• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.35-44
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• 2007

In this study was made the flutter analysis for the export model of Firefly(Bandi-ho), the small canard aircraft. Stiffness model based on internal load generation finite element model was generated. Mass model based on the weight DB for weight control was generated. Aerodynamic model based on Doublet Lattice Method was generated. Preliminary flutter analysis was made. Based on it, major vibration modes are identified and experimentally obtained via the ground vibration test. The obtained normal mode frequencies were used to correlate the finite element model. Flutter analysis was made again and major flutter mechanisms were summarized. The most important flutter root was identified as a coupled root between rigid body roll mode and anti-symmetric wing pitching mode.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.34-36
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• 2006

In this paper, we will treat the diagnosis problem to accurately determine fault types. The judgement of fault types is accomplished by observing the cluster newly formed with faults and clustering the input current waveforms to intrinsically show the conditions with the dignet that is a clustering algorithm. The types of input current waveforms are, however, constrained during normal operation, though it considers the load character. In case of faults. new clusters are generated outside the clusters. which appear during normal operation, because the input current waveforms of the induction motor are generated by the type which is not observed in case of faults. The diagnosis about the types of faults is essential to building a fault tree about the induction motor, and it removes the causes of the faults using a fuzzy logic. We, first, constitute a fault tree, which connects with the parts and the entire system of the induction motor, and investigate fault modes which can be generated from the fault tree and the relationship of the cause and the effect of each part (of the motor). Also, we distinguish the faults of each part by means of inducing the said of fuzzy relation equations encapsulating the relationship of the fault modes and each part.

• ETRI Journal
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• v.44 no.1
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• pp.85-93
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• 2022

We propose an efficient method for synthesizing mesh-based realistic computer-generated hologram (CGH). In a previous nonanalytic mesh-based CGH synthesis, the angular spectrum of the two-dimensional (2D) plane is calculated using the fast Fourier transform (FFT) with the same size as the resolution of the final hologram. Because FFT increases the computation time as the size of the input matrix increases, the previous method has a problem: The higher the resolution of the hologram, the greater the computational load, thereby delaying synthesis time. In this study, when calculating the angular spectrum of the 2D plane in mesh-based CGH synthesis, we propose a method to calculate the angular spectrum by defining the 2D plane with an arbitrary size smaller than the resolution of the final hologram. The resolution adjustment method reduces the computation time and can be applied to occlusion culling and texturing for the realistic effect of mesh-based CGH. We describe the principle, error analysis, application of realistic effect, and experimental results of the proposed method.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.719-723
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• 2014

For effective implementation of total maximum daily load (TMDL), this study presented the improving plans of non-point source pollution management including the classification of non-point source pollution, calculation of non-point source pollution load (generated, discharged), selection of non-point source pollution management regions and management of non-point source pollutant. First of all, the definition of point source pollution and non-point source pollution based on the legal and scientific viewpoint should be precisely classified and managed. Especially, the forest, grassland and river without occurrence of environmental damage by activity of business and human should be separately classified natural background pollutants. The unit for generated and discharged non-point source pollution should be preferentially changed according to actual condition of watershed. The calculation methods of generated and discharged non-point source pollution should be corrected consideration on the amount and duration of rainfall. While the TMDL is implemented, non-point source pollution management regions should be selected in the watersheds exceed the targeted water quality standards by the rainfall. The non-point source pollution management regions should be selected in the minimal regions where have high values of discharged non-point source pollution density in the urban area, farmland and site area except forest, grassland in the whole watershed. The non-point source pollutant treatment facilities, which take into consideration non-point source pollution load per unit area, duration of the excess concentration, realizable possibility of treatment, effectiveness of treatment cost versus point source pollutant, should be established in the regions with a large generated non-point source pollution load and a high concentration of water quality exceed the targeted water quality standards by the rainfall.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.108-113
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• 2005

