• 대한족부족관절학회지
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• 제7권2호
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• pp.151-156
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• 2003

Purpose: Proximal crescentic metatarsal osteotomy(PMO) is one of the most common procedures for correcting moderate to severe degree hallux valgus deformity. Although screw fixation is used for osteotomy site stability, loss of reduction can occur. The purpose of this study is to compare the sagittal plane stability of the conventional crescentic PMO fixed with a single screw with that of the crescentic PMO fixed with 1 screw and 2 supplemental K -wires. Material and Methods: Ten matched pairs of cadaveric foot specimens were used for the proximal crescentic metatarsal osteotomy. For one foot specimen of each pair, crescentic osteotomy was fixed with 4mm long threaded cannulated screw, while the matched pair was prepared by adding two axial 1.6mm K-wires to the conventionally fixed 4mm screw. The extensometer was used to measure the osteotomy gap as the metatarsal head was loaded continuously until failure using a servohydraulic MTS Mini Bionix test frame. The strength of fixation was normalized with the bone mineral density (BMD) of the paired specimen $(N{\times}cm^{2}/gm)$, Result: The average strength of the crescentic PMO with axial K-wire fixation ($458.8cm^{2}/gm$, S.D. 434.3) was significantly higher than the standard crescentic PMO ($367.5cm^{2}/gm$, S.D. 397,9) (p=0.05). Conclusion: Supplemental fixation with two axial K-wires can be added to the crescentic PMO to enhance the initial fixation stability to prevent the loss of reduction or dorsal malunion.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.381-382
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• 2002

The Fluid film between the valve plate and the cylinder block was measured by use of a gap sensor and the mercury-cell slip ring unit under real working conditions. During the operating periods, experiments with discharge pressure, revolution speed, and valve geometry was carried out for the fluid film on the valve plate. To investigate the effect of the valve shape, we designed two valve plates each having a different shape; the first valve plate was a plane valve plate. while the second valve plate was a spherical valve plate. It was noted that these two valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rate and the shan torque were also investigated in order to clarify the difference between these two types of valve plates. From the results of this study. we found that the spherical valve plate estimated good fluid film patterns and performance more than the other valve plate in oil hydraulic axial piston pumps.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.655-663
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• 2005

Tribological characteristics in the sliding parts of oil hydraulic piston pumps are very important in increasing overall efficiency. In this study, the fluid film between the valve plate and the cylinder block was measured by using a gap sensor and the mercury-cell slip ring unit under real working conditions. To investigate the effect of the valve shape, we designed three valve plates each having a different shape. One of the valve plates was without bearing pad, another valve plate had bearing pad and the last valve plate was a spherical valve plate. It was noted that these three valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rates and the shaft torque were also investigated in order to clarify the performance difference between these three types of valve plates. From the results of this study, we found that the spherical valve plate estimated good fluid film patterns and good performance more than the other valve plates in oil hydraulic axial piston pumps.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1586-1595
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• 2018

For the problem that the complexity of 3-D modeling and multi parameter optimization, as well as the uncertainty of the winding factor of axial flux permanent magnet generator with coreless windings. The complex 3-D model was simplified into 2-D analytic model, and an analytical formula for the winding factor that adapting different coreless stator winding is proposed in this paper. The analytical solution for air-gap magnetic fields, no-load back EMF, electromagnetic torque, and efficiency are calculated by using this method. The multiple objective and multivariable optimization of the maximum fundamental and the minimum harmonic content of back EMF are performed by using response surface methodology. The proposed optimum design method was applied to make a generator. The generator was tested and the calculated results are compared with the proposed method, which show good agreements.

