Cylindrical Array Research Articles

A hybrid GA-PSO optimization algorithm for conformal antenna array pattern synthesis

This paper introduces a hybrid genetic algorithm and particle swarm optimization algorithm (GA-PSO) dedicated to pattern synthesis of conformal antenna arrays. Taking advantages of both methods, the proposed hybrid GA-PSO optimization algorithm has fast convergence speed and high convergence accuracy when applied to antenna array pattern synthesis. To show the performance of the hybrid optimization algorithm, several typical test functions and optimization examples of a linear array pattern synthesis are illustrated. Finally, a 4 × 2 cylindrical conformal microstrip antenna array as a practical synthesis example is studied to demonstrate the proposed algorithm. The simulated and measured results have shown the proposed method is effective and reliable for conformal antenna array pattern synthesis.

Acute toxicity of craniospinal irradiation with volumetric-modulated arc therapy in children with solid tumors.

Craniospinal irradiation (CSI) is an important part of curative radiation therapy (RT) for many types of pediatric brain or solid tumors. After conventional CSI, long term survivors may experience sequelae due to unintended dose to normal tissue. Volumetric modulated arc therapy (VMAT) CSI reduces off-target doses at the cost of greater complexity and error risk, and we describe our initial experience in a group of pediatric patients with solid tumors presenting with disseminated or recurrent disease. Pediatric patients with brain tumors were identified at Children's Hospital Los Angeles from 2013 to 2015. Clinical characteristics, acute toxicity, and radiotherapy data were abstracted from their medical records. We identified 19 patients who received VMAT CSI. Quality assurance was performed with a cylindrical detector array and ion chamber measurements at the arc junctions. Patients had medulloblastoma or supratentorial primitive neuro-ectodermal tumor (n=14, 11 high risk), germ cell tumors (two), relapsed neuroblastoma (two), and atypical teratoid/rhabdoid tumor (one). The most common acute toxicity was hematologic, including leukopenia (11% grade [Gr] 2, 26% Gr 3, and 63% Gr 4), anemia (89% Gr 2), and thrombocytopenia (16% Gr 1-2, 26% Gr 3, and 37% Gr 4). Despite leukopenia, we encountered only two Gr 3 infections (urinary tract and lung). The majority required blood products (89% red blood cells and 68% platelets). Weight loss was also common (47% Gr 1 and 26% Gr 2). VMAT CSI, along with chemotherapy and anesthesia, is feasible with supportive care. Daily image-guided RT improves accuracy and reduces the risk of spinal cord overdose without increasing treatment time. Further research is needed to determine whether reducing doses to organs, such as thyroid, heart, or hippocampus, offsets the risk of increased volume of low-dose irradiation.

