On the 14th of February, 2015, a huge fire broke out on Łazienkowski Bridge; a five span bridge, 423 m long and 28 m wide, built in the years 1972-74. It was a fully steel structure with four plate girders and orthotropic deck. The fire started under the first span during the replacement of wooden service decks. The next day, the Department of Bridges of the Warsaw University of Technology was designated to conduct an expertise material investigation, geometrical verification, and FEM model analysis. The subject of this paper concentrates on geometrical issues. The main difficulty of this task was the lack of full reference data regarding the bridge's original structure. The old design was incomplete and there was no actual surveying results for the undamaged structure. As a conclusion, some remarks focused on surveying measurements and on the final decision regarding this bridge are given. It was eventually exchanged into a brand new one and put into public use on the 28th of October, 2015.
The aim of this publication is to design a procedure for the synthesis of an IDT (interdigital transducer) with diluted electrodes. The paper deals with the surface acoustic waves (SAW) and the theory of synthesis of the asymmetrical delay line with the interdigital transducer with diluted electrodes. The authors developed a theory, design, and implementation of the proposed design. They also measured signals. The authors analysed acoustoelectronic components with SAW: PLF 13, PLR 40, delay line with PAV 44 PLO. The presented applications have a potential practical use.
This paper presents a printed dual band monopole antenna working below 250 MHz using meander line and an added stub. Meander line approach is used to reduce the size of the low frequency monopole. The proposed antenna is fed by microstrip line and printed on FR-4 substrate with an overall size of 290 x 83 mm2. The added stub tuned dual band operation at 114 MHz and 221 MHz with measured reflection coefficient of -19 dB at both bands. The antenna has omni-directional characteristics with efficiency greater than 90% and gain of 1.87, 1.7 dBi at both bands respectively. The antenna design is optimized through a detailed parametric study. This study includes varying stub, Meander, feed and ground dimensions. The antenna has been fabricated and measured where dual band operation in the MHz range is verified.
The first step towards condition based maintenance of the milling plant is the implementation of online condition monitoring of the mill. The following paper presents and analyses methods of monitoring the key performance factors of a vertical spindle mill that is suited for implementation on older power stations, i.e. the quantity (mass flow rate) and quality (particle fineness) of the pulverised fuel produced by the mill. It is shown herein that the mill throughput can be monitored on-line using a simple mill energy balance that successfully predicts the coal throughput within 2.33% as compared to a calibrated coal feeder. A sensitivity analysis reveals that the coal moisture is a critical measurement for this method to be adopted as an on-line mass flow monitoring tool. A laser based particle size analyser tool was tested for use in the power plant environment as an online monitoring solution to measure pulverised fuel fineness. It was revealed that several factors around the set-up and operation of the instrument have an influence on the perceived results. Although the instrument showed good precision and repeatability of results, these factors must be taken into account in order to improve the accuracy of the reported results before the instrument can be commissioned as an on-line monitoring solution.
Industrial engineers gather knowledge during their bachelor studies through lectures and practical classes. The goal of practical class might be an extension of knowledge and/or a consolidation and application of already gathered knowledge. It is observed that there exists a gap between theory learnt during lectures and practical classes. If practical classes require holistic approach and solving complex tasks (problems), students strive with understanding relations and connections between parts of knowledge. The aim of this article is to show an example of a simple practical assignment that can serve as a bridge between lectures and practical classes through discussion of interactions and relations between parts of theoretical knowledge. It is an example of in-class simulating of a line and cellular layout considering discussion of elements impacting and impacted by the type of layout (e.g. learning curve, changeovers, etc.). In-class verification of the presented approach confirmed its usability for teaching industrial engineers and bridging the gap between theory delivered through lectures and more advanced practical classes.
Safety and operation efficiency of the particle accelerators strongly depend on the quality of the supplied electric current and is affected by the electric properties of all elements of the circuit. In this paper the capacitance of the superconducting bus-bars applied in the cryogenic by-pass line for the SIS100 particle accelerator at FAIR is analysed. The unit capacitance of the bus-bars is calculated numerically and found experimentally. A 2D numerical model of a cross-section of the cable is applied. The capacitance is found with three methods. The stored energy, electric displacement field and charge gathered on the surfaces of the device are calculated and analysed. The obtained values are consistent. Experimental measurements are performed using the resonance method. The measuring system is undamped using a negative conductance converter. Small discrepancies are ob- served between numerical and experimental results. The obtained values are within the requirements of the accelerator design.
