• Tribology and Lubricants
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• v.40 no.1
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• pp.8-16
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• 2024

This study conducts numerical modeling and eigen-analysis of a rod-fastened rotor, which is mainly used in aircraft gas turbine engines in which multiple disks are in contact through curvic coupling. Nayak's theory is adopted to calculate surface parameters measured from the tooth profile of the curvic coupling gear. Surface parameters are important design parameters for predicting the stiffness between contact surfaces. Based on the calculated surface parameters, elastoplastic contact analysis is performed according to the interference between two surfaces based on the Greenwood-Williamson model. The equivalent bending stiffness is predicted based on the shape and elastoplastic contact stiffness of the curvic coupling. An equation of motion of the rod-fastened rotor, including the bending stiffness of the curvic coupling, is developed. Methods for applying the bending stiffness of a curvic coupling to the equation of motion and for modeling the equation of motion of a rotor that includes both inner and outer rotors are introduced. Rotordynamic analysis is performed through one-dimensional finite element analysis, and each element is modeled based on Timoshenko beam theory. Changes in bending stiffness and the resultant critical speed change in accordance with the rod fastening force are predicted, and the corresponding mode shapes are analyzed.

• Journal of KIISE:Software and Applications
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• v.34 no.1
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• pp.1-10
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• 2007

This paper proposes a new indexing mechanism for MPEG-7 visual descriptors, especially Dominant Color and Contour Shape descriptors, that guarantees an efficient similarity search for the multimedia database whose visual meta-data are represented with MPEG-7. Since the similarity metric used in the Dominant Color descriptor is based on Gaussian mixture model, the descriptor itself could be transform into a color histogram in which the distribution of the color values follows the Gauss distribution. Then, the transformed Dominant Color descriptor (i.e., the color histogram) is indexed in the proposed indexing mechanism. For the indexing of Contour Shape descriptor, we have used a two-pass algorithm. That is, in the first pass, since the similarity of two shapes could be roughly measured with the global parameters such as eccentricity and circularity used in Contour shape descriptor, the dissimilar image objects could be excluded with these global parameters first. Then, the similarities between the query and remaining image objects are measured with the peak parameters of Contour Shape descriptor. This two-pass approach helps to reduce the computational resources to measure the similarity of image objects using Contour Shape descriptor. This paper also proposes two integration schemes of visual descriptors for an efficient retrieval of multimedia database. The one is to use the weight of descriptor as a yardstick to determine the number of selected similar image objects with respect to that descriptor, and the other is to use the weight as the degree of importance of the descriptor in the global similarity measurement. Experimental results show that the proposed indexing and integration schemes produce a remarkable speed-up comparing to the exact similarity search, although there are some losses in the accuracy because of the approximated computation in indexing. The proposed schemes could be used to build a multimedia database represented in MPEG-7 that guarantees an efficient retrieval.

• Journal of Korean Association for Spatial Structures
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• v.6 no.4 s.22
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• pp.81-92
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• 2006

This paper presents exact solutions for the free vibrations and buckling of rectangular plates having two opposite, simply supported edges subjected to linearly varying normal stresses causing pure in-plane moments, the other two edges being free. Assuming displacement functions which are sinusoidal in the direction of loading (x), the simply supported edge conditions are satisfied exactly. With this the differential equation of motion for the plate is reduced to an ordinary one having variable coefficients (in y). This equation is solved exactly by assuming power series in y and obtaining its proper coefficients (the method of Frobenius). Applying the free edge boundary conditions at y=0, b yields a fourth order characteristic determinant for the critical buckling moments and vibration frequencies. Convergence of the series is studied carefully. Numerical results are obtained for the critical buckling moments and some of their associated mode shapes. Comparisons are made with known results from less accurate one-dimensional beam theory. Free vibration frequency and mode shape results are also presented. Because the buckling and frequency parameters depend upon Poisson's ratio ( V ), results are shown for $0{\leq}v{\leq}0.5$, valid for isotropic materials.

