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Over the previous three decades, researchers have dedicated significant efforts towards the advancing of glass fiber-reinforced polymer (GFRP) bars, aiming to address the challenges arising from corrosion in traditional steel reinforcement bars. This study intended to find the most efficient relation to compute compression load capacity for concrete columns of circular sections reinforced with GFRP through surveying equations from previous research and comparing the relations of the most popular GFRP codes (JSCE, AS, CSA, and ACI). The statistical analysis of the equations depends on a comparison of practical and theoretical load capacities, Young's modulus, compressive concrete strength, ratios of longitudinal and both types of transverse reinforcement, spirals, and hoops. The results of CSA and AS were close to each other, and they were better than those of JSCE and ACI regarding being efficient, safe, and consistent. In addition, JSCE demonstrated a high level of conservative in all the studied parameters, followed by the ACI, while the CSA and AS showed very low conservative rates. Furthermore, the AS showed superiority in all the studied parameters. In terms of statistical metrics, the AS exhibited a very low error rate. It was concluded that the AS relation is the most efficient and superior relation for computing the axial load carrying capacity (ALCC) of all the studied parameters, followed closely by the CSA code equation, and with a slightly larger margin, the ACI code equation then JSCE code equation with a slightly very large margin. [ABSTRACT FROM AUTHOR]

Circular hoops, rectilinear hoops with crossties, and spirals are widely used in reinforced concrete columns as transverse reinforcement to prevent shear failure and provide confinement. Besides transverse reinforcement, many researchers have used square or circular steel tubes to provide confinement to concrete. This paper compares experimentally the application of circular steel tubes and spirals in providing confinement to concrete. Five types of compressive test specimens were tested under axial compression, comprising one type of column confined by rectilinear hoops, one type of column confined by a circular steel tube, two types of columns confined by a combination of circular steel tube and rectilinear hoops, and one type of column confined by a combination of spirals and rectilinear hoops. The result showed that circular steel tubes confined the concrete core well and provided additional axial support. The compressive test specimens using circular steel tubes had 40.74% higher axial load-carrying capacity, exhibited more ductile behavior, and had less damage than compressive test specimens using spirals. It proved that circular steel tubes were more effective in providing confinement to concrete than spirals. Rectilinear hoops with a spacing of one-fourth and one-half of the column cross-section increased the maximum axial load by 57.78% and 20.89%, respectively. The effect of the arching action on the concrete between the rectilinear hoops and the circular steel tubes could be neglected so that there was no ineffectively confined area, and the outer concrete was assumed to be fully effectively confined by the rectilinear hoops. [ABSTRACT FROM AUTHOR]

Although estimating the post-cracking torsional stiffness is vital for distributing the torsional moment in analyzing statically indeterminate reinforced concrete (RC) structures, none of the North American codes provide an analytical approach for determining the torsional stiffness after cracking. Moreover, the scarcity of experimental work has resulted in the lack of torsion design provisions for concrete box girders reinforced with glass fiber-reinforced polymer (GFRP). Therefore, the purpose of this research was to study the stiffness characteristics of RC box girders reinforced with GFRP reinforcement and to provide a simple analysis technique that can be used to predict post-cracking torsional stiffness. Fourteen concrete box girders were fabricated and tested under a pure torsional moment. In addition, data on 10 solid rectangular RC beams with GFRP reinforcement was collected from the literature. The test results indicate that the concrete strength, as well as the ratio, type, and configuration of the web reinforcement, substantially affected the post-cracking torsional stiffness of the tested specimens. An analytical model was developed for estimating the torsional stiffness after cracking. This model was based on a thin-walled tube and space truss analogy using a concept of postcracking shear modulus. The proposed model considers the effect of concrete strength, the configuration and ratio of the GFRP web reinforcement, and the ratio of the GFRP longitudinal bars. In addition, an equation to calculate the ultimate twist of the GFRP-RC members was developed. The validity of the proposed model was investigated by analytically regenerating the torque-twist curves of the tested box girders and the other specimens available in the literature. [ABSTRACT FROM AUTHOR]

Over the previous three decades, researchers have dedicated significant efforts towards the advancing of glass fiber-reinforced polymer (GFRP) bars, aiming to address the challenges arising from corrosion in traditional steel reinforcement bars. This study intended to find the most efficient relation to compute compression load capacity for concrete columns of circular sections reinforced with GFRP through surveying equations from previous research and comparing the relations of the most popular GFRP codes (JSCE, AS, CSA, and ACI). The statistical analysis of the equations depends on a comparison of practical and theoretical load capacities, Young's modulus, compressive concrete strength, ratios of longitudinal and both types of transverse reinforcement, spirals, and hoops. The results of CSA and AS were close to each other, and they were better than those of JSCE and ACI regarding being efficient, safe, and consistent. In addition, JSCE demonstrated a high level of conservative in all the studied parameters, followed by the ACI, while the CSA and AS showed very low conservative rates. Furthermore, the AS showed superiority in all the studied parameters. In terms of statistical metrics, the AS exhibited a very low error rate. It was concluded that the AS relation is the most efficient and superior relation for computing the axial load carrying capacity (ALCC) of all the studied parameters, followed closely by the CSA code equation, and with a slightly larger margin, the ACI code equation then JSCE code equation with a slightly very large margin.

