• Journal of Yeungnam Medical Science
• /
• v.15 no.1
• /
• pp.114-124
• /
• 1998

We analyzed the mammographic (n=21) findings (location, margin, shape, cluster microcalcifications, size, multiplicity) and ultrasonographic (n=12) findings (shape, border, internal echo, boundary echo, posterior echo, lateral echo, width/depth ratio) to evaluate specific radiologic findings of histopathologically proved uncommon breast cancer. The mammographic findings (n=21) are as follow; 1) single; 16, multiple; 5 2) margin (smooth; 13, irregular; 4, spiculated; 4) 3) shape (round and ovoid; 9, lobulated; 8, irregular; 4) 4) cluster micro calcifications (abscent; 20, present; 1) 5) size (1-3cm; 18, 3-5cm; 2, 5cm> ; 1) 6) location (UOQ; 13, UIQ; 4, LIQ; 3, LOQ; 1). The ultrasonographic findings (n=12) are as follow; 1) shape (round to oval; 5, lobulated; 5, irregular; 2) 2) border (smooth even; 9, rough uneven; 3) 3) internal echo (fine homogeneous; 5, coarse heterogeneous; 7) 4) boundary echo (regular fine; 4, irregular thick; 8) 5) posterior echo (enhanced; 11, no change; 1) 6) lateral echo (marked; 7, nonexistent; 5) 7) width/depth ratio (1.5> ; 1, 1.0-1.5; 7, 1.0< ; 4). Uncommon breast cancer show benign nature on mammogram, but malignant nature on ultrasonogram (especially boundary echo, internal echo, width/depth ratio).

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.22 no.3
• /
• pp.595-602
• /
• 1998

Specimens of 304 stainless steel were tested to failure at elevated temperatures under multiaxial stress states, uniaxial tension using smooth bar specimens, biaxial shearing using double shear bar specimens, and triaxial tension using notched bar specimens. Rupture times are compared for uniaxial, biaxial, and triaxial stress states with respect to the maximum principal stress, the von Mises effective stress, and the principal facet stress. The results indicate that the principal facet stress gives the best correlation for the material investigated, and this parameter can predict creep life data under multiaxial stress states with rupture data obtained with specimens under uniaxial stresses. The results also suggest that grain boundary cavitation, coupled with localized deformation processes such as grain boudary sliding, controls the lifetimes of the specimens.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.8
• /
• pp.1241-1249
• /
• 1997

The problem of structural topology optimization can be relaxed and converted into the optimal density distribution problem. The optimal density distribution must be post-processed to get the real shape of the structure. The extracted shape can then be used for the next process, which is usually shape optmization based on the boundary movement method. In the practical point of view, it is very important to get the optimal density distribution from which the corresponding shape can easily be extracted. Among many other factors, the presence of checker-board patterns is a powerful barrier for the shape extraction job. The nature of checker-board patterns seems to be a numerical locking. In this paper, an efficient algorithm is presented to suppress the checker-board patterns. At each iteration, density is re-distributed after it is updated according to the optimization rule. The algorithm also results in the optimal density distribution whose corresponding shape has smooth boundary. Some examples are presented to show the performance of the density re-distribution algorithm. Checker-board patterns are successfully suppressed and the resulting shapes are considered very satisfactory.

• Journal of the Society of Naval Architects of Korea
• /
• v.36 no.1
• /
• pp.70-81
• /
• 1999

To predict the viscous boundary layers and wakes around a ship, the CFD techniques are commonly used. For the efficient application of CFD tools to practical hull farms, a 3-D field grid generating system is developed. The present grid generating system utilizes the solution of Poisson equation. Sorenson's method developed for 2-D is extended into 3-D to provide the forcing functions controling grid interval and orthogonality on hull surface, etc. The weighting function scheme is used for the discretization of the Poisson equation and the linear equations are solved by using MSIP salver. The trans-finite interpolation is also employed to assure the smooth transition into boundary surface grids. To rove the applicability, the field grid systems around a container ship and a VLCC with bow and stem bulb are illustrated, and the procedures for generating 3-D field grid system are explained.

• Journal of Technology Innovation
• /
• v.5 no.1
• /
• pp.150-180
• /
• 1997

This article introduces the five functions of the national innovation system(NIS). As one of social systems in the national level, the five generic functions of open system - production, boundary spanning, maintenance, adaptation, management functions - are applied to the NIS. The production function is the primary process, which produces innovative products and services of the NIS. The boundary spanning function is the function of procuring input and disposing the innovation output or aiding in these processes. Experienced R&D human resources, R&D funds, technology etc. are some of the components of the input of the NIS. The maintenance function is responsible for maintaining smooth operation and upkeeping the system in terms of various conditions. The adaptation function is to help the system change and adapt, and scan the environment for problems, opportunites, and technological developments. It has outward orientation, from the long-term view for the survival of the system. The management function carries out planning and control of the overall activities for the other four functions in order to effectiving run the system as a whole. Finally, this article discusses implications of the diagnosis of the national innovation system and the decision making process of S&T policy.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.101-104
• /
• 2008

