Pathways and ToonTalk are computer programming systems for children (age 4 years old and over) to build computer games with. This paper explores how the range of representational modes made available in these two syst...
详细信息
Pathways and ToonTalk are computer programming systems for children (age 4 years old and over) to build computer games with. This paper explores how the range of representational modes made available in these two systems shape the potentials for learning with them. The analysis centres on the impact of modes (including still image, gesture, posture, speech, music, writing, and new configurations of the elements of these) on the emergence of the mathematical entities|super||opnbop|1|clobop| rule, condition and action. We show that the choice of representational modes in the design of each program is central to the potentials for user engagement. Modes (e.g. image and writing) provide the maker of an application and the user of it with different features for making meaning, in this case, for engaging with aspects of programming and building games. We conclude that a multimodal approach can offer new insights into the learning potentials of computer programming applications. [ABSTRACT FROM AUTHOR]
This paper extends the A* methodology to shortest path problems in dynamic networks, in which arc travel times are time dependent. We present efficient adaptations of the A* algorithm for computing fastest (minimum tr...
详细信息
This paper extends the A* methodology to shortest path problems in dynamic networks, in which arc travel times are time dependent. We present efficient adaptations of the A* algorithm for computing fastest (minimum travel time) paths from one origin node to one destination node, for one as well as multiple departure times at the origin node, in a class of dynamic networks the link travel times of which satisfy the first-in-first-out property. We summarize useful properties of dynamic networks and develop improved lower bounds on minimum travel times. These lower bounds are exploited in designing efficient adaptations of the A* algorithm to solve instances of the one-to-one dynamic fastest path problem. The developed algorithms are implemented and their computational performance is analyzed experimentally. The performance of the computer implementations of the adaptations of the A* algorithm are compared to a dynamic adaptation of Dijkstra's algorithm, stopped when the destination node is selected. Comparative computational results obtained demonstrate that the algorithms of this paper are efficient. Using a network containing 3000 nodes, 10000 links, and 100 time intervals, the dynamic adaptations of the A* led to a savings ratio of 11, in terms of number of nodes selected, and to a savings ratio of five in terms of computation time. The effect of the network size on the performance of these adaptations is also studied. It is shown that the computational savings in term of both the number of nodes selected and the computation time, increase with the size of the network topology.
The number of spanning trees in a (di-)graph (network) is an important, well-studied quantity. Most research about the number of spanning trees is devoted to determining exact formulae for the number of spanning trees...
详细信息
The number of spanning trees in a (di-)graph (network) is an important, well-studied quantity. Most research about the number of spanning trees is devoted to determining exact formulae for the number of spanning trees in many kinds of special graphs. In this thesis, we start by stating the general methods for counting the number of spanning trees in (di-)graphs. We then discuss our new results. We show that the number of spanning trees in the circulant graph [special characters omitted] always satisfies a recurrence relation and describe how to derive this relation. The asymptotic behavior of these quantities are also derived. Boesch and Prodinger have shown how to use Chebyshev polynomials to derive closed formulae for the number of spanning trees of graphs in certain classes. This work has been extended to develop new techniques for the evaluation of the number of spanning trees in circulant graphs and graphs related to circulant graphs. We end by describing a method of counting the number of spanning trees in one class of double fixed-step loop networks.
In this research, some novel modifications and modern applications of the Hough transform algorithms have been pursued. First, the dual points Hough transform algorithm was studied. Our approach optimises the R-Table ...
详细信息
In this research, some novel modifications and modern applications of the Hough transform algorithms have been pursued. First, the dual points Hough transform algorithm was studied. Our approach optimises the R-Table of the prototype by using some statistics techniques in order to reduce the number of entries per index in the R-Table and make the entries inside the R-Table distribute evenly. Experimental results show that our method can both speed up the process and increase the recognition accuracy. Second, a dominant point detection algorithm has also been studied. The reason for pursuing this study is that we can reduce the number of operations by employing dominant points as the features in the Hough transform process. Owing to the lack of appropriate dominant point detection algorithms for real scenes, a new dominant point detection algorithm has been proposed. Apart from the curvature points, we also defined the termination and intercept points on a digital curve as the dominant points since they indeed give useful information about the natures of the curves. A weighted mask is proposed for the initial detection. By using a look up table, all possible dominant points can be located efficiently. Experimental results show that our method achieves a better performance in terms of approximation error when compared with other methods. After the development of the dominant point detection algorithm, we have developed a Hough transform algorithm that makes use of the dominant points as the corresponding features in tracking an object in a video sequence. The user inputs a user-defined object in the first frame. Then, an R-Table is built based upon the dominant points of the selected object. When the next frame is reached, the transformation parameters of the object can then be detected by using the Hough transform. Our proposed algorithm is capable not only to track the object under a continuous deformation, but also able to recognise the object under occlusion and r
The development of intelligent transportation systems (ITS) and the resulting need for the solution of a variety of dynamic traffic network models and management problems require faster-than-real-time computation of s...
详细信息
The development of intelligent transportation systems (ITS) and the resulting need for the solution of a variety of dynamic traffic network models and management problems require faster-than-real-time computation of shortest path problems in dynamic networks. Recently, a sequential algorithm was developed to compute shortest paths in discrete time dynamic networks from all nodes and all departure times to one destination node. The algorithm is known as algorithm DOT and has an optimal worst-case running-time complexity. This implies that no algorithm with a better worst-case computational complexity can be discovered. Consequently, in order to derive algorithms to solve all-to-one shortest path problems in dynamic networks, one would need to explore avenues other than the design of sequential solution algorithms only. The use of commercially-available high-performance computing platforms to develop parallel implementations of sequential algorithms is an example of such avenue. This paper reports on the design, implementation, and computational testing of parallel dynamic shortest path algorithms. We develop two shared-memory and two message-passing dynamic shortest path algorithm implementations, which are derived from algorithm DOT using the following parallelization strategies: decomposition by destination and decomposition by transportation network topology. The algorithms are coded using two types of parallel computing environments: a message-passing environment based on the parallel virtual machine (PVM) library and a multi-threading environment based on the SUN Microsystems Multi-Threads (MT) library. We also develop a time-based parallel version of algorithm DOT for the case of minimum time paths in FIFO networks, and a theoretical parallelization of algorithm DOT on an ‘ideal’ theoretical parallel machine. Performances of the implementations are analyzed and evaluated using large transportation networks, and two types of parallel computing platforms: a distr
We have developed an improved algorithm that allows us to enumerate the number of site animals on the square lattice LIP to size 46. We also calculate the number of lattice trees up to size 44 and the radius of gyrati...
详细信息
We have developed an improved algorithm that allows us to enumerate the number of site animals on the square lattice LIP to size 46. We also calculate the number of lattice trees up to size 44 and the radius of gyration of both lattice animals and trees up to size 42. Analysis of the resulting series yields an improved estimate, lambda =4.062570(8), for the growth constant of lattice animals, and, lambda (0)=3.795254(8), for the growth constant of trees, and confirms to a very high degree of certainty that both the animal and tree generating Functions have a logarithmic divergence. Analysis of the radius of gyration series yields the estimate, nu =0.64115(5), for the size exponent.
暂无评论