Łukasz P. Szwed, Ewa Tomaszewska-Ciosk and Józef Błażewicz
Malt extracts and malt concentrates have a broad range of application in food industry. Those products are obtained by methods similar to brewing worts. The possible reduction of cost can be achieved by application of malt substitutes likewise in brewing industry. As the malt concentrates for food industry do not have to fulfill strict norms for beer production it is possible to produce much cheaper products. It was proved that by means of mathematic optimization it is possible to determine the optimal share of unmalted material for cheap yet effective production of wort.
Exploration of the structural balance of social networks is of great importance for theoretical analysis and practical use. This study modeled the structural balance of social networks as a mathematical optimization problem by using swarm intelligence, and an efficient discrete particle swarm optimization algorithm was proposed to solve the modeled optimization problem. To take advantage of the topologies of social networks in the algorithm design, the discrete representation of the particle was redefined, and the discrete particle update principles were redesigned. To validate the efficiency of the proposed algorithm, experiments were conducted using synthetic and real-world social networks. The experiments demonstrate that the proposed algorithm not only achieves a balanced social network structure, but also automatically detects the community topology of networks.
A method for selection of parameters of ship propulsion system fitted with compromise screw propeller
This paper concerns an algorithmic method for preliminary selection of parameters of ship propulsion system fitted with fixed screw propeller in the case when the ship's operation is associated with significant changes of waterway depth and width, hull resistance of the ship and its service speed. Mathematical model arguments of the considered design problem are main ship design parameters identified in the preliminary design stage. Structure of the formulated model complies with formal requirements for continuous- discrete mathematical optimization problems. The presented examples of application of the method concern an inland waterways ship fitted with compromise screw propeller optimized in the sense of minimization of fuel consumption for passing a given route distance within a given time. The elaborated method may be especially useful in designing such ships as: coasters, inland waterways ships, tugs, pushers, trawlers, mine sweepers, icebreakers etc.
The first step in the transformer design process is to find the active part’s key design parameters. This is a non-linear mathematical optimisation task, which becomes more complex if the economic conditions are considered by the capitalisation of the losses. Geometric programming combined with the method of branch and bound can be an effective and accurate tool for this task even in the case of core-form power transformers, when formulating the short-circuit impedance in the required form is problematic. Most of the preliminary design methods consider only the active part of the transformer and the capitalised costs in order to determine the optimal key design parameters. In this paper, an extension of this meta-heuristic transformer optimisation model, which takes the cost of the insulating oil and the cooling equipment into consideration, is presented. Moreover, the impact of the new variables on the optimal key design parameters of a transformer design is examined and compared with the previous algorithm in two different economic scenarios. Significant difference can be found between the optimal set of key-design parameters if these new factors are considered.
The Bistrita city bypass crosses obliquely at km 14+162 the Bistrita river and a local road. In the area where the bridge is situated the river has a width of about 50.00m and the local road has 5.00m, being located at 12.00m from the bank of Bistrita. The bridge should provide a roadway that is 7.80m wide and two sidewalks of 1.50m.
The challenge is to design a bridge that allows the crossing of the two barriers (the river and the local road) in the most efficient way possible from an economical point of view, but in such a way that both the geometrical constraints and the design requirements contained in the family of the European standards Eurocodes are respected.
In order to achieve this goal, the author has investigated the design situation by comparing different possible technical solutions, by conducting a series of parametric studies and by utilizing mathematical optimization techniques.
Following these investigations a 100.00m long bridge resulted. The superstructure is a continuous beam with three spans: 20.00m + 60.00m + 20.00m and consists of a composite steel - concrete deck. The deck cross section is composed of two steel beams with variable height and a reinforced concrete slab disposed on top. This configuration of the superstructure leads to the development of negative reaction forces in the bearings located at the end points of the deck.
The study has covered 8 key steps as follows:
- Establishing the technical solution.
- Establishing the number and the length of the spans.
- Setting the static scheme.
- Determining the optimal cross section of the steel beams.
- Setting longitudinal beam geometry.
- Establishing the number of beams in the cross section.
- Determining the optimal mounting order of the concrete slabs.
- Establishing the optimal type and distribution of the bearing devices.
In this article, the impact of selected parameters of heating using a gas torch on the hardness of hardened alloy steels C45 was presented. The staff of the ship’s engine room sometimes uses flame hardening during casual repairs of the machines weared as a result of operational extortions. The purpose of emergency repairs is to restore the possibility of work of ship machinery and equipment for the duration of the vessel’s journey. An acetylene-oxygen torch was used to heat the steel. As the analysed parameters of the technological process, the heating time and the distance between the nozzle and the workpiece were selected. The values of the mentioned parameters have been selected so that the temperature of hardened steel is in the range from 800 to 1250 °C. The following values of the adopted machining parameters were used: the heating time was 60, 85 and 110 seconds, while the distance of the torch nozzle was 10, 20 and 30 mm. After heating, the samples were cooled by immersing in water. The research was based on a randomized orthogonal experiment plan. The purpose of the quantitative assessment of the influence of heating parameters on the hardness of hardened C45 steel, done statistical analysis variance analysis, multiple regression and mathematical optimization by the Tagichi method. Conducted tests and statistical analysis showed a significant effect of selected parameters of flame heating on the hardness of hardened C45 steel. The greatest influence on the hardness of the steel is the distance between the nozzle and the workpiece. The highest value of hardness was obtained using the following parameters of flame hardening: nozzle distance 30 mm, heating time 60 seconds.
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