Reflection Phase Research Articles

Frequency-multiplexed multifunctional coding metasurface based on transmission and reflection modes

In this work, a frequency-multiplexed multifunctional coding metasurface is proposed, which can realize focusing lens at the lower frequency and multiple scattering beams at the higher frequency. The two functions can be manipulated independently. The proposed metasurface is composed of the top metal patch with a circular ring, two fan rings and two rectangle patches (CFRP), the bottom metal patch with C-shaped and rectangular metal slots (CRS) and a dielectric substrate. By changing the opening direction and size of CRS and the tilt direction and fan ring size of CFRP, the amplitude and phase of transmission and reflection can be modulated, respectively. The transmission mode works at 7 GHz, which can form focal points in different focal planes. The reflection mode works at 17.5 GHz, which can form multiple scattered beams in different directions in the far field. To further verify its practical feasibility, the proposed metasurface is fabricated and measured, the experimental results are in good agreement with the numerical simulation results. The proposed metasurface provides new possibilities to develop multifunctional devices.

Interleaved coding Janus metasurface with independent transmission and reflection phase modulation.

An interleaved coding Janus metasurface is proposed, which can generate bidirectional functionalities with full phase control of the reflected and transmitted waves. By introducing rotation and geometric parameter changes into the meta-atoms, the reflection and transmission channels with required energy distribution and foci are realized. More remarkably, our approach is based on a single metasurface design that arranges two types of unidirectional propagating unit structures with simultaneous desired reflection and transmission properties into a checkerboard configuration to obtain four different holograms. The results verify the excellent performances of the multifunctional metasurface, laying a foundation for manipulation of EM waves with more degree of freedom, and promoting its applications in the entire frequency spectrum.

Scaffolding Self-Regulated Learning in Operative Dentistry Through Self-Assessment Training.

This study aimed to investigate how effective self-assessment training is in improving the self-regulated learning (SRL) ability of operative dentistry students. The secondary aim was to explore students' attitudes towards self-assessment in clinical settings. Self-assessment has been the focus of dental education research for decades and has been claimed to be cornerstone in the SRL process. This is quasi-experimental study conducted at Damascus University Faculty of Dental Medicine, Syria. A modified direct observation of procedural skills (DOPS) assessment protocol with a self-assessment component was applied to a convenience sample of students across five clinical encounters in 2022. Data were collected during clinical training on the DOPS form and at the end of the experiment using a structured questionnaire with a single open-ended question. The qualitative part of the study followed a deductive theory-informed content analysis approach, relying on Zimmerman SRL theory. A total number of 32 students participated in the study, eight of whom were male. During the experiment assessment, participants showed overwhelming positive attitudes towards the utility of self-assessment (m ≥ 3.5; max:4) and the overall assessment method (3.3 ≥ m ≥ 3.5; max:4). Cronbach's alpha for the post-experiment questionnaire was 0.888. A total of 84.4% of the participants strongly agreed that self-assessment is useful in clinical training. Data collected (qualitative and quantitative) from participants revealed the positive effects of self-assessment on all three phases of SRL, especially the reflection phase. Self-assessment practice and training showed positive results in terms of improving SRL and performance in a clinical context; SRL appeared to be affected by self-assessment in all phases (forethought, performance, and reflection). Participants' perceptions of self-assessment were generally very positive. These findings imply the potential benefits of applying self-assessment training interventions to foster the SRL ability of learners within the clinical context.

Coexistence of giant Goos-Hänchen shift and high reflectance in Dirac semimetal based multilayered structure.

