Reflector Elements Research Articles

Core parametric study for enhancing the radioisotope production in the IEA-R1 research reactor

In this work a parametric study was carried to increase the production of radioisotopes in the IEA-R1 research reactor. The changes proposed to implement in the IEA-R1 reactor core were the substitution of graphite reflectors by beryllium reflectors, the removal of 4 fuel elements to reduce the core size and make available 4 additional locations to be occupied by radioisotope irradiation devices. The key variable analyzed is the thermal neutron flux in the irradiation devices. The proposed configuration with 20 fuel elements in an approximately cylindrical geometry provided higher average neutron flux (average increment of 12.9 %) allowing higher radioisotope production capability. In addition, it provided 4 more positions to install irradiation devices which allow a larger number of simultaneous irradiations practically doubling the capacity of radioisotope production in the IEA-R1 reactor. The insertion of Be reflector elements in the core has to be studied carefully since it tends to promote strong neutron flux redistribution in the core. A verification of design and safety parameters of the proposed core was carried out. The annual fuel consumption will increase about 17 % and more storage space for spent fuel will be required.

Effect of the ember element in increasing the efficiency of liquefied petroleum gas stoves

The purpose of this study was to determine the effect of use ember element from woven nickel wire to increasing the efficiency of the LPG stoves. It is supposed that high-temperature embers can burn more fuel around the wire, thereby increasing the area of complete combustion. The test was conducted by means of a Water Boiling Test (WBT) and the number of ember layers varied from one to four. It was found that the use of elements of fire without reflectors could increase efficiency by 8.32%, with the highest efficiency being with the use of a single layer ember element of the fire, of 61.71%. However, the use of elements of fire in the finned heat reflectors causes efficiency to decrease, as the pattern to put elements of fire interfere with the reflectivity. This means the heat reflection is blocked by the pattern and trapped between the reflector and pattern elements. As a result, the heat energy from the reflector reflection cannot be forwarded to the combustion zone. The test results also show that the temperature distribution from ember element use can increase the area of complete combustion.

DESIGN OF NEUTRONIC PARAMETERS OF MTR REACTOR USING WIMSD-5B/BATAN-FUEL CODES

BATAN has three aging research reactors, so it is necessary to design a new, more modern MTR type reactor using high-density, low enrichment uranium molybdenum fuel. The thermal neutron flux at the irradiation position is an important concern in the design of research reactors. This analysis is performed using standard computer codes WIMSD-5B and Batan-FUEL. The purpose of this study is to analyze the effect of the core configuration with safety control rods and neutronic parameters using the diffusion method calculation. The reactor core consists of 16 fuel elements and four control rods placed in the 5 x 5 position of the grid plate and is loaded the reflector elements outside the core. The cycle length is also a concern, not less than 20 days, and the reactor can be operated safely with a power of 50 MW. The calculation results show that for the highest fuel loading, which is 450 grams of U7Mo/Al fuel with D2O as a reflector, it will provide the lowest thermal neutron flux at the center of the core irradiation position, namely 1.0 x1015 n/cm2s. The core fuel cycle length will be up to 39 days, meeting the expected acceptance and safety criteria.

3D Beam Steering End-Fire Helical Antenna With Beamwidth Control Using Plasma Reflectors

In this article, a beam steerable antenna based on plasma reflectors is presented. The proposed antenna consists of an axial mode helical antenna surrounded by an array of plasma reflector elements forming a cup-shaped ground. In this configuration, the elements of the reflector array can be individually switched on or off to achieve different radiation characteristics for the helical antenna. Specifically, it is shown that the symmetric activation of a specified number of elements of the plasma array can be used to control the beamwidth of the antenna. Moreover, the plasma reflectors can be asymmetrically configured to steer the endfire beam pattern of the helical antenna in 3-D space. To validate the concept, the proposed antenna is designed and numerically simulated. The simulation results show that using the proposed method, the beamwidth of the proposed antenna can be changed from 37° to 50° while the beam direction can be altered in 3-D space within a solid angle of ±6°. Finally, a prototype of the designed antenna is fabricated and its radiation characteristics for various configurations of the plasma reflectors are measured. Good agreement between the simulation and measurement results validates the proposed method.

