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  • Articles  (2,297)
  • Oxford University Press  (1,244)
  • Institution of Engineering and Technology (IET)  (1,053)
  • 2010-2014  (1,739)
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  • Electrical Engineering, Measurement and Control Technology  (2,297)
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  • Articles  (2,297)
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  • 1
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: A report is presented on a novel non-enzymatic amperometric glucose sensor based on three-dimensional porous Cu, which was directly reduced by hydrogen from Cu(OH) 2 . The surface morphology of the synthesised nanoporous Cu was characterised using field-emission scanning electron microscopy and X-ray powder diffraction. Compared with the commercial Cu nanoparticles, the nanoporous Cu modified electrode shows better catalysis to glucose, which is attributed to the special porous Cu structure providing a favourable microenvironment for glucose adsorbed in large quantity. The interesting comparative study of different cross-linking agents for the immobilisation of nanoporous Cu reports that nafion, chitosan and multi-walled carbon nanotubes (MWCNTs) can all improve the catalysis effect of porous Cu on the glucose but the MWCNT shows the best sensitive response and stability. The MWCNT plays an especially important role in stability improvement by 20% of the efficiency. Under optimal conditions, a linear dependence of the catalytic current upon glucose concentration was obtained in the range of 5.0 ?? 10 ??7 ??2.0 ?? 10 ??3 M with a detection limit of 1.0 ?? 10 ??7 M, a high sensitivity of 20.11 μA μM ??1 , good stability and no current response from interfering species at the approximate physiological concentration level.
    Electronic ISSN: 1750-0443
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 2
    Publication Date: 2013-09-07
    Description: The design, synthesis and characterisation of biologically synthesised nanomaterials have become an area of significant interest. Presented is a report on the extracellular synthesis of gold nanoparticles using Punica granatum (Pomegranate) fruit extract as the reducing agent to synthesise Au nanoparticles. On treating aqueous chloroauric acid solutions with P. granatum fruit extract, rapid reduction of the chloroaurate ions is observed, leading to the formation of highly stable gold nanoparticles in solution. These nanoparticles showed an absorption peak at 536 nm in the UV??vis spectrum corresponding to the plasmon resonance of gold nanoparticles. Scanning electron microscopy analysis of the gold nanoparticles indicated that they ranged in size from 10 to 50 nm. The Fourier transform infrared spectroscopy spectrum confirmed the presence of main groups occurred in natural plant extract from P. granatum. The synthesised gold nanoparticles were active against Streptobacillus sp. and Escherichia coli.
    Electronic ISSN: 1750-0443
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  • 3
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: A novel nanocomposite was prepared by direct mixing of titania nanoparticles (nano-TiO 2 ) and gold nanoparticles (nano-Au)-modified carbon nanotubes (CNTs) in a solution of chitosan. The electrochemical performance of a TiO 2 /Au/CNT nanocomposite-modified electrode for hydroquinone detection was investigated. When measured at a scan rate of 50 mV s ?? 1, the detected amount of hydroquinone at the TiO2/ Au/CNT electrode varied linearly with hydroquinone concentration, for concentrations from 1 ?? 10 ??6 to 1 ?? 10 ??8 M; the sensitivity was 997 617 μA(mol 1 -l -1 ), and the detection limit was 1 ?? 10 ??10 M (S/N = 3). In all experiments, TiO2/Au/CNT nanocomposites exhibited better electrochemical performance than TiO 2 /CNT composites or CNTs. Enhanced current response can be attributed to the synergic effect of nano-TiO 2 , nano-Au and CNTs.
    Electronic ISSN: 1750-0443
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  • 4
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: An antibacterially bioinorganic composite has been synthesised by intercalating lysozymes (LZs) into layered titanates with a convenient and efficient exfoliation-restacking strategy. This composite exhibits a loose slab morphology with a thickness of 5??10 layers, and the interlayer space is ~4.4 nm because of intercalation of enzymes. The immobilised amount of lysozymes is up to ~68.3% in weight because of the layer-by-layer alternate and swollen structure. This composite is stable in the neutral and weakly acidic condition, and only releases 4 solution. The immobilised LZs exhibit excellent thermal stability, which retain their initial activities of about 70% at 70° for about 40 min. In addition, the residual activities of the immobilised enzymes are 68% after ten recycles reuse.
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  • 5
    Publication Date: 2013-09-07
    Description: Amlodipine besylate and atorvastatin calcium have been determined by the simultaneous voltammetric method at a multi-walled carbon nanotubes:graphite (MWCNTs:G) paste electrode. In comparison with a glassy carbon electrode, the prepared electrode showed an increase in the peak current because of the high electroactive surface area and excellent electronic conductivity of MWCNTs. The dependence of currents and potentials on pH were investigated for these components at the surface of the MWCNTs:G paste electrode. Differential pulse voltammetry was applied as a sensitive technique for simultaneous determination of the drugs in commercial tablets. By anodic differential pulse voltammetry, the calibration plot was linear in the range of 2.5??100 μg/ml with standard deviation between 2.7??7.1 and 1.8??8.3% for amlodipine and atorvastatin, respectively. The detection limit was 1 μg/ml at the prepared electrode in the buffered solution pH 6.
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  • 6
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: Uniform CdMoO 4 nanooctahedra with tunable sizes have been synthesised via a facile and mild microemulsion method at room temperature. The reaction between CdMoO4 nanooctahedra and dilute hydrochloric acid was in situ monitored using microcalorimetry at 298.15 K, and microcalorimetric heat flow curves from this reaction process were obtained. Combined with an inductively coupled plasma optical emission spectrometer technique, the size effect of CdMoO 4 nanooctahedra on standard molar reaction enthalpy (Δ r HΘm) was studied. The results indicate that the value of (Δ r HΘm decreased with decreased particle size.
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  • 7
    Publication Date: 2013-09-07
    Description: For the first time, CoCr 2 O 4 /TiO 2 nanocomposite as a novel photocatalyst with different TiO 2 contents have been prepared by the sol??gel method. The techniques of X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy (TEM) have been employed to characterise the synthesised nanocatalysts. The XRD and TEM results indicated that CoCr 2 O 4 has a cubic normal spinel structure and the particle size of CoCr 2 O 4 is about 30 nm. As the first report, degradation of methylene blue and methyl orange is performed by CoCr 2 O 4 and CoCr 2 O 4 /TiO 2 nanocomposite under ultraviolet irradiation. The results showed that the rate of degradation of dyes with CoCr 2 O 4 /TiO 2 is much higher compared with that of CoCr 2 O 4 and TiO 2 . The photocatalytic activities were carried out under varying parameters such as irradiation time, the pH of the solution, the catalyst amount and substrate concentration.
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  • 8
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: A report is presented on the local anodic oxidation of graphene film prepared by chemical vapour deposition using contact mode atomic force microscopy. Raman spectroscopy was used to check the uniformity and thickness of large area graphene film. Various kinds of patterns such as lines, ribbons and further, more complex structures, such as hexagons, two-terminal bar-like devices, were written by varying the tip voltage from ??6 to ??12 V and the tip speed from 60 to 200 nm/s. It was found that one can easily write any kind of patterns by just manipulating the tip voltage and tip speed instead of concentrating on other factors such as controlled humidity conditions, applied force on the tip and tip current. Also, it is confirmed that with an increase in tip voltage and by slowing the tip movement during lithography, one can write very narrow and sharp patterns which are important factors for the fabrication of graphene-based electronic devices.
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  • 9
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: Hierarchical porous copper bulk can be fabricated through chemical dealloying of porous CuAl intermetallics under free corrosion conditions. The obtained precursor porous CuAl intermetallics and as-dealloyed hierarchical porous copper were characterised using X-ray diffraction, a field-emission scanning electron microscope and energy dispersive X-ray spectroscopy. It was found that the hierarchical porous copper can be easily prepared by this method. The dealloying solution will dramatically influence the morphology of the resultant hierarchical porous materials. As a result, trimodal porous copper composite material and bimodal porous copper can be achieved after being dealloyed in NaOH and HCl solutions, respectively. Therefore, the mechanisms of the evolution of hierarchical pores structure are also discussed.
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  • 10
    Publication Date: 2013-09-07
    Description: The ternary composites of graphene@SiO 2 @NiO nanoflowers were fabricated by a multi-step route. Graphene oxide (GO)@SiO 2 sheets were formed by a layer of silica nanosheets coated on the surface of GO. Then, GO@SiO 2 sheets were introduced as substrates for the growth of NiO nanoflowers. The microwave absorption property of the ternary composites was studied in the frequency ranging from 2 to 18 GHz, and the effect of the thickness of the ternary composites on microwave absorption was also investigated. The results indicate that graphene@SiO2@NiO nanoflowers composites exhibit enhanced microwave absorption compared with graphene@SiO 2 . The reflection loss of graphene@SiO 2 @NiO nanoflowers below ??10 dB is 5 GHz (from 10 to 15 GHz) and the maximum absorption is ??20.5 dB at 11.3 GHz with a thickness of 3 mm.
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  • 11
    Publication Date: 2013-09-07
    Description: Two kinds of planar-type potentiometric CO 2 gas sensors using thermal evaporated Li 3 PO 4 thin film as solid electrolyte were fabricated. Alumina plates with rough and smooth surfaces were used as the substrates of the sensors. X-ray diffraction analysis, atomic force microscopy and scanning electron microscopy were used to characterise the Li 3 PO 4 films. The sensing properties were investigated in the range of 500??5000 ppm CO 2 concentrations at 480°. Both the rough substrate-based sensor (r-sensor) and the smooth substratebased sensor (s-sensor) were sensitive to CO 2 gas and showed a good Nernst behaviour. The output electromotive force (EMF) of the s-sensor showed a more stable signal than the r-senor. The ??EMF/decade values obtained from the r-sensor and the s-sensor were 45 and 55 mV/decade, respectively. The response and recovery time were not primarily influenced by the electrolyte film. It was found that the sensitivity of the s-sensor was closer to the theoretical value. The results revealed that the substrate surface roughness may influence the characteristics of Li 3 PO 4 film and the response properties of the sensors to CO 2 .
