Effect of Grid Resolution and Terrain Characteristics on Data from DTM

Previous work in digital terrain modeling (DTM) has shown that if regular gridded-data sets are used in the construction of the model, both the resolution of the gridded-data set and the characteristics of the terrain being modeled have an effect on the accuracy of digital terrain models. The main objective of this study is to test the hypothesis that both the resolution of the gridded-data set and the characteristics of the terrain being modeled have an effect on the accuracy of any derived data. To test this hypothesis, the terrain was classified in terms of its roughness. Various forms of data were derived from the terrain model; these include volumes, surface area, contours, and cross sections. The accuracy for each of these quantities was calculated by comparing them with values obtained from a control model. This research concluded that by both increasing the resolution of the regular gridded-data sets and varying the characeristics of the terrain, the accuracy of any derived data is affected.     

The effect of coupling in a compact handset receiver

This paper deals with the performance of a compact dual diversity receiver. For this study we assume that the channel is characterized by a flat Rayleigh fading and that the incoming waves can be described by a Gaussian angular power distribution. The performance of a maximal-ratio-combiner in a correlated Rayleigh fading is given. These expressions are simplified and studied for the case of a dual diversity receiver. The influence of the mutual coupling between the sensors is taken into account using a simplified model. The results are compared with results obtained from realistic antenna simulations.     

Electrical and photoluminescence properties of evaporated CuIn1−xGaxTe2 thin films

Polycrystalline thin films of CuIn_1−xGa_xTe₂ have been deposited by flash evaporation on Corning glass 7059 substrates at T_s=200°C. Hall and resistivity measurements have been carried out down to 77 K. These films are p-type and the variation of the resistivity may be linked to defects, disorder of the material or grain boundaries. The PL spectra of these films after annealing in argon atmosphere at T_a=450°C have showed a broad band emission between 0.98 and 1.12 eV in which the main peak appears at 1.05 eV (at 4.2 K).     

Contribution study of properties of copper indium diselenide thin films

Stoichiometric powder of CuInSe₂ (CIS) was prepared from molten stoichiometric quantities of the elements. The structure analyzed by X-ray diffraction powder (XRD), shows mainly the chalcopyrite phase. CIS polycrystalline thin films deposited from this powder have been grown on glass substrates in vacuum by thermal evaporation method. The structural and electrical properties of both as-deposited and annealed films were studied using X-ray diffraction and dark conductivity measurements respectively. As-prepared films at room temperature showed an amorphous structure. However, the chalcopyrite structure with (112) preferential orientation was observed after annealing in vacuum at 400 °C during 30 min. The influence of the annealing process on the dark conductivity of the films was also discussed.     

An analysis of piecewise homogeneous dielectric rod antennas

The radiation characteristic of piecewise homogeneous dielectric rod antennas is studied by using the volume equivalence principle. Experimental results are presented for comparison.     

Étude d’antennes disques imprimées à accès multiples

The cavity model is used to determine the impedance matrix of microstrip multiport circular antennas and their radiation pattern. A new very simple method of losses evaluation is proposed for calculating the impedance matrix elements. The model is then tested successfully on a threeport circular antenna, and the dualfrequency operation of such an antenna is verified theoretically.     

Trends of 4D CAD applications for construction planning

Since the early 1990s, there has been a growing interest in four‐dimensional computer aided design (4D CAD) for construction project planning. Commercial 4D CAD applications are becoming more accessible and the use of this technology allows the construction planner to produce more rigorous schedules. A review of the technical competencies of these packages highlights that most of the commercially available packages concentrate on the use of 4D CAD simulations for aesthetic visualization purposes. Very few packages offer the ability to carry out analytical tasks on the developed simulation and this is often left to the interpretation of the user. A thorough appraisal of emerging research developments in 4D planning highlights that this technology is employed for various applications; however, the amount of detail required in a 4D simulation is still ambiguous. A model is proposed to determine the attributes required for use with each of the various applications of 4D CAD simulations. Finally, various lines of future research are highlighted, including the need for improved use of data exchange standards and the automation of linking the construction tasks to the 3D CAD model.     

Providing real-estate services through the integration of 3D laser scanning and building information modelling

There is an opportunity for real-estate services sector to deliver more accurate, faster and quality building surveys and information models. This paper reports on a study, designed to establish automated procedures for the development of a digital model to assist in faster and better services and delivery of real-estate services by integrating 3D laser scanning and BIM technology. It proposes an intuitive and interactive building model that is easy to query and navigate, and thus support property developers, buyers and sellers in the property sales sector. An outline of the new approach is provided to illustrate the benefits of the proposed method to the real-estate services sector. The key arguments in the paper are consolidated by the results of a qualitative study amongst real-estate professionals, which sought to determine the added value of BIM-3D laser scanning in comparison to conventional building surveying and Computer Aided Design (CAD) methods.     

Analyse d’antennes diélectriques par une méthode de diffraction

In order to approach the radiation problem of dielectric antennas, the authors study the scattering of electromagnetic waves by heterogeneous dielectric obstacles situated in the near-field zone of a circular waveguide carrying the TE₁₁ mode. By making use of the polarisation current densities and the free-space Green’s function, the integral equation concerning the electric field inside the obstacle is derived and then solved by the moments method. Results on the scattering by bodies of various shapes and structures are given as a function of the distance between the waveguide aperture and the scatterer. Finally the method is tested on dielectric antennas, i.e., the structures for which this distance vanishes.     

A parallel FDTD algorithm using the MPI library

In this paper, we describe the essential elements of a parallel algorithm for the FDTD method using the MPI (message passing interface) library. To simplify and accelerate the algorithm, an MPI Cartesian 2D topology is used. The inter-process communications are optimized by the use of derived data types. A general approach is also explained for parallelizing the auxiliary tools, such as far-field computation, thin-wire treatment, etc. For PMLs, we have used a new method that makes it unnecessary to split the field components. This considerably simplifies the computer programming, and is compatible with the parallel algorithm