Dynamic Simulation of Radially Oriented Permanent Magnet-Type Electronically Operated Synchronous Machines with Parameters Obtained from Finite Element Field Solutions

A dynamic model for simulation of the transient interaction between radially oriented permanent magnet-type synchronous machines and their corresponding transistorized current source power conditioners is presented. Some key machine parameters used in this dynamic model were obtained from finite element field solutions. This dynamic model was used to obtain the transient interaction between a 15-hp samarium cobalt radially oriented permanent magnet electronically operated synchronous machine and its corresponding power conditioner. This machine was constructed for electric vehicle propulsion. Excellent correlation between various digitally simulated and actual test current and voltage waveforms, in various branches of the machine-conditioner network, has been achieved. These results are given. This modeling approach is applied to machines during the design stage, where the finite element modeling is the only way to obtain the necessary machine parameters for dynamic simulation. It is shown how such a combination of the computer-aided design tools can help in prevention of design mis-judgements that can prove costly to remedy once the hardware is in place. This is done through an actual design example of an additional machine being manufactured for electric propulsion applications.     

Three-Electrode Organic-Type G.M. Counter Design and Performance

The sensitivity of the organic-type G.M. tube is increased by introducing a third electrode (grid) between the cylindrical steel cathode and a concentric tungsten wire anode and applying positive potential to that grid. The optimum position of the grid inside the cathode corresponding to the minimum capacitance of the counter is determined by using the simulation technique. Plateau curves of this tube are obtained for different grid positions. It is justified that the best performance of the tube is determined with the optimum grid position. Plateau curves of the three-electrode G. M. tube are also reported, with optimum grid position, for different values of grid potential. It is found that the sensitivity of the counter can be controlled by variation of the grid potential.     

Application of nanostructured titanium dioxide pigments in paper coating: a comparison between prepared and commercially available ones

Nano-TiO₂ pigments in pure crystallographic anatase and rutile phases have been successfully prepared by hydrothermal at 120°C and hydrolysis methods, respectively. The laboratory-prepared pigments were characterized parallel to two commercial pigments of the same crystal structure. All pigments were applied in paper coating mixtures, and their influence on coated paper properties was systematically investigated. X-ray diffraction investigation showed that the laboratory-prepared pigments using the hydrothermal method at 120°C were pure anatase, whereas hydrolysis method produced pure rutile phase pigment. The application of the prepared nanopigments and the corresponding commercial TiO₂ phases in paper coating revealed that clay/rutile nano-TiO₂ pigments in paper coating mixture decreased coated paper roughness more than blending clay with anatase nano-TiO₂ pigments. Commercial nano-TiO₂ pigments increased porosity of coated paper at both the 30% and 50% addition of nano-TiO₂ pigments to clay, while laboratory-prepared nano-TiO₂ pigments highly decreased it at 30% addition of nano-TiO₂ to clay, compared to clay only. Blending of clay/nano-TiO₂ pigments improved both brightness and opacity of the coated paper where commercial pigments are more effective. Burst, tensile strength, stretching, and TEA were improved in the case of all pigments. The 50% addition of the prepared and commercial nanopigments in conjunction with clay improved the mechanical coated paper properties more than 30% addition (except the cases of stretching and TEA of the commercial pigments). The coated paper samples were offset printed. It was found that blending of clay/nano-TiO₂ pigments improved print density. Commercial nano-TiO₂ pigments improved print gloss more than the laboratory-prepared ones. This result was found consistent with the results of coated paper roughness.     

Regulator problem for uncertain linear discrete-time systems with constrained control

A necessary and sufficient condition to test the robustness of a regulator of uncertain linear systems with constrained control is given. The candidate regulator for this test is that stabilizing nominal systems. An illustrative example is also given.     

Hierarchical Reliable Multicast: Performance Analysis and Optimal Placement of Proxies

This paper studies the use of multicast together with proxy nodes for reliably disseminating data from a single source to a large number of receivers. In order to achieve reliability, data must be retransmitted in case of loss either by the source or by special network nodes, called proxies. Each proxy is responsible for reliably delivering the data to a subgroup it is assigned. The multicast tree is partitioned into subgroups that form a hierarchy rooted at the source, hence the term hierarchical reliable multicast. The performance of this approach strongly depends on the topology and the loss characteristics of the underlying tree and the location of proxies. In the first part of the paper, we study the processing and bandwidth performance of such a reliable multicast dissemination given the tree and the placement of proxies. In the second part of the paper, we develop dynamic programming algorithms that give a placement of a fixed number of proxies on an arbitrary tree that minimizes the bandwidth used for reliable transfer. The first algorithm provides an optimal solution to the multicast proxies location problem in polynomial time, in the number of nodes and proxies. The second is an approximation algorithm that gives a solution with cost within a chosen precision from the optimal, in an improved running time. An optimal and an approximate solution are also provided for the proxies location problem if unicast is used for transmissions. Applications of this dynamic programming approach to related problems are discussed.     

Embedding requirements within Model-Driven Architecture

Model-Driven Architecture (MDA) brings benefits to software development, among them the potential for connecting software models with the business domain. This paper focuses on the upstream or Computation-Independent Model (CIM) phase of MDA. Our contention is that, whilst there are many models and notations available within the CIM phase, those that are currently popular and supported by the Object Management Group (OMG) may not be the most useful notations for business analysts nor sufficient to fully support software requirements and specification. Therefore, with specific emphasis on the value of the Business Process Modelling Notation (BPMN) for business analysts, this paper provides an example of a typical CIM approach before describing an approach that incorporates specific requirements techniques. A framework extension to MDA is then introduced, which embeds requirements and specification within the CIM, thus further enhancing the utility of MDA by providing a more complete method for business analysis.     

Managing a hybrid energy smart grid with a renewable energy source

The aim of this work is to develop tools for optimal power flow management control in a micro grid (MG). The latter consists of a wind turbine, energy storage system, two gas turbines (GTs), and the main grid. Unlike the traditional approach, which is limited to the distribution of active power, this paper models an electrical system to coordinate and optimize the flow of both active and reactive power using discrete controls. The proposed optimal power distribution strategy has two objectives. First, it aims at forecasting over a time horizon of 24 hours the optimal distribution of the active and reactive power required for each power source connected to the MG. The proposed management incorporates the forecasts of consumption, weather, and tariffs. Second, it aims at reducing the CO₂ emissions rate by optimizing both the operating point of the two GTs and the usage of the storage unit. The proposed optimization problem for the energy management system is solved using the Bellman algorithm through dynamic programming. Its effectiveness is illustrated with various simulations carried out in the Matlab environment. The supremacy of the proposed management algorithm is highlighted by comparing its performance with conventional (restricted) management.