• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.191-194
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• 2006

In this paper, we present a detailed mechanism of drag reduction by dimples and roughness on a sphere by measuring the streamwise velocity above the dimpled and roughened surfaces, respectively. Dimples cause local flow separation and trigger the shear layer instability along the separating shear layer, resulting in generation of large turbulence intensity. With this increased turbulence, the flow reattaches to the sphere surface with high momentum near the wall and overcomes strong adverse pressure gradient formed in the rear sphere surface. As a result, dimples delay main separation and reduce drag significantly. The present study suggests that generation of a separation bubble, i.e. a closed-loop streamline consisting of separation and reattachment, on a body surface is an important flow-control strategy for drag reduction on a bluff body such as the sphere and cylinder. In the case of roughened sphere, the boundary layer flow is directly triggered by roughness and changes to a turbulent flow. Due to this change, the drag significantly decreases. As the Reynolds number further increases, transition to turbulence occurs earlier on the sphere surface. Because of faster growth of turbulent boundary layer by roughness, earlier transition thickens the boundary layer, resulting in earlier separation and drag increase with increasing Reynolds number

• Strategy21
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• 통권42호
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• pp.224-257
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• 2017

As the Trump administration withdraws the Paris Climate Agreement and shows its antipathy toward free trade, the U.S.'s soft power is most likely to weaken and its behaviors could be perceived as acts to surrender the U.S. hegemonic leadership in the world stage. Hegemonic stability theory notes that the existence of a hegemonic power contributes to international stability in the sense that it provides international public goods. A lack of the U.S's leadership in international politics, however, could be recognized as its denial of a hegemonic status. Is it intentional or accidental? The U.S's denial of hegemonic roles is the byproduct of the Trump administration's "American First" policy, not the showcase of its intention to transit hegemony to others. What is noteworthy is that China targets a niche market of hegemony as the U.S. denies its roles as the international leader. Put it another way, China attempts to ride hegemony for free when the U.S. denies its hegemonic roles accidentally. Faced with a niche market of hegemony, China has begun to accelerate its national strategy to make "Chinese Dream" come true. To that end, China promised again to keep the Paris Climate Agreement and attempts to play more active its roles in Shanghai Cooperation Organization(SCO), Asia Infra Investment Bank(AIIB), and "One Belt, One Road". Despite all these efforts, the U.S. is most likely to withdraw its denial of hegemony any time soon. The U.S's resumption of Freedom of Navigation Operations(FONOPs) could be a precursor of the return to a hegemonic power's willingness. In this vein, it is noteworthy that the South China Sea serves as a quasi-war zone for hegemonic conflict.

• Asian Pacific Journal of Cancer Prevention
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• 제13권5호
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• pp.1761-1766
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• 2012

Background: The appropriate interval between negative colonoscopy screenings is uncertain, but the numbers of advanced neoplasms 10 years after a negative result are generally low. We aimed to evaluate the cost-effectiveness of colorectal neoplasm screening and management based on repeat screening colonoscopy every 10 years or single colonoscopy, compared with no screening in the general population. Methods and materials: A state-transition Markov model simulated 100,000 individuals aged 50-80 years accepting repeat screening colonoscopy every 10 years or single colonoscopy, offered to every subject. Colorectal adenomas found during colonoscopy were removed by polypectomy, and the subjects were followed with surveillance every three years. For subjects with a normal result, colonoscopy was resumed within ten years in the repeat screening strategy. In single screening strategy, screening process was terminated. Direct costs such as screening tests, cancer treatment and costs of complications were included. Indirect costs were excluded from the model. The incremental cost-effectiveness ratio was used to evaluate the cost-effectiveness of the different screening strategies. Results: Assuming a first-time compliance rate of 90%, repeat screening colonoscopy and single colonoscopy can reduce the incidence of colorectal cancer by 65.8% and 67.2% respectively. The incremental cost-effectiveness ratio for single colonoscopy (49 Renminbi Yuan [RMB]) was much lower than that for repeat screening colonoscopy (474 RMB). Single colonoscopy was a more cost-effective strategy, which was not sensitive to the compliance rate of colonoscopy and the cost of advanced colorectal cancer. Conclusion: Single colonoscopy is suggested to be the more cost-effective strategy for screening and management of colorectal neoplasms and may be recommended in China clinical practice.

• 치위생과학회지
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• 제23권3호
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• pp.185-192
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• 2023

Background: The establishment of a strategy for the reduction and prevention of oral disease, a global pervasive disease, is considered one of the important national health policy strategies. In Korea, the 5th Comprehensive National Health Promotion Plan is currently in progress, but there is insufficient research on the transition process or improvement direction in the field of oral health. Methods: Changes in Comprehensive National Health Promotion Plan's Oral health sector in three countries were compared, and the direction of the three countries (Korea, the United States, and Canada) in accordance with the recent Oral health paradigm was confirmed. In this study, we reviewed the existing literature using the narrative review method to draw implications for strategies and directions for oral health promotion in Korea. Results: In Korea, the oral health promotion strategy is included in the 5th Comprehensive National Health Promotion Plan, and the project is being led by the government. The United States prepared a national-led oral health promotion strategy and suggested multi-disciplinary cooperation to improve overall oral health and reduce the oral health inequality. For more active intervention, Canada established an oral health-related department and assigned experts, while emphasizing cooperation between the government and the private sector. Conclusion: As a result of this study, Korea is also making efforts to improve oral health, but more active government intervention is needed to reduce the inequality in oral health by population group. To this end, it is necessary to establish a strong multi-sectoral cooperation system and prepare a strategy for implementation.

