Complex Reflection Research Articles

Dynamic monitoring of saturation profiles during two phase immiscible displacements in confined sand packs using time-domain analysis of the frequency domain electromagnetic sweeps

Water saturation 1D spatial profiles were monitored using real-time domain analysis of the measured frequency domain complex reflection coefficients of electromagnetic sweeps during oil and deionized water flood experiments at ambient conditions. Gravity and viscous induced fingering and piston-like displacement scenarios were explored. A patented coaxial transmission line core holder was designed to host saturated sand packs compressed in their axial and radial dimensions. An inverse chirp z-transform algorithm was used to convert the measured responses from frequency to time domain. An optimization routine was developed to convert the resulting time domain step responses to water saturation profiles at every pore volume fraction of fluids injected. Advancing and trailing fronts and their breakthrough times were detected. Darcy's flow analysis was performed to extract 1D pressure distribution spatial profiles and dynamic capillary pressure curves for 3 drainage floods. The oil ganglia flow and gravity fluid separation were detected in water floods.

Analyzing scenarios and designing initiatives toward just transitions: coproducing knowledge with(in) the dried fish sector in the Indian Sundarbans

The south-western fringe of the Indian Sundarbans hosts a number of fish drying collectives that are exposed to a bundle of mutually reinforcing social-ecological-institutional risks. Despite its wide contribution to local-regional food security and livelihoods, dried fish production has received little attention in research and policy circles so far. As part of the Social Sciences and Humanities Research Council (SSHRC) sponsored Dried Fish Matters global partnership project, our research team seeks to address this lack in two ways: (i) delineating knowledge base through a systematic literature review on intersecting social-ecological and sociohydrological dimensions of integrated fisheries and fish drying practices, and (ii) employing a knowledge co-production approach that involves participation of dry-fishers, researchers, fishworkers' forum (partner organization), and scientists for meaningful understandings about the constraints and potentials in the sector. In this essay, we applied a three-step methodology to arrive at a crisscrossing conceptual, empirical, and collective understandings on the 'invisible' dried fish value chain in the Indian Sundarbans. With detailed lessons from the field, our interdisciplinary research team acts as a liaison among the groups to build a collaborative space for interactions, recognize prevalent adaptive practices and identify pathways toward short-, intermediate-, and long-term co-interventions through which fish drying practices can be more effectively improvised upon and up scaled. The essay lays out detailed insights and sensible recommendations from the knowledge co-production workshop, organized as a part of solution-focused participatory research on climate-resilient and gender-aware dried fish practices in the Indian Sundarbans. In light of the collective observations on the complex problems and reflections on needs-driven initiatives, the authors advocate for collaborative research praxes in forging just transitions for the less explored dried fish sector.

Constructing imaginary classrooms: Teacher educators’ use of representations to direct reflection about practice

This comparative case study examines the pedagogy of six teacher educators at three institutions in the United States to ask how instructors at practice-based, progressive, and non-university-based education schools presented examples of teaching. Findings show that practice was widespread, diverse, and under the control of teacher educators. Although institutions were selected for professed pedagogical differences, each educator frequently utilized representations of practice. The differences lay in how they used these tools, as some educators prompted complex reflection, while others advocated best practices. The differences in teacher educator pedagogy encourage further study of teacher education's fine-grained conduct and consequences.

AN ETHICS CRISIS IN VIRTUAL MEDIA SPACE

This paper will address basic ethical issues in virtual space determined by global multidirectional networking through different space and time. Numerous ethical issues will be stressed which, as a result of the complex reflections of ubiquitous media convergence, determine each individual topic, from issues of personal data protection and information security, to strengthening credibility and building trust in the virtual community. In relation to the objectives and established development guidelines, different ethical dimensions, in their complexity and multi-layeredness in a digitally empowered future, should not be viewed in isolation but exclusively through their complementarity and a quality foundation for further in-depth research.

