• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.868-878
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• 1998

There are recently increasing needs for precision XYZ-stage in the fields of nanotechnology, specially in AFMs(Atomic Force Microscope) and STMs(Scanning Tunneling Microscope). Force measurements are made in the AFM by monitoring the deflection of a flexible element (usually a cantilever) in response to the interaction force between the probe tip and the sample and controlling the force neasyred constant topography can be obtained. The power of the STM is based on the strong distance dependence of the tunneling current in the vacuum chamber and the current is a feedback for the tip to trace the surface topography. Therefore, it is required for XYZ-stage to position samples with nanometer resolution, without any crosscouples and any parasitic motion and with fast response. Nanometer resolution is essential to investigate topography with reasonable shape. No crosscouples and parasitic motion is essential to investigate topography without any shape distortion. Fast response is essential to investigate topography without any undesirable interaction between the probe tip and sample surface ; sample scratch. To satisfy these requirements, this paper presents a novel XYZ-stage concept, it is actuated by PZT and has a monolithic flexible body that is made symmetric as possible to guide the motion of the moving body linearly. PZT actuators have a very fast response and infinite resolution. Due to the monolithic structure, this XYZ-stage has no crosscouples and by symmetry it has no parasitic motion. Analytical modeling of this XYZ-stage and its verification by FEM modeling are performed and optimal design that is to maximize 1st natural frequencies of the stage is also presented and with that design values stage is manufactured.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.210-225
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• 2004

Statement of problem: Implant screw loosening has been remained problem in restorative practices. Surface treatment of screw plays a role of preventing screw from loosening in implant screw mechanism. Purpose : The purpose of this study was to investigate surface characteristics of TiN and ZrN film ion plated screw with titanium and gold alloy screw and to evaluate wear resistance, surface roughness, and film adhesion on screw surface using various instruments. Material and methods : GoldTite screws and titanium screws provided by 3i (Implant Innovation, USA) and TorqTite screws or titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, korea) were selected. Ion plating which is much superior to other surface modification techniques was carried out for gold screws and titanium screws using Ti and Zr coating materials with nitrogen gas. Ion nitrided surface of each abutment screw was observed with field emission scanning electron microscopy (FE-SEM, micro-diamond scratch tester, vickers hardness tester, and surface roughness tester. Results : 1) The surface of gold screw and GoldTite is more smooth than ones of other kinds of non coated screw. 2) The ZrN and TiN coated surface is the more smooth than ones of other kinds of screw. 3) The hardness of TiN and ZrN coated surface showed higher than that of non coated surface. 4) The TiN coated titanium screw and ZrN coated gold screw have a good wear resistance and adhesion on the surface. 5) The surface of ZrN coated screw showed low surface roughness compared with the surface of TiN coated screw. Conclusion : It is considered that the TiN and ZrN coated screw which would prevent a screw from loosening can be applicable to implant system and confirmed that TiN and ZrN film act as lubricant on surface of screw due to decrease of friction for recycled tightening and loosening.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.8
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• pp.4823-4827
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• 2013

Objective: To study the mechanism of effects of AZD1480 on the SKOV3 ovarian cancer cell line. Methods: The MTT method was used to assess cellular proliferation, flow cytometry for cellular apoptosis, the scratch test to determine migration, transwell chamber assays to detect cellular invasion, plate clone experiments to detect the clone forming ability and Western blotting to determine p-STAT3 protein levels. Results: The proliferation rate, migration ability, invasiveness and the clone forming ability of SKOV3 cells were reduced after treatment with AZD1480, while apoptosis rate and chemotherapeutic susceptibility were increased. After treatment with AZD1480 plus cisplatin, the apoptosis rate increased significantly while the expression level of p-STAT3 protein was decreased. Conclusion: AZD1480 can inhibit the proliferation, invasion, metastasis and clone formation of SKOV3 cells, induce cellulsar apoptosis, increase the chemotherapeutic sensitivity and reduce the expression level of p-STAT3 protein.