One of the methods to prevent unsuitable lubrication of moving components of devices and machinery is using bi-metal and three-metal bearings. Centrifugal casting process is one of the manufacturing methods that is used for such bearings. In this study, the purpose is microstructure evaluation of the bonding location and length determination of diffusion bond in structural steel-bronze. A mold made of structural steel with inner diameter of 240mm, length of 300mm and thickness of 10mm was coated by a 6mm film of bronze under centrifugal casting process. At first, a bronze ingot with dimension of 5mm×10mm×20mm is located inside of the hollow cylindrical mold and then the two ends of it will be sealed. During mold rotation with the rate of 800 rpm, two high power flames are used for heating the mold under Ar gas atmosphere to melt the bronze ingot at 1000˚C. After 15minutes, the system is cooled rapidly. Results showed that the diffusion bonding of bronze in structural steel to depth of 1.2µm from the bonding line was obtained. In this bonding, copper element was diffused to 50% of its initial concentration.
This paper presents a concept of humanoid robot motion generation using the dedicated simplified dynamic model of the robot (Extended Cart-Table model). Humanoid robot gait with equal steps length is considered. Motion pattern is obtained here with use of Preview Control method. Motion trajectories are first obtained in simulations (off-line) and then they are verified on a test-bed. Tests performed using the real robot confirmed the correctness of the method. Robot completed a set of steps without losing its balance.
This work presents an innovative shaft-lining solution which, in accordance with a patent of the Republic of Poland, allows successive, periodic leaching of excess rock salt migrating to the shaft opening. As is commonly known, all workings in rock salt strata are exposed to an increased convergence of sidewalls, making it very difficult to use shafts properly. Rocks migrating towards the shaft opening cause very high stress on the shaft liner. As a result, if the lining does not show substantial deformability, it fails. Lining failure due to insufficient deformability has been extensively described in the literature. Also, throughout the history of mining construction, a number of solutions have been proposed for different types of lining-deformability enhancement. For instance, the KGHM mining corporation applied a deformable steel lining – a solution used in the mining construction of galleries – along a 155-m-long section of the SW-4 shaft with diameters of 7,5 m that passes through a rock salt strata. At KGHM, the SW-4 shaft passes through a rock salt strata along a section of 155 m, in which a deformable enclosed steel lining was made. After several years, the convergence of shaft sidewalls stabilised at a rate of 0.5 mm/day. This enormous activity of the rock mass made it necessary to reconstruct the entire shaft section after only four years. According to further predictions, it will be necessary to reconstruct this section at least four times by 2045. This paper discusses in short form the underlying weaknesses of the technology in question. As a solution to the problems mentioned above, the authors of this work present a very simple design of a shaft lining, called the tubing-aggregate lining, which utilises the leachability of salt rock massifs. The essential part of the lining is a layer of coarse aggregate set between the salt rock sidewall and the inner column of the tubing lining. One the one hand, coarse aggregate supports the salt rock sidewall and is highly deformable due to its compressibility, but on the other hand it allows water or low saturated brine to migrate and dissolve salt rock sidewalls. This paper presents the first stage of works on this subject. Patent No. PL 223831 B had been granted before these works commenced.
To overcome the detrimental influence of α impulse noise in power line communication and the trap of scarce prior information in traditional noise suppression schemes , a power iteration based fast independent component analysis (PowerICA) based noise suppression scheme is designed in this paper. Firstly, the pseudo-observation signal is constructed by weighted processing so that single-channel blind separation model is transformed into the multi-channel observed model. Then the proposed blind separation algorithm is used to separate noise and source signals. Finally, the effectiveness of the proposed algorithm is verified by experiment simulation. Experiment results show that the proposed algorithm has better separation effect, more stable separation and less implementation time than that of FastICA algorithm, which also improves the real-time performance of communication signal processing.
Quality of electric current delivered to the magnets of a particle accelerator is essential for safety and reliability of its operation. Even small discrepancies strongly affect the properties of particle beams. One of the sources of the disturbances is the appearance of induced currents caused by the electromagnetic interactions between the elements of the machine. In this paper the calculations of induced currents in by-pass lines of a SIS100 particle accelerator are presented. In order to find the values of the currents the self-inductances and mutual inductances of the by-pass lines are found. Due to the complex geometry of the line, especially of Ω-shaped dilatations, the numerical approach was employed. The calculations show that the size of induced currents increases with the distance between the cables in an individual bus-bar. The maximum discrepancy of the magnetic field in a dipole magnet is found to be 7.7 μT. The decrease of distance between the cables allows one to obtain a discrepancy of 1.2 μT.
