Two vibrating circular membranes radiate acoustic waves into the region bounded by three infinite baffles arranged perpendicularly to one another. The Neumann boundary value problem has been investigated in the case when both sources are embedded in the same baffle. The analyzed processes are time harmonic. The membranes vibrate asymmetrically. External excitations of different surface distributions and different phases have been applied to the sound sources’ surfaces. The influence of the radiated acoustic waves on the membranes’ vibrations has been included. The acoustic power of the sound sources system has been calculated by using a complete eigenfunctions system.
The primary aim of this research study was to model acoustic conditions of the Courtyard of the Gdańsk University of Technology Main Building, and then to design a sound reinforcement system for this interior. First, results of measurements of the parameters of the acoustic field are presented. Then, the comparison between measured and predicted values using the ODEON program is shown. Collected data indicate a long reverberation time which results in poor speech intelligibility. Then, a thorough analysis is perform to improve the acoustic properties of the model of the interior investigated. On the basis of the improved acoustic model two options of a sound reinforcement system for this interior are proposed, and then analyzed. After applying sound absorbing material it was noted that the predicted speech intelligibility increased from bad/poor rating to good category.
The ability of case-based reasoning systems to solve new problems mainly depends on their case adaptation knowledge and adaptation strategies. In order to carry out a successful case adaptation in our case-based reasoning system for a low frequency electromagnetic device design, we make use of semantic networks to organize related domain knowledge, and then construct a rule-based inference system which is based on the network. Furthermore, based on the inference system, a novel adaptation algorithm is proposed to derive a new device case from a real-world induction motor case-base with high dimensionality.
Both a classical instantaneous power method and a method based on equations of instantaneous power orthogonal components balance have been used to analyze power processes in electric circuits with semiconductor elements. Automated method of forming instantaneous power harmonic components was used to obtain analytical expressions and numerical values of instantaneous power components of analyzed electric circuits. A coefficient for estimation of a semiconductor converter nonlinearity degree has been offered.
The aim of the paper is to present the hydrodynamic, mass transfer and illumination characteristics of a laboratory helical-tube photobioreactor Biostat PBR-2S, commercially available and used in many laboratories in Poland and worldwide. The investigated hydrodynamics parameters were: mean liquid circulation rate, liquid velocity/residence time in the tubular part of the apparatus and mixing time, measured in the wide range of rotary speed of the circulation pump. The influence of the aeration intensity on these parameters was also checked. The volumetric oxygen and carbon dioxide transfer coefficients in the liquid phase and their dependency on the liquid circulation rate and gas inflow rate were determined. The experiments were performed in tap water and then in a real three-phase cultivation broth at the end of thermophilic cyanobacteria T. synechococus growth. For the final evaluation of the tested PBR there were series of test cultivations run under different conditions of illumination. The highest final concentration of the biomass of tested cyanobacteria reached the relatively high value of 4.38 g/dm3 of the dry biomass, although the process conditions were not fully optimized. The laboratory photobioreactor PBR-2S proved to be a good tool for investigations of microalgae cultivation processes. The presented results and practical observations may help to analyze and understand the mutual influence of the specific process parameters in the described PBR, especially during autotrophic organism cultivations.
The work concerns the dynamic behaviour of a porous, isothermal catalyst pellet in which a simultaneous chemical reaction, diffusion and adsorption take place. The impact of the reactant adsorption onto the pellet dynamics was evaluated. A linear isotherm and a non-linear Freundlich isotherm were considered. Responses of the pellet to sinusoidal variations of the reactant concentration in a bulk gas were examined. It was demonstrated that the dynamics of the pellet is significantly affected both by accounting for the adsorption and by the frequency of the bulk concentration variations. The sorption phenomenon causes damping of the concentration oscillations inside the pellet and damping of its effectiveness factor oscillations. Depending on the frequency of the concentration oscillations in the bulk, the remarkable oscillations can involve an entire volume of the pellet or its portion in the vicinity of the external surface.
Based on the publications regarding new or recent measurement systems for the tokamak plasma experiments, it can be found that the monitoring and quality validation of input signals for the computation stage is done in different, often simple, ways. In the paper is described the unique approach to implement the novel evaluation and data quality monitoring (EDQM) model for use in various measurement systems. The adaptation of the model is made for the GEM-based soft X-ray measurement system FPGA-based. The EDQM elements has been connected to the base firmware using PCI-E DMA real-time data streaming with minimal modification. As additional storage, on-board DDR3 memory has been used. Description of implemented elements is provided, along with designed data processing tools and advanced simulation environment based on Questa software.
The paper puts forward and implements a method of designing and creating a modelling simulation environment for extensive and complete analysis of economical lighting on highways. From a general design viewpoint, the proposed solution explores the concept of a network description language (SMOL), which has been designed to describe the necessary network functions, mechanisms, and devices for the purpose of their computer simulation and verification. The presented results of the performed research confirm the usability of intelligent lighting on highways, both in the sense of the design concept and in the aspect of saving energy.
