Complex Reflection Research Articles

Carrier frequency phase calibration method for global navigation satellite systems signal simulators

Measurements of carrier frequency phase differences of global navigation satellite system signals between multiple antennas are used in many coordinate and navigation applications. Global navigation satellite systems signal simulators are used for controlling global navigation satellite systems receiver’s instrumental errors. Therefore, it is necessary to determine the systematic error of the carrier frequency phase of generated signals for signal simulators. For this purpose a new calibration method of global navigation satellite systems simulators was developed. Method is based on refined errors model of generated phase differences of two radio frequency channels of the simulator. The proposed method was implemented using a wideband oscilloscope as an analog-to-digital converter. Approbation of the calibration method was carried out by comparison with the measurement results obtained using the State secondary standard of units of complex transmission coefficients in the range of 0...–60 dB and complex reflection coefficients in the range of 0.002–1 in the frequency range of 0.05–65 GHz (registration No. 2.1.ZZT.0210.2015). The calibration method allows one to determine carrier frequencies phase offsets of navigation signals for global navigation satellite systems simulators with expanded uncertainty (with a coverage factor of 3) of 1°. The proposed method provides the required accuracy of generating phase differences of the carrier frequencies of global navigation satellite systems signals is ensured for modern types of global navigation satellite systems simulators.

UHead

The focus of Advanced driver-assistance systems (ADAS) is extending from the vehicle and road conditions to the driver because the driver's attention is critical to driving safety. Although existing sensor and camera based methods can monitor driver attention, they rely on specialised hardware and environmental conditions. In this paper, we aim to develop an effective and easy-to-use driver attention monitoring system based on UWB radar. We exploit the strong association between head motions and driver attention and propose UHead that infers driver attention by monitoring the direction and angle of the driver's head rotation. The core idea is to extract rotational time-frequency representation from reflected signals and to estimate head rotation angles from complex head reflections. To eliminate the dynamic noise generated by other body parts, UHead leverages the large magnitude and high velocity of head rotation to extract head motion information from the dynamically coupled information. UHead uses a bilinear joint time-frequency representation to avoid the loss of time and frequency resolution caused by windowing of traditional methods. We also design a head structure-based rotation angle estimation algorithm to accurately estimate the rotation angle from the time-varying rotation information of multiple reflection points in the head. Experimental results show that we achieve 12.96° median error of 3D head rotation angle estimation in real vehicle scenes.

Spectroscopic Evaluation of Epidermis‐Equivalent Phantom in Terahertz‐Frequency Region

AbstractThe complex refractive index and reflectance of an epidermis‐equivalent phantom were evaluated in the terahertz‐frequency region. The complex refractive indices of the epidermis and the epidermis‐equivalent phantom, made using ultrapure water, mineral oil, glycerin fatty acid ester, and agar, were measured using a terahertz time‐domain spectrometer. The complex refractive indices of the epidermis and the epidermis‐equivalent phantom were in agreement. However, their mean reflectances had a difference of approximately 3%. The difference disappeared on adding surface roughness to the epidermis‐equivalent phantom. Thus, we found that roughness of the surface of the epidermis‐equivalent phantom was required to ensure a match of the reflectance of the phantom with that of the epidermis at frequencies from 0.2 THz to 0.6 THz.

Automatic optimization of projection intensity for high dynamic range 3D surface measurement

Stripe projection profilers are widely used in many fields because of their high speed, high accuracy, and clear surface textures. In the structured light projection method, the complex reflectance distribution on the surface of the high-dynamic-range objective is an important factor that affects the measurement accuracy, as it can result in image over- and under-exposure. In this study, a method is proposed to adaptively determine the number of stripe patterns and the corresponding number of light intensities of the stripe patterns based on the complex reflectance of the surface of the object being measured. A multi threshold Otsu algorithm is used to classify the histogram of the surface reflectance distribution of the measured object, and several sets of stripe patterns with optimal light intensity are generated according to the light intensity response function. The original stripe patterns acquired at different light intensities are synthesized pixel by pixel into a high dynamic range (HDR) stripe image, and a four-step phase-shifting algorithm is used to obtain the unwrapped phase from the synthesized image. Experimental results show that this method can accurately measure the target of a surface-reflectance-transformed HDR.

