Simple Parallel Plate Research Articles

Evaluation of influence of wall roughness on wall turbulence using LES simulation with MSGD model for liquid Li flow inside two-staged contraction nozzle

ABSTRACT Liquid lithium (Li) jet is planned as a beam target in fusion neutron sources (FNSs), such as IFMIF, A-FNS and IFMIF-DONES. For the safety and the efficiency of such FNSs, the high-speed Li jet need to be kept stable. For investigation of the detailed flow pattern inside the Li jet, numerical approaches using CFD simulation have been required to evaluate it because of its opacity. As one of issues about the inner flow structure, the influence of wall roughness on the vortex structure and surface variation is concerned in long-term operation of actual FNSs. In our previous simulation, in order to consider wall roughness in LES simulation, MSGD model was adopted to ANSYS Fluent using User-Defined Function, and CFD simulation in a simple parallel plate flow was conducted to confirm the performance of MSGD model. In this study, firstly, MSGD model was verified by LES simulation of Li flowing on smooth and rough plates. After that, LES simulation with MSGD model for two-staged contraction nozzle, installed into Li loop of Osaka University, was conducted. It was found that MSGD model was valid and spectrum of velocity in roughness wall cases clearly had different behavior from that in smooth wall case.

Energy alignment manipulation at the C60/TiO2(110) interface using a blanket molecular dipole approach

Modifying the energy alignment between the frontier levels of a chromophore and the band edges of a semiconductor substrate using a “blanket layer” of molecular dipoles is explored. The electronic structure, measured with ultraviolet and x-ray photoemission spectroscopy, of C60 deposited directly onto the TiO2(110) surface is compared with that of C60 deposited onto the surface covered by a blanket layer of the custom-designed helical peptide Z-(Aib)6-Ipa, which has a large dipole moment of 18.6 D oriented along its molecular axis and pointing toward the substrate. The C60 HOMO level is shifted 600 meV to deeper binding energy in the presence of the blanket layer, in good agreement with what is expected from a simple parallel plate capacitor model. These results demonstrate a simple and versatile strategy for controlling energy level alignment at organic/inorganic interfaces.

Parallel‐plates‐based Dirac Leaky Wave Antennas

In this work, the authors experimentally show Dirac Leaky Wave Antennas (DLWAs) at upper microwave frequencies. For the first time, DLWAs are implemented using simple Parallel plate waveguide (PPW) technology, while yielding desirable radiation features and continuous beam scanning through broadside, as well as extremely low profile, with significant ease of fabrication, making them well suited for Ku band applications such as satellite communication, radar and emerging fifth-generation (5G). A planar Dirac photonic crystal in PPW is shown with a closed bandgap and linear dispersion around broadside. In this work, 1D and 2D PPDLWAs are designed that provide scannable fan and pencil beams, respectively, with a symmetric beamwidth. Phase and attenuation constants are controlled with unit cell dimensions to obtain a directive beam and scanning in a wide range of angles. For the 2D design, an appropriate wideband feeding network is designed that excites the antenna appropriately. The presented PPDLWAs operate with a peak gain of about 13 dB for the fan beam and 22 dB for the pencil beam, in the frequency range from 12 to 16 GHz.

An entertaining physics: On the possibility of energy storage enhancement in electrostatic capacitors using the compensational inductive electric field

In this work, we consider the possibility of energy storage enhancement in electrostatic capacitors using the compensational method. The essence of the proposed approach is the use of inductive voltage Vind to partially compensate the electrostatic voltage q/C produced by the electric charges on the capacitor plates. We hypothesize that it may be possible to increase the amount of charge stored on the plates before the breakdown and increase the energy stored in the capacitor using the compensational inductive voltage. There are several possible scenarios of manipulating the inductive voltage to increase the amount of energy released via the discharge. We also consider several electro-magnetic capacitors for practical utilization. Potentially, the energy per volume stored in a simple parallel plate capacitor may exceed that of gasoline. The physical limits and technological shortcomings of the proposed approach are also discussed.

