Reflection Phase Research Articles

Perception to Virtual Design Studio in the Initiation, Realization and Reflection Phase: The Faculties and Students Perspective

ABSTRACT The study examines virtual design studio pedagogy in regional settings, providing a comprehensive understanding of the experiences of faculty members and students as they adapted to the virtual design studio due to the COVID-19 pandemic. The research focused on B.Arch., an undergraduate program affiliated with the University of Calicut, Malappuram, Kerala, India. A survey-based cluster sampling approach was made use of. The survey questionnaire collected information from faculties and students on various aspects of the virtual discourse, and SPSS software was used to analyze the data. The Mann-Whitney U test (non-parametric test) was employed to compare adaptation and acceptance levels of virtual design studios between faculties and students. The results indicated differences in adaptation and acceptance levels between the two groups. The research also outlines the various stage-wise phases of the virtual design studio model. Further explores the future of architecture studio pedagogy in a post-Covid scenario, with emphasis on hybrid mode, which could be an area for future research.

Peningkatan Hasil Belajar Siswa Menggunakan Model Discovery Learning Berbantuan Media Audio Visual pada Pendidikan Agama Katolik di kelas IV SDN 08 Semidang

In Dusun Semidang, Desa Suka Maju, Kecamatan Sungai Betung, Kabupaten Bengkayang, West Kalimantan Province, education faces significant challenges. The majority of the population, engaged in farming and gardening, has a low level of education, especially after completing elementary school. The low educational attainment of parents can influence their understanding of the importance of education for their children. This research focuses on Catholic Religious Education at SDN 08 Semidang, with the aim of shaping students into individuals of faith. Students have low interest in learning, lack access to textbooks, and receive inadequate family support. In the fourth grade of SDN 08 Semidang, the Discovery Learning method with the assistance of audio-visual media is applied to address these issues.This study uses two action cycles based on the Kemmis and McTaggart model, consisting of planning, action, observation, and reflection phases. In the first cycle, student learning outcomes did not meet the target, but student reflection questionnaires indicated improvement. In the second cycle, the results were better, with student attitudes reaching 83% of the 80% target. Therefore, the second cycle is considered sufficient and concluded.The results show that the discovery learning model with audio-visual media is effective in improving the learning outcomes of Catholic Religious Education and Character Education in the fourth grade at SDN 08 Semidang. Several recommendations are proposed for further development, including designing more contextual learning materials, providing teacher training, continuous evaluation, active parental participation, and further research to assess the long-term impact of this learning model..

A broadband AMC metasurface for radar cross section reduction and application in microstrip antenna

ABSTRACTA broadband checkerboard artificial magnetic conductor (AMC) metasurface with a 61% bandwidth is proposed. Two different AMC unit cells with 180° (±37°) effective reflection phase difference over a wide frequency range from 7.3–14 GHz are designed. A checkerboard metasurface is structured with two AMC unit cells and is applied in a microstip antenna for radar cross section (RCS) reduction. The simulated results show that the antenna can achieve more than 10 dB RCS reduction from 7.2–13.1 GHz. The maximum RCS reduction is 36 dB. Meanwhile, the radiation performance of the antenna has been well kept. Finally, the low RCS antenna is manufactured and measured. The measured results are in agreement with the simulations.

Ultra-low radar cross-section realized by metasurface with nonuniform elements

A novel checkerboard metasurface is proposed to realize broadband ultra-low radar cross-section reduction (RCSR). The metasurface element is a non-uniform array which contains two uniform subarrays composed of 3 × 6 metallic patches. The reflection phases of the two subarrays can be compensated each other. Based on this characteristic, the non-uniform element reflects two orthogonally polarized waves with a phase difference shrinking to 180 ± 20° in a wideband from 11.2 to 23.0 GHz. When the non-uniform elements are arranged into a checkerboard structure, two co-polarized reflective waves with phase difference of 180 ± 20° are then generated for arbitrary polarized incident waves, resulting in an ultra-low RCS reduction. Simulation results show that the proposed checkerboard metasurface achieves at least 15 dB RCS reduction from 11.2 to 23 GHz (69%) for normal incident waves. The experimental results are good agreement with the simulations.

