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The accuracy of the RCS (Radar Cross Section) test is closely related to the conductivity of the model surface. The Chinese military standard has stringent surface resistance criteria for models. If the resistance criteria are appropriately relaxed, model processing can be more effective and expenses can be reduced. However, there are few quantitative evaluations of the relationship between surface resistance and RCS test error, making it impossible to design the model surface resistance in accordance with RCS test accuracy requirements. In this paper, firstly, the influence of model surface resistance on RCS is clarified through theoretical, simulation, and experimental research. The RCS analysis approach of the finite conductivity model is established. Subsequently, taking various typical shapes as research objects, such as the sphere, cube, flying wing aircraft, wing-body combination, and stealth aircraft, the simulation analysis of radar scattering characteristics is carried out under varied sheet resistances and multiple frequencies. A more attainable surface conductivity control standard for the RCS test model has been formulated, which is relaxed by 93% and 727% for models with average RCS of less than and higher than −30dBsm compared with the indicator in the Chinese military standard.

The presence of PMMA residues resulting from the graphene transfer process on the Si/SiO2 substrate, the adsorption of H2O and O2 molecules on the graphene surface, and the surface charges trapped between graphene and the substrate can all increase the density of the positive charge carriers, thus leading to hole doping. This article investigates the doping of CVD-grown graphene transferred onto a SiO2/Si substrate, considering the effects of substrate preparation treatments (before the transfer) and thermal annealing processes of transferred graphene (to remove PMMA residues). The effect of post-transfer annealing on the doping of graphene was investigated by measuring the changes in the sheet resistance, mobility, and carrier density at 200 and 550 °C in vacuum conditions. The Five different pre-treatments of the SiO2 surface, i.e., using solvents (acetone and IPA, piranha, HF), spin-coating with HMDS, and O2 plasma, were investigated to modify the hydrophobic or hydrophilic character of the SiO2 surface. Then the effects of substrate hydrophilicity on the amount of transferred graphene cavity and doping before and after annealing were studied according to the electrical resistance and shift and intensity ratios of the graphene Raman peaks (D, G, and 2D). [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF)-derived metal oxide semiconductors (MOSs) have drawn great attention because of their abundant pore structures, large surface area, and good gas accessibility. Herein, hierarchical flower-like Sr-doped cobalt oxide (Co3O4) structure is obtained utilizing MOF as a self-sacrificing template. Compared with undoped Co3O4, the 2 mol% Sr-doped Co3O4 shows better triethylamine (TEA) sensing performance. It exhibits not only high response values of 52 (the response of undoped Co3O4 are about 3.3) and short response/recovery time (40/58 s) to 100 ppm TEA at a low working temperature of 160 °C, but also excellent selectivity and long-term stability, which show that the as-obtained flower-like Sr-doped Co3O4 structure is an effective material to detect TEA gas. The enhanced sensing properties are attributed to the synergistic effect of the creation of more oxygen vacancies and larger surface area of flower-like structure. [ABSTRACT FROM AUTHOR]

In order to provide further evidence for the improvement in tracking and erosion resistance of alumina trihydrate (ATH)-free silicone rubbers (SRs) by direct fluorination and to explore the improvement mechanisms, the ATH-free SR samples containing 15-parts per hundred parts of rubber by weight (phr) melamine cyanurate and 18-phr fumed silica were prepared, and then they were surface fluorinated using a $\text{F}_{{2}}/\text{N}_{{2}}$ mixture at 0.1 MPa and 85 °C for 120 min. Inclined plane tracking and erosion tests indicate that at 4.5-kV rms ac, all 15 fluorinated samples passed the test, while 7 of the 15 unfluorinated samples failed the test due to combustion. Analyses of erosion depth, length, and area show that the fluorinated sample, compared to the unfluorinated sample, has a larger average erosion depth but a smaller average erosion length or area. Attenuated total reflection infrared spectroscopy (ATR-IR) and X-ray photoelectron spectroscopy (XPS) analyses indicate that both the SR matrix and the fillers of melamine cyanurate and fumed silica in the surface layer were fluorinated, forming the Si–F, C–F, and N–F bonds. Scanning electron microscopy (SEM) observations show that the fluorinated layer has a thickness of $1.15~\mu \text{m}$ and a rough surface, and the fillers are uniformly dispersed in the matrix. The resistance improvement by the fluorination is attributed to these changes of the surface layer in composition, structure, and interface of the SR matrix and the fillers and is also influenced by the change in surface morphology. [ABSTRACT FROM AUTHOR]

Surface impedance represents a crucial parameter for the characterization of thin films. Indeed, materials with a sheet impedance varying as a function of their elongation could be used in radio frequency piezoresistive sensors. To estimate this quantity while having the possibility of stretching the sample under test, a waveguide-based non-contact approach is proposed. The absence of contact between the sample under test and the waveguides determines an electromagnetic field leakage, which is prevented by adopting an electromagnetic band gap (EBG) structure. The surface impedance of the sample is retrieved through an inversion procedure exploiting the scattering parameters measured using the proposed setup. The inversion procedure is based on a circuit representation of the waveguide-air-waveguide Section as a $\pi $ -junction. The reliability of the proposed measurement method has been experimentally assessed using a WR137 waveguide. The proposed method allows to accurately determine the real part of surface impedance (the sheet resistance), while higher uncertainty is achieved in the estimation of the imaginary part. [ABSTRACT FROM AUTHOR]

Through silicon via (TSV) is the key technology for 3-D integrated circuits (3-DICs) which could vertically stack homogeneous or heterogeneous dies with the high performance and density. To evaluate the electrical characteristics of TSV at the high-frequency transmission, the skin effect and surface roughness effect are necessary to be considered. However, these effects would significantly result in the TSV equivalent resistance under the high operating frequency. Thus, it is important to investigate the carbon nano tubes (CNTs) TSV which has less skin effect intrinsically. In this work, we analyze the advantage of CNTs as TSV compared to the conventional filling materials such as copper (Cu). Furtherly, we also propose the equivalent circuit model of TSV and its multi-layer structure to simulate the electrical behaviors with different TSV pitch, height, diameter, and stacking layers by using ANSYS designer and high-frequency structure simulator (HFSS). Based on the frequency-domain analysis, it can be found that CNTs TSV has the lower frequency-dependent loss than Cu due to the lower equivalent resistance. In a summary, CNTs could be a promising TSV filling material at the high-speed transmission frequency based on our study. [ABSTRACT FROM AUTHOR]

