• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.374-381
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• 2020

In order to improve the vertical position accuracy, the advantages of GPS and barometric altimeter are combined and used, but in order to fuse the two sensors, the geoid altitude must be compensated. In this paper, we proposed a technique that can calculate geoid altitude in real time even in low-cost embedded systems applied to drones or autonomous vehicles. Since the reference EGM08 is determined by a polynomial of the 2160th order, real-time calculation is impossible in the embedded system. Therefore, by introducing a linear interpolation technique, the amount of calculation was increased, and the storage space was saved by 75% by using the integer geoid height as a grid point. The accuracy of the proposed technique was evaluated through simulation, and it was confirmed that the accuracy of the maximum error is -1.215 m even in the region where the geoid change is rapid.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.1
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• pp.14-26
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• 2011

Surface currents were observed by high-frequency (HF) radars off the Keum River estuary from December 2008 to February 2009. The dataset of observed surface currents had data gaps due to the interference of electromagnetic waves and the deteriorating weather conditions. To fill the data gaps an optimal interpolation procedure was developed. The characteristics of spatial correlation in the surface currents off the Keum River estuary were investigated and the spatial data gaps were filled using the optimal interpolation. Then, the temporal and spatial distribution of the interpolated surface currents and the patterns of interpolation error were examined. The correlation coefficients between the surface currents in the coastal region were higher than 0.7 because tidal currents dominate the surface circulation. The sample data covariance matrix (C), spatially averaged covariance matrix with localization ($C^G_{sm}$) and covariance matrix fitted by an exponential function ($C_{ft}$) were used to interpolate the original dataset. The optimal interpolation filled the data gaps and suppressed the spurious data with spikes in the time series of surface current speed so that the variance of the interpolated time series was smaller than that of the original data. When the spatial data coverage was larger (smaller) than 70% of the region, the interpolation error produced by $C^G_{sm}$ ($C_{ft}$) was smaller compared with that by C.

• Geophysics and Geophysical Exploration
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• v.26 no.2
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• pp.62-76
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• 2023

Recently, machine learning (ML) techniques have been actively applied for seismic trace interpolation. However, because most research is based on training-inference strategies that treat missing trace gather data as a 2D image with a blank area, a sufficient number of fully sampled data are required for training. This study proposes trace interpolation using ML, which uses only irregularly sampled field data, both in training and inference, by modifying the training-inference strategies of trace-based interpolation techniques. In this study, we describe a method for constructing networks that vary depending on the maximum number of consecutive gaps in seismic field data and the training method. To verify the applicability of the proposed method to field data, we applied our method to time-migrated seismic data acquired from the Vincent oilfield in the Exmouth Sub-basin area of Western Australia and compared the results with those of the conventional trace interpolation method. Both methods showed high interpolation performance, as confirmed by quantitative indicators, and the interpolation performance was uniformly good at all frequencies.

• Journal of Korean Port Research
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• v.13 no.1
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• pp.167-174
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• 1999

Numerical analysis of two-fluid flows for both water and air is carried out. Free-Surface flows with an arbitrary deformation have been simulated around two dimensional submerged hydrofoil. The computation is performed using a finite volume method with unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cell-wise local mesh refinement. the integration in space is of second order based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels The linear equation systems are solved by conjugate gradient type solvers and the non-linearity of equations is accounted for through picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations the continuity equation the conservation equation of one species and the equations or two turbulence quantities.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.169-174
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• 2013

In counterfire warfare, it is important to detect and attack enemy targets faster than the enemy using sensing The grided environmental data is usually provided by the numerical simulation coupled with a data assimilation technique and various inter- or extrapolation algorithms, both of which are based on the observation spanning from simple equipments to satellites. In order to employ the gridded environmental data in the M&S system frequently cutting area and changing its resolution, interpolation algorithms such as linear, cubic spline, IDW, and Kriging methods are necessary to apply. These methods, however, require much time in the M&S system. This paper introduces a technic to reduce time to change the resolution of data. using the binary search method, which finds a point to interpolate quickly and interpolate data in the vicinity of. We also show the efficiency of proposed methods by way of measuring the respective elapsed times.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.227-232
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• 2002

This paper presents an algorithm for general 2D and 3D NURBS interpolation and deals with command generation for 3 axes milling machining, including the feedrate control in order to meet two limitations, a geometrical accuracy and a dynamic restriction. Both of the maximum chordal error and the maximum acceleration specified by machine parameter lead to limit the allowable feedrate on the curvature of NURBS tool path. So, motion commands at every sampling time are continuously generated by those two limitations and programmed feedrate. Simulation results of interpolating several NURBS curves show that proposed NURBS algorithm is favorable in the machining free-form curve

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.511-515
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• 2009

For detecting of the faulty insulator, Correlation Propagation Neural Networks(CPNN) has been proposed. Faulty insulator is reduced the rate of insulation extremely, and taken the results dirty and injured. It is necessary to detect the faulty insulator and exchange the new one. And thus, we have designed the CPNN to be detected that insulators by the real time computation method through the inter-node diffusion. In the network, a node corresponds to a state in the quantized input space. Each node is composed of a processing unit and fixed weights from its neighbor nodes as well as its input terminal. Information propagates among neighbor nodes laterally and inter-node interpolation is achieved. 1-D CPNN hardware has been implemented with general purpose. Experiments with static and dynamic signals have been done upon the CPNN hardware. Through the results of simulation experiments, we define the ability of real-time detecting the faulty insulators.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1032-1035
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• 2000

Increasing demands on precision machining with computerized numerical control (CNC) machines have necessitated that the tool to move not only position error as small as possible, but also with smoothly varying feedrates in space. This paper presents a new high precision interpolation algorithm for 3-dimensional (3D) Non-Uniform Rational B-Spline (NURBS) curve in the reference-pulse CNC technique. Based on the minimum path error strategy, real-time NURBS interpolator was developed in software and this was implemented with a PC-NC milling machine. The several experimental results have shown that the proposed NURBS interpolator is useful for the high precision machining of complex shapes. It is expected that this algorithm can be applied to the CNC machines for the machining of 3D free-form surfaces.

• Journal of Mechanical Science and Technology
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• v.14 no.7
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• pp.789-795
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• 2000

Free-surface flows with an arbitrary deformation, induced by a submerged hydrofoil, are simulated numerically, considering two-fluid flows of both water and air. The computation is performed by a finite volume method using unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cell wise local mesh refinement. The integration in space is of second order, based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels. The linear equations are solved by conjugate gradient type solvers, and the non-linearity of equations is accounted for through Picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations, the continuity equation, the conservation equation of one species, and the equations for two turbulence quantities. Finally, a comparison is quantitatively made at the same speed between the computation and experiment in which the grid sensitivity is numerically checked.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.163-169
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• 1999

The numerical procedure has been developed for simulating incompressible viscous flow around a turbine stage with rotor-stator interaction. This study solves 2-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system. The Marker-and-Cell concept is applied to efficiently solve continuity equation. To impose an accurate boundary condition, O-H multiblocked grid system is generated. O-type grid and H-type grid is generated near and outer rotor-stator The cubic-spline interpolation is applied to handle a relative motion of a rotor to the stator. Turbulent flows have been modeled by the Baldwin- Lomax turbulent model. To validate present procedure, the time averaged pressure coefficients around the rotor and stator are compared with experiment and a good agreement obtained.