Regulation of microwave absorbing performance of magnetic alloy/ferrite/carbon ternary composites by changing polydopamine-induced carbothermal reduction

Magnetic alloy/ferrite/nitrogen-doped carbon composites (CoFe/CoFe2O4/N–C) spheres were synthesized by controlled carbothermal reduction of Co-doped Fe2O3 nanospheres wrapped in polydopamine. Different dopamine hydrochloride dosages not only affected components and nanostructures, but also regulated the electromagnetic properties of CoFe/CoFe2O4/N–C composites. The results show that with the increase of dopamine hydrochloride dosage, graphitic degree of N-doped carbon layer would decrease after an initial increase, while the Ms values exhibit an opposite trend. All samples show similar μr spectra, and negative μ″ values can be obtained at high frequency, which should be related to eddy current and dielectric resonance. With the increment of polydopamine, εr would first increase due to generation of CoFe and the increase in graphitic degree, and then decrease owing to the agglomeration of spherical particles. Further research on microwave absorption shows that RL peak frequency coincides with the frequency of perfect impedance matching when good impedance matching has been achieved across a wide range of frequencies. Thanks to the synergistic effects of conduction loss, interfacial polarization, dipole polarization, natural resonance, eddy current, and complete interference cancellation, S-100 has a wide effective absorption bandwidth of 4.88 GHz at 2.0 mm and a low RL peak value of −70.48 dB at 1.95 mm. This work could offer new insights into multi-component magnetic MAMs design and illuminate the relationships between reflection loss, impedance matching, interference cancellation, phase composition, and composite structure.

Reconfigurable Amplitude-Phase-Coding Metasurface with Flexible Beamforming Capability

Recently, reconfigurable coding metasurfaces have attracted extensive attention due to their dynamic and flexible manipulation of electromagnetic (EM) waves, making them an effective solution to connect physical reality and information science. Nevertheless, most previously reported reconfigurable metasurfaces suffer from limited applications, as they solely possess either phase or amplitude modulation. In this article, we propose a reconfigurable coding metasurface that can regulate both phase and amplitude response independently. In the field of the metasurface, the phase response can tailor the wavefronts, and the amplitude response can adjust the redistribution of the energy of the EM waves. Specifically, by integrating a PIN diode into the meta-atom and controlling its bias voltage, the reflection phase can be switched between two opposite phases with a phase difference of about 180°, and the reflection amplitude can be manipulated from 0.02 to 0.98 continuously at 11 GHz. The unit element consists of simple multi-layer structures, reducing its production cost and processing difficulty. By loading 1-bit phase code and multi-bit amplitude code to each unit element severally, this metasurface can modulate the distribution of reflected EM waves in two-dimensional (2-D) space while simultaneously suppressing the sidelobes for any quantity of scattered beams over a wide operating band ranging from 10.5 to 11.5 GHz. This metasurface exhibits promising potential for manipulating the distribution of EM wave energy and shaping of EM beams, which can be expected to facilitate wireless communication technology.

Enhancement of off-body communications with a low-SAR, high-gain multiband patch antenna designed with a quad-band artificial magnetic conductor