With the process of production， the wall roughness of spirals is not quantitative and very complex， if it is not properly controlled， the material separation effect will be seriously affected. Based on the previously established spiral flow field model and particle phase computational model， the influence of the wall roughness on the slurry flow of hematite and quartz and particle separation behaviors in Φ400mm spirals was systematically investigated. The simulation results show that the slurry depth， Reynolds number， and flow velocity have notable differences in radial distribution and fluctuation characteristics. With the increase of roughness， the separation fluid space significantly contracts when the roughness height reaches 0.1mm or higher. the range of laminar flow distribution expands， while the transition flow range narrows. The velocity values exhibit a clear correlation with the roughness. Higher roughness intensifies the fluctuation of the main flow and the inner circulation， leading to noticeable disruption of the inner circulation. For roughness height below 0.1mm， increasing the roughness facilitates the convergence of coarse hematite towards the inner margin， maintaining a high separation efficiency for coarse hematite and fine quartz. However， the separation efficiency decreases significantly with the further increase of roughness. The increase of roughness intensifies the distribution of fine hematite in the middle and outer regions， resulting in a substantial decrease in the separation efficiency of fine hematite and quartz. The change of particle separation behaviors is closely related to the change of flow field characteristics. [ABSTRACT FROM AUTHOR]

Since the 1970s, astronomers have struggled with the issue of how matter can be accreted to promote black-hole growth. While low-angular-momentum stars may be devoured by a black hole, they are not a sustainable source of fuel. Gas, which could potentially provide an abundant fuel source, presents another challenge due to its enormous angular momentum. While viscous torques are not significant, gas is subject to gravity torques from non-axisymmetric potentials such as bars and spirals. Primary bars can exchange angular momentum with the gas within corotation, causing it to spiral inwards until reaching the inner Lindblad resonance. An embedded nuclear bar can then take over. As the gas reaches the black hole's sphere of influence, the torque becomes negative, fueling the center. Dynamical friction also accelerates the infall of gas clouds closer to the nucleus. However, because of the Eddington limit, growing a black hole from a stellar-mass seed is a slow process. The existence of very massive black holes in the early universe remains a puzzle that could potentially be solved through direct collapse of massive clouds into black holes or super-Eddington accretion. [ABSTRACT FROM AUTHOR]

Over the last three decades, researchers have significantly contributed to advancing fiber-reinforced polymer (FRP) bars to address corrosion issues in conventional steel reinforcement bars embedded in components of reinforced concrete structures. This research aimed to establish an ideal allowable axial compression load for concrete columns reinforced with FRP using data from previous studies. This article compares and explains the contrasts of several of the most popular FRP codes (ACI, CSA, and JSCE) with one equation proposed in previous research using empirical information gleaned from the literature review. The models' statistical analysis compares theoretical and practical loads, Young's modulus, concrete strength, longitudinal reinforcement ratio, and transverse reinforcement ratio for hoops and spirals. Estimating the effect of FRP longitudinal bars on the applied load carried by FRP-reinforced concrete columns can be done with the help of an empirical equation that uses the compressive strength of concrete to estimate the axial stress of FRP longitudinal bars in concrete columns. Results from the CSA and the ACI were almost similar, and both were superior to those from the JSCE in terms of being ideal, consistent, and safe. The results for modulus of elasticity, concrete compressive strength, and transverse reinforcement ratio for spiral reinforcement were more stable, according to the CSA. In contrast, according to the ACI, results for longitudinal and transverse reinforcement ratios of hoop reinforcement were more stable and secure. Lastly, the previously proposed equation is the best way to determine the transverse reinforcement ratio for hoop reinforcement and the compressive strength of concrete from all codes. In conclusion, the previously proposed equation is the most effective for calculating the transverse reinforcement ratio for hoop reinforcement and compressive strength.

Pretensioned Spun Precast concrete (SPC) pile has become a very popular solution for deep foundation systems for its easier installation, higher bearing capacity, and overall cost-effectiveness. The pile system also brings both material and construction sustainability to the environment through its cleaner construction process and reduced consumption of construction materials. However, the smaller shear area of SPC piles arising from its hollowness is a big concern particularly when they are subjected to earthquake-induced liquefaction situations. This paper investigates the shear behavior of hollow pre-tensioned SPC piles experimentally. A total of ten full-scale SPC piles comprising high-strength concrete (50 MPa) and high-tensioned (HT) steel strands were manufactured through the centrifugal rotation and steam curing construction process. The pile segments consist of a variation in two different diameters, numbers of strands, thicknesses, presence of spirals, and spacing. The compressive strength of concrete was determined from the compression tests of extracted core samples from the SPC piles. All pile specimens were tested under a four-point loading up to failure. The load-deformation responses, crack propagations, failure patterns, beam-deformation, and load-strain responses at the pile surface were investigated under different circumstances. The experimental results suggested that the presence of spirals plays a pivotal role in shear capacity and their failure patterns whereas the number of strands does not have a significant role in the shear capacity enhancement. The shear resistance of SPC piles was found in a range of 12–15 % and 8–11 % of their allowable axial capacity with and without the presence of spirals, respectively. The tested ultimate shear resistance is observed to be higher than that of all code-recommended values. This research offers useful information for the SPC pile’s shear design that demonstrates its application in deep foundations of the seismic regions.