Strucutral and hygrothermal analysis for a composite tube is carried out in this study, that provides critical parameters for the design of a highly dimensionally stable space telescope. Carpet plots for laminate effective engineering constants are generated and used for the best tube lay-ups with high elastic modulus and highly insensitive to thermal and moisture expansion, which is essential for maintaining optical alignment of opto-mechanical system under random force applied during a launch campaign and orbital thermal load. Despace in the longitudinal direction under hygrothermal load of the tubes constructed with the selected lay-ups is calculated for the validation of lay-up designs on the dimensionalstability. Dynamic analysis is also carried out to feature the resonant behaviour. A zig-zag triangular element accurately representing through thickness stress variations for laminated structures is developed in this study and incorporated into the structural and hygrothermal analysis.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1187-1189
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• 2002

In the case of an existing high frequency inverter is became forced extinction by quick load change, due to be connected with series inductor on switch, it is destroyed or is generated conduction loss by resistance component in reactor. And, In the operation of high current with a soft switching, conduction loss can not neglect. In this paper, for the high current power source, we make sure of soft swtching operation and reducing surge when the forced extinction by using a connected switch with series inductor. Also, we poropos a topology of the half bridge type high frequency inverter that can be realized high amplitude operation of the load current. And, analyze the circuit to decide an opmtial circuit parameter.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2255-2260
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• 2007

This Paper focuses on modeling and simulation to analyze the characteristic of hybrid vehicle. The system includes proton exchange membrane fuel cell(PEMFC), photovoltaic generator(PV), lead-acid battery, motor, vehicle and controller. Main electricity is produced by the PEMFC and battery to meet the requirements of a user load. When vehicle is parked in a sunny place, extra power is generated by the photovotaics and is charged in a battery for next drive. Further we evaluate usefulness of this hybrid vehicle by using ADVISOR - the advanced vehicle simulator written in the Matlab/Simulink environment. According to simulation results, the extra power obtained by photovoltaics which have been explored in nature conditions can help to reduce the electrical load of PEMFC and increase the efficiency (over 30%).

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.186-193
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• 2000

In this study the effect and applicability of viscoelastic dampers on the seismic reinforcement of steel framed structures are investigated in the context of the performance based design approach. The effect of the damper on dissipating the input seismic energy was investigated with a single degree of freedom system. For analysis models a five-story steel frame subjected to gravity load and a ten-story structure subjected to gravity and wind load were designed. the code-specified design spectrums were constructed for each soil type and performance objective and artificial ground excitation records to be used in the nonlinear time history analysis were generated based on the design spectrums. Interstory drift was adopted as the primary performance criterion. According to the analysis results both model structures turned out to satisfy the life safety performance level for most of the soil conditions except for the soft soil. It was also found that the seismic performance could be greatly enhanced by installing viscoelastic dampers on appropriate locations.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.412-419
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• 2011

With an increase in rail traffic, developing activities around structures of railway have been expanded. Inevitably, the changes to cross though sub-structures of railway have been getting increased. However, this situation affects on the safe operation of trains. Generated wheel load makes on the result in settlement on roadbed and damages on track materials. Therefore, via the numerical analysis were carried out for the box structure and subground using FEM analysis program called. Visual FEA/Geo 4.19. Parametric studies were performed by changing soil depth above box structure constructed in railway embankment. A standard live load was applied to simulate loads from train. Through this study, a minimum required soil depth above subground box structure was recommended based on deformation and stresses in concrete railway system.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.57-61
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• 2011

The bimodal tram was designed to drive on the dedicated track as well as on the public road. The position and speed are automatically controlled on the dedicated track by the onboard computer, whereas they are manually controlled by driver like motor vehicles on the public road. The ride comfort the passengers feel and the effect of the vibration generated during driving on the passenger's health, comfortableness and motion sickness were evaluated with driving the bimodal tram prototype in automatic and manual mode, respectively. The test was done in automatic mode on the test track with various load conditions while it was done in manual mode on the public road with empty load.