Reflection Phase Research Articles

Investigation of Optical Properties and Activity of Wheat Stripe Rust Urediospores

Stripe rust is one of the most common diseases challenging the safe production of wheat. Rapid identification and analysis of urediospores, responsible for disease transmission, are the key to preventing and controlling stripe rust. The current spore detection is time-consuming and requires auxiliary equipment, but many optical detection methods and sensors with high efficiency, sensitivity, and detection ability have been developed and widely used. Thus, the investigation of optical parameters is the prerequisite for optical sensitive detection and is detailed in this study. Firstly, the microscopic images and surface elements of wheat stripe rust urediospores were obtained using a high-resolution electron microscope and an energy spectrum analyzer. The reflectivity and absorptivity spectra in the near-infrared band of active/inactivate urediospores were measured. Further, the optical parameters, such as reflection phase shift, complex refractive index, and dielectric constant, of the urediospores were analyzed based on electromagnetic theory and Kramers–Kronig relation. The results revealed that the urediospores have a strong tolerance to near-infrared light, and the real part of the complex refractive index n was between 1.0 and 1.4. These observations indicate that whether the spores are active or not has little effect on the real part and dielectric constant of the complex refractive index but has a significant impact on the imaginary part and extinction coefficient of the complex refractive index, and the corresponding relationship between the optical properties of urediospores and biological components was established. These findings were verified with HPLC-MS and Near-Infrared Spectroscopy Analysis Technology and lay a theoretical foundation for detecting urediospores of wheat stripe rust by using optical sensors. The study provides a reference for the analysis of optical characteristics of other biological samples.

Design of Tunable Broadband Graphene-Based Metasurface with Amplitude-Phase Modulation

Due to the growing scarcity of spectrum resources in the low-frequency band, the requirement of beam-reconfigurable antennas in the millimeter wave band is urgent. In this paper, a W-band graphene-based metasurface working in a broad bandwidth is proposed with reflective amplitude coding. Here, graphene sheets play a dual role in radiating and regulating electromagnetic waves. By adjusting the Fermi levels of graphene, the reflective amplitude and phase of the metasurface can be modulated simultaneously, enabling multi-beam switching and beam deflection in far-field. The proposed metasurface achieves amplitude-phase modulation within a significantly wide bandwidth which covers 75–91.5 GHz and 99.3–115 GHz. By optimizing the coding patterns, the proposed graphene-based metasurfaces are able to not only realize 2-D beam steering, but also achieve beam switching from single beam to four beams at 87 GHz. The proposed design provides a novel solution for the flexible manipulation of millimeter waves, which can be applied to various fields such as vehicle radar, satellite communication, 6G wireless communication, and beyond.

Janus coding acoustic metasurface with reflection symmetry breaking

Coding metasurfaces with efficient procedures and simple elements have enabled a large number of novel functions in a digital manner. Designs combining coding and functional integration will undoubtedly enhance the efficiency and space utilization of compact systems. Here, we theoretically propose and numerically and experimentally demonstrate an all-passive reflective Janus coding acoustic metasurface, allowing two-faced direction-dependent coding in a decoupled manner. Exquisitely designed double-layer variable-pitch helical structures with smoothly varying acoustic impedance are used to obtain bianisotropic reflection phase responses, which can also be switched to bi-isotropic responses by changing the boundary conditions. The switchable Janus coding metasurface based on the phase state transitions can be programed to achieve switchable functions on one side without affecting the other side. For instance, the asymmetric and symmetric two-faced focusing and unidirectional switching of functions with coding metasurfaces are numerically and experimentally illustrated. We reveal the inherent essence of the structure-caused asymmetric responses and further pave a flexible way to obtain two-faced, independent wavefront operations and functional switching, which exhibit excellent potential for acoustic applications.

