Computer Graphics Laboratory

Gennadiy Nikishkov Professor	Jai Hak Park Visiting Researcher	Cary Laxer Visiting Researcher

The Computer Graphics Lab conducts research into physics-based modeling of different phenomena, their visualization and animation. Innovative approaches to graphical user interfaces and direct interaction methods, modeling, rendering, simulation and scientific visualization are under development. Created mathematical models are used for graphical representation of natural processes. Research areas include: Visualization of surface and volume data, which results from finite element, boundary element and finite difference modeling. Nanomechanics modeling. Numerical approach is used for modeling of self- positioning micro- and nanostructures with large translations and rotations. Development of molecular mechanics approach to atomic-scale modeling of nanostructures. Augmented reality interface suitable for use in different fields of activity. Using graphics processing units for animation and and general purpose computations. Development of algorithms for shape modeling, analysis and understanding (operations on shape, segmentation and reconstruction). Investigation of algorithms for the polygonization of implicit surfaces (adaptative and robust polygonization, fast polygonization). Professors of the Computer Graphics Laboratory deliver courses in Computer Graphics, Numerical Analysis, Modeling and Visualization. Graduation projects are related to computer modeling, human-computer interactions, visualization and animation.

Refereed Journal Papers

[jhpark-01:2008]	Jai Hak Park, Kyu In Shin, Chi Yong Park, and Sung Ho Lee. Allowable local thickness of wall-thinned straight pipes in ASME Code Case N-597-2. Int. J. of Pressure Vessels and Piping, 85:620–627, 2008.
	In Code Case N-597-2, the allowable local thickness of a thinned straight pipe is given through three different methods. Because of different technical bases, each method gives different thickness values and sometimes gives contradictory values. So in this paper attempts were made in order to propose a unified rule for the allowable local thickness and in order to remove or relax the restrictions on the application of the code case. For this purpose elastic stress analyses were made using the finite element method and the stress results were examined. Based on the obtained bending stress results, a very simple procedure was proposed to obtain the consistent allowable local thickness for the thinned straight pipes.
[jhpark-02:2008]	S.H. Lee, J.K. Lee, and J.H. Park. Failure behavior of elbows with local wall thinning. Modern Physics Letters B, 22(11):845–850, 2008.
	Wall thinning defect due to corrosion is one of major aging phenomena in carbon steel pipes in most plant industries, and it results in reducing load carrying capacity of the piping components. A failure test system was set up for real scale elbows containing various simulated wall thinning defects, and monotonic in-plane bending tests were performed under internal pressure to find out the failure behavior of them. The failure behavior of wall-thinned elbows was characterized by the circumferential angle of thinned region and the loading conditions to the piping system.
[niki-01:2008]	Y.Nishidate and G.P.Nikishkov. Atomic-scale modeling of self-positioning nanostructures. Computer Modeling in Engineering and Sciences, 26:91–1006, 2008.
	Atomic-scale finite element procedure for modeling of self-positioning nanostructures is developed. Our variant of the atomic-scale finite element method is based on a meshless approach and on the Tersoff interatomic potential function. The developed algorithm is used for determination of equilibrium configuration of atoms after nanostructure self-positioning. Dependency of the curvature radius of nanostructures on their thickness is investigated. It is found that for thin nanostructures the curvature radius is considerably smaller than predicted by continuum mechanics equations. Curvature radius variation with varying orientation of crystallographic axes is also modeled and results are compared to finite element continuum anisotropic solution.
[niki-02:2008]	Y.Nishidate and G.P.Nikishkov. Atomic-scale analysis of self-positioning nanostructures. e-Journal of Surface Science and Nanotechnology, 6:301–306, 2008.
	An atomic-scale analysis of self-positioning nanostructures using the atomic-scale finite element method (AFEM) and Kriging interpolation technique is reported. Equilibrium atomic configurations are modeled for varying nanostructure thicknesses and results are compared with the plane strain continuum mechanics solution. Significant decrease of equilibrium curvature radius is observed for thin structures. Large compressive strains near the free surface have been found.