In application-oriented mathematics, particularly in the context of nonlinear system analysis, phase plane analysis through SageMath offers a visual display of the qualitative behaviour of solutions to differential equations without inundating students with cumbersome calculations of the plane-phase. A variety of examples is usually given to illustrate phase-plane behaviour. We approach these problems by considering a problem containing a single real parameter that exemplifies the various situations clearly and simply. We developed two computer programs in SageMath: one program calculates aspects of the Jacobian matrix and displays the phase plane portraits, the other determines the centre manifold. Computations and images generated with computer codes are useful in understanding dynamic models in biology, physics and engineering that involve planar non-linear autonomous differential equations. This paper covers analytical and computational skills that are helpful for students and teachers. [ABSTRACT FROM AUTHOR]

Dikey karıştırıcılı öğütücüler, çeşitli maden cevherinin ekonomik olarak öğütülmesinde kullanılırlar. Karıştırma vidası öğütme haznesinin üstüne dik eksenli çalışacak şekilde yataklanması yapılır. Öğütücü karıştırma sırasında oluşan zorlanmalara karşı mukavim olması ve rijitliğini koruması istenir. Bu nedenle parçalar birleştirilirken en iyi kaynak yöntemi seçilmelidir. Kaynaklı birleştirmelerde tüm kaynak işlemleri, istenen kaynak dikişi parametreleri, minimum bozulma ile mükemmel mekanik özellikler ile kaynaklı bir bağlantı elde etmek amacıyla kullanılır. Tozaltı Ark Kaynağı (SAW) işlemi, kolay uygulanabilirliği, yüksek akım yoğunluğu ve aynı anda birden fazla tel kullanarak büyük miktarda kaynak metali biriktirme kabiliyeti nedeniyle geniş endüstriyel uygulama alanı bulmaktadır. Özellikle aşınmış parçaları onarabilme özelliğinden dolayı imalatta çokça uygulanmaktadır. Kaliteli bir bağlantı elde etmek için, SAW’ın çeşitli proses parametrelerinin incelenmesi ve kaynak kalitesini iyileştirmek için hassas bir şekilde seçilmesi gerekir. SAW, daha sonra kaynak kalitesini etkileyen biriktirme hızı, seyreltme ve sertlik gibi performans çıktılarını etkileyen çok sayıda proses parametresi ile karakterize edilir. . Bu nedenle vida yapraklarının mile kaynağı SAW yöntemi ile yapılmıştır. SAW makinesi ile kaynak yapılmış deney numuneleri Taguchi'nin deney tasarımına göre veriler toplanmış ve sürecin girdi-çıktı ilişkilerini kurmak için varyans (ANOVA) ve regrasyon analizi yapılmıştır. Optimum kaynak parametrelerini belirlemek için ANN modellerine dayalı optimizasyon prosedürlerini kullanan iyi bir dikiş geometrisi elde edilmesi amaçlanmıştır. Bu tekniklerden elde edilen optimize edilmiş değerler deneysel sonuçlarla karşılaştırılmış ve sunulmuştur.

According to Giovanni Battista Riccioli (1598–1671), planets describe orbits in a fluid heaven in a helio-geocentric model of cosmos. In his Almagestum Novum (1651) he stresses the need for a novel and rigorous geometrical explanation for the motion of heavenly bodies, which considers a separate Primum Mobile as an unnecessary hypothesis. Riccioli rejects the standard eccentric-epicycle theory as unsatisfactory and argues for what he calls "Eccentrepicyclos" or "Epicepicycles." He takes the Keplerian elliptical theory into account and includes a variable oscillation of both the mobile eccentric center and the variation of the epicycle's diameter. As a result, planets move along spiral orbits that have variable sizes. The inequalities, which astronomers had always tried to explain, are now justified: the spiral trajectory, obtained by means of the oscillation of the eccentric center, warrants the first inequality, about the variation of the planets' velocity. The variable amplitude of the spirals, obtained by the variation of the epicycle's diameter, explains the second inequality, namely the apparent retrograde or progressive planetary motion. In the later work Astronomia Reformata (1665), Riccioli uses explicitly the term "ellipse." Riccioli's innovations are of great interest and help to understand the complexity of the astronomical debates about the best world-system. [ABSTRACT FROM AUTHOR]

This paper reports on the experiences of the authors teaching action research workshops as professional development for language teachers in Europe during the Covid-19 pandemic. It describes work carried out for Action Research Communities for Language Teachers, which is funded under the Training and Consultancies programme of the European Centre for Modern Languages of the Council of Europe as part of its aim to promote quality language education in Europe. The paper focuses on the necessary pivot from face-to-face to online action research workshops and project development in a difficult global context for a group of teachers in Lithuania. It outlines the challenges experienced by the authors and teacher participants, the lessons learned in online teaching of action research, and the positive outcomes for language teachers in setting out on their action research journeys. The paper contributes to the literature on action research in language education and professional development during Covid-19. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced polymer (GFRP) reinforcements are useful alternatives to traditional steel bars in concrete structures, particularly in vertical structural elements such as columns, as they are less prone to corrosion, and impart increasing strength and endurance of buildings. There is limited research on the finite element analysis (FEA) of the structural behavior of hollow glass fiber-reinforced polymer reinforced concrete (GFRPRC) columns. The hollow portion can be used for the service duct and for reducing the self-weight of the members. Numerical analysis of the compressive response of circular hollow concrete columns reinforced with GFRP bars and spirals is performed in this study. This article aims to investigate the axial behavior of hollow GFRP concrete columns and compare it with that of solid steel reinforced concrete (RC) columns as well as hollow steel RC columns. The Abaqus software is used to construct finite element models. After calibration of modeling using an experimental test result as a control model, a parametric study is conducted. The columns with the same geometry, loading, and boundary conditions are analyzed in the parametric study. It is resulted that the hollow GFRP concrete columns provide a greater confinement effect than the solid steel RC columns. The average variation in the ultimate axial load-carrying capacities of the experimental results, from that of the FEA values, is noted to be only 3.87%, while the average difference in the corresponding deformations is 7.08%. Moreover, the hollow GFRP concrete columns possess greater axial load and deformation capacities compared with the solid steel RC columns. [ABSTRACT FROM AUTHOR]

Since the 1970s, astronomers have struggled with the issue of how matter can be accreted to promote black-hole growth. While low-angular-momentum stars may be devoured by a black hole, they are not a sustainable source of fuel. Gas, which could potentially provide an abundant fuel source, presents another challenge due to its enormous angular momentum. While viscous torques are not significant, gas is subject to gravity torques from non-axisymmetric potentials such as bars and spirals. Primary bars can exchange angular momentum with the gas within corotation, causing it to spiral inwards until reaching the inner Lindblad resonance. An embedded nuclear bar can then take over. As the gas reaches the black hole’s sphere of influence, the torque becomes negative, fueling the center. Dynamical friction also accelerates the infall of gas clouds closer to the nucleus. However, because of the Eddington limit, growing a black hole from a stellar-mass seed is a slow process. The existence of very massive black holes in the early universe remains a puzzle that could potentially be solved through direct collapse of massive clouds into black holes or super-Eddington accretion.

