Phase diagrams of period-4 spin chains consisting of three kinds of spins

We study a period-4 antiferromagnetic mixed quantum spin chain consisting of three kinds of spins. When the ground state is singlet, the spin magnitudes in a unit cell are arrayed as (s-t, s, s+t, s) with integer or half-odd integer s and t (0 <= t < s). The spin Hamiltonian is mapped onto a nonlinear sigma model (NLSM) in a previously developed method. The resultant NLSM includes only two independent parameters originating from four exchange constants for fixed s and t. The topological angle in the NLSM determines the gapless phase boundaries between disordered phases in the parameter space. The phase diagrams for various s and t shows rich structures. We systematically explain the phases in the singlet-cluster-solid picture.Comment: 8 pages (16 figures included

Direct evidence of N aggregation and diffusion in Au+Au+ irradiated GaN

A surface amorphized layer and a buried disordered structure were created in gallium nitride (GaN) irradiated using 1.0 MeV1.0MeV Au+Au+ ions to fluences of 25 and 70 Au+/nm270Au+∕nm2 at room temperature. Bubbles of N2N2 gas within both the amorphized and disordered GaN are formed. A gradient profile with a lower N concentration in the amorphized region is observed, which provides direct evidence of N loss by diffusion in the Au+Au+ irradiated GaN. These results are important to understanding the amorphization processes in GaN and may have significant implications for the design and fabrication of GaN-based devices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87811/2/021903_1.pd

Critical Successful Factors of ERP Implementation: A Review

Recently e-business has become the focus of management interest both in academics and in business. Among the major components of e-business, ERP (Enterprise Resource Planning) is the backbone of other applications. Therefore more and more enterprises attempt to adopt this new application in order to improve their business competitiveness. Owing to the specific characteristics of ERP, its implementation is more difficult than that of traditional information systems. For this reason, how to implement ERP successfully becomes an important issue for both academics and practitioners. In this paper, a review on critical successful factors of ERP in important MIS publications will be presented. Additionally traditional IS implementation and ERP implementation will be compared and the findings will be served as the basis for further researc

The mass-metallicity relation of Lyman-break analogues and its dependence on galaxy properties

We investigate the mass-metallicity relation and its dependence on galaxy physical properties with a sample of 703 Lyman-break analogues (LBAs) in local Universe, which have similar properties to high redshift star-forming galaxies. The sample is selected according to \ha luminosity, L(\ha)>10^{41.8}\,{\rm erg\,s^{-1}}, and surface brightness, I(\ha)>10^{40.5}\,{\rm erg\,s^{-1}\,kpc^{-2}}, criteria. The mass-metallicity relation of LBAs harmoniously agrees with that of star-forming galaxies at $z \sim$ 1.4-1.7 in stellar mass range of $10^{8.5}M_{\odot}<M_{*}<10^{11}M_{\odot}$. The relation between stellar mass, metallicity and star formation rate of our sample is roughly consistent with the local fundamental metallicity relation. We find that the mass-metallicity relation shows a strong correlation with the 4000\AA\, break; galaxies with higher 4000\AA\, break typically have higher metallicity at a fixed mass, by 0.06 dex in average. This trend is independent of the methodology of metallicity. We also use the metallicity estimated by $T_{\rm e}$-method to confirm it. The scatter in mass-metallicity relation can be reduced from 0.091 to 0.077 dex by a three-dimensional relation between stellar mass, metallicity and 4000\AA\, break. The reduction of scatter in mass-metallicity relation suggests that the galaxy stellar age plays an important role as the second parameter in the mass-metallicity relation of LBAs.Comment: 10 pages,8 figure

Tunneling Conductance Between Parallel Two Dimensional Electron Systems

We derive and evaluate expressions for the low temperature {\it dc} equilibrium tunneling conductance between parallel two-dimensional electron systems. Our theory is based on a linear-response formalism and on impurity-averaged perturbation theory. The disorder broadening of features in the dependence of tunneling conductance on sheet densities and in-plane magnetic field strengths is influenced both by the finite lifetime of electrons within the wells and by non-momentum-conserving tunneling events. Disorder vertex corrections are important only for weak in-plane magnetic fields and strong interwell impurity-potential correlations. We comment on the basis of our results on the possibility of using tunneling measurements to determine the lifetime of electrons in the quantum wells.Comment: 14 pages, 5 Fig. not included, revtex, IUcm92-00

Multi-Objective Optimization of Transonic Compressor Blade Using Evolutionary Algorithm

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77106/1/AIAA-14667-294.pd

Positive Lyapunov exponents calculated from time series of strange nonchaotic-attractors

Time-series methods for estimating Lyapunov exponents may give a positive exponent when they are applied to the time series of strange nonchaotic systems. Strange nonchaotic systems are characterized by expanding and contracting regions in phase space that result in repeatedly expanding or contracting trajectories. Using time-series methods, the maximum time-series Lyapunov exponent is calculated as an average of the locally most expanding exponents that characterize the divergence of nearby trajectories following a reconstructed attractor over time. A positive exponent is reported by time-series methods for trajectories in an expanding region. While in a converging region, the most expanding dynamics are related to the quasiperiodic driving force. Statistically, a zero exponent related to the quasiperiodic force is obtained through time-series methods within converging regions. As a result, the calculated maximum Lyapunov exponent is positive