• Journal of Ginseng Research
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• 제44권2호
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• pp.300-307
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• 2020

Background: Emerging evidence suggests that endothelial-to-mesenchymal transition (EndMT) in endothelial dysfunction due to persistent inflammation is a key component and emerging concept in the pathogenesis of vascular diseases. Ginsenoside Rg3 (Rg3), an active compound from red ginseng, has been known to be important for vascular homeostasis. However, the effect of Rg3 on inflammation-induced EndMT has never been reported. Here, we hypothesize that Rg3 might reverse the inflammation-induced EndMT and serve as a novel therapeutic strategy for vascular diseases. Methods: EndMT was examined under an inflammatory condition mediated by the NOD1 agonist, γ-d-glutamyl-meso-diaminopimelic acid (iE-DAP), treatment in human umbilical vein endothelial cells. The expression of EndMT markers was determined by Western blot analysis, real-time polymerase chain reaction, and immunocytochemistry. The underlying mechanisms of Rg3-mediated EndMT regulation were investigated by modulating the microRNA expression. Results: The NOD1 agonist, iE-DAP, led to a fibroblast-like morphology change with a decrease in the expression of endothelial markers and an increase in the expression of the mesenchymal marker, namely EndMT. On the other hand, Rg3 markedly attenuated the iE-DAP-induced EndMT and preserved the endothelial phenotype. Mechanically, miR-139 was downregulated in cells with iE-DAP-induced EndMT and partly reversed in response to Rg3 via the regulation of NF-κB signaling, suggesting that the Rg3-miR-139-5p-NF-κB axis is a key mediator in iE-DAP-induced EndMT. Conclusion: These results suggest, for the first time, that Rg3 can be used to inhibit inflammation-induced EndMT and may be a novel therapeutic option against EndMT-associated vascular diseases.

• 대한통합의학회지
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• 제11권3호
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• pp.59-67
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• 2023

Purpose : Epithelial-to-mesenchymal transition (EMT) is recognized as an important cellular response in metastatic proceduresand characterized by loss of cellular polarity as well as gain of mesenchymal features, which enables migration and invasion. Hepatocellular carcinoma (HCC) is one of the most common primary carcinomas in the liver and exhibits a poor prognosis due to frequent extrahepatic metastasis. Taraxacum officinale has been used for a long time in oriental medicine because of its various pharmacological activitiessuch as anti-rheumatic, anti-inflammatory, antioxidative, and anticarcinogenic activities. In this study, the anti-metastatic activity of T. officinale water extract (TOWE) and ethanol extract (TOEE) was investigated through the regulation of EMT in the Huh7 cells. Methods : The effects of TOWE and TOEE on migratory and invasive activities were investigated by wound healing and in vitro invasion assays. Western blot analysis was also applied to analyze protein expression levels associated with EMT and their upstream transcription factors in Huh7 cells. Results : TOWE and TOEE treatment potently inhibited migration and invasion of Huh7 cells compared to the untreated group. Both extracts treatment inhibited protein expression levels of N-cadherin, matrix metalloproteinase (MMP)-9, and vimentin while E-cadherin was significantly accelerated. In addition, the activated status of transcription factors, Snail, nuclear factor (NF)-κ B, and zinc finger E-box binding homeobox (ZEB)1 was also inhibited with statistical significance. In comparison to both extracts, TOEE more potently attenuated migration, invasion, and EMT markers as well as their transcription factors in Huh7 cells than TOWE, which means that TOEE might possess more functional phytochemicals than TOWE. Conclusion : Consequently, TOWE and TOEEattenuated metastatic activity of hepatocellular carcinoma through the regulation of EMT markers and their transcription factors in Huh7 cells, which means that T. officinale might be a promising strategy for a chemopreventive agent against HCC metastasis.

