• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.12-19
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• 2015

As a measure of improving the mechanical properties of a diffusion bonded joint of a ferritic/martensitic steel (FMS), the post-bonding heat treatment (PBHT) is applied. In the temperature range of normalizing condition ($950-1,050^{\circ}C$), diffusion bonding is employed with compressive stress (6 MPa). Due to the martensite structure distributed in the matrix, Vicker's hardness values of the as-bonded are much higher than those of the as-received. Through the PBHT for 1 h at $720^{\circ}C$, hardness values are recovered to as low as those of the as-received condition. Also, tensile properties of PBHT are similar to those of the as-received at up to the test temperature of $550^{\circ}C$, when the diffusion bonding is carried out over $1,000^{\circ}C$. Based on the creep-rupture testing performed at $650^{\circ}C$ in air environment, the joint efficiency of the PBHTed specimens is about 80% in, which is higher than that of the as-bonded specimens.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.4
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• pp.199-204
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• 2010

The potential therapeutic action of shikonin in an experimental model of rheumatoid arthritis (RA) was investigated. As a RA animal model, DBA/1J mice were immunized two times with type II collagen. After the second collagen immunization, mice were orally administered shikonin (2 mg/kg) once a day for 35 days, and the incidence, clinical score, bone mineral density (BMD), bone mineral content (BMC) and joint histopathology were evaluated. BMD in the proximal regions of the tibia largely increased in the shikonin treatment group compared with the control group. We also examined the effect of shikonin on inflammatory cytokines and cartilage protection. Shikonin treatment significantly reduced the incidence and severity of collagen-induced arthritis (CIA), markedly abrogating joint swelling and cartilage destruction. Shikonin also significantly inhibited the production of matrix metalloproteinase (MMP)-1 and up-regulated tissue inhibitors of metalloproteinase (TIMP)-1 in mice with CIA. In conclusion, shikonin exerted therapeutic effects through regulation of MMP/TIMP; these results suggest that shikonin is an outstanding candidate as a cartilage protective medicine for RA.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.640-647
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• 1998

Microstrip patch antennas are analyzed by a multiresolution wavelet method. The spectral Green's dyad of the structure is obtained and its joint spatial-spectral domain representations are presented. Based on the joint spatial-spectral domain representation, we show that the spectral-domain wavelets are useful in the analysis of this problem. We obtain the matrix equations of the integral equations of this Green's dyad by using the method of moment(MoM), and efficiently solve the problem using the spectral domain wavelet transform concepts in conjuction with the conjugate gradient method. The results for a single-layered square patch are compared with those of conventional MoM and CG-FFT.

• Journal of Welding and Joining
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• v.7 no.2
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• pp.35-48
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• 1989

This study is concerned with a correlation of microstructure and local brittle zone (LBZ) in offshore structural steel welds. The influence of the LBZ on fracture toughness was investigated by means of simulated heat-affected zone (HAZ) tests as well as welded joint tests. Micromechanical processes involved in void and cleavage microcrack formation were also identified using notched round tensile tests and subsequent SEM observations. The LBZ in the HAZ of a multiphase welded joint is the interstitially reheated coarse grained HAZ, which is influenced by metallurgical factors such as effective grain size, the major matrix structure and the amount of high-carbon martensite-austenite (M-A) constituents. The experimental results indicate that Chirpy energy was found to scale monotonically with the amount of M-A constituents, confirming that the M-A constituent is the major microstructural factor controlling the HAZ toughness. In addition, voids and microcracks are observed to initiate at M-A constituents by the shear cracking process. Thus, the M-A constituent played an important role in initiating the voids and microcracks, and consequently caused brittle fracture.

• The Journal of the Korea Contents Association
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• v.19 no.2
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• pp.469-476
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• 2019

Robotic motion is designed by the rotation and the translation of multiple joint coordinates in a three-dimensional space. Joint coordinates are generally modeled by homogeneous transform matrix. However, the complexity of three dimensional motions prefers the visualization methods based on simulation environments in which models and generated motions work properly. Many simulation environments have the limitations of usability and functional extension from platform dependency and interpretation of predefined commands. This paper proposes the web-based three dimensional simulation environment toward high user accessibility. Also, it covers the small size web server that is linked with Python script. The non linearities of robot control apply to verify the computing efficiency, the process management, and the extendability of user scripts.

• Smart Structures and Systems
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• v.24 no.2
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• pp.209-221
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• 2019

The classical Kalman filter (KF) provides a practical and efficient way for state estimation. It is, however, not applicable when the external excitations applied to the structures are unknown. Moreover, it is known the classical KF is only suitable for linear systems and can't handle the nonlinear cases. The aim of this paper is to extend the classical KF approach to circumvent the aforementioned limitations for the joint estimation of structural states and the unknown inputs. On the basis of the scheme of the classical KF, analytical recursive solution of an improved KF approach is derived and presented. A revised form of observation equation is obtained basing on a projection matrix. The structural states and the unknown inputs are then simultaneously estimated with limited measurements in linear or nonlinear systems. The efficiency and accuracy of the proposed approach is verified via a five-story shear building, a simply supported beam, and three sorts of nonlinear hysteretic structures. The shaking table tests of a five-story building structure are also employed for the validation of the robustness of the proposed approach. Numerical and experimental results show that the proposed approach can not only satisfactorily estimate structural states, but also identify unknown loadings with acceptable accuracy for both linear and nonlinear systems.

