Investigation of zeolitic imidazolate frameworks–derived carbon nanotubes thin film in solar vapor generation

Journal of Porous Materials - Solar vapor generation is considered a green and practical approach to take advantage of solar energy as a renewable source and provide pure water. However, developing...     

Quantitative characterization of carrier injection across metal–organic interfaces using Bardeen theory

We have investigated the contact between a metal and an organic/polymeric (o/p) material and we have introduced a relation for carrier injection using Bardeen theory. A series of narrow barriers is considered in the semiconductor side to account for the localized nature of the carriers in the o/p material. As an application of the model, we have calculated the hopping rate of carriers in terms of the contact parameters. Also, we have discussed the hopping of carriers deep into the organic dielectric. Finally, we have explored the hopping rate in practical contacts between polyfluorene-based polymers and different electrodes.     

Multi-objective Phasor Measurement Unit Placement in Electric Power Networks: Integer Linear Programming Formulation

A multi-objective optimal phasor measurement unit placement model using integer linear programming is presented in this article. The proposed model simultaneously optimizes two objectives, i.e., minimization of phasor measurement unit numbers and maximization of measurement redundancy. To calculate the redundancy criteria, the single-line outage and the phasor measurement unit loss are considered simultaneously. A linear formulation is presented for both objective functions. Also herein, to address conflicting attributes and identify Pareto optimal solutions of the multi-objective optimal phasor measurement unit placement problem, a new multi-objective mathematical programming method is proposed. Finally, a new index, i.e., minimum distance to utopia point, is implemented to select the most preferred solution among the available Pareto front based options on the goal to achieve judicious decision makers. Two test systems, i.e., a modified 9-bus and an IEEE 118-bus test systems, are used to illustrate the effectiveness of the proposed framework.     

A solidification model for prediction of castability in the precipitation-strengthened nickel-based superalloys

The Scheil equation was used to model the solidification path, microsegregation of alloying elements in the interdendritic regions, solidification temperature ranges, and to predict the formation of secondary structures and the castability behavior of as-cast superalloys. 4 experimental alloys with pre-specified γ-Ti,Nb,Al,Mo composition containing different Nb, Ti and Al contents were designed using vacuum induction melting furnace. The produced as-cast superalloys were characterized using optical and scanning electron microscopy equipped with energy dispersive X-ray spectrometer and TG–DSC analysis. The experiments showed logic conformity to the modeling results. The model and experiment confirmed the highest segregation behavior for Ti and Nb. All the experimental superalloys indicated the remarkable tendency to form secondary eutectic structures at the last stages of solidification. Superalloy with chemical composition of γ-3.5%Mo,1.8%Al,4%Ti,2.9%Nb showed the shorter solidification temperature range and the best castability.     

Genetic-based random key generator (GRKG): a new method for generating more-random keys for one-time pad cryptosystem

In this paper, a new algorithm for generating more-randomized keys for symmetrical cipher one-time pad (OTP) according to the linear congruential (LCG) method based on the idea of genetic algorithm is proposed. The method, genetic-based random key generator, is proposed for generating keys for the OTP method with a high degree of key randomness; this adds more strength to the OTP method against breaking this cryptosystem. This algorithm is composed of two parts. Initially, the first population is being generated by LCG method, and then, genetic operators for generating the next populations are being used. Generating random keys with the presented method requires seven-parameter key that increases the security of communication between the transceivers.     

Effect of long-chain monoacrylate on the residual monomer content, swelling and thermomechanical properties of SAP hydrogels