Abstract The increasing demand for wireless communication has emphasized the need for multiband antennas. This study presents a novel design for a multiband antenna with reduced specific absorption rate (SAR), high gain, and improved front-to-back ratio (FBR) achieved through the integration with a 4 × 4 artificial magnetic conductor (AMC) surface. The proposed antenna covers a wide range of wireless frequency bands, including Industrial, Scientific, and Medical, Wireless Local Area Network, Worldwide Interoperability for Microwave Access, Wi-Fi 6E, and 7, with resonating frequencies at 2.4, 3.2, 5.5, 7.5, and 10 GHz. The AMC unit cell creates four zero-degree reflection phases with double negative properties at 2.5, 3.8, 5.5, and 7.5 GHz. The compact design measures 0.23λ0 × 0.296λ0 × 0.0128λ0 and placed 0.104λ0 above an AMC surface of size 0.512λ0 × 0.512λ0 × 0.1296λ0. This structure enhances the gain by up to 8.55dBi at 6.01 GHz. The proposed antenna has −10 dB impedance bandwidth for these corresponding frequencies viz 2.34–2.43 GHz (3.77%), 2.81–3.83 GHz (30.72%), 4.82–6.21 GHz (25.20%), 7–7.65 GHz (8.87%), and 8.06–10.31 GHz (24.5%). An overall average percentage reduction value of SAR taken at these frequencies has been found to be 96.11% with AMC structure. The antenna sample was successfully fabricated, and the experimental results have been found to match well with the simulation results. This integrated design offers a promising solution for wearable off-body communication devices.

Dynamic response and liquefaction potential of porous seabed induced by partial standing ocean waves

The analysis of ocean wave-induced dynamic response of a porous seabed is particularly important for coastal and geotechnical engineers when designing and constructing maritime structures. In this study, an analytical solution is presented to analyze the dynamic response and liquefaction potential of a poro-elastic seabed induced by partial standing waves with arbitrary reflectivity. The porous seabed is modeled using Biot’s theory describing the propagation of elastic waves, and coupled deformation and water flow of porous media, whereas the ocean waves are described using linear ocean wave theory. Based on the mixed boundary-value conditions, explicit expressions of displacements, effective stresses and excess pore water pressure of seabed are derived with consideration of the effects of inertial forces, compressibility of solid and fluid, and arbitrary reflectivity of standing waves. The results of degenerated analytical solutions are compared with the existing ones to verify the correctness of the proposed method. The effects of several pertinent parameters of ocean wave-seabed system, including reflection coefficient, phase lag and period of standing waves, depth of water, permeability, degree of saturation, and shear modulus of seabed deposits, etc., on the dynamic response of seabed and liquefaction potential, are examined and discussed. It is found that the reflection of standing wave has a significant effect on the dynamic response and liquefaction potential of porous elastic seabed. Compared with that of no wave reflection, the liquefaction depth of seabed induced by fully-reflected standing waves increases 82.49% under certain conditions of wave-seabed system. In addition, phase lag, wave period, water depth and mechanical and physical properties of seabed soil such as saturation, permeability and shear modulus have different effects on the dynamic response and liquefaction potential of porous elastic seabed. The investigation of the dynamic response and liquefaction of the porous elastic seabed under partial standing ocean waves will help to better predict the influence of standing waves on breakwaters and seabed soil, and can provide some guidance for the design of offshore structures.

Mapping the mantle transition zone discontinuities across South-Central Europe using body waves from seismic noise correlations

We map the mantle transition zone (MTZ) discontinuities beneath South-Central Europe using P-wave reflection phases recovered from noise correlations. We analyze up to four years of seismic noise recordings from 900 broadband stations in the study area. By stacking noise correlations in selected summer months, we significantly improved the retrieval of typically low-amplitude body-wave reflection phases in the light of a quiet surface-wave environment and sufficient noise body-wave illumination from deep paths. We obtain reliable P-wave reflections associated with the 410 km and 660 km discontinuities in the period band of 4–10 s. These short-period reflections reveal clear lateral depth variations of the two discontinuities, indicating complex MTZ structure under the greater Alpine region. This provides new important constraints on present and past mantle dynamics, and it shows the strong potential of passive seismic imaging for studying deep-Earth discontinuities.

