Fabrication of a highly selective and sensitive Gd(III)-PVC membrane sensor based on N-(2-pyridyl)-N′-(4-nitrophenyl)thiourea

In this work we report the development of a highly selective and sensitive Gd(III) membrane based on N-(2-pyridyl)-N′-(4-nitrophenyl)thiourea (PyTu4NO₂) as an excellent neutral ion carrier. The Gd(III) sensor exhibits a Nernstian slope of 19.95 ± 0.3 mV per decade over the concentration range of 3.0 × 10⁻⁷ to 1.0 × 10⁻¹ M, and a detection limit of 3.0 × 10⁻⁷ M of Gd(III) ions. The potentiometric response of the sensor is independent of the solution pH in the range of 4.0–9.0. It manifests advantages of low detection limit, fast response time (10 s), and most significantly, very good selectivity with respect to a number of lanthanide ions (La, Ce, Sm, and Eu ions). It can be used at least for a period of 8 weeks without any significant divergences in its potential response. To assess its analytical applicability the proposed Gd(III) sensor was successfully applied as an indicator electrode in the titration of Gd(III) ion solutions with EDTA and for the determination of the fluoride ion in two mouth wash preparations. It was also used for the direct monitoring of Gd(III) ions in binary mixtures.     

Harmonic and intermodulation performance of MoS2FET- and GFET-based amplifiers

This paper presents a simple mathematical model for the output–input voltage characteristic of the graphene field effect transistor (GFET)- and the molybdenum disulfide field effect transistor (MoS₂FET)-based inverting amplifiers. The model, basically a Fourier series, yields closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output voltage resulting from a multisinusoidal input voltage. The special case of a two-tone equal-amplitude input voltage is considered in detail. The results show that the harmonic and intermodulation performance of the complementary GFET- and the MoS₂FET-based inverting amplifiers is strongly dependent on the bias voltage and the amplitudes of the input tones with the third-order intermodulation component dominating over a wide range of the input voltage amplitudes.     

Improving the economic feasibility of biodiesel production from microalgal biomass via high-value products coproduction

Microalgal biodiesel has emerged as a promising fuel source, but has still not been adopted commercially. One of the several inherent challenges is its high production cost, which mandates the need to develop an integrated process to produce other valuable coproducts economically. This article combines life cycle assessment and preliminary life cycle cost assessment of a proposed biorefinery, in which a high value product, β-carotene, is coproduced from microalgae with biodiesel. The GaBi 6 environmental management software was employed to investigate the environmental impact associated with the production life cycle. The mass flow rates and the energy consumed in all stages of biodiesel and β-carotene coproduction for the functional unit of 1 kg of biodiesel were assessed. When the coproduction of β-carotene was not taken into consideration, the total energy input for a functional unit of 1.0 kg biodiesel/m²/y and the net energy ratio, that is, energy returned on energy invested were estimated to be 128.1 GWh/y and 0.27, respectively. The life cycle cost analysis showed that although the total production cost associated with coproduction of β-carotene from Dunaliella salina was higher than that of the sole production of biodiesel, it generates a hiked revenue of up to $37 million/y. Over the system lifetime of 10 years, the sole production of biodiesel showed a loss of US$345 million per functional unit, whereas the coproduction of β-carotene achieved a net profit of US$120.7 million per functional unit. This work clearly showed that the coproduction of β-carotene with biodiesel from D. salina overcomes the cost-ineffectiveness resulting from the production of biodiesel alone.     

Optimization and feasibility analysis of a microscale pin-fins heat sink of an ultrahigh concentrating photovoltaic system

