in reference group, and 2.01 g (1.99-2.12) in test group (p=0.024). Median total blood loss was 57.18 g (52.02-59.54) in control group, 32.52 g (27.66-35.10) in reference group, and 35.52 g (25.70-38.71) in test group (p=0.008). Blood loss at 0-5 minutes and 7-9 minutes was significantly different between groups (p=0.009 and p=0.006, respectively). At necropsy, no hematomas, granulomas, or adhesions were noted in any group. Histopathological analysis revealed no changes suggesting toxicity related to SurgiGuard<SUP>®</SUP>. Conclusions: SurgiGuard<SUP>®</SUP> is as effective as Surgicel<SUP>®</SUP> in achieving hemostasis after porcine partial liver resection.
Sung Ho Lee,Gi Hong Choi,Dai Hoon Han,Kyung Sik Kim,Jin Sub Choi,Seoung Yoon Rho 한국간담췌외과학회 2021 Annals of hepato-biliary-pancreatic surgery Vol.25 No.1
Backgrounds/Aims: Despite advances in surgical techniques and perioperative supportive care, radical resection of hilar cholangiocarcinoma is the only modality that can achieve long-term survival. We chronologically investigated surgical and oncological outcomes of hilar cholangiocarcinoma and analyzed the factors affecting overall survival. Methods: We retrospectively enrolled 165 patients with hilar cholangiocarcinoma who underwent liver resection with a curative intent. The patients were divided into groups based on the period when the surgery was performed: period I (2005-2011) and period II (2012-2018). The clinicopathological characteristics, perioperative outcomes, and survival outcomes were analyzed. Results: The patients’ age, serum CA19-9 levels, and serum bilirubin levels at diagnosis were significantly higher in the period I group. There were no differences in pathological characteristics such as tumor stage, histopathologic status, and resection status. However, perioperative outcomes, such as estimated blood loss (1528.8 vs. 1034.1 mL, p=0.020) and postoperative severe complication rate (51.3% vs. 26.4%, p=0.022), were significantly lower in the period II group. Regression analysis demonstrated that period I (hazard ratio [HR]=1.591; 95% confidence interval [CI]=1.049-2.414; p=0.029), preoperative serum bilirubin at diagnosis (HR=1.585; 95% CI=1.058-2.374; p=0.026), and tumor stage (III, IV) (HR=1.671; 95% CI: 1.133-2.464; p=0.010) were significantly associated with poor prognosis. The 5-year survival rate was better in the period II patients than in the period I patients (35.1% vs. 21.0%, p=0.0071). Conclusions: The surgical and oncological outcomes were better in period II. Preoperative serum bilirubin and advanced tumor stage were associated with poor prognosis in patients with hilar cholangiocarcinoma.