Antenna Rod Research Articles

Mg‐Zn Ferrite Nanoparticles: A Brief Review on Synthesis, Characterizations, and Applications

AbstractFerrites are of great interest for both fundamental science and technological applications due to their outstanding physical, chemical, and magnetic properties. Among various ferrites, Mg‐Zn ferrites is one of the best magnetic materials for researchers due to their unique properties such as high electric resistivity, Curie temperature, low coercivity, low eddy current, dielectric losses, low cost, and better environmental stability. This makes ferrites suitable for many applications such as power transformers, microwave devices, computer memories, logic devices, recording heads, loading coils, antenna rods, color monitoring tubes, telecommunications, hyperthermia, and so forth. Mg‐Zn ferrite nanoparticles have gained increased interest for many applications such as catalysts, antimicrobial potential, and sensors for the detection of combustible gases (CH4, CO, and CO2). In this brief review, the strategies used in the synthesis of Mg‐Zn ferrite nanoparticles are summarized. The different structural, morphological, magnetic, and electric properties of these ferrites are analyzed.

Near-field coupling and wireless signal transmission using a magnetoelectric laminated composite antenna

Magnetoelectric (ME) antennas utilize the direct or converse ME effects at acoustic resonance to receive or transmit electromagnetic (EM) signals, making ultra-compact antennas feasible. This work presents a miniaturized ME antenna working at very low frequency (VLF) band. A piezoelectric wafer and magnetostrictive foils are bonded together to form the 12×2.1×0.08 cm3 ME antenna. The near-field coupling between the ME antenna and magnetic rod coil has been measured to verify the reciprocity. The proposed entire circuit simulation models agree well with the experimental results, explaining the maximum power gap and frequency offset phenomenon. In addition, both practical and simulation results confirm that near-field coupling depends on mutual inductance rather than EM radiation. Based on the emulation of circuits, L-section impedance matching networks are introduced to improve the original power transmission coefficient by 21 dB. The ME antenna is lightweight, wide-band, and easy to match compared with a conventional coil.

A High Gain Embedded Helix and Dielectric Rod Antenna with Low Side Lobe Levels for IoT Applications.

In this paper, a novel embedded helix dielectric rod antenna is presented for high gain radiation with circular polarization (CP) and low side lobe levels for IoT Applications. Different from the conventional dielectric rod antennas, this proposed antenna is an integrated structure that combines the advantages of the helix and dielectric rod antennas. The presented antenna mainly consists of three parts: a tapered helix as primary feeding for CP, a dielectric rod with printed loops embedded for higher directivity, and a dielectric rod end for improving the gain further. After studying and analyzing the working principles of each part, an optimum design operating at 8–9.7 GHz is carried out as an example. A prototype is also fabricated and tested. The measured results show that the prototype can provide 18.41 dB maximum gain within the length of 7.7 λ. The side lobe level is below −20 dB, and the axial ratio is better than 1.14 dB in the whole frequency band. Compared with the traditional helix antenna and dielectric rod antenna with the same electric length, the presented antenna has a higher gain with a lower side lobe level and with good polarization purity.

Marine cyanobacteria tune energy transfer efficiency in their light-harvesting antennae by modifying pigment coupling.

Photosynthetic light harvesting is the first step in harnessing sunlight toward biological productivity. To operate efficiently under a broad and dynamic range of environmental conditions, organisms must tune the harvesting process according to the available irradiance. The marine cyanobacteria Synechococcus WH8102 species is well-adapted to vertical mixing of the water column. By studying its responses to different light regimes, we identify a new photo-acclimation strategy. Under low light, the phycobilisome (PBS) is bigger, with extended rods, increasing the absorption cross-section. In contrast to what was reported in vascular plants and predicted by Forster resonance energy transfer (FRET) calculations, these longer rods transfer energy faster than in the phycobilisomes of cells acclimated to a higher light intensity. Comparison of cultures grown under different blue light intensities, using fluorescence lifetime and emission spectra dependence on temperature at the range of 4-200K invivo, indicates that the improved transfer arises from enhanced energetic coupling between the antenna rods' pigments. We suggest two physical models according to which the enhanced coupling strength results either from additional coupled pathways formed by rearranging rod packing or from the coupling becoming non-classical. In both cases, the energy transfer would be more efficient than standard one-dimensional FRET process. These findings suggest that coupling control can be a major factor in photosynthetic antenna acclimation to different light conditions.

