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  • Articles  (13,996)
  • MDPI  (6,217)
  • Oxford University Press  (4,934)
  • Institution of Engineering and Technology (IET)  (2,845)
  • Electrical Engineering, Measurement and Control Technology  (13,996)
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  • 1
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    Cover Page (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-09
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Published by Oxford University Press on behalf of The Japanese Electron Microscopy Society.
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  • 2
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    Subscription Page (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-09
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Published by Oxford University Press on behalf of The Japanese Electron Microscopy Society.
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  • 3
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    Recent advancements in structured-illumination microscopy toward live-cell imaging (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Description: Fluorescence microscopy allows us to observe fluorescently labeled molecules in diverse biological processes and organelle structures within living cells. However, the diffraction limit restricts its spatial resolution to about half of its wavelength, limiting the capability of biological observation at the molecular level. Structured-illumination microscopy (SIM), a type of super-resolution microscopy, doubles the spatial resolution in all three dimensions by illuminating the sample with a patterned excitation light, followed by computer reconstruction. SIM uses a relatively low illumination power compared with other methods of super-resolution microscopy and is easily available for multicolor imaging. SIM has great potential for meeting the requirements of live-cell imaging. Recent developments in diverse types of SIM have achieved higher spatial (~50 nm lateral) and temporal (~100 Hz) resolutions. Here, we review recent advancements in SIM and discuss its application in noninvasive live-cell imaging.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Published by Oxford University Press on behalf of The Japanese Electron Microscopy Society.
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  • 4
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    STED microscopy--super-resolution bio-imaging utilizing a stimulated emission depletion (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Description: One of the most popular super-resolution microscopies that breaks the diffraction barrier is stimulated emission depletion (STED) microscopy. As the optical set-up of STED microscopy is based on a laser scanning microscopy (LSM) system, it potentially has several merits of LSM like confocal or two-photon excitation LSM. In this article, we first describe the principles of STED microscopy and then describe the features of our newly developed two-photon excitation STED microscopy. On the basis of our recent results and those of other researchers, we conclude by discussing future research and new technologies in this field.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Published by Oxford University Press on behalf of The Japanese Electron Microscopy Society.
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  • 5
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    For Microscopy special feature on 'super resolution microscopy' (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 6
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    Ultrathin sectioning with DUV-pulsed laser ablation: development of a laser ablation nano tome (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Description: The electrically automated ultrathin sectioning apparatus, which has been developed in recent years, can produce consecutive ultrathin sections with a diamond knife and a gallium ion beam. These newly developed apparatuses, however, have several shortcomings, such as the limited block cutting area, thermal damage to the sample by the focused ion beam and a sample electronic charge. To overcome these faults and for easier scanning electron microscopy three-dimensional fine structural reconstruction, we have developed a new cutting method using a deep ultraviolet laser, which we have named the ‘LANTome (Light Ablation Nanotome)’. Using this method, we confirmed the widening of sectioning areas, shortening of the sectioning time, automatic smoothing of rough surfaces, no sample electronic charge and minimal heat effects on the sample tissue, such as thermal denaturation.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 7
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    A guide to use photocontrollable fluorescent proteins and synthetic smart fluorophores for nanoscopy (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Description: Recent advances in nanoscopy, which breaks the diffraction barrier and can visualize structures smaller than the diffraction limit in cells, have encouraged biologists to investigate cellular processes at molecular resolution. Since nanoscopy depends not only on special optics but also on ‘smart’ photophysical properties of photocontrollable fluorescent probes, including photoactivatability, photoswitchability and repeated blinking, it is important for biologists to understand the advantages and disadvantages of fluorescent probes and to choose appropriate ones for their specific requirements. Here, we summarize the characteristics of currently available fluorescent probes based on both proteins and synthetic compounds applicable to nanoscopy and provide a guideline for selecting optimal probes for specific applications.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 8
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    Aberrations and adaptive optics in super-resolution microscopy (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Description: As one of the most powerful tools in the biological investigation of cellular structures and dynamic processes, fluorescence microscopy has undergone extraordinary developments in the past decades. The advent of super-resolution techniques has enabled fluorescence microscopy – or rather nanoscopy – to achieve nanoscale resolution in living specimens and unravelled the interior of cells with unprecedented detail. The methods employed in this expanding field of microscopy, however, are especially prone to the detrimental effects of optical aberrations. In this review, we discuss how super-resolution microscopy techniques based upon single-molecule switching, stimulated emission depletion and structured illumination each suffer from aberrations in different ways that are dependent upon intrinsic technical aspects. We discuss the use of adaptive optics as an effective means to overcome this problem.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 9
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    Non-uniform sampling based on an adaptive level-crossing scheme (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-07
    Description: Level-crossing (LC) analog-to-digital (A/D) converters can efficiently sample certain classes of signals. An LC A/D converter is a real-time asynchronous system, which encodes the information of an analog signal into a sequence of non-uniformly spaced time instants. In particular, this class of A/D converters uses an asynchronous data conversion approach, which is a power efficient technique. In this study, the authors propose adaptive and multi-level adaptive LC sampling models as alternatives to conventional LC schemes and apply an iterative algorithm to improve the reconstruction quality of LC A/D converters. This simulation results show that multi-level adaptive LC outperforms conventional A/D converters such as sigma-delta A/D converters in terms of performance and computational complexity.
    Print ISSN: 1751-9675
    Electronic ISSN: 1751-9683
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 10
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    Epileptic seizure detection by exploiting temporal correlation of electroencephalogram signals (2015)
    Institution of Engineering and Technology (IET)
    Details
    Publication Date: 2015-08-07
    Description: Electroencephalogram (EEG) has a great potential for diagnosis and treatment of brain disorders like epileptic seizure. Feature extraction and classification of EEG signals is the crucial task to detect the stages of ictal and interictal signals for treatment and precaution of epileptic patients. However, existing seizure and non-seizure feature extraction techniques are not good enough for the classification of ictal and interictal EEG signals considering the non-abruptness phenomena and inconsistency in different brain locations. In this study, the authors present a new approach for feature extraction and classification by exploiting temporal correlation within EEG signals for better seizure detection as any abruptness in the temporal correlation within a signal represents the transition of a phenomenon. In the proposed methods, they divide an EEG signal into a number of epochs and arrange them into two-dimensional matrix and then apply different transformation/decomposition to extract a number of statistical features. These features are then used as an input into LS-SVM to classify them. Experimental results show that the proposed methods outperform the existing state-of-the-art method for better classification in terms of sensitivity, specificity and accuracy of ictal and interictal period of epilepsy for benchmark datasets and different brain locations.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 11
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    Admissible wavelet packet sub-band-based harmonic energy features for Hindi phoneme recognition (2015)
    Institution of Engineering and Technology (IET)
    Details
    Publication Date: 2015-08-07
    Description: In recent years, wavelet packet (WP) transform has been used as an important speech representation tool. WP-based acoustic features have found to be more effective than the short-time Fourier transform (STFT)-based features to capture the information of unvoiced phoneme in continuous speech. However, wavelet features fail to carry the same usefulness to represent the voiced phonemes such as vowels, nasals. This paper proposes new WP sub-band-based features by taking care of harmonic information of voiced speech signal. It has been noted that most of the voiced energy of the speech signal lies in between 250 and 2000 Hz. Thus, the proposed technique emphasises the individual sub-band harmonic energy up to 2 kHz. The speech signal is decomposed into 16 wavelet sub-bands and harmonic energy features are combined with WP cepstral (WPCC) features to enhance the performance of voiced phoneme recogniser. A standard phonetically balanced Hindi database is taken to analyse the performance of the proposed feature set. The noisy phoneme recognition task is also carried out to study the robustness. Significant improvement is obtained with the proposed feature set in voiced phoneme recognition over WPCC and conventional Mel frequency cepstral coefficient.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 12
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    Negative differential resistance in graphene nanoribbon superlattice field-effect transistors (2015)
    Institution of Engineering and Technology (IET)
    Details
    Publication Date: 2015-08-21
    Description: Different from researches in two-terminal nanoscale graphene structures, the negative differential resistance (NDR) phenomenon in graphene nanoribbon superlattice (GNSL) field-effect transistors (FETs) is studied in this reported work. Numerical analyses of two types of GNSL FETs with different gate voltages reveal that NDR occurs in some ‘Z’-type GNSL FETs under some gate voltages, which develops NDR research compared with the traditional two-terminal nanoscale structures. Based on these results, two trends are observed: the 3 m + 2 series GNSL FETs easily exhibit NDR, whereas it is more difficult to achieve this phenomenon with narrow FETs. This phenomenon is explained by the transmission coefficient as well as ab-initio calculations of the energy levels, where the entire channel of the FET is considered as a supercell. Through this analysis, the effect of gate control on energy-level localisation is uncovered, and a heterojunction-like explanation is proposed. This new explanation bridges the gap between a novel structure's physical analysis and the general semiconductor device concept, which can also provide inspiration for improving our understanding of novel nanostructure devices.
    Electronic ISSN: 1750-0443
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Institution of Engineering and Technology (IET)
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  • 13
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    Miniaturised design of coplanar waveguide-fed broadband circularly polarised slot antenna (2015)
    Institution of Engineering and Technology (IET)
    Details
    Publication Date: 2015-08-25
    Description: A novel miniaturised design of broadband circularly polarised (CP) antenna using a coplanar waveguide feed is presented. To realise CP characteristic, a pair of inverted-L strips around two opposite corners of the slot is protruded. By properly folding the modified ground plane, the 3-dB axial-ratio (AR) band is shifted to around a lower-frequency location, whereas the input impedance band is shifted downwards through the Y-shaped loading strip. The overall size of the antenna is about 0.34 λ 0 × 0.34 λ 0 × 0.009 λ 0 at 1.7 GHz. Measured results show that the proposed design can deliver 3-dB AR bandwidth of 36.8% (1.55–2.25 GHz) and 10 dB impedance bandwidth of 63.2% (1.17–2.25 GHz).
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 14
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    Miniaturised antenna design with crossed-field elements to radiate strong electromagnetic fields for near-field communications (2015)
    Institution of Engineering and Technology (IET)
    Details
    Publication Date: 2015-08-25
    Description: Near-field (NF) communications require strong energy coupling between transmitting and receiving antennas. An antenna design methodology is thus proposed to design the reader antennas that radiate strong evanescent fields in the vicinity of antenna with good radiation efficiency. This concept employs a pair of radiating elements with approximately conjugated input impedances in nature that have large reactance such that the energy will reside in the NF region. In addition, the orientations of the antenna pair are adjusted to form the relationship of crossed-fields in the electric and magnetic field components such that the relationship in Poynting vector can be established in the near zone. Both numerical and experimental results based on an antenna design example for the radio frequency identifications applications are presented to validate the concept.