SHAPE RECONSTRUCTION OF HERITAGE ASSETS BY POLARIZATION INFORMATION

Abstract. Three-dimensional modeling of heritage assets poses a challenge when high reflectance and featureless surfaces are involved. Because of the complex reflection characteristics, traditional methods, either passive or active, tend to generate noisy and incomplete reconstruction results. To address this, we introduce in this paper a shape-from-polarization system and modeling strategy for the 3-D reconstruction of heritage assets. As demonstrated, by analyzing polarization properties of reflected light, we can generate by a single image pixel-level-resolution normal and depth maps. We consider two system prototypes involving a point light source but different in the polarizing camera configurations. They provide solutions for different reconstruction requirements and acquisition conditions. Our reconstruction model is common however to both involving a closed set of simple computation steps. Our evaluations demonstrate how the proposed method significantly improves the 3-D surface model completeness and level of detail, showing its suitability and value to reach the goal of a high-resolution survey of heritage assets, where traditional approaches tend to fail.

Real-time ultrasound phase imaging

The Correlation-Based (CB) imaging method is characterized by its high spatial resolution capabilities, but it is known to require heavy computational resources due to its high complexity. This paper shows that the CB imaging method can be used to estimate the phase of the complex reflection coefficients contained in the observation window. The resulting Correlation-Based Phase Imaging (CBPI) method can be used to segment and identify different features or tissue elasticity variations in a given medium. A Numerical validation is first proposed by considering a set of fifteen point-like scatterers on a Verasonics Simulator. Then, three experimental datasets are used to show the potential of CBPI on scatterers and specular reflectors. In vitro imaging results are first presented to show that CBPI allows retrieving phase information on hyperechoic reflectors, but also on weak reflectors such as elasticity targets. It is demonstrated that CBPI helps distinguishing regions of different elasticity, but of same low-contrast echogenicity, which is otherwise impossible with standard B-mode or Synthetic Aperture Focusing Techniques (SAFT). Then, CBPI of a needle in an ex vivo chicken breast is performed to show that the method works on specular reflectors. It is shown that the phase of the different interfaces associated to the first wall of the needle are well reconstructed using CBPI. The heterogeneous architecture used to enable real-time CBPI is presented. A Nvidia GeForce RTX 2080 Ti Graphics Processing Unit (GPU) is used to process the real-time acquired signals from a Verasonics Vantage 128 research echograph. Frame rates of 18 frames per second are achieved for the whole acquisition and signal processing chain on standard a 500 × 200 pixels grid.

Investigating electronic and optical properties of pyrochlore oxides Ta2A2O7 (A = Cd and Ge) for promising optoelectronic applications

Due to their stable crystal structure and controllable lattice parameters, rare earth zirconates with pyrochlore type structures have demonstrated a promise for usage in practical applications. We have investigated the electronic and optical properties of pyrochlore oxide compound named Ta2A2O7 (A = Cd and Ge) using density functional theory based on spin–orbit coupling and Hubbard (SOC + U) corrections to consider the existence electronic d orbitals of (A) and f elements (Ta). This study focuses on the characterization and investigation of pyrochlore oxides with the A2B2O7 composition, which have significant technological applications including quantum spin ices, solid oxide fuel cells, and nuclear waste forms. No evidence regarding magnetic moment is obtained from the first run with spin-polarization setup. Also, from the spectra of TDOS was showing a similar overall profile for both spin channels. The electronic properties (total and partial) densities of states as well as the optical properties such as the complex dielectric function, refractive index, absorption coefficient and reflectivity for wavelengths in the visible spectrum have been reported to explore the potential use of these compounds in technological applications. Consequently, the investigated compounds can be used in optoelectronic device fabrication.

Centralisers, complex reflection groups and actions in the Weyl group E_6

The compact, connected Lie group E_6 admits two forms: simply connected and adjoint type. As we previously established, the Baum–Connes isomorphism relates the two Langlands dual forms, giving a duality between the equivariant K-theory of the Weyl group acting on the corresponding maximal tori. Our study of the A_n case showed that this duality persists at the level of homotopy, not just homology. In this paper we compute the extended quotients of maximal tori for the two forms of E_6, showing that the homotopy equivalences of sectors established in the A_n case also exist here, leading to a conjecture that the homotopy equivalences always exist for Langlands dual pairs. In computing these sectors we show that centralisers in the E_6 Weyl group decompose as direct products of reflection groups, generalising Springer’s results for regular elements, and we develop a pairing between the component groups of fixed sets generalising Reeder’s results. As a further application we compute the K-theory of the reduced Iwahori-spherical C^*-algebra of the p-adic group E_6, which may be of adjoint type or simply connected.