Residual monomer is an important factor, particularly in hygienic materials such as superabsorbent polymer (SAP) hydrogels. Recently, we reported different approaches to minimizing residual monomer content in SAPs. In this paper, the effect of a long-chain monomer, poly(ethylene glycol) methylether methacrylate (PEG.MEMA), on the residual monomer content of SAP networks of partially neutralized acrylic acid–PEG.MEMA is investigated. The aim of using PEG.MEMA in SAP synthesis was to reduce the glass transition temperature (T _g) of SAP. As the temperature that is conventionally used to dry SAP (70–110 °C) is lower than the T _g of ordinary SAPs, the polymer is in the glassy state during the heating stage. It was assumed that converting SAP from the glassy state to the rubbery state during drying would facilitate the removal of acrylic acid monomer (AA) from the gel, thus reducing the residual monomer content. The results showed that the use of PEG.MEMA led to a reduction in residual AA when the drying temperature was 100 °C. The residual AA was decreased from 169 to 95 ppm when the drying time was increased from 3 to 15 hours at 100 °C. This positive effect of PEG.MEMA on the level of unwanted residual AA became insignificant at a higher drying temperature (140 °C). The effects of PEG.MEMA content on the thermal and mechanical properties (in the dried state) and the rheological properties (in the water-swollen state) of the SAP hydrogels were also investigated. The swelling capacity and rate was studied in relation to the PEG.MEMA content. It was found that a high level of PEG.MEMA restricted both the absorption capacity and the rate of water absorption.     

Content-based image database system for epilepsy

We have designed and implemented a human brain multi-modality database system with content-based image management, navigation and retrieval support for epilepsy. The system consists of several modules including a database backbone, brain structure identification and localization, segmentation, registration, visual feature extraction, clustering/classification and query modules. Our newly developed anatomical landmark localization and brain structure identification method facilitates navigation through an image data and extracts useful information for segmentation, registration and query modules. The database stores T1-, T2-weighted and FLAIR MRI and ictal/interictal SPECT modalities with associated clinical data. We confine the visual feature extractors within anatomical structures to support semantically rich content-based procedures. The proposed system serves as a research tool to evaluate a vast number of hypotheses regarding the condition such as resection of the hippocampus with a relatively small volume and high average signal intensity on FLAIR. Once the database is populated, using data mining tools, partially invisible correlations between different modalities of data, modeled in database schema, can be discovered. The design and implementation aspects of the proposed system are the main focus of this paper.     

Development of a hybrid energy storage sizing algorithm associated with the evaluation of power management in different driving cycles

In this paper, a hybrid energy storage sizing algorithm for electric vehicles is developed to achieve a semi-optimum cost-effective design. Using the developed algorithm, a driving cycle is divided into its micro-trips and the power and energy demands in each micro-trip are determined. The battery size is estimated because the battery fulfills the power demands. Moreover, the ultra-capacitor (UC) energy (or the number of UC modules) is assessed because the UC delivers the maximum energy demands of the different micro-trips of a driving cycle. Finally, a design factor, which shows the power of the hybrid energy storage control strategy, is utilized to evaluate the newly designed control strategies. Using the developed algorithm, energy-saving loss, driver satisfaction criteria, and battery life criteria are calculated using a feed-forward dynamic modeling software program and are utilized for comparison among different energy storage candidates. This procedure is applied to the hybrid energy storage sizing of a series hybrid electric city bus in Manhattan and to the Tehran driving cycle. Results show that a higher aggressive driving cycle (Manhattan) requires more expensive energy storage system and more sophisticated energy management strategy.     

Electrooxidation of alcohols at a nickel oxide/multi-walled carbon nanotube-modified glassy carbon electrode

Electrocatalytic oxidation of methanol and some other primary alcohols on a glassy carbon electrode modified with multi-walled carbon nanotubes and nano-sized nickel oxide (GCE/MWNT/NiO) was investigated by cyclic voltammetry and chronoamperometry in alkaline medium. The results were compared with those obtained on a nickel oxide-modified glassy carbon electrode (GCE/NiO). Both the electrodes were conditioned by potential cycling in the range of 0.1–0.6 V versus Ag/AgCl in a 0.10 M NaOH solution. The effects of various parameters such as scan rate, alcohol concentration, thickness of NiO film, and real surface area of the modified electrodes were also investigated and compared. It was found that the GCE/MWNT/NiO-modified electrode possesses an improved electrochemical behavior over the GC/NiO-modified electrode for methanol oxidation.