    Print ISSN: 1751-8725
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 15
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    Low-power ultra-wide band pulse generator based on a PIN diode (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: Radio-frequency identification (RFID) tags (passive kind) are typically not designed to include ultra-wide band (UWB) pulse generators, but may be in the future. The reason is that the very short pulses produced by the RFID tags could be used to estimate their positions with errors of solely a few centimetres using time difference of arrival techniques. Currently, the method most commonly used to estimate tag positions relies on received signal strengths (less accurate). An UWB pulse generator based on a PIN diode is presented in this study. This pulse generator was designed to produce a positive unipolar pulse for each high-to-low transition (1.8 V to 0) it receives at its input. This trigger signal is generated by a microntroller-based battery-free RFID tag. The end result is a pulse with an amplitude of ∼300 mV and a duration of slightly 〈2 ns measured using a 50 Ω load.
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  • 16
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    Design of phased array antennas with beam switching capability in the near-field focus applications (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: This study presents the design methodology of a phased array antenna whose radiation will focus in the near zone of array aperture by using microstrip feeding circuits. A beam-forming network based on Butler matrix is also implemented to scan the radiation beam along a target area in the near zone, which may improve the energy efficiency and reduce the multipath interferences. The design approach, numerical simulation and experimental measurement over an antenna prototype in the applications of radio-frequency identification are presented to validate the feasibility.
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  • 17
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    Systematic procedure to avoid unintended polarity mismatch in the cascade connection of multiport devices with symmetric feeding lines (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: The traditional cascading of generalised scattering matrices (GSMs) assumes that the modal sets at the connected ports of a cascaded network are strictly equal. This implies a careful selection of the modal polarities, or the reference systems, of every port. Usually, the connection scheme of every device is known a priori. Then, the individual GSMs are pre-processed, or auxiliary devices, which correct possible modal mismatches at the ports, are included in appropriate positions among the cascade, so that the traditional cascading-by-pairs approach can be directly applied. This scheme clearly complicates the reutilisation of previously calculated GSMs, and mixes the cascading with the solution of the individual building blocks. In this study, a systematic procedure is proposed to define the polarity of the modes at the ports of a device fed with transmission lines or waveguides showing a single or double symmetry. The modified expressions to calculate the scattering parameters of the cascade of two multiport devices, incorporating the regular modal corrections to apply when this criterion is used to define the modal polarity at the ports, is also presented in this study. This strategy is more convenient from the point of view of programming, less error-prone and easier to implement.
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  • 18
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    Design and performance analysis of the miniaturised water-filled double-ridged horn antenna for active microwave imaging applications (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: The design and analysis of a miniaturised double-ridged horn antenna for active microwave imaging application are presented in this study. For such an application, a physically small horn is required. For effective signal penetration, a low frequency of operation (about 1.4 GHz) is selected. An array of these sensors is intended for use in a cylindrical breast imaging system, which is under development in the authors laboratory. The miniaturisation is achieved by loading the double-ridged horn antenna with distilled water ( ε r = 76), a high permittivity, but easily available material. Further size reduction is achieved by reducing the aperture size and flare length in the horn section. The frequency response and both near- and far-field patterns were studied. Two simplified prototypes were fabricated, and as per the system requirements, tested in a cylindrical container filled with distilled water. Measured and simulated reflection and transmission responses are discussed. Measured radiation patterns are compared with the simulated ones to validate the analysis.
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  • 19
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    Broadband complementary metal-oxide semiconductor phase shifter with 6-bit resolution based on all-pass networks (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: Multi-stage all-pass networks can be used to realise broadband phase shifters with low phase error. In this study, single-stage and two-stage all-pass networks with internal switched capacitors are investigated. Potentials and limitations of using the all-pass networks with internal switched capacitors for phase shifter design are examined. On the basis of the single-stage and two-stage all-pass networks, a fully-differential digital phase shifter with 6-bit resolution is designed. The digital phase shifter is implemented using a 0.18-μm complementary metal-oxide semiconductor process. The chip area is 2.80 × 1.75 mm 2 . Measurement results show that minimum root-mean-square phase error of 2° is achieved from 2.19 to 2.82 GHz, which translates into a bandwidth (BW) of 25%. The average insertion loss is 14.6 dB at the design frequency of 2.4 GHz. Over the entire BW, the return loss is greater than 9.2 dB and the amplitude error is within ±1 dB.
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  • 20
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    High-isolation microstrip patch array antenna for single channel full duplex communications (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: An orthogonally polarised stacked square microstrip patch array antenna structure with high-isolation performance is proposed for single channel full duplex wireless communications. A double symmetric microstrip array structure is collaborated with a special self-interference cancelling network called differential feeding network (DFN) in order to achieve high-isolation performance. The proposed 2 × 2 and 4 × 4 symmetric array antenna structures with the DFNs were designed to operate at the idustrial, scientific and medical band of 2.34–2.54 GHz. By measurement, the average isolation performances of 53 and 60.7 dB were obtained in 200 MHz frequency band by the 2 × 2 and 4 × 4 array antennas, respectively. The measured average gains of the 2 × 2 and 4 × 4 array antennas were found to be 14.4 and 19.4 dBi, respectively.
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  • 21
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    Design and testing of a compact circularly polarised microstrip antenna with fractal defected ground structure for L-band applications (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: A compact circularly polarised (CP) microstrip antenna for mobile satellite communication band of India (1.492–1.518 GHz) is presented. Two asymmetric length rectangular shape slots, perpendicular to each other are printed on the circular patch for realisation of CP radiation. To improve the performance parameters of patch antenna such as axial ratio (AR) bandwidth, return loss bandwidth, radiation efficiency and so on a new technique of combination of fractal theory and defected ground structure (DGS) is proposed for the first time in design of CP antennas. 44.74% size reduction in patch size, enhancements of 62.73% in AR bandwidth, 70.74% in return loss bandwidth and 4.03% in radiation efficiency is achieved as compared with conventional patch antenna, after incorporation of Koch curve fractal DGS in the ground plane. The performance of the developed antenna has been compared with other available L-band planar antennas in the literature, and it is found that the developed structure is better one in many aspects. Laboratory prototype of the antenna is fabricated and experimentally measured for cross verifying the simulated results.
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  • 22
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    Extremely low-frequency surface response caused by underground resource (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: Electromagnetic (EM) surface responses in the extremely low-frequency (ELF) band caused by possible underground resources are studied. Unlike traditional solutions, the authors apply the geodesic finite-difference time domain method to simulate ELF EM wave propagation in the whole Earth (including the crust)-ionosphere (E-I) system to study these responses. In this way, more rigorous analysis can be achieved by simulating the complex E-I environments, including the inhomogeneous crust and part of the ionosphere. Based on this method, they established a hypothetical model to study the effects of underground objects on received artificial signals. Through simulations, local surface responses and response perturbations caused by underground objects are studied and approximate formulas are obtained for predicting the behaviour of these responses. Finally, potential applications of the method and the results of this work are discussed.
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  • 23
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    Millimetre wavelength variable focusing antenna for power beaming and active denial systems (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: A design of a millimetre wavelength antenna with adjustable focal length is demonstrated in this study. This antenna is designed to operate in the near field regime, and has the ability to change the focal plane position. The structure of the antenna is based on a Cassegrain configuration in order to deliver maximum power density to a pre-defined focal plane. Possible applications are radioactive power beaming and active denial systems. The analysis and development of this antenna were carried-out using the Gaussian beam model and the ABCD matrix method in order to find the focus position and spot size as a function of the axial distance. The development of the quasi-optical components of the Cassegrain antenna, simulation results and experimental results are described in this work.
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  • 24
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    Variable step-size sign algorithm against impulsive noises (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-07
    Description: This paper proposes a new variable step-size sign algorithm through the minimisation of mean-square deviation (MSD). As it is difficult to obtain the MSD accurately, the upper bound of the MSD is derived for calculating the step size at each iteration. The proposed algorithm is not only robust to impulsive noises, but also has improved filter performance in aspects of convergence rate and steady-state estimation error owing to the proposed variable step-size strategy. The simulation results verify that the proposed algorithm has better performance than the existing algorithms in a system-identification scenario in the presence of impulsive noises.
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  • 25
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    Analysis of the complexity of the sperm acrosomal membrane by super-resolution stimulated emission depletion microscopy compared with transmission electron microscopy (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Description: The acrosome is a Golgi-derived sperm cell organelle enclosed by a continuous acrosomal membrane. The acrosomal membrane complexes with surrounding matrices containing molecules necessary for fertilization; however, the complex of acrosomal membrane and associating matrices (CAMAM) has not been visualized in detail under living conditions. Here, we analyzed the CAMAM at the nanometer level using super-resolution stimulated emission depletion (STED) fluorescence microscopy and equatorin-enhanced green fluorescent protein transgenic mice. The STED images were compared with the corresponding images taken by immunoelectron microscopy. Consequently, the substructure of CAMAM could be differentiated at nanometer-scale resolution by STED microscopy without the need for sectioning. The information obtained in this study will be beneficial not only for understanding the molecular mechanism of fertilization but also for cell imaging under living conditions.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 26
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    Non-iterative beamforming based on Huygens principle for multistatic ultrawide band radar: application to breast imaging (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: This study examines the performance of a simple microwave beamforming method using the Huygens scattering principle (called here the Huygens principle method) for detecting breast lesions. The beamforming method is similar to non-iterative time reversal in that the wave received is propagated back into the material, although differs in its treatment of attenuation. The single pass algorithm does not require a solution to an inverse model, making it computationally efficient and so able to offer a throughput appropriate for clinical use. Its performance is compared with time-delay beamforming, which may be implemented with similar computational complexity, on a set of phantoms, including a lossy medium, mimicking breast tissue. The method was used to image a commercially fabricated anatomically shaped breast phantom with multiple hidden inclusions mimicking tumours. The procedure was able to identify and localise significant scatterers inside the volume, with only approximate a-priori knowledge of the dielectric properties of the target object, in spite of its underlying assumption of a single scatterer model.
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    Common-mode suppression for balanced bandpass filters in multilayer liquid crystal polymer technology (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: A new multilayer differential transmission line for common-mode suppression fabricated using an organic liquid crystal polymer multilayer substrate is proposed and analysed. The structure consists of a pair of parallel strip lines printed on the top layer of the substrate that are capacitively coupled to conductor patches periodically etched in an intermediate interface. These patches are symmetrically connected to a solid ground plane by means of short-circuited high-impedance microstrip line sections and metalised via holes. The differential signal supported by the coupled strips is not significantly affected by the presence of the middle layer layout, whereas the common-mode signal propagation is strongly suppressed within a certain frequency band. When this structure is cascaded with a simple differential bandpass filter exhibiting poor common mode rejection, a good common mode response is achieved within the unperturbed differential passband. The measurements confirm a significant enhancement of common-mode rejection thanks to the use of the proposed differential lines.
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    Enhanced dual-circular polarised four-arm Archimedean spiral antenna with low-profile cavity backing (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: A wideband dual-circular unidirectional four-arm Archimedean spiral antenna operating from 0.6 to 2.4 GHz is presented. Without a cavity, the antenna radiates bi-directionally and the dual-circular polarisation of the spiral antenna at boresight is limited to a frequency range from 0.6 to 1.5 GHz. After adding a low-profile, 15 mm deep metallic cavity, the dual-circular polarisation at boresight is extended to more than 2.4 GHz and uni-directional radiation is realised. The four-arm spiral antenna is excited through a feed network consisting of a wideband four-way power divider and four wideband digital 2-bit phase shifters. This feed network facilitates instantaneous switching between right hand circular polarisation and left hand circular polarisation. The measured input return loss of the system is more than 10 dB for the entire two-octave bandwidth. The measured boresight gain from 0.6 to 2.4 GHz is −2.8 to 11.2 dBi and −3.1 to 8.7 dBi for RHCP and LHCP, respectively.