    Electronic ISSN: 1750-0443
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  • 12
    Publication Date: 2013-09-07
    Description: Bismuth oxybromide (BiOBr) flower-like microspheres have been successfully synthesised via a polyethylene glycol 600-assisted solvothermal process in the presence of reactable ionic liquid (IL) 1-hexadecyl-3-methylimidazolium bromide. The morphology and compositional characteristics of BiOBr were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and diffuse reflectance spectroscopy. During the reactive process, IL not only acted as a Br source but also as a template for fabrication of BiOBr flower-like microspheres. Photocatalytic activities of flower-like microspheres were evaluated by degradation of rhodamine B under visible-light irradiation. Compared with the BiOBr nanoplates, BiOBr hollow microspheres and TiO 2 (Degussa, P25), BiOBr flower-like microspheres exhibited excellent performance in visible-light-driven photocatalysis.
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  • 13
    Publication Date: 2013-09-07
    Description: Polyvinyl alcohol (PVA)/sodium dodecyl sulphate (SDS)/multi-walled carbon nanotubes (MWCNTs) composite nanofibres with various MWCNT contents (up to 10 wt%) were fabricated by electrospinning process and their microwave absorption properties were evaluated by a vector network analyser in the frequency range of 8??12 GHz (X-band) at room temperature. Scanning electron microscopy analysis of the nanofibre samples revealed that the deformation of the nanofibres increases with increasing MWCNT concentration. Very smooth surfaces of the composite electrospun nanofibres even for nanofibres with concentration of 10 wt% MWCNT have been successfully prepared because of the high stability dispersion of MWCNTs. It was observed that the absorption microwave properties improved by increasing the loading levels of MWCNTs. Finally, the PVA/SDS/MWCNT composite nanofibres sample with 10 wt% content of MWCNT has shown a reflection loss of 15 dB at a frequency of 8 GHz.
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  • 14
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: Presented is a surface nanostructuring technology for enhancing the broadband light transmittance of polymethyl methacrylate sheets. Singleside and dual-side nanostructured sheets were fabricated by a hot embossing process using nanoporous alumina moulds. The fabricated nanostructured surfaces showed appreciable broadband light transmission characteristics because of the size distribution of their nanostructures. Single-side and dual-side nanostructured sheets showed a maximum light transmittance of 96.11 and 98.74%, respectively, whereas a pristine sheet showed a light transmittance of 93.54%.
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  • 15
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: A novel thermochemical technique of depositing platinum nanoparticles (PtNPs) on a porous silicon (PS) substrate is demonstrated. Selfarranged macroporous structures, appearing as microtest tubes, are first formed on p-type, boron doped, 100 orientation silicon wafers, by the electrochemical etching method in hydrofluoric acid and N, N-dimethyl formamide solution. The macroPS substrate is then coated with PtNPs by a novel thermochemical procedure. It was observed that PtNPs deposited on the pore walls are able to arrive even at the bottom of the pores without blocking their openings. Such PtNPs-coated macroPS chips have potential biomedical applications as silicon and platinum are biocompatible.
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  • 16
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: In this reported study, hydroxyapatite (HA) nanoparticle-contained bioactive glass (BG) nanofibres with an average diameter of 500 nm have been prepared by combining a sol??gelmethod and an electrospinning technique. Themechanical property of the as-prepared fibres demonstrated that the HA-BG nanofibres had far higher mechanical strength than pure BG nanofibres, and the in vitro simulated body fluid immersion experiment verified that the growth rate of the hydroxycarbonate apatite nanocrystals on HA-BG nanofibre surfaces was the same with pure BG nanofibres.
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  • 17
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: SnO 2 nanocrystals with small diameters including nanorods, nanowires connected by nanorods and nanoparticles have been obtained in mixed solvents of oleic acid (OA) and ethanol. By simply adjusting the volume ratio of these solvents, the morphologies and structures of the SnO 2 crystals can be easily varied. All the products show pure tetragonal SnO 2 with a rutile structure and the obtained nanorods can be connected with each other in various ways to form nanowires. The nanocrystals with a volume ratio of OA and ethanol of 1:1 present the best photocatalytic properties which shows 100% degradation of Rhodamine B within 60 min.
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  • 18
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: Ternary semiconductor ZnSe 0.7 Te 0.3 nanowires (NWs) are synthesised by using a thermal evaporation method, and the as-synthesised NWs have a wurtzite structure with a growth direction of [001]. The electrical measurements are carried out based on nano-field-effect transistors fabricated by individual NWs, and the electron transport characteristics reveal that the ZnSe 0.7 Te 0.3 NWs have p-type conductivity with a highmobility (μh) of 0.9 cm 2 V ??1 S ??1 and carrier concentration (n h ) 5 ?? 10 18 cm ??3 . Photoluminescence measurements for ZnSe 0.7 Te 0.3 NWs show a dominant emission peaked at 478 nm which is the emission of free exciton.
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  • 19
    Publication Date: 2013-09-07
    Description: The successful production, via two different oxidation processes, of metal-oxide-metal (MOM) diodes is presented. An innovative reactive ion etching and plasma assisted regrowth process has been used to provide oxides, which are in the thickness range 4.0??5.1 nm. These are thinner and physically more uniform than oxides grown in a furnace, resulting in diodes which should conduct via electron tunnelling across the MOM junction. Transmission electron microscopy analysis has been used in conjunction with time of flight secondary ion mass spectrometry analysis to verify oxide thickness and uniformity.
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  • 20
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-07
    Description: During skeletal muscle development, correct cellular orientation is vital to generate desired longitudinal contraction for functional muscle fibres. In this reported study, submicron-imprint lithography was used to generate submicron-grooved surfaces on polystyrene plates to induce striated myotubes in vitro. Mouse muscle myoblast cells cultured on a submicron-grooved surface migrated faster in a directionally uniform fashion; in comparison, cells cultured on a flat surface grew and migrated slower in indiscriminate directions. Subsequent maturation of the myoblast cells formed along the submicron-groove surface resulted in a tandem of parallel myotubes that were both longer and greater in circumference than in the case of the flat surface. In a functional test, the co-culture submicron-groove-grown myotubes with neurotransmitter secreting cells further demonstrated contraction abilities, suggesting submicron-groove-guided growth served to enhance myotube formation while retaining striated motifs and physiological functionality for muscle tissue engineering.
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  • 21
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: Recent studies suggest that relay communications can be a major application to extend the range of wireless communications by forwarding the signal from the sender to the receiver. Although fixed or robust distributed relay schemes for single receiver have been previously investigated, the distributed relay beamforming (DRBF) for multiple receivers is studied here. The authors propose an algorithm to design the DRBF weights for maximising the worst received signal-tonoise ratio subject to two different types of relay power constraints, which are the total relay power constraints and individual relay power constraints. The authors also prove that the proposed algorithm with relay power constraints results in a quadratic programming optimisation problem, which can be optimally solved by using semidefinite relaxation technology. The simulation results demonstrate an effective gain of the proposed optimal scheme over other intuition schemes.
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  • 22
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: In this correspondence, the authors develop a novel method based on spherical radial cubature and Gauss??Laguerre quadrature rule for non-linear state estimation problems. The proposed filter, referred as cubature quadrature Kalman filter (CQKF) would be able to overcome inherent disadvantages associated with the earlier reported cubature Kalman filter (CKF). The theory and formulation of CQKF has been presented. Using two well-known non-linear examples, the superior performance of CQKF has been demonstrated. Owing to computational efficiency (compared to the particle and grid-based filter) and enhanced accuracy compared to the extended Kalman filter and the CKF, the developed algorithm may find place in on-board real life applications.
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  • 23
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: This study presents a semi-blind channel estimation scheme for multiple-antenna systems. With the aid of channel covariance and received signal power, the proposed scheme derives channel estimates using pilot symbols transmitted by only one of its antennas. Other transmit antennas in the scheme do not need to transmit any pilot symbols. As such, the proposed scheme has higher bandwidth efficiency compared with conventional pilot symbol-based multiple-antenna channel estimation schemes, where every antenna is required to transmit pilot symbols. It is shown that the proposed scheme is able to deliver performance on par with the conventional minimum mean-square error and least-square error multiple-channel estimation schemes. The strength of the proposed scheme lies in its ability to exploit received signal power for channel estimation.
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  • 24
    Publication Date: 2013-10-02
    Description: A target localisation estimator based on time difference of arrival (TDOA) measurement is proposed. The localisation estimator is designed in the framework of the recently developed robust least-squares (RoLS) estimator, which provides an unbiased estimation result and can be implemented with a recursive filtering structure. However, when the RoLS estimator is applied to the localisation problem, its localisation performance depends on the knowledge of the stochastic information of the TDOA measurement. This dependency means that incorrectly given information causes localisation error. Therefore to complement the dependency of the given stochastic information of the TDOA measurement, we design a compensation procedure based on the constraints on the state variables of the estimator. The performance of the proposition under several cases of incorrectly given stochastic information is verified through computer simulation, and its filtering structure is compared with other existing localisation algorithms mathematically. In addition, the entire process of the proposed localisation estimator is derived as a recursive form for real-time applications.
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  • 25
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: Sparsity is one of the key points in the compressed sensing (CS) theory, which provides a sub-Nyquist sampling paradigm. Nevertheless, apart from sparsity, structures on the sparse patterns such as block structures and tree structures can also be exploited to improve the reconstruction performance and further reduce the sampling rate in CS framework. Based on the fact that the block structure is also sparse for a widely studied block sparse signal, in this study, a double-level binary tree (DBT) hierarchical Bayesian model is proposed under the Bayesian CS (BCS) framework. The authors exploit a recovery algorithm with the proposed DBT structured model, and the block clustering in the proposed algorithm can be achieved fastly and correctly using the Markov Chain Monte Carlo method. The experimental results demonstrate that, compared with most existing CS algorithms for block sparse signals, our proposed DBT-based BCS algorithm can obtain good recovery results with less time consuming.