Armature is the key component of electromagnetic launcher (EML), but in the process of launching, its working environment is bad and the surface is seriously worn. Excessive wear will seriously weaken the mechanical properties of armature and affect the launching safety. Therefore, it is necessary to deal with the surface state of armature to reduce wear and improve the performance of armature. First, the properties of the candidate materials are analyzed. According to the principle of maximum current carrying capacity per unit mass, aluminum is the most suitable material for armature manufacturing. At the same time, the defects of material selection in single material system are pointed out. Second, based on the above problems, the surface coating design scheme is proposed. From the point of view of material melting point and hardness, it is proposed that tungsten can be used as the coating material for armature surface. According to the wear amount of armature tail under launch condition, the coating shape and thickness are designed. The best coating forming process is determined by calculating the shear force between coating and substrate; finally, the effect of the coating on the electric contact performance, system efficiency, and projectile gouging threshold velocity is analyzed. The results show that the maximum shear force between the coating and the substrate is above 171 MPa under the launching condition, and the laser cladding technology can meet the process requirements. After coating treatment, the contact resistance between the armature and rail (AR) increases by 6%, which has little effect on the system efficiency. Although it will affect the projectile gouging threshold velocity, it can be improved by modifying the tungsten coating or rail surface treatment. The analysis results are of great significance to reduce the armature wear, improve the contact performance between the AR, and improve the launch safety. [ABSTRACT FROM AUTHOR]

We study the impact of access region passivation on the electrical characteristics of hydrogen-terminated diamond MOSFETs with tungsten Carbide (WC) edge contacts. Our experiments reveal a significant improvement to both contact and extrinsic channel sheet resistance once the access regions are passivated with WO3, indicating that WO3 is an effective surface transfer-doping agent. We analyze a peculiar bump that appears in the subthreshold characteristics of the devices that prevents their effective turn-off. The bump is found to be mitigated when the access regions are passivated by WO3. Poisson–Schrödinger (P–S) simulations suggest that this bump arises from the field-effect action by the gate over the access region immediately adjoining the gate. This parasitic field effect arises when the surface is unpinned and with a light hole concentration. Owing to its increased surface transfer doping, the use of WO3 as surface passivation is effective in delivering a sharp device turn-off. [ABSTRACT FROM AUTHOR]

In this article, the correlation between the thermal contact resistance and the surface roughness characteristics of the contact interface in the press-pack insulated-gate bipolar transistor (PP-IGBT) modules during power cycling was studied by experimental measurements and finite-element (FE) simulation-based factorial design analysis. Thermal transient test technology was applied to examine the change in the thermal characteristic parameters of the PP-IGBT module. This shows that the increase in the thermal contact resistance of the Al metallization/emitter Mo contact interface occurs more dramatically during power cycling. A 3-D surface profilometer was used to evaluate the surface morphology parameters of the Al metallization/emitter Mo contact interface. The equivalent root-mean-square (RMS) roughness increases during power cycling, and the equivalent asperity slope and the equivalent spacing between asperities increase slightly. Additionally, the surface roughening in the corner area of the chip is more obvious than in other regions. A fractional factorial design analysis based on FE simulations was performed. The results indicate that the thermal contact resistance strongly depends on the main effects of the real contact area and the spacing between the asperities, and the RMS roughness and the asperity slope interaction. [ABSTRACT FROM AUTHOR]

This work focuses on making and studying steel conductors with inhomogeneous surface conductivity. Employing such materials (structures) for engineering the high-field pulsed magnets can provide them with enhanced durability. In this work, monotonically changing resistivity was realized by pack chromizing the medium-carbon steels, 30KhGSA and 40Kh, which were treated at 1000 °C in argon for 150 h under the Cr-load of 20 mg/cm2 to obtain a diffuse layer with minimal carbides at the surface. An approach to investigate the resistivity distribution across a diffuse layer after steel chromizing is suggested and involves a stepwise surface grinding, resistance measurement, and analytical processing of experimental data. The resistivity profile obtained by this method is well described by the complementary error function. At the near-surface layer, 30KhGSA and 40Kh steels have almost the same values of resistivity, about 110– $115 ~\mu $ Ohm $\cdot $ cm, which is 2.9–4.3 times higher than that in the bulk depending on steel. A strong correlation, almost a linear dependence, of resistivity with the depth-derived chromium concentration in the material was found. The proposed method allows one to measure the depth-varied resistivity for ferrous alloys with proper accuracy, while it does not require complex measuring equipment compared with other ones. [ABSTRACT FROM AUTHOR]

In order to verify the effectiveness of direct fluorination in improving the dc flashover performance of gas insulated switchgear (GIS) actual spacers and explore the effect of fluorination conditions, 126-kV disk spacers were surface fluorinated in the laboratory at the different temperatures of 35 °C, 55 °C, or 80 °C. The evaluation of surface physicochemical characteristics and basic electrical properties of the fluorinated disk spacers are realized by using the epoxy samples of the same material and simultaneously fluorinated with the disk spacers. Flashover tests indicate that direct fluorination significantly increases the dc flashover voltage of the actual spacer in SF6 gas and reduces the dispersion of flashover voltage, fluorination temperature has a significant effect on the enhancement of the flashover voltage, and the fluorination at higher temperatures can produce a larger improvement in the flashover performance. In addition, these fluorinated spacers can withstand heat treatment at 120 °C, with unchanged flashover performance. Infrared analysis and scanning electron microscopy observation show that the fluorination at different temperatures changes surface chemistry of the disk spacer substantially, forming the fluorinated layers with different thicknesses, compositions, and structures. Measurements of surface conductivity and surface potential decay consistently show that direct fluorination increases surface conduction of the spacer, and the fluorination at higher temperatures leads to a more significant increase in surface conduction. The improvement in dc flashover performance, caused by direct fluorination, is mainly attributed to the suppression of surface charge accumulation by the increase in surface conduction of the spacer. [ABSTRACT FROM AUTHOR]

A homogenization field lateral double diffused metal oxide semiconductor based on the trench-stopped depletion (TS-HOF LDMOS) is proposed and experimentally realized in this article. By solving the 3-D Poisson equation, the curvature factor ${k}$ is introduced to give the quantitative relationship between the maximum field ${E}_{\text {max}}$ and parameters of the 3-D bulk curvature effect. Based on the theory, the trench-stop concept and the TS-HOF structure were proposed to reduce ${E}_{\text {max}}$. In the new structure, the depletion of the last discrete metal insulator semiconductor (MIS) array is stopped by process compatible drain trenches for suppressing the serious 3-D bulk curvature effect especially at high voltage, which is a special technology for improving breakdown voltage ${V}_{\text {B}}$ of the complementary homogenization field (C-HOF) LDMOS. It was demonstrated by experiments that ${V}_{\text {B}}$ of the TS-HOF LDMOS is more than 15% higher than that of the C-HOF device while maintaining the same specific ON-resistance ${R} _{\text {on,sp}}$. The TS-HOF LDMOS achieved a measured ${V}_{\text {B}}$ of 675 V and a ${R} _{\text {on,sp}}$ of 49.1 $\text{m}\Omega \,\cdot $ cm2, which represents a reduction of 43.2% when compared with the theoretical value of the triple reduced surface field (RESURF) technology. [ABSTRACT FROM AUTHOR]

