• International Journal of Aeronautical and Space Sciences
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• 제7권2호
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• pp.86-103
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• 2006

Using a combination of force transducer measurement to quantify net lift force, high frame rate camera to quantify and subtract inertial contributions, and Digital Particle Image Velocimetry (DPIV) to calculate aerodynamic contributions in the spanwise plane, the contribution of spanwise flow to the generation of lift force in wings undergoing a pure flapping motion in hover is shown as a function of flapping angle throughout the flapping cycle. These experiments were repeated at various flapping frequencies and for various wing planform sizes for flat plate and span wise cambered wings. Despite the previous identification of the importance of span wise fluid structures in the generation of lift force in flapping wings throughout the existing body of literature, the direct contribution of spanwise flow to lift force generated has not previously been quantified. Therefore, in the same manner as commonly applied to investigate the chordwise lift distribution across an airfoil in flapping wings, spanwise flow due to bulk flow and rotational fluid dynamic mechanisms will be investigated to validate the existence of a direct component of the lift force originating from the flapping motion in the spanwise plane instead.

• Journal of Korean Neurosurgical Society
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• 제42권6호
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• pp.475-477
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• 2007

Choroid plexus papillomas (CPPs) are typically considered as benign tumors, with a favorable long-term prognosis. Drop metastasis of CPP into the spinal subarachnoid space is rare. We report a 42-year-old woman who presented with headache and back pain 6 years after removal of a posterior fossa CPP. Magnetic resonance imaging revealed mass lesions in the lumbosacral subarachnoid space and recurrent intracranial tumor. The lesions were resected and histologically diagnosed was CPP. We consider that CPP can spread via cerebrospinal fluid pathways and cause spinal drop metastasis. Therefore, it is necessary to evaluate the whole spinal axis and to perform periodic follow-up examinations in patients with CPP.

• ETRI Journal
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• 제28권6호
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• pp.697-708
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• 2006

Various adaptive mesh refinement techniques are often employed in numerical simulations for increasing spatial and temporal resolution beyond the limits imposed by available CPU time and memory space. Recently, an octree-based adaptive mesh structure was successfully used in fluid animation to place more grid cells efficiently in visually interesting regions of fluids. In an attempt to optimize the use of computational resources further in fluid animation, this paper extends this adaptive technique by modifying the mesh refinement scheme so that the camera's viewing properties are dynamically exploited during the simulation. Based on a simple adaptive mesh structure, we show that the new meshing strategy can save a substantial amount of computation time and memory space by using a view-dependent adaptive approach. The experimental results reveal that the proposed technique provides a good compromise between the computational effort and the simulation's fidelity, and may be used quite effectively in 3D animation production.

• International Journal of Aeronautical and Space Sciences
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• 제1권2호
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• pp.22-29
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• 2000

A method to simulate the gas turbine transient behavior is developed. The basic principles of the method and main input data required are described. Calculation results are presented in terms of whole operating regime of the engine. The influence of initial parameters such as starting engine power, moment of inertia of the rotor, fuel schedule on performance characteristics of gas turbine during transient operation is shown. In addition, the effect of bleeding air on transient behavior is also considered. For validation of the developed computer code, a comparative analysis with experimental data obtained from a heavy duty gas turbine is made. Calculation results agree well with the experimental data for the range of operating regime studied and proved applicability of the developed technique to initial design stage of control system.

• Journal of Chest Surgery
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• 제26권6호
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• pp.492-495
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• 1993

We experienced one case of surgical treatment of abdominal aortic aneurysm using retroperitoneal approach. The transperitoneal route has been the standard surgical approach for elective and emergency treatment of aneurysmal or occlusive disease. Among its cited advantages for aortic reconstruction are familarity with the exposure, easy access to the infrarenal aorta and iliac vessels, possibility of simultaneous inspection of the intra-abdominal viscera, and speed of opening and closure.Despite the proved versatility of the transperitoneal approach, it is commonly associated with prolonged ileus, increased third space fluid loss, and significant pulmonary complications. The retroperitoneal approach, on the other hand, has many advantages; excellent exposure for the repair of juxtarenal or suprarenal abdominal aortic aneurysms and visceral vessel occlusive disease, fewer postoperative complications, decreased postoperative third-space fluid losses from intraoperative evaporation and ileus, and improved postoperative pulmonary function. Atherosclerosis was most common cause of abdominal aortic aneurysm. Dacron graft[18mm] was replaced successfully.Postoperative course was uneventful and he was discharged in good condition.

