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Atherosclerotic cardiovascular disease is a major cause of human disability and mortality. Our previous study demonstrated the safety and efficacy of sonodynamic therapy (SDT) on atherosclerotic plaques. However, traditional single-element therapeutic transducer has single acoustic field, and positioning therapeutic and imaging transducers in the same position is difficult during ultrasound imaging-guided SDT. Continuously changing the position of transducers to intervene lesions in different positions is required, increasing the difficulty of treatment. Thus, an SDT device with precise theranostics is required. Therefore, we designed and fabricated a “concentric ultrasound transducer for theranostics” (CUST-T), comprising a central 8-MHz linear array transducer for ultrasound imaging, and a peripheral 1-MHz hollow two-dimensional (2-D) planar array transducer for generating phased-array focused ultrasound (PAFUS). The CUST-T exhibited high imaging resolution at a distance of up to 20 mm from the transducer and could generate a personalized complex PAFUS acoustic field to match various lesions. In vitro biomedical results showed that PAFUS-SDT induced RAW264.7-derived foam cell apoptosis leading to a targeting field apoptotic rate 4.36–6.24 times that of the nontargeting field and the significant apoptotic region was consistent with the PAFUS acoustic field. In vivo, PAFUS-SDT guided by ultrasound imaging significantly increased the lumen area (${P} < 0.05$) and collagen level (${P} < 0.01$), whereas the wall thickness (${P} < 0.05$) and lipid content (${P} < 0.01$) of rabbit femoral artery were reduced. In conclusion, CUST-T provided image guidance sufficient for accurate SDT for atherosclerotic plaques in peripheral arteries and could be applied in clinical practice. [ABSTRACT FROM AUTHOR]

Industrial ultrasonic tomography (UT) possesses unique benefits in nonintrusive detection of cross-sectional medium and has received broad attention in decades. Aiming at the complex bubble imaging, the conventional independent-transducer-based UT has low spatial resolution due to wide projection path and low projection number. Based on ultrasound phase array (UPA) transducers, this article proposes a sequential dynamic aperture focusing strategy for transmissive ultrasonic phase array tomography (UPAT). The emitting aperture focuses the ultrasound beam on a close distance to generate a high intensity and wide-angle acoustic field that covers multiple receivers in single excitation and further induces high amount of multiangle narrow projections, through which the measurement speed and imaging performance are substantially improved. Beyond numerical analysis on image accuracy and noise robustness, an experimental UPAT system with independent T/R channels is developed to evaluate the proposed method, where the improvement on imaging accuracy and speed are testified through qualitatively and quantitatively comparison with the state-of-art UT and the beam scanning UPAT techniques. The UPAT-focus strategy is proved to be advanced and feasible in imaging complex medium distribution. [ABSTRACT FROM AUTHOR]

The issue of accurately distinguishing and selectively powering multiple closely spaced devices is challenging but vital for wireless power transfer (WPT). In this article, a continuous-wave time-reversal selective radiative wireless power transfer (CWTR-SRWPT) method based on a multipoint focusing idea is proposed. With the proposed method, we realize a selective radiative WPT prototype system, which can arbitrarily select multiple devices spaced at a diffraction limited distance and power them simultaneously. The accurate positioning and high-precision spatial selection of the closely spaced energy-dissipated devices are achieved by the multipoint focusing field (MPFF) without any auxiliary positioning equipment. The MPFF is produced by a set of weight-optimized single-point focusing fields that are generated by the fundamental time-reversal technique. Theoretical analysis and full-wave simulations to the performances of the CWTR-SRWPT system are presented. The experimental demonstrations of selectively powering multiple LEDs are also conducted. The results indicate that the proposed method exhibits exciting performances of high-precision selectivity, accurate positioning, and satisfactory over-the-air efficiency. It demonstrates potential applications in selectively powering the wireless sensors distributed densely in future intelligent factories. [ABSTRACT FROM AUTHOR]

A strategy for folded reflectarray with low detectability and enhanced gain is presented. For this purpose, the folded reflectarray is engineered by combining a polarization-conversion focusing metasur face, a frequency selective rasorber (FSR), and a diffusion metasurface. The FSR is composed of a lossy layer and a single-polarized I-shaped slotted frequency selective surface (FSS) between which the diffusive metasurface is inserted for in-band and out-of-band cross-polarized low radar cross-sectional (RCS) reduction. Therein, the antenna exhibits a transmission window and two out-of-band absorptions due to the FSR for copolarized radiation. In contrast to detection, the system operated for both wave incidence. For cross-polarized wave incidence, a wideband RCS reduction is enabled due to the wave-diffusive function of the inserted metasurface. The half profile is guaranteed since the wave bounces two times between the FSS and focusing metasurface. The numerical and experimental results coincide well, both indicating that the low-RCS folded reflectarray achieves a peak gain of 23.5 dB at 10.2 GHz, corresponding to an aperture efficiency of 37.8%. Besides, the antenna achieves 10 dB monostatic RCS reduction within 4.6–8.8 GHz and 9.6–13.8 GHz under copolarization detection and a 10 dB monostatic RCS reduction from 8.4 to 19 GHz under cross-polarization detection. Moreover, good invisibility is also achieved for bistatic RCS reduction. [ABSTRACT FROM AUTHOR]

