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In this paper, a novel prototype of a cable-driven prosthetic hand with biorealisitic muscle property was developed. A pair of antagonistic muscles controlled the flexion and extension of the prosthetic index finger. Biorealistic properties of muscle were emulated using a neuromorphic model of muscle reflex in real time. The model output was coupled to a servo motor that tracked the computed muscle force. The servo motor was able to track model output within a frequency range from 0 to 8.29 (Hz) with a phase shift from 2 to 205 (deg). Surface electromyography signals collected from the amputee's forearm were used as α commands to drive the muscle model. With this prototype system, we evaluated its characteristics for force and stiffness control. Results of the force variability test showed that the standard deviation of fingertip force was linear to the mean fingertip force, indicating that force variability was proportional to the background force. At different levels of antagonistic co-contraction, the index finger and muscles displayed different levels of stiffness corresponding to the degree of co-activation. This prototype system showed the similar compliant behaviors of human limbs actuated with biological muscles. In further studies, this prototype system would be thoroughly evaluated for its biorealistic properties, and integrated with sensors to investigate feedback strategies of various sensory information for individuals with amputation. Clinical Relevance- This article established an antagonistic control of a cable-driven prosthetic hand with biorealistic properties of muscle reflex for application to individuals with amputation.

Model-based biomimetic control with neuro-muscular reflex requires accurate representation of muscle fascicle length, which affects both force generation capability of muscle and dynamics of muscle spindle. However, physiological data are insufficient to guide the selection of range of fascicle length for task control. Here a reverse engineering approach was used to investigate the effects of different fascicle length range on controller's force control ability, so as to justify the selection of operating range of muscle length for a grasp force task. We compared 3 different ranges of fascicle length for their effects on force generation, i.e. R

In this paper, we study exact hypercore maintenance in large-scale dynamic hypergraphs. A hypergraph, whose hyperedges may contain a set of vertices rather than two vertices in pairwise graphs, can represent complex interactions in more sophisticated applications. However, the exponential number of hyperedges incurs unaffordable costs to recompute the hypercore number of vertices and hyperedges when updating a hypergraph. This motivates us to propose an efficient approach for exact hypercore maintenance with the intention of significantly reducing the hypercore updating time comparing with recomputation approaches. The proposed algorithms can pinpoint the vertices and hyperedges whose hypercore numbers have to be updated by only traversing a small sub-hypergraph. Extensive experiments on real-world and temporal hypergraphs demonstrate the superiority of our algorithms in terms of efficiency.

The design of a novel planar wideband phased antenna array operating over 7.5-19.5 GHz has been presented. The array radiator consists of a feeding patch and a couple of shorting patches which are connected to the ground plane with shorting vias and isolating vias. Good impedance matching can be obtained due to the shorting vias while the common-mode resonance is eliminated by the isolating vias. Both the infinite unit-cell model and the finite simulation model have been implemented to investigate the performance of the proposed antenna array. The obtained results have shown that the active VSWR is less than 2 for wide scan in the E-plane while the active VSWR is less than 3 for 45° scan in the H-plane. The whole thickness of the radiator is 3.4mm, indicating the possibility for low-profile applications.

A feasible and viable means for performing surveillance of a hypersonic vehicle is space-based system, which has been used for providing tracking results of near-space vehicles. In this paper, an adaptive infrared tracking method to a hypersonic cruise vehicle (HCV) is proposed. This approach contains three inherent parts: coverage analysis of the system, a space-based bearing-only positioning, and an adaptive tracking approach. An adaptive scheme based on the coverage analysis and the positioning results is proposed to achieve high estimation performance and guarantee generality. Simulation results for an adaptive scaling unscented Kalman filter (ASUKF) indicate the effectiveness of this approach.

Premature breakdown of GaN HEMTs is a common phenomenon which limits their application for power switching. However, the breakdown mechanisms are rarely discussed before. In this paper, we investigate critical factors for dominant breakdown mechanisms in AlGaN/GaN HEMTs by TCAD simulation and give a clear picture of different mechanisms depending on these factors. Three leakage paths at off state are revealed in this paper. Expanding the device size makes no sense for improving breakdown voltage in specific conditions. Reducing UID concentration and improving the quality of GaN buffer is critical.

