Based on the method of stationary-phase and the mathematic techniques, analytical expressions for the TE and TM terms of an apertured circular flattened Gaussian beam (CFGB) in the far-field have been derived without any approximation, which allows one to calculate the energy flux distributions of the TE term, the TM term, and the apertured CFGB. The analytical formulae of the power of the TE term, the TM term, and the apertured CFGB are also presented. The vectorial structural properties of the far-field of an apertured CFGB are demonstrated. The influences of the f-parameter, the truncation parameter, and the parameter N on the energy flux distributions of the TE term, the TM term, and the apertured CFGB are examined. Also, the effects of the f-parameter, the truncation parameter, and the parameter N on the ratios of the power of the TE and TM terms to the power of the apertured CFGB are investigated.

Acoustic external cloak is an important device, which can cloak an object without encircling it but allows the object to exchange information with the outer region. By choosing appropriate spatial transformation, we design a cylindrical acoustic external cloak with only spatially varying bulk modulus in this paper. The general expressions of material parameters are derived, and then the performance of the external cloak is simulated based on full-wave simulations. The advantage of the cloak is that mass density elements are constants, and only bulk modulus is a function of radius, which make it easier to realize in practice. Besides, the effects of perturbations of parameters on the performance of the cloak are also investigated. This work provides a feasible way for the fabrication of the metamaterial-assisted acoustic external cloak.

This paper proposes a semi-analytical model for Pulsed Eddy Current Non-Destructive Evaluation (PEC-NDE) based on the Coupled Electromagnetic Quantities Method (CEQM). The proposed formulation is developed from coupled electric circuit’s approach in which the Crank Nicholson formula is used to derive the transient behavior. The computational model makes use of current excitation allowing the determination of the sensor voltage in the case of an axisymmetric device. The feature of the variation of voltage provides information on the electromagnetic and geometrical properties of the device. So, the second peak of voltage variation (SPVV) and second ratio between the minimum and maximum (RMM2) are used to determine these properties. The proposed model is validated by comparison with Fourier reconstitution obtained from measurements on one hand and with finite element calculations on the other hand. The developed model, associated to an inversion technique, is applied to evaluate the lift-off and the work piece thickness.

A diamond-containing material (DCM) produced by detonation was mechanically milled using KM-1 and AGO-2S mills. Experimental spectra for infrared (IR) absorption, Raman scattering and X-ray diffraction patterns (XRD) were obtained for the treated DCM samples. We compared the Raman and IR spectra for the KM-1 milled samples and concluded that the surface of the DCM particles was not uniform. The mechanical force that resulted from milling with the AGO-2S destroyed the non-diamond part of the particles and initiated irreversible physical and chemical changes in them. The destruction of the diamond grains was the consequence of these irreversible changes. It follows from the experiments that the dipole momentum of the DCM particle was caused by the presence of polar fragments of molecules. The constant dipole momentum of the particles facilitated the aggregation. Based on this, we proposed a model of a structurally inhomogeneous DCM particle.

To exploit the potential application of the conductive polymers in incorporating with carbon-based materials, polypyrrole (PPY) nanotube and polyaniline (PANI) nanofiber were synthesized and the electrochemical properties were compared. The morphology, texture and chemical structure of PPY and PANI were tested employing SEM, TEM, FTIR and XPS. The results of electrochemical tests demonstrate that the specific capacitance of PPY nanotube is as high as 463 F/g at a current density of 0.3 A/g, much higher than that of PANI nanofiber (243 F/g). Furthermore, at a current density of 0.8 A/g, the capacitance of PPY nanotube is 172 F/g, higher than that of PANI nanofiber (104 F/g). Additionally, after the long-term charge-discharge test at a current density of 1.5 A/g, the preserved capacitance of PPY nanotube is still higher than that of PANI nanofiber (106.5 F/g vs. 75 F/g). The EIS measurement illustrates that the PPY nanotube shows lower contact interface resistance and shorter ion diffusion path than the PANI nanofiber. It suggests that the PPY nanotube is a promising material to be applied in supercapacitor rather than the PANI nanofiber, because of its extended internal cavity surface area and pore volume.