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  • 26
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: This study provides an event-triggered H ∞ filtering design method for a discrete linear system under network environments. First, a periodic event-triggered communication scheme and a networked filter error system model for networked H ∞ filtering are presented. In this scheme and model: (i) the sensor is time-triggered; (ii) the transmitter is eventtriggered in a periodic manner; and (iii) the closed-loop system is modelled as a time-delay dependent filter error system. Second, under consideration of the proposed communication scheme, an H ∞ filtering analysis criterion and a stabilisation criterion are derived. Compared with those where the communication scheme and the filter must be individually designed in some existing ones, the communication and filtering parameters can be obtained simultaneously. In particular, a co-design algorithm is provided to obtain the communication and filtering parameters in a unified framework for using less network bandwidth. Finally, two examples are given to show the advantages of the proposed method.
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  • 27
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: Recently, speech scientists have been motivated by the great, success of building margin-based classifiers, and have thus proposed novel methods to estimate continuous-density hidden Markov model (HMM) for automatic speech recognition (ASR) according to the notion that the decision boundaries determined by the estimated HMMs attain the maximum classification margin as in learning support vector machines. Although a good performance has been observed, the margin used in the ASR community is often specified as a parameter that has no explicit relationship with the HMM parameters. The issues of how the margin is related to the HMM parameters and how it directly characterises the generalisation capability of HMM-based classifiers have not been addressed so far in the community. In this study, the authors attempt to formulate the margin used in the soft margin estimation framework as a function of the HMM parameters. The key idea is to relate the standard distance-based margin with the concept of divergence among competing HMM state Gaussian mixture model densities. Experimental results show that the proposed model-based margin function is a good indication about the quality of HMMs on a given ASR task without the conventional needs of running experiments extensively using a separate set of test samples.
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  • 28
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-25
    Description: The authors show that a wave with any desired polarisation state can generally be generated in any direction with respect to two crossed dipoles, and a closed-form expression is provided for the complex ratio of the required drive voltages. The authors also provide a simple projection method for the polarisation ellipse in the case where the dipole centres coincide. For achieving the authors' aim of exploiting closed-form equations to generate circularly polarised (CP)/elliptically polarised (EP)/linearly polarised in any direction, two orthogonally placed dipoles resonating at 1 GHz each are designed. By selecting complex feed solutions, which are provided from the proposed closed-form equations, it is realised precise polarisation states in a number of directions. Four separate such cases to generated CP and EP were investigated, and in all of them the numerical simulations and experiments validated the proposed theoretical predictions.
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  • 29
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-25
    Description: In this study, compact ultra-wideband (UWB) bandpass filters with single/dual-notched bands are proposed based on a ring resonator and transversal signal-interference concept. Broad passband and narrow notched bands with controlled even/oddmode resonator frequencies can be adjusted conveniently by changing the characteristic impedance of the ring resonator. Transmission zeros are introduced to improve selectivity and harmonic suppression of the proposed UWB bandpass filters with notched bands. To verify the presented strategies, three prototypes (εr = 2.65, h = 0.5 mm) with 3 dB fractional bandwidth ≫120% are designed and fabricated. Simple structure and good in/out-of-band performances can be achieved in the proposed UWB bandpass filters.
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  • 30
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-25
    Description: A dual-mode open-loop slotline resonator with a centre-loaded stub is proposed. The loaded stub is used to excite nondegenerate modes, that is, the even and odd modes. Distinct characteristics of this dual-mode resonator are investigated by using even??odd mode analysis. Also, equivalent circuit models for non-degenerate modes are given to determine the resonance conditions and the location of transmission zero. Then, two novel approaches for designing dual-mode dual-band bandpass filters are presented. One approach consists of simple microstrip feedlines and two embedded open-loop slotline resonators for single substrate configuration. The other is composed by using dual-mode open-loop resonators in the form of microstrip and slotline structures on a single substrate. A microstrip invert L-shape feeding structure is employed to simultaneously feed the microstrip and slotline resonator on different layers for broadside coupling. Both of them provide sufficient degrees of freedom to control the centre frequencies and fractional bandwidths of both passbands independently. The two filters are designed, fabricated and measured. A good agreement between the simulation and measurement verifies the validity of this design methodology.
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  • 31
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-25
    Description: In this study, a novel planar ultrawideband antenna, with a quad band-notched function, is investigated. The proposed antenna consists of a circular-shaped radiating element, a 50 Ω microstrip feed line, a modified H-shaped resonator, and a partially truncated ground plane. The proposed H-shaped resonator, with quadruple resonance characteristics, is realised without any change in its size but instead, by modifying the simplified composite right/left-handed resonator with dual resonance characteristics. By embedding the modified H-shaped resonator beside the microstrip feedline, band-rejected filtering properties in the wireless local area network/worldwide interoperability for microwave access bands are generated. By changing the modified H-shaped resonator??s dimensions, the proposed antenna shows variable quadplex-filtering characteristics, such as band-notch frequency and its bandwidth. The measured results show that the proposed antenna design exhibits a 10 dB return loss bandwidth from 2.12 to 13.63 GHz, excluding the rejection bands. Very sharp notch and high band-rejection are achieved, and relatively stable omnidirectional radiation performance over the entire frequency range is also obtained.
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  • 32
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: The electroencephalogram (EEG) signal is the manifestation of brain activity recorded as changes in electrical potentials at multiple locations over the scalp and it can be distorted by many other sources of electrical activity, called eye artefacts. It is important to remove these artefact signals before analysing the EEG signal, to obtain accurate information about brain activity and avoid mistakes in its interpretation. To deal with this problem, the present study proposes an artificial neural network, as a filter to remove ocular artefacts. In the proposed method, the number of radial basis function (RBF) neurons and input output space clustering are adaptively determined. Furthermore, the structure of the system and the parameters of the corresponding RBF units are trained automatically and relatively fast adaptation is attained. By the leastsquare error estimator techniques, the proposed system is suitable for real EEG applications. The proposed system improves results yielded by conventional techniques of ocular reduction, such as principal component analysis, support vector machines and independent component analysis systems. As a consequence, the algorithm could serve as an effective framework to reduce substantially eye interference in EEG recordings.
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  • 33
    Publication Date: 2013-09-28
    Description: This study proposes a double differentially (DDF) coherent pseudorandom code acquisition method for code-division multiple-access (CDMA) system. Nonlinear loss, false alarm probability and detection probability of this method have been analysed. Compared with real differentially coherent method, DDF method can be applied to improve detection performance in CDMA system. Furthermore, the analysis and simulations in this study illustrate that the proposed detector can provide 1??3 dB improvement compared with the complex differentially coherent detector, and 2??5 dB improvement compared with the non-coherent detector.
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  • 34
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: Automatic phoneme segmentation of a speech sequence is a basic problem in speech engineering. This study investigates unsupervised phoneme segmentation without using prior information on linguistic contents and acoustic models of an input sequence. The authors formulate the unsupervised segmentation as an optimal problem by means of maximum likelihood, and show that the optimal segmentation corresponds to minimising the coding length of the input sequence. Under different assumptions, five different objective functions are developed, namely log determinant, rate distortion (RD), Bayesian log determinant, Mahalanobis distance and Euclidean distance objectives. The authors prove that the optimal segmentations have the transformation-invariant properties, introduce a time-constrained agglomerative clustering algorithm to find the optimal segmentations, and propose an efficient implementation of the algorithm by using integration functions. The experiments are carried out on the TIMIT database to compare the above five objective functions. The results show that RD achieves the best performance, and the proposed method outperforms the previous unsupervised segmentation methods.
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  • 35
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: A modified architecture for minimised power consumption in the maximum a posteriori (MAP) decoder based on retiming for register minimisation is proposed in this study. Retiming for register minimisation technique is introduced in the trellis unit of the MAP decoder. Forward state metric and reverse state metric values are retained till the end of the time scale '(k - 1)' to calculate log-likelihood ratio (LLR) value. By applying this technique, the number of registers gets reduced, where the node has several output edges carrying the same signal. Depending on the time scale, memory latches reduces from k[(k - 1)/2] to '(k ?? 1)' in the LLR unit of MAP decoder. Using this technique, optimised architecture is derived and the authors have achieved the power consumption of 173.2 mW, which is less than 12.21% with the reported values, for K = 5, code rate ?? and time scale k = 4. When forward flip-flop retiming is applied 6.08% clock frequency increased and 5.53% total time delay reduced as compared with the register retiming technique.
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  • 36
    Publication Date: 2013-09-28
    Description: In this study, the problem of resource allocation in multiple-input multiple-output??orthogonal frequency division multiplexing-based cooperative cognitive radio networks is considered. The cooperation strategies between the secondary users is the decode-and-forward (DF) strategies. In order to obtain an optimal subcarrier pairing, relay assignment and power allocation in the system, the dual decomposition technique is recruited. The optimal resource allocation is realised under the individual power constraints in source and relays, so that the sum rate is maximised, whereas the interference induced to the primary system is kept below a pre-specified interference temperature limit. Moreover, because of the high computational complexity of the optimal approach, a suboptimal algorithm is further proposed. The joint allocation of the resources in suboptimal algorithm is carried out taking into account the channel qualities, the DF cooperation strategy, the interference induced to the primary system and the individual power budgets. The performance of the different approaches and the impact of the constraint values and deploying multiple antennas at users are discussed through the numerical simulation results.
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  • 37
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: Speech segmentation to covariance-stationary regions is of great interest in various fields of speech processing. This study presents a novel sequential segmentation algorithm relying on Random Matrix Theory (RMT). The proposed approach utilises an RMT-derived test statistic checking stationarity of sample covariance matrices. Utilising the statistical properties of the sample eigenvalues recently investigated in the RMT literature, a new expression for the decision threshold is derived in the non-asymptotic case where the number of samples is comparable with the dimension. This derivation is of great help to detect very short non-stationary intervals where the performance of most segmentation methods based on Autoregressive models degrades. Furthermore, based on the results of previous step, a new segmentation procedure is proposed. This procedure is applied to both synthetic and real-world speech data. Comparing the obtained simulation results with the stateof- the-art segmentation algorithms, the proposed approach has demonstrated good performance with extremely lower computational cost.