In this article, a fully coupled multiphysical model of multichip press-pack insulated gate bipolar transistor (PPI) considering surface roughness is proposed. This model realizes the coupling of the electrical-, thermal- and mechanical domains through contact resistance. The simultaneous prediction of temperature and stress under various surface roughness is achieved. First, the fully coupled model and the contact resistance model are established. Second, both thermomechanical stress under the clamping phase and heating phase are analyzed. The influence of the surface roughness on the thermo-mechanical stress distribution is also investigated based on the proposed model. Results show that the surface roughness does not affect the thermomechanical stress distribution under the heating phase, while the amplitudes increase with surface roughness. Third, the correctness of the model is verified by the temperature measurement and deterioration observation results. The observed fretting scratches on the additional metallization area after the power cycling test validates the correctness of the deformation prediction. Finally, the strain-life fatigue model of PPI is established, it turns out that the surface roughness has an impact on the fatigue life of the chip metallization area. [ABSTRACT FROM AUTHOR]

Intermittent faults are very common problems in various kinds of electronic devices. This article is focused on the intermittent fault phenomenon in degraded electrical connectors in vibration environments. To analyze the intermittent faults in degraded electrical connectors, a micro-state contact model is constructed to simulate the resistance variation behavior in vibration environments. The relationship between the intermittent fault behavior and the degradation state is studied, and a health indicator parameter is extracted from the signals to act as a symptom for degradation. A test platform is built to collect the intermittent fault signals from electrical connectors at different degradation states in vibration environments. The degradation curve of the health indicator is used to predict the remaining useful life (RUL) of the electrical connectors. The method of extreme learning machine (ELM) is adopted to conduct the prediction of RUL. The genetic algorithm (GA) is used to optimize the weight and bias parameters in ELM. The results reflect that the intermittent fault characteristic is a proper degradation index in the prediction of RUL for degraded electrical connectors. [ABSTRACT FROM AUTHOR]

Thermal contact resistances usually account for more than 50% of the total thermal resistance in a press-pack insulated-gate bipolar transistor (PP-IGBT) device, which affect the heat dissipation of the PP-IGBT device and lead to a high junction temperature. In this article, a method for optimizing the thermal contact resistances of the PP-IGBT device is proposed by filling the liquid metal thermal interface materials in the contact surface. Bismuth-based liquid metal with high thermal conductivity and electrical conductivity is chosen, and the material is used for filling between the insulated-gate bipolar transistor chip and the molybdenum layers. The thermal characteristics are compared with the traditional commercial PP-IGBT device using finite-element simulation and experimental methods. The high-voltage insulation reliability of the proposed optimized method is verified by blocking voltage test, and the long-term reliability of the device is verified by a power cycling test. The results show that the junction-to-case thermal resistance of the optimized PP-IGBT device can be reduced by more than 30%, which is helpful for improving the thermal reliability of large-capacity PP-IGBT devices. [ABSTRACT FROM AUTHOR]

The internal states of lithium-ion batteries need to be carefully monitored during operation to manage energy and safety. In this article, we propose a thermal-enhanced adaptive interval observer for state-of-charge (SOC) and temperature estimation for a battery pack. For a large battery pack with hundreds or thousands of heterogeneous cells, each individual cell characteristic is different from others. Practically, applying estimation algorithms on each and every cell would be mathematically and computationally intractable since battery packs are often characterized by combinations of differential equations (state dynamics) and algebraic constraints (Kirchhoff’s laws). These issues are tackled using an interval observer based on monotone/cooperative system theory, whose novelty lies in considering cell heterogeneity and state-dependent parameters as unknown, but bounded uncertainties. The resulting interval observer maps the bounded uncertainties to a feasible set of SOC and temperature estimation for all cells in the pack at each time instant. This work also addresses the significant conservatism under extreme conditions with large currents via a thermal-enhanced adaptive scheme. The proposed interval estimation is scalable and computationally tractable since it is independent of the number of cells in a pack, as numerically demonstrated in a comparison with respect to a state-of-the-art single-cell state observer. The stability and inclusion of the adaptive interval observer are proven and validated through simulations. [ABSTRACT FROM AUTHOR]

Thin-film transistors (TFTs) based on amorphous Indium-Gallium-Zinc Oxide (a-IGZO) can be used to drive the quantum-dot light-emitting diodes (QLEDs) for active-matrix (AM) displays. To reduce the fabrication complexity, Al reaction-induced conductive a-IGZO is developed as a common electrode, which simultaneously serves as a drain electrode for the TFT and as a bottom electrode for the QLED. The obtained a-IGZO electrode exhibits a low sheet resistance of 120 $\Omega $ / and a high transmittance of 92.1% at a thickness of 100 nm. With the proposed a-IGZO electrode, QLED demonstrates a high external quantum efficiency of 26%. Moreover, because both TFT and QLED share the same a-IGZO electrode, at least two patterning processes can be reduced in making a AM display. Our results suggest that Al reaction-induced conductive a-IGZO could be a promising pixel electrode for AMQLED displays. [ABSTRACT FROM AUTHOR]

The adoption of metal additive manufacturing into the production of passive microwave components is still in its relative infancy. However, it is of increasing interest due to the offer of geometrical design freedom and significant weight reduction. The electrical properties of additive manufactured components are still inferior to traditional manufacturing techniques owing to the poor surface finish, especially on overhanging surfaces, which are unavoidable in three-dimensional microwave components. In this paper we present experimental findings on the disparity in microwave surface resistance values between three common build orientations, as well as findings that establish a connection between increasing downskin laser power and a reduction in surface resistance for overhanging surfaces. Finally, additive manufactured rectangular waveguide sections are measured to assess the influence of combined upward and downward facing surfaces on surface resistance.

