• Smart Structures and Systems
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• 제6권3호
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• pp.239-262
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• 2010

Tube Lines has carried out a "knowledge and investigation programme" on the deep tube tunnels comprising the Jubilee, Northern and Piccadilly lines, as required by the PPP contract with London Underground. Many of the tunnels have been in use for over 100 years, so this assessment was considered essential to the future safe functioning of the system. This programme has involved a number of generic investigations which guide the assessment methodology and the analysis of some 5,000 individual structures. A significant amount of investigation has been carried out, including ultrasonic thickness measurement, detection of brickwork laminations using radar, stress measurement using magnetic techniques, determination of soil parameters using CPT, pressuremeter and laboratory testing, installation of piezometers, material and tunnel segment testing, and trialling of remote photographic techniques for inspection of large tunnels and shafts. Vibrating wire, potentiometer, electro level, optical and fibre-optic monitoring has been used, and laser measurement and laser scanning has been employed to measure tunnel circularity. It is considered that there is scope for considerable improvements in non-destructive testing technology for structural assessment in particular, and some ideas are offered as a "wish-list". Assessment reports have now been produced for all assets forming Tube Lines' deep tube tunnel network. For assets which are non-compliant with London Underground standards, the risk to the operating railway has to be maintained as low as reasonably practicable (ALARP) using enhanced inspection and monitoring, or repair where required. Monitoring techniques have developed greatly during recent years and further advances will continue to support the economic whole life asset management of infrastructure networks.

• 에너지공학
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• 제28권3호
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• pp.1-9
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• 2019

화력발전소에서 사용되는 급수 가열기 튜브에서는 사용중에 두께 감육이 발생하여 수명이 소진된다. 감육에 의한 파열 우려가 있으면 수명이 종료되는데, 파열조건을 결정하는 튜브 벽의 응력은 내압에 의한 원주방향 응력의 영향이 가장 큰 것으로 알려져 있지만, 튜브 내외부 온도차이에 의한 열응력에 대한 고려 또한 필요하다. 튜브 두께 방향의 온도차이는 열응력을 발생시켜 튜브의 잔여수명을 단축시키는 영향을 준다. 본 논문에서는 급수가열기 내에서 튜브 내표면과 외표면에 온도 차이가 가장 큰 과열저감구역(de-superheating zone)을 대상으로 열응력을 연구하였다. 원주방향으로 균일하게 감육된 튜브에서 두께방향의 온도차 때문에 발생하는 원주방향 응력, 반경방향 응력 및 온도분포를 평가하기 위한 해석적 수식을 제시하였다. 제시된 해석식의 정확도와 효과를 검증하기 위해 식으로부터의 계산된 결과를 유한요소해석으로 평가한 정확한 결과와 비교하였다. 또한, 유한요소해석으로 편심 감육된 튜브에 대한 응력도 평가하였다. 열응력 해석 및 온도 분포 해석에서 대류열전달 계수의 영향을 분석하기 위해 튜브 내표면 및 외표면에 여러 값의 열대류 계수를 적용하여 해석 결과를 비교하였다. 해석 결과 튜브 내표면보다 외표면의 열대류 계수가 응력 발생에 더 큰 영향을 주는 것으로 나타났다. 열하중만 고려된 경우, 균일 감육과 편심 감육 상태 모두에서 원주방향 응력이 반경방향 응력보다 크게 평가되었다.

• 인터넷정보학회논문지
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• 제22권2호
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• pp.89-107
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• 2021

본 연구는 주요 소셜(social) 미디어인 페이스북, 인스타그램, 유튜브, 핀터레스트, 트위터에 대한 적소분석을 통해 어떠한 경쟁관계를 가지고 있는지를 실증적으로 분석하였다. 이를 위해 적소이론을 활용하여 SNS 이용자를 대상으로 소셜 미디어의 이용과 충족에 관한 온라인 설문을 진행하였으며, 총 224명의 이용자를 분석대상으로 선정하였다. 온라인 설문조사 결과를 토대로 요인분석을 실시하여 관계성, 사회성, 편의성, 일상성, 오락성 등 5가지 차원의 공통요인을 추출하였다. 주요 연구결과는 다음과 같다. 우선 적소이론을 이용한 미디어의 적소폭 차이를 분석한 결과, 페이스북이 사회성(.627) 및 편의성(.636)에서 적소폭이 가장 큰 것으로 나타났고, 유튜브는 일상성(.670)과 오락성(.615)에서 적소폭이 가장 큰 것으로 나타났으며, 인스타그램은 관계성(.520)에서 적소폭이 가장 큰 것으로 나타났다. 적소중복의 경우, 페이스북과 유튜브 간의 경쟁이 관계성(1.826)과 사회성(2.696)에서 가장 강한 것으로 나타났으며, 핀터레스트와 트위터 간의 경쟁은 일상성(1.937)과 오락성(2.263)에서 가장 높은 수준의 경쟁을 보였으며, 유튜브와 트위터 간의 경쟁은 편의성(2.583)에서 가장 높은 수준의 경쟁을 보였다. 마지막으로 적소이론을 이용한 미디어 간의 경쟁우월성을 비교한 결과, 페이스북, 인스타그램 그리고 유튜브는 핀터레스트와 비교하여, 관계성, 사회성, 편의성, 일상성, 오락성에서 경쟁적 우위에 있는 것으로 나타났으며, 페이스북, 인스타그램 그리고 유튜브는 트위터에 비해 일상성을 제외한 모든 요인에서 경쟁적 우위에 있음을 확인할 수 있었다.

