12,329 research outputs found
Strategic Asset Seeking and Innovation Performance: The Role of Innovation Capabilities and Host Country Institutions
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Catalyst-free synthesis of single crystalline ZnO nanonails with ultra-thin caps
Arrays of single-crystalline ZnO nanonails with tapering diameters and ultra-thin caps have been successfully synthesized on a silicon substrate via a simple catalyst-free thermal evaporation method. Each of the ZnO nanonails consists a nanowire (stem) on the bottom and an ultra-thin symmetrical hexagonal cap on the top. Structural characterization reveals that the synthesized ZnO nanonail has a wurtzite (WZ) structure with a preferred growth direction of [0001] in the stem and in the cap. Remarkably, the ultra-thin cap shows a diameter-to-thickness ratio of over 20:1, which is much higher in magnitude than those reported in previous works. Based on the systematic morphological characterization and structural analysis, a self-catalyzed vapor–liquid–solid (VLS) mechanism followed by a vapor–solid (VS) process is proposed to explain the growth of the nanonails. Optical properties are also investigated with Raman and photoluminescence (PL) techniques, which show good crystal quality of the synthesized nanonails
Note on a new fundamental length scale instead of the Newtonian constant
The newly proposed entropic gravity suggests gravity as an emergent force
rather than a fundamental one. In this approach, the Newtonian constant
does not play a fundamental role any more, and a new fundamental constant is
required to replace its position. This request also arises from some
philosophical considerations to contemplate the physical foundations for the
unification of theories. We here consider the suggestion to derive from
more fundamental quantities in the presence of a new fundamental length scale
, which is suspected to originate from the structure of quantum space-time,
and can be measured directly from Lorentz-violating observations. Our results
are relevant to the fundamental understanding of physics, and more practically,
of natural units, as well as explanations of experimental constraints in
searching for Lorentz violation.Comment: 10 latex pages, final version for journal publicatio
Hadron-quark phase transition in asymmetric matter with dynamical quark masses
The two-Equation of State (EoS) model is used to describe the hadron-quark
phase transition in asymmetric matter formed at high density in heavy-ion
collisions. For the quark phase, the three-flavor Nambu--Jona-Lasinio (NJL)
effective theory is used to investigate the influence of dynamical quark mass
effects on the phase transition. At variance to the MIT-Bag results, with fixed
current quark masses, the main important effect of the chiral dynamics is the
appearance of an End-Point for the coexistence zone. We show that a first order
hadron-quark phase transition may take place in the region T=(50-80)MeV and
\rho_B=(2-4)\rho_0, which is possible to be probed in the new planned
facilities, such as FAIR at GSI-Darmstadt and NICA at JINR-Dubna. From isospin
properties of the mixed phase somepossible signals are suggested. The
importance of chiral symmetry and dynamical quark mass on the hadron-quark
phase transition is stressed. The difficulty of an exact location of
Critical-End-Point comes from its appearance in a region of competition between
chiral symmetry breaking and confinement, where our knowledge of effective QCD
theories is still rather uncertain.Comment: 13 pages, 16 figures (revtex
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P2-type Na2/3Ni1/3Mn2/3O2 Cathode Material with Excellent Rate and Cycling Performance for Sodium-Ion Batteries
P2-type Na2/3Ni1/3Mn2/3O2 is an air-stable cathode material for sodium-ion batteries. However, it suffers irreversible P2-O2 phase transition in 4.2-V plateau and shows poor cycling stability and rate capability within this plateau. To evaluate the practicability of this material in 2.3–4.1 V voltage range, single-crystal micro-sized P2-type Na2/3Ni1/3Mn2/3O2 with high rate capability and cycling stability is synthesized via polyvinylpyrrolidone (PVP)-combustion method. The electrochemical performance is evaluated by galvanostatic charge-discharge tests. The kinetics of Na+ intercalation/deintercalation is studied detailly with potential intermittent titration technique (PITT), galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV). The discharge capacity at 0.1 C in 2.3–4.1 V is 87.6 mAh g−1. It can deliver 91.5% capacity at 40 C rate and keep 89% after 650 cycles at 5C. The calculated theoretical energy density of full cell with hard carbon anode is 210 Wh kg−1. The moderate energy density associated with high power density and long cycle life is acceptable for load adjustment of new-energy power, showing the prospect of practical application
Early-type Stars: Most Favorable Targets for Astrometrically Detectable Planets in the Habitable Zone
Early-type stars appear to be a difficult place to look for planets
astrometrically. First, they are relatively heavy, and for fixed planetary mass
the astrometric signal falls inversely as the stellar mass. Second, they are
relatively rare (and so tend to be more distant), and for fixed orbital
separation the astrometric signal falls inversely as the distance.
Nevertheless, because early-type stars are relatively more luminous, their
habitable zones are at larger semi-major axis. Since astrometric signal scales
directly as orbital size, this gives early-type stars a strong advantage, which
more than compensates for the other two factors. Using the Hipparcos catalog,
we show that early-type stars constitute the majority of viable targets for
astrometric searches for planets in the habitable zone. We contrast this
characteristic to transit searches, which are primarily sensitive to habitable
planets around late-type stars.Comment: Submitted to ApJ Letters, 8 pages including 2 figure
A novel explicit-implicit coupled solution method of SWE for long-term river meandering process induced by dam break
YesLarge amount of sediment deposits in the reservoir area can cause dam break, which not only leads to an immeasurable loss to the society, but also the sediments from the reservoir can be transported to generate further problems in the downstream catchment. This study aims to investigate the short-to-long term sediment transport and channel meandering process under such a situation. A coupled explicit-implicit technique based on the Euler-Lagrangian method (ELM) is used to solve the hydrodynamic equations, in which both the small and large time steps are used separately for the fluid and sediment marching. The main feature of the model is the use of the Characteristic-Based Split (CBS) method for the local time step iteration to correct the ELM traced lines. Based on the solved flow field, a standard Total Variation Diminishing (TVD) finite volume scheme is applied to solve the sediment transportation equation. The proposed model is first validated by a benchmark dambreak water flow experiment to validate the efficiency and accuracy of ELM modelling capability. Then an idealized engineering dambreak flow is used to investigate the long-term downstream channel meandering process with nonuniform sediment transport. The results showed that both the hydrodynamic and morphologic features have been well predicted by the proposed coupled model.This research work is supported by Sichuan Science and Technology Support Plan (2014SZ0163), Start-up Grant for the Young Teachers of Sichuan University (2014SCU11056), and Open Research Fund of the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKLH 1409; 1512)
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