Bottom Plane Research Articles

A surface-to-surface transition based UWB bandpass filter with triple in-band notches

A Compact Ultra-Wideband (UWB) bandpass filter (BPF) designed using the surface-to-surface transition mechanism and with triple passband transmission zeros (TZs) is proposed. The geometry of basic structure consists of two microstrip lines placed facing each other on the top plane coupled with a short circuited co-planar waveguide (CPW) in the bottom plane. This basic architecture develops a UWB response with two transmission zeros (TZs) at lower/higher passband edges, which exhibits good frequency characteristics. Later, complementary folded split ring resonator (CSRR), split ring resonators (SRRs) and folded split ring resonators (FSRRs) are appended to the basic architecture to generate triple passband notches so as to circumvent interferences. A hardware prototype is finally developed and its response tested against the simulated data. The triple-notched BPF is compact covering a physical area of only 14 × 11.4 mm2.

Friction Induces Anisotropic Propulsion in Sliding Magnetic Microtriangles.

In viscous fluids, motile microentities such as bacteria or artificial swimmers often display different transport modes than macroscopic ones. A current challenge in the field aims at using friction asymmetry to steer the motion of microscopic particles. Here we show that lithographically shaped magnetic microtriangles undergo a series of complex transport modes when driven by a precessing magnetic field, including a surfing-like drift close to the bottom plane. In this regime, we exploit the triangle asymmetric shape to obtain a transversal drift which is later used to transport the microtriangle in any direction along the plane. We explain this friction-induced anisotropic sliding with a minimal numerical model capable to reproduce the experimental results. Due to the flexibility offered by soft-lithographic sculpturing, our method to guide anisotropic-shaped magnetic microcomposites can be potentially extended to many other field responsive structures operating in fluid media.

Super‐UWB MIMO antenna with high isolation

AbstractA 1 × 2 multiple‐input multiple‐output (MIMO) antenna with super‐ultra wideband (super‐UWB) operation and high isolation is proposed. The antenna element has an eye‐shape radiator fed by a tapered shape feedline on the top side and a defected ground structure etched on the bottom ground plane. A high isolation between two radiators is achieved by introducing a T‐shape and two small arm shape stubs at the center of the ground plane. The proposed design was verified by a fabricated prototype and measurement. The measured results show that the MIMO antenna achieves impedance bandwidth of 3 ~ 45 GHz, isolation of 21 dB, and a peak gain of 10.1 dBi. The envelope correlation coefficient is less than 0.02. The overall size of the design is only 0.26λ0L × 0.3λ0L (λ0L is the free space wavelength at 3 GHz).

Design of Wideband Circular-Slot Antenna for Harvesting RF Energy

The design of a wideband circular-slot antenna for RF signal harvesting is reported in this work. The proposed design frequency range accommodates the leading contributors to the available RF signals accessible by the RFEH node. These widely utilized frequency bands comprise GSM1800, UMTS2100, Wi-Fi2.450, and LTE2600. The antenna geometry comprises circular-ring radiating component filled with two orbital circular and rectangular slots. At the bottom plane, a pair of rectangular and semirectangular-circle slits are integrated. The antenna presented is designed on a double layer of 1.6 mm high FR-4 substrate. The source antenna achieved a simulated and measured impedance bandwidth (BW) of 1.510 and 1.590 GHz, amounting to 68% and 73% fractional BW (FBW), covering -10 dB reflection coefficient (|S11|) between 1.640 to 3.150 GHz and 1.550 to 3.140 GHz, in that order. The wideband circular-slot source antenna realized a maximum measured gain of 1.88, 2.13, 2.81, 3.22, and 4.32 dBi for 1.800, 2.100, 2.450, 2.650, and 3.20 GHz, respectively. The proposed design dimension on the printed board is 0.61 λ g × 0.70 λ g . The improved antenna gain is obtained from a circular parasitic patch coupled to the defected ground structure (DGS) for better RF energy harvesting in an ambient environment.