The sailfish is the fastest sea animal, reaching its maximum speed of 110km/h. On its skin, a number of V-shaped protrusions pointing downstream exist. Thus, in the present study, the possibility of reducing the skin friction using its shape is investigated in a turbulent boundary layer. We perform a parametric study by varying the height and width of the protrusion, the spanwise and streamwise spacings between adjacent ones, and their overall distribution pattern, respectively. Each protrusion induces a pair of streamwsie vortices, producing low and high shear stresses at its center and side locations, respectively. These vortices also interact with those induced from adjacent protrusions. As a result, the drag is either increased or unchanged for all the cases considered. In some cases, the skin friction itself is reduced but total drag including the form drag on the protrusions is larger than that of a smooth surface. Since the shape of present protrusions is similar to that used by Sirovich and Karlsson [Nature 388, 753 (1997)] where V-shaped protrusions pointing upstream were considered, we perform another set of experiments following their study. However, we do not obtain any drag reduction even with random distribution of those V-shaped protrusion.

• Wind and Structures
• /
• v.1 no.3
• /
• pp.225-241
• /
• 1998

The high-rise supporting towers of long-span suspension and cable-stayed bridges commonly comprise a pair of slender prisms of roughly square cross-section with a center-to-centre spacing of from perhaps 2 to 6 widths and connected by one or more cross-ties. The tower columns may have a constant spacing as common for suspension bridges or the spacing may reduce towards the top of the tower. The present paper is concerned with the aerodynamics of such towers and describes an experimental investigation of the overall aerodynamic forces acting on a pair of square cylinders in two-dimensional flow. Wind tunnel pressure measurements were carried out in smooth flow and with a longitudinal intensity of turbulence 0.10. Different angles of attack were considered between $0^{\circ}$ and $90^{\circ}$, and separations between the two columns from twice to 13 times the side width of the column. The mean values of the overall forces proved to be related to the bias introduced in the flow by the interaction between the two cylinders; the overall rms forces are related to the level of coherence between the shedding-induced forces on the two cylinders and to their phase. Plots showing the variation of the force coefficients and Strouhal number as a function of the separation, together with the force coefficients spectra and lift cross-correlation functions are presented in the paper.

• Structural Engineering and Mechanics
• /
• v.66 no.3
• /
• pp.329-341
• /
• 2018

This paper considers the smooth receding contact problem between a homogeneous half-plane and a composite laminate composed of an inhomogeneously coated elastic layer. The inhomogeneity of the elastic modulus of the coating is approximated by an exponential function along the thickness dimension. The three-component structure is pressed together by either a concentrated force or uniform pressures applied at the top surface of the composite laminate. Both semianalytical and finite element analysis are performed to solve for the extent of contact and the contact pressure. In the semianalytical formulation, Fourier integral transformation of governing equations and boundary conditions leads to a singular integral equation of Cauchy-type, which can be numerically integrated by Gauss-Chebyshev quadrature to a desired degree of accuracy. In the finite element modeling, the functionally graded coating is divided into homogeneous sublayers and the shear modulus of each sublayer is assigned at its lower boundary following the predefined exponential variation. In postprocessing, the stresses of any node belonging to sublayer interfaces are averaged over its surrounding elements. The results obtained from the semianalytical analysis are successfully validated against literature results and those of the finite element modeling. Extensive parametric studies suggest the practicability of optimizing the receding contact peak stress and the extent of contact in multilayered structures by the introduction of functionally graded coatings.

• Journal of Korea Multimedia Society
• /
• v.5 no.4
• /
• pp.386-392
• /
• 2002

In this paper, we propose a novel blocking effect reduction method based on a rational B-spline. The blocking effect results from independent coding of each image block and becomes highly visible especially coded at very low bit rates. The proposed approach adopts a rational open uniform B-spline curve that used to produce a smooth curve through a set of control points. The pixels on the block boundary are treated as control points, and the weight values, which decide the shape of curve, are determined differentially by considering the distance the position of the pixels and that of the block boundary. The simulation results show that the proposed method has excellent performance for all pattern of the blocking effect with less computational complexity.

• Steel and Composite Structures
• /
• v.25 no.6
• /
• pp.649-661
• /
• 2017

This paper is motivated by the lack of studies in the technical literature concerning to the influence of carbon nanotubes (CNTs) waviness and aspect ratio on the vibrational behavior of functionally graded nanocomposite annular sector plates resting on two-parameter elastic foundations. The carbon nanotube-reinforced (CNTR) plate has smooth variation of CNT fraction based on the power-law distribution in the thickness direction, and the material properties are also estimated by the extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. Parametric studies are carried out to highlight the influence of CNTs volume fraction, waviness and aspect ratio, boundary conditions and elastic foundation on vibrational behavior of FG-CNT thick sectorial plates. The study is carried out based on three-dimensional theory of elasticity and in contrary to two-dimensional theories, such as classical, the first- and the higher-order shear deformation plate theories, this approach does not neglect transverse normal deformations. The annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free. For an overall comprehension on 3-D vibration of annular sector plates, some mode shape contour plots are reported in this research work.