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This article presents a fabrication method for a $C$ -band, low-power, frequency-modulated continuous wave (FMCW) radar front–end technology demonstrator that is fully embedded in a representative aerospace composite structure. This demonstrator uses a structural glass-fiber-reinforced polymer laminate as both the mechanical load-bearing element and the multilayer substrate for the integrated microwave circuitry. The system design and optimization have been described in detail. The electromagnetic simulation of the technology demonstrator was shown to be in excellent agreement with the measurement results. Finally, the FMCW radar front-end was tested as a complete system and shown to yield correct distance-to-target estimations. The demonstrated integration technique will lead to smart skins where electronic circuits and complete systems are embedded in load-bearing composite structures to yield truly multifunctional capabilities.

The penetration of microwave power inside a human head model is improved by employing a dielectric loaded rectangular waveguide as the transmission source. A multi-layer reflection model is investigated to evaluate the combined material characteristics of different lossy human head tissues at 2.45 GHz. A waveguide loaded with a calculated permittivity of 3.62 is shown to maximise the microwave power penetration at the desired frequency. A Quartz (SiO2) loaded rectangular waveguide fed by a microstrip antenna is designed to validate the power penetration improvement inside an inhomogeneous human head phantom. A measured 1.33 dB power penetration increment is observed for the dielectric loaded waveguide over a standard rectangular waveguide at 50 mm inside the head, with an 81.9% reduction in the size of the transmission source.

Presented in this letter is an improved version of the point scatterer vector tracking (PSVT) method for noise estimation in microwave coherent Doppler tomography (CDT). This new process of multipeak PSVT (MP-PSVT) significantly improves the quality of the tomogram given a noisy dataset. Phase shifts caused by positional displacements between the microwave source and center of rotation are compared against multiple isotropic scatterers placed within an image plane. Correlation between a subset of estimated shifts is then used to formulate a singular noise function. This noise function is used to deembed the original dataset thereby compensating for all phase errors. The example performed in this letter leads to a 0.91 correlation coefficient in the linear regression model containing the estimated noise and the applied noise. This new MP-PSVT approach significantly outperforms the original PSVT method.

This work presents a comparison between two metasurface antennas operating at 10 GHz utilizing either a conventional hexagonal grid (with a continuous distribution of gap dimensions) or a Voronoi partition (utilizing a constant gap dimension). The Voronoi partition was generated using the point-shifting method (proposed by Lee and Sievenpiper) and is (to the authors’ knowledge) the first demonstration of this approach in the design of a radiating metasurface antenna. The traditional hexagonal artificial impedance surface (H-AIS) and Voronoi artificial impedance surface (V-AIS) antennas are shown to exhibit near identical surface impedance profiles, insertion loss, radiation efficiency, and realized gain. However, the Voronoi partition can be adapted to follow an arbitrary conformal surface, whereas the hexagonal grid is restricted to a 2-D plane. To reinforce this advantage, a third metasurface antenna on an arbitrary conformal geometry is designed utilizing numerically generated “reference” and “objective” fields. Lastly, the fabrication of all three antennas utilized a unique process that is compatible with conventional aerospace glass fiber-reinforced composite manufacturing. Hence, this work represents a significant step forward in the deployment of truly conformal multifunctional composite structures.

HD 166620 was recently identified as a Maunder Minimum candidate based on nearly 50 years of Ca II H & K activity data from Mount Wilson and Keck-HIRES (Baum et al. 2022). These data showed clear cyclic behavior on a 17-year timescale during the Mount Wilson survey that became flat when picked up later with Keck-HIRES planet-search observations. Unfortunately, the transition between these two data sets -- and therefore the transition into the candidate Maunder Minimum phase -- contained little to no data. Here we present additional Mount Wilson data not present in Baum et al. (2022) along with photometry over a nearly 30-year baseline that definitively trace the transition from cyclic activity to a prolonged phase of flat activity. We present this as conclusive evidence of the star entering a grand magnetic minimum and therefore the first true Maunder Minimum analog. We further show that neither the overall brightness nor the chromospheric activity level (as measured by S$_{\mathrm{HK}}$) is significantly lower during the grand magnetic minimum than its activity cycle minimum, implying that anomalously low mean or instantaneous activity levels are not a good diagnostic or criterion for identifying additional Maunder Minimum candidates. Intraseasonal variability in S$_{\mathrm{HK}}$, however, is lower in the star's grand minimum; this may prove a useful symptom of the phenomenon., 6 pages, 1 figure, submitted to ApJL

