Coaxial Devices Research Articles

Radially-azimuthally discretized blade-element momentum theory for skewed coaxial turbines

Marine hydrokinetic energy from rivers, tides, and ocean currents is largely underutilized. Dual rotor coaxial turbines can harness this energy more effectively than single-rotor designs – even more so when the turbine orientation is skewed against the flow. A novel blade-element momentum theory (BEMT) model which incorporates radial and azimuthal discretization, RAD-BEMT, has been developed to explicitly incorporate the effects of nonuniform inflow conditions into turbine. By compounding RAD-BEMT with a streamtube mass continuity relationship and generator configuration behavior, a solution scheme to determine the power of a coaxial rotor system in skew was developed – removing simplifying assumptions utilized in previous literature. This generalized methodology was validated against experimental data for coaxial turbines in water and air. RAD-BEMT has established a low-order foundation to analyze the distributions of loading, efficiency, and local performance, amongst other metrics, of coaxial or single rotor devices in complex inflows. This foundation can support early prototyping for dynamics and control, minimizing the need for complex computational techniques like CFD. A case study of a coaxial turbine geometry was performed with the RAD-BEMT solution scheme to demonstrate its application and the insights it can provide for coaxial turbine design.

Finite-element Adaptive Meshing Statistics of Liquid Crystal Coaxial Phase Shifters for mmW Electronics and THz Photonics Beyond Display: A Comparative Study

Sub-mmW and THz frequencies offer ultra-high-speed communications for next-generation 5G/6G networks, wherein research advancing the understanding will benefit the electronics and photonics community. Specifically, meshing resolutions across varying frequency ranges and material properties are central to the solution accuracy, reliability, and cost (memory and time) of computational mmW and THz simulations, particularly for the emerging reconfigurable coaxial phase shifters employing nematic liquid crystals (LCs) as tunable media. In the present study, a comparative meshing statistics analysis is conducted for two devices designed for 60 GHz and 0.3 THz, respectively. Each design features two distinct tuning states (LC permittivity of 2.754 and 3.3, respectively), all pertinent to the coaxial TEM (Transverse Electromagnetic) mode. By quantifying the broadband meshing and solution statistics of diverse frequencies and dielectric tuning states for the first time, we establish memory-conserving computational metrology involving reconfigurable coaxial devices operationalized with LC-filled tunable dielectrics tailored for mmW electronics and THz photonics. Full Text: PDF References M. Makowski, I. Ducin, K. Kakarenko, J. Suszek, A. Kowalczyk, "Performance of the 4k phase-only spatial light modulator in image projection by computer-generated holography", Phot. Lett. Poland 8, 1 (2016). CrossRef J.F. Li, H.R. Li, "Liquid Crystal-Filled 60 GHz Coaxially Structured Phase Shifter Design and Simulation with Enhanced Figure of Merit by Novel Permittivity-Dependent Impedance Matching", Electronics 13, 3 (2024). CrossRef J.F. Li, H.R. Li, "Modeling 0.3 THz Coaxial Single-Mode Phase Shifter Designs in Liquid Crystals with Constitutive Loss Quantifications", Crystals 14, 4 (2024). CrossRef J.F. Li, D.P. Chu, "Liquid Crystal-Based Enclosed Coplanar Waveguide Phase Shifter for 54–66 GHz Applications", Crystals 9, 12 (2019). CrossRef Z. Cendes, "The development of HFSS", USNC-URSI Radio Science Meeting (Fajardo, IEEE 2016). CrossRef T. Vaupel, "Accuracy And Modeling Improvements For An Integral Equation Framework Applied To Thin Layer Microstrip And Substrate Integrated Waveguide (Siw) Structures", EuCAP (Copenhagen, IEEE 2020). CrossRef L.J. Jiang, W.C. Chew, "Low-frequency fast inhomogeneous plane-wave algorithm (LF-FIPWA)", Microwave Opt. Tech. Lett. 40, 2 (2004). CrossRef J. Zhu, D. Jiao, "Eliminating the Low-Frequency Breakdown Problem in 3-D Full-Wave Finite-Element-Based Analysis of Integrated Circuits", IEEE Trans. Microw. Theory Tech. 58, 10 (2010). CrossRef

103 A Bifurcation Model Predicts Intravascular Catheter Herniation When Using Transradial Access in Neuroendovascular Procedures

