Structural stability studies of graphene in sintered ceramic nanocomposites

The post-sintering structural stability of graphene in alumina nanocomposites synthesised by Spark Plasma Sintering (SPS) and Hot Pressing (HP) was compared. Raman spectroscopy, thermogravimetric analyses and electrical conductivity analyses were conducted to characterise degradation of graphene due to the utilisation of different sintering techniques and conditions. Scanning Electron Microscopy confirmed good dispersion of graphene in SPSed and HPed sample. Graphene in SPSed and HPed nanocomposite samples sintered using longer durations (60 min) were found to possess higher crystallinity, thermal stability and electrical conductivity as compared to SPSed samples sintered using shorter sintering durations (10–20 min). This was attributed to the thermally induced graphitisation caused by longer sintering durations, which was lacking in SPSed samples processed using shorter sintering durations and lower temperature. No additional effect of DC pulsed current on the structural stability of graphene for nanocomposites were observed for samples prepared by SPS

A review of strategies to improve rational prescribing in asthma.

Background: There are well-recognised gaps between evidence-based recommendations and prescribing practices in asthma. While different strategies have been devised to improve rational prescribing, the impact of these is uncertain. Aim: To examine the characteristics and effectiveness of strategies to improve rational prescribing in asthma. Method: We systematically searched electronic databases to find studies that reported on strategies to improve prescribing in asthma, or included rational prescribing as one of the main components of the program. Results: There were thirteen relevant studies. All of the strategies described in these studies involved physician education using a variety of modalities; two of the trials also included patient-specific prescribing direction. Twelve of thirteen studies reported improved prescribing practice. There was significant heterogeneity in the interventions and outcome criteria employed by the studies. Conclusion: Strategies to improve rational prescribing in asthma show promise, but the significant methodological heterogeneity, and the absence in most cases of demonstrable clinical benefit, raise concerns about their applicability in clinical practice. Keywords: asthma, inappropriate prescribing, medication therapy management, physician's practice patterns, quality improvemen

On a variant and extension of Gabler inequality

We propose a Jensen-Mercer type variant and a Niezgoda type extension of Gabler inequality along with applications

Carbon Nanotube Reinforced High Density Polyethylene Materials for Offshore Sheathing Applications

Multiwall carbon nanotube (CNT)-filled high density polyethylene (HDPE) nanocomposites were prepared by extrusion and considered for their suitability in the offshore sheathing applications. Transmission electron microscopy was conducted to analyse dispersion after bulk extrusion. Monolithic and nanocomposite samples were subjected to accelerated weathering and photodegradation (carbonyl and vinyl indices) characterisations, which consisted of heat, moisture (seawater) and UV light, intended to imitate the offshore conditions. The effects of accelerated weathering on mechanical properties (tensile strength and elastic modulus) of the nanocomposites were analysed. CNT addition in HDPE produced environmentally resilient nanocomposites with improved mechanical properties. The energy utilised to extrude nanocomposites was also less than the energy used to extrude monolithic HDPE samples. The results support the mass substitution of CNT-filled HDPE nanocomposites in high-end offshore applications

Silver Columnar Thin-Film-Based Half-Wavelength Antennas for Bright Directional Emission from Nanodiamond Nitrogen-Vacancy Centers

© 2019 American Physical Society. Nitrogen-vacancy (N-V) centers in nanodiamond (ND) are a promising single-photon-source candidate for quantum technology. However, the poor N-V emission rate and low outcoupling of light significantly hinder their effective use in practical implementations. To overcome this limit, we place NDs hosting N-V centers on silver columnar thin films (CTFs) and measure an increase in emission by an order of magnitude. The CTFs consist of silver nanocolumns the length of which is chosen to be half the wavelength of the emitted light. The silver nanocolumns act as efficient optical antennas that couple to the N-V centers via the optical near field and outcouple the excitation energy of the N-V centers effectively into the optical far field. A large distribution of radiated powers from different NDs is observed. Computer simulations show this distribution to arise from the different orientations of the emitting dipoles with respect to the columnar axis. We also report that further structuring of the silver CTF into gratings yields higher photon emission

Thermally stimulated H emission and diffusion in hydrogenated amorphous silicon

We report first principles ab initio density functional calculations of hydrogen dynam- ics in hydrogenated amorphous silicon. Thermal motion of the host Si atoms drives H diffusion, as we demonstrate by direct simulation and explain with simple models. Si-Si bond centers and Si ring centers are local energy minima as expected. We also describe a new mechanism for break- ing Si-H bonds to release free atomic H into the network: a fluctuation bond center detachment (FBCD) assisted diffusion. H dynamics in a-Si:H is dominated by structural fluctuations intrinsic to the amorphous phase not present in the crystal.Comment: 4 pages, 5 figures, In press EPL (Jun. 2007

Broadband Resonant Elements for 5G Reflectarray Antenna Design

The performance investigation of two novel resonant elements is presented in this work for 5G reflectarray antenna design. Two dual resonance elements with wide reflection phase range have been developed from a square patch element by a novel corner bending tactic. The reflection loss and reflection phase range performance of the proposed elements have been compared with conventional square patch element at 26 GHz. The results have shown a reflection phase swing of 629° and 632° for Bent Width and Bent Length elements respectively. The broadband features of proposed elements can radically improve the bandwidth performance of a reflectarray antenna

Mutual Coupling Reduction between Asymmetric Reflectarray Resonant Elements

A physically asymmetric reflectarray element has been proposed for wide band operations. The dual resonant response has been introduced by tilting one side of the square path element. The numerical results have been analyzed in the frequency band between 24GHz to 28GHz where a reflection phase range of more than 600° has been achieved. The proposed asymmetric element can produce mutual coupling with adjacent elements on a reflectarray. This effect has been monitored by placing the elements in a mirror configuration on the surface of reflectarray. The single unit cell element results have been compared with conventional 4 element unit cell and proposed mirroring element configuration. The proposed mirroring element technique can be used to design a broadband reflectarray for high gain applications

A review of wideband reflectarray antennas for 5G communication systems

The advancement in the current communication technology makes it incumbent to analyze the conventional features of reflectarray antenna for future adaptability. This work thoroughly reviews the design and experimental features of reflectarray antenna for its bandwidth improvement in microwave and millimeter wave frequency ranges. The paper surveys the fundamental and advanced topologies of reflectarray design implementations which are needed particularly for its broadband features. The realization of its design approaches has been studied at unit cell and full reflectarray levels for its bandwidth enhancement. Various design configurations have also been critically analyzed for the compatibility with the high frequency 5G systems