• Structural Engineering and Mechanics
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• 제35권4호
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• pp.387-407
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• 2010

In this paper, using perturbation and Galerkin method, the response of a resonant viscoelastic microbeam to an electric actuation is obtained. The microbeam is under axial load and electrical load. It is assumed that midplane is stretched, when the beam is deflected. The equation of motion is derived using the Newton's second law. The viscoelastic model is taken to be the Kelvin-Voigt model. In the first section, the static deflection is obtained using the Galerkin method. Exact linear symmetric mode shape of a straight beam and its deflection function under constant transverse load are used as admissible functions. So, an analytical expression that describes the static deflection at all points is obtained. Comparing the result with previous research show that using deflection function as admissible function decreases the computation errors and previous calculations volume. In the second section, the response of a microbeam resonator system under primary and secondary resonance excitation has been obtained by analytical multiple scale perturbation method combined with the Galerkin method. It is shown, that a small amount of viscoelastic damping has an important effect and causes to decrease the maximum amplitude of response, and to shift the resonance frequency. Also, it shown, that an increase of the DC voltage, ratio of the air gap to the microbeam thickness, tensile axial load, would increase the effect of viscoelastic damping, and an increase of the compressive axial load would decrease the effect of viscoelastic damping.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.63-67
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• 1990

An axial flux magnet for a magnetic levitation system is designed and analysed by finite element simulations. The results are compared with those of experiment in order to verify the analysing method. Lift force, air gap flux density and temperature characteristics of the magnet showed fairly good agreement with each other.

• 한국의학물리학회지:의학물리
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• 제1권1호
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• pp.51-60
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• 1990

Dose distributions around Co- 60 moving source in high dose rate remote afterloading unit, Buchler 3K unit, were experimented with X-omat V films and calculations. In our experiments, film dosimetries have achieved to evaluated the axial dose distributions for source oscillations were 0, 3.5, 5.0 and 6.0 cm in periodically, In results, the dose distributions in axial of source movement showed apparently higher than in transverse direction caused by source locations, dwelling time and air gap in the applicator. In the calculations, the dose rate was derived by using the inverse square law, filteration corrections and Meisberger constant for scatter corrections as source movings. In our experiments and calculations, the average dose uncertainties were showed -2.1$\pm$1.9% in fixed sourdce, -2.9$\pm$1.8%, -7.4$\pm$6.1% and -6.7$\pm$4.6% at 3.5 cm, 5.0 cm and 6.0 cm source oscillations, but the calculations have showed very close to experimental dose rate within 4 cm distance from source.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.730-735
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• 2012

This paper presents a method to design the waveform of a back electromotive force (back EMF) of an axial flux permanent magnet (AFPM) motor using printed circuit board (PCB) windings. When the magnetization distribution of permanent magnet (PM) is given, the magnetic field in the air gap region is calculated by the quasi three dimensional (3D) space harmonic analysis (SHA) method. Once the flux density distribution in the winding region is determined, the required shape of the back EMF can be obtained by adjusting the winding distribution. This can be done by modifying the distance between patterns of PCB to control the harmonics in the winding distribution. The proposed method is verified by finite element analysis (FEA) results and it shows the usefulness of the method in eliminating a specific harmonic component in the back EMF waveform of a motor.

• Nuclear Engineering and Technology
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• 제29권5호
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• pp.406-416
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• 1997

A computational method is developed for predicting the steady-state temperature field in an LMR core. Detailed core-wide coolant temperature profiles are efficiently calculated using the simplified energy equation mixing model[1] and the subchannel analysis method. The $\theta$-method is employed for discretizing the energy equations in the axial direction. The interassembly coupling is achieved by interassembly gap flow. Cladding and fuel temperatures are calculated with the one-dimensional conduction model and temperature integrals of conductivities. The accuracy of the method is tested by performing several benchmark calculations for too LMR problems. The results indicate that the accuracy is comparable to the other methods based on ENERGY model. It is also shown that the implicit scheme for the axial discretization is more efficient than the explicit scheme.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.156-158
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• 2008

Along the various gap distance between shoe and swash plate and pocket diameter, lifting force of piston shoe during the compressing stage was calculated. The flow in piston, orifice, shoe, and back space was considered to be 2-dimension axisymmetric and analysed by Fluent, a commercial CFD Software. The wall boundary condition was given as nonslip and adiabatic, while the change in fluid viscosity was considered as linear along temperature. Calculated lifting force and oil leakage of shoe was used in the design of a pump to confirm the shape of the shoe.