Background: Parkinson disease (PD) is a neurodegenerative disease that has a wide range of motor symptoms, such as tremor. Tremors are involuntary movements that occur in rhythmic oscillations and are typically categorized into rest tremor or action tremor. Action tremor occurs during voluntary movements and is a debilitating symptom of PD. As noninvasive interventions are limited, there is an ever-increasing need for an effective intervention for individuals experiencing action tremors. The Microsoft Emma Watch, a wristband with 5 vibrating motors, is a noninvasive, nonpharmaceutical intervention for tremor attenuation. Objective: This pilot study investigated the use of the Emma Watch device to attenuate action tremor in people with PD. Methods: The sample included 9 people with PD who were assessed on handwriting and hand function tasks performed on a digitized tablet. Tasks included drawing horizontal or vertical lines, tracing a star, spiral, writing "elelelel" in cursive, and printing a standardized sentence. Each task was completed 3 times with the Emma Watch programmed at different vibration intensities, which were counterbalanced: high intensity, low intensity (sham), and no vibration. Digital analysis from the tablet captured kinematic, dynamic, and spatial attributes of drawing and writing samples to calculate mathematical indices that quantify upper limb motor function. APDM Opal sensors (APDM Wearable Technologies) placed on both wrists were used to calculate metrics of acceleration and jerk. A questionnaire was provided to each participant after using the Emma Watch to gain a better understanding of their perspectives of using the device. In addition, drawings were compared to determine whether there were any visual differences between intensities. Results: In total, 9 people with PD were tested: 4 males and 5 females with a mean age of 67 (SD 9.4) years. There were no differences between conditions in the outcomes of interest measured with the tablet (duration, mean velocity, number of peaks, pause time, and number of pauses). Visual differences were observed within a small subset of participants, some of whom reported perceived improvement. The majority of participants (8/9) reported the Emma Watch was comfortable, and no problems with the device were reported. Conclusions: There were visually depicted and subjectively reported improvements in handwriting for a small subset of individuals. This pilot study was limited by a small sample size, and this should be taken into consideration with the interpretation of the quantitative results. Combining vibratory devices, such as the Emma Watch, with task specific training, or personalizing the frequency to one's individual tremor may be important steps to consider when evaluating the effect of vibratory devices on hand function or writing ability in future studies. While the Emma Watch may help attenuate action tremor, its efficacy in improving fine motor or handwriting skills as a stand-alone tool remains to be demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, we discuss some very interesting curves on the plane: equiangular spirals and the closely related planar loxodromes. The planar loxodromes show the streamlines of a flat fluid with one sink and one source. As we will see, some of these curve are very curious. The paper uses elementary facts from the theory of complex variables and vector analysis. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering & Architectural Faculty of Eskisehir Osmangazi University / Eskişehir Osmangazi Üniversitesi Mühendislik ve Mimarlık Fakültesi Dergisi is the property of Eskisehir Osmangazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Partial discharge (PD) measurements under repetitive impulse voltages are critical for the qualification of inverter-fed motor insulation systems. Severe electromagnetic interference due to high frequency switching from power electronic devices can cause the traditional PD detection techniques of sinusoidal voltage unfeasible. This article presents the design of an Archimedes spiral antenna that can work effectively for PD detection under fast rise time repetitive impulse voltages. The antenna structure is optimized by a media superstrate with a high dielectric constant over the radiant surface. Through the optimized design, both the gains of the antenna in the 0.5–1.5 GHz frequency range and the signal-to-noise ratio for PD detection are increased substantially. Modeling and experimental results prove that the gain of the antenna can reach 2.5 dB in the frequency range of 500–900 MHz and become higher than 7.0 dB in the frequency range of 900–2.0 GHz, with a voltage standing–wave ratio smaller than 1.4. This seems to be a significant achievement for PD detection under fast rise time impulse voltages. [ABSTRACT FROM AUTHOR]

High-precision measurement of permittivity and thickness enables advanced quality control of microwave substrates. In this article, a subwavelength planar microwave sensor is proposed, which is composed of a single-microstrip transmission line with a pair of coupled circular complementary spiral resonators (CSRs). Thus, two robust band-stop notches in the transmission response are developed, which can be utilized for simultaneous thickness and permittivity measurements of a dielectric sheet. The mutual capacitance and inductance, which quantify the coupling effect between the two resonators, are added to the equivalent lumped circuit model. They enhance the frequency shifts, thus improving sensitivity. The results of full-wave simulations and measurements on five different types of samples verify the concept’s effectiveness. [ABSTRACT FROM AUTHOR]

