• 제목/요약/키워드: Flow triggering

검색결과 61건 처리시간 0.023초

사면안정측면에서의 보강토 옹벽 붕괴 요인 분석 (Analysis of Triggering Events of a Geosynthetic Wall Slope Failure within Slope Stability Perspective)

  • 유충식;정혜영;정혁상
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2005년도 춘계 학술발표회 논문집
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    • pp.207-215
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    • 2005
  • This paper presents a case history of a geosynthetics-reinforced segmental retaining wall, which collapsed during a sever rainfall immediately after the completion of the wall construction. In an attempt to identify possible causes for the collapse, a comprehensive investigation was carried out including physical and strength tests on the backfill, stability analyses on the as-built design based on the current design approaches, and slope stability analyses with pore pressure consideration. The investigation revealed that the inappropriate as-built design and the bad-quality backfill were mainly responsible for the collapse. This paper describes the site condition including wall design, details of the results of investigation and finally, lessons learned. Practical significance of the findings from this study is also discussed.

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Apigenin Sensitizes Huh-7 Human Hepatocellular Carcinoma Cells to TRAIL-induced Apoptosis

  • Kim, Eun-Young;Kim, An-Keun
    • Biomolecules & Therapeutics
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    • 제20권1호
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    • pp.62-67
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    • 2012
  • TNF-related apoptosis-inducing ligand (TRAIL) is a promising agent for management of cancer because of its selective cytotoxicity to cancer cells. However, some cancer cells have resistance to TRAIL. Accordingly, novel treatment strategies are required to overcome TRAIL resistance. Here, we examined the synergistic apoptotic effect of apigenin in combination with TRAIL in Huh-7 cells. We found that combined treatment of TRAIL and apigenin markedly inhibited Huh-7 cell growth compared to either agent alone by inducing apoptosis. Combined treatment with apigenin and TRAIL induced chromatin condensation and the cleavage of poly (ADP-ribose) polymerase (PARP). In addition, enhanced apoptosis by TRAIL/apigenin combination was quantified by annexin V/PI flow cytometry analysis. Western blot analysis suggested that apigenin sensitizes cells to TRAIL-induced apoptosis by activating both intrinsic and extrinsic apoptotic pathway-related caspases. The augmented apoptotic effect by TRAIL/apigenin combination was accompanied by triggering mitochondria-dependent signaling pathway, as indicated by Bax/Bcl-2 ratio up-regulation. Our results demonstrate that combination of TRAIL and apigenin facilitates apoptosis in Huh-7 cells.

토석류 규모 산정과 영향인자와의 상관성 분석 (Estimation of Magnitude of Debris Flow and Correlation Analysis Between Influencing Factors)

  • 최영남;황희석;이형호;유남재
    • 한국지반신소재학회논문집
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    • 제16권2호
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    • pp.79-87
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    • 2017
  • 본 연구에서는 2006년부터 2013년 까지 강원도 영서 인근 지역의 토석류 피해지역 43개소에 대한 현장조사 결과를 바탕으로 토석류 규모를 산정하고 영향인자가 토석류 규모에 미치는 상관성 분석을 실시하였다. 토석류의 규모는 발생지역별로 큰 차이를 보이나 계곡형이 사면형보다 약 6.5배 큰 것으로 조사되었으며 계곡형 발생부의 토석류 규모는 전체의 약 5% 정도의 규모인 것을 확인하였다. 침식률은 계곡형에서 전체 토석류 발생량이 $10,000m^3$ 보다 큰 대규모인 경우 $19m^3/m$, $10,000m^3$ 보다 작은 경우 $8m^3/m$의 값을 갖고, 사면형은 $5m^3/m$로 산정되었다. 토석류 규모의 영향인자에 대한 상관성 분석결과, 토석류 유하부의 길이와 폭은 상관성이 높은 것으로 나타났으며, 평균경사와 침식 깊이는 상관성이 낮은 것으로 나타났다. 특히, 침식깊이는 규모와 상관성 없이 0.5~2.6m의 범위로 Ikeya(1981)가 제안한 값과 유사하였다. 연속강우량, 최대시간강우량 등 토석류 유발강우와 토석류 규모는 상관성이 낮은 것으로 분석되었다.