A flexible endoscope introduces more dexterity to the image capturing in endoscopic surgery. However, manual control or automatic control based on instrument tracking does not handle the misorientation between the endoscopic video and the surgeon. We propose an automatic flexible endoscope control method that tracks the surgeon’s head with respect to the object in the surgical scene. The robotic flexible endoscope is actuated so that it captures the surgical scene from the same perspective as the surgeon. The surgeon wears a head-mounted display to observe the endoscopic video. The frustum of the flexible endoscope is rendered as an augmented reality overlay to provide surgical guidance. We developed the prototype, FlexiVision, integrating a 6-DOF robotic flexible endoscope based on the da Vinci Research Kit and Microsoft HoloLens. We evaluated the proposed automatic control method via a lesion observation task, and evaluated the AR surgical guidance in a lesion targeting task. The multi-user study results demonstrated that, for both tasks, FlexiVision significantly reduced the completion time (by 59% and 58%), number of errors (by 75% and 95%) and subjective task load level. With FlexiVision, the flexible endoscope could act as the surgeon’s eyes teleported into the abdominal cavity of the patient.

With the increasing popularity of the Internet, mobile Internet and the Internet of Things, the current network environment continues to become more complicated. Due to the increasing variety and severity of cybersecurity threats, traditional means of network security protection have ushered in a huge challenge. The network security posture prediction can effectively predict the network development trend in the future time based on the collected network history data, so this paper proposes an algorithm based on simulated annealing-particle swarm algorithm to optimize improved Elman neural network parameters to achieve posture prediction for network security. Taking advantage of the characteristic that the value of network security posture has periodicity, a simulated annealing algorithm is introduced along with an improved particle swarm algorithm to solve the problem that neural network training is prone to fall into a local optimal solution and achieve accurate prediction of the network security posture. Comparison of the proposed scheme with existing prediction methods validates that the scheme has a good posture prediction accuracy.

In this paper, an octahedron electronically beam-scanning antenna using a novel slot active frequency selective surface (AFSS) is presented. The antenna consists of eight panels of octagonal slot AFSS array and an omnidirectional feed antenna located in the center. The beam-scanning of the antenna is obtained by switching the states of the PIN diodes to reconfigure the AFSS as EM transparent or reflective to the incident electromagnetic waves. By controlling the DC bias voltages to PIN diodes which are grouped by columns, the directive beam of the antenna can be switched to cover the entire azimuth plane. A prototype is fabricated and measured. Simulation and measurement results of the antenna are presented to verify the design concept. It is shown that the designed octahedron electronically beam-scanning antenna can cover a full 360°horizontal angular range. The presented design shows obvious advantages in terms of low power consumption, low cost and easy fabrication.

This paper presents a concept of using half-power phase shifter to design a circularly polarized (CP) antenna. The half-power phase shifter is composed of an open slot and a microstrip line. By elaborately loading the open slot under the microstrip line, half-power energy is radiated and half-power energy is transmitted to the end. Interestingly, the transmission phase bandwidth obtained at the end is significantly increased owing to the loading of the open slot. By using this design method, a wideband CP antenna is developed, which is composed of a pair of wide slots and a pair of narrow slot. The narrow slot pair is loaded not only for radiation, but also for the wideband quadrature phase transmission to the wide slot pair. The developed CP was finally fabricated and measured to verify the design concept. Both the measured and simulated results show that the developed antenna can have a wide AR and impedance bandwidth from 1.95 GHz to 3.45 GHz.

A dual-polarized 2D multibeam antenna array working at millimeter-wave (mmWave) frequencies is presented in this paper. In conventional multibeam antenna arrays, low polarization discrimination (XPD) is observed when beams scan off the boresight. In our design, the differential feeding technique is employed in antenna element design to achieve high port isolation and high cross-polarization discrimination (XPD) for all beams. To validate this concept, the antenna array and the multibeam feeding network operating at 28 GHz are designed and fabricated. High XPD, high port isolation and stable radiation patterns are obtained in the designed antenna. The measured results show that the XPD for all beams are higher than 28 dB and port isolations are greater than 20 dB over the bandwidth 26.8 GHz-29.2 GHz. The proposed antenna is a promising candidate for future wireless communication systems due to good radiation performance, easy integration, low cost, and low profile.