To explore dc flashover characteristics and evaluate the dc flashover resistance of epoxy resin, an online surface potential measurement is proposed and verified in this article. Rising positive and negative dc high voltages (HVs) with a step of 0.5 kV per 5 min are applied to epoxy resin until the intensive flashover occurs, and the surface potential at the triple junction point is measured during flashover. It is found that the surface potential profile appears as the recurrence of flashover units during intensive flashover. A three-point peak-finding algorithm with threshold judgment is proposed to determine the interval between adjacent flashover units. Both appropriate surface potential difference threshold (SPDT) and flashover interval (FI) are used to evaluate the severity of flashover (i.e., the opposite of flashover resistance). It is interesting to find positive and negative flashover has different surface potential evolution characteristics. Positive flashover exhibits larger fluctuation, higher SPDT, and shorter FI, which may result from severe positive charge accumulation before every single flashover due to the low surface mobility of the positive charge. The results manifest positive flashover is more serious than negative flashover for the investigated epoxy resin. [ABSTRACT FROM AUTHOR]

The ohmic contact resistance (${R}_{C}$), surface resistance (${R}_{S}$), and channel resistance (${R}_{\text {CH}}$) of hydrogen-terminated diamond (H-diamond) MOSFETs were investigated in this study. Planar-type and T-type H-diamond MOSFETs were employed to analyze them. Because no interspaces exist between the source–drain and gate electrodes for the T-type H-diamond MOSFETs, then ${R}_{S}$ is zero. Both planar-type and T-type MOSFETs show low leakage current densities and good operations. By considering the relationships between the total resistance (${R}_{ \mathrm{\scriptscriptstyle ON}}$) and 1/ $\vert $ gate voltage-threshold voltage $\vert $ , ${R}_{C}$ and ${R}_{\text {CH}}$ for the T-type H-diamond MOSFET at a gate voltage of −10.0 V are determined to be 13.8 and 21.8 $\Omega \cdot $ mm, respectively. As ${R}_{C}$ for both MOSFETs is the same, ${R}_{S}$ and ${R}_{\text {CH}}$ for the planar-type H-diamond MOSFET are deduced to be 90.0 and 15.8 $\Omega \cdot $ mm, respectively. ${R}_{S}$ accounts for 75.3% of ${R}_{ \mathrm{\scriptscriptstyle ON}}$ for the planar-type H-diamond MOSFET, which is the main reason for its lower drain current and extrinsic transconductance than those of the T-type MOSFET. Although ${R}_{S}$ is suppressed for the T-type H-diamond MOSFET, ${R}_{C}$ occupies 38.8% of ${R}_{ \mathrm{\scriptscriptstyle ON}}$. To further improve the performance of the H-diamond MOSFETs, it is important to eliminate ${R}_{S}$ and decrease ${R}_{C}$ to further improve the electrical properties of the H-diamond MOSFETs. [ABSTRACT FROM AUTHOR]

This article describes a superior passivation of p-type (p+) Si surface by an Al2O3 thin film that is synthesized by plasma-assisted atomic layer deposition (ALD) for ultraviolet-sensitive silicon photomultipliers (SiPMs), compared to conventional SiO2 and SiNx passivation schemes. The superiority of Al2O3 passivation is due not only to a sufficiently low interface defect density, but also to a high density of built-in negative charges. A 7-nm thin Al2O3 film can yield an emitter saturation current density of ~8 fA/cm2 on a high sheet resistance p+ layer, compared to ~60 and ~1480 fA/cm2 for thermal SiO2 and SiNx passivation. This superior surface passivation allows the photon-generated carriers to have higher probabilities to reach the high-field region to trigger an avalanche event. In addition, the Al2O3 thin film provides very low values of effective surface recombination velocity on low resistivity n- and p-type Si surfaces, which can lead to well-passivated surface features on the guard ring and trench isolation regions of SiPM. These demonstrate the potential of the Al2O3 thin film passivation to improve the quantum efficiency and thus photo-detection efficiency (PDE) of ultraviolet-sensitive SiPM with p+/n−/n/n+ structure. [ABSTRACT FROM AUTHOR]

An interesting hydrogen (H2) gas sensor, synthesized by an indium oxide (In2O3) layer and evaporated palladium (Pd) nanoparticles (NPs), is manufactured and studied. The utilized Pd NPs essentially enhance the surface area/volume (${S}_{A}/{V})$ ratio and catalytic reactivity of the Pd metal. Energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), high-resolution scanning electron microscopy (HRSEM), and TEM were used to investigate the relevant material behaviors of the proposed Pd NP/In2O3 sensor device. The sensing mechanism is explicated in this study. A very high-sensing response of 5243 under 1% H2/air gas with a response time of 12 s and an extremely low-detecting content of 100 ppb H2/air were obtained at the optimal operating temperature of 225 °C. In addition, excellent selectivity toward hydrogen gas is observed for the studied device. The proposed sensor also shows advantages of simple structure, low-cost, and relatively easy fabrication process. [ABSTRACT FROM AUTHOR]

Human-friendly robot designs are often inspired by human joints that exhibit lightweight, dexterity, and large compressive load capacity. However, there is a significant problem when attaching sensors to contact joints inspired by human joints. Attaching traditional sensors for obtaining information on a joint is substantially complicated by the skewed rotation axes. To solve this problem, we propose a novel contact joint sensor suitable for 3D curved surfaces. The proposed contact joint sensor is composed of a contact resistance force-sensor module for obtaining distributed pressure measurements utilized to estimate the joint information via a learning method. Each force-sensor array arranged in the desired shape on a 3D curved surface measures the surface pressure transmitted through a heterogeneous force-transmit layer. The learning-based model estimates the joint angle and torque values while maintaining the estimation performance even under varying load conditions. We validated the proposed contact joint sensor with experiments involving various load conditions. The average root-mean-squared error (RMSE) values of the flexion/extension and radial/ulnar rotation angles are $2.2\,^{\circ }$ and $1.7\,^{\circ }$ , respectively. In addition, estimations of the torque and tension at the contact joint show good agreement with the reference values despite changes in the load conditions. [ABSTRACT FROM AUTHOR]

Current artificial magnetic conductor (AMC) designs use metallic patterns on rigid substrates and focus on shapes and sizes of AMC structures, rather than on material performance, which has hindered operation bandwidth and design flexibility. Here, we introduce printed graphene AMC-based broadband and flexible microwave radar absorbers, which not only redirect but also absorb the incident wave so to broaden the operation bandwidth. Contrasting to other reported works, the phase characteristics of the AMCs are realized through the control of the surface resistance provided by printed graphene laminates. We produced a variety of AMC structures, composed of printed graphene circular ring arrays with exactly the same shape and size, but different sheet resistances. By carefully designing the sheet resistance of printed graphene laminates, the optimized anti-phase reflection cancellation between AMCs can be achieved. With printed graphene AMCs and flexible dielectric substrate, the absorber presented in this work has a broadband effective absorption (above 90% absorptivity) from 7.58 GHz to 18, is polarization insensitive under normal incident, and can work at relatively wide incident angles. Furthermore, this absorber is capable of bending easily with notable performance, which makes it ideal for applications with irregular and uneven shapes. [ABSTRACT FROM AUTHOR]

In the voltage source inverter applications, inverter nonlinearities would affect the parameter identification process in many ways. Hence, this article proposes an offline identification method for resistance and dq-axis inductance surface by considering the inverter nonlinearity characteristics. A variable amplitude square-wave injection (VASI) scheme is proposed for the dq-axis inductance identification. The VASI method achieves the inductance identification with a novel data sampling strategy. Meanwhile, it can also establish the inductance surfaces by only a few identified data points with a polynomial fitting algorithm, which greatly reduces the identification time compared with the existing methods. The resistance identification is realized by a slope signal injection method, in which the effect of IGBT voltage drop is analyzed. In order to improve the identification accuracy, the inverter nonlinearities are compensated by a self-learning method considering the zero-axis voltage at different rotor positions. At the same time, the sampling error in zero current zones of abc-phases is researched. In order to verify the effectiveness and generality, the proposed method is carried out on two different test machines and confirmed by finite element analysis. [ABSTRACT FROM AUTHOR]

