• 제목/요약/키워드: Clearance Loss

검색결과 124건 처리시간 0.021초

자동차 밀폐형 워터펌프의 토출구 형상이 수력성능에 미치는 영향 (Effect of Shape of Discharge Port on Hydraulic Performance of Automotive Closed Type Water Pump)

  • 허형석;이기수;배석정
    • 한국자동차공학회논문집
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    • 제14권1호
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    • pp.39-47
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    • 2006
  • Recent trend in pursuit of high performance and effectiveness for automotive cooling system has changed the application of material for impeller of automotive water pump from metal to high ability engineering resin, which can achieve optimization of design of impeller geometry and realize lightweight high efficiency water pump. Closed type water pump improves hydraulic loss of fluid through the clearance between volute casing and impeller compared with that of the existing open type water pump(Although closed type is heavier than open type for the same size and same material, adoption of plastics can solve the problem.). In the present study, the characteristics of hydraulic performance of closed type water pump were investigated with respect to the angle between shroud and hub of impeller and the shape of discharge port of volute casing. Performance tests were carried out for 4 cases, that is, for 2 impellers and 2 casings. The modification of shape of only discharge port can enhance the hydraulic performance by 10 percent and the pump efficiency by 4-6 percent.

축류홴 익단누설와류의 수치적 해석 (Numerical Analysis of a Tip Leakage Vortex in an Axial Flow Fan)

  • 장춘만;김광용
    • 한국유체기계학회 논문집
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    • 제7권1호
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    • pp.36-44
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    • 2004
  • Three-dimensional vortical flow and separated flow topology near the casing wall in an axial flow fan having two different tip clearances have been investigated by a Reynolds-averaged Navier-Stokes (RANS) flow simulation. The simulation shows that the tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction. On the casing wall, a separation line is formed upstream of the leakage vortex center due to the interference between the leakage vortex and main flow. The reverse flow is observed between the separation line and the attachment line generated downstream of the trailing edge, and increased with enlarging tip clearance. The patterns of a leakage velocity vector including a leakage flow rate are also analyzed according to two tip clearances. It is noted that the understanding of the distribution of a limiting streamline on the casing wall is very important to grasp the characteristics of the vortical flow in the axial flow fan.

Ginseng alleviates microbial infections of the respiratory tract: a review

  • Iqbal, Hamid;Rhee, Dong-kwon
    • Journal of Ginseng Research
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    • 제44권2호
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    • pp.194-204
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    • 2020
  • The detrimental impact of air pollution as a result of frequent exposure to fine particles posed a global public health risk mainly to the pulmonary disorders in pediatric and geriatric population. Here, we reviewed the current literature regarding the role of ginseng and/or its components as antimicrobials, especially against pathogens that cause respiratory infections in animal and in vitro models. Some of the possible mechanisms for ginseng-mediated viral inhibition suggested are improvements in systemic and mucosa-specific antibody responses, serum hemagglutinin inhibition, lymphocyte proliferation, cell survival rate, and viral clearance in the lungs. In addition, ginseng reduces the expression levels of proinflammatory cytokines (IFN-γ, TNF-α, IL-2, IL-4, IL-5, IL-6, IL-8) and chemokines produced by airway epithelial cells and macrophages, thus preventing weight loss. In case of bacterial infections, ginseng acts by alleviating inflammatory cytokine production, increasing survival rates, and activating phagocytes and natural killer cells. In addition, ginseng inhibits biofilm formation and induces the dispersion and dissolution of mature biofilms. Most clinical trials revealed that ginseng, at various dosages, is a safe and effective method of seasonal prophylaxis, relieving the symptoms and reducing the risk and duration of colds and flu. Taken together, these findings support the efficacy of ginseng as a therapeutic and prophylactic agent for respiratory infections.

화력발전소에 사용되는 개선된 오일 디플렉터 개발 (Development of an Advanced Oil Deflector Used in Thermoelectric Power Plant)

  • 최용훈;곽효서;이창렬;김철
    • 한국정밀공학회지
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    • 제33권8호
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    • pp.661-668
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    • 2016
  • Oil deflector prevents oil leakage that occurs in thermoelectric power plant at operating lubricant facilities. Vibration of rotating rotor-induced wear of aluminum tooth in existing oil deflector leads to oil leakage as well as life shortening of the tooth. In this study, an advanced oil deflector was developed for shock absorption and prevention of wear by decreasing clearance (from 0.5 mm to 0.2 mm) between rotor and tooth to minimize oil leakage, and by replacing 2 aluminum teeth in outmost of the oil deflector with hi-performance seal made of engineering plastic. The CFD results were compared between advanced vs. existing oil deflector to determine the amount of oil loss. Structural safety was verified through impact analyses according to the three kinds of engineering plastics, considering cost efficiency, and optimal material of hi-performance seal was chosen.

