Temperature and stress state of the block-braked solid wheel in operation on Yugoslav railways

Termičko opterećenje monoblok točka železničkog vozila kočenog papučama je dominantno u odnosu na ostale vrste opterećenja. To opterećenje, koje je uglavnom posledica dugotrajnog kočenja na padovima u cilju održavanja brzine je osnovni uzrok pojave pukotina na površini kotrljanja točka i, kao krajnja posledica, loma točka. U radu su dati rezultati proračunske analize termičkog opterećenja monoblok točka na odabranoj karakterističnoj deonici pruge Jugoslovenskih železnica. Proračuni temperaturnih i naponskih stanja točka rađeni su pomoću metode konačnih elemenata.Thermal load of the block-braked solid wheel railway vehicles is dominant on the other types of loads. This load, which is mainly consequence of long-term braking on downgrades for maintaining the defined constant speed purpose, is the main cause of occurrence of cracks on treads of wheel and finally fractures of wheel. The paper gives the analysis calculation results of the thermal load of the railway vehicle block-braked solid wheel on characteristic selected line on Yugoslav Railways network. Thermal analysis was done using the finite elements method, which was also used for obtaining wheel temperature and stress states in the simulated operation conditions

Temperature and stress state of the block-braked solid wheel in operation on Yugoslav railways

Termičko opterećenje monoblok točka železničkog vozila kočenog papučama je dominantno u odnosu na ostale vrste opterećenja. To opterećenje, koje je uglavnom posledica dugotrajnog kočenja na padovima u cilju održavanja brzine je osnovni uzrok pojave pukotina na površini kotrljanja točka i, kao krajnja posledica, loma točka. U radu su dati rezultati proračunske analize termičkog opterećenja monoblok točka na odabranoj karakterističnoj deonici pruge Jugoslovenskih železnica. Proračuni temperaturnih i naponskih stanja točka rađeni su pomoću metode konačnih elemenata.Thermal load of the block-braked solid wheel railway vehicles is dominant on the other types of loads. This load, which is mainly consequence of long-term braking on downgrades for maintaining the defined constant speed purpose, is the main cause of occurrence of cracks on treads of wheel and finally fractures of wheel. The paper gives the analysis calculation results of the thermal load of the railway vehicle block-braked solid wheel on characteristic selected line on Yugoslav Railways network. Thermal analysis was done using the finite elements method, which was also used for obtaining wheel temperature and stress states in the simulated operation conditions

Slack Exploitation for Aggressive Dynamic Power Reduction in SoC

The increasing power consumption of today’s system-on-chip (SoC) outpaces the trend of increasing battery capacity. The applications offered to customers grow tremendously too, a trend that is accelerating in the future. This yields stronger requirements for lower power consumption. During design, a system is dimensioned to worst-case workload requirements. Most of the time, workload is far below this level, which results in slack in some parts of the system. Our idea is to exploit this available slack by using adequate variants of dynamic voltage and frequency scaling and power gating. For scalability reasons, we commence our research with local dynamic adaptive power and frequency scaling, based on the slack observed at run time. This paper presents the motivations and possible directions for our research

Beyond Diophantine Wannier diagrams: Gap labelling for Bloch-Landau Hamiltonians

It is well known that, given a $2d$ purely magnetic Landau Hamiltonian with a constant magnetic field $b$ which generates a magnetic flux $\varphi$ per unit area, then any spectral island $\sigma_b$ consisting of $M$ infinitely degenerate Landau levels carries an integrated density of states $\mathcal{I}_b=M \varphi$. Wannier later discovered a similar Diophantine relation expressing the integrated density of states of a gapped group of bands of the Hofstadter Hamiltonian as a linear function of the magnetic field flux with integer slope. We extend this result to a gap labelling theorem for any $2d$ Bloch-Landau operator $H_b$ which also has a bounded $\mathbb{Z}^2$-periodic electric potential. Assume that $H_b$ has a spectral island $\sigma_b$ which remains isolated from the rest of the spectrum as long as $\varphi$ lies in a compact interval $[\varphi_1,\varphi_2]$. Then $\mathcal{I}_b=c_0+c_1\varphi$ on such intervals, where the constant $c_0\in \mathbb{Q}$ while $c_1\in \mathbb{Z}$. The integer $c_1$ is the Chern character of the spectral projection onto the spectral island $\sigma_b$. This result also implies that the Fermi projection on $\sigma_b$, albeit continuous in $b$ in the strong topology, is nowhere continuous in the norm topology if either $c_1\ne0$ or $c_1=0$ and $\varphi$ is rational. Our proofs, otherwise elementary, do not use non-commutative geometry but are based on gauge covariant magnetic perturbation theory which we briefly review for the sake of the reader. Moreover, our method allows us to extend the analysis to certain non-covariant systems having slowly varying magnetic fields.Comment: 17 pages, no figure

Multiattribute prediction of terrain stability above underground mining operations