The miniaturization of devices and the increase of operating frequencies are two important issues for communication system development. This requires a high degree of integration, higher performance and lower cost. Isolator is an important non-reciprocal passive component for source protection. In most cases, the non-reciprocal effect is based on field displacement phenomenon induced by a magnetized ferrite material. In this paper we propose a new design of a coplanar isolator based on field displacement, composed of a non-symmetrical coplanar transmission line, made from a ferrite layer and ground plane below. Simulations were performed using HFSS software. Measurements were made on a first 1000 μm-thick YIG film sample giving 1 dB of insertion losses and 17 dB isolation and on a second sample made from a 150 μm-thick YIG ferrite sample giving an insertion loss lower than 2 dB. Interesting applications of this isolator structure are considered.

The transmission properties of a resonator based on one air layer sandwiched by two-layered anisotropic metamaterials with different negative-permittivity tensors are studied through analytical analysis and numerical calculations. The resonator has orthogonally polarized dual wavelength output. The difference of the two wavelengths can be adjusted through changing the permittivity tensors, and the ratio of the intensities of the two orthogonally polarized waves can also be adjusted through changing the polarization direction of incident wave. The study results may find applications in the design of laser resonator.

Off-congruent Li-deficient MgO:LiNbO3 crystals were prepared by carrying out post-grown Li-poor vapor transport equilibration (VTE) treatments on a number of 0.47 mm thick MgO (5 mol% in growth melt or 6 mol% in crystal)-doped, initially congruent LiNbO3 plates at 1100 °C over different durations ranged in 40–395 h. At first, the VTE-induced Li composition reduction was measured as a function of the VTE duration using the gravimetric method. Then, optical absorption spectroscopy was applied to study the crystal composition effects on the fundamental optical absorption edge and OH absorption characteristic parameters including the peaking position, band width, peaking absorption and band area. These crystal composition effects enable one to establish the optical methods used for determination of the crystal composition from the spectroscopic measurements. These optical methods overcome the demerit that the gravimetric method is limited to a specific VTE temperature or crystal thickness, and can be applied to design and produce an MgO-doped crystal with desired Li composition.

The efficiency of acousto-optic interaction in single-mode strip silica waveguide is analyzed theoretically by determining the overlap integral between the optical and acoustic field distributions. The results show that there is a good overlap of the optical and SAW fields in the low SAW frequency range. At high acoustic frequencies, the overlap integral decreases with increasing acoustic frequency. At 216 MHz, the maximum of 0.8544 for the overlap integral is obtained, provided the H/Λ equals 0.02. At last, the diffraction efficiencies for acoustic frequency of 216 MHz are calculated as a function of the square root of acoustic power for different acoustic apertures.

Dielectric barrier discharges (DBDs) are commonly used for gas effluent cleanup and ozone generation. For these applications, the energy efficiency of the discharge is a major concern. This paper reports on investigations carried out on the voltage shape applied to DBD reactor electrodes, aiming to evaluate a possible energy efficiency improvement for ozone production. Two DBD reactor geometries were used: pin-to-pin and cylinder-to-cylinder, both driven either by a bi-directional power supply (voltage rise rate 1 kV/μs) or by a pulsed power supply (voltage rise rate 1 kV/ns). Ozone formed in dry air was measured at the reactor outlet. Special attention was paid to discharge input power evaluation using different methods including instantaneous current-voltage product and transferred charge-applied voltage figures. The charge transferred by the discharges was also correlated to the ozone production. It is shown that, in the case of the DBD reactors under investigation, the applied voltage shape has no influence on the ozone production efficiency. For the considered voltage rise rate, the charge deposit on the dielectric inserted inside the discharge gap is the important factor (as opposed to the voltage shape) governing the efficiency of the discharge – it does this by tailoring the duration of the current peak into the tens of nanosecond range.

This paper deals with the calculation of eddy current in a copper cylinder. This cylinder rotates in an applied static magnetic field. The electromagnetic problem is solved in two-dimension by considering transient motion. Two methods for eddy current computation are compared: stochastic method and classical finite element method. The main goal of this paper is to compare these methods.