순차적 설계기법에 의한 DWT 75,000 정유운반선의 선형설계 (Stepwise Hull Form Design of DWT 75,000 Product Oil Carrier)

  • 박연석;박세라;정요한;최정규;유재훈
    • 대한조선학회논문집
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    • 제53권6호
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    • pp.456-464
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    • 2016
  • To design the modified hull form with relatively unfavorable dimensions and constraints than the parent ship the stepwise design was applied. In each design step the resistance characteristics was estimated by numerical calculations using CFD programs as Wavis 1.4, Wavis 2.1 and Fluent 12.1. The wave profiles along hull surface by potential flow calculations were investigated to improve wave resistance by modifying the bow shapes. To improve the stern shapes with a point of viscous form resistance the pressure distributions on hull surface and the limiting streamlines are investigated by viscous flow calculations. The design objectives such as shortening the LBP, enlarging the propeller tip clearance, moving forward of the LCB location and increasing the displacement were applied by stepwise to develop the new hull form of DWT 75,000 product oil carrier. Finally a new hull form was developed without the resistance performance loss compared with the parent ship.

Cell-Based Screen Using Amyloid Mimic β23 Expression Identifies Peucedanocoumarin III as a Novel Inhibitor of α-Synuclein and Huntingtin Aggregates

  • Ham, Sangwoo;Kim, Hyojung;Hwang, Seojin;Kang, Hyunook;Yun, Seung Pil;Kim, Sangjune;Kim, Donghoon;Kwon, Hyun Sook;Lee, Yun-Song;Cho, MyoungLae;Shin, Heung-Mook;Choi, Heejung;Chung, Ka Young;Ko, Han Seok;Lee, Gum Hwa;Lee, Yunjong
    • Molecules and Cells
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    • 제42권6호
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    • pp.480-494
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    • 2019
  • Aggregates of disease-causing proteins dysregulate cellular functions, thereby causing neuronal cell loss in diverse neurodegenerative diseases. Although many in vitro or in vivo studies of protein aggregate inhibitors have been performed, a therapeutic strategy to control aggregate toxicity has not been earnestly pursued, partly due to the limitations of available aggregate models. In this study, we established a tetracycline (Tet)-inducible nuclear aggregate (${\beta}23$) expression model to screen potential lead compounds inhibiting ${\beta}23$-induced toxicity. High-throughput screening identified several natural compounds as nuclear ${\beta}23$ inhibitors, including peucedanocoumarin III (PCIII). Interestingly, PCIII accelerates disaggregation and proteasomal clearance of both nuclear and cytosolic ${\beta}23$ aggregates and protects SH-SY5Y cells from toxicity induced by ${\beta}23$ expression. Of translational relevance, PCIII disassembled fibrils and enhanced clearance of cytosolic and nuclear protein aggregates in cellular models of huntingtin and ${\alpha}$-synuclein aggregation. Moreover, cellular toxicity was diminished with PCIII treatment for polyglutamine (PolyQ)-huntingtin expression and ${\alpha}$-synuclein expression in conjunction with 6-hydroxydopamine (6-OHDA) treatment. Importantly, PCIII not only inhibited ${\alpha}$-synuclein aggregation but also disaggregated preformed ${\alpha}$-synuclein fibrils in vitro. Taken together, our results suggest that a Tet-Off ${\beta}23$ cell model could serve as a robust platform for screening effective lead compounds inhibiting nuclear or cytosolic protein aggregates. Brain-permeable PCIII or its derivatives could be beneficial for eliminating established protein aggregates.

표면가공무늬가 사판식 액셜 피스톤펌프의 밸브부 윤활특성에 미치는 영향에 관한 연구 (Surface Lay Effects on the Lubrication Characteristics in the Valve Part of a Swash-plate Type Axial Piston Pump)

  • 신정훈;강보식;김경웅
    • Tribology and Lubricants
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    • 제28권1호
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    • pp.12-18
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    • 2012
  • This application study of a swash-plate type axial piston pump was concerned about the lubrication characteristics between cylinder barrel and valve plate which are the main rotating body and its opposite sliding part respectively. A computer simulation was implemented to assess bearing and sealing functions of the fluid film between cylinder barrel and valve plate. A numerical algorithm was developed to facilitate simultaneous calculations of dynamic cylinder pressure, 3 degree-of-freedom barrel motions considering inertia effect, and fluid film pressure assuming full fluid film lubrication regime. Central clearance, tilt angle, and azimuth angle of the rotating body were calculated for each time step. Surface waviness was found to be an influential factor due to the small fluid film thickness which can appear in flat land bearings. Five surface lays which can form on the lubrication surface in accordance with machining process were defined and analyzed using the simulation tool. Oil leakage flow and frictional torque in the fluid film between cylinder barrel and valve plate were also calculated to discuss in the viewpoint of energy loss. The simulation results showed that in actual sliding conditions proper surface non-flatness can make a positive effect on the energy efficiency and reliability of the thrust bearing.

