• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.244-249
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• 1997

Internal and external heat sources will cause to deform to machine elements in the contact joint of structure,which results in the change of contact pressure distribution different from initial assembly. Heat induced variations of contact pressure will change the static and dynamic properties such as contact stiffness,damping as well as contact heat conduction in the structure. In order to design and control the intelligent machine tool operating in variant conditions more sophisticatedly, the good prediction for the changes of prescribed propeties are strongly required especially in the contact elements adjacent to the rotational or linear bearing This paper presents some computational and experimental results in regard to static and dynamic characteristics of the press-fitted bush and shaft assembly which is a model of the bearing innerrace and shaft assembly. In the condition of heat generation on the outer surface of the bush,the effects of changes in the negative clearance and the heat flux on pressure distribution and dynamic properties are investigated. Results of this study show that the edge effect of the bush and the initial clearance have effects on the transient dynamic characteristics significantiy.

• International Journal of Aerospace System Engineering
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• 제2권1호
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• pp.58-61
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• 2015

Under the background of combustion instability in solid rocket motor, to study the relationship between pressure oscillations and dynamic process of propellant flames, it is necessary to simulate an oscillation environment with certain frequency, amplitude and duration. This paper presents an experimental installation of pressure oscillation based on pulse-driving technique, with which pressure oscillations features under different pulse-driving conditions were compared and analyzed. For the pulse-driver applied in this paper, a pressure oscillation with 0.15s-0.5s duration, 179Hz-210Hz first order frequency, 0.04MPa-0.35MPa amplitude is simulated. The test results show that an oscillation with higher frequency and lager amplitude can be obtained when pulse-driver is installed on the top of the installation cavity, while on the side, an oscillation with a longer duration and approximate cavity natural frequency can be simulated.

• 한국정밀공학회지
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• 제15권7호
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• pp.139-148
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• 1998

Internal and external heat sources will cause to deform to machine elements in the contact joint of structure, which results in the change of contact pressure distribution different from initial assembly. Heat induced variations of contact pressure will change the static and dynamic properties such as contact stiffness, damping as well as contact heat conduction in the structure In order to design and control the intelligent machine tool operating in variant conditions more sophisticatedly, the good prediction for the changes of prescribed properties are strongly required especially in the contact elements adjacent to the rotational or linear bearing. This paper presents some computational and experimental results in regard to static and dynamic characteristics of the press-fitted bush and shaft assembly which is a model of the bearing innerrace and shaft assembly. In the condition of heat generation on the outer surface of the bush, the effects of changes in the negative clearance and the heat flux on pressure distribution and dynamic properties are investigated. Results of this study show that the edge effect of the bush and the initial clearance have effects on the transient dynamic characteristics significantly.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2364-2373
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• 2002

In this paper, the finite element equations for the time-domain numerical analysis of transient dynamic axisymmetric problems are newly presented. which are based on the equations of motion in convolution integral as in the previous paper. A hollow cylinder subjected to a sudden internal pressure is solved first as a benchmark problem and then the dynamic stress concentrations are analyzed in detail far hollow cylinders having inner and outer circumferential grooves subjected to sudden internal or axial loadings, all the computed results are compared with the existing or the computed ones obtained by using the commercial finite element packages Nastran and Ansys to show the validity and capability of the presented method.

• Tuberculosis and Respiratory Diseases
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• 제78권4호
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• pp.455-458
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• 2015

Excessive dynamic airway collapse (EDAC) is a disease entity of excessive reduction of the central airway diameter during exhalation, without cartilage collapse. An 80-year-old female presented with generalized edema and dyspnea at our hospital. The patient was in a state of acute decompensated heart failure due to pneumonia with respiratory failure. We accordingly managed the patient with renal replacement therapy, mechanical ventilation and antibiotics. Bronchoscopy confirmed the diagnosis of EDAC. We scheduled extubation after the improvement of pneumonia and heart condition. However, extubation failure occurred due to hypercapnic respiratory failure with poor expectoration. Her EDAC was improved in response to high flow nasal oxygen therapy (HFNOT). Subsequently, the patient was stabilized and transferred to the general ward. HFNOT, which generates physiologic positive end expiratory pressure (PEEP) effects, could be an alternative and effective management of EDAC. Further research and clinical trials are needed to demonstrate the therapeutic effect of HFNOT on EDAC.