• Journal of Marine Bioscience and Biotechnology
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• v.12 no.2
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• pp.99-107
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• 2020

Osteoarthritis (OA) is an inflammatory degenerative joint disease that is accompanied by irreversible joint cartilage destruction. Recently, the antioxidant effects of Carpomitra costata, which is a type of brown algae, have been reported, but their effects on OA have not been investigated. In this study, the anti-osteoarthritic effect of the ethanol extract of C. costata (EECC) on SW1353 human chondrocytes was studied. Results showed that EECC significantly attenuated the interleukin-1β (IL-1β)-induced release of pro-inflammatory mediators, including prostaglandin E2 and nitric oxide (NO), as well as expressions of cyclo-oxygenase-2 and inducible NO synthase. EECC also inhibited the IL-1β-induced expressions of matrix metalloproteinase-1, -3, and -13 in SW1353 chondrocytes, which reduced their extracellular secretion. In addition, the oxidative stress induced by IL-1β was confirmed to be blocked by EECC due to the inhibition of reactive oxygen species generation. Moreover, EECC suppressed IL-1β-mediated translocation of nuclear factor-kappa B (NF-κB) from cytosol into the nucleus and the degradation of IκB-α, which indicates that EECC exhibits anti-inflammatory effects by inhibiting the NF-κB signaling pathway. These results are the first to demonstrate the anti-inflammatory activities of C. costata extracts in chondrocytes, thus suggesting that this algae extract may be used in the treatment of OA.

• Journal of Korean Foot and Ankle Society
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• v.27 no.2
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• pp.71-74
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• 2023

A medial opening wedge supramalleolar osteotomy (SMO) introduced by Takakura et al. is a useful realignment procedure for patients with ankle joint arthritis and varus malalignment by shifting the weight-bearing axis laterally and redistributing the loads on the ankle joint. When pain persists after arthroscopic microfracture in patients with medial osteochondral lesion of the talus (OLT), redo arthroscopy, osteochondral autograft transplantation, autologous chondrocyte implantation, or matrix-induced chondrogenesis might be indicated. On the other hand, there is insufficient scientific evidence for realignment surgery through SMO, while the effect of realignment surgery has been studied consecutively for osteochondral lesions of the knee. Therefore, this paper reports a patient with medial OLT who underwent redo arthroscopy combined with SMO for persistent pain after primary arthroscopic microfracture.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.5
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• pp.399-408
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• 2005

In the progression of the Temporomandibular Joint Disorder(TMD), not only deformation and perforation of disc occur. But also fibrotic adhesion and inflammatory changes to the retrodiscal tissue can be seen in addition to the condylar degenerative change (e.g. osteoarthritis). However, the correct diagnosis,?planning for appropriate treatment, and prediction of prognosis are limited, because there are no means to stage the progression of the disorder. In this study relative signal intensity of retrodiscal tissue in MRI and the synovial fluid concentration of matrix metalloproteinase-2 (MMP-2), MMP-9, and Interleukin-6(IL-6) in the 23 temporomandibular joints(TMJ), from 17 patients with TMD were evaluated as a possible diagnostic marker. The relative signal intensity of retrodiscal tissue was referenced to brain gray matter with same region of interest(ROI) size. The concentrations of MMP-2, MMP-9, and IL-6 were evaluated by Enzyme Linked Immunosorbent Assay (ELISA). The collected data were compared with condylar degenerative change, joint effusion and disc position observed in MRI. The relative signal intensity of the retrodiscal tissue was increased significantly when degenerative changes were present. In addition, there was significantly high signal intensity in the presence of a disc displaced without reduction. The concentration of IL-6 was significantly increased when condylar degenerative change was no observed. And there were no changes in the levels of IL-6 according to disc position and joint effusion measurement. Moreover, there were no significant relevance between the concentration of total MMP-2 and active MMP-9 in synovial fluid, relative to degenerative changes in the mandibular condyle, to joint effusion, and to disc position observed on MRI images. In conclusion, the relative signal intensity of the retrodiscal tissue can be regarded as a mean of diagnosing the procession of TMD in a non-invasive manner. But more additional studies are required for the levels of MMP-2. MMP-9, and IL-6 to determine their potentials as a diagnostic marker for TMD.

• Geophysics and Geophysical Exploration
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• v.21 no.1
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• pp.15-25
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• 2018

Seismic inversion is a high-resolution tool to delineate the subsurface structures which may contain oil or gas. On the other hand, marine controlled-source electromagnetic (mCSEM) inversion can be a direct tool to indicate hydrocarbon. Thus, the joint inversion using both EM and seismic data together not only reduces the uncertainties but also takes advantage of both data simultaneously. In this paper, we have developed a simultaneous joint inversion approach for the direct estimation of reservoir petrophysical parameters, by linking electromagnetic and seismic data through rock physics model. A cross-gradient constraint is used to enhance the resolution of the inversion image and the maximum likelihood principle is applied to the relative weighting factor which controls the balance between two disparate data. By applying the developed algorithm to the synthetic model simulating the simplified gas field, we could confirm that the high-resolution images of petrophysical parameters can be obtained. However, from the other test using the synthetic model simulating an anticline reservoir, we noticed that the joint inversion produced different images depending on the model constraint used. Therefore, we modified the algorithm which has different model weighting matrix depending on the type of model parameters. Smoothness constraint and Marquardt-Levenberg constraint were applied to the water-saturation and porosity, respectively. When the improved algorithm is applied to the anticline model again, reliable porosity and water-saturation of reservoir were obtained. The inversion results indicate that the developed joint inversion algorithm can be contributed to the calculation of the accurate oil and gas reserves directly.