MP-NeRF: More refined deblurred neural radiance field for 3D reconstruction of blurred images

Neural Radiance Fields (NeRF) has gained prominence in the domain of 3D reconstruction. Despite its popularity, NeRF algorithm typically require clear, static images to function effectively, leading to reduced performance when dealing with real-world scenarios that present non-ideal conditions such as complex reflections, low dynamic range, dark scenes and blurriness resulting from camera motion or defocus photography. The resilience of NeRF to such blurred inputs has not been sufficiently examined, presenting a gap in current research, which also tends to neglect the role of 3D scene context in image deblurring. Addressing these challenges, we introduce Multi-branch Fusion Network and Prior-based Learnable Weights NeRF (MP-NeRF), a novel approach engineered for the precise reconstruction of scenes from blurred images. MP-NeRF innovatively applies distinct priors for various blur types, thus better interpreting the blur formation mechanism. It integrates a Multi-branch Fusion Network (MBFNet) with a Prior-based Learnable Weights (PLW), which collectively enhance the capture of complex scene details, including textural and pattern information. Our experimental findings validate that MP-NeRF considerably enhances the visual accuracy of reconstructions achieved through NeRF, yielding substantial improvements in Peak Signal-to-Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM), and Learned Perceptual Image Patch Similarity (LPIPS) compared to state-of-the-art models. The source code for MP-NeRF is made available at the following URL: https://github.com/luckhui0505/MP-NeRF.

First-principles study on electronic, mechanical, and optical properties of pressure-induced vanadium-based perovskite KVO3

Vanadium-based compounds exhibit a variety of excellent characteristics due to their variable oxidation states. In this study, Density Functional Theory (DFT) is performed to investigate the structural, electronic, mechanical, and optical properties of KVO3 under high pressure. The thermodynamical and mechanical stabilities under high pressure are probed by the negative value of formation enthalpy and Born-mechanical stability criteria, respectively. KVO3 displays a nearly metallic nature in both pressurized and unpressurized systems owing to its remarkably narrow band gap. Furthermore, a positive pressure coefficient of the band gap is revealed from electronic properties. A lower effective mass value for charge carriers indicates KVO3's suitability for optoelectronic applications. The mechanical properties indicate that increasing pressure results in a slight increase in elastic constants, elastic moduli, hardness, and machinability index. Additionally, it has been disclosed that it is capable of enduring localized plastic deformation and fracturing under intense pressure in a prospective application. The calculations of the complex dielectric function, absorption, reflectivity, conductivity, refractive index, and loss function for KVO3 with and without pressure reveal a substantial behavior change. The absorption edge exhibits a significant blue shift with the applied pressure. The high peaks in the UV region suggest that it can be used in UV detectors and anti-reflection coatings. The refractive index shows promising application in waveguides.

A construction of the Shephard–Todd group $G_{32}$ through the Weyl group of type $\mathrm{E_6}$

It is well known that the quotient of the derived subgroup of the Shephard–Todd complex reflection group G_{32} (which has rank 4 ) by its center is isomorphic to the derived subgroup of the Weyl group of type \mathrm{E}_{6} . We show that this isomorphism can be realized through the second exterior power, and take the opportunity to propose an alternative construction of the group G_{32} .

Equivalence of v-decomposition matrices for blocks of Ariki-Koike algebras

We consider the representation theory of the Ariki-Koike algebra, a q-deformation of the group algebra of the complex reflection group Cr≀Sn. We examine blocks of the Ariki-Koike algebra. In particular, we prove a sufficient condition such that restriction of modules leads to a natural correspondence between the multipartitions of n whose Specht modules belong to a block B and those of n−δi(B) whose Specht modules belong to the block B′, obtained from B applying a Scopes' equivalence. This bijection gives us an equivalence for the v-decomposition numbers of the Ariki-Koike algebras.

