Deformation speed and temperature effects on magnesium AZ91 during tubular channel angular pressing

In the present paper, tubular channel angular pressing process is applied on as cast AZ91 magnesium alloy tubes at different punch speeds at two different temperatures of 150°C and 250°C. The results show that increases in the punch speed lead to higher strength and lower elongation. In addition, at a constant punch speed, an increase in the process temperature leads to a decrease in the strength, but the elongation is slightly increased. The grain size of the sample decreased to ～1?μm from the initial value of ～150?μm. The use of very low plunger speeds during the severe plastic deformation of hexagonal close packed (hcp) metals could be considered as a powerful method for increasing the elongation of ultrafine grained hcp metals while maintaining their high strengths.     

A zero-crossing based 10-bit 100 MS/s pipeline ADC with controlled current in 90 nm CMOS

In this paper, a new charging technique for low power zero-crossing based circuit pipeline analog-to-digital converters (ADCs) is presented. The charging current sources are implemented as voltage-controlled current sources in order to charge the sampling capacitors based on the error signal. Using this method, the ADC power consumption is reduced while improving the accuracy. The necessary current control block is shared between consecutive stages further reducing the power consumption and die area. The proposed technique is applied to a 10-bit 100 MS/s pipeline ADC designed in a 90 nm CMOS technology with 1 V power supply. Circuit level simulation results using Cadence Spectre show a signal-to-noise and distortion ratio of 55.6 dB with 3.56 mW power consumption resulting in a figure of merit of 72.3 fJ/conv.step without employing any calibration technique.     

The mechanics of self-similar and self-affine fractal cracks

In this paper we study the mechanical attributes of the fractal nature of fracture surfaces. The structure of stress and strain singularity at the tip of a fractal crack, which can be self-similar or self-affine, is studied. The three classical modes of fracture and the fourth mode of fracture are discussed for fractal cracks in two-dimensional and three- dimensional solid bodies. It is discovered that there are six modes of fracture in fractal fracture mechanics. The J-integral is shown to be path-dependent. It is explained that the proposed modified J-integrals in the literature that are argued to be path-independent are only locally path-independent and have no physical meaning. It is conjectured that a fractal J-integral should be the rate of potential energy release per unit of a fractal measure of crack growth. The powers of stress and strain singularities at the tip of a fractal crack in a strain-hardening material are calculated. It is shown that stresses and strains have weaker singularities at the tip of a fractal crack than they do at the tip of a smooth crack.     

A noise-shaping SAR ADC for energy limited applications in 90 nm CMOS technology

In this paper, an ultra-low-power successive approximation register analog-to-digital converter (ADC) for energy limited applications is presented. The ADC resolution is enhanced by using a noise-shaping technique which does not need any integrator and only uses a finite impulse response (FIR) filter. To provide a first-order noise-shaping, the quantization error is firstly extracted by using the digital-to-analog converter (DAC) dummy capacitor and it is then employed in the error feedback scheme. The proposed structure employs a low-gain and low-swing operational transconductance amplifier (OTA) to realize the FIR filter which operates only at the sampling phase. To minimize the power consumption of the ADC analog part, the OTA is powered off during the conversion phase. The proposed ADC is designed and simulated in a 90 nm CMOS technology using Spectre with a 0.5 V single power supply. The simulated ADC uses a fully-differential 8-bit charge redistribution DAC with an oversampling ratio of 8 and achieves 10.7-bit accuracy. The simulated average power consumption is 4.53 μW and the achieved maximum SNDR and SFDR are 66.1 and 73.1 dB, respectively, resulting in a figure of merit of 27.6 fJ/conversion-step.     

Efficiency of carbon sorbents in mitigating polar herbicides leaching from tropical soil

Clean Technologies and Environmental Policy - Imidazolinones are a group of herbicides with high potential of leaching and long half-lives that are posing a threat to water resources’ quality...     

