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This paper mainly investigates the 3-D resonant cavity problem with anisotropic and lossy media. When the media are electric lossy and not magnetic lossy, we solve the 3-D cavity model with magnetic field as a working variable by mixed finite-element method (MFEM). A Lagrange multiplier is used to enforce divergence-free condition in a weak sense. In the MFEM, we employ edge basis function of the lowest order to expand the electric field or the magnetic field, and linear element basis function to expand the Lagrange multiplier. Numerical experiments show that the MFEM can eliminate all the spurious modes to solve this type of 3-D closed cavity problem. [ABSTRACT FROM AUTHOR]

A new method is developed for integer ambiguity resolution in carrier-phase differential global navigation satellite system positioning. The method is novel in that it is simultaneously data-driven, generalized to include partial ambiguity resolution, and amenable to a full analytical characterization of the prior probabilities of correctly and incorrectly resolved ambiguities. The technique is termed generalized integer aperture bootstrapping (GIAB). A full development of the GIAB is provided herein, including sizing its integer aperture to usually produce a higher prior probability of full ambiguity resolution than comparable existing methods. In Monte-Carlo simulations, the GIAB is shown to provide nearly optimal ambiguity resolution success rates of full ambiguity resolution for relevant integrity requirements under strong models while enabling partial ambiguity resolution. [ABSTRACT FROM AUTHOR]

A full analysis of position-domain integrity is carried out for the recently introduced generalized integer aperture bootstrapping (GIAB) technique, a data-driven method for resolving and validating global navigation satellite system carrier-phase integer ambiguities suitable for high-integrity safety-critical systems. The analysis can be extended to all integer aperture (IA) techniques that are generalized in the sense of allowing partial integer fixing. It is shown that generalized IA methods produce relative position (baseline) estimates that suffer from nonnegligible biases. Key conditional distributions of the baseline computed from GIAB-validated ambiguities are rigorously derived for both full and partial ambiguity resolution. These distributions enable evaluation of the a posteriori risk from bias in the GIAB baseline estimate. Compared to enforced position-domain integrity risk of cycle resolution, the state-of-the-art high-integrity algorithm, GIAB is shown to satisfy tighter integrity requirements for the same measurement model. [ABSTRACT FROM AUTHOR]

This paper focuses on the contour extraction for the inner wires of a kind of deep hole component to achieve a high-accuracy inspection. The vision system consisting of a camera and an endoscope is developed to acquire high-quality images of the internal structure. For the acquired images, a contour extraction method is proposed, which could be divided into the following steps. First, the start points of wires referred as the prior information on the component are obtained with a predefined filter, and on the basis, several regions of interest (ROIs) are defined. Second, the multiscale probability of boundary operator is utilized to detect edges in the ROIs. Third, a Brownian motion model is established to calculate the connectivity between edges. The prior information obtained previously is used again to determine the probabilities of the edges belonging to the contours. Finally, the symmetric ratio contour method is used to form the wires’ contours with the edges. In the proposed method, the edges belonging to the wires’ contours are enhanced by making full use of the prior information, resulting in the improvement in accuracy and real-time performance. As evidenced by the experiments, the proposed method can efficiently extract the inner wires’ contours from the component’s image with low-contrast conditions, noises, and shadows. [ABSTRACT FROM AUTHOR]

A diagnostic test generation procedure targets fault pairs in a set of target faults with the goal of distinguishing all the fault pairs. When a fault pair cannot be distinguished, it prevents the diagnostic test set from providing information about the faults, and consequently, about defects whose diagnosis would have benefited from a diagnostic test for the indistinguishable fault pair. This is referred to in this paper as a diagnostic hole. This paper observes that it is possible to address diagnostic holes by targeting different but related fault pairs, possibly from a different fault model. As an example, this paper considers the case where diagnostic test generation is carried out for single stuck-at faults, and related bridging faults are used for addressing diagnostic holes. Considering fault detection, an undetectable single stuck-at fault implies that certain related bridging faults are undetectable. This paper observes that, even if a pair of single stuck-at faults is indistinguishable, a related pair of bridging faults may be distinguishable. Based on this observation, diagnostic tests for pairs of bridging faults are added to a diagnostic test set when the related single stuck-at faults are indistinguishable. Experimental results of defect diagnosis for defects that do not involve bridging faults demonstrate the importance of eliminating diagnostic holes. [ABSTRACT FROM AUTHOR]

Objective: Myoelectric hand prostheses have reached a considerable technological level and gained an increasing attention in assistive robotics. However, their abandonment rate remains high, with unintuitive control and lack of sensory feedback being major causes. Among the different types of sensory information, proprioception, e.g., information on hand aperture, is crucial to successfully perform everyday actions. Despite the many attempts in literature to restore and convey this type of feedback, much remains to be done to close the action-perception loop in prosthetic devices. Methods: With this as motivation, in this paper we introduce HapPro, a wearable, noninvasive haptic device that can convey proprioceptive information for a prosthetic hand. The device was used with an under-actuated, simple to control anthropomorphic robotic hand, providing information about hand aperture by mapping it to the position of a wheel that can run on the user's forearm. Tests with 43 able bodied subjects and one amputee subject were conducted in order to quantify the effectiveness of HapPro as a feedback device. Results: HapPro provided a good level of accuracy for item discrimination. Participants also reported the device to be intuitive and effective in conveying proprioceptive cues. Similar results were obtained in the proof-of-concept experiment with an amputee subject. Conclusions: Results show that HapPro is able to convey information on the opening of a prosthetic hand in a noninvasive way. Significance: Using this device for proprioceptive feedback could improve usability of myoelectric prostheses, potentially reducing abandonment and increasing quality of life for their users. [ABSTRACT FROM AUTHOR]