A wideband dual-band dual-polarized antenna is presented in this paper for 5G base station applications. Two squared loop patches are utilized for lower band and upper band radiations, and also the size reduction. To excited the square loop patches, a linear and H-shaped slots are used to couple the energy to the top radiating patches. Due to the requirements of dual-band operation and very low reflection coefficients, balanced open-circuited stubs and high impedance line are elaborately introduced to match the dual-band operation. The proposed antenna was designed, fabricated, and measured for verification. The measured results show that the proposed antenna can work at 3.3-3.64 GHz and 4.8-5.02 GHz with the overlapped reflection coefficients lower than -15 dB and isolation higher than 33.3 dB. In addition, unidirectional radiation patterns are achieved at both lower and upper bands for 5G base station applications.

A Wideband dual circularly polarized antenna by using composited right/left-handed transmission line (CRLH-TL) unit cell is presented in this paper. The CPLH-TL unit cell is composed of a right-hand element with the negative phase shift and a left-hand element with the positive phase shift. With these different phase shift characteristics, a feed network combined with the phase shift element are elaborately designed to feed the crossed dipoles for DCP radiation. The designed DCP antenna was also fabricated and measured for verification. It shows the presented antenna has wide impedance bandwidth and low axial ratio for DCP radiation.

By adjusting the adjacent antenna spacing in terms of the relationship between the two required directions, previous techniques can multiplex two beams by changing the phase of different antennas. In this work, to maintain the adjacent antenna spacing as a fixed value and reduce the implementation complexity, one novel design with an equal magnitude constraint for all antennas, together with the inter-subarray coding scheme is proposed, which can achieve dual-beam multiplexing for arbitrary directions to serve two users via merely changing the analogue phase shift of each antenna. Following a most recent development in this area, the idea can be easily extended to multiple beams. Designed examples are provided to demonstrate the effectiveness of the proposed method.

In this paper, a class of three dimensional nonlinear chaotic dynamic systems, which have only one equilibrium position, are studied. The least conservative linear feedback control is introduced to make the systems globally exponentially stable. For four kinds of nonlinear chaotic systems, Sport D, I, J, L presented in reference [1], since the correlation of three equations in each system are good enough, it is relatively easy to realize linear feedback to achieve the aim of controlling chaos. Simulations are proposed to verify the good performance of the controlled systems with the given linear controllers.

This paper presents a millimeter-wave dual-polarized slot antenna array by using a SIW cavity supporting TE210 and TE120 modes. A crossed slot is etched over the cavity. The antenna element can be excited from two orthogonal directions to realize dual-polarization. Thanks to the orthogonality between TE210 and TE120 mode, high isolation and low cross-polarization are achieved in the antenna. A prototype of the designed antenna array is demonstrated at the center frequency of 25 GHz. The measured and simulated results are in good agreement showing that the antenna array has high radiation efficiency, high port isolation and low cross-polarization.

Beamforming networks such as Butler Matrices are important for multibeam array antenna applications. The challenge for Butler Matrix design is that their complexity increases with the number of ports. In this paper, a novel approach of designing a $16\times 16$ Butler Matrix with significant structure simplification is presented. The eight-port hybrids with no crossovers are used to simplify the network. To ensure the network has the same magnitude and phase responses as the standard one, the location and phase shifting value of each fixed phase shifter are derived from the $S$ -matrix of each hybrid. A $16\times 16$ Butler Matrix network operating from 9 GHz–11 GHz is designed to validate this concept. The compensated microstrip 3-dB/90° directional coupler, the phase shifter with a shunt open-and-short stub and the crossover with a resonating patch are used to reduce the transmission loss and enable broadband operation.

Despite the documented benefits of ridesourcing services, recent studies show that they can slow down traffic in the densest cities significantly. To implement congestion pricing policies upon those vehicles, regulators need to estimate the degree of congestion effect. This paper studies simulation-based approaches to address the two technical challenges arising from the representation of system dynamics and the optimization for congestion price mechanisms. To estimate the traffic state, we use a metamodel representation for traffic flow and a numerical method for data interpolation. To reduce the burden of replicating evaluation in stochastic optimization, we use a simulation optimization approach to compute the optimal congestion price. This data-driven approach can potentially be extended to solve large-scale congestion pricing problems with unobservable states.