ZusammenfassungHintergrundRupturen der Rotatorenmanschette sind eine der häufigsten Erkrankungen des Bewegungsapparats. Die klinischen und strukturellen Ergebnisse nach einer arthroskopischen Rotatorenmanschettenrekonstruktion (ARCR) sind im Allgemeinen gut, aber hinsichtlich der großen Schwankungsbreite der postoperativen Resultate noch verbesserungsfähig.FragestellungZiel dieser Literaturübersicht ist es, einen Überblick über prognostische Faktoren zu geben, die das postoperative Ergebnis nach ARCR beeinflussen.Material und MethodenSystematische Reviews, welche prognostische Faktoren für das Outcome nach ARCR analysieren, wurden in diese Übersichtsarbeit eingeschlossen. Die Literatursuche erfolgte in den Datenbanken Embase, Medline (Ovid) und Scopus. In die Auswertung wurden nur prognostischen Faktoren eingeschlossen, welche in mindestens zwei Übersichtsarbeiten beschrieben wurden.ErgebnisseSieben systematische Reviews mit insgesamt 332 eingeschlossenen Artikeln wurden ausgewertet. Postoperative Ergebnisse waren Patientenzufriedenheit, Lebensqualität sowie funktionelle und strukturelle Ergebnisse. Sechzehn prognostische Faktoren wurden identifiziert und in patientenbezogene, rupturbezogene und behandlungsbezogene prognostische Faktoren untergliedert.SchlussfolgerungAnhand von patienten-, ruptur- und behandlungsbezogenen prognostischen Faktoren soll in Zukunft ein Vorhersagemodell erstellt werden können, um die individuellen Heilungschancen nach ARCR vorherzusagen und dem Patienten eine präzise Therapieempfehlung abgeben zu können.

This work presents a technique to detect forest fire using incoherent scattering of radio waves from the ionized electron cloud of combusting plant material. Superheated forest matter ionizes a certain amount of the Alkali salt in plants creating a natural plasma frequency. This work investigates this plasma using a calibrated transmission line to identify the electromagnetic plasma frequency of forest fire. A plasma frequency of approximately 500 MHz has been identified by burning 4 grams and 6 grams of dry Eucalypt leaves. The plasma frequency was found to be stable as long as the biomass density is constant.

This article demonstrates a new method of determining depth in wideband coherent Doppler tomography (CDT) using only a monostatic arrangement. The method was developed to eliminate the smearing effects present when imaging a target wrapped around a conformal surface. All that is required is the addition of isotropic targets placed around the subject under test (SUT). Using only a single data set, two images containing differing reference planes are generated. The new algorithm locates the position of these points and correlates the dispersion of the peak spectral power for each one. It has appropriately been named the dual-layer peak matching (DLPM) technique. The DLPM technique will be performed in both the measured and simulated environments to consolidate the robustness of the results generated. For both examples, positional error falls within the range resolution for the measurement setup. All steps are demonstrated from the data acquisition to the final result, allowing the user to predict the depth (from here on referred to as the “ $\boldsymbol {\Delta z}$ ” location) of multiple scatterers in space. Finally, a tomographic image will be generated that encompasses the DLPM technique to eliminate smearing in the measured example.

We present five decades of chromospheric activity measurements in 59 Sun-like stars as time series. These include and extend the 35 yr of stellar chromospheric activity observations by the Mount Wilson Survey (1966--2001), and continued observations at Keck by the California Planet Search (1996--). The Mount Wilson Survey was studied closely in 1995, and revealed periodic activity cycles similar to the Sun's 11 yr cycle. The California Planet Search provides more than five decades of measurements, significantly improving our understanding of these stars' activity behavior. We have curated the activity measurements in order to create contiguous time series, and have classified the stellar sample according to a predetermined system. We have analyzed 29 stars with periodic cycles using the Lomb-Scargle periodogram, and present best-fit sinusoids to their activity time series. We report the best-fit periods for each cycling star, along with stellar parameters (T$_{eff}$, log(g), v$sin(i)$, etc.) for the entire sample. As a first application of these data, we offer a possible Maunder minimum candidate, HD 166620., 13 pages, 4 figures, 1 figure set, 2 tables, published in The Astronomical Journal

Teaching is often described as one of the most stressful occupations, contributing to the high rates of turnover and burnout afflicting the field. Early childhood teachers, especially those who teach outside of the public school system at the pre-kindergarten level, are at particular risk for a low sense of well-being. With a focus on teachers of children from birth to age 5, this chapter defines teacher well-being, identifies influences on teacher well-being, and discusses ways in which a teacher's well-being impacts the young children in their classroom. In addition, the authors describe a preschool teacher well-being initiative that is currently being implemented in South Carolina, the Be Well Care Well project. This chapter includes a detailed description of the Be Well Care Well model, shares initial program evaluation and impact data, and provides recommendations based on the implementation of the project thus far. Future directions for policy, practice, and research are discussed.