토석류 산사태 예측을 위한 로지스틱 회귀모형 개발 (Development of a Logistic Regression Model for Probabilistic Prediction of Debris Flow)

  • 채병곤;김원영;조용찬;김경수;이춘오;최영섭
    • 지질공학
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    • 제14권2호
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    • pp.211-222
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    • 2004
  • 이 연구는 자연사면에서 발생하는 토석류(debris flow)산사태의 확률론적 예측을 위해 로지스틱 회귀분석(logistic regression analysis)을 이용하여 변성 암 및 화강암 분포지에 적용할 수 있는 예측모델을 개발한 것이다. 산사태 예측모델을 개발하기 위해 경기 남ㆍ북부지역과 경북 상주지역에서 발생한 산사태 자료를 현장조사와 실내토질시험을 통해 직접 획득ㆍ분석하였다. 산사태 발생에 영향을 미치는 인자는 기초 통계분석은 물론 로지스틱 회귀분석을 실시하여 최종적으로 7개 영향인자를 선정하였다. 이들 7개 인자는 지형요소 2개와 지질 및 토질특성 요소 5개로 구성되어 있고, 각 인자별 가중치를 부여한 점이 큰 특징이다. 개발된 모델은 신뢰성 검증을 수행한 결과 90.74%의 예측율을 확보한 것으로 나타났다. 이 모델을 이용하여 산사태 발생가능성을 확률적ㆍ정량적으로 예측할 수 있게 되었다.

The Effects of the Attractiveness of an Internet Shopping Mall and Flow on Affective Commitment

  • Kang, Sung-Ju;Kim, Jae-Yeong;Park, Young-Kyun
    • 유통과학연구
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    • 제9권4호
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    • pp.29-42
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    • 2011
  • With the many advantages of the internet, online shopping has become one of the fastest growing types of retail businesses. However, internet-based firms are much more firmly required to retain existing customers rather than secure new ones, and to make them revisit the site by strengthening trust and loyalty, thereby improving profits and outrivaling competitors. Commitment is an essential part of successful long-term relationships between buyers and sellers. Although commitments by both parties in an exchange can provide the foundation for the development of relational social norms, disproportionate commitments can lead to opportunism by the less committed partner. Moreover, flow, which is characterized by intense concentration and enjoyment, was found to be significantly linked with exploratory use behavior, which in turn was linked to the extent of computer use. The level of flow was, itself, determined by the individual's sense of being in control, and the level of challenge perceived in maneuvering a website. Website attractiveness goes hand in hand with the attractiveness of an internet shopping mall, and it can be conceptualized as the persuasive effectiveness of a message by the use of familiarity, favor, similarity, etc. It occurs when information receivers try to achieve self-satisfaction when they actually or emotionally identify themselves with an information source. This study investigates the relationship between the perceived system characteristics of an internet shopping mall and the loyalty of online consumers, and it examines how perceived website attractiveness and flow play mediating roles between the perceived system characteristics of an internet shopping mall and the affective commitment in the context of a clothes internet shopping mall. For these purposes, a structural model comprising several variables was developed. That model was tested with an analysis of moment structure (AMOS) using data from respondents who had purchased clothing through the internet during the past three months. In this model, the perceived system characteristics of an internet shopping mall, such as familiarity, reputation, uniqueness, positive emotions, self-efficacy, and interactivity, were proposed to affect the website's attractiveness and flow, and lead to a higher affective commitment over time. Thus, the perceived website attractiveness and flow were proposed as core mediating variables between perceived system characteristics and affective commitment. The results of a reliability test using Cronbach's Alpha, and a confirmatory factor analysis warranted using unidimensionality for the measures for each construct. In addition, the nomological validity of the measures was warranted from the results of a correlation analysis. The results of empirical analyses indicated that systematic attributes resulting in website attractiveness and user's characteristics, thereby triggering customers' flow, play a crucial role in inducing customers' affective commitment, and a user's characteristics are twice as important as systematic attributes in this study. Moreover, familiarity, reputation, and uniqueness all have a significant effect on website attractiveness, and the research showed that uniqueness took the first place, and that familiarity and reputation followed in order of magnitude. The fact that reputation was not the most important factor that affects the attractiveness of an internet shopping mall, with uniqueness or familiarity having a greater impact, suggests much deeper implications. Finally, positive emotion, self-efficacy, and interactivity all have a significant effect on customers' flow. In particular, the fact that positive emotion, compared to self-efficacy or interactivity, has much more impact on flow is very suggestive.