Temperature rise simulation deals with different physical domains describing heat generation and heat dissipation effects. Cigré working group A3.36 has conducted a study on temperature rise simulation of switchgear for distribution and transmission level. The working group built up new, manufacturer independent devices. Members of the working group simulated the temperature rise in advance to the tests, which were performed at laboratories of universities, as independent parties. In order to assess the simulation accuracy, the simulation results are compared to each other and to the measured results. This paper summarizes the main findings from the medium voltage device. The study has shown that when simulating the temperature rise on a completely new design, with reliable input values of contact resistances and emissivity coefficients, an accuracy of about 25% could be expected. Primary reason seems to be based on the complexity of simulating the heat dissipation mechanisms. To get a more accurate result, verification and validation is needed in order to adjust the parameters determining the heat dissipation. This study has also illustrated that it requires good knowledge (especially of the radiation) in order to adjust these parameters properly. [ABSTRACT FROM AUTHOR]

This paper investigates the tracking and erosion of silicone rubber and EPDM insulation in the DC inclined plane tracking and erosion test. Silicone rubber filled with alumina tri-hydrate fails due to combustion in the gas phase or erosion paths, but with no evidence of tracking. EPDM fails due to tracking and surface capturing fire, from dry-band arcing leaving a black residue while impinging the surface. Carbonaceous residue on EPDM gives rise to leakage current magnitude, whereas fused silica-based residue on silicone rubber is shown to promote combustion. A high amount of alumina tri-hydrate replacing the polymeric fuel in the composite is shown as a primary factor preventing failure and changing the nature of the residue in the DC inclined plane tracking and erosion test. Depolymerization is the main degradation mechanism reported for silicone rubber and EPDM, with notable degrees of crosslinking reported only for silicone rubber. Crosslinking reduces the amount of silicone rubber undergoing depolymerization, thus, the amount of fuel prone to combustion is reported to promote a coherent residue shield against the eroding dry-band arcing. [ABSTRACT FROM AUTHOR]

A novel high-temperature superconducting (HTS) thin-film device based on double-sided YBa2Cu3O7–x (YBCO) thin film, combined with roles of transformer and overcurrent limiter, is proposed and tested in this article. Due to the effective improvement on the power density, operating frequency, repeatability, functional integration, and low profile of the high-frequency converters, thin-film transformer (TFT) has been widely employed in power conversion fields. In contrast to the normal conductive materials, the surface resistance of the HTS materials is much smaller. Thus, the TFT fabricated by HTS thin film has lower Joule losses and higher power conversion efficiency. We designed the double-sided YBCO thin-film-based HTS-TFT and measured its parameters at liquid nitrogen (LN2). As a comparison, we also developed the copper (Cu) based TFT and measured the same parameters at LN2 and room temperature. Besides, we also tested the overcurrent limiting performance of the HTS-TFT, which is based on the state change from superconductivity to normal state. It can be found from the contrastive experiments that the HTS-TFT has better operating parameters than the Cu-TFT; meanwhile, the overcurrent can be limited by the HTS winding effectively. [ABSTRACT FROM AUTHOR]

A wearable flexible sensor fabricated on an ultrathin substrate is proposed for sleep respiratory monitoring in nasal cavity. The sensitive unit is composed of aurum multiturn microcoil fabricated on the surface of a polyimide catheter by the rotated lithography system, and the signal measurement is based on the principle of thermal resistance. The signal simulation and performance tests of the respiration sensor have been conducted, which demonstrate that the sensor has great performance in anti-interference, response speed, sensitivity, durability, and stability in long-time usage. The practical human tests in various simulated respiratory disease situations, mainly including apnea and hypopnea, display clear differences between normal and abnormal breathing signals measured by the sensor. The respiratory signals measured by this sensor can be utilized to analyze the various respiratory disease conditions. The presented wearable ultrathin flexible respiratory sensor has shown great potential for preliminary diagnosis of sleep respiratory diseases and sleep health monitoring. [ABSTRACT FROM AUTHOR]

Using an experimental approach, the effectiveness of nonionic surfactant, Triton™-X-100 in dispersing nano Alumina in high temperature vulcanized silicone rubber are studied in detail. Nanocomposites are prepared in varying concentrations of 0, 0.01, 0.05, 0.2, 1, and 5 phr levels by weight of the surfactant. Evidence to moderate dispersion of nano Alumina for composites at 0.01 phr and 0.05 phr weight loadings is gained from SEM pictures. Structural changes observed for the composites in FTIR spectra are examined and peaks identified. Thermogravimetric analysis shows some improvement in thermal resistance. However, an adverse effect on properties, such as volume resistivity, surface resistivity and dissipation factor are observed even at low surfactant loadings. A plausible role of surfactant as a plasticizer is explained with respect to the results of tensile strength. From this work, it can be inferred that surfactant at 0.01 phr may be taken as an optimum loading concentration for a desirable level of electrical properties, without compromising on insulation characteristics of volume resistivity and dissipation factor. Nonetheless, utmost caution needs to be exercised while employing Triton™-X-100 in compositions prepared for insulation applications because of inadequacies in values of volume resistivity, surface resistivity, dissipation factor and dry arc resistance even at low loadings. [ABSTRACT FROM AUTHOR]

Reconfigurable Intelligent Surface (RIS) is a promising solution to reconfigure the wireless environment in a controllable way. To compensate for the double-fading attenuation in the RIS-aided link, a large number of passive reflecting elements (REs) are conventionally deployed at the RIS, resulting in large surface size and considerable circuit power consumption. In this paper, we propose a new type of RIS, called active RIS, where each RE is assisted by active loads (negative resistance), that reflect and amplify the incident signal instead of only reflecting it with the adjustable phase shift as in the case of a passive RIS. Therefore, for a given power budget at the RIS, a strengthened RIS-aided link can be achieved by increasing the number of active REs as well as amplifying the incident signal. We consider the use of an active RIS to a single input multiple output (SIMO) system. However, it would unintentionally amplify the RIS-correlated noise, and thus the proposed system has to balance the conflict between the received signal power maximization and the RIS-correlated noise minimization at the receiver. To achieve this goal, it has to optimize the reflecting coefficient matrix at the RIS and the receive beamforming at the receiver. An alternating optimization algorithm is proposed to solve the problem. Specifically, the receive beamforming is obtained with a closed-form solution based on linear minimum-mean-square-error (MMSE) criterion, while the reflecting coefficient matrix is obtained by solving a series of sequential convex approximation (SCA) problems. Simulation results show that the proposed active RIS-aided system could achieve better performance over the conventional passive RIS-aided system with the same power budget. [ABSTRACT FROM AUTHOR]