An ultra-wideband phase gradient metasurface for anomalous reflection and RCS reduction

In this work, an ultra-wideband phase gradient metasurface (PGM) based on a novel polarization conversion metasurface (PCM) is proposed for anomalous reflection and radar cross section (RCS) reduction. Because the PCM can achieve ultra-wideband circular-polarization(CP)-maintaining reflection in the frequency band from 8.9 to 34.9 GHz, through the rotation of its unit cell structure, the reflection phase in the ultra-wide frequency band can be adjusted at will by the Pancharatnam–Berry (P-B) phase only generated in its co-polarized reflection coefficient under CP incidence. Thus, a PGM is proposed by gradually rotating each unit-cell structure of the PCM, and the proposed PGM can realize ultra-wideband anomalous reflection to reduce the specular RCS. In addition, when the PGM is divided into multiple square elements with different phase gradients, it can work as a diffusion metasurface to reduce the specular RCS and maximum bistatic RCS simultaneously. The simulated results show that the PGM can achieve more than 10 dB specular RCS reduction in the frequency band from 10.0 to 33.5 GHz, but its maximum bistatic RCS is very large; however, when it is changed as a diffusion metasurface, it can reduce not only the specular RCS but also the maximum bistatic RCS in the ultra-wide frequency band of 10.1–34.3 GHz with a relative band-width of 109.5%; in addition, when the incident angle is increased to 45°, the RCS reduction performance of the diffusion metasurface can still be kept well. Finally, an effective experimental verification is carried out for the diffusion metasurface.

PENINGKATAN HASIL BELAJAR SISWA KELAS I PADA MATA PELAJARAN BAHASA INDONESIA MELALUI MODEL PROBLEM BASED LEARNING DI SDN KEPUH 1 KABUPATEN KEDIRI


 This research is a class activity research to improve the learning outcomes of first-year Indonesian students at SDN Kepuh 1, Kediri Regency. The results of learning Indonesian are not the best. This study aims to improve student learning outcomes through a problem-based learning model (PBL). This collective behavior research model (CAR) uses Kemmis and Mc. Taggart. Taggart has three phases: a planning phase, an action and observation phase, and a reflection phase, and two cycles are used for implementation. The results of the first cycle of research achieved an average score of 35% to achieve classical student learning outcomes, and the results of the second cycle showed the application of a problem-based learning model (PBL). percentage reached. From the achievement of classical learning outcomes of 85% with an average score of 80. Therefore, the problem-based learning model (PBL) is material for reading and writing simple words.

DRL-based max-min fair RIS discrete phase shift optimization for MISO-OFDM systems

In this paper, we investigate a reconfigurable intelligent surface (RIS) assisted downlink orthogonal frequency division multiplexing (OFDM) transmission system. Taking into account hardware constraint, the RIS is considered to be organized into several blocks, and each block of RIS share the same phase shift, which has only 1-bit resolution. With multiple antennas at the base station (BS) serving multiple single-antenna users, we try to design the BS precoder and the RIS reflection phase shifts to maximize the minimum user spectral efficiency, so as to ensure fairness. A deep reinforcement learning (DRL) based algorithm is proposed, in which maximum ratio transmission (MRT) precoding is utilized at the BS and the dueling deep Q-network (DQN) framework is utilized for RIS phase shift optimization. Simulation results demonstrate that the proposed DRL-based algorithm can achieve almost optimal performance, while has much less computation consumption.

Meningkatkan Keterampilan Berbicara Siswa melalui Model Pembelajaran Everyone is a Teacher Here Kelas 4 SDN 14/I Sungai Baung

Speaking skills are one of the important components that must be possessed in students wherever they are. With these speaking skills students can be skilled at speaking by training and demanding students to be able to communicate with friends and the surrounding environment. In addition, with speaking skills students can express, state and convey ideas, thoughts, ideas, or feelings to others. This type of research is classroom action research (CAR). This research was conducted with an effort to improve students' speaking skills through the Everyone Is A Teacher Here learning model for class 4 SDN 14/I Sungai Baung TP. 2022/2023. This study uses observation and documentation techniques. The research process went through two stages, namely cycle I and cycle II. Through four stages, namely planning, implementation, evaluation, and reflection. The results of observations in the first cycle became a reference for improvement in the next cycle. The reflection phase refers to cycle I, the expected goals have not been achieved. Cycle II is an improvement from cycle I which was previously implemented. The deficiencies that existed in cycle I were corrected in cycle II. Cycle II was prepared and planned more carefully for student learning outcomes and behavior. Based on the discussion of students' ability in speaking skills through the Everyone Is A Teacher Here method, it was concluded: 1. The average result of cycle I was 80.1 and cycle II was 82.3 increased by 2.2. 2. The learning outcomes in cycle I achieved classical completeness of 80.9% and in cycle II it became 100%. 3. Student activity in cycle I was 56% and cycle II was 87%.