The work shows a significant effect of the focusing magnetic field on the output characteristics of the klystron. When the calculations are done using nonlinear one-dimensional models, optimization of the parameters makes it possible to obtain versions of devices with the efficiency of 0.8 – 0.9 and higher. However, when testing these options using nonlinear two-dimensional models that take into account the radial motion of electrons, there is a significant discrepancy in the output characteristics obtained from the one-dimensional and two-dimensional models. This is due to the fact that during the motion of the electron beam, the radii of the leading centers of the large particles change the coefficients of interaction of the particle fields with the electromagnetic fields of the resonators change, which leads to a change in the output characteristics of the klystrons: efficiency, output power, and gain. On the other hand, it seemed that setting a large focusing magnetic field to exclude the radial motion of particles could eliminate this drawback, however, another problem arises here - the magnetic system for focusing becomes unacceptably large and it is technically difficult to obtain magnetic induction values of more than 2 T (the weight of the magnetic system can be several hundred kilograms). Therefore, one should choose the magnetic field induction for focusing the electron beam no more than 1T. In this paper, a twodimensional nonlinear mathematical model (2.5D) is proposed that takes into account the azimuthal component in the equations of motion. In the model, the induction of the focusing magnetic field is set in the form of tables. This makes it possible to set the inhomogeneity of the magnetic field at any place in the interaction space of the klystron. The calculation of a powerful relativistic klystron with an accelerating voltage of 1000 kV and the beam current of 250 A was carried out. The use of an inhomogeneous magnetic field makes it possible to reduce the deposition of electrons in the region of the gaps. Therefore, a decrease in the electron deposition leads to an increase in the durability of klystrons.

The paper aims at deriving a curvature form of the famous Raychaudhuri equation (RE) and the associated criteria for focusing of a hyper-surface orthogonal congruence of time-like geodesic. Moreover, the paper identifies a transformation of variable related to the metric scalar of the hyper-surface which converts the first order RE into a second order differential equation that resembles an equation of a Harmonic oscillator and also gives a first integral that yields the analytic solution of the RE and Lagrangian of the dynamical system representing the congruence. [ABSTRACT FROM AUTHOR]

We study the sharp focusing of the input structured light field that has a non-uniform elliptical polarization: the parameters of the ellipse depend on the position in the input plane (we limited ourselves to the dependence only on the angular variable). Two types of non-uniformity were considered. The first type corresponds to the situation when the semi-axes of the polarization ellipse are fixed while the slope of the major semi-axis changes. The second type is determined by the situation when the slope of the major semi-axis of the polarization ellipse is constant, and the ratio between the semi-axis changes (we limited ourselves to the trigonometric dependence of this ratio on the polar angle). Theoretical and numerical calculations show that in the case of the first type of non-uniformity, if the tilt angle is a multiple of the polar angle with an integer coefficient, then the intensity distribution has rotational symmetry, and the energy flow is radially symmetric and has the negative direction near the optical axis. In this second case, the intensity symmetry is not very pronounced, but with an odd dependence of the ratio of the semi-axes of the polarization ellipse, the focused field at each point has a local linear polarization, despite the rather complex form of the input field. In addition, we investigate the distribution of the longitudinal component of the Poynting vector. The obtained results may be used for the formation of focused light fields with the desired distributions of polarization, Poynting vector density, or spin angular momentum density in the field of laser manipulation and laser matter interaction.

This paper deals with both forward and inverse electromagnetic scattering of metallic objects by focused Bessel-shaped incident field. After discussing the main features of this kind of field, it is shown that its focusing capabilities may offer new effective possibilities for the detection of metallic targets which are not so far extended with respect to the probing wavelength, i.e., not satisfying the hypotheses of physical optics approximation. Numerical examples are performed by means of full-wave simulations, and then inversion algorithms based on back-propagation and physical optics are exploited to show that more accurate reconstructions can be pursued using Bessel-shaped fields.

We go back over the analyses of the pragmatic-discursive function of the left dislocation of the subject in French, those that highlight the theming function and those that add a focusing function by postulating for the dislocated subject a status of focused theme. We retain the notion of focusing to explain the purpose of such a structure in the discourse, considering however that the subject is not the only one to benefit from focusing in this case, but that the focusing of the predicate itself is thus strengthened, which ultimately results in focusing the entire clause. To support this hypothesis, we articulate the left dislocation of the subject with other syntactic means involved in the phenomenon of focusing, then we extend the analysis to the case of the left dislocation of a complement.

