An equivalent-effect phenomenon in eddy current non-destructive testing of thin structures

The inductance/impedance due to thin metallic structures in non-destructive testing (NDT) is difficult to evaluate. In particular, in Finite Element Method (FEM) eddy current simulation, an extremely fine mesh is required to accurately simulate skin effects especially at high frequencies, and this could cause an extremely large total mesh for the whole problem, i.e. including, for example, other surrounding structures and excitation sources like coils. Consequently, intensive computation requirements are needed. In this paper, an equivalent-effect phenomenon is found, which has revealed that alternative structures can produce the same effect on the sensor response, i.e. mutual impedance/inductance of coupled coils if a relationship (reciprocal relationship) between the electrical conductivity and the thickness of the structure is observed. By using this relationship, the mutual inductance/impedance can be calculated from the equivalent structures with much fewer mesh elements, which can significantly save the computation time. In eddy current NDT, coils inductance/impedance is normally used as a critical parameter for various industrial applications, such as flaw detection, coating and microstructure sensing. Theoretical derivation, measurements and simulations have been presented to verify the feasibility of the proposed phenomenon

A novel feature extraction method of eddy current testing for defect detection based on machine learning

In eddy current testing, the trajectory of the impedance data due to a defect is presented as a Lissajous curve (LC) in the complex plane. This paper proposes a novel analytical model for describing a LC. Further, a new feature extraction method is implemented which automatically computes four geometric features (amplitude, width, angle and symmetry) from Lissajous figures. In addition, six machine learning-based classifiers are used for automatic defect identification based on these features. High detection rates are achieved for both the simulated and experimental data, which demonstrates the flexibility of the analytical model and the validity of the methodology

A Compact and Low Profile Loop Antenna with Six Resonant Modes for LTE Smart phone

In this paper, a novel six-mode loop antenna covering 660-1100 MHz, 1710-3020 MHz, 3370-3900 MHz, and 5150-5850 MHz has been proposed for the application of Long Term Evolution (LTE) including the coming LTE in unlicensed spectrum (LTE-U) and LTE-Licensed Assisted Access (LTE-LAA). Loop antennas offer better user experience than conventional Planar Inverted-F Antennas (PIFA), Inverted-F Antennas (IFA), and monopole antennas because of their unique balanced modes (1?, 2?, …). However, the bandwidth of loop antennas is usually narrower than that of PIFA/IFA and monopole antennas due to these balanced modes. To overcome this problem, a novel monopole/dipole parasitic element, which operates at an unbalanced monopole-like 0.25? mode and a balanced dipole-like 0.5? mode, is first proposed for loop antennas to cover more frequency bands. Benefiting from the balanced mode, the proposed parasitic element is promising to provide better user experience than conventional parasitic elements. To the authors’ knowledge, the balanced mode for a parasitic element is reported for the first time. The proposed antenna is able to provide excellent user experience while solving the problem of limited bandwidth in loop antennas. To validate the concept, one prototype antenna with the size of 75×10×5 mm3 is designed, fabricated and measured. Both simulations and experimental results are presented and discussed. Good performance is achieved

Assisting Clinical Decisions for Scarcely Available Treatment via Disentangled Latent Representation

Extracorporeal membrane oxygenation (ECMO) is an essential life-supporting modality for COVID-19 patients who are refractory to conventional therapies. However, the proper treatment decision has been the subject of significant debate and it remains controversial about who benefits from this scarcely available and technically complex treatment option. To support clinical decisions, it is a critical need to predict the treatment need and the potential treatment and no-treatment responses. Targeting this clinical challenge, we propose Treatment Variational AutoEncoder (TVAE), a novel approach for individualized treatment analysis. TVAE is specifically designed to address the modeling challenges like ECMO with strong treatment selection bias and scarce treatment cases. TVAE conceptualizes the treatment decision as a multi-scale problem. We model a patient's potential treatment assignment and the factual and counterfactual outcomes as part of their intrinsic characteristics that can be represented by a deep latent variable model. The factual and counterfactual prediction errors are alleviated via a reconstruction regularization scheme together with semi-supervision, and the selection bias and the scarcity of treatment cases are mitigated by the disentangled and distribution-matched latent space and the label-balancing generative strategy. We evaluate TVAE on two real-world COVID-19 datasets: an international dataset collected from 1651 hospitals across 63 countries, and a institutional dataset collected from 15 hospitals. The results show that TVAE outperforms state-of-the-art treatment effect models in predicting both the propensity scores and factual outcomes on heterogeneous COVID-19 datasets. Additional experiments also show TVAE outperforms the best existing models in individual treatment effect estimation on the synthesized IHDP benchmark dataset

Multimode Decoupling Technique with Independent Tuning Characteristic for Mobile Terminals

