Publikační činnost VŠB-TUO / Publications of VŠB-TUO
http://hdl.handle.net/10084/65861
Články akademických pracovníků VŠB-TUO indexované ve Web of Science.2018-04-22T18:33:26ZSoil heavy metal pollution and risk assessment associated with the Zn-Pb mining region in Yunnan, Southwest China
http://hdl.handle.net/10084/126218
Soil heavy metal pollution and risk assessment associated with the Zn-Pb mining region in Yunnan, Southwest China
Cheng, Xianfeng; Daněk, Tomáš; Drozdová, Jarmila; Huang, Qianrui; Qi, Wufu; Zou, Liling; Yang, Shuran; Zhao, Xinliang; Xiang, Yungang
The environmental assessment and identification of sources of heavy metals in Zn-Pb ore deposits are important steps for the effective prevention of subsequent contamination and for the development of corrective measures. The concentrations of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in soils from 40 sampling points around the Jinding Zn-Pb mine in Yunnan, China, were analyzed. An environmental quality assessment of the obtained data was performed using five different contamination and pollution indexes. Statistical analyses were performed to identify the relations among the heavy metals and the pH in soils and possible sources of pollution. The concentrations of As, Cd, Pb, and Zn were extremely high, and 23, 95, 25, and 35% of the samples, respectively, exceeded the heavy metal limits set in the Chinese Environmental Quality Standard for Soils (GB15618-1995, grade III). According to the contamination and pollution indexes, environmental risks in the area are high or extremely high. The highest risk is represented by Cd contamination, the median concentration of which exceeds the GB15618-1995 limit. Based on the combination of statistical analyses and geostatistical mapping, we identified three groups of heavy metals that originate from different sources. The main sources of As, Cd, Pb, Zn, and Cu are mining activities, airborne particulates from smelters, and the weathering of tailings. The main sources of Hg are dust fallout and gaseous emissions from smelters and tailing dams. Cr and Ni originate from lithogenic sources.
2018-01-01T00:00:00ZComprehensive characterisation of a newly developed Mg-Dy-Al-Zn-Zr alloy structure
http://hdl.handle.net/10084/126101
Comprehensive characterisation of a newly developed Mg-Dy-Al-Zn-Zr alloy structure
Kunčická, Lenka; Kocich, Radim
This is a report on the structure phases and precipitates in a newly developed Mg-10Dy-3Al-1Zn-0.2Zr alloy. Specimens from the cast alloy were heat treated at temperatures of 480 degrees C, 520 degrees C and 560 degrees C, all for 8 and 16 h, and subsequently quenched. The structures were then analysed using scanning and transmission electron microscopy, while the mechanical properties were investigated using microhardness measurements. The results showed the different temperatures, as well as times, influence both the chemical composition and morphology of the precipitated phases. The occurrence of the beta-phase changed with increasing temperature and time from grain boundary segregations through fine elongated particles to coarse plate-like precipitates. Polygon-shaped Dy-rich precipitates were observed in all the samples; however, their size decreased and their distribution homogenised with increasing annealing temperature and time. The samples annealed at 520 degrees C and 560 degrees C exhibited the presence of lamellar 18R-type long period stacking ordered (LPSO) phases. Microhardness measurements were in accordance with results of the microscopic analyses; although the values varied between 60 and 65 HV for all the material states, the most uniform distribution was observed for the 560 degrees C/8-h sample, which featured the finest precipitates and LPSO phases.
2018-01-01T00:00:00ZRelay selection for SWIPT: Performance analysis of optimization problems and the trade-off between ergodic capacity and energy harvesting
http://hdl.handle.net/10084/126100
Relay selection for SWIPT: Performance analysis of optimization problems and the trade-off between ergodic capacity and energy harvesting
Nguyen, Hoang-Sy; Nguyen, Thanh-Sang; Vozňák, Miroslav
In this paper, we focus on the optimal relay selection (RS) and ergodic capacity of an energy harvesting (EH) amplify-and-forward (AF) multi-relay network, where multiple relays cooperate with the source node and the destination node. We begin the work with the optimization of a single relay. In the first step, after the average end-to-end signal-to-noise ratio (SNR) is obtained, the high end-to-end SNR is approximated to achieve the PDF and CDF, and we jointly optimize time switching (TS) and power splitting (PS) ratios by using Alternate Convex Search algorithm, second derivatives and Hessian matrices. Following that, closed-form expressions for the outage probability and throughput in both delay-restricted and delay-tolerant transmission mode in the high SNR regime are derived. Most importantly, we achieve not only ergodic capacity in the considered EH multi relay network but also the trade-off between it and the average EH. Our theoretical results are proved by numerical simulations, in which delay-tolerant throughput outperforms delay-restricted throughput thanks to the change of number of relays. In addition, the data rate can be significantly enhanced thanks to the achievement of optimal TS and PS ratios.
2018-01-01T00:00:00ZA simplification generalized returns to scale approach for selecting performance measures in data envelopment analysis
http://hdl.handle.net/10084/126099
A simplification generalized returns to scale approach for selecting performance measures in data envelopment analysis
Toloo, Mehdi; Allahyar, Maryam
Toloo and Tichy (2015) with the aim of holding the rule of thumb in data envelopment analysis, developed a pair of models which optimally chooses some inputs and outputs among selective measures under variable returns to scale assumption. Their approach involves a lower bound for the input and output weights in the multiplier model and a penalty term in the objective function of envelopment model. These models possess an epsilon which on the one hand turns the selecting envelopment model non-linear and on the other hand increases the required computational burden for solving the selecting multiplier models. Selecting an improper value for the epsilon may cause the infeasibility and unboundedness issues for the multiplier and envelopment model, respectively. This paper demonstrates that the method of Toloo and Tichy (2015) is valid even with excluding the epsilon. The method is extended to generalized returns to scale model which considers other returns to scale assumptions, i.e. non-increasing, constant, and non-decreasing. The obtained results point out that the simplified approach is more stable and more reliable and substantially reduces the required calculations.
2018-01-01T00:00:00Z