12,173 research outputs found

    Size-dependent mechanical properties of molybdenum nanopillars

    Get PDF
    We report the deformation behavior of single crystalline molybdenum nanopillars in uniaxial compression, which exhibits a strong size effect called the “smaller is stronger” phenomenon. We show that higher strengths arise from the increase in the yield strength rather than through postyield strain hardening. We find the yield strength at nanoscale to depend strongly on sample size and not on the initial dislocation density, a finding strikingly different from that of the bulk metal

    Four-neutrino analysis of 1.5km-baseline reactor antineutrino oscillations

    Get PDF
    The masses of sterile neutrinos are not yet known, and depending on the orders of magnitudes, their existence may explain reactor anomalies or the spectral shape of reactor neutrino events at 1.5km-baseline detector. Here, we present four-neutrino analysis of the results announced by RENO and Daya Bay, which performed the definitive measurements of θ13\theta_{13} based on the disappearance of reactor antineutrinos at km-order baselines. Our results using 3+1 scheme include the exclusion curve of Δm412\Delta m^2_{41} vs. θ14\theta_{14} and the adjustment of θ13\theta_{13} due to correlation with θ14\theta_{14}. The value of θ13\theta_{13} obtained by RENO and Daya Bay with a three-neutrino oscillation analysis is included in the 1σ1\sigma interval of θ13\theta_{13} allowed by our four-neutrino analysis.Comment: 14 pages, 7 figures. arXiv admin note: text overlap with arXiv:1303.617

    Association of Family Composition and Metabolic Syndrome in Korean Adults Aged over 45 Years Old

    Get PDF
    SummaryPurposeThis study investigated the relationship between family composition and the prevalence of metabolic syndrome by gender in Korean adults aged 45 years and older.MethodsThe sample consisted of 11,291 participants in the Korea National Health and Nutrition Examination Survey from 2010 to 2012. We used complex sample analyses, including strata, cluster, and sample weighting, to allow generalization to the Korean population. Complex samples crosstabs and chi-square tests were conducted to compare the percentage of sociodemographic characteristics to the prevalence of metabolic syndrome and its components by gender and family composition. Next, a complex sample logistic regression was performed to examine the association between family composition and the prevalence of metabolic syndrome by gender.ResultsThe percentage of adults living alone was 5.6% for men and 13.9% for women. Slightly more women (14.0%) than men (10.1%) reported living with three generations. The percentage of metabolic syndrome in Korean adults aged 45 years and older was 53.2% for men and 35.7% for women. For women, we found that living with one or three generations was significantly associated with a higher risk of metabolic syndrome, blood pressure, and triglyceride abnormality after adjusting for age, education, household income, smoking, physical activity, and body mass index, when compared to living alone. No significant relationships were found for men.ConclusionsA national strategy, tailored on gender and family composition, needs to be developed in order to prevent the increase of metabolic syndrome in Korean women over middle age

    Rethinking media flow under globalisation: rising Korean wave and Korean TV and film policy since 1980s

    Get PDF
    The rising popularity of Korean contents in Asia known as Hanryu ('Korean Wave'), which was partly supported by Korean cultural policy, has many implications with regard to cultural policy in periphery countries under globalisation and the open-door versus cultural diversity debate. This thesis assesses how recent cultural opening under globalisation in Korea has affected Korea's cultural industries both quantitatively in terms of economic performance and qualitatively in terms of cultural content, identity and diversity. These questions are examined in the context of the changing relationship between the cultural industries and cultural policy in Korea since the end of the 1990s. The research draws upon statistical data, historical material and interviews. By researching how the Korean experience has developed, this thesis attempts to look at Hanryu not just as a phenomenon in its own right, but also considers the secondary impact of this phenomenon on perceptions of culture and identity. In particular the thesis considers Hanryu in terms of the cultural influence on neighbouring countries manifest through tourism and a new interest in Korean language and culture. Such cultural effects are less easily measured than economic data but are important to an understanding of causes and effects of Hanryu. Finally this thesis places the Korean experience in the broader context of cultural policy in periphery countries responding to globalisation and the relationship between national cultural policy and the global cultural economy. It is still too early to reach conclusions on the future of Korean cultural industries based simply on the recent trends However, since the mid 1990s, the Korean cultural industries have been transformed dramatically. Cultural policy has contributed to this trend and strengthened the competitiveness of Korea's cultural industries. At the same time the thesis considers some of the limitations and criticisms of Hanryu, including potential loss of cultural diversity and an anti- Korean backlash in some other Asian countries. The Korean cultural industries have benefited from imitating the Hollywood system and developing a distinctive hybrid cultural content and business model. This has made possible an alternative approach to policy and management which lies between two extremes of protectionism and free market ideology. The thesis comments on some of the difficulties and limitations in sustaining such a balance and concludes by considering the sustainability of Hanryu both in Korea and in the broader Asian context

