• 제목/요약/키워드: surface acting

검색결과 561건 처리시간 0.023초

Effect of Imperatorin on Adenosine Triphosphate-stimulated Mucin Secretion from Airway Epithelial Cells

  • Heo, Ho-Jin;Kim, Cheol-Su;Lee, Hyun-Jae;Shin, Seung-Won;Kim, Young-Sik;Kang, Sam-Sik;Park, Yang-Chun;Kim, Yun-Hee;Seo, Un-Kyo;Seok, Jeong-Ho;Lee, Choong-Jae
    • Biomolecules & Therapeutics
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    • 제14권4호
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    • pp.235-239
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    • 2006
  • Angelicae Koreanae Radix has been used for controlling inflammatory respiratory diseases in folk medicine and their components, imperatorin, marmesinin and oxypeucedanin were reported to have diverse biological effects. In this study, we investigated whether imperatorin, marmesinin and oxypeucedanin affect adenosine triphosphate(ATP)-induced mucin secretion from cultured airway epithelial cells. Confluent primary hamster tracheal surface epithelial(HTSE) cells were metabolically radiolabeled using $^3H$-glucosamine for 24 h and chased for 30 min in the presence of varying concentrations of each agent to assess the effects on $^3H$-mucin secretion. The results were as follows: 1) imperatorin significantly inhibited ATP-induced mucin secretion; 2) However, marmesinin and oxypeucedanin did not affect ATP-induced mucin secretion, significantly. We conclude that imperatorin might inhibit ATP-induced mucin secretion by directly acting on airway mucin-secreting cells. Therefore, imperatorin should further be investigated for the possible use as mucoregulators in the treatment of inflammatory airway diseases.

Flow-induced pressure fluctuations of a moderate Reynolds number jet interacting with a tangential flat plate

  • Marco, Alessandro Di;Mancinelli, Matteo;Camussi, Roberto
    • Advances in aircraft and spacecraft science
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    • 제3권3호
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    • pp.243-257
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    • 2016
  • The increase of air traffic volume has brought an increasing amount of issues related to carbon and NOx emissions and noise pollution. Aircraft manufacturers are concentrating their efforts to develop technologies to increase aircraft efficiency and consequently to reduce pollutant discharge and noise emission. Ultra High By-Pass Ratio engine concepts provide reduction of fuel consumption and noise emission thanks to a decrease of the jet velocity exhausting from the engine nozzles. In order to keep same thrust, mass flow and therefore section of fan/nacelle diameter should be increased to compensate velocity reduction. Such feature will lead to close-coupled architectures for engine installation under the wing. A strong jet-wing interaction resulting in a change of turbulent mixing in the aeroacoustic field as well as noise enhancement due to reflection phenomena are therefore expected. On the other hand, pressure fluctuations on the wing as well as on the fuselage represent the forcing loads, which stress panels causing vibrations. Some of these vibrations are re-emitted in the aeroacoustic field as vibration noise, some of them are transmitted in the cockpit as interior noise. In the present work, the interaction between a jet and wing or fuselage is reproduced by a flat surface tangential to an incompressible jet at different radial distances from the nozzle axis. The change in the aerodynamic field due to the presence of the rigid plate was studied by hot wire anemometric measurements, which provided a characterization of mean and fluctuating velocity fields in the jet plume. Pressure fluctuations acting on the flat plate were studied by cavity-mounted microphones which provided point-wise measurements in stream-wise and spanwise directions. Statistical description of velocity and wall pressure fields are determined in terms of Fourier-domain quantities. Scaling laws for pressure auto-spectra and coherence functions are also presented.

알루미늄 첨가에 따른 오스테나이트계 Fe-23Mn-0.4C 고망간강의 극저온 충격 특성 (Effect of Al Addition on the Cryogenic-Temperature Impact Properties of Austenitic Fe-23Mn-0.4C Steels)

  • 김상규;김재윤;윤태희;황병철
    • 한국재료학회지
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    • 제31권9호
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    • pp.519-524
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    • 2021
  • The impact properties of two austenitic Fe-23Mn-0.4C steels with different Al contents for cryogenic applications are investigated in this study. The 4Al steel consists mostly of austenite single-phase microstructure, while the 5Al steel exhibits a two-phase microstructure of austenite and delta-ferrite with coarse and elongated grains. Charpy impact test results reveal that the 5Al steel with duplex phases of austenite and delta-ferrite exhibits a ductile-to-brittle transition behavior, while the 4Al steel with only single-phase austenite has higher absorbed energy over 100 J at -196 ℃. The SEM fractographs of Charpy impact specimens show that the 4Al steel has a ductile dimple fracture regardless of test temperature, whereas the 5Al steel fractured at -100 ℃ and -196 ℃ exhibits a mixed fracture mode of both ductile and brittle fractures. Additionally, quasi-cleavage fracture caused by crack propagation of delta-ferrite phase is found in some regions of the brittle fracture surface of the 5Al steel. Based on these results, the delta-ferrite phase hardly has a significant effect on absorbed energy at room-temperature, but it significantly deteriorates low-temperature toughness by acting as the main site of the propagation of brittle cracks at cryogenic-temperatures.