A fiber-optic hydrophone based on extrinsic Fabry–Perot (F-P) interferometer is proposed. The sensitive element of the hydrophone is an Archimedes spiral metal diaphragm, and the inner surface of the diaphragm and the end face of the optical fiber form the F-P cavity. Due to the grooved surface of the sensitive diaphragm, the hydrophone is minimally affected by hydrostatic pressure. The geometry structure of sensor and finite element method (FEM) modeling is presented. Experiments of underwater acoustic response and sensitivity calibration of the hydrophone are carried out and the experimental phase results are demodulated by the orthogonal phase demodulation method based on birefringent crystals and polarization technology. The experiment results show that the hydrophone has a relatively flat signal-to-noise ratio (SNR) and sensitivity within 1–20 kHz, and the average sensitivity is −172.52 dB (re. 1 rad/ $\mu $ Pa) @ 1–20 kHz. We believe that this type of hydrophone has the potential to be applied in the field of underwater acoustic communication. [ABSTRACT FROM AUTHOR]

A variety of novel orbital angular momentum (OAM)-based communication or sensing systems have attracted much attention over the past decade, the superiority is brought about by nothing other than its orthogonality or vorticity. Plane spiral OAM (PSOAM) mode-group (MG) technique as a reconfigurable beamforming method can be used for building a multiple-in-multiple-out (MIMO) system to achieve the reduction in subchannel correlation, which benefits from the spiral phase distribution within the mainlobe. However, the demultiplexing process still depends on the MIMO algorithm, in which the receiver complexity is same as the conventional MIMO systems. In this article, a PSOAM MG orthogonal multiplexing communication link at the X-band using partial arc sampling receiving (PASR) scheme has been demonstrated experimentally. The MG channels have a good isolation of about 15 dB, and the existing performance can ensure the reliable 16-QAM wireless transmission. Besides, a real-time dual-channel video transmission experiment has been carried out to verify the channel isolation caused by MG’s orthogonality intuitively. More importantly, the demultiplexing procedure using the PASR scheme can be implemented by simple analog phase shifting operation with a lower receiver complexity compared with the conventional MIMO systems. [ABSTRACT FROM AUTHOR]

High-frequency converters with high power density have shown promise in recent years. Air-core planar inductors built with printed circuit boards can eliminate problems associated with the use of magnetic materials, such as iron loss and magnetic saturation. However, conventional air-core planar inductors suffer from eddy current loss. Eddy currents affect the resistance and inductance of the inductor. This article proposes a stranded wire structure to reduce eddy currents more than that in the conventional spiral wire structure. Eddy currents can be reduced by splitting the windings as well as currents of each split winding are balanced in the proposed structure. Seven types of air-core planar inductors were built, and their resistances, inductances, and impedances were measured to evaluate the effects of different structures on eddy currents. Furthermore, the temperature distribution of the planar inductors was measured while supplying a sinusoidal voltage with a power amplifier. The experimental results demonstrate the usefulness of the proposed stranded wire structure. Furthermore, the experimental result shows that the stray capacitance of the inductor can be reduced as a by-product of the proposed stranded wire structure. [ABSTRACT FROM AUTHOR]

Smart roads can potentially improve the safety and efficiency of present transportation systems and promote the future mass deployment of connected and autonomous vehicles (CAVs). In this article, based on the experience and lessons we learned from our research, field implementation, and industry engagement, we present our view about the phased and spiral development of smart roads and CAVs. A particular focus is on the development of an Internet of Things (IoT)-based system for smart roads to enable construction of a digital twin of the traffic and road system and various applications that can be built on that basis to improve the traffic safety and efficiency of current transportation systems, and the evolution of the IoT system to support the future mass deployment of CAVs. [ABSTRACT FROM AUTHOR]

Stretchable electronics are commonly used as a diverse class of interconnected architectures, which accommodate large strain during stretching. A systematic understanding of the underlying mechanism of these interconnects, i.e., stress/strain states is essential to optimize the spiral designs. Here, we demonstrate the in-depth structural response of the spiral-island system when subjected to in-plane and out-of-plane stretchings. We use numerical modeling to simulate the stresses and strains along the arm of the spiral when stretched at a prescribed displacement of 1000 μm. We show the strain contours for spirals connected in-series. Our results show that the additional spirals connected in-series share the prescribed displacement equally and thus lower the von Mises stresses and principal strains. We also compare the stress generated in arms for single spiral and triangular configurations, especially when we stretch out these configurations in-plane and out-of-plane. The evolved stress depends on the angular position of spirals for triangular configuration. For the out-of-plane case, we stretch the spirals vertically and diagonally outward, i.e., along the z direction and x-z directions, respectively. Our results show that spirals experience higher stress during stretching along the x-z direction. However, for the out-of-plane z direction stretching, the spiral's end, which is connected to the island, experiences higher stress as compared to that of x-z direction case. We use 3D printing to additively manufacture the replica for single spiral and triangular configuration and perform the tensile out-of-plane stretching. Our experimental results for elongations corroborate with numerical calculations. [ABSTRACT FROM AUTHOR]

Two-dimensional (2-D) arrays offer volumetric imaging capabilities without the need for probe translation or rotation. A sparse array with elements seeded in a tapering spiral pattern enables one-to-one connection to an ultrasound machine, thus allowing flexible transmission and reception strategies. To test the concept of sparse spiral array imaging, we have designed, realized, and characterized two prototype probes designed at 2.5-MHz low-frequency (LF) and 5-MHz high-frequency (HF) center frequencies. Both probes share the same electronic design, based on piezoelectric ceramics and rapid prototyping with printed circuit board substrates to wire the elements to external connectors. Different center frequencies were achieved by adjusting the piezoelectric layer thickness. The LF and HF prototype probes had 88% and 95% of working elements, producing peak pressures of 21 and 96 kPa/V when focused at 5 and 3 cm, respectively. The one-way −3-dB bandwidths were 26% and 32%. These results, together with experimental tests on tissue-mimicking phantoms, show that the probes are viable for volumetric imaging. [ABSTRACT FROM AUTHOR]