• 한국도서관정보학회지
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• 제52권2호
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• pp.275-301
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• 2021

본 연구는 초기 청소년들이 일상에서 가장 선호하는 정보원이자 정보검색 도구로 사용되고 있는 유튜브(YouTube) 모바일 동영상 플랫폼상에서의 정보이용행태를 분석하는 것을 목적으로 한다. 초기 청소년들의 일상생활 속에서의 고민 즉 정보요구는 무엇이며 이 정보요구를 만족시키기 위해 어떤 정보원을 어떻게 사용하고 있는지 살펴보고 유튜브 매체를 이용할 때의 정보요구와 이용행태를 분석하였다. 이를 위해 전국의 초기 청소년(12~14세)을 대상으로 설문조사를 통하여 데이터를 수집후 통계분석하여 각 인구학적 특성별로 정보이용행태에 어떤 차이를 보이는지를 분석하였다. 분석결과, 초기 청소년들은 유튜브를 이들의 일상정보요구를 만족시키는 중요 정보원으로 인식하고 있으며 특히 여가정보를 찾기 위해 가장 빈번히 그리고 적극적으로 이용하고 있었다. 또한, 초기 청소년들은 찾기 쉽고 간단하며 편리하기 때문에, 그리고 쉬운 동영상 정보가 많기 때문에 유튜브에서 정보를 주로 탐색하는 것으로 나타났다. 본 연구에서 밝혀낸 연구결과를 바탕으로 시사점을 도출하고, 학교 및 공공도서관으로 대표되는 정보기관들에서 초기 청소년들을 위한 정보서비스를 기획할 때 참고해야 할 요소들을 제언하였다.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2812-2822
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• 2000

Several methods have been developed to predict the rupture time of the boiler tubes in thermal power plant. However, existing life prediction methods give very conservative value at operating stress of power plant and rupture strain cannot be well estimated. Therefore, in this study, rupture time and strain prediction method accounting for creep, corrosion and heat transfer is newly proposed and compared with the current research results. The creep damage evolves by continuous cavity nucleation and constrained cavity growth. The corrosion damage evolves by steam side and fire side corrosion. The results showed good correlation between the theoretically predicted rupture time and the current research results. And rupture strain may be well estimated by using the proposed method.

• 한국의류산업학회지
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• 제23권1호
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• pp.44-56
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• 2021

This study analyzes the fashion video content of vegan YouTubers in order to understand how the vegan message is being conveyed in media. This study collected data with NoxInfluencer and conducted a case study of the vegan fashion YouTube content. We collected 143 videos for analysis as follows. The characteristics of vegan fashion content were divided into six categories. First, fashion know-how consisted of YouTubers' explanation on vegan fashion, from styling to where to buy vegan and fair trade products. Second, fashion haul content showed second hand products as well as certified vegan fashion products. Third, fashion daily life focused on a day in the life of a vegan YouTuber, casually showcasing fashion in real life. Fourth, fashion products reviews were about vegan YouTubers' thoughts and concerns about various vegan fashion brands and products. Fifth, fashion coordination category consisted of Lookbooks according to seasons. Last, the fashion entertainment category showed YouTubers challenging themselves to dress outside of their comfort zone. The content of the message was distinguished by consumption methods and aesthetic interaction. Also, vegan YouTubers were always anticipating the possibility of appealing to a wider demographic. This study differs from existing studies because it analyzed fashion YouTube content in order to understand the spread of a vegan message in the media environment. This study has its significance in suggesting the direction that the vegan community should take in delivering vegan messages in the future.