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Size Determination of Pollens Using Gravitational and Sedimentation Field-Flow Fractionation

  • Kang, Dong-Young;Son, Min-Seok;Eum, Chul-Hun;Kim, Won-Suk;Lee, Seung-Ho
    • Bulletin of the Korean Chemical Society
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    • 제28권4호
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    • pp.613-618
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    • 2007
  • Pollens are known to be an allergen. They penetrate human respiratory system, triggering a type of seasonal allergic rhinitis called pollen allergy (hey fever). The purpose of this study is to test two field-flow fractionation (FFF) techniques, gravitational FFF (GrFFF) and sedimentation FFF (SdFFF), for their applicability to sizecharacterization of micron-sized pollens. Both GrFFF and SdFFF are elution techniques, providing sequential elution of particles based on size. They allow the size distribution as well as the mean size of the sample to be determined from the elution time. In this study, GrFFF and SdFFF were used to determine the size distribution of Paper Mulberry and Bermuda Grass pollens. For the Paper Mulberry pollen, the mean size obtained by GrFFF is 12.7 μm, and agrees rather well with the OM data with the relative error of 8.0%. For the Bermuda Grass pollen, the mean size obtained by GrFFF is 32.6 μm with the relative error of 12.3%. The mean sizes determined by SdFFF are 12.4 (relative error = 10.1%) and 27.1 μm (relative error = 5.2%) for the Paper Mulberry and the Bermuda Grass pollen, respectively. Although SdFFF tends to yield more accurate size distribution due to lower band broadening under the field strength higher than 1 G, the sizes determined by GrFFF were not significantly different from those by SdFFF.

터널굴착 중 지하수위 강하 및 깊이별 투수계수 변화를 적용한 지하수 유입량 변화 분석 (Assessment of groundwater inflow rate into a tunnel considering groundwater level drawdown and permeability reduction with depth)

  • 문준식;쩡안치;장서용
    • 한국터널지하공간학회 논문집
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    • 제19권2호
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    • pp.109-120
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    • 2017
  • 터널 내 지하수 침투는 터널붕괴와 그에 따른 지반침하의 주요 원인 중 하나이다. 따라서 터널굴착 중 시간에 따른 지하수 침투량과 간극수압 변화를 적절히 예측하는 것이 중요하다. 실무에서는 균질한 지반조건으로 가정하는 Goodman의 산정법을 사용하여 지하수 침투량을 계산하지만, 터널굴착 중 지하수위 강하와 깊이에 따른 투수계수 변화를 고려하지 않아 설계단계에서 지하수 유입량을 과다하게 산정할 우려가 있다. 따라서 본 연구에서는 지하수위 강하 및 깊이별 투수계수의 감소를 적용한 매개변수분석을 통해 지하수 유입량 변화를 분석 비교하였으며, 시간에 따른 지하수 침투량 변화와 지하수위 및 간극수압 분포 변화를 분석하기 위해 비정상류 해석을 수행하였다.