INTRODUCTION: The speed and safety of acute ischemic stroke interventions can be improved with catheter-based revascularization performed via the transradial access versus the traditional transfemoral access. A critical source of delay and procedural failure is a phenomenon known as herniation where the catheter system suddenly buckles and deviates from the intended endovascular pathway as the surgeon attempts to track one device over or through another around a tight bend. METHODS: Recent modeling work suggests that herniation is associated with a bifurcation in strain energy. We hypothesized that herniation could be predicted by modeling the strain energy stored in a catheter based on its flexural rigidity and the vascular anatomy. To test our hypothesis, we developed a computational model using finite element analysis and an experimental benchtop model using 3D-printed patient-specific aortic arches. Our mathematical model was validated in vivo using observational data derived from patient and porcine endovascular surgeries. RESULTS: Vascular geometry and flexural rigidity were used to derive the bifurcation condition and predict catheter stability versus instability (herniation). Catheter instability criterion was predictive of herniation in our computational model (sensitivity 100.0%, PPV 93.5%, NPV 100.0%); experimental ex vivo model (sensitivity 92.3%, PPV 89.6%, NPV 90.0%); patient in vivo model (sensitivity 100.0%, PPV 80.0%, NPV 100.0%); and porcine in vivo model (sensitivity 100%, PPV 100%, NPV 100%). CONCLUSIONS: We validated a predictive model of catheter herniation based upon the hypothesis that bifurcation in strain energy drive the phenomenon. Key factors in the model are the curvature of the vascular pathway and the flexural rigidity of the coaxial devices. Results suggest that strategic selection of catheters and wires based on their known flexural rigidity can be used to prevent the bifurcation in strain energy that causes herniation.

Characterizing S-Parameters of Microwave Coaxial Devices With up to Four Ports at Temperatures of 3 K and Above for Quantum Computing Applications

Characterizing <i>S</i>-Parameters of Microwave Coaxial Devices With up to Four Ports at Temperatures of 3 K and Above for Quantum Computing Applications

Automated catheter segmentation and tip detection in cerebral angiography with topology-aware geometric deep learning

BackgroundVisual perception of catheters and guidewires on x-ray fluoroscopy is essential for neurointervention. Endovascular robots with teleoperation capabilities are being developed, but they cannot ‘see’ intravascular devices, which precludes artificial...

Solution of an Electrodynamic Problem for a Homogeneous Equivalent Segment of a Coaxial Load, Considering Heat Losses in the Conductors

Mathematical aspects of solving an electrodynamic problem in the field of designing coaxial devices in the microwave range are considered. The solution of the electrodynamic problem for a homogeneous equivalent segment of a coaxial load in the single-mode approximation, considering the heat losses in the central and outer conductors, was obtained. A mathematical model of the microwave load, linking the high-frequency and design-technological parameters of the device, was built. To refine the model, we consider second-order effects associated with considering inhomogeneities that occur in places where the cross-section of the coaxial structure changes. The design of the 50-Ω load and the results of its experimental investigation are presented for comparison with theoretical calculations.

A Novel Mode-Matching Formulation of Multifurcated Waveguide Junctions

In this paper, we present a mode-matching-based formulation for the electromagnetic analysis of multifurcated waveguide problems, that is, the junction of a number of input waveguides with an output region of larger cross-section area. A generalized scattering matrix (GSM) representation is obtained for relating the forward and backward modal field amplitudes in each of the waveguides in terms of coupling integrals representing the conservation of the reaction of the electromagnetic fields. Numerical results for several multifurcated coaxial waveguide devices are provided to validate the formulation. Comparisons against the finite-element method demonstrate that the present approach can accurately model multifurcated waveguide problems. The method introduced here provides useful matrix formulas that allow us to model multi-port waveguide devices by reusing well-known coupling integrals of two-port problems.