Polarization insensitive reflectarray for OAM beam generation over octave bandwidth for 5G applications

In this paper, a wide band, polarization-insensitive reflectarray composed of 14 × 14 unit elements is proposed to generate vortex beams of different orbital angular momentum (OAM) modes with higher mode purity. The multiple resonance architecture of the unit element is designed and achieved 750°of the reflection phase by varying geometrical dimensions, which contributes to the remarkable increase in linear phase bandwidth. The unit element provides stable responses for different incident angles of electromagnetic wave. The prototype of proposed reflectarray with the size of 350 mm × 350 mm is designed, fabricated using printed board technology, and experimentally tested. The measured results confirms that a OAM vortex beam l = +1 is successfully generated at 5.75 GHz with a high gain of 21.3 dBi and a low divergence angle of 12°.

Design and Analysis of Fractal-Shaped High-Impedance Surface Unit Cell Characteristics

Fractal geometries consistently provide solutions to several electromagnetic design problems. In this paper, fractal geometries such as Hilbert and Moore curves are used to design efficient High-Impedance Surfaces. Modern communication devices have many sensors that are needed to communicate wirelessly. The critical component of wireless communications is antennas. Planar microstrip patch antennas are popular due to their low profile, compactness, and good radiation characteristics. The structural disadvantages of microstrip antennas are that they have surface waves that propagate over the ground plane. High-Impedance Surface (HIS) planes are a prominent solution to minimize and eliminate surface waves. The HIS structures behave as active LC filters that suppress surface waves at their resonance frequency. The resonance frequency of the structure is obtained by its LC equivalent or by analyzing the reflection phase characteristics. This work presents conventional HIS structures similar to mushroom HIS and fractal HIS such as Hilbert curve and Moore curve HIS. The HIS reflection phase characteristics are obtained by applying periodic boundary conditions with plane wave illumination. The results were obtained in terms of the reflection phase angle. The conventional mushroom structures show narrow band characteristics at given dimensions of 10 mm × 10 mm and 20 mm × 20 mm. These structures are helpful in the replacement of PEC ground planes for patch antennas under sub-6 GHz. The Hilbert and Moore fractals are also designed and have a multiband response that can be useful for L, S, and C band applications. Another design challenge of HIS is protrusions, which make design difficult. The work also presents the effect of having vias and the absence of vias on reflection phase characteristics. The response shows the least and no significant effect of vias under the x-band operation.

Design of a 3-bit encoded THz ultra-wideband vortex beam generator based on a metasurface

With the rapid development of high-speed THz communications, there has been a growing interest in exploring the potential of the orbital angular momentum (OAM) of electromagnetic waves. In this study, we propose a cross-polarized reflective broadband metasurface operating in the THz band to harness the benefits of OAM in the optical field. We quantitatively analyze the reflection amplitude and phase characteristics of the metasurface elements, which supports the design of a reflective broadband element surface array with an ordered arrangement of 3-bit elements. By combining the 3-bit metasurface elements in an array, linearly polarized waves can effectively be converted into vortex beams in the operating frequency range of 0.6THz-1.3THz. The simulation results demonstrate that the designed metasurface element structure can achieve not only efficient cross-polarization reflection amplitude but also effective phase control by adjusting the size parameters. Our proposed metasurface is able to convert linearly polarized waves into vortex beams with an efficiency exceeding 85% and can achieve high-purity OAM beam acquisition. Furthermore, the metasurface structure is simple to implement and can be easily integrated with photoelectric circuits, making it ideal for use in ultrahigh-speed THz communications.