Engineering the chiral field is crucial for the flexible manipulation of chiral particles. Some complex optical setups for constructing spin-structured fields have been well developed to sort particles with opposite chiralities toward opposite transversal directions. In this work, we demonstrate the robust construction of a class of focal fields that possess laterally variant optical spin angular momentum by using the monolayer dielectric metalens. By utilizing the simultaneous modulation capacity of the phase and polarization of the dielectric metalens, we can establish a line focus with laterally tailored gradient optical helicity. The focusing property of this metalens and the polarization structure of the focal field are theoretically analyzed using a hybrid vector-focusing model and experimentally demonstrated by NA = 0.2 and 0.5 samples. We illustrate that this type of gradient helicity offers opportunities to induce a chirality-sensitive lateral force for chiral particles.

This article introduces a novel near-field focus (NFF) lens antenna with a three-dimensional (3-D) focus-steering capability operating at terahertz (THz) frequencies. The antenna consists of a pair of thin discrete dielectric lenses (DDLs) placed above a stationary feed horn. First, we demonstrate that the DDL doublet’s in- plane synchronous counter-rotation and co- rotation could scan its focus radially and azimuthally, respectively. A multi-focus synthesis method that compensates the required transmission phases at multi-focus points is developed to further improve its NFF-steering performance. The DDL-based antenna can realize 3-D focus-scanning using a combination of rotation and linear translation mechanisms. The 3-D printing is adopted to fabricate the THz antenna to simplify the manufacturing process and reduce the cost. Both numerical and experimental results demonstrate that the 15 mm-diameter antenna prototype can scan its focus in a 3-D cylindrical space with a diameter of 29 mm and a length of 8 mm at 300 GHz. The proposed 3-D focus-scanning antenna with a large field of view (FoV) of 72° will open new avenues for fast 3-D THz imaging applications. [ABSTRACT FROM AUTHOR]

In this article, a novel design of broadband circularly polarized (CP) folded reflectarray (FRA) antenna is proposed. The CP FRA consists of two kinds of metasurfaces (MSs) and a linearly polarized (LP) open waveguide antenna as the feeding source. The bottom MS functions as the main reflector, which is capable of realizing cross-polarization conversion and beam focusing simultaneously. The upper MS is utilized as a subreflector, which could reflect LP wave coming from the feeding source and transmit its orthogonal counterpart into CP wave. For demonstration, the MS-assisted CP FRA antenna is fabricated and measured. Numerical results are consistent with experimental ones, illustrating a peak gain of 24.1 dBi and a peak aperture efficiency of 51% at 9.9 GHz. The 3 dB gain bandwidth and 3 dB axial ratio (AR) bandwidth are achieved as 27.5% (8.8–11.6 GHz) and 43.9% (8–12.5 GHz), respectively. The proposed CP FRA provides a new avenue to realize broadband high-efficiency CP antenna, which may find great potentials in modern wireless communication systems. [ABSTRACT FROM AUTHOR]

This paper presents the design, simulation and experimental validation of a gradient-index (GRIN) metasurface lens operating at 8 GHz for microwave imaging applications. The unit cell of the metasurface consists of an electric-LC (ELC) resonator. The effective refractive index of the metasurface is controlled by varying the capacitive gap at the center of the unit cell. This allows the design of a gradient index surface. A one-dimensional gradient index lens is designed and tested at first to describe the operational principle of such lenses. The design methodology is extended to a 2D gradient index lens for its potential application as a microwave imaging device. The metasurface lenses are designed and analyzed using full-wave finite element (FEM) solver. The proposed 2D lens has an aperture of size 119 mm (3.17λ) × 119 mm (3.17λ) and thickness of only 0.6 mm (0.016λ). Horn antenna is used as source of plane waves incident on the lens to evaluate the focusing performance. Field distributions of the theoretical designs and fabricated lenses are analyzed and are shown to be in good agreement. A microwave nondestructive evaluation (NDE) experiment is performed with the 2D prototype lens to image a machined groove in a Teflon sample placed at the focal plane of the lens. [ABSTRACT FROM AUTHOR]

The causative construction poses a challenge to all mainstream approaches to Spanish mood. Mejías-Bikandi, Errapel. 2014. A cognitive account of mood in complements of causative predicates in Spanish. Hispania 97(4), 651–665, elaborating on his previous approach (Mejías-Bikandi, Errapel. 1998. Presupposition and old information in the use of the subjunctive mood in Spanish. Hispania 81(4), 941–948), which associates the indicative to information that is pragmatically asserted (i.e., presented as both true and new), claims that the use of the subjunctive in the complements of volitive and causative verbs results from the fact that these complements are not independently grounded and so cannot be asserted. His proposal, though, raises some serious objections. In this paper, an alternative account is presented, whereby the use of the subjunctive in this context is understood as reflecting the antagonist's viewpoint and epistemic assessment on the goal process within a force dynamics pattern. [ABSTRACT FROM AUTHOR]

