8,276 research outputs found
Economic feasibility of growing herbaceous biomass energy crops in Iowa
Depletion of natural energy resources and environmental degradation caused by current energy resources (fossil fuels) have rekindled interest in energy availability and developing environmentally benign and renewable alternative energy resources. In addition, the reduced productive capacity of soil and environmental problems in rural areas caused by the loss of topsoil has created interest in ways to conserve soil;These concerns have generated considerable attention on the production of herbaceous energy crops on marginal land as a possible solution to meeting future energy demands, addressing environmental concerns, and reducing soil erosion;This research suggests that herbaceous energy crops, especially switchgrass, can be grown productively with minimal erosion, and produced at costs only somewhat higher than fossil fuels. They also have good soil conservation properties on the marginal land in Iowa
Condensation of preformed charge density waves in kagome metals
Charge density wave (CDW) is a spontaneous spatial modulation of electric
charges in solids whose general microscopic descriptions are yet to be
completed. Layered kagome metals of VSb ( = K, Rb, Cs) provide a
unique chance to realize its emergence intertwined with dimensional effects as
well as their special lattice. Here, based on a state-of-the-art molecular
dynamics simulation, we uncover that the phase transition to charge ordered
states in kagome metals is a condensation process of incoherently preformed
CDWs. We demonstrate that charge modulation first preforms on each kagome layer
at a well defined temperature but its phase fluctuation proliferates across the
entire layers with a times slower frequency than typical phonon
vibrations until reaching its freezing temperature. We find that the
fluctuation is not random but confined to a limited number of states as a
consequence of unavoidable degeneracy in stacking layered charge orders. As the
size of interfacial alkali atom increases, the fluctuating phases are shown to
counterbalance the condensation of orderings, resulting in a maximized
transition temperature for RbVSb. Our results resolve several
controversial observations on their CDW formations and highlight a crucial role
of interlayer interactions for the charge ordering in kagome metals
Proto-type installation of a double-station system for the optical-video-detection and orbital characterisation of a meteor/fireball in South Korea
We give a detailed description of the installation and operation of a
double-station meteor detection system which formed part of a research &
education project between Korea Astronomy Space Science Institute and Daejeon
Science Highschool. A total of six light-sensitive CCD cameras were installed
with three cameras at SOAO and three cameras at BOAO observatory. A
double-station observation of a meteor event enables the determination of the
three-dimensional orbit in space. This project was initiated in response to the
Jinju fireball event in March 2014. The cameras were installed in
October/November 2014. The two stations are identical in hardware as well as
software. Each station employes sensitive Watec-902H2 cameras in combination
with relatively fast f/1.2 lenses. Various fields of views were used for
measuring differences in detection rates of meteor events. We employed the
SonotaCo UFO software suite for meteor detection and their subsequent analysis.
The system setup as well as installation/operation experience is described and
first results are presented. We also give a brief overview of historic as well
as recent meteor (fall) detections in South Korea. For more information please
consult http://meteor.kasi.re.kr .Comment: Technical/instrumentation description of a professional meteor
detection system, 23 pages, 20 figures (color/monochrome), 5 tables,
submitted to the Journal of Korean Astronomical Society (JKAS,
http://jkas.kas.org/, http://jkas.kas.org/history.html
Time Delay Effect on the Love Dynamical Model
We investigate the effect of time delay on the dynamical model of love. The
local stability analysis proves that the time delay on the return function can
cause a Hopf bifurcation and a cyclic love dynamics. The condition for the
occurrence of the Hopf bifurcation is also clarified. Through a numerical
bifurcation analysis, we confirm the theoretical predictions on the Hopf
bifurcation and obtain a universal bifurcation structure consisting of a
supercritical Hopf bifurcation and a cascade of period-doubling bifurcations,
i.e., a period doubling route to chaos.Comment: To appear in Journal of Korean Physical Societ
Nano-mechanical behavior of ultra-stable amorphous metallic thin films
Metallic glass has amorphous structure that behave mechanically like solids but show catastrophic failure due to shear band propagation induced by short range order structure, and they are generally produced by quenching. Recently, it is observed that the slower cooling rate provides the larger time available for atoms to rearrange structure before freezing in glassy state, leading to glass transition temperature and thermal stability. These glasses with enhanced thermal stability synthesized by controlled cooling rate make it useful in various field such as mechanical or oxidation protection material. However, mechanical behavior for metallic glass with extraordinary thermodynamic and kinetic stability has not been studied. In this research, we developed a ultrastable metallic glass thin film by physical vapor deposition process at ambient temperature. Thermal stability is investigated using acceleration testing. Mechanical properties are measured using in-situ tensile testing and discuss thermal stability and fracture behavior dependent on compositio
Interpolation for molecular dynamics simulations: from ions in gas phase to proteins in solution
The interpolation technique has shown many promises for simulating chemical dynamics with quantum chemical accuracy at molecular mechanics speed. This is achieved by constructing analytic potential energy surfaces with quantum chemical information at multiple conformational points, without assuming any functional form for the potentials. Here, we briefly review the course the method was developed over the past few decades, with a special focus on the activities in Korea. We also describe its strengths and weaknesses toward describing condensed phase chemical dynamics with the present implementations. Perspectives for future developments toward increasing applicability are discussed as concluding remarks. (c) 2015 Wiley Periodicals, Inc.1122Ysciescopu
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