Procedural training is a universal concern amongst pediatric residents and their teachers. We developed and implemented formative assessments to generate direct and indirect procedural feedback. We analyzed changes in residents' perceived procedural knowledge, skills, confidence, and entrustment.Senior pediatric residents rotating in the pediatric emergency department participated in video-recorded formative assessments of informed consent OSCEs and simulated toddler forehead laceration repair and infant lumbar puncture. Residents reflected on their perceived procedural knowledge, skills, confidence, and entrustment through Likert and entrustment scales. Secondary outcomes of formative assessment completion rates and proportions of procedures performed by pediatric residents tracked feasibility and potential clinical impact, respectively.Including the pilot period, 89% of residents (31 out of 35) received direct and indirect procedural feedback. Perceived composite competency and entrustment improved for laceration repair (competency: from 3.1 to 3.9,Integrating feasible procedural formative assessments into the pediatric emergency department rotation had a positive impact on senior pediatric residents' perceptions of their procedural knowledge, skills, confidence, and entrustment and was associated with increased procedural engagement.

This letter utilizes the holographic principal to design two metasurface antennas with an equivalent electromagnetic performance. The first antenna is designed with a continuous metasurface impedance variation and serves as the baseline antenna (comparable to similar antennas in the literature). The second antenna is designed using two discrete metasurface impedance values realized with two distinct unit cell geometries. Both holographic antennas are shown to exhibit the equivalent electromagnetic performance. However, the latter design (requiring only two discrete impedance values) simplifies the holographic pattern manufacture, and therefore suggests a new avenue to realize “switchable” metasurface antennas capable of beam steering. The “continuous” and “discrete” antenna designs presented in this letter are fabricated using a unique manufacturing approach to realize a structurally integrated antenna in a representative aerospace glass fiber reinforced composite laminate.

Determining the high-frequency conductivity of a material is one of the critical steps in material characterization. In this paper, we introduce a new technique for determining the conductivity which is based on shielding effectiveness measurement in a rectangular waveguide. The proposed method has been validated using the simulation and measurement. The proposed method has shown a very good accuracy for determining the conductivity and has significant advantages over traditional techniques, such as simple setup/postprocessing, no need for vector measurement, high repeatability, and being capable of measuring high conductivities precisely. Besides these advantages, the proposed method has some limitation such as being suitable for good and/or thick conductors.

This article describes the design and fabrication of an active four-port microwave switching network embedded into a multilayer aerospace composite structure. The multifunctional design is based on three broadband Integrated Device Technology (IDT) F2972 single-pole-double-throw (SP2T) RF switches and also includes a control and power supply circuit. The composite structure has been developed using a preimpregnated structural glass (S-Glass) material (Hexcel HexPly 914E). The conductive tracks of the switch and its ground plane have been fabricated using a nonwoven carbon–nickel–copper (CNC) veil material and a semiflexible conducting silver ink. This article contains an analysis of the electrical properties of both materials at microwave frequencies. The equivalent electrical conductivities of materials were determined using a curve fitting method that was then used to verify the computational modeling of the switching network. The RF switching network was developed based on a hybrid manufacturing approach. The RF transmission lines and a component of the control circuitry were transferred onto uncured pre-preg material using a laser to ablate select regions of the CNC veil material. Postcuring, flexible silver ink was additively printed onto the surface to create the remaining control circuits. The RF performance of the design has been evaluated, and it indicates that the overall performance was consistent with the measured S-parameters of the same circuit fabricated on Rogers 5880 substrate.

Ultra-wideband coherent Doppler tomography (UWB-CDT) is a method whereby complex frequency data are evaluated and back-projected at uniform angles around a subject under test (SUT). In the presence of phase shifts brought upon by the unwanted motion in the test equipment, generating a focused image becomes complex due to the nature of the back-projection integration process. This article will demonstrate a vector-based correction algorithm, which can be implemented during the nondestructive evaluation (NDE) of a target to compensate for down-range phase errors (brought upon by the factors external to the ideal measurement setup). This new method will be known as point scatterer vector tracking (PSVT). A coherent image can be constructed by using the returned scattering information contained within a complex time-domain envelope. For the proposed method, multiple vectors based on the estimated peak locations are used to track, correct, and reconstruct the path of an ideal point scatter. The demonstration of the algorithm with measured tomographic data combined with a simulated additive noise component is presented, along with a step-by-step approach to reconstruct the desired data set. It will be shown that by using this proposed method, a coherent CDT image with an average correlation coefficient of 0.71 can be recovered from the data that have been corrupted by the unwanted phase shifts.