Ammonia is harmful to human health, however, the detection limit of the sensor based on traditional semiconductor gas sensors is high and the speed is slow. Constructing heterostructure is an effective method to improve the performance of sensors. In this article, 1-D MoO3 nanorods and SnO2 nanoparticles are successfully combined to obtain MoO3/SnO2 nanocomposite. The 1-D structure can increase the speed of electron transport, while the nanoparticles on the surface increase the specific surface area, more importantly, the structure maximizes the interface area between the two materials which can transfer electronic more efficiently. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and Barrett–Joyner–Halenda (BJH) are used to analyze the microstructure and elemental composition of MoO3/SnO2. The diameter of MoO3/SnO2 nanocomposite is approximately 200 nm and the distribution is uniform. The response of MoO3/SnO2 nanocomposite to 100-ppm NH3 is 12.7 at 280 °C, and the response/recovery time is 13/2 s. The detection limit for NH3 can reach 10 ppb (response 1.3), which enables rapid detection of NH3 at low concentration. Electron transport requires more energy to overcome the contact barrier between pure SnO2 nanoparticles, which can also lead to electron emission and noise increase. However, the sensitive electrons of MoO3/SnO2 nanocomposite can transmit electrons along the 1-D rod-like structure of MoO3, which undoubtedly accelerates the efficiency of electron transmission. Moreover, n-n heterojunction formed between MoO3 and SnO2 to bend the SnO2 band and show better sensitivity to NH3. Therefore, MoO3/SnO2 nanocomposite shows a low detection limit and a rapid response/recovery speed. Nevertheless, the nanoparticles on the surface of MoO3/SnO2 nanocomposite begin to agglomerate with the increase of SnO2 content, which leads to the decrease of gas-sensitive response. The formation process of MoO3/SnO2 composites is also discussed in this article. The excellent gas sensing results show that MoO3/SnO2 composites are a promising gas sensing material. [ABSTRACT FROM AUTHOR]

A new method for accurate measurement of the microwave surface resistance of flat metal plates is proposed and verified experimentally, based on a sapphire dielectric resonator. System losses are accounted for by having continuous and controlled variation of the distance between the dielectric and the sample under test. [ABSTRACT FROM AUTHOR]

We present an experimental characterization of the electrical properties of 3-D-printed niobium. The study was performed by inserting a 3-D-printed Nb post inside an aluminum cylindrical cavity, forming a 3-D lumped element reentrant microwave cavity resonator. The resonator was cooled to temperatures below the critical temperature of niobium (9.25 K) and then aluminum (1.2 K) while measuring the quality factors of the electromagnetic resonances. This was then compared with finite element analysis of the cavity and a measurement of the same cavity with an aluminum post of similar dimensions and frequency, to extract the surface resistance of the niobium post. The 3-D-printed niobium exhibited a transition to the superconducting state below 9.25 K, as well as a surface resistance of $3.1\pm 0.54\times 10^{-4}~\Omega $. This value was comparable to many samples of traditionally machined niobium previously studied without specialized surface treatment. Furthermore, this study demonstrates a simple new method for characterizing the material properties of a relatively small and geometrically simple sample of the superconductor, which could be easily applied to other materials, particularly 3-D-printed materials. Further research and development in additive manufacturing may see the application of 3-D-printed niobium in not only superconducting cavity designs but also in the innovative technology of the future. [ABSTRACT FROM AUTHOR]

The understanding of carrier transport in metal nanostructures is indispensable for the development of nanoelectronics. In particular, Pt nanostructures have been intensively studied to realize gas sensors based on adsorbate-induced surface electron scattering. Conventionally, electron scattering at the surface of metal nanostructures has been phenomenologically described by a single specularity parameter. In this work, surface electron scattering was quantitatively studied through molecular dynamics simulations, followed by density functional nonequilibrium Green’s function calculations. Although the extracted specularity parameters qualitatively agreed with empirically treated diffusive scattering at the O-covered Pt surface and specular scattering at the H-covered Pt surface, our atomistic calculation revealed an increase in resistivity owing to H adsorption on thin Pt(111) nanosheets. [ABSTRACT FROM AUTHOR]

In the framework of ESS, a vacuum furnace dedicated to High Temperature Heat Treatment under Vacuum (VH2T2) of SRF bulk niobium (Nb) cavities was developed and commissioned in May 2016. This furnace is mainly used for the reduction of interstitial hydrogen in niobium. VH2T2 is an effective process for curing SRF cavities from the so-called Q0-deases phenomenon, which is due to Nb hydrid formation on the RF surface during the cool down of the resonator to cryogenic temperatures. IJCLab VH2T2 process is done at 650 °C during 10h00. The main differences between IJCLab recipe and the standard VH2T2 (SVH2T2) are 2 folds: 1) SVH2T2 is performed at 800 °C during 3h00, 2) IJCLab recipe is applied to spoke resonators equipped with Ti LHe tank. This process, will be applied to the whole series (26 cavities) of ESS 352 MHz Double-Spoke resonators. More than 28 cavities of various type (ESS Double-Spoke resonators, MYRRHA single spoke, ESS elliptical medium and high β cavities) were successfully heat treated according to our recipe and the last results are reported. Moreover, since 2 years we have launched the R&D program HELOISE with the financial support of IN2P3/CNRS. HELOISE is dedicated to Heat Treatment of SRF niobium cavities: it includes Low Temperature Baking, VH2T2, Nitrogen Infusion and Nitrogen Doping processes. HELOISE main objectives are: 1) understand the complex mechanisms of the physical phenomena involved in heat treatment processes, 2) investigate the effect of the parameters impacting the process, 3) develop and master, at large scale and with good reliability, heat treatment processes in order to produce low RF losses and high gradient SRF bulk niobium cavities. Finally, we will focus on the first experimental data on Nitrogen Infusion we obtained: the corresponding results are reported and discussed. [ABSTRACT FROM AUTHOR]

Nb3Sn is considered as a potential candidate for superconducting radiofrequency cavities for particle acceleration due to its higher transition temperature of 18.3 K and higher superheating field of 400 mT. Nb3Sn films can be grown inside the surface of a Nb cavity by sequentially sputtering multiple layers of Nb and Sn thin films followed by annealing at 950 °C for 3 h. We report on the properties of Nb3Sn films grown on Nb substrates by magnetron sputtering. The films’ crystal structure, surface morphology, and composition were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The films had a polycrystalline Nb3Sn structure with a fine-grain surface and an atomic Sn composition of ∼23%. The RF surface resistance of the films was measured for different temperatures at 7.4 GHz to understand the feasibility of this method for the SRF application. The RF surface resistance of the films was 5 mΩ at 12 K, which is about 2 orders of magnitude higher than 60 μΩ previously measured in Nb3Sn films grown by Sn vapor diffusion. The sputtered film had a superconducting transition at 17.2 K, which is also lower than 17.9 K observed in Nb3Sn film prepared by vapor diffusion. [ABSTRACT FROM AUTHOR]

