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Fracture Toughness Calculation by Movable Cellular Automata Method
Pak, Mik Hail,Lee, Choon Yeol,Chai, Young Suck Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.353-358 No.3
<P>Fracture toughness calculation by Movable Cellular Automata (MCA) method is demonstrated in this study in order to verify the validity of application of MCA method to the fracture problems. Two different geometries: edge-cracked strip and center cracked plate tension specimen have been considered to simulate numerically, which make place in real experiments. Soda-Lime silica glass for brittle material, AISI 1040 Steel and Aluminum Alloy 2024 for ductile materials were used, respectively. Fulfillment of basic principles of fracture mechanics has been checked. In MCA method, special fracture criterion is used to describe the process of crack propagation and critical stress and displacement was obtained, which are used as input data for evaluating the fracture toughness. In comparisons with table data, the results showed the sufficient agreement, which states the facility of the MCA method in application to the fracture problems.</P>
Pak, Kyoungjune,Cheon, Gi Jeong,Nam, Hyun-Yeol,Kim, Seong-Jang,Kang, Keon Wook,Chung, June-Key,Kim, E. Edmund,Lee, Dong Soo Society of Nuclear Medicine 2014 The Journal of nuclear medicine Vol.55 No.6
<P>We conducted a comprehensive systematic review of the literature on volumetric parameters and a meta-analysis of the prognostic value of metabolic tumor volume (MTV) and total lesion glycolysis (TLG) in patients with head and neck cancer (HNC). <B>Methods:</B> A systematic search of MEDLINE and EMBASE was performed using the key words PET, head and neck, and volume. Inclusion criteria were <SUP>18</SUP>F-FDG PET used as an initial imaging tool; studies limited to HNC; patients who had not undergone surgery, chemotherapy, or radiotherapy before PET scans; and studies reporting survival data. Event-free survival and overall survival were considered markers of outcome. The impact of MTV or TLG on survival was measured by the effect size hazard ratio (HR). Data from each study were analyzed using Review Manager. <B>Results:</B> Thirteen studies comprising 1,180 patients were included in this study. The combined HR for adverse events was 3.06 (2.33–4.01, <I>P</I> < 0.00001) with MTV and 3.10 (2.27–4.24, <I>P</I> < 0.00001) with TLG, meaning that tumors with high volumetric parameters were associated with progression or recurrence. Regarding overall survival, the pooled HR was 3.51 (2.62–4.72, <I>P</I> < 0.00001) with MTV and 3.14 (2.24–4.40, <I>P</I> < 0.00001) with TLG. There was no evidence of significant statistical heterogeneity at an I<SUP>2</SUP> of 0%. <B>Conclusion:</B> MTV and TLG are prognostic predictors of outcome in patients with HNC. Despite clinically heterogeneous HNC and the various methods adopted between studies, we can confirm that patients with a high MTV or TLG have a higher risk of adverse events or death.</P>
Pak, Sangyeon,Lee, Juwon,Lee, Young-Woo,Jang, A-Rang,Ahn, Seongjoon,Ma, Kyung Yeol,Cho, Yuljae,Hong, John,Lee, Sanghyo,Jeong, Hu Young,Im, Hyunsik,Shin, Hyeon Suk,Morris, Stephen M.,Cha, SeungNam,Sohn American Chemical Society 2017 NANO LETTERS Vol.17 No.9
<P/><P>van der Waals heterostructures composed of two different monolayer crystals have recently attracted attention as a powerful and versatile platform for studying fundamental physics, as well as having great potential in future functional devices because of the diversity in the band alignments and the unique interlayer coupling that occurs at the heterojunction interface. However, despite these attractive features, a fundamental understanding of the underlying physics accounting for the effect of interlayer coupling on the interactions between electrons, photons, and phonons in the stacked heterobilayer is still lacking. Here, we demonstrate a detailed analysis of the strain-dependent excitonic behavior of an epitaxially grown MoS<SUB>2</SUB>/WS<SUB>2</SUB> vertical heterostructure under uniaxial tensile and compressive strain that enables the interlayer interactions to be modulated along with the electronic band structure. We find that the strain-modulated interlayer coupling directly affects the characteristic combined vibrational and excitonic properties of each monolayer in the heterobilayer. It is further revealed that the relative photoluminescence intensity ratio of WS<SUB>2</SUB> to MoS<SUB>2</SUB> in our heterobilayer increases monotonically with tensile strain and decreases with compressive strain. We attribute the strain-dependent emission behavior of the heterobilayer to the modulation of the band structure for each monolayer, which is dictated by the alterations in the band gap transitions. These findings present an important pathway toward designing heterostructures and flexible devices.</P>
MIXED-MODE CRACK PROPAGATION BY MOVABLE CELLULAR AUTOMATA METHOD
Mikhail Pak,Choon Yeol Lee,Young Suck Chai 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Propagation of a mixed-mode crack in Soda-Lime silica glass using Movable Cellular Automata (MCA) method is demonstrated in this study. In MCA method, special fracture criterion is used to describe the process of crack initiation and propagation. Comparison between MCA and other crack initiation criteria results are made. The crack resistance curves and bifurcation angles under different loading angles are found. In comparisons with results of maximum circumferential tensile stress criterion, MCA result showed the sufficient agreement.
The Clinical Implication and Prediction of Diffuse Splenic FDG Uptake During Cancer Surveillance
Nam, Hyun-Yeol,Kim, Seong-Jang,Kim, In-Joo,Kim, Bum-Soo,Pak, Kyoungjune,Kim, Keunyoung Lippincott Williams Wilkins, Inc. 2010 Clinical nuclear medicine Vol.35 No.10
OBJECTIVE:: The purpose of this study was to investigate correlations between diffuse splenic FDG uptake and hematological and inflammatory parameters to clarify the significance of splenic FDG uptake on PET/CT images. METHODS:: We retrospectively analyzed the consecutive records of F-18 FDG PET/CT scans and selected 31 patients with diffuse splenic FDG uptake as patient group. A total of 25 patients who underwent F-18 FDG PET/CT scans for simple health checkup were enrolled as control group. ROIs were placed on the liver and spleen to measure maximal standardized uptake value (SUVmax). The spleen SUVmax was divided by the liver SUVmax to calculate the spleen/liver ratio. The correlations between the S/L ratio and various hematological parameters were evaluated. RESULTS:: The S/L ratio was positively correlated with serum C-reactive protein level, white blood cell count, and neutrophil count and negatively correlated with hemoglobin, hematocrit, and red blood cell count. Under multiple regression analysis, the Hb level and the C-reactive protein level were the significant predictors for diffuse splenic FDG uptake. CONCLUSION:: In conclusion, our study suggests that concurrent inflammation or anemia at the time of PET/CT study could be one of various causes of diffuse splenic FDG uptake.