Specific Angle Research Articles

Collective properties of Petitella georgiae in tube environments

The movement of biological swarms is widespread in nature, and collective behavior enhances a swarm’s adaptability to its environment. However, most research focuses on free swarm movement, overlooking the impact of environmental constraints such as tubes. This study examines the swimming behavior of Petitella georgiae through a tube. Observations of position, speed, and direction reveal that each fish is influenced by the swarm’s distribution in its field of view. The speed ratio between the middle region and edge region positively correlates with tube angles, and higher speeds are associated with higher densities within specific angle ranges.

Evolution and Significance of Sine Function in Ancient Indian Mathematics

This research article delves into the historical and mathematical intricacies of the construction of sine functions, particularly focusing on ancient Indian mathematical concepts and their evolution. It begins by highlighting the significance of sine (jya) as a fundamental trigonometric function in Indian mathematics, alongside its synonyms in Sanskrit. The historical journey of the term “sine” is traced back to ancient Indian mathematical texts, which were later translated into Arabic and then into Latin, ultimately leading to the adoption of the term “sine” in modern mathematics. The article elaborates on the definitions and interpretations of sine (ज्या), cosine (कोटिज्या), versed sine (उत्क्रमज्या), and co-versed sine (कोट्युत्क्रमज्या) in Indian mathematical traditions. It explains how these functions were conceptualized and utilized in astronomical calculations, emphasizing their geometric and trigonometric significance. Furthermore, the article discusses the division of a circle into quadrants (Vṛttapādas) and the concept of Trijyā (radius), highlighting the mathematical sophistication and terminology used by ancient Indian mathematicians. Several mathematical formulas related to the construction and calculation of sine functions are presented, including formulas for finding sine values at specific angles such as 45 degrees, 18 degrees and 72 degrees. These formulas showcase the mathematical ingenuity and problem-solving skills of ancient Indian mathematicians. Overall, this research article provides a comprehensive overview of the historical development and mathematical foundations of sine functions in ancient Indian mathematics, shedding light on their enduring legacy and contributions to modern trigonometry.

Fano Resonance-Associated Plasmonic Circular Dichroism in a Multiple-Dipole Interaction Born–Kuhn Model

Plasmon chirality has garnered significant interest in sensing application due to its strong electromagnetic field localization and highly tunable optical properties. Understanding the effects of mode coupling in chiral structures on chiral optical activity is particularly important for advancing this field. In this work, we numerically investigate the circular dichroism (CD) of elliptical nanodisk dimers arranged in an up-and-down configuration with a specific rotation angle. By adjusting the inter-particle distance and geometric parameters, we introduce the coupling between dipole and electric hexapole modes, forming an extended Born–Kuhn model that achieves strong CD. Our findings show that the coupling of dipole modes with electric hexapole modes in elliptical nanodisks can also show obvious Fano resonance and a strong CD effect, and the structure with the largest Fano asymmetry factor shows the highest CD. In addition, CD spectroscopy is highly sensitive to changes in the refractive index of the surrounding medium, especially in the visible and near-infrared regions, highlighting its potential for application in high-sensitivity refractive index sensors.

A systematic and optimal design method for replacing steel backrest in automotive seat with carbon fiber-reinforced polymer composites