Interview

Mirhamed Mirmozafari from the University of Oklahoma, USA, talks to Electronics Letters about his paper ‘A Highly Isolated Crossed Dipole Antenna with Matched Copolar Beams’, page 470. Mirhamed Mirmozafari My research interests can be broadly described as antenna theory and computational electromagnetics. Presently, I am collaborating with a group of professors and antenna engineers at the Advanced Radar Research Center (ARRC) of the University of Oklahoma. Our research includes developing planar and cylindrical radar structures. A major challenge that we face is incorporating dual-linear polarisation into phased array antennas with high isolation between their corresponding ports and patterns. In addition, we are working on simple and inexpensive solutions that reduce the fabrication costs and complexity of the assembly. Weather observation and air surveillance share the same principle of detecting electromagnetic wave scattering. Therefore, it would be more cost-effective and easier to operate if a single radar network were used in combined missions. This was the basis for multifunction phased array radar (MPAR) that was initiated by the National Oceanic Atmospheric Administration and the Federal Aviation Agency. Research activities for MPAR have begun in industry, academia, and government laboratories to identify technical challenges, mitigate risk and develop technologies. After realising the intrinsic limitations of planar array radar in making accurate polarimetric measurements, my advisor, Dr. Guifu Zhang, and his colleagues and students are developing cylindrical polarimetric phased array radar (CPPAR) at the ARRC. In this Letter, we report a port-to-port isolation that is higher than 56 dB, which to the best of our knowledge is the highest measured isolation reported in the literature to date. It is accompanied by 40 dB isolation between patterns of the antenna. These parameters indicate the ability of the proposed crossed dipole to maintain two independent polarisations. Using two identical geometries for the two polarisations, we achieved a pair of matched co-polar patterns. This, in turn, allows for accurate weather measurements and enables polarimetric phased array radar to distinguish different hydrometeor types, e.g., rain vs melting snow or hail. Crossed dipoles have been widely reported in the literature. However, what makes our proposed antenna significant is the simplicity and the symmetry of the structure. The radiation elements are simple half-wavelength dipoles. High polarisation purity is achieved owing to the symmetry of the radiation elements that are perfectly separated below the principal ground plane. This separation is accomplished by using a stripline structure for each balun. Having considered the stripline structure with two sub-ground planes, one can easily understand that the fabrication process was our major technical challenge. It is worth mentioning that the proposed crossed dipole, though non-planar, is fabricated with inexpensive printed circuit board technology. This antenna was designed for the next generation of cylindrical polarimetric phased array radar for long-range weather measurements and accurate target discrimination. The high polarisation purity achieved by this antenna satisfies the 0.2 dB differential reflectivity required by weather applications. An important objective in designing such a crossed dipole was the elimination of the thick substrate over the large ground plane resulting in a better match between copolar patterns. We plan to develop the linear and the reconfigurable 2D array of the proposed crossed dipole. The linear array will be situated in a large cylindrical array and its features will be characterised. We also plan to examine other types of the balun (e.g. Marchand balun) in order to simplify the geometry. As part of our ongoing research, we are trying to implement similar geometries with 3D printing technology. This opens the door to the next generation of easy-to-fabricate antennas. We, at the Radar Innovations Laboratory of the University of Oklahoma, have discussed the feasibility of cylindrical and planar radar for multi-mission applications and addressed their related challenges. In particular, I have proposed a solution for a phased array antenna. This work is being continued with the development of new technologies with higher performance. Our future objective will be an antenna with high polarisation purity in and out of the principal planes. This would benefit the planar array antennas by providing a high cross-polar isolation when the beam is directed off-axis.

A highly decoupled transmit-receive array design with triangular elements at 7T.

Transmit arrays are essential tools for various RF shimming or parallel excitation techniques at 7T. Here we present an array design with triangular coils to improve diversity in the B1 profiles in the longitudinal (z) direction and allow for next-nearest neighbor decoupling. Two cylindrical 8-channel arrays having the same length and diameter, 1 of triangular coils and the other of rectangular coils, were constructed and compared in phantom imaging experiments using measures of excitation distribution for a variety of RF shim settings and geometry factor maps for different accelerations on different planes. Coupling between elements was -20 dB or better for all triangular coil pairs, but worse than -12 dB for several of the rectangular coil pairs. Both coils could produce adequate shims on a central transverse plane, but the same shim produced worse results off center for the triangular coil array than for the rectangular coil array. Compared to the rectangular coil array, the maximum geometry factor for the triangular coil array was reduced by a factor of 13.1 when using a 2-fold acceleration in the z-direction. An array design with triangular coils provides effective decoupling mechanisms for nearest and next-nearest neighboring elements, as well as diversity in B1 profiles along the z-direction, although this also means that individual slices must be shimmed separately. This design is well suited for parallel transmit applications while also having high receive sensitivity.

Fabrication of parabolic cylindrical microlens array by shaped femtosecond laser

A simple and efficient technique for fabricating parabolic cylindrical microlens arrays (CMLAs) on the surface of fused silica by shaped femtosecond (fs) laser direct-writing is demonstrated. By means of spatially shaping of a Gaussian fs laser beam to a Bessel distribution, an inversed cylindrical shape laser intensity profile is formed in a specific cross-sectional plane among the shaped optical field. Applying it to experiments, large area close-packed parabolic CMLAs with line-width of 37.5 μm and array size of about 5 × 5 mm are produced. The cross-sectional outline of obtained lenslets has a satisfied parabolic profile and the numerical aperture (NA) of lenslets is more than 0.35. Furthermore, the focusing performance of the fabricated CMLA is also tested in this work and it has been demonstrated that the focusing power of the CMLA with a parabolic profile is better than that with a semi-circular one.