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  • 38
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: Increasing demand of high-speed data rate is leading to a challenging task to provide services to the users within exponentially growing market for wireless multimedia services. Subsequently, the available radio resources are becoming scarce because of different factors such as spectrum segmentation and dedicated frequency allocation to existing wireless standards. Exploring new techniques for enhancing the spectral efficiency in wireless communication has been an important research challenge. In this study, the enhancement of spectral efficiency of wireless communication systems is considered. A framework is proposed to implement the concept of compressive sampling (CS) for compressing the natural random signals. The performance of proposed framework is evaluated in the context of multiple input multiple output orthogonal frequency division multiplexing system. Simulation-based results show that 25% of resources can be saved by marginal trade-off with the quality of service (QoS) requirement applying CS to the natural random signals. Furthermore, it can be claimed that this QoS trade-off can be optimised with dynamic selection of random measurement matrices.
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  • 39
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: This study presents H ?? norm and mixed H2/H ?? norm optimal designs of digital synthesis filters of a hybrid filter bank. The problem for designing finite-impulse response (FIR) synthesis filters is cast as a H?? optimisation or mixed H 2 /H ?? optimisation problem by constructing a hybrid-induced error system. Both the problems can be solved using the theory of linear matrix inequalities such that FIR filters are directly obtained without truncation of infinite impulse responses. Two design examples are provided to illustrate the effectiveness of the proposed approaches.
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  • 40
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-09-28
    Description: In this work, the authors address the effect of spreading sequences and pulse waveforms on the performance of asynchronous direct-sequence ultra-wideband systems. Regarding spreading sequences, they consider the two cases of short and long sequences. The expression of the multi-user interference (MUI) variance is derived using long sequences at the output of a rake receiver, when propagating through multipath channels. The authors also propose the use of sequences generated with a family of spatiotemporal chaotic systems, namely piecewise coupled map lattices (PCML), as spreading sequences. Such sequences are shown to reduce the MUI variance with regard to independent identically distributed and Gold sets for both short and long sequences. Simulation results show that the use of long PCML codes in additive white Gaussian noise and multipath fading channels results in an improvement of the system average bit error rate, hence an increase of the system capacity in terms of number of active users.
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  • 41
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: A two-stage recursive least-squares identification method and a two-stage multi-innovation stochastic gradient method are derived for Box–Jenkins (BJ) systems. The key is to decompose a BJ system into two subsystems, one containing the parameters of the system model and the other containing the parameters of the noise model, and then to estimate the parameters of the system model and the noise model, respectively. The simulation examples indicate that the proposed algorithms can generate highly accurate parameter estimates and require small computational burden.
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  • 42
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: In this study, the authors focus on the state estimation of a non-linear system described by a Takagi–Sugeno multiple model submitted to unknown inputs and outputs. The proposed approach consists of a mathematical transformation which enables to consider the unknown outputs as unknown inputs that can be eliminated by a designed multiple observer. To evaluate the efficiency of the proposed approach, the convergence conditions of the state estimation error are formulated as linear matrix inequalities. Simulation examples are given to illustrate the proposed methods.
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  • 43
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: Spectrum sensing is a key component to realise the cognitive radio. The main requirements of spectrum sensing are the prediction of signal status in multiple frequency bands in a low signal-to-noise ratio (SNR) and decision reliability. This study proposes a novel multinode wideband sensing technique to predict the status of multiple frequency bands based on the integration of entropy and cyclic properties of received signals. It uses the uncertainty and auto-correlation properties of the deterministic signal and noise in the frequency domain for signal detection. To increase the decision reliability, cooperative sensing techniques are being used for spectrum sensing. Although cooperation among multiple cognitive users enhances the sensing performance, presence of few suspicious/malicious cognitive users severely degrade the decision reliability of the system. Hence, in this work, generalised extreme studentised deviate and adjusted box-plot methods are introduced to eliminate multiple malicious users in the cooperation. The proposed sensing method shows the best performance and is less severe to noise uncertainties compared to the traditional sensing methods in the literature. It enhances the sensing performance by 2.5 dB using five nodes in cooperation for same sensing parameters compared to other detection methods. It is a significant improvement for IEEE 802.22 systems that work under low SNR environment.
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  • 44
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: In this study, a novel technique that recovers the temporal structure of speech power spectrum is proposed. The histogram of average speech log power spectrum shows that the contamination of noise leads to the shift of noise peak, which in return degrades the performance of speech recognition systems. A two-step scheme is proposed to weaken the noise effects by first reducing the noise variance and then shifting the noise mean. The proposed algorithm consists of two parts, two-dimensional smoothing and controlled noise subtraction, which leads to the name SNS. The proposed algorithm manages to solve the speech probability distribution function discontinuity problem caused by traditional spectral subtraction series algorithms. In contrast to the clean speech estimation methods, the proposed algorithm does not need a prior speech/noise statistical model, which makes it simple but effective. The effectiveness of the proposed filter is tested using the AURORA2 database. Very promising results are obtained, 88.59% for noisy speech (average from signal-to-noise ratio 0–20 dB). Comparison is made against eight state-of-the-art speech recognition algorithms. Overall the proposed algorithm produces significant improvements over the comparison targets.
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  • 45
    Publication Date: 2013-10-02
    Description: In this study, an improved method based on evolutionary algorithms for denoising of satellite images is proposed. In this approach, the stochastic global optimisation techniques such as Cuckoo Search (CS) algorithm, artificial bee colony (ABC), and particle swarm optimisation (PSO) technique and their different variants are exploited for learning the parameters of adaptive thresholding function required for optimum performance. It was found that the CS algorithm and ABC algorithm-based denoising approach give better performance in terms of edge preservation index or edge keeping index (EPI or EKI) peak signal-to-noise ratio (PSNR) and signal-to-noise ratio (SNR) as compared to PSO-based denoising approach. The proposed technique has been tested on satellite images. The quantitative (EPI, PSNR and SNR) and visual (denoised images) results show superiority of the proposed technique over conventional and state-of-the-art image denoising techniques.
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  • 46
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: In order to meet the bandwidth need of modern wideband digital reconnaissance receiver, an implementation based on compressed sensing is proposed. The compressed sensing method is directly used to sample and reconstruct multi-band RF signal in this receiver. The original signal is mixed with Bernoulli random signal, and then filtered by low-pass filter. As completing the multiple narrow-band signals recovery within broadband range, the sampling signal is reconstructed in the digital domain. In this study, a novel reconstruction algorithm is proposed, which is adaptive conjugate gradient pursuit multiple measurement vectors (ACGPMMV), to overcome the drawback of orthogonal matching pursuit multiple measurement vectors (OMPMMV). Meanwhile, how to reduce the channel number of system required is also analysed, which will be reduce hardware costs. The shortcoming of limitation of sampling chip's analogue bandwidth in the parallel alternating sampling system is overcame, and the requirement of receiver bandwidth is achieved by using the lower rate sampling. In this study, the study is carried out by means of numerical simulations of multi-signals in the different system model. The conclusions illuminate the algorithm can get well-signal reconstruction results under the conditions of less channel and low sampling rate, and well-noise stability.
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  • 47
    Publication Date: 2013-10-02
    Description: In this study, a low-power and high performance architecture for finite impulse response digital filter based on the ring topology which is modelled from recurrent neural network is presented. The proposed structure is based on a ring topology reduced number of multipliers, adders and also CLK cycles. In the design, all the operators including multipliers and adders have been designed at gate level. Multiplication is a very important operation in many digital filters hence, the authors designed a novel and modified retiming serial multiplier. To increase the performance, the authors use two types of adders, a proposed high-speed logarithmic carry look ahead adder and a carry save adder with four inputs. The proposed structure is modelled and verified using FPGA and simulation results. It has been successfully synthesised and implemented with Xilinx ISE 7.1 and Virtex IV FPGA, target device Xc4vf100. The results demonstrate that the proposed method has high performance and low-power consumption.
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  • 48
    Publication Date: 2013-10-02
    Description: The dynamic behaviour of many systems can be approximated by a static non-linearity in series with a linear dynamic part. Systems with static input or output non-linearities are very common in many engineering applications. Such models are known as block-oriented models in the existing literature. The Hammerstein model is a special kind of block-oriented model, where a non-linear block is followed by a linear system. This study investigates the identification of Hammerstein systems with asymmetric two-segment piecewise-linear non-linearities. The basic idea is to employ a key-term separation technique and a corresponding auxiliary model initially. Then, the identification problem of non-linear system is changed into a nonlinear function optimisation problem over parameter space. Further, the estimates of all the parameters of the non-linear block, the linear subsystem and the noise part are obtained based on an improved particle swarm optimisation algorithm. Finally, simulation examples are included to demonstrate the effectiveness and robustness of the proposed identification scheme.
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  • 49
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: Having many benefits, phase-mode transformation technique is used frequently in beamforming with circular arrays. Owig to the fact that this transformation is frequency dependent, some techniques are used to make this transformation appropriate for broadband applications. When this technique is used with uniform circular arrays, its performance degrades because of the approximations applied to the formulations. In this study, the authors propose a new beamforming method not only robust against uncertainty in the steering vector of the desired signal, but also robust against errors caused by the phase-mode transformation. The authors assume that steering vector of the desired signal pertains to a ball set and ellipsoid sets are considered to cover the transformation matrix columns. The proposed beamforming method is based on semi-definite programming. The performance of the proposed beamforming method is compared with several other beamforming techniques by using a simulation study.
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  • 50
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: Prognostic utility of microvolt T-wave alternans (TWAs) has been established since its clinical acceptance as markers for malignant ventricular arrhythmias, leading to sudden cardiac death. Accurate detection of TWA from surface electrocardiography is a challenge because of invisible nature of the phenomenon. A novel TWA detection scheme based upon analysis of continuous-time wavelet entropy (CTWE) trend of consecutive ventricular repolarisation complexes is presented. The CTWE is computed using relative wavelet energy coefficients of continuous wavelet transform. Variety of simulated alternan waveforms, wavelet functions, frequency bands and noise levels are used to test the algorithm. The algorithm achieves a sensitivity of 100% at signal-to-noise ratio (SNR) 〉35 dB for all the selected wavelet functions and sensitivities of 99.5, 97 and 92% for Symlet4, Mexican Hat and truncated Morlet functions, respectively, at 30 dB SNR. A performance improvement of 5 dB is achieved by only computing the wavelet coefficients at the optimal frequency band. This study concludes that CTWE can successfully characterise the heterogeneity of cardiac repolarisation and detect TWA phenomenon.