Real-time simultaneous refractive index and thickness mapping of sub-cellular biology at the diffraction limit

Mapping the cellular refractive index (RI) is a central task for research involving the composition of microorganisms and the development of models providing automated medical screenings with accuracy beyond 95%. These models require significantly enhancing the state-of-the-art RI mapping capabilities to provide large amounts of accurate RI data at high throughput. Here, we present a machine-learning-based technique that obtains a biological specimen’s real-time RI and thickness maps from a single image acquired with a conventional color camera. This technology leverages a suitably engineered nanostructured membrane that stretches a biological analyte over its surface and absorbs transmitted light, generating complex reflection spectra from each sample point. The technique does not need pre-existing sample knowledge. It achieves 10−4 RI sensitivity and sub-nanometer thickness resolution on diffraction-limited spatial areas. We illustrate practical application by performing sub-cellular segmentation of HCT-116 colorectal cancer cells, obtaining complete three-dimensional reconstruction of the cellular regions with a characteristic length of 30 μm. These results can facilitate the development of real-time label-free technologies for biomedical studies on microscopic multicellular dynamics.

Physics-based supervised learning method for high dynamic range 3D measurement with high fidelity.

High dynamic range (HDR) 3D measurement is a meaningful but challenging problem. Recently, many deep-learning-based methods have been proposed for the HDR problem. However, due to learning redundant fringe intensity information, their networks are difficult to converge for data with complex surface reflectivity and various illumination conditions, resulting in non-robust performance. To address this problem, we propose a physics-based supervised learning method. By introducing the physical model for phase retrieval, we design a novel, to the best of our knowledge, sinusoidal-component-to-sinusoidal-component mapping paradigm. Consequently, the scale difference of fringe intensity in various illumination scenarios can be eliminated. Compared with conventional supervised-learning methods, our method can greatly promote the convergence of the network and the generalization ability, while compared with the recently proposed unsupervised-learning method, our method can recover complex surfaces with much more details. To better evaluate our method, we specially design the experiment by training the network merely using the metal objects and testing the performance using different diffuse sculptures, metal surfaces, and their hybrid scenes. Experiments for all the testing scenarios have high-quality phase recovery with an STD error of about 0.03 rad, which reveals the superior generalization ability for complex reflectivity and various illumination conditions. Furthermore, the zoom-in 3D plots of the sculpture verify its fidelity on recovering fine details.

Second-Order Approximate Reflection Coefficient of Thin Interbeds with Vertical Fractures

The horizontal fractures in the strata will close in the compaction effect of overlying strata, while the vertical cracks are widely developed, which can be equivalent to HTI (transverse isotropy with a horizontal axis of symmetry) medium. When an S-wave propagates into HTI media, the shear wave will divide into two types of waves: a fast S-wave and slow S-wave. When the strata of HTI are thin and overlapping, called the thin interbeds model, the wave field exhibits complex primary reflections, converted waves, and multiples. We introduce a new second-order approximation of the total reflection coefficient, with the incidence angle lower than the critical angle in thin-interbed HTI media using a recursive algorithm. We verify the effectiveness of the second-order approximation by analyzing the energy of multiples. Comparing the second-order approximate solution that degenerates the HTI medium into isotropic and Kennett’s exact solution, we find that our solution has an accuracy of over 99.9% in any azimuth, with the incidence angle lower than the critical angle under P-wave incidence. However, our solution of the SP wave field is suitable for incidence azimuth angles between 0–75° and 120–180°, with the lowest accuracy occurring at an incidence angle of 25° and a relative error of 6.4%. The approximate solution in the SS wave field has the same applicable range as the SP wave, with the maximum error of 6.3% occurring at the incident angle of 1°. This new second-order approximate formula for the total reflection coefficient of thin interbeds composed of HTI helps us to understand the reflection characteristics of complex thin interbeds. It also lays a theoretical foundation for the development of AVO (Amplitude Versus Offset) analysis and inversion techniques for lithological and stratigraphic oil and gas reservoirs.