A Compact Single-Layer Four-Port Orthogonally Polarized Yagi-Like MIMO Antenna System

A wideband compact Yagi-like directional multiple-input- multiple-output (MIMO) antenna system is presented based on a slot loop excitation. Four orthogonally polarized beams are generated by orthogonally feeding the slot loop elements using microstrip lines. The proposed design is based on a single-layer geometry with an overall size of 35 × 90 × 0.76 mm3, which is suitable for compact wireless handheld devices. The conventional vertically polarized omnidirectional beams from each slot loop element are made directional and horizontally polarized by using two passive complementary slot reflector (CSR) elements. The antenna system has a wide measured bandwidth of 620 MHz (3.26-3.88 GHz) targeting the 3.6 GHz WiMAX band. It has a maximum realized gain of 4 dBi and front to back ratio (FBR) of more than 7 dB within the band of operation. The proposed antenna system shows good MIMO performance with a minimum measured isolation of 10 dB between the adjacent ports and more than 20 dB between other ports. The orthogonal beams of the antenna system help in achieving low envelope correlation coefficient (ECC) values of less than 0.1. The measured total efficiency of the antenna system is more than 75% for all the ports of the antenna system.

A Dual-ID RFID Tag for Headgear Based on Quasi-Yagi and Dipole Antennas

In this article, we present a dual-ID radio frequency identification (RFID) headgear based on quasi-Yagi antenna where we reuse the reflector element as the second dipole antenna that provides radiation pattern upward from the user's head. Thus, we achieve simultaneously the broadside and endfire patterns without increasing the size of the antenna platform. For avoiding the unpredictable impact of the surface of the human body to the electromagnetic properties of the antenna platform, we inserted a periodic surface made up of a 2-by-2 grid of square loops beneath it. It facilitates launching of surface waves thereby enhancing the endfire radiation for the quasi-Yagi antenna and its back metal plate isolates the antenna platform from the human body. We have fitted the whole structure on the headgear by folding the quasi-Yagi antenna elements and created the antenna on a low-permittivity textile substrate. Moreover, we have modeled the antenna in both simple and anatomical head models, both including curvature, and measured the attainable read ranges of 6.8 m and 5 m, for the quasi-Yagi and dipole tags, respectively, in head-worn configuration.

Control and Positioning System for Reflector of ‘‘Millimetron’’ Observatory: Design and Development

We propose a method to control the multi-element mirror system of the telescope of the space observatory ‘‘Millimetron’’ under its tuning taking place after the opening on the orbit. For the preliminary control of the location of reflector elements, the laser rangefinder is used; for the final control, the optical method of the Foucault knife is used. We compute the optical scheme of the control system for the final tuning of the telescope and present it. We show simulation results for images obtained under deviations of reflector elements. We present computation results for the optical system, implementing the Foucault knife method.

Reconfigurable Intelligent Surfaces Assisted Secure Multicast Communications

Reconfigurable Intelligent surface (RIS) can enhance the desired signals and suppress the undesired signals by adjusting the phase shifts of its reflector elements. This letter considers secure multicast communication with the help of RIS. A multiple-antennas transmitter multicasts the common messages to a group of single-antenna receivers in the presence of a single-antenna eavesdropper, where an RIS is set up to enhance the desired signals for the receivers and suppress the signals for the eavesdropper. First, the equivalent multicast and wiretap channels are analyzed, and a secrecy capacity maximization problem is formulated. Next, this letter obtains the necessary conditions that the optimal solution needs to satisfy. Finally, a logarithmic barrier algorithm is proposed to obtain a local optimal solution.

Four-Element Microstrip Patch Array Antenna with Corporate-Series Feed Network for 5G Communication

The paper proposes a simple four-element microstrip patch array antenna fed with corporate-series technique. The paper compares the proposed design with four-element antennas fed with only series-fed and corporate-fed microstrip antennas. All three antenna designs use rectangular microstrip patch elements with two insets and slots on both sides of the patch. The patch elements are accompanied by Yagi elements: three director elements and two reflector elements. Through comparison of simulation results, the paper shows that four-element array antenna with combined corporate-series feeding technique performs better compared to antennas with only either series or corporate feeding network. The proposed corporate-series fed antenna achieves better performance with wide frequency bandwidth of 25.04–30.87 GHz and gain of 9.5 dB. The antenna has an end-fire radiation pattern. Overall performance shows that the proposed corporate-series-fed microstrip patch antenna with Yagi elements is suitable for next generation 5G communication.