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  • 51
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    Institution of Engineering and Technology (IET)
    Publication Date: 2013-10-02
    Description: In this study, the authors investigated some new inequalities on sparse representation for pairs of bases and frames, which would enrich the theory ensemble. First, for fixed pairs of bases, frames and the signal to be represented, we presented the bounds (which can be used in practice directly) of l 0 -norm of signal coefficients by the max/min cross-inner-products, as is of much importance to bases and frames selections in sparse representation. Also, the error bounds associated with the given min cross-inner-products are achieved. Moreover, the equivalence condition between l 0 solution and l 1 solution was achieved via relations of cross-inner-products, as can be applied directly for selection of optimal bases. Finally, the estimation of the parameters of cross-inner-products was shown.
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  • 52
    Publication Date: 2013-10-02
    Description: In this study, the authors present the research results on the robust investigate the robust l 2 –l ∞ filtering for Markovian jump linear systems with multiple sensor faults, uncertain probability transition matrix and time-varying delays. The multiple sensor faults are modelled as multiple independent Bernoulli processes with constant probabilities. The uncertain probability transition matrix is modelled via the polytopic uncertainties for each row in the transition matrix. By using the augmentation method, the filtering error system with stochastic variables is derived. Since of the stochastic variables, the traditional stability condition is not qualified for the analysis of the filtering error systems. Thus, the exponentially mean-square stability and the robust l 2 –l ∞ performance are adopted for the filtering error system. By choosing the Lyapunov-based method, sufficient conditions which can guarantee the exponentially mean-square stability and the robust l 2 –l ∞ performance are obtained in the forms of matrix inequalities. Based on these conditions, the filter design method is proposed and the estimator parameters can be obtained by solving a set of linear matrix inequalities. Finally, a numerical example with two modes is used to show the design procedure and the effectiveness of the proposed design approach.
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  • 53
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    Oxford University Press
    Publication Date: 2013-06-12
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 54
    Publication Date: 2013-06-12
    Description: Polysaccharides account for more than 90% of the content of fungal cell walls, but the mechanism underlying the formation of the architecture of the cell walls, which consist of microfibrils embedded in an amorphous wall matrix, remains unknown. We used electron microscopy to investigate ten different fungal cell-wall polysaccharides to determine whether they could self-assemble into the fibrillar or amorphous component of fungal cell walls in a test tube without enzymes. The ultrastructures formed by precipitating β-1,3-glucan and β-1,6-glucan are different depending on the existence of branching in the molecule. Linear β-1,3-glucan and linear β-1,6-glucan precipitate into a fibrillar ultrastructure. Branched β-1,6-glucan, mannan and glycogen precipitates are amorphous. Branched β-1,3-glucan forms a fibrillar plus amorphous ultrastructure. Self-assembly among combinations of different linear and branched cell-wall polysaccharides results in an ultrastructure that resembles that of a yeast cell wall, which suggests that self-assembly of polysaccharides may participate in the development of the three-dimensional architecture of the yeast cell wall.
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  • 55
    Publication Date: 2013-06-12
    Description: When considering drug delivery, the amount of drug that can be carried at a particular time and how the drug is incorporated efficiently into cells are important parameters. Transferrin (Tf)-conjugated nanocarriers have been used for the targeted delivery of drugs to cancer cells due to the availability of receptor-mediated clathrin-dependent endocytosis. In general, however, endocytosis seems to differ according to the size and shape of carriers. Large substances are generally internalized into cells by phagocytosis. We studied the internalization mechanism of Tf-conjugated nanoparticles (diameter, 522 nm). Tf-conjugated polystyrene particles were incorporated into cells by receptor-mediated endocytosis with large clathrin-coated vesicles even though their diameter was 〉500 nm and despite that fact that clathrin-coated vesicles have a diameter of 100 nm. This finding suggests that signals for internalization generated by stimulated Tf receptors (TfRs) activate clathrin-mediated endocytosis preferentially. Whether these larger particles could deliver drugs more efficiently than smaller particles was then examined. The toxicity of larger Tf-conjugated biodegradable nanoparticles (poly(lactic-co-glycolic acid)) encapsulating doxorubicin (diameter, 216 ± 38 nm) was appreciably dependent on the number of Tf molecules conjugated on a particle and the number of TfRs expressed on the cell membrane. Larger Tf-conjugated particles delivered drugs to cancer cells expressing many TfRs more selectively than their smaller counterparts (diameter, 56 ± 9 nm) if they were decorated with an appropriate number of Tf molecules.
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  • 56
    Publication Date: 2013-06-12
    Description: Structural biology relies on good-quality protein crystals in order for structure determination. Many factors affect the growth process of a protein crystal including the way it nucleates and the types of damage and contamination during its growth. Although the nucleation process and quality of a crystal is vital to structure determination, they are both under-studied areas of research. Our research begins to explore ways of measuring the quality of protein crystals, using TEM, thus overcoming the problems associated with viewing wet specimens in a vacuum. Our current understanding of nucleation is that it is a two-step mechanism involving the formation of nuclei from dense liquid clusters; however; it is still unclear whether nuclei first start as amorphous aggregates or as crystalline lattices. Potentially, electron diffraction may be capable of uncovering this process. Using TEM imaging and diffraction of lysozyme as a model protein crystal, we report the internal two-dimensional strain and the density of crystallites in a protein crystal, at a resolution never seen before. The TEM diffraction shows unique features of crystal mosaicity that can be directly correlated to TEM images.
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  • 57
    Publication Date: 2013-06-12
    Description: The cotyledon of legume seeds is a storage organ that provides nutrients for seed germination and seedling growth. The spatial and temporal control of the degradation processes within cotyledons has not been elucidated. Calcium oxalate (CaOx) crystals, a common calcium deposit in plants, have often been reported to be present in legume seeds. In this study, micro-computed tomography (micro-CT) was employed at the SPring-8 facility to examine the three-dimensional distribution of crystals inside cotyledons during seed maturation and germination of Lotus miyakojimae (previously Lotus japonicus accession Miyakojima MG-20). Using this technique, we could detect the outline of the embryo, void spaces in seeds and the cotyledon venation pattern. We found several sites that strongly inhibited X-ray transmission within the cotyledons. Light and polarizing microscopy confirmed that these areas corresponded to CaOx crystals. Three-dimensional observations of dry seeds indicated that the CaOx crystals in the L. miyakojimae cotyledons were distributed along lateral veins; however, their distribution was limited to the abaxial side of the procambium. The CaOx crystals appeared at stage II (seed-filling stage) of seed development, and their number increased in dry seeds. The number of crystals in cotyledons was high during germination, suggesting that CaOx crystals are not degraded for their calcium supply. Evidence for the conservation of CaOx crystals in cotyledons during the L. miyakojimae germination process was also supported by the biochemical measurement of oxalic acid levels.
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  • 58
    Publication Date: 2013-06-12
    Description: The electron irradiation damage of MFI-type zeolite was estimated under various accelerating voltages of 100, 200 and 300 kV from successively captured high-resolution transmission electron microscopy (HRTEM) images. To determine the optimal accelerating voltage for HRTEM imaging of electron-sensitive MFI zeolite, the critical dose was estimated from the disappearance of a specific fast Fourier transform spot calculated from experimental images. Based only on the electron dose, a higher voltage was more advantageous. However, taking into account the minimum dose for imaging with a CCD camera, the optimal accelerating voltage for imaging MFI zeolite was 200 kV. The minimum dose for image detection with a CCD camera was surmised from the output/input signal ratio dependence on the accelerating voltage and the contrast range in simulated HRTEM images.
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  • 59
    Publication Date: 2013-06-12
    Description: The magnetic field generated by a magnetic recording head is evaluated using electron holography. A magnetic recording head, which is connected to an electric current source, is set on the specimen holder of a transmission electron microscope. Reconstructed phase images of the region around the magnetic pole show the change in the magnetic field distribution corresponding to the electric current applied to the coil of the head. A simulation of the magnetic field, which is conducted using the finite element method, reveals good agreement with the experimental observations.
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  • 60
    Publication Date: 2013-06-12
    Description: A new multilayer-coated varied line-spaced grating, JS4000, was fabricated and tested for extending the upper limit of a grating X-ray spectrometer for electron microscopy. This grating was designed for 2–3.8 keV at a grazing incidence angle of 1.35°. It was revealed that this new multilayer structure enables us to take soft-X-ray emission spectra continuously from 1.5 to 4.3 keV at the same optical setting. The full-width at half maximum of Te-L α1,2 (3.8 keV) emission peak was 27 eV. This spectrometer was applied to indium tin oxide particles and clearly resolved Sn-L α (3444 eV) and In-L β1 (3487 eV) peaks, which could not be resolved by a widely used energy-dispersive X-ray spectrometer.
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  • 61
    facet.materialart.
    Unknown
    Oxford University Press
    Publication Date: 2013-04-02
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  • 62
    Publication Date: 2013-04-02
    Description: For development of advanced materials, characterization using a scanning transmission electron microscope (STEM) including analysis via X-ray energy-dispersive spectrometry and electron energy-loss spectrometry is essential. Recent advances in aberration-corrected instruments have offered large-scale data acquisition at a high resolution for limited acquisition times both in imaging and in analysis. Further advanced procedures are required to analyze such large-scale datasets more efficiently including quantification. In addition, more simplified tuning procedures are crucial to the best possible resolution in the latest aberration-corrected instruments. In this review article, several approaches to perform advanced electron microscopy, which the author has been developing with his colleague, are described as ‘Microscopy Hacks’. These are (i) quantification and elemental/chemical-imaging procedures, (ii) advanced statistical approaches to handle large-scale datasets and (iii) instrument characterization and tuning procedures including the latest development of an ad hoc autotuning procedure for aberration-corrected STEM imaging.