부분 침수 조건에서 작동하는 프로펠러의 공기유입과 축계 기진력에 대한 실험적 연구 (Experimental Study on Ventilation and Shaft Excitation Force of a Propeller in Partially Submerged Condition)

  • 하정수;서정화;박격포;박종열;이신형;유재훈;박수영
    • 대한조선학회논문집
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    • 제58권1호
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    • pp.40-48
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    • 2021
  • Through a series of bollard pull tests of a propeller in partially submerged condition, thrust, torque, and shaft excitation force of a conventional propeller model were measured using a six-component load cell. By variation of the Weber number and Reynolds number, a consistent towing tank model test condition was derived. The effects of propeller immersion depth on the ventilation behavior and change of force and moment acting onto the propeller shaft were investigated. The decrease in thrust owing to the inception of ventilation was confirmed, and a large degree of dispersion of the thrust and torque coefficients were also observed in the transition region where the blade tip was under the water surface. The shaft excitation force was derived from the force and moment onto the propeller shaft.

Effects of Self-Efficacy and Job Stress on Organizational Commitment among Clinical Dental Hygienists

  • Lee, Kyeong-Jin;Kim, Young-im
    • 치위생과학회지
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    • 제19권1호
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    • pp.60-66
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    • 2019
  • Background: This study aimed to provide basic data to establish a foundation for efficient operation of the organization by assessing the effects of self-efficacy and job stress (measured by self-efficacy, job demand, and job autonomy) on organizational commitment among clinical dental hygienists. Methods: This was a cross-sectional survey study that used a self-administered questionnaire to collect data. After institutional review board approval, a survey was conducted from January to May 2017, targeting dental hygienists working in dental clinics and hospitals. The final 199 questionnaires were analyzed with PASW 18.0 for Windows (IBM Corp.). The data were analyzed using mean and/or standard deviation t-test, one-way ANOVA, and multiple regression analysis. Results: The means for self-efficacy, job demand, job autonomy, and organizational commitment were $55.94{\pm}9.65$, $26.55{\pm}2.29$, $20.24{\pm}3.88$, and $49.49{\pm}8.39$, respectively. Along with self-efficacy, the other factors of organizational commitment among dental hygienists that were statistically significant included job autonomy, mean salary (2,500~2,990 thousand Korean won [KRW] and ${\geq}3,000$ thousand KRW), and employee welfare (good), which are sub-areas of the surface acting. In other words, it was found that the higher the mean salary, the better the employee welfare, the higher self-efficacy, and the higher the organizational commitment, and the explanatory power of the model was approximately 42.1%. Conclusion: These results suggest that the higher the self-efficacy, job autonomy, mean salary, and employee welfare, the higher the organizational commitment. In order to improve job demand among dental hygienists, it is necessary to establish an effective plan to improve job welfare, self-efficacy, and job autonomy.

Urea를 이용한 바나듐 레독스 흐름 전지용 카본 펠트 전극 개발 (Development of Carbon Felt Electrode Using Urea for Vanadium Redox Flow Batteries)

  • 김소연;김한성
    • Korean Chemical Engineering Research
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    • 제57권3호
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    • pp.408-412
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    • 2019
  • 본 연구에서는 urea를 이용해 질소 도핑된 카본 펠트 전극을 제조하고 이를 바나듐 레독스 흐름 전지용 전극으로 적용하였다. Urea는 암모니아 보다 취급이 용이할 뿐 아니라 고온 열분해를 통해 $NH_2$ 라디칼이 발생하여 탄소 표면에 질소 작용기를 만들고 이는 바나듐 이온의 산화/환원 반응을 향상시키는 활성점(active site)로 작용한다. Urea로 활성화된 카본 펠트 전극은 $150mA/cm^2$의 전류 밀도에서 14.9 Ah/L의 방전 용량을 보였으며 이는 산소작용기로 활성화된 카본 펠트(OGF) 및 비활성화 카본 펠트(GF)보다 각각 23% 및 187% 더 높았다. 이러한 결과는 urea로 활성화된 카본 펠트 전극이 레독스 흐름 전지용 전극 소재로 사용될 수 있는 가능성을 보여준다.

레디얼 게이트에 작용하는 지진 동수압 계산 모형 (Computational Model for Hydrodynamic Pressure on Radial Gates during Earthquakes)

  • 판홍남;이지호
    • 한국전산구조공학회논문집
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    • 제32권5호
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    • pp.323-331
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    • 2019
  • 강한 지진의 영향에 있는 레디얼 게이트에 작용하는 동수압 산정을 위한 계산 모형이 제시되었다. 지진동으로 움직이는 구조물의 영향을 호소부와의 이동경계면으로 처리함과 아울러 강한 지진동 효과를 고려하여 동적 레이어링법이 적용된 ALE 알고리즘과 호소부 자유수면 거동을 위한 SIMPLE법을 사용하는 것이 제안된다. 제안된 방법은 단순한 수직 또는 경사 댐체 벽면에 대하여 널리 알려진 실험 결과 및 그로부터 유도된 제안식과 비교하여 타당성과 유효성이 증명되었다. 계산모형에서 사용할 호소부 상류부 측의 무한경계까지의 거리를 산정하기 위한 파라미터 분석을 수행하여 호소부 수위의 2배가 최적의 길이임을 관찰하였다. 마지막으로 제안된 계산 모형을 사용하여 여러 곡률의 대형 레디얼 게이트에 작용하는 지진동수압을 성공적으로 산출하였다.