A miniaturized mm‐wave leaky wave antenna based on CRLH slow‐wave SIW for symmetric wide angle beam scanning

In this article, a novel miniaturized wide beam scanning range multi-layered mm-wave leaky-wave antenna (LWA) based on slow-wave (SW) substrate-integrated waveguide (SIW) is presented. The SW effect is introduced by loading conventional SIW with internal metalized blind vias connected to the bottom ground plane. The SW effect in the SIW structure causes the separation of the electric and magnetic field components in the structure which leads to the reduction in lateral dimensions of the proposed topology by 35% as compared to the conventional SIW. The proposed LWA exhibits a miniaturized volume of 6.6 × 0.41 × .07 λ3. The radiation in the proposed design is realized by introducing U-shaped slots in the unit cell of the SW-SIW structure. Experimental results show that the proposed SW-SIW LWA achieves almost symmetric and continuous beam scanning from −48° to 52° including the broadside direction within the impedance bandwidth of 23.7–28.1 GHz. The proposed antenna achieves a peak gain of 14.52 dBi and the half-power beamwidth of LWA is as low as 10°. The proposed antenna also exhibits radiation efficiency of above 90% within the bandwidth. The proposed design can be a potential candidate for mm-wave frequency beam scanning applications.

Modeling the deformation and breakup of a surfactant-coated droplet on a roughness solid surface in shear flow

A surfactant-coated droplet attached to a rough wall subjected to shear flow is investigated using a coupled lattice Boltzmann with the finite difference method, where a contact angle hysteresis model is introduced into the method to characterize the surface roughness. The method is first verified by the equilibrium contact angle of a semi-circular droplet setting on the bottom plane. It is then adopted to explore the surfactant role on the droplet motion and deformation on a rough wall with two representative hysteresis windows. For the hysteresis window of (0°, 180°), i.e., the contact line remains pinned, the addition of surfactants first promotes droplet deformation and then hinders droplet deformation with increasing effective capillary number. However, for the hysteresis window of (70°, 110°), the addition of surfactants always promotes droplet motion and deformation. Finally, the surfactant role on droplet breakup is presented. For the hysteresis window of (0°, 180°), the addition of surfactants hinders droplet breakup. However, for the hysteresis window of (70°, 110°), the addition of surfactants promotes droplet breakup.

Influence of the thermodynamic properties of the Internal Occulter inside the coronagraph on coronal observations.

To detect good quality coronal spectra images, the continuous optimization of stray light suppression techniques for coronagraphs is required. The internal occulter (IO) serves as the main tool for the Internally Occulted Coronagraph to suppress the direct light from the photosphere layer, and thermal stress displacements with thermodynamic properties will overcover the information of the internal corona. In this paper, a reflective distribution function model is established according to Kirchhoff's principle which is based on a ground-based Lyot coronagraph, the aperture is 200 mm, detection wavelength is 637.4 nm (Fe X) and the work field range is ±1.05-2.0 RS (RS is the solar radius), thus the absorption rate is inverted. The irradiance at different positions received by the ground is simulated, and then the temperature change of the occulter during the time of the strongest radiation is calculated. The thermal stress displacement change of the two materials was analyzed by the finite element method. Comparison of the experiment shows that the displacement variation of the conical bottom plane results in losing 0.34% RS corona information for the 2a12-t6 aluminum alloy, and losing 0.11% RS coronal information for oxygen-free copper. This way provides a new idea for the thermodynamic modeling of the IO and the direct light suppression technology in the coronagraph.

Flexible interconnected 4-port MIMO antenna for sub-6 GHz 5G and X band applications

A flexible 4-port 4-element interconnected MIMO antenna is proposed for Sub-6 GHz 5G and X-band applications. The 4-element structure attains a low profile of 0.612λ2 (at 3.34 GHz) through careful placement of antenna elements. The elementary antenna top side is formed of an inverted E and inverted L-shaped conductive structure attached to both sides of the central feed line. Two hollow tilted square-shaped assemblies are added horizontally with the inverted L for performance enhancement. The bottom plane consists of a truncated ground with a vertical stub on the side for achieving wideband performance. The MIMO configuration along with polarization diversity is attained by positioning the elementary antenna symmetrically in a sequential rotational manner. The interconnection between ground planes is ensured by placing an I-shaped strip which is further modified by adding a slotted rectangular stub on the central vertical line for better isolation. The flexible antenna demonstrated minimum efficiency and maximum gain of 70% and 4 dBi, respectively in addition to accomplishing a bandwidth of (40%) 3.34–5.01 GHz and (3.31%) 8.9–9.2 GHz while satisfying the MIMO diversity performance in terms of envelope correlation coefficient (ECC) < 0.17. Finally, the antenna performance in terms of S-parameters and MIMO diversity parameters are tested by bending the antenna along the X and Y axis that demonstrated decent performance thus making the MIMO antenna worthy for its use in Sub-6 GHz 5G and X Band Applications with tight space requirements.

Decomposition of 2,4,6-trinitrotoluene (TNT) and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) by Fe13O13 nanoparticle: density functional theory study.