The surface energy balance algorithm for land (SEBAL) model is one of the most widely used methods for estimating evapotranspiration. Numerous physical studies have conducted to mitigate the limitations of spatial-domain dependence and the annoying uncertainties in visually identifying the dry/wet pixels in SEBAL; however, they are subject to the quality of wind speed (u) observation, which is known as a high temporal–spatial variation and is not routinely available, especially in a heterogeneous area. In this study, we constructed a u-independent algorithm to calculate the dry/wet endpoints for each pixel. The wet endpoint was determined by assuming no turbulent heat exchange between a water-saturated surface and atmosphere. The dry endpoint was calculated using the assumption and consensus that pixels had equivalent neutral aerodynamic resistance under given atmospheric forcing and vegetation coverage. Then, we built a temperature-domain SEBAL (TD-SEBAL) model and validated it in the MUSOEXE between May and September 2012, located at desert-oasis transition zone in the middle reaches of the Heihe watershed across eight landscapes. The results showed that TD-SEBAL could provide reasonable dry/wet endpoint retrieval, and reliable latent heat flux estimates with a mean bias of −0.25 W/m2, a root-mean-square error of 52.9 W/m2, and a coefficient of determination of 0.91. [ABSTRACT FROM AUTHOR]

In this work, flexible hydrogen sulfide (H2 S) sensors were prepared from nanocomposite mixtures of indium oxide (In2O3), graphite flakes (Gt) and polystyrene (PS). Where In2O3 was chosen as the sensing material. Gt flakes were added to adjust the sensor resistance in the range of 300–400 k $\Omega $. Also, PS were added as a modifier to maintain the sensors integrity, adhesiveness and flexibility properties. A nanocomposite mixture of In2 O3:10%Gt:17%PS emerged as a promising nanocomposite candidate to develop high performance sensors to detect H2 S gas. The flexible sensors were fabricated on top of flexible carbon electrodes that were screen-printed on polyethylene terephthalate (PET) substrate. Herein, we propose a sensitive H2 gas sensor to detect 100 ppb at room temperature while being resistant to humidity changes. These improvements have been attributed to additional benefits for the Gt flakes and the PS modifier. Both additives contributed to enhance the surface-to-volume ratio for the sensing thin film leading to a superior sensing performance for the In2O3 based sensor. Furthermore, they improved the hydrophobic property for the sensors to develop their resistance to humidity changes. The sensing mechanism for sensors depends mainly on the sulfuration and/or partial sulfuration of In2O3 by H2 S gas to form In2S3, which is conductive and responsible to decrease the sensor resistance. [ABSTRACT FROM AUTHOR]

Electromagnetic metasurfaces enable the advanced control of surface-wave propagation by spatially tailoring the local surface reactance. Interestingly, tailoring the surface resistance distribution in space provides new, largely unexplored degrees of freedom. In this article, we show that suitable spatial modulations of the surface resistance between positive (i.e., loss) and negative (i.e., gain) values can induce peculiar dispersion effects, far beyond mere compensation. Taking inspiration from the parity-time symmetry concept in quantum physics, we put forward and explore a class of non-Hermitian metasurfaces that may exhibit extreme anisotropy mainly induced by the gain-loss interplay. Through analytical modeling and full-wave numerical simulations, we illustrate the associated phenomenon of surface-wave canalization, explore nonlocal effects and possible departures from the ideal conditions, and address the feasibility of the required constitutive parameters. Our results suggest intriguing possibilities to dynamically reconfigure the surface-wave propagation and are of potential interest for applications to imaging, sensing, and communications. [ABSTRACT FROM AUTHOR]

Low power consumption or even detecting harmful gases at room temperature is the future development trend of gas sensors. In this work, Co doped ZnO hollow microspheres were prepared by a facile water bath method. Co doping increases the electron density of ZnO and promotes the adsorption of oxygen on the surface. The surface band bending caused by oxygen adsorption further promotes the separation efficiency of photogenerated charge. The sensing results showed that 1.5 mol% Co doped ZnO exhibited the highest response of 111.6 to 50 ppm formaldehyde (HCHO) activated by UV light (6.8 mW/cm2) at room temperature. Moreover, the detection of limit can reach to 100 ppb, and the response and recovery time is 32 and 44 s, respectively. The excellent gas-sensing performance could be attributed to the increase in adsorbed negative oxygen species on the surface, the improved separation efficiency of photogenerated charge, and the porous and hollow microstructure of ZnO. In addition, the sensor possessed excellent reproducibility, selectivity, and a certain ability of moisture resistance. [ABSTRACT FROM AUTHOR]

Additive manufactured (AM) metals are a subject of much interest for their performance in passive microwave applications. However, limitations could arise due to artifacts, such as surface texture and/or roughness resulting from the manufacturing process. We have, therefore, adopted a parallel plate microwave resonator for the accurate measurement of the surface resistance of flat metal plates, allowing for microwave current flow in two orthogonal directions by simply exciting a different resonant mode (at 5.3 and 6.4 GHz), without the need to remove and refix the sample. The systematic and random errors associated with the measurement of surface resistance are very small, less than 1% and 0.1%, respectively. The technique is demonstrated with measurements on a range of samples of the alloys, AlSi10Mg and Ti6Al4V, manufactured by laser powder bed fusion, in addition to traditionally machined samples of bulk metal alloys of aluminum and brass. For AM samples of AlSi10Mg, we have studied the effect on the surface resistance of directional roughness features, generated by the laser raster paths, in directions transverse or parallel to microwave current flow. Importantly for passive microwave device applications, we demonstrate that these samples exhibit no systematic anisotropy of surface resistance associated with such surface features. [ABSTRACT FROM AUTHOR]

Long standing data from niobium thin-film accelerating cavities will be revisited and analyzed by a modified London model of radio-frequency (RF) superconductivity. First, the applicability of this model is explored using the data of the Bardeen–Cooper–Schrieffer (BCS) surface resistance and its dependence on the RF magnetic field, temperature, and mean free path. Second, the RF losses from the trapped magnetic flux are analyzed with regard to their dependence on these same parameters. [ABSTRACT FROM AUTHOR]