High-efficient light absorption of monolayer graphene via cylindrical dielectric arrays and the sensing application

The efficiency of graphene-based optoelectronic devices is typically limited by the poor absolute absorption of light. A hybrid structure of monolayer graphene with cylindrical titanium dioxide (TiO2) array and aluminum oxide (Al2O3) spacer layer on aluminum (Al) substrate has been proposed to enhance the absorption for two-dimensional (2D) materials. By combining dielectric array with metal substrate, the structure achieves multiple absorption peaks with near unity absorbance at near-infrared wavelengths due to the resonant effect of dielectric array. Completed monolayer graphene is utilized in the design without any demand of manufacture process to form the periodic patterns. Further analysis indicates that the near-field enhancement induced by surface modes gives rise to the high absorption. This favorable field enhancement and tunability of absorption not only open up new approaches to accelerate the light-graphene interaction, but also show great potential for practical applications in high-performance optoelectronic devices, such as modulators and sensors.

Preparation of superhydrophobic copper surface by a novel silk-screen printing aided electrochemical machining method

A kind of superhydrophobic copper surface with micro-nanocomposite structure has been successfully fabricated by employing a silk-screen printing aided electrochemical machining method. At first silk-screen printing technology has been used to form a column point array mask, and then the microcolumn array would be fabricated by electrochemical machining (ECM) effect. In this study, the drop contact angles have been studied and scanning electron microscopy (SEM) has been used to study the surface characteristic of the workpiece. The experiment results show that the micro-nanocomposite structure with cylindrical array can be successfully fabricated on the metal surface. And the maximum contact angle is 151° when the fluoroalkylsilane ethanol solution was used to modify the machined surface in this study.

Transduction technologies for structural acoustics sonars

This presentation will describe underwater acoustic transduction technologies that the Naval Research Laboratory (NRL) has developed for structural acoustics sonars. The NRL “Skyfish” downward-looking sonar system is deployed on a 21-inch diameter autonomous underwater vehicle (AUV) that features a pair of extendable/retractable wings, each of which houses a thirty-two element cylindrical hydrophone array. The well-behaved acoustic source consists of a pair of transducers, each covering a separate frequency band. The source is designed to provide a fairly wide acoustic aperture for looking both fore and aft as well as in the port and starboard directions. Architectural details of the source and receiver, materials considerations, amplifier design, and experimental data will be presented. [This work supported by the Office of Naval Research & ESTCP.]

An effective method of choosing vertical beam pitch angle of sonar array

In order to obtain a better array gain, the sonar main-beam should point to the incident direction of acoustic waves. For stereoscopic sonars, such as cylindrical array sonar, the incident direction of acoustic wave contains both horizontal angle and vertical pitch angle (VPA). Due to the variation of acoustic VPA caused by hydrological condition, the array gain would decrease seriously when the VPA of sonar beam doesn't match the VPA of acoustic waves. To solve the above problem, we proposed a VPA optimization method for stereoscopic sonars. First,we analyzed the variation rule of both sonar array gain and the acoustic VPA. Then,search for the VPA of the sonar beam in the vertical directions by beam scanning, so as to maximize the array gain. Simulations results are provided to validate the performance of the proposed method.