Additive manufacturing (AM) is a process that joins similar or dissimilar materials into application-oriented objects in a wide range of sizes and shapes. This article presents an overview of two additive manufacturing techniques; namely Laser metal deposition (LMD) and Wire arc additive manufacturing (WAAM). In LMD, metallic powders are contained in one or more chambers, which are then channelled through deposition nozzles. A laser heats the particles to produce metallic beads, which are deposited in layers with the aid of an in-built motion system. In WAAM, a high voltage electric arc functions as the heat source, which helps with ensuring deposition of materials, while materials in wire form are used for the feedstock. This article highlights some of the strengths and challenges that are offered by both processes. As part of the authors’ original research work, Ti-6Al-4V, Stainless steel 316L and Al-12Si were prepared using LMD, while the WAAM technique was used to prepare two Al alloys; Al-5356 and CuAl8Ni2. Microstructural analysis will focus on similarity and differences in grains that are formed in layers. This article will also offer an overall comparison on how these samples compare with other materials that have been prepared using LMD and WAAM.
Reliable monitoring for detection of damage in epicyclic gearboxes is a serious concern for all industries
in which these gearboxes operate in a harsh environment and in variable operational conditions. In this
paper, autonomous multidimensional novelty detection algorithms are used to estimate the gearbox’ health
state based on vectors of features calculated from the vibration signal. The authors examine various feature
vectors, various sources of data and many different damage scenarios in order to compare novel detection
algorithms based on three different principles of operation: a distance in the feature space, a probability
distribution, and an ANN (artificial neural network)-based model reconstruction approach. In order to compensate
for non-deterministic results of training of neural networks, which may lead to different network
performance, the ensemble technique is used to combine responses from several networks. The methods are
tested in a series of practical experiments involving implanting a damage in industrial epicyclic gearboxes,
and acquisition of data at variable speed conditions.
In general, currently employed vehicle classification algorithms based on the magnetic signature can distinguish among only a few vehicle classes. The work presents a new approach to this problem. A set of characteristic parameters measurable from the magnetic signature and limits of their uncertainty intervals are determined independently for each predefined class. The source of information on the vehicle parameters is its magnetic signature measured in a system that enables independent measurement of two signals, i.e. changes in the active and reactive component of the inductive loop impedance caused by a passing vehicle. These innovations result in high selective classification system, which utilizes over a dozen vehicle classes. The evaluation of the proposed approach was carried out for good vehicles consisting of 2-axle tractor and a 3-axle semi-trailer.
Sparse fish microremains have been found in marine limestones from the Middle Devonian (Givetian) Skały
Formation (Sitka Coral-Crinoid Limestone Member and Sierżawy Member), Świętomarz–Śniadka section,
Bodzentyn Syncline, Łysogóry Region, northern Holy Cross Mountains, associated with conodonts of the
hemiansatus to ansatus zones. Thelodont scales referred here to Australolepis sp. cf. A. seddoni come from near
Śniadka village, from samples dated as hemiansatus to rhenanus/varcus zones. This increases the known range
for the genus from its original find in Western Australia. The presence of a thelodont in the late Middle Devonian
in Poland extends the known distribution of turiniids around the peri-Gondwana shorelines of Palaeotethys.
In the paper methods for conducting Road Safety Inspections (SIs) in Italy and Poland are described and compared. The goal of the study is to improve the quality and efficiency of the safety inspections of road network by using low cost equipment (GPS, Tablet, Camera) and specific software. Particular attention was paid to the need for proper calibration of factors, causing traffic safety hazard associated with road infrastructure. The model developed according to the Italian procedures was adapted to comply with the checklists and evaluation criteria of the Polish guidelines. Overall, a good agreement between the two approaches was identified, however some modification was required to include new safety issues, characteristic for the Polish network for safety inspection of two lane rural roads. To test the applicability about 100 km of regional two lane roads in Poland were inspected with Polish and Italian procedures.
The first part of this article brings the author’s reply to the participants of the panel discussion of his book Culture as Verb (Anna Łebkowska, Jakub Momro, Tomasz Rakowski and Dorota Wolska). In the second part he outlines his premises and explains the analytical vocabulary that has enabled him to move from an active to a passive ‘verbal’ understanding of culture. He also draws a broad outline of prospective new research that would complement his project. Central to it is the exploration of what he believes is the dominant contemporary cultural experience, which is based on active participation. To characterize its most important features and forms we should make use of the following, newly defi ned analytical concepts – passivity, the present moment, immersion, and testimonial authority.
Thermoacoustic converters are devices for direct conversion of acoustic energy into thermal energy in the form of temperature difference, or vice versa – for converting thermal energy into an acoustic wave. In the first case, the device is called a thermoacoustic heat pump, in the second – thermoacoustic engine. Thermoacoustic devices can use (or produce) a standing or travelling acoustic wave. This paper describes the construction and properties of a single-stage thermoacoustic engine with a travelling wave. This kind of engine works using the Stirling cycle. It uses gas as a working medium and does not contain any moving parts. The main component of the engine is a regenerator equipped with two heat exchangers. Most commonly, a porous material or a set of metal grids is used as a regenerator. An acoustic wave is created as a result of the temperature difference between a cold and a hot heat exchanger. The influence of working gas, and such parameters as static pressure and temperature at heat exchanger on the thermoacoustic properties of the engine, primarily its efficiency, was investigated. The achieved efficiency was up to 1.4% for air as the working medium, which coincides with the values obtained in other laboratories. The efficiency for argon as working gas is equal to 0.9%.