Design and Implementation of a Test Fixture for ELF Schumann Resonance Magnetic Antenna Receiver and Magnetic Permeability Measurements

This paper presents a prototype test fixture for the absolute calibration and estimation of the equivalent magnetic flux noise of the extremely low frequency (ELF) Schumann resonant (SR) magnetic antenna receiver and rods’ magnetic permeability measurement. The test fixture, for ELF the SR detector’s calibration, consists of a constructed coil, the signal generator, and the oscilloscope. The ELF SR detector used has been operating since 2016 near the Doliana village in the Ioannina prefecture, Northwestern Greece. At precisely this spot, far away from electromagnetic noise, the whole setup and experiment took place. The experiments performed with the proposed test fixture showed a sensitivity of 70 nV/pT/Hz and an apparent magnetic permeability at around 250 for the magnetic antenna. The total sensitivity of the ELF receiver was 210 mV/pT near 20 Hz, while the total input noise was around 0.04 pT.

Cryptic Species Discrimination in Western Pine Beetle, Dendroctonus brevicomis LeConte (Curculionidae: Scolytinae), Based on Morphological Characters and Geometric Morphometrics.

The western pine beetle (WPB), Dendroctonus brevicomis LeConte, is a major mortality agent of pines in North America. A total of 706 adults of WPB from 81 geographical sites were analyzed with traditional and geometric morphometric methods to evaluate the variation of discrete and quantitative morphological characters with particular attention to the antenna, spermatheca, and seminal rod. Principal coordinates and canonical variate analyses supported three geographical groups in WPB: (1) West, from British Columbia to southern California along the Pacific coast, Idaho, and Montana; (2) East-SMOC, including Nevada, Utah, Colorado, Arizona, New Mexico, Texas, Chihuahua, and Durango; and (3) SMOR, including Coahuila, Nuevo Leon, and Tamaulipas. The pubescence length on the elytral declivity was a robust character for separating West specimens from the other groups. Additionally, the genitalia shape both female and male in dorsal view was a reliable character for discriminating among groups. Based on these results, which agree with genetic and chemical ecology evidence, we herein reinstate Dendroctonus barberi Hopkins (East-SMOC group) and remove it from synonymy with D. brevicomis (West group). Differences in the spermatheca and seminal rod shape of SMOR specimens suggest that these populations might be a different species from D. barberi and D. brevicomis.

An Assessment of Old and New Characters Using Traditional and Geometric Morphometrics for the Identification of Dendroctonus approximatus and Dendroctonus parallelocollis (Curculionidae: Scolytinae).

There have been numerous changes in the nomenclature of species of Dendroctonus. The case of Dendroctonus parallelocollis Chapuis and Dendroctonus approximatus Dietz has been particularly noteworthy. These bark beetles colonize pine trees but are not aggressive species. The high morphological similarity, their overlapping geographical distribution, and the limited knowledge of these species have resulted in taxonomic confusion. The aim of the present study was to assess morphological characters reported in the literature and to scrutinize new characters that might be useful for the separation of these species. We evaluated 26 morphological attributes and performed geometric morphometrics analysis of the antenna, pronotum, spermatheca, and seminal rod to test if the variations in the shape of these structures allow the recognition of additional discrete characters to differentiate them. Our results show that five double-state characters of external morphology are useful to identify these species, and the shape of antenna, spermatheca, and seminal rod.

Real time visualization of dynamic magnetic fields with a nanomagnetic ferrolens

Due to advancements in nanomagnetism and latest nanomagnetic materials and devices, a new potential field has been opened up for research and applications which was not possible before. We herein propose a new research field and application for nanomagnetism for the visualization of dynamic magnetic fields in real-time. In short, Nano Magnetic Vision. A new methodology, technique and apparatus were invented and prototyped in order to demonstrate and test this new application. As an application example the visualization of the dynamic magnetic field on a transmitting antenna was chosen. Never seen before high-resolution, photos and real-time color video revealing the actual dynamic magnetic field inside a transmitting radio antenna rod has been captured for the first time. The antenna rod is fed with six hundred volts, orthogonal pulses. This unipolar signal is in the very low frequency (i.e. VLF) range. The signal combined with an extremely short electrical length of the rod, ensures the generation of a relatively strong fluctuating magnetic field, analogue to the signal transmitted, along and inside the antenna. This field is induced into a ferrolens and becomes visible in real-time within the normal human eyes frequency spectrum. The name we have given to the new observation apparatus is, SPIONs Superparamagnetic Ferrolens Microscope (SSFM), a powerful passive scientific observation tool with many other potential applications in the near future.