• Journal of Korean Neurosurgical Society
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• 제49권2호
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• pp.107-111
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• 2011

Objective : The aim of this study was to evaluate the utility of volume-rendered helical computerized tomography (CT) angiography focusing tracheostomy tube and innominate artery for prevention of tracheoinnominate artery fistula. Methods : The authors retrospectively analyzed 22 patients with tracheostomy who had checked CT angiography. To evaluate the relationship between tracheostomy tube and innominate artery, we divided into three categories. First proximal tube position based on cervical vertebra, named "tracheostomy tube departure level (TTDL)". Second, distal tube position and course of innominate artery, named "tracheostomy tube-innominate artery configuration (TTIC)". Third, the gap between the tube and innominate artery, named "tracheostomy tube to innominate artery gap (TTIG)". The TTDL/TTIC and TTIG are based on 3-dimensional (3D) reconstruction around tracheostomy and enhanced axial slices of upper chest, respectively. Results : First, mean TTDL was $6.8{\pm}0.6$. Five cases (23%) were lower than C7 vertebra. Second, TTIC were remote to innominate artery (2 cases; 9.1 %), matched with it (14 cases; 63.6%) or crossed it (6 cases; 27.3%). Only 9% of cases were definitely free from innominate artery injury. Third, average TTIG was $4.3{\pm}4.6$ mm. Surprisingly, in 6 cases (27.3%), innominate artery, trachea wall and tracheostomy tube were tightly attached all together, thus have much higher probability of erosion. Conclusion : If low TTDL, match or crossing type TTIC with reverse-L shaped innominate artery, small trachea and thin TTIG are accompanied all together, we may seriously consider early plugging and tube removal.

• 한국압력기기공학회 논문집
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• 제16권1호
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• pp.49-55
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• 2020

Creep rupture data for Alloy 690 steam generator tubes in a pressurized water reactor are essentially needed to demonstrate a severe accident scenario on thermally-induced tube failures caused by hot gases in a damaged reactor core. The rupture data were obtained using the tube specimens under different applied-stress levels at 650℃, 700℃, 750℃, 800℃, and 850℃. Important creep constants were proposed using various creep laws in terms of Norton power law, Monkman-Grant (M-G) relation, damage tolerance factor (λ), and Zener-Hollomon parameter (Z). In addition, a creep activation energy (Q) value for Alloy 690 tube was reasonably determined using experimental data. Creep behaviors such as creep strength, creep rates, rupture elongation showed the results of temperature dependence well. Modified M-G plot improved a correlation of the creep rate and rupture life. Damage tolerance factor for Alloy 690 tubes was found to be λ =2.20 in an average value. Creep activation energy for Alloy 690 tube was optimized for Q=350 (kJ/mol). A plot of Z parameter obeyed a good linearity, and the same creep mechanism was inferred to be operative in the present test conditions.

• 한국산업융합학회 논문집
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• 제21권5호
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• pp.257-263
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• 2018

It is a small injection molding machine for table top considering the material heating mechanism and the design and structure stability by securing the mechanism that compresses the inside of the material heating tube by using the electric actuator and by providing space between the body and the material heating tube to reduce heat loss Develop body. An electric actuator suitable for applying pressure to the inside of a material heating tube is a mechanical system composed of a rigid structure. Since a large force is repeatedly applied to the electric actuator and the push rod, the interaction between the moving parts and the dynamic Maximum stress through analysis and prediction of fatigue life of critical parts The pushrod reflects the structural analysis results of the electric actuator and the push rod, and pushes the inside of the material heating tube by the push rod to inject the molten material from the nozzle into the mold. The pushrod operates by the operation of the electric actuator. The material heated by the coil heater is ejected through the nozzle by the pressure of the material heating tube, and the material heating tube and the nozzle are also lowered at the same time as the push rod is lowered, so that the material is closely adhered to the mold. We want to study the completion of the injection.

• BMB Reports
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• 제49권3호
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• pp.191-196
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• 2016

Vascular endothelial growth factor (VEGF) is a key mediator of angiogenesis and critical for normal embryonic development and repair of pathophysiological conditions in adults. Although phospholipase D (PLD) activity has been implicated in angiogenic processes, its role in VEGF signaling during angiogenesis in mammals is unclear. Here, we found that silencing of PLD2 by siRNA blocked VEGF-mediated signaling in immortalized human umbilical vein endothelial cells (iHUVECs). Also, VEGF-induced endothelial cell survival, proliferation, migration, and tube formation were inhibited by PLD2 silencing. Furthermore, while Pld2-knockout mice exhibited normal development, loss of PLD2 inhibited VEGF-mediated ex vivo angiogenesis. These findings suggest that PLD2 functions as a key mediator in the VEGF-mediated angiogenic functions of endothelial cells.