Size control of shape switchable micronetworks by fast two-step microfluidic templating

Shape-memory polymer micronetworks (MN) are micrometer-sized objects that can switch their outer shape upon external command. This study aims to scale MN sizes to the low micrometer range at very narrow size distributions. In a two-step microfluidic strategy, the specific design of coaxial class capillary devices allowed stabilizing the thread of the dispersed phase to efficiently produce precursor particles in the tip-streaming regime at rates up to ~ 170 kHz and final sizes down to 4 µm. In a subsequent melt-based microfluidic photocrosslinking of the methacrylate-functionalized oligo(ɛ-caprolactone) precursor material, MN could be produced without particle aggregation. A comprehensive analysis of MN properties illustrated successful crosslinking, semi-crystalline morphology, and a shape-switching functionality for all investigated MN sizes (4, 6, 9, 12, 22 µm). Such functional micronetworks tailored to and below the dimension of cells can enable future applications in technology and medicine like controlling cell interaction.Graphic abstract

Measurement methods and mathematical model of main characteristics of waveguide-coaxial connectors

Modern complex microwave radio electronic systems may use functional devices implemented on different types of transmission lines. In order to connect such devices to each other to form antenna feed system, the following three types of special connectors can be used: coaxial, waveguide, and combined microwave devices based on waveguide and coaxial segments. The main electrical characteristics of waveguide coaxial connectors (WCC) are the losses introduced by the device to the antenna feed and matching with the regular microwave path (voltage standing-wave ratio, VSWR). Standard methods and standard equipment used to measure the characteristics of coaxial or waveguide connectors cannot be applied to WCCs. This article proposes a method designed to measure the main characteristics of waveguide-coaxial connectors and presents their mathematical model (wave matrices). The proposed methods of measuring microwave characteristic are demonstrated on the example of waveguide coaxial connectors of longitudinal coaxial type. It should be noted that the proposed technique has been experimentally tested on a number of specific devices. Not only the waveguide coaxial connectors have been studied in different frequency ranges (waveguide sizes from 23×5 to 58×25 mm), but also with different coaxial channel designs (sizes 3.5/1.52; 6.0/2.6 and 7.0/3.04 mm). The proposed method provides replicable measurements results of the characteristics of waveguide coaxial connectors, which confirms its reliability.

A Six-Degree-of-Freedom Compliant Parallel Platform for Optoelectronic Packaging

Optoelectronic packaging is an important component of optical communication systems. However, it is a challenge for the packaging equipment to simultaneously have multiple degrees of freedom (DOF), wide range, and high precision. In this article, a six-degree-of-freedom (6-DOF) compliant parallel platform with all these features is presented. This platform has a parallel basic structure with large-stroke flexible joints. Based on elastokinematic analysis, the inverse kinematics solution of the platform is derived, and the effectiveness of the platform is proved by analyzing the 6-DOF motion via finite element analysis. The reachable workspace of the platform is analyzed, and its solution process is simplified using the inverse distance weighted method. Furthermore, a prototype of the proposed platform is presented and its accuracy is evaluated through experiments. Error compensation is used to significantly improve the motion accuracy of the platform. A closed-loop control that uses optical power meters instead of a multi-DOF detection device is proposed for optoelectronic packaging. The performance of the prototype applied to the packaging of coaxial optoelectronic devices is also demonstrated by experiments. The results demonstrate that the 6-DOF compliant parallel platform can successfully carry out the optical alignment of optoelectronic devices.

An improved corrugated waveguide mode purifier for TEM output in a V-band overmoded coaxial millimeter-wave oscillator

In the overmoded microwave sources, there inevitably exist multi-modes in the output microwave, so it needs to be purified to obtain the single mode output. However, due to the large longitudinal size, the traditional concave-type purifier is not suitable for coaxial devices with large overmoded ratio. The present paper proposes an improved convex-type purifier based on the coupled wave equations. With this purifier, 99.98% TEM mode can be gained effectively under the conditions of diode voltage 355 kV and beam current 3.0 kA. Compared with the traditional concave-type converter, the improved purifier has the higher coupling coefficient and its longitudinal size can be reduced by 40%.

AV-Band Overmoded Coaxial Millimeter-Wave Oscillator Based on a New Method of Asymmetric Modes Suppression

In the design of the coaxial millimeter-wave Cerenkov devices due to the low starting current and high temporal growth, asymmetric quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v1</sub> modes are always preferentially excited. This article proposes a new method of hybrid modes coupling to suppress the asymmetric modes. The results show that when the quasi-TEM (N - 1)π/N mode couples with the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> (N - 3)π/N mode, the asymmetric modes can be suppressed effectively. The external Q-factor, electric field distribution, and the beam conductance of the hybrid modes are analyzed theoretically to explain the mechanism of the asymmetric modes suppression. According to this method, a coaxial V-band millimeter-wave oscillator is proposed. The 3-D particle-in-cell simulation results show that the symmetric modes are generated and all the asymmetric modes are suppressed successfully. When the diode voltage is 355 kV and beam current is 3 kA, the dominant frequency is 62.6 GHz and the output power is 322 MW, corresponding to a beam-wave conversion efficiency of 30.2%.