Full-parameter omnidirectional transformation optical devices.

Transformation optics (TO) provides an unprecedented technique to control electromagnetic (EM) waves by engineering the constitutive parameters of the surrounding medium through a proper spatial transformation. In general, ideal transformation optical devices require simultaneous electric and magnetic responses along all three dimensions. To ease the practical implementation, previous studies usually made use of reduced parameters or other simplified approaches, which inevitably introduce extra reflection or unwanted phase shift. Up to today, experimental realizations of full-parameter transformation optical devices in free space are still quite limited. Here, a general design strategy is proposed to solve this problem. As a specific example, a full-parameter spatial-compression TO medium with constitutive parameters taking the diagonal form diag(a, a, 1/a) for the TM wave incidence was designed and realized experimentally. Such spatial-compression TO media were then applied to the implementation of an ideal omnidirectional invisibility cloak capable of concealing a large-scale object over a wide range of illumination angles. Both the simulation and experiment confirm that the cloak allows for nearly unity transmission of EM waves in the forward direction without introducing extra scattering or phase shift. This work constitutes an important stepping stone for future practical implementation of arbitrary full-parameter omnidirectional transformation optical devices.

Dual-band and high-efficiency metasurface-based circular-to-linear polarization converter.

In this paper, to achieve circular-to-linear polarization conversion, a novel polarization converter based on an anisotropic metasurface is proposed. Because the polarization converter is an orthotropic anisotropic structure with a pair of mutually perpendicular symmetric axes u and v, theoretical analysis shows that the polarization converter can achieve circular-to-linear polarization conversion if its reflection phase difference Δφuv under u-polarized and v-polarized incidences is close to ±90°. Numerical simulations show that the reflection phase difference Δφuv of the polarization converter is very close to +90° in two separated frequency ranges, so the polarization converter can achieve high-efficiency and dual-band CP-to-LP polarization conversion, it can convert right-handed circular-polarized (RHCP) and left-handed circular-polarized (LHCP) waves into y-polarized and x-polarized waves respectively in the two separated frequency bands of 8.08-9.27 GHz and 13.80-27.11 GHz; moreover, its polarization conversion rate (PCR) is kept larger than 99.7% in the two frequency bands. Finally, to validate the design, a prototype is manufactured and measured, the measured results are in good agreement with the simulated ones.

RIS-Based Wireless Sensor Networks: Passive Beamforming and Decision Gathering

By embedding each sensor into a reconfigurable intelligent surface (RIS) controller, in this letter we propose an efficient RIS-based wireless sensor network (WSN) for simultaneous passive beamforming and decision gathering. In RIS-WSN, the reflection amplitudes and phase shifts of RISs are designed to convey the local decisions made by sensors and boost the data transmission from a radio frequency source. We analyze the bit error rate (BER), decision error rate (DER), and sum rate performance of RIS-WSN over Rician fading channels by considering the presence of both direct and reflecting links. An upper bound on BER and an approximate expression for DER are derived in terms of data transmission and decision gathering, respectively. Computer simulations verify the analysis and show the superiority of RIS-WSN over the state-of-the-art method.

RIS-Assisted Ambient Backscatter Communication for SAGIN IoT

The space, air and ground integrated network (SAGIN) will greatly promote the development of the Internet of Things (IoT). Green IoT will be an important part of SAGIN. Ambient backscatter communication (AmBC) is a potential solution for green SAGIN IoT. To improve the achievable sum rate (ASR) of the AmBC system, we propose a reconfigurable intelligent surface (RIS) assisted AmBC system. In the single-BD AmBC scenario, we firstly give the phase shifts that maximize the gain of the reflection link of the AmBC system, and then give the optimal reflection coefficient. The proposed scheme does not need to solve the convex semidefinite program (SDP) problem, and has the characteristics of low computational complexity. In the multi-BD AmBC scenario, we first propose a multi-BD phase shifts initialization strategy to ensure the stability of the proposed scheme. Then, we give the optimal reflection coefficient and phase shifts based on iterative method. Simulations show that the RIS-assisted AmBC scheme is superior to the non-RIS-assisted AmBC scheme.