This paper addresses the unsupervised classification problems for multilook Polarimetric synthetic aperture radar (PolSAR) images by proposing a patch-level spatially variant Wishart mixture model (SVWMM) with double constraints. We construct this model by jointly modeling the pixels in a patch (rather than an individual pixel) so as to effectively capture the local correlation in the PolSAR images. More importantly, a responsibility parameter is introduced to the proposed model, providing not only the possibility to represent the importance of different pixels within a patch but also the additional flexibility for incorporating the spatial information. As such, double constraints are further imposed by simultaneously utilizing the similarities of the neighboring pixels, respectively, defined on two different parameter spaces (i.e., the hyperparameter in the posterior distribution of mixing coefficients and the responsibility parameter). Furthermore, the variational inference algorithm is developed to achieve effective learning of the proposed SVWMM with the closed-form updates, facilitating the automatic determination of the cluster number. Experimental results on several PolSAR data sets from both airborne and spaceborne sensors demonstrate that the proposed method is effective and it enables better performances on unsupervised classification than the conventional methods. [ABSTRACT FROM AUTHOR]

This paper presents high-isolation single-pole-single-throw (SPST) and single-pole-double-throw (SPDT) substrate integrated waveguide (SIW) mechanical switches in $V$ - and $W$ -bands. Four via holes with the proposed ring-and-cross etching patterns on the top side are placed in the middle of SIW path to block or pass the waves. As the ring-and-cross etching patterns being short-circuited, the via holes block the waves just like stockades do, in other words, turning the switch to OFF mode. And the ring-and-cross etching pattern makes the via holes invisible, turning the switch to ON mode. The $V$ - and $W$ -band SIW SPST and SPDT switches are designed and fabricated. The switches show the measured performances of better than 45-dB isolation for SPST and better than 50-dB isolation for SPDT, for $V$ -band operation, and a better than 50-dB isolation for both SPST and SPDT for $W$ -band operation. [ABSTRACT FROM AUTHOR]

The large hadron collider (LHC) upgrade, called high-luminosity LHC is planned for the next decade. A wide range of magnets and new technologies are currently under development. One of these systems will be a set of twin aperture beam orbit correctors positioned on the approaches to the ATLAS and CMS experiments. This twin aperture magnet system comprising 16 magnets, approximately 2 m long, with large 105-mm clear aperture coils. Each aperture will independently deliver 5-T·m integral field, between apertures the field vectors are rotated by 90° from each other, and individually powered. This paper presents the sequence of component developments to produce a cost-effective canted cosine theta model magnet. We describe the challenges encountered during the manufacture of the coil formers with their helical canted coil winding process which places a number of insulated wires into the 2-mm-wide 5-mm-deep slot. We describe the: pressurized impregnation process, multiple jointing to connect inner and outer sets of wires within the confines of the coil assembly, and magnet assembly into support structure and yoke. Finally, we present the quench performance and initial test results of this novel coil configuration. [ABSTRACT FROM AUTHOR]

The development of Nb3Sn quadrupole magnets for the High-Luminosity LHC upgrade is a joint venture between the US LHC Accelerator Research Program (LARP)1 and CERN with the goal of fabricating large aperture quadrupoles for the LHC interaction regions (IR). The inner triplet (low-β) NbTi quadrupoles in the IR will be replaced by the stronger Nb3Sn magnets boosting the LHC program of having 10-fold increase in integrated luminosity after the foreseen upgrades. Previously, LARP conducted successful tests of short and long models with up to 120 mm aperture. The first short 150mmaperture quadrupole modelMQXFS1 was assembled with coils fabricated by both CERN and LARP. The magnet demonstrated a strong performance at Fermilab's vertical magnet test facility reaching the LHC operating limits. This paper reports the latest results from MQXFS1 tests with changed pre stress levels. The overall magnet performance, including quench training and memory, ramp rate, and temperature dependence, is also summarized. [ABSTRACT FROM AUTHOR]

This paper presents a detailed theoretical analysis of the implications of nanoscale device structures on the average hole ballistic velocity calculated from quantum-mechanical strain-dependent 6\times 6~\text k \cdot \text p band-structure simulations. The simulations show that the crystallographic orientation of the uniaxial strain, channel, and surface affect the average ballistic velocity by modifying the energy–momentum (E − k) dispersion of the subbands (from which the ballistic velocity is calculated). Conversely, the analysis shows that semiconductor-body thickness and gate architecture influence the ballistic velocity by modifying the quantum confinement in the structure, which ultimately affects the relative hole occupation of k -states across different subbands. Key results of the work show that a 5-nm-body thickness yields a 6%–12% increase in the ballistic velocity compared to a 10-nm body. Likewise, a single-gate architecture gives up to an 11% increase over a double gate, but the improvement is dependent on the crystallographic surface orientation. Strained Ge shows a significantly enhanced ballistic velocity relative to strained Si for both {100}- and {110}-surface orientations with a predicted hole ballistic velocity exceeding 2 \times 10^7 cm/s at \textn_\texts^\textv+ = 5 \times 10^12 #/cm2. [ABSTRACT FROM PUBLISHER]