• 연구논문집
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• 통권28호
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• pp.39-47
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• 1998

Industrial electrostatic precipitation is a very complex process, which involves multiple-way interaction between the electric field, the fluid flow, and the particulate motion. This paper describes a strongly coupled calculation procedure for the rigorous computation of particle dynamics during electrostatic precipitation. The turbulent gas flow and the particle motion under electrostatic forces are calculated by using the commercial computational fluid dynamics (CFD) package FLUENT linked to a finite-volume solver for the electric field and ion charge. Particle charge is determined from both local electrical conditions and the cell residence time which the particle has experienced through its path. Particle charge density and the particle velocity are averaged in a control volume to use Lagrangian information of the particle motion in calculating the gas and electric fields. The turbulent particulate transport and the effects of particulate space charge on the electrical current flow are investigated. The calculated results for poly-dispersed particles are compared with those for mono-dispersed particles, and significant differences are demonstrated.

• Earthquakes and Structures
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• 제18권6호
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• pp.743-752
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• 2020

The phenomenon of reflection and transmission of plane waves at an interface between fluid half space and orthotropic piezothermoelastic solid half-space with two-temperature has been investigated. Energy ratios of various reflected and transmitted waves are computed with the use of amplitude ratios. The law of conservation of energy across the interface has been justified. It is found that the energy ratios are the functions of angle of incidence, frequency of independent wave and depend on the different piezothermoelastic material. A piezothermoelastic material has been considered which is in welded contact with water. Variations of energy ratios corresponding to the reflected waves and transmitted waves are computed and shown graphically for the two different models. A particular reduced case of interest is also discussed.

• Bulletin of the Korean Chemical Society
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• 제22권12호
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• pp.1375-1379
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• 2001

Monte Carlo simulations of hard-spheres confined in parallel hard walls have been carried out extensively at various densities and for various wall distances. The compressibility factors in the directions parallel and normal to the wall have been calculated from the radial free space distribution function (RFSDF) with the results showing that the compressibility factors normal to the wall are smaller than those in parallel direction and that a solid phase is formed in the direction normal to the wall while a fluid phase remains in the parallel direction. An order parameter is found to classify the phases whether a system (or a molecule) is in a fluid or a solid state. The compressibility factors of narrow wall are very small compared to those when the wall is put away. A plausible mechanism of the rise of sap in xylem vessel has been proposed.

• Nuclear Engineering and Technology
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• 제43권1호
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• pp.45-62
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• 2011

The Korean nuclear industry is developing a thermal-hydraulic analysis code for safety analysis of pressurized water reactors (PWRs). The new code is called the Safety and Performance Analysis Code for Nuclear Power Plants (SPACE). The SPACE code adopts advanced physical modeling of two-phase flows, mainly two-fluid three-field models which comprise gas, continuous liquid, and droplet fields and has the capability to simulate 3D effects by the use of structured and/or nonstructured meshes. The programming language for the SPACE code is C++ for object-oriented code architecture. The SPACE code will replace outdated vendor supplied codes and will be used for the safety analysis of operating PWRs and the design of advanced reactors. This paper describes the overall features of the SPACE code and shows the code assessment results for several conceptual and separate effect test problems.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1997년도 정기학술강연회 발표논문 초록집 Annual Meeting of Korean Society of Coastal and Ocean Engineers
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• pp.45-52
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• 1997

Ocean seabed is usually covered with various types of marine soils. A marine soil is a mixture of two phases: soil particles that forms an interlocking skeletal frame, pore fluids that occupy a major portion of pore space. When gravity water waves propagate over a porous movable seabed, a hydrodynamic pressure on the fluid-seabed interface and fluid flow in the porous medium are induced. (omitted)