Channel length scaling in graphene field-effect transistors studied with pulsed current-voltage measurements

We investigate current saturation at short channel lengths in graphene field-effect transistors (GFETs). Saturation is necessary to achieve low-output conductance required for device power gain. Dual-channel pulsed current-voltage measurements are performed to eliminate the significant effects of trapped charge in the gate dielectric, a problem common to all oxide-based dielectric films on graphene. With pulsed measurements, graphene transistors with channel lengths as small as 130 nm achieve output conductance as low as 0.3 mS/μm in saturation. The transconductance of the devices is independent of channel length, consistent with a velocity saturation model of high-field transport. Saturation velocities have a density dependence consistent with diffusive transport limited by optical phonon emission.     

An efficient interface model to develop scalable methodology of melt processing of polypropylene with graphene oxide produced by an improved and eco-friendly electrochemical exfoliation

This study developed a scalable and straightforward adaptation methodology for melt processing of polypropylene (PP) to provide a high degree of exfoliation of multilayer graphene oxide (GO) by using a high-shear mixer. GO was first produced by an improved and eco-friendly electrochemical exfoliation by using an environmentally friendly aqueous methanesulfonic acid (MSA) and a sodium sulfate salt system to minimize the environmental impact. The produced GOs then were melt blended with PP and their mechanical, thermal, and morphological properties were investigated under different GO loadings to attain ideal configuration and increase interfacial interactions between polymer matrix and reinforcer. Comparisons were made by producing different PP composites using two different GO types produced in salt and acid environments. Additionally, by applying different voltages to salt system, the effect of applied voltage on the properties of both GO material and the composites were discussed. The characterization results indicated that GO obtained in MSA solution caused a 71% increase in flexural modulus and 46% in flexural strength with the addition of 1 wt% GO. The rheological characterization also showed that dispersion and viscosity improved with lower GO loadings compared to neat polymer by providing cost-effective and scalable graphene manufacturing.     

Formalisms for query capture and data source identification to support data fusion for construction productivity monitoring

Productivity monitoring, which involves frequent monitoring and analysis of on-going construction activities, helps in assessing a project's performance and in enabling identification of opportunities for improvement. It often involves finding answers for dynamic user queries that require data to be fused from different combinations of heterogeneous data sources having different levels of detail, representations and reference systems. Digital elements of these sources are expanding exponentially, and yet fusing and processing them manually remains a challenging problem. In this paper, the authors present a formal approach for capturing dynamic user queries and identifying applicable sets of data sources from a given set of available data sources to answer such queries. This approach is an important step to enable automated and efficient multi-source data fusion.     

Optimization of Extraction of Bioactive Compounds from Black Carrot Using Response Surface Methodology (RSM)

In this study, optimum conditions for the extraction of black carrot anthocyanins were determined by response surface methodology. Central composite design of extraction factors (pH 2.5–6.5, temperature 4–72 °C, solvent/solid ratio 5:1–25:1 v/w, ethanol/water ratio 0:100–100:0?v/v) was generated as two replicates. Total phenolic content, total monomeric anthocyanin content, polymeric color, total antioxidant activity, and anthocyanin composition determined by high-performance liquid chromatography were used as responses. Except for color analysis, higher temperature, solid/solvent ratio, and ethanol concentration were observed to increase the extraction yield. However, polymeric color results were found to have minimum values at lower pH and solid/solvent ratio, lower or moderate temperature, and higher ethanol concentration. Optimum extraction conditions were found as follows: 50 °C, pH 3.5, solvent solid ratio 10:1 (v/w), and ethanol/water ratio 75:25 (v/v) when all responses were considered. The validation of the optimum conditions for black carrot extraction was performed at specified values.     

Biohydrogen production by extracted fermentation from sugar beet

In the study, the production of biohydrogen by extracted fermentation from sugar beet was evaluated. Effects of initial amount of sugar beet, biomass and particle size of sugar beet on biohydrogen formation were investigated. The hydrogen (H₂) gas was predicted to be 78.6 mL at initial dry weight of sugar beet 24.6 g L^?1 and H₂ yield was calculated as 81.9 mLH₂ g^?1TOC while biomass concentration (1 g L^?1) and particle size (0.3 cm) were constant. The peak H₂ gas volume was predicted to be 139.9 mL at the low particle size of 0.1 cm. Hydrogen gas production potential was predicted as 143.6 mL h^?1. The peak value of 197.9 mLH₂ g^?1TOC was obtained with particle size of 0.1 cm when dry weight of sugar beet and initial amount of biomass was kept constant at 24.6 g L^?1 and 1 g L^?1, respectively.