Power system state estimation is a process of real-time online modeling of an electric power system. The estimation is performed with the application of a static model of the system and current measurements of electrical quantities that are encumbered with an error. Usually, a model of the estimated system is also encumbered with an uncertainty, especially power line resistances that depend on the temperature of conductors. At present, a considerable development of technologies for dynamic power line rating can be observed. Typically, devices for dynamic line rating are installed directly on the conductors and measure basic electric parameters such as the current and voltage as well as non-electric ones as the surface temperature of conductors, their expansion, stress or the conductor sag angle relative to the plumb line. The objective of this paper is to present a method for power system state estimation that uses temperature measurements of overhead line conductors as supplementary measurements that enhance the model quality and thereby the estimation accuracy. Power system state estimation is presented together with a method of using the temperature measurements of power line conductors for updating the static power system model in the state estimation process. The results obtained with that method have been analyzed based on the estimation calculations performed for an example system - with and without taking into account the conductor temperature measurements. The final part of the article includes conclusions and suggestions for the further research.
The issue of line simplification is one of the fundamental problems of generalisation of geographical information, and the proper parameterisation of simplification algorithms is essential for the correctness and cartographic quality of the results. The authors of this study have attempted to apply computational intelligence methods in order to create a cartographic knowledge base that would allow for non-standard parameterisation of WEA (Weighted Effective Area) simplification algorithm. The aim of the conducted research was to obtain two independent methods of non-linear weighting of multi-dimensional regression function that determines the “importance” of specific points on the line and their comparison to each other. The first proposed approach consisted in the preparation of a set of cartographically correct examples constituting a basis for teaching a neural network, while the other one consisted in defining inference rules using fuzzy logic. The obtained results demonstrate that both methods have great potential, although the proposed solutions require detailed parameterisation taking into account the specificity of geometric variety of the source data.
The paper deals with the issue of constructing delay lines on the basis of surface acoustic waves and their application to single-mode oscillators. As a result of a theoretical analysis concrete delay lines are proposed. In the contribution, there is presented a theory of designing a symmetrical mismatched and matched delay line for a single-mode oscillator of electrical signals on the basis of which there were designed and fabricated acoustic-electronic components for sensors of non-electrical quantities. From the experimental results it can be stated that all of six designed and fabricated delay lines can be effectively used in the construction of single-mode oscillators.
This paper presents a piecewise line generalization algorithm (PG) based on shape characteristic analysis. An adaptive threshold algorithm is used to detect all corners, from which key points are selected. The line is divided into some segments by the key points and generalized piecewise with the Li-Openshaw algorithm. To analyze the performance, line features with different complexity are used. The experimental results compared with the DP algorithm and the Li-Openshaw algorithm show that the PG has better performance in keeping the shape characteristic with higher position accuracy.
A comprehensive comparison of the dynamic and steady state performance characteristics of permanent magnet synchronous motors (PMSM) with interior and surface rotor magnets for line-start operation is presented. The dynamic model equations of the PMSM, with damper windings, are utilized for dynamic studies. Two typical loading scenarios are examined: step and ramp loading. The interior permanent magnet synchronous motor (IPMSM) showed superior asynchronous performance under no load, attaining faster synchronism compared to the surface permanent magnet synchronous motor (SPMSM). With step load of 10 Nm at 2 s the combined effect of the excitation and the reluctance torque forced the IPMSM to pull into synchronism faster than the SPMSM which lacks saliency. The ability of the motors to withstand gradual load increase, in the synchronous mode, was examined using ramp loading starting from zero at 2 s. SPMSM lost synchronism at 12 s under 11 Nm load while the IPMSM sustained synchronism until 41 seconds under 40 Nm load. This clearly suggests that the IPMSM has superior load-withstand capability. The superiority is further buttressed with the steady state torque analysis where airgap torque in IPMSM is enhanced by the reluctance torque within 90E to 180E torque angle.
Modern electrical-power systems are often exploited for transmitting highfrequency carrier signals for communications purposes. Series-connected air-core coils represent the fundamental component allowing such applications by providing a proper filtering in the frequency domain. They must be designed, however, to withstand also the line short-circuit current. When a high-magnitude current flows through a coil, strong mechanical stresses are produced within the conductor, leading to possible damage of the coil. In this paper, an approximate analytical model is derived for the relationship between the maximum mechanical stress and the electrical/geometrical parameters of the coil. Such a model provides the guidelines for a fast and safe coil design, whereas numerical simulations are only needed for the design refinement. The presented approach can be extended to other applications such as, for example, the mechanical stress resulting from the inrush currents in the coils of power transformers.