Refereed Proceeding Papers

[jhpark-03:2008]	Jae Bong Lee, Jai Hak Park, Hong Deok Kim, and Han Sub Chung. Evaluation of ECT reliability for axial ODSCC in steam generator tubes. In Proceedings of the 7th ASINCO Workshop, pages 125–134, July 2008.
	In this paper the reliability of ECT inspection system is analyzed quantitatively. The reliability of ECT is subdivided into the reliability of size and the reliability of detection. The reliability of size is often characterized as the simplest form of a linear or linearized regression model with the measured one versus true size data. The reliability of detection is characterized in terms of the probability of detection (POD) as a function of flaw size. POD of ECT inspection system for Axial ODSCC in steam generator tubes is evaluated. Using the log-logistic regression method, POD is evaluated from hit (detection) and miss (no detection) binary data obtained from destructive and non-destructive inspection of the cracked tubes. Length and depth of cracks are considered as variables in multivariate log-logistic regression and their effects on detection capacity are assessed. The detail method of log-logistic regression and some cautions that can be introduced in the calculation of the likelihood estimator are also mentioned.
[niki-03:2008]	G.P.Nikishkov and Y.Nishidate. Atomic-scale modeling of anisotropy effects in nanostructures. , A-2. In Symposium on Surface and Nano Science SSNS9, pages A–2, Shizukuishi, Iwate, Japan, 27–30 January 2009.
	Effect of material anisotropy on the curvature radius of rolled-up nanostructures is investigated using the finite element method with appropriate transformation of the elasticity tensor. For bilayer GaAs-InAs nanostructures, dependency of the curvature radius on the material orientation angle follows periodic curve with the maximum curvature at material orientation angle 45 and 135 degrees. Direct modeling of material anisotropic effects is performed with the atomic-scale finite element (AFEM) method based on the Tersoff interatomic potential. The AFEM modeling of anisotropy effects is based on changing orientation of atomic planes during creation of atomic models. The developed AFEM code is applied to modeling of GaAs-InAs bilayer self-positioning nanostructures with different orientation of crystallographic axes.
[niki-04:2008]	K. Kanev, Z. Cheng, and N. Mirenkov. Methods and Technologies for Enhancing and Optimizing Power Plant Inspection Procedures. In Proceed- ings of the 7th IEEE International Conference on Computer and Information Technology (CIT 2007), pages 605-609, 2007.
	This paper considers different methods and approaches for improving power plant inspection procedures through innovative technological means. Main objectives are to provide timely, context dependent assistance and advice to human inspectors of power plant facilities, to minimize human errors and to increase inspection efficiency and reliability. A solution based on spatial awareness methods for inspector localization, registration and tracking through remote sensing of RFID tags and digital codes embedded in the surrounding environment is proposed. Possible extensions for industrial inspection robots are briefly discussed and potential applicability in nuclear power plant inspections is revealed.
[niki-05:2008]	G.P.Nikishkov. SGBEM-FEM modeling of stress corrosion cracking. In 16th Pacific Basin Nuclear Conference (16PBNC), pages P16P1159–1–6, Aomori, Japan, 13–18 October 2008.
	SGBEM-FEM computational procedure is used for modeling of crack growth under stress corrosion cracking (SCC) conditions. The crack is modeled by the symmetric Galerkin boundary element method (SGBEM). The finite element method (FEM) is used for stress analysis of the uncracked structural component. The solution for the structural component with the crack is obtained in an iterative procedure, which alternates between FEM solution for the uncracked body, and the SGBEM solution for the crack in an infinite medium. Computational procedure for SCC crack growth is developed. Crack growth criterion in the three-dimensional case is based on the J-integral vector.
[niki-06:2008]	Y.Nishidate and G.P.Nikishkov. Atomic-scale modeling of rolled-up thin films. In Int. Symp. on Graphene Devices: Technology, Physics and Modeling (ISGD 2008), pages W1–4, Aizu-Wakamatsu, Japan, 17–19 November 2008.
	Recently, we developed an atomic-scale finite element (AFEM) procedure for modeling of bilayer GaAs/InAs rolled-up nanostructures. The AFEM can consider atomicscale characteristics of the rolled-up nanostructures. The developed AFEM program has been applied for investigating dependency of curvature radius on the structure thickness and crystal orientations.