To obtain more insight into the mechanisms of the decomposition of energetic compounds, we performed a computational study of the interaction of Fe13O13 nanoparticles with two energetic molecules such as 2,4,6-trinitrotoluene (TNT) and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO). The density functional theory using M06-2X, B3LYP, and BLYP density functionals was applied. We found that the reactivity of these molecules strongly depends on the place of adsorption (so-called top and bottom planes of Fe13O13). Namely, only the interaction with the bottom plane results in the thermodynamic characteristics of the decomposition that provide a medium reaction rate for the studied processes. Several pathways for such decomposition were found. One of them is the inter-complex oxygen transfer of nitro-group oxygen to Fe13O13. This pathway results in the formation of adsorbed nitroso compounds. The second pathway describes a more complex decomposition that includes the transfer of the nitro-group oxygen accompanied by the hydrogen transfer. In all cases, the interaction of energetic molecules with Fe13O13 nanoparticles takes place along with a barrier-less electron transfer from Fe13O13 to TNT or NTO species.

Velocity and pressure functions of an oscillating flow in a circular Hele-Shaw cell

In this study, we have investigated the form of velocity and pressure functions of a fluid oscillating between two parallel glass sheets that form a circular Hele-Shaw cell. The flow has been considered to be radial, incompressible and laminar. The time-dependent Navier-Stokes equation has been solved in cylindrical coordinates using Fourier transform, and the oscillating flow velocity across the thickness of the cell has been obtained at different times. The flow velocity function in the unsteady state is related to the vertical component of the coordinates in the form of parabolic functions and also to the inverse of the radial component. The time dependence appears as a simple harmonic with a frequency equal to the oscillation frequency. The velocity of the flow is maximum at the middle of the cell along its height and gradually decreases from the middle towards the top or bottom plane and reaches zero. Pressure does not depend on the height and changes logarithmically with the radius. The dependence of pressure on time is also a simple harmonic with the external frequency, but it has a phase shift with respect to the velocity.

Verification of Longitudinal Level Irregularity Suppression Effect at the Structural Boundary by Ballasted Ladder Track

The ladder sleeper, which is a type of longitudinal sleeper with long beams in the longitudinal direction of the rail, was developed for the maintenance-labor saving of ballast tracks. In this study, to quantify the load distribution performance of the ladder sleepers at the structural boundary, full-scale model tests were conducted to quantify the vibration transmission reduction effect of the ladder sleepers. Following that, numerical experiments were carried out using a three-dimensional numerical analysis model and it was revealed that the ladder sleeper can reduce the pressure on the sleeper bottom plane by approximately 70% when compared to conventional prestressed concrete sleepers. Furthermore, when laying the ladder sleeper at the structural boundary, it was shown that laying across the structural boundary may be more effective in reducing the pressure on the sleeper bottom plane than laying it in front of the structural boundary. Finally, ladder sleepers were installed on the commercial line and long-term measurements of the longitudinal level irregularity verified the effect of suppressing the longitudinal level irregularity of the ballasted ladder track.

Experimental investigation on the alteration of natural frequency of a flexible pipe adjacent to a bottom plane with the consideration of pipe-plane impact

The obtainment of natural frequencies of near-wall submarine spanning pipelines is the essential basis of the prediction of vibration response and fatigue life. Nevertheless, published literature has not yet taken into account the pipe–wall impact in free attenuation tests and has not offered a method to identify the impact frequency from natural ones. Therefore, the present work experimentally investigates the free attenuation response of a horizontal flexible pipe positioned adjacent to and parallel to a bottom plane with the consideration of pipe–wall collision, aiming to figure out the influences of wall proximity and wall impact on natural frequencies and to provide a measurement method for attenuation tests of such fluid–flexible-structure–solid interaction issues. The experimental results indicate that setting a horizontal initial displacement is easier than setting a vertical initial displacement to get the vertical natural frequencies of a near-wall flexible pipe. The natural frequency of near-wall flexible pipe is a function of the added mass coefficient, decreasing with the reduction of pipe-to-wall distance. Three main alterations of natural frequencies are introduced in the presence of pipe–wall impact. With the imposition of a horizontal initial displacement, the impact and natural frequencies can be distinguished from the wavelet time-frequency contours because of their participations during different time periods.