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  • 63
    Publication Date: 2013-04-02
    Description: The crystal structure of a new type of molybdenum oxide crystal encapsulated in a single-walled carbon nanotube (CNT) was examined via diffraction and spectroscopic techniques using both X-rays and electron beams. This new type of molybdenum oxide crystal has a chemical bonding state of MoO 3 , as confirmed by X-ray absorption spectroscopy, and the MoO 3 units exhibit axial symmetry, as clarified by electron diffraction from bundled and individual CNTs encapsulating the crystal. To obtain three-dimensional information on the structure, a cross-sectional sample was prepared using a conventional dimple and ion-mill method. High-resolution transmission electron microscopy images exhibit ring-like shapes that originated from the arrangement of the MoO 3 units inside the CNTs, as observed along the tube axis. The units are spaced 0.36 nm from each other in a ring arrangement and the distance between each ring is 0.391 nm.
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  • 64
    Publication Date: 2013-04-02
    Description: This review summarizes the recent advances in three-dimensional (3D) imaging techniques and their application to polymer nanostructures, for example, microphase-separated structures of block copolymers. We place particular emphasis on the method of transmission electron microtomography (electron tomography for short; hereafter abbreviated as ET). As a result of recent developments in ET, truly quantitative 3D images of polymer nanostructures can now be obtained with subnanometer resolution. The introduction of scanning optics in ET has made it possible to obtain large amounts of 3D data from micrometer-thick polymer specimens by using conventional electron microscopes at a relatively low accelerating voltage, 200 kV. Thus, ET covers structures over a wide range of thicknesses, from a few nanometers to several hundred nanometers, which corresponds to quite an important spatial range for hierarchical polymer nanostructures. ET provides clear 3D images and a wide range of new structural information that cannot be obtained using other methods. Information traditionally derived from conventional microscopy or scattering methods can be directly acquired from 3D volume data. ET is a versatile technique that is not restricted to only polymer applications; it can also be used as a powerful characterization tool in energy applications such as fuel cells.
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  • 65
    Publication Date: 2013-04-02
    Description: The performances of a newly developed 80–200 kV cold field emission gun (CFEG) transmission electron microscope (TEM) integrating a spherical aberration corrector for a TEM image-forming lens have been evaluated. To begin, we show that the stability of both emission and probe currents makes use of this new CFEG much friendlier. The energy spread of electrons emitted from the CFEG has been measured as a function of emission current and shows a very last 0.26 eV energy resolution at 200 kV and even 0.23 eV at 80 kV. The combination of the CFEG and the CEOS™ aberration corrector, associated with enhanced mechanical and electrical stabilities of this new microscope, allows reaching an information transfer below 75 pm at 200 and 80 pm at 80 kV. This unseen resolution at 200 kV has allowed us to study the structure of CoPt nanoparticles by observing direct images of their atomic arrangement along the high indexes zone axis. We have evidenced the presence of defects in these nanostructures that are not parallel to the electron beam. The precise stoichiometry of two iron oxides, FeO and Fe 2 O 3 , has been determined from an analysis of iron valence state that was obtained from a direct analysis of EELS fine structures spectrum of the two oxides.
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  • 66
    Publication Date: 2013-04-02
    Description: Data mining from noisy data/images is one of the most important themes in modern science and technology. Statistical image processing is a promising technique for analysing such data. Automation of particle pickup from noisy electron micrographs is essential, especially when improvement of the resolution of single particle analysis requires a huge number of particle images. For such a purpose, reference-based matching using primary three-dimensional (3D) model projections is mainly adopted. In the matching, however, the highest peaks of the correlation may not accurately indicate particles when the image is very noisy. In contrast, the density and the heights of the peaks should reflect the probability distribution of the particles. To statistically determine the particle positions from the peak distributions, we have developed a density-based peak search followed by a peak selection based on average peak height, using multi-reference alignment (MRA). Its extension, using multi-reference multiple alignment (MRMA), was found to enable particle pickup at higher accuracy even from extremely noisy images with a signal-to-noise ratio of 0.001. We refer to these new methods as stochastic pickup with MRA (MRA-StoPICK) or with MRMA (MRMA-StoPICK). MRMA-StoPICK has a higher pickup accuracy and furthermore, is almost independent of parameter settings. They were successfully applied to cryo-electron micrographs of Rice dwarf virus. Because current computational resources and parallel data processing environments allow somewhat CPU-intensive MRA-StoPICK and MRMA-StoPICK to be performed in a short period, these methods are expected to allow high-resolution analysis of the 3D structure of particles.
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  • 67
    Publication Date: 2013-04-02
    Description: The sensory nerve endings of the rat tongue, cheek and palate were studied using immunohistochemical staining and transmission electron microscopy analysis. The specimens were fixed in modified Karnovsky solution and embedded in Spurr resin. Substance P, calcitonin gene-related peptide (CGRP)- and protein gene product 9.5 (PGP b9.5)-containing nerve fibers in the rat tongue, cheek and palate were examined by electronic microscopical analysis and immunohistochemical localization. These fibers run very close to the basal lamina of the epithelium and extend into the filliform and fungiform papillae. Numerous plexiform fibers immunoreactive for substance P, CGRP and PGP 9.5 were found in the connective tissue of mucosa. Electron microscopic observations showed clearly immunostained nerve fibers, which are located very close to the basal lamina of epithelial cells. Some electron-dense granules may be observed in the axoplasms of both substance P and CGRP immunoreactive fibers. Several lamellar corpuscles into the subepithelial connective tissue papillae, Merkel corpuscles and numerous thin unmyelinated and myelinated axons were observed. The terminal axons revealed numerous mitochondria, neurofilaments, microtubules and clear vesicles in the base of axoplasmic protrusions. The lamellar cells showed caveolae and interlamelar spaces filled by amorphous substance. Between the lamellar cells and axoplasmic membrane, and in the adjacent lamellae region, desmosome-type junctions were observed. The quantitative and morphometric analysis showed nerve endings with an average area of 4.83 ± 3.4 μm 2 and 19.4 internal mitochondria in this site and the organized corpuscles with an average area of 79.24 ± 27.24 μm 2 and 24.23 internal mitochondria in this place. All the structures observed are involved in the transmission of pain and mechanoreceptors stimulus of these oral mucosae.
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  • 68
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: A simple process for nickel nanoimprint stamp replication is proposed. Based on this process, the replication of a 15 x 20 mm nickel nanoimprint stamp with 60 nm grating structures was carried out. First, the nanograting structures on the master silicon stamp were transferred to a polymer substrate using the hot embossing process; then, a layer of nickel was sputtered to fill the nanostructures on the substrate surface and form the seed layer for the electroforming process; finally, the back plane of the replica is electroformed. The observation results show good correlation between the dimensions of the master stamp??s features and the corresponding replicated features. The performance test result of the replicated stamp demonstrated that the mechanical strength of the replica is sufficient for the hot embossing process.
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  • 69
    Publication Date: 2013-04-03
    Description: The microstructure and geometrical dimensions of the scales on a butterfly Papilio peranthus Fabricius wing are obtained using scanning electron microscopy and transmission electron microscopy. Two kinds of scales are found in a butterfly wing and the structural colour mainly comes from the cover scale. Different structural models of cover scale that are related to ridge and concavity are constructed and their corresponding optical properties are investigated using the finite-difference time-domain method. It is concluded that the structural colour on the cover scale mainly comes from the sculpted multilayer structure and the ridge on the scale has few effects on the structural colour. When the curvature of the sculpted multilayer structure decreases, the dominant wavelength of colour will shift to a longer wavelength and move slower and slower. The two-dimensional planar multilayer model can be used to calculate the structural colour when the curvature exceeds a certain value.
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  • 70
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: Interdigitated microelectrodes (IDμE) are always used as the sensing structure of a biosensor to detect the hormone content in the human body. To increase the sensitivity of the ID??E biosensor, the authors provide an improved method that utilises IDμE with nanodot arrays, that is, the nanodot arrays are put into the inter-electrode gap in IDμE. The nanodot arrays can reduce the conducting distance between microelectrodes, thereby reducing the resistance to electricity and improve the sensitivity of biosensors. The improved biosensor is composed of ID??E and nanodot arrays: the IDμE is made by microelectro mechanical system (MEMS) technology, whereas the fabrication of nanodot arrays makes use of the nanosphere lithography (NSL) technology. Double Cr/Au bilayers are used to make a conjunction between the MEMS and NSL process. The biosensor based on the IDμE with nanodot arrays was used in the detection of low-level thyroid-stimulating hormone (TSH), and proved to provide about three times sensitive detection than the biosensor without nanodot arrays. The TSH detection limit of the biosensor based on the IDμE with nanodot arrays can reach 0.005 mIU/l. The improved biosensors can be used in the detection of other hormones, which are critical for disease intervention strategies.
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  • 71
    Publication Date: 2013-04-03
    Description: The nanofabrication of nanometre-scale multiple-level structures by nanoimprint lithography and CF 4 /O 2 etching rates was investigated for nanoelectro mechanical systems and three-dimensional (3D) wafer-level packaging. A TiO 2 ??SiO 2 sol-gel photocurable material with high titanium concentration of 20.9 wt% was developed for CF 4 /O 2 etch selectivity with a pattern transferring carbon layer in a bi-layer process. The nanostructures of 3D micropatterns, holes with 200 nm diameter and 130 nm-wide dense lines with line edge roughness of ~10 nm were provided. The CF 4 /O 2 etching rate of the TiO 2 -SiO 2 photocurable material was ~3.7 times lower than that of the referenced SiO 2 sol??gel photocurable material. The CF 4 /O 2 etch rates of titanium-based photocurable materials were confirmed for deep plasma etching processes.