Multibeam digital metasurface reflectarray antenna for 5G millimeter wave applications

AbstractA phase‐graded multibeam high gain digital metasurface reflector array (DMSRA) antenna for 5G millimeter wave communication is proposed in this letter. The DMSRA unit‐cell element is composed of a dipole loaded with endstubs. The variation of load across the diploe manipulates the reflection phase response of the incoming electromagnetic wave. A discretized phase state of 0° and 180° is obtained for an optimized loaded dipole. The phase states mimic the binary meta bit‐0 and meta bit‐1. The metabits are distributed along the reflecting surface using a digital coding sequence to form multiple beams in the desired direction. A coding sequence of 010101… is employed to design a two‐dimensional phase‐graded metasurface to generate a four‐beam radiation pattern. The designed digital metasurface reflectarray antenna of dimensions is fabricated and measured to validate the performance. The DMSRA is excited by an antipodal Vivaldi antenna positioned at an optimized focal point of 28 mm. The measured results show a four‐beam radiation pattern obtained over the frequency range of 27.5–28.5 GHz along azimuthal and elevation planes, with a peak beam gain of 10.5 dBi at 28 GHz.

Autonomous Modeling and Design of Microstrip Unit with Accurate Steady-state Reflection Phase Suitable for Any Frequency Band

An autonomous modeling design method for microstrip units is proposed, which can obtain a high precision reflection phase in the center of any frequency band. Specifically, the metal layer pattern area of the microstrip unit is split up into microgrids. Then, whether these grids are affixed to the metal sheet is taken as the optimization object, and the unit reflection phase is taken as the optimization target, and a machine learning algorithm is given for optimization. The modeling and simulation results show that the microstrip unit can obtain a high-precision reflection phase at the target frequency and have flat phase-frequency characteristics in a wide neighbor band, which lays a good foundation for the precise design and application of a variety of wideband metasurfaces.

Energy-Efficient Optimization for RIS-Aided MIMO Covert Communications

In this work, a reconfigurable intelligent surface (RIS)-based multi-input multi-output (MIMO) covert communication system is considered and studied for Internet-of-Things (IoT) networks, while the joint optimization of precoder and RIS reflection phase is carried out to improve the covert communication performance. To solve this problem, we first derive the optimal signal-interference-to-noise ratio under covert communication and transmit power constraints. Then, we simplify the optimized function and use an iterative optimization algorithm to determine the optimal phase shift and precoding in continuous and discrete cases. Simulation results show that the RIS-aided MIMO covert communication system proposed in this paper can significantly improve the invisibility of the implementation from Willie. In addition, for covert communication, the performance of the continuous phase shift case outperforms that of the discrete phase shift and fixed phase.

Unveiling Local Optical Properties Using Nanoimaging Phase Mapping in High-Index Topological Insulator Bi2Se3 Resonant Nanostructures.

Topological insulators are materials characterized by an insulating bulk and high mobility topologically protected surface states, making them promising candidates for future optoelectronic and quantum devices. Although their electronic properties have been extensively studied, their mid-infrared (MIR) properties and prospective photonic capabilities have not been fully uncovered. Here, we use a combination of far-field and near-field nanoscale imaging and spectroscopy to study chemical vapor deposition-grown Bi2Se3 nanobeams (NBs). We extract the MIR optical constants of Bi2Se3, revealing refractive index values as high as n ∼ 6.4, and demonstrate that the NBs support Mie resonances across the MIR. Local near-field reflection phase mapping reveals domains of various phase shifts, providing information on the local optical properties of the NBs. We experimentally measure up to 2π phase-shift across the resonance, in excellent agreement with finite-difference time-domain simulations. This work highlights the potential of Bi2Se3 for quantum circuitry, nonlinear generation, high-Q metaphotonics, and photodetection.

Omnidirectional broadband phase modulation by total internal reflection.

Phase modulation plays a crucial role in shaping optical fields and physical optics. However, traditional phase modulation techniques are highly dependent on angles and wavelengths, limiting their applicability in smart optical systems. Here, we propose a first-principle theory for achieving constant phase modulation independent of incident angle and wavelength. By utilizing a hyperbolic metamaterial and engineering-specific optical parameters, different reflective phase jumps are achieved and tailored for both transverse electric (TE) and transverse magnetic (TM) waves. The aimed reflection phase difference between TE and TM waves can be thus achieved omnidirectionally and achromatically. As an example, we propose a perfect omnidirectional broadband reflection quarter wave plate. This work provides fundamental insights into manipulating optical phases through optical parameter engineering.

