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Improvement of Viscoelastic Damping in Nickel Aluminum Bronze by Indium-Tin
이태용 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.3
Reduction of the vibration noise from submarine propellers is of interest in naval operations. Such an objective can be achieved via the use of materials with the ability to dissipate energy of vibration by means of heat, i.e. high damping materials. An additional problem is that the extreme hydrostatic pressure environment of a submarine requires the chosen material to exhibit considerably high stiffness. Most materials demonstrate a compromise between the two properties, i.e. stiffness and damping. This paper aims to discuss research into high stiffness and high damping materials conducted using a dynamic mechanical analyzer (DMA) under variations of testing temperature, frequency, and strain amplitude. Alloys of nickel aluminum bronze and indium tin are the subjects of this study. Defect damping represents a large portion of the overall damping properties of the nickel aluminum bronze while increasing indium content is shown to boost the damping properties of the indium tin alloy. The study then continues with the development of a new material that combines both indium alloying and defects introduction into the nickel aluminum bronze alloy. The new alloy is observed to have high damping, as measured in its high tan δ, with minimum reduction of the stiffness |E*|.
이태용,윤달식,이준기,박옥자,박현정,김인삼,Lee, Tae-Yong,Yun, Dal-Sik,Lee, Jun-Gi,Park, Ok-Ja,Park, Hyeon-Jeong,Kim, In-Sam 한국건강관리협회 2006 한국건강관리협회지 Vol.4 No.1
Background Cardiovascular disease is becoming an important national health issue since its recent increase in incidence and mortality. The study was conducted to find out the prevalence of metabolic syndrome according to the clinical identification criteria by NCEP-ATP3 and Asia-Pacific criteria. Meterials & Methods: The subjects were 759 people -male 375 and female 384 after twenties age - who had undergone medical examinations at Korea Association of Health, Daejeon- Chungnam Branch. The prevalence of metabolic syndrome was assessed as defined by the NCEP ATP3, while abdominal obesity was assessed according to the Asia-Pacific guidelines. Anthropometric variables and cardiovascular risk factors were measured, and Associated factors with metabolic syndroms was analyzed by logistic regression analysis. Results The prevalence of metabotic syndrome was 24.O% for male and 27.1% for female The high blood pressure was the highest prevalent risk factors of metabolic syndrome. In the age group of thirties, the prevalence of metabolic syndrome was higher in men than in women, however it was significantly higher in women than in men in fifties and six ties. The metabolic syndrome was more prevalent in aged people over 50 years. and .significantly associated with BMI index(odds ratio 2.58 in male, 9.87 in female)Conclusions The prevalence of metabolic syndrome is over 20%.Early detection and intervention of risk factors by health examination and promotion are needed for prevention of metabolic syndrome.