Home OALib Journal OALib PrePrints Submit Ranking News My Lib FAQ About Us Follow Us+
 Title Keywords Abstract Author All
Search Results: 1 - 10 of 100 matches for " "
 Page 1 /100 Display every page 5 10 20 Item
 金属学报(英文版) , 2002, Abstract: The microstructure of plasma nitrided layer catalyzed by rare-earth elements has beenstudied with TEM. The results show that the grains of γ'-Fe4N phase are refinedby rare-earth elements and the plane defects in boundary are increased by rare-earthelements. The addition of rare-earth element increases the bombardment effect andthe number of crystal defects such as vacancies, dislocation loops, twins and stackingfaults in γ'-Fe4N phase and can produce the high-density dislocations in the ferrite ofdiffusion layer at a distance 0. 08mm from the surface. The production of a numberof crystal defects is one of important reasons why rare-earth element accelerates thediffusion of nitrogen atoms during plasma-nitridiug.
 Physics , 2014, DOI: 10.1103/PhysRevB.90.201309 Abstract: A longstanding puzzle for the lowest Landau level crystal phase has been an order of magnitude discrepancy between the theoretically calculated energy of the defects and the measured activation gap. We perform an extensive study of various kinds of defects in the correlated composite fermion crystal and find that the lowest energy defect is a six-fold symmetric "hyper-correlated bubble interstitial," in which an interstitial particle forms a strongly correlated bound state with a particle of the crystal. The energy of the bubble defect is a factor of $\sim$3 smaller than that of the lowest energy defect in a Hartree-Fock crystal. The anomalously low activation energies measured in transport experiments are thus a signature of the unusual quantum nature of the crystal and its defects.
 Physics , 2012, DOI: 10.1103/PhysRevA.87.050304 Abstract: We theoretically show how two impurity defects in a crystalline structure can be entangled through coupling with the crystal. We demonstrate this with a harmonic chain of trapped ions in which two ions of a different species are embedded. Entanglement is found for sufficiently cold chains and for a certain class of initial, separable states of the defects. It results from the interplay between localized modes which involve the defects and the interposed ions, it is independent of the chain size, and decays slowly with the distance between the impurities. These dynamics can be observed in systems exhibiting spatial order, viable realizations are optical lattices, optomechanical systems, or cavity arrays in circuit QED.
 Brazilian Journal of Physics , 2005, DOI: 10.1590/S0103-97332005000200022 Abstract: i show that einstein gravity can be thought of as arising from the defects in a world crystal whose lattice spacing is of the order of the planck length lp ？ 10-33 cm, and whose elastic energy is of the second-gradient type (floppy crystal). no physical experiment so far would be able to detect the lattice structure.
 Physics , 2005, DOI: 10.1103/PhysRevLett.96.095503 Abstract: Solids with spatial variations in the crystalline axes naturally evolve into cells or grains separated by sharp walls. Such variations are mathematically described using the Nye dislocation density tensor. At high temperatures, polycrystalline grains form from the melt and coarsen with time: the dislocations can both climb and glide. At low temperatures under shear the dislocations (which allow only glide) form into cell structures. While both the microscopic laws of dislocation motion and the macroscopic laws of coarsening and plastic deformation are well studied, we hitherto have had no simple, continuum explanation for the evolution of dislocations into sharp walls. We present here a mesoscale theory of dislocation motion. It provides a quantitative description of deformation and rotation, grounded in a microscopic order parameter field exhibiting the topologically conserved quantities. The topological current of the Nye dislocation density tensor is derived from a microscopic theory of glide driven by Peach-Koehler forces between dislocations using a simple closure approximation. The resulting theory is shown to form sharp dislocation walls in finite time, both with and without dislocation climb.