“Sweet Spot” for Reflection in Problem-oriented Education

This paper examines the impact of a structured, multi-dimensional reflection track of a 16-week pilot programme in experimental pedagogics (XP) in The Netherlands. XP is an elective undergraduate programme in which students investigate socially relevant educational problems in local communities and design educational interventions to address these issues through problem-oriented project work (PPL). To accompany the learning journey, students follow a reflection track structured with workshops, learning diaries, and articulated learning essays, that covers cognitive, phenomenological, relational, social and global dimensions of reflection. The design of the track was informed by an interdisciplinary reflection framework combining inputs from cognitive and critical paradigms. To evaluate and improve the impact of this novel approach to reflection in problem-oriented education, the authors undertook an Education Action Research (EAR) process with the 17 participating students. The evaluation phase of the EAR was conducted using a phenomenographic design to draw out qualitative variations in conceptions of reflection among students who participated in the pilot. Focusing on variations of conceptions allowed the teachers-as-action-researchers to gain a fine-grained understanding of reflection within the XP problem-oriented setting. The findings reveal an outcome space comprising seven increasingly complex reflection categories. A phenomenographic analysis of the categories led us to conclude that there exists a reflection “sweet spot” inside which there is growth in reflection breadth and depth. Outside the sweet spot, students either do not reflect at all, or become so entangled in reflection that an infinite reflection regress appears to derail learning. We conclude by discussing the contributions of these findings to strengthening critical, socially relevant reflection in problem-oriented project work in the context of current global crises, focusing on the role of supervisors in fostering productive reflection.

Ultra-fast 3D imaging by a big codewords space division multiplexing binary coding.

Patternless binary coding strategies have been a challenge for ultra-fast 3D imaging with structured light. This Letter proposes a big codewords space division multiplexing binary coding method. From the third to the multiple order, a special spatial binary coding instead of the Gray code is created for the first time, to the best of our knowledge, to achieve an ultra-wide unambiguous range with only one auxiliary pattern. Advantageously, a connection domain segmentation technique with anomaly detection is proposed to achieve decoding of the fringe order, which cleverly avoids the misalignment problem. Additionally, a center of gravity method is applied to compensate for the codewords of the residual connected domain. The robustness and effectiveness of the proposed method for complex, isolated, and non-uniform reflectivity objects, as well as the ultra-fast 3D imaging of dynamic measurements, are experimentally verified.

Investigation of optoelectronic & thermoelectric features of ZnCrX2 (X = S Se Te) chalcopyrite semiconductor using mBJ potential

In the present investigation, we have examined the structural, optoelectronic and thermoelectric properties of the compound ZnCrX2 (X = S, Se, Te) using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA-PBEsol) and the modified Becke–Johnson (mBJ) implemented on Wien2k code. By calculating the electronic structure, we observed that the indirect band gap was 1.76 eV, 1.68 eV, and 1.59 eV, for these selected compounds and the type of chemical bonding was ionic between Zn-X and Cr-X. For the three ternary chalcopyrites their optical properties including optical conductivity, complex dielectric functions, complex refractive index, reflectivity, energy loss, and absorption coefficient were examined. The calculated optical conductivity indicates that the studied compounds are suitable for optoelectronic applications as they have good absorbance and less energy loss in the low energy range of the electromagnetic spectrum. For ZnCrTe2, the maximum reflectivity was in the low energy range (0.48 or 48% at 9 eV). The BoltzTrap code was executed for the calculation of the thermoelectric properties and thermal efficiency of the compounds investigated, depending upon the Seebeck coefficient, thermal conductivity and electrical conductivity. The high value of the figure of merit and the Seebeck coefficient (260 uV/k) defines the high efficiency of the materials studied. Hence, the studied chalcopyrite compounds offer applications in solar cell devices and p-type semiconducting nature predictive in transport investigations.