Analytical and Numerical Estimation of Fracture Initiation and Propagation Regions around Large-Diameter, Deep Boreholes for Disposal of Long-Lived Intermediate-Level Waste

The safety of high-level radioactive waste disposal has been studied across the world considering mined geologic repositories. Here, we introduce large-diameter, deep borehole disposal as one of the potential solutions for small volumes of long-lived intermediate-level waste (ILW). The short- and long-term stability of deep disposal boreholes is critical for environmental safety and public health. In this paper, we first use a recently revisited extensional strain criterion for fracture initiation and apply analytical solutions of a two-dimensional stress model to predict the fracturing region around a 2 km deep and 0.7 m diameter disposal borehole. Analytical solutions of fracture initiation are compared with results from the numerical simulator FRACOD, while the latter model also predicts dynamic effects such as fracture propagation. Both analytical and numerical methods predicted similar fracture initiation characteristics around the minor horizontal compressive stress springline, consistent with literature data. Numerical results showed deeper fracturing zones than those predicted by analytical solutions, mainly because the analytical predictions provide static snapshots under specific given conditions, while the numerical model calculates additional dynamic effects of fracture propagation. Including stress dynamics is shown to further weaken the rock around the borehole. At the bottom plane of the borehole, three-dimensional numerical simulations showed the development of fracturing zones around the major horizontal compressive stress springline. Borehole stability analyses are essential to plan the safe operation of drilling operations while also giving insights as to what borehole depths are more prone to fracturing and hence potentially less suitable as a waste disposal zone.

Chiral Helices Formation by Self-Assembled Molecules on Semiconductor Flexible Substrates.

The crystal structure of atomically defined colloidal II-VI semiconductor nanoplatelets (NPLs) induces the self-assembly of organic ligands over thousands of square nanometers on the top and bottom basal planes of these anisotropic nanoparticles. NPLs curl into helices under the influence of the surface stress induced by these ligands. We demonstrate the control of the radii of NPL helices through the ligands described as an anchoring group and an aliphatic chain of a given length. A mechanical model accounting for the misfit strain between the inorganic core and the surface ligands predicts the helices' radii. We show how the chirality of the helices can be tuned by the ligands anchoring group and inverted from one population to another.

Same-Sense Circularly Polarized Grid-Slotted Patch Antenna With Wide Axial Ratio Bandwidth

In this communication, the same-sense circularly polarized grid-slotted patch antenna with wide axial ratio bandwidth (ARBW) is proposed. The rectangular grid-slotted patch on top and bottom planes are excited through flipped Z-shaped slots pair using a stripline feed to generate same-sense circular polarization with wider ARBW. Characteristic mode analysis is used in the design of the antenna to analyze the desired orthogonal modes. Variations of the resonant frequencies, ARBWs and local minimas with the design parameters are discussed. The antenna has a 3 dB ARBW of about 21% from 4.07 to 5.02 GHz, with the realized gain ranging from 2 to 3.5 dBic.

Ceramic‐elements‐based distributed resonators and filters

The aim of this paper is to introduce a new family of low-profile resonators and filters that achieve high performance and low insertion loss without the need for post-production tuning. The new resonator is termed ceramic-element based distributed resonator and consists of a matrix of subwavelength-length ceramic posts connected in the inter-digital fashion to the top and bottom ground planes. Such a disposition of elements is beneficial for two main reasons. First, the frequency of operation of such a resonator becomes a function of its height, unlike in the case of standard ceramic resonators. Second, the ceramic element matrix performs inherent dimensional averaging, resulting in a filter that requires no post-production tuning. As a demonstrator of the proposed technology, a two-pole filter using a ceramic with a dielectric permittivity of 37 and a loss tangent of 0.0033 and operating at a centre frequency of 3.5 GHz was designed, fabricated and tested. The measured and predicted results are in excellent agreement and are extensively discussed.

Multilayered substrate‐integrated magnetoelectric dipole antenna with low profile and wideband

In this article, a multilayered substrate-integrated magnetoelectric dipole antenna with low profile and wideband is proposed. Based on the multilayered printed circuit board technology, the magnetoelectric dipole antenna is composed of four layers of substrate. By adopting rectangular window techniques, the impedance matching at the low-frequency band is improved and a low profile of 0.08λ0 (where λ0 is the free space wavelength of the center frequency) in height is achieved. A Γ-shaped meandering unit is also adopted to guide the electric current through the rectangular window and enhance the boresight radiation. Additionally, the antenna is fed by a 1/4 wavelength microstrip line on bottom plane to easily integrate to the front-side planar circuit. The transverse size of the proposed antenna is 100 mm*50 mm (0.8λ0*0.4λ0). Through simulation and optimization, the wideband, low profile, and unidirectional radiation characteristics are obtained simultaneously. The tested impedance bandwidth ranges from 1.92 to 3.15 GHz (48.5%) for voltage standing wave ratio (VSWR) < 2. The radiation property is also validated and the boresight mean gain is 5.1 dBi. Cross polarization level at boresight is lower than −25.15 dB. Both simulated and tested results agree well with each other.

