• Journal of Power Electronics
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• v.19 no.3
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• pp.744-750
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• 2019

A new type of auto-rotary PM mechanical flux-varying PM machine (ARPMMFVPMM) is proposed in this paper, which can overcome the problem where the air-gap magnetic field of a PM machine is difficult to freely adjust. The topology structures of the machine and the mechanical flux-adjusting device are given. In addition, the operation principle of flux-adjusting is analyzed in detail. Furthermore, the deformation of a spring with the speed variation is obtained by virtual prototype technology. Electromagnetic characteristics including the flux distribution, air gap flux density, flux linkage, electromagnetic-magnetic-force (EMF), and flux weakening ability are computed by 2D finite element method (FEM). Results show that the machine has some advantages such as the good field control ability.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.4
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• pp.51-56
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• 2011

Steam generator is one of the main equipments that affect safety and long term operation in nuclear power plants. Fluid flows inside and outside of the steam generator tubes and induces vibration. To prevent the vibration the tubes are supported by AVB (anti vibration bar). When the steam generator tube contact to AVB, it is damaged by the accumulation of wear and corrosion. Therefore studies are required to determine the effects of the gap between the steam generator tube and AVB. In order to obtain the stress and the displacement distributions of the steam generator tube, three dimensional finite element analyses were performed by using the commercial program ANSYS. Using the calculated the stress and the displacement distributions, the static residual strength of the steam generator tube can be evaluated. The results show that the stress and displacement of the steam generator tube increase significantly compared with the results from a zero-gap model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.929-935
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• 2009

As modem industrialized society progresses, the demand for electric power is increasing rapidly. The electric power system is getting amazingly bigger and complicated, which can easily induce serious troubles from the potential of large fault problems and/or system failure. The monitoring and diagnosis of the electric machine for the fault detection and protection has been important part in the electric power system. Most faults in the generator appear in the winding. This paper presents the air-gap magnetic flux characteristic of a small-scale 2-pole synchronous generator according to the faults in the field winding to protect the generator from the fault. The magnetic flux patterns in air-gap of a generator under various fault conditions as well as a normal state are simulated by using finite element method. These results are successfully applied to the detection and diagnosis of the short-circuit condition in rotor windings of a high capacitor generator.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.103-104
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• 2008

this paper describes the electric field distribution analysis along a shield gap inner vacuum interrupter(VI). The equipotential line and electric field and field vector in a VI are analysed by a finite element method and experiment at shield gap. in result, The equipotential line and electric field distribution was affected to VI shield gap. The reason is as it gets distortion of equipotential line done. finally, this paper recognized whether or not affected, and proposed gap with the most suitable shield length and an external insulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.918-923
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• 2008

We proposed an embedded capacitor with the unique electrode structure, which electrodes are located on the same plane and dielectric gap was formed by electrodes. We named it 'Gap type EC', and it was analyzed by the FEM(Finite element Method) program tool. The resonant frequency of Cap type EC was obtained at more higher frequency region. Also, resonant frequency was changed with the magnitude and thickness of electrodes. The Gap type EC with the dielectric gap of $50{\mu}m$ showed capacitance density of $55pF/cm^2$. This value is the higher than that of conventional EC. So, we concluded that the Gap type EC can be a good candidate for high frequency decoupling.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.3
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• pp.206-211
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• 2011

In this paper, we report a high-precision wireless gap sensor based on a surface acoustic wave (SAW) device. The sensing element is a parallel-plate capacitor whose dimensions are $3{\times}3\;mm^2$, and is attached to the SAW device as an external load. The SAW device, equipped with an RF antenna, serves simultaneously as a signal conditioner and an RF transponder. The center frequency of the SAW device is 450 MHz. The wireless gap sensor prototype exhibits a resolution of 100 nm and a sensing range of $50{\mu}m$. The proposed sensor system can be used for remote, high-precision gap measurement in hard-to-reach environments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.9
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• pp.822-827
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• 2010

In this study, it is experimentally investigated how bell acoustics are influenced by the internal cavity of the bell and the gap between the bell bottom and the floor. Acoustic transmission function and natural frequency of a test bell are measured and analysed. Experimental study is conducted to evaluated how the resonance effect influences the bell sound and how the bell sound is different according to the striking condition and the measurement direction. Acoustic resonance frequency of the cavity-gap system is predicted by boundary element analysis using SYSNOIS and the validity of the predicted result is verified by experiment. The result of the study could be applied to determine the optimal gap size which makes the bell sound strong and long.