Algorithmic changes that increase beamforming speed have become increasingly relevant to processing synthetic aperture (SA) ultrasound data. In particular, beamforming SA data in a spatio-temporal frequency domain using the F-k (Stolt) migration have been shown to reduce the beamforming time by up to two orders of magnitude compared with the conventional delay-and-sum (DAS) beamforming, and it has been used in applications where large amounts of raw data make real-time frame rates difficult to attain, such as multistatic SA imaging and plane-wave Doppler imaging with large ensemble lengths. However, beamforming signals in a spatio-temporal Fourier space can require loading large blocks of data at once, making it memory-intensive and less suited for parallel (i.e., multithreaded) processing. As an alternative, we propose beamforming in a range-Doppler (RD) frequency domain using the range-Doppler algorithm (RDA) that has originally been developed for SA radar (SAR) imaging. Through simulation and phantom experiments, we show that RDA achieves similar lateral resolution and contrast compared with DAS and F-k migration. At the same time, higher axial sidelobes in RDA images can be reduced via (temporal) frequency binning. Like the F-k migration, RDA significantly reduces the overall number of computations relative to DAS, and it achieves ten times lower processing time on a single CPU. Because RDA uses only a spatial Fourier transform (FT), it requires two times less memory than the F-k migration to process the simulated multistatic data and can be executed on as many as a thousand parallel threads (compared with eight parallel threads for the F-k migration), making it more suitable for implementation on modern graphics processing units (GPUs). While RDA is not as parallelizable as DAS, it is expected to hold a significant speed advantage on devices with moderate parallel processing capabilities (up to several thousand cores), such as point-of-care and low-cost ultrasound devices. [ABSTRACT FROM AUTHOR]

Anisotropic diffusion is a well recognized tool in digital image processing, including edge detection and focusing. We present here a particular nonlinear time-dependent operator together with an appropriate high-order discretization for the space variable. In just a single step, the procedure emphasizes the contour lines encircling the objects, paving the way to accurate reconstructions at a very low cost. One of the main features of such an approach is the possibility of relying on a rather large set of invariant discontinuous images, whose edges can be determined without introducing any approximation. [ABSTRACT FROM AUTHOR]

Social network group decision-making (SNGDM) develops rapidly because of the popularity of online connections among experts. The current SNGDM studies mainly focus on the influence of trust on the evolution of consensus opinions through a complex process. Some situations are ignored in the existing research when trust may negatively affect the decision-making process and trust relationships may be developed or interrupted during consensus negotiation processes. To overcome such limitations, we propose a consensus model based on the trust-consensus multiplex network by combing trust social network analysis and consensus evolution networks (CENs). We design an interaction mechanism between trust and consensus based on the dynamic experts’ influence which is computed by the multiplex PageRank centrality measure, especially focusing on the negative impact of trust on consensus. Besides, we compute consensus levels based on the density and intensity of CENs to determine when should the negotiation end. The proposed model can not only consider the mutual influence between trust and consensus in SNGDM, but also detect and analyze the negative influence of trust on consensus. An example examines the effectiveness of the proposed model and a comparative analysis shows its flexibility for studying the complex consensus situation of SNGDM. [ABSTRACT FROM AUTHOR]

The time reversal symmetry of the wave equation allows wave refocusing back at the source. However, this symmetry does not hold in lossy media. We present a new strategy to compensate wave amplitude losses due to attenuation. The strategy leverages the instantaneous time mirror (ITM) which generates reversed waves by a sudden disruption of the medium properties. We create a heterogeneous ITM whose disruption is unequal throughout the space to create waves of different amplitude. The time-reversed waves can then cope with different attenuation paths as typically seen in heterogeneous and lossy environments. We consider an environment with biological tissues and apply the strategy to a 2-D digital human phantom from the abdomen. A stronger disruption is introduced where the forward waves suffer a history of higher attenuation, with a weaker disruption elsewhere. Computer simulations show heterogeneous ITM is a promising technique to improve time reversal refocusing in heterogeneous, lossy, and dispersive spaces. [ABSTRACT FROM AUTHOR]

As reconfigurable intelligent surface (RIS) is expected to be implemented with a large aperture in terms of wavelengths, using a RIS to perform near-field rather than conventional far-field communications might gain some benefits. The electric fields in the near-field region from the near-field focusing and conventional far-field RISs are simulated and compared to assess and validate the benefits. Two metrics of benefit distance and near-field gain are defined to characterize the electric fields in the near-field region. The cumulative distribution function (CDF) related to the near-field gain is calculated to describe the benefits in the area of interest where the total scan patterns from the near-field focusing and conventional far-field RISs are plotted. For demonstration, the benefit distance, near-field gain, and CDFs are presented and calculated for near-field focusing RISs with assigned focal distances of 80 and 300 mm. It is concluded that the benefit distance is a critical factor affecting the CDF directly. The effects of the size of a RIS and phase quantization of elements on the benefit distance, near-field gain, and CDF are also discussed. Moreover, the maximum focal distance of a near-field focusing RIS with a certain size is derived and specified. Finally, the electric fields of three prototypes (e.g., conventional far-field RIS, near-field focusing RISs with assigned focal distances of 500 and 1500 mm) at 26 GHz are measured and compared, where the benefit distances and near-field gains are experimentally observed. [ABSTRACT FROM AUTHOR]