Physical fields of hydroacoustic sonar arrays with baffle and cylindrical piezoceramic radiators with radial polarization

Article describes the method for calculating physical fields of the cylindrical sonar array formed with the some certain, finite number of cylindrical piezoceramic transducer with radial polarization, of compensated or strength design, and cylindrical, acoustical soft, baffle situated in the middle of the array. To obtain the equations, that allow us to calculatephysical fields of this array we have solved the “pass-through” problem of sound radiation of this array. The main feature of the studied problem was that we described the work of the transducer beginning from its electrical input, unlike the classical method, when we set the oscillating velocity of the surface of the transducer as a constant. In addition, thismethod for calculating parameters of the studied array allows us to take into consideration the interaction of the physical fields in the transducer and in the array generally, and the interaction between transducers in the array and between transducers and the baffle. Constructed mathematical model allows us to provide investigations for huge amount of cylindrical arrays of similar design, because, it allows us to change such parameters of array as its dimension generally, dimensions of the baffle, the distance between the baffle and the transducers, the working medium of the array, quantity of transducers in the array, the position of each transducer in the array and the parameters of each transducer, such as its own dimensions, such as the central diameter and the thickness of the piezoceramic rings, the filling of each transducer and the material of each transducer. The obtained solution of this problem allows us to calculate the acoustic potential and the displacement of the surface of transducer. Using these parameters we obtained the equations for calculating physical fields of transducer, such as electrical current, that used for studying electrical field, oscillating velocity of the surface of transducer, used for studying the mechanical field, and acoustic pressure, which allow us to study acoustic parameters of the array, such as its directivity characteristics.Also, the obtained solutions allow us to study the fields in the inner cavity of transducer, that is also of big interest.Bibl. 7, fig. 1.

Efficiency of the electrochemical treatment of textile effluent using two configurations of sacrificial electrodes

Textile industries have as main characteristic the generation of effluents with high color, and efficient treatment techniques are necessary. In this context, this study compared the efficiency of the electrochemical treatment for color removal from synthetic textile effluent using two configurations of sacrificial electrodes, parallel plates and array of cylindrical electrodes. For application of the electroflocculation technique, an electrochemical reactor was used, in a laboratory scale, operated in a continuous flow. The synthetic textile effluent was prepared with preset concentrations of reactive dye Blue 5G and sodium chloride. Sacrificial iron (Fe) electrodes with different configurations were used: parallel plates and cylindrical electrodes. The Hydraulic Retention Time (HRT) and electric current density (j) were controlled, and their effects on color removal were evaluated using a Central Composite Rotational Design (CCRD) composed of 12 trials. For the electrochemical treatment using parallel plates, the color removal efficiency ranged from 56.13% to 98.95% and for the electrochemical treatment using an array of cylindrical electrode, the color removal efficiency varied from 2.11% to 97.84%. The mathematical models representative of the process explained a high proportion of the total data variability, with a coefficient of variation of 99.49% and 97.21% for parallel plates and arrangement of cylindrical electrodes, respectively. The electrochemical treatment using parallel plates presents advantages over the configuration using a cylindrical electrode array, since the color removal efficiency is superior under the same operating conditions, representing economic and environmental gains.

LARGE-SCALE MIMO MC-CDMA SYSTEM USING COMBINED MULTIPLE BEAMFORMING AND SPATIAL MULTIPLEXING

This paper proposes a novel Large-scale (massive) Multi-input Multi-output Multi-carrier Code division multiple access (LS MIMO MC-CDMA) model and application to Fifth-Generation Mobile Communication Systems (5G). This system uses combined cylindrical array antenna multiple beamforming architecture with spatial multiplexing. The model is optimized by Min-Max criteria in order to minimize side lobes and maximize compression of propagation loss. The Monte Carlo simulation results unify with the analytical solution for system performance.

Fabrication of hybrid optical line generator by direct machining.

In this study, a mold of a line generator consisting of a cylindrical lens array with a triangular diffractive grating was ultra-precision diamond machined with Moore 350FG 5-axis ultra-precision machine. The design and the simulation of the hybrid structure were performed using ray tracing and exact electromagnetic theory. The machined hybrid lens structure was replicated to a UV-curable polymer and was then characterized and tested. The optical measurements show that the hybrid element works as designed.