DLP용 유체동압베어링 스핀들모터 (Fluid Dynamic Bearing Spindle Motors for DLP)

  • 김응철;성세진
    • 전기학회논문지P
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    • 제60권2호
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    • pp.82-90
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    • 2011
  • The small precision spindle motors in the high value-added products including the visible home appliances such as DLP projector require not only the energy conversion devices but also high efficiency, low vibration and sound operation. However, the spindle motors using the conventional ball bearing and sintered porous metal bearing have following problems, respectively: the vibration by the irregularity of balls and the short motor life cycle by the ball's abrasion and higher sound noises by dry contact between shaft and sleeve. In this paper, it is proposed that the spindle motor with a fluid dynamic bearing is suitable for the motor to drive the color wheel of the DLP(digital lightening processor) in the visible home appliances. The proposed spindle motor is composed of the fluid dynamic bearing with both the radial force and the thrust force. The fluid dynamic bearing is solved by the finite element analysis of the mechanical field with the Reynolds equations. The magnetic part of spindle motor, which is a type of Brushless DC Motor, is designed by the electro-magnetic field analysis coupled with the Maxwell equation. And the load capacity and the friction loss of fluid dynamic bearing are analyzed to bearing clearance variation by the fabrication error in designed motor. The design of the proposed motor is implemented by the load torque caused by the eccentricity and the unbalance of the fluid dynamic bearing when the motors are fabricated in error. The prototype of the motor with the fluid dynamic bearing is manufactured, and experiment results show the vibration, sound, and phase current at no load and color wheel load of the motors in comparison. The high performance characteristics with the low vibration, the low acoustic noise and the optimal mechanical structure are verified by the experimental results.

스마트무인기용 UHF-Band 무지향성 안테나의 탑재위치 시뮬레이션 (Mount Location Simulation of UHF-Band Omni-Directional Antenna for Smart UAV)

  • 송복섭;이현철;김승범
    • 한국통신학회논문지
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    • 제38C권11호
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    • pp.982-989
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    • 2013
  • 스마트무인기(Smart UAV)의 UHF-Band 무지향성 안테나는 비행체 상부 및 하부에 각각 하나씩 장착되어 필요시 UHF-Band 통신링크를 구성하기위해 사용된다. UHF-Band 무지향성 안테나의 통신링크는 안테나 장착위치에 따라 통신가시선(Line Of Sight)의 영향을 받게 되며, 통신 가시선 확보가 필수적이다. 본 논문에서는 스마트 무인기 비행체 형상 및 비행자세에 따른 UHF-Band 통신가시선의 영향을 분석하였다. 이를 위해 복잡한 객체의 주변(항공기, 차량, 무반사실 등) 안테나 배치에 대한 분석을 수행하였다. 안테나까지 영역 패턴을 결정하여 모델링을 할 수 있는 전자기 분석 도구 XGTD를 사용하여 시뮬레이션 하였으며, 통신이 가장 좋은 포지션에 안테나의 위치를 확정하여 선정한 후 실제로 스마트무인기에 적용하여 장착하였다.

OASL1 Traps Viral RNAs in Stress Granules to Promote Antiviral Responses

  • Kang, Ji-Seon;Hwang, Yune-Sahng;Kim, Lark Kyun;Lee, Sujung;Lee, Wook-Bin;Kim-Ha, Jeongsil;Kim, Young-Joon
    • Molecules and Cells
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    • 제41권3호
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    • pp.214-223
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    • 2018
  • Oligoadenylate synthetase (OAS) protein family is the major interferon (IFN)-stimulated genes responsible for the activation of RNase L pathway upon viral infection. OAS-like (OASL) is also required for inhibition of viral growth in human cells, but the loss of one of its mouse homolog, OASL1, causes a severe defect in termination of type I interferon production. To further investigate the antiviral activity of OASL1, we examined its subcellular localization and regulatory roles in IFN production in the early and late stages of viral infection. We found OASL1, but not OASL2, formed stress granules trapping viral RNAs and promoted efficient RLR signaling in early stages of infection. Stress granule formation was dependent on RNA binding activity of OASL1. But in the late stages of infection, OASL1 interacted with IRF7 transcripts to inhibit translation resulting in down regulation of IFN production. These results implicate that OASL1 plays context dependent functions in the antiviral response for the clearance and resolution of viral infections.