Carbon fiber-reinforced polymer composites (CFRPC) are extensively utilized in the lightweight design of automobiles due to their superior material properties. This study focuses on the automotive seat backrest as the subject of research. To address the challenge of achieving both lightweight and performance optimization in CFRPC, subsequent to replacing the steel backrest in automotive seat, a systematic optimization design method is proposed. Firstly, the experimentally validated finite element analysis model of a steel seat, subjected to four typical working conditions, is redesigned for the CFRPC backrest in automotive seat. Building upon this foundation, the optimization design of the CFRPC backrest is segmented into two phases: optimization of layup size and optimization of layup sequence. During the optimization of layup size, a sophisticated optimization strategy is employed. This strategy combines many-objective optimization and multi-criteria decision-making. It integrates the modified extensible lattice sequence experimental design, the hybrid surrogate model utilizes the global response search method in conjunction with weighted prediction error lowering, the non-dominated sorting genetic algorithm-III, the improved double combination weighting model of game theory, and the improved VIsekriterijumsko KOmpromisno Rangiranje method, which incorporates Euclidean distance and gray relational analysis (IVIKOR-ED&GRA). This approach is utilized to ascertain the optimal count and thickness of the number of layers required for each specific angle. The simulation results demonstrate that the optimized CFRPC backrest, featuring refined layup dimensions, not only fulfills regulatory requirements but also enhances a majority of performance metrics, accompanied by a substantial weight reduction of 38.66%. Ultimately, the OptiStruct optimization technique of layup sequence is employed to further enhance the performance of the CFRPC backrest seat. This is achieved by modifying the layup stacking sequence, while maintaining the original material’s weight and the number of layups for each angle unchanged.

Dual-Phase Singularity at a Single Incident Angle with Spectral Tunability in Tamm Cavities.

The phase singularity, a sudden phase change occurring at the reflection zero is widely explored using various nanophotonic systems such as metamaterials and thin film cavities. Typically, these systems exhibit a single reflection zero with a phase singularity at a specific incident angle, particularly at larger angles of incidence (>50 degrees). However, achieving multiple phase singularities at a single incident angle remains a formidable challenge. Here, the existence of a dual-phase singularity is experimentally demonstrated at a lower incident angle using a tunable Tamm plasmon polariton (TPP) cavity that consists of gold-coated ultralow-loss phase change material Sb2S3-based distributed Bragg reflector. It can excite narrowband TPP resonances from normal incidence to a wide angle of incidence for both s- and p-polarizations of light. Notably, this TPP cavity shows dual-phase singularity at lower angles of incidence since the excited TPP for s- and p-polarizations exhibits zero reflection at slightly different wavelengths for the same incident angle. A TPP cavity-based scalable hydrogen sensor is proposed and shows that the dual-phase singularity can further improve the sensitivity of singular phase-based sensing approaches. Moreover, spectrally tunable dual-phase singularity is experimentally demonstrated at a lower incident angle using a metal-free Tamm cavity.

Optimal angles for independent femoral tunnel drillings to prevent damage to anatomic structures in single-bundle anterior cruciate ligament reconstruction

PurposeTo determine the optimal angles for independent femoral tunnel drillings in single-bundle anterior cruciate ligament reconstruction (ACLR) in different races and genders with the aim of preventing damage to lateral femoral anatomic structures (LFAS), posterior cortex and medial femoral condyle.MethodsThis study included 180 volunteers, including 90 Caucasian and 90 matched Chinese. Magnetic resonance imaging (MRI) was used to scan the knees to create three-dimensional bone models, the ACL femoral footprint centre and the LFAS. In each femur model, femoral tunnels were established using a set of 16 distinct angular combinations: 15°, 30°, 45°, and 60° in the axial plane, as well as 15°, 30°, 45°, and 60° in the coronal plane. The minimum distance from the tunnel exit to the LFAS was evaluated, and the tunnel length, posterior cortex damage and medial femoral condyle injury were assessed.ResultsAmong the 180 patients with simulated ACL femoral tunnels, there was damage to the anatomical structure in parts of the model. According to the Cochran Q test results (P < 0.001), the percentage of safe tunnels varied significantly among the 16 different drilling angle combinations. The overall occurrence of the tunnel exit causing injury to LFAS were 8.3% and 8.1% in Chinese and Caucasian groups (P = 0.786). The means for tunnel length in Caucasians was 40.1 ± 7.9 mm, respectively; for Chinese, the results was 38.8 ± 6.6 mm (P < 0.001). Females had significantly shorter femoral tunnels than males in both Chinese and Caucasian (P < 0.001). The overall invasion rate of the posterior cortex and medial femoral condyle were 32.6% and 7.4% for Chinese; 31.0% and 7.4% for Caucasians, respectively.ConclusionTo reduce risks of injury to anatomical structures, such as the LFAS, posterior cortex and medial femoral condyle, specific angle combinations of 30°/45°, 45°/30°, 45°/45°, 45°/60°, 60°/30°, 60°/45° and 60°/60° should be used when creating the femoral tunnel in single-bundle ACLR. The selected drilling angles are critical for optimizing femoral tunnel placement.