Development and Assembly of a Flow Cell for Single‐Pass Continuous Electroorganic Synthesis Using Laser‐Cut Components

AbstractFlow electrolysis cells are essential for the scale up of synthetic organic electrochemistry. We have developed a simple and inexpensive parallel plate flow cell that can be easily assembled using a stack of laser‐cut Mylar foils, which act as gaskets, insulating material, interelectrode gap and flow channel. The ease with which the laser‐cutting pattern can be customized has enabled the development of interelectrode separators with mixing geometries, which improve the mass transfer and thus the current efficiency. The performance of the flow electrolysis cell has been evaluated using the anodic decarboxylative methoxylation of diphenylacetic acid as model transformation. Very high conversions and selectivities have been achieved with single‐pass processing, with nearly quantitative current efficiency in some cases.

Mechanics of reversible wrinkling in a soft dielectric elastomer.

A parallel array of wrinkles can be generated in a simple parallel plate capacitor arrangement with a soft dielectric elastomer plate constrained all around its periphery and coated with flexible electrodes. The direction of the wrinkles is predetermined and the phenomenon is reversible in a range of applied potentials. A model of the wrinkled plate as a prestretched neo-Hookean membrane with superposed small out-of-plane bending displacements yields good estimates of the potential range for wrinkling as well as the number of parallel wrinkles. The mechanics is controlled by the thickness and aspect ratios, prestretch, and a nondimensional electric potential.

Microwave pressure sensor based on transmission response of a quarter‐wavelength single stub microstrip line

AbstractA microwave pressure sensor based on variations in the transmission zero of a microstrip circuit is proposed in this article. The structure of the sensor is consisting of a microstrip line connected in parallel to a single stub, which the stub is terminated in a reactive load. When the length of stub is around quarter‐wavelength, the frequency of the transmission zero of microstrip line can be controlled by the reactance value. Therefore, by using a simple parallel plate capacitor as a transducer in which its capacitance is changed by the pressure, a microwave pressure sensor is realized. A prototype pressure sensor by using a circular‐shape parallel plate capacitor is designed and fabricated that the measurement results show a good linear variation of transmission zero with pressure with sensitivity of −0.57 MHz/kPa when the pressure changes from 0 to 466 kPa.

Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides.

The use of helical hexapeptides to establish a surface dipole layer on a TiO2 substrate, with the goal of influencing the energy levels of a coadsorbed chromophore, is explored. Two helical hexapeptides, synthesized from 2-amino isobutyric acid (Aib) residues, were protected at the N-terminus with a carboxybenzyl group (Z) and at the C-terminus carried either a carboxylic acid or an isophthalic acid (Ipa) anchor group to form Z-(Aib)6-COOH or Z-(Aib)6-Ipa, respectively. Using a combination of vibrational and photoemission spectroscopies, bonding of the two peptides to TiO2 surfaces (either nanostructured or single-crystal TiO2(110)) was found to be highly dependent on the anchor group, with Ipa establishing a monolayer much more efficiently than COOH. Furthermore, a monolayer of Z-(Aib)6-Ipa on TiO2(110) was exposed for different binding times to a solution of a zinc tetraphenylporphyrin (ZnTPP) derivative terminated with an Ipa anchor group (ZnTPP-P-Ipa). Photoemission spectroscopy revealed that ZnTPP-P-Ipa partly displaced Z-(Aib)6-Ipa, forming a coadsorbed monolayer on the oxide surface. The presence of the peptide molecular dipole shifted the HOMO levels of the ZnTPP group to lower energy by ∼300 meV, in accordance with a simple parallel plate capacitor model. These results suggest that a mixed-layer approach, involving coadsorption of a strong molecular dipole compound with a chromophore, is a versatile method to shift the energy levels of such chromophores with respect to the band edges of the substrate.