EuroCirCol is a conceptual design study for a post-LHC research infrastructure based on an energy-frontier of the 100-TeV circular hadron collider “Future Circular Collider.” In the frame of the high-field accelerator magnet design work package of this study, three different options for dipole magnets providing a field of 16 T in a 50-mm aperture are being considered: block-coils, common-coils, and cosine-theta. All options are being explored and will be compared based on the same assumptions, in particular for what regards the conductor performance, operating temperature, and margin. This paper details the cosine–theta option under development at INFN, showing the electromagnetic and mechanical choices. [ABSTRACT FROM PUBLISHER]

In Part I of this paper, we detected elements blocked by ribs during simulated and in vivo transcostal liver scans, and we turned those elements OFF to compensate for the loss in visibility of liver vasculature. Here, we apply blocked-element detection and adaptive compensation to large synthetic-aperture (SA) data collected through rib samples ex vivo, in order to reduce near-field clutter and to recover lateral resolution. To construct large synthetic transmit and receive apertures, we collected the individual-channel signals from a fully sampled matrix array at multiple and known array locations across the tissue samples. The blocked elements in SAs were detected using the method presented in Part I and retroactively turned OFF, while the subapertures covering intercostal spaces were either compounded, or coherently summed using uniform and adaptive element-weighting schemes. Turning OFF the blocked elements reduced the reverberation clutter by 5 dB on average. Adaptive weighing of the nonblocked elements to rescale the attenuated spatial frequencies reduced sidelobe levels by up to 5 dB for the transcostal acquisitions, and demonstrated a potential to restore lateral resolution to the nonblocked levels. In addition, the arrival-time surfaces were reconstructed to estimate the aberration from intercostal spaces and to offer further means to compensate for the loss of focus quality in transthoracic imaging. [ABSTRACT FROM AUTHOR]

Objective: Evolutionary stochastic global optimization algorithms are widely used in large-scale, nonconvex problems. However, enhancing the search efficiency and repeatability of these techniques often requires well-customized approaches. This study investigates one such approach. Methods: We use particle swarm optimization (PSO) algorithm to solve a 4D radiation therapy (RT) inverse planning problem, where the key idea is to use respiratory motion as an additional degree of freedom in lung cancer RT. The primary goal is to administer a lethal dose to the tumor target while sparing surrounding healthy tissue. Our optimization iteratively adjusts radiation fluence-weights for all beam apertures across all respiratory phases. We implement three PSO-based approaches: conventionally used unconstrained, hard-constrained, and our proposed virtual search. As proof of concept, five lung cancer patient cases are optimized over ten runs using each PSO approach. For comparison, a dynamically penalized likelihood (DPL) algorithm—a popular RT optimization technique is also implemented and used. Results: The proposed technique significantly improves the robustness to random initialization while requiring fewer iteration cycles to converge across all cases. DPL manages to find the global optimum in 2 out of 5 RT cases over significantly more iterations. Conclusion: The proposed virtual search approach boosts the swarm search efficiency, and consequently, improves the optimization convergence rate and robustness for PSO. Significance: RT planning is a large-scale, nonconvex optimization problem, where finding optimal solutions in a clinically practical time is critical. Our proposed approach can potentially improve the optimization efficiency in similar time-sensitive problems. [ABSTRACT FROM AUTHOR]

This communication introduces a novel periodic reflector which provides linear to circular polarization (CP) conversion in two frequency bands. Significantly, the reflector converts a slant 45° linearly polarized wave into two orthogonal CPs over two separate frequency bands while further the unit cell dimensions are maintained below the critical grating lobe limit of half wavelength. Unlike previous designs providing this performance, which are based on linear dipole elements, miniaturization is here achieved by exploiting resonances in both TE and TM polarized waves. The operating principle of the polarizer is discussed and a parametric study is presented to derive design guidelines. A prototype working in the satellite Ku-band has been designed and tested to validate the proposed design. The proposed polarizer can find applications in multiple-beam satellite antenna systems in order to reduce the number of reflector apertures in a single-feed-per-beam configuration. [ABSTRACT FROM AUTHOR]

A new structure of horizontally polarized (HP) antenna array is presented for azimuthal omnidirectional coverage. The proposed antenna array is engineered by breaking the fringing field symmetry along the typical parallel strip-lines, which is implemented by loading field-block structures alternatively and periodically. In physics, the blocking structures constrain the fringing fields inside, producing a series of rectangular open cavities operating at the \rmTM1n0 ( $n = 0.5$ ) mode. Counterintuitively, these asymmetric open cavities are able to generate an omnidirectional radiation pattern in the $E$ plane with horizontal polarization, similar to the linear magnetic current array. In order to verify the design strategy, a five-unit center-fed cascaded cavity array is fabricated and tested. The measured bandwidth is 120 MHz (5.83–5.95 GHz) with reflection coefficient lower than −10 dB. The HP omnidirectional pattern at 5.9 GHz provides a gain variation of 1.94 dB ranging from 6.7–8.64 dBi. [ABSTRACT FROM PUBLISHER]