Research on the Dynamic Spreading and Wettability Characteristics of Droplets on Coal Dust.

The dynamics of droplets spreading on surfaces have been extensively studied across various influencing factors, necessitating an exploration of their effect on wettability. Herein, the specific composition, size distribution, and contact angle of the coal dust preparation were characterized by a series of experiments to determine the conditions for the simulation. Meanwhile, the multiphase volume of the fluid method was implemented in the simulations, predicated on appropriate boundary conditions, and verified by a mesh independence test. The findings confirmed that the numerical approach for contact angle validation had a minor deviation, making it suitable for multiphase interface tracking. Besides, the typical wetting pattern of droplets was hereby identified into three stages, including the moving stage (stage I), the periodic wetting stage (stage II), and the balancing stage (stage III). The initial diameter could effectively increase the coverage area and spreading time for stage II. Obviously, the first amplitude of first maximum spreading diameter (D max-1) significantly increased with higher impact velocities, corresponding to an increase in kinetic energy. Despite the significant spreading effect of the falling height mainly on D max-1 and contact time, the increased trend of wetting efficiency was not obvious. However, the spreading factor and wetting efficiency decreased with increased roughness height. Finally, the difference in spreading wettability was illustrated based on the spreading wetting mechanism. The wetting efficiency of droplets on coal dust was remarkably influenced by the dynamic spreading behaviors of droplets. Overall, the findings from this study offer insights into the extent of spreading wetting that occurs before a droplet reaches an equilibrium state.

Optimizing Circular MIMO Array Imaging Using Partial Equivalent Method for Sidelobe Suppression

In this paper, we propose a novel approach for circular Multiple-Input Multiple-Output (MIMO) array imaging, termed the Partial Equivalent Method (PEM), aimed at sidelobe suppression. In our method, the imaging process of the circular MIMO array is initially decomposed into bistatic circular synthetic aperture radar (BCSAR) components with different bistatic angles. Components with larger bistatic angles produce equivalent channels whose wavenumber spectra are concentrated near zero frequency, leading to significant broadening of the main lobe in the corresponding point spread function (PSF). In traditional MIMO imaging, each transmit–receive antenna pair is considered an equivalent channel, and all these channels are utilized for imaging. However, components with large bistatic angles, when integrated into the MIMO imaging output, result in increased sidelobe levels. To address this issue, we employ the PEM to restrict the range of equivalent channels. This method selectively retains effective channels generated by components with specific bistatic angles, effectively mitigating the adverse effects of BCSAR components with larger bistatic angles. Through point target simulations, electromagnetic simulations, and practical experiments, we demonstrate that the PEM significantly reduces sidelobes and enhances image quality in circular MIMO array imaging.

Antenna RCS minimization using load tuning

Abstract This paper synthesizes antenna RCS using load tuning, beginning with the derivation of the theoretical load impedance to achieve minimum RCS (MRCS) based on antenna radiation and conjugate-matched scattering parameters. This condition is utilized to obtain feasible MRCS zones and minimize backward RCS (BRCS) for the dipole and microstrip patch antennas. The dipole antenna exhibits a full feasible MRCS zone with a BRCS reduction of 77 dB at the resonant frequency, a 63% relative −10dB reduction bandwidth, and a full plane of reduction angles compared to the conjugate-matched condition. However, mismatching of MRCS loading significantly affects the dipole received power. Conversely, the microstrip patch antenna has a feasible MRCS zone that excludes forward directions and demonstrates a negligible mismatching level with a BRCS reduction of 35.5 dB at the resonant frequency, a 0.67% relative reduction bandwidth, a 50° reduction in H-plane, and a 20° reduction in E-plane compared to the conjugate-matched condition. Tuning the load reactance between conjugate-matched and MRCS loadings results in a trade-off between BRCS reduction and the received power. The calculated MRCS load for specific incident direction is applicable for nearby incidence directions, demonstrating applicability with misalignment. The findings validate the efficiency of using load-tuning method with the derived condition to minimize RCS within specific incident angles.