High-Efficiency Wideband 3-D On-Chip Antennas for Subterahertz Applications Demonstrated at 200 GHz

This work presents an efficient method for realizing a laterally radiating 3-D monopole antenna for millimeter-wave and terahertz applications. The vertical antenna rod is formed with a standard $\text{17-}{\mu} \text{m}$ aluminum wire on a programmable semiautomatic ultrasonic wedge bonder, which allows for a good reproducibility. The key features are a high gain of up to 4.9 dBi, a ${\text{360}}^{\circ }$ azimuthal coverage, an estimated radiation efficiency of around 90%, a uniform behavior over a wide frequency range of 60 GHz, and a low chip area requirement of ${\text{0.06}} \text{mm}^{2}$ . The on-chip structure offers the unique ability to be alternatively utilized for direct characterization with standard measurement probes. In addition, an analytic model is derived and compared to electromagnetic field simulations. To verify the radiation performance, a physical transmission link is demonstrated for distances between 5 and 15 mm and for a frequency ranging from 140 to 220 GHz. The obtained results agree well with the theoretical and simulated estimations.

Juno model rheometry and simulation

The experiment WAVES aboard the Juno spacecraft, which will arrive at its target planet Jupiter in 2016, was devised to study the plasma and radio waves of the Jovian magnetosphere. We analyzed the WAVES antennas, which consist of two non-parallel monopoles operated as a dipole. For this investigation we applied two independent methods: the experimental technique, rheometry, which is based on a down-scaled model of the spacecraft to measure the antenna properties in an electrolytic tank; and numerical simulations, based on commercial computer codes, from which the quantities of interest (antenna impedances and effective length vectors) are calculated. In this article we focus on the results for the low-frequency range up to about 4MHz, where the antenna system is in the quasi-static regime. Our findings show that there is a significant deviation of the effective length vectors from the physical monopole directions, caused by the presence of the conducting spacecraft body. The effective axes of the antenna monopoles are offset from the mechanical axes by more than 30° and effective lengths show a reduction to about 60% of the antenna rod lengths. The antennas' mutual capacitances are small compared to the self-capacitances, and the latter are almost the same for the two monopoles. The overall performance of the antennas in dipole configuration is very stable throughout the frequency range up to about 4–5MHz, and therefore can be regarded as the upper frequency bound below which the presented quasi-static results are applicable.

Super-Paramagnetic Nanoparticles with Spinel Structure: A Review of Synthesis and Biomedical Applications

The study of ceramic materials has attracted the attention of many researchers due to the possibility of their use in nanotechnology. The spinel ferrites form a large group of materials with a broad range of applications. Some examples include electronic devices such as high-frequency transformer cores, antenna rods, induction-tuners, among many others. However, when the ferritic materials display superparamagnetic behavior, their potential for biological applications like drug delivery, hyperthermia, resonance magnetic imaging and magnetic separation, become amazingly high. Therefore, the superparamagnetism is a characteristic strongly desired for spinel ferrites. Since this phenomenon is size-dependent, the methodologies to synthesize these materials has emerged as a crucial step in order to obtain the desired properties. In this regarding, several synthetic processes have been developed. For example, co-precipitation is a fast and cheap method to synthesize superparamagnetic spinel ferrites. However, methodologies involving microwave, ultrasound or polymers frequently result in these kind of materials. Therefore, this review brings a brief historic introduction about spinel ferrites as well as essential concepts to understand their structure and magnetic properties. In addition to this, recent advances in synthesis and applications of the superparamagnetic spinel ferrites are mentioned. Contents of Paper

Refinement in the structural and magnetic properties of Co0.5Ni0.5Fe2O4 and its application as laser micro-propellant using ablation confinement