Frequency reconfigurable Yagi‐like MIMO antenna system with a wideband reflector

A compact single layer frequency reconfigurable Yagi-like multiple-input multiple-output (MIMO) antenna system is presented based on a half-ring closed loop slot excitation. The traditional omnidirectional pattern of a slot antenna is made directional by using a single slot-based complementary wideband reflector (CWBR) element. The proposed CWBR is compact in size, simple in construction, and is based on a single-layer geometry unlike complex multi-layer reflectors used in the literature. It improves the front-to-back ratio between 5 and 17 dB in the entire frequency range covering 2.5–4.5 GHz. The proposed reconfigurable MIMO antenna system covers the LTE and WiMAX bands with a minimum measured bandwidth of 200 MHz per covered bands. The frequency reconfigurability is achieved by reactively loading the slot loop with varactor diodes. The overall size of the proposed antenna system is 40 × 100 × 0.76 mm 3 , making it suitable for tablet handheld devices and access points. It has a maximum measured peak gain of 5 dBi and total measured radiation efficiency of 78%. The proposed MIMO antenna system has port isolation of > 10 dB within the entire band of operation. The radiation patterns are isolated in space from each other and ensure very low envelope correlation coefficient.

Stacked frequency reconfigurable Yagi‐like MIMO antenna system

In this work, a 2-layer frequency reconfigurable Yagi-like multiple-input–multiple-output (MIMO) antenna system is proposed based on a closed pentagonal slot-loop excitation. The MIMO system consists of 4 identical active antenna elements reactively loaded with varactor diodes to achieve frequency reconfigurability over a band from 1.5 to 2.1 GHz. The distinguishing feature of the proposed work is achieving Yagi-like directional characteristics over a very wide frequency band. The conventional omni-directional pattern of a slot antenna is made directional by using a parasitic metallic reflector layer below the substrate. By using the reflector element, the back-lobe radiation is highly suppressed and a front-to-back ratio of 5–13 dB is achieved within the entire frequency band of operation. The proposed design is compact with an overall size of , and a reflector size of . A single element has a maximum peak gain of 4 dBi and total measured radiation efficiency of 76%. The antenna system also shows good MIMO performance with high port isolation of 11.3 dB and very low envelope correlation coefficient values within the operational band.

Fiber Optic Refractive Index Distributed Multi-Sensors by Scattering-Level Multiplexing With MgO Nanoparticle-Doped Fibers

In this work, we present the architecture of a multiplexed refractive index (RI) sensing system based on the interrogation of Rayleigh backscattering. The RI sensors are fabricated by fiber wet-etching of a high-scattering MgO nanoparticle-doped fiber, without the need for a reflector or plasmonic element. Interrogation is performed by means of optical backscatter reflectometry (OBR), which allows a detection with a millimeter-level spatial resolution. Multiplexing consists of a simultaneous scan of multiple fibers, achieved by means of scattering-level multiplexing (SLMux) concept, which uses the backscattered power level in each location as a diversity element. The sensors fabricated have sensitivity in the order of 0.473-0.568 nm/RIU (in one sensing point) and have been simultaneously detected together with a distributed temperature sensing element for multi-parameter measurement. An experimental setup has been prepared to demonstrate the capability of each sensing region to operate without cross-talk, while operating multi-fiber detection.

Development of Magnetic Materials Based on Micro-Nano Particles Natural Ferrite as Microwaves Absorber Materials

Ferrite-based magnetic materials (ferrites) can be simple iron oxide compounds such as Fe2O3 or Fe3O4, and similar compounds containing other cations besides iron, such as BiFeO3, CaFe 4O7, and BaFe12O19. The solid phase of these compounds generally has varying magnetic properties, depending on the cation (A+m) which is the substitution of the iron cation (Fe+3) in its crystal structure. In addition to the magnetic properties of interest, the compound in question also has strong absorption properties in electromagnetic waves in the frequency interval of 1 - 20 GHz (microwave), which is commonly used in the world of communication and radar technology. With these properties it is possible to develop these materials for electromagnetic shielding and stealth technology applications. As a magnetic element, ferrite material requires a conductive reflector element, to form a “core - shell” or “matrix - filler” system which results in absorption properties. The research that has been developed is in the form of Fe3O4 based micro-nano magnetic powder made from natural ferrite (iron sand). The sythesized of magnetic micro-nano particles using chemical extraction-milling and coprecipitation methods. Morphology of micro-nano particles ferrites has been confirmed by using SEM and TEM. The results of measurements of absorption of microwaves using a Vector Network Analyzer showed that the ferrite nano particle powder has greater absorption power (Reflection Loss < - 20 dB) than micro particle powders with ≥ 99 % absorption in the “X-band” region. The extraction-milling method is simpler and more economical than the chemical coprecipitation method so that it is suitable to be an alternative method for producing large-scale ferrite powder.