Spiral array transducers with a sparse 2-D aperture have demonstrated their potential in realizing 3-D ultrasound imaging with reduced data rates. Nevertheless, their feasibility in high-volume-rate imaging based on unfocused transmissions has yet to be established. From a metrology standpoint, it is essential to characterize the acoustic field of unfocused transmissions from spiral arrays not only to assess their safety but also to identify the root cause of imaging irregularities due to the array’s sparse aperture. Here, we present a field profile analysis of unfocused transmissions from a density-tapered spiral array transducer (256 hexagonal elements, 220- $\mu \text{m}$ element diameter, and 1-cm aperture diameter) through both simulations and hydrophone measurements. We investigated plane- and diverging-wave transmissions (five-cycle, 7.5-MHz pulses) from 0° to 10° steering for their beam intensity characteristics and wavefront arrival time profiles. Unfocused firings were also tested for B-mode imaging performance (ten compounded angles, −5° to 5° span). The array was found to produce unfocused transmissions with a peak negative pressure of 93.9 kPa at 2 cm depth. All transmissions steered up to 5° were free of secondary lobes within 12 dB of the main beam peak intensity. All wavefront arrival time profiles were found to closely match the expected profiles with maximum root-mean-squared errors of $0.054~\mu \text{s}$ for plane wave (PW) and $0.124~\mu \text{s}$ for diverging wave. The B-mode images showed good spatial resolution with a penetration depth of 22 mm in PW imaging. Overall, these results demonstrate that the density-tapered spiral array can facilitate unfocused transmissions below regulatory limits (mechanical index: 0.034; spatial-peak, pulse-average intensity: 0.298 W/cm2) and with suppressed secondary lobes while maintaining smooth wavefronts. [ABSTRACT FROM AUTHOR]

This letter presents a $V$ -band low phase noise voltage-controlled oscillator (VCO) design using a novel integrated two-branches defected ground structure (DGS) resonator in 0.18- $\mu \text{m}$ complementary metal-oxide-semiconductor (CMOS) technology. The proposed DGS resonator is realized in the top metal layer (M6) which has not only a higher quality factor than its predecessors but is also effective to reduce the length of interconnects. The measured carrier frequency and phase noise are 49 GHz and −122.05 dBc/Hz (−102.58 dBc/Hz) at 10-MHz (1-MHz) offset frequencies, respectively. The VCO core consumes 5.5 mW of dc power from the dc supply, which results in a figure of merit (FoM) of −189 dBc/Hz. The proposed VCO using the two-branches DGS resonator may give an alternative low-cost solution for designing a high-performance VCO or frequency synthesizer at $V$ -band and beyond. [ABSTRACT FROM AUTHOR]

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In order to map the migration and introduction of farming into Europe during the seventh and sixth millennia Before Common Era, archeologists have made a connection between the study of pottery and farming migration. We are interested here in the classification of pottery into coiling and spiral types based on their manufacturing techniques. To distinguish between these two techniques, we look for the lines formed by air bubbles embedded in the pottery samples. Current methods make use of bulky systems, such as computerized tomography scanners or synchrotrons. Microwave acquisition and processing offer an interesting alternative, due to the possibility to have compact and portable systems. In this article, we investigate the classification of pottery based on low-terahertz measurements in the D-band. We process the measurements with 3-D fast Fourier transform. The resulting matrix is classified with an artificial neural network, multilayer perceptron, which is optimized with the gray wolf optimizer, a bioinspired algorithm. The first results show that the accuracy reaches up to 99% using all the acquired spatial and frequency measurements. Then, we optimize the millimeter-wave (mm-Wave) measurement system with a critical criterion on accuracy in two different scenarios. In the first scenario, we reduce the spatial acquisition but maintain the wideband operation and the results show that the accuracy is between 85% and 96%. In the second one, we reduce the spatial acquisition and use a single frequency. For this second scenario, we achieve a classification accuracy, which is between 77% and 100%. [ABSTRACT FROM AUTHOR]

The Spreading Projection Algorithm for Rapid K-space sampLING, or SPARKLING, is an optimization-driven method that has been recently introduced for accelerated 2D MRI using compressed sensing. It has then been extended to address 3D imaging using either stacks of 2D sampling patterns or a local 3D strategy that optimizes a single sampling trajectory at a time. 2D SPARKLING actually performs variable density sampling (VDS) along a prescribed target density while maximizing sampling efficiency and meeting the gradient-based hardware constraints. However, 3D SPARKLING has remained limited in terms of acceleration factors along the third dimension if one wants to preserve a peaky point spread function (PSF) and thus good image quality. In this paper, in order to achieve higher acceleration factors in 3D imaging while preserving image quality, we propose a new efficient algorithm that performs optimization on full 3D SPARKLING. The proposed implementation based on fast multipole methods (FMM) allows us to design sampling patterns with up to ${10}^{{7}}$ k-space samples, thus opening the door to 3D VDS. We compare multi-CPU and GPU implementations and demonstrate that the latter is optimal for 3D imaging in the high-resolution acquisition regime ($600\mu $ m isotropic). Finally, we show that this novel optimization for full 3D SPARKLING outperforms stacking strategies or 3D twisted projection imaging through retrospective and prospective studies on NIST phantom and in vivo brain scans at 3 Tesla taking the particular case of ${T}_{{2}}$ *-w imaging. Overall the proposed method allows for 2.5-3.75x shorter scan times compared to GRAPPA-4 parallel imaging acquisition at 3 Tesla without compromising image quality. [ABSTRACT FROM AUTHOR]