• Progress in Medical Physics
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• v.19 no.4
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• pp.227-230
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• 2008

The purpose of this study was to design and construct an ultrasound phantom for volume calibration and evaluate the volume measurement accuracy of a 2 dimensional ultrasonic system. Ultrasound phantom was designed, constructed and tested. The phantom consisted of a background material and a target. The background was made by mixing agarose gel with water. A target, made with an elastic material, was filled with water to vary its volume and shape and inserted into background material. To evaluate accuracy of a 2 dimensional ultrasonic system (128XP, ACUSON), three different shapes of targets (a sphere, 2 ellipsoids and a triangular prism) were constructed. In case of ellipsoid shape, two targets, one with same size length and width (ellipsoid 1) and another with the length 2 times longer than width (ellipsoid 2) were examined. The target volumes of each shape were varied from 94cc to 450cc and measurement accuracy was examined. The volume difference between the real and measured target of the sphere shape ranged between 6.7 and 11%. For the ellipsoid targets, the differences ranged from 9.2 to 10.5% with ellipsoid 1 and 25.7% with ellipsoid 2. The volume difference of the triangular prism target ranged between 20.8 and 35%. An easy and simple method of constructing an ultrasound phantom was introduced and it was possible to check the volume measurement accuracy of an ultrasound system.

• Communications for Statistical Applications and Methods
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• v.19 no.1
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• pp.97-105
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• 2012

The generalized canonical correlation biplot is a 2-dimensional plot to graphically investigate the relationship between more than three sets of variables and the relationship between observations and variables. Recently, Choi and Choi (2010) investigated the relationship physique, physical fitness and basic skill factors of Korea Tennis Association(KTA) players of using this biplot; however we consider the set of covariate variables affecting the linearly on two sets of variables. In this case, if we apply the generalized canonical correlation biplot, we cannot clearly interpret the other two sets of variables due to the effect of the set of covariate variables. Moreover, Yeom and Choi (2011) provided partial canonical correlation analysis that removed the linear effect of the set of covariate variables on two sets of variables. In addition, Procrustes analysis is a useful tool for comparing shape between configurations. In this study, we will investigate the relationship between physical fitness and basic skill factors of KTA players of using a partial canonical correlation biplot and Procrustes analysis. We compare shapes and shape variabilities for the generalized, partial and simple canonical correlation biplots.

• Archives of design research
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• v.18 no.4 s.62
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• pp.257-266
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• 2005

The purpose of this study is to investigate the psychological reaction to the image of the worship space in the church buildings and to quantify its contribution of the stimulation elements causing such reaction, and finally to suggest basic data for realizing emotional worship space of the church architecture. For this, 143 christians were surveyed to analyze the relationship between 23 emotional expressions extracted from the worship space and 32 images of the worship space. The combined data was described with the two dimensional dispersion using the quantification theory III. The analysis found out that 'simplicity-complexity' of the image consisted of the horizontal axis (the x-axis) and 'creativity' of the image the vertical axis(the y-axis). In addition, to extract the causal relationship between the value of emotional reaction and its stimulation elements quantitatively, the author indicated 4 emotional word groups such as simple, sublime for x-axis and typical creative for y-axis based on its similarity by the cluster analysis, The quantification theory I was also used with total value of equivalent emotional words as the standard variance and the emotional stimulation elements of the worship space as the independent variance. 9 specific examples of the emotional stimulation elements were selected including colors and shapes of the wall and the ceiling, shapes and finish of the floor materials, window shapes, and the use of the symbolic elements. Furthermore, 31 subcategories were also chosen to analyse their contribution on the emotional reaction. As a result, the color and finish of the wall found to be the most effective element on the subjects' emotional reaction, while the symbolic elements and the color of the wall found to be the least effective. It is estimated that the present study would be helpful to increase the emotional satisfaction of the users and to approach a spatial design through satisfying the types and purposes of the space.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1325-1333
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• 2014

The dispersion pattern of a near miss neutralizer has a great effect on the disablement of a threatening projectile. This study numerically investigated the dispersion pattern of cylindrical tungsten impactors by an explosion in the near miss neutralizer. The mass and shape of the explosive were considered as influencing factors on the dispersion pattern. The explosives were set using two shape models: a parallel shape with the same upper and lower thicknesses and a tapered shape with different upper and lower thicknesses. In the simulation results, the dispersed impactors formed a ring-shaped pattern on a two-dimensional plane in an arbitrary space. In addition, the fire net area increased with the explosive mass when the explosive shapes were identical. In particular, the tapered shape explosive formed a larger fire net area than the parallel shape explosive. Based on the analysis of the fire net area along with the dispersion density, both the explosive mass and shape representing the physical characteristics should be considered for controlling the dispersion pattern of impactors in a near miss neutralizer.