This paper presents the analysis of magnetic LC (MLC) resonators loaded with differential microstrip transmission lines. The analysis is based on an equivalent circuit model describing the electromagnetic behavior of the MLC resonators. It is shown that a pair of microstrip lines loaded with MLC resonators exhibit a dual-mode bandstop response in the common mode of operation, while being transparent to the differential signals. This characteristic can be used in the design of differential transmission lines with wideband common mode suppression. Circuit models together with Bloch theorem are applied for the systematic design, where the dispersion analysis helps to estimate the maximum achievable common-mode rejection bandwidth. A systematic design procedure is developed for designing differential transmission lines using this method. The theoretical analysis is validated by designing and measuring a balanced transmission line using three cascaded MLC-based cells. The measurements exhibit more than 40-dB common-mode signal suppression for a fractional bandwidth of 32% around 1.3 GHz, whereas the fraction bandwidth for 20-dB suppression level is 57.5%. The fabricated prototype has a compact size of $0.09\lambda _{g}\times 0.37\lambda _{g}$ , where $\lambda _{g}$ is the guided wavelength at 1.3 GHz. A detailed comparison between the designed MLC-based differential transmission line and the state-of-the-art designs shows a superior performance of the MLC-based transmission lines in terms of size, fabrication simplicity, and the common-mode rejection level.

A compact 3-D antenna for microwave medical diagnosis is presented. The antenna is matched with an inhomogeneous human head allowing higher signal penetration so as to obtain more meaningful data reflected from inside the brain. Utilizing a folded inverted F-like structure and a slot-loaded ground plane, the antenna is a compact $0.23\,\,\lambda \times 0.23 \,\,\lambda \times 0.04 \,\,\lambda $ in size with respect to the lowest operating frequency. The antenna is backed with a rectangular cavity to minimize sidelobe and backlobe radiation. The cavity and folded antenna configuration achieve a highly directional radiation pattern toward the head with a front-to-back ratio of more than 17 dB. A curved inhomogeneous human head phantom is fabricated to validate the antenna performance for medical diagnosis applications. An operational frequency band from 1 to 1.7 GHz is achieved with the antenna attached to the surface of the phantom. Less than 0.0147 W/kg SAR is achieved throughout the operating frequency range, which is lower than the state of the art for comparable antennas. The salient characteristics of the proposed antenna make it a suitable candidate for microwave diagnosis of the human head.

Vanadium dioxide (VO2) has been identified as a material capable of transitioning from an insulator to a metal close to room temperature. Previous works have demonstrated potential applications of this material in various microwave components or devices. However, the complex permittivity and permeability characterization of the VO2 over X-band has not been previously reported. Knowledge of these properties is essential for accurate modeling of the components and devices utilizing VO2. This paper characterizes a VO2 film deposited on a quartz substrate in a WR90 waveguide using a vector network analyzer. The S-parameters, conductivity, relative complex permittivity, and permeability of the VO2 film are determined across the transition temperature.

Biodegradable natural fibre composites are increasingly developed for lightweight structural applications in automobile and construction industries with significant environmental benefit. This work aims to explore the sound and vibration properties of natural fibre composites that inevitably suffer menace of vibrations during their operations as engineering structures. Natural fibres (bamboo, cotton, flax) and polylactic acid (PLA) fibres were blended, carded, laid up and finally needle-punched to nonwoven mats before being consolidated at elevated temperature under compression. Vibration damping and acoustic measurements were conducted on these natural fibre composites and their behaviour was compared to that of a commercial panel, made of polypropylene (PP) matrix reinforced with hemp and kenaf fibres. From both the coincidence frequency analysis and wave number amplitude analysis, the cotton/bamboo/PLA composite laminate showed the best acoustic performance (coincidence frequency of 2448 Hz) that is related to the fineness of cotton fibres, bending stiffness, natural frequency and density of the composite panel. The results suggest that the bamboo/cotton hybrid composites can be a viable candidate for engineering applications that require good bending properties, high sound absorption and vibration damping properties.

There was a time when the predominant approach to exposing children to new drugs was to protect children from research. This has evolved over the past several decades into protecting children through research. To encourage pediatric studies and approval of pediatric medicines, governments have provided financial incentives as well as obligations/requirements for pharmaceutical companies to carry out pediatric studies in certain circumstances. The unique considerations for children have been acknowledged by the various governments and drug regulatory agencies through international dialogue and cooperation among patient and patient care representatives, regulatory agencies, and academic, clinical and manufacturing stakeholders. We describe pediatric drug regulation in five of the largest international drug regulatory agencies and additionally discuss efforts at international cooperation and discussion in pediatric drug regulation.