Studies of nanocomposites based on carbon nanomaterials and RTV silicone rubber

The mechanical and electrical properties were investigated for nanocomposites based on carbon nanotubes (CNTs) and conductive carbon black (CB). Solution room‐temperature‐vulcanized silicone rubber was used as a matrix. Vulcanizates based on CNTs and CB was prepared by solution mixing. With the addition of 2 phr of CNTs to the rubber matrix, the Young's modulus increased by 272% and reached as high as ～706% at 8 phr, whereas the modulus increased only 125% for CB specimens at 10 phr. Similarly, the electrical properties at 5 phr content of CNT were ～0.7 kΩ against ～0.9 kΩ at 20 phr CB. The Kraus plot from equilibrium swelling tests shows that the high properties for CNT specimens are due to high polymer–filler interfacial interactions, the small particle size that improves the distribution of the filler in a highly exfoliated state, and high electrical connective networks among the filler particles. These improvements can especially influence medical products such as feeding tubes, seals and gaskets, catheters, respiratory masks and artificial muscles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44407.     

Corrosion Behaviors of Zirconia Refractory by CaO–SiO2–MgO–CaF2 Slag

In this work the corrosion behaviors of zirconia refractory (partially MgO-stabilized zirconia) was investigated in CaO–SiO₂–MgO–CaF₂ slag with varying CaF₂ content at 1873 K. To figure out the corrosion mechanism, the characteristics of present slag at high temperature were examined in terms of melting temperature and vaporization behaviors. Corrosion experiment and melting temperature measurement were carried out by heating microscope (HM) and the vaporization phenomenon was investigated by thermo gravimetry–differential scanning calorimetry. After experiment, the corroded interfaces of zirconia refractory by slag were analyzed by scanning electron microscope-energy dispersive spectroscopy and electron probe microanalysis. With an addition of CaF₂, three different layers were formed at the interface of slag and zirconia refractory. Furthermore, the corrosion behaviors of zirconia refractory were found to be continuously accelerated with an increase of CaF₂ which facilitated the dissolution of intermediate compound. On the other hand, melting temperature of CaO–SiO₂–MgO–CaF₂ slag showed no continuous decrease with an increase of CaF₂. Also, considerable vaporization of fluoride gas was occurred in high CaF₂ containing slag during HM experiment which might cause a gradual change of slag composition and also environmental pollution. From the results, present study suggested that a proper amount of CaF₂ should be added when it is used for enhancing refining capacity of slag in order not to cause any severe damage of zirconia-based refractory by slag.     

Multigroup pin power reconstruction with two-dimensional source expansion and corner flux discontinuity

A pin power reconstruction method that is readily applicable to multigroup problems with superior accuracy is presented for applications involving rectangular fuel assemblies. It employs a two-dimensional (2D), fourth order Legendre expansion of the source distribution that naturally leads to a group-decoupled, 2D semi-analytic solution of the neutron diffusion equation. The four surface average currents and four corner fluxes are used as the boundary conditions to uniquely specify the homogenous solution. The corner fluxes and source expansion coefficients are iteratively determined using the condition of corner point balance and the orthogonal property of the Lengedre functions. Corner discontinuity is incorporated in the calculation of the corner fluxes which turns out to be very effective in the cases of enrichment zoning. The accuracy of the proposed method is assessed by performing the two-step core calculations for the L336C5, C5G7MOX, and MOX core transient benchmark problems and then by comparing with the direct whole-core transport solutions. The results indicate that the proposed method is as accurate as the fully analytic method and works well irrespective the number of groups. However, it is also noted that somewhat larger errors are inevitable at the peripheral assemblies near the reflector in which the error associated with a prioi generation of the homogenized cross-sections and form functions is not trivial.     

A rapid method for the simultaneous determination of 25 anti-hypertensive compounds in dietary supplements using ultra-high-pressure liquid chromatography

A novel, stable, simple and specific ultra-performance liquid chromatography method with ultraviolet detection (205 nm) for the simultaneous analysis of 25 anti-hypertensive substances was developed. The method was validated according to the International Conference of Harmonisation guidelines with respect to linearity, accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ) and stability. From the ultra-performance liquid chromatography results, we identified the LOD and LOQ of solid samples to be 0.20–1.00 and 0.60–3.00 μg ml^?1, respectively, while those of liquid samples were 0.30–1.20 and 0.90–3.60 μg ml^?1, respectively. The linearity exceeded 0.9999, and the intra- and inter-day precisions were 0.15–6.48% and 0.28–8.67%, respectively. The intra- and inter-day accuracies were 82.25–111.42% and 80.70–115.64%, respectively, and the stability was lower than 12.9% (relative standard deviation). This method was applied to the monitoring of 97 commercially available dietary supplements obtained in Korea, such as pills, soft capsules, hard capsules, liquids, powders and tablets. The proposed method is accurate, precise and of high quality, and can be used for the routine, reproducible analysis and control of 25 anti-hypertensive substances in various dietary supplements. The work presented herein may help to prevent incidents related to food adulteration and restrict the illegal food market.     