• Polymer(Korea)
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• v.36 no.2
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• pp.229-234
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• 2012

This paper studied the effects of the content and the orientation of the disk shape fillers on the modulus of PP composites. The experimental results were compared with the theoretical calculations which included the three dimensional ellipsoids and analyzed by two aspect ratios, ${\rho}_{\alpha}=a_1/a_3$and ${\rho}_{\beta}=a_1/a_2$proposed by Lee and his researchers. Mica and talc were used as disk shape fillers in the composites. The shapes of mica and talc were observed by SEM and aspect ratios were statistically calculated. For the case of mica, the average aspect ratios were ${\rho}_{\alpha}=13.5$ and ${\rho}_{\beta}=1.8$, and for the case of talc, they were ${\rho}_{\alpha}=3.8$ and ${\rho}_{\beta}=1.4$. Also, the effects of two aspect ratios and the content of filler on the mechanical properties were studied: For 30 wt% of mica, $E_{11}$ increased up to about 2.7 times, and for the other case of talc, $E_{11}$ increased up to about 2.3 times, respectively.

• Journal of KIISE:Software and Applications
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• v.32 no.7
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• pp.663-673
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• 2005

An analysis model for the dynamics information of two-dimensional time-series patterns is described. In the proposed model, two novel transforms that visualize the dynamic characteristics are proposed. The first transform, referred to as speed equalization, reproduces a time-series pattern assuming a constant linear velocity to effectively model the temporal characteristics of the signing process. The second transform, referred to as velocity transform, maps the signal onto a horizontal vs. vertical velocity plane where the variation oi the velocities over time is represented as a visible shape. With the transforms, the dynamic characteristics in the original signing process are reflected in the shape of the transformed patterns. An analysis in the context of these shapes then naturally results in an effective analysis of the dynamic characteristics. The proposed transform technique is applied to an online signature verification problem for evaluation. Experimenting on a large signature database, the performance evaluated in EER(Equal Error Rate) was improved to 1.17$\%$ compared to 1.93$\%$ of the traditional signature verification algorithm in which no transformed patterns are utilized. In the case of skilled forgery experiments, the improvement was more outstanding; it was demonstrated that the parameter set extracted from the transformed patterns was more discriminative in rejecting forgeries

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.172-180
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• 2012

The $LiMn_2O_4$ cathodes for lithium ion battery were synthesized from various precursors of manganese oxides and manganese hydroxides. As the first step, nanosized precursors such as ${\alpha}-MnO_2$ (nano-sticks), ${\beta}-MnO_2$ (nano-rods), $Mn_3O_4$ (nano-octahedra), amorphous $MnO_2$(nano-spheres), and $Mn(OH)_2$ (nano-plates) were prepared by a hydrothermal or a precipitation method. Spinel $LiMn_2O_4$ with various sizes and shapes were finally synthesized by a solid-state reaction method from the manganese precursors and LiOH. Nano-sized (500 nm) octahedron $LiMn_2O_4$ showed high capacities of 107 mAh $g^{-1}$ and 99 mAh $g^{-1}$ at 1 C- and 50 C-rate, respectively. Three dimensional octahedral crystallites exhibit superior electrochemical characteristics to the other one-dimensional and two-dimensional shaped $LiMn_2O_4$ nanoparticles. After 500 consecutive charge discharge battery cycles at 10 C-rate with the nano-octahedron $LiMn_2O_4$ cathode, the capacity retention of 95% was observed, which is far better than any other morphologies studied in this work.