• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1483-1495
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• 1994

A quantitative analysis of a surface roughness for a precision machining of a sculptured surface in milling process is treated under superposition theory in this paper. The geometrical surface rouhgness is calculated as a function of feed per tooth, path interval, radii of tool and cutting edge, and radii of curvatures of workiece. Through machining experiments in a 3-axis machining center, we confirmed the adequacy of the adequacy of the analysis. While cutter mark is neglegible in ball endmilling, it is significant in flat endmilling. When feed per tooth is very small, flat endmilling gives superior finish to ball endmilling. In flat endmilling, cutting condition and cutter path should be strategically chosen to balance the cutter mark height and cusp height.

• International Journal of Control, Automation, and Systems
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• v.6 no.3
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• pp.386-393
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• 2008

A position control method for interpolating aspherical grinding and polishing tool path was reviewed and experimented in a nano precision machine. The position-base algorithm was reformed from the time-base algorithm, proposed in the previous study. The characteristics of the algorithm were in the velocity control loop with position feedback. The aspherical surface was divided by an interval at which each velocity and acceleration were calculated. The theoretical velocity was corrected by position error during processing. In the experiment, a machine was constructed and nano-scale linear encoders were installed at each axis. Relation between process parameters and the variation of position error was monitored and discussed. The best result from optimized parameters showed that the accuracy was 150nm and improved from the previous report.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.824-828
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• 2000

Prior to the downloading of the NC codes to a machining center, the NC tool-path can be verified in a computer. The Z-map is one of the tools for the verification of NC tool-path. The Z-map is a two dimensional array in which the height values of the Z-axis direction vectors are stored. The Z-axis direction vectors are arranged in a rectangular grid pattern on the XY plane. The accuracy of the simulation comes from the grid interval. In the rectangular Z-map, the distances between the grid points are different. The distance in diagonal direction is larger than those in X or Y axis directions. For the rendering of the Z-map, a rectangular grid is divided into two triangular facets. Depending on the selection of a diagonal, there are two different cases. In this paper, triangular Z-map, in which the Z-axis direction vectors are arranged in a triangular grid pattern on XY plane, is proposed. In the triangular Z-map, the distances between grid points are equal. There is no ambiguity to make triangular facets for the rendering.

• Communications for Statistical Applications and Methods
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• v.21 no.6
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• pp.521-528
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• 2014

A stochastic Gompertz diffusion model for tumor growth is a topic of active interest as cancer is a leading cause of death in Korea. The direct maximum likelihood estimation of stochastic differential equations would be possible based on the continuous path likelihood on condition that a continuous sample path of the process is recorded over the interval. This likelihood is useful in providing a basis for the so-called continuous record or infill likelihood function and infill asymptotic. In practice, we do not have fully continuous data except a few special cases. As a result, the exact ML method is not applicable. In this paper we proposed a method of parameter estimation of stochastic Gompertz differential equation via Markov chain Monte Carlo methods that is applicable for several data structures. We compared a Markov transition data structure with a data structure that have an initial point.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.4
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• pp.51-56
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• 2006

This paper proposes a control algorithm, which is verified experimentally, for aspherical surface grinding and polishing. The algorithm provides simultaneous control of the position and interpolation of an aspheric curve. The nonlinear formula for the tool position was derived from the aspheric equation and the shape of the tool. The function was partitioned at specific intervals and the control parameters were calculated at each control section. The position, acceleration, and velocity at each interval were updated during the process. A position error feedback was introduced using a rotary encoder. The feedback algorithm corrected the position error by increasing or decreasing the feed speed. In the experimental verification, a two-axis machine was controlled to track an aspherical surface using the proposed algorithm. The effects of the control and process parameters were monitored. The results demonstrated that the maximum tracking error with tuned parameters was at the submicron level for concave and convex surfaces.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.6
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• pp.159-167
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• 2014

In this study the process of normalizing hydraulic head loss rate was developed for the purpose of estimation of seepage blocking state at each seepage segment in sea dike embankment. Pore water pressure sensors were installed with some interval along seepage path, then the hydraulic head loss rate at each segment between pore water pressure sensors was calculated, and then the calculated hydraulic head loss rate was normalized based on seepage path length. The comparison of normalized hydraulic head loss rates showed that the cross section of sea dike embankment was homogeneous approximately and the width of cross section was long enough to blocking tide water.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1590-1598
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• 1997

The paper first introduces the new concept of potential diversity and signal decomposability, which establish a foundaton to generalize the existing concepts of path and frequency diversities. Then it presents a new DS/CDMA system called chip-spreading OCDM system, which is an embodiment of the petential diversity concept that combines the path diversity of the DS/CDMA system and the frequency diversity of the OFDM/CDMA system. In the chip-spreading OCDM system the chip sequences in each symbol interval are first converted into aralled streams, which then simultaneously modulate different orthogonal Walsh basis functions. In the receiver, the received signal is matched to each extended basis-function which is the union of the transmitter basis-functions and their delayed replicas, and the matched-filtered chip samples are combined together after individual channel compensation. The conventional DS/CDMA system using the maximal ratio combining. In addition, it effectively resolves the high PAR and high sensitivity to frequency offset problems which are critical in multi-carrier systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2012-2022
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• 1993

For the machining of the sculptured surfaces on 5-axis CNC milling machine, the milling cutter direction vector was determined in the study (I) with 5-axis post-processing. Thus, it was possible to cut the sculptured surfaces on five-axis CNC milling machine with the end mill cutter. Then, for smooth machined surfaces in five-axis machining of free-from surfaces, this study develops an algorithm for prediction of cusp heights. Also, it generates tool path such that the cusp heights are constrained to a constant value or under a certain value. For prediction of the cusp height between two basis points, a common plane, containing the line crossing two basis points and the summation vector of two normal vectors at two basis points, is defined. The cusp height is the maximum value of scallops on the common plane after end mill cutter passes through the common plane. Sculptured surfaces were machined with CINCINNATI MILACRON 5-axis machining center, model 20V-80, using end mill cutter. Cusp heights were verified by 3-dimensional measuring machine with laser scanner, WEGU Messtechnik GmbH.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10C
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• pp.956-963
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• 2006

This research studies multi participant consistency and dynamic data shared through 3D scenes in virtual network environments. In a distributed virtual environment of client-server structure, consistency is maintained by the static information exchange; as jerks occur by packet delay when updating messages of dynamic data exchanges are broadcasted frequence, the network bottleneck is reduced by predicting the movement path by using the Dead-reckoning algorithm. In Dynamic data path prediction, the tests the location prediction error between Dead-reckoning convergence interval and error of prediction and actual condition one time above threshold it interpolates a previously location. The shared dynamic data of the 3D virtual environment is implementation using the VRML EAI.

• Honam Mathematical Journal
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• v.42 no.4
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• pp.747-755
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• 2020

The mathematical proof for establishing some new inequalities involving arithmetic, geometric, harmonic means for the arguments lying on the paths of triangular wave function (linear) and new parabolic function (curved) over the interval (0, 1) are discussed. The results representing an extension as well as strengthening of Ky Fan Type inequalities.