• 사회복지연구
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• 제42권1호
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• pp.243-278
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• 2011

본 연구에서는 센의 실현가능능력 접근을 활용하여 보다 확대된 개념으로 빈곤을 조망하면서, 빈곤의 세대간 탈피에 관한 삶의 경험을 이해하고자 한다. 이를 위하여 생애초기 빈곤을 경험했으나 현재 이를 탈피한 자녀세대와 부모세대 참여자와의 심층 면접을 실시하였고, 빈곤의 세대간 탈피과정에서 발생하는 경험과 상호작용을 보다 심도있게 파악하고자 근거이론을 활용하였다. 분석결과 '빈곤' 의 의미는 자원 및 상황에 대하여 개인이 통제를 발휘하는 주체성의 성취와 자유가 부족한 상태임을 확인할 수 있었다. 따라서 빈곤의 탈피는 기능의 성취뿐만 아니라 실현가능능력을 회복한 상태라고 볼 수 있다. 이에 기초하여 세대간 탈피과정을 살펴본 결과, 관계로부터의 도움과 생애주기에서 단계별 이행이 연속적이었다는 것이 중심 현상으로 등장하였다. 이러한 중심현상은 빈곤의 탈피에서 중요한 사건이지만 동시에 불완전한 속성을 가지고 있다. 왜냐하면 관계로부터의 도움은 개인의 통제범위를 일정부분 벗어난 것이고, 참여자들이 이행의 과정에서 충분한 기간을 가지지 못해 2차 노동 시장에서 벗어나지 못하고 있기 때문이다. 따라서 본 연구에서는 관계로부터의 도움이 가지는 한계와 이행이 주는 소득상실의 위험을 최소화하기 위한 우선과제로서 국가복지의 확대와 이행지원 전략을 제안하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제28권1호
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• pp.83-91
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• 2024

Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor activated under hypoxic conditions, and it plays a crucial role in cellular stress regulation. While HIF-1α activity is essential in normal tissues, its presence in the tumor microenvironment represents a significant risk factor as it can induce angiogenesis and confer resistance to anti-cancer drugs, thereby contributing to poor prognoses. Typically, HIF-1α undergoes rapid degradation in normoxic conditions via oxygen-dependent degradation mechanisms. However, certain cancer cells can express HIF-1α even under normoxia. In this study, we observed an inclination toward increased normoxic HIF-1α expression in cancer cell lines exhibiting increased HDAC6 expression, which prompted the hypothesis that HDAC6 may modulate HIF-1α stability in normoxic conditions. To prove this hypothesis, several cancer cells with relatively higher HIF-1α levels under normoxic conditions were treated with ACY-241, a selective HDAC6 inhibitor, and small interfering RNAs for HDAC6 knockdown. Our data revealed a significant reduction in HIF-1α expression upon HDAC6 inhibition. Moreover, the downregulation of HIF-1α under normoxic conditions decreased zinc finger E-box-binding homeobox 1 expression and increased E-cadherin levels in lung cancer H1975 cells, consequently suppressing cell invasion and migration. ACY-241 treatment also demonstrated an inhibitory effect on cell invasion and migration by reducing HIF-1α level. This study confirms that HDAC6 knockdown and ACY-241 treatment effectively decrease HIF-1α expression under normoxia, thereby suppressing the epithelial-mesenchymal transition. These findings highlight the potential of selective HDAC6 inhibition as an innovative therapeutic strategy for lung cancer.

• International Journal of Automotive Technology
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• 제1권1호
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• pp.17-25
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• 2000

The electromechanical valve train (EMV) technology allows for a reduction in fuel consumption while operating under a stoichiometric air-fuel-ratio and preserves the ability to use conventional exhaust gas aftertreatment technology with a 3-way-catalyst. Compared with an engine with a camshaft-driven valve train, the variable valve timing concept makes possible an additional optimization of cold start, warm-up and transient operation. In contrast with the conventionally throttled engine, optimized control of load and in-cylinder gas movement can be used for each individual cylinder and engine cycle. A load control strategy using a "Late Intake Valve Open" (LIO) provides a reduction in start-up HC emissions of approximately 60%. Due to reduced wall-wetting, the LIO control strategy improves the transition from start to idle. "Late Exhaust Valve Open" (LEO) timing during the exhaust stroke leads to exhaust gas afterburning and, thereby, results in high exhaust gas temperatures and low HC emissions. Vehicle investigations have demonstrated an improved accuracy of the air-fuel-ratio during transient operation. Results in the New European Driving Cycle have confirmed a reduction in fuel consumption of more than 15％ while meeting EURO IV emission limits.

• International Journal of Aeronautical and Space Sciences
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• 제12권1호
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• pp.43-56
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• 2011

An integrated system composed of guidance, navigation and control (GNC) system for autonomous proximity operations and the docking of two spacecraft was developed. The position maneuvers were determined through the integration of the state-dependent Riccati equation formulated from nonlinear relative motion dynamics and relative navigation using rendezvous laser vision (Lidar) and a vision sensor system. In the vision sensor system, a switch between sensors was made along the approach phase in order to provide continuously effective navigation. As an extension of the rendezvous laser vision system, an automated terminal guidance scheme based on the Clohessy-Wiltshire state transition matrix was used to formulate a "V-bar hopping approach" reference trajectory. A proximity operations strategy was then adapted from the approach strategy used with the automated transfer vehicle. The attitude maneuvers, determined from a linear quadratic Gaussian-type control including quaternion based attitude estimation using star trackers or a vision sensor system, provided precise attitude control and robustness under uncertainties in the moments of inertia and external disturbances. These functions were then integrated into an autonomous GNC system that can perform proximity operations and meet all conditions for successful docking. A six-degree of freedom simulation was used to demonstrate the effectiveness of the integrated system.