HUDNet: A dynamic calibration method for automotive augmented reality head-up-displays

The automotive augmented reality head-up-display (AR-HUD) system relies on multiple free-form surfaces to project the virtual image into human eyes. A wide range of views and the extensive display area result in extraordinarily complex distortions. Providing a way to correct such distortions is a major leap forward. Methods widely used for calibration, such as lookup tables and interpolation, require considerable memory capacity, complicated calibration procedures, etc. Additionally, when attempting to meet the high-accuracy requirements for such systems, computational memory grow rapidly. In this context, we propose a fully connected neural network (HUDNet) for an automotive AR-HUD to correct dynamic distortion. Here, we propose a parallel prediction framework for the center and the edge of the image, and separate the distortion information from the disparity information in order to balance the unstable central field of view error. Ultimately, we introduce the transfer learning method to improve accuracy and its effect on accuracy is assessed. The present study provides a reference for us to apply deep learning methods to predict dynamic image distortion of various complex multi-freeform surface reflection systems in the future.

Больше, чем консерватизм: историко-политические основания российской государственности

The paper is dedicated to the problem of updating existing ideas about the historical and political foundations of Russian statehood. The main goal of the paper is to update the existing academic discourse, aimed at complex and systematic reflection of Russian political thought, and the presentation of an unorthodox reading of the intellectual and philosophical foundation of Russian politics. Regardless contemporary focus on conservative political philosophy is the most common for such studies, the author believes it is necessary to go beyond this position and turn to a more systematic and comprehensive understanding of the key positions of the Russian worldview. For this, it is necessary to turn to the underestimated, sometimes even ignored concepts of communitarianism, solidarism and Russian cosmism, which should be revealed within the framework of a civilizational approach. The main conclusion of the work is that, considered as a developing system, these concepts embody the value constants of community, sobornost’ (catholicity), harmony and solidarity that are significant for Russian civilization, and also emphasize the global rootedness of the Russian worldview with simultaneous original understanding and interpreting the ideological guidelines of the leading trends in social political thought. The author believes it is extremely important to take into account these circumstances dealing with current public opinion and the process of reforming the scientific and educational sector that has begun in Russia. It also emphasizes the need to optimize methodological work during the study of political thought - through the awareness of the indoctrination of contemporary social sciences and their conceptual apparatus, clear understanding the natural dynamics of civilizational development and the impossibility of dogmatically reducing multiform and multinational cultures to a simplified formal doctrine.

Kompleksowość procesu prawotwórczego

Kompleksowość procesu prawotwórczego

Elastic, electronic, optical and thermoelectric properties of Ca5Si2N6 and Sr5Ge2N6 ternary nitrides

In order to expand the scope of application of ternary nitrides and explore more thoroughly their potential as novel materials, ab initio calculations founded on density functional theory are executed to examine the mechanical, electronic, optical and transport properties of Ca5Si2N6 and Sr5Ge2N6 nitrides. These compounds are thermodynamically stable established on coherent energy and enthalpy of formation, with Ca5Si2N6 having the best stability. The estimated values of elastic constants and their derived properties suggest that the items under examination are mechanically stable, ductile and elastically anisotropic. Electronic properties have been evaluated using the GGA and TB-mBJ exchange-correlation potentials. The band structure calculated via TB-mBJ reveals that these nitrides are semiconductors, where Ca5Si2N6 has a direct energy gap of 3.55 eV and Sr5Ge2N6 an indirect band-gap of 3.15 eV. By combining Debye temperature and band-gap values, it was concluded that the nitridosilicate compound can be used as phosphor material. According to the optical response, which was examined in terms of dielectric function, complex refractive index, absorption, reflectivity and energy damage function, the potential applications of Ca5Si2N6 and Sr5Ge2N6 have been discussed. Further, thermoelectric properties are computed utilizing the semi-classical Boltzmann transport notion. The obtained results show a large strength operator and depressed thermal conductivity driving to rising figure of merit values, particularly at 300 K (0.978–0.986), signifying that the studied ternary nitrides are favorable nominees for thermoelectric employments at both low and room temperatures.