The transition metal-substituted cobalt ferrite nanoparticles Co0.5X0.5Fe2O4 (with X=Cu, Zn, Mn and Ni) exhibit a wide range of properties that result in their application in low loss magnetic core materials, vertical recording heads, antenna rods, memory elements, ferrofluids, biomedical applications, sensors and laser propulsion. Keeping in view its importance we investigated for the first time the structural and magnetic properties of the Co0.5Ni0.5Fe2O4 samples that were subsequently subjected to thermal treatments for different time durations. The average crystallite sizes of the synthesized samples were found in the range of 24–46nm. The values of the saturation magnetization and coercivity varied from 25.7 to 31.2emu/g and 523.59 to 927.62Oe, respectively. The XRD patterns showed that increase in thermal treatment time resulted in the refinement of the structure whereas the SEM micrographs depicted a uniform particle size distribution of the synthesized material. We also explored the application of the synthesized material as a micro-thruster. It was found that the confinement of the laser induced plasma of Co0.5×0.5Fe2O4 led to an increase in the value of coupling coefficient from the range of 5.747×10−5–7.0644×10−5N-s/J for unconfined to that of 1.41×10−4–2.68×10−4N-s/J for confined plasma corresponding to the Nd:YAG laser fluencies of 4×109J/m2–6×109J/m2.

一軸対称の薄肉開断面を有する回転軸の解析

The purpose of this paper is to analyze structural statics and dynamics of a rotating shaft with a thin-walled open cross-section having one symmetrical axis. For the shaft, flexural-torsional coupling must be considered because the centroid axis and the shear-center axis do not always coincide. After deriving the governing equations of motion for a uniform shaft rotating at a constant angular velocity, we propose methods to estimate static deflection and dynamic stability. Numerical calculations for cantilever shafts with and without internal damping indicate that the distance between the centroid and the shear-center contributes to the dynamic instability. Moreover, an application of the methods to an elastically supported model indicates that a spin-axis antenna rod for future scientific satellites under consideration is dynamically stable in the operational spin-rate.

Lateral energy transfer model for adjacent light-harvesting antennae rods of C-phycocyanins

Modeling of excitation transfer pathways have been carried out for the structure of Spirulina platensis C-phycocyanin. Calculations by Förster mechanism using the crystal structure coordinates determined in our laboratory indicate ultra-fast lateral energy transfer rates between pairs of chromophores attached to two adjacent hexamer disks. The pairwise transfer times of the order of a few pico-seconds correspond to resonance transitions between peripheral β155 chromophores. A quantitative lateral energy transfer model for C-phycocyanin light-harvesting antenna rods that is suggestive to its native structural organization emerges from this study.

Ion-beam extraction with single hole extractor from multiantenna rf ion source in NIFS

A new multiantenna system for large area radio-frequency H− ion source using a filamentless ion source was tested to extract ions from dense plasmas with high rf input power. A 1∕6 scale large helical device ion source was equipped inside a plasma chamber with four linear antenna rods. Positive-ion extraction with a single hole extractor was studied in detail, while a negative one only showed preliminary results. The positive-ion current density of 34mA∕cm2 to the collector plate was achieved with a new multiantenna after optimization of the antenna number and source gas pressure, where the number of the antennae was 2 with ∼36kW of rf input power and with a gas pressure of ∼0.1Pa with H2. If the external magnetic filter optimized for negative-ion production in the multifilament discharge source is taken off, the current density is estimated to reach about 120mA∕cm2. This corresponded closely to the value measured with a Langmuir probe near the center. Two antennae appear to be required to generate uniform plasmas as well as dense plasmas in the present size of the 35×35cm2 source. A negative-ion current density of 0.3mA∕cm2 to the collector plate was detected with hydrogen without optimization. This multiantenna rf ion source is expected to be adaptable advantageously to large area positive- and negative-ion sources, owing to not only a filamentless source but also potentially due to uniform plasmas as well as probable low-electron-temperature plasmas, compared to that with a one-turn coil system.

Crystal Structure of a Light-Harvesting Protein C-Phycocyanin from Spirulina platensis

The crystal structure of C-phycocyanin, a light-harvesting phycobiliprotein from cyanobacteria (blue-green algae) Spirulina platensis has been solved by molecular replacement technique. The crystals belong to space group P21 with cell parameters a = 107.20, b = 115.40, c = 183.04 Å; β = 90.2°. The structure has been refined to a crystallographic R factor of 19.2% (Rfree = 23.9%) using the X-ray diffraction data extending up to 2.2 Å resolution. The asymmetric unit of the crystal cell consists of two (αβ)6-hexamers, each hexamer being the functional unit in the native antenna rod of cyanobacteria. The molecular structure resembles that of other reported C-phycocyanins. However, the unique form of aggregation of two (αβ)6-hexamers in the crystal asymmetric unit, suggests additional pathways of energy transfer in lateral direction between the adjacent hexamers involving β155 phycocyanobilin chromophores.