In inverse synthetic aperture radar (ISAR) imaging of nonuniformly rotating targets, such as highly maneuvering airplanes and ships fluctuating with oceanic waves, azimuth echoes have to be modeled as cubic phase signals (CPSs) after the range migration compensation and the translational-induced phase error correction. For the CPS model, the chirp rate and the quadratic chirp rate, which deteriorate the azimuth focusing quality due to the Doppler frequency shift, need to be estimated with a parameter estimation algorithm. In this paper, by employing the proposed generalized scaled Fourier transform (GSCFT) and the nonuniform fast Fourier transform (NUFFT), a fast parameter estimation algorithm is presented and utilized in the ISAR imaging of the nonuniformly rotating target. Compared to the scaled Fourier transform-based algorithm, advantages of the fast parameter estimation algorithm include the following: 1) the computational cost is lower due to the utilization of the NUFFT, and 2) the GSCFT has a wider applicability in ISAR imaging applications. The CPS model and the algorithm implementation are verified with the real radar data of a ship target. In addition, the cross-term, which plays an important role in correlation algorithms, is analyzed for the fast parameter estimation algorithm. Through simulations of the synthetic data and the real radar data, we verify the effectiveness of the fast parameter estimation algorithm and the corresponding ISAR imaging algorithm. [ABSTRACT FROM PUBLISHER]

A finite difference time domain (FDTD) method for analyzing spheroidal open and closed structures is introduced. Its mathematical equations are derived and discretized according to a designed geometrical model. The field’s singularities at the domain’s center and vertical axis are dealt with by deriving alternative field formulas. The method is then extended to open domains by deriving an absorbing boundary condition (ABC). The stability of the obtained model is determined by deriving its mathematical condition. Finally, the method is used to characterize spheroidal cavities and a conformal patch antenna. [ABSTRACT FROM PUBLISHER]

Cavities that are partially filled with ferrite material provide a tunable resonance frequency by making use of the changing \mu-characteristics of ferrites when exposed to an external magnetic bias field. The concept of using either parallel or perpendicular magnetic biasing to reach a certain resonance frequency of a cavity has been known for many years. However, a cavity based on superposition of perpendicular and parallel magnetic fields to obtain improved ferrite characteristics was suggested in W. R. Smythe “Reducing ferrite tuner power loss by bias field rotation,” IEEE Trans. Nucl. Sci., vol. 30, no. 4, pp. 273–275, 1983, but to our knowledge was neither tested nor built. Such a 2-directional biasing is expected to provide a reduction in RF losses for an identical tuning range as compared with the classical 1-directional magnetic bias. We have successfully tested this theory with a measurement set-up consisting of a ferrite-filled cavity, exposed to external biases that allow the clear separation of the two orientations of superposed magnetic bias fields. The outcome is an enlargement of tuning range with high cavity Q and the possibility of fast tuning. In this paper, we describe the measurement set-up and present the tuning ranges that we attained by applying different bias schemes. [ABSTRACT FROM PUBLISHER]

Using the field imaging spectrometer system (FISS) recently developed by us, a new operational radiometric calibration (RC) model that takes into account three main adjustable sensor system settings, including the integration time (t), the aperture (F), and the detector temperature (T), is proposed. To better understand the influence of a single setting on the RC model, controlled experiments with one variable and two fixed settings were conducted and analyzed using a well-calibrated integrating sphere. Subsequently, a new variable was constructed with the ratio of t and F^2 to determine the system-setting-based RC model, where the radiometric offset was derived from system noise estimated by keeping the FISS entrance slit from a light source in a dark environment. Finally, the model was evaluated using experimental calibration results from the integrating-sphere data and real vegetation data. The results indicated that standard and calculated radiances were consistent over most spectral wavelengths. The proposed RC model could be effectively applied not only for the FISS and other ground-based sensors but also for future Chinese-developed intelligent remote sensing satellite systems that can automatically modify imaging settings in line with specific requirements. [ABSTRACT FROM PUBLISHER]

A microelectromechanical system tunable iris for miniaturized optical systems with a continuous tuning range of 0.45 mm to 1.56 mm is reported. In the proposed design, totally eight blades are combined together to form an octagonal aperture. These blades are evenly arranged in two chips and suspended with T-shaped beam structures, which are specially designed to convert the translatory movement provided by the electrostatic comb drive actuators into in-plane rotation of the blades. When all the blades are simultaneously rotated clockwise or counterclockwise, the aperture size will be increased or decreased accordingly. From experimental results, blade rotation angles of 10 ^\circ and 11^\circ have been demonstrated in the clockwise and counterclockwise directions, respectively. Consequently, a continuous tuning range from 0.45 mm to 1.56 mm for the aperture diameter of the as-fabricated tunable iris diaphragm has been successfully achieved. At the same time, the response time on the order of milliseconds has also been observed with the current device.\hfill[2011-0350] [ABSTRACT FROM AUTHOR]