The paper discusses the problem of a superposition wave field created by a system of coherent point sources. For the general case, the conditions for a point amplification of the superposition field are found. The focusing problem is discussed for a system of point sources located on circles with centers lying on the same straight line parallel to the planes of the circles. [ABSTRACT FROM AUTHOR]

Synthetic Aperture Radar (SAR) imaging is starting to play an essential role in the automotive industry. Its day and night sensing capability, fine resolution, and high flexibility are key aspects making SAR a very compelling instrument in this field. This paper describes and compares three algorithms used to combine low-resolution images acquired by a Multiple-Input Multiple-Output (MIMO) automotive radar to form an SAR image of the environment. The first is the well-known Fast Factorized Back-Projection (FFBP), which focuses the image in different stages. The second one will be called 3D2D, and it is a simple 3D interpolation used to extract the SAR image from the Range-Angle-Velocity (RAV) data cube. The third will be called Quick&Dirty (Q&D), and it is a fast alternative to the 3D2D scheme that exploits the same intuition. A rigorous mathematical description of each algorithm is derived, and their limits are addressed. We then provide simulated results assessing different interpolation kernels, proving which one performs better. A rough estimation of the number of operations proves that both algorithms can be deployed using a real-time implementation. Finally, we will present some experimental results based on open road campaign data acquired using an eight-channel MIMO radar at 77 GHz, considering the case of a forward-looking geometry. [ABSTRACT FROM AUTHOR]

Simultaneous axial multifocal imaging (SAMI) using a single acoustical transmission was developed to enhance the depth of field. This technique transmits a superposition of axial multifoci waveforms in a single transmission, thus increasing the frame rate. However, since all the waveforms are transmitted at a constant center frequency, there is a tradeoff between attenuation and lateral resolution when choosing a constant frequency for all the axial depths. In this work, we developed an optimized SAMI method by adding frequency dependence to each axial multifocus. By gradually increasing the frequency as a function of the focal depth, this method makes it possible to compensate for the gradually increasing F-number in order to achieve constant lateral resolution across the entire field of view. Alternatively, by gradually decreasing the axial multifoci frequencies as a function of depth, enhanced penetration depth and contrast are obtained. This method, termed frequency multiplexed SAMI (FM-SAMI), is described analytically and validated by resolution and contrast experiments performed on resolution targets, tissue-mimicking phantoms, and ex vivo biological samples. This is the first real-time implementation of a frequency multiplexing approach for axial multifoci imaging that facilitates high-quality imaging at an increased frame rate. [ABSTRACT FROM AUTHOR]

Row–column (RC) arrays have the potential to yield full 3-D ultrasound imaging with a greatly reduced number of elements compared to fully populated arrays. They, however, have several challenges due to their special geometry. This review article summarizes the current literature for RC imaging and demonstrates that full anatomic and functional imaging can attain a high quality using synthetic aperture (SA) sequences and modified delay-and-sum beamforming. Resolution can approach the diffraction limit with an isotropic resolution of half a wavelength with low sidelobe levels, and the field of view can be expanded by using convex or lensed RC probes. GPU beamforming allows for three orthogonal planes to be beamformed at 30 Hz, providing near real-time imaging ideal for positioning the probe and improving the operator’s workflow. Functional imaging is also attainable using transverse oscillation and dedicated SA sequence for tensor velocity imaging for revealing the full 3-D velocity vector as a function of spatial position and time for both blood velocity and tissue motion estimation. Using RC arrays with commercial contrast agents can reveal super-resolution imaging (SRI) with isotropic resolution below $20~ \mu \text{m}$. RC arrays can, thus, yield full 3-D imaging at high resolution, contrast, and volumetric rates for both anatomic and functional imaging with the same number of receive channels as current commercial 1-D arrays. [ABSTRACT FROM AUTHOR]

A bifunctional full-space metasurface (FS-MS) capable of generating reflective multiple vortex beams and focusing transmissive electromagnetic waves within different frequency bands is presented in this letter. The generation of vortex beams is based on the Pancharatnam–Berry (PB) phase, which exhibits the property of full phase control by rotating the orientation angle of an I-shaped patch. Meanwhile, this PB unit is backed by a metallic square loop frequency selective surface (FSS), which behaves as stopband and passband responses around 18 GHz and 12 GHz, respectively. By encoding PB phase to generate a certain phase response, four reflective vortex beams carrying orbital angular momentum (OAM) are achieved at a higher frequency band under normal incidence. On the other hand, the incident waves operating at a lower frequency band can pass through such an FSS-backed PB unit and be focused by a three-layer composite unit consisting of a polarization-conversion unit sandwiched by two orthogonal polarizers. Therefore, upon illumination of normal incident plane waves, the proposed FS-MS works as a multiple OAM beams generator and a focusing lens simultaneously. The proposed design can motivate the realizations of FS-MS and hold potential applications in intelligent housing systems. [ABSTRACT FROM AUTHOR]