Influence of scan pattern and geometry on the microstructure and soft-magnetic performance of additively manufactured Fe-Si

The influence of geometry and scan pattern on the microstructure evolution and magnetic performance of additively manufactured Fe-3Si components was investigated. To reduce eddy current losses, novel geometries were designed and built and the microstructure and properties of these samples were characterized. The laser scan pattern was shown to strongly influence both the as-built grain structure and strength of the crystallographic texture, resulting in measurable changes in the as-built magnetic performance. In thin wall samples, heat treatment resulted in an increase in the maximum relative magnetic permeability and decrease in power losses in most samples, consistent with grain growth. However, decreases in the spacing between thin walls to increase the stacking factor of the cross-section was shown to result in unwanted electrical shorting between walls and an increase in eddy current losses. Compared to simple parallel plate construction and a mesh structure, a novel cross-section design based on the Hilbert space filling curve was found to produce the lowest power losses. The mechanisms behind these results were explored using a combination of heat conduction and electromagnetic simulations, providing a route for future component and process optimization.

Translational MEMS Platform for Planar Optical Switching Fabrics.

While 3-D microelectromechanical systems (MEMS) allow switching between a large number of ports in optical telecommunication networks, the development of such systems often suffers from design, fabrication and packaging constraints due to the complex structures, the wafer bonding processes involved, and the tight alignment tolerances between different components. In this work, we present a 2-D translational MEMS platform capable of highly efficient planar optical switching through integration with silicon nitride (SiN) based optical waveguides. The discrete lateral displacement provided by simple parallel plate actuators on opposite sides of the central platform enables switching between different input and output waveguides. The proposed structure can displace the central platform by 3.37 µm in two directions at an actuation voltage of 65 V. Additionally, the parallel plate actuator designed for closing completely the 4.26 µm air gap between the fixed and moving waveguides operates at just 50 V. Eigenmode expansion analysis shows over 99% butt-coupling efficiency the between the SiN waveguides when the gap is closed. Also, 2.5 finite-difference time-domain analysis demonstrates zero cross talk between two parallel SiN waveguides across the length of the platform for a 3.5 µm separation between adjacent waveguides enabling multiple waveguide configuration onto the platform. Different MEMS designs were simulated using static structural analysis in ANSYS. These designs were fabricated with a custom process by AEPONYX Inc. (Montreal, QC, Canada) and through the PiezoMUMPs process of MEMSCAP (Durham, NC, USA).

Understanding Dielectrics: Impact of External Salt Water Bath.

As predicted by the theory of super dielectric materials, simple tests demonstrate that dielectric material on the outside of a parallel plate capacitor dramatically increases capacitance, energy density, and power density. Simple parallel plate capacitors with only ambient air between the plates behaved as per standard theory. Once the same capacitor was partially submerged in deionized water (DI), or DI with low dissolved NaCl concentrations, still with only ambient air between the electrodes, the capacitance, energy density, and power density, at low frequency, increased by more than seven orders of magnitude. Notably, conventional theory precludes the possibility that material outside the volume between the plates will in any fashion impact capacitive behavior.

Further Study of the Sensing Ring Position on the Orifice-Type Capacitive Flow Sensor

The flow head of an orifice-type capacitive flow sensor for a conducting liquid consists of a vertically mounted metallic orifice plate in a horizontal pipeline made of insulating material and a rigidly grounded metallic ring or sensing ring placed surrounding the pipeline at a small distance from the orifice plate where the capacitance between the orifice plate and the sensing ring follows a linear relationship with flow rate as reported in the literature. In this paper, a further study on the effect of position of the sensing ring on the sensor capacitance has been carried out along with the modification of the simple parallel plate capacitance principle described in the earlier work by the real disk-type capacitance principle. From this paper, it has been observed that for any position of the sensing ring near the orifice plate, the sensor capacitance decreases linearly with the increase of flow rate and follows the modified capacitance principle similarly as that observed in earlier work. It has also been observed that the sensing ring distance-sensor capacitance product increases almost linearly with the increase of sensing ring distance. From the experimental study of the proposed orifice type capacitive flow sensors installed on two different pipelines, the said modified theory of the sensor appears to be verified in the present paper where the experimental results are reported.