Активація мовленнєвого розвитку в дітей переддошкільного віку

In the process of early development of all systems, language first of all suffers, because it is a reflection of complex, individual psychological processes occurring in the child's body, which depend on many factors. Corrective and speech therapy classes started in a timely manner eliminate the general lag in the child's development, since mental and emotional development are interconnected with communication. Therefore, experts strongly recommend not to wait for the child to speak independently, or to wait until the age of 4–5 years. Time can be lost, which can lead to concomitant problems, for example with the psyche. The relevance of the topic is related to the need to stimulate the development of speech activity of young children, which will ensure the correction of primary disorders of higher mental and motor functions and prevent the appearance of secondary deviations in the child's development. The purpose of the study is the formation of active speech in children aged 2.5–3 years whose language was characterized by poor vocabulary, insufficient understanding of adult language, and a decrease in communicative functions compared to peers. We investigated the level of speech development in 10 children aged 2.5–3 years whose speech development lagged behind the age norm. In our work, we used the method of speech development of children with general language underdevelopment of the third year of life, which is based on the following stages of research: determining the level of development of general motor skills, fine motor skills, active vocabulary, passive vocabulary and identifying the level of adult language understanding. The conducted research showed that all children have a delay in speech development, but it is expressed to different degrees in different children. No child showed a high level of speech development, four children are at an average level, and six are at a low level. After the application of corrective work on language development, a control study of the results of the work was conducted using the same methods that we used at the stage of diagnosing their speech development. The comparative analysis indicates that after the correctional and speech therapy work, there is not a single child with a low level of speech development, compared to six children before the work began. The speech development of the two children is almost completely in line with the age group and is rated as high. The other eight children improved significantly in all areas of speech and are rated as children with an average level of development.

Станция «Дистанция». Диспозитив производства знания в ранних российских художественных исследованиях

The article examines the specifics of Russian artistic research. First, with the help of historical analysis of the phenomenon in the international context, the essential characteristics of artistic research are deduced. They consist in the intertwining of ontology, epistemology and methodology of a work or a process, which is enacted through a problem beyond the issues of art. Art in this situation acts as an “epistemic thing” (Henk Borgdorff), a “theoretical object” (Hubert Damisch), or an enactive environment. This boundary, or the interdependent intertwining of the subject, method, and purpose of the work, manifests itself in different ways in the various apparatuses of knowledge production in art, varying from context to context, despite the globalization of the art scene of the twenty-first century. The Russian art of the late noughties and early tens was just approaching the use of the research paradigm. Its application is conditioned by a range of reasons, including the need to construct a work of art as a complex reflection on a socially acute topic, such as issues of national identity and historical amnesia. The art segment under consideration tried to avoid merging with the common media imagery, moving away from both the dominant rhetoric and its ironic interpretations by artist predecessors and fellow contemporaries, while bypassing straightforward activist strategies. The kind of knowledge such art dealt with was often non-knowledge, the ungraspable, the erased, and the camouflaged. This knowledge found its elusive manifestation in traces of absence, scattered authorship, failures, and other forms of distancing, yet sometimes revealing through such embodiments its own communicative limitations.

A Closer Look at the Reflection Formulation in Single Image Reflection Removal.

How to model the effect of reflection is crucial for single image reflection removal (SIRR) task. Modern SIRR methods usually simplify the reflection formulation with the assumption of linear combination of a transmission layer and a reflection layer. However, the large variations in image content and the real-world picture-taking conditions often result in far more complex reflection. In this paper, we introduce a new screen-blur combination based on two important factors, namely the intensity and the blurriness of reflection, to better characterize the reflection formulation in SIRR. Specifically, we present Screen-blur Reflection Networks (SRNet), which executes the screen-blur formulation in its network design and adapts to the complex reflection on real scenes. Technically, SRNet consists of three components: a blended image generator, a reflection estimator and a reflection removal module. The image generator exploits the screen-blur combination to synthesize the training blended images. The reflection estimator learns the reflection layer and a blur degree that measures the level of blurriness for reflection. The reflection removal module further uses the blended image, blur degree and reflection layer to filter out the transmission layer in a cascaded manner. Superior results on three different SIRR methods are reported when generating the training data on the principle of the screen-blur combination. Moreover, extensive experiments on six datasets quantitatively and qualitatively demonstrate the efficacy of SRNet over the state-of-the-art methods.

Dynamic 3D shape reconstruction under complex reflection and transmission conditions using multi-scale parallel single-pixel imaging

Dynamic 3D shape reconstruction under complex reflection and transmission conditions using multi-scale parallel single-pixel imaging

The Fragility of Democratic Voices in Philip Roth's Radio

Abstract: This article explores the multifaceted role of radio in Philip Roth's novels I Married a Communist (1998) and The Plot Against America (2004). Radio, as a pervasive medium of communication and influence during the mid-20th century, is the narrative mechanism that Roth employs to convey the idea of community as drawn together or taken apart by and through acts of listening. The emphasis on listening to the radio enables a complex reflection on democracy, which is depicted as both a tool of ideological dissemination and a symbol of public sentiment, open to both admiration and criticism in these novels. In this article, I propose reading I Married a Communist and The Plot Against America through their resonance of voices as a way to reflect on the transience of political discourses and the fragility of democracy. Through close textual analysis, I argue that Roth's scrutiny of the acoustics of society may be a counterhegemonic stance representing anti-democratic forces and authoritarian systems in a substantially and formally disruptive way. Ultimately, the hermeneutics of listening developed in this article reflects on the ethics of community-building and the stakes of democratic participation, which is key to understanding the political depth of these novels.