This paper is dedicated to the problem of stability prediction of the terrain above underground mining operations. After the initial introduction to the problem, then the short analysis of the model approaches used to solve it, and giving the algorithm for rock massif stability prediction, we describe the concept of the multiattirbute terrain stability prediction method. The application of the multiattribute prediction method for stability of the terrain above underground mining operations is presented on the example of the Brown Coal Mine Aleksinac. The used method is original, essentially different from the other methods of mathematical modeling, because its prognosis of the rock massif stability under the influence of underground mining operations is based on the balance of the stability indicators. Our comparative analysis of the results obtained by multiattribute prediction and the data obtained by measurements of real deformations and terrain settling in multiple mines shows high mutual correlation, with an average deviation of less than ±10%. These results are confirmed entirely on the example of the Brown Coal Mine Aleksinac

Evaluation of fracture mechanics parameters for surface cracks by application of line spring model

Prikazan je proračun parametara mehanike loma za površinsku prslinu primenom modela niza opruga. Korišćena je Kingova metoda za određivanja otvaranja usta i vrha prsline, na osnovu čega je određen i J integral za idealno plastične materijale. Ukazano je na neke probleme u primeni ove metoda i moguće modifikacije za njihovo prevazilaženje. Takođe je ukazano i na mogućnosti rešavanja problema kao što su zaostali naponi i geometrijske nepravilnosti, koji mogu značajno da utiču na ponašanje zavarenih spojeva.Evaluation of fracture mechanics parameters for surface cracks using line spring model has been shown. King's method for crack mouth and tip displacement evaluation was applied, on basis of what the J integral for perfectly plastic materials was determined. Some problems in application of King's method are pointed out, as well as possible modifications of this method for their solution. Possibilities to solve the problems such as residual stresses and geometry imperfections, which can significantly affect welded joint behavior, are also introduced and analyzed

Evaluation of fracture mechanics parameters for surface cracks by application of line spring model

Prikazan je proračun parametara mehanike loma za površinsku prslinu primenom modela niza opruga. Korišćena je Kingova metoda za određivanja otvaranja usta i vrha prsline, na osnovu čega je određen i J integral za idealno plastične materijale. Ukazano je na neke probleme u primeni ove metoda i moguće modifikacije za njihovo prevazilaženje. Takođe je ukazano i na mogućnosti rešavanja problema kao što su zaostali naponi i geometrijske nepravilnosti, koji mogu značajno da utiču na ponašanje zavarenih spojeva.Evaluation of fracture mechanics parameters for surface cracks using line spring model has been shown. King's method for crack mouth and tip displacement evaluation was applied, on basis of what the J integral for perfectly plastic materials was determined. Some problems in application of King's method are pointed out, as well as possible modifications of this method for their solution. Possibilities to solve the problems such as residual stresses and geometry imperfections, which can significantly affect welded joint behavior, are also introduced and analyzed

Ground Surface Subsidence Monitoring Using Sentinel-1 in the “Kostolac” Open Pit Coal Mine

Open pit coal mining affects surrounding populated areas, resulting in terrain surface deformation. Surface deformation should be monitored as often as possible to control deformations and prevent potential incidents. This paper analyzes time series deformation estimated from the Sentinel-1 satellite images using the Persistent Scatterer Interferometry method to monitor subsidence rates caused by open pit mining activities. It is possible to measure deformations using classical geodetic methods, but those are rarely used in practice because they are time-consuming and expensive for application in large areas. Using the open access radar images from the Sentinel-1 mission, 513 images from the repository were downloaded between October 2016 and the end of December 2020. We present the processing steps in detail in order to establish a workflow for the automated processing of vertical displacement estimation using open source tools; a total of 402 images were processed: 215 images belonged to the ascending satellite orbit, 187 images belonged to the descending orbit, and 111 images were rejected because of adverse weather conditions. The PS InSAR technique has never been used for the mines of the Republic of Serbia or for land surveying practices related to deformation monitoring. The results based on the Sentinel-1 images were compared with results from geodetic leveling and with neotectonic uplift trends. The trend lines of vertical displacement obtained from PS and corresponding leveling are significantly similar (a Pearson correlation of 85% with a p-value of 0.015). The final evaluation reported results of vertical displacements at the leveling benchmark of −3.4 mm/year with the PS InSAR method and −2.7 mm/year with the leveling method. A comparison of the PS vertical displacements with a settlement model fits reasonably, suggesting that the measurements are valid. As four years of PS time series data is insufficient to establish undisputable conclusions on the neotectonics uplift, extending the time series (covering at least a decade) implies that this approach will become attractive in future neotectonic uplift trend estimations. This study illustrates not only the ability of Sentinel-1 data in mapping vertical deformations, but the obtained results could also be used for geohazard monitoring and land monitoring in general for the area of interest

Supplementary data for the article: Stojsavljević, A.; Trifković, J.; Rasić-Milutinović, Z.; Jovanović, D.; Bogdanović, G.; Mutić, J.; Manojlović, D. Determination of Toxic and Essential Trace Elements in Serum of Healthy and Hypothyroid Respondents by ICP-MS: A Chemometric Approach for Discrimination of Hypothyroidism. Journal of Trace Elements in Medicine and Biology 2018, 48, 134–140. https://doi.org/10.1016/j.jtemb.2018.03.020

Supplementary material for: [https://doi.org/10.1016/j.jtemb.2018.03.020]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2181]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3074