지역난방 배열 회수 보일러의 유동 가속 부식 원인 고찰 (Flow-Accelerated Corrosion Analysis for Heat Recovery Steam Generator in District Heating System)

  • 홍민기;채호병;김영수;송민지;조정민;김우철;하태백;이수열
    • 한국재료학회지
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    • 제29권1호
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    • pp.11-15
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    • 2019
  • Severe wall thinning is found on the tube of a low-pressure evaporator(LPEVA) module that is used for a heat recovery steam generator(HRSG) of a district heating system. Since wall thinning can lead to sudden failure or accidents that lead to shutdown of the operation, it is very important to investigate the main mechanism of the wall thinning. In this study, corrosion analysis associated with a typical flow-accelerated corrosion(FAC) is performed using the corroded tube connected to an upper header of the LPEVA. To investigate factors triggering the FAC, the morphology, composition, and phase of the corroded product of the tube are examined using optical microscopy, scanning electron microscopy combined with energy dispersive spectroscopy, and x-ray diffraction. The results show that the thinnest part of the tube is in the region where gas directly contacts, revealing the typical orange peel type of morphology frequently found in the FAC. The discovery of oxide scales containing phosphate indicates that phosphate corrosion is the main mechanism that weakens the stability of the protective magnetite film and the FAC accelerates the corrosion by generating the orange peel type of morphology.

정신 연습의 기전과 적용 방법 (Mechanism and Application Methodology of Mental Practice)

  • 김종순;이근희;배성수
    • The Journal of Korean Physical Therapy
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    • 제15권2호
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    • pp.75-84
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    • 2003
  • The purpose of this study was to review of mechanism and application methodology about mental practice. The mental practice is symbolic rehearsal of physical activity in the absence of any gross muscular movements. Human have the ability to generate mental correlates of perceptual and motor events without any triggering external stimulus, a function known as imagery, Practice produces both internal and external sensory consequences which are thought to be essential for learning to occur, It is for this reason that mental practice, rehearsal of skill in imagination rather than by overt physical activity, has intrigued theorists, especially those interested in cognitive process. Several studies in sport psychology have shown that mental practice can be effective in optimizing the execution of movements in athletes and help novice learner in the incremental acquisition of new skilled behaviors. There are many theories of mental practice for explaining the positive effect In skill learning and performance. Most tenable theories are symbolic learning theory, psyconeuromuscular theory, Paivio's theory, regional cerebral blood flow theory, motivation theory, modeling theory, mental and muscle movement nodes theory, insight theory, selective attention theory, and attention-arousal set theory etc.. The factors for influencing to effects of mental practice are application form, application period, time for length of the mental practice, number of repetition, existence of physical practice.

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공기분사 기법을 이용한 충돌형 제트 분사기의 연소 안정성 평가에 관한 수치적 연구 (A Numerical Study on Combustion-Stability Rating of Impinging-Jet Injector Using Air-Injection Technique)

  • 손채훈;박이선
    • 대한기계학회논문집B
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    • 제30권11호
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    • pp.1093-1100
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    • 2006
  • Combustion stability rating of jet injector is conducted numerically using air-injection technique in a model chamber, where air is supplied to oxidizer and fuel manifolds of the model five-element injector head. A sample F(fuel)-O(oxidizer)-O-F impinging-jet injector is adopted. In this technique, we can simulate mixing process of streams flowing through oxidizer and fuel orifices under cold-flow condition without chemical reaction. The model chamber was designed based on the methodologies proposed in the previous work regarding geometrical dimensions and operating conditions. From numerical data, unstable regions can be identified and they are compared with those from air-injection acoustic and hot-fire tests. The present stability boundaries are in a good agreement with experimental results. The proposed numerical method can be applied cost-effectively to stability rating of jet injectors when mixing of fuel and oxidizer jets is the dominant process in instability triggering.