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( Insun Song ),( Chandong Chang ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2
The relationship between the rock compressive strength and borehole breakout width in a vertical borehole has been widely used for constraining the magnitudes of in situ horizontal principal stresses. In such an underdetermined system (fewer equations than unknowns), however, the deterministic method yields indeterminate solutions for the two unknown stresses. We developed a new method of applying probabilistic model of rock strength to a variation of breakout width in a vertical wellbore section. The stochastic optimization method simultaneously constrains a complete set of in situ principal stresses with a reliable statistical evaluation in terms of sensitivity and uncertainty. For demonstrating the method, we use borehole images and sonic logging data obtained from the Integrated Ocean Drilling Program (IODP) Hole C0002A, a vertical hole near the seaward margin of the Kumano basin offshore from the Kii Peninsula, southwest Japan. The relation between the seismic velocity and uniaxial compressive strength of rock is used to establish the Weibull distribution model of rock strength from the sonic velocity well logging data. The local stress distribution at various breakout margins in a borehole section should correspond to the probabilistic distribution of the rock strength. This is an inverse problem because we cannot calculate the local stresses at breakout margin without the knowledge of far-field stress magnitudes. A grid search algorithm is applied to choose the best-fit set of far-field stresses by minimizing the misfit between the rock strength model and the stress distribution at breakout margins.
Insun Song,PooGyeon Park,Newcomb, Robert W. IEEE 2013 IEEE transactions on circuits and systems. a publi Vol.60 No.7
<P>This brief introduces the concept of a step-size scaler by investigating and modifying the tanh cost function for adaptive filtering with impulsive measurement noise. The step-size scaler instantly scales down the step size of gradient-based adaptive algorithms whenever impulsive measurement noise appears, which eliminates a possibility of updating weight vector estimates based on wrong information due to impulsive noise. The most attractive feature of the step-size scaler is that this is easily applicable to various gradient-based adaptive algorithms. Several representative gradient-based adaptive algorithms are performed without or with the step-size scaler in impulsive-noise environments, which shows the improvement of robustness against impulsive noise.</P>
Song, Insun,Choi, Yong Jun,Jin, Yilan,Kim, Jung-Woo,Koh, Jeong-Tae,Ji, Hyung Min,Jeong, Seon-Yong,Won, Ye-Yeon,Kim, Won,Chung, Yoon-Sok D.A. Spandidos 2017 MOLECULAR MEDICINE REPORTS Vol.16 No.4
<P>To identify novel candidate genes associated with osteoporosis, RNA-sequence analysis of human mesenchymal stem cells (hMSCs) from patients with osteoporosis (G3) and osteopenia (G2), and healthy controls (G1) was performed. Differentially expressed genes (DEGs) from among the three groups were identified. DEGs were separated into nine groups according to their gene expression patterns: UU (up and up), UF (up and flat), UD (up and down), FU (flat and up), FF (flat and flat), FD (flat and down), DU (down and up), DF (down and flat), and DD (down and down). Among the 42 DEGs between G3 and G1, eight candidate genes, namely stimulated by retinoic acid 6 (STRA6), melanophilin, neurotrophic receptor tyrosine kinase 2, cartilage oligomeric matrix protein, collagen type XI α 1 chain, integrin subunit β 2, monooxygenase DBH-like 1 and selenoprotein P, were selected, as they demonstrated consistent gene expression patterns of UU, FU, FD, and DD. Among these eight genes, STRA6 was highly expressed in the osteoporosis group and based on additional data from quantitative polymerase chain reaction analysis, it was selected for further study. In order to investigate whether STRA6 served a functional role in osteoblast or adipocyte differentiation, the effects of STRA6 expression changes in pluripotent stem cell C3H10T1/2, preosteoblast MC3T3-E1 and stromal ST2 cell lines were examined. Bone morphogenetic protein 2 enhanced STRA6 expression only at the early stage of osteoblast differentiation, and overexpression of STRA6 temporally inhibited the expression of osteoblastogenesis markers, including runt related transcription factor 2, bone sialoprotein and osteocalcin. Furthermore, the knockdown of STRA6 slightly enhanced nodule formation at the late stage of osteoblast differentiation, and overexpression of STRA6 in ST2 cells enhanced adipocyte differentiation. Taken together, STRA6 expression could be associated with the pathogenesis of osteoporosis by promoting adipocyte differentiation over osteoblast differentiation in the hMSC population.</P>
Hydraulic permeability and specific storage measurements of tight rock types
Insun Song,Yuna Lee 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10
A sudden change in pore pressure will take place when CO₂ is injected into a reservoir geologic formation. Excess pore pressure may make CO₂ geological storage vulnerable to leakage and failure. The prediction of spatial-temporal distribution of pore pressure around an injection well is essential for the safe operation of CO₂ geological storage. The pore-fluid pressure change in a porous rock formation is governed by the diffusion equation. The central parameter of the equation is the diffusivity (or diffusion coefficient) that is made up of the hydraulic permeability and specific storage of rock, and dynamic viscosity of fluid. The permeability is dominant in a steady state condition of fluid flow that is shortly reached in highly porous reservoir formation, but the specific storage becomes significantly valued in tight cap rock in which the transient flow does not disappear for a long time. We measured the hydraulic parameters of a shale sample, a potential cap rock, with different methods. The permeability measured by Darcy’s method has been regarded as a reference value worldwide. However, it does not provide the specific storage. We used two other methods, a constant rate flow injection and a transient pore pressure method, to obtain simultaneously both the permeability and specific storage of the sample. For both methods, downstream reservoir was minimized enough to be ignored. This boundary condition leads to a short transient condition. For the upstream, a fluid (water) is injected with a constant pumping rate into a cylindrical sample for the constant rate flow injection method, and with a sudden increase in upstream pressure followed by a constant pressure for transient pore pressure method. The permeability from the two different methods ranges from 10<SUP>-17</SUP> m² down to 10<SUP>-19</SUP> m² with increasing effective confining stress that was consistent with the values from Darcy’s method. The values of the specific storage with (1 - 7) × 10<SUP>-10</SUP> Pa<SUP>-1</SUP> were reasonable in comparison with the water compressibility and the rock porosity. Both permeability and specific storage of the shale was raised with decreasing effective confining stress. However, the diffusion coefficient increases with effective stress. This means that the sealing capacity is not unfavorable to CO₂ storage when the pore pressure is raised by CO₂ injection.
GATA4 negatively regulates bone sialoprotein expression in osteoblasts
( Insun Song ),( Byung-chul Jeong ),( Yong Jun Choi ),( Yoon-sok Chung ),( Nacksung Kim ) 생화학분자생물학회(구 한국생화학분자생물학회) 2016 BMB Reports Vol.49 No.6
GATA4 has been reported to act as a negative regulator in osteoblast differentiation by inhibiting the Dlx5 transactivation of Runx2 via the attenuation of the binding ability of Dlx5 to the Runx2 promoter region. Here, we determine the role of GATA4 in the regulation of bone sialoprotein (Bsp) in osteoblasts. We observed that the overexpression of Runx2 or Sox9 induced the Bsp expression in osteoblastic cells. Silencing GATA4 further enhanced the Runx2- and Sox9-mediated Bsp promoter activity, whereas GATA4 overexpression down-regulated Bsp promoter activity mediated by Runx2 and Sox9. GATA4 also interacted with Runx2 and Sox9, by attenuating the binding ability of Runx2 and Sox9 to the Bsp promoter region. Our data suggest that GATA4 acts as a negative regulator of Bsp expression in osteoblasts. [BMB Reports 2016; 49(6): 343-348]