Synergistic enhancing low-rank coal flotation mechanisms using nanocarrier collector through pore sealing and surface hydrophobicity

Low-rank coal (LRC) is difficult to float using conventional oily collectors due to the rich oxygen-containing functional groups and abundant pores on its surface. In this study, an effective nanocarrier collector containing both nanoemulsion and nanoparticle with droplet size of 10–70 nm was developed, through diesel-beeswax mixture and AEO-7 using low-energy shearing and rapid cooling emulsification to enhance the LRC flotation. The surface morphology and elemental compositions of LRC were firstly characterized using SEM and EDS, identifying its difficult-to-float mechanisms. Then, the macroscopic appearance and microscopic size distribution of nanocarriers, and flotation tests were conducted to determine the optimum formula of nanocarrier collector for LRC. The results indicated that the recovery rate of combustibles was first increased and then decreased, by increasing the mass ratio of beeswax to diesel. When the mass ratio of diesel, beeswax, and AEO-7 was 2:3:5, the recovery rate of combustibles could be achieved to 92.98 %. Finally, the BET specific surface area, water adsorption, contact angle and wrap angle experiments were conducted to clarifying the synergistic enhancing LRC flotation mechanisms of nanocarriers collector. The nanocarriers could permeate into and seal the LRC surface pores, thereby reducing the both surface pore volumes and specific surface area. In addition, the mixtures of diesel and beeswax synergistically improved the surface hydrophobicity. Consequently, this research provides new insight into the development of effective collectors for LRC flotation.

A Successive Approximate Angle Track Converter for Sinusoidal Encoders

ABSTRACTThis paper presents a novel angle track converter for sinusoidal encoders. These encoders provide electronic signals in which the position is encoded in sinusoidal form. This work aims to reduce the complexity and enhance the conversion speed of the sinusoidal‐to‐angle demodulation system. Considering the periodicity of sine and cosine signals (SCSs), the full range is evenly divided into eight segments to determine the coarse angle. According to the specific coarse angle segment, the SCSs are reshaped for proceeding demodulation. Then a fine angle is derived from reshaped signals based on division and arctangent algorithm. Division operation is achieved by a capacitor digital‐to‐analog converter, dynamic comparator, and successive approximation register. The arctangent value is obtained from the division result with the compensation by a small‐size look‐up table. The new converter fabricated in 0.18‐m BCD technology occupies an active area of 0.16 mm2 and consumes 1.5 mW at the sample rate 10 MHz. The measured maximum error is 1.8°, in the full range. Without analog‐to‐digital converters and no nonlinear operation unit, the proposed angle track converter has a significant advantage in cost, speed, and efficiency.

Impact of cochlear detailed morphology on insertion results and intracochlear trauma of a slim pre-curved electrode array: a micro-CT study.