Research on Shielding Effectiveness Calculation Method of Electromagnetic Shielding Materials

Electromagnetic shielding materials are widely used in engineering. Shielding effectiveness is an important index to measure the shielding effect of electromagnetic shielding materials. A method for calculating the shielding effectiveness of electromagnetic shielding materials is discussed in this paper. This method applies the small reflection theory in transmission line theory. Two kinds of materials are selected as samples. Firstly, the shielding performance is calculated by calculation. Then, shielding performance was measured using a network analyzer and coaxial devices. By comparing the above two results, the feasibility of this method is verified. By using this method, the shielding performance with acceptable accuracy can be obtained when the electromagnetic parameters of the material are known. Thus, the limitation for the application of electromagnetic shielding materials is reduced.

Recent Advances in Fiber-Shaped Supercapacitors and Lithium-Ion Batteries.

The rapid development in wearable electronics has spurred a great deal of interest in flexible energy storage devices, particularly fiber-shaped energy storage devices (FSESDs), such as fiber-shaped supercapacitors (FSSCs) and fiber-shaped batteries (FSBs). Depending on their electrode configurations, FSESDs can contain five differently structured electrodes, including parallel fiber electrodes (PFEs), twisted fiber electrodes (TFDs), wrapped fiber electrodes (WFEs), coaxial fiber devices (CFEs), and rolled electrodes (REs). Various rational methods have been devised to incorporate these fiber-shaped electrodes into multifunctional FSESDs, including fiber-shaped supercapacitors, lithium-ion batteries, lithium-sulfur batteries, lithium-air batteries, zinc-air batteries, and aluminum-air batteries. Although significant progress has been made in FSESDs, it remains a major challenge to make high-performance fiber-shaped devices at low cost. A focused and critical review of the recent advancements in fiber-shaped supercapacitors and lithium-ion batteries is provided here. The pros and cons for each of the aforementioned electrode configurations and FSESDs are discussed, along with current challenges and future opportunities for FSESDs.

Effect of device geometry on droplet size in co-axial flow-focusing microfluidic droplet generation devices

The Co-axial Flow Focusing (CFF) technique is an established microfluidic method for the generation of micro-droplets. It consists of a nozzle co-axially aligned in a (circular cross-section) channel with a downstream orifice. The continuous-phase (c-phase) fluid in the orifice is used to shear off droplets of the dispersed-phase (d-phase) fluid ejected from the nozzle. Circular cross-section CFF devices are preferred due to their simpler fluid hydrodynamics, but not studied extensively as compared to rectangular channels. Understanding the effect of various parameters such as the channel design and fluid properties in CFF requires the development of reliable computational models. In this paper, the effects of multiple local geometries on droplet formation in a microfluidic CFF device were investigated numerically with experimental validations. The geometries included the d-phase nozzle inner diameter, nozzle tip distance from the c-phase channel orifice, and the inner diameter and length of the flow-focusing orifice. Our model is able to successfully predict the effects of these geometrical parameters on the droplet size for a wide range of c-phase flow rates spanning both the dripping and the jetting flow regimes, with an error range of 3–6%. Based on the simulation results, the droplet size is strongly dependent on the c-phase flow rate and the sizes of both the dispensing nozzle and the flow-focusing orifice. The effects of nozzle-to-orifice distance and the length of the orifice on the droplet size were not as pronounced in the range of the simulated c-phase flow rates. Our model can be used for the design and fabrication of CFF devices which yield predetermined droplet sizes with high precision.

Characterisation of a small electrode HPGe detector

© 2019 Elsevier B.V. Small electrode HPGe detectors in an inverted coaxial geometry are increasingly in use in applications where both high efficiency and excellent energy resolution are required. The unusual electric field configuration of these detectors results in extremely long charge collection times compared to planar and coaxial devices. In this work we have characterised such a detector using gamma-ray coincidence measurements and optimised an electric field simulation to reproduce the positional variation of detector response. We show that, alongside accurate crystal geometry and applied electric potential, a temperature correction is crucial to correctly determining appropriate charge carrier mobility parameters. This work will help to guide the future development of HPGE detectors for applications including radioactive waste assay, radio-isotope dating, and fundamental nuclear physics.