Three‐dimensional metal‐only phoenix cell and its application for reflectarrays

AbstractA 3D metal‐only waveguide‐based phoenix cell for reflectarray is presented. The proposed cell consists of two concentric square waveguides and a metallic block in the centre, which offers two operation modes. The first mode uses its cross section to tune reflection phase while the second mode varies the heights of two waveguides to manipulate reflection phase. The principle of the two different modes is analysed in detail. A metal‐only reflectarray antenna at 20 GHz is designed based on the first mode of the phoenix cell. It is fabricated using selective laser melting 3D printing technology. A good agreement between simulations and measurements is achieved. The measured gain at 19.75 GHz is 30.25 dBi with an aperture efficiency of 51.17% respectively. Also, the measured 1‐dB gain bandwidth is 15% (19–22 GHz). A dual band metal‐only reflectarray operating at 20 and 25 GHz is designed based on the second mode of the phoenix cell. The two metal‐only reflectarray antennas fully demonstrate the capabilities of the proposed 3D metal‐only phoenix cell.

Low scattering design of wideband tightly coupled conformal arrays based on scattering cancelation method

The scattering reduction of wideband and wide-scanning angle conformal array is urgently demand and still a significant challenge. Toward this end, a wideband low-profile cylindrically conformal tightly coupled antenna array (TCAA) with low-scattering characteristics is designed in this paper. Based on the scattering cancelation principle, the performance of wideband low-scattering is achieved by the fully use of two different types of tightly coupled antenna elements (TCAEs) arranged in a chessboard-like. The two types of array elements are carefully designed to have similar radiation performances and required reflection phases. Moreover, to accurately measure the scattering performance of the proposed conformal array, a low-scattering metal oliva carrier is designed to embed the RF testing cables and matching loads. Finally, a 10 × 10 conformal array prototype is developed, fabricated and tested. The simulated and measured results show that the proposed conformal array prototype works from 6 GHz to 18 GHz with a scanning range of ±60° in E-plane and ±45° in H-plane, while it also achieves about 13 dB monostatic scattering cross section (SCS) reduction across a wide frequency band of 6∼18 GHz as compared with a reference array.

What Do Medical Students Learn about Community Care from Discussions with General Physicians? A Thematic Analysis.

Background and Objectives: Sustainable healthcare is fundamentally rooted in community medicine education. The COVID-19 pandemic disrupted global advancement in integrating traditional teaching and experiential learning. Additionally, an alarming decline in interest in community care has been observed among senior medical students. Here, we examined the perspectives on community care obtained from conversations with general physicians in rural medical universities. Materials and Methods: Using a constructivist lens, a qualitative methodology was employed to examine the perceptions of second-year medical students from Shimane University Medical School regarding community care, informed by dialogues with general physicians. We conducted a thematic analysis at Shimane University, Japan, an area known for its aging population. In 2023, 116 second-year students participated, none of whom had prior formal training in community care. The study was structured into three phases: (1) Pre-education: Students wrote essays about their initial understanding of community care, its advantages, disadvantages, and potential improvements; (2) Dialogue: Grouped by topic, students engaged in discussions that culminated in a comprehensive session with general physicians; and (3) Reflection: After discussions, students wrote essays reflecting any shift in their views on community care. A thematic analysis of essays from the pre-education and reflection phases provided a comparative perspective on the students' understanding. Results: Five dominant themes emerged from the thematic analysis: (1) Re-evaluating community care: Recognizing diversity and addressing societal challenges; (2) Interdisciplinary collaboration: Promoting shared roles and teamwork; (3) Learning and practice: Emphasizing hands-on experience and self-reflection; (4) Technological influence: The mutual relationship between community care and technological advancements; and (5) Challenges and resolutions: Identifying problems and crafting solutions. Conclusions: This study sheds light on the evolution of medical students' views on community care and underscores the importance of continuous adaptation in medical education programs.