A Numerical Study on the Exact Onset of Flow Instabilities in Thermo-Solutal Marangoni Convection Driven by Opposing Forces in a Half-Zone Liquid Bridge under Zero Gravity

The theoretical onset of the Marangoni convection instability occurring in a half-zone liquid bridge of the floating zone (FZ) growth of SixGe1–x has been investigated by numerical simulations. A half-zone model of the liquid bridge between a cold (bottom plane) and a hot (top plane) disk is considered. The highest Si concentration is on the top of the liquid bridge. Therefore, the driving forces for thermal and solutal Marangoni flows are in opposite directions in this configuration. The nonlinear equilibria and periodic orbits are obtained using the Newton–Krylov method, and their stability is analyzed with global linear stability analysis. A flow bifurcation analysis is conducted. The results show that when the solutal Marangoni number, MaC, ≤360, the primary flow bifurcation is from 2D axisymmetric to 3D steady flow. When MaC>360, the 2D axisymmetric flow becomes weakly periodic 2D axisymmetric, and eventually becomes chaotic. The critical thermal Marangoni number is monotonically increasing as MaC increases, and the flow is 2D axisymmetric when the solutal Marangoni forceis dominant. The stability evaluation for various thermal Marangoni number values at MaC=893 reveals that the onset of transition is from steady to periodic. However, the reverse transition does not occur at the same Marangoni number value. The simulation results show that the hysteresis behavior of the flow field exhibits an approximately 1% difference between two critical thermal Marangoni numbers. The present study suggests that the control parameters of FZ crystal growth should be smaller than the calculated critical values to avoid any flow-induced disturbances.

Carbon Nanotube Far Infrared Detectors with High Responsivity and Superior Polarization Selectivity Based on Engineered Optical Antennas.

Single-wall carbon nanotube (SWCNT) thin films are promising for sensitive uncooled infrared detection based on the photothermoelectric effect. The SWCNT film is usually shaped into a belt and diversely doped to form a p-n junction at the center. Under the illumination of a focused incident light, the temperature gradient from the junction to the contacts leads to photoresponse. When the SWCNTs are aligned in one direction, the photoresponse becomes polarization selective. Although a typical bowtie antenna can improve the responsivity and polarization extinction ratio by deep-subwavelength light focusing, the absolute absorptance of the junction region is only 0.6%. In this work, the antenna was engineered for a higher light coupling efficiency. By integrating a bottom metal plane at a specific distance from the SWCNT film and optimizing the antenna geometries, we achieved ultra-efficient impedance matching between the antenna and the SWCNTs, thus the absorptance of the junction region was further enhanced by 21.3 times and reached 13.5%, which is more than 3 orders of magnitude higher than that of the device without the engineered antenna. The peak responsivity was further enhanced by 19.9 times and responsivity reached 1500 V/W at 1 THz. The resonant frequency can be tuned by changing the size of the antenna. Over the frequency range of 0.5 THz to 1.5 THz, the peak responsivity was further enhanced by 8.1 to 19.9 times, and the polarization extinction ratio was enhanced by 2.7 to 22.3 times. The highest polarization extinction ratio reached 3.04 × 105 at 0.5 THz. The results are based on the numerical simulations of the light and the thermal fields.

3D magnetic buoyancy-driven flow of hybrid nanofluids confined wavy cubic enclosures including multi-layers and heated obstacle

This paper provides numerical simulations of the magnetic convective process based on buoyancy forces within three dimensional wavy cubic enclosures. The flow domain is partitioned into two layers specifically, a porous layer and a hybrid nanofluid layer. The upper and lower plans of the domain are adiabatic while the residual plans are mentioned to relatively low temperatures. The temperature disparity within the flow domain is a result of a rectangular heated area that is located in the bottom plane. The magnetic force is taken in the normal direction (Z-direction). As for the porous matrix, the Brinkman-extended non-Darcy model was chosen to simulate its effects. The method of solution is based on the Galerkin finite element, the outcomes are represented using various illustrations and tools. It is noticeable that changing the location of the heated area is a beneficial factor for this convective situation. Also, when Ha is altered from 0 to 100, a drop in values of the stream function is given up to 84.78%.