This study aimed to evaluate the impact of detailed cochlear dimensions, assessed using micro-CT (µCT) imaging, on insertion outcomes and associated trauma with a new slim, precurved electrode array. Eleven temporal bone specimens underwent implantation of a 22-electrode slim precurved array via the round window. High-resolution µCT scans post-implantation enabled visualization of cochlear structures and electrode positioning. Combination with subsequent scans taken after electrodes removal, we analyzed angular insertion depth (AID), insertion length, number of electrodes inserted, cochlear dimensions (specifically cochlear duct length (CDL), basal turn diameter, scala tympani dimension), and intracochlear trauma of fine structures. Statistical analyses were performed to correlate cochlear detailed dimensions and morphology with insertion outcomes and trauma. The mean AID was 351.82°, and the mean insertion length was 21.07mm. CDL showed positive correlations with AID and insertion length. Basal turn diameter (value B) positively correlated with AID and insertion length, unlike value A. Middle-basal turn (M/B) relationships (angle and height) significantly influenced insertion depth. The cochleae with smaller M/B heights and specific angles were more susceptible to insertion trauma. Larger basal turn diameters correlated with increased trauma and electrode translocation into the scala vestibuli. This study highlights the importance of precise cochlear measurements in predicting and optimizing cochlear implant outcomes. Specific cochlear dimensions and anatomical shapes were identified as critical factors affecting insertion depth, trauma risk, and electrode positioning. Utilizing micro-CT provided detailed insights into cochlear anatomy and insertion outcomes, offering valuable data for advancing cochlear implant technology and surgical practices.

Micro milling mechanism and tool wear of Unidirectional HfZrTiTaNbCu0.2 fiber reinforced aluminum matrix composites

This study delves into the micro milling and tool wear mechanisms of 2A97 aluminum matrix composites reinforced with HfZrTiTaNbCu0.2 fibers. Finite element analysis models the fibers as uniformly distributed cylindrical entities within the matrix, applying various material constitutive laws, failure, and evolution criteria to simulate milling at three specific angles (45°, 90°, 135°). The research examines the effects of milling parameters, fiber orientations, and tool coating thickness on cutting forces, temperatures, surface roughness, and tool wear. Key findings include: These forces escalate with both cutting speed and depth of cut. Notably, at a feed rate of 68 μm/z, the cutting force is 1.5 times higher compared to 58 μm/z.An increase in milling parameters leads to higher cutting temperatures. Differences of 12 °C and 10 °C were noted at varying depths of cut (10–25 μm) and cutting speeds (1000–1200 mm/s), respectively. As the fiber angle increases, cutting forces first decrease and then rise, with fibers oriented at 90° experiencing only 53 % of the force compared to those at 135°. Similarly, cutting temperatures follow this trend, with a 26 °C difference between 45° and 90° fibers. This factor is positively correlated with depth of cut and fiber angle. Surface roughness at a 55 μm depth is 4.3 times that at 10 μm, and 135° fibers show 2.7 times the roughness of 45° fibers. However, within feed rates of 48–58 μm/z and cutting speeds of 800–1200 mm/s, there is a notable decrease in surface roughness. Variations in cutting parameters, fiber orientations, and tool coating thickness significantly influence peak tool stress. Stress concentration at the central groove tends to reduce tool wear, whereas stress concentration at the peripheral edge or strain concentration at the bottom edge exacerbates it.

Design of A Self-Correctable Docking Mechanism in Disturbed Water Surface Environment

The docking mechanism is critical for unmanned surface vehicle (USV) applications, such as traction, dragging, charging, data transmission, building pontoons, etc. These applications are significant for observation, exploration, data acquisition, patrol, rescuing, etc., in aquatic environments. In this paper, a novel autonomous docking mechanism for USVs is proposed. It is capable of (1) docking the USV subject to disturbance efficiently, (2) latching without power consumption after the docking is completed, and (3) guiding the docking head to three specific angles at the end of the docking process. This paper proved the feasibility and rationality of the docking mechanism through theoretical force analysis. Experiments with three different scenarios are implemented to test the mechanism's performance. The experimental results show that the docking success rate is greater than or equal to 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> on the disturbed water surface.