Bulk Dirac semimetals (BDSs) possess Fermi energy dependent optical parameters, providing unprecedented opportunities for the study of the controllable Goos-Hänchen (GH) shift. However, the enhancement of GH shifts often comes at the cost of the reflectance in the previous BDS-based structures, which hinders their practical application. In this work, we theoretically present the investigation of the GH shift in a multilayered structure composed of one BDS film and a symmetric one-dimensional photonic crystal (1DPC) with a defect layer. We demonstrate that this well-designed structure supports a large GH shift at the specific working wavelength, whose magnitude can be enhanced up to 3883 times the incident wavelength. In particular, such an enhanced GH shift achieved in this structure is associated with high reflectance (0.94) and these remarkable features can be attributed to the sharp change in the reflective phase and the destructive interference that occurs between the simultaneously excited optical Tamm state (OTS) at the BDS/1DPC interface and the defect state at the 1D defected PC. In addition, we also explore the manipulation of the GH shift by adjusting the Fermi energy of the BDS as well as the geometrical parameter of the multilayered structure. Our results provide a new approach for realizing an enhanced and controllable GH shift in a BDS-based multilayered structure, which endows it with promising prospects for application in optical sensors, optical detectors and beam controllers.

Incident component extraction from disturbed waves around large fixed cylindrical structures

The parameters of incident waves are critical for real-time wave load estimation of structures in service. Nonetheless, it is challenging to characterize incident waves accurately using the measured wave surface elevation around large fixed cylindrical structures due to the interaction with the structure in the wave field. To provide a better understanding of incident waves, which are usually buried in directly measured waves, a new time-domain method for the extraction of first-order and second-order incident waves around large fixed cylindrical structures is proposed. In contrast to most existing separation methods that are suitable for structures with equal reflection coefficients, the amplitude and phase changes of near-field waves around cylindrical structures can be determined by considering the significant diffraction effect, and then the time-frequency characteristic of the wavelet transform is employed, which enables the extraction of incident waves in the time domain. The accuracy of the proposed method is studied using several examples with known incident waves which are generated with the OpenFOAM. The numerical results show that the deviations between the exact and extracted incident waves change from 6.16% to 16.77% for different wave conditions. To further investigate the performance of the proposed method, an experimental study on waves around a mono-pile offshore wind turbine (OWT) is conducted in the laboratory of the Ocean University of China. The predicted results basically agree well with the target waves in terms of amplitude and phase. The deviations between predicted waves using the proposed method and target waves are 110% smaller than those between directly experimental measured waves and target waves for all tested conditions. Finally, 48 h of measured wave data were obtained during calm and typhoon periods around a mono-pile OWT located near Rudong County, Jiangsu Province, in the Yellow Sea of China. There are almost 150% and 30% differences between the extraction results and measured data in the time series and statistical wave heights, respectively, which means that employing disturbed wave data as the input for calculating real-time wave loads leads to deviations that cannot be ignored.

Generating brick-like melt pools for Laser-Based Powder Bed Fusion using flexible beam shaping: a proof of concept on bead-on-plate single tracks

Despite the highest industrial maturity among additive manufacturing processes, laser-based powder bed fusion of metals (PBF-LB/M) lacks the productivity to further establish as an industrial manufacturing process. One approach for adjusting the melt pool shape to increase productivity in PBF-LB/M is spatial beam shaping. The freedom of beam shaping is almost unlimited, owing to modern optical concepts. The key is a beam shape optimized for a specific target. In this publication, the target is a brick-like melt pool cross-section. The publication demonstrates how the corresponding laser beam shape is designed using numerical optimization. The computed beam shape is reproduced using reflective spatial light phase modulators. The calculation is validated based on single-track experiments. Applying the optimized beam shape results in a melt pool shape similar to the optimization target. The width and depth of the melt track produced deviate by a maximum of 7 % from the specified target values.

Adjustable Phase-Amplitude-Phase Acoustic Metasurface for the Implementation of Arbitrary Impedance Matrices.