We investigate the vibration properties of adsorbed nanostructure on the infinite square crystalline surface. The surface is considered as an infinite slab of one atomic layer, and the nanostructure as an isolated diatomic molecule chain on the surface of a cubic lattice which is parallel to y-axis, and takes three different positions: top, hollow and bridge. The vibrational dynamics of the structure is considered within the harmonic approximation framework. The evanescent and propagating vibrational field of the perfect lattice is determined and discussed. The presence of the molecule chain breaks down the translation symmetry in one direction and gives rise to localized states on its neighborhood. The mathematical framework of the matching method is used to analyze the localization phenomena at the nanostructure boundaries. Typical dispersion curves for modes of energies along the inhomogeneity are given with their polarizations. The fine structure of the spectrum and its origins are clearly identifiable, which gives a new insight into the localization problem. Furthermore, the existence and nature of the localized phonons like modes associated with an isolated defect are derived, and the importance of the contribution of these modes to the spectral and states densities is exhibited clearly.

In this study, we reported a plasma method to generate the cold pulsed glow discharge for large-area surface modifications of various polymers, such as polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polytetrafluoroethylene (PTFE). The cold plasmas consisting of pulsed and glow-like breakdowns with peak widths of several microseconds may efficiently prevent the heat-sensitive materials from being damaged and greatly improve the surface properties of treated polymers. Analysis indicates that discharge parameters, such as the discharge pressure and gas compositions, may significantly influence the density of radicals or ions generated near the polymer surface, and their energy, which in turn determine the surface properties of treated polymers, such as surface chemical compositions and hydrophobicity. The reaction processes of activated species, such as radicals and energetic ions at the surfaces of treated polymers, are discussed based on the obtained experimental results. Compared to many other plasma techniques formed at high pressure or with a long discharge distance, the low-pressure plasmas generated through small gas spacing from this design may result in the efficient and frequent collisions between the polymer surface and activated species, thus demonstrating an efficient usage of electric energy and feed gas.

The design and construction of an instrumentation for NOX degradation in a dielectric-barrier discharge reactor (DBDR) is presented. This is endowed with a parallel plane electrode glass-glass (GG) circular geometry configuration. A solid-state multi-cellular power supply was produced in order to generate the plasma discharge. The power supply is based on a full-bridge voltage inverter commanded by three 4.33 kHz square-wave signals. Thus, the output converter signal is filtered by a resonant LC circuit, providing a 13 kHz sine wave to the DBDR. Initial results showing high removal efficiencies of about 97% have been obtained by means of this instrumentation.

The aim of this work is to propose a simple multi-physics model in order to predict the evolution of the thermodynamic variables during the combustion of kerosene vapors in each compartment of a closed vessel. A special attention is paid to the mechanical effects of combustion, e.g., the pressure evolution. The basic characteristics of the model have been developed as part of a Computational Fluid Dynamics (CFD) approach, in order to represent both the ignition stage and the flame propagation in the reactive mixture. The proposed development is validated in a single compartment vessel by investigations about the equivalence ratio and the reaction dynamics (final pressure, combustion duration, etc.). Moreover, the expected phenomenology is correctly reproduced for tanks composed of several compartments, such as, for instance, a faster combustion process in the presence of internal orifices. The impact of the ignition on the subsequent evolution of the explosion is also investigated, highlighting a strong influence of the ignition location. The model illustrates that the pressure evolution is the result of complex geometry effects: particularly, for a tank made of identical compartments, the total volume is not sufficient to describe the main trends concerning the mechanical effects of the explosion. The calculations are in agreement with classical results available in the literature for a special kind of kerosene (F.34) studied by the laboratory. Despite the proposed model relying on simple assumptions, it represents a useful tool for further vulnerability or risk assessment studies applied to aircraft kerosene tanks.

The present paper concerns itself with the insulation characteristics of c-C4F8/N2 gas mixtures and studies the possibility of applying in the gas insulation of power equipments. We aim to use the theoretical framework of the Boltzmann equation to calculate the density-normalized effective ionization coefficients (α–ƞ)/N and transport parameters of c-C4F8/N2 gas mixtures for E/N values from 180 to 550 Td (1 Td = 10−17 V cm2) in the condition of steady-state Townsend (SST) experiment. From the variation curve of (α–ƞ)/N with the c-C4F8 mixture ratio k, the limiting field strength (E/N)lim of the gas mixtures at different gas content is determined. In order to confirm the validity of the results obtained, comparisons with Monte Carlo simulation and experimental data have been performed. It is found that the insulation properties of c-C4F8 and N2 gas mixtures are much better than those of SF6 and N2 mixtures for applying in the high voltage apparatus as an insulation medium, especially if we take the global warming potential into account.