A fourth-order filtering patch antenna with a novel coupling structure is presented in this paper. Using the proposed coupling structure, both the balanced coupling feed and cross-coupling are realized. Two identical slots etched on the ground plane are utilized to excite the radiating patch with the reduced cross-polarization level. A short slot etched on the ground plane is employed for cross-coupling, which introduces two controllable radiation nulls with a steep roll-off rate. In addition, owing to the split-ring resonators and hairpin resonators, the improved impedance bandwidth is achieved with the fourth-order filtering response. To demonstrate the proposed design techniques, both the filtering antenna element and the low-sidelobe array are designed, fabricated, and measured. The measured results show that the proposed antenna has the impedance bandwidth of 12% (4.78–5.39 GHz) with the total height of $0.06\lambda _{0}$ , the cross-polarization level lower than −31 dB, and two radiation nulls with the suppression higher than 31 dB. For the low-sidelobe antenna array, wide impedance bandwidth is also obtained with the sidelobe level below −28.7 dB, the cross-polarization level below −34 dB, and the out-of-band suppression better than 25 dB.

A novel design method of a wideband dual-polarized antenna is presented by using shorted dipoles, integrated baluns, and crossed feed lines. Simulation and equivalent circuit analysis of the antenna are given. To validate the design method, an antenna prototype is designed, optimized, fabricated, and measured. Measured results verify that the proposed antenna has an impedance bandwidth of 74.5% (from 1.69 to 3.7 GHz) for VSWR

A novel dual-polarized crossed slot planar array antenna is presented in this communication. The proposed design integrates the antenna array with the feeding networks on a single laminate. The antenna element is developed by using a TE210 and TE120 mode cavity, which is constructed by inserting a number of metalized posts around the crossed region of two perpendicular substrate integrated waveguides (SIWs). The crossed slot is etched over the cavity and is excited from two orthogonal directions to realize dual-polarization. Owing to the orthogonality between the TE210 and TE120 mode, high isolation and low cross-polarization are achieved. A prototype of the designed antenna array operating at 25 GHz is fabricated and measured. The measured results confirm that the presented array antenna has high port isolation (>41 dB), high cross-polarization discrimination (XPD) (>26 dB), and high aperture efficiency (40%). With the advantages of simple configuration, good radiation performance, and easy fabrication, this proposed array antenna is a good candidate for millimeter-wave wireless systems.

In the autonomous driving industry, vehicle dynamic models are important to control-in-the-loop simulations. For current commercial self-driving simulators, vehicle dynamic models are expressed explicitly by sophisticated analytical equations, which are accurate but difficult to build and expensive to scale to fleets of vehicles of different brands. In this paper, we introduce a highly automated learning-based vehicle dynamic modeling procedure, which has been deployed on Baidu Apollo self-driving platform, to support cross-vehicle data-driven applications on a large scale. Compared with our previous analytical models, the end-to-end learning-based dynamic models can achieve high accuracy with significantly reduced re-development effort.

This paper presents a novel continuously beam-steering dual-band, dual circularly polarized (CP) reflectarray. The dual band operation of the reflectarray is obtained by using the interleaved circularly polarized triangular patches as the radiating elements. Each of the patches has two proximity feed lines that are electromagnetically coupled to a branch line coupler, where the phase shifters are integrated. The phase shifter is realized by using a new type of high-frequency tunable dielectric materials, Lead Niobate Pyrochlores $Pb _{n} Nb _{2}O_{5+ {n}}\,($ PN). By controlling the applied voltage, the dielectric permittivity of the PN material can be changed. This characteristic is utilized to the design of tunable dielectric capacitors, which is placed between the ground and the signal line of a Co-planar waveguide (CPW) transmission line. To validate the design concept, X-band passive antenna prototype was designed, fabricated and measured. Preliminary results on the designed phase shifter and tunable dielectric materials are also presented in this paper.

