A comparative study on curing characteristics and thermomechanical properties of elastomeric nanocomposites: The effects of eggshell and calcium carbonate nanofillers

After‐hatching eggshell (AHES) nanobiofiller and nanocalcium carbonate (nano‐CA) were separately added to various elastomers, such as acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), and natural rubber (NR), in various amounts of 5, 10, and 15 phr. The effect of particle size and dispersion of such nanofillers on thermomechanical properties and curing characteristics were then investigated. The ultimate tensile properties of SBR and NR nanocomposites were improved to some extent when 5 phr of AHES nanofiller was added to the rubber compound compared to CA. In the case of NBR nanocompounds, however, the mechanical properties were seemingly comparable, irrespective of the type of nanofiller. This contradictive behavior could be attributed to the alteration of crosslink density due to particular filler–matrix interaction while using mineral and natural fillers. The results of the rheometric study revealed that using AHES rather than CA slightly increases the scorch time of all types of prepared nanocomposites, whereas a significant drop in the optimum curing time was seen for NBR nanocomposites containing AHES biofiller. Moreover, thermogravimetric analysis showed similar thermal stability for SBR nanocomposites containing AHES and CA fillers. Finer particle size of CA and higher porosity of AHES at high and low loading levels were respectively the main reasons for improvement of ultimate properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Incorporating Nano-silica as a Binder to Improve Corrosion Resistance of High Alumina Refractory Castables

In this study, four types of castables as calcium-aluminate cement (CAC)-bonded and nano-silica (NS)-bonded castables based on tabular-alumina and bauxite aggregates were prepared to investigate the replacement of the calcium-aluminate cement by NS. All samples were allowed to dry at 110 °C then fired at 800 and 1200 °C. Bulk density and apparent porosity of samples were measured. The molten aluminum static corrosion test (cup test) results showed that NS-bonded specimens had higher resistance to corrosion compared to CAC-bonded samples (based on the measured average aluminum penetration depth into the refractory texture). However no penetration was observed in bauxite NS-bonded samples. The results were consistent with dynamic corrosion test in aluminum melt carried out at 800 °C for 100 h. The small pore size in NS-bonded castables was found to be the main cause for high corrosion resistance as micro-pores prevented the melt to penetrate into the refractory.     

Scattering of Dirac electrons by a random array of magnetic flux tubes

The scattering of two-dimensional (2D) massless electrons as presented in graphene in the presence of a random array of circular magnetic flux tubes is investigated. The momentum relaxation time and the Hall factor are obtained using optical theorem techniques for scattering. Electrons with energy close to those of the Landau levels of the flux tubes exhibit resonant scattering and have a long life-time to reside inside the magnetic flux tube. These resonances appear as sharp structures in the Hall factor and the magneto-resistance.     

Design of a low cross‐talk micro‐coil array for micro‐scale MRI

Design of magnetic resonance micro‐coil arrays with low cross‐talk among the coils can be the main challenge to improve the effectiveness of magnetic resonance micro‐imaging because the electrical cross‐talk which is mainly due to the inductive coupling perturbs the sensitivity profile of the array and causes image artifacts. In this work, a capacitive decoupling network with N(M ? 1) + (N ? 1)(M ? 2) capacitors is proposed to reduce the inductive coupling in an N × M array. A 3 × 3 array of optimized micro‐coils is designed using the finite element simulations and all the needed elements for the array equivalent circuit are extracted in order to evaluate the effectiveness of the proposed decoupling method by assessing the reduction of the coupled signals after employing the capacitive network on the circuit. The achieved results for the designed array show that the high cross‐talk level is reduced by the factor of 2.2–3.4 after employing the capacitive network. By employing this method of decoupling, the adjacent coils in each row and inner columns can be decoupled properly while the minimum decoupling belongs to the outer columns because of the lack of all necessary decoupling capacitances for these columns. The main advantages of the proposed decoupling method are its efficiency and design easiness which facilitates the design of dense arrays with the properly decoupled coils, especially the inner coils which are more coupled due to their neighbors. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 353–359, 2013     

A retrospective on DOSE: An interpretive approach to structure editor generation

DOSE is unique among structure editor generatiors in its interpretive approach. This approach leads to very fast turn-around time for changes and provides multi-language facilities for no aditional effort or cost. This article compares the interpretive approach to the compilation approach of other structure editor generators. It describes some of the design and implementation decisions made and remade durign this project and the lessons learned. It emphasizes the advantages and disadvantages of DOSE with respect to other structure editing systems.     

A novel double gate MOSFET by symmetrical insulator packets with improved short channel effects

In this article, we study a novel double-gate SOI MOSFET structure incorporating insulator packets (IPs) at the junction between channel and source/drain (S/D) ends. The proposed MOSFET has great strength in inhibiting short channel effects and OFF-state current that are the main problems compared with conventional one due to the significant suppressed penetrations of both the lateral electric field and the carrier diffusion from the S/D into the channel. Improvement of the hot electron reliability, the ON to OFF drain current ratio, drain-induced barrier lowering, gate-induced drain leakage and threshold voltage over conventional double-gate SOI MOSFETs, i.e. without IPs, is displayed with the simulation results. This study is believed to improve the CMOS device reliability and is suitable for the low-power very-large-scale integration circuits.     

