• Communications for Statistical Applications and Methods
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• v.25 no.3
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• pp.245-261
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• 2018

Attempts have been made to define new classes of distributions that provide more flexibility for modelling skewed data in practice. In this work we define a new extension of the generalized gamma distribution (Stacy, The Annals of Mathematical Statistics, 33, 1187-1192, 1962) for Marshall-Olkin generalized gamma (MOGG) distribution, based on the generator pioneered by Marshall and Olkin (Biometrika, 84, 641-652, 1997). This new lifetime model is very flexible including twenty one special models. The main advantage of the new family relies on the fact that practitioners will have a quite flexible distribution to fit real data from several fields, such as engineering, hydrology and survival analysis. Further, we also define a MOGG mixture model, a modification of the MOGG distribution for analyzing lifetime data in presence of cure fraction. This proposed model can be seen as a model of competing causes, where the parameter associated with the Marshall-Olkin distribution controls the activation mechanism of the latent risks (Cooner et al., Statistical Methods in Medical Research, 15, 307-324, 2006). The asymptotic properties of the maximum likelihood estimation approach of the parameters of the model are evaluated by means of simulation studies. The proposed distribution is fitted to two real data sets, one arising from measuring the strength of fibers and the other on melanoma data.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.71-80
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• 1989

In this paper, the concept of the infinite element is applied to the linear wave diffraction and radiation problems. The hydrodynamic pressure forces are assumed to be inertially dominated, and viscous effects are neglected. The near field region surrounding the solid body is modelled using the conventional finite elements, and the far field region is represented using the infinite elements .In order to represent the scattered wave potentials in the far field region more accurately, the infinite elements are developed using special shape functions derived from the asymptotic expressions for the analytical eigenseries solution of the scattered waves. The system matrices of the infinite elements are constructed by performing the integration in the infinite direction analytically to achieve computational efficiency. Numerical analyses are carried out for vertical axisymmetric bodies to validate the infinite elements developed here. Comparisons with the results by other available numerical solution methods show that the present method using the infinite elements gives fairly good results. Numerical experiments are per-formed to determine the suitable location of the infinite elements and the appropriate size of the finite elements which directly affect accuracy and efficiency of the solution.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1368-1389
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• 2014

Three-dimensional multiple-input multiple-output (3D MIMO) and large-scale MIMO are two promising technologies for upcoming high data rate wireless communications, since the inter-user interference can be reduced by exploiting antenna vertical gain and degree of freedom, respectively. In this paper, we derive the achievable sum rate of 3D MIMO systems employing zero-forcing (ZF) receivers, accounting for log-normal shadowing fading, path-loss and antenna gain. In particular, we consider the prevalent log-normal model and propose a novel closed-form lower bound on the achievable sum rate exploiting elevation features. Using the lower bound as a starting point, we pursue the "large-system" analysis and derive a closed-form expression when the number of antennas grows large for fixed average transmit power and fixed total transmit power schemes. We further model a high-building with several floors. Due to the floor height, different floors correspond to different elevation angles. Therefore, the asymptotic achievable sum rate performances for each floor and the whole building considering the elevation features are analyzed and the effects of tilt angle and user distribution for both horizontal and vertical dimensions are discussed. Finally, the relationship between the achievable sum rate and the number of users is investigated and the optimal number of users to maximize the sum rate performance is determined.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.5
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• pp.556-565
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• 2018

The age and growth of butter clams Saxidomus purpuratus were estimated using transmitted light on the shells of 364 samples from January 2017 to December 2017 in Jinhae Bay. Based on monthly variation in the marginal index (MI) of the shell, it is assumed that rings are formed once a year during the period from July to August in this species. The relationship between shell length (SL; mm) and shell height (SH; mm) was expressed by the equation SH=0.8053SL-2.9636 ($R^2=0.94$) and between SL and shell width (SW; mm) by the equation SW=0.5648SL-3.7105 ($R^2=0.90$). The relationship between SL and total weight (TW; g) was expressed by the following equation: $TW=0.00009SL^{3.2141}$ ($R^2=0.96$). von Bertalanffy's growth parameters were estimated using the regression wizard in the SigmaPlot computer program (Systat Software, Inc., v. 10.0). The maximum shell length ($SL_{\infty}$) was 126.16 mm, growth rate was 0.2030/year, theoretical age at shell length 0 ($t_0$) was -0.52 years, and asymptotic total weight ($TW_{\infty}$) was 509.17 g. Growth curves for SL and TW fitted to the von Bertalanffy's equation were expressed as follows: $SL_t=126.16(1-e^{-0.2030(t+0.52)})$, $TW_t=509.17(1-e^{-0.2030(t+0.52)})^{3.2141}$.