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    Polarisation diverse multiple input–multiple output antenna with enhanced isolation (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: In this article, two-element monopole multiple input–multiple output (MIMO) antenna with polarisation diversity for 4G and other applications has been presented. The designed antenna covers 16% (1701–2001 MHz) of bandwidth around the design frequency (1850 MHz) which includes both DCS-1800 and DCS-1900 bands. The two antennas are placed orthogonally and symmetrically with edge-to-edge spacing of 5.5 mm ( λ 0 /30). With the placement of interconnected swastika-shaped resonator between the two monopole antennas, there is an isolation enhancement of 60 dB thus reducing the envelope correlation coefficient value ranging from 0.016 to 6.12 × 10 −10 and improving the diversity gain ranging from 9.9 to 10 dB within the −10 dB bandwidth. A prototype has been fabricated and validated using measurements.
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    High-gain end-fire bow-tie antenna using artificial dielectric layers (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: This study presents a high-gain bow-tie antenna for applications in next generation base-stations operating from 2.5 to 3.9 GHz. The proposed structure consists of three circular sector patches that are attached laterally to the microstrip feed-line, which is etched on both sides of the common dielectric substrate to create symmetrical bow-tie antenna. By loading the antenna with a 2 × 5 array of enhanced end-coupled split-ring (EECSR) unit-cells results in significant enhancement in the antenna gain performance. This is because the EECSR unit-cells behave as parasitic radiators, which is analogous to Yagi–Uda antennas. The EECSR unit-cells provide a medium of high effective permittivity that effectively reduces the spacing between parasitic directors. As a consequence, a compact and miniature structure is achieved compared with conventional quasi-Yagi–Uda planar designs. The dimension of EECSR unit-cell is 33 × 36 mm 2 with inter-element spacing of 0.075 λ 0 at 3.5 GHz. A prototype of the antenna was fabricated and its performance was measured to validate the simulation results. The measured peak gain of the antenna with 4 × 5 array of EECSR is 12.65 dBi at 3.73 GHz, constituting a peak gain enhancement of 7.45 dBi in the Worldwide Interoperability for Microwave Access band compared with an equivalent conventional bow-tie antenna.
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    Synthesis of a miniaturised wireless local area network dual-band microstrip Wilkinson power divider through a general three-step optimisation process (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: Synthesis method for a novel dual-band Wilkinson power divider (DBWPD) is presented in this study. The proposed DBWPD is constructed using a novel dual-band impedance transformer (DBIT). The DBIT is made up of a kernel circuit unit cell with uniform transmission lines attached to its two ends. A non-linear system of equations ruling the DBIT performance is first built up and then successfully solved with numerical method. Design charts are provided for determining the feasible DBIT theoretical parameters. With the DBIT theoretical solutions, a microstrip DBWPD operative at 2.4/5.2 GHz is practically implemented, of which layout parameters are effectively resolved in a sequential three-step optimisation design process, and its compact size as well as good dual-band operation performance has been demonstrated by fabrication and experimental tests, confirming the proposed synthesis method.
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    Mode control in air gap dielectric resonant antennas for applications in IEEE 802.11ac wireless local area network base station antennas (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: This study investigates the characteristics of air gap dielectric resonator antennas (AGDRAs), with emphasis on their radiating modes and potential applications for the up-coming IEEE 802.11ac wireless local area network (WLAN) standard. An AGDRA differs from the conventional dielectric resonator antenna (DRA) by employing monopole supports to form an air gap between the dielectric resonator and the ground plane. This air gap offers more degrees of design freedom, wider bandwidth and a wider range of resonant modes, including the TE 112 mode, which cannot be excited in the conventional rectangular DRAs. Four examples of AGDRA designs offering wide-/dual-band, dual-/circular-polarised and pattern reconfigurable were developed by exciting different modes. Good agreement between the simulated and measured results is observed, which proves the feasibility of AGDRA structures for the IEEE 802.11ac WLAN antennas.
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    Analysis of the radiowave propagation in an underground mine based on the modified Ray launching method (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: The study presents the developed model of electromagnetic wave scattering occurring on the irregular surfaces. This model was implemented in the Ray launching (RL) method. Based on the modified RL, the analysis of electromagnetic wave propagation in an underground mine was performed. The results of theoretical analyses were compared with the results of measurements (from a copper mine) to determine the degree improvement in the electromagnetic field prediction accuracy after the developed model application.
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    Reflector antenna analysis method using Poynting vector tracing between virtual apertures (2015)
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    Publication Date: 2015-09-11
    Description: In this study, a highly efficient calculation method for analysing electrically large reflector antennas is presented. This method utilises fast Fourier transform enhanced direct integration to calculate beam propagation between parallel virtual apertures, and a novel Poynting vector tracing technique is introduced to treat wave reflections by arbitrary curved surface. Two virtual apertures are set perpendicular to the incident and reflected optical paths. As the centres of the virtual aperture planes coincide with the reflector surface, it makes the ray-tracing paths between the virtual apertures along with the reflector as short as possible. Owing to these innovative treatments, this method offers a high calculation accuracy comparable with classic physical optics (PO), but with much higher efficiency. By performing numerical comparisons with method of moments, PO algorithm implemented with commercial software FEKO and general reflector antenna software package, the advantages of the proposed method are presented in this study. The method proves to be applicable for the analysis of electrically large reflector antennas.
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    Design strategy of concurrent multi-band Doherty power amplifier (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: This paper proposes design methodologies of concurrent multi-band Doherty power amplifiers (PAs) based on multi-band impedance inverting networks and multi-band phase offset lines (POLs). Design procedures for implementing such multi-band impedance inverting networks and multi-band POLs at arbitrary frequencies are presented here. For validating the design procedures, tri/quad-band Doherty PAs are designed, fabricated and tested using continuous wave (CW) and modulated signals in discrete mode and concurrent mode. The tri-band Doherty power amplifier (DPA) is implemented at 1600, 1900 and 2200 MHz. CW signal measurement of tri-band DPA shows an efficiency of 46%, 40% and 42%, respectively, around 6 dB output power back-off (OPBO). The quad-band DPA is implemented at 1600, 1960, 2140 and 2350 MHz. Measured results using CW signal shows an efficiency of 40%, 37%, 30% and 31%, respectively, around 6 dB OPBO.
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    Substrate integrated waveguide bandstop filter using partial-height via-hole resonators in thick substrate (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: A substrate integrated waveguide (SIW) bandstop filter on thick substrate is introduced. The increased substrate height permits partial-height via holes to act as resonators whose interaction provides a wide range of possible coupling coefficients that result in wideband bandstop filters. In contrast to ridged all-metal waveguide filters, SIW filters with partial-height via holes maintain a small profile, low manufacturing cost and they can be integrated with other planar circuitry such as microstrip or coplanar waveguide. The design method of the bandstop filter relies on the well-known extracted-pole technique which allows designers to independently control the locations of reflection zeros. The parameters of the lowpass equivalent circuit of the filter are extracted and used for the initial design of the physical dimensions of the filter. The software packages µWave Wizard and CST are used for filter simulation and optimisation. A prototype bandstop filter is designed for a centre frequency of 10.74 GHz and a bandwidth of 1.58 GHz. Tolerance analyses demonstrate the influence of manufacturing inaccuracies on the filter performance. Good agreement between simulated and measured results confirms the reliability and robustness of the design method and its applicability to SIW technology on thick substrate.
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    Solution to the Klein–Gordon equation for the study of time-domain waveguide fields and accompanying energetic processes (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: In electromagnetics, power flow and energy densities are associated with time-varying electromagnetic fields. For time-harmonic waves, such quadratic characteristics are derived using the complex-valued spatial forms of field vectors resulting in time-averaged power flow and energy densities. Hence, the opportunity to study dynamic processes of the quadratic characteristics is lost in the time-harmonic electromagnetics. To overcome this drawback, the authors consider the problem of a waveform propagation in a hollow waveguide via solving the system of Maxwell's equations with time derivative in an energetic space of ‘real-valued’ functions. The transverse electric and transverse magnetic modal field components are presented as the products of modal basis elements and the modal amplitudes. The vector basis elements are obtained with required physical dimensions, volt per metre and ampere per metre . Thereby, the modal amplitudes are dimension-free scalar functions. The system of evolutionary equations for the modal amplitudes is derived and solved explicitly. The Klein–Gordon equation (KGE) plays a central role herein. A novel set of real-valued solutions to the KGE is obtained and applied for analysis of the energetic processes pertinent to the time-domain signal propagation. The velocity of transportation of the modal field energy is obtained and energetic exchange between the transverse and longitudinal field components is discussed.
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    Calculation of effective parameters of high permittivity integrated artificial dielectrics (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: An analysis is presented of the effective electromagnetic parameters of high-permittivity, anisotropic artificial dielectrics which are built by stacking arrays of metallic elements and conventional dielectric films, with adjacent arrays shifted with respect to each other. The effective parameters of the artificial dielectric are extracted from the scattering coefficients of plane electromagnetic waves which are normally or obliquely incident on a slab of the artificial material with finite thickness. These coefficients are derived from the generalised scattering matrix of a single layer of metallic elements which is computed using the integral equation technique. Both two-dimensional and three-dimensional configurations are considered. Calculations demonstrate the feasibility of artificial dielectric films with extremely high values of effective relative permittivity (several thousands) in the plane of the film at millimetre-wave (mm-wave) frequencies. These artificial dielectrics have a high potential for application in microwave and mm-wave integrated circuits because of their high-permittivity and planar layout. As a potential application, the authors propose an artificial dielectric waveguide integrated on a silicon substrate.
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    Mechanically pattern reconfigurable antenna using metasurface (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: A radiation pattern reconfigurable antenna designed using metasurface (MS) is proposed in this study. The pattern reconfigurable metasurfaced (PaRMS) antenna is composed of a planar semi-circular MS placed directly atop of a planar circular patch antenna with a diameter of 70 mm (1.2 λ 0 ), making it compact and low profile. The main-beam direction of the antenna has an angle of 32° from the boresight direction. By rotating the MS around the centre of the patch antenna, the antenna beam can be steered continuously. The PaRMS antenna is studied and designed to operate at around 5.5 GHz. To verify the results of simulation, the PaRMS antenna is fabricated and measured. Results show that the antenna has an operating bandwidth from 5.4 to 5.6 GHz and measured peak realised gain of 7.2 dBi.