Multi-Functional Reconfigurable Intelligent Surfaces for Enhanced Sensing and Communication.

In this paper, we propose a reconfigurable intelligent surface (RIS) that can dynamically switch the transmission and reflection phase of incident electromagnetic waves in real time to realize the dual-beam or quad-beam and convert the polarization of the transmitted beam. Such surfaces can redirect a wireless signal at will to establish robust connectivity when the designated line-of-sight channel is disturbed, thereby enhancing the performance of wireless communication systems by creating an intelligent radio environment. When integrated with a sensing element, they are integral to performing joint detection and communication functions in future wireless sensor networks. In this work, we first analyze the scattering performance of a reconfigurable unit element and then design a RIS. The dynamic field scattering manipulation capability of the RIS is validated by full-wave electromagnetic simulations to realize six different functions. The scattering characteristics of the proposed unit element, which incorporates two p-i-n diodes have been substantiated through practical implementation. This involved the construction of a simple prototype and the subsequent examination of its scattering properties via the free-space measurement method. The obtained transmission and reflection coefficients from the measurements are in agreement with the anticipated outcomes from simulations.

The Death Café: Effectiveness of a hospice care educational program for nursing undergraduates based on LIFE experience—A qualitative study

BackgroundNursing students' knowledge of hospice care is limited to textbooks due to the inadequate education and training system in China and student's willingness to participate in hospice care. ObjectivesTo deepen nursing students' understandings toward life and death, to improve their knowledge about hospice care, and to promote their willingness for hospice care practice. DesignThis study used a qualitative descriptive study design. SettingsThe study was conducted at a medical university in Sichuan province, China. Participants71 nursing sophomores participated in this study. MethodsThe Death Café teaching program was implemented which requires students to recall their memories about death and to imagine how they felt about dying, as if they were having a conversation in a death-themed café. During the implementation phase, a small-group interactive teaching approach was utilized. During the reflection phase, the students were asked to finish an essay answering four questions without standard right answers. The essays that students finished were used for evaluating the effectiveness of the Death Café program. The answers of the first two questions were presented as a word cloud. Graneheim and Lundman's qualitative content analysis method was used to analyze answers of the third and fourth questions. ResultsWord cloud analysis indicated that at the beginning of the program participants showed more negative emotions (i.e., fearful). Students' attitudes toward death changed from negative to positive through imagining death when role-playing the different stages of life. The program enhanced students' understanding of life and taught the students effective ways to cope with death. Students clarified the objectives and necessary preparation for providing hospice care and gained new understandings for improving their hospice skills. ConclusionsThe Death Café program can address students' negative emotions and perceptions of death. Students gained personal benefits and professional benefits of coping with life and death from the program.

An ultra-wideband coding phase gradient metasurface for RCS reduction

ABSTRACTIn this work, an ultra-wideband coding phase gradient metasurface (CPGM) is proposed for radar cross section (RCS) reduction. The design process is presented in detail, in which eight types of coding elements are proposed firstly by using Pancharatnam-Berry (P-B) phase. The eight types of coding elements have different reflection direction or phase response under the same EM-wave incidence for they can introduce a series of phase gradients with different directions or starting-values under both right-handed and left-handed circular-polarized incidences, so the proposed CPGM composed of these coding elements has excellent performance in RCS reduction. The simulated results show that, compared with a pure metallic plate with the same size, the RCS of the CPGM can be reduced more than 10 dB in the ultra-wide frequency band of 9.2–46.2 GHz under normal incidence with arbitrary polarization, the relative bandwidth is up to 133.6%; moreover, the RCS reduction under oblique incidence with arbitrary polarization can still be kept larger than 9.3 dB in the frequency band of 13.1–42.5 GHz when the incident angle is increased to 45°. Finally, one experiment is carried out, a reasonable agreement exists between the simulated and experimental results.