Geometrical modification of three electrode Clark sensor is performed to enhance the sensing amperometric current. Two types of implantable microsensors are designed and characterized for measuring dissolved oxygen (DO2). For type I sensor, the area of the reference electrode (RE) conventionally sandwiched between working electrode (WE) and counter electrode (CE), is optimized. In contrast to the conventional Clark sensors, the CE is sandwiched between WE and RE in type II sensor. Both type microsensors are fabricated using simple processes of silicon-based microfabrication technology. Electrochemical characterizations are performed on both sensors. For 96% DO2, type I and type II microsensors demonstrate a sensing current of $- 0.87\,\,\mu \text{A}$ and $- 2.35\,\,\mu \text{A}$ as compared to a sensing current of $- 0.27\,\,\mu \text{A}$ for the conventional Clark microsensor of same size. A sensitivity of $0.0094~\mu \text{A}$ /%DO2 and $0.024~\mu \text{A}$ /%DO2 are achieved with type I and type II microsensor, respectively in contrast to a sensitivity of $0.0027~\mu \text{A}$ /%DO2 of the conventional Clark microsensor of same size. The sensors show a lifetime of 48 hours. With its miniature size and enhanced sensing current the sensors have potentials for clinical and biomedical applications. [ABSTRACT FROM AUTHOR]

Polymers are plastic materials used as insulators in power supplies, pulsers, transformers, etc., because of their low cost and excellent insulating properties. However, in several applications, the insulating performance of these materials is limited by the surface flashover instead of the dielectric bulk breakdown (BD). On the other hand, many works have demonstrated that the material hydrophobicity has a huge effect on the increase of resistance to surface flashover in polymers. In this article, to change this material property, the plasma immersion ion implantation (PIII) technique has been used for the treatment of sample surfaces of two important polymers: ultrahigh molecular weight polyethylene (UHMWPE) and poly-methyl-methacrylate (PMMA) used in medical and industrial applications, respectively. By means of the PIII treatment, it was shown that the surface BD voltage of such polymers has increased, improving the resistance to surface flashover. Contact angle diagnostic and atomic force microscopy (AFM) were measured, respectively, for the surface hydrophobicity and roughness to correlate with the increase of the surface BD voltage. Moreover, a special BD testing pulser is employed to assess the polymer resistance to surface flashover by measuring the corresponding BD voltage under atmospheric pressure. [ABSTRACT FROM AUTHOR]

Post-etch surface treatment technique was developed for normally-OFF recess-gate Al2O3/AlGaN/GaN metal–oxide–semiconductor high-electron-mobility tran- sistors (MOS-HEMTs). By removing the residues and smoothing surface morphology after plasma etch, the diffusion-controlled interface oxidation (DCIO) and wet etch in MOS-HEMTs lead to a decrease in interface traps from 1.04 × 1012 to 6.3 × 1011 cm−2 with a filling voltage of 12 V. Field-effect mobility extracted in the linear region is 48 cm2/V ⋅ s for MOS-HEMTs with an optimized post-etch surface treatment process, 33% larger than the case with the conventional chemical clean process. Due to the increased electron mobility and decreased sheet resistance beneath the gate by over 30%, normally-OFF MOS-HEMTs with DCIO and wet etch exhibit a remarkable increase in output current by about 29% and an increase in peak transconductance from 35 to 41 mS/mm. The optimized post-etch surface treatment method also enhances blocking voltage from 120 to 230 V by suppressing the leakage current resulting from gate soft breakdown. Dynamic characterization shows that the normalized ON-resistance is increased by double with drain stress up to 80 V, and various post-etch surface treatment processes have little effect on current collapse. Two types of threshold voltage shifts caused by interface trapping and border trapping are observed in the normally-OFF MOS-HEMTs, which keeps stable with an increase in temperature up to 125 °C. [ABSTRACT FROM AUTHOR]

Root-cause identification of faults in a distribution network is conducive to fault inspection as well as reducing injuries and damage. In this article, a novel method based on correlation dimension and average resistance is proposed to identify the root cause of permanent single line-to-ground fault in urban small current grounding systems. First, the reliability of the grounding fault and whether the fault occurred on a dry or wet surface can be identified by the correlation dimension. Then, the average resistance of the fault is used to classify the specific root cause, including wet land, dry land, wet concrete, dry concrete, and water. Experimental results show that this method can realize the classification of root causes and is robust to sampling rate, harmonics, and line impedance. [ABSTRACT FROM AUTHOR]

A mechanically flexible and optically transparent millimeter-wave broadband absorber was proposed and fabricated. The absorber showed >90% absorption in (73.5–110) GHz, covering the whole W-band. The key frequency selective surface used a concise metal mesh structure fabricated by the electrohydrodynamics (EHD) printing technology, which formed a classic sandwich structure together with a transparent dielectric layer and a transparent and conductive backplane. The transmittance of the sample in the visible light region was 58.1%. To testify the flexibility, the absorber was conformed to cylinders with a radius of 34 and 16 mm, respectively. The measured normalized S11 increased with bending. Simulation results also showed that the absorption over W-band was >80% within (0°–45°) incident angle and was insensitive to the polarization angle. [ABSTRACT FROM AUTHOR]

In order to compensate for amplitude inconsistencies of components and circuits, the equalizer has been proposed and introduced. In the previous reports, the theory of equalizer is mainly based on the resonant circuit. In this article, the substrate integrated waveguide (SIW) equalizer fabricated on a ceramic substrate with surface resistance, operating in a millimeter- wave band, is presented first. The key point for SIW equalizer is the introduction of surface resistance instead of the copper layer in a particular location. The working principle of SIW equalizer is discussed in detail. Then, the design method and the procedure are given and demonstrated. A good agreement between the measurement and the simulation indicates its excellent performances. For measurement results, the return losses are better than −18.8 dB for the SIW equalizing values of 2.8, 5.6, and 9 dB over the whole Ka-band. Based on the previous analysis of SIW equalizer, an extensible application in SIW attenuator operating in a millimeter- wave band has been presented first. Measurement results show that the attenuation levels of 5.45 ± 0.15, 10.6 ± 0.4, 21 ± 1, and 30.75 ± 1.45 dB have been achieved in a band of 24.8–38.4 GHz. Besides, the return losses are better than −20 dB in the same frequency band. [ABSTRACT FROM AUTHOR]

Ionic polymer metal composites (IPMCs) were discovered about twenty five years ago by Prof. Oguro and his team in Japan [1], and evidence about metalizing ionomer membranes dates even earlier [2]. Since their discovery, IPMCs have been the object of intensive research across the entire globe [3]–[5]. In its simplest form, an IPMC is constituted by a hydrated ionomeric membrane (that is, an electrically-charged polymer), which is neutralized by mobile counterions in a solution and plated by noble metal electrodes. IPMCs can be used as actuators and sensors, whereby a voltage applied across the electrodes will elicit mechanical deformation, and an imposed mechanical deformation will induce a measurable voltage across the electrodes. [ABSTRACT FROM AUTHOR]