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    Analysis of radiation of antennas with a phase-gradient partially reflective surface (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: This study presents a novel model for understanding the radiation phenomena and calculating the radiation pattern properties of uniform and phase-gradient partially reflective surface (PRS) antennas. This model is extracted for one- and two-dimensional antennas using array theory along with the dispersion analysis of the unit cells. The model can calculate the main lobe radiation pattern, scan angle and half-power beamwidth of uniform and phase-gradient PRSs with broadside, conical or tilted beams with an accuracy better than 5°. Two common PRS unit cell shapes (slotted patch and dipole) are used here.
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    Dispersion analysis of a fishnet metamaterial based on the rotated transmission-line matrix method (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: A novel three-dimensional (3D) lumped circuit-based metamaterial topology to model a 2D fishnet structure is proposed. The rotated transmission-line matrix (RTLM) unit cell, obtained as one independent half cell from the typical TLM unit cell by rotating the polarisations on each TLM unit port by 45°, saves computation time and decreases the cost in processing data when a structure is analysed, especially when some specific components of the structure are processed. Here, an RTLM unit cell is used to construct the lumped circuit of a fishnet structure. The dispersion characteristics of the lumped fishnet circuit are obtained and used to analyse the eigenmode and the propagation coefficient and Bloch impedance are investigated to explain the frequency characteristics. At the frequency region considered, the same left-handed frequency behaviour of the lumped fishnet circuit is achieved by the proposed compact fishnet RTLM model, agreeing well with the simulation results.
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    Electromagnetic modelling of surfaces using method of moments with calculated phase mesh (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-11
    Description: An alternative method of moments (MoM) solution for the radiation and scattering of surfaces is presented. One limit of MoM is the high number of basis functions needed, for the segmentation of electrically large surfaces. In this study, a conventional MoM solution is defined with quadrilateral surface patches and at least eight rooftop basis functions per wavelength. Galerkin testing is applied. This conventional MoM is extended with a new approach for the surface segmentation, called the calculated phase mesh (CPM). Efficient basis functions are chosen, and their positions on the surface are calculated with the incident field. In the theory part, the number of unknowns for scatterers with electrically large dimensions is reduced by 50%, compared with conventional MoM meshes with eight functions per wavelength. The incident field on surfaces is calculated numerically. This allows the application of CPM on scattering bodies with a variety of field sources, for example, both the near and the far field of antennas. The valid frequency range for the meshes is described. Three numerical examples are presented. In one example, the number of basis functions was reduced to 69.3%, compared with conventional MoM. The third example shows the application on three-dimensional scattering bodies.
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    Hydrothermal synthesis of SnO 2 –Zn 2 SnO 4 –graphene composites with high activity for photodegradation of rhodamine B (2015)
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    Publication Date: 2015-09-22
    Description: The SnO 2 –Zn 2 SnO 4 –graphene composite photocatalysts were successfully prepared by a facile hydrothermal reaction method in an ethanol–water solvent. The as-prepared catalysts were characterised by techniques of X-ray diffraction, Raman spectroscopy, transmission electron microscopy and N 2 -sorption. The catalytic activity test results show that this SnO 2 –Zn 2 SnO 4 –graphene composite possesses higher photocatalytic degradation of rhodamine B (RhB) activity than that of pure SnO 2 –Zn 2 SnO 4 under UV-light irradiation in an aqueous solution. The improved photocatalytic activity may be due to the increased adsorbability for the RhB molecule, more active sites, more photocatalytic reaction centres and the prevention of the photogenerated electron–hole pair recombination.
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    Synthesis of magnetic graphene composites for preconcentraton trace amounts of malachite green and crystal violet from water (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-22
    Description: Graphene/silica magnetic nanocomposites are synthesised and introduced as new and reusable adsorbents for rapid and high-efficiency preconcentraton trace amounts of dye pollutants in water. This method is simple, fast, cheap and non-toxic. The optimum adsorption conditions for the preconcentraton of crystal violet (CV) and malachite green (MG) are investigated and the adsorption mechanisms are also discussed. The regeneration and reuse experiments showed the good reusability of the as-prepared adsorbent. In addition, this method was successfully applied to the preconcentraton of trace amounts of MG and CV from water samples, which presages more opportunities for application in environmental and material sciences.
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    Target cells capture and detection based on a surface plasmon resonance biosensor (2015)
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    Publication Date: 2015-09-22
    Description: A novel and effective method for target cells capture and detection is developed in a label-free and real-time mode. The cultured cell line (TZM-bl) expressed as CD4+ was used as the positive CD4+ T lymphocytes for target cells capture and detection experiments. The target cells were captured on various surfaces (such as glass, polydimethylsiloxane, and metal) based on a specific immunity method. The gold surface of the surface plasmon resonance (SPR) sensing chip modified with a nano denaturalised bovine serum albumin layer had the best capture capacity. A total of 90.9% positive CD4+ T lymphocytes were captured with a slow flow rate of 5 µl/min, whereas 84.1% of cells were kept with a fast flow rate of 2 ml/min. Furthermore, the captured positive cells on the SPR sensing chip were detected on-line by using author’s home-made SPR biosensor. From the experimental results, 75 cells/µl could produce an obvious change in the SPR response signal, which holds great potential for target cells capture, reorganisation and further analysis of CD4+ T lymphocytes in human peripheral blood.
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    Synthesis of gold nanorods with longitudinal surface plasmon resonance wavelength up to 1245 nm using gallic acid as a reductant in the presence of a binary surfactant system (2015)
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    Publication Date: 2015-09-22
    Description: Gold nanorods with the longitudinal surface plasmon resonance (LSPR) wavelength up to 1245 nm are obtained by using an improved seed-mediated wet chemistry growth method where gallic acid is used as a reductant in the presence of a binary surfactant system. The effects of the gallic acid and the seed on the synthesised gold nanorods are investigated by ultraviolet–visible–near infrared spectroscopy and transmission electron microscopy (TEM). It is found that by increasing the gallic acid amount from 200 to 600 μL, the LSPR wavelength shifts from 975 to 1170 nm; at the same time, the absorption intensity of both the transverse surface plasmon resonance and LSPR increases, indicating a more complete reduction of chloroauric acid. To achieve a longer wavelength of the gold nanorods’ LSPR peak, the seed amount was changed to a condition of 600 μL gallic acid. A redshift of the LSPR wavelength from 1135 to 1245 nm can be obtained as the seed amount increases from 30 to 70 μL. Furthermore, it was found that the redshift of the LSPR peak with increasing seed amount is in accordance with the increase trend of the aspect ratio obtained by analysing the dimensions of the gold nanorods through the TEM images. The method offers a new strategy to obtain gold nanorods with tunable LSPR wavelengths, which have wide application in many areas, such as biosensing and ultrafast optical information.
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    Nanoscale dispersion of delaminated sheets of layered double hydroxides in polyvinyl acetate (2015)
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    Publication Date: 2015-09-22
    Description: The delamination of layered double hydroxides (LDHs) was supposed to be achieved in a microemulsion composed of octane, N -lauroyl-glutamate, butanol and water. In the X-ray diffraction patterns of LDHs, the diffraction peaks at low angle regions disappeared when the amount of octane reached a proper degree in the microemulsion, indicating that LDH layers might be delaminated, which is further proved by carbonate-exchange experiments. Furthermore, polyvinyl acetate/LDH nanocomposites were prepared via in situ intercalative polymerisation, in which vinyl acetate monomer was dispersed onto the sheets of delaminated LDHs, followed by thermal polymerisation. The thermal stability of the nanocomposites was improved compared with the polymer matrix, and the enhanced extent of the thermal stability increased with increasing loading amounts of delaminated LDHs.
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    Fabrication and mechanical properties of low-loading graphene nanosheets encapsulated on the surface of graphene nanosheets/polypropylene composites (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-22
    Description: In recent years, numerous scientists have used graphene for reinforcing polymer-based composites because of its outstanding electrical, thermal and mechanical properties. Based on this present reported work, a simple manufacturing process is reported for the fabrication of low-loading graphene nanosheets (GNSs) coated on the surface of a polypropylene matrix. According to a scanning electron microscope micrograph, the GNSs were dispersed uniformly on the surface of polypropylene pellets. The mechanical properties and thermal stability of the GNSs /polypropylene composite plates were improved substantially by the addition of GNSs. X-ray diffraction was used to determine that the two-theta values of the GNSs /polypropylene composite plates correspond to the weight fraction of the added GNSs. Fourier transform infrared spectroscopy revealed that the vibration peak of the polypropylene methyl group decreased gradually when the amount of GNSs increased.
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    Photocatalytic reduction and oxidation activities of nanosheet-assembled anatase TiO 2 microspheres (2015)
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    Publication Date: 2015-09-22
    Description: Nanosheet-assembled anatase titanium dioxide (TiO 2 ) microspheres (ST) have been successfully synthesised using the hydrothermal method. The physical and chemical properties of ST were well characterised by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence and Brunauer-Emmett-Teller (BET) analysis. The photocatalytic reduction and oxidation activities of the as-prepared sample were evaluated by removing heavy metal Cr (VI) and by degradation of organic dyes (methyl orange (MO) and rhodamine B (Rh B)), respectively. P25 and commercial pure anatase TiO 2 were used for comparison. The nanosheet-assembled anatase TiO 2 microspheres displayed better photocatalytic efficiency towards the photo-reductive conversion of Cr (VI). Moreover, it also exhibited higher photocatalytic activity for the degradation of organic dyes compared with that of P25 and commercial pure anatase TiO 2 .
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    Facile fabrication of nitrogen-doped zinc oxide nanoparticles with enhanced photocatalytic performance (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-22
    Description: Nitrogen (N)-doped zinc oxide (ZnO) particles were successfully synthesised by a simple and economical ammonia-assisted hydrothermal method. The samples were characterised by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and ultraviolet–vis diffuse reflectance. It was found that N-doped ZnO exhibited higher photocatalytic activity than commercial Degussa P25 towards the liquid-phase degradation of Rhodamine B and methylene blue under simulation of solar light. The authors attribute these results to enhanced visible-light absorption ability and efficient separation of photogenerated carriers. The authors hope that this study provides valuable information on the design of specific ZnO photocatalytic materials for further industrial application.
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    Unsaturated polyester resin/epoxy-functionalised nanosilica composites constructed by in situ polymerisation (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-22
    Description: A reactable nanosilica surface capped with a silane coupling agent containing the epoxy group (denoted as RNS-E) was allowed to participate in the in situ polycondensation reaction of unsaturated polyester resin (denoted as UPR) thereby affording the UPR/RNS-E composite. The structure of the as-prepared UPR/RNS-E composites was investigated by means of Fourier transform infrared spectrometry, thermogravimetric analysis and scanning electron microscopy, and their tensile strength and impact strength were compared with those of pure UPR cured under the same condition and of UPR/RNS-E composites prepared by mechanical blending. It was found that RNS-E exhibits good strengthening effect and toughening effect for the in situ polymerised UPR/RNS-E composite, which is attributed to the formation of a heterogeneous network structure in the cured UPR/RNS-E composites via the chemical reaction among the epoxy group of RNS-E and the hydroxyl (carboxyl) group of UPR. Particularly, the UPR/RNS-E composite with 0.6% RNS-E nanofiller has the highest tensile strength and impact strength, and it is much superior to the same composite obtained by mechanical blending.