Crowd counting based on density maps is generally regarded as a regression task. Deep learning is used to learn the mapping between image content and crowd density distribution. Although great success has been achieved, some pedestrians far away from the camera are difficult to be detected. And the number of hard examples is often larger. Existing methods with simple Euclidean distance algorithm indiscriminately optimize the hard and easy examples so that the densities of hard examples are usually incorrectly predicted to be lower or even zero, which results in large counting errors. To address this problem, we are the first to propose the hard example focusing (HEF) algorithm for the regression task of crowd counting. The HEF algorithm makes our model rapidly focus on hard examples by attenuating the contribution of easy examples. Then higher importance will be given to the hard examples with wrong estimations. Moreover, the scale variations in crowd scenes are large, and the scale annotations are labor-intensive and expensive. By proposing a multiscale semantic refining strategy, lower layers of our model can break through the limitation of deep learning to capture semantic features of different scales to sufficiently deal with the scale variation. We perform extensive experiments on six benchmark datasets to verify the proposed method. Results indicate the superiority of our proposed method over the state-of-the-art methods. Moreover, our designed model is smaller and faster. [ABSTRACT FROM AUTHOR]

This paper proposes a genetic algorithm (GA) combined with ray tracer to generate a cell-free topology of massive MIMO (mMIMO) for the optimal focusing performance serving multiple users. The realistic hardware impairment, for instance the non-ideal power amplifier, is taken into account of the system modeling and topology optimization. To the best of our knowledge, this is the first attempt to apply GA in optimizing the hardware-impaired multi-user cell-free mMIMO. Although the demonstrated numerical analysis is for indoor scenario, the proposed approach is transferable for generic scenarios. In GA, the base station (BS) antennas’ placement is encoded with an adjusted binary matrix representation, which is straightforward for the subsequent genetic operations. The explored candidates by GA can evolve beyond the parents, where the fitness of individuals is evaluated dynamically via a ray tracer radio channel simulator. Compared to the traditional GA, our proposed GA can find better solutions with a faster convergence speed. The algorithm provides near-optimal results in experiments, applicable to generic environment with multiple mobile users and different signal-to-interference-plus-noise ratios. [ABSTRACT FROM AUTHOR]

The detection of anomalous paths from floating vehicle trajectories plays an increasingly important role in dynamic path planning because of its ability to identify fraudulent transport behaviors, unexpected traffic accidents, and traffic restriction areas. Existing studies mostly emphasize the significant deviations based on global shape metrics and cannot manage trajectories with missing segments. To address these problems, this study proposes a new sequential pattern mining based method for detecting anomalous paths (SPDAP) in floating vehicle trajectories. First, discrete trajectory points were transformed into consecutive road segment sequences using map matching and essential empirical information. Focusing on these segment sequences, this method constructs a directed graph and calculates the conditional occurrence probabilities of multi-order sub-paths on the graph. On this basis, we designed a sequential pattern mining algorithm by estimating kernel density distributions to adaptively extract multi-order frequent sub-paths. Finally, these anomalous paths can be identified by matching the operations with frequent paths. Comparative experiments on simulated trajectories demonstrated that SPDAP could accurately, adequately, and adaptively detect anomalous paths. Additionally, using real-life taxi trajectories, we conducted semantic analysis by considering travel time and charges to further derive four patterns from the detected anomalous paths. These patterns are expected to support the identification of fraudulent taxi trips and the discovery of candidate driving routes with a preference for saving time or charge. In the future, we will focus on tracing the intrinsic causes of anomalous paths by introducing multisource information and performing real-time anomalous path detection using adaptive time intervals. [ABSTRACT FROM AUTHOR]

It is well-known that an iterative time-reversal (TR) process, applied via a distributed sensing system, can be used to produce a space-time waveform that maximizes the energy scattered from a stationary target back to the sensors. The TR process accomplishes this by automatically focusing energy, both spatially and spectrally, on the stationary target. When scatterers are moving, however, the TR focusing can break down. This article shows how to modify the TR process so that it automatically focuses energy on a moving target. This new TR process automatically generates a distributed beam that: 1) follows the target as it moves and 2) enhances the target resonances by concentrating the energy spectrally. This focusing occurs without a priori knowledge of the target’s location or spectral response. The new TR algorithm is derived through a careful analysis of the idealized case of a single isotropic moving point scatterer. This article includes simulations that compare the TR focus both with and without the new modification. Although the simulations are carried out for the electromagnetic case, the theory applies equally well to the acoustic case when the target speed is significantly less than the ambient sound speed. Appendices are included with details of the calculations and with analysis of the range of relative velocities for which the modified TR process should be used. [ABSTRACT FROM AUTHOR]

