Impeded inverse energy transfer in the Charney--Hasegawa--Mima model of quasi-geostrophic flows

The behaviour of turbulent flows within the single-layer quasi-geostrophic (Charney--Hasegawa--Mima) model is shown to be strongly dependent on the Rossby deformation wavenumber $\lambda$ (or free-surface elasticity). Herein, we derive a bound on the inverse energy transfer, specifically on the growth rate \d\ell/\dt of the characteristic length scale $\ell$ representing the energy centroid. It is found that \d\ell/\dt\le2\norm q_\infty/(\ell_s\lambda^2), where \norm q_\infty is the supremum of the potential vorticity and $\ell_s$ represents the potential enstrophy centroid of the reservoir, both invariant. This result implies that in the potential energy dominated regime ($\ell\ge\ell_s\gg\lambda^{-1}$), the inverse energy transfer is strongly impeded, in the sense that under the usual time scale no significant transfer of energy to larger scales occurs. The physical implication is that the elasticity of the free surface impedes turbulent energy transfer in wavenumber space, effectively rendering large-scale vortices long-lived and inactive. Results from numerical simulations of forced-dissipative turbulence confirm this prediction.Comment: 8 pages, 2 figures, accepted for publication in JF

Mobile WiMAX system performance – simulated versus experimental results

This paper addresses the downlink performance of mobile WiMAX operating at 2.3GHz in an urban environment. The analysis includes a comparison of simulated and experimental results. Simulated packet error rate (PER) versus Signal to Noise Ratio (SNR) graphs are generated on a per link-speed basis using a fully compliant 512 carrier mobile WiMAX simulator. Experimental data is gathered using a carrier-class basestation, a mobile-WiMAX enabled laptop, and a suite of application layer logging software. An H264 AVC encoder and IP packetisation unit is used to transmit video to a mobile client. Results show strong agreement in terms of simulated and captured PER. Using this data, the downlink operating range is evaluated as a function of the Effective Isotropic Radiated Power (EIRP) and path loss exponent. Results indicate that at low EIRP (32 dBm) the expected outdoor operating range is around 200-400m. Applying the UK OFCOM regulations for licensed operation in the 2.5GHz band, downlink operation in excess of 2km can be achieved

Linear degree growth in lattice equations

We conjecture recurrence relations satisfied by the degrees of some linearizable lattice equations. This helps to prove linear growth of these equations. We then use these recurrences to search for lattice equations that have linear growth and hence are linearizable

Sustainable Growth and Ethics: a Study of Business Ethics in Vietnam Between Business Students and Working Adults

Sustainable growth is not only the ultimate goal of business corporations but also the primary target of local governments as well as regional and global economies. One of the cornerstones of sustainable growth is ethics. An ethical organizational culture provides support to achieve sustainable growth. Ethical leaders and employees have great potential for positive influence on decisions and behaviors that lead to sustainability. Ethical behavior, therefore, is expected of everyone in the modern workplace. As a result, companies devote many resources and training programs to make sure their employees live according to the high ethical standards. This study provides an analysis of Vietnamese business students’ level of ethical maturity based on gender, education, work experience, and ethics training. The results of data from 260 business students compared with 704 working adults in Vietnam demonstrate that students have a significantly higher level of ethical maturity. Furthermore, gender and work experience are significant factors in ethical maturity. While more educated respondents and those who had completed an ethics course did have a higher level of ethical maturity, the results were not statistically significant. Analysis of the results along with suggestions and implications are provided

Stationary solution of the ring-spinning balloon in zero air drag using a RBFN based mesh-free method

A technique for numerical analysis of the dynamics of the ring-spinning balloon based on the Radial Basis Function Networks (RBFNs) is presented in this paper. This method uses a 'universal approximator' based on neural network methodology to solve the differential governing equations which are derived from the conditions of the dynamic equilibrium of the yarn to determine the shape of balloon yarn. The method needs only a coarse finite collocation points without any finite element-type discretisation of the domain and its boundary for numerical solution of the governing differential equations. This paper will report a first assessment of the validity and efficiency of the present mesh-less method in predicting the balloon shape across a wide range of spinning conditions