Load‐balanced data gathering in Internet of Things using an energy‐aware cuckoo‐search algorithm

This paper deals with the lifetime problem in the Internet of Things. We first propose an efficient cluster‐based scheme named “Cuckoo‐search Clustering with Two‐hop Routing Tree (CC‐TRT)” to develop a two‐hop load‐balanced data aggregation routing tree in the network. CC‐TRT uses a modified energy‐aware cuckoo‐search algorithm to fairly select the best cluster head (CH) for each cluster. The applied cuckoo‐search algorithm makes the CH role to rotate between different sensors round by round. Subsequently, we extend the CC‐TRT scheme to present two methods for constructing multi‐hop data aggregation routing trees, named “Cuckoo‐search Clustering with Multi‐Hop Routing Tree (CC‐MRT)” and “Cuckoo‐search Clustering with Weighted Multi‐hop Routing Tree (CC‐WMRT).” Both CC‐MRT and CC‐WMRT rely on a two‐level structure; they not only use an energy‐aware cuckoo‐search algorithm to fairly select the best CHs but also adopt a load‐balanced high‐level routing tree to route the aggregated data of CHs to the sink node. However, CC‐WMRT slightly has a better performance thanks to its low‐level routing strategy. As an advantage, the proposed schemes balance the energy consumption among different sensors. Numerical results show the efficiency of the CC‐TRT, CC‐MRT, and CC‐WMRT algorithms in terms of the number of transmissions, remaining energy, energy consumption variance, and network lifetime.     

Towards More Practical Linear Programming-based Techniques for Algorithmic Mechanism Design

R. Lavi and C. Swamy (FOCS 2005, J. ACM 58(6), 25, 2011) introduced a general method for obtaining truthful-in-expectation mechanisms from linear programming based approximation algorithms. Due to the use of the Ellipsoid method, a direct implementation of the method is unlikely to be efficient in practice. We propose to use the much simpler and usually faster multiplicative weights update method instead. The simplification comes at the cost of slightly weaker approximation and truthfulness guarantees.     

MCM-41-supported NNO type Schiff base complexes: a highly selective heterogeneous nanocatalyst for esterification,Diels–Alder and aldol condensation

Solid catalysts have been synthesized by anchoring transition metal complexes into organically modified MCM-41. First, the surface of Si-MCM-41 was modified with 3-aminopropyl-triethoxysilane (3-APTES), the imine group of which upon condensation with DFP (4-methyl-2,6-diformylphenol) affords a N₂O-type Schiff base moiety in the mesoporous matrix. The Schiff base moieties were used to anchor Ni (II) and Cu (II) ions. The prepared catalyst have been characterized by DRS (Diffuse Reflectance Spectroscopy), FTIR (Fourier transform infrared) spectroscopy, small-angle X-ray diffraction (SAX), FESEM (Field Emission Scanning Electron Microscope), EDX (Energy-dispersive X-ray spectroscopy) and nitrogen sorption studies. The decrease of crystallinity in the multistep synthesis procedure, as evidenced by SAX (Small-angle X-ray) measurements, was observed. The prepared materials proved to be efficient catalysts for organic transformations such as esterification, Diels–Alder and Aldol condensation at ambient conditions. The immobilized complex does not leach or decompose during the catalytic reactions, showing practical advantages over the free metal complex.     

Enhanced Hilbert–Huang transform and its application to modal identification

The well‐known Hilbert–Huang transform (HHT) consists of empirical mode decomposition to extract intrinsic mode functions (IMFs) and Hilbert spectral analysis to obtain time–frequency characteristics of IMFs through the Hilbert transform. There are two mathematical requirements that limit application of the Hilbert transform. Moreover, noise effects caused by the empirical mode decomposition procedure add a scatter to derivative‐based instantaneous frequency determined by the Hilbert transform. In this paper, a new enhanced HHT is proposed in which by avoiding mathematical limitations of the Hilbert spectral analysis, an additional parameter is employed to reduce the noise effects on the instantaneous frequencies of IMFs. To demonstrate the efficacy of the proposed method, two case studies associated with structural modal identification are selected. In the first case, through identification of a typical 3‐DOF structural model subjected to a random excitation, accuracy of the enhanced method is verified. In the second case, ambient response data recorded from a real 15‐story building are analyzed, and nine modal frequencies of the building are identified. The case studies indicate that the enhanced HHT provides more accurate and physically meaningful results than HHT and is capable to be an efficient tool in structural engineering applications. Copyright © 2012 John Wiley & Sons, Ltd.