Rectangular Grid System Research Articles

A Numerical and Experimental Study of Bow Flare Slamming

A numerical method is developed to simulate the bow flare slamming of fast ships. Curved ship body boundary is represented by the Porocity method within the constraints of a rectangular grid system. Numerical simulations are conducted using a cross section of a typical container ship with a large bow flare and the simulations are compared with model experiments. The results of the computed and measured pressure histories are comparable. Conventional slamming theories based on self-similarity, on the other hand, fail to predict the measured pressure on the flare. From the experiments and simulations the authors found that high pressure persists for a long duration of time without any sharp peak on the bow flare. Large scale structural damage might be caused by this pressure since it increases simultaneously over an extensive area on the flare when the upper part of the flare comes into contact with water.

Modernization and Rural Development Strategies: A Case Study of a South Indian Village

In 1950, the small market village of Narayanadevarakere in Karnataka state, India, was relocated because its site was to be submerged by the Tungabhadra Dam reservoir. The villagers were given the choice of moving to one of two villages: Mariyammanahalli or Hagaribommanahalli. The villagers were assured of a plot of land or a home at practically no cost irrespective of whether they had been owners or tenants previously, and they were given a small relocation allowance. Both villages were laid out in a rectangular grid system of streets, and the government prebuilt the minimum infrastructure: roads, minimum public sanitation and drainage, a market, and a bus terminus. The choice as to where the villagers were to go was entirely voluntary. During the past 30 years, with national and local planning and development, there have been significant economic and social changes in the village of Hagaribommanahalli. Some of the more important elements are several new factories and workshops, new enterprises, repair shops, a regulated market, banks, increased transport service, and new schools and hospitals. A new political administrative unit located its headquarters in this new village. It is presumed that all these improvements have increased its economic activity, provided more educational and health care opportunities, created new jobs and a happier life in general. This article focuses on the longitudinal process of the 30-year overall rural development of the

Generalized prediction model of the induction motor (abstract)

The aim of the project is to develop an electromagnetic-field model of a three-phase induction motor in order to determine the flux distribution under various conditions of load, calculate certain saturation factors, predict the performance characteristics of the motor, and be able to modify the design for optimization. A mathematical model, established under certain simplifying magnetostatic assumptions, is treated as a boundary-value problem governed by nonlinear partial differential equations of the elliptic type in terms of the magnetic vector potential. A combination of different rectangular and polar grid systems is used to follow closely the contours of the steel-laminated punchings of the induction motor. The nonlinearity of ferromagnetic materials is duly taken into account. Numerical analysis consisting of iterative procedures, relaxation techniques, and difference schemes is applied for the computer-aided solution. Computer programs in fortran iv language have been developed and run successfully for the case of a 6-hp, 220-V, 3450-rpm, 60-Hz, 3-phase, 2-pole squirrel-cage induction motor. Further work is under way in order to consider the nonisotropic material properties of grain-oriented sheet steels, include the eddy-current and three-dimensional effects, and also extend the methods for the analysis of single-phase induction motors.

Prediction of flux distribution as a means to nondestructive testing of oil-pipe materials (abstract)

The flux distribution for a given excitation is determined in the cross section of an oil pipe, in its interior and exterior regions, in order to utilize this information eventually for the nondestructive testing of the material of the pipe. A two-dimensional mathematical model is established under certain simplifying assumptions and the grid system is laid out for numerical analysis. The relevant partial differential equations of the magnetic vector potential as well as their difference algorithms are developed. An innovative combination of rectangular and polar grid systems is used to follow the contours of the cross section consisting of the oil pipe and the excitation mechanism made up of a core, coil, and two steel brushes. The reluctivity of ferromagnetic materials is assumed to be a function of the magnetic induction. An iterative procedure consisting of successive-point relaxation of vector potentials with an optimum over-relaxation factor, a block-relaxation method for accelerating the convergence, relaxation of reluctivities with an optimum under-relaxation factor, and a constant monitoring of the convergence of the sum of absolute values of residuals as well as of the absolute value of the maximum residual is described. Computer programs in fortran language are developed and applied to find the flux distribution inside and outside the cross section of the oil pipe for various excitation-current densities. Analytical results are compared with experimental data. Refined analyses including eddy-current and three-dimensional effects are under way.