A new method is proposed to achieve millimeter-wave two-beam multiplexing with arbitrary directions based on the interleaved subarray architecture. Beam interference can be mitigated and beam gain augmented by multiplexing multiple beams. Previous techniques can only multiplex two beams whose directions satisfy a specific relationship. By the proposed design and the associated inter-coding technique, two-beam multiplexing for arbitrary directions to serve two users is achieved. Design examples are provided to demonstrate the effectiveness of the proposed method.

Prosthetic hands are often rejected in part due to lack of compliant manipulation in grasp control. Such capability of compliant control is achieved in humans through the neuro-musculo-skeletal properties. Previous work developed a neuromorphic model that enabled human-like reflexes, which provided a testbed for a new strategy for prosthetic control. The previous model could maintain the joint angle after a torque perturbation, but it lacked differentiation in sizes of muscle fiber, thus the development of force was not smooth under Henneman's size-principle. Here we matched the differentiation of muscle fibers to the size of motoneurons, which allowed us to examine how reflex performance may be affected by varying motor-unit distribution. In a virtual prosthetic hand controlled by the virtual reflex, simulations showed that an enlarged population of small motor units tended to overdamp the hand, and delay the recovery of hand opening. We also tested how post-perturbation trajectories were affected by refining the force-length property of the muscle model. Results showed that the refined model with smooth force-length curve reduced overshoot and recovery time. This study is the first step towards constructing a complete “virtual reflex” to be integrated in a biomimetic controller for prosthetic hands.

A compact wideband dual-polarized antenna with enhanced upper out-of-band suppression is presented in this paper. The proposed antenna is an equivalent configuration of two electric dipoles and two magnetic dipoles using the crossed shunt loops. The incorporation of the electric and magnetic dipoles enables the antenna to achieve wide impedance bandwidth and a compact radiator size. In addition, four parasitic strips are inserted near the inner edge of the four loops to enhance the antenna upper out-of-band suppression at 3.5 GHz with improved impedance bandwidth. The antenna is fed by the crossed coaxial baluns with high isolation. A shorting sheet is introduced into the baluns to enhance the upper out-of-band suppression further and create another rejection at 4.9 GHz. To demonstrate the design method, the proposed antenna prototype was fabricated and measured. Measured results show that the proposed antenna has a wide impedance bandwidth of 1.625–3.05 GHz (61%) for ${S}_{11} dB with the isolation better than 38.3 dB. The upper out-of-band suppression of the antenna is also highly enhanced with measured ${S}_{11}>-2$ dB from 3.35 to 5.25 GHz. In addition, stable antenna gain and radiation patterns are achieved for base station applications.

A compact dual-polarized patch antenna loaded with metamaterial unit cell is presented in this paper for broadband wireless communication systems. The unit cell is composed of two crossed open loop resonators, which are printed on the crossed substrates. Thanks to the loading of the unit cell, a compact patch antenna is realized with two reflection zeroes. The antenna is driven by the differential ports to obtain high isolation and low cross-polarization. The proposed antenna was fabricated and measured for verification. Measured results show that the proposed antenna has the impedance bandwidth of 17 % for S 11 < −10 dB with the cross polarization lower than -33 dB. Both the simulated and measured results prove that the proposed antenna can be a good candidate for the wireless communication.

This paper presents a broadband integrated Butler Matrix beamforming network (BFN). This proposed Butler Matrix BFN operates between the bandwidth of 28 GHz to 32 GHz and is implemented with subtrate integrated waveguides (SIWs). To facilitate the design and enhance the output amplitude and phase response, the phase shifters are incorporated into the design of directional couplers. Thus, the design of phase shifters doe not take the phase of crossover as a reference. The compensating SIW phase shifter is introduced into the design of −45° phase shifter, which helps to enhance the phase response over the operating bandwidth. The simulated phase dispersions of the designed Butler Matrix BFN are with peak to peak errors of only 13°, and the amplitude response over the bandwidth is −6 3 ± 1.2 dB. The designed Butler Matrix BFN would be a potential candidate in future 5G communications and other wireless communication systems.