Impedance metasurfaces enable accurate regulation of acoustic fields. However, they can hardly supply a flexible response as such perfect operation is accompanied by stringent requirements on the design of unit cells. Actually, an arbitrary lossless and passive target impedance matrix requires the tuning of 3 independent real parameters. The set composed of a reflection phase, a transmission amplitude, and a transmission phase, enables the representation of an arbitrary impedance matrix, possibly possessing singular elements. In this paper, a mechanism of phase-amplitude-phase modulation (PAP modulation) is developed for the generic design of the unit cells of acoustic impedance metasurfaces. Adjustable acoustic impedance metasurfaces are further available under this framework. An impedance unit with 3 mobile parts is designed based on this idea. The assembled metasurface can handle different incidences for acoustic field manipulation at a given frequency. Beam steering and beam splitting are considered as demonstration examples and are verified by numerical simulation and experiment. PAP modulation enriches the design of acoustic impedance metasurfaces and extends the range of application of impedance theory.

Reflection Phase Modulation of Subwavelength Gold Gratings with Asymmetric Boundaries

Reflection Phase Modulation of Subwavelength Gold Gratings with Asymmetric Boundaries

Comparison of a Circular Patch Unit Cell Performance for Reflector Applications between Using FR4 and F4BMX220 Substrates at 3.5 GHz Frequency

This paper presents a performance comparison of the circular patch unit cell as a unit cell for reflector application at 3.5 GHz frequency using a dielectric substrate between FR4 and F4BMX220 substrates. A circular patch is chosen as the unit cell of a reflector because it is commonly used, fabricated, and has a wider bandwidth compared to other structures. A performance comparison of the circular patch on both dielectric substrates is presented in a graph of S-parameters, reflection phase, and operating bandwidth, as well as in the table of dimensions, where the result is performed by simulation using CST software. Based on the simulated results, the F4BMX220 has a better performance compared to the FR4 in terms of the reflection value, operating bandwidth, and dielectric substrate thickness. However, a circular patch diameter when using the F4BMX220 is bigger than when using the FR4 substrate because the FR4 substrate has a higher dielectric constant than the F4BMX220, which is twice the F4BMX220 dielectric constant. Also, the F4BMX220 substrate has a narrower bandwidth compared to the FR4 substrate, which is a difference of around 0.1 GHz. The circular patch when using the F4BMX220 substrate has 0.96 of a reflection value, 0.007 of an absorption value, -6.77° of the reflection phase, and 0.24 GHz of the operating bandwidth at the normal incident wave angle (0°). Also, it can be properly worked if the incident wave angle is moving until 60°. The F4BMX220 substrate has the best performance compared to the FR4 substrate because the reflection value is much better value, even at the incident wave angle of 60°.

Online activity practices based on common knowledge constructing model: Example of radioactivity topic

The aim of this study was to examine the effect of the Common Knowledge Construction Model (CKCM) on the conceptual understanding of science teacher students about Radioactivity. CKCM was used. In order for the students to adapt the radioactivity subject, which they see as difficult and abstract, to daily life by knowledge structuring. This study was carried out with 48 students studying in the second year of science education at a public university in the western region. The research employed pretest-posttest control group random design. The Radioactivity Concept Test (RCT) with 2 phases consisting 23 multiple- choice items were used as data collection tools in the research. After the tests were applied as a pilot study to 124 students, it was used with the participants of the study after the necessary validity and reliability studies were carried out. The KR20 reliability coefficient obtained from the sample data was calculated as 0.74. In the study, experimental and control groups were formed by random assignment. While the traditional lecture method was applied to the control group, the CKCM was applied to the experimental group. When the concept test data were analyzed with the SPSS 24 package program, it was determined that the experimental group were more successful than the control group. determined that the increase in correct answers in the post-test of the experimental group was higher than that of the control group.

Strategies for Enhancing Early Childhood Science Literacy Through STEAM Education

