Oversampling ΣΔ Analog-to-Digital Converters Modeling Based on VHDL

The paper presents a VHDL model of an oversampling analog-to-digital converter created on the behavioral hierarchy level. Although VHDL has been primarily devoted to digital circuit design, it can also be applied to certain mixed-signal circuits. The model of the analog part is as simple as possible and includes only necessary parameters that enable to determine the potential resolution of a converter. The model of the digital part is described in the synthesizable subset of VHDL and parameterized according to the word length and the type of arithmetic applied. The validation process of the converter model is also shown. It is performed by a VHDL simulator and a postprocessor tool enabling to carry out FFT. Simulation results enclosed prove the efficiency of the design approach presented.     

Determining of safety pillars in the vicinity of water reservoirs in mine workings within abandoned mines in the Upper Silesian Coal Basin (USCB)

Against a background of hydrodynamic conditions connected with abandoning of significant number of mines and vast water reservoirs forming within them, basic methods of the assessment of strength of safety pillars used in coal mines in the USCB are presented. In the light of geomechanical research and conditions in mines in the USCB, the paper indicates a possibility of verification of safety pillar dimensions. On the example of one of mines in the USCB conditions for safety pillars stability in complicated mining conditions are assessed. The author also proposes a methodology of attempt and safety zones indication for existing safety pillars which would simultaneously be safety zones for designed exploitation.     

Silica functionalized by pyridinecarboximidamides as a novel sorbent of heavy metals ions

ABSTRACT

Two novel sorbents, obtained as a result of surface modification of silica gel for the Cu(II), Co(II) and Ni(II) removal from aqueous solutions were proposed. For the modification, 3-chloropropyltrimethoxysilane, N’-hydroxy-N,N-dioctylpyridine-3-carboximidamide and N’-hydroxy-N,N-dioctylpyridine-4-carboximidamides were used. A series of basic tests on the sorption of Cu(II), Co(II) and Ni(II) were carried out and the presented results indicated that the novel sorbents were able to remove all tested metals ions from the aqueous solutions, and the removal efficiency was dependent on the functionalised agent structure, dosage, metal ions concentration and pH. The Langmuir model also assumed that a monolayer sorption occurred.     

Effects of Ozone and Ozone/Hydrogen Peroxide on the Degradation of Model and Real Oil-Sands-Process-Affected-Water Naphthenic Acids

Naphthenic acids (NAs) are persistent compounds that contribute to the toxicity of oil sands process-affected water (OSPW). In this study, the effects of ozone and ozone/hydrogen peroxide on the NAs degradation in buffered water and OSPW were examined. Cyclohexanoic acid (CHA) was used as a model NAs compound in buffered water experiments at two different pHs, using radical scavengers. At pH 9, the addition of carbonate did not have any effect on CHA degradation. Additions of tert-butyl alcohol and tetranitromethane decreased the CHA degradation levels. For the OSPW experiments, degradation of acid-extractable fraction (AEF) and NAs was examined. Approximately 90% of AEF was oxidized in a semi-batch system. In a batch system, 99% of OSPW NAs were degraded. This study demonstrated that ozone and ozone/hydrogen peroxide could be suitable treatment processes for OSPW remediation.     

Modified set-point controller for underwater vehicles

A modified PD (proportional-derivative) controller for autonomous underwater vehicles (AUVs) is presented in this paper. The controller is expressed in terms of first-order equations of motion with a unit inertia matrix. The main difference between the proposed controller and the classical one relies on that the dynamics of the system is taken into account. This property ensures fast error and force convergence to the end-value. The PD controller can be applied for fully actuated AUVs. It is worth noting that the regulator gain matrices are selected based on parameters of the tested vehicle. The stability of the presented control law is proved in the sense of Lyapunov. Moreover, some advantages and observations resulting from the use of the controller are given. The performance of the controller is shown via simulations on a 6-DOF underwater vehicle.