The Effect of Anisotropic Surface Energy on the Stability of Micro and Nano Wires

A liquid thread of radius R will break up into drops if the axial wavelength of the surface perturbation L \u3e 2πR. If L \u3c 2πR, the thread is stable and will remain intact. This is Rayleigh’s stability criterion based on a continuum model. We use molecular dynamics to simulate the evolution of Lennard-Jones liquid threads with equilibrium radius R = 2.3-6.6, where R has been non-dimensionalized by the distance at which the Lennard-Jones potential equals zero. We find that if R is fixed, the wavelength L is bounded by Lmin and Lmax. For L \u3e Lmax the thread always breaks up and stays as drops, and for L \u3c Lmin the thread remains intact. However, for Lmin \u3c L \u3c Lmax, the thread oscillates continuously among several shapes. The appearance of various shapes can be explained by the energy fluctuation of the system. We also simulate the evolution of Lennard-Jones nanowires with equilibrium radius R = 1.57, 2.58, 3.59, and 4.60 by molecular dynamics. The wires are evolved at temperatures slightly below the melting temperatures, which are found by computing the bond-length fluctuation. Rayleigh’s criterion is obeyed with the critical wavelength slightly smaller than 2πR. We then introduce a marker-particle method for the computation of three-dimensional solid surface morphologies evolving by surface diffusion. We demonstrate the method by computing the evolution of perturbed cylindrical wires on a substrate. Furthermore, when the marker particles are redistributed periodically to maintain even spacing, the method can follow breakup of the wire. Modeling equilibrium crystal shapes is necessary to numerically study the stability and evolution of crystals. We model the surface stiffness of crystals instead of surface energy. And a facet is represented by Dirac delta function. Our approach is demonstrated by modeling two-dimensional axially symmetric crystals and three-dimensional axisymmetric crystals. We finally perform a linear stability analysis of three-dimensional finite axisymmetric wires with anisotropic surface energy. We arrive at an eigenvalue problem with the eigenvaule representing the growth rate of a perturbation. We find that wires are stable with length-to-radius ratio greater than 2π, which is in contrast to previous theoretical predictions

Another Argument on the Crisis Said of Comparative Literature

In her article Another Argument on the \u27Crisis Said\u27 of Comparative Literature Ping Du discusses Crisis Said , the long-lasting topic since the birth of Comparative Literature. She argues that after every crisis comes an opportunity of a new development of Comparative Literature. Du claims that comparative literature is experiencing a rebirth in the Age of Multiculturalism. She, firstly, reviews the first wave of Crisis Said , its solution and the progress of Comparative Literature, then she analyses the prevailing second wave of Crisis Said or even Death Said , and finally points out that the way-out is not merely world literature but the Chinese School and its Variation Studies which represent the future of Comparative Literature

Investigating effects of product visual designs on consumer judgments with the aid of eye-tracking

Product visual designs convey a variety of information about these products to consumers. These designs play an important role in affecting consumer judgments, which further determine purchase decisions. Understanding how consumers decode visual designs to form judgments as well as how to use visual designs to affect consumer judgments are important. Insights in these will help designers make better design decisions and also present new possibilities of product design. This dissertation employs eye-tracking technology to assist in understanding consumers\u27 decoding processes. First, eye-tracking is used to examine how consumers evaluate visual designs to determine preferences and product differences. Then, eye-tracking is utilized to help investigate influences of (1) pairing products that have both commonalities and differences and (2) visual cues on consumer judgments separately. Product features, defined as visible product attributes, are important constitutions of product visuals. Study 1 uses eye-tracking to address two topics about product features: (1) feature importance in preference decisions and (2) whether or not consumers can detect a feature\u27s size change. Results from eye-tracking how subjects evaluated product images to determine preferences showed a feature\u27s gaze data (e.g., how long the subjects fixated on the feature) significantly correlated with the feature\u27s importance rating provided by the subjects. Results from eye-tracking how subjects detected differences between product images showed noticeable and unnoticeable feature size changes had significantly different corresponding gaze data. Statistical models of gaze data can predict importance and size change saliency of a feature. Purchase decisions often require comparing products that have both commonalities and differences. Study 2 investigates how this configuration of choice alternatives influences consumer judgments by testing a model of choice from psychology, the cancellation-and-focus (C&F) model, in the product design domain. The C&F model specifies when facing two choice alternatives that have both shared and unique attributes, people tend to ignore the shared attributes and focus on the unique ones, which can affect both preferences and certain postpreference judgments. The model had only been tested with text-only stimuli, where text-described attributes represented products. Study 2 tested the model with image-only, text-only, and image-with-text stimuli separately. It tested each stimuli type with two conditions: (1) presenting stimuli sequentially and (2) side-by-side. The C&F model held only in limited situations for the tested products. Generally, the unique attribute/feature had more gaze attention than the shared one, indicating the importance of product differences in consumer preferences. While a shared attribute was canceled in decisions, a shared feature reinforced impressions. Consumers extract cues from visual designs and mentally associate them with unobservable product attributes to aid judgments. Study 3 investigates the possibility to rapidly build mental associations to influence consumer judgments. The study also compares the effectiveness of cuing holistically, through body shapes, and cuing by features. Subjects participated in an association-building task, where a visual cue was associated with either a positive or a negative judgment of environmental friendliness. Results from a latter testing task demonstrated that mental associations between body shape cues and environmental friendliness formed. Body shape cues affected products\u27 environmental friendliness ratings in the desired direction, but feature cues did not. Gaze data showed the subjects adjusted their distributions of attention to a product after the association-building task, indicating the ability of cues to promote a more efficient decision-making behavior

Experimental implementation of high-fidelity unconventional geometric quantum gates using NMR interferometer

Following a key idea of unconventional geometric quantum computation developed earlier [Phys. Rev. Lett. 91, 197902 (2003)], here we propose a more general scheme in such an intriguing way: $\gamma_{d}=\alpha_{g}+\eta \gamma _{g}$, where $\gamma_{d}$ and $\gamma_{g}$ are respectively the dynamic and geometric phases accumulated in the quantum gate operation, with $\eta$ as a constant and $\alpha_{g}$ being dependent only on the geometric feature of the operation. More arrestingly, we demonstrate the first experiment to implement a universal set of such kind of generalized unconventional geometric quantum gates with high fidelity in an NMR system.Comment: 4 pages, 3 figure