• Polymer(Korea)
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• v.25 no.4
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• pp.536-544
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• 2001

We investigate, in the viewpoint of mathematical stability, the validity of the time-strain separability hypothesis employed in polymer viscoelasticity on the basis of experimental results. There have been suggested two distinct stability criteria such as Hadamard related to quick response and dissipative stability conditions, and in the limit of high deformation rate we have proved that separable constitutive equations are either Hadamard or dissipative unstable. The fact that the separability is not valid in the short time region in stress relaxation experiments exactly coincides with the results of our analysis. Therefore, since the application of the separability hypothesis incurs thermodynamic inconsistency as well as mathematical instability, such application should be avoided in the formulation of constitutive equations. In addition, careful attention should be paid to the limit of its validity even in experiments. It is also proved that there is neither theoretical nor physical validity of using the damping function.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.38-47
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• 1992

The motion response of a ship moored in a rectangular harbor excited by long waves has been studied theoretically and experimentally. Within the framework of potential theory, matched asymptotic expansion techniques are exployed to analyze the problem. The fluid domain is divided into the ocean and the harbor regions for the analysis of wave response in a harbor without ship. The wave responses in both the ocean and the harbor sides are solved first independently in terms of Green's functions, which are the solutions of the Helmholtz equation satisfying appropriate boundary conditions. Slender body approximations are used to obtain the velocity jumps across the ship, which are associated with the symmetric motion modes of the ship. Unknowns contained in each solution are finally determined by matching at an intermediate zone between two neighboring regions. Theoretical results predict the ship motion qualitatively well. The main source of quantitative discrepancies is presumably due to real fluid effects such as separation at the harbor entrance and friction on harbor boundaries.

• Journal of the Korean Chemical Society
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• v.22 no.4
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• pp.202-220
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• 1978

Uniform semiclassical (WKB) solutions are obtained for nonseparable systems without using a close coupling formalism and are given explicitly in terms of well known analytic functions for various physically interesting and realistic cases. They do not become singular at turning points or surfaces and when taken in their asymptotic forms, they reduce to the usual WKB solutions that could be obtained if the Stokes phenomenon was properly taken care of for solutions. In obtaining such uniform solutions, the Schroedinger equations for nonseparable systems are suitably "renormalized" to solvable "normal" forms through certain transformations. Ehrenfest's adiabatic principle plays an important guiding role for obtaining such "renormalized" uniform solutions for nonseparable systems. The eigenvalues of the Hamiltonian can be calculated from the extended Bohr-Sommerfeld quantization rules when appropriate classical trajectories are obtained. An application is made to many-electron systems and for one of the simplest examples to show the utility of the method the approximate wavefunction is calculated of the ground state helium atom.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.271-278
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• 2011

When performing fire PSA in a nuclear power plant, an event mapping method, using an internal event PSA model, is widely used to reduce the resources used by fire PSA model development. Feasible initiating events and component failure events due to fire are identified to transform the fault tree (FT) for an internal event PSA into one for a fire PSA using the event mapping method. A surrogate event or damage term method is used to condition the FT of the internal PSA. The surrogate event or the damage term plays the role of flagging whether the system/component in a fire compartment is damaged or not, depending on the fire being initiated from a specified compartment. These methods usually require explicit states of all compartments to be modeled in a fire area. Fire event scenarios, when using explicit identification, such as surrogate or damage terms, have two problems: (1) there is no consideration of multiple fire propagation beyond a single propagation to an adjacent compartment, and (2) there is no consideration of simultaneous fire propagations in which an initiating fire event is propagated to multiple paths simultaneously. The present paper suggests a fire propagation equation to identify all possible fire event scenarios for an explicitly treated fire event scenario in the fire PSA. Also, a method for separating fire events was developed to make all fire events a set of mutually exclusive events, which can facilitate arithmetic summation in fire risk quantification. A simple example is given to confirm the applicability of the present method for a $2{\times}3$ rectangular fire area. Also, a feasible asymptotic approach is discussed to reduce the computational burden for fire risk quantification.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.279-286
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• 2020

In this study, we investigate the accuracy of higher order derivatives in the moving least square (MLS) difference method. An interpolation function is constructed by employing a Taylor series expansion via MLS approximation. The function is then applied to the mixed variational theorem in which the displacement and stress resultants are treated as independent variables. The higher order derivatives are evaluated by solving simply supported beams and cantilevers. The results are compared with the analytical solutions in terms of the order of polynomials, support size of the weighting function, and number of nodes. The accuracy of the higher order derivatives improves with the employment of the mean value theorem, especially for very high-order derivatives (e.g., above fourth-order derivatives), which are important in a classical asymptotic analysis.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.30.2-30.2
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• 2009

There is a growing body of evidence for the presence of multiple stellar populations in some globular clusters, including NGC 1851. For most of these peculiar globular clusters, however, the evidence for the multiple red giant-branches (RGBs) having different heavy elemental abundances as observed in $\omega$ Centauri is hitherto lacking, although spreads in some lighter elements are reported. It is therefore not clear whether they also share the suggested dwarf galaxy origin of $\omega$ Cen or not. Here we show from the CTIO 4m UVI photometry of the globular cluster NGC 1851 that its RGB is clearly split into two in the U - I color. The two distinct RGB populations are also clearly separated in the abundance of heavy elements as traced by Calcium, suggesting that the type II supernovae enrichment is also responsible, in addition to the pollutions of lighter elements by intermediate mass asymptotic giant branch stars or fast-rotating massive stars. The RGB split, however, is not shown in the V - I color, as indicated by previous observations. Our stellar population models show that this and the presence of bimodal horizontal-branch distribution in NGC 1851 can be naturally reproduced if the metal-rich second generation stars are also enhanced in helium.