Towards a theory of data structures

A formal idealization of the data structures used in many “list processing” languages is defined. It is then shown that under a natural interpretation, these data structures define exactly the context-free languages of automata theory. Then a generalization in the direction of the “patterns” of SNØBØL is made. It is observed that this generalization models the ability of SNØBØL patterns to represent noncontext-free languages. Finally, it is shown that under certain restrictions, only context-sensitive languages are represented but that in general noncontext-sensitive languages can occur

Precise Experimental Investigation of Eigenmodes in a Planar Ion Crystal

The accurate characterization of eigenmodes and eigenfrequencies of two-dimensional ion crystals provides the foundation for the use of such structures for quantum simulation purposes. We present a combined experimental and theoretical study of two-dimensional ion crystals. We demonstrate that standard pseudopotential theory accurately predicts the positions of the ions and the location of structural transitions between different crystal configurations. However, pseudopotential theory is insufficient to determine eigenfrequencies of the two-dimensional ion crystals accurately but shows significant deviations from the experimental data obtained from resolved sideband spectroscopy. Agreement at the level of 2.5 x 10^(-3) is found with the full time-dependent Coulomb theory using the Floquet-Lyapunov approach and the effect is understood from the dynamics of two-dimensional ion crystals in the Paul trap. The results represent initial steps towards an exploitation of these structures for quantum simulation schemes.Comment: 5 pages, 4 figures, supplemental material (mathematica and matlab files) available upon reques

In search of templates

This paper explores, both wit This study reflects a recent shift towards the study of early stages of expert memory acquisition for chess positions. Over the course of fifteen sessions, two subjects who knew virtually nothing about the game of chess were trained to memorise positions. Increase in recall performance and chunk size was captured by power functions, confirming predictions made by the template theory (Gobet & Simon, 1996, 1998, 2000). The human data was compared to that of a computer simulation run on CHREST (Chunk Hierarchy and REtrieval STructures), an implementation of the template theory. The model accounts for the pattern of results in the human data, although it underestimates the size of the largest chunks and the rate of learning. Evidence for the presence of templates in human subjects was found

Vietnam’s trade policy: a developing nation assessment

Aim/PurposeThis paper is a review of the progress of the Vietnam socio-economic and development plan and an assessment of the extent to which Vietnam is putting in place the critical social and economic development structures that will enable it to reach the status of “developed nation” in the time set (2020) by its national strategic plan. The research will identify and review trade patterns, trade policy and the effect of foreign aid on Vietnam’s plan to transform its economy and society from a developing nation status to status of developednation. The overriding question stands as “is” Vietnam effec-tively moving towards developed nation statussoon”?BackgroundThis paper examines the history of Vietnam from the command economy in its transition to a market driven economy, the criteria, hurdles and challenges as the country moves towards a developed country status. MethodologyApplied research based on the body of research in socio-economic develop-ment theory, international trade and market theory. The review is conducted by collecting and analyzing data on foreign trade, foreign aid, business and general economic growth, development and social wellbeing. Itidentifies and appraises the trade patterns,trade effects, socio-economic policies and the effect of foreign aid] on the economic growth and the progress of the coun-try towards becoming a developed nation state

A simplified model of the Martian atmosphere - Part 2: a POD-Galerkin analysis

In Part I of this study Whitehouse et al. (2005) performed a diagnostic analysis of a simplied model of the Martian atmosphere, in which topography was absent and in which heating was modelled as Newtonian relaxation towards a zonally symmetric equilibrium temperature field. There we derived a reduced-order approximation to the vertical and the horizonal structure of the baroclinically unstable Martian atmosphere, retaining only the barotropic mode and the leading order baroclinic modes. Our objectives in Part II of the study are to incorporate these approximations into a Proper Orthogonal Decomposition-Galerkin expansion of the spherical quasi-geostrophic model in order to derive hierarchies of nonlinear ordinary differential equations for the time-varying coefficients of the spatial structures. Two different vertical truncations are considered, as well as three different norms and 3 different Galerkin truncations. We investigate each in turn, using tools from bifurcation theory, to determine which of the systems most closely resembles the data for which the original diagnostics were performed