Transmission characteristics of Y‐type optical distributor in triangular lattice photonic crystals with Al2O3 rods

AbstractIn this work, a Y‐type optical distributor formed by triangular lattice photonic crystals is numerically and experimentally investigated. The crystals are formed by cylindrical Al2O3 rods array in the air. The band gaps of TE modes for the photonic crystals are calculated by plane wave expansion method. Three photonic band gaps appear numerically within the normalized frequency range 0∼0.8 in the triangular lattice photonic crystals. Based on a Y‐type defect structure, an equal optical distributor is realized within the first photonic band gap of 0.2380 ∼0.2823 . The transmission characteristic of the distributor is calculated by finite element method. To validate the numerical results, experiments were performed in the microwave regime. An Agilent E8361C vector network analyzer was used. The measured reflection and transmission characteristics of the photonic crystals sample agree with the numerical results between 9.77 and 9.91 GHz in the first photonic band gap. At the frequency of 9.86 GHz, the isolation of the photonic crystals reaches −39.02 dB and about 95.72% energy reflecting back to the input port. Furthermore, the equal optical distributor is also validated by making a comparison between the numerical and experimental results.

IMU-assisted RSS Fingerprint-Based Localization with Cylindrical Antennas Array

The recent growing interest for RFID based localization has created a need for easier installation and more accurate for indoor positioning. The CAA (Cylindrical Antennas Array) that consists of twelve directional antennas has been developed in this paper. In the area covered by directional antennas, only one antennas array is needed to locate the tags with the proposed method. Based on the designed system, the paper proposed a fingerprint-based localization with the aid of IMU (Inertial Measurement Unit), which is used to assist the filtering of received RF data and get the knowledge of the efficiency of current fingerprint database (radio map). In addition, the received data vectors by CAA have twelve dimensions which could improve the fingerprint-based localization accuracy. The experiments were conducted with the proposed system to position the tags and make a comparison with other indoor localization methods. The result shows it could increase the positioning accuracy of tags and enhanced the performance of RSS-based fingerprint localization.1

Study on uniform irradiance of micro curved-light-emitting diode array

The curved light-emitting diode (LED) array has so many advantages over conventional planar micro LED array such as wider viewing angles, and convenience in its actual applications:curved mobile phone screen, curved smart watch screen, and wide-angle communication illumination light source, etc. Irradiance uniformity is considered to be one of the momentous parameters for evaluating the degree of display or communication lighting devices. In order to improve the untilization of micro-curved LED array in display illumination, we focus on uniform irradiance of cylindrical and spherical micro-LED array by the method of ray-tracing. The calculation results show that the curved radius R and LED radiation parameter m are main factors affecting the uniform irradiance of the cylindrical array. We can improve the energy utilization efficiency by arranging the array pixel positions rationally. The simulation of 1010 cylindrical array with bending radius R=5 cm shows that the uniformity of maximum irradiance can reach 90.5% when detection distance z=300 cm and the detection area is defined as {(x, y)|-100 x 100, -100 y 100}. Furthermore, the irradiance distribution of spherical array is calculated and the results show that the irradiance uniformity of the single spherical array is unrelated to the number of pixels when it surpasses three. The main factors that affect the irradiance distribution of the multi-ring LED array are the ring distribution coefficient K, the normal angle 0, and the luminous flux ratio of each ring . Also the two-ring LED array model is calculated when the pixel number of the first ring is set to be 6 and the second ring is assumed to be 12. And the simulation results show that the maximum irradiance uniformity of the two-ring LED array can reach 94.8% in which the value of 0 is set to be 20, the ring distribution coefficient K=0.5 and the two ring pixel unit luminous flux ratio =20. Experimentally, we adopt the approach of the two micro LEDs to confirm the accuracy of the theory. And the results show that the irradiance distributions of two LEDs with the values of angle =13, 15 and 17 are consistent with the theoretical calculations. Thus, the theoretical and the experimental results in the paper can offer references for curved-LED display and multi-mode intelligent illumination.

Crystallographic plane and topography-dependent growth of semipolar InGaN nanorods on patterned sapphire substrates by molecular beam epitaxy.

