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남정수,이상원 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.5 No.1
This paper discusses the experimental characterization on micro-drilling process of titanium alloy (Ti-6Al-4V), which is one of representative difficult-to-cut materials, with the nanofluid minimum quantity lubrication (nMQL). The miniaturized machine tool system is set up, and then, a series of micro-drilling experiments are performed under compressed air (CA), pure MQL and nMQL for a comparison. For the nanofluid, nanodiamond particles with the sizes of 35 nm and 80 nm are chosen, and the base fluid is vegetable oil. For the micro-drilling process, an uncoated carbide twist drill having the diameter of 300 µm is used for drilling holes in the titanium alloy workpiece. The experimental results show that the nMQL can reduce the drilling torques and thrust forces, but its effect is more obvious at a low feed rate (10 mm/min). In addition, the edge corner radii and hole circularity errors are significantly reduced in the case of small size (35 nm) and high weight concentration (0.4 wt. %) of the nanodiamond particles at the low feed rate. It is also found that the nMQL effectively mitigates chip adhesion of drill tool and burr of drilled holes.
남정수,김홍섭,김규용 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.1
This study investigates the blast resistance of fiber-reinforced cementitious composite (FRCC) panels, with fiber volume fractions of 2%, subjected to contact explosions using an emulsion explosive. A number of FRCC panels with five different fiber mixtures (i.e., micro polyvinyl alcohol fiber, micro polyethylene fiber, macro hooked-end steel fiber, micro polyvinyl alcohol fiber with macro hooked-end steel fiber, and micro polyethylene fiber with macro hooked-end steel fiber) were fabricated and tested. In addition, the blast resistance of plain panels (i.e., non-fiber-reinforced high strength concrete, and non-fiberreinforced cementitious composites) were examined for comparison with those of the FRCC panels. The resistance of the panels to spall failure improved with the addition of micro synthetic fibers and/or macro hooked-end steel fibers as compared to those of the plain panels. The fracture energy of the FRCC panels was significantly higher than that of the plain panels, which reduced the local damage experienced by the FRCCs. The cracks on the back side of the micro synthetic fiber-reinforced panel due to contact explosions were greatly controlled compared to the macro hooked-end steel fiber-reinforced panel. However, the blast resistance of the macro hooked-end steel fiber-reinforced panel was improved by hybrid with micro synthetic fibers.
결직장암 간전이 진단 시 혈청 암배아항원의 임상적 의의
남정수,신진용,김경하,박정익,김운원,최창수,최영길,홍관희 대한대장항문학회 2008 Annals of Coloproctolgy Vol.24 No.6
Purpose: In numerous clinical trials to stratify prognosis of patients with liver metastases (LM) from colorectal cancer (CRC), the clinical value of serum carcinoembryonic antigen (CEA) levels at diagnosis of LM has not been fully investigated in these group. The aim of this study is to explore the relation of CEA to characteristics of LM and to analyze prognostic value of this widely used tool. Methods: We retrospectively analyzed clinical data of 143 LM patients who were performed surgical intervention or non-surgical intervention. The cohort was divided into two groups; normal CEA group (NCEAG, <5 ng/ml, n=41) and elevated CEA group (ECEAG, ≥5 ng/ml, n=102). We examined correlation between serum CEA at diagnosis of LM and other clinicopathologic factors and performed univariate and multivariate analyses to determine the clinical impact of this marker on survival. Results: Compared to ECEAG, the characteristics of LM of NCEAG was associated with unilobar distribution of LM (P=0.003), less metastases (P<0.001), less rate of synchronocity (P=0.008) and more surgical intervention of hepatic deposits (P<0.001). The 5-year survival rate for NCEAG was better than ECEAG (P=0.031). Multivariate analysis revealed that the presence of lymphatic duct invasion, no performance of chemotherapy, bilobar distribution of LM, and treatment of non-surgical intervention had a significant effect on survival. CEA elevation was identified as independently associated with bilobar distribution and non-surgical intervention of LM. Conclusions: Although CEA level is not a independent prognostic factor in this study, the clinical characteristics identified in this study and correlation to non surgical intervention of LM may help better patient selection in the management of CRC LM patients. Purpose: In numerous clinical trials to stratify prognosis of patients with liver metastases (LM) from colorectal cancer (CRC), the clinical value of serum carcinoembryonic antigen (CEA) levels at diagnosis of LM has not been fully investigated in these group. The aim of this study is to explore the relation of CEA to characteristics of LM and to analyze prognostic value of this widely used tool. Methods: We retrospectively analyzed clinical data of 143 LM patients who were performed surgical intervention or non-surgical intervention. The cohort was divided into two groups; normal CEA group (NCEAG, <5 ng/ml, n=41) and elevated CEA group (ECEAG, ≥5 ng/ml, n=102). We examined correlation between serum CEA at diagnosis of LM and other clinicopathologic factors and performed univariate and multivariate analyses to determine the clinical impact of this marker on survival. Results: Compared to ECEAG, the characteristics of LM of NCEAG was associated with unilobar distribution of LM (P=0.003), less metastases (P<0.001), less rate of synchronocity (P=0.008) and more surgical intervention of hepatic deposits (P<0.001). The 5-year survival rate for NCEAG was better than ECEAG (P=0.031). Multivariate analysis revealed that the presence of lymphatic duct invasion, no performance of chemotherapy, bilobar distribution of LM, and treatment of non-surgical intervention had a significant effect on survival. CEA elevation was identified as independently associated with bilobar distribution and non-surgical intervention of LM. Conclusions: Although CEA level is not a independent prognostic factor in this study, the clinical characteristics identified in this study and correlation to non surgical intervention of LM may help better patient selection in the management of CRC LM patients.