The primary objective of this study is to enhance young children's comprehension of scientific concepts by implementing the STEAM approach within the context of Early Childhood Education (PAUD). The STEAM (Science, Technology, Engineering, Art, and Mathematics) pedagogy for preschoolers emphasizes dynamic learning, stimulates cognitive engagement, facilitates problem-solving, nurtures structured and methodical reasoning, and enhances critical thinking skills. Conducted using the Classroom Action Research method guided by the Kemmis cycle model, this study involves a cohort of 15 participants from group B, aged 5-6 years, and spans across preliminary cycles, Cycle I, and Cycle II, comprising phases of planning, execution, observation, and reflection. The comprehensive deliberation's outcome establishes the potential for enhancing scientific literacy among young children through the implementation of STEAM education. This advancement in scientific understanding is facilitated through captivating balloon experiments, utilizing colors that resonate with children's preferences. The attainment of scientific knowledge, as evident through the STEAM approach, manifests at a rate of 10% during the Pre-Cycle, 26% during Cycle I, and an impressive 72% during Cycle II. The cumulative findings unequivocally underscore the profoundly positive role of STEAM pedagogy in augmenting scientific cognizance during the formative years of early childhood.

A three‐dimensional wideband mmWave multiple‐input multiple‐output channel model for aerial reconfigurable intelligent surface‐assisted communication systems

SummaryThis paper presents a wideband millimeter wave (mmWave) channel model for aerial reconfigurable intelligent surface (ARIS) communications, in which the reconfigurable intelligent surface (RIS) is attached to an unmanned aerial vehicle (UAV) to enable intelligent signal reflections in the air. The model is established according to standard 3GPP channel models and considers important propagation factors, for example, large‐scale fading, small‐scale fading, and radiation pattern of reflection units (RUs). In addition, the model assumes three‐dimensional (3D) rotations of RIS and can capture its effects on channel characteristics. Based on the model, we propose a design method for RIS reflection phases. Statistics including channel amplitude, spatial, temporal, and frequency correlation functions (CFs), and space‐Doppler power spectral density (SD‐PSD) are obtained. The impacts of RU number, UAV height and speed, and RIS rotation on channel statistics are investigated. Results suggest that the designed reflection phases can effectively mitigate multipath fading and Doppler effect. Compared to the yaw angle of the UAV platform, channel characteristics are more sensitive to the roll and pitch angles.

Three-dimensional imaging in reflection phase microscopy with minimal axial scanning.

Reflection phase microscopy is a valuable tool for acquiring three-dimensional (3D) images of objects due to its capability of optical sectioning. The conventional method of constructing a 3D map is capturing 2D images at each depth with a mechanical scanning finer than the optical sectioning. This not only compromises sample stability but also slows down the acquisition process, imposing limitations on its practical applications. In this study, we utilized a reflection phase microscope to acquire 2D images at depth locations significantly spaced apart, far beyond the range of optical sectioning. By employing a numerical propagation, we successfully filled the information gap between the acquisition layers, and then constructed complete 3D maps of objects with substantially reduced number of axial scans. Our experimental results also demonstrated the effectiveness of this approach in enhancing imaging speed while maintaining the accuracy of the reconstructed 3D structures. This technique has the potential to improve the applicability of reflection phase microscopy in diverse fields such as bioimaging and material science.

Photometric correction of images obtained from Chandrayaan-2 Imaging Infra-Red Spectrometer (IIRS) data

India’s second mission to the Moon, Chandrayaan-2, carried one of the most advanced imaging spectrometers ever sent to image a planetary surface – the IIRS (Imaging Infra-Red Spectrometer) – a 250 band spectrometer developed at the Space Applications Centre (SAC), ISRO, India. In this study, IIRS data between 800 and 2000 nm have been used to derive photometrically corrected reflectance from calibrated radiance data supplied by ISRO’s online archive (Pradan) of Chandrayaan-2 data. Additionally, the photometric properties of three IIRS bands (950, 1500, and 1700 nm) have been studied in detail. Since the images obtained by IIRS are at different viewing geometry orientations, the purpose of performing a photometric correction on IIRS images is to re-project each pixel to a standard viewing geometry of incidence angle, i = 30°, emission angle, e = 0° and, phase angle, α = 30°. In order to correct the lunar limb darkening effect, a combination of the Lommel-Seeliger function and McEwen’s model was used. In addition, topographic data from the merged Digital Elevation Model of Lunar Reconnaissance Orbiter – Lunar Orbiter Laser Altimeter (LRO-LOLA) and SELENE Terrain Camera (TC) were utilized to remove effects from local topography. A photometric function was then applied on four images captured by IIRS which were included in the first public release of data in August 2021. Radiance and reflectance (obtained after implementing photometric correction on IIRS images) values were compared with L1 and L2 M3 (Moon Mineralogy Mapper) data from Chandrayaan-1. It was found that although IIRS images are much darker than M3, corrected IIRS reflectance images had a much smaller variation in terms of reflectance values with M3. Moreover, the associated spectral reddening and reflectance values are within range when compared with data from other lunar missions. In addition, the reflectance spectra derived from the corrected IIRS images have been plotted for each image. However, the spectra exhibit significantly deeper absorptions than their corresponding M3 data for the same pixel. Phase functions derived from three bands have a good correlation with the reflectance values and phase angles. Consequently, this function can be applied to all IIRS images as and when more data are released to the public.