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  • 72
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: A report is presented on the preparation of surface-functionalised nanosilica from silicon tetrachloride (SiCl 4 , one of the major by-products in the polycrystalline silicon industry) by in-situ surface modification in aqueous solution. The approach uses both SiCl 4 and sodium metasilicate as the silicon sources to generate nanosilica, whereas the proportion of sodium metasilicate and SiCl 4 is adjusted to control the pH value of the reaction system. In this way, desired SiO 2 nanoparticles were in-situ surface-modified by hexamethyldisilazane as soon as they were generated in the reaction solution, which makes it feasible to prevent the severe aggregation of nanosilica that often happens during the hydrolytic process. The obtained nanosilica with uniform particle size distribution (mean diameter 35??40 nm) shows superhydrophobicity (a water contact angle of 165°) and excellent organic dispersibility. Thanks to the low cost of raw materials as well as the superhydrophobicity and lipophilicity of as-prepared nanosilica, its application for improving the selective penetration of oil is primarily investigated. The result shows that quartz sand modified by as-prepared nanosilica can separate diesel oil from water successfully, which could be significant for improving crude oil recovery efficiency.
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  • 73
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: Biomaterials is a term used to indicate materials that constitute parts of medical implants, extracorporeal devices, and disposables that have been utilised in medicine, surgery, dentistry and veterinary medicine as well as in every aspect of patient health care. Ceramics biomaterials are used as components of hip implants, dental implants, middle ear implants and heart valves. Porous or particulate calcium phosphate ceramic materials such as tricalcium phosphate (TCP) have proved successful for resorbable hard tissue replacements when low loads are applied to the material. The aim of the present work was to evaluate the biological characteristics of the biomaterial developed. Interactions of TCP with polyacrylate polymers in aqueous dispersions were characterised using X-ray diffraction, Fourier transform infrared spectroscopy, pH determination and viscosity measurements.
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  • 74
    Publication Date: 2013-04-03
    Description: Fe 3 O 4 ??ZnWO 4 composite microspheres with magnetically recyclable photocatalytic performance have been firstly synthesised by a simple refluxing method under mild conditions. The as-prepared Fe 3 O 4 ??ZnWO 4 composites show good photocatalytic efficiency in degradation of rhodamine B under UV light irradiation and can be recycled five times by magnetic separation without major loss of activity, the magnetic property of Fe 3 O 4 ??ZnWO 4 sample has been studied also. Microspheres show potential use on dye degradation from the solution considering their magnetic recovery properties.
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  • 75
    Publication Date: 2013-04-03
    Description: Compact equivalent circuit models for single-walled carbon nanotube (SWCNT) bundles are described, and the performance of SWCNT bundle interconnects is evaluated and compared with traditional Cu interconnects at different interconnect levels for through-siliconvia- based three-dimensional integration. It is shown that at local level, carbon nanotube bundle interconnects exhibit lower signal delay and smaller optimal wire size. At intermediate and global levels, delay improvement becomes more significant with technology scaling and increasing wire lengths. For 1 mm intermediate and 10 mm global level interconnects, the delay of SWCNT bundles can reach 45.49 and 51.84% of that of Cu wires, respectively.
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  • 76
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: Thiyoglycolic acid-capped CdSe nanoparticles have been synthesised at 273-279 K. A comparative study on the structural and optical characteristics of the as-synthesised and annealed samples is done using state-of-the art instruments and software. Based on these studies here the authors report a colossal change in crystallinity, particle size and red shift in the absorption spectra upon annealing. Lattice strain is also found to increase by 18.77% upon annealing. Excitation wavelength-dependent photoluminescence with giant Stokes shift and narrow full-width at half-maxima of both the samples is also reported, which may be useful for device application.
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  • 77
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: Variation of on-body millimetre-wave propagation channels with body movements has been studied experimentally. A statistical description of the propagation channel is presented, including path-loss probability distributions, level-crossing rates and average fade durations. The median path losses for the considered practical links with omnidirectional monopole antennas lied within the range of 55??88 dB. The signal variation was found to consist of two superimposed variations, in general: the long-term and short-term fadings, but was dominated by the much stronger long-term fading. The use of a simple two-state Markov process model to describe on-body communication links is also proposed and its limitations are discussed.
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  • 78
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: In this reported work, a microfluidic-based fluid electrokinetic force has been used for surface plasmon resonance or surface plasmon resonance image (SPRI) detection. In this device, a modified rectangular microarray of Au instead of previous reported square or circular gold segments was designed and microfabricated with gold segment geometries and characterised by surface morphology studies. A voltage drop of maximal 400 V/cm was applied without gold erosion to drive fluorescein isothiocyanate isomer I in a high-conductivity medium on the bare gold surface layer, enabling SPRI detection.
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  • 79
    Publication Date: 2013-04-03
    Description: The authors discuss a recently proposed analytical method for calculation of equivalent width of substrate integrated waveguide. Modifications are made to calculate the final analytical formula more accurately.
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  • 80
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: A report is presented on a new multi-mode nanofabrication method that uses a compliant conductive atomic force microscope (AFM) probe for both AFM and scanning tunnelling microscope (STM) operation and it is demonstrated that these modes can be switched 'on-the-fly' during the measurement or fabrication of nanostructures. The authors oxidised Ti with the same conductive AFM probe in AFM and STM modes, alternately in a continuous writing step. An in-plane Ti??TiO x ??Ti junction was fabricated by combining AFM and STM modes and electrically characterised by taking current images in conductive AFM mode. After measurement, additional features were written to increase the electrical isolation, thus realising in situ nanoscale modification.
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  • 81
    Publication Date: 2013-04-03
    Description: In this study, the authors propose four algorithms for directions of arrival (DoAs) estimation of multiple incoming narrowband plane waves onto electronically steerable parasitic array radiator antennas. The constraints on the proposed algorithms are the same as those imposed onto the classic subspace methods allowing superior high-resolution and localisation capabilities even for correlated sources scenarios but with more reduced computations load and processing time than existing schemes. We also demonstrate that estimating the propagator operator through both introduced real-valued orthogonal decompositions techniques not only yields to a faster DoAs estimation with a reduced computational complexity, but also it improves the robustness of the developed algorithms to noise as compared with the classic propagator algorithm. The Cram??r??Rao bound on the variance of the estimated DoAs by the proposed algorithms is analysed. The achieved performance by the developed methods is studied and compared with conventional antenna arrays. The simulation results confirm that high-resolution DoAs estimation can be achieved with the developed algorithms and prove the validity of the proposed approach.
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  • 82
    Publication Date: 2013-04-03
    Description: In this study, a novel method for designing a new monopole antenna with dual band-notched characteristic for UWB applications has been presented. The proposed antenna consists of a square radiating patch with a modified T-shaped slot, and a ground plane with two E-shaped slots and a W-shaped conductor backed-plane. By cutting two E-shaped slots in the ground plane, additional resonance is excited and hence much wider impedance bandwidth can be produced, especially at the higher band, which results in a wide usable fractional bandwidth of more than 130% (2.73??13.3 GHz). In order to generate single band-notched characteristic, the authors use a W-shaped conductor backed-plane structure on the other side of the substrate. In addition, by cutting a modified T-shaped slot in the radiating patch and microstrip feed-line, a dual band-notched function is achieved. The measured results reveal that the presented dual notch band monopole antenna offers a very wide bandwidth with two notched bands, covering all the 5.2/5.8 GHz wireless local area network, 3.5/5.5 GHz WiMAX and 4 GHz C bands. The designed antenna has a small size of 12 ?? 18 mm 2 . Good voltage standing wave ratio (VSWR) and radiation pattern characteristics are obtained in the frequency band of interest. Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for ultra-wideband (UWB) applications.
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  • 83
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: The design of a planar four-port microstrip crossover is presented. The design starts by using a half-wavelength square patch and two sets of orthogonal feeding lines. Based on the cavity theory, operation of the patch crossover is analysed. Full-wave simulations and measurements are used to support the analysis. By etching the patch as a Sierpinski carpet, resonant frequency can be lowered significantly, and this property can be employed to reduce the size of the conventional patch crossover. It is shown that the size of the crossover can be reduced by 23% with even a better performance when a second-order Sierpinski carpet microstrip patch is used. Full-wave simulations and measurements are used to validate the proposed design method. The measured data show less than 1 dB insertion loss, more than 10 dB return loss, more than 17 dB isolation and about 0.1 ns group delay deviation across 10% fractional bandwidth centred at 2.4 GHz.
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  • 84
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: A multi-implant scenario is considered using insulated dipole antennas for specific locations such as the liver, heart, spleen and the kidneys where implants communicate with a pacemaker acting as a central hub. Wireless communication within human body experiences loss in the form of attenuation and absorption, and to identify these losses, the path loss is studied in this paper for an adult and child heterogeneous human model. Link performance is calculated to investigate the applicability of in-body communication. The specific absorption rate for all these locations is also studied to verify compliance with international safety guidelines.
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  • 85
    Publication Date: 2013-04-02
    Description: The F-actin cytoskeleton of Cryptococcus neoformans is known to comprise actin cables, cortical patches and cytokinetic ring. Here, we describe a new F-actin structure in fungi, a perinuclear F-actin collar ring around the cell nucleus, by fluorescent microscopic imaging of rhodamine phalloidin-stained F-actin. Perinuclear F-actin rings form in Cryptococcus neoformans treated with the microtubule inhibitor Nocodazole or with the drug solvent dimethyl sulfoxide (DMSO) or grown in yeast extract peptone dextrose (YEPD) medium, but they are absent in cells treated with Latrunculin A. Perinuclear F-actin rings may function as ‘funicular cabin’ for the cell nucleus, and actin cables as intracellular ‘funicular’ suspending nucleus in the central position in the cell and moving nucleus along the polarity axis along actin cables.
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  • 86
    Publication Date: 2013-04-02
    Description: To evaluate the advantages of combination of two advanced electron microscopic technologies such as serial block-face scanning electron microscopy and double-axis electron beam tomography, we analyzed the three-dimensional morphology of cellular relationships between dendritic and plasma cells in the synovial membrane from patients with rheumatoid arthritis, using the combined approach.