An optofluidic iris, which uses the absorption of an opaque liquid in combination with a second transparent liquid for defining optical apertures of variable diameters, tuned by directly deforming a ring-shaped liquid–liquid interface using electrowetting on dielectrics, is presented. The novelty lies not only in the absence of any moving parts or membranes but also in the design of the liquid ring, which allows planar microfabrication processes to be used exclusively for defining all functional parts of the iris. When compared to other optofluidic approaches, this concept combines ultracompactness, full integration, moderate drive voltage (75 V), low power consumption (< 5 mW), highly robust and repeatable tunability, adequate tuning speed (< 1 s), high uniform transmission (> 86\%), and an optical quality suitable for imaging applications, with a fabrication process which will allow mass fabrication.\hfill[2012-0061] [ABSTRACT FROM AUTHOR]

This paper presents a 3-D near-field imaging algorithm that is formulated for 2-D wideband multiple-input–multiple-output (MIMO) imaging array topology. The proposed MIMO range migration technique performs the image reconstruction procedure in the frequency–wavenumber domain. The algorithm is able to completely compensate the curvature of the wavefront in the near-field through a specifically defined interpolation process and provides extremely high computational efficiency by the application of the fast Fourier transform. The implementation aspects of the algorithm and the sampling criteria of a MIMO aperture are discussed. The image reconstruction performance and computational efficiency of the algorithm are demonstrated both with numerical simulations and measurements using 2-D MIMO arrays. Real-time 3-D near-field imaging can be achieved with a real-aperture array by applying the proposed MIMO range migration techniques. [ABSTRACT FROM AUTHOR]

A through-the-wall radar image (TWRI) bears little resemblance to the equivalent optical image, making it difficult to interpret. To maximize the intelligence that may be obtained, it is desirable to automate the classification of targets in the image to support human operators. This paper presents a technique for classifying stationary targets based on the high-range resolution profile (HRRP) extracted from 3-D TWRIs. The dependence of the image on the target location is discussed using a system point spread function (PSF) approach. It is shown that the position dependence will cause a classifier to fail, unless the image to be classified is aligned to a classifier-training location. A target image alignment technique based on deconvolution of the image with the system PSF is proposed. Comparison of the aligned target images with measured images shows the alignment process introducing normalized mean squared error (NMSE) \leq 9%. The HRRP extracted from aligned target images are classified using a naive Bayesian classifier supported by principal component analysis. The classifier is tested using a real TWRI of canonical targets behind a concrete wall and shown to obtain correct classification rates \geq97%. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a hole-filling based memory controller of a disparity modification system for multiview three-dimensional video. Three-dimensional video provides realistic perception and is one component of the next generation of video. The key technique for three-dimensional displays is accurate disparity recording and hole filling in multiview three-dimensional video. In order to solve these problems, we present a hole-filling based memory controller to repair incorrect depth values using a hole-filling recorder in multiview three-dimensional video. Also, we adopt a three-camera approach to record the multiview stereo video and modify disparities in the system. [ABSTRACT FROM AUTHOR]

The contribution of synthetic aperture radar polarimetry in target detection is described and found to add valuable information. A new target detection methodology that makes novel use of the polarization fork of the target is described. The detector is based on a correlation procedure in the target space, and other target representations (e.g., Huynen parameters or a angle) can be employed. The mathematical formulation is general and can be applied to any kind of single target; however, in this paper, the detection is optimized for the odd and even bounces (the first two elements of the Pauli scattering vector) and for the oriented dipoles. Validation against real data shows significant agreement with the expected results based on the theoretical description. Index Terms-Polarimetry, polarization fork (PF), synthetic aperture radar (SAR), target detection, target recognition. [ABSTRACT FROM AUTHOR]

A specific feature of the acoustoelectric scattering of the nonuniform surface acoustic wave (SAW) beams by the straight metal strips placed on the piezoelectric substrates is discussed. A closed-form solution is obtained to describe the influence of diffraction on the reflective delay line with finite aperture. The found results allow us to develop the fast simulation and synthesis tool that can be applied to evaluate and compensate for the diffraction effect in SAW tags of arbitrary architectures. Efficiency of the proposed approach is illustrated by example of SAW tag synthesized on 128°-LiNbO3. [ABSTRACT FROM AUTHOR]

A dual-series approach is used to formulate scattering of a TE-polarized plane wave by a circular, PEC cylinder, having a longitudinal slot and enclosing two, eccentric, cylindrical dielectric layers. The dual-series equations are analytically regularized to a matrix Fredholm equation of the second kind by use of the Abel integral-transform method. The resulting infinite set of linear algebraic equations (i.s.l.a.e.) is truncated and solved numerically. The aforementioned analytical-numerical solution intrinsically takes into consideration the correct edge behavior of the field. Furthermore, the addition theorem of cylindrical wave functions is used to match the field components on any cylindrical interface. The numerical application manifests how the structure of the inner loading of this cylindrical cavity is imprinted on backscattering. Moreover, it is shown how the location of the innermost dielectric cylinder may contribute to the suppression or enhancement of resonances. [ABSTRACT FROM AUTHOR]

It is important to determine the severity of valvular regurgitation accurately because surgery is indicated only in severe regurgitations. The evaluation of, for example, mitral regurgitation is complex, and the current methods have limitations. We have developed a 3-D Doppler method to estimate the cross-sectional area and the geometry of a regurgitant jet at the vena contracta just downstream from the actual orifice. The back-scattered Doppler signal from multiple beams distributed over the area of interest was measured. The received power from these beams was then calibrated using both a priori knowledge of the lateral extent of the beams and a reference beam that was completely enclosed by the vena contracta. To isolate the Doppler signal received from the core of a regurgitant jet, a high pulse repetition frequency and a steep clutter filter are required. The method has been implemented and verified by computer simulations and by in vitro experiments using a pulsatile flow phantom and prosthetic valves with a range of holes. We were able to distinguish between mild, moderate, and severe valvular regurgitation. We were also able to quantify the regurgitational area as well as show the geometry of the regurgitation. [ABSTRACT FROM AUTHOR]