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    Silicon anisotropic etching in Triton-mixed and isopropyl alcohol-mixed tetramethyl ammonium hydroxide solution (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-22
    Description: The anisotropic silicon (Si) etching characteristics of Si (100) in 25 wt.% tetramethyl ammonium hydroxide (TMAH) solutions containing Triton X-100 and isopropyl alcohol (IPA) were studied. The etch rate, convex corners and roughness of the etched surface were investigated. In this reported work two central goals, a mirror-like surface finish and a high reduction of undercutting, have been achieved. The best etched result was obtained in 25 wt.% TMAH + 0.25%v/v Triton + 16%v/v IPA, which has minimum convex corner undercutting and a smooth etched surface ( R a = 1 nm). This study is useful for engineering applications where the fabrication of microstructures for high-quality devices should simultaneously contain smooth surfaces on a large area and less convex corner undercutting.
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    Optimum current-voltage characteristics of GaAs/AlAs intraband microwave devices (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-09-22
    Description: In this reported work, both high peak current density and high peak-to-valley current ratio (PVCR) in AlAs/GaAs triple-barrier quantum-well intraband resonant tunnelling diodes (TBQW IRTDs) were accomplished. The valley current density ( J V ) of TBQW IRTDs can be degraded as the barrier thickness reaches 4 nm thickness. This result suggests narrow barrier thickness is due to the slight band bending effect in the conduction band of i -AlAs barrier layers. The peak current density ( J P ) of the TBQW IRTDs will be 〈2.43 KA/cm 2 as the i -AlAs barriers thickness of the TBQW IRTD reaches 5 nm thickness. The optimal thickness of barrier layers should be selected at 4 nm thickness to obtain the highest PVCR value (about 4270), in which the sample with barrier layers of 4 nm thickness possesses the lowest valley current density.
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    Ensemble empirical mode decomposition-based optimised power line interference removal algorithm for electrocardiogram signal (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: This study proposes an optimised algorithm to remove power line interference (PLI) from electrocardiogram (ECG) signal based on ensemble empirical mode decomposition (EEMD). A computationally efficient algorithm is one of the important requirements for real-time monitoring of cardio activities and diagnosis of arrhythmias. Computational complexity in EEMD is significantly reduced by using the EMD as the preprocessing stage. The noisy ECG signal is decomposed into intrinsic mode functions (IMFs) using EMD. ECG signals which are affected by PLI are automatically identified based on the simple ratio of the zero crossing number of IMF components. EEMD is used to decompose only ECG segments constructed from the noisy IMF components. The proposed algorithm is evaluated by real ECG signals available in MIT-BIH arrhythmia database in terms of signal-to-noise ratio and root mean square error. The computational efficiency of this new framework is measured using MATLAB profiling functions and compared with EMD, EEMD, sign-based adaptive and EMD with wavelet-based methods. Results show that the proposed algorithm performs better than the EMD, EEMD, sign-based adaptive and EMD with wavelet-based methods and it is computationally more efficient than EMD and EEMD methods.
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    Extended target tracking filter with intermittent observations (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: This study addresses the problem of tracking extended target with intermittent observations. Based on practical applications, two Bernoulli distributed random variables are employed to describe the intermittent phenomenon of the positional measurements and the measurements of target extent, respectively. First, a machine vision algorithm is developed to solve the target shape parameters. Then, four sub-filters are designed according to the received observations and the achieved target shape parameters. The output of the proposed tracking filer can be obtained by the weighted-confidence fusion of the sub-filters. Finally, the machine vision algorithm is evaluated by the virtual target images created in OpenGL (Open Graphics Library) and the real images of a moving ship. The performance of the designed tracking filter is compared with the traditional tracking filter. The experiment results show the effectiveness of the machine vision approach; also the Monte-Carlo runs demonstrate that the provided tracking filter outperforms the traditional one with respect to accuracy.
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    Ant-colony algorithm with interference cancellation for cooperative transmission (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: Despite the large bandwidth available for all users in high-speed wireless networks, resources allocation and user scheduling remain essential to combat interference, increase throughput and reduce complexity. As the number of users increases, the computational complexity tends to increase significantly. The trade-off between the complexity reduction and capacity improvement is the challenge. Hence a unique ant-colony optimisation method is implemented with successive interference cancellation to reduce complexity and provide higher capacity to more users. The incurred complexity is at least 50% less than other schemes. The average mean square error achieved is around 4 dB smaller than that of the existing scheme.
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    Blind deblurring from single motion image based on adaptive weighted total variation algorithm (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: Blind image deblurring is an important topic which is widely used in many research fields such as photography, optics, astronomy, medical images, monitoring, military and so on. Although many algorithms have been proposed to improve the deblurring result in the past years, most of them cannot perform perfectly in some challenging cases. This study presents a novel blind deblurring method based on an adaptive weighted total variation (TV) algorithm. The blur kernel estimation is based on the image structure, the sparsity and continuity prior of point spread function is also taken into account. To get better effect of removing the ringing artefacts, adaptive weight calculated according to the property of the higher-order partial derivatives in the local image is proposed in TV algorithm to alleviate the ill-posed inverse problem and stabilise the solution for latent image restoration. The experimental results prove that the proposed algorithm can suppress the ringing artefacts to a great extent in the latent image, and can get much better effect in both vision and theoretical results than traditional algorithms.
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    Kalman particle filtering algorithm for symmetric alpha-stable distribution signals with application to high frequency time difference of arrival geolocation (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: In this study, a non-linear filtering algorithm for state estimation with symmetric alpha-stable (SαS) noise is presented. The dynamic system model investigated here can be described by a linear state-space equation and a non-linear observation equation. The contribution of this study can be summarised as follows. First, particle filtering approach is employed for coarse estimation of the unknown parameters and then Kalman filter is performed to achieve better estimation. Second, SαS noise is considered as the additive disturbance in the observed signal and Gaussian approximation is used to compute the characteristics. Third, the calculation complexity is analysed according to the proposed algorithm. The proposed method is compared with the standard particle filter, extended Kalman filter and unscented Kalman filter for static parameter estimation of a periodic signal. As a practical application, the proposed method is used in high frequency source localisation based on time difference of arrival measurements.
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    Error-free computation of 8-point discrete cosine transform based on the Loeffler factorisation and algebraic integers (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: An 8-point discrete cosine transform (DCT) fast algorithm based on the Loeffler DCT factorisation and algebraic integer (AI) representation is proposed. The proposed algorithm is an error-free implementation of the Loeffler algorithm and it is capable of computing the 8-point DCT multiplierlessly. Decoding architectures are also proposed for mapping AI encoded quantities back to usual fixed point arithmetic using canonical signed digit representation and the expansion factor method. The proposed algorithm is mapped into systolic-array digital architectures and physically realised as digital prototype circuits using field-programmable gate array technology on a Reconfigurable Open Architecture Computing Hardware board and mapped to 0.18 μm complementary metal–oxide–semiconductor technology using AMS Encounter Digital Implementation libraries at 1.8 V supply.
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    Riemann–Liouville operator-based fractional normalised least mean square algorithm with application to decision feedback equalisation of multipath channels (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: In this study, the authors modify the mapping function by introducing a non-linear term based on Riemann–Liouville definition of fractional derivatives and its application to the mean squared error in addition to the first-order partial derivatives; thus create fractional variants of the least mean square (LMS) algorithm and its normalised version. The introduction of fractional term helps increase the convergence rate through the non-linear update term which depends on the fractional order and the in-process LMS weights; for steep gradient of the error measure, large changes are made to the weights which help the equaliser filter to better track the effects of multipath fading channels. They verify and validate the working of the proposed technique in the decision feedback equalisation of multipath fading channels for higher-order quadrature amplitude modulations; comparative results are shown in terms of performance metrics as symbol-error rate for various fractional orders and step sizes, combined equaliser and channel responses for different number of training symbols; simulations show that the proposed approach outperforms the conventional counterpart.
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    Nuclear norm regularised dynamic mode decomposition (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: As a data-driven, equation-free decomposition method, the DMD can characterise dynamic behaviour of a non-linear system by using the DMD modes and eigenvalues. However, all current provable algorithms suffer from a separate procedure for obtaining the DMD modes and determining the number of modes. In this study, the authors propose a nuclear norm regularised DMD (NNR-DMD) algorithm that produces low-dimensional spatio-temporal modes. A nuclear norm regularisation term is added to the optimisation problem of the standard DMD algorithm for prompting the sparsity of the projected DMD modes. Split Bregman method is applied to solve the regularised convex, but non-smooth optimisation problem. Several numerical examples demonstrate the potential of the proposed NNR-DMD algorithm: (i) it can identify the low-dimensional spatio-temporal DMD modes in which each of them possesses a single temporal frequency; (ii) the reconstruction errors based on the sparse DMD modes can be reduced when it compares with the sparsity-promoting DMD algorithm penalising the l 1 -norm of the vector of DMD amplitudes; and (iii) it can obtain low-dimensional coherent structures when the NNR-DMD algorithm is applied to coherency identification of generators in an interconnected power system.
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    Near-optimal estimation of radar pulse modulation waveform (2016)
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    Publication Date: 2016-07-22
    Description: In this study, the authors focus on pulse modulation waveform estimation based on a sequence of intercepted pulses from the same radar emitter. In general, modulation waveform estimators first perform pulse alignment in time and frequency separately, and then accumulate the aligned pulses to estimate the waveform. However, commonly used alignment methods may lead to considerable alignment errors which are difficult to detect and compensate, especially under low signal-to-noise ratio (SNR) conditions, resulting in non-ideal effects of accumulation. This study proposes a robust and nearly optimal modulation waveform estimation algorithm. The new algorithm first aligns pulses in time and frequency jointly via the cross-ambiguity function to avoid the transfer and accumulation of alignment errors. After that, an iterative maximum-likelihood estimator is invoked to achieve the waveform estimation. Theoretical analysis and extensive experiments show that the proposed algorithm has much smaller alignment errors and better modulation waveform and modulation parameter estimation ability than competing methods at low SNRs, and can approach the ideal case. Moreover, this algorithm does not make any assumption on the type of modulation and is computationally efficient, thus having broad applications.
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    DA based approach for the implementation of block adaptive decision feedback equaliser (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: Adaptive decision feedback equalisers (ADFEs) are used in wireless transmission systems for mitigating the InterSymbol Interference (ISI) that occurs due to multipath propagation of the transmitted signal. In case of high speed communications which involve rapid-varying channels, fast convergent and low complexity ADFEs are required. Frequency domain block processing of signals is an effective means of handling the increased complexities in such high speed systems. However, block ADFEs being inherently non-causal, the feedback filter (FBF) suffers from the lack of unknown decisions in every block computation. In this study, the authors propose an efficient approach for the computation of these unknown decisions. For this, the authors tried to minimise a cost function based on two criteria mean-absolute difference (MAD) and mean-square difference between the ADFE output and the adder that sums up the feedforward filter (FFF) and FBF. A bank of registers which store all the symbols used in the modulation scheme is also utilised for this purpose. Using the proposed solution, the authors recast block ADFE equations in the frequency domain using distributed arithmetic (DA). The algorithm has a good convergence performance and utilises only few computations compared with the existing schemes.