Implementation of Worksheets Based on Experiments on The Subject of Biotechnology to Develop Students' Scientific Literacy

This study aimed at bolstering students' scientific literacy in biotechnology through the implementation of Experiment-Based Learning and Creativity Worksheets (LKPD). Utilizing a classroom action research framework, the investigation was conducted over two cycles, incorporating planning, action, observation, evaluation, and reflection phases. It involved 30 students and used observational sheets for monitoring teacher and student activities, along with multiple-choice and essay questions to assess students' scientific literacy. The findings revealed a notable enhancement in both teaching methods and student learning outcomes, facilitated by the LKPD usage. Specifically, teacher performance improved from achieving 80% of the set criteria in the first cycle to 90% in the second, upgrading their rating from 'Good' to 'Very Good'. This improvement was paralleled by a rise in students' average scores from 85.33 to 90.58, indicating a heightened engagement with and comprehension of biotechnological principles. The employment of LKPDs proved critical not just for expanding knowledge but for the practical application of scientific concepts, as demonstrated by an average literacy score of 88. Furthermore, an uplift in the average scientific literacy score from 76.59 in the first cycle to 84.89 in the second emphasizes the significance of LKPDs in enhancing students' grasp of scientific theories. Overall, the interventions across the cycles successfully elevated the caliber of teaching, enriched the student learning experience, and significantly improved science literacy, thus contributing to an enhancement in educational quality

Development of quantitative precipitation estimation (QPE) relations for dual-polarization radars based on raindrop size distribution measurements in Metro Manila, Philippines

Quantitative precipitation estimates (QPE) can be further improved using estimation algorithms derived from localized raindrop size distribution (DSD) observations. In this study, DSD measurements from two disdrometer stations within Metro Manila during the Southwest monsoon (SWM) period were used to investigate the microphysical properties of rainfall and develop localized dual-polarimetric relations for different radar bands and rainfall types. Observations show that the DSD in Metro Manila is more distributed to larger diameters compared to Southern Luzon and neighboring countries and regions in the Western Pacific. This is reflected by the relatively higher mass-weighted mean diameter (Dm) and smaller shape (μ) and slope (Λ) parameters measured in the region. The average values of Dm and normalized intercept parameter (Nw) in convective rain samples also suggest that convective rains in Metro Manila are highly influenced by both continental and oceanic convective processes. Dual-polarimetric variables simulated using the T-matrix scattering method showed good agreement with disdrometer-derived reflectivity (ZH) values. The 0.5 dB and 0.3° km−1 thresholds for the differential reflectivity (ZDR) and specific differential phase (KDP) based on the blended algorithm of Cifelli (J Atmos Ocean Technol 28:352-364, 2011) and Thompson et al. (2017) are proven to be useful since the utility of the dual-polarimetric variables as rainfall estimators are shown to have dependencies on the radar band and rainfall type. Evaluation of the QPE products with respect to the C-band shows that R (KDP, ZDR) has the best performance among the dual-pol relations and statistically outperformed the conventional Marshall & Palmer relation [R(ZMP)]. The results show that dual-polarimetric variables such as ZDR and KDP can better represent the DSD properties compared to one-dimensional Z, hence providing more accurate QPE products than the conventional R(Z) relations.