• Nutrition Research and Practice
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• v.9 no.3
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• pp.256-261
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• 2015

BACKGROUND/OBJECTIVES: Yacon (Samallanthus sonchifolius), a common edible plant grown throughout the world, is well known for its antidiabetic properties. It is also known to have several other pharmacological properties including anti-inflammatory, anti-oxidant, anti-allergic, and anti-cancer effects. To date, the effect of yacon on gliomas has not been studied. In this study, we investigated the effects of yacon on the migration and proliferation of C6 glioma cells stimulated by fetal bovine serum (FBS). MATERIALS/METHODS: Cell growth and proliferation were determined by evaluating cell viability using an EZ-Cytox Cell Viability Assay Kit. FBS-induced migration of C6 glioma cells was evaluated by performing the scratch wound healing assay and the Boyden chamber assay. We also used western blot analysis to determine the expression levels of extracellular signal-regulated kinase 1/2 (ERK1/2), a major regulator of migration and proliferation of glioma cells. Matrix metallopeptidase (MMP) 9 and TIMP-1 levels were measured by performing reverse transcription PCR. RESULTS: Yacon ($300{\mu}g/mL$) reduced both the FBS-induced proliferation of C6 glioma cells and the dose-dependent migration of the FBS-stimulated C6 cells. FBS-stimulated C6 glioma cells treated with yacon (200 and $300{\mu}g/mL$) showed reduced phosphorylation of ERK1/2 and inhibition of MMP 9 expression compared to those shown by the untreated FBS-stimulated C6 cells. In contrast, yacon (200 and $300{\mu}g/mL$) induced TIMP-1 expression. CONCLUSIONS: On the basis of these results, we suggest that yacon may exert an anti-cancer effect on FBS-stimulated C6 glioma cells by inhibiting their proliferation and migration. The most likely mechanism for this is down-regulation of ERK1/2 and MMP9 and up-regulation of TIMP-1 expression levels.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.505-512
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• 2012

In this study, an inspection system based on an optical scanning mechanism is developed for the inspection of silicon wafers in solar cells. In particular, a structured hybrid illumination system that can satisfy the illumination requirement for the detection of various defects is designed. In the hybrid illumination system, the optimum illumination conditions are selected by considering the design of experiment in master glass and silicon wafer. The illumination conditions available are B-high, BG-high, BR-high, and BGR-high for master glass and R-middle-B-medium for silicon wafers. By using the illumination conditions for silicon wafers, numerous surface defects like pinhole, scratch, and chipping, can be accurately detected. The hybrid illumination system is expected to be widely used for the inspection of silicon wafers in solar cells.

• Journal of the Korean institute of surface engineering
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• v.45 no.6
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• pp.257-263
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• 2012

CrN/AlN multilayer coatings with various bilayer periods in the range of 1.8 to 7.4 nm were synthesized using a closed-field unbalanced magnetron sputtering method. Their crystalline structure, chemical compositions and mechanical properties have been investigated with Auger electron spectroscopy, X-ray diffractometry, atomic force microscopy, nanoindentation, scratch tests. The properties of the multilayer coatings varied strongly depending upon the magnitude of the bilayer period. The multilayer coating with a bilayer period of 1.8 nm showed the maximum hardness and an elastic modulus of approximately 37.6 and 417 GPa, respectively, which was 1.54 times higher than the hardness predicted by the rule of mixture from the CrN and AlN coatings. The hardness of the multilayer coating increased as the bilayer period decreased, i.e. as the rotation speed increased. The Hall-Petch type relationship, hardness being related to (1/periodicity)$^{-1/2}$, suggested by Lehoczky was confirmed for the CrN/AlN multilayer coatings with bilayer period close to the 5-10 nm range. With decreasing bilayer period, the surface morphology of the films became rougher and the critical load of films for adhesion strength gradually decreased.

• Tribology and Lubricants
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• v.35 no.5
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• pp.274-285
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• 2019

Chemical mechanical polishing (CMP), which is a material removal process involving chemical surface reactions and mechanical abrasive action, is an essential manufacturing process for obtaining high-quality semiconductor surfaces with ultrahigh precision features. Recent rapid growth in the industries of digital devices and semiconductors has accelerated the demands for processing of various substrate and film materials. In addition, to solve many issues and challenges related to high integration such as micro-defects, non-uniformity, and post-process cleaning, it has become increasingly necessary to approach and understand the processing mechanisms for various substrate materials and abrasive particle behaviors from a tribological point of view. Based on these backgrounds, we review recent CMP R&D trends in this study. We examine experimental and analytical studies with a focus on substrate materials and abrasive particles. For the reduction of micro-scratch generation, understanding the correlation between friction and the generation mechanism by abrasive particle behaviors is critical. Furthermore, the contact stiffness at the wafer-particle (slurry)-pad interface should be carefully considered. Regarding substrate materials, recent research trends and technologies have been introduced that focus on sapphire (${\alpha}$-alumina, $Al_2O_3$), silicon carbide (SiC), and gallium nitride (GaN), which are used for organic light emitting devices. High-speed processing technology that does not generate surface defects should be developed for low-cost production of various substrates. For this purpose, effective methods for reducing and removing surface residues and deformed layers should be explored through tribological approaches. Finally, we present future challenges and issues related to the CMP process from a tribological perspective.