A novel high-efficiency polarization-selective bifunctional metasurface (MS) is proposed, which can realize cross-polarized focusing transmission for left-handed circular polarization (LHCP) incidence and co-polarized specular reflection for right-handed circular polarization (RHCP) incidence. As an example of its practical application, the designed MS is applied to form an RHCP folded transmitarray antenna (FTA) whose feed source (FS) is integrated with the bottom metallic surface. To prove the concept, a prototype of millimeter-wave (MMW) FTA based on the proposed MS is numerically simulated, physically implemented, and experimentally measured. The measured results coincide well with the simulated ones, showing a peak gain of 23.6 dBi at 27.7 GHz with the peak aperture efficiency of 43.1%, a 3 dB gain bandwidth of 15.8% (25–29.3 GHz), and a 3 dB axial-ratio (AR) bandwidth over 29.6%. The proposed high-performance antenna has the advantages of low profile, high efficiency, integration design, and broad bandwidth, which may have promising applications in the fifth-generation MMW communication system. The proposed MS and its application to high-gain antenna may promote the uses of MS to real-world applications in satellite communication, radar detection, and wireless communication. [ABSTRACT FROM AUTHOR]

The parameters for a kilowatt-level high-power terahertz amplifier were explored based on the higher-order mode and extended-interaction mechanism. It has been demonstrated that the antisymmetric electrical field mode (TM21) has a unique advantage in achieving high power. Physical factors on power extraction were studied. In particular, the heavily reduced ${Q}_{{0}}$ has a great effect on the coupling characteristic as well as the output power. It is found that the critical coupling state, i.e., ${Q}_{e} = {Q}_{{0}}$ , defines an upper limit of the power that can be extracted from the output circuit. The design of a complete interaction circuit was accomplished. The particle-in-cell (PIC) simulations showed that a saturated power of 1.2 kW can be achieved at 220 GHz with a voltage of 45 kV and a total current of $2\times0.6$ A where two beams were used. The saturated gain is over 30 dB with a 3-dB bandwidth of $\sim 400$ MHz. [ABSTRACT FROM AUTHOR]

Making sense of our existence is one of the most demanding aspects of being human. Studies have shown that meaning is robustly associated with well-being and mental health. In this study with 358 Dutch-speaking participants during the covid-19 pandemic, we tested if the practice of contacting one's felt sense (focusing attitude) would predict life satisfaction, psychological distress, and existential anxiety. We also tested whether the effect of this focusing attitude would be partially mediated by the experience of meaning in life. Our hypotheses were confirmed. This suggests that the focusing attitude predicts more life satisfaction, less psychological distress, and less existential anxiety. The associations are also partially mediated by the experience of meaning in life. Focusing training variables suggested that attending one's felt sense can be learned. However, our study also suggests that focusing-partnership deserves closer study. [ABSTRACT FROM AUTHOR]

Radar sounders (RSs) are gaining importance in planetary missions thanks to their unique capability of providing direct measurements of subsurface (SS) structures. To support their design and data interpretation, several electromagnetic (e.m.) simulation techniques have been developed with enhanced capabilities for emulating the RS acquisition process. However, the raw simulated radargrams obtained from e.m. simulators are difficult to interpret and analyze without a focusing operation, which results in an underestimation of the RS detection performance. While frequency methods for range and azimuth compression of real RS data are well-established, their use on simulated data is not addressed in the literature and requires major modifications. This article presents a novel method that implements azimuth compression using unfocused and focused processing on simulated raw data. The proposed method is based on an adaptation of the range-Doppler algorithm to the case of raw data generated by a coherent RS simulator. The method is demonstrated in three case studies to show the similarity between simulated and real data processing: 1) simple geometries; 2) a simulated SHAllow RADar (SHARAD) radargram compared with the real data product; and 3) a real application scenario for supporting the design of a new RS instrument. The results indicate higher fidelity of the focused simulated data with the real data product and the target structure, confirming the usefulness of the proposed approach in obtaining realistic processing of simulated radargrams. [ABSTRACT FROM AUTHOR]

Objective: Two-dimensional (2D) photoacoustic (PA) imaging based on array transducers provide high spatial resolution in the lateral direction by adopting receive dynamic focusing. However, the quality of PA image is often deteriorated by poor elevational resolution which is achieved by an acoustic lens. To overcome this limitation, we present a three-dimensional (3D) image reconstruction method using a commercial one-dimensional (1D) array transducer. Methods: In the method, the elevational resolution is improved by applying synthetic aperture focusing (SAF) technique along the elevational direction. For this, a commercially available 1D array transducer with an acoustic lens is modeled and appropriate synthetic focusing delay that can minimize the effect of the acoustic lens is derived by mathematical analysis. Results: From the simulation and experiment results, it was demonstrated that the proposed method can enhance the image quality of PA imaging, i.e., elevational resolution and signal-to-noise ratio (SNR). Conclusion: 3D PA images with improved elevational resolution were achieved using a clinical 1D array transducer. Significance: The presented method may be useful for clinical application such as detecting microcalcification, imaging of tumor vasculature and guidance of biopsy in real time. [ABSTRACT FROM AUTHOR]