A novel waveguide slot filtering antenna with an embedded metamaterial is presented. This filtering antenna consists of a common waveguide slot antenna with longitudinal slots cut on the top broad wall of its rectangular waveguide and a metamaterial surface embedded in the bottom broad wall. The metasurface replaces the conventional metal plane in the form of a bed of nails. In the operating frequency band, the metasurface works as a perfect electric conductor, so the antenna radiates as the traditional waveguide slot antennas. While in the stopband, the metasurface performs as a perfect magnetic conductor to suppress the propagation of electromagnetic wave in the waveguide cavity, so the interference signal is rejected and a filter function is achieved. To show the design process and verify its feasibility, a filtering antenna prototype working in the $C$ -band and having a stopband in the $X$ -band is designed, fabricated, and tested. A good agreement between simulation and measurement is obtained, demonstrating efficient radiations in the working band and a strong suppression of more than 35 dB in the stopband.

Motivated by the meteoric rise in the adoption of both ride-hailing services (DiDi, Uber, Lyft, etc.) and dockless bikesharing services (Ofo, Mobike, LimeBike, etc.), we propose a multimodal system where passengers ride a dockless bikeshare to/from hubs where they switch modes to/from a carpool. The proposed mutlimodal system is a generalization of the existing Uber ExpressPool service. The goal of this paper is to test empirically the feasibility of the proposed multimodal system. We accomplish this goal with the aid of time-stamped taxi origin/destination data from New York City. The analysis has two steps: network design and trip assignment. First, we identify 17 carpool hub locations with a coverage of 1 km to capture all taxi trip demand within Manhattan during peak hours. After designing the network, we then assign trips to carpools, within each hub, that have similar trip start times and destinations. We formulate the assignment problem as an offline matching algorithm on a bipartite graph. We found that over 80 percent of all trips can be assigned to carpools at almost all hubs. Compared to a single-modal system, the multimodal system served the same number of passengers with 40 percent fewer taxis. We found the matching rate to be consistent for every month in 2015. These results provide initial evidence that multimodal connections between ride-hailing and dockless bikesharing are feasible, reduces passenger trip times, and decreases road congestion.

Tightly coupled array (TCA) antenna has become a hot topic of research recently, due to its\ud potential of enabling one single antenna array to operate over an extremely wide frequency range. Such an\ud array antenna is promising for applications in numerous wideband/multi-band and multi-function wireless\ud systems such as wideband high-resolution radars, 5G mobile communications, satellite communications,\ud global navigation satellite systems, sensors, wireless power transmission, internet of things and so on. Many\ud papers on this topic have been published by researchers internationally. This paper provides a detailed\ud review of the recent development on TCA that utilizes the capacitive coupling. The basic principles and the\ud historical evolution of the TCAs are introduced firstly. Then, recent development in the analysis and design\ud of TCAs, such as equivalent circuit analysis, bandwidth limitation analysis, array elements, feed structures,\ud substrates/superstrates loading, etc., are explained and discussed. The performances of the state-of-the-art\ud TCAs are presented and a comparison amongst some TCAs reported recently is summarized and discussed.\ud To illustrate the practical designs of TCA, one case study is provided, and the detailed design procedures of\ud the TCA are explained so as to demonstrate the TCA design methodology. Simulated results including the\ud VSWR at different angles of scanning, patterns and antenna gain are shown and discussed. A conclusion\ud and future work are given in the end.

This letter presents a wideband transmitarray (TA) with reduced profile. A novel unit cell based on a wideband bandpass filter is developed and applied to the design of the TA. The TA consists of two identical trilayer frequency selective surfaces (FSSs), thus it has a lower profile compared to traditional designs that use at least four FSS layers separated by quarter-wavelength air gaps to obtain the $\text{360}^\circ $ phase shift range. The FSS has a pair of square patches printed on the top and bottom layers, and a square slot loaded by four microstrip lines printed on the middle layer. The phase shift is achieved by simultaneously adjusting the size of the square patches. Within the frequency band of interest, the developed unit cell shows low insertion loss and sufficient phase shift range. An equivalent circuit model is developed to better understand the operating principles of the FSS. To validate the design concept, one prototype operating at 13.5 GHz is designed, fabricated, and measured. The measurement results show that the designed TA achieves $ {\text{16}}\%$ 1 dB gain bandwidth and $ {\text{60}}\%$ aperture efficiency. The developed unit cell has symmetric configurations so it can also be applied to the design of dual-polarized or circularly polarized TAs.