Phase-field-crystal model for fcc ordering

We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to and reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free- energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a non-vanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a non-vanishing tetragonal shear modulus (C11 - C12)/2. We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.Comment: 14 figure

Concept of history in the theology of Karl Barth

This thesis provides a complete, chronological view of Barth’s concept of history throughout his theological career. The purpose of undertaking this hitherto unattempted task is to demonstrate that, ever since his full engagement with dogmatics in the mid-1920s, Barth has unequivocally affirmed the reality of the history which revelation becomes and is. Though he continues to insist upon the transcendence of revelation, he does so by way of an increasingly christocentric theology, so that both divine sovereignty and human dignity are firmly upheld. This is especially evident in his later theology, with his concentration on the history of Jesus Christ on the basis of the doctrine of election. This thesis thus rejects both the charge that Barth’s theology is ahistorical or anti-historical on the one hand, and the charge that it is excessively historical on the other

A Reduced-Complexity Fast Algorithm for Software Implementation of the IFFT/FFT in DMT Systems

The discrete multitone (DMT) modulation/demodulation scheme is the standard transmission technique in the application of asymmetric digital subscriber lines (ADSL) and very-high-speed digital subscriber lines (VDSL). Although the DMT can achieve higher data rate compared with other modulation/demodulation schemes, its computational complexity is too high for cost-efficient implementations. For example, it requires 512-point IFFT/FFT as the modulation/demodulation kernel in the ADSL systems and even higher in the VDSL systems. The large block size results in heavy computational load in running programmable digital signal processors (DSPs). In this paper, we derive computationally efficient fast algorithm for the IFFT/FFT. The proposed algorithm can avoid complex-domain operations that are inevitable in conventional IFFT/FFT computation. The resulting software function requires less computational complexity. We show that it acquires only 17% number of multiplications to compute the IFFT and FFT compared with the Cooly-Tukey algorithm. Hence, the proposed fast algorithm is very suitable for firmware development in reducing the MIPS count in programmable DSPs

Ginzburg-Landau theory of crystalline anisotropy for bcc-liquid interfaces

The weak anisotropy of the interfacial free-energy $\gamma$ is a crucial parameter influencing dendritic crystal growth morphologies in systems with atomically rough solid-liquid interfaces. The physical origin and quantitative prediction of this anisotropy are investigated for body-centered-cubic (bcc) forming systems using a Ginzburg-Landau theory where the order parameters are the amplitudes of density waves corresponding to principal reciprocal lattice vectors. We find that this theory predicts the correct sign, $\gamma_{100}>\gamma_{110}$, and magnitude, $(\gamma_{100}-\gamma_{110}) / (\gamma_{100}+\gamma_{110})\approx 1$, of this anisotropy in good agreement with the results of MD simulations for Fe. The results show that the directional dependence of the rate of spatial decay of solid density waves into the liquid, imposed by the crystal structure, is a main determinant of anisotropy. This directional dependence is validated by MD computations of density wave profiles for different reciprocal lattice vectors for $\{110\}$ crystal faces. Our results are contrasted with the prediction of the reverse ordering $\gamma_{100}<\gamma_{110}$ from an earlier formulation of Ginzburg-Landau theory [Shih \emph{et al.}, Phys. Rev. A {\bf 35}, 2611 (1987)].Comment: 9 pages, 5 figure

The Symbolic Meaning Effect on Smartphone Repurchase: A Comparison of Android and IOS

With Android and iOS as the dominating operation systems, the growth of one player’s influence in the market translates into the loss of its opponent’s market share. In the marketing discipline, expectation confirmation theory is used to study how a consumer’s satisfaction influences his/her willingness to repurchase the product. Scholars extended the theory and developed a post-acceptance model of information system continuance and applied the model to consumers’ continuance with information technological products. This paper will analyse consumers’ repurchase with Android and iOS-based smartphones. More, satisfied customers may still be switching to competitor\u27s product/service. This study therefore explores possible moderators between user satisfaction and repurchase

THE EFFECTS OF PUSH-PULL-MOORING ON THE SWITCHING MODEL FOR SOCIAL NETWORK SITES MIGRATION

Although the number of users has been growing exponentially in SNSs, some SNSs are facing a financial crisis and might be shut down in the near future. Therefore, understand users\u27 incentives to switch to another SNS has great influence on operators\u27 business performance. The study extended Push-Pull-Mooring migratory theory to explain the switching behaviors of users in SNS. Structural equation modeling will applied to analyze data collected from a filed survey. The result can construct a solid switching framework and help operators to understand their customer better

Why Differentiation Strategy Fails?

Differentiation strategy has been considered critical for securing a competitive advantage. However, not all firms can create competitive advantages through differentiation. In this paper, we draw on a Taiwanese hotel, restaurant, and TV program provider to show why differentiation strategy fails. On the basis of these three cases, three failed differentiation strategies are proposed and a framework for implementing a differentiation strategy is provided. Finally, we present the discussion and conclusions for the theory and practice of differentiation strategy