Resource Allocation for IRS-Assisted Uplink URLLC Systems

We study the resource allocation optimization in an intelligent reflecting surface (IRS)-assisted uplink ultra reliable and low-latency communication (URLLC) system. The transmit power of users, the receive beamformer at the base station (BS) and the IRS reflection phase shifts are jointly optimized to maximize the achievable sum finite blocklength (FBL) rate, which turns out to be a complicated non-convex problem. To tackle this problem, we develop a low-complexity minorization-maximization (MM)-based algorithm, which only involves calculating closed-form expressions in each iteration. Compared with an existing quadratic transform based scheme, the proposed design achieves better performance while with reduced complexity.

Crustal structure and its tectonic implications beneath the middle–lower Yangtze metallogenic belt in Anhui Province: 3D deep seismic sounding results from airgun source in inland waters

To evaluate the effectiveness of using airguns as seismic sources in inland waters to detect the regional crustal structure, a mobile large-capacity airgun excitation experiment was conducted in October 2015 in the Anhui section of the middle–lower Yangtze metallogenic belt. In this study, we extracted 1,957 first-arrival phases (Pg) and 2,179 Moho reflection phases (PmP) from the airgun seismic signals, and performed joint inversion of the traveltimes. The inversion results reveal the P-wave high-velocity anomalies above 7 km depth in the upper crust beneath the ore clustering areas, suggesting the source of mineralized materials. The crustal velocity structure characteristics substantially differed above and below a depth of 7 km, indicating the existence of a regional basement detachment surface. The velocity structure in the middle–lower crust, especially in the lower crust show lateral uniformity characteristic, which could be related to that the middle–lower Yangtze metallogenic belt had undergone a MASH metallization process. The Moho is 30–36 km deep, and its uplift zone extends from southwest to northeast in a “V” shape, which is consistent with the planar spreading characteristics of the metallogenic belt, indicating that the asthenosphere uplift and crustal thinning have had a controlling effect on the formation of the metallogenic belt. This study suggests the present-day crust in the region along the Yangtze River in Anhui retains the traces of lithosphere delamination-thinning and basaltic magma underplating during the Yanshan period. Our results indicates that airgun source detection in inland waters can effectively determine the continental crustal structure.

Six-channel programmable coding metasurface simultaneously for orthogonal circular and linear polarizations

Metasurfaces have intrigued long-standing research interests and developed multitudinous compelling applications owing to their unprecedented capability for manipulating electromagnetic waves, and the emerging programmable coding metasurfaces (PCMs) provide a real-time reconfigurable platform to dynamically implement customized functions. Nevertheless, most existing PCMs can only act on the single polarization state or perform in the limited polarization channel, which immensely restricts their practical application in multitask intelligent metadevices. Herein, an appealing strategy of the PCM is proposed to realize tunable functions in co-polarized reflection channels of orthogonal circularly polarized waves and in co-polarized and cross-polarized reflection channels of orthogonal linearly polarized waves from 9.0 to 10.5 GHz. In the above six channels, the spin-decoupled programmable meta-atom can achieve high-efficiency reflection and 1-bit digital phase modulation by selecting the specific ON/OFF states of two diodes, and the phase coding sequence of the PCM is dynamically regulated by the field-programmable gate array to generate the desired function. A proof-of-concept prototype is constructed to verify the feasibility of our methodology, and numerous simulation and experimental results are in excellent agreement with the theoretical predictions. This inspiring design opens a new avenue for constructing intelligent metasurfaces with higher serviceability and flexibility, and has tremendous application potential in communication, sensing, and other multifunctional smart metadevices.