The rapid development of low-power consumption electronics and the possibility of harvesting energy from environmental sources can make totally autonomous wireless devices. Using piezoelectric materials to convert the mechanical energy into electrical energy for batteries of wireless devices in order to extend the lifetime is the focus in many researches in the recent years. It is important and efficient to improve the energy harvesting by designing an optimal interface between piezoelectric device and the load. In this paper, a self-powered piezoelectric energy harvesting device is proposed based on the velocity control synchronized switching harvesting on inductor technique (V–SSHI). Comparing to the standard full bridge rectifier technique, the synchronized switching harvesting on inductor (SSHI) technique can highly improve harvesting efficiency. However, in real applications when the energy harvesting device is associated with wireless sensor network (WSN), the SSHI technique needs to be implemented and requires being self-powered. The conventional technique to implement self-powered SSHI is to use bipolar transistors as voltage peak detector. In this paper, a new self-powered device is proposed, using velocity control to switch the MOSFET more accurately than in the conventional technique. The concept of design and the theoretical analysis are presented in detail. Experimental results are examined.

This paper presents two radar simulation platforms that have been developed and evaluated. One is based on the Advanced Design System (ADS) and the other on Matlab. Both platforms are modeled using homodyne front-end 77 GHz radar, based on commercially available monolithic microwave integrated circuits (MMIC). Known linear modulation formats such as the frequency modulation continuous wave (FMCW) and three-segment FMCW have been studied, and a new variant, the dual FMCW, is proposed for easier association between beat frequencies, while maintaining an excellent distance estimation of the targets. In the signal processing domain, new algorithms are proposed for the three-segment FMCW and for the dual FMCW. While both of these algorithms present the choice of either using complex or real data, the former allows faster signal processing, whereas the latter enables a simplified front-end architecture. The estimation performance of the modulation formats has been evaluated using the Cramer-Rao and Barankin bounds. It is found that the dual FMCW modulation format is slightly better than the other two formats tested in this work. A threshold effect is found at a signal-to-noise ratio (SNR) of 12 dB which means that, to be able to detect a target, the SNR should be above this value. In real hardware, the SNR detection limit should be set to about at least 15 dB.

We have developed a setup that offers a vacuum compatible, vibration-free experimental space with active thermal stabilization around room temperature, suitable for high sensitivity measurements. In this paper we describe the experimental setup from the thermal viewpoint and the design and implementation of the thermal control. Then we characterize the long-term performances of the control loop by using experimental data collected over 1 month: we show that our control is effective in reducing room temperature variations by a factor 100 over a few weeks, even in the presence of an internal dc heat source of 2 W.

In this paper, the tape-helix model is firstly introduced in the field of intense electron beam accelerator to analyze the dispersion effects on the electromagnetic parameters of helical Blumlein pulse forming line (PFL). Work band and dispersion relation of the PFL are analyzed, and the normalized coefficients of spatial harmonics are calculated. Dispersion effects on the important electromagnetic parameters of PFL, such as phase velocity, slow-wave coefficient, electric length and pulse duration, are analyzed as the central topic. In the PFL, electromagnetic waves with different frequencies in the work band of PFL have almost the same phase velocity. When de-ionized water, transformer oil and air are used as the PFL filling dielectric, respectively, the pulse duration of the helical Blumlein PFL is calculated as 479.6 ns, 81.1 ns and 53.1 ns in order. Electromagnetic wave simulation and experiments are carried out to demonstrate the theoretical calculations of the electric length and pulse duration which directly describe the phase velocity and dispersion of the PFL. Simulation results prove the theoretical analysis and calculation on pulse duration. Experiment is carried out based on the tape-helix Blumlein PFL and magnetic switch system. Experimental results show that the pulse durations are tested as 460 ns, 79 ns and 49 ns in order when de-ionized water, transformer oil and air are used respectively. Experimental results basically demonstrate the theoretical calculations and the analyses of dispersion.