Analysis of DC and AC properties of a humidity sensor based on polyaniline–chromium oxide composites

Polyaniline–Chromia (PANI–Cr₂O₃) composites were synthesized by in situ polymerization. The prepared composites were characterized by scanning electron microscopy, X-ray diffraction and Fourier transforms infrared spectroscopy. The structural studies confirm the polymerization of aniline over Cr₂O₃ particles which results into strong interaction between PANI and Cr₂O₃ particles. Direct current conductivity of composites increases with increase in temperature. Among all composites, 30 wt% shows high conductivity. The humidity sensing mechanism of the PANI–Cr₂O₃ composites is studied and change in its resistance with respect to percentage relative humidity ranging from 20 to 95 % is recorded. The humidity sensing studies shows that the change in the resistance is due to the uncurling of polymer chains by the absorption of water vapor which leads to increase in conduction paths. The results indicate better humidity sensing response by the addition of Cr₂O₃ particles to PANI, among all the composites, 30 wt% composite shows higher sensitivity.     

Residential Load Management Under Stochastic Weather Condition in Developing Countries

Abstract—This article focuses on offline residential load management in a developing country. This load management is based on scheduling linear load models under the stochastic weather conditions. The weather condition is modeled using the probability theory and Monte Carlo simulation. The seasonality effect, the type of day, and the stochastic hourly variation of weather conditions are considered as factors governing load management.     

Effects of Sintering Temperature on Open‐Volume Defects and Thermoluminescence of Yttria and Lutetia Ceramics

The effects of different processing steps and processing conditions for the fabrication of Y₂O₃ and Lu₂O₃ ceramics were investigated, particularly the effects of calcination, and sintering temperature on the content of open‐volume and electronic defects. Ceramic bodies were prepared from calcined powders by sintering from 1400°C to 1700°C for 20 h. Density was determined by the Archimedes method and showed pellets reached about 99% of Y₂O₃ density for temperatures ≥1450°C, and reached 98% for sintering at 1700°C for Lu₂O₃. The content of open‐volume defects was followed by positron annihilation lifetime (PAL) measurements. For both materials, two lifetimes were obtained. The faster lifetime, 211 ps for Y₂O₃ and 204 ps for Lu₂O₃, was assigned to bulk annihilation with possible contribution of grain boundaries. The longer lifetime was assigned to positronium annihilation in open‐volume defects with radii of 2–4 Å. Doppler broadening analysis revealed the same type of defect in Lu₂O₃ ceramics for all sintering temperatures. PAL analysis results showed that densification was achieved through the elimination and agglomeration of open‐volume defects. Thermoluminescence (TL) measurements of Y₂O₃ showed that sintering is beneficial in eliminating traps and/or recombination centers, and that higher sintering temperatures increase TL signal.     

Ultrasound-assisted extraction of natural antioxidants from betel leaves (Piper betle): Extraction kinetics and modeling

Present study investigated the extraction kinetics of antioxidants from Piper betle by ultrasound-assisted extraction for three extraction variables: temperature, solute to solvent ratio and ethanol concentration. Based on the results of yield, total phenolic content and antioxidant activity, the optimum results were obtained at 50°C, 1:20 g/mL and 80% ethanol, respectively. Statistical coefficients of R² ≥ 0.961 and RMSE ≤ 0.508 for two-site kinetic model confirm the use of proposed models for simulation and prediction purpose. Comparison with ascorbic acid and butylated hydroxytoluene solidifies the use of Piper betle as feasible source of natural antioxidants. The presence of hydroxychavicol and eugenol was affirmed by high-performance liquid chromatography assay.     

Size-tunable nanoparticles composed of dextran-b-poly(D,L-lactide) for drug delivery applications

Nanoparticles (NPs) formulated using self-assembly of block copolymers have attracted significant attention as nano-scaled drug delivery vehicles. Here we report the development of a biodegradable NP using self-assembly of a linear amphiphilic block copolymer, Dex-b-PLA, composed of poly(D,L-lactide), and dextran. The size of the NPs can be precisely tuned between 15 and 70 nm by altering the molecular weight (M _W) of the two polymer chains. Using doxorubicin as a model drug, we demonstrated that the NPs can carry up to 21% (w/w) of the drug payload. The release profile of doxorubicin from NPs showed sustained release for over 6 days. Using a rat model, we explored the pharmacokinetics profiles of Dex-b-PLA NPs, and showed proof-of-concept that long circulation lifetime of the NPs can be achieved by tuning the M _W of Dex-b-PLA block copolymer. While the terminal half-life of Dex-b-PLA NPs (29.8 h) was similar to that observed in poly(ethylene glycol)-coated (PEG-coated) NPs (27.0 h), 90% of the injected Dex-b-PLA NPs were retained in the blood circulation for 38.3 h after injection, almost eight times longer than the PEG-coated NPs. The area under curve (AUC) of Dex-b-PLA NPs was almost four times higher than PEG-based NPs. The biodistribution study showed lower accumulation of Dex-b-PLA NPs in the spleen with 19.5% initial dose per gram tissue (IDGT) after 24 h compared to PEG-coated poly(lactide-co-glycolide) (PLGA) NPs (29.8% IDGT). These studies show that Dex-b-PLA block copolymer is a promising new biomaterial for making controlled nanoparticles as drug delivery vehicles.      

A City for Education

Ameena Ahmadi is Architecture Manager at the Qatar Foundation, overseeing the development of the masterplan and facilities of Education City in Doha, a multi-institution educational campus, incorporating schools and universities. Ahmadi describes how education is a significant cornerstone for Qatar's national transition ‘to a knowledge-based’ economy from a ‘hydrocarbon-based’ one. This is symbolised by substantial investment in the flagship Education City with its Arata Isozaki masterplan and its individual schools and universities designed by premier international architects.     

Dynamic behavior of multi-carrier energy market in view of investment incentives

Electrical Engineering - In this study, a dynamic two-level framework is proposed to model investment incentives in a multi-carrier energy market from a strategic company’s point of view....     

Smart Home Activities: A Literature Review

Abstract

The increasing interest in smart home technologies has created a need for a comprehensive literature survey. This article reviews the goals of a smart home energy management system, along with related definitions, applications, and information about the manufacturing of its components. The challenges associated with smart home energy management systems and possible solutions are examined, and the energy factors that contribute to a customer's electricity bill are discussed. A number of price schemes and the load models needed for solving related scheduling optimization problems are also presented, including a review of the literature related to energy management system scheduling with respect to its control, automation, and communication.