• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.37-45
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• 2009

A method of conflict detection and resolution is described by using simple geometric approach. Two VAVs are dealt with and considered as point masses with constant velocity. This paper discusses en route aircraft which are assumed to be linked by real time data bases like ADS-B. With this data base, all DAVs share the information each other. Calculating PCA (Point of Closest Approach), we can evaluate the worst conflict condition between two VAVs. This paper proposes one resolution maneuvering logic, which can be called 'Vector Sharing Resolution'. In case of conflict, using miss distance vector in PCA, we can decide the directions for two VAVs to share the conflict region. With these directions, VAVs are going to maneuver cooperatively. First of all, this paper describes some '2-D' conflict scenarios and then extends to '3-D' conflict scenarios.

• Korean Journal of Computational Design and Engineering
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• v.17 no.4
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• pp.253-261
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• 2012

In order to make dental implant surgery successful, it is important to perform proper planning for dental implant placement. In this paper, we propose a decent approach to dental implant placement planning based on geometric processing of 3D models of jawbones, a nerve curve and neighboring teeth around a missing tooth. Basically, the minimum enclosing cylinders of the neighboring teeth around the missing tooth are properly used to determine the position and direction of the implant placement. The position is computed according to the radii of the cylinders and the center points of their top faces. The direction is computed by the weighted average of the axes of the cylinders. For a cylinder whose axis passes the position along the direction, its largest radius and longest length are estimated such that it does not interfere with the neighboring teeth and the nerve curve, and they are used to select the size and type of an implant fixture. From the geometric and spatial information of the jawbones, the teeth and the fixture, we can construct the 3D model of a surgical guide stent which is crucial to perform the drilling operation with ease and accuracy. We have shown the validity of the proposed approach by performing the finite element analysis of the influence of implant placement on bone stress distribution. Adopted in 3D simulation of dental implant placement, the approach can be used to provide dental students with good educational contents. It is also expected that, with further work, the approach can be used as a useful tool to plan for dental implant surgery.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1599-1603
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• 2004

Based on the idea that nonlinear PWM controller design can be directly applied to the attitude tracking problem of thruster-controlled spacecraft because it constitutes a sub-class of nonlinear PWM controlled system, nonlinear and output error feedback PWM controlled system is considered to describe the behavior of thruster-controlled spacecraft, and to determine actual thruster on-time which guarantees system stability. A differential geometric approach is utilized to show an asymptotical stability of average PWM system, which finally guarantees the stability of closed loop PWM controlled system. Simulation results show that the motions of PWM controlled system occurs very closely around those of the average model of PWM controlled system.

• Steel and Composite Structures
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• v.9 no.1
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• pp.59-75
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• 2009

In this study, a simple approach for bending analysis of Reissner-Mindlin plates is presented using the four-node quadrilateral domain transformation based on discrete singular convolution. In the proposed approach, irregular physical domain is transformed into a rectangular domain by using the geometric coordinate transformation. The DSC procedures are then applied to discrete the governing equations and boundary conditions. The accuracy of the proposed method is verified by comparison with known solutions obtained by other numerical or analytical methods. Results for Reissner-Mindlin plates show a satisfactory agreement with the analytical and numerical solutions.

• Communications for Statistical Applications and Methods
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• v.24 no.4
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• pp.397-419
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• 2017

A four-parameter extended fatigue lifetime model called the odd Birnbaum-Saunders geometric distribution is proposed. This model extends the odd Birnbaum-Saunders and Birnbaum-Saunders distributions. We derive some properties of the new distribution that include expressions for the ordinary moments and generating and quantile functions. The method of maximum likelihood and a Bayesian approach are adopted to estimate the model parameters; in addition, various simulations are performed for different parameter settings and sample sizes. We propose two new models with a cure rate called the odd Birnbaum-Saunders mixture and odd Birnbaum-Saunders geometric models by assuming that the number of competing causes for the event of interest has a geometric distribution. The applicability of the new models are illustrated by means of ethylene data and melanoma data with cure fraction.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.1227-1233
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• 1993

In this paper we present the differential geometric approach for the analysis and design of sliding modes in nonlinear variable structure feedback systems. We also design the robust controller for the nonlinear system using variable structure control theory on the basis of differential geometric methods and feedback linearization applying Min-Max control based on the Lyapunov second method. The robustness against parameter uncertainties for robot manipulators with flexible joint is considered. Simulation results are presented and show the advantage of the proposed nonlinear control method.

• Journal of the Korean Data and Information Science Society
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• v.22 no.3
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• pp.549-553
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• 2011

In this paper, we deal with the problem of deciding the length of data for estimating the parameters in geometric Brownian motion. As an approach to this problem, we consider the change point test and introduce simple test statistic based on the cumulative sum of squares test (cusum test). A real data analysis is performed for illustration.

• Journal of the Chungcheong Mathematical Society
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• v.20 no.1
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• pp.31-35
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• 2007

In dealing with transformation group, topological approach is very natural. But, it is not sufficient to investigate geometric properties of transformation group and we need geometric method. Frankel-McDuff Conjecture is very interesting in the point that it shows struggling between topological method and geometric method. In this paper, the author suggest generalized Frankel-McDuff conjecture as a topological version of the conjecture and construct a counterexample for the generalized version, and from this we assert that topological method does not work for Frankel-McDuff Conjecture.

• Journal of the Korean Mathematical Society
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• v.36 no.6
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• pp.1169-1180
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• 1999

Two-point comparison theorems between hyperbolic and euclidean geometry for convex regions in the complex plane are known([5], [6]). We give new geometric proofs of sharp two-point comparison theorems for convex regions.

• International Journal of CAD/CAM
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• v.9 no.1
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• pp.61-69
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• 2010

Based on the equivalence principles of physical properties, geometric properties and externally applied forces between a surface and the corresponding curves, we present a fast physics and example based skin deformation method for character animation in this paper. The main idea is to represent the skin surface and its deformations with a group of curves whose computation incurs much less computing overheads than the direct surface-based approach. The geometric and physical properties together with externally applied forces of the curves are determined from those of the surface defined by these curves according to the equivalence principles between the surface and the curves. This ensures the curve-based approach is equivalent to the original problem. A fourth order ordinary differential equation is introduced to describe the deformations of the curves between two example skin shapes which relates geometric and physical properties and externally applied forces to shape changes of the curves. The skin deformation is determined from these deformed curves. Several examples are given in this paper to demonstrate the application of the method.