The development of a distributed generation will influence the structure of the power transmission and distribution network. Distributed sources have lower power and therefore the lines of lower voltage are used. Therefore, the electric field intensity near such lines is lower. On the other hand magnetic field intensity may prove essential. The main aim of the paper is to present a method estimating the “ballast” of the natural environment at 50 Hz electric and magnetic fields in the power system, with distributed and centralized generation in real operating conditions.
Transmission of the electric power is accompanied with generation of low –frequency electromagnetic fields. Electromagnetic compatibility studies require that the fields from sources of electric power be well known. Unfortunately, many of these sources are not defined to the desired degree of accuracy. This applies e.g. to the case of the twisted-wire pair used in telephone communication; already practiced is twisting of insulated high-voltage three phase power cables and single-phase distribution cables as well. The paper presents a theoretical study of the calculation of magnetic fields in vicinity of conductors having helical structure. For the helical conductor with finite length the method is based on the Biot-Savart law. Since the lay-out of the cables is much more similar to a broken line than to strait line, in the paper the magnetic flux densities produced by helical conductor of complex geometry are also derived. The analytical formulas for calculating the 3D magnetic field can be used by a software tool to model the magnetic fields generated by e.g. twisted wires, helical coils, etc.
Surface Acoustic Wave (SAW) devices like delay lines, filters, resonators etc., are nowadays extensively used as principal solid state components in many electronic applications and chemical vapour sensors. To bring out the best from these SAW devices, computational design and modelling are resorted too. The present paper proposes the modelling of 400 MHz ST-X Quartz based SAW delay line, by three models namely, Impulse Response Model (IRM), Crossed-field Equivalent Circuit Model (ECM) and Couplingof- Modes (COM) model. MATLABr is employed as a computational tool to model the experimental output of the SAW device. A comparative discussion of the modelled device results is also provided.
The paper describes the construction, operation and test results of three most popular interpolators from a viewpoint of time-interval (TI) measurement systems consisting of many tapped-delay lines (TDLs) and registering pulses of a wide-range changeable intensity. The comparison criteria include the maximum intensity of registered time stamps (TSs), the dependency of interpolator characteristic on the registered TSs’ intensity, the need of using either two counters or a mutually-complementing pair counter-register for extending a measurement range, the need of calculating offsets between TDL inputs and the dependency of a resolution increase on the number of used TDL segments. This work also contains conclusions about a range of applications, usefulness and methods of employing each described TI interpolator. The presented experimental results bring new facts that can be used by the designers who implement precise time delays in the field-programmable gate arrays (FPGA).
A novel method for thermal diffusivity evolution of thin-film materials with pulsed Gaussian beam and infrared video is reported. Compared with common pulse methods performed in specialized labs, the proposed method implements a rapid on-line measurement without producing the off-centre detection error. Through mathematical deduction of the original heat conduction model, it is discovered that the area s, which is encircled by the maximum temperature curve rTMAX(θ), increases linearly over elapsed time. The thermal diffusivity is acquired from the growth rate of the area s. In this study, the off-centre detection error is avoided by performing the distance regularized level set evolution formulation. The area s was extracted from the binary images of temperature variation rate, without inducing errors from determination of the heat source centre. Thermal diffusivities of three materials, 304 stainless steel, titanium, and zirconium have been measured with the established on-line detection system, and the measurement errors are: −2.26%, −1.07%, and 1.61% respectively.
The designing process of high resolution time interval measurement systems creates many problems that need to be eliminated. The problems are: the latch error, the nonlinearity conversion, the different duty cycle coefficient of the clock signal, and the clock signal jitter. Factors listed above affect the result of measurement. The FPGA (Field Programmable Gate Array) structure also imposes some restrictions, especially when a tapped delay line is constructed. The article describes the high resolution time-to-digital converter, implemented in a FPGA structure, and the types of errors that appear there. The method of minimization and processing of data to reduce the influence of errors on the measurement is also described.
The synthesis problem for optimal control systems in the class of discrete controls is under consideration. The problem is investigated by reducing to a linear programming (LP) problem with consequent use of a dynamic version of the adaptive method of LP. Both perfect and imperfect information on behavior of control system cases are studied. Algorithms for the optimal controller, optimal estimators are described. Results are illustrated by examples.
The article presents state of work in technology of free-space optical communications (Free Space Optics − FSO). Both commercially available optical data links and their further development are described. The main elements and operation limiting factors of FSO systems have been identified. Additionally, analyses of FSO/RF hybrid systems application are included. The main aspects of LasBITer project related to such hybrid technology for security and defence applications are presented.