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A Better Heuristic Algorithm for Finding the Closest Trio of 3-colored Points from a Given Set of 3-colored Points on a Plane

Nguyen N. T., Duong A. D.

Fundamenta Informaticae

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2014

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Vol. 130, nr 2

219--229

EN

We consider the following problem: Given n red points, m green points and p blue points on a plane, find a trio of red-green-blue points such that the distance between them is smallest. This problem could be solved by an exhaustive search algorithm: test all trios of 3 different colored points and find the closest trio. However, this algorithm has the complexity of O(N3), N = max(n, p, q). In our previous research, we already showed a heuristic algorithm with a good complexity to solve this problem based on 2D Voronoi diagram. In this paper, we introduce a better heuristic algorithm for solving this problem. This new heuristic algorithm has the same complexity but it performs much better than the old one.

2

Topography of the Moho and earth crust structure beneath the East Vietnam Sea from 3D inversion of gravity field data

Nguyen N.T., Nguyen T.H.

Acta Geophysica

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2013

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Vol. 61, no. 2

357--384

EN

The Moho depth, crustal thickness and fault systems of the East Vietnam Sea (EVS) are determined by 3D interpretation of satellite grav- ity. The Moho depth is calculated by 3D Parker inversion from residual gravity anomaly that is obtained by removing the gravity effects of sea- floor and Pre-Cenozoic sediment basement topographies from the free air anomaly. The 3D inversion solution is constrained by power density spectrum of gravity an omaly and seismic data. The calculated Moho depths in the EVS vary from 30-31 km near the coast to 9 km in the Central Basin. A map of the lithosphere extension factor in the Cenozoic is constructed from Moho and Pre-Cenozoic sediment basement depths. The fault systems constructed by the maximum horizontal gradient approach include NE-SW, NW-SE, and N-S oriented faults. Based on the interpretation results, the EVS is sub-divided into five structural zones which demonstrated the different characteristics of the crustal structure.

3

A method for learning scenario determination and modification in intelligent tutoring systems

Kozierkiewicz-Hetmańska A., Nguyen N. T.

International Journal of Applied Mathematics and Computer Science

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2011

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Vol. 21, no 1

69-82

EN

Computers have been employed in education for years. They help to provide educational aids using multimedia forms such as films, pictures, interactive tasks in the learning process, automated testing, etc. In this paper, a concept of an intelligent e-learning system will be proposed. The main purpose of this system is to teach effectively by providing an optimal learning path in each step of the educational process. The determination of a suitable learning path depends on the student's preferences, learning styles, personal features, interests and knowledge state. Therefore, the system has to collect information about the student, which is done during the registration process. A user is classified into a group of students who are similar to him/her. Using information about final successful scenarios of students who belong to the same class as the new student, the system determines an opening learning scenario. The opening learning scenario is the first learning scenario proposed to a student after registering in an intelligent e-learning system. After each lesson, the system tries to evaluate the student's knowledge. If the student has a problem with achieving an assumed score in a test, this means that the opening learning scenario is not adequate for this user. In our concept, for this case an intelligent e-learning system offers a modification of the opening learning scenario using data gathered during the functioning of the system and based on a Bayesian network. In this paper, an algorithm of scenario determination (named ADOLS) and a procedure for modifying the learning scenario AMLS with auxiliary definitions are presented. Preliminary results of an experiment conducted in a prototype of the described system are also described.

4

Prise en compte de l'effet de la mise en place dans la modélisation numérique en 3D des colonnes ballastées dans l'argile molle

Nguyen N. T., Foray P., Flavigny E.

Studia Geotechnica et Mechanica

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2008

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Vol. 30, nr 1-2

189-198

EN

This paper presents a comparison of numerical modelling of the behaviour of reinforcements in the form of stone columns in very soft clay. The simulation is run using the software finite elements Plaxis, first in 2D, then in 3D. We are particularly interested in taking into account the application of the columns in modelling. Indeed, in practice, due to the expansion of the column, the ground in its close vicinity undergoes a lateral compaction and the horizontal stresses are increased. This lateral expansion of the stone column can be simulated numerically, with the values of volume deformation which correspond to those observed in practice, and which can be connected with those usually adopted for the ratio between the modulus of the column and the reinforced ground. It is shown that this expansion induces a significant decrease in the stone columns.

5

Using Distance Functions to Solve Representation Choice Problems

Nguyen N.T.

Fundamenta Informaticae

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2001

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Vol. 48, nr 4

295-314

EN

A representation choice problem is based on the selection of an object (or objects), which should at best represent a given set of objects. In this paper we propose to solve this problem by using distance functions between objects. These distance functions are used to define representation choice functions. Six postulates for representation choice functions are given and their analysis is presented. The theoretical results provide us with some interesting relationships between classes of choice functions specified by the accepted postulates. They also make it possible to specify essential properties of considered choice functions. In particular, it has been proved that in practical settings it is suggested to use functions from two particular classes, for they preserve important features. Less popular representation choice functions are also pointed at and analyzed.

6

Reconciling inconsistent profiles of agents' knowledge states in distributed multiagent systems using consensus methods

Katarzyniak R. P., Nguyen N. T.

Systems Science

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2000

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Vol. 26, nr 4

93-119

EN

In this paper, a partial model of a multiagent system is presented. This multiagent system is built of agents that use consensus methods to construct and update their knowledge of recognizable world states. Each agent in this system encapsulates a private database containing representations of empirically verified parts of knowledge of experienced world states (so-called encapsulated world profiles). In each agent and for each object of the world, this knowledge is computed by the agent as the consensus of encapsulated update resources. These update resources consist of the agent's perceptions of the object and similar perceptions communicated to the agent by other members of the same multiagent population. An example of encapsulated update resources is given and a list of related requirements for consensus computation is discussed.