    Effective indenter radius and frame compliance in instrumented indentation testing using a spherical indenter

    Get PDF
    We introduce a novel method to correct for imperfect indenter geometry and frame compliance in instrumented indentation testing with a spherical indenter. Effective radii were measured directly from residual indentation marks at various contact depths (ratio of contact depth to indenter radius between 0.1 and 0.9) and were determined as a function of contact depth. Frame compliance was found to depend on contact depth especially at small indentation depths, which is successfully explained using the concept of an extended frame boundary. Improved representative stress-strain values as well as hardness and elastic modulus were obtained over the entire contact depth

    Incipient plasticity and fully plastic contact behavior of copper coated with a graphene layer

    Get PDF
    Cu coated with a graphene layer increases the elastic modulus from 163.4 GPa to 176.7 GPa, as analyzed for the initial elastic loading during nanoindentation by the Hertzian contact theory. This is attributed to stiffening, due to the ultra-high elastic modulus of the graphene layer, and the compressive in-plane residual stresses in the Cu surface volume introduced by the lattice mismatch between graphene and Cu. The graphene layer induces incipient plasticity, manifested by pop-in events during nanoindentation loading, at shallower indentation depths. This could be due to the compressive in-plane residual stress in the Cu surface volume; however, this compressive stress does not significantly change the critical resolved shear stress for the incipient plasticity. Even in the fully plastic contact region, at an indentation depth of 100 nm, the graphene layer affects the stress distribution underneath the indenter, resulting in a lower pile-up height. When considering this reduced pile-up height, the graphene layer is found to enhance elastic modulus by 5%, whereas it has no effect on hardness

    Highly-stretchable and water impermeable thermally-grown silicon dioxide thin film with wavy structures

    Get PDF
    To ensure chemical stability and long-term operation, organic electronic devices require encapsulation layer with low water vapor transmittance rate because organic components in organic electronic device are vulnerable to humidity. Encapsulation of commercialized OLEDs are rigid glass and epoxy resin, which are not suitable for flexible devices requiring high flexibility. TFE (thin-film encapsulation) technique has been studied for flexible device encapsulation. Amorphous materials are selected for TFE materials because they are dense and transparent and do not have fast diffusion paths like grain boundary. Thermally-grown silicon dioxide, oxidized from single crystal silicon substrate at high temperature, has ultra-low water vapor transmittance rate due to high density without pinholes and defects. However, the thermally-grown silicon dioxide thin films have a low elastic limit (\u3c 1%) and show brittle fracture alike typical amorphous materials. For that reasons, it is necessary to improve the mechanical properties of the thermally-grown silicon dioxide thin film for flexible encapsulation. In this study, we tried to improve the stretchability by applying the wavy structure to thermally-grown silicon dioxide and developed the wavy structure texturing of single crystal silicon substrate by using photo-lithography and various etching process. we fabricated a highly-stretchable wavy thermally-grown silicon dioxide TFE by oxidizing wavy textured crystalline silicon substrate. Also, we carried out cyclic tensile test of submicron scale wavy thermally-grown silicon dioxide films and defined the elastic limit, and the stretchability. And then, we analyze the enhancement of stretchability by finite element analysis on the wavy and flat thermally-grown silicon dioxide TFE and discussed about the correlation between the improvement of stretchability and wavy structure

    Numerical analysis of high-index nanocomposite encapsulant for light-emitting diodes

    Full text link
    We used two-dimensional Finte-Difference-Time-Domain (FDTD) software to study the transition behavior of nano-particles from scatterers to an optically uniform medium. We measured the transmission efficiency of the dipole source, which is located in the high refractive index medium(index=2.00) and encapsulated by low index resin(index=1.41). In an effort to compose index-matched resin and to reduce internal reflection, high-index nano-particles are added to low-index resin in simulations of various sizes and densities. As the size of the nano-particles and the average spacing between particles are reduced to 0.02 lambda and 0.07 lambda respectively, the transmission efficiency improves two-fold compared to that without nanoparticles. The numerical results can be used to understand the optical behavior of nano-particles and to improve the extraction efficiency of high brightness light-emitting-diodes(LEDs), through the use of nano-composite encapsulant.Comment: 9 pages, 5 jpg figure