A synthesis of (arylthio-ethylidene)indolin-2-ones via S-arylation of oxoindolin-ethanethiolates with aryl halides

Aryl-sulfur bond formation between aryl halides and 1-(2-oxoindolin-3-ylidene)-2-aroylethanethiolates, prepared from isatin, 1-aryl-2-thiocyanatoethan-1-ones, and aryl halides, catalyzed by copper(I) iodide in DMF at 80°C afforded a nearly 1:1 mixture of (Z/E)-3-(2-oxo-2-aryl-1-(arylthio)ethylidene)indolin-2-ones, in good yields. The stereochemistry of these products has been confirmed by X-ray diffraction studies.     

The occurrence,fate, and distribution of natural and synthetic hormones in different types of wastewater treatment plants in Iran

Over the past few years, the presence of steroid estrogens in the environment has become a major concern. In this study, the concentrations of estrone(E1), 17β-estradiol(E2), and 17α-ethinyl estradiol(EE2) were measured in some wastewater treatment plants(WWTPs) in Iran. These samples were collected from the municipal, rural,livestock, commercial, and hospital WWTPs, extracted by dispersive liquid–liquid micro extraction(DLLME)technique, derivatized, and detected by GC/MS. In these treatment plants, various processes including conventional activated sludge(CAS), aerated lagoon(AL), moving bed biofilm reactor(MBBR), and activated sludge with wetland(AS + WL) are used. The highest concentration of hormones was observed in the influents and effluents of livestock, municipal, commercial, and hospital WWTPs, respectively. The maximum elimination rate was obtained in MBBR followed by AS + WL, CAS and AL. The biodegradation and adsorption rates along with adsorption coefficients of lg kdand lg kocwere measured for all target compounds.     

Evaluation of the effects of AlkylPhenolic compounds on kinetic coefficients and biomass activity in MBBR by means of respirometric techniques

The presence of AlkylPhenols (APs) in aquatic systems is considered as one of the environmental concerns in recent decades which are generally used as surfactants. APs are endocrine disruptors and estrogen-mimicking, causing harmful effects such as feminization and carcinogenesis on aquatic environment and human health. The most commercially important APs are 4-NonylPhenol (4-NP) and 4-tert-OctylPhenol (4-t-OP). Moving bed biofilm reactor (MBBR), which combined attached and suspended growth advantages, is an advanced biological treatment process for municipal and industrial wastewaters that has drawn considerable attention from many researchers to remove toxic pollutants from wastewater. The aim of this research was to evaluate Bacterial activities and kinetic coefficients in the presence of APs. This study was carried out using laboratory-scale MBBR fed with synthetic wastewater containing 4-NP and 4-t-OP. The reactor was operated at different loads of chemical oxygen demand (COD) and APs and different hydraulic retention time (HRT). The respirometric technique was applied to investigate the effect of APs on heterotrophic and autotrophic activity and kinetic coefficients in biomass obtained from MBBR. Respirometric technique demonstrates a reliable tool in order to assess the biofilm kinetic coefficients and biomass viability to insert in the mathematical models. The calculated kinetic parameters were in the range of conventional and extended aeration activated sludge processes. The results demonstrate that APs have significant inhibitory effects on activity and growth rate of heterotrophic and autotrophic bacteria, heterotrophs have been less affected by the presence of 4-NP and 4-t-OP, and these compounds had greater inhibitory effects on autotrophic bacteria.     

On the free volume kinetics during isochronal structural relaxation of Pd-based metallic glass: effect of temperature and deformation

Free volume changes of amorphous Pd_42.5Cu₃₀Ni_7.5P₂₀ due to structural relaxation under isochronal heat treatments have been quantified using in situ synchrotron X-ray diffraction measurements. The analysis of the first diffraction peak position during the annealing process has allowed us to follow the free volume change during relaxation. The data obtained were successfully fitted to relaxation equations based on free volume model (FVM) and the drawn conclusion is that the FVM remain a useful tool for describing the relaxation phenomena in metallic glasses well below glass transition. The effect of deformation and temperature on kinetics of structural relaxation of the amorphous structure has been quantitatively investigated.