Design and Analysis of Asynchronous Sampling Duty Cycle Corrector

This paper presents a duty cycle correction scheme based on asynchronous sampling and associated settling analysis. The proposed duty cycle corrector circuit consumes less power and area compared to other corrector circuits due to the low-frequency operation of asynchronous sampling. However, the settling behavior of an asynchronous sampling duty cycle corrector is limited in some operation conditions, which degrades its robustness and performance. This paper, therefore, performs analysis on the settling behavior of the asynchronous sampling in various operating conditions and proposes a control scheme to avoid the lagged settling. To verify the proposed duty cycle corrector and its analysis, a prototype design is implemented in a 40-nm CMOS process and its performance is verified by post-layout simulations. The proposed duty cycle corrector achieved very small duty cycle errors (less than 0.8%) and consumed 540 uW per one DCC unit.

Study of Separately and in Combination Impacts of Zinc-Oxide and Multiwall-Carbon-Nanotube on the Freshwater Prawn (Macrobrachium Nipponense De Haan, 1849), in Laboratory Condition

Nanomaterials (NMs) have settling behavior and accumulate in the benthic area of the aquatic ecosystems. Because of deposit-omnivorous feeding behavior of decapod crustaceans, these order species are appropriate biological models to assay NMs eco-toxicological effects. The present study evaluated the toxicity effects of ZnO and MWCNTs nanomaterials as separately and in combination on antioxidant enzymes activities, CHH hormone, hematology, reproductive performance, and hepatopancreas lesions of the Macrobrachium nipponense. The study was carried out in two stages. At the first experiment, concentrations of ZnO (0, 1, 10, 30, 50 mg/L) and MWCNTs (0, 5, 10, 15, 20 mg/L) were assayed then at the second experiment, two higher concentrations of the NMs in the first stage were compared in combined treatments. The experimental tanks (500 l RAS system) were stocked 12 females and four males during 60 days. Both NMs showed dose-dependent toxicity effects on M. nipponense reproductive parameters and especially eggs fertilization rate. Also, the results depicted that by increasing the NMs concentrations, inter-molt and inter-spawn periods were postponed so that in 50 ppm ZnO and 15 and 50 ppm MWCNTs treatments reproduction activities were stopped. The findings showed that CHH hormone release and superoxide dismutase (SOD) enzyme activity have direct relations to the NMs levels independently and in combination. Also, the results demonstrated that large granular hemocyte (LGH) deal with NMs detoxification in decapod crustacean’s hemolymph mainly. The NMs did not show any effect on ALT and AST enzymes activities in muscle tissue independently, but the NMs combined effects on these enzymes activities were significant. Also, the NMs caused hepatocyte enlargement, melanization, apoptosis, and necrosis damages in the hepatopancreas. The findings showed that ZnO and MWCNTs NMs have strongly adverse effects on M. nipponense, and this species is an appropriate bio-indicator and bio-monitor organism for NMs contaminations in the freshwater aquatic environments.

EFFECT OF PH CONDITIONS ON GOETHITE BEHAVIOR IN THE PRESENCE/ABSENCE OF DIFFERENT DISPERSANTS

Dispersion and settling behavior of goethite has been studied and effect of pH values on surface properties of goethite particles with /without dispersants has been discussed. A prerequisite for the successful flocculation is the stabilization of the system which is achieved by the good dispersion of particles. The effect of pH, sodium silicate (Na2SiO3), sodium hexametaphosphate (Na6P6O18) and sodium pyrophosphate (Na4P2O7), on the surface charges of goethite was studied. The IEP of natural goethite was found by measuring zeta potential at pH value of 6.6. With the use of sodium silicate the IEP of goethite moves to pH 4.95. An IEP could not be detected when the poly-phosphates were used and the surface charge is negative from pH 2 to pH 12. The relatively high zeta potential values indicate a fairly stable dispersion, especially when the sodium hexametaphosphate were used as dispersant.

Comparison of the influence of polyacrylamide and sodium oleate on selective flocculation of goethite from sludge

The paper represents a part of research conducted with the aim of examining the possibility of applying selective flocculation of goethite from sludge that occurs in the process of iron ore production. The aim of this study was to compare the influence of polyacrylamide and sodium oleate as a flocculant on the settling behavior of goethite under different conditions. The paper presents the results of the research on the influence of the flocculants based on polyacrylamide and sodium oleate, as well as pH values on the settling rate of a natural goethite sample. The results showed that the settling rate of goethite was influenced by pH value and the type of flocculant, while the concentration of flocculant did not significantly affect the settling rate. Measurements of zeta potential showed the effect of flocculants on the surface of the goethite.