Deep convolutional architectures for optimizing multi-element airfoil systems

The investigation of aerodynamic properties in multi-element airfoils is historically challenging and impractical for real-time applications. Predicting specific angles to achieve predetermined lift and drag forces has been elusive. Advances in machine learning (ML) and deep learning (DL) offer new possibilities, but their application to multi-wing system (multi-element airfoils) is limited by scarce datasets. This study explores development, design, and comparative analysis of ML and novel DL algorithms to predict the aerodynamic coefficients generated by multi-element airfoils given airfoil shape, angle of orientation of each airfoil, and their velocity, a previously unexplored area. Using datasets generated via ANSYS Fluent, the proposed models predict aerodynamic coefficients based on variables such as velocity, airfoil angle, and images of the airfoil system with high accuracy, achieving a mean squared error of 0.0049. The proposed approach also significantly reduces the computational time for predicting the aerodynamic coefficients from 10 to 15 min in a traditional computational fluid dynamics simulation to 1–6 ms using our approach. This real-time prediction capability allows for assessing various angle combinations to find optimal orientations for specific drag and lift forces.

4D-printed intelligent reflecting surface with improved beam resolution via both phase modulation and space modulation

Recently, intelligent reflecting surfaces (IRSs) have emerged as potential candidates for overcoming the line-of-sight issue in 5 G/6 G wireless communication. These IRSs can manipulate the direction of reflected beams, enabling efficient beam steering to enhance the performance of wireless communication. Each unit cell (or unit structure) of an IRS commonly consists of electrical elements for phase modulation. However, by employing phase modulation alone, an IRS can steer the reflected electromagnetic waves toward only discrete and specific angles, leaving a wide range of out-of-beam areas. In this work, an IRS that uses both phase modulation and space modulation is presented to improve the beam resolution and continuously cover out-of-beam areas that phase modulation alone cannot address. A positive-intrinsic-negative diode is mounted on a unit cell for phase modulation, and a 4D-printed reconfigured structure is fabricated to demonstrate space modulation. The beam-steering function is achieved by alternating the states of the diodes in the same columns, while the beam resolution is improved by controlling the gaps between the columns. The functions are first theoretically and numerically analyzed and then experimentally verified, demonstrating that additional angles of −46°/+50°, −22°/+14°, and −16°/+12° are achieved with space modulation and −60°/+62°, −30°/+22°, and ±16° are achieved by phase modulation alone. The proposed IRS offers the possibility of functional integration in a variety of indoor applications within the wireless communication field.

Optimal Design of Smart Antenna Arrays for Beamforming, Direction Finding, and Null Placement Using the Soft Computing Method

ABSTRACTThe urge of modern communication system is to design and development of the smart antennas with adaptive radiation characteristics. The multifold capabilities of fourth‐dimensional antenna arrays can cater that much needed adaptiveness if properly designed. Compared to the conventional arrays, the fourth‐dimensional arrays have one added advantage as the ‘Time’ of all the switched‐on antenna elements can be managed to generate the required amplitude and phase tapering without even using attenuators and phase shifters. However, one inherent limitation of fourth‐dimensional control parameter is the generation of harmonics or sidebands. This article proposes various means of radiation pattern synthesis in fourth‐dimensional linear antenna arrays with pulse shifting, pulse splitting, and a combination of both. First of all, the pulse splitting and shifting techniques are combinedly proposed by reducing the sidelobe levels and sideband levels of the beamforming antenna arrays to enhance directivities and efficiencies. Then, this mathematical proposition of the direction finding fourth‐dimensional arrays is developed. Finally, broad nulls over a specific angle of arrival region are created for jamming and interference mitigation. For all these cases, the sidelobe level and the unwanted higher‐order sideband levels are suppressed to reduce the unwanted interferences and power losses. The optimal time schemes for all the synthesized patterns are generated by proposing a chaos‐based soft computing algorithm. The radiofrequency signals at each radiating array element are processed by the optimal time schemes proposed for specific applications. The outcomes are validated and compared with other state‐of‐the‐art works of this domain to prove the competency of the proposed work. The qualitative and quantitative comparisons presented for beamforming array is aimed for a good improvement over other reported works by targeting ultralow (less than −40 dB) sidelobe and sideband levels. For direction‐finding array, the proposed idea has also targeted ultralow sidelobes for the main as well as steered beam patterns. Furthermore, the null placement over a region has been aimed to cover more area for jamming and sidelobe reduction for interference mitigation. Overall, the optimal designs proposed for these advanced applications are beneficial for cutting‐edge communication systems.