A new method for grating and side lobes suppression in ultrasound images is presented. It is based on an analysis of the phase diversity at the aperture data. Two coherence factors, namely the phase coherence factor (PCF) and the sign coherence factor (SCF), are proposed to weight the coherent sum output. Different from other approaches, phase rather than amplitude information is used to perform the correction action. Besides achieving the main goal, the method obtains improvements in lateral resolution and SNR. Implementation of the SCF technique is quite straightforward, operating in real-time, and can be added to any virtually existing beamformer to improve the resolution, contrast, SNR, and dynamic range of the images. A programmable parameter allows adjusting the sensitivity of the method to out-of-phase signals, from zero to a strict coherence criterion. The theoretical basis for the 2 methods are given and their performances evaluated by simulation. Then, experiment are conducted to provide results that are in good agreement with those expected from theory and simulation. [ABSTRACT FROM AUTHOR]

The mutual coupling between dipole antenna array elements using a planar meta-surface as superstrate is experimentally investigated. The meta-surface is based on grids of short metal strips and continuous wires. A comparison between the mutual coupling when the dipoles are radiating in free space and in presence of the superstrate is presented. On average, between 3 to 14 dB reduction of the mutual coupling is achieved when the superstrate is used. The effect of the mutual coupling on the radiation performance of the array is studied by spherical near-field measurements of the radiation pattern when one driven dipole is fed and the others are matched with 50 Ω loads. The back-projected field on the aperture and on the E-plane is shown. [ABSTRACT FROM AUTHOR]

Defence R&D Canada has an active research and development program on detection of explosive devices using nuclear methods. One system under development is a coded aperture-based X-ray backscatter imaging detector designed to provide sufficient speed, contrast and spatial resolution to detect antipersonnel landmines and improvised explosive devices. The successful development of a hand-held imaging detector requires, among other things, a light-weight, ruggedized detector with low power requirements, supplying high spatial resolution. The University of California, San Diego-designed HEXIS detector provides a modern, large area, high-temperature CZT imaging surface, robustly packaged in a light-weight housing with sound mechanical properties. Based on the potential for the HEXIS detector to be incorporated as the detection element of a hand-held imaging detector, the authors initiated a collaborative effort to demonstrate the capability of a coded aperture-based X-ray backscatter imaging detector. This paper will discuss the landmine and lED detection problem and review the coded aperture technique. Results from initial proof-of-principle experiments will then be reported. [ABSTRACT FROM AUTHOR]

An extensive 2-D computational model of the fundamental ionization and transport processes that occur inside electric propulsion hollow cathodes has. been developed over the last few years. The computed charged-particle fluxes from the plasma to the internal cathode surfaces have been used as input to a rudimentary hollow-cathode thermal model also developed recently. It is shown that, in hollow cathodes with a very small diameter orifice, the plasma density peaks inside the orifice and that the cathode is heated primarily by the orifice plate which is, in turn, heated by the plasma inside the orifice and along the orifice plate. As the orifice diameter increases the peak plasma density moves upstream of the orifice with ions and electrons contributing to the heating of both the orifice plate and the insert. In hollow cathodes with a very large diameter orifice the plasma extends along much of the insert, the plasma density peaks well within the insert region, and the cathode is heated primarily by ion bombardment of the insert. By solving a 2-D axisymmetric boundary value problem, it is also shown that when a voltage is applied between the ends of a long cylindrical channel the potential in the absence of the plasma falls almost by one order of magnitude with each radius downstream of the entrance. The implication is that cathodes with orifices of large length-to-radius ratio will be harder to ignite. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the impact of the spatiotemporal aperture of a channel sounding system equipped with antenna arrays at the transmitter and receiver on the accuracy of joint estimation of Doppler frequency and bidirection. The contribution of this paper is threefold. First, we state a spatiotemporal model that can describe parallel as well as switched sounding systems. The proposed model is applicable for arbitrary layouts of the spatial arrays. To simplify the derivations, we investigate the special case of linear spatial arrays. However, the results obtained for linear arrays can be generalized to arbitrary arrays. Secondly, we give the necessary and sufficient conditions for a spatiotemporal array to yield the minimum Cramér-Rao lower bound (CRLB) in the single-path case and Bayesian CRLB in the multipath case. The obtained conditions amount to an orthogonality condition on the spatiotemporal array. Thirdly, we define the Doppler-bidirection ambiguity function and derive the necessary and sufficient conditions for a linear spatiotemporal array to be ambiguous. Based on the ambiguity function, we define the normalized side-lobe level, which we propose to use as a figure of merit in the design of spatiotemporal arrays. [ABSTRACT FROM AUTHOR]