The Peripheral Culture Museum and its articulations: perspectives of an organic intellectual about Brazilian Sociomuseology

Viviane Conceição Rodrigues is an important Brazilian organic intellectual. Born in 1982 on the outskirts of Maceió, it became part of a series of networked cultural articulations and was fundamental element in the founding of the Peripheral Culture Museum, one of the 12 Memory Spots Pioneers, headquartered in the Jacintinho neighborhood. An award-winning Afro-entrepreneur, she has a degree in Public Relations from the Federal University of Alagoas (UFAL, 2008) and Master from the Universidad Pablo de Olavid (2020), in Spain. His personal trajectory mixes with the trajectory of Brazilian comunity museums, spreading out in territories far beyond the geographic, having participated in the constitution of a set of public policies for the field of Museology in Brazil. In an interview granted to us, generous, affectionate and patient, shared fundamental aspects for thinking Sociomuseology through the hands of those who live on the border between academia and social militancy, in a constant flux between putting into practice in favor of the community the most complex popular and scientific reflections in a way connected.

An analogue of Aldous’s theorem on mixing times of a random walk for complex reflection groups

The subject of this paper is the mixing time of random walks on minimal Cayley graphs of complex reflection groups G(m,1,n). The key role in estimating it is played by the coupling of distributions, which has been used before for the same task on symmetric groups. The difficulty with its adaptation for the current case is that there are now two components in a walk, which are to be coupled, and they influence each other’s behaviour. To solve this problem, random walks are split into several blocks for each of which the time needed for their states to match is estimated separately. The result is upper and lower bounds on mixing times of random walks on complex reflection groups, analogous to those obtained by Aldous for a symmetric group.

Prototype of a sensor for measuring moisture of a single rapeseed (Brassica napus L.) using microwave reflectometry

Rapeseed moisture content is one of the key physicochemical parameters of the seeds, because of its importance for ensuring optimal conditions for seed storage, as well as for determining the time of harvesting. There are many devices available on the market for measuring rapeseed moisture content. Measurement techniques usually use a large sample of seeds (in the case of capacitance meters e.g., 100 g). Therefore, the obtained result is an average value representative for the tested sample, but does not give the range of moisture of single seeds in a given batch of material. The paper presents a prototype of a sensor and a method of measuring moisture content of individual rapeseeds. The system utilizes multiple measurements of a complex reflection coefficient that correspond to different positions and orientations of a seed under test along the sensor. As a result, the impact of non-uniform shape and inner heterogeneity of the seeds on the measurement results is limited. A novel robust algorithm for moisture determination is proposed, which does not need any calibration of the microwave measurement circuitry realized as a six-port reflectometer operating at 2.4 GHz.

Strain tuning of the electronic structure and optical properties of novel Janus MgBrI monolayer: Insights from first-principles calculations

Using first-principles calculations in the framework of density functional theory (DFT), we systematically carry out the dynamic stability, electronic and optical properties of the Janus MgBrI monolayer and its parent MgI2 and MgBr2 monolayers. Our findings show that these systems have no imaginary frequencies in the entire Brillouin zone (BZ), which means they are very stable. At the equilibrium state, the results indicate that the Janus MgBrI monolayer is a direct band gap insulator with an energy gap of 3.475 eV, which is smaller than the bandgap of MgI2 and MgBr2 monolayers. The studied optical properties including the complex dielectric function, refractive index, reflectivity, extinction coefficient and absorption coefficient as a function of the photon energy have been investigated. The absorption coefficient shows a strong absorption of the light in the ultraviolet (UV) region. We studied how biaxial strain effects the electronic and optical properties of the Janus MgBrI monolayer. When the strain ranged from −10% to 10%, the Janus MgBrI monolayer showed an insulator characteristic with a direct band gap, which changed to an indirect band gap when the biaxial compressive strain was −10%. In addition, the Janus MgBrI displays an absorption of around 105 cm−1 in the ultra-violet (UV) region. Our results highlight an intriguing new two-dimensional (2D) material that could be used in optoelectronic devices and UV absorbers.

“My country, my enemy”: representing and questioning American politics through radical activism in

In the novel The Darling, published by Russell Banks in 2004, a young American woman, Hannah Musgrave, decides to rebel against her bourgeois upbringing in the 1960s by embracing the radicalism of the Weather Underground. After being accused of terrorism, she has to live under a fake name and she eventually flees the United States to settle in Liberia. This article aims at studying the ways in which Banks draws on his fictional character’s personal experience to question the impact of revolutionary ideals on American society. The protagonist’s multiple identities, which reflect the political upheavals and the inner conflicts of her country, as well as the constant blurring of the boundaries between reality and fiction enable Banks to offer a complex reflection on the building and the staging of American political history in the second half of the twentieth century.