Nowadays, the most recent optical configuration based on Cassegrain and Fresnel lens designs of concentrator photovoltaic(CPV) has shown a race to achieve the ultrahigh concentration ratio. Still, none of those has experimentally shown an optical concentration ratio (GC) beyond 2000 suns. This is because their energy concentration ratios are challenged by the excessive temperature raised throughout the optical stages, which diminishes the efficiency of the solar cell. In this context, this research work aims to numerically investigate a microscale pin-fins heat sink configuration to enhance the thermal performance and the cost-competitivity of ultrahigh CPV thermal receiver. The impacts of the solar cell area, cell efficiency, and heat sink's material have been analyzed and discussed. The results showed that a circular pin-fins heat sink could accomplish a drop of 23.28% in the maximum operating cell temperature at 10 000 suns for cell area of 1 × 1 mm² relatively compared to the conventional flat-plate heat sink. Furthermore, for a circular pin-fins heat sink with a cell area of 2 × 2 mm², the cell temperature started exceeding the safe operating range of temperature (80°C) at 8000 suns with an average temperature of 96.1°C and reaching a maximum of 113.91°C at 10 000 suns. A gradient temperature on the planar direction of the aluminum circular pin-fins heat sink was about 1.187°C at 10 000 suns whereas 0.703°C was recorded in the case of a copper circular pin-fins heat sink. The circular pin-fins heat sink showed the highest thermal performance resulting in maintaining the solar cell temperature within its safe operating range even beyond 10 000 suns. From an economic point of view, aluminum circular pin-fins heat sink has been found to be less costly than the copper one. Finally, it was found that at 8000 suns, the flat-plate heat sink cost is more expensive than the traditional pin-fins heat sink by 14.7%, where the flat-plate heat sink becomes the worst economic configuration at 10 000 suns. At that concentration ratio, the cost has increased by 43.38%, 5.75%, and 10.61% compared to the traditional pin-fins heat sink, cylindrical pin-fins heat sink, and circular pin-fins heat sink, respectively.     

Effect of Electromagnetic Interference (EMI) on the DC Shift,Harmonic and Intermodulation Performance of Diode-Connected NMOSFET

In this paper a new approximation is presented for the nonlinear relationship between the gate-to-source voltage and the current of a diode-connected NMOSFET. Using this expression closed-form expressions are obtained for the DC and the amplitudes of the fundamental, second- and third-harmonic and intermodulation components of the gate-to-source voltage resulting from exciting the diode-connected NMOSFET by a DC biasing current plus a superimposed multisinusoidal EMI. Comparison between calculated and simulated results is included.     

Design and manufacturing of a straight bevel gear in hot precision forging process using finite volume method and CAD/CAE technology

Forging simulation offers significant cost and time advantages by providing detailed insight into the forging process before tool selection and process decisions are made on the shop floor. Process data such as material flow, stresses, strains and temperature are readily accessible to a user at any point throughout the simulation process, as well as at any location within the forged part. Potential defects such as laps and under-fill of die cavities can be easily identified and corrected before part production begins. In addition, the influence of the process conditions such as lubrication and pre-form can be easily quantified and assessed. In the present work, hot precision forging process of the straight bevel gear is simulated numerically using finite volume method and computer-aided design/computer-aided engineering technology. The required force for the forging process, as well as the final shape of the bevel gear, is determined through numerical estimation. The simulation results are confirmed through the comparison with the experimental data available in DIN standards. Finally, the pre-form dies, the final die, and the bevel gear are manufactured. It is concluded that this method can be effectively used to optimize the forging process to maximize the mechanical strength, minimize material scrap, and hence reduce the overall cost of manufacture.     

Wavelet and ANN combination model for prediction of daily suspended sediment load in rivers

In this research, a new wavelet artificial neural network (WANN) model was proposed for daily suspended sediment load (SSL) prediction in rivers. In the developed model, wavelet analysis was linked to an artificial neural network (ANN). For this purpose, daily observed time series of river discharge (Q) and SSL in Yadkin River at Yadkin College, NC station in the USA were decomposed to some sub-time series at different levels by wavelet analysis. Then, these sub-time series were imposed to the ANN technique for SSL time series modeling. To evaluate the model accuracy, the proposed model was compared with ANN, multi linear regression (MLR), and conventional sediment rating curve (SRC) models. The comparison of prediction accuracy of the models illustrated that the WANN was the most accurate model in SSL prediction. Results presented that the WANN model could satisfactorily simulate hysteresis phenomenon, acceptably estimate cumulative SSL, and reasonably predict high SSL values.     

Real-time automatic tuning of noise suppression algorithms for cochlear implant applications

The performance of cochlear implants deteriorates in noisy environments compared to quiet conditions. This paper presents an adaptive cochlear implant system, which is capable of classifying the background noise environment in real time for the purpose of adjusting or tuning its noise suppression algorithm to that environment. The tuning is done automatically with no user intervention. Five objective quality measures are used to show the superiority of this adaptive system compared to a conventional fixed noise-suppression system. Steps taken to achieve the real-time implementation of the entire system, incorporating both the cochlear implant speech processing and the background noise suppression, on a portable PDA research platform are presented along with the timing results.