Kinetics of energy transfer processes in C-phycocyanin complexes

The antenna system of algae for photosynthesis is a functional entity composed of various phycobiliproteins and the linker polypeptides. Up to now, high-resolution crystal structure data have been available only for the isolated phycohiliproteins. To have an understanding of the functional connection between different phycobiliproteins, it is necessary to study the complexes composed of different phycobiliproteins. The energy transfer processes in C-phycocyanin complexes were studied through computer simulation because it is dificult to be studied by conventional experimental methods. The main pathways of energy flow and the dynamic property of the energy transfer were obtained. A fast transfer process between two neighboring disks was observed through analyzing the distribution curves of excitation energy over time. According to the definition of the time constants for energy transfer in time-resolved spectrum techniques, for a complex with three C-phycocyanin hexamer disks, a fluorescence-rising component with several picoseconds was obtained in disk 2 and 20 ps in disk 3 when the chromophores in disk 1 were excited by an ideal Δ pulsed laser beam. The results showed clearly that the energy transfer between the disks in an antenna rod was very fast and that energy transfer was fast and efficient in an intact antenna system of algae.

Isolation, crystallization, crystal structure analysis and refinement of constitutive C-phycocyanin from the chromatically adapting cyanobacterium Fremyella diplosiphon at 1.66 Å resolution

Constitutive phycocyanin from cyanobacterium Fremyella diplosiphon ( Calothrix sp. PCC 7601) grown in green light, has been isolated and crystallized. The crystals belong to the space group R3 with cell constants a = b = 180.26 A ̊ , c = 61.24 A ̊ , α = β = 90 °, γ = 120 ° . The crystal structure has been determined by Patterson search techniques using the molecular model of C-phycocyanin from the cyanobacterium Agmenellum quadruplicatum. The asymmetric unit of the crystal cell consists of two (αβ)-monomers related by a local dyad. Three asymmetric units are arranged around a crystallographic triad and form an (αβ) 6-hexamer, the functional unit in the native antenna rod. The initial structure has been refined in a cyclic manner by energy-restrained crystallographic refinement and modelling until the conventional crystallographic R-factor converged at 18.1% with data to a resolution of 1.66 Å. The molecular structure resembles closely the C-phycocyanins of Mastigocladus laminosus and A. quadruplicatum. The conformation and configuration of the α-84 and β-84 chromophores is very similar to the corresponding chromophores in the trimeric C-phycocyanin of M. laminosus, whereas the β-155 chromophore differs in configuration with C (4)- Z, C (10)- Z and C (15)- Z compared to C (4)- Z, C (10)- Z, C (15)- Z, E. The stereochemistry of the β-155 chiral centres is C (2)- RC (3)- R and C (31)- S, respectively, whereas α-84 and β-84 have C (2)- R C (3)- R and C (31)- R. The amino acid sequences of constitutive and inducible phycocyanin differ mainly in residues located on the surface of the β-subunits that mediate the inter-hexameric contacts.

International standards for magnetic materials and components

In practically all of the industrially developed countries of the world there are strong national standards organizations. The International Electrotechnical Commission (IEC) coordinates and unifies electrical and electronic standards by drafting international recommendations from which member countries may draw for national standards. The benefits derived from this work include better understanding among electrical and electronic engineers and scientists, and a means for initiating and expanding international trade. The upsurge in development and application of ferrites led the IEC to establish a committee on ferromagnetic oxide parts 15 years ago, which rapidly expanded into a full technical committee on magnetic materials and components (TC 51). The magnetic activities include recommendations for terms and definitions, dimensional standardization, measurement methods, inductors and transformers, data storage devices, strip-wound cores and laminations, variability (temperature and time), gyromagnetic applications (microwave), and antenna rods. Eleven TC 51 IEC publications are now available. Numerous others are in process.

Properties of Ferrite Antenna Rods Made from Iron Ore and Its Effect on Receiver Performance

Properties of Ferrite Antenna Rods Made from Iron Ore and Its Effect on Receiver Performance