Compact, broadband, and high gain directional endfire antenna

AbstractA broadband directional endfire printed antenna is proposed with a simple unbalanced feed, compact size, stable gain, and high front to back ratio (F/B). The antenna consists of a microstrip driven with U‐shaped ground and reflector elements to reduce the antenna size. The reflector increases the directivity and F/B in the lower frequency band. The parasitic element, which is located close to the driven element and also acts like director, enhances the bandwidth (BW) and gain in the upper frequency band. Prototype of the proposed antenna is fabricated with antenna size of 0.48λo × 0.35λo. Experiment results demonstrate that the proposed antenna provides 62.6% (1.606‐3.07 GHz) BW with stable gain (5‐6.8 dBi) and min F/B of 15 dB. The proposed endfire antenna is a good candidate for wireless applications in 2G, 3G, 4G, Wi‐Fi, and lower WiMAX bands.

Wide Dynamic Range, Angle-Sensing, Long-Wave Infrared Detector Using Nano-Antenna Arrays

We present a new technique for designing angle-sensing, long-wave infrared (LWIR) detectors. Angle detection in the proposed detector is achieved by measuring the ratio of the absorbed power in two closely-spaced, directive infrared antennas. Each directive LWIR antenna is in the form of a three-element Yagi-Uda array sharing a common reflector element with its neighbor. The structure of each antenna is optimized to act both as the collector of the infrared energy from the desired direction and as a distributed bolometer that senses the received radiation. The resistivity of each bolometer-antenna changes as a function of the absorbed power by the antenna. This change of resistance is sensed by biasing each antenna with a constant DC voltage and measuring the change of current passing through the antenna. Following this approach, by measuring the ratio of the resistance change in the two antennas, the angle of arrival of the LWIR signal can be determined. We present the design, fabrication, and measurement results of an angle-sensing detector optimized to operate at the wavelength of λ = 10.6 μm. The proposed detector has subwavelength dimensions occupying an aperture having dimensions of approximately 0.6 λ0 × 0.4λ0. The response of the detector was measured and shows the angle sensing dynamic range of 22 dB within the field of view of ±60°.

Enhancing isolation and bandwidth in planar monopole multiple antennas using thin inductive line resonator

This paper presents efficient mutual coupling reduction and bandwidth enhancement method in planar monopole multiple antennas. High isolation and bandwidth extension are achieved by integrating a thin inductive line resonator as reflector and parasitic element between the antenna elements. A 36.9% bandwidth (4.69–6.5 GHz) is achieved at 4.9 GHz, which encompasses the sub-6 GHz (4.8–5.0 GHz) 5G and 5.15–5.85 GHz WLAN bands. The thin inductive line resonator provides an effective means of controlling the electromagnetic wave propagation. Approximately 45 dB isolation and 4.9 dB maximum gain can be achieved between two parallel monopole antennas with 0.36λ0 spacing. The physical meaning of electromagnetic propagation in MIMO antenna is studied by discussing the coupling mode between antennas and the working mechanism of thin inductive line as parasitic elements and reflectors. Furthermore, a four-element antenna with orthogonal polarization diversity is also proposed based on the thin inductive line. Correlation coefficients (CC) are well below 0.05 across the operating bandwidth.