Imaging Channel Connectivity in Nafion Using Electrostatic Force Microscopy.

Channel connectivity is an important material property that is considered in making higher-performance proton-exchange membranes. Our group has previously demonstrated that nearly 50% of the aqueous surface domains in Nafion films do not have a connected path to the opposite side of the membrane. These so-called "dead-end" channels lead to a loss in the conductance efficiency of the membrane. Understanding the structure of these dead-end channels is an important step in improving the conductance of the membrane. Although conductive atomic force microscopy is able to provide insight into the connected channels, it does directly report on the dead-end channels. To address this, we use electrostatic force microscopy (EFM) to probe channel connectivity in a Nafion thin film (100-300 nm) under ambient conditions. EFM provided an image of the capacitive phase shift, which is influenced by surface charge, dielectric permittivity, and tip-sample geometry. We studied several individual channels and measured the quadratic dependence of the EFM signal with the bias voltage. Applying a simple parallel plate model allowed us to assign differences in the EFM signal to particular channel shapes: connected cylindrical channels, dead-end cylinder channels, and bottleneck channels.

CMUTs with high-K atomic layer deposition dielectric material insulation layer.

Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (Six)Ny)) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2) such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD Six)Ny) and 100-nm HfO2) insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure.

Charge transfer of single laser crystallized intrinsic and phosphorus-doped Si-nanocrystals visualized by Kelvin probe force microscopy

Isolated intrinsic and phosphorus doped (P-doped) Si-nanocrystals (Si-NCs) on n- and p-Si substrates are fabricated by excimer laser crystallization techniques. The formation of Si-NCs is confirmed by atomic force microscopy (AFM) and conductive AFM measurements. Kelvin probe force microscopy (KPFM) is then carried out to visualize the trapped charges in a single Si-NC dot which derives from the charge transfer between Si-NCs and Si substrates due to their different Fermi levels. The laser crystallized P-doped Si-NCs have a similar Fermi level around the mid-gap to the intrinsic counterparts, which might be caused by the inactivated impurity atoms or the surface states-related Fermi level pinning. A clear rise of the Fermi level in P-doped Si-NCs is observed after a short time thermal annealing treatment, indicating the activation of dopants in Si-NCs. Moreover, the surface charge quantity can be estimated using a simple parallel plate capacitor model for a quantitative understanding of the KPFM results at the nanoscale.

The possibility of using a simple pulse mode parallel plate gas ionization chamber, without Frisch grid, both for energy estimation and Z-identification of moderate energy light heavy ions

This work explores theoretically the possibility of using a simple pulse mode parallel plate gas ionization chamber, having no Frisch grid, both for energy estimation and Z-identification of moderate energy light heavy ions. A mathematical expression for the energy of a heavy ion that enters into the ionization chamber through the cathode window and gets stopped in the sensitive volume is derived. An expression for a quantity similar to the range of the heavy ion is also derived. The plot of energy against this quantity is expected to give an opportunity to use a simple pulse mode parallel plate gas ionization chamber, without Frisch grid, as a light heavy Z-identifier. This work is based on the measurement of the electron collection pulse height and two other heights that the electron collection pulse reaches at two pre-calculated instants of time during the pulse rise time. A 'preset pulse clipper', the basic principle of which was proposed in a previous paper, may be used to measure the heights. Measuring heights - without using the 'preset pulse clipper' - by means of digital sampling and software based processing techniques may be possible if it be possible to determine the start time of the digitized pulse. One possible method for determining the start time of the digitized pulse is evaluated. The simulated plots, which represent the expected identification capability of this method, are made considering all the phenomena relevantly associated from physical point of view.