• 드라이브 ㆍ 컨트롤
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• 제12권4호
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• pp.15-20
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• 2015

Unlike a typical metal spring, a gas spring uses compressed gas contained in a cylinder and compressed by a piston to exert a force. A common application includes automobiles where gas spring are incorporated into the design of open struts that support the weight of tail gate. They are also used in furniture such as office chairs, and in medical and aerospace applications. The gas spring works by the application of pressurized gas (nitrogen) contained in a cylinder. The internal pressure of the gas spring greatly exceeds atmospheric pressure. This differential in pressure exists at any rod position and generates an outward force on the rod, making the gas spring extend. In this paper, we investigated the dynamic characteristics of a gas spring on an automotive tail gate system.

• 한국생산제조학회지
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• 제19권6호
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• pp.883-888
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• 2010

This study have goal with conceptual design for Offshore Structures of high pressure control valve for localization. Ball valve for development accomplished with flow analysis based on provision of ANSI B16.34, ANSI B16.10, ANSI B16.25 In order to localize the Offshore Structures high pressure control valve. Numerical simulation using CFD (Computational Fluid Dynamic) in order to predict a mass flow rate and a flow coefficient form flow dynamic point of view. The working fluid assumed the glycerin (C3H8O3). The valve inlet and outlet setup a pressure boundary condition. The outlet pressure was fixed by atmospheric pressure and calculated until increasing 1bar to 10bar. CFD analysis used STAR-CCM+ which is commercial code and Governing equations were calculated by moving mesh which is rotated 90 degrees when ball valve operated opening and closing in 1 degree interval. The result shows change of mass flow rate according to opening and closing angle of valve, Flow decrease observed open valve that equal percentage flow paten which is general inclination of ball valve. Relation with flow and flow coefficient can not be proportional according to inlet pressure when compare with mass flow rate. Because flow coefficient have influence in flow and pressure difference. Namely, flow can be change even if it has same Cv value. The structural analysis used ANSYS which is a commercial code. Stress analysis result of internal pressure in valve showed lower than yield strength. This is expect to need more detail design and verification for stem and seat structure.

• 비파괴검사학회지
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• 제32권5호
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• pp.526-539
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• 2012

본 연구에서는 기존의 방광 내압 측정의 문제점을 근본적으로 해결할 수 있는 새로운 접근법인 '초음파를 이용한 비침습적 방광 내압 측정 기술'을 제안한다. 제안된 기술은 초음파에 의한 캐비테이션 현상을 이용한다. 즉, 체외에서 조사된 고강도 초음파 펄스에 의해 방광 내에 생성된 기포의 동 특성은 방광 내압에의 영향을 받는다는 물리적인 현상에 근거한다. 본 논문에서는 초음파 방광 내압의 측정 기술의 이론적 기초를 제시하고 및 초기적인 측정 실험을 통해 실현 가능성을 입증했다. 제안된 초음파 방광 압력 측정법은 비침습적이며, 성별, 연령에 관계없이 적용 가능하고, 상시 측정이 가능하여 향후 방광 및 배뇨 장애 관련 진단 및 치료에 크게 기여할 것으로 기대된다.

• Tribology and Lubricants
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• 제19권6호
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• pp.370-375
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• 2003

The radial acting load of vane on the camring in oil hydraulic vane pumps with and without intra­vanes have been investigated. The influences of the discharge pressure and rotating speed of the vane to the load were discussed. The variations of the radial acting load of a vane were calculated on the basis of the results measured for the dynamic internal pressure in the four chambers surrounding a vane. It provides essential information for the study of pump dynamics and control, the pump design and the analysis of tribological problems in the sliding components.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1716-1721
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• 2006

The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke's chart, which is an improvement over Johnson's chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.