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    Vibration detection method for optical fibre pre-warning system (2016)
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    Publication Date: 2016-07-22
    Description: The measurement of optical fibre vibration is a key part of optic fibre pre-warning system, which has gradually focused on phase-sensitive optical time-domain reflectometer. However, for this instrument, false alarm rate is very high and some unstable intrusion signals cannot be detected by using its fixed threshold method in the actual application. It needs to develop new vibration detection method to overcome the above defect. The vibration signals normally consist of three parts, that is, noise, interference and intrusion signals. After a large number of data analysis, the authors find that the system noise is time varying and follows the Rayleigh distribution. Hence, the authors innovatively use the constant false alarm rate (CFAR) method to detect this type of intrusion. Considering interference is also time varying and diverse, a good detection performance cannot be obtained only by using the conventional CFAR. For this reason, a background homogeneity adaptive CFAR (BHA-CFAR) method is further proposed to detect the vibration signals in this study. The BHA-CFAR consists of two detectors, cell averaging CFAR (CA-CFAR) detector and greatest-of/smallest-of CFAR (GO/SO-CFAR) detector. A parameter, homogeneity of background, is estimated first to classify the surrounding. Then CA-CFAR and GO/SO-CFAR are optionally used according to the surrounding is homogeneous or heterogeneous, respectively. This new detection method can adapt to any background surrounding and has a good detection performance. In order to check the feasibility and validity of the BHA-CFAR method, several experiments were carried out in Da Gang oilfield. The detection results show that the proposed method can provide a good tradeoff between the detection performance and computation time.
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    Loop analysis of adaptive notch filters (2016)
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    Publication Date: 2016-07-22
    Description: Adaptive notch filters have been the focus of intense research for more than three decades. Low computational requirements and good performance make them attractive for tracking frequency modulated signals. Despite the extensive literature on adaptive notch filters, algorithm extensions and new models for describing the dynamics of the notch frequency continue to be proposed. In this study, the equivalence between adaptive notch filters using a plain gradient (PG) algorithm and frequency lock loops (FLLs) with exponential filtering is established. FLL theory is then used to analyse the noise performance and signal tracking capabilities of adaptive notch filters. A linear model describing the dynamics of the filter adaptation process is derived and the concepts of loop and Doppler bandwidths are introduced. Criteria based on the loop and Doppler bandwidths are suggested to set the PG adaptation step. Finally, algorithm extensions based on the FLL theory are proposed. Theoretical results are supported by Monte Carlo simulations which show the validity of the analysis performed.
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    Improved single channel phase-aware speech enhancement technique for low signal-to-noise ratio signal (2016)
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    Publication Date: 2016-07-22
    Description: In the state-of-the-art single channel speech enhancement techniques, the short-time spectral amplitude is modified while the effect of the phase corruption due to the contamination of additive noise is neglected. This study introduces an improved speech enhancement algorithm based on a phase-aware multi-band spectral subtraction technique which estimates the spectral amplitude of the clean speech signal by considering the phase of the speech and noise signal components, and uses the estimated phase of the clean speech signal for signal reconstruction in the time domain. Experimental results show that the proposed algorithm yields better performance in terms of various objective and composite quality measures and other intelligibility assessment metrics while compared with other existing spectral subtraction methods. Using the composite objective measure quality evaluation technique, it is observed that the overall signal quality of the enhanced speech signal is improved on an average by 70% at 0 dB global input signal-to-noise ratio by using the proposed approach.
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    Resistivity and optical transmittance dependence on length and diameter of nanowires in silver nanowire layers in application to transparent conductive coatings (2016)
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    Publication Date: 2016-07-08
    Description: Optical absorption spectra and electrical conductivity of silver nanowires with mean diameters of 56, 73, and 106 nm and mean length of 10.4, 12.6, and 32.0 µm, respectively have been experimentally studied. The size dependent effective permittivity of silver nanowire layers is calculated using mixing equations as for anisotropic materials according to the Maxwell-Garnett theory. The absorption spectra peak positions of nanowires with various diameters are interpreted according to the theoretical calculations based on the Mie theory, which allow to predict dependence of the optical properties on the nanowire diameter. The sheet resistance measurements show that 13–15 Ω/sq at the level of 80–90% transmittance at 550 nm wavelength can be achieved.
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    Bistable memory and logic-gate devices fabricated by intercrossed stacking of graphene–ferroelectric hybrid ribbons (2016)
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    Publication Date: 2016-07-08
    Description: A ferroelectric-gated graphene field-effect transistor was fabricated by consecutively stacking two distinct graphene–ferroelectric hybrid ribbons at right angles. Two graphene layers play different roles. One graphene layer acts as a gate electrode and the other graphene layer acts as a channel between two electrodes, source and drain. Electric gating at the gate graphene modulates the resistance of the channel graphene. By means of ferroelectric polarisation, bistable resistance states of the channel graphene could be recorded, and the retention time of bistability was estimated to be 460 days by extrapolating of two resistance values in time–resistance relationships. Furthermore, the underlying concept to fabricate bistable memory device was extended to the methodology to realise a logic-gate device by stacking three distinct graphene–ferroelectric hybrid ribbons.
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    Iron phthalocyanine nanorods for ethanol sensoring (2016)
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    Publication Date: 2016-07-08
    Description: Iron phthalocyanine (FePc) nanorods were synthesised by a solvothermal method without any surfactant. The as-synthesised materials were monoclinic FePc phase according to X-ray diffraction. The FePc nanorods were applied as gas sensor to detect the ethanol with good sensitivity and selectivity. The results demonstrated that FePc nanorods were excellent candidates for gas sensor to ethanol.
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    Nanostructured ZnO thin film with improved optical and electrochemical properties prepared by hydrothermal electrochemical deposition technique (2016)
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    Publication Date: 2016-07-08
    Description: Zinc oxide (ZnO) thin films were grown on fluorine-doped tin oxide coated glass substrate by the hydrothermal electrochemical deposition (HTED) route using slightly acidic aqueous zinc acetate solution at 80°C and were characterised by various techniques. The deposited films showed n-type behaviour with improved carrier concentration. The steady state photocurrent densities were found to be 0.4 mA/cm 2 (under UV irradiation) and 8 µA/cm 2 (under visible light illumination) at zero bias potential. Significant improvement of optical, electrochemical and photoelectrochemical properties of deposited films could be achieved using HTED technique.
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    One-step in-situ fabrication of silver-modified Cu 2 O crystals with enhanced visible photocatalytic activity (2016)
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    Publication Date: 2016-07-08
    Description: Silver-modified cuprous oxide (Cu 2 O) crystals (SMCCs) were successfully created by a facile one-step in-situ Ag-loading reaction under room temperature. The samples were studied by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance spectra and transmission electron microscopy. The photocatalytic performance of the SMCCs were estimated by using methyl orange aqueous solution as a standard pollutant under visible light irradiation. As a result, the SMCCs show a higher photocatalytic activity than the pure phase Cu 2 O. The silver nanoparticles which adhered on the surface of Cu 2 O of different size and content can greatly effects the photocatalytic efficiency. The enhanced photocatalytic activity owed to the effective charge transfer of excited electron-hole pairs by loading Ag.
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    Physics-based simulation study of high-performance gallium arsenide phosphide–indium gallium arsenide tunnel field-effect transistor (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: For the first time, this work presents a novel combination of gallium arsenide phosphide (GaAsP) and indium gallium arsenide (InGaAs) as drain/channel and source materials, respectively, of tunnel field-effect transistor (TFET) for high-performance ultra-low-power applications. With this combination, the ON-state current of the proposed device is improved ten times as compared with GaAs–Ge TFET; however, the ambipolar current remains equal to the OFF-state current. It also exhibits a very low threshold voltage (half in amount) as compared with GaAs–Ge TFET. Apart from these, GaAsP–InGaAs TFET shows huge reduction in the subthreshold slope for better switching operation.
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    Application of micro–meso hierarchical porous carbon for toluene adsorption treatment (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: Organic waste gases from petrochemical industry cause air pollution. Due to the environmental effects of refractory organic gas, the development of effective adsorbent is imperative. The micro–meso hierarchical porous carbon with high surface area was synthesised by the hard-template method. With MCM-41 as template, this material was prepared using phenolic resin as carbon source. Dynamic adsorption performance of toluene on micro–meso hierarchical porous carbon was studied by gas chromatographic techniques. Effects of toluene initial concentration, temperature and bed height on adsorption capacity were also researched. The results showed that when toluene concentration was 1750 mg/m 3 , equilibrium amount of toluene adsorbed was 358.8 mg/g by micro–meso hierarchical porous carbon, 79.41 mg/g by MCM-41. The adsorption capacity increased with the increase of initial concentration and bed height, while the adsorption capacity decreased along with the increase of temperature. Due to strong toluene adsorption capacity, this micro–meso hierarchical porous carbon manifests profound theoretical and practical significance in petrochemical organic waste gas treatment.
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    Monolithic nanoporous copper fabricated through decomposition and sintering of oxalate (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: Two more simple methods were used for preparation of the monolithic nanoporous copper. One was that through decomposition and sintering of copper oxalate precipitate directly. The other was that through decomposition and sintering of copper oxalate and manganese oxalate. The effects of sintered temperature and holding time on the morphology of the monolithic nanoporous copper were investigated. Thermal decomposition, composition and morphology of copper oxalate precipitate, as well as microscopic morphology and specific surface area of the monolithic nanoporous copper were analysed by thermogravimetric analysis, X-ray diffraction, scanning electron microscope and nitrogen adsorption–desorption. The preferable nanoporous copper can be prepared by decomposition and sintering of copper oxalate directly at 400°C for 30 min. The prepared monolithic nanoporous copper is of open and interconnected pores and is made up of copper grains with the size of about 100 nm, which is as high as 69.9 m 2 g −1 in specific surface area.
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    Folate-intercalated layered double hydroxide as a vehicle for cyclophosphamide, a non-ionic anti-cancer drug (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: Layered double hydroxides (LDH) are matrices with interlayer anions that can be exchanged with several types of organic or inorganic anions. Due to the anion-exchange capability, hundreds of new materials have been prepared in the past two decades. Conversely, attempts to intercalate neutral molecules (and increase the range of applications) have been achieved by expanding the interlayer space with long-chain surfactants, thus allowing to exclusively retain highly hydrophobic molecules. This work describes a folate-intercalated LDH structure, where folate pillars are capable of forming both hydrogen bonds and hydrophobic interactions with neutral molecules. Infrared spectroscopy and X-ray diffraction data indicated that imidazole, urea and cyclophosphamide were successfully intercalated. This evidence increases the opportunity to prepare more novel materials with neutral molecules in LDH. The cyclophosphamide-LDH product here obtained represents a remarkable example of an LDH-based vehicle for a non-ionic anti-cancer drug used in current chemotherapies.