Novel Synthesis of Generalized Strongly Coupled Resonator Triplet Filters With Complex Reflection Zeros

Complex reflection zeros (CRZs) are introduced into generalized strongly coupled resonator triplet (GSCRT) filter synthesis for the first time to reliably eliminate negative couplings, thus facilitating physical implementation. CRZs bring more flexibility in synthesis and can be preassigned and regulated as needed to guarantee nonnegative couplings in different topologies and achieve varying electrical performance. Besides, CRZs bring the advantage of self-suppressed spikes, which can save extra band-stop modules in the system. To provide useful guidelines for designers, the selection of suitable CRZs is discussed in detail. With the introduced CRZs, the responses of GSCRT filters feature nonideal “in-between” performance, which shows a tradeoff between electrical performance and physical realization. Also, a comparison between the performance of GSCRT filters, extracted-zero, and path filters is given, which aims to help designers choose the most suitable configuration in practical use. Finally, the good measurement results of an anti-interference satellite filter have strongly validated the proposed theories.

A first-principles investigation on the structural, electronic and optical characteristics of tetragonal compounds XAgO (X = Li, Na, K, Rb)

First-principles calculations employing the density functional theory full-potential (linearized) augmented plane-wave plus local orbitals (FP-(L)/APW + lo) method were conducted to investigate the structural, electronic and optical characteristics of silver-based ternary oxides XAgO (X = Li, Na, K, and Rb). The GGA-PBEsol and TB-mBJ functionals were employed to describe the exchange-correlation potential. The optimized lattice parameters and atomic positions obtained from the calculations exhibit good agreement with both theoretical predictions and experimental measurements. Various exchange-correlation functionals were employed to evaluate the electronic properties, revealing that the newly developed Tran–Blaha modified Becke–Johnson functional yields a significant improvement in the band gap value. All XAgO compounds under consideration are categorized as semiconductor materials where the band gap value decreases as the atomic size of the X element increases. The study also explored the total and site-projected l-decomposed densities of states. Additionally, the complex dielectric function, refractive index, extinction coefficient, reflectivity, and loss function spectra were calculated for the incident radiation polarized parallel to both the [100] and [001] crystalline directions. The interband transitions that contribute effectively to the observed peaks in the imaginary part of the dielectric function were identified.

The Ethics of World‐Building in Normative Case Studies

AbstractNormative case studies are designed to offer richly detailed “worlds of possibility” that invite complex reflection and discussion about authentic ethical dilemmas in education. In this essay, Tatiana Geron and Meira Levinson argue that authors' choices of what details to include in a case are themselves ethical decisions that require significant ethical responsibility. Case details can shape which avenues of ethical inquiry are open to readers, whether and how institutional and structural conditions get considered, whose perspectives are included and legitimized, and what political issues are understood as “open” or “closed.” At its best, case “world‐building” can help readers understand the full complexity of ethical decision‐making in education. However, for this to occur, case authors must seek out expert and dissenting perspectives, field test the case with diverse audiences, and remain reflexive about their own perspectives and how these shape their world‐building decisions.

An inversion statistic on the generalized symmetric groups

In this paper, we construct a mixed-base number system over the generalized symmetric group G(m,1,n), which is a complex reflection group with a root system of type Bn(m). We also establish one-to-one correspondence between all positive integers in the set {1,⋯,mnn!} and the elements of G(m,1,n) by constructing the subexceedant function in relation to this group. In addition, we provide a new enumeration system for G(m,1,n) by defining the inversion statistic on G(m,1,n). Finally, we prove that the flag-major index is equi-distributed with this inversion statistic on G(m,1,n). Therefore, the flag-major index is a Mahonian statistic on G(m,1,n) with respect to the length function L.