Field-dependent quantum nucleation of antiferromagnetic bubbles

The phenomenon of quantum nucleation is studied in a nanometer-scale antiferromagnet with biaxial symmetry in the presence of a magnetic field at an arbitrary angle. Within the instanton approach, we calculate the dependence of the rate of quantum nucleation and the crossover temperature on the orientation and strength of the field for bulk solids and two-dimensional films of antiferromagnets, respectively. Our results show that the rate of quantum nucleation and the crossover temperature from thermal-to-quantum transitions depend on the orientation and strength of the field distinctly, which can be tested with the use of existing experimental techniques.Comment: 21 pages, 5 figures, Final version and accepted by Eur. Phys. J

Periodic Radio Variability in NRAO 530: Phase Dispersion Minimization Analysis

In this paper, a periodicity analysis of the radio light curves of the blazar NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved Phase Dispersion Minimization (PDM) technique. The result, which shows two persistent periodic components of $\sim 6$ and $\sim 10$ years at all three frequencies, is consistent with the results obtained with the Lomb-Scargle periodogram and weighted wavelet Z-transform algorithms. The reliability of the derived periodicities is confirmed by the Monte Carlo numerical simulations which show a high statistical confidence. (Quasi-)Periodic fluctuations of the radio luminosity of NRAO 530 might be associated with the oscillations of the accretion disk triggered by hydrodynamic instabilities of the accreted flow. \keywords{methods: statistical -- galaxies: active -- galaxies: quasar: individual: NRAO 530}Comment: 8 pages, 5 figures, accepted by RA

A Study of Online Customer Loyalty Based on the Theory of Planned Behavior

The Internet has introduced major changes in the way companies conduct business. Practically, rising numbers of customers are using the Internet for Electronic Commerce (EC). In the respect of customer relationship, Business-to-Consumer (B2C) EC provides ongoing information, service, and support that have changed the approaches of communication and interaction with customers. The nature of online customer behavior in the EC transaction is therefore different from the one in a traditional retailing channel. This research focuses on the online customer behavior through examining the relationship between the behavior intention and the online behavior itself. Based on the Theory of Planned Behavior (TPB), a base model of Online Customer Loyalty is developed. The research also proposes an alternative model in which Satisfaction is adopted as a mediated variable. Four hundred and twenty-three questionnaires are collected for the empirical experiment. The method of Structural Equation Modeling (SEM) is used to evaluate the measurement and structural models. The result indicates that TPB can be used to explain the behavior of Online Customer Loyalty. The structure relationship between Behavior Intention and Online Customer Loyalty is significant. The three constructs influencing Behavior Intention including Attitude toward Behavior, Subjective Norm and Perceived Behavioral Control also have indirectly positive effects on the behavior of Online Customer Loyalty. The two competing models are compared. Both models are acceptable when judged by the criteria of goodness-of-fit measures. However, the alternative model has a higher explained proportion of variance in Online Customer Loyalty

Nonlinear optomechanical resonance entering a self-organized energy transfer pattern

The energy transfer between different subsystems or different vibration modes is always one of the most interested problems in the study of the resonance phenomena in coupled nonlinear dynamical systems. With an optomechanical system operating in the regime of unresolved sideband, where its mechanical frequency is lower than the cavity field damping rate, we illustrate the existence of a special nonlinear resonance phenomenon. This type of previously unknown resonance manifests an organized pattern of the coupled cavity field and mechanical oscillation, so that the cavity field precisely pushes the mechanical oscillator within an appropriate small time window in each mechanical oscillation period and the mechanical energy will increase by a jump of almost fixed amount after each oscillation cycle. The scenario is realized at a resonance point where the frequency difference of two driving fields matches the mechanical frequency of the system, and this condition of drive-frequency match is found to trigger a mechanism to lock the two subsystems of an unresolved-sideband optomechanical system into a highly ordered energy transfer as the above mentioned. Due to a significantly enhanced nonlinearity in the vicinity of the resonance point, optical frequency combs can be generated under pump powers of thousand times lower, as compared to the use of a single-tone driving field for the purpose. An unresolved sideband system under the drives without satisfying the resonance condition also demonstrates other interesting dynamical behaviors. Most of all, by providing a realistic picture for the nonlinear optomechanical dynamics in unresolved sideband regime, our study points to a direction to observe novel dynamical phenomena and realize other applications with the systems of less technical restrictions.Comment: 13 pages, 13 figures. To be published on Chaos, Solitons & Fractal

BigraphTalk: verified design of IoT applications

Graphical IoT device management platforms, such as IoTtalk, make it easy to describe interactions between IoT devices. Applications are defined by dragging-and-dropping devices and specifying how they are connected, e.g. a door sensor controlling a light. While this allows simple and rapid development, it remains possible to specify unwanted device configurations – such as using the same device to drive a motor up and down simultaneously, risking damaging the motor. We propose , a verification framework for IoTtalk that utilizes formal techniques, based on bigraphs, to statically guarantee that unwanted configurations do not arise. In particular, we check for invalid connections between devices, as well as type errors, e.g. passing a float to a boolean switch. To the best of our knowledge, is the first platform to support the graphical specification of correct-by-design IoT applications. provides fully automated verification and feedback without end-users ever needing to specify a bigraph. This means any application, specifiable in IoTtalk, is guaranteed, so long as verification succeeds, not to violate the given configuration constraints when deployed; with no extra cost to the user