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    Influence of colloidal silica dispersion on the decrease of roughness in silicon chemical mechanical polishing (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: Colloidal silica with different dispersion states during silicon chemical mechanical polishing (CMP) are investigated in detail. As the dispersion of colloidal silica is improved, the roughness ( R a ) decreases gradually during polishing. The silicon surface has a minimum R a of 0.118 nm when the polydispersity index of particles is 0.078. Comparing with surface polished by colloidal silica in poor dispersion, the surface quality has great improvement. The important role of dispersant is presented by the results of investigations. The research results indicate that dispersant makes aggregate micelles dispersed into many smaller uniform colloidal silica particles. The uniformly dispersed colloidal silica forms a thin film between the surfaces of silicon and polishing pad during CMP, which is beneficial for the stability of friction, and therefore greatly decreases roughness of silicon surface after polishing.
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    Energy dissipation of quantum-dot cellular automata logic gates (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: Quantum-dot cellular automata (QCA) is a new paradigm in nanoelectronics, where binary information is represented by charge configuration in cells. Ideal QCA logic gates are thought to be dissipationless, since there is no intercell charge transfer and no current flows out of cells. This work presents that these gates dissipate energy and compare energy consumptions of conventional QCA logic gates in electrostatic and thermodynamic approaches. The results show that increasing the number of inputs, concentration of the geometry and the unbalanced numbers of ‘0’ and ‘1’ output states in the gate's truth table add to the energy dissipation of a QCA gate.
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    Influence of carbon black with different concentration on dynamic properties and heat buildup of semi-efficient natural rubber composites (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: High abrasion furnace black (HAF) filler has long been recognised as reinforcing filler, but the impact of concentration on dynamic mechanics performance and heat buildup of vulcanisates is rarely reported. Therefore, natural rubber (NR) composites filled by N330 with different concentration were prepared. Payne effect and heat buildup of HAF/NR composites increases with an increase of HAF loadings during to that filler network structure become stronger with an increase of HAF loadings. Moreover, tensile strength, tear strength as well as modulus increase with an increase of HAF loadings is attributed to better dispersion and improved interfacial interaction between HAF and NR matrices. The results reveal that composites with 60 per hundreds of rubber (phr) of HAF exhibit better overall mechanical properties and lower heat buildup.
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    Synthesis of unequally-spaced linear array using modified central force optimisation algorithm (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: In this study, a modified version of the central force optimisation (MCFO) algorithm is presented. This modified version is based on the idea of combining the ability of social thinking in particle swarm optimisation (PSO) with the search capability of the original CFO, along with the addition of time-varying acceleration coefficients, to effectively control the global search and enhance the CFO convergence capability. The convergence capability of the MCFO approach is compared with that of other recent evolutionary-based algorithms, using 12 benchmark functions grouped into unimodal and multimodal functions. Furthermore, the MCFO algorithm is considered for the synthesis of unequally-spaced linear arrays with minimum sidelobe levels and/or null placement in certain directions as well as a specified maximum null-to-null beamwidth. The comparison of the simulations of different algorithms shows that the MCFO technique is superior to other evolutionary algorithms such as the genetic algorithm, ant colony optimisation, PSO algorithm, and gravitational search algorithm, as well as other improved CFO algorithms.
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    Prospects of Zn(O,S) as an alternative buffer layer for Cu 2 ZnSnS 4 thin-film solar cells from numerical simulation (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: Zn(O,S) is an attractive alternative to CdS as a buffer layer of Cu 2 ZnSnS 4 (CZTS)-based solar cell due to its higher bandgap and environmental friendliness. In this work, CZTS solar cell with a structure of CZTS/Zn(O,S)/Al:ZnO was simulated by Solar Cell Capacitance Simulator (SCAPS). The impacts of thickness and acceptor concentration of CZTS, thickness and donor concentration of Zn(O,S) and operating temperature on the performance of CZTS solar cells were investigated. It has been obtained that the optimum thickness of CZTS is between 2000 and 3000 nm and that of Zn(O,S) is about 50 nm. The suitable doping concentrations of CZTS and Zn(O,S) layers are around 10 16 and 10 17 cm −3 , respectively. The temperature coefficient of efficiency is about −0.023 %/K in the CZTS solar cell. All these simulation results will provide some important guidelines for fabricating high efficient CZTS solar cells.
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    Forced vibration analysis of a viscoelastic polymeric piezoelectric microplate with fluid interaction (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: The equations of motion for a viscoelastic polymeric piezoelectric microplate are established based on the thin plate theory and Kelvin–Voigt laws. Polyvinylidene fluoride is chosen as the polymeric piezoelectric material. The plate is assumed to be rectangular and the boundary conditions are clamped at all edges. Liquid is modelled as a damping foundation beneath the plate. The equations are solved using assumed-mode method along with Newmark's β method. The effects of variation in the input voltage, damping coefficient, viscoelastic parameter, and excitation frequency are discussed. The results are compared with the developed finite element method. An excellent agreement is observed between the two methods.
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    Planar pattern reconfigurable antenna with eight switchable beams for WiMax and WLAN applications (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: A planar pattern reconfigurable antenna designed for IEEE 802.11 b/g standard 2.4 GHz WiMax and WLAN applications is presented. The design is realised using a uniform arrangement of eight switch-controlled tapered strips symmetrically placed around a central circular disc on the top layer of an FR4 board. The antenna has a compact circular structure with overall diameter of 0.64 λ 0 in the free space for 2.4 GHz. To control the radiation pattern of the antenna, each of the tapered strips is connected to the ground via a PIN diode. Depending on the switching status of the eight PIN diodes, the tapered strips work in grounded or open-ended mode and thus the antenna offers eight switchable patterns. To validate the design, the antenna is prototyped and its performance is verified in a far-field anechoic chamber. The simulated and measured results prove the antenna's reconfigurability of the main beam in eight directions with 45° steps in the azimuth plane and a vertical tilting angle of 36°. Over the operating band 2.35–2.61 GHz, the antenna has a stable gain of around 4.5 dBi, and front-to-back ratio of more than 18 dB. Compared with recent designs, this antenna is more compact, has larger beam deflection off the boresight and more beam steering states.
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    Simulation of orbital angular momentum radio communication systems based on partial aperture sampling receiving scheme (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: The incoherent orbital angular momentum (OAM) radio waves can be used to transmit different information on the same frequency and have a great potential in wireless communication system. However, it needs a large aperture size to receive and demultiplex the orthogonal OAM waves due to the amplitude null in the beam centre and the beam divergence. An improved receiving scheme named partial aperture sampling receiving (PASR) is proposed to solve this problem. The theoretical analysis of PASR is first presented and simulations of OAM radio communication link are carried on to evaluate the performance of PASR. The effects of some non-ideal receiver conditions, e.g. radial deviation and angular deviation on the PASR scheme and the superiority of PASR are explored. These simulated results will give a helpful guide on the manipulation of practical OAM-based wireless communication systems.
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    Modification of enhanced distorted Born iterative method for the 2D inverse problem (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: This study presents a modified method based on the enhanced distorted Born iterative method for solving the 2D inverse problem. The proposed method overcomes two shortcomings of the enhanced distorted Born iterative method: (i) the regularisation parameter has to be determined artificially beforehand; (ii) The effects of the two regularisation processes in the enhanced distorted Born iterative method are redundant. The synthetic numerical reconstruction results, as well as the experimental reconstruction results, show that the proposed algorithm is capable and efficient for solving the 2D inverse scattering problem.
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    Design of continuous-mode GaN power amplifier with compact fundamental impedance solutions on package plane (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: A novel methodology for designing broadband Class-J power amplifiers (PAs) with compact fundamental impedances on the package plane is presented. A simple transistor model with knee voltage region is built to predict efficiency performance and clipping waveforms caused by the clipping effects. To realise the proposed impedance solutions, a broadband matching network is presented based on the shot-stepped Chebyshev impedance transformer. A broadband Gallium Nitride (GaN) PA is designed using this method and achieve a very wide operation band from 0.8 to 3.6 GHz. More than 10 dB gain, 55.8–74.1% drain efficiency and around −30 dBc adjacent channel power ratio are measured without linearisation throughout the entire band. At 33 dBm average output power level, an average power-added efficiency of 27% and adjacent power leakage ratio of −46.3 dBc is obtained with 9 dB peak-to-average power ratio 20 MHz long-term evolution test signals at 2.4 GHz.
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    Effect of radiation surface error in multi-scales on planar waveguide slotted arrays in Ku-band (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: This paper investigates effect of radiation surface error on the electrical properties of waveguide slotted arrays. For the waveguide slotted arrays working in Ku band, the radiation surface error caused by exterior loads and processing contains three components in different scales. Power spectrum conversion and Gaussian filtering are applied to error components separation, and three kinds of statistical models are introduced for error modelling. The multi-scale error model is obtained by weighted stacking. Based on the error model, effective mechanism formulations are developed with errors through the analysis of the positional difference of radiating slots in the aperture field. As a method of verification, an antenna prototype is manufactured and tested. A novel simulation method is proposed, which is tested by a contrast experiment on radiating surface's flatness. A comparison between results of the multi-scale error model and test data to the ideal case indicates that the proposed error model is closer to the test data. Influence degrees of all error components in different scales are compared and discussed. Reducing the error in the manufacturing process is an effective way to make sure the design accuracy of arrays, reduce production costs and shorten production cycles.
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    Fabrication of silver/beta-tricalcium phosphate particle by a simple liquid chemical reduction method (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: Using beta-tricalcium phosphate (beta-TCP), silver nitrate and glucose as the carrier, silver resource and reducing agent, silver/beta-TCP particle was successfully fabricated by a novel liquid chemical reduction method to overcome the infection problem of beta-TCP. The X-ray diffraction pattern of the as-obtained sample confirmed the existence of metallic silver in the particle. The addition of silver nanoparticle affected the thermal stability of beta-TCP and prevented the transformation from beta-TCP to alpha-TCP. Transmission electron microscopy images and the corresponding calculation result proved the mean size and size distribution of silver nanoparticles in the silver/beta-TCP particle could be controlled by varying the molar ratio between beta-TCP and silver nitrate. Moreover, the mean size and size distribution of silver nanoparticles also could be changed by using different stabilisers. The prepared silver/beta-TCP particle is a potential biomaterial to replace pure beta-TCP particle and utilise for coating material and other applications.
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    Synthesis and optimisation of new wideband symmetrical six-port junction (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: In this study, the authors propose a new approach for the synthesis of wideband symmetrical six-port junctions. The suggested approach is based on a novel microstrip topology that can be optimised using genetic algorithm. The proposed approach has been numerically validated through the synthesis of single and double cell six-port junctions. As an experimental validation single and double cell six-port junctions with centre frequencies of 2.5 and 5.3 GHz, respectively, have been realised and measured. The obtained experimental results have revealed the performance of the proposed synthesis approach, its robustness and its superiority compared to the conventional empirical design techniques.