Development of a compact high current low emittance RF ion source

A 13.56MHz inductively coupled plasma based RF ion source is developed for production of high brightness focused ion beams of heavy gaseous elements for high speed milling and light ions for high speed imaging. In order to obtain ion beams with low emittance, no magnetic field of any kind is used in the ion source. However, to achieve the high plasma density, the plasma chamber volume is reduced to couple RF power as high as 8–12W/cm3 to the plasma. Measurements show that the normalized rms emittance of 0.6mA Ar1+ beam to be as low as 0.0075mm-mrad while it is 0.004mm-mrad for 1.2mA of ion beam from hydrogen plasma. With a simple parallel plate extraction system with an aperture of 2mm diameter, 80mA/cm2 of ion beam from hydrogen plasma could be extracted at 3.5kV extraction potential and 300W of RF power. The ion source has been operated with other heavy gases and results show that more than 1mA of xenon and krypton ion beam could easily be extracted at 5kV extraction potential and 200W of RF power. In this article, the capability of the ion source to produce high current, low emittance heavy as well as light ion beams is presented.

Simulating Capacitances to Silicon Quantum Dots: Breakdown of the Parallel Plate Capacitor Model

Many electrical applications of quantum dots rely on capacitively coupled gates; therefore, to make reliable devices we need those gate capacitances to be predictable and reproducible. We demonstrate in silicon nanowire quantum dots that gate capacitances are reproducible to within 10% for nominally identical devices. We demonstrate the experimentally that gate capacitances scale with device dimensions. We also demonstrate that a capacitance simulator can be used to predict measured gate capacitances to within 20%. A simple parallel plate capacitor model can be used to predict how the capacitances change with device dimensions; however, the parallel plate capacitor model fails for the smallest devices because the capacitances are dominated by fringing fields. We show how the capacitances due to fringing fields can be quickly estimated.

3-D numerical analysis of EHD turbulent flow and mono-disperse charged particle transport and collection in a wire-plate ESP

The present study attempts to develop a detailed numerical approach and a simulation procedure to predict the motion of gas, ions and particles inside a simple parallel plate channel containing a single corona wire. A hybrid Finite Element (FEM)-Flux Corrected Transport (FCT)-Finite Volume (FVM) method is used: the FEM–FCT numerical algorithm is applied for modeling the steady-state corona discharge, while the turbulent gas flow and the particle motion under electrostatic forces are modeled using the commercial CFD code FLUENT. Calculations for the gas flow are carried out by solving the Reynolds-averaged Navier–Stokes equations and turbulence is modeled using the k– ɛ turbulence model. An additional source term is added to the gas flow equation to include the effect of the electric field, obtained by solving a coupled system of the electric field and charge transport equations using User-Defined Functions (UDFs). The particle phase is simulated based on the Lagrangian approach, where a large number of particles is traced with their motion affected by the gas flow and electrostatic forces using the Discrete Phase Model (DPM) in FLUENT. The developed model is useful to gain insight into the particle collection phenomena that take place inside an ESP.

Aluminum oxynitride dielectrics for multilayer capacitors with higher energy density and wide temperature properties

Amorphous aluminum oxynitride (AlON) possesses unique properties of high dielectric strength, high resistivity, low loss, high decomposition temperature, chemical inertness, and high thermal conductivity. These properties make it a candidate for a next generation capacitor dielectric. DC pulsed magnetron reactive sputtering is used to produce amorphous AlON films on various substrates. Dielectric properties are optimized by adjusting DC power, pulse frequency, total pressure, substrate temperature, and gas ratio. Simple parallel plate structures are utilized to characterize the dielectric properties. Clearable electrodes are evaluated in device performance. Defects cleared without significant loss of capacitance. Temperature dependent dielectric properties were evaluated from − 200 °C to + 400 °C. Stacked multilayer capacitor device is developed for high energy density and wide temperature applications.