(Mg + Al2Ca)로 개량된 AA7075 합금의 미세조직, 기계적 특성, 그리고 고주기 피로 특성에 미치는 T6 및 T73 열처리의 효과 (Effect of T6 and T73 Heat Treatments on Microstructure, Mechanical Responses and High Cycle Fatigue Properties of AA7075 Alloy Modified with Mg and Al2Ca)

  • 황유진;김관영;김규식;김세광;윤영옥;이기안
    • 소성∙가공
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    • 제30권1호
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    • pp.5-15
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    • 2021
  • The effects of heat treatments (T6 and T73) on the microstructure, mechanical properties, and high cycle fatigue behavior of modified AA7075 alloys were investigated. A modified 7075 alloy was manufactured using modified-Mg (Mg-Al2Ca) instead of the conventional element Mg. Based on the microstructure, the average grain size was 4.5 ㎛ (T6) and 5.2 ㎛ (T73). Regardless of heat treatment, the modified AA7075 alloys consisted of Al matrix containing homogeneously distributed Al2CuMg and MgZn2 phases with reduced Fe-intermetallic compound. Room temperature tensile tests showed that the properties of modified 7075-T6 (Y.S.: 622MPa, T.S: 675MPa, elongation: 15.4%) were superior to those of T73 alloy (Y.S.: 492MPa, T.S: 548MPa, elongation: 12.8%). Experimental data show that the fatigue life of T6 was 400 MPa, about 64% of its yield strength. However, the fatigue life of T73 alloy was 330 MPa and 67%. Irrespective of the stress level, all crack initiation points were located on the specimen surface, and no inclusions acting as stress concentrators were seen. Superior mechanical properties and high cycle fatigue behavior of modified AA7075-T6 alloy are attributed to the fine grains and homogeneous distribution of small second phases such as MgZn2 and Al2CuMg, in addition to reduced Fe-intermetallic compounds.

TBM 굴진향상을 위한 연속굴착형 TBM 부품개조 및 제어기술 소개 (Continuous Excavation Type TBM Parts Modification and Control Technology for Improving TBM Performance)

  • 최영태;이동건;김문규;오주영;조정우
    • 터널과지하공간
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    • 제32권6호
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    • pp.345-352
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    • 2022
  • 도심지 터널 건설에서 발파공법은 민원이 제기되는 문제점이 있어 적용에 제약받고 있다. 이에 대한 대안으로 TBM 및 기계굴착 공법 적용이 필수적으로 검토되고 있다. 이 중 쉴드 TBM(Tunnel Boring Machine)은 굴진과 세그먼트 체결이 번갈아 반복되며 굴진하는 공정을 가지고 있는데, 세그먼트 체결 동안 굴진을 멈추게 된다. 이러한 가동 정지시간을 최소화하고자 세그먼트 체결 중에도 가동할 수 있는 연속굴착형 TBM 기술이 개발되고 있다. 나선형 세그먼트의 굴진 반력을 확보하기 위해 추진잭을 개조하고 신뢰성을 확보하는 연구가 진행 중이다. 또한 체결 중 세그먼트를 제외한 나머지 부분의 추진잭을 가동하는 유압제어 및 유압시스템 설계기술이 개발될 예정이다. 본 보고는 연속굴착형 TBM 과제 중 부품개조 및 유압제어 기술에 대한 일부 내용을 소개한다.

자동차 조향장치 부품 요크의 온간 밀폐 단조 적용을 위한 금형 응력 저감 설계 및 온간 단조품의 기계적 특성 분석 (Die Stress Reduction Design and Mechanical Properties Analysis of Warm Forging Process for the Application of Warm-Closed Forging of Automative Steering Unit Yoke)

  • 성상규;김기한;이영선;이상용;윤은유
    • 소성∙가공
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    • 제31권2호
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    • pp.51-56
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    • 2022
  • In this study, finite element analyses were performed by applying a stress ring and split die design to relieve the tensile stress acting on the die due to high surface pressure during warm-closed forging. The applied material was a yield-ratio-control-steel (YRCS). It was used without quenching or tempering after forging. In the case of stress rings design, the number of stress rings and the tolerance for shrink fit were different. Vertical and horizontal splits were applied for insert die split design. Case 5 die with three stress rings, 0.2 % shrink fit tolerance, and vertical split was selected as an effective die design for tensile stress reduction. Based on die stress reduction analyses, Case 5 die for warm-closed forging was produced and smooth forgeability was secured, making it possible to manufacture forging product of yoke with the required geometry. In addition, controlled cooling using warm forging heat was applied to secure mechanical properties of yokes. When oil cooling was used for direct controlled cooling after warm-closed forging, a relatively uniform Rockwell hardness distribution and high mechanical properties could be obtained.