Development and Research of Mathematical Models of Deployment of Mobole Parts of Transformable Space Construction. Part I

The process of deployment elements of constructions and adjustment of the radio-reflecting network of large-sized transformable space-based reflector with the use of a cable-stayed form maintenance system is considered. The deployment process can be broken down into separate phases. At each stage, the movement is due to the impact on the design of the actuator — the element of the control system. Energy for the deployment of the reflector elements is produced by drives, in particular an electric machine. The use of this type of actuator allows you to control the process of disclosure. Due to the fact that currently achieved a huge process in computer technology that allows you to perform three-dimensional computing operations in a short time, it is particularly important to use optimal control algorithms. When deployment the reflector for two types of motion — rotational and translational — mathematical models based on Lagrange equations of the II-kind are obtained. These mathematical models take into account such parameters as dissipation, the presence of longitudinal and transverse deformation. The models provide for the presence of a stop and a lock, as an Executive element in the deployment selected brushless DC motor. All the observations made allow us to formulate a smooth statement disclose items on the stop with minimum oscillation of the structure. The developed models allow to analyze the n-th number of natural oscillation frequencies. Modeling with different parameters of the model is carried out. The parameters of the transition process of the spoke at the opening of the first link with the other links embedded in it and at the fully covered spoke are analyzed. It is shown that depending on the mass-dimensional parameters there is a significant change in the dynamics. For the spoke extension stage, the weight and size characteristics have little effect on the opening dynamics. The smaller the Young’s modulus and density of the material, the greater the damped longitudinal oscillations.. The simulation of this stage with a spoke made of different materials is carried out. Various methods are proposed to reduce the opening time at all stages and minimize transverse and longitudinal oscillations. The possibility of application of the developed mathematical models for a wide range of tasks is shown.

Designing Stainless Steel Reflector at VR-1 Training Reactor

Light-water reactor cores are commonly surrounded by a stainless steel and water reflector. The reflectors are improving power distribution in the core, reducing the leakage of neutrons and thus also protecting the pressurized vessel from the neutron irradiation and the following embrittlement. Contrary to the standard procedures utilized for generation of the fuel assembly data, the reflector elements require a special approach. The major difficulty with the reflectors is represented by an absence of neutron sources in the reflector elements. Some artificial neutron source simulating the realistic source of neutrons from neutron leakage from the surrounding fuel assemblies must be added in the calculation model. The reflector data in the full-core calculations have a great impact on the power distribution in the core. The research in this field is usually focused on the square geometry, and therefore the accurate data for the hexagonal geometry are lacking. Improvements in this area are needed. Training Reactor VR-1 is used for measurements related to nuclear engineering. Department of Nuclear Reactors operating this reactor at the Czech Technical University in Prague is currently designing reflector elements containing stainless steel in order to provide measurable characteristics that can be compared to calculations realized by either Monte-Carlo codes or macroscopic core simulators. This article summarizes the methodology of development of the reflector assemblies to improve their similarity with the VVER-1000 reflector. The impact of the evaluated nuclear data is assessed. Further improvements of the proposed design is necessary to reach better agreement with the neutron spectrum in VVER-1000 reactor reflectors. The influence of evaluated data on the global characteristics was found negligible.

Optimising the design of phased array feeds for survey speed

The scientific capability of an astronomical phased array feed receiver can be quantified by combining the bandwidth, sensitivity, and field of view into the overall survey speed of the instrument. The authors investigate the relationships between survey speed and reflector geometry, array layout, element spacing and element configuration using numerical simulations, to determine the values of these parameters that lead to optimal system performance. They characterise the array element spacing that leads to maximum survey speed as a function of the reflector f/D. To further improve survey speed in relation to the overall number of array elements, the authors explore the possibility of using elements with modest levels of superdirectivity to sample more of the focal plane Airy pattern and increase optimal spacing for survey speed figure of merit. The results explain how optimal survey speed is controlled primarily by the influence of element type and array layout on the peak achievable aperture efficiency.

Communication Through a Large Reflecting Surface With Phase Errors

Assume the communication between a source and a destination is supported by a large reflecting surface (LRS), which consists of an array of reflector elements with adjustable reflection phases. By knowing the phase shifts induced by the composite propagation channels through the LRS, the phases of the reflectors can be configured such that the signals combine coherently at the destination, which improves the communication performance. However, perfect phase estimation or high-precision configuration of the reflection phases is unfeasible. We study the transmission through an LRS with phase errors that have a generic distribution. We show that the LRS-based composite channel is equivalent to a direct channel with Nakagami scalar fading. This equivalent representation allows for theoretical analysis of the performance and can help the system designer study the interplay between performance, the distribution of phase errors, and the number of reflectors. Numerical evaluation of the error probability for a limited number of reflectors confirms the theoretical prediction and shows that the performance is remarkably robust against the phase errors.