Automation of S-parameters measurements of high-power microwave transistors in a contact device with tunable strip matching circuits

In the practice by microwave power transistor amplifiers developing, the variable load method is usually used to determine the impedances of matching circuits in the complex conjugate matching mode. This solution involves the use of expensive equipment - coaxial impedance tuners and contact devices for mounting transistors in low impedance strip lines. An even more complicated and expensive way is the concept of X- parameters, based on the use of unique measuring equipment - a non-linear vector network analyzer, and a simulator for non-linear circuits design. The article proposes an alternative solution adapted to the operation of the transistor in real conditions and allowing to design the output stages of microwave power amplifiers using analysis and optimization of linear electrical circuits. The essence of the proposed solution is to automate the measurement of non-linear S-parameters of high-power microwave transistors in a contact device with tunable strip matching circuits for various DC supply voltage, frequency and input power mode in case of continuous or pulse input signal. The nonlinear S-parameters of the contact device are measured using the method of spatially remote variable load in the frequency range, in which the line conditioning and the maximum output power are achieved. The minimum of the reflected wave amplitude and the maximum gain are reached using movable strip matching transformers. The S-parameters measured in the coaxial line are automatically recalculated to the physical boundaries of the transistor by registering the positions of the input and output strip transformers.

A 57GHz overmoded coaxial relativistic backward wave oscillator with high conversion efficiency and pure TM01 mode output

A 57GHz overmoded relativistic backward wave oscillator (RBWO) operating on the quasi-TEM mode with pure TM01 mode output is presented in this paper, by using outer trapezoidal slow wave structure (SWS) with large distance between inner and outer conductors. The large overmoded ratio can be obtained in coaxial devices to improve power handling capacity, while the large distance between inner and outer conductors can guarantee the electron beam transmit effectively. The 8π/9 mode of quasi-TEM synchronously interacts with the electron beam, while the TM01 mode diffracted by the quasi-TEM mode outputs. The existence of TM01 6π/9 mode in SWS can extract energy from the quasi-TEM mode (which has a high value of Qe) thus increasing the power handling capacity. Particle-in-cell simulation shows that generation with high power 560 MW and efficiency 43.5% is obtained under the diode voltage 520 kV and current 2.47 kA. And the microwave has the pure frequency spectrum of 56.8 GHz radiates in the pure TM01 mode (about 98%).

Flexible, silver nanowire network nickel hydroxide core-shell electrodes for supercapacitors

Abstract We present a novel one-dimensional coaxial architecture composed of silver nanowire (Ag NW) network core and nickel hydroxide (Ni(OH)2) shell for the realization of coaxial nanocomposite electrode materials for supercapacitors. Ag NWs are formed conductive networks via spray coating onto polyethylene terephthalate (PET) substrates and Ni(OH)2 is gradually electrodeposited onto the Ag NW network to fabricate core-shell electrodes for supercapacitors. Synergy of highly conductive Ag NWs and high capacitive Ni(OH)2 facilitate ion and electron transport, enhance electrochemical properties and result in a specific capacitance of 1165.2 F g−1 at a current density of 3 A g−1. After 3000 cycles, fabricated nanocomposite electrodes show 93% capacity retention. The rational design explored in this study points out the potential of nanowire based coaxial energy storage devices.

Key comparison SIM.EM.RF-K5b.CL: scattering coefficients by broad-band methods, 2 GHz–18 GHz — type N connector

The first key comparison in microwave frequencies within the SIM (Sistema Interamericano de Metrología) region has been carried out. The measurands were the S-parameters of 50 ohm coaxial devices with Type-N connectors and were measured at 2 GHz, 9 GHz and 18 GHz. SIM.EM.RF-K5b.CL was the identification assigned and it was based on a parent CCEM key comparison named CCEM.RF-K5b.CL. For this reason, the measurements standards and their nominal values were selected accordingly, i.e. two one-port devices (a matched and a mismatched load) to cover low and high reflection coefficients and two attenuators (3dB and 20 dB) to cover low and high transmission coefficients. This key comparison has met the need for ensuring traceability in high-frequency measurements across America by linking SIM's results to CCEM. Six NMIs have participated in this comparison which was piloted by the Instituto Nacional de Tecnología Industrial (Argentina). A linking method of multivariate values was proposed and implemented in order to allow the linking of 2-dimensional results.KEY WORDS FOR SEARCHMain textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).