The isolation between antenna elements is a key metric in some promising 5G technologies such as beamforming and in-band full-duplex (IBFD). However, multimode decoupling technology remains a great challenge especially for mobile terminals. One difficulty in achieving multi decoupling modes is that the operating modes of closely-packed decoupling elements have very strong mutual effect, which makes the tuning complicated and even unfeasible. Thus, in physical principle, a novel idea of achieving the stability of the boundary conditions of decoupling elements is proposed to solve the mutual effect problem; in physical structure, a metal boundary is adopted to realize the stability. One distinguished feature of the proposed technique is that the independent tuning characteristic can be maintained even if the number of decoupling elements increases. Therefore, wideband/multiband high isolation can be achieved by using multi decoupling elements. To validate the concept, two case studies are given. In a quad-mode decoupling design, the isolation is enhanced from 12.7 dB to > 21 dB within 22.0% bandwidth by using a 0.295?0 × 0.059?0 × 0.007?0 decoupling structure. The mechanism of decoupling technique and the mutual effect between decoupling elements are investigated

FUEL IMPINGEMENT ANALYSIS OF FLASH-BOILING SPRAY IN A SPARK-IGNITION DIRECT-INJECTION ENGINE

Fuel impingement has been recognized as one of the major causes for the soot formation in spark-ignition direct-injection (SIDI) engines. Previous study demonstrated that flash-boiling fuel spray provided desirable spray structure with shorter penetration, more homogeneous fuel distribution, smaller droplets and better evaporation. However, it is still unknown whether the flash-boiling spray is capable of reducing fuel impingement compared with the conventional non-flash-boiling spray. In this study, crank-angle resolved Mie-scattered spray images for multiple cycles are recorded to investigate the spray impingement phenomenon in an optical SIDI engine for both the non-flash-boiling spray and flash-boiling spray. An eight-hole direct-injection injector is utilized, and gasoline fuel is heated to achieve flash-boiling spray condition. Image processing algorithm is developed to reveal the fuel impingement in a quantitative manner. It is found that the flash-boiling spray is effective to reduce the overall fuel impingement. In addition, the cycle-to-cycle variation of fuel impingement is demonstrated for both the non-flash-boiling spray and flash-boiling spray.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140986/1/ChenH_ILASS-Asia2013.pdfDescription of ChenH_ILASS-Asia2013.pdf : Conference proceedin

A Novel Low-Cost H-plane Decoupling Technique for Two Closely Placed Patch Antennas Using Electric and Magnetic Coupling Cancellation

This paper presents a novel low-cost method for decoupling two closely-placed H -plane arranged patch antennas. This new electric and magnetic coupling cancellation (EMCC) decoupling concept is simple yet highly effective, requiring no additional decoupling structures or complicated manufacturing processes. According to the proposed concept, the mutual coupling between two patches can be suppressed by controlling the weight of the electric ( E ) and magnetic ( H ) coupling between them. When the E -coupling and H -coupling are comparable, a deep null will arise on the mutual coupling curve, resulting in high isolation in the band of interest. To validate the approach, two prototypes for both 2-element and 4-element multi-input multi-output (MIMO) arrays, are designed, fabricated, and measured. The experimental results agree well with the simulations, highlighting the advantages of this method, including low cost, high isolation, and simple antenna structures

A Highly Integrated MIMO Antenna UnitA Highly Integrated MIMO Antenna Unit A: Differential/Common Mode Design

Abstract—A novel concept of antenna design, termed as differential/common mode (DM/CM) design, is proposed to achieve highly integrated multi-input multi-output (MIMO) antenna unit in mobile terminals. The inspiration comes from a dipole fed by a differential line which can be considered as a differential mode (DM) feed. What will happen if the DM feed is transformed into a common mode (CM) feed? Some interesting features are found in this research. By symmetrically placing one DM antenna and one CM antenna together, a DM/CM antenna can be achieved. Benefitting from the coupling cancellation of anti-phase currents and the different distributions of the radiation currents, a DM/CM antenna can obtain high isolation and complementary patterns, even if the radiators of the DM and CM antennas are overlapped. Therefore, good MIMO performance can be realized in a very compact volume. To validate the concept, a miniaturized DM/CM antenna unit is designed for mobile phones. 24.2 dB isolation and complementary patterns are achieved in the dimension of 0.330λ0×0.058λ0×0.019λ0 at 3.5 GHz. One 8×8 MIMO antenna array is constructed by using four DM/CM antenna units and shows good overall performance. The proposed concept of DM/CM design may also be promising for other applications that need high isolation between closely-packed antenna elements and wide-angle pattern coverage

A Cascaded Resonator Decoupling Network for Two Filtering Antennas

In this paper, a novel method for the decoupling between two filtering antennas is presented. The mutual coupling between two filtering antennas is investigated and a coupled-resonator decoupling network (DN) is developed. This coupled-resonator DN is co-designed with the coupled filtering antennas with little effect on the original filtering responses. By connecting this network to the coupled antennas in parallel, the mutual coupling between two 2 nd order filtering antennas can be suppressed dramatically. A step-by-step realization of the DN is provided. To verify the concept, a prototype using the proposed DN was fabricated and measured. Full-wave simulations and measurements indicate that this coupled-resonator DN can enhance the isolation between two filtering antennas up to 30 dB without significantly affecting the filtering performance of each antenna, at a cost of 1.15 dB efficiency drop