A theoretical approach to the kinetics of calcite ⇌ aragonite transition: application to laboratory experiments

A theoretical approach to the calcite ? aragonite transformation is presented for the case of a dislocation glide mechanism obeying first-order kinetics. The kinetic parameters are determined from recent experimental data from the literature; the sensitivity of the model to these and other parameters like the grain size and the deviatoric stresses are discussed.The model results in the definition of what could be the actual transformation domains of the CaCO₃ polymorphs in the (P,T) plane. These domains are different from the classical ones, i.e. different from the stability fields defined with respect to Clapeyron's curve; they can evolve in the (P,T) plane when a deviatoric stress is applied to the system. In this case, we can define a domain in which the two senses of the calcite ? aragonite transition are activated simultaneously.The application of the model to laboratory experiments needs the integration of the kinetic differential equation (K varying withP andT). Using this method, we demonstrate the role of (P,T,t) path on reaction rate and the role of experimental uncertainties on the reaction parametersK andn.Finally, we discuss the problem of the synthesis of polymorphs out of their stability field and of their formation by grinding; these problems, difficult to tackle in terms of diffusion, can be approached with the proposed dislocation transformation kinetic model.     

Regional and urban population size weights in Saudi Arabia, 1962–1974

The aim of this paper 3s to study the development of population weights for regions and urban centres in Saudi Arabia through the period 1962–1974. In order to achieve this aim some non-parametric statistical rules have been used such as rank-size rule and the four-city index. The results show non-balanced distribution of population on both regional and urban scales. The concentration of people in urban centres is more pronounced than the concentration in regions. This is due to internal and external movement of population towards largesized urban centres. The paper recommends that the official authorities should give more consideration to economic and service development in rural and urban areas that are retreating in ranking and decreasing in population.     

Geographic analysis of manufacturing industry in Saudi Arabia

The study focuses on the analysis of manufacturing industry in Saudi Arabia by examining development, structure and spatial distribution. The analysis has shown that Saudi manufacturing is basically of recent development and is highly capital- and energy-intensive, particularly the hydrocarbon-based groups. Perhaps the most conspicuous weakness of Saudi industrialization is the almost total dependence on expatriate labour. Foreign capital and expertise share in the building and development of the industrial sector by providing technical, managerial, and marketing skills. Saudi industry is heavily subsidized by the government, and the public sector plays a commanding role in industrial development. Large-scale basic industries are owned and run by the government, while light manufacturing of the import-substitution type is dominated by the private sector. One of the main characteristics of manufacturing industry is that it is scantily diversified, modestly concentrated and remarkably linked geographically but not functionally or structurally. Although the authorities are exerting tremendous efforts to achieve a regional balance in industrial development, Saudi manufacturing industry is significantly polarized, urban-oriented and highly associated with the major axes of population scatter. Like all developing countries beginning to industrialize, Saudi manufacturing industry faces certain problems which have to be resolved so as to lay the foundations for a sound and prosperous industrial future. The paper goes on to indicate problems and to suggest solutions.     

TEM investigation of the crystal microstructures in a quartz-coesite assemblage of the western alps

Atransmission electron microscope (TEM) study of quartz-coesite inclusions in garnet in crustal rocks from the Western Alps is presented. Coesite shows a low dislocation density (<10⁷ cm^?2), and quartz a higher density of defects, Brasil twins (10⁴ cm^?1) and dislocations (10⁸ cm^?2). It is concluded that coesite has been not or only slightly plastically deformed and that the yield strength of coesite is higher than that of quartz. The large scale deformation implications are briefly discussed. TEM observations show no systematic topotactic relationship between the two polymorphs and their boundaries have a scalloped morphology which suggests that growth of quartz from coesite was controlled by a diffusion process.     

Planning in Nigeria: The agricultural base 1962–1985

This paper critically examines some of the causes and the problems of agricultural development in Nigeria. It also discusses very minimally, the rise and the contribution of the petroleum industry to the Nigerian economy and its effect on the agricultural sector. Finally, some possible suggestions are made in order to ameliorate the situation of agriculture and to overcome the shortage of food production in the country.     

Is there any hope for agriculture in California's rapid growth areas?

The experience of San Diego County, California, indicates that none of the commonly used legislative methods of preserving valuable agricultural land (large lot zoning, differential taxation, purchase or transfer of development rights, creation of exclusive agricultural districts) may be successful in very rapidly urbanizing metropolitan areas. Unless a local municipality can purchase the land outright, the profits to be made from selling greatly appreciated suburban land for development will tempt even the most dedicated farmer to sell and seek out less vulnerable land elsewhere. Steps such as large lot zoning need to be taken early to keep large blocks of agricultural land intact, the retention of these lands must be made part of a mandatory rather than a voluntary program in order to be successful, and the local jurisdictions must be sure that adequate economic incentives are available for those persons who do wish to continue farming the land.     

The Integration of Cooperation Model and Genetic Algorithm

In the photogrammetry,some researchers have applied genetic algorithms in aerial image texture classification and reducing hyper-spectrum remote sensing data.Genetic algorithm can rapidly find the solutions which are close to the optimal solution.But it is not easy to find the optimal solution.In order to solve the problem,a cooperative evolution idea integrating genetic algorithm and ant colony algorithm is presented in this paper.On the basis of the advantages of ant colony algorithm,this paper proposes the method integrating genetic algorithms and ant colony algorithm to overcome the drawback of genetic algorithms.Moreover,the paper takes designing texture classification masks of aerial images as an example to illustrate the integration theory and procedures.     

Shape Similarity measures of Linear Entities

The essential of feature matching technology lies in how to measure the similarity of spatial entities.Among all the possible similarity measures,the shape similarity measure is one of the most important measures because it is easy to collect the necessary parameters and it is also well matched with the human intuition.In this paper a new shape similarity measure of linear entities based on the differences of direction change along each line is presented and its effectiveness is illustrated.     

Possibilities of GPS Kinematic Measurements for Geological Survey in East Slovakia

This paper deals with transformation procedures for observed GPS data from the world geodetic system WGS-84 into the national geodetic grid datum S-UTCN(system of united trigonometric cadaster network) and Baa(the Baltic Sea after adjustment).Transformation from WGS-84 into SUTCN is performed most frequently by means of the 7-element Helmert transformation with three identical points.Geodetic network was adjusted by two ways.