To further optimize the electromagnetic characteristics of square spiral resonator (SSR) in wireless power transfer (WPT) system, the SSR fractal finite element model is established in the high frequency structure simulator (HFSS) simulation software based on Koch curve and Hilbert curve. The mechanism of the effect of Koch and Hilbert fractal structure on frequency and permeability characteristics of SSR is analyzed in depth. The inductance of the resonant coil is calculated by the Maxwell software and then a magnetically coupling resonant WPT (MCR-WPT) system operating at 6.78 MHz is constructed in HFSS. The influence mechanism of the spiral metamaterial (MM) structure combined with the Koch/Hilbert fractal on the transfer performance of MCR-WPT system is analyzed. The simulation and experimental results show that the power transfer efficiency (PTE) of the system can be improved effectively when the negative permeability/hybrid MM slab (NMS/HMS) based on Koch/Hilbert/initial SSRs is inserted in the middle of the transfer distance. In the experiment, the PTE of the HMS based on Hilbert fractal can be improved by up to 21.62%. [ABSTRACT FROM AUTHOR]

This article presents a new analytical approach for the calculation of mutual inductance based on magnetic vector potential (MVP). To demonstrate the proposed mutual inductance calculation method, planar spiral coils of polygonal shape with an arbitrary number of sides are discussed. The coils considered in this work are coaxial and assumed to be composed of concentric filaments. The flux produced by the primary and linking the secondary is calculated by the line integral of the MVP. In order to simplify the calculation strategy, the MVP contribution of only one side of each single-turn filament of the primary is considered due to the symmetry of the coils’ shapes. Accordingly, coupling flux across the surface surrounded by each turn of the secondary is calculated by the line integral of the MVP over half path of the filament’s turn. The accuracy of the new analytical approach is confirmed by examining coil systems with a different primary and secondary in terms of the number of sides, the number of turns, and size. Results of the new approach are compared with those obtained from Ansys Maxwell, analytical studies in the literature, and experimental to demonstrate the validity of the proposed method. Results from this work are in good agreement with those obtained from simulation, studies in the literature, and experiment that proves the feasibility of formulas used in this work. [ABSTRACT FROM AUTHOR]

Magnetic screws are characterized by their noncontact features, thus eliminating the disadvantage of friction loss inherent in traditional screws. Some applications require spiral-shaped screws; however, commercially available magnets are rarely spiral in shape. To obtain spiral-shaped screws, manufactures require molds or the magnets are spliced to desired shape. Unfortunately, these two fabrication processes both have drawbacks, which include, discontinuity in the magnetic flux, high cost, and reduced efficiency. This article therefore presents alternative approach that involves the design and fabrication of spiral magnetic screws via 3-D printing with magnetic materials. The prototypes were fabricated using two 3-D printing techniques, pellet deposit melting (PDM) and hybrid soft magnet selective laser melting (SLM). Finite element method is adopted to simulate and validate the fabricated magnetic screw. Experiment results, using the PDM fabricated magnets and the hybrid soft magnet SLM combined with commercial sintered NdFeB magnet are also provided, along with, verification of the design characteristics and the simulation results. [ABSTRACT FROM AUTHOR]

This brief presents a miniaturized bandpass filter (BPF) based on the shielded Archimedes spiral resonators using the multilayer printed circuit board (PCB) technology. The spiral resonators are incorporated inside a substrate integrated waveguide cavity, resulting in miniaturization by introducing additional coil-to-ground capacitance, and the enhancement of electromagnetic compatibility (EMC) due to the enclosed metal cavity. Detailed theoretical derivation for the resonator is presented to prove its miniaturized effect. A miniaturized 4th-order BPF for 5G N78 application is developed with the proposed resonators. Compactness is further realized by the multilayer geometrical arrangement, consisting of two types of inter-stage coupling. One is the horizontal edge coupling and the other is the vertical space coupling through the spiral slot. Transmission zeros (TZs) are generated on each side of the passband by source-to-load coupling. The proposed filter is featured with an extremely small volume, low loss, together with good surface-mountable characteristic. [ABSTRACT FROM AUTHOR]

Vortex electromagnetic (EM) waves carrying orbital angular momentum (OAM) have a helical phase front and a field strength with a singularity along the axial center, which is expected to obtain resolutions beyond the Rayleigh limit for imaging systems, and provide new instruments for accurate radar targets imaging. However, since the vortex EM beams feature a doughnut-like intensity profile with a central dark zone and the inconsistent divergence angles of the main lobe, it is difficult to simultaneously illuminate the target for vortex EM beams with different OAM mode, which results in limited echo energy. In addition, the restricted elevation resolution hinders the acquisition of target spatial information, which limits the development of the OAM-based radar detection technique. This contribution offers a new set of ideas and solutions for achieving the 3D ISAR imaging using the superposition of different plane spiral OAM (PSOAM) waves. First, eigenmode beam steering techniques based on radio PSOAM waves is introduced. Subsequently, the PSOAM-based ISAR imaging model for maneuvering targets is derived and the echo characteristics are analyzed. Third, the effective imaging method, based on the amplitude phase compensation and fast Tensor-SL0 reconstruction algorithm, is proposed to solve the 3D sparse imaging problem in a tensor way. Finally, simulations are carried out to verify that the proposed method not only significantly reduces the computational complexity of the image reconstruction, but also generates the 3D image with sidelobes and artifacts removed remarkably from sparse measurements. [ABSTRACT FROM AUTHOR]