流れ計算のための航空機外郭と物理空間の計算格子

For the purpose of numerical analysis of threedimensional compressible steady flow around an airplane, it is necessary to find quantitatively local positions of an out surface of the airplane and local directions of the surface in a rectangular computational grid system in physical space. The out surface of airplane is made up of many elements of small triangular planes. The local positions of the out surface in the grid system are determined by local intersections of axes of the grid with these triangular planes. Directions of the triangular planes are substituted for the local directions of the out surfaces. Using these results, views of the out surface of airplane are drawn in sheets of paper.

Correcting for the Edge Effect in Density Estimation: Explorations around a New Method

Edge effect denotes that animals trapped in a grid stem are caught in border traps at disproportionately high frequencies. This is presumed due partly to home ranges overlapping the grid and partly to immigration onto the grid after depletion of population. A new method of correcting for this edge effect is developed. It consists of two steps the first of which is essentially to correct for the edge effect while the second estimates the number of true residents on the grid area. The second step may be replaced by any alternative method of estimating the number in a closed population, if the assumptions are met. No special trapping design is required; the method needs only a andard square or rectangular grid system of trap station. This feature is of prime importance since this method is thus applicable to data derived from the most common type of trap design. By using data from various small mammal studies in Scandinavia, the method is demonstrated to fit data and to work. From the total number of animals caught on a trapping grid, the edge effect is estimated to account for up to 65%.

Optimal spacings for a rectangular grid transportation network—I: A hierarchy structure

An idealized rectangular grid transportation network is considered for serving a uniformly developed urban area in which trip origin-destination characteristics are translationally symmetric. The object is to choose the spacings between different types of roads so as to minimize the sum of travel and construction costs, subject to the hypothesis that travelers choose routes of (approximate) minimum travel costs. It is shown that rectangular grid systems are, generally, superior to square grids and that an efficient network will contain a hierarchy structure. Estimates are made of the spacings between roads in each direction and in each hierarchy.

Planning Major Activity Center Distributor Systems

Automobile and transit trips destined to a major activity center terminate at peripheral locations, and each tripmaker completes the journey either by transferring to a distributor system or by walking. The mode by which each traveler completes his journey is specified as that which requires least travel time. The major activity center is represented by a two-dimensional, rectangular coordinate grid system and trip end data are assigned to each node. Optimum station locations are tested in relation to the grid reference. Since exhaustive search of all possible station location combinations for a generalized system consisting of k stations is computationally infeasible, a random search method is described for a major metropolitan CBD. The results of the study indicate that for this type of transportation system a relatively small amount of input data can be efficiently utilized to render a comprehensive systems analysis.

Archaeological Use of the Universal Transverse Mercator Grid

AbstractThe Universal Transverse Mercator Grid is a rectangular grid system now used on all standard military maps. Archaeologists could use this system for site location, which would prove especially beneficial in areas where townships and range grids have not been drawn. The use of the series of numbers in the system would help eliminate duplication in state or regional site files.

Trend analysis of geophysical data

Trend analysis of aeromagnetic data has been treated in a few publications during recent years. In this paper a short review is given of the methods used and results from comparisons between different methods. It is attempted to make a more general use of one of the methods presented—the triangle method—on all sorts of geophysical data, including terrain analysis. By the aid of a computer programme for rectangular grid systems the trend analysis is easily performed. The results are given as frequency polygons and polar diagrams, and a discussion is made over the reliability of the resulting frequencies. The amount of information from one analysis can be increased by using two different lengths of the class intervals and by operating with two grid spacings. The triangle method is tested with random and dependent data. Finally an example related to the treatment of gravimetric, magnetic, and topographic maps over a small survey area is presented.

Rectification of Oblique Photographs to Obtain Base-Surge Contours

Rectification of oblique aerial photographs is one means used to obtain contours of the base surge formed by an underwater nuclear explosion. An analytic photogrammetric method of rectification, based on the visible horizon and altitude of the photo aircraft, is described. This method gives the position of any point on the photograph in terms of its coordinates in a rectangular grid system on the water surface. The supplemental information needed to rectify an oblique photograph also is discussed.

The Use of Photographic Triangulation in Determining the Positions of Objects in Large-Scale Experiments

The positions of objects relative to the point of an explosion are often determined by means of photographic triangulation. A computer program has been developed to locate the positions of these objects in terms of their coordinates in a rectangular grid system. The experimental program for which the computer program was developed is described and the principles of photo triangulation, the computer program and the results obtained are discussed.