• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.5 s.176
• /
• pp.1331-1342
• /
• 2000

In power generation systems a variety of structural components typically operate at high temperature and pressure. Therefore a life assessment methodology accounting for gradual creep fracture is increasingly needed for these components. The most critical defects in such structure are generally found in the form of semi-elliptical surface cracks in the welded tubular joints. Therefore the analysis of a semi-elliptical surface crack in a plate or a shell is an important problem in engineering fracture mechanics. On this background, via shell/line-spring finite element analyses of such surface cracks in the welded T and L joints under various loadings, we investigate J-integral along the crack front We first develop T and L joints auto mesh generation program providing ABAQUS input file composed of shell/line-spring finite elements. We then further develop a T and L joints life assessment program based on the experimental creep crack growth law and auto mesh generation program in a graphical user interface format Finally the remaining life of T and L joints for various analytical parameters are assessed using the developed life assessment program.

• Steel and Composite Structures
• /
• v.2 no.1
• /
• pp.35-50
• /
• 2002

A series of tests on simple-welded plate specimens (SWPS) and T-stub tension specimens simulating some of the joint details in moment frame connections were conducted in this investigation. The effects of weld strength mismatch and weld metal toughness on structural behavior of these specimens were considered under both static and dynamic loading conditions. Finite element analyses were performed by taking into account typical weld residual stress distributions and weld metal strength mismatch conditions to facilitate the interpretation of the test results. The major findings are as follows: (a) Sufficient specimen size requirements are essential in simulating both load transfer and constraint conditions that are relevant to moment frame connections, (b) Weld residual stresses can significantly elevate stress triaxiality in addition to structural constraint effects, both of which can significantly reduce the plastic deformation capacity in moment frame connections, (c) Based on the test results, dynamic loading within a loading rate of 0.02 in/in/sec, as used in this study, premature brittle fractures were not seen, although a significant elevation of the yield strength can be clearly observed. However, brittle fracture features can be clearly identified in T-stub specimens in which severe constraint effects (stress triaxiality) are considered as the primary cause, (d) Based on both the test and FEA results, T-stub specimens provide a reasonable representation of the joint conditions in moment frame connections in simulating both complex load transfer mode and constraint conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.685-686
• /
• 2007

• The Pure and Applied Mathematics
• /
• v.5 no.2
• /
• pp.109-114
• /
• 1998

Let H be a separable complex H be a space and let (equation omitted)(H) be the *-algebra of all bounded linear operators on H. An operator T in (equation omitted)(H) is said to be p-hyponormal if ($T^{\ast}T)^p - (TT^{\ast})^{p}\geq$ 0 for 0 ＜ p ＜ 1. If p = 1, T is hyponormal and if p = $\frac{1}{2}$, T is semi-hyponormal. In this paper, by using a technique introduced by S. K. Berberian, we show that the approximate point spectrum $\sigma_{\alpha p}(T) of a pure p-hyponormal operator T is empty, and obtains the compact perturbation of T.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.4
• /
• pp.9-16
• /
• 1998

The joint characteristics are necessary to be determined in the early stage of the vehicle body design. Researches on identification of joints in a vehicle body have been performed until the recent year. In this study, the joint characteristics of vehicle struct- ure were expressed as condensed forms from the full joint stiffness and mass matrix. The condensed joint stiffness and mass matrix were applied to typical T-type and Edge-type joints, and the usefulness was confirmed. In addition, those were applied to center pillar and full vehicle body to validate the practical application.