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  • 87
    Publication Date: 2013-04-02
    Description: The low-energy Ar-ion milling method was used to prepare ultrathin specimens for transmission electron microscope observation. The samples were thinned initially by a usual focused ion beam technique or typical Ar-ion milling with a high energy of 2–10 keV and were thinned additionally by an Ar-ion beam with an energy less than 1 keV, typically 500–900 eV. This low-energy ion beam was scanned over the specimen, and secondary electrons induced by the ion beam could be detected to form secondary electron images with a resolution of a few micrometre. Because a desired area can be selected and thinned by the low-energy ion beam, redeposition or cross contamination from irradiation of a metal grid that supports the sample can be prevented. It was shown that the low-energy Ar-ion beam thins a surface amorphous damage layer preferentially and effectively rather than a crystal specimen. Images from ultrathin specimens of two different materials revealed a detailed structure.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 88
    Publication Date: 2013-04-03
    Description: The hexagonal rotor-like cerium carbonate hydroxide (CeCeO 3 OH) and CeCeO 2 nanostructures were successfully synthesised via a facile hydrothermal method using Ce(NO 3 ) 3 ?? 6HCeO 2 O as the cerium resource, HNOCeO 3 additive to form an acidic solution, CO(NHCeO 2 ) 2 as both precipitator and carbon source and polyvinylpyrrolidone as surfactant. Characterisation techniques using an X-ray diffractometer, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, thermogravimetric differential thermal analysis apparatus and UV??vis absorption spectrum have been used for studying the roles of Ce(NO 3 ) 3 ?? 6H 2 O and HNO 3 . It was found that the amount of Ce(NOCeO 3 ) 3 ?? 6H 2 O has an obvious effect on the morphology of the as-synthesised CeCO 3 OH and CeO 2 nanostructures, whereas HNO 3 has a significant influence on the crystalline phase. CeOCeO 2 has a higher UV absorption than as-synthesised CeCOCeO 3 OH, which is likely associated with the charge-transition between Ce3 + and Ce4 + .
    Electronic ISSN: 1750-0443
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 89
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: The electrocatalytic performance of commercial PtRu/C is significantly enhanced by directly mixing a few SnO 2 nanoparticles. The composite catalysts show enhanced CO oxidation, higher activity and better stability than commercial PtRu/C. Among the different ratios of SnO 2 nanoparticles (10??40%), the SnO 2 ??PtRu/C (20%) composite catalyst shows the best catalytic activity for methanol oxidation. The effect of temperature on methanol oxidation was also investigated and the apparent activation energy (E a ) value of catalyst was obtained. The results here suggest a simple route to enhance the catalytic efficiency for commercial PtRu/C catalyst.
    Electronic ISSN: 1750-0443
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 90
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: Different shapes of silicon (Si) nanotip arrays using reactive ion etching with various mask patterns were fabricated, and the surface profile, surface roughness and quantitative etch characteristics of the Si nanotip were characterised. It was found that the geometry as well as etch characteristics of Si nanotip arrays could be modified by changing the initial mask patterns. Pyramidal and conical shaped Si nanotips could be obtained from square and circular mask patterns, respectively. The alternate square array pattern resulted in a Si nanotip with a wavy array whereas the honeycomb mask pattern resulted in a Si nanotip in a hexagonal array. In terms of etch rate, the circular pattern mask showed faster etching than the square patterns. Also, the parallel pattern showed faster etching than the alternate pattern under the same conditions. The tip size and height of Si nanotip structures determined by atomic force microscopy measurement were in the range of 50??80 and 450??750 nm, respectively.
    Electronic ISSN: 1750-0443
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 91
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: The quartz double-ended tuning fork (DETF) resonator is well known to be sensitive to longitudinal force and is widely used as the sensing element in modern accelerometer, force and pressure sensors. The quartz DETF resonator works in-plane, with anti-phase flexural mode vibration, which is driven into oscillation by internal strains created by AC voltages applied to electrode patterns on the beams. The DETF vibration modes and vibration characteristics are determined by the electrode pattern and its electromechanical coupling efficiency. Presented are three kinds of electrode patterns for different applications, and the effect of electrode patterns on the vibration performances are investigated experimentally. With the fundamental frequency at 65 KHz, the DETF resonator is designed and fabricated using the wet etching-based quartz MEMS technique. The vibration characteristics including Q-value, and equivalent parameters, are evaluated using a 4294 A impedance analyser. Experimental results demonstrated that the vibration characteristics of quartz DETFs are affected by the electrode patterns including pattern location and widths. These results are expected to be useful for designing quartz DETF based devices.
    Electronic ISSN: 1750-0443
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 92
    Publication Date: 2013-04-03
    Description: In this study, a compact ultra-wideband (UWB) two-layer printed microstrip line monopole-slot antenna with triple band-rejection characteristics is investigated. The proposed antenna consists of a planar UWB monopole-slot antenna with a size of 40 ?? 47 ?? 1.016 mm 3 and a modified half-mode substrate-integrated waveguide (M-HMSIW) cavity with folded defected ground structure slot. The antenna is fabricated using two-layer printed circuit board process. To generate bandnotched characteristics, M-HMSIW cavity in the bottom layer of the antenna are utilised. By tuning the dimension of MHMSIW, triple notched bands with sharp rejection can be achieved at WiMAX band (3.3??3.69 GHz), along with a major part of the C-band (3.7??4.2 GHz), lower wireless local area network (WLAN) band (5.15??5.35 GHz), and upper WLAN band (5.725??5.825 GHz). The simulated and measured impedance matching, radiation patterns and gain results of antenna are investigated. The results of the fabricated antenna show that this antenna is a good candidate for various UWB applications.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 93
    Publication Date: 2013-04-03
    Description: This study presents the findings of an empirical channel characterisation for an ultra-wideband off-body optic fibre-fed multiple-antenna array within an office and corridor environment. The results show that for received power experiments, the office and corridor were best modelled by lognormal and Rician distributions, respectively [for both line of sight (LOS) and non-LOS (NLOS) scenarios]. In the office, LOS measurements for t mean and t RMS were both described by the Normal distribution for all channels, whereas NLOS measurements for tmean and t RMS were Nakagami and Weibull distributed, respectively. For the corridor measurements, LOS for tmean and t RMS were either Nakagami or normally distributed for all channels, with NLOS measurements for t mean and t RMS being Nakagami and normally distributed, respectively. This work also shows that achievable diversity gain was influenced by both mutual coupling and cross-correlation co-efficients. Although the best diversity gains were 1.8 dB for three-channel selective diversity combining, the authors present recommendations for improving these results.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 94
    Publication Date: 2013-04-03
    Description: In this study, the efficient full-wave analysis of passive devices composed of circular and arbitrarily-shaped waveguides is considered. For this purpose, the well-known boundary integral-resonant mode expansion (BI??RME) method has been properly extended. Circular waveguides are used for resonant mode expansion, whereas the arbitrary contour is defined by any combination of straight, circular and elliptical segments, thus allowing the exact representation of the most widely used geometries. The proposed algorithm extends previous implementations of the BI??RME method based on circular waveguides by considering circular and elliptical arcs for defining arbitrary geometries. Similarly, it allows the efficient analysis of passive devices based on circular waveguides with arbitrary perturbations, thus providing more accurate results with less computational efforts than a rectangular waveguide-based BI??RME approach. The extended method has been successfully tested with several practical application examples, having compared its performance with the BI??RME method based on rectangular waveguides.
    Print ISSN: 1751-8725
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  • 95
    facet.materialart.
    Unknown
    Institution of Engineering and Technology (IET)
    Publication Date: 2013-04-03
    Description: The design and analysis of a decade bandwidth 3 dB 180° hybrid coupler using tandem connection of two similar wideband 8.34 dB hybrids is presented. The designed coupler has return loss better than 12 dB over a decade bandwidth, insertion loss below 6 dB, amplitude balance within ?? 1 dB, phase balance of ?? 20° and isolation above 18 dB. Gap and overlap ground patterns at the junction of the tightly coupled to uncoupled region are introduced to improve isolation by preventing odd-mode field coupling and preserving equal even- and odd-mode phase velocities across the junction.
    Print ISSN: 1751-8725
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  • 96
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    Unknown
    Oxford University Press
    Publication Date: 2013-04-02
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 97
    facet.materialart.
    Unknown
    Oxford University Press
    Publication Date: 2013-04-02
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 98
    Publication Date: 2013-09-25
    Description: Stability and dispersion analysis of higher-order three-step locally one-dimensional (LOD) finite-difference timedomain (FDTD) method is presented here. This method uses higher order cell-centred finite-difference approximation for the spatial differential operator and second-order finite difference approximation for the time differential operator. Unconditional stability of the higher-order three-step LOD-FDTD method is analytically proven and numerically verified. Numerical results show improvement in the overall performance of higher-order three-step LOD-FDTD method compared with that of second order. Also, the effects of the order of approximation, the time step and the mesh size on numerical dispersion are explained through analytical results and verified by simulation results.
    Print ISSN: 1751-8725
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  • 99
    Publication Date: 2013-09-25
    Description: A new physical-mathematical model for predicting first-order rain attenuation statistics for slant-path links is presented in this study. It is assumed that point rain rate and slant-path rain attenuation follow the inverse Gaussian (IG) distribution. The statistical parameters of the IG distribution of the induced rain attenuation on a slant path are calculated in terms of the rain rate statistical parameters by adopting a spatial inhomogeneity model for specific rain attenuation. The method is validated using experimental data taken from Database of Study Group 3 (radiowave propagation) of International Telecommunication Union-Radio (ITU-R), hereafter named DBSG3 and with simulated rain attenuation data using the Synthetic Storm Technique on recent rain rate measurements in Athens, Greece. Its performance is also compared to the ITU-R P. 618-10 model. The proposed model shows better performance comparing to the ITU-R model and the results are very encouraging.
    Print ISSN: 1751-8725
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  • 100
    Publication Date: 2013-09-25
    Description: An innovative strategy for the robust design of linear antenna arrays is presented. Being the array elements characterised by tolerance errors, the synthesis is aimed at determining the intervals of values fitting the user-defined mask constraints on the radiated power pattern. With reference to the upper and lower bounds of the power pattern analytically determined for given tolerances through interval analysis, the nominal excitations of the array elements are then optimised by means of a global stochastic optimiser suitably customised to deal with interval numbers. A set of numerical examples is reported to show the behaviour of the proposed method as well as to assess its potentials in dealing with the robust synthesis of pencil and shaped beams.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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