In this article, miniaturization of the wire monopole antenna with the help of high refractive index (HRI) metamaterial is presented. For the first time, HRI medium is realized by using the array of single ring split ring resonator. By surrounding the wire monopole with the array of SR‐SRRs, the effective wavelength is squeezed in the vicinity of the near field dominance. By the loading of the monopole with such an HRI medium, the size of the antenna is reduced from 29.5 to 16 mm, without any deformation in the current distribution and radiation pattern corresponding to the fundamental resonance. The simulated and measured results are agreed to the same. 相似文献
A coaxial‐fed tri‐band zeroth‐order resonance (ZOR) circularly polarized antenna with higher gains for all the excited ZORs is designed and analyzed in this paper. Epsilon negative transmission line (ENG TL) and pseudo‐open termination (P‐OT) unit cells with different series capacitances (CS and CS1 ) resonate shunt ZOR (fsh ) and two series ZORs (fse and fse1 ), respectively. Asymmetric unit cell concept is applied to ENG‐TL and P‐OT unit cells to create vertical and horizontal components, and the 90° phase shift is provided by the ZOR, resulting in circular polarization (CP). Left‐hand CP (LHCP) is achieved by creating two 90° right bends to the extended stubs in ENG TL and P‐OT unit cells. Higher gains for all the excited ZORs are achieved by shifting the shorting pins of ENG TL and P‐OT unit cells far away from the center position. After fabrication, the measured resonances occur at 4.64 GHz (fsh ), 4.04 GHz (fse ), and 3.86 GHz (fse1 ) with fractional bandwidths of 1.62%, 1.73%, and 1.6%, respectively. The measured LHCP peak gains are 4.05 dBic (fsh ), 3.85 dBic (fse ), and 3.94 dBic (fse1 ). The average axial ratio obtained is less than 3‐dB in the 10‐dB fractional bandwidth of the proposed antenna. 相似文献
Selected mapping (SLM) is one of the promising techniques used for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) system. One of the major drawbacks in this technique is that, the transmitter is forced to transmit more amount of side information (SI) bits in order to recover the original data at the receiver, which leads to data rate loss and inefficient transmission. In this paper, a new phase sequence generation method using Lehmer Random Number Generator (LRNG) called Lehmer sequence is proposed for SLM technique. Using the periodicity property of this sequence, the SI bits are embedded within the transmitted data block for 16-PSK modulation, which ensures that SI bits are not explicitly sent. The simulation results show that the proposed SLM (PSLM) provides a slight improvement in PAPR reduction without compromising the bit error rate (BER) for higher values of an expansion factor when compared to conventional SLM (CSLM).
Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom
transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the
reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis.
This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out
in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as
0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized
magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared
and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite
core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting
reaction. 相似文献
Abstract The surface-initiated ATRP of benzyl methacrylate, methyl methacrylate, and styrene from magnetite nanoparticle is investigated,
without the use of sacrificial (free) initiator in solution. It is observed that the grafting density obtained is related
to the polymerization kinetics, being higher for faster polymerizing monomer. The grafting density was found to be nearly
2 chains/nm2 for the rapidly polymerizing benzyl methacrylate. In contrast, for the less rapidly polymerizing styrene, the grafting density
was found to be nearly 0.7 chain/nm2. It is hypothesized that this could be due to the relative rates of surface-initiated polymerization versus conformational
mobility of polymer chains anchored by one end to the surface. An amphiphilic diblock polymer based on 2-hydroxylethyl methacrylate
is synthesized from the polystyrene monolayer. The homopolymer and block copolymer grafted MNs form stable dispersions in
various solvents. In order to evaluate molecular weight of the polymer that was grafted on to the surface of the nanoparticles,
it was degrafted suitably and subjected to gel permeation chromatography analysis. Thermogravimetric analysis, transmission
electron microscopy, and Fourier transform infrared spectroscopy were used to confirm the grafting reaction.
Graphical Abstract
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Blends of maleated ethylene propylene diene rubber (EPDM) and thermoplastic polyurethane (TPU) have been studied to understand the effect of the maleation level of EPDM on the compatibility and morphology of the blends. Blends with different maleation levels on EPDM (0.25, 0.50, and 0.75 wt%) were compared for mechanical, thermal, and other properties. The appearance of single Tg for 0.5% and 0.75% confirms that a maleation level of more than 0.5 wt% is required for EPDM blends with TPU. However, best mechanical properties are obtained for 0.5% maleated EPDM and TPU blends. Aging, filler reinforcement, and weather resistance measurements were also studied for the blends of varying maleation levels. 相似文献
Performance measurement models are essential to support various decision making problems that may arise during life cycle of a facilities layout. Available models are only suitable for early stages in the design phase of life cycle. However, measurement models have a great consequence in other phases also such as production planning, control and when modification to be incorporated due to the changes in market demand, which happens very often in today's global competition. In addition, the existing models have considered only material handling cost as the performance measurement factor. Nevertheless, the empty travel of material handling equipment, layout flexibility and area utilisation have a significant contribution towards the layout effectiveness. It is therefore necessary to have a measurement model to determine the facilities layout's effectiveness by considering all significant factors. A measurement model considering a set of three layout effectiveness factors—facilities layout flexibility (FLF), productive area utilisation (PAU) and closeness gap (CG)—is developed in our research. The proposed model will enable the decision-maker of a manufacturing enterprise to analyse a layout in three different aspects, based on which they can make decision towards productivity improvement. This paper mainly discusses about the measurement of the CG. The CG is developed with respect to the objective of bringing closer the highly interactive facilities/departments. The CG presented in this paper extends other related works by incorporating numerous aspects of layout that include empty travel of material handling equipment, information flow, personnel flow and equipment flow. 相似文献