• Journal of Korean Society of Steel Construction
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• v.11 no.3 s.40
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• pp.271-279
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• 1999

Recently, studies on semi-rigid beam-to-column connections have been done to develop a T-stub element with separators between column face and T-stub flange. In this paper, inelastic analyses for the improved T-stub element are performed, and their results are compared with existing experimental results. The inelastic analyses using gap elements between column face and the separator, and initial stresses at the high-tension bolts result in good agreement with experimental results. Simplified design methods estimating the initial stiffness and the strength of the semi-rigid connection for compression force are proposed.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.82-89
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• 2011

In general, a number of lifting lugs have been used in shipbuilding industry and the D-type lugs are mainly used. The aim of this paper is to increase the cycle of the use and to reduce the size of lifting lugs to introduce lightweight shackle. In this study, nonlinear elasto-plastic analysis has been performed to confirm the ultimate strength of lifting lugs. In order to evaluate the proper design-load distribution around lug eye, the contact force between lifting lug and shackle pin has been realized by gab element model. Gap element modeling and nonlinear analysis are carried out using the finite element program MSC/PATRAN & ABQUS. Additionally the ultimate strength tests were performed to verify the structural adequacy of newly designed lifting lug and to insure safety of it. The D-10, 15, 20 & 40 ton models which are mainly used in the block erection are selected in the strength test. According to the results of the analysis and strength test, the ultimate strength of the newly designed lifting lugs has been estimated to exceed 3 times of design working load.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.432-461
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• 1995

The basic principles in the design of Class II amalgam cavity preparations have been modified but not changed in essence over the last 90 years. The early essential principle was "extension for prevention". Most of the modifications have served to reduce the extent of preparation and, thus, increase the conservation of sound tooth structure. A more recent concept relating to conservative Class II cavity preparations involves elimination of occlusal preparation if no carious lesion exists in this area. To evaluate the ideal ClassII cavity preparation design, if carious lesion exists only in the interproximal area, three cavity design conditions were studied: Rodda's conventional cavity, simple proximal box cavity and proximal box cavity with retention grooves. In this study, MO amalgam cavity was prepared on maxillary first premolar. Three dimensional finite element models were made by serial photographic method. Linear, eight and six-nodal, isoparametric brick elements were used for the three dimensional finite element model. The periodontal ligament and alveolar bone surrounding the tooth were excluded in these models. Three types model(B option, Gap option and R option model) were developed. B option model was assumed perfect bonding between the restoration and cavty wall. Gap option model(Gap distance: $2{\mu}m$) was assumed the possibility of play at the interface simulated the lack of real bonding between the amalgam and cavity wall (enamel and dentin). R option model was assumed non-connection between the restoration and cavty wall. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as followed. 1. Rodda's cavity form model showed greater amount of displacement with other two models. 2. The stress and strain were increased on the distal marginal ridge and buccopulpal line angle in Rodda's cavity form model. 3. The stress and strain were increased on the central groove and a part of distal marginal ridge in simple proximal box model and proximal box model with retention grooves. 4. With Gap option, Rodda's cavity form model showed the greatest amount of the stress on distal marginal ridge followed by proximal box model with retention grooves and simple proximal box model in descending order. 5. With Gap option, simple proximal box model showed greater amount of stress on the central groove with proximal box model with retention grooves. 6. Retention grooves in the proximal box played the role of supporting the restorations opposing to loads.