Directional difference chain codes with quasi-lossless compression and run-length encoding

This paper considers a new contour-based representation of binary objects in raster images. Low processing and storage requirements of the decoder, satisfactory compression ratio and generality make this chain coding technique interesting for storing predefined graphical objects in embedded systems. Three improvements of the DDCC code were introduced. Extra Huffman codes are assigned to two frequent pairs of symbols, 135° directional differences in concave angles are omitted since they do not affect the outer object shape and, finally, longer line segments are run-length encoded. Comparison with six other chain coding techniques of similar implementation complexity confirms that the new technique represents an efficient alternative way to encode 8-connected contours.     

Fuzzy control for the illumination and temperature comfort in a test chamber

The paper deals with the controlled dynamic thermal and illumination response of human-built environment in real-time conditions. The aim is to harmonize the thermal and optical behavior of a building with regulated energy flows through the envelope. A control system with fuzzy elements for changeable transparent elements of the building envelope was developed. For this purpose a test chamber with an opening on the south aside was built. Energy flows through the envelope are controlled with changeable geometry of the window, realized with the external roller blind, which is automatically positioned. The fuzzy controller for the corresponding positioning of the roller blind in a given combination of outside conditions as external disturbances is the subject of this paper.     

Hybrid fuzzy predictive control based on genetic algorithms for the temperature control of a batch reactor

In this paper we describe the design of hybrid fuzzy predictive control based on a genetic algorithm (GA). We also present a simulation test of the proposed algorithm and a comparison with two hybrid predictive control methods: Explicit Enumeration and Branch and Bound (BB). The experiments involved controlling the temperature of a batch reactor by using two on/off input valves and a discrete-position mixing valve. The GA-hybrid predictive control strategy proved to be a suitable method for the control of hybrid systems, giving similar performance to that of typical hybrid predictive control strategies and a significant saving with respect to the computation time.     

Quantitative assessment of thermal–hydraulic codes used for heavy water reactor calculations

The RD-14M large LOCA test, characterized by a reliable set of experimental data, was selected for an international standard problem exercise (SPE) entitled “Intercomparison and validation of computer codes for thermal–hydraulics safety analyses”. The activity was performed within the frame of International Atomic Energy Agency's (IAEAs) Technical Working Group on Advanced Technologies for Heavy Water Reactors (TWG-HWR). In this study, the recently improved fast Fourier transform based method (FFTBM) was used for accuracy quantification of RD-14M large LOCA test B9401 calculations of six participants using four different thermal–hydraulic codes. In addition, developing the capability to calculate the accuracy as a function of time-continues-valued accuracy, did further improvement of FFTBM. Namely, in the past only single valued accuracy parameters for selected time windows and time intervals were calculated. The objective of the study was to demonstrate that the new FFTBM is a powerful tool for quantitative assessment of thermal–hydraulic codes. For demonstration, the test from the facility simulating heavy water reactor was used. The blind accuracy analysis was completed based on solely experimental and calculated data. However, short discussions were held with the representative from Italy (co-author, here) regarding phenomenological windows, variables and void fraction weights selection. In general, the open accuracy analysis confirmed the results obtained in blind accuracy analysis. The main conclusions from accuracy analysis agree with the conclusions from the SPE intercomparison report, which was written independently. Finally, the results suggest that the accuracy of the best calculations of the RD-14M test is comparable with the best calculations of light water reactor experiments.     

Hierarchic modeling of heat transfer processes in heat exchangers

An alternate approach based on hierarchic modeling is proposed to simulate fluid and heat flow in heat exchangers. On the first level, the direct simulations have been performed for the geometry that is similar to a segment of the examined heat sink. Based on the obtained results, the Reynolds number dependencies of the scaling factors f and StPr^2/3 have been established. On the second level, the integral model of the whole heat sink has been built using the volume averaging technique (VAT). The averaging of the transport equations leads to a closure problem. The direct model Reynolds number dependencies f and StPr^2/3 have been used to calculate the local values of the drag coefficient and the heat transfer coefficient , which are needed in the integral model. The example calculations have been performed for 14 different pressure drops across the aluminum heat sink. The whole-section drag coefficient and Nusselt number have been calculated and compared with the experimental data [M. Rizzi, M. Canino, K. Hu, S. Jones, V. Travkin, I. Catton, Experimental investigation of pin fin heat sink effectiveness, in: Proc. of the 35th National Heat Transfer Conference Anaheim, California, 2001]. A good agreement between the modeling results and the experiment data has been reached with same discrepancies in the transitional regime. The constructed computational algorithm offers possibilities for geometry improvements and optimization, to achieve higher thermal effectiveness.     

Zur Optimierung der Gasreduktion-Eisenschwamm-Verfahren

Vergleich des Wärmebedarfs der Roheisenherstellung im Hochofen und der Eisenschwammerzeugung. Ermittlung des theoretischen Stoff- und Wärmeumsatzes der Gasreduktion-Eisenschwamm-Verfahren. Kennzeichnung der optimalen Arbeitsweise im Schachtofen und bei der Reduktionsgaserzeugung. Erörterung der Entfernung von Wasserdampf und Kohlendioxid aus dem Gaskreislauf. Beispiele optimal arbeitender Gasreduktion-Eisenschwamm-Verfahren mit unterschiedlichen Gaserzeugern.     

Point-in-polygon tests for geometric buffers

The point-in-polygon problem is often encountered in geographical information systems. The algorithms usually work on polygons defined by straight edges. In some situations, however, polygons containing circular arcs are applied. In geographical information systems these polygons are usually considered as geometric buffers, geodesic offsets, or geodesic parallels. This paper presents three algorithms suitable for providing information about the containment of a point in geometric buffers: the Ray-crossing method, the Cell-Based Algorithm and the Approximate approach. An extensive experimental section allows the reader to select the most efficient algorithm for practical problems.     

Hybrid Fuzzy Modelling for Model Predictive Control

Model predictive control (MPC) has become an important area of research and is also an approach that has been successfully used in many industrial applications. In order to implement a MPC algorithm, a model of the process we are dealing with is needed. Due to the complex hybrid and nonlinear nature of many industrial processes, obtaining a suitable model is often a difficult task. In this paper a hybrid fuzzy modelling approach with a compact formulation is introduced. The hybrid system hierarchy is explained and the Takagi–Sugeno fuzzy formulation for the hybrid fuzzy modelling purposes is presented. An efficient method for identifying the hybrid fuzzy model is also proposed. A MPC algorithm suitable for systems with discrete inputs is treated. The benefits of the MPC algorithm employing the hybrid fuzzy model are verified on a batch-reactor simulation example: a comparison between the proposed modern intelligent (fuzzy) approach and a classic (linear) approach was made. It was established that the MPC algorithm employing the proposed hybrid fuzzy model clearly outperforms the approach where a hybrid linear model is used, which justifies the usability of the hybrid fuzzy model. The hybrid fuzzy formulation introduces a powerful model that can faithfully represent hybrid and nonlinear dynamics of systems met in industrial practice, therefore, this approach demonstrates a significant advantage for MPC resulting in a better control performance.