Terahertz Wave Tunable Metalens Based on Phase Change Material Coded Metasurface

Based on phase change material and Pancharatnam-Berry phase principle, a tunable coded metasurface is designed to realize terahertz wave metalens. When the vanadium dioxide phase change material is reversibly converted from metal state to medium state, the lens can achieve the tunable function of reflection focusing and transmission focusing. The unique feature of our tunable metalens is that when the vanadium dioxide material is in the medium state, the silicon cuboid column plays the main role. We can rotate the silicon column structure to obtain the geometric phase coding unit. When the phase change material is in the metallic state, the vanadium dioxide metal rod structure plays the main role and rotates the element structure to obtain the reflective geometric phase coding element. In order to control the focus position of the transmission-reflection tunable metalens, we further designed non-central focusing and bifocal focusing metalens.

Rapid Hot-Spot Detection Based on Weak Reflection Point and Phase Demodulation OFDR

Rapid Hot-Spot Detection Based on Weak Reflection Point and Phase Demodulation OFDR

2–Bit Programmable Metasurface for Low Radar Cross Section Antenna and Beam Steering Applications

AbstractIn this paper, a 2‐bit water‐based programmable digital metasurface for beam steering and backscatter field reduction applications is presented, a reflective and transmissive type water based programmable metasurface (WPMS) for RCS reduction and the antenna's beam steering is suggested, respectively. It has been demonstrated that a 2‐bit water‐based programmable unit cell can reduce RCS by changing its state (0/1). If the unit cell channel is empty, the state is “0,” if the channel is filled, the state is “1.” So at different resonance frequencies, the four phase and reflection coefficient responses are achieved as "00"01"10"11". This functionality enables beam steering in both the elevation and azimuth axis and also backscattering reduction of the antenna. Furthermore, the impacts of the number of unit cells and reflection phase states on the far‐field pattern are examined. Beam steering of ±45° in the elevation is attained with 10‐dB impedance bandwidth of 4.25–4.40 GHz, radiation gain of more than 7.1 dBi is maintained. With the present antenna, it is possible to achieve volumetric beamsteering performance directly. The patterns of far‐field radiation that are predicted theoretically coincide well with full waves simulations. As such, the proposed prototype can be a good option for applications that require a low RCS platform including beam steering in radars, 5G/6G, etc.

STUDY ON COST CONTROL IN THE CONSTRUCTION INDUSTRY BASED ON VALUE CHAIN THEORY - TAKE CHANG'AN CONSTRUCTION COMPANY AS AN EXAMPLE

In the face of scarce resources and the law of competition for survival of the fittest, cost control is an eternal topic for enterprises. In traditional accounting, people tend to pay too much attention to the cost of product production. The control of cost is concentrated on the manufacturing cost within the enterprise, and only a single driving factor is the cause of the cost. This causes the traditional cost control to be more and more unable to adapt to the development of modern enterprises. 
 The research objectives of this paper were: 
 
 To analyze the structure of Chang'an Construction Company's value chain.
 To analyze the cost control of Chang'an Construction Company when doing a project based on its value chain structure.
 
 This paper adopts the case study method, starting from the theoretical foundation of value chain cost control, to study the cost control system based on the value chain of Chang'an Construction Company. It seeks to gain relevant insights and draw conclusions from the analysis. 
 Through the in-depth study of value chain cost control in Chang'an Construction Company, several important conclusions have been drawn. A professional bidding process lays the foundation for cost-effectiveness and project profitability. The region-specific strategy adopted by Chang'an Construction makes bid preparation relevant and effective. The division of cost management into preparation and construction phases is critical. Careful cost planning, based on comprehensive site analysis, guides spending during the construction phase. Ongoing monitoring and timely adjustments are critical to align with that plan. Post-completion is not only an end point but also a phase of reflection and optimization of strategy. Efficient resource allocation and regular stakeholder engagement at the end of a project not only reduce future costs but also enhance a company's reputation.