Microphysical Characteristics of Raindrop Size Distribution and Implications for Dual-Polarization Radar Quantitative Precipitation Estimations in the Tianshan Mountains, China

In order to improve the understanding of the microphysical characteristics of raindrop size distribution (DSD) under different rainfall rates (R) classes, and broaden the knowledge of the impact of radar wavelengths and R classes on the QPE of dual-polarization radars in the Tianshan Mountains, a typical arid area in China, we investigated the microphysical characteristics of DSD across R classes and dual-polarimetric radar QPE relationships across radar wavelengths and R classes, based on the DSD data from a PARSIVEL2 disdrometer at Zhaosu in the Tianshan Mountains during the summers of 2020 and 2021. As the R class increased, the DSD became wider and flatter. The mean value of the mass-weighted mean diameters (Dm) increased, while the mean value of logarithm normalized intercept parameters (log10 Nw) decreased after increasing from C1 to C3, as the R class increased. The largest contributions to R and the radar reflectivity factor from large raindrops (diameter > 3 mm) accounted for approximately 50% and 97%, respectively, while 84% of the total raindrops were small raindrops (diameter < 1 mm). Dual-polarization radars—horizontal polarization reflectivity (Zh), differential reflectivity (Zdr), and specific differential phase (Kdp)—were retrieved based on the DSD data using the T-matrix scattering method. The DSD-based polarimetric radar QPE relations of a single-parameter (R(Zh), R(Kdp)), and double-parameters (R(Zh,Zdr), R(Kdp,Zdr)) on the S-, C-, and X-bands were derived and evaluated. Overall, the performance of the R(Kdp) (R(Kdp,Zdr)) scheme was better than that of R(Zh) (R(Zh,Zdr)) for the QPE in the three bands. Furthermore, we have for the first time confirmed and quantified the performance differences in the QPE relationship of dual-polarization radars under different schemes, radar wavelengths, and R classes in typical arid areas of China. Therefore, selecting an appropriate dual-polarization radar band and QPE scheme for different R classes is necessary to improve the QPE ability compared with an independent scheme under all R classes.

Integrated Control of Radiations and In‐Band Co‐Polarized Reflections by a Single Programmable Metasurface

AbstractIntegrated control of radiated and reflected electromagnetic (EM) waves is of great importance in information science and engineering, which are mostly achieved by elaborately integrating metasurfaces and antennas. However, most of the radiation‐reflection‐integrated designs remain difficulties to modulate the radiated waves directly without cascading additional radio‐frequency (RF) modules. More importantly, the completely independent control of radiated waves and in‐band co‐polarized reflected waves has rarely been achieved. Herein, direct, dynamic and integrated control of radiated waves and in‐band co‐polarized reflected waves is realized merely by a single programmable metasurface. The radiation‐reflection‐integrated programmable metasurface (RRIPM) can dynamically choose to radiate EM waves only or reflect incident EM waves only, and even dynamically modulate the radiation phases and reflection phases, thus realizing arbitrary radiation functions and in‐band co‐polarized reflection functions without crosstalk. To illustrate the capabilities of RRIPM, an ultra‐compact and broadband RRIPM prototype is designed and fabricated, and this is used for the radiation and reflection of multiple beams with arbitrary energy distributions, low‐gain‐fluctuation reflection‐beam scanning, and low‐side‐lobe‐level broadside radiation.

High-temperature resistant electromagnetic protection bilayer structure based on the low-reflection metasurface and wave-absorbing material.

In this paper, we propose a high-temperature resistant bilayer structure for electromagnetic protection with low reflection, consisting of a metasurface and an absorbing layer. The bottom metasurface decreases the reflected energy by using a phase cancellation mechanism to make electromagnetic wave scattering in the 8-12 GHz range. While the upper absorbing layer assimilates the incident electromagnetic energy through electrical losses and simultaneously regulates the reflection amplitude and phase of the metasurface to enhance scattering and expand its operating bandwidth. Research shows that the bilayer structure achieves a low reflection of -10 dB in the range of 6.7-11.4 GHz due to the combined effect of the above two physical mechanisms. In addition, long-term high-temperature and thermal cycling tests verified the stability of the structure in the temperature range of 25-300°C. This strategy provides the feasibility of electromagnetic protection in high-temperature conditions.