Passive Stylus Tracking: A Systematic Literature Review

Passive stylus systems offer a simple and cost-effective solution for digital input, compatible with a wide range of surfaces and devices. This study reviews the domain of passive stylus tracking on passive surfaces, a topic previously underexplored in existing literature. We answer four key research questions: what type of systems exist in this domain, what methods do they use for tracking styli, how accurate are they, and what are their limitations? A systematic literature review resulted in 24 papers describing passive stylus systems. Their methods primarily fall into four categories: monocular cameras with image processing, multiple camera systems with image processing, machine learning systems using high-speed cameras or motion capture hardware, and radio frequency signal-based systems with signal processing. We found the system with the highest accuracy used a single monocular camera. In many systems, markers such as retroreflective spheres, tape, or fiducial markers were used to enhance the feature matching. We have also found stagnation and in some cases, regression in the precision and reliability of these systems over time. The limitations in these systems include the lack of varied stylus form factor support, the restriction to specific camera positions and angles, and the requirement of expensive hardware. Given these findings, we discuss the important characteristics and features of passive stylus systems and propose ways forward in this field.

Heart Rate Estimation Considering Reconstructed Signal Features Based on Variational Mode Decomposition via Multiple-Input Multiple-Output Frequency Modulated Continuous Wave Radar.

Accurate heart rate estimation using Doppler radar and Frequency Modulated Continuous Wave (FMCW) radar is highly valued for privacy protection and the ability to measure through clothing. Conventional methods struggle to isolate the heartbeat from respiration and body motion. This paper introduces a novel heart rate estimation method using Variational Mode Decomposition (VMD) via Multiple-Input Multiple-Output (MIMO) FMCW radar. The proposed method first estimates human positions within the radar's coverage, reducing noise by focusing on signals from these positions. The signal is then decomposed into multiple Intrinsic Mode Function (IMF) signals using VMD, and the heartbeat-specific IMF is extracted based on its center frequency. The heart rate signal is reconstructed using weighted addition of IMF signals for each radar cell, with cells defined by specific angles and distances within the coverage area. Peak detection is used to estimate heart rate from these reconstructed signals. To ensure accuracy, the method selects the heart rate estimate with the highest energy and periodicity for the first four time windows. From the fifth time window onward, it selects the estimate closest to the average of the previous four, minimizing extraneous variations. Experiments conducted with one and two subjects showed promising results. In case 1, with one subject, the method achieved a Mean Absolute Error (MAE) of 2.54 BPM and an exclusion rate of 0.94% using MIMO FMCW radar, compared to 4.72% with Doppler radar. In case 2, with two subjects, the method achieved an MAE of 2.28 BPM, confirming accurate simultaneous heart rate estimation.

Annealing effect of Ca3TaGa3Si2O14 catangasite crystals on their optical activity

The spectral dependences of transmission and absorption in the wavelength range of 200–2500 nm were measured for Ca3TaGa3Si2O14 crystals cut perpendicular to the optical axis in the initial state (without annealing) and after isothermal annealing in vacuum and in air. It was found that annealing in vacuum leads to a decrease, and annealing in air leads to an increase in the intensity of absorption bands. A spectrophotometric method for measuring and calculating the specific rotation angle ρ of the plane of polarization of light in gyrotropic crystals from the transmission coefficient spectra at different angles between the polarizer and the analyzer is considered. The transmission spectra were normalized in order to eliminate shifts in the spectra associated with measurement features. Spectral dependences of the values of ρ for all three samples, which are approximated by the extended Drude formula, are obtained; the influence of the annealing atmosphere on the values of the coefficients of this formula is established.