• Progress in Medical Physics
• /
• v.19 no.4
• /
• pp.269-275
• /
• 2008

Although MR imaging is generally applicable to depict knee joint deterioration it, is sometimes occurred to mis-read and mis-diagnose the common knee joint diseases. In this study, we employed magnetization transfer ratio (MTR) method to improve the diagnosis of the various knee joint diseases. Spin-echo (SE) T2-weighted images (TR/TE 3,400-3,500/90-100 ms) were obtained in seven cases of knee joint deterioration, FSE T2-weighted images (TR/TE 4,500-5,000/100-108 ms) were obtained in seven cases of knee joint deterioration, gradient-echo (GRE) T2-weighted images (TR/TE 9/4.56/$50^{\circ}$ flip angle, NEX 1) were obtained in 3 cases of knee joint deterioration, In six cases of knee joint deterioration, fat suppression was performed using a T2-weighted short T1/tau inverse recovery (STIR) sequence (TR/TE =2,894-3,215 ms/70 ms, NEX 3, ETL 9). Calculation of MTR for individual pixels was performed on registration of unsaturated and saturated images. After processing to make MTR images, the images were displayed in gray color. For improving diagnosis, three-dimensional isotropic volume images, the MR tristimulus color mapping and the MTR map was employed. MTR images showed diagnostic images quality to assess the patients' pathologies. The intensity difference between MTR images and conventional MRI was seen on the color bar. The profile graph on MTR imaging effect showed a quantitative measure of the relative decrease in signal intensity due to the MT pulse. To diagnose the pathologies of the knee joint, the profile graph data was shown on the image as a small cross. The present study indicated that MTR images in the knee joint were feasible. Investigation of physical change on MTR imaging enables to provide us more insight in the physical and technical basis of MTR imaging. MTR images could be useful for rapid assessment of diseases that we examine unambiguous contrast in MT images of knee disorder patients.

• Physical Therapy Korea
• /
• v.17 no.2
• /
• pp.43-50
• /
• 2010

The purpose of this study was to investigate the effects of Evjenth-Hamberg stretching on the active range of motion (ROM) of the hip joint and the pennation angle of the semitendinosus muscle. Eighty healthy adults participated in this study. The active ROM of the hip joint was measured by a goniometer and the pennation angle of the semitendinosus muscle was measured by ultrasonographic imaging (USI). Both ROM and pennation angle were recorded before and after the static stretching and the Evjenth-Hamberg stretching, respectively. Data were analyzed using paired t-lest and independent t-test at p<.05. The results were as follows: 1) The active ROM of the hip joint increased significantly after both stretching interventions compared with the baseline (p<.001). However, the active ROM of the hip joint increased significantly in Evjenth-Hamberg stretching compared with static stretching. 2) The pennation angle decreased significantly after both stretching interventions compared with the baseline (p<.001). However, the pennation angle decreased significantly in Evjenth-Hamberg stretching compared with static stretching. 3) Reliability data showed that there was a high consistency in USl measurements (ICC=.978). Our findings suggest that the Evjenth-Hamberg stretching was more effective than static stretching in increasing the active ROM of the hip joint and decreasing the pennation angle of the semitendinosus muscle.

• Korean Journal of Mathematics
• /
• v.14 no.1
• /
• pp.1-5
• /
• 2006

We will introduce tensor product spectrums on the tensor product spaces. And we will show that ${\sigma}[P(T_1,T_2,{\ldots},T_n)]=P[({\sigma}(T_1),{\sigma}(T_2){\ldots},{\sigma}(T_n)]={\sigma}(T_1,T_2{\ldots},T_n)$.

• Journal of Korean Society of Steel Construction
• /
• v.15 no.1
• /
• pp.69-76
• /
• 2003

This paper described the ultimate strength and deformation limit of new uniplanar T-joints in cold-formed square hollow sections. The new T-joint had the configuration that only a branch member was oriented at 45 degrees to a chord member in the plane of the truss. This study focused on the branch-rotated T-joints governed by chord web failure. Based on the test results of the T-joint in cold-formed square hollow sections, the deformation lirnit was found to be 3%B for $16.7{\leq}2(B/T){\leq}33.3$ and $0.63{\leq}(b_1/B)=0.7$. Existing strength formulas for traditional T-joint were investigated, and the new strength formula for the branch-rotated T-joint was proposed. This proposed formula was based on column buckling theory considering the rounded corners of cold-formed square hollow sections. Finally, the optimization condition of yield stress and $2{\gamma}$ was recommended to select the optimized chord section.

• Communications for Statistical Applications and Methods
• /
• v.10 no.3
• /
• pp.749-764
• /
• 2003

In this paper we explain that normal theory likelihood-ratio tests(z, t, $x^2$. F) for mean(s) or variance(s) can be geometrically related to volume of difference of two joint pdf's. One is an estimated joint pdf under null parameter space $\omega$ and the other is an estimated joint pdf under full parameter space $\Omega$. For explanations, ‘distance between two distributions’ is defined. We study properties of it, and derive some results on the distance between two multivariate normal distributions.