In this article, we address the problem of synthesized magnetic field focusing (SMF) of the pulsed eddy-current (PEC) technology for the non-destructive testing (NDT) of oil and gas well casing pipes. The electromagnetic response excited by multiple transmitters was derived using the signal model of downhole PEC system. The magnetic field was shown to be adjustable by modifying the currents of the multiple transmitting array. Based on this property, magnetic fields were synthesized with the mean squared error (MMSE) criterion to be focused on the center of the transmitting array, and a weighted MMSE (WMMSE)-based SMF was also proposed to achieve an optimal synthetic magnetic field. Furthermore, the primal-dual interior-point method was used to solve the WMMSE optimization problem with the total and single transmit power constraints for the practical application. Simulations and experimental results showed that the SMF with the PEC array effectively focuses the eddy-current field on the center of the transmitting array. [ABSTRACT FROM AUTHOR]

In this paper, using the frequency-dependent finite-difference time-domain method, a femtosecond cylindrical vector beam of second-order focusing binary zone plates (BZP) is investigated. It is shown that the relief material has a significant effect on the electromagnetic field formed in the focal plane. It is also shown that, in the case of tight focusing of a second-order cylindrically polarized laser pulse, a reverse energy flux is formed in the focus near the optical axis. For the quartz BZP, the energy backflow is maximum. For aluminum and chromium BZPs, the reverse energy flux is approximately two times less, and there is no energy backflow in the focus formed by the gold BZP. This study will be useful for surface nanostructuring applications where a focused short pulse is applied. [ABSTRACT FROM AUTHOR]

Simulation experts are now well acquainted with machine learning (ML) techniques, using them to find patterns in data that can later be turned into rules of a simulation or enabling their simulated entities to adapt and learn. In the other direction, ML experts occasionally make use of simulated data to create controlled experiments in which learning algorithms can be evaluated. In this article, we go beyond these typical uses by focusing on current opportunities that have the potential to bring the two research communities together. These opportunities can be realized in areas where the potential of hybrid ML/simulation methods has not been fully attained yet. Such applications also motivate the development of innovative methods, for example, to combine the accuracy of ML with the interpretability of simulation models. Using select examples from our interdisciplinary team, this article reflects on opportunities in applications and techniques to promote productive conversations across research areas. [ABSTRACT FROM AUTHOR]

Large antenna arrays and high-frequency bands are two key features of future wireless communication systems. The combination of large-scale antennas with high transmission frequencies often results in the communicating devices operating in the near-field (Fresnel) region. In this paper, we study the potential of beam focusing, feasible in near-field operation, in facilitating high-rate multi-user downlink multiple-input multiple-output (MIMO) systems. As the ability to achieve beam focusing is dictated by the transmit antenna, we study near-field signalling considering different antenna structures, including fully-digital architectures, hybrid phase shifter-based precoders, and the emerging dynamic metasurface antenna (DMA) architecture for massive MIMO arrays. We first provide a mathematical model to characterize near-field wireless channels as well as the transmission pattern for the considered antenna architectures. Then, we formulate the beam focusing problem for the goal of maximizing the achievable sum-rate in multi-user networks. We propose efficient solutions based on the sum-rate maximization task for fully-digital, (phase shifters based-) hybrid and DMA architectures. Simulation results show the feasibility of the proposed beam focusing scheme for both single- and multi-user scenarios. In particular, the designed focused beams provide a new degree of freedom to mitigate interference in both angle and distance domains, which is not achievable using conventional far-field beam steering, allowing reliable communications for uses even residing at the same angular direction. [ABSTRACT FROM AUTHOR]

The article defines the concept of «strategy» as: plan, competitive actions, behavior model, market position, conception and perspective. The strategy is a comprehensive, unified and integrated plan, a set of actions and measures to solve a specific problem situation, achieving targeted goals that are developed in advance for a certain period of time. Current trends in the implementation of strategies include ensuring the quality of products, focusing on individual groups of consumers and improving products and services. The strategies of leadership, cost minimization and differentiation are typically focused on gaining a competitive advantage within a wide range of industry sector segments, while the focusing strategy involves gaining cost advantages or differentiation in narrow segments of the industry sector. Modern trends in the implementation of strategies of leadership, cost minimization and differentiation focus are identified on the example of enterprises of the EU countries. Three of the most popular company strategies are: 1) high quality focus – 52.3% of the EU companies use this strategy; 2) focus on satisfying established groups of consumers – 50.3%, which reflects the world-view or ways of thinking of entrepreneurs in these markets and confirms the theoretical idea that the strategy is a conception that has a manifestation in the world-view of stakeholders and business owners; 3) focus on improving the existing products and services, which are used by an average of 41.5% of companies. In addition, 37.7% of the EU firms use the focus on appealing to new consumer groups, and 36.7% of organizations use a specific solution for a client. It is proved that most companies in the EU use two or more strategies that are built on innovation activities (products, services, business processes) at the same time.