This paper presents a microfabricated planar patch-clamp electrode design and looks at the impact of several physical characteristics on seal formation. The device consists of a patch aperture, 1.5-2.5 μm in diameter and 7-12 μm in depth, with a reverse-side deep-etched 80-μm well. The patch aperture was coated with either thermal oxide or plasma-enhanced chemical vapor deposited (PECVD) SiO2. Some of the thermal oxide devices were converted into protruding nozzle structures, and some were boron-doped. Seal formation was tested with cultured N2a neuroblastoma cells. The PECVD oxide devices produced an average seal resistance of 34 MΩ(n = 24), and the thermal oxide devices produced an average seal resistance of 96 MΩ(n = 59). Seal resistance was found to positively correlate with patch aperture depth. Whole-cell recordings were obtained from 14% of cells tested with the thermal oxide devices, including a single recording where a gigaohm seal was obtained. [ABSTRACT FROM AUTHOR]

This paper describes a new approach for laser bone treatment according to a preoperative plan. The advantages of using laser systems are the free choice of the cutting geometry and the possibility of bone treatment without any severe thermal damage. On the other hand, the control of bone removal depth is difficult. Due to the lack of haptical feedback, it is only possible to control the bone removal visually. In addition, by selecting wrong laser parameters and incorrect handling, the tissue can sustain thermal damage. To solve this problem, an approach of navigated and model-based calculation of depth ablation has been investigated. The focus of this paper was to verify the feasibility of precise and safe laser bone removal by combining navigation information with mathematical and volumetric modeling. For the mathematical modeling, known approaches are used. On the basis of CT data, cavities in a bovine bone were planned with a navigation system. With an optical measurement system, the position of the laser handpiece was calculated relative to the bone. Using a mathematical model, the theoretical cavity depth was calculated for each laser pulse and displayed on the navigation screen. Thereby, the material removal was determined in a volume model. With this information, five cavities were created by the laser using constant energy settings. A final measurement of the cavities' depths showed an error of less than 1 mm. [ABSTRACT FROM AUTHOR]

The magnetic field of three scaled-radial-sector fixed field alternating gradient (FFAG)-magnets has been measured. The magnets have very large horizontal (1 m) and vertical (0.3 m) apertures to store muons and achieve phase rotation in an FFAG ring. The measurements results are compared to a three-dimensional field analysis using the TOSCA code; the generated magnetic field agrees satisfactorily with the TOSCA calculation in a range of 0.5\% for a large transversal (x-y-z) area. The three magnets show satisfactory performance for use in a ten-sector ring for a high-brightness muon source. [ABSTRACT FROM AUTHOR]

In this paper, a practical implementation of the spatial images technique for the analysis of shielded multilayered printed circuits inside convex cavities is proposed. A new method is introduced in order to automatically locate the images surrounding the structure in order to impose the appropriate boundary conditions for the potentials. The boundary conditions are imposed at discrete points along the cavity wall and, therefore, the technique proposed is an approximation to the exact cavity modeling. Furthermore, for the analysis of electrically long cavities, the use of several rings of images surrounding the entire cavity at different heights is employed. Using the special features of the formulation, a new method of moments implementation combined with the spatial images technique is proposed in order to efficiently analyze practical multilayered printed filters, considerably reducing the computational cost. Several examples with CPU time comparisons are provided, demonstrating the accuracy and efficiency of the new technique. A novel transversal filter in a trapezium-shaped cavity is designed, manufactured, and tested for the first time using the spatial images technique. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the problem of computing multiband filtering characteristics with a guarantee on their global optimality with respect to a Zolotarev-like criterion. An iterative algorithm based on linear programming is presented. This algorithm ensures quadratic convergence to the optimal solution. We also provide an equiripple-like criterion that allows one to check in a very simple manner whether a computed filtering function is optimal or not. The latter is used to analyze two practical design examples based on asymmetric dual-band specifications. In particular, it is shown that the selectivity of the dual-band response does not necessarily increase with the filter's order. This study yields some striking results when compared to the usual single-band situation, and introduces the idea that for certain asymmetric specifications some of the filter order values are more suitable than others. Finally, the practical implementations of the filtering devices in inline dual-mode cavities and stacked single-mode cavities are detailed. [ABSTRACT FROM AUTHOR]

Silicon pad-detectors fabricated from diffused oxygenated silicon were irradiated with reactor neutrons with fluences between 1 · 1014neq/cm² and 1 · 1015 neq/cm². The transient current technique was used to measure the trapping probability for holes and electrons. The results obtained support the model of a linear increase with fluence. Also the temperature dependence of the trapping time constant for electrons is investigated. This temperature dependence was found independent on the irradiated fluence. [ABSTRACT FROM AUTHOR]

We developed a new pseudoMOSFET technique by using an additional metallization, which directly contacts the Si-film to source and drain by Schottky contacts. In contrast to probe measurements, the drain current characteristics are independent of mechanical forces, and geometrical edge effects do not appear in electrical characteristics. We examined a variety of different contact metals in order to measure the mobility of electrons as well as holes. A theoretical explanation for the influence of the metal contacts on the electrical characteristics is presented. [ABSTRACT FROM AUTHOR]