Condition monitoring scheme via one-class support vector machine and multivariate control charts

A condition-based maintenance (CBM) has been widely employed to reduce maintenance cost by predicting the health status of many complex systems in prognostics and health management (PHM) framework. Recently, multivariate control charts used in statistical process control (SPC) have been actively introduced as monitoring technology. In this paper, we propose a condition monitoring scheme to monitor the health status of the system of interest. In our condition monitoring scheme, we first define reference data set using one-class support vector machine (OC-SVM) to construct the control limit of multivariate control charts in phase I. Then, parametric control chart or non-parametric control chart is selected according to the results from multivariate normality tests. The proposed condition monitoring scheme is applied to sensor data of two anemometers to evaluate the performance of fault detection power.

     

Strain‐Visualization with Ultrasensitive Nanoscale Crack‐Based Sensor Assembled with Hierarchical Thermochromic Membrane

As eidetic signal recognition has become important, displaying mechanical signals visually has imposed huge demands for simple readability and without complex signal processing. Such visualization of mechanical signals is used in delicate urgent medical or safety‐related industries. Accordingly, chromic materials are considered to facilitate visualization with multiple colors and simple process. However, the response and recovery time is very long, such that rapid regular signals are unable to be detected, i.e., physiological signals, such as respiration. Here, the simple visualization of low strain ≈2%, with ultrasensitive crack‐based strain sensors with a hierarchical thermochromic layer is suggested. The sensor shows a gradient color change from red to white color in each strain, which is attributed to the hierarchical property, and the thermal response (recovery) time is dramatically minimized within 0.6 s from 45 to 37 °C, as the hierarchical membrane is inspired by termite mounds for efficient thermal management. The fast recovery property can be taken advantage of in medical fields, such as monitoring regular respiration, and the color changes can be delicately monitored with high accuracy by software on a mobile phone.     

Miniaturized Flexible Electronic Systems with Wireless Power and Near‐Field Communication Capabilities

A class of thin, lightweight, flexible, near‐field communication (NFC) devices with ultraminiaturized format is introduced, and systematic investigations of the mechanics, radio frequency characteristics, and materials aspects associated with their optimized construction are presented. These systems allow advantages in mechanical strength, placement versatility, and minimized interfacial stresses compared to other NFC technologies and wearable electronics. Detailed experimental studies and theoretical modeling of the mechanical and electromagnetic properties of these systems establish understanding of the key design considerations. These concepts can apply to many other types of wireless communication systems including biosensors and electronic implants.     

Energy‐efficient power control for uplink spectrum‐sharing heterogeneous networks

This article considers energy‐efficient power control schemes for interference management in uplink spectrum‐sharing heterogeneous networks that maximize the energy efficiency of users, protect the macro base station, and support users with QoS consideration. In the first scenario, we define the objective function as the weighted sum of the energy efficiencies and develop an efficient global optimization algorithm with global linear and local quadratic rate of convergence to solve the considered problem. To ensure fairness among individual user equipments (UEs) in terms of energy efficiency, we consider the max‐min problem, where the objective is defined as the weighted minimum of the energy efficiencies, and a fractional programming theory and the dual decomposition method are jointly used to solve the problem and investigate an iterative algorithm. As by‐products, we further discuss the global energy efficiency problem and consider near‐optimal schemes. Numerical examples are provided to demonstrate significant improvements of the proposed algorithms over existing interference management schemes.     

Simultaneous Formation of Ohmic Contacts on p +- and n +-4H-SiC Using a Ti/Ni Bilayer

In this work, Ti/Ni bilayer contacts were fabricated on both p ⁺- and n ⁺-4H-SiC formed by ion implantation, and the effects of the Ti interlayer on the contact resistance and interfacial microstructure were studied. Adoption of a thin (10 nm) Ti interlayer resulted in specific contact resistance of 4.8 μΩ cm² and 1.3 mΩ cm² on n ⁺- and p ⁺-4H-SiC, respectively, comparable to the values for contacts using only Ni. Moreover, contacts using Ti/Ni provide a flat and uniform interface between Ni₂Si and SiC, whereas discontinuous, agglomerated Ni₂Si islands are formed without the use of a Ti interlayer. In addition, the Ti interlayer was demonstrated to effectively dissociate the thin oxide film on SiC, which is advantageous for low-resistance, reliable ohmic contact formation. In summary, use of a Ti/Ni bilayer is a promising solution for one-step formation of ohmic contacts on both p ⁺- and n ⁺-4H-SiC, being especially suitable for SiC n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET) fabrication.     

Mobile Oriented Future Internet (MOFI):Architectural Design and Implementations

With the recent growth in smartphone services, the “mobile” environment has become a key factor to consider in the design of the future Internet. In this paper, we propose Mobile‐Oriented Future Internet (MOFI), which is a new architecture for the future Internet for mobile‐oriented environments. The MOFI architecture is designed with three functional features: global identifier and local locator in the identifier‐locator separation, query‐first data delivery for route optimization, and distributed control of identifier‐locator mapping. The proposed architecture and functional operations are implemented and tested using the Linux platform. From the experiment results, we see that the MOFI architecture performs better than the existing identifier‐locator separation schemes, such as Proxy Mobile IP and Host Identity Protocol, in terms of data throughout, mapping control overhead, and handover delay.