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    Enhancing the performance of EBG resonator antennas by individually truncating the superstructure layers (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: The role of superstructure finiteness in improving the peak directivity and the directivity bandwidth (DBW) of electromagnetic band gap (EBG) resonator antennas (ERAs) is studied. Simple one- and two-layer superstructures consisting of unprinted dielectric slabs are used for this purpose. In the latter case, each dielectric slab is truncated individually to improve the ERA performance. Initially, existing analytical models that only take into account the reflection characteristics of the superstructure are used to predict the peak obtainable directivity and the directivity bandwidth. Detailed numerical studies are then conducted to observe the validity of these analytical predictions and to study the ERA performance for various finite sizes of the superstructure. It is found that DBW as well as the peak directivity of the antenna is strongly influenced by the size of the superstructure. Moreover, in case of two-layer superstructures, carefully designing each layer to have a different finite size improved the DBW product of an ERA by more than 65%. Experimental results of three ERA prototypes are presented to validate the trends observed in the numerical findings.
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    Highly-selective, closely-spaced, dual-band FSS with second-order characteristic (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: In this study, a closely-spaced, dual-band, band-pass frequency selective surface (FSS) is presented by cascading a two-layer periodic array. The proposed FSS provides two compact pass-bands separated by two transmission zeros, leading to highly selective response. Each pass-band contains two transmission poles, which results in a broad band performance. In addition, the FSS has wide out-of-band rejection due to that the other two transmission zeros occur at upper side of the higher pass-band. The simulation is implemented using full wave electromagnetic wave simulator CST Microwave Studio. The proposed FSS structure is fabricated and measured. Both measured and simulated results show that the operating frequencies of the two pass-bands are, respectively, centred at 9.25 and 11.3 GHz, which are very close to each other. Furthermore, the FSS has the merits of polarisation insensitivity and incident angle stability.
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    Reconfigurable narrow-frame antenna for LTE/WWAN metal-rimmed smartphone applications (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: A reconfigurable narrow-frame coupled-loop antenna capable of providing hepta-band long term evolution/wireless wide area network (LTE/WWAN) for metal-rimmed smartphone applications is proposed. The ground clearance of this proposed antenna is only 7 × 70 mm 2 which is promising for narrow-frame smartphone applications. Moreover, this proposed antenna can realise the miniaturisation by employing a positive intrinsic negative diode (PIN diode), which can provide two working states. When the PIN diode is OFF, it can provide coverage for GSM850/DCS/PCS/UMTS2100/LTE2300/2500 operations. When the PIN diode is ON, the obtained bands are GSM900/DCS/PCS/UMTS2100/LTE2300/2500. Hence, by combining these two working states, GSM850/900/DCS/PCS/UMTS2100/LTE2300/2500 operations are achieved. In addition, the feasibility of realising decoupled multi-antennas is demonstrated and its performances are well-suited for future smartphone applications. Detailed design considerations of the proposed antenna are described. Both experimental and simulated results are also presented and discussed.
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    Instantaneous power variance and radio frequency to dc conversion efficiency of wireless power transfer systems (2016)
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    Publication Date: 2016-07-08
    Description: This study compares the maximum rectifier radio frequency (RF)–dc conversion efficiency for various input signals with random modulation. The instantaneous power variance (IPV) is proposed as an easy to compute parameter to classify the effect of modulation on the obtained rectifier efficiency. A prototype ultra high frequency (UHF) rectifier is used to simulate as well as measure the performance of randomly modulated signals with binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), 8 phase-shift keying (PSK) and 64 quadrature amplitude modulation (QAM) modulations. In addition to considering different modulation formats, the roll-off factor of the baseband filter is also varied due to the fact that it has a strong impact on the time-varying nature of the signal envelope. For the given rectifier, it is shown that the peak RF–dc conversion efficiency versus the output load is shifted to larger load values for signals with higher IPV. Furthermore, by comparing signals with different time-varying envelope characteristics, it is shown that IPV represents a more accurate signal characteristic than peak-to-average power ratio in terms of properly characterising the effect of modulation on the rectifier efficiency.
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    Dual band complementary split-ring resonator-loaded printed dipole antenna arrays for pattern diversity multiple-input–multiple-output applications (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: In this study, a dual-band multiple-input–multiple-output (MIMO) antenna with pattern diversity is designed, targeting at the 2.4 GHz wireless local area network and 1.8 GHz global system of mobile communication application bands. The proposed scheme utilises arrays of printed dipoles fed with signals of equal amplitude but different input-phase values to achieve diverse radiation patterns in the operating frequency bands. The printed dipoles are loaded with complementary split-ring resonators to obtain one additional lower-frequency resonance, ensuring simultaneous miniaturisation and dual-band characteristics. The impedance, radiation and diversity performances of the proposed MIMO configuration are analysed by full-wave simulations in ANSYS high-frequency structure simulator. It is observed that both the antennas in the MIMO configuration cover the common frequency range of 1.7–1.8 and 2.25–2.5 GHz, with satisfactory average gain and stable radiation pattern in the working bands. Experimental results on the fabricated structure are in good agreement with simulation results, confirming validity of the proposed concept.
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    Research on characteristics of first-order sea clutter for high-frequency sky–surface wave radar (2016)
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    Publication Date: 2016-07-08
    Description: In high-frequency (HF) hybrid sky–surface wave radar, the first-order sea clutter broadening is severe under the influence of the ionosphere and bistatic angle. This affects the detection of ship targets. Thereby a comprehensive analysis is essential and will be presented in this study. First, according to the geometry configuration and detection characteristics of this new system radar, the positioning principle and the range of grazing angle are analysed. Then, the first-order sea clutter Bragg frequency is presented and broadening model is given on the basis of the system configuration. Next, the mechanism of first-order sea clutter frequency shift and broadening is explained and, based on the system layout, simulation is provided to illustrate the effects of various factors on first-order sea clutter, including ionosphere, grazing angle and bistatic angle. Moreover, the characteristics of sea clutter frequency shift and broadening in different range and azimuth are analysed. Finally, the results of theoretical analysis are compared with the experimental data based on the newly-developed integrated experimental system, and the dominant factor of sea clutter broadening is studied. Simulation results show that the results of experiment are consistent with that of theoretical analysis.
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    Ka-band doherty power amplifier with 26.9 dBm output power, 42% peak PAE and 32% back-off PAE using GaAs PHEMTS (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: The authors present the design and development of a two stage Doherty power amplifier (DPA) in the Ka-band. The amplifier is fabricated in a 0.15-µm gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) process. The DPA has a centre frequency of 26.6 GHz, a measured small signal gain of 10.5 dB, output power at 1-dB compression point (P1 dB) of 26.9 dBm, maximum power added efficiency (PAE) of 42%, and PAE of 32% at 6 dB back-off power. To the best of the author's knowledge, this DPA is the first millimetre-wave (mm-wave) power amplifier to achieve a record 32% PAE at 6-dB back-off power from 26.9 dBm at Ka-band.
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    Equivalent circuit of a reconfigurable triple-slot reflectarray cell (2016)
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    Publication Date: 2016-07-08
    Description: This study presents an equivalent model for a multiple-resonance reflectarray cell. It allows predicting the different phase-states of the cell from only a very few full-wave simulations. Demonstrations are first given for a passive cell where different geometrical parameters are varied. Then, the approach is generalised to a reconfigurable cell. Finally, a canonical reflectarray with a steered beam has been synthesised in order to illustrate the capabilities of the proposed equivalent circuit.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Institution of Engineering and Technology (IET)
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    Performance improvement by transmit diversity technique for implant ultra-wideband communication (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-08
    Description: In implant body area networks (BANs), an ultra-wideband (UWB) technology is a promising candidate to accomuplish high data rate. However, due to its frequency, the UWB signals suffer from large attenuation in the implant communication link. This fact suggests the difficulty on achieving reliable communication. For achieving reliable communication, it is well known that a spatial diversity technique is efficient. In this study, the authors pay attention to the fact that it is possible to further miniaturise the UWB antenna due to its very high frequency. Then, the authors aim to develop a transmit polarisation diversity antenna for implant UWB communications, and apply the developed transmit diversity system to a UWB-impulse radio (UWB-IR) scheme and a multiband-orthogonal frequency division multiplexing (MB-OFDM) scheme, respectively. For evaluating the proposed system, the authors first analyse the propagation characteristics in the implant UWB channel, using the finite difference time domain numerical analysis technique. Then, the authors evaluate and discuss the communication performances of the both modulation schemes for the transmit polarisation diversity. As a result, at a communication distance of 7 cm, the throughputs have accomplished to 300 Mbps for the MB-OFDM scheme and 30 Mbps for UWB-IR scheme, respectively.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Institution of Engineering and Technology (IET)
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  • 98
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    Lifting-based design of two-channel biorthogonal graph filter bank (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: In this study, the lifting scheme is first employed to design two-channel biorthogonal graph filter bank. The biorthogonal condition is parameterised by imposing a single-level lifting structure on the analysis and synthesis graph kernels. Based on the parametric structure, the two kernels are separately optimised by constrained quadratic programming. The obtained two-channel biorthogonal graph filter banks are of structurally perfect reconstruction. Numerical results and comparison are included to show the proposed algorithm can lead to biorthogonal graph filter banks with improved performance.
    Print ISSN: 1751-9675
    Electronic ISSN: 1751-9683
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 99
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    Multi-objective optimisation of wavelet features for phoneme recognition (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: State-of-the-art speech representations provide acceptable recognition results under optimal conditions, though their performance in adverse conditions still needs to be improved. In this direction, many advances involving wavelet processing have been reported, showing significant improvements in classification performance for different kinds of signals. However, for speech signals, the problem of finding a convenient wavelet-based representation is still an open challenge. This study proposes the use of a multi-objective genetic algorithm for the optimisation of a wavelet-based representation of speech. The most relevant features are selected from a complete wavelet packet decomposition in order to maximise phoneme classification performance. Classification results for English phonemes, in different noise conditions, show significant improvements compared with well-known speech representations.
    Print ISSN: 1751-9675
    Electronic ISSN: 1751-9683
    Topics: Electrical Engineering, Measurement and Control Technology
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    Two-dimensional autofocus technique for high-resolution spotlight synthetic aperture radar (2016)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2016-07-22
    Description: Motion errors are inevitably introduced when data is acquired and considerably degrade the image quality in terms of geometric resolution, radiometric accuracy and image contrast, especially in high-resolution spotlight synthetic aperture radar (SAR) imagery. In this study, the authors present a novel two-dimensional (2D) autofocus algorithm directly inserted into polar format algorithm, which compensates the envelop error and the phase error sequentially. A coarse error correction is first performed by global positioning system or inertial navigation system in the range-compressed domain, then a new envelop compensation strategy, stage-by-stage approach, is designed, obtaining promising results for removing range cell migration after 2D interpolation. Additionally, a weighed contrast enhancement autofocus algorithm based on spatially variant model is developed to compensate for the residual phase error, which remarkably improves the estimation accuracy. The presented algorithm is very robust to deal with substantial errors over a variety of scenes even in conditions of homogenous areas with no prominent point scatterers and enables the utilisation of fast Fourier transform. The experimental results obtained by the proposed algorithm confirm that the analysis extends well to realistic situations.
    Print ISSN: 1751-9675
    Electronic ISSN: 1751-9683
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Institution of Engineering and Technology (IET)
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