Micropixellated InGaN light-emitting diodes (micro-LEDs) have a wide number of potential applications in areas including microdisplays, fluorescence-based assays and microscopy, and cell micromanipulation. Here, we present fabrication and performance details of matrix-addressable micro-LED devices which show significant improvements over their earlier counterparts. Devices with 64 × 64 micropixel elements, each of them having a 16-μm-diameter emission aperture on a 50-μm pitch, have been fabricated at blue (470 nm), green (510 nm), and UV (370 nm) wavelengths, respectively. Importantly, we have adopted a scheme of running n-metal tracks adjacent to each n-GaN mesa, so that resistance variation between the devices is reduced to below 8%, in contrast to the earlier fivefold resistance variation encountered. We have also made improvements to the spreading-layer formation scheme, resulting in significant increases in output power per element, improved current handling, and reduced turn-on voltages. These devices have been combined with a computer-driven programmable driver interface operating in constant-current mode, and representative microdisplay outputs are presented. [ABSTRACT FROM AUTHOR]

We propose a novel measurement system that evaluates the frequency stability of high-precision oscillators such as atomic oscillators. This measurement system consists of a pair of high-speed analog-to-digital converters (ADCs) and digital- signal-processing (DSP) circuits on a field programmable gate array. The pair of high-speed ADCs simultaneously digitizes the two sinusoidal-voltage outputs from the oscillator under test and a reference oscillator. The DSP circuits calculate the phase difference between the two sinusoidal voltages. The frequency stability evaluated as the Allan deviation σγ(τ) is calculated from the phase difference. The main advantage of this system is that the hardware configuration is much more compact than the conventional systems using a dual mixer and a local oscillator. Nonetheless, the system noise floor of the prototype at the nominal frequency of 5 MHz is σγ(1000 s) = 6.8 × 10-17, which is sufficient to evaluate a commercial hydrogen maser oscillator and is better by a factor of 5 than our previously reported system. We have verified that the measurement accuracy of the prototype depends on the nominal frequency and the level of the sinusoidal voltages, but it does not depend on the initial phase difference and offset frequency. [ABSTRACT FROM AUTHOR]

High-performance P-channel Ge FinFETs have been fabricated based on the rapid-melt-growth method. The fully depleted Ge FinFET has an OFF-state drain leakage current that is two orders of magnitude lower than the partially depleted one. The channel on the {110} surfaces provides an enhancement of the effective hole mobility of 60% and 28% at an effective field of 0.4 MV/cm compared with, respectively, silicon universal hole mobility and our previous work with {100} Ge-on-insulator pMOSFETs. [ABSTRACT FROM AUTHOR]

A new approach for multiport network modeling (MNM) of multilayer planar circuits coupled through slots in ground plane is introduced. Generalized network formulation for aperture problems is combined with Okoshi's model for planar circuits to obtain a unified circuit model for two irregularly shaped planar circuits coupled through a slot of arbitrary shape in their common ground plane. The methodology, which can be generalized to structures having more than two layers, is described by applying the method to a two-layer structure. Results for several sample structures will also be presented. [ABSTRACT FROM AUTHOR]

Alternating-aperture phase shift masking (AAPSM), a form of strong resolution enhancement technology, will be used to image critical features on the polysilicon layer at smaller technology nodes. This technology imposes additional constraints on the layouts beyond traditional design rules. Of particular note is the requirement that all critical features be flanked by opposite-phase shifters while the shifters obey minimum width and spacing requirements. A layout is called phase assignable if it satisfies this requirement. Phase conflicts have to be removed to enable the use of AAPSM for layouts that are not phase assignable. Previous work has sought to detect a suitable set of phase conflicts to be removed as well as correct them. This paper has two key contributions: 1) a new computationally efficient approach to detect a minimal set of phase conflicts, which when corrected will produce a phase-assignable layout, and 2) a novel layout modification scheme for correcting these phase conflicts with small layout area increase. Unlike previous formulations of this problem, the proposed solution for the conflict detection problem does not frame it as a graph bipartization problem. Instead, a simpler and more computationally efficient reduction is proposed. This simplification greatly improves the runtime while maintaining the same improvements in the quality of results obtained in Chiang et al. (Proc. DATE, 2005, p. 908). An average runtime speedup of 5.9× is achieved using the new flow. A new layout modification scheme suited for correcting phase conflicts in large standard-cell blocks is also proposed. The experiments show that the percentage area increase for making standard-cell blocks phase assignable ranges from 1.7% to 9.1%. [ABSTRACT FROM AUTHOR]

Most conventional blood flow estimation methods measure only the axial component of the blood velocity vector. In this study, we developed a new method for two-dimensional (2-D) velocity vector estimation in which time shifts resulting from blood motion are calculated for the individual channels using aperture domain data. This allows the construction of a time-shift profile along the array direction as a function of channel index, which is approximated by a first-order polynomial whose zeroth-order and first-order terms can be used to determine the axial and lateral velocity components, respectively. The efficacy of the proposed method was verified by simulations and experiments in which the transducer array had 64 elements, an aperture size of 1.96 cm, and a center frequency of 5 MHz. The flow velocity ranged from 5 to 35 cm/s and the Doppler angle ranged from 00 to 900. The experimental results show that the accuracy of axial velocity estimation is higher for the new method than for the autocorrelation-based conventional method when the signal-to-noise ratio is larger than 0 dB. The mean estimation error for the axial velocity component is 2.18% for the new method, compared to 4.51% for the conventional method. The mean estimation error for the lateral velocity component is 15%, which is comparable to existing methods. [ABSTRACT FROM AUTHOR]