This letter presents a frequency selective absorber (FSR) with a passband and two wide absorption bands. The structure is composed of a resistive layer and a bandpass frequency selective surface (FSS) layer. The resistive layer is a combination of metal lines with loaded resistors and rectangular spiral resonators, which generate parallel resonances. Square slots are designed in the bandpass FSS to produce parallel resonance inside the passband and perform as a metal plane outside the passband. A nearly transparent window can be obtained by adjusting the parallel resonant frequencies of two layers to be consistent. The simulation results show that the 3 dB transmission band ranges from 6.5 to 7.76 GHz, and the minimum insertion loss is 0.05 dB at 7.09 GHz. The dual-polarized FSR presents stable operating characteristics and realizes two absorption bands on both sides of the passband, and the fractional bandwidth of the reflection coefficient lower than −10 dB is up to 127%, which ranges from 2.69 to 12.04 GHz. In addition, the FSR is manufactured and measured, and the measurement results are consistent with the simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a novel implementation of Frequency Steerable Acoustic Transducers (FSATs) for guided waves (GWs) inspections. Unlike the conventional phased array systems, which demand a large number of transducers and complex wiring, FSATs benefit from inherent directional properties for generation and sensing ultrasonic guided waves, resulting in significant hardware simplification and cost reductions for GWs-based systems. The FSATs exploit the frequency-dependent spatial filtering effect, leading to a direct relationship between the direction of propagation and the frequency content of the transmitted signal. The proposed Piezoceramic FSAT is fabricated through patterning the spiral electrodes on a Piezoelectric (PZT) plate bonded on a supporting aluminum plate. In light of the need to investigate the influence of the generated stiffness caused by the PZT plate on the coupling behavior between the FSAT and the aluminum plate, Finite Element (FE) simulations were carried out. Furthermore, experimental validations were conducted using a Scanning Laser Doppler Vibrometer (SLDV) to highlight the directional capabilities of such devices. The results show that the generation of directional GWs in a host structure is substantially improved thanks to the high actuation strength of Piezoceramic materials employed in the proposed transducer. [ABSTRACT FROM AUTHOR]

Orbital angular momentum (OAM) carrying vortex beams has been studied and realized using different methods. However, the designed devices are usually capable of generating fixed OAM modes. Here, the concept of a modular radiating system based on tightly cascaded transmitarrays (TAs) provi- ding a compact and user-accessible modular radiating system suitable for affordable detecting and imaging systems is presented. The TA is based on a novel compact unit cell. The unit cell characteristics are explained and then cascaded for the TAs’ operation. Several prototype TA modules are realized, and their interactions for OAM mode interconversion are investigated. A restricted method for determining the OAM mode purity of the generated beams is employed. The simulated and experimental results are consistent with the theory, verifying the employed strategy. [ABSTRACT FROM AUTHOR]

Excitable media are systems which are at rest in the absence of external input but which respond to a sufficiently strong stimulus by sending a wave of "excitation" across the medium. Examples include cardiac, cortical, and other tissue in the central nervous system. In each of these examples evidence of rotating spiral waves has been observed and associated with abnormalities. How such waves are initiated is not well understood. In this numerical study of a standard mathematical model of excitable media, we obtain spirals and other oscillatory patterns by a method, simple in design, which had previously been ruled out. This method applies in a parameter range of "low excitability." We analyze the early stages of this process and show that long term stable oscillatory behavior, including spiral waves, can start with very simple initial conditions, such as two small spots of excitation and all other areas at rest, and no subsequent input or disturbance. Thus, there are no refractory cells in the initial condition. For this model, even random spots of stimulation result in periodic patterns relatively often, leading us to suggest that this could happen in living tissue. [ABSTRACT FROM AUTHOR]

With the proliferation of Internet of Things (IoT) technology, the number of devices and gadgets used per person is ever-increasing. There is an indispensable need for the extension of wireless power transfer (WPT) to charge multiple devices simultaneously without compromising the charging efficiency. To accommodate multiple units (tens) of wireless devices, planar transmitter coils are constrained by space and their efficiency is sensitive to the variation in receiver position and orientation. Hence in this letter, we adapt the concept of volume birdcage coil from magnetic resonance imaging (MRI) and design a cylindrical transmitter coil for WPT with a diameter of 500 mm and a length of 300 mm, called birdcage WPT charging bin, to efficiently charge multiple wireless devices in the bin at various positions and orientations. The designed birdcage WPT charging bin supplies a homogeneous and circularly polarized magnetic field which leads to a stable efficiency for the receivers at different locations and orientations around the bin axis in the bin. The bin was built and measurement was conducted for validating the performance. [ABSTRACT FROM AUTHOR]

This letter work develops a liquid metal-based spiral antenna for frequency reconfiguration over an ultrawide band and polarization reconfiguration at a partial operating band. Dual-layer polymethylmethacrylate microfluidic is glued on the dielectric substrate to provide channels for liquid metal flow. The syringe could smoothly control the liquid metal to change the lengths of the spiral antenna arms and result in effective frequency reconfiguration. Moreover, polarization reconfiguration between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) is achieved by redistributing the liquid metal from the upper layer microfluidic channels to the lower layer microfluidic channels. Experimental results demonstrate that the proposed antenna supports continuous frequency reconfiguration from 0.6 to 13.5 GHz and realizes polarization reconfiguration between RHCP and LHCP from 1 to 2.5 GHz. The presented design enabled robust communications over a broad frequency spectrum. [ABSTRACT FROM AUTHOR]

Low-profile wideband spiral antennas suffer from poor impedance matching and cross polarization at lower frequencies or high variation in gain at higher frequencies. These significant differences, primarily caused by electromagnetic coupling with a conventional conductive backing, and the resulting interference are addressed in this letter by suitably designing the profile of the conductor. The proposed geometry has a maximum height of 0.08 $\lambda _{m}$ at the minimum operating frequency and has wideband circular polarization performance with a good boresight gain response over 2–18 GHz range. After numerical investigations, a prototype antenna is fabricated and characterized. An excellent impedance matching and circular polarization behavior are measured close to 2 GHz while the variation in gain is limited between 5.8 and 8.6 dBic above 10 GHz. [ABSTRACT FROM AUTHOR]