Books

[niki-07:2008]	E.M.Morozov and G.P.Nikishkov. The Finite Element Method in Fracture Mechanics. URSS, Moscow, Russia, 2008.
	The book presents finite element algorithms and their use for solution of linear and nonlinear fracture mechanics problems.

Chapters in Book

[niki-08:2008]

G.P.Nikishkov and Y.Nishidate. Continuum and atomic-scale modeling of self-positioning microstructures and nanostructures, pages 271–294. Trends in Engineering Computational Technology. Saxe-Coburg, Stirlingshire, Scotland, 2008.

This article presents investigations of self-positioning microstructures and nanostructures by analytical techniques, finite element analysis and atomic-scale modeling. Closed-form solutions for curvature radius of self-positioning hinge structures are obtained for plane strain and generalized plane strain deformation. The finite element method is used for predicting hinge curvature radius for self-positioning structures of variable width and anisotropic structures. An algorithm of the atomic-scale finite element method (AFEM) based on the Tersoff interatomic potential has been developed. The AFEM is applied to modeling of GaAs and InAs bi-layer self-positioning nanostructures.

Grants

[niki-09:2008]

Gennadiy Nikishkov. Tohoku Nuclear Cluster, 2008.

Academic Activities

[niki-10:2008]	Gennadiy Nikishkov, 2008. Member of the Editorial Board, International Journal ’Computer Modeling in Engineering and Sciences’.
[niki-11:2008]	Gennadiy Nikishkov, March 2009. Member of the Program Committee, Int. Conf. on Computational and Experimental Engineering and Sciences ICCES 2009, Phuket, Thailand.
[niki-12:2008]	Gennadiy Nikishkov, February 2009. Member of the Program Committee, Int. Conf. on Computer Graphics Theory and Applications GRAPP 2009, Lisboa, Portugal.
[niki-13:2008]	Gennadiy Nikishkov, October 2008. Section chair, The 16th Pacific Basin Nuclear Conference (16PBNC), Aomori, Japan.
[niki-14:2008]	Gennadiy Nikishkov, July 2008. Member of the Program Committee, IEEE 8th International Conference on Computer and Information Technology (CIT2008), Sydney, Australia.
[niki-15:2008]	Gennadiy Nikishkov, June 2008. Member of the Program Committee, International Conference on Computational Science (ICCS’2008), Krakow, Poland.
[niki-16:2008]	Gennadiy Nikishkov, September 2008. Member of the Editorial Board, Ninth International Conference on Computational Structures Technology CST 2008, Athens, Greece.
[niki-17:2008]	Gennadiy Nikishkov, 2008. Reviewer, Computers and Structures.
[niki-18:2008]	Gennadiy Nikishkov, 2008. Reviewer, Journal of ASTM International.
[niki-19:2008]	Gennadiy Nikishkov, 2008. Reviewer, Journal of Virtual Reality and Broadcasting.

Ph.D, Master and Bachelor Theses

[niki-20:2008]	Youhei Nishidate. PhD Thesis: Modeling of self-positioning nanostructures, University of Aizu, 2009. Thesis Advisor: Gennadiy Nikishkovv
[niki-21:2008]	Akiha Iwase. Master Thesis: Augmented virtuality for 3D data visualization, University of Aizu, 2009. Thesis Advisor: Gennadiy Nikishkov
[niki-22:2008]	Mio Kanai. Graduation Thesis: Augmented reality for learning environment, University of Aizu, 2009. Thesis Advisor: Gennadiy Nikishkov
[niki-23:2008]	Satoru Ishibashi. Graduation Thesis: Performance of 3D graphics on mobile devices, University of Aizu, 2009. Thesis Advisor: Gennadiy Nikishkov


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