• Journal of Gastric Cancer
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• v.21 no.4
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• pp.439-456
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• 2021

Purpose: Gastric cancer (GC) has high morbidity and mortality and is a serious threat to public health. The flavonoid compound vitexin is known to exhibit anti-tumor activity. In this study, we explored the therapeutic potential of vitexin in GC and its underlying mechanism. Materials and Methods: The viability, migration, and invasion of GC cells were determined using MTT, scratch wound healing, and transwell assays, respectively. Target molecule expression was determined by western blotting. Tumor growth and liver metastasis were evaluated in vivo using nude mice. Protein expression in the tumor tissues was examined by immunohistochemistry. Results: Vitexin inhibited GC cell viability, migration, invasion, and epithelial-mesenchymal transition (EMT) in a dose-dependent manner. Vitexin treatment led to the inactivation of phosphatidylinositol-3-kinase (PI3K)/AKT/hypoxia-inducible factor-1α (HIF-1α) pathway by repressing HMGB1 expression. Vitexin-mediated inhibition in proliferation, migration, invasion and EMT of GC cells were counteracted by hyper-activation of PI3K/AKT/HIF-1α pathway or HMGB1 overexpression. Finally, vitexin inhibited the xenograft tumor growth and liver metastasis in vivo by suppressing HMGB1 expression. Conclusions: Vitexin inhibited the malignant progression of GC in vitro and in vivo by suppressing HMGB1-mediated activation of PI3K/Akt/HIF-1α signaling pathway. Thus, vitexin may serve as a promising therapeutic agent for the treatment of GC.

• Journal of Ginseng Research
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• v.47 no.2
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• pp.246-254
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• 2023

Background: Here, we aimed to assess the inhibitory effect of a new compound from Panax ginseng on the migration of human ovarian cancer cells and tube formation of human umbilical vein endothelial cells (HUVECs). Methods: A new compound, ginsenglactone A (1), was isolated from ginseng roots, together with seven known compounds (2-8). Spectroscopic data were used to elucidate the chemical structure of 1. The tubular structure formation in HUVECs was assessed by Mayer's hematoxylin staining. The migration of A2780 cells was evaluated using the scratch wound healing assay. Results: HUVECs treated with 1 had the statistically significant decrease in tubular structure formation compared to the HUVECs treated with compounds 2-8. This effect was enhanced by co-treatment with inhibitors for phosphatidylinositol 3-kinase (PI3K) (LY294002) and extracellular signal-regulated kinase (ERK) (U0126). Treatment with 1 decreased the expression of phosphorylation of ERK, PI3K, vascular endothelial growth factor receptor2 (VEGFR2), Akt, and mammalian target of rapamycin (mTOR). In addition, the ability of A2780 cells to cover the scratched area were also decreased. This effect was enhanced by co-treatment with U0126. Lastly, treatment with 1 decreased the phosphorylation of ERK, matrix metalloproteinase-9 (MMP-9), and MMP-2. Conclusion: These results suggest that ginsenglactone A is a potential inhibitor of HUVEC tubular structure formation and A2780 cellular migration, which may be helpful for understanding its anticancer mechanism.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.189-200
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• 2001

This paper proposes a memory allocation model for Real-Time Linux. The proposed model allows users to create several continuous memory regions in an application, to specify an appropriate region allocation policy for each memory region, and to request memory blocks from a necessary memory region. Instead of using single memory management module in order to support the proposed model, we adopt two-layered structure that is consisted of region allocators implementing allocation policies and a region manager controlling regions and region allocator modules. This structure separates allocation policy from allocation mechanism, thus allows system developers to implement same allocation policy using different algorithms in case of need. IN addition, it enables them to implement new allocation policy using different algorithms in case of need. In addition, it enables them to implement new allocation policy easily as long as they preserver predefined internal interfaces, to add the implemented policy into the system, and to remove unnecessary allocation policies from the system, Because the proposed model provides various allocation policies implemented previously, system builders can also reconfigure the system by just selecting most appropriate policies for a specific application without implementing these policies from scratch.