A new method for measurement of sludge blanket height (SBH) based on image analysis is presented. The proposed method uses a histogram back-projection algorithm to distinguish between the settling sludge and supernatant and can be used with sludge possessing different coloring characteristics both in the sludge color and the color of supernatant produced. Individual pixels in the acquired image are compared with a histogram of a representative sludge region. Therefore, the proposed method relies neither on the assumed shape of light intensity profile nor on the dominant sludge or supernatant color. Batch sedimentation tests are presented for different initial sludge concentrations and different background colors to simulate different sludge characteristics. Parameters of a settling velocity function are estimated based on the obtained results. Additionally, an algorithm is proposed that enables the zone settling velocity (ZSV) to be estimated before the batch sedimentation test is completed.
Is the world’s power engineering at a crossroads? Will ongoing climate changes and rise of new technologies such as the Internet of Things (IoT), Smart City or e-mobility give us a completely different perspective on the world’s future energy? What are our actual visions and development forecasts in this matter? Who is right concerning this matter, large energy companies and some politicians, environmentalists, climate researchers and all kinds of visionaries? Is transformation based on solar energy and hydrogen a holy grail for the energy sector? The author of this article tries to find answers to these and many other questions. Today we can already accept as a proven thesis that rapid and dangerous climate changes for our civilisation can also be attributed to high carbon and low-efficient power engineering. Power engineering and climate neutrality are no longer just problems for politicians, companies, and scientists, but have become a challenge for our civilisation. If we are to save the Earth, our civilisation has to change its mentality and develop ideas that will not prioritise economic growth and high consumption but sustainable growth in harmony with nature. For this to happen, the way people think about energy and global transformation must also change. The foregoing general remarks, but also the fact that a gradual transition from traditional large-scale fossil fuel-based energy generation to distributed energy generation based on renewable resources is inevitable, constitute the main message of this article. The article also aims to discuss the role of the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences (IMP PAN) in Gdańsk in the process of energy transformation in our country. The institute, as the coordinating entity of over a dozen of high-budgeted national and European projects in the field of environmentally-friendly power engineering, has contributed to some extent to the creation of conditions required for the development of prosumer power engineering (or more broadly: civic power engineering) in our country.
Activated tungsten inert gas (ATIG) welding has a good depth of penetration (DOP) as compared to the conventional tungsten inert gas (TIG) welding. This paper is mainly focused on ATIG characterization and mechanical behavior of aluminum alloy (AA) 6063-T6 using SiO2 flux. The characterization of the base material (BM), fusion zone (FZ), heat affected zone (HAZ) and, partially melted zone is carried out using the suitable characterization methods. The weld quality is characterized using ultrasonic-assisted non-destructive evaluation. A-scan result confirms that the ATIG welded samples have more DOP and less bead width as compared to conventional TIG. The recorded tensile strength of ATIG with SiO2 is better than the conventional TIG welding. The failure mode is ductile for ATIG welding with larger fracture edges and is brittle in the case of conventional TIG welding.
This work attempts to use nitrogen gas as a shielding gas at the cutting zone, as well as for cooling purposes while machining stainless steel 304 (SS304) grade by Computer Numerical Control (CNC) lathe. The major influencing parameters of speed, feed and depth of cut were selected for experimentation with three levels each. Totally 27 experiments were conducted for dry cutting and N2 gaseous conditions. The major influencing parameters are optimized using Taguchi and Firefly Algorithm (FA). The improvement in obtaining better surface roughness and Material Removal Rate (MRR) is significant and the confirmation results revealed that the deviation of the experimental results from the empirical model is found to be within 5%. A significant improvement of reduction of the specific cutting energy by 2.57 % on average was achieved due to the reduction of friction at the cutting zone by nitrogen gas in CNC turning of SS 304 alloy.
Convolutional Neural Networks (CNN) have achieved huge popularity in solving problems in image analysis and in text recognition. In this work, we assess the effectiveness of CNN-based architectures where a network is trained in recognizing handwritten characters based on Latin script. European languages such as Dutch, French, German, etc., use different variants of the Latin script, so in the conducted research, the Latin alphabet was extended by certain characters with diacritics used in Polish language. To evaluate the recognition results under the same conditions, a handwritten Latin dataset was also developed. The proposed CNN architecture produced an accuracy of 96% for the extended character set. This is comparable to state-of-the-art results found in the domain of identifying handwritten characters. The presented approach extends the usage of CNN-based recognition to different variants of the Latin characters and shows it can be successfully used for a set of languages based on that script. It seems to be an effective technique for a set of languages written using the Latin script.
This paper discusses the configuration of a space-effective rack cell for storing a given set of heterogeneous items. Rack cells are the primary components of rack storage areas. A rack cell configuration problem (RCCP) for heterogeneous storage is formulated as a combinatorial mathematical model. An effective heuristic for solving the RCCP in practical cases is presented. The proposed heuristic consists of multistage brute force searching of defined sets of feasible solutions and solving linear integer assignment problems by the branch-and-bound method. The developed algorithm was implemented and tested, and the rack cell obtained meets the modularity requirements in the design and operation of heterogeneous storage areas.
The effectiveness of lightning protection on the power and distribution grid is a significant factor, which influences the power distribution reliability and the failure rate of system elements. As part of this article, a mathematical model will be presented, taking into account selected parameters that affect the assessment of the lightning hazard of an overhead line. The proposed model will consider the location of the object near the line and the adjustment of line conductor overhangs. Moreover, the mentioned mathematical model allows for analyzing the impact of considered parameters on the protection level of the power system, and transient overvoltages that occur in this system. The article contains also a detailed description of an effective and fast method to assess the lightning discharge impact on the power system with insufficient data. The introduced model was tested to verify the correctness of its operation by comparison of calculation results and functional data. High convergence of calculated and functional data and uncomplicated model structure ensure a wide range of applications for the proposed solution to easily prevent emergency situations in the power system. Furthermore, the described model gives the opportunity to assess the reduction of the range of selectivity zone associated with the power line, in conjunction with the impact of constructional peculiarities and a near object.
The paper presents a multi-phase doubly fed induction machine operating as a DC voltage generator. The machine consists of a six-phase stator circuit and a three-phase rotor circuit. Two three-phase six-pulse diode rectifiers are connected to each three-phase machine section on the stator side and in parallel to the common DC circuit feeding the isolated load. The same DC bus is also common for the rotor side power electronics converter responsible for machine control. Two methods – direct torque control DTC and field oriented control FOC – were implemented for machine control and compared by means of simulation tests. Field oriented control was implemented in the laboratory test bench.
Short-circuit analysis is conducted based on the nodal impedance matrix, which is the inversion of the nodal admittance matrix. If analysis is conducted for sliding faults, then for each fault location four elements of the nodal admittance matrix are subject to changes and the calculation of the admittance matrix inversion needs to be repeated many times. For large-scale networks such an approach is time consuming and unsatisfactory. This paper proves that for each new fault location a new impedance matrix can be found without recalculation of the matrix inversion. It can be found by a simple extension of the initial nodal impedance matrix calculated once for the input model of the network. This paper derives formulas suitable for such an extension and presents a flowchart of the computational method. Numerical tests performed for a test power system confirm the validity and usefulness of the proposed method.