A low-cost, high-efficiency, and catalyst-free method for fabricating well-aligned and uniform semipolar InGaN nanorods (NRs) by molecular beam epitaxy (MBE) is proposed using an optimized patterned sapphire substrate (PSS) with high Miller index crystallographic planes. The dense, obliquely aligned, and high-quality semipolar (11[combining macron]02) InGaN NRs are fabricated on hexagonal pyramid arrays of the PSS for the first time in this work. A unique semipolar (11[combining macron]02) and polar (0001) InGaN NR array composite structure is thus achieved on a hexagonal pyramid PSS. The connected, uniform, and obliquely aligned NRs are formed on the PSS with cylindrical arrays. The cylindrical and hexagonal pyramid arrays of PSSs are structured by the standard photolithography process and etching techniques. Both pattern topography and crystallographic plane of the PSS significantly affect the morphology, dimension, and crystallographic orientation of InGaN NRs. It is clearly demonstrated that the PSS with exposed high Miller index crystallographic planes, with well-organized step-terrace structures, facilitates the growth of ordered and dense semipolar InGaN NRs. This work contributes to the thorough understanding of the nucleation and growth mechanisms of InGaN NRs on a high Miller index plane of the PSS with different topographies, as well as of those of controllably fabricating dense and uniform semipolar NRs, thus facilitating the fabrication of NR-based optoelectronic devices with enhanced performance.

The numerical simulation and experiment on extrusion roller embossing of light diffusion plate with micro-structure

Extrusion roller embossing process has demonstrated the ability to produce polymer film with micro-structure. However the influence of various parameters on the forming quality has not been understood clearly. In this paper, a light diffusion plate with semi cylindrical micro-structure array as the research object, the influence of the main processing parameters such as roller speed, pressuring distance and polymer film temperature to the rolling quality was investigated in detail by simulation and experimental methods. The results show that the thickness of the light diffusion plate and the micro-structure fitting diameter increases with the increasing of the roll speed and the polymer film temperature, and decreases with the increasing of the pressing distance. Besides, the simulation results conformed well to the experimental results.

Spatial Correlation Models of Large-Scale Antenna Topologies Using Maximum Power of Offset Distribution and its Application

In this paper, we present an approximate expression for spatial correlation of cylindrical and uniform rectangular arrays regarding the maximum power of offset distributions useful for evaluating geometry-based stochastic channel models. The underlying concept of the proposed spatial correlation expression is that the maximum power of arrival varies relative to the offset distribution in the azimuth and zenith domains. Verification is accomplished with the help of computer simulation, where perfect agreement between theoretical and Monte Carlo simulation results is found. Toward the implementation of large-scale MIMO transmitters in constrained physical spaces to accomplish the demands for the next generation of wireless systems, we examine the effect of the proposed spatial correlation model on the downlink (DL) performance of massive multi-input-multi-output (MIMO) system. Results illustrate that the DL capacity does not demonstrate any sensitivity to the effect of correlation by increasing the number of elements in a realistic massive MIMO channel. Surprisingly, while the spatial correlation restricts the DL capacity at a reduced number of transmit antennas, the restriction becomes insignificant as the number of transmit antennas increases. This supports existing developments that user channels decorrelate when the number of antennas at the base station increases. Finally, experimental results show that separation of more than half wavelength is inadequate to decorrelate the antenna elements.

Nano-Cylinder-Metal Biochemical Sensor Based on the Square Arrangement

This paper presents a novel geometrical structure of NPs on optical fiber for high-sensitivity biochemical sensors, which comprised a single-mode fiber and a cylindrical metallic nanoparticle array. The sensor performed detection through a metallic nanoparticle array, which was arranged in a pattern that rendered the sensor highly sensitive. To effectively reduce the resource of the simulation server, both finite element method and the eigenmode expansion method were performed in combination with a perfectly matched layer, a perfectly reflecting boundary, an object meshing method, and a boundary meshing method. With the area of the triangular elements used as a basis, the object boundary, small object, medium object, and large objects were meshed at a ratio of 1: 10: 146: 728. Results of the simulations indicated that the proposed sensor was short in physical length (approximately 320 $\mu \text{m}$ ), high in resolution (approximately −140 dB), and high in sensitivity (135221.334 nm/RIU).