 Physics , 2000, DOI: 10.1103/PhysRevE.63.051605 Abstract: We analyze a two-dimensional phase field model designed to describe the dynamics of crystalline grains. The phenomenological free energy is a functional of two order parameters. The first one reflects the orientational order while the second reflects the predominant local orientation of the crystal. We consider the gradient flow of this free energy. Solutions can be interpreted as ensembles of grains (in which the phase of the order parameter is approximately constant in space) separated by grain boundaries. We study the dynamics of the boundaries as well as the rotation of the grains. In the limit of the infinitely sharp interface, the normal velocity of the boundary is proportional to both its curvature and its energy. We obtain explicit formulas for the interfacial energy and mobility and study their behavior in the limit of a small misorientation. We calculate the rate of rotation of a grain in the sharp interface limit and find that it depends sensitively on the choice of the model.
 Physics , 2011, DOI: 10.1103/PhysRevLett.107.207210 Abstract: Recently there have been several theoretical and experimental studies of the prospects for magnetic field sensors based on crystal defects, especially nitrogen vacancy (NV) centres in diamond. Such systems could potentially be incorporated into an AFM-like apparatus in order to map the magnetic properties of a surface at the single spin level. In this Letter we propose an augmented sensor consisting of an NV centre for readout and an `amplifier' spin system that directly senses the local magnetic field. Our calculations show that this hybrid structure has the potential to detect magnetic moments with a sensitivity and spatial resolution far beyond that of a simple NV centre, and indeed this may be the physical limit for sensors of this class.
 Physics , 2000, DOI: 10.1103/PhysRevLett.86.492 Abstract: Using the path-integral Monte Carlo method, we calculate the energy to form single and pair vacancies and interstitials in a two-dimensional Wigner crystal of electrons. We confirm that the lowest-lying energy defects of a 2D electron Wigner crystal are interstitials, with a creation energy roughly 2/3 that of a vacancy. The formation energy of the defects goes to zero near melting, suggesting that point defects might mediate the melting process. In addition, we find that the interaction between defects is strongly attractive, so that most defects will exist as bound pairs.
 Physics , 2001, DOI: 10.1051/0004-6361:20011782 Abstract: We present new data of the dwarf galaxy NGC 1569 at 450 $\mu$m, 850 $\mu$m and 1200$\mu$m taken with SCUBA at the JCMT and the bolometer array at the IRAM 30m telescope. After including data from IRAS at 12, 25, 60 and 100 $\mu$m, we have successfully fitted the dust grain population model of D\'esert et al. (1990) to the observed midinfrared-to-millimeter spectrum. The fit requires a combination of both large and very small grains exposed to a strong radiation field as well as an enhancement of the number of very small grains relative to the number of large grains. We interpret this as the consequence of large grain destruction due to shocks in the turbulent interstellar medium of NGC 1569. The contribution of polyaromatic hydrocarbons (PAH's) is found to be negligible. Comparison of the dust emission maps with an HI map of similar resolution shows that both dust and molecular gas distributions peak close to the radio continuum maximum and at a minimum in the HI distribution. From a comparison of these three maps and assuming that the gas-to-dust mass ratio is the same everywhere, we estimate the ratio of molecular hydrogen column density to integrated CO intensity to be about 25 -- 30 times the local Galactic value. The gas-to-dust ratio is 1500 -- 2900, about an order of magnitude higher than in the Solar Neighbourhood.
 Heng-Tung Hsu;Min-Hung Lee;Tzong-Jer Yang;Yu-Chao Wang;Chien-Jang Wu PIER , 2011, DOI: 10.2528/PIER11051403 Abstract: Optical filtering properties in a multichanneled transmission filter based on one-dimensional photonic crystal containing the coupled defects are theoretically investigated. The resonant transmission peaks are designed to be located within the photonic band gap of a defect-free photonic crystal. The number of peaks is directly equal to the number of the coupled defects. The positions of resonant peaks can be tuned by varying the refractive index of the defect layer. In addition, extremely resonant peaks can be produced by adding the Bragg mirrors at the front and rear sides of the structure.
 Page 1 /100 Display every page 5 10 20 Item